The ASCA X-Ray Spectrum Of The Broad-Line Radio Galaxy Pictor A: A Simple Power Law With No Fe K-alpha Line

We present the X-ray spectrum of the broad-line radio galaxy Pictor A as observed by ASCA in 1996. The main objective of the observation was to detect and study the profiles of the Fe~K$\alpha$ lines. The motivation was the fact that the Balmer lines of this object show well-separated displaced peaks, suggesting an origin in an accretion disk. The 0.5-10 keV X-ray spectrum is described very well by a model consisting of a power law of photon index 1.77 modified by interstellar photoelectric absorption. We find evidence for neither a soft nor a hard (Compton reflection) excess. More importantly, we do not detect an Fe K-alpha line, in marked contrast with the spectra of typical Seyfert galaxies and other broad-line radio galaxies observed by ASCA. The 99%-confidence upper limit on the equivalent width of an unresolved line at a rest energy of 6.4 keV is 100 eV, while for a broad line (FWHM of approximately 60,000 km/s) the corresponding upper limit is 135 eV. We discuss several possible explanations for the weakness of the Fe K-alpha line in Pictor~A paying attention to the currently available data on the properties of Fe K-alpha lines in other broad-line radio galaxies observed by ASCA. We speculate that the absence of a hard excess (Compton reflection) or an Fe K-alpha line is an indication of an accretion disk structure that is different from that of typical Seyfert galaxies, e.g., the inner disk may be an ion torus.Comment: To appear in the Astrophysical Journal (18 pages, including 8 postscript figures; uses psfig.tex

Mathers Systematic Theology - Chapter 2

INSPIRATION OF THE SCRIPTURES 2.1 The Inspiration of the Scriptures involves the accurate recording of the revelation. 2.1.1 Central Passages establish the inspiration of the Scriptures. 2.1.1.1 2 Timothy 3:16-1

Writing and the zeitgeist

Have contemporary writers anything to say about their times and, if so, have they the nerve to say it? This article argues that there is much failure of vision and failure of nerve on the part of today's writers. Because they lack the clarity and courage to come to terms with the times, they succumb to its deceptions and seductions. Its thesis is is that the power and value of writing is in the scope and depth of its engagement with the zeitgeist; in how perceptively a writer captures the spirit of the age, expresses the temper of the times; in how much of what is there in the air, throbbing in the collective psyche, pulsing in the ever shifting social order, a writer gathers up and expresses in accurate and resonant images, in provocative and paradigmatic stories. This is pursued in reflection on attitudes expressed at two international writers conferences and in polemic against the prevailing views expressed

Optimum Quantum Error Recovery using Semidefinite Programming

Quantum error correction (QEC) is an essential element of physical quantum information processing systems. Most QEC efforts focus on extending classical error correction schemes to the quantum regime. The input to a noisy system is embedded in a coded subspace, and error recovery is performed via an operation designed to perfectly correct for a set of errors, presumably a large subset of the physical noise process. In this paper, we examine the choice of recovery operation. Rather than seeking perfect correction on a subset of errors, we seek a recovery operation to maximize the entanglement fidelity for a given input state and noise model. In this way, the recovery operation is optimum for the given encoding and noise process. This optimization is shown to be calculable via a semidefinite program (SDP), a well-established form of convex optimization with efficient algorithms for its solution. The error recovery operation may also be interpreted as a combining operation following a quantum spreading channel, thus providing a quantum analogy to the classical diversity combining operation.Comment: 7 pages, 3 figure

Decisiveness

This paper investigates how the presence of strong leadership influences an organization's ability to acquire and process information. The key concept is the leader's decisiveness. A decisive leader can make a bold move in response to a large change in the underlying landscape, whereas an indecisive leader biases her position excessively towards the status quo. An organization led by an indecisive leader needs to accumulate unrealistically strong evidence before it changes the course of action, thereby hindering the organization's ability to adapt to a changing environment. The analysis identifies several attributes and environmental factors that impair one's decisiveness and illuminates how leadership emerges or fades in organizations. The paper also sheds light on a classical issue of whether leaders can be made, rather than are born: our answer is partially `yes' in that mutual trust among members of the organization is a critical ingredient of effective leadership.Decisiveness, Transformational leadership, Charismatic leadership, Information acquisition, Career concerns.

Computational multi-depth single-photon imaging

We present an imaging framework that is able to accurately reconstruct multiple depths at individual pixels from single-photon observations. Our active imaging method models the single-photon detection statistics from multiple reflectors within a pixel, and it also exploits the fact that a multi-depth profile at each pixel can be expressed as a sparse signal. We interpret the multi-depth reconstruction problem as a sparse deconvolution problem using single-photon observations, create a convex problem through discretization and relaxation, and use a modified iterative shrinkage-thresholding algorithm to efficiently solve for the optimal multi-depth solution. We experimentally demonstrate that the proposed framework is able to accurately reconstruct the depth features of an object that is behind a partially-reflecting scatterer and 4 m away from the imager with root mean-square error of 11 cm, using only 19 signal photon detections per pixel in the presence of moderate background light. In terms of root mean-square error, this is a factor of 4.2 improvement over the conventional method of Gaussian-mixture fitting for multi-depth recovery.This material is based upon work supported in part by a Samsung Scholarship, the US National Science Foundation under Grant No. 1422034, and the MIT Lincoln Laboratory Advanced Concepts Committee. We thank Dheera Venkatraman for his assistance with the experiments. (Samsung Scholarship; 1422034 - US National Science Foundation; MIT Lincoln Laboratory Advanced Concepts Committee)Accepted manuscrip

The X-ray spectrum of a disk illuminated by ions

The X-ray spectrum from a cool disk embedded in an ion supported torus is computed. The interaction of the hot ions with the disk increases the hard X-ray luminosity of the system}. A surface layer of the disk is heated by the protons from the torus. The Comptonized spectrum produced by this layer has a shape that depends only weakly on the incident energy flux and the distance from the accreting compact object. It consists of a `blue bump' of unComptonized soft photons and a flat high energy tail, reminiscent of the observed spectra. The hard tail becomes flatter as the thermalization depth in the cool disk is increased. Further evidence for ion illumination are the Li abundance in the secondaries of low mass X-ray binaries and the 450 keV lines sometimes seen in black-hole transient spectra.Comment: 7p, to appear in Monthly Notice