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Long-term monitoring of active stars. IX. Photometry collected in 1993
As a part of an extensive program focused on the global properties andevolution of active stars, high-precision UBV(RI)_c and UBV photometryof 31 selected stars is presented. The UBV(RI)_c observations werecollected at the European Southern Observatory over the 31 December1992-18 January 1993 and the 20 November-3 December 1993 intervals.Additional UBV photometry obtained by the ``Phoenix" and by the CataniaAstrophysical Observatory Automatic Photoelectric Telescopes from 1990to 1993 is also presented for some of the program stars. Significantevolution of the light curves, period variations and evidence forlong-term variability of the global degree of spottedness are found.Some spectral classifications are revised and the inferred photometricparallaxes are compared, whenever possible, with the values measured bythe Hipparcos satellite. These observations are finalized to theconstruction of an extended photometric database, which can giveimportant clues on topics such as the stability of spotted areas,differential rotation, solar-like cycles and the correlation betweeninhomogeneities at different atmospheric levels. Based on data collectedat the European Southern Observatory, La Silla, Chile. Tables and thecomplete data set are also available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/367/910
| 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
| Il Hydrae: New Orbital Solutions and BV Photometry
We present new orbital solutions of the primary of IL Hya combining allthe available radial velocity measurements. We also present BVphotometry obtained on 9 nights during January--March 1993.
| UBV(RI)_C and UVBY photometry of HD 81410 and starspot distribution in RS CVn objects
We present UBVRI and uvby photometry of HD 81410 obtained on a total of40 nights during 1987-90, and an analysis of its long-term photometricbehaviour. The star is found to show two well-separated minima in itslight curve most of the time; probably there are two preferred effectivelongitudes about which spots are mainly formed. The migration of thephase of the light minimum usually seen in RS CVn stars is absent in HD81410. The rather small spread in the maximum V amplitudes observed inactive RS CVn objects seen at different inclinations of rotational axisimplies that the longitudinal asymmetry in the distribution of spots,which causes the light modulation, is largely restricted to withinaround +/-40(deg) latitudes. The total ranges of rotational periodswhich are quoted in the literature for several spotted stars based onlong-term photometry also imply a similar latitudinal extent of spotsabout the equator. We find that the light and colour curves produced byan equatorial band of spots limited by latitudes and covering the fullrange of longitudes across the hemisphere visible at light minimum canbe approximated reasonably well by two well-separated circular spots.Further, we find that the net effect in the colours produced bylimb-darkening depends on the exact distribution of spots on the stellarsurface; it could be even negligible for certain spot distributions.From the spot modeling of the light and colour curves of HD 81410 wefind that the maximum temperature difference between the photosphere andspots is around 1400 K. We also find that the light modulation is causedby several small individual spots, and during the epochs of shallowminimum spots are spread out, both latitudinally and longitudinally,over a wider region, as indicated by a higher temperature for theequivalent circular spots at those epochs. It seems that in RS CVn starsthe spots occur largely distributed about the equator as in the case ofthe Sun and the solutions which indicate polar spots result fromlimiting the number of spots in the modeling to a few. Based on theobservations collected at the European Southern Observatory, La Silla
| Long-term monitoring of active stars. VIII. UBV(RI)_(c) photometry collected in February 1992
As a part of an extensive program focusing on the global properties andevolution of active stars, high-precision UBV(RI)_c photometry of 31selected stars, collected at the European Southern Observatory over the14-29 February 1992 interval, is presented. Significant evolution of thelight curves, period variations and evidence for long-term variabilityof the global degree of spottedness are found. Some spectralclassifications are revised and the inferred photometric parallaxes arecompared, whenever possible, with the values measured by the Hipparcossatellite. Flare events were detected for the star HD16157 = CC Eri, EXO 055609-3804.4 TY Coland HD 119285 = V851 Cen. Optical variability wasdiscovered for the Pop II binary HD 89499. Theseobservations contribute to the establishment of a time-extendedphotometric database which can give important clues on topics such asthe stability of spotted areas, differential rotation, solar-like cyclesand the correlation between inhomogeneities at different atmosphericlevels. based on data collected at the European Southern Observatory, LaSilla, Chile.
