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A NICER Thermonuclear Burst from the Millisecond X-Ray Pulsar SAX J1808.4–3658

Bult, Peter and Jaisawal, Gaurava K. and Güver, Tolga and Strohmayer, Tod E. and Altamirano, Diego and Arzoumanian, Zaven and Ballantyne, David R. and Chakrabarty, Deepto and Chenevez, Jérôme and Gendreau, Keith C. and Guillot, Sebastien and Ludlam, Renee M. (2019) A NICER Thermonuclear Burst from the Millisecond X-Ray Pulsar SAX J1808.4–3658. Astrophysical Journal Letters, 885 (1). Art. No. L1. ISSN 2041-8213.

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The Neutron Star Interior Composition Explorer (NICER) has extensively monitored the 2019 August outburst of the 401 Hz millisecond X-ray pulsar SAX J1808.4–3658. In this Letter, we report on the detection of a bright helium-fueled Type I X-ray burst. With a bolometric peak flux of (2.3 ± 0.1) × 10⁻⁷ erg s⁻¹ cm⁻², this was the brightest X-ray burst among all bursting sources observed with NICER to date. The burst shows a remarkable two-stage evolution in flux, emission lines at 1.0 and 6.7 keV, and burst oscillations at the known pulsar spin frequency, with ≈4% fractional sinusoidal amplitude. We interpret the burst flux evolution as the detection of the local Eddington limits associated with the hydrogen and helium layers of the neutron star envelope. The emission lines are likely associated with Fe, due to reprocessing of the burst emission in the accretion disk.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Jaisawal, Gaurava K.0000-0002-6789-2723
Güver, Tolga0000-0002-3531-9842
Strohmayer, Tod E.0000-0001-7681-5845
Altamirano, Diego0000-0002-3422-0074
Ballantyne, David R.0000-0001-8128-6976
Chakrabarty, Deepto0000-0001-8804-8946
Chenevez, Jérôme0000-0002-4397-8370
Guillot, Sebastien0000-0002-6449-106X
Ludlam, Renee M.0000-0002-8961-939X
Additional Information:© 2019 The American Astronomical Society. Received 2019 September 8; revised 2019 September 29; accepted 2019 October 4; published 2019 October 23. This work was supported by NASA through the NICER mission and the Astrophysics Explorers Program, and made use of data and software provided by the High Energy Astrophysics Science Archive Research Center (HEASARC). P.B. was supported by an NPP fellowship at NASA Goddard Space Flight Center. G.K.J. was supported by the Marie Skłodowska-Curie Actions grant No. 713683 (H2020). D.A. acknowledges support from the Royal Society. R.M.L. acknowledges the support of NASA through Hubble Fellowship Program grant HST-HF2-51440.001. Facilities: ADS - , HEASARC - , NICER. - Software: heasoft (v6.26), nicerdas (v6a), xspec (v12.10).
Funding AgencyGrant Number
NASA Hubble FellowshipHST-HF2-51440.001
NASA Postdoctoral ProgramUNSPECIFIED
Marie Curie Fellowship713683
NASA Einstein FellowshipUNSPECIFIED
Subject Keywords:X-ray bursts; Millisecond pulsars
Issue or Number:1
Classification Code:Unified Astronomy Thesaurus concepts: X-ray bursts (1814); Millisecond pulsars (1062)
Record Number:CaltechAUTHORS:20191023-155157476
Persistent URL:
Official Citation:Peter Bult et al 2019 ApJL 885 L1
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:99426
Deposited By: Tony Diaz
Deposited On:23 Oct 2019 23:10
Last Modified:09 Mar 2020 13:18

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