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Surface abundances of light elements for a large sample of early B-type stars - IV. The magnesium abundance in 52 stars - a test of metallicity
From high-resolution spectra a non-local thermodynamic equilibriumanalysis of the MgII 4481.2-Åfeature is implemented for 52 earlyand medium local B stars on the main sequence (MS). The influence of theneighbouring line AlIII 4479.9-Åis considered. The magnesiumabundance is determined; it is found that logɛ(Mg) = 7.67 +/-0.21 on average. It is shown that uncertainties in the microturbulentparameter Vt are the main source of errors inlogɛ(Mg). When using 36 stars with the most reliableVt values derived from OII and NII lines, we obtain the meanabundance logɛ(Mg) = 7.59 +/- 0.15. The latter value isprecisely confirmed for several hot B stars from an analysis of the MgII7877-Åweak line. The derived abundance logɛ(Mg) = 7.59 +/-0.15 is in excellent agreement with the solar magnesium abundancelogɛsolar (Mg) = 7.55 +/- 0.02, as well as with theproto-Sun abundance logɛps(Mg) = 7.62 +/- 0.02. Thus,it is confirmed that the Sun and the B-type MS stars in ourneighbourhood have the same metallicity.
| B Star Rotational Velocities in h and χ Persei: A Probe of Initial Conditions during the Star Formation Epoch?
Projected rotational velocities (vsini) have been measured for 216 B0-B9stars in the rich, dense h and χ Persei double cluster and comparedwith the distribution of rotational velocities for a sample of fieldstars having comparable ages (t~12-15 Myr) and masses (M~4-15Msolar). For stars that are relatively little evolved fromtheir initial locations on the zero-age main sequence (ZAMS) (those withmasses M~4-5 Msolar), the mean vsini measured for the h andχ Per sample is slightly more than 2 times larger than the meandetermined for field stars of comparable mass, and the cluster and fieldvsini distributions differ with a high degree of significance. Forsomewhat more evolved stars with masses in the range 5-9Msolar, the mean vsini in h and χ Per is 1.5 times thatof the field; the vsini distributions differ as well, but with a lowerdegree of statistical significance. For stars that have evolvedsignificantly from the ZAMS and are approaching the hydrogen exhaustionphase (those with masses in the range 9-15 Msolar), thecluster and field star means and distributions are only slightlydifferent. We argue that both the higher rotation rates and the patternof rotation speeds as a function of mass that differentiatemain-sequence B stars in h and χ Per from their field analogs werelikely imprinted during the star formation process rather than a resultof angular momentum evolution over the 12-15 Myr cluster lifetime. Wespeculate that these differences may reflect the effects of the higheraccretion rates that theory suggests are characteristic of regions thatgive birth to dense clusters, namely, (1) higher initial rotationspeeds; (2) higher initial radii along the stellar birth line, resultingin greater spin-up between the birth line and the ZAMS; and (3) a morepronounced maximum in the birth line radius-mass relationship thatresults in differentially greater spin-up for stars that become mid- tolate-B stars on the ZAMS.
| An empirical temperature calibration for the Δ a photometric system . I. The B-type stars
We establish an empirical effective temperature calibration of mainsequence, luminosity class V to III B-type stars for the Δ aphotometric system which was originally developed to detect magneticchemically peculiar objects of the upper main sequence (early B-type toearly F-type) at 5200 Å. However, this system provides the index(g_1-y) which shows an excellent correlation with (B-V) as well as (b-y)and can be used as an indicator of the effective temperature. This issupplemented by a very accurate color-magnitude diagram, y or V versus(g_1-y), which can be used, for example, to determine the reddening,distance and age of an open cluster. This makes the Δ aphotometric system an excellent tool to investigate theHertzsprung-Russell-Diagram (HRD) in more detail. Using thereddening-free parameters and already established calibrations withinthe Strömgren uvbyβ, Geneva 7-color and Johnson UBV systems, apolynomial fit of third degree for the averaged effective temperaturesto the individual (g_1-y)0 values was derived. For thispurpose, data from the literature as well as new observations were takenresulting in 225 suitable bright normal B-type objects. The statisticalmean of the error for this sample is 238 K which is sufficient toinvestigate the HRD of distant galactic open clusters as well asextragalactic aggregates in the future.
