Cooling of young neutron stars in GRB associated to supernovae

et al. 2013

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Context. It has been proposed that the temporal coincidence of a gamma-ray burst (GRB) and a type Ib/c supernova (SN) can be explained with the concept of induced gravitational collapse (IGC), induced by the matter ejected from an SN Ib/c accreting onto a neutron star (NS). The NS is expected to reach the critical mass necessary for it to collapse to a black hole (BH) and emit a GRB. We found a standard luminosity light curve behavior in the late-time X-ray emission of this subclass of GRBs. Aims. We test if this standard behavior in the luminosity found in this subclass of GRBs can become a redshift estimator of these sources. Methods. We selected a sample of GRBs that belong to this subclass of IGC GRBs associated to an SN (IGC GRB-SN sources). These sources have an isotropic energy E iso > 10 52 erg and their cosmological redshifts are in the range of z = 0.49−1.261. We focused on the corresponding X-ray luminosity light curves. Results. We find that all GRBs of the sample with measured redshift present a standard luminosity late-time light curve in the 0.3−10 keV rest-frame energy range. We used these results to estimate the GRB redshift of the sample without a measured redshift and found results consistent with other possible redshift indicators. Conclusions. The standard late-time X-ray luminosity light curve of all GRBs of the sample shows a common physical mechanism in this particular phase of the X-ray emission, possibly related to the creation of the NS from the SN process. This scaling law moreover represents strong evidence of very low or even absent beaming in this late phase of the X-ray afterglow emission process. This could be a fundamental tool for estimating the redshift of GRBs that belong to this subclass of events. We are currently expanding this subclass of GRBs to further verify the universal validity of this new redshift estimation method.

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confidence: 59%

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confidence: 97%

Novel distance indicator for gamma-ray bursts associated with supernovae

Pisani

Izzo

et al. 2013

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“…The X-ray light curve is composed of an early steep decay, a plateau, and a late decay. The analysis of the late decay of the afterglow luminosity has been identified with the cooling of the newly born NS, left by the SN explosion (Negreiros et al 2012).…”

Section: Discussionmentioning

confidence: 99%

GRB 110709B in the induced gravitational collapse paradigm

Penacchioni

Bianco

et al. 2013

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Context. Gamma-ray burst (GRB) 110709B is the first source for which Swift-BAT was triggered twice, with a time separation of ∼10 min. The first emission (called here episode 1) lasted from 40 s before the first trigger time until 60 s after it. The second emission (hereafter episode 2) lasted from 35 s before the second trigger time until 100 s after it. These features reproduce those of GRB 090618, which has recently been interpreted within the induced gravitational collapse (IGC) paradigm. In line with this paradigm, we assume the progenitor to be a close binary system composed of the core of an evolved star and a neutron star (NS). The evolved star explodes as a supernova (SN) and ejects material that is partially accreted by the NS. We identify this process with episode 1. The accretion process accumulates more than the critical mass of the NS, which gravitationally collapses into a black hole (BH). This process leads to the GRB emission, episode 2. The two trigger episodes have for the first time provided the possibility to cover the X-ray emission observed by XRT both prior to and during the prompt phase of GRB 110709B. Aims. We analyze the spectra and time variability of episodes 1 and 2 and compute the relevant parameters of the binary progenitor, as well as the astrophysical parameters both in the SN and the GRB phase in the IGC paradigm. Methods. We performed a time-resolved spectral analysis of episode 1 by fitting the spectrum with a blackbody (BB) plus a power-law (PL) spectral model. From the BB fluxes and temperatures of episode 1 and the luminosity distance d L , we evaluated the evolution with time of the radius of the BB emitter, associated here to the evolution of the SN ejecta. We analyzed episode 2 within the fireshell model, identifying the proper GRB (P-GRB) and simulating the light curve and spectrum. We established the redshift to be z = 0.75, following the phenomenological methods described in the literature, and our analysis of the late X-ray afterglow. It is most remarkable that the determination of the cosmological redshift on the basis of scaling the late X-ray afterglow, which was already verified in GRB 090618 and GRB 101023, is again verified by this analysis. Results. We find for episode 1 a temperature of the BB component that evolves with time following a broken PL, with the slope of the PL at early times α = 0 (constant function) and the slope of the PL at late times β = −4 ± 2. The break occurs at t = 41.21 s. The total energy of episode 1 is E (1) iso = 1.42 × 10 53 erg. The total energy of episode 2 is E (2) iso = 2.43 × 10 52 erg. We find at transparency a Lorentz factor Γ ∼ 1.73 × 10 2 , laboratory radius of 6.04 × 10 13 cm, P-GRB observed temperature kT P−GRB = 12.36 keV, baryon load B = 5.7 × 10 −3 and P-GRB energy of E P−GRB = 3.44 × 10 50 erg. We find a remarkable coincidence of the cosmological redshift by scaling the XRT data and with three other phenomenological methods. Conclusions. We interpret GRB 110709B as a member of the IGC sources, together with G...

