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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
earth and planetary sciences
On the area of accretion curtains from fast aperiodic time variability of the intermediate polar EX Hya
Monthly Notices of the Royal Astronomical Society, Volume 442, No. 2, Year 2014
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Description
We present results of a study of the fast timing variability of the magnetic cataclysmic variable (mCV) EXHya. Itwas previously shown that one may expect the rapid flux variability of mCVs to be smeared out at time-scales shorter than the cooling time of hot plasma in the post-shock region of the accretion curtain near the white dwarf (WD) surface. Estimates of the cooling time and the mass accretion rate, thus provide us with a tool to measure the density of the postshock plasma and the cross-sectional area of the accretion funnel at the WD surface. We have probed the high frequencies in the aperiodic noise of one of the brightestmCVEX Hya with the help of optical telescopes, namely Southern African Large Telescope and the South African Astronomical Observatory 1.9 m telescope. We place upper limits on the plasma cooling time-scale τ < 0.3 s, on the fractional area of the accretion curtain footprint f < 1.6 × 10-4, and a lower limit on the specific mass accretion rate Ṁ/A > 3 gs-1 cm-2. We show that measurements of accretion column footprints via eclipse mapping highly overestimate their areas. We deduce a value of Λr/r ≲ 10-3 as an upper limit to the penetration depth of the accretion disc plasma at the boundary of the magnetosphere. © 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.
Authors & Co-Authors
Semena, Andrey N.
Russian Federation, Moscow
Space Research Institute of the Russian Academy of Sciences
Revnivtsev, M.
Russian Federation, Moscow
Space Research Institute of the Russian Academy of Sciences
Buckley, David A.H.
South Africa, Cape Town
South African Astronomical Observatory
South Africa, Observatory
Southern African Large Telescope Foundation
Kotze, Marissa M.
South Africa, Cape Town
South African Astronomical Observatory
Khabibullin, I.
Russian Federation, Moscow
Space Research Institute of the Russian Academy of Sciences
Breytenbach, Hannes B.
South Africa, Cape Town
South African Astronomical Observatory
South Africa, Cape Town
University of Cape Town
Sickafoose, A. A.
South Africa, Cape Town
South African Astronomical Observatory
Coppejans, R.
Netherlands, Nijmegen
Radboud Universiteit
Potter, Stephen B.
South Africa, Cape Town
South African Astronomical Observatory
Statistics
Citations: 9
Authors: 9
Affiliations: 5
Identifiers
Doi:
10.1093/mnras/stu897
ISSN:
00358711
e-ISSN:
13652966
Study Design
Cross Sectional Study