J. Schneider’s research while affiliated with Paris Observatory and other places

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Publications (189)


The PLATO Mission
  • Preprint
  • File available

June 2024

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344 Reads

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3 Citations

Heike Rauer

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[...]

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Konstanze Zwintz

PLATO (PLAnetary Transits and Oscillations of stars) is ESA's M3 mission designed to detect and characterise extrasolar planets and perform asteroseismic monitoring of a large number of stars. PLATO will detect small planets (down to <2 R_(Earth)) around bright stars (<11 mag), including terrestrial planets in the habitable zone of solar-like stars. With the complement of radial velocity observations from the ground, planets will be characterised for their radius, mass, and age with high accuracy (5 %, 10 %, 10 % for an Earth-Sun combination respectively). PLATO will provide us with a large-scale catalogue of well-characterised small planets up to intermediate orbital periods, relevant for a meaningful comparison to planet formation theories and to better understand planet evolution. It will make possible comparative exoplanetology to place our Solar System planets in a broader context. In parallel, PLATO will study (host) stars using asteroseismology, allowing us to determine the stellar properties with high accuracy, substantially enhancing our knowledge of stellar structure and evolution. The payload instrument consists of 26 cameras with 12cm aperture each. For at least four years, the mission will perform high-precision photometric measurements. Here we review the science objectives, present PLATO's target samples and fields, provide an overview of expected core science performance as well as a description of the instrument and the mission profile at the beginning of the serial production of the flight cameras. PLATO is scheduled for a launch date end 2026. This overview therefore provides a summary of the mission to the community in preparation of the upcoming operational phases.

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The “Drake Equation” of Exomoons—A Cascade of Formation, Stability and Detection

February 2024

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50 Reads

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2 Citations

Universe

After 25 years of the prediction of the possibility of observations, and despite the many hundreds of well-studied transiting exoplanet systems, we are still waiting for the announcement of the first confirmed exomoon. We follow the “cascade” structure of the Drake equation but apply it to the chain of events leading to a successful detection of an exomoon. The scope of this paper is to reveal the structure of the problem, rather than to give a quantitative solution. We identify three important steps that can lead us to discovery. The steps are the formation, the orbital dynamics and long-term stability, and the observability of a given exomoon in a given system. This way, the question will be closely related to questions of star formation, planet formation, five possible pathways of moon formation; long-term dynamics of evolved planet systems involving stellar and planetary rotation and internal structure; and the proper evaluation of the observed data, taking the correlated noise of stellar and instrumental origin and the sampling function also into account. We highlight how a successful exomoon observation and the interpretations of the expected further measurements prove to be among the most complex and interdisciplinary questions in astrophysics.




Six transiting planets and a chain of Laplace resonances in TOI-178

January 2021

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191 Reads

Determining the architecture of multi-planetary systems is one of the cornerstones of understanding planet formation and evolution. Resonant systems are especially important as the fragility of their orbital configuration ensures that no significant scattering or collisional event has taken place since the earliest formation phase when the parent protoplanetary disc was still present. In this context, TOI-178 has been the subject of particular attention since the first TESS observations hinted at a 2:3:3 resonant chain. Here we report the results of observations from CHEOPS, ESPRESSO, NGTS, and SPECULOOS with the aim of deciphering the peculiar orbital architecture of the system. We show that TOI-178 harbours at least six planets in the super-Earth to mini-Neptune regimes, with radii ranging from 1.152(-0.070/+0.073) to 2.87(-0.13/+0.14) Earth radii and periods of 1.91, 3.24, 6.56, 9.96, 15.23, and 20.71 days. All planets but the innermost one form a 2:4:6:9:12 chain of Laplace resonances, and the planetary densities show important variations from planet to planet, jumping from 1.02(+0.28/-0.23) to 0.177(+0.055/-0.061) times the Earth's density between planets c and d. Using Bayesian interior structure retrieval models, we show that the amount of gas in the planets does not vary in a monotonous way, contrary to what one would expect from simple formation and evolution models and unlike other known systems in a chain of Laplace resonances. The brightness of TOI-178 allows for a precise characterisation of its orbital architecture as well as of the physical nature of the six presently known transiting planets it harbours. The peculiar orbital configuration and the diversity in average density among the planets in the system will enable the study of interior planetary structures and atmospheric evolution, providing important clues on the formation of super-Earths and mini-Neptunes.


