The modulation of SiO maser polarization by Jovian planets

TL;DR

This paper proposes a novel method to detect Jovian planets around AGB stars by observing periodic modulation in SiO maser polarization caused by precessing magnetospheres, offering a complementary approach to traditional planet searches.

Contribution

It introduces models predicting polarization modulation in SiO masers due to Jovian magnetospheres, and suggests observational strategies combining single-dish and VLBI techniques for detection.

Findings

Polarization is periodically modulated by precessing Jovian magnetospheres.

Detection requires dense time sampling and careful calibration.

Linear polarization is more affected by confusion than circular polarization.

Abstract

Searching for planets in the atmosphere of AGB stars is difficult, due to confusion with the stellar wind and pulsations. The aim here is to provide a complementary strategy for planet search in such a dense environment. The polarization properties of SiO masers, especially their circular polarization, are, under certain conditions, good tracers for rapid magnetospheric events. A Jovian planet with a magnetosphere whose dipole axis is misaligned with its rotation axis, naturally provides such conditions. Here I present several models showing that the polarization will be periodically modulated. Single-dish monitoring with a sufficiently dense time sampling and a carefully calibrated polarimeter, in combination with VLBI observations, are suited to detect and locate a periodic modulation of the circular maser polarization due to a precessing Jovian magnetosphere. The phenomenon will be rare, because a favourable arrangement of maser and magnetosphere is needed, otherwise the polarization may be below the detection threshold, especially if the maser is unsaturated. Linear polarization, though exhibiting a qualitatively similar modulation, is likely to suffer more from confusion due to beam dilution, even in VLBI observations.