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Публикации по объекту
Photometry of 39 PMS Variables in the Taurus-Auriga Region
Thirty nine PMS variable stars were observed in the direction of theTaurus-Auriga star-forming region.
| A kinematic study of the Taurus-Auriga T association
Aims.This is the first paper in a series dedicated to investigating thekinematic properties of nearby associations of young stellar objects.Here we study the Taurus-Auriga association, with the primary objectiveof deriving kinematic parallaxes for individual members of this low-massstar-forming region. Methods: .We took advantage of a recentlypublished catalog of proper motions for pre-main sequence stars, whichwe supplemented with radial velocities from various sources found in theCDS databases. We searched for stars of the Taurus-Auriga region thatshare the same space velocity, using a modified convergent point methodthat we tested with extensive Monte Carlo simulations. Results:.Among the sample of 217 Taurus-Auriga stars with known proper motions,we identify 94 pre-main sequence stars that are probable members of thesame moving group and several additional candidates whose pre-mainsequence evolutionary status needs to be confirmed. We derive individualparallaxes for the 67 moving group members with known radial velocitiesand give tentative parallaxes for other members based on the averagespatial velocity of the group. The Hertzsprung-Russell diagram for themoving group members and a discussion of their masses and ages arepresented in a companion paper.
| Formation and Evolution of Planetary Systems (FEPS): Primordial Warm Dust Evolution from 3 to 30 Myr around Sun-like Stars
We present data obtained with the Infrared Array Camera (IRAC) aboardthe Spitzer Space Telescope (Spitzer) for a sample of 74 young (t<30Myr old) Sun-like (0.7
| 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.
| Evolution of Cold Circumstellar Dust around Solar-type Stars
We present submillimeter (Caltech Submillimeter Observatory 350 μm)and millimeter (Swedish-ESO Submillimetre Telescope [SEST] 1.2 mm, OwensValley Radio Observatory [OVRO] 3 mm) photometry for 127 solar-typestars from the Formation and Evolution of Planetary Systems SpitzerLegacy program that have masses between ~0.5 and 2.0 Msolarand ages from ~3 Myr to 3 Gyr. Continuum emission was detected towardfour stars with a signal-to-noise ratio>=3: the classical T Tauristars RX J1842.9-3532, RX J1852.3-3700, and PDS 66 with SEST, and thedebris-disk system HD 107146 with OVRO. RX J1842.9-3532 and RXJ1852.3-3700 are located in projection near the R CrA molecular cloud,with estimated ages of ~10 Myr (Neuhäuser et al.), whereas PDS 66is a probable member of the ~20 Myr old Lower Centaurus-Crux subgroup ofthe Scorpius-Centaurus OB association (Mamajek et al.). The continuumemission toward these three sources is unresolved at the 24" SESTresolution and likely originates from circumstellar accretion disks,each with estimated dust masses of ~5×10-5Msolar. Analysis of the visibility data toward HD 107146(age~80-200 Myr) indicates that the 3 mm continuum emission is centeredon the star within the astrometric uncertainties and resolved with aGaussian-fit FWHM size of (6.5"+/-1.4")×(4.2"+/-1.3"), or185AU×120 AU. The results from our continuum survey are combinedwith published observations to quantify the evolution of dust mass withtime by comparing the mass distributions for samples with differentstellar ages. The frequency distribution of circumstellar dust massesaround solar-type stars in the Taurus molecular cloud (age~2 Myr) isdistinguished from that around 3-10 Myr and 10-30 Myr old stars at asignificance level of ~1.5 and ~3 σ, respectively. These resultssuggest a decrease in the mass of dust contained in small dust grainsand/or changes in the grain properties by stellar ages of 10-30 Myr,consistent with previous conclusions. Further observations are needed todetermine if the evolution in the amount of cold dust occurs on evenshorter timescales.
