J/A+A/693/A90 Radii, masses, and TTVs of TOI-396 (Bonfanti+, 2025)
Radii, masses, and transit-timing variations of the three-planet system orbiting
the naked-eye star TOI-396.
Bonfanti A., Amateis I., Gandolfi D., Borsato L., Egger J.A., Cubillos P.E.,
Armstrong D., Leao 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., Palle E., Persson C.M., Serrano L.M., Strom P.A., Udry S.,
Wheatley P.J.
<Astron. Astrophys. 693, A90 (2025)>
=2025A&A...693A..90B 2025A&A...693A..90B (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Photometry ;
Radial velocities ; Optical
Keywords: techniques: photometric - techniques: radial velocities 0
planets and satellites: fundamental parameters -
stars: fundamental parameters
Abstract:
TOI-396 is an F6 V, bright, naked-eye star (V∼6.4) orbited by three
transiting small (Rp∼2R☉) planets discovered thanks to
space-based photometry from 2 TESS sectors. The orbital periods of the
two innermost planets, namely TOI-396 b and c, are close to the 5:3
commensurability (Pb∼3.6d and Pc∼6.0d), suggesting that the
planets might be trapped in a mean motion resonance (MMR)
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 4 TESS sectors.
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.
Our analysis confirms that the three planets have similar sizes
(Rb=2.004-0.047+0.045R☉;
Rc=1.979-0.051+0.054R☉;
Rd=2.001-0.064+0.063R☉), in agreement with previous
findings. Notably, our measurements are ∼1.4 times more precise,
thanks to the use of two additional TESS sectors. For the first time,
we determine RV masses for TOI-396 b and d, and find them to be
Mb=3.55-0.96+0.94M☉ and Md=7.1±1.6M☉, implying
bulk densities of rhob=2.44-0.68+0.69g/cm3 and
rhod=4.9-1.1+1.2g/cm3, 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 Prot=6.7±1.3d, in agreement with the value predicted from
logR'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 Mc,dyn=2.24+0.13-0.67M☉, 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.
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 5 hours over a temporal baseline of ∼5.2 years, which
should be duly taken into account when scheduling future observations
of TOI-396.
Description:
Tables of the Appendix of the paper reporting (i) the RV time series
along with relevant ancillary parameters, (ii) the polynomial
detrending baseline applied to TESS light curves, (iii) the transit
timings of the single transit events and the corresponding TTVs,
(iv-v) the results of our interior structure modelling applied to
TOI-396 b and d.
Objects:
-----------------------------------------------------
RA (2000) DE Designation(s)
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02 51 56.24 -30 48 52.2 TOI-396 = HD 17926
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 58 78 RV time series extracted from HARPS
tablea2.dat 30 41 Polynomial detrending applied to TESS LCs
tablea3.dat 42 48 Transit timings and TTVs
tablea4.dat 128 9 Interior structure parameters of TOI-396 b
tablea5.dat 119 9 Interior structure parameters of TOI-396 d
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 11 F11.6 --- BJD Observation time (TDB) (BJD-2450000)
13- 18 F6.3 m/s RV Radial velocity as extracted from the
SN fit onto the CCFs
20- 24 F5.3 m/s e_RV Error on the radial velocity
26- 31 F6.3 km/s FWHMSN FWHM of the fitted skew-Normal function
33- 38 F6.3 % A Contrast of the fitted skew-Normal function
40- 45 F6.4 --- gamma Skewness of the fitted skew-Normal function
47- 52 F6.3 m/s RVd Detrended Radial velocity
54- 58 F5.3 m/s e_RVd Errors on the detrended radial velocity
(jitter included)
