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Period-colour and amplitude-colour relations in classical Cepheid variables - IV. The multiphase relations
The superb phase resolution and quality of the Optical GravitationalLensing Experiment (OGLE) data on the Large Magellanic Cloud (LMC) andSmall Magellanic Cloud (SMC) Cepheids, together with existing data onGalactic Cepheids, are combined to study the period-colour (PC) andamplitude-colour (AC) relations as a function of pulsation phase. Ourresults confirm earlier work that the LMC PC relation (at mean light) ismore consistent with two lines of differing slopes, separated at aperiod of 10 d. However, our multiphase PC relations reveal much newstructure which can potentially increase our understanding of Cepheidvariables. These multiphase PC relations provide insight into why theGalactic PC relation is linear but the LMC PC relation is non-linear.This is because the LMC PC relation is shallower for short (logP < 1)and steeper for long (logP > 1) period Cepheids than thecorresponding Galactic PC relation. Both of the short- and long-periodCepheids in all three galaxies exhibit the steepest and shallowestslopes at phases around 0.75-0.85, respectively. A consequence is thatthe PC relation at phase ~ 0.8 is highly non-linear. Further, theGalactic and LMC Cepheids with logP > 1 display a flat slope in thePC plane at phases close to the maximum light. When the LMCperiod-luminosity (PL) relation is studied as a function of phase, weconfirm that it changes with the PC relation. The LMC PL relation in Vand I band near the phase of 0.8 provides compelling evidence that thisrelation is also consistent with two lines of differing slopes joined ata period close to 10 d.
| Mean Angular Diameters and Angular Diameter Amplitudes of Bright Cepheids
We predict mean angular diameters and amplitudes of angular diametervariations for all monoperiodic PopulationI Cepheids brighter than=8.0 mag. The catalog is intended to aid selecting mostpromising Cepheid targets for future interferometric observations.
| 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
| Two Period-Radius Relations for Classical Cepheids: Determining the Pulsation Mode and the Distance Scale
Not Available
| 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
| 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
| Photoelectric Ubvri/c Photometry of Southern Cepheids
Not Available
| Photoelectric Observations of Cepheids in 1994
Not Available
| NSV 11802 - a new Algol-type eclipsing binary
Not Available
| Photoelectric observations of Cepheids in 1992
During August-September 1992, 1635 UBVR photometric observations for 74Cepheids were obtained with the 60-cm reflector of the Mt. MaidanakObservatory of the Tashkent Astronomical Institute. Tables ofobservations and plots of light curves are given. These observationstogether with previously published ones will be used to study the periodvariability of Cepheids and to determine their radii and light excesses.
| Photoelectric observations of Cepheids in 1991
Observations of 2233 photoelectric UBVR-observations for 99 Cepheidsobtained in August 1991 at the Mt. Maidanak observatory are reported. Atable of observations and graphs of light curves are presented. Theobservations obtained, in concert with earlier-published observations,will be used to research the period variability of Cepheids, determinetheir color excesses, and study the light curves of bimodal Cepheids.
| A magnitude-limited survey of Cepheid companions in the ultraviolet
Results of a magnitude-limited survey of classic Cepheids brighter than8th mag carried out to search for hot main-sequence companions arepresented. Spectra of 76 stars obtained with the IUE satellite in the2000-3200-A region were compared with the spectra of nonvariablesupergiants and also the single Cepheid Delta Cep to search for excessflux at 2500 A from possible companions. Photometric companions werefound for 21 percent of the sample. When the Cepheids known to be binaryfrom either orbital motion or spectra in the 1200-2000-A region areincluded, the percentage of companions rises to 29 percent. If astatistical correction from stars with orbital motion is included, 34percent have companions. This percentage is compared with that found byAbt et al. (1990) for B2-B5 main-sequence stars. If only systems withperiods longer than a year and separations not more than 30 arcsec areconsidered, only 18 percent of the B stars will become Cepheids withcompanions.
