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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
| Rotational velocities of A-type stars. I. Measurement of v sin i in the southern hemisphere
Within the scope of a Key Programme determining fundamental parametersof stars observed by HIPPARCOS, spectra of 525 B8 to F2-type starsbrighter than V=8 have been collected at ESO. Fourier transforms ofseveral line profiles in the range 4200-4500 Å are used to derivev sin i from the frequency of the first zero. Statistical analysis ofthe sample indicates that measurement error is a function of v sin i andthis relative error of the rotational velocity is found to be about 6%on average. The results obtained are compared with data from theliterature. There is a systematic shift from standard values from\citet{Slk_75}, which are 10 to 12% lower than our findings. Comparisonswith other independent v sin i values tend to prove that those fromSlettebak et al. are underestimated. This effect is attributed to thepresence of binaries in the standard sample of Slettebak et al., and tothe model atmosphere they used. Based on observations made at theEuropean Southern Observatory (ESO), La Silla, Chile, in the frameworkof the Key Programme 5-004-43K. Table 4 is only available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.125.5)or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/381/105
| delta Scuti and related stars: Analysis of the R00 Catalogue
We present a comprehensive analysis of the properties of the pulsatingdelta Scuti and related variables based mainly on the content of therecently published catalogue by Rodríguez et al.(\cite{retal00a}, hereafter R00). In particular, the primaryobservational properties such as visual amplitude, period and visualmagnitude and the contributions from the Hipparcos, OGLE and MACHOlong-term monitoring projects are examined. The membership of thesevariables in open clusters and multiple systems is also analyzed, withspecial attention given to the delta Scuti pulsators situated ineclipsing binary systems. The location of the delta Scuti variables inthe H-R diagram is discussed on the basis of HIPPARCOS parallaxes anduvbybeta photometry. New borders of the classical instability arepresented. In particular, the properties of the delta Scuti pulsatorswith nonsolar surface abundances (SX Phe, lambda Boo, rho Pup, delta Deland classical Am stars subgroups) are examined. The Hipparcos parallaxesshow that the available photometric uvbybeta absolute magnitudecalibrations by Crawford can be applied correctly to delta Scutivariables rotating faster than v sin i ~ 100 km s{-1} withnormal spectra. It is shown that systematic deviations exist for thephotometrically determined absolute magnitudes, which correlate with vsin i and delta m1. The photometric calibrations are found tofit the lambda Boo stars, but should not be used for the group ofevolved metallic-line A stars. The related gamma Dor variables and thepre-main-sequence delta Scuti variables are also discussed. Finally, thevariables catalogued with periods longer than 0fd 25 are examined on astar-by-star basis in order to assign them to the proper delta Scuti, RRLyrae or gamma Dor class. A search for massive, long-period delta Scutistars similar to the triple-mode variable AC And is also carried out.
| On the Variability of A3-F0 Luminosity Class III-V Stars
I investigate the Hipparcos Satellite photometry of A3-F0 stars ofluminosity classes III-V to learn about their variability and identify afew stars for which further study is desirable.
