Volume 547, November 2012
|Number of page(s)||7|
|Published online||31 October 2012|
The optical SN 2012bz associated with the long GRB 120422A⋆
1 INAF – Brera Astronomical Observatory, via E. Bianchi 46, 23807 Merate (LC), Italy
2 Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
3 INAF – Trieste Astronomical Observatory, via G.B. Tiepolo 11, 34143 Trieste, Italy
4 INFN, Sezione di Pisa, Largo Pontecorvo 3, 56127 Pisa, Italy
5 Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
6 Departamento de Astrofisica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
7 ASI, Science Data Centre, via Galileo Galilei, 00044 Frascati, Italy
8 INAF – Roma Astronomical Observatory, via Frascati 33, 00040 Monteporzio Catone, Italy
9 INAF, IASF Bologna, via P. Gobetti 101, 40129 Bologna, Italy
10 Max Planck Institute for Astrophysics, Karl-Schwarzschild-Strasse 1, 85748 Garching, Germany
11 INAF – Padova Astronomical Observatory, vicolo dell’Osservatorio 5, 35122 Padova, Italy
12 INAF – Capodimonte Astronomical Observatory, Salita Moiariello 16, 80131 Napoli, Italy
13 ICRANET, Piazza della Republica 10, 65122 Pescara, Italy
14 Physics Department, University of Ferrara, via Saragat 1, Ferrara 44122, Italy
15 ARI, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead, CH41 1LD, UK
16 Departamento de Ciencias Fisicas, Universidad Andrés Bello, Av. República 252, Santiago, Chile
17 Instituto de Astrofísica de Andalucía, CSIC, Glorieta de la Astronomía s/n, 18. 008 Granada, Spain
18 National Astronomical Observatories, CAS – 100012 Beijing, PR China
19 Department of Astronomy, University of California, Berkeley, CA 94720-3411, USA
20 NASA Marshall Space Flight Center, Huntsville, Alabama 35805, USA
21 Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo, Kashiwa, 277-8583 Chiba, Japan
22 European Southern Observatory, Alonso de Cordova 3107, Santiago, Chile
23 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
24 INAF, IASF Milano, via E. Bassini 15, 20133 Milano, Italy
25 Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK
26 National Astronomical Observatory of Japan, Mitaka, 181-8588 Tokyo, Japan
27 GEPI, Observatoire de Paris, CNRS, Univ. Paris Diderot, 5 Pl. Jules Janssen, 92190 Meudon, France
Received: 20 June 2012
Accepted: 28 September 2012
Aims. The association of Type Ic supernovae (SNe) with long-duration gamma-ray bursts (GRBs) is well established. We endeavor, through accurate ground-based observational campaigns, to characterize these SNe at increasingly high redshifts.
Methods. We obtained a series of optical photometric and spectroscopic observations of the Type Ic SN 2012bz associated with the Swift long-duration GRB 120422A (redshift z = 0.283) using the 3.6-m TNG and the 8.2-m VLT telescopes during the time interval between 4 and 36 days after the burst.
Results. The peak times of the light curves of SN 2012bz in various optical filters differ, with the B-band and i’-band light curves reaching maximum at 9 ± 4 and 23 ± 3 rest-frame days, respectively. The bolometric light curve has been derived from individual bands photometric measurements, but no correction for the unknown contribution in the near-infrared (probably around 10–15%) has been applied. Therefore, the present light curve should be considered as a lower limit to the actual UV-optical-IR bolometric light curve. This pseudo-bolometric curve reaches its maximum (Mbol = −18.56 ± 0.06) at 13 ± 1 rest-frame days; it is similar in shape and luminosity to the bolometric light curves of the SNe associated with z < 0.2 GRBs and more luminous than those of SNe associated with X-ray flashes (XRFs). A comparison with the model generated for the bolometric light curve of SN 2003dh suggests that SN 2012bz produced only about 15% less 56Ni than SN 2003dh, about 0.35 M⊙. Similarly the VLT spectra of SN 2012bz, after correction for Galactic extinction and for the contribution of the host galaxy, suggest comparable explosion parameters with those observed in SN 2003dh (EK ~ 3.5 × 1052 erg, Mej ~ 7 M⊙) and a similar progenitor mass (~25–40 M⊙). GRB 120422A is consistent with the Epeak − Eiso and the EX,iso − Eγ,iso − Epeak relations. GRB 120422A / SN 2012bz shows the GRB-SN connection at the highest redshift so far accurately monitored both photometrically and spectroscopically.
Key words: gamma-ray burst: general / supernovae: individual: SN2012bz
Based on observations made with the Italian 3.6-m Telescopio Nazionale Galileo (TNG), operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Instituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias under program A25TAC_11, and with the ESO 8.2-m Very Large Telescope (VLT) at Paranal Observatory under program 089.D-0033(A).
© ESO, 2012
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