Fast radio bursts (FRBs) are a recently discovered class of GHz-band,
ms-duration, Jy-level-flux astrophysical transients, which origin is still a
mystery. Exploring their gamma-ray counterpart is crucial for constraining
their origin and emission mechanism. Thanks to more than 13 years of gamma-ray
data collected by the Fermi-Large Area Telescope, and to more than 1000 FRB
events, one of the largest sample created as of today, we perform the largest
and deepest search for gamma-ray emission from FRB sources to date. In addition
to the study of individual FRB events on different time-scales (from few
seconds up to several years), we performed, for the first time, a stacking
analysis on the full sample of FRB events as well as a search for triplet
photons in coincidence with the radio event. We do not detect significant
emission, reporting the most stringent constraints, on short time scales, for
the FRB-like emission from SGR 1935+2154 with E<1041 erg, corresponding to
a factor <107 with respect to the emitted radio energy. For the stacked
signal of steady emission from all repeaters, the obtained upper limit (UL) on
the FRBs luminosity (L<1.6×1043 erg s−1) is more than two orders
of magnitudes lower than those derived from the individual sources. Finally, no
individual or triplet photons have been significantly associated with FRB
events. We derived the LAT ms energy sensitivity to be E<1047 (DL​/150
Mpc)2 erg, ruling out a gamma-ray-to-radio energy ratio greater than 109
on ms timescales. The results reported here represent the most stringent UL
reported so far on the high-energy emission from FRBs on short and long time
scales, as well as on cumulative emission and individual photon searches. While
the origin of FRBs is still unclear, our work provides important constraints
for FRB modeling, which might shed light on their emission mechanism.Comment: 18 pages, 15 figures, Accepted for publication on Astronomy &
Astrophysic