arXiv subjects

J. Rodrigo Sacahui

Publications and source records attributed to J. Rodrigo Sacahui.

4 recordsLinked to original sources

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↗

arXiv2021

Analyzing the gamma-ray activity of neutrino emitter candidates: comparing TXS 0506+056 with other blazars

On 22nd of September 2017 the IceCube collaboration sent an alert for an EHE (Extreme High Energy) event, corresponding to the reconstruction of a muonic neutrino (IC-170922A) with energy $\sim 290$ TeV. A multi-wavelength follow-up campaign associated this neutrino event with a gamma-ray flaring state of the BL Lac TXS 0506+056 located at z=0.3365. From the same position of the sky a muonic neutrino excess is observed in a time window of 110 days around 13th of December 2014. These observations together suggest TXS 0506+056 as a possible neutrino emitter. We report here a long term gamma-ray monitoring of this source and we compare it with other blazars spatially correlated with astrophysical muonic neutrino events observed by IceCube. We characterise the most significant gamma-ray flares of the blazars in the sample and introduce the blazar duty cycle as an important parameter to be considered when assessing a possible neutrino counterpart. For the selected blazars we show the expected neutrino flux variability with different time binning assuming the gamma-rays observed by Fermi-LAT as a product of a leptohadronic emission scenario. The neutrino expectations from the blazar sample are then compared with the IceCube discovery flux searching for the optimal time bin in a multi-messenger context. This analysis indicates that the detection of a single flare represents a challenge for a single cubic kilometer detector, underlining the importance of increasing the size of current neutrino telescopes and obtaining a good monitoring of the entire sky through a global neutrino network.

astro-ph.HE↗

arXiv2019

Constraining GRBs pseudo-redshift using different empirical correlations

The determination of distances is highly constrained to a small number of Gamma-Ray Bursts (GRBs) because it requires observations at different wavelengths. Some empirical functions to estimate redshifts have been identified using populations of GRBs with reported redshifts. For example, the Amati correlation relates $E_{peak}$ of the spectrum when modeled with a Band function and the total energy emitted $E_{iso}$ in a time integrated analysis. A multiple-component scenario has been proposed in order to explain GRBs spectra, and in this context when a fine-time spectral analysis is performed a correlation between the non-thermal component's peak energy and the luminosity ($E_{peak,i} - L_i$) appears. This correlation is also used to infer distances to GRBs. In this work we present a sample of bright GRBs and apply these empirical correlations to constrain the pseudo-redshift of the selected burst sample. Our results for GRB080916C, GRB090926A and GRB150214A with reported redshift are totally consistent. Another three bursts with lower luminosities were selected. For these bursts, the pseudo-redshift range obtained with the two correlations are not totally in agreement.

astro-ph.HE↗

arXiv2015

The protoMIRAX Hard X-ray Imaging Balloon Experiment

The protoMIRAX hard X-ray imaging telescope is a balloon-borne experiment developed as a pathfinder for the MIRAX satellite mission. The experiment consists essentially in a coded-aperture hard X-ray (30-200 keV) imager with a square array (13$\times$13) of 2mm-thick planar CZT detectors with a total area of 169 cm$^2$. The total, fully-coded field-of-view is $21^{\circ}\times 21^{\circ}$ and the angular resolution is 1$^{\circ}$43'. In this paper we describe the protoMIRAX instrument and all the subsystems of its balloon gondola, and we show simulated results of the instrument performance. The main objective of protoMIRAX is to carry out imaging spectroscopy of selected bright sources to demonstrate the performance of a prototype of the MIRAX hard X-ray imager. Detailed background and imaging simulations have been performed for protoMIRAX balloon flights. The 3$σ$ sensitivity for the 30-200 keV range is ~1.9 $\times$ 10$^{-5}$ photons cm$^{-2}$ s$^{-1}$ for an integration time of 8 hs at an atmospheric depth of 2.7 g cm$^{-2}$ and an average zenith angle of 30$^{\circ}$. We have developed an attitude control system for the balloon gondola and new data handling and ground systems that also include prototypes for the MIRAX satellite. We present the results of Monte Carlo simulations of the camera response at balloon altitudes, showing the expected background level and the detailed sensitivity of protoMIRAX. We also present the results of imaging simulations of the Crab region. The results show that protoMIRAX is capable of making spectral and imaging observations of bright hard X-ray source fields. Furthermore, the balloon observations will carry out very important tests and demonstrations of MIRAX hardware and software in a near space environment.

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