The size of the X-ray emitting region in SWIFT J2127.4+5654 via a broad line region cloud X-ray eclipse

We present results obtained from the time-resolved X-ray spectral analysis of the Narrow-Line-Seyfert 1 galaxy SWIFT J2127.4+5654 during a ~130 ks XMM-Newton observation. We reveal large spectral variations, especially during the first ~90 ks of the XMM-Newton exposure. The spectral variability can be attributed to a partial eclipse of the X-ray source by an intervening low-ionization/cold absorbing structure (cloud) with column density N_H = 2.0^{+0.2}_{-0.3}e22 cm^-2 which gradually covers and then uncovers the X-ray emitting region with covering fraction ranging from zero to ~43 per cent. Our analysis enables us to constrain the size, number density, and location of the absorbing cloud with good accuracy. We infer a cloud size (diameter) of $D_c < 1.5e13 cm, corresponding to a density of n_c > 1.5e9 cm^-3 at a distance of R_c > 4.3e16 cm from the central black hole. All of the inferred quantities concur to identify the absorbing structure with one single cloud associated with the broad line region of SWIFT J2127.4+5654. We are also able to constrain the X-ray emitting region size (diameter) to be D_s < 2.3e13 cm which, assuming the black hole mass estimated from single-epoch optical spectroscopy (1.5e7 M_sun), translates into D_s < 10.5 gravitational radii (r_g) with larger sizes (in r_g) being associated with smaller black hole masses, and viceversa. We also confirm the presence of a relativistically distorted reflection component off the inner accretion disc giving rise to a broad relativistic Fe K emission line and small soft excess (small because of the high Galactic column density), supporting the measurement of an intermediate black hole spin in SWIFT J2127.4+5654 that was obtained from a previous Suzaku observation.Comment: 8 pages, 7 figures, accepted for publication in MNRA

Broad-band X-ray observation of broad-line radio galaxy 3C 109

We present a study of the central engine in the broad-line radio galaxy 3C 109. To investigate the immediate surrounding of this accreting, supermassive black hole, we perform a multi-epoch broad-band spectral analysis of a joint NuSTAR/XMM observation (2017), an archival xmm observation (2005) and the 105-month averaged Swift-BAT data. We are able to clearly separate the spectrum into a primary continuum, neutral and ionized absorption, and a reflection component. The photon index of the primary continuum has changed since 2005 ($\Gamma = 1.61 \substack{+0.02 \\ -0.01} \rightarrow 1.54 \pm{0.02}$), while other components remain unchanged, indicative of minimal geometric changes to the central engine. We constrain the high-energy cutoff of 3C 109 (E$_{\text{cut}}= 49 \substack{+7 \\ -5}$\,keV ) for the first time. The reflector is found to be ionized (log $\xi$ = $2.3 \substack{+0.1 \\ -0.2}$) but no relativistic blurring is required by the data. SED analysis confirms the super-Eddington nature of 3C 109 initially ($\lambda_{Edd} >$ 2.09). However, we do not find any evidence for strong reflection (R = $0.18 \substack{+0.04 \\ -0.03}$) or a steep power law index, as expected from a super-Eddington source. This puts the existing virial mass estimate of 2 $\times 10^{8}$M$_{\odot}$ into question. We explore additional ways of estimating the Eddington ratio, some of which we find to be inconsistent with our initial SED estimate. We obtain a new black hole mass estimate of 9.3 $\times 10^{8}$M$_{\odot}$, which brings all Eddington ratio estimates into agreement and does not require 3C 109 to be super-Eddington.Comment: 13 pages, 8 figure

An infrared survey of brightest cluster galaxies: Paper I

We report on an imaging survey with the Spitzer Space Telescope of 62 brightest cluster galaxies with optical line emission. These galaxies are located in the cores of X-ray luminous clusters selected from the ROSAT All-Sky Survey. We find that about half of these sources have a sign of excess infrared emission; 22 objects out of 62 are detected at 70 microns, 18 have 8 to 5.8 micron flux ratios above 1.0 and 28 have 24 to 8 micron flux ratios above 1.0. Altogether 35 of 62 objects in our survey exhibit at least one of these signs of infrared excess. Four galaxies with infrared excesses have a 4.5/3.6 micron flux ratio indicating the presence of hot dust, and/or an unresolved nucleus at 8 microns. Three of these have high measured [OIII](5007A)/Hbeta flux ratios suggesting that these four, Abell 1068, Abell 2146, and Zwicky 2089, and R0821+07, host dusty active galactic nuclei (AGNs). 9 objects (including the four hosting dusty AGNs) have infrared luminosities greater than 10^11 L_sol and so can be classified as luminous infrared galaxies (LIRGs). Excluding the four systems hosting dusty AGNs, the excess mid-infrared emission in the remaining brightest cluster galaxies is likely related to star formation.Comment: accepted for publication in ApJ

