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Discovery of pulsations from NGC 300 ULX1 and its fast period evolution

Carpano, S. and Haberl, F. and Maitra, C. and Vasilopoulos, G. (2018) Discovery of pulsations from NGC 300 ULX1 and its fast period evolution. Monthly Notices of the Royal Astronomical Society: Letters, 476 (1). L45-L49. ISSN 1745-3925. doi:10.1093/mnrasl/sly030.

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The supernova impostor SN 2010da located in the nearby galaxy NGC 300, later identified as a likely supergiant B[e] high-mass X-ray binary, was simultaneously observed by NuSTAR and XMM–Newton between 2016 December 16 and 20, over a total time span of ∼310 ks. We report the discovery of a strong periodic modulation in the X-ray flux with a pulse period of 31.6 s and a very rapid spin-up, and confirm therefore that the compact object is a neutron star. We find that the spin period is changing from 31.71 s to 31.54 s over that period, with a spin-up rate of −5.56 × 10^(−7) s s^(−1), likely the largest ever observed from an accreting neutron star. The spectrum is described by a power-law and a disc blackbody model, leading to a 0.3–30 keV unabsorbed luminosity of 4.7 × 10^(39) erg s^(−1). Applying our best-fitting model successfully to the spectra of an XMM–Newton observation from 2010, suggests that the lower fluxes of NGC 300 ULX1 reported from observations around that time are caused by a large amount of absorption, while the intrinsic luminosity was similar as seen in 2016. A more constant luminosity level is also consistent with the long-term pulse period evolution approaching an equilibrium value asymptotically. We conclude that the source is another candidate for the new class of ultraluminous 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. Accepted 2018 February 23. Received 2018 February 16; in original form 2018 January 31. Published: 27 February 2018. This research has made use of data obtained with XMM–Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA, and data obtained from the NuSTAR Data Archive. The XMM–Newton project is supported by the Bundesministerium für Wirtschaft und Technologie/Deutsches Zentrum für Luft- und Raumfahrt (BMWI/DLR, FKZ 50OG1601) and the Max Planck Society.
Subject Keywords:stars: neutron, pulsars: individual: NGC 300 ULX1– galaxies: individual: NGC 300, X-rays: binaries
Issue or Number:1
Record Number:CaltechAUTHORS:20180308-140547917
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Official Citation:S Carpano, F Haberl, C Maitra, G Vasilopoulos; Discovery of pulsations from NGC 300 ULX1 and its fast period evolution, Monthly Notices of the Royal Astronomical Society: Letters, Volume 476, Issue 1, 1 May 2018, Pages L45–L49,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:85210
Deposited By: Joy Painter
Deposited On:08 Mar 2018 22:18
Last Modified:15 Nov 2021 20:26

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