Measurements of Starspot Parameters on Active Stars using Molecular Bands in Echelle Spectra

Details Measurements of Starspot Parameters on Active Stars using Molecular Bands in Echelle Spectra Measurements of Starspot Parameters on Active Stars using Molecular Bands in Echelle Spectra

Nov 1998

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998apj...507..919o&link_type=abstract

The Astrophysical Journal, Volume 507, Issue 2, pp. 919-937.

Astronomy and Astrophysics

Astronomy

44

Stars: Binaries: Spectroscopic, Stars: Activity, Stars: Fundamental Parameters, Stars: Late-Type, Stars: Spots

Scientific paper

We present results from a study of starspot areas (f_S) and temperatures (T_S), primarily on active, single-lined spectroscopic binaries, determined using molecular absorption bands. Expanding upon our previous studies, we have analyzed multiorder echelle spectra of eight systems to simultaneously measure several different molecular bands and chromospheric emission lines. We determined starspot parameters by fitting the molecular bands of interest, using spectra of inactive G and K stars as proxies for the nonspotted photosphere of the active stars, and using spectra of M stars as proxies for the spots. At least two bands with different T_eff sensitivities are required. We found that fitting bands other than the TiO 7055 and 8860 Å features does not greatly extend the temperature range or sensitivity of our technique. The 8860 Å band is particularly important because of its sharply different temperature sensitivity. We did not find any substantial departures from f_S or T_S that we have measured previously based on single-order spectra. We refined our derived spot parameters using contemporaneous photometry where available. We found that using M giants as spot proxies for subgiant active stars often underestimates f_S needed to fit the photometry; this is presumably due to the increase in strength of the TiO bands with decreasing gravity. We also investigated correlations between f_S and chromospheric emission, and we developed a simple method to measure nonspot temperature (T_Q) solely from our echelle spectra.

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