# University of Hertfordshire

## Polarization of hot Jupiter systems: a likely detection of stellar activity and a possible detection of planetary polarization

Research output: Contribution to journalArticlepeer-review

### Documents

Final published version, 878 KB, PDF document

• Jeremy Bailey
• Kimberly Bott
• Daniel V. Cotton
• Lucyna Kedziora-Chudczer
• Jinglin Zhao
• Dag Evensberget
• Jonathan P. Marshall
• Duncan Wright
• P. W. Lucas
Original language English 2331-2345 15 Monthly Notices of the Royal Astronomical Society 502 2 25 Jan 2021 https://doi.org/10.1093/mnras/stab172 Published - 1 Apr 2021

### Abstract

We present high-precision linear polarization observations of four bright hot Jupiter systems ($\tau$ Boo, HD 179949, HD 189733 and 51 Peg) and use the data to search for polarized reflected light from the planets. The data for 51 Peg are consistent with a reflected light polarization signal at about the level expected with 2.8$\sigma$ significance and a false alarm probability of 1.9 per cent. More data will be needed to confirm a detection of reflected light in this system. HD 189733 shows highly variable polarization that appears to be most likely the result of magnetic activity of the host star. This masks any polarization due to reflected light, but a polarization signal at the expected level of $\sim$20 ppm cannot be ruled out. $\tau$ Boo and HD 179949 show no evidence for polarization due to reflected light. The results are consistent with the idea that many hot Jupiters have low geometric albedos. Conclusive detection of polarized reflected light from hot Jupiters is likely to require further improvements in instrument sensitivity.

### Notes

© 2021 The Authors. This is the final published version of an article which has been published in final form at https://doi.org/10.1093/mnras/stab172

ID: 24725572