Multisite observations of surface structures on AB Doradus in 1994 November
We present time-resolved optical spectroscopy and broad-band photometryof the rapidly rotating southern K0 dwarf star AB Doradus, obtainedduring 1994 November. The data were obtained as part of a collaborationdedicated to MUlti-SIte COntinuous Spectroscopy (MUSICOS), and entailedcoordinated observations on three continents to obtain the fullest phasecoverage possible subject to limitations of local weather conditions.The Doppler images from the three consecutive nights of the run showexcellent mutual agreement, with a dark polar cap and numerousintermediate- and low-latitude features. Simultaneous optical photometryshowed numerous short-duration U-band flares, and two longer durationoptical flares with durations of the order of hours. The latter producedbroad-band continuum enhancements throughout the optical spectrum. Wheresimultaneous spectroscopy was available, both types of flare were seento have counterparts in Hα and the Caii H line. Simultaneoustime-resolved ultraviolet spectroscopy from the Goddard High ResolutionSpectrograph (GHRS) aboard the Hubble Space Telescope, reportedelsewhere, shows that at least one of the short-duration U-band flareswas also observed in Civ with the GHRS. Time-series Hα spectrashowed significant evolution of the circumstellar prominence system overfive consecutive stellar rotations. One prominence underwent a dramaticincrease in distance from the stellar rotation axis. We speculate thatthis event may have been associated with one of the long-durationflares.
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EC11575-1845: a new close binary with a large reflection effect discovered by the Edinburgh-Cape Survey
EC11575-1845 is a non-eclipsing binary consisting of an sdO primary anda late M-type secondary showing a large reflection effect. UBVRIphotometry reveals an orbital period of 7.86h, with the amplitude of thereflection effect increasing with wavelength as expected. Thespectroscopic behaviour reveals absorption lines from the primary andvariable intensity emission-line features from the heated face of thesecondary. The radial velocity variations of both components restrictthe mass ratio to M_2/M_1=0.29-0.32. A self-consistent model can bederived for the system using Napier's algorithm, which constrains themasses and radii of the components, the orbital inclination and theeffective temperature of the primary. From evolutionary considerationsit is shown that EC11575-1845 belongs to a small class of progenitors ofcataclysmic variable stars which on a time-scale of 10^8-10^10 yr maydevelop cataclysmic activity.
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Secondary UVBY standards in the Harvard E-regions
Photoelectric uvby photometry for 201 stars which are already UBV (RI)cstandards is presented. The photoelectric data are closely tied to theCousins uvby standards and the stars should be suitable for use asfainter (7-11 mag) secondary standards.
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Secondary standards for H-beta photometry in the Southern Hemisphere (second series).
Not Available
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Secondary standards for H-beta photometry in the E regions.
Not Available
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UBV (RI)c standard stars in the E- and F-regions and in the Magellanic Clouds - a revised catalogue.
Not Available
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Secondary standards for the Stromgren UVBY system
Observations of 158 E region stars have been made in the Stromgrensystem, using the 46-cm reflector at Cape Town. They are mostly brighterthan eighth magnitude and are intended for use as secondary standardsfor the four-color system. The E region relative zero points are definedwith a precision of + or - 0.001 mag, and the internal standard errorsof the colors life between + or - 0.001 and + or - 0.002 mag.
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HD 47147 - A small-amplitude extreme metal-poor RRab pulsating variable
The photometric variations and physical and kinematical properties of HD47147, a ninth magnitude metal-deficient star, are discussed. The longperiod (0.79732 days), the small amplitude (0.17 mag in the visualband), and the mean effective temperature of 6160 K of this RR Lyraepulsating variable can be understood by its location near the red edgeof the instability strip. The extreme Population II characteristics ofHD 47147 are confirmed by its kinematical properties. The temperatureand the relatively high luminosity derived are consistent with bothpossibilities that HD 47147 is a red horizontal branch star or that itis a suprahorizontal branch star actually evolving redward toward theasymptotic branch. Its low amplitude suggests the possibility that thered edge of the instability strip corresponds to a smooth transitionfrom variable to non-variable stars.
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Up-To UBVRI Values for the E-Region Standard Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1981A&AS...46....7V&db_key=AST
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Photometric standard stars for the UBV and (RI)KC systems.
Not Available
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VRI standards in the E regions
Not Available
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Standard Stars for VRI Photometry with S25 Response Photocathodes [Errata: 1974MNSSA..33....1C]
Not Available
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Standard magnitudes in the E regions.
Not Available
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