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arXiv · 2206.04071

TESS Shines Light on the Origin of the Ambiguous Nuclear Transient ASASSN-18el

Jason T. Hinkle·Christopher S. Kochanek·Benjamin J. Shappee·Patrick J. Vallely·Katie Auchettl·Michael Fausnaugh·Thomas W. -S. Holoien·Helena P. Treiber·Anna V. Payne·B. Scott Gaudi·Keivan G. Stassun·Todd A. Thompson·John L. Tonry·Steven Villanueva Jr
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Abstract

We analyze high-cadence data from the Transiting Exoplanet Survey Satellite (TESS) of the ambiguous nuclear transient (ANT) ASASSN-18el. The optical changing-look phenomenon in ASASSN-18el has been argued to be due to either a drastic change in the accretion rate of the existing active galactic nucleus (AGN) or the result of a tidal disruption event (TDE). Throughout the TESS observations, short-timescale stochastic variability is seen, consistent with an AGN. We are able to fit the TESS light curve with a damped-random-walk (DRW) model and recover a rest-frame variability amplitude of $\hatσ = 0.93 \pm 0.02$ mJy and a rest-frame timescale of $τ_{DRW} = 20^{+15}_{-6}$ days. We find that the estimated $τ_{DRW}$ for ASASSN-18el is broadly consistent with an apparent relationship between the DRW timescale and central supermassive black hole mass. The large-amplitude stochastic variability of ASASSN-18el, particularly during late stages of the flare, suggests that the origin of this ANT is likely due to extreme AGN activity rather than a TDE.

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Jason T. Hinkle, Christopher S. Kochanek, Benjamin J. Shappee, Patrick J. Vallely, Katie Auchettl, Michael Fausnaugh, Thomas W. -S. Holoien, Helena P. Treiber, Anna V. Payne, B. Scott Gaudi, Keivan G. Stassun, Todd A. Thompson, John L. Tonry, Steven Villanueva Jr. 2024-08-26. TESS Shines Light on the Origin of the Ambiguous Nuclear Transient ASASSN-18el. https://doi.org/10.1093/mnras%2Fstad746

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