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Peculiar Multimodality on the Horizontal Branch of the Globular Cluster NGC 2808

Sosin, Craig and Dorman, Ben and Djorgovski, S. George and Piotto, Giampaolo and Rich, R. Michael and King, Ivan R. and Liebert, James and Phinney, E. Sterl and Renzini, Alvio (1997) Peculiar Multimodality on the Horizontal Branch of the Globular Cluster NGC 2808. Astrophysical Journal, 480 (1). L35-L38. ISSN 0004-637X. doi:10.1086/310606.

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We present distributions of colors of stars along the horizontal branch (HB) of the globular cluster NGC 2808, from Hubble Space Telescope Wide Field Planetary Camera 2 imaging in B, V, and an ultraviolet filter (F218W). This cluster's HB is already known to be strongly bimodal, with approximately equal-sized HB populations widely separated in the color-magnitude diagram. Our images reveal a long blue tail with two gaps, for a total of four nearly distinct HB groups. These gaps are very narrow, corresponding to envelope-mass differences of only ~0.01 M_☉. This remarkable multimodality may be a signature of mass-loss processes, subtle composition variations, or dynamical effects; we briefly summarize the possibilities. The existence of narrow gaps between distinct clumps on the HB presents a challenge for models that attempt to explain HB bimodality or other peculiar HB structures.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Djorgovski, S. George0000-0002-0603-3087
Rich, R. Michael0000-0003-0427-8387
Renzini, Alvio0000-0002-7093-7355
Additional Information:© 1997. The American Astronomical Society. Received 1997 January 13; accepted 1997 February 6. This work was supported by NASA grant GO-6095 from STScI, as well as by NASA grants NAG5-700, NAGW-4106 (B. D.), and NAG5-2756 (E. S. P.), by the Bressler Foundation (S. G. D.), and by the Agenzia Spaziale Italiana and the Ministero dell'Università e della Ricerca Scientifica e Tecnologica (G. P. and A. R.). Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.
Funding AgencyGrant Number
Bressler FoundationUNSPECIFIED
Agenzia Spaziale Italiana (ASI)UNSPECIFIED
Ministero dell'Università e della Ricerca Scientifico-Tecnologica (MURST)UNSPECIFIED
NASANAS 5-26555
Subject Keywords:globular clusters: individual (NGC 2808) ; stars: horizontal-branch
Issue or Number:1
Record Number:CaltechAUTHORS:20190205-142100559
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Official Citation:Craig Sosin et al 1997 ApJ 480 L35
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:92692
Deposited By: George Porter
Deposited On:05 Feb 2019 23:04
Last Modified:16 Nov 2021 03:52

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