# Panic at the ISCO: the visible accretion disks powering optical variability
in ZTF AGN

Charlotte Ward Department of Astrophysical Sciences, Princeton University,
Princeton, NJ 08544, USA  Suvi Gezari Space Telescope Science Institute, 3700
San Martin Dr., Baltimore, MD 21218, USA  Peter Nugent Lawrence Berkeley
National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720, USA  Department of
Astronomy, University of California, Berkeley, Berkeley, CA 94720, USA
Matthew Kerr Space Science Division, U.S. Naval Research Laboratory,
Washington, DC 20375, USA  Michael Eracleous Department of Astronomy &
Astrophysics and Institute for Gravitation and the Cosmos, 525 Davey
Laboratory, The Pennsylvania State University, University Park, PA 16802, USA
Sara Frederick Department of Physics and Astronomy, Vanderbilt University,
6301 Stevenson Center, Nashville, TN 37235  Erica Hammerstein Department of
Astronomy, University of Maryland, College Park, MD 20742, USA  Matthew J.
Graham Division of Physics, Mathematics, and Astronomy, California Institute
of Technology, Pasadena, CA 91125, USA  Sjoert van Velzen Leiden Observatory,
Leiden University, Postbus 9513, 2300 RA, Leiden, the Netherlands  Mansi M.
Kasliwal Division of Physics, Mathematics, and Astronomy, California Institute
of Technology, Pasadena, CA 91125, USA  Russ R. Laher IPAC, California
Institute of Technology, 1200 E. California Blvd, Pasadena, CA 91125, USA
Frank J. Masci IPAC, California Institute of Technology, 1200 E. California
Blvd, Pasadena, CA 91125, USA  Josiah Purdum Caltech Optical Observatories,
California Institute of Technology, Pasadena, CA 91125, USA  Benjamin Racine
Aix Marseille Univ, CNRS/IN2P3, CPPM, Marseille, France  Roger Smith Caltech
Optical Observatories, California Institute of Technology, Pasadena, CA 91125

###### Abstract

About 3-10% of Type I active galactic nuclei (AGN) have double-peaked broad
Balmer lines in their optical spectra originating from the motion of gas in
their accretion disk. Double-peaked profiles arise not only in AGN, but
occasionally appear during optical flares from tidal disruption events and
changing-state AGN. In this paper we identify 250 double-peaked emitters
(DPEs) amongst a parent sample of optically variable broad-line AGN in the
Zwicky Transient Facility (ZTF) survey, corresponding to a DPE fraction of
19%. We model spectra of the broad H$\alpha$ emission line regions and provide
a catalog of the fitted accretion disk properties for the 250 DPEs. Analysis
of power spectra derived from the 5 year ZTF light curves finds that DPEs have
similar amplitudes and power law indices to other broad-line AGN, but have
lower turnover frequencies. Follow-up spectroscopy of 12 DPEs reveals that
$\sim$50% display significant changes in the relative strengths of their red
and blue peaks over long $10-20$ year timescales, indicating that broad-line
profile changes arising from spiral arm or hotspot rotation are common amongst
optically variable DPEs. Analysis of the accretion disk parameters derived
from spectroscopic modeling provides evidence that DPEs are not in a special
accretion state, but are simply normal broad-line AGN viewed under the right
conditions for the accretion disk to be easily visible. We compare the radio
variability properties of the two samples and present radio jet imaging of 3
DPEs with disks of inclination angle $\sim 14-35$°. We discuss some objects
with notable light curves or unusual broad line profiles which are outliers
amongst the variable DPE population. We include inspiraling SMBH binary
candidate SDSSJ1430+2303 in our analysis, and discuss how its photometric and
spectroscopic variability is consistent with the disk-emitting AGN population
in ZTF.

††software:  Ampel (Nordin et al., 2019), Astropy (Robitaille et al., 2013;
Price-Whelan et al., 2018), GROWTH Marshal (Kasliwal et al., 2019), pPXF
(Cappellari & Emsellem, 2003; Cappellari, 2017)

##  1 Introduction

The vast majority of massive galaxies host a supermassive black hole (SMBH) in
their center (Magorrian et al., 1998). Understanding how efficiently SMBHs
grow via accretion of gas in galaxy nuclei is essential if we are to determine
how SMBHs formed in the early Universe and how they have co-evolved with their
host galaxies over time (Pacucci et al., 2015). Direct emission from the gas
disks around SMBHs has been observed in optical spectra of some galactic
nuclei and provides important observational data for comparison to simulations
of SMBH accretion and for understanding the efficiency of various active
galactic nuclei (AGN) accretion states.

Emission from AGN accretion disks is sometimes observable as broad double-
peaked H$\alpha$ and H$\beta$ emission lines with each peak at $\pm(500-3000)$
km/s from the rest velocity (Eracleous & Halpern, 1994; Chen & Halpern, 1989;
Eracleous et al., 1997; Strateva et al., 2003; Eracleous et al., 2009). AGN
with double-peaked broad Balmer emission lines are called double-peaked
emitters (DPEs). The double-peaked Balmer lines are usually well-modeled as
emission from a geometrically thin and optically thick relativistic Keplerian
accretion disk, where Doppler boosting results in asymmetry between the red
and blue peaks (Chen & Halpern, 1989; Strateva et al., 2003). Factors such as
turbulent broadening and the emissivity profile of the disk generate a variety
of disk profile shapes.

Over the last three decades, increasing numbers of AGN have been found to
exhibit long-lived double-peaked disk emission from a stable accretion disk
(e.g. the canonical DPE Arp102B; Chen et al., 1989; Popović et al., 2014a).
Estimates of DPE fractions amongst the wider broad-line AGN population range
from $\sim 3-30$% (Eracleous & Halpern, 1994; Ho et al., 1997; Strateva et
al., 2003). Some DPEs show substantial changes in the relative flux of the
blue and red peaks over timescales of years to decades which is well modeled
by the rotation of spiral arms or hotspots in the disk (Storchi-Bergmann et
al., 2002; Lewis et al., 2010; Gezari et al., 2007; Schimoia et al., 2012,
2017).

Over the past few years, spectroscopic follow-up of transient phenomena in
wide-field optical time-domain surveys has revealed new classes of disk-
emitters: those with transient double-peaked emission from a temporary
accretion disk associated with tidal disruption of a star or the onset of a
new AGN accretion episode in a previously inactive AGN. Tidal disruption
events (TDEs) occur when a star passing an SMBH is disrupted by tidal forces,
causing the formation a disk of material which is partially accreted onto the
SMBH and produces a flare in the optical, UV and X-rays (Rees, 1988; Evans &
Kochanek, 1989; Ulmer, 1999). Some recently reported TDEs have exhibited the
appearance of a double-peaked Balmer profile associated with the onset of the
initial optical flare, which in some cases has been followed by fading of the
disk profile over the following year (Short et al., 2020; Nicholl et al.,
2020; Hung et al., 2020; Holoien et al., 2019). The periodic nuclear transient
ASASSN-14ko, likely a repeating partial TDE (Payne et al., 2021), exhibited a
double-peaked spectrum consistent with a circular disk containing a spiral
arm, and the calculated precession timescale of that spiral arm matched the
periodic flaring timescale of $\sim 114$ days (Tucker et al., 2021).

Double-peaked and asymmetric broad lines have also been observed amongst
populations of changing-state AGN (or changing-look AGN; CLAGN). Changing-
state AGN are identified by the appearance or disappearance of broad Balmer
emission lines indicating a change in the presence of gas in the vicinity of
the SMBH, and are often associated with the onset or termination of optical
variability (see Ricci & Trakhtenbrot, 2022, for a review of changing-state
AGN). Changing-look LINERS NGC 1097 and NGC 3065 have irregularly shaped
broad-line profiles which may be ascribed to accretion disk emission
(Storchi‐Bergmann et al., 2003; Eracleous & Halpern, 2001), as do three of the
changing-look LINERS found via follow-up of variability-selected changing-look
AGN candidates from optical time-domain survey data (Frederick et al., 2019).
A double-peaked profile appeared in nuclear transient ZTF19aagwzod after an
X-ray flare and the onset of strong optical variability (Frederick et al.,
2020). J0950+5128, an AGN observed to switch from radio-quiet to radio-loud in
VLASS (Nyland et al., 2020; Zhang et al., 2022), also exhibits evidence for an
evolving disk profile (Breiding et al., 2021).

Some members of other unusual AGN sub-populations, discovered in time-domain
surveys, also exhibit double-peaked Balmer profiles. Five of the AGN which
were found to be spatially offset from their host galaxy nuclei in ZTF imaging
were DPEs (Ward et al., 2021). A double-peaked profile was also observed in
SDSSJ1430+2303 (ZTF18aarippg). Jiang et al. (2022) attributed periodic-like
features in the optical light curve of SDSSJ1430+2303 to the decaying orbit of
an SMBH binary with a highly eccentric orbit and uneven mass ratio. The
double-peaked profile showed a change in the relative strength of the blue and
red peaks compared to 10 year old archival data and this was interpreted as
the orbital motion of two broad-line regions in the binary. However, continued
optical monitoring supported an alternative hypothesis of a single, rotating
accretion disk (Dotti et al., 2022), suggesting that the profile evolution was
due to the more typical disk evolution processes observed in DPEs. NICER
monitoring of SDSSJ1430+2303 revealed the presence of quasi-periodic hard
X-ray flares caused by magnetic reconnection events in the corona, which may
provide clues into the accretion state of the object (Masterson et al., 2023).
More generally, the binary supermassive black hole interpretation has been
shown to be incompatible with line profiles that have well-defined double
peaks (Doan et al., 2020, and references therein).

The various recent discoveries of disk emission from variability-selected AGN
and other transient phenomena in time-domain surveys motivates a large-scale
population analysis of optically variable double-peaked emitters. In
particular, if we are able to understand the population-wide properties of the
longer-lived accretion disks in AGN, we will be better placed to understand
the different properties of transient disks appearing in single TDE-driven
accretion episodes.

Optical variability is also an important clue for understanding physical
differences between DPEs and other broad-line AGN which are implied by other
multi-wavelength signatures. Double-peaked H$\alpha$ and H$\beta$ profiles are
most commonly visible in low luminosity, low-accretion rate AGN (Eracleous &
Halpern, 1994; Ho et al., 2000; Ho, 2008). They are also associated with
radio-loud elliptical hosts with large bulge and black hole masses (Eracleous
& Halpern, 1994, 2003). DPEs are 1.6$\times$ more likely to have radio
emission and 1.5$\times$ more likely to have soft X-ray emission than other
broad-line AGN (Strateva et al., 2003). Zhang & Feng (2017) found that that
the optical variability properties of DPEs differed from other broad-line AGN,
having damped random walk (DRW) characteristic timescales $2.7\times$ larger
than a control sample in CSS and SDSS light curves.

Providing an explanation for the differences between DPEs and other broad-line
AGN while accounting for these many population differences is challenging.
Storchi-Bergmann et al. (2017) predict that double peaked profiles are
ubiquitous in broad-line AGN, but are only observed when the inclination angle
is $\gtrsim 20$° so that the separate peaks of the accretion disk are
observable, but $\lesssim 37$° so that the accretion disk emission is not
blocked by the obscuring torus. This would result in an observed $\sim 60$%
fraction of broad-line AGN with double peaks, but other factors may reduce
this fraction. For example, if the AGN is in a high accretion state,
contributions from gas that is not part of the disk (e.g., gas that is
outflowing or accelerating away from the disk) is expected to dominate the
broad-line emission and fill the dip between the peaks (Storchi-Bergmann et
al., 2017).

Some broad-line AGN emission models invoke two phases: outflowing sub-critical
density gas produces broad Gaussian lines, while supercritical gas close to
the disk surface produces double-peaked emission. These models may explain the
transition between Type I and true Type II AGN and may also explain the higher
incidence of double-peaked broad Balmer profiles in low-luminosity AGN
(Popović et al., 2004; Bon et al., 2009; La Mura et al., 2009; Elitzur et al.,
2014). Disk-wind AGN models may also explain the higher luminosity of double-
peaked structures relative to broad line gas in low-luminosity AGN compared to
standard Seyfert 1 nuclei (Elitzur et al., 2014; Storchi-Bergmann et al.,
2017). These models are supported by reverberation mapping of Seyfert 1 nuclei
showing that even when the H$\beta$ profiles are not double peaked, the root
mean square taken across time series of H$\beta$ spectra still often shows a
double-peaked profile, implying that the most variable, innermost broad line
gas is in a disk (Denney et al., 2010; Schimoia et al., 2017; Storchi-Bergmann
et al., 2017).

In this paper we present, for the first time, a large-scale population study
of disk-emitting AGN with both comprehensive time-domain and spectroscopic
analysis. For our variability analysis we have used observations from the
Zwicky Transient Facility (ZTF; Bellm et al., 2019; Graham et al., 2019;
Dekany et al., 2020), an ongoing optical survey which began in March 2018 and
achieves single epoch limiting magnitudes of $\sim 21$ in the g-, r- and
i-bands over a survey footprint of 23,675 deg2. For our sample of 250 DPEs, we
present both power spectrum analysis of ZTF light curves and spectroscopically
derived disk geometries from fits to the double-peaked line profiles.

Figure 1: Examples of different disk profile morphologies for 16 DPEs
identified in the parent sample. We include the profiles of 3 DPEs with radio
jet imaging in Figure 7 (ZTF18aaqdmih (m), ZTF18aarywbt (k) and
ZTF19abizomu(n)) and DPEs with notable light curves presented in Figure 4
(ZTF18aarippg (a) and ZTF18aaznjgn (p)). We note that in rare cases like
ZTF18accwjao (j), the relative strengths of the blue and red peaks could not
be fully accounted for when the spiral arm contrast ratio was restricted to
$<8$. When the parameters describing internal structure within the disk were
more flexible, a better model was found.

In Section 2 we describe the selection of optically variable broad-line AGN in
ZTF and the spectroscopic criteria used to identify the sub-sample of DPEs. We
present fitting of the spectra of the double-peaked profiles with accretion
disk models and provide a catalog of accretion disk properties for the 250
DPEs. In Section 3 we characterize the optical variability properties of the
DPEs compared to the control sample of broad-line AGN and present examples of
notable light curves from the DPE population. In Section 4 we analyze the
radio properties of the DPEs and present 20-34 cm imaging of radio jets for 3
objects. In Section 5 we present spectroscopic monitoring a DPE sub-sample,
showing that 50% exhibit large changes in the relative strengths of the red
and blue peaks over decade-long timescales. We also discuss the unusual
properties of two objects which are atypical for disk emitters and may be
worthy of additional follow-up. In Section 6 we discuss the overall accretion
disk and variability properties of the DPE and AGN populations in light of
other transients with visible accretion disks, as well as the search for SMBH
binary candidates in time-domain data. We summarize our conclusions in Section
7.

##  2 Spectroscopic classification of DPEs

###  2.1 Selection of variable broad-line AGN with SDSS spectroscopy

To produce a parent sample of 1549 optically variable broad-line AGN we
started with the 5000 variable AGN identified in ZTF time-domain survey data
in Ward et al. (2021) and required the AGN to have redshifts $z<0.4$ and to
have an increase in flux of 1.5 magnitudes in either the g- or r-band
difference image photometry and to be classified as GALAXY AGN BROADLINE’ or
‘QSO BROADLINE’ in the SDSS DR14 spectroscopic catalog (Blanton et al., 2017).
The redshift distribution of the AGN sample, split into sub-classes of DPEs
and ‘normal’ broad-line AGN, is shown later in Figure 3.

Table 1: Properties of the 250 DPE candidates from ZTF (full table in
Appendix)

ZTF ID | RA | Dec | z | Log Amp. | PL index | Turn. | VLASS E1 | VLASS E2 | RACS
---|---|---|---|---|---|---|---|---|---
| (hms) | (dms) |  |  |  | (yr-1) | (Jy) | (Jy) | (Jy)
ZTF18aaaotwe | 13:13:10.376 | 15:45:3.347 | $0.0657$ | $-2.8^{+0.3}_{-0.3}$ | $4.2^{+1.7}_{-2.4}$ | $3.2^{+1.6}_{-2.0}$ | ND | ND | ND
ZTF18aaaovpz | 10:39:13.82 | 09:40:2.779 | $0.217$ | $-2.8^{+0.4}_{-0.7}$ | $2.2^{+3.3}_{-1.0}$ | $0.3^{+1.1}_{-0.3}$ | ND | ND | ND
ZTF18aaavwka | 12:35:44.246 | 16:05:35.978 | $0.0711$ | $-2.5^{+0.0}_{-0.1}$ | $2.5^{+3.4}_{-2.4}$ | $68.0^{+28.1}_{-46.4}$ | ND | ND | ND
ZTF18aabkubl | 11:25:58.744 | 20:05:54.825 | $0.133$ | $-1.2^{+0.0}_{-0.1}$ | $3.9^{+1.9}_{-2.5}$ | $4.2^{+0.7}_{-2.1}$ | $469.95\pm 3.08$ | $469.95\pm 3.08$ | ND
ZTF18aabylvn | 14:17:59.554 | 25:08:12.59 | $0.0163$ | $-1.4^{+0.0}_{-0.0}$ | $0.0^{+0.1}_{-0.0}$ | $3.3^{+1.7}_{-2.9}$ | $3.21\pm 0.29$ | $3.21\pm 0.29$ | ND
ZTF18aacajqc | 10:29:46.791 | 40:19:13.636 | $0.0673$ | $-3.2^{+0.3}_{-0.3}$ | $4.0^{+1.9}_{-2.7}$ | $1.1^{+1.4}_{-0.9}$ | ND | ND | -
ZTF18aacbjdm | 12:32:3.637 | 20:09:29.529 | $0.0636$ | $-1.6^{+0.1}_{-0.2}$ | $2.4^{+2.5}_{-2.0}$ | $4.2^{+0.8}_{-2.6}$ | ND | ND | $3.6\pm 1.07$
ZTF18aaccaxc | 13:37:39.948 | 39:09:16.941 | $0.0198$ | $-3.3^{+0.1}_{-0.2}$ | $1.1^{+3.3}_{-0.6}$ | $0.8^{+3.9}_{-0.8}$ | $1.54\pm 0.27$ | $1.54\pm 0.27$ | -
ZTF18aacckko | 14:05:44.376 | 40:51:16.676 | $0.0664$ | $-2.0^{+0.3}_{-0.2}$ | $3.0^{+2.8}_{-1.6}$ | $1.8^{+2.2}_{-1.6}$ | ND | ND | -
ZTF18aacddjc | 13:42:20.173 | 38:42:9.52 | $0.0788$ | $-3.7^{+0.4}_{-0.5}$ | $3.3^{+2.7}_{-2.6}$ | $3.2^{+92.7}_{-2.8}$ | ND | ND | -
ZTF18aacdpbi | 09:05:14.486 | 41:51:53.493 | $0.1764$ | $-2.7^{+0.3}_{-0.2}$ | $1.5^{+0.8}_{-0.4}$ | $0.1^{+0.7}_{-0.1}$ | ND | ND | -
ZTF18aacdvjp | 09:37:28.578 | 32:45:48.31 | $0.127$ | $-2.2^{+0.3}_{-0.3}$ | $2.1^{+3.2}_{-0.9}$ | $0.9^{+2.5}_{-0.8}$ | ND | ND | -
ZTF18aachojf | 08:39:49.67 | 48:47:1.667 | $0.0392$ | $-2.4^{+0.0}_{-0.1}$ | $4.7^{+1.3}_{-2.6}$ | $3.9^{+1.0}_{-2.0}$ | ND | ND | -
ZTF18aacrkse | 09:05:14.481 | 41:51:53.825 | $0.176$ | $-2.7^{+0.3}_{-0.3}$ | $1.7^{+2.8}_{-0.7}$ | $0.5^{+2.5}_{-0.4}$ | ND | ND | -
ZTF18aadgbva | 09:11:13.384 | 40:01:11.238 | $0.201$ | $-2.5^{+0.3}_{-0.2}$ | $3.2^{+2.6}_{-1.6}$ | $1.7^{+2.2}_{-1.5}$ | ND | ND | -
ZTF18aaercku | 09:19:10.523 | 25:49:53.96 | $0.366$ | $-2.9^{+0.3}_{-0.3}$ | $2.8^{+3.1}_{-1.4}$ | $0.8^{+1.7}_{-0.8}$ | ND | ND | ND
ZTF18aahfere | 10:38:53.307 | 39:21:51.218 | $0.0548$ | $-2.5^{+0.3}_{-0.3}$ | $2.4^{+3.3}_{-0.9}$ | $0.4^{+1.0}_{-0.4}$ | $1.08\pm 0.24$ | $1.08\pm 0.24$ | -
ZTF18aahfhsm | 10:19:6.786 | 23:18:37.839 | $0.0646$ | $-2.2^{+0.3}_{-0.3}$ | $2.5^{+3.4}_{-1.6}$ | $1.8^{+2.8}_{-1.8}$ | ND | ND | ND
ZTF18aahfohe | 12:16:7.085 | 50:49:30.174 | $0.031$ | $-2.1^{+0.3}_{-0.2}$ | $1.7^{+1.6}_{-0.6}$ | $0.4^{+1.8}_{-0.4}$ | $3.46\pm 0.25$ | $3.46\pm 0.25$ | -
ZTF18aahfssj | 12:30:59.742 | 35:45:42.828 | $0.1004$ | $-1.4^{+0.1}_{-0.2}$ | $4.4^{+1.5}_{-2.9}$ | $3.1^{+1.4}_{-2.5}$ | ND | ND | -
ZTF18aahgojc | 13:37:39.821 | 39:09:16.036 | $0.0198$ | $-3.6^{+0.3}_{-0.6}$ | $1.4^{+3.6}_{-0.9}$ | $1.2^{+3.6}_{-1.1}$ | $1.54\pm 0.27$ | $1.54\pm 0.27$ | -
ZTF18aahhuol | 11:37:24.523 | 35:09:12.619 | $0.263$ | $-3.1^{+0.3}_{-0.3}$ | $3.8^{+2.1}_{-1.7}$ | $0.8^{+0.9}_{-0.7}$ | ND | ND | -
ZTF18aahhvqh | 12:26:30.999 | 25:25:22.045 | $0.134$ | $-2.5^{+0.3}_{-0.3}$ | $2.4^{+2.7}_{-0.9}$ | $0.7^{+1.8}_{-0.7}$ | ND | ND | ND
ZTF18aahiqst | 11:03:40.32 | 37:29:25.08 | $0.0745$ | $-3.0^{+0.3}_{-0.3}$ | $4.3^{+1.6}_{-2.7}$ | $0.7^{+0.7}_{-0.7}$ | $2.15\pm 0.24$ | $2.15\pm 0.24$ | -

