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

Wong, Ian and Shporer, Avi and Zhou, George and Kitzmann, Daniel and Komacek, Thaddeus D. and Tan, Xianyu and Tronsgaard, René and Buchhave, Lars A. and Vissapragada, Shreyas and Greklek-McKeon, Michael and Rodriguez, Joseph E. and Ahlers, John P. and Quinn, Samuel N. and Furlan, Elise and Howell, Steve B. and Bieryla, Allyson and Heng, Kevin and Knutson, Heather A. and Collins, Karen A. and McLeod, Kim K. and Berlind, Perry and Brown, Peyton and Calkins, Michael L. and de Leon, Jerome P. and Esparza-Borges, Emma and Esquerdo, Gilbert A. and Fukui, Akihiko and Gan, Tianjun and Girardin, Eric and Gnilka, Crystal L. and Ikoma, Masahiro and Jensen, Eric L. N. and Kielkopf, John and Kodama, Takanori and Kurita, Seiya and Lester, Kathryn V. and Lewin, Pablo and Marino, Giuseppe and Murgas, Felipe and Narita, Norio and Pallé, Enric and Schwarz, Richard P. and Stassun, Keivan G. and Tamura, Motohide and Watanabe, Noriharu and Benneke, Björn and Ricker, George R. and Latham, David W. and Vanderspek, Roland and Seager, Sara and Winn, Joshua N. and Jenkins, Jon M. and Caldwell, Douglas A. and Fong, William and Huang, Chelsea X. and Mireles, Ismael and Schlieder, Joshua E. and Shiao, Bernie and Noel Villaseñor, Jesus (2021) TOI-2109: An Ultrahot Gas Giant on a 16 hr Orbit. Astronomical Journal, 162 (6). Art. No. 256. ISSN 0004-6256. doi:10.3847/1538-3881/ac26bd.

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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.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Wong, Ian0000-0001-9665-8429
Shporer, Avi0000-0002-1836-3120
Zhou, George0000-0002-4891-3517
Kitzmann, Daniel0000-0003-4269-3311
Komacek, Thaddeus D.0000-0002-9258-5311
Tan, Xianyu0000-0003-2278-6932
Tronsgaard, René0000-0003-1001-0707
Buchhave, Lars A.0000-0003-1605-5666
Vissapragada, Shreyas0000-0003-2527-1475
Greklek-McKeon, Michael0000-0002-0371-1647
Rodriguez, Joseph E.0000-0001-8812-0565
Ahlers, John P.0000-0003-2086-7712
Quinn, Samuel N.0000-0002-8964-8377
Furlan, Elise0000-0001-9800-6248
Howell, Steve B.0000-0002-2532-2853
Bieryla, Allyson0000-0001-6637-5401
Heng, Kevin0000-0003-1907-5910
Knutson, Heather A.0000-0002-5375-4725
Collins, Karen A.0000-0001-6588-9574
McLeod, Kim K.0000-0001-9504-1486
Brown, Peyton0000-0002-2546-9708
Calkins, Michael L.0000-0002-2830-5661
de Leon, Jerome P.0000-0002-6424-3410
Esparza-Borges, Emma0000-0002-2341-3233
Esquerdo, Gilbert A.0000-0002-9789-5474
Fukui, Akihiko0000-0002-4909-5763
Gan, Tianjun0000-0002-4503-9705
Girardin, Eric0000-0002-5443-3640
Gnilka, Crystal L.0000-0003-2519-6161
Ikoma, Masahiro0000-0002-5658-5971
Jensen, Eric L. N.0000-0002-4625-7333
Kielkopf, John0000-0003-0497-2651
Kodama, Takanori0000-0001-9032-5826
Lester, Kathryn V.0000-0002-9903-9911
Lewin, Pablo0000-0003-0828-6368
Marino, Giuseppe0000-0001-8134-0389
Murgas, Felipe0000-0001-9087-1245
Narita, Norio0000-0001-8511-2981
Pallé, Enric0000-0003-0987-1593
Schwarz, Richard P.0000-0001-8227-1020
Stassun, Keivan G.0000-0002-3481-9052
Tamura, Motohide0000-0002-6510-0681
Watanabe, Noriharu0000-0002-7522-8195
Benneke, Björn0000-0001-5578-1498
Ricker, George R.0000-0003-2058-6662
Latham, David W.0000-0001-9911-7388
Vanderspek, Roland0000-0001-6763-6562
Seager, Sara0000-0002-6892-6948
Winn, Joshua N.0000-0002-4265-047X
Jenkins, Jon M.0000-0002-4715-9460
Caldwell, Douglas A.0000-0003-1963-9616
Fong, William0000-0003-0241-2757
Huang, Chelsea X.0000-0003-0918-7484
Mireles, Ismael0000-0002-4510-2268
Schlieder, Joshua E.0000-0001-5347-7062
Shiao, Bernie0000-0001-7842-3714
Alternate Title:TOI-2109b: An Ultrahot Gas Giant on a 16 hr Orbit
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 (, processed by the Gaia Data Processing and Analysis Consortium (DPAC, 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).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Japan Society for the Promotion of Science (JSPS)JP18H05439
Japan Science and Technology AgencyJPMJPR1775
Japan Society for the Promotion of Science (JSPS)JP17H04574
Japan Society for the Promotion of Science (JSPS)JP18H05439
Japan Society for the Promotion of Science (JSPS)JP18H05442
Japan Society for the Promotion of Science (JSPS)JP15H02063
Japan Society for the Promotion of Science (JSPS)JP21K13975
Japan Society for the Promotion of Science (JSPS)JP22000005
National Institutes of Natural Sciences of JapanAB031010
National Institutes of Natural Sciences of JapanAB031014
Gaia Multilateral AgreementUNSPECIFIED
Heising-Simons Foundation51 Pegasi b Fellowship
NSF Graduate Research FellowshipUNSPECIFIED
Paul and Daisy Soros Fellowship for New AmericansUNSPECIFIED
Subject Keywords:Exoplanet astronomy; Hot Jupiters; Exoplanet detection methods; Transit photometry; Radial velocity
Issue or Number:6
Classification Code:Unified Astronomy Thesaurus concepts: Exoplanet astronomy (486); Hot Jupiters (753); Exoplanet detection methods (489); Transit photometry (1709); Radial velocity (1332)
Record Number:CaltechAUTHORS:20211203-204700862
Persistent URL:
Official Citation:Ian Wong et al 2021 AJ 162 256
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:112198
Deposited By: George Porter
Deposited On:06 Dec 2021 18:17
Last Modified:06 Dec 2021 18:17

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