arXiv subjects

L. Combi

Publications and source records attributed to L. Combi.

3 recordsLinked to original sources

arXiv2023

Non-thermal radiation from dual jet interactions in supermassive black hole binaries

Supermassive black hole binaries (SMBHBs) are natural by-products of galaxy mergers and are expected to be powerful multi-messenger sources. They can be powered by the accretion of matter and then radiate across the electromagnetic spectrum, much like normal active galactic nuclei (AGNs). Current electromagnetic observatories have a good chance of detecting and identifying these systems in the near future. However, precise observational indicators are needed to distinguish individual AGNs from SMBHBs. In this paper, we propose a novel electromagnetic signature from SMBHBs: non-thermal emission produced by the interaction between the jets ejected by the black holes. We study close SMBHBs, which accrete matter from a circumbinary disc and the mini-discs formed around each hole. Each black hole ejects a magnetically dominated jet in the direction of its spin through the Blandford--Znajeck mechanism. We argue that in such a situation, the interaction between the jets can trigger strong magnetic reconnection events, where particles are accelerated and emit non-thermal radiation. Depending on whether the jets are aligned or misaligned, this radiation can have different periodicities. We model the evolution of the particles accelerated during the dual jet interaction and calculate their radiative output, obtaining spectra and providing estimates for the variability timescales. We finally discuss how this emission compares with that of normal AGNs.

astro-ph.HE↗

arXiv2020

PSR J0437-4715: The Argentine Institute of Radioastronomy 2019-2020 Observational Campaign

The Argentine Institute of Radio astronomy (IAR) is equipped with two single-dish 30-m radio antennas capable of performing daily observations of pulsars and radio transients in the southern hemisphere at 1.4 GHz. We aim to contribute to pulsar timing studies related to short time-scale interstellar scintillation and searches for sources of continuous gravitational waves. We performed high-cadence (almost daily) and long-duration observations of the bright millisecond pulsar J0437$-$4715 for over a year, gathering more than 700 hours of good-quality data with timing precision better than 1~$\mu$s. We characterize the white and red timing noise in IAR's observations of J0437$-$4715. We quantify the effects of scintillation in this data set and perform single pulsar searches of continuous gravitational waves, setting constraints in the nHz--$\mu$Hz frequency range. We demonstrate IAR's potential for performing pulsar monitoring in the 1.4 GHz radio band for long periods of time with a daily cadence. In particular, we conclude that the ongoing observational campaign of the millisecond pulsar J0437$-$4715 can contribute to increase the sensitivity of the existing pulsar timing arrays.

astro-ph.GA↗

arXiv2019

Upgraded antennas for pulsar observations in the Argentine Institute of Radio astronomy

The Argentine Institute of Radio astronomy (IAR) is equipped with two single-dish 30mts radio antennas capable of performing daily observations of pulsars and radio transients in the southern hemisphere at 1.4 GHz. We aim to introduce to the international community the upgrades performed and to show that IAR observatory has become suitable for investigations in numerous areas of pulsar radio astronomy, such as pulsar timing arrays, targeted searches of continuous gravitational waves sources, monitoring of magnetars and glitching pulsars, and studies of short time scale interstellar scintillation. We refurbished the two antennas at IAR to achieve high-quality timing observations. We gathered more than $1\,000$ hours of observations with both antennas to study the timing precision and sensitivity they can achieve. We introduce the new developments for both radio telescopes at IAR. We present observations of the millisecond pulsar J0437$-$4715 with timing precision better than 1~$\mu$s. We also present a follow-up of the reactivation of the magnetar XTE J1810--197 and the measurement and monitoring of the latest (Feb. 1st. 2019) glitch of the Vela pulsar (J0835--4510). We show that IAR is capable of performing pulsar monitoring in the 1.4 GHz radio band for long periods of time with a daily cadence. This opens the possibility of pursuing several goals in pulsar science, including coordinated multi-wavelength observations with other observatories. In particular, observations of the millisecond pulsar J0437$-$4715 will increase the gravitational wave sensitivity of the NANOGrav array in their current blind spot. We also show IAR's great potential for studying targets of opportunity and transient phenomena such as magnetars, glitches, and fast-radio-burst sources.

astro-ph.IM↗