@article{7460942ddc684067ba431b575c57c9b9,
title = "Transit timing variations for AU Microscopii b and c",
abstract = "We explore the transit timing variations (TTVs) of the young (22 Myr) nearby AU Mic planetary system. For AU Mic b, we introduce three Spitzer (4.5 μm) transits, five TESS transits, 11 LCO transits, one PEST transit, one Brierfield transit, and two transit timing measurements from Rossiter–McLaughlin observations; for AU Mic c, we introduce three TESS transits. We present two independent TTV analyses. First, we use EXOFASTv2 to jointly model the Spitzer and ground-based transits and obtain the midpoint transit times. We then construct an O − C diagram and model the TTVs with Exo-Striker. Second, we reproduce our results with an independent photodynamical analysis. We recover a TTV mass for AU Mic c of 10.8−2.2+2.3 M⊕. We compare the TTV-derived constraints to a recent radial velocity (RV) mass determination. We also observe excess TTVs that do not appear to be consistent with the dynamical interactions of b and c alone or due to spots or flares. Thus, we present a hypothetical nontransiting “middle-d” candidate exoplanet that is consistent with the observed TTVs and candidate RV signal and would establish the AU Mic system as a compact resonant multiplanet chain in a 4:6:9 period commensurability. These results demonstrate that the AU Mic planetary system is dynamically interacting, producing detectable TTVs, and the implied orbital dynamics may inform the formation mechanisms for this young system. We recommend future RV and TTV observations of AU Mic b and c to further constrain the masses and confirm the existence of possible additional planet(s).",
author = "Wittrock, {Justin M.} and Stefan Dreizler and Reefe, {Michael A.} and Morris, {Brett M.} and Plavchan, {Peter P.} and Lowrance, {Patrick J.} and Brice-Olivier Demory and Ingalls, {James G.} and Gilbert, {Emily A.} and Thomas Barclay and Cale, {Bryson L.} and Collins, {Karen A.} and Collins, {Kevin I.} and Crossfield, {Ian J. M.} and Diana Dragomir and Eastman, {Jason D.} and Mufti, {Mohammed El} and Dax Feliz and Jonathan Gagn{\'e} and Eric Gaidos and Peter Gao and Geneser, {Claire S.} and Leslie Hebb and Henze, {Christopher E.} and Horne, {Keith D.} and Jenkins, {Jon M.} and Jensen, {Eric L. N.} and Kane, {Stephen R.} and Laurel Kaye and Eder Martioli and Monsue, {Teresa A.} and Enric Pall{\'e} and Quintana, {Elisa V.} and Radford, {Don J.} and Veronica Roccatagliata and Schlieder, {Joshua E.} and Schwarz, {Richard P.} and Avi Shporer and Stassun, {Keivan G.} and Christopher Stockdale and Thiam-Guan Tan and Tanner, {Angelle M.} and Andrew Vanderburg and Vega, {Laura D.} and Songhu Wang",
note = "P.P.P. acknowledges support from NASA (Exoplanet Research Program award No. 80NSSC20K0251, TESS Cycle 3 Guest Investigator Program award No. 80NSSC21K0349, JPL Research and Technology Development, and Keck Observatory Data Analysis), the NSF (Astronomy and Astrophysics grant Nos. 1716202 and 2006517), and the Mt. Cuba Astronomical Foundation. D.D. acknowledges support from the TESS Guest Investigator Program grant No. 80NSSC21K0108 and NASA Exoplanet Research Program grant No. 18-2XRP18_2-0136. E.G. acknowledges support from NASA Exoplanet Research Program award No. 80NSSC20K0251. The material is based upon work supported by NASA under award No. 80GSFC21M0002. L.D.V. acknowledges funding support from the Heising-Simons Astrophysics Postdoctoral Launch Program through a grant to Vanderbilt University.",
year = "2022",
month = jul,
day = "1",
doi = "10.3847/1538-3881/ac68e5",
language = "English",
volume = "164",
journal = "Astronomical Journal",
issn = "0004-6256",
publisher = "American Astronomical Society",
number = "1",
}