Skip to main content
New Swift-BAT/GUANO and IceCube Notice Types Available! See news and announcements

GCN Circular 22180

GRB 171205A: VLT/X-shooter optical counterpart and spectroscopic observations
2017-12-05T11:01:51Z (6 years ago)
Jonatan Selsing at DARK/NBI <>
L. Izzo (HETH/IAA-CSIC), J. Selsing (DARK), J. Japelj (API, Univ. Amsterdam), B.
Milvang-Jensen, J. P. U. Fynbo (both DARK), D. Xu (NAOC), D. A. Kann
(HETH/IAA-CSIC), N. R. Tanvir, R. Starling (both U. Leicester), A. J. Levan, K.
Wiersema (both U. Warwick), G. Pugliese (API, Univ. Amsterdam), V. D'Elia
(ASI-SSDC), and S. Campana (INAF-Brera) report on behalf of the Stargate

We observed the optical afterglow of GRB 171205A (V. D'Elia et al. GCN #22177)
with the ESO VLT/X-shooter spectrograph, covering the wavelength range
3500-20000 AA. Spectroscopy started at 08:56:18 UT on 2017-12-05 (i.e., 1.5 hr
after the GRB) and consisted of 1 exposure of 600 s taken in twilight.

From the acquisition image prior to the spectroscopy, a new optical transient is
clearly detected in the outskirts of the putative host galaxy (L. Izzo et al.
GCN #22178) at the following coordinates:

RA(J2000) = 11h 09m 39.573s Dec.(J2000) = -12d 35' 17.37"

This source is inside the error box reported by (J.P. Osborne et al. GCN
#22179). From the acquisition image we measure this source to have m(r)~16.0
mag, calibrated with a nearby Pan-STARRS star.

The source continuum is well detected across the entire spectral coverage and
clear emission lines are superposed on it identified as Halpha, [N II] 6584, and
[S II] 6717/32 located at z = 0.0368, suggesting an association with the nearby
galaxy. Additionally, a tentative detection of absorption lines identified as
NaI 5891/5897 in the continuum further supports z = 0.0368 as the redshift of
the GRB.

We acknowledge the excellent support from the ESO staff, particularly Jose
Velasquez and Zahed Wahhaj in obtaining these observations.
Looking for U.S. government information and services? Visit