תוכן
תמונות
הוסף תמונה שלך
DSS Images Other Images
מאמרים קשורים
Spectroscopic analysis of southern B and Be stars
Spectroscopic monitoring of 141 southern field B-type stars, 114 of themknown to exhibit the Be phenomenon, allowed the estimation of theirprojected rotational velocities, effective temperatures and superficialgravities from both line and equivalent width fitting procedures.Stellar ages, masses and bolometric luminosities were derived frominternal structure models. Without taking into account the effects ofgravity darkening, we note the occurrence of the Be phenomenon in laterstages of main-sequence phase.
| Autocorrelation Analysis of Hipparcos Photometry of Short-Period Be Stars
We have used Hipparcos epoch photometry and a form of autocorrelationanalysis to investigate the amplitude and timescale of the short-periodvariability of 82 Be stars, including 46 Be stars that were analyzed byHubert & Floquet using Fourier and CLEAN analysis and 36 other Bestars that were suspected of short-period variability. Our method hasgiven useful information for about 84% of these stars; for the rest, thetime distribution of the Hipparcos epoch photometry limits thecapability of our technique.
| A Search for High-Velocity Be Stars
We present an analysis of the kinematics of Be stars based uponHipparcos proper motions and published radial velocities. We findapproximately 23 of the 344 stars in our sample have peculiar spacemotions greater than 40 km s-1 and up to 102 kms-1. We argue that these high-velocity stars are the resultof either a supernova that disrupted a binary or ejection by closeencounters of binaries in young clusters. Be stars spun up by binarymass transfer will appear as high-velocity objects if there wassignificant mass loss during the supernova explosion of the initiallymore massive star, but the generally moderate peculiar velocities of BeX-ray binaries indicate that the progenitors lose most of their massprior to the supernova (in accordance with model predictions). Binaryformation models for Be stars predict that most systems bypass thesupernova stage (and do not receive runaway velocities) to createultimately Be+white dwarf binaries. The fraction of Be stars spun up bybinary mass transfer remains unknown, since the post-mass transfercompanions are difficult to detect.
| Statistical analysis of intrinsic polarization, IR excess and projected rotational velocity distributions of classical Be stars
We present the results of statistical analyses of a sample of 627 Bestars. The parameters of intrinsic polarization (p*),projected rotational velocity (v sin i), and near IR excesses have beeninvestigated. The values of p* have been estimated for a muchlarger and more representative sample of Be stars (~490 objects) thanpreviously. We have confirmed that most Be stars of early spectral typehave statistically larger values of polarization and IR excesses incomparison with the late spectral type stars. It is found that thedistributions of p* diverge considerably for the differentspectral subgroups. In contrast to late spectral types (B5-B9.5), thedistribution of p* for B0-B2 stars does not peak at the valuep*=0%. Statistically significant differences in the meanprojected rotational velocities (/line{vsin i}) are found for differentspectral subgroups of Be stars in the sense that late spectral typestars (V luminosity class) generally rotate faster than early types, inagreement with previously published results. This behaviour is, however,not obvious for the III-IV luminosity class stars. Nevertheless, thecalculated values of the ratio vt/vc of the truerotational velocity, vt, to the critical velocity forbreak-up, vc, is larger for late spectral type stars of allluminosity classes. Thus, late spectral type stars appear to rotatecloser to their break-up rotational velocity. The distribution of nearIR excesses for early spectral subgroups is bi-modal, the position ofthe second peak displaying a maximum value E(V-L)~ 1 . m 3for O-B1.5 stars, decreasing to E(V-L)~0. m8 for intermediatespectral types (B3-B5). It is shown that bi-modality disappears for latespectral types (B6-B9.5). No correlations were found betweenp* and near IR excesses and between E(V-L) and vsin i for thedifferent subgroups of Be stars. In contrast to near IR excesses, arelation between p* and far IR excesses at 12 mu m is clearlyseen. A clear relation between p* and vsin i (as well asbetween p* and /line{vsin i}/vc) is found by thefact that plots of these parameters are bounded by a ``triangular"distribution of p*: vsin i, with a decrease of p*towards very small and very large vsin i (and /line{vsini}/vc) values. The latter behaviour can be understood in thecontext of a larger oblateness of circumstellar disks for the stars witha rapid rotation. From the analysis of correlations between differentobservational parameters we conclude that circumstellar envelopes forthe majority of Be stars are optically thin disks with the range of thehalf-opening angle of 10degr
| UBV beta Database for Case-Hamburg Northern and Southern Luminous Stars
A database of photoelectric UBV beta photometry for stars listed in theCase-Hamburg northern and southern Milky Way luminous stars surveys hasbeen compiled from the original research literature. Consisting of over16,000 observations of some 7300 stars from over 500 sources, thisdatabase constitutes the most complete compilation of such photometryavailable for intrinsically luminous stars around the Galactic plane.Over 5000 stars listed in the Case-Hamburg surveys still lackfundamental photometric data.
| A Radial Velocity Database for Stephenson-Sanduleak Southern Luminous Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....113..823R&db_key=AST
| 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
| 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.
| A spectroscopic database for Stephenson-Sanduleak Southern Luminous Stars
A database of published spectral classifications for objects in theStepenson-Sanduleak Luminous Stars in the Southern Milky Way catalog hasbeen compiled from the literature. A total of 6182 classifications for2562 stars from 139 sources are incorporated.
