The active RS Canum Venaticorum binary II Pegasi. I. Stellar and orbital parameters

Details The active RS Canum Venaticorum binary II Pegasi. I. Stellar and orbital parameters The active RS Canum Venaticorum binary II Pegasi. I. Stellar and orbital parameters

Jun 1998

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998a%26a...334..863b&link_type=abstract

Astronomy and Astrophysics, v.334, p.863-872 (1998)

Astronomy and Astrophysics

Astrophysics

53

Stars: Binaries: Spectroscopic, Stars: Fundamental Parameters, Stars: Abundances, Stars: Activity, Stars: Individual: Ii Peg

Scientific paper

A detailed model atmosphere analysis of high-resolution and high S/N CCD spectra of II Peg has yielded for the first time a self-consistent set of fundamental parameters of the primary component: {T_eff}=4600 K, {log g=3.2, [M/H]=-0.4, {xi_t }=2.0 {km s(-1) }. In addition, 121 new high quality radial velocity measurements allowed us to determine improved orbital parameters, resulting in a new orbital ephemeris of T_conj=2449582.9268+6.724333E. The position of the primary of II Peg in the HR diagram with the new parameters corresponds to a K2 IV star with mass ~0.8 M_&sun;. The evolved character of the star is confirmed by the C/N ratio, which is reduced significantly relative to the solar value. The unspotted V magnitude of the star of 6fm 9 is estimated from the observed variations of the TiO bands and quasi-simultaneous photometry. The blend of Li{ i 6707 Angstroms is suspected to vary in equivalent width due to spot modulation. The lithium abundance for the unspotted star, Li/H=1.0±m0.1, is found to be consistent with other post-main sequence chromospherically active stars. Combining all parameters, the radius R ~ 3.4 R_&sun; and the inclination i ~ 60° of the primary are estimated with the assumption that its rotational axis is perpendicular to the orbital plane. The secondary is probably a M0-M3 V star with a mass of about 0.4 M_&sun;.
Based on observations collected at the Nordic Optical Telescope (NOT), La Palma, Spain; the 2.6 m telescope of the Crimean Astrophysical Observatory, Ukraine; the 2.7 m and 2.1 m telescopes of the McDonald Observatory, USA; the coudé feed telescope of the Kitt Peak National Observatory, USA
Table 2 is also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html.

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