Characterization of two new transiting sub-Neptunes and a terrestrial planet around M-dwarf hosts

E. Poultourtzidis; G. Lacedelli; E. Pallé; I. Carleo; C. Magliano; S. Geraldía-González; J. A. Caballero; G. Morello; J. Orell-Miquel; H. M. Tabernero; F. Murgas; G. Covone; F. J. Pozuelos; P. J. Amado; V. J. S. Béjar; S. Chairetas; C. Cifuentes; D. R. Ciardi; K. A. Collins; I. J. M. Crossfield; E. Esparza-Borges; G. Fernández-Rodríguez; A. Fukui; Y. Hayashi; A. P. Hatzes; Th. Henning; E. Herrero; K. Horne; S. B. Howell; K. Isogai; J. M. Jenkins; Y. Kawai; F. Libotte; E. Matthews; P. Meni-Gallardo; I. Mireles; J. C. Morales; N. Narita; B. B. Ogunwale; H. Parviainen; A. Quirrenbach; A. Reiners; I. Ribas; R. Sefako; A. Shporer; R. P. Schwarz; G. Srdoc; L. Tal-Or; S. Vanaverbeke; N. Watanabe; C. N. Watkins; F. Zong Lang

doi:10.1051/0004-6361/202557155

Characterization of two new transiting sub-Neptunes and a terrestrial planet around M-dwarf hosts

E. Poultourtzidis^*
, G. Lacedelli
, E. Pallé
, I. Carleo
, C. Magliano
, S. Geraldía-González
, J. A. Caballero
, G. Morello
, J. Orell-Miquel
, H. M. Tabernero
, F. Murgas
, G. Covone
, F. J. Pozuelos
, P. J. Amado
, V. J. S. Béjar
, S. Chairetas
, C. Cifuentes
, D. R. Ciardi
, K. A. Collins
, I. J. M. Crossfield

E. Esparza-Borges, G. Fernández-Rodríguez, A. Fukui, Y. Hayashi, A. P. Hatzes, Th. Henning, E. Herrero, K. Horne, S. B. Howell, K. Isogai, J. M. Jenkins, Y. Kawai, F. Libotte, E. Matthews, P. Meni-Gallardo, I. Mireles, J. C. Morales, N. Narita, B. B. Ogunwale, H. Parviainen, A. Quirrenbach, A. Reiners, I. Ribas, R. Sefako, A. Shporer, R. P. Schwarz, G. Srdoc, L. Tal-Or, S. Vanaverbeke, N. Watanabe, C. N. Watkins, F. Zong Lang

^*Corresponding author for this work

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

Abstract

We report the confirmation of three transiting exoplanets orbiting TOI-1243 (LSPM J0902+7138), TOI-4529 (G 2-21), and TOI-5388 (Wolf 346) that were initially detected by TESS through ground-based photometry and radial velocity follow-up measurements with CARMENES. The planets present short orbital periods of 4.65, 5.88, and 2.59 days, and they orbit early-M dwarfs (M2.0 V, M1.5 V, and M3.0 V, respectively). We were able to precisely determine the radius of all three planets with a precision of <7%, the mass of TOI-1243 b with a precision of 19%, and upper mass limits for TOI-4529 b and TOI-5388 b. The radius of TOI-1243 b is 2.33 ± 0.12 R ⊕ , its mass is 7.7 ± 1.5 M ⊕ , and the mean density is 0.61 ± 0.15 ρ_⊕ . The radius of TOI-4529b is 1.77_−0.08^+0.09 R ⊕ , the 3 σ upper mass limit is 4.9 M_⊕ , and the 3σ upper density limit is 0.88 ρ_⊕ . The third planet, TOI-5388 b, is Earth-sized with a radius of 0.99_−0.06^+0.07 R_⊕ , a 3σ upper mass limit of 2.2 M_⊕ , and a 3 σ upper density limit of 2.2 ρ_⊕ . While TOI-5388 b is most probably rocky, given its Earth-like radius, TOI-1243 b and TOI-4529 b are located in a highly degenerate region in the mass-radius space. TOI-4529 b appears to lean toward a water-world composition. TOI-1243 b has enough mass to host a significant H-He envelope, although a water-world and pure rocky compositions are also consistent with the data. Our analysis indicates that future atmospheric observations using JWST can aid in determining their real composition. The sample of small planets around M dwarfs is widely used to understand planet formation and composition theories, and our study adds three planets to this sample.

