|Search for solid HDO in low-mass protostars|
We present ground-based 2.1 to 4.2 mu m observations of four low-massprotostars. We searched for the 4.1 mu m OD stretch band, characteristicof solid HDO in grain mantles. We did not detect solid HDO in any of thefour sources, but we derive 3sigma upper limits from 0.5% to 2% for theHDO/H_2O ratio depending on the source. These ratios provide strongconstraints to solid-state deuteration models when compared to deuteriumfractionation values observed in the gas phase. We discuss variousscenarios that could lead to such a low water deuteration compared tothe high formaldehyde and methanol deuteration observed in thegas-phase.
|1-4 Micron Spectrophotometry of Dust in the Taurus Dark Cloud: Water Ice Distribution in Heiles Cloud 2|
We have conducted near infrared spectroscopy of 61 background starstoward Heiles Cloud 2 in the Taurus molecular cloud complex. We used alow-dispersion spectrometer, PASP2, which can simultaneously obtain thespectrum with a wavelength coverage between 1.3 and 4.2 μm. For 56 of61 objects, the visual extinction (AV) and theoptical depth of water ice at λ=3.1 μm (τICE)have been estimated: for 50 of 56 objects, these were systematicallyestimated from our data only. In order to investigate the water icedistribution in Heiles Cloud 2, we have constructed a ``water ice map''in which τICE is plotted at the position of each object.The water ice map is then compared with the C18O (J=1-0) mapobtained by millimeter observations performed by Sunada & Kitamura.We find that the distribution of water ice is closely correlated withthat of C18O. Strong water ice absorption is seen only towardthe dense C18O clumps, while less water ice absorption isdetected toward the outer region of the cloud. There is anAV threshold for the positive ice detection(AV0), as suggested by previous observations, but with asignificant scatter; AV0=2-5 mag. The scatter might be causedby the different contribution of the inner water-containing portion ofthe cloud along the line of sight. The value of τICEincreases with increasing of AV and the slope ofΔτICE/ΔAV is 0.067,consistent with the previously observed values for the Taurus molecularcloud.
|On the HIPPARCOS photometry of chemically peculiar B, A, and F stars|
The Hipparcos photometry of the Chemically Peculiar main sequence B, A,and F stars is examined for variability. Some non-magnetic CP stars,Mercury-Manganese and metallic-line stars, which according to canonicalwisdom should not be variable, may be variable and are identified forfurther study. Some potentially important magnetic CP stars are noted.Tables 1, 2, and 3 are available only in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (188.8.131.52) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
|ICCD Speckle Observations of Binary Stars.XV.An Investigation of Lunar Occultation Systems|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....112.2260M&db_key=AST
|V1061 Tauri: Analysis of a Newly Discovered Eclipsing Binary|
We present the first light curve of the newly-discovered eclipsingbinary V1061 Tauri (HD 31679), consisting of 376 observations in the Vpassband. The primary eclipse appears to be flat-bottomed, indicating atotal eclipse, but the eclipse is only 0.35 magnitudes deep. Anexamination of more than 600 Harvard College Observatory patrol platesyielded 30 times of primary minimum, and we present an ephemeris for thesystem. Analysis of the light curve with the Wilson-Devinney programreveals that the system may contain a large amount of third light, theorigin of which is presently unknown. (SECTION: Stars)
|The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJS...99..135A&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.
|Probable open clusters NGC 1750 and NGC 1758 behind the Taurus dark clouds|
The area of 2.5 x 2.5 deg in the direction of the Taurus dark cloudscontaining stellar groupings NGC 1746, NGC 1750, and NGC 1758 isinvestigated in the Vilnius photometric system. Magnitudes V, colorindices, color excesses, interstellar extinctions, and distances aredetermined for 116 stars, some of which are as faint as V = 13. It isconcluded that NGC 1746 is probably not a cluster. Other two groupingsof stars, NGC 1750 and NGC 1758, if real, may be open clusters at 510and 680 pc distances. Interstellar reddenings E(B-V) of both groups are0.42 and 0.37 mag, respectively. The distance of the Taurus dark cloudsin the area is found to be 175 pc, i.e. by 45 pc larger than in otherdirections farther to the south from the galactic equator.
|Fifth fundamental catalogue. Part 2: The FK5 extension - new fundamental stars|
The mean positions and proper motions for 3117 new fundamental starsessentially in the magnitude range about 4.5 to 9.5 are given in thisFK5 extension. Mean apparent visual magnitude is 7.2 and is on average2.5 magnitudes fainter then the basic FK5 which has a mean magnitude of4.7. (The basic FK5 gives the mean positions and proper motions for theclassical 1535 fundamental stars). The following are discussed: theobservational material, reduction of observations, star selection, andthe system for the FK5 extension. An explanation and description of thecatalog are given. The catalog of 3117 fundamental stars for the equinoxand epoch J2000.0 and B1950.0 is presented. The parallaxes and radialvelocities for 22 extension stars with large forecasting effects aregiven. Catalogs used in the compilation of the FK5 fundamental catalogare listed.
