H-alpha photometry of dwarf K and M stars - Chromospheric activity

Herbst, W.; Miller, J. Michael

doi:10.1086/115035

Cited by 31 publications

(33 citation statements)

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“…Stauffer & Hartmann (1986) found an H α EW of 0.40 Å. Herbst & Miller (1989) found 0.44 Å, Herbst & Layden (1987) found 0.36 Å, and here we also find 0.36±0.05 Å. This is a weak H α EW according to Paper VI.…”

Section: Gl 908supporting

confidence: 79%

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Observation and modelling of main sequence star chromospheres

Houdebine¹,

Junghans²,

Heanue

et al. 2009

A&A

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Aims. We report on high resolution observations of chromospheric lines for M and K dwarfs. Methods. We observed up to 13 spectral lines per star: the H α , H β , H , Pa , Pa 8 , CaII H, CaII IR triplet, CaI 6572Å, NaI D 1 /D 2 and HeI D 3 lines. We observed two dMe stars, one dM(e) star, 5 dM stars and 3 dK stars. Results. We observed a self-reversal in the emission core of the CaII H line for the brightest stars only, indicating a rather optically thick region of formation. We present original spectra of the NaI doublet and the CaII IR triplet for active dMe stars and less active dM stars. Core emission is detected in the Sodium lines and the CaII IR triplet lines for the most active M dwarf AU Mic. We investigate the difference spectra between active dMe stars and dM stars and show that these provide interesting new constraints for the NLTE-radiation transfer modelling of the chromospheres. In our sample, emission H α profiles have a rather homogeneous FWHM of about 1.5 Å. This, according to our previous modelling, can be interpreted as the signature of a rather constant temperature break in the chromosphere. We found that one of our targets (MCC 332) is a binary with a faint but active H α emission component. For the first time we detect the Pa line for six dwarfs. It appears as weak absorption with possible weak wing emission in AU Mic. The region of the Pa 8 line was observed but the line was not detected.

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Section: Gl 908supporting

confidence: 79%

“…They also measured an H α equivalent width of 750 mÅ. Herbst & Miller (1989) performed some H α photometry and measured an H α equivalent width of 850 mÅ. Here we report a significantly smaller equivalent width of 650 ± 50 mÅ.…”

Section: Gl 664mentioning

confidence: 50%

Observation and modelling of main sequence star chromospheres

Houdebine¹,

Junghans²,

Heanue

et al. 2009

A&A

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“…We have calculated the Hα luminosity (L Hα ) for our sample as in Herbst & Miller (1989) and Hodgkin et al (1995). The ratio of L Hα to bolometric luminosity (L Hα /L bol ) is independent of the surface area and represents the fraction of the total energy output in Hα.…”

Section: K7 M0mentioning

confidence: 99%

Lithium and Hαin stars and brown dwarfs ofσ Orionis

Osorio

Béjar

Pavlenko

et al. 2002

A&A

156

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Abstract. We present intermediate-and low-resolution optical spectra around Hα and Li i λ6708Å for a sample of 25 low mass stars and 2 brown dwarfs with confirmed membership in the pre-main sequence stellar σ Orionis cluster. Our observations are intended to investigate the age of the cluster. The spectral types derived for our target sample are found to be in the range K6-M8.5, which corresponds to a mass interval of roughly 1.2-0.02 M on the basis of state-of-the-art evolutionary models. Radial velocities (except for one object) are found to be consistent with membership in the Orion complex. All cluster members show considerable Hα emission and the Li i resonance doublet in absorption, which is typical of very young ages. We find that our pseudo-equivalent widths of Hα and Li i (measured relative to the observed local pseudo-continuum formed by molecular absorptions) appear rather dispersed (and intense in the case of Hα) for objects cooler than M3.5 spectral class, occurring at the approximate mass where low mass stars are expected to become fully convective. The least massive brown dwarf in our sample, S Ori 45 (M8.5, ∼0.02 M ), displays variable Hα emission and a radial velocity that differs from the cluster mean velocity. Tentative detection of forbidden lines in emission indicates that this brown dwarf may be accreting mass from a surrounding disk. We also present recent computations of Li i λ6708Å curves of growth for low gravities and for the temperature interval (about 4000-2600 K) of our sample. The comparison of our observations to these computations allows us to infer that no lithium depletion has yet taken place in σ Orionis, and that the observed pseudo-equivalent widths are consistent with a cluster initial lithium abundance close to the cosmic value. Hence, the upper limit to the σ Orionis cluster age can be set at 8 Myr, with a most likely value around 2-4 Myr.

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“…Spectral classes (Col. 4) are from different older sources and, after "/", from homogeneous classification by Hawley et al (1996). Equivalent widths of the H-alpha emission line approximated to 0.1Å for 321 stars from Hawley et al (1996) and, marked by asterisks, from spectral data of Stauffer & Hartmann (1986) and from photometric measurements by Herbst & Miller (1989) are given in Col. 5. UBV photometric data are listed in Cols.…”

Section: Catalogue Descriptionmentioning

confidence: 99%