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
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New periodic variables from the Hipparcos epoch photometry
Two selection statistics are used to extract new candidate periodicvariables from the epoch photometry of the Hipparcos catalogue. Theprimary selection criterion is a signal-to-noise ratio. The dependenceof this statistic on the number of observations is calibrated usingabout 30000 randomly permuted Hipparcos data sets. A significance levelof 0.1 per cent is used to extract a first batch of candidate variables.The second criterion requires that the optimal frequency be unaffectedif the data are de-trended by low-order polynomials. We find 2675 newcandidate periodic variables, of which the majority (2082) are from theHipparcos`unsolved' variables. Potential problems with theinterpretation of the data (e.g. aliasing) are discussed.
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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.
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The radial pulsation of AI Aurigae
We present an analysis of eleven years of Strömgren by photometryof the red semiregular variable star AI Aurigae. An early perioddetermination of 63.9 days is confirmed by the long-term light curvebehaviour. The light curve shows semi-regular changes with a mean periodof 65 days reaching an amplitude of 0\fm6 in some cycles. The b-y colourchanges perfectly parallel the V light curve, suggesting radialoscillation to be the main reason for the observed variations. Weestimate the main characteristics of the star (mass, radius, effectivetemperature) that suggest radial pulsation in fundamental or firstovertone mode.
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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.
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Proper motion study of the globular cluster M 92.
We present proper motions for stars in the field of the galacticglobular cluster NGC6341 (M92). This study continues the series ofpapers from the Bonn programme of globular cluster proper motions.Plates taken with the Bonn double refractor and the Rozhen observatory2m Ritchey-Chretien telescope with a maximal epoch difference of 94yearswere used. Relative proper motions for all well-measurable stars in the1.5degx1.5deg field covered by the plates were derived. Median propermotion errors are 0.8milliarcsec/year (mas/a) for stars brighter thanabout V=16.7mag. The cluster membership of UV-bright and variable starsis discussed. The proper motions are compared with the accurate relativeproper motions of Rees (1992) and with the absolute proper motions fromSchmidt plates referred to galaxies of Scholz et al. (1994). The lattercomparison enables us to tie the proper motions of the stars and themean proper motion of M92 to an inertial system. This calibration has anuncertainty of about 1.0mas/a. The absolute proper motions of Hipparcosstars in the field will be useful for the extragalactic calibration ofthe Hipparcos proper motion system. The data for 642 stars within 18.6'from the cluster centre is available via the CDS (Centre des DonneesAstronomiques Strasbourg) Data Centre.
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The 68th Name-List of Variable Stars
Not Available
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Photoelectric photometry of the red variable HD 157010
Data from UBV photoelectric observations of HD 157010 obtained using thesolar-variation equipment on the 21-inch reflector at Lowell Observatoryon a number of nights in 1964-1965 are presented in tables and graphsand characterized. The star is found to be an M-type giant with cyclicrather than periodic light variations (0.5 mag in B, 0.04 mag in B-V,and 0.18 mag in U-B) and is classified as SRb using the criteria of thecatalog of Kukarkin et al. (1969). Correction factors for thetemperature sensitivity of the continuous spectrum and the TiOblanketing effect in red giants are given, updating the results of Smak(1964). An upper limit of 0.02 mag on the interstellar reddening of thenearby globular cluster M92 is determined, in agreement with that ofMcNamara and Langford (1969).
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On the 16 unstudied variable stars in BV - list.
Not Available
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