arXiv subjects

J. Benáček

Publications and source records attributed to J. Benáček.

9 recordsLinked to original sources

arXiv2026

Understanding Pulsar Magnetospheres with the SKAO

The SKA telescopes will bring unparalleled sensitivity across a broad radio band, a wide field of view across the Southern sky, and the capacity for sub-arraying, all of which make them the ideal instruments for studying the pulsar magnetosphere. This chapter describes the advances that have been made in pulsar magnetosphere physics over the last decade, and details how these have been made possible through the advances of modern radio telescopes, particularly SKA precursors and pathfinders. It explains how the SKA telescopes would transform the field of pulsar magnetosphere physics through a combination of large-scale monitoring surveys and in-depth follow-up observations of unique sources and new discoveries. Finally, it describes how the specific observing opportunities available with the AA* and AA4 configurations will achieve the advances necessary to solve the problem of pulsar radio emission physics in the coming years.

astro-ph.HE↗

arXiv2025

A broadband study of FRB20240114A with the Effelsberg 100-m radio telescope

We present Effelsberg 100-m telescope observations of the hyperactive repeating fast radio burst source FRB 20240110A, discovered by CHIME/FRB in January 2024. Using the Ultra BroadBand (UBB) receiver, spanning 1.3-6.0 GHz, we detected over 700 unique bursts across four observing epochs. A comprehensive analysis of their temporal and spectral properties reveals four distinct spectro-temporal morphologies, including simple, complex and frequency-drifting structures. No bursts were detected across the full UBB band, confirming the band-limited emission typical of repeating FRBs. We find modest frequency evolution in burst widths but constant fractional bandwidths, and strong variability in burst rates that may be influenced by scintillation. The waiting-time distributions indicate predominantly independent burst events, with occasional clustering suggesting a characteristic emission timescale of $\sim$10 ms. Additionally, this study presents a multi-frequency analysis of waiting-time distributions, offering new insights into the complex frequency drifts commonly observed in repeating FRBs. These broadband observations provide a detailed view of the frequency-dependent burst behavior of FRB 20240110A and offer insights into the variability and temporal structure of repeating FRB emission.

astro-ph.HE↗

arXiv2025

Dispersion properties of neutron star magnetospheric plasmas with relativistic kappa distribution

The various distribution functions can encompass the diverse characteristics of the magnetospheric plasma of surrounding neutron stars in both hot and cold environments; however, the Maxwell-Jüttner distribution is so far widely used to characterize these plasmas. We aim to analyze the linear dispersion properties yielded from the relativistic kinetic dispersion relation for the neutron star magnetospheric plasmas. We developed a numerical dispersion solver to investigate plasmas with arbitrary velocity distributions and focus on the comparison of relativistic kappa and Maxwell-Jüttner distribution functions as analytical representatives. By considering different kappa distribution indices and using analytical and numerical approaches, the dispersion properties of the kappa and Maxwell-Jüttner distributions approach each other for high wave numbers and low temperatures, indicating that the choice of distribution functions has little effect on high wave numbers $ck/ω_p \gg 1$ and high inverse temperatures $ρ=100$. However, each distribution function exhibits unique yet complementary properties in semi-relativistic to relativistic inverse temperatures $ρ\leq 10^{-1}$ and at lower wave numbers $ck/ω_p\leq 1$. This highlights the necessity of utilizing such a dispersion solver for these wave numbers to properly comprehend the dispersion properties of the neutron star magnetospheric plasmas.

astro-ph.HE↗

arXiv2024

Science with a small two-band UV-photometry mission II: Observations of stars and stellar systems

We outline the impact of a small two-band UV-photometry satellite mission on the field of stellar physics, magnetospheres of stars, binaries, stellar clusters, interstellar matter, and exoplanets. On specific examples of different types of stars and stellar systems, we discuss particular requirements for such satellite missions in terms of specific mission parameters such as bandpass, precision, cadence, and mission duration. We show that such a mission may provide crucial data not only for hot stars that emit most of their light in UV, but also for cool stars, where UV traces their activity. This is important, for instance, for exoplanetary studies, because the level of stellar activity influences habitability. While the main asset of the two-band UV mission rests in time-domain astronomy, an example of open clusters proves that such a mission would be important also for the study of stellar populations. Properties of the interstellar dust are best explored when combining optical and IR information with observations in UV. It is well known that dust absorbs UV radiation efficiently. Consequently, we outline how such a UV mission can be used to detect eclipses of sufficiently hot stars by various dusty objects and study disks, rings, clouds, disintegrating exoplanets or exoasteroids. Furthermore, UV radiation can be used to study the cooling of neutron stars providing information about the extreme states of matter in the interiors of neutron stars and used for mapping heated spots on their surfaces.

astro-ph.SR↗

arXiv2024

Particle-in-cell simulations of electron-positron cyclotron maser forming pulsar radio zebras

