GRB 221009A/SN 2022xiw: A Supernova Obscured by a Gamma-Ray Burst Afterglow?

Abstract We present optical photometry for the afterglow of GRB 221009A, in some respects the most extraordinary gamma-ray burst (GRB) ever observed. Good quality in the R -band light curve is obtained, covering 0.32–19.57 days since the Fermi-Gamma-Ray Burst Monitor trigger. We find that a weak bump emerges from the declining afterglow at t ≈ 11 days; a supernova (SN) may be responsible. We use a smooth broken power-law and 56 Ni model to fit the light curve. The best-fitting results reveal that the SN ejected a total mass of M ej = 3.70 M ⊙ , a 56 Ni mass of M Ni = 0.23 M ⊙ , and a kinetic energy of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>E</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>SN</mml:mi> <mml:mo>,</mml:mo> <mml:mi mathvariant="normal">K</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>2.35</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>52</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em"/> <mml:mi>erg</mml:mi> </mml:math> . We also compare GRB 221009A with other GRB–SN events based on a GRB-associated SN sample and find that only SN 2003lw and SN 2011kl can be obviously revealed in the afterglow of GRB 221009A by setting these objects at its distance. This suggests that a supernova (SN 2022xiw) is possibly obscured by the brighter afterglow emission from GRB 221009A.