GRB 140606B/iPTF14bfu: detection of shock-breakout emission from a cosmological γ-ray burst?
We present optical and near-infrared photometry of GRB 140606B (z = 0.384), and optical photometry and spectroscopy of its associated supernova (SN). The results of our modelling indicate that the bolometric properties of the SN (M_(Ni) = 0.4 ± 0.2 M_⊙, M_(ej) = 5 ± 2 M_⊙, and E_K = 2 ± 1 × 10^(52) erg) are fully consistent with the statistical averages determined for other γ-ray burst (GRB)-SNe. However, in terms of its γ-ray emission, GRB 140606B is an outlier of the Amati relation, and occupies the same region as low luminosity (ll) and short GRBs. The γ-ray emission in llGRBs is thought to arise in some or all events from a shock breakout (SBO), rather than from a jet. The measured peak photon energy (E_p ≈ 800 keV) is close to that expected for γ-rays created by an SBO (≳ 1 MeV). Moreover, based on its position in the M_(V, p)-L_(iso, γ) plane and the E_K–Γβ plane, GRB 140606B has properties similar to both SBO-GRBs and jetted-GRBs. Additionally, we searched for correlations between the isotropic γ-ray emission and the bolometric properties of a sample of GRB-SNe, finding that no statistically significant correlation is present. The average kinetic energy of the sample is E¯_K = 2.1×10^(52) erg. All of the GRB-SNe in our sample, with the exception of SN 2006aj, are within this range, which has implications for the total energy budget available to power both the relativistic and non-relativistic components in a GRB-SN event.
© 2015 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2015 June 10. Received 2015 June 10. In original form 2015 May 13. First published online July 23, 2015. We thank Giorgos Leloudas for his expertise in analysing the optical spectra of the SN. We also thank Y. Cao for carrying out the Keck observations. ZC is funded by a Project Grant from the Icelandic Research Fund. PJ and MF acknowledge support by the University of Iceland Research fund. JPUF acknowledges support from the ERC-StG grant EGGS-278202. DM acknowledges the Instrument center for Danish Astrophysics (IDA) for support. The Dark Cosmology Centre is funded by the DNRF. SS acknowledges support from CONICYT-Chile FONDECYT 3140534, Basal-CATA PFB-06/2007, and Project IC120009 'Millennium Institute of Astrophysics' (MAS) of Iniciativa Científica Milenio del Ministerio de Economía, Fomento y Turismo.
Submitted - 1505.03522v2.pdf
Published - 1535.full.pdf