#  The calm before the (next) storm: no third outburst in 2019–2020, and
ongoing monitoring of the transient AGN IC 3599

Dirk Grupe Northern Kentucky University, Department of Physics, Geology, and
Engineering Technology, Nunn Drive, Highland Heights, KY 41099, USA  S.
Komossa Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn,
Germany  Salem Wolsing  Northern Kentucky University, Department of Physics,
Geology, and Engineering Technology, Nunn Drive, Highland Heights, KY 41099,
USA

(Received 2024 February 29; Accepted 2024 April 18)

###### Abstract

We report on follow-up observations of the Seyfert 1.9 galaxy IC 3599 with the
NASA Neil Gehrels Swift mission. The detection of a second X-ray outburst in
2010 by Swift after the first discovery of a bright X-ray outburst in 1990 by
ROSAT led to the suggestion of two very different explanations: The first one
assumed that IC 3599 exhibits outbursts due to repeated partial tidal
stripping of a star, predicting another outburst of IC 3599 in 2019/2020. The
second, alternative scenario assumed that the event observed in X-rays is due
to an accretion disk instability which would suggest a much longer period
between the large outbursts. Our continued monitoring campaign by Swift
allowed us to test the first scenario which predicted a repetition of high
amplitude flaring activity in 2019/2020. We do not find any evidence of
dramatic flaring activity with factors of 100 since the last X-ray outburst
seen in 2010. These observations support the accretion disk scenario. Further,
while IC 3599 remains in low emission states, the long-term X-ray light curve
of IC 3599 reveals ongoing strong variability of a factor of a few. The most
remarkable event is a mini flare of a factor of 10 in X-rays in December 2022.
After that flare, the otherwise supersoft X-ray spectrum shows an exceptional
hardening, reminiscent of a temporary corona formation.

active galactic nuclei – supermassive black holes – X-rays: galaxies –
ultraviolet: galaxies – quasars: individual (IC 3599)

††facilities: NASA Neil Gehrels Swift observatory (XRT and UVOT).††software:
HEASoft (https://heasarc.gsfc.nasa.gov/docs/software/heasoft/) with XSPEC
(Arnaud, 1996), ESO-MIDAS (https://www.eso.org/sci/software/esomidas/), the R
programming language (https://www.r-project.org/), and SuperMongo
(https://www.astro.princeton.edu/~rhl/sm/).

##  1 Introduction

Since the proposed scenario of the tidal disruption of a stars by a
supermassive black holes (e.g., Rees, 1988), there have been many observations
confirming this scenario. In the 1990s the X-ray mission ROSAT (Truemper,
1982) had been instrumental for the discovery of the first stellar tidal
disruption events (TDEs), in the form of giant-amplitude X-ray outbursts from
quiescent host galaxies (e.g., NGC 5905 (Bade et al., 1996; Komossa & Bade,
1999), RX J624.9+7554 (Grupe et al., 1999), and RX J1242.6–1119 (Komossa &
Greiner, 1999)). More recently, TDEs have been detected by all major X-ray
observatories, including the discovery of jetted events with the Neil Gehrels
Swift observatory, first in Swift J164449.3+573451 (e.g., Burrows et al.,
2011; Bloom et al., 2011; Zauderer et al., 2011). The discovery of TDEs from
quiescent galaxies, however, is not limited to the X-ray sky. GALEX led to the
first detection of events in the UV-optical band (Gezari et al., 2006), and
SDSS enabled the first identification of events with transient optical
emission lines such as HeII, broad Balmer lines, and coronal lines (Komossa et
al., 2008). TDE candidates continue to be identified at all wavebands (see
Komossa, 2015; van Velzen et al., 2021; Webb et al., 2023; Komossa & Grupe,
2023, for recent reviews).

Although the TDE model is required to explain sudden, luminous X-ray outbursts
in non-active galaxies, this picture is far from being clear in AGN. In the
case of an AGN, the power is coming from a long-lived accretion disk
surrounding the central supermassive black hole. This power is not constant
and varies, and in extreme cases a significant change in the disk properties
can cause a dramatic increase in the AGN luminosity. An increasing number of
optical changing-look AGN which do change their luminosity output along with
their optical broad emission lines, have been identified in recent years (see
Komossa & Grupe, 2023, for a review) even though the first cases were known
already in the 1970s–80s (e.g., Penston & Perez, 1984; Alloin et al., 1985).
Different theoretical scenarios related to accretion disk instabilities or
other disk processes have been explored in recent years (e.g., Nicastro, 2000;
Grupe et al., 2015; Ross et al., 2018; Noda & Done, 2018; Dexter & Begelman,
2019; Sniegowska et al., 2020; Pan et al., 2021; Kaaz et al., 2023; Cao et
al., 2023). There will be a major discovery space for both, TDEs and changing-
look AGN once the Vera Rubin Telescope will go
online111https://rubinobservatory.org/.

One of the earliest examples of an AGN that might have exhibited either a TDE
or an accretion disk instability was the Seyfert 1.9 galaxy IC 3599 (Zw
159.034; 1RXS J123741.2$+264227$; $\alpha_{2000}$ = $12^{\rm h}37^{\rm
m}41.^{\rm s}2$, $\delta_{2000}$ =
$+26^{\circ}42^{\prime}27^{{}^{\prime\prime}}$, z=0.0215). IC 3599 was
discovered as a very X-ray bright AGN during the ROSAT All-Sky Survey (RASS,
Voges et al., 1999) in 1990. Subsequent pointed ROSAT observations during the
following years revealed that it had faded by a factor of initially 60 and
even more than 100 in later observations. Both, Brandt et al. (1995) and Grupe
et al. (1995) speculated at the time that this was caused by either a TDE or
high-amplitude AGN variability.

What made both scenarios plausible was the discovery of a strong evolution in
the optical emission line spectrum. The spectrum taken about half a year after
the RASS observation shown in Brandt et al. (1995) showed very strong
permitted lines from Hydrogen and Helium along with transitions from other
elements. These strong emission lines led Brandt et al. (1995) to classify IC
3599 as a Narrow-Line Seyfert 1 galaxy (NLS1), albeit without FeII emission.
Grupe et al. (1995) showed spectra obtained years after the RASS which
displayed the spectrum of a Seyfert 2 galaxy but with fading coronal iron
lines. The fading coronal lines were confirmed by new optical spectroscopy of
Komossa & Bade (1999) who still detected a broad component in H$\alpha$,
making IC 3599 a Seyfert 1.9 galaxy. These authors re-emphasized that TDEs are
best identified in quiescent host galaxies, because in AGN, accretion-disk-
related activity is the most plausible explanation for variability Rees (see
also 1990). Note, no FeII lines, the signature lines in Narrow Line Seyfert 1
galaxies, were present at any time in the optical data of IC 3599. Doubt
remained given that this is an AGN, if a TDE really was an explanation of the
X-ray outburst. Instead, the spectacular changes in its optical emission-line
spectrum combined with the dramatic X-ray variability make IC 3599 one of the
most extreme examples of a changing-look AGN (Komossa & Grupe, 2023).

After ROSAT, IC 3599 was again observed in X-rays by Chandra in 2002 (Vaughan
et al., 2004) and was still found in an X-ray low state. In two observations
by the Neil Gehrels Swift mission (Gehrels et al., 2004, Swift hereafter) in
2010, it was seen again in an X-ray outburst state with its X-ray flux at a
similar level as during the RASS (Grupe et al., 2015). Based on the RASS
observation from 1991, the Chandra observation from 2002, and the Swift
observation from 2010, Campana et al. (2015) speculated that the 2010 outburst
was due to the tidal stripping of a star, repeating an initial 1991 tidal
stripping event of a star orbiting the black hole, with a low black hole mass
of $3\times 10^{5}M_{\odot}$ and a 9.5-year orbital period. This kind of
repeated flaring has been suggested e.g. by Payne et al. (2021) to explain the
quasi-periodic eruptions in ESO 253-G003/AT2014ko. Campana et al. (2015)
predicted that another outburst in IC 3599 would be visible in 2019/2020.
Although this is an intriguing model, Grupe et al. (2015) argued that the 1990
and the 2010 outbursts were due to accretion disk instabilities. Major
arguments were the optical light curve from the Catalina observatory which
showed a relatively gradual increase in the optical flux, as well as a low
black hole mass not being supported by any observational parameter (instead,
it was measured to be of the order of $2-20\times 10^{6}M_{\odot}$).

To test these different models, we continued to monitor IC 3599 with Swift
typically once per month for a nine-month period each year. Swift is unable to
observe IC 3599 for a three-month period between August and November due to
the sun-constraint (a 45∘ sun avoidance angle). Here we report on the entire
Swift monitoring campaign from 2010 to June 2023. During the entire monitoring
period no further outbursts have been observed in IC 3599, supporting the
accretion disk instability scenario suggested by Grupe et al. (2015). Over the
last few years there has been, however, a general trend of IC 3599 slowly
becoming brighter in X-rays, and it has recently been observed in an
intermediate state.

This paper is organized as follows: in Section 2 we will describe the Swift
observations, present the results in Section 3, and then discuss them in
Section 4. Throughout the paper spectral indices are denoted as
$F_{\nu}\propto\nu^{-\alpha}$. Luminosities are calculated assuming a
$\Lambda$CDM cosmology with $\Omega_{\rm M}$=0.286, $\Omega_{\Lambda}$=0.714
and a Hubble constant of $H_{0}$=70 km s-1 Mpc-1, resulting in a luminosity
distance of $D$=91.4 Mpc using the cosmology calculator by Wright (2006). All
errors are 1$\sigma$ unless stated otherwise.

##  2 Swift Observations and Data Reduction

Swift has observed IC 3599 since 2010. When it was discovered in 2013 that it
had exhibited an X-ray outburst in 2010 (Grupe et al., 2015) we started
observing it once a month. These observations were supported by another set of
monthly observations (PI Campana) in 2019 which essentially made it a two-week
cadence. All Swift observations are listed in Table 4. The full machine-
readable table is available on Zenodo: 10.5281/zenodo.10899673 (catalog
10.5281/zenodo.10899673).

The Swift X-ray telescope (XRT; Burrows et al., 2005) was operating in photon
counting mode (pc mode, Hill et al., 2005) and the data were reduced by the
task xrtpipeline which is part the HEASOFT package 6.30.1. Source counts were
extracted in a circle with a radius of 47.1${}^{{}^{\prime\prime}}$ (except
the 2010 outburst observation for which we used 70.7${}^{{}^{\prime\prime}}$).
The background counts were extracted in a nearby circular region with a radius
of 247.5${}^{{}^{\prime\prime}}$. For all spectra we used the most recent
response file swxpc0to12s6_20130101v014.rmf. The X-ray spectra were analyzed
using XSPEC version 12.12.1 (Arnaud, 1996). If a sufficient number of counts
($>$30) was available, we used W-statistics (Cash, 1979) for single
observations. Although often the number of counts was too low to allow for a
spectral analysis, we still determined a hardness ratio, defined as
$HR=\frac{hard-soft}{hard+soft}$ with the soft and hard bands in the 0.3-1.0
and 1.0-10 keV range, respectively by applying the program by Park et al.
(2006). The count rates in the XRT were determined by using the Swift XRT
product page at the Swift Data Center at the University of
Leicester222https://www.swift.ac.uk/user_objects/ (Evans et al., 2007), as
well as the Living Swift XRT Point Source Catalogue
333https://www.swift.ac.uk/LSXPS/ (Evans et al., 2023).

To perform a spectral analysis of different X-ray flux states, we merged the
data of various time periodd into single data sets within XSELECT. These
periods and spectral analysis results are listed in the appendix in Table 2.
We then constructed the auxiliary response files (arf) by using the FTOOLS
command addarf, using the weighting factor of each individual arf by dividing
the individual exposure time of each single observation by the total exposure
time of the merged spectrum.

The UV-optical telescope (UVOT; Roming et al., 2005) data of each segment were
co-added in each filter with the UVOT task uvotimsum. In general, all
observations were performed in all 6 UVOT filters, except if the observation
was interrupted by Gamma-Ray Burst detections or higher priority Target of
Opportunity observations. Source counts in all 6 UVOT filters were selected in
a circle with a radius of 5${}^{{}^{\prime\prime}}$ and background counts in a
nearby source free region with a radius of 20${}^{{}^{\prime\prime}}$. UVOT
magnitudes and fluxes were measured with the task uvotsource based on the most
recent UVOT calibration as described in Poole et al. (2008) and Breeveld et
al. (2010). The UVOT data were corrected for Galactic reddening ($E_{\rm
B-V}=0.015$; Schlegel et al., 1998). The correction factor in each filter was
calculated with equation (2) in Roming et al. (2009) who used the standard
reddening correction curves by Cardelli et al. (1989).

##  3 Results

###  3.1 X-ray and UV/Optical Light Curves

####  3.1.1 Light Curves

The fluxes in X-rays and in the UV/optical obtained by Swift are listed in
Table 3. This table also contains the observations published already in Grupe
et al. (2015) which were re-analyzed due to updates in the calibration files.
The full machine-readable table is available on Zenodo:
10.5281/zenodo.10899673 (catalog 10.5281/zenodo.10899673). Note that many
0.3-10 keV fluxes were estimated from the count rates derived from the
Leicester Swift-XRT Product tool (see footnote 1) and then converted to fluxes
based on the closest X-ray data that allowed a spectral analysis. These
estimated fluxes are marked in Table 3.

Figure 1 displays the long-term X-ray light curve of IC 3599. The data for
this light curve are available on Zenodo: 10.5281/zenodo.10899673 (catalog
10.5281/zenodo.10899673). The light curves clearly show the two giant
outbursts seen by ROSAT and Swift about 20 years apart. The long-term light
curve also displays a mini flare which shows an increase in X-ray flux by a
factor of about 10 in December 2022.

