The Broadband XMM-Newton and NuSTAR X-ray Spectra of Two Ultraluminous X-ray Sources in the Galaxy IC 342

Understand

We present results for two Ultraluminous X-ray Sources (ULXs), IC 342 X-1 and IC 342 X-2, using two epochs of XMM-Newton and NuSTAR observations separated by $\sim$7 days.

• We observe little spectral or flux variability above 1 keV between epochs, with unabsorbed 0.3--30 keV luminosities being $1.04^{+0.08}_{-0.06} \times 10^{40}$ erg s$^{-1}$ for IC 342 X-1 and $7.40\pm0.20 \times 10^{39}$ erg s$^{-1}$ for IC 342 X-2, so that both were observed in a similar, luminous state.
• Both sources have a high absorbing column in excess of the Galactic value.
• Neither source has a spectrum consistent with a black hole binary in low/hard state, and both ULXs exhibit strong curvature in their broadband X-ray spectra.