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Correlations between Lithium and Technetium Absorption Lines in the Spectra of Galactic S Stars
Correlations between the presence of the 6707 Å line of lithiumand the resonance lines of technetium (4238 and 4262 Å) in a largesample of Galactic S stars are analyzed. Half of the sample stars areintrinsic S stars (those exhibiting technetium in their spectra), and1/3 of these stars also have strong lithium lines in their spectra.Stars having both lithium and technetium in their spectra areinterpreted as intermediate-mass thermally pulsating asymptotic giantbranch (TP-AGB) stars in which lithium is produced by the Cameron-Fowlermechanism. The production of lithium is predicted to occur inhigh-luminosity (Mbol<=-6) TP-AGB stars by the hot-bottomburning (HBB) mechanism. Data on the carbon isotope ratios of stars inour sample agree with the predictions of HBB; however, oxygen isotoperatios in these stars do not agree with the predictions of HBB.Furthermore, the available luminosities for our sample stars are belowthe minimum value necessary for HBB to occur in available models.Cool-bottom processing (CBP) is one possible explanation for thepresence of lithium in the spectra of these stars. Intrinsic S starshaving technetium but no lithium in their spectra are interpreted aslower mass (1.5-3 Msolar) thermally pulsating AGB stars thathave not undergone CBP. Extrinsic S stars constitute the remaining halfof the sample. Carbon and oxygen isotope ratios, as well as the lack oftechnetium and lithium in the spectra of these stars, are consistentwith these being low-mass red giant branch stars (1-2Msolar), with mass transfer from a now extinct thermallypulsating AGB star being responsible for the enhanced abundance ofs-process elements.
| 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
| Beobachtungssergebnisse Bundesdeutsche Arbeitsgemeinschaft fuer Veraenderliche Sterne e.V.
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| Beobachtungsergebnisse Bundesdeutsche Arbeitsgemeinschaft fur Veranderlichen Serne e.V.
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| Reprocessing the Hipparcos data of evolved stars. III. Revised Hipparcos period-luminosity relationship for galactic long-period variable stars
We analyze the K band luminosities of a sample of galactic long-periodvariables using parallaxes measured by the Hipparcos mission. Theparallaxes are in most cases re-computed from the Hipparcos IntermediateAstrometric Data using improved astrometric fits and chromaticitycorrections. The K band magnitudes are taken from the literature andfrom measurements by COBE, and are corrected for interstellar andcircumstellar extinction. The sample contains stars of several spectraltypes: M, S and C, and of several variability classes: Mira, semiregularSRa, and SRb. We find that the distribution of stars in theperiod-luminosity plane is independent of circumstellar chemistry, butthat the different variability types have different P-L distributions.Both the Mira variables and the SRb variables have reasonablywell-defined period-luminosity relationships, but with very differentslopes. The SRa variables are distributed between the two classes,suggesting that they are a mixture of Miras and SRb, rather than aseparate class of stars. New period-luminosity relationships are derivedbased on our revised Hipparcos parallaxes. The Miras show a similarperiod-luminosity relationship to that found for Large Magellanic CloudMiras by Feast et al. (\cite{Feast-1989:a}). The maximum absolute Kmagnitude of the sample is about -8.2 for both Miras and semi-regularstars, only slightly fainter than the expected AGB limit. We show thatthe stars with the longest periods (P>400 d) have high mass lossrates and are almost all Mira variables.Based on observations from the Hipparcos astrometric satellite operatedby the European Space Agency (ESA \cite{Hipparcos}).Table \ref{Tab:data1} 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/cgi-bin/qcat?J/A+A/403/993
| 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
| Angular Size Measurements of Mira Variable Stars at 2.2 Microns. II.
We present angular size measurements of 22 oxygen-rich Mira variablestars. These data are part of a long-term observational program usingthe Infrared Optical Telescope Array to characterize the observablebehavior of these stars. Complementing the infrared angular sizemeasurements, values for variable star phase, spectral type, bolometricflux, and distance were established for stars in the sample; flux anddistance led to values for effective temperature (Teff) andlinear radius, respectively. Additionally, values for the K-[12] colorexcess were established for these stars, which is indicative of dustymass loss. Stars with higher color excess are shown to be systematically120 Rsolar larger than their low color excess counterparts,regardless of period. This analysis appears to present a solution to along-standing question presented by the evidence that some Mira angulardiameters are indicative of first-overtone pulsation, while otherdiameters are more consistent with fundamental pulsation. A simpleexamination of the resultant sizes of these stars in the context ofpulsation mode is consistent with at least some of these objectspulsating in the fundamental mode.
