2009/02/05 by G. Matt, S. Bianchi, H. Awaki +5
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Emission spectrum #Galaxies: Formation, Evolution, Phenomena #Galaxy #Line (geometry) #Phoenix #Spectral density #Variation (astronomy) #astro-ph.CO #astro-ph.HE
paper · pdf · doi:10.1051/0004-6361/200811049
Accepted for publication in Astronomy & Astrophysics
arxiv created 2009/02/05 · openalex publication_date 2009/02/09 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
<i>Context. <i/>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.<i>Aims. <i/>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.<i>Methods. <i/>The spectrum was analyzed, and the results compared with previous ASCA and XMM-<i>Newton<i/> observations. <i>Results. <i/>The source was caught in a Compton-thin state, as in XMM-<i>Newton<i/>, but differently from ASCA. Comparing the and XMM-<i>Newton<i/> 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.