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X-ray spectrum of the BL Lacertae object PKS 2155-304.

Koyama, K.; Warwick, R. S.; Makishima, K. +4 more

The BL Lacertae object PKS 2155-304 was observed with Ginga for two days in May 1987. The 2-35 keV intensity showed a significant variability, the most rapid change being a 30 percent increase in 3 hr. The X-ray spectrum was described by a single power-law model with photon spectral index ranging between 2.7 and 2.9, but the power-law slope showed…