| 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
| Radial velocities of HIPPARCOS southern B8-F2 type stars
Radial velocities have been determined for a sample of B8-F2 type starsobserved by the Hipparcos satellite. Observations were obtained withinthe framework of an ESO key-program. Radial velocities have beenmeasured using a cross-correlation method, the templates being a grid ofsynthetic spectra. The obtained precision depends on effectivetemperature and projected rotational velocity of the star as well as ona possible asymmetry of the correlation peak generally due to secondarycomponents. New spectroscopic binaries have been detected from theseasymmetries and the variability of the measured radial velocity.Simulations of binary and triple systems have been performed. Forbinaries our results have been compared with Hipparcos binary data.Adding the variable radial velocities, the minimum binary fraction hasbeen found 60% for physical systems. Radial velocities have beendetermined for 581 B8-F2 stars, 159 being new. Taking into accountpublished radial velocities, 39% south A-type stars with V magnitudelower than 7.5 have a radial velocity. Based on observations obtained atthe European Southern Observatory (ESO, La Silla, Chile) and on datafrom the ESA Hipparcos astrometry satellite.}\fnmsep \thanks{Tables 7, 8and 9 are only available in electronic form at the CDS via anonymous ftpto cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| An extensive Delta a-photometric survey of southern B and A type bright stars
Photoelectric photometry of 803 southern BS objects in the Deltaa-system as detection tool for magnetic chemically peculiar (=CP2) starshas been carried out and compared to published spectral types. Thestatistical yield of such objects detected by both techniques ispractically the same. We show that there are several factors whichcontaminate the search for these stars, but this contamination is onlyof the order of 10% in both techniques. We find a smooth transition fromnormal to peculiar stars. Our sample exhibits the largest fraction ofCP2 stars at their bluest colour interval, i.e. 10% of all stars in thecolour range -0.19 <= B-V < -0.10 or -0.10 <= b-y < -0.05.No peculiar stars based on the Delta a-criterion were found at bluercolours. Towards the red side the fraction of CP2 stars drops to about3% for positive values of B-V or b-y with red limits roughlycorresponding to normal stars of spectral type A5. The photometricbehaviour of other peculiar stars: Am, HgMn, delta Del, lambda Boo, Heabnormal stars, as well as Be/shell stars and supergiants shows someslight, but definite deviations from normal stars. Spectroscopic andvisual binaries are not distinguished from normal stars in their Delta abehaviour. The results of this work justify larger statistical work(e.g. in open clusters) employing more time-saving photometric methods(CCD). \newpage Based on observations obtained at the European SouthernObservatory, La Silla, Chile. This research has made use of the Simbaddatabase, operated at CDS, Strasbourg, France. Table 2 is only availablein electronic form via anonymous ftp 130.79.128.5 orhttp://cdsweb.u-strasbg.fr/Abstract.html
| Amplitude variations of the multimode nonradial δ Scuti pulsator 4 CVn
New photoelectric photometry of the δ Scuti variable 4 CVn revealslong-term slow variations of multimode pulsational frequencies and theiramplitudes. We have confirmed 5(f1, f2,f3, f5, f7) of the 7 frequenciesidentified in the literature. Besides presenting the long-termvariations of the different amplitudes, we have found three newsuspected frequencies in the new data. Although Blazhko effect and moderesonance along with its coupling between different nonradial modesthrough interaction can be reasonably used to explain the observedchanges of periods and amplitudes, it should be carefully checked andanalyzed before RR Lyr-like light curve shape and new pulsation modescan be established with certainty.
| Amplitude variations of the multimode nonradial delta Scuti pulsator 4 CVn.
Not Available
| CCD photometry of a δ Scuti variable in an open cluster: V650 Tau in the Pleiades.
Time resolved CCD differential photometry was carried out for theδ Scuti variable V650 Tau on fourteen nights between November andDecember, 1993(total 3707 points of differential B magnitudes duringabout 81 hours observation). By applying the Fourier analysis to theobserved data, we have detected five frequencies(f_1_=377.7μHz,f_2_=197.3μHz, f_3_=292.8μHz, f_4_=333.0μHz, f_5_=214.1μHz).Among these, the amplitudes of two frequencies, f_1_ and f_2_, show somedifferences from the preliminary results of STEPHI network(Michel et al.1995). The comparison of observed frequency ratios and pulsationconstants with theoretical ones suggests that V650 Tau may pulsatesimultaneously in two dominant radial(F, 3H) and three nonradial modes.
