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Observational constraints on s-process nucleosynthesis in massive galactic O-rich AGB stars.
Using high resolution optical spectroscopy (R40,000-50,000) we havederived the Li and Zr abundances of a large sample of galactic O-richAGB stars. Our chemical analysis shows that some stars are Lioverabundant while others are not. The observed Li overabundances areattributed to the activation of the so-called ``hot bottom burning''(HBB) process, confirming that they are actually massive AGB stars.However, these stars do not show the zirconium enhancement (taken as arepresentative for the s-process element enrichment) usually associatedto the third dredge-up. Our study reveals that the s-process elementabundances of the more massive O-rich AGB stars in our Galaxy aredramatically different from those found in the equivalent population ofAGB stars in the Magellanic Clouds. We conclude that probably thedifferent metallicity environment can explain the differences observed.
| The Unusual Silicate Dust around HV 2310, an Evolved Star in the Large Magellanic Cloud
The spectrum of HV 2310, an evolved star in the Large Magellanic Cloud,taken with the Infrared Spectrograph (IRS) on the Spitzer SpaceTelescope, reveals the presence of an optically thin shell of silicatedust with unusual spectral structure in the 10 μm feature: anemission peak at 9.7 μm, a saddle at 10.4 μm, and an extendedshoulder to 11.2 μm. This structure is similar to spectra fromcrystalline silicate grains, and of the available optical constants,forsterite provides the best fit. The spectrum also shows structure at14 μm that may arise from an unidentified dust feature.
| Two Micron All Sky Survey, Infrared Astronomical Satellite, and Midcourse Space Experiment Color Properties of Intrinsic and Extrinsic S Stars
We attempt to select new candidate intrinsic and extrinsic S stars inthe General Catalogue of Galactic S Stars (GCGSS) by combining data fromthe Two Micron All Sky Survey, the Infrared Astronomical Satellite, andthe Midcourse Space Experiment. Catalog entries are cross-identified,yielding 528 objects, out of which 29 are known extrinsic S stars and 31are known intrinsic S stars. Their color-color diagrams,(H-[12])-(K-[12]) and (K-[12])-(J-[25]), are drawn and used to identifya new sample of 147 extrinsic and 256 intrinsic S star candidates, whilethe nature of 65 stars remains identified. We infer that about 38%+/-10%of the GCGSS objects are of extrinsic type. Moreover, we think thatcolors such as J-[25] can be used to split off the two categories of Sstars, while single colors are not appropriate. The color-colordiagrams, such as (H-[12])-(K-[12]) and (K-[12])-(J-[25]), are proven tobe powerful tools for distinguishing the two kinds of S stars.
| Phase Lags in the Optical-Infrared Light Curves of Asymptotic Giant Branch Stars
To search for phase lags in the optical-infrared light curves ofasymptotic giant branch stars, we have compared infrared data from theCOBE DIRBE satellite with optical light curves from the AAVSO and othersources. We found 17 examples of phase lags between the times ofinfrared and optical maximum, and 4 stars with no observed lags. Thereis a clear difference between the Mira variables and the semiregularvariables in the sample, with the maximum in the optical preceding thatin the near-infrared in the Miras, while in most of the semiregularvariables no lags are observed. Comparison to published theoreticalmodels indicates that the phase lags in the Miras are due to strongtitanium oxide absorption in the visual at stellar maximum, and suggeststhat Miras pulsate in the fundamental mode, while at least somesemiregular variables are first-overtone pulsators. There is a clearoptical-near-infrared phase lag in the carbon-rich Mira V CrB; this islikely due to C2 and CN absorption variations in the optical.
| Mass-loss properties of S-stars on the AGB
We have used a detailed non-LTE radiative transfer code to model newAPEX CO(J = 3 → 2) data, and existing CO radio line data, on asample of 40 AGB S-stars. The derived mass-loss-rate distribution has amedian value of 2 × 10-7~Mȯyr-1, and resembles values obtained for similar samples ofM-stars and carbon stars. Possibly, there is a scarcity ofhigh-mass-loss-rate (≥10-5~Mȯyr-1) S-stars. The distribution of envelope gas expansionvelocities is similar to that of the M-stars, the median is 7.5 kms-1, while the carbon stars, in general, have higher gasexpansion velocities. The mass-loss rate correlates well with the gasexpansion velocity, in accordance with results for M-stars and carbonstars.
