Recent advances in astronomical instrumentation have opened up exciting new frontiers in exoplanetary science, allowing us to probe the chemical compositions of exoplanetary atmospheres and try to connect them to their birthplace. In this talk, we will explore the cutting-edge techniques and methods used to study exoplanetary atmospheres, and how these observations are used to infer the physical and chemical properties of these distant worlds. We will examine the latest discoveries in exoplanetary science, including robust detection of molecules such as water, carbon dioxide, and sulfur dioxide by space- and ground-based telescopes, and discuss the implications of these findings for our understanding of planetary formation, evolution, and habitability. Join me as we embark on a journey to the forefront of exoplanetary science, where we push the boundaries of what we know about the universe and our place within it, thanks to the advances that have been made within SPP1992 collaboration and beyond.

Author(s): John Lee Grenfell, Fabian Wunderlich, Nicolas Iro, Konstantin Herbst, Miriam Sinnhuber, Andreas Bartenschlager, Heike Rauer

Abstract:

A central issue in exoplanetary atmospheric biosignature science is the influence of high energy particles upon climate and photochemistry. Stellar flaring events could be particularly important in this regard for Earth-like planets orbiting in the close-in habitable zones of active, cooler stars.
In this work we apply our atmospheric climate-photochemical column model 1D TERRA to estimate such effects on Proxima Centauri b. For this work we apply a newly-developed model version including a parameterisation for time-dependent effects and study a 100 year-period. We assume a surface pressure of 1.1 bar with
5% CO2 (needed to attain habitable conditions) but otherwise an Earth-like development and biosphere.
We study the influence of applying random stellar flares upon atmospheric biosignatures and calculate theoretical spectra. Results suggest variations in biosignature abundances by up to several orders of magnitude.

Author(s): Konstantin Herbst, J. Lee Grenfell, Miriam Sinnhuber, Andreas Bartenschlager, Nicolas Iro, and Fabian Wunderlich

Abstract:

The harsh stellar radiation and particle environment of planets in the habitable zone of active cool stars could lead to photochemical loss of atmospheric biosignatures. Herbst et al. (2019) and Herbst et al. (2022) developed a self-consistent model suite of combined state-of-the-art tools to study the impact of the radiation and particle environment on atmospheric particle interactions, composition, and climate interactions. Here we present the most recent updates to the model suite to study a wide range of possible exoplanetary atmospheres and stellar environments, tackling the following questions: (1) What processes determine whether (rocky) worlds around cooler stars can retain their atmospheres? (2) How do different atmospheres evolve for cool star systems? and (3) How do results from our studies compare with observations?

Author(s): Andreas Bartenschlager, John Lee Grenfell, Konstantin Herbst, Nicolas Iro, Heike Rauer, Miriam Sinnhuber, Ben Taysum and Fabian Wunderlich

Abstract:

The launch of the James Webb Space Telescope (JWST) in December 2021 opens up the possibility of studying the composition of exoplanetary atmospheres in habitable zones, such as TRAPPIST-1e, in the near future. With the help of numerical models of the exoplanetary atmospheres, the observations and the processes behind them can be better understood and interpreted (Herbst et al., 2022). We investigate the influence of stellar energetic particles (SEPs) and galactic cosmic rays (GCR) on the atmospheric chemistry of exoplanets around a very active M-star using the ion chemistry model ExoTIC. In collaboration with the University of Kiel and DLR Berlin, we perform model experiments with different N2 or CO2 dominated atmospheres, depending on the initial CO2 partial pressure, as well as humid and dry conditions (Wunderlich et al., 2020), taking into account the ionization rates for such events. A further specification regarding the scenarios results from the distinction between dead and alive atmospheres, which are characterized by a lower or higher oxygen fraction in the initial conditions. Within ExoTIC we can calculate the impact of the ionization events on theses atmospheres both as a single and as a series of events with different strengths. Preliminary results show a significant impact of SEP events on the chemical composition of the atmosphere, including biosignatures such as O3. The strength and structure of these impacts depend on the composition of the starting atmosphere, in particular on the availability of oxygen as well as N2 and water vapour.

