HE 1327-2326, an Unevolved Star with [Fe/H]<-5.0. I. A Comprehensive Abundance Analysis
We present the elemental abundances of HE 1327-2326, the mostiron-deficient star known, determined from a comprehensive analysis ofspectra obtained with the Subaru Telescope High Dispersion Spectrograph.HE 1327-2326 is either in its main-sequence or subgiant phase ofevolution. Its non-LTE-corrected iron abundance is [Fe/H]=-5.45, 0.2 dexlower than that of HE 0107-5240, the previously most iron-poor objectknown, and more than 1 dex lower than those of all other metal-poorstars. Both HE 1327-2326 and HE 0107-5240 exhibit extremely largeoverabundances of carbon ([C/Fe]~+4). The combination of extremely highcarbon abundance with outstandingly low iron abundance in these objectsclearly distinguishes them from other metal-poor stars. The large carbonexcesses in these two stars are not the result of a selection effect.There also exist important differences between HE 1327-2326 and HE0107-5240. While the former shows remarkable overabundances of the lightelements (N, Na, Mg, and Al), the latter shows only relatively smallexcesses of N and Na. The neutron-capture element Sr is detected in HE1327-2326, but not in HE 0107-5240 its Sr abundance is significantlyhigher than the upper limit for HE 0107-5240. The Li I λ6707line, which is detected in most metal-poor dwarfs and warm subgiantshaving the same temperature as HE 1327-2326, is not found in thisobject. The upper limit of its Li abundance [logε(Li)<1.5] isclearly lower than the Spite plateau value. These data provide newconstraints on models of nucleosynthesis processes in thefirst-generation objects that were responsible for metal enrichment atthe earliest times. We discuss possible scenarios to explain theobserved abundance patterns.Based on data collected with the Subaru Telescope, which is operated bythe National Astronomical Observatory of Japan.
|
B Star Rotational Velocities in h and χ Persei: A Probe of Initial Conditions during the Star Formation Epoch?
Projected rotational velocities (vsini) have been measured for 216 B0-B9stars in the rich, dense h and χ Persei double cluster and comparedwith the distribution of rotational velocities for a sample of fieldstars having comparable ages (t~12-15 Myr) and masses (M~4-15Msolar). For stars that are relatively little evolved fromtheir initial locations on the zero-age main sequence (ZAMS) (those withmasses M~4-5 Msolar), the mean vsini measured for the h andχ Per sample is slightly more than 2 times larger than the meandetermined for field stars of comparable mass, and the cluster and fieldvsini distributions differ with a high degree of significance. Forsomewhat more evolved stars with masses in the range 5-9Msolar, the mean vsini in h and χ Per is 1.5 times thatof the field; the vsini distributions differ as well, but with a lowerdegree of statistical significance. For stars that have evolvedsignificantly from the ZAMS and are approaching the hydrogen exhaustionphase (those with masses in the range 9-15 Msolar), thecluster and field star means and distributions are only slightlydifferent. We argue that both the higher rotation rates and the patternof rotation speeds as a function of mass that differentiatemain-sequence B stars in h and χ Per from their field analogs werelikely imprinted during the star formation process rather than a resultof angular momentum evolution over the 12-15 Myr cluster lifetime. Wespeculate that these differences may reflect the effects of the higheraccretion rates that theory suggests are characteristic of regions thatgive birth to dense clusters, namely, (1) higher initial rotationspeeds; (2) higher initial radii along the stellar birth line, resultingin greater spin-up between the birth line and the ZAMS; and (3) a morepronounced maximum in the birth line radius-mass relationship thatresults in differentially greater spin-up for stars that become mid- tolate-B stars on the ZAMS.
|
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.
|
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.
|
Rotational Velocity Determinations for 164 Be and B Stars
Rotational velocities, v sin i, have been obtained for 96 Be and 68normal B stars by measurements of the FWHM of the He I lambda-4471 line(for spectral types B0-B4.5) and Mg II lambda-4481 (for types B5-B9.5).The consistency of various published sources is examined. (SECTION:Stars)
|
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.
|
Radial-velocity measurements. V - Ground support of the HIPPARCOS satellite observation program
The paper presents data on 1070 radial velocity measurements of starsdistributed in 39 fields measuring 4 deg x 4 deg. The PPO series ofFehrenbach et al. (1987) and Duflot et al. (1990) is continued using theFehrenbach objective prism method.
|
Photoelectric photometry of bright stars in the vicinity of the North Galactic Pole
Not Available
|
Four-color and H-beta photometry near SA 57
Stromgren uvby and H-beta photometry has been obtained for 37 stars inand near the region of SA 57, the Selected Area nearest the northgalactic pole. These stars can serve as secondary standards forphotometric work in this region. Comparisons with previous photometryshows reasonable agreement. The data are analyzed to determineinterstellar reddening, metal abundances of the F-type stars, anddistances. On the average, the stars are somewhat weak lined, comparedto the sun. The reddening is close to zero.
