Exoplanets Research Articles

An impact-free mechanism to deliver water to terrestrial planets and exoplanets

Context. The origin of water, particularly on Earth, is still a matter of heated debate. To date, the most widespread scenario is that the Earth originated without water and that it was brought to the planet mainly as a result of impacts by wet asteroids coming from further out in space. However, many uncertainties remain as to the exact processes that supplied an adequate amount of water to inner terrestrial planets. Aims. In this article, we explore a new mechanism that would allow water to be efficiently transported to planets without impacts. We propose that primordial asteroids were icy and that when the ice sublimated, it formed a gaseous disk that could then reach planets and deliver water. Methods. We have developed a new model that follows the sublimation of asteroids on gigayear (Gyr) timescales, taking into account the variable luminosity of the Sun. We then evolved the subsequent gas disk using a viscous diffusion code, which leads to the gas spreading both inwards and outwards in the Solar System. We can then quantify the amount of water that can be accreted onto each planet in a self-consistent manner using our code. Results. We find that this new disk-delivery mechanism is effective and equipped to explain the water content on Earth (with the correct D/H ratio) as well as on other planets and the Moon. Our model shows most of the water being delivered between 20 and 30 Myr after the birth of the Sun, when the Sun’s luminosity increased sharply. Our scenario implies the presence of a gaseous water disk with substantial mass for hundreds of millions of years, which could be one of the key tracers of this mechanism. We show that such a watery disk could be detected in young exo-asteroid belts with ALMA. Conclusions. We propose that viscous water transport is inevitable and more generic than the impact scenario. We also suggest it is a universal process that may also occur in extrasolar systems. The conditions required for this scenario to unfold are indeed expected to be present in most planetary systems: an opaque proto-planetary disk that is initially cold enough for ice to form in the exo-asteroid belt region, followed by a natural outward-moving snow line that allows this initial ice to sublimate after the dissipation of the primordial disk, creating a viscous secondary gas disk and leading to the accretion of water onto the exo-planets.

A Fourth Planet in the Kepler-51 System Revealed by Transit Timing Variations

Kepler-51 is a ≲1 Gyr old Sun-like star hosting three transiting planets with radii ≈6–9 R ⊕ and orbital periods ≈45–130 days. Transit timing variations (TTVs) measured with past Kepler and Hubble Space Telescope (HST) observations have been successfully modeled by considering gravitational interactions between the three transiting planets, yielding low masses and low mean densities (≲0.1 g cm−3) for all three planets. However, the transit time of the outermost transiting planet Kepler-51d recently measured by the James Webb Space Telescope 10 yr after the Kepler observations is significantly discrepant from the prediction made by the three-planet TTV model, which we confirmed with ground-based and follow-up HST observations. We show that the departure from the three-planet model is explained by including a fourth outer planet, Kepler-51e, in the TTV model. A wide range of masses (≲M Jup) and orbital periods (≲10 yr) are possible for Kepler-51e. Nevertheless, all the coplanar solutions found from our brute-force search imply masses ≲10 M ⊕ for the inner transiting planets. Thus, their densities remain low, though with larger uncertainties than previously estimated. Unlike other possible solutions, the one in which Kepler-51e is around the 2:1 mean motion resonance with Kepler-51d implies low orbital eccentricities (≲0.05) and comparable masses (∼5 M ⊕) for all four planets, as is seen in other compact multiplanet systems. This work demonstrates the importance of long-term follow-up of TTV systems for probing longer-period planets in a system.

