Ýçindekiler
Görüntüler
Resim Yükleyin
DSS Images Other Images
Ýlgili Makaleler
Do the Nearby Blue Horizontal Branch Stars Belong to the Thick Disk or the Halo?
We study the Milky Way region (|Z|< 3.0 kpc) where the thickdisk and inner halo overlap by using the kinematics of local bluehorizontal branch (BHB) stars (within 1 kpc) and new samples of BHBstars and A-type stars from the Century Survey. We derive Galactic U, V,and W velocities for these BHB and A-type star samples using propermotions from the NOMAD catalog. The mean velocities and the velocitydispersions of the BHB samples (|Z| < 3 kpc) are characteristicof the halo, while those of the Century Survey A-type stars arecharacteristic of the thick disk. There is no evidence from our samplesthat the BHB stars rotate with the thick disk in the region |Z| <3 kpc. Nearly a third of the nearby local RR Lyrae stars have diskkinematics and are more metal rich than [Fe/H] ~ –1. Only a fewpercent of the Century Survey BHB (CBHB) stars have these properties.Only one nearby BHB star (HD 130201) is likely to be such a disk starbut selection based on high proper motions will have tended to excludesuch stars from the local sample. The scale height derived from a sampleof local RR Lyrae stars agrees with that of the CBHB stars. The localsamples of BHB stars and metal-weak red giants are too incomplete for asimilar comparison.
| The luminosities and distance scales of type II Cepheid and RR Lyrae variables
Infrared and optical absolute magnitudes are derived for the type IICepheids κ Pav and VY Pyx using revised Hipparcos parallaxes andfor κ Pav, V553 Cen and SW Tau from pulsational parallaxes.Revised Hipparcos and HST parallaxes for RR Lyrae agree satisfactorilyand are combined in deriving absolute magnitudes. Phase-corrected J, Hand Ks mags are given for 142 Hipparcos RR Lyraes based onTwo-Micron All-Sky Survey observations. Pulsation and trigonometricalparallaxes for classical Cepheids are compared to establish the bestvalue for the projection factor (p) used in pulsational analyses.The MV of RR Lyrae itself is 0.16 +/- 0.12 mag brighter thanpredicted from an MV-[Fe/H] relation based on RR Lyrae starsin the Large Magellanic Cloud (LMC) at a modulus of 18.39 +/- 0.05 asfound from classical Cepheids. This is consistent with the prediction ofCatelan & Cortés that it is overluminous for its metallicity.The results for the metal- and carbon-rich Galactic disc stars, V553 Cenand SW Tau, each with small internal errors (+/-0.08 mag) have a meandeviation of only 0.02 mag from the period-luminosity (PL) relationestablished by Matsunaga et al. for type II Cepheids in globularclusters and with a zero-point based on the same LMC-scale. Comparingdirectly the luminosities of these two stars with published data on typeII Cepheids in the LMC and in the Galactic bulge leads to an LMC modulusof 18.37 +/- 0.09 and a distance to the Galactic Centre of R0= 7.64 +/- 0.21kpc. The data for VY Pyx agree with these results withinthe uncertainties set by its parallax. Evidence is presented thatκ Pav may have a close companion and possible implications of thisare discussed. If the pulsational parallax of this star is incorporatedin the analyses, the distance scales just discussed will be increased by~0.15 +/- 0.15 mag. V553 Cen and SW Tau show that at optical wavelengthsPL relations are wider for field stars than for those in globularclusters. This is probably due to a narrower range of masses in thelatter case.
| Pulsational and evolutionary analysis of the double-mode RR Lyrae star BSCom
We derive the basic physical parameters of the field double-mode RRLyrae star BSCom from its observed periods and the requirement ofconsistency between the pulsational and evolutionary constraints. Byusing the current solar-scaled horizontal branch evolutionary models ofPietrinferni et al. and our linear non-adiabatic purely radiativepulsational models, we get M/Msolar = 0.698 +/- 0.004,log(L/Lsolar) = 1.712 +/- 0.005, Teff = 6840 +/-14K, [Fe/H] = -1.67 +/- 0.01, where the errors are standard deviationsassuming uniform age distribution along the full range of uncertainty inage. The last two parameters are in a good agreement with the onesderived from the observed BVIC colours and the updated ATLAS9stellar atmosphere models. We get Teff = 6842 +/- 10K, [Fe/H]= -1.58 +/- 0.11, where the errors are purely statistical ones. It isremarkable that the derived parameters are nearly independent of stellarage at early evolutionary stages. Later stages, corresponding to theevolution towards the asymptotic giant branch, are most probablyexcluded because the required high temperatures are less likely tosatisfy the constraints posed by the colours. We also show that ourconclusions are only weakly sensitive to non-linear period shiftspredicted by current hydrodynamical models.
