Volume 412, Number 3, December IV 2003
|Page(s)||711 - 720|
|Published online||08 December 2003|
Wide band X-ray and optical observations of the BL Lac object 1ES 1959+650 in high state
INAF-Osservatorio Astronomico di Brera, via Bianchi 46, 23807 Merate, Italy
2 ASI Science Data Center, Via Galileo Galilei, 00044 Frascati, Italy
3 Dipartimento di Fisica, Università La Sapienza, P.le Aldo Moro 2, 00185 Roma, Italy
4 Dipartimento di Fisica e Osservatorio Astronomico, Università di Perugia, Perugia, Italy
Corresponding author: G. Tagliaferri, firstname.lastname@example.org
Accepted: 10 September 2003
The blazar 1ES 1959+650 was observed twice by BeppoSAX in September 2001 simultaneously with optical observations. We report here the X-ray data together with the optical, RC magnitude light curve since August 1995. The BeppoSAX observations were triggered by an active X-ray status of the source. The X-ray spectra are brighter than the previously published X-ray observations, although the source was in an even higher state a few months later, as monitored by the ASM onboard RossiXTE, when it was also detected to flare in the TeV band. Our X-ray spectra are well represented by a continuosly curved model up to 45 keV and are interpreted as synchrotron emission, with the peak moving to higher energies. This is also confirmed by the slope of the X-ray spectrum which is harder than in previous observations. Based on our optical and X-ray data, the synchrotron peak turns out to be in the range 0.1–0.7 keV. We compare our data with non-simultaneous radio to TeV data and model the spectral energy distribution with a homogeneous, one-zone synchrotron inverse Compton model. We derive physical parameters that are typical of low power High Energy peaked Blazars, characterised by a relatively large beaming factor, low luminosity and absence of external seed photons.
Key words: galaxies: BL Lacertae objects: general / galaxies: BL Lacertae objects: individual: 1ES 1959+650 / X-rays: galaxies
© ESO, 2003
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