The TESS-Keck Survey. III. A Stellar Obliquity Measurement of TOI-1726 c

October 2020 • 2020AJ....160..193D

Authors • Dai, Fei • Roy, Arpita • Fulton, Benjamin • Robertson, Paul • Hirsch, Lea • Isaacson, Howard • Albrecht, Simon • Mann, Andrew W. • Kristiansen, Martti H. • Batalha, Natalie M. • Beard, Corey • Behmard, Aida • Chontos, Ashley • Crossfield, Ian J. M. • Dalba, Paul A. • Dressing, Courtney • Giacalone, Steven • Hill, Michelle • Howard, Andrew W. • Huber, Daniel • Kane, Stephen R. • Kosiarek, Molly • Lubin, Jack • Mayo, Andrew • Mocnik, Teo • Akana Murphy, Joseph M. • Petigura, Erik A. • Rosenthal, Lee • Rubenzahl, Ryan A. • Scarsdale, Nicholas • Weiss, Lauren M. • Van Zandt, Judah • Ricker, George R. • Vanderspek, Roland • Latham, David W. • Seager, Sara • Winn, Joshua N. • Jenkins, Jon M. • Caldwell, Douglas A. • Charbonneau, David • Daylan, Tansu • Günther, Maximilian N. • Morgan, Edward • Quinn, Samuel N. • Rose, Mark E. • Smith, Jeffrey C.

Abstract • We report the measurement of a spectroscopic transit of TOI-1726c, one of two planets transiting a G-type star with V = 6.9 in the Ursa Major Moving Group (∼400 Myr). With a precise age constraint from cluster membership, TOI-1726 provides a great opportunity to test various obliquity excitation scenarios that operate on different timescales. By modeling the Rossiter-McLaughlin (RM) effect, we derived a sky-projected obliquity of $-{1}_{-32}^{{+35}^\circ} $ . This result rules out a polar/retrograde orbit and is consistent with an aligned orbit for planet c. Considering the previously reported, similarly prograde RM measurement of planet b and the transiting nature of both planets, TOI-1726 tentatively conforms to the overall picture that compact multitransiting planetary systems tend to have coplanar, likely aligned orbits. TOI-1726 is also a great atmospheric target for understanding differential atmospheric loss of sub-Neptune planets (planet b 2.2 R and c 2.7 R both likely underwent photoevaporation). The coplanar geometry points to a dynamically cold history of the system that simplifies any future modeling of atmospheric escape.


IPAC Authors


Benjamin Fulton

Assistant Scientist