arXiv subjects

Rudolf Gális

Publications and source records attributed to Rudolf Gális.

12 recordsLinked to original sources

arXiv2026

New Online Database of Symbiotic Variables: Catalog and Statistical Overview of Symbiotic Binaries

We present the New Online Database of Symbiotic Variables (NODSV), a comprehensive and publicly accessible catalog of known and candidate symbiotic stars in the Milky Way and nearby galaxies. The database provides an up-to-date census of confirmed symbiotic binaries and systematically compiles information previously scattered across the literature, including photometric and spectroscopic properties, orbital parameters, and characteristics of both their cool and hot stellar components. It further records auxiliary diagnostics such as detected emission lines, flickering, X-ray emission, jets, or information about outburst activity. In its current release, NODSV contains nearly 1 400 objects, classified into confirmed symbiotic stars, three categories of candidates, and misidentified sources. Based on the collected data, though originating from heterogeneous studies, we present a statistical overview of the confirmed symbiotic population, highlighting the distributions of orbital parameters and the properties of the cool giants and their hot companions. Designed as a dynamic and evolving resource, NODSV provides a foundation for future observational campaigns and theoretical investigations of symbiotic binaries.

astro-ph.SR↗

arXiv2023

The thermal history of the intergalactic medium at $3.9 \leq z \leq 4.3$

A new determination of the temperature of the intergalactic medium over $3.9 \leq z \leq 4.3$ is presented. We applied the curvature method on a sample of 10 high resolution quasar spectra from the Ultraviolet and Visual Echelle Spectrograph on the VLT/ESO. We measured the temperature at mean density by determining the temperature at the characteristic overdensity, which is tight function of the absolute curvature irrespective of $γ$. Under the assumption of fiducial value of $γ= 1.4$, we determined the values of temperatures at mean density $T_{0} = 7893^{+1417}_{-1226}$ K and $T_{0} = 8153^{+1224}_{-993}$ K for redshift range of $3.9 \leq z \leq 4.1$ and $4.1 \leq z \leq 4.3$, respectively. Even though the results show no strong temperature evolution over the studied redshift range, our measurements are consistent with an intergalactic medium thermal history that includes a contribution from He II reionization.

astro-ph.CO↗

arXiv2022

Gaia22eor: Symbiotic star V2756 Sgr detected in a deep eclipse

V2756 Sgr is a long-known S-type symbiotic binary that was recently detected in $\sim$ 1 mag eclipse-like fading by the Gaia satellite. This behavior was reported as a Gaia Science Alert under the designation Gaia22eor. V2756 Sgr has not been reported as an eclipsing symbiotic system. In this contribution, we have investigated the recent light curves of this target obtained by Gaia and ASAS-SN survey and supplemented these data by the photometry from the ASAS survey and DASCH archive. In addition, low-resolution BP/RP spectra from Gaia were examined. Based on the presented analysis, we conclude that the observed fading is indeed an eclipse of the hot component of V2756 Sgr by the cool giant. The data also allowed us to refine the orbital period to 725 $\pm$ 3 days.

astro-ph.SR↗

arXiv2022

DeGaPe 35: Amateur discovery of a new southern symbiotic star

In this work, we present the discovery and characterization of a new southern S-type symbiotic star, DeGaPe 35. We have obtained the low-resolution spectroscopic observations and supplemented them with photometry from Gaia DR3 and other surveys. The optical spectra of this target show prominent emission lines, including highly ionized [Fe VII] and O VI lines. The cool component of this symbiotic binary is an M4-5 giant with effective temperature ~ 3 380 - 3 470 K and luminosity ~ 3 000 L$_\odot$ (for the adopted distance of 3 kpc). The hot component is a shell-burning white dwarf. The photometric observations of the Gaia satellite, published recently in the Gaia DR3 suggested the variability with the period of about 700 - 800 days that we tentatively attributed to the orbital motion of the binary.

astro-ph.SR↗

arXiv2021

Thermal state of the intergalactic medium near to the optical limit for the Ly-$α$ forest

In this article, the temperature-density relation of the intergalactic medium was studied in the region $1.6 \leq z < 2.0$ divided into two bins. For this purpose, the Ly-$α$ forest decomposition into individual absorption profiles was used for the study of 35 publicly available quasar spectra obtained by the Ultraviolet and Visual Echelle Spectrograph (UVES) on the Very Large Telescope (ESO) and by the High Resolution Echelle Spectrometer (HIRES) on the Keck Telescope. For the determination of the thermal state sensitive cut-off position in the $b - N_{HI}$ distribution, the iterative fitting procedure was adopted. The measurements were calibrated using mock Ly-$α$ forest data generated by 23 hydrodynamical simulations with different thermal histories. The value of the temperature at mean density corresponds to the decreasing trend predicted by various models at the lower redshifts. In the case of power law index, determined values are close to 1.6, which is expected after all reionization events in various models assuming the balance of photoheating with adiabatic cooling.

astro-ph.CO↗

arXiv2020

The nature of the symbiotic candidate 2MASS J07363415+6538548 in the field of NGC 2403

New Online Database of Symbiotic Variables includes several poorly characterised objects and candidate symbiotic stars, not only in the Milky Way but also in other galaxies. The goal of the research presented in this paper was to reveal the nature of 2MASS J07363415+6538548, the object discovered as an X-ray source in the field of NGC 2403, and tentatively classified as a symbiotic candidate or a cataclysmic variable. By analysis of available photometric data from ground-based surveys, together with high precision photometry from TESS, remarkable astrometric measurements of the Gaia satellite, and observations of other surveys spanning from X-rays to infrared, we have found that the object is not a symbiotic star nor a cataclysmic variable but rather an active K-type dwarf. The star is located in the distance of 415 pc, has an effective temperature of 4 275 K, luminosity of 0.14 L$\odot$, a mass of 0.7 M$\odot$, and radius of 0.7 R$\odot$. It has a rotational period ~ 3 days and is a strong X-ray source with the X-ray luminosity of ~ $10^{30}$ erg/s. Gyrochronology and isochrone fitting confirmed that the star is young.

