Discovery and Characterization of a Rare Magnetic Hybrid Cephei Slowly Pulsating B-type Star in an Eclipsing Binary in the Young Open Cluster NGC 6193
arXiv:2102.06151 · doi:10.3847/1538-4357/abe5a8
Abstract
As many as 10\% of OB-type stars have global magnetic fields, which is surprising given their internal structure is radiative near the surface. A direct probe of internal structure is pulsations, and some OB-type stars exhibit pressure modes ( Cep pulsators) or gravity modes (slowly pulsating B-type stars; SPBs); a few rare cases of hybrid Cep/SPBs occupy a narrow instability strip in the H-R diagram. The most precise fundamental properties of stars are obtained from eclipsing binaries (EBs), and those in clusters with known ages and metallicities provide the most stringent constraints on theory. Here we report the discovery that HD 149834 in the 5 Myr cluster NGC 6193 is an EB comprising a hybrid Cep/SPB pulsator and a highly irradiated low-mass companion. We determine the masses, radii, and temperatures of both stars; the 9.7 M primary resides in the instability strip where hybrid pulsations are theoretically predicted. The presence of both SPB and Cep pulsations indicates that the system has a near-solar metallicity, and is in the second half of the main-sequence lifetime. The radius of the 1.2 M companion is consistent with theoretical pre-main-sequence isochrones at 5 Myr, but its temperature is much higher than expected, perhaps due to irradiation by the primary. The radius of the primary is larger than expected, unless its metallicity is super-solar. Finally, the light curve shows residual modulation consistent with the rotation of the primary, and Chandra observations reveal a flare, both of which suggest the presence of starspots and thus magnetism on the primary.
arXiv commentAccepted for publication in The Astrophysical Journal, 15 pages, 14 figures
References in corpus (75)
- emcee: The MCMC Hammer
- PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
- The Transiting Exoplanet Survey Satellite
- Binary interaction dominates the evolution of massive stars
- Gaia Data Release 2: The astrometric solution
- Accurate masses and radii of normal stars: modern results and applications
- The Revised TESS Input Catalog and Candidate Target List
- Gaia Data Release 2: using Gaia parallaxes
- A Gaia DR2 view of the Open Cluster population in the Milky Way
- Multiple Stellar Populations in Globular Clusters
- Classical Be Stars: Rapidly Rotating B Stars with Viscous Keplerian Decretion Disks
- The Galactic O-Star Spectroscopic Survey (GOSSS). II. Bright Southern Stars
- Bayesian Blocks, A New Method to Analyze Structure in Photon Counting Data
- Limb and gravity-darkening coefficients for the TESS satellite at several metallicities, surface gravities, and microturbulent velocities
- Binning is sinning: morphological light-curve distortions due to finite integration time
- Sub-surface convection zones in hot massive stars and their observable consequences
- Initial Characteristics of Kepler Short Cadence Data
- Internal Gravity Waves in Massive Stars: Angular Momentum Transport
- Tight asteroseismic constraints on core overshooting and diffusive mixing in the slowly rotating pulsating B8.3V star KIC 10526294
- Low-frequency gravity waves in blue supergiants revealed by high-precision space photometry
- LSPM J1112+7626: detection of a 41-day M-dwarf eclipsing binary from the MEarth transit survey
- Delay Times and Rates for Type Ia Supernovae and Thermonuclear Explosions from Double-detonation Sub-Chandrasekhar Mass Models
- Stellar Rotation in Young Clusters. I. Evolution of Projected Rotational Velocity Distributions
- Evidence for nonlinear resonant mode coupling in the Beta Cep star HD 180642 (V1449 Aql) from CoRoT space-based photometry
- Populating the Galaxy with low-mass X-ray binaries
- Variability of OB stars from TESS southern Sectors 1-13 and high-resolution IACOB and OWN spectroscopy
- Untangling the Galaxy. II. Structure within 3 kpc
- Variability in the CoRoT photometry of three hot O-type stars. HD 46223, HD 46150 and HD 46966
- Photometric detection of internal gravity waves in upper main-sequence stars. II. Combined TESS photometry and high-resolution spectroscopy
- Three-Dimensional Simulations of Massive Stars: I. Wave Generation and Propagation
- Diverse Variability of O and B Stars Revealed from 2-minute Cadence Light Curves in Sectors 1 and 2 of the TESS Mission: Selection of an Asteroseismic Sample
