# Disentangling the Signatures of Blended-Light Atmospheres in L/T Transition
Brown Dwarfs

Afra Ashraf Department of Physics & Astronomy, Barnard College
3009 Broadway, New York, NY 10027, USA  Department of Astrophysics, American
Museum of Natural History
200 Central Park West, New York, NY 10024, USA  Daniella C. Bardalez Gagliuffi
Department of Astrophysics, American Museum of Natural History
200 Central Park West, New York, NY 10024, USA  Elena Manjavacas AURA for the
European Space Agency (ESA), ESA Office, Space Telescope Science Institute,
3700 San Martin Drive, Baltimore, MD, 21218 USA  Johanna M. Vos Department of
Astrophysics, American Museum of Natural History
200 Central Park West, New York, NY 10024, USA  Claire Mechmann  Department of
Physics & Astronomy, Lehman College, City University of New York
250 Bedford Park Blvd W, The Bronx, NY 10468, USA  Jacqueline K. Faherty
Department of Astrophysics, American Museum of Natural History
200 Central Park West, New York, NY 10024, USA

###### Abstract

We present a technique to identify spectrophotometrically variable L7$-$T3
brown dwarfs with single-epoch, low-resolution, near-infrared SpeX spectra. We
calculated spectral indices on known variable brown dwarfs and used them to
select 11 index-index parameter spaces where known variables can be
distinguished from the rest of the general population of brown dwarfs. We find
62 candidate variables, 12 of which show significant variability amplitude in
independent photometric monitoring surveys. This technique constitutes the
first formal method to identify a time-dependent effect such as variability
from peculiarities in their integrated light spectra. This technique will be a
useful tool to prioritize targets for future photometric and spectroscopic
monitoring in the era of JWST and 30 m-class telescopes.

Brown dwarfs (185), L dwarfs (894), T dwarfs (1679), Atmospheric variability
(2119), Astronomical techniques (1684), Near infrared astronomy (1093),
Spectroscopy (1558)

††journal: ApJ††facilities: IRTF(SpeX)††software: SPLAT (Burgasser & Splat
Development Team, 2017)

##  1 Introduction

Substellar variability is a time-dependent phenomenon caused by an
inhomogeneous atmosphere over the course of an object’s rotation period, and
it is characterized by a change in flux over time. Photometric variability is
dominated by magnetic activity in M dwarfs and early-L dwarfs (Hawley, 1993)
and by inhomogenous cloud coverage in cooler brown dwarfs (Gelino et al.,
2002). The cool temperatures of L and T-type brown dwarf atmospheres permit
the condensation of different species, resulting in patchy layers of large-
scale cloud and haze structures (Ackerman & Marley, 2001). Different elements
and compounds reach their condensation equilibrium at varying temperatures and
pressures, such that clouds can form at different altitudes in the atmosphere.
Silicate and iron condensates begin to form in the atmospheres of L-dwarfs
below 2400 K (Lodders & Fegley, 2006). Towards the end of the L sequence,
silicate and iron clouds sink beneath the photosphere in what is known as
“rain out” (Knapp et al., 2004). By the time an object has cooled down to T
dwarf temperatures, their clouds have sunken below the photospheres. The
sudden increase in brightness in the $J$-band for late-L/early-T brown dwarfs
(called the “J-band bump”) has been interpreted as evidence for this process
(Burgasser et al., 2002a; Dahn et al., 2002; Tinney et al., 2003; Vrba et al.,
2004). An alternative explanation for photometric variability is a cloudless
model, where variations arise due to a convective atmosphere dominated by
CO/CH4 radiative convection as shown in Tremblin et al. (2015, 2016, 2017,
2019, 2020).

The L/T transition is a critical phase in the evolution of brown dwarfs which
happens over a relatively short range of effective temperatures
($1150\,\text{K}\lesssim T_{eff}\lesssim 1350\,\text{K}$; Vos et al. 2019a;
Filippazzo et al. 2015) and is characterized by the appearance of methane in
near-infrared (NIR) spectra and a shift towards blue in $J-H$ and $H-K$
colors. Strong NIR variability is most common within this spectral type range,
with a 24% variability occurrence (amplitudes $>2\%$) compared to only 3.2%
outside of the L/T transition (Radigan, 2014). Since variability is thought to
be more prevalent in this spectral type region, we have the best chance of
identifying suitable targets amenable for further study.

However, variability studies are extremely resource intensive. Reliable light
curves require precision photometric monitoring over the course of several
hours for each target, covering a significant portion of an object’s rotation
period. For example, in their photometric variability survey, Radigan et al.
(2014) obtained 62 light curves of L4$-$T9 dwarfs with $2-3$ m aperture
ground-based telescopes spanning roughly 2-5 hours per target. Accounting for
telescope slewing, target acquisition and data read out, these observations
amounted to almost 250 hours of on-sky time, resulting in variability
detection in 16% of their targets. In their space-based variability survey,
Metchev et al. (2015) targeted 44 L3$-$T8 brown dwarfs and identified 19
objects, i.e. $61^{+17}_{-20}\%$ of L dwarfs and $31^{+35}_{-17}\%$ of T
dwarfs, as having photometric variability with an amplitude of $0.2-4.6$%
using the Spitzer Space Telescope. Likewise, Buenzli et al. (2014) found 6
variable brown dwarfs in a sample of 22 observed with the Hubble Space
Telescope. These surveys are crucial to understand the occurrence of
variability and to study the time-dependent atmospheric dynamics and vertical
structure of brown dwarf atmospheres at a population level, yet such surveys
cannot pre-select candidates based on their likelihood to show variability
because currently there is no systematic way to prioritize candidates for
variability studies.

Spectral binaries may hold a clue for such a technique. Spectral binaries are
systems of two brown dwarfs of different spectral types with a combined
peculiar unresolved, low-resolution, NIR spectrum (Cruz et al., 2004;
Burgasser, 2007a; Burgasser et al., 2010; Bardalez Gagliuffi et al., 2014).
Spectral binary candidates are identified using spectral indices and binary
template fitting, and later confirmed through high resolution imaging, radial
velocity or astrometric variability (e.g., Bardalez Gagliuffi et al., 2015;
Burgasser et al., 2016; Sahlmann et al., 2020). However, a handful of spectral
binary candidates have not shown signs of binarity in high resolution follow-
up and instead are known to show photometric variability. The young early-T
dwarfs 2MASS J21392676+0220226 (hereafter J2139+0220, Burgasser et al., 2006a)
and 2MASS J13243553+6358281 (hereafter J1324+6358, Looper et al., 2007), were
originally suggested to be spectral binary candidates (Burgasser et al., 2010)
of L4 and T5 components, but are actually single, photometrically variable
brown dwarfs (Radigan et al., 2012; Metchev et al., 2015). This suggests that
the spectral binary technique may also be inadvertently sensitive to the type
of inhomogeneous atmospheres that drive variability.

Khandrika et al. (2013) searched for photometric variability in $J$ and
$K$-bands using the Gemini infrared camera on the 3-meter Shane Telescope at
Lick Observatory for 15 L and T-type brown dwarfs, including 7 spectral binary
candidates. They found variability in 4 objects, two of which were spectral
binary candidates at the time, 2MASS J2139+0220 and SDSS J141624.08+134826.7A
(hereafter J1416+1348A, Scholz, 2010). In their spectroscopic variability
program with Hubble Space Telescope’s Wide Field Camera 3, Manjavacas et al.
(2019) used the spectral binary technique to identify peculiar sources and
multiple systems. However, they discovered that five of the eight spectral
binary candidates they found had been previously identified in the literature
as photometrically variable. Sources like 2MASS J2139+0220, 2MASS J1324+6358,
and SDSS J1416+1348A, while originally selected as spectral binary candidates,
present no compelling signs of binarity and instead show significant
variability amplitudes. These motivating examples suggest that the spectral
signatures caused by two separate sources at different temperatures on an
unresolved spectrum are similar to those of a single object with multiple
cloudy, patchy layers at different temperatures. The peculiarities in the
spectra selected by index-based spectral binary techniques may instead be
occasionally caused by cloud-driven variability.

Cloud-driven brown dwarf variability is also correlated with age. Young brown
dwarfs have redder near-infrared and mid-infrared colors in comparison to
field objects of the same spectral type. This is likely due to their low
surface gravity and extended radii from their ongoing contraction, leading to
slower sedimentation efficiency of scattering particles like dust grains in
their atmospheres (Faherty et al., 2016). In the Weather on Other Worlds
survey by Metchev et al. (2015), they found an association with 92% confidence
between low surface gravity and high-amplitude variability among L3 - L5.5
dwarfs. Vos et al. (2019b) calculated a variability occurrence rate in a
sample of L0-L8.5 young, low-gravity objects using the New Technology
Telescope (NTT) and the United Kingdom InfraRed Telescope (UKIRT) of
$30_{-8}^{+16}\%$ which they compared to the results of Radigan et al. (2014)
where the field dwarfs have a variability occurrence rate of
$11_{-4}^{+13}\%$. These results suggest that variability occurs more
frequently and has a higher amplitude in young brown dwarfs. Marley et al.
(2012) suggests that this correlation could be caused by high altitude clouds
in low-gravity atmospheres, increasing the contrast between different cloud
layers. In a recent variability survey, Vos et al. (2022) indeed finds that
the maximum variability amplitudes observed for low-gravity L dwarfs are
higher compared to field objects.

Variability studies in brown dwarfs are precursors to future studies of
exoplanet climates. Brown dwarfs are characterized by physical properties that
are very similar in nature to extrasolar planets, in particular directly-
imaged exoplanets or young giant planets. L and T-type dwarfs overlap in
temperature range ($500\,\text{K}$ $\lesssim T_{eff}\lesssim 2300\,\text{K}$;
Filippazzo et al. 2015) with young giant exoplanets ($1300\,\text{K}\lesssim
T_{eff}\lesssim 3000\,\text{K}$; Madhusudhan et al. 2014), a parallel
reflected in their atmospheric spectra. However, brown dwarfs are much easier
to image than exoplanets since they are typically unobstructed by a host star,
making atmospheric studies more accessible. Apai et al. (2016) and Biller et
al. (2021) probed the giant exoplanets in the HR8799 system for variability
using VLT/SPHERE, but neither could achieve high enough sensitivity to
confidently detect variability. This highlights the importance of studying
isolated planetary-mass objects as analogs to exoplanets in orbit around a
bright host star.

The emergence of next-generation telescopes, such as the James Webb Space
Telescope (JWST), will permit detailed characterization of exoplanets (Carter
et al., 2021), and the techniques used to study brown dwarf atmospheres will
be important predecessors to surface mapping and characterizing exoplanet
atmospheres. We can analyze light curves to obtain variability amplitudes and
rotation periods. By using stellar and substellar light curves, we can map the
surface inhomogeneities of stars with topological light curve inversion and
modeling (Apai et al., 2017; Luger et al., 2019), albeit with degeneracies.
The same techniques will be applied to exoplanets with time-resolved high-
contrast imaging. Our technique potentially offers an opportunity to probe the
vertical structure of the atmosphere to complement the surface information
provided by light curves and compare to 3D global circulation models (Showman
et al., 2019; Tan & Showman, 2021a).

In this paper we present a new technique to identify high likelihood
variability candidates among L7$-$T3 dwarfs based on spectral indices of
single-epoch, low resolution, NIR spectra. In Section 2, we discuss the
characteristics of our sample. In Section 3, we use our technique to identify
variability candidates for follow-up photometric monitoring. In Section 4 we
discuss the stability of SpeX as an instrument, calculate our variability
fractions, and examine the possible surface features that could cause
different variability amplitudes. Finally in Section 5 we present our
conclusions.

##  2 SpeX Spectral Sample

Our spectral sample was retrieved from the SpeX Prism Library (SPL; Burgasser
2014) and is composed of 325 spectra from 270 unique objects within the
L7$-$T3 dwarf spectral type range ($1150\,\text{K}\lesssim T_{eff}\lesssim
1350\,\text{K}$). The SPL contains over 2000 NIR spectra of ultracool and
brown dwarfs collaboratively collected since the year 2000 with SpeX, a
spectrograph mounted on the 3-m NASA Infrared Telescope Facility in Mauna Kea,
HI (Vacca et al., 2003; Rayner et al., 2003). We used spectra in the SPL
acquired with the prism-dispersed mode of SpeX, which samples wavelengths
between 0.75 and 2.5$\mu$m at a dispersion of 20–30 Å pixel-1. The spectra
contained in the SPL have been homogeneously obtained with the same observing
strategy (see e.g., Bardalez Gagliuffi et al. 2014, 2019; Burgasser et al.
2010 for technical details on acquisition, integration, calibration, and
reduction of SpeX spectra).

Since we are interested in identifying differences between variable and non-
variable objects across spectral features, such as a peculiar slope or depth
of absorption lines and bands, we restrict our sample to spectra acquired in a
single epoch. This means that we are not using spectra intended for
spectroscopic variability, which involves a series of short-exposure spectra
in a large field of view including reference stars to evaluate the change of
spectral features over time. Depending on how well the slit was aligned with
the parallactic angle to avoid slit losses, and the duration of integration at
the time of observations, the flux of an individual spectrum may fluctuate
between 1-2% of the total flux on separate epochs because of atmospheric
turbulence (M. Connelley, priv. comm.).

Figure 1: Spectral type distribution of our sample with benchmark variables in
red.

We use the SpeX spectral classifications from the SPL, which follow the
Kirkpatrick et al. (2010) standards and method that only use the $J$-band for
spectral classification for L-dwarfs and the Burgasser et al. (2006a) near-
infrared spectral type standards for T-dwarfs. We excluded subdwarfs and
sources in star-forming regions as we wanted to focus on differences in
spectra caused by cloud-driven variability, not by other factors like
reddening or low metallicity that would result in unusual spectra. The spectra
were calibrated to absolute flux densities using their 2MASS $J$-band
magnitudes and the empirical relations of Filippazzo et al. (2015), with the
flux calibration function within the SPLAT package.

