TOI-1842b: A Transiting Warm Saturn Undergoing Reinflation around an Evolving Subgiant

• Published in: The Astronomical journal Vol. 163; no. 2; pp. 82 - 96
• Main Authors: Wittenmyer, Robert A., Clark, Jake T., Trifonov, Trifon, Addison, Brett C., Wright, Duncan J., Stassun, Keivan G., Horner, Jonathan, Lowson, Nataliea, Kielkopf, John, Kane, Stephen R., Plavchan, Peter, Shporer, Avi, Zhang, Hui, Bowler, Brendan P., Mengel, Matthew W., Okumura, Jack, Rabus, Markus, Johnson, Marshall C., Harbeck, Daniel, Tronsgaard, René, Buchhave, Lars A., Collins, Karen A., Collins, Kevin I., Gan, Tianjun, Jensen, Eric L. N., Howell, Steve B., Furlan, E., Gnilka, Crystal L., Lester, Kathryn V., Matson, Rachel A., Scott, Nicholas J., Ricker, George R., Vanderspek, Roland, Latham, David W., Seager, S., Winn, Joshua N., Jenkins, Jon M., Rudat, Alexander, Quintana, Elisa V., Rodriguez, David R., Caldwell, Douglas A., Quinn, Samuel N., Essack, Zahra, Bouma, Luke G.
• Format: Journal Article
• Language: English
• Published: Madison The American Astronomical Society 01-02-2022; IOP Publishing
• Subjects: Astronomy; Atmospheric models; Exoplanet detection methods; Extrasolar gaseous giant planets; Extrasolar planets; Gas giant planets; Ground-based observation; Orbits; Planetary atmospheres; Radial velocity; Saturn; Scale height; Space telescopes; Star brightness; Stellar evolution; Telescopes; Transit; Transit photometry
• ISSN: 0004-6256; 1538-3881
• DOI: 10.3847/1538-3881/ac3f39

Abstract
The imminent launch of space telescopes designed to probe the atmospheres of exoplanets has prompted new efforts to prioritize the thousands of transiting planet candidates for follow-up characterization. We report the detection and confirmation of TOI-1842b, a warm Saturn identified by TESS and confirmed with ground-based observations from M
inerva
-Australis, NRES, and the Las Cumbres Observatory Global Telescope. This planet has a radius of
1.04
−
0.05
+
0.06
R
J
, a mass of
0.214
−
0.038
+
0.040
M
J
, an orbital period of
9.5739
−
0.0001
+
0.0002
days, and an extremely low density (
ρ
= 0.252 ± 0.091 g cm
−3
). TOI-1842b has among the best known combinations of large atmospheric scale height (893 km) and host-star brightness (
J
= 8.747 mag), making it an attractive target for atmospheric characterization. As the host star is beginning to evolve off the main sequence, TOI-1842b presents an excellent opportunity to test models of gas giant reinflation. The primary transit duration of only 4.3 hr also makes TOI-1842b an easily-schedulable target for further ground-based atmospheric characterization.