arXiv subjects

Christos Panagiotou

Publications and source records attributed to Christos Panagiotou.

At least 19 recordsLinked to original sources

arXiv2026

Extreme AGN Variability in WISE: Powerful Flares and Candidate Tidal Disruption Events in AGN

We present first results from a systematic study of extreme mid-infrared variability of active galaxies across the $>10$-year baseline of the Wide-field Infrared Survey Explorer (WISE) mission. WISE, which observed the full sky with a six-month cadence, is sensitive to transient events in both unobscured and obscured galaxies. This paper focuses on extreme flares in active galactic nuclei (AGNs). Previous studies identified flares such as tidal disruption events (TDEs) in inactive galaxies, typically from optical or X-ray surveys. However, flares are also expected in AGN and optical/X-ray searches are insensitive to events in dust-enshrouded AGN. In this pilot study, we present flares in two AGN identified from extreme mid-infrared color variability. One flare was also detected at optical wavelengths. While both events showed broadened H$\alpha$ emission several years after the flare peak, more recent spectroscopy reveals continued broadened emission only from the source with the optical flare. After considering several potential physical causes of the flares, including supernovae and micro-lensing, we suggest both events are TDEs in AGN. Intriguingly, the optical flare decays much faster than the expected $t^{-5/3}$ fallback rate expected for TDEs in quiescent galaxies, suggesting either a partial disruption or the tidal disruption of a star by an intermediate mass black hole embedded in the accretion disk of an AGN. This work demonstrates the power of WISE to identify the full census of TDEs, including events in dust-obscured AGN. Mid-infrared data probes the nature of the event and provides a bolometric measure of the flare energetics.

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arXiv2026

A Suppressed Volumetric Rate of High-Luminosity Mid-Infrared Selected Tidal Disruption Events

Tidal Disruption Events (TDEs) serve as direct probes of the population of supermassive black holes in the center of galaxies and are nowadays regularly detected in optical wide-field time-domain sky surveys. Recent studies have demonstrated that a large fraction of TDEs can be uniquely identified in the infrared (IR) waveband, but these studies have to date been limited to relatively nearby events. In this work, we searched for highly luminous IR-bright TDEs that are rare and thus missed by searches in the local universe. We performed a systematic search of the NEOWISE archive and developed a new selection criterion based on the evolution of the W1-W2 color to select TDE candidates. We identified 10 IR bright TDEs with peak luminosities above $L_{\rm peak\, W2} \simeq 3 \times 10^{43}$ erg s$^{-1}$ and estimated an event rate of $1.2^{+0.5}_{-0.4}\times10^{-10}$ Mpc$^{-3}$year$^{-1}$ for the luminosity range of our sample. Compared to the existing local luminosity function of lower luminosity events, we detect a suppressed rate for these highly luminous events. This turn-over in the luminosity function can be naturally explained by the suppressed amount of TDEs taking place in systems with larger black hole masses, thereby confirming the TDE nature of our sources.

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arXiv2026

Observation of A Solar Like Magnetic Reconnection Event in an AGN Corona with XRISM

The X-ray source in AGN is commonly referred to as the corona by analogy to stellar coronae. The similarities between the two suggest that the heating mechanism of AGN coronae is magnetic reconnection -- as in cool stars -- but this has not yet been directly observed. This work presents the first observational evidence for a magnetic reconnection flare in an AGN corona. We report on a flare in NGC 3783, which was observed with XRISM/Xtend and XMM-Newton/EPIC-PN exhibiting distinct temporal evolution in soft ($<2.0\,$keV) and hard ($>2.0\,$keV) X-rays. An Ultra-Fast Outflow (UFO) was detected during the event. The flare features the Neupert effect -- a temporal signature of the hard light curve correlating with the time derivative of the soft light curve, which shows that the flare is powered by magnetic reconnection, The Neupert effect is widely observed in the Sun, with Coronal Mass Ejections (CMEs) playing a role analogous to the UFO. We derive an upper limit of $30 \, R_g$ on the height of the magnetic loop from which the flare originates. Using the UFO's measured properties to characterize the magnetic field, we obtain $B > 1.3 \times 10^4\,$G for the field annihilated during the flare from total energy considerations, and $B \approx 500\,$G for the momentary magnetic field during reconnection from a dynamical consideration.

