High-energy studies of variable sources
In addition to the primary research on spiral galaxy halos and some related studies, X-ray observations of starburst galaxies led to the discovery of a few X-ray and (serendipitous) extreme ultra-violet variable sources, as described in:
- RE J1255+266: Detection of an extremely bright EUV transient (M. Dahlem et al. 1995, A&A, 295, L13)
- Detection of an extremely soft X-ray outburst in the HII-like nucleus of NGC 5905 (N. Bade et al. 1995, A&A, 309, L35)
One of these sources belongs to a previously unknown class of objects, the so-called "intermediate-luminosity X-ray objects" (IXOs) or "ultra-luminous X-ray sources" (ULXs):
- The nuclear X-ray source in NGC 3628: A strange active galactic nucleus or the most luminous high-mass X-ray binary known? (M. Dahlem et al. 1995, ApJ, 442, 49)
- Another intermediate mass black hole in a starburst galaxy?: The luminous X-ray source in NGC 3628 reappears (D. Strickland et al. 2001, AJ, 560, 707)