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Pulkovo compilation of radial velocities for 35495 stars in a common system.
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| CHARM2: An updated Catalog of High Angular Resolution Measurements
We present an update of the Catalog of High Angular ResolutionMeasurements (CHARM, Richichi & Percheron \cite{CHARM}, A&A,386, 492), which includes results available until July 2004. CHARM2 is acompilation of direct measurements by high angular resolution methods,as well as indirect estimates of stellar diameters. Its main goal is toprovide a reference list of sources which can be used for calibrationand verification observations with long-baseline optical and near-IRinterferometers. Single and binary stars are included, as are complexobjects from circumstellar shells to extragalactic sources. The presentupdate provides an increase of almost a factor of two over the previousedition. Additionally, it includes several corrections and improvements,as well as a cross-check with the valuable public release observationsof the ESO Very Large Telescope Interferometer (VLTI). A total of 8231entries for 3238 unique sources are now present in CHARM2. Thisrepresents an increase of a factor of 3.4 and 2.0, respectively, overthe contents of the previous version of CHARM.The catalog is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/431/773
| Automated Classification of 2000 Bright IRAS Sources
An artificial neural network (ANN) scheme has been employed that uses asupervised back-propagation algorithm to classify 2000 bright sourcesfrom the Calgary database of Infrared Astronomical Satellite (IRAS)spectra in the region 8-23 μm. The database has been classified into17 predefined classes based on the spectral morphology. We have beenable to classify over 80% of the sources correctly in the firstinstance. The speed and robustness of the scheme will allow us toclassify the whole of the Low Resolution Spectrometer database,containing more than 50,000 sources, in the near future.
| Mass-loss from dusty, low outflow-velocity AGB stars. I. Wind structure and mass-loss rates
We present the first results of a CO(2-1), (1-0), and 86 GHz SiO masersurvey of AGB stars, selected by their weak near-infrared excess. Amongthe 65 sources of the present sample we find 10 objects with low COoutflow velocities, vexp <~ 5 km s-1.Typically, these sources show (much) wider SiO maser features.Additionally, we get 5 sources with composite CO line profiles, i.e. anarrow feature is superimposed on a broader one, where both componentsare centered at the same stellar velocity. The gas mass-loss rates,outflow velocities and velocity structures suggested by these lineprofiles are compared with the results of hydrodynamical modelcalculations for dust forming molecular winds of pulsating AGB stars.The observations presented here give support to our recent lowoutflow-velocity models, in which only small amounts of dust are formed.Therefore, the wind generation in these models is dominated by stellarpulsation. We interpret the composite line profiles in terms ofsuccessive winds with different characteristics. Our hydrodynamicalmodels, which show that the wind properties may be extremely sensitiveto the stellar parameters, support such a scenario.Based on observations obtained at the European Southern Observatory, LaSilla, Chile and at the IRAM, Pico Veleta, Spain.
| Infrared Colors and Variability of Evolved Stars from COBE DIRBE Data
For a complete 12 μm flux-limited sample of 207 IRAS sources(F12>=150 Jy, |b|>=5deg), the majority ofwhich are AGB stars (~87%), we have extracted light curves in seveninfrared bands between 1.25 and 60 μm using the database of theDiffuse Infrared Background Experiment (DIRBE) instrument on the CosmicBackground Explorer (COBE) satellite. Using previous infrared surveys,we filtered these light curves to remove data points affected by nearbycompanions and obtained time-averaged flux densities and infraredcolors, as well as estimates of their variability at each wavelength. Inthe time-averaged DIRBE color-color plots, we find clear segregation ofsemiregulars, Mira variables, carbon stars, OH/IR stars, and red giantswithout circumstellar dust (i.e., V-[12]<5) and with little or novisual variation (ΔV<0.1 mag). The DIRBE 1.25-25 μm colorsbecome progressively redder and the variability in the DIRBE databaseincreases along the oxygen-rich sequence nondusty slightly varying redgiants-->SRb/Lb-->SRa-->Mira-->OH/IR and the carbon-richSRb/Lb-->Mira sequence. This supports previous assertions that theseare evolutionary sequences involving the continued production andejection of dust. The carbon stars are redder than their oxygen-richcounterparts for the same variability type, except in theF12/F25 ratio, where they are bluer. Of the 28sources in the sample not previous noted to be variable, 18 are clearlyvariable in the DIRBE data, with amplitudes of variation of ~0.9 mag at4.9 μm and ~0.6 mag at 12 μm, consistent with them being verydusty Mira-like variables. We also present individual DIRBE light curvesof a few selected stars. The DIRBE light curves of the semiregularvariable L2 Pup are particularly remarkable. The maxima at1.25, 2.2, and 3.5 μm occur 10-20 days before those at 4.9 and 12μm, and, at 4.9 and 12 μm, another maximum is seen between the twonear-infrared maxima.
