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Echelle Long-Slit Optical Spectroscopy of Evolved Stars
We present echelle long-slit optical spectra of a sample of objectsevolving off the asymptotic giant branch (AGB), most of them in thepreplanetary nebula (PPN) phase, obtained with the ESI and MIKEspectrographs at the 10 m Keck II and 6.5 m Magellan-I telescopes,respectively. The total wavelength range covered with ESI (MIKE) is~3900-10900 Å (~3600-7200 Å). In this paper, we focus ouranalysis mainly on the Hα profiles. Prominent Hα emission isdetected in half of the objects, most of which show broad Hα wings(with total widths of up to ~4000 km s-1). In the majority ofthe Hα-emission sources, fast, post-AGB winds are revealed byP-Cygni profiles. In ~37% of the objects Hα is observed inabsorption. In almost all cases, the absorption profile is partiallyfilled with emission, leading to complex, structured profiles that areinterpreted as an indication of incipient post-AGB mass loss. The restof the objects (~13%) are Hα nondetections. We investigatecorrelations between the Hα profile and different stellar andenvelope parameters. All sources in which Hα is seen mainly inabsorption have F-G type central stars, whereas sources with intenseHα emission span a larger range of spectral types from O to G,with a relative maximum around B, and also including very late C types.Shocks may be an important excitation/ionization agent of the closestellar surroundings for objects with late type central stars. Sourceswith pure emission or P Cygni Hα profiles have larger J-K colorexcess than objects with Hα mainly in absorption, which suggeststhe presence of warm dust near the star in the former. The two classesof profile sources also segregate in the IRAS color-color diagram in away that intense Hα-emitters have dust grains with a larger rangeof temperatures. Spectral classification of the central stars in oursample is presented. For a subsample (13 objects), the stellarluminosity has been derived from the analysis of the O I 7771-7775Å infrared triplet. The location in the HR diagram of most ofthese targets, which represent ~30% of the whole sample, is consistentwith relatively high final (and, presumably, initial) masses in therange Mf~0.6-0.9 Msolar (Mi~3-8Msolar).
| High-precision effective temperatures of 161 FGK supergiants from line-depth ratios
Precise effective temperatures (Teff) are determined for 161FGK supergiants using method of line-depth ratios. We obtain a set of131 relations for temperatures of supergiants as a function of linedepths. These relations have been calibrated against previouslypublished accurate temperature estimates. The application range of themethod is 3600-7800 K (F0I-K5I). The internal error of a singlecalibration is less than 110 K, while combination of all calibrationsreduces uncertainty to only 5-30 K (standard error). The error in thezero-point is estimated to be less than 100-200 K. A significantadvantage of the line ratio method is its independence of theinterstellar reddening, and only modest sensitivity to abundance,macroturbulence, rotation and other factors.
| Sixth Catalogue of Fundamental Stars (FK6). Part III. Additional fundamental stars with direct solutions
The FK6 is a suitable combination of the results of the HIPPARCOSastrometry satellite with ground-based data, measured over a longinterval of time and summarized mainly in the FK5. Part III of the FK6(abbreviated FK6(III)) contains additional fundamental stars with directsolutions. Such direct solutions are appropriate for single stars or forobjects which can be treated like single stars. Part III of the FK6contains in total 3272 stars. Their ground-based data stem from thebright extension of the FK5 (735 stars), from the catalogue of remainingSup stars (RSup, 732 stars), and from the faint extension of the FK5(1805 stars). From the 3272 stars in Part III, we have selected 1928objects as "astrometrically excellent stars", since their instantaneousproper motions and their mean (time-averaged) ones do not differsignificantly. Hence most of the astrometrically excellent stars arewell-behaving "single-star candidates" with good astrometric data. Thesestars are most suited for high-precision astrometry. On the other hand,354 of the stars in Part III are Δμ binaries in the sense ofWielen et al. (1999). Many of them are newly discovered probablebinaries with no other hitherto known indication of binarity. The FK6gives, besides the classical "single-star mode" solutions (SI mode),other solutions which take into account the fact that hidden astrometricbinaries among "apparently single-stars" introduce sizable "cosmicerrors" into the quasi-instantaneously measured HIPPARCOS proper motionsand positions. The FK6 gives, in addition to the SI mode, the "long-termprediction (LTP) mode" and the "short-term prediction (STP) mode". TheseLTP and STP modes are on average the most precise solutions forapparently single stars, depending on the epoch difference with respectto the HIPPARCOS epoch of about 1991. The typical mean error of anFK6(III) proper motion in the single-star mode is 0.59 mas/year. This isa factor of 1.34 better than the typical HIPPARCOS errors for thesestars of 0.79 mas/year. In the long-term prediction mode, in whichcosmic errors are taken into account, the FK6(III) proper motions have atypical mean error of 0.93 mas/year, which is by a factor of about 2better than the corresponding error for the HIPPARCOS values of 1.83mas/year (cosmic errors included).
| Photometry of F-K type bright giants and supergiants. I - Intermediate band and H-Beta observations
Over 1500 observations of 560 bright giants and supergiants of types F-Kare presented and compared to the observations by Gray and Olsen (1991).The present results include intermediate-band which is slightlydifferent from the Stromgren data by Gray and Olsen due to a differentwidth for the v filter. A systematic difference in m(1) - M(1) withdecreasing temperature is noted in the two H-Beta data sets, and thecorrelations are defined.
| The calibration of the Stromgren photometric system for A, F and early G supergiants. I - The observational data
An empirical calibration of the Stromgren uvby-beta photometric systemfor the A, F, and early G supergiants is being derived. This paperexplains the observational program and the photometric reductiontechniques used and presents a catalog of new Stromgren photometry forover 600 A, F, and G supergiants.
| 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.
| UBVRI photometry of FK4 and FK4 supplement stars
Photometric UBVRI observations of 172 Southern Hemisphere stars of theFK4 and FK4-Supplement catalogs, obtained using a dry-ice-cooledphotomultiplier on the 50-cm telescope at ESO on 37 nights during1982-1983 are reported. The data are presented in tables and graphs andbriefly characterized.
| The reddening, metal abundance, and luminosity of high-luminosity G-type stars
The abundance parameters of the sample of 100 G-type bright giants andsupergiants whose photometry is presently discussed indicate Fe/H valuesof between about + 0.6 dex and the solar value, using a preliminarycalibration of the photometric indices. The few long period Cepheidsthat are not heavily blanketed F-type stars give reddening values thatare in agreement with current results from other methods of analysis.Supergiants show no clear gradients in the galactic distribution ofabundances, and those nearest the sun range from an Fe/H of about + 0.3dex, for members of the Pleiades Group, to near solar abundance. A smallsample of Large Magellanic Cloud supergiants shows nearly the same rangein metal abundance as the galactic stars, and gives a modulus for thisCloud of 18.3 + or - 0.20 mag.
| Five-channel photometry of cepheids and supergiants in the southern Milky Way.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976A&AS...24..413P&db_key=AST
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | מחוגה |
| התרוממות ימנית: | 15h23m51.10s |
| סירוב: | -57°19'50.3" |
| גודל גלוי: | 6.766 |
| מרחק: | 1754.386 פארסק |
| תנועה נכונה: | -1.5 |
| תנועה נכונה: | -4.2 |
| B-T magnitude: | 8.307 |
| V-T magnitude: | 6.894 |
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