The K2-ESPRINT project. VI. K2-105 b, a hot Neptune around a metal-rich G-dwarf

Norio Narita; Teruyuki Hirano; Akihiko Fukui; Yasunori Hori; Fei Dai; Liang Yu; John Livingston; Tsuguru Ryu; Grzegorz Nowak; Masayuki Kuzuhara; Bun'ei Sato; Yoichi Takeda; Simon Albrecht; Tomoyuki Kudo; Nobuhiko Kusakabe; Enric Palle; Ignasi Ribas; Motohide Tamura; Vincent Van Eylen; Joshua N. Winn

doi:10.1093/pasj/psx002

The K2-ESPRINT project. VI. K2-105 b, a hot Neptune around a metal-rich G-dwarf

Norio Narita, Teruyuki Hirano, Akihiko Fukui, Yasunori Hori, Fei Dai, Liang Yu, John Livingston, Tsuguru Ryu, Grzegorz Nowak, Masayuki Kuzuhara, Bun'ei Sato, Yoichi Takeda, Simon Albrecht, Tomoyuki Kudo, Nobuhiko Kusakabe, Enric Palle, Ignasi Ribas, Motohide Tamura, Vincent Van Eylen, Joshua N. Winn

Astrophysical Sciences

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7 Scopus citations

Abstract

We report on the confirmation that the candidate transits observed for the star EPIC 211525389 are due to a short-period Neptune-sized planet. The host star, located in K2 campaign field 5, is a metal-rich ([Fe/H] = 0.26 ± 0.05) G-dwarf (T_eff = 5430 ± 70 K and log g = 4.48 ± 0.09), based on observations with the High Dispersion Spectrograph (HDS) on the Subaru 8.2 m telescope. High spatial resolution AO imaging with HiCIAO on the Subaru telescope excludes faint companions near the host star, and the false positive probability of this target is found to be <10^-6 using the open source vespa code. A joint analysis of transit light curves from K2 and additional ground-based multicolor transit photometry with MuSCAT on the Okayama 1.88 m telescope gives an orbital period of P = 8.266902 ± 0.000070 d and consistent transit depths of R_p/R_{black star} ∼ 0.035 or (R_p/R_{black star})² ∼ 0.0012. The transit depth corresponds to a planetary radius of R_p = 3.59_-0.39^+0.44 R_⊕, indicating that EPIC 211525389 b is a short-period Neptune-sized planet. Radial velocities of the host star, obtained with the Subaru HDS, lead to a 3 σ upper limit of 90 M_⊕ (0.00027 M_⊙) on the mass of EPIC 211525389 b, confirming its planetary nature. We expect this planet, newly named K2-105 b, to be the subject of future studies to characterize its mass, atmosphere, and spin-orbit (mis)alignment, as well as investigate the possibility of additional planets in the system.

Original language	English (US)
Article number	29
Journal	Publications of the Astronomical Society of Japan
Volume	69
Issue number	2
DOIs	https://doi.org/10.1093/pasj/psx002
State	Published - Apr 2017

All Science Journal Classification (ASJC) codes

Astronomy and Astrophysics
Space and Planetary Science

Keywords

Planets and satellites: individual (K2-105 b = EPIC 211525389 b)
Stars: individual (TYC 807-1019-1 = EPIC 211525389)
Techniques: high angular resolution
Techniques: photometric
Techniques: radial velocities
Techniques: spectroscopic

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Narita, N., Hirano, T., Fukui, A., Hori, Y., Dai, F., Yu, L., Livingston, J., Ryu, T., Nowak, G., Kuzuhara, M., Sato, B., Takeda, Y., Albrecht, S., Kudo, T., Kusakabe, N., Palle, E., Ribas, I., Tamura, M., Van Eylen, V., & Winn, J. N. (2017). The K2-ESPRINT project. VI. K2-105 b, a hot Neptune around a metal-rich G-dwarf. Publications of the Astronomical Society of Japan, 69(2), [29]. https://doi.org/10.1093/pasj/psx002

