Contents
Images
Upload your image
DSS Images Other Images
Related articles
Automatic Detection of Expanding H I Shells in the Canadian Galactic Plane Survey Data
The identification of expanding H I shells is difficult because of theirvariable morphology. In this paper we present an automatic detector forH I shells, based on the more stable dynamical characteristics ofexpanding bubbles with radii <40 pc. The detection is performed intwo stages. First, artificial neural networks are trained to recognizethe dynamical signature of an expanding bubble in the velocity spectraof 21 cm data. The second stage consists of subsequent validations basedon the potential bubble's morphology. The technique is tested on 11known bubbles, and 10 of them are successfully detected. Conducting asystematic detection on a 48deg×9deg regionin the Perseus arm, we obtain 7100 detections with spatial distributionfollowing the stellar distribution of the Galactic disk. The estimatedradius and expansion velocity distributions for objects with R<=10 pcagree with the distributions predicted by models of adiabaticallyexpanding bubble populations. The fraction of the Perseus arm volumeoccupied by the detected objects, which can be interpreted as the smallbubbles' contribution to the Galactic porosity Q, is calculated toQR<40pc=0.007+0.025-0.003. Four newbubble cases and eight serious candidates, related to known progenitors,are proposed.
| Bright OB stars in the Galaxy. II. Wind variability in O supergiants as traced by Hα
We investigate the line-profile variability (lpv) of Hα for alarge sample of O-type supergiants (15 objects between O4 and O9.7), inan objective, statistically rigorous manner. We employed the TemporalVariance Spectrum (TVS) analysis, developed for the case of photosphericabsorption lines and modified by us to take into account the effects ofwind emission. By means of a comparative analysis we place constraintson the properties of this variability - quantified in terms of a meanand a newly defined fractional amplitude of deviations - as a functionof stellar and wind parameters. The results of our analysis show thatall the stars in the sample show evidence of significant lpv inHα, mostly dominated by processes in the wind. The variationsoccur between zero and 0.3 v_&infy; (i.e., below 1.5 R_star ), in goodagreement with results from similar studies. A comparison between theobservations and corresponding line-profile simulations indicates thatfor stars with intermediate wind densities the properties of theHα variability can be explained by simple models consisting ofcoherent or broken shells (blobs) uniformly distributed over the windvolume, with an intrinsic scatter in the maximum density contrast ofabout a factor of two. For stars at lower and higher wind densities, onthe other hand, we found certain inconsistencies between theobservations and our predictions, most importantly concerning the meanamplitude and the symmetry properties of the TVS. This disagreementmight be explained by the presence of coherent large-scale structures,partly confined in a volume close to the star. Interpreted in terms of avariable mass-loss rate, the observed variations of Hα indicatechanges of ±4% with respect to the mean value of dot M for starswith stronger winds and of ± 16% for stars with weaker winds. Theeffect of these variations on the corresponding wind momenta is ratherinsignificant (less than 0.16 dex), increasing only the local scatterwithout affecting the Wind Momentum Luminosity Relationship.
| A Galactic O Star Catalog
We have produced a catalog of 378 Galactic O stars with accuratespectral classifications that is complete for V<8 but includes manyfainter stars. The catalog provides cross-identifications with othersources; coordinates (obtained in most cases from Tycho-2 data);astrometric distances for 24 of the nearest stars; optical (Tycho-2,Johnson, and Strömgren) and NIR photometry; group membership,runaway character, and multiplicity information; and a Web-based versionwith links to on-line services.
| Bright OB stars in the Galaxy. I. Mass-loss and wind-momentum rates of O-type stars: A pure H\alpha analysis accounting for line-blanketing
We study mass-loss and wind momentum rates of 29 Galactic O-type starswith luminosity classes I, III and V by means of a pure H\alpha profileanalysis and investigate to what extent the results compare to thoseoriginating from a state-of-the-art, complete spectral analysis. Ourinvestigation relies on the approximate method developed by\citet{Puls96} which we have modified to account for the effects ofline-blanketing. Effective temperatures and gravities needed to obtainquantitative results from such a simplified approach have been derivedby means of calibrations based on most recent spectroscopic NLTEanalyses and models of Galactic stars by \citet{Repo03} and\citet{Martins02}. Comparing (i) the derived wind-densities to thosedetermined by \citet{Repo03} for eleven stars in common and (ii) theWind-momentum Luminosity Relationship (WLR) for our sample stars tothose derived by other investigations, we conclude that our approximateapproach is actually able to provide consistent results. Additionally,we studied the consequences of ``fine tuning'' some of the direct andindirect parameters entering the WLR, especially by accounting fordifferent possible values of stellar reddening and distances. Combiningour data set with the corresponding data provided by \citet{Herrero02}and \citet{Repo03} we finally study the WLR for the largest sample ofGalactic O-type stars gathered so far, including an elaborate errortreatment. The established disagreement between the theoreticalpredictions and the ``observed'' WLRs being a function of luminosityclass is suggested to be a result of wind clumping. Different strategiesto check this hypothesis are discussed, particularly by comparing theH\alpha mass-loss rates with the ones derived from radio observations.
