# Mapping the Inner 0.1 pc of a Supermassive Black Hole Environment with the
Tidal Disruption Event and Extreme Coronal Line Emitter AT 2022upj

Megan Newsome Las Cumbres Observatory, 6740 Cortona Drive, Suite 102, Goleta,
CA 93117-5575, USA  Department of Physics, University of California, Santa
Barbara, CA 93106-9530, USA  Iair Arcavi School of Physics and Astronomy, Tel
Aviv University, Tel Aviv 69978, Israel  D. Andrew Howell Las Cumbres
Observatory, 6740 Cortona Drive, Suite 102, Goleta, CA 93117-5575, USA
Department of Physics, University of California, Santa Barbara, CA 93106-9530,
USA  Curtis McCully Las Cumbres Observatory, 6740 Cortona Drive, Suite 102,
Goleta, CA 93117-5575, USA  Giacomo Terreran Las Cumbres Observatory, 6740
Cortona Drive, Suite 102, Goleta, CA 93117-5575, USA  Griffin Hosseinzadeh
Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson,
AZ 85721-0065, USA  Yael Dgany School of Physics and Astronomy, Tel Aviv
University, Tel Aviv 69978, Israel  Joseph Farah Las Cumbres Observatory, 6740
Cortona Drive, Suite 102, Goleta, CA 93117-5575, USA  Department of Physics,
University of California, Santa Barbara, CA 93106-9530, USA  Sara Faris School
of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978, Israel
Estefania Padilla-Gonzalez Las Cumbres Observatory, 6740 Cortona Drive, Suite
102, Goleta, CA 93117-5575, USA  Department of Physics, University of
California, Santa Barbara, CA 93106-9530, USA  Craig Pellegrino Department of
Astronomy, University of Virginia, Charlottesville, VA 22904, USA  Moira
Andrews Las Cumbres Observatory, 6740 Cortona Drive, Suite 102, Goleta, CA
93117-5575, USA  Department of Physics, University of California, Santa
Barbara, CA 93106-9530, USA

###### Abstract

Extreme coronal line emitters (ECLEs) are objects showing transient high-
ionization lines in the centers of galaxies. They have been attributed to
echoes of high-energy flares of ionizing radiation, such as those produced by
tidal disruption events (TDEs), but have only recently been observed within
hundreds of days after an optical transient was detected. AT 2022upj is a
nuclear UV-optical flare at $z=0.054$ with spectra showing $[$Fe X$]$
$\lambda$6375 and $[$Fe XIV$]$ $\lambda$5303 during the optical peak, the
earliest presence of extreme coronal lines during an ongoing transient. AT
2022upj is also the second ever ECLE (and first with a concurrent flare) to
show broad He II $\lambda$4686 emission, a key signature of optical/UV TDEs.
We also detect X-ray emission during the optical transient phase, which may be
related to the source of ionizing photons for the extreme coronal lines.
Finally, we analyze the spectroscopic evolution of each emission line and find
that $[$Fe X$]$ and $[$Fe XIV$]$ weaken within 400d of optical peak, while
$[$Fe VII$]$ $\lambda$5720, $[$Fe VII$]$ $\lambda 6087$, and $[$O III$]$
$\lambda$$\lambda$4959,5007 emerge over the same period. The velocities of the
iron lines indicate circumnuclear gas within 0.1pc of the central supermassive
black hole (SMBH), while a dust echo inferred from NEOWISE data indicates that
circumnuclear dust lies at a minimum of 0.4pc away, providing evidence of
stratified material around a SMBH. AT 2022upj is thus the first confirmed
ECLE-TDE with clear signatures of both classes and with spectroscopic
evolution on a $\sim$year-long timescale. This event helps unveil the impact
of highly energetic flares such as TDEs on the complex environments around
SMBHs.

††facilities: LCO, ZTF, SOAR, Swift (XRT and UVOT), WISE††software: astropy
(Astropy Collaboration et al., 2013, 2018), lcogtsnpipe (Valenti et al.,
2016), Light Curve Fitting (Hosseinzadeh & Gomez, 2022), PyRAF (Science
Software Branch at STScI, 2012), MOSFiT (Guillochon et al., 2018), TDEMass
(Ryu et al., 2020), HOTPANTS (Alard & Lupton, 1998; Becker, 2015), HEAsoft
(NASA HEASARC, 2014), BAGPIPES (Carnall et al., 2018)

##  1 Introduction

Supermassive black holes (SMBHs) at the centers of galaxies produce tidal
forces that can disrupt a star’s self-gravity upon close contact (Hills, 1975;
Rees, 1988). These tidal disruption events (TDEs) create a stream of stellar
material that accretes onto the SMBH, producing a flare in the X-ray,
ultraviolet, and/or optical bands that can outshine the host galaxy.
Observations of TDEs thus offer a window into the otherwise quiescent SMBH
population, and can teach us about accretion physics, jet formation and the
environments around SMBHs. The discovery rate of TDEs is rapidly increasing
(e.g. Graham et al., 2019; Gezari, 2021), with over 60 events reported to the
Transient Name Server111https://www.wis-tns.org/ in the last five years. With
these larger samples, we now see groupings of TDE types by spectral
signatures, with most showing broad emission of only H$\alpha$ $\lambda$6563,
only He II $\lambda$4686, or both (e.g. Gezari et al., 2012; Gezari, 2021; van
Velzen et al., 2021a; Nicholl et al., 2022; Hammerstein et al., 2023).

Figure 1: Archival image of host galaxy WISEA J002356.88-142523.9 from Pan-
STARRS1 in $g$-band (left) compared with the location of the transient as
observed in subtracted $g$-band images with Las Cumbres Observatory (right).
The transient is located within $0.1^{\prime\prime}$ (0.1 kpc) from the host’s
center at (RA, Dec) = (00:23:56.9, $-$14:25:24) as marked by the red crossbar.

Another type of transient phenomenon associated with SMBHs, extreme coronal
line emitters (ECLEs), was initially identified in seven galaxies which showed
nuclear emission of highly ionized $[$Fe X$]$ $\lambda$6375 and $[$Fe XIV$]$
$\lambda$5303 (Komossa et al., 2008; Wang et al., 2011, 2012; Yang et al.,
2013). Despite having no simultaneous direct evidence of tidal disruption
flares, these spectral features were suggested to result from an extreme
ultraviolet to soft X-ray outburst of radiation associated with a TDE.

Clark et al. (2024) followed these early-identified ECLEs and confirmed five
as single transient events likely to be caused by a TDE due to their lack of
recurring coronal lines. Nine recent ECLEs have been found to show the
emergence of coronal lines after the detection of an optical brightening in a
nuclear source (Neustadt et al., 2020; Onori et al., 2022; Hinkle et al.,
2024; Li et al., 2023; Short et al., 2023; Somalwar et al., 2023; Yao et al.,
2023; Koljonen et al., 2024, Clark et al. in prep), which were all reported to
also be TDEs, but in each case the coronal lines were not detected until
dozens to hundreds of days after optical peak, as listed in Table 1. From this
TDE-ECLE sample only AT 2017gge (Onori et al., 2022) and AT 2019qiz (Short et
al., 2023) exhibited X-ray activity prior to, or concurrent with, the coronal
lines. For the other five objects, the ionizing X-ray source was either not
detected at all, or only detected after the emergence and disappearance of
coronal iron lines, which may mean X-ray emission was previously obscured in
these cases.

ECLEs can thus be used as indicators of obscured TDEs. Indeed, Hinkle et al.
(2024) made the first statistical argument for a connection between ECLEs and
TDEs via host property analysis of all known ECLEs. Furthermore, ECLEs can
serve as probes of the circumnuclear gas around SMBHs, which is otherwise
inaccessible observationally.

