Shock Dynamics in Stellar Outbursts. I. Shock Formation

Ro, Stephen; Matzner, Christopher D.

doi:10.3847/1538-4357/aa6d5c

Cited by 32 publications

(21 citation statements)

References 39 publications

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“…This suggests that shocks will not necessarily form already at the base of the hydrogen envelope. According to Ro & Matzner (2017), shocks may form even more robustly than we have estimated here by examining the behavior of kξ. This will exacerbate the likelihood that gravity waves from the carbon-burning shell will dissipate in shocks at the base of the outer convective envelope, but might still mean that the weak waves from core helium burning survive that process.…”

Section: Shock Dissipationmentioning

confidence: 78%

The Betelgeuse Project II: asteroseismology

Nance

Sullivan

Díaz

et al. 2018

Monthly Notices of the Royal Astronomical Society

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We explore the question of whether the interior state of massive red supergiant supernova progenitors can be effectively probed with asteroseismology. We have computed a suite of ten models with ZAMS masses from 15 to 25 M in intervals of 1 M including the effects of rotation, with the stellar evolutionary code MESA. We estimate characteristic frequencies and convective luminosities of convective zones at two illustrative stages, core helium burning and off-center convective carbon burning. We also estimate the power that might be delivered to the surface to modulate the luminous output considering various efficiencies and dissipation mechanisms. The inner convective regions should generate waves with characteristic periods of ∼ 20 days in core helium burning, ∼10 days in helium shell burning, and 0.1 to 1 day in shell carbon burning. Acoustic waves may avoid both shock and diffusive dissipation relatively early in core helium burning throughout most of the structure. In shell carbon burning, years before explosion, the signal generated in the helium shell might in some circumstances be weak enough to avoid shock dissipation, but is subject to strong thermal dissipation in the hydrogen envelope. Signals from a convective carbon-burning shell are very likely to be even more severely damped by within the envelope. In the most optimistic case, early in core helium burning, waves arriving close to the surface could represent luminosity fluctuations of a few millimagnitudes, but the conditions in the very outer reaches of the envelope suggest severe thermal damping there.

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Section: Shock Dissipationmentioning

confidence: 78%

The Betelgeuse Project II: asteroseismology

Nance

Sullivan

Díaz

et al. 2018

Monthly Notices of the Royal Astronomical Society

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“…However, one can show from linear theory that the power carried by the sound pulse is approximately conserved (Dewar 1970;Ro & Matzner 2017), such that the velocity immediately behind the sound pulse satisfies…”

Section: Physical Picture and Estimatesmentioning

confidence: 99%

A physical model of mass ejection in failed supernovae

Coughlin

Quataert

Fernández

et al. 2018

Monthly Notices of the Royal Astronomical Society

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During the core collapse of massive stars, the formation of the protoneutron star is accompanied by the emission of a significant amount of mass-energy (∼ 0.3 M ) in the form of neutrinos. This mass-energy loss generates an outward-propagating pressure wave that steepens into a shock near the stellar surface, potentially powering a weak transient associated with an otherwise-failed supernova. We analytically investigate this mass-loss-induced wave generation and propagation. Heuristic arguments provide an accurate estimate of the amount of energy contained in the outgoing sound pulse. We then develop a general formalism for analyzing the response of the star to centrally concentrated mass loss in linear perturbation theory. To build intuition, we apply this formalism to polytropic stellar models, finding qualitative and quantitative agreement with simulations and heuristic arguments. We also apply our results to realistic precollapse massive star progenitors (both giants and compact stars). Our analytic results for the sound pulse energy, excitation radius, and steepening in the stellar envelope are in good agreement with full time-dependent hydrodynamic simulations. We show that prior to the sound pulses arrival at the stellar photosphere, the photosphere has already reached velocities ∼ 20 − 100% of the local sound speed, thus likely modestly decreasing the stellar effective temperature prior to the star disappearing. Our results provide important constraints on the physical properties and observational appearance of failed supernovae.

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“…The form of the wave pulse resembles a standard N-wave, with a forward shock front, rarefaction wave, and a reverse shock at the tail (Courant & Friedrichs 1948). Both the rarefaction wave and the tail, however, display more complicated behavior than for the strictly hydrodynamic N-wave (Ro & Matzner 2017), pointing to the unique behavior of MHD shocks and the possible influence of reconnection outflows on the tail. Fractional density change along the slow shock trajectory at time t = 6.0tN .…”

Section: Slow Shocks Along the Separatricesmentioning

confidence: 99%

The Formation and Dissipation of Current Sheets and Shocks due to Compressive Waves in a Stratified Atmosphere Containing a Magnetic Null

Tarr

Linton

2019

ApJ

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We study the propagation and dissipation of magnetohydrodynamic waves in a set of numerical models that each include a solar-like stratified atmosphere and a magnetic field with a null point. All simulations have the same magnetic field configuration but different transition region heights. Compressive wave packets introduced in the photospheric portion of the simulations refract towards the null and collapse it into a current sheet, which then undergoes reconnection. The collapsed null forms a current sheet due to a strong magnetic pressure gradient caused by the inability of magnetic perturbations to cross the null. Although the null current sheet undergoes multiple reconnection episodes due to repeated reflections off the lower boundary, we find no evidence of oscillatory reconnection arising from the dynamics of the null itself. Wave mode conversion around the null generates a series of slow mode shocks localized near each separatrix. The shock strength is asymmetric across each separatrix, and subsequent shock damping therefore creates a tangential discontinuity across each separatrix, with long-lived current densities. A parameter study of the injected wave energy to reach the null confirms our previous WKB estimates. Finally, using current estimates of the photospheric acoustic power, we estimate that the shock and Ohmic heating we describe may account for ≈ 1 − 10% of the radiative losses from coronal bright points with similar topologies, and are similarly insufficient to account for losses from larger structures such as ephemeral regions. At the same time, the dynamics are comparable to proposed mechanisms for generating type-II spicules.

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Shock Dynamics in Stellar Outbursts. I. Shock Formation

Cited by 32 publications

References 39 publications

The Betelgeuse Project II: asteroseismology

The Betelgeuse Project II: asteroseismology

A physical model of mass ejection in failed supernovae

The Formation and Dissipation of Current Sheets and Shocks due to Compressive Waves in a Stratified Atmosphere Containing a Magnetic Null

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