Contents
Images
Upload your image
DSS Images Other Images
Related articles
Estimation of the solar galactocentric distance and galactic rotation velocity from near-solar-circle objects
We have tested the method of determining the solar Galactocentricdistance R 0 and Galactic rotation velocity V 0modified by Sofue et al. using near-solar-circle objects. The motion ofobjects relative to the local standard of rest has been properly takeninto account. We show that when such young objects as star-formingregions or Cepheids are analyzed, allowance for the perturbationsproduced by the Galactic spiral density wave improves the statisticalsignificance of the estimates. The estimate of R 0 = 7.25± 0.32 kpc has been obtained from 19 star-forming regions. Thefollowing estimates have been obtained from a sample of 14 Cepheids(with pulsation periods P > 5 d ): R 0 = 7.66± 0.36 kpc and V 0 = 267 ± 17 kms-1. We consider the influence of the adopted Oort constant Aand the character of stellar proper motions (Hipparcos or UCAC4). Thefollowing estimates have been obtained from a sample of 18 Cepheids withstellar proper motions from the UCAC4 catalog: R 0 = 7.64± 0.32 kpc and V 0 = 217 ± 11 kms-1.
| Galactic restrictions on iron production by various types of supernovae
We propose a statistical method for decomposition of contributions toiron production from various sources: Type II supernovae and thesubpopulations of Type Ia supernovae, prompt (their progenitors areshort-lived stars with ages lower than ˜100 Myr) and tardy (theirprogenitors are long-lived stars with ages >100 Myr). To do that, wedevelop a theory of oxygen and iron synthesis that takes into accountthe influence of the spiral arms on the amount of the above elementssynthesized by both Type II supernovae and prompt Type Ia supernovae. Inthe framework of the theory, we processed statistically the new, moreprecise, observational data on Cepheid abundances, which, as is wellknown, demonstrate non-trivial radial distributions of oxygen and ironin the Galactic disc with bends in the gradients. In our opinion, suchfine structure in the distribution of elements along the Galactic discenables one to decompose the amount of iron unambiguously into threecomponents produced by the above three sources. In addition, by means ofour statistical methods we solve this task without any preliminarysuppositions about the ratios between the proportions of ironsynthesized by the above sources.The total mass supplied to the Galactic disc during its life by alltypes of supernovae is ˜(4.0 ± 0.4) × 107M&sun;, while the mass of iron occurring in the presentinterstellar medium (ISM) is ˜(1.20 ± 0.05) ×107 M&sun;, i.e. about two thirds of iron iscontained in stars and stellar remnants.The relative proportion of iron synthesized by tardy type Ia supernovaefor the lifetime of the Galaxy is ˜35 per cent (in the present ISMthis portion is ˜50 per cent). Correspondingly, the totalproportion of iron supplied to the disc by Type II supernovae and promptType Ia supernovae is ˜65 per cent (in the present ISM thisproportion is ˜50 per cent). The above result depends slightly onthe adopted mass of oxygen and iron synthesized during one supernovaexplosion and the shape (bimodal or smooth) of the so-called delay-timedistribution function.The proportions of iron mass distributed between short-lived supernovaeare usually as follows: depending on the ejected masses of oxygen oriron during one Type II supernova event, the relative proportion of ironsupplied to the Galactic disc for its age varies in the range 12-32 percent (in the present ISM 9-25 per cent); the proportion supplied byprompt Type Ia supernovae to the Galactic disc is 33-53 per cent (in theISM 26-42 per cent).Our method also confirms that the bend in the observed slope of theoxygen radial distribution and the minimum in [O/Fe] at ˜7 kpcform in the vicinity of the location of the corotation resonance.
| The Distribution of the Elements in the Galactic Disk. II. Azimuthal and Radial Variation in Abundances from Cepheids
This paper reports on the spectroscopic investigation of 101 Cepheids inthe Carina region. These Cepheids extend previous samples by about 35%in number and increase the amount of the Galactic disk coverageespecially in the direction of l ? 270°. The new Cepheids do notadd much information to the radial gradient, but provide a substantialincrease in azimuthal coverage. We find no azimuthal dependence inabundance over an 80° angle from the Galactic center in an annulusof 1 kpc depth centered on the Sun. A simple linear fit to the Cepheiddata yields a gradient d[Fe/H]/dRG = -0.055 ± 0.003dex kpc-1 which is somewhat shallower than found from ourprevious, smaller Cepheid sample.
| Photoelectric observations of Cepheids in UBV(RI)c (Berdnikov, 2008)
This catalog gathers the observation of 894 Cepheids made between 1986to 2004.Observations are listed in alphabetical order of the constellations. Thestandard deviation for every magnitude and color is 0.01mag.This version supersedes the 1997 edition (Cat. )(3 data files).
