439 research outputs found
Modeling and Maximum Likelihood Fitting of Gamma-Ray and Radio Light Curves of Millisecond Pulsars Detected with Fermi
Pulsed gamma rays have been detected with the Fermi Large Area Telescope
(LAT) from more than 20 millisecond pulsars (MSPs), some of which were
discovered in radio observations of bright, unassociated LAT sources. We have
fit the radio and gamma-ray light curves of 19 LAT-detected MSPs in the context
of geometric, outer-magnetospheric emission models assuming the retarded vacuum
dipole magnetic field using a Markov chain Monte Carlo maximum likelihood
technique. We find that, in many cases, the models are able to reproduce the
observed light curves well and provide constraints on the viewing geometries
that are in agreement with those from radio polarization measurements.
Additionally, for some MSPs we constrain the altitudes of both the gamma-ray
and radio emission regions. The best-fit magnetic inclination angles are found
to cover a broader range than those of non-recycled gamma-ray pulsars.Comment: 4 pages, 3 figures, 2011 Fermi Symposium proceedings - eConf C110509
-- v2 corrects caption of Figure 1, v3 corrects missing fil
Constraining Relativistic Bow Shock Properties in Rotation-Powered Millisecond Pulsar Binaries
Multiwavelength followup of unidentified Fermi sources has vastly expanded
the number of known galactic-field "black widow" and "redback" millisecond
pulsar binaries. Focusing on their rotation-powered state, we interpret the
radio to X-ray phenomenology in a consistent framework. We advocate the
existence of two distinct modes differing in their intrabinary shock
orientation, distinguished by the phase-centering of the double-peaked X-ray
orbital modulation originating from mildly-relativistic Doppler boosting. By
constructing a geometric model for radio eclipses, we constrain the shock
geometry as functions of binary inclination and shock stand-off . We
develop synthetic X-ray synchrotron orbital light curves and explore the model
parameter space allowed by radio eclipse constraints applied on archetypal
systems B1957+20 and J1023+0038. For B1957+20, from radio eclipses the
stand-off is -- fraction of binary separation from the
companion center, depending on the orbit inclination. Constructed X-ray light
curves for B1957+20 using these values are qualitatively consistent with those
observed, and we find occultation of the shock by the companion as a minor
influence, demanding significant Doppler factors to yield double peaks. For
J1023+0038, radio eclipses imply while X-ray light curves
suggest (from the pulsar). Degeneracies in the
model parameter space encourage further development to include transport
considerations. Generically, the spatial variation along the shock of the
underlying electron power-law index should yield energy-dependence in the shape
of light curves motivating future X-ray phase-resolved spectroscopic studies to
probe the unknown physics of pulsar winds and relativistic shock acceleration
therein.Comment: Accepted to ApJ, 36 pages, 15 figures; comments welcom
Cyclopropenium Salts as Cyclable, High‐Potential Catholytes in Nonaqueous Media
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136488/1/aenm201602027-sup-0001-S1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136488/2/aenm201602027.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136488/3/aenm201602027_am.pd
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