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Публикации по объекту
Search for evolutionary changes in Cepheid periods using the Harvard plate collection: NSV 9159
We have obtained 530 photographic magnitude estimates for thelong-period classical Cepheid NSV 9159 ( P = 39d) in theplate collections of the Harvard Observatory and the SternbergAstronomical Institute. Together with the currently available CCDobservations from the ASAS-3 catalog, our data have allowed us toconstruct an O-C diagram spanning a time interval of 119 years. The O-Cdiagram has the shape of a parabola, which has made it possible todetermine for the first time the quadratic light elements and tocalculate the rate of evolutionary decrease in the period, 314.4(±7.3) s yr?1, in agreement with the results oftheoretical calculations for the second crossing of the instabilitystrip. The available data reduced by the Eddington-Plakidis method donot reveal any noticeable random fluctuations in the period.
| The reliability of Cepheid reddenings based on BVIC photometry
Externally determined values of E(B - V) (Espacered) for 40Galactic Cepheids are compared to reddenings determined using B - V andV - IC colour indices and the method of Dean, Warren &Cousins (EBVIC), updated to allow for metallicitycorrections. With three stars omitted on the grounds of uncertainty intheir space reddenings, we find thatThe two scales agree well in scale and zero-point, and there is nosignificant trend with period. Given the non-zero errors in the Cepheidspace reddenings, the estimated error in BVIC Cepheidreddenings is no more than 0.02.The above results are not significantly changed whether one corrects thereddenings for metallicity using older Bell models, or using more recentmodels by Sandage, Bell & Tripicco. Using the SBT models to correctthe reddenings of Cloud Cepheids for metallicity gives slightly smallerreddenings at a given metal deficiency, yielding `new' median reddeningsof 0.056 (Small Magellanic Cloud) and 0.076 (Large Magellanic Cloud) ifwe assume the same metal deficiencies as Caldwell and Coulson. Withmetal deficiencies of [M/H] = -0.7 and -0.25, the median reddenings are0.040 and 0.058.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Astrophysics in 2003
Five coherent sections appear this year, addressing solar physics,cosmology (with WMAP highlights), gamma-ray bursters (and theirassociation with Type Ia supernovae), extra-solar-system planets, andthe formation and evolution of galaxies (from reionization to assemblageof Local Group galaxies). There are also eight incoherent sections thatdeal with other topics in stellar, galactic, and planetary astronomy andthe people who study them.
| The Power of Archival Astronomy
Examples are given of the extreme usefulness of the Harvard CollegeObservatory Photographic Plate Collection for the study of variablestars that possess only limited published observational data. Programobjects studied with the aid of archival photographic data include: (i)the eclipsing binary HD 174403, (ii) the semiregular variable BC Cygni,(iii) V439 Cygni, now recognized as a gamma Cassiopeiae variable, and(iv) the classical Cepheid T Antliae. In the Case of T Antliae, theplate archives yielded not only data for the star's brightnessvariations but also for the spectral characteristics of all starsbrighter than B = 12 in the field.
| The nature of the Cepheid T Antliae
The variable star T Antliae, sometimes suspected to be a type IIpulsator, is demonstrated to be a classical Cepheid in the thirdcrossing of the instability strip. It exhibits a positive period changeof +0.514 +/- 0.016 s yr-1, consistent with a star on theblue side of the instability strip and evolving through it for the thirdtime. The Cepheid exhibits no random fluctuations in pulsation period,although superimposed upon its evolutionary O-C trend are very subtlevariations that may be indicative of orbital motion about an unseencompanion. Archival spectroscopic data also indicate that the star sitson the edge of a putative cluster of B-type stars that may be physicallyassociated with the Cepheid. Additional photometric and spectroscopicdata for the Cepheid and cluster are needed to strengthen the case. Thefield reddening of T Ant established from nearby early-type stars isEB-V=0.30 +/- 0.01 (EB-V(B0)=0.316 +/- 0.014).