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arXiv2026

Discovery of Quasar Variability and Early Accretion Disk Signatures at Cosmic Dawn

In the nearby universe, quasars are well known to exhibit variability in their brightness over time, offering a powerful tool to probe the physics of accretion onto the SMBH and directly measure the mass of the SMBH. However, detecting variability in early quasars remains challenging. Here, we report the detection of multi-wavelength infrared and X-ray variability in a quasar observed just 850 million years after the Big Bang. The infrared variability spans five filters, tracing rest-frame ultraviolet and optical emission from the accretion disk, while the X-ray variability probes the corona. The variable spectrum reveals that the accretion disk has a geometrically thin, optically thick structure. This provides observational constraints on the accretion disk structure at early times, when quasars are accreting at high Eddington ratios and reside in extreme environments. Our findings demonstrate the feasibility of characterizing accretion physics using variability in the early universe, laying the groundwork for studies exploiting upcoming facilities such as the Rubin Observatory and Roman Space Telescope. These facilities will discover large samples of variable high-redshift quasars, enabling population-level variability studies of accretion physics and black hole masses, filling key missing ingredients in understanding early SMBH growth.

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arXiv2026

Delving into the depths of NGC 3783 with XRISM: V. Broad-band modeling of ionized outflows

The Seyfert 1 galaxy NGC 3783 hosts a multiphase warm absorber (WA) that has been extensively studied in the X-ray band. High-resolution spectra from 2000-2001 revealed a complex outflow with multiple ionization and velocity components. Two decades later, new XMM-Newton and XRISM observations allow us to investigate the long-term evolution of these outflows. We perform joint spectral modeling of the XMM-Newton/RGS and XRISM/Resolve time-averaged spectra using the pion photoionization code within SPEX. We derive the ionization parameter, column density, turbulent velocity, and outflow velocity for each absorption component, and investigate their thermal stability and Absorption Measure Distribution (AMD) to characterize the physical and dynamical properties of the WA in NGC 3783 in 2024. We compare these results with the 2000-2001 epoch to assess long-term variability, stability, and possible changes in the absorber population. We identify eight WA components spanning log $\xi =$ 1.08-3.38 and outflow velocities of 480-1230 km s$^{-1}$. The ranges of column densities and turbulent velocities remain broadly consistent with the WAs from 2000-2001, but the earlier data contained more low-ionization, high-velocity components. The total column density in 2024 is 1.5 times larger than in 2000-2001, requiring replenishment by fresh material. The dominant Unresolved Transition Array (UTA) absorber (Comp. B3) has increased its column density by a factor of three while maintaining a similar ionization parameter. The WAs in NGC 3783 have undergone significant structural and dynamical evolution over the past 24 years.

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arXiv2026

Persistence of the Millihertz X-ray Quasi-Periodic Oscillation in the Active Galactic Nucleus 1ES 1927+654

1ES 1927+654 is an extreme active galactic nucleus (AGN) that has defied our canonical expectations for how AGN appear across the electromagnetic spectrum and how they vary on short timescales. In 2022, this source began showing a X-ray quasi-periodic oscillation (QPO) at mHz frequencies, along with a newly launched radio jet. Unlike the handful of other known AGN QPOs, the QPO in 1ES 1927+654 showed a significant frequency evolution, spanning from 0.9-2.4 mHz from 2022-2024. In this work, we present the last 1.5 years of monitoring with XMM-Newton (250 ks) up to January 2026, which reveals that the QPO persists but has plateaued at a constant frequency of approximately 2.5 mHz. We perform detailed spectral-timing analyses on this exquisite dataset, consisting of over 900 QPO cycles, more than any AGN QPO to date. Our main findings are: (1) the stacked XMM-Newton power spectra shows no significant second harmonic, (2) a soft (reverberation-like) lag is observed at all frequencies and remains remarkably stable even as the QPO frequency evolved from 2022-2024, and (3) extreme X-ray jumps on the QPO period (up to ~80% baseline flux) persist to present day with a remarkably stable dip-rise-fall pattern. Finally, we also detect the first AGN QPO in NuSTAR observations, which is present from 2023 to 2026 at frequencies consistent with the XMM-Newton detections. While we explore models for eclipses and coupled disk-corona behavior to simultaneously explain the lags, dips, and QPO, these new observations strain such models.