@article{0ef4105bbe8f47cc9b069a9137451eef,

title = "The K2-ESPRINT project. VI. K2-105 b, a hot Neptune around a metal-rich G-dwarf",

abstract = "We report on the confirmation that the candidate transits observed for the star EPIC 211525389 are due to a short-period Neptune-sized planet. The host star, located in K2 campaign field 5, is a metal-rich ([Fe/H] = 0.26 ± 0.05) G-dwarf (Teff = 5430 ± 70 K and log g = 4.48 ± 0.09), based on observations with the High Dispersion Spectrograph (HDS) on the Subaru 8.2 m telescope. High spatial resolution AO imaging with HiCIAO on the Subaru telescope excludes faint companions near the host star, and the false positive probability of this target is found to be <10-6 using the open source vespa code. A joint analysis of transit light curves from K2 and additional ground-based multicolor transit photometry with MuSCAT on the Okayama 1.88 m telescope gives an orbital period of P = 8.266902 ± 0.000070 d and consistent transit depths of Rp/Rblack star ∼ 0.035 or (Rp/Rblack star)2 ∼ 0.0012. The transit depth corresponds to a planetary radius of Rp = 3.59-0.39+0.44 R⊕, indicating that EPIC 211525389 b is a short-period Neptune-sized planet. Radial velocities of the host star, obtained with the Subaru HDS, lead to a 3 σ upper limit of 90 M⊕ (0.00027 M⊙) on the mass of EPIC 211525389 b, confirming its planetary nature. We expect this planet, newly named K2-105 b, to be the subject of future studies to characterize its mass, atmosphere, and spin-orbit (mis)alignment, as well as investigate the possibility of additional planets in the system.",

keywords = "Planets and satellites: individual (K2-105 b = EPIC 211525389 b), Stars: individual (TYC 807-1019-1 = EPIC 211525389), Techniques: high angular resolution, Techniques: photometric, Techniques: radial velocities, Techniques: spectroscopic",

author = "Norio Narita and Teruyuki Hirano and Akihiko Fukui and Yasunori Hori and Fei Dai and Liang Yu and John Livingston and Tsuguru Ryu and Grzegorz Nowak and Masayuki Kuzuhara and Bun'ei Sato and Yoichi Takeda and Simon Albrecht and Tomoyuki Kudo and Nobuhiko Kusakabe and Enric Palle and Ignasi Ribas and Motohide Tamura and {Van Eylen}, Vincent and Winn, {Joshua N.}",

note = "Funding Information: This work was supported by Japan Society for Promotion of Science (JSPS) KAKENHI Grant Numbers JP25247026, JP16K17660, 25-8826, JP16K17671, and JP15H02063. This work was also supported by the Astrobiology Center Project of National Institutes of Natural Sciences (NINS) (Grant Numbers AB271009, AB281012 and JY280092). I.R. acknowledges support by the Spanish Ministry of Economy and Competitiveness (MINECO) through grant ESP2014-57495-C2-2-R. We acknowledge Roberto Sanchis-Ojeda, who established the ESPRINT collaboration. We thank Akito Tajitsu and Hikaru Nagumo for support for our Subaru HDS observation, Jun Hashimoto for the Subaru HiCIAO observation, and Timothy Brandt for the HiCIAO data reduction. This paper is based on data collected at the Subaru telescope and Okayama 188 cm telescope, which are operated by the National Astronomical Observatory of Japan. The data analysis was in part carried out on a common use data analysis computer system at the Astronomy Data Center, ADC, of the National Astronomical Observatory of Japan. PyFITS and PyRAF were useful for our data reduction. PyFITS and PyRAF are products of the Space Telescope Science Institute, which is operated by AURA for NASA. Our analysis is also based on observations made with the NASA/ESA Hubble Space Telescope, and obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute, the Space Telescope European Coordinating Facility (ST-ECF/ESA), and the Canadian Astronomy Data Centre (CADC/NRC/CSA). This work has made use of data from the European Space Agency (ESA) mission Gaia (http://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, http://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. We acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous people in Hawai'i. Publisher Copyright: {\textcopyright} The Author 2017. Published by Oxford University Press on behalf of the Astronomical Society of Japan. All rights reserved.",

