Laboratory of Astrophysics of Bordeaux

Abstract We present the analysis of OGLE-2014-BLG-1760, a planetary system in the galactic bulge. We combine Keck Adaptive Optics follow-up observations in K-band with re-reduced light-curve data to confirm the source and lens star identifications and stellar types. The re-reduced Microlensing Observations in Astrophysics data set had an important impact on the light-curve model. We find the Einstein ring crossing time of the event to be ∼2.5 days shorter than previous fits, which increases the planetary mass-ratio and decreases the source angular size by a factor of 0.25. Our OSIRIS images obtained 6 yr after the peak of the event show a source-lens separation of 54.20 ± 0.23 mas, which leads to a relative proper motion of μ rel = 9.14 ± 0.05 mas yr−1 and is larger than the previous light-curve-only models. Our analysis shows that the event consists of a Jupiter-mass planet of M p = 0.931 ± 0.117 M Jup orbiting a K-dwarf star of M * = 0.803 ± 0.097 M ⊙ with a K-magnitude of K L = 18.30 ± 0.05, located in the galactic bulge or bar. We also attempt to constrain the source properties using the source angular size θ * and K-magnitude. Our results favor the scenario of the source being a younger star in the galactic disk, behind the galactic bulge, but future multicolor observations are needed to constrain the source and thus the lens properties.

Abstract A bombardment of comets is thought to have occurred in the inner solar system as a result of a dynamical instability among the giant planets after gas disk dispersal. Vesta, the second largest asteroid in the main asteroid belt, likely differentiated before gas disk dispersal, implying its crust witnessed the cometary bombardment. The composition of howardite, eucrite, and diogenite (HED) meteorites, which represent fragments of Vesta’s crust, could therefore have been altered by cometary impacts. Here we combine noble gas mass spectrometry measurements, N-body simulations, collision rate calculations, and impact simulations to estimate the cometary contribution to Vesta. While our dynamical simulations indicate that Vesta likely underwent a significant number of collisions with large comets, we find no xenon cometary signature in HED meteorites. This apparent contradiction arises due to the fact that cometary impacts were at high speeds and Vesta’s weak gravitational attraction made it incapable of retaining cometary material. Smaller asteroids are even less likely to retain such material. Therefore, if a cometary xenon signature is ever detected in an asteroid belt object, it must have been acquired during formation, within the same source region as comet 67P/Churyumov-Gerasimenko, and have been implanted later into the asteroid belt.

Observations of protoplanetary disks have revealed dust rings that are likely due to the presence of pressure bumps in the disk. Because these structures tend to trap drifting pebbles, it has been proposed that pressure bumps may play an important role in the planet formation process. In this paper, we investigate the orbital evolution of a 0.1 M⊕ protoplanet embedded in a pressure bump using 2D hydrodynamical simulations of protoplanetary disks consisting of gas and pebbles. We examine the role of thermal forces generated by the pebble accretion-induced heat release, taking into account the feedback between the luminosity and the eccentricity. We also study the effect of the pebble-scattered flow on the planet’s orbital evolution. Due to the accumulation of pebbles at the pressure bump, the planet’s accretion luminosity is high enough to induce significant eccentricity growth through thermal forces. Accretion luminosity is also responsible for vortex formation at the planet’s position through baroclinic effects, which cause the planet to escape from the dust ring if dust feedback on the gas is neglected. Including the effect of the dust feedback leads to weaker vortices, which enable the planet to remain close to the pressure maximum on an eccentric orbit. Simulations in which the planet mass is allowed to increase as a consequence of pebble accretion result in the formation of giant planet cores with masses in the range of 5–20 M⊕ over ~2 × 104 yr. This occurs for moderate values of the Stokes number, St ≈ 0.01, such that the pebble drift velocity is not too high and the dust ring mass not too small. Our results suggest that pressure bumps mays be preferred locations for the formation of giant planets, but this requires a moderate level of grain growth within the disk.

