Mass Loss on the Red Giant Branch and the Second-Parameter Phenomenon
نویسنده
چکیده
The “second-parameter effect” is characterized by the existence of globular clusters (GCs) with similar metallicity [Fe/H] (the “first parameter”) but different horizontal-branch (HB) morphologies. One of the primary second-parameter candidates is cluster age. In the present paper, we address the following issue: “Are the age differences between second-parameter GCs, as derived from their main-sequence turnoff properties, consistent with their relative HB types?” In order to provide an answer to this question, several analytical formulae for the mass loss rate on the red giant branch are analyzed and employed. The case of M5 vs. Palomar 4/Eridanus is specifically discussed. Our results show that, irrespective of the mass loss formula employed, the relative turnoff ages of GCs are insufficient to explain the second-parameter phenomenon, unless GCs are younger than 10 Gyr.
منابع مشابه
Horizontal-branch Models and the Second-parameter Effect. Iii. the Impact of Mass Loss on the Red Giant Branch, and the Case of M5 and Palomar 4/eridanus
Deep Hubble Space Telescope (HST) photometry has recently been presented for the outer-halo globular clusters Palomar 4 and Eridanus. The new high-precision color-magnitude diagrams obtained for these globulars have allowed a measurement of their ages relative to M5 (NGC 5904), which is a wellobserved, much closer cluster. Assuming that the globular clusters share the same chemical composition,...
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