Letter to the Editor

A rapidly variable narrow X-ray iron line in Mkn 841

¹ Laboratoire d'Astrophysique de Grenoble, BP 43, 38041 Grenoble Cedex 9, France
² Osservatorio Astronomico di Brera, via Brera 28, 02121 Milano, Italy
³ Service d'Astrophysique, DSM/DAPNIA/SAp, CE Saclay, 91191 Gif-sur-Yvette Cedex, France
⁴ Dipartimento di Fisica, Università degli Studi “Roma tre”, via della Vasca Navale 84, 00046 Roma, Italy
⁵ LUTH, Observatoire de Paris, Section de Meudon, 92195 Meudon Cedex, France
⁶ Università dell'Insubria, via Lucini 3, 22100 Como, Italy

Corresponding author: P. O. Petrucci, petrucci@obs.ujf-grenoble.fr

Received: 26 February 2002
Accepted: 5 April 2002

Abstract

We report on the detection of a rapidly variable narrow Fe Kα line in Mkn 841. The source has been observed two times by XMM-Newton and simultaneously with BeppoSAX. The two observations, of about 10 ks long each, were separated by ~15 hours. The line flux reaches a maximum during the first observation and is significantly reduced in the second one. The continuum shape and flux, instead, keep roughly constant between the two pointings. Such rapid variability of a narrow (unresolved by the XMM-pn instrument) line has never been reported in the past. These results are not easily explained in the standard cold reflection model where the narrow line component is supposed to be produced far from the primary X-ray source (e.g. from the torus) and is thus not expected to vary rapidly. Different interpretations are discussed.