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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
| On the Period-Luminosity-Colour-Metallicity relation and the pulsational characteristics of lambda Bootis type stars
Generally, chemical peculiarity found for stars on the upper mainsequence excludes delta Scuti type pulsation (e.g. Ap and Am stars), butfor the group of lambda Bootis stars it is just the opposite. This makesthem very interesting for asteroseismological investigations. The groupof lambda Bootis type stars comprises late B- to early F-type,Population I objects which are basically metal weak, in particular theFe group elements, but with the clear exception of C, N, O and S. Thepresent work is a continuation of the studies by Paunzen et al.(\cite{Pau97}, \cite{Pau98}), who presented first results on thepulsational characteristics of the lambda Bootis stars. Since then, wehave observed 22 additional objects; we found eight new pulsators andconfirmed another one. Furthermore, new spectroscopic data (Paunzen\cite{Pau01}) allowed us to sort out misidentified candidates and to addtrue members to the group. From 67 members of this group, only two arenot photometrically investigated yet which makes our analysis highlyrepresentative. We have compared our results on the pulsationalbehaviour of the lambda Bootis stars with those of a sample of deltaScuti type objects. We find that at least 70% of all lambda Bootis typestars inside the classical instability strip pulsate, and they do sowith high overtone modes (Q < 0.020 d). Only a few stars, if any,pulsate in the fundamental mode. Our photometric results are inexcellent agreement with the spectroscopic work on high-degree nonradialpulsations by Bohlender et al. (\cite{Boh99}). Compared to the deltaScuti stars, the cool and hot borders of the instability strip of thelambda Bootis stars are shifted by about 25 mmag, towards smaller(b-y)_0. Using published abundances and the metallicity sensitiveindices of the Geneva 7-colour and Strömgren uvbybeta systems, wehave derived [Z] values which describe the surface abundance of theheavier elements for the group members. We find that thePeriod-Luminosity-Colour relation for the group of lambda Bootis starsis within the errors identical with that of the normal delta Scutistars. No clear evidence for a statistically significant metallicityterm was detected. Based on observations from the Austrian AutomaticPhotoelectric Telescope (Fairborn Observatory), SAAO and Siding SpringObservatory.
| Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
| Observing roAp Stars with WET: A Primer
We give an extensive primer on roAp stars -- introducing them, puttingthem in context and explaining terminology and jargon, and giving athorough discussion of what is known and not known about them. Thisprovides a good understanding of the kind of science WET could extractfrom these stars. We also discuss the many potential pitfalls andproblems in high-precision photometry. Finally, we suggest a WETcampaign for the roAp star HR 1217.
| A revised catalogue of delta Sct stars
An extensive and up-dated list of delta Sct stars is presented here.More than 500 papers, published during the last few years, have beenrevised and 341 new variables have been added to our last list, sixyears ago. This catalogue is intended to be a comprehensive review onthe observational characteristics of all the delta Sct stars known untilnow, including stars contained in earlier catalogues together with othernew discovered variables, covering information published until January2000. In summary, 636 variables, 1149 references and 182 individualnotes are presented in this new list. Tables 1 and 2 will be accessibleonly in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| UVBY photometry of the magnetic CP stars HD 36668, 36 Lyncis, HD 86592, and HR 8861
Differential Strömgren uvby photometric observations from the FourCollege Automated Photoelectric Telescope (FCAPT) are presented for themagnetic CP stars HD 36668, 36 Lyn, HD 86592, and HR 8861. Using theFCAPT values, North's period for HD 36668 is refined to 2.11884 days.The 3.834 day period of Shore et al. for 36 Lyn, which was found frommagnetic field measurements, is confirmed by photometry. The FCAPTobservations also support the 2.8867 day period of Babel & North forHD 86592, demonstrate that this star is a large amplitude variable in v(0.13 mag.), and show that y varies crudely out of phase from u, v, andb which are in phase with one another. The variability of HR 8861appears to be correlated with the meridional passages of regions of Siover- and underabundance as found by Piskunov et al. Tables~2, 3, 4 and5 are only available in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| ET And, HD 219891, or HD 219668 - which one shows short-term variability?
