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Register a new userA pair of warm giant planets near the 2:1 mean motion resonance around the K-dwarf star TOI-2202
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Trifon Trifonov Ph.D.
Publication date
2021
fields
Physics
and research's language is
English
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TOI-2202 b is a transiting warm Jovian-mass planet with an orbital period of P=11.91 days identified from the Full Frame Images data of five different sectors of the TESS mission. Ten TESS transits of TOI-2202 b combined with three follow-up light curves obtained with the CHAT robotic telescope show strong transit timing variations (TTVs) with an amplitude of about 1.2 hours. Radial velocity follow-up with FEROS, HARPS and PFS confirms the planetary nature of the transiting candidate (a$_{rm b}$ = 0.096 $pm$ 0.002 au, m$_{rm b}$ = 0.98 $pm$ 0.06 M$_{rm Jup}$), and dynamical analysis of RVs, transit data, and TTVs points to an outer Saturn-mass companion (a$_{rm c}$ = 0.155 $pm$ 0.003 au, m$_{rm c}$= $0.37 pm 0.10$ M$_{rm Jup}$) near the 2:1 mean motion resonance. Our stellar modeling indicates that TOI-2202 is an early K-type star with a mass of 0.82 M$_odot$, a radius of 0.79 R$_odot$, and solar-like metallicity. The TOI-2202 system is very interesting because of the two warm Jovian-mass planets near the 2:1 MMR, which is a rare configuration, and their formation and dynamical evolution are still not well understood.
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We present the confirmation of the eccentric warm giant planet TOI-201 b, first identified as a candidate in textit{TESS} photometry (Sectors 1-8, 10-13, and 27-28) and confirmed using ground-based photometry from NGTS and radial velocities from FEROS, HARPS, CORALIE, and textsc{Minerva}-Australis. TOI-201 b orbits a young ($mathrm{0.87^{+0.46}_{-0.49} , Gyr}$) and bright(V=9.07 mag) F-type star with a $mathrm{52.9781 , d}$ period. The planet has a mass of $mathrm{0.42^{+0.05}_{-0.03}, M_J}$, a radius of $mathrm{1.008^{+0.012}_{-0.015}, R_J}$, and an orbital eccentricity of $0.28^{+0.06}_{-0.09}$; it appears to still be undergoing fairly rapid cooling, as expected given the youth of the host star. The star also shows long-term variability in both the radial velocities and several activity indicators, which we attribute to stellar activity. The discovery and characterization of warm giant planets such as TOI-201 b is important for constraining formation and evolution theories for giant planets.
AU Mic is a young, active star whose transiting planet was recently detected. We report our analysis of its TESS data, where we modeled the BY Draconis type quasi-periodic rotational modulation by starspots simultaneously to the flaring activity and planetary transits. We measured a flare occurrence rate of 6.35 flares per day for flares with amplitudes in the range of $0.06% < f_{rm max} < 1.5%$ of the star flux. We employed a Bayesian MCMC analysis to model the five transits of AU Mic b, improving the constraints on the planetary parameters. The planet radius of $4.07pm0.17$~R$_{oplus}$ and a mean density of $1.4pm0.4$~g~cm$^{-3}$ confirms that it is a Neptune-size moderately inflated planet. While a single feature possibly due to a second planet was previously reported in the former TESS data, we report the detection of two additional transit-like events in the new TESS observations of July 2020. This represents substantial evidence for a second planet (AU Mic c) in the system. We analyzed its three transits and obtained an orbital period of $18.859019pm0.000016$~d and a planetary radius of $3.24pm0.16$~R$_{oplus}$, which defines it as a warm Neptune-size planet with an expected mass in the range of 2.2~M$_{oplus}$~$< M_{rm c} < $25.0~M$_{oplus}$. The two planets in the system are in near 9:4 mean-motion resonance. We show that this configuration is dynamically stable and should produce transit-timing variations (TTV). Our non-detection of significant TTV in AU Mic b suggests an upper limit for the mass of AU Mic c of $<7$~M$_{oplus}$, indicating that this planet is also likely to be inflated. As a young multi-planet system with at least two transiting planets, AU Mic becomes a key system for the study of atmospheres of infant planets and of planet-planet and planet-disk dynamics at the early stages of planetary evolution.