Table 1: Tidal disruption events that were later discovered to show extreme coronal line emission, where the Phase column shows the number of days after discovery that the coronal lines were measured. No nuclear transient has been discovered with coronal iron lines that were concurrent with the optical peak of the flare before AT 2022upj. We also list the transients for which $g$ or $c$-band forced photometry exists with magnitude errors $<0.25$ mag beyond +200d from optical peak in the fourth column, used to compare light curve evolution with AT 2022upj. Name | Phase | Source | +200d $g/c$?
---|---|---|---
| (days) |  |
AT 2017gge | +200 | Onori et al. (2022) | No
AT 2018bcb | +35 | Neustadt et al. (2020) | Yes
AT 2018dyk |  $\cdots$ | Clark et al. (in prep.) | Yes
AT 2019qiz | +428 | Short et al. (2023) | No
AT 2020vdq | +529 | Somalwar et al. (2023) | No
AT 2021dms | +175 | Hinkle et al. (2024) | Yes
AT 2021qth | +300 | Yao et al. (2023) | No
AT 2021acak | +170 | Li et al. (2023) | Yes
AT 2022fpx | +11 | Koljonen et al. (2024) | Yes
AT 2022upj | 0 | This work | Yes

AT 2022upj was discovered by the Zwicky Transient Facility (ZTF) on MJD
59822.39 (August 31 2022) as a nuclear transient (Fremling, 2022). Its
location in the center of the galaxy WISEA J002356.88-142523.9 at
(RA${}_{\text{J2000}}$, Dec${}_{\text{J2000}}$) = (00:23:56.86,
$-$14:25:23.4), as shown in Figure 1, and blue color ($g-r=-0.068$) upon first
available multi-band detection (MJD = 59846.3, from ZTF) indicated a possible
TDE origin, after which we began our ground-based optical follow-up with Las
Cumbres Observatory (Brown et al., 2013). Spectroscopy from Las Cumbres
Observatory’s Faulkes Telescope South revealed the bright and narrow high-
ionization emission lines $[$Fe X$]$ $\lambda$6375$\lambda$6375 and $[$Fe
XIV$]$ $\lambda$5303, each matched to a redshift of $z=0.054$, as early as MJD
59885.0, classifying AT 2022upj as an ECLE (Newsome et al., 2022a, b). An
additional broad He II $\lambda$4686 emission feature, typical of TDEs is also
present, seen only once before in SDSS 0748+4712 (Wang et al., 2011).

AT 2022upj is the first nuclear transient to show coronal lines concurrent
with the optical peak of the light curve. Subsequent observations with the
Niel Gehrels Swift Observatory (Swift) also make AT 2022upj the first ECLE to
show concurrent soft X-ray emission alongside the transient peak and coronal
lines, providing potential evidence of the high-energy ionizing source.

Figure 2: Top: Host-subtracted and Galactic-extinction corrected optical and
UV light curves of AT 2022upj as observed by Las Cumbres Observatory, ZTF, and
Swift. The light curves in each filter are offset from one another for
clarity. The $gri$ points from Las Cumbres were subtracted with PS1 archival
templates. Vertical black tick marks indicate when spectroscopy was
simultaneously obtained. Middle: AT 2022upj X-ray (0.1–10keV) luminosity from
Swift XRT (red diamonds or downward arrows for $3\sigma$ upper limits)
compared to the pseudo-bolometric luminosity, calculated from blackbody fits
to the Swift UVOT and Las Cumbres + ZTF optical photometry (black pentagons).
Bottom: The ratio of $L_{\text{XRT}}$ to $L_{\text{bol}}$ (green x-marks). The
observed X-ray output is less than $2\%$ of the UV-optical pseudo-bolometric
luminosity until after +300d from optical peak. The data behind this figure
are available as a machine-readable table.

Here we present the UV, optical, X-ray, and mid-IR light curve as well as the
optical spectroscopic evolution of AT 2022upj from continued follow-up via Las
Cumbres Observatory, ZTF, Swift, and the Wide-field Infrared Survey Explorer
(WISE; Wright et al., 2010). We review our methods of data extraction and
reduction in §2, review the results of the data including coronal line flux
evolution and line ratio evolution in §3, discuss the implications of the
coronal line observations on the properties of the circumnuclear material
including proximity to the central SMBH and relationship to host evolution in
§4, and summarize the novelty of the short-term ECLE variation in §5.
Throughout this work we adopt the Planck Collaboration et al. (2020) cosmology
with H0 = 67.7 km s-1 Mpc-1.

##  2 Observations and Data Processing

Throughout this work, we use observations taken by Las Cumbres Observatory,
ZTF, Swift, and WISE. We correct all photometry for Galactic extinction with
$A_{V}=0.083$ mag (Schlafly & Finkbeiner, 2011) using the Calzetti dust law
(Calzetti et al., 2000).

###  2.1 Las Cumbres and ZTF Photometry

We obtained $gri$-band images with the Sinistro cameras on Las Cumbres’ 1.0m
telescopes, performed image subtraction, and extracted point-spread-function
(PSF) photometry with the lcogtsnpipe
pipeline222https://github.com/LCOGT/lcogtsnpipe (Valenti et al., 2016).
Zeropoints for all bands were calculated from the magnitudes of field stars as
listed in the AAVSO Photometry All-Sky Survey (Henden et al., 2009). Archival
images from the Panoramic Survey Telescope and Rapid Response System, Pan-
STARRS1 (PS1; Kaiser et al., 2010), were used as templates for the image
subtraction, which was performed using
HOTPANTS333https://github.com/acbecker/hotpants (Alard & Lupton, 1998; Becker,
2015), with normalization to the science image and convolution to the template
image. We present the host-subtracted $gri$-band photometry calibrated to the
AB magnitude system in Figure 2.

Supplemental photometry in the $gr$-bands was obtained from the ZTF forced
photometry server444https://ztfweb.ipac.caltech.edu/cgi-
bin/requestForcedPhotometry.cgi (Masci et al., 2019). We excluded data from
both sets with magnitude errors greater than 0.1 mag. Las Cumbres subtractions
with PS1 templates were compared with ZTF forced photometry to ensure
similarity between subtraction methods, taking into account the expected
variation between ZTF and Las Cumbres $r$-bands as measured in Newsome et al.
(2024).

###  2.2 Swift Photometry

UV observations were obtained with the Ultraviolet Optical Telescope (UVOT;
Roming et al., 2005) on board Swift in the UVW2, UVM2, UVW1, $U$, $B$, and $V$
filters beginning MJD 59897.56, near the time of maximum light. A total of 14
epochs were observed through MJD 60103.0. The data were reduced with the Swift
Ultraviolet/Optical Supernova Archive pipeline (Brown et al., 2014), using the
aperture corrections and zero-points of Breeveld et al. (2011). Swift
photometry is presented in Vega magnitudes alongside Las Cumbres and ZTF
photometry in Figure 2. Because there are no archival images in the Swift UVOT
bands of the host galaxy, these data are not host-subtracted.

Swift’s X-ray Telescope (XRT) simultaneously observed AT 2022upj in photon-
counting mode during the UVOT follow-up. Following the Swift XRT Data
Reduction
Guide555https://www.swift.ac.uk/analysis/xrt/files/xrt_swguide_v1_2.pdf, we
processed cleaned X-ray event files with
xselect666https://www.swift.ac.uk/analysis/xrt/xselect.php to create a light
curve binned by observation where photons are selected within 40″ of the event
coordinates and the background is a region with no sources and a radius 150″.
We use the online tool PIMMS777https://cxc.harvard.edu/toolkit/pimms.jsp to
convert these count rates into fluxes assuming a power law with a photon index
of $\Gamma=2.55$ at early times and $\Gamma=3.1$ at late times (see §A). We
display this light curve alongside the pseudo-bolometric luminosity of AT
2022upj (see §3.2) as well as the evolving ratio between the two in Figure 2.

Figure 3: Unsubtracted WISE photometry at the position of AT 2022upj since
2014. Top: $W1$ $3.6\mu$m in blue circles and median quiescent value in a
darker blue horizontal line; middle: $W2$ $4.5\mu$m in pink circles and median
quiescent value in a darker pink horizontal line; bottom: $W1-W2$ colors in
green pentagons. The host of AT 2022upj never approaches the expected AGN
color-cut of $W1-W2>0.8$ until the brightening in both bands after transient
discovery at MJD 59822.39 (marked in the red vertical dashed line).

