GCN Circular 32742
Subject
MAXI GRB 221006A: Redshifts of the possible host galaxies
Date
2022-10-13T19:01:48Z (2 years ago)
From
C. C. Thoene at HETH/IAA-CSIC <christina.thoene@gmail.com>
P. A. C. Cunha (Univ. do Porto/CAUP), G. Ma (DAWN/NBI), R. O���Rourke Brogan
(AIP), C. C. Thoene (ASU-CAS), A. de Ugarte Postigo (OCA, Nice), D. A. Kann
(Goethe Univ.), J. F. Agui Fernandez (IAA-CSIC), L. Izzo (DARK/NBI), J.P.U.
Fynbo (DAWN/NBI), N. R. Tanvir (Univ. Leicester), M. Blazek (Prague) and D.
Garcia Alvarez (GTC) report:
We observed the possible host galaxies of the MAXI GRB (GCN 32626, Mikhara
et al) underlying the candidate afterglow at RA 22:28:58.99, DEC
+15:42:49.6 (GCN 32628, Sbarufatti et al., confirmed to be fading in GCN
32731, Sbarufatti et al.), which we already reported in GCN 32710,
(O���Rourke Brogan et al.). Observations were obtained with OSIRIS at the
10.4m GTC telescope in La Palma starting on Oct. 10, 2022 at 20:10 UT with
a total exposure time of 3x600s using the R1000R grism (5100-10100��) and a
1 arcsec slit aligned across both putative hosts.
We clearly detect the traces of both galaxies in the combined spectrum and
determine redshifts of z=0.731 for G1 and z=0.464 for G2 based on emission
lines of [OII], [OIII] Hb and Ha. Based on the distance from the X-ray
afterglow candidate we determined G1 to be the likely host of GRB 221006A
(GCN 32710, O���Rourke Brogan et al.) and hence assume a redshift of z=0.731
for its possible host galaxy.
We acknowledge two very enjoyable weeks at the NEON observing school during
which these follow-up observations were obtained.