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Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i
This work is the second part of the set of measurements of v sin i forA-type stars, begun by Royer et al. (\cite{Ror_02a}). Spectra of 249 B8to F2-type stars brighter than V=7 have been collected at Observatoirede Haute-Provence (OHP). Fourier transforms of several line profiles inthe range 4200-4600 Å are used to derive v sin i from thefrequency of the first zero. Statistical analysis of the sampleindicates that measurement error mainly depends on v sin i and thisrelative error of the rotational velocity is found to be about 5% onaverage. The systematic shift with respect to standard values fromSlettebak et al. (\cite{Slk_75}), previously found in the first paper,is here confirmed. Comparisons with data from the literature agree withour findings: v sin i values from Slettebak et al. are underestimatedand the relation between both scales follows a linear law ensuremath vsin inew = 1.03 v sin iold+7.7. Finally, thesedata are combined with those from the previous paper (Royer et al.\cite{Ror_02a}), together with the catalogue of Abt & Morrell(\cite{AbtMol95}). The resulting sample includes some 2150 stars withhomogenized rotational velocities. Based on observations made atObservatoire de Haute Provence (CNRS), France. Tables \ref{results} and\ref{merging} are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.125.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/393/897
| Further Improvement of the Period and New R Light Curve of CQ UMa
We report new period improvement for CQ UMa based on new photoelectricobservations. A new light-curve in the red region is published.
| A spectroscopic survey for lambda Bootis stars. II. The observational data
lambda Bootis stars comprise only a small number of all A-type stars andare characterized as nonmagnetic, Population i, late B to early F-typedwarfs which show significant underabundances of metals whereas thelight elements (C, N, O and S) are almost normal abundant compared tothe Sun. In the second paper on a spectroscopic survey for lambda Bootisstars, we present the spectral classifications of all program starsobserved. These stars were selected on the basis of their Strömgrenuvbybeta colors as lambda Bootis candidates. In total, 708 objects insix open clusters, the Orion OB1 association and the Galactic field wereclassified. In addition, 9 serendipity non-candidates in the vicinity ofour program stars as well as 15 Guide Star Catalogue stars were observedresulting in a total of 732 classified stars. The 15 objects from theGuide Star Catalogue are part of a program for the classification ofapparent variable stars from the Fine Guidance Sensors of the HubbleSpace Telescope. A grid of 105 MK standard as well as ``pathological''stars guarantees a precise classification. A comparison of our spectralclassification with the extensive work of Abt & Morrell(\cite{Abt95}) shows no significant differences. The derived types are0.23 +/- 0.09 (rms error per measurement) subclasses later and 0.30 +/-0.08 luminosity classes more luminous than those of Abt & Morrell(\cite{Abt95}) based on a sample of 160 objects in common. The estimatederrors of the means are +/- 0.1 subclasses. The characteristics of oursample are discussed in respect to the distribution on the sky, apparentvisual magnitudes and Strömgren uvbybeta colors. Based onobservations from the Observatoire de Haute-Provence, OsservatorioAstronomico di Padova-Asiago, Observatório do Pico dosDias-LNA/CNPq/MCT, Chews Ridge Observatory (MIRA) and University ofToronto Southern Observatory (Las Campanas).
| Does Rotation Alone Determine Whether an A-Type Star's Spectrum Is Abnormal or Normal?
As noted by Abt & Morrell, virtually all of the metallic line (Am)and peculiar A (Ap) stars have equatorial rotational velocities lessthan 120 km s-1, and most of the normal A0-F0 main-sequencestars have equatorial rotational velocities greater than 120 kms-1. However, at all spectral types there are some (10%-20%)of the normal stars that have smaller rotational velocities. If thisoverlap is real, then a star's rotational velocity is insufficient toexplain its abnormal or normal spectra. We studied the A5-F0 and A2-A4stars and found in both cases that there are stars classified as``normal'' that have unusually weak Ca II K lines and/or that occur inshort-period binaries. Therefore, the overlap seems to be due toundetected marginal abnormal stars. Among the A0-A1 stars we find thatour inability to distinguish consistently the class IV from the class Vstars can explain the overlap because the class IV stars have lowerrotational velocities than class V stars. We conclude from statisticalarguments that rotation alone can explain the appearance of an A star aseither abnormal or normal.
| The ROSAT all-sky survey catalogue of optically bright main-sequence stars and subgiant stars
We present X-ray data for all main-sequence and subgiant stars ofspectral types A, F, G, and K and luminosity classes IV and V listed inthe Bright Star Catalogue that have been detected as X-ray sources inthe ROSAT all-sky survey; several stars without luminosity class arealso included. The catalogue contains 980 entries yielding an averagedetection rate of 32 percent. In addition to count rates, sourcedetection parameters, hardness ratios, and X-ray fluxes we also listX-ray luminosities derived from Hipparcos parallaxes. The catalogue isalso available in electronic form via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The Pulkovo Spectrophotometric Catalog of Bright Stars in the Range from 320 TO 1080 NM
A spectrophotometric catalog is presented, combining results of numerousobservations made by Pulkovo astronomers at different observing sites.The catalog consists of three parts: the first contains the data for 602stars in the spectral range of 320--735 nm with a resolution of 5 nm,the second one contains 285 stars in the spectral range of 500--1080 nmwith a resolution of 10 nm and the third one contains 278 stars combinedfrom the preceding catalogs in the spectral range of 320--1080 nm with aresolution of 10 nm. The data are presented in absolute energy unitsW/m(2) m, with a step of 2.5 nm and with an accuracy not lower than1.5--2.0%.
| UvbyHbeta_ photometry of main sequence A type stars.