“…The mass of the SN ejecta assumed to be M ej,0 = M core − M rem , where M rem is the mass of the central compact remnant (NS) left by the SN explosion. Here we assumed M core = (3-8) M at the epoch of the SN explosion, and M rem = 1.3 M , following some of the type Ic SN progenitors studied in Nomoto & Hashimoto (1988);Nomoto et al (1994);Iwamoto et al (1994).…”

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confidence: 99%

“…The most likely explanation for SN Ib/c, which lack H and He in their spectra, is that the SN progenitor star is in a binary system with an NS, see also Nomoto & Hashimoto (1988); Nomoto et al (1994); Iwamoto et al (1994) and also Tutukov & Fedorova (2007);Chevalier (2012) In the current literature, the GRB-SN connection has at time been assumed to originate from a particularly violent SN process called hypernova or a collapsar (see e.g. Woosley & Bloom 2006, and references therein).…”

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confidence: 99%

GRB 090618: a candidate for a neutron star gravitational collapse onto a black hole induced by a type Ib/c supernova

Izzo

Rueda

2012

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A novel concept has recently been proposed for explaining the temporal coincidence of some gamma ray bursts (GRBs) with an associated supernova (SN) in terms of the gravitational collapse of a neutron star (NS) onto a black hole (BH), induced by a type Ib/c SN explosion. We applied these considerations to the exceptional case of GRB 090618, for which there is evidence of an SN ∼ 10 days after the GRB occurrence. We calculated the accretion rate and total accreted mass onto an NS from an SN Ib/c that originated from a companion evolved star. These calculations show that the NS reaches the critical mass in a few seconds and undergoes gravitational collapse onto a BH, leading to the emission of a GRB. We find for the mass of the NS companion, M NS , and for the SN core progenitor, M core , the following mass ranges: 1.8 M NS /M 2.1 and 3 ≤ M core /M ≤ 8. Finally, we discuss the complementarity of these considerations to alternative processes explaining long and short GRBs.Key words. accretion, accretion disks -binaries: general -gamma-ray burst: general -stars: neutron -supernovae: generalThe temporal coincidence of some gamma ray bursts (GRBs) and their associated supernovae (SNe) represent one of the most outstanding and hottest topic in relativistic physics and astrophysics. We recall that the optical emission of an SN reaches its maximum about 15 days after the SN explosion (see e.g. Arnett 1996). This implies that the onset of SNe and the occurrence of the GRB can be almost simultaneous (see e.g. Della Valle 2011; Hjorth & Bloom 2011, for a recent review on GRB-SN systems). For these reasons the concept of the induced gravitational collapse (IGC) was initially proposed (Ruffini et al. 2001) and further developed in Ruffini et al. (2008). Recently we have theoretically developed the basic equations describing this concept (Rueda & Ruffini 2012). In Rueda & Ruffini (2012) the GRB-SN connection has been explained in terms of the final stage of the evolution of a close binary system composed of an evolved star (likely a C+O star in the case of SN Ic) with a neutron star (NS) companion. The explosion of the SN Ib/c in this system leads to an accretion process onto the NS companion. The NS reaches the critical mass value in a few seconds, undergoing gravitational collapse onto a black hole (BH). The process of gravitational collapse onto a BH leads to the emission of the GRB. We have evaluated the accretion rate onto the NS and have given the explicit expression of the accreted mass as a function of the nature of the components and the binary parameters.We turn now to an explicit quantitative description of the IGC process and compare the results with the observational data of GRB-SN. We apply these considerations in this Letter to the specific case of GRB 090618 and its associated SN. We recall that GRB 090618 is one of the nearest (z = 0.54) and at the same time more energetic GRBs (E iso = 3 × 10 53 erg) ever observed. Indeed, no beaming appears to be present from the data. These two important properties ...