| Cepheid parallaxes and the Hubble constant
Revised Hipparcos parallaxes for classical Cepheids are analysedtogether with 10 Hubble Space Telescope (HST)-based parallaxes. In areddening-free V, I relation we find that the coefficient of logP is thesame within the uncertainties in our Galaxy as in the Large MagellanicCloud (LMC), contrary to some previous suggestions. Cepheids in theinner region of NGC4258 with near solar metallicities confirm thisresult. We obtain a zero-point for the reddening-free relation and applyit to the Cepheids in galaxies used by Sandage et al. to calibrate theabsolute magnitudes of Type Ia supernova (SNIa) and to derive the Hubbleconstant. We revise their result for H0 from 62 to 70 +/-5kms-1Mpc-1. The Freedman et al. value is revisedfrom 72 to 76 +/- 8kms-1Mpc-1. These results areinsensitive to Cepheid metallicity corrections. The Cepheids in theinner region of NGC4258 yield a modulus of 29.22 +/- 0.03 (int.)compared with a maser-based modulus of 29.29 +/- 0.15. Distance modulifor the LMC, uncorrected for any metallicity effects, are 18.52 +/- 0.03from a reddening-free relation in V, I; 18.47 +/- 0.03 from aperiod-luminosity relation at K; 18.45 +/- 0.04 from aperiod-luminosity-colour relation in J, K. Adopting a metallicitycorrection in V, I from Macri et al. leads to a true LMC modulus of18.39 +/- 0.05.
| New Period-Luminosity and Period-Color relations of classical Cepheids: I. Cepheids in the Galaxy
321 Galactic fundamental-mode Cepheids with good B, V, and (in mostcases) I photometry by Berdnikov et al. (\cite{Berdnikov:etal:00}) andwith homogenized color excesses E(B-V) based on Fernie et al.(\cite{Fernie:etal:95}) are used to determine their period-color (P-C)relation in the range 0.4~ 1.4). The latter effect is enhanced by asuggestive break of the P-L relation of LMC and SMC at log P = 1.0towards still shallower values as shown in a forthcoming paper.Table 1 is only available in electronic form at the CDS via anonymousftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/404/423
| 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.
| 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
| Multi-colour PL-relations of Cepheids in the bt HIPPARCOS catalogue and the distance to the LMC
We analyse a sample of 236 Cepheids from the hipparcos catalog, usingthe method of ``reduced parallaxes'' in V, I, K and the reddening-free``Wesenheit-index''. We compare our sample to those considered by Feast& Catchpole (1997) and Lanoix et al. (1999), and argue that oursample is the most carefully selected one with respect to completeness,the flagging of overtone pulsators, and the removal of Cepheids that mayinfluence the analyses for various reasons (double-mode Cepheids,unreliable hipparcos solutions, possible contaminated photometry due tobinary companions). From numerical simulations, and confirmed by theobserved parallax distribution, we derive a (vertical) scale height ofCepheids of 70 pc, as expected for a population of 3-10 Msunstars. This has consequences for Malmquist- and Lutz-Kelker (Lutz &Kelker 1973, Oudmaijer et al. 1998) type corrections which are smallerfor a disk population than for a spherical population. The V and I datasuggest that the slope of the Galactic PL-relations may be shallowerthan that observed for LMC Cepheids, either for the whole period range,or that there is a break at short periods (near log P_0 ~ 0.7-0.8). Westress the importance of two systematic effects which influence thedistance to the LMC: the slopes of the Galactic PL-relations andmetallicity corrections. In order to assess the influence of thesevarious effects, we present 27 distance moduli (DM) to the LMC. Theseare based on three different colours (V,I,K), three different slopes(the slope observed for Cepheids in the LMC, a shallower slope predictedfrom one set of theoretical models, and a steeper slope as derived forGalactic Cepheids from the surface-brightness technique), and threedifferent metallicity corrections (no correction as predicted by one setof theoretical models, one implying larger DM as predicted by anotherset of theoretical models, and one implying shorter DM based onempirical evidence). We derive DM between 18.45 +/- 0.18 and 18.86 +/-0.12. The DM based on K are shorter than those based on V and I andrange from 18.45 +/- 0.18 to 18.62 +/- 0.19, but the DM in K could besystematically too low by about 0.1 magnitude because of a bias due tothe fact that NIR photometry is available only for a limited number ofstars. From the Wesenheit-index we derive a DM of 18.60 +/- 0.11,assuming the observed slope of LMC Cepheids and no metallicitycorrection, for want of more information. The DM to the LMC based on theparallax data can be summarised as follows. Based on the PL-relation inV and I, and the Wesenheit-index, the DM is 18.60 ± 0.11(± 0.08 slope)(^{+0.08}_{-0.15} ;metallicity), which is ourcurrent best estimate. Based on the PL-relation in K the DM is ;;;;18.52 +/- 0.18 (± 0.03 ;slope) (± 0.06 ;metallicity)(^{+0.10}_{-0} ;sampling ;bias). The random error is mostly due to thegiven accuracy of the hipparcos parallaxes and the number of Cepheids inthe respective samples. The terms between parentheses indicate thepossible systematic uncertainties due to the slope of the GalacticPL-relations, the metallicity corrections, and in the K-band, due to thelimited number of stars. Recent work by Sandage et al. (1999) indicatesthat the effect of metallicity towards shorter distances may be smallerin V and I than indicated here. From this, we point out the importanceof obtaining NIR photometry for more (closeby) Cepheids, as for themoment NIR photometry is only available for 27% of the total sample.This would eliminate the possible bias due to the limited number ofstars, and would reduce the random error estimate from 0.18 to about0.10 mag. Furthermore, the sensitivity of the DM to reddening,metallicity correction and slope are smallest in the K-band. Based ondata from the ESA HP astrometry satellite.