Note. — Properties of the 250 variable DPE candidates in ZTF. Objects in the
table are arranged in lexigraphical order by ZTF name. Spectroscopic redshifts
from SDSS are shown in the 4th column. In columns 5-7 we show the amplitude,
power law index and turnover frequency from modeling of the power spectrum
derived from the g-band ZTF light curve (see Section 3). In columns 8-10 we
show the the radio fluxes for epoch 1 (2017-2018) and epoch 2 (2019-2021) of
the 20cm VLASS survey and for epoch 1 of the 34cm RACS-low survey. Non-
detections are indicated by ND, and a dash indicates that the source was not
within the surveyed region.

Table 2: Best-fit accretion disk parameters (full table in appendix).

ZTF ID | $\xi_{1}$ | $\xi_{2}$ |  $\sigma$ (km/s) |  $i$ (deg) | $q$ |  $w$ (deg) | $A_{s}$ |  $\psi$ (deg) |  $\phi$ (deg)
---|---|---|---|---|---|---|---|---|---
ZTF18aaaotwe | $160^{+20}_{-40}$ | $2350^{+1140}_{-1100}$ | $2220^{+140}_{-110}$ | $12^{+1}_{-1}$ | $2.0^{+0.3}_{-0.3}$ | $70^{+10}_{-7}$ | $7^{+1}_{-1}$ | $40^{+10}_{-10}$ | $330^{+40}_{-40}$
ZTF18aaaovpz | $210^{+70}_{-140}$ | $1770^{+200}_{-250}$ | $1040^{+300}_{-430}$ | $30^{+2}_{-1}$ | $1.2^{+0.3}_{-1.0}$ | $59^{+6}_{-6}$ | $7^{+1}_{-1}$ | $310^{+10}_{-10}$ | $190^{+10}_{-10}$
ZTF18aaavwka | $310^{+100}_{-100}$ | $2550^{+40}_{-40}$ | $230^{+60}_{-70}$ | $18^{+1}_{-1}$ | $1.1^{+0.2}_{-0.3}$ | $62^{+14}_{-13}$ | $1^{+1}_{-1}$ | $50^{+30}_{-10}$ | $320^{+60}_{-320}$
ZTF18aabkubl | $180^{+50}_{-50}$ | $310^{+70}_{-80}$ | $670^{+120}_{-120}$ | $13^{+1}_{-1}$ | $1.6^{+0.5}_{-0.6}$ | $55^{+19}_{-16}$ | $5^{+1}_{-1}$ | $30^{+20}_{-20}$ | $290^{+30}_{-20}$
ZTF18aabylvn | $210^{+10}_{-20}$ | $3980^{+20}_{-10}$ | $1400^{+20}_{-10}$ | $19^{+1}_{-1}$ | $1.7^{+0.0}_{-0.0}$ | $70^{+2}_{-2}$ | $7^{+1}_{-1}$ | $330^{+10}_{-10}$ | $140^{+10}_{-10}$
ZTF18aacajqc | $130^{+20}_{-10}$ | $3380^{+420}_{-390}$ | $590^{+60}_{-50}$ | $19^{+1}_{-1}$ | $0.9^{+0.1}_{-0.1}$ | $69^{+7}_{-6}$ | $7^{+1}_{-1}$ | $300^{+10}_{-10}$ | $200^{+10}_{-10}$
ZTF18aacbjdm | $220^{+10}_{-10}$ | $760^{+70}_{-60}$ | $1450^{+10}_{-10}$ | $8^{+1}_{-1}$ | $2.4^{+0.1}_{-0.1}$ | $77^{+3}_{-2}$ | $7^{+1}_{-1}$ | $310^{+10}_{-10}$ | $250^{+10}_{-10}$
ZTF18aaccaxc | $160^{+30}_{-50}$ | $3820^{+10}_{-10}$ | $940^{+120}_{-120}$ | $11^{+1}_{-1}$ | $1.9^{+0.2}_{-0.2}$ | $69^{+19}_{-8}$ | $6^{+1}_{-1}$ | $40^{+40}_{-20}$ | $350^{+10}_{-10}$
ZTF18aacckko | $200^{+20}_{-30}$ | $3420^{+10}_{-10}$ | $1620^{+0}_{-0}$ | $21^{+1}_{-1}$ | $1.9^{+0.1}_{-0.1}$ | $41^{+22}_{-28}$ | $3^{+2}_{-2}$ | $360^{+10}_{-10}$ | $240^{+10}_{-230}$
ZTF18aacddjc | $320^{+80}_{-90}$ | $2090^{+20}_{-30}$ | $1620^{+260}_{-190}$ | $17^{+1}_{-1}$ | $1.4^{+0.4}_{-0.6}$ | $33^{+19}_{-31}$ | $3^{+2}_{-2}$ | $360^{+40}_{-50}$ | $30^{+70}_{-40}$
ZTF18aacdpbi | $190^{+30}_{-40}$ | $2430^{+50}_{-50}$ | $1870^{+60}_{-50}$ | $13^{+1}_{-1}$ | $1.3^{+0.2}_{-0.2}$ | $75^{+6}_{-4}$ | $7^{+1}_{-1}$ | $320^{+10}_{-10}$ | $210^{+30}_{-30}$
ZTF18aacdvjp | $170^{+10}_{-10}$ | $3900^{+150}_{-70}$ | $1250^{+40}_{-40}$ | $17^{+1}_{-1}$ | $1.6^{+0.0}_{-0.0}$ | $37^{+8}_{-7}$ | $7^{+1}_{-1}$ | $340^{+10}_{-10}$ | $70^{+20}_{-20}$
ZTF18aachojf | $190^{+20}_{-20}$ | $1010^{+20}_{-120}$ | $730^{+30}_{-30}$ | $11^{+1}_{-1}$ | $1.4^{+0.3}_{-0.3}$ | $79^{+1}_{-0}$ | $8^{+1}_{-1}$ | $60^{+10}_{-10}$ | $290^{+10}_{-10}$
ZTF18aacrkse | $200^{+40}_{-50}$ | $2550^{+70}_{-70}$ | $1870^{+60}_{-60}$ | $13^{+1}_{-1}$ | $1.4^{+0.2}_{-0.3}$ | $74^{+6}_{-4}$ | $7^{+1}_{-1}$ | $320^{+10}_{-10}$ | $210^{+20}_{-20}$
ZTF18aadgbva | $250^{+30}_{-40}$ | $3730^{+360}_{-200}$ | $280^{+80}_{-80}$ | $18^{+1}_{-1}$ | $1.5^{+0.1}_{-0.1}$ | $31^{+23}_{-34}$ | $0^{+1}_{-1}$ | $0^{+40}_{-40}$ | $140^{+250}_{-260}$
ZTF18aaercku | $290^{+60}_{-90}$ | $2260^{+830}_{-1220}$ | $1250^{+80}_{-120}$ | $11^{+1}_{-1}$ | $1.9^{+0.5}_{-0.4}$ | $50^{+25}_{-19}$ | $6^{+3}_{-1}$ | $30^{+30}_{-10}$ | $220^{+10}_{-10}$
ZTF18aahfere | $230^{+30}_{-30}$ | $1220^{+190}_{-310}$ | $1250^{+70}_{-60}$ | $12^{+1}_{-1}$ | $1.7^{+0.5}_{-0.6}$ | $38^{+6}_{-15}$ | $6^{+1}_{-1}$ | $320^{+10}_{-20}$ | $200^{+20}_{-20}$
ZTF18aahfhsm | $200^{+20}_{-20}$ | $1370^{+80}_{-80}$ | $1000^{+50}_{-50}$ | $11^{+1}_{-1}$ | $1.5^{+0.3}_{-0.3}$ | $78^{+4}_{-2}$ | $7^{+1}_{-1}$ | $50^{+10}_{-10}$ | $290^{+10}_{-10}$
ZTF18aahfohe | $240^{+10}_{-10}$ | $3960^{+70}_{-30}$ | $900^{+90}_{-110}$ | $23^{+1}_{-1}$ | $1.7^{+0.1}_{-0.1}$ | $44^{+5}_{-11}$ | $7^{+1}_{-1}$ | $340^{+10}_{-10}$ | $70^{+10}_{-10}$
ZTF18aahfssj | $1880^{+170}_{-90}$ | $3800^{+320}_{-140}$ | $2040^{+120}_{-160}$ | $15^{+5}_{-3}$ | $1.5^{+0.5}_{-0.6}$ | $44^{+29}_{-25}$ | $2^{+1}_{-2}$ | $20^{+40}_{-30}$ | $290^{+20}_{-10}$
ZTF18aahgojc | $190^{+40}_{-30}$ | $3820^{+10}_{-10}$ | $510^{+290}_{-460}$ | $14^{+3}_{-2}$ | $1.9^{+0.2}_{-0.2}$ | $35^{+15}_{-34}$ | $7^{+1}_{-1}$ | $310^{+10}_{-100}$ | $30^{+140}_{-210}$
ZTF18aahhuol | $130^{+10}_{-10}$ | $1000^{+10}_{-10}$ | $1470^{+1020}_{-1050}$ | $53^{+4}_{-4}$ | $1.8^{+0.7}_{-0.6}$ | $37^{+27}_{-35}$ | $6^{+1}_{-1}$ | $350^{+40}_{-60}$ | $320^{+80}_{-250}$
ZTF18aahhvqh | $110^{+30}_{-80}$ | $1930^{+10}_{-10}$ | $880^{+0}_{-10}$ | $17^{+1}_{-1}$ | $0.8^{+0.0}_{-0.5}$ | $14^{+6}_{-10}$ | $0^{+1}_{-1}$ | $360^{+10}_{-10}$ | $360^{+10}_{-80}$
ZTF18aahiqst | $100^{+20}_{-10}$ | $1310^{+40}_{-50}$ | $750^{+40}_{-40}$ | $21^{+1}_{-1}$ | $0.8^{+0.0}_{-0.0}$ | $68^{+6}_{-6}$ | $3^{+1}_{-1}$ | $300^{+10}_{-10}$ | $190^{+10}_{-10}$

Note. — Best-fit disk parameters from modeling the H$\alpha$ broad-line
regions of the AGN with the circular accretion disk model from Chen & Halpern
(1989). We show the following H$\alpha$ disk parameters: inner radius
$\xi_{1}$ (gravitational radii), outer radius $\xi_{2}$ (gravitational radii),
turbulent broadening $\sigma$ (km/s), inclination angle $i$ (deg), spiral arm
width $w$ (deg), spiral arm amplitude expressed as contrast ratio $A_{s}$,
spiral arm pitch angle $\psi$ (deg) and spiral arm phase $\phi$ (deg).

In order to find the AGN with double-peaked broad lines amongst the sample of
1549 broad-line AGN, we modeled the archival SDSS spectra of the AGN. We first
used Penalized Pixel Fitting (pPXF) (Cappellari & Emsellem, 2003; Cappellari,
2017) to model and subtract the stellar continuum and absorption lines. The
continuum-subtracted spectra of the full AGN sample have been made available
in a github repo containing the intermediate data
products111https://github.com/charlotteaward/ZTF-DPEs.

###  2.2 Fitting of broad H$\alpha$ profiles with circular accretion disk
models

After continuum subtraction we modeled the H$\alpha$ broad-line region of each
AGN, regardless of whether there were discernible double peaks or shoulders,
with the circular accretion disk model from Chen & Halpern (1989). We fit a
circular accretion disk model describing the H$\alpha$ broad emission line
regions combined with the narrow emission lines from H$\alpha$, [S ii]
$\lambda$6717, 6731, [N ii] $\lambda$6550, 6575, and [O i] $\lambda$6302,
6366. The circular accretion disk model was chosen over an elliptical
accretion disk model because circular models with rotating spiral arms have
been shown to better reproduce the timescale of profile variability observed
in DPEs compared to precessing elliptical disks (Eracleous et al., 2009).

The disk models had the following free parameters: the inclination angle $i$
(deg) where 0° is face-on and 90° is edge-on, a local turbulent broadening
parameter $\sigma$ (km/s), the emissivity power law index $q$, and the inner
and outer dimensionless gravitational radii of the disk $\xi_{1}$ and
$\xi_{2}$. We enabled a single spiral arm with free parameters amplitude
$A_{s}$ (expressed as a contrast ratio relative to the rest of the disk),
orientation angle $\phi$ (deg), width $w$ (deg), and pitch angle $\psi$ (deg).
This was required to describe the flux ratio of the red and blue shoulders
being $>$1 in a fraction of spectra, which has been commonly observed in other
disk emitters (e.g. Storchi‐Bergmann et al., 2003). We applied the following
bounds on some parameters via a uniform prior: $\xi_{1}>50$, $w<80$,
$0<\psi<60$, and $A_{s}<8$, based on typical parameters found for DPEs with
detailed spiral arm modeling of multi-epoch spectra (e.g. Schimoia et al.,
2012, 2017). We did not include a disk wind (Murray & Chiang, 1996; Flohic et
al., 2012; Nguyen et al., 2018; Chajet & Hall, 2013) in the models because the
circular disk with a single spiral arm adequately described all spectra.

The disk model was fitted simultaneously with a model for the forbidden narrow
emission lines overlapping the H$\alpha$ broad-line region. The [N ii], [S
ii], [O i] doublet flux ratios were fixed to theoretical values of 2.95, 1.3,
and 0.33 respectively. The narrow lines were described by two component
Gaussians of the same central wavelength with 3 free parameters which were
common for all narrow lines: the width of the first Gaussian component
$\sigma_{1}$, the width of the second Gaussian component $\sigma_{2}$, and the
flux ratio of the two components $f_{1}/f_{2}$. The amplitudes of the spectral
lines are linear parameters, and so for computational expediency, we used a
profile likelihood technique in which, for a given set of narrow line, broad
line, and disk model parameters, we determined the amplitudes via least
squares optimization.

We first found a reasonable initial fit using the nonlinear least-squares
optimisation implemented in Python using the scipy package. We then explored
the posteriors using emcee (Foreman-Mackey et al., 2013) with 60 walkers
initialized at the best-fit values from the least-squares fit, distributed
according to the 1$\sigma$ error found from the least-squares covariance
matrix. For each spectrum, the emcee fitting was run for 2400 iterations with
a burn-in time of 1800 iterations.

Figure 2: Distribution of the three disk parameters used to separate DPEs from
AGN with ‘normal’ broad lines. DPEs were classified as those with inclination
angle $>14$ °, turbulent broadening $>600$ km/s, and inner radius $<1200$
gravitational radii.

###  2.3 Results from disk model fitting: profile shapes and DPE fractions

We produced disk models for 1302 out of the 1549 AGN: the remainder had
H$\alpha$ regions too strongly dominated by the narrow emission lines to
produce reliable fits to the broad-line component. The H$\alpha$ broad lines
for all AGN in the sample were well-described by our disk$+$narrow line model.
Examples of double-peaked H$\alpha$ disk profiles and their fits are shown in
Figure 1. We note that the broad lines and corresponding disk models show a
variety of shapes, including well-separated blue and red peaks (e.g.
ZTF18aahiqst: Figure 1f), a large blue-red shoulder flux ratio such that they
appear to have a single velocity-offset broad-line (ZTF18accwjao: Figure 1j),
closely separated peaks which still require a dip in the center to correctly
describe the profile (ZTF19aadgigp: Figure 1d), and very boxy profiles
(ZTF18achchge: Figure 1e) – all are well described by a circular disk model
with typical disk parameters.

In order to separate the visually classifiable DPEs from other broad-line AGN
without a dip between shoulders or a velocity-offset peak, we applied cutoffs
to particular disk parameters. We found that requiring an inclination angle
$i>14$°, turbulent broadening $\sigma>600$ km/s, and inner radius
$\xi_{1}<1200$ was extremely effective at identifying almost all classical
DPEs with obvious shoulders or asymmetries such as those shown in Figure 1,
while removing AGN with more symmetric profiles monotonically increasing to
the central velocity. The distributions of the three parameters used for DPE
classification and their cutoffs are shown in Figure 2. The cutoffs resulted
in automatic classification of 260 sources as DPEs and 1042 as ‘normal’ broad-
line AGN. We then visually inspected both samples to ensure that all DPE
candidates had either: a clear dip or plateau between shoulders, a velocity
offset between the peak of the broad line and the H$\alpha$ narrow line $>500$
km/s, or a $>0.8$ flux ratio asymmetry between red and blue peaks. We found
that 22 DPE candidates did not have clear evidence for any of these features
and they were moved to the control sample. Similarly, we inspected the control
sample for spectra containing the aforementioned features of a DPE profile,
and found that 12 DPEs were missed by the disk parameter classification
criteria. These were moved from the control sample to the DPE sample.

