TY - JOUR
T1 - A Sub-Neptune-sized Planet Transiting the M2.5 Dwarf G 9-40
T2 - Validation with the Habitable-zone Planet Finder
AU - Stefansson, Gudmundur
AU - Cañas, Caleb
AU - Wisniewski, John
AU - Robertson, Paul
AU - Mahadevan, Suvrath
AU - Maney, Marissa
AU - Kanodia, Shubham
AU - Beard, Corey
AU - Bender, Chad F.
AU - Brunt, Peter
AU - Clemens, J. Christopher
AU - Cochran, William
AU - Diddams, Scott A.
AU - Endl, Michael
AU - Ford, Eric B.
AU - Fredrick, Connor
AU - Halverson, Samuel
AU - Hearty, Fred
AU - Hebb, Leslie
AU - Huehnerhoff, Joseph
AU - Jennings, Jeff
AU - Kaplan, Kyle
AU - Levi, Eric
AU - Lubar, Emily
AU - Metcalf, Andrew J.
AU - Monson, Andrew
AU - Morris, Brett
AU - Ninan, Joe P.
AU - Nitroy, Colin
AU - Ramsey, Lawrence
AU - Roy, Arpita
AU - Schwab, Christian
AU - Sigurdsson, Steinn
AU - Terrien, Ryan
AU - Wright, Jason T.
N1 - Funding Information:
2020-03-01 2020-02-12 15:17:02 cgi/release: Article released bin/incoming: New from .zip National Science Foundation AST-1006676 National Science Foundation AST-1126413 National Science Foundation AST-1310885 National Science Foundation AST-1517592 National Science Foundation AST-1310875 NASA Astrobiology Institute NNA09DA76A NASA Earth and Space Science Fellowship NNX16AO28H NASA Earth and Space Science Fellowship 80NSSC18K1114 Heising-Simons Foundation 2017-0494 yes
Publisher Copyright:
© 2020. The American Astronomical Society. All rights reserved..
PY - 2020/3
Y1 - 2020/3
N2 - We validate the discovery of a 2-Earth-radii sub-Neptune-sized planet around the nearby high-proper-motion M2.5 dwarf G 9-40 (EPIC 212048748), using high-precision, near-infrared (NIR) radial velocity (RV) observations with the Habitable-zone Planet Finder (HPF), precision diffuser-assisted ground-based photometry with a custom narrowband photometric filter, and adaptive optics imaging. At a distance of d = 27.9 pc, G 9-40b is the second-closest transiting planet discovered by K2 to date. The planet's large transit depth (∼3500 ppm), combined with the proximity and brightness of the host star at NIR wavelengths (J = 10, K = 9.2), makes G 9-40b one of the most favorable sub-Neptune-sized planets orbiting an M dwarf for transmission spectroscopy with James Webb Space Telescope, ARIEL, and the upcoming Extremely Large Telescopes. The star is relatively inactive with a rotation period of ∼29 days determined from the K2 photometry. To estimate spectroscopic stellar parameters, we describe our implementation of an empirical spectral-matching algorithm using the high-resolution NIR HPF spectra. Using this algorithm, we obtain an effective temperature of Teff = 3404 ± 73 K and metallicity of [Fe/H] = -0.08 ± 0.13. Our RVs, when coupled with the orbital parameters derived from the transit photometry, exclude planet masses above 11.7M ⊕ with 99.7% confidence assuming a circular orbit. From its radius, we predict a mass of M =5.0-1.9+3.8inf>M⊕ and an RV semiamplitude of K= 4.1-1.6+3.1 m s-1, making its mass measurable with current RV facilities. We urge further RV follow-up observations to precisely measure its mass, to enable precise transmission spectroscopic measurements in the future.
AB - We validate the discovery of a 2-Earth-radii sub-Neptune-sized planet around the nearby high-proper-motion M2.5 dwarf G 9-40 (EPIC 212048748), using high-precision, near-infrared (NIR) radial velocity (RV) observations with the Habitable-zone Planet Finder (HPF), precision diffuser-assisted ground-based photometry with a custom narrowband photometric filter, and adaptive optics imaging. At a distance of d = 27.9 pc, G 9-40b is the second-closest transiting planet discovered by K2 to date. The planet's large transit depth (∼3500 ppm), combined with the proximity and brightness of the host star at NIR wavelengths (J = 10, K = 9.2), makes G 9-40b one of the most favorable sub-Neptune-sized planets orbiting an M dwarf for transmission spectroscopy with James Webb Space Telescope, ARIEL, and the upcoming Extremely Large Telescopes. The star is relatively inactive with a rotation period of ∼29 days determined from the K2 photometry. To estimate spectroscopic stellar parameters, we describe our implementation of an empirical spectral-matching algorithm using the high-resolution NIR HPF spectra. Using this algorithm, we obtain an effective temperature of Teff = 3404 ± 73 K and metallicity of [Fe/H] = -0.08 ± 0.13. Our RVs, when coupled with the orbital parameters derived from the transit photometry, exclude planet masses above 11.7M ⊕ with 99.7% confidence assuming a circular orbit. From its radius, we predict a mass of M =5.0-1.9+3.8inf>M⊕ and an RV semiamplitude of K= 4.1-1.6+3.1 m s-1, making its mass measurable with current RV facilities. We urge further RV follow-up observations to precisely measure its mass, to enable precise transmission spectroscopic measurements in the future.
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U2 - 10.3847/1538-3881/ab5f15
DO - 10.3847/1538-3881/ab5f15
M3 - Article
AN - SCOPUS:85085310545
SN - 0004-6256
VL - 159
JO - Astronomical Journal
JF - Astronomical Journal
IS - 3
M1 - 100
ER -