Radii, masses, and transit-timing variations of the three-planet system orbiting the naked-eye star TOI-396
Context . TOI-396 is an F6 V bright naked-eye star ( V ≈ 6.4) orbited by three small ( R p ≈ 2 R ⊕ ) transiting planets discovered thanks to space-based photometry from two TESS sectors. The orbital periods of the two innermost planets, namely TOI-396 b and c, are close to the 5:3 commensurability (...
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| Veröffentlicht in: | Astronomy and astrophysics (Berlin) 2025-01, Vol.693, p.A90 |
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| creator | Bonfanti, A. Amateis, I. Gandolfi, D. Borsato, L. Egger, J. A. Cubillos, P. E. Armstrong, D. Leão, I. C. Fridlund, M. Canto Martins, B. L. Sousa, S. G. De Medeiros, J. R. Fossati, L. Adibekyan, V. Collier Cameron, A. Grziwa, S. Lam, K. W. F. Goffo, E. Nielsen, L. D. Rodler, F. Alarcon, J. Lillo-Box, J. Cochran, W. D. Luque, R. Redfield, S. Santos, N. C. Barros, S. C. C. Bayliss, D. Dumusque, X. Keniger, M. A. F. Livingston, J. Murgas, F. Nowak, G. Osborn, A. Osborn, H. P. Pallé, E. Persson, C. M. Serrano, L. M. Strøm, P. A. Udry, S. Wheatley, P. J. |
| description | Context . TOI-396 is an F6 V bright naked-eye star ( V ≈ 6.4) orbited by three small ( R p ≈ 2 R ⊕ ) transiting planets discovered thanks to space-based photometry from two TESS sectors. The orbital periods of the two innermost planets, namely TOI-396 b and c, are close to the 5:3 commensurability ( P b ~ 3.6 d and P c ~ 6.0 d), suggesting that the planets might be trapped in a mean motion resonance (MMR).
Aims . To measure the masses of the three planets, refine their radii, and investigate whether planets b and c are in MMR, we carried out HARPS radial velocity (RV) observations of TOI-396 and retrieved archival high-precision transit photometry from four TESS sectors.
Methods . We extracted the RVs via a skew-normal fit onto the HARPS cross-correlation functions and performed a Markov chain Monte Carlo joint analysis of the Doppler measurements and transit photometry, while employing the breakpoint method to remove stellar activity from the RV time series. We also performed a transit timing variation (TTV) dynamical analysis of the system and simulated the temporal evolution of the TTV amplitudes of the three planets following an N-body numerical integration.
Results . Our analysis confirms that the three planets have similar sizes ( R b = 2.004 −0.047 +0.045 R ⊕ ; R c = 1.979 −0.051 +0.054 R ⊕ ; R d = 2.001 −0.064 +0.063 R ⊕ ) and is thus in agreement with previous findings. However, our measurements are ~ 1.4 times more precise thanks to the use of two additional TESS sectors. For the first time, we have determined the RV masses for TOI-396 b and d, finding them to be M b = 3.55 −0.96 +0.94 M ⊕ and M d = 7.1 ± 1.6 M ⊕ , which implies bulk densities of ρ b = 2.44 −0.68 +0.69 g cm −3 and ρ d = 4.9 −1.1 +1.2 g cm −3 , respectively. Our results suggest a quite unusual system architecture, with the outermost planet being the densest. Based on a frequency analysis of the HARPS activity indicators and TESS light curves, we find the rotation period of the star to be P rot,⋆ = 6.7 ± 1.3 d, in agreement with the value predicted from log R ′ HK -based empirical relations. The Doppler reflex motion induced by TOI-396 c remains undetected in our RV time series, likely due to the proximity of the planet’s orbital period to the star’s rotation period. We also discovered that TOI-396 b and c display significant TTVs. While the TTV dynamical analysis returns a formally precise mass for TOI-396 c of M c ,dyn = 2.24 −0.67 +0.13 M ⊕ , the result might not be accurate, ow |
