scholarly journals Flare Stars Database

1994 ◽  
Vol 161 ◽  
pp. 380-382
Author(s):  
M. Tsvetkov ◽  
M. Chukova ◽  
K. Tsvetkova
Keyword(s):  
Wide Field ◽  
Flare Activity ◽  
The Galaxy ◽  
Statistical Regularities ◽  
Ceti Type ◽  
Formation And Evolution ◽  
Flare Stars ◽  
Machine Readable

The important role of flare stars (UV Ceti type variables) in astrophysics is due to the fact that the flare activity is not only typical for red stars with small masses but is a necessary stage during their evolution. The flare star search in stellar aggregates has led to the accumulation of rich observational material allowing us to look for statistical regularities in star formation and evolution. At present, there are more than 1500 known flare stars in the Galaxy; these were discovered mainly during the last 30 years. Most results of the long term monitoring with wide-field telescopes are listed in existing catalogues of flare stars in stellar aggregates and in the solar neighbourhood. These catalogues and their machine-readable versions were the basis for the present database of flare stars in the Galaxy.

scholarly journals The formation of brightest cluster galaxies: the case of ABELL 407

2015 ◽  
Vol 48 (1) ◽  
Author(s):  
Louise O.V. Edwards
Keyword(s):  
Galaxy Formation ◽  
Cluster Galaxy ◽  
Cluster Galaxies ◽  
Brightest Cluster Galaxies ◽  
Galaxy Formation And Evolution ◽  
The Galaxy ◽  
Formation And Evolution ◽  
Intracluster Light

This article begins with a general introduction to galaxy formation and evolution and ends with a discussion of the long-term spectroscopic study: The Role of Close Companions in the Formation of Brightest Cluster Galaxies and Intracluster Light. To illustrate the power, goals and aims of this larger project, preliminary data for one of the galaxy clusters in our sample is presented, Abell 407, which appears to be caught in the act of forming its Brightest Cluster Galaxy (BCG).

scholarly journals The Role of Flare Stars in Cosmic-ray Origin

1995 ◽  
Vol 151 ◽  
pp. 185-192
Author(s):  
Maurice M. Shapiro
Keyword(s):  
Alternative Hypothesis ◽  
Cosmic Ray ◽  
Optical Data ◽  
Seed Particles ◽  
Cosmic Ray Acceleration ◽  
The Galaxy ◽  
Flare Stars ◽  
Far Ultraviolet ◽  
Ultraviolet Observations

AbstractSupernovae and their expanding shock fronts are evidently the main agents of cosmic-ray acceleration. The thermal gas in the interstellar medium has been regarded as the reservoir of seed particles destined to become cosmic-ray nuclei. This assumption is, however, at variance with the source composition of galactic cosmic iays. In an alternative hypothesis, the seed particles are injected into the interstellar material as suprathermal seed ions, and it has been surmised that flare stars provide the initial boost. We find that the dMe and dKe stars are probably the principal sources of cosmic-ray seed particles. Most stars in the Galaxy are red dwarfs and many of these flares much more powerfully and frequently than solar flares. Augmenting the optical data, recent X-ray and far-ultraviolet observations now permit a better estimate of the energy budget. Altogether, dMe and dKe stars seem to be the most promising class of cosmic-ray injectors.

scholarly journals Young and Old Subsystems of Flare Stars

1995 ◽  
Vol 151 ◽  
pp. 63-64
Author(s):  
L.V. Mirzoyan ◽  
V.V. Hambarian
Keyword(s):  
Evolutionary Status ◽  
Wide Field ◽  
Flare Activity ◽  
Multiple Systems ◽  
Star Evolution ◽  
Orion Association ◽  
Evolutionary Connection ◽  
Long Time ◽  
Flare Stars ◽  
T Tau

Photographic observations with wide-field telescopes of flare stars in the Orion association and the Pleiades cluster have been carried out since 40 years. About 500 flare stars were found in each of these systems. The ages of these stellar systems differ by one or two orders of magnitude (Mirzoyan 1991). This fact allows us to compare them, in order to show that they fit into the concept, suggested first by Haro (1957), that the evolutionary status of flare stars is a stage of red dwarf star evolution which follows that of the T Tau stars (Haro 1976, Ambartsumian & Mirzoyan 1970).The basic difference between the Orion and Pleiades subsystems of flare stars has been known for a long time: the coexistence of flare stars and T Tau stars in the Orion association, and the absence of the latter group in the Pleiades. Some of the T Tau stars show flare activity (Haro 1964). This fact and the existence of multiple systems of trapezium type, which are dynamically unstable, in the Orion association, are arguments in favour of an evolutionary connection between these two types of stars.