Figure 3: Distribution of three key quantities derived from disk profile
fitting after splitting the sample into DPEs and ‘normal’ broad-line AGN.
Left: The ratio of the sine of the inclination angle to the square root of the
outer radius, which determines the separation between the two peaks. Center:
The ratio of the outer to inner radius, which determines the how distinct the
two peaks of the profile are and whether the profile is ‘boxy’. Right: The
best-fit redshifts of the DPE sample and the broad-line AGN control sample.

Our automatic classification procedure, followed by visual reclassification of
34 (3%) of spectra, resulted in final sample sizes of 250 DPEs and 1052
control AGN. This resulted in 19.2% of our strongly variable broad-line AGN
sample being classified as DPEs. The best-fit H$\alpha$ disk parameters of the
objects classified as DPEs are shown in Table 2 and histograms of each
parameter are shown in the Appendix in Figure 10.

In Figure 3 we show three key quantities derived from the disk modeling for
the DPE and control AGN samples. Firstly, we show that the two samples are
well-separated when we plot their distributions of $\sin i/\sqrt{\xi_{2}}$,
which describes the separation between the blue and red shoulders in the
circular disk model. This indicates that our sample separation criteria has
achieved what we expect - to discriminate between broad-lines with well-
separated shoulders, regardless of their relative strengths (which may be
affected by phenomena such as spiral arms). Secondly, we show the outer to
inner radius ratio $\xi_{2}/\xi_{1}$, which determines how distinct the two
peaks of the profile appear and how “boxy” the profile appears. We find that
the DPEs tend to have larger ratios of $\xi_{2}/\xi_{1}$. Finally, we show the
redshift distribution of the two populations, where we can see that our
classification criteria is not strongly biased by redshift for our redshift
range of $z<0.4$.

##  3 Variability analysis

###  3.1 Construction of optical and mid-IR light curves

In order to produce light curves of the DPEs and AGN control sample using both
positive and negative photometry from ZTF difference imaging, we used the ZTF
forced photometry service (Masci et al., 2019). We extracted all available
photometry from the ZTF public and partnership fields between 2018-01-01 and
2023-05-01. After removing poor quality images by requiring the procstatus
flag be $=0$, we measured the baseline flux from the reference images, applied
zeropoints, and combined the baseline flux measured from the reference images
and the single epoch fluxes to produce g- and r-band light curves of the two
samples.

Figure 4: Notable optical (ZTF) and mid-IR (WISE) light curves of selected
DPEs. The left y-axes display the ZTF AB magnitudes while the right y-axes
display the WISE Vega magnitudes. We include light curves of previously
reported SMBH merger candidate (ZTF18aarippg (a)), a DPE with a complex and
time-varying double-peaked profile shown later in Figure 9 (ZTF18aaymybb (b)),
a previously reported CLAGN candidate (ZTF19aagwzod (c)), a DPE with a clear
IR echo (ZTF18aaznjgn (d)), and two DPEs exhibiting quasi-regular fluctuations
(ZTF18aalslhk (e) and ZTF18aakehue (f)).

Examples of optical light curves of selected DPEs are shown in Figure 4. We
present the updated ZTF light curve of ZTF18aarippg, the previously reported
candidate for an inspiraling SMBH binary (Jiang et al., 2022). We have also
selected the particular examples ZTF18aalslhk and ZTF18aakehue because, by
eye, it appears that the light curves may be better fit by a damped harmonic
oscillator model over a typical AGN damped random walk model, making them most
comparable to ZTF18aarippg. We note that apparently quasi-periodic variability
arises naturally in a fraction damped random walk light curves, but we
nonetheless present these specific cases as possible subjects of interest for
periodicity analysis in future work. We also present the light curves of 2
DPEs for which we present time-domain spectroscopic monitoring in Section 5
(ZTF18aaymybb, and ZTF19aagwzod).

The AGN and DPE samples also had recent mid-IR photometry available in W1
(3.4$\mu$m) and W2 (4.6$\mu$m) bands from the WISE mission (Mainzer et al.,
2011, 2014). We obtained the neoWISE light curves from
IRSA222https://irsa.ipac.caltech.edu/Missions/wise.html. NeoWISE observes each
field with a $\sim 6$ month cadence, taking multiple observations over a short
$<2$ day period. We report the median and standard deviation of the
observations taken upon each $\sim 6$ monthly visit to the field. The mid-IR
light curves of selected DPEs are also shown in Figure 4.

In a number of cases, the WISE light curves show the presence of mid-IR dust
echoes with delays of $\sim 200$ days relative to the optical (e.g.
ZTF19aagwzod, ZTF18aaznjgn, as well as ZTF18acvcadu which is not pictured). In
other cases the delays appear to be very long, on timescales of $>1000$ days
(ZTF18abzweee, not pictured, had such a delay). For a large fraction of cases,
the WISE light curve follows the long term variation of the optical light
curve, but we do not resolve shorter timescale ($<$1 year) variability (e.g.
ZTF18aalslhk, ZTF18aaymybb). Future work could investigate the relationship
between best-fit inclination angles from the disk model fitting and the delay
of the mid-IR echo from the dusty torus. The ZTF and WISE light curves of the
full AGN sample have also been made available in the github repo containing
the intermediate data products (see footnote 1).

###  3.2 Power spectrum analysis

In order to quantify the characteristic timescales and amplitude of optical
variability in the DPE and control AGN populations, we generated power spectra
of the ZTF light curves. We adopted the following method to produce g and
r-band power spectra from the unevenly sampled ZTF data. To prepare the light
curves for power spectra production we first removed low-significance
observations with uncertainties $>$10 times the median uncertainty. To reduce
outliers we normalized the fluxes by the best-fit linear trend and removed
data which deviated by more than 7 median absolute deviations. This outlier-
removal approach may result in smoothing or suppression of rapid fluctuations
in the light curve, but is nonetheless required to remove poor quality
photometric data points.

Figure 5: For three DPE and one control AGN example Left: The g- and r-band
relative flux vs time from ZTF; Center: The power spectrum of the g-band light
curve derived from the GLS method (green), the Welch periodogram (orange), the
best-fit power law + white noise + low frequency turnover model with free
power law index (blue solid), the best-fit power law + white noise + low
frequency turnover model with power law index fixed to 2 (blue dashed), and
the light curve noise range estimate (gray shaded); Right: The same as above
but for the r-band light curve. These four power spectra were selected to
display the range of power law spectral indices and high frequency turnovers
observed in the sample. Figure 6: Histograms of three parameters derived from
fitting of g-band ZTF power spectra: PSD amplitude, power law index and
position of the low frequency break. We show the distributions for the DPE and
control AGN samples, and note the locations of parameters derived for 5
notable DPEs: the SMBH merger candidate (ZTF18aarippg), the flaring CLAGN
candidate (ZTF19aagwzod), a DPE with a quasi-periodic signal (ZTF18aalslhk),
and two DPEs with unusual double-peaked profiles (ZTF18aaymybb and
ZTF18abxxohm; see section 5). Note that break frequencies less than 1.8 (the
inverse of $0.1\times$ the light curve baseline) may be unreliable.

We next binned the data to uniform time bins with full width 7.0 d. For each
bin we estimated the mean flux as the uncertainty-weighted sum of the
individual fluxes. The binned measurements were more robust against single-
observation outliers, so we further filtered out flux points which differed
from the resulting mean values by $>$5$\sigma$, where $\sigma$ refers to the
uncertainty on the average flux obtained by propagation of uncertainty. We did
this iteratively until no individual outliers remained. We next eliminated
bins with large flux uncertainties, $>10$ times the median, typically those
which contain only a single low-significance observation. To identify outlying
time bins, we computed the difference in mean flux between each bin and its
neighbors, computed the standard deviation of this population of differences,
and removed any time bins with a difference greater than 5 standard
deviations. The resulting uniformly binned light curves generally retained
$>$90% of the original data, and most obvious outliers were automatically
removed.

We computed the power spectral density with a generalized least squares (GLS)
method following the approach of Coles et al. (2011). Specifically, we adopted
a model for the data in the time domain,

$F(t)=F_{0}+F_{1}(t-t_{0})+\sum_{k=1}^{N}\Bigg{\\{}a_{k}\sin\left[2\pi
k(t-t_{0})\over T\right]\quad$ $\hbox to100.00015pt{\hss}+b_{k}\cos\left[2\pi
k(t-t_{0})\over T\right]\Bigg{\\}},$ (1)

with $T$ the total data span. In other words, the model comprises a mean flux,
a linear flux ramp, and a Fourier series with coefficients $a_{k}$ and $b_{k}$
describing the variability. To constrain the many degrees of freedom in the
Fourier series, we assumed a model for the power spectral density (PSD, P(f,
$\lambda$)) and that the Fourier coefficients were distributed as a normal
distribution with width $\sqrt{P}/2$. Our final model for P(f) was a power law
of index $\gamma$ with an additional white noise component (W) at high
frequencies and a turnover to a flat spectrum at low frequencies ($f_{c}$):

$P(f)=W+A\left(f^{2}+f_{c}^{2}\over 1+f_{c}^{2}\right)^{-\gamma/2}$ (2)

To determine the parameters of these models, $\lambda$, along with the time-
domain components $F_{0}$, $F_{1}$, and the Fourier coefficients, we used
generalized least squares optimization. We selected $N$, the number of Fourier
components, as half of the number of data points, such that the highest
frequency $N/T$ was the Nyquist frequency. The resulting fit simultaneously
provided estimates of the PSD parameters, the PSD itself (via the Fourier
components), and the total log likelihood for the model. We then used emcee
(Foreman-Mackey et al., 2013) to sample over each free parameter for 500
iterations with a burn-in time of 100 iterations to determine the best-fit
values and $1\sigma$ uncertainties for the amplitude, power spectral index,
white noise level and low frequency turnover. We also produced an alternative
set of models with a power law index fixed to a value of 2, for comparison to
the models in which the power law index was allowed to vary. Examples of 4 DPE
light curves and their corresponding power spectra are shown in Figure 5.

For comparison to the power spectral densities (PSDs) generated via the GLS
method, we additionally estimated a model independent power spectral density
using Welch’s method, based on the weighted, overlapped sum of Hann-windowed
Fourier transforms. Our choice of 128 data points per segment reduced noise
while retaining reasonable sensitivity to low-frequency power. The PSD
estimate obtained in this way is shown in orange solid lines in the power
spectra plots of Figure 5.

The power spectra shown in Figure 5 demonstrate how a high frequency turnover
is required in a fraction of cases in order to model an intrinsic white noise
component above the noise level which naturally arises from flux uncertainties
in the light curve (shown in gray). ZTF18aarippg is an example of a DPE with a
clear high frequency white noise component. In other cases, (e.g.
ZTF18aalslhk) the power law reaches the light curve noise level before the
intrinsic AGN white noise induces a high frequency turnover. The spectral
indices of the PSDs have a large range: some objects, such as ZTF18aacjtlo,
have steep spectral indices of $\sim 2.4$, while other objects, such as
ZTF18aaadgxi, have very shallow power spectra with spectral indices $\sim
1.3$.

###  3.3 Variability properties of the DPE and control AGN samples

The best-fit power spectrum parameters derived from ZTF g-band light curves
are shown for all DPEs in Table 1. The distributions of power spectral index,
PSD amplitude and turnover frequency are shown in Figure 6. The DPE sample had
a median log amplitude and standard deviation of $-2.65$ and $0.49$
respectively, and a median power law index and standard deviation of $2.50$
and $0.96$. To find the median break frequency we first removed values $<1.8$
yr-1 (the inverse of $0.1\times$ the light curve baseline, where the best-fit
turnovers may be unreliable (Burke et al., 2021)) as well as outliers $>6$
yr-1 arising from poor fits. We found a median break frequency and standard
deviation of $0.77$ and $0.7$ yr-1 respectively for the DPE sample. By
comparison, the control AGN population had a median log amplitude and standard
deviation of $-2.68$ and $0.48$, a median power law index and standard
deviation of $2.55$ and $0.94$, and a median break frequency and standard
deviation of $1.1$ and $0.7$ yr-1. Because the high frequency white noise
turnover was only detected at sufficient S/N for a fraction of light curves,
we do not report the white noise levels for each population.

We applied a two sample KS test to each power spectrum parameter to determine
the probability with which we can reject the null hypothesis that the AGN and
DPE power spectrum parameters were drawn from the same distributions. For the
amplitude and power law index parameters we obtain p-values of 0.46 and 0.52,
indicating that we do not have evidence that they were drawn from different
distributions. For the turnover frequency parameter we obtain a p-value of
0.0072, so we can reject the hypothesis that they were drawn from the same
distribution at $>3\sigma$. We also note that a power law index $>2$ was ruled
out to 95% confidence for only 10.1% of AGN and 11.1% of DPEs.

We searched for correlations between the PSD amplitude, turnover frequency and
spectral index parameters from the power spectra and each disk geometry
parameter derived from the spectroscopic fits of the DPE sample. We calculated
the Spearman correlation coefficient and associated p-value for each parameter
combination and found no evidence for correlations between optical variability
parameters and accretion disk geometry parameters.

In summary, our analysis of the power spectra of optical ZTF light curves
finds a wide distribution of variability amplitudes, power law spectra index,
and low frequency turnovers for the ZTF AGN population. We do not find
significant differences between the variability amplitudes and power law
spectral indices of the DPE and control AGN populations, but we do find some
evidence that the low frequency break occurs at lower frequencies for DPEs
compared to ‘normal’ broad-line AGN.

##  4 Radio detections and jet imaging

We undertook a search for radio emission from the DPE and control AGN samples
in the Karl G. Jansky Very Large Array Sky Survey (VLASS; Lacy et al., 2020).
This survey covers a total of 33,885 deg2 in the 2-4 GHz range with an angular
resolution of $\sim 2^{\prime\prime}.5$ and will obtain a coadd $1\sigma$
sensitivity of 1 $\mu$Jy/beam by survey end in 2024. We searched for
crossmatches within $10^{\prime\prime}$ in Table 2 of the VLASS Epoch 1 and 2
Quick Look Catalogues which contains $\sim 700,000$ compact radio sources with
$>1$ mJy/beam detections associated with mid-IR hosts from the unWISE catalog
(Gordon et al., 2021).

Figure 7: Radio imaging cutouts from RACS and VLASS showing the radio jets
around three DPEs with intermediate inclination angles: ZTF18aarywbt
($i=19^{+1}_{-1}$), ZTF19abizomu ($i=14^{+1}_{-2}$) and ZTF18aaqdmih
($i=35^{+2}_{-2}$). The greyscale colors indicate the observed fluxes in
linear space while the contour intervals are in log space. In all cases the
AGN is in the image center.

We also searched for radio emission in the Rapid ASKAP Continuum Survey
(RACS), with first epoch observations covering the whole southern sky to +41
deg declination with the Australia Square Kilometre Array Pathfinder at a
central wavelength of 887.5 MHz (Hale et al., 2021). We crossmatched our
sample with a $10^{\prime\prime}$ radius to the first Stokes I Source
Catalogue Data Release, which has an estimated 95% point source completeness
at an integrated flux density of $\sim 3$ mJy.

The radio fluxes and non-detections from the two surveys are displayed in
Table 1. Of the DPEs, 29 of 235 in the VLASS survey area were detected (12.3%)
while 23 of 121 in the RACS survey area were detected (19.0%). 66 of 1239
control AGN within the VLASS survey area (5.3%) were detected and 104 of 576
control AGN in the RACS survey area (18.1%) were detected. DPEs were therefore
2.3 times more likely than the control AGN to be detected at 20cm in VLASS. By
contrast, DPEs were just as likely as the control AGN to be detected at 34cm
in RACS.

For those objects with radio detections, we compared the distributions of
radio fluxes measured from VLASS imaging between the DPE and control AGN
samples and found that they were very similar. A two-sample Kolmogorov-Smirnov
test found no evidence to reject the null hypothesis that the radio fluxes of
the two samples were drawn from the same distribution with a p-value of 0.24.
We also found no evidence that any of the disk parameters derived from the
spectroscopic modeling were significantly different between the radio-detected
and radio-undetected samples.

We compared the radio fluxes across the two available VLASS epochs to
determine the fraction of DPEs and control AGN with $>3\sigma$ variability
between 2017-2018 and 2018-2021. We found that 6% of DPEs and 25% of the
control AGN with radio detections exhibited flux changes greater than 3 times
the flux uncertainties between the two epochs.

We checked the RACs and VLASS imaging of radio-detected DPEs using the CIRADA
Image Cutout Web Service333http://cutouts.cirada.ca/ to determine if the radio
detections associated with DPEs were all point sources or if there were
additional radio jets visible in the imaging. We noted that 3 DPEs
(ZTF18aarywbt, ZTF19abizomu and ZTF18aaqdmih, which had inclination angles of
$14<i<35$), had large radio jets emanating from a point source coincident with
the AGN. The RACS and VLASS imaging showing these jet structures is shown in
Figure 7.

##  5 Spectroscopic evolution of DPEs

In order to search for changes in disk morphology over 10-20 year timescales
we obtained follow-up spectra of 12 DPEs for comparison to archival SDSS
spectra. Spectra were taken with either the DeVeny spectrograph on the Lowell
discovery Telescope using a $1.5^{\prime\prime}$ slit, central wavelength of
5700 Å, a spectroscopic coverage of 3600-8000 Å and total exposure times
ranging from 1000-3000 s. Three spectra were taken with the Keck LRIS
spectrograph using a $1.0^{\prime\prime}$ slit, a 400/8500 grating, and
600/4000 grism to obtain spectroscopic coverage over 3500-9500Å, and total
exposure times of 1500 s. Comparisons between recent LDT/LRIS and archival
SDSS spectra, with time intervals ranging from 13-18 years, are shown in
Figure 8.

Of the 12 objects, six show notable changes in the relative fluxes or
positions of the two shoulders in the double-peaked profile. ZTF19aarlffl
(Figure 8e), which had a bright blue shoulder in 2004, exhibited instead a
prominent red shoulder in 2021. ZTF18aarywbt (Figure 8a) and ZTF18aalslhk
(Figure 8c), which had bright blue and red shoulders in 2005 and 2004
respectively, now exhibit only blue shoulders with a smoother shape.
ZTF19aayjrsx (Figure 8i), an off-nuclear AGN candidate from Ward et al. (2021)
showed a decrease in the peak velocity of the red shoulder, while ZTF19aautrth
(Figure 8h), another off-nuclear AGN candidate, shows no line profile changes.
ZTF18aarippg (Figure 8d) now has prominent blue and red shoulders and high
velocity when it previously only had a fainter blue shoulder, as previously
noted by Jiang et al. (2022). Such substantial variations in relative flux of
the blue and red shoulders have been noted in many other DPEs such as Arp
102B, 3C 390.3, NGC 1097, NGC 7213, 3C 59 and 1E 0450.3–1817 and have been
modeled by precession of hotspots and spiral arms (Storchi-Bergmann et al.,
2002; Sergeev et al., 2002; Gezari et al., 2007; Lewis et al., 2010; Jovanović
et al., 2010; Popović et al., 2011; Schimoia et al., 2012; Shapovalova et al.,
2013; Popović et al., 2014b; Schimoia et al., 2017).

