The Central Parsecs of Centaurus A: High-excitation Gas, a Molecular Disk, and the Mass of the Black Hole
We present two-dimensional gas-kinematic maps of the central region inCentaurus A. The adaptive optics (AO) assisted SINFONI data from the VLThave a resolution of 0.12" in K band. The ionized gas species(Brγ, [Fe II], [Si VI]) show a rotational pattern that isincreasingly overlaid by nonrotational motion for higher excitationlines in the direction of Cen A's radio jet. The emission lines ofmolecular hydrogen (H2) show regular rotation and nodistortion due to the jet. The molecular gas seems to be well settled inthe gravitational potential of the stars and the central supermassiveblack hole, and we thus use it as a tracer to model the mass in thecentral +/-1.5". These are the first AO integral-field observations onthe nucleus of Cen A, enabling us to study the regularity of therotation around the black hole, well inside the radius of influence, andto determine the inclination angle of the gas disk in a robust way. Thegas kinematics are best modeled through a tilted-ring model thatdescribes the warped gas disk; its mean inclination angle is ~34°and the mean position angle of the major axis is ~155°. The best-fitblack hole mass isMBH=(4.5+1.7-1.0)×107Msolar (3 σ error), based on a kinematically hot diskmodel where the velocity dispersion is included through the Jeansequation. This black hole mass estimate is somewhat lower than, butconsistent with, the mass values previously derived from ionized gaskinematics. It is also consistent with the stellar dynamical measurementfrom the same AO observations, which we present in a separate paper. Itbrings Cen A into agreement with the MBH-σ relation.Based on observations collected at the European Southern Observatory,Paranal, Chile, ESO Programs 74.A-9011(A), 75.B-0490(A).
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Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
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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.
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A study of interstellar Nai D absorption lines towards the Lupus molecular clouds
Intermediate-resolution (60000<=R<=120000) observations ofinterstellar Nai lines towards 29 stars in the general direction of theLupus molecular clouds (330°<~l<~350°0°<~b<~25°) are presented. Previously published spectratowards an additional seven stars are also included. Based on theHipparcos distances to these stars, and the minimum distance at whichstrong interstellar Nai lines appear in the spectra, I obtain a distanceof ~150+/-10pc to the Lupus molecular complex. While in agreement with anumber of other independent estimates, this result is at odds with thevalue of 100pc recently obtained by Knude & Høg from aHipparcos-based study of interstellar extinction. A possible explanationfor this discrepancy is discussed, and it is concluded that the value of150+/-10pc obtained here is to be preferred. In addition, theseobservations have some other implications for the structure of theinterstellar medium in this direction, and these are briefly considered.
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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
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Far-Ultraviolet Stellar Photometry: Fields Centered on rho Ophiuchi and the Galactic Center
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996ApJS..104..101S&db_key=AST
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A homogeneous catalog of new UBV and H-beta photometry of B- and A-type stars in and around the Scorpius-Centaurus OB association
B- and A-type stars in and near the Sco-Cen OB association areinvestigated with UBV and H-beta photometry to acquire data relevant tothe luminosity function of Sco-Cen. The measurements generally consistof two 10-s integrations of U, B, V, (W, N) filters, and theobservations are corrected iteratively for atmospheric extinction andinstrumental response. The data presented give the mean V magnitude,mean B-V, mean U-B, and the estimated uncertainties for these values.The catalog provides a homogeneous catalog of data for a large fieldwith stellar objects delineating membership to the association Sco-Cenand that affect the luminosity function of the aggregate.
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An Einstein Observatory SAO-based catalog of B-type stars
About 4000 X-ray images obtained with the Einstein Observatory are usedto measure the 0.16-4.0 keV emission from 1545 B-type SAO stars fallingin the about 10 percent of the sky surveyed with the IPC. Seventy-fourdetected X-ray sources with B-type stars are identified, and it isestimated that no more than 15 can be misidentified. Upper limits to theX-ray emission of the remaining stars are presented. In addition tosummarizing the X-ray measurements and giving other relevant opticaldata, the present extensive catalog discusses the reduction process andanalyzes selection effects associated with both SAO catalog completenessand IPC target selection procedures. It is concluded that X-rayemission, at the level of Lx not less than 10 exp 30 ergs/s, is quitecommon in B stars of early spectral types (B0-B3), regardless ofluminosity class, but that emission, at the same level, becomes lesscommon, or nonexistent, in later B-type stars.
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Selection of standard stars for photometric observations with the 91-cm reflector at Okayama
Not Available
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Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
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Empirical temperature calibrations for early-type stars
Three temperature calibrations of suitable photometric quantities havebeen derived for O and B stars. A sample of 120 stars with reliableT(eff.) determinations has been used for establishing each calibration.The different calibrations have been critically discussed and compared.Temperature determinations for 1009 program stars have been obtainedwith an accuracy of the order of 10 percent.
