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Observational studies of Cepheid amplitudes. I. Period-amplitude relationships for Galactic Cepheids and interrelation of amplitudes
Context: The dependence of amplitude on the pulsation period differsfrom other Cepheid-related relationships. Aims: We attempt torevise the period-amplitude (P-A) relationship of Galactic Cepheidsbased on multi-colour photometric and radial velocity data. Reliable P-Agraphs for Galactic Cepheids constructed for the U, B, V, R_C, andIC photometric bands and pulsational radial velocityvariations facilitate investigations of previously poorly studiedinterrelations between observable amplitudes. The effects of bothbinarity and metallicity on the observed amplitude, and the dichotomybetween short- and long-period Cepheids can both be studied. Methods: A homogeneous data set was created that contains basicphysical and phenomenological properties of 369 Galactic Cepheids.Pulsation periods were revised and amplitudes were determined by theFourier method. P-A graphs were constructed and an upper envelope to thedata points was determined in each graph. Correlations between variousamplitudes and amplitude-related parameters were searched for, usingCepheids without known companions. Results: Large amplitudeCepheids with companions exhibit smaller photometric amplitudes onaverage than solitary ones, as expected, while s-Cepheids pulsate withan arbitrary (although small) amplitude. The ratio of the observedradial velocity to blue photometric amplitudes, AV_RAD/A_B,is not as good an indicator of the pulsation mode as predictedtheoretically. This may be caused by an incorrect mode assignment to anumber of small amplitude Cepheids, which are not necessarily firstovertone pulsators. The dependence of the pulsation amplitudes onwavelength is used to identify duplicity of Cepheids. More than twentystars previously classified as solitary Cepheids are now suspected tohave a companion. The ratio of photometric amplitudes observed invarious bands confirms the existence of a dichotomy among normalamplitude Cepheids. The limiting period separating short- andlong-period Cepheids is 10.47 days. Conclusions:Interdependences of pulsational amplitudes, the period dependence of theamplitude parameters, and the dichotomy have to be taken into account asconstraints in modelling the structure and pulsation of Cepheids.Studies of the P-L relationship must comply with the break at 10.47°instead of the currently used “convenient” value of 10 days.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/504/959
| A Catalog of Extended Green Objects in the GLIMPSE Survey: A New Sample of Massive Young Stellar Object Outflow Candidates
Using images from the Spitzer Galactic Legacy Infrared Mid-Plane SurveyExtraordinaire (GLIMPSE), we have identified more than 300 extended 4.5?m sources (Extended Green Objects (EGOs), for the common coding ofthe [4.5] band as green in three-color composite InfraRed Array Cameraimages). We present a catalog of these EGOs, including integrated fluxdensity measurements at 3.6, 4.5, 5.8, 8.0, and 24 ?m from GLIMPSEand the Multiband Imaging Photometer for Spitzer Galactic Plane Survey.The average angular separation between a source in our sample and thenearest IRAS point source is greater than 1'. The majority of EGOs areassociated with infrared dark clouds (IRDCs), and where high-resolution6.7 GHz CH3OH maser surveys overlap the GLIMPSE coverage,EGOs and 6.7 GHz CH3OH masers are strongly correlated.Extended 4.5 ?m emission is thought to trace shocked molecular gas inprotostellar outflows; the association of EGOs with IRDCs and 6.7 GHzCH3OH masers suggests that the extended 4.5 ?m emissionmay pinpoint outflows specifically from massive protostars. The mid-IRcolors of EGOs lie in regions of color-color space occupied by youngprotostars still embedded in infalling envelopes.
