ESA's Holland-Area Exoplanet Science Meeting (HAESM) 2023


Uniting all ESA and Holland-area exoplaneteers for a day of science, discussions, and collaboration; our colleagues from ESAC, STScI, and external collaborators are equally encouraged to join us remotely.
Friday, 9 June 2023, 13:00 - 17:00 CEST, in ESTEC (room Einstein Aj033) and online (via WebEx).




Time (CEST) Speaker Affiliation Title Format
13:00 - 13:20 Matthew Kenworthy Leiden Observatory The suprisingly eccentric orbit of the directly imaged exoplanet YSES 2b  In person
13:20 - 13:40 Saugata Barat University of Amsterdam V1298 Tau: The story of a warm gas giants orbiting an adolescent star In person
13:40 - 14:00 Philippe Gondoin ESA exoplanet team On the formation history of nearby Sun-like stars and their planetary systems In person
14:00 - 14:20 Coffee Break      
14:20 - 14:40 David Doelman SRON  Chasing rainbows and ocean glints: Inner working angle constraints for the Habitable Worlds Observatory In person
14:40 - 15:00 Robert Kavanagh ASTRON Hunting for hidden exoplanets via magnetic star-planet interactions In person
15:00 - 15:20 Timothy Wing Hei Yiu ASTRON Radio emission as a stellar activity indicator In person
15:20 - 15:40 Coffee Break      
15:40 - 16:00 Sanne Bloot ASTRON/Kapteyn Astronomical Institute The radio star AU Microscopii: Hunting for signatures of star-planet interaction in the presence of stellar activity In person
16:00 - 16:20 Fabienne Nail University of Amsterdam Anisotropic Planetary Winds: Insights from the Helium Line In person
16:20 - 16:40 Nicolas Crouzet Leiden Observatory One year of observations with JWST MIRI In person
16:40 - 17:00 Isabel Rebollido Vázquez Centro de Astrobiología (CAB-CSIC) Exocomets and the gas around A-type stars Remote




The suprisingly eccentric orbit of the directly imaged exoplanet YSES 2b (Matthew Kenworthy, Leiden Observatory)

There are several possible formation pathways for the formation of planets and their attendant moons. Radial velocity and transit surveys have mapped out the architecture of exoplanet systems with decreasing completeness to 20 astronomical units. Direct imaging of exoplanets complements these detections by searching from 20 to hundreds of astronomical units, completing the exoplanet demographic. We have detected three planets in the Young Suns Exoplanet Survey (YSES), and multiple observations of the 8 Jupiter mass gas giant exoplanet YSES 2b at around 110 au projected separation from the one solar mass star YSES 2 shows that it is on a very eccentric orbit of 0.8, with a periastron distance of 50 au. The planet did not form in such an eccentric orbit, and we hypothesise that it was scattered out to its current position either through secular evolution or by gravitational scattering with a second companion. An acceleration in the proper motion of the star is seen in a 30 year baseline, implying the existence of this second companion with a mass the stellar and substellar boundary. We will present our observations and place them in the context of planet formation and evolution.


V1298 Tau: The story of a warm gas giants orbiting an adolescent star (Saugata Barat)

We present the atmospheric characterization of a young sub-Neptune. We focus on the V1298 Tau b, which is a part of a four planet system  orbiting  the young (23Myr) T Tauri star V1298 Tau. We have observed one primary transit of planet V1298 Tau b with HST to learn about its atmospheric properties.  We present the results from this observing programme and discuss the challenges of transit observations around young stars and the techniques we use to overcome these challenges. We derive constraints on the atmospheric abundances, planet mass and also find evidence of disequilibrium processes in the planet's atmosphere. Although sub-Neptunes/super-Earths are quite common in the planet population, there are several open questions regarding the formation mechanisms of these systems. The V1298 Tau system is a missing link between forming planets in disks and the mature planet population and promises to tackle the questions related to the early evolution of these systems. In this presentation we discuss our findings in the context of planet formation, comparative exoplanetology with other young systems as well as within the same system. We discuss our plan of combining HST observations of planet V1298 Tau c and JWST observations of V1298 Tau b with the current analysis to further constrain atmospheric properties like metallicity and C / O ratios to gain a more complete overview of this rich and diverse multiplanet system. 


