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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).
| A search for Technetium in semiregular variables
We searched for the lines of Tc in the spectra of Semiregular variables(SRVs) in the wavelength region from 4180 to 4300 Å using highresolution spectroscopy. Tc as an s-process element is produced on thethermally pulsing AGB and is therefore a good indicator for theevolutionary status of Semiregular variables. Combining our results withprevious investigations we get a database large enough for a statisticalstudy. Tc is not found in SRVs with periods below 100 days, spectraltypes earlier than M5 and photospheric IRAS colours. These objects are`blue' SRVs in the classification system of Kerschbaum & Hron(\cite{KH94}). Among the `red' SRVs (periods longer than 100 days) thefraction of stars showing Tc in their spectra is about 15 % with aprobably lower fraction among the stars with periods above 150 days.This is significantly lower than for the typical Miras. Taking intoaccount the probable conditions for the occurence of the third dredge-upand the expected behavior of the Tc abundance along an evolutionarytrack on the AGB, our results support an evolutionary scenario from`blue' SRVs (early AGB) to `red' SRVs (early TP-AGB) and on to longperiod Miras. Only the most massive (masses above 2M_ȯ) stars showTc during the SRV stage. The luminosities of the Tc-rich SRVs and Mirasare compatible with theoretical estimates of the minimum core massrequired for the third dredge-up. Based on observations collected at theEuropean Southern Observatory, La Silla, Chile (ESO No.54.E-0350), theGerman Spanish Astronomical Centre, Calar Alto, operated by theMax-Planck-Institute for Astronomy, Heidelberg, jointly with the SpanishNational Commission for Astronomy, and Kitt Peak National Observatory,USA.
| Semiregular variables of types SRa and SRb - Basic properties in the visual and the IRAS-range
The pulsational properties, T(eff)s, mass loss rates, luminosities,scale heights, and volume densities in the Galactic plane are presentedfor samples of optical semiregular variables of types SRa and SRbcorrelated with the IRAS point source catalog. These properties arecompared to the corresponding characteristics of optical Mira variables.It is found that the SRa's are not a distinct class of variables but amixture of 'intrinsic' Miras and SRb's. The O-rich SRb's form a quitehomogeneous group in terms of periods, amplitudes, and temperatures.They consist of a 'blue' group with no indication of circumstellarshells, with P less than 150 d and T(eff) greater than 3200 K, and a'red' group with temperatures and mass loss rates comparable to Mirasbut periods about a factor of two smaller. The C-rich SRVs generallyhave smaller periods and are more abundant than C-rich Miras. Theevolutionary status of the SRVs is discussed.
| 58th Name-List of Variable Stars
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| The varibility of M-stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1971MNRAS.152..165S&db_key=AST
| Standard magnitudes in the E regions.
Not Available
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