Journal article
High energy emission powered by accreting companions of Be/γ Cas stars
Astrophysics and space science, Vol.370(10), 108
10/10/2025
DOI: 10.1007/s10509-025-04497-6
Abstract
The origin of the hard, bright X-ray emission that defines the γ Cas analog class of Be stars remains an outstanding question in Be star literature. This work explores the possibility that the X-ray flux is produced by accretion onto a white dwarf companion. We use three-dimensional smoothed particle hydrodynamics simulations to model the prototype γ Cas system assuming a white dwarf companion and investigate the accretion of the circumstellar material by the secondary star. We contrast these results to a model for 59 Cyg, a non-γ Cas Be star system with a stripped companion. We find that the secondary stars in both systems form disk-like accretion structures with Keplerian characteristics, similar to those seen in the Be decretion disks. We also find that white dwarf accretion can produce X-ray fluxes that are consistent with the observed values for γ Cas, while the predicted X-ray luminosities are significantly lower for the non-degenerate companion in 59 Cyg. In addition, using the three-dimensional radiative transfer code, HDUST , we find that these models produce Hα emission consistent with the observations for both γ Cas and 59 Cyg, and that the predicted polarization degrees across optical and UV wavelengths are at detectable levels. Finally, we discuss the impact that future UV spectropolarimetry missions could have on our understanding of these systems.
Details
- Title: Subtitle
- High energy emission powered by accreting companions of Be/γ Cas stars
- Creators
- Rina G. Rast - Western UniversityYaël Nazé - University of LiègeJonathan Labadie-Bartz - Technical University of DenmarkCarol E. Jones - Western UniversityChristiana Erba - Space Telescope Science InstituteKen Gayley - University of IowaAsif ud-Doula - Pennsylvania State UniversityCoralie Neiner - Université Paris CitéJeremy J. Drake - Lockheed Martin (United States)
- Resource Type
- Journal article
- Publication Details
- Astrophysics and space science, Vol.370(10), 108
- DOI
- 10.1007/s10509-025-04497-6
- ISSN
- 0004-640X
- eISSN
- 1572-946X
- Publisher
- Springer Netherlands
- Grant note
- Natural Sciences and Engineering Research Council of Canada (NSERC)NSERCNASA: TM4-25001A, NAS8-03060 European Union (ERC): 101126182
RGR received funding from the Natural Sciences and Engineering Research Council of Canada (NSERC) Postgraduate Scholarship-Doctoral program. CEJ received support from the NSERC Discovery Research program. AuD has received research support from NASA through Chandra Award number TM4-25001A issued by the Chandra X-ray Observatory 27 Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of NASA under contract NAS8-03060. JLB received funding from the European Union (ERC, MAGNIFY, Project 101126182). The authors have no relevant financial or non-financial interests to disclose.
- Language
- English
- Date published
- 10/10/2025
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9985014869602771
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