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[25.13] Searching for chirp oscillations in thermonuclear X-ray bursts

J.M. Hartman, D. Chakrabarty, D.K. Galloway (MIT CSR)

We present the results of a search of type-I X-ray bursts from accreting neutron stars for ``chirps,'' high-frequency oscillations in X-ray flux with a frequency derivative large enough to cause a loss of coherence in standard Fourier searches. Recent theoretical work predicts such chirps: the propagation of the nuclear burning front may produce chirps during the burst rise, and oscillatory modes induced on the surface of the neutron star may result in chirps that persist throughout the burst. We apply our search algorithm to ~900 type-I bursts with high-resolution timing data from the Rossi X-ray Timing Explorer. This broad sample includes burst sources both with and without known millisecond oscillations. We report on an initial search of a large region of frequency / frequency derivative phase space, as well as a more focused search for the signals predicted by specific burst models.

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Bulletin of the American Astronomical Society, 36 #3
© 2004. The American Astronomical Soceity.