Figure 1: Long-term 0.2-2.0 keV X-ray light curve of IC 3599. The data during
the 1990s are from ROSAT, the 2002 observation from Chandra, and all others
after 2010 from Swift. Data are available at 10.5281/zenodo.10899673 (catalog
10.5281/zenodo.10899673)

Figure 2 displays the full Swift light curve between 2010 and August 2023.
Note that due to the low background in the Swift XRT even a low number of
counts results in a 3$\sigma$ detection. However, the number of counts is
often too low to allow for a reliable determination of the hardness ratio. It
displays the outburst in 2010 and the remarkable flat light curve since Swift
resumed the observations with our monitoring program in 2013. The green
vertical lines mark the year 2019 when Campana et al. (2015) predicted that
the hypothetic star would return and undergo another partial disruption event
while going through periastron and thus form a temporary accretion disk around
the black hole again, causing another outburst. Clearly, this did not happen.
There are no signs of unusual activity in X-rays or UV, yet. There is,
however, a general trend since about 2021 that IC 3599 is slowly becoming
brighter in X-rays (see below in Section 3.1.3). The hardness-ratio light
curve suggests strong spectral variability in X-rays as well.

Figure 3 shows the Swift XRT and UVOT light curves from November 2022 to
August 2023. It shows a very dense monitoring phase in January 2023 due to the
unusually high count rate of 0.03 counts s-1 seen in December 2022. This is a
factor of 10 higher than typically observed when it is in its very low state
(see also Figure 2). The light curve also displays a remarkable hardening of
the X-ray spectrum after the mini flare from being very soft at almost HR=-1
to becoming harder with HR$>$0\. However, from about March 2023 to the end of
the observing campaign in August 2023, IC 3599 has become softer again.

Figure 2: Observed Swift X-ray to optical light curve of IC 3599 from 2010 to
August 2023. The fluxes in the X-ray and UVOT bands are given in units of
$10^{-16}$ W m-2. The grey-shaded area displays the range of the 2023 Swift
light curve displayed in Figure 3.  Figure 3: Observed Swift X-ray to optical
light curve of IC 3599 from 2022 November to 2023 August. The fluxes in the
X-ray and UVOT bands are given in units of $10^{-15}$ W m-2.

####  3.1.2 Variability Analysis

We have monitored IC 3599 regularly since 2013 which has led to a total number
of more than 100 observations. This rich data set allows for a detailed
temporal analysis. As the first step we can apply the Fractional Excess
Variance $F_{\rm var}=\frac{\sqrt{\sigma^{2}-\delta^{2}}}{<f>}$ as defined by
Rodríguez-Pascual et al. (1997) with an uncertainty of
$\sigma_{F_{var}}=\frac{1}{F_{\rm
var}}\sqrt{\frac{1}{2N}}\frac{\sigma^{2}}{<f>^{2}}$ following the definition
by Edelson et al. (2002). Here, $\sigma$ is the variance of the light curve,
$\delta$ is the mean value of the uncertainties of the fluxes/count rates, and
$<f>$ is the mean value of the fluxes/count rates. We applied this to the
Swift XRT and UVOT light curves including and excluding the 2010 outburst
data. The results of the fractional excess variance are listed in Table 1.

Table 1:  Fractional excess variance and the mean fluxes $<f>$ of the Swift XRT and UVOT light curves including all data and only the low state 2013-2023 data.  | All Data | 2013-2022 low state
---|---|---
Band | $F_{var}$ | $<f>$ | $F_{var}$ | $<f>$
$F_{X}$ | 2.616$\pm$0.159 | 3.911 | 0.759$\pm$0.055 | 2.735
UVW2 | 0.140$\pm$0.010 | 2.451 | 0.048$\pm$0.006 | 2.415
UVM2 | 0.156$\pm$0.011 | 2.531 | 0.037$\pm$0.010 | 2.482
UVW1 | 0.131$\pm$0.010 | 2.691 | 0.018$\pm$0.013 | 2.656
U | 0.112$\pm$0.008 | 3.786 | 0.041$\pm$0.006 | 3.741
B | 0.042$\pm$0.005 | 7.302 | 0.007$\pm$0.015 | 7.276
V | 0.119$\pm$0.009 | 9.419 | 0.114$\pm$0.008 | 9.373

While the results of the fractional excess variance including the 2010
outburst data seem to follow the decrease of $F_{\rm var}$ with increasing
wavelength as expected from accretion disc reprocessing models (e.g. Cackett
et al., 2007), excluding these data shows a different picture: The same
overall trend is still visible, however 2 bands (U and V) deviate from the
systematic trend.

When working with a variance and mean, the assumption is that the underlying
distribution is Gaussian (Gauß, 1821). We checked the flux distributions in
X-rays and in each UVOT filter using R (e.g., Craweley, 2009) by looking at
the histogram of the flux distribution as well as at the quantile-quantile
plot (QQ plot). We found that this assumption is well-justified for the UVOT
observations. Except for the high state data from 2010, the data of all UVOT
observations are well-described by a Gaussian distribution in all 6 filters.
Figure 4 displays the distribution and the QQ plot of the W2 magnitudes of IC
3599 which clearly shows that this is a Gaussian distribution. The other UVOT
filters show similar distributions which are all consistent with a Gaussian
distribution.

Figure 4: Histogram and QQ-Plot of the W2 fluxes of IC 3599 (in unites of
$10^{-15}W~{}m^{-2}$)

Figure 5: Histogram and QQ-Plot of the 0.3-10 keV X-ray fluxes of IC 3599 (in
units of $10^{-16}W~{}m^{-2}$)

However, the X-ray flux variations are not represented by a Gaussian
distribution. This is clearly shown in Figure 5 which displays the histogram
and the QQ-plot.

For non-Gaussian distributions, the variance and the mean are not good
measures of a sample and in these cases, the median is a much better measure
than the mean. In order to study the overall variability in all Swift XRT and
UVOT light curves we designed a new measure: a variability parameter

$P_{\rm var}=\frac{1}{\sqrt{N}}\frac{1}{x_{\rm
med}}\sqrt{\sum_{i}{(x_{i}-x_{\rm
med})^{2}}\times\frac{\delta_{med}^{2}}{\delta_{i}^{2}}}$ (1)

which is like a reduced $\chi^{2}$ value. This parameter, $P_{\rm var}$, is a
measure of how strongly a source deviates from the median value. Here $x_{\rm
med}$ and $\delta_{\rm med}$ are the sample median values of the fluxes and
the median of the uncertainties. The values $x_{i}$ and $\delta_{i}$ are the
individual values with their uncertainties. The term
$\frac{\delta_{med}^{2}}{\delta_{i}^{2}}$ is a weighing factor that takes the
individual uncertainties into account so that values with large uncertainties
carry less weight in the calculations than those values with small
uncertainties. We estimate the uncertainties on the values of $P_{\rm var}$ by
$\Delta P_{\rm var}=\frac{\delta_{med}}{x_{med}}P_{\rm var}$. The values for
$P_{\rm var}$ are listed in Table 2. These values also confirm the stronger
variability in X-rays than in the UV and optical. The variability parameter
$P_{\rm var}$ also shows that these values are not dominated by the 2010
outburst measurements. It allows a direct comparison with the variability
strength between Gaussian distributed data and non-Gaussian data, like the
X-ray flux distribution of IC 3599, simply because it does not assume a
Gaussian distribution and it is therefore a more general measure of the
variability.

Table 2: Variability parameter $P_{\rm var}$ and the median flux $f_{med}$ of the Swift XRT and UVOT light curves of the low state 2013-2023 data  | all data | 2013-2022 low state
---|---|---
band | $P_{var}$ | $f_{med}$ | $P_{var}$ | $f_{med}$
$F_{X}$ | 1.072$\pm$0.410 | 1.830 | 0.808$\pm$0.306 | 1.820
UVW2 | 0.107$\pm$0.006 | 2.457 | 0.073$\pm$0.004 | 2.457
UVM2 | 0.112$\pm$0.007 | 2.508 | 0.073$\pm$0.005 | 2.508
UVW1 | 0.107$\pm$0.006 | 2.667 | 0.059$\pm$0.003 | 2.667
U | 0.093$\pm$0.004 | 3.772 | 0.060$\pm$0.003 | 3.772
B | 0.049$\pm$0.002 | 7.318 | 0.039$\pm$0.002 | 7.319
V | 0.094$\pm$0.005 | 9.529 | 0.088$\pm$0.004 | 9.529

Just a Gaussian flux distribution by itself does not prove that these are just
random fluctuations. In order to check on any variability we performed a
periodogram within R using spec.pgram. Besides some red noise at lower
frequencies, we only found white noise in the data. The V filter data are
dominated by white noise. This variability pattern is typical for type 2 AGN
(Wang et al., 2024) and may suggest that IC 3599 remains in its Seyfert 1.9
state at this time.

####  3.1.3 Merged XRT and UVOT Light Curves

Figure 6 displays the long-term Swift XRT light curve with the data averaged
over each year, except for the 2013-2016 period because the number of
observations is relatively small and the count rate was low, of the order of
0.003 counts s-1. We binned the 2013-2015 and 2015-2017 observations into one
bin each and after 2017, the observations of each year were combined. The
binned data are displayed as red data points in Figure 6. The 0.3-10 keV
fluxes and the hardness ratios for these periods are listed in Table 2. There
is clearly an overall slow brightening in X-rays over the last decade. The
hardness ratio light curve also suggests spectral variability with IC 3599
becoming softer from 2013 to 2020, but becoming harder again since. However,
there is no correlation between the hardness ratio and the X-ray brightness of
IC 3599.

Figure 6: Swift XRT 0.3-10 keV flux (in units of $10^{-16}$ W m-2) and
hardness ratio long-term light curves. The black data points displayed in
Figure 2 show detections. The red data points display merged data.

Figure 7 displays the UVOT light curves between 2013 and 2023 with the merged
data shown in red. Overall, there is no significant variability from year to
year. The results for the merged data are listed in Table 4. Figure 7 and
Table 4 show that there is no significant variability on long or short time
scales, not even a trend like seen in X-rays. This is somewhat expected given
the Gaussian distribution of the UVOT data.

Figure 7: Swift UVOT long-term light curves. The fluxes are given in units of
$10^{-15}$ W m-2. The black data points display as in Figure 2 each
observation with a detection. The red data points display merged data as
listed in Table 4. The vertical green lines mark the median values in each of
the filters.

###  3.2 X-ray Spectral Analysis

For the comparison of the high and low states we merged the 2010 February and
May data into a high state spectrum and did the same for the low state by
merging all data from 2013 to 2023. The high and low state data were then
fitted with various spectral models. The results of these fits are listed in
Table 3. All models were fitted with the z=0 absorption fixed to the Galactic
value of $1.17\times 10^{20}cm^{-2}$.

Figure 8: Upper panel: Swift XRT spectrum of all low state 2013-2023 data
merged fitted by an absorbed single power law model. Lower panel: The ratio
between the data and the model.

The total exposure time of the high state spectrum was 3354s and the count
rate 0.115 counts s-1 which means a total number of source counts of 260
counts which account for 99.3% of the counts in the spectrum. The relatively
low number of counts in the high-state spectrum only allowed for an analysis
using W statistics (Cash, 1979).

The overall count rate of the low-state spectrum is 0.0046 counts s-1 and has
a total exposure time of 302 ks. This results in a total number of about 1400
source counts, which accounts for 89% of the counts in the spectrum. The
relatively large number of counts allows us to fit the low-state spectrum with
$\chi^{2}$ statistics. The binning of the low-state spectrum was 20 counts per
bin. This spectrum is displayed in Figure 8.

The high and low flux state spectra were first fitted by a single power law
model. While in the high state case the data can be fitted by this model
acceptably, the low state spectrum clearly deviates from a simple power law
model as shown from the fit parameters in Table 3 and in Figure 8. One thing
to keep in mind is that the number of counts in the high state data above 1.5
keV is so low that we do not have any information on the spectrum above this
energy. Next, we applied a broken power law model and a blackbody plus power
law model. These are phenomenological models that can describe the spectra
quite well in both cases. Finally, we used a neutral partial covering absorber
model. For the high state data, the parameters of the partial covering
absorber are unconstrained. There are no data at higher energies that are
needed to fit this model. For the low state data however, the spectrum is well
described by a partial covering absorber model with a column density of
$6\times 10^{22}cm^{-2}$ and a covering fraction of 80%.

Table 3:  Spectral analysis of the high and low state XRT spectra. The high
state data were fitted with W statistics, while for the low state data,
$\chi^{2}$ statistics was applied.

Parameter | 2010 High | 2013-2023 Low
---|---|---
powerlaw
$\Gamma$ | 4.32$\pm$0.20 | 3.12$\pm$0.10
$\chi^{2}/\nu$ | 111/82 | 87.9/53
broken power law
$\Gamma_{1}$ | 3.51$\pm$0.40 | 3.29$\pm$0.15
$E_{\rm break}$ [keV] | 0.85$\pm$0.13 | 1.53${}^{+0.62}_{-0.38}$
$\Gamma_{2}$ | 7.30$\pm$1.50 | 1.96${}^{+0.43}_{-0.67}$
$\chi^{2}/\nu$ | 76/82 | 61.3/51
blackbody + power law
kT [eV] | 112$\pm$12 | 95$\pm$9
$\Gamma$ | 4.56$\pm$1.65 | 2.18$\pm$0.26
$F_{\rm bb}$ [W m-2] | $3.8\times 10^{-15}$ | 7.5$\times 10^{-17}$
$F_{\rm po}$ [W m-2] | $2.0\times 10^{-15}$ | 9.6$\times 10^{-17}$
$\chi^{2}/\nu$ | 76/82 | 57.9/51
xpcfabs $\times$ power law
$N_{H}^{1}$ | 6.302 | 6.30${}^{+4.62}_{-2.51}$
$f_{pc}$ | 0.053 | 0.80${}^{+0.07}_{-0.11}$
$\Gamma$ | 4.32$\pm$0.20 | 3.27$\pm$0.12
$\chi^{2}/\nu$ | 111/82 | 60.1/51

1 The redshifted (z=0.021) partial covering absorber column density is given
in units of $10^{22}cm^{-2}$. 2 The partial covering absorber column density
is fixed to $6.3\times 10^{22}cm^{-2}$. 3 not constraint

Figure 9 displays an absorbed blackbody plus power law model fit to the merged
high state data from 2010 and the 2013-2022 low state data. Note, that for
display purposes the high state data have been binned, however the spectral
fits were performed with unbinned data using W-statistics (Cash, 1979). The
blackbody component is displayed in red while the power law component is shown
in green. As for the change between the high and low state black body and
power law components, the black body component changes by a factor of
48$\pm$13 and the power law component by a factor of 23$\pm$6\. This suggests
that the blackbody component decreased stronger than the power law component.

