Konus-Wind detection of GRB 241213A (EP 241213a)

The long-duration GRB 241213A (Swift-BAT detection: Gupta et al., GCN 38547; INTEGRAL-SPI-ACS detection: Barria et al., GCN 38556), associated with the fast X-ray transient EP241213a (Zhou et al., GCN 38554; Barria et al., GCN 38556), triggered Konus-Wind at T0=8344.058 s UT (02:19:04.058). The burst light curve shows a single pulse, which starts at ~T0-3.1 s and has a total duration of ~7.6 s. The emission is seen up to ~2 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB241213_T08344/ As observed by Konus-Wind, the burst had a fluence of 1.04(-0.07,+0.07)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+1.056 s, of 4.78(-1.05,+1.06)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+8.448 s) is best fit in the 20 keV - 10 MeV range by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -0.88(-0.17,+0.18) and Ep = 236(-24,+30) keV (chi2 = 74/77 dof). Fitting by a GRB (Band) model yields the same alpha and Ep, and an upper limit on the high energy photon index: beta < -2.6 (chi2 = 73/76 dof). All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.