Physical parameters and orbit of the eclipsing binary BD +66 1663 = GSC 4479 412
We have obtained the first UBV( RI) C photoelectric lightcurves of the recently discovered eclipsing binary BD +66 1663 = GSC4479 412 ( P = 7.04d, V = 10.14). We have derived relativeand absolute parameters of the binary, and analyzed the interstellarextinction towards the object. Though the star is located in the fieldof the young open cluster Be 59, we demonstrate that it is not a member.
|
Stellar contents and star formation in the young star cluster Be 59
We present UBV Ic CCD photometry of the young open cluster Be59 with the aim to study the star formation scenario in the cluster. Theradial extent of the cluster is found to be ~10 arcmin (2.9 pc). Theinterstellar extinction in the cluster region varies between E(B - V) ~=1.4 to 1.8 mag. The ratio of total-to-selective extinction in thecluster region is estimated as 3.7 +/- 0.3. The distance of the clusteris found to be 1.00 +/- 0.05 kpc. Using near-infrared (NIR) colours andslitless spectroscopy, we have identified young stellar objects (YSOs)in the open cluster Be 59 region. The ages of these YSOs range between<1 and ~2 Myr, whereas the mean age of the massive stars in thecluster region is found to be ~2 Myr. There is evidence forsecond-generation star formation outside the boundary of the cluster,which may be triggered by massive stars in the cluster. The slope of theinitial mass function, ?, in the mass range 2.5
|
A Preliminary Investigation of the Diffuse Interstellar Line at 8621 Å
We have obtained high-resolution spectra at the Dominion AstrophysicalObservatory, the Calar Alto Observatory, and the European SouthernObservatory of hot stars in the near-infrared region to study thediffuse interstellar band (DIB) at 8621 Å. Field stars as well asselected members of the Perseus spiral arm, the ρ Ophiuchi complex,and the Cygnus OB2 association were observed and the equivalent widthsof the band measured, as well as interstellar K I absorption at 7699Å. In total we measure the equivalent width of the 8621 band in 64stars. In a series of figures we show the correlations of the DIB withreddening, polarization, K I, and strengths of other DIBs at 5780, 5797,and 6613 Å. The quality of the correlations are discussed by meansof the Spearman rank correlation test. Good correlations are found withreddening and, among the other DIBs, 8621 correlates best with 5780. Byexamining the three special regions mentioned above we confirm theweakness of the 8621 DIB in the hot stars of the ρ Oph star-formingregion. In the Perseus spiral arm region we find that the DIBs areformed largely in foreground clouds but not in the gas that appears tohave been blown away from the young massive stars of the Perseus arm. InCyg OB2 we find that the equivalent widths of the 8621 line lie abovethe linear correlation of equivalent width with E(B-V) and theirstrength does not vary as strongly with reddening. The heavily reddenedCyg OB2 star 12 is the most extreme example of the relativeinsensitivity of the 8621 equivalent width to reddening in the CygnusOB2 region.
|
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.
|
Interstellar absorption lines toward Cep OB4
An analysis of optical echelle spectra towards nine stars in the Cep OB4association is presented. Interstellar absorption lines which arise inthe (1, 0) and (2, 0) bands of the CN A 2Π - X2Σ+ red system towards BD+66o1661, BD+66o 1674, and BD+66o 1675 are used toinfer accurate CN column densities N(CN). A comparison with earliermeasurements in the CN violet system allows to infer a CN Doppler bparameter of b(CN) = 1.2{-}2.4 km s-1. Molecular carbonabsorption lines which arise in the (1, 0), (2, 0) and (3, 0) bands ofthe C2 A1Πu -X1Σg+ Phillips system is used toinfer gaskinetic temperatures of 35±10 K and densities of n = 700± 200 cm-3 towards BD+66o 1661 andBD+66o 1675, and a temperature of 60±10 K and adensity of 800 ± 400 cm-3 towards BD+66o1674. The R(1) line of the (0, 0) band of the CH A2Δ -X2Π system is detected towards 6 stars. A tightcorrelation exists between N(C2) and N(CH). N(CN) increaseswith N(CH) and with N(C2). Interstellar CH+ ismarginally detected towards four stars. Inferred CH+ columndensities are significantly lower than towards other lines of sight withsimilar reddening. The velocity structure towards Cep OB4 and thechemical abundances suggest that CN, C2, CH, andCH+ are formed in quiescent material. A previous suggestionthat the molecules form in a photon-dominated region close to the starsis not supported by the observations.Based on observations collected at the Centro Astronómico HispanoAlemán (CAHA) at Calar Alto, operated jointly by the Max-PlanckInstitut für Astronomie and the Instituto de Astrofisica deAndalucia (CSIC).