Figure 9: Swift XRT merged high and low state spectra (left and right,
respectively) The red line displays the black body spectrum and the green
line, the power law component.

###  3.3 Strong X-ray Spectral Change in January 2023

As shown in the hardness ratio light curve in Figure 3 there is a strong
spectral change from being a very soft source to a significantly harder AGN
around MJD 59954-59977 (2023-January-10 to 31). In order to study the change
in the X-ray spectrum, we merged the data after IC 3599 emerged from its sun
constraint on 2022-October-31 to 2023-January-10 when it was in the soft state
and between 2023-February-10 and May-01 when it was in the hard state. Both
spectra can be fitted by simple power law models. For the soft and hard
phases, the photon indices were $\Gamma=4.03^{+0.37}_{-0.33}$ and
$\Gamma=1.70^{+0.87}_{-0.54}$, respectively. During the soft state the AGN is
also brighter with a flux of $F_{0.3-10keV}=(4.33\pm 0.40)\times
10^{-16}Wm^{-2}$, while during the hard state the flux was at $(1.34\pm
0.58)\times 10^{-16}Wm^{-2}$. Since about March 2023 IC 3599 has transitioned
again into a softer X-ray state.

###  3.4 UV Morphology

Figure 10 displays the W2 image which was merged from all low-state W2 data
from 2013-2023. This image has a total exposure time of 99 ks. The image
clearly shows the spiral structure of the host galaxy, tracing the young,
blue, stars in the spiral arms. The projected angular diameter of the galaxy
is about 75” which corresponds to a physical size of 33 kpc; larger than a
typical dwarf galaxy, suggesting that the SMBH mass of IC 3599 is not
particularly low.

Figure 10: Swift UVOT W2 image of IC 3599. At the distance of IC 3599, 10”
corresponds to 4.4 kpc.

###  3.5 UV Colors

Although the Gaussian distributions of the magnitudes in all 6 UVOT filters
during the low state suggest random fluctuations, we still checked if there
may be any dependence on the colors with fluxes in X-rays and the UV. For this
purpose, we calculated U-B and W2-W1 colors and correlated them with various
properties, like W2 magnitude, count rate and hardness ratio. As expected, we
did not find any correlations among these parameters.

###  3.6 Spectral Energy Distribution

The Spectral Energy Distribution (SED) of IC 3599 during the February 2010
outburst and the 2013-2023 low state is shown in Figure 11. It displays how
dramatically different the SED of IC 3599 was during the 2010 outburst. The
optical/UV to X-ray spectral slope $\alpha_{\rm ox}$444The optical/UV to X-ray
spectral slope $\alpha_{\rm ox}$ is defined by Tananbaum et al. (1979) as
$\alpha_{\rm ox}$= $-0.384\times(log(l_{\rm 2keV})-log(l_{2500\AA}))$, where
$l_{\rm 2500\AA}$ and $l_{\rm 2keV}$ are the luminosity densities at 2500Å and
2 keV. during the outburst was $\alpha_{\rm ox}$=1.57$\pm$0.07 and during the
low state $\alpha_{\rm ox}$=1.79$\pm$0.04. Note that the uncertainties on the
$\alpha_{\rm ox}$ value during the outburst maybe larger, because to determine
the 2 keV data point we assumed a simple power law model, which may not be the
correct model at 2 keV, but with the lack of available data it is the value
derived from the X-ray spectral fit.

Figure 11: The SED of IC 3599 between the outburst in February 2010 (red), the
merged 2013-2023 low state data (blue), the mini flare data in December 2022
(magenta), and the merged data after the mini flare (green). Note that the
UVOT data during this flare are not shown due to their similarity to the
overall low-state data.

For the 2010 outburst data and applying the simple power law model, we derived
a 0.2-2.0 keV luminosity of $L_{X}=(9.9\pm 0.8)\times 10^{35}W$. Applying the
relation $logL_{\rm bol}=1.23\times log(L_{X})-7.36$ as given in Grupe et al.
(2010) we estimated the bolometric luminosity as $8\times 10^{36}$ W. Assuming
a black hole mass of IC 3599 of 2.5$\times 10^{6}M_{\odot}$ the Eddington
luminosity is $3.15\times 10^{37}W$ which then results in an Eddington ratio
of $L/L_{\rm Edd}$ = 0.25.

As for the low state 2013-2023 data, assuming the broken power law model as
shown in Table 3, the 0.2 - 2.0 keV luminosity is $1.8\times 10^{34}W$ which
results in a bolometric luminosity of $6\times 10^{34}W$ and an Eddington
ratio of $L/L_{\rm Edd}=2\times 10^{-3}$.

In addition, the SED (Figure 11) also displays the SED of the data during the
December 2022 flare period (open magenta circles) and the data after the mini
flare from February to May 2023 (open green triangles). Note that for
visualization purposes we have binned the data with a binning of 10. For the
spectral fits, no binned data were used applying W statistics (Cash, 1979).
The X-ray data after the mini flare indicate a significant flux increase in
the hard X-ray band. The spectral analysis of these data results in a very
flat X-ray spectrum with $\Gamma=1.70^{+0.81}_{-0.51}$, significantly flatter
than what has been observed during the entire 2013-2022 low state period. Note
that the low number of counts did not allow for a more sophisticated spectral
analysis.

##  4 Discussion

###  4.1 High-Amplitude Variability of AGN

In principle, any single one of a huge number of small or large flares in any
blazar or radio-quiet AGN could be a TDE. However, TDEs are very rare events,
and almost every single AGN or blazar is known to vary (see Ulrich et al.,
1997; Gaskell, 2008; Gallo, 2018, for reviews). Therefore, exceptional
positive evidence is required for any claim of a TDE in an AGN, as emphasized
by, e.g., Rees (1988) and Komossa & Bade (1999). The situation is completely
different, when a quiescent galaxy suddenly shows a huge X-ray outburst,
because the only known model to explain a quasar-luminosity outburst in a
galaxy without long-lived accretion disk is a TDE. IC 3599 is a bona fide AGN
with a long-lived NLR (Komossa & Bade, 1999; Grupe et al., 2015), and closely
resembles the increasing number of changing-look AGN identified in recent
years (e.g. Alloin et al., 1986; Runco et al., 2016; MacLeod et al., 2019;
Frederick et al., 2019; Ochmann et al., 2024).

Therefore, so far, no definite positive evidence for a rare TDE in this highly
variable AGN has been presented. However, we note that Mandel & Levin (2015)
mentioned in passing the possibility of tidal disruption of one star and later
tidal stripping of the second star of a binary star system in context of IC
3599. In that case, the near-identical peak luminosities of the two outbursts
of IC 3599 would be unexpected. Further, w.r.t. the two outbursts of IC 3599,
Komossa et al. (2014) pointed out that during certain phases of binary SMBH
evolution, or in the presence of a recoiling SMBH, TDE rates can be
temporarily strongly enhanced (Chen et al., 2009; Komossa & Merritt, 2008;
Stone & Loeb, 2011), but two events within decades would still be rare, and IC
3599 does not show evidence for a recent major merger (e.g., Figure 10), and
the near-identical peak luminosities of the two outbursts would have to be
coincidence. Therefore, Komossa et al. (2014) re-emphasized that TDEs are most
reliably identified in quiescent galaxies. Further, Grupe et al. (2015)
commented on the TDE model of Liu et al. (2009) (see also Liu et al., 2014) in
application to IC 3599. Liu et al. (2009) predicted TDE light curves for
stellar disruption in a binary SMBH system, showing characteristic recurrent
flare and dip events. However, the timing and amplitudes of IC 3599 did not
fit that model. 555Even though not discussed further here, we note that
multiple outburst events in quiescent galaxies have been interpreted as
possible partial stripping events; for example the case of RXJ133157.6324319.7
(Hampel et al., 2022) which showed a second outburst (Malyali et al., 2023)
$\sim$30 yrs after the first.

The one TDE model with explicit predictions which we can now test and rule out
with the new monitoring data presented here, is the published repeat-tidal-
stripping scenario for IC 3599, because that model made testable predictions
for the time frame covered in our new observations. We come back to this model
in the following paragraphs. Beyond that, we continue to consider AGN
scenarios, rather than TDE scenarios, for this highly variable AGN. Below, we
also discuss the other aspects of the long-term variability of IC 3599,
unrelated to the two big outbursts.

###  4.2 No Outburst of IC 3599 in 2019/2020

Campana et al. (2015) predicted that there would be another outburst due to
the partial tidal stripping of an orbiting star in 2019 and 2020. They
predicted a 9.5 year period. The model also assumed a black hole mass of the
order of a few $10^{5}M_{\odot}$. While in general a TDE scenario cannot be
excluded in principle, as pointed out by Grupe et al. (2015) and Komossa &
Bade (1999), IC 3599 is an AGN and the dramatic flaring in IC 3599 does not
have to be associated with a tidal disruption event and that given the black
hole mass estimates of IC 3599 of the order of several millions of solar
masses, an accretion disk instability scenario would be more likely. Campana
et al. (2015)’s prediction of repeat flaring made it possible to test the
tidal stripping scenario. The Swift monitoring programs from 2019 and 2020
initiated by us and Campana clearly show that there is no outburst seen during
this period (see Figure 2). This result clearly favors the accretion disk
scenario as suggested by Grupe et al. (2015).

###  4.3 Slow Increase in X-ray Flux

Figure 6 suggests that there has been a slow overall increase in X-ray flux
since about 2018. In the accretion disk scenario that could be explained by a
slow fill-up of the inner part of the accretion disk which emptied out during
the last outburst in 2010. In Grupe et al. (2015) we estimated the fill-up
time to be several decades, following the relation $\tau_{\rm
fill}=0.33\alpha^{-8/10}M_{6}^{6/5}\dot{M}^{-3/10}_{\rm edd}(R_{\rm
trunc}^{5/4}-R_{0}^{5/4})$ given in units of month following the relation by
Saxton et al. (2015). The other parameters are the viscosity $\alpha$ for
which we assumed a standard value of 0.1, the black hole mass $M_{6}$ in units
of $10^{6}M_{\odot}$, the infill rate $\dot{M_{\rm edd}}$ in units of the
Eddington limit. The truncation radius $R_{\rm trunc}$ and the inner radius
$R_{0}$ are given in units of the gravitational radius
$R_{g}=\frac{GM}{c^{2}}$.

While the X-ray flux seems to develop some long-term trend to become slightly
brighter, there is no sign of any significant variability in the optical and
UV. IC 3599 seems to be fairly constant in all 6 UVOT filters and the
fluctuations seem to be random, which is supported by the Gaussian
distributions of the magnitudes seen in each filter.

###  4.4 X-ray Mini Flare and Spectral Hardening Event in 2022/2023

As shown in Figure 6, there is an X-ray mini flare at the beginning of
December 2022. Right after this short-lasting flare we see a dramatic
hardening of the X-ray spectrum, as shown in the hardness ratio light curve in
Figure 6. This hardening of the spectrum can also be seen in the spectral
energy distribution in Figure 11. The data from this hardening event as
displayed as green open triangles.

The mini flare started on 2022 December 01 and peaked on December 10 with a
peak flux of 1.29$\pm$0.45 $\times 10^{-15}W~{}m^{-2}$, which is a factor of
about 10 higher than the flux on December 01 (see also Table 3). While the
spectrum was very soft during the flare, the onset of the spectral hardening
started around 2023 January 03 and reached the hardest state with a hardness
ratio of 0.73$\pm$0.25 on March 31. The spectrum became soft again by the end
of May 2023 and has remained soft in all observations after that.

The question is raised, which physical process(es) cause this temporary
spectral hardening. The hard X-ray spectral component, typically observed in
all AGN, is usually interpreted as the presence of an accretion-disk corona.
It is therefore possible that a corona formed temporarily, following the mini
flare, and disappeared again in the low-state. Alternatively, we might
speculate that a temporary absorption event caused an apparent spectral
hardening. For instance, it is possible that due to the flaring activity a
temporary outflow was triggered because of the increase in the accretion
luminosity (Takeuchi et al., 2013). When a clumpy outflow partially covers the
intrinsic emission, a spectral hardening can result. However, even at the peak
of the mini flare, $L/L_{\rm Edd}$ is only about 0.02, whereas launching of
radiation-pressure driven outflows requires values closer to 1.

The Swift snapshot observations do not contain enough photon statistics to
distinguish between these different spectral models (like emission from a
temporary corona, versus partial covering absorption, or more complex spectral
models involving the interplay of several components). Deeper, triggered,
follow-up observations during the flare decline phase will be very useful, if
new mini flares are detected in the future.

###  4.5 Black Hole Mass Estimates

While the repeating TDE model of Campana et al. (2015) requires a small black
hole mass of a few $10^{5}M_{\odot}$, all observational parameters, like the
width of the [OIII]$\lambda$5007 line, suggest a black hole mass that is at
least 10 times lager (see our discussion in Grupe et al. (2015), where we also
used BLR line width). The large physical size of IC 3599 as shown in Figure 10
may support a larger black hole mass as well, but the previous SMBH mass
estimates using the various scaling relations are the most restrictive.

###  4.6 Conclusions

Despite the speculation in 1995 by Brandt et al. (1995) and Grupe et al.
(1995), and the repeated-TDE model by Campana et al. (2015) that the X-ray
outburst seen during the RASS could have been caused by a TDE, our long-term
Swift monitoring campaign suggests otherwise, since the third outburst
predicted by the repeat-TDE model in 2019/2020 did not happen. The X-ray
outbursts seen in 1990 by ROSAT and 2010 by Swift are most likely caused by an
accretion disk instability as favored by Grupe et al. (2015), since IC 3599 is
not a quiescent galaxy but a bona fide AGN. In fact, IC 3599 is an extreme
case of an optical changing-look AGN (Komossa & Grupe, 2023; Xu et al., 2024).

