Eyes on K2-3: A system of three likely sub-Neptunes characterized with HARPS-N and HARPS

M. Damasso; A. S. Bonomo; N. Astudillo-Defru; X. Bonfils; L. Malavolta; A. Sozzetti; E. Lopez; L. Zeng; R. D. Haywood; J. M. Irwin; A. Mortier; A. Vanderburg; J. Maldonado; A. F. Lanza; L. Affer; J. M. Almenara; S. Benatti; K. Biazzo; A. Bignamini; F. Borsa; F. Bouchy; L. A. Buchhave; A. C. Cameron; I. Carleo; D. Charbonneau; R. Claudi; R. Cosentino; E. Covino; X. Delfosse; S. Desidera; L. Di Fabrizio; C. Dressing; M. Esposito; R. Fares; P. Figueira; A. F.M. Fiorenzano; T. Forveille; P. Giacobbe; E. González-Álvarez; R. Gratton; A. Harutyunyan; J. Asher Johnson; D. W. Latham; G. Leto; M. Lopez-Morales; C. Lovis; A. Maggio; L. Mancini; S. Masiero; M. Mayor; G. Micela; E. Molinari; F. Motalebi; F. Murgas; V. Nascimbeni; I. Pagano; F. Pepe; D. F. Phillips; G. Piotto; E. Poretti; M. Rainer; K. Rice; N. C. Santos; D. Sasselov; G. Scandariato; D. Ségransan; R. Smareglia; S. Udry; C. Watson; A. Wünsche

doi:10.1051/0004-6361/201732459

Eyes on K2-3: A system of three likely sub-Neptunes characterized with HARPS-N and HARPS

M. Damasso, A. S. Bonomo, N. Astudillo-Defru, X. Bonfils, L. Malavolta, A. Sozzetti, E. Lopez, L. Zeng, R. D. Haywood, J. M. Irwin, A. Mortier, A. Vanderburg, J. Maldonado, A. F. Lanza, L. Affer, J. M. Almenara, S. Benatti, K. Biazzo, A. Bignamini, F. BorsaF. Bouchy, L. A. Buchhave, A. C. Cameron, I. Carleo, D. Charbonneau, R. Claudi, R. Cosentino, E. Covino, X. Delfosse, S. Desidera, L. Di Fabrizio, C. Dressing, M. Esposito, R. Fares, P. Figueira, A. F.M. Fiorenzano, T. Forveille, P. Giacobbe, E. González-Álvarez, R. Gratton, A. Harutyunyan, J. Asher Johnson, D. W. Latham, G. Leto, M. Lopez-Morales, C. Lovis, A. Maggio, L. Mancini, S. Masiero, M. Mayor, G. Micela, E. Molinari, F. Motalebi, F. Murgas, V. Nascimbeni, I. Pagano, F. Pepe, D. F. Phillips, G. Piotto, E. Poretti, M. Rainer, K. Rice, N. C. Santos, D. Sasselov, G. Scandariato, D. Ségransan, R. Smareglia, S. Udry, C. Watson, A. Wünsche