| doi_str_mv | 10.1051/0004-6361/202451300 |
| format | Article |
| fullrecord | <record><control><sourceid>swepub_cross</sourceid><recordid>TN_cdi_crossref_primary_10_1051_0004_6361_202451300</recordid><sourceformat>XML</sourceformat><sourcesystem>PC</sourcesystem><sourcerecordid>oai_research_chalmers_se_24016ceb_04db_4782_a7e1_0a27980e17a8</sourcerecordid><originalsourceid>FETCH-LOGICAL-c1650-b37f642848cc718cd7189eee9f384082602b622918819f62cd722fc08c3dc6183</originalsourceid><addsrcrecordid>eNo9kd1qHDEMRk1JoZu0T9AbP0DcyD_r8VyGkLSBQKBNr43Go-m62ZlZLCdh374zpOyFJASHA_okxFcN3zRs9RUAOOWt11cGjNtqC_BBbLSzRkHj_JnYnIhP4pz577IaHexGPP_EPudLOSIz8aXEqZe14MS5qprHPP2Rr1gy1jxPLOdB1h0tVYjUYY8TVclHrjTKuXS5rvgKTPhMvaIjSa5Y5NPjvbKt_yw-Drhn-vJ_Xojfd7dPNz_Uw-P3-5vrB5W034LqbDN4Z4ILKTU6pH5pLRG1gw0OgvFgOm9Mq0PQ7eDNAhgzJAjJ9skvV12IX-9efqPDSxcPJY9YjnHGHAsxYUm7mHa4H6lwZIrGgfaJugiu76JrgonYkI6ApmkDkG5wtdp3ayozc6Hh5NUQ1y_ENeO4ZhxPX7D_ADyVeQs</addsrcrecordid><sourcetype>Open Access Repository</sourcetype><iscdi>true</iscdi><recordtype>article</recordtype></control><display><type>article</type><title>Radii, masses, and transit-timing variations of the three-planet system orbiting the naked-eye star TOI-396</title><source>Bacon EDP Sciences France Licence nationale-ISTEX-PS-Journals-PFISTEX</source><source>Elektronische Zeitschriftenbibliothek - Frei zugängliche E-Journals</source><source>SWEPUB Freely available online</source><source>EDP Sciences</source><creator>Bonfanti, A. ; Amateis, I. ; Gandolfi, D. ; Borsato, L. ; Egger, J. A. ; Cubillos, P. E. ; Armstrong, D. ; Leão, I. C. ; Fridlund, M. ; Canto Martins, B. L. ; Sousa, S. G. ; De Medeiros, J. R. ; Fossati, L. ; Adibekyan, V. ; Collier Cameron, A. ; Grziwa, S. ; Lam, K. W. F. ; Goffo, E. ; Nielsen, L. D. ; Rodler, F. ; Alarcon, J. ; Lillo-Box, J. ; Cochran, W. D. ; Luque, R. ; Redfield, S. ; Santos, N. C. ; Barros, S. C. C. ; Bayliss, D. ; Dumusque, X. ; Keniger, M. A. F. ; Livingston, J. ; Murgas, F. ; Nowak, G. ; Osborn, A. ; Osborn, H. P. ; Pallé, E. ; Persson, C. M. ; Serrano, L. M. ; Strøm, P. A. ; Udry, S. ; Wheatley, P. J.</creator><creatorcontrib>Bonfanti, A. ; Amateis, I. ; Gandolfi, D. ; Borsato, L. ; Egger, J. A. ; Cubillos, P. E. ; Armstrong, D. ; Leão, I. C. ; Fridlund, M. ; Canto Martins, B. L. ; Sousa, S. G. ; De Medeiros, J. R. ; Fossati, L. ; Adibekyan, V. ; Collier Cameron, A. ; Grziwa, S. ; Lam, K. W. F. ; Goffo, E. ; Nielsen, L. D. ; Rodler, F. ; Alarcon, J. ; Lillo-Box, J. ; Cochran, W. D. ; Luque, R. ; Redfield, S. ; Santos, N. C. ; Barros, S. C. C. ; Bayliss, D. ; Dumusque, X. ; Keniger, M. A. F. ; Livingston, J. ; Murgas, F. ; Nowak, G. ; Osborn, A. ; Osborn, H. P. ; Pallé, E. ; Persson, C. M. ; Serrano, L. M. ; Strøm, P. A. ; Udry, S. ; Wheatley, P. J.</creatorcontrib><description>Context . TOI-396 is an F6 V bright naked-eye star ( V ≈ 6.4) orbited by three small ( R p ≈ 2 R ⊕ ) transiting planets discovered thanks to space-based photometry from two TESS sectors. The orbital periods of the two innermost planets, namely TOI-396 b and c, are close to the 5:3 commensurability ( P b ~ 3.6 d and P c ~ 6.0 d), suggesting that the planets might be trapped in a mean motion resonance (MMR).
