FERMI/Gamma-ray Burst Monitor upper limits assuming a magnetar origin for the repeating Fast Radio Burst source, FRB 121102
ATel #8781; George Younes (GWU), Chryssa Kouveliotou (GWU), Daniela Huppenkothen (NYU), Ersin Gogus (Sabanci University), Yuki Kaneko (Sabanci University), Alexander van der Horst (GWU)
on 6 Mar 2016; 00:27 UT
Credential Certification: George Younes (gyounes@email.gwu.edu)
Subjects: Radio, X-ray, Gamma Ray, Neutron Star, Soft Gamma-ray Repeater, Transient, Pulsar
Spitler et al. (2016, 10.1038/nature17168) reported a repeating Fast Radio Burst source, FRB 121102, with a rate of about 3 bursts/hr. We searched the FERMI/Gamma-ray Burst Monitor (GBM) for possible gamma-ray counterparts for these events. Three out of 11 FRBs were visible to GBM (bursts 3, 4, 5 in Table 1 of Spitler et al. 2016). We searched in a 20 second interval centered at the peak of each of the 3 FRBs, using only the GBM NaI detectors with angles <60 deg to the direction of the source, in the energy range 10-100 keV. We used the GBM high-resolution (2 microseconds) Time Tagged Event (TTE) data in 3 different bin sizes: 0.016, 0.064, and 0.128 seconds. The photon arrival times were corrected to the solar system barycenter.
We do not find a gamma-ray signal in the energy range 10-100 keV coincident with any of the 3 FRBs. Adding the different detector light curves for all bursts also results in a null detection. Assuming that the origin of the FRBs might be magnetar bursts with a typical duration of about 0.2 s, and spectrum best fit with a Comptonized model with Epeak = 40 keV and spectral index of -1.0 (van der Horst 2012 ApJ, 749, 122V), we derive a 3 and 5 sigma flux upper limits of 5.3E-8 erg/s/cm2 and 1.0E-7 erg/s/cm2, respectively. Assuming the upper range of the LogN-LogS diagram for magnetar bursts (not including the rare Giant Flares) with a luminosity of ~ 10^42 erg/s, these fluxes translate to an upper limit on the source distance of about 400 and 280 kpc, respectively. If indeed a magnetar is the source of the FRBs, our results imply that FRB 121102 should be at a distance larger than a few hundred kpc.