Given the correlation between variability and age, we identified young objects
within our sample following the literature. Of the 325 spectra examined, there
are a total of 51 young spectra from 49 young objects, of which 4 are
confirmed variables from photometric monitoring. We consider objects as
“young” according to the literature, given spectral features and kinematics
significantly different from those in field objects, which are evident up to
roughly 150 Myr old (e.g., the age of the AB Doradus moving group, Faherty et
al. 2016). Objects with high space velocities relative to the Sun tend to have
older ages, as they have had a long time to accumulate energy kicks from
gravitational interactions with other stars on their orbit around the galactic
center. Gravity estimates can be obtained from spectral features in low
resolution spectra (Allers & Liu, 2013) and age estimates by kinematic
association to a young moving group, which like the Pleiades, AB Doradus, or
the Hyades, are coeval, gravitationally-bound groups of stars. Additionally,
we identify 13 spectra from 8 confirmed spectral binaries. The spectral type
distribution of our final sample is shown in Figure 1, highlighting variable
sources. Since the SPL is a general repository of spectra observed for a
variety of science cases, we do not claim our selected sample to be unbiased
or complete.

##  3 Identification of Candidate Variables

###  3.1 Benchmarks

From our sample of L/T transition objects, we select as “benchmarks” 21
spectra from 15 objects that have confirmed light curve amplitudes $>1\%$ in
$J$, [3.6], or [4.5] bands from previous time-resolved, photometric monitoring
across several variability studies varying in sensitivity and/or wavelength
coverage (see Table 3.1 and Vos et al. 2020 for a summary of sources with
measured variability). Ground-based near-infrared surveys (e.g. Radigan et
al., 2014; Vos et al., 2019b) are generally sensitive to variations greater
than $1-2\%$, and can only observe each target as long as it is visible.
Variability studies that use the WFC3 instrument on the Hubble Space Telescope
(e.g. Apai et al., 2013; Buenzli et al., 2014) reach precisions of
$0.01-0.02\%$, but have generally been limited in observing duration. Finally,
variability studies using the Spitzer Space Telescope (e.g. Metchev et al.,
2015; Vos et al., 2022) achieve both sub-percent precision and relatively long
monitoring duration ($\sim 20~{}$hr). Variability monitoring with the Spitzer
Space Telescope is likely the most sensitive to date for detecting variability
in L and T brown dwarfs, yielding lower mid-IR amplitudes when compared to
near-IR amplitudes. Our strict benchmark selection process discounted 8
objects from the literature with either upper limits in variability amplitudes
(i.e., no variability or variability below the sensitivity limit) or previous
identification as spectral binary candidates from the benchmark list that were
later recovered as variability candidates: SDSS J0758+3247, SDSS J0858+3256,
2MASS J1119-1137, SDSS J1219+3128, SDSS J1254-0122, SDSS J1516+3053, 2MASS
J1632+1904, 2MASS J2224-0158. This was also the case for Luhman 16A, which we
decided to exclude from the benchmarks list due to contrasting reports of
variability in the NIR and MIR.

The variability amplitudes in the NIR for our benchmarks range from 1.2% to
26% for 2MASS J21392676+0220226 (Radigan et al., 2012) in $J$-band, including
Luhman 16B (11% in WFC3-IR at 1.1-1.66 $\mu$m Buenzli et al., 2015b). Three of
our benchmarks only have variability measurements in Spitzer [3.6] or [4.5]
bands with amplitudes between 1-3%. While 2MASS J20025073-0521524 and 2MASSW
J0310599+164816 do not have a measured rotation period, the rest of our
benchmarks have periods between 2-19 h. While the planetary-mass, L7 dwarf PSO
318.5-22 (Liu et al., 2013) qualifies as a benchmark given our criteria, we
did not have a SpeX spectrum of this source in the SPL. Sources that had been
previously selected as spectral binary candidates and for which no high-
resolution imaging is available were excluded. This cut affected SDSS
J075840.33+324723.4 and SDSS J151643.01+305344.4, both of which were
identified as variability candidates with our technique. We excluded the
blended light spectrum of Luhman 16AB from our benchmark list, but kept the
individual spectrum of the spatially resolved B component. The B component is
a T0 dwarf with a large variability amplitude of $\sim$ 11% (Gillon et al.,
2013), which gets diminished in the combined-light spectrum. We also excluded
the unresolved spectrum of 2MASSI J0423485$-$041403 (hereafter 2MASS
J0423$-$0414), because even though it is a known variable (0.8% $J$-band
amplitude, Radigan et al. 2014), it is also an astrometric binary system
(Dupuy & Liu, 2012).

Table 1: Confirmed variability sources used as benchmarks in our study.

| Spectral type |  | Reference
---|---|---|---
Source | Optical | NIR SpeX | Young? | (Optical SpT; Youth; Variability)
WISEP J004701.06+680352.1 | L7pec | L7 | Y | 7; 8; 12, 20
SDSSp J010752.33+004156.1 | L8 | L7 | Y | 9; $\cdots$ ; 15
SIMP J013656.57+093347.3 |  $\cdots$ | T2 | Y |  $\cdots$ ; 3; 16
2MASSW J0310599+164816 | L8 | T0 | N | 10; $\cdots$ ; 1
2MASSI J0825196+211552 | L7.5 | L8 | N | 10; $\cdots$ ; 15
SDSS J104335.08+121314.1 |  $\cdots$ | L9 | N |  $\cdots$ ; $\cdots$ ; 15
WISE J104915.57$-$531906.1B | T1 | T1 | N | 11; $\cdots$ ; 5
SDSS J105213.51+442255.7 |  $\cdots$ | T0 | N |  $\cdots$ ; $\cdots$ ; 6
2MASS J11472421$-$2040204 |  $\cdots$ | L7 | Y |  $\cdots$ ; 18; 15
2MASS J13243553+6358281 |  $\cdots$ | T3 | Y |  $\cdots$ ; 4; 15
2MASS J16291840+0335371 (PSO J247.3273+03.5932) |  $\cdots$ | T2 | N |  $\cdots$ ; $\cdots$ ; 16
2MASS J20025073$-$0521524 | L6 | L7 | N | 2; $\cdots$ ; 21
2MASS J21392676+0220226 |  $\cdots$ | T2 | Y |  $\cdots$ ; 23; 17
HN Peg B |  $\cdots$ | T3 | Y |  $\cdots$ ; 14; 15
2MASS J21481628+4003593 | L6 | L7.0 | Y | 13; 22; 15, 19

References. — (1) Buenzli et al. (2015b); (2) Cruz et al. (2007); (3) Gagné et
al. (2017a); (4) Gagné et al. (2018a); (5) Gillon et al. (2013); (6) Girardin
et al. (2013); (7) Gizis et al. (2012); (8) Gizis et al. (2015); (9) Hawley et
al. (2002); (10) Kirkpatrick et al. (2000); (11) Kniazev et al. (2013); (12)
Lew et al. (2016), (13) Looper et al. (2008); (14) Luhman et al. (2007); (16)
Metchev et al. (2015);(15) Radigan (2014); (17) Radigan et al. (2014); (18)
Schneider et al. (2016b); (19) Vos et al. (2017); (20) Vos et al. (2018); (21)
Vos et al. (2019b); (22) Vos et al. (2020); (23) Zhang et al. (2021)

###  3.2 Selection regions in index-index spaces

In order to identify signatures of variability from single-epoch spectra, we
modified the spectral indices techniques from Bardalez Gagliuffi et al. (2014)
and Burgasser et al. (2010), originally designed to identify spectral binary
candidates of late-M and L dwarf primaries with a T-dwarf companion. The 13
indices examined are: H2O-$J$, CH4-$J$, $J$-curve, CH4-$H$, H2O-$H$, $K/J$,
$J$-slope, H2O-$Y$, $H$-bump, $H$-dip, H2O-$K$, CH4-$K$, and $K$-slope, which
are specified in Bardalez Gagliuffi et al. (2014) and span the NIR range
across $J$, $H$, and $K$ bands. The wavelength ranges that correspond to each
spectral index are shown in Figure 2 and Table 3.2. We calculated spectral
indices by integrating the flux column enclosed by these wavelength regions
and finding the ratio between them.

Figure 2: Locations of wavelength regions used to calculate spectral indices
superimposed on a sample brown dwarf spectrum. Spectral indices are obtained
by integrating the flux column defined by these wavelength regions and finding
the ratio between them. For cases where 3 flux columns are used, an average of
two flux columns of the same color are used as either numerator or
denominator.  Table 2: Wavelength Ranges of Spectral Indices

Spectral Index | Numerator Range ($\mu$m) | Denominator Range ($\mu$m) | Feature | Reference
---|---|---|---|---
H2O-$J$ | 1.14-1.165 | 1.26-1.285 | 1.15 $\mu$m H2O | 1
CH4-$J$ | 1.315-1.335 | 1.26-1.286 | 1.32 $\mu$m CH4 | 1
$J$-curve | 1.04-1.07 + 1.26-1.29 | 1.14-1.17 | Curvature across $J$-band | 4
CH4-$H$ | 1.635-1.675 | 1.56-1.60 | 1.65 $\mu$m CH4 | 1
$H$-bump | 1.54-1.57 | 1.66-1.69 | Slope across $H$-band peak | 4
$H$-dip | 1.61-1.64 | 1.56-1.59 + 1.66-1.69 | 1.63 $\mu$m FeH/CH4 | 2
H2O-$K$ | 1.975-1.995 | 2.08-2.10 | 1.90 $\mu$m H2O | 1
CH4-$K$ | 2.215-2.255 | 2.08-2.12 | 2.20 $\mu$m CH4 | 1
$K$-slope | 2.06-2.10 | 2.10-2.14 |  $K$-band shape/CIA H2 | 3

Note. — Numerical values of the wavelength regions of the spectral indices
shown in Figure 2. For the indices where the range has a plus sign, the range
is the average of the two wavelength ranges listed.

References. — (1) Burgasser et al. (2006a); (2) Burgasser et al. (2010); (3)
Burgasser et al. (2002b); (4) Bardalez Gagliuffi et al. (2014).

We measured these indices on our entire spectral sample and compared them
against each other to identify regions of variability based on visual
inspection. We visually examined 78 index-index plots using 21 spectra of 15
sources with confirmed variability from photometric monitoring as our
benchmarks (see Section 3.1) to define variability regions in each index-index
plot. From these index-index plots, we selected 11 parameter spaces where the
benchmark variables were differentiated from the general spectral sample
(Figure 3). We defined polygonal regions within these plots which
conservatively contain all the benchmark variables. The limits for each region
in the index-index plots are shown in Table 3 and illustrated in Figure 3.

We defined variability candidacy based on the number of times a spectrum was
found within our variability regions. Figure 5 shows the frequency with which
spectra were identified in a given number of index-index plots. All of our
benchmark sources, which are confirmed variables, are found in all 11 index-
index plots by design, except for one of the two spectra of the L5.5 dwarf
2MASS J20025073-0521524 (hereafter 2MASS J2002-0521, Vos et al., 2019b). For
this reason, we define weak candidates as sources which fall in 10 regions and
strong candidates those which are found in all 11 regions in our index-index
plots. This criterion results in 51 strong and 11 weak candidate variable
sources amenable for future photometric monitoring.

Figure 3: The 11 index-index plots used to identify variability candidates.
The red stars indicate our benchmark variables. The blue triangles indicate
confirmed spectral binaries. The open stars and open circles indicate youth,
while everything that is filled in is a field object.

Figure 3: continued Figure 5: Histogram showing the number of times a spectrum
falls in one of our selection regions. Benchmark variables are shown in red,
confirmed spectral binaries in blue, and the rest of the spectral sample in
gray. The final candidates are the sources found in 10 or more parameter
spaces, as shown by the dashed line. Table 3: Region limits for each index-
index correlation plot.

x-axis | y-axis | coordinates | x-range | y-range
---|---|---|---|---
H2O-$J$ | CH4-$H$ | [[0.2,0.84],[0.5,0.84],[0.72,1.08],[0.72,1.3],[0.2,1.3],[0.2,0.84]] | [0.2,1] | [0.6,1.3]
H2O-$J$ |  $H$-bump | [[0.2,1.11],[0.5,1.11],[0.72,0.86],[0.72,0.6],[0.2,0.6],[0.2,1.11]] | [0.3,1] | [0.6,1.6]
CH4-$J$ | CH4-$H$ | [[0.3,0.84],[0.58,0.84],[0.78,1.09],[0.78,1.3],[0.3,1.3],[0.3,0.84]] | [0.3,0.9] | [0.6,1.3]
CH4-$J$ |  $H$-bump | [[0.3,1.11],[0.57,1.11],[0.78,0.86],[0.78,0.6],[0.3,0.6],[0.3,1.11]] | [0.4,0.9] | [0.6,1.6]
CH4-$H$ | H2O-$K$ | [[0.84,0.2],[0.84,0.3],[1.13,0.385],[1.3,0.385],[1.3,0.2],[0.84,0.2]] | [0.6,1.3] | [0.25,0.5]
CH4-$H$ | CH4-$K$ | [[0.8,0.5],[1.3,0.5],[1.3,1.11],[1.16,1.11],[0.8,0.5]] | [0.6,1.3] | [0.3,1.2]
CH4-$H$ |  $H$-dip | [[0.84,0.493],[1.3,0.493],[1.3,0.54],[0.84,0.54],[0.84,0.493]] | [0.6,1.3] | [0.4,0.54]
CH4-$H$ |  $J$-curve | [[1.05,2.29],[1.3,2.29],[1.3,5.5],[0.84,5.5],[0.84,3.4],[1.05,2.29]] | [0.4,1.3] | [1.5,5.0]
H2O-$K$ |  $H$-bump | [[0.2,1.11],[0.3,1.11],[0.385,0.83],[0.385,0.6],[0.2,0.6],[0.2,1.11]] | [0.25,0.5] | [0.6,1.6]
$H$-dip |  $K$-slope | [[0.493,1],[0.55,1],[0.55,0.875],[0.493,0.875],[0.493,1]] | [0.425,0.55] | [0.875,1.05]
$H$-dip |  $H$-bump | [[0.493,1.11],[0.55,1.11],[0.55,0.6],[0.493,0.6],[0.493,1.11]] | [0.4,0.54] | [0.6,1.6]

Note. — Each set of coordinates forms a polygon with 4 or 5 sides.

###  3.3 Notable Sources

####  3.3.1 Strong Candidates

1) WISE J00164397+2304265

This object was first identified following a crossmatch of the PanSTARRS
(Kaiser et al., 2010) and WISE (Wright et al., 2010) surveys as a T0 brown
dwarf by Best et al. (2015). The $H$-band showed no signs of methane, which is
a hallmark of the T dwarf class (Burgasser et al., 1999), but the $J$-band
peak resembles that of a T2 dwarf. Thus it was flagged as a spectral binary
candidate for its unusual spectrum (Best et al., 2015), finding a closest
match with the confirmed L6 + T2 dwarf binary, SDSS J0423–0414 (Burgasser et
al., 2005; Geballe et al., 2002). This source has a 93% probability of
belonging to the field using parallaxes from Best et al. (2020) in BANYAN
$\Sigma$ (Gagné et al., 2018b).