| Comments on Inferences of Star Formation Histories and Birth Lines
Palla & Stahler have recently argued that star formation in Taurusand other nearby molecular clouds extends over a period of at least 10Myr, implying quasi-static cloud evolution and star formation. Theirconclusions contradict other recent results indicating that molecularclouds are transient objects and star formation proceeds rapidly. ThePalla & Stahler picture implies that most molecular clouds shouldhave extremely low rates of star formation and that in such inactivestages, the stellar initial mass function (IMF) should be stronglyskewed toward producing stars with masses >~1Msolarneither prediction is supported by observations. I show that the Palla& Stahler conclusions for Taurus depend almost entirely on a smallnumber of stars with masses >~1Msolar the lower mass starsshow no evidence for such an extended period of star formation. Ifurther show that most of the stars apparently older than 10 Myr in thedirection of Taurus are probably foreground nonmembers. I also presentbirth line calculations that support the idea that the ages of the starswith masses >~1Msolar have been systematicallyoverestimated because birth line age corrections have beenunderestimated; such birth lines would eliminate the need to postulateskewed IMFs. The simplest and most robust explanation of currentobservations characterizing the vast majority of young stars inmolecular clouds is that cloud and star formation is rapid and dynamic.
| Star Formation in Space and Time: Taurus-Auriga
To understand the formation of stellar groups, one must first documentcarefully the birth pattern within real clusters and associations. Inthis study of Taurus-Auriga, we combine pre-main-sequence ages from ourown evolutionary tracks with stellar positions from observationalsurveys. Aided by the extensive millimeter data on the molecular clouds,we develop a picture of the region's history. Star formation began, at arelatively low level and in a spatially diffuse manner, at least107 yr in the past. Within the last few million years, newstars have been produced at an accelerating rate, almost exclusivelywithin a confined group of striated cloud filaments. The gas both insideand around the filaments appears to be in force balance. Thus, theappearance of the filaments is due to global, quasi-static contractionof the parent cloud material. Gravity drives this contraction and shockdissipation mediates it, but the internal motion of the gas does notappear to be turbulent. The accelerating nature of recent star formationmeans that the condensation of cloud cores is a threshold phenomenon,requiring a minimum background density. Other, nearby cloud regions,including Lupus and Chamaeleon, contain some locales that have attainedthis density, and others that have not. In the latter, we find extensiveand sometimes massive molecular gas that is still devoid of young stars.
| Photometric observations of weak-line T Tauri stars . II. WTTS in Taurus-Auriga, Orion and Scorpius OB2-2
We present uvby-$beta a photometry of 116 X-ray flux-selected activestars in the directions of the Orion (40), Taurus-Auriga (58) andScorpius OB2-2 (18) star forming regions. Additionally, we give near IRJHK photometry of 20 active stars in the Taurus-Auriga direction. Theprogram stars were selected from the R_\odotsat All Sky Survey andEINSTEIN X-ray surveys and are spectroscopically confirmed weak-line TTauri stars and weak-line T Tauri star candidates. The photometryconfirms the young nature of the program stars and also indicates that asignificant fraction of the sample could be foreground objects. The datagiven here probably represent the largest homogeneous uvby-beta a$photometric sample of new WTTS and WTTS candidates. Many objects in thesample are observed photometrically for the first time. Based onobservations collected at the Observatorio Astronómico Nacionalin Sierra San Pedro Mártir, Baja California, México.Tables 1-4 are also 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 study of Li-rich stars discovered by ROSAT in Taurus-Auriga
In recent years, large numbers of lithium-rich stars were discoverednear several nearby star forming regions (SFRs). We present a detailedstudy of those stars discovered in and near the central region of theTaurus-Auriga T Tauri association, based on high-resolution echellespectroscopy and proper motion data. We find that about 60 per cent ofour sample can be regarded as pre-main sequence (PMS) stars, while theremaining stars likely are foreground zero-age main sequence (ZAMS)stars. We conclude that the PMS stars are likely associated with theTaurus-Auriga SFR, while the ZAMS stars may represent a population ofsomewhat older Gould Belt stars. The fraction of ZAMS stars in theTaurus-Auriga sample studied in this work is larger than in a similarsample in the Lupus SFR, and we argue that this may be explained by thespatial structure of the Gould Belt and the Sun's location within it.Based on observations obtained at Observatoire de Haute Provence. Someof the observations reported here were obtained with the Multiple MirrorTelescope, a joint facility of the Smithsonian Institution and theUniversity of Arizona.