Six transiting planets and a chain of Laplace resonances in TOI-178

January 2021

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49 Reads

Determining the architecture of multi-planetary systems is one of the cornerstones of understanding planet formation and evolution. Resonant systems are especially important as the fragility of their orbital configuration ensures that no significant scattering or collisional event has taken place since the earliest formation phase when the parent protoplanetary disc was still present. In this context, TOI-178 has been the subject of particular attention since the first TESS observations hinted at the possible presence of a near 2:3:3 resonant chain. Here we report the results of observations from CHEOPS, ESPRESSO, NGTS, and SPECULOOS with the aim of deciphering the peculiar orbital architecture of the system. We show that TOI-178 harbours at least six planets in the super-Earth to mini-Neptune regimes, with radii ranging from 1.152‒0.070+0.073 to 2.87‒0.13+0.14 Earth radii and periods of 1.91, 3.24, 6.56, 9.96, 15.23, and 20.71 days. All planets but the innermost one form a 2:4:6:9:12 chain of Laplace resonances, and the planetary densities show important variations from planet to planet, jumping from 1.02‒0.23+0.28 to 0.177‒0.061+0.055 times the Earth's density between planets c and d. Using Bayesian interior structure retrieval models, we show that the amount of gas in the planets does not vary in a monotonous way, contrary to what one would expect from simple formation and evolution models and unlike other known systems in a chain of Laplace resonances. The brightness of TOI-178 (H = 8.76 mag, J = 9.37 mag, V = 11.95 mag) allows for a precise characterisation of its orbital architecture as well as of the physical nature of the six presently known transiting planets it harbours. The peculiar orbital configuration and the diversity in average density among the planets in the system will enable the study of interior planetary structures and atmospheric evolution, providing important clues on the formation of super-Earths and mini-Neptunes.


Fig. 1.1: Number of dwarf spheroidal galaxy stars within a high precision astrometry missionfield with expected plane-of-sky errors lower than half the galaxy's velocity dispersion as a function of the galaxy's estimated mass-to-light ratio within the effective (half-projected-light) radius of the galaxy. Luminosities and total masses within the half-light radii are mainly from Walker et al. (2009).
Fig. 1.4: Expected proper motions of HVS5 under different assumptions about the shape and orientation of the DM halo. The families of models are shown with the halo major axis along the Galactic X-(red squares), Y-(blue triangles), and Z-(green circles) coordinates. The solid line shows how the centroid of the proper motions will shift with a different distance to HVS5.
Fig. 1.5: Example of a reconstruction of the Galactic halo shape from a high precision astrometry mission measurement of proper motion of HVS5. The assumed proper motions correspond to a prolate model with q X = q Y = 0.8 q Z , marked by a red square. Shaded contours represent confidence limits corresponding to the expected 1, 2, and 3 σ µ proper motion errors.
Fig. 1.6: Face-on view of the evolution of the perturbation of a Galactic Disc due to a DM subhalo of mass 3% of the mass of the disc crossing the disc from above. The upper and lower panels are before and after the crossing, respectively, for different times 125, 75 and 25 Myr before the crossing and 25,75,125 Myr after (from left to right). The mean displacement amplitude is indicated in the color bar, while the contours indicate the amplitude of the bending mode in velocity space, using plain lines for positive values and dashed lines for negative values. The green line shows the projected orbit of the subhalo (dashed line after the impact with the disc). The green triangle shows the current location of the subhalo on its orbit. The red lines are our potential lines of sight for Theia, spaced by 10 • in longitude with one pointing above the plane and one below the plane, that will allow us to map the disc perturbation behind the Galactic Center.
Fig. 1.11: An example where astrometry breaks the degeneracy. Two simulated planetary systems are around a solar-type star at 10 pc, with two Jupiter-like planets at 0.5 and 2.5 AU (left). One is co-planar (dotted black line), the other has a mutual inclination of 30 • (full red line). The two corresponding RV curves are shown (middle), as well as the two astrometric ones (right). Curves are identical in the former case, but clearly separated in the latter revealing the inclined orbits.

