Оглавление
Изображения
Загрузить ваше изображение
DSS Images Other Images
Публикации по объекту
Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| New Estimates of the Solar-Neighborhood Massive Star Birthrate and the Galactic Supernova Rate
The birthrate of stars of masses >=10 Msolar is estimatedfrom a sample of just over 400 O3-B2 dwarfs within 1.5 kpc of the Sunand the result extrapolated to estimate the Galactic supernova ratecontributed by such stars. The solar-neighborhood Galactic-plane massivestar birthrate is estimated at ~176 stars kpc-3Myr-1. On the basis of a model in which the Galactic stellardensity distribution comprises a ``disk+central hole'' like that of thedust infrared emission (as proposed by Drimmel and Spergel), theGalactic supernova rate is estimated at probably not less than ~1 normore than ~2 per century and the number of O3-B2 dwarfs within the solarcircle at ~200,000.
| Catalog of Galactic OB Stars
An all-sky catalog of Galactic OB stars has been created by extendingthe Case-Hamburg Galactic plane luminous-stars surveys to include 5500additional objects drawn from the literature. This work brings the totalnumber of known or reasonably suspected OB stars to over 16,000.Companion databases of UBVβ photometry and MK classifications forthese objects include nearly 30,000 and 20,000 entries, respectively.
| BeppoSAX survey of Be/X-ray binary candidates
We present a BeppoSAX survey of five Be/X-ray binary candidates. Wereport on the identification of two of them, HD 110432 and HD 141926, aslow luminosity Be/X-ray binaries. For HD 110432 we report on thedetection of a pulsation period of ~ 14 ks. Because the luminosity ofthese sources is low and their spectra do not require non-thermalemission models, these systems are good Be+White Dwarf candidates. Ifthe pulsation period for HD 110432 is confirmed, this system would bethe most firm Be+WD candidate found up to date. The other three objectsHD 65663, HD 249179 and BD+53 2262 did not show detectable X-rayemission. We argue that, while the properties of BD+53 2262 are stillconsistent with a quiescent Be+Neutron Star scenario, the lack ofdetection for the other two objects implies that they are most probablynot X-ray binaries.
| The Hard X-Ray Luminosity of OB Star Populations: Implications for The Contribution of Star Formation to the Cosmic X-Ray Background
We present an empirical analysis of the integrated X-ray luminosityarising from populations of OB stars. In particular, we utilize resultsfrom the All-Sky Monitor on RXTE, along with archival data from previousmissions, to assess the mean integrated output of X-rays in the 2-10 keVband from accreting early-type binaries within 3 kpc of the Sun. Using arecent OB star census of the solar neighborhood, we then calculate thespecific X-ray luminosity per O star from accretion-powered systems. Wealso assess the contribution to the total X-ray luminosity of an OBpopulation from associated T Tauri stars, stellar winds, and supernovae.We repeat this exercise for the major Local Group galaxies, concludingthat the total X-ray luminosity per O star spans a broad range from 2 to20×1034 ergs s-1. Contrary to previousresults, we do not find a consistent trend with metallicity; in fact,the specific luminosities for M31 and the SMC are equal, despite havingmetallicities that differ by an order of magnitude. In light of theseresults, we assess the fraction of the observed 2-10 keV emission fromstarburst galaxies that arises directly from their OB star populations,concluding that, while binaries can explain most of the hard X-rayemission in many local starbursts, a significant additional component orcomponents must be present in some systems. A discussion of the natureof this additional emission, along with its implications for thecontribution of starbursts to the cosmic X-ray background, concludes ourreport.
| Evidence for Period Change in V393 Carinae
This paper describes a joint campaign carried out by InstitutoCopérnico and Observatorio Cristo Rey, both in Argentina, in atypical professional-amateur relationship. The target object was thebright Delta Scuti star V393 Carinae, lying close to the open clusterNGC 2516 in the southern Milky Way. We performed several CCD observingruns during different nights. The complete set of observations appearsto show slight variations in the mean period and phase shift, comparedto previous observations.
