r‐Modes on Rapidly Rotating, Relativistic Stars. I. Do Type I Bursts Excite Modes in the Neutron Star Ocean?

During a Type-I burst, the turbulent deflagation front may excite waves inthe neutron star ocean and upper atmosphere with frequencies, $\omega \sim 1$Hz. These waves may be observed as highly coherent flux oscillations during theburst. The frequencies of these waves changes as the upper layers of theneutron star cool which accounts for the small variation in the observed QPOfrequencies. In principle several modes could be excited but the fundamentalbuoyant $r-$mode exhibits significantly larger variability for a givenexcitation than all of the other modes. An analysis of modes in the burninglayers themselves and the underlying ocean shows that it is unlikely thesemodes can account for the observed burst oscillations. On the other hand,photospheric modes which reside in a cooler portion of the neutron staratmosphere may provide an excellent explanation for the observed oscillations.Comment: 18 pages, 1 figure, substantial changes and additions to reflect version to appear in Ap