Tartalom
Képek
Kép feltöltése
DSS Images Other Images
Kapcsolódó cikkek
A study of the behaviour of the NaI/KI column density ratio in the interstellar medium using the Na ultraviolet doublet
Here we make a new study of the behaviour of the NaI/KI column densityratio in the interstellar medium, using a sample of new observations of28 stars obtained at the Nordic Optical Telescope (NOT) in 1996 and1997, and previously published observations (obtained by some of theauthors) of 21 stars. The sightlines cover a range of distances anddirections, including into the Galactic halo. We make use of newobservations of the NaI ultraviolet (UV) doublet for some 18 stars. Thisdoublet is much weaker than the NaI D doublet and so is less susceptibleto saturation effects, and it is well known that it can be used toobtain more accurate NaI column densities with a smaller error range. Wefind an average N(NaI)/N(KI) ratio from the NaI UV data of about 90,which is rather higher than that found previously by Hobbs and Lequeux.The Na UV-KI ratio shows a small increase in value with increasingcolumn density, while we also find a sample of low N(NaI)/N(KI) ratioclouds generally seen towards distant objects on high-latitudesightlines that reach into the halo, so that the ratio decreases moresharply at lower column densities. As the values of the ratio for thesehalo clouds (10-20) bracket the cosmic Na/K abundance ratio, we suggestthat these ratios result from a harder radiation field in the lowerhalo, such that the ionized fractions of NaI and KI become similar.Clearly caution needs to be applied in using any kind of `standardvalue' for the NaI/KI column density ratio.
| LS 5039: A runaway microquasar ejected from the galactic plane
We have compiled optical and radio astrometric data of the microquasarLS 5039 and derived its proper motion. This, togetherwith the distance and radial velocity of the system, allows us to statethat this source is escaping from its own regional standard of rest,with a total systemic velocity of about 150 km s-1 and acomponent perpendicular to the galactic plane larger than 100 kms-1. This is probably the result of an acceleration obtainedduring the supernova event that created the compact object in thisbinary system. We have computed the trajectory of LS5039 in the past, and searched for OB associations andsupernova remnants in its path. In particular, we have studied thepossible association between LS 5039 and thesupernova remnant G016.8-01.1, which, despite ourefforts, remains dubious. We have also discovered and studied an H Icavity in the ISM, which could have been created by the stellar wind ofLS 5039 or by the progenitor of the compact object inthe system. Finally, in the symmetric supernova explosion scenario, weestimate that at least 17 Msun were lost in order to producethe high eccentricity observed. Such a mass loss could also explain theobserved runaway velocity of the microquasar.
| 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
| 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.
| The distance and structure of L379
UBV and H-beta photometry has been carried out on 107 stars locatedwithin the more obscured region of the dark galactic cloud L379. Most ofthe measured stars are fainter than 10.0 m and their spectralclassification is not available in the literature. Spectral types werefound for 47 stars using movement along the reddening line coupled withthe assumption that all stars are on the main sequence. For each star,the extinction A(v) (mag) and the distance r(kpc) were derived, and fromthe A(v)-r graph, an attempt was made to determine the structure ofL379.
| UBV photometry in the vicinity of L379
UBV photometric sequence is presented for 102 stars in the vicinity ofL379, which was obtained for distance determinations of L379, anisolated dark cloud which has been identified as a source of bipolarmolecular flow. Of these stars, 76 are those with known MK spectraltypes. The available data were insufficient for an accurate distancedetermination of L379, and additional UBV photometry within the cloud isplanned.
| 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.
| Catalog of O-B stars observed with Tokyo Meridian Circle
A catalog of the O-B stars, selected from 'Blaauw-Parenago' list andRubin's catalog, has been compiled on the FK4 system by the observationsmade with Gautier 8-inch Meridian Circle at the Tokyo AstronomicalObservatory during the period, 1971 to 1979. It contains 1059 stars andwas compiled for the future establishment of high precision propermotions of O-B stars.
| New UBVRI photometry for 900 supergiants
A description is presented of the results obtained in connection with asystematic program of supergiant photometry on the Johnson UBVRI system.During the eight years after the start of the program, almost 1000 starshave been observed, about 400 three or more times each. The originalselection of stars used the spectral type catalog of Jaschek et al.(1964) to choose supergiants. Since observations were possible from bothChile and Canada, no declination limits were imposed, and no particularselection criteria were imposed other than to eliminate carbon stars.These are so red as to require enormous extrapolations of thetransformation equations.
| Studies in Galactic STRUCTURE.II.LUMINOSITY Classification for 1270 Blue Giant Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1955ApJS....2...41M&db_key=AST
| A Finding List of O and B Stars of High Luminosity.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1951ApJ...113..141N&db_key=AST
|
Új cikk hozzáadása
Kapcsolódó hivatkozások
- - (nincs kapcsolódó hivatkozás) -
Új link hozzáadása
Besorolás csoportokba:
|
Pozíciós és asztrometriai adatok
| Csillagkép: | Pajzs |
| Rektaszcenzió: | 18h26m23.69s |
| Deklináció: | -15°37'48.7" |
| Vizuális fényesség: | 7.338 |
| Távolság: | 657.895 parszek |
| RA sajátmozgás: | 0.7 |
| Dec sajátmozgás: | -1.8 |
| B-T magnitude: | 7.329 |
| V-T magnitude: | 7.338 |
Katalógusok és elnevezések:
|
