Magnetic braking saturates: evidence from the orbital period distribution of low-mass detached eclipsing binaries from ZTF

Abstract

We constrain the orbital period ($P_{\mathrm{orb}}$) distribution of low-mass detached main-sequence eclipsing binaries (EBs) with light curves from the Zwicky Transient Facility (ZTF), which provides a well-understood selection function and sensitivity to faint stars. At short periods ($P_{\mathrm{orb}}\lesssim 2$ days), binaries are predicted to evolve significantly due to magnetic braking (MB), which shrinks orbits and ultimately brings detached binaries into contact. The period distribution is thus a sensitive probe of MB. We find that the intrinsic period distribution of low-mass ($0.1\lesssim M_1/M_{\odot }<0.9$) binaries is basically flat ($\mathrm{d}N/\mathrm{d}{P}_{\mathrm{orb}}\propto P_{\mathrm{orb}}^0$), from $P_{\mathrm{orb}}=10$ days down to the contact limit. This is strongly inconsistent with predictions of classical MB models based on the Skumanich relation, which are widely used in binary evolution calculations and predict $\mathrm{d}N/\mathrm{d}{P}_{\mathrm{orb}}\propto P_{\mathrm{orb}}^{7/3}$ at short periods. The observed distributions are best reproduced by models in which the magnetic field saturates at short periods, with a MB torque that scales roughly as $\dot{J}\propto P_{\mathrm{orb}}^{-1}$, as opposed to $\dot{J}\propto P_{\mathrm{orb}}^{-3}$ in the standard Skumanich law. We also find no significant difference between the period distributions of binaries containing fully and partially convective stars. Our results confirm that a saturated MB law, which was previously found to describe the spin-down of rapidly rotating isolated M dwarfs, also operates in tidally locked binaries. We advocate using saturated MB models in binary evolution calculations. Our work supports previous suggestions that MB in cataclysmic variables (CVs) is much weaker than assumed in the standard evolutionary model, unless mass transfer leads to significant additional angular momentum loss in CVs.

Table 1 included in source files. Accepted to MNRAS

References in corpus (35)

• The Zwicky Transient Facility: System Overview, Performance, and First Results
• The Catalina Surveys Periodic Variable Star Catalog
• Measuring the rotation period distribution of field M-dwarfs with Kepler
• A million binaries from Gaia eDR3: sample selection and validation of Gaia parallax uncertainties
• Tertiary companions to close spectroscopic binaries
• The H$\alpha$ emission of nearby M dwarfs and its relation to stellar rotation
• The Donor Stars of Cataclysmic Variables
• Gaia Early Data Release 3: The Gaia Catalogue of Nearby Stars
• The Zwicky Transient Facility Catalog of Periodic Variable Stars
• The Mass-Dependence of Angular Momentum Evolution in Sun-Like Stars
• The active lives of stars: a complete description of rotation and XUV evolution of F, G, K, and M dwarfs
• Magnetism, rotation, and nonthermal emission in cool stars -- Average magnetic field measurements in 292 M dwarfs
• The origin and evolution of magnetic white dwarfs in close binary stars
• Tidal Synchronization and Differential Rotation of Kepler Eclipsing Binaries
• Close companions around young stars
• Re-visiting the relations: Galactic thin disc age-velocity dispersion relation
• A classifier for spurious astrometric solutions in Gaia EDR3
• I Spy Transits and Pulsations: Empirical Variability in White Dwarfs Using Gaia and the Zwicky Transient Facility
• The formation of low-mass helium white dwarfs orbiting pulsars: Evolution of low-mass X-ray binaries below the bifurcation period
• Effective Temperatures of Cataclysmic Variable White Dwarfs as a Probe of their Evolution
• The short period end of the contact binary period distribution based on the All Sky Automated Survey (ASAS)
• Flare Rates, Rotation Periods. and Spectroscopic Activity Indicators of a Volume-Complete Sample of Mid-to-Late M dwarfs within 15 Parsecs
• The Metastable Dynamo Model of Stellar Rotational Evolution
• Evolution of Cataclysmic Variables and Related Binaries Containing a White-Dwarf
• Evidence for reduced magnetic braking in polars from binary population models
• The Missing Magnetic Morphology Term in Stellar Rotation Evolution
• 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
• Structure and evolution of low-mass W UMa type systems -- II. with angular momentum loss
• Birth of the ELMs: a ZTF survey for evolved cataclysmic variables turning into extremely low-mass white dwarfs
• Eclipsing binaries in the MACHO database: New periods and classifications for 3031 systems in the Large Magellanic Cloud
• Evolution of intermediate-mass X-ray binaries driven by magnetic braking of Ap/Bp stars: I. ultracompact X-ray binaries
• Novae heat their food: mass transfer by irradiation
• The Value-Added Catalog of ASAS-SN Eclipsing Binaries: Parameters of Thirty Thousand Detached Systems
• Convection and rotation boosted prescription of magnetic braking: application to the formation of extremely low-mass white dwarfs

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