The orbital period of the hot Jupiter WASP-4b appears to be decreasing at a rate of $-8.64 \pm 1.26$ msec/yr, based on transit-timing measurements spanning 12 years. Proposed explanations for the period change include tidal orbital decay, apsidal precession, and acceleration of the system along the line of sight. To investigate further, we performed new radial velocity measurements and speckle imaging of WASP-4. The radial-velocity data show that the system is accelerating towards the Sun at a rate of $-0.0422\pm 0.0028$ m/s/day. The associated Doppler effect should cause the apparent period to shrink at a rate of $-5.94 \pm 0.39$ msec/yr, comparable to the observed rate. Thus, the observed change in the transit period is mostly or entirely produced by the line-of-sight acceleration of the system. This acceleration is probably caused by a wide-orbiting companion of mass 10-300$\,M_{\rm Jup}$ and orbital distance 10-100$\,$AU, based on the magnitude of the radial-velocity trend and the non-detection of any companion in the speckle images. We expect that the orbital periods of 1 out of 3 hot Jupiters will change at rates similar to WASP-4b, based on the hot-Jupiter companion statistics of Knutson et al. (2014). Continued radial velocity monitoring of hot Jupiters is therefore essential to distinguish the effects of tidal orbital decay or apsidal precession from line-of-sight acceleration.
WASP-47 hosts a remarkable planetary system containing a hot Jupiter (WASP-47 b; P = 4.159 days) with an inner super-Earth (WASP-47 e; P = 0.7896 days), a close-orbiting outer Neptune (WASP-47 d; P = 9.031 days), and a long period giant planet (WASP-47 c; P = 588.4 days). We use the new TESS photometry to refine the orbital ephemerides of the transiting planets in the system, particularly the hot Jupiter WASP-47 b, for which we find an update equating to a 17.4 min shift in the transit time. We report new radial velocity measurements from the ESPRESSO spectrograph for WASP-47, which we use to …
We hypothesise that differences in the temperatures at which the rocky material condensed out of the nebula gas can lead to differences in the composition of key rocky species (e.g., Fe, Mg, Si, Ca, Al, Na) and thus planet bulk density. Such differences in the observed bulk density of planets may occur as a function of radial location and time of planet formation. In this work we show that the predicted differences are on the cusp of being detectable with current instrumentation. In fact, for HD 219134, the 10 % lower bulk density of planet b compared to planet c could be explained by enhancem…
We present precise radial velocity observations of WASP-47, a star known to host a hot Jupiter, a distant Jovian companion, and, uniquely, two additional transiting planets in short-period orbits: a super-Earth in a ~19 hour orbit, and a Neptune in a ~9 day orbit. We analyze our observations from the HARPS-N spectrograph along with previously published data to measure the most precise planet masses yet for this system. When combined with new stellar parameters and reanalyzed transit photometry, our mass measurements place strong constraints on the compositions of the two small planets. We find…
We report nine new transit epochs of the extrasolar planet, observed in the Bessell-I band with SOAR at the Cerro Pachon Observatory and with the SMARTS 1-m Telescope at CTIO, between August 2008 and October 2009. The new transits have been combined with all previously published transit data for this planet to provide a new Transit Timing Variations (TTVs) analysis of its orbit. We find no evidence of TTVs RMS variations larger than 1 min over a 3 year time span. This result discards the presence of planets more massive than about 5 M_earth, 1 M_earth and 2 M_earth around the 1:2, 5:3 and 2:1 …
High-resolution Doppler-resolved spectroscopy has presented new opportunities for studying the atmospheres of exoplanets. While the 'classical' cross-correlation approach has proven to be efficient at finding atmospheric species, it is unable to perform direct atmospheric retrievals. Recent work has shown that retrievals are possible using a direct likelihood evaluation or likelihood 'mappings'. The unique aspect of high-resolution retrievals is that the data-processing methods required to remove the stellar and telluric lines also distort the underlying exoplanet's signal and therefore the fo…
Two photometric follow-up transit (primary eclipse) observations on WASP-43 b and four observations on TrES-3 b are performed using the Xuyi Near-Earth Object Survey Telescope. After differential photometry and light curve analysis, the physical parameters of the two systems are obtained and are in good match with the literature. Combining with transit data from a lot of literature, the residuals ($O-C$) of transit observations of both systems are fitted with the linear and quadratic functions. With the linear fitting, the periods and transit timing variations (TTVs) of the planets are obtaine…
