A targeted search for FRB counterparts with Konus-Wind

Abstract

We present results of the search for hard X-ray/soft $\gamma$-ray emission in coincidence with publicly reported (via Transient Name Server, TNS; http://www.wis-tns.org/) fast radio bursts (FRBs). The search was carried out using continuous Konus-Wind data with 2.944 s time resolution. We perform a targeted search for each individual burst from 581 FRBs, along with a stacking analysis of the bursts from 8 repeating sources in our sample and a separate stacking analysis of the bursts from the non-repeating FRBs. We find no significant associations in either case. We report upper bounds on the hard X-ray (20 - 1500 keV) flux assuming four spectral models, which generally describe spectra of short and long GRBs, magnetar giant flares, and the short burst, coincident with FRB 200428 from a Galactic magnetar. Depending on the spectral model, our upper bounds are in the range of $(0.1 - 2) \times10^{-6}$ erg cm$^{-2}$. For 18 FRBs with known distances we present upper bounds on the isotropic equivalent energy release and peak luminosity. For the nearest FRB 200120E, we derive the most stringent upper bounds of $E_{\text{iso}}\leq$2.0 $\times 10^{44}$ erg and $L_{\text{iso}}\leq$1.2 $\times 10^{44}$ erg s$^{-1}$. Furthermore, we report lower bounds on radio-to-gamma-ray fluence ratio $E_{\text{radio}}/E_{\text{iso}} \geq 10^{-11}-10^{-9}$ and compare our results with previously reported searches and theoretical predictions for high-energy counterparts to FRBs.