|
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.
|
The relation between far-UV and visible extinctions
For directions of sufficient reddening (/E(B-V)>~0.25), there is asimple relation between the slope of the extinction curve in the far-UVand /E(B-V). Regardless of direction, the far-UV extinction curve isproportional to 1/λn e-2E(B-V)/λ(/λ in μm, /n=4), in accordance with the idea that reddenedstars spectra are contaminated by scattered light (Zagury, 2001b). Thisrelation is not compatible with the standard theory of extinction whichstates that far-UV and visible extinctions are due to different classesof particle. In that model the two (far-UV and visible) extinctions varythus independently according to the proportion of each type of particle.In preceding papers I have shown that the standard theory cannot explainUV observations of nebulae, and is contradicted by the UV spectra ofstars with very low reddening: for how long shall the standard theory beconsidered as the interpretation of the extinction curve?
|
Classification and properties of UV extinction curves
The catalog of Savage et al. (\cite{ref27}) reporting colour excesses of1415 stars from ANS photometry offers the opportunity to deeplyinvestigate the characteristics of UV extinction curves which differfrom the standard extinction of the diffuse interstellar medium. To thisaim we have selected a sample of 252 curves, which have been comparedwith the relations derived by Cardelli et al. (\cite{ref4}; CCM in thefollowing) for a variety of R_V values in the range 2.4-5 and have beenclassified as normal if they fit at least one of the CCM curves oranomalous otherwise. We find that normal curves with small R_V are justas numerous as those with large R_V. The anomalous objects are arrangedinto two groups according to the strength of the bump at 0.217 mu . Fora given value of c_2 this increases along the sequence: type Aanomalous, normals and type B anomalous, suggesting that this sequenceshould correspond to an increase of the amount of small grains along thesightline. Considerations concerning the environmental characteristicsindicate that the anomalous behaviour is not necessarily tied to theexistence of dense gas clouds along the line of sight.
|
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
|
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.
|
Radio continuum emission from stars: a catalogue update.
An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed.
|
New spectral classifications for O-type stars in the Northern Hemisphere
In order to update the classifications of O and B stars in the vicinityof the sun, moderate-resolution spectra have been obtained in thewavelength region about 4000 A to about 5000 A of 32 O and B starswithout published luminosity classifications. Normalized spectra andrevised spectral classifications are presented. Two of the stars arefound to be members of the O3 spectral class.
|
The upper main sequence of OB associations. II - The single-lined O stars: Spectral classification of northern stars and lines of C and N
The properties of the stars close to the upper main sequence of OBassociations are studied in order to provide constraints on the theoryof evolution of massive stars. The spectral classification of northernsingle-lined O stars, most of them belonging to the associations CygOB1, Per OB1 and Cas OB6, is presented. The classification is performedaccording to Conti's classification scheme for O stars, amended byMathys (1988). The behavior of the C and N lines of the stars isstudied, in order to determine whether CNO-processed material is visibleat their surface. Three new ON stars have been discovered: BD + 36 deg4063 (O9.71), HD 13268 (O8V), and HD 110360 (O7V).
|
A survey of radio emission from Galactic OB stars
Radio continuum observations of 88 O-type and early B-type stars areexamined. Results are presented for a subset of these stars which formsa distance-limited sample of all OB stars within 2.5 kpc of the sun.Mass loss rates are derived for HD 15570, HD 166734, HD 151804, HD152408, Alpha Cam, HD 169454, and Zeta Sco. All of these very luminousOB stars are found to be losing mass at a rate on the order of 10 to the-5 solar masses/yr. Multifrequency observations confirm the free-freeinterpretation for Zeta Pup and provide evidence for variability in thefree-free sources P Cygni and Cyg OB2 No. 12.