| 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
| On the origin of the difference between the runaway velocities of the OB-supergiant X-ray binaries and the Be/X-ray binaries
The recent finding by Chevalier & Ilovaisky (1998) from Hipparcosobservations that OB-supergiant X-ray binaries have relatively largerunaway velocities (mean peculiar tangential velocity avvt = 42 +/- 14\kms), whereas Be/X-ray binaries have low runaway velocities (avvt = 15+/- 6 \kms), provides confirmation of the current models for theformation of these two types of systems. These predict a difference inrunaway velocity of this order of magnitude. This difference basicallyresults from the variation of the fractional helium core mass as afunction of stellar mass, in combination with the conservation oforbital angular momentum during the mass transfer phase that precededthe formation of the compact object in the system. This combinationresults into: (i) Systematically narrower pre-supernova orbits in theOB-supergiant systems than in the Be-systems, and (ii) A largerfractional amount of mass ejected in the supernovae in high-mass systemsrelative to systems of lower mass. Regardless of possible kickvelocities imparted to neutron stars at birth, this combination leads toa considerable difference in average runaway velocity between these twogroups. If one includes the possibility for non-conservative masstransfer the predicted difference between the runaway velocity of thetwo groups becomes even more pronounced. The observed low runawayvelocities of the Be/X-ray binaries confirm that in most cases not morethan 1 to 2 \msun\ was ejected in the supernovae that produced theirneutron stars. This, in combinatioThe values given here are not identical (though similar) to those listedin Chevalier & Ilovaisky (1998). The corrections we applied areoutlined below.
| A catalogue of high-mass X-ray binaries
We present a catalogue of high-mass X-ray binaries. The catalogue is anupdated version of the catalogue of van Paradijs (1995). This newcatalogue contains 130 sources, 61 new high-mass X-ray binaries inaddition to the 69 sources listed in van Paradijs' catalogue. Most ofthe new sources are identified to be Be/X-ray binaries. Some sources,however, are only tentatively identified as high-mass X-ray binaries onthe basis of a transient character and/or a hard X-ray spectrum. Furtheridentification in other wavelength bands is needed to finally determinethe features of these sources. The aim of this catalogue is to providethe reader with some basic information on the X-ray sources and theircounterparts in other wavelength ranges (UV, optical, IR, radio). Incases where there is some doubt about the high-mass nature of the X-raybinary this is mentioned. Some doubtful cases have not been included inthe catalogue although they had been suggested by some authors to behigh-mass X-ray binaries, for example GRS 1915+105 and 1WGAJ1958.2+3232. The catalogue and references are also available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://vizier.u-strasbg.fr/cgi-bin/qcat?J/A+AS/147/25
| Absolute proper motions of open clusters. I. Observational data
Mean proper motions and parallaxes of 205 open clusters were determinedfrom their member stars found in the Hipparcos Catalogue. 360 clusterswere searched for possible members, excluding nearby clusters withdistances D < 200 pc. Members were selected using ground basedinformation (photometry, radial velocity, proper motion, distance fromthe cluster centre) and information provided by Hipparcos (propermotion, parallax). Altogether 630 certain and 100 possible members werefound. A comparison of the Hipparcos parallaxes with photometricdistances of open clusters shows good agreement. The Hipparcos dataconfirm or reject the membership of several Cepheids in the studiedclusters. Tables 1 and 2 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Radial Velocities, Binarity, and Kinematic Membership in the Open Cluster NGC 2516
We present echelle spectroscopic observations for 36 bright (V<9.6)stars in the open cluster NGC 2516, including several blue stragglercandidates and four red giants. Radial velocities are derived bycross-correlations using high signal-to-noise ratio standard spectra astemplates. From 22 cluster members a mean cluster velocity of+22.0+/-0.2 km s-1 was derived. Membership probabilities ofthe observed stars are computed on the basis of their distance to thecluster center and kinematic criteria. We report the discovery of threedouble-lined spectroscopic binaries and several probable binaries amongmain-sequence stars. A binary frequency of more than 26% is found amongthe high-mass main-sequence stars. The blue straggler HD 66341 is aslowly rotating cluster member with constant velocity, while HD 66194 isa fast-rotating Be star with probable variations in radial velocity.Other blue straggler candidates, such as HD 65663, 65950, 66066, and65987, must be considered turnoff stars. The observations presented herewere obtained at the Complejo Astronómico El Leoncito (CASLEO),which is operated under agreement between the Consejo Nacional deInvestigaciones Científicas y Técnicas de laRepública Argentina (CONICET) and the national universities of LaPlata, Córdoba, and San Juan.
