Neutron star crust can support a large ellipticity

J. A. Morales, C. J. Horowitz

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


Non-axisymmetrical deformations of the crust on rapidly rotating neutron stars are one of the main targets of searches for continuous gravitational waves. The maximum ellipticity, or fractional difference in moments of inertia, which can be supported by deformations of the crust (known as 'mountains'), provides an important upper limit on the strength of these continuous gravitational wave sources. We use the formalism developed by Gittins and Andersson, along with a deforming force that acts mainly in the transverse direction, to obtain a maximum ellipticity of 7.4 × 10-6. This is larger than the original results that Gittins and Andersson obtained but consistent with earlier calculations by Ushomirsky, Cutler, and Bildsten. This suggests that rotating neutron stars could be strong sources of continuous gravitational waves.

Original languageEnglish
Pages (from-to)5610-5616
Number of pages7
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - 1 Dec 2022
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2022 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.


This work is partially supported by the US Department of Energy, grants DE-FG02-87ER40365 and DE- SC0018083.

FundersFunder number
U.S. Department of EnergyDE- SC0018083, DE-FG02-87ER40365


    • gravitational waves
    • stars: neutron


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