Original language	English
Pages (from-to)	A106
Number of pages	20
Journal	Astronomy & Astrophysics
Volume	707
DOIs	https://doi.org/10.1051/0004-6361/202557155
Publication status	Published - 13 Mar 2026

Keywords

Techniques: photometric
Techniques: radial velocities
Planets and satellites: detection
Stars: individal: TOI-1243
Stars: individual: TOI-5388

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Poultourtzidis_2026_AaA_Characterization-transiting-sub-Neptunes_CC
© The Authors 2026. 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.
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TOI-1243, TOI-4529, TOI-5388 RV datasets : J/A+A/707/A106
Horne, K. (Creator), VizieR On-line Data Catalog, 2026
DOI: 10.26093/cds/vizier/bc-p3/lbag, https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/707/A106
Dataset

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Poultourtzidis, E., Lacedelli, G., Pallé, E., Carleo, I., Magliano, C., Geraldía-González, S., Caballero, J. A., Morello, G., Orell-Miquel, J., Tabernero, H. M., Murgas, F., Covone, G., Pozuelos, F. J., Amado, P. J., Béjar, V. J. S., Chairetas, S., Cifuentes, C., Ciardi, D. R., Collins, K. A., ... Zong Lang, F. (2026). Characterization of two new transiting sub-Neptunes and a terrestrial planet around M-dwarf hosts. Astronomy & Astrophysics, 707, A106. https://doi.org/10.1051/0004-6361/202557155

@article{f5aa7cbcedd748f3b790153ff67bf26e,

title = "Characterization of two new transiting sub-Neptunes and a terrestrial planet around M-dwarf hosts",

abstract = "We report the confirmation of three transiting exoplanets orbiting TOI-1243 (LSPM J0902+7138), TOI-4529 (G 2-21), and TOI-5388 (Wolf 346) that were initially detected by TESS through ground-based photometry and radial velocity follow-up measurements with CARMENES. The planets present short orbital periods of 4.65, 5.88, and 2.59 days, and they orbit early-M dwarfs (M2.0 V, M1.5 V, and M3.0 V, respectively). We were able to precisely determine the radius of all three planets with a precision of <7\%, the mass of TOI-1243 b with a precision of 19\%, and upper mass limits for TOI-4529 b and TOI-5388 b. The radius of TOI-1243 b is 2.33 ± 0.12 R ⊕ , its mass is 7.7 ± 1.5 M ⊕ , and the mean density is 0.61 ± 0.15 ρ⊕ . The radius of TOI-4529b is 1.77−0.08+0.09 R ⊕ , the 3 σ upper mass limit is 4.9 M⊕ , and the 3σ upper density limit is 0.88 ρ⊕ . The third planet, TOI-5388 b, is Earth-sized with a radius of 0.99−0.06+0.07 R⊕ , a 3σ upper mass limit of 2.2 M⊕ , and a 3 σ upper density limit of 2.2 ρ⊕ . While TOI-5388 b is most probably rocky, given its Earth-like radius, TOI-1243 b and TOI-4529 b are located in a highly degenerate region in the mass-radius space. TOI-4529 b appears to lean toward a water-world composition. TOI-1243 b has enough mass to host a significant H-He envelope, although a water-world and pure rocky compositions are also consistent with the data. Our analysis indicates that future atmospheric observations using JWST can aid in determining their real composition. The sample of small planets around M dwarfs is widely used to understand planet formation and composition theories, and our study adds three planets to this sample.",

