1,583 research outputs found
Erratum: Prospects for multimessenger detection of binary neutron star mergers in the fourth LIGO-Virgo-KAGRA observing run (Monthly Notices of the Royal Astronomical Society (2022) 513 (4159) DOI: 10.1093/mnras/stac1167)
No full textThere is a typo in equation (8) of Patricelli et al. (2022). The isotropic-equi v alent luminosity observed at a viewing angle θj is (Salafia et al. 2015, 2019): (Equation Presented). where the relativistic Doppler factor δ appears to the power of three. This modification does not affect any of the results presented in Patricelli et al. (2022), that were obtained using the correct formula (equation 1) and not the one written in equation (8) of Patricelli et al. (2022). ACKNOWLEDGEMENT We thank Om Sharan Salafia for pointing out the typo in our manuscript
Can we constrain the aftermath of binary neutron star mergers with short gamma-ray bursts?
No full textThe joint observation of GW170817 and GRB170817A proved that binary neutron star (BNS) mergers are progenitors of short gamma-ray bursts (SGRBs): this established a direct link between the still unsettled SGRB central engine and the outcome of BNS mergers, whose nature depends on the equation of state (EOS) and on the masses of the NSs. We propose a novel method to probe the central engine of SGRBs based on this link. We produce an extended catalogue of BNS mergers by combining recent theoretically predicted BNS merger rate as a function of redshift and the NS mass distribution inferred from measurements of Galactic BNSs. We use this catalogue to predict the number of BNS systems ending as magnetars (stable or supramassive NS) or BHs (formed promptly or after the collapse of a hypermassive NS) for different EOSs, and we compare these outcomes with the observed rate of SGRBs. Despite the uncertainties mainly related to the poor knowledge of the SGRB jet structure, we find that for most EOSs the rate of magnetars produced after BNS mergers is sufficient to power all the SGRBs, while scenarios with only BHs as possible central engine seem to be disfavoured
Constraints on fast radio burst emission in the aftermath of gamma-ray bursts
No full textContext. Fast radio bursts (FRBs) are highly energetic radio transients with a duration of some milliseconds. Their physical origin is still unknown. Many models consider magnetars as possible FRB sources, which is supported by the observational association of FRBs with the galactic magnetar SGR 1935+2154. Magnetars are also thought to be the source of the power of a fraction of gamma-ray bursts (GRBs), which means that the two extreme phenomena might have a common progenitor.
Aims. We placed constrains on this hypothesis by searching for possible associations between GRBs and FRBs with currently available catalogues and by estimating whether an association can be ruled out based on the lack of a coincident detection.
Methods. We cross-matched all the Neil Gehrels Swift Observatory (Swift) GRBs detected so far with all the well-localised FRBs reported in the FRBSTATS catalogue, and we looked for FRB-GRB associations considering both spatial and temporal constraints. We also simulated a synthetic population of FRBs associated with Swift GRBs to estimate how likely a joint detection with current and future radio facilities is.
Results. We recovered two low-significance possible associations that were reported before from a match of the catalogues: GRB 110715A/FRB 20171209A and GRB 060502B/FRB 20190309A. However, our study shows that based on the absence of any unambiguous association so far between Swift GRBs and FRBs, we cannot exclude that the two populations are connected because of the characteristics of current GRB and FRB detectors.
Conclusions. Currently available observational data are not sufficient to clearly exclude or confirm whether GRBs and FRBs are physically associated. In the next decade, the probability of detecting joint GRB-FRB events will be higher with new generations of GRB and FRB detectors, if any: future observations will therefore be key to placing more stringent constraints on the hypothesis that FRBs and GRBs have common progenitors
Three-peak GRBs and their implications for central engines
No full textGRB 110709B presented a peculiar three-peak lightcurve; this burst twice triggered the BAT detector onboard Swift. The two triggers were separated by similar to 10 min. 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 toward 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. (C) 2015 Elsevier B.V. All rights reserved
On the Charge to Mass Ratio of Neutron Cores and Heavy
No full textWe determine theoretically the relation between the total number of protons Np and the mass number A (the charge to mass ratio) of nuclei and neutron cores with the model recently proposed by Ruffini et al. (2007) and we compare it with other Np versus A relations: The empirical one, related to the Periodic Table, and the semi-empirical relation, obtained by minimizing the Weizsäcker mass formula. We find that there is a very good agreement between all the relations for values of A typical of nuclei, with differences of the order of per cent. Our relation and the semi-empirical one are in agreement up to A∼104; for higher values, we find that the two relations differ.We interprete the different behaviour of our theoretical relation as a result of the penetration of electrons (initially confined in an external shell) inside the core, that becomes more and more important by increasing A; these effects are not taken into account in the semi-empirical mass-formula. © 2008 American Institute of Physics
Estimation of the TeV gamma-ray duty cycle of Mrk 421 with the Milagro observatory
No full textMarkarian 421 (Mrk 421) is one the brightest and closest (z=0.031) blazars known (de Vaucouleurs et al., 1991 [1]). It is also one of the fastest varying TeV γ-ray sources, with a flaring activity on time scales as short as tens of minutes. The activity of Mrk 421 at different frequencies may reflect the radiation mechanisms involved. Tluczykont et al. (2007) [2] estimated the TeV activity of Mrk 421 through calculating the fraction of time spent in flaring states at TeV energies (TeV duty cycle) by using data from several imaging atmospheric Cherenkov telescopes (IACTs). Since IACT observations are biased towards high flux states they overestimated the TeV duty cycle of Mrk 421. Here we propose an alternative approach to calculate the TeV duty cycle of Mrk 421 that takes advantage of the continuous monitoring of the source by the Milagro experiment, a water Cherenkov detector sensitive to primary γ-rays between 100 GeV and 100 TeV. We present our estimation of the TeV duty cycle and study its robustness. © 2013 Elsevier B.V
Searching for gamma-ray counterparts to gravitational waves from merging binary neutron stars with the Cherenkov Telescope Array
No full textComputational challenges for multimodal astrophysics
No full textIn the coming decades, we will face major computational challenges, when the improved sensitivity of third-generation gravitational wave detectors will be such that they will be able to detect a high number (of the order of 7 x10(4) per year) of multi-messenger events from binary neutron star mergers, similar to GW170817. In this Perspective, we discuss the application of multimodal artificial intelligence techniques for multi-messenger astrophysics, fusing the information from different signal emissions
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