|
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 galactic reddening law - The evidence from uvby-beta photometry of B stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1985A&A...142..189T&db_key=AST
|
Radial velocities of northern Mercury stars
About 200 radial velocities of 96 bright northern Hg-Mn or candidateHg-Mn stars are presented. Past and present data have been reexaminedfor periodic variability in cases that were neither previously known tobe binaries with well determined orbits nor were considered to haveconstant velocity. One definite new orbit was found (that of HR 3361)and several possible orbital solutions are given.
|
Four-colour photometry of B stars north of B = + 45 deg and comparison with the south
Four-color photometry of 33 Henry Draper B stars north of b = + 45 degis presented. Most are little-reddened B or intermediate-A stars. A newAm star is discovered. The new measures essentially complete uvbyphotometry of all HD B stars within 45 deg of either galactic pole. Thenorthern and southern cones of HD B stars are compared, and selectioneffects deduced. Far from the galactic plane, it appears that B starsmay be equally distributed north and south of the plane; closer to thesun, an asymmetry associated with Gould's Belt is evident.
|
Detection of double stars with the two-color refractometer
A technique for detecting double stars using the two-color refractometer(TCR) being developed at the University of Maryland to measureatmospheric refraction is presented. The design of the TCR comprises twonondeviating dispersive wedges to null the incoming dispersion, acolor-filter wheel rotating at 3600 rpm, two guiding mirrors, abeam-extraction mirror for acquisition and focusing, aneutral-density-filter wheel to optimize count rate, and a four-quadrantphoton-counting detector. The angular position of the binary can bedetermined directly from the angular portion of the dispersionmeasurement, but more information is required to find the angulardistance of the components. Sample results obtained with the 24-in.reflecting telescope at USNO are shown.
|
Further Studies of A-Stars and F-Stars in the Region of the North Galactic Pole - Part Four - a Catalogue of Uvbyr Photometry and Derived Quantities
Not Available
|
Further Studies of A-Stars and F-Stars in the Region of the North Galactic Pole - Part Three - a Catalogue of Star Names and Positions
Not Available
|
Geneva photometric boxes. II - The reddening towards the galactic poles
It is noted that photometric boxes allow a very accurate estimation ofindividual reddenings for B- and early A-type stars. A catalog of 129stars with galactic latitudes higher than 30 deg is given. A small butsignificant reddening is seen in the direction of both the northern andsouthern galactic poles: E(B-V) approximately 0.04.
|
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.
|
The photometric constancy of Maia / = 20 Tauri/ and related stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978PASP...90..703P&db_key=AST
|
Late B-type stars - Rotation and the incidence of HgMn stars
High-dispersion spectrograms for an unbiased sample of 256 late B-typestars are examined in an attempt to determine whether slow rotation isnecessary and sufficient for the appearance of HgMn anomalies innonmagnetic stars. The peculiar stars in the sample are identified,values of v sin i are derived for all the stars observed, and theradial-velocity variations of the identified HgMn stars are analyzed.The distribution of rotational velocities for late B-type stars isobtained, and the role of rotation in producing extended envelopes isevaluated. The binary frequency and mass-ratio distribution are derivedfor systems containing HgMn components, the effect of duplicity on thedistribution of rotational velocities is estimated, and the role of suchfactors as rotation, age, and binary characteristics in determiningwhether HgMn anomalies are present is investigated. The results clearlyshow that HgMn stars occur only within a limited temperature range, thatall such stars rotate slowly, but that rotation, effective temperature,age, surface gravity, and binary properties do not serve to determinewhether a star will exhibit abundance anomalies.
|
Studies of A and F stars in the region of the North galactic pole-I. Radial velocities and MK Classifications
Not Available
|
Structure and age of the local association /Pleiades group/
Intermediate-band indices are used to derive luminosities for some 500early-type stars with well-determined proper motions and radialvelocities. Space motion vectors and galactic coordinates are computedfor the stars considered. It is found that the local association membersare mainly concentrated in the Sco-Cen region in the Southern Hemisphereand the Cas-Tau region in the north.
|
The manganese stars
Ultraviolet spectrograms of 194 middle and late B-type stars wereobtained in a search for Mn stars. The 24 Mn stars found in this searchlay within the limited temperature range from 0.33 to 0.48. Theirobserved rate of incidence and rotational velocity distributionsubstantiate the hypothesis that the Mn stars constitute a considerablefraction of the slowly rotating stars in this temperature range. If theatmospheres of these stars are sufficiently stable for diffusionprocesses to be effective, then it also becomes possible to account forthe temperature range in which the Mn overabundance occurs.
|
Four-color and H beta photometry for the bright B8 and B9 type stars north of declination -10 degre.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973AJ.....78..738C&db_key=AST
|
Star catalogs for the Washington and Richmond photographic zenith tubes.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973AJ.....78..642M&db_key=AST
|
The Helium-Weak Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972ApJ...175..453M&db_key=AST
|
Observations of the 21-CM Hydrogen Line Toward High-Latitude Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1969ApJ...157.1101G&db_key=AST
|
Polarimetric Observations of Nearby Stars in the Directions of the Galactic Poles and the Galactic Plane
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968ApJ...151..907A&db_key=AST
|