Physics and Astronomy

Research output: Contribution to journal › Article › peer-review

24 Citations (Scopus)

Abstract

Context. M-dwarf stars are promising targets for identifying and characterizing potentially habitable planets. K2-3 is a nearby (45 pc), early-typeMdwarf hosting three small transiting planets, the outermost of which orbits close to the inner edge of the stellar (optimistic) habitable zone. The K2-3 system is well suited for follow-up characterization studies aimed at determining accurate masses and bulk densities of the three planets. Aims. Using a total of 329 radial velocity measurements collected over 2.5 years with the HARPS-N and HARPS spectrographs and a proper treatment of the stellar activity signal, we aim to improve measurements of the masses and bulk densities of the K2-3 planets. We use our results to investigate the physical structure of the planets. Methods. We analysed radial velocity time series extracted with two independent pipelines using Gaussian process regression. We adopted a quasi-periodic kernel to model the stellar magnetic activity jointly with the planetary signals. We used Monte Carlo simulations to investigate the robustness of our mass measurements of K2-3 c and K2-3 d, and to explore how additional high-cadence radial velocity observations might improve these values. Results. Even though the stellar activity component is the strongest signal present in the radial velocity time series, we are able to derive masses for both planet b (M_b = 6.6 ± 1.1 M_⊙) and planet c (Mc = 3.1+1.3 -1:2 M_⊙). The Doppler signal from K2-3 d remains undetected, likely because of its low amplitude compared to the radial velocity signal induced by the stellar activity. The closeness of the orbital period of K2-3 d to the stellar rotation period could also make the detection of the planetary signal complicated. Based on our ability to recover injected signals in simulated data, we tentatively estimate the mass of K2-3 d to be Md = 2.7+1.2 -0:8 M_⊙. These mass measurements imply that the bulk densities and therefore the interior structures of the three planets may be similar. In particular, the planets may either have small H/He envelopes (<1%) or massive water layers, with a water content ~50% of their total mass, on top of rocky cores. Placing further constraints on the bulk densities of K2-3 c and d is difficult; in particular, we would not have been able to detect the Doppler signal of K2-3 d even by adopting a semester of intense, high-cadence radial velocity observations with HARPS-N and HARPS.

Original language	English
Article number	A69
Journal	Astronomy and Astrophysics
Volume	615
DOIs	https://doi.org/10.1051/0004-6361/201732459
Publication status	Published - 1 Jul 2018

Bibliographical note

Funding Information:
Acknowledgements. MD acknowledges funding from INAF through the Progetti Premiali funding scheme of the Italian Ministry of Education, University, and Research. We used high performance computing resources made available by INAF through the pilot programme CHIPP (through the proposal Precise planetary mass determination in radial velocity data collected with the HARPS and HARPS-N spectrographs: facing the challenges posed by the time sampling and the presence of stellar noise). We especially thank F. Vitello (INAF-OACt) for his assistance within the CHIPP programme. This research has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant Agreement No. 313014 (ETAEARTH). Parts of this work have been supported by NASA under grants No. NNX15AC90G and NNX17AB59G issued through the Exoplanets Research Program. AVa acknowledges support from the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. PF acknowledges support by Fundação para a Ciência e a Tecnologia (FCT) through Investigador FCT contract of reference IF/01037/2013/CP1191/CT0001, and POPH/FSE (EC) by FEDER funding through the programme “Programa Operacional de Factores de Competitividade -COMPETE”. NCS acknowledges support by Fundação para a Ciência e a Tecnologia (FCT, Portugal) through the research grant through national funds and by FEDER through COMPETE2020 by grants UID/FIS/04434/2013 & POCI-01-0145-FEDER-007672 and PTDC/FIS-AST/1526/2014 & POCI-01-0145-FEDER-016886, as well as through Investigador FCT contract nr. IF/00169/2012/CP0150/CT0002.

Publisher Copyright:
© ESO 2018.

Keywords

Planets and satellites: composition
Planets and satellites: detection
Stars: individual: 2MASS 11292037-0127173
Stars: individual: EPIC 201367065
Stars: individual: K2-3
Techniques: radial velocities

ASJC Scopus subject areas

Astronomy and Astrophysics
Space and Planetary Science

Access to Document

10.1051/0004-6361/201732459

Cite this

Damasso, M., Bonomo, A. S., Astudillo-Defru, N., Bonfils, X., Malavolta, L., Sozzetti, A., Lopez, E., Zeng, L., Haywood, R. D., Irwin, J. M., Mortier, A., Vanderburg, A., Maldonado, J., Lanza, A. F., Affer, L., Almenara, J. M., Benatti, S., Biazzo, K., Bignamini, A., ... Wünsche, A. (2018). Eyes on K2-3: A system of three likely sub-Neptunes characterized with HARPS-N and HARPS. Astronomy and Astrophysics, 615, Article A69. https://doi.org/10.1051/0004-6361/201732459

