Astronomy and Astrophysics – Astrophysics
Scientific paper
1998-09-02
Astronomy and Astrophysics
Astrophysics
19 pages, AASTeX, to appear in the December 1998 AJ
Scientific paper
10.1086/300653
Recent years have seen a substantial improvement both in photometry of low luminosity stars in globular clusters and in modelling the stellar atmospheres of late-type dwarfs. We build on these observational and theoretical advances in undertaking the first determination of the distance to a globular cluster by main-sequence fitting using stars on the lower main sequence. The calibrating stars are extreme M subdwarfs, as classified by Gizis (1997), with parallaxes measured to a precision of better than 10%. Matching against King et al's (1998) deep (V, (V-I)) photometry of NGC 6397, and adopting E_{B-V}=0.18 mag, we derive a true distance modulus of 12.13 +- 0.15 mag for the cluster. This compares with (m-M)_0=12.24 +- 0.1 derived through conventional main-sequence fitting in the (V, (B-V)) plane. Allowing for intrinsic differences due to chemical composition, we derive a relative distance modulus of delta (m-M)_0=2.58 mag between NGC 6397 and the fiducial metal-poor cluster M92. We extend this calibration to other metal-poor clusters, and examine the resulting RR Lyrae (M_V, [Fe/H]) relation.
Gizis John E.
Reid Iain Neill
No associations
LandOfFree
The distance to NGC 6397 by M-subdwarf main-sequence fitting does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The distance to NGC 6397 by M-subdwarf main-sequence fitting, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The distance to NGC 6397 by M-subdwarf main-sequence fitting will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-464056