Author(s): Giulia Roccetti, Tommaso Grassi, Barbara Ercolano, Karan Molaverdikhani, Aurélien Crida, Dieter Braun, Andrea Chiavassa

Abstract:

Free-floating planets (FFPs) can result from dynamical scattering processes happening in the first few million years of a planetary system’s life. Several models predict the possibility, for these isolated planetary-mass objects, to retain exomoons after their ejection [1,2]. The tidal heating mechanism and the presence of an atmosphere with a relatively high optical thickness may support the formation and maintenance of oceans of liquid water on the surface of these satellites [3]. In order to study the timescales over which liquid water can be maintained, we perform dynamical simulations of the ejection process and infer the resulting statistics of the population of surviving exomoons around free-floating planets. The subsequent tidal evolution of the moons’ orbital parameters is a pivotal step to determine when the orbits will circularize, with a consequential decay of the tidal heating. We find that close-in (a < 25 RJ) Earth-mass moons with CO2-dominated atmospheres could retain liquid water on their surfaces for long timescales, depending on the mass of the atmospheric envelope and the surface pressure assumed. Massive atmospheres are needed to trap the heat produced by tidal friction that makes these moons habitable. For Earth-like pressure conditions (p0 = 1 bar), satellites could sustain liquid water on their surfaces up to 52 Myr. For higher surface pressures (10 and 100 bar), moons could be habitable up to 276 Myr and 1.6 Gyr, respectively. Close-in satellites experience habitable conditions for long timescales, and during the ejection of the FFP remain bound with the escaping planet, being less affected by the close encounter.

References
[1] Rabago, I. and Steffen, J. H. (2019) MNRAS 489(2), 2323-2329.

[2] Hong, Y.-C. et al. (2018) AJ 852(2), 85.

[3] Ávila, P. J. et al. (2021) IJA 20(4), 300-311.

Author(s): Philipp Baumeister, Nicola Tosi

Abstract:

Characterizing the interior structure of exoplanets is an essential part in understanding the diversity of observed exoplanets, their formation processes and their evolution. As the interior of an exoplanet is inaccessible to observations, an inverse problem must be solved, where numerical structure models need to conform to observed parameters such as mass and radius. Since the relative proportions of iron, silicates, water ice, and volatile elements are not known, this is a highly degenerate problem whose solution often relies on computationally-expensive and time-consuming inference methods such as Markov Chain Monte Carlo.

We present here ExoMDN, a new machine-learning-based approach to the interior characterization of observed exoplanets using Mixture Density Networks that improves upon our previous work (1). This improved model, trained on a large database of 5.6 million synthetic interior structures, can make a complete probabilistic inference about possible planetary interior structures within a fraction of a second, without the need for extensive modeling of each exoplanet’s interior. We can demonstrate how the model, trained on different sets of (potentially) observable parameters including the received irradiation at the planet’s orbit and the fluid Love number, can help to further constrain the interior of a large number of exoplanets. In particular, we can show how precisely these parameters need to be measured in order to do so.

References
(1) Baumeister et al., 2020. Machine-learning Inference of the Interior Structure of Low-mass Exoplanets. ApJ 889, 42. https://doi.org/10.3847/1538-4357/ab5d32

Author(s): Vincent Böning, Wieland Dietrich, and Johannes Wicht

Abstract:

Hot Jupiters are among the most common types of exoplanets. They are tidally locked Jupiter-sized gas planets orbiting their host stars in close proximity. The high atmospheric dayside temperatures are due to permanent stellar irradiation and cause sizeable electrical conductivities. Magnetic induction processes therefore likely play a significant role in shaping the atmospheric winds and the hot spot shift. Here, we study the nature of atmospheric induction processes in typical Hot Jupiters characterized by a range of surface temperatures. We use a set of numerical magneto-hydrodynamic simulations of a stably stratified, yet locally irradiated, atmosphere with electrical conductivities varying with surface temperature. At the lowest temperatures (around 1000 K), magnetic effects are not important. At intermediate temperatures (1500-2500 K), induction effects generate strong magnetic fields, largely due to the shearing of a background field. The strong magnetic fields alter the atmospheric circulation and we provide first estimates of the corresponding change of the hot spot location. At the largest temperatures (above 3000 K), the setup is numerically extremely challenging. Preliminary results show turbulent and chaotic behavior. When fed into radiative atmospheric models, our results have the potential of predicting the hot spot shift and aiding to detect exoplanetary magnetic fields.

The SPP 1992 outreach team is developing a planetarium show „Diversity of Exoplanets“ in cooperation with Björn Voss of the Hamburg Planetarium as well as other planetariums. We will give an overview of the project including goals, central ideas, and current status. 

