The Type I Seyfert galaxy Markarian 509 was observed with Suzaku in 2010 November , for a gross time span of 2.2 days .
Timing and spectral properties of the 0.5–45 keV X-rays , detected with the XIS and HXD , consistently revealed the presence of a soft spectral component that remained constant while the total X-ray intensity varied by \pm 10 % .
This stable soft component , found in the 0.5–3.0 keV range , was interpreted as a result of thermal Comptonization in a corona with a temperature of \sim 0.5 keV and an optical depth of \sim 18 .
The time-avearged 0.5–45 keV Suzaku spectrum was reproduced successfully , as a combination of this thermal Comptonization component , a harder power-law of photon index \sim 1.8 , moderate reflection , and an iron K-emission line .
By analyzing four archival Suzaku datasets of the same object obtained in 2006 , the thermal Comptonization component , which was stable during the 2.2 day pointing in 2010 , was found to vary on time scales of a few weeks , independently of the power-law component .
Implications of these results are discussed in terms of the “ multi-zone Comptonization ” view , obtained with Suzaku from the black hole binary Cygnus X-1 .