Contents
Images
Upload your image
DSS Images Other Images
Related articles
CHARM2: An updated Catalog of High Angular Resolution Measurements
We present an update of the Catalog of High Angular ResolutionMeasurements (CHARM, Richichi & Percheron \cite{CHARM}, A&A,386, 492), which includes results available until July 2004. CHARM2 is acompilation of direct measurements by high angular resolution methods,as well as indirect estimates of stellar diameters. Its main goal is toprovide a reference list of sources which can be used for calibrationand verification observations with long-baseline optical and near-IRinterferometers. Single and binary stars are included, as are complexobjects from circumstellar shells to extragalactic sources. The presentupdate provides an increase of almost a factor of two over the previousedition. Additionally, it includes several corrections and improvements,as well as a cross-check with the valuable public release observationsof the ESO Very Large Telescope Interferometer (VLTI). A total of 8231entries for 3238 unique sources are now present in CHARM2. Thisrepresents an increase of a factor of 3.4 and 2.0, respectively, overthe contents of the previous version of CHARM.The catalog is 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/431/773
| Deconstructing HD 28867
The 3" pair of B9 stars HD 28867 is one of the brightest X-ray sourcesin the Taurus-Auriga star-forming region. In this multiwavelength study,we attempt to deduce the source of the X-ray emission. We show that theeast component is the X-ray source. The east component has a near-IRexcess and displays narrow absorption lines in the optical, both ofwhich are consistent with a cool stellar companion. This companion isone of the brightest low-mass pre-main-sequence stars in Tau-Aur at 2μm, it and the B9 star are equally bright. We see evidence of radialvelocity variability in the cool component of over 34 km s-1.It is not visible in K-band speckle imaging, which constrains thecompanion to lie within 14 AU of the B star. We also report on apossible fourth member of the group, an M1 star 18" south of HD 28867.
| uvby FCAPT photometry of the metallic-lined stars 60 Tau and HR 1528 and the magnetic CP stars HR 8216 and HR 8770
Differential Strömgren uvby observations from the Four CollegeAutomated Photoelectric Telescope (FCAPT) are presented for themetallic-lined stars 60 Tau and HR 1528 and the magnetic ChemicallyPeculiar stars HR 8216 and HR 8770. The first star, which is a deltaScuti variable, was found not to change its mean magnitudes. HR 1528 isbest described as constant. A decade of photometry of HR 8216 shows thatits b and y values have changed by -0.016 and -0.010 mag, respectively,over this time and now can be considered a photometric variable. For HR8770 a period of 5.3923 days is derived with the photometric variabilitybeing generally in phase. The light curves also suggest possible surfaceabundance inhomogeneities.Tables 2, 3, 4 and 6 are only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/401/357
| Rotational Velocities of B Stars
We measured the projected rotational velocities of 1092 northern B starslisted in the Bright Star Catalogue (BSC) and calibrated them againstthe 1975 Slettebak et al. system. We found that the published values ofB dwarfs in the BSC average 27% higher than those standards. Only 0.3%of the stars have rotational velocities in excess of two-thirds of thebreakup velocities, and the mean velocity is only 25% of breakup,implying that impending breakup is not a significant factor in reducingrotational velocities. For the B8-B9.5 III-V stars the bimodaldistribution in V can be explained by a set of slowly rotating Ap starsand a set of rapidly rotating normal stars. For the B0-B5 III-V starsthat include very few peculiar stars, the distributions in V are notbimodal. Are the low rotational velocities of B stars due to theoccurrence of frequent low-mass companions, planets, or disks? Therotational velocities of giants originating from late B dwarfs areconsistent with their conservation of angular momentum in shells.However, we are puzzled by why the giants that originate from the earlyB dwarfs, despite having 3 times greater radii, have nearly the samerotational velocities. We find that all B-type primaries in binarieswith periods less than 2.4 days have synchronized rotational and orbitalmotions; those with periods between 2.4 and 5.0 days are rotating withina factor 2 of synchronization or are ``nearly synchronized.'' Thecorresponding period ranges for A-type stars are 4.9 and 10.5 days, ortwice as large. We found that the rotational velocities of the primariesare synchronized earlier than their orbits are circularized. The maximumorbital period for circularized B binaries is 1.5 days and for Abinaries is 2.5 days. For stars of various ages from 107.5 to1010.2 yr the maximum circularized periods are a smoothexponential function of age.
