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Magnetar-like Spectral Index Flattening of the High Magnetic Field Pulsar PSR J1119- 6127

ATel #9870; Aaron B. Pearlman (Caltech, JPL), Walid A. Majid (JPL, Caltech), Shinji Horiuchi (CSIRO), Jonathon Kocz (Caltech), Jonas Lippuner (Caltech, JPL), Thomas A. Prince (Caltech, JPL)
on 17 Dec 2016; 00:55 UT
Credential Certification: Walid Majid (majidw@gmail.com)

Subjects: Radio, X-ray, Gamma Ray, Neutron Star, Transient, Pulsar, Magnetar

Dramatic changes in pulsed radio emission have been reported by Majid et al. (2016; arXiv:1612.02868) from the high magnetic field pulsar PSR J1119-6127 at S-band (2.3 GHz) and X-band (8.4 GHz) following the reactivation of its radio emission (Burgay et al., ATel #9366). Magnetar-like outbursts have also been observed in X-rays and gamma-rays (Kennea et al., GCN Circular #19735; Younes et al., GCN Circular #19736; Kenna et al., ATel #9274; Archibald et al. (2016); Go?g?u?s? et al. (2016)). We report our observations of PSR J1119-6127, spanning 1.7 hours on 03 December 2016 starting at UT 15:36:52, using the 70-m diameter Deep Space Network (DSN) radio dish (DSS- 43) in Canberra, Australia. The data were recorded in filterbank search mode using 512 us time resolution. The receivers and data acquisition system are described in detail in Majid et al. (2016; arXiv:1612.02868). Pulsations were detected at S-band (2.3 GHz, 96 MHz bandwidth) and X-band (8.4 GHz, 480 MHz bandwidth) in dual circular polarization mode at a period of 0.40996974(6) s using the PRESTO pulsar search package (http://www.cv.nrao.edu/~sransom/presto). Both polarizations were combined in quadrature, and pulsed emission was seen at S/X-band with a peak signal-to- noise ratio (SNR) of 17.2/54.5. The pulse profile at S-band appears roughly singly peaked, with a smaller secondary peak near the dominant emission component. At X-band, the pulse profile shows a strong, narrow single peak. We measure a mean flux density of 0.18(4)/0.08(2) mJy at S/X-band, which represents an order of magnitude decrease at S-band and roughly a factor of 2 decrease at X-band compared to previous measurements by Majid et al. (2016; arXiv:1612.02868). Using these flux density values, we derive a spectral index -0.6(2). We also divided the X-band data into five equal 96 MHz bandwidths and detected pulsations in each subband. Mean flux densities at each subband were measured, and together with our mean flux density value at S-band, we find a spectral index of -0.52(6) in agreement with our initial result. The spectral index has flattened by a factor of approximately 4 compared to previous measurements by Majid et al. (2016; arXiv:1612.02868) across these frequency bands. We interpret this change as evidence of additional magnetar-like behavior from PSR J1119-6127, as these spectral index measurements are similar to those observed from other magnetars, such XTE J1810-197 (Camilo et al. (2007); Lazaridis et al. (2008)), SGR J1745-2900 (Torne et al. (2015)), and PSR J1622-4950 (Anderson et al. (2012)). We are continuing to monitor changes in the spectrum of PSR J1119-6127 at S-band and X-band, and we encourage further observations across multiple wavelengths. We thank the DSN and Canberra Deep Space Communication Complex teams for scheduling these observations.