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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
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| Technetium and the third dredge up in AGB stars. I. Field stars
We searched for Tc in a sample of long period variables selected bystellar luminosity derived from Hipparcos parallaxes. Tc, as an unstables-process element, is a good indicator for the evolutionary status ofstars on the asymptotic giant branch (AGB). In this paper we study theoccurrence of Tc as a function of luminosity to provide constraints onthe minimum luminosity for the third dredge up as estimated from recentstellar evolution models.A large number of AGB stars above the estimated theoretical limit forthe third dredge up are found not to show Tc. We confirm previousfindings that only a small fraction of the semiregular variables show Tclines in their spectra. Contrary to earlier results by Little et al.(\cite{llmb87}) we find also a significant number of Miras without Tc.The presence and absence of Tc is discussed in relation to the massdistribution of AGB stars. We find that a large fraction of the stars ofour sample must have current masses of less than 1.5 Msun .Combining our findings with stellar evolution scenarios we conclude thatthe fraction of time a star is observed as a SRV or a Mira is dependenton its mass.Partly based on observations collected at the European SouthernObservatory, Paranal, Chile (ESO-Programme 65.L-0317(A)).
| ``Thermal'' SiO radio line emission towards M-type AGB stars: A probe of circumstellar dust formation and dynamics
An extensive radiative transfer analysis of circumstellar SiO``thermal'' radio line emission from a large sample of M-type AGB starshas been performed. The sample contains 18 irregulars of type Lb (IRV),7 and 34 semiregulars of type SRa and SRb (SRV), respectively, and 12Miras. New observational data, which contain spectra of several groundvibrational state SiO rotational lines, are presented. The detectionrate was about 60% (44% for the IRVs, and 68% for the SRVs). SiOfractional abundances have been determined through radiative transfermodelling. The abundance distribution of the IRV/SRV sample has a medianvalue of 6*E-6, and a minimum of 2*E-6 and amaximum of 5*E-5. The high mass-loss rate Miras have a muchlower median abundance, la 10-6. The derived SiO abundancesare in all cases well below the abundance expected from stellaratmosphere equilibrium chemistry, on average by a factor of ten. Inaddition, there is a trend of decreasing SiO abundance with increasingmass-loss rate. This is interpreted in terms of depletion of SiOmolecules by the formation of silicate grains in the circumstellarenvelopes, with an efficiency which is high already at low mass-lossrates and which increases with the mass-loss rate. The high mass-lossrate Miras appear to have a bimodal SiO abundance distribution, a lowabundance group (on average 4*E-7) and a high abundance group(on average 5*E-6). The estimated SiO envelope sizes agreewell with the estimated SiO photodissociation radii using an unshieldedphotodissociation rate of 2.5*E-10 s-1. The SiOand CO radio line profiles differ in shape. In general, the SiO lineprofiles are narrower than the CO line profiles, but they havelow-intensity wings which cover the full velocity range of the CO lineprofile. This is interpreted as partly an effect of selfabsorption inthe SiO lines, and partly (as has been done also by others) as due tothe influence of gas acceleration in the region which produces asignificant fraction of the SiO line emission. Finally, a number ofsources which have peculiar CO line profiles are discussed from thepoint of view of their SiO line properties.Based on observations using the SEST at La Silla, Chile, the 20 mtelescope at Onsala Space Observatory, Sweden, the JCMT on Hawaii, andthe IRAM 30 m telescope at Pico Veleta, Spain.
| 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.
| Long periodic variable stars
The information on Mira-type stars and stars adjacent to them at theHertzsprung -- Russel diagram is presented. A detailed description oftheir observational characteristics is given. We give a survey ofimportant observational works concerning: multicolor photometry withspecial attention to the IR emission, maser emission, shock waves, massloss, binarity, the problem of the pulsational mode, direct measurementsof angular and linear dimensions, statistic investigations, study ofkinematic characteristics etc. The most interesting problems regardinglong periodic variable stars are specified. Some attention is given tothe classification and evolutionary stage of these objects.
| 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
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| Velocity variability of semiregular and irregular variables
We compare velocities from near infrared lines with center-of-massvelocities for a sample of semiregular and irregular variables to searchfor indications for a convective blueshift. It is shown that a generalblueshift is present but that the light variability is obviously notdominated by convective cells but rather by stellar pulsation. All starsof our sample show a similar shape and amplitude in the velocityvariations. Long secondary periods are a common feature in these objectsand strongly influence the measured velocity shifts. The star V366 Aqlis found to be the first SRV showing line doubling.
