Refining the properties of the TOI-178 system with CHEOPS and TESS

L. Delrez; A. Leleu; A. Brandeker; M. Gillon; M. J. Hooton; A. Collier Cameron; A. Deline; A. Fortier; D. Queloz; A. Bonfanti; V. Van Grootel; T. G. Wilson; J. A. Egger; Y. Alibert; R. Alonso; G. Anglada; J. Asquier; T. Bárczy; D. Barrado y Navascues; S. C. C. Barros; W. Baumjohann; M. Beck; T. Beck; W. Benz; N. Billot; X. Bonfils; L. Borsato; C. Broeg; M. Buder; J. Cabrera; V. Cessa; S. Charnoz; Sz. Csizmadia; P. E. Cubillos; M. B. Davies; M. Deleuil; O. D. S. Demangeon; B.-O. Demory; D. Ehrenreich; A. Erikson; L. Fossati; M. Fridlund; D. Gandolfi; M. Güdel; J. Hasiba; S. Hoyer; K. G. Isaak; J. M. Jenkins; L. L. Kiss; J. Laskar; D. W. Latham; A. Lecavelier Des Etangs; M. Lendl; C. Lovis; R. Luque; D. Magrin; P. F. L. Maxted; C. Mordasini; V. Nascimbeni; G. Olofsson; R. Ottensamer; I. Pagano; E. Pallé; G. Peter; G. Piotto; D. Pollacco; R. Ragazzoni; N. Rando; H. Rauer; I. Ribas; G. Ricker; N. C. Santos; G. Scandariato; S. Seager; D. Ségransan; A. E. Simon; A. M. S. Smith; S. G. Sousa; M. Steller; Gy. M. Szabó; N. Thomas; S. Udry; R. Vanderspek; J. Venturini; V. Viotto; N. A. Walton; J. N. Winn

doi:10.1051/0004-6361/202245479

Refining the properties of the TOI-178 system with CHEOPS and TESS

L. Delrez^*, A. Leleu, A. Brandeker, M. Gillon, M. J. Hooton, A. Collier Cameron, A. Deline, A. Fortier, D. Queloz, A. Bonfanti, V. Van Grootel, T. G. Wilson, J. A. Egger, Y. Alibert, R. Alonso, G. Anglada, J. Asquier, T. Bárczy, D. Barrado y Navascues, S. C. C. BarrosW. Baumjohann, M. Beck, T. Beck, W. Benz, N. Billot, X. Bonfils, L. Borsato, C. Broeg, M. Buder, J. Cabrera, V. Cessa, S. Charnoz, Sz. Csizmadia, P. E. Cubillos, M. B. Davies, M. Deleuil, O. D. S. Demangeon, B.-O. Demory, D. Ehrenreich, A. Erikson, L. Fossati, M. Fridlund, D. Gandolfi, M. Güdel, J. Hasiba, S. Hoyer, K. G. Isaak, J. M. Jenkins, L. L. Kiss, J. Laskar, D. W. Latham, A. Lecavelier Des Etangs, M. Lendl, C. Lovis, R. Luque, D. Magrin, P. F. L. Maxted, C. Mordasini, V. Nascimbeni, G. Olofsson, R. Ottensamer, I. Pagano, E. Pallé, G. Peter, G. Piotto, D. Pollacco, R. Ragazzoni, N. Rando, H. Rauer, I. Ribas, G. Ricker, N. C. Santos, G. Scandariato, S. Seager, D. Ségransan, A. E. Simon, A. M. S. Smith, S. G. Sousa, M. Steller, Gy. M. Szabó, N. Thomas, S. Udry, R. Vanderspek, J. Venturini, V. Viotto, N. A. Walton, J. N. Winn

^*Corresponding author for this work

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

Abstract

Context. The TOI-178 system consists of a nearby late K-dwarf transited by six planets in the super-Earth to mini-Neptune regime, with radii ranging from ~1.1 to 2.9 R_⊕ and orbital periods between 1.9 and 20.7 days. All planets but the innermost one form a chain of Laplace resonances. Mass estimates derived from a preliminary radial velocity (RV) dataset suggest that the planetary densities do not decrease in a monotonic way with the orbital distance to the star, contrary to what one would expect based on simple formation and evolution models.