The result of recent photometric observations of the CP star ET And,published by Weiss et al. (1998), shows that the known brightnessvariation of about 145 min has to be obviously assigned to thecomparison star HD 219891. In order to test this statement weinvestigate the Hipparcos photometry of ET And, HD 219891 and the checkstar, HD 219668, on the existence of pulsations. The significance ofpeaks found in the periodograms is estimated using empiricallydetermined false alarm probability distributions derived from a largenumber of synthetic data sets. Results show that the probability oflarge peaks produced in the periodograms by only noise cannot bedescribed by the well-known statistics valid for an evenly spaced timesampling. In the photometry of ET And we find a period of 0\fd103966with a false alarm probability of 6% or less. For the two comparisonstars we could not detect any signal in the data.
| Determination of the temperatures of selected ISO flux calibration stars using the Infrared Flux Method
Effective temperatures for 420 stars with spectral types between A0 andK3, and luminosity classes between II and V, selected for a fluxcalibration of the Infrared Space Observatory, ISO, have been determinedusing the Infrared Flux Method (IRFM). The determinations are based onnarrow and wide band photometric data obtained for this purpose, andtake into account previously published narrow-band measures oftemperature. Regression coefficients are given for relations between thedetermined temperatures and the photometric parameters (B2-V1), (b-y)and (B-V), corrected for interstellar extinction through use ofHipparcos parallaxes. A correction for the effect of metallicity on thedetermination of integrated flux is proposed. The importance of aknowledge of metallicity in the representation of derived temperaturesfor Class V, IV and III stars by empirical functions is discussed andformulae given. An estimate is given for the probable error of eachtemperature determination. Based on data from the ESA HipparcosAstrometry Satellite.
| Are metallic A-F giants evolved AM stars? Rotation and rate of binaries among giant F stars
We test the hypothesis of Berthet (1992) {be91} which foresees that Amstars become giant metallic A and F stars (defined by an enhanced valueof the blanketing parameter Delta m_2 of the Geneva photometry) whenthey evolve. If this hypothesis is right, Am and metallic A-FIII starsneed to have the same rate of binaries and a similar distribution ofvsin i. From our new spectroscopic data and from vsin i and radialvelocities in the literature, we show that it is not the case. Themetallic giant stars are often fast rotators with vsin i larger than 100kms(-1) , while the maximum rotational velocity for Am stars is about100 kms(-1) . The rate of tight binaries with periods less than 1000days is less than 30% among metallic giants, which is incompatible withthe value of 75% for Am stars - [Abt & Levy 1985] {ab85}).Therefore, the simplest way to explain the existence of giant metallic Fstars is to suggest that all normal A and early F stars might go througha short ``metallic" phase when they are finishing their life on the mainsequence. Besides, it is shown that only giant stars with spectral typecomprised between F0 and F6 may have a really enhanced Delta m_2 value,while all A-type giants seem to be normal. Based on observationscollected at Observatoire de Haute Provence (OHP), France.
| Photometry of ET Andromedae and pulsation of HD 219891
ET And is a binary system with a B9p(Si) star as the main component. Wereport on the photometric observing campaigns in 1988, 1989 and 1994which confirmed the rotation period of 1.618875 deg for ET And whilerefuting other published values. Furthermore, the controversial issue ofpulsational stability of ET And is resolved since we have discoveredpulsation for HD 219891, which was the main comparison star andsometimes exclusively used. The frequency of 10.0816 d(-1) , asemi-amplitude of 2.5 mmag, T_eff\ and M_v suggest this comparison starto be a delta Scuti variable close to the blue border of the instabilitystrip. The pulsational stability of ET And could be clearly establishedand hence no need exists to derive new driving mechanisms for starsbetween the classical instability strip and the region of slowlypulsating B-type (SPB) stars. Based on observations obtained at theBulgarian National Observatory, Crimean Astrophysical Observatory(Ukraine), Lowell Observatory (USA), Mauna Kea (USA), Mt. Dushak-Erekdak(Turkmenistan), San Pedro (Mexico), Skalnate Pleso (Slovakia), Tien Shan(Kazakhstan) and Wise Observatory (Israel)
| Spectroscopic and photometric investigations of MAIA candidate stars
Including our own observational material and the Hipparcos photometrydata, we investigate the radial velocity and brightness of suspectedMaia variable stars which are classified also in some examples aspeculiar stars, mainly for the existence of periodic variations withtime-scales of hours. The results lead to the following conclusions: (1)Short-term radial velocity variations have been unambiguously proved forthe A0 V star gamma CrB and the A2 III star gamma UMi. The stars pulsatein an irregular manner. Moreover, gamma CrB shows a multiperiodstructure quite similar to some of the best-studied neighbouring deltaScu stars. (2) In the Hipparcos photometry as well as in our photometricruns we find significant short- and long-term variations in the stars HD8441, 2 Lyn, theta Vir, gamma UMi, and gamma CrB. For ET And theHipparcos data confirm a short-period variation found already earlier.Furthermore, we find changes of the colour index in theta Vir and gammaCrB on a time-scale of days. (3) No proofs for the existence of aseparate class of variables, designated as Maia variables, are found. Ifthe irregular behaviour of our two best-investigated stars gamma CrB andgamma UMi is typical for pulsations in this region of theHertzsprung-Russell diagram, our observational runs are too short andthe accuracy of the measurements too low to exclude such pulsations inthe other stars, however. (4) The radial velocities of the binariesalpha Dra and ET And have been further used for a recalculation of theorbital elements. For HD 8441 and 2 Lyn we estimated the orbitalelements for the first time. (5) Zeeman observations of the stars gammaGem, theta Vir, alpha Dra, 4 Lac, and ET And give no evidence of thepresence of longitudinal magnetic field strengths larger than about 150gauss. Based on spectroscopic observations taken with the 2\,m telescopeat the Th{ü
| Hot Inner Disks that Appear and Disappear around Rapidly Rotating A-Type Dwarfs
At any one time, approximately one-quarter of the most rapidly rotatingnormal A-type dwarfs (V sin i >= 200 km s-1) show shell lines of TiII in the near-ultraviolet. Our observations during 22 years show thatthe lines appear and disappear on timescales of decades but do notdisplay significant changes within 1 year. This implies that they arenot remnants of the star formation but rather are probably caused bysporadic mass-loss events. A working hypothesis is that all A-type starsthat are rotating near their limits have these shells, but for onlyone-quarter of the time. Because these lines do not appear in stars withsmaller sin i, the shells must be disks. These are hot inner disks thatmay or may not be related to the cool outer disks seen by Smith andTerrile around beta Pic or through infrared excesses around Vega andother A-type dwarfs. The similar, limited line widths indicate that thedisks are ~7 R* above the stellar surfaces.
