http://arxiv.org/abs/1612.02532
We calculate the total galactic Shapiro delay to the Crab pulsar by including the contributions from the dark matter as well as baryonic matter along the line of sight. The total delay due to dark matter potential is about 3.4 days. For baryonic matter, we included the contributions from both the bulge and the disk, which are approximately 0.12 and 0.32 days respectively. The total delay from all the matter distribution is therefore 3.84 days. We also calculate the limit on violations of Einstein’s equivalence principle by using observations of “nano-shot” giant pulses from the Crab pulsar with time-delay $<0.4$ ns as well as using time differences between radio and optical photons observed from this pulsar. Using the former, we obtain a limit on violation of Einstein’s equivalence principle in terms of the PPN parameter $\Delta \gamma < 2.41\times 10^{-15}$. From the time-difference between simultaneous optical and radio observations, we get $\Delta \gamma < 1.54\times 10^{-9}$.
S. Desai and E. Kahya
Fri, 9 Dec 16
44/62
Comments: 3 pages, 1 figure
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