| Stellar and circumstellar evolution of long period variable stars
In a first paper, HIPPARCOS astrometric and kinematic data were used tocalibrate both infrared K and IRAS luminosities at the same time askinematic parameters of Long Period Variable stars (LPVs). Individualestimated absolute magnitudes and a probabilistic assignation togalactic populations were deduced from these calibrations for each LPVof our sample. Here we propose a scenario of simultaneous stellar andcircumstellar evolution according to the galactic populations. Thetransitory states of S and Tc stars allow us to confirm the location ofthe first dredge-up at Mbol=-3.5. There is also evidencesuggesting that a previous enrichment in s-elements from a more evolvedcompanion may accelerate the evolution along the AGB. The possibleevolution to OH LPVs is included in this scenario, and any of thesestars may have a mass at the limit of the capability for a C enrichmentup to C/O > 1. A list of bright massive LPVs with peculiar envelopeand luminosity properties is proposed as Hot Bottom Burning candidates.The He-shell flash star, R Cen, is found to be exceptionally bright andcould become, before leaving the AGB, a C-rich LPV brighter than theusual luminosity limit of carbon stars.
| 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).
| Speckle Interferometry of New and Problem Hipparcos Binaries. II. Observations Obtained in 1998-1999 from McDonald Observatory
The Hipparcos satellite made measurements of over 9734 known doublestars, 3406 new double stars, and 11,687 unresolved but possible doublestars. The high angular resolution afforded by speckle interferometrymakes it an efficient means to confirm these systems from the ground,which were first discovered from space. Because of its coverage of adifferent region of angular separation-magnitude difference(ρ-Δm) space, speckle interferometry also holds promise toascertain the duplicity of the unresolved Hipparcos ``problem'' stars.Presented are observations of 116 new Hipparcos double stars and 469Hipparcos ``problem stars,'' as well as 238 measures of other doublestars and 246 other high-quality nondetections. Included in these areobservations of double stars listed in the Tycho-2 Catalogue andpossible grid stars for the Space Interferometry Mission.
| 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.
| 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.
| 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
| 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.
| 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
| SiO Maser Survey of Late-Type Stars. II. Statistical Study
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1996AJ....111.1987C&db_key=AST
| SiO maser survey of late-type stars. I. Simultaneous observations of six transitions of ^28^SiO and ^29^SiO.
Simultaneous observations of the ^28^SiO v=0, 1, 2, and 3, J=1-0 and^29^SiO v=0 and 1, J=1-0 transitions for 102 late-type stars were madewith a sensitivity of about 2Jy at the 3σ level using the 45 mtelescope of Nobeyama Radio Observatory (NRO). SiO maser emission wasdetected in 83 stars; seven of them being new detections. The v=3 maserwas detected in 12 stars with eight new detections. Most of the v=3masers occur at the same radial velocity of the strongest spikes of thev=1 and 2 masers. We also newly found the ^29^SiO v=0 maser in sixstars. The ^29^SiO v=0 line is stronger and narrower than the ^28^SiOv=0 line, indicating that the ^29^SiO line is masing. In most cases, the^29^SiO line shows a single narrow profile (FWHM=1 to 3km/s), with peakradial velocities coincident with the stellar velocity derived from OHmaser and/or SiO/CO thermal lines within 1km/s. Therefore, this maserline provides excellent means to measure the stellar velocities oflate-type stars. The ^28^SiO v=0, J=1-0 line was detected in elevenstars, with three new detections.
| 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 search for observational evidence of OH molecule photoproduction
Observational evidence for OH molecule photoproduction by theinterstellar UV radiation in the circumstellar envelopes of Miravariables has been searched for. A sample of Me-type Miras was observedin the main OH maser lines with the Nancay radio telescope. Two newlines were detected. The intensity of the 156.5-nm wavelengthinterstellar radiation is estimated by integration of the observed UVlight of OB stars in common star catalogues. A statistically significanttrend is found that OH Miras are illuminated by stronger UV fields thannon-OH objects.
