The 0.1-200 keV spectrum of the blazar PKS 2005-489 during an active state

¹ Osservatorio Astronomico di Brera, Via Bianchi 46, 23807 Merate, Italy
² SAX Science Data Center, ASI, Via Corcolle, 19, 00131 Roma, Italy
³ SISSA/ISAS, via Beirut 2-4, 34014 Trieste, Italy
⁴ Istituto di Fisica Cosmica G.Occhialini, CNR, Via Bassini 15, 20133 Milano, Italy
⁵ South African Astronomical Observatory, PO Box 9, Observatory 7935, South Africa
⁶ Osservatorio Astronomico di Brera, Via Brera, 28, 20121 Milano, Italy
⁷ Istituto di Fisica, Università dell'Insubria, Via Lucini 3, 22100 Como, Italy

Corresponding author: G. Tagliaferri, gtagliaf@merate.ni.astro.it

Received: 10 November 2000
Accepted: 20 December 2000

Abstract

The bright BL Lac object PKS 2005-489 was observed by BeppoSAX on November 1-2, 1998, following an active X-ray state detected by RossiXTE. The source, detected between 0.1 and 200 keV, was in a very high state with a continuum well fitted by a steepening spectrum due to synchrotron emission only. Our X-ray spectrum is the flattest ever observed for this source. The different X-ray spectral slopes and fluxes, as measured by various satellites, are consistent with relatively little changes of the peak frequency of the synchrotron emission, always located below 10¹⁷ Hz. We discuss these results in the framework of synchrotron self-Compton models. We found that for the BeppoSAX observation, the synchrotron peak frequency is between 10¹⁵ and 2.5 10¹⁶ Hz, depending on the model assumptions.