Tuesday, February 21, 2023

Systematic Near-Infrared Follow-up of Type Ic-BL Supernovae

Came across this interesting paper on the arXiv focusing on Type Ic-BL supernovae and their ability to produce rapid neutron-capture process (r-process) material. Also, they performed their photometric follow-up using the Las Cumbres Observatory, which is pretty neat!


We present the first systematic study of 25 SNe Ic-BL -- discovered with the Zwicky Transient Facility and from the literature -- in the optical/near-infrared bands to determine what quantity of r-process material, if any, is synthesized in these explosions. Using semi-analytic models designed to account for r-process production in SNe Ic-BL, we perform light curve fitting to derive constraints on the r-process mass for these SNe. We also perform independent light curve fits to models without r-process. 

Most of the SNe in our sample show no compelling evidence for r-process production. In our model fits, the general trend we observe is that the best fit consistently under-predicts the peak of the optical light curve, while performing better at predicting the NIR flux. In some cases, the under-prediction is egregious, while in other cases it is more modest. In general under-prediction indicates that the optical-NIR color of the SN is actually bluer than predicted by the models, providing stronger evidence towards favoring r -process-free models over the enriched models.

There is still potentially a link between r-process material and GRBs, but this study was unable to probe it due to the nature of the sample used. 

The fact that none of these SNe are linked to standard, classical long GRBs prevents us from exploring the proposed theoretical connection between the GRB energetics and r -process production. If the GRB jet energy, which scales with the mass accreted by the disk, correlates with the amount of r -process mass produced in the disk winds, then collapsars with no GRBs may not be able to produce detectable r-process signatures.

The work has a few important caveats as well.

First, we note that the r-process enriched and r-process-free models make different predictions about the relationship between nickel mass and SN luminosity...As a result, the amounts of nickel inferred by each model for a given luminosity are inconsistent.

Furthermore, differences between kilonovae and r -process-enriched SN (e.g., in their densities or their compositions) may mean that nebular-phase emission from the former is not a perfect predictor of nebular phase emission from the latter. 

Finally, we acknowledge the limitations of the dataset we present here for testing whether collapsars synthesize r -process elements. Due to the nature of our classical observing runs with WIRC, our NIR light curves are very sparse, and in some cases our upper limits are too shallow to be constraining.

Overall, an exciting paper. Type II/Ib/Ic supernovae have long been potential candidates for detection of prominent r-process influence. This fairly comprehensively presents a case to exclude SNe Type Ic from consideration. 

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