Author(s): Joanna Drążkowska

Abstract:

The classical planet formation theory was established when the Solar System was the only planetary system we knew. In this talk, I will explain how the growing population of planets orbiting stars other than the Sun triggered the revision of the classical theory of planet formation. I will present the new, emerging picture of how planets form and outline current research directions in our field. I will pay special attention to the early stages of planet formation when dust grains grow to pebbles and the first gravitationally bound building blocks of planets, the planetesimals, precursors of asteroids and comets, form.

Author(s): Luca Delussu, Til Birnstiel, Anna Miotello, Paola Pinilla and Giovanni Rosotti

Abstract:

The advent of the Atacama Large Millimeter/Sub-Millimeter Array (ALMA) has marked a fundamental turning point in the field of protoplanetary disks. Large sample surveys of entire star-forming regions have uncovered remarkable correlations between several disk-star observables. In this context, the importance of disk population studies emerges as they make it possible to investigate such correlations.

We carried out a disk population study which simulated the evolution of dust and gas over millions of years of the protoplanetary disk’s life to constrain the initial conditions needed to reproduce the correlations and distributions observed. We exploited the twopoppy evolution code, which captures the viscous evolution of gas and dust surface density and particle size with high accuracy and short simulation times, thus providing a perfect tool for disk population studies. In particular, we focused on the distributions observed for disks‘ spectral index in the Lupus, Taurus and Ophiuchus regions.

Our simulations have shown the importance and necessity of the presence of substructures to reproduce the observed spectral indexes. Moreover, we outlined the characteristics of the required substructures and constrained the disks‘ initial conditions.

Author(s): Thomas Pfeil, Til Birnstiell, Hubert Klahrl, Miles Cranmer, Shirley Ho, Phil Armitage

Abstract:

Modeling dust coagulation is essential for simulations of the early stages of planet formation. The sizes and distribution of the dust grains determine the optical depth and opacities, thus, linking the dust coagulation and transport processes to continuum observations of protoplanetary disks. The grain size evolution sets the initial conditions for planetesimal formation and the formation of entire planetary systems. Here, we present two new approaches for simplified models of dust coagulation that can be used as subgrid models in vertically integrated (2D) hydrodynamic simulations of protoplanetary disks. Both models work within a two-population prescription, where the dust size distribution is approximated by a truncated power law. Dust evolution is simulated using either semi-analytic expressions for growth and fragmentation (model 1, called 2pop) or a neural network that predicts the time evolution (model 2, called 2popML). We show that both models are in good agreement with local and global full dust coagulation simulations (DustPy), at a substantially faster runtime. This makes it possible to use them in two-dimensional hydrodynamic simulations.

Author(s): David Melon Fuksman, Mario Flock, Hubert Klahr

Abstract:

Understanding the signatures produced by turbulence in protoplanetary disks is a necessary step toward identifying the fingerprints of accreting exoplanets. In weakly ionized regions of protoplanetary disks, turbulence is most likely controlled by hydrodynamical instabilities. Among these, the vertical shear instability (VSI) stands out as a rather robust mechanism due to its few requirements to operate, namely a baroclinic stratification and short thermal relaxation timescales. In this talk I will summarize some recent results of radiation-hydrodynamical axisymmetric simulations of the VSI in passive irradiated disks around T Tauri stars. Considering varying degrees of dust depletion due to coagulation, we quantify the produced turbulent heating and obtain stability maps for our disk models, which we then compare to current observations of protoplanetary disks. Our results suggest that the heating produced by the VSI in the regions where it can operate is insufficient to lead to any significant temperature increase in protoplanetary disks. We also obtain that, depending on the gas molecular composition, the VSI can operate at surface layers even in regions where the midplane is stable. This picture is consistent with current ALMA observations of disks showing thin midplane mm-sized dust layers while appearing vertically extended in optical and near-infrared wavelengths.

Author(s): Sz. Csizmadia, K. W. F. Lam 

Abstract:

