arXiv subjects

Vojtech Simon

Publications and source records attributed to Vojtech Simon.

3 recordsLinked to original sources

arXiv2026

GRINTA: a new Probe of the Dynamic Universe

Recent observations of the transient sky at all wavelengths are increasingly revealing the importance of the multi-messenger and multi-wavelength approach. The GRINTA (Gamma-Ray INternational Transient Array Observatory) mission, proposed for launch around the middle of the next decade, is conceived as a small mission with good sensitivity, excellent angular resolution and fast follow-up capability for studying transient sources at timescales from ms to hours, at the same time ensuring optimal integration with multi-messenger networks. The GRINTA mission will carry two complementary payloads to cover in total the 5 keV-10 MeV band, that will detect and localise gamma-ray bursts covering $\sim$ half of the sky and will be able to perform imaging surveys with sub-arcmin resolution. GRINTA will operate in synergy with the most powerful electromagnetic, gravitational wave and neutrino observatories foreseen to be operational after 2035.

astro-ph.IM↗

arXiv2022

The activity of the post-nova V1363 Cyg on long timescales

V1363 Cyg is a cataclysmic variable (CV) and a post-nova. Our analysis of its long-term optical activity used the archival data from the AAVSO database and literature. We showed that the accretion disk of V1363 Cyg is exposed to the thermal-viscous instability (TVI) for at least part of the time. The time fraction spent in the high state or the outbursts dramatically changed on the timescale of decades. Highly variable brightness of V1363 Cyg displayed several episodes of a strong brightening (bumps in the light curve) from a cool disk in the TVI zone. In the interpretation, their vastly discrepant decay rates show that only some of these bumps can be attributed to the dwarf nova outbursts without strong irradiation of the disk by the hot white dwarf. The Bailey relation of the decay rate, if ascribed to a DN outburst of V1363 Cyg, speaks in favor of its orbital period $P_{\rm orb}$ very long for a CV, about 20-40 hr. A dominant cycle length of about 435 d was present in the brightness changes all the time, even when the disk was well inside the TVI zone. We interpret it as modulation of the companion's mass outflow by differential rotation of the active region(s).

astro-ph.HE↗

arXiv2021

The activity of the dwarf nova RU Pegasi with rapidly changing outburst types

RU Peg is a dwarf nova (DN) of the U Gem type. Our analysis of its long-term optical activity uses the data from the AAVSO database. It concentrates on investigating the properties of the individual outbursts and the time evolution of the ensemble of these events. No significant irradiation of the disc by the white dwarf was detected. In the interpretation, a variable steepness of the rising branches of the individual outbursts shows that the start of outbursts of RU Peg can occur at various distances from the disc centre without remarkable changes of the outburst recurrence time $T_{\rm C}$. The disc overflow of the inflowing mass stream, varying with time, could contribute to the changes in the starting position of the heating front, hence the variations of the outburst types. A typical length of $T_{\rm C}$ was 90 days. The segments of the relatively stable length of $T_{\rm C}$ were accompanied by the primarily little variable and small values of the fluence (the energy radiated in the optical band in the individual outbursts). Jumps of $T_{\rm C}$, accompanied by the big scatter of the fluences, sometimes replaced them. In the interpretation, a combination of variations of $T_{\rm C}$ with the unstable properties of the outbursts, including an unstable mass transfer rate between the components, shows the influence of several mechanisms on the state of the disc in various time segments.

astro-ph.HE↗