| Hipparcos red stars in the HpV_T2 and V I_C systems
For Hipparcos M, S, and C spectral type stars, we provide calibratedinstantaneous (epoch) Cousins V - I color indices using newly derivedHpV_T2 photometry. Three new sets of ground-based Cousins V I data havebeen obtained for more than 170 carbon and red M giants. These datasetsin combination with the published sources of V I photometry served toobtain the calibration curves linking Hipparcos/Tycho Hp-V_T2 with theCousins V - I index. In total, 321 carbon stars and 4464 M- and S-typestars have new V - I indices. The standard error of the mean V - I isabout 0.1 mag or better down to Hp~9 although it deteriorates rapidly atfainter magnitudes. These V - I indices can be used to verify thepublished Hipparcos V - I color indices. Thus, we have identified ahandful of new cases where, instead of the real target, a random fieldstar has been observed. A considerable fraction of the DMSA/C and DMSA/Vsolutions for red stars appear not to be warranted. Most likely suchspurious solutions may originate from usage of a heavily biased color inthe astrometric processing.Based on observations from the Hipparcos astrometric satellite operatedby the European Space Agency (ESA 1997).}\fnmsep\thanks{Table 7 is onlyavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/397/997
| CHARM: A Catalog of High Angular Resolution Measurements
The Catalog of High Angular Resolution Measurements (CHARM) includesmost of the measurements obtained by the techniques of lunaroccultations and long-baseline interferometry at visual and infraredwavelengths, which have appeared in the literature or have otherwisebeen made public until mid-2001. A total of 2432 measurements of 1625sources are included, along with extensive auxiliary information. Inparticular, visual and infrared photometry is included for almost allthe sources. This has been partly extracted from currently availablecatalogs, and partly obtained specifically for CHARM. The main aim is toprovide a compilation of sources which could be used as calibrators orfor science verification purposes by the new generation of largeground-based facilities such as the ESO Very Large Interferometer andthe Keck Interferometer. The Catalog is available in electronic form atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/386/492, and from theauthors on CD-Rom.
| Long period variable stars: galactic populations and infrared luminosity calibrations
In this paper HIPPARCOS astrometric and kinematic data are used tocalibrate both infrared luminosities and kinematical parameters of LongPeriod Variable stars (LPVs). Individual absolute K and IRAS 12 and 25luminosities of 800 LPVs are determined and made available in electronicform. The estimated mean kinematics is analyzed in terms of galacticpopulations. LPVs are found to belong to galactic populations rangingfrom the thin disk to the extended disk. An age range and a lower limitof the initial mass is given for stars of each population. A differenceof 1.3 mag in K for the upper limit of the Asymptotic Giant Branch isfound between the disk and old disk galactic populations, confirming itsdependence on the mass in the main sequence. LPVs with a thin envelopeare distinguished using the estimated mean IRAS luminosities. The levelof attraction (in the classification sense) of each group for the usualclassifying parameters of LPVs (variability and spectral types) isexamined. Table 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/cgi-bin/qcat?J/A+A/374/968 or via ASTRIDdatabase (http://astrid.graal.univ-montp2.fr).
| Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
| Stars with the Largest Hipparcos Photometric Amplitudes
A list of the 2027 stars that have the largest photometric amplitudes inHipparcos Photometry shows that most variable stars are all Miras. Thepercentage of variable types change as a function of amplitude. Thiscompilation should also be of value to photometrists looking forrelatively unstudied, but large amplitude stars.