Orbital dynamics provide valuable insights into the evolution and diversity of exoplanetary systems. Currently, only one hot Jupiter, WASP-12b, is confirmed to have a decaying orbit. Another, WASP-4b, exhibits hints of a changing orbital period that could be caused by orbital decay, apsidal precession, or the acceleration of the system towards the Earth. We have analyzed all data sectors from NASA's Transiting Exoplanet Survey Satellite together with all radial velocity (RV) and transit data in the literature to characterize WASP-4b's orbit. Our analysis shows that the full RV data set is cons…
We report the discovery of two additional planetary companions to WASP-41 and WASP-47. WASP-41 c is a planet of minimum mass 3.18 $\pm$ 0.20 M$_{\rm Jup}$ and eccentricity 0.29 $\pm$ 0.02, and it orbits in 421 $\pm$ 2 days. WASP-47 c is a planet of minimum mass 1.24 $\pm$ 0.22 M$_{\rm Jup}$ and eccentricity 0.13 $\pm$ 0.10, and it orbits in 572 $\pm$ 7 days. Unlike most of the planetary systems that include a hot Jupiter, these two systems with a hot Jupiter have a long-period planet located at only $\sim$1 au from their host star. WASP-41 is a rather young star known to be chromospherically a…
We report precise radial velocity (RV) measurements of WASP-47, a G star that hosts three transiting planets in close proximity (a hot Jupiter, a super-Earth and a Neptune-sized planet) and a non-transiting planet at 1.4 AU. Through a joint analysis of previously published RVs and our own Keck-HIRES RVs, we significantly improve the planet mass and bulk density measurements. For the super-Earth WASP-47e ($P$ = 0.79 days), we measure a mass of 9.11 $\pm$ 1.17 $M_\oplus$, and a bulk density of 7.63 $\pm$ 1.90 g cm$^{-3}$, consistent with a rocky composition. For the hot Jupiter WASP-47b ($P$ = 4…
We report twelve new transit observations of the exoplanet WASP-4b from the Transit Monitoring in the South Project (TraMoS) project. These transits are combined with all previously published transit data for this planet to provide an improved radius measurement of Rp = 1.395 +- 0.022 Rjup and improved transit ephemerides. In a new homogeneous analysis in search for Transit Timing Variations (TTVs) we find no evidence of those with RMS amplitudes larger than 20 seconds over a 4-year time span. This lack of TTVs rules out the presence of additional planets in the system with masses larger than …
We report three newly discovered exoplanets from the SuperWASP survey. WASP-127b is a heavily inflated super-Neptune of mass 0.18 +/- 0.02 M_J and radius 1.37 +/- 0.04 R_J. This is one of the least massive planets discovered by the WASP project. It orbits a bright host star (Vmag = 10.16) of spectral type G5 with a period of 4.17 days. WASP-127b is a low-density planet that has an extended atmosphere with a scale height of 2500 +/- 400 km, making it an ideal candidate for transmission spectroscopy. WASP-136b and WASP-138b are both hot Jupiters with mass and radii of 1.51 +/- 0.08 M_J and 1.38 …
Using new data from the K2 mission, we show that WASP-47, a previously known hot Jupiter host, also hosts two additional transiting planets: a Neptune-sized outer planet and a super-Earth inner companion. We measure planetary properties from the K2 light curve and detect transit timing variations, confirming the planetary nature of the outer planet. We performed a large number of numerical simulations to study the dynamical stability of the system and to find the theoretically expected transit timing variations (TTVs). The theoretically predicted TTVs are in good agreement with those observed,…
The class of exotic Jupiter-mass planets that orbit very close to their parent stars were not explicitly expected before their discovery. The recently found transiting planet WASP-12b has a mass Mp = 1.4(+/-0.1) Jupiter masses (MJ), a mean orbital distance of only 3.1 stellar radii (meaning it is subject to intense tidal forces), and a period of 1.1 days. Its radius 1.79(+/- 0.09) RJ is unexpectedly large and its orbital eccentricity 0.049(+/-0:015) is even more surprising as such close orbits are in general quickly circularized. Here we report an analysis of its properties, which reveals that…
With high-resolution spectroscopy we can study exoplanet atmospheres and learn about their chemical composition, temperature profiles, and presence of clouds and winds, mainly in hot, giant planets. State-of-the-art instrumentation is pushing these studies towards smaller exoplanets. Of special interest are the few planets in the 'Neptune desert', a lack of Neptune-size planets in close orbits around their hosts. Here, we assess the presence of water in one such planet, the bloated super-Neptune WASP-166 b, which orbits an F9-type star in a short orbit of 5.4 days. Despite its close-in orbit, …