Aims . To measure the masses of the three planets, refine their radii, and investigate whether planets b and c are in MMR, we carried out HARPS radial velocity (RV) observations of TOI-396 and retrieved archival high-precision transit photometry from four TESS sectors.
Methods . We extracted the RVs via a skew-normal fit onto the HARPS cross-correlation functions and performed a Markov chain Monte Carlo joint analysis of the Doppler measurements and transit photometry, while employing the breakpoint method to remove stellar activity from the RV time series. We also performed a transit timing variation (TTV) dynamical analysis of the system and simulated the temporal evolution of the TTV amplitudes of the three planets following an N-body numerical integration.
Results . Our analysis confirms that the three planets have similar sizes ( R b = 2.004 −0.047 +0.045 R ⊕ ; R c = 1.979 −0.051 +0.054 R ⊕ ; R d = 2.001 −0.064 +0.063 R ⊕ ) and is thus in agreement with previous findings. However, our measurements are ~ 1.4 times more precise thanks to the use of two additional TESS sectors. For the first time, we have determined the RV masses for TOI-396 b and d, finding them to be M b = 3.55 −0.96 +0.94 M ⊕ and M d = 7.1 ± 1.6 M ⊕ , which implies bulk densities of ρ b = 2.44 −0.68 +0.69 g cm −3 and ρ d = 4.9 −1.1 +1.2 g cm −3 , respectively. Our results suggest a quite unusual system architecture, with the outermost planet being the densest. Based on a frequency analysis of the HARPS activity indicators and TESS light curves, we find the rotation period of the star to be P rot,⋆ = 6.7 ± 1.3 d, in agreement with the value predicted from log R ′ HK -based empirical relations. The Doppler reflex motion induced by TOI-396 c remains undetected in our RV time series, likely due to the proximity of the planet’s orbital period to the star’s rotation period. We also discovered that TOI-396 b and c display significant TTVs. While the TTV dynamical analysis returns a formally precise mass for TOI-396 c of M c ,dyn = 2.24 −0.67 +0.13 M ⊕ , the result might not be accurate, owing to the poor sampling of the TTV phase. We also conclude that TOI-396 b and c are close to but out of the 5:3 MMR.
Conclusions . A TTV dynamical analysis of additional transit photometry evenly covering the TTV phase and super-period is likely the most effective approach for precisely and accurately determining the mass of TOI-396 c. Our numerical simulation suggests TTV semi-amplitudes of up to five hours over a temporal baseline of ~ 5.2 years, which should be duly taken into account when scheduling future observations of TOI-396.</description><identifier>ISSN: 0004-6361</identifier><identifier>ISSN: 1432-0746</identifier><identifier>EISSN: 1432-0746</identifier><identifier>DOI: 10.1051/0004-6361/202451300</identifier><language>eng</language><subject>planets and satellites: fundamental parameters ; stars: fundamental parameters ; techniques: photometric ; techniques: radial velocities</subject><ispartof>Astronomy and astrophysics (Berlin), 2025-01, Vol.693, p.A90</ispartof><lds50>peer_reviewed</lds50><oa>free_for_read</oa><woscitedreferencessubscribed>false</woscitedreferencessubscribed><cites>FETCH-LOGICAL-c1650-b37f642848cc718cd7189eee9f384082602b622918819f62cd722fc08c3dc6183</cites><orcidid>0000-0003-1257-5146 ; 0000-0001-9662-3496 ; 0000-0002-5899-7750 ; 0000-0002-8863-7828 ; 0000-0002-7823-1090 ; 0000-0002-4671-2957 ; 0000-0001-8218-1586 ; 0000-0002-0601-6199 ; 0000-0002-5254-2499 ; 0000-0001-5845-947X ; 0000-0002-0855-8426 ; 0009-0005-2761-9190 ; 0000-0003-3370-4058 ; 0000-0003-1452-2240 ; 0000-0002-1916-5935 ; 0000-0001-5578-7400 ; 0000-0001-9670-961X ; 0000-0003-0066-9268 ; 0000-0001-9087-1245 ; 0000-0001-9211-3691 ; 0000-0002-4047-4724 ; 0000-0002-5080-4117 ; 0000-0002-9910-6088 ; 0000-0002-7031-7754 ; 