GCN Circular 31851
Subject
Chandra upper limit at the location of GRB 220408A
Date
2022-04-08T10:23:23Z (2 years ago)
From
Sergio Campana at INAF-OAB <sergio.campana@brera.inaf.it>
S. Campana (INAF - Osservatorio astronomico di Brera) reports
that Chandra serendipitously observed the location of GRB 220408A
(Caputo et al. 2022, GCN 31848; Fermi team 2022, GCN 31847).
The UVOT position (Caputo et al. 2022) falls at the edge of the S4 chip
of ACIS-S. The obsid 23474 observation lasted 36.6 ks and was taken on
Dec 21, 2020.
No source is visible at this position.
We run srcflux (under CIAO 4.13 and CALDB 4.9.7) and derive a 3-sigma
upper limit of 0.000206 c/s (2.38E-05,0.000432) on the 0.5-7 keV count
rate. Assuming a power law photon index of 2 and a column density of
2x10^20 cm^-2, we derive an upper limit on the 0.5-7 keV unabsorbed flux
of 2.1e-14 erg/cm2/s.
If the GRB were at the M51 distance (8.58 Mpc), this translates into an
upper limit on the 0.5-7 keV luminosity of 1.8e38 erg/s.