We present the results of the first transient survey from the Owens Valley Radio Observatory Long Wavelength Array ( OVRO–LWA ) using 31 hr of data , in which we place the most constraining limits on the instantaneous transient surface density at timescales of 13 s to a few minutes and at frequencies below 100 MHz .
The OVRO–LWA is a dipole array that images the entire viewable hemisphere with 58 MHz of bandwidth from 27 to 84 MHz at 13 s cadence .
No transients are detected above a 6.5 \sigma flux density limit of 10.5 Jy , implying an upper limit to the transient surface density of 2.5 \times 10 ^ { -8 } deg ^ { -2 } at the shortest timescales probed , which is orders of magnitude deeper than has been achieved at sub-100 MHz frequencies and comparable flux densities to date .
The nondetection of transients in the OVRO–LWA survey , particularly at minutes-long timescales , allows us to place further constraints on the rate of the potential population of transients uncovered by .
From their transient rate , we expect a detection of 8.4 ^ { +31.8 } _ { -8.0 } events , and the probability of our null detection is 1.9 ^ { +644 } _ { -1.9 } \times 10 ^ { -3 } , ruling out a transient rate > 1.4 \times 10 ^ { -4 } \text { days } ^ { -1 } \text { deg } ^ { -2 } with 95 % confidence at a flux density limit of 18.1 Jy , under the assumption of a flat spectrum and wide bandwidth .
We discuss the implications of our nondetection for this population and further constraints that can be made on the source spectral index , intrinsic emission bandwidth , and resulting luminosity distribution .