Simultaneous X-ray and Radio Observations of the Repeating Fast Radio Burst FRB 180916.J0158+65
Abstract
We report on simultaneous radio and X-ray observations of the repeating fast radio burst source FRB 180916.J0158+65 using the Canadian Hydrogen Intensity Mapping Experiment (CHIME), Effelsberg, and Deep Space Network (DSS-14 and DSS-63) radio telescopes and the Chandra X-ray Observatory. During 33 ks of Chandra observations, we detect no radio bursts in overlapping Effelsberg or Deep Space Network observations and a single radio burst during CHIME/FRB source transits. We detect no X-ray events in excess of the background during the Chandra observations. These non-detections imply a 5-σ limit of <5×10-10 erg cm-2 for the 0.5--10 keV fluence of prompt emission at the time of the radio burst and 1.3×10-9 erg cm-2 at any time during the Chandra observations at the position of FRB 180916.J0158+65. Given the host-galaxy redshift of FRB 180916.J0158+65 (z0.034), these correspond to energy limits of <1.6×1045 erg and <4×1045 erg, respectively. We also place a 5-σ limit of <8×10-15 erg s-1 cm-2 on the 0.5--10\,keV absorbed flux of a persistent source at the location of FRB 180916.J0158+65. This corresponds to a luminosity limit of <2×1040 erg s-1. Using Fermi/GBM data we search for prompt gamma-ray emission at the time of radio bursts from FRB 180916.J0158+65 and find no significant bursts, placing a limit of 4×10-9 erg cm-2 on the 10--100 keV fluence. We also search Fermi/LAT data for periodic modulation of the gamma-ray brightness at the 16.35-day period of radio-burst activity and detect no significant modulation. We compare these deep limits to the predictions of various fast radio burst models, but conclude that similar X-ray constraints on a closer fast radio burst source would be needed to strongly constrain theory.