| The Distance Scale for Classical Cepheid Variables
New radii, derived from a modified version of the Baade-Wesselink (BW)method that is tied to published KHG narrowband spectrophotometry, arepresented for 13 bright Cepheids. The data yield a best-fittingperiod-radius relation given bylog=1.071(+/-0.025)+0.747(+/-0.028)logP0. In combination with other high-quality radiusestimates recently published by Laney & Stobie, the new data yield aperiod-radius relation described bylog=1.064(+/-0.0006)+0.750(+/-0.006)logP0, which simplifies to ~P3/4.The relationship is used to test the scale of Cepheid luminositiesinferred from cluster zero-age main-sequence (ZAMS) fitting, for whichwe present an updated list of calibrating Cepheids located in stellargroups. The cluster ZAMS-fitting distance scale tied to a Pleiadesdistance modulus of 5.56 is found to agree closely with the distancescale defined by Hipparcos parallaxes of cluster Cepheids and alsoyields Cepheid luminosities that are a good match to those inferred fromthe period-radius relation. The mean difference between absolute visualmagnitudes based on cluster ZAMS fitting,C, and those inferred for 23 clusterCepheids from radius and effective temperature estimates,BW, in the sense of C-BW is+0.019+/-0.029 s.e. There is no evidence to indicate the need for amajor revision to the Cepheid cluster distance scale. The absolutemagnitude differences are examined using available [Fe/H] data for thecluster Cepheid sample to test the metallicity dependence of theperiod-luminosity relation. Large scatter and a small range ofmetallicities hinder a reliable estimate of the exact relationship,although the data are fairly consistent with predictions from stellarevolutionary models. The derived dependence isΔMV(C-BW)=+0.06(+/-0.03)-0.43(+/-0.54)[ Fe/H].
| Photometry and radial velocities of cepheids and other variable stars in the Galaxy and the LMC
UBVRIc and radial velocity measurements are presented for Galactic andLMC Cepheids, and for several variables of other type. The photometrycomprises 168 objects with 1790 phases, and the speedometry 15 objectswith 97 phases.
| Photoelectric Observations of Southern Cepheids in 2001
A total of 2097 photometric observations in the BVIc systemare presented for 117 Cepheids located in the southern hemisphere. Themain purpose of the photometry is to provide new epochs of maximumbrightness for studying Cepheid period changes, as well as to establishcurrent light elements for the Cepheids.
| 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
| 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.
| Galactic Cepheids. Catalogue of light-curve parameters and distances
We report a new version of the catalogue of distances and light-curveparameters for Galactic classical Cepheids. The catalogue listsamplitudes, magnitudes at maximum light, and intensity means for 455stars in BVRI filters of the Johnson system and (RI)_C filters of theCron-Cousins system. The distances are based on our new multicolour setof PL relations and on our Cepheid-based solution for interstellarextinction law parameters and are referred to an LMC distance modulus of18.25. The catalogue is only available in electronic form at the CDS viaanonymous ftp (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Period Changes in Population II Cepheids: TX Del and W Vir
We have used the Hipparcos database of epoch photometry to study thevariability of two Population II Cepheids: TX Del and W Vir. We haveconstructed (O-c) diagrams for these stars, using the new data and datafrom the literature. The period of TX Del is decreasing, at a ratewhich is consistent with evolutionary predictions. THe periodchange ofW Vir is uncertain because of the many recent gaps in the data of thisstar. We urge AAVSO visual and photoelectric observers to monitorPopulation II Cepheids more systematically, since amny of these starshave unstable periods, and at least one has an unstable amplitude.
| I- and JHK-band photometry of classical Cepheids in the HIPPARCOS catalog
By correlating the \cite[Fernie et al. (1995)]{F95} electronic databaseon Cepheids with the ``resolved variable catalog'' of the hipparcosmission and the simbad catalog one finds that there are 280 Cepheids inthe hipparcos catalog. By removing W Vir stars (Type ii Cepheids),double-mode Cepheids, Cepheids with an unreliable solution in thehipparcos catalog, and stars without photometry, it turns out that thereare 248 classical Cepheids left, of which 32 are classified asfirst-overtone pulsators. For these stars the literature was searchedfor I-band and near-infrared data. Intensity-mean I-band photometry onthe Cousins system is derived for 189 stars, and intensity-mean JHK dataon the Carter system is presented for 69 stars.
| Baade-Wesselink Radius Determination of Type II Cepheids
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....113.1833B&db_key=AST
| Photometric Parameters for Short-Period Cepheids
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....111.1313E&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.