| NaI and CaII absorption components observed towards the Orion-Eridanus Superbubble
We present medium-resolution spectra (R ~ 7.5 km s-1) of theinterstellar NaI and CaII interstellar absorption lines observed towards16 early-type stars with distances of 160-1 kpc in the line-of-sighttowards the Orion-Eridanus Superbubble (OE-S). These data have beensupplemented with measurements of NaI absorption towards a further 13stars with similar sight-lines taken from the literature. We detect twomajor absorption components with velocities of Vlsr ~ +7.0and -8.0 km s-1. The former component, seen in 70% of thesight-lines is associated with the boundary to the Local Bubble cavitylocated at a distance of 140-150 pc. The other absorption component isonly detected towards a limited region of the sky bounded by (190°< l < 215°) and (-50° < b < -30°). If gas withthis velocity is associated with an outer expansion shell of the OE-S,then we can place its distance at 163-180 pc in agreement with theestimate by Guo et al. (1995, ApJ, 453, 256). Several other negativevelocity components at Vlsr ~ -20.4, -28.5 and -33.5 kms-1 have also been detected for sight-line distances > 220pc within an area coincident with that of the 0.75 keV X-ray enhancementof the OE-S. Column density ratios, N(NaI)/N(CaII), for the mostnegative velocity components have values < 1.0, suggesting that thisgas has been disrupted by a possible shock event. Our data do notsupport a simple model for the OE-S that involves a single stellarbubble cavity that stretches from the Orion Nebula to high galacticlatitudes. Instead, our detection of multiple positive and negativevelocity components suggests the presence of several gas shells producedby supernovae and/or stellar wind-driven shocks. We also confirm thatthe prominent "hook-like" feature of H-α emission thatcharacterizes the OE-S, in in fact composed of two physically separateemission arcs, with the brighter Arc A being at a distance > 500 pc.Finally, we place a similar distance limit for any coherently structuredrear shell of neutral gas associated with expansion of the OE-S towardsthe galactic halo.
| Surface abundances of light elements for a large sample of early B-type stars - III. An analysis of helium lines in spectra of 102 stars
Non-local thermodynamic equilibrium analysis of He I lines in spectraof 102 B stars is implemented in order to derive the helium abundanceHe/H, the microturbulent parameter Vt and the projectedrotation velocity v sini. A simultaneous determination of He/H andVt for the stars is effected by analysing equivalent widthsof the 4471- and 4922-Å lines primarily as indicators of He/H andthe 4713-, 5016-, 5876- and 6678-Å lines primarily as indicatorsof Vt. The rotation velocities v sini are found from profilesof the same lines. It is shown that, when Vt > 7 kms-1, the Vt(He I) values determined from He Ilines are systematically overestimated as compared with theVt(OII, NII) values derived from OII and NII lines. Thisdiscrepancy is especially appreciable for hot evolved B giants withVt(He I) = 16-23 km s-1 and may indicate a failureof classical model atmospheres to represent the strong He I lines forthese stars.Two programme stars, HR 1512 and 7651, are found to be helium-weakstars. The remaining 100 stars are divided into three groups accordingto their masses M. The microturbulent parameter Vt(He I) islow for all stars of group A (M= 4.1-6.9 Msolar) and