arXiv subjects

Juan C. Rodríguez-Ramírez

Publications and source records attributed to Juan C. Rodríguez-Ramírez.

5 recordsLinked to original sources

arXiv2026

Slingshot on compact binaries in the nuclear region of galaxies as the origin of large offset gamma-ray bursts

A growing number of gamma-ray bursts (GRBs) have been observed at large projected offsets from the centres of their putative host galaxies, sometimes extending to several tens of kiloparsecs. When the GRB is associated with a kilonova, a compact binary with at least one neutron star is expected to be involved, and the cause of the offset can be attributed to the neutron star natal kick. In this work, we explore an alternative mechanism: the gravitational scattering of compact binaries populating the nuclear region of the host galaxy, by an intermediate-mass black hole or secondary supermassive black hole. We specifically consider populations of neutron star-neutron star (NS-NS), neutron star-black hole (NS-BH), and neutron star-white dwarf (NS-WD) binaries, and analyse the ejection of bound systems from the nuclear region through a gravitational-slingshot effect. We proceed analytically to derive the conditions for binary survival and to parametrise the post-encounter velocity. To quantify the associated merger offsets, we numerically integrate the post-slingshot trajectory of the binary centre-of-mass in host-galaxy potentials that include the primary SMBH, the stellar component, and the dark-matter halo, considering both elliptical-like and spiral-like galaxy profiles. Our parameter sampling shows that NS-NS and NS-WD binaries typically merge farther from the galactic centre than NS-BH systems, with approximately 30-45% of successful ejections merging at three-dimensional distances exceeding 100 kpc; these extreme-offset mergers occur within $\sim$0.1-10 Gyr after ejection. These results motivate the analysed mechanism as a candidate channel for observed extreme-offset transients.

astro-ph.HE↗

arXiv2026

TeV gamma-ray spectral spikes produced by magnetic reconnection in blazar jets: the case of the 2014 high state of Markarian 501

Multi-wavelength monitoring of the flaring blazar Markarian 501 during July 2014 revealed a TeV gamma-ray spike feature with 3-4$σ$ significance and coincident with a prominent enhancement in its X-ray flux. The appearance of this spectral feature strongly suggests the presence of an extra emission component in addition to the usual one-zone SSC scenario. Several possible explanations for the origin of this novel behavior have been discussed, including stochastic particle acceleration, magnetospheric vacuum gap, and pion decay. In this paper, we show that the TeV narrow feature, simultaneous with an increase in the X-ray flux, can be produced with two leptonic emission regions in a jet undergoing magnetic reconnection energy dissipation along its propagation axis. In this scenario, the stable spectral components are produced in the region of maximum magnetic dissipation. A second region produces a flare upstream in the jet in a slower, more magnetized, and much smaller region compared to the stable one, which is responsible for increasing the X-ray flux and producing the TeV spike. The macroscopic properties of these two emission regions are consistent with a magnetically striped jet model discussed in previous works, where the acceleration of the jet flow and its non-thermal emission is driven by turbulent-induced magnetic reconnection. We employ this jet-reconnection scenario to model the 2014 high state of the blazar Markarian 501, considering the sequence of SED datasets corresponding to MJD 56855.91, 56857.98, 56858.98, and 56859.97, with the second dataset being the one that exhibits the TeV spike.

astro-ph.HE↗

arXiv2026

A Turbulence-Driven Magnetic Reconnection Model for the High-Energy Neutrino Emission from NGC 1068

