The Angular Diameter and Fundamental Parameters of Sirius A

Abstract

The Sydney University Stellar Interferometer (SUSI) has been used to make a new determination of the angular diameter of Sirius A. The observations were made at an effective wavelength of 694.1nm and the new value for the limb-darkened angular diameter is 6.048+/-0.040mas (+/-0.66%). This new result is compared with previous measurements and is found to be in excellent agreement with a conventionally calibrated measurement made with the European Southern Observatory's Very Large Telescope Interferometer (VLTI) at 2.176μm (but not with a second globally calibrated VLTI measurement). A weighted mean of the SUSI and first VLTI results gives the limb-darkened angular diameter of Sirius A as 6.041+/-0.017mas (+/-0.28%). Combination with the Hipparcos parallax gives the radius equal to 1.713+/-0.009R_solar. The bolometric flux has been determined from published photometry and spectrophotometry and, combined with the angular diameter, yields the emergent flux at the stellar surface equal to (5.32+/-0.14)×10⁸Wm^-2 and the effective temperature equal to 9845+/-64K. The luminosity is 24.7+/-0.7L_solar.