Diversity of gamma-ray burst energetics vs. supernova homogeneity: SN 2013cq associated with GRB 130427A^⋆,⋆⋆

¹ INAF – Osservatorio Astronomico di Brera, via E. Bianchi 46, 23807 Merate, Italy
e-mail: andrea.melandri@brera.inaf.it
² Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
³ INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica, via P. Gobetti 101, 40129 Bologna, Italy
⁴ INFN, Sezione di Pisa, Largo Pontecorvo 3, 56127 Pisa, Italy
⁵ ASI, Science Data Centre, via del Politecnico snc, 00133 Roma, Italy
⁶ INAF – Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monte Porzio Catone, Italy
⁷ INAF – Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, 80131 Napoli, Italy
⁸ ICRANET, Piazza della Repubblica 10, 65122 Pescara, Italy
⁹ ARI, Liverpool John Moores University, IC2 Liverpool Science Park 146 Brownlow Hill, Liverpool L3 5RF, UK
¹⁰ INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
¹¹ Max-Planck Institute for Astrophysics, Garching, Karl-Schwarzschild-Str. 1, Postfach 1317, 85741 Garching, Germany
¹² Centre of Astrophysics and Cosmology, Science Institute, University of Iceland, Dunhagi 5, 107 Reykjavik, Iceland
¹³ Department of Physics, University of Warwick, Coventry CV4 7AL, UK
¹⁴ European Southern Observatory, Karl-Schwarzschildstrasse 2, 85748 Garching bei München, Germany
¹⁵ Departamento de Ciencias Fisicas, Universidad Andres Bello, Avda. Republica 252, 837025 Santiago, Chile
¹⁶ Instituto de Astrofísica de Andalucía, Glorieta de la Astronomía s/n, 18008 Granada, Spain
¹⁷ University of California, Berkeley, Space Sciences Laboratory, 7 Gauss Way, Berkeley CA 94720-7450, USA
¹⁸ Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
¹⁹ Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
²⁰ INAF – Istituto di Astrofisica Spaziale e Fisica Cosmica Milano, via E. Bassini 15, 20133 Milano, Italy
²¹ Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK
²² National Astronomical Observatory of Japan, Mitaka, 181-8588 Tokyo, Japan
²³ GEPI, Observatoire de Paris, CNRS, Univ. Paris Diderot, 5 place Jules Janssen, 92195 Meudon, France

Received: 4 February 2014
Accepted: 23 April 2014

Abstract

Aims. Long-duration gamma-ray bursts (GRBs) have been found to be associated with broad-lined type-Ic supernovae (SNe), but only a handful of cases have been studied in detail. Prompted by the discovery of the exceptionally bright, nearby GRB 130427A (redshift z = 0.3399), we aim at characterising the properties of its associated SN 2013cq. This is the first opportunity to test the progenitors of high-luminosity GRBs directly.

Methods. We monitored the field of the Swift long-duration GRB 130427A using the 3.6 m TNG and the 8.2 m VLT during the time interval between 3.6 and 51.6 days after the burst. Photometric and spectroscopic observations revealed the presence of the type Ic SN 2013cq.

Results. Spectroscopic analysis suggests that SN 2013cq resembles two previous GRB-SNe, SN 1998bw and SN 2010bh, associated with GRB 980425 and X-ray flash (XRF) 100316D, respectively. The bolometric light curve of SN 2013cq, which is significantly affected by the host galaxy contribution, is systematically more luminous than that of SN 2010bh (~2 mag at peak), but is consistent with SN 1998bw. The comparison with the light curve model of another GRB-connected SN 2003dh indicates that SN 2013cq is consistent with the model when brightened by 20%. This suggests a synthesised radioactive ⁵⁶Ni mass of ~0.4M_⊙. GRB 130427A/SN 2013cq is the first case of low-z GRB-SN connection where the GRB energetics are extreme (E_γ,iso ~ 10⁵⁴ erg). We show that the maximum luminosities attained by SNe associated with GRBs span a very narrow range, but those associated with XRFs are significantly less luminous. On the other hand the isotropic energies of the accompanying GRBs span 6 orders of magnitude (10⁴⁸ erg <E_γ,iso< 10⁵⁴ erg), although this range is reduced when corrected for jet collimation. The GRB total radiated energy is in fact a small fraction of the SN energy budget.