| Galactic abundance gradients from Cepheids. On the iron abundance gradient around 10-12 kpc
Context: Classical Cepheids are excellent tracers of intermediate-massstars, since their distances can be estimated with very high accuracy.In particular, they can be adopted to trace the chemical evolution ofthe Galactic disk. Aims: Homogeneous iron abundance measurements for 33Galactic Cepheids located in the outer disk together with accuratedistance determinations based on near-infrared photometry are adopted toconstrain the Galactic iron gradient beyond 10 kpc. Methods: Ironabundances were determined using high resolution Cepheid spectracollected with three different observational instruments: ESPaDOnS@CFHT,Narval@TBL and FEROS@2.2m ESO/MPG telescope. Cepheid distances wereestimated using near-infrared (J,H,K-band) period-luminosity relationsand data from SAAO and the 2MASS catalog. Results: The least squaressolution over the entire data set indicates that the iron gradient inthe Galactic disk presents a slope of -0.052±0.003 textrm {dexkpc}-1 in the 5-17 kpc range. However, the change of the ironabundance across the disk seems to be better described by a linearregime inside the solar circle and a flattening of the gradient towardthe outer disk (beyond 10 kpc). In the latter region the iron gradientpresents a shallower slope, i.e. -0.012±0.014 textrm {dexkpc}-1. In the outer disk (10-12 kpc) we also found thatCepheids present an increase in the spread in iron abundance. Currentevidence indicates that the spread in metallicity depends on theGalactocentric longitude. Finally, current data do not support thehypothesis of a discontinuity in the iron gradient at Galactocentricdistances of 10-12 kpc. Conclusions: The occurrence of a spread in ironabundance as a function of the Galactocentric longitude indicates thatlinear radial gradients should be cautiously treated to constrain thechemical evolution across the disk.
| A high-sensitivity 6.7 GHz methanol maser survey toward H2O sources
We present the results of a high sensitivity survey for 6.7 GHz methanolmasers towards 22 GHz water masers using the 100 m Efflesberg telescope.A total of 89 sources were observed and 10 new methanol masers weredetected. The new detections are relatively faint with peak fluxdensities of between 0.5 and 4.0 Jy. A nil detection rate from low-massstar forming regions enhances the conclusion that the masers are onlyassociated with massive star formation. Even the faintest methanol maserin our survey, with a luminosity of 1.1 × 10-9L_?, is associated with massive stars, as inferred from itsinfrared luminosity.Table 3 is only available in electronic form at http://www.aanda.org
| New BVIc Observations of VY Car, HQ Car, and EW Sct
Not Available
| New homogeneous iron abundances of double-mode Cepheids from high-resolution echelle spectroscopy
Aims.We define the relationship between the double-mode pulsation ofCepheids and metallicity in a more accurate way, determine the empiricalmetallicities of double-mode Cepheids from homogeneous, high-resolutionspectroscopic data, and study of the period-ratio - metallicitydependence. Methods: The high S/N echelle spectra obtained with theFEROS spectrograph were analyzed using a self-developed IRAF script, andthe iron abundances were determined by comparing with synthetic spectraassuming LTE. Results: Accurate [Fe/H] values of 17 galactic beatCepheids were determined. All these stars have solar or slightlysubsolar metallicity. Their period ratio (P1 / P_0) showsstrong correlation with their derived [Fe/H] values. The correspondingperiod ratio - metallicity relation has been evaluated.Based on observations taken with the ESO 2.2-m telescope at La Silla,Chile (Proposal 073.D-0072) and the 1.82 m telescope at David DunlapObservatory, Canada.
| 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.
