1,720,959 research outputs found
Discovery of two high magnetic field radio pulsars
No full textWe report the discovery of two young isolated radio pulsars with very high inferred magnetic fields. PSR J1119-6127 has period P = 0.407 s, and the largest period derivative known among radio pulsars, P = 4.0 x 10(-12). Under standard assumptions these parameters imply a characteristic spin-down age of only tau(c) = 1.6 kyr and a surface dipole magnetic field strength of B = 4.1 x 10(13) G. We have measured a stationary period second derivative for this pulsar, resulting in a braking index of n = 2.91 +/- 0.05. We have also observed a glitch in the rotation of the pulsar, with fractional period change Delta P/P = -4.4 x 10(-9). Archival radio imaging data suggest the presence of a previously uncataloged supernova remnant centered on the pulsar. The second pulsar, PSR J1814-1744 has P = 3.975 s and P = 7.4 x 10(-13). These parameters imply tau(c) = 85 kyr, and B = 5.5 x 1013 G, the largest of any known radio pulsar. Both PSR J1119-6127 and PSR J1814-1744 show apparently normal radio emission in a regime of magnetic field strength where some models predict that no emission should occur. Also, PSR J1814-1744 has spin parameters similar to the anomalous X-ray pulsar (AXP) 1E 2259 + 586, but shows no discernible X-ray emission. If AXPs are isolated, high magnetic field neutron stars ("magnetars"), these results suggest that their unusual attributes are unlikely to be merely a consequence of their very high inferred magnetic fields
Two young radio pulsars coincident with EGRET sources
No full textWe report the discovery and follow-up timing observations of two young energetic radio pulsars. PSR J1420-6048 has a period P = 68 ms and period derivative (P) over dot = 83 x 10(-15), implying a characteristic age tau (c) = 13 kyr and a surface dipole magnetic field strength B = 2.4 x 10(12) G. PSR J1837-0604 has P = 96 ms and (P) over dot = 45 x 10(-15), implying tau (c) = 34 kyr and B = 2.1 x 10(12) G. The two objects have large spin-down luminosities, and, on the basis of an empirical comparison of their properties with those of other young radio pulsars, they are expected to be observable as pulsed gamma -ray sources. In fact, they lie within the error circles of gamma -ray sources detected by the EGRET instrument on the Gamma Ray Observatory. We show that the pulsars are plausibly associated with the EGRET sources
The Parkes Multibeam Pulsar Survey: PSR J1811-1736, a pulsar in a highly eccentric binary system
No full textWe are undertaking a high-frequency survey of the Galactic plane for radio pulsars, using the 13-element multibeam receiver on the 64-m Parkes radio telescope. We describe briefly the survey system and some of the initial results. PSR J1811-1736, one of the first pulsars discovered with this system, has a rotation period of 104 ms. Subsequent timing observations using the 76-m radio telescope at Jodrell Bank show that it is in an 18.8-d, highly eccentric binary orbit. We have measured the rate of advance of periastron which indicates a total system mass of 2.6 +/- 0.9 M., and the minimum companion mass is about 0.7 M.. This, the high orbital eccentricity and the recycled nature of the pulsar suggest that this system is composed of two neutron stars, only the fourth or fifth such system known in the disc of the Galaxy
Discovery of a young radio pulsar in a relativistic binary orbit
No full textWe report on the discovery of PSR J1141 - 6545, a radio pulsar in an eccentric, relativistic 5 hr binary orbit. The pulsar shows no evidence of being recycled, having a pulse period P = 394 ms, a characteristic age tau (c) = 1.4 x 10(6) yr, and an inferred surface magnetic dipole field strength B = 1.3 x 10(12) G. From the mass function and measured rate of periastron advance, we determine the total mass in the system to be 2.300 +/- 0.012 M(.), assuming that the periastron advance is purely relativistic. Under the same assumption we constrain the pulsar's mass to be M(p) less than or equal to 1.348 M(.), and the companion's mass to be M(c) > 0.968 M, (both with 99% confidence). Given the total system mass and the distribution of measured neutron star masses, the companion is probably a massive white dwarf that formed prior to the birth of the pulsar. Optical observations can test this hypothesis
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Variations on the Author
Full text link“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
Full text linkWe 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
Discovery of five binary radio pulsars
No full textWe report on five binary pulsars discovered in the Parkes multibeam Galactic plane survey. All of the pulsars are old, with characteristic ages (1-11) x 10(9) yr, and have relatively small inferred magnetic fields, (5-90) x 10(8) G. The orbital periods range from 1.3 to 15 days. As a group these objects differ from the usual low-mass binary pulsars (LMBPs): their spin periods of 9-88 ms are relatively long; their companion masses, 0.2-1.1 M., are, in at least some cases, suggestive of CO or more massive white dwarfs; and some of the orbital eccentricities, 10(-5) less than or similar to e less than or similar to 0.002 are unexpectedly large. We argue that these observed characteristics reflect binary evolution that is significantly different from that of LMBPs. We also note that intermediate-mass binary pulsars apparently have a smaller scale height than LMBPs
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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