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The Far Ultraviolet Spectroscopic Explorer Survey of O VI Absorption in the Disk of the Milky Way
To probe the distribution and physical characteristics of interstellargas at temperatures T~3×105 K in the disk of the MilkyWay, we have used the Far Ultraviolet Spectroscopic Explorer (FUSE) toobserve absorption lines of O VI λ1032 toward 148 early-typestars situated at distances >1 kpc. After subtracting off a mildexcess of O VI arising from the Local Bubble, combining our new resultswith earlier surveys of O VI, and eliminating stars that showconspicuous localized X-ray emission, we find an average O VI midplanedensity n0=1.3×10-8 cm-3. Thedensity decreases away from the plane of the Galaxy in a way that isconsistent with an exponential scale height of 3.2 kpc at negativelatitudes or 4.6 kpc at positive latitudes. Average volume densities ofO VI along different sight lines exhibit a dispersion of about 0.26 dex,irrespective of the distances to the target stars. This indicates that OVI does not arise in randomly situated clouds of a fixed size anddensity, but instead is distributed in regions that have a very broadrange of column densities, with the more strongly absorbing cloudshaving a lower space density. Line widths and centroid velocities aremuch larger than those expected from differential Galactic rotation, butthey are nevertheless correlated with distance and N(O VI), whichreinforces our picture of a diverse population of hot plasma regionsthat are ubiquitous over the entire Galactic disk. The velocity extremesof the O VI profiles show a loose correlation with those of very stronglines of less ionized species, supporting a picture of a turbulent,multiphase medium churned by shock-heated gas from multiple supernovaexplosions.
| Mass distribution in the most X-ray-luminous galaxy cluster RX J1347.5-1145 studied with XMM-Newton
Context: We report on the analysis of XMM-Newton observations of RXJ1347.5-1145 (z=0.451), the most X-ray-luminous galaxy cluster. Aims:We present a detailed total and gas mass determination up to largedistances (~1.7 Mpc), study the scaling properties of the cluster, andexplore the role of AGN heating in the cluster cool core. Methods: Bymeans of spatially resolved spectroscopy we derive density, temperature,entropy, and cooling time profiles of the intra-cluster medium. Wecompute the total mass profile of the cluster in the assumption ofhydrostatic equilibrium. Results: If the disturbed south-east regionof the cluster is excluded from the analysis, our results on shape,normalization, scaling properties of density, temperature, entropy, andcooling time profiles are fully consistent with those of relaxed, coolcore clusters. We compare our total and gas mass estimates with previousX-ray, lensing, dynamical, and SZ studies. We find good agreement withother X-ray results, dynamical mass measurements, weak lensing massesand SZ results. We confirm a discrepancy of a factor ~2 between stronglensing and X-ray mass determinations and find a gross mismatch betweenour total mass estimate and the mass reconstructed through thecombination of both strong and weak lensing. We explore the effervescentheating scenario in the core of RX J1347.5-1145 and find support to thepicture that AGN outflows and heat conduction are able to quenchradiative cooling.
| A search for counterparts to massive X-ray binaries using photometric catalogues
Context: The X-ray and γ-ray observatory INTEGRAL has discoveredlarge numbers of new hard X-ray sources, many of which are believed tobe high mass X-ray binaries. However, for a significant fraction, theircounterparts remain unidentified. Aims: We explore the use ofphotometric catalogues to find optical counterparts to high mass X-raybinaries and search for objects likely to be early-type stars within theerror circles of several INTEGRAL sources. Methods: Candidates wereselected from 2MASS photometry by means of a reddening free Q parameter.Sufficiently bright candidates were spectroscopically observed. Results: Many of the candidates selected turned out to be moderatelyreddened late A or early F stars. Optically visible OB stars are veryscarce even in these Galactic Plane fields. Our method is able toidentify the counterpart to IGR J16207-5129, confirmed by a Chandralocalisation. We classify this object as a B0 supergiant. In the fieldof AX J1820.5-1434, we find a mid or early B-type star, but we cannotconfirm it as the counterpart. For IGR J16320-4751 we rule out theoptically visible candidate as a possible counterpart. For AXJ1700.2-4220, we do not find any suitable candidate within the ASCAerror circle. We classify HD 153295, a marginal candidate to be thecounterpart, as B0.5 IVe, and find a distance compatible with membershipin Sco OB1. In the case of IGR J17091-3624, the object associated with avariable radio source in the field is a late F star. We derive aspectral type B0 IIIe for HD 100199, previously identified as thecounterpart to IGR J11305-6256. Conclusions: .The procedure used isable to correctly identify OB stars and, in about one third of thecases, may lead to the localisation of the correct counterpart. However,the majority of INTEGRAL error circles do not contain any suitableoptically visible counterpart. Deep infrared searches are going to benecessary in order to locate the counterparts to these sources.