| Deconstructing HD 28867
The 3\arcsec pair of B9 stars, HD 28867, is one of the brightest X-raysources in the Taurus-Auriga star forming region. We show that the Eastcomponent is the X-ray source. The East component has a near-IR excessand displays narrow absorption lines in the optical, both of which areconsistent with a mid-K spectral type companion. This companion is oneof the brightest low mass pre-main sequence stars in Tau-Aur; at 2microns it and the B9 star are equally bright. It is not a radialvelocity variable, and is not separable in K band speckle imaging, whichconstrains the K star to lie within 30 AU of the B star. We also reporton a possible fourth member of the group, an early M star 18\arcsecsouth of HD 28867.
| CHARM: A Catalog of High Angular Resolution Measurements
The Catalog of High Angular Resolution Measurements (CHARM) includesmost of the measurements obtained by the techniques of lunaroccultations and long-baseline interferometry at visual and infraredwavelengths, which have appeared in the literature or have otherwisebeen made public until mid-2001. A total of 2432 measurements of 1625sources are included, along with extensive auxiliary information. Inparticular, visual and infrared photometry is included for almost allthe sources. This has been partly extracted from currently availablecatalogs, and partly obtained specifically for CHARM. The main aim is toprovide a compilation of sources which could be used as calibrators orfor science verification purposes by the new generation of largeground-based facilities such as the ESO Very Large Interferometer andthe Keck Interferometer. The Catalog is available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/386/492, and from theauthors on CD-Rom.
| 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
| Research Note Hipparcos photometry: The least variable stars
The data known as the Hipparcos Photometry obtained with the Hipparcossatellite have been investigated to find those stars which are leastvariable. Such stars are excellent candidates to serve as standards forphotometric systems. Their spectral types suggest in which parts of theHR diagrams stars are most constant. In some cases these values stronglyindicate that previous ground based studies claiming photometricvariability are incorrect or that the level of stellar activity haschanged. Table 2 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/cgi-bin/qcat?J/A+A/367/297
| Speckle Interferometry at the US Naval Observatory. IV.
The results of 1314 speckle interferometric observations of 625 binarystars, ranging in separation from 0.2" to 5.2" with a limiting secondarymagnitude of V=11, are tabulated. These observations were obtained usingthe 66 cm refractor at the US Naval Observatory in Washington, DC, withan intensified CCD detector. This is the fourth in a series of paperspresenting measures obtained with this equipment and covers the period1997 January 1 through December 31. Random errors for all measures areestimated to be 18 mas in separation and 0.57d/rho in position angle,where rho is the separation in arcseconds.
| Speckle Interferometry at the US Naval Observatory. III.
Position angles and separations resulting from 2578 speckleinterferometric observations of 590 binary stars are tabulated. This isthe third in a series of papers presenting measures obtained using the66 cm refractor at the US Naval Observatory in Washington, DC, andcovers the period from 1995 June through 1996 December. Program starsrange in separation from 0.2" to 4.3", with a limiting magnitude ofV=11. Random errors are estimated to be 17.0 mas in separation and0.56d/rho in position angle, where rho is the separation in arcseconds.These are the first results acquired using an improved intensified CCDdetector. The new detector, in concert with an intensity-filteringtechnique applied in software, has permitted a 1 mag increase in dynamicrange, to 3.5 mag, for pairs separated by about 2". The instrumentationand calibration are briefly described, with an emphasis on thecharacteristics of the new detector. The software filter used toincrease the dynamic range is also described.
