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Positional reference stars in the Magellanic Clouds
The equatorial coordinates are determined of 926 stars (mainly ofgalactic origin) in the direction of the Magellanic Clouds at the meanepoch T = 1978.4 with an overall accuracy characterized by the meanvalues of the O-C coordinates, Sa = 0.35 arcsec and Sd = 0.38 arcsec,calculated from the coordinates of the Perth reference stars. Thesevalues are larger than the accuracy expected for primary standard stars.They allow the new positions to be considered as those of reliablesecondary standard stars. The published positions correspond to anunquestionable improvement of the quality of the coordinates provided inthe current catalogs. This study represents an 'astrometric step' in thestarting of a 'Durchmusterung' of the Magellanic Clouds organized by deBoer (1988, 1989).
| A first look at the eclipsing cataclysmic variable Lanning 10
Photometry and spectroscopy of a new cataclysmic variable star, Lanning10 are presented. The star is shown to be an eclipsing binary with a 7h42m orbital period. Blue flickering is observed to occur on a time scaleof 10 minutes. The light curve is analyzed with a numerical simulationof the eclipse of the accretion disk by the lobe-filling star. The disknearly spans the Roche lobe of the white dwarf, and its surfacebrightness is a steep function of radius. Spectra show broad H alpha andHe I 6678 A emission lines from the accretion disk and a weak absorptionfeature from the red dwarf. Radial velocity measurements of the H alphaemission line vary systematically with binary phase. The observedvelocity amplitude 240 km/s, gives the mass function 0.46 solar masses.A phase shift of the velocity curve relative to the eclipse ephemerisindicates that a brightness asymmetry exists in the inner parts of thedisk.
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