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arXiv · 2309.03000

A search for the afterglows, kilonovae, and host galaxies of two short GRBs: GRB 211106A and GRB 211227A

M. Ferro·R. Brivio·P. D'Avanzo·A. Rossi·L. Izzo·S. Campana·L. Christensen·M. Dinatolo·S. Hussein·A. J. Levan·A. Melandri·M. G. Bernardini·S. Covino·V. D'Elia·M. Della Valle·M. De Pasquale·B. P. Gompertz·D. Hartmann·K. E. Heintz·P. Jakobsson·C. Kouveliotou·D. B. Malesani·A. Martin-Carrillo·L. Nava·A. Nicuesa Guelbenzu·G. Pugliese·C. Salvaggio·R. Salvaterra·S. Savaglio·T. Sbarrato·N. R. Tanvir·R. A. M. J. Wijers·T. Zafar
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Abstract

Context: GRB 211106A and GRB 211227A are recent gamma-ray bursts (GRBs) with initial X-ray positions suggesting associations with nearby galaxies (z < 0.7). Their prompt emission characteristics indicate GRB 211106A is a short-duration GRB and GRB 211227A is a short GRB with extended emission, likely originating from compact binary mergers. However, classifying solely based on prompt emission can be misleading. Aims: These short GRBs in the local Universe offer opportunities to search for associated kilonova (KN) emission and study host galaxy properties in detail. Methods: We conducted deep optical and NIR follow-up using ESO-VLT FORS2, HAWK-I, and MUSE for GRB 211106A, and ESO-VLT FORS2 and X-Shooter for GRB 211227A, starting shortly after the X-ray afterglow detection. We performed photometric analysis to look for afterglow and KN emissions associated with the bursts, along with host galaxy imaging and spectroscopy. Optical/NIR results were compared with Swift X-Ray Telescope (XRT) and other high-energy data. Results: For both GRBs we placed deep limits to the optical/NIR afterglow and KN emission. Host galaxies were identified: GRB 211106A at photometric z = 0.64 and GRB 211227A at spectroscopic z = 0.228. Host galaxy properties aligned with typical short GRB hosts. We also compared the properties of the bursts with the S-BAT4 sample to further examined the nature of these events. Conclusions: Study of prompt and afterglow phases, along with host galaxy analysis, confirms GRB 211106A as a short GRB and GRB 211227A as a short GRB with extended emission. The absence of optical/NIR counterparts is likely due to local extinction for GRB 211106A and a faint kilonova for GRB 211227A.

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M. Ferro, R. Brivio, P. D'Avanzo, A. Rossi, L. Izzo, S. Campana, L. Christensen, M. Dinatolo, S. Hussein, A. J. Levan, A. Melandri, M. G. Bernardini, S. Covino, V. D'Elia, M. Della Valle, M. De Pasquale, B. P. Gompertz, D. Hartmann, K. E. Heintz, P. Jakobsson, C. Kouveliotou, D. B. Malesani, A. Martin-Carrillo, L. Nava, A. Nicuesa Guelbenzu, G. Pugliese, C. Salvaggio, R. Salvaterra, S. Savaglio, T. Sbarrato, N. R. Tanvir, R. A. M. J. Wijers, T. Zafar. 2023-09-06. A search for the afterglows, kilonovae, and host galaxies of two short GRBs: GRB 211106A and GRB 211227A. https://doi.org/10.1051/0004-6361%2F202347113

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