We carried out a systematic search for phase curve variations in the TESS data. Our goal is to study whether the planetary albedos and surface/atmospheric emissions of the planets depend on orbital period/insolation. We are also interested to determine the limit in terms of scaled semi-major axis until that points TESS is able to detect the secondary transits. This allows us to make predictions how successful PLATO can be in the detection of phase curves and secondary transit events at different orbital distances and magnitudes.
To reach this goal, we decided to re-analyze all transiting exoplanet light curves from the Transiting Exoplanet Survey Satellite in the range of period 0-30 days and TESS-magnitude 6-12. We selected only those systems where 2 minute cadence (or shorter) light curves were available and a radial velocity curve was published previously.
We used Transit and Light Curve Modeller and we carried out joint radial velocity and light curve fits with different limb darkening laws (quadratic and power-2) as well as we fitted the light curve with and without phase curve variations (reflection, beaming and ellipsoidal effects and possible occultation event was also included). We also treated the noise with the successful wavelet-based noise model which was simultaneously fitted with the transit and phase curve model. This approach overpasses the preliminary similar studies where only the light curves were fitted without radial velocities, or the photometric noise was not managed in the photometric data with a simultaneous fit. This work is a logical continuation of the work we presented in the previous all-hands on the desk meeting where we have shown that the wavelet-based noise treatment method is a very effective tool to remove the stellar activity, pulsation and instrumental noise.
The result is the most extensive dataset of accurate, precise and homogeneous catalogue of transiting exoplanet data.

Author(s): Anton Krieger and Sebastian Wolf

Abstract:

We investigate the capabilities of high-contrast VIS/NIR imaging of directly detecting and characterizing low-mass planets in gaps and identify the most promising observing wavelengths for these challenging tasks. Observations show, that concentric gaps make up one of the most commonly observed substructures, which are then often attributed to the presence of embedded forming planets. However, direct detections of these planets are extremely rare, and ambiguities regarding the origin of most gap features remain. In this study, we generated models of protoplanetary disks, each with a gap that harbors an accreting planet, which itself is surrounded by a circumplanetary disk. The system is then simulated using Monte Carlo radiative transfer simulations to generate synthetic observations. We particularly make use of advanced radiative transfer methods, that significantly boost the performance of the simulation of optically thick regions like the circumplanetary disk. Based on our simulations, we quantify the impact of five key model parameters on the determined planetary signal strength. Finally, we assess the capabilities of the instrument SPHERE/VLT of detecting embedded planets and identify for each of the investigated model parameters the most promising observing wavelengths that enable us to distinguish between different underlying parameter values.

Author(s): Sandra V Jeffers and the RedDots team

Abstract:

The nearest exoplanets to the Sun provide the best possibilities for detailed study, including searching for evidence of life outside the Solar System. The RedDots planet search program aims to
detect all terrestrial planets within 5pc building on the success of our high-profile discoveries of Proxima b, Barnard’s star b and GJ 887 b and c. Since we are completing a volume-limited sample,
we are also developing strategies for detecting exoplanets orbiting magnetically active stars. In this talk I will present updates on our latest observations and on new techniques that we are developing to accurately determine the masses of planets in multiplanet systems.

Author(s): Florian Liebing, Sandra V. Jeffers

Abstract:

Markov-Chain Monte-Carlo (MCMC) Simulations have become the primary way to do Bayesian parameter inference in Astrophysics, besides variati0ns of Nested-Sampling. This is not just due to the avaiability of ready-made and easy to use software implementations, such as emcee, but also the fairly intuitive logic behind the algorithm, easy to interpret results, and built-in uncertatainty determination and propagation. Like all statistics tools available to scientists however, one has to be carefull about the use-case. Between hard boundaries, acidentally-informative parameter transformations and overly strong bayesian priors it is easy to obtain technically correct, visually accurate but factually biased parameter inferences.

Here, I will present a selection of examples, based on my ongoing work, where one might encounter such pitfalls when attempting to infer the orbital parameters of an exoplanet, how they can manifest in biased estimates, how one can recognize them, and a set of best-practices for doing and presenting MCMC inference in the literature.

Author(s): Dhruv Muley, Julio David Melon Fuksman, Hubert Klahr

Abstract:

In circumstellar disks around T Tauri stars, visible/near-infrared stellar irradiation is intercepted by dust at the disk’s optical surface and reprocessed into thermal infrared; this subsequently undergoes radiative diffusion through the optically thick bulk of the disk. The gas component—overwhelmingly dominant by mass, but contributing little to the opacity—is heated primarily by gas-grain collisions. In hydrodynamical simulations, however, the most common models for disk heating (local isothermality, beta-cooling, two-temperature radiation hydrodynamics) incorporate simplifying assumptions that limit their range of validity. To build on these methods, we develop a „three-temperature“ numerical scheme that self-consistently models energy exchange between gas, dust, and radiation as a module for the PLUTO radiation-hydrodynamics code. With a range of test problems, we demonstrate the efficacy of our method, and make the case for its applicability to a wide range of problems in disk physics, including instabilities, disk-planet interaction, and accretion onto planets.

