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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
| 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.
| Absolute proper motion and space motion of the globular cluster M15
We have separated cluster members and field stars for stars in a regionaround the globular cluster M15. The membership of ultraviolet brightstars of M15 is discussed. The absolute proper motion of M15 has beendetermined with respect to the PPM catalog. An extragalactic calibrationof the proper motions has been performed. The calibration was done bymeasurements of galaxies on the Palomar Sky Survey glass copies andplates from the Schmidt telescope of the Observatoire de la Cote d'Azur(CERGA). We compare the three different methods of establishing absoluteproper motion for the globular cluster M15. The orbital parameters ofM15 have been derived. As a by-product of our work, we obtained foreight stars of the HIPPARCOS input catalog absolute proper motions,which may be used for the calibration of the HIPPARCOS proper motionsystem.
| An astrometric catalogue of stars in the region of M15
We present positions and proper motions with respect to the PPMcatalogue of 863 stars in a field of 8 deg x 6 deg centered on theglobular cluster M15. The catalogue is based on measurements of 136plates from the Carte du Ciel telescope of Bordeaux, the CERGA Schmidttelescope, and the double refractor of Bonn. The modal accuracy of theproper motions is +/- 0 arcsec 15/100 a.
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