| The GEOS RR Lyr Survey
Not Available
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| Analysis of RR Lyrae Stars in the Northern Sky Variability Survey
We use data from the Northern Sky Variability Survey (NSVS), obtainedfrom the first-generation Robotic Optical Transient Search Experiment(ROTSE-I), to identify and study RR Lyrae variable stars in the solarneighborhood. We initially identified 1197 RRab (RR0) candidate starsbrighter than the ROTSE median magnitude V=14. Periods, amplitudes, andmean V magnitudes are determined for a subset of 1188 RRab stars withwell-defined light curves. Metallicities are determined for 589 stars bythe Fourier parameter method and by the relationship between period,amplitude, and [Fe/H]. We comment on the difficulties of clearlyclassifying RRc (RR1) variables in the NSVS data set. Distances to theRRab stars are calculated using an adopted luminosity-metallicityrelation with corrections for interstellar extinction. The 589 RRabstars in our final sample are used to study the properties of the RRabpopulation within 5 kpc of the Sun. The Bailey diagram of period versusamplitude shows that the largest component of this sample belongs toOosterhoff type I. Metal-rich ([Fe/H]>-1) RRab stars appear to beassociated with the Galactic disk. Our metal-rich RRab sample mayinclude a thin-disk, as well as a thick-disk population, although theuncertainties are too large to establish this. There is some evidenceamong the metal-rich RRab stars for a decline in scale height withincreasing [Fe/H], as was found by Layden. The distribution of RRabstars with -1<[Fe/H]<-1.25 indicates that within this metallicityrange the RRab stars are a mixture of stars belonging to halo and diskpopulations.
| The GEOS RR Lyr Survey
Not Available
| 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.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| 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.
| The GEOS RR Lyr Survey
Not Available
| Photoelectric Minima of Selected Eclipsing Binaries and Maxima of Pulsating Stars
Not Available
| Photoelectric Maxima of Selected Pulsating Stars
Not Available
| A pulsational approach to near-infrared and visual magnitudes of RR Lyr stars
In this paper, we present an improved theoretical scenario concerningnear-infrared and visual magnitudes of RR Lyr variables, as based onup-to-date pulsating models. New relations connecting V and K absolutemagnitudes with periods, mass, luminosity and metal content arediscussed separately for fundamental and first-overtone pulsators. Wealso show that the V-K colours are predicted to supply tight constraintson the pulsator intrinsic luminosity. On this basis, we revisit the caseof the prototype variable RR Lyr, showing that the parallax inferred bythis new pulsational approach appears in close agreement with HubbleSpace Telescope absolute parallax. Moreover, available K and Vmeasurements for field and cluster RR Lyr variables with known reddeningand metal content are used to derive a relation connecting the Kabsolute magnitude to period and metallicity (MK-[Fe/H]-logP)as well as a new calibration of the MV-[Fe/H] relation. Thecomparison between theoretical prescriptions and observations suggeststhat RR Lyr stars in the field and in galactic globular clusters (GGCs)should have quite similar evolutionary histories. The comparison betweentheory and observations also discloses a general agreement that supportsthe reliability of the current pulsational scenario. On the contrary,current empirical absolute magnitudes based on the Baade-Wesselink (BW)method suggest relations with a zero-point which is fainter than ispredicted by pulsation models, together with a milder metallicitydependence. However, preliminary results based on a new calibration ofthe BW method provided by Cacciari et al. (2000) for RR Cet and SW Andappear in a much better agreement with the pulsational predictions.
| Consistent distances from Baade-Wesselink analyses of Cepheids and RR Lyraes
By using the same algorithm in the Baade-Wesselink analyses of GalacticRR Lyrae and Cepheid variables, it is shown that, within 0.03-mag1σ statistical error, they yield the same distance modulus for theLarge Magellanic Cloud. By fixing the zero-point of thecolour-temperature calibration to those of the current infrared fluxmethods and using updated period-luminosity-colour relations, we get anaverage value of 18.55 for the true distance modulus of the LMC.
| Ein Hoch auf die Hochs Helga und Liljana.
Not Available
| Zur qualitat der visuellen Beobachtung kurzperiodisch Veranderlicher.
Not Available
| Beobachtungsegebnisse Bundesdeutsche Arbeitsgemainschaft fur Veranderliche Sterne e.V.
