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The 2001 Superoutburst of WZ Sagittae
We report the results of a worldwide campaign to observe WZ Sagittaeduring its 2001 superoutburst. After a 23 yr slumber at V=15.5, the starrose within 2 days to a peak brightness of 8.2, and showed a maineruption lasting 25 days. The return to quiescence was punctuated by 12small eruptions, of ~1 mag amplitude and 2 day recurrence time; these``echo outbursts'' are of uncertain origin, but somewhat resemble thenormal outbursts of dwarf novae. After 52 days, the star began a slowdecline to quiescence. Periodic waves in the light curve closelyfollowed the pattern seen in the 1978 superoutburst: a strong orbitalsignal dominated the first 12 days, followed by a powerful commonsuperhump at 0.05721(5) day, 0.92(8)% longer than Porb. Thelatter endured for at least 90 days, although probably mutating into a``late'' superhump with a slightly longer mean period [0.05736(5) day].The superhump appeared to follow familiar rules for such phenomena indwarf novae, with components given by linear combinations of two basicfrequencies: the orbital frequency ωo and an unseen lowfrequency Ω, believed to represent the accretion disk's apsidalprecession. Long time series reveal an intricate fine structure, with~20 incommensurate frequencies. Essentially all components occurred at afrequency nωo-mΩ, with m=1, ..., n. But duringits first week, the common superhump showed primary components atnωo-Ω, for n=1, 2, 3, 4, 5, 6, 7, 8, 9 (i.e., m=1consistently); a month later, the dominant power shifted to componentswith m=n-1. This may arise from a shift in the disk's spiral-armpattern, likely to be the underlying cause of superhumps. The greatmajority of frequency components are redshifted from the harmonics ofωo, consistent with the hypothesis of apsidal advance(prograde precession). But a component at 35.42 cycles day-1suggests the possibility of a retrograde precession at a different rate,probably N=0.13+/-0.02 cycles day-1. The eclipses permitmeasuring the location and brightness of the mass-transfer hot spot. Thedisk must be very eccentric and nearly as large as the white dwarf'sRoche lobe. The hot-spot luminosity exceeds its quiescent value by afactor of up to 60. This indicates that enhanced mass transfer from thesecondary plays a major role in the eruption.
| GSC 01621-02192: A New W UMa Eclipsing Binary
New BVI photometry of GSC 01621-02192 reveals that it is an W UMaeclipsing binary system with period 0.3690 days.
| Photometry of Stars Near WZ Sge
This report presents UBVRI magnitudes of comparison stars for WZ Sge.
| WZ Sagittae
IAUC 7669 available at Central Bureau for Astronomical Telegrams.
| An unbiased survey of field star X-ray emission
To determine the X-ray luminosity function of normal stars, 1700 starsbrighter than 10th magnitude were surveyed by the imaging proportionalcounter aboard the Einstein Observatory. Seventy star positions werefound to contain excess X-ray counting rates. The number of stars persquare degree in a number of magnitude intervals was calculated as afunction of spectral type and luminosity class, and the total number ofstars for each spectral type brighter than magnitude 9.5 derived in thismanner was compared with the 1700-star sample. The agreement is good, asis that between the surface density of soft X-ray sources and the numberof stellar emitters predicted from the field star survey. It isconcluded that stars probably do not contribute significantly to thediffuse soft X-ray background. The findings are consistent with thenotion that stellar age and/or rotation velocity are importantdeterminants of stellar X-ray emission level.
| Photometry of the Recurrent Nova WZ Sagittae at Outburst
Not Available
| Variabler Planetarischer Nebel FG Sagittae 1973.
Not Available
| Absolute Emission-Line Intensities in Planetary Nebulae. I.
Not Available
| Binary Stars among Cataclysmic Variables. V. Photoelectric and Spectroscopic Observations of the Ultra-Short Binary Nova WZ Sagittae.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1964ApJ...140..921K&db_key=AST
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