| Mass loss rates of a sample of irregular and semiregular M-type AGB-variables
We have determined mass loss rates and gas expansion velocities for asample of 69 M-type irregular (IRV 22 objects) and semiregular (SRV; 47objects) AGB-variables using a radiative transfer code to model theircircumstellar CO radio line emission. We believe that this sample isrepresentative for the mass losing stars of this type. The (molecularhydrogen) mass loss rate distribution has a median value of 2.0 x10-7 Msun yr-1, and a minimum of 2.0 x10-8 Msun yr-1 and a maximum of 8 x10-7 Msun yr-1. M-type IRVs and SRVswith a mass loss rate in excess of 5 x 10-7 Msunyr-1 must be very rare, and among these mass losing stars thenumber of sources with mass loss rates below a few 10-8Msun yr-1 must be small. We find no significantdifference between the IRVs and the SRVs in terms of their mass losscharacteristics. Among the SRVs the mass loss rate shows no dependenceon the period. Likewise the mass loss rate shows no correlation with thestellar temperature. The gas expansion velocity distribution has amedian of 7.0 km s-1, and a minimum of 2.2 km s-1and a maximum of 14.4 km s-1. No doubt, these objects samplethe low gas expansion velocity end of AGB winds. The fraction of objectswith low gas expansion velocities is very high, about 30% havevelocities lower than 5 km s-1, and there are objects withvelocities lower than 3 km s-1: V584 Aql,T Ari, BI Car, RXLac, and L2 Pup. The mass loss rate and thegas expansion velocity correlate well, a result in line with theoreticalpredictions for an optically thin, dust-driven wind. In general, themodel produces line profiles which acceptably fit the observed ones. Anexceptional case is R Dor, where the high-quality,observed line profiles are essentially flat-topped, while the model onesare sharply double-peaked. The sample contains four sources withdistinctly double-component CO line profiles, i.e., a narrow featurecentered on a broader feature: EP Aqr, RVBoo, X Her, and SV Psc.We have modelled the two components separately for each star and derivemass loss rates and gas expansion velocities. We have compared theresults of this M-star sample with a similar C-star sample analysed inthe same way. The mass loss rate characteristics are very similar forthe two samples. On the contrary, the gas expansion velocitydistributions are clearly different. In particular, the number oflow-velocity sources is much higher in the M-star sample. We found noexample of the sharply double-peaked CO line profile, which is evidenceof a large, detached CO-shell, among the M-stars. About 10% of theC-stars show this phenomenon.
| 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).
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| 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.
| Hipparcos parallaxes for Mira-like long-period variables
This paper concerns the calibration of the K period-luminosity relationfor Mira variables using Hipparcos parallaxes. K magnitudes areavailable for 255 Mira-like variables which were observed by Hipparcos.Period-luminosity zero-points are evaluated for various subgroups ofdata. The best solution for oxygen-rich Miras, which uses 180 stars,omitting the short-period red group (which had different kinematics fromthe short-period blue stars) and the low-amplitude variables, provides azero-point of σ2σ2π +(0.4605)2π2PL(K)σ2K + σ2PL(K),0.84+/-0.14mag, which implies a distance modulus for the LargeMagellanic Cloud of σK = 0.3ΔK√N,18.64+/-0.14mag, or perhaps slightly greater if a metallicity correctionis required, in good agreement with the value derived from Cepheids. Thezero-point of the period-luminosity relation for carbon stars is brieflydiscussed. Linear diameters are derived for red variables with measuredangular diameters and parallaxes, and are used to examine thelong-standing question of the pulsation mode(s) of these stars. Evidenceis presented to suggest that most of them are pulsating in the same modeand, if published model atmospheres are correct, this is probably thefirst overtone. Some discussion is given of sequences in theperiod-luminosity and period-colour diagrams and their bearing on thepulsation mode problem.