for allstars with the relative ages t/tMS < 0.8 of group B (M=7.0-11.2 Msolar). Their Vt(He I) values are withinthe 0 to 5 km s-1 range, as a rule; the mean value isVt= 1.7 km s-1. Only evolved giants of group B,which are close to the termination of the main-sequence (MS)evolutionary phase (t/tMS > 0.8), show Vt(He I)up to 11 km s-1. The helium abundance He/H is correlated withthe relative age t/tMS in both groups; the averaged He/Henhancement during the MS phase is 26 per cent. For group C, containingthe most massive stars (M= 12.4-18.8 Msolar), theVt(He I) values display a correlation with t/tMS,varying from 4 to 23 km s-1. The He/H determination for hotevolved B giants of the group with Vt(He I) > 15 kms-1 depends on a choice between the Vt(He I) andVt(OII, NII) scales. The mean He/H enrichment by 67 per centduring the MS phase is found, if the abundances He/H are based on theVt(OII, NII) scale; however, two evolved giants withespecially high v sini, HR 7446 and 7993, show the He/H enhancement byabout a factor of 2.5. When using the same Vt scale, we founda trend of He/H with projected rotational velocities v sini a largedispersion for v sini > 150 km s-1 can result fromdifferences in masses M.A comparison with the stellar model computations with rotationallyinduced mixing shows that the observed helium enrichment during the MSphase can be explained by rotation with initial velocities 250-400 kms-1. The He/H distribution on M and v sini based on theVt(OII, NII) scale seems to be in better agreement with thetheory than one based on the Vt(He I) scale. The mean valueHe/H = 0.10 derived for stars in the zero age main sequence (ZAMS)vicinity can be adopted as the typical initial helium abundance forearly B stars in the solar neighbourhood.
| Kinematic Masses of Super-Star Clusters in M82 from High-Resolution Near-Infrared Spectroscopy
Using high-resolution (R~22,000) near-infrared (1.51-1.75 μm) spectrafrom Keck Observatory, we measure the kinematic masses of two super-starclusters in M82. Cross-correlation of the spectra with template spectraof cool evolved stars gives stellar velocity dispersions ofσr=15.9+/-0.8 km s-1 for J0955505+694045(MGG-9) and σr=11.4+/-0.8 km s-1 forJ0955502+694045 (MGG-11). The cluster spectra are dominated by the lightof red supergiants and correlate most closely with template supergiantsof spectral types M0 and M4.5. King model fits to the observed profilesof the clusters in archival Hubble Space Telescope/Near-Infrared Cameraand Multi-Object Spectometer images give half-light radii ofrhp=2.6+/-0.4 pc for MGG-9 and rhp=1.2+/-0.17 pcfor MGG-11. Applying the virial theorem, we determine masses of1.5+/-0.3×106 Msolar for MGG-9 and3.5+/-0.7×105 Msolar for MGG-11 (where thequoted errors include σr, rhp, and thedistance). Population synthesis modeling suggests that MGG-9 isconsistent with a standard initial mass function (IMF), whereas MGG-11appears to be deficient in low-mass stars relative to a standard IMF.There is, however, evidence of mass segregation in the clusters, inwhich case the virial mass estimates would represent lower limits.Based on observations made at the W. M. Keck Observatory, which isoperated as a scientific partnership among the California Institute ofTechnology, the University of California, and the National Aeronauticsand Space Administration. The Observatory was made possible by thegenerous financial support of the W. M. Keck Foundation.