Author(s): Jingyi Mah and Bertram Bitsch

Abstract:

We investigate the formation of iron-rich rocky exoplanets, also termed ’super-Mercuries‘, via pebble accretion in discs around their respective host stars. We employ a disc evolution model which includes the evaporation and condensation of pebbles at various ‚icelines‘ and take into account stellar abundances when computing the initial disc composition. Our simulations are able to reproduce the observed compositions of the super-Mercuries if the disc viscosity is low. The combined effects of long viscous evolution and orbital migration timescales in low-viscosity discs facilitate the growth of iron-rich planets near the iron evaporation front. Furthermore, we also find a decreasing trend in planet iron mass fraction with increasing stellar Mg/Si ratio. This implies that super-Mercuries are more likely to form around stars with low Mg/Si, in agreement with observational data.

Author(s): Leonard Benkendorff, Francesco Flammini Dotti, Katja Stock, Rainer Spurzem

Abstract:

Hot Jupiters (HJ) are defined as jupiter-mass exoplanets orbiting around their host star with a semi-major axis of less than 0.1 au. It is generally believed that they cannot form near their observed location but migrate inwards. Recent discoveries showed that star clusters are likely to contribute to the formation of HJ. We use NBody6++GPU and LPS to simulate the dynamics of sets of 200 identical planetary systems around Sun-mass stars in dense star clusters with 32 000 and 64 000 members. We use different sets with 3, 4 or 5 Jupiter-like planets. We show that close stellar encounters and internal planetary dynamics as well as tidal migration can form HJ in multi-planetary systems. All found HJ have inclined orbits. Furthermore, systems with sufficent angular momentum deficit (AMD) are common in both star clusters. Denser star clusters are more likely to form HJ for planetary systems with close orbiting planets whereas less dense star clusters are more likely to form HJ for planetary systems with planets with a semi-major axis beyond 5 au. Destructive close encounters and tidal disruption are factors that narrow down the fraction of HJ. We show that systems with more planets probably only increase the HJ fraction in less dense star clusters. Additionally, our results indicate that young Hot Jupiters with an age of less than 100 Myrs may be obtained in planetary systems with a planet orbiting at initially 1 au. No young Hot Jupiter were witnessed in systems with with a planet orbiting at initially 5 au.

Author(s): Alexandre Emsenhuber, Oliver Schib, Kristina Monsch, Giovanni Picogna, Barbara Ercolano, Thomas Preibisch, Christoph Mordasini, Yann Alibert, Jeremy J. Drake

Abstract:

We investigate how the interaction between X-ray internal photoevaporation and gap opening by planets is able to create pileups and deserts in the exoplanet population. For this, we compute synthetic planet populations that include disc evolution, core and gas accretion by planets, gas-driven migration, and X-ray internal photoevaporation of the disc. We confirm that the X-ray photoevaporation enhances the pile-up at 1-2 AU; however, the pile-up is already obtained without X-ray internal photoevaporation. In this case, we find that X-ray photoevaporation causes a too strong drop in the planet occurrence rate near the gravitational radius compared to radial velocity surveys (Fernandes et al. 2019; Fulton et al. 2021). In contrast, internal photoevaporations causes an increased number of planets in the sub-Saturn desert (10-100 MEarth). This is due to internal photoevaporation reducing the mass in the vicinity of the planets at the time they undergo runaway gas accretion. Thus, X-ray internal photoevaporation could help reconcile models with recent studies that find no such desert (e.g. Bennett et al. 2021).

References:

Bennett, Ranc, and Fernandes (2021), AJ 162:342

Fernandes, Mulders, Pascucci, Mordasini, Emsenhuber (2019), ApJ 874:81

Fulton, Rosenthal, Hirsch, et al. (2021) ApJS 255:14

Author(s): J.-V. Harre, A. M. S. Smith et al.

Abstract:

Tidal orbital decay is suspected to occur for hot Jupiters in particular, with the only observationally confirmed case of this being WASP-12 b. By examining this effect, information on the properties of the host star can be obtained using the so-called stellar modified tidal quality factor Q⋆’, which describes the efficiency of the planetary kinetic energy dissipation within the star. In this study, we aim to improve constraints on the tidal decay of the KELT-9, KELT-16, and WASP-4 systems, making it possible to constrain the Q⋆’ value for each star. In addition, we aim to test the existence of the TTVs in the HD 97658 system, which previously favoured a quadratic trend with increasing orbital period. Making use of newly acquired photometric observations from CHEOPS and TESS, combined with archival data, we fit three models to the data, namely a constant-period model, an orbital-decay model, and an apsidal-precession model. We find that the KELT-9 system is best described by an apsidal-precession model for now, with an orbital decay trend at over 2𝜎 being a possibility as well. A Keplerian orbit model provides the best fit to the transit timings of KELT-16 b because of the scatter and scale of their error bars. The WASP-4 system is best represented by an orbital decay model at a 5𝜎 significance, although apsidal precession cannot be ruled out. For HD 97658 b, we find no conclusive evidence for the suspected trend in the data.

