The TESS-Keck Survey. XVIII. A Sub-Neptune and Spurious Long-period Signal in the TOI-1751 System

Creators: Desai, Anmol¹; Turtelboom, Emma V.¹; Harada, Caleb K.¹; Dressing, Courtney D.¹; Rice, David R.²; Murphy, Joseph M. Akana³; Brinkman, Casey L.⁴; Chontos, Ashley⁵; Crossfield, Ian J. M.⁶; Dai, Fei⁷; Hill, Michelle L.⁸; Fetherolf, Tara^{8, 9}; Giacalone, Steven⁷; Howard, Andrew W.⁷; Huber, Daniel^{4, 10}; Isaacson, Howard^{1, 11}; Kane, Stephen R.⁸; Lubin, Jack¹²; MacDougall, Mason G.¹³; Mayo, Andrew W.^{1, 14}; Močnik, Teo¹⁵; Polanski, Alex S.⁶; Rice, Malena¹⁶; Robertson, Paul¹²; Rubenzahl, Ryan A.⁷; Van Zandt, Judah¹³; Weiss, Lauren M.¹⁷; Bieryla, Allyson¹⁸; Buchhave, Lars A.¹⁹; Jenkins, Jon M.²⁰; Kostov, Veselin B.^{21, 22}; Levine, Alan M.²³; Lillo-Box, Jorge²⁴; Paegert, M.¹⁸; Rabus, Markus²⁵; Seager, S.²³; Stassun, Keivan G.²⁶; Ting, Eric B.²⁰; Watanabe, David²⁷; Winn, Joshua N.⁵

1. University of California, Berkeley
2. Open University of Israel
3. University of California, Santa Cruz
4. University of Hawaii at Manoa
5. Princeton University
6. University of Kansas
7. California Institute of Technology
8. University of California, Riverside
9. California State University, San Marcos
10. University of Sydney
11. University of Southern Queensland
12. University of California, Irvine
13. University of California, Los Angeles
14. University of Copenhagen
15. Gemini North Observatory
16. Yale University
17. University of Notre Dame
18. Harvard-Smithsonian Center for Astrophysics
19. Technical University of Denmark
20. Ames Research Center
21. Goddard Space Flight Center
22. Search for Extraterrestrial Intelligence
23. Massachusetts Institute of Technology
24. Centro de Astrobiología
25. Catholic University of the Most Holy Conception
26. Vanderbilt University
27. Planetary Discoveries

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Abstract

We present and confirm TOI-1751 b, a transiting sub-Neptune orbiting a slightly evolved, solar-type, metal-poor star (T_eff = 5996 ± 110 K, log(g)=4.2±0.1, V = 9.3 mag, [Fe/H] = −0.40 ± 0.06 dex) every 37.47 days. We use TESS photometry to measure a planet radius of 2.77_(−0.07)_(+0.15)R⊕. We also use both Keck/HIRES and APF/Levy radial velocities (RV) to derive a planet mass of 14.5_(−3.14)_(+3.15)M⊕, and thus a planet density of 3.6 ± 0.9 g cm⁻³. There is also a long-period (∼400 days) signal that is observed in only the Keck/HIRES data. We conclude that this long-period signal is not planetary in nature and is likely due to the window function of the Keck/HIRES observations. This highlights the role of complementary observations from multiple observatories to identify and exclude aliases in RV data. Finally, we investigate the potential compositions of this planet, including rocky and water-rich solutions, as well as theoretical irradiated ocean models. TOI-1751 b is a warm sub-Neptune with an equilibrium temperature of ∼820 K. As TOI-1751 is a metal-poor star, TOI-1751 b may have formed in a water-enriched formation environment. We thus favor a volatile-rich interior composition for this planet.

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

Some of the data presented in this paper 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 sacred mountain which is now colonized land.

This paper made use of data collected by the TESS mission and is publicly available from the Mikulski Archive for Space Telescopes (MAST) operated by the Space Telescope Science Institute (STScI; MAST Team 2021). Funding for the TESS mission is provided by NASA's Science Mission Directorate. 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.

J. Akana Murphy, C. Brinkman, F. Dai, S. Giacalone, J. Lubin, M. Rice, and J. van Zandt contributed >10 observations of TOI-1751 using Keck/HIRES.

We thank Artem Aguichine for useful discussions on interpreting composition models and Andreia Carrillo for insight on the galactic context of TOI-1751. We also acknowledge Erik Petigura and BJ Fulton for their contributions to the construction, design, and team management of the TESS-Keck Survey.

M. Rice acknowledges support from the Heising-Simons Foundation grant. #2023-4478. J.M.A.M. is supported by the National Science Foundation (NSF) Graduate Research Fellowship Program (GRFP) under grant No. DGE-1842400. A.D. would like to acknowledge the UC Berkeley Physics Undergraduate Research Scholars Program and the UC Berkeley Mathematical & Physical Sciences Scholars for funding their work. E.V.T. acknowledges support from a David & Lucile Packard Foundation grant. C.H. acknowledges support from the National Science Foundation Graduate Research Fellowship Program under grant No. DGE 2146752. D.H. acknowledges support from the Alfred P. Sloan Foundation, the National Aeronautics and Space Administration (80NSSC21K0652), and the Australian Research Council (FT200100871). M.H. would like to acknowledge NASA support via the FINESST Planetary Science Division, NASA award number 80NSSC21K1536.

Facilities

Keck :I - , APF - , TESS - .

Software References

This research made use of exoplanet (Foreman-Mackey et al. 2021, 2021) and its dependencies (Astropy Collaboration et al. 2013; Salvatier et al. 2016; Theano Development Team 2016; Astropy Collaboration et al. 2018; Kumar et al. 2019; Agol et al. 2020; Astropy Collaboration et al. 2022). This research also made use of Lightkurve, a Python package for Kepler and TESS data analysis (Lightkurve Collaboration et al. 2018), and its dependencies (Astropy Collaboration et al. 2013, 2018; Brasseur et al. 2019; Ginsburg et al. 2019). Additionally, this work made use of the following Python packages: numpy (Harris et al. 2020), pandas (pandas development team 2020), matplotlib (Hunter 2007), corner (Foreman-Mackey 2016), RadVel (Fulton et al. 2018), SpecMatch-Emp (Yee et al. 2017), SpecMatch-Synth (Petigura et al. 2017), and CMasher (Van der Velden 2020).

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Resource type: Journal Article
Publisher: American Astronomical Society
Published in: Astronomical Journal, 167(5), 194, ISSN: 0004-6256.
Languages: English