Astrometry with the Hubble Space Telescope: A Parallax of the Fundamental Distance Calibrator RR Lyrae

Authors

G. Fritz Benedict
B. E. McArthur
L. W. Fredrick
T. E. Harrison
J. Lee
C. L. Slesnick
J. Rhee
R. J. Patterson
E. Nelan
W. H. Jefferys
W. van Altena
P. J. Shelus
O. G. Franz
L. H. Wasserman
Paul D. Hemenway, University of Rhode Island
R. L. Duncombe
D. Story
A. L. Whipple
A. J. Bradley

Document Type

Article

Date of Original Version

2002

Abstract

We present an absolute parallax and relative proper motion for the fundamental distance scale calibrator, RR Lyrae. We obtain these with astrometric data from FGS 3, a white-light interferometer on the Hubble Space Telescope. We find π_abs = 3.82 ± 0.2 mas. Spectral classifications and VRIJHKT₂M and DDO 51 photometry of the astrometric reference frame surrounding RR Lyr indicate that field extinction is low along this line of sight. We estimate A_V = 0.07 ± 0.03 for these reference stars. The extinction suffered by RR Lyr becomes one of the dominant contributors to the uncertainty in its absolute magnitude. Adopting theaverage field absorption A_V = 0.07 ± 0.03, we obtain M = 0.61. This provides a distance modulus for the Large Magellanic Cloud (LMC) of m - M = 18.38–18.53, with the average extinction-corrected magnitude of RR Lyrae variables in the LMC, V(RR), remaining a significant uncertainty. We compare this result with more than 80 other determinations of the distance modulus of the LMC.

Citation/Publisher Attribution

Benedict, G. F., McArthur, B. E., Fredrick, L. W., Harrison, T. E., Lee, J., Slesnick, C. L., Rhee, J.,...Bradley, A. J. (2002). Astrometry with the Hubble Space Telescope: A Parallax of the Fundamental Distance Calibrator RR Lyrae. The Astronomical Journal, 123(1), 473-484. doi: 10.1086/338087

Available at: http://dx.doi.org/10.1086/338087