###  2.3 WISE photometry

The Wide-field Infrared Survey Explorer (WISE; Wright et al., 2010) first
observed the host galaxy of AT 2022upj with the ALLWISE survey in 2010, and
its observations resumed in 2013 when the survey reactivated as NEOWISE-R
(Mainzer et al., 2011, 2014). We collected $W1$ ($3.4\mu$m) and $W2$
($4.6\mu$m) data from the Infrared Science
Archive888https://irsa.ipac.caltech.edu, producing 19 epochs of mid-infrared
photometry each separated by six months, one of which was taken after the
discovery of AT 2022upj. We selected detections with good-quality frames
($\texttt{qi\\_fact}>1$), no contamination and confusion
($\texttt{cc\\_flag}=0$) and with magnitude errors $<0.15$ mag; filtering out
$\sim 10\%$ of observations across all epochs. Figure 3 shows all epochs,
including both raw data and weighted binned magnitudes per epoch, and the
magnitude of the quiescent stage based on minimal variability prior to MJD
59822.39, when the transient was discovered. The quiescent magnitudes are
measured from taking the median of all epochs per filter preceding the TDE
detection. We also display the $W1-W2$ color, which does not exceed the AGN
color-cut of $W1-W2\geq 0.8$ (Stern et al., 2012) at any epoch.

Figure 4: FLOYDS (unlabeled) and SOAR spectra of AT 2022upj, continuum-
normalized, and offset with varying hues for clarity. Spectra are labeled by
the number of rest-frame days from optical peak at which the observation was
taken. We label the prominent narrow H$\alpha$, H$\beta$ and He II
$\lambda$4686 lines in gray, and the high-ionization coronal lines ($[$Fe
XIV$]$ $\lambda$5303, $[$Fe VII$]$, $[$Fe X$]$ $\lambda$6375, $[$S XII$]$
$\lambda$7611.0 and $[$Fe XI$]$ $\lambda$7891.8) in red. We also label the
$[$O III$]$ $\lambda$$\lambda$4959, 5007 doublet which is not evident in AT
2022upj until after +190d from peak, when the $[$Fe VII$]$ also becomes
prominent and the $[$Fe X$]$ line weakens.

###  2.4 Spectroscopy

Eight optical spectra were taken with the FLOYDS instruments mounted on the
Las Cumbres 2m Faulkes Telescopes North and South (FTN/FTS), using a 2″ slit
and reduced using the floydsspec
pipeline999https://github.com/svalenti/FLOYDS_pipeline/, as described in
Valenti et al. (2014). The pipeline performs flux and wavelength calibration,
cosmic-ray removal, and final spectrum extraction. The original spectra cover
3500 to 10,000 Å, at a resolution $R\approx 300-600$ and epochs from $0$ to
$+408$ days with respect to the $g$-band peak at MJD = 59884.95 (calculated by
fitting a template TDE light curve to the observations with a least-squares
method and finding the time of maximum light from the template; see §3.2).
Four additional spectra were obtained using the Goodman High Throughput
Spectrograph on the Southern Astrophysical Research (SOAR) 4.1 m telescope,
each using a 1″ slit and the 400 mm-1 line grating. Two used the blue camera
in mode M1 (3000–7050 Å), one used the red camera in mode M1 (3000–7050 Å),
and one used the red camera in mode M2 (5000-9050 Å). We used the Goodman
Spectroscopic Data Reduction Pipeline101010https://github.com/soar-
telescope/goodman_pipeline to perform bias and flat correction and cosmic-ray
removal, and then performed wavelength and sky-line calibration and extraction
using PyRAF (Science Software Branch at STScI, 2012). We calibrated fluxes to
a standard star observed on the same nights with the same instrumental setup.
The dates and phases of each spectrum we report are listed in Table 2. We
present all spectra and label the notable emission lines in Figure 4.

Table 2: The MJD and rest-frame phase at which each reported spectrum was taken by FLOYDS (Faulkes Telescope North, FTN, or Faulkes Telescope South, FTS) or SOAR, where phase is the number of rest-frame days from peak in $g$-band (at MJD 59884.95). MJD | Phase (d) | Airmass | Exp. Time (s) | Telescope
---|---|---|---|---
59885 | +0 | 1.37 | 3600 | FTS
59900 | +14 | 1.62 | 3600 | FTS
59911 | +24 | 1.32 | 3600 | FTS
59912 | +25 | 1.23 | 1800 | SOAR
59917 | +30 | 1.22 | 1800 | SOAR
59925 | +37 | 1.55 | 3600 | FTS
60086 | +190 | 1.57 | 3600 | FTS
60103 | +206 | 1.62 | 3600 | FTS
60151 | +252 | 1.05 | 3600 | FTS
60313 | +406 | 1.49 | 2100 | SOAR
60316 | +408 | 1.49 | 3600 | FTN
60317 | +409 | 1.53 | 2100 | SOAR

##  3 Results

We assess the multi-band photometric data by comparing the light curve’s late-
time behavior against that of a “typical” TDE, calculating blackbody radii and
temperatures of the event across epochs, and using the light curve properties
to determine the masses of the central BH and the stellar progenitor via
assumptions of two different emission mechanisms.

###  3.1 Slow Decline

Figure 5: The $g$-band light curve of AT 2022upj (black line) compared to that
of a sample of TDEs (thin gray lines) for which data, with magnitude errors
$<0.25$mag, exists beyond +200 days from the $g$-band peak (AT 2018hco, AT
2018iih, AT2018 jbv, AT 2018zr, AT 2019ehz, AT 2020mot, AT 2020opy, AT
2020qhs, AT 2020ysg, AT 2020yue, AT 2021nwa, AT 2022gri, AT 2022lri, AT
2022wtn; photometry all obtained from van Velzen et al., 2021b; Hammerstein et
al., 2023; Yao et al., 2023; Neustadt et al., 2020; Hinkle et al., 2024; Li et
al., 2023; Koljonen et al., 2024). Other ECLEs concurrent with optical
transients (AT 2018bcb, AT 2018dyk, AT 2021dms, AT 2021acak, AT 2022fpx) are
overplotted in color. AT 2021dms is shown in the ATLAS $c$-band due to lack of
ZTF coverage. All light curves are corrected for each object’s redshift and
shown in the rest-frame. The TDEs in the background sample show a median power
law decline of $\alpha=2.14\pm 0.96$ prior to +200d from peak (after which a
plateau phase is common in TDEs; Yao et al., 2023) while the ECLEs have a
power law decline following $\alpha=0.65\pm 0.21$ over the same period,
indicating a significant difference between the behavior of long-lasting TDEs
versus ECLEs.

We compare the $g$-band light curve of AT 2022upj to a sample of TDEs and
ECLEs for which there existed $g$-band (or ATLAS $c$-band) photometry after
200 days from each transient’s peak (van Velzen et al., 2021b; Hammerstein et
al., 2023; Yao et al., 2023; Neustadt et al., 2020; Hinkle et al., 2024; Li et
al., 2023; Koljonen et al., 2024), as shown in Figure 5. AT 2022upj follows a
power-law decline in the first 200d post $g$-band peak with $L\propto
t^{-\alpha}$ where we find $\alpha=0.78\pm 0.05$, substantially shallower than
the typical TDE expectation of $\alpha=5/3$. In fact, for all ECLEs with light
curves detected over more than 250 days, we find an overall decline rate of
$\alpha=0.65\pm 0.27$, while the sample of TDEs (that are not also ECLEs)
collectively shows a decline with $\alpha=2.14\pm 0.96$ over the same period.

###  3.2 Blackbody Fitting

We fit the UV and optical spectral energy distribution (SED) of AT 2022upj to
a blackbody across its light curve to estimate the photospheric radius and
temperature of the flaring region over time. We require five or more filters
(ensuring only epochs with UV data) of data per epoch range (5 days) to fit a
blackbody. Our fitting therefore starts from MJD = 59884.95 at $g$-band peak,
using the lightcurve_fitting package from Hosseinzadeh & Gomez (2022).

