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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.
| 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
| A comparison of OH and H_2O maser properties of Mira and semiregular variable stars
A sample of 17 Miras and nine semiregular variable stars wassimultaneously observed in the OH and H_2O maser lines withsensitivities of 0.15 and 0.6 Jy, respectively. One new H_2O source wasdetected. Among Miras the H_2O maser luminosity is well correlated withthe OH maser luminosity. The ratio of H_2O to OH maser luminositiesdecreases by about four orders of magnitude from the semiregulars to theMiras as a result of an increase in the mass-loss rate. Somesemiregulars have maser properties typical of Mira stars. H_2O emissionis most likely to be detected from Miras at velocities close to thestellar velocity, while emission at blueshifted velocities dominates thedetections from semiregulars. OH emission from the semiregulars usuallyoccurs at greater redshifts and blueshifts with respect to the stellarvelocities than OH emission observed from the Miras. The differences inthe average composite maser profiles in both groups of stars can berelated to the velocity gradients in the maser regions. It is suggestedthat some semiregular variables with maser emission may be in a laterstage of stellar evolution than the Miras.
| 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
| 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.
| Radio continuum emission from stars: a catalogue update.
An updated version of my catalogue of radio stars is presented. Somestatistics and availability are discussed.
| Spectral evolution of the H2O maser in late-type stars
We have carried out almost simultaneous observations of H2O and SiO (J =1-0, v = 1) masers for 171 known late-type maser stars with the 34 mradio telescope at Kashima. We found a systematic change in the H2Omaser spectra related to the evolution of the stars. Typically, H2Omaser spectral profiles are singly peaked in Mira variables, but doublypeaked in IRC/AFGL objects and OH/IR stars. The expansion velocity ofH2O masers increases with decreasing IRAS color temperature. This isexplained by the shock excitation model proposed by Cooke and Elitzur(1985). The blue shifted peak in the profiles is more prominent than thered shifted peak in most of the IRC/AFGL objects and OH/IR stars. Ablocking model of the redshifted peak is introduced.
| Near Infrared Observation and Study of Stellar Maser Sources
Not Available
| Long-period oxygen-rich optical Miras in the solar neighborhood
The spatial distribution of the oxygen-rich Miras with periods longerthan 400 days in the neighborhood of the sun were determined usingavailable survey and the K-band period luminosity relationship. It isfound that the exponential scale height of these stars is near 240 pc.There is a marked contrast between the Mira population at about 1 kpcfrom the Galactic center where there are nearly as many long-periodoxygen-rich Miras as intermediate-period oxygen-rich Miras. It ishypothesized that, at about 1 kpc from the Galactic center, the mainsequence stars with masses larger than 1 solar mass have highermetallicities than main-sequence stars with the same masses in the solarneighborhood. In the solar neighborhood such main sequence stars becomecarbon-rich on the AGB and in the region near the Galactic center theybecome long-period oxygen-rich Miras.
| (Si-29)O and (Si-30)O maser emission from evolved stars
Results are presented from a systematic study of the v = 0 emission of(Si-29)O and (Si-30)O in 38 evolved stars previously known as intense (vgreater than 0) (Si-28)O maser sources, including 30 Mira-typevariables, two giant semiregular variables, and six supergiants. The v =0 J = 1-0 (Si-29)O transition was observed in all 38 objects, includingeight new sources; the transition of (Si-30)O was observed in 13 stars,including one new detection. The observational characteristics of boththe (Si-29)O and (Si-30)O lines confirm that they are produced by maseramplification. The very simple and narrow profiles of the (Si-29)O and(Si-30)O v = 0 masers found in the observed objects contrasted with thelarge width of the thermal lines and with profiles of OH masers(contrary to the assumption of previously published models that (Si-29)Oand (Si-30)O profiles are similar to those observed in OH emission).
| A reference catalogue of maser and thermal emission from circumstellar SiO molecules
A catalog of 191 stellar objects has been compiled showing SiO maser orthermal emission in at least one transition. These are 128 M-Supergiantsand Mira variables, 29 IRC- and AFGL-sources, 32 OH/IR stars, thestar-forming region Orion Kl, and the symbiotic star H 1-36. For eachtransition, individual references are given. Special observationalset-ups as polarization or VLBI measurements or monitor programs arenoted. It is indicated in the reference list if source coordinatesand/or non-detected objects are given. The literature search is completetill December 13, 1988, but several papers published early in 1989 areincluded.