| 3D mapping of the dense interstellar gas around the Local Bubble
We present intermediate results from a long-term program of mapping theneutral absorption characteristics of the local interstellar medium,motivated by the availability of accurate and consistent parallaxes fromthe Hipparcos satellite. Equivalent widths of the interstellar NaID-line doublet at 5890 Å are presented for the lines-of-sighttowards some 311 new target stars lying within ~ 350 pc of the Sun.Using these data, together with NaI absorption measurements towards afurther ~ 240 nearby targets published in the literature (for many ofthem, in the directions of molecular clouds), and the ~ 450lines-of-sight already presented by (Sfeir et al. \cite{sfeir99}), weshow 3D absorption maps of the local distribution of neutral gas towards1005 sight-lines with Hipparcos distances as viewed from a variety ofdifferent galactic projections.The data are synthesized by means of two complementary methods, (i) bymapping of iso-equivalent width contours, and (ii) by densitydistribution calculation from the inversion of column-densities, amethod devised by Vergely et al. (\cite{vergely01}). Our present dataconfirms the view that the local cavity is deficient in cold and neutralinterstellar gas. The closest dense and cold gas ``wall'', in the firstquadrant, is at ~ 55-60 pc. There are a few isolated clouds at closerdistance, if the detected absorption is not produced by circumstellarmaterial.The maps reveal narrow or wide ``interstellar tunnels'' which connectthe Local Bubble to surrounding cavities, as predicted by the model ofCox & Smith (1974). In particular, one of these tunnels, defined bystars at 300 to 600 pc from the Sun showing negligible sodiumabsorption, connects the well known CMa void (Gry et al. \cite{gry85}),which is part of the Local Bubble, with the supershell GSH 238+00+09(Heiles \cite{heiles98}). High latitude lines-of-sight with the smallestabsorption are found in two ``chimneys'', whose directions areperpendicular to the Gould belt plane. The maps show that the LocalBubble is ``squeezed'' by surrounding shells in a complicated patternand suggest that its pressure is smaller than in those expandingregions.We discuss the locations of several HI and molecular clouds. Usingcomparisons between NaI and HI or CO velocities, in some cases we areable to improve the constraints on their distances. According to thevelocity criteria, MBM 33-37, MBM 16-18, UT 3-7, and MBM 54-55 arecloser than ~ 100 pc, and MBM 40 is closer than 80 pc. Dense HI cloudsare seen at less than 90 pc and 85 pc in the directions of the MBM 12and MBM 41-43 clouds respectively, but the molecular clouds themselvesmay be far beyond. The above closest molecular clouds are located at theneutral boundary of the Bubble. Only one translucent cloud, G192-67, isclearly embedded within the LB and well isolated.These maps of the distribution of local neutral interstellar NaI gas arealso briefly compared with the distribution of both interstellar dustand neutral HI gas within 300 pc.Tables 1 and 2 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp:cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/411/447
| Surface abundances of light elements for a large sample of early B-type stars - II. Basic parameters of 107 stars
Effective temperatures Teff, surface gravities logg andinterstellar extinctions AV are found for 107 B stars.Distances d of the stars, which are based on the derivedTeff, logg and AV values, show good agreement withthose obtained from the Hipparcos parallaxes. Comparing theTeff and logg values with evolutionary computations, we infermasses, radii, luminosities, ages and relative ages of the stars.Empirical relations between the Teff and logg parameters, onthe one hand, and the photometric indices Q, [c1] and β,on the other hand, are constructed; these relations give a fast methodfor the Teff and logg estimation of early and medium B stars.Inclusion of the infrared J, H and K colours into the Teff,logg and AV determination shows that (i) the Teffand logg parameters are altered only slightly; (ii) the AVvalue is rather sensitive to these colours, so an accuracy better than0.05mag in the JHK data is necessary for precise AVevaluation.
| Rotational Velocities of B Stars
We measured the projected rotational velocities of 1092 northern B starslisted in the Bright Star Catalogue (BSC) and calibrated them againstthe 1975 Slettebak et al. system. We found that the published values ofB dwarfs in the BSC average 27% higher than those standards. Only 0.3%of the stars have rotational velocities in excess of two-thirds of thebreakup velocities, and the mean velocity is only 25% of breakup,implying that impending breakup is not a significant factor in reducingrotational velocities. For the B8-B9.5 III-V stars the bimodaldistribution in V can be explained by a set of slowly rotating Ap starsand a set of rapidly rotating normal stars. For the B0-B5 III-V starsthat include very few peculiar stars, the distributions in V are notbimodal. Are the low rotational velocities of B stars due to theoccurrence of frequent low-mass companions, planets, or disks? Therotational velocities of giants originating from late B dwarfs areconsistent with their conservation of angular momentum in shells.However, we are puzzled by why the giants that originate from the earlyB dwarfs, despite having 3 times greater radii, have nearly the samerotational velocities. We find that all B-type primaries in binarieswith periods less than 2.4 days have synchronized rotational and orbitalmotions; those with periods between 2.4 and 5.0 days are rotating withina factor 2 of synchronization or are ``nearly synchronized.'' Thecorresponding period ranges for A-type stars are 4.9 and 10.5 days, ortwice as large. We found that the rotational velocities of the primariesare synchronized earlier than their orbits are circularized. The maximumorbital period for circularized B binaries is 1.5 days and for Abinaries is 2.5 days. For stars of various ages from 107.5 to1010.2 yr the maximum circularized periods are a smoothexponential function of age.
