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A photometric pilot study on Sonneberg archival patrol plates. How many ``constant'' stars are in fact long-term variables?
The light curves of 216 arbitrarly chosen field stars and of 23 knownvariables in the Aur/Tau/Ori region were derived (7.8 m ≤ B ≤12.2 m) from scanned, blue-sensitive archival patrol plates, covering atotal of 34 years (1961-1995). We achieved a photometric accuracy of0.07 ... 0.12 mag in spite of rather unfavourable locations of moststars near the plate borders. 17 field stars turned out to be variables,most of them with time scales of 1000-8000 days in the form of slowwaves with amplitudes between 0.1 and 0.3 mag, i.e. below the thresholdof traditional variable searches on photographic plates. About 50% ofthese new long-term variables exhibit drifts indicating periodic orerratic variability at much longer time scales than covered here. Forthe 23 known variables we achieved improvements in their periods andamplitudes and detected long-term variations (drifts, waves) in about50% of them. The above fraction of low-amplitude long-term variablesamong field stars implies that a total of about 45 000 new variablesshould be detectable in the Sonneberg patrol plate archive. They willrepresent a new, hitherto not investigated population of variable starswith a possibly significant impact on our understanding of the stellarinterior and evolution.Tables 2 and 3 are only available in electronic form athttp://www.edpsciences.org
| 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)
| New position determinations, and other data, for 1280 known Hα-emission stars in the milky way.
Not Available
| Spectroscopic Observations of be Stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1951ApJ...113..624M&db_key=AST
| 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
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