T. Campbell — Page 3

arXiv2007

Late-Type Near-Contact Eclipsing Binary [HH97] FS Aur-79

The secondary photometric standard star #79 for the FS Aur field (Henden & Honeycutt 1997) designated as [HH97] FS Aur-79 (GSC 1874 399) is a short period (0.2508 days) eclipsing binary whose light curve is a combination of the $β$ Lyr and BY Dra type variables. High signal-to-noise multi-color photometry were obtained using the USNO 1-m telescope. These light curves show asymmetry at quadrature phases (O'Connell effect), which can be modeled with the presence of star spots. A low resolution spectrum obtained with the 3.5-m WIYN telescope at orbital phase 0.76 is consistent with a spectral type of dK7e and dM3e. A radial velocity curve for the primary star was constructed using twenty-four high resolution spectra from the 9.2 m HET. Spectra show H-alpha and H-beta in emission confirming chromospheric activity and possibly the presence of circumstellar material. Binary star models that simultaneously fit the U, B, V, R and RV curves are those with a primary star of mass 0.59+-0.02 Msun, temperature 4100+-25 K, mean radius of 0.67 Rsun, just filling its Roche lobe and a secondary star of mass 0.31+-0.09 Msun, temperature 3425+-25 K, mean radius of 0.48 Rsun, just within its Roche lobe. An inclination angle of 83+-2 degrees with a center of mass separation of 1.62 Rsun is also derived. Star spots, expected for a rotation period of less than a day, had to be included in the modeling to fit the O'Connell effect.

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arXiv2002

The 2001 Superoutburst of WZ Sagittae

We report the results of a worldwide campaign to observe WZ Sagittae during its 2001 superoutburst. After a 23-year slumber at V=15.5, the star rose within 2 days to a peak brightness of 8.2, and showed a main eruption lasting 25 days. The return to quiescence was punctuated by 12 small eruptions, of ~1 mag amplitude and 2 day recurrence time; these "echo outbursts" are of uncertain origin, but somewhat resemble the normal outbursts of dwarf novae. After 52 days, the star began a slow decline to quiescence. Periodic waves in the light curve closely followed the pattern seen in the 1978 superoutburst: a strong orbital signal dominated the first 12 days, followed by a powerful /common superhump/ at 0.05721(5) d, 0.92(8)% longer than P_orb. The latter endured for at least 90 days, although probably mutating into a "late" superhump with a slightly longer mean period [0.05736(5) d]. The superhump appeared to follow familiar rules for such phenomena in dwarf novae, with components given by linear combinations of two basic frequencies: the orbital frequency omega_o and an unseen low frequency Omega, believed to represent the accretion disk's apsidal precession. Long time series reveal an intricate fine structure, with ~20 incommensurate frequencies. Essentially all components occurred at a frequency n(omega_o)-m(Omega), with m=1, ..., n. But during its first week, the common superhump showed primary components at n (omega_o)-Omega, for n=1, 2, 3, 4, 5, 6, 7, 8, 9 (i.e., m=1 consistently); a month later, the dominant power shifted to components with m=n-1. This may arise from a shift in the disk's spiral-arm pattern, likely to be the underlying cause of superhumps. The great majority of frequency components ... . (etc., abstract continues)

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