A tidal disruption-like X-ray flare from the quiescent galaxy SDSS J120136.02+300305.5

TL;DR

This paper reports the detection and analysis of a tidal disruption-like X-ray flare from a quiescent galaxy, showing flux evolution consistent with stellar debris fallback, but with spectral and optical features that challenge standard models.

Contribution

It provides detailed temporal and spectral analysis of a tidal disruption event candidate in a quiescent galaxy, highlighting unusual spectral softness and lack of jet activity.

Findings

X-ray flux increased 56-fold over previous upper limits

Flux decayed following a t^-5/3 trend over 300 days

No evidence of jet formation from radio non-detection

Abstract

SDSS J120136.02+300305.5 was detected in an XMM-Newton slew from June 2010 with a flux 56 times higher than an upper limit from ROSAT, corresponding to Lx~3x10^44 ergs/s. It has the optical spectrum of a quiescent galaxy (z=0.146). Overall the X-ray flux has evolved consistently with the canonical t^-5/3 model, expected for returning stellar debris from a tidal disruption event, fading by a factor ~300 over 300 days. In detail the source is very variable and became invisible to Swift between 27 and 48 days after discovery, perhaps due to self-absorption. The X-ray spectrum is soft but is not the expected tail of optically thick thermal emission. It may be fit with a Bremsstrahlung or double-power-law model and is seen to soften with time and declining flux. Optical spectra taken 12 days and 11 months after discovery indicate a deficit of material in the broad line and coronal line regions of this galaxy, while a deep radio non-detection implies that a jet was not launched during this event.