2) 2MASS J00310928+5749364

2MASS J0031+5749 was classified as an L9 brown dwarf by Best et al. (2013)
using spectral indices from Burgasser et al. (2006a). This source has a 88%
membership probability in Carina Near according to BANYAN $\Sigma$ (Gagné et
al., 2018b) with kinematic measurements from Best et al. (2015), giving it an
age estimate of $13.3^{+1.1}_{-0.6}$ Myr (Booth et al., 2021). This source was
independently monitored for variability with the _Spitzer Space Telescope_ and
found to be variable by Vos et al. (2022), who measured an amplitude of
0.35$\pm$0.03% at [3.6] and a period of 1.64$\pm$0.01 h. The SPL contains two
spectra of this object, both found in all 11 index-index regions.

3) 2MASS J02062493+2640237

The $J$-band spectrum of this object matches that of an L9 dwarf, but the $H$
and $K$-bands are unusually red, such that it was classified as an L9pec by
Kirkpatrick et al. (2011). This object is a part of a rare class of L dwarfs
that are red for reasons not attributable to low gravity and appear to have
older kinematics than field L dwarfs (Kirkpatrick et al., 2011). This object
has a 66.9% probability of belonging to the field according to BANYAN
$\Sigma$.

4) WISE J023038.90-022554.0

This object was classified as a peculiar L8 dwarf by Thompson et al. (2013)
using spectral standards from Kirkpatrick et al. (2010), who noted the
object’s $H$-band divot near 1.6 $\mu$m as well as methane at 2.2 $\mu$m,
which are typically indicative of an unresolved T dwarf companion. Thompson et
al. (2013) suggested that this spectrum could better be explained as a
spectral binary of L7 and T2 components instead of a singular L8 object,
however no high resolution imaging exists of this object. According to BANYAN
$\Sigma$ (Gagné et al., 2018b), this object has a 48.6% membership probability
in the Hyades (an age of $625\pm 0.5$ Myr; Brandt & Huang (2015)) and 34.3% in
Carina Near ($13.3^{+1.1}_{-0.6}$ Myr).

5) 2MASS J03264225-2102057

The NIR spectrum of this object was noted by Cruz et al. (2007) to be redder
than typical for its spectral type and therefore younger than 500 Myr. Gagné
et al. (2015b) later classified 2MASS J0326-2102 as an L5$\beta$, the $\beta$
signifying intermediate surface gravity. This object is also a high likelihood
member of the AB Doradus moving group ($130\pm 20$ Myr; Barrado y Navascués et
al. (2004)). 0326-2102 shows a variability amplitude of 0.34% $\pm$ 0.04,
albeit a long period of $32.84^{+4.69}_{-4.62}$ h, in the _Spitzer_ survey of
Vos et al. (2022).

6) 2MASS J06420559+4101599

This object is an unusually red L9 dwarf. Using solely the $J$-band, this
object would result in a T spectral type but shows no sign of CH4, so the
redness could result from a dusty photosphere. It was classified as a medium
binary candidate by Best et al. (2015) using criteria from Burgasser et al.
(2010). This object was given a 78.6% probability of membership in the AB
Doradus Moving Group by the BANYAN II online tool (Gagné et al., 2015a), yet
updated with BANYAN $\Sigma$ to 86% membership probability in AB Doradus (Vos
et al., 2022) and thus an age of approximately $130\pm 20$ Myr. This source
has been confirmed as a photometric variable in the _Spitzer_ survey of Vos et
al. (2022) with an amplitude of $2.16\pm 0.16$% in Spitzer and period of
$10.11\pm 0.06$ h.

7) 2MASS J06522224+4127366 (PSO J103.0927+41.4601)

Using spectral standards from Burgasser et al. (2006a), this object was
classified as a T0.5. However, Best et al. (2013) discovered that this object
is a close spectral match to the L6+T2 binary SDSS J0423-0414AB, one of the
known variable objects for which only the blended light spectrum was available
in our spectral library. This is a field source based on BANYAN $\Sigma$.

8) SDSS J075840.33+324723.4

This source was selected as a weak spectral binary candidate of T0.0+T3.5
dwarf components by Burgasser et al. (2010). It is classified as a T2 dwarf
from its SpeX spectrum (Knapp et al., 2004), being only slightly bluer in the
$J$-band than its best-fit single template. _HST_ imaging did not resolve this
source into two components (Burgasser et al., 2006b). SDSS J0758+3247 has a
93.9% membership probability in Carina Near ($13.3^{+1.1}_{-0.6}$ Myr)
according to BANYAN $\Sigma$ (Gagné et al., 2018b) and a $4.8\pm 0.2\%$
variability amplitude in $J$-band from a Spitzer Space Telescope variability
monitoring campaign (Vos et al., 2020).

9) SDSS J080959.01+443422.2

Chiu et al. (2006) identified this object as an L6 spectral type brown dwarf
from Burgasser et al. (2010) standards. Faherty et al. (2016) proposed that
this object is an ambiguous member of either the Argus (40 - 50 Myr; Zuckerman
(2019)) or AB Doradus ($130\pm 20$ Myr) moving groups from its spectrum and
kinematics. An ambiguous member requires updated astrometric precision as it
either appeared to be part of more than one group or could not be
differentiated from the field. This object was observed twice with SpeX, with
one of its spectra found in all 11 of our 11 index-index regions, while the
other one is only found in 10. This source shows a flat light curve in the
_Spitzer_ survey of Vos et al. (2022).

10) 2MASS J08300825+4828482

2MASS J0830+4828 was classified as an L9.5 object by Schneider et al. (2014)
using the L dwarf classification scheme in Kirkpatrick et al. (2010).
H$\alpha$ emission was detected in this object by Schmidt et al. (2007),
indicative of magnetic activity and suggestive of youth. However, according to
BANYAN $\Sigma$, this object has a 99.9% probability of having field
kinematics. The SPL contains two spectra of this object which were both found
in all 11 index-index regions.

11) SDSS J083717.21-000018.0

This object was one of the earliest L/T transition objects discovered
(Burgasser et al., 2000) and classified as a T1 brown dwarf. Of note, it is
one of a handful of T-dwarfs with H$\alpha$ emission (Kirkpatrick et al.,
2008). Its kinematics are consistent with field membership (99.9%
probability). This object has 3 spectra in our library, two appearing in all
11 index-index regions, and one in only 10.

12) 2MASS J08503593+1057156

Burgasser et al. (2011) posited that this might be a triple system with an
equal mass unresolved binary due to the fact that one of the objects was twice
as bright as the other despite being of the same spectral type. Later, Faherty
et al. (2011) identified a potential binary comover. The SpeX spectrum of
2MASS J0850+1057 was later modeled as a L6.5$\pm$1 and L8.5$\pm$1 spectral
binary and the comover was disproved with more precise astrometry (Dupuy &
Liu, 2012). However, HST photometry for this object (Brock et al., 2021)
suggested the large differences in component brightness across several bands
hinted that the A component is indeed a binary itself, as originally suggested
by Burgasser et al. (2011). This object was also originally thought to have
signatures of youth, but Gagné et al. (2015b) concluded that it is most likely
a field object, positing that its unusually red spectrum could be explained by
the presence of thicker/higher clouds in the atmosphere. There are 2 spectra
of this system in our SpeX Prism Library, both of them appearing in all 11
index-index regions.

13) SDSS J085234.90+472035.0

Using the L dwarf classification scheme developed by Kirkpatrick et al.
(2010), this object was classified as an L9.5 dwarf (Schneider et al., 2014).
While thought to potentially belong to a young moving group (Gagné et al.,
2015b), with the updated BANYAN $\Sigma$ it has 99.9% probability of being
part of the field. Manjavacas et al. (2016) identified SDSS J0852+4720 as a
weak candidate for spectral binarity of L7+T1 dwarf components using the
spectral indices from Bardalez Gagliuffi et al. (2014) and Burgasser et al.
(2010).

14) SDSS J093109.56+032732.5

SDSS J0931+0327 is unusually blue for its spectral type of L7.5 (Knapp et al.,
2004). According to BANYAN $\Sigma$, this object has a 89.9% probability of
belonging to the Carina Near moving group ($13.3^{+1.1}_{-0.6}$ Myr). Using
cloud models, Knapp et al. (2004) calculated that its unusually blue colors
might indicate a high sedimentation efficiency and a low cloud optical depth.
Radigan et al. (2014) obtained a light curve for this object as a part of a
variability survey and did not detect significant variability. They detected a
peak to peak variability amplitude of 0.041%, which was not significant as the
white noise estimate for the relative-flux light curve was 0.036%. This object
was identified as a spectral binary candidate by Bardalez Gagliuffi et al.
(2015) through visual inspection, yet an adaptive optics image with Keck/NIRC2
did not reveal a secondary companion (Bardalez Gagliuffi et al., 2015).

15) 2MASS J09553336-0208403

2MASS J0955-0208 is a known young L7 brown dwarf (Gagné et al., 2017b),
although its membership probabilities point to 55.5% for field and 33.5% for
AB Doradus ($130\pm 20$ Myr). This object has a very red $J-K$ color, a
triangular-shaped $H$-band continuum, and weak K I absorption lines, which are
all indicative of low surface gravity.

16) 2MASS J09560810-1447065

Best et al. (2015) classified this brown dwarf as an L9 type using visual
comparisons with field standards and a T0.0$\pm$0.5 type brown dwarf using
index-based classification. They flagged this object as a medium binary
candidate because of subtle signs of methane absorption indicative of a
T-dwarf using the spectral indices method (Burgasser et al., 2010; Bardalez
Gagliuffi et al., 2014). 2MASS J0956-1447 is a known field object (Schneider
et al., 2017).

17) 2MASSI J1043075+222523

Cruz et al. (2007) discovered this object and performed an optical
spectroscopy follow-up of this object and classified it as an unusually red L8
dwarf. They provided the possible explanation that the object was an
unresolved spectral binary as a reason for its peculiar spectrum. 2MASS
J1043+2225 is classified as an intermediate gravity object with the scheme
from Allers & Liu (2013). This object has measured H$\alpha$ emission (Pineda
et al., 2016) and a measured rotation period of $2.21^{+0.14}_{-0.13}$ hours
in 8-12 GHz radio frequencies (Kao et al., 2018).

18) Luhman 16A (WISE J104915.57$-$531906.1A)

Luhman 16A was discovered in 2013 by Luhman (2013) using multi-epoch
astrometry from the Wide-field Infrared Survey Explorer (WISE), as one
component of a 3 AU separated flux reversal binary, meaning that the two
components switch in relative brightness at different bands. The B component
is brighter at $J$, but fainter in the $K$ band, which is a phenomenon that
can potentially be explained by thick clouds (Burgasser et al., 2013).
Luhman16AB is located at $1.9980\pm 0.0004$ pc, making it the third closest
system to the Sun after Alpha Centauri ($d=1.3475\pm 0.256025$ pc; Henry et
al. 2018) and Barnard’s star ($d=1.8282\pm 0.00013$ pc; Lindegren et al.
2021). Burgasser et al. (2013) classified this object as an L7.5$\pm$0.9
spectral type brown dwarf, and its companion as a T0.5$\pm$0.7 dwarf using
indices and spectral type/index relations (Geballe et al., 2002; Burgasser et
al., 2006a; Burgasser, 2007a). Luhman 16A is one of the reddest L dwarfs known
($J-K=2.08\pm 0.08$ mag, Burgasser et al. 2013), suggestive of thick cloud
coverage (Faherty et al., 2014).

The individual components of Luhman 16 have been monitored for variability
multiple times in the past. Buenzli et al. (2015b) used _HST_ /WFC3 at
$1.1$–$1.66\,\mu$m for spectroscopic variability and found an upper limit for
Luhman 16A of 0.4%, whereas the B component showed variability amplitudes of
7-11% changing within a single rotation period. Later _HST_ /WFC3 observations
in the $0.8$-$1.15\,\mu$m range found a 4.5% amplitude in Luhman 16A (Buenzli
et al., 2015a). Using TESS data of the system, the period of Luhman 16A was
determined to be 6.94 hours, and this periodicity is much lower amplitude than
that of the B component (Apai et al., 2021). Mutli-wavelength photometric
monitoring with the 2.2-m MPG/ESO GROND telescope covering $rizJHK$ bands
found 2% and 3% variability amplitudes for Luhamn 16A in i and z bands,
respectively (Biller et al., 2013). However, no variability was detected in
r-band or the NIR $JHK$ bands. The NIR spectrum of Luhman 16A can be modeled
with an intermediate thickness, single cloud layer at 1200 K (Buenzli et al.,
2015b). The B component of this binary system is a known variable brown dwarf
and a benchmark variable in our analysis.

19) 2MASS J11193254-1137466

2MASS J1119-1137 or TWA 42 is one of the reddest sources known with a $J-K$
color of $2.62\pm 0.15$ mag (Kellogg et al., 2015). This source is a high
likelihood member of the 10 Myr old TW Hydrae association according to its
kinematics and spectra (Faherty et al., 2016). However, updated kinematics
yield a BANYAN Sigma estimate of 63.2% probability of field membership (Best
et al., 2020). TWA 42 was discovered to be an approximately equal magnitude
binary of L7 dwarfs with a separation of $0\farcs 14$ ($3.6\pm 0.9$ AU; Best
et al. 2017). Both components are among the lowest-mass brown dwarfs in the
solar neighborhood ($M\approx 4M_{\mathrm{Jup}}$). Schneider et al. (2018)
performed time-series photometry of this object with _Spitzer_ [3.6] and [4.5]
bands and found low amplitude variability of $0.230^{+0.036}_{-0.0035}\%$ and
$0.453\pm 0.037\%$ , respectively, but could not quantify the effects of
binarity on the system’s rotational parameters.

20) SDSS J121951.45+312849.4

SDSS J1219+3128 is an L9 dwarf (Schneider et al., 2014), and known variable
from the Hubble Space Telescope Near-Infrared Spectroscopic Survey for
variability, but it only has a lower limit for variability ($>2\%$) as they
were not able to observe the full period (Buenzli et al., 2014). Therefore we
did not include it in our benchmark variable objects. Manjavacas et al. (2019)
searched for whether confirmed photometrically variable objects also were
candidates for having composite spectra using the Burgasser et al. (2010) and
Bardalez Gagliuffi et al. (2014) techniques and found that it was a strong
spectral binary candidate with a best matching fit of an L8 and T4 ($\Delta
T_{\mathrm{eff}}\approx$200 K).

