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Creators/Authors contains: "Shapiro, Stuart"

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  1. ; (, The Astrophysical Journal)
    Abstract Numerical hydrodynamics simulations of gases dominated by ideal, nondegenerate matter pressure and thermal radiation pressure in equilibrium entail finding the temperature as part of the evolution. Since the temperature is not typically a variable that is evolved independently, it must be extracted from the evolved variables (e.g., the rest-mass density and specific internal energy). This extraction requires solving a quartic equation, which, in many applications, is done numerically using an iterative root-finding method. Here we show instead how the equation can be solved analytically and provide explicit expressions for the solution. We also derive Taylor expansions in limiting regimes and discuss the respective advantages and disadvantages of the iterative versus analytic approaches to solving the quartic. 
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    Free, publicly-accessible full text available March 26, 2026
  2. (, Physical Review D)
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  3. ; ; (, Physical Review D)
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  4. ; ; ; ; (, Physical Review D)
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  5. ; ; ; (, Physical Review D)
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  6. ; (, Physical Review D)
  7. ; ; (, Monthly Notices of the Royal Astronomical Society)
    ABSTRACT We assess whether gravity darkening, induced by a tidal interaction during a stellar fly-by, might be sufficient to explain the Great Dimming of Betelgeuse. Adopting several simple approximations, we calculate the tidal deformation and associated gravity darkening in a close tidal encounter, as well as the reduction in the radiation flux as seen by a distant observer. We show that, in principle, the duration and degree of the resulting stellar dimming can be used to estimate the minimum pericentre separation and mass of a fly-by object, which, even if it remains undetected otherwise, might be a black hole, neutron star, or white dwarf. Our estimates show that, while such fly-by events may occur in other astrophysical scenarios, where our analysis should be applicable, they likely are not large enough to explain the Great Dimming of Betelgeuse by themselves. 
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  8. ; ; ; (, Physical Review D)
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  9. ; ; ; (, Physical Review Letters)
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  10. ; ; (, Physical Review D)
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