Search for periodicity in emission of very high energy gamma-rays from the supernova remnant MSH 15-52 / Isak Delberth Davids

Abstract

For the first time in the history of very high energy γ'-ray astronomy, diffuse emission of γ-rays from a pulsar wind nebula, was observed from the supernova remnant, MSH 15-52, by the H.E.S.S., in 2004. Along with MSH 15-52, H.E.S.S. discovered very high energy (VHE) γ-ray emission from 14 extended pulsar wind nebulae (PWNe) in a Galactic plane survey. Furthermore, H.E.S.S. (High Energy Stereoscopic System) found no pulsed VHE γ-ray emission from 13 young pulsars at their radio periods. The supernova remnant (SNR), MSH 15-52,consisting of a PWN which is powered by a ~ 150millisecond relatively young and energetic pulsar, B1509-58, was observed with H.E.S.S. during 23 nights. The likelihood of the pulsar periodicity being propagated into the PWN emission was investigated, by searching for periodicity of VHE γ-ray emission at and near the radio period from the entire composite supernova remnant. An exhaustive approach, using Fourier analysis techniques were employed for searching for a pulsed signal. This was done via the well-known universally most powerful (UMP) test, the Rayleigh test, and the H-test. No coherent sinusoidal pulsed emission, with > 1% signal strength, could be seen using the Rayleigh test, between 151.282 and 151.301ms, in observations with a 120 minute average duration. The Eadie combination method of Rayleigh test results, also showed no evidence of strong flares or non-coherent pulsed emission between 151.277 and 151.301ms, during a night observation. No coherent pulsed signal with signal strength of > 0.3%, between 151.288661 and 151.288675ms, was detected with the application of the Rayleigh test on the 3.9 month bulk data. Moreover, the H-test proved that there was no presence of any non-sinusoidal pulsed emission, again between 151.282 and 151.301ms, during a night observation. Therefore, no pulsed VHE γ-ray emission was detected from the supernova remnant MSH 15-52 at and near the pulsar radio period.