A Suzaku, NuSTAR, and XMM-Newton view on variable absorption and relativistic reflection in NGC 4151

We disentangle X-ray disk reflection from complex line-of-sight absorption in the nearby Seyfert NGC 4151, using a suite of Suzaku, NuSTAR, and XMM-Newton observations. Extending upon earlier published work, we pursue a physically motivated model using the latest angle-resolved version of the lamp-post geometry reflection model relxillCp_lp together with a Comptonization continuum. We use the long-look simultaneous Suzaku/NuSTAR observation to develop a baseline model wherein we model reflected emission as a combination of lamp-post components at the heights of 1.2 and 15.0 gravitational radii. We argue for a vertically extended corona as opposed to two compact and distinct primary sources. We find two neutral absorbers (one full-covering and one partial-covering), an ionized absorber ($\log \xi = 2.8$), and a highly-ionized ultra-fast outflow, which have all been reported previously. All analyzed spectra are well described by this baseline model. The bulk of the spectral variability between 1 keV and 6 keV can be accounted for by changes in the column density of both neutral absorbers, which appear to be degenerate and inversely correlated with the variable hard continuum component flux. We track variability in absorption on both short (2 d) and long ($\sim$1 yr) timescales; the observed evolution is either consistent with changes in the absorber structure (clumpy absorber at distances ranging from the broad line region (BLR) to the inner torus or a dusty radiatively driven wind) or a geometrically stable neutral absorber that becomes increasingly ionized at a rising flux level. The soft X-rays below 1 keV are dominated by photoionized emission from extended gas that may act as a warm mirror for the nuclear radiation.Comment: 21 pages, 19 figures, 8 tables, accepted for publication by A&

Investigating source confusion in PMN J1603−-4904

PMN J1603$-$4904 is a likely member of the rare class of $\gamma$-ray emitting young radio galaxies. Only one other source, PKS 1718$-$649, has been confirmed so far. These objects, which may transition into larger radio galaxies, are a stepping stone to understanding AGN evolution. It is not completely clear how these young galaxies, seen edge-on, can produce high-energy $\gamma$-rays. PMN J1603$-$4904 has been detected by TANAMI Very Long Baseline Interferometry (VLBI) observations and has been followed-up with multiwavelength observations. A Fermi/LAT $\gamma$-ray source has been associated with it in the LAT catalogs. We have obtained Chandra observations of the source in order to consider the possibility of source confusion, due to the relatively large positional uncertainty of Fermi/LAT. The goal was to investigate the possibility of other X-ray bright sources in the vicinity of PMN J1603$-$4904 that could be counterparts to the $\gamma$-ray emission. With Chandra/ACIS, we find no other sources in the uncertainty ellipse of Fermi/LAT data, which includes an improved localization analysis of 8 years of data. We further study the X-ray fluxes and spectra. We conclude that PMN J1603$-$4904 is indeed the second confirmed $\gamma$-ray bright young radio galaxy.Comment: 4 pages, 3 figures, accepted for publication in A&

Complex X-ray spectral variability in Mkn 421 observed with XMM-Newton

The bright blazar Mkn 421 has been observed four times for uninterrupted durations of ~ 9 - 13 hr during the performance verification and calibration phases of the XMM-Newton mission. The source was strongly variable in all epochs, with variability amplitudes that generally increased to higher energy bands. Although the detailed relationship between soft (0.1 - 0.75 keV) and hard (2 - 10 keV) band differed from one epoch to the next, in no case was there any evidence for a measurable interband lag, with robust upper limits of $| \tau | < 0.08$ hr in the best-correlated light curves. This is in conflict with previous claims of both hard and soft lags of ~1 hr in this and other blazars. However, previous observations suffered a repeated 1.6 hr feature induced by the low-Earth orbital period, a feature that is not present in the uninterrupted XMM-Newton data. The new upper limit on $|\tau|$ leads to a lower limit on the magnetic field strength and Doppler factor of B \delta^{1/3} \gs 4.7 G, mildly out of line with the predictions from a variety of homogeneous synchrotron self-Compton emission models in the literature of $B \delta^{1/3} = 0.2 - 0.8$ G. Time-dependent spectral fitting was performed on all epochs, and no detectable spectral hysteresis was seen. We note however that the source exhibited significantly different spectral evolutionary behavior from one epoch to the next, with the strongest correlations in the first and last and an actual divergance between soft and hard X-ray bands in the third. This indicates that the range of spectral variability behavior in Mkn 421 is not fully described in these short snippets; significantly longer uninterrupted light curves are required, and can be obtained with XMM-Newton.Comment: 21 pages, 4 figures, accepted for ApJ, scheduled for August 1, 200

Optimal Investment in the Development of Oil and Gas Field

Let an oil and gas field consists of clusters in each of which an investor can launch at most one project. During the implementation of a particular project, all characteristics are known, including annual production volumes, necessary investment volumes, and profit. The total amount of investments that the investor spends on developing the field during the entire planning period we know. It is required to determine which projects to implement in each cluster so that, within the total amount of investments, the profit for the entire planning period is maximum. The problem under consideration is NP-hard. However, it is solved by dynamic programming with pseudopolynomial time complexity. Nevertheless, in practice, there are additional constraints that do not allow solving the problem with acceptable accuracy at a reasonable time. Such restrictions, in particular, are annual production volumes. In this paper, we considered only the upper constraints that are dictated by the pipeline capacity. For the investment optimization problem with such additional restrictions, we obtain qualitative results, propose an approximate algorithm, and investigate its properties. Based on the results of a numerical experiment, we conclude that the developed algorithm builds a solution close (in terms of the objective function) to the optimal one