| Detailed chemical composition of Galactic Cepheids. A determination of the Galactic abundance gradient in the 8-12 kpc region
Aims.The recent introduction of high-resolution/large spectral-rangespectrographs has provided the opportunity to investigate the chemicalcomposition of classical Cepheids in detail. This paper focusses on newabundance determinations for iron and 6 light metals (O, Na, Mg, Al, Si,Ca) in 30 Galactic Cepheids. We also give a new estimate of the Galacticradial abundance gradient. Methods: The stellar effective temperatureswere determined using the method of line depth ratios, and the surfacegravity and the microturbulent velocity vt by imposing theionization balance between Fe I and Fe II with the help of curves ofgrowth. Abundances were calculated with classical LTE atmosphere models. Results: Abundances were obtained with rms accuracies of about0.05-0.10 dex for Fe, and 0.05-0.20 dex for the other elements. Cepheidsin our sample have solar-like abundances, and current measurements agreequite well with previous determinations. We computed "single zone"Galactic radial abundance gradients for the 8-12 kpc region and found aslope for iron of -0.061 dex kpc-1.Based on observations made with the 1.52 m ESO Telescope at La Silla,Chile.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Ammonia cores in high mass star formation regions
We observed a sample of 35 water masers not coincident with known HIIregions and/or low mass young stellar objects (YSOs) with the Effelsberg100 m telescope in the NH3 (J,K) = (1, 1), (2, 2), (3, 3) and(4, 4) transitions. Sixteen sources were detected in the NH{3} emission.The detection rate is 46%. All these sixteen sources have NH{3} (1, 1)and (2, 2) emission, among which four sources have NH{3} (3, 3)emission. Comparing with the IRAS and the 2MASS data, we analyzed therelationship between the detection rate and the infrared color, the dusttemperature and the source distance. All the detected sources weremapped and 17 cores were obtained (one source IRAS 20215+3725 has twocores). From the detected sources five cores do not coincide with radiocontinuum or IRAS and MSX point sources. Excluding one core that has noMSX data available, the remaining eleven cores are coincident with IRASor MSX point sources. The typical size and mass of the cores are 1.6 pcand 1.5 × 103 M?, respectively. Theaverage line widths of the NH{3} (1, 1) and (2, 2) are 1.54 and 1.73 kms-1. The average kinetic temperature of the gas is about 19K. These values are much larger than those of low mass cores. The NH{3}cores that coincide with IRAS sources (referred to as Group I) haveslightly larger line widths (1.65 and 1.75 km s-1 for the (1,1) and (2, 2) lines, respectively) and larger masses(1.8×103 M?) than the mean values ofthe sample. For this type of core the kinetic temperature correlateswith the line width. The line width appears to correlate with thebolometric luminosity and the core size. Despite the average luminosityof 2.9×104 L?, there is no detectable 6cm emission. These are candidates for high mass protostars or precursorsof UC HII regions. The NH3 cores with peaks offset from infrared sources(referred to as Group II) have an average size of 1.7 pc and an averageline width of 1.50 km s-1 for the (1, 1) line. The line widthof the (1, 1) emission is smaller than that of the group I. The averagemass is 9.4×102 M?. One possibleexplanation for the deviation is that the NH{3} peak and the infraredsource correspond to different clumps. These cores are potential highmass star formation sites and may be at an earlier evolutionary stagethan those with IRAS point sources. This type of core is seen in mappingobservations, and can be easily missed by single-spectrum observationstoward the IRAS position.
| The Discovery of a Massive SCUBA Core with both Inflow and Outflow Motions
We report the discovery of a massive SCUBA core with evidence of inflowand outflow motions. This core is detected by SCUBA at both 450 and 850?m. Barely resolved by the telescope beam at 450 ?m, it has a sizeof 10", corresponding to 0.28 pc at a distance of 5.7 kpc. The dusttemperature is estimated to be <=29 K, the total mass is 820Msolar, and the average density is 1.1×106cm-3 in a region with a radius of 5". Follow-up spectral lineobservations, including HCN (3-2), HCO+ (3-2),H13CO+ (3-2), and C17O (2-1), reveal atypical blue profile indicating that this core is collapsing. The CO(3-2) line profile is as broad as 38 km s-1, indicatingoutflow motions in this region. This core is approximately 1.5 pc awayfrom the known H II region G25.4NW, but there are no obvious radio,IRAS, MSX, or Spitzer sources associated with it. We suggest that thiscore is at a very early stage of massive star or cluster formation.
| 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.
| Sodium enrichment of the stellar atmospheres. II. Galactic Cepheids
The present paper is a continuation of our study of the sodium abundancein supergiant atmospheres (Andrievsky et al. 2002a). We present theresults on the NLTE abundance determination in Cepheids, and the derivedrelation between the sodium overabundance and their masses.
