1998/02/28 by K. Z. Stanek, P. M. Garnavich · 1 citation
Physics and Astronomy · #astro-ph
paper · pdf · doi:10.1086/311539
published as Astrophys.J.503:L131,1998 · accepted by the ApJ Letters, 11 pages, 4 figures
arxiv created 1998/03/06 · arxiv updated 2009/12/01
Following an approach by Paczyński & Stanek we compare red clump stars with parallaxes known to better than 10% in the Hipparcos catalog with the red clump stars observed in three fields in M31 using the HST. There are ∼ 600 and ∼ 6,300 such stars in the two data sets, respectively. The local red clump luminosity function is well represented by a Gaussian with the peak at MI,m=-0.23, and the dispersion σRC≈0.2 mag. This allows a single step determination of the distance modulus to M31 μ0,M31 = 24.471± 0.035 ± 0.045 mag (statistical plus systematic error) and the corresponding distance RM31= 784± 13± 17 kpc. The number of red clump stars is large enough that the formal statistical error in the distance is only \lesssim 2%. We also correct the treatment of the local interstellar extinction by Paczyński & Stanek and we obtain the Galactocentric distance modulus μ0,GC=14.57 ±0.04 ± 0.04 mag (statistical plus systematic error), and the corresponding Galactocentric distance R0=8.2 ±0.15 ± 0.15 kpc.