Stellar model chromospheres. XII. High-resolution, absolute flux profiles of the Ca II H and K lines in dMe and non--dMe stars

Journal Article · Mon Jun 01 04:00:00 EDT 1981 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/158950· OSTI ID:6184878

Giampapa, M S; Worden, S P; Schneeberger, T J; Cram, L E

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), Journal Name: Astrophys. J.; (United States) Vol. 246:2; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ATMOSPHERES
CALCIUM IONS
CHARGED PARTICLES
DWARF STARS
EMISSION
ENERGY SPECTRA
IONS
LINE WIDTHS
RADIATION FLUX
SPECTRA
STARS
STELLAR ATMOSPHERES
STELLAR FLARES
VARIABLE STARS