Obscured clusters. IV. The most massive stars in [DBS2003] 179
Aims: We report new results for the massive evolved and mainsequence members of the young galactic cluster DBS2003 179. We determinethe physical parameters and investigate the high-mass stellar content ofthe cluster, as well as of its close vicinity. Methods: Ouranalysis is based on ISAAC/VLT moderate-resolution (R ≈ 4000)infrared spectroscopy of the brightest cluster members. We derivestellar parameters for sixteen of the stellar members, using fullnon-local thermodynamic equilibrium modeling of the obtained spectra. Results: The cluster contains three late WN or WR/LBV stars (Obj4, Obj 15, and Obj 20:MDM 32) and at least five OIf and five OV stars.According to the Hertzsprung-Russell diagram for DBS2003 179, the WRstars show masses above 85 ℳ&sun;, the OIf stars arebetween 40 and 80 ℳ&sun;, and the main sequence Ostars are >20 ℳ&sun;. There are indications ofbinarity for Obj 4 and Obj 11, and Obj 3 shows a variable spectrum. Thecluster is surrounded by a continuous protostar formation region mostprobably triggered by DBS2003 179. Conclusions: We confirm thatDBS2003 179 is young massive cluster (2.5 × 104ℳ&sun;) very close to the Galactic center at thedistance of 7.9 ± 0.8 kpc.Based on observations gathered with ISAAC,VLT and VISTA of the ESO andthe 8.2-m GEMINI telescope within observing programs 81.D-0471,179.B-2002, and GS-2009A-Q-81.
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On the Apparent Lack of Be X-Ray Binaries with Black Holes
In our Galaxy there are 64 Be X-ray binaries known to date. Out ofthese, 42 host a neutron star (NS), and for the remainder the nature ofthe companion is unknown. None, so far, are known to host a black hole(BH). There seems to be no apparent mechanism that would preventformation or detection of Be stars with BHs. This disparity is referredto as a missing Be-BH X-ray binary problem. We point out that currentevolutionary scenarios that lead to the formation of Be X-ray binariespredict that the ratio of binaries with NSs to the ones with BHs israther high, F NStoBH ~ 10-50, with the more likely formationmodels providing the values at the high end. The ratio is a naturaloutcome of (1) the stellar initial mass function that produces more NSsthan BHs and (2) common envelope evolution (i.e., a major mechanisminvolved in the formation of interacting binaries) that naturallyselects progenitors of Be X-ray binaries with NSs (binaries withcomparable mass components have more likely survival probabilities) overones with BHs (which are much more likely to be common envelopemergers). A comparison of this ratio (i.e., F NStoBH ~ 30)with the number of confirmed Be-NS X-ray binaries (42) indicates thatthe expected number of Be-BH X-ray binaries is of the order of only~0-2. This is entirely consistent with the observed Galactic sample.
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Corrections to the Hipparcos Proper Motions in Declination for 807 Stars
We used the data on latitude variations obtained from observations with10 classical photographic zenith tubes (PZT) in order to improve theHipparcos proper motions in declinations ?_{?} for 807 stars.Part of observing programmes, carried out during the last century forthe purpose of studying the Earth's rotation, were realized by using PZTinstruments. These observations were performed within in the intervals(tens of years) much longer than that of the Hipparcos mission (lessthan 4 years). In addition, the annual number of observations for everyPZT-programme star is several hundreds on the average. Though theaccuracy of the star coordinates in the Hipparcos Catalogue is by twoorders of magnitude better than that of the star coordinates from thePZT observations, the large number of observations performed a muchlonger time interval makes it possible to correct the Hipparcos propermotions and to improve their accuracy with respect to the accuracy givenin the Hipparcos Catalogue. Long term examinations of latitude and timevariations were used to form the Earth Orientation Catalogue (EOC-2),aimed at a more accurate determination of positions and proper motionsfor the stars included. Our method of calculating the corrections of theproper motions in declination from the latitude variations is differentfrom the method used in obtaining the EOC-2 Catalogue. Comparing theresults we have established a good agreement between our ?_{?}and the EOC-2 ones for the star sample used in the present paper.
