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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
earth and planetary sciences
INTEGRAL and XMM-Newton observations of IGR J16418-4532: Evidence of accretion regime transitions in a supergiant fast X-ray transient
Monthly Notices of the Royal Astronomical Society, Volume 433, No. 1, Year 2013
Notification
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Description
We report on combined INTEGRAL and XMM-Newton observations of the supergiant fast X-ray transient (SFXT) IGR J16418-4532. The observations targeted the X-ray eclipse region of IGR J16418-4532's orbit with continuous INTEGRAL observations across ~25 per cent of orbital phase and two quasi-simultaneous XMM-Newton observations of length 20 and 14 ks, occurring during and just after the eclipse, respectively. An enhanced INTEGRAL emission history is provided with 19 previously unreported outbursts identified in the archival 18-60 keV data set. The XMM-Newton eclipse observation showed prominent Fe emission and a flux of 2.8 × 10-13 erg cm10-2 s10-1 (0.5-10 keV). Through the comparison of the detected eclipse and post-eclipse flux, the supergiant mass-loss rate through the stellar wind was determined as Mw = 2.3-3.8 × 110-7 M· yr10-1. The post-eclipse XMM-Newton observation showed a dynamic flux evolution with signatures of the X-ray pulsation, a period of flaring activity, structured nH variations and the first ever detection of an X-ray intensity dip, or'off-state', in a pulsating SFXT. Consideration is given to the origin of the X-ray dip, and we conclude that the most applicable of the current theories of X-ray dip generation is that of a transition between Compton-cooling-dominated and radiative-cooling-dominated subsonic accretion regimes within the 'quasi-spherical' model of wind accretion. Under this interpretation, which requires additional confirmation, the neutron star in IGR J16418-4532 possesses a magnetic field of ~1014 G, providing tentative observational evidence of a highly magnetized neutron star in a SFXT for the first time. The implications of these results on the nature of IGR J16418-4532 itself and the wider SFXT class are discussed. © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.
Authors & Co-Authors
Drave, Sebastian P.
United Kingdom, Southampton
University of Southampton
Bird, Antony J.
United Kingdom, Southampton
University of Southampton
Sidoli, L.
Italy, Milan
Inaf Istituto Di Astrofisica Spaziale e Fisica Cosmica, Milan
Sguera, Vito
Italy, Bologna
Inaf Istituto Di Astrofisica Spaziale e Fisica Cosmica, Bologna
McBride, Vanessa A.
South Africa, Cape Town
University of Cape Town
South Africa, Cape Town
South African Astronomical Observatory
Hill, Adam B.
United Kingdom, Southampton
University of Southampton
United States, Menlo Park
Slac National Accelerator Laboratory
Bazzano, Angela
Italy, Rome
Inaf Istituto Di Astrofisica Spaziale e Fisica Cosmica, Rome
Goossens, Maximiliane E.
United Kingdom, Southampton
University of Southampton
Statistics
Citations: 27
Authors: 8
Affiliations: 7
Identifiers
Doi:
10.1093/mnras/stt754
ISSN:
00358711
e-ISSN:
13652966
Research Areas
Environmental