Two substellar survivor candidates: one found and one missing

ABSTRACT This study presents observations of two possible substellar survivors post-main sequence engulfment, currently orbiting white dwarf stars. Infrared and optical spectroscopy GD 1400 reveals a 9.98 h orbital period, where the benchmark brown has M2 = 68 ± 8 MJup, Teff ≈ 2100 K, cooling age under 1 Gyr. A mass in lower range allowed values is favoured by gravitational redshift primary. Synthetic spectra are able to reproduce observed CO bands, but lines below bandhead notably overpredicted. The known infrared excess towards PG 0010+281 consistent with companion, yet no radial velocity or photometric variability found despite extensive searches. Three independent stellar determinations all suggest enhanced mass-loss associated binary evolution, youngest total for an isolated star 7.5 2.5 solution this conundrum cannibalization one more giant planets, which sequence, were ultimately destroyed. 0010 + 281 likely orbited debris disc that comfortably exterior Roche limit, adding growing number non-canonical discs dwarfs. At present, only L-type (brown) dwarfs survive direct engulfment during whereas T- Y-type companions persist at wide separations. These demographics indicate roughly 50 MJup required robustly avoid annihilation, suggesting closely planets consumed, may contribute magnetic-field generation their immediate progenitors.