| OH properties of Mira stars
OH observations of a large and representative sample of oxygen-rich Mirastars are presented, and the OH luminosity function is deduced fromthese data. The 1667 MHz and 1665 MHz main lines and the 1612 MHzsatellite line are analyzed, and the differences between these threemasers are discussed. A comparison is made with OH/IR objects, whichemphasizes the period-velocity relation and the dependency between theOH and the far infrared emissions. It is shown that in Miras, thepumping of main lines is likely due to the overlap of far IR lines.
| 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.
| SiO maser emission in evolved stars - Relation to IR continuum
The present observations of SiO masers at 43 GHz have detected 11 newSiO stars; an analysis of these SiO and mid-IR measurements yields agood correlation between maser intensity and 8-micron continuum foroxygen-rich Mira variables and late-type supergiants. This correlationimplies a maser radiative pump mechanism rather than collisional models,and is useful in the characterization of the SiO maser emitters; thecomparison of the respective regions occupied by these groups of objectsin the SiO-IR diagram shows that the emission of the C stars is morethan about 100 times weaker than that of the oxygen-rich objects.
| A classification of miras from their visual and near-infrared light curves - an attempt to correlate them with their evolution
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1985A&A...144..463M&db_key=AST
| Suggested Identifications for Infrared Sources
Not Available
| High-sensitivity search for OH emission from Mira variables
A high-sensitivity search for 18 cm OH emission from Mira variables hasresulted in the detection of five previously unknown OH Mira variables(R Tau, RT Aql, RX Tau, FX Mon, and AW Tau). R Tau, RT Aql, and RX Tauare known microwave H2O sources, and RT Aql is also a known SiO source.RX Tau has a visual-light-curve shape slightly different than that ofpreviously discovered OH Miras. The OH properties of AW Tau are veryanomalous for the period determined from its visual light curve, but areconsistent with a much shorter period for this star. It is possible thatthe period of AW Tau has decreased by several hundred days in the last40 years.
| A low-detection limit search for OH emission from infrared stars
We have used the 300 m telescope of the Arecibo Observatory to examine154 cool luminous stars for 18 cm OH emission. Six of the stars (RU Ari,R Com, T Com, RX Oph, UU Peg, and RT Vir) were found to show OHemission. For the stars without OH emission, we have establisheddetection limits several times smaller than those of previous surveys.
| OH Mira variables - The light curve shapes and implications for mass loss
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1977A&A....57..115B&db_key=AST
| A search for variable 430 MHz continuum emission from red giant stars.
Abstract image available at:http://adsabs.harvard.edu/abs/1976ApJ...209..503F
| Water emission from infrared stars
Twenty-two new infrared stars with microwave water-vapor emission havebeen found, all but four of which are optically identified long-periodvariables. They are heavily reddened, late M stars that commonly showtime variations. Hydroxyl emission is present in all but a fewinstances. Excited-state SiO emission is seen in many H2O-infrared stars(although about half have not yet been checked). Those that are Miravariables always have a visual change of more than 6 magnitudes duringtheir light cycle. Other optical and infrared properties are discussed.
| Classification of 831 two-micron sky survey sources south of +5 degrees.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1975AJ.....80.1011H&db_key=AST
| A study of Mira variables - Implications of OH stars and galactic evolution
A maximum likelihood method has been used to study the properties oftype I OH Mira variables and the kinematical evolution of the Galaxy.The method takes into account dispersion in magnitude and employs propermotions and radial velocities. The V-I excess of type I OH stars withrespect to non OH stars is confirmed, and interpreted in terms of a hot,circumstellar disk around the OH Mira variables. The results support thenotion of a gradual flattening of the Galaxy as proposed by theories ofcollisional collapse.
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| Csillagkép: | Pegazus |
| Rektaszcenzió: | 22h12m16.16s |
| Deklináció: | +14°33'12.1" |
| Vizuális fényesség: | 11.252 |
| RA sajátmozgás: | 0 |
| Dec sajátmozgás: | 0 |
| B-T magnitude: | 12.307 |
| V-T magnitude: | 11.34 |
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