The Solar Neighborhood. LV. M Dwarf Twin Binaries -- One in Five Twin Sibling Pairs Are Mismatched in Activity and/or Rotation

Abstract

We report on a study of 36 pairs of `twin' M dwarfs in wide binaries and assess how similarly the stars behave. Stars in each twin pair have BP, RP, $J$, $H$, and $K_s$ differing by $<$0.10 mag, mass estimates matching within $<$3%, and presumably the same age and composition. We utilize short- and long-term photometry, multi-epoch spectroscopy, and archival data to measure rotation periods, photometric activity levels, and H$\alpha$ equivalent widths for many systems. Speckle imaging, radial velocities, and long-term astrometry are used to identify unresolved companions, yielding three systems with unseen components. Among the 33 remaining twin systems, numerous remarkable pairs show nearly identical rotation rates and activity levels between their twin components, including cases throughout the lower main sequence and across a broad range of rotation-activity parameter space. In contrast, mismatches with $>$25% differences exist in rotation period for $21{\%}_{-7\%}^{+14\%}$ of twin pairs, in rotation amplitude for $67{\%}_{-15\%}^{+10\%}$ of pairs, in multi-year photometric variability for $33{\%}_{-9\%}^{+12\%}$ of pairs, and in H$\alpha$ activity for $21{\%}_{-6\%}^{+9\%}$ of pairs, with fully convective systems generally mismatched more often. Thus, roughly one out of five M dwarf twin sets does not match in rotation and/or activity despite otherwise identical fundamental parameters. Furthermore, we compile three key systems showing larger relative active/inactive H$\alpha$ mismatches. We propose the various mismatches likely stem from factors such as dynamo stochasticity, activity cycles, formative disk aspects, and/or star-planet interactions, depending on the system. These well-vetted twins offer ripe targets for many future investigations.

60 pages, 18 figures, 7 tables, submitted to AJ

References in corpus (80)

