XMM-Newton Observations of NGC 4051: Temporal Flux and Spectral Variability during Transition to the Faintest Phase in NGC 4051
| Autor: | Keigo Fukumura, Andrew C. Liebmann, Sachiko Tsuruta, Hideyo Kunieda, Yoshito Haba |
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| Rok vydání: | 2008 |
| Předmět: |
Luminous infrared galaxy
Physics Radio galaxy Astrophysics::High Energy Astrophysical Phenomena Astronomy Flux Astronomy and Astrophysics Starburst region Astrophysics::Cosmology and Extragalactic Astrophysics Galaxy Hubble sequence symbols.namesake Space and Planetary Science Galaxy group symbols Disc Astrophysics::Galaxy Astrophysics |
| Zdroj: | Publications of the Astronomical Society of Japan. 60:1257-1266 |
| ISSN: | 2053-051X 0004-6264 |
| Popis: | We report on the results from temporal and spectral analyses of NGC 4051 observed with XMM-Newton. The X-ray variabilities in the higher-flux states are well explained by the combination of a variable, direct power law and a temporally stable, absorbed component. In low-flux states, however, spectral variations are mainly due to flux changes of the absorbed component. Furthermore, when the source enters into the lowest-flux state, the absorbed component no longer appears. One promising interpretation is that part of the central emission region is covered by a temporally stable material, while the size of the emission region varies so as to produce a flux variation predominantly in direct power-law component. Once the emission region becomes smaller than the size of the absorber, however, the absorbed flux also begins to decrease. Finally, when the emission region is reduced sufficiently, both the direct and absorbed components disappear (i.e., “switched off” state). In this state, we found the signature of thermal emission, whose temperature of 0.8 keV is in agreement with the average value obtained from statistical analyses of Seyfert 2 galaxies with starburst activity. This could suggest that NGC 4051 possesses a nuclear starburst region. |
| Databáze: | OpenAIRE |
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