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The young Galactic star cluster [DBS2003] 179
Context: Recent near- and mid-infrared surveys have brought evidencethat the Milky Way continues to form massive clusters. Aims: Wecarry out a program to determine the basic physical properties of thenew massive cluster candidate [DBS2003] 179. Methods:Medium-resolution K-band spectra and deep near-infrared images of[DBS2003] 179 were used to derive the spectral types of eight memberstars, and to estimate the distance and reddening to the cluster. Results: Seven of ten stars with spectra show emission lines.Comparison with template spectra indicated that they are early O-typestars. The mean radial velocity of the cluster is V_rad=-77 ± 6km s-1. Knowing the spectral types of the members and thecolor excesses, we determined extinction AV ˜ 16.6 anddistance modulus (m-M)0 ˜ 14.5 mag (D˜7.9 Kpc).The presence of early O-stars and a lack of red supergiants suggests acluster age of 2-5 Myr. The total cluster mass is approximated to 0.7× 10 ^4~M&sun; and it is not yet dynamically relaxed.Conclusions: The candidate [DBS2003] 179 further increases thefamily of the massive young clusters in the Galaxy, although it appearsless massive than the prototypical starburst clusters.Based on observations collected with the Very Large Telescope of theEuropean Southern Observatory within the Observing Program79.D-0149(A).This paper includes data gathered with the 6.5 m MagellanTelescopes located at Las Campanas Observatory, Chile.
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Finding Periods in High Mass X-Ray Binaries
This is a call for amateur astronomers who have the equipment andexperience for producing high quality photometry to contribute to aprogram of finding periods in the optical light curves of high massX-ray binaries (HMXB). HMXBs are binary stars in which the lighter staris a neutron star or a black hole and the more massive star is a Type Osupergiant or a Be type main sequence star. Matter is transferred fromthe ordinary star to the compact object and X-rays are produced as thegravitational energy of the accreting gas is converted into light. HMXBsare very bright, many are brighter than 10th magnitude, and so makeperfect targets for experienced amateur astronomers with photometrycapable CCD equipment coupled with almost any size telescope.
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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.
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High-energy sources before INTEGRAL. INTEGRAL reference catalog
We describe the INTEGRAL reference catalog which classifies previouslyknown bright X-ray and gamma-ray sources before the launch of INTEGRAL.These sources are, or have been at least once, brighter than ~ 1 mCrababove 3 keV, and are expected to be detected by INTEGRAL. This catalogis being used in the INTEGRAL Quick Look Analysis to discover newsources or significantly variable sources. We compiled several publishedX-ray and gamma-ray catalogs, and surveyed recent publications for newsources. Consequently, there are 1122 sources in our INTEGRAL referencecatalog. In addition to the source positions, we show an approximatespectral model and expected flux for each source, based on which wederive expected INTEGRAL counting rates. Assuming the default instrumentperformances and at least ~ 105 s exposure time for anypart of the sky, we expect that INTEGRAL will detect at least ~ 700sources below 10 keV and ~ 400 sources above 20 keV over the missionlife.The Catalog is available in electronic form at the CDS via anonymous ftpto cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?/A+A/411/L59
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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.