Planet Mass Function around M Stars at 1–10 au: A Plethora of Sub-Earth Mass Objects

Small planets (≲1 M ⊕) at intermediate orbital distances (∼1 au) represent an uncharted territory in exoplanetary science. The upcoming microlensing survey by the Nancy Grace Roman Space Telescope will be sensitive to objects as light as Ganymede and unveil the small planet population at 1–10 au. Instrumental sensitivity to such planets is low, and the number of objects we will discover is strongly dependent on the underlying planet mass function. In this work, we provide a physically motivated planet mass function by combining the efficiency of planet formation by pebble accretion with the observed disk mass function. Because the disk mass function for M dwarfs (0.4–0.6 M ⊙) is bottom heavy, the initial planet mass function is also expected to be bottom heavy, skewing toward Ganymede and Mars mass objects, more so for heavier initial planetary seeds. We follow the subsequent dynamical evolution of planetary systems over ∼100 Myr varying the initial eccentricity and orbital spacing. For initial planet separations of ≥3 local disk scale heights, we find that Ganymede and Mars mass planets do not grow significantly by mergers. However, Earth-like planets undergo vigorous merging and turn into super-Earths, potentially creating a gap in the planet mass function at ∼1 M ⊕. Our results demonstrate that the slope of the mass function and the location of the potential gap in the mass function can probe the initial architecture of multiplanet systems. We close by discussing implications on the expected difference between bound and free-floating planet mass functions.

The overflowing atmosphere of WASP-121 b. High-resolution transmission spectroscopy with VLT/CRIRES+

Transmission spectroscopy is a prime method to study the atmospheres of extrasolar planets. We obtained a high-resolution spectral transit time series of the hot Jupiter with CRIRES$^+$ to study its atmosphere via transmission spectroscopy of the triplet lines. Our analysis shows a prominent absorption feature moving along with the planetary orbital motion, which shows an observed, transit-averaged equivalent width of approximately 30\,m a slight redshift, and a depth of about 2\,<!PCT!>, which can only be explained by an atmosphere overflowing its Roche lobe. We carried out 3D hydrodynamic modeling to reproduce the observations, which favors asymmetric mass loss with a more pronounced leading tidal tail, possibly also explaining observational evidence for additional absorption stationary in the stellar rest frame. A trailing tail is not detectable. From our modeling, we derived estimates of $ for the stellar and $5.4 for the planetary mass loss rate, which is consistent with X-ray and extreme-ultraviolet (XUV) driven mass loss in

First comparative exoplanetology within a transiting multi-planet system: Comparing the atmospheres of V1298 Tau b and c

The V1298 Tau system is a multi-planet system that provides the opportunity to perform comparative exoplanetology between planets orbiting the same star. Because of its young age (20-30 Myr), this system also provides the opportunity to compare the planet's early evolutionary properties, right after their formation. We present the first atmospheric comparison between two transiting exoplanets within the same multiple planet system: V1298 Tau b and V1298 Tau c. We observed one primary transit for each planet with the Hubble Space Telescope (HST), using Grism 141 (G141) of Wide Field Camera 3 (WFC3). We fit the spectroscopic light curves using state-of-the-art techniques to derive the transmission spectrum for planet c and adopted the transmission spectrum of planet b obtained with the same observing configuration and data analysis methods from previous studies. We measured the mass of planet b and c ($8_ $ M$_ oplus $; respectively) from the transmission spectrum and found the two planets to have masses in the Neptune or sub-Neptune regime. Using atmospheric retrievals, we measured and compared the atmospheric metallicities of planet b and c (logZ/Z$_ $, logZ/Z$_ $, respectively), and found them to be consistent with the solar or sub-solar, which is low (at least one order of magnitude) compared to known mature Neptune and sub-Neptune planets. This discrepancy could be explained by ongoing early evolutionary mechanisms, which are expected to enrich the atmospheres of such young planets as they mature. Alternatively, the observed spectrum of planet c can be explained by atmospheric hazes, which is in contrast to planet b, where efficient haze formation can be ruled out. Higher haze formation efficiency in planet c could be due to differences in atmospheric composition, temperature and/or higher UV flux compared to planet b. In addition, planet c is likely to experience a higher fraction of mass loss compared to planet b, given its proximity to the host star.