| Infrared colours for Mira-like long-period variables found in the (Mȯ<~10-7 Msolar yr-1) Hipparcos Catalogue
Near-infrared, JHKL, photometry is presented for 193 Mira andsemi-regular variables that were observed by Hipparcos; periods,bolometric magnitudes and amplitudes are derived for 92 of them. Becauseof the way in which the Hipparcos targets were selected, this group ofstars provides a useful data base of Miras with low mass-loss rates(Mȯ<~10-7Msolaryr-1).Various period-colour relationships are discussed in detail. The colour,particularly BCK = 10.86 - 38.10 K (J - K)0 +64.16(J - K)20 - 50.72(J -K)30 + 19, K-L, at a given period is found todepend on the pulsation amplitude of the star. A comparison with modelssuggests that this is a consequence of atmospheric extension, in thesense that large-amplitude pulsators have very extended atmospheres andredder Mȯ<10-7Msolaryr-1, K-L and H-K but bluerJ-H than their lower amplitude counterparts. The stars with veryextended atmospheres also have higher values of K-[12] and hence highermass-loss rates. This finding provides further evidence for the causalconnection between pulsation and mass loss. Two sequences are identifiedin the Hp-K versus logP diagram (where Hp is the Hipparcos broad-bandmagnitude) at short periods (logP<2.35). At a given period these twogroups have, on average, the same pulsation amplitude, but differentJHKL colours and spectral types. The short-period stars in the bluersequence have similar near-infrared colours to the Miras found inglobular clusters. Long-term trends in the infrared light curves arediscussed for stars that have sufficient data.
| Mira kinematics from Hipparcos data: a Galactic bar to beyond the Solar circle
The space motions of Mira variables are derived from radial velocities,Hipparcos proper motions and a period-luminosity relation. Thepreviously known dependence of Mira kinematics on the period ofpulsation is confirmed and refined. In addition, it is found that Miraswith periods in the range 145-200d in the general Solar neighbourhoodhave a net radial outward motion from the Galactic Centre of75+/-18kms-1. This, together with a lag behind the circularvelocity of Galactic rotation of 98+/-19kms-1, is interpretedas evidence for an elongation of their orbits, with their major axesaligned at an angle of ~17° with the Sun-Galactic Centre line,towards positive Galactic longitudes. This concentration seems to be acontinuation to the Solar circle and beyond of the bar-like structure ofthe Galactic bulge, with the orbits of some local Miras probablypenetrating into the bulge. These conclusions are not sensitive to thedistance scale adopted. A further analysis is given of the short-period(SP) red group of Miras discussed in companion papers in this series. InAppendix A the mean radial velocities and other data for 842 oxygen-richMira-like variables are tabulated. These velocities were derived frompublished optical and radio observations.
| Processing of Amateur Observations of Mira-Type Stars from Large Databases: Problems and Results
The problems of finding light curve characteristics of long-periodvariables and methods of light curve fit are discussed. A new``asymptotic parabolae" method is proposed for this task. The catalogueof individual cycle characteristics of LPVs is compiled. The resultsconcerning long-term variability of these stars and their classificationare listed.
| 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.
| Orbiting Molecular Reservoirs around Evolved Red Giant Stars
We report molecular emission from the circumstellar envelopes of twocarbon-rich stars with oxygen-rich envelopes, EU And and BM Gem. We finda narrow (FWHM~5 km s^-1) CO (2-1) emission line from EU And and an evennarrower (FWHM ~ 1 km s^-1) ^13CO emission line from BM Gem. We alsoplace upper limits to the emission of HCN, SiO, SO, HCO^+, and CS fromBM Gem. We argue that the narrow CO emission lines are signatures oflong-lived reservoirs of orbiting gas and that standard models for COemission from red giant winds are not appropriate for these two stars.By including the Red Rectangle and AC Her, narrow CO emissioncharacteristic of gravitationally bound gas has been detected from fourpost-main-sequence systems, and we can begin to characterize theseapparently similar environments. Some common characteristics are thefollowing: (1) Their diameters are typically between ~100 and ~1000 AU.(2) The masses of CO are near 10^27 g. (3) Unlike the envelopes aroundmass-losing carbon stars where M_CO/M_dust~ 2, the circumstellarorbiting reservoirs often appear to have M_CO
| Oxygen-rich semiregular and irregular variables. A catalogue of circumstellar CO observations
Using the SEST, the Onsala 20 m telescope, the JCMT, and the IRAM 30 mtelescope we have carried out a survey of circumstellar CO(J=1-0, 2-1,3-2, and 4-3) emission on a large sample of oxygen-rich semiregular (SRaand SRb) and irregular variables (Lb). A total of 109 stars wereobserved in at least one CO line: 66 were shown to have circumstellar COline emission (7 SRa, 36 SRb, and 23 Lb variables), ~ 60% of thesemiregulars and all but one of the irregulars were detected for thefirst time. Most stars were observed in at least two transitions. Thereis a total of 138 detected CO lines. For twelve stars stronginterference from interstellar CO emission precluded detection. Wepresent here a catalogue of all observational data and the spectra ofall detections, as well as brief discussions on detection statistics(including its dependence on variability type, period, IRAS-colour, IRASLRS-class, and M-subclass), line profiles (including line shapeasymmetry, multi-component line shapes, and line intensity ratios), gasexpansion velocity distributions, and correlations between CO line andIR continuum fluxes (including implications for the mass-lossmechanism). Based on observations collected using at the EuropeanSouthern Observatory, La Silla, Chile, the Onsala Space Observatory,Chalmers Tekniska Högskola, Sweden, the James Clerk MaxwellTelescope, Hawaii and the IRAM 30~m telescope, Pico Veleta, Spain.
