Study of photospheric, chromospheric and coronal activities of V1147 Tau

Abstract

We present analyses of optical photometric, spectroscopic, polarimetric and X-ray observations of the K5V binary star, V1147 Tau. Nearly 20 yr of optical observations show that V1147 Tau is a periodic variable with a photometric period of 1.4845±0.0001 d. Light curves observed at 16 epochs show changes in minima, amplitude and shape indicating that the variability is due to the presence of surface inhomogeneities. The surface coverage of spots was found to be in the range of 9–22 per cent. Most of the time, the spots were resolved as two active longitudes. Switching of dominant active longitudes was also seen. The optical spectroscopy revealed that Hα is present in emission, indicating a high level of chromospheric activity. The polarimetric observations yield average values of polarization to be 0.40 ± 0.03, 0.22 ± 0.05, 0.17 ± 0.07 and 0.12 ± 0.04 per cent in B, V, R and I bands, respectively, which indicates the possibility of scattering by thin circumstellar material. The X-ray light curve was found to be rotationally modulated and was anticorrelated with optical light curves observed at quasi-simultaneous epochs. The corona of V1147 Tau consists of a two temperature plasma with kT₁ = 0.07 keV and kT₂ = 0.66 keV. The X-ray luminosity in the 0.2–2.4 keV energy band was found to be 4.4–6.8 × 10^29 erg s ⁻¹. Flaring features were also seen in the X-ray light curve.