| A Photometric Study of the delta Scuti Star FG Virginis Undertaken during 1985/6
93 hours of photoelectric photometry of FG Virginis were obtained during1985 and 1986. Seven frequencies of pulsation with significantdetections could be extracted from the photometry. The seven detectedfrequencies agree with those found in a larger, independent photometricstudy by Breger et al. carried out during 1993, in which ten frequencieswere found. The present data also show the 8th and 9th frequencies foundduring 1993, but below the signal-to-noise limit of significance adoptedin our studies. The y amplitudes determined from the present work andthe 1993 data agree to +- 1.0 millimag, suggesting that no significantamplitude variations occurred during the eight years. For the dominantfrequency of 12.72 c/d a phase shift of theta-b-y - theta-y = 7 degreesis found, compatible with a nonradial p mode of 1=1 and 2. (SECTION:Stars)
| 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
| Ca II H and K Filter Photometry on the UVBY System. II. The Catalog of Observations
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1995AJ....109.2828T&db_key=AST
| Stability of frequency content in light curves of 44 Tauri
A CCD time series photometry was performed for 44 Tau, a multiperiodicdelta Scuti star. The light curves were obtained over 19 nights from1992 October to 1993 February. From the analysis of the data by means ofFourier transform and nonlinear least-squares fitting, the sevenfrequencies identified by Poretti et al. (1992) were derived. Theanalysis of the new data confirmed the existence of two very closefrequencies, 6.90 and 7.01 c/d; it was also found that the frequencycomponent of 9.56 c/d which was the seventh strongest one three yearsago, was strengthened to the third during the period of ourobservations. On the other hand, the frequency of 9.12 c/d which was thethird strongest component three years ago, appeared as the weakest onein our observations.
| A catalogue of variable stars in the lower instability strip.
Identifications, positions, photometry, spectra, some pulsationalfeatures, other astrophysical parameters and literature for 302pulsating variable stars in the lower instability strip, near the ZAMS,are given. About 185 stars have near homogeneous photometric informationin the Stroemgren's uvby-β photometric system. Thiscatalogue/database covers information published until November 1993.
| δ Scuti stars: a new revised list
An extensive and up to date list of δ Sct stars is presented. Thiscatalogue is intended to be a comprehensive review of observationalcharacteristics of all the δ Sct stars known until now, includingstars contained in earlier catalogues together with other new discoveredvariables, covering information published until November 1993. Globalinformation in the form of histograms and diagrams are also shown.
| Multi-period pulsation of the delta Scuti star 63 Herculis
Multisite photoelectric B and V photometry of the delta Scuti star 63Her was obtained on three continents. Three frequencies of pulsation(f1 = 11.32, f2 = 20.07 and f3 = 7.72c/d) were detected with a signal/noise amplitude ratio greater than or =4.0. The three frequencies fit all the available data ranging back to1968. Reports in the literature of discepant behavior of the 1968measurements were probably caused by overinterpretation. The newfrequency values are in excellant agreement with the results found byReed & Welch from their 1983 data, except for a 1 c/d alias in theirvalue for f2. Two additional pulsation frequencies in thelow-frequency g-mode domain with amplitudes near two millimag reportedby the STEPHI group are not seen in the new campaign data. The new datashow average noise levels just below one millimag in this frequencydomain, so that the existence of these two frequencies cannot bedisproved from the new data alone. However, a reanalysis of the STEPHIdata also suggests that these frequencies might not be real. The resultsfrom the two multisite campaigns should be free of 1 c/d aliasing, sothat a resonance hypothesis involving f2 = f1 +f3 can be rejected. The value of the pulsation constantassociated with f3, Q = 0.046 +/- 0.008 d, is too high by 2standard deviations to be explained by radial pulsation. The Q value isincompatible with those of nonradial p1 to p4modes commonly found in delta Scuti stars.
| Long-term amplitude and period variations of delta Scuti stars: A sign of chaos?