Aims. To improve the characterisation of this key system and prepare for future studies (in particular with JWST), we performed a detailed photometric study based on 40 new CHEOPS visits, one new TESS sector, and previously published CHEOPS, TESS, and NGTS data.

Methods. First we updated the parameters of the host star using the new parallax from Gaia EDR3. We then performed a global analysis of the 100 transits contained in our data to refine the physical and orbital parameters of the six planets and study their transit timing variations (TTVs). We also used our extensive dataset to place constraints on the radii and orbital periods of potential additional transiting planets in the system.

Results. Our analysis significantly refines the transit parameters of the six planets, most notably their radii, for which we now obtain relative precisions of ≲3%, with the exception of the smallest planet, b, for which the precision is 5.1%. Combined with the RV mass estimates, the measured TTVs allow us to constrain the eccentricities of planets c to g, which are found to be all below 0.02, as expected from stability requirements. Taken alone, the TTVs also suggest a higher mass for planet d than that estimated from the RVs, which had been found to yield a surprisingly low density for this planet. However, the masses derived from the current TTV dataset are very prior-dependent, and further observations, over a longer temporal baseline, are needed to deepen our understanding of this iconic planetary system.

Original language	English
Article number	A200
Number of pages	19
Journal	Astronomy & Astrophysics
Volume	678
DOIs	https://doi.org/10.1051/0004-6361/202245479
Publication status	Published - 27 Oct 2023

Keywords

Planetary systems
Stars: individual: TOI-178
Techniques: photometric

Access to Document

10.1051/0004-6361/202245479Licence: CC BY

Delrez_2023_AaA_Refining-properties-TOI-178-system_CC
© The Authors 2023. Open Access article, published under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Final published version, 8.85 MBLicence: CC BY

Cite this

Delrez, L., Leleu, A., Brandeker, A., Gillon, M., Hooton, M. J., Collier Cameron, A., Deline, A., Fortier, A., Queloz, D., Bonfanti, A., Van Grootel, V., Wilson, T. G., Egger, J. A., Alibert, Y., Alonso, R., Anglada, G., Asquier, J., Bárczy, T., Barrado y Navascues, D., ... Winn, J. N. (2023). Refining the properties of the TOI-178 system with CHEOPS and TESS. Astronomy & Astrophysics, 678, Article A200. https://doi.org/10.1051/0004-6361/202245479

@article{83341f126d7b4f04a4870e7c7bb3e77e,

title = "Refining the properties of the TOI-178 system with CHEOPS and TESS",

abstract = "Context. The TOI-178 system consists of a nearby late K-dwarf transited by six planets in the super-Earth to mini-Neptune regime, with radii ranging from \textasciitilde{}1.1 to 2.9 R⊕ and orbital periods between 1.9 and 20.7 days. All planets but the innermost one form a chain of Laplace resonances. Mass estimates derived from a preliminary radial velocity (RV) dataset suggest that the planetary densities do not decrease in a monotonic way with the orbital distance to the star, contrary to what one would expect based on simple formation and evolution models. Aims. To improve the characterisation of this key system and prepare for future studies (in particular with JWST), we performed a detailed photometric study based on 40 new CHEOPS visits, one new TESS sector, and previously published CHEOPS, TESS, and NGTS data. Methods. First we updated the parameters of the host star using the new parallax from Gaia EDR3. We then performed a global analysis of the 100 transits contained in our data to refine the physical and orbital parameters of the six planets and study their transit timing variations (TTVs). We also used our extensive dataset to place constraints on the radii and orbital periods of potential additional transiting planets in the system. Results. Our analysis significantly refines the transit parameters of the six planets, most notably their radii, for which we now obtain relative precisions of ≲3\%, with the exception of the smallest planet, b, for which the precision is 5.1\%. Combined with the RV mass estimates, the measured TTVs allow us to constrain the eccentricities of planets c to g, which are found to be all below 0.02, as expected from stability requirements. Taken alone, the TTVs also suggest a higher mass for planet d than that estimated from the RVs, which had been found to yield a surprisingly low density for this planet. However, the masses derived from the current TTV dataset are very prior-dependent, and further observations, over a longer temporal baseline, are needed to deepen our understanding of this iconic planetary system.",