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The Hard X-Ray Luminosity of OB Star Populations: Implications for The Contribution of Star Formation to the Cosmic X-Ray Background
We present an empirical analysis of the integrated X-ray luminosityarising from populations of OB stars. In particular, we utilize resultsfrom the All-Sky Monitor on RXTE, along with archival data from previousmissions, to assess the mean integrated output of X-rays in the 2-10 keVband from accreting early-type binaries within 3 kpc of the Sun. Using arecent OB star census of the solar neighborhood, we then calculate thespecific X-ray luminosity per O star from accretion-powered systems. Wealso assess the contribution to the total X-ray luminosity of an OBpopulation from associated T Tauri stars, stellar winds, and supernovae.We repeat this exercise for the major Local Group galaxies, concludingthat the total X-ray luminosity per O star spans a broad range from 2 to20×1034 ergs s-1. Contrary to previousresults, we do not find a consistent trend with metallicity; in fact,the specific luminosities for M31 and the SMC are equal, despite havingmetallicities that differ by an order of magnitude. In light of theseresults, we assess the fraction of the observed 2-10 keV emission fromstarburst galaxies that arises directly from their OB star populations,concluding that, while binaries can explain most of the hard X-rayemission in many local starbursts, a significant additional component orcomponents must be present in some systems. A discussion of the natureof this additional emission, along with its implications for thecontribution of starbursts to the cosmic X-ray background, concludes ourreport.
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Broadband Photometry of Northern-Hemisphere Luminous Stars. VI. UBV Photometry for 62 case-Hamburg Stars
CCD-based UBV photometry for 62 intrinsically luminous stars (fifty-ninepreviously unobserved photometrically) drawn from volumes I, III, and Vof the Luminous Stars in the Northern Milky Way catalog is reported.These 62 stars include a number of bright giants and supergiants ofspectral types B, A, and F.
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IR spectra of the microquasar GRS 1915+105 during a low state
There is controversy regarding the nature of the suspected donor star tothe microquasar GRS 1915+105, and hence whether GRS 1915+105 is a highmass X-ray binary (HMXB) or a low-mass X-ray binary (LMXB). In order toclarify this issue, we obtained an infrared (J, H and K) spectrum of GRS1915+105 in its low state which shows a steeper continuum than theprototype X-ray binary Sco X-1. We did not detect any HeII emission at2.189 mu m from GRS 1915+105 in our quiescent spectrum, indicating thatthe line is transient and is only observed during episodes of high X-rayactivity. For our instrument configuration, there is no detection of the12CO lines which are characteristic of late-type stars eitherin GRS 1915+105 or Sco X-1.
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UKIRT IR Spectra of the Microquasar GRS 1915+105
The UKIRT JHK-band spectrum of GRS 1915+105 shows strong He I (2.059μm) and Brγ (2.166 μm) emission lines. Eikenberry et al.(1998) found flux variations of a factor of 5 in these lines on a 5 mintimescale. Based on the detection or not of the He II emission line, itwas suggested that the companion could be a LMXB or a HMXB,respectively. Since the spectral type of the companion star of GRS1915+105 is still an open question we attempt to clarify the issue byrevisiting the object and comparing the JHK spectrum with that of the Bestar DM +49 3718 and the prototype X-ray binary Sco X-1.
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A catalogue of high-mass X-ray binaries
We present a catalogue of high-mass X-ray binaries. The catalogue is anupdated version of the catalogue of van Paradijs (1995). This newcatalogue contains 130 sources, 61 new high-mass X-ray binaries inaddition to the 69 sources listed in van Paradijs' catalogue. Most ofthe new sources are identified to be Be/X-ray binaries. Some sources,however, are only tentatively identified as high-mass X-ray binaries onthe basis of a transient character and/or a hard X-ray spectrum. Furtheridentification in other wavelength bands is needed to finally determinethe features of these sources. The aim of this catalogue is to providethe reader with some basic information on the X-ray sources and theircounterparts in other wavelength ranges (UV, optical, IR, radio). Incases where there is some doubt about the high-mass nature of the X-raybinary this is mentioned. Some doubtful cases have not been included inthe catalogue although they had been suggested by some authors to behigh-mass X-ray binaries, for example GRS 1915+105 and 1WGAJ1958.2+3232. The catalogue and references are also available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://vizier.u-strasbg.fr/cgi-bin/qcat?J/A+AS/147/25
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The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
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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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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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HIPPARCOS results on massive X-ray binaries
We present results on parallaxes, magnitudes and proper motions for 17optically identified massive X-ray binaries (MXRB) which were observedduring the Hipparcos astrometry mission. This sample includes thesources detected in the medium-energy range (2-10 keV) having opticalcounterparts brighter than V=12. We compare the Hipparcos results withground-based optical data and derive probable values for absolutemagnitudes and peculiar tangential velocities (vt). The 4 OBsupergiant systems in our sample are high-velocity objects (the averagevalue of vt is greater than 60 km/s), while the 13 Be systemshave low velocities ( = 11.3 +/- 6.7 km/s),suggesting a different formation mechanism for the two subgroups. Theunusual X-ray/radio source LSI+61(deg) 303 lies much closer thanpreviously believed and its low optical luminosity (MV =+2.2) and blue intrinsic colors now suggest it may be a peculiar type oflow-mass X-ray binary.
