Search

The rotation of a star and the revolutions of its planets are not necessarily aligned. This article reviews the measurement techniques, key findings, and theoretical interpretations related to the obliquities (spin-orbit angles) of planet-hosting stars. The best measurements are for stars with short-period giant planets, which have been found on prograde, polar, and retrograde orbits. It seems likely that dynamical processes such as planet-planet scattering and secular perturbations are responsible for tilting the orbits of close-in giant planets, just as those processes are implicated in exciting orbital eccentricities. The observed dependence of the obliquity on orbital separation, planet mass, and stellar structure suggests that in some cases, tidal dissipation damps a star's obliquity within its main-sequence lifetime. The situation is not as clear for stars with smaller or wider-orbiting planets. Although the earliest measurements of such systems tended to find low obliquities, some glaring exceptions are now known in which the star's rotation is misaligned with respect to the coplanar orbits of multiple planets. In addition, statistical analyses based on projected rotation velocities and photometric variability have found a broad range of obliquities for F-type stars hosting compact multiple-planet systems. The results suggest it is unsafe to assume that stars and their protoplanetary disks are aligned. Primordial misalignments might be produced by neighboring stars or more complex events that occur during the epoch of planet formation., Invited Review PASP. This is the accepted version. The PASP and this version differ in that this version has a table of contents

DI Herculis is an eclipsing binary famous for a longstanding disagreement between theory and observation of the apsidal precession rate, which was resolved when both stars were found to be severely misaligned with the orbit. We used data from the Transiting Exoplanet Survey Satellite (TESS) to refine our knowledge of the stellar obliquities and sharpen the comparison between the observed and theoretical precession rates. The TESS data show variations with a 1.07-day period, which we interpret as rotational modulation from starspots on the primary star. This interpretation is supported by the detection of photometric anomalies during primary eclipses consistent with starspot crossings. The secondary eclipse light curve shows a repeatable asymmetry which we interpret as an effect of gravity darkening. By combining the TESS data with previously obtained data, we determined the three-dimensional spin directions of both stars. Using this information, the updated value of the theoretical apsidal precession rate (including the effects of tides, rotation, and general relativity) is $1.35^{+0.58}_{-0.50}$ arcsec/cycle. The updated value of the observed rate (after including new TESS eclipse times) is $1.41^{+0.39}_{-0.28}$ arcsec/cycle. Given the agreement between the observed and theoretical values, we fitted all the relevant data simultaneously assuming the theory is correct. This allowed us to place tighter constraints on the stellar obliquities, which are $75^{+3}_{-3}$ and $80^{+3}_{-3}$ degrees for the primary and secondary stars, respectively., Comment: Accepted by ApJ, 13 pages, 10 figures

TOI-640 b is a hot, puffy Jupiter with a mass of 0.57 ± 0.02 MJ and radius of 1.72 ± 0.05 RJ, orbiting a slightly evolved F-type star with a separation of 6.33−0.06+0.07 R⋆. Through spectroscopic in-transit observations made with the HARPS spectrograph, we measured the Rossiter-McLaughlin effect, analysing both in-transit radial velocities and the distortion of the stellar spectral lines. From these observations, we find the host star to have a projected obliquity of λ = 184 ± 3°. From the TESS light curve, we measured the stellar rotation period, allowing us to determine the stellar inclination, i⋆ = 23−2+3°, meaning we are viewing the star pole-on. Combining this with the orbital inclination allowed us to calculate the host star obliquity, ψ = 104 ± 2°. TOI-640 b joins a group of planets orbiting over stellar poles within the range 80°–125°. The origin of this orbital configuration is not well understood.

