GCN Circular 31851
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.