Figure 8: Comparison of Balmer broad line structures from recent spectra LDT
or Keck spectra (orange) and archival SDSS spectra (green) of 12 DPEs. Six of
twelve show changes in the relative fluxes of the blue and red shoulder.

###  5.1 Spectroscopic monitoring of two unusual DPEs and a candidate CLAGN

While undertaking spectroscopic follow-up of ZTF transients, we
serendipitously discovered two new and atypical DPEs. ZTF18aaymybb was
observed to have a complex double-peaked profile with a large dip between the
central wavelength and the red shoulder which cannot be well-described by a
circular disk model. Another object, ZTF18abxxohm, had two triangular-shaped
broad lines: one at the rest H$\alpha$ wavelength and one at a velocity of
$\sim 2500$ km/s from the rest wavelength. We also undertook detailed
spectroscopic follow-up of changing-look AGN candidate, ZTF19aagwzod, which
was discovered after an optical flare (Frederick et al., 2020). The broad-line
profile of ZTF19aagwzod is typical for DPEs which are well-described by a
circular disk model and the disk parameters can be found in Table 4.

We took 4-7 follow-up spectra of ZTF18aaymybb, ZTF18abxxohm and ZTF19aagwzod
with LDT DeVeny and Keck LRIS during 2018 to 2023 to search for changes to the
profiles on the timescales of months to years. These spectra are shown in
Figure 9. ZTF19aagwzod and ZTF18aaymybb did not show significant changes in
the flux of the blue and red shoulders, although ZTF18aaymybb showed changes
in the shape and peak velocity of the blue shoulder between 2018 and 2023. We
attribute the small, time-varying, spiky structures on the red shoulder of the
ZTF18aaymybb to imperfect removal of the telluric H2O absorption bands in the
wavelength range 8100-8300$\AA$.

ZTF18abxxohm exhibited a gradual decrease in the flux ratio between the red
broad line and the central broad line over the course of 4 years. This is most
obvious in the H$\beta$ profile evolution in the bottom row of Figure 8. The
peak velocity of the red broad line also varied by a few hundred km s-1 over
the course of the 4 years.

Figure 9: H$\alpha$ (above) and $H\beta$ (below) spectra from LDT and Keck
monitoring of 3 new DPEs. The H$\alpha$ spectrum of ZTF18abxxohm has masked
regions due to the presence of a strong telluric absorption line.

##  6 Discussion

###  6.1 Comparing the DPE and control AGN populations

The disk parameter distributions that we find for our optically variable DPE
population are similar to those found in a previous spectroscopically-selected
sample of 116 DPEs in SDSS (Strateva et al., 2003). While the inner radii of
our DPE sample extend to values as high as $\xi_{1}\sim 1800$, most DPEs have
inner radii within the $50<\xi_{1}<800$ range found in the spectroscopically
selected sample. While we do find DPEs at high inclinations in the range
$30<i<50$°, the majority of the population have inclinations in the range
$15<i<30$, which is in agreement with both the disk modeling results of
Strateva et al. (2003) and studies of disk inclination angles from Fe
K$\alpha$ lines (Nandra et al., 1997). This is consistent with the overall
picture that DPEs are usually only detectable at inclinations $i>15$°when the
shoulders have sufficient separation, but are increasingly obscured by the
dusty torus at inclinations $i>30$°(Storchi-Bergmann et al., 2017).

We note that the best-fit parameters for the DPE sample show a strong
preference for high spiral arm amplitudes 10. The spiral arm model is flexible
enough that it can represent a very wide variety of brightness distributions
(e.g. Schimoia et al., 2012) and may therefore simply be a useful
parameterization of different phenomena causing time-varying asymmetric
structures in the disk such as irradiation induced warps. For DPEs like
ZTF18accwjao, which has such a large peak flux ratio between the blue and red
peaks such that it appears to have a single velocity-offset broad-line, a
spiral arm contrast ratio at the limit of $A_{s}=8$ was insufficient to fully
describe the observed double-peaked profile. However, when a greater value of
$A_{s}$ was allowed, the disk model was able to account for the large flux
ratio. We take this to imply that the disk of ZTF18accwjao has an internal
structure which is atypical for most DPEs, and that the circular model
therefore needs greater degrees of freedom to fully model the observed
profile.

Our finding that ZTF DPEs are twice as likely to be radio emitters based on
VLASS survey results is consistent with the FIRST detection rates of the
Strateva et al. (2003) DPE population. However, our finding that DPEs have
similar radio detection rates to the control AGN sample at longer wavelengths
in the RACS survey may point to a steeper and harder radio spectrum in DPEs
arising from their larger than average inclination. We note that the VLASS
catalog required the presence of an associated infrared detection in WISE data
for the radio detection to appear in the catalog, while the RACS survey did
not have this requirement. The longer interferometric baselines of RACS also
meant that AGN with extended jets were more likely to appear in the catalog.
The finding that the radio-detected control AGN were $5\times$ more likely
than radio-detected DPEs to have variable radio fluxes in VLASS on 1-3 year
timescales may arise due to the expected smaller disk inclination angles of
the control AGN. The presence of radio jets in a fraction of DPEs provides
further opportunity to relate jet and spectroscopically-fitted disk
inclinations in subset of the radio-loud population (e.g. Gabányi et al.,
2021).

Our determination that DPEs have similar distributions in variability
amplitude and PSD spectral index compared to other broad-line AGN suggests
that the presence of a visible accretion disk is not associated with a
significant change in the level of optical variability. This is once again
consistent with the idea that the primary difference between DPEs and ‘normal’
broad-line AGN is the viewing angle rather than a difference in the accretion
state of the AGN. We do, however, find that the DPE population has a
statistically significant difference in the location of the low frequency
turnover in the power spectrum, with DPEs having their turnovers appear at a
smaller median frequency of 0.8 yr-1 in comparison to 1.1 yr-1 for normal
broad-line AGN. This finding is comparable to the results from previous
analysis of 8 year light curves from the Catalina Sky Survey Data Release 2
and SDSS Stripe 82 for DPEs and control AGN respectively, where it was found
that that DPEs have characteristic timescales $\sim 2.7\times$ longer than
other broad-line AGN (Zhang & Feng, 2017). We now reach similar conclusions
with a uniform sample of light curves across the DPE and control populations
from a single time-domain survey.

Previous analysis of 67 AGN with $\lesssim 20$ year baseline light curves
found a strong positive correlation between AGN mass and characteristic
timescale of
$\tau=107^{+11}_{-12}\text{days}\left(\frac{M_{\text{BH}}}{10^{8}M_{\odot}}\right)^{0.38^{+0.05}_{-0.04}}$
over a BH mass range of $10^{4}-10^{10}M_{\odot}$ (Burke et al., 2021). We
therefore considered the possibility that the shorter break frequencies
(longer characteristic timescales) of DPE light curves arose because the DPEs
in our sample have intrinsically larger masses than the control AGN, or
because AGN are more likely to be observable as DPEs at higher masses when the
turbulent broadening of the gas in the disk may be larger (see our criteria
for DPE classification, which required that the turbulent broadening parameter
be $>600$ km s-1; Figure 2). To check for a mass–break frequency correlation
in our ZTF power spectra, we searched for a correlation between the best-fit
break frequency and the virial masses measured from broad line widths in Ho &
Kim (2015) for the control AGN sample. We undertook this check with the
control AGN sample because the the black hole mass scaling relations have been
calibrated for quasars with these types of line profiles. We found no obvious
correlation between break frequency and mass for the 312 AGN in the control
AGN sample with available virial masses and with break frequencies $>1.8$ yr-1
where they can be reliably measured with the 5.5 year ZTF baselines. We
confirmed the lack of mass–break frequency correlation by calculating the
Spearman correlation coefficient and obtaining a p-value of 0.33 for the null
hypothesis that they are uncorrelated. We note that the correlation between
mass and break frequency in AGN spectra was also not reproduced in a previous
analysis of $\sim 3$ year baseline AGN light curves from the VLT Survey
Telescope (De Cicco et al., 2022). We are therefore unable to use the masses
of the populations to account for the break frequency differences between the
two samples with the data at hand.

###  6.2 Comparison of disk-emitting AGN and previously reported disk-emitting
tidal disruption events

The distribution of disk parameters we have found for variable AGN makes a
useful point of comparison to accretion disk parameters derived from modeling
of broad-line profiles in transients such as tidal disruption events. Fitting
of an elliptical accretion disk model to the X-ray faint TDE AT2018hyz yielded
parameters $q\sim 2.0$, $i\sim 52-68$, $\sigma\sim 370-640$, $\xi_{1}\sim
1200-1800$, and $\xi_{2}\sim 2600-3100$ which are typical of the ZTF DPE
population except for the large inner radius, large inclination angle, and
small turbulent broadening parameter (Hung et al., 2020). The atypical disk
parameters for AT2018hyz may have arisen from the use of an elliptical disk
model over a circular disk model, as the elliptical disk model has alternative
ways to broaden the profile and account for asymmetries between peaks. The
spiral arm circular disk model fitted to spectra of the repeating TDE
ASASSN14ko derived disk parameters of $i=12$, $\sigma=800$,$A_{s}=2.0$,
$p=-55$ (pitch angle), $\xi_{1}=80$, $\xi_{2}=1600$ which are all typical
values amongst ZTF AGN (Tucker et al., 2021).

###  6.3 Discussion of notable objects

####  6.3.1 Inspiraling SMBH binary candidate ZTF18aaripgg

Our population of 250 optically variable DPEs, many of which have evolving
flux ratios between the red and blue shoulders of the double-peaked profile
over 10-20 year timescales, provides additional context for the original
hypothesis that SDSSJ1430+2303 (ZTF18aarippg) is an inspiraling SMBH binary.
The newly updated light curve of ZTF18aarippg is notable for its continued
possibly quasi-periodic variability, although the original orbital model fit
by Jiang et al. (2022) might not be able to account for the increase in
peak–peak time difference in the most recent 2 cycles.

We expect that the apparently periodic and ringing-down signals arising in
some DPE light curves are the ‘phantom’ periodicities arising naturally from
correlated noise in the AGN light curves. Simulations of light curves arising
from DRW power spectra with $\tau=200$ days and slopes of $\gamma=2$ in 9-yr
CRTS datasets by Vaughan et al. (2016) found that $\sim 1-2$ per 1000 light
curves showed periodic behaviour well-fit by a sinusoidal model. Furthermore,
they found that the fraction with false periods increased to $\sim 1$ in 200
when the spectral index of the PSD was increased from 2 to 3. We note that
large spectral indices of up to 4 were found in a fraction of ZTF AGN power
spectra, and ZTF18aarippg has a relatively large power spectral index of 3.79
relative to the overall DPE and AGN distributions (Figure 6). Given the
expected rates of phantom periodicities and evolving double-peaked broad lines
that we find, we expect that SDSSJ1430+2303 is likely to be a single disk-
emitting AGN, consistent with arguments in other follow-up studies (Dotti et
al., 2022). This conclusion is also consistent with recent theoretical
predictions on the spectroscopic and variability signatures of SMBH binaries
which paint a pessimistic picture for the existence of kinematically
observable SMBH binaries (Kelley, 2020; Kelley et al., 2019).

####  6.3.2 ZTF18aalslhk: A possibly quasi-periodic DPE with an evolving disk
profile

While ZTF18aalslhk appears to have quasi-periodic variability over 4-5 cycles
in its optical light curve, its power spectrum properties are fairly typical
for the observed DPE and AGN distributions, with the light curve having a
larger than median variability amplitude but average values of the power law
index and break frequency (Figure 6). Its disk profile shows major structural
changes likely caused by the precession of a spiral arm or hotspot. Detailed
spectroscopic monitoring of this object over the next few years could test for
a relationship between spiral arm phase and optical flux variations.

####  6.3.3 ZTF18aarywbt: Asymmetric radio jets and an evolving disk profile

ZTF18aarywbt, with fitted disk inclination angle 19°, has a radio point source
at the AGN location visible in 20cm VLASS images, and asymmetric, multi-lobed
radio jets spanning $\sim 1^{\prime}$ ($\sim 10$ kpc) which are visible in
both VLASS and 34cm RACS images. It is also X-ray bright (e.g. Ricci et al.,
2017). This source shows a dramatic change in the double-peaked profile
between archival SDSS spectra from 2005 and follow-up LDT spectra in 2021,
with the complete disappearance of the red shoulder and a decrease in the
velocity of the blue shoulder. Future analysis could investigate whether the
radio jet structures and disk evolution are indicative of disk precession.

####  6.3.4 ZTF18aaymybb: A complex disk profile with disappearing small scale
structure

Previously unreported DPE ZTF18aaymybb has an H$\alpha$ profile which stands
out amongst other disk-emitters because the shoulders are not as smooth and
rounded as the majority of the DPE sample. The cuspiness of the shoulders in
fact makes this object more comparable to Arp102B, the original archetypal DPE
(Chen et al., 1989). The peak velocity of the blue shoulder decreased by $\sim
500$ km/s between 2018 and 2023. We attribute the time-varying, narrow ($\sim
50$ km/s) peaks on the red shoulder of the disk profile to imperfect removal
of telluric H2O absorption features, rather than real features which may arise
due to shocks or local disk motions (Gezari et al., 2007; Lewis et al., 2010),
because they do not appear in the H$\beta$ profile as well. The ZTF light
curve power spectrum of ZTF18aaymybb is fairly typical for the DPE/AGN
population (Figure 5).

####  6.3.5 ZTF18abxxohm: An unusual and evolving velocity-offset broad line

Newly identified DPE ZTF18abxxohm does not have a typical double-peaked
profile which is well described by a circular disk model, instead showing one
broad line at the rest velocity and a second broad line, with no associated
narrow lines, at $\sim 2000$ km/s red of the rest velocity. The red shoulder
exhibited a gradual decrease in the flux over the course of 4 years (Figure
8). The variation in the peak velocity of the red shoulder by a few hundred km
s-1 may be attributable to radial velocity jitter arising from fluctuations in
the continuum which illuminates the broad line gas (Barth et al., 2015; Guo et
al., 2019; Doan et al., 2020). This object has a fairly typical AGN light
curve for this population, with a g-band power spectral index of 3.13.
ZTF18abxxohm may be worthy of further follow-up as an SMBH binary candidate or
an AGN with a high velocity outflow.

####  6.3.6 ZTF19aagwzod: A previously reported CLAGN candidate with a stable
disk profile

ZTF19aagwzod was originally reported as a candidate CLAGN due to its dramatic
increase in magnitude from g=19.6 mag to g=17.9 mag over 34 days observed in
December 2019 (Frederick et al., 2020). The four follow-up spectra taken from
2020-01-23 to 2020-12-06 show a stable disk profile with very little change
over the course of the year following the flare (Figure 8). The initial
discovery report also noted in 2019 that it was UV and X-ray bright, with an
X-ray power law spectral index of $1.8\pm 0.1$ consistent with an AGN
(Frederick et al., 2020).

##  7 Summary and conclusions

We have presented a population of 250 optically variable AGN with double-
peaked or velocity-offset H$\alpha$ and H$\beta$ broad-line profiles
consistent with emission from a circular accretion disk. We found that 19.2%
of broad-line AGN in ZTF with $>1.5$ magnitude optical variability are DPEs.
We have modeled the H$\alpha$ broad line regions as circular disks for both
the DPE sample and control AGN population, and provide a catalog of disk
parameters for the 250 DPEs. We have presented the distributions of best-fit
disk parameters for the DPE population.

We generated power spectra of the DPE and control AGN light curves and fit
them with a power law model with a low frequency turnover and a high frequency
intrinsic white noise component. We have provided a catalog of the power
spectrum parameters derived from the ZTF light curves. We found that DPEs and
other broad-line AGN have similar distributions in PSD amplitude and power law
spectral index, but that DPEs tend to have a turnover in their power spectra
at lower frequencies (and therefore longer characteristic timescales) than
other broad-line AGN.

We have shown that DPEs have much higher radio detection fractions at 20cm
wavelengths than the control AGN sample, but that this is not the case at 34cm
wavelengths. We presented radio imaging of three DPEs with notable jet
structures associated with accretion disks at inclinations of $\sim 14-35$°.

Spectroscopic follow-up of 12 DPEs indicated that $\sim 50$% show significant
changes in the relative strengths of the blue and red shoulders over $\sim 15$
year timescales (Figure 8). There are also many examples of DPE and other AGN
light curves that appear to show quasi-regular fluctuations in their 4-year
optical light curves. The population statistics presented in this paper could
be used to inform future calculation of false positive rates for variability
and spectroscopic selection of SMBH binary candidates.

Our sample of DPEs exhibits only minor differences in optical variability
behavior compared to the remaining broad-line AGN in our ZTF sample. The
results of our spectroscopic and light curve analysis are consistent with the
interpretation that DPEs do not have major physical differences to other
broad-line AGN, and their differing spectroscopic and radio properties may
merely arise from selection effects such as preferences for intermediate disk
viewing angles.

As part of this paper, we have made available the regularly-sampled 5 year
optical ZTF light curves and the corresponding mid-IR WISE light curves
showing delayed dust echos. We have also produced catalogs of
spectroscopically-derived accretion disk geometry parameters, radio fluxes,
and optical power spectrum properties for 250 DPEs. We have presented spectra,
light curves and radio jet imaging of unusual DPEs which may be worthy of
further investigation. As time-domain surveys like ZTF – and, in the near
future, the Legacy Survey of Space and Time at the Vera C. Rubin Observatory
(Ivezić et al., 2019) – continue to discover evolving DPEs, changing-state
AGN, and tidal disruption events with disk-like profiles, we hope that this
population study provides useful context as we work to understand the ways
SMBH accretion disks form and evolve in various scenarios.

##  8 Acknowledgements

Based on observations obtained with the Samuel Oschin Telescope 48-inch and
the 60-inch Telescope at the Palomar Observatory as part of the Zwicky
Transient Facility project. ZTF is supported by the National Science
Foundation under Grant No. AST-2034437 and a collaboration including Caltech,
IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm
University, the University of Maryland, Deutsches Elektronen-Synchrotron and
Humboldt University, the TANGO Consortium of Taiwan, the University of
Wisconsin at Milwaukee, Trinity College Dublin, Lawrence Livermore National
Laboratories, and IN2P3, France. Operations are conducted by COO, IPAC, and
UW. The ZTF forced-photometry service was funded under the Heising-Simons
Foundation grant 12540303 (PI: Graham). This work was supported by the GROWTH
project (Kasliwal et al., 2019) funded by the National Science Foundation
under Grant No 1545949.

This work was supported by a NASA Keck PI Data Award, administered by the NASA
Exoplanet Science Institute. Data presented herein were obtained at the W. M.
Keck Observatory from telescope time allocated to the National Aeronautics and
Space Administration through the agency’s scientific partnership with the
California Institute of Technology and the University of California. The
Observatory was made possible by the generous financial support of the W. M.
Keck Foundation. This research has made use of the Keck Observatory Archive
(KOA), which is operated by the W. M. Keck Observatory and the NASA Exoplanet
Science Institute (NExScI), under contract with the National Aeronautics and
Space Administration.

This research has made use of the CIRADA cutout service at URL
cutouts.cirada.ca, operated by the Canadian Initiative for Radio Astronomy
Data Analysis (CIRADA). CIRADA is funded by a grant from the Canada Foundation
for Innovation 2017 Innovation Fund (Project 35999), as well as by the
Provinces of Ontario, British Columbia, Alberta, Manitoba and Quebec, in
collaboration with the National Research Council of Canada, the US National
Radio Astronomy Observatory and Australia’s Commonwealth Scientific and
Industrial Research Organisation.