astro-ph.SR↗

arXiv2020

Yellow symbiotic star AG Draconis in the scope of the New Online Database of Symbiotic Variables

Symbiotic stars are strongly interacting binaries, consisting of a white dwarf and a cool giant, mainly of spectral type M. AG Draconis belongs to a less numerous group of the yellow symbiotic systems, as the cool component in this binary is of a spectral type earlier than K4. Recently, after seven years of quiescence, this symbiotic star exhibited a very unusual active stage with the four minor outbursts observed. Thanks to the excellent involvement of amateur astronomers and professional observatories, we can study the activity of AG Draconis in unprecedented details. In the present work, we discuss the activity and peculiarities of this interacting system within the entire group of symbiotic stars whose properties have recently been presented in our New Online Database of Symbiotic Variables.

astro-ph.SR↗

arXiv2019

The activity of the symbiotic binary Z Andromedae and its latest outburst

Z Andromedae is a prototype of classical symbiotic variable stars. It is characterized by alternating of quiescent and active stages, the later ones are accompanied by changes in both photometry and spectral characteristics of this object. The current activity of Z And began in 2000, and the last outburst was recorded at the turn of the years 2017 and 2018. An important source of information about the behaviour of this symbiotic binary during the ongoing active stage is photometric and spectroscopic observations obtained with small telescopes by amateur astronomers. In this paper, we present the results of analysis of these observations, with an emphasis on the significant similarity of the last outburst of Z And with the previous ones, during which jets from this symbiotic system were observed. The presented results point to the importance of long-term monitoring of symbiotic binaries.

astro-ph.SR↗

arXiv2019

The peculiar outburst activity of the symbiotic binary AG Draconis

AG Draconis is a strongly interacting binary system which manifests characteristic symbiotic activity of alternating quiescent and active stages. The latter ones consist of the series of individual outbursts repeating at about a one-year interval. After seven years of flat quiescence following the 2006-2008 major outbursts, in the late spring of 2015, the symbiotic system AG Dra started to become brighter again toward what appeared to be a new minor outburst. The current outburst activity of AG Dra was confirmed by the following three outbursts in April 2016, May 2017 and April 2018. The photometric and spectroscopic observations suggest that all these outbursts are of the hot type. Such behaviour is considerably peculiar in almost 130-year history of observing of this object, because the major outbursts at the beginning of active stages are typically cool ones. In the present work, the current peculiar activity of the symbiotic binary AG Dra is described in detail.

astro-ph.SR↗

arXiv2018

Recent outburst activity of the symbiotic binary AG Draconis

The symbiotic binary AG Dra regularly undergoes quiescent and active stages which consist of several outbursts repeating with about 360d interval. The recent outburst activity of AG Dra started by the minor outburst in the late spring of 2015 and was definitely confirmed by the outbursts in April 2016 and May 2017. In the presented work, the photometric and spectroscopic behaviour of the recent outburst activity of AG Dra is presented in detail. Moreover, the temperature of the white dwarf in AG Dra is studied based on the behaviour of the prominent emission lines. We show that a disentanglement of particular effects in the observed changes of the emission lines is crucial to investigate the intrinsic white dwarf temperature variations related to outburst activity of this strongly interacting binary. We also report the effects of the low excitation lines orbital variations and of the H$_β$ absorption component on their equivalent widths as well as consequences of the approximations used in our previous works.

astro-ph.SR↗

arXiv2017

Recent outburst activity of the super-soft X-ray binary AG Draconis

AG Draconis is a bright symbiotic binary consisting of a white dwarf and a pulsating cool giant. Moreover, it is the most intense X-ray source among symbiotic stars, and one of the best representatives of the super-soft X-ray objects. The system undergoes characteristic symbiotic activity with alternating quiescent and active stages. The active ones consist of several outbursts repeating at about a one-year interval. The recent activity stage of AG Dra began with the weak pre-outburst in 2015 followed by a more prominent outburst in 2016. According to photometric and some spectroscopic observations, both brightenings belong to the minor (hot) outbursts of AG Dra. Such behavior of the active stage is quite unusual because more often, the activity of AG Dra starts with a major (cool) outburst. Moreover, the behavior of Raman scattered OVI lines at λ 6825 Å and λ 7082 Å suggest that the minor outburst of AG Dra in April 2016 has the characteristics of both the hot and cool outbursts. Based on the above, an open question is the next evolution of activity of the symbiotic binary AG Dra in 2017 and beyond.

astro-ph.SR↗

arXiv2015

Spectroscopic view on the outburst activity of the symbiotic binary AG Draconis

Variations of the emission lines in the spectrum of the yellow symbiotic star AG Dra have been studied for over 14 years (1997 - 2011), using more than 500 spectra obtained on the 1.5-metre telescope at Tartu Observatory, Estonia. The time interval covered includes the major (cool) outburst of AG Dra that started in 2006. Main findings can be summarized as follows: (i) cool and hot outbursts of AG Dra can be distinguished from the variations of optical emission lines; (ii) the Raman scattered emission line of O VI at $λ\,6825$ almost disappeared during the cool outburst; (iii) lower excitation emission lines did not change significantly during the cool outburst, but they vary in hot outbursts and also follow orbital motion; (iv) similarity of variations in AG Dra to those in the prototypical symbiotic star Z And allows to suggest that a "combination nova" model proposed for the latter object might also be responsible for the outburst behaviour of AG Dra.

astro-ph.SR↗