|The stellar temperature scale for stars of spectral types from O8 to F6 and the standard deviation of the MK spectral classification|
Empirical effective temperature of 211 early-type stars found in aprevious investigation (Kontizas and Theodossiou, 1980; Theodossiou,1985) are combined with the effective temperatures of 313 early-typestars from the literature. From these effective temperatures of a totalnumber of 524 early-type stars of spectral types from O8 to F6 a newstellar temperature scale is developed along with the standard deviationof the MK spectral classification.
|KPNO lunar occultation summary. II|
The results from 65 lunar occultation observations between August 1984and July 1986 are discussed. The instrumentation and reductionprocedures used in the study are described. Parameters are given fornine different double/multiple stars and for two stars with measurableangular diameters. Three newly discovered double stars, SAO 77310, SAO79241, and the brighter component of SAO 77837, are examined. Inaddition, a fourth star, the brighter component of SAO 76862, isresolved for the first time.
|Observations of interstellar diffuse absorption band at 4430 A|
Observations of the interstellar diffuse absorption band at 4430 A for800 O and B stars in Neckel's (1967) catalog are being carried out, and482 spectra obtained up to September 1983 have been reduced. It isconfirmed that the strength of the interstellar diffuse absorption bandat 4430 A does not simply relate to the abundance of interstellar grainson the line of sight. The relation between the color excess E(B-V) andthe equivalent width of the band to the direction of l = 130-140 deg andb = -5 to +5 deg shows that some parameter(s) other than E(B-V) is (are)needed to understand the cause of this band.
|The local system of early type stars - Spatial extent and kinematics|
Published uvby and H-beta photometric data and proper motions arecompiled and analyzed to characterize the structure and kinematics ofthe bright early-type O-A0 stars in the solar vicinity, with a focus onthe Gould belt. The selection and calibration techniques are explained,and the data are presented in extensive tables and graphs and discussedin detail. The Gould belt stars of age less than 20 Myr are shown togive belt inclination 19 deg to the Galactic plane and node-lineorientation in the direction of Galactic rotation, while the symmetricaldistribution about the Galactic plane and kinematic properties (purecircular differential rotation) of the belt stars over 60 Myr oldresemble those of fainter nonbelt stars of all ages. The unresolveddiscrepancy between the expansion observed in the youngest nearby starsand the predictions of simple models of expansion from a point isattributed to the inhomogeneous distribution of interstellar matter.
|Meridian observations made with the Carlsberg Automatic Meridian Circle at Brorfelde (Copenhagen University Observatory) 1981-1982|
The 7-inch transit circle instrument with which the present position andmagnitude catalog for 1577 stars with visual magnitudes greater than11.0 was obtained had been equipped with a photoelectric moving slitmicrometer and a minicomputer to control the entire observationalprocess. Positions are reduced relative to the FK4 system for each nightover the whole meridian rather than the usual narrow zones. Thepositions of the FK4 stars used in the least squares solution are alsogiven in the catalog.
|UBV photometry of FK4 and FK4 supplement stars|
Traditional UBV filters, together with a photomultiplier, have been usedin 40-m Cassegrain telescope observations of all northern stars of theFK4 catalog and its supplement, which have heretofore lacked V and V-Bmeasurements. The resulting UBV photometry for 320 stars is presented intabular form.
|Late B-type stars - Rotation and the incidence of HgMn stars|
High-dispersion spectrograms for an unbiased sample of 256 late B-typestars are examined in an attempt to determine whether slow rotation isnecessary and sufficient for the appearance of HgMn anomalies innonmagnetic stars. The peculiar stars in the sample are identified,values of v sin i are derived for all the stars observed, and theradial-velocity variations of the identified HgMn stars are analyzed.The distribution of rotational velocities for late B-type stars isobtained, and the role of rotation in producing extended envelopes isevaluated. The binary frequency and mass-ratio distribution are derivedfor systems containing HgMn components, the effect of duplicity on thedistribution of rotational velocities is estimated, and the role of suchfactors as rotation, age, and binary characteristics in determiningwhether HgMn anomalies are present is investigated. The results clearlyshow that HgMn stars occur only within a limited temperature range, thatall such stars rotate slowly, but that rotation, effective temperature,age, surface gravity, and binary properties do not serve to determinewhether a star will exhibit abundance anomalies.
|Spectral classification from the ultraviolet line features of S2/68 spectra. III - Early A-type stars|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978A&AS...33...15C&db_key=AST
|Rotational Velocities of a0 Stars|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974ApJS...28..101D&db_key=AST
|Four-color and H beta photometry for the bright B8 and B9 type stars north of declination -10 degre.|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973AJ.....78..738C&db_key=AST
|Catalog of Indidual Radial Velocities, 0h-12h, Measured by Astronomers of the Mount Wilson Observatory|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970ApJS...19..387A&db_key=AST
|U, b, v, and Hβ Photometry for the Bright B8- and B9-TYPE Stars.|
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1963ApJ...137..530C&db_key=AST