JWST COMPASS: The 3–5 μm Transmission Spectrum of the Super-Earth L 98-59 c

We present a JWST Near-InfraRed Spectrograph (NIRSpec) transmission spectrum of the super-Earth exoplanet L 98-59 c. This small (R p = 1.385 ± 0.085R ⊕, M p = 2.22 ± 0.26 R ⊕), warm (T eq = 553 K) planet resides in a multiplanet system around a nearby, bright (J = 7.933) M3V star. We find that the transmission spectrum of L 98-59 c is featureless at the precision of our data. We achieve precisions of 22 ppm in NIRSpec G395H’s NRS1 detector and 36 ppm in the NRS2 detector at a resolution R ∼ 200 (30 pixel wide bins). At this level of precision, we are able rule out primordial H2–He atmospheres across a range of cloud pressure levels up to at least ∼0.1 mbar. By comparison to atmospheric forward models, we also rule out atmospheric metallicities below ∼300× solar at 3σ (or, equivalently, atmospheric mean molecular weights below ∼10 g mol−1). We also rule out pure methane atmospheres. The remaining scenarios that are compatible with our data include a planet with no atmosphere at all, or higher-mean-molecular-weight atmospheres, such as CO2- or H2O-rich atmospheres. This study adds to a growing body of evidence suggesting that planets ≲1.5 R ⊕ lack extended atmospheres.

Yuti: A General-purpose Transit Simulator for Arbitrary Shaped Objects Orbiting Stars

We present a versatile transit simulator (Yuti) aimed at generating light curves for arbitrarily shaped objects transiting stars. Utilizing a Monte Carlo algorithm, it accurately models the stellar flux blocked by these objects, producing precise light curves. The simulator adeptly handles realistic background stars, integrating effects such as tidal distortions and limb darkening, alongside the rotational dynamics of transiting objects of arbitrary geometries. We showcase its wide-ranging utility through successful simulations of light curves for single- and multiplanet systems, tidally distorted planets, eclipsing binaries, and exocomets. Additionally, our simulator can simulate light curves for hypothetical alien megastructures of any conceivable shape, providing avenues to identify interesting candidates for follow-up studies. We demonstrate applications of Yuti in modeling a Dyson swarm in construction, Dyson rings, and Dyson disks, discussing how tidally locked Dyson disks can be distinguished from planetary light curves.

An ultra-short-period super-Earth with an extremely high density and an outer companion

We present the discovery and characterization of a new multi-planetary system around the Sun-like star K2-360 (EPIC 201595106). K2-360 was first identified in K2 photometry as the host of an ultra-short-period (USP) planet candidate with a period of 0.88 d. We obtained follow-up transit photometry, confirming the star as the host of the signal. High precision radial velocity measurements from HARPS and HARPS-N confirm the transiting USP planet and reveal the existence of an outer (non-transiting) planet with an orbital period of ∼\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\sim$$\\end{document}10 d. We measure a mass of 7.67±0.75\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$7.67 \\pm 0.75$$\\end{document} M⊕\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$M_{\\oplus }$$\\end{document} and a radius of 1.57±0.08\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$1.57 \\pm 0.08$$\\end{document} R⊕\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$R_{\\oplus }$$\\end{document} for the transiting planet, yielding a high mean density of 11±2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$11 \\pm 2$$\\end{document} g cm-3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\hbox {cm}^{-3}$$\\end{document}, making it the densest well-characterized USP super-Earth discovered to date. We measure a minimum mass of 15.2±1.8\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$15.2 \\pm 1.8$$\\end{document} M⊕\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$M_{\\oplus }$$\\end{document} for the outer planet, and explore a migration formation pathway via the von Zeipel–Kozai–Lidov (ZKL) mechanism and tidal dissipation.