| HIPPARCOS results on massive X-ray binaries
We present results on parallaxes, magnitudes and proper motions for 17optically identified massive X-ray binaries (MXRB) which were observedduring the Hipparcos astrometry mission. This sample includes thesources detected in the medium-energy range (2-10 keV) having opticalcounterparts brighter than V=12. We compare the Hipparcos results withground-based optical data and derive probable values for absolutemagnitudes and peculiar tangential velocities (vt). The 4 OBsupergiant systems in our sample are high-velocity objects (the averagevalue of vt is greater than 60 km/s), while the 13 Be systemshave low velocities ( = 11.3 +/- 6.7 km/s),suggesting a different formation mechanism for the two subgroups. Theunusual X-ray/radio source LSI+61(deg) 303 lies much closer thanpreviously believed and its low optical luminosity (MV =+2.2) and blue intrinsic colors now suggest it may be a peculiar type oflow-mass X-ray binary.
| Near-IR photometry of southern X-ray binary systems
We report IR measurements of 30 optical counterparts to a group ofpossible and probable High Mass X-ray Binaries (HMXRBs). In the majorityof the systems these measurements represent the first reported IR fluxvalues. In common with many other similar systems, the results show thepresence of a strong, frequently variable IR signal. The implications ofsome of the results are discussed.
| ROSAT survey of stellar X-ray sources in the young open cluster NGC 2516.
The ROSAT PSPC detector was used to obtain a deep pointing with itscenter on the young open cluster NGC 2516 and total integration time of9284 sec. Altogether 64 X-ray sources were detected showing strongconcentration towards the optical cluster centre. This suggests thatmost of the sources are actually associated with NGC 2516. 42 of thesesources could be identified with optical stars in the field of thecluster; after correction for a mean offset between optical and nominalROSAT positions of about 13", optical star and X-ray source positionsare found to agree, on the average, within about 9", while maximumobserved positional differences amount to 27". X-ray sources identifiedwith optical cluster stars include HR 3147 (=HD 66194; B2.5IVe), thevisually brightest B star in the cluster, three close visual late B-typebinaries (h 4027 A,B, h 4031 A,B, and I 1104 A,B) with projectedseparations ranging between about 4x10^16^cm and 6x10^16^cm, as well asseveral (six) chemically peculiar Bp/Ap(Si) and Ap(SrCrEu) stars.According to their known spectral or photometric properties, opticalcounterparts for most identified cluster X-ray sources are main-sequencestars between spectral types B9 and K0. No indication for a pulsedcomponent of the X-ray flux pointing to a compact companion could bedetected from X-ray photon arrival times for the prominent bluestraggler star HR 3147, while one of the visual binary counterparts ofX-ray cluster sources (I 1104 A/B) possibly exhibits a pulsed component.The fact that about half of the chemically peculiar Bp/Ap stars known inthe cluster, all of them of the (magnetic) CP2 variety, are found to becounterparts to ROSAT X-ray sources, can be taken to suggest thatstellar magnetic fields play a role in generating X-ray fluxes fromearly-type main-sequence stars. Luminosities of X-ray sources detectedin the cluster are rather uniform, ranging betweenL_x_(0.1-2.5keV)=0.4x10^30^ and 4.5x10^30^erg/s. 80 percent of thesources have relatively hard spectra, X-ray photons being recorded onlyin PSPC high-energy channels above 0.5keV. For only very few (six)bright X-ray sources in the field of NGC 2516, at least 30% of observedX-ray quanta fall into the low-energy channels between 0.16 and 0.5keV;four of these soft-spectrum sources could be identified with opticallate-type stars in front of the cluster, including the nearby solar-typestar HR 3138 (=HD 65907, MK: G0V).
| A catalog of far-ultraviolet point sources detected with the fast FAUST Telescope on ATLAS-1
We list the photometric measurements of point sources made by the FarUltraviolet Space Telescope (FAUST) when it flew on the ATLAS-1 spaceshuttle mission. The list contains 4698 Galactic and extragalacticobjects detected in 22 wide-field images of the sky. At the locationssurveyed, this catalog reaches a limiting magnitude approximately afactor of 10 fainter than the previous UV all-sky survey, TDl. Thecatalog limit is approximately 1 x 10-14 ergs A sq cm/s,although it is not complete to this level. We list for each object theposition, FUV flux, the error in flux, and where possible anidentification from catalogs of nearby stars and galaxies. Thesecatalogs include the Michigan HD (MHD) and HD, SAO, the HIPPARCOS InputCatalog, the Position and Proper Motion Catalog, the TD1 Catalog, theMcCook and Sion Catalog of white dwarfs, and the RC3 Catalog ofGalaxies. We identify 2239 FAUST sources with objects in the stellarcatalogs and 172 with galaxies in the RC3 catalog. We estimate thenumber of sources with incorrect identifications to be less than 2%.
| Catalogue of blue stragglers in open clusters.
