A comprehensive search for hot subdwarf stars using <i>Gaia</i> and TESS

<jats:p><jats:italic>Context</jats:italic>. Hot subdwarfs are compact, evolved stars that serve as critical testbeds for understanding binary evolution, stellar remnants, and pulsation physics. Their formation is often attributed to binary interactions, but a significant fraction are apparently single, suggesting multiple formation pathways. Pulsating hot subdwarfs, whether in binaries or single, offer valuable opportunities for asteroseismic investigations to probe their internal structure and evolution.</jats:p>
<jats:p><jats:italic>Aims</jats:italic>. We aim to expand the known population of pulsating hot subdwarfs and explore their formation channels by investigating both binary and single systems.</jats:p>
<jats:p><jats:italic>Methods</jats:italic>. Using TESS light curves, we conducted a systematic variability search for hot subdwarf candidates identified from <jats:italic>Gaia</jats:italic> EDR3 and the TESS Input Catalogue. Variability was assessed using periodograms and applying a S/N > 5 threshold. Stars with multiple frequencies were classified as pulsators, while single-frequency sources were checked for binarity signatures such as harmonics or eclipses. Variability detections were verified with the TESS-Localize tool. Additionally, we performed follow-up spectroscopy for 11 targets, and carried out spectral energy distribution (SED) fitting to constrain the binary nature and fundamental stellar parameters.</jats:p>
<jats:p><jats:italic>Results</jats:italic>. We present 42 new variable hot subdwarfs, including 22 pulsators, 3 candidates for pulsating hot subdwarfs in binary systems (including one sdO star), and 13 additional binary candidates. The variability of 4 stars remains to be confirmed. Our spectroscopic and SED analyses of 11 stars provide improved constraints on stellar parameters and reveal new details about their binary nature.</jats:p>
<jats:p><jats:italic>Conclusions</jats:italic>. This work significantly expands the sample of known pulsating hot subdwarfs and binary candidates and demonstrates the importance of combined space-based photometry and ground-based follow-up in understanding the formation and evolution of hot subdwarf stars.</jats:p>