J/A+A/705/A142 Physical properties study of planet systems (Rossi+, 2026)
True spin-orbit obliquities distribution:
Data-driven confirmation of no clustering of misaligned orbits.
Rossi A.M, Rainer M., Borsa F., Facchini S.
<Astron. Astrophys. 705, A142 (2026)>
=2026A&A...705A.142R 2026A&A...705A.142R (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Binaries, orbits ;
Effective temperatures ; Radial velocities ;
Rotational velocities ; Stars, ages
Keywords: techniques: radial velocities -
planets and satellites: dynamical evolution and stability
Abstract:
True spin-orbit obliquities offer valuable insights into the
evolutionary history of exoplanetary systems. Previous studies have
suggested that exoplanets tend to occupy either aligned or
perpendicular orbits. However, recent research has indicated potential
biases caused by the small sample, questioning whether this dichotomy
would persist with a larger dataset. Simultaneously, a similar
dichotomous behavior has been suggested for Neptune-sized planets.
We aim to investigate the distribution of true spin-orbit
obliquities with an enlarged sample, looking for confirmation of the
disputed dichotomy previously found, with a focus also on the
obliquities of Neptunes.
Starting from a sample of 264 projected obliquities, we homogeneously
compute true obliquities for 116 planets using the rotation period
method. We combine them with 4 further values gathered from literature
and we then study their distribution, also as a function of various
star-planet system parameters.
Our data-driven work based on 120 true obliquities - the largest
sample to date - strongly confirms the presence of a single cluster of
aligned planets, followed by an isotropic distribution of misaligned
planets with no preferred misalignment. This result is based on a
uniform distribution of stellar inclinations, for which non-uniformity
could have biased previous interpretations of the arrangement of true
obliquities. We confirm that Neptunians show a tentative dichotomous
distribution with data available today, but its veracity needs
confirmation with an enlarged sample, also because an anisotropic
distribution of stellar inclination may be one of the factors
hindering the real distribution.
The future increase of the measured true obliquity sample over
different planet types will allow better investigation of the relation
between misalignment and system properties and help to depict a more
comprehensive picture of the planetary evolution processes.
Description:
We tabulate true spin-orbit obliquities and stellar inclinations
computed using the rotation period method, also known as the vsini
method for the wider collection of exoplanets to date. Tabulated
values gathered from literature include planet identification (planet
name along with the Gaia DR3 ID of its host star); planet mass;
projected obliquities; true obliquities; stellar effective
temperature; planet orbital inclination; stellar radius; stellar
projected rotational velocities; stellar rotational period; stellar
age. Values computed in this work include true obliquities; stellar
inclinations.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 451 120 Physical properties of our planets sample
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See also:
J/A+A/690/A379 : Obliquities of exoplanet host stars (Knudstrup+, 2024)
J/A+A/666/A47 : MASCARA-4 b light and RV curves (Zhang+, 2022)
J/A+A/658/A75 : MASCARA-1 b occultation and transit light curves
(Hooton+, 2022)
J/A+A/650/A66 : DS Tuc A radial velocity curve (Benatti+, 2021)
J/A+A/635/A73 : Multiplicity study of transiting exoplanet hosts. I.
(Bohn+, 2020)
J/A+A/635/A74 : Transiting planet WASP-76 (Southworth+, 2020)
J/A+A/631/A34 : KELT-9b radial velocity curve (Borsa+ 2019)
J/A+A/619/A1 : 55 Cnc radial velocities and photometry (Bourrier+, 2018)
J/A+A/613/A41 : 5 exoplanet light and RV curves (Mancini+, 2018)
J/A+A/602/A107 : 231 transiting planets eccentricity and mass (Bonomo+, 2017)
J/A+A/579/A136 : HAT-P-36 and WASP-11/HAT-P-10 light curves (Mancini+, 2015)
J/A+A/511/A3 : Light curves of CoRoT-2 in z-band, 4.5um and 8um
(Gillon+, 2010)
J/MNRAS/423/1503 : RV curves of WASP-16, 25 and 31 (Brown+, 2012)
J/ApJ/757/18 : Radial velocities for 16 hot Jupiter host stars
(Albrecht+, 2012)
J/ApJS/255/17 : Surface rotation & activity for Kepler stars. II.