keywords = "Planetary systems, Stars: individual: TOI-178, Techniques: photometric",

author = "L. Delrez and A. Leleu and A. Brandeker and M. Gillon and Hooton, \{M. J.\} and \{Collier Cameron\}, A. and A. Deline and A. Fortier and D. Queloz and A. Bonfanti and \{Van Grootel\}, V. and Wilson, \{T. G.\} and Egger, \{J. A.\} and Y. Alibert and R. Alonso and G. Anglada and J. Asquier and T. B{\'a}rczy and \{Barrado y Navascues\}, D. and Barros, \{S. C. C.\} and W. Baumjohann and M. Beck and T. Beck and W. Benz and N. Billot and X. Bonfils and L. Borsato and C. Broeg and M. Buder and J. Cabrera and V. Cessa and S. Charnoz and Sz. Csizmadia and Cubillos, \{P. E.\} and Davies, \{M. B.\} and M. Deleuil and Demangeon, \{O. D. S.\} and B.-O. Demory and D. Ehrenreich and A. Erikson and L. Fossati and M. Fridlund and D. Gandolfi and M. G{\"u}del and J. Hasiba and S. Hoyer and Isaak, \{K. G.\} and Jenkins, \{J. M.\} and Kiss, \{L. L.\} and J. Laskar and Latham, \{D. W.\} and \{Lecavelier Des Etangs\}, A. and M. Lendl and C. Lovis and R. Luque and D. Magrin and Maxted, \{P. F. L.\} and C. Mordasini and V. Nascimbeni and G. Olofsson and R. Ottensamer and I. Pagano and E. Pall{\'e} and G. Peter and G. Piotto and D. Pollacco and R. Ragazzoni and N. Rando and H. Rauer and I. Ribas and G. Ricker and Santos, \{N. C.\} and G. Scandariato and S. Seager and D. S{\'e}gransan and Simon, \{A. E.\} and Smith, \{A. M. S.\} and Sousa, \{S. G.\} and M. Steller and Szab{\'o}, \{Gy. M.\} and N. Thomas and S. Udry and R. Vanderspek and J. Venturini and V. Viotto and Walton, \{N. A.\} and Winn, \{J. N.\}",

