Observations of Soft X-ray Emission from Classical Nova AT 2018bej

Recent observations of the classical nova AT 2018bej have revealed significant findings regarding its soft X-ray emissions. The eROSITA telescope, part of the Spectrum-Roentgen-Gamma observatory, identified a bright supersoft X-ray source (SSS) associated with this nova during its all-sky survey (eRASS1). This nova is located in the Large Magellanic Cloud and has been monitored through multiple epochs, including eRASS1 and eRASS2, as well as an XMM-Newton grating spectrum obtained near the eRASS1 epoch.

The study, conducted by A. Tavleev and six co-authors, utilized local thermodynamic equilibrium (LTE) atmosphere models to analyze the X-ray spectra from eROSITA and XMM-Newton. The research focused on the evolution of the white dwarf's properties between the monitoring epochs, particularly the changes in carbon abundance. The analysis indicated that the effective temperature of the white dwarf was approximately 600,000 K, with a radius between 8,000 and 8,700 km. Notably, the simultaneous fitting of spectra from both eRASS epochs suggested a marginal decrease in effective temperature, an increase in radius, and a decrease in carbon abundance, although these changes were within the margin of error.

The derived mass of the white dwarf was estimated to be between 1.05 and 1.15 solar masses. These findings contribute to the understanding of classical novae and their behavior during the supersoft X-ray phase, suggesting that LTE model atmospheres can effectively analyze X-ray spectra of classical novae during their SSS stage. The implications of this research extend to the broader study of stellar evolution and the lifecycle of novae.

For further details, the full paper titled "Soft X-ray emission from the classical nova AT 2018bej" can be accessed at arXiv:2408.14171.