On short time-scales of under a year, the vast majority of delta Scutistars studied in detail show completely regular multiperiodic pulsation.Nonradial pulsation is characterized by the excitation of a large numberof modes with small amplitudes. Reports of short-term irregularity ornon-periodicity in the literature need to be examined carefully, sinceinsufficient observational data can lead to an incorrect impression ofirregularity. Some interesting cases of reported irregularities areexamined. A few delta Scuti stars, such as 21 Mon, have shown stablevariations with sudden mode switching to a new frequency spectrum. Thissituation might be an indication of deterministic chaos. However, theobservational evidence for mode switching is still weak. One the otherhand, the case for the existence of long-term amplitude and periodchanges is becoming quite convincing. Recently found examples ofnonradial pulsators with long-term changes are 4 CVn, 44 Tau, tau Pegand HD 2724. Neither the amplitude nor the period changes are periodic,although irregular cycles with time scales between a few and twentyyears can be seen. While the amplitude changes can be very large, theperiod changes are quite small. The nonperiodic long-term changes areinterpreted in terms of resonances between different nonradial modes. Itis shown that a large number of the nonradial acoustic modes can be inresonance with other modes once the mode interaction terms, differentradial orders and rotational m-mode splitting are considered. Theseresonances are illustrated numerically by the use of pulsation model.Observational evidence is presented that these interaction modes existin the low-frequency domain.
| Simultaneous UVBY Photometry of 28-ANDROMEDAE
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&A...273..473R&db_key=AST
| Study of Delta Scuti stars in the Geneva photometric system. II - The complex case of HD 2724 (= HR 119)
The results of the frequency analyses for the complex case of HD 2724are presented. Although based on a large and accurate data set coveringmore than one year, we were unable to derive a common frequency solutionfor the data of different years. Two frequencies can be unambiguouslyidentified in the proposed multiperiodic solution, with sufficient proofof their reliability. The possible modal content of HD 2724 is discussedin view of its physical parameters derived in the Geneva PhotometricSystem. HD 2724 is a plausible candidate for amplitude modulation inmultimode Delta Scuti stars.
| Amplitude variations of the Delta Scuti variable HR 2724
Multisite photometric measurements of the Delta Scuti variable HR 2724during 19 nights at SAAO and 6 nights at ESO in January 1990 show thatsince 1981 the amplitude of variability has decreased by a factor ofthree. Only the frequency of 5.80 cycles/d is common in both 1981 and1990. The frequency of 4.0 cycles/d is dominant in the new data fromboth observatories. A comparison of the behavior of HR 2724 with that ofother luminous nonradially pulsating delta Scuti stars is consistentwith the hypothesis that a number of p modes are excited with slowlyvariable amplitudes. With limited amounts of data this may lead to theimpression of frequency changes.
| Amplitude variations of the multimode nonradial pulsator 4 Canum Venaticorum
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990A&A...240..308B&db_key=AST
| The 67th Name-List of Variable Stars
Not Available
| Information on the Photoelectric Observations of Variable Stars Deposited at Odessa Astronomical Observatory
Not Available
| HR 2724 - A new bright variable in the Delta Scuti instability strip
HR 2724 is found to be a new Delta Scuti star of low amplitude by uvbyphotometry, with periods of 0.222 and 0.148 days and a possible thirdperiod of 0.191 days. Several possible mode identifications arediscussed in light of derived period ratios. Pulsation constants of0.034 and 0.026 for the second and third periods are in agreement withtheories of radial stellar pulsation, and suggest that the third periodconstant corresponds to the fundamental, and the second period constantto the first harmonic mode. It is shown by four spectrograms that radialvelocity is only slightly variable, while chemical composition isnormal. On the basis of spectral type and mean photometric data, HR 2724is seen as close to the high temperature and high luminosity boundary ofthe Delta Scuti instability strip.
| A search for Beta Canis Majoris stars
The results of a search for southern Beta CMa stars are presented.Photoelectric photometry of thirty-one candidates shows that eight ofthese are previously unrecognized probable or certain Beta CMavariables. Four of these stars are members of the galactic cluster NGC3293. One Delta Sct variable and one eclipsing binary were discovered. Afew other stars are probably ellipsoidal variables.
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| קבוצת-כוכבים: | כלב גדול |
| התרוממות ימנית: | 07h12m24.10s |
| סירוב: | -27°28'27.0" |
| גודל גלוי: | 6.59 |
| מרחק: | 251.889 פארסק |
| תנועה נכונה: | -12.4 |
| תנועה נכונה: | -8 |
| B-T magnitude: | 6.807 |
| V-T magnitude: | 6.613 |
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