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ESA Voyage 2050 white paper -- Faint objects in motion: the new frontier of high precision astrometry

October 2019

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54 Reads

Sky survey telescopes and powerful targeted telescopes play complementary roles in astronomy. In order to investigate the nature and characteristics of the motions of very faint objects, a flexibly-pointed instrument capable of high astrometric accuracy is an ideal complement to current astrometric surveys and a unique tool for precision astrophysics. Such a space-based mission will push the frontier of precision astrometry from evidence of earth-massed habitable worlds around the nearest starts, and also into distant Milky way objects up to the Local Group of galaxies. As we enter the era of the James Webb Space Telescope and the new ground-based, adaptive-optics-enabled giant telescopes, by obtaining these high precision measurements on key objects that Gaia could not reach, a mission that focuses on high precision astrometry science can consolidate our theoretical understanding of the local universe, enable extrapolation of physical processes to remote redshifts, and derive a much more consistent picture of cosmological evolution and the likely fate of our cosmos. Already several missions have been proposed to address the science case of faint objects in motion using high precision astrometry ESA missions: NEAT for M3, micro-NEAT for S1 mission, and Theia for M4 and M5. Additional new mission configurations adapted with technological innovations could be envisioned to pursue accurate measurements of these extremely small motions. The goal of this white paper is to address the fundamental science questions that are at stake when we focus on the motions of faint sky objects and to briefly review quickly instrumentation and mission profiles.


Transiting exoplanets from the CoRoT space mission. XXIX. The hot Jupiters CoRoT-30 b and CoRoT-31 b

March 2019

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59 Reads

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1 Citation

Astronomy and Astrophysics

Aims. We report the discovery as well as the orbital and physical characterizations of two new transiting giant exoplanets, CoRoT-30 b and CoRoT-31 b, with the CoRoT space telescope. Methods. We analyzed two complementary data sets: photometric transit light curves measured by CoRoT, and radial velocity curves measured by the HARPS spectrometer. To derive the absolute masses and radii of the planets, we modeled the stars from available magnitudes and spectra. Results. We find that CoRoT-30 b is a warm Jupiter on a close-to-circular 9.06-day orbit around a G3V star with a semi-major axis of about 0.08 AU. It has a radius of 1.01 ± 0.08 RJ, a mass of 2.90 ± 0.22 MJ, and therefore a mean density of 3.45 ± 0.65 g cm−3. The hot Jupiter CoRoT-31 b is on a close-to-circular 4.63-day orbit around a G2 IV star with a semi-major axis of about 0.05 AU. It has a radius of 1.46 ± 0.30 RJ, a mass of 0.84 ± 0.34 MJ, and therefore a mean density of 0.33 ± 0.18 g cm−3. Conclusions. Neither system seems to support the claim that stars hosting planets are more depleted in lithium. The radii of both planets are close to that of Jupiter, but they differ in mass; CoRoT-30 b is ten times denser than CoRoT-31 b. The core of CoRoT-30 b would weigh between 15 and 75 Earth masses, whereas relatively weak constraints favor no core for CoRoT-31 b. In terms of evolution, the characteristics of CoRoT-31 b appear to be compatible with the high-eccentricity migration scenario, which is not the case for CoRoT-30 b. The angular momentum of CoRoT-31 b is currently too low for the planet to evolve toward synchronization of its orbital revolution with stellar rotation, and the planet will slowly spiral-in while its host star becomes a red giant. CoRoT-30 b is not synchronized either: it looses angular momentum owing to stellar winds and is expected reach steady state in about 2 Gyr. CoRoT-30 and 31, as a pair, are a truly remarkable example of diversity in systems with hot Jupiters.


Co-orbital exoplanets from close-period candidates: The TOI-178 case

February 2019

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87 Reads

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30 Citations

Astronomy and Astrophysics

Despite the existence of co-orbital bodies in the solar system, and the prediction of the formation of co-orbital planets by planetary system formation models, no co-orbital exoplanets (also called trojans) have been detected thus far. Here we study the signature of co-orbital exoplanets in transit surveys when two planet candidates in the system orbit the star with similar periods. Such a pair of candidates could be discarded as false positives because they are not Hill-stable. However, horseshoe or long-libration-period tadpole co-orbital configurations can explain such period similarity. This degeneracy can be solved by considering the transit timing variations (TTVs) of each planet. We subsequently focus on the three-planet-candidate system TOI-178: the two outer candidates of that system have similar orbital periods and were found to have an angular separation close to π3 during the TESS observation of sector 2. Based on the announced orbits, the long-term stability of the system requires the two close-period planets to be co-orbital. Our independent detrending and transit search recover and slightly favour the three orbits close to a 3:2:2 resonant chain found by the TESS pipeline, although we cannot exclude an alias that would put the system close to a 4:3:2 configuration. We then analyse the co-orbital scenario in more detail, and show that despite the influence of an inner planet just outside the 2:3 MMR, this potential co-orbital system could be stable on a gigayear time-scale for a variety of planetary masses, either on a trojan or a horseshoe orbit. We predict that large TTVs should arise in such a configuration with a period of several hundred days. We then show how the mass of each planet can be retrieved from these TTVs.


