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Red variables in ASAS, part I, 0h - 2h
Based on the rationale outlined by Greaves (2005) the 2MASS survey wasdata-mined for entries that matched the following criteria: dec <0.000 and j_m - k_m >1.2 and vr_m_opt - j_m >6 and j_m <6.00. Atotal of 4,128 stars matched these four criteria. The publicallyavailable ASAS light curves for those matching stars - between 0 and 2hrs in right ascension - are presented.
| 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.
| 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.
| Classification of 2.4-45.2 Micron Spectra from the Infrared Space Observatory Short Wavelength Spectrometer
The Infrared Space Observatory observed over 900 objects with the ShortWavelength Spectrometer in full-grating scan mode (2.4-45.2 μm). Wehave developed a comprehensive system of spectral classification usingthese data. Sources are assigned to groups based on the overall shape ofthe spectral energy distribution (SED). The groups include naked stars,dusty stars, warm dust shells, cool dust shells, very red sources, andsources with emission lines but no detected continuum. These groups arefurther divided into subgroups based on spectral features that shape theSED such as silicate or carbon-rich dust emission, silicate absorption,ice absorption, and fine-structure or recombination lines. Caveatsregarding the data and data reduction, as well as biases intrinsic tothe database, are discussed. We also examine how the subgroups relate tothe evolution of sources to and from the main sequence and how thisclassification scheme relates to previous systems. Based on observationswith the Infrared Space Observatory (ISO), a European Space Agency (ESA)project with instruments funded by ESA Member States (especially thePrinciple Investigator countries: France, Germany, Netherlands, andUnited Kingdom) and with the participation of the Institute of Space andAstronautical Science and the National Aeronautics and SpaceAdministration (NASA).
| 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.
| 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.
| Trend analysis of 51 carbon long-period variables.
Not Available
| CO observations and mass loss of MS- and S-stars
We present (12) CO J = 1-0 and 2-1 observations of 14 S-stars, andreport 6 new detections. Two stars were observed in the (13) CO J = 1-0and 2-1 lines, and one tentative 2-1 detection is reported. Acompilation is presented of all CO observations of S-stars. The stars inthis sample are separated into ``intrinsic'' and ``extrinsic'' S-stars,based on direct observation of the Technetium line, or infraredproperties. The dust mass loss rate per unit distance is derived fromIRAS 60 mu m data taking into the fact that for small mass loss ratesthe observed flux is an overestimate of the excess emission due to dust.The gas mass loss rate per unit distance is derived from CO data.Distances and luminosities are estimated, partly from hipparcos parallaxdata. The largest mass loss rate derived is that for W Aql with(0.8-2.0) x 10(-5) {Msun} yr(-1) , and the lowest is that foro Ori with <1.2 x 10(-9) {Msun} yr(-1) . The S-starswithout Tc have smaller mass loss rates, than those with Tc. Diagramsshowing mass loss rate, dust-to-gas ratio and expansion velocity versuspulsation period are presented, and compared to similar data for carbon-and oxygen-rich Miras. The S-Miras stand not out in any way from the C-or O-Miras in these diagrams. In the diagram with expansion velocityversus pulsation period, the S-SRs span the same range in velocity asthe S-Miras, but they have periods which are about a factor of 2.5shorter. This was previously noted for O-rich SRs. As in that case, themost straightforward explanantion is that the SRs among the S-starspulsate in a higher order pulsation mode. Based on data from the ESAhipparcos astrometry satellite.
| 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.
| First Byurakan spectral sky survey. Stars of late spectral types. IX. -15 deg < delta < -11 deg belt.
Not Available
| Proper motions, absolute magnitudes and spatial distribution of zirconium stars.
Not Available
| 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
| Additional Emission-Line Candidates From the HK Survey
We present a list of 218 additional candidate emission-line objectsdiscovered with the northern and southern HKinterference-filter/objective prism survey of Beers and collaborators.The objects have apparent magnitudes in the range 10 <= B <= 16,several magnitudes fainter than obtained with previous prism surveys ofsimilar resolution. Of the new candidates, 73 have been previouslyidentified. The total list of HK- survey emission-line candidates nownumbers 376 objects, 104 of which were noted by previous surveys.
