Das BAV-programm der Delta-Scuti-Veraenderlichen - teil 1.
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A list of minima and maxima timings
The list contains minima of eclipsing and maxima of pulsating stars, itcontinues the list published in OEJV 0073.
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Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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Pulkovo compilation of radial velocities for 35495 stars in a common system.
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Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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Beobachtungssergebnisse Bundesdeutsche Arbeitsgemeinschaft fuer Veraenderliche Sterne e.V.
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Photoelectric Maxima of Selected Pulsating Stars
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A search for period changes in delta Scuti stars with the super-LOTIS sky patrol system
We have observed a sample of delta Scuti stars discovered by the ROTSEcollaboration in 1999 with Super-LOTIS in order to characterize changesin their pulsation periods over a time baseline of roughly three years.Achieving these goals required the creation of an automated astrometricand photometric data reduction pipeline for the Super-LOTIS camera.Applying this pipeline to data from a June 2002 observing campaign, wedetect pulsations in 18 objects, and find that in two cases the periodshave changed significantly over the three years between the ROTSE andSuper-LOTIS observations. Since theory predicts that evolutionary periodchanges should be quite small, sources of non-evolutionary periodchanges due to the interactions of pulsations modes are discussed.
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A photometric monitoring of bright high-amplitude delta Scuti stars. I. The double-mode pulsation of V567 Ophiuchi
We present the first results of an observational project, whichaddresses the period changing behaviour of a sample of high-amplitudedelta Scuti stars. In this paper we discuss the double-mode nature ofV567 Ophiuchi. It was observed on 15 nights in two consecutive years inorder to resolve the long-standing ambiguity related to its secondaryperiod. A frequency analysis of almost 5000 individual single-filteredCCD V measurements resulted in two independent frequencies(f1=6.6879 d-1 and f2=11.8266d-1) with a ratio of f1/f2=0.565.Earlier data taken from the literature were used to refine the dominantperiod, and the re-analysis supports the existence of the secondaryperiod. Possible asteroseismological implications are briefly discussed.
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δ Scuti stars and their related objects
δ Scuti stars are a group of stars located on or a little abovethe main sequence of H-R diagram with spectral type from A3 to F5. Theyare low amplitude single or multi period pulsators with period shorterthan 0.3 d. Within the same area there are several groups of variablesor special stars correlated with them, e.g., Dwarf Cepheids, γ Dorvariables, Blue Stragglers, Am stars, Ap stars, ROAp variables, λBoo variables and δ Del variables. In this paper a general reviewin this field, including the number of new variables discovered after1995, is presented. The most reliable period variation rates for all thehigh amplitude variables and several low amplitude variables are listed.Statistic shows the higher the rotation rate v sin i is, the lower thelight variation amplitude is. Thus within young open clusters highamplitude variables cannot be found. The amplitudes-periods distributionhave 3 peaks with the highest of 1.0 mag in V at 0.17 d in period. Forδ Scuti variables in stellar systems the shorter the averageperiod is, the lower the metallicity and the older the age of thestellar system are.
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Zwei helle Algosterne fur den Sommer.
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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
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Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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Stars with the Largest Hipparcos Photometric Amplitudes
A list of the 2027 stars that have the largest photometric amplitudes inHipparcos Photometry shows that most variable stars are all Miras. Thepercentage of variable types change as a function of amplitude. Thiscompilation should also be of value to photometrists looking forrelatively unstudied, but large amplitude stars.
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Preliminary Baade-Wesselink Radii Solutions for Several Dwarf Cepheids
It has been shown (Laney 1995) that VJHK photometry when combined withradial velocities leads to improved Baade-Wesselink radii solutions forCepheids. Preliminary results indicate the same method can be applied todwarf Cepheids (also known as High-Amplitude Delta Scuti stars). Ourobservations obtained at the South African Astrophysical Observatoryinclude echelle spectroscopy with simultaneous visual and infraredphotometry. This procedure helps remove phase discrepancies andstrengthen the radius solution. Initial results for BS Aqr, AD CMi, RYLep, and EH Lib are presented. Special thanks to SAAO for the observingtime, support from the American Astronomical Society through a smallresearch grant, and continued funding from the Department of Physics andAstronomy at Brigham Young University.