Independent of the nature of the big outbursts or their absence in 2019/2020
in particular, we have also studied the long-term X-ray flux and spectral
variability properties of IC 3599 during its more quiescent levels. IC 3599
turns out to be highly variable in the X-ray regime. One event stood out: We
found that IC 3599 exhibited an increase in its X-ray flux by a factor of
about 10 in December 2022. This mini flare was followed by a remarkable
hardening of the X-ray spectrum in the following months. One possible
explanation for such a behavior could be the temporary formation of an
accretion disk corona.

We will continue to monitor IC 3599 with Swift. It depends on the model, if
and when a new outburst is expected. For instance, if the previous two
outbursts were powered by a disk instability, it would depend on the evolving
and variable AGN disk properties, if and when a new instability occurs (note
that the X-ray emission of IC 3599 in low-state is not constant but still
varies, as in the majority of AGN). If, instead, there was an underlying
strictly periodic process behind the outbursts, like variants of binary SMBH
models where for instance a secondary SMBH interacts with the primary’s disk
once during its orbit, or binary SMBH models where stream-feeding from a
circum-binary disk occurs, then the next outburst is expected around the year
2030. In case IC 3599 will exhibit another X-ray outburst again, we have a
pre-approved ToO program with XMM that would allow us to study the inner-most
environment of the central black hole.

We would like to thank Swift PI Brad Cenko for approving our continued
requests to observe IC 3599 and the Swift Science Operations team for
executing the observations. We would also like to thank the anonymous referee
for useful comments and suggestions. This research has made use of the
NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion
Laboratory, Caltech, under contract with the National Aeronautics and Space
Administration. This work made use of data supplied by the UK Swift Science
Data Centre at the University of Leicester (Evans et al., 2007). This research
has made use of the XRT Data Analysis Software (XRTDAS) developed under the
responsibility of the ASI Science Data Center (ASDC), Italy. This research has
made use of data obtained through the High Energy Astrophysics Science Archive
Research Center Online Service, provided by the NASA/Goddard Space Flight
Center.

##  5 Data Availability

The raw Swift data of our project are available in the Swift archive at
https://swift.gsfc.nasa.gov/archive/. The reduced results are available at
Zenodo: 10.5281/zenodo.10899673 (catalog 10.5281/zenodo.10899673).

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##  Appendix A Swift Observations

Table 4: Swift XRT and UVOT observations of IC 3599 . The full machine-
readable table is available on Zenodo: 10.5281/zenodo.10899673. (catalog
10.5281/zenodo.10899673)

Target ID | Segment | MJD1 |  $T_{\rm start}$ (UT) |  $T_{\rm end}$ (UT) | $T_{\rm XRT}$ | $T_{\rm V}$ | $T_{\rm B}$ | $T_{\rm U}$ | $T_{\rm W1}$ | $T_{\rm M2}$ | $T_{\rm W1}$
---|---|---|---|---|---|---|---|---|---|---|---
37507 | 001 | 55252.365 | 2010-02-25 07:46 | 2010-02-25 09:44 | 2120 | 176 | 176 | 176 | 352 | 486 | 704
| 003 | 55333.049 | 2010-05-17 00:58 | 2010-05-17 01:19 | 1234 | 105 | 105 | 105 | 210 | 264 | 421
| 004 | 56595.160 | 2013-10-30 00:34 | 2013-10-30 07:13 | 3771 | 312 | 312 | 312 | 624 | 795 | 1250
| 005 | 56602.208 | 2013-11-06 02:24 | 2013-11-06 07:27 | 4832 | — | — | — | — | 4780 | —
| 006 | 56742.583 | 2014-03-26 07:50 | 2014-03-26 19:08 | 3596 | 101 | 101 | 101 | 204 | 2630 | 407
37569 | 001 | 56877.306 | 2014-08-08 07:07 | 2014-08-08 07:35 | 1613 | 132 | 132 | 132 | 263 | 381 | 526
| 002 | 56976.313 | 2014-11-15 04:12 | 2014-11-15 10:49 | 4615 | 107 | 107 | 3390 | 214 | 290 | 430
| 003 | 56984.375 | 2014-11-23 08:57 | 2014-11-23 09:03 | 352 | — | — | 354 | — | — | —
| 004 | 57110.970 | 2015-03-29 21:37 | 2015-03-30 00:50 | 2829 | 229 | 229 | 229 | 460 | 675 | 920
| 005 | 57209.167 | 2015-07-06 00:33 | 2015-07-06 04:08 | 4840 | 134 | 134 | 134 | 268 | 352 | 3740
| 006 | 57215.146 | 2015-07-12 01:43 | 2015-07-12 06:40 | 1648 | — | 324 | 348 | 699 | — | 204
| 007 | 57218.438 | 2015-07-15 07:57 | 2015-07-15 12:52 | 2377 | 193 | 193 | 193 | 387 | 528 | 779
| 008 | 57220.604 | 2015-07-19 14:18 | 2015-07-19 14:44 | 1528 | 121 | 120 | 121 | 242 | 418 | 484
| 009 | 57229.149 | 2015-07-26 02:37 | 2015-07-26 04:35 | 1913 | 158 | 158 | 158 | 317 | 430 | 635
| 010 | 57236.194 | 2015-08-02 03:51 | 2015-08-02 05:43 | 1191 | 112 | 112 | 112 | 226 | 123 | 451
| 011 | 57239.361 | 2015-08-05 08:34 | 2015-08-05 08:51 | 989 | 81 | 81 | 81 | 160 | 240 | 322
| 012 | 57243.316 | 2015-08-09 05:01 | 2015-08-09 10:11 | 2000 | 164 | 164 | 164 | 328 | 471 | 658
| 013 | 57327.104 | 2015-11-01 00:03 | 2015-11-01 05:20 | 4697 | 130 | 132 | 132 | 3370 | 379 | 527
| 014 | 57387.375 | 2015-12-31 04:27 | 2015-12-31 13:43 | 3385 | — | — | — | 1915 | — | –
| 015 | 57466.333 | 2016-03-19 00:44 | 2016-03-19 15:11 | 4014 | 105 | 105 | 105 | 211 | 3010 | 423
| 016 | 57589.506 | 2016-07-20 11:54 | 2016-07-20 12:22 | 1663 | 136 | 136 | 136 | 272 | 409 | 545
| 017 | 57590.399 | 2016-07-21 07:10 | 2016-07-21 12:02 | 3274 | 264 | 264 | 264 | 530 | 783 | 1058
| 018 | 57762.924 | 2017-01-09 20:44 | 2016-01-09 23:42 | 2412 | 135 | 135 | 135 | 270 | 1142 | 539
| 019 | 57765.253 | 2017-01-12 03:03 | 2017-01-12 06:10 | 2515 | 75 | 75 | 75 | 149 | 236 | 1873
| 020 | 57798.750 | 2017-02-14 14:34 | 2017-02-14 21:11 | 1543 | 117 | 117 | 117 | 234 | 441 | 469
| 021 | 57810.667 | 2017-02-26 10:34 | 2017-02-26 23:30 | 1471 | 117 | 117 | 117 | 231 | 352 | 463
| 022 | 57826.507 | 2017-03-12 12:13 | 2017-03-12 12:19 | 3446 | — | — | 81 | 259 | — | —
| 023 | 57828.439 | 2017-03-16 08:53 | 2017-03-16 12:11 | 1735 | 140 | 140 | 140 | 280 | 414 | 561
| 024 | 57838.632 | 2017-03-26 14:11 | 2017-03-26 16:05 | 2008 | 165 | 165 | 165 | 329 | 459 | 661
| 025 | 57852.750 | 2017-04-09 03:30 | 2017-04-09 08:25 | 1331 | 105 | 106 | 106 | 212 | 304 | 425
| 026 | 57866.910 | 2017-04-23 21:37 | 2017-04-23 22:05 | 1623 | 134 | 134 | 134 | 268 | 390 | 537
| 027 | 57880.552 | 2017-05-07 06:05 | 2017-05-07 20:25 | 1918 | 155 | 155 | 155 | 310 | 462 | 622
| 028 | 57894.899 | 2017-05-21 04:42 | 2017-05-22 13:12 | 2093 | 169 | 169 | 169 | 338 | 515 | 677
| 029 | 57908.858 | 2017-06-04 19:50 | 2017-06-04 21:32 | 1216 | 107 | 107 | 145 | 313 | 78 | 429
| 030 | 57969.344 | 2017-08-04 00:09 | 2017-08-04 16:16 | 2115 | 171 | 171 | 171 | 273 | 482 | 547
| 031 | 58065.042 | 2017-11-08 00:03: | 2017-11-08 01:42 | 1756 | 150 | 150 | 150 | 300 | 514 | 600
10375 | 001 | 58072.705 | 2017-11-15 15:17 | 2017-11-15 18:35 | 3718 | 249 | 381 | 381 | 763 | 689 | 1144
| 002 | 58076.618 | 2017-11-19 14:40 | 2017-11-19 14:59 | 1139 | 96 | 96 | 96 | 193 | 233 | 386
| 003 | 58103.928 | 2017-12-16 22:12 | 2017-12-16 22:24 | 694 | 60 | 60 | 60 | 121 | 172 | 242
| 004 | 58105.486 | 2017-12-17 23:38 | 2017-12-18 23:41 | 4078 | 340 | 340 | 340 | 679 | 922 | 1361
| 005 | 58133.514 | 2018-01-15 05:01 | 2018-01-15 19:37 | 4545 | 347 | 347 | 410 | 832 | 1056 | 1390
| 006 | 58164.500 | 2018-02-15 02:23 | 2018-02-15 21:45 | 4825 | 388 | 388 | 388 | 776 | 1131 | 1554
| 007 | 58192.318 | 2018-03-15 01:09 | 2018-03-15 14:04 | 4730 | 390 | 387 | 390 | 785 | 983 | 1567
| 008 | 58223.566 | 2018-04-15 09:35 | 2018-04-15 17:44 | 4877 | 405 | 405 | 405 | 811 | 1042 | 1625
| 009 | 58253.625 | 2018-05-15 13:10 | 2018-05-15 16:43 | 2944 | 233 | 233 | 233 | 469 | 731 | 935
| 010 | 58256.708 | 2018-05-18 16:07 | 2018-05-18 17:57 | 1830 | 89 | 170 | 170 | 341 | 263 | 681
| 011 | 58284.448 | 2018-06-15 08:57 | 2018-06-15 12:29 | 4935 | 481 | 407 | 407 | 813 | 1134 | 1628
| 012 | 58315.421 | 2018-07-15 22:05 | 2018-07-16 22:10 | 4635 | 362 | 362 | 362 | 727 | 1139 | 1455