| Forty Years of Spectroscopic Stellar Astrophysics in Japan
The development of Japanese spectroscopic stellar astrophysics in therecent 40 years is reviewed from an observational point of view. In thisarticle, the research activities are provisionally divided into fourfields: hot stars, hot emission-line (Be) stars, cool stars, and otherstars. Historical developments of the observational facilities atOkayama Astrophysical Observatory (spectrographs and detectors) are alsosummarized in connection with the progress in scientific researchactivities.
| Oscillator strength calculations in neutral technetium
Ab initio multiconfiguration calculations are performed for theoscillator strengths of the λ= 4238, 4262 and 4297 ÅTcIresonance lines of astrophysical interest. Electron correlation istreated through multiconfiguration expansions built from elaboratecorrelation models, while relativistic effects are introduced in theperturbation Breit-Pauli approximation or in the multiconfigurationDirac-Fock-Breit variational approach. The calculated gf-values aresensitively lower (~30 per cent) than the values obtained with thepseudo-relativistic Hartree-Fock wavefunctions calculated from aparametric analysis of TcI by Palmeri & Wyart. The inclusion of acore-polarization potential in the latter approach confirms the presentab initio results when different ionic cores are used for the differenttransition arrays. The strong lines of TcI are revisited adopting thismodel, giving rise to a systematic reduction in the oscillator strengthscale due to core polarization. The astrophysical implications arediscussed.
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| Diameters of Mira Stars Measured Simultaneously in the J, H, and K' Near-Infrared Bands
We present the first spatially resolved observations of a sample of 23Mira stars simultaneously measured in the near-infrared J, H, and K'bands. The technique used was optical long-baseline interferometry, andwe present for each star visibility amplitude measurements as a functionof wavelength. We also present characteristic sizes at each spectralband, obtained by fitting the measured visibilities to a simple uniformdisk model. This approach reveals the general relation J diameter < Hdiameter < K' diameter.
| Secular Evolution in Mira Variable Pulsations
Stellar evolution theory predicts that asymptotic giant branch (AGB)stars undergo a series of short thermal pulses that significantly changetheir luminosity and mass on timescales of hundreds to thousands ofyears. These pulses are confirmed observationally by the existence ofthe short-lived radioisotope technetium in the spectra of some of thesestars, but other observational consequences of thermal pulses are subtleand may only be detected over many years of observations. Secularchanges in these stars resulting from thermal pulses can be detected asmeasurable changes in period if the star is undergoing Mira pulsations.It is known that a small fraction of Mira variables exhibit largesecular period changes, and the detection of these changes among alarger sample of stars could therefore be useful in evolutionary studiesof these stars. The American Association of Variable Star Observers(AAVSO) International Database currently contains visual data for over1500 Mira variables. Light curves for these stars span nearly a centuryin some cases, making it possible to study the secular evolution of thepulsation behavior on these timescales. In this paper we present theresults of our study of period change in 547 Mira variables using datafrom the AAVSO. We use wavelet analysis to measure the period changes inindividual Mira stars over the span of available data. By making linearfits to the period versus time measurements, we determine the averagerates of period change, dlnP/dt, for each of these stars. We findnonzero dlnP/dt at the 2 σ significance level in 57 of the 547stars, at the 3 σ level in 21 stars, and at the level of 6 σor greater in eight stars. The latter eight stars have been previouslynoted in the literature, and our derived rates of period change largelyagree with published values. The largest and most statisticallysignificant dlnP/dt are consistent with the rates of period changeexpected during thermal pulses on the AGB. A number of other starsexhibit nonmonotonic period change on decades-long timescales, the causeof which is not yet known. In the majority of stars, the periodvariations are smaller than our detection threshold, meaning theavailable data are not sufficient to unambiguously measure slowevolutionary changes in the pulsation period. It is unlikely that morestars with large period changes will be found among heretoforewell-observed Mira stars in the short term, but continued monitoring ofthese and other Mira stars may reveal new and serendipitous candidatesin the future.
| 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
| The analysis of indexed astronomical time series - IX. A period change test
A frequency domain test statistic is applied to the full time series ofbrightness maxima and minima in order to test for changes in the meanpulsation periods of 382 Mira stars. The test statistic depends on twoparameters that are related to the intrinsic cycle-to-cycle scatter inthe period, and to the measurement error, respectively. It is shown thatthe former is strongly related to the mean pulsation period of the star.