The microwave radio dynamic spectra of the Crab pulsar interpulse contain fine structures represented via narrowband quasiharmonic stripes. The pattern significantly constrains any potential emission mechanism. Similar to the zebra patterns observed, for example, in type IV solar radio bursts or decameter and kilometer Jupiter radio emission, the double plasma resonance (DPR) effect of the cyclotron maser instability may allow for interpretion of observations of pulsar radio zebras. We present electromagnetic relativistic particle-in-cell (PIC) simulations of the electron-positron cyclotron maser for cyclotron frequency smaller than the plasma frequency. In four distinct simulation cycles, we focused on the effects of varying the plasma parameters on the instability growth rate and saturation energy. The physical parameters were the ratio between the plasma and cyclotron frequency, the density ratio of the "hot" loss-cone to the "cold" background plasma, the loss-cone characteristic velocity, and comparison with electron-proton plasma. In contrast to the results obtained from electron-proton plasma simulations, we find that the pulsar electron-positron maser instability does not generate distinguishable X and Z modes. On the contrary, a singular electromagnetic XZ mode was generated in all studied configurations close to or above the plasma frequency. For low density ratios, the highest peak of the XZ mode is at double the frequency of the highest peak of the Bernstein modes, indicating that the radio emission is produced by a coalescence of two Bernstein modes with the same frequency and opposite wave numbers. Our estimate of the radiative flux generated from the simulation is up to $\sim$30 mJy from an area of 100 km$^2$ for an observer at 1 kpc distance without the inclusion of relativistic beaming effects, which may account for multiple orders of magnitude.

astro-ph.HE↗

arXiv2024

Science with a small two-band UV-photometry mission I: Mission description and follow-up observations of stellar transients

This is the first in a collection of three papers introducing the science with an ultra-violet (UV) space telescope on an approximately 130~kg small satellite with a moderately fast re-pointing capability and a real-time alert communication system approved for a Czech national space mission. The mission, called Quick Ultra-Violet Kilonova surveyor - QUVIK, will provide key follow-up capabilities to increase the discovery potential of gravitational wave observatories and future wide-field multi-wavelength surveys. The primary objective of the mission is the measurement of the UV brightness evolution of kilonovae, resulting from mergers of neutron stars, to distinguish between different explosion scenarios. The mission, which is designed to be complementary to the Ultraviolet Transient Astronomy Satellite - ULTRASAT, will also provide unique follow-up capabilities for other transients both in the near- and far-UV bands. Between the observations of transients, the satellite will target other objects described in this collection of papers, which demonstrates that a small and relatively affordable dedicated UV-space telescope can be transformative for many fields of astrophysics.

astro-ph.HE↗

arXiv2022

Quick Ultra-VIolet Kilonova surveyor (QUVIK)

We present a near-UV space telescope on a ~70kg micro-satellite with a moderately fast repointing capability and a near real-time alert communication system that has been proposed in response to a call for an ambitious Czech national mission. The mission, which has recently been approved for Phase 0, A, and B1 study shall measure the brightness evolution of kilonovae, resulting from mergers of neutron stars in the near-UV band and thus it shall distinguish between different explosion scenarios. Between the observations of transient sources, the satellite shall perform observations of other targets of interest, a large part of which will be chosen in open competition.

astro-ph.IM↗

arXiv2021

A Survey of Novae in M83

The results of the first synoptic survey of novae in the barred spiral and starburst galaxy, M83 (NGC 5236), are presented. A total of 19 novae and one background supernova were discovered during the course of a nearly seven-year survey comprised of over 200 individual nights of observation between 2012 December 12 and 2019 March 14. After correcting for the limiting magnitude and the spatial and temporal coverage of the survey, the nova rate in M83 was found to be $R=19^{+5}_{-3}$ yr$^{-1}$. This rate, when normalized to the $K$-band luminosity of the galaxy, yields a luminosity-specific nova rate, $ν_K = 3.0^{+0.9}_{-0.6}\times10^{-10}$ yr$^{-1} L_{\odot,K}^{-1}$. The spatial distribution of the novae is found to be more extended than the overall galaxy light suggesting that the observed novae are likely dominated by a disk population. This result is consistent with the observed nova light curves which reveal that the M83 novae are on average more luminous at maximum light and fade faster when compared with novae observed in M31. Generally, the more luminous M83 novae were observed to fade more rapidly, with the complete sample being broadly consistent with a linear Maximum-Magnitude vs Rate of Decline relation.

astro-ph.GA↗

arXiv2015

B.R.N.O. Contributions #39 Times of minima

This paper presents 1463 times of minima for 455 objects acquired by 46 members and cooperating observers of the Variable Star and Exoplanet Section of the Czech Astronomical Society (B.R.N.O. Observing project). Observations were carried out between October 2013 - September 2014. Some neglected southern eclipsing binaries and newly discovered stars by the observers of project B.R.N.O. are included in the list.

astro-ph.SR↗