Savoury, C. D. J., Littlefair, S. P., Dhillon, V. S., Marsh, T. R., Gänsicke, B. T. (Boris T.), Copperwheat, C. M., Kerry, P., Hickman, R. D. G. (Richard D. G.) and Parsons, S. G. (2011) Cataclysmic variables below the period gap : mass determinations of 14 eclipsing systems. Monthly Notices of the Royal Astronomical Society, Vol.415 (No.3). pp. 2025-2041. doi:10.1111/j.1365-2966.2011.18707.x

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Abstract

We present high-speed, three-colour photometry of the eclipsing cataclysmic variables CTCV J1300-3052, CTCV J2354-4700 and SDSS J115207.00+404947.8. These
systems have orbital periods of 128.07, 94.39 and 97.52 minutes respectively, placing
all three systems below the observed “period gap” for cataclysmic variables. For each
system we determine the system parameters by fitting a parameterised model to the
observed eclipse light curve by χ2 minimisation.
We also present an updated analysis of all other eclipsing systems previously
analysed by our group. The updated analysis utilises Markov Chain Monte Carlo
techniques which enable us to arrive confidently at the best fits for each system with
more robust determinations of our errors. A new bright spot model is also adopted, that
allows better modelling of bright-spot dominated systems. In addition, we correct a
bug in the old code which resulted in the white dwarf radius being underestimated, and
consequently both the white dwarf and donor mass being overestimated. New donor
masses are generally between 1 and 2σ of those originally published, with the exception
of SDSS 1502 (−2.9σ, Mr = −0.012M⊙) and DV UMa (+6.1σ, Mr = +0.039M⊙).
We note that the donor mass of SDSS 1501 has been revised upwards by 0.024M⊙
(+1.9σ). This system was previously identified as having evolved passed the minimum
orbital period for cataclysmic variables, but the new mass determination suggests
otherwise. Our new analysis confirms that SDSS 1035 and SDSS 1433 have evolved
past the period minimum for cataclysmic variables, corroborating our earlier studies.
We find that the radii of donor stars are oversized when compared to theoretical
models, by approximately 10 percent. We show that this can be explained by invoking
either enhanced angular momentum loss, or by taking into account the effects of star
spots. We are unable to favour one cause over the other, as we lack enough precise
mass determinations for systems with orbital periods between 100 and 130 minutes,
where evolutionary tracks begin to diverge significantly.
We also find a strong tendency towards high white dwarf masses within our sample,
and no evidence for any He-core white dwarfs. The dominance of high mass white
dwarfs implies that erosion of the white dwarf during the nova outburst must be
negligible, or that not all of the mass accreted is ejected during nova cycles, resulting
in the white dwarf growing in mass.

Item Type:	Journal Article
Subjects:	Q Science > QB Astronomy
Divisions:	Faculty of Science > Physics
Library of Congress Subject Headings (LCSH):	Eclipsing binaries, Cataclysmic variable stars
Journal or Publication Title:	Monthly Notices of the Royal Astronomical Society
Publisher:	Wiley
ISSN:	00358711
Official Date:	August 2011
Dates:	Date Event August 2011 Published
Volume:	Vol.415
Number:	No.3
Page Range:	pp. 2025-2041
DOI:	10.1111/j.1365-2966.2011.18707.x
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Funder:	Science and Technology Facilities Council (Great Britain) (STFC), Research Councils UK (RCUK)
Grant number:	ST/F002599/1 (STFC), ST/G003092/1 (STFC)

Data sourced from Thomson Reuters' Web of Knowledge

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