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Search Results: 1 - 10 of 461958 matches for " A. Romani "
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Gamma-Ray Pulsars and Massive Stars in the Solar Neighborhood
I. -A. Yadigaroglu,Roger W. Romani
Physics , 1996, DOI: 10.1086/303601
Abstract: We revisit the association of unidentified Galactic plane EGRET sources with tracers of recent massive star formation and death. Up-to-date catalogs of OB associations, SNRs, young pulsars, HII regions and young open clusters were used in finding counterparts for a recent list of EGRET sources. It has been argued for some time that EGRET source positions are correlated with SNRs and OB associations as a class; we extend such analyses by finding additional counterparts and assessing the probability of individual source identifications. Among the several scenarios relating EGRET sources to massive stars, we focus on young neutron stars as the origin of the gamma-ray emission. The characteristics of the candidate identifications are compared to the known gamma-ray pulsar sample and to detailed Galactic population syntheses using our outer gap pulsar model of gamma-ray emission. Both the spatial distribution and luminosity function of the candidates are in good agreement with the model predictions; we infer that young pulsars can account for the bulk of the excess low latitude EGRET sources. We show that with this identification, the gamma-ray point sources provide an important new window into the history of recent massive star death in the solar neighborhood.
Gamma-Ray Pulsars: Beaming Evolution, Stats and Unident. EGRET Sources
I. -A. Yadigaroglu,Roger W. Romani
Physics , 1994, DOI: 10.1086/176047
Abstract: We compute the variation of the beaming fraction with the efficiency of high energy gamma-ray production in the outer gap pulsar model of Romani and Yadigaroglu. This allows us to correct the fluxes observed for pulsars in the EGRET band and to derive a simple estimate of the variation of efficiency with age. Integration of this model over the population of young neutron stars gives the expected number of gamma-ray pulsars along with their distributions in age and distance. This model also shows that many of the unidentified EGRET plane sources should be pulsars, and predicts the gamma-ray fluxes of known radio pulsars. The contribution of unresolved pulsars to the background flux in the EGRET band is found to be about 5 %. For an animation of our pulsar model see http://geminga.stanford.edu/users/ion/home.html .
$γ$-Ray Pulsars: Emission Zones and Viewing Geometries, A Computer Animation
I. -A. Yadigaroglu,Roger W. Romani
Physics , 1994,
Abstract: The computer animation illustrates the geometries described in a paper by the same authors. The preprint is available as number 9401045. The opening scene shows dipole field lines emanating from the polar caps of a rotating neutron star. The dipole axis is inclined along the green rods. The field lines shown are defined from the condition that they be tangent to the light cylinder (the cylindrical radius at which the tangential velocity of rotation reaches the speed of light). The static dipole field lines are smoothly morphed into the correct retarted-potential vacuum solutions. A red surface spanning these field lines is painted. In the next scene the blue surfaces represent the outer gaps above the surface of last closed field lines. High energy emission (blue) is produced in these outer gaps, and is beamed tangentially along the field lines. The radio emission (green) originates close to the surface of the star and is beamed along the dipole axes. The inclination angle $\alpha$ of the dipole and the viewing angle $\zeta$ are chosen to match the Crab parameters; $\alpha$ = 70, $\zeta$ = 65. The corresponding light curve is computed and shown for these angles, and the red dot traces rotation phase. The next scene shows the situation for angles appropriate to PSR1706-44; $\alpha$ = 45, $\zeta$ = 65. The final scene is a possibility for Geminga; $\alpha$ = 20, $\zeta$ = 75. These angles are poorly constrained as there is no radio emission.
$γ$-Ray Pulsars: Emission Zones and Viewing Geometries
Roger W. Romani,I. -A. Yadigaroglu
Physics , 1994, DOI: 10.1086/175076
Abstract: There are now a half dozen young pulsars detected in high energy photons by the Compton GRO, showing a variety of emission efficiencies and pulse profiles. We present here a calculation of the pattern of high energy emission on the sky in a model which posits $\gamma$-ray production by charge depleted gaps in the outer magnetosphere. This model accounts for the radio to $\gamma$-ray pulse offsets of the known pulsars, as well as the shape of the high energy pulse profiles. We also show that $\sim 1/3$ of emitting young radio pulsars will not be detected due to beaming effects, while $\sim 2.5 \times$ the number of radio-selected $\gamma$-ray pulsars will be viewed only high energies. Finally we compute the polarization angle variation and find that the previously misunderstood optical polarization sweep of the Crab pulsar arises naturally in this picture. These results strongly support an outer-magnetosphere location for the $\gamma-$ray emission.