| BCD spectrophotometry of stars with the B[e] phenomenon. I. Fundamental parameters
Low resolution spectra in the lambda lambda3500 -4600 Å wavelengthrange of 23 stars with the B[e] phenomenon are presented. Spectralclassification of 15 program stars was performed using the BCDspectrophotometric system, based on the study of the Balmerdiscontinuity, which is independent of interstellar and circumstellardust extinctions and of circumstellar gas emissions and/or absorptions.From calibrations of the (lambda1 ,D) BCD parameters wedetermined the (Teff,log g, Mbol) of the studiedstars. For stars where this method could not be applied, we tried toestimate the temperature of the central star by using the Balmer and Hei emission lines and/or their visible energy distribution. The colourtemperature and the temperatures obtained from the study of Balmer andHe i lines are consistent with each other. The new results are comparedwith those obtained previously by other authors and discussed for eachstar individually. For some stars, differences between the effectivetemperatures derived using the BCD classification system and thoseobtained elsewhere, based on photometric or spectroscopic analysis,imply spectral-type classification disagreements ranging from 2-3 up to6 B sub-spectral types. The fundamental parameters of AS 119,CD-24°5721, Hen2-91, HD 316375 and BD-11°4747 were determinedfor the first time. A simple method was introduced to calculate total(interstellar+circumstellar) dust extinction towards the studied stars.For HD 53179, which is a double stellar system, and for HD 45677 and HD50138, which are suspected to be binaries, we predicted thecharacteristics of the components that are consistent with the observed(lambda1 ,D) parameters. However, the possible binarity of HD45677 and HD 50138 still needs to be confirmed spectroscopically. Dataobtained in CASLEO operated under agreement between the CONICET and theUniversities of La Plata, Córdoba and San Juan, Argentina.Partially based on observations done at ESO La Silla, Chili.
| Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
| Surface abundances of light elements for a large sample of early B-type stars - I. Spectral observations of 123 stars; measurements of hydrogen and helium lines; infrared photometry
High-resolution spectral observations of 123 B0-B5 stars in the mainsequence evolutionary phase were obtained at two observatories, namelythe McDonald Observatory (McDO) and the Crimean AstrophysicalObservatory (CrAO). Accurate equivalent widths W of two Balmer lines,Hβ and Hγ, and ten Hei lines were obtained for all the stars,as well as of the Heiiλ4686 line for the hottest ones. A carefulanalysis of the measured equivalent widths was performed. It is shownthat there is a very good agreement between the W values derived fromthe McDO and CrAO spectra for 14 common stars. A comparison withpublished data leads to the conclusion that the W values measuredearlier by some authors for strong Hei lines are very likely to beunderestimated. Infrared photometric observations in the J, H, and Kbands were performed for 70 programme stars. All these data will be usedin other papers: in particular for the Teff and loggdetermination and for the He, C, N and O abundance analyses.
| Dating Ptolemy's star catalogue through proper motions : the Hipparchan epoch.