We report the discovery of one super-Earth- (TOI-1749b) and two sub-Neptune-sized planets (TOI-1749c and TOI-1749d) transiting an early M dwarf at a distance of 100~pc, which were first identified as planetary candidates using data from the TESS photometric survey. We have followed up this system from the ground by means of multiband transit photometry, adaptive-optics imaging, and low-resolution spectroscopy, from which we have validated the planetary nature of the candidates. We find that TOI-1749b, c, and d have orbital periods of 2.39, 4.49, and 9.05 days, and radii of 1.4, 2.1, and 2.5 $R_oplus$, respectively. We also place 95% confidence upper limits on the masses of 57, 14, and 15 $M_oplus$ for TOI-1749b, c, and d, respectively, from transit timing variations. The periods, sizes, and tentative masses of these planets are in line with a scenario in which all three planets initially had a hydrogen envelope on top of a rocky core, and only the envelope of the innermost planet has been stripped away by photoevaporation and/or core-powered mass loss mechanisms. These planets are similar to other planetary trios found around M dwarfs, such as TOI-175b,c,d and TOI-270b,c,d, in the sense that the outer pair has a period ratio within 1% of 2. Such a characteristic orbital configuration, in which an additional planet is located interior to a near 2:1 period-ratio pair, is relatively rare around FGK dwarfs.
We present radial-velocity (RV) measurements for the K giant $ u$ Oph (= HIP88048, HD163917, HR6698), which reveal two brown dwarf companions with a period ratio close to 6:1. For our orbital analysis we use 150 precise RV measurements taken at Lick Observatory between 2000 and 2011, and we combine them with RV data for this star available in the literature. Using a stellar mass of $M = 2.7,M_odot$ for $ u$ Oph and applying a self-consistent N-body model we estimate the minimum dynamical companion masses to be $m_1sin i approx 22.2,M_{mathrm{Jup}}$ and $m_2sin i approx 24.7,M_{mathrm{Jup}}$, with orbital periods $P_1 approx 530$ d and $P_2 approx 3185$ d. We study a large set of potential orbital configurations for this system, employing a bootstrap analysis and a systematic $chi_{ u}^2$ grid-search coupled with our dynamical fitting model, and we examine their long-term stability. We find that the system is indeed locked in a 6:1 mean motion resonance (MMR), with $Delta omega$ and all six resonance angles $theta_{1}, ldots, theta_{6}$ librating around 0$^circ$. We also test a large set of coplanar inclined configurations, and we find that the system will remain in a stable resonance for most of these configurations. The $ u$ Oph system is important for probing planetary formation and evolution scenarios. It seems very likely that the two brown dwarf companions of $ u$ Oph formed like planets in a circumstellar disk around the star and have been trapped in a MMR by smooth migration capture.
Warm, large exoplanets with 10-100 day orbital periods pose a major challenge to our understanding of how planetary systems form and evolve. Although high eccentricity tidal migration has been invoked to explain their proximity to their host stars, a handful reside in or near orbital resonance with nearby planets, suggesting a gentler history of in situ formation or disk migration. Here we confirm and characterize a pair of warm, large exoplanets discovered by the TESS Mission orbiting K-dwarf TOI-216. Our analysis includes additional transits and transit exclusion windows observed via ground-based follow-up. We find two families of solutions, one corresponding to a sub-Saturn-mass planet accompanied by a Neptune-mass planet and the other to a Jupiter in resonance with a sub-Saturn-mass planet. We prefer the second solution based on the orbital period ratio, the planet radii, the lower free eccentricities, and libration of the 2:1 resonant argument, but cannot rule out the first. The free eccentricities and mutual inclination are compatible with stirring by other, undetected planets in the system, particularly for the second solution. We discuss prospects for better constraints on the planets properties and orbits through follow-up, including transits observed from the ground.
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