Optical and X-Ray Studies of Chromospherically Active Stars: FR Cancri, HD 95559, and LO Pegasi

We present a multiwavelength study of three chromospherically active stars,namely FR Cnc (= BD +16\degr 1753), HD 95559 and LO Peg (=BD +22\degr 4409),including newly obtained optical photometry, low-resolution opticalspectroscopy for FR Cnc, as well as archival IR and X-ray observations. The BVRphotometry carried out during the years 2001 - 2004 has found significantphotometric variability to be present in all three stars. For FR Cnc, aphotometric period $0.8267 \pm 0.0004 \rm {d}$ has been established. The strongvariation in the phase and amplitude of the FR Cnc light curves when folded onthis period implies the presence of evolving and migrating spots or i spotgroups on its surface. Two independent spots with migration periods of 0.97 and0.93 years respectively are inferred. The photometry of HD 95559 suggests theformation of a spot (group) during the interval of our observations. We inferthe existence of two independent spots or groups in the photosphere of LO Peg,one of which has a migration period of 1.12 years. The optical spectroscopy ofFR Cnc carried out during 2002-2003, reveals the presence of strong andvariable Ca II H and K, H$_\beta$ and $H_{\alpha}$ emission features indicativeof high level of chromospheric activity. The value of 5.3 for the ratio of theexcess emission in $H_{\alpha}$ to $H_{\beta}$, $E_{H_{\alpha}}/E_{H_{\beta}}$,suggests that the chromospheric emission may arise from an extended off-limbregion. We have also analyzed archival X-ray observations of HD 95559 and LOPeg carried out by with the ROSAT observatory. The best fit models to theirX-ray spectra imply the presence of two coronal plasma components of differingtemperatures and with sub-solar metal abundances.Comment: 40 pages, 11 figures, 6 tables, Accepted for the publication in A