The total-to-selective extinction ratio determined from near IR photometry of OB stars
The paper presents an extensive list of the total to selectiveextinction ratios R calculated from the infrared magnitudes of 597 O andB stars using the extrapolation method. The IR magnitudes of these starswere taken from the literature. The IR colour excesses are determinedwith the aid of "artificial standards" - Wegner (1994). The individualand mean values of total to selective extinction ratios R differ in mostcases from the average value R=3.10 +/-0.05 - Wegner (1993) in differentOB associations. The relation between total to selective extinctionratios R determined in this paper and those calculated using the "methodof variable extinction" and the Cardelli et al. (1989) formulae isdiscussed. The R values presented in this paper can be used to determineindividual absolute magnitudes of reddened OB stars with knowntrigonometric parallaxes.
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Statistical analysis of intrinsic polarization, IR excess and projected rotational velocity distributions of classical Be stars
We present the results of statistical analyses of a sample of 627 Bestars. The parameters of intrinsic polarization (p*),projected rotational velocity (v sin i), and near IR excesses have beeninvestigated. The values of p* have been estimated for a muchlarger and more representative sample of Be stars (~490 objects) thanpreviously. We have confirmed that most Be stars of early spectral typehave statistically larger values of polarization and IR excesses incomparison with the late spectral type stars. It is found that thedistributions of p* diverge considerably for the differentspectral subgroups. In contrast to late spectral types (B5-B9.5), thedistribution of p* for B0-B2 stars does not peak at the valuep*=0%. Statistically significant differences in the meanprojected rotational velocities (/line{vsin i}) are found for differentspectral subgroups of Be stars in the sense that late spectral typestars (V luminosity class) generally rotate faster than early types, inagreement with previously published results. This behaviour is, however,not obvious for the III-IV luminosity class stars. Nevertheless, thecalculated values of the ratio vt/vc of the truerotational velocity, vt, to the critical velocity forbreak-up, vc, is larger for late spectral type stars of allluminosity classes. Thus, late spectral type stars appear to rotatecloser to their break-up rotational velocity. The distribution of nearIR excesses for early spectral subgroups is bi-modal, the position ofthe second peak displaying a maximum value E(V-L)~ 1 . m 3for O-B1.5 stars, decreasing to E(V-L)~0. m8 for intermediatespectral types (B3-B5). It is shown that bi-modality disappears for latespectral types (B6-B9.5). No correlations were found betweenp* and near IR excesses and between E(V-L) and vsin i for thedifferent subgroups of Be stars. In contrast to near IR excesses, arelation between p* and far IR excesses at 12 mu m is clearlyseen. A clear relation between p* and vsin i (as well asbetween p* and /line{vsin i}/vc) is found by thefact that plots of these parameters are bounded by a ``triangular"distribution of p*: vsin i, with a decrease of p*towards very small and very large vsin i (and /line{vsini}/vc) values. The latter behaviour can be understood in thecontext of a larger oblateness of circumstellar disks for the stars witha rapid rotation. From the analysis of correlations between differentobservational parameters we conclude that circumstellar envelopes forthe majority of Be stars are optically thin disks with the range of thehalf-opening angle of 10degr
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Transient supersoft X-ray emission from V 751 Cygni during the optical low-state
We have observed V 751 Cyg with the ROSAT HRI in a target-of-opportunitymode during its recent optical low state and clearly detect it at acount rate of 0.015 cts s(-1) . The X-ray intensity is a factor of 7-19(depending on the exact X-ray spectral shape) higher than the upperlimit obtained with the ROSAT PSPC during the optical high state, thussuggesting an anti-correlation of X-ray and optical intensity. Spectralinvestigations suggest a very soft X-ray spectrum. We investigatearchival IUE data of V 751 Cyg and derive a distance of V 751 Cyg ofd~500 pc based on the extinction estimate of E(B-V)=0.25+/-0.05. Thisimplies that the X-ray emission is very luminous, on the order of 10(34)-10(36) erg s(-1) . We have obtained quasi-simultaneous opticalphotometry and spectroscopy. The spectrum during the optical low-stateis characterized by a very blue continuum and the presence of strongemission lines of the Balmer series and HeI. Also, HeII 4686 Angstromsis clearly detected. We establish that V 751 Cyg is a transientsupersoft X-ray source and speculate that other VY Scl stars may also beof similar type.
