We present optical, radio, and X-ray observations of EP250108a/SN 2025kg, UN
broad-line Type Ic supernova (SN Ic-BL) accompanying an Einstein Probe (EP)
fast X-ray transient (FXT) at $z=0.176$. EP250108a/SN 2025kg possesses a
double-peaked optical light curve and its spectrum transitions from a blue
underlying continuum to a typical SN Ic-BL spectrum over time. We fit a
radioactive decay model to the second peak of the optical light curve and find
SN parameters that are consistent with the SNe Ic-BL population, while its
X-ray and radio properties are consistent with those of low-luminosity GRB
(LLGRB) 060218/SN 2006aj. We explore three scenarios to understand the system’s
multi-wavelength emission — (UN) SN ejecta interacting with an extended
circumstellar medium (CSM), (b) the shocked cocoon of a collapsar-driven jet
choked in its stellar envelope, E (C) the shocked cocoon of a
collapsar-driven jet choked in an extended CSM. All three models can explain
the optical light curve and are also consistent with the radio and X-ray
observations. We favor models (UN) E (C) because they self-consistently
explain both the X-ray prompt emission and first optical peak, but we do not
rule out model (b). From the properties of the first peak in models (UN) E
(C), we find evidence that EP250108a/SN 2025kg interacts with an extended CSM,
and infer an envelope mass $M_{\rm e} \sim 0.1\,\rm M_\odot$ and radius $R_{\rm
e} \sim 4 \times 10^{13}$ cm. EP250108a/SN 2025kg’s multi-wavelength properties
make it a close analog to LLGRB 060218/SN 2006aj, and highlight the power of
early follow-up observations in mapping the environments of massive stars prior
to core collapse.

Questo articolo esplora i giri e le loro implicazioni.

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