Oral Abstract

Oral Contribution (O0.8) Deepak Eappachen (SRON/ Radboud University)

The origin of fast X-ray transients

Fast X-ray Transients (FXRTs) are as-yet unexplained phenomena. They are energetic X-ray flares that last a few tens to a few thousand seconds. Over the past few years, ~30 extragalactic FXRTs have been discovered in Chandra, XMM-Newton, Swift/XRT and eROSITA data. Numerous proposed explanations include a tidal disruption of a white dwarf by an intermediate-mass black hole, a supernova shock breakout, and a binary neutron star merger. So far, FXRTs lack multi-wavelength counterparts, and hence we rely on the host properties to understand their nature. The X-ray properties and host or hostless associations of the FXRTs imply that probably there are at least two origins of these FXRTs. We present the new population of FXRTs serendipitously discovered from Chandra archival data and deep optical search for the host, mainly for two FXRTs. Also, we investigate the host properties and nature of the recently reported FXRTs from XMM-Newton data classified as supernova shock breakouts.