| Early Radio Positions of Stars
Early radio positions for a sample of 100 Hipparcos stars, threeTycho-only stars, and nine radio stars with optical positions referredto the Hipparcos/ICRS frame are analyzed. The optical proper motions areused to compare the optical and radio positions. From an original sampleof 247 radio positions for the above 112 stars, a set of 220 showscoincidence between the optical and radio centers of emission closerthan 500 mas. This set is analyzed for systematic departures between theoptical and radio positions. A smaller subset of 136 early radiopositions for 72 stars show radio-minus-optical offsets smaller than 100mas and are useful for monitoring of the spin of the Hipparcos frame.
| New binary stars discovered by lunar occultations. IV
We report on a total of 20 sources observed in the near infrared in thecourse of routine lunar occultation programs at the TIRGO and Calar Altoobservatories. The results consist either in discoveries of newbinaries, or in re-observations of known or suspected binaries whereonly incomplete information was previously available. For the firsttime, a companion has been detected around the following 6 stars:DO 2779, SAO 162001, SAO93083, IRC -20444, SAO162521, and GCVS 980. Additionally,SAO 93746 is discovered to be a triple system, withprojected separations at the 0farcs01 level. For the following 7 stars,our observations confirm previous reports of binarity and providecomplementary information in the infrared: SAO96746-A, SAO 161202, SAO94060, AG +16 403, SAO98270, SAO 93950 and SAO94554. Finally, for the following 4 stars, a companion hadbeen previously observed or suspected, but we could not detect it forvarious reasons: SAO 96810, SAO93961, SAO 93975 and SAO93981. The projected separations in our positive results rangefrom 0farcs01 to 0farcs57 , and the brightness ratios up to Delta K=4.4mag. In addition, two visual doubles, namely SAO184176 and SAO 94002, have also beenobserved and their projected angular separations and infrared brightnessratios are reported here. This paper is the fourth in a series, bringingto 58 the total number of binary sources studied by our group by meansof lunar occultations. Based on observations collected at TIRGO(Gornergrat, Switzerland), and at Calar Alto (Spain). TIRGO is operatedby CNR--CAISMI Arcetri, Italy. Calar Alto is operated by theGerman--Spanish Astronomical Center.
| HIPPARCOS distances of X-ray selected stars: implications on their nature as stellar population.
We present the parallaxes, measured by Hipparcos, for a sample of X-rayselected stars. The stars belong to the stellar sample of the EinsteinExtended Medium Sensitivity Survey. They are all at galactic latitude|b|>20deg, and are generally far away from known star formingregions. Several of these stars show lithium abundance and activitylevel typical of very young stars with ages comparable to that of thePleiades. We show that the majority of our sample stars are on the mainsequence, with only =~20% being giants. We do not find a significantpresence of pre-main sequence stars in our sample, notwithstanding thefact that some of our stars have a considerable lithium abundance,showing that the stars observed are most likely young and activemain-sequence objects.
| X-Ray-emitting T Tauri Stars in the L1551 Cloud
Low-mass pre-main-sequence stars in the nearby Lynds 1551 star-formingcloud are studied with the ROSAT and ASCA X-ray satellites. An 8 ksROSAT image reveals 38 sources including seven well-known T Tauri stars,two likely new weak-lined T Tauri stars, five potential new weak-lined TTauri stars, one young B9 star, and the remaining sources are unrelatedto the cloud or poorly identified. A 40 ks ASCA image of the clouddetects seven of the ROSAT sources. Spectral fitting of the brighterX-ray-emitting stars suggests the emission is produced in either amulti-temperature plasma, with temperatures near 0.2 and 1 keV, or asingle-temperature plasma with low metal abundances. XZ Tau, a youngclassical T Tauri star, is much stronger in ASCA than ROSATobservations, showing a harder (1.5-2.0 keV) component. Timing analysisreveals all but one of the T Tauri stars are variable on timescalesranging from 1 hr to 1 year. A powerful flare, emitting 3 x 10^34^ ergswithin a 40 minute rise and fall, was observed by ASCA on the weak-linedT Tauri star V826 Tau. The event was preceded and followed by constantquiescent X-ray emission. The extreme classical T Tauri star XZ Tau wasalso caught during both high and low states, varying by a factor of 15between the ASCA and ROSAT observations. Neither of the luminousinfrared embedded protostars L1551 IRS 5 or L1551NE were detected byROSAT or ASCA.
| The TIRGO Lunar Occultation Program: Summary of the 1985-1995 Observations
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....112.2786R&db_key=AST
| ICCD Speckle Observations of Binary Stars.XV.An Investigation of Lunar Occultation Systems
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....112.2260M&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.
| Optical positions of radio emitting stars.