0000-0002-1347-2600 ; 0000-0001-8627-9628 ; 0000-0003-4422-2919 ; 0000-0003-1628-4231 ; 0000-0003-2434-3625 ; 0009-0007-0410-6215 ; 0000-0001-7576-6236 ; 0000-0003-3786-3486 ; 0000-0001-9047-2965 ; 0000-0003-4426-9530 ; 0000-0002-9332-2011 ; 0000-0003-0987-1593 ; 0000-0002-4881-3620 ; 0000-0001-6023-1335 ; 0000-0003-3742-1987</orcidid></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><link.rule.ids>230,314,550,776,780,881,3713,4009,27902,27903,27904</link.rule.ids><backlink>$$Uhttps://research.chalmers.se/publication/544816$$DView record from Swedish Publication Index$$Hfree_for_read</backlink></links><search><creatorcontrib>Bonfanti, A.</creatorcontrib><creatorcontrib>Amateis, I.</creatorcontrib><creatorcontrib>Gandolfi, D.</creatorcontrib><creatorcontrib>Borsato, L.</creatorcontrib><creatorcontrib>Egger, J. A.</creatorcontrib><creatorcontrib>Cubillos, P. E.</creatorcontrib><creatorcontrib>Armstrong, D.</creatorcontrib><creatorcontrib>Leão, I. C.</creatorcontrib><creatorcontrib>Fridlund, M.</creatorcontrib><creatorcontrib>Canto Martins, B. L.</creatorcontrib><creatorcontrib>Sousa, S. G.</creatorcontrib><creatorcontrib>De Medeiros, J. R.</creatorcontrib><creatorcontrib>Fossati, L.</creatorcontrib><creatorcontrib>Adibekyan, V.</creatorcontrib><creatorcontrib>Collier Cameron, A.</creatorcontrib><creatorcontrib>Grziwa, S.</creatorcontrib><creatorcontrib>Lam, K. W. F.</creatorcontrib><creatorcontrib>Goffo, E.</creatorcontrib><creatorcontrib>Nielsen, L. D.</creatorcontrib><creatorcontrib>Rodler, F.</creatorcontrib><creatorcontrib>Alarcon, J.</creatorcontrib><creatorcontrib>Lillo-Box, J.</creatorcontrib><creatorcontrib>Cochran, W. D.</creatorcontrib><creatorcontrib>Luque, R.</creatorcontrib><creatorcontrib>Redfield, S.</creatorcontrib><creatorcontrib>Santos, N. C.</creatorcontrib><creatorcontrib>Barros, S. C. C.</creatorcontrib><creatorcontrib>Bayliss, D.</creatorcontrib><creatorcontrib>Dumusque, X.</creatorcontrib><creatorcontrib>Keniger, M. A. F.</creatorcontrib><creatorcontrib>Livingston, J.</creatorcontrib><creatorcontrib>Murgas, F.</creatorcontrib><creatorcontrib>Nowak, G.</creatorcontrib><creatorcontrib>Osborn, A.</creatorcontrib><creatorcontrib>Osborn, H. P.</creatorcontrib><creatorcontrib>Pallé, E.</creatorcontrib><creatorcontrib>Persson, C. M.</creatorcontrib><creatorcontrib>Serrano, L. M.</creatorcontrib><creatorcontrib>Strøm, P. A.</creatorcontrib><creatorcontrib>Udry, S.</creatorcontrib><creatorcontrib>Wheatley, P. J.</creatorcontrib><title>Radii, masses, and transit-timing variations of the three-planet system orbiting the naked-eye star TOI-396</title><title>Astronomy and astrophysics (Berlin)</title><description>Context . TOI-396 is an F6 V bright naked-eye star ( V ≈ 6.4) orbited by three small ( R p ≈ 2 R ⊕ ) transiting planets discovered thanks to space-based photometry from two TESS sectors. The orbital periods of the two innermost planets, namely TOI-396 b and c, are close to the 5:3 commensurability ( P b ~ 3.6 d and P c ~ 6.0 d), suggesting that the planets might be trapped in a mean motion resonance (MMR).
Aims . To measure the masses of the three planets, refine their radii, and investigate whether planets b and c are in MMR, we carried out HARPS radial velocity (RV) observations of TOI-396 and retrieved archival high-precision transit photometry from four TESS sectors.
Methods . We extracted the RVs via a skew-normal fit onto the HARPS cross-correlation functions and performed a Markov chain Monte Carlo joint analysis of the Doppler measurements and transit photometry, while employing the breakpoint method to remove stellar activity from the RV time series. We also performed a transit timing variation (TTV) dynamical analysis of the system and simulated the temporal evolution of the TTV amplitudes of the three planets following an N-body numerical integration.