Table 3: MJD, bolometric luminosity, blackbody radius, and blackbody temperature for AT 2022upj determined by fitting a blackbody to epochs with Swift UVOT photometry alongside Las Cumbres and ZTF optical photometry. MJD | $L_{\text{bol}}$ | $R$ | $T$
---|---|---|---
|  $10^{43}$ (erg s-1) |  $10^{-4}$ (pc) | (K)
59898.9 | $5.83\pm 0.29$ | $1.71\pm 0.04$ | $23300\pm 2500$
59910.5 | $5.61\pm 0.33$ | $1.63\pm 0.04$ | $23700\pm 2500$
59913.5 | $6.18\pm 0.41$ | $1.43\pm 0.04$ | $25800\pm 2500$
59939.2 | $4.25\pm 0.20$ | $1.59\pm 0.03$ | $22300\pm 2500$
59947.2 | $4.12\pm 0.50$ | $1.52\pm 0.10$ | $22700\pm 2500$
60091.8 | $1.48\pm 0.08$ | $1.40\pm 0.04$ | $18300\pm 2500$
60248.9 | $1.00\pm 0.09$ | $2.00\pm 0.11$ | $13900\pm 2500$
Figure 6: Blackbody physical properties inferred for AT 2022upj (black lines)
compared to TDEs (gray lines) and ECLEs (colored lines) for which blackbody
data was publicly available (AT2018bcb, AT2018dyk, AT2018hco, AT2018zr,
AT2019ehz, AT2020mot) Top: Blackbody luminosity in erg s-1. Middle: Radius in
cm. Bottom: Temperature in K. AT 2022upj luminosity evolution is consistent
with TDEs, and its peak radius and temperatures are also in line with TDEs,
although there is deviation in both at late times.

The code uses Markov Chain Monte–Carlo (MCMC) sampling with the emcee package
(Foreman-Mackey et al., 2013) with a broad log-flat prior of $10,000$ K $\leq
T\leq 100,000$ K and $10R_{\odot}$ $(\sim 10^{-7}\text{pc})\leq R\leq
10^{6}R_{\odot}$ $(\sim 10^{-2}\text{pc})$.

We use the host-subtracted photometry from Las Cumbres and ZTF, and non-
subtracted Swift UVW1, UVM2, and UVW2 bands, in which host galaxy brightness
is negligible (see §C).

Figure 7: Close-up of the first SOAR spectrum of AT 2022upj focusing on the
broad He II $\lambda$4686 emission feature, with the same spectral segment
shown for the extreme coronal line emitter SDSS 0748+4712 (green; Wang et al.,
2011) and the TDE AT 2020mot (purple; Newsome et al., 2024). SDSS 0748+4712
was the only ECLE from the SDSS sample which simultaneously showed broad He
II, making AT 2022upj only the second instance of both features clearly
detected, and the first for which the detections coincide with an observed
optical transient.

Though this package provides errors on estimated parameters, we quantify our
temperature measurements with the systematic uncertainties found in Arcavi
(2022) for the bounds on light curve fits to blackbodies with UV and optical
data, as these values exceed the statistical errors found by the package. We
find the temperature stays relatively constant between $T_{\text{BB}}=24300\pm
2500$ K and $T_{\text{\text{BB}}}=25000\pm 2500$ K over the first 60d. The
blackbody radius is found to decrease over the same period from
$R_{\text{BB}}=5.0\pm 0.12\times 10^{14}$ cm to $R_{\text{BB}}=3.8\pm
0.12\times 10^{14}$ cm. After this early period the temperature decreases to a
steady $T_{\text{BB}}\sim 15000$ K over 200d. These temperatures and radii are
consistent with other TDE observations ($T\sim 10000-50000$ K; e.g. van Velzen
et al., 2021a). We plot these values, and compare them to blackbody parameters
that were publicly available for TDEs and ECLEs in our aforementioned sample,
in Figure 6.

###  3.3 Black Hole and Pre-Disruption Stellar Masses

Table 4: Estimates of the mass of the SMBH based on analyzing the UV-optical light curve as TDE emission with MOSFiT and TDEMass (which inherently assume different emission mechanisms) compared with the estimate from the scaling relation between black hole mass and bulge mass extended to the lower-mass regime by Scott et al. (2013). Method | $M_{\mathrm{BH}}$ | Source
---|---|---
| ($10^{6}M_{\odot}$) |
MOSFiT | $0.61^{+0.1}_{-0.07}$ | Mockler et al. (2019)
TDEMass | $1.6^{+0.48}_{-0.72}$ | Ryu et al. (2020)
$M_{\mathrm{BH}}-M_{\mathrm{bulge}}$ | $0.83^{+1.56}_{-0.66}$ | Scott et al. (2013)
$M_{\mathrm{BH}}-M_{\mathrm{bulge}}$ | $1.00^{+0.56}_{-0.36}$ | Greene et al. (2020)

Assuming the UV-optical flare is due to a TDE, we model the light curve using
both the Modular Open Source Fitter for Transients, which attributes the
emission to reprocessed accretion (MOSFiT; Guillochon et al., 2018; Mockler et
al., 2019) and TDEMass (Ryu et al., 2020), which assumes the emission is from
outer shocks of stream-stream collisions (Piran et al., 2015). The MOSFiT
parameters are the black hole mass $M_{\mathrm{BH}}$, the mass of the star
before disruption $M_{*}$, and eight other physical parameters detailed in §B,
including the efficiency of the conversion of fallback mass to energy
$\epsilon$ which can be used to account for additional emission sources. In
contrast, TDEMass fits only the peak bolometric luminosity and corresponding
temperature to analytically estimate the black hole and stellar masses. The
detailed outputs of both fitting results are included in §B.

We include photometry in all host-subtracted bands (i.e. all bands except
$BV$, as for the blackbody fits) for fitting with MOSFiT’s nested sampling
method and find $M_{\mathrm{BH}}=6.1^{+1.0}_{-0.7}\times 10^{5}M_{\odot}$ and
a mass of $M_{*}=0.32^{+0.44}_{-0.16}M_{\odot}$ for the disrupted star. In
contrast, when using $L_{\mathrm{bol}}=6.26\times 10^{43}$ erg s-1 and
$T=3.41\times 10^{42}$ K (interpolated values at the peak of the optical light
curve), TDEMass finds $M_{\mathrm{BH}}=1.6^{+0.48}_{-0.72}\times
10^{6}M_{\odot}$ and $M_{*}=0.88^{+0.06}_{-0.07}M_{\odot}$. These values,
while outside of one another’s errors, indicate broadly a subsolar stellar
progenitor and a SMBH that is likely less than $10^{7}M_{\odot}$, well within
expectations and comparable to findings of other TDEs (e.g. Nicholl et al.,
2022).

As another measure of the SMBH mass, we use the Scott et al. (2013) relation
between the stellar mass of Sérsic galaxies and their black hole mass by using
the estimated stellar mass from the host SED fits (see §C). We choose this
method due to the host’s spheroidal nature, well fit with
GalSim111111https://github.com/GalSim-developers/GalSim by a Sérsic profile
with index $n>6.0$ indicating strong central concentration of brightness. As a
check on this conclusion we also fit the host image with photutils and find an
ellipticity of 0 fits the host with minimal residuals. Therefore, we proceed
with using the stellar mass as the bulge mass and find
$M_{\mathrm{BH}}=0.83^{+1.56}_{-0.66}\times 10^{6}M_{\odot}$, in agreement
with the former two estimates which assume a TDE nature of the UV-optical
light curve. As a further check we also use the same values in the
$M_{\mathrm{BH}}-M_{\mathrm{bulge}}$ relation from Greene et al. (2020) and
find $M_{\mathrm{BH}}=1.00^{+0.56}_{-0.36}\times 10^{6}M_{\odot}$ again
agreeing with all prior estimates.

###  3.4 X-ray Properties

The X-ray light curve of AT 2022upj reveals a relatively constant flux between
optical peak and +200d later, when Swift XRT data is binned per observation
and requiring a minimum of 4 counts per epoch, as shown in Figures 2 and 9.
The data prior to +200d are either $3\sigma$ detections or upper limits, so it
is possible that the X-ray emission was variable around the detection limit
over this period.

