Speaker
Glennys Farrar
(NYU)
Description
- A simple and well-motivated modification of QCD at ultrahigh energy naturally explains the observed Xmax distribution above 10^18 eV, with a purely protonic composition. This removes the need for a fine-tuned source composition and very hard injection spectrum as required if UHECRs have a mixed composition, and eliminates the need to postulate an additional population of extragalactic protons filling in the spectrum below the ankle. (Time permitting, new stronger limits on a light Galactic component in the 10^17.5-18 eV range will be presented.)
- It is shown that if UHECRs are protons, their sources must be transient.
- Tidal Disruption Jets are shown to satisfy the three essential requirements for being the source of all UHECRs. Multi-wavelength observations and modeling of Swift J1644, a TDE jet observed in blazar mode, show that the product of field strength and characteristic size of the jet satisfies BR >~ 3 10^17 G-cm, the Hillas criterion for accelerating protons to 10^20 eV. The total UHECR energy injection rate from TDE jets and the number of contributing sources within the GZK volume, can be estimated from the recently-measured TDE rate; both are ample to explain UHECR requirements. Thus TDE jets are a strong candidate for being the sources of all or most UHECRs.
Author
Glennys Farrar
(NYU)
