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Abstract Eruptive mass loss likely produces the energetic outbursts observed from some massive stars before they become core-collapse supernovae (SNe). The resulting dense circumstellar medium may also cause the subsequent SNe to be observed as Type IIn events. The leading hypothesis of the cause of these outbursts is the response of the envelope of the red supergiant (RSG) progenitor to energy deposition in the months to years prior to collapse. Early theoretical studies of this phenomenon were limited to 1D, leaving the 3D convective RSG structure unaddressed. UsingFLASH's hydrodynamic capabilities, we explore the 3D outcomes by constructing convective RSG envelope models and depositing energies less than the envelope binding energies on timescales shorter than the envelope dynamical time deep within them. We confirm the 1D prediction of an outward-moving acoustic pulse steepening into a shock, unbinding the outermost parts of the envelope. However, we find that the initial 2–4 km s−1convective motions seed the intrinsic convective instability associated with the high-entropy material deep in the envelope, enabling gas from deep within the envelope to escape and increasing the amount of ejected mass compared to an initially “quiescent” envelope. The 3D models reveal a rich density structure, with column densities varying by ≈10× along different lines of sight. Our work highlights that the 3D convective nature of RSG envelopes impacts our ability to reliably predict the outburst dynamics, the amount, and the spatial distribution of the ejected mass associated with deep energy deposition.
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Shock Breakout in Three-dimensional Red Supergiant Envelopes
Abstract UsingAthena++, we perform 3D radiation-hydrodynamic calculations of the radiative breakout of the shock wave in the outer envelope of a red supergiant (RSG) that has suffered core collapse and will become a Type IIP supernova. The intrinsically 3D structure of the fully convective RSG envelope yields key differences in the brightness and duration of the shock breakout (SBO) from that predicted in a 1D stellar model. First, the lower-density “halo” of material outside of the traditional photosphere in 3D models leads to a shock breakout at lower densities than 1D models. This would prolong the duration of the shock breakout flash at any given location on the surface to ≈1–2 hr. However, we find that the even larger impact is the intrinsically 3D effect associated with large-scale fluctuations in density that cause the shock to break out at different radii at different times. This substantially prolongs the SBO duration to ≈3–6 hr and implies a diversity of radiative temperatures, as different patches across the stellar surface are at different stages of their radiative breakout and cooling at any given time. These predicted durations are in better agreement with existing observations of SBO. The longer durations lower the predicted luminosities by a factor of 3–10 (Lbol∼ 1044erg s−1), and we derive the new scalings of brightness and duration with explosion energies and stellar properties. These intrinsically 3D properties eliminate the possibility of using observed rise times to measure the stellar radius via light-travel time effects.
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- Award ID(s):
- 1663688
- PAR ID:
- 10368997
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 933
- Issue:
- 2
- ISSN:
- 0004-637X
- Format(s):
- Medium: X Size: Article No. 164
- Size(s):
- Article No. 164
- Sponsoring Org:
- National Science Foundation
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