Title: Kepler observations of the beaming binary KPD 1946+4340
Authors: Bloemen, Steven ×
Marsh, T. R
Ostensen, Roy
Charpinet, S
Fontaine, G
Degroote, Pieter
Heber, U
Kawaler, S. D
Aerts, Conny
Green, E. M
Telting, J
Brassard, P
Gaensicke, B. T
Handler, G
Kurtz, D. W
Silvotti, R
Van Grootel, V
Lindberg, J. E
Pursimo, T
Wilson, P. A
Gilliland, R. L
Kjeldsen, H
Christensen-Dalsgaard, J
Borucki, W. J
Koch, D
Jenkins, J. M
Klaus, T. C #
Issue Date: Feb-2011
Publisher: Priestley and Weale
Series Title: Monthly Notices of the Royal Astronomical Society vol:410 issue:3 pages:1787-1796
Abstract: The Kepler Mission has acquired 33.5 d of continuous 1-min photometry of KPD 1946+4340, a short-period binary system that consists of a subdwarf B star (sdB) and a white dwarf. In the light curve, eclipses are clearly seen, with the deepest occurring when the compact white dwarf crosses the disc of the sdB (0.4 per cent) and the more shallow ones (0.1 per cent) when the sdB eclipses the white dwarf. As expected, the sdB is deformed by the gravitational field of the white dwarf, which produces an ellipsoidal modulation of the light curve. Spectacularly, a very strong Doppler beaming (also known as Doppler boosting) effect is also clearly evident at the 0.1 per cent level. This originates from the sdB's orbital velocity, which we measure to be 164.0 +/- 1.9 km s-1 from supporting spectroscopy. We present light-curve models that account for all these effects, as well as gravitational lensing, which decreases the apparent radius of the white dwarf by about 6 per cent, when it eclipses the sdB. We derive system parameters and uncertainties from the light curve using Markov chain Monte Carlo simulations. Adopting a theoretical white dwarf mass-radius relation, the mass of the subdwarf is found to be 0.47 +/- 0.03 M-circle dot and the mass of the white dwarf 0.59 +/- 0.02 M-circle dot. The effective temperature of the white dwarf is 15 900 +/- 300 K. With a spectroscopic effective temperature of T-eff = 34 730 +/- 250 K and a surface gravity of log g = 5.43 +/- 0.04, the subdwarf has most likely exhausted its core helium, and is in a shell He burning stage.
ISSN: 0035-8711
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Institute of Astronomy
× corresponding author
# (joint) last author

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