Contingut
Imatges
Carregar la teva Imatge
DSS Images Other Images
Articles Relacionats
A photometric study of Be stars located in the seismology fields of COROT
Context: In preparation for the COROT mission, an exhaustive photometricstudy of Be stars located in the seismology fields of the mission hasbeen performed. The very precise and long-time-spanned photometricobservations gathered by the COROT satellite will give important clueson the origin of the Be phenomenon. Aims: The aim of this work is tofind short-period variable Be stars located in the seismology fields ofCOROT, and to study and characterise their pulsational properties. Methods: Light curves obtained at the Observatorio de Sierra Nevada,together with data from Hipparcos and ASAS-3 for a total of 84 Be stars,were analysed in order to search for short-term variations. We appliedstandard Fourier techniques and non-linear least-square fitting to thetime series. Results: We found 7 multiperiodic, 21 mono-periodic and 26non-variable Be stars. Short-term variability was detected in 74% ofearly-type Be stars and in 31% of mid- to late-type Be stars. We showthat non-radial pulsations are more frequent among Be stars than inslow-rotating B stars of the same spectral range.Appendix A is only available in electronic form at http://www.aanda.org
| Fundamental parameters of Be stars located in the seismology fields of COROT
In preparation for the COROT space mission, we determined thefundamental parameters (spectral type, temperature, gravity, V sin i) ofthe Be stars observable by COROT in its seismology fields (64 Be stars).We applied a careful and detailed modeling of the stellar spectra,taking into account the veiling caused by the envelope, as well as thegravitational darkening and stellar flattening due to rapid rotation.Evolutionary tracks for fast rotators were used to derive stellar massesand ages. The derived parameters will be used to select Be stars assecondary targets (i.e. observed for 5 consecutive months) and short-runtargets of the COROT mission. Furthermore, we note that the main part ofour stellar sample falls in the second half of the main sequence lifetime, and that in most cases the luminosity class of Be stars isinaccurate in characterizing their evolutionary status.
| Statistical analysis of intrinsic polarization, IR excess and projected rotational velocity distributions of classical Be stars
We present the results of statistical analyses of a sample of 627 Bestars. The parameters of intrinsic polarization (p*),projected rotational velocity (v sin i), and near IR excesses have beeninvestigated. The values of p* have been estimated for a muchlarger and more representative sample of Be stars (~490 objects) thanpreviously. We have confirmed that most Be stars of early spectral typehave statistically larger values of polarization and IR excesses incomparison with the late spectral type stars. It is found that thedistributions of p* diverge considerably for the differentspectral subgroups. In contrast to late spectral types (B5-B9.5), thedistribution of p* for B0-B2 stars does not peak at the valuep*=0%. Statistically significant differences in the meanprojected rotational velocities (/line{vsin i}) are found for differentspectral subgroups of Be stars in the sense that late spectral typestars (V luminosity class) generally rotate faster than early types, inagreement with previously published results. This behaviour is, however,not obvious for the III-IV luminosity class stars. Nevertheless, thecalculated values of the ratio vt/vc of the truerotational velocity, vt, to the critical velocity forbreak-up, vc, is larger for late spectral type stars of allluminosity classes. Thus, late spectral type stars appear to rotatecloser to their break-up rotational velocity. The distribution of nearIR excesses for early spectral subgroups is bi-modal, the position ofthe second peak displaying a maximum value E(V-L)~ 1 . m 3for O-B1.5 stars, decreasing to E(V-L)~0. m8 for intermediatespectral types (B3-B5). It is shown that bi-modality disappears for latespectral types (B6-B9.5). No correlations were found betweenp* and near IR excesses and between E(V-L) and vsin i for thedifferent subgroups of Be stars. In contrast to near IR excesses, arelation between p* and far IR excesses at 12 mu m is clearlyseen. A clear relation between p* and vsin i (as well asbetween p* and /line{vsin i}/vc) is found by thefact that plots of these parameters are bounded by a ``triangular"distribution of p*: vsin i, with a decrease of p*towards very small and very large vsin i (and /line{vsini}/vc) values. The latter behaviour can be understood in thecontext of a larger oblateness of circumstellar disks for the stars witha rapid rotation. From the analysis of correlations between differentobservational parameters we conclude that circumstellar envelopes forthe majority of Be stars are optically thin disks with the range of thehalf-opening angle of 10degr
| The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.
| Rotational Velocity Determinations for 164 Be and B Stars
Rotational velocities, v sin i, have been obtained for 96 Be and 68normal B stars by measurements of the FWHM of the He I lambda-4471 line(for spectral types B0-B4.5) and Mg II lambda-4481 (for types B5-B9.5).The consistency of various published sources is examined. (SECTION:Stars)
| Distances, reddenings and distribution of emission B-stars in the galactic centre region /l/ not greater than 45 deg
The distribution of Be stars in the region surrounding the Galacticcenter and their correlation to the spiral structure of the Galaxy hasbeen studied. The results are discussed in terms of reddenings anddistances of these stars. Data are presented on the Galacticcoordinates, colors, interstellar color excesses, reddening-freemagnitudes and colors, adopted absolute magnitudes, distances in kpc,distances from the Galactic plane, and MK spectral type.
| Photometric observations of emission B-stars in the southern Milky Way
In order to study the distribution of Be stars and their correlation tothe local spiral structure of the Galaxy photoelectric UBV photometrywas carried out for a total of 488 Be stars located in the southernMilky Way between galactic longitudes 315 and 45 deg. UBV magnitudes arepresented for these stars.
| Second Supplement to the Mount Wilson Catalogue and Bibliography of Stars of Classes B and a whose Spectra have Bright Hydrogen Lines.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1949ApJ...110..387M&db_key=AST
|
Enviar un nou article
Enllaços Relacionats
- - No s'ha trobat enllaços -
Enviar un nou enllaç
Membre dels grups següents:
|
Dades d'Observació i Astrometria
| Constel·lació: | Aquila |
| Ascensió Recta: | 18h59m15.19s |
| Declinació: | -07°08'00.9" |
| Magnitud Aparent: | 8.953 |
| Distancia: | 740.741 parsecs |
| Moviment propi RA: | 2.1 |
| Moviment propi Dec: | -1.5 |
| B-T magnitude: | 9.18 |
| V-T magnitude: | 8.972 |
Catàlegs i designacions:
|
