Presenter: Artemenko, S.; Babina, E.; Petrov, P.; Grankin, K.

Title: Accretion and wind modulation in T Tauri star RY Tau: a planet at 0.2 AU?

Abstract: Spectral and photometric monitoring of CTTS RY Tau in 2013-2021 revealed variations in the H-alpha and NaI D lines at radial velocities of infall (accretion) and out ow (wind) with a period of about 22 days. The NaI D absorption in the infalling and out owing gas changes in anti-phase: an increase in the density of infalling gas is accompanied by a decrease in the wind density, and vice versa. The fluctuations remain coherent for several years of observation. We assume that the observed effect may be due to processes at the disk-magnetosphere boundary in MHD propeller mode. The stability of the oscillation phase indicates the possible presence of a massive planet, causing azimuthal asymmetry of the accretion and wind flows. If the observed period (22 days) is Keplerian, then the planet is located at a distance of 0.2 AU and moves with an orbital velocity of 100 km s-1


Presenter: Aldana Cotrina, Naira Azucena; Reyes, Carlos

Title: Study Of Orbits of Planetary Nebulae in the Large Magellanic Cloud

Abstract: The result of a study of orbits of Planetary Nebulae (PN) in the Large Magellanic Cloud (LMC) is presented, using a velocity distribution model in an Isotropic Gaussian Field. It is proposed that these orbits are related to different populations of the several PN. It was possible through the statistical study of their radial positions and velocities. Allowing to discriminate between old and young star systems; which can be related to its physical and chemical parameters. Contributing  to understand the chemical and dynamic evolution of this galaxy poor in metals.


Presenter: Baratella, Martina

Title: The chemical characterisation of young stars

Abstract: The determination of the detailed chemical composition of stars is critical in many astrophysical fields, including (but not limited to) the characterisation of planetary systems. Previous studies seem to indicate an anomalous chemical pattern of the young(est) stellar populations in the solar vicinity. The chemical peculiarities include sub-solar [Fe/H] ratios, over-abundances of ionised atoms, and the Ba puzzle. Our investigation suggests that these effects are related to abundance analysis techniques, which have important limitations when applied to young stars. The main role is played by the intense stellar activity, although a comprehensive understanding of this complex behaviour is still wanting. It shapes the spectral lines, altering the derivation of the stellar parameters (and also the chemical abundances) when derived in a standard way. For these reasons, new spectroscopic techniques are needed especially to analyse young stars.  


Presenter: Bellotti, Stefano; Korhonen, Heidi

Title: Simulating starspot activity jitter for spectral types F–M: realistic estimates for a representative sample of known exoplanet hosts
Abstract:Stellar activity represents a serious limitation to exoplanet radial velocity (RV) searches. In fact, surface inhomogeneities due to magnetic activity such as spots produce distortions in the spectral line profiles and therefore spurious RV shifts (know as “jitter”) up to several m/s that drown small planet signals or undermine the accuracy of planetary characterisation. Modelling the spot-driven RV variability is therefore important to design efficient activity-filtering techniques and inform observing strategies. Our aim is to characterise starspots and simulate the radial velocity curves they induce to determine typical jitter amplitudes for a representative sample of known host stars spanning between F and M spectral type.


Presenter: Cifuentes San Román, Carlos

Title: Luminosities of of cool stars

Abstract: Once the flux of a star in multiple passbands (from UV to mid-IR) is known, one can produce a low-resolution spectrum or spectral energy distribution (SED) and derive the bolometric luminosity from it. We did this in Cifuentes et al. (2020) on almost 2500 cool stars. We determined the average values of very important astrophysical parameters, including absolute magnitudes, temperatures, masses or radii


