1806.00554
The science advantage of a redder filter for WFIRST
Stauffer, et al
WFIRST will be capable of providing Hubble-quality imaging performance over several thousand square degrees of the sky. the wide-area, high spatial resolution survey data from WFIRST will be unsurpassed for many decades into the future. With the current baseline design the WFIRST filter complement will extend from the bluest wavelength allows by the optical design to a reddest filter (F184W) that has a red cutoff at 2.0 microns. In this white paper, outline some of the science advantages for adding a Ks filter with a 2.15 micron central wavelength in order to extend the wavelength coverage for WFIRST as far to the red as the possible given the thermal performance of the observatory and the sensitivity of the detectors.
1806.00590
The photospheric origin of the Yonetoku relation in gamma-ray bursts
Ito, et al
Long duration GRBs, the brightest events since the Big Bang itself, are believed to originate in an ultra-relativistic jet breaking out from a massive stellar envelope. Despite decades of study, there is still no consensus on their emission mechanism. One unresolved question is the origin of the tight correlation between the spectral peak energy Ep and peak luminosity Lp discovered in observations. This Yonetoku relation is the tightest correlation found in the properties of the prompt phase of GRB emission, providing the best diagnostic for the radiation mechanism. Here, present 3D hydrosims, and post-process radiation transfer calculations, of photospheric emission from a relativistic jet. The simulations reproduce the Yonetoku relation as a natural consequence of viewing angle. Although jet dynamics depend sensitively on luminosity, the Ep-Lp correlation holds regardless. This realist strongly suggests that photospheric emission is the dominant component in the props phase of GRBs.
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