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Physical parameters of stars in the Scorpio-Centaurus OB association
Walraven photometry is presented of established and probable members ofthe Scorpio-Centaurus OB association. For each star, effectivetemperature and surface gravity are derived using Kurucz (1979)atmosphere models. From the Straizys and Kuriliene (1981) tables,absolute magnitudes are calculated. Distance moduli and visualextinctions are determined for all stars. From a comparison of theHR-diagrams of the stars in each subgroup with theoretical isochrones,the ages of the three subgroups are derived. The distances to the threesubgroups are shown to be different; there is a general trend (alsowithin each subgroup) for the distances to be larger at higher galacticlongitudes. The visual extinction in the youngest subgroupUpper-Scorpius, is well correlated with the IRAS 100-micron map. Thedistance toward the Ophiuchus dark clouds is found to be 125 pc, basedon the photometric distances to the stars. Most of the early-type starsin Upper-Scorpius are located at the far side of the dark clouds.
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The velocity field of the outer Galaxy in the southern hemisphere. III - Determination of distances to O, B, and A type stars in the Walraven photometric system
The Walraven photometric system has been used to derive distances tostars of spectral types earlier than A7. The details of the observingprocedure are given, and the way the data were analyzed is described.The accuracy of the data is discussed, and the results are compared withthose of Gathier et al. (1986). The observational results for stars ineight well-studied star cluster are presented, compared with theliterature, and discussed.
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A catalog of ultraviolet interstellar extinction excesses for 1415 stars
Ultraviolet interstellar extinction excesses are presented for 1415stars with spectral types B7 and earlier. The excesses with respect to Vare derived from Astronomical Netherlands Satellite (ANS) 5-channel UVphotometry at central wavelengths of approximately 1550, 1800, 2500, and3300 A. A measure of the excess extinction in the 2200-A extinction bumpis also given. The data are valuable for investigating the systematicsof peculiar interstellar extinction and for studying the character of UVinterstellar extinction in the general direction of stars for which theextinction-curve shape is unknown.
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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.
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Visual multiples. VII - MK classifications
Classifications are given for 865 components of visual multiples; theyshow no systematic differences from the MK system, and the random errorsare one subclass in type and two-thirds of a luminosity class. It isfound that at least 1% of the F-type IV and V stars are weak-lined, 32%of the A4-F1 IV and V stars are Am, and 5% of the A0-A3 IV and V starsare early-type Am. Attention is called to the large fraction (55%) ofthe A3-A9 III-V stars that are of luminosity classes III or IV, unlikethe percentage (16%) at neighboring types.
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An ultraviolet extinction study of the rho Ophiuchi dark cloud
Five-band ultraviolet spectrophotometry has been carried out for 54stars in the upper Scorpius complex. Of these, 14 stars in the rhoOphiuchi dark cloud and 13 in the surrounding area are found to be freeof spectral peculiarities and contamination by scattered light fromnearby bright stars. The dark cloud stars give extinction curves whichare significantly lower than the average extinction curves derived byother investigators and also those observed for localized regions suchas the area around Cygnus X-1 and the Cepheus OB III cluster. Thisimplies that the dust in the upper Scorpius region, especially that inthe rho Ophiuchi dark cloud has larger average size than the normalinterstellar medium. R, the ratio of total-to-selective extinction, isfound to be 4.2. The effects of a lower extinction curve on thechemistry of a dark cloud is also briefly discussed.
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On the origin of intermediate-latitude OB stars
An attempt is made to trace the origin of early-type stars observed atappreciable distances from the galactic plane. Because uncertainties inthe proper motions make space motions and hence dynamical lifetimesrather inaccurate, a theory of oscillations normal to the plane has beenused to compute radial velocities for 138 intermediate-latitude OBstars. These theoretical values are then compared with the observedradial velocities, and it is found that the low-velocity stars wereprobably ejected from the plane some time after formation, while thehigh-velocity stars were ejected very soon after formation. Velocitiesof ejection perpendicular to the plane are computed and show a narrowdistribution with a mean absolute value of 7 km/s together with a spreadof velocities from about 40 to over 200 km/s. The data are in reasonableagreement with a 'sling' effect and 'runaway' origin for the stars inthe sample.
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Radial velocities of southern early-type stars at intermediate galactic latitudes.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975MNRAS.172..649K&db_key=AST
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H-beta photometry of southern early-type stars and galactic structure away from the plane
H-beta photoelectric photometry is reported for 165 early-type stars atintermediate and high galactic latitudes. The data are combined withearlier UBV and spectroscopic results to determine the stellar spacedistribution. Stars of type B2 and earlier, at distances of up to 1 kpcfrom the galactic plane, appear to follow spiral structure in the plane.The available material, particularly the derived color excesses, is usedto select a number of blue stars which may be subluminous.
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UBV photometry of southern early-type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974MNRAS.168..451H&db_key=AST
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UVBY and beta observations of B-type stars in the Scorpio-Centaurus association.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971AJ.....76.1041G&db_key=AST
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A Photometric Investigation of the SCORPlO-CENTAURUS Association
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968ApJS...15..459G&db_key=AST
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Some Characteristics of the B and A Stars in the Upper Scorpius Complex
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1967ApJ...147.1003G&db_key=AST
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A Study of the II Scorpii Asscoiation.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1961ApJ...133..843H&db_key=AST
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A new photo-electric method of classification of luminosity and spectral type for O-and B-type stars
Not Available
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Ansolute Magnitudes of Stars in the Scorpo-Centaurus Association.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1958ApJ...128..533B&db_key=AST
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INHABITED SKY
