FR Cnc=BD+16°1753- a young active main-sequence star

Abstract

The star BD+16°1753(α₂₀₀₀=08^h32 ^m30^s·5 and {delta}₂₀₀₀=+15°49'26") of V=10.43 mag and spectral type K8V is an optical counterpart of the bright soft X-ray source 1ES 0829 + 15.9=1RXS J083230.9+154940 (Elvis et al. 1992; Schachter et al. 1996; Voges et al. 1999). BD +16°1753 is 33±2 pc distant (Perryman et al. 1997) implying an absolute magnitude of 7.8 and a ratio of X-ray to bolometric luminosity f_x/f_bol of ~10⁻³ which shows that the star has an active corona at at the 'saturation' limit. It has been classified as an 'unsolved' Hipparcos variable star (FR Cnc) of 0.17 magnitudes amplitude variability (Perryman et al., 1997), and as a suspected BY Dra-type variable, i.e., having variability due to the rotational modulation of starspots, by Kazarovets et al. (1999). Using the mean radial velocity of 25.5 km/s (Upgren et al. 2002) and the Hipparcos Catalogue distance and proper motions, the galactic space velocity components (U, V, W) of BD +16°1753 are (−24.1, −22.8, −5.1) km/s. This clearly places the star inside the young disk population boundaries in the (U, V) and (V, W) diagram (Montes et al. 2001). Broad band BVR photometric observations of FR Cnc were carried out from the State Observatory Naini Tal using the 2K×2K CCD camera during the years 2001-2002. We have also taken low resolution spectra from 104-cm telescope at State Observatory Naini Tal using the HR-320 spectrograph with the 1K×1K CCD camera. The dispersion of the spectrograph was 100 Å/mm. Both photometric and spectroscopic data were reduced using the standard packages under IRAF.