TOI-2109: An Ultrahot Gas Giant on a 16 hr Orbit

Creators: Wong, Ian; Shporer, Avi; Zhou, George; Kitzmann, Daniel; Komacek, Thaddeus D.; Tan, Xianyu; Tronsgaard, René; Buchhave, Lars A.; Vissapragada, Shreyas; Greklek-McKeon, Michael; Rodriguez, Joseph E.; Ahlers, John P.; Quinn, Samuel N.; Furlan, Elise; Howell, Steve B.; Bieryla, Allyson; Heng, Kevin; Knutson, Heather A.; Collins, Karen A.; McLeod, Kim K.; Berlind, Perry; Brown, Peyton; Calkins, Michael L.; de Leon, Jerome P.; Esparza-Borges, Emma; Esquerdo, Gilbert A.; Fukui, Akihiko; Gan, Tianjun; Girardin, Eric; Gnilka, Crystal L.; Ikoma, Masahiro; Jensen, Eric L. N.; Kielkopf, John; Kodama, Takanori; Kurita, Seiya; Lester, Kathryn V.; Lewin, Pablo; Marino, Giuseppe; Murgas, Felipe; Narita, Norio; Pallé, Enric; Schwarz, Richard P.; Stassun, Keivan G.; Tamura, Motohide; Watanabe, Noriharu; Benneke, Björn; Ricker, George R.; Latham, David W.; Vanderspek, Roland; Seager, Sara; Winn, Joshua N.; Jenkins, Jon M.; Caldwell, Douglas A.; Fong, William; Huang, Chelsea X.; Mireles, Ismael; Schlieder, Joshua E.; Shiao, Bernie; Noel Villaseñor, Jesus

Abstract

We report the discovery of an ultrahot Jupiter with an extremely short orbital period of 0.67247414 ± 0.00000028 days (∼16 hr). The 1.347 ± 0.047 R_(Jup) planet, initially identified by the Transiting Exoplanet Survey Satellite (TESS) mission, orbits TOI-2109 (TIC 392476080)—a T_(eff) ∼ 6500 K F-type star with a mass of 1.447 ± 0.077 M_☉, a radius of 1.698 ± 0.060 R_☉, and a rotational velocity of v sin i_* = 81.9 ± 1.7 km s⁻¹. The planetary nature of TOI-2109b was confirmed through radial-velocity measurements, which yielded a planet mass of 5.02 ± 0.75 M_(Jup). Analysis of the Doppler shadow in spectroscopic transit observations indicates a well-aligned system, with a sky-projected obliquity of λ = 1.°7 ± 1.°7. From the TESS full-orbit light curve, we measured a secondary eclipse depth of 731 ± 46 ppm, as well as phase-curve variations from the planet's longitudinal brightness modulation and ellipsoidal distortion of the host star. Combining the TESS-band occultation measurement with a K_s-band secondary eclipse depth (2012 ± 80 ppm) derived from ground-based observations, we find that the dayside emission of TOI-2109b is consistent with a brightness temperature of 3631 ± 69 K, making it the second hottest exoplanet hitherto discovered. By virtue of its extreme irradiation and strong planet–star gravitational interaction, TOI-2109b is an exceptionally promising target for intensive follow-up studies using current and near-future telescope facilities to probe for orbital decay, detect tidally driven atmospheric escape, and assess the impacts of H₂ dissociation and recombination on the global heat transport.

Additional Information

© 2021. The American Astronomical Society. Received 2021 July 23; revised 2021 September 2; accepted 2021 September 13; published 2021 November 23. Funding for the TESS mission is provided by NASA's Science Mission directorate. This paper includes data collected by the TESS mission, which are publicly available from the Mikulski Archive for Space Telescopes (MAST). Resources supporting this work were provided by the NASA High-end Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center for the production of the SPOC data products. This work makes use of observations from the LCOGT network. Part of the LCOGT telescope time was granted by NOIRLab through the Mid-Scale Innovations Program (MSIP). MSIP is funded by the National Science Foundation (NSF). This article is partly based on observations made with the MuSCAT2 instrument, developed by ABC, at Telescopio Carlos Sánchez operated on the island of Tenerife by the Instituto de Astrofísica de Canarias in the Spanish Observatorio del Teide. This paper is also based on observations made with the MuSCAT3 instrument, developed by the Astro-biology Center and under financial support by JSPS KAKENHI (JP18H05439) and JST PRESTO (JPMJPR1775), at Faulkes Telescope North on Maui, HI, operated by the Las Cumbres Observatory. This work is partly supported by JSPS KAKENHI grant Nos. JP17H04574, JP18H05439, JP18H05442, JP15H02063, JP21K13975, JP22000005, JST PRESTO grant No. JPMJPR1775, and the Astrobiology Center of the National Institutes of Natural Sciences (grant Nos. AB031010 and AB031014). We thank the Palomar Observatory team, particularly Paul Nied and Kevin Rykoski, for enabling the K_s-band secondary eclipse observations and facilitating remote operations on the Hale 200" Telescope. Some of the observations in this paper made use of the High-Resolution Imaging instrument 'Alopeke. 'Alopeke was funded by the NASA Exoplanet Exploration Program and built at the NASA Ames Research Center by Steve B. Howell, Nic Scott, Elliott P. Horch, and Emmett Quigley. Data were reduced using a software pipeline originally written by Elliott Horch and Mark Everett. 'Alopeke was mounted on the Gemini-North telescope of the international Gemini Observatory, a program of NSF's OIR Lab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation on behalf of the Gemini partnership: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). This paper is partially based on observations made with the Nordic Optical Telescope, operated by the Nordic Optical Telescope Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain, of the Instituto de Astrofísica de Canarias. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with NASA under the Exoplanet Exploration Program. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. I.W. and T.D.K. acknowledge funding from the 51 Pegasi b Fellowship in Planetary Astronomy sponsored by the Heising–Simons Foundation. S.V. is supported by an NSF Graduate Research Fellowship and the Paul & Daisy Soros Fellowship for New Americans. H.A.K. acknowledges support from NSF CAREER grant 1555095. M.T. is supported by JSPS KAKENHI grant Nos. JP18H05442, JP15H02063, and JP22000005. Facilities: TESS - , FLWO/KeplerCam - , ULMT - , LCOGT/McD - , LCOGT/SSO - , LCOGT/SAAO - , LCOGT/CTIO - , MLO - , TCS/MuSCAT2 - , WBRO - , Grand-Pra Observatory - , FTN/MuSCAT3 - , Palomar/WIRC - , Gemini-North/'Alopeke - , FLWO/TRES - , NOT/FIES - . Software: AstroImageJ (Collins et al. 2017), astropy (Astropy Collaboration et al. 2018), BANZAI (McCully et al. 2018), batman (Kreidberg 2015), emcee (Foreman-Mackey et al. 2013), EXOFASTv2 (Eastman et al. 2013, 2019; Eastman 2017), ExoTEP (Benneke et al. 2019; Wong et al. 2020a), FastChem (Stock et al. 2018), HELIOS (Malik et al. 2017, 2019), HELIOS-K (Grimm & Heng 2015), matplotlib (Hunter 2007), numpy (Harris et al. 2020), photutils (Bradley et al. 2020), radvel (Fulton et al. 2018), scipy (Virtanen et al. 2020), Tapir (Jensen 2013).

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