This publication also makes use of data products from NEOWISE, which is a
project of the Jet Propulsion Laboratory/California Institute of Technology,
funded by the Planetary Science Division of the National Aeronautics and Space
Administration.

This research has made use of the NASA/IPAC Infrared Science Archive, which is
funded by the National Aeronautics and Space Administration and operated by
the California Institute of Technology.

This research used resources of the National Energy Research Scientific
Computing Center, a DOE Office of Science User Facility supported by the
Office of Science of the U.S. Department of Energy under Contract No. DE-
AC02-05CH11231. P.E.N. acknowledges support from the DOE under grant DE-
AC02-05CH11231, Analytical Modeling for Extreme-Scale Computing Environments.

Work at NRL is supported by NASA.

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##  9 Appendix

Table 3: Properties of the 250 DPE candidates from ZTF

ZTF ID | RA | Dec | z | Amp. | PL index | Turn. | VLASS E1 | VLASS E2 | RACS
---|---|---|---|---|---|---|---|---|---
| (hms) | (dms) |  |  |  | (yr-1) | (Jy) | (Jy) | (Jy)
ZTF18aaaotwe | 13:13:10.376 | 15:45:3.347 | $0.0657$ | $-2.8^{+0.3}_{-0.3}$ | $4.2^{+1.7}_{-2.4}$ | $3.2^{+1.6}_{-2.0}$ | ND | ND | ND
ZTF18aaaovpz | 10:39:13.82 | 09:40:2.779 | $0.217$ | $-2.8^{+0.4}_{-0.7}$ | $2.2^{+3.3}_{-1.0}$ | $0.3^{+1.1}_{-0.3}$ | ND | ND | ND
ZTF18aaavwka | 12:35:44.246 | 16:05:35.978 | $0.0711$ | $-2.5^{+0.0}_{-0.1}$ | $2.5^{+3.4}_{-2.4}$ | $68.0^{+28.1}_{-46.4}$ | ND | ND | ND
ZTF18aabkubl | 11:25:58.744 | 20:05:54.825 | $0.133$ | $-1.2^{+0.0}_{-0.1}$ | $3.9^{+1.9}_{-2.5}$ | $4.2^{+0.7}_{-2.1}$ | $469.95\pm 3.08$ | $469.95\pm 3.08$ | ND
ZTF18aabylvn | 14:17:59.554 | 25:08:12.59 | $0.0163$ | $-1.4^{+0.0}_{-0.0}$ | $0.0^{+0.1}_{-0.0}$ | $3.3^{+1.7}_{-2.9}$ | $3.21\pm 0.29$ | $3.21\pm 0.29$ | ND
ZTF18aacajqc | 10:29:46.791 | 40:19:13.636 | $0.0673$ | $-3.2^{+0.3}_{-0.3}$ | $4.0^{+1.9}_{-2.7}$ | $1.1^{+1.4}_{-0.9}$ | ND | ND | -
ZTF18aacbjdm | 12:32:3.637 | 20:09:29.529 | $0.0636$ | $-1.6^{+0.1}_{-0.2}$ | $2.4^{+2.5}_{-2.0}$ | $4.2^{+0.8}_{-2.6}$ | ND | ND | $3.6\pm 1.07$
ZTF18aaccaxc | 13:37:39.948 | 39:09:16.941 | $0.0198$ | $-3.3^{+0.1}_{-0.2}$ | $1.1^{+3.3}_{-0.6}$ | $0.8^{+3.9}_{-0.8}$ | $1.54\pm 0.27$ | $1.54\pm 0.27$ | -
ZTF18aacckko | 14:05:44.376 | 40:51:16.676 | $0.0664$ | $-2.0^{+0.3}_{-0.2}$ | $3.0^{+2.8}_{-1.6}$ | $1.8^{+2.2}_{-1.6}$ | ND | ND | -
ZTF18aacddjc | 13:42:20.173 | 38:42:9.52 | $0.0788$ | $-3.7^{+0.4}_{-0.5}$ | $3.3^{+2.7}_{-2.6}$ | $3.2^{+92.7}_{-2.8}$ | ND | ND | -
ZTF18aacdpbi | 09:05:14.486 | 41:51:53.493 | $0.1764$ | $-2.7^{+0.3}_{-0.2}$ | $1.5^{+0.8}_{-0.4}$ | $0.1^{+0.7}_{-0.1}$ | ND | ND | -
ZTF18aacdvjp | 09:37:28.578 | 32:45:48.31 | $0.127$ | $-2.2^{+0.3}_{-0.3}$ | $2.1^{+3.2}_{-0.9}$ | $0.9^{+2.5}_{-0.8}$ | ND | ND | -
ZTF18aachojf | 08:39:49.67 | 48:47:1.667 | $0.0392$ | $-2.4^{+0.0}_{-0.1}$ | $4.7^{+1.3}_{-2.6}$ | $3.9^{+1.0}_{-2.0}$ | ND | ND | -
ZTF18aacrkse | 09:05:14.481 | 41:51:53.825 | $0.176$ | $-2.7^{+0.3}_{-0.3}$ | $1.7^{+2.8}_{-0.7}$ | $0.5^{+2.5}_{-0.4}$ | ND | ND | -
ZTF18aadgbva | 09:11:13.384 | 40:01:11.238 | $0.201$ | $-2.5^{+0.3}_{-0.2}$ | $3.2^{+2.6}_{-1.6}$ | $1.7^{+2.2}_{-1.5}$ | ND | ND | -
ZTF18aaercku | 09:19:10.523 | 25:49:53.96 | $0.366$ | $-2.9^{+0.3}_{-0.3}$ | $2.8^{+3.1}_{-1.4}$ | $0.8^{+1.7}_{-0.8}$ | ND | ND | ND
ZTF18aahfere | 10:38:53.307 | 39:21:51.218 | $0.0548$ | $-2.5^{+0.3}_{-0.3}$ | $2.4^{+3.3}_{-0.9}$ | $0.4^{+1.0}_{-0.4}$ | $1.08\pm 0.24$ | $1.08\pm 0.24$ | -
ZTF18aahfhsm | 10:19:6.786 | 23:18:37.839 | $0.0646$ | $-2.2^{+0.3}_{-0.3}$ | $2.5^{+3.4}_{-1.6}$ | $1.8^{+2.8}_{-1.8}$ | ND | ND | ND
ZTF18aahfohe | 12:16:7.085 | 50:49:30.174 | $0.031$ | $-2.1^{+0.3}_{-0.2}$ | $1.7^{+1.6}_{-0.6}$ | $0.4^{+1.8}_{-0.4}$ | $3.46\pm 0.25$ | $3.46\pm 0.25$ | -
ZTF18aahfssj | 12:30:59.742 | 35:45:42.828 | $0.1004$ | $-1.4^{+0.1}_{-0.2}$ | $4.4^{+1.5}_{-2.9}$ | $3.1^{+1.4}_{-2.5}$ | ND | ND | -
ZTF18aahgojc | 13:37:39.821 | 39:09:16.036 | $0.0198$ | $-3.6^{+0.3}_{-0.6}$ | $1.4^{+3.6}_{-0.9}$ | $1.2^{+3.6}_{-1.1}$ | $1.54\pm 0.27$ | $1.54\pm 0.27$ | -
ZTF18aahhuol | 11:37:24.523 | 35:09:12.619 | $0.263$ | $-3.1^{+0.3}_{-0.3}$ | $3.8^{+2.1}_{-1.7}$ | $0.8^{+0.9}_{-0.7}$ | ND | ND | -
ZTF18aahhvqh | 12:26:30.999 | 25:25:22.045 | $0.134$ | $-2.5^{+0.3}_{-0.3}$ | $2.4^{+2.7}_{-0.9}$ | $0.7^{+1.8}_{-0.7}$ | ND | ND | ND
ZTF18aahiqst | 11:03:40.32 | 37:29:25.08 | $0.0745$ | $-3.0^{+0.3}_{-0.3}$ | $4.3^{+1.6}_{-2.7}$ | $0.7^{+0.7}_{-0.7}$ | $2.15\pm 0.24$ | $2.15\pm 0.24$ | -
ZTF18aahirnj | 10:51:13.642 | 38:50:15.367 | $0.216$ | $-2.5^{+0.3}_{-0.3}$ | $1.9^{+2.0}_{-0.6}$ | $0.2^{+1.4}_{-0.2}$ | $5.44\pm 0.23$ | $5.44\pm 0.23$ | -
ZTF18aahisvf | 12:05:56.015 | 49:59:55.962 | $0.0632$ | $-2.6^{+0.3}_{-0.2}$ | $4.2^{+1.7}_{-2.5}$ | $3.4^{+1.4}_{-2.2}$ | $0.91\pm 0.27$ | ND | -
ZTF18aahlveu | 14:22:53.483 | 47:32:52.258 | $0.1991$ | $-2.6^{+0.3}_{-0.3}$ | $1.7^{+3.0}_{-0.8}$ | $0.7^{+3.2}_{-0.7}$ | ND | ND | -
ZTF18aahpbal | 09:36:41.055 | 10:14:15.811 | $0.06$ | $-1.9^{+0.3}_{-0.3}$ | $2.3^{+3.5}_{-1.3}$ | $1.7^{+2.9}_{-1.6}$ | $6.13\pm 0.22$ | $6.13\pm 0.22$ | $17.21\pm 1.92$
ZTF18aahujbh | 12:07:22.114 | 38:52:15.919 | $0.3073$ | $-3.0^{+0.3}_{-0.4}$ | $2.2^{+3.5}_{-1.1}$ | $0.6^{+2.7}_{-0.6}$ | ND | ND | -
ZTF18aahvkih | 13:43:57.511 | 27:12:41.129 | $0.0772$ | $-2.6^{+0.3}_{-0.3}$ | $1.7^{+2.8}_{-0.6}$ | $0.3^{+2.2}_{-0.3}$ | ND | ND | ND
ZTF18aaiemyk | 11:39:38.731 | 48:20:44.793 | $0.101$ | $-3.7^{+0.4}_{-1.1}$ | $3.1^{+2.9}_{-2.9}$ | $158.5^{+140.8}_{-144.9}$ | $2.58\pm 0.24$ | $2.58\pm 0.24$ | -
ZTF18aaisbew | 12:31:55.975 | 35:30:15.324 | $0.131$ | $-2.8^{+0.4}_{-0.3}$ | $1.6^{+2.6}_{-0.5}$ | $0.2^{+2.4}_{-0.2}$ | $2.84\pm 0.38$ | $2.84\pm 0.38$ | -
ZTF18aaisuhc | 11:28:51.052 | 23:10:37.172 | $0.117$ | $-2.4^{+0.3}_{-0.3}$ | $1.7^{+3.1}_{-0.7}$ | $0.4^{+2.1}_{-0.4}$ | ND | ND | $2.92\pm 1.05$
ZTF18aaizewi | 14:35:10.3 | 49:48:19.027 | $0.166$ | $-2.2^{+0.3}_{-0.3}$ | $3.3^{+2.5}_{-2.1}$ | $2.6^{+2.1}_{-2.2}$ | $3.64\pm 0.22$ | $3.64\pm 0.22$ | -
ZTF18aaizioy | 15:05:7.311 | 43:50:4.763 | $0.0935$ | $-2.8^{+0.3}_{-0.3}$ | $1.7^{+3.5}_{-0.9}$ | $1.1^{+3.5}_{-1.1}$ | ND | ND | -
ZTF18aajpluq | 14:04:31.409 | 21:34:15.477 | $0.0839$ | $-2.5^{+0.3}_{-0.2}$ | $2.0^{+3.0}_{-1.4}$ | $2.4^{+2.5}_{-2.3}$ | ND | ND | ND
ZTF18aajytjt | 14:05:15.618 | 54:24:57.68 | $0.0833$ | $-2.2^{+0.1}_{-0.3}$ | $3.2^{+2.5}_{-2.2}$ | $3.6^{+1.3}_{-2.7}$ | ND | ND | -
ZTF18aajywbu | 13:41:48.756 | 37:00:47.093 | $0.197$ | $-3.2^{+0.3}_{-0.3}$ | $2.3^{+2.0}_{-0.7}$ | $0.4^{+1.3}_{-0.4}$ | ND | ND | -
ZTF18aakebod | 13:44:19.625 | 51:26:24.658 | $0.0629$ | $-1.8^{+0.1}_{-0.2}$ | $4.2^{+1.7}_{-3.0}$ | $3.5^{+1.3}_{-3.1}$ | ND | ND | -
ZTF18aakkvuf | 13:33:29.435 | 15:45:50.036 | $0.2462$ | $-2.4^{+0.3}_{-0.3}$ | $2.1^{+2.8}_{-0.8}$ | $0.6^{+2.0}_{-0.5}$ | ND | ND | ND
ZTF18aalrqbo | 15:13:34.465 | 50:31:28.292 | $0.0736$ | $-2.9^{+0.3}_{-0.2}$ | $2.5^{+3.0}_{-1.9}$ | $3.1^{+1.8}_{-3.0}$ | ND | ND | -
ZTF18aalslhk | 13:04:58.02 | 45:35:33.588 | $0.1831$ | $-2.1^{+0.3}_{-0.3}$ | $2.2^{+2.6}_{-0.9}$ | $0.7^{+2.2}_{-0.7}$ | ND | ND | -
ZTF18aaltric | 16:17:26.545 | 38:25:53.275 | $-$ | $-2.6^{+0.3}_{-0.3}$ | $3.5^{+2.4}_{-2.2}$ | $2.9^{+1.9}_{-2.3}$ | ND | ND | -
ZTF18aaluviz | 08:04:13.207 | 30:51:16.854 | $0.142$ | $-2.5^{+0.3}_{-0.2}$ | $2.6^{+3.0}_{-1.8}$ | $2.5^{+2.3}_{-2.4}$ | ND | ND | -
ZTF18aamcwcc | 12:49:50.391 | 44:50:54.378 | $0.106$ | $-2.2^{+0.4}_{-0.4}$ | $3.4^{+2.4}_{-1.5}$ | $0.7^{+1.5}_{-0.6}$ | ND | ND | -
ZTF18aamfoai | 16:29:56.094 | 27:48:0.523 | $0.221$ | $-2.6^{+0.3}_{-0.3}$ | $2.4^{+2.7}_{-0.8}$ | $0.5^{+1.2}_{-0.5}$ | ND | ND | ND
ZTF18aamfryk | 15:08:54.637 | 21:21:25.854 | $0.0801$ | $-2.7^{+0.3}_{-0.2}$ | $1.4^{+0.6}_{-0.4}$ | $0.1^{+0.5}_{-0.1}$ | $0.67\pm 0.19$ | ND | ND
ZTF18aamtcmw | 11:39:38.868 | 57:29:11.507 | $0.0703$ | $-3.8^{+0.4}_{-0.7}$ | $2.5^{+3.3}_{-1.4}$ | $0.8^{+2.7}_{-0.8}$ | ND | ND | -
ZTF18aamvdwm | 15:18:38.916 | 40:45:0.615 | $0.0652$ | $-3.9^{+0.3}_{-0.5}$ | $2.1^{+3.6}_{-1.6}$ | $2.7^{+2.2}_{-2.6}$ | $36.79\pm 0.23$ | $36.79\pm 0.23$ | -
ZTF18aanstge | 16:45:31.221 | 29:50:25.713 | $0.0534$ | $-4.2^{+0.5}_{-0.5}$ | $3.4^{+2.6}_{-3.1}$ | $20.3^{+109.1}_{-19.6}$ | ND | ND | ND
ZTF18aaodqus | 14:23:38.454 | 27:20:9.44 | $0.0642$ | $-2.3^{+0.3}_{-0.3}$ | $2.5^{+1.7}_{-0.7}$ | $0.4^{+0.9}_{-0.3}$ | ND | ND | ND
ZTF18aaoxkmt | 17:02:11.125 | 60:58:47.796 | $0.165$ | $-2.4^{+0.3}_{-0.3}$ | $2.0^{+2.9}_{-0.7}$ | $0.4^{+1.9}_{-0.4}$ | ND | $2.92\pm 1.05$ | -
ZTF18aapiodw | 12:02:15.499 | 44:03:19.818 | $0.101$ | $-3.6^{+0.3}_{-0.3}$ | $2.1^{+3.2}_{-1.0}$ | $0.7^{+2.2}_{-0.7}$ | ND | ND | -
ZTF18aaqdmih | 11:40:53.161 | 25:25:46.47 | $0.2988$ | $-2.4^{+0.3}_{-0.3}$ | $3.3^{+2.5}_{-1.6}$ | $0.6^{+0.9}_{-0.5}$ | $3.17\pm 0.24$ | $3.17\pm 0.24$ | $557.85\pm 39.69$
ZTF18aaqdump | 13:22:34.175 | 60:57:5.611 | $0.119$ | $-2.3^{+0.3}_{-0.3}$ | $1.4^{+3.2}_{-0.5}$ | $0.2^{+2.9}_{-0.2}$ | ND | ND | -
ZTF18aaqdzys | 12:55:5.216 | 43:03:55.265 | $0.3$ | $-2.4^{+0.3}_{-0.3}$ | $1.5^{+2.2}_{-0.6}$ | $0.4^{+2.6}_{-0.3}$ | $1.72\pm 0.36$ | $1.72\pm 0.36$ | -
ZTF18aaqgbag | 15:33:10.024 | 27:29:20.299 | $0.0719$ | $-2.3^{+0.3}_{-0.3}$ | $2.8^{+3.0}_{-1.5}$ | $1.3^{+2.2}_{-1.2}$ | $1.83\pm 0.23$ | $1.83\pm 0.23$ | $5.47\pm 1.01$
ZTF18aaqmaet | 15:20:8.243 | 46:16:15.21 | $0.1763$ | $-2.1^{+0.4}_{-0.3}$ | $1.8^{+3.3}_{-1.2}$ | $1.9^{+2.9}_{-1.8}$ | ND | ND | -
ZTF18aaqmfxu | 14:19:35.64 | 64:21:28.245 | $0.322$ | $-2.4^{+0.3}_{-0.3}$ | $2.2^{+2.8}_{-0.8}$ | $0.5^{+1.9}_{-0.5}$ | ND | ND | -
ZTF18aaqnift | 13:58:57.386 | 45:56:30.196 | $0.173$ | $-2.7^{+0.3}_{-0.4}$ | $4.0^{+1.9}_{-2.8}$ | $4.2^{+1.8}_{-3.0}$ | ND | ND | -
ZTF18aaqqukd | 16:04:47.062 | 39:19:3.464 | $0.237$ | $-1.9^{+0.3}_{-0.3}$ | $2.7^{+3.0}_{-1.4}$ | $1.6^{+2.5}_{-1.4}$ | ND | ND | -
ZTF18aarippg | 14:30:15.998 | 23:03:44.536 | $0.0811$ | $-2.6^{+0.3}_{-0.2}$ | $4.1^{+1.7}_{-2.6}$ | $3.1^{+1.7}_{-2.3}$ | ND | ND | ND
ZTF18aarltmo | 12:27:37.794 | 08:44:6.812 | $0.0854$ | $-3.5^{+0.4}_{-0.6}$ | $2.6^{+3.1}_{-1.3}$ | $0.7^{+2.4}_{-0.7}$ | ND | ND | ND
ZTF18aarnmzg | 11:32:23.403 | 64:19:58.434 | $0.21$ | $-2.0^{+0.4}_{-0.4}$ | $2.8^{+3.0}_{-1.7}$ | $1.5^{+2.3}_{-1.4}$ | ND | ND | -
ZTF18aarnpwk | 12:30:52.645 | 14:33:5.589 | $0.115$ | $-2.7^{+0.4}_{-0.3}$ | $1.6^{+2.3}_{-0.5}$ | $0.3^{+2.1}_{-0.3}$ | ND | ND | ND
ZTF18aarqemn | 14:27:59.932 | 54:32:34.759 | $0.322$ | $-2.9^{+0.3}_{-0.2}$ | $1.6^{+0.8}_{-0.5}$ | $0.2^{+0.7}_{-0.1}$ | ND | ND | -
ZTF18aarqlnq | 17:00:46.779 | 29:19:26.529 | $0.0683$ | $-2.8^{+0.3}_{-0.2}$ | $4.1^{+1.8}_{-2.2}$ | $2.0^{+1.3}_{-1.5}$ | ND | $3.01\pm 0.95$ | ND
ZTF18aarywbt | 12:17:9.908 | 07:11:30.889 | $0.0076$ | $-2.1^{+0.4}_{-0.3}$ | $1.8^{+3.3}_{-1.2}$ | $1.9^{+2.9}_{-1.8}$ | $4.97\pm 0.29$ | $4.97\pm 0.29$ | ND
ZTF18aasehvh | 14:05:15.551 | 54:24:57.982 | $0.0833$ | $-2.2^{+0.0}_{-0.0}$ | $0.6^{+1.9}_{-0.6}$ | $3.9^{+1.1}_{-3.3}$ | ND | ND | -
ZTF18aasupgp | 11:55:15.867 | 38:02:35.059 | $0.144$ | $-2.4^{+0.4}_{-0.4}$ | $2.0^{+3.5}_{-0.8}$ | $0.7^{+2.8}_{-0.6}$ | ND | ND | -
ZTF18aasupvx | 11:27:57.916 | 44:00:37.827 | $-$ | $-2.3^{+0.3}_{-0.2}$ | $1.8^{+1.1}_{-0.5}$ | $0.3^{+0.9}_{-0.3}$ | ND | ND | -
ZTF18aaswkjp | 13:38:44.96 | 11:54:34.637 | $0.144$ | $-2.4^{+0.3}_{-0.3}$ | $2.3^{+3.3}_{-1.2}$ | $0.9^{+2.4}_{-0.9}$ | ND | ND | ND
ZTF18aataelo | 14:38:28.505 | 50:45:35.595 | $0.171$ | $-2.6^{+0.3}_{-0.3}$ | $2.9^{+2.9}_{-1.6}$ | $1.8^{+2.4}_{-1.6}$ | ND | ND | -
ZTF18aatnuln | 16:28:4.041 | 51:46:31.871 | $0.0727$ | $-3.4^{+0.3}_{-0.3}$ | $3.1^{+2.8}_{-2.2}$ | $2.4^{+2.3}_{-2.4}$ | $142.03\pm 0.79$ | $142.03\pm 0.79$ | -
ZTF18aauvptt | 13:46:28.612 | 17:36:59.413 | $0.1747$ | $-1.7^{+0.4}_{-0.3}$ | $2.1^{+1.4}_{-0.6}$ | $0.2^{+0.8}_{-0.2}$ | ND | ND | ND
ZTF18aavkkay | 16:16:48.303 | 30:01:3.922 | $0.134$ | $-3.5^{+0.4}_{-0.3}$ | $1.8^{+3.3}_{-0.7}$ | $0.4^{+2.6}_{-0.4}$ | ND | ND | -
