An Earth-sized Planet on the Verge of Tidal Disruption

Creators: Dai, Fei^{1, 2}; Howard, Andrew W.²; Halverson, Samuel³; Orell-Miquel, Jaume⁴; Pallé, Enric⁴; Isaacson, Howard^{5, 6}; Fulton, Benjamin⁷; Price, Ellen M.⁸; Plotnykov, Mykhaylo⁹; Rogers, Leslie A.⁸; Valencia, Diana⁹; Paragas, Kimberly²; Greklek-McKeon, Michael²; Gomez Barrientos, Jonathan²; Knutson, Heather A.²; Petigura, Erik A.¹⁰; Weiss, Lauren M.¹¹; Lee, Rena¹; Brinkman, Casey L.¹; Huber, Daniel^{1, 12}; Stefánsson, Gumundur¹³; Masuda, Kento¹⁴; Giacalone, Steven²; Lu, Cicero X.¹⁵; Kite, Edwin S.⁸; Hu, Renyu^{3, 2}; Gaidos, Eric¹; Zhang, Michael⁸; Rubenzahl, Ryan A.²; Winn, Joshua N.¹⁶; Han, Te¹⁷; Beard, Corey¹⁷; Holcomb, Rae¹⁷; Householder, Aaron¹⁸; Gilbert, Gregory J.¹⁰; Lubin, Jack¹⁰; Ong, J. M. Joel¹; Polanski, Alex S.¹⁹; Saunders, Nicholas¹; Van Zandt, Judah¹⁰; Yee, Samuel W.²⁰; Zhang, Jingwen¹; Zink, Jon²; Holden, Bradford²¹; Baker, Ashley²; Brodheim, Max²²; Crossfield, Ian J. M.¹⁹; Deich, William²¹; Edelstein, Jerry⁵; Gibson, Steven R.²; Hill, Grant M.²²; Jelinsky, Sharon R⁵; Kassis, Marc²²; Laher, Russ R.⁷; Lanclos, Kyle²²; Lilley, Scott²²; Payne, Joel N.²²; Rider, Kodi⁵; Robertson, Paul¹⁷; Roy, Arpita²³; Schwab, Christian²⁴; Shaum, Abby P.²; Sirk, Martin M.⁵; Smith, Chris⁵; Vandenberg, Adam²²; Walawender, Josh²²; Wang, Sharon X.²⁵; Wang, Shin-Ywan (Cindy)⁷; Wishnow, Edward⁵; Wright, Jason T.²⁶; Yeh, Sherry²²; Caballero, José A.²⁷; Morales, Juan C.^{28, 29}; Murgas, Felipe^{4, 30}; Nagel, Evangelos³¹; Reiners, Ansgar³¹; Schweitzer, Andreas³²; Tabernero, Hugo M.³³; Zechmeister, Mathias³¹; Spencer, Alton³⁴; Ciardi, David R.⁷; Clark, Catherine A.^{3, 7}; Lund, Michael B.⁷; Caldwell, Douglas A.³⁵; Collins, Karen A.²⁰; Schwarz, Richard P.²⁰; Barkaoui, Khalid^{36, 18, 4}; Watkins, Cristilyn²⁰; Shporer, Avi¹⁸; Narita, Norio^{4, 37}; Fukui, Akihiko^{4, 37}; Srdoc, Gregor³⁸; Latham, David W.²⁰; Jenkins, Jon M.³⁹; Ricker, George R.¹⁸; Seager, Sara¹⁸; Vanderspek, Roland¹⁸

1. University of Hawaii at Manoa
2. California Institute of Technology
3. Jet Propulsion Lab
4. Instituto de Astrofísica de Canarias
5. University of California, Berkeley
6. University of Southern Queensland
7. NASA Exoplanet Science Institute
8. University of Chicago
9. University of Toronto
10. University of California, Los Angeles
11. University of Notre Dame
12. University of Sydney
13. University of Amsterdam
14. Osaka University
15. Gemini North Observatory
16. Princeton University
17. University of California, Irvine
18. Massachusetts Institute of Technology
19. University of Kansas
20. Harvard-Smithsonian Center for Astrophysics
21. University of California, Santa Cruz
22. W.M. Keck Observatory
23. Schmidt Sciences
24. Macquarie University
25. Tsinghua University
26. Pennsylvania State University
27. Centro de Astrobiología
28. Institute of Space Sciences
29. Institut d'Estudis Espacials de Catalunya
30. University of La Laguna
31. University of Göttingen
32. Universität Hamburg
33. Complutense University of Madrid
34. Western Connecticut State University
35. Search for Extraterrestrial Intelligence
36. University of Liège
37. University of Tokyo
38. Kotizarovci Observatory
39. Ames Research Center