21) SDSSp J125453.90-012247.4

SDSSp J1254-01222 is a T2 dwarf with weak $H\alpha$ emission at $6563$
Å(Burgasser et al., 2003). Metchev et al. (2015) detected an upper limit of
variability for this object of $<0.15\%$ at [3.6] and $<0.3$% at [4.5] with
_Spitzer_ , which is very low-level variability. This object is also a field
age dwarf (Filippazzo et al., 2015).

22) DENIS J132620.0-272936

DENIS J1326-2729 is an L5 dwarf in the optical (Gizis, 2002) and an L7 in the
NIR. This object has a spectrum sloped towards red wavelengths and a
characteristic peaked $H$-band suggesting youth. While this object has been
flagged as a potential member of the Argus young moving group (Gagné et al.,
2015b) meaning an age estimate of 40 - 50 Myr, BANYAN $\Sigma$ gives an 88%
probability of membership in Carina Near ($13.3^{+1.1}_{-0.6}$ Myr).

23) SDSS J133148.92-011651.4

SDSS J1331-0116 is an L8 brown dwarf in the infrared with unusually blue
colors for its spectral type, similar to another candidate SDSS J0931+0327
(Knapp et al., 2004), potentially due to low metallicity. Its atypical
spectral features usually point to a blend of binary compositions, but Best et
al. (2021) calculated a binary spectral decomposition of L6+T5 with $\Delta
J=1.97\pm 0.18$ mag which is much larger than the observed magnitude
difference of 0.6 mag, making it unlikely that the peculiarity is due to
binarity. This object has three observations in the SPL, which were all found
in all 11 index-index regions.

24) 2MASS J15164306+3053443

This object is a weak spectral binary candidate with no high resolution
imaging (Burgasser et al., 2010; Bardalez Gagliuffi et al., 2015), potentially
composed of an L8+L9.5 dwarfs. However, the binary template fitting of
Burgasser et al. (2010) could not rule out the possibility that this object
was single with an unusual atmosphere. 2MASS J1516+3053 is also a confirmed
variable object from _Spitzer_ (Metchev et al., 2015) with amplitudes of
$2.4\pm 0.2\%$ at [3.6] and $3.1\pm 1.6$% at [4.5] bands and a period of $6.7$
hr.

25) 2MASSW J1632291+190441

2MASSW J1632+1904 is one of the earliest discovered late L dwarfs (L8, Reid et
al., 1999), and identified as a weak binary candidate by Burgasser et al.
(2010). Metchev et al. (2015) found this object to have amplitudes of $0.42\pm
0.08\%$ at [3.6] and $0.5\pm 0.3$% at [4.5] and a period of $3.9\pm 0.2$ hr,
and thus we did not use it as a benchmark variable due to its low-level
variability ($<1\%$). This object contains two spectra in the SPL.

26) WISE J164715.57+563208.3

This L9 brown dwarf is unusually red with $J-K=2.20\pm 0.10$ mag. In a red
optical survey with Keck/LRIS, Pineda et al. (2016) obtains optical spectra
for WISE J1647+5632 and suggests that it is an unresolved binary system from
its spectra. This object is unlikely to be young from its proper motion,
photometric distance estimate, and spectrum (Schneider et al., 2017). This
source has been independently confirmed as variable by the _Spitzer_ survey of
Vos et al. (2022) with an amplitude of $0.47\pm 0.06$% and period of
$9.234_{-0.25}^{+0.23}$ hours.

27) WISE J173859.27+614242.1

WISE J1738+6142 was discovered in 2013 with WISE. This object is a late
L/early T, but it defies a standard spectral classification because of its
highly unusual spectrum (Mace et al., 2013). It has excess flux on the blue
side of the $H$ and $K$ bands, hinting at a T dwarf secondary and is thought
to have rapid changes in atmospheric conditions.

28) 2MASS J17410280-4642218

This object is an L5 dwarf and was noted to likely be a member of $\beta$-Pic
or AB Doradus moving groups (Faherty et al., 2016). 2MASS J1741-4642 is now a
confirmed member of AB Dor (Kirkpatrick et al., 2021) and thus $130\pm 20$ Myr
old. Vos et al. (2019b) observed this object for photometric variability using
the New Technology Telescope (NTT) and the United Kingdom Infrared Telescope
(UKIRT) using the $J_{S}$ band (1.16-1.32 $\mu$m), but did not observe any
variability. However, the NTT observation was of short duration and therefore
amplitudes would have had to be greater than 10% to detect significant
variations. This source has been confirmed as a photometric variable in the
_Spitzer_ survey of Vos et al. (2022) with an amplitude of $0.35\pm 0.03$ and
period of $15_{-0.57}^{+0.71}$ hours.

29) WISEP J183058.57+454257.9

This object was first identified by Kirkpatrick et al. (2011) with WISE and
classified as an L9 dwarf. It was identified as a medium binary candidate
(Best et al., 2015) using the criteria from Burgasser et al. (2010), showing
signs of methane absorption.

30) WISE J185101.83+593508.6

WISE J1851+5935 was classified as L9 when evaluated as a single template (Best
et al., 2013). However, the $H$ and $K$-band peaks have lower flux than
typical L9 standards (Kirkpatrick et al., 2010). Thompson et al. (2013)
analyzed this spectrum as an unresolved binary, and found that it was better
fit as an L7 and T2 binary than as a single source. However, WISE J1851+5935
does not appear as a spectral binary candidate in Burgasser et al. (2010) or
Bardalez Gagliuffi et al. (2014).

31) 2MASSW J2101154+175658

This object was discovered by Kirkpatrick et al. (2000). It was identified as
a binary system by Bouy et al. (2003) and composed of L7 and L8 dwarfs (Dupuy
& Liu, 2012). 2MASSW J2101+1756 is a potential member of the Scorpius
Centaurus Complex (SCC) (Gagné et al., 2015b) which is $\sim 10$ Myr old (Song
et al., 2012), but the updated Banyan $\Sigma$ gives a 56% field probability.
There are two spectra of this object in the SPL.

32) 2MASS J21243864+1849263

From a crossmatch of SDSS, 2MASS, and WISE, 2MASS J2124+1849 was identified as
an L-dwarf with unusual red colors that could suggest low surface gravity or
unusual dust content and cloud properties. (Kellogg et al., 2015). According
to BANYAN $\Sigma$, this object has a 79.7% membership probability in Carina
Near $13.3^{+1.1}_{-0.6}$ Myr.

33) 2MASS J21315444-0119374

This object was identified from imaging data of the Sloan Digital Sky Survey
(SDSS) (Chiu et al., 2006). Schneider et al. (2014) classified this object as
an L9.5 in the near infrared using the L dwarf classification scheme found in
Kirkpatrick et al. (2010). This object is a widely separated common proper
motion companion of the low-mass stars NLTT 51469AB, which is a close binary
of M3 and M6 components (Gauza et al., 2019).

34) 2MASS J22153705+2110554

2MASS J2215+2110 was discovered very recently by Kellogg et al. (2015), as it
was previously overlooked in SDSS. This T0.0 dwarf is only a weak candidate
binary using the indices from Burgasser et al. (2010), but it has a peculiar
spectrum and a lack of flux in the $H$-band compared to other early T dwarfs.
Eriksson et al. (2019) identified this object as a strong variable with a
$10.7\pm 0.4\%$ amplitude in the $J$ band and noted that it seems unlikely
that this object is an unresolved binary system as previously suggested. We
did not include this object as one of our benchmark objects, because it was
discovered to be variable after the curation of our benchmark list. However,
the SPL contains two observations of this object both found in all 11 index-
index regions.

35) 2MASS J22443167+2043433

This object is an L6 spectral type brown dwarf (Faherty et al., 2016). 2MASS
J2244+2043 is a bona fide member of AB Doradus (Faherty et al., 2016) meaning
that it is $130\pm 20$ Myr old. Morales-Calderón et al. (2006) detected
sinusoidal variability with a period of 4.6 hours for this object using the
Spitzer/IRAC 4.5 $\mu$m and 8 $\mu$m band passes. Vos et al. (2018) identified
a longer period of 11$\pm$2 h with _Spitzer_ light curves, seeing a
variability amplitude of 0.8$\pm$0.2% in [3.6]. However, Vos et al. (2019b)
observed a 5.5$\pm$0.6% variability amplitude in $J$-band. The change in
period is most likely due to the short observing window of 8.2 h in Morales-
Calderón et al. (2006).

36) WISE J232728.74-273056.6

WISE J2327-2730 is an L9 object with slightly redder WISE colors than usual
(Kirkpatrick et al., 2011). They suggest that low gravity would cause the NIR
spectrum to be unusually red. They also eliminate the possibility that the
peculiarity arises from binarity, because the estimated companion would have
to be a T6.5 dwarf, which would cause a much more peculiar NIR spectrum. Thus,
the peculiarity in color is unexplained, and we propose it might be due to
cloud-driven variability.

37) WISE J233527.07+451140.9

This object was discovered by (Thompson et al., 2013) and visually classified
as an L7 dwarf (Liu et al., 2016). Gagné et al. (2014) identified this object
as an old field candidate with a 97% probability using BANYAN II, confirmed by
BANYAN $\Sigma$ (99.9% field probability). WISE J2335+4511 is a very red
peculiar brown dwarf that does not show signs of weaker K I lines expected in
a low gravity object (Thompson et al., 2013), so it is a part of a class of
brown dwarfs that are unusually red objects that are not young.

####  3.3.2 Weak Candidates

1) 2MASSI J0028394+150141

2MASSI J0028+1501 is an unusually red mid L dwarf. Knapp et al. (2004)
suggests that the redness could be due to variability between $5-10\%$.
However, no follow-up photometry exists for this object. This source has a 91%
membership probability in Argus according to BANYAN $\Sigma$.

2) DENIS J025503.3-470049

DENIS J0255-4700 is an L9 brown dwarf (Schneider et al., 2014). Variability
was not detected in red optical bands $I$ and $R$ in a search by Koen (2005).

3) 2MASSI J0328426+230205

2MASSI J0328+2302 is an L9.5 spectral type brown dwarf (Knapp et al., 2004). A
NIR variability amplitude of 0.43$\pm$0.16 mag was detected in this object by
Enoch et al. (2003), but they were unable to differentiate whether this
variability was intrinsic to the brown dwarf or the comparison star. When
later observed by Radigan et al. (2014), they found no significant variability
in the target over a 3.7 hr observation. Burgasser et al. (2010) noted that
this object is overluminous for its spectral type, therefore could be an
unresolved binary system.

4) SDSS J085834.42+325627.7

This object was first identified by Chiu et al. (2006) as a T1 dwarf.
Photometric monitoring set variability upper limits of $<0.27\%$ at [3.6] and
$<0.64$% at [4.5] (Metchev et al., 2015). SDSS J0858+3256 is unusually red
with a large tangential velocity ($V_{tan}=66\pm 3$ km s-1; Faherty et al.
(2009)) and a 99.9% probability from BANYAN $\Sigma$ of being a field object.

5) SDSSp J132629.82-003831.5

SDSSp J1326-0038 is an L7 brown dwarf and a candidate member of Argus (40 - 50
Myr) with a $85$% probability (Gagné et al., 2015b) from BANYAN II. With the
updated BANYAN $\Sigma$, however, it has a 100% probability of being a field
object. When observed by Radigan et al. (2014), this object only had a 0.047%
peak-to-peak amplitude in $J$-band.

6) WISEA J161628.32+062135.1 (PSO J244.1180+06.3598)

This object was first identified following a crossmatch of the PanSTARRS and
WISE surveys as a T0 brown dwarf by Best et al. (2015), although it has also
been classified as an unusually red L9 brown dwarf. The spectra shows
indication of youth because of redder-than-usual colors and triangular
$H$-band shape. However, this object has an 99.9% probability of belonging to
the field from BANYAN $\Sigma$.

7) SDSS J175024.01+422237.8

SDSS J1750+4222 is a T1 spectral type brown dwarf (Geballe et al., 2002). This
object has a reported light-curve by Radigan et al. (2014). They found a
marginal detection of $1.5\pm 0.3$% variability amplitude and a $2.7\pm 0.2$
hr period due to quality concerns with the light curve.

8) 2MASS J21522609+0937575

This object was discovered by Reid et al. (2006a). 2MASS J2152+0937 is an
equal mass/equal luminosity binary system of L6 spectral type (Reid et al.,
2008).

