Long-term monitoring of active stars

Abstract

Abstract. As a part of an extensive program focused on the global properties and evolution of active stars, high-precision UBV (RI)c and UBV photometry of 31 selected stars is presented. The UBV (RI)c observations were collected at the European Southern Observatory over the 31 December 1992-18 January 1993 and the 20 November-3 December 1993 intervals. Additional UBV photometry obtained by the "Phoenix" and by the Catania Astrophysical Observatory Automatic Photoelectric Telescopes from 1990 to 1993 is also presented for some of the program stars. Significant evolution of the light curves, period variations and evidence for longterm variability of the global degree of spottedness are found. Some spectral classifications are revised and the inferred photometric parallaxes are compared, whenever possible, with the values measured by the Hipparcos satellite. These observations are finalized to the construction of an extended photometric database, which can give important clues on topics such as the stability of spotted areas, differential rotation, solar-like cycles and the correlation between inhomogeneities at different atmospheric levels.

Starspots and active regions on the emission red dwarf star $LQ~Hydrae$

“…We compared values of the stellar brightness in UBRI Johnson bands with the V band ones. The data by Cutispoto (1991Cutispoto ( , 1993Cutispoto ( , 1996Cutispoto ( , 1998a, Cutispoto et al (2001) and Strassmeier et al (1993Strassmeier et al ( , 1997 in RI bands were reduced from the Cousins system into the Johnson one using the dependences found by Bessel (1979). From this comparison we can see that the brightnesses in the UBRI bands depend linearly on V band magnitude.…”

“…Later these observations were continued by Strassmeier & Hall (1988) and Boyd et al (1990). Long-term series of photometric observations carried out by Jetsu (1993), Cutispoto (1991Cutispoto ( , 1993Cutispoto ( , 1996Cutispoto ( , 1998a, Cutispoto et al (2001), Strassmeier et al (1993Strassmeier et al ( , 1997 suggest the presence of the cycle of stellar activity like the solar one (Oláh et al 2000). Strassmeier et al (1993) and Alekseev & Gershberg (1996a) …”

A spectroscopy study of nearby late-type stars, possible members of stellar kinematic groups

“…-HIP 13402 (HD 17925): Although it is classified as an RS CVn variable (Eker et al 2008), Cutispoto et al (2001) shows that the binary hypothesis does not seem to be consistent with the Hipparcos photometric data. The estimated EW Li i = 182.52 ± 4.63 mÅ agrees with the 208 mÅ given by Montes et al (2001a) and the 197 mÅ given by Favata et al (1995), which suggests an age similar to the Pleaides (≈80 Myr).…”

Simultaneous optical and X-ray observations of flares and rotational modulation on the RS CVn binary HR 1099 (V711 Tau) from the MUSICOS 1998 campaign

“…In order to obtain a homogeneous data set the measurements from the two telescopes were first converted into differential values with respect to the same comparison star HD 22796 and then converted into standard values. Details on the observation techniques, reduction procedures and accuracy of the Phoenix and the Catania APT-80 photometry are given in Rodonò & Cutispoto (1992) and Cutispoto et al (2001), respectively. The V-band flux modulation shown by HR 1099 in 1998.89 (see top panel of Fig.…”