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Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| δ Scuti-type nature of the high-amplitude variable star GSC4619-450
We present the results of spectroscopy and B, V CCD photometry carriedout from 2003 to 2005 of GSC4619-450, a high-amplitude pulsatingvariable discovered by Zhang et al., [Zhang, X.B., Deng, L., Zhou, X.,Xin, Y., 2004. MNRAS, 355, 1369]. From this study, the star isclassified as a high-amplitude δ Scuti star. A Fourier analysisbased on the B and V photometric data indicates that GSC 4619-450 is amono-periodic radial pulsator, with a period of 0.13341195 days. From ashort time line we find that the pulsating period of this star isincreasing rapidly with a rate of 9.1 × 10‑2s/yr, and is thus suggested to be highly evolved and undergoing rapidevolving at the present time. A spectral type of F0 is assigned to thevariable considering the results from both the spectroscopy andphotometry.
| Times of Maxima for Selected Delta Scuti 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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| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| SZ Lyn: New pulsational and orbital elements based on old and recent photometric observations
SZ Lyncis (=HD 67390) is a high amplitude Delta Scuti star, discoveredby Hoffmeister in 1949. Van Genderen (1967) noticed that the residualsin the O-C diagrams followed a sinusoidal variation with a period ofPorb = 3.091 years. Several years later, Barnes & Moffett (1975)improved this period to Porb = 3.138 years and suggested that thesinusoidal variations in the O-C diagrams, observed by van Genderen(1967), originate from the light travel time effect, since SZ Lyn is amember of a binary system. This hypothesis was confirmed by Bardin &Imbert (1984) with measurements of radial velocities. Soliman et al.(1986) found the pulsation period to be 0.120534896 days and the orbitalperiod 1173.5 days.
| SZ Lyn: New BVRI CCD observations and improved pulsational and orbital elements
New BVRI CCD observations of the pulsating star SZ Lyn are presented.The light curves are analyzed using Fourier transform techniques and anew period is determined. A new ephemeris, based on recent times ofmaxima, is proposed. The photometric data collected over the last 40years are used to determine the pulsational and orbital elements, sinceSZ Lyncis is a member of a binary system. The results are compared withthose found in previous studies.
| Photoelectric Maxima of Selected Pulsating Stars
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| A photometric monitoring of bright high-amplitude delta Scuti stars. II. Period updates for seven stars
We present new photometric data for seven high-amplitude delta Scutistars. The observations were acquired between 1996 and 2002, mostly inthe Johnson photometric system. For one star (GW UMa), our observationsare the first since the discovery of its pulsational nature from theHipparcos data. The primary goal of this project was to update ourknowledge on the period variations of the target stars. For this, wehave collected all available photometric observations from theliterature and constructed decades-long O-C diagrams of the stars. Thistraditional method is useful because of the single-periodic nature ofthe light variations. Text-book examples of slow period evolution (XXCyg, DY Her, DY Peg) and cyclic period changes due to light-time effect(LITE) in a binary system (SZ Lyn) are updated with the newobservations. For YZ Boo, we find a period decrease instead of increase.The previously suggested LITE-solution of BE Lyn (Kiss &Szatmáry \cite{Kiss95}) is not supported with the new O-Cdiagram. Instead of that, we suspect the presence of transient lightcurve shape variations mimicking small period changes.
| 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.
| 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
| 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.
| 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.