Observations have confirmed the existence of multiple-planet systems containing a hot Jupiter and smaller planetary companions. Examples include WASP-47, Kepler-730, and TOI-1130. We examine the plausibility of forming such systems in situ using $N$-body simulations that include a realistic treatment of collisions, an evolving protoplanetary disc and eccentricity/inclination damping of planetary embryos. Initial conditions are constructed using two different models for the core of the giant planet: a 'seed-model' and an 'equal-mass-model'. The former has a more massive protoplanet placed among…
We present spectroscopic measurements of the Rossiter-McLaughlin effect for WASP-148b, the only known hot Jupiter with a nearby warm-Jupiter companion, from the WIYN/NEID and Keck/HIRES instruments. This is one of the first scientific results reported from the newly commissioned NEID spectrograph, as well as the second obliquity constraint for a hot Jupiter system with a close-in companion, after WASP-47. WASP-148b is consistent with being in alignment with the sky-projected spin axis of the host star, with $λ=-8^{\circ}.2^{{+8^{\circ}.7}}_{-9^{\circ}.7}$. The low obliquity observed in the WAS…
We present improved physical parameters for four hot Jupiters: KELT-7 b, HAT-P-14 b, WASP-29 b, WASP-95 b, and a hot Neptune: WASP-156 b, by performing critical and rigorous analysis of the time-series observations from the Transiting Exoplanet Survey Satellite (TESS). Being a space-based telescope, the transit photometric data obtained by TESS are free from any noise component due to the interference of Earth's atmosphere. In our analysis of the observed data, we have used critical noise reduction techniques, e.g., the wavelet denoising and Gaussian process regression, in order to effectively…
Towards Doppler eclipse mapping of hot Jupiters. An observational perspective on WASP-33 b with SPIRou
Institut de Planétologie et Astrophysique de Grenoble（格勒诺布尔行星与天体物理研究所）；McGill University（麦吉尔大学）；Institut de Recherche en Astrophysique et Planétologie（天体物理学与行星学研究所）；Centro de Astrobiología (CAB), CSIC-INTA（天文生物学中心（CAB），西班牙国家研究委员会-国家航空航天技术研究所）；Université Côte d’Azur, Observatoire de la Côte d’Azur（蔚蓝海岸大学，蔚蓝海岸天文台）；Laboratoire Lagrange（拉格兰日实验室）；Université de Montréal（蒙特利尔大学）
In this work we investigate the problem concerning the presence of additional bodies gravitationally bounded with the WASP-3 system. We present eight new transits of this planet and analyse all the photometric and radial velocity data published so far. We did not observe significant periodicities in the Fourier spectrum of the observed minus calculated (O-C) transit timing and radial velocity diagrams (the highest peak having false-alarm probabilities of 56 per cent and 31 per cent, respectively) or long-term trends. Combining all the available information, we conclude that the radial velocity…
We study mass transfer by Roche lobe overflow in close-in exoplanetary systems. The planet's atmospheric gas passes through the inner Lagrangian point and flows along a narrow stream, accelerating to 100-$200\kms$ velocity before forming an accretion disk. We show that the cylinder-shaped accretion stream can have an area (projected in the plane of the sky) comparable to that of the planet and a significant optical depth to spectral line absorption. Such a "transiting cylinder" may produce an earlier ingress of the planet transit, as suggested by recent HST observations of the WASP-12 system. …
Planets that reside close-in to their host star are subject to intense high-energy irradiation. Extreme-ultraviolet (EUV) and X-ray radiation (together, XUV) is thought to drive mass loss from planets with volatile envelopes. We present $\textit{XMM-Newton}$ observations of six nearby stars hosting transiting planets in tight orbits (with orbital period, $P_\text{orb} < 10\,$d), wherein we characterise the XUV emission from the stars and subsequent irradiation levels at the planets. In order to reconstruct the unobservable EUV emission, we derive a new set of relations from Solar $\textit{TIME…
The carbon-to-oxygen ratio (C/O) in a planet provides critical information about its primordial origins and subsequent evolution. A primordial C/O greater than 0.8 causes a carbide-dominated interior as opposed to a silicate-dominated composition as found on Earth, and the atmospheres can also differ from those in the Solar System. The solar C/O is 0.54. Here we report an analysis of dayside multi-wavelength photometry of the transiting hot-Jupiter WASP-12b that reveals C/O >= 1 in its atmosphere. The atmosphere is abundant in CO. It is depleted in water vapor and enhanced in methane by over t…
