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Further thoughts: ES Model
ES model suffers from being Œunconventional¹ but nevertheless:
a)provides the best interpretation of the data
b)evidently works in astrophysical systems (Jupiter)
Predicts the right shape of X-ray light curve (retrograde spin on primary WD)
Lifetime of the system is ~106 years, short but not particularly short – NOTE: the 103 years quoted by Marsh & Steeghs (2002) is a misinterpretation of the text in Wu et al (2002)
It is an expected end point for double WD pairs if one has a modest (<1MG) field; secondary is not necessarily in contact with Roche Lobe – expect many of these systems?
Predicts decreasing orbital period, as observed for both systems