GCN Circular 14552
Subject
GRB 130502B: possible TNG counterpart
Date
2013-05-04T09:19:10Z (11 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@dark-cosmology.dk>
D. Malesani (DARK/NBI), P. D'Avanzo (INAF/OABr), S. Covino (INAF/OABr),
A. Melandri (INAF/OABr), V. D'Elia (INAF/OAR and ASI/ASDC), S. Campana
(INAF/OABr), D. Fugazza (INAF/OABr), G. Tagliaferri (INAF/OABr), B. Blu,
L. Di Fabrizio (INAF/FGG), C. P. Padilla-Torres (INAF/FGG), report on
behalf of the CIBO collaboration:
We observed the field of the LAT-detected GRB 130502B (Von Kienlin &
Younes, GCN 14530; Kocevski et al., GCN 14532; Golenetskii et al., GCN
14542) with the TNG equipped with the DOLoRes imager. Observations were
carried out starting on 2013 May 3.872 UT (1.54 days after the trigger),
for a total of 30 min on source in the R band, at a high airmass of
around 2.2. The seeing was 1.2".
No bright object is detected inside the X-ray error circle (Melandri &
Immler, GCN 14540; see also http://www.swift.ac.uk/xrt_positions/), down
to a 3-sigma limit of R = 23.7 (calibration based on several nearby USNO
stars). However, a faint flux enhancement is seen consistent with the
XRT position, at coordinates (J2000):
RA = 04:27:02.82
Dec = +71:03:38.5
A finding chart is shown at
http://www.astro.ku.dk/~malesani/GRB/130502B/GRB130502B_finder.jpg
We estimate the magnitude of this marginally detected source to be R =
24.7 +- 0.5. At the moment, we have no information about its
variability, and it could be either the GRB counterpart or its host galaxy.
Last, independently of the reality of the object, this GRB can be
classified as dark. Considering the limit R > 23.7, and a Galactic
extinction A_V = 0.57 (Schlafly & Finkbeiner 2011, ApJ, 737, 103), the
optical-to-X-ray spectral index is beta_OX < 0.47 (if the object is
real, then beta_OX = 0.34 +- 0.07). The presence of significant excess
column density in the X-ray spectrum (Melandri & Immler, GCN 14540; see
also http://www.swift.ac.uk/xrt_spectra/00020266/) suggests an
extinguished event.
[GCN OPS NOTE(04may13): Per author's request, the URL in the last paragraph
was change from the team-internal version to the public version.]
