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arXiv · 1309.4440

A ~3.8 hour Periodicity from an Ultrasoft Active Galactic Nucleus Candidate

Dacheng Lin·Jimmy A. Irwin·Olivier Godet·Natalie A. Webb·Didier Barret
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Abstract

Very few galactic nuclei are found to show significant X-ray quasi-periodic oscillations (QPOs). After carefully modeling the noise continuum, we find that the ~3.8 hr QPO in the ultrasoft active galactic nucleus (AGN) candidate 2XMM J123103.2+110648 was significantly detected (~5sigma) in two XMM-Newton observations in 2005, but not in the one in 2003. The QPO rms is very high and increases from ~25% in 0.2-0.5 keV to ~50% in 1-2 keV. The QPO probably corresponds to the low-frequency type in Galactic black hole X-ray binaries, considering its large rms and the probably low mass (~10^5 msun) of the black hole in the nucleus. We also fit the soft X-ray spectra from the three XMM-Newton observations and find that they can be described with either pure thermal disk emission or optically thick low-temperature Comptonization. We see no clear X-ray emission from the two Swift observations in 2013, indicating lower source fluxes than those in XMM-Newton observations.

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Dacheng Lin, Jimmy A. Irwin, Olivier Godet, Natalie A. Webb, Didier Barret. 2013-12-30. A ~3.8 hour Periodicity from an Ultrasoft Active Galactic Nucleus Candidate. https://doi.org/10.1088/2041-8205%2F776%2F1%2Fl10

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