After a decade of near stability at P -0.146 d, the photometric "superhump" periodicity of the old nova V603 Aquilae experienced a remarkable change between 1991and 1992 . Observation in 1992-1994 indicates that the dominant signal was then at a period in the range 0.1338-0.1345 d, 3% shorter than the orbital period. Like its predecessor, the new signal also wanders in period on a timescale of a few months. The full amplitude in 1994 was 0.20 mag, more than twice as great as the superhump displayed during 1980-1991. An intensive observing campaign in 1994 revealed that the old superhump at 0.146 d was still present with approximately undiminished amplitude (averaging 0.07 mag). In a precession model, the simultaneous presence of superhumps above and below the orbital period strongly suggests identification with two independent types of precessional sideband. The observed periods and period changes are consistent with a simple hypothesis: that the longer period ("positive superhump") arises from the prograde motion of the line of apsides, and the shorter period ("negative superhump") arises from the retrograde motion of the line of nodes. A detailed account of how a fluid disk manages to maintain such well-organized motions is sorely needed.

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

The rapid localization of GRB 021004 by the HETE-2 satellite allowed nearly continuous monitoring of its early optical afterglow decay, as well as high-quality optical spectra that determined a redshift of z 3 ¼ 2:328 for its host galaxy, an active starburst galaxy with strong Ly emission and several absorption lines. Spectral observations show multiple absorbers at z 3A ¼ 2:323, z 3B ¼ 2:317, and z 3C ¼ 2:293 blueshifted by $450, $990, and $3155 km s À1 , respectively, relative to the host galaxy Ly emission. We argue that these correspond to a fragmented shell nebula that has been radiatively accelerated by the gamma-ray burst (GRB) afterglow at a distance e0.3 pc from a Wolf-Rayet star GRB progenitor. The chemical abundance ratios indicate that the nebula is overabundant in carbon and silicon. The high level of carbon and silicon is consistent with a swept-up shell nebula gradually enriched by a carbon-rich late-type Wolf-Rayet progenitor wind over the lifetime of the nebula prior to the GRB onset. The detection of statistically significant fluctuations and color changes about the jetlike optical decay further supports this interpretation, since fluctuations must be present at some level as a result of irregularities in a clumpy stellar wind medium or if the progenitor has undergone massive ejection prior to the GRB onset. This evidence suggests that the mass-loss process in a Wolf-Rayet star might lead naturally to an iron core collapse with sufficient angular momentum that could serve as a suitable GRB progenitor. Even though we cannot rule out definitely the alternatives of a dormant QSO, large-scale superwinds, or a several hundred year old supernova remnant responsible for the blueshifted absorbers, these findings point to the likelihood of a signature for a massive-star GRB progenitor.

We discuss the nature of V Sagittae and T Pyxidis, two enigmatic blue variable stars commonly classed among the cataclysmic variables. These stars have bolometric luminosities in the range 36(1-50) # 10 ergs s Ϫ1 , far exceeding that of any accretion-powered cataclysmic variable. They also show extremely blue colors ( and after dereddening) and orbital light curves that are quite similar and yet are3 not seen in any normal cataclysmic variable. But in all these respects, as well as in the rich and highly excited emission-line spectrum, the stars provide a good match for the newly discovered class of "supersoft" X-ray binaries, probably powered by quasi-steady nuclear burning of accreted gas on a white dwarf. Both stars show photometric waves at the orbital period. V Sge also shows a deep minimum, a true eclipse of the accretion disk arising from fairly high binary inclination. T Pyx is nearly face-on (probably ), which results ini∼10 -20 narrow lines and a low amplitude for the orbital signal. T Pyx shows a very stable photometric wave at P ϭ days, but interpretation of this is hampered by another transient signal at 0.1098 days. This might be 0.076227 construed as evidence for a magnetic white dwarf. X e f f stars are now known (Greiner 1996

We present spectroscopy and time-series photometry of the newly discovered dwarf nova 1RXS J232953.9+062814. Photometry in superoutburst reveals a superhump with a period of 66.06(6) minutes. The low state spectrum shows Balmer and HeI emission on a blue continuum, and in addition shows a rich absorption spectrum of type K4 ± 2. The absorption velocity is modulated sinusoidally at P orb = 64.176(5) min, with semi-amplitude K = 348(4) km s −1 . The low-state light curve is double-humped at this period, and phased as expected for ellipsoidal variations. The absorption strength does not vary appreciably