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arXiv2026

Variability of the X-ray obscuring wind in Mrk 335 with XMM-Newton/RGS

Transient X-ray obscuration in Seyfert 1 galaxies likely arises from clumpy accretion-disk winds near the broad-line region (BLR), but the wind structure and short-timescale variability are difficult to measure because high-resolution spectra are often suppressed during deep low states. We analyse a coordinated XMM-Newton/NuSTAR campaign on Mrk 335 in June 2021, with long-term Swift monitoring, capturing the source in an intermediate-flux state with strong RGS absorption features. We model the broadband SED to determine the ionising continuum for self-consistent photoionisation modelling of the RGS spectra. The stacked RGS spectrum requires three photoionised absorbers with log xi ~ 3.69, 2.97, and 1.91, outflowing at |v_out| ~ 5800, 3200, and 2100 km/s, respectively. Their properties are consistent with the three-phase obscurer reported in 2009, indicating that a similar multi-phase obscuring wind can persist over decade timescales. Using five consecutive RGS observations, we track the wind evolution on day timescales and find strong variability in column density and ionisation in all phases, together with smaller but coherent velocity changes. During a flare, the low-ionisation phase shows a significant drop in opacity, while in the subsequent epoch all phases show increased outflow velocities, suggesting a possible connection between continuum variability and changes in the line-of-sight absorber. The high-ionisation phase responds most directly to changes in ionising luminosity, while the lowest-ionisation phase shows at most a delayed response. Order-of-magnitude constraints place the obscurer at BLR scales, ~10^3-10^5 Rg, with kinetic power potentially reaching the percent level of L_bol for plausible assumptions on geometry and clumpiness.

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arXiv2026

Fading into darkness: A weak mass ejection and low-efficiency fallback accompanying black hole formation in M31-2014-DS1

Stellar-mass black holes (BHs) can form from the near-complete collapse of massive stars, causing them to abruptly disappear. The star M31-2014-DS1 in the Andromeda galaxy was reported to exhibit such a disappearance between 2014 and 2022, with properties consistent with the failed explosion of a $\approx 12 - 13$ M$_\odot$ yellow supergiant leading to the formation of a $\approx 5$ M$_\odot$ BH. We present mid-infrared (MIR) observations of the remnant obtained with the James Webb Space Telescope (JWST) and X-ray observations from the Chandra X-ray Observatory in 2024. The JWST MIRI/NIRSpec data reveal an extremely red source, showing strong blueshifted absorption from molecular gas (CO, CO$_2$, H$_2$O, SO$_2$) and deep silicate dust features. Modeling the dust continuum confirms continued bolometric fading of the central source to $\log(L/L_\odot)\approx3.88$ ($\approx7-8$% of the progenitor luminosity), surrounded by a dust shell spanning $\approx40-200$ au. Modeling of the molecular gas indicates $\sim 0.1$ M$_\odot$ of gas expanding at $\approx 100$ km s$^{-1}$ near the inner edge of the dust shell. No X-ray source is detected down to a luminosity limit of $L_X\lesssim1.5\times10^{35}$ erg s$^{-1}$. We show that the panchromatic observations are explained by (i) a low-energy ($\approx10^{46}$ erg) ejection of the outer H-rich progenitor envelope and (ii) a fading central BH powered by inefficient ($\sim0.1$% in mass) accretion of loosely bound fallback material. The analysis robustly establishes the bolometric fading of M31-2014-DS1 and provides the first cohesive insights into BH formation via low-energy explosions and long-term fallback.

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arXiv2026

X-ray Spectral-Timing Properties of Tidal Disruption Events

We perform the first systematic study of the minute-to-hours-timescale stochastic variability observed in the X-ray luminosity of tidal disruption events (TDEs) using XMM-Newton data and Fourier analysis methods. We measure the spectral properties, power spectral densities (PSDs), fractional variability amplitudes, and energy dependence of the variability for 18 TDEs spanning 54 observations, of which 27 occur in thermal disk-dominated states and 27 show a nonthermal hard X-ray corona. Compared to pure thermal sources, we find TDEs with coronae are more X-ray variable and show steeper PSDs indicating longer correlation timescales. This state-transition behavior is qualitatively similar to X-ray binaries, which show higher fractional variability in the hard state than in the soft state. However, newborn TDE coronae show systematically flatter PSDs and softer energy spectra than their long-lived AGN counterparts. We also show that the variability amplitude of thermal TDEs increases with photon energy, consistent with variations sourced by local temperature fluctuations and exponentially enhanced in the Wien tail. Our work demonstrates that combining spectral and timing properties of X-ray TDEs can probe the microphysics of newly formed accretion flows around supermassive black holes, and that the coronae formed in TDEs fundamentally differ from those in AGN.

