Testing a scaling relation between coherent radio emission and physical parameters of hot magnetic stars

Abstract

Coherent radio emission via electron cyclotron maser emission (ECME) from hot magnetic stars was discovered more than two decades ago, but the physical conditions that make the generation of ECME favourable remain uncertain. Only recently was an empirical relation, connecting ECME luminosity with the stellar magnetic field and temperature, proposed to explain what makes a hot magnetic star capable of producing ECME. This relation was, however, obtained with just fourteen stars. Therefore, it is important to examine whether this relation is robust. With the aim of testing the robustness, we conducted radio observations of five hot magnetic stars. This led to the discovery of three more stars producing ECME. We find that the proposed scaling relation remains valid after the addition of the newly discovered stars. However we discovered that the magnetic field and effective temperature correlate for $T_{\mathrm{eff}}\lesssim 16$ kK (likely an artifact of the small sample size), rendering the proposed connection between ECME luminosity and $T_{\mathrm{eff}}$ unreliable. By examining the empirical relation in light of the scaling law for incoherent radio emission, we arrive at the conclusion that both types of emission are powered by the same magnetospheric phenomenon. Like the incoherent emission, coherent radio emission is indifferent to $T_{\mathrm{eff}}$ for late-B and A-type stars, but $T_{\mathrm{eff}}$ appears to become important for early-B type stars, possibly due to higher absorption, or, higher plasma density at the emission sites suppressing the production of the emission.

arXiv comment14 pages, 12 figures, accepted for publication in MNRAS

References in corpus (52)

• Gaia Data Release 2. Summary of the contents and survey properties
• The Gaia mission
• The LOFAR Two-metre Sky Survey - II. First data release
• The Rapid ASKAP Continuum Survey I: Design and First Results
• A Magnetic Confinement vs. Rotation Classification of Massive-Star Magnetospheres
• Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: II. The Effects of Field-Aligned Rotation
• Periodic Bursts of Coherent Radio Emission from an Ultracool Dwarf
• Magnetic fields of M dwarfs
• VAST: An ASKAP Survey for Variables and Slow Transients
• The Strongest Magnetic Fields on the Coolest Brown Dwarfs
• Magnetic field topology of the unique chemically peculiar star CU Virginis
• The Magnetic Early B-type Stars III: A main sequence magnetic, rotational, and magnetospheric biography
• X-ray emission from magnetic massive stars
• The Magnetic Early B-type Stars I: Magnetometry and Rotation
• Discovery of Rotational Braking in the Magnetic Helium-Strong Star Sigma Orionis E
• The population of M dwarfs observed at low radio frequencies
• An all-sky survey of circular polarisation at 200 MHz
• Revisiting the Rigidly Rotating Magnetosphere model for sigma Ori E. I. Observations and Data Analysis
• Auroral Radio Emission from Stars: the case of CU Virginis
• Monitoring the radio emission of Proxima Centauri
• MOBSTER -- VI. The crucial influence of rotation on the radio magnetospheres of hot stars
• Basic parameters and properties of the rapidly rotating magnetic helium strong B star HR7355
• The Magnetic Early B-type Stars IV: Breakout or Leakage? H$\alpha$ emission as a diagnostic of plasma transport in centrifugal magnetospheres
• A circular polarisation survey for radio stars with the Australian SKA Pathfinder
• A scaling relationship for non-thermal radio emission from ordered magnetospheres: from the top of the Main Sequence to planets
• Magnetic field topologies of the bright, weak-field Ap stars theta Aurigae and epsilon Ursae Majoris
• Discovery of a strong magnetic field in the rapidly rotating B2Vn star HR 7355
• The detection of variable radio emission from the fast rotating magnetic hot B-star HR7355 and evidence for its X-ray aurorae
• Magnetic field detection in the B2Vn star HR 7355
• How the breakout-limited mass in B-star centrifugal magnetospheres controls their circumstellar H-alpha emission
• First Detection of a Strong Magnetic Field on a Bursty Brown Dwarf: Puzzle Solved
• Centrifugal breakout reconnection as the electron acceleration mechanism powering the radio magnetospheres of early-type stars
• Magnetic field topology and chemical abundance distributions of the young, rapidly rotating chemically peculiar star HR5624
• The Magnetic Early B-type Stars II: stellar atmospheric parameters in the era of Gaia
• The surface magnetic field and chemical abundance distributions of the B2V helium-strong star HD184927
• Discovery of electron cyclotron MASER emission from the magnetic Bp star HD 133880 with the Giant Metrewave Radio Telescope
• Evidence for radio and X-ray auroral emissions from the magnetic B-type star rho Oph A
• An Analysis of the Rapidly Rotating Bp Star HD 133880
• First detections of 610 MHz radio emission from hot magnetic stars
• The magnetic field and spectral variability of the He-weak star HR 2949
• Discovery of Two Rare Rigidly-Rotating Magnetosphere Stars in the APOGEE Survey
• HD 35502: a hierarchical triple system with a magnetic B5IVpe primary
• The polarization mode of the auroral radio emission from the early-type star HD142301
• Simulating radio emission from Low Mass Stars
• The fifth main sequence magnetic B-type star showing coherent radio emission: is this really a rare phenomenon?
• Detection of coherent emission from the Bp star HD 142990 at uGMRT frequencies
• Searching for CU Vir-type cyclotron maser from σOri E: The role of the magnetic quadrupole component
• Radio masers on WX UMa: hints of a Neptune-sized planet, or magnetospheric reconnection?
• The auroral radio emission of the magnetic B-type star rho OphC
• Large closed-field corona of WX UMa evidenced from radio observations
• Unraveling the complex magnetosphere of the B star HD 133880 via wideband observation of coherent radio emission
• What leads to premature upper cut-off frequencies of auroral radio emission from hot magnetic stars?

Cited by in corpus (4)

• Magnetism in High-Mass Stars
• Discovery of Magnetospheric Interactions in the Doubly-Magnetic Hot Binary $\epsilon$ Lupi
• Spatially resolved centrifugal magnetosphere caught in motion around the secondary component of $\rho$ Oph A
• X-ray and radio data obtained by XMM-Newton and VLA constrain the stellar wind of the magnetic quasi-Wolf-Rayet star in HD45166