Results . Our analysis confirms that the three planets have similar sizes ( R b = 2.004 −0.047 +0.045 R ⊕ ; R c = 1.979 −0.051 +0.054 R ⊕ ; R d = 2.001 −0.064 +0.063 R ⊕ ) and is thus in agreement with previous findings. However, our measurements are ~ 1.4 times more precise thanks to the use of two additional TESS sectors. For the first time, we have determined the RV masses for TOI-396 b and d, finding them to be M b = 3.55 −0.96 +0.94 M ⊕ and M d = 7.1 ± 1.6 M ⊕ , which implies bulk densities of ρ b = 2.44 −0.68 +0.69 g cm −3 and ρ d = 4.9 −1.1 +1.2 g cm −3 , respectively. Our results suggest a quite unusual system architecture, with the outermost planet being the densest. Based on a frequency analysis of the HARPS activity indicators and TESS light curves, we find the rotation period of the star to be P rot,⋆ = 6.7 ± 1.3 d, in agreement with the value predicted from log R ′ HK -based empirical relations. The Doppler reflex motion induced by TOI-396 c remains undetected in our RV time series, likely due to the proximity of the planet’s orbital period to the star’s rotation period. We also discovered that TOI-396 b and c display significant TTVs. While the TTV dynamical analysis returns a formally precise mass for TOI-396 c of M c ,dyn = 2.24 −0.67 +0.13 M ⊕ , the result might not be accurate, owing to the poor sampling of the TTV phase. We also conclude that TOI-396 b and c are close to but out of the 5:3 MMR.
Conclusions . A TTV dynamical analysis of additional transit photometry evenly covering the TTV phase and super-period is likely the most effective approach for precisely and accurately determining the mass of TOI-396 c. Our numerical simulation suggests TTV semi-amplitudes of up to five hours over a temporal baseline of ~ 5.2 years, which should be duly taken into account when scheduling future observations of TOI-396.</description><subject>planets and satellites: fundamental parameters</subject><subject>stars: fundamental parameters</subject><subject>techniques: photometric</subject><subject>techniques: radial velocities</subject><issn>0004-6361</issn><issn>1432-0746</issn><issn>1432-0746</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2025</creationdate><recordtype>article</recordtype><sourceid>D8T</sourceid><recordid>eNo9kd1qHDEMRk1JoZu0T9AbP0DcyD_r8VyGkLSBQKBNr43Go-m62ZlZLCdh374zpOyFJASHA_okxFcN3zRs9RUAOOWt11cGjNtqC_BBbLSzRkHj_JnYnIhP4pz577IaHexGPP_EPudLOSIz8aXEqZe14MS5qprHPP2Rr1gy1jxPLOdB1h0tVYjUYY8TVclHrjTKuXS5rvgKTPhMvaIjSa5Y5NPjvbKt_yw-Drhn-vJ_Xojfd7dPNz_Uw-P3-5vrB5W034LqbDN4Z4ILKTU6pH5pLRG1gw0OgvFgOm9Mq0PQ7eDNAhgzJAjJ9skvV12IX-9efqPDSxcPJY9YjnHGHAsxYUm7mHa4H6lwZIrGgfaJugiu76JrgonYkI6ApmkDkG5wtdp3ayozc6Hh5NUQ1y_ENeO4ZhxPX7D_ADyVeQs</recordid><startdate>202501</startdate><enddate>202501</enddate><creator>Bonfanti, A.</creator><creator>Amateis, I.</creator><creator>Gandolfi, D.</creator><creator>Borsato, L.</creator><creator>Egger, J. A.</creator><creator>Cubillos, P. E.</creator><creator>Armstrong, D.</creator><creator>Leão, I. C.</creator><creator>Fridlund, M.</creator><creator>Canto Martins, B. L.</creator><creator>Sousa, S. G.</creator><creator>De Medeiros, J. R.</creator><creator>Fossati, L.</creator><creator>Adibekyan, V.</creator><creator>Collier Cameron, A.</creator><creator>Grziwa, S.</creator><creator>Lam, K. W. F.</creator><creator>Goffo, E.</creator><creator>Nielsen, L. D.</creator><creator>Rodler, F.</creator><creator>Alarcon, J.</creator><creator>Lillo-Box, J.</creator><creator>Cochran, W. D.</creator><creator>Luque, R.</creator><creator>Redfield, S.</creator><creator>Santos, N. C.</creator><creator>Barros, S. C. C.</creator><creator>Bayliss, D.</creator><creator>Dumusque, X.</creator><creator>Keniger, M. A. F.