GRB060614: a "fake" short GRB from a merging binary system

Abstract

(Shortened) CONTEXT: [...] GRB060614 is the first nearby long duration GRB clearly not associated to a bright Ib/c supernova. Moreover, its duration (T_{90} ~ 100s) makes it hardly classifiable as a short GRB. It presents strong similarities with GRB970228, the prototype of the new class of "fake" short GRBs that appear to originate from the coalescence of binary neutron stars or white dwarfs spiraled out into the galactic halo. AIMS: Within the "canonical" GRB scenario based on the "fireshell" model, we test if GRB060614 can be a "fake" or "disguised" short GRB. [...] METHODS: We fit GRB060614 light curves in Swift's BAT (15-150keV) and XRT (0.2-10keV) energy bands. Within the fireshell model, light curves are formed by two well defined and different components: the Proper-GRB (P-GRB), emitted at the fireshell transparency, and the extended afterglow, due to the interaction between the leftover accelerated baryonic and leptonic shell and the CBM. RESULTS: We determine the two free parameters describing the GRB source within the fireshell model. [...] A small average CBM density [...] is inferred, typical of galactic halos. The first spikelike emission is identified with the P-GRB and the following prolonged emission with the extended afterglow peak.[...] CONCLUSIONS: The anomalous GRB060614 finds a natural interpretation within our canonical GRB scenario: it is a "disguised" short GRB. [...] This result points to an old binary system, likely formed by a white dwarf and a neutron star, as the progenitor of GRB060614 and well justify the absence of an associated SN Ib/c. Particularly important for further studies of the final merging process are the temporal structures in the P-GRB down to 0.1s.

7 pages, 5 figures, to appear on Astronomy & Astrophysics. This new version fixes a typo in one label of Fig. 3

References in corpus (17)

• The Supernova -- Gamma-Ray Burst Connection
• An optical supernova associated with the X-ray flash XRF 060218
• No supernovae associated with two long-duration gamma ray bursts
• An enigmatic long-lasting gamma-ray burst not accompanied by a bright supernova
• The Galaxy Population Hosting Gamma-Ray Bursts
• Making a Short Gamma-Ray Burst from a Long one: Implications for the Nature of GRB 060614
• SN 2006aj and the nature of low-luminosity gamma-ray bursts
• The Host Galaxies of Short-Duration Gamma-Ray Bursts: Luminosities, Metallicities, and Star Formation Rates
• Swift observations of GRB 060614: an anomalous burst with a well behaved afterglow
• On the consistency of the peculiar GRBs 060218 and 060614 with the Ep,i - Eiso correlation
• A general scheme for modeling gamma-ray burst prompt emission
• SN 2006aj Associated with XRF 060218 At Late Phases: Nucleosynthesis-Signature of A Neutron Star-Driven Explosion
• Thermalization of a nonequilibrium electron-positron-photon plasma
• The Amati relation in the "fireshell" model
• The "fireshell" model and the "canonical" GRB scenario
• Short and canonical GRBs
• Progenitors of Long Gamma-ray Bursts

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