2,074 research outputs found
Discovery and evolution of the new black hole candidate Swift J1539.2-6227 during its 2008 outburst
We report on the discovery by the Swift Gamma-Ray Burst Explorer of the black
hole candidate Swift J1539.2-6227 and the subsequent course of an outburst
beginning in November 2008 and lasting at least seven months. The source was
discovered during normal observations with the Swift Burst Alert Telescope
(BAT) on 2008 November 25. An extended observing campaign with the Rossi X-Ray
Timing Explorer (RXTE) and Swift provided near-daily coverage over 176 days,
giving us a good opportunity to track the evolution of spectral and timing
parameters with fine temporal resolution through a series of spectral states.
The source was first detected in a hard state during which strong low-frequency
quasi-periodic oscillations (QPOs) were detected. The QPOs persisted for about
35 days and a signature of the transition from the hard to soft intermediate
states was seen in the timing data. The source entered a short-lived thermal
state about 40 days after the start of the outburst. There were variations in
spectral hardness as the source flux declined and returned to a hard state at
the end of the outburst. The progression of spectral states and the nature of
the timing features provide strong evidence that Swift J1539.2-6227 is a
candidate black hole in a low-mass X-ray binary system.Comment: Accepted by the Astrophysical Journa
Towards More Precise Survey Photometry for PanSTARRS and LSST: Measuring Directly the Optical Transmission Spectrum of the Atmosphere
Motivated by the recognition that variation in the optical transmission of
the atmosphere is probably the main limitation to the precision of ground-based
CCD measurements of celestial fluxes, we review the physical processes that
attenuate the passage of light through the Earth's atmosphere. The next
generation of astronomical surveys, such as PanSTARRS and LSST, will greatly
benefit from dedicated apparatus to obtain atmospheric transmission data that
can be associated with each survey image. We review and compare various
approaches to this measurement problem, including photometry, spectroscopy, and
LIDAR. In conjunction with careful measurements of instrumental throughput,
atmospheric transmission measurements should allow next-generation imaging
surveys to produce photometry of unprecedented precision. Our primary concerns
are the real-time determination of aerosol scattering and absorption by water
along the line of sight, both of which can vary over the course of a night's
observations.Comment: 41 pages, 14 figures. Accepted PAS
Spectral line shape of resonant four-wave mixing induced by broad-bandwidth lasers
We present a theoretical and experimental study of the line shape of resonant four-wave mixing induced by broad-bandwidth laser radiation that revises the theory of Meacher, Smith, Ewart, and Cooper (MSEC) [Phys. Rev. A 46, 2718 (1992)]. We adopt the same method as MSEC but correct for an invalid integral used to average over the distribution of atomic velocities. The revised theory predicts a Voigt line shape composed of a homogeneous, Lorentzian component, defined by the collisional rate Î, and an inhomogeneous, Doppler component, which is a squared Gaussian. The width of the inhomogeneous component is reduced by a factor of â2 compared to the simple Doppler width predicted by MSEC. In the limit of dominant Doppler broadening, the width of the homogeneous component is predicted to be 4Î, whereas in the limit of dominant homogeneous broadening, the predicted width is 2Î. An experimental measurement is reported of the line shape of the four-wave-mixing signal using a broad-bandwidth, "modeless", laser resonant with the Q1 (6) line of the A2 ÎŁ - X2 Î (0,0) system of the hydroxyl radical. The measured widths of the Voigt components were found to be consistent with the predictions of the revised theory
ChlVPP alternating with PABlOE is superior to PABlOE alone in the initial treatment of advanced Hodgkin's disease: results of a British National Lymphoma Investigation/Central Lymphoma Group randomized controlled trial
The purpose of this randomized trial was to compare the efficacy of 6 cycles of prednisolone, Adriamycin (doxorubicin), bleomycin, vincristine (Oncovin) and etoposide (PABlOE) with 3 cycles of PABIOE that alternate with 3 cycles of chlorambucil, vinblastine, procarbazine and prednisone (ChlVPP) in patients with advanced Hodgkin's disease. Between October 1992 and April 1996, 679 patients were entered onto the study. 41 of these did not match the protocol requirements on review and were excluded from further analysis, most of these being reclassified as NHL on histological review. Of the remaining 638 patients, 319 were allocated to receive PABIOE and 319 were allocated to receive ChlVPP/PABlOE. The complete remission (CR) rates were 78% and 64%, for ChlVPP/PABlOE and PABIOE respectively after initial chemotherapy (P< 0.0001). 124 patients were re-evaluated subsequently following radiotherapy to residual masses. The CR rates changed from 78% to 88% for ChlVPP/PABlOE and from 64% to 77% for PABlOE when re-evaluated in this manner (treatment difference still significant P = 0.0002). The treatment associated mortality in the PABlOE arm was 2.2% (7 deaths), while there were no such deaths in the ChlVPP/PABlOE arm (P = 0.015). The failure-free survival was significantly greater in the ChlVPP/PABlOE arm (P< 0.0001) as was the overall survival (P = 0.01). The failure-free and overall survival rates at 3 years were 77% and 91% in the ChlVPP/PABlOE arm, compared with 58% and 85% in the PABIOE arm, respectively. These results indicate that ChlVPP alternating with PABIOE is superior to PABIOE alone as initial treatment for advanced Hodgkin's disease.© 2001 Cancer Research Campaign www.bjcancer.co
