[vsnet-grb-info 5276] GRB 071021: optical and NIR observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6968
SUBJECT: GRB 071021: optical and NIR observations
DATE:    07/10/22 00:31:34 GMT
FROM:    Alberto Castro-Tirado at Inst.de Astro. de Andalucia  <ajct at iaa.es>

A. J. Castro-Tirado (IAA-CSIC Granada), A. de Ugarte Postigo (ESO
Santiago), M. Jelínek, J. Gorosabel, A. Marín Fernández de Capel
(IAA-CSIC), C. Abia (Universidad de Granada), D. Pérez-Ramírez (Univ. de
Jaén & U Leceister), D. Malesani (DARK/NBI), S. Guziy (Univ. of
Nikolaev) and R. Oreiro (IAC), on behalf of a larger collaboration,
report:

"Following the detection of GRB 071021 by SWIFT (Barthelmy et al. GCNC
6958) we have obtained JHK-band observations (300s each) with the 3.5m
Telescopio Nazionale Galileo at Observatorio del Roque de los Muchachos
in La Palma and optical observations with the 2.5m Nordic Optical
Telescope (1200s, R-band)
and with the 1.5m telescope (3960s, I-band) at Observatorio de Sierra
Nevada.
The NIR frames were obtained  starting on 21.872 Oct (i.e. 11.25 hr after
the BAT trigger).

Within the XRT error box (Page et al. GCNC 6963) there seems to be an
indication of a faint source at RA(J2000) = 10:58:11.3  Dec(J2000)=
+53:50:56 (+/- 1"). The object seems to be barely detected in the -H
and -K bands, but not in J,  indicating a highly obscured object or a
very high-z (~10) event, supporting in the latter case the SWIFT high-z
indications (Sakamoto et al. GCNC 6967).

A finding chart is available at:

http://www.iaa.es/~deugarte/GRBs/071021/GRB071021_JHK.jpg

Further analysis is ongoing.

Additional NIR observations are needed to confirm the reality of this
source and whether this is the NIR afterglow to  GRB 071021."