| Unveiling the nature of INTEGRAL objects through optical spectroscopy. IV. A study of six new hard X-ray sources
We present further results from our onging optical spectrophotometriccampaign at the Astronomical Observatory of Bologna in Loiano (Italy) onunidentified hard X-ray sources detected by INTEGRAL. We observedspectroscopically the putative optical counterparts of the INTEGRALsources IGR J00234+6141, IGR J01583+6713, IGR J06074+2205, IGRJ13091+1137 and IGR J20286+2544. We find that the first two are Galacticobjects, namely a Cataclysmic Variable at a distance d 300 pc anda Be/X transient High-Mass X-ray Binary (HMXB) located at ~6.4 kpc,respectively, whereas the last one is identified with MCG +04-48-002, aStarburst/H ii galaxy at redshift z = 0.013 hiding a Seyfert 2 nucleus.We identify IGR J13091+1137 as the (likely Seyfert 2 type) activenucleus of galaxy NGC 4992, which we classify as an X-ray Bright,Optically Normal Galaxy; this is the first example of this type ofobject to be detected by INTEGRAL, and one of the closest of this class.We moreover confirm the possible Be/X nature of IGR J06074+2205, and weestimate it to be at a distance of ~1 kpc. We also reexamine thespectrum of the z = 0.087 elliptical radio galaxy PKS 0352-686, thepossible counterpart of the INTEGRAL source IGR J03532-6829, and we findthat it is a BL Lac. Physical parameters for these sources are alsoevaluated by discussing our findings in the context of the availablemultiwavelength information. These identifications further stress theimportance of INTEGRAL in the study of the hard X-ray spectrum of ActiveGalactic Nuclei, HMXBs and Cataclysmic Variables.
| Unveiling the nature of INTEGRAL objects through optical spectroscopy. III. Observations of seven southern sources
Context: . The detection, thanks to the INTEGRAL satellite, of a numberof new hard X-ray sources calls for the identification of their natureby means of observations at longer wavelengths. Aims. In our continuingcampaign to identify longer-wavelength counterparts of thesenewly-discovered hard X-ray sources detected by INTEGRAL, we observedthe putative optical counterparts of seven southern sources at the SouthAfrican Astronomical Observatory and at the European SouthernObservatory. Methods. Optical spectroscopy was performed on allcandidates of these X-ray sources. For two of these objects, opticalphotometry was also acquired. Results. These observations firmlyestablished the nature of four of these sources: we found that IGRJ10404-4625 (=LEDA 93974), 4U 1344-60 and IGR J16482-3036 are ActiveGalactic Nuclei (AGNs) at redshifts z = 0.0237, 0.013 and 0.0313,respectively, and that 2RXP J130159.6-635806 is a Galactic High-MassX-ray Binary (HMXB). We also give possible optical identifications forthree further objects, namely IGR J11215-5952, IGR J11305-6256 and IGRJ16207-5129, which are consistent with being Galactic HMXBs. Physicalparameters for these objects are also evaluated by collecting anddiscussing the available multiwavelength information. Conclusions. Thedetection of four definite or likely HMXBs out of seven objects in oursample further stresses INTEGRAL's crucial contribution in hunting thisclass of object. Also, the determination of the extragalactic nature ofa substantial fraction of the INTEGRAL survey sources underlines theimportance of hard X-ray observations for the study of background AGNslocated beyond the "Zone of Avoidance" of the Galactic Plane.
| The Carina Spiral Feature: Strömgren-Hβ photometry approach. I. The photometric data-base
A data-base collating all uvbybeta photometry available at present forO-B9 stars brighter than 10th visual magnitude in the field of theCarina Spiral Feature is presented. The completeness and homogeneity ofthe data-base are discussed.Based on CDS data.Table 1 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/410/523
| A Search for High-Velocity Be Stars
We present an analysis of the kinematics of Be stars based uponHipparcos proper motions and published radial velocities. We findapproximately 23 of the 344 stars in our sample have peculiar spacemotions greater than 40 km s-1 and up to 102 kms-1. We argue that these high-velocity stars are the resultof either a supernova that disrupted a binary or ejection by closeencounters of binaries in young clusters. Be stars spun up by binarymass transfer will appear as high-velocity objects if there wassignificant mass loss during the supernova explosion of the initiallymore massive star, but the generally moderate peculiar velocities of BeX-ray binaries indicate that the progenitors lose most of their massprior to the supernova (in accordance with model predictions). Binaryformation models for Be stars predict that most systems bypass thesupernova stage (and do not receive runaway velocities) to createultimately Be+white dwarf binaries. The fraction of Be stars spun up bybinary mass transfer remains unknown, since the post-mass transfercompanions are difficult to detect.
