Location: T2, second floor
Zoom link: https://macquarie.zoom.us/j/81099211834
Slack channel: #asa2023-planets
Chair: Laura Driessen, Co-Chair: Daniel Zucker
1:15pm: Spectroscopic Data for Molecule Identification in Exoplanets and Cool Stars - Laura McKemmish, University of New South Wales
New telescopes (particularly JWST) and observational techniques (notably high-resolution cross-correlation, HRCC) offer tantalizing opportunities for astronomers to study in unprecedented detail the chemical composition of a variety of exoplanet atmospheres. However, these studies are only possible if sufficiently high-quality spectroscopic data is available for the molecules of interest.
Modern methods for producing molecular spectroscopic data are advanced and can, for the right molecules and spectral regions, address the dual challenges of accuracy and completeness. They accomplish this by careful use of both experimental and theoretical data.
But what if your observed spectrum doesn’t match your model? Have you used the wrong input parameters? Is the atmospheric model wrong? Or is the underlying line list wrong? As a producer of line lists, I can help you answer the last question.
I will tell you how we produce these line lists and, most importantly, where we expect errors to occur and where they will not occur (as well as tell you about what sort of errors and their magnitude). For example, if you are looking at water absorption in the infrared, then the line lists will be near perfect. Looking at TiO in the visible, not so much.
1:30pm: Transit Depth Variations Reveal TOI-216 b to be a Super-Puff - Brendan McKee*, University of New South Wales
Transit timing variations are a powerful tool in exoplanet characterisation, allowing planetary masses to be determined using transits alone. In orbital resonances perturbations add constructively to push transits earlier or later than expected from a strict periodicity. Only a small number of systems have transit timing variations large enough to determine the masses of the planets using transits alone, without seeking further data from radial velocity measurements. The planets of TOI-216 exhibit the most extreme periodic timing variations known, with deviations of up to 3 days from the expected arrival time out of its 17-day orbit. Using new observations, we find that the depth of the transit of TOI-216 b also changes over time as interplanetary forces cause the planet to cross more of the face of the star. This rare feature allows us to precisely characterise the orbital architecture, along with both the masses and radii of each planet. We find that this system has a typical gas giant as the outer planet, while the inner planet has the same mass as Neptune, despite having 8 times the volume. While the origins of super-puff planets are unclear, TOI-216 b represents a growing class of these objects in orbital resonances and with a companion in a nearly circular orbit, suggesting their early evolution is driven by smooth disk migration.
1:45pm: Direct Imaging of Protoplanet HD 169142 b - Iain Hammond*, Monash University
We present the re-detection of a compact source in the face-on protoplanetary disc surrounding HD 169142, using VLT/SPHERE data in YJH bands. The source is found at a separation of ∼37 au from the star. Three lines of evidence argue in favour of the signal tracing a protoplanet: (i) it is found in the annular gap separating the two bright rings of the disc, as predicted by theory; (ii) it is moving at the expected Keplerian velocity for an object at ∼37 au in the 2015, 2017, and 2019 data sets; and (iii) we also detect a spiral-shaped signal whose morphology is consistent with the expected outer spiral wake triggered by a planet in the gap, based on dedicated hydrodynamical simulations of the system. The YJH colours we extracted for the object are consistent with tracing scattered starlight, suggesting that the protoplanet is enshrouded in a significant amount of dust, as expected for a circumplanetary disc or envelope surrounding a gap-clearing Jovian-mass protoplanet.
2:00pm: Do you want to detect a non-transiting exoplanet? Then you should put a ring on it. - Jaime Andres Alvarado Montes*, Macquarie University
The two most accomplished techniques for exoplanet detection are transits and radial velocity (RV). However, these methods have a bias towards close-in, low-inclination orbits, which means that certain orbital configurations are not detectable. Here, we aim to develop a robust photometric model to study the complete phase curve of gas giants with rings, since spatially unresolved dusty rings can modify the total flux of reflected starlight. We base our radiative transfer calculations on an adding-doubling algorithm and compute the reflected flux, linearly polarized flux, and degree of polarization curves, varying properties such as the ring orientation, size, particle albedo, optical thickness, and the planet orbital inclination. Additionally, we populate rings with irregularly shaped particles with optical properties based on measurements. Our findings show that dusty rings produce sharp discontinuities in the degree of polarization curves at the planet's apoastron and periastron. We also predict the reflected and polarized flux of the "puffed-up" planet HIP 41378f, proving that while it cannot yet be directly imaged, polarimetry in future observations will significantly aid in characterising ringed exoplanets. By investigating the reflected flux and polarization curves of planets, we can cover orbits that are undetectable using transits and RVs, thus increasing the probability of discovering new extrasolar systems that may be invisible to existing techniques.
2:15pm: Exploring spin-orbit alignment of exoplanet and binary star systems - Tony Wells*, University of Southern Queensland
Until the discovery of exoplanets, theories on planet formation and orbital evolution were based on observations of the one known planetary system – the Solar System. Recent observations of exoplanet and binary star systems however have revealed planets and stellar companions in orbits wildly different from those observed in the Solar System, including bodies in polar and even retrograde orbits. Such observations have raised difficult questions as to the nature of the processes that drive the planets/stars to these remarkable orbits. One powerful indicator of the dynamical history of a planetary system is the stellar obliquity, (or spin-orbit angle), which describes the angle between the stellar rotational axis and the planetary (or stellar companion) orbital axis. Unfortunately, obliquity studies to date have been limited to a small number of system types. In this study we aim to expand this data base by determining obliquities for lesser studied system types including those featuring smaller planets and those on longer orbits, as well as binary star and brown dwarf systems. In this way we will create a more universal test bed of data with which to better understand the migratory processes driving the evolution of exoplanet and binary star systems. In this presentation I will discuss various formation and migratory scenarios, outline the study methodology, and present some preliminary findings.
2:30pm: Hunting cold planets: Breaking the low mass planet detection limit with Euclid and Roman - Efstathia Natalia Rektsini*, University of Tasmania
The ESA EUCLID mission and NASA Nancy Grace Roman Space telescope mission have the potential to detect thousands of planets across a broad range of masses and semi-major axes. The ROMAN telescope will utilize the gravitational microlensing technique which is a unique tool for detecting and studying cold exoplanets of masses in the range Mars to Jupiter, orbiting any kind of star or stellar remnant all the way to the Galactic Bulge.
Gravitational microlensing relies on the chance alignment of two or more stars in our galaxy. Over 100 planets have so far been found using this technique, and the Roman Telescope is expected to increase that by a factor of ten. Both ROMAN and EUCLID will be located in halo orbits at the Earth-Sun L2 point, with a potential separation between them of up to 600.000 km, while observing the same sky frame.
Using simulated early EUCLID images of a star field containing 1691 microlensing events that ROMAN will observe, I will explain the complementarity of the two missions. I will show how two joint-surveys will better constrain the mass and distance of microlensing events, increase the detection of “free-floating” planets (FFPs) and lead to a breakthrough in our understanding of cold planet demographics and planetary formation theories.
Poster sparklers in this session:
P21: Kathryn Ross, ICRAR/Curtin Uni.
P33: Sarah Bradbury*, ANU
P36: Nikhel Gupta, CSIRO
P72: Tania Ahmed*, Macquarie Uni.