A. Melandri (INAF-OAB), L. Izzo (HETH/IAA-CSIC), P. D'Avanzo (INAF-OAB), D. Malesani (DAWN/NBI and DARK/NBI), M. Della Valle (INAF-OAC), E. Pian (INAF-OAS), N. R. Tanvir (U. of Leicester), F. Ragosta (U. Federico II/OAC), F. Olivares (MAS/U. de Chile), R. Carini (INAF-OAR), E. Palazzi (INAF-OAS), S. Piranomonte (INAF-OAR), P. Jonker (SRON), A. Rossi (INAF-OAS), D. A. Kann (HETH/IAA-CSIC), D. Hartmann (Clemson U.), C. Inserra (Cardiff), E. Kankare (Turku), K. Maguire (QUB), S. J. Smartt (QUB), O. Yaron (Weizmann), D. R. Young (QUB), I. Manulis (Weizmann) on behalf of a larger collaboration
We report the discovery of the supernova associated with the gamma-ray burst GRB 190114C (Gropp et al., GCN 23688) at z=0.42 (Selsing et al., GCN 23695; Castro-Tirado et al., GCN 23708; Kann et al., GCN 23710). An observational campaign lasting about 50 days has been carried out with the VLT+FORS2, the NTT+EFOSC2 and the REM+ROS2 at the European Southern Observatory (Chile), the TNG+DOLORES, the LBT+MODS2 located at Mount Graham (Arizona), and the WHT+ACAM located at the Roque de los Muchachos Observatory (Canary Islands). These observations show, at about 15 days after the burst, an apparent flattening of the afterglow light curves, in the i and z filters, in excess of the host galaxy flux, as measured in our latest epochs. This is the consistent with the emergence of a SN associated with GRB 190114C, as observed in several previous events.
By modelling the overall light curve between 0.01 and 15 days after the burst trigger (including also data from GCN circulars) with a broken power-law (afterglow contribution) + constant (host galaxy contribution), the residual fluxes in the observed i and z bands show a peak of brightness of ~23.9 and ~23.5 mag (AB), respectively. With these values we derive an estimate for the rest frame visual absolute magnitude of the SN associated with GRB 190114C of about -18 mag. This value is about 1 mag fainter than SN 1998bw (Patat et al. 2001, ApJ, 555, 900). However, the two SNe could have a comparable brightness considering the significant extinction, yet to be quantified, suffered by this event (see e.g. Kann et al., GCN 23710).
We caution that the reported values for the SN peak brightness strongly depend on the modelling of the temporal behaviour of the overall light curve. Further photometric and spectroscopic analysis is on going.
We thank the VLT, TNG, LBT and WHT staffs for executing these observations. Part of these data have been obtained under the extended Public ESO Spectroscopic Survey for Transient Objects (ePESSTO; see Smartt et al. 2015, A&A, 579, 40; http://www.pessto.org <http://www.pessto.org/>).