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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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| A catalogue of RR Lyrae stars from the Northern Sky Variability Survey
A search for RR Lyrae stars has been conducted in the publicly availabledata of the Northern Sky Variability Survey. Candidates have beenselected by the statistical properties of their variation; the standarddeviation, skewness and kurtosis with appropriate limits determined froma sample 314 known RRab and RRc stars listed in the General Catalogue ofVariable Stars. From the period analysis and light-curve shape of over3000 candidates 785 RR Lyrae have been identified of which 188 arepreviously unknown. The light curves were examined for the Blazhkoeffect and several new stars showing this were found. Six double-mode RRLyrae stars were also found of which two are new discoveries. Somepreviously known variables have been reclassified as RR Lyrae stars andsimilarly some RR Lyrae stars have been found to be other types ofvariable, or not variable at all.
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
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| Proper identification of RR Lyrae stars brighter than 12.5 mag
RR Lyrae stars are of great importance for investigations of Galacticstructure. However, a complete compendium of all RR-Lyraes in the solarneighbourhood with accurate classifications and coordinates does notexist to this day. Here we present a catalogue of 561 local RR-Lyraestars (V_max ≤ 12.5 mag) according to the magnitudes given in theCombined General Catalogue of Variable Stars (GCVS) and 16 fainter ones.The Tycho2 catalogue contains ≃100 RR Lyr stars. However, manyobjects have inaccurate coordinates in the GCVS, the primary source ofvariable star information, so that a reliable cross-identification isdifficult. We identified RR Lyrae from both catalogues based on anintensive literature search. In dubious cases we carried out photometryof fields to identify the variable. Mennessier & Colome (2002,A&A, 390, 173) have published a paper with Tyc2-GCVSidentifications, but we found that many of their identifications arewrong.
| RR Lyrae stars: kinematics, orbits and z-distribution
RR Lyrae stars in the Milky Way are good tracers to study the kinematicbehaviour and spatial distribution of older stellar populations. Arecently established well documented sample of 217 RR Lyr stars withV<12.5 mag, for which accurate distances and radial velocities aswell as proper motions from the Hipparcos and Tycho-2 catalogues areavailable, has been used to reinvestigate these structural parameters.The kinematic parameters allowed to calculate the orbits of the stars.Nearly 1/3 of the stars of our sample have orbits staying near the MilkyWay plane. Of the 217 stars, 163 have halo-like orbits fulfilling one ofthe following criteria: Θ < 100 km s-1, orbiteccentricity >0.4, and normalized maximum orbital z-distance>0.45. Of these stars roughly half have retrograde orbits. Thez-distance probability distribution of this sample shows scale heightsof 1.3±0.1 kpc for the disk component and 4.6±0.3 kpc forthe halo component. With our orbit statistics method we found a(vertical) spatial distribution which, out to z=20 kpc, is similar tothat found with other methods. This distribution is also compatible withthe ones found for blue (HBA and sdB) halo stars. The circular velocityΘ, the orbit eccentricity, orbit z-extent and [Fe/H] are employedto look for possible correlations. If any, it is that the metal poorstars with [Fe/H] <1.0 have a wide symmetric distribution aboutΘ=0, thus for this subsample on average a motion independent ofdisk rotation. We conclude that the Milky Way possesses a halo componentof old and metal poor stars with a scale height of 4-5 kpc having randomorbits. The presence in our sample of a few metal poor stars (thus partof the halo population) with thin disk-like orbits is statistically notsurprising. The midplane density ratio of halo to disk stars is found tobe 0.16, a value very dependent on proper sample statistics.
| Variable Stars in the Field of NGC 6882/6885: The Case of V381 Vulpeculae and V382 Vulpeculae
We present photometric and spectroscopic results for two reportedδ Scuti stars in the field of NGC 6882/6885. We find that V381 Vulhas a period of 0.1185 days and is a δ Scuti variable, aspreviously reported. The spectra of V382 Vul shows it to be a B3 starand therefore not a δ Scuti. All evidence points to V382 Vul beinga β Cephei star with a period of 0.1808 days. Additionally, wereport five new variables and eight suspected variable stars. Of thefive new variables, two are pulsators and three are eclipsing binarysystems. In our search for new variable stars, we use a ``robust medianstatistic'' that is proven to be better at finding low-amplitudevariables than the traditional error curve approach.
| 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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| The Monoperiodic δ Scuti Star UY Camelopardalis: An Analog to SX Phoenicis and RR Lyrae Variables
We present the results of a 4 year photometric study of thehigh-amplitude δ Scuti (HADS) star UY Camelopardalis. Analysis ofthe available data from 1985 to 2003 shows that UY Cam is monoperiodic.Fourier solutions for individual data sets do not reveal period changesin the star. Although forced parabolic fits to the O-C residualsindicate a measurable period change, the distribution of the data pointsin the O-C diagram and the deviations between fits and observationssuggest that the existence of the period change still has not beenestablished. We demonstrate the presence of amplitude variations fromcycle to cycle and on longer timescales. The pulsation amplitude seemedto change from 1985 to the 2000s, but it remained constant in 2000-2003.UY Cam is located in the upper portion of the δ Scuti instabilityregion. Its photometric properties and estimated physical parametersreveal that UY Cam is an interesting object in terms of its poormetallicity, long period, high luminosity, low surface gravity, andlarge radius among the HADS stars. UY Cam could be a younger (0.7+/-0.1Gyr) Population I HADS star with low metal abundance (Z=0.004) evolvingon its post-main-sequence shell hydrogen burning evolutionary phase. UYCam intervenes among the Population I/II HADS and type c RR Lyraevariables. These characteristics suggest the star to be an analog ofHADS, SX Phoenicis, and RRc variables.
