Astronomers Discovered A Warm Sub-Neptune Transiting A Bright Solar Twin (Planetary Science)

Using Transiting Exoplanet Survey Satellite (TESS), a team of international astronomers reported the discovery of a transiting warm sub-Neptune planet, ‘HD 183579b’, around the nearby bright (𝑉 = 8.75 mag, 𝐾 = 7.15 mag) solar twin HD 183579. Their study recently appeared in Arxiv.

HD 183579 is a G2V star with a spectrum nearly identical to that of the Sun. The star has been studied extensively through a dedicated RV planet search and spectroscopic abundance survey targeting solar twin stars with the High Accuracy Radial velocity Planet Searcher spectrograph (HARPS). The transiting planet, however, was not detected until TESS data became available.

Now, a team of international astronomers characterized the HD 183579 planetary system using both space and ground-based photometric data from TESS and LCO as well as the spectroscopic data from HARPS and Minerva-Australis.

They found that the host star is located 56.8 pc away with a radius of 𝑅∗ = 0.97 𝑅 and a mass of 𝑀∗ = 1.03 𝑀. They also found that HD 183579b (TOI-1055b) has a radius of 𝑅𝑝 = 3.53 𝑅 on a 17.47 day orbit with a mass of 𝑀𝑝 = 11.2 𝑀 (3𝜎 mass upper limit of 27.4 𝑀).

Taken together, they found the resulting planetary bulk density of 1.4 g cm¯3, which implies the presence of an extended atmosphere, making this system an excellent candidate for transmission spectroscopic follow-up.

Finally, by performing a line-by-line differential analysis using the high resolution and signal-to-noise ratio HARPS spectra, they found that HD 183579 does not show a similar depletion in the abundance of refractory elements as our Sun.

“HD 183579b is the fifth brightest known sub-Neptune planet system in the sky, making it an excellent target for future studies of the interior structure and atmospheric properties.”

— they concluded.

Featured image: The mass radius diagram in Earth units. HD 183579b is marked as a red square. The confirmed planets with well measured radius and mass are shown as black points (uncertainty smaller than 20%) while grey points represent the planet with poor constraint (data are retrieved from NASA Exoplanet Archive). The colored lines are the theoretical M-R models for different planetary compositions © Tianjun Gan et al.

Reference: Tianjun Gan, Megan Bedell, Sharon Xuesong Wang, Daniel Foreman-Mackey, Jorge Meléndez, Shude Mao, Keivan G. Stassun, Steve B. Howell, Carl Ziegler, Robert A. Wittenmyer, Coel Hellier, Karen A. Collins, Avi Shporer, George R. Ricker, Roland Vanderspek, David W. Latham, Sara Seager, Joshua N. Winn, Jon M. Jenkins, Brett C. Addison, Sarah Ballard, Thomas Barclay, Jacob L. Bean, Brendan P. Bowler, César Briceño, Ian J. M. Crossfield, Jason Dittman, Jonathan Horner, Eric L. N. Jensen, Stephen R. Kane, John Kielkopf, Laura Kreidberg, Nicholas Law, Andrew W. Mann, Matthew W. Mengel, Edward H. Morgan, Jack Okumura, Hugh P. Osborn, Martin Paegert, Peter Plavchan, Richard P. Schwarz, Bernie Shiao, Jeffrey C. Smith, Lorenzo Spina, C. G. Tinney, Guillermo Torres, Joseph D. Twicken, Michael Vezie, Gavin Wang, Duncan J. Wright, Hui Zhang, “HD 183579b: A Warm Sub-Neptune Transiting a Solar Twin Detected by TESS”, Arxiv, pp. 1-20, 2021.

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