An extensive survey of blue straggler candidates in galactic openclusters of both hemispheres is presented. The blue stragglers wereselected considering their positions in the cluster colour-magnitudediagrams.They were categorized according to the accuracy of thephotometric measurements and membership probabilities. An amount of 959blue straggler candidates in 390 open clusters of all ages wereidentified and classified. A set of basic data is given for everycluster and blue straggler. The information is arranged in the form of acatalogue. Blue stragglers are found in clusters of all ages. Thepercentage of clusters with blue stragglers generally grows with age andrichness of the clusters. The mean ratio of the number of bluestragglers to the number of cluster main sequence stars is approximatelyconstant up to a cluster age of about 10^8.6^ yr and rises for olderclusters. In general, the blue stragglers show a remarkable degree ofcentral concentration.
| X-Ray Emission from Be Star/X-Ray Binaries
Not Available
| UBV photometry and the structure of the galactic cluster NGC 2516
UBV photoelectric magnitudes and colors for 106 stars, along withphotographic magnitudes and colors for 486 stars, in the vicinity of NGC2516 are presented. A true distance modulus of 8.18 + or - 0.38 mag isobtained which corresponds to a linear distance of 430 (-70,+80) pc.Evolutionary ages for the sample are found to average about 1.1 x 10 tothe 8th yr, while some of the brightest stars are much younger. Possibleexplanations for these different age groups are proposed.
| Photometric variability of some CP stars
The photometric data relative to twenty-three southern CP stars havebeen re-analyzed. New or improved parameters of the lightcurves arepresented for eleven of them.
| Be stars in open clusters
Rotational velocities and spectral types have been determined for Bestars in 12 open clusters in both the northern and the southern sky, andcolor-magnitude or H-R diagrams constructed for each from availablephotometric data. The location of the Be stars in the color-magnitudediagrams shows again that Be stars may exist in various evolutionarystages, including the essentially unevolved stage. Although many Bestars are considerably off the zero-age main sequence, it does notnecessarily follow that these are in the core-contraction stage becausecircumstellar reddening and rotationally induced gravity darkening ofthe underlying star will also move stars to the right of the mainsequence in a colormagnitude diagram. The evolutionary status of Bestars seems still to be quite uncertain.
| Stellar Content of Young Open Clusters - Part Two - Be-Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1982A&A...109...48M&db_key=AST
| A Catalogue of Be-Stars
Not Available
| A photoelectric investigation of Ap-stars in open clusters. I - NGC 2516 and NGC 1662
A photoelectric search for Ap-stars in the rather old open clusters NGC2516 and NGC 1662 was undertaken using the photoelectric peculiarityindex proposed by Maitzen (1976). This index allows not only theidentification of even weak Ap stars, but also a quantitativedescription of the peculiarity, which can be related to the age of thecluster stars. The outstanding NGC 2516 shows a large range ofpeculiarity degrees among its Ap-members. All existing spectroscopicallyfound Ap stars were also recognized by this photoelectric technique.Three additional mild peculiar Ap stars were found, but needconfirmation by subsequent observations. Variability search for 3 starsin NGC 2516 resulted in constant light for the object Cox 15 (asuspected Ap eclipsing binary) and small amplitudes for Cox 26 and Coxc.
| UVBY BET photometry of equatorial and southern bright stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977A&AS...27...47H&db_key=AST
| Evolved stars in open clusters.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976ApJS...30..451H&db_key=AST
| Photometric study of the open cluster NGC 2516
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973A&AS....9..233F&db_key=AST
| A spectroscopic study of the peculiar stars in the open cluster NGC 2516.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972A&A....21..373D&db_key=AST
| Photoelectric UBV photometry of the open cluster NGC 2516.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970A&A.....5..312D&db_key=AST
|
Добавить новую статью
Внешние ссылки
- - Внешних ссылок не найдено -
Добавить внешнюю ссылку
Группы:
|
Наблюдательные данные и астрометрия
| Созвездие: | Киль |
| Прямое восхождение: | 07h56m15.77s |
| Склонение: | -61°05'58.0" |
| Видимая звёздная величина: | 6.729 |
| Расстояние: | 401.606 парсек |
| Собственное движение RA: | -4.7 |
| Собственное движение Dec: | 13.1 |
| B-T magnitude: | 6.726 |
| V-T magnitude: | 6.729 |
Каталоги и обозначения:
|
INHABITED SKY