Presenter: Delgado Mena, Elisa 

Title: Carbon abundances and C/O ratios for planet hosts 

Abstract: We present homogeneous carbon abundances for a sample of 757 FGK stars in the HARPS-GTO sample, from which 101 stars host Jupiter-mass companions and 22 hosts Neptunian-mass companions. We derive C/O ratios using oxygen abundances from the 6300A [OI] forbidden line (low excitation potential) and with the 6158A line (high excitation potential as the CI optical lines used to determine carbon abundances). We find a tentative evidence that stars with low-mass planets at lower metallicities have higher [C/Fe] ratios than stars without planets at the same metallicity, in the same way as previously found for alpha elements and Zn. The elemental C/O ratios for the vast majority of our stars are below 0.8 when using the oxygen line at 6158Å but the forbidden oxygen line at 6300Å provides systematically higher C/O values (going above 1.2 in few cases) which also show a dependence on Teff. Moreover, by using different atmosphere models the C/O ratios can have a non negligible difference for cool stars. Therefore, C/O ratios should be scaled to a common solar reference in order to correctly evaluate its behaviour. We find no significant differences in the distribution of C/O ratios for the different populations of planet hosts except when comparing the stars without detected planets with the stars hosting Jupiter type planets. However, we note that this difference might be caused by the different metallicity distributions of both populations. 


Presenter: Flammini Dotti, Francesco Maria

Title: The dynamical consequences of the star clusters' long term evolution on planets

Abstract: Since most stars tends to aggregate in dense clusters, the study of the dynamics of planetary systems and free-floating planet can explain the proprieties of the exoplanets found in our Galaxy. Using the NBODY6++GPU code for the star cluster dynamics and REBOUND for the planetary systems, we present how planetary systems and free-floating planets interact with the clustered environment. We use different clusters’ The Star-Planet Connection – Poster Abstracts initial conditions, including the presence of an intermediate massive black hole in the cluster center. The encounter strength, the relative velocity of the encountering star and the star cluster density are the main factors that alter the planetary system architecture. The black hole plays also a role in the planetary ejections in the first Myrs of the star cluster evolution.

Presenter: Gillet, Alexandre

Title: Clouds on Ultra Hot Jupiters and secondary eclipse variability

Abstract: The atmospheres of transiting planets can be studied and analysed through primary transits, secondary eclipses and the phase curve modulation. With the secondary eclipse technique, one can study the emission of the full day-side and the thermal structure of the planet. One may expect a change in the secondary eclipse depth, symptomatic of a variation of the albedo due to the presence of clouds on their hot sides. We analysed the secondary eclipse variability from orbit to orbit of four Ultra Hot Jupiters : WASP-18b, KELT-9b, KELT-1b and WASP-121b. They belong to a class of tidally locked giant gaseous exoplanets with short orbital period, small semi-major axis and very high equilibrium temperature (greater than 2000K). Each eclipses and transits were fit with a Mandel & Agol Model analysed with an MCMC and STEPPAR procedure. Unfortunately, the level of scatter found in secondary eclipse depth was similar to the one found in transit depth which cannot be attributed only by the presence of clouds. 


Presenter: Hao, Wei 

Title: Few body simulations of stellar encounters on multi-planet systems in open clusters 

Abstract: The cumulative effect of stellar encounters can substantially affect the dynamical evolution of existing planetary systems, especially during their secular evolution after the perturbation brought by the encounters. In this poster, we present the results on the cumulative effect of distant stellar encounters on multi-planet systems in star clusters, and how these results depend on the properties of the star cluster in which a planetary system is born.


Presenter: Jofré, Emiliano 

Title: The peculiar chemical pattern of the WASP-160 binary system: signatures of planetary formation?

Abstract: Wide binary stars with similar components hosting planets provide a favorable opportunity for exploring the star-planet chemical connection. In this contribution, we present a detailed characterization of the solar-type stars in the WASP-160 binary system. No planet has been reported yet around WASP-160A while WASP-160B is known to host a transiting Saturn-mass planet, WASP-160B b. For this planet, we also derive updated properties from both literature and new observations. Furthermore, using TESS photometry, we constrain the presence of transiting planets around WASP-160A and additional ones around WASP-160B. The stellar characterization includes, for the first time, the computation of high-precision differential atmospheric and chemical abundances based on high-quality Gemini-GRACES spectra. Our analysis reveals evidence of a correlation between the differential abundances and the condensation temperatures of the elements. In particular, we find both a small but significant deficit of volatiles and an enhancement of refractory elements in WASP-160B relative to WASP-160A. After WASP94, this is the second stellar pair among the shortlist of planet-hosting binaries showing this kind of anomalous chemical pattern. Although we discuss several plausible planet formation and evolution scenarios for WASP-160A and B that could explain the observed chemical pattern, none of them can be conclusively accepted or rejected. 