| The separation of S-Cepheids from classical Cepheids and a new definition of the class
Fourier decomposition has been applied to a sample of 184 classical andS-Cepheids with P less than 8 d and a careful evaluation of errors inthe determination of the parameters has been made. The S-Cepheids starsare redefined by the authors as Population I Cepheids that do not followthe Hertzsprung progression, but have a progression of their own. In thephi(21)-P plane, the S- and classical Cepheids are characterized by twosequences well separated for P less than 5.5 d. In the period range Pbetween 3d and 5.5 d, two different progressions are also present in thephi(31)-P plane while a discriminating value R(21) = 0.20 can be seen inthe R(21)-P plane. The first overtone pulsation seems to be wellestablished for S-Cepheids with P less then 3.2 d; it is probable forall the stars of the redefined subclass. A discontinuity is clearlyvisible at about 3 d in the S-Cepheid sequence in the phi(21)-P plane;it is interpreted as a resonance effect. An apparent decrease in thenumber of stars is present in the classical sequence for P less than 3d.
| Color Excesses on a Uniform Scale for 328 Cepheids
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1990ApJS...72..153F&db_key=AST
| The Binary Type II Cepheids IX CAS and TX Del
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1989AJ.....98..981H&db_key=AST
| Absolute and relative amplitudes of variations in radius of classical Cepheids
An analysis of observations of the absolute Delta R and relative DeltaR/R amplitudes of variations in radius of 85 galactic classical Cepheidshas yielded four empirical relations. Results are presented forlong-period, short-period, and s Cepheids. For a given group ofvariables, it is shown that Delta R and Delta R/R values increase withboth pulsation period (P) values and with P(Delta V) values (where DeltaV is the amplitude of light variations).
| Population I pulsating stars. II - Period-age (-colour) relations
Ages corresponding to various evolutionary phases of population Ipulsating stars (89 Delta Scuti variables and 155 classical cepheids)are interpolated in the evolutionary track systems of Iben (1967) andPaczynski (1970). The stellar ages are considerably less in the lattersystem than in the former one. The undertainty of the age of a star isestimated when various evolutionary phases are possible for this star (agreater age corresponds to a later phase). Semiempiricalperiod-age-color (P-t-C) and period-age (P-1) relations are derived forvarious modes, groups of stars, color indices (and effectivetemperature), and evolutionary phases. For Delta Scuti stars, theuncertainty of ages calculated from the P-t relations for differentmodes, is estimated. Theoretical P-t-C and P-t relations for Delta Scutistars are obtained and compared with semiempirical relations (such acomparison of P-t relations is performed for classical cepheids too).The improvement of the age accuracy is estimated when a P-t-C relationis used instead of the corresponding P-t relation. The theoretical andsemiempirical period ratios of radial pulsations, derived from the P-trelations for Delta Scuti stars, are compared. There is relatively goodagreement between the P-t relations for the two types of population Ipulsating stars, but a 'gap' exists between them.
| Population I pulsating stars. I - Period-luminosity (-colour) relations
Luminosities of Population I pulsating stars (Delta Scuti variables andclassical cepheids) are investigated. From data for 80 Delta Scutistars, semiempirical period-luminosity-color (P-L-C) relations andperiod-luminosity (P-L) relations are obtained for the four lowest modesof radial pulsations. The improvement of the accuracy of the stellarluminosity is determined when a P-L-C relation is used instead of thecorresponding P-L relation. From data for 155 classical cepheids,empirical P-L relations are derived for short-period stars, long-periodstars, and s-cepheids. The comparison of the P-L relations for the twotypes of variable stars shows good agreement, but between them there isa 'gap' with a dim nature.
| The importance of colour-colour loops in the determination of the physical parameters of pulsating variables
Attention is drawn to the importance of studying the surface brightnessof pulsating stars as a function of two colors, in order to disentanglethe contributions of temperature and gravity variations to the observedcurve from that due to the simultaneous variation of the emittingsurface of the star. The area of the observed color-color loops obtainedwith different colors is compared with the area delta B of thesurface-brightness color loop, inferred from calibrations. The existenceof the color-color loops and the dependence of the loop area on thepulsation period, very similar to that of delta B, is easily explained,under the assumption of quasi-static approximation, by the existence ofa loop in the plane of effective temperature and effective gravity, thearea of which varies with the period. The consistency and adequacy ofthe whole picture on which the CORS method (used to determine the radiusof classical Cepheids) is based are strongly supported by theexperimental evidence.
