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Blue Horizontal Branch Stars in M92

Cohen, J. G. and McCarthy, J. K. (1997) Blue Horizontal Branch Stars in M92. Astronomical Journal, 113 (4). pp. 1353-1358. ISSN 0004-6256. doi:10.1086/118348.

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We have analyzed high dispersion and high precision spectra of 5 blue horizontal branch stars in the globular cluster M92 to establish that the projected rotational velocity for these stars ranges from 15 to 40 km s^(-1). This is larger than that expected based on the rotation of their main sequence progenitors, the spin down of rotation with age, and the conservation of angular momentum. Possible explanations include a rapidly rotating stellar core. An abundance analysis of these spectra of these blue HB stars in M92 yields the same results as have been obtained from the giants in this cluster. There is a hint of a trend of higher abundance as the projected surface rotational velocity increases, which could be chance and requires confirmation.

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Cohen, J. G.0000-0002-8039-4673
Additional Information:© 1997 American Astronomical Society. Provided by the NASA Astrophysics Data System. Received 1996 December 2; revised 1997 January 2. Based in large part on observations obtained at the W.M. Keck Observatory, which is jointly operated by the California Institute of Technology and the University of California. We are grateful to R. Earle Luck for providing the computer-ready compendium of gf-values as well as for the LTE model atmosphere and abundance analysis codes provided by Bob Kurucz and Chris Sneden. We are grateful to Mike Fahre for providing the infrared photometry for the M92 blue HB stars. It is a pleasure to thank the W.M. Keck Foundation, and its late President Emeritus, Howard B. Keck, for the generous grant that made the Keck Observatory possible. We thank Theresa Chelminiak for observing assistance at the telescope.
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W. M. Keck FoundationUNSPECIFIED
Issue or Number:4
Record Number:CaltechAUTHORS:20190530-082701082
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:95950
Deposited By: Tony Diaz
Deposited On:30 May 2019 16:20
Last Modified:16 Nov 2021 17:17

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