תוכן
תמונות
הוסף תמונה שלך
DSS Images Other Images
מאמרים קשורים
Probing the inner halo and IVC gas through the Local Interstellar Chimney
We present an absorption study of the interstellar gas at high positivegalactic latitudes in the direction close to the axis of the LocalChimney (LC), which is an extension of the rarefied local cavity thatreaches out from the galactic disk to a z-distance of at least 250 pcinto the lower halo region. Our study includes high-resolution (R 1.7 km s-1) spectral observations of the interstellar NaI andCaII absorption lines seen towards 6 early-type stars with distancesranging from 225 to 500 pc contained within a radius of6° along the sight-line (l = 160°, b= +55°). These visible data are supplemented withfar-ultraviolet absorption measurements of the interstellar sight-linestowards two hot white dwarf stars, RE J1043+490 (d = 230 pc) and REJ1059+512 (d = 315 pc), taken with the NASA Far UltravioletSpectroscopic Explorer (FUSE) satellite.Our observations reveal interstellar gas clouds with velocities in the-20 to -60 km s-1 range that appear to be falling towards thegalactic disk. In particular, we have detected absorption with avelocity of V_helio -55 km s-1 towards two sight-lines(HD 89501 and HD 88545) that can be associated with an intermediatevelocity (IV) cloud called the IV Arch. Our observations place aprobable z-distance to this IVC of 275-320 pc, this being much nearerthan previously thought.The far UV spectra of the two hot white dwarfs show only a few (10)interstellar absorption lines, which is indicative of the very lowdensity phase of the interstellar gas contained within the LC region. Wehave derived relative elemental abundance ratios for C, N, O, Si, Ar andFe for these two sight-lines and find that the abundance patterns arevery similar to those found for other sight-lines in the local cavity.The high ionization line of OVIłambda1032 Å has beendetected towards RE J1043+490 with a column density of 7 ×1012 cm-2, which is consistent with the averagespace density of this ion recently found in the Local Bubble region.Finally, we (tentatively) propose a possible connection between theformation of the Gould Belt, the Local Bubble cavity, the Local Chimneyand the overlying IV Arch clouds.
| A spectroscopic survey for lambda Bootis stars. II. The observational data
lambda Bootis stars comprise only a small number of all A-type stars andare characterized as nonmagnetic, Population i, late B to early F-typedwarfs which show significant underabundances of metals whereas thelight elements (C, N, O and S) are almost normal abundant compared tothe Sun. In the second paper on a spectroscopic survey for lambda Bootisstars, we present the spectral classifications of all program starsobserved. These stars were selected on the basis of their Strömgrenuvbybeta colors as lambda Bootis candidates. In total, 708 objects insix open clusters, the Orion OB1 association and the Galactic field wereclassified. In addition, 9 serendipity non-candidates in the vicinity ofour program stars as well as 15 Guide Star Catalogue stars were observedresulting in a total of 732 classified stars. The 15 objects from theGuide Star Catalogue are part of a program for the classification ofapparent variable stars from the Fine Guidance Sensors of the HubbleSpace Telescope. A grid of 105 MK standard as well as ``pathological''stars guarantees a precise classification. A comparison of our spectralclassification with the extensive work of Abt & Morrell(\cite{Abt95}) shows no significant differences. The derived types are0.23 +/- 0.09 (rms error per measurement) subclasses later and 0.30 +/-0.08 luminosity classes more luminous than those of Abt & Morrell(\cite{Abt95}) based on a sample of 160 objects in common. The estimatederrors of the means are +/- 0.1 subclasses. The characteristics of oursample are discussed in respect to the distribution on the sky, apparentvisual magnitudes and Strömgren uvbybeta colors. Based onobservations from the Observatoire de Haute-Provence, OsservatorioAstronomico di Padova-Asiago, Observatório do Pico dosDias-LNA/CNPq/MCT, Chews Ridge Observatory (MIRA) and University ofToronto Southern Observatory (Las Campanas).
| Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
| Radial velocities. Measurements of 2800 B2-F5 stars for HIPPARCOS
Radial velocities have been determined for a sample of 2930 B2-F5 stars,95% observed by the Hipparcos satellite in the north hemisphere and 80%without reliable radial velocity up to now. Observations were obtainedat the Observatoire de Haute Provence with a dispersion of 80Ä,mm(-1) with the aim of studying stellar and galactic dynamics.Radial velocities have been measured by correlation with templates ofthe same spectral class. The mean obtained precision is 3.0 km s(-1)with three observations. A new MK spectral classification is estimatedfor all stars. Based on observations made at the Haute ProvenceObservatory, France and on data from The Hipparcos Catalogue, ESA.Tables 4, 5 and 6 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr or viahttp://cdsweb.u-strasbg.fr/Abstract.htm
| Apparent radii and other parameters for 416 B5 V-F5 V stars of the catalogue of the Geneva Observatory
Apparent radius, visual brightness, effective temperature and absoluteradius for 416 B5 v-F5 v stars of the catalogue of the GenevaObservatory (Rufener, 1976) have been determined. Twenty-eight stars,anomalous in log a" versus (m~)o diagrams, have been singled out. A goodcorrelation for seven stars, in common with the list of Hanbury Brown etal. (1974), has been found. Similar parameters determined for 279 B5v-F5 v stars of two preceding papers (Fracassini et al., 1973, 1975)have allowed us to determine the averaged diagrams , and versus (B -V)0 for 695 B5 v-F5 v stars. Moreover, in the present paper a goodcorrelation versus and carefulrelation = -7.40 + 3.31 for B5v-F5 V stars have been determined. Plain correlations between log R/R0and blanketing parameter m2 for some spectral types seem to point outthat there are real differences in the absolute radii of stars of thesame spectral type, in agreement with recent researches on the HRdiagram (Houck and Fesen, 1978). Systematic differences between double(spectroscopic and visual) and single stars are found. In particular,the averaged relation versus shows that A2v-F5 v double stars may have a higher metallicity index m2 and smallerabsolute radii than single stars. Finally, the diagram log v sin iversus log R/R0 confirms some properties of binary systems found byother researchers (Huang, 1966; Plavec, 1970; Levato, 1974; Kitamura andKondo, 1978)
| H-beta photometry of A-type stars near the north galactic pole.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971AJ.....76..567P&db_key=AST
| Photoelectric photometry of A-type stars near the north galactic pole.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968AJ.....73.1000P&db_key=AST
| Spectra and colors of A-type stars in a north galactic pole region.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968AJ.....73..152S&db_key=AST
| A finding-list of stars of spectral type F2 and earlier in a north galactic pole region.
Not Available
|
הכנס מאמר חדש
לינקים קשורים
הכנס לינק חדש
משמש של הקבוצה הבאה
|
תצפית ומידע אסטרומטרי
קטלוגים וכינוים:
|
