@article {41739,
	title = {Discovery of pulsations from NGC 300 ULX1 and its fast period evolution},
	volume = {476},
	year = {2018},
	month = {2018/05/1},
	pages = {L45 - L49},
	publisher = {OUP},
	abstract = {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 {\texttimes} 10<SUP>-7</SUP> s s<SUP>-1</SUP>, 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 {\texttimes} 10<SUP>39</SUP> erg s<SUP>-1</SUP>. 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.},
	keywords = {Astrophysics - High Energy Astrophysical Phenomena, pulsars: individual: NGC 300 ULX1- galaxies: individual: NGC 300, stars: neutron, X-rays: binaries},
	isbn = {0035-8711},
	url = {https://ui.adsabs.harvard.edu/abs/2018MNRAS.476L..45C},
	author = {Carpano, S. and Haberl, F. and Maitra, C. and Vasilopoulos, G.}
}