note = "Funding: L.D. is an F.R.S.-FNRS Postdoctoral Researcher. This work has been carried out within the framework of the NCCR PlanetS supported by the Swiss National Science Foundation under grants 51NF40\_182901 and 51NF40\_205606. A.Br. was supported by the SNSA. M.G. is an F.R.S.-FNRS Senior Research Associate. A.C.C. acknowledges support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant number ST/R003203/1. This work was also partially supported by a grant from the Simons Foundation (PI Queloz, grant number 327127). V.V.G. is an F.R.S.-FNRS Research Associate. A.C.C. and T.G.W. acknowledge support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant number ST/R003203/1. Y.A. and M.J.H. acknowledge the support of the Swiss National Fund under grant 200020\_172746. We acknowledge support from the Spanish Ministry of Science and Innovation and the European Regional Development Fund through grants ESP2016-80435-C2-1-R, ESP2016-80435-C2-2-R, PGC2018-098153- B-C33, PGC2018-098153-B-C31, ESP2017-87676-C5-1-R, MDM-2017-0737 Unidad de Excelencia Maria de Maeztu-Centro de Astrobiolog{\'i}a (INTA- CSIC), as well as the support of the Generalitat de Catalunya/CERCA programme. The MOC activities have been supported by the ESA contract No. 4000124370. S.C.C.B. acknowledges support from FCT through FCT contracts nr. IF/01312/2014/CP1215/CT0004. X.B., S.C., D.G., M.F. and J.L. acknowledge their role as ESA-appointed CHEOPS science team members. L.Bo., G.Br., V.Na., I.Pa., G.Pi., R.Ra., G.Sc., V.Si., and T.Zi. acknowledge support from CHEOPS ASI-INAF agreement n. 2019-29-HH.0. P.E.C. is funded by the Austrian Science Fund (FWF) Erwin Schroedinger Fellowship, program J4595-N. This project was supported by the CNES. This work was supported by FCT – Funda{\c c}{\~a}o para a Ci{\^e}ncia e a Tecnologia through national funds and by FEDER through COMPETE2020 – Programa Operacional Competitividade e Internacionalizac{\~a}o by these grants: UID/FIS/04434/2019, UIDB/04434/2020, UIDP/04434/2020, PTDC/FIS-AST/32113/2017 and POCI-01-0145-FEDER- 032113, PTDC/FIS-AST/28953/2017 and POCI-01-0145-FEDER-028953, PTDC/FIS-AST/28987/2017 and POCI-01-0145-FEDER-028987. O.D.S.D. is supported in the form of work contract (DL 57/2016/CP1364/CT0004) funded by national funds through FCT. B.-O.D. acknowledges support from the Swiss State Secretariat for Education, Research and Innovation (SERI) under contract number MB22.00046. This project has received funding from the European Research Council (ERC) under the European Union{\textquoteright}s Horizon 2020 research and innovation programme (project FOUR ACES, grant agreement No 724427). It has also been carried out in the frame of the National Centre for Competence in Research PlanetS supported by the Swiss National Science Foundation (SNSF). D.E. acknowledges financial support from the Swiss National Science Foundation for project 200021\_200726. M.F. gratefully acknowledges the support of the Swedish National Space Agency (DNR 65/19, 174/18). D.G. gratefully acknowledges financial support from the CRT foundation under Grant No. 2018.2323 {\textquoteleft}Gaseous or rocky? Unveiling the nature of small worlds{\textquoteright}. S.H. gratefully acknowledges CNES funding through the grant 837319. M.L. acknowledges support of the Swiss National Science Foundation under grant number PCEFP2\_194576. R.L. acknowledges funding from University of La Laguna through the Margarita Salas Fellowship from the Spanish Ministry of Universities ref. UNI/551/2021-May 26, and under the EU Next Generation funds. P.M. acknowledges support from STFC research grant number ST/M001040/1. I.Ri. acknowledges support from the Spanish Ministry of Science and Innovation and the European Regional Development Fund through grant PGC2018-098153-B-C33, as well as the support of the Generalitat de Catalunya/CERCA programme. S.G.S. acknowledges support from FCT through FCT contract nr. CEECIND/00826/2018 and POPH/FSE (EC). Gy.M.Sz. acknowledges the support of the Hungarian National Research, Development and Innovation Office (NKFIH) grant K-125015, a PRODEX Experiment Agreement No. 4000137122, the Lend{\"u}let LP2018-7/2021 grant of the Hungarian Academy of Science and the support of the city of Szombathely. N.A.W. acknowledges UKSA grant ST/R004838/1.",

year = "2023",

month = oct,

day = "27",

doi = "10.1051/0004-6361/202245479",

language = "English",

volume = "678",

journal = "Astronomy \& Astrophysics",

issn = "0004-6361",

publisher = "EDP Sciences",

}

Delrez, L, Leleu, A, Brandeker, A, Gillon, M, Hooton, MJ, Collier Cameron, A, Deline, A, Fortier, A, Queloz, D, Bonfanti, A, Van Grootel, V, Wilson, TG, Egger, JA, Alibert, Y, Alonso, R, Anglada, G, Asquier, J, Bárczy, T, Barrado y Navascues, D, Barros, SCC, Baumjohann, W, Beck, M, Beck, T, Benz, W, Billot, N, Bonfils, X, Borsato, L, Broeg, C, Buder, M, Cabrera, J, Cessa, V, Charnoz, S, Csizmadia, S, Cubillos, PE, Davies, MB, Deleuil, M, Demangeon, ODS, Demory, B-O, Ehrenreich, D, Erikson, A, Fossati, L, Fridlund, M, Gandolfi, D, Güdel, M, Hasiba, J, Hoyer, S, Isaak, KG, Jenkins, JM, Kiss, LL, Laskar, J, Latham, DW, Lecavelier Des Etangs, A, Lendl, M, Lovis, C, Luque, R, Magrin, D, Maxted, PFL, Mordasini, C, Nascimbeni, V, Olofsson, G, Ottensamer, R, Pagano, I, Pallé, E, Peter, G, Piotto, G, Pollacco, D, Ragazzoni, R, Rando, N, Rauer, H, Ribas, I, Ricker, G, Santos, NC, Scandariato, G, Seager, S, Ségransan, D, Simon, AE, Smith, AMS, Sousa, SG, Steller, M, Szabó, GM, Thomas, N, Udry, S, Vanderspek, R, Venturini, J, Viotto, V, Walton, NA & Winn, JN 2023, 'Refining the properties of the TOI-178 system with CHEOPS and TESS', Astronomy & Astrophysics, vol. 678, A200. https://doi.org/10.1051/0004-6361/202245479

