Diving Beneath the Sea of Stellar Activity: Chromatic Radial Velocities of the Young AU Mic Planetary System
Barclay, Thomas; Latham, David W.; Quinn, Samuel N.; Berlind, Perry; Calkins, Michael L.; Esquerdo, Gilbert A.; Dreizler, Stefan; Tamura, Motohide; Kane, Stephen R.; Gaidos, Eric; Hirano, Teruyuki; Fulton, Benjamin J.; Howard, Andrew W.; Teske, Johanna; Collins, Kevin I.; Narita, Norio; Gagné, Jonathan; Twicken, Joseph D.; Plavchan, Peter; Reiners, Ansgar; Quirrenbach, Andreas; Gao, Peter; Tanner, Angelle; Wright, Duncan; Zohrabi, Farzaneh; Anglada-Escudé, Guillem; Geneser, Claire; Martioli, Eder; Reefe, Michael; Pallé, Enric; Klein, Baptiste; Kotani, Takayuki; Henze, Christopher; Cale, Bryson L.; El Mufti, Mohammed; Vermilion, David; Wittrock, Justin; Gilbert, Emily A.; Jenkins, Jon; Caballero, José A.; Boyd, Patricia; Ribas, Ignasi; Burke, Christopher; Addison, Brett; Stibbards, Caitlin; Villaseñor, Joel; Béjar, Víctor J. S.; Xuesong Wang, Sharon; Amado, Pedro J.; Lee, Rena A.; Lodieu, Nicolas; Rosa Zapatero Osorio, María; Wittenmyer, Robert; Kotnana, Srihan; Kidwell, Richard
United States, Canada, Spain, Germany, China, United Kingdom, France, Brazil, Australia, Japan
Abstract
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 ~ 8.46 days, ${R}_{b}={4.38}_{-0.18}^{+0.18}\ {R}_{\oplus }$ , P c ~ 18.86 days, ${R}_{c}={3.51}_{-0.16}^{+0.16}\ {R}_{\oplus }$ . With visible RVs from Calar Alto high-Resolution search for M dwarfs with Exo-earths with Near-infrared and optical echelle Spectrographs (CARMENES)-VIS, CHIRON, HARPS, HIRES, MINERVA-Australis, and Tillinghast Reflector Echelle Spectrograph, as well as near-infrared (NIR) RVs from CARMENES-NIR, CSHELL, IRD, iSHELL, NIRSPEC, and SPIRou, we provide a 5σ upper limit to the mass of AU Mic c of M c ≤ 20.13 M ⊕ 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 multiwavelength Gaussian process model, we demonstrate the ability to recover injected planets at 5σ significance with semi-amplitudes down to ≈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 ~50% for such signals with our model.