The X-ray flux over time does not exceed $2\%$ of the bolometric luminosity
until after +300d from optical peak. This is similar to the extreme coronal
line emitter AT 2018bcb (ASASSN-18jd; Neustadt et al., 2020). However, our
data does not indicate any significant softening nor hardening with time (see
below), and the luminosity evolution shows no sudden spikes in brightness as
all epochs are within one another’s errors, so we can only infer generally
constant evolution through +300d from optical peak. The observed X-ray
luminosity stays within $L_{\text{XRT}}\sim 10^{41}-10^{42}$ erg s-1 which is
comparable to X-ray selected TDEs (Gezari, 2021). Afterwards there is a clear
increase in X-ray luminosity at +350d, similar to what was seen for the TDE
ASASSN-15oi (Gezari et al., 2017), which is maintained over all subsequent
observations. The reason for this evolution may be the onset of accretion, an
accretion state change, or the emergence of pre-existing accretion that had
been previously obscured, but analysis of the late X-ray emission will be
presented in future work.

We bin the X-ray data into two epochs labeled “pre-burst” and “burst”, to
measure the X-ray spectrum at these two stages, and fit each with power law
and blackbody models using XSPEC and the corresponding online data products
tool (Evans et al., 2009, see fits in §A). For this spectroscopic fitting we
include all counts detected within each bin. The spectra are better fit by the
power-law model which has substantially lower W-stat values for each epoch.
The power law fits find an increasing photon index, from
$\Gamma=2.55^{+1.37}_{-0.35}$ near peak to $\Gamma=3.08^{+0.23}_{-0.21}$ at
late times, consistent with no change within the errors. The blackbody fits,
which assume the source of X-ray emission is a thermal disk, find a
temperature of from $200\pm 50$ eV across both periods, which is within the
range observed in X-ray selected TDEs (Gezari, 2021), but may be misleading as
the spectra are not well described by a blackbody. Regardless, even the weak
early-time X-ray detections are direct evidence for the presence of a
simultaneous ionizing source during the optical flare energetic enough to
produce the forbidden iron lines.

Figure 8: Gaussian fits for key emission lines across the four higher-
resolution SOAR spectra taken at +25, +30, +406, and +409 rest-frame days from
optical peak. Left: High-ionization lines $[$O III$]$ $\lambda$5007, $[$Fe
XIV$]$ $\lambda$5303, $[$Fe VII$]$ $\lambda$5720, $[$Fe VII$]$ $\lambda$6087,
and $[$Fe X$]$ $\lambda$6375\. Right: H$\beta$ and H$\alpha$. The gray lines
are the photometrically-calibrated data offset from one another for clarity,
and the overlaying purple lines are the Gaussian fits to the data. The first
two detections of $[$O III$]$ and $[$Fe VII$]$ are less than 3-$\sigma$
detections, as are the last two observations of $[$Fe XIV$]$.

Archival GALEX measurements used in host galaxy SED fitting (see C) indicate
no X-ray detection, down to 1.92 $\times 10^{-31}$ erg s-1cm-2, 10 years prior
to the transient. Therefore we proceed with the assumption that the detected
X-ray emission is caused by a TDE as opposed to background host emission from
an AGN. However we note that, since our earliest observations show coronal
lines without first showing quiescence, we cannot exclude the possibility that
the host became active over the last ten years.

###  3.5 Spectral Evolution

The spectra of AT 2022upj indicate the nuclear transient flare’s interaction
with circumnuclear material, firmly putting the transient within the class of
extreme coronal line emitters. Importantly, the spectra also show broad He II
$\lambda$4686 as shown in Figure 7, a clear TDE signature (as defined by
Gezari et al. 2012 and Arcavi et al. 2014). This is the first event to show
both broad He II and highly-ionized coronal lines simultaneously since SDSS
J0748+4712 (Wang et al., 2011), here further coinciding with the peak of a UV-
optical flare. AT 2022upj is thus the first optical transient to strongly link
ECLEs with TDE origins.

The first spectrum of AT 2022upj, taken at optical peak, shows strong narrow
$[$Fe X$]$ $\lambda$6375 and $[$Fe XIV$]$ $\lambda$5303 lines. The initial
absence of [O III] emission differentiates AT 2022upj from AGN, as coronal
line strengths measured by integrated flux in Seyfert galaxies are normally
only a few percent of the [O III] doublet line strength (Nagao et al., 2000).

The first three spectra taken by FLOYDS show little evolution in line presence
and strength. Afterwards the higher-resolution SOAR blue and red spectra,
taken 5 days apart at +25 and +30 rest-frame days from peak respectively, show
weak $[$Fe VII$]$ $\lambda$5720 and $\lambda 6087$ in addition to the strong
$[$Fe X$]$ $\lambda$6375 and $[$Fe XIV$]$ $\lambda$5303 lines. The SOAR
spectra also confirm the presence of [S XII] $\lambda 7611$ and [Fe XI]
$\lambda 7892$ by +30d after peak. The red fringing in the FLOYDS spectra
unfortunately make the [S XII] lines indistinguishable from the continuum,
however the [Fe XI] line is strong enough in each epoch to observe clearly
despite fringing, but not to resolve its equivalent width.

We measure the photometrically calibrated fluxes and equivalent widths of the
high-ionization lines that are observed in every spectrum: $[$Fe XIV$]$
$\lambda$5303, $[$Fe VII$]$ $\lambda$5720 (labeled “[Fe VIIa]” in figures),
$[$Fe VII$]$ $\lambda$6087 (“[Fe VIIb] in figures), and $[$Fe X$]$
$\lambda$6375\. We fit a univariate spline to the continuum around each line,
normalize to the continuum level, and fit a Gaussian to each line at each
epoch to measure the FWHM and fluxes. We show the Gaussian fits to the higher-
resolution SOAR spectra in Figure 8. We note that the first two detections of
$[$O III$]$ and $[$Fe VII$]$ are less than 3-$\sigma$ detections, as are the
last two observations of $[$Fe XIV$]$, thus we do not infer FWHM values from
these measurements.

Comparing the steady H$\alpha$ flux to that of each high-ionization line,
shown in Figure 9, reveals intriguing trends. Specifically, $[$Fe X$]$
$\lambda$6375 and $[$Fe XIV$]$ $\lambda$5303 weaken after +190 days while
$[$Fe VII$]$ $\lambda$5720 and $\lambda 6088$ are only first detected above a
3$-\sigma$ level at this point, and strengthen afterwards.

Finally, we emphasize that $[$O III$]$ $\lambda\lambda$4959,5007 clearly
emerges only after +400d from peak, when the coronal lines are dominated by
$[$Fe VII$]$ while $[$Fe X$]$ has weakened. Wang et al. (2011, 2012) also
observed an increase in [O III] flux after the fading of high-ionization
coronal lines in their ECLE samples. There, the change took place over many
years, while the change in AT 2022upj is visible within 13 months.

Figure 9: X-ray flux (red diamonds) from Swift XRT alongside the
photometrically-calibrated fluxes of the prominent emission lines $[$Fe X$]$
$\lambda$6375 (dark orange small dots), $[$Fe XIV$]$ $\lambda$5303 $\lambda
5303$ (purple stars), “[Fe VIIa]” $\lambda$5720 (blue diamonds), “[Fe VIIb]”
$\lambda 6087$ (green pentagons), and H$\alpha$ $\lambda$6563.

##  4 Discussion

Figure 10: Map of the distance between the coronal-line-emitting circumnuclear
gas and the SMBH based on the line FWHM and the assumption of virialized
motion. Using only the FWHMs measured from Gaussian fits of the coronal lines
in the higher-resolution SOAR spectra, the gas shows consistent velocities
across all epochs. Within the range of black hole masses found for AT 2022upj
by light curve fitting and $M_{\mathrm{BH}}-M_{\mathrm{bulge}}$ relations, the
gas is situated within 0.1pc of the SMBH.

