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Публикации по объекту
Pre-main sequence star Proper Motion Catalogue
We measured the proper motions of 1250 pre-main sequence (PMS) stars andof 104 PMS candidates spread over all-sky major star-forming regions.This work is the continuation of a previous effort where we obtainedproper motions for 213 PMS stars located in the major southernstar-forming regions. These stars are now included in this present workwith refined astrometry. The major upgrade presented here is theextension of proper motion measurements to other northern and southernstar-forming regions including the well-studied Orion and Taurus-Aurigaregions for objects as faint as V≤16.5. We improve the precision ofthe proper motions which benefited from the inclusion of newobservational material. In the PMS proper motion catalogue presentedhere, we provide for each star the mean position and proper motion aswell as important photometric information when available. We providealso the most common identifier. The rms of proper motions vary from 2to 5 mas/yr depending on the available sources of ancient positions anddepending also on the embedding and binarity of the source. With thiswork, we present the first all-sky catalogue of proper motions of PMSstars.
| A photometric catalogue of southern emission-line stars
We present a catalogue of previously unpublished optical and infraredphotometry for a sample of 162 emission-line objects and shell starsvisible from the southern hemisphere. The data were obtained between1978 and 1997 in the Walraven (WULBV), Johnson/Cousins(UBV(RI)c) and ESO and SAAO near-infrared (JHKLM) photometricsystems. Most of the observed objects are Herbig Ae/Be (HAeBe) stars orHAeBe candidates appearing in the list of HAeBe candidates of Théet al. (1994), although several B[e] stars, LBVs and T Tauri stars arealso included in our sample. For many of the stars the data presentedhere are the first photo-electric measurements in the literature. Theresulting catalogue consists of 1809 photometric measurements. Opticalvariability was detected in 66 out of the 116 sources that were observedmore than once. 15 out of the 50 stars observed multiple times in theinfrared showed variability at 2.2 mu m (K band). Based on observationscollected at the European Southern Observatory, La Silla, Chile and onobservations collected at the South African Astronomical Observatory.Tables 2-4 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/380/609
| Search for young stars among ROSAT All-Sky Survey X-ray sources in and around the R CrA dark cloud
We present the ROSAT All-Sky Survey data in a 126 deg2 areain and around the CrA star forming region. With low-resolutionspectroscopy of unidentified ROSAT sources we could find 19 new pre-mainsequence stars, two of which are classical T Tauri stars, the othersbeing weak-lined. The spectral types of these new T Tauri stars rangefrom F7 to M6. The two new classical T Tauri stars are located towardstwo small cloud-lets outside of the main CrA cloud. They appear to be ~10 Myrs old, by comparing their location in the H-R diagram withisochrones for an assumed distance of 130 pc, the distance of the mainCrA dark cloud. The new off-cloud weak-line T Tauri stars may haveformed in similar cloudlets, which have dispersed recently.High-resolution spectra of our new T Tauri stars show that they havesignificantly more lithium absorption than zero-age main-sequence starsof the same spectral type, so that they are indeed young. From thosespectra we also obtained rotational and radial velocities. For somestars we found the proper motion in published catalogs. The directionand velocity of the 3D space motion - south relative to the galaticplane - of the CrA T Tauri stars is consistent with the dark cloud beingformed originally by a high-velocity cloud impact onto the galacticplane, which triggered the star formation in CrA. We also present VRIJHKphotometry for most of the new T Tauri stars to derive theirluminosities, ages, and masses. Partly based on observations collectedat the 1.52 m and 3.5 m telescopes of the European Southern Observatory,Chile, in programs 55.E-0549, 57.E-0646, and 63.L-0023, and onobservations collected at the 0.9 m, 1.5 m, and 4.0 m CTIO telescope.
