scholarly journals Flare stars in nearby Galactic open clusters based on TESS data

2021 ◽  
Vol 51 (1) ◽  
Author(s):  
O. Maryeva ◽  
K. Bicz ◽  
C. Xia ◽  
M. Baratella ◽  
P. Čechvala ◽  
...  
Keyword(s):  
Open Clusters ◽  
Flare Stars

scholarly journals Use of CCDs in Schmidt Telescopes for the Investigation of Hα Emission of Flare Stars

1995 ◽  
Vol 148 ◽  
pp. 60-64
Author(s):  
Gábor Szécsényi-Nagy
Keyword(s):  
Open Clusters ◽  
Good Resolution ◽  
Focal Surface ◽  
Stellar Flares ◽  
Recent Developments ◽  
Traditional Mode ◽  
Hα Emission ◽  
Flare Stars ◽  
Characteristic Features ◽  
Silicon Based

AbstractThe use of Schmidt telescopes in their traditional mode for the detection of stellar flares and for the UV and PG photometry of these stars proved to be very productive. The fast optical system and reliable sensitivity of modern photographic emulsions resulted in a photometric time-resolution of several minutes even in the case of distant objects. One of the most important characteristics of flare stars may be the tendency for coexistence with more massive and more luminous member stars of young stellar aggregates (mainly open clusters). Although the vast majority of flare stars discovered seem to belong to clusters, a great many of them are neighbours of our sun. These can be investigated in depth because a sufficient number of their photons can be collected and recorded in narrow photometric bands or even in spectra of good resolution. The direct comparison of solar vicinity flare stars with flare-active members of distant clusters has been almost impossible. However recent developments in silicon-based photon-detecting technology offer the advantage of incredibly high detector quantum efficiency (DQE) in many spectral regions where photographic materials never reached an acceptable level. Hα emission is one of the most characteristic features of flare stars, and the wavelength of Hα photons fits extremely well with the peak of the spectral sensitivity curves of silicon photon detectors. CCD chips placed in the focal surface of Schmidt telescopes seem to be very promising for the future investigation of Hα emission of flare stars.

scholarly journals Flare Stars in Star Clusters and Associations

1975 ◽  
Vol 67 ◽  
pp. 1-14 ◽  
Author(s):  
V. A. Ambartsumian ◽  
L. V. Mirzoyan
Keyword(s):  
Stellar Evolution ◽  
Star Clusters ◽  
Open Clusters ◽  
Point Of View ◽  
Flare Activity ◽  
Theoretical Point ◽  
Star Clusters And Associations ◽  
Stellar Flare ◽  
Dwarf Stars ◽  
Flare Stars

The study of stellar evolution can be undertaken either from a purely theoretical point of view or from a more observational approach. The present standpoint is the second one. It starts from the concepts of stellar evolution in associations and open clusters and from stellar flare activity. Statistical considerations show that flare activity is a regular stage in the evolution of stars through which all the dwarf stars go.

scholarly journals Flare stars as age indicators in open clusters

1990 ◽  
Vol 137 ◽  
pp. 117-120
Author(s):  
L. Pigatto
Keyword(s):  
Chemical Composition ◽  
Age Determination ◽  
Absolute Magnitude ◽  
New Age ◽  
Open Clusters ◽  
Flare Star ◽  
Evolutionary Models ◽  
Evolutionary Implication ◽  
Flare Stars

A new set of isochrones derived from overshooting evolutionary models, allows one to give a homogeneous age determination for open clusters with solar chemical composition and in a range of age 4 107 ÷ 1.5 109 yr. In this context is derived an empirical new age calibration - absolute magnitude of the supposed brightest flare star in a cluster versus log age -. The evolutionary implication in finding or not finding flare stars in candidate open clusters is also examined.

scholarly journals On the Applicability of Fibre-Fed Multi-Object Spectrographs in Flare Star Research

1995 ◽  
Vol 148 ◽  
pp. 85-89
Author(s):  
Gábor Szécsényi-Nagy
Keyword(s):  
Near Infrared ◽  
Focal Length ◽  
Open Cluster ◽  
Variable Stars ◽  
Open Clusters ◽  
Flare Star ◽  
Spectral Studies ◽  
Wide Field ◽  
New Device ◽  
Flare Stars

