THE FUNDAMENTAL PARAMETERS OF THE CHROMOSPHERICALLY ACTIVE K2 DWARF EPSILON-ERIDANI

Regions exhibiting calcium and iron lines in the spectrum of the chromospherically active K2 dwarf epsilon Eri have been recorded at a resolution of lambda/DELTAlambda = 120,000 and with signal-to-noise ratio greater-than-or-equal-to 200 using a silicon array detector. A fine analysis of the resulting spectra has yielded the following fundamental parameters: Effective temperature: T(eff) = 5180 +/- 50 K Surface gravity: log g = 4.75 +/- 0.1 dex Logarithmic iron abundance (relative to the Sun): [Fe/H] = -0.09 +/- 0.05 Logarithmic calcium abundance (relative to H = 12.00): Ca/H = 6.26 +/- 0.05 Microturbulence: xi = 1.25 +/- 0.1 km s-1. Three high-excitation lines of Fe i were found to yield anomalously low iron abundances; it is postulated that the origin of the anomaly lies in nonthermal excitation of the upper photosphere caused by chromospheric emission. A comparison between the observed profile of the very strong Ca II 8542 angstrom line and theoretical profiles calculated using different model atmospheres has confirmed that a scaled solar model, based on the Holweger & Muller solar model, provides an optimal T(tau) relation for epsilon Eri. Our fundamental parameters have been used to demonstrate that epsilon Eri is in an evolutionary stage consistent with an M/M. = 0.85 theoretical zero-age main-sequence model. Considered with the existing evidence of high chromospheric activity and brisk rotation, our results suggest that epsilon Eri is almost certainly a young star of slightly less than one solar mass.