Abstract

Poster - Splinter CloseBinaries   (MW-0250)

Hot Subdwarfs Beyond the Thin Disc: A Volume-Limited Survey to 700 pc

Doruk Gogus, Harry Dawson, Matti Dorsch, James Munday, Stephan Geier
Institute for Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Potsdam, Germany

Hot subdwarfs are core helium burning stars that tend to lie on the Extreme Horizontal Branch (EHB). Binarity plays a crucial role in their formation. Although their formation channels are not yet completely understood, spectra play a crucial role in better understanding their composition, motions and origins. In this poster we present a volume-limited, spectroscopic survey conducted with the Australian National University (ANU) 2.3m telescope using the WiFeS Spectrograph. This work extends upon the volume-complete sample from 500pc (Dawson et al. 2024) to ~700pc in the southern hemisphere, to characterise the properties of the older thick disc population of the galaxy. In total, this survey consists of 120 stars with 96 of them being hot subdwarfs. We have conducted spectroscopic analyses of the sample to derive the atmospheric parameters such as effective temperature, surface gravity and helium abundance accompanied by radial velocity measurements for each star. Spectral energy distributions (SEDs) were constructed and combined with Gaia parallaxes to derive stellar radii, luminosities and masses. Here we present the current status and preliminary results to the survey.