Altitude Limits for Rotating Vector Model Fitting of Pulsar Polarization
H. A. Craig,Roger W. Romani
Physics , 2012, DOI: 10.1088/0004-637X/755/2/137
Abstract: Traditional pulsar polarization sweep analysis starts from the point dipole rotating vector model (RVM) approximation. If augmented by a measurement of the sweep phase shift, one obtains an estimate of the emission altitude (Blaskiewicz, Cordes, & Wasserman). However, a more realistic treatment of field line sweepback and finite altitude effects shows that this estimate breaks down at modest altitude ~ 0.1R_{LC}. Such radio emission altitudes turn out to be relevant to the young energetic and millisecond pulsars that dominate the \gamma-ray population. We quantify the breakdown height as a function of viewing geometry and provide simple fitting formulae that allow observers to correct RVM-based height estimates, preserving reasonable accuracy to R ~ 0.3R_{LC}. We discuss briefly other observables that can check and improve height estimates.
Genetic parameters for casein and urea content in the Italian Brown Swiss dairy cattle
A.B. Samoré,C. Romani,A. Rossoni,E. Frigo
Italian Journal of Animal Science , 2010, DOI: 10.4081/ijas.2007.1s.201
Abstract: A total of 137,753 test day records of 20,745 Italian Brown Swiss dairy cows from 26 provinces of Italy were used to estimate heritability for casein and urea content in milk and their genetic correlations with other production traits and milk somatic cell score. Milk component values were obtained by Fourier Transformed Infrared (IR) Spectroscopy from milk samples collected during national routine recording and were analysed using test day repeatability animal models. Fixed effects included 1,001 levels of herd-test date, 15 classes of days in milk, and 13 classes of age at calving within parity. The variation among cows was large for most of the traits. The heritability value for casein content was 0.31, as for protein content, and genetic and phenotypic correlations between these two traits were large (0.99 and 0.97 respectively). Milk urea content had a heritability of 0.17 and a positive genetic relationship with fat (0.12), null with protein (0.03) and casein (0.002) content and a negative genetic correlation with milk yield (-0.17) suggesting that the genetic improvement for milk urea content would be possible, but genetic gain would be affected by other traits included as selection criteria in the economic index and by their relative economic emphasis.
X-ray Emission from the Guitar Nebula
Roger W. Romani,James M. Cordes,I. -A. Yadigaroglu
Physics , 1997, DOI: 10.1086/310796
Abstract: We have detected weak soft X-ray emission from the Pulsar Wind Nebula trailing the high velocity star PSR 2224+65 (the `Guitar Nebula'). This X-ray flux gives evidence of \gamma~10^7 eV particles in the pulsar wind and constrains the properties of the post-shock flow. The X-ray emission is most easily understood if the shocked pulsar wind is partly confined in the nebula and if magnetic fields in this zone can grow to near equipartition values.
Clevelandia, Oiapoque: cartografias e heterotopias na década de 1920
Romani, Carlo;
Boletim do Museu Paraense Emílio Goeldi. Ciências Humanas , 2011, DOI: 10.1590/S1981-81222011000300003
Abstract: despite the oyapock river border had been attached to brazilian territory in 1900, the official colonization occurred only in the 1920's. the brazilian federal government strategy was to build an agro-colony called clevelandia. between 1924 and 1927, it was transformed into a penal colony, causing the failure of the agro-colony experience. the populating process moved to nearly martinique village, an oldest black and riverine community, after renamed to oyapock. this article presents human and social relations established at those places in three different moments: the agro-colony, the penal-colony and the new martinique community. the historical sources were used to map these places. the objective is to understand, with the aid of 'cartography', which kind of relationship among this diverse population was established and how it was happened. despite the governmental hierarchizing of space, the individual real life reinvented it creating social relations not planned by the power of state: the 'heterotopias'.
A história entre o oficial e o lendário: intera es culturais no Oiapoque
Carlo Romani
Antíteses , 2010,
Abstract: A fronteira franco-brasileira do Oiapoque foi palco de um longo litígio entre ambos os países que se estendeu por mais de duzentos anos até dezembro de 1900. Este artigo estuda as migra es ocorridas nessa regi o, algumas induzidas pelos estados nacionais e outras realizadas espontaneamente, e as trocas culturais estabelecidas por essas diferentes popula es (índios, créoles e caboclos) que a habitaram. Além das migra es históricas mais antigas, tivemos dois movimentos migratórios importantes no início do século XX. Popula es vindas do norte, das ilhas do Caribe, em sua maioria da Martinica, e outras vindas do sul, dos estados do Pará e do Ceará, encontraram-se no Oiapoque produzindo um complexo caldeir o cultural. A rica troca musical, a culinária e a mistura de costumes desses diferentes povos criaram na atualidade uma peculiar e sugestiva cultura que podemos denominar de caribenho-amaz nica.
Il tornante sociale della normatività - Le tournant social de la normativité , Dipartimento di Scienze Storiche, Geografiche e dell’Antichità, Padova, 28-29 settembre 2012 Il tornante sociale della normatività - Le tournant social de la normativité , Dipartimento di Scienze Storiche, Geografiche e dell’Antichità, Padova, 28-29 settembre 2012
Anna Romani
Scienza & Politica : per una Storia delle Dottrine , 2012, DOI: 10.6092/issn.1825-9618/3205
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