| Period-Luminosity-Colour distribution and classification of Galactic oxygen-rich LPVs. I. Luminosity calibrations
The absolute K magnitudes and kinematic parameters of about 350oxygen-rich Long-Period Variable stars are calibrated, by means of anup-to-date maximum-likelihood method, using Hipparcos parallaxes andproper motions together with radial velocities and, as additional data,periods and V-K colour indices. Four groups, differing by theirkinematics and mean magnitudes, are found. For each of them, we alsoobtain the distributions of magnitude, period and de-reddened colour ofthe base population, as well as de-biased period-luminosity-colourrelations and their two-dimensional projections. The SRa semiregulars donot seem to constitute a separate class of LPVs. The SRb appear tobelong to two populations of different ages. In a PL diagram, theyconstitute two evolutionary sequences towards the Mira stage. The Mirasof the disk appear to pulsate on a lower-order mode. The slopes of theirde-biased PL and PC relations are found to be very different from theones of the Oxygen Miras of the LMC. This suggests that a significantnumber of so-called Miras of the LMC are misclassified. This alsosuggests that the Miras of the LMC do not constitute a homogeneousgroup, but include a significant proportion of metal-deficient stars,suggesting a relatively smooth star formation history. As a consequence,one may not trivially transpose the LMC period-luminosity relation fromone galaxy to the other Based on data from the Hipparcos astrometrysatellite. Appendix B is only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| A search for Technetium in semiregular variables
We searched for the lines of Tc in the spectra of Semiregular variables(SRVs) in the wavelength region from 4180 to 4300 Å using highresolution spectroscopy. Tc as an s-process element is produced on thethermally pulsing AGB and is therefore a good indicator for theevolutionary status of Semiregular variables. Combining our results withprevious investigations we get a database large enough for a statisticalstudy. Tc is not found in SRVs with periods below 100 days, spectraltypes earlier than M5 and photospheric IRAS colours. These objects are`blue' SRVs in the classification system of Kerschbaum & Hron(\cite{KH94}). Among the `red' SRVs (periods longer than 100 days) thefraction of stars showing Tc in their spectra is about 15 % with aprobably lower fraction among the stars with periods above 150 days.This is significantly lower than for the typical Miras. Taking intoaccount the probable conditions for the occurence of the third dredge-upand the expected behavior of the Tc abundance along an evolutionarytrack on the AGB, our results support an evolutionary scenario from`blue' SRVs (early AGB) to `red' SRVs (early TP-AGB) and on to longperiod Miras. Only the most massive (masses above 2M_ȯ) stars showTc during the SRV stage. The luminosities of the Tc-rich SRVs and Mirasare compatible with theoretical estimates of the minimum core massrequired for the third dredge-up. Based on observations collected at theEuropean Southern Observatory, La Silla, Chile (ESO No.54.E-0350), theGerman Spanish Astronomical Centre, Calar Alto, operated by theMax-Planck-Institute for Astronomy, Heidelberg, jointly with the SpanishNational Commission for Astronomy, and Kitt Peak National Observatory,USA.
| A homogeneous temperature calibration for K and M giants with an extension to the coolest stars
In this paper we present a new estimate of the effective temperatures of32 giant stars in the spectral range K0 to M10. The sample includes also4 Mira stars. The temperatures are based on a homogeneous set of angulardiameters obtained by our group by the technique of lunar occultations,and using a photometric and spectroscopic coverage with a combination oforiginal measurements and literature data. Most of this basic materialhad been presented in previous papers, but in the present work we deriveimproved effective temperatures by using for the first time a grid ofnumerical center-to-limb darkening models. We use this revision toderive a new calibration of the effective temperature of K and M giantstars, which has the advantage of being based on only one, highlyhomogeneous set of data (while previous calibrations often used mixeddata sets). The resulting calibration is extended to the coolest stars,reaching for the first time M9 for the non-Mira stars, and M10 for theMira stars. In this latter case the calibration does not account forpulsation phase variations and is only tentative. In the region ofoverlap with previously existing calibrations, we find a largelysatisfactory agreement, although some differences exist and arediscussed. In particular, it appears that the calibration of theeffective temperature of cool Mira stars requires additionalobservational as well as theoretical effort. Seven of the stars in oursample appear to exhibit an effective temperature that departssignificantly from the mean relation (~ 900 K cooler between K1 and M8),and no simple explanation in terms of possible bias or experimentalerror could be found. Based on observations collected at TIRGO(Gornergrat, Switzerland), at Calar Alto (Spain) and at the EuropeanSouthern Observatory in La Silla (Chile). TIRGO is operated by CNR --CAISMI Arcetri, Italy. Calar Alto is operated by the German-SpanishAstronomical Center.
