TESS photometry of the pulsating hot subdwarf star V585 Peg

Abstract

ABSTRACT We report on the first space-based observations of the bright, high-amplitude hybrid pulsator V585 Peg (Balloon 090100001). TESS observed V585 Peg for 28 d during Sector 56 from which we detect 14 g-mode pulsations, 20 p-mode pulsations, and 26 combination frequencies. These pulsations are unusual and interesting in a number of ways; V585 Peg is a rare hybrid pulsator where both regions have many (>10) pulsations, the p-mode pulsations have clear frequency multiplets and overtone spacings while the g-mode pulsations do not, its multiplets have shown changes in splittings between years, and it appears to have two stochastic pulsations while most are stable. From p-mode multiplets, we find an average rotation period of 6.91 ± 0.83 d in which the different ℓ and m indices indicate latitudinal differential rotation. Unresolved g-mode multiplets limit rotation periods to be longer then 9.3 d for dipole modes, indicating V585 Peg to also be a radially differential rotator. We detect one secure p-mode overtone of 950 $\mu$Hz and four less sure ones of 314, 410, 440, and 554 $\mu$Hz. Two frequencies show stochastic properties indicating mode lifetimes of 3.5 and 6.2 h, which would be the shortest yet discovered.