Rotation Period of 213 FGK Companions in Wide sdOB Binaries from TESS 1–83 Sectors

Hot subdwarf B (sdB) stars are compact, core-helium-burning objects with thin hydrogen envelopes, occupying the extreme horizontal branch (EHB). Their formation is widely attributed to binary interactions—common envelope (CE) ejection or stable Roche-lobe overflow (RLOF) or double WD merger. However, the apparent isolation of up to 30% of sdBs has spurred single-star scenarios invoking enhanced RGB winds or helium mixing. Pelisoli et al. (2020) challenged these models by analyzing 123 composite sdBs in early TESS sectors (S1–S20), finding that almost all FGK companions exhibited rapid rotation (peaking at ≈2.5 days), indicative of past mass transfer, and a scarcity of sdBs in wide common proper motion (CPM) pairs. Here, we expand this work using TESS Cycles 1–6 (S1–S83, 4833 sdBs) to measure companion rotation periods via light-curve analysis, testing whether all systems show spin-up signatures. By combining SED decomposition, FELIX-based rotational signal extraction, and positional cross-checks within TESS TPF to confirm signal origin, we identify ≈1600 sdBs with infrared excess, of which at least 500 exhibit unambiguous spin-up signatures, confirming their ubiquity and definitively ruling out single-star formation channels. Future work will leverage Gaia DR3 and upcoming DR4 data to systematically probe sdBs in wide CPM pairs, further constraining their binary origins and companion demographics.