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Published September 2021 | Submitted + Published
Journal Article Open

NuSTAR reveals the hidden nature of SS433


SS433 is the only Galactic binary system known to persistently accrete at highly super-critical (or hyper-critical) rates, similar to those in tidal disruption events, and likely needed to explain the rapid growth of those very high redshift quasars containing massive SMBHs. Probing the inner regions of SS433 in the X-rays is crucial to understanding this system, and super-critical accretion in general, but is highly challenging due to obscuration by the surrounding wind, driven from the accretion flow. NuSTAR observed SS433 in the hard X-ray band across multiple phases of its 162 d superorbital precession period. Spectral-timing tools allow us to infer that the hard X-ray emission from the inner regions is likely being scattered towards us by the walls of the wind-cone. By comparing to numerical models, we determine an intrinsic X-ray luminosity of ≥ 2 × 10³⁷ erg s⁻¹ and that, if viewed face on, we would infer an apparent luminosity of >1 × 10³⁹ erg s⁻¹, confirming SS433's long-suspected nature as an ultraluminous X-ray source (ULX). We present the discovery of a narrow, ∼100 s lag due to atomic processes occurring in outflowing material travelling at least 0.14–0.29c, which matches absorption lines seen in ULXs and – in the future – will allow us to map a super-critical outflow for the first time.

Additional Information

© 2021 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model). Accepted 2021 April 27. Received 2021 April 6; in original form 2020 May 29. Published: 06 May 2021. The authors thank the anonymous referee for their valuable suggestions. MJM and DJW appreciate support via STFC Ernest Rutherford Fellowships. WNA is supported by an ESA research fellowship. This research was partially supported by the Australian Government through the Australian Research Council's Discovery Projects funding scheme (project DP200102471). The authors thank Keith Arnaud for useful suggestions. This research has made use of data obtained with NuSTAR, a project led by Caltech, funded by NASA and managed by NASA/JPL, and has utilized the NUSTARDAS software package, jointly developed by the ASDC (Italy) and Caltech (USA). Data Availability: The data underlying this article were accessed from the HEASARC NuSTAR data repository at https://heasarc.gsfc.nasa.gov/docs/archive.html. The derived data generated in this research will be shared on reasonable request to the corresponding author.

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Published - stab1280.pdf

Submitted - 1810.10518.pdf


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August 20, 2023
October 20, 2023