The ionization potentials of 125 eV for $[$Fe VII$]$ (Kramida et al., 2022),
235 eV for $[$Fe X$]$ $\lambda$6375, 262 eV for [Fe XI], and 361 eV for $[$Fe
XIV$]$ $\lambda$5303 (Ferland & Osterbrock, 1987) necessitate a strong
ionizing continuum in the regime of extreme ultraviolet to soft X-rays. Our
XRT observations show a weak X-ray flare (Figure 2) and an overall soft
spectrum ($\Gamma\sim 3.0$) over the first 300d from optical peak, such that
the fraction of flux above the necessary ionizing potentials as measured from
the power-law fit is 40–48$\%$ of the total measured X-ray flux. This fraction
of X-ray flux is still 22.3–26.3 times brighter than the measured strength of
the coronal lines seen 14.5d later, providing more than enough of the ionizing
photons to explain the line fluxes.

Table 5: Median FWHM for each high-ionization coronal line, $[$O III$]$ $\lambda$5007, and combined H$\alpha$ and H$\beta$ across SOAR-measured spectral epochs, and the corresponding virial distance for each line, where $R_{\mathrm{min}}$ corresponds to the distance assuming $M_{\mathrm{BH}}=5\times 10^{5}M_{\odot}$ and $R_{\mathrm{max}}$ corresponds to the distance assuming $M_{\mathrm{BH}}=2\times 10^{6}M_{\odot}$. These distances correspond to light travel times of 10–80 days. Line | FWHM | $R_{\mathrm{min}}$ | $R_{\mathrm{max}}$
---|---|---|---
| (km s-1) | (1016cm) | (1016cm)
$[$Fe XIV$]$ | 556.4 $\pm$ 20.8 | 2.32 $\pm$ 0.2 | 8.92 $\pm$ 0.6
$[$Fe VIIa$]$ | 371.0 $\pm$ 12.4 | 5.21 $\pm$ 0.3 | 20.06 $\pm$ 1.3
$[$Fe VIIb$]$ | 400.8 $\pm$ 11.0 | 4.46 $\pm$ 0.2 | 17.19 $\pm$ 0.9
$[$Fe X$]$ | 406.6 $\pm$ 4.1 | 4.33 $\pm$ 0.1 | 16.69 $\pm$ 0.3
$[$O IIIb$]$ | 278.9 $\pm$ 23.9 | 9.21 $\pm$ 1.4 | 35.48 $\pm$ 5.4
H$\alpha$, H$\beta$ | 439.9 $\pm$ 8.8 | 3.70 $\pm$ 0.1 | 14.26 $\pm$ 0.6

In §3.3 we find BH mass estimates of $M_{\mathrm{BH}}\sim 0.5-2\times
10^{6}M_{\odot}$. Using this approximate range, we can determine lower and
upper distance estimates of the coronal line-emitting gas. We use the FWHM
from the Gaussian fits of each line measured in the SOAR spectra121212We do
not use the FLOYDS spectra here as their resolution is $\sim$500 km s-1,
whereas the SOAR resolution is $\sim$150 km s-1. as a measure of the virial
velocity of the emitting gas and thus find the virial radius for each line.
The median FWHM for each line across all epochs, and each line’s corresponding
virial distances, are listed in Table 5. The velocity found for $[$Fe X$]$ is
faster than the same line FWHM measured in AT 2019qiz (273–368 km s-1; Short
et al., 2023) and VT 1008 (212–370 km s-1; Somalwar et al., 2023).

The inferred radii correspond to light crossing times of 10–80 days,
consistent within the first detection by ZTF which was 57 rest-frame days
prior to peak, given that X-ray activity prior to the first Swift detection
near peak cannot be ruled out.

Figure 10 shows a schematic of where the emitting material is located relative
to the SMBH based on the virial distance estimates for the two ends of the
black hole mass estimate. In either case we see the closest material is within
0.1pc of the SMBH. We note that we cannot use reverberation mapping between
the X-ray and the emergence of coronal lines to also infer the light-crossing
time, as the first XRT observation was made +11 rest-frame days after coronal
lines were already observed. The initial X-ray flare we observe may have
peaked prior to observations, and if so, the coronal lines seen at optical
peak may be indicative of an earlier X-ray flare that peaked before the
optical bands (Komossa et al., 2008).

We add that the spectroscopic changes of AT 2022upj occur while the WISE
fluxes (as shown in Figure 3) were still increasing as a likely dust echo of
the initial flare, indicating a stratified circumnuclear environment. Taking
the most recent NEOWISE observation at +466d from optical peak to be a lower
limit on the peak time of the dust echo (and therefore as the reverberation
lag time), the dust is inferred at a distance of at least 0.40pc from the
SMBH. Thus AT 2022upj is the first case of an ECLE-TDE whose multilayered
circumnuclear material has been unveiled by the combination of multiband
photometry and short-term spectroscopic followup.

##  5 Conclusions

We present AT 2022upj as the first confirmed ECLE-TDE with concurrent X-ray
emission, an optical-UV flare and evolving emission lines over $\sim$year-long
timescales. The association of ECLEs with TDEs has been assumed due to the
energetics required which rule out supernovae and AGN, but the possibility of
AGN accretion state changes and the growing sample of ambiguous nuclear
transients made this connection tenuous, until now. The detection of broad He
II $\lambda$4686 here provides evidence for a TDE origin of ECLE signatures.

Our XRT observations provide the earliest detection of X-ray emission in an
ECLE during an optical transient, providing more than enough ionizing flux to
explain the extreme coronal lines. Furthermore, the virial motion of the
coronal lines around the central SMBH of mass $M_{\mathrm{BH}}\sim 0.5-2\times
10^{6}M_{\odot}$ reveals that the closest emitting material is situated within
0.1pc of the SMBH. These findings, in conjunction with the dust echo detected
in WISE mid-IR bands indicating dust at a minimum of 0.4pc, confirm the
detection of stratified circumnuclear material around a SMBH at among the
smallest scales yet probed. Finally, the emergence of $[$O III$]$ alongside
the increase in X-ray brightness may indicate a dramatic change in accretion
state or the unveiling of pre-existing accretion from obscuring material,
providing an opportunity to investigate the emission mechanisms of TDEs(e.g.
Dai et al., 2018; Ryu et al., 2020).

Our observations and analyses of AT 2022upj unveil the smallest-scale
circumnuclear gas around a SMBH while highlighting the intricacies of emission
from a tidal disruption event in a gas-rich and dusty environment. We have
shown the power of early-time spectroscopic monitoring of nuclear transients
to probe extreme and obscured extragalactic environments. We encourage earlier
monitoring of TDEs for signs of coronal line emission and immediate follow-up
with X-ray telescopes to identify the ionizing source and constrain the
emission mechanism of the central flare.

The Las Cumbres Observatory group is supported by NSF grants AST-1911151 and
AST-1911225. I.A., Y.D. and S.F. acknowledge support from the European
Research Council (ERC) under the European Union Horizon 2020 research and
innovation program (grant No. 852097). I.A. further acknowledges support from
the Israel Science Foundation (grant No. 2752/19),from the United
States—Israel Binational Science Foundation (BSF; grant number 2018166), and
from the Pazy foundation (grant number 216312). This research makes use of
observations from the Las Cumbres Observatory global telescope network as well
as the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet
Propulsion Laboratory, California Institute of Technology, under contract with
NASA.

