Astrophys. J., 852, 53-53 (2018/January-1)
Early X-ray flares in GRBs.
RUFFINI R., WANG Y., AIMURATOV Y., DE ALMEIDA U.B., BECERRA L., BIANCO C.L., CHEN Y.C., KARLICA M., KOVACEVIC M., LI L., MELON FUKSMAN J.D., MORADI R., MUCCINO M., PENACCHIONI A.V., PISANI G.B., PRIMORAC D., RUEDA J.A., SHAKERI S., VERESHCHAGIN G.V. and XUE S.-S.
Abstract (from CDS):
We analyze the early X-ray flares in the GRB "flare-plateau-afterglow" (FPA) phase observed by Swift-XRT. The FPA occurs only in one of the seven GRB subclasses: the binary-driven hypernovae (BdHNe). This subclass consists of long GRBs with a carbon-oxygen core and a neutron star (NS) binary companion as progenitors. The hypercritical accretion of the supernova (SN) ejecta onto the NS can lead to the gravitational collapse of the NS into a black hole. Consequently, one can observe a GRB emission with isotropic energy Eiso 1052 erg, as well as the associated GeV emission and the FPA phase. Previous work had shown that gamma-ray spikes in the prompt emission occur at ∼1015–1017 cm with Lorentz Gamma factors Γ∼102–103. Using a novel data analysis, we show that the time of occurrence, duration, luminosity, and total energy of the X-ray flares correlate with Eiso. A crucial feature is the observation of thermal emission in the X-ray flares that we show occurs at radii ∼1012 cm with Γ4. These model-independent observations cannot be explained by the "fireball" model, which postulates synchrotron and inverse-Compton radiation from a single ultrarelativistic jetted emission extending from the prompt to the late afterglow and GeV emission phases. We show that in BdHNe a collision between the GRB and the SN ejecta occurs at ≃1010 cm, reaching transparency at ∼1012 cm with Γ4. The agreement between the thermal emission observations and these theoretically derived values validates our model and opens the possibility of testing each BdHN episode with the corresponding Lorentz Gamma factor.
© 2018. The American Astronomical Society. All rights reserved.
binaries: general - black hole physics - gamma-ray burst: general - hydrodynamics - stars: neutron - supernovae: general - supernovae: general
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<Available at CDS (J/ApJ/852/53): table3.dat table5.dat table7.dat table9.dat>
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