ZTF18aavssbq | 13:22:13.365 | 21:47:21.849 | $0.0852$ | $-2.5^{+0.3}_{-0.2}$ | $1.8^{+0.8}_{-0.5}$ | $0.2^{+0.6}_{-0.2}$ | ND | ND | $3.41\pm 1.07$
ZTF18aavtfaw | 14:31:38.538 | 30:06:51.171 | $0.163$ | $-3.5^{+0.5}_{-1.0}$ | $3.2^{+2.6}_{-2.6}$ | $0.6^{+3.8}_{-0.6}$ | ND | ND | -
ZTF18aawffic | 15:03:2.143 | 38:21:18.476 | $0.0754$ | $-3.1^{+0.3}_{-0.3}$ | $2.3^{+3.3}_{-1.3}$ | $1.6^{+3.0}_{-1.5}$ | ND | ND | -
ZTF18aawgsel | 15:19:36.132 | 28:38:26.904 | $0.269$ | $-3.2^{+0.4}_{-0.4}$ | $3.1^{+2.7}_{-1.3}$ | $0.3^{+0.6}_{-0.3}$ | ND | ND | ND
ZTF18aawruuc | 15:46:17.76 | 50:08:24.288 | $0.286$ | $-2.9^{+0.3}_{-0.3}$ | $2.4^{+3.3}_{-1.3}$ | $0.9^{+2.4}_{-0.8}$ | $17.63\pm 0.5$ | $17.63\pm 0.5$ | -
ZTF18aawwfep | 08:54:41.731 | 30:57:54.717 | $0.197$ | $-2.7^{+0.3}_{-0.2}$ | $2.3^{+3.2}_{-1.2}$ | $1.2^{+2.7}_{-1.1}$ | ND | ND | -
ZTF18aaxnnrx | 12:07:55.843 | 06:04:2.745 | $0.1362$ | $-2.3^{+0.3}_{-0.3}$ | $1.5^{+3.9}_{-0.7}$ | $0.6^{+3.9}_{-0.6}$ | ND | ND | ND
ZTF18aaxqiyo | 12:15:39.692 | 33:55:10.322 | $0.319$ | $-2.7^{+0.3}_{-0.3}$ | $3.1^{+2.7}_{-1.8}$ | $1.2^{+2.0}_{-1.2}$ | ND | ND | -
ZTF18aaxwrji | 17:23:18.431 | 27:56:1.638 | $0.183$ | $-3.0^{+0.3}_{-0.2}$ | $1.4^{+0.9}_{-0.5}$ | $0.3^{+1.2}_{-0.2}$ | ND | ND | ND
ZTF18aaxzcvd | 13:28:38.687 | 12:09:52.71 | $0.205$ | $-2.0^{+0.3}_{-0.3}$ | $4.6^{+1.3}_{-2.1}$ | $1.9^{+1.2}_{-1.1}$ | ND | ND | ND
ZTF18aayigdr | 11:50:0.58 | 35:03:56.678 | $0.0611$ | $-2.6^{+0.3}_{-0.3}$ | $2.6^{+3.2}_{-1.3}$ | $1.3^{+2.8}_{-1.2}$ | ND | ND | -
ZTF18aaykmko | 14:43:21.131 | 19:03:52.101 | $0.299$ | $-2.5^{+0.4}_{-0.3}$ | $3.1^{+2.7}_{-1.3}$ | $0.4^{+0.7}_{-0.3}$ | ND | ND | ND
ZTF18aaylbyr | 15:42:13.921 | 18:34:59.716 | $0.0724$ | $-1.7^{+0.3}_{-0.2}$ | $4.5^{+1.4}_{-2.5}$ | $3.4^{+1.4}_{-1.9}$ | $1.53\pm 0.26$ | ND | $4.37\pm 1.08$
ZTF18aaympoe | 15:27:31.773 | 38:43:7.616 | $0.3999$ | $-3.1^{+0.4}_{-0.4}$ | $3.9^{+2.0}_{-2.3}$ | $0.7^{+1.1}_{-0.6}$ | ND | ND | -
ZTF18aaymybb | 19:14:37.612 | 50:28:54.774 | $0.231$ | $-2.4^{+0.3}_{-0.3}$ | $3.4^{+2.4}_{-1.3}$ | $0.9^{+1.0}_{-0.8}$ | $2.01\pm 0.38$ | $2.01\pm 0.38$ | -
ZTF18aaytaot | 17:06:6.627 | 30:51:57.244 | $0.315$ | $-2.8^{+0.3}_{-0.3}$ | $2.1^{+2.5}_{-0.7}$ | $0.4^{+1.2}_{-0.4}$ | ND | ND | -
ZTF18aazgind | 12:41:58.99 | 56:40:3.273 | $0.088$ | $-1.9^{+0.4}_{-0.3}$ | $1.9^{+3.4}_{-0.8}$ | $0.5^{+2.6}_{-0.5}$ | ND | $1.54\pm 0.27$ | -
ZTF18aaziudx | 14:02:0.575 | 42:04:41.484 | $0.168$ | $-2.9^{+0.3}_{-0.2}$ | $1.6^{+0.8}_{-0.5}$ | $0.2^{+0.7}_{-0.1}$ | ND | ND | -
ZTF18aaznjgn | 11:18:7.972 | 59:28:43.9 | $0.3942$ | $-2.0^{+0.3}_{-0.3}$ | $3.7^{+2.0}_{-1.0}$ | $0.5^{+0.7}_{-0.4}$ | $2.99\pm 0.21$ | $2.99\pm 0.21$ | -
ZTF18aazogyo | 14:56:27.399 | 30:53:45.692 | $0.0814$ | $-2.9^{+0.3}_{-0.2}$ | $2.4^{+3.3}_{-1.4}$ | $1.5^{+2.8}_{-1.4}$ | ND | ND | -
ZTF18aazxduh | 15:42:12.899 | 25:05:3.147 | $0.187$ | $-3.0^{+0.3}_{-0.3}$ | $3.1^{+2.7}_{-1.7}$ | $0.9^{+1.5}_{-0.9}$ | ND | ND | ND
ZTF18aazxwty | 16:23:42.937 | 27:18:10.677 | $0.216$ | $-2.9^{+0.3}_{-0.3}$ | $2.4^{+3.3}_{-1.4}$ | $1.3^{+3.1}_{-1.3}$ | ND | ND | ND
ZTF18aazzfia | 17:08:59.118 | 21:53:8.268 | $0.0719$ | $-1.8^{+0.2}_{-0.2}$ | $5.0^{+1.0}_{-2.3}$ | $3.2^{+1.3}_{-1.5}$ | ND | ND | $2.19\pm 0.82$
ZTF18abaenqh | 12:51:42.769 | 22:27:25.155 | $0.121$ | $-2.7^{+0.3}_{-0.2}$ | $1.5^{+0.5}_{-0.4}$ | $0.1^{+0.3}_{-0.1}$ | ND | ND | ND
ZTF18abafuvn | 14:10:41.978 | 31:40:31.172 | $0.188$ | $-3.1^{+0.3}_{-0.3}$ | $1.5^{+2.8}_{-0.6}$ | $0.4^{+3.2}_{-0.4}$ | ND | ND | -
ZTF18abakpye | 12:19:25.649 | 08:07:56.42 | $0.0931$ | $-2.4^{+0.4}_{-0.3}$ | $2.8^{+2.7}_{-1.0}$ | $0.5^{+1.0}_{-0.4}$ | ND | ND | ND
ZTF18abaltla | 14:04:4.192 | 46:42:9.737 | $0.237$ | $-3.4^{+0.3}_{-0.3}$ | $3.9^{+2.0}_{-2.4}$ | $1.8^{+2.4}_{-1.5}$ | ND | ND | -
ZTF18abazsgj | 17:02:50.492 | 33:44:9.845 | $0.202$ | $-2.8^{+0.3}_{-0.3}$ | $2.7^{+2.9}_{-1.2}$ | $0.8^{+1.8}_{-0.7}$ | ND | ND | -
ZTF18abbppru | 16:27:55.399 | 46:42:48.792 | $0.2135$ | $-2.5^{+0.3}_{-0.2}$ | $1.8^{+0.8}_{-0.5}$ | $0.1^{+0.6}_{-0.1}$ | $3.72\pm 0.21$ | $3.72\pm 0.21$ | -
ZTF18abcshvz | 13:38:48.191 | 60:26:43.784 | $0.0721$ | $-3.3^{+0.4}_{-0.3}$ | $1.7^{+1.3}_{-0.5}$ | $0.2^{+1.1}_{-0.1}$ | ND | ND | -
ZTF18abdgzzr | 15:43:16.418 | 54:05:26.31 | $0.245$ | $-2.9^{+0.4}_{-0.5}$ | $2.5^{+3.0}_{-1.1}$ | $0.2^{+0.6}_{-0.2}$ | ND | ND | -
ZTF18abdinhh | 14:47:46.148 | 22:52:5.317 | $0.333$ | $-2.2^{+0.4}_{-0.3}$ | $2.0^{+1.6}_{-0.6}$ | $0.2^{+1.1}_{-0.2}$ | ND | ND | ND
ZTF18abdipqu | 15:24:22.157 | 26:42:23.535 | $0.236$ | $-2.5^{+0.3}_{-0.3}$ | $1.8^{+1.0}_{-0.6}$ | $0.2^{+0.8}_{-0.2}$ | ND | ND | ND
ZTF18abeakzq | 15:56:54.46 | 25:32:33.483 | $0.164$ | $-3.3^{+0.3}_{-0.3}$ | $2.5^{+3.3}_{-1.8}$ | $1.4^{+3.0}_{-1.3}$ | $2.27\pm 0.21$ | $2.27\pm 0.21$ | $3.99\pm 0.88$
ZTF18abglwpn | 16:18:46.33 | 51:00:35.254 | $0.319$ | $-2.5^{+0.4}_{-0.4}$ | $3.3^{+2.6}_{-1.8}$ | $0.7^{+1.1}_{-0.7}$ | ND | ND | -
ZTF18abjzard | 15:48:44.37 | 12:33:55.881 | $0.0964$ | $-2.4^{+0.3}_{-0.3}$ | $1.9^{+3.4}_{-0.7}$ | $0.6^{+2.5}_{-0.6}$ | ND | ND | ND
ZTF18abjzfwh | 16:18:5.815 | 21:28:22.975 | $0.0861$ | $-3.5^{+0.3}_{-0.2}$ | $1.9^{+3.1}_{-0.8}$ | $1.0^{+3.0}_{-0.9}$ | ND | ND | ND
ZTF18ablmemb | 14:40:34.332 | 24:22:50.252 | $0.0733$ | $-2.5^{+0.3}_{-0.3}$ | $1.7^{+3.8}_{-0.8}$ | $0.7^{+3.4}_{-0.6}$ | ND | ND | ND
ZTF18abqkzlv | 15:53:50.442 | 56:22:30.768 | $0.178$ | $-3.2^{+0.3}_{-0.3}$ | $4.3^{+1.6}_{-1.9}$ | $1.2^{+1.0}_{-0.9}$ | ND | ND | -
ZTF18abszfur | 22:07:15.888 | 12:10:59.896 | $0.291$ | $-2.6^{+0.3}_{-0.2}$ | $1.8^{+0.8}_{-0.4}$ | $0.2^{+0.5}_{-0.2}$ | ND | ND | ND
ZTF18abujdpn | 08:48:15.403 | 49:54:32.852 | $0.219$ | $-2.7^{+0.3}_{-0.3}$ | $1.7^{+2.5}_{-0.6}$ | $0.5^{+2.4}_{-0.5}$ | ND | ND | -
ZTF18abuvtlx | 01:29:46.713 | 15:04:57.253 | $0.3649$ | $-2.1^{+0.4}_{-0.3}$ | $3.8^{+2.0}_{-1.2}$ | $0.5^{+0.7}_{-0.4}$ | ND | ND | ND
ZTF18abvskoa | 00:08:5.611 | 14:50:23.555 | $0.0456$ | $-1.7^{+0.0}_{-0.0}$ | $0.8^{+1.9}_{-0.8}$ | $4.1^{+0.9}_{-2.8}$ | ND | ND | ND
ZTF18abwpfja | 23:09:20.262 | 00:45:23.473 | $0.0324$ | $-2.7^{+0.3}_{-0.3}$ | $1.2^{+2.8}_{-1.1}$ | $3.2^{+1.8}_{-3.1}$ | ND | ND | ND
ZTF18abzvagt | 15:28:56.107 | 53:43:11.918 | $0.284$ | $-2.8^{+0.3}_{-0.3}$ | $2.6^{+3.0}_{-1.6}$ | $2.0^{+2.7}_{-1.8}$ | ND | ND | -
ZTF18abzweee | 22:24:7.813 | 04:09:13.079 | $0.0975$ | $-2.3^{+0.3}_{-0.3}$ | $2.1^{+3.7}_{-1.2}$ | $1.1^{+3.2}_{-1.1}$ | ND | ND | ND
ZTF18acajjwa | 00:04:26.038 | 02:09:3.67 | $0.235$ | $-2.1^{+0.4}_{-0.3}$ | $4.8^{+1.2}_{-2.3}$ | $1.8^{+1.2}_{-1.2}$ | ND | ND | ND
ZTF18acapafh | 09:56:27.058 | 54:04:14.959 | $0.207$ | $-2.3^{+0.4}_{-0.3}$ | $3.6^{+2.2}_{-2.4}$ | $3.5^{+1.4}_{-2.4}$ | ND | ND | -
ZTF18acbweyd | 10:20:38.497 | 24:37:8.461 | $0.189$ | $-2.2^{+0.3}_{-0.3}$ | $2.3^{+2.8}_{-0.7}$ | $0.3^{+1.0}_{-0.3}$ | ND | ND | ND
ZTF18accdmzk | 12:06:18.612 | 57:52:47.842 | $0.257$ | $-2.8^{+0.4}_{-0.3}$ | $3.0^{+2.8}_{-1.2}$ | $0.4^{+0.8}_{-0.4}$ | ND | ND | -
ZTF18accmzgh | 08:45:18.531 | 14:20:33.984 | $0.0605$ | $-2.8^{+0.3}_{-0.3}$ | $2.8^{+3.0}_{-1.6}$ | $1.5^{+2.7}_{-1.4}$ | $4.0\pm 0.22$ | $4.0\pm 0.22$ | $11.85\pm 1.92$
ZTF18accwjao | 11:42:26.064 | 30:16:55.18 | $0.149$ | $-3.0^{+0.3}_{-0.3}$ | $2.2^{+3.4}_{-1.2}$ | $1.2^{+2.8}_{-1.2}$ | ND | ND | -
ZTF18acdvqzz | 08:53:30.282 | 10:58:28.021 | $0.2731$ | $-2.5^{+0.3}_{-0.3}$ | $3.0^{+2.8}_{-1.5}$ | $1.2^{+1.8}_{-1.0}$ | ND | ND | ND
ZTF18aceasjg | 02:33:18.121 | 00:11:29.274 | $0.246$ | $-2.1^{+0.3}_{-0.3}$ | $3.3^{+2.5}_{-1.4}$ | $1.3^{+1.7}_{-1.1}$ | ND | ND | ND
ZTF18acefdrv | 07:59:47.742 | 11:25:7.361 | $0.337$ | $-2.8^{+0.4}_{-0.5}$ | $3.9^{+2.0}_{-1.6}$ | $0.3^{+0.5}_{-0.3}$ | $7.71\pm 0.31$ | $7.71\pm 0.31$ | $4.1\pm 1.11$
ZTF18acefilb | 09:59:59.454 | 29:19:27.039 | $0.28$ | $-2.4^{+0.3}_{-0.3}$ | $2.4^{+2.0}_{-0.7}$ | $0.5^{+1.4}_{-0.4}$ | ND | ND | ND
ZTF18acegevf | 13:24:18.29 | 58:49:11.742 | $0.192$ | $-2.7^{+0.3}_{-0.3}$ | $3.1^{+2.6}_{-1.4}$ | $0.9^{+1.6}_{-0.8}$ | $3.25\pm 0.19$ | $3.25\pm 0.19$ | -
ZTF18aceylbs | 10:57:30.693 | 18:21:50.437 | $0.232$ | $-2.5^{+0.3}_{-0.2}$ | $2.0^{+1.3}_{-0.5}$ | $0.3^{+0.8}_{-0.3}$ | $1.04\pm 0.21$ | $1.04\pm 0.21$ | $2.46\pm 1.05$
ZTF18aceypmr | 10:19:25.075 | 28:30:21.317 | $-$ | $-3.0^{+0.3}_{-0.3}$ | $2.9^{+2.9}_{-1.4}$ | $0.6^{+1.3}_{-0.6}$ | ND | ND | ND
ZTF18aceyxxa | 12:39:37.122 | 60:27:44.0 | $0.19$ | $-2.6^{+0.3}_{-0.3}$ | $3.1^{+2.7}_{-1.5}$ | $1.0^{+1.6}_{-1.0}$ | ND | ND | -
ZTF18acezafs | 12:39:5.612 | 37:32:12.232 | $0.212$ | $-2.8^{+0.4}_{-0.5}$ | $3.4^{+2.5}_{-2.1}$ | $1.0^{+1.7}_{-0.9}$ | ND | ND | -
ZTF18achchge | 08:38:26.513 | 37:19:6.815 | $0.2111$ | $-1.5^{+0.4}_{-0.4}$ | $3.9^{+2.0}_{-2.5}$ | $1.8^{+8.1}_{-1.6}$ | ND | ND | -
ZTF18aclmlqy | 07:58:50.294 | 09:35:20.684 | $0.0458$ | $-2.7^{+0.0}_{-0.0}$ | $0.1^{+0.8}_{-0.1}$ | $3.8^{+1.2}_{-3.3}$ | ND | ND | ND
ZTF18acmqplu | 08:38:10.93 | 24:53:43.031 | $0.0287$ | $-3.1^{+0.1}_{-0.2}$ | $3.9^{+2.0}_{-2.8}$ | $3.1^{+1.7}_{-2.9}$ | $35.27\pm 0.31$ | $35.27\pm 0.31$ | $93.11\pm 7.12$
ZTF18acnboko | 13:24:51.892 | 21:35:48.448 | $0.13$ | $-2.9^{+0.3}_{-0.2}$ | $1.9^{+0.9}_{-0.5}$ | $0.1^{+0.5}_{-0.1}$ | $1.23\pm 0.3$ | ND | ND
ZTF18acpcxna | 10:05:7.893 | 34:14:24.643 | $0.162$ | $-2.7^{+0.5}_{-0.4}$ | $4.0^{+1.9}_{-2.4}$ | $1.2^{+2.4}_{-1.1}$ | ND | $3.01\pm 0.95$ | -
ZTF18acppxbf | 09:27:25.377 | 11:34:19.641 | $0.135$ | $-2.8^{+0.3}_{-0.2}$ | $1.4^{+0.7}_{-0.4}$ | $0.1^{+0.5}_{-0.1}$ | ND | ND | ND
ZTF18acqtdnj | 12:37:7.422 | 07:40:24.859 | $0.132$ | $-2.5^{+0.3}_{-0.3}$ | $2.6^{+3.2}_{-1.4}$ | $1.2^{+2.8}_{-1.2}$ | ND | ND | ND
ZTF18acqzgwt | 11:22:15.922 | 16:03:24.166 | $0.1603$ | $-3.1^{+0.4}_{-0.5}$ | $4.2^{+1.7}_{-3.0}$ | $0.7^{+1.7}_{-0.6}$ | ND | ND | ND
ZTF18acrnhtg | 14:19:2.683 | 16:30:7.551 | $0.342$ | $-2.0^{+0.3}_{-0.3}$ | $4.2^{+1.6}_{-1.7}$ | $1.1^{+0.8}_{-0.8}$ | $13.17\pm 0.3$ | $13.17\pm 0.3$ | $69.69\pm 5.86$
ZTF18acsouqh | 09:37:2.411 | 26:00:8.889 | $0.298$ | $-2.7^{+0.4}_{-0.8}$ | $3.6^{+2.3}_{-2.1}$ | $0.5^{+0.9}_{-0.5}$ | ND | ND | ND
ZTF18acszbbf | 02:50:3.034 | 01:09:30.927 | $0.194$ | $-2.2^{+0.3}_{-0.3}$ | $3.0^{+2.4}_{-1.0}$ | $0.7^{+1.2}_{-0.6}$ | ND | ND | ND
ZTF18acvcadu | 00:20:24.085 | 33:47:7.28 | $0.065$ | $-3.1^{+0.3}_{-0.2}$ | $1.6^{+0.8}_{-0.4}$ | $0.2^{+0.8}_{-0.2}$ | ND | ND | -
ZTF18acvgjne | 09:27:58.43 | 57:12:34.518 | $0.227$ | $-3.1^{+0.3}_{-0.3}$ | $3.0^{+2.7}_{-1.4}$ | $0.9^{+1.6}_{-0.8}$ | ND | ND | -
ZTF18acvgogz | 10:15:57.614 | 48:38:0.152 | $0.385$ | $-2.7^{+0.4}_{-0.4}$ | $2.8^{+2.5}_{-0.8}$ | $0.2^{+0.6}_{-0.2}$ | $2.31\pm 0.27$ | $2.31\pm 0.27$ | -
ZTF18acvgvpn | 12:26:41.507 | 05:59:6.8 | $0.29$ | $-2.5^{+0.3}_{-0.3}$ | $3.2^{+2.6}_{-1.7}$ | $1.2^{+1.8}_{-1.2}$ | ND | ND | ND
ZTF18acvhhgk | 09:01:0.882 | 35:38:8.808 | $0.302$ | $-2.2^{+0.3}_{-0.3}$ | $2.4^{+2.7}_{-0.7}$ | $0.3^{+1.1}_{-0.3}$ | $3.92\pm 0.24$ | $3.92\pm 0.24$ | -
ZTF18acviafl | 15:45:1.458 | 11:35:18.192 | $0.237$ | $-2.3^{+0.3}_{-0.3}$ | $4.4^{+1.5}_{-1.8}$ | $1.7^{+1.2}_{-1.1}$ | ND | ND | ND
ZTF18acvwmvf | 13:06:50.961 | 28:59:50.317 | $0.184$ | $-1.8^{+0.1}_{-0.2}$ | $4.2^{+1.7}_{-3.0}$ | $3.5^{+1.3}_{-3.1}$ | ND | ND | ND
ZTF18acwyxcm | 13:33:12.413 | 01:30:23.729 | $0.2171$ | $-2.5^{+0.4}_{-0.4}$ | $3.3^{+2.6}_{-1.8}$ | $0.7^{+1.1}_{-0.7}$ | $1.27\pm 0.25$ | $1.27\pm 0.25$ | ND
ZTF18acxcttu | 15:08:53.965 | 00:11:49.093 | $0.0542$ | $-1.5^{+0.0}_{-0.0}$ | $4.0^{+1.8}_{-2.8}$ | $4.3^{+0.7}_{-2.1}$ | $11.04\pm 0.25$ | $11.04\pm 0.25$ | $33.0\pm 2.93$
ZTF18acydjfe | 14:37:1.496 | 26:40:19.231 | $0.2185$ | $-2.1^{+0.3}_{-0.3}$ | $2.3^{+3.2}_{-1.5}$ | $2.4^{+2.5}_{-2.3}$ | $3.99\pm 0.23$ | $3.99\pm 0.23$ | $12.2\pm 1.63$
ZTF18acytxmx | 07:56:52.801 | 29:19:42.072 | $0.0676$ | $-2.6^{+0.0}_{-0.0}$ | $1.0^{+2.1}_{-0.9}$ | $4.0^{+1.0}_{-3.7}$ | $0.8\pm 0.22$ | $0.8\pm 0.22$ | ND
ZTF18acyxobm | 14:30:8.673 | 55:56:28.782 | $0.156$ | $-2.5^{+0.3}_{-0.3}$ | $4.2^{+1.8}_{-1.9}$ | $1.0^{+0.9}_{-0.7}$ | ND | ND | -