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Catalogue of H-alpha emission stars in the Northern Milky Way
The ``Catalogue of Stars in the Northern Milky Way Having H-alpha inEmission" appears in Abhandlungen aus der Hamburger Sternwarte, Band XIin the year 1997. It contains 4174 stars, range {32degr <= l() II< 214degr , -10degr < b() II < +10degr } having the Hαline in emission. HBH stars and stars of further 99 lists taken from theliterature till the end of 1994 were included in the catalogue. We givethe cross-identification of stars from all lists used. The catalogue isalso available in the Centre de Données, Strasbourg ftp130.79.128.5 or http://cdsweb.u-strasbg.fr and at the HamburgObservatory via internet.
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Interstellar Extinction Law in the Vicinity of the North America and Pelican Nebulae
The interstellar reddening law is derived for 15 heavily reddened starsin the area which includes the North America and Pelican nebulae and thedark cloud between them. The method is based on photometry of thesestars in the Vilnius seven-color system and on their MK spectral types.The mean law in this area is very similar to the law for a much widerarea in Cygnus derived earlier by other authors. It differs from thenormal law by exhibiting somewhat stronger extinction in the violet andthe near ultraviolet spectral region, i.e., it shows a smaller ``knee"in the blue part of the spectrum.
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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.
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Catalogue of stars in the northern Milky Way having H-alpha in emission
Not Available
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Rotational Velocity Determinations for 164 Be and B Stars
Rotational velocities, v sin i, have been obtained for 96 Be and 68normal B stars by measurements of the FWHM of the He I lambda-4471 line(for spectral types B0-B4.5) and Mg II lambda-4481 (for types B5-B9.5).The consistency of various published sources is examined. (SECTION:Stars)
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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.
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Radio continuum emission from stars: a catalogue update.
An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed.
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Uvbyβ photometry of Orion population stars and related objects associated with six star forming regions
Homogeneous uvbyβ photometry of 150 stars associated with the starforming regions Taurus-Auriga, Orion, Canis Mayoris, Ophiuchus, Serpensand Cygnus, is presented here. We also present uvbyβ photometry of10 Herbig Ae/Be stars not belonging to the specific regions studiedhere. Using the (V,b-y), (β,[m1]), ([c1],[m1]) and ([u-b], T_eff_)diagrams we study the photometric properties of the sample. The effectsof duplicity, stellar rotation, and interstellar extinction on thelocation in the magnitude-color and color-color diagrams of our programstars are briefly investigated. We derive reliable photometric spectraltypes and discuss membership to the regions and to the Orion population,as well as peculiarities of the individual stars. We also find new Bstars associated with the CMa R1 star forming region and newintermediate-low mass PMS members associated with theBD+404124/BD+413731 region. The FU-Orionis stars Z CMa, V1515 Cyg andV1057 Cyg have a peculiar position in the reddening free (β,[m1])diagram. With diagrams such as (V-M _v_-5 log r+5) vs. E(b-y), E(c1) vs.E(b-y), E(m1) vs. E(b-y) and E(u-b) vs. E(b-y) we investigate the ISextinction law towards the star-forming regions. We find that the totalto selective extinction ratio to these regions is steeper than normalwith R_y_=5.4 (R_v_=4.0) and the coefficients E(c1)/E(b-y) andE(m1)/E(b-y) used to define the reddening free indices [c1] and [m1]should be numerically smaller than the generally adopted values.
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Galactic OB associations in the northern Milky Way Galaxy. I - Longitudes 55 deg to 150 deg
The literature on all OB associations was reviewed, and their IRAS pointsource content was studied, between galactic longitude 55 and 150 deg.Only one third of the 24 associations listed by Ruprecht et al. (1981)have been the subject of individual studies designed to identify thebrightest stars. Distances to all of these were recomputed using themethod of cluster fitting of the B main sequence stars, which makes itpoossible to reexamine the absolute magnitude calibration of the Ostars, as well as for the red supergiant candidate stars. Also examinedwas the composite HR diagram for these associations. Associations withthe best defined main sequences, which also tend to contain very youngclusters, referred to here as OB clusters, have extremely few evolved Band A or red supergiants. Associations with poorly defined mainsequences and few OB clusters have many more evolved stars. They alsoshow an effect in the upper HR diagram referred to as a ledge byFitzpatrick and Garmany (1990) in similar data for the Large MagellanicCloud. It is suggested that the differences in the associations are notjust observational selection effects but represent real differences inage and formation history.
