The in-flight spectroscopic performance of the Swift XRT CCD camera during 2006-2007

The Swift X-ray Telescope focal plane camera is a front-illuminated MOS CCD, providing a spectral response kernel of 135 eV FWHM at 5.9 keV as measured before launch. We describe the CCD calibration program based on celestial and on-board calibration sources, relevant in-flight experiences, and developments in the CCD response model. We illustrate how the revised response model describes the calibration sources well. Comparison of observed spectra with models folded through the instrument response produces negative residuals around and below the Oxygen edge. We discuss several possible causes for such residuals. Traps created by proton damage on the CCD increase the charge transfer inefficiency (CTI) over time. We describe the evolution of the CTI since the launch and its effect on the CCD spectral resolution and the gain.Comment: 8 pages, 5 colour figures, submitted to SPI

The Swift X-Ray Telescope: Status and Performance

We present science highlights and performance from the Swift X-ray Telescope (XRT), which was launched on November 20, 2004. The XRT covers the 0.2-10 keV band, and spends most of its time observing gamma-ray burst (GRB)afterglows, though it has also performed observations of many other objects. By mid-August 2007, the XRT had observed over 220 GRB afterglows, detecting about 96% of them. The XRT positions enable followup ground-based optical observations, with roughly 60% of the afterglows detected at optical or near IR wavelengths. Redshifts are measured for 33% of X-ray afterglows. Science highlights include the discovery of flaring behavior at quite late times, with implications for GRB central engines; localization of short GRBs, leading to observational support for compact merger progenitors for this class of bursts; a mysterious plateau phase to GRB afterglows; as well as many other interesting observations such as X-ray emission from comets, novae, galactic transients, and other objects.Comment: 9 pages, 14 figure

The BeppoSAX High Energy Large Area Survey HELLAS, II: Number counts and X-ray spectral properties

The BeppoSAX High Energy Large Area Survey (HELLAS) has surveyed about 85 deg^2 of sky in the 5-10 keV band down to a flux of 4-5 10^-14 erg cm-2 s-1. The source surface density of 16.9+-6.4 deg$^{-2}$ at the survey limit corresponds to a resolved fraction of the 5-10 keV X-ray background (XRB) of the order of 20-30 %. Hardness ratios analysis indicates that the spectra of a substantial fraction of the HELLAS sources (at least one third) are harder than a alpha_E = 0.6 power law. This hardness may be due to large absorbing columns. The hardness ratio analysis also indicates that many HELLAS sources may have a spectrum more complex than a single absorbed power law. A soft component, superimposed to a strongly cut-off power law, is likely to be present in several sources.Comment: to appear in MNRA

Lexicality and frequency in specific language impairment: accuracy and error data from two nonword repetition tests

Purpose: Deficits in phonological working memory and deficits in phonological processing have both been considered potential explanatory factors in Specific Language Impairment (SLI). Manipulations of the lexicality and phonotactic frequency of nonwords enable contrasting predictions to be derived from these hypotheses. Method: 18 typically developing (TD) children and 18 children with SLI completed an assessment battery that included tests of language ability, non-verbal intelligence, and two nonword repetition tests that varied in lexicality and frequency. Results: Repetition accuracy showed that children with SLI were unimpaired for short and simple high lexicality nonwords, whereas clear impairments were shown for all low lexicality nonwords. For low lexicality nonwords, greater repetition accuracy was seen for nonwords constructed from high over low frequency phoneme sequences. Children with SLI made the same proportion of errors that substituted a nonsense syllable for a lexical item as TD children, and this was stable across nonword length. Conclusions: The data show support for a phonological processing deficit in children with SLI, where long-term lexical and sub-lexical phonological knowledge mediate the interpretation of nonwords. However, the data also suggest that while phonological processing may provide a key explanation of SLI, a full account is likely to be multi-faceted

First AGILE Catalog of High Confidence Gamma-Ray Sources

We present the first catalog of high-confidence gamma-ray sources detected by the AGILE satellite during observations performed from July 9, 2007 to June 30, 2008. Catalogued sources are detected by merging all the available data over the entire time period. AGILE, launched in April 2007, is an ASI mission devoted to gamma-ray observations in the 30 MeV - 50 GeV energy range, with simultaneous X-ray imaging capability in the 18-60 keV band. This catalog is based on Gamma-Ray Imaging Detector (GRID) data for energies greater than 100 MeV. For the first AGILE catalog we adopted a conservative analysis, with a high-quality event filter optimized to select gamma-ray events within the central zone of the instrument Field of View (radius of 40 degrees). This is a significance-limited (4 sigma) catalog, and it is not a complete flux-limited sample due to the non-uniform first year AGILE sky coverage. The catalog includes 47 sources, 21 of which are associated with confirmed or candidate pulsars, 13 with Blazars (7 FSRQ, 4 BL Lacs, 2 unknown type), 2 with HMXRBs, 2 with SNRs, 1 with a colliding-wind binary system, 8 with unidentified sources.Comment: Revised version, 15 pages, 3 figures, 3 tables. To be published in Astronomy and Astrophysics. Text improved and clarified. Refined analysis of complex regions of the Galactic plane yields a new list of high-confidence sources including 47 sources (compared with the 40 sources appearing in the first version