scholarly journals RR Lyrae stars as probes of the Milky Way structure and formation

2015 ◽  
Vol 11 (S317) ◽  
pp. 116-119
Author(s):  
Pawel Pietrukowicz ◽  
Keyword(s):  
Galactic Center ◽  
Variable Stars ◽  
Wide Field ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
The Galaxy ◽  
First Results ◽  
Formation And Evolution ◽  
Lyrae Stars ◽  
Distance Indicators

AbstractRR Lyrae stars being distance indicators and tracers of old population serve as excellent probes of the structure, formation, and evolution of our Galaxy. Thousands of them are being discovered in ongoing wide-field surveys. The OGLE project conducts the Galaxy Variability Survey with the aim to detect and analyze variable stars, in particular of RRab type, toward the Galactic bulge and disk, covering a total area of 3000 deg2. Observations in these directions also allow detecting background halo variables and unique studies of their properties and distribution at distances from the Galactic Center to even 40 kpc. In this contribution, we present the first results on the spatial distribution of the observed RRab stars, their metallicity distribution, the presence of multiple populations, and relations with the old bulge. We also show the most recent results from the analysis of RR Lyrae stars of the Sgr dwarf spheroidal galaxy, including its center, the globular cluster M54.

scholarly journals Clocking the formation of today’s largest galaxies: wide field integral spectroscopy of brightest cluster galaxies and their surroundings

2019 ◽  
Vol 491 (2) ◽  
pp. 2617-2638 ◽  
Author(s):  
Louise O V Edwards ◽  
Matthew Salinas ◽  
Steffanie Stanley ◽  
Priscilla E Holguin West ◽  
Isabella Trierweiler ◽  
...  
Keyword(s):  
Velocity Dispersion ◽  
Minor Component ◽  
High Signal ◽  
Wide Field ◽  
Cluster Galaxies ◽  
Brightest Cluster Galaxies ◽  
The Galaxy ◽  
Formation And Evolution ◽  
Intracluster Light ◽  
A Minor

ABSTRACT The formation and evolution of local brightest cluster galaxies (BCGs) is investigated by determining the stellar populations and dynamics from the galaxy core, through the outskirts and into the intracluster light (ICL). Integral spectroscopy of 23 BCGs observed out to $4\, r_{e}$ is collected and high signal-to-noise regions are identified. Stellar population synthesis codes are used to determine the age, metallicity, velocity, and velocity dispersion of stars within each region. The ICL spectra are best modelled with populations that are younger and less metal-rich than those of the BCG cores. The average BCG core age of the sample is $\rm 13.3\pm 2.8\, Gyr$ and the average metallicity is $\rm [Fe/H] = 0.30\pm 0.09$, whereas for the ICL the average age is $\rm 9.2\pm 3.5\, Gyr$ and the average metallicity is $\rm [Fe/H] = 0.18\pm 0.16$. The velocity dispersion profile is seen to be rising or flat in most of the sample (17/23), and those with rising values reach the value of the host cluster’s velocity dispersion in several cases. The most extended BCGs are closest to the peak of the cluster’s X-ray luminosity. The results are consistent with the idea that the BCG cores and inner regions formed quickly and long ago, with the outer regions and ICL forming more recently, and continuing to assemble through minor merging. Any recent star formation in the BCGs is a minor component, and is associated with the cluster cool core status.

scholarly journals Photometric Research of Pre-flare and Extra-flare Activity of Flare Stars

1995 ◽  
Vol 151 ◽  
pp. 110-111
Author(s):  
G. Roizman ◽  
L. Pustil’nik ◽  
D. Pundak
Keyword(s):  
Spectral Lines ◽  
Flare Star ◽  
Flare Activity ◽  
Jordan Valley ◽  
Preliminary Results ◽  
Regional College ◽  
Flare Stars ◽  
Ev Lac ◽  
Low Amplitude

Preliminary results of a photometric search for non-flare activity of the flare star EV Lac during June-August 1994 are presented. These observations are part of the long-term project entitled “Investigation of pre-flare processes on flare stars” being carried out at the Observatory of the Jordan Valley Regional College since July 1994. The project was motivated by reports of the existence of slow, low-amplitude non-periodic variability of both spectral lines and continuum outside/between flares (Rodono et al. 1979, Roizman et al. 1984).

