[vsnet-grb-info 19456] GRB 170531A: ePESSTO NTT observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21176
SUBJECT: GRB 170531A: ePESSTO NTT observations
DATE:    17/06/01 01:29:05 GMT
FROM:    Paolo D'Avanzo at INAF-OAB  <paolo.davanzo at brera.inaf.it>

G. Pignata (Univ. Andres Bello), L. Wang (CASSACA), P. D'Avanzo (INAF-OAB), D. Malesani (Dark/NBI), L. Izzo (IAA-CSIC), S. Campana (INAF OAB), J. Anderson (ESO), R. Cartier (Southampton), L. Galbany (Univ. de Chile), C. Inserra (QUB), E. Kankare (QUB), K. Maguire (ESO), S. Smartt (QUB), K. W. Smith (QUB), M. Sullivan (Southampton), S. Valenti (UC Davis), O. Yaron (Weizmann), D. Young (QUB), I. Manulis (Weizmann)

We observed GRB 170531A (Evans et al., GCN 21170) under the extended Public ESO Spectroscopic Survey for Transient Objects (ePESSTO; see Smartt et al. 2015, A&A, 579, 40 http://www.pessto.org ). The observations were performed on the ESO New Technology Telescope at La Silla with the EFOSC2 instrument in imaging mode starting from 2017-05-31 at 23:12:07 UT (i.e. 3.1 hours from the burst).

We obtained two consecutive images each one lasting 150s with the r filter. No optical afterglow is detected in the coadded image within the XRT error circle (http://www.swift.ac.uk/xrt_positions/) down to a limiting magnitude of r > 23 (AB; 3sigma c.l.). The photometric calibration was carried out assuming r=17.07 (AB) for the star at RA(J2000), Dec(J2000) = 08:05:00.30, -14:01:21.3, as reported in the PANSTARRS catalogue.