Planets, candidates, and binaries from the CoRoT/Exoplanet programme

November 2018

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5 Reads

The CoRoT space mission observed 163 665 stars over 26 stellar fields in the faint star channel. The exoplanet teams detected a total of 4123 transit-like features in the 177 454 light curves. We present the complete re-analysis of all these detections carried out with the same softwares so that to ensure their homogeneous analysis. Although the vetting process involves some human evaluation, it also involves a simple binary flag system over basic tests: detection significance, presence of a secondary, difference between odd and even depths, colour dependence, V-shape transit, and duration of the transit. We also gathered the information from the large accompanying ground-based programme carried out on the planet candidates and checked how useful the flag system could have been at the vetting stage of the candidates. From the initial list of transit-like features, we identified and separated 824 false alarms of various kind, 2269 eclipsing binaries among which 616 are contact binaries and 1653 are detached ones, 37 planets and brown dwarfs, and 557 planet candidates. We provide the catalogue of all these transit-like features, including false alarms. For the planet candidates, the catalogue gives not only their transit parameters but also the products of their light curve modelling: reduced radius, reduced semi-major axis, and impact parameter, together with a summary of the outcome of follow-up observations when carried out and their current status. For the detached eclipsing binaries, the catalogue provides, in addition to their transit parameters, a simple visual classification. Among the planet candidates whose nature remains unresolved, we estimate that eight (within an error of three) planets are still to be identified. After correcting for geometric and sensitivity biases, we derived planet and brown dwarf occurrences and confirm disagreements with Kepler estimates, as previously reported by other authors from the analysis of the first runs: small-size planets with orbital period less than ten days are underabundant by a factor of three in the CoRoT fields whereas giant planets are overabundant by a factor of two. These preliminary results would however deserve further investigations using the recently released CoRoT light curves that are corrected of the various instrumental effects and a homogeneous analysis of the stellar populations observed by the two missions.


Citations (43)


... For a given ω, maximizing the likelihood with respect to A and B is equivalent to to minimizing the sum of squares, and it is a linear problem. The Lomb-Scargle periodogram is then the difference of the log-likelihoods of models H0 and Kω as a function of ω. , and ∆ log R ′ HK (Noyes 1984)), and RV time series (RV) of the ESPRESSO (Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations) data of the star TOI 178178 (Leleu et al. 2021). The time series of ∆BIS, log R ′ HK and RV are shown in Fig. 7. Periodograms are expressed in reduction in sum of squares (RSS), normalized -that is, the difference between residual sum of squares after fitting H0 and Kω, divided by that of the H0 residuals (see Eqs. 11. and 12.). ...

Reference:

Statistical Methods for Exoplanet Detection with Radial Velocities
Six transiting planets and a chain of Laplace resonances in TOI-178
  • Citing Article
  • May 2021

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Y. Alibert

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N. C. Hara

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M. Zapatero Osorio

... Specific 3-body systems were studied by different means. Let us only mention some of those like the asteroids in the Solar System (Nesvornỳ and Morbidelli 1998) and exoplanetary systems like TRAPPIST-1 (Gillon et al. 2017;Luger et al. 2017) or TOI-178 (Leleu et al. 2021). A model for zeroth-order 3-body resonances was provided by Quillen (2011) who also derived a resonance overlap criterion. ...

Six transiting planets and a chain of Laplace resonances in TOI-178

... As a result, the mission faced significant challenges in detecting and confirming planets. Nevertheless, CoRoT successfully identified several dozen hot Jupiters and discovered CoRoT-7 b, the first known transiting super-Earth orbiting a Sun-like star (see the green points in Figure 1; Deleuil et al. 2018). ...