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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
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Stability in the Light Curves of High-Amplitude delta Scuti Stars: Selected Monoperiodic Stars
We have analyzed all the reliable photometric data sets available in thebibliography for a selected sample of monoperiodic high-amplitude deltaScuti stars in order to study the stability of their light curves. Atotal of 169 data sets and more than 22,000 points have been consideredfor seven stars: ZZ Mic, EH Lib, BE Lyn, YZ Boo, SZ Lyn, AD CMi, and DYHer. The results do not reveal significant long-term changes ofamplitude of the light curves for any of these stars.
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Mode identification and asteroseismology of delta Scuti stars
The use of multicolour photometry for mode identification in pulsatingstars is discussed. We present a new, statistically based, algorithm forfinding the best estimate of the spherical harmonic degree, and aconfidence level from which the uniqueness can be ascertained. Themethod is applied to some well-observed delta Sct stars with multicolourphotometry. We also propose an algorithm to deduce the effectivetemperature, luminosity and equatorial velocity from the observedfrequencies. We find that fixing the modes of at least some frequenciesis essential for a unique solution. The method is applied to a subset ofthe delta Sct stars which have a suitable number of frequencies and modeidentifications.
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Mode and period changes in pulsating stars near the main sequence : delta Scuti stars.
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The delta Scuti Star GSC 2985-01044
GSC 2985-01044 is a delta Scuti star with a period of 0.0933584 days anda V-magnitude range of 11.85-12.05 its light curve is slightly variable.The location, space motion, and other properties of this star indicatethat it is a higher amplitude delta Scuti star (or ``dwarf Cepheid'')that is a member of the old disk population. The problem of determiningthe local space densities of the various populations of the higheramplitude delta Scuti stars is discussed.
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Studies of Large-Amplitude delta Scuti Variables. III. DY Pegasi
This is the third in a series of papers on large-amplitude delta Scutiand related stars intended to determine Baade-Wesselink radii andluminosities with precision. The first two papers discussed our methodof analysis and its application to the delta Scuti variables EH Libraeand DY Herculis; in the present paper we discuss the observations andanalysis of the SX Phoenicis variable DY Pegasi. Optical (BVI) andinfrared (JH) photometry and cross-correlated radial velocity data havebeen obtained and analyzed. Fourier representations for the BVIH lightcurves and for the radial velocity curve were used to derive a value forthe minimum radius for each of 22 combinations of flux and color index,from which we obtain a mean value for the minimum radius ofR_min=2.09+/-0.25 R_solar. When combined with effective temperaturesfrom Burki & Meylan, we find a mean bolometric luminosity of=11.34 L_solar and a mean absolute magnitude of=2.11. The radial excursion (R_max-R_min) is 0.073 R_solar.
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Period changes of delta Scuti stars and stellar evolution
Period changes of delta Scuti stars have been collected or redeterminedfrom the available observations and are compared with values computedfrom evolutionary models with and without convective core overshooting.For the radial pulsators of Pop. I, the observations indicate (1/P)dP/dt values around 10(-7) year(-1) with equal distribution betweenperiod increases and decreases. The evolutionary models, on the otherhand, predict that the vast majority should show increasing periods.This increase should be a factor of about ten times smaller thanobserved. For nonradial delta Scuti pulsators of Pop. I, thediscrepancies are even larger. The behavior suggests that for theserelatively unevolved stars the rate of evolution cannot be deduced fromthe period changes. The period changes of most Pop. II delta Scuti (SXPhe) stars are characterized by sudden jumps of the order of Delta P/P ~10(-6) . However, at least one star, BL Cam, shows a large, continuousperiod increase. The variety of observed behavior also seems to excludean evolutionary origin of the changes. Model calculations show that theevolutionary period changes of pre-MS delta Scuti stars are a factor of10 to 100 larger than those of MS stars. Detailed studies of selectedpre-MS delta Scuti stars are suggested.
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HIPPARCOS parallaxes and period-luminosity relations of high-amplitude delta Scuti stars
Hipparcos parallaxes of high-amplitude delta Scuti stars are used toderive a period-luminosity relation with a scatter of about +/-0.1 mag,which is independent from photometric calibrations to absoluteluminosities. Comparisons with several P-L relations from the literatureshow satisfactory agreement, and all deviations from the Hipparcos meanrelation can be explained by uncertainties in the data available beforeHipparcos. Hipparcos data for a few stars of relatively small anduncertain parallaxes indicate that they may have systematically very lowluminosity. However, briefly discussing Lutz-Kelker corrections andconsidering the full sample of high-amplitude delta Scuti stars, it isconcluded that this sample is homogeneous and has similar basic physicalproperties as the ``normal'' low-amplitude delta Scuti stars. It isemphasized that the Hipparcos P-L relation defines a new distance scalewhich is independent from those of the classical Cepheids and RR Lyraestars. Therefore, observations of high-amplitude delta Scuti stars canbe used to check fundamental distance determinations to e.g. globularclusters, the Galactic bulge and the Magellanic Clouds.
