Debris discs are belts of planetesimals and dust, like the Asteroid Belt and Kuiper Belt in our Solar System. These discs are a fundamental component of planetary systems, and many such discs have been resolved around other stars. Debris discs show a broad diversity of locations, shapes and features, and we do not understand the origin of this diversity. However, these discs must be telling us something about the architecture, formation and evolution of planetary systems.

One reason that debris discs are important is that they contain imprints of historical dynamical interactions, which can persist long after the events that caused them. For example, planets can gravitationally interact with debris, and this interaction generates disc features like gaps, warps and clumps. Similarly, stellar flybys can produce long-lasting debris structures in the outer regions of planetary systems. Now, with the arrival of new dynamical theory and observational capabilities, we are extremely well placed to interpret the clues that debris discs are giving us.

In this talk, I will summarise what planets or flybys would do to debris discs. In particular, I will focus on the observable signatures that these interactions would leave on discs. I will describe why conventional debris models often rely on such interactions having occurred, and what it would mean for debris science if this assumption proved incompatible with observations. I will also discuss how upcoming theory and observations may finally answer some key questions about debris and planetary systems. A wealth of new debris-disc data will arrive over the next few years, and as a community we must be prepared to interpret it.

How to cite: Pearce, T.: Why are planets and flybys important for debris discs?, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-498, https://doi.org/10.5194/epsc2024-498, 2024.

We analyzed the potential to infer the presence of an exoplanet via spatially resolved observations of a coexisting debris disk.
Using numerical simulations, we investigated the observable effects on a cold debris disk that are caused by secular gravitational perturbations. The perturbations originate from an exoplanet on an eccentric orbit either within (~ 40 au) or outside (~ 500 au) the planetesimal belt. We identified features in the resulting brightness distributions that are suitable to distinguish between those two types of systems and showed that these features are possibly detectable with present observatories, especially with combined observations using JWST/MIRI and ALMA.

How to cite: Stuber, T., Löhne, T., and Wolf, S.: Using debris disk observations to infer exoplanets orbiting within or outside a planetesimal belt, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-1197, https://doi.org/10.5194/epsc2024-1197, 2024.

High-resolution surveys with ALMA have revealed that substructures such as rings and gaps are common in protoplanetary disks, however it is not clear whether this is also true for debris disks due to their lower surface brightness and therefore the tendency for observations to be obtained at lower resolution with ALMA. Lower resolution observations do not commonly reveal systems of rings with radial gaps in debris disks, but the handful of high-resolution debris disk images with ALMA do resolve radial gaps in most, however this sample of only a few systems is insufficient to draw strong conclusions. Recently, the ALMA survey to Resolve exoKuiper belt Substructures (ARKS) was carried out to understand the high resolution structure of 18 debris disks. The sample spans a range of inclinations, allowing us to study both the radial and vertical structure in debris disks in detail. With an increasing volume of theoretical work exploring the signatures of planets imprinted on disks, understanding the high-resolution disk structure is important both for testing planet formation models and for constraining planetary system architecture. In this talk, we will present observations from the ARKS program and discuss ongoing modelling efforts, focusing particularly on the radial structure and non-parametric modelling approaches. We will discuss the prevalence of radial substructures in debris disks, present ongoing analyses on any correlations between disk features and outline some of the implications of the findings on planetary dynamics in these systems.

How to cite: Han, Y. and the ARKS Team: The high-resolution structure of debris disks revealed by the ARKS ALMA program, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-254, https://doi.org/10.5194/epsc2024-254, 2024.

Debris disks represent the last phase of the evolution of protoplanetary disks. As a by-product of the planet formation process, debris disks might host planetesimal belts, dust, and gas.  One of the possible events responsible for the formation and/or evolution of debris disk systems  are flybys. 

To constrain the influence of encounters in the formation and evolution of debris disks, Bertini et al. (2023) reconstructed the flybys experienced by a statically significant sample of debris disks in the last 5 Myr and predicted for the next 2 Myr. 

