Speaker:
Dan Hooper
Institution:
Univ. of Chicago
Speaker Link:
Date:
Wednesday, March 15, 2017
Time:
3:00 pm
Location:
FRH 4135
ABSTRACT:
Recent measurements of the Geminga and B0656+14 pulsars by the gamma-ray telescope HAWC (along with earlier measurements by Milagro) indicate that these objects generate significant fluxes of very high-energy electrons. From the measured gamma-ray intensity and spectrum of these pulsars, one can calculate and constrain their expected contributions to the local cosmic-ray positron spectrum. Among models that are capable of reproducing the observed characteristics of the gamma-ray emission, we find that pulsars invariably produce a flux of high-energy positrons that is similar in spectrum and magnitude to the positron fraction measured by PAMELA and AMS-02. In light of this result, it appears very likely that pulsars provide the dominant contribution to the long perplexing cosmic-ray positron excess.
Host:
Sheldon Campbell
Iftah Galon
Felix Kling
Sebastian Trojanowski