Bhagwan, Jai; Gupta, A. C.; Papadakis, I. E.; Wiita, Paul J.
(Oxford University Press, 2014-11-11)
We have used all 20 archival XMM–Newton observations of PKS 2155 − 304 with simulta-
neous X-ray and UV/optical data to study its long-term flux and spectral variability. We find
significant variations, in all bands, on ...