- Carina OB Stars: X-ray Signatures of Wind Shocks and Magnetic Fields
- Investigating the lack of main-sequence companions to massive Be stars
- NGC 1866: First Spectroscopic Detection of Fast Rotating Stars in a Young LMC Cluster
- Different stellar rotation in the two main sequences of the young globular cluster NGC1818: first direct spectroscopic evidence
- The eccentric massive binary V380 Cyg: revised orbital elements and interpretation of the intrinsic variability of the primary component
- KIC 3240411 - the hottest known SPB star with the asymptotic g-mode period spacing
- Testing the effects of opacity and the chemical mixture on the excitation of pulsations in B stars of the Magellanic Clouds
- Stellar Rotation in Young Clusters. II. Evolution of Stellar Rotation and Surface Helium Abundance
- Core-Halo Age Gradients and Star Formation in the Orion Nebula and NGC~2024 Young Stellar Clusters
- The Impact of Enhanced Iron Opacity on Massive Star Pulsations: Updated Instability Strips
- The ESO Diffuse Interstellar Bands Large Exploration Survey: EDIBLES I. Project description, survey sample and quality assessment
- Cluster kinematics and stellar rotation in NGC 419 with MUSE and adaptive optics
- Fully compressible simulations of waves and core convection in main-sequence stars
- Domains of pulsational instability of low-frequency modes in rotating upper main-sequence stars
- Magnetic OB[A] Stars with TESS: probing their Evolutionary and Rotational properties (MOBSTER) - I. First-light observations of known magnetic B and A stars
- Resolved astrometric orbits of ten O-type binaries
- A Young Cluster With an Extended Main Sequence Turnoff: Confirmation of a Prediction of the Stellar Rotation Scenario
- K2 photometry and HERMES spectroscopy of the blue supergiant rho Leo: rotational wind modulation and low-frequency waves
- Confirmation of simultaneous p and g mode excitation in HD 8801 and Gamma Peg from time-resolved multicolour photometry of six candidate "hybrid" pulsators
- Low-frequency variability in massive stars: Core generation or surface phenomenon?
- Evidence for a physically bound third component in HD 150136
- Discovery of Cep pulsations in the eclipsing binary V453 Cygni
- Pulsation among TESS A and B stars and the Maia variables
- Discrepancies in the ages of young star clusters; evidence for mergers?
- X-ray and IR Point Source Identification and Characteristics in the Embedded, Massive Star-Forming Region RCW 108
- Order Out of Chaos: Slowly Reversing Mean Flows Emerge from Turbulently Generated Internal Waves
- The CoRoT B-type binary HD50230: a prototypical hybrid pulsator with g-mode period and p-mode frequency spacings
- Two-Dimensional Simulations of Internal Gravity Waves in The Radiation Zones of Intermediate-Mass Stars
- The Projected Rotational Velocity Distribution of a Sample of OB stars from a Calibration based on Synthetic He I lines
- A New Class of Nascent Eclipsing Binaries with Extreme Mass Ratios
- Chandra X-ray Observations of the Young Stellar Cluster NGC 6193 in the Ara OB1 Association
- The BinaMIcS project: understanding the origin of magnetic fields in massive stars through close binary systems
- Three-dimensional orbits of the triple-O stellar system HD 150136
- Isochrone-cloud fitting of the extended Main-Sequence Turn-Off of young clusters
- Pulsating B-type stars in the open cluster NGC 884: frequencies, mode identification and asteroseismology
- The Cep/SPB star 12 Lacertae: extended mode identification and complex seismic modelling
- The Ara OB1a association: Stellar population and star formation history
- The effects of the overshooting of the convective core on main-sequence turnoffs of young- and intermediate-age star clusters
- Ensemble asteroseismology of pulsating B-type stars in NGC 6910
- A remarkable change of the spectrum of the magnetic Of?p star HD 148937 reveals evidence of an eccentric, high-mass binary
- Direct Detection of the Tertiary Component in the Massive Multiple HD 150 136 with VLTI
- Compositional differences between the component stars of eclipsing close binary systems showing chemical peculiarities
- The 2003-4 multisite photometric campaign for the Beta Cephei and eclipsing star 16 (EN) Lacertae with an Appendix on 2 Andromedae, the variable comparison star
- Interstellar extinction in twenty open star clusters