Table 4: Variability candidates with spectral types between L7$-$T3

|  |  | Variability | Reference
---|---|---|---|---
Source | Spectral Type | BANYAN $\Sigma$ | Filter | Amplitude ($\%$ ) | Youth; Variability; Spectral Binary Candidate
_Strong candidates_
2MASS J00164364+2304262 | T1.0 | 93$\%$ FLD |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; (2)
2MASS J00310928+5749364 | L9.0 | 96$\%$ CARN | [3.6] | 0.35 $\pm$ 0.03 | (3) ; (3) ; $\cdots$
2MASS J01020186+0355405 | T0.0 | 98$\%$ FLD |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; $\cdots$
2MASS J02062493+2640237 | L8.0 | 67$\%$ FLD |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; $\cdots$
WISE J023038.90-022554.0 | L9.0 | 49$\%$ HYA, 34$\%$ CARN* |  $\cdots$ |  $\cdots$ | (1) ; $\cdots$ ; (4)
2MASS J03185403-3421292 | L8.0 | 100$\%$ FLD |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; $\cdots$
WISE J032301.86+562558.0 | L7.0 | 100$\%$ FLD |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; $\cdots$
$\dagger$ 2MASS J03264225-2102057 | L9.0 | 92$\%$ ABDMG | [3.6] | 0.34 $\pm$ 0.04, | (3) ; (3) ; $\cdots$
$\dagger$ 2MASS J06420559+4101599 | L8.0 | 86$\%$ ABDMG | [3.6] | $2.16\pm 0.16$ | (3) ; (3) ; $\cdots$
2MASS J06522224+4127366 | T0.0 | 100$\%$ FLD* |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; (5)
$\dagger$ SDSS J075840.33+324723.4 | T2.0 | 94$\%$ CARN* | J | 4.8$\pm$0.2 | (1) ; (6) ; (7)
SDSS J080959.01+443422.2 | L7.0 | 89$\%$ FLD | [3.6] | 0.77$\pm$0.06 |  $\cdots$ ; (3) ; $\cdots$
SDSS J082030.12+103737.0 | T0.0 | 75.5$\%$ FLD* |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; $\cdots$
2MASSW J0829570+265510 | L7.0 | 50$\%$ FLD, 50$\%$ ARG* |  $\cdots$ |  $\cdots$ | (1) ; $\cdots$ ; $\cdots$
SDSSp J083008.12+482847.4 | T0.0 | 100$\%$ FLD |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; $\cdots$
SDSSp J083717.22-000018.3 | T1.0 | 100$\%$ FLD |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; $\cdots$
2MASSs J0850359+105716 | L7.0 | 51$\%$ FLD, 47$\%$ CARN |  $\cdots$ |  $\cdots$ | (1) ; $\cdots$ ; (8), (9)
SDSS J085234.90+472035.0 | T0.0 | 100$\%$ FLD* |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ (10)
SDSSp J085758.45+570851.4 | L8.0 | 100$\%$ FLD |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; $\cdots$
2MASSI J0859254-194926 | L7.0 | 98$\%$ FLD |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; $\cdots$
$\dagger$ 2MASSW J0929336+342952 | L8.0 | 69$\%$ ARG* |  $\cdots$ |  $\cdots$ | (1) ; $\cdots$ ; $\cdots$
$\dagger$ SDSS J093109.56+032732.5 | T0.0 | 90$\%$ CARN* | J | 0.041 $\pm$ 0.036 | (1) ; (11) ; (12)
2MASS J09553336-0208403 | L8.0 | 56$\%$ FLD, 34$\%$ ABDMG* |  $\cdots$ |  $\cdots$ | (1) ; $\cdots$ ; $\cdots$
2MASS J09560810-1447065 | T0.0 | 100$\%$ FLD* |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; (2)
SDSS J100711.74+193056.2 | L9.0 | 86$\%$ ARG* |  $\cdots$ |  $\cdots$ | (1) ; $\cdots$ ; $\cdots$
2MASS J10430758+2225236 | T0.0 | 100$\%$ FLD* |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; (13)
WISE J104915.57-531906.1A | L9.0 | 89$\%$ ARG | J | 4.5$\%$ | (1) ; (20) ; $\cdots$
2MASS J11193254-1137466 | L7.0 | 63.2$\%$ FLD | [3.6], [4.5] |  $0.230^{+0.036}_{-0.0035}$, $0.453\pm 0.037$ |  $\cdots$ ; (14); $\cdots$
$\dagger$ 2MASS J12010443+5730040 | T0.0 | 71.1$\%$ UMA* |  $\cdots$ |  $\cdots$ | (1) ; $\cdots$ ; $\cdots$
SDSS J121951.45+312849.4 | T0.0 | 100$\%$ FLD* | J | $>2$ |  $\cdots$ ; (15) ; $\cdots$
SDSSp J125453.90-012247.4 | T2.0 | 100$\%$ FLD | [3.6], [4.5] |  $<0.15$, $<0.36$ |  $\cdots$ ; (16) ; $\cdots$
$\dagger$ 2MASSW J1326201-272937 | L7.0 | 88$\%$ CARN |  $\cdots$ |  $\cdots$ | (1) ; $\cdots$ ; $\cdots$
SDSS J133148.92-011651.4 | T0.0 | 100$\%$ FLD |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; $\cdots$
WISE J151314.61+401935.6 | L9.0 | 100$\%$ FLD* |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; $\cdots$
SDSS J151506.11+443648.3 | L7.0 | 100$\%$ FLD* |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; $\cdots$
SDSS J151643.01+305344.4 | T2.0 | 83$\%$ FLD* | [3.6], [4.5] |  $2.4\pm 0.2$, $3.1\pm 1.6$ |  $\cdots$ ; (16) ; $\cdots$
SDSS J154009.36+374230.3 | L9.0 | 100$\%$ FLD* |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; $\cdots$
SDSS J163030.53+434404.0 | L9.0 | 100$\%$ FLD* |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; $\cdots$
2MASSW J1632291+190441 | L8.0 | 100$\%$ FLD | [3.6], [4.5] |  $0.42\pm 0.08$, $0.5\pm 0.3$ |  $\cdots$ ; (16) ; (7)
WISE J164715.57+563208.3 | L8.0 | 66$\%$ FLD | [3.6] | 0.47 $\pm$ 0.06 | (3) ; (3) ; $\cdots$
WISE J173859.27+614242.1 | L7.0 | 83$\%$ FLD* |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; $\cdots$
$\dagger$ WISE J174102.78-464225.5 | L7.0 | 99$\%$ ABDMG | [3.6] | $0.35\pm 0.03$ | (3) ; (3) ; $\cdots$
WISE J183058.56+454257.4 | L9.0 | 92$\%$ FLD* |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; (2)
2MASS J18510178+5935040 | L9.0 | 100$\%$ FLD |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; (4)
2MASSW J2101154+175658 | L8.0 | 56$\%$ FLD |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; $\cdots$
$\dagger$ 2MASS J21243864+1849263 | T0.0 | 80$\%$ CARN* |  $\cdots$ |  $\cdots$ | (1) ; $\cdots$ ; $\cdots$
SDSS J213154.43-011939.3 | L9.0 |  $\cdots$ |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; $\cdots$
2MASS J22153705+2110554 | T0.0 |  $\cdots$ | J | 10.7$\pm$0.4 |  $\cdots$ ; (7) ; (17)
$\dagger$ 2MASSW J2244316+204343 | L7.0 | 100$\%$ ABDMG | J | 5.5$\pm$0.6 | (1) ; (18); $\cdots$
WISE J232728.74-273056.6 | T0.0 |  $\cdots$ |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; $\cdots$
2MASS J23352734+4511442 | L7.0 | 100$\%$ FLD |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; $\cdots$
_Weak candidates_
$\dagger$ 2MASSI J0028394+150141 | L7.0 | 91$\%$ ARG* |  $\cdots$ |  $\cdots$ | (1) ; $\cdots$ ; $\cdots$
SDSSp J003259.36+141036.6 | L9.0 | 62$\%$ FLD, 38$\%$ CARN |  $\cdots$ |  $\cdots$ | (1) ; $\cdots$ ; $\cdots$
WISE J02022929+2305139 | L7.0 | 72$\%$ ARG* |  $\cdots$ |  $\cdots$ | (1) ; $\cdots$ ; $\cdots$
DENIS J025503.3-470049 | L9.0 | 100$\%$ FLD | JHK | flat |  $\cdots$ ; (19) ; $\cdots$
2MASSI J0328426+230205 | T0.0 | 100$\%$ FLD | J | 0.013 |  $\cdots$ ; (11) ; (7)
SDSS J073922.26+661503.5 | T2.0 | 100$\%$ FLD* |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; $\cdots$
SDSS J085834.42+325627.7 | T0.0 | 100$\%$ FLD* | [3.6], [4.5] |  $<0.27$, $<0.64$ |  $\cdots$ ; (16) ; $\cdots$
SDSSp J132629.82-003831.5 | L7.0 | 100$\%$ FLD | J | 0.047 |  $\cdots$ ; (11) ; $\cdots$
WISEA J161628.32+062135.1 | L7.0 | 100$\%$ FLD |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; $\cdots$
SDSS J175024.01+422237.8 | T2.0 | 60$\%$ ARG, 40$\%$ FLD* | J | 2.7$\pm$0.2 | (1) ; (11) ; $\cdots$
2MASS J21522609+0937575 | L7.0 | 100$\%$ FLD* |  $\cdots$ |  $\cdots$ |  $\cdots$ ; $\cdots$ ; $\cdots$

††footnotetext: These objects are young based on our classifications which
come from both moving group association and spectral indicators of youth in
the literature.

**footnotetext: These objects do not have measured parallaxes.

References. — (1) This paper; (2) Best et al. (2015); (3) Vos et al. (2022);
(4) Thompson et al. (2013); (5 - Best et al. (2013); (6) Vos et al. (2020);
(7) Burgasser et al. (2010); (8) Burgasser et al. (2011); (9) Brock et al.
(2021); (10) Manjavacas et al. (2016); (11) Radigan et al. (2014); (12)
Bardalez Gagliuffi et al. (2015); (13) Cruz et al. (2007); (14) Schneider et
al. (2018); (15) Buenzli et al. (2014); (16) Metchev et al. (2015); (17)
Eriksson et al. (2019); (18) Vos et al. (2019b); (19) Koen et al. (2005); (20)
Buenzli et al. (2015a)

Note. — In this table we summarize the literature research on all 62 of our
candidates. The spectral type is the spectral type designated by the SpeX
spectral classifications. For youth, we provide the BANYAN $\Sigma$
probability of belonging to a young moving group (FLD - field; CARN - Carina
Near; ABDMG - AB Doradus; ARG - Argus; UMA - Ursa Major). For objects with
previous variability monitoring, we designate the wavelength of the
observations and the amplitude of the modulations. Lastly, when available we
provide the reference to papers that comment on spectral binary candidacy of
any of our objects. Refer to section 3.1 for a discussion of notable
candidates.

###  3.4 Contamination by spectral binaries

Blended-light spectra can have a binary origin (Burgasser et al., 2010;
Bardalez Gagliuffi et al., 2014) or be the consequence of patchy atmospheric
layers at various temperatures, as shown in this study. In order to estimate
the contamination fraction of variability candidates by spectral binaries, we
modeled synthetic spectral binary systems and applied our variability
detection technique on them. We use our entire spectral library of 325 spectra
of L7$-$T3 dwarfs and applied the Burgasser et al. (2010) technique which is
designed to identify T dwarf companions to L7-T3 dwarf primaries. Following
this analysis, we remove 87 spectra from 76 sources from our library, which we
identify as spectral binary candidates from the Burgasser et al. (2010)
technique, many of which have been already confirmed with high resolution
follow-up observations. The confirmed and candidate spectral binaries are
listed in Table B for further reference. These spectra, as well as spectra
from confirmed variables and our variability candidates, were removed from our
sample leaving 147 presumably single, non-variable spectra.

We generated spectral binary templates by interpolating all remaining spectra
onto a common wavelength range and then adding every two spectra together. In
total, we generated 10731 spectral binary templates, which were all classified
according to the Kirkpatrick et al. (2010) prescription. Finally, we apply our
variability detection technique on this sample of synthetic spectral binaries.
We found that only 2.3% of synthetic spectral binaries were selected as weak
variability candidates, and an additional 2.3% as strong variability
candidates, amounting to a total 4.6% contamination rate of our variability
technique by true spectral binaries with similar spectral features as those
flagged by our technique. These features could be dependent on the effective
temperature of the object, cloud composition, cloud coverage fraction,
strength of vertical transport to name a few variables.

As a complement, we can also provide a rough estimate of the number of
candidate and confirmed spectral binaries from our list of 62 variability
candidates. We find that 2MASS J0850+1057 is a confirmed closely-separated
binary system, whose unresolved spectrum is best fit by a binary template of
nearly equal flux components, hence not considered a spectral binary. Six
other objects are candidate spectral binaries. However, upon closer
inspection, we find that 2 of them are not selected by either the Burgasser et
al. (2010) or the Bardalez Gagliuffi et al. (2014) spectral binary techniques:
WISE J0016+2304 was selected only by indices (Best et al., 2015) and WISE
J0230$-$0225 identified as a potential binary by visual inspection (Thompson
et al., 2013). Two other sources, SDSS J0758+3247 and SDSS J0931+0327, do not
show any companion on high resolution follow-up (Burgasser et al. 2010 and
Bardalez Gagliuffi et al. 2014, respectively). Finally, 2MASS J1516+3053 and
SDSS J1219+3128 are spectral binary candidates, yet both previously tagged to
have unusual atmospheric properties (Burgasser et al. 2010 and Manjavacas et
al. 2019, respectively). This spot check on spectral binaries within our
variability candidate list further suggests that our index-based technique
will have little contamination from spectral binary systems.

##  4 Discussion

###  4.1 Variability Fractions

Table 5: Comparison of variability fractions with the literature

Sample | This Paper | Radigan et al. (2014) | Metchev et al. (2015)
---|---|---|---
L7$-$T3 spectral type range
Total sources | 270 | 25 | 16
Confirmed variables | 15 | 5 | 7
Candidates | 62 |  $\cdots$ |  $\cdots$
Variability Fraction |  $5_{-1}^{+2}$% |  $19_{-9}^{+11}$% |  $43_{-17}^{+26}$%
Variability Fraction (inc. cand.aaThis fraction assumes that the total number of variables is the number of benchmarks plus 67% of the variability candidates. These fractions increase to $28_{-3}^{+4}$% and $33_{-5}^{+6}$% for L7$-$T3 and L9$-$T3 spectral type ranges, respectively, if 100% of candidates were to show significant variability amplitudes.) |  $21\pm 3$% |  $\cdots$ |  $\cdots$
L9$-$T3 spectral type range
Total sources | 140 | 15 | 12
Confirmed variables | 9 | 5 | 4
Candidates | 37 |  $\cdots$ |  $\cdots$
Variability Fraction |  $6\pm 2$% |  $33_{-16}^{+21}$% |  $33_{-18}^{+25}$%
Variability Fraction (inc. cand.aaThis fraction assumes that the total number of variables is the number of benchmarks plus 67% of the variability candidates. These fractions increase to $28_{-3}^{+4}$% and $33_{-5}^{+6}$% for L7$-$T3 and L9$-$T3 spectral type ranges, respectively, if 100% of candidates were to show significant variability amplitudes.) |  $24^{+5}_{-4}$% |  $\cdots$ |  $\cdots$

Note. — For the variability fraction including candidates, we consider both
strong and weak candidates.

In order to assess the success of our technique in predicting variability, we
compare variability fractions including our candidates with results from
variability surveys from the literature. However, as discussed in Section 3.1,
it is important to note that surveys carried out at different wavelengths and
with different instruments achieve a wide range of precision and variability
amplitudes which differ as a function of wavelength. The comparisons presented
here should be interpreted as a rough check of the proportion of candidate
variables obtained using our variability indices.