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Catalogue of stars in the Northern Milky Way having H-alpha in emission.
The catalogue contains 4174 stars in the Northern Milky Way, range32° ? lII< 214°, -10° < bII< +10°, having the H? line in emission. The HBH list (mainlist, Schmidt camera Hamburg-Bergedorf, red plates taken in the years1964-70) contains 1979 objects partly identical with those in otherlists of H? emission-line stars given in the literature up till1994. Non-stellar objects (e.g. H II regions, planetary nebulae) havenot been included in this catalogue except for those objects containingcentral stars which have the H? line in emission, and also forsome doubtful cases. In Part 1 the authors give the equatorial (2000.0)and galactic coordinates, the brightness and the spectrum (if existingin the literature), the membership of HBH, the estimation of continuumand H?-line intensity, the reference to the finding chart in Part2 and the cross-identification of 100 lists mostly of H? emissionline stars. In Part 2 the authors present the finding charts for morethan half of the objects; they have the "normal" orientation and mainlysize 7 arcmin square. At the end they give elementary statistics of thepresent data showing also gaps in the material.
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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
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X-Ray Emission from Be Star/X-Ray Binaries
Not Available
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Near-infrared photometric observations of Be stars.
Not Available
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Long-term monitoring of high mass X-ray binaries.
Not Available
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Mean positions and proper motions of 305 stars obtained from the combination of PZT observations at Ondrejov with AGK positions
Observations of 305 stars carried out at the Ondrejov Observatory in theperiod 1973-1983 were compared to the positions of the same stars in theAGK 2 and AGK 3 catalogs in order to obtain their mean positions andproper motions. The observations were performed in the course of 1140nights using the PZT telescope and comprise more than 32 thousand startransits. The average mean errors in the right ascension and declinationof a star that was observed thoughout the whole period were + or -0.0019 s and + or - 0.019 arcsec in the epoch around 1979. It ispredicted that the errors will increase + or - 0.0055 sec and + or -0.059 arcsec in the year 2000. A table listing the errors in the rightascension and declination is provided.
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The HEAO A-1 X-ray source catalog
The catalog of X-ray sources detected during the NRL Large Area SkySurvey (LASS) with the HEAO 1 satellite is presented. The catalog isderived from the first six months of data from HEAO 1 and includessources detected during one full scan. Positions and intensities for atotal of 842 different sources are included, with a limiting flux of 250nJy at 5 keV. The catalog is more than 90 percent complete at a fluxlevel equivalent to 1.5 microjoules at 5 keV for a Crab-like spectrum.Cross-references with published literature are provided and coincidentalidentifications are proposed for some of the sources which have beennever studied before. A cross-sectional line drawing of the sensormodule of HEAO I is also provided.
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The determination of mean positions and proper motions of 304 stars from PZT observations at Ondrejov
Not Available
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Supplement to the Mount Wilson Catalogue and Bibliography of Stars of Classes B and a whose Spectra have Bright Hydrogen Lines.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1943ApJ....98..153M&db_key=AST
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Discovery and Observations of Stars of Class Be. Third Paper.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1942ApJ....96...15M&db_key=AST
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INHABITED SKY
