The velocity distribution of outflows driven by choked jets in stellar envelopes

Abstract

Many stripped envelope supernovae (SNe) present a signature of high-velocity material responsible for broad absorption lines in the observed spectrum. These include SNe that are associated with long gamma-ray bursts (LGRBs) and low-luminosity GRBs (llGRBs), and SNe that are not associated with GRBs. Recently it was suggested that this high velocity material originates from a cocoon that is driven by a relativistic jet. In LGRBs this jet breaks out successfully from the stellar envelope, while in llGRBs and SNe that are not associated with GRBs the jet is choked. Here we use numerical simulations to explore the velocity distribution of an outflow that is driven by a choked jet and its dependence on the jet and progenitor properties. We find that in all cases where the jet is not choked too deep within the star, the outflow carries a roughly constant amount of energy per logarithmic scale of proper velocity over a wide range of velocities, which depends mostly on the cocoon volume at the time of its breakout. This is a universal property of jets driven outflows, which does not exist in outflows of spherically symmetric explosions or when the jets are choked very deep within the star. We therefore conclude that jets that are choked (not too deep) provide a natural explanation to the fast material seen in the early spectra of stripped envelope SNe that are not associated with LGRBs and that properties of this material could reveal information on the otherwise hidden jets.

The Origin of Low-redshift Event Rate Excess as Revealed by the Low-luminosity Gamma-Ray Bursts

“…Lan et al (2021) showed that the low-luminosity lGRBs are not the straightforward extension of high-luminosity ones through the luminosity distribution of their sample. Pais et al (2023) mentioned that a cocoon breakout is most likely the origin of low-luminosity GRBs. Broad absorption lines produced in such a process have been observed in several SNe associated with low-luminosity lGRBs (e.g., Bufano et al 2012;Xu et al 2013;Izzo et al 2019).…”

Diagnosing the ejecta properties of engine-driven supernovae from observables in their initial phase

“…In addition to the original CO138 density structure, we test a power-law density distribution, e.g., 𝜌 0 (𝑣) ∝ 𝑣 −6 ; the energy input by a central engine introduces substantial mixing within the ejecta, and the resulting density structure is well described by a power-law distribution with the index of −5 to −6 as a function of the velocity (Suzuki & Maeda 2017. A similar mixing effect is found for a jet-like energy injection along the jet axis (Eisenberg et al 2022;Suzuki & Maeda 2022;Pais et al 2023), and our one-dimensional simulation may also be regarded as a rough approximation along the jet axis which is expected to be aligned with the line-of-sight for GRB-SNe (see also Section 4 for further discussion). The power-law distribution is constructed by hands, keeping the same ejecta mass and kinetic energy as in the original CO138 model.…”

“…The composition structure is also mixed (Suzuki & Maeda 2021). These features are also found at least qualitatively in a jet-like energy input from the central engine, especially along the jet direction Tominaga et al 2007;Eisenberg et al 2022;Suzuki & Maeda 2022;Pais et al 2023). The scenario further suggests a link between GRB-SNe and SLSNe (Metzger et al 2017); a key may be the difference in the time duration in which the central engine operates, with short-duration and long-duration systems resulting in GRB-SNe and SLSNe, respectively (Suzuki & Maeda 2021).…”

“…This quantity depends on the hydrodynamics of the shock propagation in the steeply decreasing progenitor density structure (Matzner & McKee 1999), together with the energy redistribution following the shock breakout due to the radiation loss (Falk & Arnett 1977;Ensman & Burrows 1992;Suzuki et al 2016). The operation of the central engine further provides an additional factor, again through the combined effect of the hydrodynamic evolution Pais et al 2023) and radiation loss (Suzuki & Maeda 2021). In other word, our aim here is to clarify what observables keep the information on the outermost ejecta velocity, and how the observations can be used to constrain it; we thus aim at providing possible diagnostics on the nature of the central engine through 𝑣 max .…”

“…The scenario further suggests a link between GRB-SNe and SLSNe (Metzger et al 2017); a key may be the difference in the time duration in which the central engine operates, with short-duration and long-duration systems resulting in GRB-SNe and SLSNe, respectively (Suzuki & Maeda 2021). Depending on the engine-operation duration, the outermost ejecta velocity may also be different (Eisenberg et al 2022;Suzuki & Maeda 2022;Pais et al 2023), which is further affected by the radiation loss (Suzuki & Maeda 2021).…”