科研之友
微信
新浪微博
Facebook
分享链接
摘要
We present a spectroscopic study of the eclipsing binary system AS Camelopardalis, the first such study based on phase-resolved CCD echelle spectra. Via a spectral disentangling analysis we measure the minimum masses of the stars to be M(A) sin(3) i = 3.213 +/- 0.032 M(circle dot) and M(B) sin(3) i = 2.323 +/- 0.032 M(circle dot), their effective temperatures to be T(eff)(A) = 12,840 +/- 120 K and T(eff)(B) = 10,580 +/- 240 K, and their projected rotational velocities to be v(A) sin i(A) = 14.5 +/- 0.1 km s(-1) and v(B) sin i(B) <= 4.6 +/- 0.1 km s(-1). These projected rotational velocities appear to be much lower than the synchronous values. We show that measurements of the apsidal motion of the system suffer from a degeneracy between orbital eccentricity and apsidal motion rate. We use our spectroscopically measured e = 0.164 +/- 0.004 to break this degeneracy and measure (omega) over dot(bs) = 0 degrees.133 +/- 0 degrees.010 yr(-1). Subtracting the relativistic contribution of (omega) over dot(GR) = 0 degrees.0963 +/- 0 degrees.0002 yr(-1) yields the contribution due to tidal torques: (omega) over dot(cl) = 0 degrees.037 +/- 0 degrees.010 yr(-1). This value is much smaller than the rate predicted by stellar theory, 0 degrees.40-0 degrees.87 yr(-1). We interpret this as a misalignment between the orbital axis of the close binary and the rotational axes of its component stars, which also explains their apparently low rotational velocities. The observed and predicted apsidal motion rates could be brought into agreement if the stars were rotating three times faster than synchronous about axes perpendicular to the orbital axis. Measurement of the Rossiter-McLaughlin effect can be used to confirm this interpretation.
- 出版日期2011-6-20