Author(s): H. L. Ruh, P. Capone, S. Dreizler, T. Henning, A. Quirrenbach, A. Reiners and M. Zechmeister

Abstract:

Ultra-cool M-dwarfs are challenging for RV searches of exoplanets due to their faintness and stellar activity, and thus almost no planets have been detected in this regime. We investigate the relationship between activity-induced RV jitter, magnetic field strength, and stellar rotation in M dwarfs from the CARMENES survey in preparation of a dedicated survey. With the uniquely suited high-resolution spectrograph HPF at the 10m HET telescope, we obtain high-precision RV measurements of ten ultra-cool (Teff < 2800K) M-dwarfs. Our high-precision RV measurements allow us to search for rocky exoplanets in the habitable zones of those stars. We give an update on our survey and display the RV precision reached in our observations of ultra-cool M-dwarfs.

Author(s): Gabriel-Dominique Marleau, Olga V. Zakhozhay, Sasha Hinkley, et al.

Abstract:

I present briefly two recent results involving radial-velocity (RV) observations. One concerns HD 114082 b, a transiting warm super-Jovian planet around a young star with a debris disk (Zakhozhay et al. 2022). It is essentially too small, too massive, and/or too young to be explainable by theory, while its properties are very well determined. Further observations are clearly needed, but it might be the member of a new class of puzzling young gas giants.

The second system is HD 206893, in which an additional, inner companion was recently discovered thanks to astrometry (Hinkley et al. 2023). The precise mass determination can be used to constrain cooling curves. Here, the luminosities and masses of the object force the conclusion that deuterium burning and clouds in the 13-Jupiter-mass companion are required. A precious corollary is the 10-percent precision on the age determination. All of this showcases the power of optical interferometry.

Author(s): Eike W. Guenther, Frank Grupp, Hanna Kellermann, Arno Riffeser

Abstract:

Despite decades of research on hot Jupiter’s (HJs), there are still several theories for their formation. One possibility is that HJs form beyond the ice-line in a protoplanetary disk and then migrate inward through the interaction between the planet and the disc. Another hypothesis is that planets migrate inwards via planet-planet interaction. Other possibilities include Kozai-Lidov cycles, or fly-by encounters between two planetary systems in a cluster. All these theories can explain why HJs exist. The disk-migration scenario furthermore explains the resonant chains of planets and the planet-planet scattering scenario explains why planets with long orbital periods have eccentric orbits. Unfortunately, none of the proposed scenarios explains all properties of all HJs. For example, a prediction of all migration scenarios is that HJs must be lonely, but not all HJs are lonely. It thus seems likely that there are several ways to form a HJ. Additional constrains may come from atmospheric studies. However, potential targets must be well characterised prior to the atmospheric studies. We review the various formation scenarios for HJs and present five new discoveries that are suitable for atmospheric characterisation.

Author(s): Ekatarina Ilin

Abstract:

One of the most surprising results in exoplanet research is the diversity of star-planet system architectures. In particular, the past two decades revealed that planets can occur in orbits so close to their host star that they could be considered to live inside the stellar atmosphere. At this proximity, the planet exerts significant force, gravitational and magnetic, both short- and long-term, on its host — a phenomenon unknown to the Solar System.

Understanding star-planet interactions holds promise to provide important insights into the habitability of the entire system. Planets involved in such interactions can be viewed as in-situ probes of the system’s space weather, and could prospectively reveal otherwise difficult to measure planetary properties such as the strength and extent of their magnetic fields.

In this talk, I will introduce the basic mechanisms that drive star-planet interactions in short-period systems, and present recent efforts to observationally constrain their subtle effects. I will close by considering the challenges we face when studying a planet’s influence on its host star, and present some promising ways to overcome them.

