Diving Beneath the Sea of Stellar Activity: Chromatic Radial Velocities of the Young AU Mic Planetary System

Kavli Affiliate: Christopher Burke

| First 5 Authors: Bryson Cale, Michael Reefe, Peter Plavchan, Angelle Tanner, Eric Gaidos

| Summary:

We present updated radial-velocity (RV) analyses of the AU Mic system. AU Mic
is a young (22 Myr) early M dwarf known to host two transiting planets –
$P_{b}sim8.46$ days, $R_{b}=4.38_{-0.18}^{+0.18} R_{oplus}$,
$P_{c}sim18.86$ days, $R_{c}=3.51_{-0.16}^{+0.16} R_{oplus}$. With visible
{textsc{Minerva}}}-Australis, and TRES, as well as near-infrared (NIR) RVs
from CARMENES-NIR, CSHELL, IRD, iSHELL, NIRSPEC, and SPIRou, we provide a
$5sigma$ upper limit to the mass of AU Mic c of $M_{c}leq20.13 M_{oplus}$
and present a refined mass of AU Mic b of $M_{b}=20.12_{-1.57}^{+1.72}
M_{oplus}$. Used in our analyses is a new RV modeling toolkit to exploit the
wavelength dependence of stellar activity present in our RVs via
wavelength-dependent Gaussian processes. By obtaining near-simultaneous visible
and near-infrared RVs, we also compute the temporal evolution of RV-“color”
and introduce a regressional method to aid in isolating Keplerian from stellar
activity signals when modeling RVs in future works. Using a multi-wavelength
Gaussian process model, we demonstrate the ability to recover injected planets
at $5sigma$ significance with semi-amplitudes down to $approx$
10,m,s$^{-1}$ with a known ephemeris, more than an order of magnitude below
the stellar activity amplitude. However, we find that the accuracy of the
recovered semi-amplitudes is $sim$50% for such signals with our model.

| Search Query: ArXiv Query: search_query=au:”Christopher Burke”&id_list=&start=0&max_results=10

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