| Observations of OB-stars at the former Leiden Southern Station
About 700 stars, mostly OB-stars, were observed by the author at theformer Leiden Southern Station at Hartebeespoortdam, South Africa, inthe observing seasons 1965, 1968, 1969, 1974, 1977, 1978. Observationswere made in the five channels of the Walraven photometric system. Dueto weathering of the telescope mirror the W channel gave no reliableresults for the faintest stars (m = 11 mag); in these cases the U-Wcolour index is not given. The change in sensitivity in the V channel,supposedly having occurred in 1968, was not recognised. Table~5 is onlyavailable 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/qcat?J/A+A/369/527
| 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
| Five-colour photometry of OB-stars in the Southern Hemisphere
Observations of OB-stars, made in 1959 and 1960 at the Leiden SouthernStation near Hartebeespoortdam, South Africa, with the VBLUW photometerattached to the 90 cm light-collector, are given in this paper. They arecompared with photometry obtained by \cite[Graham (1968),]{gra68}\cite[Walraven & Walraven (1977),]{wal77} \cite[Lub & Pel(1977)]{lub77} and \cite[Van Genderen et al. (1984).]{gen84} Formulaefor the transformation of the present observations to those of\cite[Walraven & Walraven (1977)]{wal77} and \cite[Lub & Pel(1977)]{lub77} are given. Table 4 is only available in electronic format the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) orvia http://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.
| A Radial Velocity Database for Stephenson-Sanduleak Southern Luminous Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....113..823R&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.
| A spectroscopic database for Stephenson-Sanduleak Southern Luminous Stars
A database of published spectral classifications for objects in theStepenson-Sanduleak Luminous Stars in the Southern Milky Way catalog hasbeen compiled from the literature. A total of 6182 classifications for2562 stars from 139 sources are incorporated.
| Stromgren and H-Beta Photometry of Associations and Open Clusters - Part Three - CENTAURUS-OB1 and CRUX-OB1
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1994MNRAS.269..289K&db_key=AST
| Exciting stars and the distances of the diffuse nebulae
Not Available
| New UBVRI photometry for 900 supergiants
A description is presented of the results obtained in connection with asystematic program of supergiant photometry on the Johnson UBVRI system.During the eight years after the start of the program, almost 1000 starshave been observed, about 400 three or more times each. The originalselection of stars used the spectral type catalog of Jaschek et al.(1964) to choose supergiants. Since observations were possible from bothChile and Canada, no declination limits were imposed, and no particularselection criteria were imposed other than to eliminate carbon stars.These are so red as to require enormous extrapolations of thetransformation equations.
| UBV photometry for southern OB stars
New UBV photometry of 1227 OB stars in the southern Milky Way ispresented. For 1113 of these stars, MK spectral types have been reportedpreviously in a comprehensive survey to B = 10.0 mag.
| 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
| MK spectral classifications for southern OB stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977ApJS...35..111G&db_key=AST
| Observations of southern emission-line stars
A catalog of 1929 stars showing H-alpha emission on photographic platesis presented which covers the entire southern sky south of declination-25 deg to a red limiting magnitude of about 11.0. The catalog providesprevious designations of known emission-line stars equatorial (1900) andgalactic coordinates, visual and photographic magnitudes, H-alphaemission parameters, spectral types, and notes on unusual spectralfeatures. The objects listed include 16 M stars, 25 S stars, 37 carbonstars, 20 symbiotic stars, 40 confirmed or suspected T Tauri stars, 16novae, 14 planetary nebulae, 11 P Cygni stars, 9 Bep stars, 87 confirmedor suspected Wolf-Rayet stars, and 26 'peculiar' stars. Two new Tassociations are discovered, one in Lupus and one in Chamaeleon. Objectswith variations in continuum or H-alpha intensity are noted, and thedistribution by spectral type is analyzed. It is found that the skydistribution of these emission-line stars shows significantconcentrations in the region of the small Sagittarius cloud and in theCarina region.
| Equivalent widths and rotational velocities of southern early-type stars
Not Available
| A new determination from OB stars of the galactic rotation constants and the distance to the galactic centre.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974MNRAS.167..621B&db_key=AST
| Structure and motions in the CAR spiral feature.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972A&A....20...29H&db_key=AST
| The space distribution and kinematics of supergiants
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970AJ.....75..602H&db_key=AST
| Photometric standards for the southern hemisphere.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1969AJ.....74.1125B&db_key=AST
| The OB stars in Carina-Centaurus
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1969MNRAS.143..273F&db_key=AST
| The radial velocities of distant cepheids and galactic models
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1967MNRAS.136..141F&db_key=AST
| Photoelectric measures of the 4430 A diffuse interstellar band
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1963MNRAS.125..141W&db_key=AST
| Spectral classification and photometry of southern B stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1961MNRAS.122..239F&db_key=AST
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| קבוצת-כוכבים: | קנטאור |
| התרוממות ימנית: | 11h31m06.91s |
| סירוב: | -62°56'48.9" |
| גודל גלוי: | 8.168 |
| מרחק: | 1538.462 פארסק |
| תנועה נכונה: | -5.5 |
| תנועה נכונה: | 0.9 |
| B-T magnitude: | 8.145 |
| V-T magnitude: | 8.167 |
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