In this talk I will present the sample of 254 debris disks with ages between 2 Myr and 8 Gyr. The Gaia eDR3 position, proper motions and radial velocities have been used to reconstruct the relative linear motions between each debris disk and all possible perturbed in volume of the sky around it. We found that 90% of the analyzed systems have at least a close flyby, implying that the very high incidence of encounters (in particular, close encounters) experienced by the systems in the last 5 Myr. I will also discuss the debris disk systems with known planets, companions and/or flyby(s). It is important to highlight that also our solar system itself experienced at least a close encounter. This implies the fundamental impact of flybys in the evolution of debris disks. The confirmation of the statistical significance of flybys in debris disk systems can also be responsible for stirring of debris material.

How to cite: Roccatagliata, V. and Kim, M.: The impact of flybys on the evolution of solar system analogs, the debris disk systems., Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-972, https://doi.org/10.5194/epsc2024-972, 2024.

Debris disks are the remnants of planet formation and therefore extremely important for understanding exoplanet system architecture. They were long thought to be completely depleted in gas, different from protoplanetary disks. In recent years, however, detections of CO gas in a number of debris disks has caused questions about the nature and origin of this class of gas-rich debris disks. A sample of five CO-rich debris disks has now been observed with JWST's MIRI Medium Resolution Spectrograph (MRS) as part of the MINDS (MIRI mid-INfrared Disk Survey) GTO program. Our program resulted in high quality spectra from 5 to 27 micron, which are spatially resolved for most of the targets providing a unique opportunity to gain new insights into these objects.

For the first time this data allows us to conduct a sensitive search for mid-IR atomic and molecular emission lines and dust features in debris disks for which CO gas was detected with ALMA. It also allows us to map the spatial distribution of the dust as a function of wavelength for most of our targets, bridging the gap between optical/near infrared imaging observation and sub-millimeter observations. In this talk we present the first exciting results and highlights coming out of this JWST survey.

How to cite: Samland, M. and the MINDS collaboration: The MINDS gas-rich debris disk sample observed with JWST/MIRI MRS, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-1118, https://doi.org/10.5194/epsc2024-1118, 2024.

Combining the resolved observations of debris discs with ALMA and the enhanced sensitivity of JWST presents a unique opportunity to deepen our understanding of planetary systems. Over the past 5 years, ALMA has revealed substructures within debris discs, suggestive of planetary influence, yet the direct detection of these putative planets remains elusive. Now with JWST's advanced capabilities, we have an unprecedented opportunity to detect the population of planets at 10s of au currently inferred by ALMA.

While only three debris discs have shown gaps so far, we are becoming more aware that these gaps might be common. Similar to observations in our Solar System, the presence of gaps in debris components hints towards the presence of planets. These gaps could either be carved by planets in situ or by inner planets exercising secular resonances.

In this talk, I will present JWST Cycle 1 MIRI 11um observations targeting three known debris discs with gaps: HD107146, HD92945, HD206893. I will show how planet-disc interactions combined with astrometric accelerations allow us to constrain the population of planets in the inner regions of these systems, at the disc inner edge and in the gap location, ultimately evaluating the degenerate scenarios proposed as the origin of these gaps.

How to cite: Bendahan-West, R.: JWST observations constraining the population of planets in debris disc systems with gaps, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-248, https://doi.org/10.5194/epsc2024-248, 2024.

Bodies forming debris disks collide each other due to the presence of planets. In debris disks around stars without any type of massive companions (other stars or planets), bodies for which non-gravitational forces are negligible would follow  perfectly keplerian orbits, whose shapes and orientation are fixed in space. In such conditions, mutual orbital crossing, and consequently, mutual collisions would not be possible. In presence of one or more perturbing planets secular perturbation theory predicts departures from pure keplerian motion. The osculating elements of the bodies vary in a way depending on the orbital properties of the perturbers.