| New C18O (1-0) emission of massive young stellar objects
Observations of C18O (1-0) line emission toward 74 massive young stellarobjects (YSOs) or its candidates were carried out by using the 13.7mmillimeter wave telescope of Purple Mountain Observatory at the QinghaiStation. 63 observed objects show the C18O (1-0) emission. 57 of themwere first detected in C18O (1-0) lines. According to the line radiationtemperature (TR*) and the line half width (? V), the C18O(1-0) opticaldepths and C18O column densities were derived for all with LTE method.Besides, we discussed the line intensity ratio and integral intensityratio for 13CO(1-0) and C18O (1-0).
| Using Cepheids to determine the galactic abundance gradient. I. The solar neighbourhood
A number of studies of abundance gradients in the galactic disk havebeen performed in recent years. The results obtained are ratherdisparate: from no detectable gradient to a rather significant slope ofabout -0.1 dex kpc-1. The present study concerns theabundance gradient based on the spectroscopic analysis of a sample ofclassical Cepheids. These stars enable one to obtain reliable abundancesof a variety of chemical elements. Additionally, they have welldetermined distances which allow an accurate determination of abundancedistributions in the galactic disc. Using 236 high resolution spectra of77 galactic Cepheids, the radial elemental distribution in the galacticdisc between galactocentric distances in the range 6-11 kpc has beeninvestigated. Gradients for 25 chemical elements (from carbon togadolinium) are derived. The following results were obtained in thisstudy. Almost all investigated elements show rather flat abundancedistributions in the middle part of galactic disc. Typical values foriron-group elements lie within an interval from ~-0.02 to ~-0.04 dexkpc-1 (in particular, for iron we obtainedd[Fe/H]/dRG =-0.029 dex kpc-1). Similar gradientswere also obtained for O, Mg, Al, Si, and Ca. For sulphur we have founda steeper gradient (-0.05 dex kpc-1). For elements from Zr toGd we obtained (within the error bars) a near to zero gradient value.This result is reported for the first time. Those elements whoseabundance is not expected to be altered during the early stellarevolution (e.g. the iron-group elements) show at the solargalactocentric distance [El/H] values which are essentially solar.Therefore, there is no apparent reason to consider our Sun as ametal-rich star. The gradient values obtained in the present studyindicate that the radial abundance distribution within 6-11 kpc is quitehomogeneous, and this result favors a galactic model including a barstructure which may induce radial flows in the disc, and thus may beresponsible for abundance homogenization. Based on spectra collected atMcDonald - USA, SAORAS - Russia, KPNO - USA, CTIO - Chile, MSO -Australia, OHP - France. Full Table 1 is only available in electronicform at http://www.edpsciences.org Table A1 (Appendix) is only, andTable 2 also, available in electronic form at the CDS via anonymous ftpto cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/381/32
| 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.