|
Mid-infrared excess and ultraviolet extinction
Recent suggestions that the mid-infrared excess and the 2174 Aextinction bump have the same origin are investigated. For this purpose,correlations between the mid infrared excess and the ultravioletextinction parameters are examined, using a sample of 61 stars reportedto have peculiar extinction properties. No correlation is found betweenthe mid-infrared excess and the ultraviolet extinction bump or the farultraviolet extinction rise. This result suggests that the carriers ofthe ultraviolet bump and the mid-infrared emission are different.
|
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.
|
Exciting stars and the distances of the diffuse nebulae
Not Available
|
The initial mass function for massive stars
A machine readable catalog of over 750 galactic O stars with publishedphotometry, spectral types, and luminosity classes has been compiled.The catalog is probably complete to a distance of about 2.5 kpc. Fromthis volume-limited data, the initial mass function (IMF) for stars moremassive than 20 solar masses has been derived. This IMF differs fromthat of Miller and Scalo (1979) and of Lequeux (1979), in havingproportionately more O type stars and not as steep a fall-off in numberof stars with increasing mass. Dividing the sample into stars inside andoutside the solar circle, a substantial difference in the IMF of themost massive stars is found. There are proportionally more toward thegalactic center. This gradient in the IMF may be related to the observedspace density of Wolf-Rayet stars, which are descendants of O typestars.
|
The law of interstellar absorption in the wave-number interval 0.95/micron to 3.03/microns
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1982A&A...115..347A&db_key=AST
|
Radio-wavelength observations of CH in the direction of nearby bright stars
Observations of the 9 cm F = 1-1 Lambda doublet transition of the CHmolecule have been made in the direction of 22 stars which lie in thevicinity of diffuse interstellar clouds. Positive detections were madetoward 14 of the regions. In some cases more than one emission featurewas detected. The ratio of the column densities of CH in the radio andoptical spectral regions is 1.11 + or - 0.4. The velocities and widthsof the CH lines differ from those of the CH(+) lines in the direction ofZeta Oph, Chi 2 Ori and Chi Oph, providing support for the theory thatthe CH(+) molecules are formed in a hot compressed gas produced by apassing interstellar shock wave.
|
21-cm observations of the CEP IV star-formation region
The Cep IV star-formation region has been mapped at 21 cm. The resultingH I distribution indicates that the available gas forms a broken ringcoincident with the optical nebulosity. Comparison of this feature withother kinematic data for both stars and gas suggests that sequentialstar formation is an ongoing process in this region.
|
A catalogue of stellar spectrophotometric data
A list of 378 sets of stellar energy distributions for 356 stars basedon photoelectric spectrophotometry is presented. Data from eight sourceshave been transformed to the Hayes-Latham calibration of Alpha Lyrae.The procedure follows that of Breger (1976) and the present list extendsprevious data, especially for stars of earliest and intermediatespectral types.
|
2.8 and 6 CM wavelength observations of NGC 7822
Abstract image available at:http://adsabs.harvard.edu/abs/1977A&A....61..285A
|
Isolated Stroemgren spheres as a source of galactic H alpha emission
The isolated H alpha emission features reported by Reynolds et al. areidentified with Stroemgren spheres surrounding observed O stars; theroot mean square electron densities and Stroemgren radii are calculatedfrom the observed emission measure and stellar type. The density has anaverage value of 2 per cu cm but increases to 3.3 per cu cm for starswithin 200 pc of the galactic plane. An analysis of the Catalogue ofGalactic O Stars shows that enhanced H alpha emission is observed aroundall known O stars. The diffuse component of H alpha emission is what onewould expect from the line-of-sight overlapping of isolated Stroemgrenspheres surrounding B stars and appears to correlate with features onextinction maps, as derived. There is no compelling reason to suggestany large-scale intercloud ionization from H alpha data alone.
|
A catalogue of galactic O stars. The ionization of the low density interstellar medium by runaway stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974RMxAA...1..211C&db_key=AST
|
Wavelength dependence of polarization. XXV. Rotation of the position angle by the interstellar medium.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974AJ.....79..565C&db_key=AST
|
Spectroscopic observations of stars in HII regions.
Not Available
|
A new general O type stars catalogue
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973A&AS...12..277G&db_key=AST
|
Individual reddening laws from O type stars. I. Computation method, first results.
Not Available
|
A Comparison of Radio Observations of NGC 7822 (Wi) with the OB Stars in the Coph IV Association
Abstract image available at:http://adsabs.harvard.edu/abs/1970A&A.....4..309C
|
