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

Journal article


Publication Details

Author(s): Brumback MC, Hickox RC, Bachetti M, Ballhausen R, Furst FS, Pike S, Pottschmidt K, Tomsick JA, Wilms J
Journal: Astrophysical Journal Letters
Publisher: IOP PUBLISHING LTD
Publication year: 2018
Volume: 861
Journal issue: 1
ISSN: 2041-8205
eISSN: 2041-8213


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.


FAU Authors / FAU Editors

Ballhausen, Ralf
Dr.Karl-Remeis-Sternwarte Bamberg, Astronomisches Institut
Wilms, Jörn Prof. Dr.
Professur für Astronomie und Astrophysik


External institutions with authors

California Institute of Technology (Caltech)
Dartmouth College
European Space Agency (ESA)
INAF-Osservatorio Astronomico di Cagliari
University of California, Berkeley
University of Maryland, Baltimore County


How to cite

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).

BibTeX: 

Last updated on 2019-23-08 at 08:33