| A study of RV in Galactic O stars from the 2MASS catalogue
We present new measurements of the interstellar reddening parameterRV=AV/E(B-V) towards 185 O stars, using J, H,Ks photometry from the 2MASS project. The results arecombined with data from the literature of 95 stars where RVhas been derived with the same technique, 22 of which in common with ourpresent sample from the 2MASS project catalogue. The averageRV from these 258 O stars is of 3.19 +/- 0.50. All objectswhose RV departs from this value by more than 2 sigma havebeen recognized. Ten objects have RV higher than this valueand two lower. It is found that anomalous RV can scarcely beassociated with anomalies in the general interstellar medium, e.g. withdifferent behaviour in different spiral arms. They are clearly linked tolocal cloud effect. In the Cygnus region RV values follow thebehaviour of the general interstellar medium, while in the Carina arm,in spite of the relatively larger distance, local cloud effects prevail.An explanation for this is suggested. The relatively few stars of oursample whose Hipparcos parallaxes are reliable, are found to havedistances systematically smaller than the distances derived by thespectroscopic parallaxes. We argue that this effect is consistent withthe recently claimed discovery of grey extinction towards OB stars.This publication makes use of data products from the Two Micron All SkySurvey (2MASS), which is a joint project of the University ofMassachusetts and the Infrared Processing and Analysis Center/CaliforniaInstitute of Technology, funded by the National Aeronautics and SpaceAdministration and the National Science Foundation.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/410/905
| Three Lynds Bright Nebulae
The region from l=139.5d-141.0d, b=-2.5d-3.0d contains three faint LyndsBright Nebulae. LBN 140.77-1.42 and the lower portion of LBN 140.07+1.64are associated with an intriguing arc of neutral hydrogen at Perseus Armvelocities and morphologically associated CO and dust emission. Youngstellar objects (YSOs) are found along the length of the H I feature,several with velocities indicating a connection with the features in themolecular and neutral material. The arc-shaped ionized emission from LBN139.57+2.70 is associated with a hole in H I also at Perseus Armvelocities and contains a YSO at its edge. The hole is consistent with awind-driven bubble blown by an early B star. This paper uses data fromthe Canadian Galactic Plane Survey to characterize these regions,studying the gas, dust, and YSO components of the nebulae and thesources of illumination for the ionized gas.
| Radio observations of interstellar bubbles surrounding massive stars}
We show radio continuum observations of the WR ring nebulae around WR101 and WR 113 obtained using the VLA and HI 21 cm line data of theinterstellar bubble around the O type stars BD +24 deg 3866 and BD+25deg 3952 obtained with the DRAO Synthesis Telescope. We review previousradio continuum and HI line results toward WR and O-type stars.
| Massive Stars in the Arches Cluster
We present and use new spectra and narrowband images, along withpreviously published broadband images, of stars in the Arches cluster toextract photometry, astrometry, equivalent width, and velocityinformation. The data are interpreted with a wind/atmosphere code todetermine stellar temperatures, luminosities, mass-loss rates, andabundances. We have doubled the number of known emission-line stars, andwe have also made the first spectroscopic identification of the mainsequence for any population in the Galactic center. We conclude that themost massive stars are bona fide Wolf-Rayet (W-R) stars; are some of themost massive stars known, havingMinit>100Msolar and have prodigious winds,M>10-5 Msolar yr-1, that areenriched with helium and nitrogen; with these identifications, theArches cluster contains about 5% of all known W-R stars in the Galaxy.We find an upper limit to the velocity dispersion of 22 kms-1, implying an upper limit to the cluster mass of7×104 Msolar within a radius of 0.23 pc; wealso estimate the bulk heliocentric velocity of the cluster to bevcluster,solar~+95 km s-1. Taken together, theseresults suggest that the Arches cluster was formed in a short, butmassive, burst of star formation about 2.5+/-0.5 Myr ago, from amolecular cloud that is no longer present. The cluster happens to beapproaching and ionizing the surface of a background molecular cloud,thus producing the thermal arched filaments. We estimate that thecluster produces 4×1051 ionizing photonss-1, more than enough to account for the observed thermalradio flux from the nearby cloud, 3×1049 ionizingphotons s-1. Commensurately, it produces 107.8Lsolar in total luminosity, providing the heating source forthe nearby molecular cloud, Lcloud~107Lsolar. These interactions between a cluster of hot stars anda wayward molecular cloud are similar to those seen in the``Quintuplet/Sickle'' region. The small spread of formation times forthe known young clusters in the Galactic center and the relative lack ofintermediate-age stars(τage=107.0-107.3 yr) suggest thatthe Galactic center has recently been host to a burst of star formation.Finally, we have made new identifications of near-infrared sources thatare counterparts to recently identified X-ray and radio sources. Basedon observations with the NASA/ESA Hubble Space Telescope, obtained atthe Space Telescope Science Institute, which is operated by theAssociation of Universities for Research in Astronomy, Inc., under NASAcontract NAS5-26555.
