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  • A 500 pc volume-limited sam...
    Dawson, H; Geier, S; Heber, U; Pelisoli, I; Dorsch, M; Schaffenroth, V; Reindl, N; Culpan, R; Pritzkuleit, M; Vos, J; Soemitro, A A; Roth, M M; Schneider, D; Uzundag, M; Vučković, M; L. Antunes Amaral; Istrate, A G; Justham, S; Østensen, R H; Telting, J H; Djupvik, A A; Raddi, R; Green, E M; Jeffery, C S; Kepler, S O; Munday, J; Steinmetz, T; Kupfer, T

    Astronomy and astrophysics (Berlin), 06/2024, Letnik: 686
    Journal Article

    We present the first volume-limited sample of spectroscopically confirmed hot subluminous stars out to 500 pc, defined using the accurate parallax measurements from the Gaia space mission data release 3 (DR3). The sample comprises a total of 397 members, with 305 (~77%) identified as hot subdwarf stars, including 83 newly discovered systems. Of these, we observe that 178 (~58%) are hydrogen-rich sdBs, 65 are sdOBs (~21%), 32 are sdOs (~11%), and 30 are He-sdO/Bs (~10%). Among them, 48 (~16%) exhibit an infrared excess in their spectral energy distribution fits, suggesting a composite binary system. The hot subdwarf population is estimated to be 90% complete, assuming that most missing systems are these composite binaries located within the main sequence (MS) in the Gaia colour-magnitude diagram. The remaining sources in the sample include cataclysmic variables, blue horizontal branch stars, hot white dwarfs, and MS stars. We derived the mid-plane density ρ0 and scale height hz for the non-composite hot subdwarf star population using a hyperbolic sechant profile (sech2). The best-fit values are ρ0 = 5.17 ± 0.33 × 10−7 stars pc−3 and hz = 281 ± 62 pc. When accounting for the composite-colour hot subdwarfs and their estimated completeness, the mid-plane density increases to ρ0 = 6.15−0.53+1.16 × 10−7 stars pc−3. This corrected space density is an order of magnitude lower than predicted by population synthesis studies, supporting previous observational estimates.