| Doppler imaging of stellar surface structure. V. The long-period RSCVn binary HD81410 = ILHydrae
Multiwavelength Doppler images of the long-period RS CVn binary ILHydrae from March 1994 and Feb.-March 1995 reveal a cool polar spot andseveral features at low latitudes. Their average temperature isapproximately 500K below the photospheric temperature of 4700K. Due tothe relatively small rotational velocity of 26.5+/-1 kms(-1) \ and therelatively cool, low-gravity atmosphere with many weak absorptionblends, Doppler imaging of IL Hydrae is challenging but resulted inencouragingly similar maps from altogether seven spectral regions near6400 Angstroms. Latitude-dependent differential rotation is detectedfrom our Doppler maps and indicate faster rotation at the stellarequator as compared to the polar regions. Lines from the secondarycomponent are sometimes seen in our red-wavelength spectra and adouble-lined spectroscopic orbit is presented. We also give a moreprecise rotational period from three consecutive years of V-bandphotometry. A spectral classification of K0III-IV and a mass of2.2+/-0.2 M_sun for the primary, and mid to late F main sequence ormaybe ~G0V-IV and a mass of 1.3+/-0.2 M_sun for the secondary, aresuggested. Hα \ equivalent widths measured over a single rotationcycle exhibit a sinusoidal variation in phase with the photosphericV-band light curve. The maximum of the residual Hα \ emissioncoincides with the lightcurve minimum and is thus likely linked to thestarspot-covered stellar surface. A steady, redshifted absorptioncomponent possibly indicates an isotropic inward flow at the Hα \line-forming region at approximately 60 kms(-1) .
| Long-term monitoring of active stars. VII. UBV(RI)_c photometry collected in March 1991
In the framework of an extensive program focusing on the globalproperties and evolution of active stars, high-precision UBV(RI)_cphotometry of 19 selected stars, collected at the European SouthernObservatory over the 15-31 March 1991 interval is presented. Significantevolution of the light curves, period variations and evidence forlong-term variability of the global degree of spottedness are found.Most of the spectral classifications are discussed. A flare event wasdetected for the star HD 127535 = V 841 Cen. These observationscontribute to the establishment of a time-extended photometric databasewhich can give important clues on topics such as the stability ofspotted areas, differential rotation, solar-like cycles and thecorrelation between inhomogeneities at different atmospheric levelsFigure 1 to 24 are only available on the on-line version of A&A athttp://www.ed-phys.fr}. based on data collected at the European SouthernObservatory, La Silla, Chile. Tables and the complete data set are alsoavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr or via http://cdsweb.u-strasbg.fr/Abstract.html
| Long-term monitoring of active stars. IV. UBV(RI)_c_ observations obtained at La Silla in December 1989.
High-precision UBV(RI)_c_ photometry of 23 selected acitve stars,collected at the European Southern Observatory (La Silla, Chile) overthe period 9-28 December 1989, is presented. This paper is part of alarger program focusing on the global properties and evolution of activestars and is aimed at establishing a time-extended database which cangive important clues on topics such as the stability of the spottedareas, differential rotation and solar-like cycles. Significantevolution of the wave-like light curves, period variations and, in mostcases, evidence for long-term variability of the global degree ofspottedness are found for the observed stars. Some spectralclassifications are rediscussed and evidence for a newly discoveredvariable star is given.
| Longterm Monitoring of Active Stars - Part Three - UBV Ri/c Photometry of 14 Southern Hemisphere Variables
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..102..655C&db_key=AST
| Longterm Photometry of Variables at ESO - Part Two - the Second Data Catalogue 1986-1990
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&AS..102...79S&db_key=AST
| Long-term photometry of variables at ESO. I - The first data catalogue (1982-1986)
This paper presents the catalog of photometric data in the Stromgrensystem obtained during the first four years (October 1982 - September1986) of the Long-Term Photometry of Variables (LTPV) program at ESO.The data are available in computer-readable form.
| Photometric Variability of HD 81410 in 1988
Not Available
| UBV(RI)c photometry for CaII emission stars. II - Observations at Mt. John University Observatory and at Mt. Stromlo
UBV(RI)c data are given for 17 stars with strong Ca II H and K emission.Techniques of observation and reduction are described briefly.
| HD 81410 - A new RS CVn binary
B and V photometry of HD 81410 obtained on 34 nights between January 3and March 14 of 1981 is presented. In both B and V, the amplitudes arefound to be approximately 0.15 mag. It is also found that a 12.86833 dayperiod satisfies all the available photometric data. Orbital elements ofthe system are derived from the published radial velocity measurements.The orbital period, strong Ca II H and K emission, and the spectraltypes of the components suggest that HD 81410 is a member of the RS CVngroup. The star is seen to become redder at fainter visual magnitudes.This is attributed to the relatively cooler temperatures of the 'darkerregions' present on the visible hemisphere.
| On the Photometric Period of HD 81410
Not Available
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| Сазвежђа: | Хидра |
| Ректацензија: | 09h27m58.14s |
| Deклинација: | -23°40'45.6" |
| Apparent магнитуда: | 8.016 |
| Даљина: | 353.357 parsecs |
| Proper motion RA: | 13.7 |
| Proper motion Dec: | -30.9 |
| B-T magnitude: | 9.259 |
| V-T magnitude: | 8.119 |
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