1,724,278 research outputs found
Possible NIR counterpart to the AXP 1E 1547.0-5408
No full textOn 2008 October 3rd, Swift-BAT triggered on several short bursts from the direction of the Anomalous X-ray Pulsar (AXP) 1E1547.0-5408 (Krimm et al. GCN 8311, 8312; Rea et al. Atel #1756). This is the second known transient radio AXP discovered to date (Gelfand & Gaensler 2007; Camilo et al. 2007), and it showed the previous X-ray outburst around June 2007 (Halpern et al. 2008). During the decay of the 2007 X-ray outburst we observed 1E 1547.0-5408 in the Ks band (on 2007 July 8th, 12th, and August 17th) with the NAOS -CONICA (NACO) instrument mounted at the ESO- VLT (Mignani, Rea, Testa, et al., 2008 submitted)
Результати аналізу криптосистем на ідентифікаторах, аналіз документів IEEE P1636.3, RFC 5091, RFC 5408
No full textУ даній статті представлений загальний опис та характеристика документів криптографічних систем на ідентифікаторах, таких, як RFC 5091, RFC 5408 та IEEE P1636.3™/D1 в області форматів даних і загальної інфраструктури передачі даних в IBE системах. У документі RFC 5408 наводиться архітектура безпеки, необхідні структури даних для криптосистем на ідентифікаторах. Документи RFC 5091 і IEEE P1636.3™/D1 описують системи відкритого ключа на ідентифікаторах, засновані на білінійних спарюваннях
Back to radio: Parkes detection of radio pulses from the transient AXP 1E1547.0-5408
No full textFollowing the recent re-activation of the AXP 1E1547.0-5408 (GCNs #8833, #8835, #8837) we triggered our Parkes target of opportunity program for transient magnetars. We observed 1E1547.0-5408 at 10cm on 2009 January 23rd and 25th, for ~1.2hrs per day. Radio pulsations were not detected in our first observation on January 23rd (no detection resulted also from the data taken on January 22nd: Atel #1907)
VLT/NACO near-infrared observations of the transient radio magnetar 1E 1547.0-5408
Get PDFContext: Despite about a decade of observations, very little is known about the optical and infrared (IR) emission properties of the soft gamma-ray repeaters (SGRs) and of the anomalous X-ray pulsars (AXPs), the magnetar candidates, and about the physical processes which drive their emission at these wavelengths. This is mainly due to the limited number of identifications achieved so far, five in total, and to the sparse spectral coverage obtained from multi-band optical/IR photometry.
Aims: The aim of this work is to search for a likely candidate counterpart to the recently discovered transient radio AXP 1E 1547.0-5408.
Methods: We performed the first deep near-IR (NIR) observations (Ks band) of 1E 1547.0-5408 with the Very Large Telescope (VLT) on three nights (July 8th, 12th, and August 17th), after the X-ray source rebrightening and during the subsequent decay reported around June 2007.
Results: We detected four objects within, or close to, the 3σ radio position of 1E 1547.0-5408. The faintest of them (object 1) has a brightness Ks = 20.27 ± 0.05, which would yield an unabsorbed X-ray-to-NIR flux ratio F_X/FKs ̃ 800 for 1E 1547.0-5408, i.e. on average lower than those derived for other magnetars. The non-detection of object 1 on the nights of July 8th and August 17th only allowed us to set an upper limit of Δ Ks ̃ 0.2 on its NIR variability, which prevented us from searching for correlations with the radio or X-ray flux. We detected no other object at the radio position down to a limit of Ks ̃ 21.7 (at 5 σ), computed in our deepest VLT image (July 12th).
Conclusions: From our observations we cannot confidently propose a NIR counterpart to 1E 1547.0-5408. More NIR observations of object 1, e.g. to determine its colors and to monitor variability, would be conclusive to determine whether or not it can be considered a plausible candidate
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Challenging times: a re-analysis of NGC 5408 X-1
Get PDFThe ultraluminous X-ray source (ULX), NGC 5408 X-1, is one of only 3 such objects to show a quasi-periodic oscillation (QPO) in its power spectrum. Previous analysis of this signal identified it with the well-studied type C low-frequency QPO (LFQPO) seen in black hole binaries (BHBs), implying an intermediate mass black hole (IMBH). However, in BHBs this QPO has a centroid frequency which scales tightly with the position of the low-frequency break in the broad band power spectrum. We use this relation to predict the frequency of the power spectral break in NGC 5408 X-1, and show that this is inconsistent with the break frequencies in both available, archival XMM-Newton observations. Thus the broad band power spectral shape does not support this identification of the QPO. The energy spectra also do not support an IMBH interpretation. They can be fit by a two-component model, best described by soft thermal emission at low energies, together with low-temperature, optically thick Comptonisation producing a tail which dominates above 2 keV. The parameters of the tail are unlike those seen in any of the sub-Eddington BHB spectral states. The energy dependent variability supports this deconvolution, as it is consistent with the soft thermal component below 2 keV diluting extreme variability of the high energy tail. The only objects with similar spectra which have similar amounts of variability are the BHB, GRS 1915+105, and some extreme NLS1s. This suggests that NGC 5408 X-1 is in a similar super-Eddington state, placing a natural limit on the mass of 100M⊙. Its QPO could then be similar to the ultra- LFQPO seen occasionally in GRS 1915+105, consistent with a large stellar mass black hole. We suggest a model geometry which may explain the spectra and variability of highly super-Eddington sources
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Two magnetars: SGR 1627–41 and 1E 1547–5408
No full textWe describe the results obtained with Target of Opportunity observations of the galactic sources SGR 1627-41 and 1E 1547-5408. These two transients show several similarities supporting the interpretation of Anomalous X-ray Pulsars and Soft Gamma-ray Repeaters as a single class of strongly magnetized neutron stars
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