(Santos+, 2021)
J/AJ/168/116 : NEID radial velocities of TOI-5126 and TOI-5398
(Radzom+, 2024)
J/AJ/168/297 : JWST transmission spectrum of HIP 67522b (Thao+, 2024)
J/AJ/165/164 : Tull RVels, rotation periods and Inclinations (Bowler+,2023)
J/AJ/165/33 : HIRES TOI-1136s planets and planet b radial velocities
(Dai+, 2023)
J/AJ/163/207 : 67 binary stars with exoplanet(s) from Gaia EDR3
(Christian+, 2022)
J/AJ/157/31 : Differential photometry & radial velocities of HATS-70
(Zhou+, 2019)
J/PASP/134/H2001 : Stellar obliquities in exoplanetary systems (Albrecht+,2022)
Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- Name Planet name (Name)
18- 45 A28 --- GaiaDR3 Gaia DR3 identifier (GaiaDR3)
47- 48 A2 --- Type Planet type (Type) (1)
50- 56 F7.1 Mgeo Mpl Planet mass (Mpl)
58- 63 F6.1 Mgeo E_Mpl ? Upper error on planet mass
65- 69 F5.1 Mgeo e_Mpl ? Lower error on planet mass
71 I1 --- f_Mpl [0/1] Mpl flag
(0 = known value, 1 = upper limit)
73- 91 A19 --- r_Mpl Planet mass reference
93- 98 F6.1 deg lambda ? Projected obliquity (λ)
100-103 F4.1 deg E_lambda ? Upper error on projected obliquity
105-108 F4.1 deg e_lambda ? Lower error on projected obliquity
110-128 A19 --- r_lambda Projected obliquity reference
130-134 F5.1 deg psiLit ? Literature true obliquity
(Ψliterature)
136-139 F4.1 deg E_psiLit ? Upper error on literature true obliquity
141-144 F4.1 deg e_psiLit ? Lower error on literature true obliquity
146-164 A19 --- r_psiLit Literature true obliquity reference
166-169 I4 K Teff Star effective temperature (Teff)
171-173 I3 K E_Teff Upper error on star effective temperature
175-177 I3 K e_Teff Lower error on star effective temperature
179-197 A19 --- r_Teff Star effective temperature reference
199-203 F5.2 deg iorb Planet orbital inclination (i)
205-208 F4.2 deg E_iorb Upper error on planet orbital inclination
210-213 F4.2 deg e_iorb Lower error on planet orbital inclination
215-233 A19 --- r_iorb Planet orbital inclination reference
235-240 F6.4 Rsun Rstar Stellar radius (R*)
242-247 F6.4 Rsun E_Rstar Upper error on stellar radius
249-254 F6.4 Rsun e_Rstar Lower error on stellar radius
256-274 A19 --- r_Rstar Stellar radius reference (2)
276-281 F6.2 km/s vsini ? Projected rotational velocity (vsini*)
283-287 F5.2 km/s E_vsini ? Upper error on projected rotational
velocity
289-293 F5.2 km/s e_vsini ? Lower error on projected rotational
velocity
295-313 A19 --- r_vsini Projected rotational velocity reference
315-319 F5.2 d Prot ? Star rotational period (Prot)
321-325 F5.2 d E_Prot ? Upper error on star rotational period
327-330 F4.2 d e_Prot ? Lower error on star rotational period
332 I1 --- f_Prot [0/1]? Upper limit flag of Prot
(0 = known value, 1 = upper limit)
334-352 A19 --- r_Prot Star rotational period reference
354-359 F6.3 Gyr Age ? Stellar age (age)
361-365 F5.3 Gyr E_Age ? Upper error on stellar age
367-371 F5.3 Gyr e_Age ? Lower error on stellar age
373-417 A45 --- r_Age Stellar age reference
419-423 F5.1 deg psi ? True obliquity (Ψ) (3)
425-428 F4.1 deg E_psi ? Upper error on true obliquity (3)
430-433 F4.1 deg e_psi ? Lower error on true obliquity (3)
435-439 F5.2 deg i* ? Stellar inclination (i*) (3)
441-445 F5.2 deg E_i* ? Upper error on stellar inclination (3)
447-451 F5.2 deg e_i* ? Lower error on stellar inclination (3)
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Note (1): According to Stevens & Gaudi (2013PASP..125..933S 2013PASP..125..933S) classification are
as follows:
e = Earth, 6 sources in our sample
n = Neptune, 32 sources in our sample
j = Jupiter, 71 sources in our sample
sj = super-Jupiter, 10 sources in our sample
bd = Brown dwarf, 1 source in our sample
Note (2): Reference 2023A&A...674A..34G 2023A&A...674A..34G corresponds to stars whose radius
has been gathered from Gaia DR3.
Note (3): Values computed in this work. HD 89345 b, KELT-9 b, Kepler-408 b, and
WASP-131 b are missing the psi value because the rotation period was
not applicable due to the lack of parameters needed for the rotation
period method. HD 89345 b and WASP-131 b have their stellar
inclination gathered from the same paper from which we collected the
literature value of true obliquity psiLit.
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Acknowledgements:
Rossi Alessandro, alessandromatteo.rossi(at)studenti.unimi.it
(End) Alessandro Rossi, [Univ. di Milano], Luc Trabelsi [CDS] 25-Nov-2025