## References

  * Alard & Lupton (1998) Alard, C., & Lupton, R. H. 1998, ApJ, 503, 325, doi: 10.1086/305984
  * Arcavi (2022) Arcavi, I. 2022, ApJ, 937, 75, doi: 10.3847/1538-4357/ac90c0
  * Arcavi et al. (2014) Arcavi, I., Gal-Yam, A., Sullivan, M., et al. 2014, ApJ, 793, 38, doi: 10.1088/0004-637X/793/1/38
  * Astropy Collaboration et al. (2013) Astropy Collaboration, Robitaille, T. P., Tollerud, E. J., et al. 2013, A&A, 558, A33, doi: 10.1051/0004-6361/201322068
  * Astropy Collaboration et al. (2018) Astropy Collaboration, Price-Whelan, A. M., Sipőcz, B. M., et al. 2018, AJ, 156, 123, doi: 10.3847/1538-3881/aabc4f
  * Becker (2015) Becker, A. 2015, HOTPANTS: High Order Transform of PSF ANd Template Subtraction, Astrophysics Source Code Library, record ascl:1504.004.  http://ascl.net/1504.004
  * Breeveld et al. (2011) Breeveld, A. A., Landsman, W., Holland, S. T., et al. 2011, in American Institute of Physics Conference Series, Vol. 1358, Gamma Ray Bursts 2010, ed. J. E. McEnery, J. L. Racusin, & N. Gehrels, 373–376, doi: 10.1063/1.3621807
  * Brown et al. (2014) Brown, P. J., Breeveld, A. A., Holland, S., Kuin, P., & Pritchard, T. 2014, Ap&SS, 354, 89, doi: 10.1007/s10509-014-2059-8
  * Brown et al. (2013) Brown, T. M., Baliber, N., Bianco, F. B., et al. 2013, PASP, 125, 1031, doi: 10.1086/673168
  * Bruzual & Charlot (2003) Bruzual, G., & Charlot, S. 2003, MNRAS, 344, 1000, doi: 10.1046/j.1365-8711.2003.06897.x
  * Calzetti et al. (2000) Calzetti, D., Armus, L., Bohlin, R. C., et al. 2000, ApJ, 533, 682, doi: 10.1086/308692
  * Carnall et al. (2018) Carnall, A. C., McLure, R. J., Dunlop, J. S., & Davé, R. 2018, MNRAS, 480, 4379, doi: 10.1093/mnras/sty2169
  * Chabrier (2003) Chabrier, G. 2003, PASP, 115, 763, doi: 10.1086/376392
  * Clark et al. (2024) Clark, P., Graur, O., Callow, J., et al. 2024, MNRAS, 528, 7076, doi: 10.1093/mnras/stae460
  * Dai et al. (2018) Dai, L., McKinney, J. C., Roth, N., Ramirez-Ruiz, E., & Miller, M. C. 2018, ApJ, 859, L20, doi: 10.3847/2041-8213/aab429
  * Evans et al. (2009) Evans, P. A., Beardmore, A. P., Page, K. L., et al. 2009, MNRAS, 397, 1177, doi: 10.1111/j.1365-2966.2009.14913.x
  * Ferland & Osterbrock (1987) Ferland, G. J., & Osterbrock, D. E. 1987, ApJ, 318, 145, doi: 10.1086/165357
  * Foreman-Mackey et al. (2013) Foreman-Mackey, D., Hogg, D. W., Lang, D., & Goodman, J. 2013, PASP, 125, 306, doi: 10.1086/670067
  * Fremling (2022) Fremling, C. 2022, Transient Name Server Discovery Report, 2022-2690, 1
  * Gezari (2021) Gezari, S. 2021, ARA&A, 59, 21, doi: 10.1146/annurev-astro-111720-030029
  * Gezari et al. (2017) Gezari, S., Cenko, S. B., & Arcavi, I. 2017, ApJ, 851, L47, doi: 10.3847/2041-8213/aaa0c2
  * Gezari et al. (2012) Gezari, S., Chornock, R., Rest, A., et al. 2012, Nature, 485, 217, doi: 10.1038/nature10990
  * Graham et al. (2019) Graham, M. J., Kulkarni, S. R., Bellm, E. C., et al. 2019, PASP, 131, 078001, doi: 10.1088/1538-3873/ab006c
  * Greene et al. (2020) Greene, J. E., Strader, J., & Ho, L. C. 2020, ARA&A, 58, 257, doi: 10.1146/annurev-astro-032620-021835
  * Guillochon et al. (2018) Guillochon, J., Nicholl, M., Villar, V. A., et al. 2018, ApJS, 236, 6, doi: 10.3847/1538-4365/aab761
  * Hammerstein et al. (2023) Hammerstein, E., van Velzen, S., Gezari, S., et al. 2023, ApJ, 942, 9, doi: 10.3847/1538-4357/aca283
  * Henden et al. (2009) Henden, A. A., Welch, D. L., Terrell, D., & Levine, S. E. 2009, , 214, 407.02
  * Hills (1975) Hills, J. G. 1975, Nature, 254, 295, doi: 10.1038/254295a0
  * Hinkle et al. (2024) Hinkle, J. T., Shappee, B. J., & Holoien, T. W. S. 2024, MNRAS, 528, 4775, doi: 10.1093/mnras/stae022
  * Hosseinzadeh & Gomez (2022) Hosseinzadeh, G., & Gomez, S. 2022, Light Curve Fitting, v0.6.0, Zenodo, doi: 10.5281/zenodo.6519623
  * Kaiser et al. (2010) Kaiser, N., Burgett, W., Chambers, K., et al. 2010, in Society of Photo-Optical Instrumentation Engineers (SPIE) Conference Series, Vol. 7733, Ground-based and Airborne Telescopes III, ed. L. M. Stepp, R. Gilmozzi, & H. J. Hall, 77330E, doi: 10.1117/12.859188
  * Koljonen et al. (2024) Koljonen, K. I. I., Liodakis, I., Lindfors, E., et al. 2024, arXiv e-prints, arXiv:2403.04877, doi: 10.48550/arXiv.2403.04877
  * Komossa et al. (2008) Komossa, S., Zhou, H., Wang, T., et al. 2008, ApJ, 678, L13, doi: 10.1086/588281
  * Kramida et al. (2022) Kramida, A., Ryabtsev, A. N., & Young, P. R. 2022, The Astrophysical Journal Supplement Series, 258, 37, doi: 10.3847/1538-4365/ac3a7e
  * Li et al. (2023) Li, J., Wang, Z.-X., Zheng, D., et al. 2023, Research in Astronomy and Astrophysics, 23, 025012, doi: 10.1088/1674-4527/acae6f
  * Mainzer et al. (2011) Mainzer, A., Bauer, J., Grav, T., et al. 2011, ApJ, 731, 53, doi: 10.1088/0004-637X/731/1/53
  * Mainzer et al. (2014) Mainzer, A., Bauer, J., Cutri, R. M., et al. 2014, ApJ, 792, 30, doi: 10.1088/0004-637X/792/1/30
  * Masci et al. (2019) Masci, F. J., Laher, R. R., Rusholme, B., et al. 2019, PASP, 131, 018003, doi: 10.1088/1538-3873/aae8ac
  * Mockler et al. (2019) Mockler, B., Guillochon, J., & Ramirez-Ruiz, E. 2019, ApJ, 872, 151, doi: 10.3847/1538-4357/ab010f
  * Nagao et al. (2000) Nagao, T., Taniguchi, Y., & Murayama, T. 2000, AJ, 119, 2605, doi: 10.1086/301411
  * NASA HEASARC (2014) NASA HEASARC. 2014, HEAsoft: Unified Release of FTOOLS and XANADU, Astrophysics Source Code Library, record ascl:1408.004
  * Neustadt et al. (2020) Neustadt, J. M. M., Holoien, T. W. S., Kochanek, C. S., et al. 2020, MNRAS, 494, 2538, doi: 10.1093/mnras/staa859
  * Newsome et al. (2022a) Newsome, M., Arcavi, I., Dgany, Y., & Pellegrino, C. 2022a, Transient Name Server AstroNote, 236, 1
  * Newsome et al. (2022b) Newsome, M., Dgany, Y., Arcavi, I., et al. 2022b, Transient Name Server Classification Report, 2022-3231, 1
  * Newsome et al. (2024) Newsome, M., Arcavi, I., Howell, D. A., et al. 2024, ApJ, 961, 239, doi: 10.3847/1538-4357/ad036e
  * Nicholl et al. (2022) Nicholl, M., Lanning, D., Ramsden, P., et al. 2022, MNRAS, 515, 5604, doi: 10.1093/mnras/stac2206
  * Onori et al. (2022) Onori, F., Cannizzaro, G., Jonker, P. G., et al. 2022, MNRAS, 517, 76, doi: 10.1093/mnras/stac2673
  * Piran et al. (2015) Piran, T., Svirski, G., Krolik, J., Cheng, R. M., & Shiokawa, H. 2015, ApJ, 806, 164, doi: 10.1088/0004-637X/806/2/164
  * Planck Collaboration et al. (2020) Planck Collaboration, Aghanim, N., Akrami, Y., et al. 2020, A&A, 641, A6, doi: 10.1051/0004-6361/201833910
  * Rees (1988) Rees, M. J. 1988, Nature, 333, 523, doi: 10.1038/333523a0
  * Roming et al. (2005) Roming, P. W. A., Kennedy, T. E., Mason, K. O., et al. 2005, Space Sci. Rev., 120, 95, doi: 10.1007/s11214-005-5095-4
  * Ryu et al. (2020) Ryu, T., Krolik, J., & Piran, T. 2020, ApJ, 904, 73, doi: 10.3847/1538-4357/abbf4d
  * Schlafly & Finkbeiner (2011) Schlafly, E. F., & Finkbeiner, D. P. 2011, ApJ, 737, 103, doi: 10.1088/0004-637X/737/2/103
  * Science Software Branch at STScI (2012) Science Software Branch at STScI. 2012, PyRAF: Python alternative for IRAF, Astrophysics Source Code Library, record ascl:1207.011
  * Scott et al. (2013) Scott, N., Graham, A. W., & Schombert, J. 2013, ApJ, 768, 76, doi: 10.1088/0004-637X/768/1/76
  * Short et al. (2023) Short, P., Lawrence, A., Nicholl, M., et al. 2023, MNRAS, 525, 1568, doi: 10.1093/mnras/stad2270
  * Somalwar et al. (2023) Somalwar, J. J., Ravi, V., & Lu, W. 2023, arXiv e-prints, arXiv:2310.03795, doi: 10.48550/arXiv.2310.03795
  * Stern et al. (2012) Stern, D., Assef, R. J., Benford, D. J., et al. 2012, ApJ, 753, 30, doi: 10.1088/0004-637X/753/1/30
  * Valenti et al. (2014) Valenti, S., Sand, D., Pastorello, A., et al. 2014, MNRAS, 438, L101, doi: 10.1093/mnrasl/slt171
  * Valenti et al. (2016) Valenti, S., Howell, D. A., Stritzinger, M. D., et al. 2016, MNRAS, 459, 3939, doi: 10.1093/mnras/stw870
  * van Velzen et al. (2021a) van Velzen, S., Pasham, D. R., Komossa, S., Yan, L., & Kara, E. A. 2021a, Space Sci. Rev., 217, 63, doi: 10.1007/s11214-021-00835-6
  * van Velzen et al. (2021b) van Velzen, S., Gezari, S., Hammerstein, E., et al. 2021b, ApJ, 908, 4, doi: 10.3847/1538-4357/abc258
  * Wang et al. (2012) Wang, T.-G., Zhou, H.-Y., Komossa, S., et al. 2012, ApJ, 749, 115, doi: 10.1088/0004-637X/749/2/115
  * Wang et al. (2011) Wang, T.-G., Zhou, H.-Y., Wang, L.-F., Lu, H.-L., & Xu, D. 2011, ApJ, 740, 85, doi: 10.1088/0004-637X/740/2/85
  * Wright et al. (2010) Wright, E. L., Eisenhardt, P. R. M., Mainzer, A. K., et al. 2010, AJ, 140, 1868, doi: 10.1088/0004-6256/140/6/1868
  * Yang et al. (2013) Yang, C.-W., Wang, T.-G., Ferland, G., et al. 2013, ApJ, 774, 46, doi: 10.1088/0004-637X/774/1/46
  * Yao et al. (2023) Yao, Y., Ravi, V., Gezari, S., et al. 2023, ApJ, 955, L6, doi: 10.3847/2041-8213/acf216

