An Outer Gap Model of High-Energy Emission from Rotation-Powered Pulsars

We describe a refined calculation of high energy emission from rotation-powered pulsars based on the Outer Gap model of Cheng, Ho \&~Ruderman (1986a,b). We have improved upon previous efforts to model the spectra from these pulsars (e. g. Cheng, et al. 1986b; Ho 1989) by following the variation in particle production and radiation properties with position in the outer gap. Curvature, synchrotron and inverse-Compton scattering fluxes vary significantly over the gap and their interactions {\it via} photon-photon pair production build up the radiating charge populations at varying rates. We have also incorporated an approximate treatment of the transport of particle and photon fluxes between gap emission zones. These effects, along with improved computations of the particle and photon distributions, provide very important modifications of the model gamma-ray flux. In particular, we attempt to make specific predictions of pulse profile shapes and spectral variations as a function of pulse phase and suggest further extensions to the model which may provide accurate computations of the observed high energy emissions.Comment: 13 pages, LaTeX, for figures send request to [email protected]

Echelle Spectroscopy of gamma-ray binary 1FGL J1018.6-5856

We observed the Fermi-discovered gamma-ray binary 1FGL J1018.6-5856 at 20 epochs over 50 days using the CHIRON spectrograph, obtaining spectra at R~25,000 covering 4090-8908A. The average spectrum confirms an O6 V((f)) spectral type and extinction E(B-V) = 1.35+/-0.04. Variable absorption line equivalent widths suggest substantial contamination by wind line features. The limited S/N ratio hindered accurate continuum definition and prevented measurement of a high quality radial velocity curve. Nevertheless, the best data indicate a radial velocity amplitude <40 km/s for the He II lines and substantially lower for H I. We argue that this indicates a most likely compact object mass <2.2Msun. While black hole solutions are not excluded, a neutron star source of the gamma-ray emission seems preferred.Comment: 5 figures. To appear in the Astrophysical Journa

First Astronomical Application of a Cryogenic TES Spectrophotometer

We report on the first astronomical observations with a photon counting pixel detector that provides arrival time- (delta t = 100ns) and energy- (delta E_gamma < 0.15eV) resolved measurements from the near IR through the near UV. Our test observations were performed by coupling this Transition Edge Sensor (TES) device to a 0.6m telescope; we have obtained the first simultaneous optical near-IR phase-resolved spectra of the Crab pulsar. A varying infrared turnover gives evidence of self-absorption in the pulsar plasma. The potential of such detectors in imaging arrays from a space platform are briefly described.Comment: 4 pages, 5 figure

A search for giant pulses in Vela-like pulsars

We have carried out a survey for `giant pulses' in 6 young, Vela-like pulsars. In no cases did we find single pulses with flux densities more than 10 times the mean flux density. However, in PSR B1706-44 we have detected giant micro-pulses very similar to those seen in the Vela pulsar. In PSR B1706-44 these giant micro-pulses appear on the trailing edge of the profile and have an intrinsic width of ~1 ms. The cumulative probability distribution of their intensities is best described by a power-law. If the power-law continues to higher intensities, then 3.7x10^6 rotations are required to obtain a pulse with 20 times the mean pulse flux. This number is similar to the giant pulse rate in PSR B1937+21 and PSR B1821-24 but significantly higher than that for the Crab.Comment: 6 pages, 5 figures, Accepted for publication in MNRA