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S. Mazzou

Publications and source records attributed to S. Mazzou.

5 recordsLinked to original sources

On Accretion and Neutrino Investigations of Thermodynamically Reconstructed Black Holes from Three-Parameter Generalized Entropy

We study accretion and neutrino-sensitive thermal signatures of a static black hole reconstructed from a three-parameter generalized entropy. The construction is thermodynamic by design: the entropy deformation is not mapped to a radial-coordinate redefinition or to a prescribed Reissner--Nordstr\"om-like correction. Instead, the generalized entropy fixes the horizon response factor $\Xi_h=dS_G/dS|_{S_h}$. The effective exterior geometry is then reconstructed by requiring its surface-gravity temperature to reproduce the generalized thermodynamic temperature. As a result, the metric preserves the horizon area and the Schwarzschild asymptotics, and reduces smoothly to Schwarzschild when $\Xi_h\to1$. The deformation is controlled by $\lambda_G=1/\Xi_h-1$, while the integer $p\geq2$ determines the radial localization of the near-horizon correction. We compute the photon sphere, critical shadow scale, circular geodesics, ISCO, Novikov--Thorne flux, disk temperature, radiative efficiency, energy-at-infinity luminosity, a redshifted spectral proxy, and neutrino-sensitive temperature moments. In particular, positive $\lambda_G$ moves the photon sphere and ISCO inward, decreases the shadow scale, raises the radiative efficiency, and concentrates the energy release toward the inner disk. By contrast, negative $\lambda_G$ produces the opposite trend. Finally, the neutrino sector is modeled conservatively using dimensionless temperature moments instead of a full neutrino-dominated accretion flow or annihilation-deposition calculation. The hierarchy among the $ n=4$, $n=6$, and $n=9$ moments reveals that entropy-induced disk deformation becomes increasingly apparent with higher temperature exponents. Thus, observable changes in compact orbits and thin-disk emission can be directly linked to generalized entropy via the horizon response.

gr-qc

ANTARES upper limits on the multi-TeV neutrino emission from the GRBs detected by IACTs

The first gamma-ray burst detections by Imaging Atmospheric Cherenkov Telescopes have been recently announced: GRB 190114C, detected by MAGIC, GRB 180720B and GRB 190829A, observed by H.E.S.S. A dedicated search for neutrinos in space and time coincidence with the gamma-ray emission observed by IACTs has been performed using ANTARES data. The search covers both the prompt and afterglow phases, yielding no neutrinos in coincidence with the three GRBs studied. Upper limits on the energetics of the neutrino emission are inferred. The resulting upper limits are several orders of magnitude above the observed gamma-ray emission, and they do not allow to constrain the available models.

astro-ph.HE

ANTARES search for point-sources of neutrinos using astrophysical catalogs: a likelihood stacking analysis

A search for astrophysical point-like neutrino sources using the data collected by the ANTARES detector between January 29, 2007 and December 31, 2017 is presented. A likelihood stacking method is used to assess the significance of an excess of muon neutrinos inducing track-like events in correlation with the location of a list of possible sources. Different sets of objects are tested in the analysis: a) a sub-sample of the \textit{Fermi} 3LAC catalog of blazars, b) a jet-obscured AGN population, c) a sample of soft gamma-ray selected radio galaxies, d) a star-forming galaxy catalog , and e) a public sample of 56 very-high-energy track events from the IceCube experiment. None of the tested sources shows a significant association with the sample of neutrinos detected by ANTARES. The smallest p-value is obtained for the radio galaxies catalog with an equal weights hypothesis, with a pre-trial p-value equivalent to a $2.8 \, σ$ excess, equivalent to $1.6 \, σ$ post-trial. In addition, the results of a dedicated analysis for the blazar MG3 J225517+2409 are also reported: this source is found to be the most significant within the \textit{Fermi} 3LAC sample, with 5 ANTARES events located at less than one degree from the source. This blazar showed evidence of flaring activity in \textit{Fermi} data, in space-time coincidence with a high-energy track detected by IceCube. An \emph{a posteriori} significance of $2.0\, σ$ for the combination of ANTARES and IceCube data is reported.

astro-ph.HE

Constraining the contribution of Gamma-Ray Bursts to the high-energy diffuse neutrino flux with 10 years of ANTARES data

Addressing the origin of the astrophysical neutrino flux observed by IceCube is of paramount importance. Gamma-Ray Bursts (GRBs) are among the few astrophysical sources capable of achieving the required energy to contribute to such neutrino flux through p$γ$ interactions. In this work, ANTARES data have been used to search for upward going muon neutrinos in spatial and temporal coincidence with 784 GRBs occurred from 2007 to 2017. For each GRB, the expected neutrino flux has been calculated in the framework of the internal shock model and the impact of the lack of knowledge on the majority of source redshifts and on other intrinsic parameters of the emission mechanism has been quantified. It is found that the model parameters that set the radial distance where shock collisions occur have the largest impact on neutrino flux expectations. In particular, the bulk Lorentz factor of the source ejecta and the minimum variability timescale are found to contribute significantly to the GRB-neutrino flux uncertainty. For the selected sources, ANTARES data have been analysed, by maximising the discovery probability of the stacking sample through an extended maximum-likelihood strategy. Since no neutrino event passed the quality cuts set by the optimisation procedure, 90\% confidence level upper limits (with their uncertainty) on the total expected diffuse neutrino flux have been derived, according to the model. The GRB contribution to the observed diffuse astrophysical neutrino flux around 100 TeV is constrained to be less than 10\%.

astro-ph.HE

Monte Carlo simulations for the ANTARES underwater neutrino telescope

Monte Carlo simulations are a unique tool to check the response of a detector and to monitor its performance. For a deep-sea neutrino telescope, the variability of the environmental conditions that can affect the behaviour of the data acquisition system must be considered, in addition to a reliable description of the active parts of the detector and of the features of physics events, in order to produce a realistic set of simulated events. In this paper, the software tools used to produce neutrino and cosmic ray signatures in the telescope and the strategy developed to represent the time evolution of the natural environment and of the detector efficiency are described.

astro-ph.HE