| Proper motions of pre-main sequence stars { } in southern star-forming regions
We present proper motion measurements of pre-main sequence (PMS) starsassociated with major star-forming regions of the southern hemisphere(Chamaeleon, Lupus, Upper Scorpius - Ophiuchus, Corona Australis),situated in the galactic longitude range l = 290degr to l = 360degr . Alist of PMS stars as complete as possible was established based on theHerbig and Bell catalogue and many new catalogues like the PDS survey,the catalogue of Herbig Ae/Be stars by Thé et al. (\cite{the}),X-rays surveys, etc. The measurements made use of public material(mainly AC2000 and USNO-A2.0 catalogues) as well as scans of SERC-JSchmidt plates with the MAMA measuring machine (Paris) and Valinhos CCDmeridian circle observations (Brazil). We derived proper motions for 213stars, with an accuracy of 5 to 10 mas/yr depending mainly on thedifference of epochs between the position sources. The maincharacteristics of the sample are discussed. We show that systematicmotions of groups of stars exist, which are not explained by the reflexsolar motion. Based on observations made at Valinhos CCD MeridianCircle. Based on measurements made with MAMA automatic measuringmachine. Table 4 is 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/Abstract.html
| A HIPPARCOS Census of the Nearby OB Associations
A comprehensive census of the stellar content of the OB associationswithin 1 kpc from the Sun is presented, based on Hipparcos positions,proper motions, and parallaxes. It is a key part of a long-term projectto study the formation, structure, and evolution of nearby young stellargroups and related star-forming regions. OB associations are unbound``moving groups,'' which can be detected kinematically because of theirsmall internal velocity dispersion. The nearby associations have a largeextent on the sky, which traditionally has limited astrometricmembership determination to bright stars (V<~6 mag), with spectraltypes earlier than ~B5. The Hipparcos measurements allow a majorimprovement in this situation. Moving groups are identified in theHipparcos Catalog by combining de Bruijne's refurbished convergent pointmethod with the ``Spaghetti method'' of Hoogerwerf & Aguilar.Astrometric members are listed for 12 young stellar groups, out to adistance of ~650 pc. These are the three subgroups Upper Scorpius, UpperCentaurus Lupus, and Lower Centaurus Crux of Sco OB2, as well as VelOB2, Tr 10, Col 121, Per OB2, alpha Persei (Per OB3), Cas-Tau, Lac OB1,Cep OB2, and a new group in Cepheus, designated as Cep OB6. Theselection procedure corrects the list of previously known astrometricand photometric B- and A-type members in these groups and identifiesmany new members, including a significant number of F stars, as well asevolved stars, e.g., the Wolf-Rayet stars gamma^2 Vel (WR 11) in Vel OB2and EZ CMa (WR 6) in Col 121, and the classical Cepheid delta Cep in CepOB6. Membership probabilities are given for all selected stars. MonteCarlo simulations are used to estimate the expected number of interloperfield stars. In the nearest associations, notably in Sco OB2, thelater-type members include T Tauri objects and other stars in the finalpre-main-sequence phase. This provides a firm link between the classicalhigh-mass stellar content and ongoing low-mass star formation. Detailedstudies of these 12 groups, and their relation to the surroundinginterstellar medium, will be presented elsewhere. Astrometric evidencefor moving groups in the fields of R CrA, CMa OB1, Mon OB1, Ori OB1, CamOB1, Cep OB3, Cep OB4, Cyg OB4, Cyg OB7, and Sct OB2, is inconclusive.OB associations do exist in many of these regions, but they are eitherat distances beyond ~500 pc where the Hipparcos parallaxes are oflimited use, or they have unfavorable kinematics, so that the groupproper motion does not distinguish it from the field stars in theGalactic disk. The mean distances of the well-established groups aresystematically smaller than the pre-Hipparcos photometric estimates.While part of this may be caused by the improved membership lists, arecalibration of the upper main sequence in the Hertzsprung-Russelldiagram may be called for. The mean motions display a systematicpattern, which is discussed in relation to the Gould Belt. Six of the 12detected moving groups do not appear in the classical list of nearby OBassociations. This is sometimes caused by the absence of O stars, but inother cases a previously known open cluster turns out to be (part of) anextended OB association. The number of unbound young stellar groups inthe solar neighborhood may be significantly larger than thoughtpreviously.
| ISOCAM observations of the RCrA star formation region
The results of an ISOCAM survey of the RCrA star formation region arepresented. The survey was carried out in two broad-band filters, LW2(5-8.5 mu m) and LW3 (12-18 mu m). Although it was not possible to mapthe densest, central region due to saturation problems, 21 sources wereidentified which showed mid-IR excesses. Most of these sources have notpreviously been recognised as YSOs (Young Stellar Objects), mainlybecause they are relatively faint. We find evidence for a population ofvery low mass stars which are probably brown dwarfs in their earlycontraction phases. ISO is an ESA project with instruments funded by ESAMember States (especially the PI countries: France, Germany, theNetherlands and the United Kingdom) and with the participation of ISASand NASA.
