ASTRONOMY AND ASTROPHYSICS Colour - magnitude diagrams of the inner halo globular clusters NGC 5986 and NGC 6712 ?
نویسنده
چکیده
We present V and I photometry for NGC 5986 and B and V for NGC 6712. NGC 5986 has a blue extended horizontal branch, while NGC 6712 has a composite red and blue horizontal branch, where the latter extends to unusual bluer colours. Both clusters have RR Lyrae. We derive a reddening E(B-V) ≈ 0.29 and a distance from the Sun d ≈ 11.2 kpc for NGC 5986, and E(B-V) ≈ 0.33 and d ≈ 7.9 kpc for NGC 6712. Their galactocentric distances of RGC = 5.2 and 3.6 kpc respectively, locate them in the inner halo; NGC 6712 could be considered to be located in the bulge. NGC 6712 has |z| ≈ 500 pc, indicating that the cluster is crossing the disk. We estimate metallicities of [Fe/H] = -1.6 and -1.0 respectively for NGC 5986 and NGC 6712.
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