J. C. Pandey et al. 2005 The Astronomical Journal 130 1231 doi:10.1086/432539
J. C. Pandey1, K. P. Singh2, S. A. Drake3,4 and R. Sagar1
Show affiliationsWe present a multiwavelength study of three chromospherically active stars, namely, FR Cnc (BD +16°1753), HD 95559, and LO Peg (BD +22°4409), including newly obtained optical photometry and low-resolution optical spectroscopy for FR Cnc, as well as archival IR and X-ray observations. The BVR photometry carried out from 2001 to 2004 has found significant photometric variability to be present in all three stars. For FR Cnc, a photometric period of 0.8267 ± 0.0004 days has been established. The strong variation in the phase and amplitude of the FR Cnc light curves when folded on this period implies the presence of evolving and migrating spots or spot groups on its surface. Two independent spots with migration periods of 0.97 and 0.93 yr, respectively, are inferred. The photometry of HD 95559 suggests the formation of a spot (group) during the interval of our observations. We infer the existence of two independent spots or groups in the photosphere of LO Peg, one of which has a migration period of 1.12 yr. The optical spectroscopy of FR Cnc carried out during 2002–2003 reveals the presence of strong and variable Ca II H and K, Hβ, and Hα emission features indicative of a high level of chromospheric activity. The value of 5.3 for the ratio of the excess emission in Hα to Hβ, EHα/EHβ, suggests that the chromospheric emission may arise from an extended off-limb region. We have searched for the presence of color excesses in the near-IR JHK bands of these stars using Two Micron All Sky Survey data, but none of them appear to have any significant color excess. We have also analyzed archival X-ray observations of HD 95559 and LO Peg carried out with the ROSAT observatory. The best-fit models to their X-ray spectra imply the presence of two coronal plasma components of differing temperatures and with subsolar metal abundances. The inferred emission measures and temperatures of these systems are similar to those found for other active dwarf stars. The kinematics of FR Cnc suggest that it is a very young (35–55 Myr) main-sequence star and a possible member of the IC 2391 supercluster. LO Peg also has young disk-type kinematics and has been previously suggested to be a member of the 100 Myr old Local Association (Pleiades moving group). The kinematics of HD 95559 indicate it is a possible member of the 600 Myr old Hyades supercluster.
binaries: general; stars: activity; stars: individual (FR Cancri, LO Pegasi, HD 95559); X-rays: stars
Issue 3 (2005 September)
Received 2005 March 9, accepted for publication 2005 May 31
J. C. Pandey et al. 2005 The Astronomical Journal 130 1231
Dagny L. Looper et al. 2008 ApJ 686 528
Naoki Yoshida et al. 2004 ApJ 605 579
Deidre A. Hunter and Bruce G. Elmegreen 2004 The Astronomical Journal 128 2170
K. M. Huffenberger et al 2006 ApJ 651 L81
S. Komossa and David Merritt 2008 ApJ 689 L89
P. Panuzzo et al. 2007 ApJ 656 206
E. D. Grundstrom et al. 2007 ApJ 656 437
T. H. Jarrett et al. 2007 The Astronomical Journal 133 979
Marie E. Machacek et al. 2000 ApJ 532 118