year = "2017",

month = apr,

doi = "10.1093/pasj/psx002",

language = "English (US)",

volume = "69",

journal = "Publication of the Astronomical Society of Japan",

issn = "0004-6264",

publisher = "Astronomical Society of Japan",

number = "2",

}

Narita, N, Hirano, T, Fukui, A, Hori, Y, Dai, F, Yu, L, Livingston, J, Ryu, T, Nowak, G, Kuzuhara, M, Sato, B, Takeda, Y, Albrecht, S, Kudo, T, Kusakabe, N, Palle, E, Ribas, I, Tamura, M, Van Eylen, V & Winn, JN 2017, 'The K2-ESPRINT project. VI. K2-105 b, a hot Neptune around a metal-rich G-dwarf', Publications of the Astronomical Society of Japan, vol. 69, no. 2, 29. https://doi.org/10.1093/pasj/psx002

TY - JOUR

T1 - The K2-ESPRINT project. VI. K2-105 b, a hot Neptune around a metal-rich G-dwarf

AU - Narita, Norio

AU - Hirano, Teruyuki

AU - Fukui, Akihiko

AU - Hori, Yasunori

AU - Dai, Fei

AU - Yu, Liang

AU - Livingston, John

AU - Ryu, Tsuguru

AU - Nowak, Grzegorz

AU - Kuzuhara, Masayuki

AU - Sato, Bun'ei

AU - Takeda, Yoichi

AU - Albrecht, Simon

AU - Kudo, Tomoyuki

AU - Kusakabe, Nobuhiko

AU - Palle, Enric

AU - Ribas, Ignasi

AU - Tamura, Motohide

AU - Van Eylen, Vincent

AU - Winn, Joshua N.

N1 - Funding Information: This work was supported by Japan Society for Promotion of Science (JSPS) KAKENHI Grant Numbers JP25247026, JP16K17660, 25-8826, JP16K17671, and JP15H02063. This work was also supported by the Astrobiology Center Project of National Institutes of Natural Sciences (NINS) (Grant Numbers AB271009, AB281012 and JY280092). I.R. acknowledges support by the Spanish Ministry of Economy and Competitiveness (MINECO) through grant ESP2014-57495-C2-2-R. We acknowledge Roberto Sanchis-Ojeda, who established the ESPRINT collaboration. We thank Akito Tajitsu and Hikaru Nagumo for support for our Subaru HDS observation, Jun Hashimoto for the Subaru HiCIAO observation, and Timothy Brandt for the HiCIAO data reduction. This paper is based on data collected at the Subaru telescope and Okayama 188 cm telescope, which are operated by the National Astronomical Observatory of Japan. The data analysis was in part carried out on a common use data analysis computer system at the Astronomy Data Center, ADC, of the National Astronomical Observatory of Japan. PyFITS and PyRAF were useful for our data reduction. PyFITS and PyRAF are products of the Space Telescope Science Institute, which is operated by AURA for NASA. Our analysis is also based on observations made with the NASA/ESA Hubble Space Telescope, and obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute, the Space Telescope European Coordinating Facility (ST-ECF/ESA), and the Canadian Astronomy Data Centre (CADC/NRC/CSA). This work has made use of data from the European Space Agency (ESA) mission Gaia (http://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, http://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. We acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous people in Hawai'i. Publisher Copyright: © The Author 2017. Published by Oxford University Press on behalf of the Astronomical Society of Japan. All rights reserved.

