4.48. IXOs 78-81 These four IXOs are located in the spiral arms of
NGC 5194 (M51; see Fig. 13). See Ehle, Pietsch, & Beck (1995) and
RPS97 for more detailed discussions of these IXOs. From the measured
count rates from multiple HRI observations of these IXOs (Table 2), we
find that IXO 79 varies by a factor of ~3, while IXO 81 shows ~50%
variability. See also Palumbo et al. (1985), Fabbiano & Trinchieri
(1987), FKT92, Marston et al. (1995), and RW2000.