scholarly journals GCVS Problems with Flare Stars

1995 ◽  
Vol 151 ◽  
pp. 416-418
Author(s):  
Elena V. Kazarovets ◽  
Nikolai N. Samus
Keyword(s):  
Globular Clusters ◽  
Variable Star ◽  
Star Clusters ◽  
Fold Increase ◽  
Variable Stars ◽  
Star Clusters And Associations ◽  
The Past ◽  
The Status ◽  
Flare Stars ◽  
New Variables

The astrometric aspect of cataloguing variable stars becomes more and more important. During the past thirty years there has been approximately an three-fold increase of the number of known variables; now the rate of new discoveries becomes extremely high, and we may expect a new twofold increase in a couple of years due to discoveries made with space-borne instruments. To avoid confusion, we should continue our policy of naming new variables, and this is impossible without checking identifications with known variable stars, requiring good coordinates and/or finding charts. Operation of automatic telescopes also needs excellent coordinates just for pointing. For all these reasons, we are now working on improving considerably the accuracy standard of variable star coordinates, providing at least reasonably good coordinates for extragalactic variables (GCVS, 4th Edition, Vol. V, now in press, gives coordinates mainly to a second of arc) and variables in globular clusters, identifying variables, including those with rough published positions, with positional catalogues, etc.Flare stars are very important variables; potentially they are one of the most abundant types of variable stars. Their identification in minimum light may be rather complicated, especially for dense regions of star clusters and associations. Most regretfully, there are many cases of papers on flare stars introducing additional confusion connected with wrong designations, wrong coordinates, missing finding charts. Thus, there appear problems preventing us from incorporating some flare stars in the GCVS. Many definite variables remain in the status of “suspects”, being positionally close to known variables, and no finding chart being available either for the earlier known variable or for the new one. Sometimes we do include such a “pretender” into the GCVS, and years after a finding chart or good coordinates appear, and it turns out that we have two entries for the same star (see, for instance, numerous cases of duplicated names for flare stars in Taurus in the GCVS Vol. III).

scholarly journals Commission 37: Star Clusters and Associations

1982 ◽  
Vol 18 (1) ◽  
pp. 499-526
Keyword(s):  
Globular Cluster ◽  
Working Group ◽  
Globular Clusters ◽  
Star Clusters ◽  
Open Clusters ◽  
General Assembly ◽  
Active Period ◽  
Star Clusters And Associations ◽  
The Past ◽  
Good Number

The past triennium has been a very active period in most branches of cluster research. Some controversial subjects, notably globular cluster abundances and ages have received much attention. A good number of photometric papers on clusters as well as associations have been published. Observational effects of mass loss have been discussed by several astronomers.This report has been assembled by the president of the commission although several sections have been contributed by other members. The report will first list some highlights in the activities of our commission. Then follow the tables containing current investigations of OB associations, open clusters and globular clusters. These have been assembled by B. Balázs, G. Harris and R. White, respectively. After these tables comes a section by D. Heggie about dynamics of star clusters. A working group under the chairmanship of A. Moffat has made a proposal about the numbering of stars in clusters. The proposal, which is included here will be discussed by our commission at the IAU General Assembly.

scholarly journals Future of the General Catalogue of Variable Stars from the Experience of Recent Name-lists

2021 ◽  
Vol 30 (1) ◽  
pp. 122-126
Author(s):  
Nikolay N. Samus ◽  
Elena V. Kazarovets ◽  
Olga V. Durlevich ◽  
Natalia N. Kireeva ◽  
Elena N. Pastukhova ◽  
...  
Keyword(s):  
Globular Clusters ◽  
Variable Star ◽  
Star Clusters ◽  
Positional Information ◽  
Variable Stars ◽  
Photometric Data ◽  
Star Data ◽  
General Catalogue ◽  
The Future ◽  
History Of

Abstract We briefly outline the history of the General Catalogue of Variable Stars (GCVS) and the New Catalogue of Suspected Variable Stars (NSV catalogue). Recently, we have completed a revision of the NSV catalogue. Positional information was checked for all its stars and, in many cases, new photometric data were added. As a result, one third of all NSV stars have been transferred to the GCVS. Having determined equatorial coordinates for variable stars in globular star clusters, we began to add them to the GCVS. Two Name-lists published so far contain more than 1700 variable stars in 36 globular clusters; an additional Name-list (about 900 variable stars in 27 globular clusters) will be published before the end of 2021. We discuss problem cases in the literature and in the Catalogue of Variable Stars in Galactic Globular Clusters revealed during our preparation of the Name-lists. The future of traditional catalogues of variable stars (GCVS; AAVSO Variable-star Data Index VSX) is discussed.

scholarly journals Observations of low mass stars in clusters: Some constraints and puzzles for stellar evolution theory

1984 ◽  
Vol 105 ◽  
pp. 123-138
Author(s):  
R.D. Cannon
Keyword(s):  
Globular Clusters ◽  
Main Sequence ◽  
Star Clusters ◽  
Variable Stars ◽  
Open Clusters ◽  
Low Mass Stars ◽  
Theory Of Evolution ◽  
Theoretical Predictions ◽  
Low Mass ◽  
Red Giant

This review will attempt to do two things: (i) discuss some of the data which are available for testing the theory of evolution of low mass stars, and (ii) point out some problem areas where observations and theory do not seem to agree very well. This is of course too vast a field of research to be covered in one brief review, so I shall concentrate on one particular aspect, namely the study of star clusters and especially their colour-magnitude (CM) diagrams. Star clusters provide large samples of stars at the same distance and with the same age, and the CM diagram gives the easiest way of comparing theoretical predictions with observations, although crucial evidence is also provided by spectroscopic abundance analyses and studies of variable stars. Since this is primarily a review of observational data it is natural to divide it into two parts: (i) galactic globular clusters, and (ii) old and intermediate-age open clusters. Some additional evidence comes from Local Group galaxies, especially now that CM diagrams which reach the old main sequence are becoming available. For each class of cluster I shall consider successive stages of evolution from the main sequence, up the hydrogen-burning red giant branch, and through the helium-burning giant phase.

