Astronomy and Astrophysics – Astrophysics
Scientific paper
Sep 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994a%26a...289..169h&link_type=abstract
Astronomy and Astrophysics (ISSN 0004-6361), vol. 289, no. 1, p. 169-184
Astronomy and Astrophysics
Astrophysics
34
Chromosphere, Line Spectra, Main Sequence Stars, Radiative Transfer, Stellar Activity, Stellar Interiors, Stellar Models, Stellar Temperature, Balmer Series, Lyman Spectra, Pressure Distribution, Stellar Spectrophotometry, Temperature Distribution, Turbulence
Scientific paper
In this new series we present observations and modeling of spectral lines formed in main sequence star chromospheres (from G0 to M8). In this paper, we discuss the Hydrogen line formations in very active dMe stellar chromospheres. We present the conclusions drawn from our modeling approach to the AU Mic (dM2e) spectrum. Our final model atmosphere is described in the next paper in this series. Here, we investigate the effects of some stellar (Teff, v sin i) and atmospheric (turbulence, temperature structure) parameters on the line formation. We found that observations are best reproduced by a chromospheric structure including a constant temperature gradient (in a log(M) scale) in the chromosphere and transition region. We show that a very thin transition region is required to account for the observed Ly-alpha to H-alpha surface flux ratio. Then, to drive the Balmer lines into emission and reproduce the H-alpha and H-beta self-reversal and FWHM, the chromospheric gradient and transition region pressure must be quite high for the most active stars. We put forward a complete set of important constraints on the possible structures of such active region atmospheres from 5,000 K to 50,000 K. Finally, we further compare our results to observations and propose some general properties that could be tested with future observations.
Doyle Gerry J.
Houdebine E. R.
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