Search

Short gamma-ray bursts (sGRBs) have widely been accepted to arise from a compact object binary merger; neutron star–neutron star or neutron star–black hole. During the merger of a binary neutron star system, magnetic field can be amplified beyond magnetar field strength ( ∼ 10 15 – 10 16 G ) by Kelvin–Helmholtz instabilities. Considering this effect on the GRB “fireball” dynamics, we study the emission, propagation and oscillation of multi MeV–GeV neutrinos through their self-energies and using these we compute the neutrino effective potential up to order M W − 4 . Additionally, we calculate the number of neutrino events and neutrino flavor ratios that we would expect on Hyper-Kamiokande and DeepCore experiments. We found that MeV neutrinos in a strong magnetic field could provide information of the topology of the field, and that the number of GeV neutrinos expected in DeepCore detector would be directly affected by the strength of the field. It is worth noting that our estimates correspond to the only trustworthy method for verifying the effect of the magnetic field amplification.

GRB 110709B presented a peculiar three-peak lightcurve; this burst twice triggered the BAT detector onboard Swift. The two triggers were separated by $\sim 10$ minutes. In order to explain such an event, we unify into a single description the millisecond (ms) protomagnetar and the collapsar central-engine models. We find that such a scenario could produce GRBs with three peaks. One for the ms-protomagnetar stage, a second one for the BH-formation event and a third one for the collapsar phase. We show that the three peaks for GRB 110709B originate from different phases of the same collapsing object. We estimate the energies and timescales of the different episodes of this burst using our model and compare with previous results as well as with a reanalysis we perform on the data. We show that not only the light curve, but also the photon index evolution and the delay between the prompt emission and the afterglow of the second central-engine activity phase point towards a model like the one proposed here. We find that, with reasonable assumptions, our model correctly describes the activity in GRB 110709B. We further suggest careful study of future GRBs lightcurves which may help show the validity of our model. If our model is correct, this would be the first time that the formation of a BH from a core-collapse event is observed unimpededly., Comment: 13 pages, 2 figures. Accepted in New Astronomy

Long TeV $\gamma$-ray campaigns have been carried out to study the spectrum, variability and duty cycle of the BL Lac object Markarian 421. These campaigns have given some evidence of the presence of protons in the jet: i) Its spectral energy distribution which shows two main peaks; one at low energies ($\sim$ 1 keV) and the other at high energies (hundreds of GeV), has been described by using synchrotron proton blazar model. ii) The study of the variability at GeV $\gamma$-rays and X-rays has indicated no significant correlation. iii) TeV $\gamma$-ray detections without activity in X-rays, called "orphan flares" have been observed in this object.\\ Recently, The Telescope Array Collaboration reported the arrival of 72 ultra-high-energy cosmic rays with some of them possibly related to the direction of Markarian 421. The IceCube Collaboration reported the detection of 37 extraterrestrial neutrinos in the TeV - PeV energy range collected during three consecutive years. In particular, no neutrino track events were associated with this source. In this paper, we consider the proton-photon interactions to correlate the TeV $\gamma$-ray fluxes reported by long campaigns with the neutrino and ultra-high-energy cosmic ray observations around this blazar. Considering the results reported by The IceCube and Telescope Array Collaborations, we found that only from $\sim$ 25\% to 70\% of TeV fluxes described with a power law function with exponential cutoff can come from the proton-photon interactions., Comment: Accepted for publication in Astroparticle Physics (12 pages, 4 figures)