PY - 2017/4

Y1 - 2017/4

N2 - We report on the confirmation that the candidate transits observed for the star EPIC 211525389 are due to a short-period Neptune-sized planet. The host star, located in K2 campaign field 5, is a metal-rich ([Fe/H] = 0.26 ± 0.05) G-dwarf (Teff = 5430 ± 70 K and log g = 4.48 ± 0.09), based on observations with the High Dispersion Spectrograph (HDS) on the Subaru 8.2 m telescope. High spatial resolution AO imaging with HiCIAO on the Subaru telescope excludes faint companions near the host star, and the false positive probability of this target is found to be <10-6 using the open source vespa code. A joint analysis of transit light curves from K2 and additional ground-based multicolor transit photometry with MuSCAT on the Okayama 1.88 m telescope gives an orbital period of P = 8.266902 ± 0.000070 d and consistent transit depths of Rp/Rblack star ∼ 0.035 or (Rp/Rblack star)2 ∼ 0.0012. The transit depth corresponds to a planetary radius of Rp = 3.59-0.39+0.44 R⊕, indicating that EPIC 211525389 b is a short-period Neptune-sized planet. Radial velocities of the host star, obtained with the Subaru HDS, lead to a 3 σ upper limit of 90 M⊕ (0.00027 M⊙) on the mass of EPIC 211525389 b, confirming its planetary nature. We expect this planet, newly named K2-105 b, to be the subject of future studies to characterize its mass, atmosphere, and spin-orbit (mis)alignment, as well as investigate the possibility of additional planets in the system.

AB - We report on the confirmation that the candidate transits observed for the star EPIC 211525389 are due to a short-period Neptune-sized planet. The host star, located in K2 campaign field 5, is a metal-rich ([Fe/H] = 0.26 ± 0.05) G-dwarf (Teff = 5430 ± 70 K and log g = 4.48 ± 0.09), based on observations with the High Dispersion Spectrograph (HDS) on the Subaru 8.2 m telescope. High spatial resolution AO imaging with HiCIAO on the Subaru telescope excludes faint companions near the host star, and the false positive probability of this target is found to be <10-6 using the open source vespa code. A joint analysis of transit light curves from K2 and additional ground-based multicolor transit photometry with MuSCAT on the Okayama 1.88 m telescope gives an orbital period of P = 8.266902 ± 0.000070 d and consistent transit depths of Rp/Rblack star ∼ 0.035 or (Rp/Rblack star)2 ∼ 0.0012. The transit depth corresponds to a planetary radius of Rp = 3.59-0.39+0.44 R⊕, indicating that EPIC 211525389 b is a short-period Neptune-sized planet. Radial velocities of the host star, obtained with the Subaru HDS, lead to a 3 σ upper limit of 90 M⊕ (0.00027 M⊙) on the mass of EPIC 211525389 b, confirming its planetary nature. We expect this planet, newly named K2-105 b, to be the subject of future studies to characterize its mass, atmosphere, and spin-orbit (mis)alignment, as well as investigate the possibility of additional planets in the system.

KW - Planets and satellites: individual (K2-105 b = EPIC 211525389 b)

KW - Stars: individual (TYC 807-1019-1 = EPIC 211525389)

KW - Techniques: high angular resolution

KW - Techniques: photometric

KW - Techniques: radial velocities

KW - Techniques: spectroscopic

UR - http://www.scopus.com/inward/record.url?scp=85019448276&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85019448276&partnerID=8YFLogxK

U2 - 10.1093/pasj/psx002

DO - 10.1093/pasj/psx002

M3 - Article

AN - SCOPUS:85019448276

SN - 0004-6264

VL - 69

JO - Publication of the Astronomical Society of Japan

JF - Publication of the Astronomical Society of Japan

IS - 2

M1 - 29

ER -

The K2-ESPRINT project. VI. K2-105 b, a hot Neptune around a metal-rich G-dwarf

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