• Array Programming with NumPy
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• Gaia Data Release 3: Summary of the content and survey properties
• The Transiting Exoplanet Survey Satellite
• The Zwicky Transient Facility: System Overview, Performance, and First Results
• The generalised Lomb-Scargle periodogram. A new formalism for the floating-mean and Keplerian periodograms
• The K2 Mission: Characterization and Early results
• The Zwicky Transient Facility: Data Processing, Products, and Archive
• The All-Sky Automated Survey for Supernovae (ASAS-SN) Light Curve Server v1.0
• Gaia Early Data Release 3: Photometric content and validation
• How to Constrain Your M Dwarf: measuring effective temperature, bolometric luminosity, mass, and radius
• Second ROSAT all-sky survey (2RXS) source catalogue
• Measuring the rotation period distribution of field M-dwarfs with Kepler
• Assessing statistical significance of periodogram peaks
• The SRG/eROSITA all-sky survey: First X-ray catalogues and data release of the western Galactic hemisphere
• The H$\alpha$ emission of nearby M dwarfs and its relation to stellar rotation
• A Re-appraisal of the Habitability of Planets Around M Dwarf Stars
• The first XMM-Newton slew survey catalogue: XMMSL1
• The Zwicky Transient Facility Catalog of Periodic Variable Stars
• Trumpeting M Dwarfs with CONCH-SHELL: a Catalog of Nearby Cool Host-Stars for Habitable ExopLanets and Life
• The Solar Neighborhood XXXVII: The Mass-Luminosity Relation for Main Sequence M Dwarfs
• Gaia Data Release 3: Processing and validation of BP/RP low-resolution spectral data
• Magnetic Cycles and Rotation Periods of Late Type Stars from photometric time series
• Generalized investigation of the rotation-activity relation: Favouring rotation period instead of Rossby number
• TESS Eclipsing Binary Stars. I. Short cadence observations of 4584 eclipsing binaries in Sectors 1-26
• The Solar Neighborhood XLV. The Stellar Multiplicity Rate of M Dwarfs Within 25 pc
• CARMENES input catalogue of M dwarfs. I. Low-resolution spectroscopy with CAFOS
• Steady-state planet migration by the Kozai-Lidov mechanism in stellar binaries
• Magnetism, rotation, and nonthermal emission in cool stars -- Average magnetic field measurements in 292 M dwarfs
• The Sixth Data Release of the Radial Velocity Experiment (RAVE) -- I: Survey Description, Spectra and Radial Velocities
• The Factory and The Beehive II. Activity and Rotation in Praesepe and the Hyades
• Gaia Data Release 3. Astrometric binary star processing
• Gaia Data Release 3. Summary of the variability processing and analysis
• Gaia Data Release 1, Pre-processing and source list creation
• Stellar rotation periods from K2 Campaigns 0-18 -- Evidence for rotation period bimodality and simultaneous variability decrease
• The Solar Neighborhood XLIX: Nine Giant Planets Orbiting Nearby K Dwarfs, and the CHIRON Spectrograph's Radial Velocity Performance
• The global and small-scale magnetic fields of fully convective, rapidly spinning M dwarf pair GJ65A and B
• The Empirical Limits of Gyrochronology
• The Impact of Metallicity on the Evolution of Rotation and Magnetic Activity of Sun-Like Stars
• The SUPERWIDE Catalog: A Catalog of 99,203 Wide Binaries Found in Gaia and Supplemented by the SUPERBLINK High Proper Motion Catalog
• The Occurrence Rate of Terrestrial Planets Orbiting Nearby Mid-to-late M Dwarfs from TESS Sectors 1-42
• The Ca II infrared triplet's performance as an activity indicator compared to Ca II H and K
• Calibration of the Halpha Age-Activity relation for M dwarfs
• Evaluating Rotation Periods of M Dwarfs Across the Ages
• Surprisingly different starspot distributions on the near equal-mass equal-rotation-rate stars in the M dwarf binary GJ 65 AB
• Gaia Data Release 3: Gaia scan-angle dependent signals and spurious periods
• The Effect of Binarity on Stellar Rotation - Beyond the Reach of Tides
• SOAR Adaptive Module (SAM): seeing improvement with a UV laser
• Evidence for Metallicity-Dependant Spin Evolution in the Kepler field
• Gaia Data Release 3: Properties of the line broadening parameter derived with the Radial Velocity Spectrometer (RVS)
• Persistent starspot signals on M dwarfs: multi-wavelength Doppler observations with the Habitable-zone Planet Finder and Keck/HIRES
• Galactic Kinematics and Observed Flare Rates of a Volume-Complete Sample of Mid-to-Late M-dwarfs: Constraints on the History of the Stellar Radiation Environment of Planets Orbiting Low-mass Stars
• The unpopular Package: a Data-driven Approach to De-trend TESS Full Frame Image Light Curves
• Robo-AO M Dwarf Multiplicity Survey: Catalog
• Bridging the gap -- the disappearance of the intermediate period gap for fully convective stars, uncovered by new ZTF rotation periods
• Obliquities of Exoplanet Host Stars: 19 New and Updated Measurements, and Trends in the Sample of 205 Measurements
• The red dwarf pair GJ65AB: inflated, spinning twins of Proxima
• Photometric variability as a proxy for magnetic activity and its dependence on metallicity
• The beta Pictoris association low-mass members: membership assessment, rotation period distribution, and dependence on multiplicity
• Wide twin binaries are extremely eccentric: evidence of twin binary formation in circumbinary disks
• The Solar Neighborhood XLIX: New Discoveries and Orbits of M Dwarf Multiples with Speckle Interferometry at SOAR
• The influence of the environment on the spin evolution of low-mass stars. I. External photoevaporation of circumstellar disks
• Gaia Data Release 3. Stellar chromospheric activity and mass accretion from Ca II IRT observed by the Radial Velocity Spectrometer
• Stellar Cycles in Fully Convective Stars and a New Interpretation of Dynamo Evolution
• The Solar Neighborhood. XLVI. Revealing New M Dwarf Binaries and their Orbital Architectures
• Towards understanding dynamo action in M dwarfs
• Evidence from stellar rotation for early disc dispersal owing to close companions
• Complete X-ray census of Mdwarfs in the solar Neighborhood I. GJ 745 AB: Coronal-hole Stars in the 10 pc Sample
• Active Stars in the Spectroscopic Survey of Mid-to-Late M Dwarfs Within 15pc
• Rotation at the Fully Convective Boundary: Insights from Wide WD + MS Binary Systems
• Mind the Gap I: H$\alpha$ Activity of M Dwarfs Near the Partially/Fully Convective Boundary and a New H$\alpha$ Emission Deficiency Zone on the Main Sequence
• Photometric rotation periods for 107 M dwarfs from the APACHE survey
• Estimating the Convective Turnover Time
• The Solar Neighborhood LI: A Variability Survey of Nearby M Dwarfs with Planets from Months to Decades with TESS and the CTIO/SMARTS 0.9 m Telescope
• H$\alpha$ Emission From Active Equal-mass, Wide M Dwarf Binaries
• Towards a holistic magnetic braking model from the evolution of cataclysmic variables to stellar spin-down -- I: the spin-down of fully convective M-dwarfs
• Transitions in magnetic behavior at the substellar boundary
• Measuring Long Stellar Rotation Periods (>10 days) from TESS FFI Light Curves is Possible: An Investigation Using TESS and ZTF
• The Solar Neighborhood LII: M Dwarf Twin Binaries -- Presumed Identical Twins Appear Fraternal in Variability, Rotation, H$\alpha$, and X-rays
• Too fast to be single: Tidal evolution and photometric identification of stellar and planetary companions