| A survey of the 6.7 GHz methanol maser emission from IRAS sources. I. Data
We report the first results of a search for 6.7 GHz methanol masers inthe direction of 1399 IRAS objects north of declination-20deg with the flux densities greater than 100 Jy at 60 mu mand the flux density ratio F60/F25>1.Observations were made with the sensitivity of 1.7 Jy and the velocityresolution of 0.04 km s-1 using the 32-m Toruń radiotelescope. Maser emission was found in 182 sources, including 70 newdetections. 32 new sources were identified with objects of radioemission associated with star-forming regions. Comparison of the presentdata set with other observations suggests that about 65% of methanolmasers exhibit moderate or strong variations on time-scales of about 4and 8 years. Table 2 is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Sixth Catalogue of Fundamental Stars (FK6). Part III. Additional fundamental stars with direct solutions
The FK6 is a suitable combination of the results of the HIPPARCOSastrometry satellite with ground-based data, measured over a longinterval of time and summarized mainly in the FK5. Part III of the FK6(abbreviated FK6(III)) contains additional fundamental stars with directsolutions. Such direct solutions are appropriate for single stars or forobjects which can be treated like single stars. Part III of the FK6contains in total 3272 stars. Their ground-based data stem from thebright extension of the FK5 (735 stars), from the catalogue of remainingSup stars (RSup, 732 stars), and from the faint extension of the FK5(1805 stars). From the 3272 stars in Part III, we have selected 1928objects as "astrometrically excellent stars", since their instantaneousproper motions and their mean (time-averaged) ones do not differsignificantly. Hence most of the astrometrically excellent stars arewell-behaving "single-star candidates" with good astrometric data. Thesestars are most suited for high-precision astrometry. On the other hand,354 of the stars in Part III are Δμ binaries in the sense ofWielen et al. (1999). Many of them are newly discovered probablebinaries with no other hitherto known indication of binarity. The FK6gives, besides the classical "single-star mode" solutions (SI mode),other solutions which take into account the fact that hidden astrometricbinaries among "apparently single-stars" introduce sizable "cosmicerrors" into the quasi-instantaneously measured HIPPARCOS proper motionsand positions. The FK6 gives, in addition to the SI mode, the "long-termprediction (LTP) mode" and the "short-term prediction (STP) mode". TheseLTP and STP modes are on average the most precise solutions forapparently single stars, depending on the epoch difference with respectto the HIPPARCOS epoch of about 1991. The typical mean error of anFK6(III) proper motion in the single-star mode is 0.59 mas/year. This isa factor of 1.34 better than the typical HIPPARCOS errors for thesestars of 0.79 mas/year. In the long-term prediction mode, in whichcosmic errors are taken into account, the FK6(III) proper motions have atypical mean error of 0.93 mas/year, which is by a factor of about 2better than the corresponding error for the HIPPARCOS values of 1.83mas/year (cosmic errors included).
| 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 Radial Velocity of Double-mode Cepheid BD -10 4669
We present the first radial velocity measurements of the recentlydiscovered double-mode Cepheid BD
| 6.7 GHz Methanol Masers Associated with IRAS-Selected Sources
New detections of eight 6.7 GHz methanol masers have been made towardthree samples of IRAS-selected objects. Two of the methanol masersources have associated 1.6 GHz hydroxyl masers, and one has anassociated 12.2 GHz methanol maser. The detection rate of the methanolmasers is strongly dependent upon the IRAS colors of the sources. Thisdependence may arise from the conditions required for masing and reflectevolutionary changes in the star-forming regions. The reddest IRASsources are the youngest.
| A catalog of Cepheid radial velocities measured in 1995-1998 with the correlation spectrometer.
Not Available
| Classification and Identification of IRAS Sources with Low-Resolution Spectra
IRAS low-resolution spectra were extracted for 11,224 IRAS sources.These spectra were classified into astrophysical classes, based on thepresence of emission and absorption features and on the shape of thecontinuum. Counterparts of these IRAS sources in existing optical andinfrared catalogs are identified, and their optical spectral types arelisted if they are known. The correlations between thephotospheric/optical and circumstellar/infrared classification arediscussed.
| A survey of star-forming regions in the 5 CM lines of OH.
