arXiv subjects

María Magdalena González

Publications and source records attributed to María Magdalena González.

5 recordsLinked to original sources

arXiv2026

Inverse Compton scattering occurring in a reverse-shock scenario involving a kilonova: A channel of TeV gamma-ray photons

Gamma-ray bursts (GRBs) are among the most luminous transients in the Universe and constitute prime targets for multimessenger studies, particularly in connection with gravitational-wave events. The detection of very-high-energy (TeV) photons from GRBs would provide valuable constraints on the physical conditions in the outflow, including the bulk Lorentz factor, circumburst density, radiation processes, and microphysical parameters. The possible detection of TeV emission temporally associated with an optical-infrared kilonova (KN), as suggested for GRB 160821B, presents a challenge to standard synchrotron self-Compton scenarios. In this work, we explore an alternative mechanism in which TeV photons are produced during the afterglow phase via external inverse Compton (EIC) scattering. In this scenario, electrons accelerated in the reverse shock upscatter seed photons originating from the KN. We derive the corresponding EIC light curves and spectra for a reverse shock evolving in the thin-shell regime within a constant-density medium, and apply the model to GRB 160821B. We further constrain the parameter space for TeV detectability by incorporating the high KN luminosity observed in AT2017gfo, as well as flux upper limits reported by H.E.S.S. and HAWC. We find that TeV emission is more likely under conditions of very low magnetic energy fraction, $ε_{\rm B_r} \lesssim 10^{-6}$, combined with a bright KN and relatively low redshift. This mechanism predicts TeV photons on timescales of hours to a few days after the burst.

astro-ph.HE↗

arXiv2024

On the correlation between X-rays and TeV gamma-rays in HBL Blazars

The gamma-ray emission in blazars can be attributed to the leptonic Synchrotron Self-Compton (SSC) model, photo-hadronic interactions, or a combination thereof. While evidence supports both models, their specific contributions remain uncertain. One supportive piece of evidence for the SSC model is the correlation between synchrotron and SSC fluxes in some blazar's Spectral Energy Distribution (SED), indicating the relative contributions of leptonic and hadronic mechanisms. Observational studies of the HBL blazar Markarian 421 over several years, spanning TeV gamma rays and X-rays, have reported a linear correlation across various timescales, which breaks at the highest gamma-ray fluxes. Extending this analysis to four High synchrotron peaked BL Lac (HBL) blazars -- Markarian 501, 1ES 1959+650, PKS 2155-304 and 1ES 2344+514.-- we utilize multiwavelength data from ground-based Imaging Atmospheric Cherenkov Telescopes (IACTs) for gamma rays and satellite observations for X-rays. Our long-term study confirms a linear correlation between fluxes across these energy bands, except for Markarian 501, which shows a correlation index of $1.45 \pm 0.01$. Notably, the exceptional flaring episode of PKS 2155-304 exhibits a correlation index of 2 with extreme values of gamma-ray fluxes. We observe outliers with high gamma-ray fluxes, suggesting the involvement of another mechanism, either of hadronic or leptonic origin. Finally, all other correlations exhibit alignment with a general correlation, suggesting a common acceleration mechanism among them with slight variations likely due to individual magnetic field strengths.

astro-ph.HE↗

arXiv2017

Observation of radio galaxies with HAWC

The High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory is an extensive air shower array located in Puebla, Mexico. The closest radio galaxy within the HAWC field of view, M87, has been detected in very high energies. In this work we report upper limits on the TeV γ-ray flux of the radio galaxy M87. At a distance of 16 Mpc, M87 is a supergiant elliptical galaxy located in the Virgo Cluster that has been observed from radio wavelengths to TeV γ-rays. Although a single-zone synchrotron self-Compton model has been successfully used to explain the spectral energy distribution of this source up to a few GeV, the γ-ray spectrum at TeV has been interpreted within different theoretical models. We discuss the implications of these upper limits on the photo-hadronic interactions, as well as the number of neutrino events expected in the IceCube neutrino telescope.

astro-ph.HE↗

arXiv2017

X-ray/gamma-ray flux correlations in the BL Lacs Mrk 421 and 501 using HAWC data

The HAWC gamma ray observatory is located at the Sierra Negra Volcano in Puebla, Mexico, at an altitude of 4,100 meters. HAWC is a wide field of view array of 300 water Cherenkov detectors that are continuously surveying ~ 2sr of the sky, operating since March 2015. The large collected data sample allows HAWC to perform an unbiased monitoring of the BL Lac Mrk 421. This is the closest and brightest known extragalactic high-synchrotron-peaked BL Lac in the gamma-ray/X- ray bands and is extensively monitored by the Large Area Telescope (LAT) on-board the Fermi satellite, and the BAT and XRT instruments of the Swift satellite. In this work, we use 25 months of HAWC data together with Swift-XRT data to characterize potential correlations between both wavelengths. This analysis shows that HAWC and Swift-XRT data are correlated even stronger than expected for quasi-simultaneous observations.

astro-ph.HE↗

arXiv2014

Scientific Verification of the High Altitude Water Cherenkov observatory

The High Altitude Water Cherenkov (HAWC) observatory is a TeV gamma-ray and cosmic-ray detector currently under construction at an altitude of 4100 m close to volcano Sierra Negra in the state of Puebla, Mexico. The HAWC observatory is an extensive air-shower array comprised of 300 optically-isolated water Cherenkov detectors (WCDs). Each WCD contains $\sim$200,000 liters of filtered water and four upward-facing photomultiplier tubes. In Fall 2014, when the HAWC observatory will reach an area of 22,000 m$^{2}$, the sensitivity will be 15 times higher than its predecessor Milagro. Since September 2012, more than 30 WCDs have been instrumented and taking data. This first commissioning phase has been crucial for the verification of the data acquisition and event reconstruction algorithms. Moreover, with the increasing number of instrumented WCDs, it is important to verify the data taken with different configuration geometries. In this work we present a comparison between Monte Carlo simulation and data recorded by the experiment during 24 hours of live time between 14 and 15 April of 2013 when 29 WCDs were active.

astro-ph.IM↗