In order to contribute to the alignment of the radio and opticalreference frames, 50 stars with confirmed radio emission and publishedradio positions were observed by astrographical means. Additionally, twoconfirmed radio-stars of fainter magnitude were observed using a CCDdirect camera with a long focus, large aperture telescope. Thereductions are made relative to four catalogues: the Carlsberg MeridianCatalogue #4, the International Reference Stars Catalogue, the Positionsand Proper Motion Catalogue and the Astrographical Catalogue ofReference Stars. The best results were obtained with the CAMC catalogue.The plate error of a radio star position is 0.07" for both rightascension and declination, rising to 0.10"-0.20" for bright stars. Tenof the program stars are not in the HIPPARCOS Input Catalogue and 12 donot belong to any of the major reference catalogues used. As soon as theHIPPARCOS results become available, its reference stars already measuredin the plates will enable us to get positions for those 10 radio starsin the HIPPARCOS system.
| Mesures et decouvertes d'etoiles doubles effectuees a la lunette de 50cm de l'Observatoire de Nice. Measures and discoveries of visual double stars made with the 50cm refractor at the Nice Observatory.
Measures and discoveries of visual double stars made at the Observatoirede la Cote d'Azur at Nice, between 1988 and 1994, with the 50cmrefractor equipped with a filar micrometer and electronic recordingdevice. The programs proposed by J. Dommanget involve the complement ofthe C.C.D.M. (resolving problems of identification of double stars andof coherency in the Index) and the INput CAtalog Hipparcos (resolutionof ambiguities on the binarity and on the position of certain doublestars which have seldom or never been observed again from the epoch ortheir discovery). The author has discovered three new binaries: JCT1,JCT2 and JCT3.
| New weak-line T Tauri stars in Taurus-Auriga.
On the basis of the ROSAT All-Sky-Survey, a study of the Taurus-Aurigastar forming region has been performed in order to search for hithertoundiscovered TTauri stars. Our study covers an area of about 280 squaredegrees, located between 4^h^ and 5^h^ in right ascension and between15deg and 34deg in declination. Identification of ROSAT All-Sky Surveysources in this area by means of optical spectroscopy revealed 2 newclassical T Tauri stars (CTTS) and 66 new weak-line-T Tauri stars (WTTS)with Wlambda_(Hα)<=10A. Additional pointed ROSATobservations led to the identification of 6 more WTTS and 2 CTTS, givinga total of 76 new T Tauri stars. The large area of our study, ascompared with previous works, allows us to study the spatialdistribution of WTTS in this star forming region. We find the WTTS ofour survey to be distributed over the whole region investigated. Thereis a noticeable decline of the surface density from south to northwithin our study area, but the spatial distribution extends mostprobably beyond our study region. No clustering towards the populationof TTauri stars known prior to ROSAT in Taurus-Auriga could be observed.We suggest that the WTTS found in our study might in part be somewhatolder than the previously known TTauri stars in Taurus-Auriga, and thattheir broad spatial distribution is due to the typical velocitydispersion of a few km/s measured for Taurus TTauri stars, in which casefor some of our WTTS an age on the order of 10^7^years would be requiredfor reaching the observed distances from the Taurus dark clouds. Weestimate a WTTS/CTTS ratio of about 6 within our study area, butconclude that because of the different spatial distribution of WTTS andCTTS this ratio will be most probably significantly larger for a moreextended area.
| The Einstein Extended Medium-Sensitivity Survey Second Epoch: Results for the Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJS...99..701F&db_key=AST
| Photographic observations of visual double stars.
We present the results of photographic observations of 399 visual doublestars of the Hipparcos Input Catalogue (HIC), observed in the years 1980and 1990-1991 with the 60-cm double-refractor of the Bosscha Observatoryat Lembang, Java.
| 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.
| Radio continuum emission from stars: a catalogue update.