keywords = "Techniques: photometric, Techniques: radial velocities, Planets and satellites: detection, Stars: individal: TOI-1243, Stars: individual: TOI-5388",

author = "E. Poultourtzidis and G. Lacedelli and E. Pall{\'e} and I. Carleo and C. Magliano and S. Gerald{\'i}a-Gonz{\'a}lez and Caballero, \{J. A.\} and G. Morello and J. Orell-Miquel and Tabernero, \{H. M.\} and F. Murgas and G. Covone and Pozuelos, \{F. J.\} and Amado, \{P. J.\} and B{\'e}jar, \{V. J. S.\} and S. Chairetas and C. Cifuentes and Ciardi, \{D. R.\} and Collins, \{K. A.\} and Crossfield, \{I. J. M.\} and E. Esparza-Borges and G. Fern{\'a}ndez-Rodr{\'i}guez and A. Fukui and Y. Hayashi and Hatzes, \{A. P.\} and Th. Henning and E. Herrero and K. Horne and Howell, \{S. B.\} and K. Isogai and Jenkins, \{J. M.\} and Y. Kawai and F. Libotte and E. Matthews and P. Meni-Gallardo and I. Mireles and Morales, \{J. C.\} and N. Narita and Ogunwale, \{B. B.\} and H. Parviainen and A. Quirrenbach and A. Reiners and I. Ribas and R. Sefako and A. Shporer and Schwarz, \{R. P.\} and G. Srdoc and L. Tal-Or and S. Vanaverbeke and N. Watanabe and Watkins, \{C. N.\} and \{Zong Lang\}, F.",

note = "Funding: The authors acknowledge financial support from the Agencia Estatal de Investigaci{\'o}n (AEI/10.13039/501100011033) of the Ministerio de Ciencia e Innovaci{\'o}n and the ERDF {\textquotedblleft}A way of making Europe{\textquotedblright} through projects PID2023-150468NBI00, PID2022-137241NB-C4[1:4], PID2021-125627OB-C31, PRE2020-093107 (FPI-SO), RYC2022-037854-I, the internal project 20235AT003 associated to RYC2021-031640-I, and the Centre of Excellence {\textquotedblleft}Severo Ochoa{\textquotedblright} and {\textquotedblleft}Mar{\'i}a de Maeztu{\textquotedblright} awards to Instituto de Astrof{\'i}sica de Andaluc{\'i}a (CEX2021-001131S) and Institut de Ci{\`e}ncies de l{\textquoteright}Espai (CEX2020-001058-M). This work is partly supported by JSPS KAKENHI Grant Numbers JP24H00017, JP24K00689, JSPS Bilateral Program Number JPJSBP120249910, JSPS Grant-in-Aid for JSPS Fellows Grant Numbers JP25KJ1036, JP25KJ0091, and JST SPRING, Grant Number JPMJSP2108.BBO and LT-O acknowledge support from The Israel Ministry of Innovation, Science, and Technology through Grant number 0008107, and by The Israel Science Foundation through grant No. 1404/22.",

year = "2026",

month = mar,

day = "13",

doi = "10.1051/0004-6361/202557155",

language = "English",

volume = "707",

pages = "A106",

journal = "Astronomy \& Astrophysics",

issn = "0004-6361",

publisher = "EDP Sciences",

}

Poultourtzidis, E, Lacedelli, G, Pallé, E, Carleo, I, Magliano, C, Geraldía-González, S, Caballero, JA, Morello, G, Orell-Miquel, J, Tabernero, HM, Murgas, F, Covone, G, Pozuelos, FJ, Amado, PJ, Béjar, VJS, Chairetas, S, Cifuentes, C, Ciardi, DR, Collins, KA, Crossfield, IJM, Esparza-Borges, E, Fernández-Rodríguez, G, Fukui, A, Hayashi, Y, Hatzes, AP, Henning, T, Herrero, E, Horne, K, Howell, SB, Isogai, K, Jenkins, JM, Kawai, Y, Libotte, F, Matthews, E, Meni-Gallardo, P, Mireles, I, Morales, JC, Narita, N, Ogunwale, BB, Parviainen, H, Quirrenbach, A, Reiners, A, Ribas, I, Sefako, R, Shporer, A, Schwarz, RP, Srdoc, G, Tal-Or, L, Vanaverbeke, S, Watanabe, N, Watkins, CN & Zong Lang, F 2026, 'Characterization of two new transiting sub-Neptunes and a terrestrial planet around M-dwarf hosts', Astronomy & Astrophysics, vol. 707, pp. A106. https://doi.org/10.1051/0004-6361/202557155