| Northern Cepheids: Period Update and Duplicity Effects
O-C diagrams have been continued for 64 northern Cepheids with theprimary aim of studying the effects of duplicity on the pulsationperiod. Because the light-time effect in the O-C diagrams of binaryCepheids has to be accompanied with properly phased variations in theγ-velocity, the radial velocity of the programme stars has beenstudied, as well. Light-time effect is suspected in the O-C diagram ofFM Aql, RW Cam, Y Lac and RS Ori, and confirmed for AW Per. One or morephase jumps are present or suspected in the O-C diagram of 19 northernCepheids (FF Aql, BY Cas, DD Cas, DL Cas, X Cyg, SU Cyg, SZ Cyg, DT Cyg,V532 Cyg, V924 Cyg, TX Del, DX Gem, X Lac, CV Mon, RS Ori, SV Per, SZTau, T Vul, X Vul). In addition to the Cepheids with known spectroscopicorbit, the spectroscopic binary nature based on the variability of theγ-velocity has been confirmed, revealed or suspected for themajority of the programme stars. The most probable new spectroscopicbinary Cepheids are: KL Aql, Eta Aql, SU Cas, V636 Cas, BZ Cyg, MW Cyg,V386 Cyg, W Gem, RZ Gem, AD Gem, RS Ori, SV Per, SW Tau, T Vul and UVul. A preliminary value of the orbital period is suggested for Eta Aql,SU Cas, RZ Gem, T Vul and U Vul.
| 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
| 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.
| 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.
| Cepheids and nonvariable supergiants
Photometric parameters for Cepheids in a previous paper are adapted foruse with nonvariable supergiants of similar temperature. The closecorrelation between the abundance and luminosity parameters forclassical, short-period Cepheids (SPC) confirms the nearlydispersionless luminosity temperature relation for these variables. Theassumptions that (1) the C-type variables are transiting the Cepheidtemperature for the first time, (2) the classical SPC are mostlytransiting for the second time, and (3) the long-period Cepheids (LPC)are a mixture of stars transiting for the first to third or fourth timesare found to be consistent with the various correlations of temperatureand luminosity parameters. The nonvariable supergiants with photometricparameters similar to those for the Cepheids are found to haveluminosities consistent with their spectroscopic luminosity class. Few,if any, nonvariable supergiants have temperatures and luminositiessimilar to the LPC.
| Physical parameters and pulsational mode of short-period small-amplitude Cepheids
Nine galactic short-period (P less than 8 days) small-amplitude Cepheidshave been the subject of a study to determine their physical parametersand pulsational properties. UBVRI photometry and radial velocities wereobtained in the same observing seasons. The wings of H-alpha were usedto determine effective temperatures. Empirical radii, luminosities, andmasses were determined. The short-period stars lie inside and seem to beon the red side of the observational Cepheid instability strip. It wasfound that these stars are likely pulsating in the radial fundamentalmode except HR 8084 (DT Cyg) which is suspected to be a first overtonepulsator. As the small-amplitude Cepheids in the LMC are thought to befirst overtone pulsators, it is suggested that small-amplitudesinusoidal variations are not the consequence of pulsation in the firstovertone, but rather the response to a more general amplitude trendacross the instability strip in a particular galactic system.
| Classification of intrinsic variables. IX - The Cepheid domain
The present H-beta, RI and intermediate band observations obtained for135 high mass, long- and short-period Cepheids (LPC and SPC) throughoutthe cycle of variation are combined with observations for 100 ultrashortperiod Cepheids in order to delineate the Cepheid domain in the (beta,/C1/) and (M-bol, log Te) planes. The independently derived luminositycalibrations for bright giants and supergiants previously published arefound to closely reproduce the luminosities derived from theSandage-Tammann (1968) PL relation for most variables. The majority ofthe LPC appear to be overabundant in metals by comparison to the sun,and reddening determinations for the LPC suggest a small systematiccorrection to previous results.
| Note on the nature of HD 179315
MK classification and UBVRI photometry is carried out to determinewhether the HD 179315 star is a cepheid or an ellipsoidal binary. Thespectral type proved to be G1Ib, classifying the star as a seven-daycepheid. This is supported by UBVRI data, from which is derived E(B-V) =0.48 plus or minus 0.03 on the Parsons-Bell color excess scale. The staris distinctly cooler than most seven-day cepheids, and is probably closeto the red edge of the instability strip, which may account for its lowamplitude of 0.3 magnitudes.
| Radial-velocity observations of two low-amplitude Cepheids
Not Available
| 65th Name-List of Variable Stars
Not Available
| BD +4 4009, a New Bright Cepheid Variable
Not Available
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Observation and Astrometry data
| Constellation: | Aquila |
| Right ascension: | 19h11m59.17s |
| Declination: | +04°21'17.5" |
| Apparent magnitude: | 7.786 |
| Proper motion RA: | -1.3 |
| Proper motion Dec: | -5 |
| B-T magnitude: | 9.37 |
| V-T magnitude: | 7.917 |
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