Outcomes of Sub-Neptune Collisions

Observed high multiplicity planetary systems are often tightly packed. Numerical studies indicate that such systems are susceptible to dynamical instabilities. Dynamical instabilities in close-in tightly packed systems, similar to those found in abundance by Kepler, often lead to planet–planet collisions. For sub-Neptunes, the dominant type of observed exoplanets, the planetary mass is concentrated in a rocky core, but the volume is dominated by a low-density gaseous envelope. For these, using the traditional perfect merger assumption (also known as the “sticky-sphere” approximation) to resolve collisions is questionable. Using both N-body integration and smoothed-particle hydrodynamics, we have simulated sub-Neptune collisions for a wide range in realistic kinematic properties such as impact parameters ( b′ ) and impact velocities ( vim ) to study the possible outcomes in detail. We find that the majority of the collisions with kinematic properties similar to what is expected from dynamical instabilities in multiplanet systems may not lead to mergers of sub-Neptunes. Instead, both sub-Neptunes survive the encounter, often with significant atmosphere loss. When mergers do occur, they can involve significant mass loss and can sometimes lead to complete disruption of one or both planets. Sub-Neptunes merge or disrupt if b′<bc′ , a critical value dependent on vim /v esc, where v esc is the escape velocity from the surface of the hypothetical merged planet assuming perfect merger. For vim/vesc≲2.5 , bc′∝(vim/vesc)−2 , and collisions with b′<bc′ typically leads to mergers. On the other hand, for vim/vesc≳2.5 , bc′ ∝ vim /v esc, and the collisions with b′<bc′ can result in complete destruction of one or both sub-Neptunes.

Unravelling sub-stellar magnetospheres

At the sub-stellar boundary, signatures of magnetic fields begin to manifest at radio wavelengths, analogous to the auroral emission of the magnetised solar system planets. This emission provides a singular avenue for measuring magnetic fields at planetary scales in extrasolar systems. So far, exoplanets have eluded detection at radio wavelengths. However, ultracool dwarfs (UCDs), their higher mass counterparts, have been detected for over two decades in the radio. Given their similar characteristics to massive exoplanets, UCDs are ideal targets to bridge our understanding of magnetic field generation from stars to planets. In this work, we develop a new tomographic technique for inverting both the viewing angle and large-scale magnetic field structure of UCDs from observations of coherent radio bursts. We apply our methodology to the nearby T8 dwarf WISE J062309.94-045624.6 (J0623) which was recently detected at radio wavelengths, and show that it is likely viewed pole-on. We also find that J0623's rotation and magnetic axes are misaligned significantly, reminiscent of Uranus and Neptune, and show that it may be undergoing a magnetic cycle with a period exceeding 6 months in duration. These findings demonstrate that our method is a robust new tool for studying magnetic fields on planetary-mass objects. With the advent of next-generation low-frequency radio facilities, the methods presented here could facilitate the characterisation of exoplanetary magnetospheres for the first time.

Accelerating Giant-impact Simulations with Machine Learning

Constraining planet-formation models based on the observed exoplanet population requires generating large samples of synthetic planetary systems, which can be computationally prohibitive. A significant bottleneck is simulating the giant-impact phase, during which planetary embryos evolve gravitationally and combine to form planets, which may themselves experience later collisions. To accelerate giant-impact simulations, we present a machine learning (ML) approach to predicting collisional outcomes in multiplanet systems. Trained on more than 500,000 N-body simulations of three-planet systems, we develop an ML model that can accurately predict which two planets will experience a collision, along with the state of the postcollision planets, from a short integration of the system’s initial conditions. Our model greatly improves on non-ML baselines that rely on metrics from dynamics theory, which struggle to accurately predict which pair of planets will experience a collision. By combining with a model for predicting long-term stability, we create an ML-based giant-impact emulator, which can predict the outcomes of giant-impact simulations with reasonable accuracy and a speedup of up to 4 orders of magnitude. We expect our model to enable analyses that would not otherwise be computationally feasible. As such, we release our training code, along with an easy-to-use user interface for our collision-outcome model and giant-impact emulator (https://github.com/dtamayo/spock).

