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No radio emission from soft gamma repeater SGR 0418+5729

ATel #2096; D. R. Lorimer (WVU), S. Edel (WVU), V. I. Kondratiev (WVU), M. A. McLaughlin (WVU), J. R. Boyles (WVU), D. A. Ludovici (WVU), J. P. Ridley (WVU)
on 24 Jun 2009; 01:12 UT
Credential Certification: Duncan Lorimer (duncan.lorimer@mail.wvu.edu)

Subjects: Radio, Soft Gamma-ray Repeater

Following the Fermi/Konus/Swift discovery of bursts from the Soft Gamma Repeater SGR 0418+5729 (van der Horst et al. 2009; Atel #2077) and the identification of coherent 9-s pulsations with RXTE (Gogus et al. 2009; Atel #2076), we carried out a 72-min observation of the new source with the Green Bank Telescope (GBT) on June 19. Data were acquired with the Green Bank Ultimate Pulsar Processor which sampled a 200 MHz wide band centered at 820 MHz. Due to the long period of the source, a relatively low sampling rate was employed for these observations and 1024 spectral channels were detected every 5.2 ms. We have carried out blind periodicity, single pulse and direct folding searches aimed at detecting radio pulsations from this source and were sensitive to dispersion measures in the range 0-1000 pc/cc. No periodic signals with signal-to-noise greater than five were found and we place an upper limit of 0.1*sqrt(delta) mJy for a periodic signal of duty cycle delta. The single pulse search was optimally sensitive to boxcar pulses of widths (2^n)*5.2 ms, where n is an integer in the range 0-9. No individual pulses with signal-to-noise greater than ten were found and we place an upper limit of 200 mJy / sqrt(2^n) for individual events.