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arXiv2026

Disappearance of a massive star in the Andromeda Galaxy due to formation of a black hole

When a massive star reaches the end of its lifetime, its core collapses and releases neutrinos that drive a shock into the outer layers (stellar envelope). A sufficiently strong shock ejects the envelope, producing a supernova. If the shock fails to eject it, the envelope is predicted to fall back onto the collapsing core, producing a stellar-mass black hole (BH) and causing the star to disappear. We report observations of M31-2014-DS1, a hydrogen-depleted supergiant in the Andromeda Galaxy. In 2014 it brightened in the mid-infrared. From 2017 to 2022 it faded by factors of $\gtrsim10^4$ in optical light, becoming undetectable, and $\gtrsim10$ in total light. We interpret these observations, and those of a previous event in NGC 6946, as evidence for failed supernovae forming stellar-mass BHs.

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arXiv2026

Testing the Association of Supermassive Black Hole Infrared Flares and High-energy Neutrinos

The physical origin of the observed cosmic neutrinos remains an open question and the subject of active research. While matter accretion onto supermassive black holes is long thought to accelerate particles to high energies, it has recently been suggested that tidal disruption events, and accretion flares in general, with prominent IR echoes can account for a fraction of the diffuse high-energy neutrino signal. Motivated by this result, we compile a sample of nearby accretion flares detected in the NEOWISE survey featuring strong IR echoes, and we cross-match it with the latest catalog of neutrino alerts, IceCat-1. We recover only a single spatial coincidence between the two catalogs, consistent with a chance coincidence. We find no temporal and spatial coincidences between the two samples, which, given the properties of our sample, appears to challenge previous conclusions. We discuss the physical implications of our results and potential future explorations.

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arXiv2025

Delving into the depths of NGC 3783 with XRISM IV. Mapping of the accretion flow with Fe K$α$ emission lines

Using XRISM/Resolve $439 \, \rm ks$ time-averaged spectra of the well-known Seyfert-1.5 active galactic nucleus (AGN) in NGC 3783, we investigate the nature of the Fe K$α$ emission line at 6.4 keV, the strongest and most common X-ray line observed in AGN. Even the narrow component of the line is resolved with evident Fe K$α_{1}$ (6.404 keV) and K$α_{2}$ (6.391 keV) contributions in a 2:1 flux ratio, fully consistent with a neutral gas with negligible bulk velocity. The narrow and intermediate-width components have a full-width at half maximum (FWHM) of 350 $\pm$ 50 km/s and $3510 \pm 470 \, \rm km/s$, respectively, suggesting that they arise in the outer disk/torus and/or BLR. We detect a $10\%$ excess flux around 4 $-$ 7 keV that is not well described by a symmetric Gaussian line, but is consistent with a relativistically broadened emission line. In this paper, we take the simplest approach to model the asymmetric line as a single emission line (assuming either neutral, He-like or H-like iron) convolved with a relativistic disk line model. As expected, the inferred inclination angle is highly sensitive to the assumed ionization state, and ranges between $i=17-44^{ \circ}$. This model also constrains the black hole spin via the extent of the red wing: the required gravitational redshift in the fitted disk-line profile disfavors a non-spinning (Schwarzschild) black hole. The derived inner radius is close to the radius of the innermost stable circular orbit $r_{\rm ISCO}$ and strongly correlated with the black hole spin. To better constrain the spin, we fix the inner radius at $r_{\rm ISCO}$ and derive a lower limit on the spin of $a \ge 0.29$ at the 3 $σ$ confidence level. A Compton shoulder is detected in our data as well as a $2-3 \, σ$ detection of the Cr K$α$ and Ni K$α$ lines.