| A CO(3-2) survey of nearby Mira variables
A survey of CO(3-2) emission from optically visible oxygen-rich Miravariable stars within 500 pc of the Sun was conducted. A molecularenvelope was detected surrounding 36 of the 66 stars examined. Some ofthese stars have lower outflow velocities than any Miras previouslydetected in CO. The average terminal velocity of the ejected materialwas 7.0 km/s, about half the value found in Miras selected by infraredcriteria. None of the stars with spectral types earlier than M5.5 weredetected. The terminal velocity increases as the temperature of thestellar photosphere decreases, as would be expected for a radiationdriven wind. Mass-loss rates for the detected objects were calculated,and it was found that there is no correlation between the infrared colorof a Mira variable, and its mass-loss rate. The mass-loss rate iscorrelated with the far-infrared luminosity, although a few stars appearto have extensive dust envelopes without any detectable molecular wind.A power-law relationship is found to hold between the mass-loss rate andthe terminal velocity of the ejected material. This relationshipindicates that the dust envelope should be optically thick in the nearinfrared and visible regions of the spectrum when the outflow velocityis greater than or approximately 17 km/s. At the low end of the range ofoutflow velocities seen, the dust drift velocity may be high enough tolead to the destruction of the grains via sputtering. Half of the starswhich were detected were reobserved in the CO(4-3) transition. Acomparison of the outflow velocities obtained from these observationswith those obtained by other investigators at lower frequencies shows noevidence for gradual acceleration of the outer molecular envelope.
| Evolution of H alpha emission profiles in s-type mira stars
High dispersion observations of the H alpha profile in S-type Mira starshave been obtained at a number of different phases. Because it isdifficult to obtain wide phase coverage on individual stars (withtypical periods of around 300 days), observations obtained from a numberof different stars were combined and anylzed as if they were all fromthe same star. This procedure yielded quite consistent results. Theprofiles, considered by previous authors to consist of two components,have been modeled as the sum of three emission components of equalwidth, two of which are blended. Supplemental H beta anbd H gammaobservations show a single feature close to the velocity of the middle Halpha emission component. The relative amplitudes of these components,as well as the velocity of the red component, vary smoothly withadvancing phase. Although it is uncertain, the three components maycorrespond to physically distinct emitting regions.
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| A catalogue of associations between IRAS sources and S stars.
Cross identifications between the General Catalogue of Galactic S Stars(GCGSS), the IRAS Point Source Catalogue (PSC), and the Guide StarCatalogue (GSC) are presented. The purpose of the present catalogue isi) to provide a clean sample of S stars with far-IR data, and ii) toprovide accurate GSC positions for S stars, superseding those listed inthe GCGSS. The IRAS colour-colour diagram and the galactic distributionof S stars associated with an IRAS source are presented. Several S starshaving extended images in at least one IRAS band have also beenidentified.
| Circumstellar CO emission in S stars. I. Mass-loss with little or no dust.
47 S stars have been searched for circumstellar CO (J=1-0 and/or 2-1)emission, and 29 have been detected, including 4 which show no evidenceof dust in their IRAS LRS spectra, and one with possibly no Tc (andtherefore not an AGB star). Six stars show anomalous features in theirprofiles, showing the presence of more than one kinematic component inthe expanding outflow. Two stars may have detached-shell envelopes. Theexpansion velocity distribution for S stars envelopes is different thanthat for C-rich stars, with the former having a slightly lower meanexpansion velocity, and a significantly higher fraction of objects withvery low expansion velocities (<~5.5km/s). In most S stars, themass-loss rates are >2x10^-7^Msun_/yr and the gas-to-dustratios are >1000. Our detection of CO in S stars with little or nodetectable dust implies substantial mass-loss in these objects. Theexpansion velocities and mass-loss rates of the relatively dust-freestars show a much steeper dependence on the the far-infrared excess({DELTA}IR_e_), as compared to the more dusty stars. This suggests thatwhen the amount of dust becomes small, mass-loss may be partially drivenby a different mechanism than radiation pressure on grains, whichprobably dominates in the dusty envelopes.
| A millimeter-wavelength survey of S stars for mass loss and chemistry
We report the results of a survey of 27 S stars within 1 kpc of the Sunfor emission from the J = 1 goes to 0 and 2 goes to 1 lines of CO. Forthose stars with strong detections in CO, we also searched for emissionfrom the J = 1 goes to 0 line of HCN and the J = 2 goes to 1, nu = 0emission lines of SiO. In addition, we searched for SiO J = 2 goes to 1,nu = 1 maser emission in a total of 14 stars in our sample. We derivemass-loss rates for the S stars detected in CO and compare with otherestimates. Our mass loss rates from the CO J = 1 goes to 0 line are wellcorrelated with the rates derived by Jura (1988) from IR flux densitiesand a dust model, but our values are systematically higher than Jura'sby about a factor of 2. The derived gas mass-loss rates for our sampleare very similar to those found for carbon stars. We find, however, thatthe average dust/gas ratio of our sample of S stars is lower than thatfor carbon stars, suggesting that S stars are less efficient atproducing grains, per unit of ejected mass, than are carbon stars. Fourof the eight stars surveyed show definite detections of HCN in theircircumstellar envelopes. Five of seven stars have thermal (nu = 0) SiOemission, while eight of the 14 surveyed show maser (nu = 1) SiOemission. We use our results to estimate HCN and SiO abundances andcompare these with the results of thermodynamic equilibrium models forthe formation of these species under photospheric conditions with C/Onearly equal to unity. The HCN and SiO abundances indicate that theformation of these species must occur at temperatures low enough forgrain formation to be important, which may serve to enhance productionof HCN. Our results show no evidence that S stars experience a cessationof mass loss, contrary to recent suggestions.