| The Low-Mass Membership of the R CrA T Association
Presented here are the preliminary results of a survey which identifies38 stars as likely members of the R CrA T association. This more thandoubles the number of well-established member stars that were previouslyknown in this region. Using a combination of ROSAT imagery with newground-based VRI photometry and classification spectroscopy, the likelyoptical counterparts to 17 X-ray sources seen in the vicinity of thestar R CrA are identified. Seven of these counterparts are believed tobe previously undiscovered association members. New VRI photometry andspectroscopy were also obtained for 39 stars with uncertain membershipstatus from previous Hα/near-IR surveys of this region. Seventeenof these stars are now considered to be likely association members.
| Candidate Main-Sequence Stars with Debris Disks: A New Sample of Vega-like Sources
Vega-like sources are main-sequence stars that exhibit IR fluxes inexcess of expectations for stellar photospheres, most likely due toreradiation of stellar emission intercepted by orbiting dust grains. Wehave identified a large sample of main-sequence stars with possibleexcess IR radiation by cross-correlating the Michigan Catalog ofTwo-dimensional Spectral Types for the HD Stars with the IRAS FaintSource Survey Catalog. Some 60 of these Vega-like sources were not foundduring previous surveys of the IRAS database, the majority of whichemployed the lower sensitivity Point Source Catalog. Here, we providedetails of our search strategy, together with a preliminary examinationof the full sample of Vega-like sources.
| Comparison of Star Formation in Five Nearby Molecular Clouds
We have calculated bolometric temperature (Tbol) and bolometricluminosity (Lbol) for 383 young stellar objects (YSOs) in five molecularclouds within 200 pc in Corona Australis (CrA), Ophiuchus (Oph), Taurus(Tau), Chamaeleon (Cha), and Lupus (Lup). We used Tbol, Lbol, andbolometric luminosity-temperature (BLT) diagrams to characterize andcompare the overall-star-formation activity of the clouds on aself-consistent basis. The main results are the following: (1) the YSOpopulations in the clouds can be differentiated by the fraction of theirlow-Tbol sources, which increases systematically from Lup and Cha to Tauand to Oph and CrA. This trend is interpreted as increasing currentstar-forming activity in the same order; (2) the clouds with higher coldsource fractions also seem to have higher bright source fractions; (3)In the BLT diagram, the CrA and Oph sources are more uniformlydistributed while the Cha and Lup sources are aggregated near thezero-age mainsequence (ZAMS). Tau sources appear to be an intermediatecase. Taurus also seems to contain more cold (Tbol < 1000 K) andlow-luminosity (Lbol < 1 Lȯ) sources than the other complexes;(4) the YSOs show a characteristic distribution in the median BLTdiagram. This distribution is qualitatively consistent with the earlyYSO evolution from a protostar to a pre--main-sequence star and providesa unique observational test to star-formation models; (5) for Luppre--main-sequence stars, the ratio of their Tbol to Teff increasesduring their approach to the ZAMS. This increase can be explained by thedisk and envelope dissipation during the pre--main-sequence evolution;(6) the most active star-forming clouds (Oph and CrA) also have densermolecular cores as measured by C18O J = 1--0 line emission, suggestingthat the star formation occurs in the densest parts of the molecularclouds; and (7) we find an anti-correlation between Tbol and C18Oemission for the class 0 and I Tau sources (Tbol < 650 K). This showsthat Tbol measures the intrinsic redness of YSOs, rather than theirdisk-envelope orientation. The disk orientation may have a moreimportant effect on Tbol of the pre--main-sequence stars.
| X-Ray Sources in Regions of Star Formation. VI. The R CRA Association as Viewed by Einstein.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114.1544W&db_key=AST
| The ROSAT all-sky survey catalogue of optically bright OB-type stars.
