Detection of coherent emission from the Bp star HD 142990 at uGMRT frequencies

Abstract

HD 142990 is a Bp-type star with a nearly dipolar surface magnetic field of kG strength. Recently Lenc et al. (2018) reported the tentative discovery of Electron Cyclotron Maser Emission (ECME) from this star at 200 MHz. This type of emission has been observed from only three other hot magnetic stars. In this paper, we present our observations of HD 142990 with the upgraded Giant Metrewave Radio telescope (uGMRT) at 550-804 MHz and with the legacy GMRT at 1420 MHz near the rotational phases of the nulls of the longitudinal magnetic field. We found strong enhancements in flux density in both circular polarisations suggesting an ECME bandwith of at least 1.2 GHz (200-1420 MHz). In one of the observation sessions, we observed enhancements with opposite circular polarisations from the same magnetic pole. This has not been reported in any other hot magnetic star known to exhibit ECME. In order to explain this unusual finding, we suggest a scenario that involves a transition of the dominant mode of ECME between the magneto-ionic modes.

arXiv commentAccepted for publication in the ApJ

References in corpus (20)

• Grids of stellar models with rotation - I. Models from 0.8 to 120 Msun at solar metallicity (Z = 0.014)
• Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: I. Isothermal, Nonrotating, Radially Driven Flow
• A Magnetic Confinement vs. Rotation Classification of Massive-Star Magnetospheres
• Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: III. Angular Momentum Loss and Rotational Spindown
• The MiMeS survey of magnetism in massive stars: Magnetic analysis of the O-type stars
• Evolutionary state of magnetic chemically peculiar stars
• Magnetic field topology of the unique chemically peculiar star CU Virginis
• The Magnetic Early B-type Stars I: Magnetometry and Rotation
• An all-sky survey of circular polarisation at 200 MHz
• Auroral Radio Emission from Stars: the case of CU Virginis
• K2 space photometry reveals rotational modulation and stellar pulsations in chemically peculiar A and B stars
• Surprising variations in the rotation of the chemically peculiar stars CU Virginis and V901 Orionis
• The radio lighthouse CU Virginis: the spindown of a single main sequence star
• 3D-modelling of the stellar auroral radio emission
• The Magnetic Early B-type Stars II: stellar atmospheric parameters in the era of Gaia
• Discovery of electron cyclotron MASER emission from the magnetic Bp star HD 133880 with the Giant Metrewave Radio Telescope
• First detections of 610 MHz radio emission from hot magnetic stars
• Observations and modelling of pulsed radio emission from CU Virginis
• Observations of radio pulses from CU Virginis
• The polarization mode of the auroral radio emission from the early-type star HD142301

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• Testing a scaling relation between coherent radio emission and physical parameters of hot magnetic stars
• Unraveling the complex magnetosphere of the B star HD 133880 via wideband observation of coherent radio emission
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