| Direct calibration of the Cepheid period-luminosity relation
After the first release of Hipparcos data, Feast & Catchpole gave anew value for the zero-point of the visual Cepheid period-luminosityrelation, based on trigonometric parallaxes. Because of the largeuncertainties on these parallaxes, the way in which individualmeasurements are weighted is of crucial importance. We thereforeconclude that the choice of the best weighting system can be aided by aMonte Carlo simulation. On the basis of such a simulation, it is shownthat (i) a cut-off in π or in σ_ππ introduces a strongbias; (ii) the zero-point is more stable when only the brightestCepheids are used; and (iii) the Feast & Catchpole weighting givesthe best zero-point and the lowest dispersion. After correction, theadopted visual period-luminosity relation is=-2.77logP-1.44+/-0.05. Moreover, we extend this study to thephotometric I band (Cousins) and obtain=-3.05logP-1.81+/-0.09.
| 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.
| The shape and scale of Galactic rotation from Cepheid kinematics
A catalog of Cepheid variables is used to probe the kinematics of theGalactic disk. Radial velocities are measured for eight distant Cepheidstoward l = 300 deg; these new Cepheids provide a particularly goodconstraint on the distance to the Galactic center, R0. We model the diskwith both an axisymmetric rotation curve and one with a weak ellipticalcomponent, and find evidence for an ellipticity of 0.043 +/- 0.016 nearthe sun. Using these models, we derive R0 = 7.66 +/- 0.32 kpc andv(circ) = 237 +/- 12 km/s. The distance to the Galactic center agreeswell with recent determinations from the distribution of RR Lyraevariables and disfavors most models with large ellipticities at thesolar orbit.
| Galactic kinematics of Cepheids from HIPPARCOS proper motions
The Hipparcos proper motions of 220 Galactic Cepheids, together withrelevant ground-based photometry, have been analyzed. The effects ofGalactic rotation are very clearly seen. Mean values of the Oortconstants, A = 14.82 +/- 0.84 km/s kpc, and B = -12.37 +/- 0.64 km/skpc, and of the angular velocity of circular rotation at the sun, 27.19+/- 0.87 km/s kpc, are derived. A comparison of the value of A withvalues derived from recent radial velocity solutions confirms, withinthe errors, the zero-points of the period-luminosity andperiod-luminosity-color relations derived directly from the Hipparcostrigonometrical parallaxes of the same stars. The proper motion resultssuggest that the Galactic rotation curve is declining slowly at thesolar distance from the Galactic Center (-2.4 +/- 1.2 km/s kpc). Thecomponent of the solar motion towards the North Galactic Pole is foundto be +7.61 +/- 0.64 km/s. Based on the increased distance scale deducedin the present paper, the distance to the Galactic Center derived in aprevious radial velocity study is increased to 8.5 +/- 0.5 kpc.
| 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.