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Byte-by-byte Description of file: tablea2.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- LC-ID TESS LC identifier
7- 11 A5 --- Planet Planet(s) transiting in that LC
13- 30 A18 --- Detrend Polynomials applied for detrending the LCs
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Byte-by-byte Description of file: tablea3.dat
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Bytes Format Units Label Explanations
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1- 9 F9.4 d JD Transit timing
11- 16 F6.4 d e_JD Lower error on transit timing
18- 23 F6.4 d E_JD Upper error on transit timing
25- 29 F5.1 min TTV TTV amplitude wrt linear ephemerides
31- 34 F4.1 min e_TTV Lower error on the TTV amplitude
36- 39 F4.1 min E_TTV Upper error on the TTV amplitude
41- 42 I2 --- Sector TESS sector containing the transit event
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Byte-by-byte Description of file: tablea4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Fractions Mass- (w), molar- (x), or water (Z) fractions
13- 16 F4.1 % WR-A1 Water-rich scenario Stellar priors on Si-Mg-Fe
18- 21 F4.1 % e_WR-A1 Lower errors on WR_A1 fractions
23- 26 F4.1 % E_WR-A1 Upper errors on WR_A1 fractions
28- 31 F4.1 % WR-A2 Water-rich scenario Fe-enriched priors
33- 36 F4.1 % e_WR-A2 Lower errors on WR_A2 fractions
38- 41 F4.1 % E_WR-A2 Upper errors on WR_A2 fractions
43- 46 F4.1 % WR-A3 Water-rich scenario Free priors on Si-Mg-Fe
48- 51 F4.1 % e_WR-A3 Lower errors on WR_A3 fractions
53- 56 F4.1 % E_WR-A3 Upper errors on WR_A3 fractions
58- 64 F7.4 % WP-B1 Water-poor scenario Stellar priors on Si-Mg-Fe
66- 72 F7.4 % e_WP-B1 Lower errors on WP_B1 fractions
74- 80 F7.4 % E_WP-B1 Upper errors on WP_B1 fractions
82- 88 F7.4 % WP-B2 Water-poor scenario Fe-enriched priors
90- 96 F7.4 % e_WP-B2 Lower errors on WP_B2 fractions
98-104 F7.4 % E_WP-B2 Upper errors on WP_B2 fractions
106-112 F7.4 % WP-B3 Water-poor scenario Free priors on Si-Mg-Fe
114-120 F7.4 % e_WP-B3 Lower errors on WP_B3 fractions
122-128 F7.4 % E_WP-B3 Upper errors on WP_B3 fractions
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Byte-by-byte Description of file: tablea5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 A11 --- Fractions Mass- (w), molar- (x), or water (Z) fractions
13- 16 F4.1 % WR-A1 Water-rich scenario Stellar priors on Si-Mg-Fe
18- 21 F4.1 % e_WR-A1 Lower errors on WR_A1 fractions
23- 26 F4.1 % E_WR-A1 Upper errors on WR_A1 fractions
28- 31 F4.1 % WR-A2 Water-rich scenario Fe-enriched priors
33- 36 F4.1 % e_WR-A2 Lower errors on WR_A2 fractions
38- 41 F4.1 % E_WR-A2 Upper errors on WR_A2 fractions
43- 46 F4.1 % WR-A3 Water-rich scenario Free priors on Si-Mg-Fe
48- 51 F4.1 % e_WR-A3 Lower errors on WR_A3 fractions
53- 56 F4.1 % E_WR-A3 Upper errors on WR_A3 fractions
58- 63 F6.3 % WP-B1 Water-poor scenario Stellar priors on Si-Mg-Fe
65- 70 F6.3 % e_WP-B1 Lower errors on WP_B1 fractions
72- 77 F6.3 % E_WP-B1 Upper errors on WP_B1 fractions
79- 84 F6.3 % WP-B2 Water-poor scenario Fe-enriched priors
86- 91 F6.3 % e_WP-B2 Lower errors on WP_B2 fractions
93- 98 F6.3 % E_WP-B2 Upper errors on WP_B2 fractions
100-105 F6.3 % WP-B3 Water-poor scenario Free priors on Si-Mg-Fe
107-112 F6.3 % e_WP-B3 Lower errors on WP_B3 fractions
114-119 F6.3 % E_WP-B3 Upper errors on WP_B3 fractions
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Acknowledgements:
Andrea Bonfanti, Andrea.Bonfanti(at)oeaw.ac.at
(End) Andrea Bonfanti [OeAW, Austria], Patricia Vannier [CDS] 25-Nov-2024