The Angular Diameter and Fundamental Parameters of Sirius A

TL;DR

This study precisely measures Sirius A's angular diameter and fundamental parameters using interferometry, resulting in improved estimates of its size, temperature, and luminosity, and compares these with previous measurements.

Contribution

It provides a new, highly precise measurement of Sirius A's angular diameter and fundamental stellar parameters, improving the accuracy of stellar models for this star.

Findings

Angular diameter of Sirius A is 6.048 +/- 0.040 mas.

Effective temperature of Sirius A is 9845 +/- 64 K.

Luminosity of Sirius A is 24.7 +/- 0.7 L_sun.

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 694.1 nm 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 2.176 microns (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_sun. 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)x10^8 Wm^-2 and the effective temperature equal to 9845 +/- 64 K. The luminosity is 24.7 +/- 0.7 L_sun.