| Far-ultraviolet stellar photometry: Fields in Sagittarius and Scorpius
Far-ultraviolet photometry for 741 objects in a field in Sagittariuscentered near M8 and 541 objects in a field centered near sigma Scorpiiis presented. These data were extracted from electographic imagesobtained with two cameras during a shuttle flight in 1991 April/May. Thecameras provided band passes with lambdaeff = 1375 A andlambdaeff = 1781 A. Synthetic colors show that these bandsare sensitive to effective temperature for hot stars. Our measurementswere placed on a quantitative far-ultraviolet magnitude scale byconvolving the spectra of stars observed by IUE with our cameras'spectral response functions. Fifty-eight percent of the ultravioletobjects were identified with visible stars using the SIMBAD databasewhile another 40% of the objects are blends of early type stars tooclose together to separate with our resolution. Our photometry iscompared with that from the TD-1, OAO 2, and ANS satellites and the S201(Apollo 16) far-ultraviolet camera and found to agree at the level of afew tenths of a magnitude. Unlike previous studies, almost half of theidentified visual counterparts to the ultraviolet objects are early Bstars. A plot of distance modulus against ultraviolet color excessreveals a significant population of stars with strong ultravioletexcess.
| Uvby-beta observations of 528 type B stars with V between the 8th and 9th magnitude
The paper presents uvby-beta measurements of 528 type B stars selectedfrom the SAO Catalog on the basis of two criteria: the spectral types inthe range B3-B5 and mV between the 8th and the 9th magnitude. Reddeningindependent (c1) values are estimated from the spectral classificationand compared to the observed values. No systematic trend with observed(b-y), H-beta, or spectral type appears to be present, but the range of(c1) residuals is surprisingly large. A rather large part of the starshas small beta values, smaller than for the BIa supergiants. Only twoare classified as O stars and most of them have the suffix e, ne, ornne. Most beta values for the O type stars are slightly above the upperlimit of 2.585 m.
| The 68th Name-List of Variable Stars
Not Available
| Distances, reddenings and distribution of emission B-stars in the galactic centre region /l/ not greater than 45 deg
The distribution of Be stars in the region surrounding the Galacticcenter and their correlation to the spiral structure of the Galaxy hasbeen studied. The results are discussed in terms of reddenings anddistances of these stars. Data are presented on the Galacticcoordinates, colors, interstellar color excesses, reddening-freemagnitudes and colors, adopted absolute magnitudes, distances in kpc,distances from the Galactic plane, and MK spectral type.
| Photometric observations of emission B-stars in the southern Milky Way
In order to study the distribution of Be stars and their correlation tothe local spiral structure of the Galaxy photoelectric UBV photometrywas carried out for a total of 488 Be stars located in the southernMilky Way between galactic longitudes 315 and 45 deg. UBV magnitudes arepresented for these stars.
| 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.
| HD 172256 Revisited
Not Available
| UBV photometry for southern OB stars
New UBV photometry of 1227 OB stars in the southern Milky Way ispresented. For 1113 of these stars, MK spectral types have been reportedpreviously in a comprehensive survey to B = 10.0 mag.
| A Note on Two Be Stars
Not Available
| On the 4430 A interstellar band - A visual classification
A system of visual classification of the strength of the interstellarband 4430 A has been developed, based on spectra taken at spectralclassification dispersion. The intensity of the band was divided into 8main classes, defined by a group of selected standard stars. The systemwas applied to 1,111 southern OB stars contained in the catalog ofspectral types by Garrison, Hiltner, and Schild (1977). The mean errorin the classification was estimated to be plus or minus 1 class.Equivalent widths were measured for 100 stars; an excellent correlationwith the visual estimations was obtained. A calibration between thesetwo parameters is given.
| Observations of southern emission-line stars
A catalog of 1929 stars showing H-alpha emission on photographic platesis presented which covers the entire southern sky south of declination-25 deg to a red limiting magnitude of about 11.0. The catalog providesprevious designations of known emission-line stars equatorial (1900) andgalactic coordinates, visual and photographic magnitudes, H-alphaemission parameters, spectral types, and notes on unusual spectralfeatures. The objects listed include 16 M stars, 25 S stars, 37 carbonstars, 20 symbiotic stars, 40 confirmed or suspected T Tauri stars, 16novae, 14 planetary nebulae, 11 P Cygni stars, 9 Bep stars, 87 confirmedor suspected Wolf-Rayet stars, and 26 'peculiar' stars. Two new Tassociations are discovered, one in Lupus and one in Chamaeleon. Objectswith variations in continuum or H-alpha intensity are noted, and thedistribution by spectral type is analyzed. It is found that the skydistribution of these emission-line stars shows significantconcentrations in the region of the small Sagittarius cloud and in theCarina region.
| General Catalogue of Stellar Radial Velocities
Not Available
| Supplement to the Mount Wilson Catalogue and Bibliography of Stars of Classes B and a whose Spectra have Bright Hydrogen Lines.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1943ApJ....98..153M&db_key=AST
|
הכנס מאמר חדש
לינקים קשורים
הכנס לינק חדש
משמש של הקבוצה הבאה
|
תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | קשת |
| התרוממות ימנית: | 18h40m11.01s |
| סירוב: | -22°39'49.8" |
| גודל גלוי: | 8.723 |
| מרחק: | 1754.386 פארסק |
| תנועה נכונה: | -1.4 |
| תנועה נכונה: | -4.5 |
| B-T magnitude: | 8.75 |
| V-T magnitude: | 8.726 |
קטלוגים וכינוים:
|
