Ýçindekiler
Görüntüler
Resim Yükleyin
DSS Images Other Images
Ýlgili Makaleler
Evolution from AGB to planetary nebula in the MSX survey
We investigate the evolution of oxygen- and carbon-rich AGB stars,post-AGB objects, and planetary nebulae using data collected mainly fromthe MSX catalogue. Magnitudes and colour indices are compared with thosecalculated from a grid of synthetic spectra that describe the post-AGBevolution beginning at the onset of the superwind. We find that carbonstars and OH/IR objects form two distinct sequences in the (K-[8.3])×([8.3]-[14.7]) MSX colour diagram. OH/IR objects are distributedin two groups: the bluest ones are crowded near [14.7]-[21.3]≃ 1and [8.3]-[14.7]≃ 2, and a second, redder group is spread over alarge area in the diagram, where post-AGB objects and planetary nebulaeare also found. High mass-loss rate OH/IR objects, post-AGB stars, andplanetary nebulae share the same region in the (K-[8.3])×([8.3]-[14.7]) and [14.7]-[21.3]×([8.3]-[14.7]) colour-colourdiagrams. This region in the diagram is clearly separated from a bluerone where most OH/IR stars are found. We use a grid of models ofpost-AGB evolution, which are compared with the data. The gap in thecolour-colour diagrams is interpreted as the result of the rapidtrajectory in the diagram of the stars that have just left the AGB.Based on results obtained by the MSX survey.Tables 1 to 3 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/431/565
| A catalog of rotational and radial velocities for evolved stars. II. Ib supergiant stars
Rotational velocity vsin i and mean radial velocity are presented for asample of 231 Ib supergiant stars covering the spectral region F, G andK. This work is the second part of the large survey carried out with theCORAVEL spectrometer to establish the behavior of the rotation for starsevolving off the main sequence (De Medeiros & Mayor 1999). Thesedata will add constraints to the study of the rotational behavior inevolved stars, as well as solid information concerning tidalinteractions in binary systems and on the link between rotation,chemical abundance and activity in stars of intermediate masses. Basedon observations collected at the Haute-Provence Observatory,Saint-Michel, France and at the European Southern Observatory, La Silla,Chile Table 1 is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/395/97
| A uvbyβ photometric calibration of iron abundances in supergiant stars.
A photometric reddening-free calibration for [Fe/H] valid for giant andsupergiant stars of intermediate temperature, has been obtained usingthe Stroemgren uvbyβ system. Galactic supergiants, supergiants inthe Magellanic Clouds and Galactic metal deficient red giants withspectroscopic determinations of [Fe/H] were used as calibrators. Thecalibration can be used to predict [Fe/H] with an accuracy of 0.33 dex,valid for stars with 0.14<[m_1_]<0.70 in the iron abundance range-2.5<[Fe/H]<+0.3. This shows the potential of supergiant stars astracers of iron abundances in other galaxies. Evidence that Galacticluminous F-G stars are intrinsically bluer than their counterparts inthe Magellanic Clouds is offered.
| Colour excesses of F-G supergiants and Cepheids from Geneva photometry.
A reddening scale for F-G supergiants and Cepheids is presented.Supergiants with low reddenings or in clusters form the basis of thecalibration. In this sense, it is entirely empirical. The data have beenobtained in the Geneva photometric system. Comparisons with otherreddening scales show no disagreement. The only problem is with Fernie'sscale for Cepheids (1990), where a systematic trend exists. Its originis not clear. It is suggested to extend the number of supergiants withindependently obtained colour excesses in order to test the existence ofa possible luminosity dependence of the calibration. A period-colourrelation for Cepheids is deduced, on the basis of the present reddeningcorrections. It gives strong support for V473 Lyr being a secondovertone pulsator.
| Calibrations of Mv, (Fe/H), and log G for yellow supergiant stars from O I 7774 and uvby-beta data
New calibrations of the absolute magnitude Mv from O I 7774data are derived from narrow-band photometry and low dispersionspectroscopy for AO-G2 low and high luminosity stars. The nonlineardependence of Mv from the equivalent width W(OI) and therelevance of the stellar temperature in the calibration are confirmed inagreement with previous calibrations obtained from high resolutionspectroscopy. Also functional formulas to estimate (Fe/H) and log g fromuvby-beta data for FO-G3 supergiants are offered. These calibrationspredict iron abundances and gravities for yellow supergiants withuncertainties not much higher than good spectroscopic determinations.
| SAO stars with infrared excess in the IRAS Point Source Catalog
We have undertaken a search for SAO stars with infrared excess in theIRAS Point Source Catalog. In contrast to previous searches, the entireIRAS (12)-(25)-(60) color-color diagram was used. This selection yieldeda sample of 462 stars, of which a significant number are stars withcircumstellar material. The stars selected can be identified aspre-main-sequence stars, Be stars, protoplanetary systems, post-AGBstars, etc. A number of objects are (visual) binary stars.Characteristic temperatures and IR excesses are calculated and theirrelations to spectral type are investigated.
| 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.
| A survey of Balmer-line profiles and IRAS fluxes in forty yellow supergiants
Results of a survey of yellow supergiants (predominantly F and G) thatwas undertaken to search for distorted Balmer lines are presented. Acomparison between the photometrically variable and nonvariablesupergiants is made with respect to the distorted and undistortedBalmer-line profiles. To complement the analysis, IRAS data are used todetect excess infrared emission, to infer circumstellar dust, and tosuggest a possible prior M supergiant evolutionary phase. Plans forfuture work are briefly discussed.
| O stars and supergiants south of declination -53 0.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1976AJ.....81..116H&db_key=AST
|
Yeni bir Makale Öner
Ýlgili Baðlantýlar
Yeni Bir Baðlantý Öner
sonraki gruplarýn üyesi:
|
Gözlemler ve gökölçümü verileri
| Takýmyýldýz: | Yelken |
| Sað Açýklýk: | 09h26m53.32s |
| Yükselim: | -54°21'06.2" |
| Görünürdeki Parlaklýk: | 6.862 |
| Uzaklýk: | 413.223 parsek |
| özdevim Sað Açýklýk: | -7.6 |
| özdevim Yükselim: | 6.5 |
| B-T magnitude: | 8.191 |
| V-T magnitude: | 6.972 |
Kataloglar ve belirtme:
|