| The Infrared Spectral Classification of Oxygen-rich Dust Shells
This paper presents infrared spectral classifications for a flux-limitedsample of 635 optically identified oxygen-rich variables includingsupergiants and sources on the asymptotic giant branch (AGB). Severalclasses of spectra from oxygen-rich dust exist, and these can bearranged in a smoothly varying sequence of spectral shapes known as thesilicate dust sequence. Classification based on this sequence revealsseveral dependencies of the dust emission on the properties of thecentral star. Nearly all S stars show broad emission features fromalumina dust, while most of the supergiants exhibit classic featuresfrom amorphous silicate dust. Mira variables with symmetric light curvesgenerally show broad alumina emission, while those with more asymmetriclight curves show classic silicate emission. These differences may arisefrom differences in the photospheric C/O ratio.
| Radii and effective temperatures for K and M giants and supergiants. II.
Not Available
| Circumstellar Shells of the Mass-Losing Asymptotic Giant Branch Stars: Limits for the Dust-Driven Winds
We investigated whether the radiation pressure on dust grains alone mayaccount for driving winds in semiregular, irregular and non-variable AGBstars. A simple theoretical model is employed to calculate the limitsfor the radiatively driven winds and to compare theoretical predictionswith observations. Present analysis indicates, that for most of theobjects in the studied sample of 67 oxygen-rich and 40 carbon-richmass-losing AGB stars radiation pressure on dust grains alone is noteffective enough to drive the observed circumstellar outflows.
| HIPPARCOS Astrometry of Infrared-Selected Sources and the Connection Between Optical and Infrared Reference Frames
Astrometric data from the Hipparcos satellite are reported for theoptical counterparts of 87 bright infrared sources. These sources may beuseful in defining a reference frame for infrared observations. The dataare also useful in studying the locations of circumstellar SiO masers.(SECTION: Stars)
| 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 Renewed Search for Water Maser Emission from Mira Variables.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1997AJ....114.1602L&db_key=AST
| Semiregular variables of types SRa and SRb. Silicate dust emission features.
We have analysed the IRAS-LRS spectra of representative samples ofO-rich Semiregular (SR) variables of types SRa and SRb and of Miravariables. The silicate features were extracted by fitting the energydistribution with two blackbodies, approximating the continuous emissionfrom the photosphere and the circumstellar dust. The shape and strengthof the silicate features in the LRS range were then studied by computingthe residual fluxes in 5 selected wavelength regions covering the whole10μm and 18μm features and parts of the 10μm feature assignedto emission from olivine and possibly corundum. We compare our approachwith previous investigations and argue that a quantitative study ofdetails in the feature shape requires subtraction of the stellar and thedust continuum and the use of flux ratios rather than a discreteclassification system. The Miras form an extension of the SRb's towardslower stellar temperatures and higher dust shell opacities and they haveslightly higher average dust temperatures. The SRa's seem to be moresimilar to the Miras in their dust shell properties. The average 10μmfeature shapes of the three groups of variables agree, but taking intoaccount the photospheric and dust shell parameters, systematicdifferences show up. For stars hotter than about 2900K, the 10μmfeature width shows a wide range of values but no clear trend with thestellar temperature or the optical depth of the dust shell. These starsare generally SRb variables and have the thinnest dust envelopes. Atcooler stellar temperatures, where mostly Miras are found, the opticaldepth of the dust shell determines the feature width in the sense thatthicker shells have narrower features. It appears that the 13μmfeature is obvious only in a narrow range of effective temperature andoptical depth of the dust shell. We discuss our results in terms ofradiative transfer effects, differences in the average grain size,annealing and hydration of amorphous silicates and contributions fromother dust components. Of these possibilities the last one seems to bemost plausible with regard to the behavior of the 10μm feature width.The observations can be interpreted in terms of changing contributionsfrom olivine and corundum possibly caused by an increasing amount ofdust processing (Miras) and the influence of the atmospheric structureon the formation of these dust components (SRb's).
| The TIRGO Lunar Occultation Program: Summary of the 1985-1995 Observations
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....112.2786R&db_key=AST
| Circumstellar dust envelopes of oxygen-rich AGB stars.