Chandra survey in the AKARI North Ecliptic Pole Deep Field. I. X-ray data, point-like source catalog, sensitivity maps, and number counts

We present data products from the 300 ks Chandra survey in the AKARI North Ecliptic Pole (NEP) deep field. This field has a unique set of 9-band infrared photometry covering 2-24 micron from the AKARI Infrared Camera, including mid-infrared (MIR) bands not covered by Spitzer. The survey is one of the deepest ever achieved at ~15 micron, and is by far the widest among those with similar depths in the MIR. This makes this field unique for the MIR-selection of AGN at z~1. We design a source detection procedure, which performs joint Maximum Likelihood PSF fits on all of our 15 mosaicked Chandra pointings covering an area of 0.34 square degree. The procedure has been highly optimized and tested by simulations. We provide a point source catalog with photometry and Bayesian-based 90 per cent confidence upper limits in the 0.5-7, 0.5-2, 2-7, 2-4, and 4-7 keV bands. The catalog contains 457 X-ray sources and the spurious fraction is estimated to be ~1.7 per cent. Sensitivity and 90 per cent confidence upper flux limits maps in all bands are provided as well. We search for optical MIR counterparts in the central 0.25 square degree, where deep Subaru Suprime-Cam multiband images exist. Among the 377 X-ray sources detected there, ~80 per cent have optical counterparts and ~60 per cent also have AKARI mid-IR counterparts. We cross-match our X-ray sources with MIR-selected AGN from Hanami et al. (2012). Around 30 per cent of all AGN that have MID-IR SEDs purely explainable by AGN activity are strong Compton-thick AGN candidates.Comment: 23 pages, 20 figures; catalogs, sensitivity maps, and upper limit flux maps are available from the VizieR Servic

X-ray Variability Characteristics of the Seyfert 1 Galaxy NGC 3783

We have characterized the energy-dependent X-ray variability properties of the Seyfert~1 galaxy NGC 3783 using archival XMM-Newton and Rossi X-ray Timing Explorer data. The high-frequency fluctuation power spectral density function (PSD) slope is consistent with flattening towards higher energies. Light curve cross correlation functions yield no significant lags, but peak coefficients generally decrease as energy separation of the bands increases on both short and long timescales. We have measured the coherence between various X-ray bands over the temporal frequency range of 6e-8 to 1e-4 Hz; this range includes the temporal frequency of the low-frequency power spectral density function (PSD) break tentatively detected by Markowitz et al. and includes the lowest temporal frequency over which coherence has been measured in any AGN to date. Coherence is generally near unity at these temporal frequencies, though it decreases slightly as energy separation of the bands increases. Temporal frequency-dependent phase lags are detected on short time scales; phase lags are consistent with increasing as energy separation increases or as temporal frequency decreases. All of these results are similar to those obtained previously for several Seyfert galaxies and stellar-mass black hole systems. Qualitatively, these results are consistent with the variability models of Kotov et al. and Lyubarskii, wherein the X-ray variability is due to inwardly propagating variations in the local mass accretion rate.Comment: Accepted for publication in The Astrophysical Journal, 2005, vol. 635, p. 180; version 2 has minor grammatical changes; 23 pages; uses emulateapj

On the Lifshitz tail in the density of states of a superconductor with magnetic impurities

We argue that any superconductor with magnetic impurities is gapless due to a Lifshitz tail in the density of states extending to zero energy. At low energy the density of states $\nu(E \to 0)$ remains finite. We show that fluctuations in the impurity distribution produce regions of suppressed superconductivity, which are responsible for the low energy density of states.Comment: 4 pages, uuencoded latex file + ps figure file

A redshifted Fe Kα\alpha line from the unusual gamma-ray source PMN J1603-4904

Multiwavelength observations have revealed the highly unusual properties of the gamma-ray source PMN J1603-4904, which are difficult to reconcile with any other well established gamma-ray source class. The object is either a very atypical blazar or compact jet source seen at a larger angle to the line of sight. In order to determine the physical origin of the high-energy emission processes in PMN J1603-4904, we study the X-ray spectrum in detail. We performed quasi-simultaneous X-ray observations with XMM-Newton and Suzaku in 2013 September, resulting in the first high signal-to-noise X-ray spectrum of this source. The 2-10 keV X-ray spectrum can be well described by an absorbed power law with an emission line at 5.44$\pm$0.05 keV (observed frame). Interpreting this feature as a K{\alpha} line from neutral iron, we determine the redshift of PMN J1603-4904 to be z=0.18$\pm$0.01, corresponding to a luminosity distance of 872$\pm$54 Mpc. The detection of a redshifted X-ray emission line further challenges the original BL Lac classification of PMN J1603-4904. This result suggests that the source is observed at a larger angle to the line of sight than expected for blazars, and thus the source would add to the elusive class of gamma-ray loud misaligned-jet objects, possibly a {\gamma}-ray bright young radio galaxy.Comment: 5 pages, 1 figure, A&A accepte