S Dor-Type Variables in Other Galaxies

Sharov, A. S.

doi:10.1017/s007418090001038x

Cited by 11 publications

(14 citation statements)

References 16 publications

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“…Some of the S Dor variables in M 31 and M 33 also show an activity lasting at least 100 yr (AF And in M 31,Var.A in M 33), others are only active at intervals of 20 yr (e.g. Var.C in M 33) in between periods of quiescence lasting a few decades (Hubble & Sandage 1953;Sharov 1975Sharov , 1990Rosino & Bianchini 1973;Humphreys et al 1988).…”

Section: The Duration Of Maximum and Minimum Statementioning

confidence: 99%

S Doradus variables in the Galaxy and the Magellanic Clouds

Genderen¹

2001

A&A

196

105

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Abstract. The goal in writing this paper is five fold: (1) to summarize the scientific achievements in the 20th century on S Dor variables (or LBVs); (2) to present an inventory of these variables in the Galaxy and the Magellanic Clouds with a description of their physical state and instability properties; (3) to emphasize the photometric achievements of the various types of instabilities. Generally this seems to be a neglected item resulting in a number of misunderstandings continuously wandering through literature; (4) to investigate the structure of the S Dor-area on the HR-diagram; (5) to estimate the total numbers of S Dor variables in the three stellar systems. The position of the strong active S Dor variables in minimum brightness obey the following linear relation on the HR-diagram:log L/L = 1.37 log T eff − 0.03. The relatively small dispersion of less active and supposed exand dormant S Dor variables with respect to this relation is twice as large at the blue side than at the red side. This might be caused by evolution to the WR stage and/or to high rotation. S Dor variables can be subject to five types of instabilities: the very rare genuine eruptive episodes (the "SD-eruptions"), two different brightening phases caused by slow pulsations (the "SD-phases"): one on a time scale of years, the other on a time scale of decades at a more or less constant luminosity and two types of microvariations: one on a time scale of weeks, the other on a time scale of about 100 d. So far, no periodicities of light curve characteristics of any of these instabilities have ever been found. The durations of active and non-active stages are estimated for about half of the sample based on scattered magnitude estimations such as from historical records, and on modern monitoring campaigns. It would be a misunderstanding to believe that all S Dor variables should be always spectacular. It is estimated that most of them will not be spectacular at all for at least 70% of their lifetime as an S Dor variable.

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Section: The Duration Of Maximum and Minimum Statementioning

confidence: 99%

S Doradus variables in the Galaxy and the Magellanic Clouds

Genderen¹

2001

A&A

196

105

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“…The values of 1.6 mag/kpc and 114 pc were accepted for a 0 and β, respectively, according to Sharov's (1963) study. Malkov & Kilpio (2002) have shown that this map, although rather old, quite adequately represents interstellar extinction for relatively short (up to 1 kpc) distances, where most of orbital binaries reside.…”

Section: The Orbit List Compilationmentioning

confidence: 99%

Dynamical masses of a selected sample of orbital binaries

Malkov

Tamazian

Docobo

et al. 2012

A&A

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Orbital binary stars are essential objects for determining dynamical and physical properties of stars through a combined analysis of photometric and astrometric data. We compiled a set of orbital binaries with known trigonometric parallaxes and orbits of high quality, using data from current versions of the Catalogue of Orbits and Ephemerides of Visual Double Stars and the Sixth Catalog of Orbits of Visual Binary Stars as well as including updated information from WDS and SIMBAD. We constructed distributions of orbital binaries among dynamical mass, period, semi-major axis, and eccentricity of systems, which characterize the set. Some problems related to the parameterization of orbital binaries are also discussed in the paper.

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“…B magnitudes were calculated for data points taken from Hubble & Sandage (1953), Sharov (1973), Rosino & Bianchini (1973), Lovas & Zsoldos (1988), and Sharov (1990). In case no tabulated data existed, m pg data points were extracted from given light curves using DEXTER (Demleitner et al 2001).…”

Section: Historical Data Taken From Literaturementioning

confidence: 99%

Var C: Long-term photometric and spectral variability of a luminous blue variable in M 33

Burggraf

Weis

Bomans

et al. 2015

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Aims. So far the highly unstable phase of luminous blue variables (LBVs) has not been understood well. It is still uncertain why and which massive stars enter this phase. Investigating the variabilities by looking for a possible regular or even (semi-)periodic behaviour could give a hint at the underlying mechanism for these variations and might answer the question of where these variabilities originate. Finding out more about the LBV phase also means understanding massive stars better in general, which have (e.g. by enriching the ISM with heavy elements, providing ionising radiation and kinetic energy) a strong and significant influence on the ISM, hence also on their host galaxy. Methods. Photometric and spectroscopic data were taken for the LBV Var C in M 33 to investigate its recent status. In addition, scanned historic plates, archival data, and data from the literature were gathered to trace Var C's behaviour in the past. Its long-term variability and periodicity was investigated. Results. Our investigation of the variability indicates possible (semi-)periodic behaviour with a period of 42.3 years for Var C. That Var C's light curve covers a time span of more than 100 years means that more than two full periods of the cycle are visible. The critical historic maximum around 1905 is less strong but discernible even with the currently rare historic data. The semi-periodic and secular structure of the light curve is similar to the one of LMC R71. Both light curves hint at a new aspect in the evolution of LBVs.

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S Dor-Type Variables in Other Galaxies

Abstract: The variability of these objects, almost the brightest ones found in galaxies, is discussed, followed by a description of colour indices and spectra. In the last sections the classification problems and items for further investigation are mentioned.

Cited by 11 publications

References 16 publications

S Doradus variables in the Galaxy and the Magellanic Clouds

S Doradus variables in the Galaxy and the Magellanic Clouds

Dynamical masses of a selected sample of orbital binaries

Var C: Long-term photometric and spectral variability of a luminous blue variable in M 33

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