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Session 109 - Novae & Cataclysmic Variables.
Display session, Saturday, January 10
Exhibit Hall,

[109.13] Orbital Period and Spectral Behavior of LS Peg (S193)

C. J. Taylor, J. R. Thorstensen (Dartmouth College)

We present time-resolved spectroscopy of the bright (V \approx 13.0 -- Szkody et al. 1997, AJ, 113, 2276) cataclysmic variable LS Peg (= S193), which has no formally published period. Our data are from five observing runs spanning July 1996 to June 1997, using both the McGraw-Hill 1.3 m and the Hiltner 2.4 m telescopes at the Michigan-Dartmouth-MIT Observatory. The Balmer lines exhibit broad Doppler-shifted wings (about 2000 km s^-1 at the edges) while the \ionHe1 lines show phase-dependent absorption features similar to SW Sex stars, in addition to emission through most of the phase. The \ionC3/\ionN3 blend does not show any phase-dependence in velocity or intensity.

Because of the confusion in the line cores, we determined the radial velocities of H\alpha by measuring by hand the bisector of the zero-intensity points of the broad emission wings. From the velocities measured in this way, we unambiguously determine an orbital period of 0.174774 \pm 0.000003 d (= 4.1946 h).

Program listing for Saturday