The Chameleon on the branches: spectral state transition and dips in NGC 247 ULX-1
The Chameleon on the branches: spectral state transition and dips in NGC 247 ULX-1
ABSTRACT Soft Ultra-Luminous X-ray (ULXs) sources are a subclass of the ULXs that can switch from a supersoft spectral state, where most of the luminosity is emitted below 1 keV, to a soft spectral state with significant emission above 1 keV. In a few systems, dips have been observed. The …