A Mini-Neptune Orbiting the Metal-poor K Dwarf BD+29 2654
Article
Dai, Fei, Schlaufman, Kevin C., Reggiani, Henrique, Bouma, Luke, Howard, Andrew W,, Chontos, Ashley, Pidhorodetska, Daria, Van Zandt, Judah, Akana Murphy, Joseph M., Rubenzahl, Ryan A., Polanski, Alex S., Lubin, Jack, Beard, Corey, Giacalone, Steven, Holcomb, Rae, Batalha, Natalie M., Crossfield, Ian, Dressing, Courtney, Fulton, Benjamin, ..., Ciardi, David R.. 2023. "A Mini-Neptune Orbiting the Metal-poor K Dwarf BD+29 2654." The Astronomical Journal. 166 (2). https://doi.org/10.3847/1538-3881/acdee8
Article Title | A Mini-Neptune Orbiting the Metal-poor K Dwarf BD+29 2654 |
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ERA Journal ID | 1048 |
Article Category | Article |
Authors | Dai, Fei, Schlaufman, Kevin C., Reggiani, Henrique, Bouma, Luke, Howard, Andrew W,, Chontos, Ashley, Pidhorodetska, Daria, Van Zandt, Judah, Akana Murphy, Joseph M., Rubenzahl, Ryan A., Polanski, Alex S., Lubin, Jack, Beard, Corey, Giacalone, Steven, Holcomb, Rae, Batalha, Natalie M., Crossfield, Ian, Dressing, Courtney, Fulton, Benjamin, Huber, Daniel, Isaacson, Howard and Ciardi, David R. |
Journal Title | The Astronomical Journal |
Journal Citation | 166 (2) |
Article Number | 49 |
Number of Pages | 14 |
Year | 2023 |
Publisher | IOP Publishing |
Place of Publication | United States |
ISSN | 0004-6256 |
1538-3881 | |
Digital Object Identifier (DOI) | https://doi.org/10.3847/1538-3881/acdee8 |
Web Address (URL) | https://iopscience.iop.org/article/10.3847/1538-3881/acdee8 |
Abstract | We report the discovery and Doppler mass measurement of a 7.4 days 2.3 R ? mini-Neptune around a metal-poor K dwarf BD+29 2654 (TOI-2018). Based on a high-resolution Keck/HIRES spectrum, the Gaia parallax, and multiwavelength photometry from the UV to the mid-infrared, we found that the host star has T eff = 4174 ? 42 + 34 K, log g = 4.62 ? 0.03 + 0.02 , [Fe/H] = ? 0.58 ± 0.18, M * = 0.57 ± 0.02 M ?, and R * = 0.62 ± 0.01 R ?. Precise Doppler measurements with Keck/HIRES revealed a planetary mass of M p = 9.2 ± 2.1 M ? for TOI-2018 b. TOI-2018 b has a mass and radius that are consistent with an Earthlike core, with a ?1%-by-mass hydrogen/helium envelope or an ice-rock mixture. The mass of TOI-2018 b is close to the threshold for runaway accretion and hence giant planet formation. Such a threshold is predicted to be around 10M ? or lower for a low-metallicity (low-opacity) environment. If TOI-2018 b is a planetary core that failed to undergo runaway accretion, it may underline the reason why giant planets are rare around low-metallicity host stars (one possibility is their shorter disk lifetimes). With a K-band magnitude of 7.1, TOI-2018 b may be a suitable target for transmission spectroscopy with the James Webb Space Telescope. The system is also amenable to metastable Helium observation; the detection of a Helium exosphere would help distinguish between a H/He-enveloped planet and a water world. |
Keywords | Exoplanets (498); Mini Neptunes (1063); Ocean planets (1151) |
ANZSRC Field of Research 2020 | 510109. Stellar astronomy and planetary systems |
Byline Affiliations | Division of Geological and Planetary Sciences, United States |
California Institute of Technology (Caltech), United States | |
Johns Hopkins University, United States | |
Carnegie Institution for Science, United States | |
Princeton University, United States | |
University of Hawaii, United States | |
University of California, United States | |
University of California Los Angeles, United States | |
University of Kansas, United States | |
University of California Irvine, United States | |
University of California Berkeley, United States | |
NASA Exoplanet Science Institute, United States | |
University of Sydney | |
Centre for Astrophysics |
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