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| The Indo-US Library of Coudé Feed Stellar Spectra
We have obtained spectra for 1273 stars using the 0.9 m coudéfeed telescope at Kitt Peak National Observatory. This telescope feedsthe coudé spectrograph of the 2.1 m telescope. The spectra havebeen obtained with the no. 5 camera of the coudé spectrograph anda Loral 3K×1K CCD. Two gratings have been used to provide spectralcoverage from 3460 to 9464 Å, at a resolution of ~1 Å FWHMand at an original dispersion of 0.44 Å pixel-1. For885 stars we have complete spectra over the entire 3460 to 9464 Åwavelength region (neglecting small gaps of less than 50 Å), andpartial spectral coverage for the remaining stars. The 1273 stars havebeen selected to provide broad coverage of the atmospheric parametersTeff, logg, and [Fe/H], as well as spectral type. The goal ofthe project is to provide a comprehensive library of stellar spectra foruse in the automated classification of stellar and galaxy spectra and ingalaxy population synthesis. In this paper we discuss thecharacteristics of the spectral library, viz., details of theobservations, data reduction procedures, and selection of stars. We alsopresent a few illustrations of the quality and information available inthe spectra. The first version of the complete spectral library is nowpublicly available from the National Optical Astronomy Observatory(NOAO) via ftp and http.
| VLBA observations of SiO masers towards Mira variable stars
We present new total intensity and linear polarization VLBA observationsof the ν=2 and ν=1 J=1-0 maser transitions of SiO at 42.8 and 43.1GHz in a number of Mira variable stars over a substantial fraction oftheir pulsation periods. These observations were part of an observingprogram that also includes interferometric measurements at 2.2 and 3.6micron \citep{Mennesson2002}; comparison of the results from differentwavelengths allows studying the envelope independently of the poorlyknown distances to these stars. Nine stars were observed at from one tofour epochs during 2001. The SiO emission is largely confined to ringswhich are smaller than the inner radius of the dust shells reported by\citet{Danchi1994}. Two stars (U Orionis, R Aquarii) have maser ringswith diameters corresponding to the size of the hot molecular layer asmeasured at 3.6 micron; in the other cases, the SiO rings aresubstantially larger. Variations of ring diameter for most, but not allstars, had an rms amplitude in agreement with the models of\citet{Humphreys2002} although the expected relationship between thediameter and pulsation phase was not seen. The ring diameter in UOrionis shows remarkably small variation. A correlation between the2.2/3.6 μm diameter ratio with that of the SiO/3.6 μm diameterratio is likely due to differences in the opacities at 2.2 and 3.6 μmin a molecular layer. A further correlation with the inner size of thedust shell reported by \citet{Danchi1994} suggest some differences inthe temperature structure. Clear evidence is seen in R Aquarii for anequatorial disk similar to that reported by \citet{Hollis2001}; rotationis possibly also detected in S Coronae Boralis.
| 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.
| Infrared investigation from earth and space on the evolutionary state of a sample of LPV
We selected a sample of highly reddened AGB stars among the sourcesobserved with the SWS instrument on the ISO satellite. These SWS dataallow us to compute the source's photometry in the mid-IR filters of thecamera TIRCAM at the TIRGO telescope. Our photometric data, supplementedwith other measurements taken from the literature, permit to select thecarbon-rich sources in the sample. For these stars, a linear relationholds between dust mass loss and the color index [8.8]-[12.5]. One maythen, from photometric data alone, evaluate the total mass loss (forwhich we used the estimate of \citet{loup}, based on radio data). Theoxygen-rich sources, on the other hand, are distributed in two branches,of which the upper one appears superimposed with carbon stars; the starsin this group have both high luminosity and high wind velocity andtherefore higher masses. Finally S stars lie between the carbon-starbranch and the low-mass oxygen-rich stars, in agreement with theirintermediate evolutionary status.
