The Curious Case of ASASSN-20hx: A Slowly-Evolving, UV and X-ray Luminous, Ambiguous Nuclear Transient

Hinkle, Jason T.; Holoien, Thomas W. -S.; Shappee, Benjamin. J.; Neustadt, Jack M. M.; Auchettl, Katie; Vallely, Patrick J.; Shahbandeh, Melissa; Kluge, Matthias; Kochanek, Christopher S.; Stanek, K. Z.; Huber, Mark E.; Post, Richard S.; Bersier, David; Ashall, Christopher; Tucker, Michael A.; Williams, Jonathan P.; de Jaeger, Thomas; Do, Aaron; Fausnaugh, Michael; Gruen, Daniel; Hopp, Ulrich; Obermeier, Christian; Payne, Anna V.; Thompson, Todd A.

doi:10.48550/arxiv.2108.03245

Cited by 4 publications

(4 citation statements)

References 164 publications

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“…In the case of "rapid turn-on" events, the blue continuum and broad lines appear on time scales of a few months (e.g., Gezari et al 2017;Frederick et al 2019;Gromadzki et al 2019;Trakhtenbrot et al 2019a;Ricci et al 2020). There are also ANTs which share characteristics of both TDEs and more normal AGN variability (Neustadt et al 2020;Hinkle et al 2021c;Holoien et al 2021;Yu et al 2022).…”

Section: Introductionmentioning

confidence: 99%

Chandra, HST/STIS, NICER, Swift, and TESS Detail the Flare Evolution of the Repeating Nuclear Transient ASASSN-14ko

Payne¹,

Auchettl²,

Shappee³

et al. 2022

Preprint

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ASASSN-14ko is a nuclear transient at the center of the AGN ESO 253−G003 that undergoes periodic flares. Optical flares were first observed in 2014 by the All-Sky Automated Survey for Supernovae (ASAS-SN) and their peak times are well-modeled with a period of 115.2 +1.3 −1.2 days and period derivative of −0.0026 ± 0.0006. Here we present ASAS-SN, Chandra, HST /STIS, NICER, Swift, and TESS data for the flares that occurred in

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Section: Introductionmentioning

confidence: 99%

Chandra, HST/STIS, NICER, Swift, and TESS Detail the Flare Evolution of the Repeating Nuclear Transient ASASSN-14ko

Payne¹,

Auchettl²,

Shappee³

et al. 2022

Preprint

Self Cite

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“…Indeed, an increasing number of TDE candidates have been found in galaxies with pre-existing AGN activity (e.g., van Velzen et al 2016;Blanchard et al 2017;Shu et al 2018;Liu et al 2020). However, in this case, identifying whether nuclear outburst is due to a TDE or a particular episode of AGN variability is not trivial (Saxton et al 2015;Auchettl et al 2018;Trakhtenbrot et al 2019;Hinkle et al 2021). On the other hand, in the presence of a TDE, the innermost regions of the accretion flow can be affected by the evolution of stellar debris, leading to unique and remarkable AGN X-ray variabilities (Blanchard et al 2017;Chan et al 2019;Ricci et al 2020Ricci et al , 2021.…”

Section: Introductionmentioning

confidence: 99%

Discovery of late-time X-ray flare and anomalous emission line enhancement after the nuclear optical outburst in a narrow-line Seyfert 1 Galaxy

Zhang

Shu

Sheng

et al. 2022

A&A

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CSS J102913+404220 is an atypical narrow-line Seyfert 1 galaxy with an energetic optical outburst occurring co-spatially with its nucleus. We present a detailed analysis of multi-wavelength photometric and spectroscopic observations of this object covering a period of a decade since outburst. We detect mid-infrared (MIR) flares delayed by about two months relative to the optical outburst and with an extremely high peak luminosity of L4.6 μm > 1044 erg s−1. The MIR peak luminosity is at least an order of magnitude higher than any known supernovae explosions, suggesting the optical outburst might be due to a stellar tidal disruption event (TDE). We find late-time X-ray brightening by a factor of ≳30 with respect to what is observed about 100 days after the optical outburst peak, followed by a flux fading by a factor of ∼4 within two weeks, making it one of the active galactic nuclei (AGNs) with extreme variability. Despite the dramatic X-ray variability, there are no coincident strong flux variations in optical, UV, and MIR bands. This unusual variability behavior has been seen in other highly accreting AGNs and could be attributed to absorption variability. In this scenario, the decrease in the covering factor of the absorber with accretion rate could cause the X-ray brightening, possibly induced by the TDE. Most strikingly, while the UV/optical continuum remains almost unchanged with time, an evident enhancement in the flux of the Hα broad emission line is observed about a decade after the nuclear optical outburst, which is an anomalous behavior never seen in any other AGN. Such an Hα anomaly could be explained by the replenishment of gas clouds and excitation within the broad line region (BLR) that perhaps originates from its interaction with outflowing stellar debris. Our results highlight the importance of the late-time evolution of a TDE, which can affect the accreting properties of the AGN, as suggested by recent simulations.