1 The Modified Julian Date (MJD) is given for the middle of the observation
period.

Table 1: Continued

Target ID | Segment | MJD1 |  $T_{\rm start}$ (UT) |  $T_{\rm end}$ (UT) | $T_{\rm XRT}$ | $T_{\rm V}$ | $T_{\rm B}$ | $T_{\rm U}$ | $T_{\rm W1}$ | $T_{\rm M2}$ | $T_{\rm W1}$
---|---|---|---|---|---|---|---|---|---|---|---
10375 | 013 | 58339.170 | 2018-08-09 02:18 | 2018-08-09 05:52 | 4580 | 235 | 235 | 235 | 469 | 749 | 941
| 014 | 58422.882 | 2018-10-31 18:52 | 2018-10-31 23:30 | 4949 | 397 | 397 | 397 | 794 | 1205 | 1592
| 015 | 58423.389 | 2018-11-01 05:48 | 2018-11-01 12:42 | 5002 | 413 | 413 | 413 | 828 | 1107 | 1659
| 016 | 58452.387 | 2018-11-30 09:22 | 2018-11-30 14:31 | 4540 | 350 | 317 | 362 | 724 | 1122 | 1450
| 017 | 58453.542 | 2018-12-01 15:35 | 2018-12-01 17:31 | 2532 | 207 | 207 | 207 | 414 | 584 | 829
| 018 | 58482.979 | 2018-12-30 22:31 | 2018-12-31 00:34 | 3219 | 268 | 268 | 268 | 536 | 772 | 1074
| 019 | 58488.059 | 2019-01-05 01:14 | 2019-01-05 01:34 | 1209 | 101 | 101 | 101 | 203 | 258 | 405
| 020 | 58492.747 | 2019-01-09 17:04 | 2019-01-09 18:47 | 862 | — | 180 | 180 | 361 | — | 98
| 021 | 58496.694 | 2019-01-13 16:27 | 2019-01-13 16:51 | 1409 | 115 | 115 | 115 | 230 | 331 | 460
| 022 | 58500.344 | 2019-01-17 01:46 | 2019-01-17 15:02 | 4755 | 386 | 386 | 386 | 775 | 1059 | 1552
| 023 | 58514.403 | 2019-01-31 00:42 | 2019-01-31 20:01 | 1306 | 82 | 141 | 141 | 331 | 219 | 331
| 024 | 58519.486 | 2019-02-05 03:41 | 2019-02-05 19:33 | 1928 | 146 | 146 | 146 | 393 | 439 | 586
| 025 | 58521.085 | 2019-02-08 01:33 | 2019-02-08 03:22 | 1726 | 140 | 140 | 140 | 281 | 392 | 563
| 026 | 58531.542 | 2019-02-17 06:50 | 2019-02-17 15:06 | 4448 | 362 | 362 | 362 | 727 | 999 | 1457
| 027 | 58546.101 | 2019-03-03 13:25 | 2019-03-04 15:03 | 4902 | 398 | 398 | 398 | 802 | 1169 | 1604
| 028 | 58559.278 | 2019-03-17 00:54 | 2019-03-17 12:19 | 3652 | 263 | 263 | 263 | 531 | 765 | 1059
| 029 | 58573.531 | 2019-03-31 09:13 | 2019-03-31 16:07 | 4817 | 396 | 396 | 396 | 795 | 1056 | 1590
| 030 | 58590.403 | 2019-04-17 04:26 | 2019-04-17 14:20 | 4880 | 391 | 391 | 390 | 786 | 1190 | 1575
| 031 | 58620.403 | 2019-05-17 06:22 | 2019-05-17 13:00 | 3985 | 323 | 323 | 323 | 645 | 931 | 1293
| 032 | 58634.524 | 2019-05-31 02:07 | 2019-05-31 23:16 | 2869 | 164 | 280 | 280 | 684 | 392 | 921
| 033 | 58651.483 | 2019-06-17 03:25 | 2019-06-17 07:15 | 4905 | 403 | 403 | 403 | 803 | 1149 | 1610
| 034 | 58665.295 | 2019-07-01 02:05 | 2019-07-01 12:04 | 4001 | 348 | 348 | 348 | 696 | 663 | 1397
| 035 | 58681.139 | 2019-07-17 00:46 | 2019-07-17 06:00 | 4470 | 369 | 369 | 369 | 739 | 1015 | 1479
| 036 | 58704.569 | 2019-08-09 01:34 | 2019-08-10 01:53 | 3861 | 225 | 225 | 225 | 500 | 736 | 906
| 037 | 58788.138 | 2019-11-01 01:32 | 2019-11-01 05:07 | 4253 | 345 | 345 | 345 | 690 | 1024 | 1381
| 038 | 58808.292 | 2019-11-21 04:22 | 2019-11-21 09:35 | 3047 | 250 | 250 | 250 | 499 | 714 | 999
| 040 | 58814.549 | 2019-11-27 00:37 | 2019-11-28 02:23 | 4192 | 346 | 346 | 346 | 693 | 943 | 1387
| 041 | 58834.819 | 2019-12-17 16:26 | 2019-12-17 22:58 | 3696 | 181 | 376 | 376 | 751 | 612 | 1372
| 042 | 58865.354 | 2020-01-17 00:33 | 2019-01-17 16:40 | 2642 | 237 | 237 | 237 | 474 | 413 | 947
| 044 | 58886.552 | 2020-02-07 06:49 | 2019-02-07 19:45 | 2113 | 171 | 172 | 172 | 343 | 465 | 689
| 045 | 58909.708 | 2020-03-01 13:39 | 2019-03-01 20:23 | 2315 | 188 | 188 | 188 | 376 | 548 | 751
| 046 | 58943.500 | 2020-04-03 23:27 | 2020-04-04 23:34 | 2233 | 182 | 182 | 182 | 365 | 514 | 731
| 047 | 58970.292 | 2020-05-01 01:19 | 2020-05-01 12:39 | 2068 | 166 | 166 | 166 | 333 | 474 | 668
| 048 | 59001.656 | 2020-06-01 15:51 | 2020-06-01 16:02 | 642 | 53 | 54 | 54 | 107 | 125 | 214
| 049 | 59002.426 | 2020-06-02 06:10 | 2020-06-02 14:19 | 1129 | 87 | 87 | 87 | 178 | 280 | 349
| 050 | 59031.104 | 2020-07-01 00:07 | 2020-07-01 05:06 | 1743 | 144 | 144 | 144 | 288 | 377 | 575
| 051 | 59062.650 | 2020-08-01 14:37 | 2020-08-01 16:37 | 2290 | 187 | 187 | 187 | 374 | 534 | 747
| 052 | 59154.500 | 2020-11-01 03:58 | 2020-11-01 20:03 | 1935 | 158 | 158 | 158 | 315 | 439 | 632
| 053 | 59184.813 | 2020-12-01 17:02 | 2020-12-01 22:02 | 1626 | 134 | 134 | 134 | 306 | 344 | 534
| 054 | 59188.892 | 2020-12-05 21:13 | 2020-12-05 21:35 | 1291 | 107 | 107 | 107 | 214 | 286 | 428
| 055 | 59215.674 | 2021-01-01 15:10 | 2021-01-01 17:11 | 3042 | 246 | 246 | 246 | 493 | 739 | 985
| 056 | 59246.594 | 2021-02-01 02:47 | 2021-02-01 23:47 | 3112 | 245 | 245 | 245 | 491 | 788 | 985
| 057 | 59274.087 | 2021-02-28 22:01 | 2021-03-01 06:11 | 1973 | 159 | 159 | 159 | 317 | 469 | 637
| 058 | 59305.792 | 2021-04-01 18:45 | 2021-04-01 20:37 | 1201 | 98 | 98 | 98 | 195 | 256 | 393
| 059 | 59340.125 | 2021-05-06 02:18 | 2021-05-06 04:10 | 1538 | 122 | 122 | 122 | 243 | 381 | 485
| 061 | 59372.774 | 2021-06-06 05:26 | 2021-06-07 21:42 | 1713 | 132 | 132 | 132 | 265 | 425 | 532
| 062 | 59374.155 | 2021-06-09 03:38 | 2021-06-09 03:48 | 567 | 45 | 45 | 45 | 89 | 131 | 179
| 063 | 59378.597 | 2021-06-13 14:15 | 2021-06-13 14:28 | 789 | 62 | 62 | 62 | 125 | 197 | 249

1 The Modified Julian Date (MJD) is given for the middle of the observation
period.

Table 1: Continued

Target ID | Segment | MJD1 |  $T_{\rm start}$ (UT) |  $T_{\rm end}$ (UT) | $T_{\rm XRT}$ | $T_{\rm V}$ | $T_{\rm B}$ | $T_{\rm U}$ | $T_{\rm W1}$ | $T_{\rm M2}$ | $T_{\rm W1}$
---|---|---|---|---|---|---|---|---|---|---|---
10375 | 064 | 59396.359 | 2021-07-01 06:07 | 2021-07-01 11:08 | 1508 | 118 | 118 | 118 | 237 | 375 | 474
| 065 | 59427.389 | 2021-08-01 05:56 | 2021-08-01 12:38 | 2290 | 182 | 182 | 182 | 362 | 580 | 725
| 066 | 59522.399 | 2021-11-04 06:55 | 2021-11-04 12:10 | 3366 | 273 | 273 | 273 | 548 | 812 | 1096
| 067 | 59527.740 | 2021-11-09 12:47 | 2021-11-09 22:45 | 2277 | 180 | 180 | 180 | 360 | 572 | 721
| 068 | 59552.469 | 2021-12-04 05:47 | 2021-12-04 18:37 | 2605 | 178 | 247 | 284 | 568 | 526 | 710
| 069 | 59556.222 | 2021-12-08 05:19 | 2021-12-08 05:23 | 245 | — | — | 34 | 203 | — | —
| 070 | 59560.128 | 2021-12-12 02:54 | 2021-12-12 03:13 | 1126 | 94 | 94 | 94 | 188 | 239 | 377
| 071 | 59583.910 | 2022-01-04 21:02 | 2022-01-04 23:07 | 3479 | 281 | 281 | 281 | 563 | 853 | 1128
| 073 | 59674.611 | 2022-04-05 13:46 | 2022-04-05 15:34 | 1181 | 91 | 91 | 91 | 183 | 296 | 366
| 074 | 59703.993 | 2022-05-04 05:44 | 2022-05-04 12:02 | 1888 | 146 | 146 | 146 | 294 | 435 | 588
| 075 | 59704.432 | 2022-05-05 10:27 | 2022-05-05 16:43 | 1721 | 141 | 141 | 141 | 281 | 380 | 563
| 076 | 59734.146 | 2022-06-03 17:50 | 2022-06-04 11:25 | 2375 | 197 | 197 | 197 | 396 | 514 | 792
| 077 | 59764.390 | 2022-07-04 06:08 | 2022-07-04 12:37 | 4163 | 328 | 328 | 328 | 656 | 1063 | 1313
| 078 | 59795.644 | 2022-08-04 01:49 | 2022-08-04 21:04 | 3334 | 266 | 266 | 266 | 530 | 779 | 1064
| 079 | 59883.310 | 2022-10-31 07:19 | 2022-10-31 15:47 | 2055 | 175 | 175 | 175 | 348 | 416 | 693
| 080 | 59914.585 | 2022-12-01 03:09 | 2022-12-01 20:59 | 1024 | 44 | 89 | 181 | 363 | 122 | 179
| 081 | 59919.955 | 2022-12-06 22:51 | 2022-12-06 22:56 | 405 | — | 69 | 69 | 138 | — | 109
| 082 | 59923.339 | 2022-12-10 08:05 | 2022-12-10 08:12 | 414 | 37 | 37 | 37 | 75 | 49 | 150
| 083 | 59936.658 | 2022-12-23 15:34 | 2022-12-23 16:03 | 1716 | 141 | 141 | 141 | 280 | 404 | 562
| 084 | 59944.535 | 2022-12-31 12:37 | 2022-12-31 13:04 | 1576 | 135 | 135 | 135 | 270 | 318 | 539
| 085 | 59948.812 | 2023-01-04 18:54 | 2023-01-04 20:05 | 817 | — | 157 | 157 | 314 | — | 145
| 086 | 59949.630 | 2023-01-05 15:00 | 2023-01-05 15:16 | 913 | 79 | 79 | 79 | 157 | 192 | 315
| 087 | 59950.838 | 2023-01-06 19:59 | 2023-01-06 20:15 | 926 | 76 | 76 | 76 | 151 | 211 | 303
| 088 | 59951.623 | 2023-01-07 14:49 | 2023-01-07 15:05 | 844 | 71 | 71 | 71 | 142 | 172 | 283
| 089 | 59952.411 | 2023-01-08 09:51 | 2023-01-08 10:05 | 804 | 65 | 65 | 65 | 130 | 187 | 261
| 090 | 59953.011 | 2023-01-09 00:09 | 2023-01-09 00:23 | 794 | 70 | 70 | 70 | 139 | 134 | 278
| 091 | 59954.007 | 2023-01-10 00:05 | 2023-01-10 00:17 | 694 | 71 | 71 | 71 | 142 | 30 | 283
| 092 | 59955.596 | 2023-01-11 14:11 | 2023-01-11 14:25 | 819 | 69 | 69 | 69 | 137 | 163 | 276
| 093 | 59956.868 | 2023-01-12 20:42 | 2023-01-12 20:58 | 914 | 75 | 75 | 75 | 149 | 202 | 300
| 094 | 59957.791 | 2023-01-13 18:52 | 2023-01-13 19:06 | 824 | 67 | 67 | 67 | 134 | 188 | 269
| 095 | 59964.619 | 2023-01-20 06:52 | 2023-01-20 22:51 | 1156 | 97 | 97 | 97 | 194 | 221 | 389
| 096 | 59974.341 | 2023-01-30 08:05 | 2023-01-30 08:17 | 660 | 68 | 68 | 68 | 136 | — | 272
| 097 | 59975.276 | 2023-01-31 06:30 | 2023-01-31 09:57 | 1503 | 46 | 170 | 170 | 341 | 156 | 564
| 098 | 59977.793 | 2023-02-02 18:59 | 2023-02-02 19:08 | 534 | 47 | 47 | 47 | 93 | 81 | 188
| 099 | 59984.472 | 2023-02-09 11:14 | 2023-02-09 11:25 | 642 | 50 | 50 | 50 | 100 | 160 | 201
| 100 | 59994.269 | 2023-02-19 06:21 | 2023-02-19 06:34 | 789 | 68 | 68 | 68 | 136 | 143 | 272
| 101 | 60004.532 | 2023-03-01 12:41 | 2023-03-01 12:51 | 604 | 54 | 54 | 54 | 108 | 87 | 216
| 102 | 60009.765 | 2023-03-06 18:14 | 2023-03-06 18:31 | 979 | — | 128 | 128 | 257 | — | 439
| 103 | 60014.532 | 2023-03-11 07:54 | 2023-03-11 17:38 | 1174 | 101 | 101 | 101 | 201 | 202 | 403
| 104 | 60024.925 | 2023-03-21 22:05 | 2023-03-21 22:19 | 821 | 66 | 66 | 66 | 132 | 195 | 264
| 105 | 60034.588 | 2023-03-31 07:46 | 2023-03-31 20:29 | 1400 | 122 | 122 | 122 | 244 | 238 | 489
| 106 | 60044.968 | 2023-04-10 23:05 | 2023-04-10 23:24 | 1096 | 90 | 90 | 90 | 182 | 240 | 364
| 107 | 60054.563 | 2023-04-20 13:24 | 2023-04-20 13:38 | 817 | 68 | 68 | 68 | 137 | 168 | 273
| 108 | 60065.357 | 2023-05-01 08:21 | 2023-05-01 08:48 | 1613 | 132 | 132 | 132 | 264 | 384 | 527
| 109 | 60095.205 | 2023-05-31 04:05 | 2023-05-31 05:46 | 1214 | 159 | 65 | 65 | 318 | 408 | 637
| 110 | 60126.288 | 2023-07-01 02:52 | 2023-07-01 10:58 | 1900 | 165 | 165 | 165 | 328 | 348 | 657
| 111 | 60156.127 | 2023-07-31 02:50 | 2023-07-31 03:16 | 1518 | 124 | 124 | 124 | 249 | 358 | 498

1 The Modified Julian Date (MJD) is given for the middle of the observation
period.

Table 2: Merged XRT data as shown in Figure 6

MJD Range | MJDcenter | bin width1 | $F_{0.3-10keV}^{2}$ | HR3
---|---|---|---|---
56595 - 57243 | 56916.0 | 648.0 | 0.943$\pm$0.120 | +0.00$\pm$0.10
57327 - 57969 | 57648.0 | 642.0 | 0.906$\pm$0.100 | -0.36$\pm$0.15
58065 - 58339 | 58202.0 | 137.0 | 0.615$\pm$0.059 | -0.22$\pm$0.12
58422 - 58704 | 58563.0 | 141.0 | 1.008$\pm$0.065 | -0.39$\pm$0.12
58788 - 59062 | 58925.0 | 137.0 | 1.870$\pm$0.131 | -0.66$\pm$0.07
59154 - 59427 | 59290.5 | 136.5 | 2.170$\pm$0.219 | -0.54$\pm$0.07
59527 - 59795 | 59661.0 | 134.0 | 3.080$\pm$0.260 | -0.36$\pm$0.08
59883 - 599754 | 59929.0 | 46.0 | 4.557$\pm$0.817 | -0.68$\pm$0.05
59977 - 600655 | 60021.0 | 44.0 | 1.340$\pm$0.558 | +0.22$\pm$0.18

1 given in days

2 The observed 0.3-10 keV fluxes are given in units of $10^{-16}$ W m-2.

3 The hardness ratio is defined as $HR=\frac{hard-soft}{hard+soft}$ with the
soft and hard bands in the 0.3-1.0 and 1.0-10 keV bands, respectively,
applying the BEHR program by citetpark2006

4 The data from the mini flare in December 2022.

5 After flare data from February to May 2023

Table 3: Swift XRT and UVOT fluxes of IC 3599 The full machine-readable table
is available on Zenodo: 10.5281/zenodo.10899673 (catalog
10.5281/zenodo.10899673).