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| Guilt by Association: The 13 Micron Dust Emission Feature and Its Correlation to Other Gas and Dust Features
A study of all full-scan spectra of optically thin oxygen-richcircumstellar dust shells in the database produced by the ShortWavelength Spectrometer on ISO reveals that the strength of severalinfrared spectral features correlates with the strength of the 13 μmdust feature. These correlated features include dust features at 19.8and 28.1 μm and the bands produced by warm carbon dioxide molecules(the strongest of which are at 13.9, 15.0, and 16.2 μm). The databasedoes not provide any evidence for a correlation of the 13 μm featurewith a dust feature at 32 μm, and it is more likely that a weakemission feature at 16.8 μm arises from carbon dioxide gas ratherthan dust. The correlated dust features at 13, 20, and 28 μm tend tobe stronger with respect to the total dust emission in semiregular andirregular variables associated with the asymptotic giant branch than inMira variables or supergiants. This family of dust features also tendsto be stronger in systems with lower infrared excesses and thus lowermass-loss rates. We hypothesize that the dust features arise fromcrystalline forms of alumina (13 μm) and silicates (20 and 28 μm).Based on observations with the ISO, a European Space Agency (ESA)project with instruments funded by ESA member states (especially thePrincipal Investigator countries: France, Germany, the Netherlands, andthe United Kingdom) and with the participation of the Institute of Spaceand Astronautical Science (ISAS) and the National Aeronautics and SpaceAdministration (NASA).
| 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.
| How many Hipparcos Variability-Induced Movers are genuine binaries?
Hipparcos observations of some variable stars, and especially oflong-period (e.g. Mira) variables, reveal a motion of the photocentercorrelated with the brightness variation (variability-induced mover -VIM), suggesting the presence of a binary companion. A re-analysis ofthe Hipparcos photometric and astrometric data does not confirm the VIMsolution for 62 among the 288 VIM objects (21%) in the Hipparcoscatalogue. Most of these 288 VIMs are long-period (e.g. Mira) variables(LPV). The effect of a revised chromaticity correction, which accountsfor the color variations along the light cycle, was then investigated.It is based on ``instantaneous'' V-I color indices derived fromHipparcos and Tycho-2 epoch photometry. Among the 188 LPVs flagged asVIM in the Hipparcos catalogue, 89 (47%) are not confirmed as VIM afterthis improved chromaticity correction is applied. This dramatic decreasein the number of VIM solutions is not surprising, since the chromaticitycorrection applied by the Hipparcos reduction consortia was based on afixed V-I color. Astrophysical considerations lead us to adopt a morestringent criterion for accepting a VIM solution (first-kind risk of0.27% instead of 10% as in the Hipparcos catalogue). With this moresevere criterion, only 27 LPV stars remain VIM, thus rejecting 161 ofthe 188 (86%) of the LPVs defined as VIMs in the Hipparcos catalogue.Based on observations from the Hipparcos astrometric satellite operatedby the European Space Agency (ESA 1997).Table 1 is also 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/399/1167
| 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
| Mira Variables explained by a planetary companion interaction: A means to drop the pulsation paradigm?
We emphasize the limits of the classical paradigm explaining theperiodic appearance of emission lines by shock waves induced by radialperiodic pulsations. In particular, we argue that, if pulsation occurs,it would not be purely radial and the light curve resulting from thecontribution of zones at different phases would have a shape differentfrom what we actually observe. The discovery of low mass companions tonumerous G stars, some of them very close to the star, led us to look atthe fate and the influence of this companion when the star becomes agiant. After Rudnitskij (\cite{rudnitskij}), we suggest that thebehavior of the Mira variables is mainly due to the presence of acompanion in the tenuous atmosphere of the giant instead of the effectof a pulsating atmosphere explaining the presence of emission lines andthe periodicity of these variables. We argue that the presence of acompanion may account for the shape of the light curve and the observedphase lag between the maximum visual and the maximum maser light.
