We present the X-ray monitoring campaign of AT2022tsd in the time range δtrest=23−116 d rest-frame since discovery. With an initial 0.3-10 keV X-ray luminosity of Lx≈1044 erg s−1 at δtrest≈ 23 d, AT2022tsd is the most luminous FBOT to date and rivals even the most luminous GRBs. We find no statistical evidence for spectral evolution. The average X-ray spectrum is well described by an absorbed simple power-law spectral model with best-fitting photon index Γ=1.89−0.08+0.09 and marginal evidence at the 3σ confidence level for intrinsic absorption NHint≈4×1019 cm−2. The X-ray light-curve behavior can be either interpreted as a power-law decay Lx∝tα with α≈−2 and superimposed X-ray variability, or as a broken power-law with a steeper post-break decay as observed in other FBOTs such as AT2018cow. We briefly compare these results to accretion models of TDEs and GRB afterglow models.
@article{arxiv.2306.01114,
title = {Unprecedented X-ray Emission from the Fast Blue Optical Transient AT2022tsd},
author = {D. J. Matthews and R. Margutti and B. D. Metzger and D. Milisavljevic and G. Migliori and T. Laskar and D. Brethauer and E. Berger and R. Chornock and M. Drout and E. Ramirez-Ruiz},
journal= {arXiv preprint arXiv:2306.01114},
year = {2023}
}