Highly magnetized neutron stars as the engines of Ultra-luminous X-ray sources.

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• Filippos Koliopanos (CNRS IRAP)
• Wednesday 05 December 2018, 14:30-15:30
• Physics West 117.

If you have a question about this talk, please contact Sean McGee.

In light of recent discoveries of pulsating ultra-luminous X-ray sources (ULXs) and recently introduced models placing neutron stars as the engines of ULXs, we revisit the spectra of eighteen well-known ULXs, in search of indications that favor or reject this hypothesis. We find that the notable (>6keV) spectral curvature observed in most ULXs, is commensurate with the Wien tail of a hot (T>1keV) multicolor black-body component and confirm that a double thermal model (comprised of a ”cool” and ”hot” thermal component) with the addition of a faint non-thermal tail describes all ULX spectra in our list. More importantly, we offer a new physical interpretation for the dual thermal spectrum, where it is the result of accretion onto high-B NSs rather than black holes. We estimate the magnetic-field strength and demonstrate that it correlates strongly with the source luminosity and the temperature of the hot component. We also discuss the application of our model on the most recent pulsating ULX “NGC 300 ULX1 ”, casting doubts on the claimed presence of a cyclotron scattering feature in its spectrum. Our findings offer an additional and compelling argument in favor of NSs as prime candidates for powering ULXs, as has been also suggested by (e.g.) King & Lasota 2016; King et al. 2017. In my talk I will briefly review the observational history of ULXs and present the most widely accepted theoretical considerations for their origin. I will then present our novel physical interpretation along with its major implications.

This talk is part of the Astrophysics Talks Series series.

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• Astrophysics Talks Series
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