| Micrometer Measures of Double Stars
Micrometer measures of 795 double stars made with the 26 inch (0.66 m)refractor of the US Naval Observatory from 1984 to 1990 are presented.
| Multiplicity of T Tauri stars in Taurus after ROSAT
We surveyed a sample of 75 T Tauri stars in the Taurus star formingregion for companions. These stars were discovered with the help ofROSAT. The separation range covered is 0.13'' to 13'', where the lowerlimit is given by the diffraction limit of the telescope and the upperlimit by confusion with background stars. Combined with the results ofthe preceding survey by Leinert et al. (\cite{Leinert93}), we now havesurveyed a sample of 178 young stars in Taurus, 63 classical, 106weak-line, and 9 unclassified T Tauri stars. Within this sample, we find68 binaries, 9 triples, and 3 quadruples. After corrections to accountfor confusion with background stars and for a bias induced through X-rayselection, we count 74 binaries or multiples with a total of 85companions in 174 systems. This corresponds to a degree of multiplicity(number of binaries or multiples divided by number of systems) of(42.5+/- 4.9)%, or to a duplicity, measured by the number of companionsper system, of (48.9+/- 5.3)%, which is higher by a factor of (1.93+/-0.26) compared to solar-type main-sequence stars. We find no differencein duplicity between classical and weak-line T Tauri stars. There is adifference between close and wide pairs in the sense that close pairshave a flat distribution of flux ratios, while the flux ratios of widepairs are peaked towards small values.
| Radio Emission from ROSAT-discovered Young Stars in and around Taurus-Auriga
An 8.4 GHz VLA survey of 91 recently discovered lithium-rich late-typestars from the ROSAT All-Sky Survey and pointed observations ispresented. These objects lie in the vicinity of the Taurus-Aurigastar-forming region (d ~= 140 pc); however, some are dispersed nearly 30deg from known active star-forming cloud cores. This sample represents aspatially complete, flux-limited population of X-ray-bright young starsboth within and away from the primary Tau-Aur stellar nurseries. Of the91 sources, 29 are detected in this radio survey with a sensitivitylimit of ~0.15 mJy. If they are at the distance of the star-formingclouds, we find that 32% of widely distributed young stars with LX >=5 x 1028 ergs s-1 have radio luminosity densities in excess of 3.5 x1015 ergs s-1 Hz-1. This detection rate, the ranges of radio and X-rayluminosities, and the LR/LX ratios are consistent with known youngweak-lined T Tauri stars (ages ~106 yr) that reside within the Taurusmolecular clouds, but they are considerably higher than a zero-agemain-sequence population such as the Pleiades (age ~=7 x 107 yr). Theradio properties thus support the pre-main-sequence classification ofthe stars. They fitted well among other active young stars on theempirical LR versus LX diagram, implying that solar-type gyrosynchrotronactivity is the radio emission mechanism.
| New proper motions of pre-main sequence stars in Taurus-Auriga
We present proper motions of 72 T Tauri stars located in the centralregion of Taurus-Auriga (Tau-Aur). These proper motions are taken from anew proper motion catalogue called STARNET. Our sample comprises 17classical T Tauri stars (CTTS) and 55 weak-line T Tauri stars (WTTS),most of the latter discovered by ROSAT. 53 stars had no proper motionmeasurement before. Kinematically, 62 of these stars are members of theassociation. A velocity dispersion of less than 2-3km/s is found whichis dominated by the errors of the proper motions. This velocitydispersion correlates with a spread in distances. Furthermore we presentproper motions of 58 stars located in a region just south of the Taurusmolecular clouds and compare the kinematics of the youngest stars inthis sample (younger than 3.5x10^7^yrs) with the kinematics of thepre-main sequence stars (PMS) in the Taurus-Auriga association. From acomparison of the space velocities we find that the stars in the centralregion of Tau-Aur are kinematically different from the stars in thesouthern part. Among the stars with large proper motions far off theTaurus mean motion we find 2 Pleiades candidates and 7 possible Pleiadesrunaway stars.
