Contenuti
Immagini
Carica la tua immagine
DSS Images Other Images
Articoli relazionati
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.
| The mass loss rates of OH/IR 32.8-0.3 and OH/IR 44.8-2.3.
In a previous paper a model was presented to calculate the thermalemission of molecules around a central star. The model includes aself-consistent determination of the gas kinetic temperature,photoelectric heating, cooling by water molecules and the constraintthat the presence of dust puts on the molecular excitation. The model isapplied to the CO(1-0) and CO(2-1) observations of the OH/IR stars OH32.8-0.3 and OH 44.8-2.3 (abbreviated to OH 32.8 and OH 44.8). Both comefrom the sample observed by Heske et al. (1990) who noted that in theless extreme OH/IR stars (like OH 44.8) the mass loss rate derived frominfrared properties agrees reasonably well with that estimated from theCO emission but that in extreme OH/IR stars (like OH 32.8) the mass lossrate derived from the infrared is an order of magnitude larger than thatderived from CO emission. For a dust opacity at 60μm of 228cm^2^g^-1^ the best model for OH 44.8 has the following parameters:˙(M)=9.0x10^-6^Msun_/yr, dust-to-gas ratio {PSI}=0.0035and mean dust grain size a=0.14μm. The derived mass loss rate isinsensitive to the adopted opacity. The results are relativelyinsensitive to any model assumptions. For OH 32.8 no model is found thatfits the observed line profiles for a constant mass loss rate throughoutthe envelope. For a grain size of a=0.125μm, an opacity of 228cm^2^/g (following the result for OH 44.8) and a mass loss history inwhich the mass loss rate drops by a factor of 10 for radial distanceslarger than a critical distance R_c_, the following model reproduces theobserved intensities: (present-day)˙(M)=2.0x10^-5^Msun_/yr, {PSI}=0.015 withR_c_~1.3x10^17^cm (corresponding to a timescale of about 2800 years).Models with ˙(M)>4.0x10^-5^Msun_/yr cannot be made tofit the observations, models with˙(M)<2.0x10^-5^Msun_/yr probably can, but result inhigher dust-to-gas ratios ({PSI}~˙(M)^-1^). The distinction made byHeske et al. (1990) between moderate OH/IR stars (like OH 44.8) andextreme OH/IR stars (like OH 32.8) can be understood as follows: the COshell in the extreme OH/IR stars is so large that the outer part samplesa previous phase of lower mass loss, several 10^3^ yrs ago. Finally, Icomment on the possibility that in extreme mass losing stars thetemperature in the outer parts of the circumstellar shells drops belowthe cosmic background radiation temperature. Based on the models for thetwo OH/IR stars I derive that this occurs if˙(M)_-5_>4.8Q_0.01_L_4_^4/3^v_10_^1/3^, where Q_0.01_ is theeffective absorption coefficient in units of 0.01, ˙(M)_-5_ is themass loss rate in 10^-5^ Msun_/yr, L_4_ the stellarluminosity in 10^4^ Lsun_ and v_10_ the expansion velocity ofthe shell in 10 km/s. This relation is expected to be valid foroxygen-rich stars and standard values for the dust opacity and thephotoelectric heating rate.
| Radial-velocity measurements. V - Ground support of the HIPPARCOS satellite observation program
The paper presents data on 1070 radial velocity measurements of starsdistributed in 39 fields measuring 4 deg x 4 deg. The PPO series ofFehrenbach et al. (1987) and Duflot et al. (1990) is continued using theFehrenbach objective prism method.
|
Sottometti un nuovo articolo
Link relazionati
Sottometti un nuovo link
Membro dei seguenti gruppi:
|
Osservazione e dati astrometrici
| Costellazione: | Ercole |
| Ascensione retta: | 17h50m57.27s |
| Declinazione: | +29°59'44.9" |
| Magnitudine apparente: | 6.776 |
| Distanza: | 123.305 parsec |
| Moto proprio RA: | -4.5 |
| Moto proprio Dec: | 2.3 |
| B-T magnitude: | 6.869 |
| V-T magnitude: | 6.784 |
Cataloghi e designazioni:
|
INHABITED SKY