</creator><creator>Livingston, J.</creator><creator>Murgas, F.</creator><creator>Nowak, G.</creator><creator>Osborn, A.</creator><creator>Osborn, H. 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A. ; Cubillos, P. E. ; Armstrong, D. ; Leão, I. C. ; Fridlund, M. ; Canto Martins, B. L. ; Sousa, S. G. ; De Medeiros, J. R. ; Fossati, L. ; Adibekyan, V. ; Collier Cameron, A. ; Grziwa, S. ; Lam, K. W. F. ; Goffo, E. ; Nielsen, L. D. ; Rodler, F. ; Alarcon, J. ; Lillo-Box, J. ; Cochran, W. D. ; Luque, R. ; Redfield, S. ; Santos, N. C. ; Barros, S. C. C. ; Bayliss, D. ; Dumusque, X. ; Keniger, M. A. F. ; Livingston, J. ; Murgas, F. ; Nowak, G. ; Osborn, A. ; Osborn, H. P. ; Pallé, E. ; Persson, C. M. ; Serrano, L. M. ; Strøm, P. A. ; Udry, S. ; Wheatley, P. J.</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-c1650-b37f642848cc718cd7189eee9f384082602b622918819f62cd722fc08c3dc6183</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>2025</creationdate><topic>planets and satellites: fundamental parameters</topic><topic>stars: fundamental parameters</topic><topic>techniques: photometric</topic><topic>techniques: radial velocities</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Bonfanti, A.</creatorcontrib><creatorcontrib>Amateis, I.</creatorcontrib><creatorcontrib>Gandolfi, D.</creatorcontrib><creatorcontrib>Borsato, L.</creatorcontrib><creatorcontrib>Egger, J. A.</creatorcontrib><creatorcontrib>Cubillos, P. E.</creatorcontrib><creatorcontrib>Armstrong, D.</creatorcontrib><creatorcontrib>Leão, I. C.</creatorcontrib><creatorcontrib>Fridlund, M.</creatorcontrib><creatorcontrib>Canto Martins, B. L.</creatorcontrib><creatorcontrib>Sousa, S. G.</creatorcontrib><creatorcontrib>De Medeiros, J. R.</creatorcontrib><creatorcontrib>Fossati, L.</creatorcontrib><creatorcontrib>Adibekyan, V.</creatorcontrib><creatorcontrib>Collier Cameron, A.</creatorcontrib><creatorcontrib>Grziwa, S.</creatorcontrib><creatorcontrib>Lam, K. W. F.</creatorcontrib><creatorcontrib>Goffo, E.</creatorcontrib><creatorcontrib>Nielsen, L. D.</creatorcontrib><creatorcontrib>Rodler, F.</creatorcontrib><creatorcontrib>Alarcon, J.</creatorcontrib><creatorcontrib>Lillo-Box, J.</creatorcontrib><creatorcontrib>Cochran, W. D.</creatorcontrib><creatorcontrib>Luque, R.</creatorcontrib><creatorcontrib>Redfield, S.</creatorcontrib><creatorcontrib>Santos, N. C.</creatorcontrib><creatorcontrib>Barros, S. C. C.</creatorcontrib><creatorcontrib>Bayliss, D.</creatorcontrib><creatorcontrib>Dumusque, X.</creatorcontrib><creatorcontrib>Keniger, M. A. F.</creatorcontrib><creatorcontrib>Livingston, J.</creatorcontrib><creatorcontrib>Murgas, F.</creatorcontrib><creatorcontrib>Nowak, G.</creatorcontrib><creatorcontrib>Osborn, A.</creatorcontrib><creatorcontrib>Osborn, H. P.</creatorcontrib><creatorcontrib>Pallé, E.</creatorcontrib><creatorcontrib>Persson, C. M.</creatorcontrib><creatorcontrib>Serrano, L. M.</creatorcontrib><creatorcontrib>Strøm, P. A.</creatorcontrib><creatorcontrib>Udry, S.</creatorcontrib><creatorcontrib>Wheatley, P. J.</creatorcontrib><collection>CrossRef</collection><collection>SWEPUB Chalmers tekniska högskola full text</collection><collection>SwePub</collection><collection>SwePub Articles</collection><collection>SWEPUB Freely available online</collection><collection>SWEPUB Chalmers tekniska högskola</collection><collection>SwePub Articles full text</collection><jtitle>Astronomy and astrophysics (Berlin)</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Bonfanti, A.</au><au>Amateis, I.</au><au>Gandolfi, D.</au><au>Borsato, L.</au><au>Egger, J. A.</au><au>Cubillos, P. E.</au><au>Armstrong, D.</au><au>Leão, I. C.</au><au>Fridlund, M.