Pulse Morphology of the Galactic Center Magnetar PSR J1745–2900
We present results from observations of the Galactic Center magnetar, PSR J1745–2900, at 2.3 and 8.4 GHz with the NASA Deep Space Network 70 m antenna, DSS-43. We study the magnetar's radio profile shape, flux density, radio spectrum, and single pulse behavior over a ~1 year period between MJDs 57233 and 57621. In particular, the magnetar exhibits a significantly negative average spectral index of ⟨α⟩ = -1.86 ± 0.02 when the 8.4 GHz profile is single-peaked, which flattens considerably when the profile is double-peaked. We have carried out an analysis of single pulses at 8.4 GHz on MJD 57479 and find that giant pulses and pulses with multiple emission components are emitted during a significant number of rotations. The resulting single pulse flux density distribution is incompatible with a log-normal distribution. The typical pulse width of the components is ~1.8 ms, and the prevailing delay time between successive components is ~7.7 ms. Many of the single pulse emission components show significant frequency structure over bandwidths of ~100 MHz, which we believe is the first observation of such behavior from a radio magnetar. We report a characteristic single pulse broadening timescale of ⟨τ_d⟩ = 6.9 ± 0.2 at 8.4 GHz. We find that the pulse broadening is highly variable between emission components and cannot be explained by a thin scattering screen at distances ≳1 kpc. We discuss possible intrinsic and extrinsic mechanisms for the magnetar's emission and compare our results to other magnetars, high magnetic field pulsars, and fast radio bursts.
© 2018 The American Astronomical Society. Received 2018 April 30; revised 2018 August 23; accepted 2018 August 30; published 2018 October 24. We thank the referee for valuable comments that helped us improve this paper. We also thank Professor Roger Blandford for insightful discussions and suggestions. A. B. Pearlman acknowledges support by the Department of Defense (DoD) through the National Defense Science and Engineering Graduate Fellowship (NDSEG) Program and by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1144469. We thank the Jet Propulsion Laboratory and Caltech's President's and Director's Fund for partial support at JPL and the Caltech campus. We also thank Joseph Lazio and Charles Lawrence for providing programmatic support for this work. A portion of this research was performed at the Jet Propulsion Laboratory, California Institute of Technology and the Caltech campus, under a Research and Technology Development Grant through a contract with the National Aeronautics and Space Administration. U.S. government sponsorship is acknowledged.
Accepted Version - 1809.02140.pdf
Published - Pearlman_2018_ApJ_866_160.pdf