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| Paper: |
The Absolute Magnitude of RR Lyrae Stars derived from the Hipparcos Catalogue |
| Volume: |
167, Harmonizing Cosmic Distance Scales in a Post-Hipparcos Era |
| Page: |
332 |
| Authors: |
Tsujimoto, Takuji; Yoshii, Yuzuru |
| Abstract: |
The present determination of the absolute magnitude of RR Lyrae stars MV(RR) is twofold, relying upon Hipparcos proper motions and trigonometric parallaxes separately. First, applying the statistical parallax method to the proper motions, we find <MV(RR)>=0.69±0.10 for 99 halo RR Lyrae stars with <[Fe/H]> =-1.58. Second, applying the Lutz-Kelker correction to the RR Lyrae HIP95497 with the most accurately measured parallax, we obtain MV(RR)=(0.58-0.68)+0.28-0.31 at [Fe/H]=-1.6. Furthermore, allowing full use of low accuracy and negative parallaxes as well for 125 RR Lyrae stars with -2.49<=[Fe/H]<=0.07, the maximum likelihood estimation yields the relation, MV(RR)=(0.59±0.37)+(0.20±0.63)([Fe/H] +1.60), which formally agrees with the recent preferred relation. The same estimation yields again <MV(RR)> = 0.65±0.33 for the 99 halo RR Lyrae stars. Although the formal errors in the latter three parallax estimates are rather large, all of the four results suggest the fainter absolute magnitude, MV(RR)≈0.6-0.7 at [Fe/H]=-1.6. The present results are consistent with the LMC distance modulus recently determined and still provide the lower limit on the age of the universe which is inconsistent with a flat, matter-dominated universe with current estimates of the Hubble constant. |
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