Within our sample of 270 L7$-$T3 dwarfs (most of which lack photometric
monitoring observations), we used 15 sources as benchmark variables, leading
to a raw variability fraction of $5_{-1}^{+2}\%$ with asymmetrical
uncertainties representing the central 68% of a Poisson distribution (see
Table 5). Radigan et al. (2014) obtained ground-based light curves in $J$-band
for 62 L4–T9 brown dwarfs. From their study, we calculate a raw variability
fraction of $19_{-9}^{+11}$% (5/25) in the L7$-$T3 range that we focus on for
this work. Our raw variability fraction is at least $1\sigma$ lower than the
one from Radigan et al. (2014) because only a small part of our sample has
been followed up with photometric monitoring. Similarly, Metchev et al. (2015)
obtained _Spitzer_ light curves in [3.6] and [4.5] bands for 44 L3–T8 dwarfs.
Within the L7$-$T3 range, they find 7 variable sources out of 16, leading to a
raw fraction of $43_{-18}^{+24}$%. This fraction is significantly higher than
the ground-based fractions from Radigan et al. (2014) and our study because
_Spitzer_ is more sensitive to low-level variability amplitudes.

A comprehensive photometric monitoring follow-up survey of our candidates is
needed to determine the false positive rate of our technique. Among the strong
candidates, 14 have previous light curves (including 4 from the new _Spitzer_
survey of Vos et al. (2022)). Of these, 12 objects have a significant
amplitude, whereas 2 do not show significant variability in this wavelength
range. From the weak candidates, 4 have previous light curves, none of which
exhibit significant variability. Therefore, from this preliminary assessment,
it is likely that $67\%$ (12/18) of our candidates will show significant light
curve amplitudes after photometric monitoring. Our technique would return
almost three times as many significantly variable light curves for L/T
transition sources as a randomly-selected sample, using the independent
analysis of the near-infrared Brown dwarf Atmosphere Monitoring survey by
Radigan (2014) as a comparison ($24^{+11}_{-9}\%$ for L7-T3.5 dwarfs). If this
trend continues, 67% of our 62 of our variability candidates should show
significant variability, and our variability fraction would increase to $21\pm
3\%$, which is comparable to the upper limit of Radigan et al. (2014).
However, in order to fully describe our confusion matrix, we would need to
homogeneously obtain NIR light curves for every object in our sample, in order
to evaluate the effectiveness of our selection technique at identifying those
light curves showing significant variability.

Radigan et al. (2014) also carried out a focused analysis on 16 L9–T3.5
dwarfs, out of which 4 had variable light curves, arriving at a fraction of
$39^{+16}_{-14}$% after correcting for their sensitivity to astrophysical
signals. Since our spectral type range technically only goes to T3, we
recalculated the Radigan et al. (2014) variability fraction for L9-T3 dwarfs
(excluding one T3.5 from their sample) and obtain $33_{-16}^{+21}$%. We find
the same fraction for the Metchev et al. (2015) sample reduced accordingly to
L9-T3, $33_{-18}^{+25}$%. Within this spectral type range, our raw variability
fraction is $6\pm 2\%$ for confirmed variables.

###  4.2 Atmospheric Structure: Bands, Spots, Inclination Effects

Variability in a brown dwarf light curve is caused by a heterogeneous cloud
coverage of its atmosphere, implying that each longitudinal slice has a
different brightness. This difference in brightness in L/T transition objects
is probably due to patchy clouds in the atmosphere (Ackerman & Marley, 2001).
However, not all cloud structures result in variability. If a brown dwarf has
zonally or longitudinally symmetric atmospheric cloud features, it will have a
flat light curve as the brightness remains the same during the rotation
period. Within the solar system, cloud-banding can be seen in Jupiter.
Jupiter’s banded structure is caused by belts, dark colored bands, and zones,
light colored bands. The bands of Jupiter display some variability, but the
bulk features remain relatively constant (Ge et al., 2019). Atmospheric
dynamical simulations show that zonal banding likely occurs for brown dwarfs
and giant exoplanets (Tan & Showman, 2021b). Our technique, which probes the
spectra, may be sensitive to blended-light signatures that correspond to cloud
patchiness, even if the light curve shows no variability.

In addition to photometric and spectroscopic studies, brown dwarfs in our
candidate sample can also be studied through polarimetry to detect clouds or
hazes in their atmosphere if they show flat light-curves. Luhman 16 is one of
the few accessible targets with polarimetry due to its brightness and distance
to Earth. Millar-Blanchaer et al. (2020) took H-band Very Large Telescope/NaCo
linear polarization measurements of the nearby Luhman 16 binary system, and
they found that Luhman 16A shows longitudinal cloud bands. Luhman 16A has
shown only mild signs of variability in $iz$ bands through photometric
monitoring (Biller et al., 2013) and in _HST_ /WFC3 G102, which covers the
peak in the $Y$ band(Buenzli et al., 2015a), although no variability has been
detected in longer wavelengths. However, polarimetric measurements from
Millar-Blanchaer et al. (2020) suggests cloud morphology of banded structures
in the NIR. This suggests that the symmetric, banded structure and spin axis
inclination of Luhman 16A compound to produce variability amplitudes close to
zero (Buenzli et al., 2015b) in the NIR, but we can recover the signature of a
blended-light atmosphere (e.g., from different temperature bands) with our
empirical technique.

Vos et al. (2017) studied a sample of known Spitzer Space Telescope [3.6] and
J-band variable brown dwarfs, computing the inclination angles of 19 variable
brown dwarfs. All objects in the sample with mid-IR variability have an
inclination angle greater than 20∘, and objects with J-band variability have
an inclination angle greater than 35∘. Vos et al. (2017) determined that
J-band observations could be more affected by inclination, as they probe
deeper into the atmosphere. Their study shows that there is a correlation
between inclination and variability detection, and even if a brown dwarf does
not show variability, this may be due to inclination effects (Vos et al.,
2017): if observed pole-on ($i=0^{\circ}$), there will be less rotational
variations than if observed equator-on ($i=90^{\circ}$). However, since pole-
on orientations are significantly less probable than equator-on (Jackson &
Jeffries, 2010), it is unlikely that most of our variability candidates with
future flat light curves would be oriented pole-on. Understanding whether the
variability indices technique has a dependence on inclination will be an
important step in validating and assessing the technique in future work.

##  5 Conclusions

In this paper, we have designed a technique to predict cloud-driven
variability in L/T transition brown dwarf atmospheres by studying archival,
single-epoch, low-resolution, near-infrared SpeX spectra. We applied the
spectral binary indices from Bardalez Gagliuffi et al. (2014) to a sample of
270 L7$-$T3 brown dwarfs with SpeX prism spectra available in the SPL,
originally used to highlight differences between unresolved binary systems and
single source spectra, in order to identify whether certain indices pinpointed
peculiarities in the spectrum caused by variability. We identified regions of
the index-index plots where benchmark variables were highly concentrated while
minimizing the number of non-variable contaminants. We selected the sources
that were repeatedly found in multiple regions of variability and chose them
as our candidates for variability study. The candidates found in 10 or 11 of
the 11 regions are considered variable candidates, and we recommend them for
photometric monitoring follow-up. Our conclusions are as follows:

  1. 1.

We propose a technique to pre-select photometrically variable L7-T3 dwarfs for
future monitoring campaigns. Currently there is no method to pre-select which
brown dwarfs have higher chances of being variable for monitoring studies.
Using this technique can significantly save future resources in next
generation telescopes when detecting variability in brown dwarfs.

  2. 2.

We have identified 62 variability candidates from our sample of 325 L7$-$T3
integrated light, NIR SpeX spectra following this technique, out of which 50
are entirely new discoveries.

  3. 3.

Most of our variability candidates have had peculiar spectra or red colors
reported in the literature since their discovery and we suggest that their
peculiarities are due to variability. Out of our 62 candidates, 14 are
confirmed young or show kinematic signatures suggestive of youth. Since
variability is more prominent among young sources (Vos et al., 2017), our
technique might be biased to identify young variable sources.

  4. 4.

We are conducting a ground-based NIR survey to further verify our method to
find brown dwarf variables. In a future paper we will demonstrate the
efficiency of our novel method.

  5. 5.

Flat light curves of our variability candidates might indicate symmetric
surface features such as zonal banding or pole-on inclinations.

  6. 6.

Based on preliminary photometric monitoring follow up with _Spitzer_ , we
expect that $\sim 67\%$ of our candidates will show a significant variability
amplitude.

We have conducted a spectroscopic analysis of photometric variability, finding
62 unique L7$-$T3 dwarf candidates for variability from their peculiar
spectra. If we can indeed identify variability from single-epoch spectra, we
can further investigate spectral characteristics of variable brown dwarfs.
This will provide further insight into the chemistry of brown dwarf
atmospheres and cloud-formation mechanisms.

D.B.G and A.A. acknowledge funding support from the Astrophysics Data Analysis
Program of the National Aeronautics and Space Administration under Grant No.
80NSSC19K0532. This research has made heavy use of the VizieR catalogue access
tool and SIMBAD database, operated at CDS, Strasbourg, France. The original
description of the VizieR service was published in Ochsenbein et al. (2000),
and the SIMBAD astronomical database was published in Wenger et al. (2000).
This publication makes use of data from the SpeX Prism Spectral Libraries,
maintained by Adam Burgasser at http://www.browndwarfs.org/spexprism. We would
also like to thank the anonymous reviewer for their careful and thorough
comments on our manuscript and their insightful suggestions, which
significantly improved our draft. The authors wish to recognize and
acknowledge the very significant cultural role and reverence that the summit
of Mauna Kea has always had within the indigenous Hawaiian community. We are
most fortunate to have the opportunity to conduct observations from this
mountain.