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arXiv2025

Delving into the depths of NGC 3783 with XRISM III. Birth of an ultrafast outflow during a soft flare

The 2024 X-ray/UV observation campaign of NGC 3783, led by XRISM, revealed the launch of an ultrafast outflow (UFO) with a radial velocity of 0.19c (57000 km/s). This event is synchronized with the sharp decay, within less than half a day, of a prominent soft X-ray/UV flare. Accounting for the look-elsewhere effect, the XRISM Resolve data alone indicate a low probability of 2e-5 that this UFO detection is due to random chance. The UFO features narrow H-like and He-like Fe lines with a velocity dispersion of 1000 km/s, suggesting that it originates from a dense clump. Beyond this primary detection, there are hints of weaker outflow signatures throughout the rise and fall phases of the soft flare. Their velocities increase from 0.05c to 0.3c over approximately three days, and they may be associated with a larger stream in which the clump is embedded. The radiation pressure is insuffcient to drive the acceleration of this rapidly evolving outflow. The observed evolution of the outflow kinematics instead closely resembles that of solar coronal mass ejections, implying magnetic driving and, conceivably, reconnection near the accretion disk as the likely mechanisms behind both the UFO launch and the associated soft flare.

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arXiv2025

The Accretion Disk Size Problem in AGN Disk Reverberation Mapping is an Obscuration Effect: A Uniform AGN Sample Study with Swift

In the past decade, Swift has performed several AGN high-cadence reverberation mapping campaigns, and generally found that the UV/optical interband lags are $\sim$3 times longer than predicted for a standard thin disk, thus coined "the accretion disk size problem". Here we present a systematic sample of Swift-monitored AGN. In this analysis, we confirm the accretion disk size problem, but find that the lag excess occurs only in the subset of obscured AGN, which show a significantly elevated mean normalization of $5.21 \pm 0.47$ ($p = 0.008$), whereas the unobscured AGN exhibit a mean excess consistent with standard disk predictions ($1.00 \pm 0.31$). Correlation and regression analyses similarly reveal X-ray column density as the strongest predictor of lag excess, explaining over 80% of its variance. We interpret these results as line-of-sight obscuration being linked to the too-long lags via additional reprocessed emission from the absorbing material itself. The consistency of lags in the unobscured subgroup with standard disk predictions suggests that the accretion disk size problem is not the result of shortcomings of standard accretion disk theory nor contamination by the broad-line region (BLR). X-ray to UV lag amplitudes and correlations show more complex and variable behavior in obscured AGN, suggesting that obscuration may disrupt or complicate the connection between high- and low-energy emission potentially through reprocessing, scattering, and/or ionization changes.

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arXiv2025

Radio Emission from the Infrared Tidal Disruption Event WTP14adeqka: The First Directly Resolved Delayed Outflow from a TDE

We present detailed radio observations of the mid-infrared (MIR) tidal disruption event (TDE) WTP14adeqka. We detect rising radio emission starting $\approx 4$ years after the discovery of the MIR emission (and about 2 years after its peak), peaking at $\approx 6.5$ years and declining thereafter, reminiscent of the delayed radio emission recently identified in optically discovered TDEs. The peak radio luminosity, $νL_ν\approx 2\times 10^{39}$ erg s$^{-1}$, is comparable to the brightest radio emission in optical TDEs. Multi-frequency radio observations at 8.9 and 9.7 years reveal a non-relativistic outflow with a mean expansion velocity of $\approx 0.021c$ (for an assumed launch at the time of disruption) and an energy of $\approx 10^{50.7}$ erg, about an order of magnitude larger than in typical optical TDEs. More importantly, Very Long Baseline Array (VLBA) observations at the same epochs directly resolve the radio source and reveal an increase in size from approximately 0.11 pc to 0.13 pc (with no apparent astrometric shift), corresponding to an expansion velocity of $\approx 0.05c$, and a likely delayed launch by about 2 years. The VLBA size measurements rule out an off-axis jet launched at the time of disruption, which would have an expected size of $\gtrsim {\rm pc}$ on these timescales; the possibility of a delayed jet can be evaluated with future VLBA observations. We conclude that MIR TDEs can launch energetic, delayed outflows. Ongoing radio observations of the full MIR TDE sample will reveal whether this behavior is ubiquitous.

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arXiv2025

Delving into the depths of NGC 3783 with XRISM. I. Kinematic and ionization structure of the highly ionized outflows

