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A catalogue of young runaway Hipparcos stars within 3 kpc from the Sun
Traditionally, runaway stars are O- and B-type stars with large peculiarvelocities. We would like to extend this definition to young stars (upto ?50 Myr) of any spectral type and to identify those present in theHipparcos catalogue by applying different selection criteria, such aspeculiar space velocities or peculiar one-dimensional velocities.Runaway stars are important for studying the evolution of multiple starsystems or star clusters, as well as for identifying the origins ofneutron stars. We compile the distances, proper motions, spectral types,luminosity classes, V magnitudes and B-V colours, and we utilizeevolutionary models from different authors to obtain star ages. We studya sample of 7663 young Hipparcos stars within 3 kpc from the Sun. Theradial velocities are obtained from the literature. We investigate thedistributions of the peculiar spatial velocity and the peculiar radialvelocity as well as the peculiar tangential velocity and itsone-dimensional components and we obtain runaway star probabilities foreach star in the sample. In addition, we look for stars that aresituated outside any OB association or OB cluster and the Galactic planeas well as stars for which the velocity vector points away from themedian velocity vector of neighbouring stars or the surrounding local OBassociation/cluster (although the absolute velocity might be small). Wefind a total of 2547 runaway star candidates (with a contamination ofnormal Population I stars of 20 per cent at most). Thus, aftersubtracting these 20 per cent, the runaway frequency among young starsis about 27 per cent. We compile a catalogue of runaway stars, which isavailable via VizieR.
| The Subdwarf Database: Released
The work on the Subdwarf Database, presented at the previous meeting,has been completed, and the tool is now publicly available. The firstrelease contains data from close to 240 different literature sources,but more still awaits entry. The database interface includes advancedsearch capabilities in coordinate, magnitude and color space. Outputtables can be generated in HTML with hyperlinks to automaticallygenerated finding charts, the Aladin viewer and a detailed data sheetthat displays all registered data for each target, including physicaldata such as temperature, gravity and helium abundance, together with afinding chart. Search results can be visualized automatically asinteractive position, magnitude or color diagrams.
| New Estimates of the Solar-Neighborhood Massive Star Birthrate and the Galactic Supernova Rate
The birthrate of stars of masses >=10 Msolar is estimatedfrom a sample of just over 400 O3-B2 dwarfs within 1.5 kpc of the Sunand the result extrapolated to estimate the Galactic supernova ratecontributed by such stars. The solar-neighborhood Galactic-plane massivestar birthrate is estimated at ~176 stars kpc-3Myr-1. On the basis of a model in which the Galactic stellardensity distribution comprises a ``disk+central hole'' like that of thedust infrared emission (as proposed by Drimmel and Spergel), theGalactic supernova rate is estimated at probably not less than ~1 normore than ~2 per century and the number of O3-B2 dwarfs within the solarcircle at ~200,000.
| Catalog of Galactic OB Stars
An all-sky catalog of Galactic OB stars has been created by extendingthe Case-Hamburg Galactic plane luminous-stars surveys to include 5500additional objects drawn from the literature. This work brings the totalnumber of known or reasonably suspected OB stars to over 16,000.Companion databases of UBVβ photometry and MK classifications forthese objects include nearly 30,000 and 20,000 entries, respectively.
| Infrared flux excesses from hot subdwarfs. II. 72 more objects
In our search, started in February, 1994, for JHK excess fluxes amongthe hot subdwarf population as an indicator for the presence of binarycompanions, results for 72 more hot objects (=63 hot subdwarfs + 1Horizontal Branch B star + 7 white dwarfs + 1 non-subdwarf object)observed with the Carlos Sanchez CVF IR photometer (in June and October,1994), are presented. The exact number of binary hot subdwarfs hasgained renewed importance after the recent discovery of pulsators withG-F companions. The total number of candidates we propose may help toset some constraints; for example, out of 41 objects with excesses, 13may have G-type binary companions. From our new sample, 14 discoveriesof binary candidates have been found: BD+25 4655, Feige 108, HD 4539, HD149382, HD 216135, KPD 2109+440, LSI+63 198, LSIV+10 9, LSV+22 38, PG0011+221, PG 0116+242, PG 0314+103, PG 2151+100 and TON 139. Besides, 2more from reanalysis of February, 1994, data - BD+37 1977 and BD+481777, may now be found to be IR excess candidates. Two suspectedbinaries, PB 8555 and SB 7, are also confirmed. By fitting \cite[Kurucz(1993)]{kur93} model spectra and assuming zero-age main sequencecompanions, we find upper limits on the subdwarf gravities. Thedistributions of upper limits on log(g), mostly between about 5.25 and6.5, are nearly identical for both sdBs and sdOs. Figure~1 is onlyavailable in the electronic version of the paper(http://www.edpsciences.com)
| Infrared flux excesses from hot subdwarfs.