##  Appendix A Summary of selection regions for the full sample

Table A.1: Region limits for each index  $-$ index correlation plot. Name | SpeX SpT | Youth | (1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) | (11) | Total
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---
WISE J000622.67$-$131955.2 | L8 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 2
WISE J00062785+1857288 | L7 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 3
2MASS J00132229$-$1143006 | T3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
2MASS J00133470+1109403 | L7 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 5
2MASS J00150206+2959323 | L8 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
PSO J004.1834+23.0741 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
WISE J00164397+2304265 | T1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
PSO J004.7148+51.8918 | L7 | 0 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 9
2MASSI J0028394+150141 | L7 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 10
2MASSW J0030300$-$145033 | L7 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 5
WISE J003110.04+574936.3 | L9 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
WISE J003110.04+574936.3 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSSp J003259.36+141036.6 | L9 | 0 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 10
SDSSp J003259.36+141036.6 | L9 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 9
2MASS J00440332+0228112 | L7 | 0 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 0 | 1 | 1 | 8
WISE J00440339+0228106 | L7 | 0 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 7
2MASS J00452972+4237438 | L8 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 3
WISEP J004701.06+680352.1 | L7 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
WISE J004928.48+044059.9 | L9 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 8
WISEA J010202.11+035541.4 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
2MASSI J0103320+193536 | L7 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 8
2MASSI J0103320+193536 | L7 | 0 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 7
SDSSp J010752.33+004156.1 | L7 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSSp J010752.33+004156.1 | L7 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSSp J010752.33+004156.1 | L7 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J011912.22+240331.6 | T2 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 0 | 0 | 8
2MASS J01262109+1428057 | L7 | 1 | 1 | 1 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 6
2MASS J01303563$-$4445411B | L8 | 0 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 9
PSO J023.8557+02.0884 | L8 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 9
SIMP J013656.57+093347.3 | T2 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
WISE J013836.58$-$032221.2 | T3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
2MASS J01453520$-$0314117 | L9 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 5
WISE J01453523$-$0314129 | L9 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 8
WISE J015010.89+382724.1 | L9 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 8
WISE J015010.89+382724.1 | L9 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 1 | 7
SDSS J015141.69+124429.6 | L9 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 7
WISE J02022929+2305139 | L7 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 10
DENIS$-$P J0205.4$-$1159 | L9 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 1 | 7
WISE J020625.27+264023.6 | L8 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
WISE J02260916$-$1610004 | L7 | 0 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 8
WISE J023038.90$-$022554.0 | L9 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSSp J023617.93+004855.0 | L9 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 5
SDSS J024749.90$-$163112.6 | T2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
DENIS$-$P J0255$-$4700 | L9 | 0 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 10
2MASS J02572581$-$3105523 | L8 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 9
2MASSW J0306268+154514 | L7 | 0 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 9
2MASSW J0310599+164816 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SIMP J03162759+2650277 | T3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
2MASS J03185403$-$3421292 | L8 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
WISE J032301.86+562558.0 | L7 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
2MASS J03231004$-$4631263 | L7 | 1 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 1
WISE J03244023$-$1919056 | L8 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 | 1 | 1 | 4
2MASS J03264225$-$2102057 | L7 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
2MASSI J0328426+230205 | T0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 10
2MASS J03432548+3155165 | L7 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 5
2MASS J03435056+3203180 | L7 | 1 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1
2MASS J03435721+3201337 | L7 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 5
Cl* IC 348 LRL 30003 | L7 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
Cl* IC 348 LRL 1923 | L7 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
2MASS J03440291+3152277 | L8 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 3
Cl* IC 348 LRL 1925 | L7 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 1 | 1 | 6
2MASS J03441150+3218094 | L8 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 5
2MASS J03441386+3156539 | L7 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 5
$[\mathrm{PSZ2003}]$ J034426.5+320820 | L7 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 3
$[\mathrm{PSZ2003}]$ J034427.2+320346 | L8 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 5
2MASS J03443687+3214363 | L7 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 3
Cl* IC 348 MM 74 | L7 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 3
$[\mathrm{PSZ2003}]$J034444.9+321411 | L7 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 3
2MASS J03444520+3201197 | L7 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 1 | 1 | 6
2MASS J03445853+3158270 | L7 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 3
2MASS J03450644+3159394 | L7 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 3
2MASS J03451604+3205140 | L7 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
2MASS J03452212+3205450 | L7 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 3
IC 348 IRS J03452901+3217551 | L8 | 1 | 0 | 0 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 4
PSO J057.2893+15.2433 | L7 | 0 | 1 | 1 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 7
SDSS J035104.37+481046.8 | T2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
2MASS J03552337+1133437 | L7 | 1 | 1 | 1 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 7
2MASS J03582213$-$4116144 | L7 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 0 | 1 | 1 | 1 | 8
2MASS J04144158+2809583 | L7 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 3
V410 Anon 13 | L7 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 3
IRAS F04262+2654 | L7 | 1 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 4
2MASS J04325026+2422115 | L7 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 5
CFHT 1 | L7 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 3
2MASS J0435145$-$141446 | L7 | 1 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 4
2MASS J04354290+1323449 | L7 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | 2
2MASS J04373705+2331080 | L7 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 3
2MASS J04381486+2611399 | L7 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 3
CFHT 4 | L8 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 3
WISE J044633.45$-$242956.9 | T0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 4
PSO J071.8769$-$12.2713 | T1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
WISE J045746.08$-$020719.2 | T2 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 1
2MASS J05012406$-$0010452 | L7 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 8
2MASS J05185995$-$2828372 | T2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
WISE J060738.65+242953.5 | L9 | 0 | 0 | 0 | 1 | 1 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 6
WISE J060738.65+242953.5 | L9 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 8
WISE J061135.13$-$041024.0 | T0 | 0 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 0 | 1 | 1 | 1 | 8
2MASS J06244595$-$4521548 | L7 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 2
WISE J062905.13+241804.9 | T0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
2MASS J06420559+4101599 | L8 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
PSO J103.0927+41.4601 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
WISE J065609.59+420531.9 | T3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1
WISE J07053400$-$1839256 | L8 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 4
SDSS J073922.26+661503.5 | T2 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 10
SDSS J073922.26+661503.5 | T1 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 3
2MASSI J0756252+124456 | T0 | 0 | 1 | 1 | 1 | 1 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 6
SDSS J075840.33+324723.4 | T2 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J080531.84+481233.0 | L7 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1
SDSS J080531.84+481233.0 | T0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 2
WISE J080700.23+413026.8 | L8 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 5
SDSS J080959.01+443422.2 | L7 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J080959.01+443422.2 | L7 | 0 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 10
SDSS J082030.12+103737.0 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J082030.12+103737.0 | T0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 10
2MASSI J0825196+211552 | L8 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
2MASSW J0829570+265510 | L7 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSSp J083008.12+482847.4 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSSp J083008.12+482847.4 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
2MASSI J0835425$-$081923 | L7 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | 4
SDSSp J083717.22$-$000018.3 | T1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSSp J083717.22$-$000018.3 | T1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSSp J083717.22$-$000018.3 | T1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 10
2MASSs J0850359+105716 | L7 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
2MASSs J0850359+105716 | L7 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J085234.90+472035.0 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSSp J085758.45+570851.4 | L8 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J085834.42+325627.7 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 10
SDSS J085834.42+325627.7 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 7
2MASSI J0859254$-$194926 | L7 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
2MASSI J0859254$-$194926 | L8 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 9
2MASSI J0859254$-$194926 | L8 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 9
SDSS J090900.73+652527.2 | T1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 3
Gl 337CD | L9 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 1 | 3
Gl 337CD | T0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 5
2MASS J09175418+6028065 | L7 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 7
2MASSW J0920122+351742 | L9 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 9
WISE J092055.40+453856.3 | T0 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 9
2MASSW J0929336+342952 | L8 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J093109.56+032732.5 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
2MASS J09490860$-$1545485 | T2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
2MASS J09490860$-$1545485 | T2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
LP 261$-$75B | L7 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 4
2MASS J09553336$-$0208403 | L8 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SIMP J09560810$-$1447065 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
PSO J149.1907$-$19.1730 | T0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 2
2MASS J10020752+1358556 | L7 | 0 | 0 | 1 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 2
G 196$-$3B | L7 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 7
G 196$-$3B | L7 | 0 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 7
SDSS J100711.74+193056.2 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J100711.74+193056.2 | L9 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J102109.69$-$030420.1 | T3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
SDSS J102552.43+321234.0 | L8 | 0 | 0 | 0 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 8
SDSS J102552.43+321234.0 | L8 | 0 | 1 | 0 | 1 | 0 | 1 | 0 | 1 | 1 | 0 | 1 | 0 | 6
2MASS J10293958+5715445 | L9 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 8
SDSS J103026.78+021306.4 | L9 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 8
SDSS J103321.92+400549.5 | L7 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 7
2MASSW J1036530$-$344138 | L9 | 0 | 0 | 0 | 1 | 1 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 6
SDSS J103931.35+325625.5 | T2 | 0 | 0 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 4
SDSS J103931.35+325625.5 | T2 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 7
2MASS J10430758+2225236 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J104335.08+121314.1 | L9 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J104335.08+121314.1 | L9 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J104409.43+042937.6 | L8 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 8
SDSS J104829.21+091937.8 | T2 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 1
WISE J104915.57$-$531906.1A | L9 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
WISE J104915.57$-$531906.1B | T1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J105213.51+442255.7 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
2MASS J11061191+2754215 | T2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
2MASS J11181292$-$0856106 | L9 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | 4
2MASS J11181292$-$0856106 | L9 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 1 | 7
2MASS J11193254$-$1137466 | L7 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J112118.57+433246.5 | T0 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 9
2MASS J11220826$-$3512363 | T2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
2MASS J11472421$-$2040204 | L7 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J115553.86+055957.5 | L9 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 9
WISE J120035.40$-$283657.5 | T0 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 8
WISE J120035.40$-$283657.5 | L9 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 8
WISE J12010457+5730042 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J120602.51+281328.7 | T3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
SDSS J120747.17+024424.8 | T0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 5
2MASS J12095613$-$1004008 | T3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
2MASS J12095613$-$1004008 | T3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
SDSS J121951.45+312849.4 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
2MASS J12304602+2827515 | L7 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
SDSSp J125453.90$-$012247.4 | T2 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
2MASS J13043568+1542521 | T0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
WISE J13052306$-$3951049 | L8 | 0 | 1 | 1 | 0 | 1 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 5
2MASS J13064517+4548552 | L9 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 0 | 1 | 6
WISEA J130729.56$-$055815.4 | L8 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 4
PSO J201.0320+19.1072 | T3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
2MASS J13243553+6358281 | T3 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
2MASSW J1326201$-$272937 | L7 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSSp J132629.82$-$003831.5 | L7 | 0 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 10
SDSS J133148.92$-$011651.4 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J133148.92$-$011651.4 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J133148.92$-$011651.4 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
WISE J134310.44$-$121628.8 | T0 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 8
SIMP J13441371$-$1614022 | T0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 2
WISE J134806.99+660328.4 | L8 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 9
SDSS J140023.12+433822.3 | L8 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 5
WISE J140035.40$-$385013.5 | T3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
2MASS J14025564+0800553 | T0 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 3
2MASS J14044948$-$3159330 | T2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
2MASS J14111847+2948515 | T0 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | 4
SDSS J141530.05+572428.7 | T3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
SDSS J141659.78+500626.4 | L7 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 1 | 7
WISE J14321117+3244338 | L7 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 8
SDSS J143553.25+112948.6 | T2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
SDSS J143945.86+304220.6 | T2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
WISE J150406.66$-$455223.9 | L8 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 5
PSO J226.2599$-$28.8959 | T1 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 1 | 0 | 1 | 1 | 1 | 5
SDSS J151114.66+060742.9 | L9 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1
SDSS J151114.66+060742.9 | T0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1
WISE J151314.61+401935.6 | L9 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J151506.11+443648.3 | L7 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J151603.03+025928.9 | T0 | 0 | 0 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 3
SDSS J151643.01+305344.4 | T2 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J152039.82+354619.8 | T0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 6
SDSS J152039.82+354619.8 | L9 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 9
SDSS J152103.24+013142.7 | T2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
Gliese 584C | L8 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 9
WISE J15335852+4757069 | L7 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 9
SDSS J153417.05+161546.1AB | T3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
SDSS J154009.36+374230.3 | L9 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J154009.36+374230.3 | L9 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
2MASS J15423630$-$0045452 | T0 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 8
SDSS J154508.93+355527.3 | L8 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 3
2MASS J15461461+4932114 | T2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
2MASS J15461461+4932114 | T2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
SDSS J154849.02+172235.4 | L8 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 8
2MASS J15515237+0941148 | L7 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 3
2MASS J15515237+0941148 | L7 | 0 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 7
WISE J155254.84+503307.6 | L9 | 0 | 0 | 1 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 3
2MASSW J1553214+210907 | L7 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 8
2MASS J16154255+4953211 | L7 | 1 | 1 | 1 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 7
2MASS J16154255+4953211 | L7 | 0 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 9
2MASS J16154255+4953211 | L7 | 0 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 9
PSO J244.1180+06.3598 | L7 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 10
PSO J247.3273+03.5932 | T2 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J163030.53+434404.0 | L9 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
2MASSW J1632291+190441 | L8 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
2MASSW J1632291+190441 | T0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 10
SDSS J163239.34+415004.3 | T1 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 3
WISE J164715.57+563208.3 | L8 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
2MASS J17021901$-$2235022 | L7 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 1 | 3
2MASSI J1711457+223204 | T0 | 0 | 1 | 1 | 1 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 5
2MASSI J1721039+334415 | T0 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 8
WISEA J172120.69+464025.9 | T0 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 1 | 7
2MASSW J1728114+394859 | L7 | 0 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 9
2MASSW J1728114+394859 | L7 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 9
WISE J173035.99+420742.1 | T0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
SDSS J173101.41+531047.9 | L7 | 0 | 0 | 1 | 1 | 1 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | 5
2MASS J17373467+5953434 | L9 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 2
WISE J173859.27+614242.1 | L7 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
2MASS J17392515+2454421 | L7 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 1 | 7
WISE J17405782+1317094 | L9 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 5
WISE J174102.78$-$464225.5 | L7 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J175024.01+422237.8 | T2 | 0 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 10
SDSSp J175032.96+175903.9 | T3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
WISE J175510.28+180320.2 | T1 | 0 | 0 | 0 | 1 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 3
WISEP J180026.60+013453.1 | L8 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 9
WISE J180952.53$-$044812.5 | T0 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 8
WISE J180952.53$-$044812.5 | T0 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 8
WISE J180952.53$-$044812.5 | T1 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 8
WISE J183058.56+454257.4 | L9 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
WISE J185101.83+593508.6 | L9 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
WISE J185101.83+593508.6 | L9 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 1 | 7
DENIS J19013910$-$3700170 | L7 | 1 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 4
WISE J191915.54+304558.4 | L7 | 0 | 0 | 0 | 1 | 1 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 6
2MASS J20025073$-$0521524 | L7 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 10
2MASS J20025073$-$0521524 | L7 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
2MASS J20025073$-$0521524 | L7 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
WISE J201204.10+672607.9 | L7 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 0 | 1 | 0 | 0 | 2
WISE J203042.79+074934.7 | T1 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 6
WISE J203042.79+074934.7 | T1 | 0 | 0 | 0 | 1 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 7
SDSS J204317.69$-$155103.4 | L9 | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 7
SDSS J204317.69$-$155103.4 | L9 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 5
SDSS J204317.69$-$155103.4 | L9 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 8
WISE J204356.42+622049.0 | T1 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 9
SDSS J204749.61$-$071818.3 | L9 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 8
WISEA J205202.06$-$204313.0 | L8 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 3
SDSS J205235.31$-$160929.8 | T0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 0 | 1 | 4
SDSS J205235.31$-$160929.8 | T0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 1 | 4
SDSS J205235.31$-$160929.8 | T1 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 1 | 1 | 1 | 6
2MASSW J2101154+175658 | L9 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
2MASSW J2101154+175658 | L7 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 5
2MASSW J2101154+175658 | L8 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
PSO J319.3102$-$29.6682 | T0 | 0 | 0 | 0 | 1 | 0 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 7
2MASS J21243864+1849263 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
SDSS J213154.43$-$011939.3 | L9 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
2MASS J21321145+1341584 | L7 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 5
2MASS J21324898$-$1452544 | T3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
2MASS J21392676+0220226 | T2 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
HN Peg B | T3 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
2MASS J21481628+4003593 | L7 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
2MASS J21481628+4003593 | L7 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
2MASS J21513979+3402444 | L8 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 5
2MASS J21522609+0937575 | L7 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 10
PSO J331.6058+33.0207 | T1 | 0 | 0 | 0 | 1 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 0 | 4
2MASS J22092183$-$2711329 | T2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
2MASS J22120703+3430351 | L7 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 4
2MASS J22153705+2110554 | T1 | 0 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 10
2MASS J22153705+2110554 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
PSO J334.1193+19.8800 | T3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
WISE J222219.93+302601.4 | L8 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 9
PSO J336.9036$-$18.9148 | L7 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 5
ULAS J222958.30+010217.2 | T3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
WISEA J223343.53$-$133140.9 | T2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
WISE J223937.55+161716.1 | T3 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
2MASSW J2244316+204343 | L7 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
2MASS J22490917+3205489 | L7 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
PSO J342.3797$-$16.4665 | T0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 1 | 1 | 3
SDSSp J224953.45+004404.2AB | L7 | 1 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 8
SDSSp J224953.45+004404.2AB | L7 | 0 | 0 | 0 | 1 | 1 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 6
BRLT 317 | T0 | 0 | 0 | 0 | 1 | 1 | 1 | 0 | 1 | 0 | 1 | 1 | 1 | 7
DENIS$-$P J225210.73$-$173013.4 | T0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 2
WISEA J230329.45+315022.7 | T2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
WISEA J230329.45+315022.7 | T2 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0
PSO J348.8808+06.2873 | L7 | 1 | 0 | 0 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 4
WISE J23230708+0541130 | L8 | 0 | 0 | 0 | 1 | 1 | 0 | 0 | 1 | 0 | 1 | 1 | 1 | 6
2MASS J23254530+4251488 | L8 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 9
WISE J232728.74$-$273056.6 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
CFBDS J233051$-$084454 | L8 | 0 | 0 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 9
2MASS J23322678+1234530 | T0 | 0 | 1 | 1 | 1 | 1 | 1 | 0 | 0 | 1 | 1 | 0 | 0 | 7
2MASS J23352734+4511442 | L7 | 0 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 1 | 11
WISE J23542231$-$0811297 | L7 | 0 | 1 | 1 | 1 | 1 | 0 | 1 | 1 | 0 | 0 | 1 | 1 | 8

##  Appendix B Candidate and confirmed spectral binaries in the sample

Table A.2: L7$-$T3 dwarf spectral binary candidates from our index-selection
technique.

