Two hot pre-white dwarfs inside the red giant branch planetary nebula Pa 13: double-core evolution or common-envelope-induced rejuvenation
The close binary central stars of planetary nebulae (PNe) offer a unique window for investigating the conditions that immediately follow the ejection of a common envelope (CE). Double-eclipsing and double-lined double systems are particularly valuable as they provide minimally model-dependent constr...
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| Autori principali: | , , , , , , |
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| Natura: | Article (Journal) |
| Lingua: | inglese |
| Pubblicazione: |
12 May 2026
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| In: |
Astronomy and astrophysics
Year: 2026, Volume: 709, Pages: 1-12 |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/202659031 |
| Accesso online: | Verlag, kostenfrei, Volltext: https://doi.org/10.1051/0004-6361/202659031 Verlag, kostenfrei, Volltext: https://www.aanda.org/articles/aa/abs/2026/05/aa59031-26/aa59031-26.html 
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| Note sull'autore: | Nicole Reindl, David Jones, Todd Hillwig, Marcelo M. Miller Bertolami, Matti Dorsch, Nicholas Chornay, and Max Pritzkuleit |
| Riassunto: | The close binary central stars of planetary nebulae (PNe) offer a unique window for investigating the conditions that immediately follow the ejection of a common envelope (CE). Double-eclipsing and double-lined double systems are particularly valuable as they provide minimally model-dependent constraints on fundamental binary parameters. In this context, we report that the nucleus of Pa 13 (P = 0.3988 d) belongs to this rare class of systems and we present a comprehensive analysis of its double-degenerate binary. We performed a two-component nonlocal thermodynamic equilibrium spectral analysis based on phase-resolved X-shooter spectroscopy, multiband light-curve modeling, spectral energy distribution fitting, and a kinematic analysis. Both stars are found to be hot pre-white dwarfs, with Star 1 being cooler but larger (Teff = 50.0 kK, R = 0.40 R⊙) than Star 2 (Teff = 75.0 kK, R = 0.16 R⊙). The weakness of the spectral lines of Star 2 made both the atmospheric and radial velocity (RV) analyses challenging, and we uncovered a strong sensitivity of the assumed surface ratio to its derived RV curve. However, the RV curve and Kiel mass of Star 1 (M1 = 0.41 ± 0.02 M⊙) could be determined precisely, which allowed for a dynamical mass determination of Star 2 (M = 0.39 ± 0.04 M⊙). Moreover, we uncovered that Pa 13 exhibits a small but significant orbital eccentricity (e = 0.02 ± 0.01), which makes it only the second post-CE binary central star with a measured eccentricity. Our kinematic analysis shows that Pa 13 belongs to the Galactic halo, implying a system age of ≈11 Gyr. We conclude that Pa 13 provides the strongest evidence so far that PNe can be observed around post-red giant branch stars. Immediately after the CE ejection, Star 1 likely still filled its Roche lobe, which suggests that Pa 13 is a more evolved, detached descendant of over-contact double-degenerate systems such as Hen 2-428. Since the mass ratio of Pa 13 is close to unity, the system may have formed through double-core CE evolution. Alternatively, there must exist an efficient CE-induced rejuvenation mechanism capable of reheating the cool white dwarf in the binary, as already indicated by the Hen 2-428 system. |
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| Descrizione del documento: | Gesehen am 09.07.2026 |
| Descrizione fisica: | Online Resource |
| ISSN: | 1432-0746 |
| DOI: | 10.1051/0004-6361/202659031 |