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Публикации по объекту
AGB variables and the Mira period-luminosity relation
Published data for large-amplitude asymptotic giant branch variables inthe Large Magellanic Cloud (LMC) are re-analysed to establish theconstants for an infrared (K) period-luminosity relation of the formMK = ρ[logP - 2.38] + δ. A slope of ρ = -3.51+/- 0.20 and a zero-point of δ = -7.15 +/- 0.06 are found foroxygen-rich Miras (if a distance modulus of 18.39 +/- 0.05 is used forthe LMC). Assuming this slope is applicable to Galactic Miras we discussthe zero-point for these stars using the revised Hipparcos parallaxestogether with published very long baseline interferometry (VLBI)parallaxes for OH masers and Miras in globular clusters. These result ina mean zero-point of δ = -7.25 +/- 0.07 for O-rich Galactic Miras.The zero-point for Miras in the Galactic bulge is not significantlydifferent from this value.Carbon-rich stars are also discussed and provide results that areconsistent with the above numbers, but with higher uncertainties. Withinthe uncertainties there is no evidence for a significant differencebetween the period-luminosity relation zero-points for systems withdifferent metallicity.
| Proper-motion binaries in the Hipparcos catalogue. Comparison with radial velocity data
Context: .This paper is the last in a series devoted to the analysis ofthe binary content of the Hipparcos Catalogue. Aims: .Thecomparison of the proper motions constructed from positions spanning ashort (Hipparcos) or long time (Tycho-2) makes it possible to uncoverbinaries with periods of the order of or somewhat larger than the shorttime span (in this case, the 3 yr duration of the Hipparcos mission),since the unrecognised orbital motion will then add to the propermotion. Methods: .A list of candidate proper motion binaries isconstructed from a carefully designed χ2 test evaluatingthe statistical significance of the difference between the Tycho-2 andHipparcos proper motions for 103 134 stars in common between the twocatalogues (excluding components of visual systems). Since similar listsof proper-motion binaries have already been constructed, the presentpaper focuses on the evaluation of the detection efficiency ofproper-motion binaries, using different kinds of control data (mostlyradial velocities). The detection rate for entries from the NinthCatalogue of Spectroscopic Binary Orbits (S_B^9) is evaluated, as wellas for stars like barium stars, which are known to be all binaries, andfinally for spectroscopic binaries identified from radial velocity datain the Geneva-Copenhagen survey of F and G dwarfs in the solarneighbourhood. Results: .Proper motion binaries are efficientlydetected for systems with parallaxes in excess of ~20 mas, and periodsin the range 1000-30 000 d. The shortest periods in this range(1000-2000 d, i.e., once to twice the duration of the Hipparcos mission)may appear only as DMSA/G binaries (accelerated proper motion in theHipparcos Double and Multiple System Annex). Proper motion binariesdetected among S_B9 systems having periods shorter than about400 d hint at triple systems, the proper-motion binary involving acomponent with a longer orbital period. A list of 19 candidate triplesystems is provided. Binaries suspected of having low-mass(brown-dwarf-like) companions are listed as well. Among the 37 bariumstars with parallaxes larger than 5 mas, only 7 exhibit no evidence forduplicity whatsoever (be it spectroscopic or astrometric). Finally, thefraction of proper-motion binaries shows no significant variation amongthe various (regular) spectral classes, when due account is taken forthe detection biases.Full Table [see full textsee full text] is only available in electronicform at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5)or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/464/377
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Angular Diameter Measurements of Evolved Variables by Lunar Occultations at 2.2 and 3.8 Microns
We report the angular diameters of two Mira variables (U Ari and Z Sco),three semiregular (SR) and irregular variables (SW Vir, η Gem, andμ Gem), and a supergiant SR variable (TV Gem) by lunar occultationobservations in the near-IR broad K band (2.2 μm). Lunar occultationsof η Gem and μ Gem were also observed for the first timesimultaneously in both the K and L' bands, yielding angular diameters at2.2 and 3.8 μm. Effective temperatures and linear radii are alsoderived for all the observed sources and compared with earliermeasurements. The mode of pulsation of both Mira and SR sources in oursample is discussed.
| 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.
| Statistical Constraints for Astrometric Binaries with Nonlinear Motion
Useful constraints on the orbits and mass ratios of astrometric binariesin the Hipparcos catalog are derived from the measured proper motiondifferences of Hipparcos and Tycho-2 (Δμ), accelerations ofproper motions (μ˙), and second derivatives of proper motions(μ̈). It is shown how, in some cases, statistical bounds can beestimated for the masses of the secondary components. Two catalogs ofastrometric binaries are generated, one of binaries with significantproper motion differences and the other of binaries with significantaccelerations of their proper motions. Mathematical relations betweenthe astrometric observables Δμ, μ˙, and μ̈ andthe orbital elements are derived in the appendices. We find a remarkabledifference between the distribution of spectral types of stars withlarge accelerations but small proper motion differences and that ofstars with large proper motion differences but insignificantaccelerations. The spectral type distribution for the former sample ofbinaries is the same as the general distribution of all stars in theHipparcos catalog, whereas the latter sample is clearly dominated bysolar-type stars, with an obvious dearth of blue stars. We point outthat the latter set includes mostly binaries with long periods (longerthan about 6 yr).
| 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.
| 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
| 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).