TY - JOUR

T1 - Characterization of two new transiting sub-Neptunes and a terrestrial planet around M-dwarf hosts

AU - Poultourtzidis, E.

AU - Lacedelli, G.

AU - Pallé, E.

AU - Carleo, I.

AU - Magliano, C.

AU - Geraldía-González, S.

AU - Caballero, J. A.

AU - Morello, G.

AU - Orell-Miquel, J.

AU - Tabernero, H. M.

AU - Murgas, F.

AU - Covone, G.

AU - Pozuelos, F. J.

AU - Amado, P. J.

AU - Béjar, V. J. S.

AU - Chairetas, S.

AU - Cifuentes, C.

AU - Ciardi, D. R.

AU - Collins, K. A.

AU - Crossfield, I. J. M.

AU - Esparza-Borges, E.

AU - Fernández-Rodríguez, G.

AU - Fukui, A.

AU - Hayashi, Y.

AU - Hatzes, A. P.

AU - Henning, Th.

AU - Herrero, E.

AU - Horne, K.

AU - Howell, S. B.

AU - Isogai, K.

AU - Jenkins, J. M.

AU - Kawai, Y.

AU - Libotte, F.

AU - Matthews, E.

AU - Meni-Gallardo, P.

AU - Mireles, I.

AU - Morales, J. C.

AU - Narita, N.

AU - Ogunwale, B. B.

AU - Parviainen, H.

AU - Quirrenbach, A.

AU - Reiners, A.

AU - Ribas, I.

AU - Sefako, R.

AU - Shporer, A.

AU - Schwarz, R. P.

AU - Srdoc, G.

AU - Tal-Or, L.

AU - Vanaverbeke, S.

AU - Watanabe, N.

AU - Watkins, C. N.

AU - Zong Lang, F.

N1 - Funding: The authors acknowledge financial support from the Agencia Estatal de Investigación (AEI/10.13039/501100011033) of the Ministerio de Ciencia e Innovación and the ERDF “A way of making Europe” through projects PID2023-150468NBI00, PID2022-137241NB-C4[1:4], PID2021-125627OB-C31, PRE2020-093107 (FPI-SO), RYC2022-037854-I, the internal project 20235AT003 associated to RYC2021-031640-I, and the Centre of Excellence “Severo Ochoa” and “María de Maeztu” awards to Instituto de Astrofísica de Andalucía (CEX2021-001131S) and Institut de Ciències de l’Espai (CEX2020-001058-M). This work is partly supported by JSPS KAKENHI Grant Numbers JP24H00017, JP24K00689, JSPS Bilateral Program Number JPJSBP120249910, JSPS Grant-in-Aid for JSPS Fellows Grant Numbers JP25KJ1036, JP25KJ0091, and JST SPRING, Grant Number JPMJSP2108.BBO and LT-O acknowledge support from The Israel Ministry of Innovation, Science, and Technology through Grant number 0008107, and by The Israel Science Foundation through grant No. 1404/22.

