The High Frequency Radio Emission of the Galactic Center Magnetar SGR J1745-29 During a Transitional Period

Abstract

The origin of the high-frequency radio emission detected from several magnetars is poorly understood. In this paper, we report the ~40 GHz properties of SGR J1745-29 as measured using Jansky Very Large Array (JVLA) and Robert C. Byrd Green Bank Telescope (GBT) observations between 2013 October 26 and 2014 May 31. Our analysis of a Q-band (45 GHz) GBT observation on 2014 April 10 resulted in the earliest detection of pulsed radio emission at high frequencies (>20 GHz); we found that the average pulse has a singly peaked profile with width ~75 ms (~2% of the 3.764 s pulse period) and an average pulsed flux density of ~100 mJy. We also detected very bright, short (<10 ms) single pulses during ~70% of this neutron star's rotations, and the peak flux densities of these bright pulses follow the same log-normal distribution as measured at 8.5 GHz. Additionally, our analysis of contemporaneous JVLA observations suggest that its 41/44 GHz flux density varied between ~1-4 mJy during this period, with a ~2x change observed on ~20 minute timescales during a JVLA observation on 2014 May 10. Such a drastic change over short time-scales is inconsistent with the radio emission resulting from a shock powered by the magnetar's supersonic motion through the surrounding medium, and instead is dominated by pulsed emission generated in its magnetosphere.

9 pages, 4 figure, 2 tables, published in The Astrophysical Journal

References in corpus (11)

• Transient pulsed radio emission from a magnetar
• Untwisting magnetospheres of neutron stars
• 1E 1547.0-5408: a radio-emitting magnetar with a rotation period of 2 seconds
• Dynamics of Ionized Gas at the Galactic Center: VLA Observations of the 3D Velocity Field and Location of the Ionized Streams in Sagittarius A West
• The magnetar 1E 1547.0-5408: radio spectrum, polarimetry, and timing
• Radio emission evolution, polarimetry and multifrequency single pulse analysis of the radio magnetar PSR J1622-4950
• The variable radio-to-X-ray spectrum of the magnetar XTE J1810-197
• Simultaneous multifrequency radio observations of the Galactic Centre magnetar SGR J1745-2900
• Simultaneous multi-frequency single-pulse properties of AXP XTE J1810-197
• Electrodynamics of Magnetars III: Pair Creation Processes in an Ultrastrong Magnetic Field and Particle Heating in a Dynamic Magnetosphere
• Electrodynamics of Magnetars IV: Self-Consistent Model of the Inner Accelerator, with Implications for Pulsed Radio Emission

Cited by in corpus (2)

• Observations of Radio Magnetars with the Deep Space Network
• Detection of a dense group of hyper-compact radio sources in the central parsec of the Galaxy