H-alpha photometry of dwarf K and M stars

Abstract

view Abstract Citations (37) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Hα Photometry of Dwarf K and M Stars Herbst, William ; Layden, Andrew C. Abstract Hα photometry of 188 dM and dK stars has been obtained with the Perkin telescope at Van Vleck Observatory. The photometric index, N-W, has been calibrated using 56 stars with equivalent widths determined spectroscopically by Stauffer and Hartmann (1986). An external standard error of 0.08 Å is found for the equivalent width (EW) measurements of non-emission stars; it may be higher for those with emission lines. The distribution of stars in the N-W, R-I plane is discussed. Most lie along a single "main sequence" of absorption which slopes up towards 0 EW with increasing R-I. Eighteen dKe or dMe stars are found, all clearly separated from the absorption sequence. The absorption EWs are large compared with expectation based on photospheric models, indicating either that the models are in error or that chromospheres are present in essentially all late-type dwarfs. Three stars (Gl 182, Gl 873AB, and Gl 890) were found to vary significantly in N-W. All are emission stars, and the variability can probably be attributed to flares. Publication: The Astronomical Journal Pub Date: July 1987 DOI: 10.1086/114457 Bibcode: 1987AJ.....94..150H Keywords: Dwarf Stars; H Alpha Line; K Stars; M Stars; Stellar Spectrophotometry; Variable Stars; Emission Spectra; Hertzsprung-Russell Diagram; Main Sequence Stars; Stellar Magnitude; Astrophysics; STARS: ABUNDANCES; STARS: SPECTRAL CLASSIFICATION full text sources ADS | data products SIMBAD (171)