Stellar model chromospheres. XII. High-resolution, absolute flux profiles of the Ca II H and K lines in dMe and non--dMe stars
We present 142 mA resolution spectra of the cores and wings of the Ca II H and K lines in three dMe and four comparison dwarf M stars, obtained with the KPNO 4 m echelle spectrograph and blue image tube. The narrow-band photometry of Willstrop and the Barnes and Evans relations for stellar angular diameters convert the observed relative flux to absolute surface flux units with an estimated uncertainty of +- 15%. We derive chromospheric radiative loss rates in the H and K lines and discuss trends in these loss rates with effective temperature. Monochromatic surface fluxes are tabulated for different features in the H and K lines, and radiation temperatures are derived from the mean surface fluxes at K/sub 1/ and H/sub 1/, respectively. We find T/sub R/(H/sub 1/)>T/sub R/(K/sub 1/), consistent with partial redistribution theory. The T/sub R/(K/sub 1/)/T/sub eff/ ratio is higher in these M dwarfs than the giants studied in Paper X, and it is anomalously high for the dMe flare star YZ CMi. If T/sub R/(K/sub 2/)/T/sub eff/ is an empirical age indicator, then the result for YZ CMi implies that flare activity and youth are directly correlated, as has been suggested by other investigators. Moreover, the result implies that a high degree of nonradiative heating is present in the upper photospheres of dMe stars. Measurements of line widths at H/sub 1/ and K/sub 1/ are presented together with FWHM data for the H and K lines. We find that the scaling law proposed by Ayres generally agrees with the observed trend exhibited by the K/sub 1/ widths. We also discuss chromospheric radiative loss rates in the Hepsilon line compared with loss rates in the H and K lines, and present corrected FWHM(K) widths and compare them to the widths predicted by the Wilson-Bappu relation as calibrated by Lutz.
- Research Organization:
- Steward Observatory, University of Arizona; and Joint Institute for Laboratory Astrophysics, National Bureau of Standards and University of Colorado
- OSTI ID:
- 6184878
- Journal Information:
- Astrophys. J.; (United States), Vol. 246:2
- Country of Publication:
- United States
- Language:
- English
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GENERAL PHYSICS
DWARF STARS
ENERGY SPECTRA
STELLAR ATMOSPHERES
VARIABLE STARS
CALCIUM IONS
EMISSION
LINE WIDTHS
RADIATION FLUX
STELLAR FLARES
ATMOSPHERES
CHARGED PARTICLES
IONS
SPECTRA
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640102* - Astrophysics & Cosmology- Stars & Quasi-Stellar
Radio & X-Ray Sources