The conventional observables to identify a habitable or inhabited environment in exoplanets, such as an ocean glint or abundant atmospheric O$_2$, will be challenging to detect with present or upcoming observatories. Here we suggest a new signature. A low carbon abundance in the atmosphere of a temperate rocky planet, relative to other planets of the same system, traces the presence of substantial amount of liquid water, plate tectonic and/or biomass. We show that JWST can already perform such a search in some selected systems like TRAPPIST-1 via the CO$_2$ band at $4.3\,\rm \mu m$, which falls in a spectral sweet spot where the overall noise budget and the effect of cloud/hazes are optimal. We propose a 3-step strategy for transiting exoplanets: 1) detection of an atmosphere around temperate terrestrial planets in $\sim 10$ transits for the most favorable systems, (2) assessment of atmospheric carbon depletion in $\sim 40$ transits, (3) measurements of O$_3$ abundance to disentangle between a water- vs biomass-supported carbon depletion in $\sim100$ transits. The concept of carbon depletion as a signature for habitability is also applicable for next-generation direct imaging telescopes.

ABSTRACT Atmospheric characterization of exoplanets from the ground is an actively growing field of research. In this context, we have created the ATMOSPHERIX consortium: a research project aimed at characterizing exoplanets atmospheres using ground-based high-resolution spectroscopy. This paper presents the publicly available data analysis pipeline and demonstrates the robustness of the recovered planetary parameters from synthetic data. Simulating planetary transits using synthetic transmission spectra of a hot Jupiter that were injected into real SPIRou observations of the non-transiting system Gl 15 A, we show that our pipeline is successful at recovering the planetary signal and input atmospheric parameters. We also introduce a deep learning algorithm to optimize data reduction which proves to be a reliable, alternative tool to the commonly used principal component analysis. We estimate the level of uncertainties and possible biases when retrieving parameters such as temperature and composition and hence the level of confidence in the case of retrieval from real data. Finally, we apply our pipeline onto two real transits of HD 189733 b observed with SPIRou and obtain similar results than in the literature. In summary, we have developed a publicly available and robust pipeline for the forthcoming studies of the targets to be observed in the framework of the ATMOSPHERIX consortium, which can easily be adapted to other high resolution instruments than SPIRou (e.g. VLT-CRIRES, MAROON-X, ELT-ANDES).

Several errors were inadvertently introduced in two tables during the production process. In Table 1 , the left arrows were changed to right arrows, and in Table A .1, spaces were inserted before the decimal points of the values. The corrected tables are presented here.

Close-in giant exoplanets with temperatures greater than 2,000 K (‘ultra-hot Jupiters’) have been the subject of extensive efforts to determine their atmospheric properties using thermal emission measurements from the Hubble Space Telescope (HST) and Spitzer Space Telescope1–3. However, previous studies have yielded inconsistent results because the small sizes of the spectral features and the limited information content of the data resulted in high sensitivity to the varying assumptions made in the treatment of instrument systematics and the atmospheric retrieval analysis3–12. Here we present a dayside thermal emission spectrum of the ultra-hot Jupiter WASP-18b obtained with the NIRISS13 instrument on the JWST. The data span 0.85 to 2.85 μm in wavelength at an average resolving power of 400 and exhibit minimal systematics. The spectrum shows three water emission features (at >6σ confidence) and evidence for optical opacity, possibly attributable to H−, TiO and VO (combined significance of 3.8σ). Models that fit the data require a thermal inversion, molecular dissociation as predicted by chemical equilibrium, a solar heavy-element abundance (‘metallicity’, {rm{M/H}}=1.0{3}_{-0.51}^{+1.11} times solar) and a carbon-to-oxygen (C/O) ratio less than unity. The data also yield a dayside brightness temperature map, which shows a peak in temperature near the substellar point that decreases steeply and symmetrically with longitude towards the terminators.