| Coordinates and Identifications for Sonneberg Variables on MVS 308-316
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| Kinematics of Metal-poor Stars in the Galaxy. II. Proper Motions for a Large Nonkinematically Selected Sample
We present a revised catalog of 2106 Galactic stars, selected withoutkinematic bias and with available radial velocities, distance estimates,and metal abundances in the range -4.0<=[Fe/H]<=0.0. This updateof the 1995 Beers & Sommer-Larsen catalog includes newly derivedhomogeneous photometric distance estimates, revised radial velocitiesfor a number of stars with recently obtained high-resolution spectra,and refined metallicities for stars originally identified in the HKobjective-prism survey (which account for nearly half of the catalog)based on a recent recalibration. A subset of 1258 stars in this cataloghave available proper motions based on measurements obtained with theHipparcos astrometry satellite or taken from the updated AstrographicCatalogue (second epoch positions from either the Hubble Space TelescopeGuide Star Catalog or the Tycho Catalogue), the Yale/San Juan SouthernProper Motion Catalog 2.0, and the Lick Northern Proper Motion Catalog.Our present catalog includes 388 RR Lyrae variables (182 of which arenewly added), 38 variables of other types, and 1680 nonvariables, withdistances in the range 0.1 to 40 kpc.
| Kinematics of Metal-poor Stars in the Galaxy. III. Formation of the Stellar Halo and Thick Disk as Revealed from a Large Sample of Nonkinematically Selected Stars
We present a detailed analysis of the space motions of 1203solar-neighborhood stars with metal abundances [Fe/H]<=-0.6, on thebasis of a catalog, of metal-poor stars selected without kinematic biasrecently revised and supplemented by Beers et al. This sample, havingavailable proper motions, radial velocities, and distance estimates forstars with a wide range of metal abundances, is by far the largest suchcatalog to be assembled to date. We show that the stars in our samplewith [Fe/H]<=-2.2, which likely represent a ``pure'' halo component,are characterized by a radially elongated velocity ellipsoid(σU,σV,σW)=(141+/-11,106+/-9, 94+/-8) km s-1 and small prograde rotation=30 to 50 km s-1, consistent withprevious analysis of this sample by Beers and Sommer-Larsen based onradial velocity information alone. In contrast to the previous analysis,we find a decrease in with increasingdistance from the Galactic plane for stars that are likely to be membersof the halo population(Δ/Δ|Z|=-52+/-6 km s-1kpc-1), which may represent the signature of a dissipativelyformed flattened inner halo. Unlike essentially all previouskinematically selected catalogs, the metal-poor stars in our sampleexhibit a diverse distribution of orbital eccentricities, e, with noapparent correlation between [Fe/H] and e. This demonstrates, clearlyand convincingly, that the evidence offered in 1962 by Eggen,Lynden-Bell, & Sandage for a rapid collapse of the Galaxy, anapparent correlation between the orbital eccentricity of halo stars withmetallicity, is basically the result of their proper-motion selectionbias. However, even in our nonkinematically selected sample, we haveidentified a small concentration of high-e stars at [Fe/H]~-1.7, whichmay originate, in part, from infalling gas during the early formation ofthe Galaxy. We find no evidence for an additional thick disk componentfor stellar abundances [Fe/H]<=-2.2. The kinematics of theintermediate-abundance stars close to the Galactic plane are, in part,affected by the presence of a rapidly rotating thick disk component with ~=200 km s-1 (with a verticalvelocity gradient on the order ofΔ/Δ|Z|=-30+/-3 km s-1kpc-1) and velocity ellipsoid (σU,σV, σW)=(46+/-4, 50+/-4, 35+/-3) kms-1. The fraction of low-metallicity stars in the solarneighborhood that are members of the thick disk population is estimatedas ~10% for -2.2<[Fe/H]<=-1.7 and ~30% for -1.7<[Fe/H]<=-1.We obtain an estimate of the radial scale length of the metal-weak thickdisk of 4.5+/-0.6 kpc. We also analyze the global kinematics of thestars constituting the halo component of the Galaxy. The outer part ofthe halo, which we take to be represented by local stars on orbitsreaching more than 5 kpc from the Galactic plane, exhibits no systematicrotation. In particular, we show that previous suggestions of thepresence of a ``counter-rotating high halo'' are not supported by ouranalysis. The density distribution of the outer halo is nearly sphericaland exhibits a power-law profile that is accurately described asρ~R-3.55+/-0.13. The inner part of the halo ischaracterized by a prograde rotation and a highly flattened densitydistribution. We find no distinct boundary between the inner and outerhalo. We confirm the clumping in angular-momentum phase space of a smallnumber of local metal-poor stars noted in 1999 by Helmi et al. We alsoidentify an additional elongated feature in angular-momentum phase spaceextending from the clump to regions with high azimuthal rotation. Thenumber of members in the detected clump is not significantly increasedfrom that reported by Helmi et al., even though the total number of thesample stars we consider is almost triple that of the previousinvestigation. We conclude that the fraction of halo stars that may havearisen from the precursor object of this clump may be smaller than 10%of the present Galactic halo, as previously suggested. The implicationsof our results for the formation of the Galaxy are discussed, inparticular in the context of the currently favored cold dark mattertheory of hierarchical galaxy formation.
