[vsnet-grb-info 27705] GRB 210411C: ePESSTO+ NTT optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  29808
SUBJECT: GRB 210411C: ePESSTO+ NTT optical observations
DATE:    21/04/12 20:22:21 GMT
FROM:    Daniele B Malesani at DTU Space  <malesani at space.dtu.dk>

P. Pessi (ESO), G. Csoernyei, A. Holas, S. Taubenberger, C. Vogl (MPA 
Garching), A. Floers (GSI), G. Pignata (UNAB), J. Teffs (Liverpool), M. 
Dennefeld (IAP), D. B. Malesani (DTU Space), P. D'Avanzo (INAF/Brera), 
J. Anderson (ESO), T. Müller Bravo (Southampton), T.-W. Chen 
(Stockholm), M. Gromadzki (Warsaw), C. Inserra (Cardiff), E. Kankare 
(Turku), M. Nicholl (Birmingham), O. Yaron (Weizmann), D. Young (QUB), 
E. Zimmerman (Weizmann) report:

We observed the optical afterglow of GRB 210411C (Sbarrato et al., GCN 
29794; Strausbaugh & Cucchiara, GCN 29802; de Ugarte Postigo et al., GCN 
29806) under the the advanced Public ESO Spectroscopic Survey for 
Transient Objects (ePESSTO+; see Smartt et al. 2015, A&A, 579, 40 and 
http://www.pessto.org ). The observations were performed on the ESO New 
Technology Telescope (NTT) at La Silla with the EFOSC2 instrument. A 
single 5-min exposure was acquired in the Gunn r filter, with mean epoch 
2021 Apr 12.234 UT (14.55 hr after the GRB).

The optical afterglow is well detected and we report the following 
coordinates (calibrated against the Gaia catalog):

RA = 19:46:26.83
Dec = -39:23:52.7

For the afterglow, we measure a magnitude R = 21.28 +- 0.04 (Vega), 
assuming R = 17.31 for the USNO star at RA = 19:46:25.68, Dec = 
-39:23:48.9 . An extra uncertainty of ~0.3 mag should be added to 
account for the photometric calibration error of the USNO catalog.