Solving the radiative transfer problem in SPH simulations of contact binary mergers using FluxCal

• Author / Creator

  Hatfull,Roger

• V1309 Sco was observed in 2008 as a luminous red nova and presents as some of the best time-resolved spectral data of a contact binary merger. However, the parameters of its progenitor and the physics behind the morphology of its light curve remain uncertain. We use the Smoothed Particle Hydrodynamics (SPH) code StarSmasher to model the progenitor primary star, using a MESA model at the base of the red giant branch with M = 1.52 Msun, R = 3.715 Rsun and total particle numbers N = 1x10^5, N = 2x10^5, and N = 3x10^5. We vary spatial resolutions in each of the models to find total energy profiles that match the initial MESA model well near the surface.

  We analyze all three models using a new code we developed called FluxCal, which solves the radiative transfer problem in SPH simulations using an envelope fitting method for inherently optically thick particles and a Runge-Kutta ray tracing method in the LTE approximation. FluxCal allows for the first time ever the calculation of spectral properties at SPH simulation boundaries with optically thick particles. We observe an accuracy improvement of ~2 orders of magnitude in the effective temperature of an SPH stellar model over a traditional ray tracing method.

  We simulate a contact binary merger with the M = 1.52 Msun, R = 3.715 Rsun, N = 2x10^5 red giant primary and a M = 0.16 Msun, R = 0.203 Rsun, N = 1x10^4 secondary with StarSmasher out to ~14 days (~4 months wall time) to model the V1309 Sco merger. We use FluxCal to calculate the effective temperatures in 10 hour intervals which we use to calculate luminosities. The merger in our simulations evolved on timescales shorter than expected from observations. This may be due to the primary's envelope artificially expanding during relaxation to a larger radius than the initial MESA model, which leads to Roche lobe overflow and loss of angular momentum at larger separations. Calculated luminosities peak at values similar to that observed in V1309 Sco. We require additional simulation time or a simulation with lower resolution to view late-time spectrotemporal dynamics.

• Subjects / Keywords

  • LTE
  • lobe
  • curve
  • luminosity
  • observation
  • energy
  • Sco
  • novae
  • V838
  • Roche
  • thermodynamic
  • ray
  • nova
  • Lagrange
  • V1309
  • mergeburst
  • light
  • infrared
  • profile
  • transients
  • local
  • giant
  • simulation
  • LRN
  • Runge
  • stellar
  • brown
  • binary
  • hydrodynamics
  • tracing
  • StarSmasher
  • fluxcal
  • visible
  • Mon
  • visual
  • equilibrium
  • stars
  • intermediate
  • trace
  • particle
  • transfer
  • smoothed
  • dwarf
  • red
  • mergers
  • nnopt
  • outflow
  • Kutta
  • SPH
  • MESA
  • overflow
  • relaxation
  • contact
  • radiative

• Graduation date

  Fall 2019

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-j6xb-2x88

• License

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