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Extinction law survey based on UV ANS photometry
The paper presents an extensive survey of interstellar extinction curvesderived from the ANS photometric measurements of early type starsbelonging to our Galaxy. This survey is more extensive and deeper thanany other one, based on spectral data. The UV color excesses aredetermined with the aid of 'artificial standards', a new techniqueproposed by the authors which allows the special check of Sp/L match ofa target and the selected standard. The results indicate that extinctionlaw changes from place to place.
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Photoelectric photometry of OB stars in the Vilnius system
Not Available
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Photoelectric Photometry of Stars in the Vilnius System in the Area of the North America and Pelican Nebulae
Not Available
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The interstellar 217 NM band - A third catalogue of equivalent widths
A catalog of equivalent widths of the 217 nm interstellar absorptionband as well as other parameters characterizing the extinction curve inthe ultraviolet has been compiled for 790 O and B stars. A relativelytight correlation between the equivalent width of the 217 nm band andE(B-V) indicates that the absorber of this band is connected with thepopulation of larger interstellar grains responsible for the visualextinction. The parameter characterizing the amount of extinction in thefar UV is only weakly correlated with E(B-V), a result in accord withthe assumption that a second population of very small grains causes therapid increase of the far-UV extinction.
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Accurate Positions for Young Objects NGC7000 and IC5070
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1984RMxAA...9...31D&db_key=AST
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Ultraviolet interstellar extinction toward 1367 stars observed by ANS
Five-band UV photometry is used to investigate the character ofinterstellar extinction toward 1367 stars of spectral type B3 andearlier, with observations producing a galactic average of 5.11, 4.78,6.52, 4.10 and 1.95 at 1550, 1800, 2200, 2500, and 3300 A, respectively.Differences in the strengths of the UV extinction features of thesestars appear to be independent, since objects with either strong or weak2200 A extinction can have strong, normal or weak far-UV extinction.Further investigation reveals that some of the deviant stars areembedded in localized regions whose average extinction curves divergedramatically from the galactic mean. The anomalous extinction of theseregions attests to localized inhomogeneities in the UV characteristicsof interstellar dust. Because the evaluation of UV extinction toward aparticular star would be more accurate if based on the average curve ofthe region immediately surrounding that star rather than that of theentire Galaxy, it is recommended that the galactic average presented beused with caution to correct astronomical data of individual objects.
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Some remarks on the Hα-emission stars in and near NGC 7000 discovered by Welin
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976A&AS...26..367G&db_key=AST
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Near infrared magnitudes of 248 early-type emission-line stars and related objects.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973MNRAS.161..145A&db_key=AST
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Infra-red observations of young stars. I. Stars in young clusters.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973MNRAS.161...85C&db_key=AST
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Photometry and Polarimetry of V 1057 Cygni
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972PASP...84...37R&db_key=AST
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Be stars and galactic rotation.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968AJ.....73..338C&db_key=AST
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Catalogue d'etoiles O et B.
Not Available
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Photoelectric 4430 A observations of 506 O, B and A stars.
Not Available
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KURZE MITTEILUNG. Zur Expansion der Assoziation Cep III
Not Available
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Photoelectric observations of the intensity of the 4430 band in 147 O, B, and A stars in the Northern Milky Way.
Not Available
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Photoelectric observations of the intensity of the 4430 band in 147 O,B, and A stars in the Northern Milky Way
Not Available
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La mesure des vitesses radiales au prisme objectif. XII. 5ème Liste de vitesses radiales déterminées au prisme objectif à vision directe
Not Available
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NGC 7000, IC 5070, and the Associated Emission-Line Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1958ApJ...128..259H&db_key=AST
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INHABITED SKY