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“…Indeed, an increasing number of TDE candidates have been found in galaxies with preexisting AGN activity (e.g., van Velzen et al 2016;Blanchard et al 2017;Shu et al 2018;Liu et al 2020). In this case, however, identifying whether nuclear outburst is due to a TDE or a particular episode of AGN variability is not trivial (Saxton et al 2015;Auchettl et al 2018;Trakhtenbrot et al 2019;Hinkle et al 2021). On the other hand, in the presence of TDE, the innermost regions of the accretion flow can be affected by the evolution of stellar debris, leading to unique and remarkable AGN X-ray variabilities (Blanchard et al 2017;Chan et al 2019;Ricci et al 2020Ricci et al , 2021.…”

Section: Introductionmentioning

confidence: 99%

Discovery of late-time X-ray flare and anomalous emission line enhancement after the nuclear optical outburst in a narrow-line Seyfert 1 Galaxy

Zhang,

Shu,

Sheng

et al. 2022

Preprint

View full text Add to dashboard Cite

CSS J102913+404220 is an atypical narrow line Seyfert 1 galaxy with an energetic optical outburst occurred in coincidence with its nucleus. We present a detailed analysis of its multi-wavelength photometric and spectroscopic observations covering a period of decade since outburst. We detect mid-infrared (MIR) flares delayed by about two months relative to the optical outburst, with an extremely high peak luminosity of L 4.6µm > 10 44 erg s −1 . The MIR peak luminosity is at least an order of magnitude higher than any known supernovae explosions, suggesting the optical outburst might be due to a stellar tidal disruption event (TDE). We find late-time X-ray brightening by a factor of > ∼ 30 with respect to what is observed about 100 days after the optical outburst peak, followed by a flux fading by a factor of ∼4 within two weeks, making it one of Active Galactic Nuclei (AGNs) with extreme variability. Despite the dramatic X-ray variability, there are no coincident strong flux variations in optical, UV and MIR bands. This unusual variability behavior has been seen in other highly accreting AGNs and could be attributed to absorption variability. In this scenario, the decrease in the covering factor of absorber with accretion rate could cause the X-ray brightening, possibly induced by the TDE. Most strikingly, while the UV/optical continuum remains little changes with time, an evident enhancement in the flux of Hα broad emission line is observed, about a decade after the nuclear optical outburst, which is an anomalous behavior never seen in any other AGNs. Such an Hα anomaly could be explained by the replenishment of gas clouds and excitation within Broad Line Region (BLR) that originates, perhaps from the interaction of outflowing stellar debris with BLR. The results highlight the importance of late-time evolution of TDE that could affect the accreting properties of AGN, as suggested by recent simulations.

show abstract

The Curious Case of ASASSN-20hx: A Slowly-Evolving, UV and X-ray Luminous, Ambiguous Nuclear Transient

Cited by 4 publications

References 164 publications

Chandra, HST/STIS, NICER, Swift, and TESS Detail the Flare Evolution of the Repeating Nuclear Transient ASASSN-14ko

Chandra, HST/STIS, NICER, Swift, and TESS Detail the Flare Evolution of the Repeating Nuclear Transient ASASSN-14ko

Discovery of late-time X-ray flare and anomalous emission line enhancement after the nuclear optical outburst in a narrow-line Seyfert 1 Galaxy

Discovery of late-time X-ray flare and anomalous emission line enhancement after the nuclear optical outburst in a narrow-line Seyfert 1 Galaxy

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