An Extreme X-ray Disk Wind in the Black Hole Candidate IGR J17091-3624

{\it Chandra} spectroscopy of transient stellar-mass black holes in outburst has clearly revealed accretion disk winds in soft, disk--dominated states, in apparent anti-correlation with relativistic jets in low/hard states. These disk winds are observed to be highly ionized, dense, and to have typical velocities of $\sim$1000 km/s or less projected along our line of sight. Here, we present an analysis of two {\it Chandra} High Energy Transmission Grating spectra of the Galactic black hole candidate IGR J17091$-$3624 and contemporaneous EVLA radio observations, obtained in 2011. The second {\it Chandra} observation reveals an absorption line at 6.91$\pm$0.01 keV; associating this line with He-like Fe XXV requires a blue-shift of $9300^{+500}_{-400}$ km/s (0.03$c$, or the escape velocity at 1000 R$_{Schw}$). This projected outflow velocity is an order of magnitude higher than has previously been observed in stellar-mass black holes, and is broadly consistent with some of the fastest winds detected in active galactic nuclei. A potential feature at 7.32 keV, if due to Fe XXVI, would imply a velocity of $\sim 14600$ km/s (0.05$c$), but this putative feature is marginal. Photoionization modeling suggests that the accretion disk wind in IGR J17091$-$3624 may originate within 43,300 Schwarzschild radii of the black hole, and may be expelling more gas than accretes. The contemporaneous EVLA observations strongly indicate that jet activity was indeed quenched at the time of our {\it Chandra} observations. We discuss the results in the context of disk winds, jets, and basic accretion disk physics in accreting black hole systems.Comment: 6 pages, 2 figures, Accepted to ApJLetter

Revealing the High Energy Emission from the Obscured Seyfert Galaxy MCG -5-23-16 with Suzaku

We report on a 100 ks Suzaku observation of the bright, nearby (z=0.008486) Seyfert 1.9 galaxy MCG -5-23-16. The broad-band (0.4-100 keV) X-ray spectrum allows us to determine the nature of the high energy emission with little ambiguity. The X-ray continuum consists of a cutoff power-law of photon index $\Gamma=1.9$, absorbed through Compton-thin matter of column density $N_{\rm H}=1.6\times10^{22}$ cm$^{-2}$. A soft excess is observed below 1 keV and is likely a combination of emission from scattered continuum photons and distant photoionized gas. The iron K line profile is complex, showing narrow neutral iron K$\alpha$ and K$\beta$ emission, as well as a broad line which can be modeled by a moderately inclined accretion disk. The line profile shows either the disk is truncated at a few tens of gravitational radii, or the disk emissivity profile is relatively flat. A strong Compton reflection component is detected above 10 keV, which is best modeled by a combination of reflection off distant matter and the accretion disk. The reflection component does not appear to vary. The overall picture is that this Seyfert 1.9 galaxy is viewed at moderate (50 degrees) inclination through Compton-thin matter at the edge of a Compton-thick torus covering $2\pi$ steradians, consistent with unified models.Comment: 14 pages, inc 9 figures. Accepted for publication in PASJ (Suzaku Special Issue

Aspect Ratio Dependence of the Free-Fall Time for Non-Spherical Symmetries

We investigate the collapse of non-spherical substructures, such as sheets and filaments, which are ubiquitous in molecular clouds. Such non-spherical substructures collapse homologously in their interiors but are influenced by an edge effect that causes their edges to be preferentially accelerated. We analytically compute the homologous collapse timescales of the interiors of uniform-density, self-gravitating filaments and find that the homologous collapse timescale scales linearly with the aspect ratio. The characteristic timescale for an edge driven collapse mode in a filament, however, is shown to have a square root dependence on the aspect ratio. For both filaments and circular sheets, we find that selective edge acceleration becomes more important with increasing aspect ratio. In general, we find that lower dimensional objects and objects with larger aspect ratios have longer collapse timescales. We show that estimates for star formation rates, based upon gas densities, can be overestimated by an order of magnitude if the geometry of a cloud is not taken into account.Comment: 10 pages, 2 figures, accepted by ApJ, minor grammatical errors fixe

X-ray Reverberation Mapping of Ark 564 using Gaussian Process Regression

Ark 564 is an extreme high-Eddington Narrow-line Seyfert 1 galaxy, known for being one of the brightest, most rapidly variable soft X-ray AGN, and for having one of the lowest temperature coronae. Here we present a 410-ks NuSTAR observation and two 115-ks XMM-Newton observations of this unique source, which reveal a very strong, relativistically broadened iron line. We compute the Fourier-resolved time lags by first using Gaussian processes to interpolate the NuSTAR gaps, implementing the first employment of multi-task learning for application in AGN timing. By fitting simultaneously the time lags and the flux spectra with the relativistic reverberation model RELTRANS, we constrain the mass at $2.3^{+2.6}_{-1.3} \times 10^6M_\odot$, although additional components are required to describe the prominent soft excess in this source. These results motivate future combinations of machine learning, Fourier-resolved timing, and the development of reverberation models.Comment: 19 pages, 9 figures. Accepted for publication in The Astrophysical Journa

The Reflection Component from Cygnus X-1 in the Soft State Measured by NuSTAR and Suzaku

The black hole binary Cygnus X-1 was observed in late 2012 with the Nuclear Spectroscopic Telescope Array (NuSTAR) and Suzaku, providing spectral coverage over the ~1-300 keV range. The source was in the soft state with a multi-temperature blackbody, power law, and reflection components along with absorption from highly ionized material in the system. The high throughput of NuSTAR allows for a very high quality measurement of the complex iron line region as well as the rest of the reflection component. The iron line is clearly broadened and is well described by a relativistic blurring model, providing an opportunity to constrain the black hole spin. Although the spin constraint depends somewhat on which continuum model is used, we obtain ɑ_* > 0.83 for all models that provide a good description of the spectrum. However, none of our spectral fits give a disk inclination that is consistent with the most recently reported binary values for Cyg X-1. This may indicate that there is a >13° misalignment between the orbital plane and the inner accretion disk (i.e., a warped accretion disk) or that there is missing physics in the spectral models