The XMM-Newton and BeppoSAX view of the Ultra Luminous Infrared Galaxy MKN 231

¹ INAF – Osservatorio Astronomico di Brera, Milano, Italy
² Dipartimento di Astronomia, Università di Padova, Italy
³ IASF – CNR, Bologna, Italy
⁴ XMM-SOC (VILSPA), ESA, Madrid, Spain
⁵ Institute of Astronomy, University of Cambridge, Madingley Road Cambridge CB3 OHA, UK
⁶ INAF – Osservatorio Astronomico di Padova, Italy
⁷ Dipartimento di Astronomia, Università di Bologna, Italy
⁸ INAF – Osservatorio Astronomico di Trieste, Italy
⁹ INAF – Osservatorio Astrofisico di Arcetri, Firenze, Italy
¹⁰ Harvard-Smithsonian Center for Astrophysics, Cambridge, USA

Corresponding author: V. Braito, braito@brera.mi.astro.it

Received: 28 May 2003
Accepted: 15 January 2004

Abstract

We discuss XMM-Newton and BeppoSAX observations of MKN 231, the lowest-redshift Broad Absorption Line (BAL) QSO known so far and one of the best-studied Ultra Luminous Infrared Galaxies. By combining the XMM-Newton spectral resolution and the high-energy bandpass of BeppoSAX we have been able to study in more detail than previously possible its 0.2–50 keV spectral properties. The BeppoSAX PDS data unveiled, for the first time, a highly absorbed ( cm^-2) power-law component. We find that: a) below 10 keV we are seeing only reprocessed radiation through reflection and/or scattering; b) the intrinsic 2–10 keV luminosity of MKN 231 is  erg s^-1, i.e. more than an order of magnitude greater than previous measurements; c) the starburst activity significantly contributes to the soft ( keV) X-ray emission.