Comprehensive X-ray Observations of the Exceptional Ultra-long X-ray and Gamma-ray Transient GRB 250702B with Swift, NuSTAR, and Chandra: Insights from the X-ray Afterglow Properties
Brendan O’Connor, Ramandeep Gill, James DeLaunay, Jeremy Hare, Dheeraj Pasham, Eric R. Coughlin, Ananya Bandopadhyay, Akash Anumarlapudi, Paz Beniamini, Jonathan Granot, Igor Andreoni, Jonathan Carney, Michael J. Moss, Ersin G"ou{g}"uc{s}, Jamie A. Kennea, Malte Busmann, Simone Dichiara, James Freeburn, Daniel Gruen, Xander J. Hall, Antonella Palmese, Tyler Parsotan, Samuele Ronchini, Aaron Tohuvavohu, Maia A. Williams
arXiv:2509.22787v1 Announce Type: new
Abstract: GRB 250702B is an exceptional transient that produced multiple episodes of luminous gamma-ray radiation lasting for $>25$ ks, placing it among the class of ultra-long gamma-ray bursts (GRBs). However, unlike any known GRB, a soft X-ray precursor was discovered by the Einstein Probe up to 24 hours before the gamma-ray triggers. We present comprehensive X-ray observations of the transient’s afterglow obtained with the Neil Gehrels Swift Observatory, the Nuclear Spectroscopic Telescope Array, and the Chandra X-ray Observatory between 0.5 to 65 days (observer frame) after the initial high-energy trigger. The X-ray emission decays steeply as $sim t^{-1.9}$, and shows short timescale X-ray variability ($Delta T/T arXiv:2509.22787v1 Announce Type: new
Abstract: GRB 250702B is an exceptional transient that produced multiple episodes of luminous gamma-ray radiation lasting for $>25$ ks, placing it among the class of ultra-long gamma-ray bursts (GRBs). However, unlike any known GRB, a soft X-ray precursor was discovered by the Einstein Probe up to 24 hours before the gamma-ray triggers. We present comprehensive X-ray observations of the transient’s afterglow obtained with the Neil Gehrels Swift Observatory, the Nuclear Spectroscopic Telescope Array, and the Chandra X-ray Observatory between 0.5 to 65 days (observer frame) after the initial high-energy trigger. The X-ray emission decays steeply as $sim t^{-1.9}$, and shows short timescale X-ray variability ($Delta T/T