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A systematic study of variability among OB-stars based on HIPPARCOS photometry
Context: Variability is a key factor for understanding the nature of themost massive stars, the OB stars. Such stars lie closest to the unstableupper limit of star formation. Aims: In terms of statistics, thedata from the HIPPARCOS satellite are unique because of time coverageand uniformity. They are ideal to study variability in this large,uniform sample of OB stars. Methods: We used statisticaltechniques to determine an independant threshold of variabilitycorresponding to our sample of OB stars, and then applied an automaticalgorithm to search for periods in the data of stars that are locatedabove this threshold. We separated the sample stars into 4 maincategories of variability: 3 intrinsic and 1 extrinsic. The intrinsiccategories are: OB main sequence stars (~2/3 of the sample), OBe stars(~10%) and OB Supergiant stars (~1/4).The extrinsic category refers toeclipsing binaries. Results: We classified about 30% of the wholesample as variable, although the fraction depends on magnitude level dueto instrumental limitations. OBe stars tend to be much more variable(≈80%) than the average sample star, while OBMS stars are belowaverage and OBSG stars are average. Types of variables include αCyg, β Cep, slowly pulsating stars and other types from the generalcatalog of variable stars. As for eclipsing binaries, there arerelatively more contact than detached systems among the OBMS and OBestars, and about equal numbers among OBSG stars.
| 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.
| The Burst and Transient Source Experiment (BATSE) Earth Occultation Catalog of Low-Energy Gamma-Ray Sources
The Burst and Transient Source Experiment (BATSE), aboard the ComptonGamma Ray Observatory (CGRO), provided a record of the low-energygamma-ray sky (~20-1000 keV) between 1991 April and 2000 May (9.1 yr).BATSE monitored the high-energy sky using the Earth occultationtechnique (EOT) for point sources whose emission extended for times onthe order of the CGRO orbital period (~92 min) or greater. Using the EOTto extract flux information, a catalog of sources using data from theBATSE Large Area Detectors has been prepared. The first part of thecatalog consists of results from the all-sky monitoring of 58 sources,mostly Galactic, with intrinsic variability on timescales of hours toyears. For these sources, we have included tables of flux and spectraldata, and outburst times for transients. Light curves (or fluxhistories) have been placed on the World Wide Web.We then performed a deep-sampling of these 58 objects, plus a selectionof 121 more objects, combining data from the entire 9.1 yr BATSE dataset. Source types considered were primarily accreting binaries, but asmall number of representative active galaxies, X-ray-emitting stars,and supernova remnants were also included. The sample represents acompilation of sources monitored and/or discovered with BATSE and otherhigh-energy instruments between 1991 and 2000, known sources taken fromthe HEAO 1 A-4 and Macomb & Gehrels catalogs. The deep sampleresults include definite detections of 83 objects and possibledetections of 36 additional objects. The definite detections spannedthree classes of sources: accreting black hole and neutron starbinaries, active galaxies, and supernova remnants. The average fluxesmeasured for the fourth class, the X-ray emitting stars, were below theconfidence limit for definite detection.Flux data for the deep sample are presented in four energy bands: 20-40,40-70, 70-160, and 160-430 keV. The limiting average flux level (9.1 yr)for the sample varies from 3.5 to 20 mcrab (5 σ) between 20 and430 keV, depending on systematic error, which in turn is primarilydependent on the sky location.To strengthen the credibility of detection of weaker sources (~5-25mcrab), we generated Earth occultation images, searched for periodicbehavior using FFT and epoch folding methods, and critically evaluatedthe energy-dependent emission in the four flux bands. The deep sampleresults are intended for guidance in performing future all-sky surveysor pointed observations in the hard X-ray and low-energy gamma-ray band,as well as more detailed studies with the BATSE EOT.
| The Carina Spiral Feature: Strömgren-Hβ photometry approach. I. The photometric data-base
A data-base collating all uvbybeta photometry available at present forO-B9 stars brighter than 10th visual magnitude in the field of theCarina Spiral Feature is presented. The completeness and homogeneity ofthe data-base are discussed.Based on CDS data.Table 1 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/410/523
| 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.
