A team of international astronomers reported on the discovery of a Neptune-sized exoplanet, “TOI-1231 b” orbiting TOI-1231 (NLTT 24399, L 248-27, 2MASS J10265947-5228099), a V = 12.3 mag M3V dwarf star in the Vela constellation at distance 27.493 pc. Their study recently appeared in Arxiv.
TOI-1231 was first reported as a high proper motion star (0″.35 yr¯1) by Luyten in 1957, and later in the Revised NLTT catalog. Over the past decade, the star has appeared in several surveys of high proper motion 2MASS and WISE stars and nearby M dwarfs.
In the current study, astronomers detected the planet using photometric data from the Transiting Exoplanet Survey Satellite and followed up with observations from the Las Cumbres Observatory and the Antarctica Search for Transiting ExoPlanets program.
Combining the photometric data sets, they found that the newly discovered planet has a radius of 3.65 R, and an orbital period of 24.246 days. While, radial velocity measurements obtained with the Planet Finder Spectrograph on the Magellan Clay telescope confirm the existence of the planet and lead to a mass measurement of 15.5 M. In addition, they found that the planet has a bulk density of 1.74 g cm¯3 which makes it slightly denser than Neptune (ρNep = 1.638 g cm¯3) .
Moreover, it has been suggested that, TOI-1231 b has an equilibrium temperature of just 330K, which makes it one of the coolest small planets accessible for atmospheric studies so far. In addition, its volatile rich atmosphere, long transit duration and small host star, makes it one of the most promising small exoplanets for transmission spectroscopy with HST and JWST detected by the TESS mission. Finally, its high systemic radial velocity makes it a particularly attractive target for atmospheric escape observations via the H I Lyman α, and possibly the meta-stable He I line.
“Future atmospheric observations would enable the first comparative planetology efforts in the 250-350 K temperature regime via comparisons with K2-18 b.”— concluded authors of the study
Reference: Jennifer A. Burt, Diana Dragomir, Paul Mollière, Allison Youngblood, Antonio García Muñoz, John McCann, Laura Kreidberg, Chelsea X. Huang, Karen A. Collins, Jason D. Eastman, Lyu Abe, Jose M. Almenara, Ian J. M. Crossfield, Carl Ziegler, Joseph E. Rodriguez, Eric E. Mamajek, Keivan G. Stassun, Samuel P. Halverson, Steven Jr. Villanueva, R. Paul Butler, Sharon Xuesong Wang, Richard P. Schwarz, George R. Ricker, Roland Vanderspek, David W. Latham, S. Seager, Joshua N. Winn, Jon M. Jenkins, Abdelkrim Agabi, Xavier Bonfils, David Ciardi, Marion Cointepas, Jeffrey D. Crane, Nicolas Crouzet, Georgina Dransfield, Fabo Feng, Elise Furlan, Tristan Guillot, Arvind F. Gupta, Steve B. Howell, Eric L. N. Jensen, Nicholas Law, Andrew W. Mann, Wenceslas Marie-Sainte, Rachel A. Matson, Elisabeth C. Matthews, Djamel Mékarnia, Joshua Pepper, Nic Scott, Stephen A. Shectman, Joshua E. Schlieder, François-Xavier Schmider, Daniel J. Stevens, Johanna K. Teske, Amaury H.M.J. Triaud, David Charbonneau, Zachory K. Berta-Thompson, Christopher J. Burke, Tansu Daylan, Thomas Barclay, Bill Wohler, C. E. Brasseur, “TOI-1231 b: A Temperate, Neptune-Sized Planet Transiting the Nearby M3 Dwarf NLTT 24399”, Arxiv, pp. 1-20, 2021. https://arxiv.org/abs/2105.08077
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