Using IRAS observational data, the best-fitting models are searched foroxygen-rich AGB stars in various evolutionary stages from opticallyvisible red giant stars to OH/IR stars with heavy mass loss. The modelinfrared spectral energy distributions of the red giant stars withcircumstellar dust envelopes are calculated with the use of a radiativetransfer code. It is found that the oxygen-rich IRAS AGB starssurrounded by circumstellar dust envelopes are divided into threegroups, which can be clearly distinguished by their mass loss rate andthe grain temperature at the inner boundary of the circumstellar dustenvelopes. One group corresponds to Mira type objects with a moderatemass loss rate and a grain formation temperature of about 500 K, thesecond to OH/IR star type objects with a large mass loss rate and a highgrain formation temperature, and the third to M stars with a very coldgrain temperature at the inner boundary, indicating that the moderatemass loss stopped a considerable time ago in these objects. The highergrain formation temperature of the OH/IR star type objects indicates agrain formation point closer to the stellar surface, suggesting aneffective acceleration of dust grains by radiation pressure. Such aneffective acceleration can play an important role in the mass lossphenomena of OH/IR stars with large mass loss rates. From the modelfitting results, it is suggested that an AGB star undergoes severaldozen phases of moderate mass loss of˙(M)~10^-7^-10^-6^Msun_/yr for a period of10^3^-10^4^years with interruptions of 10^3^-10^4^years during theordinary Mira variable phase before becoming an OH/IR star with a massloss rate exceeding 10^-5^Msun_/yr and a lifetime of about10^3^-10^4^years.
| Circumstellar CO around bright oxygen-rich semi-regulars.
We report high signal to noise millimeter wave observations of 11 nearbySemi-Regular variables, most with periods between 89 and 160 days, inthe transitions ^12^CO (J=2-1) and (J=1-0) and ^13^CO (J=2-1). The lineprofiles have been fitted by a model including molecular excitation andradiative transfer and the derived envelope properties (expansionvelocity, mass loss rate, outer radius, kinetic temperaturedistribution) are compared to the predictions of theoretical models. Themass loss properties of this sample of Semi-Regulars appear to be verysimilar with those of longer period (300<=P<400 days) Miras,observed with the same telescope. This result is consistent with theview that the Semi-Regulars are overtone pulsators while the Miras arein the fundamental pulsational mode. The pulsational mode does notstrongly affect the mass loss from the star.
| Semiregular variables of types SRa and SRb. New JHKL'M-photometry for 200 stars.
This paper presents new JHKL'M observations of 200 Semiregular variables(SRVs) of types SRa and SRb. The sample was defined in Kerschbaum &Hron (1992a, Paper I) by means of a certain limit in bolometricalmagnitude. From the sample of 350 objects, 260 now have near infrared(NIR) photometry - for 60 of these stars data from the literature areused. In total 290 datasets are available because of some multipleobservations. We briefly compare the photometry obtained at differentobservatories. Small but significant differences are found. A firstanalysis of the photometry supports one of the main findings of Paper I.The, in many aspects inhomogeneous, O-rich semiregular variables oftypes SRa and SRb can be successfully split in two subgroups called the`blue' and `red'/`Mira' SRVs. A separation of the `red' SRVs fromintrinsic Miras additionally requires variability information.
| 86 GHz SiO, v=1, J=2--> 1 survey of southern IRAS point sources. II. Detection of 74 new maser sources
The detection of 74 new southern stellar SiO, v=1, J=2->1 masersassociated with IRAS point sources is reported. 57 of these were foundin an IRAS based survey of oxygen rich stellar envelopes. The detectionrate in this survey was 45%. 17 further new maser sources were detectedduring a search for strong pointing sources for the Swedish-ESOSubmillimeter Telescope (SEST). The distribution of the IRAS lowresolution spectral (LRS) classes of all the SiO masers (this paper andliterature) peaks sharply at class 15. The distribution of the LRSclasses of the maser sources from 21 to 29 is similar to thedistribution of these classes of all the point sources in the pointsource catalogue except for class 25. Only few maser sources of thisspectral class are known. This is possibly explained by a selectioneffect.