| A photometric catalogue of southern emission-line stars
We present a catalogue of previously unpublished optical and infraredphotometry for a sample of 162 emission-line objects and shell starsvisible from the southern hemisphere. The data were obtained between1978 and 1997 in the Walraven (WULBV), Johnson/Cousins(UBV(RI)c) and ESO and SAAO near-infrared (JHKLM) photometricsystems. Most of the observed objects are Herbig Ae/Be (HAeBe) stars orHAeBe candidates appearing in the list of HAeBe candidates of Théet al. (1994), although several B[e] stars, LBVs and T Tauri stars arealso included in our sample. For many of the stars the data presentedhere are the first photo-electric measurements in the literature. Theresulting catalogue consists of 1809 photometric measurements. Opticalvariability was detected in 66 out of the 116 sources that were observedmore than once. 15 out of the 50 stars observed multiple times in theinfrared showed variability at 2.2 mu m (K band). Based on observationscollected at the European Southern Observatory, La Silla, Chile and onobservations collected at the South African Astronomical Observatory.Tables 2-4 are 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/380/609
| Absolute proper motions of open clusters. I. Observational data
Mean proper motions and parallaxes of 205 open clusters were determinedfrom their member stars found in the Hipparcos Catalogue. 360 clusterswere searched for possible members, excluding nearby clusters withdistances D < 200 pc. Members were selected using ground basedinformation (photometry, radial velocity, proper motion, distance fromthe cluster centre) and information provided by Hipparcos (propermotion, parallax). Altogether 630 certain and 100 possible members werefound. A comparison of the Hipparcos parallaxes with photometricdistances of open clusters shows good agreement. The Hipparcos dataconfirm or reject the membership of several Cepheids in the studiedclusters. Tables 1 and 2 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
| Polarimetry of southern peculiar early-type stars
We present and discuss optical polarimetry of a large group (60 objects)of peculiar early-type stars (Herbig Ae/Be stars and candidate members,B[e] stars, extreme emission line objects etc.). Most were taken from``A new catalogue of members and candidate members of Herbig Ae/Bestellar group'' \cite[The et al. (1994)]{the2}. For 40 out of the 60objects polarization was measured for the first time. On the basis ofthe data we draw conclusions about the circumstellar shell configurationand orientation for several objects. Polarimetric variability ondifferent time-scales (minutes \ldots hours \ldots days) wasinvestigated, as well as comparison with earlier measurements toinvestigate variability over longer time-scales. No circularpolarization was detected to a 5sigma level in most of the investigatedstars. Polarimetric data obtained here as well as data available fromthe literature were analyzed from the point of investigating theevolutionary status of the objects. The relationship between thepolarimetric and photometric data was also investigated. Tables 6 to 22are only available in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsarc.u-strasbg.fr/Abstract.html
| UBV beta Database for Case-Hamburg Northern and Southern Luminous Stars
A database of photoelectric UBV beta photometry for stars listed in theCase-Hamburg northern and southern Milky Way luminous stars surveys hasbeen compiled from the original research literature. Consisting of over16,000 observations of some 7300 stars from over 500 sources, thisdatabase constitutes the most complete compilation of such photometryavailable for intrinsically luminous stars around the Galactic plane.Over 5000 stars listed in the Case-Hamburg surveys still lackfundamental photometric data.
| Stromgren and Hβ photometry of OB stars in the region of the Carina Spiral Feature
Stromgren and Hβ photometry of 130 stars in the Carina section ofthe Milky Way is presented. The color excesses and the distances of allstars are obtained. A good agreement is found between the CM and HRdiagrams and the spatial distribution of these stars. Tables 1, 2, 4 and5 are only available in electronic form at the CDS via anonymous ftp to130.79.128.5 or via http://cdsweb.u-strasbg.fr/Abstract.html
| Derivation of the Galactic rotation curve using space velocities
We present rotation curves of the Galaxy based on the space-velocitiesof 197 OB stars and 144 classical cepheids, respectively, which rangeover a galactocentric distance interval of about 6 to 12kpc. Nosignificant differences between these rotation curves and rotationcurves based solely on radial velocities assuming circular rotation arefound. We derive an angular velocity of the LSR of{OMEGA}_0_=5.5+/-0.4mas/a (OB stars) and {OMEGA}_0_=5.4+/-0.5mas/a(cepheids), which is in agreement with the IAU 1985 value of{OMEGA}_0_=5.5mas/a. If we correct for probable rotations of the FK5system, the corresponding angular velocities are {OMEGA}_0_=6.0mas/a (OBstars) and {OMEGA}_0_=6.2mas/a (cepheids). These values agree betterwith the value of {OMEGA}_0_=6.4mas/a derived from the VLA measurementof the proper motion of SgrA^*^.
