Contents
Images
Upload your image
DSS Images Other Images
Related articles
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.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| 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.
| On the identification of the C60+ interstellar features
The identity of the carriers of the diffuse interstellar bands (DIBs) isone of the most fascinating puzzles of modern spectroscopy. Over thelast few years the number of known DIBs has grown substantially. In thispaper we discuss the two recently discovered near-infrared weakinterstellar features which have already been proposed as fingerprintsof the buckminsterfullerene [formmu2] We present and discussmeasurements of the two related DIBs within a larger sample of reddenedtargets, observed with different spectrometers, telescopes and siteconditions. We provide additional arguments in favour of theinterstellar origin of the two bands. We find evidence around the9577-Å DIB of far-wing structures, which may affect broad-bandmeasurements. We estimate corrections and errors for telluric andstellar blends, and show that the cores of the two DIBs are wellcorrelated with a ratio near unity within 20per cent. Finally, wediscuss their relation to the laboratory spectra of [formmu3] and thesearch for two expected weaker [formmu4] transitions.
| Interstellar velocity components towards reddened stars
The paper analyses the profiles of interstellar features observedtowards heavily reddened stars. All the features show spectacularDoppler-splitting but the radial velocities of the single components aswell as the number of such components vary from feature to feature inthe same spectrum. Implications concerning the wavelengths ofunidentified interstellar lines or bands are briefly discussed.
| Narrow Diffuse Interstellar Bands: A Survey with Precise Wavelengths
We present an atlas of 271 diffuse interstellar bands (DIBs) between4460 and 8800 Å based on echelle spectra (R=45,000), of which morethan 100 are new DIBs discovered in this survey. The atlas is restrictedmostly to narrow features, and we describe the tests for an interstellarorigin. The rest wavelength of each DIB was determined in a high-qualitycomposite spectrum of the star HD 23180 using the interstellar Na I (D1and D2) lines to establish the radial velocity of the single interveningcloud. DIB wavelengths are quoted to 0.01 Å and are probablyaccurate to ~0.1 Å. Other, weak DIBs found in the spectra ofheavily reddened stars are included with a lower wavelength precision.
| Polycyclic Aromatic Hydrocarbons and the Diffuse Interstellar Bands: A Survey
We discuss the proposal relating the origin of some of the diffuseinterstellar bands (DIBs) to neutral and ionized polycyclic aromatichydrocarbons (PAHs) present in interstellar clouds. Laboratory spectraof several PAHs, isolated at low temperature in inert gas matrices, arecompared with the spectra of five reddened early-type stars selectedfrom an extensive set of astronomical spectra. From this comparison, itis concluded that PAH ions are good candidates to explain some of theDIBs. Unambiguous assignments are difficult, however, because of theshift in wavelengths and the band broadening induced in the laboratoryspectra by the solid matrix. This situation is illustrated by acomparison with the gas-phase spectra made available recently for twoPAH ions. Definitive band assignments and, ultimately, the test of theproposal that PAH ions carry some of the DIBs must await theavailability of a larger set of gas-phase measurements in thelaboratory. The present assessment offers a guideline for futurelaboratory experiments by allowing the preselection of promising PAHmolecules to be studied in jet expansions.
| Galactic B-supergiants: A non-LTE model atmosphere analysis to estimate atmospheric parameters and chemical compositions
A non-LTE model atmosphere analysis of moderate resolution (R ~ 5 000)spectra of 46 Galactic B-type supergiants is presented. Standardtechniques are adopted, viz. plane-parallel geometry and radiative andhydrostatic equilibrium. Spectroscopic atmospheric parameters (T_eff,log g & v_turb) and chemical abundances (He, C, N, O, Mg & Si)are estimated, both as a test of the validity of such an approach and inan attempt to provide consistent results for supergiants covering asignificant range of spectral types. The values of the estimatedatmospheric parameters and their dependence on the physics adopted inthe model atmospheres calculations are discussed. The absolute metalabundances are compared to those of main sequence B-type stars and, ingeneral, their chemical compositions appear to be similar. Theabundances for He, C, N & O are considered in some detail and arediscussed in the context of possible evolutionary histories for thisstellar sample. Specifically, it is found that the supergiant sample canbe subdivided into a number of evolutionarily distinct groups. The lowermass objects are predominantly chemically near-normal i.e. theirphotospheres show little or no evidence for chemical processing, whereasthe higher mass supergiants have CNO ratios which are indicative of CNand possibly NO-cycle burning. An attempt is made to quantify thedifference in nitrogen and carbon abundances between the high and lowmass targets but this is hampered by theoretical uncertainties. Thepossibilities that the most highly processed supergiants may have eitherlarger rotational velocities or have undergone mass transfer within abinary system are discussed.