@article{80cd6c05efc44bf19482514c842fe461,

title = "Eyes on K2-3: A system of three likely sub-Neptunes characterized with HARPS-N and HARPS",

abstract = "Context. M-dwarf stars are promising targets for identifying and characterizing potentially habitable planets. K2-3 is a nearby (45 pc), early-typeMdwarf hosting three small transiting planets, the outermost of which orbits close to the inner edge of the stellar (optimistic) habitable zone. The K2-3 system is well suited for follow-up characterization studies aimed at determining accurate masses and bulk densities of the three planets. Aims. Using a total of 329 radial velocity measurements collected over 2.5 years with the HARPS-N and HARPS spectrographs and a proper treatment of the stellar activity signal, we aim to improve measurements of the masses and bulk densities of the K2-3 planets. We use our results to investigate the physical structure of the planets. Methods. We analysed radial velocity time series extracted with two independent pipelines using Gaussian process regression. We adopted a quasi-periodic kernel to model the stellar magnetic activity jointly with the planetary signals. We used Monte Carlo simulations to investigate the robustness of our mass measurements of K2-3 c and K2-3 d, and to explore how additional high-cadence radial velocity observations might improve these values. Results. Even though the stellar activity component is the strongest signal present in the radial velocity time series, we are able to derive masses for both planet b (Mb = 6.6 ± 1.1 M⊙) and planet c (Mc = 3.1+1.3 -1:2 M⊙). The Doppler signal from K2-3 d remains undetected, likely because of its low amplitude compared to the radial velocity signal induced by the stellar activity. The closeness of the orbital period of K2-3 d to the stellar rotation period could also make the detection of the planetary signal complicated. Based on our ability to recover injected signals in simulated data, we tentatively estimate the mass of K2-3 d to be Md = 2.7+1.2 -0:8 M⊙. These mass measurements imply that the bulk densities and therefore the interior structures of the three planets may be similar. In particular, the planets may either have small H/He envelopes (<1%) or massive water layers, with a water content ~50% of their total mass, on top of rocky cores. Placing further constraints on the bulk densities of K2-3 c and d is difficult; in particular, we would not have been able to detect the Doppler signal of K2-3 d even by adopting a semester of intense, high-cadence radial velocity observations with HARPS-N and HARPS.",

keywords = "Planets and satellites: composition, Planets and satellites: detection, Stars: individual: 2MASS 11292037-0127173, Stars: individual: EPIC 201367065, Stars: individual: K2-3, Techniques: radial velocities",

author = "M. Damasso and Bonomo, {A. S.} and N. Astudillo-Defru and X. Bonfils and L. Malavolta and A. Sozzetti and E. Lopez and L. Zeng and Haywood, {R. D.} and Irwin, {J. M.} and A. Mortier and A. Vanderburg and J. Maldonado and Lanza, {A. F.} and L. Affer and Almenara, {J. M.} and S. Benatti and K. Biazzo and A. Bignamini and F. Borsa and F. Bouchy and Buchhave, {L. A.} and Cameron, {A. C.} and I. Carleo and D. Charbonneau and R. Claudi and R. Cosentino and E. Covino and X. Delfosse and S. Desidera and {Di Fabrizio}, L. and C. Dressing and M. Esposito and R. Fares and P. Figueira and Fiorenzano, {A. F.M.} and T. Forveille and P. Giacobbe and E. Gonz{\'a}lez-{\'A}lvarez and R. Gratton and A. Harutyunyan and Johnson, {J. Asher} and Latham, {D. W.} and G. Leto and M. Lopez-Morales and C. Lovis and A. Maggio and L. Mancini and S. Masiero and M. Mayor and G. Micela and E. Molinari and F. Motalebi and F. Murgas and V. Nascimbeni and I. Pagano and F. Pepe and Phillips, {D. F.} and G. Piotto and E. Poretti and M. Rainer and K. Rice and Santos, {N. C.} and D. Sasselov and G. Scandariato and D. S{\'e}gransan and R. Smareglia and S. Udry and C. Watson and A. W{\"u}nsche",

