내용
사진
사진 업로드
DSS Images Other Images
관련 글
Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| The Vienna-KPNO search for Doppler-imaging candidate stars. I. A catalog of stellar-activity indicators for 1058 late-type Hipparcos stars
We present the results from a spectroscopic Ca ii H&K survey of 1058late-type stars selected from a color-limited subsample of the Hipparcoscatalog. Out of these 1058 stars, 371 stars were found to showsignificant H&K emission, most of them previously unknown; 23% withstrong emission, 36% with moderate emission, and 41% with weak emission.These spectra are used to determine absolute H&K emission-linefluxes, radial velocities, and equivalent widths of theluminosity-sensitive Sr ii line at 4077 Ä. Red-wavelengthspectroscopic and Strömgren y photometric follow-up observations ofthe 371 stars with H&K emission are used to additionally determinethe absolute Hα -core flux, the lithium abundance from the Li i6708 Å equivalent width, the rotational velocity vsin i, theradial velocity, and the light variations and its periodicity. Thelatter is interpreted as the stellar rotation period due to aninhomogeneous surface brightness distribution. 156 stars were found withphotometric periods between 0.29 and 64 days, 11 additional systemsshowed quasi-periodic variations possibly in excess of ~50 days. Further54 stars had variations but no unique period was found, and four starswere essentially constant. Altogether, 170 new variable stars werediscovered. Additionally, we found 17 new SB1 (plus 16 new candidates)and 19 new SB2 systems, as well as one definite and two possible new SB3systems. Finally, we present a list of 21 stars that we think are mostsuitable candidates for a detailed study with the Doppler-imagingtechnique. Tables A1--A3 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Correlation of the HIPPARCOS and Allegheny Observatory Parallax Catalogs
No significant difference is found between the systems of the Hipparcosand Allegheny Observatory MAP parallax catalogs. The correlation of theparallaxes of 63 stars common to both programs is 0.9995 +/- 0.0001,with an average standard deviation of the difference of 0.0023". Whilethere is no indication of systematic difference in the two programs, ourstudy suggests that the formal errors in one or both catalogs aresomewhat underestimated.
| Radial-velocity measurements. V - Ground support of the HIPPARCOS satellite observation program
The paper presents data on 1070 radial velocity measurements of starsdistributed in 39 fields measuring 4 deg x 4 deg. The PPO series ofFehrenbach et al. (1987) and Duflot et al. (1990) is continued using theFehrenbach objective prism method.
| Photometry of astrometric reference stars
UBVRI, DDO, and uvby, H-beta photometry of astrometric reference starsis presented. Spectral types and luminosity classifications made fromthe colors are used to determine their spectroscopic parallaxes. In thispaper, colors for 309 stars in 25 regions are given, and classificationsfor 210 stars have been made. These stars form reference frames in theAllegheny Observatory Multichannel Astrometric Photometer astrometricprogram, and in the Praesepe cluster reduced by Russell (1976). It isfound that the present photometric spectral types are reliable to within2.5 spectral subclasses.
| The multichannel astrometric photometer and atmospheric limitations in the measurement of relative positions
The operational Multichannel Astrometric Photometer (MAP) now in use inthe Allegheny Observatory astrometric program is the culmination of adecade of design and development effort. A detailed description of thesystem and its related software is followed by analysis of data acquiredin four stellar regions. The study indicates an accuracy (in the senseof conformity to the best model), per night, for stars of the eighthmagnitude or brighter, of 0.003 arcsec or better. These data points eachhave approximately twice the precision of the annual normal pointsobtained in our photographic program. Accuracy is shown to depend on:(1) the photon-count rate of the target star (it follows that the numberof photons from the reference frame is also in important factor), (2)the duration of the observation, (3) the angular size of the referenceframe, and (4) the quality of the astronomical seeing. Since (4) and, toa lesser extent, (1) involve the atmospheric characteristics at the timeof observation, the probable performance at more favorable sites isdiscussed briefly.
|
새 글 등록
관련 링크
새 링크 등록
다음 그룹에 속해있음:
|
관측 및 측정 데이터
천체목록:
|