MJD | $F_{\rm 0.3-10keV}^{1}$ | HR2 | $F_{\rm V}^{3}$ | $F_{\rm B}^{3}$ | $F_{\rm U}^{3}$ | $F_{\rm W1}^{3}$ | $F_{\rm M2}^{3}$ | $F_{\rm W2}^{3}$
---|---|---|---|---|---|---|---|---
55252.365 | 105.8$\pm$6.00 | -0.91$\pm$0.03 | 13.03$\pm$0.48 | 10.01$\pm$0.37 | 7.25$\pm$0.27 | 5.83$\pm$0.21 | 5.69$\pm$0.26 | 5.13$\pm$0.19
55333.049 | 29.09$\pm$3.14 | -0.86$\pm$0.07 | 11.77$\pm$0.55 | 9.47$\pm$0.35 | 6.80$\pm$0.25 | 5.22$\pm$0.24 | 5.48$\pm$0.31 | 5.04$\pm$0.23
56595.160 | 1.15$\pm$0.454 | -0.18$\pm$0.30 | 8.85$\pm$0.33 | 7.31$\pm$0.27 | 3.60$\pm$0.16 | 2.71$\pm$0.12 | 2.24$\pm$0.12 | 2.39$\pm$0.08
56602.208 | 1.08$\pm$0.404 | — | — | — | — | — | 2.50$\pm$0.09 | —
56742.583 | 0.73$\pm$0.334 | — | 9.52$\pm$0.53 | 7.45$\pm$0.27 | 3.91$\pm$0.18 | 2.66$\pm$0.17 | 2.48$\pm$0.09 | 2.45$\pm$0.13
56877.306 | — | — | 9.35$\pm$0.43 | 7.18$\pm$0.26 | 3.77$\pm$0.17 | 2.79$\pm$0.15 | 2.62$\pm$0.17 | 2.52$\pm$0.11
56976.188 | 1.51$\pm$0.404 | — | 9.10$\pm$0.51 | 7.66$\pm$0.35 | 3.56$\pm$0.13 | 2.38$\pm$0.15 | 2.02$\pm$0.15 | 2.28$\pm$0.12
57110.970 | 0.47$\pm$0.224 | — | 8.77$\pm$0.32 | 6.92$\pm$0.25 | 3.43$\pm$0.16 | 2.36$\pm$0.13 | 2.08$\pm$0.11 | 2.08$\pm$0.09
57209.167 | — | — | 9.35$\pm$0.43 | 7.52$\pm$0.28 | 3.53$\pm$0.16 | 2.89$\pm$0.16 | 2.74$\pm$0.18 | 2.47$\pm$0.09
57215.146 | 1.40$\pm$0.754 | — | — | 6.98$\pm$0.26 | 3.53$\pm$0.13 | 2.52$\pm$0.11 | — | 2.32$\pm$0.15
57218.438 | 1.00$\pm$0.554 | — | 9.02$\pm$0.42 | 7.18$\pm$0.26 | 3.34$\pm$0.15 | 2.66$\pm$0.15 | 2.32$\pm$0.15 | 2.36$\pm$0.11
57220.604 | 1.55$\pm$0.754 | — | 9.53$\pm$0.44 | 7.18$\pm$0.26 | 3.73$\pm$0.17 | 2.52$\pm$0.16 | 2.53$\pm$0.16 | 2.59$\pm$0.14
57229.149 | 1.15$\pm$0.754 | — | 8.53$\pm$0.39 | 7.38$\pm$0.34 | 3.70$\pm$0.17 | 2.69$\pm$0.15 | 2.80$\pm$0.18 | 2.54$\pm$0.11
57236.194 | 1.55$\pm$1.124 | — | 9.71$\pm$0.54 | 7.80$\pm$0.36 | 3.63$\pm$0.20 | 2.61$\pm$0.17 | 2.74$\pm$0.26 | 2.30$\pm$0.13
57239.361 | 2.90$\pm$1.204 | — | 9.80$\pm$0.55 | 7.80$\pm$0.36 | 3.34$\pm$0.22 | 3.03$\pm$0.20 | 2.43$\pm$0.18 | 2.52$\pm$0.14
57243.316 | — | — | 9.80$\pm$0.45 | 7.59$\pm$0.28 | 3.77$\pm$0.17 | 2.74$\pm$0.15 | 2.53$\pm$0.16 | 2.59$\pm$0.12
57327.104 | 0.86$\pm$0.204 | — | 9.35$\pm$0.52 | 7.25$\pm$0.27 | 3.53$\pm$0.19 | 2.59$\pm$0.09 | 2.72$\pm$0.18 | 2.45$\pm$0.13
57387.375 | 1.35$\pm$0.454 | 0.01$\pm$0.37 | — | — | — | 2.71$\pm$0.10 | — — |
57466.333 | 0.68$\pm$0.304 | — | 8.53$\pm$0.48 | 6.67$\pm$0.31 | 3.43$\pm$0.16 | 2.47$\pm$0.16 | 2.46$\pm$0.06 | 2.32$\pm$0.13
57590.500 | 1.00$\pm$0.354 | -0.11$\pm$0.35 | 9.27$\pm$0.34 | 7.18$\pm$0.26 | 3.60$\pm$0.13 | 2.76$\pm$0.12 | 2.48$\pm$0.14 | 2.39$\pm$0.11
57762.924 | 3.76$\pm$1.014 | -0.59$\pm$0.17 | 9.35$\pm$0.43 | 7.18$\pm$0.26 | 3.84$\pm$0.18 | 2.71$\pm$0.17 | 2.39$\pm$0.11 | 2.59$\pm$0.12
57765.253 | — | — | 9.80$\pm$0.55 | 6.79$\pm$0.31 | 3.80$\pm$0.21 | 2.74$\pm$0.18 | 2.50$\pm$0.19 | 2.15$\pm$0.80
57798.750 | — | — | 9.71$\pm$0.45 | 7.45$\pm$0.27 | 3.84$\pm$0.18 | 2.74$\pm$0.18 | 2.24$\pm$0.14 | 2.62$\pm$0.14
57810.667 | 2.15$\pm$1.004 | — | 10.16$\pm$0.47 | 7.38$\pm$0.27 | 4.13$\pm$0.19 | 2.89$\pm$0.19 | 2.65$\pm$0.07 | 2.54$\pm$0.14
57826.507 | 1.76$\pm$0.814 | — | 8.69$\pm$0.40 | 7.31$\pm$0.27 | 3.98$\pm$0.18 | 2.79$\pm$0.15 | 2.82$\pm$0.18 | 2.69$\pm$0.12
57838.632 | — | — | 8.93$\pm$0.41 | 7.18$\pm$0.26 | 3.53$\pm$0.16 | 2.57$\pm$0.14 | 2.65$\pm$0.17 | 2.36$\pm$0.11
57852.750 | 1.82$\pm$1.694 | — | 9.62$\pm$0.54 | 7.11$\pm$0.26 | 3.43$\pm$0.19 | 2.52$\pm$0.16 | 2.46$\pm$0.16 | 2.32$\pm$0.13
57866.910 | 1.49$\pm$1.074 | — | 9.53$\pm$0.44 | 7.18$\pm$0.26 | 3.91$\pm$0.18 | 2.89$\pm$0.16 | 2.60$\pm$0.17 | 2.47$\pm$0.14
57880.552 | — | — | 9.71$\pm$0.45 | 6.92$\pm$0.25 | 3.40$\pm$0.15 | 2.89$\pm$0.16 | 2.22$\pm$0.14 | 2.32$\pm$0.10
57894.899 | 2.14$\pm$0.814 | — | 8.61$\pm$0.40 | 7.18$\pm$0.26 | 3.77$\pm$0.17 | 2.74$\pm$0.15 | 2.50$\pm$0.16 | 2.52$\pm$0.11
57908.858 | — | — | 9.62$\pm$0.54 | 7.38$\pm$0.27 | 3.63$\pm$0.17 | 2.84$\pm$0.16 | 2.28$\pm$0.31 | 2.36$\pm$0.13
57969.344 | 1.81$\pm$0.814 | — | 9.35$\pm$0.43 | 7.05$\pm$0.26 | 3.63$\pm$0.17 | 2.64$\pm$0.17 | — | 2.57$\pm$0.12
58065.042 | — | — | 9.10$\pm$0.51 | 6.92$\pm$0.25 | 3.34$\pm$0.15 | 2.19$\pm$0.12 | 1.99$\pm$0.13 | 1.73$\pm$0.97
58072.705 | 1.50$\pm$0.544 | — | 9.62$\pm$0.35 | 7.11$\pm$0.26 | 3.56$\pm$0.13 | 2.57$\pm$0.12 | 2.48$\pm$0.14 | 2.30$\pm$0.10
58076.618 | — | — | 9.98$\pm$0.56 | 6.73$\pm$0.31 | 3.84$\pm$0.21 | 2.52$\pm$0.16 | 2.48$\pm$0.18 | 2.36$\pm$0.13
58103.928 | — | — | 10.30$\pm$0.78 | 7.11$\pm$0.40 | 4.05$\pm$0.26 | 2.81$\pm$0.21 | 2.87$\pm$0.24 | 2.10$\pm$0.13
58105.486 | 1.18$\pm$0.464 | — | 9.01$\pm$0.33 | 7.18$\pm$0.26 | 3.60$\pm$0.13 | 2.50$\pm$0.11 | 2.55$\pm$0.11 | 2.45$\pm$0.09
58133.514 | — | — | 9.27$\pm$0.34 | 7.11$\pm$0.26 | 3.56$\pm$0.13 | 2.57$\pm$0.12 | 2.50$\pm$0.11 | 2.47$\pm$0.09
58164.500 | 1.02$\pm$0.434 | -0.63$\pm$0.37 | 9.35$\pm$0.34 | 7.18$\pm$0.26 | 3.70$\pm$0.13 | 2.57$\pm$0.12 | 2.67$\pm$0.12 | 2.66$\pm$0.09
58192.318 | 1.74$\pm$0.464 | -0.31$\pm$0.24 | 8.93$\pm$0.33 | 7.11$\pm$0.26 | 3.77$\pm$0.14 | 2.59$\pm$0.12 | 2.57$\pm$0.12 | 2.54$\pm$0.09
58223.566 | 1.58$\pm$0.524 | -0.57$\pm$0.32 | 9.27$\pm$0.34 | 7.11$\pm$0.26 | 3.80$\pm$0.14 | 2.61$\pm$0.12 | 2.48$\pm$0.11 | 2.43$\pm$0.09
58253.625 | 2.12$\pm$0.70 | -0.32$\pm$0.30 | 9.89$\pm$0.36 | 7.38$\pm$0.27 | 3.66$\pm$0.13 | 2.81$\pm$0.13 | 2.53$\pm$0.14 | 2.54$\pm$0.11
58256.708 | 1.484$\pm$0.90 | — | 9.62$\pm$0.54 | 7.05$\pm$0.26 | 3.87$\pm$0.18 | 2.69$\pm$0.15 | 2.57$\pm$0.17 | 2.45$\pm$0.11
58284.448 | 1.05$\pm$0.58 | +0.03$\pm$0.26 | 9.10$\pm$0.33 | 7.38$\pm$0.27 | 3.66$\pm$0.13 | 2.79$\pm$0.13 | 2.55$\pm$0.11 | 2.54$\pm$0.09
58315.421 | 0.83$\pm$0.304 | -0.48$\pm$0.36 | 9.53$\pm$0.35 | 7.31$\pm$0.27 | 3.77$\pm$0.17 | 2.74$\pm$0.12 | 2.57$\pm$0.12 | 2.45$\pm$0.06

1 The observed 0.3-10 keV fluxes are given in units of $10^{-16}$ W m-2.

2 The hardness ratios are as defined in Table 2

3 The Fluxes in the UVOT filters are given in units of $10^{-15}$ W m-2.

4 0.3-10 keV fluxes estimated from the course rates based on the latest
possible spectral analysis.

