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The infrared void in the Lupus dark clouds revisited: a polarimetric approach
The results of B-band CCD imaging linear polarimetry obtained for starsfrom the Hipparcos catalogue are used to re-examine the distribution ofthe local interstellar medium towards the IRAS 100-μm emission voidin the Lupus dark clouds. The analysis of the obtainedparallax-polarization diagram assigns to the dark cloud Lupus1 adistance between 130 and 150pc and assures the existence of a low columndensity region coincident with the observed infrared void. Moreover,there are clear indications of the existence of absorbing material atdistances closer than 60-100pc, which may be associated with theinterface boundary between the Local Bubble and its neighbourhood LoopIsuperbubble.
| Dust around First-Ascent Red Giants
We examine models for the physical conditions in the dust envelopesaround the closest and most conspicuous examples of luminosity class IIIred giants with infrared excesses such as delta And. (1) It has beenpreviously suggested that the dust is sporadically ejected from thestars, but for most such stars, this model seems unlikely. (2) Anotherpossibility is that in some cases we might be witnessing emission frominterstellar dust that happens to be near the star, a ``cirrus hotspot.'' Since 70% of the red giants with infrared excesses lie within100 pc of the Galactic plane where this phenomenon must sometimes occur,many of the excesses might be explained by this effect. However, adifficulty with this model for at least a few bright sources is that ifthe clouds have a uniform density, we expect sizes at 60 μm that areabout a factor of 10 larger than found for the best studied examples. Itseems likely that some class III giants do possess circumstellar dust.(3) The inferred mass of dust around some class III red giants is largerthan 10^26 g, more matter than would be expected when a Vega-type starevolves off the main sequence. Because the dust is inferred to be morethan 100 AU from the star, we hypothesize that the large inferred dustmasses is the result of the disintegration of comets. This model can betested by using the Space Infrared Telescope Facility to measure the 60μm sizes.
| A Search for Lithium-Rich Giants among Stars with Infrared Excesses
The unusual nature of the single, rapidly rotating, lithium-rich K giantHDE 233517, which is currently undergoing significant mass loss,prompted a search for giants with similar properties. High-dispersionspectroscopic observations were obtained of HD 219025, a knownlithium-rich infrared-excess giant, plus 39 stars from a list of G and Kgiants with excess far-infrared emission. The projected rotationalvelocities of the vast majority of infrared-excess giants appear to besimilar to those of normal G and K giants. Six giants have lithiumabundances at or above theoretical upper envelope values. The percentageof such stars in the sample of 39 infrared-excess giants is similar tothat of normal giants. The three giants with the largest lithiumabundances have previously been discovered. None of the sample of 39giants have an Hα line similar to the broadened and veryasymmetric line of HDE 233517. The star with optical properties mostsimilar to HDE 233517 is HD 219025.
| Giants with infrared excess.
We have correlated optical and infrared catalogs in order to extract alarge sample of luminosity class III stars with known infrared fluxdensities. For a non-negligible fraction of G and K giants, afar-infrared excess emission was found, starting beyond 25μm. Anexplanation in terms of present-day mass loss thus becomes unlikely,since the dust should then be warmer and the excess emission less far inthe infrared. We believe that the far-infrared excesses of theseobjects, most likely first-ascent giants, are related to the Vegaphenomenon. The dusty disks around these stars, gradually cooled downduring their main-sequence phase, could be reheated once the star leavesthe main sequence and enters the luminous post-main-sequence phase. Thefairly large sample we constructed enables us to derive an estimationfor the occurrence of excesses. This fraction of G or K giants withfar-infrared excess appears to be distinctly smaller than amongmain-sequence stars. Since the higher radiation field of giants couldlead to a larger evaporation rate of the circumstellar debris, this factdoes not conflict with our hypothesis.
| Luminosity Class III Stars with Excess Far-Infrared Emission
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJ...446L..79Z&db_key=AST
| SANTIAGO 91, a right ascension catalogue of 3387 stars (equinox J2000).
The positions in right ascension of 3387 stars belonging to the Santiago67 Catalogue, observed with the Repsold Meridian Circle at Cerro Calan,National Astronomical Observatory, during the period 1989 to 1994, aregiven. The average mean square error of a position, for the wholeCatalogue, is +/-0.009 s. The mean epoch of the catalogue is 1991.84.
| Walraven photometry of nearby southern OB associations
Homogeneous Walraven (VBLUW) photometry is presented for 5260 stars inthe regions of five nearby southern OB associations: Scorpio Centaurus(Sco OB2), Orion OB1, Canis Major OB1, Monoceros OB1, and Scutum OB2.Derived V and (B - V) in the Johnson system are included.
| E. W. Fick Observatory stellar radial velocity measurements. I - 1976-1984
Stellar radial velocity observations made with the large vacuumhigh-dispersion photoelectric radial velocity spectrometer at FickObservatory are reported. This includes nearly 2000 late-type starsobserved during 585 nights. Gradual modifications to this instrumentover its first eight years of operation have reduced the observationalerror for high-quality dip observations to + or - 0.8 km/s.
| Radial velocities of southern stars obtained with the photoelectric scanner CORAVEL. III - 790 late-type bright stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1985A&AS...59...15A&db_key=AST
| Radial velocities of southern HR stars. II
Fick Observatory's second major installment of radial-velocitymeasurements of bright southern stars is presented. This includes 373radial-velocity measurements for 90 stars which were obtained betweenJanuary 1978 and June 1981. Fifteen new possible velocity variables andone new double-line spectroscopic binary (HD 1782) have been detected.Subsequent velocity measurements of stars from the first southern HRstudy (Beavers and Eitter, 1980) found that (1) two stars (HR 0745 andHR 5428), originally classified as possible variables, are actuallyconstant velocity variables, and that (2) HR 0953 is a definite velocityvariable covering a range of at least -1 to +14 km/sec. This study, whencombined with the earlier southern HR observations and those reported byGriffin (1972), result in a total of 280 HR objects with newradial-velocity determinations.
| Visual multiples. VII - MK classifications
Classifications are given for 865 components of visual multiples; theyshow no systematic differences from the MK system, and the random errorsare one subclass in type and two-thirds of a luminosity class. It isfound that at least 1% of the F-type IV and V stars are weak-lined, 32%of the A4-F1 IV and V stars are Am, and 5% of the A0-A3 IV and V starsare early-type Am. Attention is called to the large fraction (55%) ofthe A3-A9 III-V stars that are of luminosity classes III or IV, unlikethe percentage (16%) at neighboring types.
| On the kinematics and ages of wide binaries containing a white dwarf
Radial velocities are reported for the bright nondegenerate members of12 common proper-motion binaries containing a white dwarf. Combiningthese with data already published, the kinematics of 24 systems can bestudied. This sample appears to be a mixture of high- and low-velocityobjects relative to the sun, and some have UVW motions that make themappear to be kinematically young, although some of these pairs can beeliminated after consideration of their cooling times. The additionalspectroscopic clues of emission lines and peculiar spectral typessuggest youth and strengthen the conclusion that the white dwarfcomponents of some of these low-velocity pairs evolved from parent starsthat belong to a young stellar population.
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| Takýmyýldýz: | Akrep |
| Sað Açýklýk: | 16h02m39.40s |
| Yükselim: | -29°08'09.0" |
| Görünürdeki Parlaklýk: | 6.03 |
| Uzaklýk: | 138.313 parsek |
| özdevim Sað Açýklýk: | 34.5 |
| özdevim Yükselim: | -10.1 |
| B-T magnitude: | 7.776 |
| V-T magnitude: | 6.206 |
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