NGTS-7Ab: An ultra-short period brown dwarf transiting a tidally-locked and active M dwarf

Abstract

We present the discovery of NGTS-7Ab, a high mass brown dwarf transiting an M dwarf with a period of 16.2 hours, discovered as part of the Next Generation Transit Survey (NGTS). This is the shortest period transiting brown dwarf around a main or pre-main sequence star to date. The M star host (NGTS-7A) has an age of roughly 55 Myr and is in a state of spin-orbit synchronisation, which we attribute to tidal interaction with the brown dwarf acting to spin up the star. The host star is magnetically active and shows multiple flares across the NGTS and follow up lightcurves, which we use to probe the flare-starspot phase relation. The host star also has an M star companion at a separation of 1.13 arcseconds with very similar proper motion and systemic velocity, suggesting the NGTS-7 system is a hierarchical triple. The combination of tidal synchronisation and magnetic braking is expected to drive ongoing decay of the brown dwarf orbit, with a remaining lifetime of only 5-10 Myr.

arXiv comment21 pages, 16 figures, accepted for publication in the Monthly Notices of the Royal Astronomical Society

References in corpus (83)

• Astropy: A Community Python Package for Astronomy
• emcee: The MCMC Hammer
• Gaia Data Release 2. Summary of the contents and survey properties
• The Gaia mission
• PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
• The Transiting Exoplanet Survey Satellite
• Intrinsic Colors, Temperatures, and Bolometric Corrections of Pre-Main Sequence Stars
• Gaia Data Release 2: The astrometric solution
• A new extensive library of PHOENIX stellar atmospheres and synthetic spectra
• A Survey of Stellar Families: Multiplicity of Solar-Type Stars
• Estimating distances from parallaxes IV: Distances to 1.33 billion stars in Gaia Data Release 2
• Evolutionary models for cool brown dwarfs and extrasolar giant planets. The case of HD 20945
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• Evolutionary models for very-low-mass stars and brown dwarfs with dusty atmospheres
• Models of Stars, Brown Dwarfs and Exoplanets
• The stellar activity-rotation relationship and the evolution of stellar dynamos
• Gaia Data Release 2: Photometric content and validation
• The Mass Dependence Between Protoplanetary Disks and their Stellar Hosts
• How to Constrain Your M Dwarf: measuring effective temperature, bolometric luminosity, mass, and radius
• Gaia Data Release 2: Catalogue validation
• BANYAN. XI. The BANYAN $\Sigma$ multivariate Bayesian algorithm to identify members of young associations within 150 pc
• Superflares on Solar Type Stars Observed with Kepler I. Statistical Properties of Superflares
• Tidal dissipation in stars and giant planets
• How Dry is the Brown Dwarf Desert?: Quantifying the Relative Number of Planets, Brown Dwarfs and Stellar Companions around Nearby Sun-like Stars
• SkyMapper Southern Survey: First Data Release (DR1)
• Gaia Data Release 1: Catalogue validation
• The Transit Light Source Effect: False Spectral Features and Incorrect Densities for M-dwarf Transiting Planets
• Kepler Flares I. Active and Inactive M dwarfs
• How to Constrain Your M dwarf II: the mass-luminosity-metallicity relation from 0.075 to 0.70$M_{\odot }$
• An ALMA Survey of Protoplanetary Disks in the $\sigma$ Orionis Cluster
• The Next Generation Transit Survey (NGTS)
• The stellar rotation--activity relationship in fully convective M dwarfs
• On the tidal evolution of Hot Jupiters on inclined orbits
• LDTk: Limb Darkening Toolkit
• The Solar Neighborhood XXXVII: The Mass-Luminosity Relation for Main Sequence M Dwarfs
• Spin-Orbit Evolution Of Short-Period Planets