The location of magnetic reconnection at the Earth's magnetopause is a longstanding question in the field of magnetospheric physics. Various models  (Alexeev et al. 1998, Borovsky 2013, Trattner et al. 2007, etc) predicting the position of the X-line have been proposed. These models often rely on quantities whose global spatial distributions at the magnetopause are typically obtained through numerical simulations. In this study, we attempt to reconstruct these global distributions using only in-situ measurements. To do this, we have used statistical learning to automatically select in-situ data from four missions (Cluster, Doublestar, THEMIS, MMS). The 3D reconstruction of the magnetic field draping in the dayside magnetosheath (Michotte de Welle et al. 2022) reveals significant differences with the model of Kobel et Fluckiger 1994 for a certain range of IMF orientations. As this magnetostatic model is frequently used to predict magnetic shear at the magnetopause, we will examine the implications of these differences on the X-lines maximizing this quantity (Trattner et al. 2007). We will also extend this discussion to other relevant quantities such as current density and the Cassak-Shay reconnection rate, which can also be accessed using in-situ measurements.

Context.Gas phase Elemental abundances in molecular CloudS (GEMS) is an IRAM 30-m Large Program aimed at determining the elemental abundances of carbon (C), oxygen (O), nitrogen (N), and sulfur (S) in a selected set of prototypical star-forming filaments. In particular, the elemental abundance of S remains uncertain by several orders of magnitude, and its determination is one of the most challenging goals of this program.Aims.This paper aims to constrain the sulfur elemental abundance in Taurus, Perseus, and Orion A based on the GEMS molecular database. The selected regions are prototypes of low-mass, intermediate-mass, and high-mass star-forming regions, respectively, providing useful templates for the study of interstellar chemistry.Methods.We have carried out an extensive chemical modeling of the fractional abundances of CO, HCO+, HCN, HNC, CS, SO, H2S, OCS, and HCS+to determine the sulfur depletion toward the 244 positions in the GEMS database. These positions sample visual extinctions fromAV~ 3 mag to >50 mag, molecular hydrogen densities ranging from a few × 103cm−3to 3 × 106cm−3, andTk~ 10–35 K. We investigate the possible relationship between sulfur depletion and the grain charge distribution in different environments.Results.Most of the positions in Taurus and Perseus are best fitted assuming early-time chemistry,t= 0.1 Myr, ζH2~ (0.5−1) × 10−16s−1, and [S/H] ~ 1.5 × 10−6. On the contrary, most of the positions in Orion are fitted witht= 1 Myr and ζH2~ 10−17s−1. Moreover, ~40% of the positions in Orion are best fitted assuming the undepleted sulfur abundance, [S/H] ~ 1.5 × 10−5. We find a tentative trend of sulfur depletion increasing with density.Conclusions.Our results suggest that sulfur depletion depends on the environment. While the abundances of sulfur-bearing species are consistent with undepleted sulfur in Orion, a depletion factor of ~20 is required to explain those observed in Taurus and Perseus. We propose that differences in the grain charge distribution might explain these variations. Grains become negatively charged at a visual extinction ofAV~ 3.5 mag in Taurus and Perseus. At this low visual extinction, the S+abundance is high,X(S+) > 10−6, and the electrostatic attraction between S+and negatively charged grains could contribute to enhance sulfur depletion. In Orion, the net charge of grains remains approximately zero until higher visual extinctions (AV~ 5.5 mag), where the abundance of S+is already low because of the higher densities, thus reducing sulfur accretion. The shocks associated with past and ongoing star formation could also contribute to enhance [S/H].

Reliable neutron star mass measurements are key to determining the equation of state of cold nuclear matter, but such measurements are rare. Black widows and redbacks are compact binaries consisting of millisecond pulsars and semi-degenerate companion stars. Spectroscopy of the optically bright companions can determine their radial velocities, providing inclination-dependent pulsar mass estimates. Although inclinations can be inferred from subtle features in optical light curves, such estimates may be systematically biased due to incomplete heating models and poorly understood variability. Using data from the Fermi Large Area Telescope, we have searched for gamma-ray eclipses from 49 spider systems, discovering significant eclipses in 7 systems, including the prototypical black widow PSR B1957+20. Gamma-ray eclipses require direct occultation of the pulsar by the companion, and so the detection, or significant exclusion, of a gamma-ray eclipse strictly limits the binary inclination angle, providing new robust, model-independent pulsar mass constraints. For PSR B1957+20, the eclipse implies a much lighter pulsar (1.81 ± 0.07 solar masses) than inferred from optical light curve modelling.