note = "Funding Information: Acknowledgements. MD acknowledges funding from INAF through the Progetti Premiali funding scheme of the Italian Ministry of Education, University, and Research. We used high performance computing resources made available by INAF through the pilot programme CHIPP (through the proposal Precise planetary mass determination in radial velocity data collected with the HARPS and HARPS-N spectrographs: facing the challenges posed by the time sampling and the presence of stellar noise). We especially thank F. Vitello (INAF-OACt) for his assistance within the CHIPP programme. This research has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant Agreement No. 313014 (ETAEARTH). Parts of this work have been supported by NASA under grants No. NNX15AC90G and NNX17AB59G issued through the Exoplanets Research Program. AVa acknowledges support from the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. PF acknowledges support by Funda{\c c}{\~a}o para a Ci{\^e}ncia e a Tecnologia (FCT) through Investigador FCT contract of reference IF/01037/2013/CP1191/CT0001, and POPH/FSE (EC) by FEDER funding through the programme “Programa Operacional de Factores de Competitividade -COMPETE”. NCS acknowledges support by Funda{\c c}{\~a}o para a Ci{\^e}ncia e a Tecnologia (FCT, Portugal) through the research grant through national funds and by FEDER through COMPETE2020 by grants UID/FIS/04434/2013 & POCI-01-0145-FEDER-007672 and PTDC/FIS-AST/1526/2014 & POCI-01-0145-FEDER-016886, as well as through Investigador FCT contract nr. IF/00169/2012/CP0150/CT0002. Publisher Copyright: {\textcopyright} ESO 2018.",

year = "2018",

month = jul,

day = "1",

doi = "10.1051/0004-6361/201732459",

language = "English",

volume = "615",

journal = "Astronomy and Astrophysics",

issn = "0004-6361",

publisher = "EDP Sciences",

}

Damasso, M, Bonomo, AS, Astudillo-Defru, N, Bonfils, X, Malavolta, L, Sozzetti, A, Lopez, E, Zeng, L, Haywood, RD, Irwin, JM, Mortier, A, Vanderburg, A, Maldonado, J, Lanza, AF, Affer, L, Almenara, JM, Benatti, S, Biazzo, K, Bignamini, A, Borsa, F, Bouchy, F, Buchhave, LA, Cameron, AC, Carleo, I, Charbonneau, D, Claudi, R, Cosentino, R, Covino, E, Delfosse, X, Desidera, S, Di Fabrizio, L, Dressing, C, Esposito, M, Fares, R, Figueira, P, Fiorenzano, AFM, Forveille, T, Giacobbe, P, González-Álvarez, E, Gratton, R, Harutyunyan, A, Johnson, JA, Latham, DW, Leto, G, Lopez-Morales, M, Lovis, C, Maggio, A, Mancini, L, Masiero, S, Mayor, M, Micela, G, Molinari, E, Motalebi, F, Murgas, F, Nascimbeni, V, Pagano, I, Pepe, F, Phillips, DF, Piotto, G, Poretti, E, Rainer, M, Rice, K, Santos, NC, Sasselov, D, Scandariato, G, Ségransan, D, Smareglia, R, Udry, S, Watson, C & Wünsche, A 2018, 'Eyes on K2-3: A system of three likely sub-Neptunes characterized with HARPS-N and HARPS', Astronomy and Astrophysics, vol. 615, A69. https://doi.org/10.1051/0004-6361/201732459

TY - JOUR

T1 - Eyes on K2-3

T2 - A system of three likely sub-Neptunes characterized with HARPS-N and HARPS

AU - Damasso, M.

AU - Bonomo, A. S.

AU - Astudillo-Defru, N.

AU - Bonfils, X.

AU - Malavolta, L.

AU - Sozzetti, A.

AU - Lopez, E.

AU - Zeng, L.

AU - Haywood, R. D.

AU - Irwin, J. M.

AU - Mortier, A.

AU - Vanderburg, A.

AU - Maldonado, J.

AU - Lanza, A. F.

AU - Affer, L.

AU - Almenara, J. M.

