A Copernicus survey of MG II emission in late-type stars

Weiler, E. J.; Oegerle, W. R.

doi:10.1086/190585

Cited by 38 publications

(12 citation statements)

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“…(2) indicates that dwarf stars have an excess of Mg  k luminosity which increases with increasing magnitude. Equation (2) is in very good agreement with the result of Weiler & Oegerle (1979) based on stars brighter than M V = 4 but it is quite different from our fit in Paper II because this last was performed on the whole sample of dwarfs and giants together. Other authors (e.g.…”

Section: Line Intensity-luminosity Relationsupporting

confidence: 81%

“…The last Column is according to CABS except for TZ Tri and IL Hya (see Montes et al 1995 andFekel et al 1999 respectively). Weiler & Oegerle 1979;Basri & Linsky 1979) report, on the basis of a sample mainly containing giant and supergiant stars and only few dwarfs, that the ratio of the Mg  flux rate to stellar luminosity is not dependent on stellar luminosity. On the basis of the present analysis, we confirm that this is true only for evolved stars but is not true for main sequence stars.…”

Section: Hip Namementioning

confidence: 99%

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Mg II chromospheric radiative loss rates in cool active and quiet stars

Cardini¹

2005

A&A

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Abstract. The Mg  k emission line is a good indicator of the level of chromospheric activity in late-type stars. We investigate the dependence of this activity indicator on fundamental stellar parameters. To this purpose we use IUE observations of the Mg  k line in 225 late-type stars of luminosity classes I-V, with different levels of chromospheric activity. We first re-analyse the relation between Mg  k line luminosity and stellar absolute magnitude, performing linear fits to the points. The ratio of Mg  surface flux to total surface flux is found to be independent of stellar luminosity for evolved stars and to increase with decreasing luminosity for dwarfs. We also analyse the Mg  k line surface flux-metallicity connection. The Mg  k emission level turns out to be not dependent on metallicity. Finally, the Mg  k line surface flux-temperature relation is investigated by treating separately, for the first time, a large sample of very active and normal stars. The stellar surface fluxes in the k line of normal stars are found to be strongly dependent on the temperature and slightly dependent on the gravity, thus confirming the validity of recently proposed models. In contrast, data relative to RS CVn binaries and BY Dra stars, which show very strong chromospheric activity, are not justified in the framework of a description based only on acoustic waves and uniformly distributed magnetic flux tubes so that they require more detailed models.

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Section: Line Intensity-luminosity Relationsupporting

confidence: 81%

Section: Hip Namementioning

confidence: 99%

Mg II chromospheric radiative loss rates in cool active and quiet stars

Cardini¹

2005

A&A

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“…Relationships similar to the "Wilson-Bappu effect" were subsequently found for other resonance lines, such as Mg ii k 2796 and Ly 1216 (McClintock et al, 1975;Weiler and Oegerle, 1979). Numerous explanations were advanced, but Ayres (1979), using scaling laws for the extent and density of the chromosphere, argued that the Wilson-Bappu width is "a stellar barometer, not a tachometer"; i.e., rather than arising from details of chromospheric flows, it is primarily a hydrostatic equilibrium acting in concert with the partial ionization of hydrogen and resonance line cooling to postpone the onset of the sharp thermal instability that gives rise to the corona.…”

Section: Long-term Observations Of Ca II H and Ksupporting

confidence: 57%

Stellar Chromospheric Activity

Hall

2008

Living Rev. Solar Phys.

167

131

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The Sun, stars similar to it, and many rather dissimilar to it, have chromospheres, regions classically viewed as lying above the brilliant photosphere and characterized by a positive temperature gradient and a marked departure from radiative equilibrium. Stellar chromospheres exhibit a wide range of phenomena collectively called activity, stemming largely from the time evolution of their magnetic fields and the mass flux and transfer of radiation through the complex magnetic topology and the increasingly optically thin plasma of the outer stellar atmosphere. In this review, I will (1) outline the development of our understanding of chromospheric structure from 1960 to the present, (2) discuss the major observational programs and theoretical lines of inquiry, (3) review the origin and nature of both solar and stellar chromospheric activity and its relationship to, and effect on, stellar parameters including total energy output, and (4) summarize the outstanding problems today.

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“…A similar relationship has been obtained by Weiler & Oegerle (1979) from OAO 3 moderate-resolution (0.51 Å) observations of 73 late-type stars. The difference in the coefficients might be ascribed to the different resolution and accuracy level of the two space experiments or, more likely, to the mixture of quiet and active stars in their sample.…”

Section: Normal Starssupporting

confidence: 84%

A study of the Mg II 2796.34 Å emission line in late–type normal and RS CVn stars

Cardini

Cassatella

Badiali

et al. 2003

A&A

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Abstract.We carry out an analysis of the Mg  2796.34 Å emission line in RS CVn stars and make a comparison with the normal stars studied in a previous paper (Paper I). The sample of RS CVn stars consists of 34 objects with known HIPPARCOS parallaxes and observed at high resolution with IUE. We confirm that RS CVn stars tend to possess wider Mg  lines than normal stars having the same absolute visual magnitude. However, we could not find any correlation between the logarithmic line width log W • and the absolute visual magnitude M V (the Wilson-Bappu relationship) for these active stars, contrary to the case of normal stars addressed in Paper I. On the contrary, we find that a strong correlation exists in the (M V , log L Mg ii ) plane (L Mg ii is the absolute flux in the line). In this plane, normal and RS CVn stars are distributed along two nearly parallel straight lines with RS CVn stars being systematically brighter by ≈1 dex. Such a diagram provides an interesting tool to discriminate active from normal stars. We finally analyse the distribution of RS CVn and of normal stars in the (log L Mg ii , log W • ) plane, and find a strong linear correlation for normal stars, which can be used for distance determinations.

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A Copernicus survey of MG II emission in late-type stars

Cited by 38 publications

References 0 publications

Mg II chromospheric radiative loss rates in cool active and quiet stars

Mg II chromospheric radiative loss rates in cool active and quiet stars

Stellar Chromospheric Activity

A study of the Mg II 2796.34 Å emission line in late–type normal and RS CVn stars

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