We present our study of the XRISM observation of the Seyfert-1 galaxy NGC 3783. XRISM's Resolve microcalorimeter has enabled, for the first time, a detailed characterization of the highly ionized outflows in this active galactic nucleus. Our analysis constrains their outflow and turbulent velocities, along with their ionization parameter ($ξ$) and column density ($N_{\rm H}$). The high-resolution Resolve spectrum reveals a distinct series of Fe absorption lines between 6.4 and 7.8 keV, ranging from Fe XVIII to Fe XXVI. At lower energies, absorption features from Si, S, and Ar are also detected. Our spectroscopy and photoionization modeling of the time-averaged Resolve spectrum uncovers six outflow components, five of which exhibit relatively narrow absorption lines with outflow velocities ranging from 560 to 1170 km/s. In addition, a broad absorption feature is detected, which is consistent with Fe XXVI outflowing at 14,300 km/s (0.05 $c$). The kinetic luminosity of this component is 0.8-3% of the bolometric luminosity. Our analysis of the Resolve spectrum shows that more highly ionized absorption lines are intrinsically broader than those of lower-ionization species, indicating that the turbulent velocity of the six outflow components (ranging from 0 to 3500 km/s) increases with $ξ$. Furthermore, we find that the $N_{\rm H}$ of the outflows generally declines with $ξ$ up to $\log ξ= 3.2$ but rises beyond this point, suggesting a complex ionization structure. The absorption profile of the Fe XXV resonance line is intriguingly similar to UV absorption lines (Ly$α$ and C IV) observed by the HST, from which we infer that the outflows are clumpy in nature. Our XRISM/Resolve results support a "hybrid wind" scenario in which the observed outflows have multiple origins and driving mechanisms. We explore various interpretations of our findings within AGN wind models.

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arXiv2025

JWST's First View of Tidal Disruption Events: Compact, Accretion-Driven Emission Lines & Strong Silicate Emission in an Infrared-selected Sample

Mid-infrared (MIR) emission from tidal disruption events (TDEs) is a powerful probe of the circumnuclear environment around dormant supermassive black holes. This emission arises from the reprocessing of intrinsic emission into thermal MIR emission by circumnuclear dust. While the majority of optical- and X-ray-selected TDEs show only weak dust echoes consistent with primarily unobscured sight lines, there have been growing efforts aimed at finding TDEs in obscured environments using MIR selection methods. In this work, we present the first JWST observations of 4 MIR-selected TDEs with JWST Mid-Infrared Instrument (MIRI) Medium-Resolution Spectrometer (MRS). Two of these sources show flares in other wavelength bands (one in optical, one in X-ray), while the other two are MIR-only transients. None of these TDEs showed pre-outburst nuclear activity, but all of the MIRI/MRS observations reveal emission lines associated with highly ionized gas in the nucleus, implying ionization from TDE accretion. Additionally, all four sources show silicate emission features around 10 and 18 $μ$m that are much stronger than the features seen in active galactic nuclei (AGN). We suggest that the emitting dust is optically thin to its own emission and show that the MIR spectrum is consistent with emission from optically thin dust in the nucleus. All four sources show an excess at short wavelengths ($λ< 8\, μ$m), which could arise from a late-time plateau in the intrinsic flare, akin to what is seen in late-time UV observations of unobscured TDEs, although self-consistent dust modeling is required to fully assess the strength of this late-time plateau.

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arXiv2025

Discovery of Quasi-periodic Eruptions in the Tidal Disruption Event and Extreme Coronal Line Emitter AT2022upj: implications for the QPE/TDE fraction and a connection to ECLEs

Quasi-periodic eruptions (QPEs) are recurring soft X-ray transients emerging from the vicinity of supermassive black holes (SMBHs) in nearby, low-mass galaxy nuclei; about ten QPE hosts have been identified thus far. Here we report the \textit{NICER} discovery of QPEs in the optically-selected Tidal Disruption Event (TDE) and Extreme Coronal Line Emitter (ECLE) AT2022upj, exhibiting a large spread in recurrence times from 0.5-3.5 days, durations from 0.3-1 days, peak luminosities from $10^{42.5-43.0}$ erg s$^{-1}$, and erratic flare profiles. A wealth of evidence now links at least some QPEs to the newly-formed accretion flows emerging from TDEs; AT2022upj is the third QPE reported in an optically discovered TDE. Marginalizing over the uncertain distributions of QPE peak luminosity, recurrence time, delay after TDE peak, and lifetime, we use the burgeoning sample to make a Bayesian estimate that the fraction of optical TDEs resulting in QPEs within 5 years post-disruption is $9^{+9}_{-5}$\%. Along with AT2019qiz, AT2022upj also marks the second of the three optical TDE+X-ray QPEs showing coronal line emission, suggesting ECLEs may represent a subset of TDEs particularly efficient at forming QPEs and/or that sustained QPE X-ray emission contributes to coronal line emission in some galaxy nuclei.

astro-ph.HE↗