| 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.
| Mesures de vitesses radiales. VII. Accompagnement AU sol DU programme d'observation DU satellite Hipparcos. Radial velocities. VII. Ground based measurements for Hipparcos.
We publish 734 radial velocities of stars distributed in 28 fields of4x4deg. We continue the PPO series (Fehrenbach et al. 1987; Duflot etal. 1990 and 1992), using the Fehrenbach objective prism method.
| 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.
| Stellar spectrophotometric standards. II
Not Available
| 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.
| Two B and V time series of ET And
Two time series of B and V observations of the multiple-periodicvariable CP2 star ET And are presented. From both records observed intwo consecutive nights, a new period of 180 min is detected.
| Metallicism among A and F giant stars
132 stars considered as A and F giants have been studied for theirproperties in the Geneva photometric system. It is shown that thissystem to derive the temperature, absolute magnitude and Fe/H value forstars in this part of the HR diagram. 36 percent of the stars of oursample exhibit an enhanced value Delta m2 that can be interpreted interms of Fe/H. The red limit of stars having an enhanced Fe/H value is0.225 in B2-V1 or 6500 K in Teff. This corresponds to the limit definedby Vauclair and Vauclair (1982) where the diffusion timescale is equalto the stellar lifetime and permits the assumption that the diffusion isthe process responsible for the metallicism observed in the A and Fgiants.
| The Widening of the Dynamic Range of the Data-Measuring System of Five-Channel Spectrophotometer
Not Available
| The Light Variations of the Ap-Star HR8861
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1980A&AS...39..127B&db_key=AST
| On the Period of the Ap Variable HR 8861
Not Available
| Lichtelektrische Beobachtungen von 14 Ap-Sterne.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1978A&AS...31...83R&db_key=AST
| Photoelectric H-alpha line photometry of early-type stars
A total of 293 bright stars of spectral types O, B, A, F and ofluminosity classes I through V have been measured with a photoelectricphotometer equipped with two interference filters of 30-A bandwidth, onecentered on H-alpha and the other at 6622 A. A correction term has beenallowed for the response of the photometric system and for the continuumenergy distribution in the two spectral regions considered. Theresulting photometric alpha indices of H-alpha line strength arecompared with previous H-alpha, H-beta, and H-gamma photometricmeasures, H-alpha equivalent widths, the MK spectral type, /u-b/, /c1/,and b-y indices of the uvby photometric system. The results emphasizethe advantage of using H-alpha line photometry to discriminate betweenemission-line effects and luminosity effects in early-type stars and todetect emission-line variability.
| Investigations of the light variation of twelve AP stars in ten spectral regions
Twelve Ap stars of known period and large amplitude were photometricallyinvestigated with the seven-color system based on glass filtersaccording to Straizys (1971) supplemented by three Schott filtercombinations in the red (total range 3400 to 7600 A). The light curvesfor each spectral range are presented, and some conclusions regardingthe importance of the data for possible model representations of theatmospheres of magnetic stars are set forth.
| Rotation and shell spectra among A-type dwarfs.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1973ApJ...182..809A&db_key=AST
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| Takýmyýldýz: | Zincirli Prenses |
| Sað Açýklýk: | 23h19m02.40s |
| Yükselim: | +45°08'14.0" |
| Görünürdeki Parlaklýk: | 6.5 |
| Uzaklýk: | 125.628 parsek |
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| B-T magnitude: | 6.709 |
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