Plausibility of Capture into High-obliquity States for Exoplanets in the M Dwarf Habitable Zone

For temperate exoplanets orbiting M-dwarf hosts, the proximity of the habitable zone to the star necessitates careful consideration of tidal effects. Spin synchronization of the planetary orbital period and rotation period, tidal locking, and the subsequent impact on surface conditions frames common assumptions about M-dwarf planets. We investigate the plausibility of capture into Cassini State 2 (CS2) for a known sample of 280 multiplanet systems orbiting M-dwarf hosts. This resonance of the spin precession and orbital precession frequencies can excite planets into stable nonzero rotational obliquities, breaking tidal locking and inducing a version of “day” and “night.” Considering each planetary pair and estimating the spin and orbital precession frequencies, we find that 75% of detected planets orbiting M dwarfs may be plausibly excited to a high obliquity and maintain it through subsequent tidal dissipation over long timescales. We also investigate two possible mechanisms for capture into CS2: quantifying the orbital migration or primordial obliquity necessary for CS2. We find orbital migrations by a factor of ≲2 and an isotropic initial spin distribution can produce high-obliquity planets, aligning with similar findings for planets orbiting close-in to FGK dwarfs. Many of the planets in our sample reside in both CS2 and within their stellar habitable zone. Over half of the planets with T eq < 400 K around host stars with T eff < 3000 K could possess nonzero obliquity due to residence in CS2. This overlap renders the potential capture into Cassini States extremely relevant to understanding the galaxy’s most common temperate planets.

Diversities and similarities exhibited by multi-planetary systems and their architectures. I. Orbital spacings

The rich diversity of multi-planetary systems and their architectures is greatly contrasted by the uniformity exhibited within many of these systems. Previous studies have shown that compact Kepler systems tend to exhibit a peas-in-a-pod architecture: Planets in the same system tend to have similar sizes and masses and be regularly spaced in orbits with low eccentricities and small mutual inclinations. This work extends on previous research and examines a larger and more diverse sample comprising all the systems with a minimum of three confirmed planets, resulting in 282 systems and a total of 991 planets. We investigated the system architectures, focusing on the orbital spacings between adjacent planets as well as their relationships with the planets' sizes and masses. We also quantified the similarities of the sizes, masses, and spacings of planets within each system, conducting both intra- and inter-system analyses. Our results corroborate previous research showing that planets orbiting the same star tend to be regularly spaced and that pairs of adjacent planets with radii $&lt; 1\, R_ predominantly have orbital period ratios (PRs) smaller than two. In contrast to other studies, we identified a significant similarity of adjacent orbital spacings not only at PRs &lt; 4 but also at 1.17 &lt; PRs &lt; 2662 . For the systems with transiting planets, we additionally found that the reported correlation between the orbital PRs and the average sizes of adjacent planets disappears when planet pairs with $R &lt; 1\, R_ are excluded. Furthermore, we examined the data for possible correlations between the intra-system dispersions of the orbital spacings and those of the planetary radii and masses. Our findings indicate that these dispersions are uncorrelated for the systems in which all the pairs of adjacent planets have PRs &lt; 6 and even for the compact systems where all PRs &lt; 2 . Notably, planets in the same system can be similarly spaced even if they do not have similar masses or sizes.

SWEET-Cat: A view on the planetary mass-radius relation

Aims. SWEET-Cat (Stars With ExoplanETs Catalog) was originally introduced in 2013, and since then, the number of confirmed exoplanets has increased significantly. A crucial step for a comprehensive understanding of these new worlds is the precise and homogeneous characterization of their host stars. Methods. We used a large number of high-resolution spectra to continue the addition of new stellar parameters for planet-hosting stars in SWEET-Cat following the new detection of exoplanets listed both in the Extrasolar Planets Encyclopedia and in the NASA exoplanet archive. We obtained high-resolution spectra for a significant number of these planet-hosting stars, either observed by our team or collected through public archives. For FGK stars, the spectroscopic stellar parameters were derived for the spectra following the same homogeneous process using ARES+MOOG as for the previous SWEET-Cat releases. The stellar properties were combined with the planet properties to study possible correlations that could shed more light on the star-planet connection studies. Results. We have increased the number of stars with homogeneous parameters by 232 (~25% – from 959 to 1191). We focus on the exoplanets that have had both mass and radius determined to review the mass-radius relation, and we find results consistent with the ones previously reported in the literature. For the massive planets, we also revisit the radius anomaly, confirming a metallicity correlation for the radius anomaly already hinted at in previous results.

