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Energy Distribution and Variability of BL LAC Objects. The Cases of PKS 2155–304 and 3C 66A.

Published online by Cambridge University Press:  04 August 2017

L. Maraschi ,
D. Maccagni ,
E. G. Tanzi ,
M. Tarenghi  and
A. Treves
L. Maraschi
Affiliation:
Istituto di Fisica Cosmica, CNR, Milano, Italy Istituto di Fisica dell'Università, Milano, Italy
D. Maccagni
Affiliation:
Istituto di Fisica Cosmica, CNR, Milano, Italy
E. G. Tanzi
Affiliation:
Istituto di Fisica Cosmica, CNR, Milano, Italy
M. Tarenghi
Affiliation:
European Southern Observatory, Garching bei Muenchen, FRG
A. Treves
Affiliation:
Istituto di Fisica Cosmica, CNR, Milano, Italy Istituto di Fisica dell'Università, Milano, Italy

Extract

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PKS 2155–304 was repeatedly observed in 1979 and 1980 with the International Ultraviolet Explorer. Variations up to a factor of 2 in one year and by 20% in a day are found. The maximum amplitude of variation in X-rays is similar but the timescales are much shorter (a factor of 2 in one day; Urry and Mushotzky, 1982). In all cases the 1200–3100 A continuum is well fitted by a power law with frequency spectral index αUV between −0.7±0.03 and −0.9±0.03. Optical and ultraviolet observations taken within one day show different spectral slopes (Fig. 1). Separate power law fits in the two bands yield αopt = −0.46±0.01 and αUV = −0.80±0.02. The observations by Urry and Mushotzky indicate that the energy distribution steepens further in the soft X-ray region.

Type
Research Article
Information
Symposium - International Astronomical Union , Volume 104: Early Evolution of the Universe and Its Present Structure , 1983 , pp. 39 - 40
Copyright
Copyright © Reidel 1983 

References

Konigl, A., 1981, Ap. J., 243, 700.Google Scholar
Maraschi, L., Tanzi, E.G., Tarenghi, M., Treves, A., 1980, Nature, 285, 555.Google Scholar
Urry, C.M., and Mushotzky, R.F., 1982, Ap. J., 253, 38.Google Scholar