We present Stroemgren uvby and Hbeta_ photometry for a set of575 northern main sequence A type stars, most of them belonging to theHipparcos Input Catalogue, with V from 5mag to 10mag and with knownradial velocities. These observations enlarge the catalogue we began tocompile some years ago to more than 1500 stars. Our catalogue includeskinematic and astrophysical data for each star. Our future goal is toperform an accurate analysis of the kinematical behaviour of these starsin the solar neighbourhood.
| The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995ApJS...99..135A&db_key=AST
| 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 determination of T_eff_ of B, A and F main sequence stars from the continuum between 3200 A and 3600 A.
A method of determination of the effective temperature of B, A and Fmain sequence stars is proposed, using the slope of the continuumbetween 3200A and 3600A. The effective temperature calibration is basedon a sample of stars with energy distributions known from UV to the red.We have determined the Balmer jump and the effective temperatures for235 main sequence stars. The temperatures found have been compared withthose derived by Underhill et al. (1979), Kontizas & Theodossiou(1980), Theodossiou (1985), Morossi & Malagnini (1985). Thecomparison showed good agreement for most of the stars in common. On theother hand, the temperatures derived from the reddening-free colourfactor QUV, from the colour index (m1965-V) and from (B-V), given inGulati et al. (1989), are systematically lower than our temperatures,however the differences are within one-sigma error.
| Reliable photometric reductions to the standard UBV (or uvby) system and accurate UBV magnitudes of bright standard stars from the northern part of the international Be program
A modified method of computer reduction of UBV (or uvby) photoelectricobservations to standard systems, which combines advantages of what hasso far been achieved in this area, is described in detail. A completereduction of over 46000 UBV observations obtained at Hvar Observatorybetween 1972 and 1991, and of nearly 5000 UBV observations secured atSkalnate Pleso Observatory between 1980 and 1987, was carried out usingthe new technique. It is argued that replacing the original Johnson'sUBV values for the non-variable stars that were observed by the meanvalues based on repeated observations over several years and applyingthe new reduction technique can ensure a stable reproduction of UBVmagnitudes, obviously quite close to the standard Johnson's ones, overmany years and from observatories situated at very different altitudesabove sea level within about 0.01mag in all three UBV magnitudes. A listof new accurate mean UBV values of 191 stars which were regularlyobserved at Hvar - and a part of them also at Skalnate Pleso - ascomparison, check and standard stars in the Be- and Ap-star observingprograms, is included for future use by photometric observers in theNorthern Hemisphere. For a number of these stars, we can guaranteesecular constancy within 0.mag01 during the past 5 to 15 years.
| UBV photometry of stars whose positions are accurately known. VI
Results are presented from UBV photometric observations of 1000 stars ofthe Bright Star Catalogue and the faint extension of the FK5.Observations were carried out between July 1987 and December 1990 withthe 40-cm Cassegrain telescope of the Kvistaberg Observatory.
| The Postdam compilation of data on photometric variability of AP magnetic stars.
Not Available
| Spectrophotometry of peculiar B and A stars. XVII - 63 Andromedae, HD 34452, Epsilon Ursae Majoris, CQ Ursae Majoris, CU Virginis, CS Virginis and Beta Coronae Borealis
Optical region spectrophotometry results are presented for seven Apstars. Additional data for two silicon stars, HD 34452 and CU Vir, showthat both have energy distributions that can be fit by a single globalmodel atmosphere, except for the 4200 and 5200 A broad absorptionfeatures. These features are strong in HD 34452, and show no evidence ofvariation, while they are weak in CU Vir but show clear evidence ofvariations. The energy distributions of the five cooler Ap stars cannotbe fit by a single model atmosphere. CQ UMa, CS Vir and Beta CrB allshow complicated variations with phase at different wavelengths. Theirenergy distributions show combined effects of flux redistribution anddifferential line blanketing. Except for Epsilon UMa, none of these fivestars show evidence of variations of the 4200 or 5200 A broad absorptionfeatures.
| Entwiclung., Erprobung Eines Sternfotometers MIT einstellbaren Spektralbereichen.
Not Available
| Photometry of six peculiar A-type stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975PASP...87..231W&db_key=AST
| Absolute luminosity calibration of Stroemgren's 'intermediate group'
A relation defining the luminosity index for Stroemgren's (1966)intermediate group (A0 to A3 stars) in terms of absolute magnitude iscalibrated using a method based on the principle of maximum likelihood.This relation is also calibrated for the case when the 'a' index iscorrected for reddening. For both relations, calculations are made ofthe magnitude dispersion, the mean velocity components and correspondingdispersion, and the precision of each parameter. The results are shownto be in fairly good agreement with Stroemgren's (1966) values, and arelation incorporating the corrected 'a' index is proposed formain-sequence stars. The absolute magnitudes obtained with a relation ofthe present type are compared with those derived from trigonometricparallaxes and with those obtained by Eggen (1972).
| Über die Veränderlichkeit der Sterne des Spektraltyps A
Not Available
| Four-color and Hβ photometry for the brighter AO type stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972A&AS....5..109C&db_key=AST
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| Takýmyýldýz: | Buyuk Ayi |
| Sað Açýklýk: | 13h50m27.70s |
| Yükselim: | +58°32'22.0" |
| Görünürdeki Parlaklýk: | 6.46 |
| Uzaklýk: | 82.508 parsek |
| özdevim Sað Açýklýk: | -20.5 |
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| B-T magnitude: | 6.558 |
| V-T magnitude: | 6.456 |
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