Title: Mapping Starspots on AU Mic to Complement Hubble Transmission Spectroscopy of its
Young Planet

Abstract: AU Mic is a 24 Myr pre-main sequence M dwarf in the stellar neighborhood (10pc) which is very active and has a rotation period of 4.86 days. There are at least two known planets orbiting AU Mic, AU Mic b and c are both warm Neptunes (R_p,_b = 4.1 R_e and R_p,_c = 3.2 R_e) on 8.46 and 18.86-day periods, respectively [see Plavchan+ 2020 and Martioli+ 2021]. AU Mic has a heavily spotted surface as evidenced in its strong photometric rotational modulations. The transmission spectrum of AU Mic b is being observed with Hubble, and we aim to better understand unocculted starspots using ground-based photometry and spectra in order to complement those observations and better constrain the planetary transmission spectrum. Unocculted spots can introduce spurious transit depth variations seen in transmission spectra, known as the Transit Light Source Effect (TLSE) (Rackham+ 2018). Unocculted spots affect not only the in-transit interpretation of transmission spectra, but also the out-of-transit temporal and wavelength variations in the stellar flux. By studying the stellar spectrum out of transit, we may be able to independently constrain the spectral signatures of AU Mic’s starspots so we can correct their effect in the atmospheric observations of the planet. We gathered LCO 0.4m SBIG photometry in broad bandpasses to study the star’s rotational modulations and LCO NRES high-resolution spectra to model the effect of multiple spectral components on the integrated spectrum of the star. Our expanded use of various techniques to study starspots will help us better understand this system and may have applications for interpreting the transmission spectra for exoplanets transiting stars of a wide range of activity levels.

Host: Michael Palumbo

Seminar held in 538 Davey or please email CEHW-SEMINAR-QUESTIONS@lists.psu.edu to attend virtually.