Optical I-band Linear Polarimetry of the Magnetar 4U 0142+61 with Subaru

Understand

The magnetar 4U~0142+61 has been well studied at optical and infrared wavelengths and is known to have a complicated broad-band spectrum over the wavelength range.

• Here we report the result from our linear imaging polarimetry of the magnetar at optical $I$-band.
• From the polarimetric observation carried out with the 8.2-m Subaru telescope, we determine the degree of linear polarization $P=1.0\pm$3.4\%, or $P\leq$5.6\% (90\% confidence level).
• Considering models suggested for optical emission from magnetars, we discuss the implications of our result.