Continuous Gravitational Waves from White Dwarf Mountains*

Continuous gravitational waves (CGWs) from non-axisymmetrical deformations on neutron stars (NSs), better known as mountains, can reveal much about the crust of a NS, the interior of a NS, and the fundamental symmetries of nature. Recently, Gittins. et. al. [1] indicated that the maximum mountain that a NS crust can support is an order of magnitude smaller than the previous calculation made by Ushomirsky et. al. [2]. This discrepancy could have a serious impact on the detectability of CGWs from NS mountains. In this project, we present the calculation of the maximum mountain that solid white dwarfs (WDs) can support. The purpose of this calculation is two-fold: (1) it is easier to handle than the calculation of a maximum mountain of a realistic NS, which will enable us to explore deeper how and why the various maximum mountain calculations differ, (2) the equation of state and structure of WDs are better known than those of NSs, so the calculation has much less uncertainty. We present results for the maximum ellipticity of a solid WD and discuss the observability of CGWs from a rotating WD with LISA.

[1]: G. Ushomirsky, C. Cutler, and L. Bildsten, Deformations of accreting neutron star crusts and gravitational wave emission, Mon. Not. R. Astron. Soc. 319, 902 (2000), astro-ph/0001136.

[2]: F. Gittins, N. Andersson,  and D.I. Jones, Modelling neutron star mountains, Mon. Not. R.  Astron. Soc. 500(4) (2020)