Discovery of Pulsation Dropout and Turn-on during the High State of the Accreting X-Ray Pulsar LMC X-4

Brumback MC, Hickox RC, Bachetti M, Ballhausen R, Furst FS, Pike S, Pottschmidt K, Tomsick JA, Wilms J (2018)


Publication Status: Published

Publication Type: Journal article

Publication year: 2018

Journal

Publisher: IOP PUBLISHING LTD

Book Volume: 861

Article Number: ARTN L7

Journal Issue: 1

DOI: 10.3847/2041-8213/aacd13

Abstract

Two Nuclear Spectroscopic Telescope Array (NuSTAR) observations of the luminous X-ray pulsar LMC X-4 in 2015 October and November captured several bright accretion flares from this source, which has a long history of stable pulse and superorbital behavior. We present a timing analysis of these data in which we detect a rapid pulse "turn-on" in association with the accretion flares, during which the source reaches super-Eddington luminosities. Pulsations, which are normally seen from this source, are found to only occur for approximately one hour before and during the bright flares. Beyond one hour before and after the flares, we find pulsations to be weak or nonexistent, with fractional rms amplitudes of less than 0.05. At the onset of the flare, the pulse profiles exhibit a phase shift of 0.25 cycles that could be associated with a change in the emission geometry. This increase in pulse strength occurring well before the flare cannot be explained by the propeller effect, and potentially offers a connection between the magnetic properties of pulsars that accrete close to their Eddington limits and ultraluminous X-ray pulsars.

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APA:

Brumback, M.C., Hickox, R.C., Bachetti, M., Ballhausen, R., Furst, F.S., Pike, S.,... Wilms, J. (2018). Discovery of Pulsation Dropout and Turn-on during the High State of the Accreting X-Ray Pulsar LMC X-4. Astrophysical Journal Letters, 861(1). https://dx.doi.org/10.3847/2041-8213/aacd13

MLA:

Brumback, Mckinley C., et al. "Discovery of Pulsation Dropout and Turn-on during the High State of the Accreting X-Ray Pulsar LMC X-4." Astrophysical Journal Letters 861.1 (2018).

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