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HIPPARCOS Parallaxes and Distances of High-Amplitude δ Scuti Stars
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Analyses of Delta Scuti stars.
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Luminosities of SX Phoenicis, Large-Amplitude Delta Scuti, and RR Lyrae Stars
Strömgren _uvbyβ photometry of SX Phoenicis andlarge-amplitude δ Scuti variables is analyzed to determine themean temperatures, metal abundances, and surface gravities of the stars.The mean temperatures and fundamental periods are used in conjunctionwith the pulsation equation and stellar models to derive masses, radii,surface gravities, and M_bol of the variables. The stars exhibit aperiod-luminosity relation. With the aid of Hipparcos trigonometricparallaxes the zero-point of the M_v, p is set. We find M_v = -3.725 logP - 1.933. This P-L relation is utilized to find the M-v values of RRLyrae stars or horizontal-branch stars in globular clusters and theCarina galaxy-objects that contain both SX Phe, and RR Lyrae variables,or horizontal-branch stars. The M_v values of the metal-poor RR Lyraestars are found to be consistent with M_v [Fe/H] calibrations derived bySandage (1993) and by McNamara (1997) from revised Baade- Wesselink M_vvalues. At [Fe/H] = -1.9 M_v is 0.42. Feast and Catchpole (1997)suggestion that M_v = 0.25 at [Fe/H] = -1.9 for RR Lyrae is discussed.This M_v value is too luminous because it makes the (T_eff) of RR Lyraestoo high-well off any (T_eff) = _f (color index) calibration. (SECTION:Stars)
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Luminosity and related parameters of δ Scuti stars from HIPPARCOS parallaxes. General properties of luminosity.
The absolute magnitudes of δ Scuti stars derived from parallaxesmeasured by the Hipparcos astrometric satellite are discussed andcompared with the previous estimates based on photometric uvbyβindices. There are significant differences which are related tophotometric effects of metallicity and rotational velocity, but thepossible effect of a close companion on the measured apparent magnitudeshould be also taken into account. The possibility of differentgroupings of δ Scuti stars based on the absolute magnitudes isbriefly discussed. Some high amplitude δ Scuti stars withintermediate or normal metallicity and small and uncertain parallax haveapparently a very low luminosity; this could be a systematic effectrelated to the observational errors.
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Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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Spectroscopic survey of delta Scuti stars. I. Rotation velocities and effective temperatures
Projected rotational velocities and effective temperatures for 68 deltaSct stars as well as 41 non-variable stars of similar spectral type andluminosity are presented here. The rotational velocities have beencalculated following the method developed in \cite[Gray (1992)]{ref38}and effective temperatures have been derived using the Balmer lineprofiles. The temperatures obtained from this method are shown to be inreasonable agreement with those calculated using the Infrared FluxMethod (IRFM) or spectrophotometric methods. This result has allowed usto use our temperatures to compare different uvby beta photometriccalibrations. We find that the calibration given by \cite[Moon \&Dworetsky (1985)]{ref72} is the most consistent. In the second part ofthis paper we have studied the relation between the pulsationalproperties (periods and amplitudes) and the physical parameters (v sin iand Teff). Where pulsation modes have been determined, thelow amplitude $\delta$ Scutis tend to be multimode (radial andnon-radial) pulsators, consistent with the theory that non-linearcoupling between modes acts to limit the amplitude in these stars. Wehave compared the distribution of v sin i for low amplitude $\delta$Scutis and non-variable stars. This shows the $\delta$ Scutis have abroader distribution in v sin i suggesting that a high rotation velocitymay favour pulsation. We find that the large amplitude delta Scuti starstend to have longer periods, cooler temperatures and lower rotationvelocities. Given that the large amplitude stars are also relativelyrare all the above are consistent with the hypothesis that these starsare more evolved (sub-giants) than the low amplitude delta Scutis (mainsequence or early post-main sequence).
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Structural Properties of Pulsating Star Light Curves Through Fuzzy Divisive Hierarchical Clustering
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INHABITED SKY