We have undertaken a comprehensive search for 5 cm OH masers in regionsvisible from Effelsberg with the 100-m telescope (i.e., those withdeclinations above -29^o^). Our sample is based on bright sources takenfrom the IRAS Point Source Catalog and/or from previous 18 cm OH and H_2_O surveys. Among the 165 sources observed, 16 are new (15 exhibitemission and one source shows both absorption and emission). Two newabsorption line sources have been tentatively detected. The generalproperties of the 5 cm OH sources are presented and discussed. The6035MHz line is more often detected than the 6031MHz line. Nevertheless,the latter line is frequently present, a fact that is not explained bypresent OH excitation models. Simple calculations tend to show thatthere are enough FIR photons to pump the 6035 and 6031MHz masers, and wefound that the statistics of the ratio S_ radio_/S_ IR_ at 18, 5 and 6cm suggest that the maser pumping efficiency decreases with increasingOH excitation. Variability on short (months) or long (years) time-scalesis a common feature in many 5 cm OH sources. We also presentobservations of the 6 GHz satellite lines and report, besides W3(OH), ontwo certain and perhaps two newly detected weak sources. Someimplications on the excitation of OH are briefly discussed. Clearly,there is no efficient maser mechanism for the satellite lines. We derivethe percentage of circular polarization in detected 6035 and 6031 MHzemission sources and suggest the identifications of possible Zeemanpatterns. We have found several features having > 90 % polarization.Combining our magnetic field measurements with other published resultswe find that the dominant field alignment is consistent with thedirection of the Galactic rotation. However, there is no convincingcorrelation of the field direction with the Galactic spiral pattern, andit is possible that the field direction is not preserved in the starformation process.
| A catalogue of [Fe/H] determinations: 1996 edition
A fifth Edition of the Catalogue of [Fe/H] determinations is presentedherewith. It contains 5946 determinations for 3247 stars, including 751stars in 84 associations, clusters or galaxies. The literature iscomplete up to December 1995. The 700 bibliographical referencescorrespond to [Fe/H] determinations obtained from high resolutionspectroscopic observations and detailed analyses, most of them carriedout with the help of model-atmospheres. The Catalogue is made up ofthree formatted files: File 1: field stars, File 2: stars in galacticassociations and clusters, and stars in SMC, LMC, M33, File 3: numberedlist of bibliographical references The three files are only available inelectronic form at the Centre de Donnees Stellaires in Strasbourg, viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5), or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The galactic double-mode Cepheids. II. Properties of the generalized phase differences.
By considering the least-squares fits of the double-mode Cepheid lightcurves discussed in Paper I we defined their properties by their Fourierparameters and generalized phase differences G_i,j_. When plotting thelatter quantities as a function of the order, the second order terms areconfined in the region just below 3π/2; the third order terms haveπ/2
| The galactic double-mode Cepheids. I. Frequency analysis of the light curves and comparison with single-mode Cepheids.
We submitted the available photometric V data of all the known galacticDouble Mode Cepheids (DMCs) to a careful frequency analysis with the aimof detecting in each case the importance of the harmonics and of thecross coupling terms. For each object, starting from different datasubsets, we progressively built a homogenous set of data, checking theconsistency of the results step by step. It was demonstrated that eachstar displays a different content, showing that no a priori fit can beapplied. Up to 4 harmonics were found for the fundamental radial mode(F); in every case, 2 harmonics were found for the first overtone radialmode (1O). We also proceeded to a preliminar analysis of the Fourierparameters of the DMC light curves and we found a very close similaritybetween i) the light curves of the classical Cepheids and those of theF-mode of the DMCs; ii) the light curves of the s-Cepheids and those ofthe 1O-mode of the DMCs. The analysis of DMC light curves offers thepossibility of unifying the light curves of classical and s-Cepheids.The case of the unique DMC CO Aur is also discussed.
| Radial Velocity Curves and First Calculations of the Radii for Four Double-mode Cepheids
Not Available
| A catalogue of massive young stellar objects.
A catalogue of massive young stellar objects which contains about 250objects is presented. This catalogue is an updated version of thecatalogue of Henning et al. (1984). It provides comprehensiveinformation on infrared and radio flux densities, molecular line data,association with maser sources, and outflow phenomena.
| A catalog of Cepheid radial velocities measured in 1992-1995 with a correlation spectrometer.
Not Available
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Observation and Astrometry data
| Constellation: | Ασπίς |
| Right ascension: | 18h37m51.11s |
| Declination: | -06°47'48.5" |
| Apparent magnitude: | 7.963 |
| Distance: | 892.857 parsecs |
| Proper motion RA: | 5.1 |
| Proper motion Dec: | 2.8 |
| B-T magnitude: | 9.99 |
| V-T magnitude: | 8.131 |
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