Revisiting the extremely long-period cataclysmic variables V479 Andromedae and V1082 Sagitarii
arXiv:2508.21358 · doi:10.1051/0004-6361/202556385
Abstract
The overwhelming majority of CVs have orbital periods shorter than 10 hr. However, a few have much longer periods, and their formation and existence pose challenges for the CV evolution models. These extremely long-period CVs must host nuclearly evolved donor stars, as otherwise, the companion of the white dwarf would be too small to fill its Roche lobe. This makes them natural laboratories for testing binary evolution models and accretion processes with subgiant donors. To shed light on the formation and evolution of accreting compact objects with subgiant companions, we investigated two extremely long-period CVs in detail, namely V479 And and V1082 Sgr. We searched for reasonable formation pathways to explain their refined stellar and binary parameters. We used a broad set of new observations, including ultraviolet and infrared spectroscopy, results of circular polarimetry, and improved Gaia distance estimates to determine fundamental parameters to be confronted with numerical simulations. Furthermore, we utilized the MESA code to conduct numerical simulations, employing state-of-the-art prescriptions, such as the CARB model for strong magnetic braking. Both systems have unusual chemical compositions and very low masses for their assigned spectral classes. This most likely indicates that they underwent thermal timescale mass transfer. We found models for both that can reasonably reproduce their properties. We conclude that the donor stars in both V479 And and V1082 Sgr are filling their Roche lobes. Our findings suggest that orbital angular momentum loss is stronger due to magnetic braking in CVs with subgiant donors compared to those with unevolved donors. In addition, our findings suggest that extremely long-period CVs could significantly contribute to the population of double white dwarf binaries in close orbits.
17 pages, 12 figures, 2 Appendices; accepted by the Astronomy \& Astropysics
References in corpus (32)
- Modules for Experiments in Stellar Astrophysics (MESA)
- The Transiting Exoplanet Survey Satellite
- Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3
- Modules for Experiments in Stellar Astrophysics (MESA): Pulsating Variable Stars, Rotation, Convective Boundaries, and Energy Conservation
- Modules for Experiments in Stellar Astrophysics (MESA): Time-Dependent Convection, Energy Conservation, Automatic Differentiation, and Infrastructure
- Line and Mean Opacities for Ultracool Dwarfs and Extrasolar Planets
- Updated Electron-Conduction Opacities: The Impact on Low-Mass Stellar Models
- Coulomb tunneling for fusion reactions in dense matter: Path integral Monte Carlo versus mean field
- Skye: A Differentiable Equation of State
- The formation of low-mass helium white dwarfs orbiting pulsars: Evolution of low-mass X-ray binaries below the bifurcation period
- Evolution of LMXBs under Different Magnetic Braking Prescriptions
- The evolutionary status of Cataclysmic Variables: Eclipse modelling of 15 systems
- A catalogue of cataclysmic variables from 20 years of the Sloan Digital Sky Survey with new classifications, periods, trends and oddities
- Low Mass X-ray Binaries: The Effects of the Magnetic Braking Prescription
- Formation of millisecond pulsars with helium white dwarfs, ultra-compact X-ray binaries and gravitational wave sources
- 123-321 Models of Classical Novae
- Magnetic braking saturates: evidence from the orbital period distribution of low-mass detached eclipsing binaries from ZTF
- The thermal equilibrium mass loss model and its applications in binary evolution
- Birth of the ELMs: a ZTF survey for evolved cataclysmic variables turning into extremely low-mass white dwarfs
- Convective boundary mixing in main-sequence stars: theory and empirical constraints
- The cataclysmic variable orbital period gap: More evident than ever
- Reversing the verdict: Cataclysmic variables could be the dominant progenitors of AM CVn binaries after all
- EMIR, the near-infrared camera and multi-object spectrograph for the GTC
- Abundance Derivations for the Secondary Stars in Cataclysmic Variables from Near-Infrared Spectroscopy
- Convection and rotation boosted prescription of magnetic braking: application to the formation of extremely low-mass white dwarfs
- Further evidence of saturated, boosted, and disrupted magnetic braking from evolutionary tracks of cataclysmic variables
- The peculiar chemical abundance of the transitional millisecond pulsar PSR J1023+0038 -- Li enhancement
- Constraining Progenitors of Observed LMXBs Using CARB Magnetic Braking
- The C/N ratio from FUV spectroscopy as a constraint upon the past evolution of HS0218+3229
- Anomalous orbital expansion of low-mass X-ray binary 2A 1822-371: the existence of a circumbinary disk?
- Resolution of a paradox: SDSS J1257+5428 can be explained as a descendant of a cataclysmic variable with an evolved donor
- X-ray spectroscopy method of white dwarf mass determination in intermediate polars. External systematic uncertainties