| 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.
| 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.
| 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
| 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
Not Available
| Early evolution of the Galactic halo revealed from Hipparcos observations of metal-poor stars
The kinematics of 122 red giant and 124 RR Lyrae stars in the solarneighborhood are studied using accurate measurements of their propermotions obtained by the Hipparcos astrometry satellite, combined withtheir published photometric distances, metal abundances, and radialvelocities. A majority of these sample stars have metal abundances of(Fe/H) = -1 or less and thus represent the old stellar populations inthe Galaxy. The halo component, with (Fe/H) = -1.6 or less, ischaracterized by a lack of systemic rotation and a radially elongatedvelocity ellipsoid. About 16 percent of such metal-poor stars have loworbital eccentricities, and we see no evidence of a correlation between(Fe/H) and e. Based on the model for the e-distribution of orbits, weshow that this fraction of low-e stars for (Fe/H) = -1.6 or less isexplained by the halo component alone, without introducing the extradisk component claimed by recent workers. This is also supported by theabsence of a significant change in the e-distribution with height fromthe Galactic plane. In the intermediate-metallicity range, we find thatstars with disklike kinematics have only modest effects on thedistributions of rotational velocities and e for the sample at absolutevalue of z less than 1 kpc. This disk component appears to constituteonly 10 percent for (Fe/H) between -1.6 and -1 and 20 percent for (Fe/H)between -1.4 and -1.
| The impact of HIPPARCOS on the RR Lyrae Distance Scale
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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)
| 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.
| Radial velocities and iron abundances of field RR Lyraes. I.
We present systemic velocities and iron abundances for 56 RR Lyraes, themajority of which have been observed by the HIPPARCOS satellite.Comparison between our systemic velocities and previous valuesidentifies several binary candidates only one of which, TU UMa, waspreviously suspected of being a binary. However, spectra of the unusualRR Lyrae BB Vir show no evidence of line doubling and hence do notsupport the recent claims that this star may have a Blue HorizontalBranch companion. Comparison between our abundances and previousdeterminations shows reasonable agreement except with the recent work of\cite[Layden (1994)]{Lay94} where we find systematic differences.Several of the stars included on the HIPPARCOS observing list as RRLyraes are shown to be mis-classified. Of particular interest are thestars V363 Cas and AT And which, by analogy with XZ Cet, may beanomalous Cepheids. The Appendix is available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Structural Properties of Pulsating Star Light Curves Through Fuzzy Divisive Hierarchical Clustering
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| Photoelectric Minima and Maxima of Selected Eclipsing and Pulsating Variables
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| 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.
| Kinematics of metal-poor stars in the galaxy
We discuss the kinematic properties of a sample of 1936 Galactic stars,selected without kinematic bias, and with abundances (Fe/H) is less thanor equal to -0.6. The stars selected for this study all have measuredradial velocities, and the majority have abundances determined fromspectroscopic or narrow-/intermediate-band photometric techniques. Incontrast to previous examinations of the kinematics of the metal-poorstars in the Galaxy, our sample contains large numbers of stars that arelocated at distances in excess of 1 kpc from the Galactic plane. Thus, amuch clearer picture of the nature of the metal-deficient populations inthe Galaxy can now be drawn.
| Summary of Delta S metallicity measurements for bright RR Lyrae variables observed at Lick Observatory and KPNO between 1972 and 1987
From 1972 to 1987 we conducted a survey of the metallicity of faint RRLyrae variables in the Galactic halo, using the 'Butler system' of DeltaS. As part of the calibration of this program, we made approximately 500observations of bright RR Lyraes as abundance standards. We summarizeall the observations of these bright field RR Lyraes and provideaveraged values for the metallicity parameter Delta S. These averagesrepresent the most precise definition of the Butler system for themeasurement of RR Lyrae metallicities. The typical mean error is 0.3units in Delta S, which corresponds to 0.05 dex in (Fe/H). We alsobriefly discuss the weaknesses in the determination of (Fe/H) from DeltaS.
| 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.
| Infrared photometry and radial velocities of field RR Lyraes
Infrared photometry of 110 field RR Lyraes is presented along withradial velocities of 13 field RR Lyraes. The methods used are described.
| A re-analysis of the period shifts in RR Lyrae stars
The period shift in both field and globular cluster RR Lyrae stars isexamined. The stellar pulsation theory called the Sandage Period Shiftto determine the mean M(V) of RR Lyrae stars is investigated. Theadvantages of (V-K) compared to (B-V) as a temperature indicator for RRLyraes are discussed in detail. Period shift-metallicity relations arederived using recently published infrared photometry of field RR Lyraesand globular cluster RR Lyraes. Other method for determining mean M(V)for RR Lyraes are critically reviewed. It is argued that results formain sequence fitting, statistical parallax, and Red Giant Branch theoryare presently too uncertain to be used. The slope of themass-metallicity relation from pulsation theory is in seriousdisagreement with that from Horizontal Branch Theory.
| Detection of a galactic color gradient for blue horizontal-branch stars of the halo field and implications for the halo age and density distributions
Abstract image available at:http://adsabs.harvard.edu/abs/1991ApJ...375..121P
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Datos observacionales y astrométricos
| Constelación: | Piscis, Peces |
| Ascensión Recta: | 01h20m52.36s |
| Declinación: | +21°43'43.2" |
| Magnitud Aparente: | 11.021 |
| Movimiento Propio en Ascensión Recta: | 0.1 |
| Movimiento Propio en Declinación: | -1.9 |
| B-T magnitude: | 11.413 |
| V-T magnitude: | 11.054 |
Catálogos y designaciones:
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