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Starspot photometry with robotic telescopes. UBV(RI)_C and by light curves of 47 active stars in 1996/97
We present continuous multicolor photometry for 47 stars from October1996 through June 1997. Altogether, 7073 V(RI)_c, UBV, and by datapoints, each the average of three individual readings, were acquiredwith three automatic photoelectric telescopes (APTs) at FairbornObservatory in southern Arizona. Most of our targets arechromospherically active single and binary stars of spectral type G to Kbut there are also four pre-main-sequence objects and three pulsatingstars in our sample. The light variability is generally due torotational modulation of an asymmetrically spotted stellar surface andtherefore precise rotational periods and their seasonal variations aredetermined from Fourier analysis. We also report on photometricvariations of gamma CrB (A0V) with a period of 0.44534 days. All dataare available in numerical form. All data are available from CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| The Tokyo PMC catalog 90-93: Catalog of positions of 6649 stars observed in 1990 through 1993 with Tokyo photoelectric meridian circle
The sixth annual catalog of the Tokyo Photoelectric Meridian Circle(PMC) is presented for 6649 stars which were observed at least two timesin January 1990 through March 1993. The mean positions of the starsobserved are given in the catalog at the corresponding mean epochs ofobservations of individual stars. The coordinates of the catalog arebased on the FK5 system, and referred to the equinox and equator ofJ2000.0. The mean local deviations of the observed positions from theFK5 catalog positions are constructed for the basic FK5 stars to comparewith those of the Tokyo PMC Catalog 89 and preliminary Hipparcos resultsof H30.
| Rotation periods of four T Tauri stars
BVR photometry of nine T Tauri and related stars was obtained on 13nights in January 1988, in an attempt to confirm reported periodicitiesand discover new ones. Each star was observed an average of six timesper night. Rotation periods previously reported for T Tau by Herbst etal.(1986) and HM 4 (LHα 332-20) and HM 30 (LHα 332-21) byBouvier et al.(1986) were confirmed. A periodicity of 1.28 days wasdiscovered for TW Hya; it was also the only star to show significantvariations during the course of a single night. Analysis of a similardataset for TW Hya obtained by Rucinski and Krautter (1983) shows asimilar periodic variation, but with a 1.8 day cycle. SU Aur, RY Tau, BFOri, V380 Ori, and Fu Ori all exhibited variability, but withoutdetectable periodicity. This is in agreement with a previous suggestionthat periodicity is more easily found in the later-typepre-main-sequence stars (i.e., later than about KO).
| Photometric variations of Orion population stars. V - A search for periodicities
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1987AJ.....94..137H&db_key=AST
| Photometric variations of Orion population stars. II Ae-irregular variables and T Tauri stars
UBVRI and H-alpha photometry of five T Tauri stars and threeAe-irregular variables obtained during the 1982/83 observing season atVVO and KPNO is presented. RY Tau shows very little change in color withbrightness, except in (V-R) where it actually becomes bluer as it fades.The 'turnaround' in (U-B) suggested in last year's data on CO Ori hasbeen confirmed when faint, the star ceases becoming redder as it dimsand begins to get bluer. The turnaround is also now clearly seen in B -V. Similar turnarounds are found in two of the Ae stars, BF Ori and UXOri, the latter confirming Zajtseva's (1973) result. These 'blueing'trends make interpretations of the variability based on dust obscurationimplausible. The Ae stars monitored were nearly indistinguishable intheir photometric behavior from the G-type weak emission line T Tauristars SU Aur and CO Ori, suggesting a common mechanism for theirvariability. A general scheme for integrating the diverse properties ofthese variables is proposed, which involves photospheric andchromospheric responses to strong surface magnetic fields.
| Optical monitoring of Orion population stars. I - Results for some T Tauri and Herbig Ae/Be stars
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1982AJ.....87.1710H&db_key=AST
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