Optical Spectra of the 4 ULXs Observed with the Subaru Telescope (2 of 3) (IMAGE)
Caption
Image 2: Optical spectra of the four ULXs was observed with the Subaru Telescope (from upper to lower, Holmberg II X-1, Holmberg IX X-1, NGC 4559 X-7, NGC 5204 X-1). He II and Hα denote the spectral lines from helium ions and from hydrogen atoms, respectively.
Credit
Kyoto University
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