For the detailed statistical analysis of the X-ray emission of hot starswe selected all stars of spectral type O and B listed in the Yale BrightStar Catalogue and searched for them in the ROSAT All-Sky Survey. Inthis paper we describe the selection and preparation of the data andpresent a compilation of the derived X-ray data for a complete sample ofbright OB stars.
| 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.
| 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.
| IRAS observations of young stellar objects in the Corona Australis dark cloud
The young stellar object (YSO) population associated with the dark cloudcomplex in Corona Australis is studied by synthesizing IRAS data withnewly obtained near-IR and mid-IR photometry and previously publishedoptical/IR data. Twenty-four YSOs in the Cr A complex are identified.The observed range of spectral energy distribution shapes and bolometricluminosities are consistent with those observed in other dark clouds.The duration and efficiency of star formation are found to be similar tothe Rho Ophiuchi IR cluster. The low number of YSOs compared to otherdark clouds is understood by a reevaluation of the molecular mass of theR Cr A cloud which shows it to be much less massive than previouslyassumed.
| 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.
| Far-infrared observations of young clusters embedded in the R Coronae Australis and Rho Ophiuchi dark clouds
Multicolor far-infrared maps in two nearby dark clouds, R CoronaeAustralis and Rho Ophiuchi, have been made in order to investigate theindividual contribution of low-mass stars to the energetics and dynamicsof the surrounding gas and dust. Emission from cool dust associated withfive low-mass stars has been detected in CrA and four in Rho Oph; theirfar-infrared luminosities range from 2 solar luminosities to 40 solarluminosities. When an estimate of the bolometric luminosity waspossible, it was found that typically more than 50 percent of the star'senergy was radiated longward of 20 microns. Meaningful limits to thefar-infrared luminosities of an additional 11 association members in CrAand two in Rho Oph were also obtained. The dust optical depthsurrounding the star R CrA appears to be asymmetric and may control thedynamics of the surrounding molecular gas. The implications of theseresults for the cloud energetics and star formation efficiency in thesetwo clouds are discussed.
| The local system of early type stars - Spatial extent and kinematics
Published uvby and H-beta photometric data and proper motions arecompiled and analyzed to characterize the structure and kinematics ofthe bright early-type O-A0 stars in the solar vicinity, with a focus onthe Gould belt. The selection and calibration techniques are explained,and the data are presented in extensive tables and graphs and discussedin detail. The Gould belt stars of age less than 20 Myr are shown togive belt inclination 19 deg to the Galactic plane and node-lineorientation in the direction of Galactic rotation, while the symmetricaldistribution about the Galactic plane and kinematic properties (purecircular differential rotation) of the belt stars over 60 Myr oldresemble those of fainter nonbelt stars of all ages. The unresolveddiscrepancy between the expansion observed in the youngest nearby starsand the predictions of simple models of expansion from a point isattributed to the inhomogeneous distribution of interstellar matter.
| The S201 far-ultraviolet imaging survey. III - A field in Sagittarius
Far-ultraviolet imagery of a 20 deg diameter field in Sagittarius,centered near (1950) R.A. 18 h 34 m, decl. -30 deg 25 arcmin, wasobtained by the S201 far-ultraviolet camera during the Apollo 16mission. In a 10-minute exposure covering the 1250-1600 A wavelengthrange, 1034 star images are detectable, with a limiting ultravioletmagnitude of about 10. Most of these objects are identified withearly-type stars listed in the Smithsonian Astrophysical ObservatoryStar Catalog, the Catalog of Stellar Identifications, or both, but 203objects remain unidentified or are identified with late-type stars. Thephotometric measurements appear to be in reasonable agreement with thoseof the International Ultraviolet Explorer for stars in common, and withexpectations for A0 stars. A detailed photometric study was made of theMessier 8 region, and it is concluded that dust-scattered starlightcontributes about half of the total radiation observed from the centralregion of M8.
| Is star formation bimodal ? II. The nearest early-type stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977PASP...89..187E&db_key=AST
| Infrared photometry in the R CrA association.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975MNRAS.172..227G&db_key=AST
| A young stellar group in the vicinity of R CrA.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973ApJ...179..847K&db_key=AST
| Double stars of equal components.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972A&A....18..341S&db_key=AST
| Radial velocities of 200 southern B stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1965MNRAS.130..281B&db_key=AST
| Radial Velocities of 360 Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1952ApJ...115..157W&db_key=AST
| A general study of diffuse galactic nebulae.
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Группы:
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Наблюдательные данные и астрометрия
| Созвездие: | Южная Корона |
| Прямое восхождение: | 19h01m03.20s |
| Склонение: | -37°03'39.0" |
| Видимая звёздная величина: | 6.69 |
| Расстояние: | 134.228 парсек |
| Собственное движение RA: | 8.4 |
| Собственное движение Dec: | -29.3 |
| B-T magnitude: | 6.534 |
| V-T magnitude: | 6.58 |
Каталоги и обозначения:
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INHABITED SKY