TY - JOUR

T1 - Refining the properties of the TOI-178 system with CHEOPS and TESS

AU - Delrez, L.

AU - Leleu, A.

AU - Brandeker, A.

AU - Gillon, M.

AU - Hooton, M. J.

AU - Collier Cameron, A.

AU - Deline, A.

AU - Fortier, A.

AU - Queloz, D.

AU - Bonfanti, A.

AU - Van Grootel, V.

AU - Wilson, T. G.

AU - Egger, J. A.

AU - Alibert, Y.

AU - Alonso, R.

AU - Anglada, G.

AU - Asquier, J.

AU - Bárczy, T.

AU - Barrado y Navascues, D.

AU - Barros, S. C. C.

AU - Baumjohann, W.

AU - Beck, M.

AU - Beck, T.

AU - Benz, W.

AU - Billot, N.

AU - Bonfils, X.

AU - Borsato, L.

AU - Broeg, C.

AU - Buder, M.

AU - Cabrera, J.

AU - Cessa, V.

AU - Charnoz, S.

AU - Csizmadia, Sz.

AU - Cubillos, P. E.

AU - Davies, M. B.

AU - Deleuil, M.

AU - Demangeon, O. D. S.

AU - Demory, B.-O.

AU - Ehrenreich, D.

AU - Erikson, A.

AU - Fossati, L.

AU - Fridlund, M.

AU - Gandolfi, D.

AU - Güdel, M.

AU - Hasiba, J.

AU - Hoyer, S.

AU - Isaak, K. G.

AU - Jenkins, J. M.

AU - Kiss, L. L.

AU - Laskar, J.

AU - Latham, D. W.

AU - Lecavelier Des Etangs, A.

AU - Lendl, M.

AU - Lovis, C.

AU - Luque, R.

AU - Magrin, D.

AU - Maxted, P. F. L.

AU - Mordasini, C.

AU - Nascimbeni, V.

AU - Olofsson, G.

AU - Ottensamer, R.

AU - Pagano, I.

AU - Pallé, E.

AU - Peter, G.

AU - Piotto, G.

AU - Pollacco, D.

AU - Ragazzoni, R.

AU - Rando, N.

AU - Rauer, H.

AU - Ribas, I.

AU - Ricker, G.

AU - Santos, N. C.

AU - Scandariato, G.

AU - Seager, S.

AU - Ségransan, D.

AU - Simon, A. E.

AU - Smith, A. M. S.

AU - Sousa, S. G.

AU - Steller, M.

AU - Szabó, Gy. M.

AU - Thomas, N.

AU - Udry, S.

AU - Vanderspek, R.

AU - Venturini, J.

AU - Viotto, V.

AU - Walton, N. A.

AU - Winn, J. N.

