Discovery of an ~2-h high-frequency X-ray QPO and iron Kα reverberation in the active galaxy MS 2254.9-3712

We report the discovery of a $\sim 1.5 \times 10^{-4}$ Hz ($\sim 2$ hr) X-ray quasi-periodic oscillation (QPO) in the active galaxy MS 2254.9-3712, using a $\sim 70$ ks XMM-Newton observation. The QPO is significantly detected ($\sim 3.3 \sigma$) 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, $M_{\rm bh} \sim 4 \times 10^{6} M_{\rm sun}$, 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

Revealing the ultrafast outflow in IRAS 13224-3809 through spectral variability

We present an analysis of the long-term X-ray variability of the extreme narrow-line Seyfert 1 (NLS1) galaxy IRAS 13224-3809 using principal component analysis (PCA) and fractional excess variability (Fvar) spectra to identify model-independent spectral components. We identify a series of variability peaks in both the first PCA component and Fvar spectrum which correspond to the strongest predicted absorption lines from the ultra-fast outflow (UFO) discovered by Parker et al. (2017). We also find higher order PCA components, which correspond to variability of the soft excess and reflection features. The subtle differences between RMS and PCA results argue that the observed flux-dependence of the absorption is due to increased ionization of the gas, rather than changes in column density or covering fraction. This result demonstrates that we can detect outflows from variability alone, and that variability studies of UFOs are an extremely promising avenue for future research

The remarkable X-ray variability of IRAS 13224-3809 - I. The variability process

We present a detailed X-ray timing analysis of the highly variable NLS1 galaxy, IRAS 13224-3809. The source was recently monitored for 1.5 Ms with XMM-Newton which, combined with 500 ks archival data, makes this the best studied NLS1 galaxy in X-rays to date. We apply standard time- and Fourier-domain in order to understand the underlying variability process. The source flux is not distributed lognormally, as would be expected for accreting sources. The first non-linear rms-flux relation for any accreting source in any waveband is found, with $\mathrm{rms} \propto \mathrm{flux}^{2/3}$. The light curves exhibit significant strong non-stationarity, in addition to that caused by the rms-flux relation, and are fractionally more variable at lower source flux. The power spectrum is estimated down to $\sim 10^{-7}$ Hz and consists of multiple peaked components: a low-frequency break at $\sim 10^{-5}$ Hz, with slope $\alpha < 1$ down to low frequencies; an additional component breaking at $\sim 10^{-3}$ Hz. Using the high-frequency break we estimate the black hole mass $M_\mathrm{BH} = [0.5-2] \times 10^{6} M_{\odot}$, and mass accretion rate in Eddington units, $\dot m_{\rm Edd} \gtrsim 1$. The non-stationarity is manifest in the PSD with the normalisation of the peaked components increasing with decreasing source flux, as well as the low-frequency peak moving to higher frequencies. We also detect a narrow coherent feature in the soft band PSD at $0.7$ mHz, modelled with a Lorentzian the feature has $Q \sim 8$ and an $\mathrm{rms} \sim 3$ %. We discuss the implication of these results for accretion of matter onto black holes

Black hole spin: theory and observation

In the standard paradigm, astrophysical black holes can be described solely by their mass and angular momentum - commonly referred to as `spin' - resulting from the process of their birth and subsequent growth via accretion. Whilst the mass has a standard Newtonian interpretation, the spin does not, with the effect of non-zero spin leaving an indelible imprint on the space-time closest to the black hole. As a consequence of relativistic frame-dragging, particle orbits are affected both in terms of stability and precession, which impacts on the emission characteristics of accreting black holes both stellar mass in black hole binaries (BHBs) and supermassive in active galactic nuclei (AGN). Over the last 30 years, techniques have been developed that take into account these changes to estimate the spin which can then be used to understand the birth and growth of black holes and potentially the powering of powerful jets. In this chapter we provide a broad overview of both the theoretical effects of spin, the means by which it can be estimated and the results of ongoing campaigns.Comment: 55 pages, 5 figures. Published in: "Astrophysics of Black Holes - From fundamental aspects to latest developments", Ed. Cosimo Bambi, Springer: Astrophysics and Space Science Library. Additional corrections mad

Ultraviolet and X-ray variability of active galactic nuclei with Swift

We analyse a sample of 21 active galactic nuclei (AGN) using data from the Swift satellite to study the variability properties of the population in the X-ray, UV and optical band. We find that the variable part of the UV-optical emission has a spectrum consistent with a powerlaw, with an average index of $-2.21\pm0.13$, as would be expected from central illumination of a thin disc (index of -7/3). We also calculate the slope of a powerlaw from UV to X-ray variable emission, $\alpha_{\rm OX,Var}$; the average for this sample is $\alpha_{\rm OX,Var} = -1.06 \pm 0.04$. The anticorrelation of $\alpha_{\rm OX}$ with the UV luminosity, $L_{\rm UV}$, previously found in the average emission is also present in the variable part: $\alpha_{\rm OX,Var} = (-0.177 \pm 0.083) {\rm log} (L_{\rm \nu,Var} (2500\,\AA)) + (3.88 \pm 2.33)$. Correlated variability between the emission in X-rays and UV is detected significantly for 9 of the 21 sources. All these cases are consistent with the UV lagging the X-rays, as would be seen if the correlated UV variations were produced by the reprocessing of X-ray emission. The observed UV lags are tentatively longer than expected for a standard thin disc.ACF, AML and DJKB acknowledge support from the ERC Advanced Grant FEEDBACK 340442. WNA acknowledges support from the European Union Seventh Framework Programme (FP7/2013-2017) under grant agreement n.312789, StrongGravity. DB acknowledges an STFC studentship. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester.This is the final version of the article. It first appeared from Oxford University Press via https://doi.org/10.1093/mnras/stw248

Gender, governance and climate change adaptation

This chapter attempts to highlight the role that gender plays in the context of climate change adaptation. It uses a discourse analysis approach to comparatively present a review of the role gender plays in climate change adaptation. Currently, two discourse storylines dominate the exploration of gender and climate change. One tells a story about women being disproportionately impacted by climate change and constructs them as ongoing victims. The other storyline explores the role women play in building adaptation and simultaneously presents women as both being more resilient and having more agency in these contexts. Applying a gender lens to governance could include enhancing the role of existing communities of practice. This chapter attempts to provide a detailed review of and means by which to understand and present how climate change and climate change adaptation is driven by gender and the implications of this for ongoing adaptive governance. This chapter adds to gender analyses by considering the role of communities of practice arguing that their deliberate utilization can enable gender to be productively rather than negatively utilized to build robust, socially just, and innovative adaptation regimes.Melissa Nursey-Bra