Kavli Affiliate: Dheeraj Pasham
| First 5 Authors: Jonathan Carney, Jonathan Carney, , ,
| Summary:
GRB 250702B was the longest gamma-ray burst ever observed, with a duration
that challenges standard collapsar models and suggests an exotic progenitor. We
collected a rich set of optical and infrared follow-up observations of its
rapidly fading afterglow using a suite of telescopes including the W. M. Keck
Observatory, the Gemini telescopes, the Magellan Baade Telescope, the Victor M.
Blanco 4-meter telescope, and the Fraunhofer Telescope at Wendelstein
Observatory. Our analysis reveals that the afterglow emission is well described
by forward shock emission from a highly obscured relativistic jet. Deep
photometric observations of the host galaxy reveal a massive 10^10.66 solar
masses, dusty, and extremely asymmetric system that is consistent with two
galaxies undergoing a major merger. The galactocentric offset, host galaxy
properties, and jet characteristics do not definitively distinguish between
competing progenitor scenarios. We find that the afterglow and host are
consistent with a range of progenitors including a collapsar, a merger between
a helium star and a stellar mass black hole, the disruption of a star by a
stellar mass compact object, and the tidal disruption of a star by an
off-nuclear intermediate mass black hole.
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