GRB 190919B: Rapid optical rise explained as a flaring activity

0558961 - ASÚ 2023 RIV FR eng J - Journal Article
Jelínek, Martin - Topinka, M. - Karpov, Sergey - Maleňáková, A. - Hu, Y.D. - Rigoselli, M. - Štrobl, Jan - Ebr, Jan - Cunniffe, Ronan - Thöne, Christina - Mašek, Martin - Janeček, Petr - Fernandez-Garcia, E. - Hiriart, D. - Lee, W. H. - Vítek, S. - Hudec, René - Trávníček, Petr - Castro-Tirado, A.J. - Prouza, Michael
GRB 190919B: Rapid optical rise explained as a flaring activity.
Astronomy & Astrophysics. Roč. 662, June (2022), č. článku A126. ISSN 0004-6361. E-ISSN 1432-0746
R&D Projects: GA MŠMT LTT18004; GA MŠMT EF15_003/0000437; GA MŠMT EF16_013/0001402; GA MŠMT(CZ) EF18_046/0016010
Research Infrastructure: AUGER-CZ II - 90102
Institutional support: RVO:67985815 ; RVO:68378271
Keywords : techniques * photometric * gamma-ray burst
OECD category: Astronomy (including astrophysics,space science); Astronomy (including astrophysics,space science) (FZU-D)
Impact factor: 6.5, year: 2022
Method of publishing: Open access

Following the detection of a long GRB 190919B by INTEGRAL (INTErnational Gamma-Ray Astrophysics Laboratory), we obtained an optical photometric sequence of its optical counterpart. The light curve of the optical emission exhibits an unusually steep rise similar to 100 s after the initial trigger. This behaviour is not expected from a 'canonical' GRB optical afterglow. As an explanation, we propose a scenario consisting of two superimposed flares: an optical flare originating from the inner engine activity followed by the hydrodynamic peak of an external shock. The inner-engine nature of the first pulse is supported by a marginal detection of flux in hard X-rays. The second pulse eventually concludes in a slow constant decay, which, as we show, follows the closure relations for a slow cooling plasma expanding into the constant interstellar medium and can be seen as an optical afterglow sensu stricto.
Permanent Link: https://hdl.handle.net/11104/0332727