Disentangling the synchrotron and inverse Compton variability in the X-ray emission of the intermediate BL Lacertae object S5 0716+71

Free access article

Issue		A&A Volume 457, Number 1, October I 2006


Page(s)		133 - 144
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20065317

A&A 457, 133-144 (2006)
DOI: 10.1051/0004-6361:20065317

Disentangling the synchrotron and inverse Compton variability in the X-ray emission of the intermediate BL Lacertae object S5 0716+71

E. Ferrero, S. J. Wagner, D. Emmanoulopoulos and L. Ostorero

Landessternwarte Heidelberg, Königstuhl, 69117 Heidelberg, Germany
e-mail: eferrero@lsw.uni-heidelberg.de

(Received 29 March 2006 / Accepted 30 June 2006)

Abstract
Context.The possibility to detect simultaneously in the X-ray band the synchrotron and Inverse Compton (IC) emission of intermediate BL Lac objects offers the unique opportunity to study contemporaneously the low- and high-energy tails of the electron distribution in the jets of these sources.
Aims.We attempted to disentangle the X-ray spectral variability properties of both the low- and high-energy ends of the synchrotron and Inverse Compton emission of the intermediate BL Lac object S5 0716+71.
Methods.We carried out spectral, temporal and cross-correlation analyses of the data from a long XMM-Newton pointing of S5 0716+71 and we compared our findings with previous results from past X-ray observations.
Results.Strong variability was detected during the XMM exposure. Both the synchrotron and Inverse Compton components were found to vary on time scales of hours, implying a size of the emitting region of $R\la 0.7\delta /(1+z)$ light-hours. The synchrotron emission was discovered to become dominant during episodes of flaring activity, following a harder-when-brighter trend. Tight correlations were observed between variations in different energy bands. Upper limits on time lags between the soft and hard X-ray light curves are of the order of a few hundred seconds.

Key words: galaxies: active -- galaxies: BL Lacertae objects: general -- galaxies: BL Lacertae objects: individual: S5 0716+71 -- X-rays: individuals: S5 0716+71 -- radiation mechanisms: non-thermal

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