IPN triangulation of GRB 210427A

Report: The long-duration GRB 210427A (Fermi-GBM detection: The Fermi GBM team, GCN Circ. 29903; BALROG localization: Biltzinger et al., GCN Circ. 29905; GECAM detection: Xie et al., GCN Circ. 29906) was detected by Fermi (GBM trigger 641192237), Konus-Wind, Swift (BAT), outside the coded FoV, Mars-Odyssey (HEND), and GECAM-B at about 17832 s UT (04:57:12). We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 177.792 (11h 51m 10s) -52.866 (-52d 51' 57") Corners: 176.862 (11h 47m 27s) -54.591 (-54d 35' 28") 176.750 (11h 47m 00s) -54.533 (-54d 31' 59") 178.678 (11h 54m 43s) -51.138 (-51d 08' 18") 178.782 (11h 55m 08s) -51.196 (-51d 11' 46") --------------------------------------------- The error box area is 1036 sq. arcmin, and its maximum dimension is 3.6 deg (the minimum one is 4.8 arcmin). The Sun distance was 93 deg. This box may be improved. The IPN localization is consistent with, but reduces the area of, the Fermi RoboBA and BALROG localizations (GCN Circ. 29903 and 29905). It was inside the Transiting Exoplanet Survey Satellite (TESS) field of view. We thank Robert Wilson for pointing out the TESS/IPN coincidence. A triangulation map is posted at http://www.ioffe.ru/LEA/GRBs/GRB210427_T17835/IPN/ The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular.