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Formation of phase lags at the cyclotron energies in the pulse profiles of magnetized, accreting neutron stars

Schönherr, G. and Schwarm, F.-W. and Falkner, S. and Dauser, T. and Ferrigno, C. and Kühnel, M. and Klochkov, D. and Kretschmar, P. and Becker, P. A. and Wolff, M. T. and Pottschmidt, K. and Falanga, M. and Kreykenbohm, I. and Fürst, F. and Staubert, R. and Wilms, J. (2014) Formation of phase lags at the cyclotron energies in the pulse profiles of magnetized, accreting neutron stars. Astronomy and Astrophysics, 564 . Art. No. L8. ISSN 0004-6361. doi:10.1051/0004-6361/201322448.

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Context. Accretion-powered X-ray pulsars show highly energy-dependent and complex pulse-profile morphologies. Significant deviations from the average pulse profile can appear, in particular close to the cyclotron line energies. These deviations can be described as energy-dependent phase lags, that is, as energy-dependent shifts of main features in the pulse profile. Aims. Using a numerical study we explore the effect of cyclotron resonant scattering on observable, energy-resolved pulse profiles. Methods. We generated the observable emission as a function of spin phase, using Monte Carlo simulations for cyclotron resonant scattering and a numerical ray-tracing routine accounting for general relativistic light-bending effects on the intrinsic emission from the accretion columns. Results. We find strong changes in the pulse profile coincident with the cyclotron line energies. Features in the pulse profile vary strongly with respect to the average pulse profile with the observing geometry and shift and smear out in energy additionally when assuming a non-static plasma. Conclusions. We demonstrate how phase lags at the cyclotron energies arise as a consequence of the effects of angular redistribution of X-rays by cyclotron resonance scattering in a strong magnetic field combined with relativistic effects. We also show that phase lags are strongly dependent on the accretion geometry. These intrinsic effects will in principle allow us to constrain a system’s accretion geometry.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Falkner, S.0000-0001-5209-991X
Dauser, T.0000-0003-4583-9048
Kretschmar, P.0000-0001-9840-2048
Wolff, M. T.0000-0002-4013-5650
Pottschmidt, K.0000-0002-4656-6881
Kreykenbohm, I.0000-0001-7335-1803
Fürst, F.0000-0003-0388-0560
Wilms, J.0000-0003-2065-5410
Additional Information:© 2014 ESO. Received 6 August 2013. Accepted 9 March 2014. Published online 04 April 2014. We thank the International Space Science Institute ISSI in Bern (CH) for granting two International Team meetings on “The physics of the accretion column of X-ray pulsars”, which have much inspired this collaborative work. We also thank the Bundesministerium für Wirtschaft und Technologie for funding through Deutsches Zentrum für Luft- und Raumfahrt grant 50 OR 1113. M.T.W. is supported by the US Office of Naval Research and the NASA ADAP Program under grant NNH13AV18I. We thank the anonymous referee for very useful comments.
Funding AgencyGrant Number
International Space Science Institute (ISSI)UNSPECIFIED
Deutsches Zentrum für Luft- und Raumfahrt (DLR)50 OR 1113
Office of Naval Research (ONR)UNSPECIFIED
Subject Keywords:X-rays: binaries, stars: neutron, methods: numerical
Record Number:CaltechAUTHORS:20140603-143146615
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Official Citation:Formation of phase lags at the cyclotron energies in the pulse profiles of magnetized, accreting neutron stars G. Schönherr, F.-W. Schwarm, S. Falkner, T. Dauser, C. Ferrigno, M. Kühnel, D. Klochkov, P. Kretschmar, P. A. Becker, M. T. Wolff, K. Pottschmidt, M. Falanga, I. Kreykenbohm, F. Fürst, R. Staubert and J. Wilms A&A 564 L8 (2014) DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:46057
Deposited By: Ruth Sustaita
Deposited On:03 Jun 2014 22:10
Last Modified:10 Nov 2021 17:20

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