Stability of the r-modes in white dwarf stars -: art. no. 064007

The stability of the r-modes in rapidly rotating white dwarf stars is investigated. Improved estimates of the growth times of the gravitational-radiation driven instability in the r-modes of the observed DQ Her objects are found to be longer (probably considerably longer) than 6 X 10(9) yr. This rules out the possibility that the r-modes in these objects are emitting gravitational radiation at levels that could be detectable by LISA. More generally it is shown that the r-mode instability can only be excited in a very small subset of very hot (T greater than or similar to 10(6) K), rather massive (M greater than or similar to 0.9 M.) and very rapidly rotating (P-min less than or equal to P less than or similar to 1.2P(min)) white dwarf stars. Further, the growth times of this instability are so long that these conditions must persist for a very long time (t greater than or similar to 10(9) yr) to allow the amplitude to grow to a dynamically significant level. This makes it extremely unlikely that the r-mode instability plays a significant role in any real white dwarf stars. [S0556-2821(99)01818-4].