N1 - Funding: L.D. is an F.R.S.-FNRS Postdoctoral Researcher. This work has been carried out within the framework of the NCCR PlanetS supported by the Swiss National Science Foundation under grants 51NF40_182901 and 51NF40_205606. A.Br. was supported by the SNSA. M.G. is an F.R.S.-FNRS Senior Research Associate. A.C.C. acknowledges support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant number ST/R003203/1. This work was also partially supported by a grant from the Simons Foundation (PI Queloz, grant number 327127). V.V.G. is an F.R.S.-FNRS Research Associate. A.C.C. and T.G.W. acknowledge support from STFC consolidated grant numbers ST/R000824/1 and ST/V000861/1, and UKSA grant number ST/R003203/1. Y.A. and M.J.H. acknowledge the support of the Swiss National Fund under grant 200020_172746. We acknowledge support from the Spanish Ministry of Science and Innovation and the European Regional Development Fund through grants ESP2016-80435-C2-1-R, ESP2016-80435-C2-2-R, PGC2018-098153- B-C33, PGC2018-098153-B-C31, ESP2017-87676-C5-1-R, MDM-2017-0737 Unidad de Excelencia Maria de Maeztu-Centro de Astrobiología (INTA- CSIC), as well as the support of the Generalitat de Catalunya/CERCA programme. The MOC activities have been supported by the ESA contract No. 4000124370. S.C.C.B. acknowledges support from FCT through FCT contracts nr. IF/01312/2014/CP1215/CT0004. X.B., S.C., D.G., M.F. and J.L. acknowledge their role as ESA-appointed CHEOPS science team members. L.Bo., G.Br., V.Na., I.Pa., G.Pi., R.Ra., G.Sc., V.Si., and T.Zi. acknowledge support from CHEOPS ASI-INAF agreement n. 2019-29-HH.0. P.E.C. is funded by the Austrian Science Fund (FWF) Erwin Schroedinger Fellowship, program J4595-N. This project was supported by the CNES. This work was supported by FCT – Fundação para a Ciência e a Tecnologia through national funds and by FEDER through COMPETE2020 – Programa Operacional Competitividade e Internacionalizacão by these grants: UID/FIS/04434/2019, UIDB/04434/2020, UIDP/04434/2020, PTDC/FIS-AST/32113/2017 and POCI-01-0145-FEDER- 032113, PTDC/FIS-AST/28953/2017 and POCI-01-0145-FEDER-028953, PTDC/FIS-AST/28987/2017 and POCI-01-0145-FEDER-028987. O.D.S.D. is supported in the form of work contract (DL 57/2016/CP1364/CT0004) funded by national funds through FCT. B.-O.D. acknowledges support from the Swiss State Secretariat for Education, Research and Innovation (SERI) under contract number MB22.00046. This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (project FOUR ACES, grant agreement No 724427). It has also been carried out in the frame of the National Centre for Competence in Research PlanetS supported by the Swiss National Science Foundation (SNSF). D.E. acknowledges financial support from the Swiss National Science Foundation for project 200021_200726. M.F. gratefully acknowledges the support of the Swedish National Space Agency (DNR 65/19, 174/18). D.G. gratefully acknowledges financial support from the CRT foundation under Grant No. 2018.2323 ‘Gaseous or rocky? Unveiling the nature of small worlds’. S.H. gratefully acknowledges CNES funding through the grant 837319. M.L. acknowledges support of the Swiss National Science Foundation under grant number PCEFP2_194576. R.L. acknowledges funding from University of La Laguna through the Margarita Salas Fellowship from the Spanish Ministry of Universities ref. UNI/551/2021-May 26, and under the EU Next Generation funds. P.M. acknowledges support from STFC research grant number ST/M001040/1. I.Ri. acknowledges support from the Spanish Ministry of Science and Innovation and the European Regional Development Fund through grant PGC2018-098153-B-C33, as well as the support of the Generalitat de Catalunya/CERCA programme. S.G.S. acknowledges support from FCT through FCT contract nr. CEECIND/00826/2018 and POPH/FSE (EC). Gy.M.Sz. acknowledges the support of the Hungarian National Research, Development and Innovation Office (NKFIH) grant K-125015, a PRODEX Experiment Agreement No. 4000137122, the Lendület LP2018-7/2021 grant of the Hungarian Academy of Science and the support of the city of Szombathely. N.A.W. acknowledges UKSA grant ST/R004838/1.

