CO emission from discs around isolated HAeBe and Vega-excess stars
We describe results from a survey for J = 3-2 12CO emissionfrom visible stars classified as having an infrared excess. The line isclearly detected in 21 objects, and significant molecular gas(>=10-3 Jupiter masses) is found to be common in targetswith infrared excesses >=0.01 (>=56 per cent of objects), but rarefor those with smaller excesses (~10 per cent of objects).A simple geometrical argument based on the infrared excess implies thatdisc opening angles are typically >=12° for objects with detectedCO; within this angle, the disc is optically thick to stellar radiationand shields the CO from photodissociation. Two or three CO discs have anunusually low infrared excess (<=0.01), implying the shielding discis physically very thin (<=1°).Around 50 per cent of the detected line profiles are double-peaked,while many of the rest have significantly broadened lines, attributed todiscs in Keplerian rotation. Simple model fits to the line profilesindicate outer radii in the range 30-300 au, larger than found throughfitting continuum SEDs, but similar to the sizes of debris discs aroundmain-sequence stars. As many as five have outer radii smaller than theSolar System (50 au), with a further four showing evidence of gas in thedisc at radii smaller than 20 au. The outer disc radius is independentof the stellar spectral type (from K through to B9), but there isevidence of a correlation between radius and total dust mass. Also themean disc size appears to decrease with time: discs around stars of age3-7 Myr have a mean radius ~210 au, whereas discs of age 7-20 Myr are afactor of three smaller. This shows that a significant mass of gas (atleast 2 M⊕) exists beyond the region of planetformation for up to ~7 Myr, and may remain for a further ~10Myr withinthis region.The only bona fide debris disc with detected CO is HD9672; this shows adouble-peaked CO profile and is the most compact gas disc observed, witha modelled outer radius of 17 au. In the case of HD141569, detailedmodelling of the line profile indicates gas may lie in two rings, withradii of 90 and 250 au, similar to the dust structure seen in scatteredlight and the mid-infrared. In both AB Aur and HD163296 we also findthat the sizes of the molecular disc and the dust scattering disc aresimilar; this suggests that the molecular gas and small dust grains areclosely co-located.
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Merged catalogue of reflection nebulae
Several catalogues of reflection nebulae are merged to create a uniformcatalogue of 913 objects. It contains revised coordinates,cross-identifications of nebulae and stars, as well as identificationswith IRAS point sources.The catalogue is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/399/141
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ICCD Speckle Observations of Binary Stars. XXIII. Measurements during 1982-1997 from Six Telescopes, with 14 New Orbits
We present 2017 observations of 1286 binary stars, observed by means ofspeckle interferometry using six telescopes over a 15 year period from1982 April to 1997 June. These measurements constitute the 23dinstallment in CHARA's speckle program at 2 to 4 m class telescopes andinclude the second major collection of measurements from the MountWilson 100 inch (2.5 m) Hooker Telescope. Orbital elements are alsopresented for 14 systems, seven of which have had no previouslypublished orbital analyses.
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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
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Infrared and submillimetre studies of Vega-excess stars
We report new infrared and submillimetre observations of a sample of 24candidate Vega-excess stars, and derive CO masses, dust masses, gas todust ratios and the strengths of various emission lines. Most of thesestars have dustier discs than the class archetypes (Vega, Fomalhaut,beta Pic, etc.), yet, like the archetypes, all the stars observed in COshow the gas content of their discs to be depleted compared withmolecular cloud values. We discuss how the extra dust content mightimply that these stars are less evolved than the archetypes, and useother infrared and submillimetre characteristics to support thiscontention.
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Conditions of search for magnetic stars at early evolution stages.
Not Available
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CH(+) in the interstellar medium
This paper describes observations of interstellar CH(+) along the linesof sight to O and B stars with E(B-V)s up to +1.13. Along some lines ofsight with strong detections of CH(+), we find distinct radial velocityshifts between the CH(+) lines and other neutral species, such as Ca Iand CH. The shifts are small but are predicted by shock models of CH(+)formation in which the shock is inclined with respect to the observer.We have also found no column densities exceeding approximately1013.8/sq cm. When these data are examined along with theother CH(+) data collected from the literature, the previously seentendency of CH(+) column density to increase with E(B-V) does notcontinue beyond reddenings of about +0.6. These findings offer supportto the shock model of CH(+) formation for at least some lines of sight.
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A Study of the Kinematics of the Local Dark Clouds
Not Available
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SAO stars with infrared excess in the IRAS Point Source Catalog
We have undertaken a search for SAO stars with infrared excess in theIRAS Point Source Catalog. In contrast to previous searches, the entireIRAS (12)-(25)-(60) color-color diagram was used. This selection yieldeda sample of 462 stars, of which a significant number are stars withcircumstellar material. The stars selected can be identified aspre-main-sequence stars, Be stars, protoplanetary systems, post-AGBstars, etc. A number of objects are (visual) binary stars.Characteristic temperatures and IR excesses are calculated and theirrelations to spectral type are investigated.