| A spectroscopic database for Stephenson-Sanduleak Southern Luminous Stars
A database of published spectral classifications for objects in theStepenson-Sanduleak Luminous Stars in the Southern Milky Way catalog hasbeen compiled from the literature. A total of 6182 classifications for2562 stars from 139 sources are incorporated.
| A new catalogue of members and candidate members of the Herbig Ae/Be (HAEBE) stellar group
A new up-to-date catalogue of Herbig Ae/Be (HAEBE) stars and relatedobjects is certainly needed, for both well-seasoned researchers and, inparticular, for new investigators starting to study the many interestingastrophysical properties of these very young objects. We present a briefdiscussion of the current observational characteristics that distinguishthis class from their main sequence counterparts. The HAEBE and relatedstars are listed in five tables, containing 287 objects. Table 1contains all Ae and Be stars which historically are recognized as trueHAEBE stars or potential candidate members. Table 2 gives the stars ofspectral type Fe, and emission line stars with very uncertain or unknownspectral type. In Table 3 are given all known Extreme Emission LineObjects (EELOs), of which most have not been identified to belong to anyspecific group. Table 4a and b list other Bep or B[e] stars with strongIR-excess and unknown spectral type. Table 5 contains the non-emissionline possible young objects. Furthermore, Table 6 contains 35 starsrejected from former published lists of HAEBE stars. In these tables weare including coordinates, spectral types, visual magnitudes, ranges inphotometric variability and references of several key publicationsrelated to each object. Relevant remarks, such as the presence of anebula in the vicinity of an object, are also given.
| Bright blue stars in VELA observed with the 'Glazar' space telescope
Seventy-one stars brighter than about 9 m have been detected at 1640 Ain the Vela region with the space telescope Glazar. It is shown thatmost of the detected stars belong to a B-type stellar association at adistance of 460 pc and to two OB stellar associations at distances of1100 pc and 1700 pc. The existence of B-type stellar association at adistance of 110 pc is suspected. A new O-type star cluster, which is apossible nucleus of the OB stellar association at 1700 pc, has beendetected. The distribution of the absorbing matter in the observed areais studied. We presume that the stars HD 75 063 and 76 534 are probablyembedded in a circumstellar dust shell. All observed stars, includingthose with unknown spectra, are early type stars.
| Distribution of hot stars and interstellar dust in Carina.
Not Available
| An Einstein Observatory SAO-based catalog of B-type stars
About 4000 X-ray images obtained with the Einstein Observatory are usedto measure the 0.16-4.0 keV emission from 1545 B-type SAO stars fallingin the about 10 percent of the sky surveyed with the IPC. Seventy-fourdetected X-ray sources with B-type stars are identified, and it isestimated that no more than 15 can be misidentified. Upper limits to theX-ray emission of the remaining stars are presented. In addition tosummarizing the X-ray measurements and giving other relevant opticaldata, the present extensive catalog discusses the reduction process andanalyzes selection effects associated with both SAO catalog completenessand IPC target selection procedures. It is concluded that X-rayemission, at the level of Lx not less than 10 exp 30 ergs/s, is quitecommon in B stars of early spectral types (B0-B3), regardless ofluminosity class, but that emission, at the same level, becomes lesscommon, or nonexistent, in later B-type stars.