| Multiperiodicity in semiregular variables. I. General properties
We present a detailed period analysis for 93 red semiregular variablesby means of Fourier and wavelet analyses of long-term visualobservations carried out by amateur astronomers. The results of thisanalysis yield insights into the mode structure of semiregular variablesand help to clarify the relationship between them and Mira variables.After collecting all available data from various international databases(AFOEV, VSOLJ, HAA/VSS and AAVSO) we test the accuracy and reliabilityof data. We compare the averaged and noise-filtered visual light curveswith simultaneous photoelectric V-measurements, the effect of the lengthversus the relatively low signal-to-noise ratio is illustrated by periodanalysis of artificial data, while binning effects are tested bycomparing results of frequency analyses of the unbinned and averagedlight curves. The overwhelming majority of the stars studied showmultiperiodic behaviour. We found two significant periods in 44variables, while there are definite signs of three periods in 12 stars.29 stars turned out to be monoperiodic with small instabilities in theperiod. Since this study deals with the general trends, we wanted tofind only the most dominant periods. The distribution of periods andperiod ratios is examined through the use of the (log P_0, log P_1) and(log P_1, log P_0/P_1) plots. Three significant and two less obvioussequences are present which could be explained as the direct consequenceof different pulsational modes. This hypothesis is supported by theresults for multiperiodic variables with three periods. Finally, thesespace methods are illustrated by several interesting case studies thatshow the best examples of different special phenomena such as long-termamplitude modulation, amplitude decrease and mode switching.
| 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.
| Are low-order resonances observed in Mira pulsation?
The possibility of a low-order, two-mode resonance in the pulsation ofLPVs is investigated by means of Fourier analysis of lightcurves,supplemented by spectral types and by kinematic population analysisbased on HIPPARCOS astrometric data. The question might be positivelyanswered. Based on data from the HIPPARCOS astrometry satellite.
| Infrared high angular resolution measurements of stellar sources. III. Angular diameters and effective temperatures of eleven late-type giants
Near-infrared lunar occultation observations of eleven late-type giantsin the spectral range K0 to M6 (including one carbon star) are reportedhere. These stars are resolved from our observations carried out at2.2mu m, resulting in accurate determinations of their angular sizes,with values in the range 1.4 to 7.1 milliseconds of arc (mas) and atypical accuracy of 0.12 mas. Nine out of eleven sources are resolvedfor the first time. In addition, near infrared photometric observationsof some of the sources have been carried out to compute stellarbolometric fluxes, and hence derive the effective temperatures. Ouraccurate angular diameter measurements (at least in the case of eightsources) have the potential to provide effective temperatures with anaccuracy less than 3% when bolometric fluxes become available with anaccuracy less than 10%. The observed sources are discussed inconjunction with earlier high angular resolution observations andavailable photometric data. A comparison of the current performance oflunar occultations and long baseline interferometry in the field ofangular diameters and effective temperatures is presented. Based onobservations collected at TIRGO (Gornergrat, Switzerland), at Calar Alto(Spain), and at the European Southern Observatory (La Silla, Chile).TIRGO is operated by CNR-CAISMI Arcetri, Italy. Calar Alto is operatedby the German-Spanish Astronomical Center.
| 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
| Mean light curves of long-period variables and discrimination between carbon- and oxygen-rich stars
Using 75 years of AAVSO data, mean light curve parameters of a sample of355 long period M, S, and C mira and semi-regular variable stars areinvestigated. We present a classification of the light curves of LPVsinto 6 distinct groups. Combining this classification with IRAS colorsmakes it possible to distinguish oxygen-rich from carbon-rich miras.Table 2 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/Abstract.html
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| Vizuális fényesség: | 8.947 |
| Távolság: | 321.543 parszek |
| RA sajátmozgás: | -13.2 |
| Dec sajátmozgás: | -17 |
| B-T magnitude: | 10.705 |
| V-T magnitude: | 9.093 |
Katalógusok és elnevezések:
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