Exploiting the Kepler transit data, we uncover a dramatic distinction in the prevalence of sub-Jovian companions, between systems that contain hot Jupiters (periods inward of 10 days) and those that host warm Jupiters (periods between 10 and 200 days). Hot Jupiters, with the singular exception of WASP-47b, do not have any detectable inner or outer planetary companions (with periods inward of 50 days and sizes down to $2 R_{\rm Earth}$). Restricting ourselves to inner companions, our limits reach down to $1 R_{\rm Earth}$. In stark contrast, half of the warm Jupiters are closely flanked by smal…
We present a comprehensive theoretical study on the spin evolution of a planet under the combined effects of tidal dissipation and gravitational perturbation from an external companion. Such a "spin + companion" system (called Colombo's top) appears in many [exo]planetary contexts. The competition between the tidal torque (which drives spin-orbit alignment and synchronization) and the gravitational torque from the companion (which drives orbital precession of the planet) gives rise to two possible spin equilibria ("Tidal Cassini Equilibria", tCE) that are stable and attracting: the "simple" tC…
Exoplanets at small orbital distances from their host stars are submitted to intense levels of energetic radiations, X-rays and extreme ultraviolet (EUV). Depending on the masses and densities of the planets and on the atmospheric heating efficiencies, the stellar energetic inputs can lead to atmospheric mass loss. These evaporation processes are observable in the ultraviolet during planetary transits. The aim of the present work is to quantify the mass-loss rates (dm/dt), heating efficiencies (eta), and lifetimes for the whole sample of transiting exoplanets, now including hot jupiters, hot n…
The most challenging limitation in transit photometry arises from the noises in the photometric signal. In particular, the ground-based telescopes are heavily affected by the noise due to perturbation in the Earth's atmosphere. Use of telescopes with large apertures can improve the photometric signal-to-noise ratio (S/N) to a great extent. However, detecting a transit signal out of a noisy light curve of the host star and precisely estimating the transit parameters call for various noise reduction techniques. Here, we present multi-band transit photometric follow-up observations of five hot-Ju…
Some close-in gaseous exoplanets are nearly in Roche-lobe contact, and previous studies show tidal decay can drive hot Jupiters into contact during the main sequence of their host stars. Improving upon a previous model, we present a revised model for mass transfer in a semi-detached binary system that incorporates an extended atmosphere around the donor and allows for an arbitrary mass ratio. We apply this new formalism to hypothetical, confirmed, and candidate planetary systems to estimate mass loss rates and compare with models of evaporative mass loss. Overflow may be significant for hot Ne…
In 2015, K2 observations of the bright (V = 8.9, K = 7.7) star HIP 41378 revealed a rich system of at least five transiting exoplanets, ranging in size from super-Earths to gas giants. The 2015 K2 observations only spanned 74.8 days, and the outer three long-period planets in the system were only detected with a single transit, so their orbital periods and transit ephemerides could not be determined at that time. Here, we report on 50.8 days of new K2 observations of HIP 41378 from summer 2018. These data reveal additional transits of the long-period planets HIP 41378 d and HIP 41378 f, yieldi…
ExoEcho: Exoplanet Ephemerides Change Observations. III. A JWST Survey for Transit Timing Variations of 37 Exoplanets
School of Physics and Astronomy, Sun Yat-sen University（中山大学物理学院）；CSST Science Center for the Guangdong-Hong Kong-Macau Great Bay Area, Sun Yat-sen University（中山大学粤港澳大湾区空间望远镜科学中心）
Useful information can be retrieved by analysing the transit light curve of a planet-hosting star or induced radial velocity oscillations. However, inferring the physical parameters of the planet, such as mass, size, and semi-major axis, requires preliminary knowledge of some parameters of the host star, especially its mass or radius, which are generally inferred through theoretical evolutionary models. We seek to present and test a whole algorithm devoted to the complete characterisation of an exoplanetary system thanks to the global analysis of photometric or radial velocity time series comb…
What makes the study of exoplanetary atmospheres so hard is the extraction of its tiny signal from observations, usually dominated by telluric absorption, stellar spectrum and instrumental noise. The High Resolution Spectroscopy has emerged as one of the leading techniques for detecting atomic and molecular species (Birkby 2018), but although it is particularly robust against contaminant absorption in the Earth's atmosphere, the non-stationary stellar spectrum -- in the form of either Doppler shift or distortion of the line profile during planetary transits -- creates a non-negligible source o…
