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A far-ultraviolet survey of 47 Tucanae. I. Imaging

A far-ultraviolet survey of 47 Tucanae. I. Imaging
A far-ultraviolet survey of 47 Tucanae. I. Imaging
We present results from the imaging portion of a far-ultraviolet (FUV) survey of the core of 47 Tucanae. We have detected 767 FUV sources, 527 of which have optical counterparts in archival HST/WFPC2 images of the same field. Most of our FUV sources are main-sequence (MS) turnoff stars near the detection limit of our survey. However, the FUV/optical color-magnitude diagram (CMD) also reveals 19 blue stragglers (BSs), 17 white dwarfs (WDs), and 16 cataclysmic variable (CV) candidates. The BSs lie on the extended cluster MS, and four of them are variable in the FUV data. The WDs occupy the top of the cluster cooling sequence, down to an effective temperature of Teff~=20,000 K. Our FUV source catalog probably contains many additional, cooler WDs without optical counterparts. Finally, the CV candidates are objects between the WD cooling track and the extended cluster MS. Four of the CV candidates are previously known or suspected cataclysmics. All of these are bright and variable in the FUV. Another CV candidate is associated with the semidetached binary system V36 that was recently found by M. D. Albrow and coworkers. V36 has an orbital period of 0.4 or 0.8 days, blue optical colors, and is located within 1" of a Chandra X-ray source. A few of the remaining CV candidates may represent chance superpositions or SMC interlopers, but at least half are expected to be real cluster members with peculiar colors. However, only a few of these CV candidates are possible counterparts to Chandra X-ray sources. Thus, it is not yet clear which, if any, of them are true CVs, rather than noninteracting MS/WD binaries or helium WDs.
stars, blue stragglers, galaxy, globular clusters, 47 Tucanae, novae, cataclysmic variables, ultraviolet, white dwarfs
0004-637X
752-759
Knigge, C
ac320eec-631a-426e-b2db-717c8bf7857e
Zurek, D.R.
4745ee98-520b-4e26-a05a-113c0c563b97
Shara, M.M.
4d9c7bc7-3420-4773-b421-b1f5c362ab5b
Long, K.S.
91417b3d-d408-475a-8907-eec131e17c66
Knigge, C
ac320eec-631a-426e-b2db-717c8bf7857e
Zurek, D.R.
4745ee98-520b-4e26-a05a-113c0c563b97
Shara, M.M.
4d9c7bc7-3420-4773-b421-b1f5c362ab5b
Long, K.S.
91417b3d-d408-475a-8907-eec131e17c66

Knigge, C, Zurek, D.R., Shara, M.M. and Long, K.S. (2002) A far-ultraviolet survey of 47 Tucanae. I. Imaging. The Astrophysical Journal, 579 (2), 752-759. (doi:10.1086/342835).

Record type: Article

Abstract

We present results from the imaging portion of a far-ultraviolet (FUV) survey of the core of 47 Tucanae. We have detected 767 FUV sources, 527 of which have optical counterparts in archival HST/WFPC2 images of the same field. Most of our FUV sources are main-sequence (MS) turnoff stars near the detection limit of our survey. However, the FUV/optical color-magnitude diagram (CMD) also reveals 19 blue stragglers (BSs), 17 white dwarfs (WDs), and 16 cataclysmic variable (CV) candidates. The BSs lie on the extended cluster MS, and four of them are variable in the FUV data. The WDs occupy the top of the cluster cooling sequence, down to an effective temperature of Teff~=20,000 K. Our FUV source catalog probably contains many additional, cooler WDs without optical counterparts. Finally, the CV candidates are objects between the WD cooling track and the extended cluster MS. Four of the CV candidates are previously known or suspected cataclysmics. All of these are bright and variable in the FUV. Another CV candidate is associated with the semidetached binary system V36 that was recently found by M. D. Albrow and coworkers. V36 has an orbital period of 0.4 or 0.8 days, blue optical colors, and is located within 1" of a Chandra X-ray source. A few of the remaining CV candidates may represent chance superpositions or SMC interlopers, but at least half are expected to be real cluster members with peculiar colors. However, only a few of these CV candidates are possible counterparts to Chandra X-ray sources. Thus, it is not yet clear which, if any, of them are true CVs, rather than noninteracting MS/WD binaries or helium WDs.

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More information

Published date: 10 November 2002
Keywords: stars, blue stragglers, galaxy, globular clusters, 47 Tucanae, novae, cataclysmic variables, ultraviolet, white dwarfs

Identifiers

Local EPrints ID: 26873
URI: http://eprints.soton.ac.uk/id/eprint/26873
ISSN: 0004-637X
PURE UUID: 2ff1fbbc-9ed3-4f4c-a769-d9440d1a816a

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Date deposited: 24 Apr 2006
Last modified: 15 Jul 2019 19:13

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