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The cool circumstellar environment of IRAS 08182-6000: radiative transfer modelling of TiO absorption bands
IRAS 08182-6000 has very red infrared colours, with an excess at K andL, and a silicate absorption feature at 9.7 μm. Optical spectra showstrong, narrow absorption bands of TiO and AlO and weaker bands of VOthat are indicative of formation in a very cool region, superimposed ona late F-type or early G-type spectrum. It is similar to the unusualstar U Equ = IRAS 20547+0247 and both are high-velocity stars. Thesecharacteristics, together with spectroscopic indications of low surfacegravity, suggest that these stars are of low mass and are possibly at apost-AGB stage of evolution. IRAS 08182-6000 brightened by severalmagnitudes during 12 yr of photometric observation. Photospheric andsome circumstellar atomic absorption lines are evident, as well asatomic lines seen in emission that differ in radial velocity from thosein absorption by c. 50 km s-1. Molecular bands of theγ, γ' and α systems of circumstellar TiO have beenmodelled using a one-dimensional radiative transfer code that makes useof the most recent laboratory and theoretical spectroscopic data on TiO.It was found necessary to invoke a non-local thermodynamic equilibriummodel, which resulted in the determination of different rotational,spin-orbit and vibrational temperatures for the TiO gas, all of whichlie well below the temperature at which TiO begins to deplete from thegas phase due to grain formation.
| 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.
| Evolved GK stars near the sun. I - The old disk population
A sample of nearly two thousand GK giants with intermediate band, (R,I),DDO and Geneva photometry has been assembled. Astrometric data is alsoavailable for most of the stars. The some 800 members of the old diskpopulation in the sample yield accurate luminosities (from two sources),reddening values and chemical abundances from calibrations of thephotometric parameters. Less than one percent of the objects arepeculiar in the sense that the flux distribution is abnormal. Thepeculiarity is signaled by strong CH (and Ba II) and weak CH. The CH+stars are all spectroscopic binaries, probably with white dwarfcompanions, whereas the CH- stars are not. A broad absorption band,centered near 3500 A, is found in the CH+ stars whereas the CH- objectshave a broad emission feature in the same region. The intensity of theseabsorptions and emissions are independent of the intensity of abnormalspectral features. Ten percent of the old disk sample have a heavyelement abundance from one and a half to three times the solar value.The distribution of the heavy element abundances is nearly a normal onewith a peak near solar abundance and ranges three times to one sixthsolar. The distribution of the (U, V) velocities is independent of theheavy element abundance and does not appear to be random. Ten percent ofthe old disk stars show a CN anomaly, equally divided between CN strongand CN weak. Several stars of individual astrometric or astrophysicalimportance are isolated.
| A list of MK standard stars
Not Available
| The Perkins catalog of revised MK types for the cooler stars
A catalog is presented listing the spectral types of the G, K, M, and Sstars that have been classified at the Perkins Observatory in therevised MK system. Extensive comparisons have been made to ensureconsistency between the MK spectral types of stars in the Northern andSouthern Hemispheres. Different classification spectrograms have beengradually improved in spite of some inherent limitations. In thecatalog, the full subclasses used are the following: G0, G5, G8, K0, K1,K2, K3, K4, K5, M0, M1, M2, M3, M4, M5, M6, M7, and M8. Theirregularities are the price paid for keeping the general scheme of theoriginal Henry Draper classification.
| 1988 Revised MK Spectral Standards for Stars GO and Later
Not Available
| 1985 revised MK spectral standards : stars GO and later
Not Available
| Revised MK Spectral Standard Stars Later than G0
Not Available
| The corrected magnitudes and colours of 278 stars near S.A. 1-139 in the UBV system
Not Available
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Pozíciós és asztrometriai adatok
| Csillagkép: | Holló |
| Rektaszcenzió: | 12h27m49.40s |
| Deklináció: | -16°37'55.0" |
| Vizuális fényesség: | 6.35 |
| Távolság: | 392.157 parszek |
| RA sajátmozgás: | -10.5 |
| Dec sajátmozgás: | 5.6 |
| B-T magnitude: | 7.384 |
| V-T magnitude: | 6.391 |
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INHABITED SKY