Author(s): E. Sanchis, L. Noack, K.G. Kislyakova, M. Kervazo, L. Fossati, G.G. Valyavin, G.J. Golabek, and M. Güdel

Abstract:

White dwarfs are the latest evolutionary stage for the majority of main sequence stars. Recently, a number of planets and planetary remnants have been discovered orbiting white dwarfs. These objects draw close attention as targets for transit observations due to their large planet-to-star radius ratio. Especially interesting is the possible outgassing from such objects and their eventual observational prospects.
Here, we investigate whether electromagnetic induction heating can drive additional volcanic outgassing from small planetary remnants orbiting white dwarfs. This mechanism can be important for such bodies in addition to tidal heating due to the extremely strong magnetic fields of some white dwarfs and close orbital distances of planets to their host stars. We calculate the heating and related magmatic effects for a Moon-size body around a GD 356-like white dwarf using an analytical model for induction heating and a numerical model for mantle convection and melt production. We show that induction heating can melt most of the mantle of a Moon-size object within a geologically short time, leading to a magma ocean stage, which a standard mantle convection model cannot handle.
We therefore adapted our numerical mantle convection model to be able to treat mixtures of solid rock and molten material by applying an effective viscosity, density and conductivity scaling with melt fractions from 0 to 100%, and are now able to simulate the influence of induction heating on the long-term thermal evolution of the mantle for strongly heated bodies. We show that magma oceans produced by induction heating remain stable over time and evolve into a steady-state system, where magma ocean cooling equals heating (by both induction heating and radiogenic heating, even though the latter decreases over time).
These findings can have important implications for the evolution of rocky bodies orbiting white dwarfs and the potential detection of their outgassing.

Author(s): Flammini Dotti, Francesco; Spurzem, Rainer; Kouwenhoven, M.B.N.; Kamlah, A.W.H.; Hao, Wei; Tsai, Maxwell

Abstract:

The dynamical evolution of planetary systems is an important field that aims to explain how the majority of planets eventually obtain their actual architecture. In a star cluster, it may explain the diversity of their architectures due to their different encounter history. Moreover, there is a relative large abundance of free-floating planets in our galaxy. The star clusters may be a consistent source due to their ejected free-floating planets.

I will explain how the star cluster density and the presence of a cluster-centric intermediate-mass black hole eventually affects Solar-like systems (i.e., a complex planetary system) and single-planet systems respectively. Furthermore, I will introduce global rotation in the star cluster, and discuss its role in the ejection of both stars and free-floating planets.

I will use NBODY6++GPU (a N-body code which performs simulations with a large number of particles, i.e., star clusters) and LonelyPlanets (another N-body code which performs simulations with a low number of particles, i.e., planetary systems).

The results confirm that the density of the star cluster is one of the major characteristic in the ejection of planets from their host star, and the planetary architecture has also a predominant role. The intermediate-mass black hole enhances the ejection of planets from the planetary systems as well. Moreover, the ejection of both stars and planets from the star cluster is enhanced as well. Finally, the global rotation of star clusters diminish the ejection of planets from their star cluster even at mid-slow rotational speeds.

References:

Akiyama K., Sugimoto D., 1989, PASJ, 41, 991
Einsel C., Spurzem R., 1999, MNRAS, 302, 81
Flammini Dotti F., Kouwenhoven M. B. N., Cai M. X., Spurzem R., 2019, MNRAS, 489, 2280
Flammini Dotti F., et al., 2020, MNRAS, 497, 3623
Kamlah A., et al., 2022a, MNRAS, 511, 4060
Kamlah A. W. H., Spurzem R., Berczik P., Sedda M. A., Flammini Dotti F., et al. 2022b, MNRAS, 516, 3266
Spurzem R., 1999, Journal of Computational and Applied Mathematics, 109, 407
Wang L., et al., 2015b, MNRAS, 449, 3543

Author(s): R. Sfair, C. M. Schäfer, J. Boskovic, K. Trivedi

Abstract:

The number of exoplanets detected is constantly growing, many in multi-planetary systems. A remarkable system is TOI-178 which hosts six planets rapidly evolving with orbital periods from 1.9 to 20.7 days and estimated masses ranging from 1.5 to 7.7 M_Earth. Besides the peculiar differences in the density of the planets, the five outer planets are in a chain of 2:4:6:9:12 resonance, one of the largest Laplace resonant chains known to date. This particular orbital configuration raises questions about how this intricate dynamics shapes the stability regions within the system. Thus, we carried out numerical simulations considering 1×106 test particles radially distributed encompassing the entire region of the planets and integrated the system for 500 years. We determined the limits in the (a,e) space where particles may survive and recorded a large number of close encounters, mainly with the most massive planets (TOI-178f and TOI-178g). Temporary captures by all planets were detected, with a more significant probability with TOI-178c. This led us to investigate the evolution of putative trojan objects initially placed in each planet’s L4 and L5 regions. Our results show that all planets can keep particles in tadpole orbits, with TOI178-f trojans being the most stable. Furthermore, no significant asymmetry was found between the two Lagrangian points.