Presenter: Klevas, Jonas

Title: Properties of M-type dwarfs from 3D hydrodynamical model atmospheres

Abstract: We present the first results from 3D hydrodynamical M-dwarf atmosphere simulations with the CO5BOLD model atmosphere code covering a range in Teff, log g and [M/H] typical to M0-M5 spectral type dwarfs. We provide a brief overview of the physical properties of the model atmospheres, with a focus on the validity of mixing length approximation for treating convection in the atmospheres of M-type dwarfs. We show that the mean entropy stratification can be matched only partially by changing the mixing length parameter in the 1D model atmospheres. Generally, a good agreement between the 3D and 1D temperature profiles is found to approximately log tau Ross = -2 where convection stops in the 1D models. Importantly, there is no convective overshoot in the 1D models by definition whereas in case of 3D models extra convective overshoot leads to lower temperatures in the outer atmospheric layers. We discuss this and other implications that point to the necessity of using 3D hydrodynamical model atmospheres in the studies of Mtype dwarfs

Presenter: Kunitomo, Masanobu 

Title: Consequences of planet formation on the stellar composition 

Abstract: Circumstellar disks have an evolving composition due to planet formation processes such as grain growth, planetesimal formation, and disk winds. Therefore, the accretion of disk gas may alter the stellar composition. In order to determine the magnitude of this effect, a key ingredient is the stellar surface convective zone whose thickness determines the dilution of the “planet pollution” signature. Thus, first I will present the thermal evolution of young stellar objects. From stellar evolution calculations, we find that the evolution can deviate from the standard picture depending on accretion heat. Using up-to-date stellar evolution models, we estimate the compositional changes due to planet formation. In this talk, I will focus particularly on the Sun. The Sun has a refractorypoor surface composition compared to solar twins. We find that if the ice-to-rock ratio in the Solar-System planets is less than 0.23, then the anomaly can be originated from the accretion of predominantly volatile elements in the early Solar System due to planet formation. We also find that the signature of planet formation is imprinted in the central region. The central metallicity is enhanced by up to 5%, which is qualitatively in accordance with recent neutrino observations. Therefore, we conclude that accretion including planet formation processes is crucial for a realistic solar model.


Presenter: Lafarga Magro, Marina 

Title: Mapping magnetic activity indicators across the M dwarf domain 

Abstract: Stellar activity poses one of the main obstacles for the detection and characterisation of exoplanets around cool stars, as it can induce radial velocity (RV) signals that can hide or mimic the presence of companions. Several activity indicators are routinely used to identify activity-related signals in RV measurements, but not all indicators trace exactly the same effects, nor are any of them always effective in all stars. In this work, we evaluate the performance of a set of common spectroscopic activity indicators for 98 M dwarfs observed with CARMENES. We find that different indicators behave differently depending on the mass and activity level of the target star. In addition, we also observe that stars at the low-mass end of the sample show the lowest RV scatter, which could potentially hint at different manifestations of activity compared to higher-mass stars, as well as being better candidates for planet searches. Overall, our results show that when assessing the origin of an RV signal, it is critical to take into account a large set of indicators, or at least the most effective ones considering the characteristics of the star, as failing to do so may lead to false planet claims. 


Presenter: Maldonado, Jesus

Title: The curious case of GJ 9689 b: A super-Earth with a period close to half the stellar rotation period

Abstract: Low-mass stars are optimal targets around which to search for small rocky planets with the potential capabilities of hosting life. However, the detection of truly Earth twins is hampered by the short-term stellar activity of the host stars. The evolution and decay of active regions has a characteristic timescale comparable with the stellar rotation period and disentangling ‘true’ Keplerian signals from stellar variations is highly complex. In this contribution we discuss several complementary and imaginative approaches used to study the radial velocity variations observed in low-mass stars. In particular, we discuss the case of the M dwarf GJ 9689. This is an interesting case of study, as the proposed planetary period is very close to half the stellar rotation period.