scholarly journals A SAURON view of double-barred galaxies

2009 ◽  
Vol 5 (S262) ◽  
pp. 323-324
Author(s):  
Adriana de Lorenzo-Cáceres ◽  
Alexandre Vazdekis ◽  
Jesús Falcón-Barroso ◽  
Inma Martínez-Valpuesta
Keyword(s):  
Galaxy Formation ◽  
Spectroscopic Data ◽  
Stellar Population ◽  
Population Analysis ◽  
Barred Galaxies ◽  
Galaxy Formation And Evolution ◽  
The Galaxy ◽  
Central Regions ◽  
Formation And Evolution

Double bars might be the key mechanisms to transport gas to the very central regions of galaxies, so double-barred galaxies are key objects to better understand the galaxy formation and evolution scenarios. In order to disentangle the role of double bars in the galaxy build up, we are performing a whole kinematical and stellar population analysis of these objects from high S/N spectroscopic data.

scholarly journals Statistical studies of flare stars and other flashing objects carried out at the Byurakan Observatory

2021 ◽  
pp. 150-162
Author(s):  
A. A. Akopian
Keyword(s):  
Open Clusters ◽  
Physical Parameters ◽  
Evolutionary Status ◽  
Flare Activity ◽  
Short Term ◽  
T Tauri ◽  
Statistical Studies ◽  
Flare Stars

The review briefly presents the statistical studies of flare stars and related objects carried out at the Byurakan Astrophysical Observatory, in particular: i) determination of the evolutionary status of flare stars, ii) an explanation of the observed difference between flare stars of the galactic field (type UV Cet) and flare stars of systems (open clusters, associations), iii) the connection between flare stars and T Tauri stars, iv) short-term and long-term (evolutionary) variability of flare activity, v) original statistical methods developed for the study of flare stars and their systems, vi) recent advances in research on flashing objects. This review does not present such important areas of research on flare stars as the determination of physical parameters, photometry and colorimetry of stars and their flares, detailed studies of individual stars, theoretical works on possible mechanisms of flares. These areas were well presented in many books and reviews by Ambartsumian and Mirzoyan.

scholarly journals Wide-Field Photographic Versus Wide-Field CCD Techniques in the Activity Analysis of dM Stars

1994 ◽  
Vol 161 ◽  
pp. 61-64
Author(s):  
G. Szécsényi-Nagy
Keyword(s):  
Variable Stars ◽  
Activity Level ◽  
Wide Field ◽  
Dwarf Stars ◽  
Photoelectric Photometry ◽  
Stellar Flares ◽  
Red Dwarfs ◽  
The Galaxy ◽  
Flare Stars ◽  
Red Dwarf Stars

The Galaxy is abundant in red dwarf stars. According to statistical analyses, their majority is unstable. Simultaneously, more than 60% of the variable stars known in the solar vicinity (r < 20 pc) are flare stars and taking into account the number of BY Dra stars too the proportion of red dwarfs amongst local variables is superior to three quarters. Their absolute visual magnitudes range from +6 to +17.5 or even more (Szécsényi-Nagy 1986a). During flare events their brightness may reach a maximum corresponding to an enhancement of 1000–10,000 times. The amplitude of a large flare in the U band may be as high as 8–10 magnitudes. The events take place nonperiodically in unpredictable moments; no unquestionable periodicity has been found in the time distribution of stellar flares. However the activity level of various flare stars is considerably different. Some of them show observable flare ups with a mean frequency of 1 per hour whilst others produce only one event per annum. For the scarcity of the phenomenon, traditional photoelectric photometry of individual stars is not an adequate means to a better understanding of flare stars.

scholarly journals Flare stars in star clusters, associations and solar vicinity

1990 ◽  
Vol 137 ◽  
pp. 1-13
Author(s):  
L.V. Mirzoyan
Keyword(s):  
Star Clusters ◽  
Evolutionary Stage ◽  
Flare Activity ◽  
Star Clusters And Associations ◽  
Dwarf Stars ◽  
Stellar Flares ◽  
Ceti Type ◽  
Flare Stars ◽  
Red Dwarf Stars ◽  
T Tau

The observational data on flare stars observed in star clusters and associations as well as in the solar vicinity (the UV Ceti type stars) are discussed. The analysis of these data show that they constitute one common class of objects possessing flare activity and the differences between them are conditioned by the age differences. The stage of flare activity is an evolutionary stage, one of the earliest stages of evolution passed by all red dwarf stars. It comes before the end of their T Tau stage of evolution. The UV Ceti type flare stars in the solar vicinity seem to be the population of the general galactic field, which were formed in the systems, already desintegrated. Most probably the stellar flares are the result of the release of the the surplus energy having intra-stellar origin.

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