On the pre-main-sequence nature of the prototype spotted flare star by Draconis

Details On the pre-main-sequence nature of the prototype spotted flare star by Draconis On the pre-main-sequence nature of the prototype spotted flare star by Draconis

Dec 1979

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1979apj...234..958v&link_type=abstract

Astrophysical Journal, Part 1, vol. 234, Dec. 15, 1979, p. 958-963. Research supported by the University of Texas.

Astronomy and Astrophysics

Astrophysics

41

Binary Stars, Flare Stars, Main Sequence Stars, Spectrum Analysis, Stellar Evolution, Stellar Models, Dwarf Stars, High Dispersion Spectrographs, Stellar Luminosity, Stellar Mass, Stellar Rotation

Scientific paper

A series of high-dispersion Reticon spectra of BY Draconis, from which to redetermine its orbit, mass ratio, and luminosity ratio are examined. The mass ratio of primary to secondary is found to be 1.02 plus or minus 0.05, yet the luminosity ratio at lambda 6500 is found to be 1.93 plus or minus 0.3. From a high-resolution coude echelle spectrum, we find V sin i equals 8.5 plus or minus 2 km/s for the primary. This result, in conjunction with the inclination derived from the orbital solution, and the accurately known rotation period (from photometric studies), leads to the unexpectedly large radius of greater than 0.9 solar radii for the dM0e primary. Accurate V and R photometry combined with the Barnes-Evans visual surface brightness relation also support this large value for the primary's radius. These observations indicate that the spotted primary lies slightly above, and is still contracting to, the zero-age main sequence, in support of the hypothesis that the BY Draconis syndrome is a fading remnant of previous T Tauri activity. With a few notable exceptions, spotted dMe flare stars probably represent the final stages of pre-main-sequence evolution at the low-mass end of the T Tauri group.

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