Two substellar survivor candidates - one found and one missing

The brown dwarf companion of GD 1400 is confirmed and (partly) characterized.

Two substellar survivor candidates; one found and one missing

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This study presents observations of two possible substellar survivors of post-main sequence engulfment, currently orbiting white dwarf stars. Infrared and optical spectroscopy of GD 1400 reveal a 9.98 h orbital period, where the benchmark brown dwarf has M₂=65±3 M_Jup, Teff≈1900 K, and an age close to 1 Gyr. The 0.558±0.005 M⊙ mass of GD 1400A suggests the substellar companion escaped contact with the RGB host, but was later enveloped during the AGB. The known infrared excess towards PG 0010+281 is consistent with a substellar companion, yet no radial velocity or photometric variability is found despite multiple instrument searches. Three independent mass determinations for PG 0010+281 all suggest enhanced mass loss associated with binary evolution, where the youngest total age for an isolated star is 7.5±2.5 Gyr. A possible solution to this conundrum is the cannibalization of one or more giant planets, which enhanced mass loss post-main sequence, but were ultimately destroyed. Thus, PG 0010+281 is likely orbited by a debris disk that is comfortably exterior to the Roche limit, adding to the growing number of non-canonical disks orbiting white dwarfs. At present, only L-type (brown) dwarfs are known to survive direct engulfment during the post-main sequence, whereas T- and Y-type substellar companions persist at wide separations. These demographics suggest that roughly 50 M_Jup is required to robustly avoid post-main sequence annihilation, suggesting all closely-orbiting giant planets are consumed, which may contribute to mass loss and magnetic field generation in white dwarfs and their immediate progenitors.