On the formation history of nearby Sun-like stars and their planetary systems (Philippe Gondoin)

Nearby Sun-like stars are prime targets for the detection and characterization of exo-planets and possibly exo-Earths. Determining the age of these stars and of their planetary systems is thus essential. The presentation addresses the formation history of nearby G-type stars inferred from the emission reversal in the cores of their Ca II H&K lines used as an age indicator.


Chasing rainbows and ocean glints: Inner working angle constraints for the Habitable Worlds Observatory (David Doelman, SRON)

NASA recently announced the Habitable Worlds Observatory (HabWorlds), a coronagraphic space mission to detect rocky planets in habitable zones, establish their habitability, and search them for biosignatures. Surface liquid water is central to the definition of planetary habitability. Photometric and polarimetric phase curves of starlight reflected by an exoplanet can reveal ocean glint, rainbows and other phenomena caused by scattering by clouds or atmospheric gas. Direct imaging missions are optimised for planets near quadrature, and HabWorlds' coronagraph may obscure the phase angles where such optical features are strongest. The range of accessible phase angles for a given exoplanet will depend on the planet's orbital inclination and/or the coronagraph's
inner working angle (IWA). For planets in near edge-on orbits, accessible phase angles are limited by coronagraphic obscuration. In this talk, we use HabWorlds' catalogue of 160 target stars to estimate the number of exo-Earths that could be searched for ocean glint, rainbows, and Rayleigh scattering. We will demonstrate that high-contrast polarimetry with HabWorlds is key to search for habitability and show how the coronagraph choice affects the search for these features in nearby Earth-like exoplanets.


Hunting for hidden exoplanets via magnetic star-planet interactions (Robert Kavanagh, ASTRON)

Recent radio observations suggest that some nearby M dwarfs could be interacting magnetically with exoplanets that remain undetected by traditional methods. The detected form of radio emission is expected when planets orbit sufficiently close to their host stars, in the region where the plasma is dominated by the star's magnetic field. The boundary of this region is known as the Alfvén surface. Such a scenario is particularly favourable for M dwarfs, as they are likely to possess large Alfvén surfaces due to their strong surface magnetic fields. The underlying mechanism responsible for producing this emission is the electron cyclotron maser (ECM) instability. ECM emission is analogous to a lighthouse beam, being only visible for brief windows. The epochs at which it is visible are highly dependent on the underlying system geometry, resulting in a signature that is both distinct from radial velocities/transits, and complex in morphology. Due to this strong geometric dependence, detection of such signatures may be more favourable at certain orbital phases and/or from systems with architectures contrasted to the currently-known population of exoplanets. In this talk, I will discuss our recent work utilising numerical models to explore these two ideas.


Radio emission as a stellar activity indicator (Timothy Wing Hei Yiu, ASTRON)

Radio observations are excellent probes of the environmental conditions in the coronae/magnetospheres of stars and brown dwarfs. In particular, radio emission traces the impact of stellar plasma on exoplanet atmospheres, the processes of coronal heating, and key parameters for assessing exo-habitability. The strong magnetic field of these stellar systems leads to radio emission via different mechanisms such as gyrosynchrotron radiation, electron cyclotron maser instability, and plasma oscillation. As the ongoing LOFAR Two-metre Sky Survey (LoTSS) and VLA Sky Survey (VLASS) are some of the deepest and most sensitive radio sky surveys ever conducted, I shall present our latest efforts on identifying different radio emissions from stellar systems in these surveys. By using the radio-detected population's properties, I shall differentiate the two possible acceleration mechanisms (the so-called engines): (a) chromospheric/coronal acceleration similar to that observed on the Sun, and (b) magnetospheric acceleration occurring far from the stellar surface similar to that observed on Jupiter. Since one expects stars to have Sun-like engines, and brown dwarfs to have Jupiter-like engines, our aim is to search for a transition from one to another in the realm of M dwarfs: the tail of the main-sequence stars. Furthermore, to understand how stellar activity impacts radio detectability, I shall also investigate whether the radio detection rate in our samples correlate with canonical activity indicators in the optical and X-ray bands.