Disc and atmosphere composition of multi-planet systems

In protoplanetary discs, small millimetre-centimetre-sized pebbles drift inwards which can aid in planetary growth and influence the chemical composition of their natal discs. Gaps in protoplanetary discs can hinder the effective inward transport of pebbles by trapping the material in pressure bumps. In this work, we explore how multiple planets change the vapour enrichment by gap opening. For this, we extended the chemcomp code to include multiple growing planets and investigated the effect of 1, 2, and 3 planets on the water content and C/O ratio in the gas disc as well as the final composition of the planetary atmosphere. We followed planet migration over evaporation fronts and found that previously trapped pebbles evaporate relatively quickly and enrich the gas. We also found that in a multi-planet system, the atmosphere composition can be reduced in carbon and oxygen compared to the case without other planets, due to the blocking of volatile-rich pebbles by an outer planet. This effect is stronger for lower viscosities because planets migrate further at higher viscosities and eventually cross inner evaporation fronts, releasing previously trapped pebbles. Interestingly, we found that nitrogen remains super-stellar regardless of the number of planets in the system such that super-stellar values in N/H of giant planet atmospheres may be a tracer for the importance of pebble drift and evaporation.

Viewing the PLATO LOPS2 field through the lenses of TESS

ABSTRACT PLATO will begin observing stars in its Southern Field (LOPS2) after its launch in late 2026. By this time, TESS will have observed the stars in LOPS2 for at least four years. We find that by 2025, on average each star in the PLATO field will have been monitored for 330 d by TESS, with a subset of stars in the TESS continuous viewing zone having over 1000 d of monitoring. There are currently 101 known transiting exoplanets in the LOPS2 field, with 36 of these residing in multiplanet systems. The LOPS2 field also contains more than 500 TESS planet candidate systems, 64 exoplanets discovered by radial velocity only, over 1000 bright (V&amp;lt;13) eclipsing binary systems, 7 transiting brown dwarf systems, and 2 bright white dwarfs (G&amp;lt;13). We calculate TESS and PLATO sensitivities to detecting transits for the bright FGK stars that make up the PLATO LOPS2 P1 sample. We find that TESS should have discovered almost all transiting giant planets out to approximately 30 d within the LOPS2 field, and out to approximately 100 d for the regions of the LOPS2 field within the TESS CVZ ($\sim 20$ per cent of the LOPS2 field). However, we find that for smaller radius planets in the range 1 – 4 R$_{\oplus }$PLATO will have significantly better sensitivity, and these are likely to make up the bulk of new PLATO discoveries.

Analysis the State-of-art Exoplanets Exploring Schemes: Radial Velocity, Transit and Gravitational Microlensing

Since the first planet beyond the solar system managed to be examined in 1995, the concept of “exoplanet” has been created. The exoplanet, officially defined as extrasolar planets circling other stars that are not part of the solar system, quickly arose an influential curiosity, as scientists began to consider how many stars and planets truly exist in the periphery of the solar system and what the properties of these objects have. In the following years, a series of detection schemes appeared and applied to this theme. This study has listed five of them that are utilized most in current decades, providing a specific view of the Radial velocity method, Transit method, and Gravitational microlensing method. Each of these three explores exoplanets depends on different theories, like Doppler shifts of the RV method, the light variations of the transit method caused by the shadow of planets, and the subtle peaks of luminance of the microlensing method. By outlining the information of several instruments, the goal is to obtain a comprehensive understanding and concise synopsis of the methods employed in the exoplanetary area, which may provide with fresh inspiration to create more sophisticated appliances by understanding the underlying principles of the ones that already exist.