• A Kepler Study of Starspot Lifetimes with Respect to Light Curve Amplitude and Spectral Type
• Statistical Properties of Brown Dwarf Companions: Implications for Different Formation Mechanisms
• The Discovery of Ellipsoidal Variations in the Kepler Light Curve of HAT-P-7
• ELLC - a fast, flexible light curve model for detached eclipsing binary stars and transiting exoplanets
• WASP-42 b and WASP-49 b: two new transiting sub-Jupiters
• Tidal Synchronization and Differential Rotation of Kepler Eclipsing Binaries
• Variability in the Atmosphere of the Hot Giant Planet HAT-P-7 b
• Gaia Data Release 1, Pre-processing and source list creation
• Transiting exoplanets from the CoRoT space mission. XV. CoRoT-15b: a brown dwarf transiting companion
• Wide Binaries in Tycho-{\it Gaia}: Search Method and the Distribution of Orbital Separations
• An Empirical Correction for Activity Effects on the Temperatures, Radii, and Estimated Masses of Low-Mass Stars and Brown Dwarfs
• LHS6343C: A Transiting Field Brown Dwarf Discovered by the Kepler Mission
• Age Determination in Upper Scorpius with Eclipsing Binaries
• NGTS-1b: A hot Jupiter transiting an M-dwarf
• New low-mass eclipsing binary systems in Praesepe discovered by K2
• Are falling planets spinning up their host stars?
• Fifteen new T dwarfs discovered in the UKIDSS Large Area Survey
• Tracers of Chromospheric Structure I: Observations of Ca II K and H alpha in M Dwarfs
• The brown dwarf desert as a consequence of orbital migration
• NGTS-4b: A sub-Neptune Transiting in the Desert
• A high binary fraction for the most massive close-in giant planets and brown dwarf desert members
• Effect of the stellar spin history on the tidal evolution of close-in planets
• New ultra-cool and brown dwarf candidates in Gaia DR2
• NLTT 41135: a field M-dwarf + brown dwarf eclipsing binary in a triple system, discovered by the MEarth observatory
• HATS-17b: A Transiting Compact Warm Jupiter in a 16.3 Days Circular Orbit
• Investigating the Rotational Phase of Stellar Flares on M dwarfs Using K2 Short Cadence Data
• Evolution of angular-momentum-losing exoplanetary systems : Revisiting Darwin stability
• The effect of starspots on the radii of low-mass pre-main sequence stars
• The discovery of WASP-151b, WASP-153b, WASP-156b: Insights on giant planet migration and the upper boundary of the Neptunian desert
• EPIC201702477b: A Long Period Transiting Brown Dwarf from K2
• On the Selection of Photometric Planetary Transits
• Detection of a giant flare displaying quasi-periodic pulsations from a pre-main sequence M star with NGTS
• WASP-128b: a transiting brown dwarf in the dynamical-tide regime
• K2-137 b: an Earth-sized planet in a 4.3-hour orbit around an M-dwarf
• WISE J080822.18-644357.3 - a 45 Myr-old accreting M dwarf hosting a primordial disc
• Four new eclipsing mid M-dwarf systems from the New Luyten Two Tenths catalog
• New substellar discoveries from Kepler and K2: Is there a brown dwarf desert?
• Centroid vetting of transiting planet candidates from the Next Generation Transit Survey
• Exploring the Brown Dwarf Desert: New Substellar Companions from the SDSS-III MARVELS Survey
• Identifying Ultra-Cool Dwarfs at Low Galactic Latitudes: A Southern Candidate Catalogue
• Ground-based detection of G star superflares with NGTS
• Short duration high amplitude flares detected on the M dwarf star KIC 5474065
• Evolution of Exoplanets and their Parent Stars
• NGTS-2b: An inflated hot-Jupiter transiting a bright F-dwarf
• Can brown dwarfs survive on close orbits around convective stars?
• Validating TGAS wide binaries with Gaia DR2 Radial Velocities and Parallaxes
• A transiting M-dwarf showing beaming effect in the field of Ruprecht 147

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