The 2001 Superoutburst of WZ Sagittae
| Autor: | Robert E. Fried, Rudolf Novak, Tut Campbell, Tonny Vanmunster, Stacey Davis, Michael Richmond, Stan Walker, Gianluca Masi, O. Brettman, Arne Henden, D. Starkey, T. Davis, Edward Beshore, J. Foote, Lew Cook, P. Niarchos, Dieter Husar, Joseph Patterson, Elena P. Pavlenko, Thomas Krajci, Jeff W. Robertson, Robert Rea, Jonathan Kemp, Brian Martin, David R. Skillman, Nestor Mirabal, William E. Allen, Arto Oksanen |
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| Rok vydání: | 2002 |
| Předmět: | |
| DOI: | 10.48550/arxiv.astro-ph/0204126 |
| Popis: | 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) Comment: PDF, 54 pages, 4 tables, 21 figures, 1 appendix; accepted, in press, to appear July 2002, PASP; more info at http://cba.phys.columbia.edu/ |
| Databáze: | OpenAIRE |
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