| Circumstellar shells resolved in the IRAS survey data. I - Data processing procedure, results, and confidence tests
We have examined the IRAS 60 and 100 micron survey data covering 512evolved stars and young planetary nebulae for evidence of spatiallyresolved structure. A simple model, consisting of a central unresolvedsource surrounded by a resolved isothermal shell, was fitted to the datafor each star. Seventy-six stars were found to be resolved in the 60micron data. Tests have been performed to verify that the extendedstructure seen is not an artifact of the data-processing algorithm.
| CO and HCN observations of circumstellar envelopes. A catalogue - Mass loss rates and distributions
We have searched the literature for all observations of the (C-12)O(1-0), (C-12)O (2-1), and HCN (1-0) lines in circumstellar envelopes oflate type stars published between January 1985 and September 1992. Wereport data for 1361 observations (stellar velocity, expansion velocity,peak intensity, integrated area, noise level). This CO-HCN sample nowcontains 444 sources; 184 are identified as O-rich, 205 as C-rich, andthere are 9 S stars. About 85 percent of the sources are AGB stars.There are 32 planetary nebulae and about thirty post-AGB starscandidates. Besides results of mm-observations, we also listidentifications, coordinates, IRAS data, and chemical and spectral typesfor every source. For AGB stars, we have estimated (or compiled)bolometric fluxes and distances for 349 sources, and mass loss ratesdeduced from CO results for 324 sources, taking into account theinfluence of the CO photodissociation radius. We also list mass lossrates derived from detailed models of CO emission in the literature.
| Oxygen-rich semiregular and irregular variables
All the known oxygen-rich semiregulars and irregulars of spectralclasses K and M with the absolute value of B not greater than 30 deg,Delta(m) not less than 0.5 mag, and, for the semiregulars, periods inthe range of 50 to 400 d are compiled. On the basis of theirdistributions on the sky and their brightnesses in the K band at 2.2microns, it is argued that the semiregulars with a period of 300-400 dappear to belong to the same population as the 'thin disk' Miras in thesame period range and have an exponential scale height from the Galacticplane of about 250 pc. The semiregulars with a period range of 200 to300 d belong to the population of the 'thick disk' Miras with anexponential scale height from the Galactic plane of about 500 pc. On thebasis of the similarities of their space distributions and the presenceof Tc in their atmospheres, and using the pulsational mode calculationsby Ostlie and Cox (1986), it is suggested that the semiregulars with aperiod range of 100-150 d are first and second overtone pulsations ofthe same population of AGB stars as the Miras in their fundamentalpulsational mode with periods longer than 300 d.
| Accurate angular diameter and effective temperature of seven late-type stars
We analyze and discuss lunar occultation lightcurves obtained at the 1.5m TIRGO telescope. Angular diameters are reported for seven stars in thespectral range G8-M9; four stars are resolved for the first time.Effective temperatures of the sources are derived from the measuredangular diameters, in conjunction with bolometric fluxes obtained bymeans of photometric measurements complemented by previously availabledata. We discuss in detail the error associated with the angulardiameter values, and remove the bias introduced by atmosphericscintillation. The achieved accuracy, on averages less than 5 percent,makes the present results a valuable check for theoretical models. Wealso compare our diameters with previous occultation and infrared fluxmethod results.
| Near-infrared photometry of a sample of IRAS point sources
This paper presents the J, H, K, L, M photometry of 516 sourcespertaining to a sample of 787 sources which has been extracted from theIRAS Point Source Catalog in order to study the late stages of stellarevolution and the concomitant phenomena of mass loss. Three differentclssifications of these sources based on broad-band photometry and IRASlow-resolution spectra are given, and the distributions of the sourcesin terms of these classifications are presented. A subsample of peculiarsources, believed to have recently undergone a helium flash, has beenisolated using the K - L, (12-micron) color diagram. Some objectsmeriting further study are also mentioned.
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Посматрања и Астрометриски подаци
| Сазвежђа: | Јарац |
| Ректацензија: | 21h07m15.43s |
| Deклинација: | -16°25'21.5" |
| Apparent магнитуда: | 8.364 |
| Даљина: | 10000000 parsecs |
| Proper motion RA: | 2.4 |
| Proper motion Dec: | -30.9 |
| B-T magnitude: | 9.909 |
| V-T magnitude: | 8.492 |
Каталог и designations:
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