arXiv subjects

Javier Rodrigo Martinez

Publications and source records attributed to Javier Rodrigo Martinez.

2 recordsLinked to original sources

arXiv2025

Probing the detectability of electromagnetic signatures from Galactic isolated black holes

Context: A large number of isolated black holes (IBHs) are expected to populate the Galaxy. However, only one has been confirmed by the analysis of a microlensing event, and no confirmed emission detection from an IBH has been reported so far. Aims: We analysed the detectability of electromagnetic signatures from IBHs moving in the Galaxy. Methods: We considered accretion from the interstellar medium onto an IBH and assumed the formation of an outflow. We modelled the accretion process and the interaction of the outflow with the surrounding medium on large scales, including mechanical feedback on the accretion process. Furthermore, we also calculated the emission from three different regions: the accretion region, the radiation from the outflow medium interaction structure, and the emission of relativistic particles that diffuse in the surrounding medium. Results: Multiwavelength emission associated with Galactic IBHs can be detected in systems moving through a very dense medium. Thermal emission from accretion could be observed in the mid infrared and in hard X rays with current and forthcoming observatories. Thermal and non thermal emission from the outflow medium shock could also be detected in the radio and millimetre ranges. Moreover, detection of the emission from particles diffusing in a dense medium could be feasible in gamma rays. Applying our model to the IBH associated with the gravitational microlensing event MOA2011BLG191 OGLE2011BLG0462, we inferred that radio and infrared detection of the IBH is plausible. Also, we derived that IBHs could be modest Galactic cosmic ray contributors, potentially reaching a 1% contribution at 1 PeV. Finally, by extending our model to primordial black holes, we conclude that efficient leptonic acceleration in their outflow medium interactions would rule them out as a major dark matter component.

astro-ph.HE↗

arXiv2023

Probing the non-thermal physics of stellar bow shocks using radio observations

We aim to interpret the radio emission of stellar bow shocks and assess under which conditions it could be either thermal or non-thermal, and how to use the observational data to infer their physical properties. We used an extended non-thermal emission model for stellar bow shocks for which we incorporated a consistent calculation of the thermal emission from the forward shock. We fitted this model to the available radio data, including largely unexplored data at low frequencies. In addition, we used a simplified one-zone model to estimate the gamma-ray emission from particles escaping the bow shocks. We can only explain the radio data from (BD+43°3654 and BD+60°2522) assuming a hard electron energy distribution below $\sim$1 GeV, a high efficiency of conversion of (shocked) wind kinetic power into relativistic electrons, and a relatively high magnetic-to-thermal pressure ratio. In the other systems, the interpretation of the observed flux density is ambiguous, although a non-thermal scenario is also favoured. We also show how complementary observations at other frequencies can allow us to place stronger constraints in the model. We also estimated the gamma-ray fluxes from the HII regions around the bow shocks of BD+43°3654 and BD+60°2522, and obtained luminosities at GeV energies of $\sim 10^{33}$~erg\,s$^{-1}$ and $10^{32}$~erg\,s$^{-1}$, respectively. Stellar bow shocks can potentially be very efficient particle accelerators. This work provides multi-wavelength predictions of their emission and demonstrates the key role of low-frequency radio observations in unveiling particle acceleration processes. The prospects of detections with next-generation observatories such as SKA and ngVLA are promising. Finally, BD+43°3654 may be detected in GeV in the near future, while bow shocks in general may turn out to be non-negligible sources of low-energy cosmic rays.

astro-ph.HE↗