| Intermediate-band and H-beta observations of short-period Cepheids
Intermediate-band and H-beta observations along with light and colorcurves for short-period Cepheids are presented. Although mainlysouthern, a few northern variables are included. Two of the variablesare briefly discussed.
| The period-luminosity-abundance relations for galactic Cepheids
The median photometric parameters from intermediate and H-betaphotometry of 106 Cepheids are used to test the Sandage-Tammann resultthat dispersions in the PL and PC relations are correlated with theamplitude of the light curves, as measured by the amplitude defect F(B).The correlation of both color and luminosity dispersions from mean PLand PC relations with F(B) are found to be the result of a correlationbetween abundance and amplitude. The short-period Cepheids (SPC) aredistinctly divided between type C and normal Cepheids, with type Cvariables defined by F(B). The C-type and normal SPC are separated by0.65 mag at a given period and abundance, or about 300 K at a givenluminosity, with the C-type Cepheids being fainter and bluer,respectively. The light curves of nine-day Cepheids with strong humpsmay be misinterpreted in that the hump has mistakenly been taken formaximum light.
| A catalogue of field Type II Cepheids
A catalogue of field Type II Cepheids is presented. The primary listconsists of 152 Cepheids sufficiently far from the galactic plane to bevery probably Type II stars. A second list contains 56 additional starsthat are likely, but less certain, Type II Cepheids, including bothstars estimated to be at large distances from the galactic plane butwith uncertain distances and stars close to the galactic plane believedto be Type II for independent reasons.
| A survey of Cepheid sizes
The radius is one of the fundamental physical parameters governing aCepheid's pulsation. If the radius of a Cepheid can be establishedindependently of its luminosity and temperature, that radius, combinedwith a temperature scale, can yield the Cepheid's luminosity. TheBaade-Wesselink (BW) method provides an approach for determining aCepheid's radius independently of any temperature or luminosity scale.In connection with the present investigation, data regarding individualBW radius determinations are provided in a table. The best BW radii areselected and a period-radius (P-R) relation is determined. The obtainedrelation is compared to theoretical P-R relations. The BW andtheoretical relations are compared to one obtained from the luminositiesand temperatures of Cepheids in open clusters and associations.
| Kinematics of field Type II Cepheid variables
The spectra of 49 field Type II Cepheids have been assembled andcombined with 14 additional stars with previously published radialvelocities in order to investigate the kinematics and spectralcharacteristics of these stars. Many of the stars have low peculiarvelocities consistent with circular rotation around the galaxy, whilesome are high-velocity stars. Outside the nuclear bulge, the velocitiesare correlated with photometric metallicities in the sense thatmetal-rich stars show a nearly normal, disklike rotation velocity and alow velocity dispersion. This correlation shows that the low-velocity,metal-rich stars have an old-disk origin. Fewer Cepheids are found inthe field than expected relative to clusters, suggesting a differencebetween the populations of the halo field and clusters. The kinematicproperties of Cepheids in the nuclear bulge appear to be different inthat both metal-poor and metal-rich Cepheids have a high velocitydispersion and show little systematic galactic rotation.
| Observational determination of pulsation modes and photometric masses of Cepheid variables
An attempt is made to characterize the pulsation modes and crossingnumbers of Cepheids analytically, based on observational data. Theobservations cover 66 Cepheids and their mean and maximum Wesselinkradii, the log P - log R relationship, and the mass-luminosity ratio.The inherent inaccuracies of current data weight the actual values withprobabilities. Calculation of instabilities among the Cepheids are foundto require at least three variables, e.g., luminosity, period, radius,etc. Five stars have been identified as first overtone pulsators: BGCru, BF Oph, V 482 Sco, Y Sgr, and U Aql. It is concluded that the trackof stellar evolution of normal stars must be modified when analyzingpulsating stars in the instability region, except for calculations basedon the luminosity-effective temperature relationship.
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Наблюдательные данные и астрометрия
| Созвездие: | Насос |
| Прямое восхождение: | 09h33m50.86s |
| Склонение: | -36°36'56.8" |
| Видимая звёздная величина: | 9.27 |
| Собственное движение RA: | -7.2 |
| Собственное движение Dec: | 3.9 |
| B-T magnitude: | 10.081 |
| V-T magnitude: | 9.337 |
Каталоги и обозначения:
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