Not Available
| Times of Light Maxima of Some RRab Stars
Not Available
| BVI Time-Series Data of the Galactic Globular Cluster NGC 3201. I. RR Lyrae Stars
We present Johnson BV- and Kron-Cousins I-band time-series datacollected over three consecutive nights in a region of 13arcmin2 centered on the Galactic globular cluster (GGC) NGC3201. The time sampling of current CCD data allowed us to deriveaccurate light curves and, in turn, mean magnitudes and colors for asample of 53 RR Lyrae stars. To overcome the thorny problem ofdifferential reddening affecting this cluster, we derived new empiricalrelations connecting the intrinsic B-V and V-I colors of fundamental(RRab) RR Lyrae stars to the luminosity amplitude, the metallicity, andthe pulsation period. The key features of these relations are thefollowing: (1) they rely on stellar parameters, which are not affectedby reddening; (2) they supply accurate estimates of intrinsic colorsacross the fundamental instability strip and cover a wide metallicityrange; (3) they were derived by neglecting the RR Lyrae stars that areaffected by amplitude modulation. Moreover, the zero point of the E(B-V)reddening scale was empirically checked using the large sample of RRLyrae stars in M3 from Corwin & Carney, a GGC affected by avanishing reddening. According to these relations we estimatedindividual reddenings for RR Lyrae stars in our sample and the mainresults we found are the following: (1) The mean cluster reddening basedon E(B-V) color excesses is =0.30+/-0.03. This estimate isslightly higher than the mean reddening evaluations available in theliterature or based on the dust infrared map by Schlegel, Finkbeiner,& Davis, i.e., =0.26+/-0.02. Note that the angularresolution of this map is ~6', whereas for current reddening map it is~1'. (2) The mean cluster reddening based on E(V-I) color excesses is=0.36+/-0.05. This estimate is only marginally inagreement with the mean cluster reddening obtained using the reddeningmap by von Braun & Mateo and derived by adopting cluster turnoffstars, i.e., =0.25+/-0.07. On the other hand, currentintrinsic spread among individual reddenings (~0.2 mag) agrees quitewell with the estimate provided by previous authors. It is noteworthythat previous mean cluster reddenings are in very good agreement withvalues obtained using the empirical relations for intrinsic RR Lyraecolors provided by Kovacs & Walker. (3) According to currentindividual E(B-V) and E(V-I) reddenings and theoretical predictions forhorizontal-branch stars, we found that the true distance modulus forthis cluster is 13.32+/-0.06 mag. This determination is somehowsupported by the comparison between predicted and empirical pulsationamplitudes. (4) The comparison between present luminosity amplitudes andestimates available in the literature discloses that approximately 30%of fundamental RR Lyrae stars are affected by amplitude modulation (theBlazhko effect). This finding confirms empirical evidence originallybrought out by Szeidl and by Smith. Based on observations collected atthe European Southern Observatory, La Silla, Chile.
| Subsystems of RR Lyrae Variable Stars in Our Galaxy
We have used published, high-accuracy, ground-based and satelliteproper-motion measurements, a compilation of radial velocities, andphotometric distances to compute the spatial velocities and Galacticorbital elements for 174 RR Lyrae (ab) variable stars in the solarneighborhood. The computed orbital elements and published heavy-elementabundances are used to study relationships between the chemical,spatial, and kinematic characteristics of nearby RR Lyrae variables. Weobserve abrupt changes of the spatial and kinematic characteristics atthe metallicity [Fe/H]≈-0.95 and also when the residual spatialvelocities relative to the LSR cross the critical value V res≈290km/s. This provides evidence that the general population of RR Lyraestars is not uniform and includes at least three subsystems occupyingdifferent volumes in the Galaxy. Based on the agreement between typicalparameters for corresponding subsystems of RR Lyrae stars and globularclusters, we conclude that metal-rich stars and globular clusters belongto a rapidly rotating and fairly flat, thick-disk subsystem with a largenegative vertical metallicity gradient. Objects with larger metaldeficiencies can, in turn, be subdivided into two populations, but usingdifferent criteria for stars and clusters. We suggest that field starswith velocities below the critical value and clusters with extremelyblue horizontal branches form a spherical, slowly rotating subsystem ofthe protodisk halo, which has a common origin with the thick disk; thissubsystem has small but nonzero radial and vertical metallicitygradients. The dimensions of this subsystem, estimated from theapogalactic radii of orbits of field stars, are approximately the same.Field stars displaying more rapid motion and clusters with redderhorizontal branches constitute the spheroidal subsystem of the accretedouter halo, which is approximately a factor of three larger in size thanthe first two subsystems. It has no metallicity gradients; most of itsstars have eccentric orbits, many display retrograde motion in theGalaxy, and their ages are comparatively low, supporting the hypothesisthat the objects in this subsystem had an extragalactic origin.
