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HD 198327


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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.

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.

The 74th Special Name-list of Variable Stars
We present the Name-list introducing GCVS names for 3153 variable starsdiscovered by the Hipparcos mission.

Photoelectric photometry of M-type stars
UBVRI photoelectric photometry was obtained for 110 M-type starscontained in the Caltech Two-Micron Survey and the revised AFGL Catalog.Of the 110 stars, 58 have a color index (B-R) greater than or equal to 4mag. A graph is given of (V-R) versus (V-I) for the present stars.

Near-infrared photometry of unidentified IRC stars. III - The Mira variables of spectral type M10
Less than two dozen visually bright Mira variables are known to exceedthe extremely late spectral type of M9.5 at minimum light. Near-infraredphotometry of the reddest unidentified sources in the Two-Micron SkySurvey has led to the identification and spectral classification of agroup of 38 additional M type Mira variables that reach M9.5, but whichon the average exhibit significantly larger amplitudes at 1 micron,longer periods, later spectral types, and redder near-infrared colorsthan the ones whose mean properties previously defined the coolest Miravariables. Periods and epochs of maximum light are given for 13 stars.Near-infrared magnitudes and photometric spectral types are also givenfor 107 additional unidentified IRC stars having less extreme spectraltypes, including 13 highly reddened early-M supergiants and four coolcarbon stars.

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观测天体数据

星座:天龍座
右阿森松:20h39m43.29s
赤纬:+80°29'59.9"
视星:8.828
距离:641.026 天文距离
右阿森松适当运动:-3.5
赤纬适当运动:-3.5
B-T magnitude:10.945
V-T magnitude:9.003

目录:
适当名称   (Edit)
HD 1989HD 198327
TYCHO-2 2000TYC 4593-263-1
USNO-A2.0USNO-A2 1650-02305485
HIPHIP 101960

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