TY - JOUR
T1 - Stellar variability in the central populations of 47 tucanae from WF/PC observations with the hubble space telescope. II. Binary systems
AU - Edmonds, Peter D.
AU - Gilliland, Ronald L.
AU - Guhathakurta, Puragra
AU - Petro, Larry D.
AU - Saha, Abhijit
AU - Shara, Michael M.
N1 - Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.
PY - 1996
Y1 - 1996
N2 - Stars in the core of 47 Tue have been intensively surveyed for variability, using differential time series photometry, with the Planetary Camera of the Hubble Space Telescope. Some 20,000 stars were surveyed in the U band (F336W) in a 66″ × 66″ field centered on the core of 47 Tue, with almost continuous observing over 38.5 hr, and using 1000 s exposure times. Using aperture photometry, PSF fitting, and power spectrum techniques, two W UMa systems were discovered, as well as six semidetached or detached binaries with periods between 0.41 and 1.5 days. The two faintest variables found are within the error circles of two highly variable X-ray sources and are good candidates for neutron star binaries or magnetic cataclysic variables. Two other certain variables were found, one of which is a possible cataclysmic variable. The radial distribution of the binaries is significantly more centrally concentrated than the average star, but it is consistent with the radial distribution of the blue stragglers found in the core. We show that the contact binary frequency and the period distribution of the binaries imply that few, if any, of the binaries are primordial.
AB - Stars in the core of 47 Tue have been intensively surveyed for variability, using differential time series photometry, with the Planetary Camera of the Hubble Space Telescope. Some 20,000 stars were surveyed in the U band (F336W) in a 66″ × 66″ field centered on the core of 47 Tue, with almost continuous observing over 38.5 hr, and using 1000 s exposure times. Using aperture photometry, PSF fitting, and power spectrum techniques, two W UMa systems were discovered, as well as six semidetached or detached binaries with periods between 0.41 and 1.5 days. The two faintest variables found are within the error circles of two highly variable X-ray sources and are good candidates for neutron star binaries or magnetic cataclysic variables. Two other certain variables were found, one of which is a possible cataclysmic variable. The radial distribution of the binaries is significantly more centrally concentrated than the average star, but it is consistent with the radial distribution of the blue stragglers found in the core. We show that the contact binary frequency and the period distribution of the binaries imply that few, if any, of the binaries are primordial.
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U2 - 10.1086/177687
DO - 10.1086/177687
M3 - Article
AN - SCOPUS:33749168519
SN - 0004-637X
VL - 468
SP - 241
EP - 260
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1 PART I
ER -