ZTF18acyygbx | 16:18:11.135 | 09:30:52.362 | $0.26$ | $-2.1^{+0.3}_{-0.3}$ | $2.9^{+2.8}_{-1.2}$ | $1.0^{+1.7}_{-0.8}$ | ND | ND | ND
ZTF18aczeodr | 10:46:10.631 | 03:50:31.361 | $0.366$ | $-2.8^{+0.3}_{-0.3}$ | $1.9^{+0.9}_{-0.5}$ | $0.1^{+0.4}_{-0.1}$ | ND | ND | ND
ZTF18aczeoen | 11:06:49.836 | 10:17:38.678 | $0.1678$ | $-2.4^{+0.3}_{-0.3}$ | $3.0^{+2.9}_{-1.8}$ | $1.7^{+2.4}_{-1.6}$ | ND | ND | ND
ZTF18aczergd | 14:23:52.461 | 22:47:45.505 | $0.2814$ | $-2.7^{+0.3}_{-0.2}$ | $4.3^{+1.6}_{-1.9}$ | $1.3^{+1.0}_{-0.9}$ | ND | ND | $5.25\pm 1.04$
ZTF18adalgnn | 14:51:9.328 | 29:26:26.368 | $0.0755$ | $-2.8^{+0.3}_{-0.5}$ | $2.5^{+3.3}_{-1.2}$ | $0.5^{+1.4}_{-0.5}$ | ND | ND | ND
ZTF19aaapkzq | 14:37:3.682 | 12:10:34.593 | $0.189$ | $-2.4^{+0.4}_{-0.4}$ | $1.6^{+3.3}_{-1.5}$ | $2.0^{+2.9}_{-1.9}$ | ND | ND | ND
ZTF19aaaplwg | 13:35:15.177 | 01:05:27.247 | $-$ | $-3.0^{+0.5}_{-0.5}$ | $4.3^{+1.6}_{-2.4}$ | $0.3^{+0.5}_{-0.3}$ | ND | ND | ND
ZTF19aaapujo | 12:23:10.582 | 06:45:54.953 | $0.2352$ | $-2.3^{+0.4}_{-0.4}$ | $3.2^{+2.5}_{-1.2}$ | $0.6^{+1.1}_{-0.5}$ | ND | ND | ND
ZTF19aaaqhdw | 16:29:38.114 | 36:24:52.403 | $0.125$ | $-2.9^{+0.3}_{-0.2}$ | $1.8^{+0.7}_{-0.4}$ | $0.1^{+0.4}_{-0.1}$ | ND | ND | -
ZTF19aacixeg | 16:03:6.177 | 13:25:2.111 | $0.21$ | $-2.3^{+0.3}_{-0.2}$ | $1.9^{+1.0}_{-0.5}$ | $0.2^{+0.8}_{-0.2}$ | ND | ND | ND
ZTF19aaczuwm | 11:45:31.526 | 32:57:37.219 | $0.243$ | $-2.4^{+0.3}_{-0.3}$ | $2.2^{+2.2}_{-0.7}$ | $0.3^{+1.4}_{-0.3}$ | ND | ND | -
ZTF19aadfycj | 13:20:20.294 | 00:34:28.228 | $-$ | $-2.0^{+0.3}_{-0.3}$ | $3.9^{+1.9}_{-1.4}$ | $0.8^{+0.8}_{-0.7}$ | ND | ND | ND
ZTF19aadgigp | 14:47:2.87 | 27:37:46.627 | $0.2241$ | $-1.9^{+0.3}_{-0.2}$ | $1.3^{+0.7}_{-0.4}$ | $0.1^{+0.7}_{-0.1}$ | ND | ND | ND
ZTF19aadgijf | 14:26:14.328 | 27:29:56.421 | $0.262$ | $-2.6^{+0.3}_{-0.2}$ | $1.7^{+0.6}_{-0.4}$ | $0.1^{+0.4}_{-0.1}$ | ND | ND | ND
ZTF19aafyhnt | 08:45:56.674 | 34:09:35.765 | $0.0656$ | $-3.9^{+0.4}_{-0.4}$ | $3.8^{+2.1}_{-2.4}$ | $0.7^{+1.1}_{-0.6}$ | ND | ND | -
ZTF19aagwzod | 04:28:38.767 | 00:00:39.698 | $0.0713$ | $-2.5^{+0.3}_{-0.3}$ | $2.0^{+3.4}_{-1.4}$ | $2.1^{+2.7}_{-2.0}$ | ND | ND | ND
ZTF19aailtrm | 17:03:20.177 | 37:37:24.909 | $0.0646$ | $-2.4^{+0.3}_{-0.3}$ | $2.6^{+2.9}_{-1.3}$ | $1.2^{+2.2}_{-1.1}$ | $1.15\pm 0.22$ | $1.15\pm 0.22$ | -
ZTF19aaipqls | 09:38:12.256 | 07:43:39.968 | $0.022$ | $-2.4^{+0.0}_{-0.0}$ | $0.1^{+0.7}_{-0.1}$ | $3.8^{+1.2}_{-3.4}$ | ND | ND | ND
ZTF19aakjemw | 15:50:7.613 | 27:28:13.758 | $0.147$ | $-2.8^{+0.4}_{-0.3}$ | $4.0^{+2.0}_{-2.8}$ | $3.2^{+2.9}_{-3.1}$ | ND | ND | ND
ZTF19aalckts | 15:23:30.078 | 00:43:34.33 | $0.24$ | $-2.4^{+0.4}_{-0.3}$ | $1.9^{+2.1}_{-0.7}$ | $0.3^{+1.3}_{-0.3}$ | ND | ND | ND
ZTF19aaldqkg | 11:32:23.382 | 64:19:59.637 | $0.21$ | $-2.5^{+0.4}_{-0.3}$ | $2.0^{+3.2}_{-0.7}$ | $0.4^{+2.3}_{-0.4}$ | ND | ND | -
ZTF19aalepov | 15:10:48.211 | 47:05:46.789 | $0.321$ | $-3.1^{+0.5}_{-0.7}$ | $3.3^{+2.5}_{-1.8}$ | $0.3^{+0.8}_{-0.3}$ | ND | ND | -
ZTF19aamadtt | 13:29:16.869 | 49:08:38.404 | $0.237$ | $-1.9^{+0.4}_{-0.3}$ | $1.7^{+1.8}_{-0.6}$ | $0.2^{+1.6}_{-0.2}$ | ND | ND | -
ZTF19aamgxav | 11:06:40.211 | 05:19:5.596 | $0.0906$ | $-2.4^{+0.4}_{-0.3}$ | $3.4^{+2.5}_{-2.2}$ | $1.8^{+5.0}_{-1.7}$ | ND | ND | ND
ZTF19aanffdv | 08:44:19.287 | 50:31:52.154 | $-$ | $-2.3^{+0.4}_{-0.3}$ | $2.5^{+1.1}_{-0.6}$ | $0.2^{+0.6}_{-0.2}$ | ND | ND | -
ZTF19aangfed | 11:48:31.418 | 28:20:27.96 | $0.281$ | $-2.9^{+0.3}_{-0.3}$ | $2.0^{+3.5}_{-0.7}$ | $0.3^{+1.0}_{-0.3}$ | ND | ND | ND
ZTF19aannwar | 07:24:29.078 | 40:46:43.094 | $0.0501$ | $-3.8^{+0.5}_{-0.8}$ | $4.2^{+1.7}_{-1.7}$ | $0.3^{+0.5}_{-0.2}$ | ND | ND | -
ZTF19aanuvep | 14:42:47.587 | 00:55:31.901 | $0.243$ | $-2.7^{+0.4}_{-0.3}$ | $2.3^{+2.2}_{-0.7}$ | $0.3^{+1.2}_{-0.3}$ | ND | ND | ND
ZTF19aanxfap | 13:15:40.41 | 21:41:32.239 | $0.243$ | $-3.1^{+0.4}_{-0.4}$ | $3.0^{+2.8}_{-1.4}$ | $0.4^{+0.9}_{-0.4}$ | ND | ND | ND
ZTF19aaohukq | 11:16:14.676 | 06:17:36.275 | $0.0753$ | $-2.8^{+0.4}_{-0.3}$ | $1.6^{+1.7}_{-0.5}$ | $0.2^{+1.9}_{-0.1}$ | ND | ND | ND
ZTF19aaomkbg | 16:13:36.808 | 23:39:49.362 | $0.149$ | $-2.5^{+0.3}_{-0.2}$ | $1.4^{+0.9}_{-0.4}$ | $0.2^{+1.0}_{-0.2}$ | $2.09\pm 0.2$ | $2.09\pm 0.2$ | $4.68\pm 1.08$
ZTF19aaoyjsq | 12:05:30.637 | 16:49:41.839 | $0.217$ | $-2.6^{+0.3}_{-0.3}$ | $4.6^{+1.4}_{-2.1}$ | $1.5^{+1.1}_{-1.0}$ | ND | ND | ND
ZTF19aaozprp | 13:24:4.226 | 43:34:7.139 | $0.338$ | $-2.6^{+0.3}_{-0.3}$ | $3.7^{+2.1}_{-1.8}$ | $1.0^{+1.1}_{-0.9}$ | $3.09\pm 0.36$ | $3.09\pm 0.36$ | -
ZTF19aapehvs | 13:18:58.835 | 57:30:6.596 | $0.0977$ | $-3.3^{+0.3}_{-0.3}$ | $1.7^{+3.5}_{-0.8}$ | $0.8^{+3.6}_{-0.8}$ | ND | ND | -
ZTF19aapkuvx | 08:21:25.374 | 42:19:8.549 | $0.2217$ | $-2.3^{+0.4}_{-0.3}$ | $2.0^{+1.1}_{-0.5}$ | $0.2^{+0.6}_{-0.2}$ | ND | ND | -
ZTF19aapuscr | 13:16:24.552 | -2:05:25.332 | $0.114$ | $-2.9^{+0.3}_{-0.3}$ | $3.1^{+2.7}_{-1.6}$ | $1.2^{+2.0}_{-1.1}$ | $1.63\pm 0.26$ | $1.63\pm 0.26$ | $3.01\pm 0.95$
ZTF19aaqfmmm | 15:35:8.513 | 13:17:30.256 | $0.0935$ | $-3.6^{+0.3}_{-0.2}$ | $1.6^{+0.9}_{-0.5}$ | $0.2^{+1.0}_{-0.2}$ | $1.12\pm 0.23$ | $1.12\pm 0.23$ | $4.11\pm 1.25$
ZTF19aarjtww | 13:49:28.538 | 03:59:5.54 | $0.2535$ | $-2.3^{+0.3}_{-0.3}$ | $3.1^{+2.7}_{-1.6}$ | $1.1^{+2.0}_{-1.1}$ | ND | ND | ND
ZTF19aarnent | 11:15:18.35 | 05:10:37.75 | $0.183$ | $-2.5^{+0.3}_{-0.3}$ | $1.8^{+1.0}_{-0.6}$ | $0.2^{+0.8}_{-0.2}$ | ND | ND | ND
ZTF19aasceup | 12:05:33.898 | 49:17:33.629 | $0.215$ | $-3.2^{+0.3}_{-0.4}$ | $3.0^{+2.8}_{-1.7}$ | $0.9^{+1.8}_{-0.9}$ | ND | ND | -
ZTF19aaseyqn | 15:11:43.405 | 21:01:3.939 | $0.0805$ | $-2.3^{+0.3}_{-0.2}$ | $1.7^{+0.6}_{-0.4}$ | $0.1^{+0.3}_{-0.1}$ | ND | ND | ND
ZTF19aasfagu | 12:11:26.259 | 16:36:59.475 | $0.305$ | $-2.9^{+0.3}_{-0.3}$ | $3.1^{+2.7}_{-1.9}$ | $1.9^{+2.6}_{-1.7}$ | ND | ND | ND
ZTF19aatllxr | 14:40:5.315 | 33:19:44.615 | $0.179$ | $-3.0^{+0.5}_{-0.4}$ | $2.5^{+3.2}_{-1.5}$ | $1.6^{+3.1}_{-1.5}$ | ND | ND | -
ZTF19aatlxtt | 16:46:52.796 | 24:09:27.376 | $-$ | $-2.9^{+0.6}_{-1.1}$ | $4.2^{+1.8}_{-2.7}$ | $0.5^{+3.0}_{-0.5}$ | ND | ND | ND
ZTF19aaujqrd | 14:47:45.264 | 51:48:39.636 | $0.185$ | $-3.1^{+0.3}_{-0.2}$ | $1.9^{+0.7}_{-0.5}$ | $0.1^{+0.4}_{-0.1}$ | ND | ND | -
ZTF19aavlvye | 14:10:10.728 | 30:15:29.497 | $0.194$ | $-2.8^{+0.3}_{-0.3}$ | $2.0^{+2.8}_{-0.7}$ | $0.4^{+1.8}_{-0.4}$ | ND | ND | -
ZTF19aavqqkh | 10:28:22.859 | 23:51:25.705 | $0.174$ | $-2.8^{+0.4}_{-0.4}$ | $3.0^{+2.8}_{-1.5}$ | $0.8^{+1.7}_{-0.8}$ | ND | ND | ND
ZTF19aavwtcb | 11:40:57.203 | -2:17:10.055 | $0.0485$ | $-3.3^{+0.3}_{-0.2}$ | $3.0^{+3.0}_{-2.8}$ | $349.5^{+336.9}_{-328.2}$ | ND | ND | ND
ZTF19aawgugc | 12:45:35.782 | 47:01:8.475 | $0.1511$ | $-2.7^{+0.3}_{-0.3}$ | $2.3^{+3.0}_{-1.7}$ | $3.1^{+1.9}_{-2.9}$ | ND | ND | -
ZTF19aawlmtf | 22:56:11.828 | 14:50:59.54 | $0.251$ | $-1.8^{+0.4}_{-0.3}$ | $3.2^{+1.8}_{-0.8}$ | $0.3^{+0.8}_{-0.3}$ | $0.93\pm 0.27$ | ND | ND
ZTF19aawompn | 15:25:9.028 | 01:26:24.505 | $0.3$ | $-3.0^{+0.3}_{-0.5}$ | $2.7^{+3.1}_{-1.2}$ | $0.4^{+1.0}_{-0.4}$ | ND | ND | ND
ZTF19aawonnx | 14:37:51.235 | 06:49:57.311 | $0.0855$ | $-2.8^{+0.3}_{-0.3}$ | $2.7^{+3.0}_{-1.6}$ | $1.3^{+2.8}_{-1.2}$ | ND | ND | ND
ZTF19aawoseu | 12:36:18.935 | 58:00:15.786 | $0.2088$ | $-2.9^{+0.3}_{-0.3}$ | $3.4^{+2.4}_{-2.3}$ | $2.2^{+2.4}_{-2.0}$ | ND | ND | -
ZTF19aawotzd | 15:16:48.072 | 59:25:44.563 | $0.352$ | $-2.7^{+0.3}_{-0.2}$ | $2.0^{+1.0}_{-0.5}$ | $0.2^{+0.7}_{-0.1}$ | ND | ND | -
ZTF19abaumgw | 14:03:35.423 | 46:13:29.679 | $0.317$ | $-3.0^{+0.3}_{-0.3}$ | $1.9^{+0.7}_{-0.5}$ | $0.2^{+0.5}_{-0.1}$ | ND | ND | -
ZTF19abbtscb | 14:01:36.652 | 04:16:27.021 | $0.164$ | $-3.0^{+0.3}_{-0.3}$ | $2.6^{+3.1}_{-1.8}$ | $2.0^{+2.7}_{-1.9}$ | ND | ND | ND
ZTF19abcnoja | 16:30:29.102 | 00:26:20.21 | $-$ | $-2.7^{+0.4}_{-0.3}$ | $1.9^{+1.5}_{-0.6}$ | $0.2^{+0.9}_{-0.2}$ | ND | ND | ND
ZTF19abcvvut | 16:31:24.245 | 25:30:54.729 | $-$ | $-2.6^{+0.4}_{-0.3}$ | $2.8^{+2.5}_{-0.9}$ | $0.4^{+1.0}_{-0.4}$ | $1.65\pm 0.24$ | $1.65\pm 0.24$ | $6.04\pm 1.13$
ZTF19abewcfn | 15:57:59.239 | 29:20:19.459 | $0.275$ | $-2.3^{+0.3}_{-0.3}$ | $2.5^{+1.7}_{-0.7}$ | $0.4^{+0.9}_{-0.3}$ | ND | ND | ND
ZTF19abfqiaq | 01:51:5.789 | 00:34:26.191 | $-$ | $-2.3^{+0.4}_{-0.4}$ | $3.8^{+2.1}_{-1.7}$ | $0.5^{+0.7}_{-0.4}$ | $2.94\pm 0.56$ | $2.94\pm 0.56$ | ND
ZTF19abixawb | 00:10:14.881 | 00:08:20.994 | $0.102$ | $-3.5^{+0.4}_{-0.8}$ | $3.1^{+2.8}_{-2.0}$ | $1.5^{+2.8}_{-1.4}$ | ND | ND | ND
ZTF19abizomu | 01:57:38.093 | 13:09:31.595 | $0.2207$ | $-2.7^{+0.5}_{-0.4}$ | $4.7^{+1.3}_{-2.6}$ | $1.4^{+1.2}_{-1.2}$ | $7.9\pm 0.55$ | $7.9\pm 0.55$ | $77.37\pm 7.87$
ZTF19abknctx | 15:01:25.553 | 11:13:56.53 | $0.152$ | $-3.2^{+0.3}_{-0.3}$ | $1.7^{+1.7}_{-0.6}$ | $0.2^{+0.8}_{-0.2}$ | ND | ND | ND
ZTF19abrtrno | 22:33:36.711 | -7:43:37.284 | $0.175$ | $-2.4^{+0.4}_{-0.3}$ | $3.6^{+2.3}_{-2.3}$ | $2.3^{+2.3}_{-2.1}$ | ND | ND | ND
ZTF19abvqtsj | 14:21:38.62 | 17:35:36.095 | $0.0499$ | $-3.2^{+0.3}_{-0.3}$ | $1.6^{+1.5}_{-0.6}$ | $0.3^{+1.7}_{-0.3}$ | ND | ND | ND
ZTF19acbvtcx | 08:34:29.312 | 06:03:25.132 | $0.11$ | $-2.8^{+0.3}_{-0.3}$ | $2.1^{+3.5}_{-1.0}$ | $0.5^{+1.6}_{-0.5}$ | ND | ND | ND
ZTF19accdfdh | 09:14:59.134 | 05:02:43.82 | $0.143$ | $-2.7^{+0.3}_{-0.3}$ | $3.7^{+2.2}_{-1.8}$ | $1.1^{+1.4}_{-0.9}$ | ND | ND | ND
ZTF19acdtzdd | 08:31:39.767 | 19:56:5.466 | $0.2111$ | $-2.4^{+0.3}_{-0.3}$ | $1.7^{+2.1}_{-0.6}$ | $0.3^{+2.1}_{-0.3}$ | $1.61\pm 0.29$ | $1.61\pm 0.29$ | ND
ZTF19acljmbq | 12:24:44.748 | 26:59:50.563 | $0.138$ | $-3.8^{+0.3}_{-0.3}$ | $1.6^{+2.0}_{-0.6}$ | $0.2^{+1.2}_{-0.2}$ | ND | ND | ND
ZTF19acmxncj | 10:00:6.781 | 03:46:4.356 | $0.151$ | $-3.2^{+0.4}_{-0.4}$ | $2.5^{+3.3}_{-1.5}$ | $1.0^{+2.7}_{-0.9}$ | ND | ND | ND
ZTF19acvrkqc | 08:59:56.916 | 53:29:7.075 | $0.373$ | $-2.6^{+0.3}_{-0.2}$ | $2.3^{+1.0}_{-0.5}$ | $0.2^{+0.6}_{-0.2}$ | ND | ND | -
ZTF19acxqawl | 14:12:38.758 | -1:20:34.084 | $0.14$ | $-3.1^{+0.4}_{-0.4}$ | $3.9^{+2.0}_{-2.3}$ | $0.7^{+1.1}_{-0.6}$ | ND | ND | ND
ZTF19adajvop | 10:38:57.933 | 04:48:39.054 | $0.355$ | $-2.7^{+0.3}_{-0.3}$ | $3.2^{+2.6}_{-1.4}$ | $0.9^{+1.5}_{-0.9}$ | ND | ND | ND
ZTF19adakivb | 12:00:39.504 | 38:51:25.793 | $0.212$ | $-3.2^{+0.4}_{-0.3}$ | $1.9^{+1.8}_{-0.6}$ | $0.2^{+1.2}_{-0.2}$ | ND | ND | -
ZTF19adceiab | 09:38:43.265 | 60:52:7.949 | $0.168$ | $-3.3^{+0.3}_{-0.3}$ | $2.9^{+2.9}_{-1.6}$ | $0.9^{+1.6}_{-0.9}$ | ND | ND | -
ZTF19adceobn | 08:14:25.885 | 29:41:15.881 | $0.374$ | $-2.2^{+0.3}_{-0.3}$ | $2.6^{+2.3}_{-0.8}$ | $0.5^{+1.3}_{-0.4}$ | $4.37\pm 0.35$ | $4.37\pm 0.35$ | ND
ZTF19adcftma | 13:25:49.16 | 20:31:52.714 | $0.201$ | $-2.7^{+0.3}_{-0.3}$ | $1.9^{+2.4}_{-0.7}$ | $0.6^{+2.1}_{-0.5}$ | ND | ND | ND
ZTF20aaemupc | 12:10:6.022 | 33:36:2.998 | $0.226$ | $-3.1^{+0.3}_{-0.3}$ | $3.7^{+2.1}_{-2.1}$ | $1.5^{+1.8}_{-1.2}$ | ND | ND | -
ZTF20aaigcqa | 14:27:26.657 | 00:19:50.232 | $0.222$ | $-2.3^{+0.3}_{-0.3}$ | $3.9^{+2.0}_{-2.5}$ | $1.7^{+2.6}_{-1.4}$ | ND | ND | ND
ZTF20aajbxci | 13:11:40.614 | 56:08:35.292 | $-$ | $-2.5^{+0.4}_{-0.3}$ | $2.5^{+2.1}_{-0.6}$ | $0.3^{+1.1}_{-0.2}$ | ND | ND | -
ZTF20aalrkkq | 13:50:7.695 | 12:46:57.102 | $0.141$ | $-3.3^{+0.3}_{-0.3}$ | $1.8^{+2.6}_{-0.7}$ | $0.5^{+2.4}_{-0.5}$ | ND | ND | ND
ZTF20aalyhuc | 13:15:49.178 | 12:49:36.628 | $0.0712$ | $-3.5^{+0.3}_{-0.5}$ | $2.3^{+3.2}_{-1.7}$ | $2.1^{+2.7}_{-2.1}$ | ND | ND | ND
ZTF20aamaqmq | 14:19:35.69 | 64:21:28.571 | $0.322$ | $-2.4^{+0.3}_{-0.3}$ | $2.1^{+3.2}_{-0.8}$ | $0.5^{+2.1}_{-0.5}$ | ND | ND | -
ZTF20aaosbad | 09:41:34.394 | 35:35:10.672 | $0.31$ | $-2.7^{+0.3}_{-0.3}$ | $1.9^{+2.0}_{-0.7}$ | $0.4^{+1.7}_{-0.4}$ | ND | ND | -
ZTF20aatuinl | 14:45:5.096 | 52:43:42.038 | $0.325$ | $-3.0^{+0.4}_{-0.3}$ | $2.2^{+1.2}_{-0.6}$ | $0.2^{+0.7}_{-0.2}$ | ND | ND | -
ZTF20aavyrfh | 13:43:52.804 | 01:00:9.33 | $0.255$ | $-3.0^{+0.3}_{-0.3}$ | $2.9^{+2.9}_{-1.8}$ | $2.1^{+2.6}_{-1.8}$ | ND | ND | ND