| Bias Properties of Extragalactic Distance Indicators. XI. Methods to Correct for Observational Selection Bias for RR Lyrae Absolute Magnitudes from Trigonometric Parallaxes Expected from the Full-Sky Astrometric Mapping Explorer Satellite
A short history is given of the development of the correction forobservation selection bias inherent in the calibration of absolutemagnitudes using trigonometric parallaxes. The developments have beendue to Eddington, Jeffreys, Trumpler & Weaver, Wallerstein,Ljunggren & Oja, West, Lutz & Kelker, after whom the bias isnamed, Turon Lacarrieu & Crézé, Hanson, Smith, andmany others. As a tutorial to gain an intuitive understanding of severalcomplicated trigonometric bias problems, we study a toy bias model of aparallax catalog that incorporates assumed parallax measuring errors ofvarious severities. The two effects of bias errors on the derivedabsolute magnitudes are (1) the Lutz-Kelker correction itself, whichdepends on the relative parallax error δπ/π and the spatialdistribution, and (2) a Malmquist-like ``incompleteness'' correction ofopposite sign due to various apparent magnitude cutoffs as they areprogressively imposed on the catalog. We calculate the bias propertiesusing simulations involving 3×106 stars of fixedabsolute magnitude using Mv=+0.6 to imitate RR Lyraevariables in the mean. These stars are spread over a spherical volumebounded by a radius 50,000 pc with different spatial densitydistributions. The bias is demonstrated by first using a fixed rmsparallax uncertainty per star of 50 μas and then using a variable rmsaccuracy that ranges from 50 μas at apparent magnitude V=9 to 500μas at V=15 according to the specifications for the Full-SkyAstrometric Mapping Explorer (FAME) satellite to be launched in 2004.The effects of imposing magnitude limits and limits on the``observer's'' error, δπ/π, are displayed. We contrast themethod of calculating mean absolute magnitude directly from theparallaxes where bias corrections are mandatory, with an inverse methodusing maximum likelihood that is free of the Lutz-Kelker bias, althougha Malmquist bias is present. Simulations show the power of the inversemethod. Nevertheless, we recommend reduction of the data using bothmethods. Each must give the same answer if each is freed from systematicerror. Although the maximum likelihood method will, in theory, eliminatemany of the bias problems of the direct method, nevertheless the biascorrections required by the direct method can be determined empiricallyvia Spaenhauer diagrams immediately from the data, as discussed in theearlier papers of this series. Any correlation of the absolute(trigonometric) magnitudes with the (trigonometric) distances is thebias. We discuss the level of accuracy that can be expected in acalibration of RR Lyrae absolute magnitudes from the FAME data over themetallicity range of [Fe/H] from 0 to -2, given the known frequency ofthe local RR Lyrae stars closer than 1.5 kpc. Of course, use will alsobe made of the entire FAME database for the RR Lyrae stars over thecomplete range of distances that can be used to empirically determinethe random and systematic errors from the FAME parallax catalog, usingcorrelations of derived absolute magnitude with distance and position inthe sky. These bias corrections are expected to be much more complicatedthan only a function of apparent magnitude because of variousrestrictions due to orbital constraints on the spacecraft.
| BAV-Beobachtungen an Programmsternen des Typs RR-Lyrae von 1951 bis 2001.
Not Available
| Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veraenderliche Sterne e.V.
Not Available
| Distances and Metallicities of High- and Intermediate-Velocity Clouds
A table is presented that summarizes published absorption linemeasurements for the high- and intermediate-velocity clouds (HVCs andIVCs). New values are derived for N(H I) in the direction of observedprobes, in order to arrive at reliable abundances and abundance limits(the H I data are described in Paper II). Distances to stellar probesare revisited and calculated consistently, in order to derive distancebrackets or limits for many of the clouds, taking care to properlyinterpret nondetections. The main conclusions are the following. (1)Absolute abundances have been measured using lines of S II, N I, and OI, with the following resulting values: ~0.1 solar for one HVC (complexC), ~0.3 solar for the Magellanic Stream, ~0.5 solar for a southern IVC,and ~solar for two northern IVCs (the IV Arch and LLIV Arch). Finally,approximate values in the range 0.5-2 solar are found for three moreIVCs. (2) Depletion patterns in IVCs are like those in warm disk or halogas. (3) Most distance limits are based on strong UV lines of C II, SiII, and Mg II, a few on Ca II. Distance limits for major HVCs aregreater than 5 kpc, while distance brackets for several IVCs are in therange 0.5-2 kpc. (4) Mass limits for major IVCs are0.5-8×105 Msolar, but for major HVCs theyare more than 106 Msolar. (5) The Ca II/H I ratiovaries by up to a factor 2-5 within a single cloud, somewhat morebetween clouds. (6) The Na I/H I ratio varies by a factor of more than10 within a cloud, and even more between clouds. Thus, Ca II can beuseful for determining both lower and upper distance limits, but Na Ionly yields upper limits.