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An Einstein Observatory SAO-based catalog of B-type stars
About 4000 X-ray images obtained with the Einstein Observatory are usedto measure the 0.16-4.0 keV emission from 1545 B-type SAO stars fallingin the about 10 percent of the sky surveyed with the IPC. Seventy-fourdetected X-ray sources with B-type stars are identified, and it isestimated that no more than 15 can be misidentified. Upper limits to theX-ray emission of the remaining stars are presented. In addition tosummarizing the X-ray measurements and giving other relevant opticaldata, the present extensive catalog discusses the reduction process andanalyzes selection effects associated with both SAO catalog completenessand IPC target selection procedures. It is concluded that X-rayemission, at the level of Lx not less than 10 exp 30 ergs/s, is quitecommon in B stars of early spectral types (B0-B3), regardless ofluminosity class, but that emission, at the same level, becomes lesscommon, or nonexistent, in later B-type stars.
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LkH-alpha 198 and V 376 Cassiopeiae - Speckle interferometric and polarimetric observations of circumstellar dust
The circumstellar material close to the stellar sources is investigated,and its distribution and its relations to the general optical appearanceand the orientation of the molecular outflow are determined. Speckleobservations were carried out with a near-infrared speckleinterferometer between September 1986 and October 1989. LkH-alpha 198shows a complicated structure without clear alignment, and this is alsotrue on subarcsec (less than 1000 AU) scales. V 376 Cas appears to be abipolar nebula, seen nearly edge-on, oriented at position angle 120 deg.The orientations of LkH-alpha 198 and V 376 show no obvious relationswith the interstellar field direction. The near-infrared albedo ofcircumstellar dust is quite high both in the case of LkH-alpha 198 and V376 Cas, which indicates a larger particle size than typical forinterstellar dust.
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ICCD speckle observations of binary stars. V - Measurements during 1988-1989 from the Kitt Peak and the Cerro Tololo 4 M telescopes
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990AJ.....99..965M&db_key=AST
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The compact star-forming regions associated with the Herbig Ae/Be stars LK H-alpha 198 and LK H-alpha 234
Photoelectric photometry and spectral classification are presented for19 stars in the region of Lk H-alpha 198 and 35 stars in the region ofLk H-alpha 234. Interstellar extinction in compact star-forming regionis compared with the CO emission map. It is found that the distance tothe Lk H-alpha 198 region is 630 + or - 30 pc. The distance to the LkH-alpha region is 1250 + or - 50 pc. The extensions of the regions are 2pc and 10 pc for Lk H-alpha 198 and 234, respectively. Also, the totalmasses of the regions are found to be 800 solar masses for Lk H-alpha198 and 2000 solar masses for Lk H-alpha 234. The light curve sectionsfor the regions and results of polarimetry for the stars in the LkH-alpha 234 region are given.
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Eight-colour photometry of stars associated with selected Sharpless H II regions at L exp II of about 190 deg - S 252, S 254, S 255, S 257, and S 261
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1987A&A...171..216C&db_key=AST
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Herbig's AE and Be star LkH-alpha 198, a flare star candidate
Eight-color, intermediate band photometry in the 13-color photometricsystem is presented for Herbig's (1960) Ae and Be star LkH-alpha 198,and for the relatively bright BD stars associated with its dark cloud.While integrating the 0.52 magnitude of LkH-alpha 198, two flares wereobserved within 5 min. The luminosity observed for this star imposes astrong constraint on its spectral type; late B-intermediate A is themost likely. LkH-alpha 198 is suggested to be the driving source of thebipolar wind observed in the cloud that is located southward of thesymmetry axis of the observed pattern.
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Metal abundance and microturbulence in F0-G2 stars and the calibration of the Stromgren m1 index
The strengths of two narrow groups of metal lines are measuredphotoelectrically by means of an echelle spectrometer for 16 F0-G2 giantfield stars and for 12 Hyades main-sequence stars. A model-atmosphereanalysis of these observations and similar observations of main-sequencefield stars observed earlier results in the determination of the metalabundance for 179 stars. In addition, the microturbulence parameter isdetermined for 73 of these stars. The internal accuracy of the resultsis estimated to be plus or minus 0.08 for the logarithmicmetal-to-hydrogen ratio and plus or minus 0.2 km/sec for themicroturbulence parameter. The metal abundances are found to agree verysatisfactorily with values of the logarithmic iron-to-hydrogen ratiodetermined from classical coude spectroscopy regarding both zero pointand scale. It is found that the microturbulence parameter is a functionof the effective temperature and the surface gravity. It increases from1.2 km/sec for solar type stars to approximately 3.0 km/sec for earlyF-type giants.
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Mesures d'etoiles doubles faites a Nice.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978A&AS...33..275M&db_key=AST
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Micrometer observations of double stars.8.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975ApJS...29..315H&db_key=AST
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Mikrometermessungen von Doppelsternen. VII
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970A&AS....1..393H&db_key=AST
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Stars in reflection nebulae
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968AJ.....73..233R&db_key=AST
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A study of reflection nebulae.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1966AJ.....71..990V&db_key=AST
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Mesures d'étoiles doubles faites au réfracteur de 38 cm de l'Observatoire de Nice
Not Available
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The Spectra of Be- and Ae-TYPE Stars Associated with Nebulosity
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1960ApJS....4..337H&db_key=AST
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Mesures d'étoiles doubles faites au réfracteur de 38 cm de l'Observatoire de Nice
Not Available
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INHABITED SKY