| 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
| 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.
| A review of the O-C method and period change.
The classical O--C curves are discussed in different cases in whichvarious period changes involved. Among them, the analytic O--C curveswith frequency, amplitude modulations and with double modes are closelyinspected, respectively. As a special, the light-time effect isillustrated. The features of period change noise and period change tometallicity are added at the end.
| 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.
| 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.
| 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)
| 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.
| Structural Properties of Pulsating Star Light Curves Through Fuzzy Divisive Hierarchical Clustering
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| On the nature of the AM phenomenon or on a stabilization and the tidal mixing in binaries. I. Orbital periods and rotation.
The paper casts a questioning eye on the unique role of the diffusiveparticle transport mechanism in explaining the Am phenomenon and arguesthat the so-called tidal effects might be of great importance incontrolling diffusion processes. A short period cutoff at =~1.2d as wellas a 180-800d gap were found in the orbital period distribution (OPD) ofAm binaries. The existence of the former can be ascribed to the state ofthe primaries with the almost-filled Roche lobes. The latter couldresult from the combined effects of the diffusion, tidal mixing andstabilization processes. Because the tidal mixing might surpassdiffusion in the binaries with the orbital periods P_orb_ less thanseveral hundred days and might thus sustain the He convection zone,which would otherwise disappear, no Am stars should lie below thisboundary. The fact that they are nevertheless seen there implies theexistence of some stabilization mechanism (as, e.g., that recentlyproposed by Tassoul & Tassoul 1992) for the binaries with orbitalperiods less than 180d. Further evidence is given to the fact that theOPD for the Am and the normal binaries with an A4-F1 primary arecomplementary to each other, from which it stems that Am stars are closeto the main sequence. There are, however, indications that they haveslightly larger radii (2.1-3 Rsun_) than expected for theirspectral type. The generally accepted rotational velocity cutoff at=~100km/s is shown to be of little value when applied on Am binaries ashere it is not a single quantity but, in fact, a function of P_orb_whose shape is strikingly similar to that of the curves of constantmetallicity as ascertained from observations. This also leads to thewell known overlap in rotational velocities of the normal and Am starsfor 402.5d.We have exploited this empirical cutoff function to calibrate thecorresponding turbulent diffusion coefficient associated with tidalmixing, having found out that the computed form of the lines of constantturbulence fits qualitatively the empirical shape of the curves ofconstant metallicity. As for larger orbital periods(20d55km/s found by Burkhart(1979) would then be nothing but a manifestation of insufficientlypopulated corresponding area of larger P_orb_.
| Pulsation in high amplitude delta Scuti stars.
It has been pointed out by earlier authors that radial pulsation seemsto be the only type present in high amplitude δ Sct stars, atleast for monoperiodic stars. In order to confirm this or not, we havecollected all the multicolor data available for these stars in theStroemgren and Johnson photometric systems. Then, the type of pulsationhas been analysed on the basis of the phase shifts and amplitude ratiosbetween observed light and colour variations. The results indicate thatall the stars analysed, including both high amplitude δ Sct(Population I) and SX Phe (Population II) stars, are radial pulsators.This is also true for the monoperiodic medium amplitude δ Sctstars analysed.
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