| On the Absolute Magnitudes of the O Stars
The conclusion published in 1992 by Garmany & Stencel from a studyof northern OB associations, that the absolute magnitudes of the O starsshow ``a large scatter ... intrinsic to the classification system,'' iscritically examined. It is found that the differences between theirderived absolute magnitudes of O stars and this author's 1973calibration exhibit large systematic effects in several associations,ranging from -0.74 to +1.02 mag with substantially smaller dispersions.Of course, when these results are combined, the scatter equals the fullrange of the systematic effects. To investigate the possibility ofdistance errors, the Garmany & Stencel B0-B2.5 stars in the sameassociations are subjected to the same analysis. The results for the Bstars show no significant systematic differences, eliminating errors inthe association distances derived by Garmany & Stencel from the Bstars as the source of the differences found for the O stars. It isnoteworthy that the dispersions in the absolute magnitudes of the Bstars within a given association are similar to or larger than those ofthe O stars. An examination of the distribution on the sky of the starsshows that the O and B stars in the discrepant associations aregenerally not colocated; such was already known to be the case for theimportant Perseus OB1 association. It is suggested that despite theirefforts to improve them, significant problems remain with theassociation memberships adopted by Garmany & Stencel; the relativelysmall dispersions of the O star absolute magnitudes even in thediscrepant cases indicate that they belong to different, usually moredistant associations near the lines of sight to the B associations withwhich they have been mistakenly connected. Several individual cases ofunrecognized multiple systems and classification errors are also foundin the Garmany & Stencel sample. It is concluded that the scatter inthe absolute magnitudes of the O stars is not as large as found byGarmany & Stencel, and not larger than that of the B stars.
| 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
| A Search for Interstellar Bubbles surrounding Massive Stars in Perseus OB1
We have examined the interstellar medium in the vicinity of massivestars belonging to the Per OB1 association based on neutral hydrogen 21cm observations obtained with the 100 m radio telescope at Effelsberg(HPBW=8.4′) and complementary data from the Leiden-Dwingeloo H ISurvey (HPBW=36'). The higher angular resolution H I observationsallowed us to discover probable wind-blown bubbles related to fourmassive stars in the association, namely, HD 14442 [O5n(f)p], HD 14947[O5If+], HD 13022 [O9.5II-III((n))], and HD 13338 [O9.5V], while thedetection of a wind-blown bubble associated with HD 16691 [O5If+] isless conclusive. A clear H I shell coincident in position with two B1IIIstars (HD 15233 and Hilt 311) was also detected. Some of these featuresalso have infrared and/or molecular counterparts. The energetics of thestructures related to each massive star is analyzed. The new H Iinterstellar bubbles appear to be similar to the ones found surroundingWolf-Rayet stars and other Of stars. The large-scale maps obtained usingthe lower angular resolution H I data show that most of the early-typestars belonging to Per OB1 are placed in a region of low H I emission.The association could have blown a H I shell of about 350×550 pcin size. This large H I shell has an infrared counterpart.
| 1-m spectroscopy of normal OB stars
We have obtained spectra of 70 normal OB stars in the near-IR I(1-μm) band. The strongest features are those due to lines of thehydrogen Paschen series and neutral and ionized helium, which are, forthe most part, in absorption. The information content in this spectralrange is sufficient for only a rough classification of hot stars into`early O', `late O' and `B' types. Curiously, the leading He i tripletline, He i λ1.0830 μm, is usually not detectable, although ina few stars it is in emission; its behaviour generally correlates withthe leading helium singlet line, He i λ 2.058 μ m. These twofeatures appear to be present in emission only in stars with extremes ofmass loss or wind extension.
| 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.
| On the normal energy distribution in stellar spectra: O5-O8 stars
The spectral energy curves for a number of O4-O8 stars are analyzedusing measurements taken from six sources of spectrophotometric data.Based on the normal UBV color indices for O stars, these stars aredivided into three groups (O5, O6-O7, and O8), for each of which thenormal energy distribution is derived and presented. Comparison of thesedistributions indicates clear differences between the O5 and O8subclasses at UV wavelengths. A single normal distribution curve is,therefore, insufficient to characterize the O spectral class as a whole.