AU - Benatti, S.

AU - Biazzo, K.

AU - Bignamini, A.

AU - Borsa, F.

AU - Bouchy, F.

AU - Buchhave, L. A.

AU - Cameron, A. C.

AU - Carleo, I.

AU - Charbonneau, D.

AU - Claudi, R.

AU - Cosentino, R.

AU - Covino, E.

AU - Delfosse, X.

AU - Desidera, S.

AU - Di Fabrizio, L.

AU - Dressing, C.

AU - Esposito, M.

AU - Fares, R.

AU - Figueira, P.

AU - Fiorenzano, A. F.M.

AU - Forveille, T.

AU - Giacobbe, P.

AU - González-Álvarez, E.

AU - Gratton, R.

AU - Harutyunyan, A.

AU - Johnson, J. Asher

AU - Latham, D. W.

AU - Leto, G.

AU - Lopez-Morales, M.

AU - Lovis, C.

AU - Maggio, A.

AU - Mancini, L.

AU - Masiero, S.

AU - Mayor, M.

AU - Micela, G.

AU - Molinari, E.

AU - Motalebi, F.

AU - Murgas, F.

AU - Nascimbeni, V.

AU - Pagano, I.

AU - Pepe, F.

AU - Phillips, D. F.

AU - Piotto, G.

AU - Poretti, E.

AU - Rainer, M.

AU - Rice, K.

AU - Santos, N. C.

AU - Sasselov, D.

AU - Scandariato, G.

AU - Ségransan, D.

AU - Smareglia, R.

AU - Udry, S.

AU - Watson, C.

AU - Wünsche, A.

N1 - Funding Information: Acknowledgements. MD acknowledges funding from INAF through the Progetti Premiali funding scheme of the Italian Ministry of Education, University, and Research. We used high performance computing resources made available by INAF through the pilot programme CHIPP (through the proposal Precise planetary mass determination in radial velocity data collected with the HARPS and HARPS-N spectrographs: facing the challenges posed by the time sampling and the presence of stellar noise). We especially thank F. Vitello (INAF-OACt) for his assistance within the CHIPP programme. This research has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant Agreement No. 313014 (ETAEARTH). Parts of this work have been supported by NASA under grants No. NNX15AC90G and NNX17AB59G issued through the Exoplanets Research Program. AVa acknowledges support from the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. PF acknowledges support by Fundação para a Ciência e a Tecnologia (FCT) through Investigador FCT contract of reference IF/01037/2013/CP1191/CT0001, and POPH/FSE (EC) by FEDER funding through the programme “Programa Operacional de Factores de Competitividade -COMPETE”. NCS acknowledges support by Fundação para a Ciência e a Tecnologia (FCT, Portugal) through the research grant through national funds and by FEDER through COMPETE2020 by grants UID/FIS/04434/2013 & POCI-01-0145-FEDER-007672 and PTDC/FIS-AST/1526/2014 & POCI-01-0145-FEDER-016886, as well as through Investigador FCT contract nr. IF/00169/2012/CP0150/CT0002. Publisher Copyright: © ESO 2018.

