SN 2013dx associated with GRB 130702A: a detailed photometric and spectroscopic monitoring and a study of the environment

Abstract

<BR /> Aims: Long-duration gamma-ray bursts (GRBs) and broad-line, type Ic supernovae (SNe) are strongly connected. We aim at characterizing SN 2013dx, which is associated with GRB 130702A, through a sensitive and extensive ground-based observational campaign in the optical-IR band. <BR /> Methods: We monitored the field of the Swift GRB 130702A (redshift z = 0.145) using the 8.2 m VLT, the 3.6 m TNG and the 0.6 m REM telescopes during the time interval between 4 and 40 days after the burst. Photometric and spectroscopic observations revealed the associated type Ic SN 2013dx. Our multiband photometry allowed constructing a bolometric light curve. <BR /> Results: The bolometric light curve of SN 2013dx resembles that of 2003dh (associated with GRB 030329), but is ~10% faster and ~25% dimmer. From this we infer a synthesized <SUP>56</SUP>Ni mass of ~0.2 M<SUB>☉</SUB>. The multi-epoch optical spectroscopy shows that the SN 2013dx behavior is best matched by SN 1998bw, among the other well-known low-redshift SNe associated with GRBs and XRFs, and by SN 2010ah, an energetic type Ic SN not associated with any GRB. The photospheric velocity of the ejected material declines from ~2.7 × 10<SUP>4</SUP> km s<SUP>-1</SUP> at 8 rest frame days from the explosion, to ~3.5 × 10<SUP>3</SUP> km s<SUP>-1</SUP> at 40 days. These values are extremely close to those of SN1998bw and 2010ah. We deduce for SN 2013dx a kinetic energy of ~35 × 10<SUP>51</SUP> erg and an ejected mass of ~7 M<SUB>☉</SUB>. This suggests that the progenitor of SN2013dx had a mass of ~25-30 M<SUB>☉</SUB>, which is 15-20% less massive than that of SN 1998bw. Finally, we studied the SN 2013dx environment through spectroscopy of the closeby galaxies: 9 out of the 14 inspected galaxies lie within 0.03 in redshift from z = 0.145, indicating that the host of GRB 130702A/SN 2013dx belongs to a group of galaxies, an unprecedented finding for a GRB-associated SN and, to our knowledge, for long GRBs in general. <P />Based on observations collected at the Italian 3.6-m Telescopio Nazionale Galileo (TNG), operated on the island of La Palma by the Fundacion Galileo Galilei of the INAF (Instituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias under program A27TAC 5, and at the European Southern Observatory, ESO, the VLT/Antu telescope, Paranal, Chile, proposal code: 291.D-5032(A).Appendix A is available in electronic form at <A href="http://www.aanda.org/10.1051/0004-6361/201425381/olm">http://www.aanda.org