Presenter: Mugrauer, Markus 

Title: ESA-Gaia Multiplicity Study of Exoplanet Host Stars 

Abstract: The latest results of a survey are presented, which explores the data releases of the ESA-Gaia mission, in order to study the multiplicity of exoplanet host stars, located at distances closer than about 625 pc around the Sun. In total, 280 binaries, 27 hierarchical triples, and one quadruple stellar systems are detected among 1898 exoplanet host stars, whose multiplicity is investigated, yielding a multiplicity rate of at least 16%. The equidistance and the common proper motion of all detected companions and their exoplanet host stars are proven with their accurate Gaia astrometry. Companions with masses in the range between about 0.015 and 1.7 Msun are detected, which exhibit projected separations to the exoplanet host stars between about 30 and 10000 au. Beside many low-mass main sequence stars also 14 brown dwarfs are identified as companions of exoplanet host stars. In addition, 15 white dwarf companions are detected, whose true nature is revealed by their photometric properties. These degenerated companions and the exoplanet host stars form evolved stellar systems with exoplanets, which have survived (physically but also dynamically) the post main sequence evolution of the former primary stars in these systems.


Presenter: Mustill, Alexander

Title: Planet-planet scattering and binary Lidov-Kozai excitation generate high planetary eccentricity

Abstract: Binary stellar companions can have a significant impact on the orbital evolution of a planetary system. Here I study the excitation of eccentricity in wide binary systems, exemplified by the planet HR5183b (a=18au, e=0.84) which has a wide binary companion. I explore three scenarios for the excitation of the eccentricity of the planet in binary systems such as this. The first two are planet-planet scattering and Lidov-Kozai cycles from the binary acting on a single-planet system; both of these have been commonly invoked in the past to explain high orbital eccentricities. I also study a novel combination of both mechanisms, where Lidov-Kozai cycles from the binary act after planet-planet scattering in an initially unstable two-planet system. I show that this is much more likely to lead to a high orbital eccentricity than either of the two processes acting alone. The combination of scattering and Lidov–Kozai forcing may also be at work in other wide-orbit eccentric giant planets, which have a high rate of stellar binary companions.


Presenter: Singla, Manika 

Title: Reflection Spectra of Terrestrial Exoplanets Arround Stars of F, G, K and M Spectral Types 

Abstract: In order to recognise a habitable exoplanet from observed spectra, we model the reflected flux for modern and prebiotic (3.9 Ga) Earth-like exoplanets orbiting at the habitable zone of stars of F, G, K and M spectral types. As special cases, we include model reflected spectra of Proxima Centauri b and Trappist-1e. We estimate the geometric albedo for the modern Earth-like exoplanets with increased abundance of greenhouse gases. For this, we employ the opacity data derived by using the open source package ”Exo-Transmit” and adopt observed Temperature- Pressure profile of the Earth. We use the observed spectra of F, G and K spectral types and synthetic spectra for M spectral type as the incident stellar flux. We solve the multiple scattering Radiative Transfer Equations to generate the reflected spectra for both the types of exoplanets. We compare our model reflected spectra with both the observed reflected spectrum of modern Earth and with published theoretical model spectra for modern and prebiotic Earth. We demonstrate that the modern Earth-like exoplanets with an increased abundances of greenhouse gases in their atmosphere and the prebiotic Earth-like exoplanets scatter more starlight in the optical as compared to the planets having atmospheric abundance similar to that of the present Earth.

Presenter: Taylor, Stuart F.