Table 3: Continued

MJD | $F_{\rm 0.3-10keV}^{1}$ | HR2 | $F_{\rm V}^{3}$ | $F_{\rm B}^{3}$ | $F_{\rm U}^{3}$ | $F_{\rm W1}^{3}$ | $F_{\rm M2}^{3}$ | $F_{\rm W2}^{3}$
---|---|---|---|---|---|---|---|---
58339.170 | 0.64$\pm$0.25 | -0.46$\pm$0.22 | 10.30$\pm$0.38 | 7.05$\pm$0.26 | 3.98$\pm$0.18 | 2.71$\pm$0.15 | 2.80$\pm$0.15 | 2.66$\pm$0.12
58422.882 | — | — | 9.44$\pm$0.35 | 7.11$\pm$0.26 | 3.80$\pm$0.17 | 2.69$\pm$0.12 | 2.67$\pm$0.12 | 2.54$\pm$0.09
58423.389 | 0.68$\pm$0.234 | -0.44$\pm$0.23 | 9.62$\pm$0.54 | 7.18$\pm$0.26 | 3.87$\pm$0.14 | 2.66$\pm$0.12 | 2.50$\pm$0.11 | 2.52$\pm$0.09
58452.387 | 1.36$\pm$0.454 | -0.66$\pm$0.28 | 9.35$\pm$0.34 | 7.11$\pm$0.26 | 3.66$\pm$0.13 | 2.64$\pm$0.12 | 2.37$\pm$0.11 | 2.50$\pm$0.09
58453.542 | 1.29$\pm$0.404 | -0.30$\pm$0.19 | 9.89$\pm$0.36 | 7.25$\pm$0.27 | 3.53$\pm$0.13 | 2.61$\pm$0.14 | 2.48$\pm$0.14 | 2.47$\pm$0.11
58482.979 | 1.50$\pm$0.504 | -0.47$\pm$0.25 | 9.80$\pm$0.36 | 7.18$\pm$0.26 | 3.60$\pm$0.16 | 2.81$\pm$0.13 | 2.69$\pm$0.15 | 2.47$\pm$0.11
58488.059 | — | — | 10.25$\pm$0.57 | 7.66$\pm$0.28 | 3.80$\pm$0.21 | 2.54$\pm$0.16 | 2.57$\pm$0.17 | 2.54$\pm$0.14
58492.747 | — | — | — | 7.11$\pm$0.26 | 3.77$\pm$0.17 | 2.74$\pm$0.15 | — | 2.57$\pm$0.24
58496.694 | — | — | 10.25$\pm$0.48 | 7.05$\pm$0.33 | 4.21$\pm$0.19 | 2.79$\pm$0.18 | 2.55$\pm$0.16 | 2.64$\pm$0.14
58500.344 | 0.93$\pm$0.314 | -0.75$\pm$0.15 | 9.44$\pm$0.35 | 7.18$\pm$0.26 | 3.84$\pm$0.14 | 2.59$\pm$0.12 | 2.57$\pm$0.12 | 2.45$\pm$0.09
58514.403 | 1.41$\pm$0.524 | +0.12$\pm$0.34 | 9.62$\pm$0.54 | 7.31$\pm$0.27 | 3.84$\pm$0.18 | 2.66$\pm$0.15 | 2.32$\pm$0.17 | 2.64$\pm$0.14
58519.486 | 1.41$\pm$0.35 | -0.96$\pm$0.04 | 9.27$\pm$0.43 | 7.31$\pm$0.27 | 3.87$\pm$0.18 | 2.69$\pm$0.15 | 2.48$\pm$0.16 | 2.69$\pm$0.12
58521.085 | — | — | 9.89$\pm$0.46 | 7.73$\pm$0.28 | 3.91$\pm$0.18 | 2.76$\pm$0.15 | 2.57$\pm$0.17 | 2.54$\pm$0.11
58531.542 | 1.08$\pm$0.264 | -0.63$\pm$0.20 | 9.61$\pm$0.35 | 7.31$\pm$0.27 | 3.84$\pm$0.18 | 2.81$\pm$0.13 | 2.41$\pm$0.11 | 2.47$\pm$0.09
58546.101 | 1.78$\pm$0.30 | -0.30$\pm$0.24 | 9.98$\pm$0.27 | 7.31$\pm$0.27 | 3.91$\pm$0.14 | 2.74$\pm$0.12 | 2.37$\pm$0.11 | 2.62$\pm$0.09
58559.278 | 1.45$\pm$0.504 | -0.20$\pm$0.32 | 9.53$\pm$0.35 | 7.31$\pm$0.27 | 3.91$\pm$0.14 | 2.76$\pm$0.12 | 2.46$\pm$0.13 | 2.39$\pm$0.11
58573.531 | 1.38$\pm$0.384 | -0.15$\pm$0.28 | 9.35$\pm$0.34 | 7.18$\pm$0.26 | 3.56$\pm$0.13 | 2.66$\pm$0.12 | 2.48$\pm$0.11 | 2.43$\pm$0.09
58590.403 | 2.31$\pm$0.42 | -0.95$\pm$0.05 | 9.18$\pm$0.34 | 7.31$\pm$0.27 | 3.73$\pm$0.13 | 2.54$\pm$0.11 | 2.43$\pm$0.11 | 2.43$\pm$0.09
58620.403 | 2.05$\pm$0.634 | -0.45$\pm$0.27 | 9.53$\pm$0.35 | 7.31$\pm$0.27 | 3.77$\pm$0.17 | 2.61$\pm$0.12 | 2.55$\pm$0.11 | 2.39$\pm$0.08
58634.524 | 1.15$\pm$0.454 | -0.87$\pm$0.13 | 9.27$\pm$0.43 | 7.45$\pm$0.27 | 3.73$\pm$0.13 | 2.79$\pm$0.13 | 2.50$\pm$0.16 | 2.52$\pm$0.11
58651.483 | 1.81$\pm$0.50 | -0.07$\pm$0.21 | 9.62$\pm$0.35 | 7.38$\pm$0.27 | 3.84$\pm$0.14 | 2.66$\pm$0.12 | 2.62$\pm$0.12 | 2.50$\pm$0.09
58665.295 | 1.98$\pm$0.69 | -0.51$\pm$0.23 | 9.02$\pm$0.33 | 7.05$\pm$0.26 | 3.47$\pm$0.12 | 2.64$\pm$0.12 | 2.28$\pm$0.12 | 2.28$\pm$0.08
58681.139 | 0.96$\pm$0.324 | +0.30$\pm$0.35 | 9.27$\pm$0.34 | 7.38$\pm$0.27 | 3.60$\pm$0.13 | 2.64$\pm$0.12 | 2.28$\pm$0.10 | 2.28$\pm$0.08
58704.569 | 0.58$\pm$0.314 | -0.42$\pm$0.24 | 9.44$\pm$0.35 | 7.38$\pm$0.27 | 4.02$\pm$0.18 | 2.71$\pm$0.12 | 2.62$\pm$0.14 | 2.45$\pm$0.11
58788.138 | 2.04$\pm$0.45 | -0.91$\pm$0.09 | 9.71$\pm$0.36 | 7.45$\pm$0.27 | 3.70$\pm$0.17 | 2.71$\pm$0.12 | 2.60$\pm$0.12 | 2.41$\pm$0.90
58808.292 | 1.77$\pm$0.54 | -0.47$\pm$0.29 | 9.98$\pm$0.37 | 7.11$\pm$0.26 | 3.80$\pm$0.17 | 2.59$\pm$0.12 | 2.50$\pm$0.14 | 2.50$\pm$0.11
58814.549 | 3.32$\pm$0.67 | -0.67$\pm$0.16 | 10.16$\pm$0.37 | 7.31$\pm$0.27 | 3.87$\pm$0.18 | 2.74$\pm$0.12 | 2.46$\pm$0.11 | 2.52$\pm$0.09
58834.819 | 1.04$\pm$0.424 | +0.06$\pm$0.38 | 9.53$\pm$0.44 | 7.45$\pm$0.27 | 3.77$\pm$0.14 | 2.57$\pm$0.12 | 2.53$\pm$0.14 | 2.36$\pm$0.08
58865.354 | 1.82$\pm$0.664 | -0.71$\pm$0.29 | 9.62$\pm$0.35 | 7.38$\pm$0.27 | 3.70$\pm$0.13 | 2.57$\pm$0.14 | 2.41$\pm$0.13 | 2.26$\pm$0.10
58886.552 | 3.28$\pm$0.884 | -0.76$\pm$0.24 | 10.25$\pm$0.48 | 7.45$\pm$0.27 | 3.91$\pm$0.18 | 2.69$\pm$0.15 | 2.74$\pm$0.18 | 2.66$\pm$0.12
58909.708 | 3.16$\pm$0.884 | -0.35$\pm$0.25 | 9.71$\pm$0.45 | 7.25$\pm$0.27 | 4.17$\pm$0.15 | 2.79$\pm$0.15 | 2.85$\pm$0.16 | 2.64$\pm$0.12
58943.500 | 1.93$\pm$0.814 | -0.95$\pm$0.05 | 9.35$\pm$0.43 | 7.59$\pm$0.28 | 4.21$\pm$0.15 | 2.84$\pm$0.16 | 2.50$\pm$0.14 | 2.47$\pm$0.11
58970.292 | 2.78$\pm$0.964 | -0.78$\pm$0.23 | 9.44$\pm$0.71 | 8.02$\pm$0.45 | 4.13$\pm$0.27 | 2.43$\pm$0.20 | 2.72$\pm$0.26 | 2.45$\pm$0.16
59002.426 | 4.75$\pm$1.73 | -0.79$\pm$0.21 | 10.54$\pm$0.59 | 7.45$\pm$0.34 | 3.98$\pm$0.22 | 2.76$\pm$0.18 | 2.46$\pm$0.16 | 2.45$\pm$0.16
59031.104 | 2.64$\pm$0.794 | — | 9.62$\pm$0.45 | 7.59$\pm$0.28 | 4.02$\pm$0.18 | 2.79$\pm$0.18 | 2.32$\pm$0.15 | 2.59$\pm$0.12
59062.650 | 1.17$\pm$0.374 | -0.72$\pm$0.28 | 8.30$\pm$0.46 | 5.50$\pm$0.25 | 2.51$\pm$0.21 | 2.38$\pm$0.18 | 2.55$\pm$0.16 | 2.39$\pm$0.11
59154.500 | 1.92$\pm$0.60 | -0.58$\pm$0.22 | 9.80$\pm$0.45 | 7.38$\pm$0.27 | 4.05$\pm$0.19 | 2.66$\pm$0.15 | 2.53$\pm$0.16 | 2.43$\pm$0.11
59184.813 | 0.75$\pm$0.354 | — | 9.02$\pm$0.50 | 6.92$\pm$0.25 | 3.91$\pm$0.18 | 2.57$\pm$0.14 | 2.37$\pm$0.15 | 2.36$\pm$0.13
59188.892 | 1.95$\pm$0.484 | — | 9.80$\pm$0.55 | 7.80$\pm$0.29 | 3.80$\pm$0.21 | 2.66$\pm$0.17 | 2.65$\pm$0.17 | 2.28$\pm$0.12
59215.674 | 1.97$\pm$0.734 | — | 9.44$\pm$0.35 | 7.38$\pm$0.27 | 3.66$\pm$0.13 | 2.74$\pm$0.12 | 2.48$\pm$0.14 | 2.39$\pm$0.11
59246.594 | 1.66$\pm$0.60 | -0.29$\pm$0.24 | 9.62$\pm$0.35 | 7.11$\pm$0.26 | 3.91$\pm$0.14 | 2.79$\pm$0.13 | 2.62$\pm$0.14 | 2.69$\pm$0.12
59274.087 | 0.86$\pm$0.394 | — | 9.44$\pm$0.44 | 7.38$\pm$0.27 | 3.60$\pm$0.16 | 2.38$\pm$0.15 | 2.26$\pm$0.15 | 2.28$\pm$0.10
59305.792 | 1.83$\pm$0.714 | — | 9.80$\pm$0.55 | 7.45$\pm$0.34 | 3.56$\pm$0.20 | 2.66$\pm$0.20 | 2.32$\pm$0.17 | 2.59$\pm$0.14
59340.125 | 1.41$\pm$0.524 | — | 9.62$\pm$0.45 | 7.52$\pm$0.28 | 3.80$\pm$0.17 | 2.45$\pm$0.16 | 2.26$\pm$0.15 | 2.26$\pm$0.12
59372.774 | 1.18$\pm$0.414 | -0.20$\pm$0.30 | 9.27$\pm$0.43 | 7.38$\pm$0.27 | 3.73$\pm$0.17 | 2.81$\pm$0.18 | 2.65$\pm$0.22 | 2.54$\pm$0.14
59374.155 | — | — | 9.53$\pm$0.72 | 7.52$\pm$0.42 | 4.45$\pm$0.33 | 2.92$\pm$0.25 | 2.24$\pm$0.23 | 2.26$\pm$0.17

1 The observed 0.3-10 keV fluxes are given in units of $10^{-16}$ W m-2.

2 The hardness ratio is defined as $HR=\frac{hard-soft}{hard+soft}$ with the
soft and hard bands in the 0.3-1.0 and 1.0-10 keV bands, respectively, appying
the BEHR program by Park et al. (2006)

3 The Fluxes in the UVOT filters are given in units of $10^{-15}$ W m-2.

4 0.3-10 keV fluxes estimated from the course rates based on the latest
possible spectral analysis.

