http://arxiv.org/abs/1710.02024
This paper presents X-ray broad-band spectral observations of the Ultra Luminous X-ray source (ULXs) NGC7793 P13 obtained by NuSTAR and XMM-Newton satellites. Reduced data were successfully fitted with only single spectral emission component from non-spherical system: neutron star plus accretion disk. We obtained the very good fit with the reduced $\chi^2$ per degree of freedom equal 1.08. Furthermore, the normalization of our model constrains the distance to the source. The resulting distance to the ULX source P13, $D=3.41^{+0.11}_{-0.10}$~Mpc, is with perfect agreement with the distance determination based on the Cepheid method to the hosting galaxy NGC7793. Our result shows that the ULX sources may contain central hot neutron star and the accretion disk. When the outgoing emission is computed by integration over the whole non-spherical system and successfully fitted to the data, then the resulting model normalization is the direct distance indicator.
A. Rozanska, K. Bresler, B. Beldycki, et. al.
Fri, 6 Oct 17
2/51
Comments: 5 pages, 3 figures, submitted to ApJ
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