Author(s): Hubert Klahr

Abstract:

We present a parameter study of planet disk interaction over a wide parameter range of interest for direct observation of gas accretion onto embedded planets. We perform this study in three-dimensional radiation hydro simulations including the irradiation by the central star and a constant viscous alpha value. Gas is removed from the centre of the Hill sphere and replaced by the equivalent release of accretion energy.
The central star is a typical T-Tauri star of half a solar mass and the range of disk masses is from 10\% down to 0.01 \% solar mass. Planets from 10 Earth masses to 5 Jupiter masses are put in the disk at $10$, $30$ and $50$ au. We measure the accretion rate and luminosity as a function of numerical resolution and prescription for the accretion process.
In most cases we find agreement with the general disk morphology as reported in the literature, i.e.\ gap opening and spiral pattern. However, for high disk masses and closer in planets we find the heating via the accretion luminosity to prevent a clean gap opening.
For planets at large distances the gap opening occurs at larger than naively expected planet masses, as the irradiated disk flares significantly.
This catalogue of planet-disk simulations forms the data base for studies of observational appearance of accreting planets is circumstellar disks.

Author(s): Sebastian Stammler, Luca Delussu, Tilman Birnstiel

Abstract:

Estimating the masses of protoplanetary disks from millimeter observations remains challenging. To convert millimeter fluxes to dust masses assumptions on the optical thickness, the temperature, and the opacities have to be made. To convert gas line emissions into total disk masses additional conversion factors have to be applied.

We trained a neural network to estimate dust and gas masses from simulated multi-wavelength observations. These millimeter fluxes were computed from tens of thousands population synthesis protoplanetary disk models simulated with TwoPopPy. The neural network performs significantly better than the traditional methods allowing us to constrain disk masses form unresolved multi-wavelengths observations.

Author(s): Sascha Grziwa, Martin Pätzold

Abstract:

Most confirmed planets are found through analyzing high resolution stellar light curves collected by space missions like CoRoT, Kepler, K2, and TESS. Automatic detection pipelines search these light curves for periodic transits using algorithms like Box leased square (BLS) or frequency analysis. However, single transits of shallow depth, especially for small planets like Neptune or Super-Earths in light curves are often missed by these algorithms. To address this issue, we developed a new wavelet-based algorithm called SINGLETRANS to search especially for these single transits. By searching the available archive data of CoRoT, Kepler, K2, and TESS for previously unknown single transits we are able to detect additional candidates with larger periods. This algorithm can also detect quasi-periodic transits, which makes it also suitable for detecting circumbinary planets or those with strong transit timing variations (TTV). The newly detected candidates are analyzed statistically and compared to those found using only the BLS algorithm. New suitable candidates will be selected for further study and follow-up observation in the KESPRINT collaboration. The goal of this research is to increase the diversity of exoplanets by identifying more candidates with larger orbital periods.

Author(s): Tobias O. B. Schmidt

Abstract:

Using a published analysis of a disk around the primary star with ALMA and GAIA we were able to reclassify the age of a directly imaged exoplanet to about 1.2 Myr. With additional data to increase the wavelength coverage we were able to narrow down the temperature and thus the mass of the companion, having strong deviations to atmospheric models, which has an impact on classification of other directly imaged objects. Using polarimetric imaging data we could identify a circumplanetary disk around the companion, that will be analyzed soon with granted JWST observations. We further present evidence that the object was likely formed by disk fragmentation and put it into context of other directly imaged planet candidates that have directly or indirectly linked dynamic methods, like RV or GAIA astrometry, leading to dynamically determined masses or ages.

Acknowledgements:

We thank the SHINE consortium, the ISpy Team, especially Dr. André Müller, and the Destinys Team, especially Dr. Christian Ginski as well as Dr. Rob van Holstein, Dr. Gabriel-Dominique Marleau and Dr. Yuhiko Aoyama as well as several other co-authors for contributions to this upcoming publication. A special thank you to Prof. Dr. Takashi Tsuji for providing exceptional atmospheric models.