Not Available
| The Second Extreme Ultraviolet Explorer Right Angle Program Catalog
We present the detection of 235 extreme ultraviolet sources, of which169 are new detections, using the Extreme Ultraviolet Explorer's (EUVE)Right Angle Program (RAP) data. This catalog includes observations sincethe first EUVE RAP catalog (1994 January) and covers 17% of the sky. TheEUVE RAP uses the all-sky survey telescopes (also known as``scanners''), mounted at right angles to the Deep Survey andspectrometer instruments, to obtain photometric data in four wavelengthbands centered at ~100 Å (Lexan/B), ~200 Å (Al/Ti/C), ~400Å (Ti/Sb/Al), and ~550 Å (Sn/SiO). This allows the RAP toaccumulate data serendipitously during pointed spectroscopicobservations. The long exposure times possible with RAP observationsprovide much greater sensitivity than the all-sky survey. We presentEUVE source count rates and probable source identifications from theavailable catalogs and literature. The source distribution is similar toprevious extreme ultraviolet (EUV) catalogs with 2% early-type stars,45% late-type stars, 8% white dwarfs, 6% extragalactic, 24% with no firmclassification, and 15% with no optical identification. We also present36 detections of early-type stars that are probably the result ofnon-EUV radiation. We have detected stellar flares from approximately 12sources, including: EUVE J0008+208, M4 star G32-6 (EUVE J0016+198), anew source EUVE J0202+105, EUVE J0213+368, RS CVn V711 Tau (EUVEJ0336+005), BY Draconis type variable V837 Tau (EUVE J0336+259), the newK5 binary EUVE J0725-004, EUVE J1147+050, EUVE J1148-374, EUVE J1334-083(EQ Vir), EUVE J1438-432 (WT 486/487), EUVE J1808+297, and the M5.5estar G208-45 (EUVE J1953+444). We present sample light curves for thebrighter sources.
| Carbon and nitrogen abundances in early B-stars. I. NLTE calculations for a sample of stars with small V sin i values
Abundances of carbon and nitrogen in a sample of hot main sequence starswere determined in the NLTE approximation. All calculations were basedon Kurucz atmosphere models. Atmospheric parameters for the programstars have been determined using spectroscopic and photometric methods.In most cases the derived atmospheric abundances appear to be subsolarand probably unaltered by stellar evolution. This is in agreement withthe general conclusions on C and N abundances for B main sequence starsreached by other investigators. Based on the spectra collected with the1.52-m telescope of Haute Provence Observatoire
| An extensive Delta a-photometric survey of southern B and A type bright stars
Photoelectric photometry of 803 southern BS objects in the Deltaa-system as detection tool for magnetic chemically peculiar (=CP2) starshas been carried out and compared to published spectral types. Thestatistical yield of such objects detected by both techniques ispractically the same. We show that there are several factors whichcontaminate the search for these stars, but this contamination is onlyof the order of 10% in both techniques. We find a smooth transition fromnormal to peculiar stars. Our sample exhibits the largest fraction ofCP2 stars at their bluest colour interval, i.e. 10% of all stars in thecolour range -0.19 <= B-V < -0.10 or -0.10 <= b-y < -0.05.No peculiar stars based on the Delta a-criterion were found at bluercolours. Towards the red side the fraction of CP2 stars drops to about3% for positive values of B-V or b-y with red limits roughlycorresponding to normal stars of spectral type A5. The photometricbehaviour of other peculiar stars: Am, HgMn, delta Del, lambda Boo, Heabnormal stars, as well as Be/shell stars and supergiants shows someslight, but definite deviations from normal stars. Spectroscopic andvisual binaries are not distinguished from normal stars in their Delta abehaviour. The results of this work justify larger statistical work(e.g. in open clusters) employing more time-saving photometric methods(CCD). \newpage Based on observations obtained at the European SouthernObservatory, La Silla, Chile. This research has made use of the Simbaddatabase, operated at CDS, Strasbourg, France. Table 2 is only availablein electronic form via anonymous ftp 130.79.128.5 orhttp://cdsweb.u-strasbg.fr/Abstract.html
| Long-term photometry of Be stars. III. Evidence for periodic outbursts of lambda ERI and photometric activity in HR2142