Source | SpeX SpT |  $J$ mag |  $K$ mag | Total | SNR | ReferenceaaSpectrum; Spectral Binary Candidate; Confirmed Binarity/Variability
---|---|---|---|---|---|---
Confirmed Spectral Binaries
2MASS J04473039-1216155 | T1.0 | 16.48$\pm$0.11 | 15.55$\pm$0.22 | 5 | 10.10 | 3;1;3
2MASS J05185995$-$2828372 | T2.0 | 15.978$\pm$0.1 | 14.162$\pm$0.07 | 6 | 56.00 | 13;13;5
WISE J061135.13$-$041024.0 | T0.0 | 15.489$\pm$0.06 | 14.221$\pm$0.07 | 3 | 23.00 | 20;18;18
SDSS J080531.84+481233.0 | L7.0 | 14.734$\pm$0.04 | 13.444$\pm$0.04 | 3 | 23.00 | 12;7;15
Gl 337CD | L9.0 | 15.512$\pm$0.08 | 14.043$\pm$0.06 | 2 | 84.00 | 9;1;15
SDSS J102109.69-030420.1 | T3.0 | 16.253$\pm$0.09 | 15.126$\pm$0.17 | 6 | 31.00 | 5;18;15
WISE J104915.57$-$531906.1A | L9.0 | 11.511$\pm$0.03 | 9.559$\pm$0.03 | 2 | 133.00 | 10;10;23
2MASS J11061191+2754215 | T2.0 | 14.879$\pm$0.03 | 13.788$\pm$0.04 | 4 | 78.00 | 24;9;30
2MASS J12095613$-$1004008 | T3.0 | 15.914$\pm$0.07 | 15.062$\pm$0.14 | 4 | 15.00 | 11;9;25
2MASS J14044948$-$3159330 | T2.0 | 15.577$\pm$0.06 | 14.538$\pm$0.1 | 6 | 33.00 | 24;18;15
SDSS J153417.05+161546.1AB | T3.0 | 16.753$\pm$0.13 |  $>$16.411 | 5 | 20.00 | 12;18;28
SDSS J151114.66+060742.9 | L9.0 | 16.016$\pm$0.08 | 14.544$\pm$0.1 | 6 | 15.00 | 12;9;11
SDSS J205235.31$-$160929.8 | T0.0 | 16.334$\pm$0.12 | 15.123$\pm$0.15 | 2 | 4.00 | 12;9;15
DENIS-P J225210.73$-$173013.4 | T0.0 | 14.313$\pm$0.03 | 12.901$\pm$0.02 | 2 | 125.00 | 33;9;33
Confirmed Variable Sources
SDSS J075840.33+324723.4 | T2.0 | 14.947$\pm$0.04 | 13.879$\pm$0.06 | 2 | 113.00 | 8;9; $\cdots$
SDSS J085834.42+325627.7 | T0.0 | 16.453$\pm$0.12 | 14.756$\pm$0.1 | 4 | 20.00 | 12;1; $\cdots$
2MASS J11220826$-$3512363 | T2.0 | 15.019$\pm$0.04 | 14.383$\pm$0.07 | 2 | 50.00 | 5;1; $\cdots$
2MASS J13243553+6358281 | T3.0 | 15.596$\pm$0.07 | 14.058$\pm$0.06 | 2 | 39.00 | 24;9; $\cdots$
2MASS J16291840+0335371 | T2.0 | 15.29$\pm$0.04 | 14.18$\pm$0.06 | 2 | 75.00 | 16;1; $\cdots$
WISE J180952.53$-$044812.5 | T0.0 | 15.14$\pm$0.05 | 13.96$\pm$0.06 | 2 | 56.00 | 29;1; $\cdots$
SDSS J204317.69$-$155103.4 | L9.0 | 16.625$\pm$0.16 | 15.402$\pm$0.21 | 2 | 8.00 | 12;1; $\cdots$
HN Peg B | T3.0 | 15.86$\pm$0.03 | 15.12$\pm$0.03 | 3 | 55.00 | 26;1; $\cdots$
2MASS J22153705+2110554 | T1.0 | 16.0$\pm$0.08 | 14.82$\pm$0.11 | 2 | 53.71 | 32;21; $\cdots$
Candidate Spectral Binaries
WISE J000622.67$-$131955.2 | L8.0 | 16.67$\pm$0.13 | 15.12$\pm$0.13 | 3 | 20.00 | 27;1; $\cdots$
WISE J00164397+2304265 | T1.0 | 16.412$\pm$0.0 | 14.973$\pm$0.0 | 2 | 32.80 | 3;3; $\cdots$
SDSS J011912.22+240331.6 | T2.0 | 17.017$\pm$0.18 |  $>$17.042 | 4 | 24.00 | 12;9; $\cdots$
SDSS J024749.904$-$163112.6 | T2.0 | 17.186$\pm$0.18 | 15.616$\pm$0.19 | 6 | 24.00 | 12;9; $\cdots$
SIMP J03162759+2650277 | T3.0 | 16.585$\pm$0.15 |  $>$15.159 | 4 | 33.74 | 32;3; $\cdots$
SDSS J035104.37+481046.8 | T2.0 | 16.466$\pm$0.13 | 14.996$\pm$0.12 | 6 | 14.00 | 12;9; $\cdots$
WISE J045746.08$-$020719.2 | T2.0 | 14.897$\pm$0.04 | 14.022$\pm$0.06 | 3 | 87.00 | 38;1; $\cdots$
WISE J062905.13+241804.9 | T0.0 | 16.34$\pm$0.13 | 15.13$\pm$0.15 | 6 | 22.00 | 29;29; $\cdots$
PSO J103.0927+41.4601 | T0.0 | 15.48$\pm$0.06 | 13.89$\pm$0.05 | 2 | 73.00 | 2;3; $\cdots$
SDSS J073922.26+661503.5 | T1.0 | 16.823$\pm$0.13 | 15.831$\pm$0.18 | 2 | 15.00 | 12;1; $\cdots$
2MASSI J0756252+124456 | T0.0 | 16.659$\pm$0.14 | 14.73$\pm$0.12 | 2 | 34.00 | 38;1; $\cdots$
SDSSp J083717.22$-$000018.3 | T1.0 | 17.101$\pm$0.21 |  $>$15.674 | 2 | 10.00 | 5;1; $\cdots$
SDSS J090900.73+652527.2 | T1.0 | 16.034$\pm$0.09 | 15.171$\pm$0.15 | 2 | 30.00 | 12;9; $\cdots$
2MASS J09490860$-$1545485 | T2.0 | 16.149$\pm$0.12 | 15.227$\pm$0.17 | 2 | 19.00 | 5;9; $\cdots$
2MASS J09564583$-$1910227 | T0.0 | 15.208$\pm$0.05 | 13.853$\pm$0.05 | 3 | 47.40 | 3;3; $\cdots$
2MASS J10020752+1358556 | L7.0 | 17.19$\pm$0.26 | 15.59$\pm$0.2 | 4 | 18.49 | 21;21; $\cdots$
SDSS J103931.35+325625.5 | T2.0 | 16.405$\pm$0.15 | 15.151$\pm$0.16 | 3 | 15.00 | 12;9; $\cdots$
SDSS J120602.51+281328.7 | T3.0 | 16.541$\pm$0.11 |  $>$15.817 | 2 | 24.00 | 12;9; $\cdots$
SDSS J120747.17+024424.8 | T0.0 | 15.58$\pm$0.07 | 13.986$\pm$0.06 | 2 | 88.00 | 24;9; $\cdots$
2MASS J12304602+2827515 | L7.0 | 16.073$\pm$0.09 | 14.434$\pm$0.06 | 2 | 8.00 | 34;1; $\cdots$
2MASS J13043568+1542521 | T0.0 | 17.32$\pm$0.19 | 15.67$\pm$0.19 | 6 | 41.92 | 21;21; $\cdots$
2MASS J13064517+4548552 | L9.0 | 17.009$\pm$0.2 | 15.499$\pm$0.16 | 2 | 14.46 | 22;21; $\cdots$
WISE J140035.40$-$385013.5 | T3.0 | 16.04$\pm$0.1 |  $>$16.07 | 2 | 10.00 | 29;1; $\cdots$
2MASS J14025564+0800553 | T0.0 | 16.85$\pm$0.03 | 15.73$\pm$0.03 | 6 | 49.17 | 21;21; $\cdots$
2MASS J14111847+2948515 | T0.0 | 16.2$\pm$0.09 | 15.09$\pm$0.11 | 2 | 29.15 | 32;1; $\cdots$
SDSS J141530.05+572428.7 | T3.0 | 16.734$\pm$0.16 |  $>$15.544 | 6 | 19.00 | 9;9; $\cdots$
SDSS J143553.25+112948.6 | T2.0 | 17.137$\pm$0.23 |  $>$16.906 | 5 | 7.00 | 12;9; $\cdots$
SDSS J143945.86+304220.6 | T2.0 | 17.223$\pm$0.23 |  $>$15.881 | 4 | 22.00 | 12;9; $\cdots$
WISE J150406.66$-$455223.9 | L8.0 | 16.56$\pm$0.11 | 14.83$\pm$0.1 | 2 | 14.00 | 37;1; $\cdots$
2MASS J15050230$-$2853408 | T1.0 | 15.83$\pm$0.07 | 15.06$\pm$0.13 | 2 | 47.00 | 14;1; $\cdots$
SDSS J151603.03+025928.9 | T0.0 | 17.23$\pm$0.2 | 15.433$\pm$0.18 | 4 | 29.00 | 9;9; $\cdots$
SDSS J151643.01+305344.4 | T2.0 | 16.848$\pm$0.15 | 15.081$\pm$0.09 | 2 | 33.00 | 9;9; $\cdots$
2MASS J15461461+4932114 | T2.0 | 15.902$\pm$0.07 |  $>$14.9 | 3 | 16.00 | 31;1; $\cdots$
WISE J155254.84+503307.6 | L9.0 | 17.13$\pm$0.24 | 15.46$\pm$0.16 | 4 | 12.00 | 37;1; $\cdots$
2MASSI J1711457+223204 | T0.0 | 17.089$\pm$0.18 | 14.727$\pm$0.1 | 6 | 23.00 | 9;9; $\cdots$
WISEA J172120.69+464025.9 | T0.0 | 16.859$\pm$0.15 | 15.234$\pm$0.13 | 2 | 15.40 | 36;1; $\cdots$
WISE J173035.99+420742.1 | T0.0 | 16.95$\pm$0.18 |  $>$15.65 | 5 | 35.00 | 29;1; $\cdots$
2MASS J17373467+5953434 | L9.0 | 16.879$\pm$0.16 | 15.719$\pm$0.26 | 2 | 24.00 | 19;21; $\cdots$
WISE J17405782+1317094 | L9.0 |  $>$17.468 | 15.195$\pm$0.15 | 2 | 19.09 | 35;1; $\cdots$
SDSSp J175032.96+175903.9 | T3.0 | 16.34$\pm$0.1 | 15.478$\pm$0.19 | 2 | 33.00 | 11;1; $\cdots$
WISE J175510.28+180320.2 | T1.0 | 16.02$\pm$0.09 | 16.02$\pm$0.09 | 2 | 39.00 | 27;1; $\cdots$
2MASS J21171431$-$2940034 | T0.0 | 15.601$\pm$0.06 | 14.15$\pm$0.07 | 2 | 21.40 | 3;3; $\cdots$
2MASS J21392676+0220226 | T2.0 | 15.264$\pm$0.05 | 13.582$\pm$0.04 | 2 | 10.00 | 5;9; $\cdots$
2MASS J22092183$-$2711329 | T2.0 |  $>$15.786 |  $>$15.097 | 2 | 45.00 | 38;1; $\cdots$
2MASS J22120703+3430351 | L7.0 | 16.316$\pm$0.1 | 14.37$\pm$0.07 | 2 | 11.00 | 9;1; $\cdots$
ULAS J222958.30+010217.2 | T3.0 | 17.88$\pm$0.02 |  $\cdots$ | 6 | 11.00 | 38;17; $\cdots$
WISEA J223343.53$-$133140.9 | T2.0 | 16.451$\pm$0.13 | 15.494$\pm$0.22 | 2 | 19.60 | 36;1; $\cdots$
WISE J223937.55+161716.1 | T3.0 | 16.079$\pm$0.08 |  $>$14.89 | 6 | 50.00 | 20;1; $\cdots$
WISE J232728.74$-$273056.6 | T0.0 | 16.681$\pm$0.14 | 14.756$\pm$0.1 | 2 | 41.00 | 20;1; $\cdots$
2MASS J23322678+1234530 | T0.0 | 16.89$\pm$0.19 | 15.7$\pm$0.31 | 2 | 29.80 | 21;21; $\cdots$

Note. — Order of columns (1) H2O$-$J vs. CH${}_{4}-$H, (2) H2O$-$J vs.
H$-$bump, (3) CH${}_{4}-$J vs. CH${}_{4}-$H, (4) CH${}_{4}-$J vs. H$-$bump,
(5) CH${}_{4}-$H vs. H2O$-$K, (6) CH${}_{4}-$H vs. CH${}_{4}-$K, (7)
CH${}_{4}-$H vs. H$-$dip, (8) CH${}_{4}-$H vs. J$-$curve, (9) H2O$-$K vs.
H$-$bump, (10) H$-$dip vs. K$-$slope, (11) H$-$dip vs. H$-$bump

References. — (1) This paper; (2) Best et al. (2013); (3) Best et al. (2015);
(4) Burgasser et al. (2004); (5) Burgasser et al. (2006a); (6) Burgasser et
al. (2006b); (7) Burgasser (2007b); (8) Burgasser et al. (2008); (9) Burgasser
et al. (2010); (10) Burgasser et al. (2013); (11) Bardalez Gagliuffi et al.
(2015); (12) Chiu et al. (2006); (13) Cruz et al. (2004); (14) Deacon et al.
(2011); (15) Dupuy & Liu (2012); (16) Deacon et al. (2012); (17) Day-Jones et
al. (2013); (18) Gelino et al. (2014); (19) Geißler et al. (2011); (20)
Kirkpatrick et al. (2011); (21) Kellogg et al. (2015);(22) Kellogg et al.
(2017) (23) Luhman (2013); (24) Looper et al. (2007); (25) Liu et al. (2010);
(26) Luhman et al. (2007); (27) Luhman & Sheppard (2014); (28) Liu et al.
(2006); (29) Mace et al. (2013); (30) Manjavacas et al. (2013); (31) Metchev
et al. (2008); (32) Robert et al. (2016); (33) Reid et al. (2006b); (34)
Sheppard & Cushing (2009); (35) Schneider et al. (2017); (36) Schneider et al.
(2016a); (37) Thompson et al. (2013); (38) Burgasser et al. inprep.

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