Abstract

Contributed Talk - Splinter JungeAG

Tuesday, 10 September 2024, 14:05   (S25)

Spectrophotometric investigations of hot subdwarf stars in the Plato field with Gaia DR3

Anna Gebhardt
FAU Erlangen-Nürnberg

Hot, small, and out of place - Hot subdwarf stars of spectral types O and B are located close to the hot end of the horizontal branch and represent late stages of stellar evolution. With radii of about 0.2 R☉ and surface temperatures of more than 20000 K, the majority of these are core helium-burning stars as they lack the extensive hydrogen envelopes found at cooler horizontal branch stars. This combination differs from standard stellar evolution models, therefore most of them are thought to result from binary interaction with mass loss of the primary hot subdwarf star. Still, the driving mechanisms behind the formation and the evolutionary connection to other stellar classes are not fully understood. An overview of the properties of hot subdwarf stars in the Plato field, a roughly 50° x 50° field located in the Southern Hemisphere, is presented. This forms a significant sample for the upcoming Plato-mission and beyond an important step towards understanding the complex formation and evolution. For this, data from Gaia are a treasure trove. The Gaia space mission has provided photometric and astrometric measurements for more than one billion stars, a great enrichment for hot subdwarf research, and in combination with other spectroscopic and photometric surveys this huge data set enables the investigation of statistically significant samples of the comparatively rare hot subdwarf stars. Objects to be studied in the Plato field were selected first via numerous catalogues and various stellar properties have been constrained to prepare the sample. Investigations by extensive photometric data from various sky surveys have been carried out to determine atmospheric properties. The analysis of spectral energy distributions (SEDs), covered from the UV to the infra-red, combined with Gaia parallaxes enabled the determination of the fundamental stellar parameters radius and luminosity and identified main-sequence companions to hot subdwarf stars, in particular in the stellar population of the Plato field. The findings from the spectrophotometric investigations can be combined with spectral analysis and binary evolution models to shed light on the diverse formation mechanisms of hot subdwarf stars and their evolution.