PY - 2018/7/1

Y1 - 2018/7/1

N2 - Context. M-dwarf stars are promising targets for identifying and characterizing potentially habitable planets. K2-3 is a nearby (45 pc), early-typeMdwarf hosting three small transiting planets, the outermost of which orbits close to the inner edge of the stellar (optimistic) habitable zone. The K2-3 system is well suited for follow-up characterization studies aimed at determining accurate masses and bulk densities of the three planets. Aims. Using a total of 329 radial velocity measurements collected over 2.5 years with the HARPS-N and HARPS spectrographs and a proper treatment of the stellar activity signal, we aim to improve measurements of the masses and bulk densities of the K2-3 planets. We use our results to investigate the physical structure of the planets. Methods. We analysed radial velocity time series extracted with two independent pipelines using Gaussian process regression. We adopted a quasi-periodic kernel to model the stellar magnetic activity jointly with the planetary signals. We used Monte Carlo simulations to investigate the robustness of our mass measurements of K2-3 c and K2-3 d, and to explore how additional high-cadence radial velocity observations might improve these values. Results. Even though the stellar activity component is the strongest signal present in the radial velocity time series, we are able to derive masses for both planet b (Mb = 6.6 ± 1.1 M⊙) and planet c (Mc = 3.1+1.3 -1:2 M⊙). The Doppler signal from K2-3 d remains undetected, likely because of its low amplitude compared to the radial velocity signal induced by the stellar activity. The closeness of the orbital period of K2-3 d to the stellar rotation period could also make the detection of the planetary signal complicated. Based on our ability to recover injected signals in simulated data, we tentatively estimate the mass of K2-3 d to be Md = 2.7+1.2 -0:8 M⊙. These mass measurements imply that the bulk densities and therefore the interior structures of the three planets may be similar. In particular, the planets may either have small H/He envelopes (<1%) or massive water layers, with a water content ~50% of their total mass, on top of rocky cores. Placing further constraints on the bulk densities of K2-3 c and d is difficult; in particular, we would not have been able to detect the Doppler signal of K2-3 d even by adopting a semester of intense, high-cadence radial velocity observations with HARPS-N and HARPS.

AB - Context. M-dwarf stars are promising targets for identifying and characterizing potentially habitable planets. K2-3 is a nearby (45 pc), early-typeMdwarf hosting three small transiting planets, the outermost of which orbits close to the inner edge of the stellar (optimistic) habitable zone. The K2-3 system is well suited for follow-up characterization studies aimed at determining accurate masses and bulk densities of the three planets. Aims. Using a total of 329 radial velocity measurements collected over 2.5 years with the HARPS-N and HARPS spectrographs and a proper treatment of the stellar activity signal, we aim to improve measurements of the masses and bulk densities of the K2-3 planets. We use our results to investigate the physical structure of the planets. Methods. We analysed radial velocity time series extracted with two independent pipelines using Gaussian process regression. We adopted a quasi-periodic kernel to model the stellar magnetic activity jointly with the planetary signals. We used Monte Carlo simulations to investigate the robustness of our mass measurements of K2-3 c and K2-3 d, and to explore how additional high-cadence radial velocity observations might improve these values. Results. Even though the stellar activity component is the strongest signal present in the radial velocity time series, we are able to derive masses for both planet b (Mb = 6.6 ± 1.1 M⊙) and planet c (Mc = 3.1+1.3 -1:2 M⊙). The Doppler signal from K2-3 d remains undetected, likely because of its low amplitude compared to the radial velocity signal induced by the stellar activity. The closeness of the orbital period of K2-3 d to the stellar rotation period could also make the detection of the planetary signal complicated. Based on our ability to recover injected signals in simulated data, we tentatively estimate the mass of K2-3 d to be Md = 2.7+1.2 -0:8 M⊙. These mass measurements imply that the bulk densities and therefore the interior structures of the three planets may be similar. In particular, the planets may either have small H/He envelopes (<1%) or massive water layers, with a water content ~50% of their total mass, on top of rocky cores. Placing further constraints on the bulk densities of K2-3 c and d is difficult; in particular, we would not have been able to detect the Doppler signal of K2-3 d even by adopting a semester of intense, high-cadence radial velocity observations with HARPS-N and HARPS.

KW - Planets and satellites: composition

KW - Planets and satellites: detection

KW - Stars: individual: 2MASS 11292037-0127173

KW - Stars: individual: EPIC 201367065

KW - Stars: individual: K2-3

KW - Techniques: radial velocities

UR - http://www.scopus.com/inward/record.url?scp=85056663058&partnerID=8YFLogxK

U2 - 10.1051/0004-6361/201732459

DO - 10.1051/0004-6361/201732459

M3 - Article

AN - SCOPUS:85056663058

SN - 0004-6361

VL - 615

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

M1 - A69

ER -

Eyes on K2-3: A system of three likely sub-Neptunes characterized with HARPS-N and HARPS

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Keywords

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