The radio star AU Microscopii: Hunting for signatures of star-planet interaction in the presence of stellar activity (Sanne Bloot, ASTRON/Kapteyn Astronomical Institute)

A key question in stellar astronomy is whether there are habitable planets around stars other than our Sun. An important factor in determining this is stellar activity, as stellar eruptions have direct impact on the atmosphere of an exoplanet. Radio emission, especially with a high degree of circular polarization, can provide a direct measurement of the magnetic field and the plasma properties of the star. Although many stars have been observed at radio frequencies, very few have been studied extensively enough to see the full phenomenology of radio emission. In this talk, I will present our year-long observing campaign of AU Microscopii, a young M-dwarf system with three detected planets. This system has been studied in detail at many wavelengths, but not at radio frequencies. With over 200 hours of observations, this campaign has allowed us to describe and categorize different types of stellar radio emission in a detail never before attainable for a single star. This includes characterizing rare types of emission such as those similar to solar radio bursts and Jovian magnetospheric emission. I will conclude with an interpretation of the physical processes causing these types of emission. 


Anisotropic Planetary Winds: Insights from the Helium Line (Fabienne Nail, University of Amsterdam)

Understanding the escape of atmospheres from close-in exoplanets is crucial for deciphering the characteristics of planetary populations. In this context, the blueshift observed in almost all helium observations hints at a potential flux from the day to the night side of these planets. Our study delves into the implications of anisotropic planetary winds, arising from day-to-night temperature gradients in tidally-locked gas giants, on the helium triplet at 1083 nm. Through 3D hydrodynamic simulations and a radiative transfer analysis, we investigate the interplay between anisotropic winds and the helium line characteristics. Our findings reveal fascinating correlations between the degree of anisotropy and the properties of the helium line. Moreover, our parametric study sheds light on the effects of key factors such as stellar mass loss rate, orbital distance, and the thermal-to-gravitational potential ratio of the planet. By unveiling these connections, our study uncovers new insights into the dynamics of planetary winds and their impact on helium observations. Join us in this captivating journey as we explore the fascinating world of anisotropic planetary winds and their influence on the helium line shift, offering a deeper understanding of exoplanet atmospheres and their unique dynamics.


One year of observations with JWST MIRI (Nicolas Crouzet, Leiden Observatory)

JWST's science observations began in July 2022. The Netherlands community played a major role in the development of the Mid-Infrared Instrument (MIRI) in particular in its Medium Resolution Spectrometer (MRS) through NOVA. MIRI is the only instrument onboard JWST that covers wavelengths beyond 5 microns and is used to investigate a wide variety of objects, from galaxies to star forming regions, protoplanetary disks, and exoplanets. In this talk, I will present science highlights broadly related to exoplanets that were enabled by MIRI in its first year of operation.


Exocomets and the gas around A-type stars (Isabel Rebollido Vázquez, Centro de Astrobiología [CAB-CSIC])

The presence of gas in debris disks is now accepted as a common occurrence, particularly around A-type stars, where the Atacama Large sub-Millimeter Array (ALMA) has found CO in over 20 objects.
However, the presence of gas in main-sequence stars has been observed for almost 40 years through variable absorption features in metallic lines, usually attributed to falling evaporating bodies or exocomets. Combining the information we have obtained through the years from UV to millimetric wavelengths, we are closer to disentangling the origin of this gas, and its relevance to planet formation and evolution. 


Registration and abstract submission

If you would like to join us for HAESM 2023 - whether in person or remotely, whether to network, listen in, or to present your own resarch highlights - please use the form below to register and submit your abstract by 31 May 2023 (registration and submission are now closed).

Science presentations will be 15+5 minutes (talk+questions), depending on the number of abstracts submitted. HAESM 2023 seeks to give everyone a platform to present their work, and especially encourages contributions from early career scientists. HAESM 2023 also actively encourages any and all "unconference" approaches, and as such the form below is also open to submissions of ideas for group discussions, brainstormings, diversity workshops, and other events that fit the scope.



All in-person attendees are invited to arrive at the gatehouse of ESTEC (Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands) latest by 11:15 CEST to collect their badges for the day. We will walk together from there to the wonderful ESTEC cafeteria, and enjoy a joint lunch (self-paid). The presentations will start from 13:00 CEST, with a mix of in-person and virtual presentations. We aim to enjoy a relaxing evening in the Dutch Sun and continue with informal science discussions during a borrel at the ESCAPE lounge from around 17:00 CEST.