Observations of 27 hot subdwarf stars and white dwarfs have beenperformed with an IR photometer in a search for excess fluxes in the JHKbands. 22 of the objects are observed for the first time in theinfrared. In 11 of the stars a significant excess flux was found, 2 ofwhich are new discoveries: GD 274 and GD 299. We confirm the suspicionof Moehler et al. (1990) that PG0232+095 is a composite system, and wereinforce the suggestion of Thejll et al. (1991, 1994a) that Feige 34 isa composite system. The excesses are most likely due to companion stars,mainly of spectral types A - K. We estimate the subdwarf gravities,assuming zero-age main sequence companions, and thus find upper limitson log(g). For the hot sdO Feige 34 we estimate from the publishedtrigonometric parallaxes an absolute magnitude M_v_^F34^=5.6^+0.9^_-1.6_and surface gravity log(gpi_)=6.8^+0.3^_-0.7_.
| The Henry Draper Extension Charts: A catalogue of accurate positions, proper motions, magnitudes and spectral types of 86933 stars
The Henry Draper Extension Charts (HDEC), published in the form offinding charts, provide spectral classification for some 87000 starsmostly between 10th and 11th magnitude. This data, being highlyvaluable, as yet was practically unusable for modern computer-basedastronomy. An earlier pilot project (Roeser et al. 1991) demonstrated apossibility to convert this into a star catalogue, using measurements ofcartesian coordinates of stars on the charts and positions of theAstrographic Catalogue (AC) for subsequent identification. We presenthere a final HDEC catalogue comprising accurate positions, propermotions, magnitudes and spectral classes for 86933 stars of the HenryDraper Extension Charts.
| A catalogue of spectroscopically identified hot subdwarf stars.
Not Available
| Ultraviolet and optical studies of binaries with luminous cool primaries and hot companions. II - BVRI observations
Johnson system BVRI measurements are presented for 117 stars, most ofthem with no previous R and I photometry and many with no previous B andV. The prime objects for measurement are unresolved or nearly unresolvedbinaries containing a late-type giant or supergiant and an early-typecompanion. Other objects on the program include suspected binaries andother F-G giants and supergiants lacking at least R and I magnitudes.The variable F and G supergiants 1 Mon, 89 Her, HR 7308, HR 8157, HR8752, and rho-Cas and the eclipsing systems W Ser and ST Aqr wereobserved; HR 8752 showed significant dimming and cooling over 125 days.Several of Halliwell's (1979) candidates for nearby stars were measured.
| Degenerate stars. XII - Recognition of hot nondegenerates
Fifty-one newly observed degenerate stars and 14 nondegenerates include13 faint red stars, most of which do not show any lines except DF, Gr554. Hot subdwarfs and an X-ray source are discussed along with theproblem of low-resolution spectroscopic classification of dense hotstars. The multichannel spectrum of the carbon-rich magnetic star LP790-29 is examined by fitting the undisturbed parts of the spectrum to ablack body of 7625 K by the least squares method; the Swan bands absorb600 A of the spectrum assuming that the blocked radiation isredistributed in the observed region.
| Atmospheres for hot, high-gravity stars. I - Pure hydrogen models
An extensive grid of pure hydrogen model atmospheres for hot,high-gravity stars is presented. The models are intended to aid theanalysis of visual, ultraviolet, and soft X-ray spectra of hot DA whitedwarfs and EUV sources. The grid extends from log g equals 4.0(1.0)9.0and T(eff) ranges from 20,000 K up to the Eddington limit for mostsurface gravities. Most of the models are LTE unblanketed calculations,but selected NLTE models and blanketed LTE models have also beencomputed in order to assess the importance of these effects. For eachmodel, continuum fluxes are tabulated covering the entire range ofwavelengths for which there is significant flux. Stromgren colors, UBVcolors, and bolometric corrections are also given. Profiles andequivalent widths of the L-alpha, L-beta, L-gamma, H-alpha, H-beta,H-gamma, and H-delta lines are given as well.
| Three new hot subdwarfs: AGK2 +81 266, BD +39 3226, BD +34 1543.
Abstract image available at:http://adsabs.harvard.edu/abs/1978A&A....64L...9B
| A hot subluminous star - HDE 283048
The star HDE 283048 located at alpha = 3(h)50(m)3, delta = +25 deg 36min shows a strong ultraviolet continuum. Ground-based observationsindicate a hot-dominated composite spectrum. Several lines of evidencesuggest that the hot component is a hot subdwarf.
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | שור |
| התרוממות ימנית: | 03h53m13.72s |
| סירוב: | +25°45'21.9" |
| גודל גלוי: | 10.467 |
| תנועה נכונה: | 5.9 |
| תנועה נכונה: | -20.6 |
| B-T magnitude: | 10.486 |
| V-T magnitude: | 10.469 |
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