6,435 research outputs found
G328.4+0.2 : A large and luminous Crab-like supernova remnant
We report on radio continuum and HI observations of the radio source
G328.4+0.2 using the Australia Telescope Compact Array. Our results confirm
G328.4+0.2 to be a filled-center nebula with no surrounding shell, showing
significant linear polarization and an almost flat spectral index. These
results lead us to conclude that G328.4+0.2 is a Crab-like, or ``plerionic'',
supernova remnant (SNR), presumably powered by an unseen central pulsar. HI
absorption towards G328.4+0.2 puts a lower limit on its distance of 17.4 +/-
0.9 kpc, making it the largest (D=25 pc) and most luminous (L_R = 3e35 erg/s)
Crab-like SNR in the Galaxy. We infer G328.4+0.2 to be significantly older than
the Crab Nebula, but powered by a pulsar which is fast spinning (P<20 ms) and
which has a comparatively low magnetic field (B<1e12 G). We propose G328.4+0.2,
G74.9+1.2 and N157B as a distinct group of large-diameter, high-luminosity
Crab-like SNRs, all powered by fast-spinning low-field pulsars.Comment: 7 pages, 3 embedded EPS figures, uses emulateapj.sty. Accepted to
ApJ. Abstract corrected so that distance is now in kpc, not pc
A cross impact methodology for the assessment of US telecommunications system with application to fiber optics development, volume 2
The appendices for the cross impact methodology are presented. These include: user's guide, telecommunication events, cross impacts, projection of historical trends, and projection of trends in satellite communications
A cross impact methodology for the assessment of US telecommunications system with application to fiber optics development, volume 1
A cross impact model of the U.S. telecommunications system was developed. It was necessary to prepare forecasts of the major segments of the telecommunications system, such as satellites, telephone, TV, CATV, radio broadcasting, etc. In addition, forecasts were prepared of the traffic generated by a variety of new or expanded services, such as electronic check clearing and point of sale electronic funds transfer. Finally, the interactions among the forecasts were estimated (the cross impact). Both the forecasts and the cross impacts were used as inputs to the cross impact model, which could then be used to stimulate the future growth of the entire U.S. telecommunications system. By varying the inputs, technology changes or policy decisions with regard to any segment of the system could be evaluated in the context of the remainder of the system. To illustrate the operation of the model, a specific study was made of the deployment of fiber optics throughout the telecommunications system
Radiative neutrino decay and CP-violation in R-parity violating supersymmetry
We calculate the radiative decay amplitude for Majorana neutrinos in
trilinear R-parity violating supersymmetric framework. Our results make no
assumption regarding the masses and mixings of fermions and sfermions. The
results obtained are exemplary for generic models with loop-generated neutrino
masses. Comparison of this amplitude with the neutrino mass matrix shows that
the two provide independent probes of CP-violating phases.Comment: Latex, uses axodraw, 14 pages (small changes implemented
Recent Type II Radio Supernovae
We present the results of radio observations, taken primarily with the Very
Large Array, of Supernovae 1993J, 2001gd, 2001em, 2002hh, 2004dj, and 2004et.
We have fit a parameterized model to the multi-frequency observations of each
supernova. We compare the observed and derived radio properties of these
supernovae by optical classification and discuss the implications.Comment: 5 pages, 2 figures, 1 table Conference Proceedings: "Supernova 1987A:
20 Years After: Supernovae and Gamma-Ray Bursters" AIP, New York, eds. S.
Immler, K.W. Weiler, and R. McCra
Pulsar "Drifting"-Subpulse Polarization: No Evidence for Systematic Polarization-Angle Rotations
Polarization-angle density displays are given for pulsars B0809+74 and
B2303+30, which exhibit no evidence of the systematic polarization-angle
rotation within individual subpulses previously reported for these two stars.
The ``drifting'' subpulses of both pulsars exhibit strikingly linear and
circular polarization which appears to reflect the characteristics of two
nearly orthogonally polarized emission ``modes''--along which the severe
average-profile depolarization that is characteristic of their admixture at
comparable overall intensities.Comment: Accepted for publication in Astronomy & Astrophysic
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