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 E iso 10 52 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 ∼ 10 15 -10 17 cm with Lorentz gamma factor Γ ∼ 10 2 -10 3 . Using a novel data analysis we show that the time of occurrence, duration, luminosity and total energy of the X-ray flares correlate with E iso . A crucial feature is the observation of thermal emission in the X-ray flares that we show occurs at radii ∼ 10 12 cm with Γ 4. These model independent observations cannot be explained by the "fireball" model, which postulates synchrotron and inverse Compton radiation from a single ultra relativistic 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 10 10 cm reaching transparency at ∼ 10 12 cm with Γ 4. 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.

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Nonlinear QED interactions induce different polarization properties on a given probe beam. We consider the polarization effects caused by the photon-photon interaction in laser experiments, when a laser beam propagates through a constant magnetic field or collides with another laser beam. We solve the quantum Boltzmann equation within the framework of the Euler-Heisenberg Lagrangian for both time-dependent and constant background field to explore the time evolution of the Stokes parameters Q, U, and V describing polarization. Assuming an initially linearly polarized probe laser beam, we also calculate the induced ellipticity and rotation of the polarization plane.Comment: 14 pages, 4 figure

It has previously been discovered that there is a universal power law behavior exhibited by the late X-ray emission (LXRE) of a "golden sample" (GS) of six long energetic GRBs, when observed in the rest-frame of the source. This remarkable feature, independent of the different isotropic energy (E iso ) of each GRB, has been used to estimate the cosmological redshift of some long GRBs. This analysis is extended here to a new class of 161 long GRBs, all with E iso > 10 52 erg. These GRBs are indicated as binary-driven hypernovae (BdHNe) in view of their progenitors: a tight binary system composed of a carbon-oxygen core (CO core ) and a neutron star undergoing an induced gravitational collapse (IGC) to a black hole triggered by the CO core explosion as a supernova (SN). We confirm the universal behavior of the LXRE for the "enlarged sample" (ES) of 161 BdHNe observed up to the end of 2015, assuming a double-cone emitting region. We obtain a distribution of half-opening angles peaking at θ = 17.62• , with a mean value of 30.05• , and a standard deviation of 19.65• . This, in turn, leads to the possible establishment of a new cosmological candle. Within the IGC model, such universal LXRE behavior is only indirectly related to the GRB and originates from the SN ejecta, of a standard constant mass, being shocked by the GRB emission. The fulfillment of the universal relation in the LXRE and its independence of the prompt emission, further confirmed in this article, establishes a crucial test for any viable GRB model.

The XENON1T collaboration recently reported the excess of events from recoil electrons, possibly giving an insight into new area beyond the Standard Model (SM) of particle physics. We try to explain this excess by considering effective interactions between the sterile neutrinos and the SM particles. In this paper, we present an effective model based on one-particle-irreducible interaction vertices at low energies that are induced from the SM gauge symmetric four-fermion operators at high energies. The effective interaction strength is constrained by the SM precision measurements, astrophysical and cosmological observations. We introduce a novel effective electromagnetic interaction between sterile neutrinos and SM neutrinos, which can successfully explain the XENON1T event rate through inelastic scattering of the sterile neutrino dark matter from Xenon electrons. We find that sterile neutrinos with masses around 90 keV and specific effective coupling can fit well with the XENON1T data where the best fit points preserving DM constraints and possibly describe the anomalies in other experiments.

We revisit the efficiency of Schwinger mechanism in creating charged pairs during inflation. We consider a minimal setup of inflation in which the inflaton field is a complex scalar field charged under a U (1) gauge field. There is a time dependent conformal coupling which pumps energy from the inflaton field to the gauge field to furnish a nearly constant background electric field energy density to drive the Schwinger mechanism. The coupling between the gauge field and the scalar field induces a time dependent effective mass for the inflaton field. The requirement of a long period of slow-roll inflation causes the Schwinger mechanism to be highly inefficient during inflation. The non-perturbative Schwinger mechanism can be relevant only towards the end of inflation and only on very small scales. This is in contrast to hypothetical models studied in literature in which the complex scalar field is a test field and a constant electric field is imposed on the dS background by hand. We calculate the number of pairs of charged particles created perturbatively during inflation. We show that it is proportional to the amplitude of the quadrupolar statistical anisotropy and it is very small. Consequently, the back-reactions of created particles on magnetogenesis on large scales are negligible. * s.shakeri@ipm.ir † gorji@ipm.ir ‡ firouz@ipm.ir arXiv:1903.05310v2 [hep-th]

Abstract. In the presence of strong magnetic fields near pulsars, the QED vacuum becomes a birefringent medium due to nonlinear QED interactions. Here, we explore the impact of the effective photon-photon interaction on the polarization evolution of photons propagating through the magnetized QED vacuum of a pulsar. We solve the quantum Boltzmann equation within the framework of the Euler-Heisenberg Lagrangian to find the evolution of the Stokes parameters. We find that linearly polarized X-ray photons propagating outward in the magnetosphere of a rotating neutron star can acquire high values for the circular polarization parameter. Meanwhile, it is shown that the polarization characteristics of photons besides photon energy depend strongly on parameters of the pulsars such as magnetic field strength, inclination angle and rotational period. Our results are clear predictions of QED vacuum polarization effects in the near vicinity of magnetic stars which can be tested with the upcoming X-ray polarimetric observations.

We explore the presence of self-interacting bosonic dark matter (DM) whithin neutron stars (NSs) in light of the latest mass-radius measurements of the Neutron Star Interior Composition Explorer (NICER). The bosonic DM is distributed in NSs as a core for DM particles with high mass, low fraction and low self-coupling constant or as a halo for particles with low mass, high fraction and high self-coupling constant leading to formation of DM admixed NSs. We focus on the evolution of the visible and dark radius of the mixed object due to DM model parameters and fractions. It is shown that DM core formation reduces the visible radius and total mass pushing them below observational limits while halo formation is in favor of the latest mass-radius constraints. Applying joint constraints for radius of 1.4M NSs and the maximum mass from NICER and LIGO/Virgo observations, we scan over the parameter space of the bosonic DM model to obtain an allowed region. It turns out that the maximum mass limit provides a more stringent constraint compare to the radius one. Our investigation allows for the exclusion of a large portion of DM fractions for sub-GeV bosons and limited the amount of accumulated DM to be less than ∼ 4% for the entire mass range at the strong coupling regime λ = π. In this paper, we introduce main features of the pulse profile corresponding to the DM admixed NS and the effect of DM halo on the light bending is considered extensively as an independent probe for the DM model. We find that the depth of minimum fluxes in the pulse profiles crucially depend on the amount of DM distributed around NS and its compactness. The current/future astrophysics missions via precise measurements of compact object properties may test the possibility of the existence of DM within NSs and break the degeneracies between different scenarios to interpret exotic observations.