Evidence of an Internal Dissipation Origin for the High-energy Prompt Emission of GRB 170214A

The origin of the prompt high-energy ($>100$MeV) emission of Gamma-ray Bursts (GRBs), detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope, is still under debate, for which both the external shock origin and internal dissipation origin have been suggested. In the internal dissipation scenario, the high energy emission is expected to exhibit significant temporal variability, tracking the keV/MeV fast variable behavior. Here, we report a detailed analysis on the Fermi data of GRB~170214A, which is sufficiently bright in the high energy to enable a quantitative analysis of the correlation between high-energy emission and keV/MeV emission with high statistics. Our result shows a clear temporal correlation between high-energy and keV/MeV emission in the whole prompt emission phase as well as in two decomposed short time intervals. Such correlation behavior is also found in some other bright LAT GRBs, i.e., GRB 080916C, 090902B and 090926A. For these GRBs as well as GRB 090510, we also find the rapid temporal variability in the high-energy emission. We thus conclude that the prompt high-energy emission in these bright LAT GRBs should be due to internal origin.Comment: 12 pages, 4 figures, Accepted for publication in Ap

Characteristics of Postural Muscle Activity in Response to A Motor-Motor Task in Elderly

The purpose of the current study was to evaluate postural muscle performance of older adults in response to a combination of two motor tasks perturbations. Fifteen older participants were instructed to perform a pushing task as an upper limb perturbation while standing on a fixed or sliding board as a lower limb perturbation. Postural responses were characterized by onsets and magnitudes of muscle activities as well as onsets of segment movements. (Please see full abstract article