Interferometry and asteroseismology: The radius of τ Cet
Abstract: We have determined from interferometry the radius of the nearby star τ Cet, using recent observations with the VINCI instrument on VLTI using the siderostats. The limb-darkened disk diameter is determined, with an unprecedented internal precision of 0.5%, to be 1.971 ± 0.009(int.) ± 0.05(ext.) mas, corresponding to a physical radius of 0.773 ± 0.004(int.) ± 0.02(ext.) R� . With this determination τ Cet becomes a prime target for asteroseismic campaigns to determine its internal structure, and thereby test stellar evolution theory. We discuss implications for asteroseismology and present predictions for oscillation properties.
Cites background or methods from "Interferometry and asteroseismology..."
...The simulation converges with a luminosity log (L/L ) = −0.296 (to be compared with log (L/L ) = −0.284±0.0240.026, Pijpers et al. 2003), an effective temperature Teff = 5377 K and a linear radius of 0.821 R in agreement with the VLTI determination....
...Pijpers et al. (2003) have chosen to adopt a larger helium content but with a much smaller mass (0.77 M ) to account for both spectroscopic observations and their interferometric measurement....
...12 to 16. τCeti: The size of τCet has recently been estimated by Pijpers et al. (2003) from the same initial set of observations....
...Its size has already been inferred from the VLTI data by Pijpers et al. (2003) and we will give in this section a revised value for its angular diameter, on the basis of a more extended calibration procedure and after the revision of its main calibrator’s size, θCet....
...Indeed, we cannot confirm from our analysis the discrepancy observed by Pijpers et al. (2003) between the interferometric and spectroscopic diameters....
...The evolution tracks were computed using the evolution code of Christensen-Dalsgaard (1982), with the EFF equation of state (Eggleton et al. 1973), OPAL opacities (Iglesias & Rogers 1996), Bahcall & Pinsonneault (1995) nuclear cross sections, and the mixing-length formalism (MLT) for convection....
...For θ Cet the uniform disk diameter has been estimated to be 2.69± 0.03mas, using absolutely calibrated spectra over a wide spectral range (Cohen et al. 1999)....
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