| Not Available
Not Available
| 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.
| Circumstellar Properties of S Stars. I. Dust Features
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993ApJ...416..769C&db_key=AST
| S stars: infrared colors, technetium, and binarity
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&A...271..463J&db_key=AST
| On the Infrared Properties of S-Stars with and Without Technetium
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&A...271..180G&db_key=AST
| Infrared Spectra and Circumstellar Emission of Late-Type Stars. III. S-Type Stars
Near-infrared photometry was carried out at the J, H, K, and L bands for73 S-type stars. The statistical characteristics of the infrared spectraand the circumstellar emission of S-type stars were examined usingnear-infrared photometric data, IRAS photometric data, and thelow-resolution spectra obtained by IRAS. The characteristics of thephotometric spectra of S-type stars were compared with those ofoxygen-rich stars and carbon stars. We found that MS and SC stars haveinfrared spectral characteristics similar to those of both oxygen-richstars and carbon stars, respectively. However, mild S, medium S, andstrong S stars were found to have a variety of spectral characteristicsin the infrared region. Correlations between the 10-mu m spectralfeatures and infrared photometric spectra were examined. It was foundthat S-type stars show a variety of spectral characteristics regardingboth the 10-mu m spectral feature and photometric spectra.
| Carbon stars at high Galactic latitude
Photometry and kinematics are presented for a sample of objective prismselected carbon stars toward the north and south Galactic poles.Distances are determined by fitting the infrared colors to a giantbranch. If these stars are like the carbon stars seen in dwarfspheroidal galaxies, the median distance of the sample is 28 kpc. Ifthey are more like the carbon stars found recently in the Galacticbulge, they may be only half as distant. The surface density of carbonstars as a function of distance is remarkably consistent with an R exp1/4 density profile for the Galactic halo. This density profile can betraced to about 15 scale radii and fills a volume similar to thatoccupied by globular clusters. The data yields an effective radius ofeither 7.0 or 3.5 kpc depending on choice of distance scale. Thevelocity dispersion of the sample is 96 + or - 12 km/s. A kinematicmodel in which vertical velocity dispersion is independent of heightabove the Galactic plane seems in best accord with the data.
| Photoelectric photometry of G-M stars in the Vilnius system
Not Available
| Red giants with unusual dust shells. I - The database
A number of red giants are classified as type M (oxygen-rich) but aredefined in the IRAS LRS Catalog as having SiC emission (a characteristicof carbon-rich environments). It is shown that the NIR spectra arecharacteristic of oxygen-rich stars, but that at least some appear tohave C/O abundance ratios close to unity (in other words they should beclassified as S stars). It is suggested that, when C/O approaches unity,dust condensation theories assuming chemical and thermodynamicequilibrium may not be realistic. It is postulated that a number ofcarbon stars which have been found to have silicate dust features mayalso have C/O abundance ratios close to unity.
| Circumstellar CO emission and pulsational properties of cool giants and supergiants
The CO line profiles in circumstellar envelopes of cool giants andsupergiants are investigated, emphasizing the kinematics. New highspectral resolution data are presented which point to nonsphericallysymmetric outflows in the envelope of the carbon-rich stars TX Psc andpossibly Y CVn. This indicates that the kinematics of envelopes dependsensitively on the pulsation of the star, and that mass loss insupergiants can be rather erratic, resulting in a nonspherical geometry.The influence of stellar infrared emission and pulsational properties oncircumstellar CO emission is studied, revealing a correlation between4.7 micron flux and CO(1-0) temperature for carbon-rich stars. Nocorrelation is found for oxygen-rich and S-type stars. It is found thatthe relation between pulsational period of Mira variables and outflowvelocity of the circumstellar gas may be a step function rather thancontinuous.
| The Westerlund-Olander sample of S stars in the southern Milky Way
Infrared (JHKL) photometry and spectroscopy (5200-7700 A, 6 Aresolution) is given for 72 stars classed as type S by Westerlund andOlander. There are 38 S stars, 26 M stars, of which most aresupergiants, and eight stars without prominent absorption bands. The Sstars are predominantly of the nearly pure S type ( S indexapproximately 6) and represent a substantial addition to the knownsample of such stars. Several probable Mira variables and three starswith strong Li I 6707 A are included. A wide range in LaO strength forstars of similar temperature and ZrO strength may result from differingratios of heavy to light s-process elements. A possible dependence of NaD strength on luminosity is found. The galactic distribution of the Sstars is not significantly different from that of carbon stars in thesame field, excluding the suggestion that these S stars are of muchhigher mass than carbon stars. The infrared colors, taken in conjunctionwith IRAS data, reveal heavy interstellar reddening as well ascircumstellar shells around many stars of all three groups. One of thebandless stars, WO48, has a particularly extensive shell.
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