| Uvby-beta observations of 528 type B stars with V between the 8th and 9th magnitude
The paper presents uvby-beta measurements of 528 type B stars selectedfrom the SAO Catalog on the basis of two criteria: the spectral types inthe range B3-B5 and mV between the 8th and the 9th magnitude. Reddeningindependent (c1) values are estimated from the spectral classificationand compared to the observed values. No systematic trend with observed(b-y), H-beta, or spectral type appears to be present, but the range of(c1) residuals is surprisingly large. A rather large part of the starshas small beta values, smaller than for the BIa supergiants. Only twoare classified as O stars and most of them have the suffix e, ne, ornne. Most beta values for the O type stars are slightly above the upperlimit of 2.585 m.
| Early-type emission-line stars with large infrared excesses
A catalog is presented of early-type emission-line stars obtained bycross-identification between Wackerling's catalog and the IRAS catalogof point sources. A study of the distribution in space of the starsshows that these stars belong to the extreme Population I; thus thepresent compilation provides a rather complete sample for further studyof the evolution of pre- and post-main sequence stars of medium and highmasses.
| The calibration of the Stromgren photometric system for A, F and early G supergiants. I - The observational data
An empirical calibration of the Stromgren uvby-beta photometric systemfor the A, F, and early G supergiants is being derived. This paperexplains the observational program and the photometric reductiontechniques used and presents a catalog of new Stromgren photometry forover 600 A, F, and G supergiants.
| Observations of a region of the Carina OB 1 association using the "Glazar" space telescope.
Not Available
| A Catalogue of Be-Stars
Not Available
| The value of R in IC 2581.
Abstract image available at:http://adsabs.harvard.edu/abs/1978AJ.....83.1081T
| High-sensitivity search for OH emission from Mira variables
A high-sensitivity search for 18 cm OH emission from Mira variables hasresulted in the detection of five previously unknown OH Mira variables(R Tau, RT Aql, RX Tau, FX Mon, and AW Tau). R Tau, RT Aql, and RX Tauare known microwave H2O sources, and RT Aql is also a known SiO source.RX Tau has a visual-light-curve shape slightly different than that ofpreviously discovered OH Miras. The OH properties of AW Tau are veryanomalous for the period determined from its visual light curve, but areconsistent with a much shorter period for this star. It is possible thatthe period of AW Tau has decreased by several hundred days in the last40 years.
| The spatial distribution of young stars in VELA (l=250 to 284).
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977A&AS...27..343D&db_key=AST
| Observations of southern emission-line stars
A catalog of 1929 stars showing H-alpha emission on photographic platesis presented which covers the entire southern sky south of declination-25 deg to a red limiting magnitude of about 11.0. The catalog providesprevious designations of known emission-line stars equatorial (1900) andgalactic coordinates, visual and photographic magnitudes, H-alphaemission parameters, spectral types, and notes on unusual spectralfeatures. The objects listed include 16 M stars, 25 S stars, 37 carbonstars, 20 symbiotic stars, 40 confirmed or suspected T Tauri stars, 16novae, 14 planetary nebulae, 11 P Cygni stars, 9 Bep stars, 87 confirmedor suspected Wolf-Rayet stars, and 26 'peculiar' stars. Two new Tassociations are discovered, one in Lupus and one in Chamaeleon. Objectswith variations in continuum or H-alpha intensity are noted, and thedistribution by spectral type is analyzed. It is found that the skydistribution of these emission-line stars shows significantconcentrations in the region of the small Sagittarius cloud and in theCarina region.
| Luminous Stars in the Cores of H II Regions
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973PASP...85..586J&db_key=AST
| Differential reddening in the open cluster IC 2581.
Abstract image available at:http://adsabs.harvard.edu/abs/1973AJ.....78..597T
| The space distribution of the OB stars in Car.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970AJ.....75..703G&db_key=AST
| The OB stars in Carina-Centaurus
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1969MNRAS.143..273F&db_key=AST
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| קבוצת-כוכבים: | שדרית |
| התרוממות ימנית: | 10h26m00.19s |
| סירוב: | -57°49'37.0" |
| גודל גלוי: | 9.329 |
| תנועה נכונה: | -7.3 |
| תנועה נכונה: | 2.3 |
| B-T magnitude: | 9.417 |
| V-T magnitude: | 9.337 |
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