GCN Circular 35877
Subject
GRB 240218A: Chandra Detection and Jet Break Confirmation
Event
Date
2024-03-05T21:39:51Z (3 years ago)
From
corinna.pena@utah.edu
Via
Web form
C. Peña, T. Laskar (Utah), G. Schroeder (Northwestern), and K. D. Alexander (Arizona) report:
We observed GRB 240218A (Page et al., GCN 35742; Veres et al., GCN 35755; Svinkin et al., GCN 35758) with Chandra/ACIS-S beginning on 2024 Mar 4 at 23:02:14 UT (16 days post-burst) for a total exposure of 20ks. In preliminary analysis, we detect a point source with a count rate of 5.5e-4 counts/s (0.3-8 keV; observer frame) at a position consistent with the VLA and XRT position (Schroeder et al., GCN 35794; Evans et al. GCN 35748). Using spectral parameters from the Swift/XRT PC-mode spectrum at a redshift z=6.782 (Saccardi et al., GCN 35756), we find a preliminary unabsorbed flux of ~ 1.2e-14 erg/(s cm^2) in the 0.3-8 keV band (observer frame).
This measurement confirms a potential break in the Swift/XRT observations at ~ 0.8 days after the trigger. The post-break decay rate of ~ -1.9 is consistent with a jet break. Further analysis is underway.
We thank Pat Slane, Douglas Swartz, and James Steiner for approving our DDT request. We thank Jen Lauer along with the rest of the CXC staff for arranging and executing the observations.