</au><au>Canto Martins, B. L.</au><au>Sousa, S. G.</au><au>De Medeiros, J. R.</au><au>Fossati, L.</au><au>Adibekyan, V.</au><au>Collier Cameron, A.</au><au>Grziwa, S.</au><au>Lam, K. W. F.</au><au>Goffo, E.</au><au>Nielsen, L. D.</au><au>Rodler, F.</au><au>Alarcon, J.</au><au>Lillo-Box, J.</au><au>Cochran, W. D.</au><au>Luque, R.</au><au>Redfield, S.</au><au>Santos, N. C.</au><au>Barros, S. C. C.</au><au>Bayliss, D.</au><au>Dumusque, X.</au><au>Keniger, M. A. F.</au><au>Livingston, J.</au><au>Murgas, F.</au><au>Nowak, G.</au><au>Osborn, A.</au><au>Osborn, H. P.</au><au>Pallé, E.</au><au>Persson, C. M.</au><au>Serrano, L. M.</au><au>Strøm, P. A.</au><au>Udry, S.</au><au>Wheatley, P. J.</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Radii, masses, and transit-timing variations of the three-planet system orbiting the naked-eye star TOI-396</atitle><jtitle>Astronomy and astrophysics (Berlin)</jtitle><date>2025-01</date><risdate>2025</risdate><volume>693</volume><spage>A90</spage><pages>A90-</pages><issn>0004-6361</issn><issn>1432-0746</issn><eissn>1432-0746</eissn><abstract>Context . TOI-396 is an F6 V bright naked-eye star ( V ≈ 6.4) orbited by three small ( R p ≈ 2 R ⊕ ) transiting planets discovered thanks to space-based photometry from two TESS sectors. The orbital periods of the two innermost planets, namely TOI-396 b and c, are close to the 5:3 commensurability ( P b ~ 3.6 d and P c ~ 6.0 d), suggesting that the planets might be trapped in a mean motion resonance (MMR).
Aims . To measure the masses of the three planets, refine their radii, and investigate whether planets b and c are in MMR, we carried out HARPS radial velocity (RV) observations of TOI-396 and retrieved archival high-precision transit photometry from four TESS sectors.
Methods . We extracted the RVs via a skew-normal fit onto the HARPS cross-correlation functions and performed a Markov chain Monte Carlo joint analysis of the Doppler measurements and transit photometry, while employing the breakpoint method to remove stellar activity from the RV time series. We also performed a transit timing variation (TTV) dynamical analysis of the system and simulated the temporal evolution of the TTV amplitudes of the three planets following an N-body numerical integration.
Results . Our analysis confirms that the three planets have similar sizes ( R b = 2.004 −0.047 +0.045 R ⊕ ; R c = 1.979 −0.051 +0.054 R ⊕ ; R d = 2.001 −0.064 +0.063 R ⊕ ) and is thus in agreement with previous findings. However, our measurements are ~ 1.4 times more precise thanks to the use of two additional TESS sectors. For the first time, we have determined the RV masses for TOI-396 b and d, finding them to be M b = 3.55 −0.96 +0.94 M ⊕ and M d = 7.1 ± 1.6 M ⊕ , which implies bulk densities of ρ b = 2.44 −0.68 +0.69 g cm −3 and ρ d = 4.9 −1.1 +1.2 g cm −3 , respectively. Our results suggest a quite unusual system architecture, with the outermost planet being the densest. Based on a frequency analysis of the HARPS activity indicators and TESS light curves, we find the rotation period of the star to be P rot,⋆ = 6.7 ± 1.3 d, in agreement with the value predicted from log R ′ HK -based empirical relations. The Doppler reflex motion induced by TOI-396 c remains undetected in our RV time series, likely due to the proximity of the planet’s orbital period to the star’s rotation period. We also discovered that TOI-396 b and c display significant TTVs. While the TTV dynamical analysis returns a formally precise mass for TOI-396 c of M c ,dyn = 2.24 −0.67 +0.13 M ⊕ , the result might not be accurate, owing to the poor sampling of the TTV phase. We also conclude that TOI-396 b and c are close to but out of the 5:3 MMR.
