Magnetic Interactions in Orbital Dynamics

Bromley, Benjamin C.; Kenyon, Scott J.

doi:10.3847/1538-3881/ac9301

Cited by 5 publications

(1 citation statement)

References 68 publications

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“…Since magnetic forces between stars generally decline more rapidly with separation than tidal forces (e.g. Bromley & Kenyon 2022), the tidal effects will dominate in DMPP-3AB. A number of binary systems show signs of stimulated activity around periastron passage, suggesting a connection with tidal effects induced by the companion star (Moreno et al 2011).…”

Section: Periastron Eventsmentioning

confidence: 99%

DMPP-3: confirmation of short-period S-type planet(s) in a compact eccentric binary star system, and warnings about long-period RV planet detections

Stevenson,

Haswell,

Barnes

et al. 2023

Monthly Notices of the Royal Astronomical Society

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We present additional HARPS radial velocity observations of the highly eccentric (e ∼ 0.6) binary system DMPP-3AB, which comprises a K0V primary and a low-mass companion at the hydrogen burning limit. The binary has a 507 d orbital period and a 1.2 au semi-major axis. The primary component harbours a known 2.2 M⊕ planet, DMPP-3A b, with a 6.67 day orbit. New HARPS measurements constrain periastron passage for the binary orbit and add further integrity to previously derived solutions for both companion and planet orbits. Gaia astrometry independently confirms the binary orbit, and establishes the inclination of the binary is 63.89 ± 0.78○. We performed dynamical simulations which establish that the previously identified ∼800 d RV signal cannot be attributed to an orbiting body. The additional observations, a deviation from strict periodicity, and our new analyses of activity indicators suggest the ∼800 d signal is caused by stellar activity. We conclude that there may be long period planet “detections” in other systems which are similar misinterpreted stellar activity artefacts. Without the unusual eccentric binary companion to the planet-hosting star we could have accepted the ∼800 d signal as a probable planet. Further monitoring of DMPP-3 will reveal which signatures can be used to most efficiently identify these imposters. We also report a threshold detection (0.2 per cent FAP) of a ∼2.26 d periodicity in the RVs, potentially attributed to an Earth-mass S-type planet interior to DMPP-3A b.

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Section: Periastron Eventsmentioning

confidence: 99%

DMPP-3: confirmation of short-period S-type planet(s) in a compact eccentric binary star system, and warnings about long-period RV planet detections

Stevenson,

Haswell,

Barnes

et al. 2023

Monthly Notices of the Royal Astronomical Society

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Unravelling the Electrical Conductivity of Earth and Planets

Grayver

2024

Surv Geophys

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This review presents the progress made in the last decade in the field of large-scale electromagnetic (EM) induction with natural sources, which fluctuate at periods from seconds to years and originate in oceans, ionosphere and magnetosphere. These mechanisms produce field variations that can be used to image subsurface electrical structure of Earth and planets across scales and depths from the shallow crust to the lower mantle. In the last decade, we have seen a substantial progress made in different areas related to methods, observations and 3-D numerical modelling of EM phenomena at crustal and mantle scales. Specifically, new methods for handling complex ionospheric and magnetospheric sources were proposed, accompanied by more efficient forward and inverse modelling tools that allowed us to combine several broadband sources and constrain electrical conductivity on multiple scales simultaneously. Magnetic signals due to oceanic tides were established as a new source to probe conductivity of the sub-oceanic upper mantle. Further, the launch of ESA Swarm satellites in 2013 and their successful ongoing operation have marked a new era in the field of large-scale EM induction, unlocking a set of new opportunities, but also posing new challenges. These developments were backed by new lab measurements of electrical conductivity for mantle minerals at temperatures and pressures that are getting closer to the relevant pressure and temperature conditions in the mantle, alleviating the need for inaccurate extrapolations. The latter enabled more plausible quantitative estimates of water content, melt fractions and temperature in the mantle. In parallel, crust and mantle conductivity models along with developed modelling techniques have become an integral part of geomagnetic field and geomagnetically induced currents (GICs) modelling workflows, establishing new inter-disciplinary knowledge domains.

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Secular dipole-dipole stability of magnetic binaries

Aykroyd¹,

Bourgoin²,

Poncin-Lafitte³

et al. 2023

A&A

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Context. The presence of strong large-scale stable magnetic fields in a significant portion of early-type stars, white dwarfs, and neutron stars is well established. Despite this, the origins of these fields remain a subject of ongoing investigation, with theories including fossil fields, mergers, and shear-driven dynamos. One potential key for understanding the formation of these fields could lie in the connection between magnetism and binarity. Indeed, magnetism can play a significant role in the long-term orbital and precessional dynamics of binary systems. In gravitational wave astronomy, the advanced sensitivity of upcoming interferometric detectors such as LISA and the Einstein Telescope will enable the characterisation of the orbital inspirals of compact systems, including their magnetic properties. A comprehensive understanding of the dynamics of magnetism in these systems is necessary for the interpretation of the gravitational wave signals and to avoid bi the wdes in the calibration of instruments. This knowledge can additionally be used to create new magnetic population models and provide insight into the nature and origins of their internal magnetic fields. Aims. The aim of this study is to investigate the secular spin precession dynamics of binary systems under pure magnetic dipole-dipole interactions, with a focus on stars with strong, stable, and predominantly dipolar fields. Methods. We employed an orbit-averaging procedure for the spin precession equations from which we derived an effective secular description. By minimising the magnetic interaction energy of the system, we obtained the configurations of spin equilibrium and their respective stabilities. Finally, we also derived a set of conditions required for the validity of our assumptions to hold. Results. We show that among the four states of equilibrium, there is a single secular state that is globally stable, corresponding to the configuration where the spin and magnetic axes of one star are reversed with respect to the companions’, and orthogonal to the orbital plane. Our results are compared to traditional methods of finding instantaneous states of equilibrium, in which orbital motion is generally neglected. Finally, we provide analytical solutions in the neighbourhood of the stable configuration, which can be used to derive secular orbital evolution in the context of gravitational wave astronomy.

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Magnetic Interactions in Orbital Dynamics

Cited by 5 publications

References 68 publications

DMPP-3: confirmation of short-period S-type planet(s) in a compact eccentric binary star system, and warnings about long-period RV planet detections

DMPP-3: confirmation of short-period S-type planet(s) in a compact eccentric binary star system, and warnings about long-period RV planet detections

Unravelling the Electrical Conductivity of Earth and Planets

Secular dipole-dipole stability of magnetic binaries

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