Program: GS-2023A-DD-105

Title:The near-IR counterpart to GRB 230307A
PI:Andrew Levan
Co-I(s): Wen-fai Fong, Jillian Rastinejad, Ben Gompertz, Daniele Malesani, Nial Tanvir

Abstract

We request a single IR observation of the afterglow of GRB 230307A. This is the second brightest GRB ever observed, but appears to have a faint afterglow and no obvious host galaxy. It is possible either that it lies at an unusually high redshift for such a bright burst, or that it has been kicked from a nearby galaxy. In the first case it would be the most intrinsically energetic burst of all time, in the second a rare example of a long-GRB created from a merging compact object. A single K-band observaiton has a strong capability to distinguish between the possibilities as a merger should appear very red at epochs of ~10 days compared to a long GRB from a collapsar. There is currently no other sensitive IR available in the southern hemisphere.