ExoMol line lists – LXII. Ro-vibrational energy levels and line strengths for the propadienediylidene (C3) in its ground electronic state

ABSTRACT Improved opacities are needed for modelling the atmospheres and evolution of cool carbon-rich stars and extra-solar planets; in particular, contributions made by the astrophysically important propadienediylidene (${\mathrm{C}}_{3}$) molecule need, at a minimum, to be determined using a line list which includes all significant transitions in the energy range of interest. We report variational calculations giving ro-vibrational energy levels and corresponding line strengths for $^{12}{\mathrm{C}}_3$, $^{12}{\mathrm{C}}^{13}{\mathrm{C}}^{12}{\mathrm{C}}$, and $^{12}{\mathrm{C}}^{12}{\mathrm{C}}^{13}{\mathrm{C}}$. In the $^{12}{\mathrm{C}}_3$ case, we obtain 2166 503 ro-vibrational state energies $\leqslant$2000 cm−1 for the electronic $\tilde{X}{\, }^{1}{\Sigma _{\rm g}}^{+}$ ground state. Comparison with experiment indicates a maximum error of $\pm 0.03$ ${\rm cm}^{-1}$ in calculated positions of lines involving an upper state energy $\lessapprox$4000 cm−1. For lines with upper state energies $\gtrapprox$4000 cm−1 to have comparable line-position accuracies, conical intersections would need to be accounted for in an adopted potential energy surface. Line lists and associated opacities are provided in the ExoMol data base (http://www.exomol.com).

Planetary nebulae seen with TESS: New and revisited short-period binary central star candidates from Cycles 1 to 4

Context. High-precision and high-cadence photometric surveys such as Kepler or TESS are making huge progress not only in the detection of new extrasolar planets but also in the study of a great number of variable stars. This is the case for central stars of planetary nebulae (PNe), which have similarly benefited from the capabilities of these missions, increasing the number of known binary central stars and helping us to constrain the relationship between binarity and the complex morphologies of their host PNe. Aims. In this paper, we analyse the TESS light curves of a large sample of central stars of PNe with the aim of detecting signs of variability that may hint at the presence of short-period binary nuclei. This will have important implications in understanding PN formation evolution as well as the common envelope phase. Methods. We analysed 62 central stars of true, likely, or possible PNe and modelled the detected variability through an MCMC approach accounting for three effects: reflection, ellipsoidal modulations due to tidal forces, and the so-called Doppler beaming. Among the 62 central stars, only 38 are amenable for this study. The remaining 24 show large contamination from nearby sources preventing an optimal analysis. Also, eight targets are already known binary central stars, which we revisit here with the new high precision of the TESS data. Results. In addition to recovering the eight already known binaries in our sample, we find that 18 further central stars show clear signs of periodic variability in the TESS data, probably resulting from different physical effects compatible with the binary scenario. We propose them as new candidate binary central stars. We also discuss the origin of the detected variability in each particular case by using the TESS_localize algorithm. Finally, 12 targets show no or only weak evidence of variability at the sensitivity of TESS. Conclusions. Our study demonstrates the power of space-based photometric surveys in searching for close binary companions of central stars of PNe. Although our detections can only be catalogued as candidate binaries, we find a large percentage of possible stellar pairs associated with PNe, supporting the hypothesis that binarity plays a key role in shaping these celestial structures.

Formation of Close-in Neptunes around Low-mass Stars through Breaking Resonant Chains

Conventional planet formation theories predict a paucity of massive planets around small stars, especially very low-mass (0.1−0.3 M ⊙) mid-to-late M dwarfs. Such tiny stars are expected to form planets of terrestrial sizes but not much bigger. However, this expectation is challenged by the recent discovery of LHS 3154 b, a planet with period of 3.7 days and minimum mass of 13.2 M ⊕ orbiting a 0.11 M ⊙ star. Here, we propose that close-in Neptune-mass planets like LHS 3154 b formed through an anomalous series of mergers from a primordial compact system of super-Earths. We perform simulations within the context of the “breaking the chains” scenario, in which super-Earths initially form in tightly spaced chains of mean-motion resonances before experiencing dynamical instabilities and collisions. Planets as massive and close-in as LHS 3154 b (M p ∼ 12−20 M ⊕, P < 7 days) are produced in ∼1% of simulated systems, in broad agreement with their low observed occurrence. These results suggest that such planets do not require particularly unusual formation conditions but rather are an occasional by-product of a process that is already theorized to explain compact multiplanet systems. Interestingly, our simulated systems with LHS 3154 b-like planets also contain smaller planets at around ∼30 days, offering a possible test of this hypothesis.