Title: Newly Discovered Gap in the Early Solar System is in Same Place as the ``PeakGap-Peak'' of Exoplanet Semi-Major Axes

Abstract: The recent discovery of a gap in the early solar system (Borlina et al., 2021) follows a prediction to look for precursors in proto-planetary disks of a ``peak-gap-peak'' (PGP) feature in the distribution of semi-major axes of exoplanets hosted by stars that are most like the sun, or more metal-rich than the sun. Proto-planetary disks are often thought to form separate inner and outer disks separated by a gap, but seeing this structure in the distribution of exoplanet semi-major axes is unexpected due to how it is thought that primordial features are erased by subsequent planet migration. Such a PGP structure has been shown to be present in the distribution of semi-major axes a of planets of metal-rich single stars of low enough mass to have convective zones. Just as would be expected from the inner and outer disk picture, the boundary of the gap with the outer peak is the sharpest boundary. We now find that the a of this boundary exhibits a dependence on the square root of the stellar mass, consistent with the distance corresponding to what could have been the same equilibrium temperature Teq at a time when the luminosity of the protostar was proportional to its mass. Proto-planetary disks can be expected to contain the precursors of such features in the distribution of exoplanets. We find that the peak which for solar-mass stars is located starting from 1.9 AU outward represents the semi-major axis of maximum planet formation. We hypothesize that this may be the most common starting location for planet formation to start. It is reasonable that there are favored locations with favored equilibrium temperatures for planet formation.


Presenter: Volvach, Alexandr

Title: Composite powerful flare of extremely short duration in IRAS 16293-2422

Abstract: We performed detailed monitoring, over about 1 yr, of the water-vapour maser of the protostellar, nearly solar mass object, IRAS 16293. We examine a composite powerful flare of extremely short duration ( 12 d). An unusual powerful short maser flare ∼ occurred on top of a longer duration but less powerful flare, possibly initiating a powerful maser radiation of the shorter flare. The unsaturated state of the two most powerful maser flares have been confirmed and some significant water maser parameters were obtained.


Presenter: Su, Xiang-Ning; Xie, Ji-wei

Title: Demographics of Exoplanets in Binaries: Architecture of Planetary Systems Revealed by the RV sample

Abstract: Although the sample of exoplanets in binaries has been greatly expanded, the sample heterogeneity and observational bias are obstacles toward a clear figure of exoplanet demographics in the binary environment. To overcome the obstacles, we conduct a statistical study that focuses on S-type (circumstellar) planetary systems detected by the Radial Velocity (RV) method. We try to account for observational biases by estimating, from available RV data, planet detection efficiencies for each individual system. Our main results are as follows. (1) Single (resp. multiple) planetary systems are mostly found in close (wide) binaries with separation less (more) than 100-300 AU. (2) In binaries, single and multiple-planet systems are similar in 1-D distributions of mass and period as well as eccentricity (in contrast to the “eccentricity dichotomy” found in single star systems) but different in the 2-D period-mass diagram. (3) There is a rising upper envelope in the period-mass diagram for planets in wide binaries as well as in single stars but not in close binaries. We suggest that enhanced planetary migration, collision and/or ejection in close binaries could be the potential underlying explanation for these three features.


Presenter: Yana Galarza, Jhon

Title: Evidence of rocky planet engulfment in the binary system HIP 71726/HIP 71737

Abstract: Binary stars are supposed to be chemically homogeneous, as they are born from the same molecular cloud. However, high precision chemical abundances show that some binary systems display chemical differences between the components, which could be due to planet accretion. In this work, we determine precise fundamental parameters and chemical abundances for the binary system HIP 71726/ HIP 71737. Our results show that the component HIP 71726 is more metal-rich than HIP 71737 in the refractory elements such as iron, with Δ[Fe/H] = 0,11 ±0,01 dex. Also, it has a lithium abundance ~1 dex higher than HIP 71737. The ingestion of ~10 Earth masses fully explains both the enhancement in refractory elements and the high lithium content observed in HIP 71726, reinforcing the planet engulfment scenario in some binary systems.



Keywords: Exoplanet characterization | exoplanet detection | exoplanet dynamical evolution and stability | precise stellar parameters | stellar abundances | binary stars and multiple systems | stellar magnetic activity

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