Conclusions . A TTV dynamical analysis of additional transit photometry evenly covering the TTV phase and super-period is likely the most effective approach for precisely and accurately determining the mass of TOI-396 c. Our numerical simulation suggests TTV semi-amplitudes of up to five hours over a temporal baseline of ~ 5.2 years, which should be duly taken into account when scheduling future observations of TOI-396.</abstract><doi>10.1051/0004-6361/202451300</doi><orcidid>https://orcid.org/0000-0003-1257-5146</orcidid><orcidid>https://orcid.org/0000-0001-9662-3496</orcidid><orcidid>https://orcid.org/0000-0002-5899-7750</orcidid><orcidid>https://orcid.org/0000-0002-8863-7828</orcidid><orcidid>https://orcid.org/0000-0002-7823-1090</orcidid><orcidid>https://orcid.org/0000-0002-4671-2957</orcidid><orcidid>https://orcid.org/0000-0001-8218-1586</orcidid><orcidid>https://orcid.org/0000-0002-0601-6199</orcidid><orcidid>https://orcid.org/0000-0002-5254-2499</orcidid><orcidid>https://orcid.org/0000-0001-5845-947X</orcidid><orcidid>https://orcid.org/0000-0002-0855-8426</orcidid><orcidid>https://orcid.org/0009-0005-2761-9190</orcidid><orcidid>https://orcid.org/0000-0003-3370-4058</orcidid><orcidid>https://orcid.org/0000-0003-1452-2240</orcidid><orcidid>https://orcid.org/0000-0002-1916-5935</orcidid><orcidid>https://orcid.org/0000-0001-5578-7400</orcidid><orcidid>https://orcid.org/0000-0001-9670-961X</orcidid><orcidid>https://orcid.org/0000-0003-0066-9268</orcidid><orcidid>https://orcid.org/0000-0001-9087-1245</orcidid><orcidid>https://orcid.org/0000-0001-9211-3691</orcidid><orcidid>https://orcid.org/0000-0002-4047-4724</orcidid><orcidid>https://orcid.org/0000-0002-5080-4117</orcidid><orcidid>https://orcid.org/0000-0002-9910-6088</orcidid><orcidid>https://orcid.org/0000-0002-7031-7754</orcidid><orcidid>https://orcid.org/0000-0002-1347-2600</orcidid><orcidid>https://orcid.org/0000-0001-8627-9628</orcidid><orcidid>https://orcid.org/0000-0003-4422-2919</orcidid><orcidid>https://orcid.org/0000-0003-1628-4231</orcidid><orcidid>https://orcid.org/0000-0003-2434-3625</orcidid><orcidid>https://orcid.org/0009-0007-0410-6215</orcidid><orcidid>https://orcid.org/0000-0001-7576-6236</orcidid><orcidid>https://orcid.org/0000-0003-3786-3486</orcidid><orcidid>https://orcid.org/0000-0001-9047-2965</orcidid><orcidid>https://orcid.org/0000-0003-4426-9530</orcidid><orcidid>https://orcid.org/0000-0002-9332-2011</orcidid><orcidid>https://orcid.org/0000-0003-0987-1593</orcidid><orcidid>https://orcid.org/0000-0002-4881-3620</orcidid><orcidid>https://orcid.org/0000-0001-6023-1335</orcidid><orcidid>https://orcid.org/0000-0003-3742-1987</orcidid><oa>free_for_read</oa></addata></record> |
| fulltext | fulltext |
| identifier | ISSN: 0004-6361 |
| ispartof | Astronomy and astrophysics (Berlin), 2025-01, Vol.693, p.A90 |
| issn | 0004-6361 1432-0746 1432-0746 |
| language | eng |
| recordid | cdi_crossref_primary_10_1051_0004_6361_202451300 |
| source | Bacon EDP Sciences France Licence nationale-ISTEX-PS-Journals-PFISTEX; Elektronische Zeitschriftenbibliothek - Frei zugängliche E-Journals; SWEPUB Freely available online; EDP Sciences |
| subjects | planets and satellites: fundamental parameters stars: fundamental parameters techniques: photometric techniques: radial velocities |
| title | Radii, masses, and transit-timing variations of the three-planet system orbiting the naked-eye star TOI-396 |
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