scholarly journals Star Clusters in Irregular Galaxies in the Local Group

2002 ◽  
Vol 207 ◽  
pp. 94-104
Author(s):  
Eva K. Grebel
Keyword(s):  
Globular Clusters ◽  
Local Group ◽  
Cluster Formation ◽  
Star Clusters ◽  
Open Clusters ◽  
High Angular Resolution ◽  
Star Clusters And Associations ◽  
Star Forming ◽  
Star Forming Regions ◽  
Irregular Galaxies

I summarize our knowledge of star clusters and associations in irregular galaxies other than the Magellanic Clouds in the Local Group. Surveys affording complete area coverage at high angular resolution are still lacking. Confirmed globular clusters are known only in NGC 6822 and WLM. Very few dIrrs contain populous or sparse open clusters. There is a pronounced deficiency of intermediate-age and young clusters. Apart from parent galaxy mass, the lack of interactions may be a key reason for the lack of cluster formation in the dIrrs. All dIrrs have one or several short-lived OB associations in the star-forming regions in their centers.

scholarly journals The Red Dwarf Star Population in the Galaxy

1995 ◽  
Vol 151 ◽  
pp. 55-56 ◽  
Author(s):  
L.V. Mirzoyan
Keyword(s):  
Star Clusters ◽  
Space Distribution ◽  
Dwarf Star ◽  
Star Clusters And Associations ◽  
Dwarf Stars ◽  
The Galaxy ◽  
Flare Stars ◽  
Red Dwarf Stars ◽  
T Tau ◽  
Stellar Associations

Red dwarf stars in the Galaxy occur in three forms: as flare stars, T Tau stars and red dwarf stars of constant brightness. Haro (1957) suggested that all these stars present regular evolutionary stages of red dwarf stars.The space distribution of UV Cet flare stars in the solar vicinity indicates that these low luminosity stars belong to the disk population of the Galaxy. Therefore one can suppose that all red dwarf stars have a space distribution which is similar to that of the flare stars (Mirzoyan et al. 1988a). Only a small part of them is found in star clusters and associations. The T Tau stars are an exception: because of their very short lifetime, all of them are found in stellar associations.The space distribution of red dwarf stars is determined by the fact that all of them are formed in star clusters and associations and are finally lost from their stellar systems and merge into the general galactic field (Mirzoyan 1995).

scholarly journals CCD VI time-series of the extremely metal-poor globular cluster M92: revisiting its variable star population

2020 ◽  
Vol 494 (3) ◽  
pp. 3212-3226 ◽  
Author(s):  
M A Yepez ◽  
A Arellano Ferro ◽  
D Deras
Keyword(s):  
Time Series ◽  
Globular Cluster ◽  
Variable Star ◽  
Variable Stars ◽  
Frequency Spectra ◽  
Fourier Decomposition ◽  
Rr Lyrae ◽  
Blazhko Effect ◽  
New Variables ◽  
Gaia Dr2

ABSTRACT We present an analysis of VI CCD time-series photometry of the Oo II type globular cluster M92. The variable star population of the cluster is studied with the aim of revising their classifications, identifications, frequency spectra, and to select indicators of the parental cluster metallicity and distance. The Fourier decomposition of RR Lyrae light curves lead to the estimation of mean [Fe/H]spec = −2.20 ± 0.18 and distance of 8.3 ± 0.2 kpc. Four new variables are reported: one RRd (V40), a multimode SX Phe (V41), an SR (V42), and one RRc (F1) that is most likely not a cluster member. The AC nature of V7 is confirmed. The double mode nature of the RRc star V11 is not confirmed and its amplitude modulations are most likely due to the Blazhko effect. Two modes are found in the known RRc variable V13. It is argued that the variable V30, previously classified as RRab is, in fact, a BL Her-type star not belonging to the cluster. Using the Gaia-DR2 proper motions, we identified 5012 stars in the field of the cluster, which are very likely cluster members, and for which we possess photometry, enabling the production of a refined colour–magnitude diagram. This also allowed us to identify a few variable stars that do not belong to the cluster. The RR Lyrae pulsation modes on the HB are cleanly separated by the first overtone red edge, a common feature in all Oo II-type clusters.

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.

Variable star clusters. New variable stars.

1898 ◽  
Vol 7 ◽  
pp. 208 ◽  
Author(s):  
E. C. Pickering ◽  
S. I. Bailey ◽  
W. P. Fleming ◽  
E. F. Leland ◽  
L. D. Wells
Keyword(s):  
Variable Star ◽  
Star Clusters ◽  
Variable Stars

scholarly journals COMMISSION 27: VARIABLE STARS

2008 ◽  
Vol 4 (T27A) ◽  
pp. 254-259
Author(s):  
Steven D. Kawaler ◽  
Gerald Handler ◽  
Conny Aerts ◽  
Timothy R. Bedding ◽  
Márcio Catelán ◽  
...  
Keyword(s):  
Search Engines ◽  
Variable Star ◽  
Time Frame ◽  
Variable Stars ◽  
The Past ◽  
On Line

The Organizing Committee of Commission 27 has decided to again provide a somewhat abbreviated bibliography as part of this triennial report, as astronomy-centered search engines and on-line publications continue to blossom. We focus on selected highlights in variable star research over the past three years. Further results can be found in numerous proceedings of conferences held in the time frame covered by this report.

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