##  Appendix A XRT Power-Law Fits

We use HEASOFT v6.32131313https://www.swift.ac.uk/user_objects/ (NASA HEASARC,
2014) to extract source and background count rates for each observation using
a source region with a radius of 40″ centered and background region with
radius of 150″. All count rates were corrected for encircled energy fraction.
The results of the fits are in Figure 11.

Figure 11: Top: Power-law fit to AT 2022upj during the “pre-burst” phase
(first 250 days from optical peak). The photon index for this phase is
$\Gamma=2.55^{+1.37}_{-0.35}$. Bottom: Power-law fit to AT 2022upj during the
“burst” phase (after 250 days from optical peak) The photon index for this
phase is $\Gamma=3.08^{+0.23}_{-0.21}$.

##  Appendix B Light Curve Model Fitting Outputs

Here we provide the outputs from MOSFiT and TDEMass which estimate TDE
parameters for AT 2022upj from each model. Figure 12 shows the fit to the UV-
optical light curve from MOSFiT, while Figure 13 shows the corner plot of
fitted parameters: photospheric radius $R_{\mathrm{ph0}}$, viscous time delay
$T_{\text{viscous}}$, scaled impact parameter $\beta$, mass of the
supermassive black hole $M_{h}$, efficiency parameter $\epsilon$, photosphere
power-law exponent $l$, host column density $n_{\mathrm{H,host}}$, mass of the
disrupted star, time between first observation and disruption
$t_{\mathrm{exp}}$, and white noise parameter $\sigma$ (Mockler et al., 2019).
Figure 14 shows the solution space for the mass of the SMBH $M_{\mathrm{BH}}$
and the disrupted star $M_{\star}$ from TDEMass (Ryu et al., 2020).

Figure 12: Light curve fitting output from MOSFiT to the multiband optical and
UV photometry from Las Cumbres, ZTF, and Swift of AT 2022upj. Figure 13:
Corner plot of fitted parameters via nested sampling light curve fitting from
MOSFiT. Figure 14: The solution for stellar mass and black hole mass from the
peak temperature and bolometric luminosity of AT 2022upj as determined by
TDEMass.

##  Appendix C Host Galaxy Fits

BAGPIPES (Carnall et al., 2018) fits spectroscopic models of galaxies to
observed photometry in order to estimate the host’s stellar mass and star
formation history, metallicity, dust content, and age. We use the same choice
of SFH and priors as in Carnall et al. (2018) for our initial fit. We use the
stellar synthesis models as outlined in Bruzual & Charlot (2003) and updated
in 2016141414http://www.bruzual.org/~gbruzual/bc03/Updated_version_2016/
assuming a Chabrier (2003) initial mass function. The star formation history
is modeled as a double-power law with log-flat priors on the exponents in the
power law ($\alpha$ and $\beta$ in Equation 10 of Carnall et al. 2018) in
which we also use a uniform prior on metallicity and the Calzetti et al.
(2000) dust law with a uniform prior on extinction. We fix the redshift to the
spectroscopically determined value $z=0.054$. The host photometry used in
these fits is listed in Table 6 and the result of the spectroscopic fit is in
Figure 15.

Figure 15: BAGPIPES spectral fit (orange line) and synthetic photometry (orange points) to the J003113.52+850031.8 photometrical SED (blue points) from the values in Table 6. Figure 16: BAGPIPES corner plot of fitted parameters of the host galaxy of AT 2022upj. Table 6: Photometry of the host galaxy WISEA J002356.88-142523.9 used in fitting with BAGPIPES. All magnitudes are given in the Vega system except for $grizy$ magnitudes, given in the AB system. Filter | Source | Magnitude | Flux
---|---|---|---
|  |  |  $\mu$Jy
FUV | GALEX | 20.19 | 1.82
NUV | GALEX | 19.83 | 3.58
$g$ | Pan-STARRS | 18.46 | 259.89
$r$ | Pan-STARRS | 17.73 | 378.18
$i$ | Pan-STARRS | 17.34 | 418.40
$z$ | Pan-STARRS | 17.02 | 566.01
$y$ | Pan-STARRS | 16.77 | 714.14
$J$ | 2MASS | 15.54 | 1350.0
$H$ | 2MASS | 14.37 | 1490.0
$K$ | 2MASS | 14.47 | 1380.0
$W1$ | WISE | 13.93 | 1310.0
$W2$ | WISE | 13.89 | 736.0