Revisiting the HIP 41378 system with K2 and Spitzer
We present new observations of the multiplanet system HIP 41378, a bright star (V = 8.9, K_s = 7.7) with five known transiting planets. Previous K2 observations showed multiple transits of two Neptune-sized bodies and single transits of three larger planets (R_P = 0.33R_J , 0.47R_J , 0.88R_J ). K2recently observed the system again in Campaign 18 (C18). We observe one new transit each of two of the larger planets d/f, giving maximal orbital periods of 1114/1084 days, as well as integer divisions of these values down to a lower limit of about 50 days. We use all available photometry to determine the eccentricity distributions of HIP 41378 d & f, finding that periods ≾300 days require non-zero eccentricity. We check for overlapping orbits of planets d and f to constrain their mutual periods, finding that short periods (P < 300 days) for planet f are disfavored. We also observe transits of planets b and c with Spitzer/Infrared Array Camera (IRAC), which we combine with the K2observations to search for transit timing variations (TTVs). We find a linear ephemeris for planet b, but see a significant TTV signal for planet c. The ability to recover the two smaller planets with Spitzer shows that this fascinating system will continue to be detectable with Spitzer, CHEOPS, TESS, and other observatories, allowing us to precisely determine the periods of d and f, characterize the TTVs of planet c, recover the transits of planet e, and further enhance our view of this remarkable dynamical laboratory.
Additional Information© 2019 The American Astronomical Society. Received 2018 September 28; revised 2019 March 7; accepted 2019 March 12; published 2019 April 22. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech. D.B. and I.J.M.C. acknowledge support from NSF AAG grant 1616648, D.B. acknowledges support from an NSERC PGS-D scholarship, and I.J.M.C. acknowledges support from NASA K2 GO grants NNH15ZDA001N-15-K2GO4_2-0018 and NNH16ZDA001N-16-K2GO5_2-0005. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Facility: Kepler, K2, Spitzer, Keck I, Gaia.
Published - Berardo_2019_AJ_157_185.pdf
Submitted - 1809.11116.pdf