The recently discovered system J0651 is the tightest known detached white dwarf ( WD ) binary .
Since it has not yet initiated Roche-lobe overflow , it provides a relatively clean environment for testing our understanding of tidal interactions .
I investigate the tidal heating of each WD , parameterized in terms of its tidal Q parameter .
Assuming that the heating can be radiated efficiently , the current luminosities are consistent with Q _ { 1 } \approx 7 \times 10 ^ { 10 } and Q _ { 2 } \approx 2 \times 10 ^ { 7 } , for the He and C/O WDs , respectively .
Conversely , if the observed luminosities are merely from the cooling of the WDs , these estimated values of Q represent upper limits .
A large Q _ { 1 } for the He WD means its spin velocity will be slower than that expected if it was tidally locked , which , since the binary is eclipsing , may be measurable via the Rossiter-McLaughlin effect .
After one year , gravitational wave emission shifts the time of eclipses by 5.5 { s } , but tidal interactions cause the orbit to shrink more rapidly , changing the time by up to an additional 0.3 { s } after a year .
Future eclipse timing measurements may therefore infer the degree of tidal locking .