An extreme Ultraluminous X-ray source X-1 in NGC 5055. (arXiv:2008.02178v1 [astro-ph.HE])
<a href="http://arxiv.org/find/astro-ph/1/au:+Mondal_S/0/1/0/all/0/1">Samaresh Mondal</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Rozanska_A/0/1/0/all/0/1">Agata Rozanska</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Lai_E/0/1/0/all/0/1">Eleonora Veronica Lai</a> (1), <a href="http://arxiv.org/find/astro-ph/1/au:+Marco_B/0/1/0/all/0/1">Barbara De Marco</a> (1) ((1) Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, Warsaw, Poland)
Aims. We analyzed multi-epoch X-ray data of the Ultraluminous X-ray source
(ULX) NGC 5055 X-1, with luminosity up to $2.32times10^{40} rm erg s^{-1}$,
in order to constrain the physical parameters of the source. Methods. We
performed timing and spectral analysis of Chandra and XMM-Newton observations.
We used spectral models which assume the emission is from an accreting black
hole system. We fit the data with a multicolor disk (MCD) combined with a
powerlaw (PL) or a thermal Comptonization (NTHCOMP) component, and compared
those fits with a slim disk model. Results. The lightcurves of the source do
not show significant variability. From the hardness ratios (3-10 keV/0.3-3 keV
flux) we infer that the source is not spectrally variable. We found that the
photon index is tightly, positively correlated with the unabsorbed 0.3-10 keV
flux and the hydrogen column density. Furthermore, the temperature emissivity
profile indicates a deviation from the standard sub-Eddington thin disk model.
The source shows an inverse correlation between luminosity and inner disk
temperature in all fitted models. Conclusions. Our analysis favors the source
to be in an ultraluminous soft state. The positive correlations between the
photon index and the flux, and between the photon index and the hydrogen column
density may suggest the source is accreting at high Eddington ratios and might
indicate the presence of a wind. The inverse luminosity relation with the inner
disk temperature for all spectral models may indicate that the emission is
geometrically beamed by an optically thick outflow.
Aims. We analyzed multi-epoch X-ray data of the Ultraluminous X-ray source
(ULX) NGC 5055 X-1, with luminosity up to $2.32times10^{40} rm erg s^{-1}$,
in order to constrain the physical parameters of the source. Methods. We
performed timing and spectral analysis of Chandra and XMM-Newton observations.
We used spectral models which assume the emission is from an accreting black
hole system. We fit the data with a multicolor disk (MCD) combined with a
powerlaw (PL) or a thermal Comptonization (NTHCOMP) component, and compared
those fits with a slim disk model. Results. The lightcurves of the source do
not show significant variability. From the hardness ratios (3-10 keV/0.3-3 keV
flux) we infer that the source is not spectrally variable. We found that the
photon index is tightly, positively correlated with the unabsorbed 0.3-10 keV
flux and the hydrogen column density. Furthermore, the temperature emissivity
profile indicates a deviation from the standard sub-Eddington thin disk model.
The source shows an inverse correlation between luminosity and inner disk
temperature in all fitted models. Conclusions. Our analysis favors the source
to be in an ultraluminous soft state. The positive correlations between the
photon index and the flux, and between the photon index and the hydrogen column
density may suggest the source is accreting at high Eddington ratios and might
indicate the presence of a wind. The inverse luminosity relation with the inner
disk temperature for all spectral models may indicate that the emission is
geometrically beamed by an optically thick outflow.
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