GCN Circular 23181
Subject
GRB 180728A: classification of the associated SN 2018fip
Date
2018-08-27T23:18:21Z (6 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@dark-cosmology.dk>
J. Selsing (DAWN/NBI), L. Izzo (HETH/IAA-CSIC), A. Rossi (INAF/OAS),
D. B. Malesani (DAWN/NBI and DARK/NBI), K. E. Heintz (Univ. Iceland and
DAWN/NBI), A. de Ugarte Postigo (HETH/IAA-CSIC), P. Schady (Univ. Bath),
R. L. C. Starling (Univ. Leicester), J. Sollerman (OKC Stockholm),
G. Leloudas (DTU space), Z. Cano (BCA), J. P. U. Fynbo (DAWN/NBI),
M. Della Valle (INAF-Naples), E. Pian (INAF/OAS), D. A. Kann (HETH/IAA-CSIC),
D. A. Perley (LJMU), E. Palazzi (INAF/OAS), S. Klose (TLS Tautenburg),
J. Hjorth (DARK/NBI), S. Covino (INAF-OAB), V. D'Elia (SSDC),
N. R. Tanvir (Univ. Leicester), A. J. Levan (Univ. Warwick),
D. Hartmann (Clemson U.), and C. Kouveliotou (GWU)
report on behalf of a larger collaboration:
We observed again the SN associated with GRB 180728A (Starling et al.,
GCN 23046; Izzo et al., GCN 23142) with the ESO VLT UT2 equipped with
X-shooter. Observations had a mean epoch of 2018 August 21.078 UT (23.3
days after the GRB) and spanned the wavelength range 3200-20,900 AA.
The features previously observed in our spectroscopic sequence (Izzo et
al., GCN 23142) have evolved and become more prominent. Using the
Superfit tool (Howell et al. 2005, ApJ, 634, 1190;
http://www.dahowell.com/superfit.html) we find a convincing match with
the type-Ic SN 2002ap at a phase of 8 days after maximum. The timing is
consistent with the epoch of our observation (21 days after the GRB
after correcting for cosmic time dilation). We thus conclusively
classify the SN as a broad-lined type-Ic SN. We note however that the
velocity measured at this epoch (~10,000 km/s) is at the low end of what
measured for GRB-associated SNe (e.g. Modjaz et al. 2016, 832, 108).
The SN associated to GRB 180728A has been dubbed SN 2018fip via the
Transient Name Server: https://wis-tns.weizmann.ac.il/object/2018fip
[GCN OPS NOTE(28aug18): Per author's request, AdUP was added to the
author list.]