Discovery of an similar to 2-h high-frequency X-ray QPO and iron K alpha reverberation in the active galaxy MS 2254.9-3712

作者：Alston W N^*; Parker M L; Markeviciute J; Fabian A C; Middleton M; Lohfink A; Kara E; Pinto C

来源：Monthly Notices of the Royal Astronomical Society, 2015, 449(1): 467-476.

DOI：10.1093/mnras/stv351

• galaxies: individual: MS 2254.9-3712
• galaxies: Seyfert
• X-rays: galaxies

We report the discovery of an similar to 1.5 x 10(-4) Hz (similar to 2 h) X-ray quasi-periodic oscillation (QPO) in the active galaxy MS 2254.9-3712, using an similar to 70 ks XMM-Newton observation. The QPO is significantly detected (similar to 3.3 sigma) in the 1.2-5.0 keV band only, connecting its origin with the primary X-ray power-law continuum. We detect a highly coherent soft lag between the 0.3-0.7 keV and 1.2-5.0 keV energy bands at the QPO frequency and at a frequency band in a 3: 2 ratio, strongly suggesting the presence of a QPO harmonic. An iron K alpha reverberation lag is found at the harmonic frequency, indicating the reflecting material subtends some angle to the primary continuum, which is modulated by the QPO mechanism. Frequency-resolved spectroscopy reveals the QPO and harmonic to have a hard energy dependence. These properties of the QPO variability, together with the current black hole mass estimate, M-BH similar to 4 x 10(6) M-circle dot, are consistent with the QPO originating from the same process as the high-frequency QPO phenomenon observed in black hole X-ray binaries. Principle component analysis reveals the spectral variability in MS 2254.9-3712 is similar to that of the active galaxy RE J1034+396, a source which also displays an X-ray QPO. This suggests a distinct spectral-variability pattern for accreting black holes when in a state where QPOs are present.

• 出版日期2015-5-1