Planets, candidates, and binaries from the CoRoT/Exoplanet programme: The CoRoT transit catalogue

Astronomy and Astrophysics

... Re-analysing the 5.5 years of the CoRoT/Exoplanet programme with an homogeneous transit detection pipeline and selecting the candidates to minimise the bias introduced by the follow-up observations, Deleuil et al. (2018) derived final values for the occurrence rates of hot jupiters in each of the CoRoT eyes. They reported values of 0.95±0.26% ...

Planets, candidates, and binaries from the CoRoT/Exoplanet program The CoRoT transit catalog
  • Citing Article
  • January 2018

Astronomy and Astrophysics

... In the last three decades, we have seen tremendous progress on discovering new exoplanets using multi-prong detection methods including transit photometry, radial velocity (RV), direct imaging, pulsar/variable star timing, astrometry, and microlensing [1]. With on-going space telescopes including Gaia [2], the Transiting Exoplanet Survey Satellite (TESS) [3], the CHaracterising ExOPlanets Satellite (CHEOPS) [4] and the James Webb Space Telescope (JWST) [5], along with planned future telescopes [6][7][8][9], we will not only discover more exoplanets, but also study their properties in great detail. Other than searching for potentially habitable exoplanets, many science questions like planet formation and evolution, planet interiors, and atmospheric properties will be addressed. ...

Reference:

Dark Exoplanets
The PLATO 2.0 mission
  • Citing Article
  • October 2013

... This is likely due to the existence of local minima at high eccentricity (see fig. 4, section 2.2.3). We simulate a one planet system on CoRoT-9 28 measurements (Bonomo et al. 2017b), the eccentricity is generated with a Beta distribution (a=0.867, b=3.03), angles are uniformly distributed and the period is fixed to 95 days. ...

A deeper view of the CoRoT-9 planetary system. A small non-zero eccentricity for CoRoT-9b likely generated by planet-planet scattering

Astronomy and Astrophysics

... The second row in each planetary entry give the accuracy of the result. Note that when asymmetrical error bars were provided, we give here the largest value 20 Deleuil et al. (2012), 21 Pätzold et al. (2012), 22 Moutou et al. (2014), 23 Rouan et al. (2012), 24 Alonso et al. (2014), 25 Almenara et al. (2013), 26 Almenara et al. (2013), 26 Parviainen et al. (2014), 27 Cabrera et al. (2015), 28 Bordé et al. (2018), 29 Boufleur et al. (2018), 30 Csizmadia et al. (2015) Despite the complexity of the CoRoT detection and vetting processes which involved different pipelines and methods that evolved during the mission lifetime and the lack of a proper estimate of the mission detection sensitivity, these planets were used to derive first-order occurrence rates (Deleuil et al. 2018). ...

CoRoT-22 b: a validated 4.9 R-circle plus exoplanet in 10-d orbit
  • Citing Article
  • November 2014

... The presence of starspots and faculae, for example, can induce almost periodic variations in Kepler's light curves over time scales of weeks to months. These stellar activity signatures are seen as the main source of noise in the search for transits of small exoplanets (Earths and Super-Earths) and can lead to incorrect measurements of the planet's radius (Barros et al., 2014). ...

Revisiting the transits of CoRoT-7b at a lower activity level
  • Citing Article
  • September 2014

... The second row in each planetary entry give the accuracy of the result. Note that when asymmetrical error bars were provided, we give here the largest value 20 Deleuil et al. (2012), 21 Pätzold et al. (2012), 22 Moutou et al. (2014), 23 Rouan et al. (2012), 24 Alonso et al. (2014), 25 Almenara et al. (2013), 26 Almenara et al. (2013), 26 Parviainen et al. (2014), 27 Cabrera et al. (2015), 28 Bordé et al. (2018), 29 Boufleur et al. (2018), 30 Csizmadia et al. (2015) Despite the complexity of the CoRoT detection and vetting processes which involved different pipelines and methods that evolved during the mission lifetime and the lack of a proper estimate of the mission detection sensitivity, these planets were used to derive first-order occurrence rates (Deleuil et al. 2018). ...

Transiting exoplanets from the CoRoT space mission. XXIV. CoRoT-25b and CoRoT-26b: two low-density giant planets
  • Citing Article
  • January 2013

Astronomy and Astrophysics