Full list of authors: Tran, Quang H.; Bowler, Brendan P.; Endl, Michael; Cochran, William D.; MacQueen, Phillip J.; Gandolfi, Davide; Persson, Carina M.; Fridlund, Malcolm; Palle, Enric; Nowak, Grzegorz; Deeg, Hans J.; Luque, Rafael; Livingston, John H.; Kabáth, Petr; Skarka, Marek; Šubjak, Ján; Howell, Steve B.; Albrecht, Simon H.; Collins, Karen A.; Esposito, Massimiliano; Van Eylen, Vincent; Grziwa, Sascha; Goffo, Elisa; Huang, Chelsea X.; Jenkins, Jon M.; Karjalainen, Marie; Karjalainen, Raine; Knudstrup, Emil; Korth, Judith; Lam, Kristine W. F.; Latham, David W.; Levine, Alan M.; Osborne, H. L. M.; Quinn, Samuel N.; Redfield, Seth; Ricker, George R.; Seager, S.; Serrano, Luisa Maria; Smith, Alexis M. S.; Twicken, Joseph D.; Winn, Joshua N.--This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited., We report the discovery of two transiting planets around the bright (V = 9.9 mag) main-sequence F7 star TOI-1670 by the Transiting Exoplanet Survey Satellite. TOI-1670 b is a sub-Neptune (${R}_{{\rm{b}}}={2.06}_{-0.15}^{+0.19}$ R⊕) on a 10.9 day orbit, and TOI-1670 c is a warm Jupiter (${R}_{{\rm{c}}}={0.987}_{-0.025}^{+0.025}$ RJup) on a 40.7 day orbit. Using radial velocity observations gathered with the Tull Coudé Spectrograph on the Harlan J. Smith telescope and HARPS-N on the Telescopio Nazionale Galileo, we find a planet mass of ${M}_{{\rm{c}}}={0.63}_{-0.08}^{+0.09}$ MJup for the outer warm Jupiter, implying a mean density of ${\rho }_{c}={0.81}_{-0.11}^{+0.13}$ g cm−3. The inner sub-Neptune is undetected in our radial velocity data (Mb < 0.13 MJup at the 99% confidence level). Multiplanet systems like TOI-1670 hosting an outer warm Jupiter on a nearly circular orbit (${e}_{{\rm{c}}}={0.09}_{-0.04}^{+0.05}$) and one or more inner coplanar planets are more consistent with "gentle" formation mechanisms such as disk migration or in situ formation rather than high-eccentricity migration. Of the 11 known systems with a warm Jupiter and a smaller inner companion, eight (73%) are near a low-order mean-motion resonance, which can be a signature of migration. TOI-1670 joins two other systems (27% of this subsample) with period commensurabilities greater than 3, a common feature of in situ formation or halted inward migration. TOI-1670 and the handful of similar systems support a diversity of formation pathways for warm Jupiters. © 2022. The Author(s). Published by the American Astronomical Society., Q.H.T. and B.P.B. acknowledge support from a NASA FINESST grant (80NSSC20K1554). This work benefited from involvement in ExoExplorers, which is sponsored by the Exoplanets Program Analysis Group (ExoPAG) and NASA's Exoplanet Exploration Program Office (ExEP). B.P.B. acknowledges support from National Science Foundation grant AST-1909209 and NASA Exoplanet Research Program grant 20-XRP20_2-0119. C.M.P. and M.F. gratefully acknowledge the support of the Swedish National Space Agency (DNR 65/19 and 177/19). J.K. gratefully acknowledges the support of the Swedish National Space Agency (SNSA; DNR 2020-00104). P.K., M.S., J.S., and R.K. acknowledge the financial support of Inter-transfer grant No. LTT-20015. M.K. acknowledges support from ESAs PEA4000127913. M.E. acknowledges the support of the DFG priority program SPP 1992 "Exploring the Diversity of Extrasolar Planets" (HA 3279/12-1). Funding for the Stellar Astrophysics Centre is provided by the Danish National Research Foundation (grant agreement No. DNRF106). D.G. and L.M.S. gratefully acknowledge financial support from the Cassa di Risparmio di Torino (CRT) foundation under grant No. 2018.2323 "Gaseous or rocky? Unveiling the nature of small worlds." This work is partly supported by JSPS KAKENHI grant No. JP20K14518 and SATELLITE Research from Astrobiology Center (AB022006). Funding for the TESS mission is provided by NASA's Science Mission Directorate. This research has made use of the Exoplanet Follow-up Observation Program website, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. We acknowledge the use of public TESS data from pipelines at the TESS Science Office and the TESS Science Processing Operations Center. Resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center for the production of the SPOC data products. This paper includes data collected by the TESS mission that are publicly available from the Mikulski Archive for Space Telescopes (MAST)., With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.

We report the confirmation and characterisation of TOI-1820~b, TOI-2025~b, and TOI-2158~b, three Jupiter-sized planets on short-period orbits around G-type stars detected by TESS. Through our ground-based efforts using the FIES and Tull spectrographs, we have confirmed these planets and characterised their orbits, and find periods of around $4.9$~d, $8.9$~d, and $8.6$~d for TOI-1820~b, TOI-2025~b, and TOI-2158~b, respectively. The sizes of the planets range from 0.96 to 1.14 Jupiter radii, and their masses are in the range from 0.8 to 4.4 Jupiter masses. For two of the systems, namely TOI-2025 and TOI-2158, we see a long-term trend in the radial velocities, indicating the presence of an outer companion in each of the two systems. For TOI-2025 we furthermore find the star to be well-aligned with the orbit, with a projected obliquity of $9^{+33}_{-31}$~$^\circ$. As these planets are all found in relatively bright systems (V$\sim$10.9-11.6 mag), they are well-suited for further studies, which could help shed light on the formation and migration of hot and warm Jupiters., Comment: Accepted for publication in A&A. 19 pages, 15 figures