Abstract

Contributed Talk - Splinter StellarEndpoints

Friday, 11 September 2026, 16:32   (MW-2235)

Searching for isolated white dwarf stars in eROSITA data

S. Friedrich(1), K. Werner(2), K. Dennerl. (1), C. Maitra. (3,1), A. Schwope (4), B. Stelzer (2), S. Sheth (4)
(1) Max-Planck-Institut für extraterrestrische Physik, (2) Institut für Astronomie & Astrophysik, Eberhard-Karls-Universität Tübingen, (3) Inter-University Centre for Astronomy and Astrophysics (IUCAA), Ganeshkhind, Pune 411007, India, (4) Leibniz-Institut für Astrophysik Potsdam (AIP)

The first all-sky X-ray survey was performed by the ROSAT X-ray observatory in the 0.1–2.4 keV energy range (Trümper 1982). It was not until almost 30 years later that an all-sky X-ray survey was to be carried out again with the SRG/eROSITA X-ray mission. Between December 2019 and February 2022 four all-sky surveys were completed; a fifth one was only one-third completed. The sensitivity of eROSITA at soft energies is not as good as ROSAT's. However, we have previously shown that it is possible to detect white dwarfs in eROSITA data. Among the 38,000 very soft sources, almost 300 white dwarfs from Gentile-Fusillo et al. (2021), with a probability of more than 90 percent of being a white dwarf, were identified in the current cumulative eROSITA all-sky data from the surveys 1–4(5), which are limited at lower energies to 0.2 keV (Friedrich et al. 2025). Some of already known white dwarfs, however, could only be detected by processing eROSITA data with a lower energy threshold of 0.1 keV instead of 0.2 keV. Simulations are currently underway with a lower energy threshold of 0.1 keV to optimize data processing. It is planned to reprocess the eROSITA data with this lower energy threshold of about 0.1 keV to not only increase the number of white dwarfs detected in the X-ray range, but also to obtain more information about other soft sources, such as cataclysmic variables, isolated neutron stars, and even AGN.