The BL Lacertae objects OQ 530 and S5 0716+714

Free access article

Issue		A&A Volume 400, Number 2, March III 2003


Page(s)		477 - 486
Section		Galactic structure and dynamics
DOI		http://dx.doi.org/10.1051/0004-6361:20021916

A&A 400, 477-486 (2003)
DOI: 10.1051/0004-6361:20021916

Simultaneous observations in the X-rays, radio, optical and TeV bands

G. Tagliaferri¹, M. Ravasio¹, G. Ghisellini¹, P. Giommi², E. Massaro³, R. Nesci³, G. Tosti⁴, M. F. Aller⁵, H. D. Aller⁵, A. Celotti⁶, L. Maraschi⁷, F. Tavecchio¹ and A. Wolter⁷

¹ 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
⁵ Department of Astronomy, University of Michigan, Dennison Building, Ann Arbor MI 48109-1090, USA
⁶ SISSA/ISAS, via Beirut 2-4, 34014 Trieste, Italy
⁷ INAF - Osservatorio Astronomico di Brera, Via Brera 28, 20121 Milano, Italy

(Received 25 October 2002 / Accepted 20 December 2002 )

Abstract
We present the results of the BeppoSAX observations of two BL Lacs, OQ 530 and S5 0716+714, as part of a ToO program for the simultaneous observation at radio, optical, X-ray and TeV energies. Both sources are detected in the LECS and MECS, with S5 0716+714 visible also in the PDS band, up to about ~60 keV. The X-ray spectra of both sources are better fitted by a double power-law model, with a steep soft X-ray component flattening at harder energies, with breaks at 0.3 and 1.5 keV, respectively. The concave shape of the spectra in both objects is consistent with soft X-rays being produced by the synchrotron and harder X-rays by the inverse Compton processes. Also the X-ray variability properties confirm this scenario; in particular, for S5 0716+714 our observation shows variations by about a factor of 3 over one hour below ~3 keV and no variability above. Their simultaneous broad-band energy spectral distributions can be successfully interpreted within the frame of a homogeneous synchrotron and inverse Compton model, including a possible contribution from an external source of seed photons with the different spectral states of S5 0716+714 being reproduced by changing the injected power. The resulting parameters are fully consistent with the two sources being intermediate objects within the "sequence" scenario proposed for blazars.

Key words: BL Lacertae objects: general -- X-rays: galaxies -- BL Lacertae objects: individual: OQ 530, S5 0716+714

Offprint request: G. Tagliaferri, gtagliaf@merate.mi.astro.it

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