| On the relation between diffuse interstellar bands and simple molecular species
We present observations of the major diffuse interstellar bands (DIBs)at 5780 and 5797 Ä as well as literature data and our ownobservations of the violet lines of CH and CH(+) , in the lines of sighttoward some 70 stars representing various degrees of the interstellarreddening. The correlations are shown and discussed in the context ofindicators such as far-UV extinction parameters and neutral molecularabundances. The results show that the DIBs in question (lambda lambda5797 and 5780) both probably form in diffuse cloud interiors, in arelated regime where CH and H_2 form. The ratio of the two DIBscorrelates with CH abundance, confirming that the lambda 5797 carrier isfavoured in enhanced molecular gas regions over the lambda 5780 carrier.The ratio of the two DIBs correlates poorly with CH(+) abundance. Ourcompilation of observational data also suggests that the DIB ratio maybe equally useful as a cloud type indicator as is R_V, the ratio oftotal to selective extinction, and much more readily observed. Based onobservations obtained at the Russian Special Astrophysical Observatory(SAO), Terskol Observatory (TER), Canada France Hawaii Telescope (CFHT),European Southern Observatory (ESO), Observatoire de Haute-Provence(OHP)
| 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.
| GAIA Spectroscopy: Proposing the 8500--8750 Angstroms Region and Evaluating the Performances
We propose the Gaia spectroscopic observations to be performed over thewavelength interval 8500--8750 Angstroms, with an optimal dispersion of0.25 Angstroms/pix (or 1000 pixels budget per spectrum) and a 2 pixelPSF. In this paper, on the base of extensive observations as well assynthetic spectra and simulations, we review the spectroscopicperformances expected for Gaia: radial and rotational velocities,spectral classification, detection of mass-loss and spectralpeculiarities, chemical abundance analysis and reddening estimates fromthe 8620 Angstroms diffuse interstellar band. Lower dispersion spectra(corresponding to smaller pixel budgets) are considered too.
| Near-Infrared H-Band Features in Late O and B Stars
We examine the spectral characteristics of normal OB stars withhigh-signal-to-noise ratio (>120) H-band (1.6 μm) spectra at aresolution of 2000. We find that several atomic lines vary smoothly withstellar temperature, as first shown by Blum et al. However, we find apreviously unreported, significant variation in the strength of some ofthese lines with stellar luminosity. B supergiant stars show stronger Hei and weaker Br 11 as compared with low-luminosity B dwarf stars of thesame spectral class. It is for this reason that luminosity class mustalso be determined to obtain an accurate spectral type for a given starusing H-band spectra. We suggest a method for estimating the spectraltype and luminosity of an OB star over the wavelength range from 1.66 to1.72 μm using hydrogen Br 11 at 1.681 mum, He i at 1.700 mum, and Heii at 1.693 mum. The use of the near-infrared spectral range forclassification has obvious advantages over optical classification whenapplied to heavily reddened stars, such as in star-forming regions ordeeply embedded lines of sight within the plane of the Galaxy, such asthe Galactic center. Furthermore, the H band is less likely to becontaminated by infrared excess emission, which is frequently seenaround massive young stellar objects beyond 2 mum.
| High resolution spectroscopy of the galactic candidate LBV MWC 314
The results of high-resolution optical spectroscopy obtained for arecently suggested LBV candidate, MWC 314, are presented. Photosphericlines mostly of N ii and S ii have been found for the first time with aresolution of 0.4 - 0.8 Angstroms. They imply a N/O overabundancepreviously reported for AG and HR Car since no O ii absorptions weredetected. Nearly 400 emission lines have been identified in the spectrumbetween 4190 and 8864 Angstroms many of which appear double-peaked. Nosignificant P Cyg-type absorption components have been found for theoptically thick Balmer lines. This suggests that the stellar wind of MWC314 is non-spherical and the circumstellar envelope is viewed notedge-on. The systemic velocity measured using the emission lines ofionized metals turned out to be +55 km s(-1) , which corresponds to adistance towards the object of 3.0 +/- 0.2 kpc, according to thegalactic rotation curve. Our analysis of the characteristics of bothphotospheric and wind lines resulted in an estimate of the object'sT_eff of nearly 25000 K, which, however, needs further improvement. Theother stellar parameters were found to be as follows: log L_bol / Lsun =6.1 +/- 0.3, R_* = 60(+30}_{-10) \ Rsun. Our study confirms that MWC 314is one of the most luminous stars in the Milky Way. Tables 1--4 areavailable in electronic form at the CDS via anonymous ftp 130.79.128.5
| 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.
| Catalogue of stars in the northern Milky Way having H-alpha in emission
Not Available
| 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.
| Spectroscopic and Polarimetric Observations of the Nova Cassiopeiae 1993
Not Available
| Hypergiant 6 CAS and association CAS OB5.
