Complete spectral energy distribution of the hot, helium-rich white dwarf RX J0503.9-2854

TL;DR

This study provides a comprehensive spectral energy distribution of the white dwarf RX J0503.9-2854, identifying numerous metal lines across a broad wavelength range and comparing observations with advanced models.

Contribution

It offers the first complete line list for this star, including 1272 identified lines, and discusses discrepancies in EUV flux modeling, highlighting potential missing opacities or temperature revisions.

Findings

Identified 1272 spectral lines, 279 newly assigned.

Detected 287 lines remain unidentified.

Observed EUV flux discrepancies suggest missing opacities or temperature adjustments.

Abstract

In the line-of-sight toward the DO-type white dwarf RX J0503.9-2854, the density of the interstellar medium (ISM) is very low, and thus the contamination of the stellar spectrum almost negligible. This allows us to identify many metal lines in a wide wavelength range from the extreme ultraviolet to the near infrared. In previous spectral analyses, many metal lines in the ultraviolet spectrum of RX J0503.9-2854 have been identified. A complete line list of observed and identified lines is presented here. We compared synthetic spectra that had been calculated from model atmospheres in non-local thermodynamical equilibrium, with observations. In total, we identified 1272 lines (279 of them were newly assigned) in the wavelength range from the extreme ultraviolet to the near infrared. 287 lines remain unidentified. A close inspection of the EUV shows that still no good fit to the observed shape of the stellar continuum flux can be achieved although He, C, N, O, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Mn, Fe, Cr, Ni Zn, Ga, Ge, As, Kr, Zr, Mo, Sn, Xe, and Ba are included in the stellar atmosphere models. There are two possible reasons for the deviation between observed and synthetic flux in the EUV. Opacities from hitherto unconsidered elements in the model-atmosphere calculation may be missing and/or the effective temperature is slightly lower than previously determined.