| Lumnosity attenuation and distances of red giant stars
The Mv of M red variable stars is increased by the molecularTiO bands which grow from M0 to M10 in an inherent spectral darkeningsequence. The Mv is the result of both the effective visualflux and the equivalent radius. The equivalent radius is apparentlysmaller than the empirical radius due to a molecular covering process instars later than M3. The full range of optical red giant stars forms asequence from the brightest M early spectral types (S Car, M0(max),Mv approx = -3.2 mag) to the faintest M-latest spectral types(IK Tau, M10.5 min), Mv approx. = 16.5 mag). The typicalMiras and SR stars of M-medium and M-late spectral types are betweenthese two extremes. The sequence has a range of 20 mag on the visual(HR) diagram which extends from the red giant branch (RGB) passingbeyond the Mv of red dwarf stars as far as the point where itintercepts with the prolongation of the zero-age main sequence (ZAMS) inthe latest spectral type. Typical M10-stars at 200 pc has a V approx. =20 mag. M-latest stars at larger distances are unobservable stars in thevisual band. The distances of 134 variable stars are also given. Thedistances to 86 stars were determined by using a pure photometricmethod, while preliminary distances (less than 200 pc) for the remaining48 M-latest stars were determined by the spectral-photometric method.Since the local stellar density of M stars up to 100 pc rises at least7.5 times, it is possible to discuss that the long-standing problem ofdark matter in spiral galaxies could be resolved by these very dimmassive giant stars and by the molecular covered stars at the extremeend of the attenuating sequence. Furthermore, post M-latest stars may bethe only nonvisual stellar objects that can explain the enormousquantity of faint and point infrared sources found by IRAS. These weakobjects suggest the existence of an infrared Milky Way which is moredense than the optical one.
| 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.
| New OH/IR stars from color-selected IRAS sources. 3: A complete survey
We present the results of 1612 MHz observations conducted at the AreciboObservatory of 571 color-selected sources from the IRAS Point SourceCatalog. Of these sources we detect 132, 113 for the first time. This isthe third part of an Arecibo survey of color-selected IRAS sources. Theearlier two parts together detected a total of 268 sources of 1612 MHzemission. An analysis of the properties of the OH/IR stars detected inall three parts of the survey is included. In particular we compute thelimiting 1612 MHz peak flux of the entire survey to be approximately 40mJy. The correlation between the IRAS infrared fluxes and the 1612 MHzflux of the 132 sources detected in part III of the survey is smallerthan that found in the earlier parts of the survey. This is to beexpected from the intrinsic variability of OH/IR stars and the longertime gap between the 1612 MHz observations and the IRAS measurements. Weidentify a subset of 54 stars as being near the tangent point of thegalactic rotation curve. Using the kinematical distances to these starswe find that the efficiency of momentum transfer varies exponentiallywith the (25 - 12) micrometer color, consistent with the stellar outflowbeing driven by radiation pressure. Further the IR pump efficiencyincreases with increasing optical depth of the circumstellar shell, asexpected for radiative pumping. The bolometric luminosity function isfound to decrease sharply above LBol = 5600 solar luminosity,and the 1612 MHz luminosity function shows a corresponding falloff aboveL1612 = 1.8 x 10-8 solar luminosity. We also finddirect confirmation of the expectation that sources with large expansionvelocity are more luminous than sources with small expansion velocity.
| 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.
| 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
| Not Available
Not Available
| A survey of circumstellar CO emission from a sample of IRAS point sources
The first results from a survey of circumstellar CO(1-0) emission arepresented. The sources were selected from the IRAS point source catalogaccording to the IRAS color criteria described in van der Veen andHabing (1988). The sources have good quality fluxes at 12, 25, and 60microns, flux densities larger than 20 Jy at 25 microns, and aresituated more than 5 deg away from the Galactic plane. The survey isundertaken to study the relationship between mass loss rates, dustproperties, and the evolution along the AGB. The sample consists of 787sources and contains both oxygen and carbon-rich stars, including Miravariables, OH/IR objects, protoplanetary nebulae, planetary nebulae, and60-micron excess sources. So far, 519 objects, situated on both thenorthern and the southern sky, have been observed; 163 sources werefound to have circumstellar CO emission, and in 58 of these CO emissionhas not previously been detected.
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Osservazione e dati astrometrici
| Costellazione: | Pegaso |
| Ascensione retta: | 00h00m06.56s |
| Declinazione: | +25°53'11.2" |
| Magnitudine apparente: | 10.498 |
| Moto proprio RA: | 13.2 |
| Moto proprio Dec: | -10 |
| B-T magnitude: | 11.327 |
| V-T magnitude: | 10.567 |
Cataloghi e designazioni:
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