TESS Giants Transiting Giants. IV. A Low-density Hot Neptune Orbiting a Red Giant Star

Samuel K. Grunblatt; Nicholas Saunders; Daniel Huber; Daniel Thorngren; Shreyas Vissapragada; Stephanie Yoshida; Kevin C. Schlaufman; Steven Giacalone; Mason Macdougall; Ashley Chontos; Emma Turtelboom; Corey Beard; Joseph M. Akana Murphy; Malena Rice; Howard Isaacson; Ruth Angus; Andrew W. Howard

doi:10.3847/1538-3881/ad4149

The Astronomical Journal (Jan 2024)

TESS Giants Transiting Giants. IV. A Low-density Hot Neptune Orbiting a Red Giant Star

Samuel K. Grunblatt,
Nicholas Saunders,
Daniel Huber,
Daniel Thorngren,
Shreyas Vissapragada,
Stephanie Yoshida,
Kevin C. Schlaufman,
Steven Giacalone,
Mason Macdougall,
Ashley Chontos,
Emma Turtelboom,
Corey Beard,
Joseph M. Akana Murphy,
Malena Rice,
Howard Isaacson,
Ruth Angus,
Andrew W. Howard

Affiliations

Samuel K. Grunblatt: ORCiD; William H. Miller III Department of Physics and Astronomy, Johns Hopkins University , 3400 N Charles Street, Baltimore, MD 21218, USA
Nicholas Saunders: ORCiD; Institute for Astronomy, University of Hawai‘i at Mānoa , 2680 Woodlawn Drive, Honolulu, HI 96822, USA
Daniel Huber: ORCiD; Institute for Astronomy, University of Hawai‘i at Mānoa , 2680 Woodlawn Drive, Honolulu, HI 96822, USA
Daniel Thorngren: ORCiD; William H. Miller III Department of Physics and Astronomy, Johns Hopkins University , 3400 N Charles Street, Baltimore, MD 21218, USA
Shreyas Vissapragada: ORCiD; Department of Astronomy, Harvard University , 60 Garden Street, Cambridge, MA 02138, USA
Stephanie Yoshida: ORCiD; Department of Astronomy, Harvard University , 60 Garden Street, Cambridge, MA 02138, USA
Kevin C. Schlaufman: ORCiD; William H. Miller III Department of Physics and Astronomy, Johns Hopkins University , 3400 N Charles Street, Baltimore, MD 21218, USA
Steven Giacalone: ORCiD; Department of Astronomy, University of California Berkeley , Berkeley, CA 94720, USA
Mason Macdougall: ORCiD; Department of Physics & Astronomy, University of California Los Angeles , Los Angeles, CA 90095, USA
Ashley Chontos: ORCiD; Institute for Astronomy, University of Hawai‘i at Mānoa , 2680 Woodlawn Drive, Honolulu, HI 96822, USA; Department of Astrophysical Sciences, Princeton University , 4 Ivy Lane, Princeton, NJ 08544, USA
Emma Turtelboom: ORCiD; Department of Astronomy, University of California Berkeley , Berkeley, CA 94720, USA
Corey Beard: ORCiD; Department of Physics & Astronomy, University of California Irvine , Irvine, CA 92697, USA
Joseph M. Akana Murphy: ORCiD; Department of Astronomy and Astrophysics, University of California , Santa Cruz, CA 95064, USA
Malena Rice: ORCiD; Department of Astronomy, Yale University , New Haven, CT 06511, USA
Howard Isaacson: ORCiD; Department of Astronomy, University of California Berkeley , Berkeley, CA 94720, USA; Centre for Astrophysics, University of Southern Queensland , Toowoomba, QLD 4350, Australia
Ruth Angus: ORCiD; American Museum of Natural History , 200 Central Park West, Manhattan, NY 10024, USA; Center for Computational Astrophysics, Flatiron Institute , 162 5th Avenue, Manhattan, NY 10010, USA; Department of Astronomy, Columbia University , 550 West 120th Street, New York, NY 10027, USA
Andrew W. Howard: ORCiD; Cahill Center for Astronomy & Astrophysics, California Institute of Technology , Pasadena, CA 91125, USA

DOI: https://doi.org/10.3847/1538-3881/ad4149
Journal volume & issue: Vol. 168, no. 1
p. 1

Abstract

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Hot Neptunes, gaseous planets smaller than Saturn (∼3–8 R _⊕ ) with orbital periods less than 10 days, are rare. Models predict this is due to high-energy stellar irradiation stripping planetary atmospheres over time, often leaving behind only rocky planetary cores. Using our TESS full-frame-image pipeline giants in conjunction with Keck/HIRES radial velocity measurements, we present the discovery of TIC365102760 b, a 6.2 R _⊕ (0.55 R _J ), 19.2 M _⊕ (0.060 M _J ) planet transiting a red giant star every 4.21285 days. The old age and high equilibrium temperature yet remarkably low density of this planet ( ${\rho }_{p}={0.58}_{-0.20}^{+0.30}{\rho }_{{\rm{J}}}$ ) suggest that its gaseous envelope should have been stripped by high-energy stellar irradiation billions of years ago. The present-day planet mass and radius suggest the atmospheric stripping was slower than predicted. Unexpectedly low stellar activity and/or late-stage planet inflation could be responsible for the observed properties of this system. Further studies of this system with more precise photometry in multiple passbands will be capable of revealing more details of this planet’s atmosphere.

Published in The Astronomical Journal

ISSN: 0004-6256 (Print); 1538-3881 (Online)
Publisher: IOP Publishing
Country of publisher: United Kingdom
LCC subjects: Science: Astronomy
Website: https://iopscience.iop.org/journal/1538-3881

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