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The polluted white dwarf (WD) system SDSS J122859.93+104032.9 (SDSS J1228)shows variable emission features interpreted as originating from a solid corefragment held together against tidal forces by its own internal strength,orbiting within its surrounding debris disk. Estimating the size of thisorbiting solid body requires modeling the accretion rate of the pollutingmaterial that is observed mixing into the WD surface. That material is suppliedvia sublimation from the surface of the orbiting solid body. The sublimationrate can be estimated as a simple function of the surface area of the solidbody and the incident flux from the nearby hot WD. On the other hand,estimating the accretion rate requires detailed modeling of the surfacestructure and mixing in the accreting WD. In this work, we present MESA WDmodels for SDSS J1228 that account for thermohaline instability and mixing inaddition to heavy element sedimentation to accurately constrain the sublimationand accretion rate necessary to supply the observed pollution. We derive atotal accretion rate of $\dot M_{\rm acc}=1.8\times 10^{11}\,\rm g\,s^{-1}$,several orders of magnitude higher than the $\dot M_{\rm acc}=5.6\times10^{8}\,\rm g\,s^{-1}$ estimate obtained in earlier efforts. The larger massaccretion rate implies that the minimum estimated radius of the orbiting solidbody is r$_{\rm{min}}$ = 72 km, which, although significantly larger than priorestimates, still lies within upper bounds (a few hundred km) for which theinternal strength could no longer withstand tidal forces from the gravity ofthe WD.

astrophysical journal/the astrophysical journal

Reinterpreting the Polluted White Dwarf SDSS J122859.93+104032.9 in  Light of Thermohaline Mixing Models: More Polluting Material from a Larger  Orbiting Solid Body