2002MNRAS.336..611B

We employ high-resolution echelle spectroscopy to measure the projected rotational velocity, V_rotsin i, in the post-common-envelope binaries EG UMa, HZ 9 and RE J1629 + 780. For EG UMa we obtain consistent V_rot sin i measurements from the Na i doublet at 8183, 8195 Å (31.2±3.7 km.s^–1 ), the Fe and Ti intrinsically narrow metal (INM) lines in the region 8374-8430 Å (26.6±2.7 and 27.8±3.0 km.s^–1) and the K i line at 7698.9 Å (26.2 ±3.5 km.s^–1). This is in contrast to previous measurements of V_rot sin i from the Na i doublet and INM features derived using lower-resolution spectra, which were not consistent. Possible origins for the disagreement observed previously are discussed, including the inaccurate removal of telluric absorption. The values of V_rotsin i measured from the high-resolution EG UMa spectra are also consistent with that expected from system parameters derived from previous observational data. We also update the ephemeris and orbital period of EG UMa.

We obtained rotation rate measurements of 34.3±3.8 km.s^–1 for HZ 9 and 25.1±2.3 km.s^–1 for RE J1629+780 , as measured from the Na i doublet at 8183, 8195 Å and the INM lines. In both systems there is agreement between the V_rotsin i values measured from the two regions. The value of V_rotsin i measured in HZ 9 is similar to that measured for EG UMa. This is expected, as these systems share a similar orbital period and secondary star spectral type. The measurement of V_rot sin i in RE J1629+780 indicates that this system, which lacks radial velocity shifts due to orbital motion, is a wide binary as opposed to a low-inclination system.