Effects of ultrafast outflows on X-ray time lags in active galactic nuclei

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Table 2.

Significance of the deviation between low-frequency lag-energy spectra of two stacked observations in AGNs with a transient UFO.

Names	$P_{null}^{Cal}$ $P_{\mathrm{null}}^{\mathrm{Cal}}$	σ_Cal	$P_{null}^{MC}$ $P_{\mathrm{null}}^{\mathrm{MC}}$	σ_MC
PG 1448+273	0.006	2.7	0.003	2.8
IRAS 13224-3809	6.6 × 10⁻⁸	5.4	1.9 × 10⁻⁸	5.6
PG 1211+143	3.4 × 10⁻⁷	5.1	1.7 × 10⁻⁶	4.7

Notes. Two kinds of null hypothesis probability, P_null, and the significance σ of deviation were calculated by the χ² statistics of lags with uncertainties using the method in Nowak & Vaughan (1996) and the MC method, respectively. Both approaches confirm that the low-frequency lag-energy spectra in the “low-flux w/ UFO” state are different from those of the “high-flux w/o UFO” state.

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