XMM-Newton observations of Markarian 421^*

¹ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, 85740 Garching, Germany
² X-Ray Astronomy Group, Department of Physics and Astronomy, University of Leicester, LE1 7RH, UK
³ Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey, RH5 6NT, UK
⁴ Science Operation Centre, Villafranca Satellite Tracking Station, 28080 Madrid, Spain
⁵ Istituto di Fisica Cosmica "G. Occhialini", Via Bassini 15, 20133, Italy

Corresponding author: W. Brinkmann, wpb@mpe.mpg.de

Received: 2 October 2000
Accepted: 30 October 2000

Abstract

The BL Lac object Mrk 421 was observed on May 25, 2000 during the XMM-Newton Cal/PV phase. The high throughput of the X-ray telescopes and the spectral capabilities of the instruments allow an uninterrupted temporal and spectral study of the source with unprecedented time resolution. Mrk 421 was found at a relatively high state with a 2-6 keV flux of (1.3-1.9) 10^-10 erg cm^-2 s^-1. The observed intensity variations by more than a factor of three at highest X-ray energies are accompanied by complex spectral variations with only a small time lag ( s) between the hard and soft photons. The (0.2-10) keV spectrum can be well fitted by a broken power law and no absorption structures are found in the source spectrum at the high spectral resolution of the transmission gratings.