PY - 2023/10/27

Y1 - 2023/10/27

N2 - Context. The TOI-178 system consists of a nearby late K-dwarf transited by six planets in the super-Earth to mini-Neptune regime, with radii ranging from ~1.1 to 2.9 R⊕ and orbital periods between 1.9 and 20.7 days. All planets but the innermost one form a chain of Laplace resonances. Mass estimates derived from a preliminary radial velocity (RV) dataset suggest that the planetary densities do not decrease in a monotonic way with the orbital distance to the star, contrary to what one would expect based on simple formation and evolution models. Aims. To improve the characterisation of this key system and prepare for future studies (in particular with JWST), we performed a detailed photometric study based on 40 new CHEOPS visits, one new TESS sector, and previously published CHEOPS, TESS, and NGTS data. Methods. First we updated the parameters of the host star using the new parallax from Gaia EDR3. We then performed a global analysis of the 100 transits contained in our data to refine the physical and orbital parameters of the six planets and study their transit timing variations (TTVs). We also used our extensive dataset to place constraints on the radii and orbital periods of potential additional transiting planets in the system. Results. Our analysis significantly refines the transit parameters of the six planets, most notably their radii, for which we now obtain relative precisions of ≲3%, with the exception of the smallest planet, b, for which the precision is 5.1%. Combined with the RV mass estimates, the measured TTVs allow us to constrain the eccentricities of planets c to g, which are found to be all below 0.02, as expected from stability requirements. Taken alone, the TTVs also suggest a higher mass for planet d than that estimated from the RVs, which had been found to yield a surprisingly low density for this planet. However, the masses derived from the current TTV dataset are very prior-dependent, and further observations, over a longer temporal baseline, are needed to deepen our understanding of this iconic planetary system.

AB - Context. The TOI-178 system consists of a nearby late K-dwarf transited by six planets in the super-Earth to mini-Neptune regime, with radii ranging from ~1.1 to 2.9 R⊕ and orbital periods between 1.9 and 20.7 days. All planets but the innermost one form a chain of Laplace resonances. Mass estimates derived from a preliminary radial velocity (RV) dataset suggest that the planetary densities do not decrease in a monotonic way with the orbital distance to the star, contrary to what one would expect based on simple formation and evolution models. Aims. To improve the characterisation of this key system and prepare for future studies (in particular with JWST), we performed a detailed photometric study based on 40 new CHEOPS visits, one new TESS sector, and previously published CHEOPS, TESS, and NGTS data. Methods. First we updated the parameters of the host star using the new parallax from Gaia EDR3. We then performed a global analysis of the 100 transits contained in our data to refine the physical and orbital parameters of the six planets and study their transit timing variations (TTVs). We also used our extensive dataset to place constraints on the radii and orbital periods of potential additional transiting planets in the system. Results. Our analysis significantly refines the transit parameters of the six planets, most notably their radii, for which we now obtain relative precisions of ≲3%, with the exception of the smallest planet, b, for which the precision is 5.1%. Combined with the RV mass estimates, the measured TTVs allow us to constrain the eccentricities of planets c to g, which are found to be all below 0.02, as expected from stability requirements. Taken alone, the TTVs also suggest a higher mass for planet d than that estimated from the RVs, which had been found to yield a surprisingly low density for this planet. However, the masses derived from the current TTV dataset are very prior-dependent, and further observations, over a longer temporal baseline, are needed to deepen our understanding of this iconic planetary system.

KW - Planetary systems

KW - Stars: individual: TOI-178

KW - Techniques: photometric

UR - https://www.scopus.com/pages/publications/85176108636

U2 - 10.1051/0004-6361/202245479

DO - 10.1051/0004-6361/202245479

M3 - Article

AN - SCOPUS:85176108636

SN - 0004-6361

VL - 678

JO - Astronomy & Astrophysics

JF - Astronomy & Astrophysics

M1 - A200

ER -

Refining the properties of the TOI-178 system with CHEOPS and TESS

Abstract

Keywords

Access to Document

Other files and links

Fingerprint

AO2 - Professor Andrew Cameron: Project AO2 - Andrew Cameron

Support for the PLATO Development: Support for the PLATO Development Phase 2017-2022: Planet candidate ranking and validation