Saint Marie-Alphonsine and the resurrection of Jubra'il Dabdoub

In 1909 two worlds collided in Bethlehem. A successful and cosmopolitan merchant from the town was brought back from the dead by a local nun who had never left Palestine. This article presents an experiment in biographical writing by reconstructing the miracle and the lives that unfolded around it. At first glance, the two protagonists could not appear more different. The merchant, Jubra’il Dabdoub (1860−1931), was among Bethlehem’s ‘pioneer’ generation of merchant migrants − young men who boarded steamships setting sail from Jaffa in the 1870s and 1880s, to travel all over the world in a bid to make their fortunes. The nun, Marie-Alphonsine (1843–1927), born in Jerusalem, was a fiercely devout woman who embraced a life of poverty and founded a religious order, the Congregation of the Rosary Sisters (still active today), devoted to serving local Arab girls and women. In 2015 she and Mariam Bawardi were canonized by Pope Francis as the first Catholic Palestinian female saints.Despite the apparently divergent biographies of these characters, they were both products of the same local society. The article below attempts to place the reader within the world views of Jubra’il Dabdoub and Marie Alphonsine, rather than argue through a detached, analytical style of writing. More specifically, it employs a magical realist mode of storytelling to create a mood in which supernatural occurrences are experienced as routine events while the manifestations of global capitalism are looked upon with wonder and trepidation. As a literary genre, magical realism constantly seeks to destabilize the reader’s sense of the mundane and the extraordinary, the illusory and the real. As such it has much to offer historians interested in adapting their writing to mirror subjects who seem unfazed Jerusalem Quarterly 73 [ 11 ] by supernatural events while simultaneously living through great social, political or economic upheaval. In the case of Bethlehem, as with Palestine more broadly, profoundly unsettling changes were occurring at the turn of the twentieth century. The article seeks to capture these upheavals through the eyes of the local inhabitants, especially in terms of migration, technology, and the pull of Arab identity, while asserting the sense of magic and piety that underpinned people’s experiences of these changes. To achieve consistency in style, I have at times embellished historical sources by drawing on wider research to imagine how a person might have experienced a given event. This is particularly the case with Jubra’il Dabdoub who left behind no written reflections on his life, but only fragments of sources relating to his activities as an itinerant merchant. I have indicated clearly in the endnotes where I have gone beyond the empirically available evidence. Jubra’il Dabdoub is also the subject of a monograph I am currently writing that will explore in more depth the potential of fictional and folkloric narrative techniques to capture the lives of these types of historical actors

The Swift X-Ray Te1escope: Status and Performance

We present science highlights and performance from the Swift X-ray Telescope (XRT), which was launched on November 20,2004. The XRT covers the 0.2-10 keV band, and spends most of its time observing gamma-ray burst (GRB) afterglows, though it has also performed observations of many other objects. By mid-August 2007, the XRT had observed over 220 GRB afterglows, detecting about 96% of them. The XRT positions enable followup ground-based optical observations, with roughly 60% of the afterglows detected at optical or near IR wavelengths. Redshifts are measured for 33% of X-ray afterglows. Science highlights include the discovery of flaring behavior at quite late times, with implications for GRB central engines; localization of short GRBs, leading to observational support for compact merger progenitors for this class of bursts; a mysterious plateau phase to GRB afterglows; as well as many other interesting observations such as X-ray emission from comets, novae, galactic transients, and other objects

Characteristics and performance of the Swift X-Ray telescope

The X-ray Telescope (XRT), on board the Swift satellite, has been built to provide: automated source detection and position with few arcsecond accuracy within 5 seconds of target acquisition; CCD spectroscopy and imaging capability (0.2–10 keV), with a detection sensitivity of 2 × 10−14 erg cm−2 s−1 in 104 s; automatic adjusting of the CCD readout mode to optimize the science return as the source fades. XRT can observe GRB afterglows over several orders of magnitude in flux. The first results obtained during the in-flight performance verification phase confirm that XRT is fully compliant with the requirements and is providing excellent results