The evolutionary history of ultra-compact accreting binaries. I. Chemical abundances and formation channel of the eclipsing AM CVn system ZTF J225237.05-051917.4 from HST spectroscopy

Abstract

AM Canum Venaticorum (AM CVn) stars are ultra-compact binary systems composed of a white dwarf (WD) primary accreting from a H-deficient donor. They are important as potential progenitors of Type Ia supernovae and laboratories for gravitational-wave studies, yet their evolutionary history remains unsolved. Three formation channels have been proposed: the WD channel, the He-star channel, and the cataclysmic variable (CV) channel. We aim to provide the first accurate measurements of the fundamental parameters of the accretor in ZTFJ225237.05-051917.4, including the abundances of key elements such as C, N, and Si, by analysing UV spectra obtained with the Hubble Space Telescope. These measurements provide new insight into the system's evolutionary history and establish it as a benchmark to develop our pipeline for application to a larger sample of AM CVns. We determine the binary parameters from photometric modelling and constrain the atmospheric parameters of the WD accretor, including Teff, logg, and chemical abundances, by fitting the UV spectrum with synthetic spectral models. We then infer the system's formation channel by comparing our results with theoretical evolutionary models. We measure a Teff=23300$\pm$600K and a surface gravity of logg=8.4$\pm$0.3, which implies an accretor mass of 0.86$\pm$0.16 solar masses. We find a high N/C abundance ratio by mass of >153. The accretor is significantly hotter than previous estimates based on simplified blackbody fits to the spectral energy distribution, underscoring the importance of detailed spectral modelling for determining accurate system parameters. Our results show that UV spectroscopy is well-suited to constraining the formation channels of AM CVn systems. We conclude that the He-star channel can be excluded based on the high N/C ratio, while the WD and CV channels remain consistent with the observations.

arXiv commentAccepted for publication in A&A, 12 pages, 12 figures, 3 tables

References in corpus (58)

• emcee: The MCMC Hammer
• Modules for Experiments in Stellar Astrophysics (MESA)
• Modules for Experiments in Stellar Astrophysics (MESA): Giant Planets, Oscillations, Rotation, and Massive Stars
• LSST: from Science Drivers to Reference Design and Anticipated Data Products
• Modules for Experiments in Stellar Astrophysics (MESA): Binaries, Pulsations, and Explosions
• Modules for Experiments in Stellar Astrophysics (MESA): Convective Boundaries, Element Diffusion, and Massive Star Explosions
• The Zwicky Transient Facility: System Overview, Performance, and First Results
• TianQin: a space-borne gravitational wave detector
• Modules for Experiments in Stellar Astrophysics (MESA): Pulsating Variable Stars, Rotation, Convective Boundaries, and Energy Conservation
• A 3D Dust Map Based on Gaia, Pan-STARRS 1 and 2MASS
• Las Cumbres Observatory Global Telescope Network
• Evolutionary Binary Sequences for Low- and Intermediate-Mass X-ray Binaries
• Double-detonation sub-Chandrasekhar supernovae: can minimum helium shell masses detonate the core?
• Faint Thermonuclear Supernovae from AM Canum Venaticorum Binaries
• On the Spectral Evolution of Hot White Dwarf Stars. I. A Detailed Model-Atmosphere Analysis of Hot White Dwarfs from SDSS DR12
• Data analysis recipes: Using Markov Chain Monte Carlo
• COSMIC Variance in Binary Population Synthesis
• Short-period AM CVn systems as optical, X-ray and gravitational wave sources
• Post-common-envelope binaries from SDSS. XI: The white dwarf mass distributions of CVs and pre-CVs
• Sub-Chandrasekhar-mass white dwarf detonations revisited
• Three Hypervelocity White Dwarfs in Gaia DR2: Evidence for Dynamically Driven Double-Degenerate Double-Detonation Type Ia Supernovae
• Hydrogen Burning on Accreting White Dwarfs: Stability, Recurrent Novae, and the Post-Novae Supersoft Source
• Updated Gaia-2MASS 3D maps of Galactic interstellar dust
• LISA verification binaries with updated distances from Gaia Data Release 2
• Physical properties of IP Pegasi: an eclipsing dwarf nova with an unusually cool white dwarf
• Three-dimensional extinction maps: Inverting inter-calibrated extinction catalogues
• Mass-accreting white dwarfs and type Ia supernovae
• AE Aquarii: how CVs descend from supersoft binaries
• The chemical composition of donors in AM CVn stars and ultra-compact X-ray binaries: observational tests of their formation
• Population Synthesis of Cataclysmic Variables: I. Inclusion of Detailed Nuclear Evolution
• The Evolution of Cool Algols
• Evolution of Low-Mass Helium Stars in Semidetached Binaries
• Effective Temperatures of Cataclysmic Variable White Dwarfs as a Probe of their Evolution
• Observationally driven Galactic double white dwarf population for LISA
• The physical properties of AM CVn stars: new insights from Gaia DR2
• The Thermal Evolution of the Donors in AM CVn Binaries
• Accreting Double white dwarf binaries: Implications for LISA
• The population of AM CVn stars from the Sloan Digital Sky Survey
• Most Double Degenerate Low Mass White Dwarf Binaries Merge
• Discovery and characterization of five new eclipsing AM CVn systems
• High-Speed Photometry of Gaia14aae: An Eclipsing AM CVn That Challenges Formation Models
• Spectroscopic evidence for the binary nature of AM CVn
• Phases of Mass Transfer from Hot Subdwarfs to White Dwarf Companions and Their Photometric Properties
• The BlackGEM telescope array I: Overview
• Spectroscopic and Photometric Periods of Six Ultracompact Accreting Binaries
• Mass Transfer and Stellar Evolution of the White Dwarfs in AM CVn Binaries
• Asymmetry in the number of L4 and L5 Jupiter Trojans driven by jumping Jupiter
• Reversing the verdict: Cataclysmic variables could be the dominant progenitors of AM CVn binaries after all
• On the progenitors of AM CVn stars as LISA sources: the evolved donor star channel
• TACOS: TESS AM~CVn Outbursts Survey
• The outburst of a 60 min AM CVn reveals peculiar color evolution: implications for outbursts in long period double white dwarfs
• Evolution of AM CVn binaries with WD donors
• Dynamical He Flashes in Double White Dwarf Binaries
• Evolved cataclysmic variables as progenitors of AM CVn stars
• A Catalogue of Ultracompact Mass-Transferring White Dwarf Binaries
• The C/N ratio from FUV spectroscopy as a constraint upon the past evolution of HS0218+3229
• Evolution of binaries containing a hot subdwarf and a white dwarf to double white dwarfs, and double detonation supernovae with hypervelocity runaway stars
• Revisiting the extremely long-period cataclysmic variables V479 Andromedae and V1082 Sagitarii

Cited by in corpus (1)

• Ultra-compact X-ray Binaries: A Review