An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed.
| Radio observations of weak-lined T Tauri stars
We report the results of a search for radio-continuum emission fromweak-lined T Tauri stars selected on the basis of a range of criteria. Acorrelation is found with strong X-ray emission and with youth. All thestars in the survey older than about 20 million years were not detectedas radio sources. A flare was seen on one of the survey targets, with arise time of several hours. Circular polarization was also seen in twoof the targets, providing the first direct confirmation of the presenceof magnetic fields on these stars.
| 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.
| The Einstein Slew Survey
A catalog of 819 sources detected in the Einstein IPC Slew Survey of theX-ray sky is presented; 313 of the sources were not previously known asX-ray sources. Typical count rates are 0.1 IPC count/s, roughlyequivalent to a flux of 3 x 10 exp -12 ergs/sq cm s. The sources havepositional uncertainties of 1.2 arcmin (90 percent confidence) radius,based on a subset of 452 sources identified with previously knownpointlike X-ray sources (i.e., extent less than 3 arcmin).Identifications based on a number of existing catalogs of X-ray andoptical objects are proposed for 637 of the sources, 78 percent of thesurvey (within a 3-arcmin error radius) including 133 identifications ofnew X-ray sources. A public identification data base for the Slew Surveysources will be maintained at CfA, and contributions to this data baseare invited.
| A preliminary compilation of DS-programme star positions
A catalog is presented of the double-star-program (DS-program) starpositions, listing right ascensions for 930 DSs and declinations for1225 DSs of the program. The positions were compiled from the observedvalues obtained between 1980 and 1987 with the meridian circles of sixUSSR observatories (the Moscow, Kazan', Kiev, Khar'kov, Odessa, andTashkent Observatories) and the Belgrade Observatory. The measurementsand the treatment of the observational material were performed using therelative method, and the FK-4 system stars were used as reference stars.
| A 5 GHz radio survey of selected POST T Tauri and naked T Tauri stars
Results of a radio survey of weak-lined T Tauri (variably classified aseither post T Tauri or naked T Tauri) stars at 5 GHz are reported.Thirty-two targets, chosen on the basis of known high-activity levels oryouth indications, were observed, and 15, including eight previouslyunknown radio sources, were detected. It is suggested that mostweak-lined T Tauris with high activity levels, e.g., as indicated by ahigh X-ray flux, are likely to be detectable radio sources at some time,but the radio emission goes through high and low phases. For thesubsample of 14 stars observed in Taurus-Auriga which were thoroughlystudied at IR, optical, and X-ray wavelengths, a clear association isfound between radio activity and youth.
| The Einstein Observatory Extended Medium-Sensitivity Survey. II - The optical identifications
The optical identifications are presented of the Einstein ExtendedMedium-Sensitivity Survey (EMSS), including the methodology used tooptically identify the EMSS sources and the uncertainties involved withthat process. The optical properties of the classes of X-ray, optical,and radio data for each of the identified and, as yet, unidentifiedsources of the survey are described. A new class of X-ray emitters,cooling flow galaxies, is proposed. The criteria used to determinewhether the proposed optical counterpart to the X-ray source is aplausible identification are described. Plausibility is based on theoptical classification of the counterpart, e.g., AGN, cluster, G star,and the X-ray-to-optical flux ratios previously observed for theseclasses of X-ray emitters. Two independent schemes of opticalclassification of the counterparts are used to check the plausibility ofthese identifications; one is based on moderate-resolution opticalspectroscopy, and the other, on inferred X-ray luminosity and theoverall energy distribution.
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
| Constellation: | おうし座 |
| Right ascension: | 04h33m32.90s |
| Declination: | +18°01'00.0" |
| Apparent magnitude: | 6.25 |
| Distance: | 129.702 parsecs |
| Proper motion RA: | 25.2 |
| Proper motion Dec: | -21.5 |
| B-T magnitude: | 7.039 |
| V-T magnitude: | 7.015 |
Catalogs and designations:
|
INHABITED SKY