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Abstract

TOI-6255 b (GJ 4256) is an Earth-sized planet (1.079 ± 0.065 R_⊕) with an orbital period of only 5.7 hr. With the newly commissioned Keck Planet Finder and CARMENES spectrographs, we determine the planet's mass to be 1.44 ± 0.14 M_⊕. The planet is just outside the Roche limit, with P_orb/P_Roche = 1.13 ± 0.10. The strong tidal force likely deforms the planet into a triaxial ellipsoid with a long axis that is ∼10% longer than the short axis. Assuming a reduced stellar tidal quality factor Q⋆′≈10⁷, we predict that tidal orbital decay will cause TOI-6255 to reach the Roche limit in roughly 400 Myr. Such tidal disruptions may produce the possible signatures of planet engulfment that have been seen on stars with anomalously high refractory elemental abundances compared to their conatal binary companions. TOI-6255 b is also a favorable target for searching for star–planet magnetic interactions, which might cause interior melting and hasten orbital decay. TOI-6255 b is a top target (with an Emission Spectroscopy Metric of about 24) for phase-curve observations with the James Webb Space Telescope.

Copyright and License

Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

Acknowledgement

We thank Henrique Reggiani for an independent investigation of the stellar spectrum. We thank Doug Lin, Luke Bouma, Eugene Chiang, Darryl Seligman, Saul Rappaport, Jennifer van Saders, Ji Wang, and Li Zeng for insightful discussions. We also thank Connie Rockosi for their contribution to the successful construction of the KPF.

Support for this work was provided by NASA through the NASA Hubble Fellowship grant HST-HF2-51503.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555.

A NASA Key Strategic Mission Support titled "Pinning Down Masses of JWST Ultra-short-period Planets with KPF" (PI: F. Dai) provided the telescope access and funding for the completion of this project.

This work was supported by a NASA Keck PI Data Award, administered by the NASA Exoplanet Science Institute. The data presented herein were obtained at the W. M. Keck Observatory from telescope time allocated to the National Aeronautics and Space Administration through the agency's scientific partnership with the California Institute of Technology and the University of California. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

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.

We acknowledge the use of public TESS data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. 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 paper made use of data collected by the TESS mission that are publicly available from the Mikulski Archive for Space Telescopes (MAST) operated by the Space Telescope Science Institute (STScI).

Funding for the TESS mission is provided by NASA's Science Mission Directorate. K.A.C. and C.N.W. acknowledge support from the TESS mission via subaward s3449 from MIT.

This research has made use of the Exoplanet Follow-up Observation Program (ExoFOP) website (NExScI 2022), which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program.

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 NSF.

This work is partly supported by JSPS KAKENHI grant No. JPJP24H00017 and JSPS Bilateral Program Number JPJSBP120249910. This article is based on observations made with the MuSCAT2 instrument, developed by ABC, at Telescopio Carlos Sánchez, operated on the island of Tenerife by the IAC in the Spanish Observatorio del Teide. This paper is based on observations made with the MuSCAT3 instrument, developed by the Astrobiology Center and under financial support from JSPS KAKENHI (JP18H05439) and JST PRESTO (JPMJPR1775), at Faulkes Telescope North on Maui, HI, operated by the Las Cumbres Observatory.

This research was carried out in part at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004).

We acknowledge financial support from the Agencia Estatal de Investigación of the Ministerio de Ciencia e Innovación MCIN/AEI/10.13039/501100011033 and the ERDF "A way of making Europe" through project PID2021-125627OB-C32, and from the Centre of Excellence "Severo Ochoa" award to the Instituto de Astrofisica de Canarias.

D.H. acknowledges support from the Alfred P. Sloan Foundation, the National Aeronautics and Space Administration (80NSSC21K0652), and the Australian Research Council (FT200100871).

D.R.C. and C.A.C. acknowledge support from NASA 18-2XRP18_2-0007.

Facilities

Keck:I (KPF) - KECK I Telescope, 3.5m Calar Alto - , TESS - , LCOGT - Las Cumbres Observatory Global Telescope, MuSCAT2 - , MuSCAT3 - , WASP - , Palomar - .

Software References

AstroImage (Collins et al. 2017), Isoclassify (Huber et al. 2017), isochrones (Morton 2015), MIST (Choi et al. 2016), SpecMatch-Syn (Petigura 2015), Batman (Kreidberg 2015), emcee (Foreman-Mackey et al. 2013).

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