The political import of deconstructionâDerridaâs limits?: a forum on Jacques Derridaâs specters of Marx after 25 Years, part I
Jacques Derrida delivered the basis of The Specters of Marx: The State of the Debt, the Work of Mourning, & the New International as a plenary address at the conference âWhither Marxism?â hosted by the University of California, Riverside, in 1993. The longer book version was published in French the same year and appeared in English and Portuguese the following year. In the decade after the publication of Specters, Derridaâs analyses provoked a large critical literature and invited both consternation and celebration by figures such as Antonio Negri, Wendy Brown and Frederic Jameson. This forum seeks to stimulate new reflections on Derrida, deconstruction and Specters of Marx by considering how the futures past announced by the book have fared after an eventful quarter century. Maja Zehfuss, Antonio VĂĄzquez-Arroyo and Dan Bulley and Bal Sokhi-Bulley offer sharp, occasionally exasperated, meditations on the political import of deconstruction and the limits of Derridaâs diagnoses in Specters of Marx but also identify possible paths forward for a global politics taking inspiration in Derridaâs work of the 1990s
The BBC, Austerity and Broadcasting the 1948 Olympic Games
Based on original archive research, including papers held in the BBC Written Archives Centre, and interviews with those involved, this paper analyses the historical importance for the BBC of the 1948 Games as the first publicly televised Olympics. In particular, the paper addresses the management of operations by the Head of Outside Broadcasting at the BBC, Seymour Joly de Lotbiniere. De Lotbiniere had been an important figure in the development of outside broadcasting commentaries during the inter-war period and was given the task of organising the radio and television coverage of the London Games in 1948. The paper examines the technical, operational and ideological issues raised by the event for the BBC and its legacy for the development of live televised outside broadcasts from sport. The analysis suggests the BBCâs ability to host international broadcasters became a matter of prestige and its forays into television a sign of its emerging post-War modernity
Threat of falling high status and corporate bribery: Evidence from the revealed accounting records of two South Korean presidents
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142958/1/smj2747-sup-0001-SuppInfo.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142958/2/smj2747.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142958/3/smj2747_am.pd
Two years of monitoring Supergiant Fast X-ray Transients with Swift
We present two years of intense Swift monitoring of three SFXTs, IGR
J16479-4514, XTE J1739-302, and IGR J17544-2619 (since October 2007).
Out-of-outburst intensity-based X-ray (0.3-10keV) spectroscopy yields absorbed
power laws with by hard photon indices (G~1-2). Their outburst broad-band
(0.3-150 keV) spectra can be fit well with models typically used to describe
the X-ray emission from accreting NSs in HMXBs. We assess how long each source
spends in each state using a systematic monitoring with a sensitive instrument.
These sources spend 3-5% of the total in bright outbursts. The most probable
flux is 1-2E-11 erg cm^{-2} s^{-1} (2-10 keV, unabsorbed), corresponding to
luminosities in the order of a few 10^{33} to 10^{34} erg s^{-1} (two orders of
magnitude lower than the bright outbursts). The duty-cycle of inactivity is 19,
39, 55%, for IGR J16479-4514, XTE J1739-302, and IGR J17544-2619, respectively.
We present a complete list of BAT on-board detections further confirming the
continued activity of these sources. This demonstrates that true quiescence is
a rare state, and that these transients accrete matter throughout their life at
different rates. X-ray variability is observed at all timescales and
intensities we can probe. Superimposed on the day-to-day variability is
intra-day flaring which involves variations up to one order of magnitude that
can occur down to timescales as short as ~1ks, and whichcan be explained by the
accretion of single clumps composing the donor wind with masses
M_cl~0.3-2x10^{19} g. (Abridged)Comment: Accepted for publication in MNRAS. 17 pages, 11 figures, 8 table
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