Table 3: Continued

MJD | $F_{\rm 0.3-10keV}^{1}$ | HR2 | $F_{\rm V}^{3}$ | $F_{\rm B}^{3}$ | $F_{\rm U}^{3}$ | $F_{\rm W1}^{3}$ | $F_{\rm M2}^{3}$ | $F_{\rm W2}^{3}$
---|---|---|---|---|---|---|---|---
59378.597 | — | — | 9.44$\pm$0.62 | 6.92$\pm$0.39 | 3.56$\pm$0.27 | 2.71$\pm$0.20 | 2.77$\pm$0.21 | 2.69$\pm$0.15
59396.359 | 2.60$\pm$0.784 | -0.51$\pm$0.22 | 9.89$\pm$0.46 | 7.73$\pm$0.36 | 3.53$\pm$0.19 | 2.57$\pm$0.17 | 2.62$\pm$0.17 | 2.66$\pm$0.15
59427.389 | 2.12$\pm$0.95 | -0.97$\pm$0.03 | 10.16$\pm$0.47 | 7.31$\pm$0.34 | 4.02$\pm$0.18 | 2.74$\pm$0.15 | 2.57$\pm$0.14 | 2.69$\pm$0.12
59522.399 | 1.61$\pm$0.40 | -0.38$\pm$0.22 | 9.71$\pm$0.36 | 7.25$\pm$0.33 | 3.80$\pm$0.14 | 2.54$\pm$0.11 | 2.43$\pm$0.13 | 2.26$\pm$0.10
59527.740 | 2.59$\pm$0.62 | -0.61$\pm$0.18 | 9.53$\pm$0.44 | 7.18$\pm$0.33 | 3.80$\pm$0.17 | 2.52$\pm$0.14 | 2.41$\pm$0.13 | 2.22$\pm$0.10
59552.469 | 2.75$\pm$0.74 | +0.18$\pm$0.18 | 8.85$\pm$0.41 | 7.18$\pm$0.33 | 3.60$\pm$0.13 | 2.79$\pm$0.13 | 2.69$\pm$0.15 | 2.34$\pm$0.11
59556.222 | — | — | — | — | 3.84$\pm$0.36 | 2.76$\pm$0.18 | — | —
59560.128 | — | — | 9.02$\pm$0.50 | 6.86$\pm$0.32 | 3.80$\pm$0.21 | 2.34$\pm$0.15 | 2.35$\pm$0.20 | 2.10$\pm$0.13
59583.910 | 1.41$\pm$0.41 | -0.40$\pm$0.22 | 9.62$\pm$0.35 | 7.31$\pm$0.27 | 3.73$\pm$0.17 | 2.71$\pm$0.12 | 2.62$\pm$0.12 | 2.47$\pm$0.11
59674.611 | 3.67$\pm$2.334 | -0.65$\pm$0.35 | 10.74$\pm$0.60 | 7.25$\pm$0.33 | 3.28$\pm$0.18 | 2.59$\pm$0.17 | 2.55$\pm$0.16 | 2.39$\pm$0.13
59703.993 | 2.52$\pm$0.804 | -0.20$\pm$0.22 | 9.02$\pm$0.42 | 7.18$\pm$0.33 | 3.91$\pm$0.18 | 2.76$\pm$0.15 | 2.65$\pm$0.14 | 2.50$\pm$0.11
59734.146 | 2.75$\pm$0.99 | -0.25$\pm$0.23 | 10.16$\pm$0.37 | 7.38$\pm$0.27 | 3.80$\pm$0.14 | 2.84$\pm$0.16 | 2.57$\pm$0.14 | 2.59$\pm$0.12
59764.390 | 5.00$\pm$0.53 | -0.54$\pm$0.12 | 9.98$\pm$0.37 | 7.38$\pm$0.27 | 3.91$\pm$0.14 | 2.71$\pm$0.12 | 2.53$\pm$0.11 | 2.47$\pm$0.09
59795.644 | 2.96$\pm$0.70 | -0.38$\pm$0.21 | 9.98$\pm$0.37 | 7.31$\pm$0.27 | 3.80$\pm$0.14 | 2.66$\pm$0.12 | 2.39$\pm$0.13 | 2.34$\pm$0.11
59883.310 | 4.65$\pm$0.44 | -0.63$\pm$0.18 | 9.52$\pm$0.45 | 7.45$\pm$0.28 | 3.67$\pm$0.17 | 2.37$\pm$0.13 | 2.53$\pm$0.17 | 2.24$\pm$0.11
59914.585 | 1.41$\pm$0.114 | — | 8.61$\pm$0.74 | 7.59$\pm$0.36 | 3.57$\pm$0.17 | 2.69$\pm$0.15 | 2.12$\pm$0.25 | 2.20$\pm$0.17
59919.955 | 6.27$\pm$3.414 | — | — | 6.93$\pm$0.39 | 3.77$\pm$0.25 | 2.14$\pm$0.18 | — | 2.48$\pm$0.21
59923.339 | 12.93$\pm$4.504 | -0.59$\pm$0.25 | 9.27$\pm$0.80 | 7.32$\pm$0.48 | 3.57$\pm$0.31 | 1.99$\pm$0.23 | 2.68$\pm$0.42 | 2.08$\pm$0.18
59936.658 | 4.49$\pm$1.214 | -0.79$\pm$0.20 | 9.98$\pm$0.47 | 7.59$\pm$0.28 | 3.99$\pm$0.19 | 2.62$\pm$0.15 | 2.46$\pm$0.16 | 2.50$\pm$0.14
59944.535 | 8.89$\pm$2.054 | -0.76$\pm$0.12 | 10.16$\pm$0.48 | 7.39$\pm$0.28 | 3.60$\pm$0.17 | 2.82$\pm$0.16 | 2.55$\pm$0.17 | 2.46$\pm$0.14
59948.812 | 5.82$\pm$2.204 | -0.79$\pm$0.21 | — | 6.99$\pm$0.26 | 3.57$\pm$0.17 | 2.43$\pm$0.16 | — | 2.16$\pm$0.19
59949.630 | 9.92$\pm$1.39 | -0.83$\pm$0.16 | 9.18$\pm$0.61 | 7.32$\pm$0.34 | 4.17$\pm$0.24 | 2.62$\pm$0.17 | 2.51$\pm$0.22 | 2.39$\pm$0.16
59950.838 | 6.52$\pm$1.754 | -0.81$\pm$0.19 | 9.18$\pm$0.61 | 7.25$\pm$0.34 | 3.28$\pm$0.22 | 2.74$\pm$0.18 | 2.37$\pm$0.20 | 2.18$\pm$0.14
59951.623 | 8.64$\pm$2.034 | -0.70$\pm$0.18 | 8.77$\pm$0.58 | 6.67$\pm$0.38 | 3.95$\pm$0.22 | 2.43$\pm$0.19 | 2.46$\pm$0.21 | 2.26$\pm$0.15
59952.411 | 7.13$\pm$2.154 | -0.74$\pm$0.21 | 9.89$\pm$0.65 | 6.86$\pm$0.39 | 3.64$\pm$0.24 | 3.01$\pm$0.23 | 2.70$\pm$0.23 | 2.18$\pm$0.17
59953.011 | 6.43$\pm$2.034 | -0.64$\pm$0.21 | 8.22$\pm$0.54 | 7.66$\pm$0.36 | 3.32$\pm$0.22 | 2.20$\pm$0.17 | 1.96$\pm$0.21 | 1.93$\pm$0.15
59954.007 | 4.43$\pm$2.214 | -0.68$\pm$0.32 | 9.35$\pm$0.62 | 7.52$\pm$0.36 | 3.70$\pm$0.26 | 2.57$\pm$0.20 | 2.16$\pm$0.48 | 2.24$\pm$0.13
59955.596 | 6.49$\pm$2.154 | -0.51$\pm$0.22 | 10.64$\pm$0.60 | 6.86$\pm$0.39 | 3.44$\pm$0.23 | 2.67$\pm$0.20 | 2.27$\pm$0.22 | 2.24$\pm$0.15
59956.868 | 8.37$\pm$2.52 | -0.40$\pm$0.21 | 9.98$\pm$0.66 | 7.59$\pm$0.36 | 3.77$\pm$0.25 | 2.67$\pm$0.20 | 2.05$\pm$0.20. | 2.20$\pm$0.15
59957.791 | 5.25$\pm$3.704 | — | 9.02$\pm$0.60 | 7.05$\pm$0.40 | 3.50$\pm$0.23 | 2.72$\pm$0.21 | 2.49$\pm$0.21 | 2.30$\pm$0.15
59964.619 | 6.62$\pm$1.70 | -0.26$\pm$0.23 | 9.02$\pm$0.51 | 7.12$\pm$0.33 | 3.95$\pm$0.22 | 2.62$\pm$0.20 | 2.25$\pm$0.19 | 2.35$\pm$0.13
59974.341 | 6.61$\pm$2.794 | -0.26$\pm$0.35 | 10.16$\pm$0.67 | 6.86$\pm$0.39 | 3.81$\pm$0.25 | 2.55$\pm$0.19 | — | 2.37$\pm$0.16
59975.276 | 5.03$\pm$1.674 | -0.33$\pm$0.25 | 9.53$\pm$0.72 | 7.32$\pm$0.27 | 3.84$\pm$0.18 | 2.57$\pm$0.15 | 2.53$\pm$0.22 | 2.48$\pm$0.14
59977.793 | — | — | 11.25$\pm$0.75 | 6.93$\pm$0.394 | 3.74$\pm$0.28 | 2.84$\pm$0.24 | 2.44$\pm$0.33 | 2.48$\pm$0.16
59984.472 | 4.67$\pm$2.094 | +0.16$\pm$0.37 | 9.27$\pm$0.71 | 7.81$\pm$0.44 | 3.77$\pm$0.29 | 2.69$\pm$0.23 | 2.60$\pm$0.22 | 2.50$\pm$0.17
59994.269 | 7.28$\pm$3.704 | — | 10.07$\pm$0.67 | 7.88$\pm$0.37 | 3.60$\pm$0.24 | 2.87$\pm$0.22 | 2.37$\pm$0.23 | 2.46$\pm$0.16
60004.532 | — | — | 10.74$\pm$0.71 | 7.52$\pm$0.43 | 4.17$\pm$0.28 | 2.52$\pm$0.22 | 2.99$\pm$0.35 | 2.24$\pm$0.15
60009.765 | — | — | — | 6.93$\pm$0.26 | 3.64$\pm$0.17 | 2.32$\pm$0.15 | — | 2.10$\pm$0.12
60014.532 | 2.79$\pm$1.154 | +0.09$\pm$0.31 | 9.18$\pm$0.52 | 7.25$\pm$0.34 | 3.84$\pm$0.22 | 2.59$\pm$0.17 | 2.18$\pm$0.19 | 2.46$\pm$0.14
60024.925 | — | — | 8.38$\pm$0.55 | 7.25$\pm$0.34 | 3.54$\pm$0.23 | 2.55$\pm$0.19 | 1.94$\pm$0.17 | 2.18$\pm$0.14
60034.588 | 3.52$\pm$1.154 | +0.73$\pm$0.25 | 9.10$\pm$0.43 | 7.12$\pm$0.27 | 3.57$\pm$0.17 | 2.59$\pm$0.17 | 2.48$\pm$0.21 | 2.06$\pm$0.12
60044.968 | — | — | 9.98$\pm$0.56 | 7.45$\pm$0.35 | 4.10$\pm$0.23 | 2.67$\pm$0.18 | 2.21$\pm$0.17 | 2.22$\pm$0.15
60054.563 | 2.78$\pm$1.444 | +0.06$\pm$0.42 | 9.89$\pm$0.65 | 6.86$\pm$0.39 | 3.08$\pm$0.20 | 2.64$\pm$0.23 | 2.56$\pm$0.22 | 2.22$\pm$0.15
60065.357 | 1.38$\pm$0.774 | +0.33$\pm$0.36 | 9.10$\pm$0.43 | 7.32$\pm$0.27 | 3.88$\pm$0.18 | 2.30$\pm$0.15 | 2.42$\pm$0.16 | 2.37$\pm$0.14
60095.205 | 4.22$\pm$1.604 | -0.02$\pm$0.31 | 8.85$\pm$0.42 | 8.03$\pm$0.45 | 3.91$\pm$0.26 | — | 2.18$\pm$0.15 | —
60126.288 | 3.95$\pm$1.114 | -0.31$\pm$0.26 | 9.80$\pm$0.46 | 7.32$\pm$0.27 | 3.67$\pm$0.17 | 2.62$\pm$0.15 | 2.32$\pm$0.15 | 2.30$\pm$0.13
60156.127 | 1.89$\pm$0.994 | -0.46$\pm$0.54 | 9.36$\pm$0.53 | 6.55$\pm$0.31 | 3.70$\pm$0.21 | 2.67$\pm$0.18 | 2.42$\pm$0.16 | 2.30 $\pm$0.13

1 The observed 0.3-10 keV fluxes are given in units of $10^{-16}$ W m-2.

2 The hardness ratio is defined as $HR=\frac{hard-soft}{hard+soft}$ with the
soft and hard bands in the 0.3-1.0 and 1.0-10 keV bands, respectively, appying
the BEHR program by Park et al. (2006)

3 The Fluxes in the UVOT filters are given in units of $10^{-15}$ W m-2.

4 0.3-10 keV fluxes estimated from the course rates based on the latest
possible spectral analysis.

Table 4: Merged UVOT data as shown in Figure 7.

MJD Range | MJDcenter | bin width1 | $F_{\rm V}^{2}$ | $F_{\rm B}^{2}$ | $F_{\rm U}^{2}$ | $F_{\rm W1}^{2}$ | $F_{\rm M2}^{2}$ | $F_{\rm W2}^{2}$
---|---|---|---|---|---|---|---|---
56595 - 57590 | 57092.5 | 497.5 | 9.22$\pm$0.26 | 7.23$\pm$0.21 | 3.56$\pm$0.10 | 2.59$\pm$0.08 | 2.53$\pm$0.08 | 2.37$\pm$0.07
57762 - 57969 | 57865.5 | 103.5 | 9.24$\pm$0.26 | 7.07$\pm$0.21 | 3.67$\pm$0.11 | 2.76$\pm$0.10 | 2.56$\pm$0.10 | 2.39$\pm$0.07
58065 - 58339 | 58202.0 | 137.0 | 9.30$\pm$0.18 | 7.07$\pm$0.21 | 3.64$\pm$0.11 | 2.63$\pm$0.08 | 2.58$\pm$0.10 | 2.43$\pm$0.07
58422 - 58704 | 58563.0 | 141.0 | 9.40$\pm$0.18 | 7.20$\pm$0.21 | 3.74$\pm$0.11 | 2.70$\pm$0.08 | 2.54$\pm$0.07 | 2.43$\pm$0.07
58788 - 59062 | 58925.0 | 137.0 | 9.57$\pm$0.27 | 7.25$\pm$0.21 | 3.92$\pm$0.11 | 2.73$\pm$0.08 | 2.61$\pm$0.10 | 2.43$\pm$0.10
59154 - 59427 | 59290.5 | 136.5 | 9.46$\pm$0.27 | 7.25$\pm$0.21 | 3.74$\pm$0.11 | 2.68$\pm$0.11 | 2.54$\pm$0.10 | 2.47$\pm$0.10
59527 - 59795 | 59661.0 | 134.0 | 9.51$\pm$0.27 | 7.20$\pm$0.21 | 3.74$\pm$0.11 | 2.68$\pm$0.08 | 2.56$\pm$0.10 | 2.35$\pm$0.07
59883 - 60156 | 60019.5 | 136.5 | 9.51$\pm$0.28 | 7.29$\pm$0.21 | 3.71$\pm$0.11 | 2.55$\pm$0.10 | 2.45$\pm$0.10 | 2.20$\pm$0.09
56595 - 60156 | 58375.5 | 1780.5 | 9.45$\pm$0.23 | 7.15$\pm$0.14 | 3.68$\pm$0.11 | 2.66$\pm$0.09 | 2.55$\pm$0.06 | 2.42$\pm$0.06

1 given in days

2 The reddening-corrected UVOT fluxes are given in units of $10^{-15}$ W m-2.