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Collapsars as Sites of r-process Nucleosynthesis

Presentation #200.02 in the session “Multi-Messenger and Time Domain Astronomy (Oral)”.

Published onApr 01, 2022
Collapsars as Sites of r-process Nucleosynthesis

A rare sub-class of massive star explosions, known as broad-lined Ic supernovae (Ic-BL SNe), have been highlighted as one of the potential sites of r-process nucleosynthesis capable of enriching the Universe with heavy elements. These supernovae, stripped of their hydrogen and helium layers, are associated with long-duration gamma-ray bursts originating from collapsing massive stars (collapsars), and exhibit broad features in their spectra characteristic of their high velocity (>10,000 km/s) ejecta. Recent simulations show that heavy r-process elements can form in the disk surrounding the newly formed, black hole central engine resulting from a collapsar. The main observational prediction from these simulations is an excess in the near-IR lightcurve compared to the optical starting 30 days post-peak. We present one of the first observational campaigns to systematically hunt for near-IR excesses in Ic-BL SNe identified with the Zwicky Transient Facility and followed-up with the Wide InfraRed Camera at Palomar observatory. With updated collapsar r-process lightcurve models, we place constraints on the r-process ejecta mass yield from collapsars. Investigating collapsars as r-process sites can shed light on whether kilonovae are one amongst many sites, or the only site responsible for enriching our solar neighborhood with heavy elements.

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