When the eccentricity of the orbit of the perturbing planet is small (as in the case of Jupiter for the Main Belt Asteroids in our Solar System) the effect of the forced eccentricity of the debris' orbits is to produce a quasi uniform circulation of the orbits (variation of pericenters and node longitudes) and limited variations of the other elements, along with a typical distribution of the instantaneous distance from the star (fig. 1). Under those conditions, classical methods for the investigation of the impact statistics (Bottke et al. 1994) are suitable for the computation of the impact rates among the Main Belt Asteroids.

Instead, the larger the eccentricity of the planet's orbit the less uniform the circulation of the debris' orbits. Furthermore, and even more importantly, in such conditions strong correlations between orientation and eccentricities of the orbits arise, entailing a completely different radial distributions of the particles (fig. 2 and 3). More general methods (Dell’Oro & Paolicchi, 1998) are able to improve the investigation of the impact statistics, but they cannot account for the effect of strong orbital element correlations in computing collision probabilities and distribution of the impact velocities.

In the last decade, a new model for the investigation of the statistics of impacts among orbiting bodies has been developed (Dell’Oro, 2017). The new numerical model is able to reproduce the exact spatial and velocity distribution of the particles forming a debris disk perturbed by one or more planets or virtually in many other complex dynamical conditions. The method is based of a completely new and independent mathematical approach, and it has been used to validate and confirm the results of the classical methods.

In particular, for what concerns the typical case of debris disks around other stars,  the new tool, unlike the previous ones, is not limited to the case of low orbital eccentricity of the perturbing planets, typical of our Solar System. Here some preliminary results are shown in comparison with analytic theories (Mustill & Wyatt, 2009), when possible.

The analytic theory is limited to the case of small orbital inclinations. Moreover it ignores the effect of the disk borders where the particles density drops to zero, and where the  particles at the internal (external) edge interact only with particles of larger (smaller) semimajor axes.  

In the case of null orbital inclinations, analytic theory (fig. 4, black solid line) overestimates systematically the mean impact speed by 10-20 % with respect to our numerical computation (fig. 4, red dots). Outside of the zero inclinations case, mean impact speed increases as dispersion of the inclinations grows, as expected, but also the variation of the impact speed as function of the distance from the star is different. The analytic theory predicts that if the perturbing planet is internal (external) to the disk the mean impact speed decreases (increases) with distance from the star. In the case of internal planet, our numerical computation shows that allowing inclinations to increase, the dependence of the average velocity with the distance from the star is reversed (fig. 4). A similar result is obtained for the external planet case.  Another difference with respect to the analytic theory concerns the effect of the eccentricity of the planet, in the sense that the mean impact speed would be proportional to the planet eccentricity. While in the case of an internal planet numerical computation confirms
this trend, with an external perturbing planet the mean impact speed results to be less than proportional to the planet eccentricity.

REFERENCES
Bottke W.F. et al. 1994, Icarus, 107, 255-268.
Dell’Oro A. 2017. Monthly Notices of the Royal Astronomical Society, 467, 4817-4840.
Dell'Oro A., Paolicchi P. 1998. Icarus, 136, 328-339.
Marzari F., Dell'Oro A. 2017. Monthly Notices of the Royal Astronomical Society, 466, 3973-3988.
Mustill A.J., Wyatt M.C. 2009. Monthly Notices of the Royal Astronomical Society, 399, 1403-1414 .

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How to cite: Dell'Oro, A.: A numerical tool for the impact statistics in debris disks, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-128, https://doi.org/10.5194/epsc2024-128, 2024.

How to cite: Picogna, G. and Marzari, F.: Dust dynamics in forming resonant planetary systems, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-965, https://doi.org/10.5194/epsc2024-965, 2024.

