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A survey for pulsating subdwarf B stars with the Nordic Optical Telescope
Context. A search programme for pulsating subdwarf B stars was conductedwith the Nordic Optical Telescope on La Palma over 59 nights between1999 and 2009. Aims: The purpose of the programme was tosignificantly extend the number of rapidly pulsating sdB stars to betterunderstand the properties of this new group of variable compact stars. Methods: Candidates were selected initially from the HS and HEsurveys, but were supplemented with additional objects from othersurveys. Short sequences of time-series photometry were made on thecandidates to determine the presence of rapid pulsations. Results: In total twenty new pulsators were found in this survey, mostof which have already been published and some extensively studied. Wepresent four new short period pulsators, bringing the total of suchpulsators up to 49. We also give limits on pulsation amplitudes for 285objects with no obvious periodic variations, summarise the results ofthe survey, and provide improved physical parameters on the compositepulsators for which only preliminary estimates were published earlier.Full Table 5 is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/513/A6
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Studying the populations of our Galaxy using the kinematics of sdB stars
We have analysed the kinematics of a sample of 114 hot subdwarf stars.For 2/3 of the stars, new proper motions, spectroscopic and photometricdata are presented. The vast majority of the stars show a kinematicbehaviour that is similar to that of Thick Disk stars. Some stars havevelocities rather fitting to solar, i.e. Thin Disk, kinematics. About˜15 objects have orbital velocities which differ considerably fromthose of Disk stars. These are members of the Galactic Halo. Weinvestigated the velocity dispersions and calculated the orbits. Moststars feature orbits with disk character (eccentricity of less than0.5), a few reach far above the Galactic plane and have very eccentricorbits (eccentricity of more than 0.7). The intermediate eccentricityrange is poorly populated. This seems to indicate that the (Thick) Diskand the Halo are kinematically disjunct. Plotting a histogram of theorbit data points along z leads to the z-distance probabilitydistribution of the star; doing this for the whole sample leads to thez-distance probability distribution of the sample. The logarithmichistogram shows two slopes, each representing the scale height of apopulation. The disk component has a scale height of 0.9 (±0.1)kpc, which is consistent with earlier results and is similar to that ofthe Thick Disk. The other slope represents a component with a scaleheight ˜7 kpc, a much flatter gradient than for the diskcomponent. This shows that the vast majority of the sdBs are disk stars,but a Halo minority is present, too. The kinematic history andpopulation membership of the sdB stars on the whole is different fromthat of the cooler HBA stars, which are predominantly or evenexclusively Halo objects. This leads to the question, whether the HalosdB stars are of similar origin as the HBA stars, or whether theirkinematical behaviour possibly represents another origin, such asinfalling stellar aggregates or inner disk events.Based on data obtained at the 1.54 m telescope of the European SouthernObservatory, runs 58.D-0478, 60.D-0306, 62.L-0220, 64.L-0077,64.H-0023(A), 65.H-0250, 65.H-0341(A) and 68.D-0192(A).
| Metal abundances of sdB stars
The surface abundance patterns of 13 sdB stars have been determined fromhigh resolution, high S/N, optical spectra. As typical in early B typestars, the metal lines are few and very weak. The metal abundancepatterns are compared with the atmospheric parameters to search forpossible trends, which are predicted by diffusion theory. However, it isremarkable that some metals (e.g. N, Mg, Fe) have similar abundancesirrespective of the stellar parameters, whereas other metals (e.g. C, O)and the helium abundances vary considerably from star to star. Threepeculiar sdB stars were found which show an enormous enrichment of irongroup elements. An isotopic anomaly of helium has been found in two sdBstars. In these stars 4He is largely replaced by the isotope3He. We discovered additionally four single lined, shortperiod radial velocity variable sdB stars and measured their radialvelocity curves.
| The Montreal-Cambridge-Tololo Survey of Southern Subluminous Blue Stars: The South Galactic Cap
Results for the south Galactic cap region of theMontréal-Cambridge-Tololo survey of blue subluminous stars arepresented. This region overlaps the 840 deg2 region studiedalmost three decades ago by Slettebak & Brundage. We present a list ofequatorial coordinates, photographic photometry, and spectroscopicidentifications, as well as finding charts, for 188 blue objects[(U-B)pg<=-0.6] brighter than Bpg=16.5 in thisarea. Completeness of the survey and comparisons with other similarefforts are discussed.
| Supplementary southern standards for UBV(RI)c photometry
We present UBV(RI)c photometry for 80 southern red and blue stars foruse as additional standards. The data are tied to the Johnson UBV andCousins (RI)c systems and extend the range of the available stars forcolor equation determination, especially in (U-B) for blue stars and(V-R) and (V-I) for red stars. Comparisons with published data are madeand particularly good agreement is found with Bessell for the red(Gliese) stars.
| Broad-band photometry of selected southern ultraviolet-bright stars.
Not Available
| A catalogue of spectroscopically identified hot subdwarf stars.
Not Available
| The atmosphere of subluminous B stars
The spectra of eight high galactic latitude B stars, suspected to besubluminous, are analyzed for effective temperature, gravity, and heliumto hydrogen ratio. Model atmospheres include (LTE) UV line blanketing(for T/eff/ less than or equal to 30,000 K) and NLTE effects (for T/eff/greater than 30,000 K). Among the eight confirmed subdwarfs, six havetemperatures around 26,000 K. Two objects are considerably hotter(34,000 K and 41,000 K) and belong to the sdOB subclass. Gravity rangesfrom log g = 5.0 to 5.5 for the sdB's, the sdOB's having log g = 5.7 and6.0, respectively. Helium is strongly depleted in the sdB's and sdOB's:from He I 4471 (if present) the number fraction obtained is 0.0016n(He)/n(H) = 0.0016-0.016. From the g, T(eff)-diagram it is concludedthat the subluminous B stars and sdOB stars are (generalized) heliummain sequence stars with approximately 0.5 solar mass. The heliumdeficiency of the envelope is brought about by diffusion.
| A survey of ultraviolet objects
An all-sky survey of ultraviolet objects is presented together with astatistical analysis that leads to the conclusion that there is asignificantly higher population of hot subdwarfs lying below themain-sequence than hitherto thought. The distribution of all ultravioletobjects, main sequence ultraviolet objects, and MK unclassifiedultraviolet objects are shown in galactic coordinates, and the absolutemagnitudes and color-color diagrams for these groups are presented.Scale heights are derived, giving values similar to planetary nebulaefor the hottest groups.
| Photometry of faint blue stars. V - A third list of southern stars
Stromgren photometry is presented for 37 faint blue stars, six of whichhave been identified by ultraviolet observations made with the ESRO TD-1satellite. The stars are classified using their observed photometricindices.
| Spectroscopically peculiar stars near the south galactic pole.
Abstract image available at:http://adsabs.harvard.edu/abs/1973AJ.....78..295G
| A finding list of early-type stars near the south galactic pole.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971AJ.....76..338S&db_key=AST
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| Takýmyýldýz: | Yontar |
| Sað Açýklýk: | 23h44m22.01s |
| Yükselim: | -34°27'00.4" |
| Görünürdeki Parlaklýk: | 10.979 |
| özdevim Sað Açýklýk: | -19.5 |
| özdevim Yükselim: | -3 |
| B-T magnitude: | 10.608 |
| V-T magnitude: | 10.949 |
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