| The Tokyo PMC catalog 90-93: Catalog of positions of 6649 stars observed in 1990 through 1993 with Tokyo photoelectric meridian circle
The sixth annual catalog of the Tokyo Photoelectric Meridian Circle(PMC) is presented for 6649 stars which were observed at least two timesin January 1990 through March 1993. The mean positions of the starsobserved are given in the catalog at the corresponding mean epochs ofobservations of individual stars. The coordinates of the catalog arebased on the FK5 system, and referred to the equinox and equator ofJ2000.0. The mean local deviations of the observed positions from theFK5 catalog positions are constructed for the basic FK5 stars to comparewith those of the Tokyo PMC Catalog 89 and preliminary Hipparcos resultsof H30.
| 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 Henry Draper Extension Charts: A catalogue of accurate positions, proper motions, magnitudes and spectral types of 86933 stars
The Henry Draper Extension Charts (HDEC), published in the form offinding charts, provide spectral classification for some 87000 starsmostly between 10th and 11th magnitude. This data, being highlyvaluable, as yet was practically unusable for modern computer-basedastronomy. An earlier pilot project (Roeser et al. 1991) demonstrated apossibility to convert this into a star catalogue, using measurements ofcartesian coordinates of stars on the charts and positions of theAstrographic Catalogue (AC) for subsequent identification. We presenthere a final HDEC catalogue comprising accurate positions, propermotions, magnitudes and spectral classes for 86933 stars of the HenryDraper Extension Charts.
| Mesures d'etoiles doubles faites a Nice, etoiles doubles nouvelles (24eme serie) decouvertes a Nice.
Table 1 gives 1182 measurements of 682 binaries observed with the 74 and50 cm refractors. Table 2 lists 26 new binaries discovered with the 50cm refractor.
| Measurements of binary stars obtained at Pic-du-Midi and at Nice
A total of 112 visual measurements of 82 close binaries observed with 2mtelescope at Pic-du-Midi are presented. In addition, 344 measurements of163 close binaries were observed with the 74-cm and 50-cm refractors atNice. All measurements were made by a micrometer with illuminated wires.
| Binary star measurements made at Nice with the 50-cm reflector
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1989A&AS...77..125L&db_key=AST
| Measurements of binary stars made at Nice
Results are presented for 753 measurements of 267 binary stars that weremade with the 50- and 74-cm refractors at Nice Observatory. Coordinatesfor the equinox of 1950 are provided, along with apparent magnitudes,spectral types, and probable periods. It is noted that three-quarters ofthese systems are recently discovered close binaries.
| Mesures d'etoiles doubles faites a Nice.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978A&AS...33..275M&db_key=AST
| Measurements of double stars made at Nice
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975A&AS...20..391C&db_key=AST
| Mesures d'étoiles doubles faites à Nice aux lunettes de 50 et de 74 CM
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970A&AS....3...51C&db_key=AST
| Mesures d'etoiles doubles faites a Nice a la lunette de 50 cm.
Not Available
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Наблюдательные данные и астрометрия
| Созвездие: | Телец |
| Прямое восхождение: | 04h05m40.58s |
| Склонение: | +22°48'12.0" |
| Видимая звёздная величина: | 9.4 |
| Собственное движение RA: | 5.5 |
| Собственное движение Dec: | -14.7 |
| B-T magnitude: | 10.12 |
| V-T magnitude: | 9.46 |
Каталоги и обозначения:
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