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SWIFT J1756.9−2508: spectral and timing properties of its 2018 outburst

Sanna, A. and Pintore, F. and Riggio, A. and Mazzola, S. M. and Bozzo, E. and Di Salvo, T. and Ferrigno, C. and Gambino, A. F. and Papitto, A. and Iaria, R. and Burderi, L. (2018) SWIFT J1756.9−2508: spectral and timing properties of its 2018 outburst. Monthly Notices of the Royal Astronomical Society, 481 (2). pp. 1658-1666. ISSN 0035-8711.

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We discuss the spectral and timing properties of the accreting millisecond X-ray pulsar SWIFT J1756.9−2508 observed by XMM–Newton, NICER, and NuSTARduring the X-ray outburst occurred in April 2018. The spectral properties of the source are consistent with a hard state dominated at high energies by a non-thermal power-law component with a cut-off at ∼70 keV. No evidence of iron emission lines or reflection humps has been found. From the coherent timing analysis of the pulse profiles, we derived an updated set of orbital ephemerides. Combining the parameters measured from the three outbursts shown by the source in the last ∼11 yr, we investigated the secular evolution of the spin frequency and the orbital period. We estimated a neutron magnetic field of 3.1 × 10^8 < B_(PC) < 4.5 × 10^8 G and measured an orbital period derivative of −4.1 × 10^(−12) < P˙_(orb) < 7.1 × 10^(−12) s s^(−1). We also studied the energy dependence of the pulse profile by characterizing the behaviour of the pulse fractional amplitude in the energy range 0.3–80 keV. These results are compared with those obtained from the previous outbursts of SWIFT J1756.9−2508 and other previously known accreting millisecond X-ray pulsars.

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Additional Information:© 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2018 August 18. Received 2018 August 18; in original form 2018 June 17. Published: 27 August 2018. We thank N. Schartel for providing us with the possibility to perform the ToO observation in the Director Discretionary Time, and the XMM–Newton team for the technical support. We also use Director Discretionary Time on NuSTAR, for which we thank Fiona Harrison for approving and the NuSTAR team for the technical support. We acknowledge financial contribution from the agreements ASI-INAF I/037/12/0 and ASI-INAF 2017-14-H.O. This work was partially supported by the Regione Autonoma della Sardegna through POR-FSE Sardegna 2007-2013, L.R. 7/2007, Progetti di Ricerca di Base e Orientata, Project N. CRP-60529. AP acknowledges funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement 660657-TMSP-H2020-MSCA-IF-2014, as well as the International Space Science Institute (ISSIBern) which funded and hosted the international team ‘The disc magnetosphere interaction around transitional millisecond pulsar’.
Subject Keywords:accretion, accretion disc – stars: neutron – X-rays: binaries
Issue or Number:2
Record Number:CaltechAUTHORS:20180827-122554035
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Official Citation:A Sanna, F Pintore, A Riggio, S M Mazzola, E Bozzo, T Di Salvo, C Ferrigno, A F Gambino, A Papitto, R Iaria, L Burderi; SWIFT J1756.9−2508: spectral and timing properties of its 2018 outburst, Monthly Notices of the Royal Astronomical Society, Volume 481, Issue 2, 1 December 2018, Pages 1658–1666,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:89172
Deposited By: Joy Painter
Deposited On:27 Aug 2018 19:36
Last Modified:03 Oct 2019 20:13

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