Stromgren differential uvby photometry of lambda Eri and HR2142 isanalyzed. The data were taken during the time interval 1983-1994 in theframework of the Long-Term Photometry of Variables project at La Silla.lambda Eri exhibited four photometric events (probably associated withline emission episodes) that last several months and which werecharacterized by a common pattern of change in all passbands ( ~ +/-10(-3) mag/day) along with an apparent decrease of the amplitude of theshort-term variability and an increase of the stellar temperature. Asearch for periodicities reveals that these events fit a 486d recurrencetime. On the other hand, HR2142 showed a relatively ``quiet" long-termphotometric behaviour, the orbital period being detected only marginallyin the photometric data set. In contrast, a 344d period optimally fitsthe data. We discuss the possibility of an internal ``clock" regulatingthe outburst activity of lambda Eri and show that the photometricvariability of HR2142 can hardly be explained by its interacting binarynature. We also discuss an empirical relationship found between frac{partial c1}{partial u} and v sini in a sample of 11 Bestars. Based on observations obtained at ESO, Chile
| The Pulkovo Spectrophotometric Catalog of Bright Stars in the Range from 320 TO 1080 NM
A spectrophotometric catalog is presented, combining results of numerousobservations made by Pulkovo astronomers at different observing sites.The catalog consists of three parts: the first contains the data for 602stars in the spectral range of 320--735 nm with a resolution of 5 nm,the second one contains 285 stars in the spectral range of 500--1080 nmwith a resolution of 10 nm and the third one contains 278 stars combinedfrom the preceding catalogs in the spectral range of 320--1080 nm with aresolution of 10 nm. The data are presented in absolute energy unitsW/m(2) m, with a step of 2.5 nm and with an accuracy not lower than1.5--2.0%.
| The ROSAT all-sky survey catalogue of optically bright OB-type stars.
For the detailed statistical analysis of the X-ray emission of hot starswe selected all stars of spectral type O and B listed in the Yale BrightStar Catalogue and searched for them in the ROSAT All-Sky Survey. Inthis paper we describe the selection and preparation of the data andpresent a compilation of the derived X-ray data for a complete sample ofbright OB stars.
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| The determination of T_eff_ of B, A and F main sequence stars from the continuum between 3200 A and 3600 A.
A method of determination of the effective temperature of B, A and Fmain sequence stars is proposed, using the slope of the continuumbetween 3200A and 3600A. The effective temperature calibration is basedon a sample of stars with energy distributions known from UV to the red.We have determined the Balmer jump and the effective temperatures for235 main sequence stars. The temperatures found have been compared withthose derived by Underhill et al. (1979), Kontizas & Theodossiou(1980), Theodossiou (1985), Morossi & Malagnini (1985). Thecomparison showed good agreement for most of the stars in common. On theother hand, the temperatures derived from the reddening-free colourfactor QUV, from the colour index (m1965-V) and from (B-V), given inGulati et al. (1989), are systematically lower than our temperatures,however the differences are within one-sigma error.
| An IUE survey of interstellar H I LY alpha absorption. 1: Column densities
We measure Galactic interstellar neutral hydrogen column densities byanalyzing archival interstellar Ly alpha absorption line data toward 554B2 and hotter stars observed at high resolution with the IUE satellite.This study more than doubles the number of lines of sight with measuresof N(H I) based on Ly alpha. We have included the scattered lightbackground correction algorithm of Bianchi and Bohlin in our datareduction. We use the correlation between the Balmer discontinuity(c1) index and the stellar Ly alpha absorption in order toassess the effects of stellar Ly alpha contamination. Approximately 40%of the B stars with measured (c1) index, exhibit seriousstellar Ly alpha contamination. One table contains the derived values ofthe interstellar N(H I) for 393 stars with at most small amounts ofstellar contamination. Another lists the observed values of total N(H I)for 161 stars with suspected stellar Ly alpha contamination and/oruncertain stellar parameters.