We model the Seyfert II AGN NGC 1068 within a turbulence-induced magnetic reconnection framework to explain its high-energy emission. Observations reveal a neutrino flux excess higher than the observed GeV gamma-ray emission by orders of magnitude, with no detected TeV counterpart, suggesting efficient hadronic acceleration in the nuclear region with strong gamma-ray absorption. Assuming that proton acceleration occurs in a turbulent reconnection layer via a first-order Fermi process, we use a lepto-hadronic model based on a coronal-accretion disk configuration in which magnetic field lines anchored to the $2 \times 10^{7} M_{\odot}$ black hole horizon reconnect with field lines from the inner accretion disk corona. Our model matches the observed spectral energy distribution with a magnetic field $B_{c} \sim 10^{4}$ G and magnetic reconnection power $\dot{W_{B}} \sim 10^{43}$ erg s$^{-1}$, with $\sim 50\%$ efficiency in proton acceleration. Unlike previous studies, we find that both particle acceleration and emission take place in the inner region, where protons reach $\sim 10^{14}$ eV via first-order Fermi acceleration within the turbulent reconnection layer, rather than drift acceleration. These protons interact with disk photons, coronal X-rays, and coronal protons, producing neutrinos, predominantly via $pp$ interactions, at levels consistent with IceCube detections. The associated gamma-rays are attenuated by $γγ$ annihilation, remaining below current upper limits. Turbulence-driven reconnection is thus a viable mechanism for neutrino production in the coronal region of NGC 1068 and similar sources.

astro-ph.HE↗

arXiv2026

High-Energy Neutrino Emission in NGC1068 driven by Turbulent Magnetic Reconnection

Astrophysical neutrinos from Active Galactic Nuclei (AGN) offer a unique window into high-energy particle acceleration in obscured environments. The nearby Type II Seyfert galaxy NGC 1068 is a compelling example, exhibiting evidence of a high-energy neutrino excess without an associated TeV $γ$-ray counterpart. This suggests that hadronic processes may occur within an inner, magnetically dominated region, where the TeV emission is suppressed by $γγ$ absorption and reprocessed via electromagnetic cascades in the dense, obscured environment. Building on our framework, which establishes turbulence-driven magnetic reconnection as the main driver for particle acceleration in this source, we present a refined lepto-hadronic model based on de Gouveia Dal Pino & Lazarian (2005) and Kadowaki et al. (2015). In these proceedings, we adopt a conservative inner disk radius compared to our previous results, moving the acceleration region further from the innermost stable circular orbit. We estimate the high-energy neutrino emission from hadronic and photo-hadronic processes, constrained by the acceleration timescale for first-order Fermi acceleration within the turbulent current sheet. The estimated model reproduces the IceCube neutrino flux excess, providing an essential technical complement and validation for our forthcoming comprehensive publication.

astro-ph.HE↗

arXiv2025

Optical and UV Flares from Binary Black Hole Mergers in Active Galactic Nuclei

Stellar mass, binary black hole (BBH) mergers dominates the sources of gravitational wave (GW) events so far detected by the LIGO/Virgo/KAGRA (LVK) experiment. The origin of these BBHs is unknown, and no electromagnetic (EM) counterpart has been undoubtedly associated to any of such GW events. The thin discs of active galactic nuclei (AGNs) might be viable environments where BBHs can form and at the same time produce observable radiation feedback. This paper presents new physically motivated light-curve (LC) solutions for thermal flares driven by the remnant of a BBH merger within the disc of an AGN. Following previous analyses, we consider that the BBH likely creates an under-density cavity in the disc prior to its coalescence. Depending on the merger conditions, the black hole (BH) remnant can leave the cavity, interact with the unperturbed disc, and drive a transient BH wind. The wind expels disc material that expands above and below the disc plane and we consider the emission of these plasma ejections as the EM counterpart to the merger GW. We model the LC of such eruptions as mini supernovae explosions finding that stellar mass merger remnants can drive distinguishable flares in optical and UV bands, with time lags of $\sim 10-100$ days after the GW event, when occurring in AGN with central engines of $\sim 10^{6-8}$ M$_\odot$. The Vera C. Rubin Observatory can potentially detect the optical component of these EM counterparts up to redshifts of $z \sim 0.7 - 1.2$, accordingly. The present model provide constraints on multi-messenger observables, such as the binary effective spin, mass ratio, remnant mass, and the time delay of the EM signature. These constraints are useful to localise flaring AGNs as sources of multi-messenger emission following GW alerts.

astro-ph.HE↗