Note. — Properties of the 250 variable DPE candidates in ZTF. Objects in the
table are arranged in lexigraphical order by ZTF name. Spectroscopic redshifts
from SDSS are shown in the 4th column. In columns 5-7 we show the amplitude,
power law index and turnover frequency from modeling of the power spectrum
derived from the g-band ZTF light curve (see Section 3). In columns 8-10 we
show the the radio fluxes for epoch 1 (2017-2018) and epoch 2 (2019-2021) of
the 20cm VLASS survey and for epoch 1 of the 34cm RACS-low survey. Non-
detections are indicated by ND, and a dash indicates that the source was not
within the surveyed region.

Table 4: Best-fit accretion disk parameters.

ZTF ID | $\xi_{1}$ | $\xi_{2}$ |  $\sigma$ (km/s) |  $i$ (deg) | q |  $w$ (deg) | $A_{s}$ |  $\psi$ (deg) |  $\phi$ (deg)
---|---|---|---|---|---|---|---|---|---
ZTF18aaaotwe | $160^{+20}_{-40}$ | $2350^{+1140}_{-1100}$ | $2220^{+140}_{-110}$ | $12^{+1}_{-1}$ | $2.0^{+0.3}_{-0.3}$ | $70^{+10}_{-7}$ | $7^{+1}_{-1}$ | $40^{+10}_{-10}$ | $330^{+40}_{-40}$
ZTF18aaaovpz | $210^{+70}_{-140}$ | $1770^{+200}_{-250}$ | $1040^{+300}_{-430}$ | $30^{+2}_{-1}$ | $1.2^{+0.3}_{-1.0}$ | $59^{+6}_{-6}$ | $7^{+1}_{-1}$ | $310^{+10}_{-10}$ | $190^{+10}_{-10}$
ZTF18aaavwka | $310^{+100}_{-100}$ | $2550^{+40}_{-40}$ | $230^{+60}_{-70}$ | $18^{+1}_{-1}$ | $1.1^{+0.2}_{-0.3}$ | $62^{+14}_{-13}$ | $1^{+1}_{-1}$ | $50^{+30}_{-10}$ | $320^{+60}_{-320}$
ZTF18aabkubl | $180^{+50}_{-50}$ | $310^{+70}_{-80}$ | $670^{+120}_{-120}$ | $13^{+1}_{-1}$ | $1.6^{+0.5}_{-0.6}$ | $55^{+19}_{-16}$ | $5^{+1}_{-1}$ | $30^{+20}_{-20}$ | $290^{+30}_{-20}$
ZTF18aabylvn | $210^{+10}_{-20}$ | $3980^{+20}_{-10}$ | $1400^{+20}_{-10}$ | $19^{+1}_{-1}$ | $1.7^{+0.0}_{-0.0}$ | $70^{+2}_{-2}$ | $7^{+1}_{-1}$ | $330^{+10}_{-10}$ | $140^{+10}_{-10}$
ZTF18aacajqc | $130^{+20}_{-10}$ | $3380^{+420}_{-390}$ | $590^{+60}_{-50}$ | $19^{+1}_{-1}$ | $0.9^{+0.1}_{-0.1}$ | $69^{+7}_{-6}$ | $7^{+1}_{-1}$ | $300^{+10}_{-10}$ | $200^{+10}_{-10}$
ZTF18aacbjdm | $220^{+10}_{-10}$ | $760^{+70}_{-60}$ | $1450^{+10}_{-10}$ | $8^{+1}_{-1}$ | $2.4^{+0.1}_{-0.1}$ | $77^{+3}_{-2}$ | $7^{+1}_{-1}$ | $310^{+10}_{-10}$ | $250^{+10}_{-10}$
ZTF18aaccaxc | $160^{+30}_{-50}$ | $3820^{+10}_{-10}$ | $940^{+120}_{-120}$ | $11^{+1}_{-1}$ | $1.9^{+0.2}_{-0.2}$ | $69^{+19}_{-8}$ | $6^{+1}_{-1}$ | $40^{+40}_{-20}$ | $350^{+10}_{-10}$
ZTF18aacckko | $200^{+20}_{-30}$ | $3420^{+10}_{-10}$ | $1620^{+0}_{-0}$ | $21^{+1}_{-1}$ | $1.9^{+0.1}_{-0.1}$ | $41^{+22}_{-28}$ | $3^{+2}_{-2}$ | $360^{+10}_{-10}$ | $240^{+10}_{-230}$
ZTF18aacddjc | $320^{+80}_{-90}$ | $2090^{+20}_{-30}$ | $1620^{+260}_{-190}$ | $17^{+1}_{-1}$ | $1.4^{+0.4}_{-0.6}$ | $33^{+19}_{-31}$ | $3^{+2}_{-2}$ | $360^{+40}_{-50}$ | $30^{+70}_{-40}$
ZTF18aacdpbi | $190^{+30}_{-40}$ | $2430^{+50}_{-50}$ | $1870^{+60}_{-50}$ | $13^{+1}_{-1}$ | $1.3^{+0.2}_{-0.2}$ | $75^{+6}_{-4}$ | $7^{+1}_{-1}$ | $320^{+10}_{-10}$ | $210^{+30}_{-30}$
ZTF18aacdvjp | $170^{+10}_{-10}$ | $3900^{+150}_{-70}$ | $1250^{+40}_{-40}$ | $17^{+1}_{-1}$ | $1.6^{+0.0}_{-0.0}$ | $37^{+8}_{-7}$ | $7^{+1}_{-1}$ | $340^{+10}_{-10}$ | $70^{+20}_{-20}$
ZTF18aachojf | $190^{+20}_{-20}$ | $1010^{+20}_{-120}$ | $730^{+30}_{-30}$ | $11^{+1}_{-1}$ | $1.4^{+0.3}_{-0.3}$ | $79^{+1}_{-0}$ | $8^{+1}_{-1}$ | $60^{+10}_{-10}$ | $290^{+10}_{-10}$
ZTF18aacrkse | $200^{+40}_{-50}$ | $2550^{+70}_{-70}$ | $1870^{+60}_{-60}$ | $13^{+1}_{-1}$ | $1.4^{+0.2}_{-0.3}$ | $74^{+6}_{-4}$ | $7^{+1}_{-1}$ | $320^{+10}_{-10}$ | $210^{+20}_{-20}$
ZTF18aadgbva | $250^{+30}_{-40}$ | $3730^{+360}_{-200}$ | $280^{+80}_{-80}$ | $18^{+1}_{-1}$ | $1.5^{+0.1}_{-0.1}$ | $31^{+23}_{-34}$ | $0^{+1}_{-1}$ | $0^{+40}_{-40}$ | $140^{+250}_{-260}$
ZTF18aaercku | $290^{+60}_{-90}$ | $2260^{+830}_{-1220}$ | $1250^{+80}_{-120}$ | $11^{+1}_{-1}$ | $1.9^{+0.5}_{-0.4}$ | $50^{+25}_{-19}$ | $6^{+3}_{-1}$ | $30^{+30}_{-10}$ | $220^{+10}_{-10}$