| 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
| Long-Term Changes in Mira Stars. I. Period Fluctuations in Mira Stars
It has been known since the pioneering work of Eddington & Plakidisthat the period changes in Mira stars are dominated by the effects ofrandom cycle-to-cycle fluctuations in period, at least in the limitedsample of stars that were studied. We have extended their work, using aportion of the American Association of Variable Star Observers (AAVSO)international database of variable star observations: times andmagnitudes of maximum and minimum magnitude of 391 bright Mira starsover 75 yr (Kowalsky et al.). The Eddington & Plakidis model fitsthe data in almost every case, at least over a time interval of severaltens of cycles. There is a weak correlation between the fractionalperiod fluctuation, per cycle, and the period (or color) of the star,but not with the amplitude or chemical type (M, S, or C).
| 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.
| 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. 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.
| 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.
| 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.
| Emission features in IRAS LRS spectra of M Mira variables
A total of 291 M Mira variables with IRAS low-resolution spectrometer(LRS) spectra that have 8-micron fluxes greater than 15 Jy have beenanalyzed. After subtraction of a 2500 K blackbody energy distributionfrom the spectrum, the remaining difference spectra can be classifiedinto seven groups, depending on the shape of their spectral emissionfeatures around 10 microns: Sil, Sil(+) Sil(2+), S, three-component,'broad', and no feature. The spectral emission features are interpretedas being produced primarily by amorphous silicates with differingamounts of crystalline olivine. A weak broad feature at 9-13 microns ispossibly produced by aluminum oxide and/or a size distribution ofsilicate particles that favors larger grains. The 8-22-micron IR excess,defined as the fraction of energy above the 2500 K continuum, shows onlya slight tendency to correlate with period and no tendency to correlatewith mass loss rate. Maser emission from OH and H2O is much morefrequently detected in stars that show the Sil or Sil(+) emissionfeature, but SiO maser emission is detected with the same percentage inall emission feature classes with the exception of the S feature. Starsshowing the S feature appear to be closely related to the MS and Sstars.
| Maxima and minima of long period variables, 1949-1975
Not Available
| A study of M Mira variables based on IRAS LRS observations. II - Model FITS and derived parameters for 109 Miras
Dust shell models have been fitted to the IRAS LRS spectra of 109 M Miravariables. Best fit models are calculated for each star. A model iscompletely determined by five parameters: the dust temperatures at theinner boundaries of the aluminum oxide and 'silicate' dust shells, thecolumn densities of each dust grain component, and the distance to thestar. It turns out that the 1 - 200 micron IR energy distributionscalculated for the best fit parameters also provide quite satisfactoryfits to the observed NIR and FIR.
| Lunar occultations of IRAS point sources, 1991-2000
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1989ApJS...69..651C&db_key=AST
| IRAS low resolution spectrograph spectral class and M and S Miras
A large sample of 177 M and S Miras, as revealed by their IRAS LRSspectral class, have been examined to determine the dependence ofsilicate emission on the visual light curve asymmetry factor, f. It isconfirmed that 9.7-micron silicate emission feature not only in M but inS Miras also occurs only when f is not greater than 0.45. However, notall stars with f of not greater than 0.45 show the silicate emission;this nondetection reveals dependence on other parameters like the meanvisual light amplitude. Though strong emission feature in M Miras mayoccur for any value of f, very weak features are absent for small valuesof f, and the strongest features tend to appear for larger values of f.Infrared excess tends to increase with the strength of the silicateemission as well as with decrease in the value of f. The probability ofdetection of silicate emission is very high for the visual light curveclasses (Ludendorff, 1928) alpha 1, alpha 2, and alpha 3, decreases foralpha 4 and gamma 1, and is negligible for the beta class.
| Criteria for OH maser emission from circumstellar envelopes of oxygen-rich Mira-type red giants
A large and representative sample of oxygen-rich Mira stars was selectedand observed in the 18 cm OH lines at their optical maximum. A total of14 new OH sources were detected. The OH maser emission is found in theintrinsically bright far-IR objects with late M spectral type. Othercharacteristics of the Miras are high (H-K) and (K-L) colors. Theirperiods are on average longer and their (25-12) colors on average redderthan those of non-OH Miras. The (J-H) and (60-25) colors are the samefor OH and non-OH stars. In most cases, OH and H2O masers existsimultaneously. The observed stars form a sequence along which theperiod and the stellar luminosity increase, the stellar radiusincreases, the dust shell radius increases by a smaller factor, thephotospheric temperature decreases but the dust shell temperature isroughly constant, and the mass loss rate and thus the thickness and thebrighntess of the envelope increase considerably.
| Classification of Mira variables based on visual light curve shape
The paper presents classifications of 368 Mira variables of M, S and Cspectral classes based on the shape of their visual light curve. Theclassification is esentially based on Ludendorff's (1928) scheme and thelight curves used are mainly from the compilation of Campbell (1955).The distribution of light curves over period, mean amplitude, lightcurve asymmetry factor, period variability, and spectral class atmaximum is discussed.
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Группы:
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Наблюдательные данные и астрометрия
| Созвездие: | Скорпион |
| Прямое восхождение: | 16h06m00.70s |
| Склонение: | -21°43'59.6" |
| Видимая звёздная величина: | 10.504 |
| Собственное движение RA: | -4.7 |
| Собственное движение Dec: | -7 |
| B-T magnitude: | 12.889 |
| V-T magnitude: | 10.701 |
Каталоги и обозначения:
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