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Photometry of 20 eclipsing and ellipsoidal binary systems
ERRATUM: In the published paper the phase diagrams of pi Sco and AL Sclwere ommitted. The version reproduced in JAD11, 7 is the completeversion. A total of almost 2000 V observations of 20 eclipsing andellipsoidal bright binary stars was collected between 1991 and 2001 forthe purpose of determining more recent epoch ephemerides for the lightcurves than are available in the literature. The original purpose was toprovide the Sydney University Stellar Interferometer (SUSI) with orbitalperiods and particularly the accurate times of minimum separation (lightcurve minima), so that the SUSI observations need not be used todetermine them.This paper provides the periods, the times of primary minima and thephases of secondary minima for the 20 stars at an epoch as near aspossible to the year 2000. No attempt has been made in this report todetermine other parameters such as {apsidal motion} or stellar radii.Since the program was started in 1991, data for these stars taken in theperiod from late 1989 to early 1993 has also been available from theHipparcos satellite; the light curves shown here include both sets ofobservations.
| Spectral Classification of Stars in A Supplement to the Bright Star Catalogue
MK spectral types are given for about 584 stars in A Supplement to theBright Star Catalogue. These are compared with Hipparcos parallaxes tocheck the reliability of those classifications. The estimated errors are+/-1.2 subtypes, and 10% of the luminosity classes may be wrong.
| The X-Ray Emission of A-Type Stars
From X-ray images in the ROSAT public archives, we determine soft X-rayfluxes, or flux upper limits, for 74 A-type stars, which have beenobserved during deep integrations with the PSPC. Nine supposedly single,late A stars (0.20 < B-V < 0.35) are found to coincide with X-raysources. The X-ray luminosities we infer for these stars range fromlevels comparable to the Active Sun, at log L_x ~27.6, to much brighteremission levels similar to those observed for active late-type binarysystems, near log L_x ~30.1. Another 10 sources are identified withearly A stars (0.0 < B-V < 0.2). Five of these are confirmeddouble stars, the rest are ostensibly single. The maximum luminosity wedetect in the early A stars, log L_x = 30.1, is 3.5 orders of magnitudebrighter than the X-ray upper limits for the nondetected stars.Additional study, including radial velocity monitoring and/or opticalinterferometry, will be needed to determine whether the putativelysingle X-ray emitting stars are in fact single, or whether theiremission is produced entirely or in part by unknown or unresolved binarycompanions. The level of X-ray emission associated with chemicallynormal, single A stars thus far appears to be uncorrelated with anyobvious stellar property, including the rotation rate, which is known togreatly influence the dynamo activity and the X-ray emission levels oflower mass stars. (SECTION: Stars)
| UBV photometry of eclipsing binaries with visual companions
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971PASP...83...69H&db_key=AST
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