| Rotation curve of the system of classical Cepheids and the distance to the galactic center
Not Available
| New radial velocities for classical cepheids. Local galactic rotation revisited
New centre-of-mass radial velocities are calculated for 107 classicalcepheids from CORAVEL observations. We generally determine thesevelocities from four to six measurements carefully spaced in phase, byfitting a "typical" radial velocity curve or the mirror image of thelight curve. A decomposition in Fourier series is used for stars withmore than 10 measurements. Distances are then computed through aperiod-luminosity-colour relation for 278 classical cepheids with knownradial velocity, and an axisymmetric galactic rotation model is appliedto the sample, using a generalised non-linear least square method withuncertainties on both the velocities and the distances. The bestresults, with a rotation curve modelled as a third order polynomial,are: Rsun_=8.09 +/-0.30 kpc, A=15.92 +/-0.34 km/s/kpc, 2ARsun_=257 +/-7 km/s, A2=d^2theta(R)/d R^2^=-3.38+/-0.38 km/s/kpc^2^, A3=d^3theta(R)/d R^3^=1.99 +/-0.62km/s/kpc^3^, u_0_=9.32 +/-0.80 km/s, v_0_=11.18 +/-0.65 km/s. The effectof modifying the distance scale of cepheids, the absorption coefficientor the fitting procedure algorithm are examined. It appears that theproduct 2 A Rsun_ is very robust towards these changes. Theextended sample of classical cepheids with known radial velocitypresented in this paper seems to imply a higher value for A thananterior studies. The radial velocity residuals show a systematic k-termof about 2 km/s. New evidence from cluster cepheids excludes anintrinsic cause for this shift, and a dynamical cause is proposed from acomparison with a N-body simulation of the Galaxy. The simulation showsthat a systematic bias of this magnitude is typical. The structure ofthe local residual velocity field is examined in some detail.
| 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
| Classical Cepheids - Their distances and space distribution
A simplified method of calculating classical Cepheid distances isproposed. It is based on photometric data, without the use of thereddenings. By means of results obtained in this way the followingproblems are discussed: Cepheid double and more numerous aggregates andproperties of the cluster and association Cepheid.
| Milky Way rotation and the distance to the galactic center from Cepheid variables
The compiled photometry, reddenings, and radial velocities of GalacticCepheids are fit with an axisymmetric Galactic rotation model. R(0) =7.8 + or - 0.7 kpc and 2AR(0) = 228 + or - 19 km/s are derived. The LMCdistance modulus is 18.45 on the same absolute calibration. ObservedCepheid gamma velocities appear on average to be 30 + or - 1 km/s morenegative than the true corresponding center-of-mass velocities. Thetrend of increasing blueness toward larger Galactocentric radiusconfirms the radial metallicity gradient found spectroscopically.
| The catalogue of light curves parameters, distances and space coordinates of classical Cepheids.
Not Available
| The Catalogue of Distances and Light Absorption for Cepheids
Not Available
| The structure of the Cepheid instability strip
The properties of Cepheids in the Galaxy, LMC, and SMC are analyzed tocompare them with theoretical models. The PLC relationships of the LMCand SMC agree with theoretically derived PLC relationships when fittingof data is done by the maximum likelihood method. Differences in the tworelationships can be ascribed to abundance differences. Empirical blueedges in the period-color plane agree with models for log P not greaterthan 1.1, but have significantly steeper slopes at longer periods; theredoes not seem to be any satisfactory explanation of this.
| Intrinsic colours and physical properties of Cepheids
Reddening-free colors and VBLUW color excesses are determined for 170Southern Hemisphere galactic Cepheids. The Cepheid colors are correctedfor interstellar reddening, the VBLUW color excesses are compared withcolor excesses obtained in other studies of Cepheids, and physicalproperties are derived by comparing the reddening-free colors withtheoretical colors previously computed from a grid of model-atmospherefluxes. The cyclic behavior of temperature, gravity, luminosity, andradius is calculated along with the equilibrium values of thesequantities for 98 Cepheids with periods shorter than 11 days. It isfound that at least 25% of the Cepheids studied show evidence of abinary companion and that the computed velocity curves are in reasonableagreement with observed radial-velocity curves. It is concluded that theuse of hydrostatic-equilibrium model atmospheres is not too unrealisticfor the continuum colors of Cepheids.
| A method for constructing envelopes and the period-amplitude relationof cepheids.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977A&A....61..827E&db_key=AST
| The light curve parameters of photoelectrically observed galactic Cepheids
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971A&AS....4..265S&db_key=AST
| The Normal Color Indices and Color Excesses of Long-Period Cepheids.
Not Available
| A catalogue of fundamental data for classical cepheids in the galaxies.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968AJ.....73..492F&db_key=AST
| The radial velocities of distant cepheids and galactic models
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1967MNRAS.136..141F&db_key=AST
| Galactic Structure and Galactic Rotation from Cepheids.
Abstract image available at:http://adsabs.harvard.edu/abs/1963ApJ...137..249K
|
Submit a new article
Related links
Submit a new link
Member of following groups:
|
Observation and Astrometry data
| Constellation: | Vela |
| Right ascension: | 10h36m08.61s |
| Declination: | -56°02'35.7" |
| Apparent magnitude: | 10.655 |
| Proper motion RA: | -5.3 |
| Proper motion Dec: | 6.3 |
| B-T magnitude: | 12.409 |
| V-T magnitude: | 10.8 |
Catalogs and designations:
|