| Accurate Two-dimensional Classification of Stellar Spectra with Artificial Neural Networks
We present a solution to the long-standing problem of automaticallyclassifying stellar spectra of all temperature and luminosity classeswith the accuracy shown by expert human classifiers. We use the 15Angstroms resolution near-infrared spectral classification systemdescribed by Torres-Dodgen & Weaver in 1993. Using the spectrum withno manual intervention except wavelength registration, artificial neuralnetworks (ANNs) can classify these spectra with Morgan-Keenan types withan accuracy comparable to that obtained by human experts using 2Angstroms resolution blue spectra, which is about 0.5 types (subclasses)in temperature and about 0.25 classes in luminosity. Accuratetemperature classification requires a hierarchy of ANNs, whileluminosity classification is most successful with a single ANN. Wepropose an architecture for a fully automatic classification system.
| A Spectral Atlas of Hot, Luminous Stars at 2 Microns
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJS..107..281H&db_key=AST
| Infrared Spectra of Massive Stars in Transition: WNL, Of, Of/WN, Be, B[e], and Luminous Blue Variable Stars
Abstract image available at:http://adsabs.harvard.edu/abs/1996ApJ...470..597M
| The Discovery of Hot Stars near the Galactic Center Thermal Radio Filaments
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJ...461..750C&db_key=AST
| 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.
| Diffuse interstellar bands and UV extinction curves. The missing link.
The connection between diffuse interstellar bands and components of theinterstellar ultraviolet extinction curve, decomposed according to theFitzpatrick & Massa scheme, is analysed from new observations ofseveral DIBs in the line of sight to 28 stars measured by IUE. We findthat the strength of the 217.5nm bump positively correlates with DIBstrength, whereas correlations with a negative slope exist with the FUVnon-linear rise and the width of the bump. There is no correlation withlinear rise. The relation of bump height versus DIB strength does notpass through zero. The results are interpreted within the polycyclicaromatic hydrocarbon (PAH) framework. They strengthen the hypothesisthat the FUV non-linear rise is produced by neutral PAHs, whereas DIBcarriers are found among some ionised or radical PAHs.
| Of-type stars HD 16691 and HD 190429 show WN-like spectra in infrared K band
We present 2 micrometer K-band spectra of two early-type Of stars thathave infrared emission-line morphology similar to that of WN stars.Archival International Ultraviolet Explorer (IUE) spectra of these twostars indicate they appear to be Of type, rather than WN. Recentlyacquired optical spectra of these stars are quantitatively similar tothat in the past, namely, Of attributes. We suggest that these two Ofstars have stellar wind characteristics closer to WN type than other Ofstars. We discuss the consequences for K-band classification of highlyobscured hot stars that might not otherwise be visible in optical or UVwavelengths.
| Radio continuum emission from stars: a catalogue update.
An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed.
| The Diffuse Ionized Interstellar Medium: Structures Resulting from Ionization by O Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993ApJ...417..579M&db_key=AST
| Tracing the Roots of Interstellar Mid Infrared Emission
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&A...275..549J&db_key=AST
| Environment Dependence of Interstellar Extinction Curves
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&A...274..439J&db_key=AST
| A new library of stellar optical spectra
Attention is given to a new digital optical stellar library consistingof spectra covering 3510-8930 R at 11-A resolution for 72 differentstellar types. These types extend over the spectral classes O-M andluminosity classes I-V. Most spectra are of solar metallicity stars butsome metal-rich and metal-poor spectra are included. This new library isquantitatively compared to two previously published libraries. It offersseveral advantages over them: it is photometrically well-calibratedindividually and consistently from star to star. Good temperature andluminosity coverage has been achieved. The incorporation of stars withwell-determined temperature, metallicity, and surface gravity parametersincreases the accuracy of the spectral type assigned to each compositelibrary star.
| 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.
| Distribution and motions of OB stars in the direction of H and KHI Perseus.
Not Available
| 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).
| Mass loss from stars : the universal formula for mass loss rate
Not Available
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
| Constellation: | Perseus |
| Right ascension: | 02h42m52.03s |
| Declination: | +56°54'16.5" |
| Apparent magnitude: | 8.709 |
| Distance: | 10000000 parsecs |
| Proper motion RA: | -2.5 |
| Proper motion Dec: | -5.3 |
| B-T magnitude: | 9.169 |
| V-T magnitude: | 8.747 |
Catalogs and designations:
|
INHABITED SKY