| High-resolution CA II observations of the local interstellar medium
High-resolution absorption measurements of the interstellar Ca II K lineobserved toward 46 early-type stars in the local ISM (LISM) arepresented. Ca II was detected in 36 of the 46 stars with 82 individualcloud components identified. Ca II was detected to most of the starscloser than 50 pc, except in the region of the Galactic quadrant l =180-270 degrees which also contains the empty line of sight to B CMa at220 pc. The mean local standard of rest velocity of the 82 Ca IIcomponents implies that the LISM clouds are associated with the motionof the solar neighborhood and not the sun. If the present data arecombined with other nearby Ca II component velocities taken from theliterature, then a cloud centered approximately at l = 90 deg, b = -40deg moving coherently with the local interstellar wind vector issupported at a significance level of 99 percent. The Ca II data havebeen combined with Na I data for the same stars to produce a N(NaI)/N(Ca II) ratio for each identified absorption feature. This ratioplotted against the local standard of rest velocities of the cloudsshows that the Routly-Spitzer effect exists down to +/- 10 km/s, whichsupports grain desorption/destruction models that are efficient atreturning calcium to the gas phase at these low velocities.
| Rotational velocity of Be stars correlated with extinction law
The paper presents the comparison of the extinction curves extractedfrom spectra of 35 Be stars. It is suggested that high rotationalvelocity relates to 'peculiar' shape of extinction curve i.e., the lackof the 2200 A bump. This phenomenon occurs only if the total reddeningis not very high. We assume that such extinction curves originate solelyin circumstellar disks surrounding the high rotational velocity stars.Other objects are probably also obscured by some additional interstellarclouds.
| Longterm Photometry of Variables at ESO - Part Two - the Second Data Catalogue 1986-1990
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..102...79S&db_key=AST
| The stellar temperature scale for stars of spectral types from O8 to F6 and the standard deviation of the MK spectral classification
Empirical effective temperature of 211 early-type stars found in aprevious investigation (Kontizas and Theodossiou, 1980; Theodossiou,1985) are combined with the effective temperatures of 313 early-typestars from the literature. From these effective temperatures of a totalnumber of 524 early-type stars of spectral types from O8 to F6 a newstellar temperature scale is developed along with the standard deviationof the MK spectral classification.
| Long-term photometry of variables at ESO. I - The first data catalogue (1982-1986)
This paper presents the catalog of photometric data in the Stromgrensystem obtained during the first four years (October 1982 - September1986) of the Long-Term Photometry of Variables (LTPV) program at ESO.The data are available in computer-readable form.
| Broad-band photometry of selected southern ultraviolet-bright stars.
Not Available
| Intrinsic Energy Distributions in Spectra of Early Type Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990MNRAS.246..408P&db_key=AST
| Studies of the local interstellar medium. VIII - Morphology and kinematics of the diffuse interstellar clouds toward Orion
Interstellar clouds in the direction of the Orion association show onlypositive velocities for target stars within 190 pc of the sun, and bothpositive and negative velocities for more distant target stars,confirming an earlier prediction by Cowie, Songaila, and York (1979).The nearby positive velocity cloud, designated here as Orion-Lepus 70(OL 70), is a standard diffuse interstellar cloud: it is subject to theambient galactic radiation field, with properties consistent with Tabout equal to 100 K and n about equal to 3/cu cm. Combined with acolumn density log N(H) = 19.8-20.0/sq cm, these values imply a cloudthickness of about 7 pc. The kinematics of OL 70 are consistent witheither an origin as part of the expanding Loop I superbubble shell, oras part of Lindbald's expanding ring, or a synthesis of the two models.The negative velocity interstellar components seen in stars at d notless than 200 pc are caused by interstellar matter accelerated by theexpanding Ori-Eri superbubble. Relatively dense interstellar gas atpositive LSR velocities is also found within the Orion association, sothat it is difficult to pick out OL 70 components in the spectra of thedistant stars.
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| Takýmyýldýz: | Irmak |
| Sað Açýklýk: | 05h01m26.30s |
| Yükselim: | -07°10'26.0" |
| Görünürdeki Parlaklýk: | 4.81 |
| Uzaklýk: | 293.255 parsek |
| özdevim Sað Açýklýk: | -1.2 |
| özdevim Yükselim: | 5.3 |
| B-T magnitude: | 4.562 |
| V-T magnitude: | 4.752 |
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