| Empirical relations for cluster RR Lyrae stars revisited
Our former study on the empirical relations between the Fourierparameters of the light curves of the fundamental mode RR Lyrae starsand their basic stellar parameters has been extended to considerablylarger data sets. The most significant contribution to the absolutemagnitude MV comes from the period P and from the firstFourier amplitude A1, but there are statistically significantcontributions also from additional higher order components, mostimportantly from A3 and in a lesser degree from the Fourierphase varphi51. When different colors are combined inreddening-free quantities, we obtain basically period-luminosity-colorrelations. Due to the log Teff(B-V,log g,[Fe/H]) relationfrom stellar atmosphere models, we would expect some dependence also onvarphi 31. Unfortunately, the data are still not extensiveand accurate enough to decipher clearly the small effect of this Fourierphase. However, with the aid of more accurate multicolor data on fieldvariables, we show that this Fourier phase should be present either inV-I or in B-V or in both. From the standard deviations of the variousregressions, an upper limit can be obtained on the overall inhomogeneityof the reddening in the individual clusters. This yields sigmaE(B-V)<~ 0.012 mag, which also implies an average minimumobservational error of sigmaV >~ 0.018 mag.
| Absolute Magnitudes and Kinematic Parameters of the Subsystem of RR Lyrae Variables
The statistical parallax technique is applied to a sample of 262 RRabLyrae variables with published photoelectric photometry, metallicities,and radial velocities and with measured absolute proper motions.Hipparcos, PPM, NPM, and the Four-Million Star Catalog (Volchkov et al.1992) were used as the sources of proper motions; the proper motionsfrom the last three catalogs were reduced to the Hipparcos system. Wedetermine parameters of the velocity distribution for halo [(U_0, V_0,W_0) = (-9 +/- 12, -214 +/- 10, -16 +/- 7) km/s and (sigma_U, sigma_V,sigma_W) = (164 +/- 11, 105 +/- 7, 95 +/- 7) km/s] and thick-disk [(U_0,V_0, W_0) = (-16 +/- 8, -41 +/- 7, -18 +/- 5) km/s and (sigma_U,sigma_V, sigma_W) = (53 +/- 9, 42 +/- 8, 26 +/- 5) km/s] RR Lyrae, aswell as the intensity-averaged absolute magnitude for RR Lyrae of thesepopulations: = 0.77 +/- 0.10 and = +1.11 +/-0.28 for the halo and thick-disk objects, respectively. The metallicitydependence of the absolute magnitude of RR Lyrae is analyzed(=(0.76 +/- 0.12) + (0.26 +/- 0.26) x ([Fe/H] + 1.6) = 1.17 +0.26 x [Fe/H]). Our results are in satisfactory agreement with the_(RR)-[Fe/H] relation from Carney et al. (1992)(_(RR) = 1.01 + 0.15 x [Fe/H]) obtained by Baade-Wesselink'smethod. They provide evidence for a short distance scale: the LMCdistance modulus and the distance to the Galactic center are 18.22 +/-0.11 and 7.4 +/-±0.5 kpc, respectively. The zero point ofthe distance scale and the kinematic parameters of the RR Lyraepopulations are shown to be virtually independent of the source ofabsolute proper motions used and of whether they are reduced to theHipparcos system or not.
| Aus der Sektion RR-Lyrae-Sterne.
Not Available
|
Yeni bir Makale Öner
Ýlgili Baðlantýlar
Yeni Bir Baðlantý Öner
sonraki gruplarýn üyesi:
|
Gözlemler ve gökölçümü verileri
| Takýmyýldýz: | Ejderha |
| Sað Açýklýk: | 12h17m46.63s |
| Yükselim: | +69°30'38.2" |
| Görünürdeki Parlaklýk: | 10.561 |
| özdevim Sað Açýklýk: | -23.9 |
| özdevim Yükselim: | -6.9 |
| B-T magnitude: | 10.931 |
| V-T magnitude: | 10.592 |
Kataloglar ve belirtme:
|
