Suzaku observation of the Phoenix galaxy

¹ Dipartimento di Fisica, Università degli Studi Roma Tre, via della Vasca Navale 84, 00146 Roma, Italy e-mail: matt@fis.uniroma3.it
² Department of Physics, Faculty of Science, Ehime University, Bunkyo-cho, Matsuyama, Ehime 790-8577, Japan
³ INAF – Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
⁴ European Space Astronomy Center of ESA, Apartado 50727, 28080 Madrid, Spain
⁵ Instituto de Astronoma, UNAM, Apartado 70264, 04510 Ciudad de Mexico, Mexico
⁶ INAF – Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monteporzio Catone, Roma, Italy

Received: 27 September 2008
Accepted: 7 January 2009

Abstract

Context. In recent years, several Seyfert 2 galaxies have been discovered that change state when observed in X-rays a few years apart, switching from Compton-thin to reflection-dominated or viceversa.

Aims. We observed a member of this class of “Changing-look” sources, the Phoenix galaxy, with , with the aim of better understanding the nature of the variations.

Methods. The spectrum was analyzed, and the results compared with previous ASCA and XMM-Newton observations.

Results. The source was caught in a Compton-thin state, as in XMM-Newton, but differently from ASCA. Comparing the and XMM-Newton observations, a variation in the column density of the absorber on a time scale of years is discovered. A similar change, but on much shorter time scales (i.e. ks) may also explain the count-rate variations during the observations. 
A soft excess is also present, likely due to continuum and line emission from photoionized circumnuclear matter.