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| High Angular Resolution Observations of Late-Type Stars
This paper presents speckle observations of Mira (o Cet) and late-typestars with the PISCO speckle camera of Pic du Midi during the period1995-1998. A survey for binarity among a sample of late-type stars wasperformed, which led to seven positive detections out of 36 objects.Photometric and color variations of the companion of Mira were searchedfor, but no significant brightness variations could be found over atimescale of ~5-10 minutes. The position and photometry measurements,the restored images with high angular resolution of the binary systemMira A-B (ADS 1778) are in full agreement with Hubble Space Telescopedata obtained at the same epoch. A new orbit has been derived for MiraA-B.
| Period-doubling events in the light curve of R Cygni: Evidence for chaotic behaviour
A detailed analysis of the century long visual light curve of thelong-period Mira star R Cygni is presented and discussed. The data werecollected from the publicly available databases of the AFOEV, the BAAVSSand the VSOLJ. The full light curve consists of 26655 individual pointsobtained between 1901 and 2001. The light curve and its periodicity wereanalysed with help of the O-C diagram, Fourier analysis andtime-frequency analysis. The results demonstrate the limitations ofthese linear methods. The next step was to investigate the possiblepresence of low-dimensional chaos in the light curve. For this, asmoothed and noise-filtered signal was created from the averaged dataand with the help of time delay embedding, we have tried to reconstructthe attractor of the system. The main result is that R Cygni shows suchperiod-doubling events that can be interpreted as being caused by arepetitive bifurcation of the chaotic attractor between a period 2Torbit and chaos. The switch between these two states occurs in a certaincompact region of the phase space, where the light curve ischaracterized by ~ 1500-day long transients. The Lyapunov spectrum wascomputed for various embedding parameters confirming the chaoticattractor, although the exponents suffer from quite high uncertaintybecause of the applied approximation. Finally, the light curve iscompared with a simple one zone model generated by a third-orderdifferential equation which exhibits well-expressed period-doublingbifurcation. The strong resemblance is another argument for chaoticbehaviour. Further studies should address the problem of global flowreconstruction, including the determination of the accurate Lyapunovexponents and dimension.
| Near-infrared observations of candidate extrinsic S stars
Photometric observations in the near infrared for 161 S stars, including18 Tc-rich (intrinsic) stars, 19 Tc-deficient (extrinsic) ones and 124candidates for Tc-deficient S stars, are presented in this paper. Basedon some further investigations into the infrared properties of bothTc-rich and Tc-deficient S stars, 104 candidates are identified as verylikely Tc-deficient S stars. The large number of infrared-selectedTc-deficient S stars provides a convenient way to study the physicalproperties and the evolutionary status of this species of S stars.
| 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.
| CO 1st overtone spectra of cool evolved stars: Diagnostics for hydrodynamic atmosphere models
We present spectra covering the wavelength range 2.28 to 2.36 mu m at aresolution of Delta lambda = 0.0007 mu m (or R = 3500) for a sample of24 cool evolved stars. The sample comprises 8 M supergiants, 5 M giants,3 S stars, 6 carbon stars, and 2 RV Tauri variables. The wavelengthscovered include the main parts of the 12C16O v =2-0 and 3-1 overtone bands, as well as the v = 4-2 and 13CO v= 2-0 bandhead regions. CO lines dominate the spectrum for all the starsobserved, and at this resolution most of the observed features can beidentified with individual CO R- or P-branch lines or blends. Theobserved transitions arise from a wide range of energy levels extendingfrom the ground state to E/k > 20 000 K. We looked for correlationsbetween the intensities of various CO absorption line features and otherstellar properties, including IR colors and mass loss rates. Two usefulCO line features are the v = 2-0 R14 line, and the CO v = 2-0 bandhead.The intensity of the 2-0 bandhead shows a trend with K-[12] color suchthat the reddest stars (K-[12] > 3 mag) exhibit a wide range in 2-0bandhead depth, while the least reddened have the deepest 2-0 bandheads,with a small range of variation from star to star. Gas mass loss ratesfor both the AGB stars and the red supergiants in our sample correlatewith the K-[12] color, consistent with other studies. The data implythat stars with dot M_gas < 5x 10-7 Msuny-1 exhibit a much narrower range in the relative strengthsof CO 2-0 band features than stars with higher mass loss rates. Therange in observed spectral properties implies that there are significantdifferences in atmospheric structure among the stars in this sample.Figures 4-9, 11-14, 16, 17, 19-21, 23, 24 are only avalaible inelectronic form at http://www.edpsciences.org
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