Directly imaged debris discs can be a signpost in the darkness for finding exoplanets; those with sharp inner edges can be evidence for exoplanets, and can be responsible for sculpting these inner edges. All three targets in our JWST Cycle 1 proposal, HD202628, HD21997, and GJ14, have well-resolved ALMA imaging and all show evidence of having sharp inner edges. With the goal of utilising the deep mid-infrared sensitivity of the JWST-MIRI instrument, we used pre-launch performance estimates to customise our observations to be sensitive to sub-Jovian mass companions. In this talk, I will present these MIRI coronagraphic observations at 11.4 microns with emphasis on the new detection parameter space we cover and the sensitives we reach utilising the streamlined python package SpaceKLIP. Although our results have shown no evidence for planets down to ∼ 1MJup in all cases, combined with other factors such as proper motion anomalies - which we are exploring in our JWST Cycle 2 proposal - we can place important constraints on the presence of any bodies that might be responsible for these sharp inner edges.

How to cite: James, A.: Directly imaging massive planets sculpting the inneredges of debris discs with JWST-MIRI, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-1043, https://doi.org/10.5194/epsc2024-1043, 2024.

Debris disks are circumstellar disks made of dust and rocky material that orbit stars. In the Solar System, the Asteroid and Kuiper Belt are debris disks similar to the ones we observe around other stars. Debris disks provide valuable insights into planetary system dynamics that complement findings from planet and protoplanetary disc studies. Our research probes the implications of the vertical profile shape on the characteristics of the debris disk environment, with a specific focus on the intriguing case of HD 32297. 

One key aspect of our research is the differentiation between the influences of planets, flyby stars and large planetesimals on the vertical shape of debris disks. By understanding these distinct influences, we can gain a deeper understanding of the dynamics of these systems.

We present a multi-wavelength analysis of HD 32297's edge-on debris disk, a well-known disk orbiting a young A star. This system exhibits one of the largest infrared excesses observed among main-sequence stars. HD 32297's disk is highly edge-on and very narrow in mm-dust, so it is one of the best disks to examine the vertical structure profile.

Our high-resolution data enable us to measure the disk's vertical thickness for different radii and, therefore, to create a vertical thickness profile along the radial direction. This makes the system an excellent test bed, allowing us to examine various dynamical models for debris disk interactions.

How to cite: Luppe, P.: Exploring the Dynamics of Debris Disks through Vertical Thickness Analysis: Case Study of HD32297, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-532, https://doi.org/10.5194/epsc2024-532, 2024.

Interferometric near- and mid-infrared observations revealed that about one-fifth of nearby stars are surrounded by dust of as yet unknown origin - hot exozodiacal dust (HEZD). Since HEZD is located  at orbital radii comparable to those of close-in exoplanets, its presence has a potential influence on the analysis of the scattered-light polarization of close-in exoplanets and vice versa.

We analyze the impact of HEZD around main-sequence stars on the polarimetric characterization of close-in exoplanets and vice versa by identifying characteristic polarimetric signatures of HEZD and close-in exoplanet. We find that the dust grain radius has the strongest influence on a polarimetric analysis due to its significant impact on the wavelength-dependent polarization characteristics and the total order of magnitude of the scattered-light polarization. In certain scenarios, the scattered-light polarization of the HEZD even exceeds that of the close-in exoplanet, for example for a dust grain radius of 0.1 μm, a HEZD mass of 8*10^-10 Μ_⊕ , an orbital HEZD radius of 0.04 au and an orbital inclination of 90°.
 
In summary, the presence of HEZD needs to be considered in any effort to characterize exoplanets via polarimetric observations. Stricter constraints on the model parameters (especially on the dust grain radii) are required to restrict the potentially resulting scattered-light polarization.

How to cite: Ollmann, K., Wolf, S., Lietzow-Sinjen, M., and Stuber, T.: Impact of hot exozodiacal dust on the polarimetric analysis of close-in exoplanets, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-605, https://doi.org/10.5194/epsc2024-605, 2024.

How to cite: Kim, M. and Roccatagliata, V.: An imprint of low-mass companions in the substructures of debris disks, Europlanet Science Congress 2024, Berlin, Germany, 8–13 Sep 2024, EPSC2024-682, https://doi.org/10.5194/epsc2024-682, 2024.