Not Available
| Galactic B-supergiants. II - Line strengths in the visible: Evidence for evolutionary effects?
Following the discovery by Lennon et al. (1992) of anomalously weakcarbon lines in the Galactic B-supergiants, a search was conducted forthe signatures of CNO processed material in the atmospheres of thesestars. It was found that the NII line strengths around spectral type B2correlate with luminosity, but exhibit a clear anticorrelation with theCII lines. It is suggested that this trend may be evidence for CNOprocessed material contaminating the atmospheres of the most luminousstars. The CNO processing signature was found to be most pronounced inthe more luminous supergiants, in qualitative agreement with stellarevolution calculations (provided that such stars have passed through aprevious red-supergiant phase of evolution).
| Galactic B-supergiants. I - an atlas of O9-B9 supergiant spectra from 3950 A to 4950 A
CCD spectra are presented for supergiants of spectral types O9-B9 andluminosity subclasses Ia and Ib. They cover the wavelength region fromapproximately 3950 A to 4950 A at a resolution of 0.8 A, and normallyhave a signal-to-noise in excess of 150 at 4600 A. The spectra arediscussed in respect to their classification. A number of stars showclear evidence of the 'filling in' of hydrogen lines by emission fromthe stellar wind, while HD 190603, a B1.5 Ia(+) hypergiant, exhibits anH-beta P-Cygni type line-profile. Also reported is the finding of a newnitrogen weak star, HD 13866, in the Per OB1 association which isclassified here as BC2 Ib.
| 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.
| 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.
| 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.
| Catalog of O-B stars observed with Tokyo Meridian Circle
A catalog of the O-B stars, selected from 'Blaauw-Parenago' list andRubin's catalog, has been compiled on the FK4 system by the observationsmade with Gautier 8-inch Meridian Circle at the Tokyo AstronomicalObservatory during the period, 1971 to 1979. It contains 1059 stars andwas compiled for the future establishment of high precision propermotions of O-B stars.
| The distribution of interstellar matter toward Tycho's supernova remnant and its relation to distance estimates
Observations of interstellar absorption lines in the spectra of fivestars in the direction of Tycho's Supernova Remnant are presented. Theprofiles show significant absorption at large negative velocities, - 50to - 60 km/s (LSR). This information, together with the distances of thebackground stars, permits limiting distances to be assigned to thecorresponding velocity components in the H I 21-cm line absorptionspectrum of the supernova remnant itself. The 21-cm absorption line datafor Tycho's Supernova Remnant are entirely consistent with a distance assmall as 2 kpc. Distances based upon simple kinematic models of galacticrotation can be confused by well-known noncircular motions in thisdirection. The interstellar line data also reveal a relatively highcolumn density of CO toward HD 108.
| A study of B-type supergiants with the uvby,beta photometric system
The applicability of the uvby,beta photometric system to theclassification and study of B-type supergiants (BTS) is investigatedusing published data on 157 BTS and observations of 17 BTS made with the36-in. reflector at McDonald Observatory. The results are presented intabular form and analyzed to produce preliminary calibrations ofluminosity class vs. beta index and of absolute magnitude (Mv) vs. beta(or delta Mv vs. delta beta) for four associations of stars. Theeffectiveness of various color indices as temperature indicators isdiscussed. It is shown that there is good correspondence between MK anduvby,beta classifications of B-type main-sequence stars, giants, andBTS, confirming the usefulness of the uvby,beta system in furtherresearch on BTS.
| A survey of interstellar neutral potassium. I - Abundances and physical conditions in clouds toward 188 early-type stars
Observations of interstellar absorption in the resonance doublet 7664,7698 A of neutral potassium toward 188 early-type stars at a spectralresolution of 8 km/s are reported. The 7664 A line is successfullyseparated from nearly coincident telluric O2 absorption for all but afew of the 165 stars for which K I absorption is detected, makingpossible an abundance analysis by the doublet ratio method. Therelationships between the potassium abundances and other atomicabundances, the abundance of molecular hydrogen, and interstellarreddening are investigated.
| Studies of luminous stars in nearby galaxies. I. Supergiants and O stars in the Milky Way.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978ApJS...38..309H&db_key=AST
| Observations in linearly polarized light of the intensity of the diffuse lam 6180 absorption band in 56 southern O, B and A stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978A&A....70..195G&db_key=AST
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
| Constellation: | Cassiopeia |
| Right ascension: | 23h54m42.12s |
| Declination: | +61°50'20.1" |
| Apparent magnitude: | 7.242 |
| Distance: | 10000000 parsecs |
| Proper motion RA: | -3.3 |
| Proper motion Dec: | 0.3 |
| B-T magnitude: | 7.98 |
| V-T magnitude: | 7.303 |
Catalogs and designations:
|