PY - 2026/3/13

Y1 - 2026/3/13

N2 - We report the confirmation of three transiting exoplanets orbiting TOI-1243 (LSPM J0902+7138), TOI-4529 (G 2-21), and TOI-5388 (Wolf 346) that were initially detected by TESS through ground-based photometry and radial velocity follow-up measurements with CARMENES. The planets present short orbital periods of 4.65, 5.88, and 2.59 days, and they orbit early-M dwarfs (M2.0 V, M1.5 V, and M3.0 V, respectively). We were able to precisely determine the radius of all three planets with a precision of <7%, the mass of TOI-1243 b with a precision of 19%, and upper mass limits for TOI-4529 b and TOI-5388 b. The radius of TOI-1243 b is 2.33 ± 0.12 R ⊕ , its mass is 7.7 ± 1.5 M ⊕ , and the mean density is 0.61 ± 0.15 ρ⊕ . The radius of TOI-4529b is 1.77−0.08+0.09 R ⊕ , the 3 σ upper mass limit is 4.9 M⊕ , and the 3σ upper density limit is 0.88 ρ⊕ . The third planet, TOI-5388 b, is Earth-sized with a radius of 0.99−0.06+0.07 R⊕ , a 3σ upper mass limit of 2.2 M⊕ , and a 3 σ upper density limit of 2.2 ρ⊕ . While TOI-5388 b is most probably rocky, given its Earth-like radius, TOI-1243 b and TOI-4529 b are located in a highly degenerate region in the mass-radius space. TOI-4529 b appears to lean toward a water-world composition. TOI-1243 b has enough mass to host a significant H-He envelope, although a water-world and pure rocky compositions are also consistent with the data. Our analysis indicates that future atmospheric observations using JWST can aid in determining their real composition. The sample of small planets around M dwarfs is widely used to understand planet formation and composition theories, and our study adds three planets to this sample.

AB - We report the confirmation of three transiting exoplanets orbiting TOI-1243 (LSPM J0902+7138), TOI-4529 (G 2-21), and TOI-5388 (Wolf 346) that were initially detected by TESS through ground-based photometry and radial velocity follow-up measurements with CARMENES. The planets present short orbital periods of 4.65, 5.88, and 2.59 days, and they orbit early-M dwarfs (M2.0 V, M1.5 V, and M3.0 V, respectively). We were able to precisely determine the radius of all three planets with a precision of <7%, the mass of TOI-1243 b with a precision of 19%, and upper mass limits for TOI-4529 b and TOI-5388 b. The radius of TOI-1243 b is 2.33 ± 0.12 R ⊕ , its mass is 7.7 ± 1.5 M ⊕ , and the mean density is 0.61 ± 0.15 ρ⊕ . The radius of TOI-4529b is 1.77−0.08+0.09 R ⊕ , the 3 σ upper mass limit is 4.9 M⊕ , and the 3σ upper density limit is 0.88 ρ⊕ . The third planet, TOI-5388 b, is Earth-sized with a radius of 0.99−0.06+0.07 R⊕ , a 3σ upper mass limit of 2.2 M⊕ , and a 3 σ upper density limit of 2.2 ρ⊕ . While TOI-5388 b is most probably rocky, given its Earth-like radius, TOI-1243 b and TOI-4529 b are located in a highly degenerate region in the mass-radius space. TOI-4529 b appears to lean toward a water-world composition. TOI-1243 b has enough mass to host a significant H-He envelope, although a water-world and pure rocky compositions are also consistent with the data. Our analysis indicates that future atmospheric observations using JWST can aid in determining their real composition. The sample of small planets around M dwarfs is widely used to understand planet formation and composition theories, and our study adds three planets to this sample.

KW - Techniques: photometric

KW - Techniques: radial velocities

KW - Planets and satellites: detection

KW - Stars: individal: TOI-1243

KW - Stars: individual: TOI-5388

U2 - 10.1051/0004-6361/202557155

DO - 10.1051/0004-6361/202557155

M3 - Article

SN - 0004-6361

VL - 707

SP - A106

JO - Astronomy & Astrophysics

JF - Astronomy & Astrophysics

ER -

Characterization of two new transiting sub-Neptunes and a terrestrial planet around M-dwarf hosts

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Keywords

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TOI-1243, TOI-4529, TOI-5388 RV datasets : J/A+A/707/A106

Cite this