AbstractThe use of optical fibres has recently allowed the full field of some Schmidt telescopes to be accessed for multi-object spectroscopy. The new device: the MOS (multi-object spectrograph) is to revolutionize the field of astronomical spectroscopy. Cosmic objects grouped into aggregates having apparent angular diameters of 1 to 6 degrees and similar apparent brightness in the visual or near infrared spectral range are to be the most probable future targets of MOSs. Flare stars — as it has been demonstrated convincingly by various authors (see Szecsenyi-Nagy 1986, and references therein) — are the most abundant type of variable stars but because of their low luminosity and relatively late discovery we have only very limited amount of spectroscopic data about most of these objects. It is a real bonanza that most of the catalogued flare stars are associated with young open clusters and this fact of course suggests them as really promising targets for wide-field Schmidt cameras equipped with MOSs. In an average open cluster scrutinized for its flare star members some dozen or some hundred representatives of this species are known which are distributed over a sky field of 10–20 square degrees. Fortunately, they are never packed into unresolvable concentrations and even short focal length cameras are able to produce separate images of all cluster member flare stars for an accurate photographic photometry of the objects. The apparent visual brightness of these stars most often fits a 5–7 magnitude range. This seems to be profitable also for the effectiveness of using fibre-fed MOSs in flare star spectroscopy. The first steps of such a program should be the study of radial velocities and the comparison of the measured values with the accepted radial velocity of the cluster. These measurements could provide new and independent arguments for (or against?) the cluster membership of the flare stars observed in the fields of catalogued open clusters. Later, more detailed spectral studies should collect information about the time dependent features of the spectra of flare stars.

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 Data filtering in statistical studies of flares recorded in sky fields of stellar aggregates - demonstrated with the example of the Pleiades

1990 ◽  
Vol 137 ◽  
pp. 71-76
Author(s):  
G. Szécsényi-Nagy
Keyword(s):  
Statistical Modelling ◽  
Individual Characteristics ◽  
Open Clusters ◽  
Data Sets ◽  
Active Object ◽  
Probable Number ◽  
Statistical Studies ◽  
Flare Stars ◽  
Complete Catalogue ◽  
Common Field

Photometric data on flares of cluster flare stars published by different observers were - as a rule - collected during decades by different instruments and amidst various conditions. The uncritical use of these data in global statistical studies is usually unfair since such a collection is an indefinite mixture of high and low quality results. In order to make these investigations more reliable even the best and most complete photometric catalogues have to be filtered.The first step of the procedure described in the paper is rejecting all flare events having too small amplitudes - seeing that they are under-represented in the catalogue as opposed to medium and large amplitude flares. Then the photographic coverage of the aggregate has to be checked and all events observed in partially covered regions have to be excluded. Next any non-randomness in the time distribution of flares of each active object is to be unveiled and flares of the doubtful stars have to be omitted. Finally some objects are to be rejected for their individual characteristics.The usefulness of the method is demonstrated with the example of the Pleiades, one of the richest open clusters known. More than 3000 hours of effective observing time has been devoted to flare photometry in fields centered upon Eta Tauri and the outcome of the programme the CPFS - the most complete catalogue of flare stars of the region - contains data of 519 flare stars and their 1532 flare events. Earlier versions of this catalogue or subsets of its data have been used to estimate the probable number of flare stars in the Pleiades region. Results of these attempts range from 600 to 2700 partly owing to the unreliability and incompatibility of the data sets. The method presented here is able to give much more reliable estimates but of course in the limited largest common field (LCF) only. As a result of the filtering the LCF contains 77% of the objects and 67% of the flares listed in the CPFS. Time sequence analysis of the 1026 flare events observed on 402 flare stars and statistical modelling of the phenomena suggested in an earlier paper fit each other almost perfectly.The conclusion of the study is that the most likely number of flare stars in the reach of the telescopes used in this programme is between 520 and 600 in the LCF of the Eta Tauri fields. Their average flare frequency is about 1/2400h and the CPFS lists 70% of these objects. In order to be able to compare the Pleiades field flare stars and those of other aggregates the method of filtering will be carried out throughout the analysis of the most extended data sets available.

Search for Southern Open Cluster Flare Stars: M7, IC 2602, IC 2391 and NGC 2516

1991 ◽  
Vol 9 (2) ◽  
pp. 277-278 ◽  
Author(s):  
K. L. Jones ◽  
A. A. Page
Keyword(s):  
Open Cluster ◽  
Open Clusters ◽  
Flare Stars

AbstractWe summarise the results, to date, of a long-term program of searching for flare stars in the region of open clusters selected on the basis of distance and age.

Observations of neutral hydrogen in open clusters

1967 ◽  
Vol 31 ◽  
pp. 41-43
Author(s):  
Th. Schmidt-Kaler ◽  
R. Schwartz
Keyword(s):  
Neutral Hydrogen ◽  
Open Clusters

Neutral hydrogen is found in every young cluster observed, usually extending beyond the optical diameter, and in some cases showing expanding motions.

A Search for Microflaring Activity on dMe Flare Stars. II. Observations of YZ Canis Minoris

1999 ◽  
Vol 516 (2) ◽  
pp. 916-923 ◽  
Author(s):  
R. D. Robinson ◽  
K. G. Carpenter ◽  
J. W. Percival
Keyword(s):  
Flare Stars
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