DALI physical-chemical disk models presented in 'Azimuthal C/O Variations in a Planet-Forming Disk' (Keyte et al. 2023). There are two individual models included here. The 'baseline' model is used to produce outputs for the region of the disk where C/O=0.5. The 'elevated' model is used to produce outputs for the regions of the disk where C/O=1.5. The baseline model can be run in the normal way, but the outputs themselves are already included in the folder. The 'elevated' model will not run in the regular way. The source code has been edited so that it can take in the abundances from a previous run as the starting point for the chemistry (in the form of an out.dat style table). The outputs are already included, but should you want to rerun the model yourself, follow the steps in the readme file within the folder. The final 'composite' model presented in the paper is created by splicing together the outputs (as described in Keyte et al. 2023). This is achieved using a custom Python script, please contact me if you would like to use this.
Context. Few exoplanets around hot stars with radiative envelopes have been discovered, although new observations from the TESS mission are improving this. Stars with radiative envelopes have little mixing at their surface, and thus their surface abundances provide a sensitive test case for a variety of processes, including potentially star–planet interactions. Atomic diffusion is particularly important in these envelopes, producing chemically peculiar objects such as Am and HgMn stars. Aims. An exoplanet candidate around the B6 star HD 235349 was identified by TESS. Here we determine the nature of this transiting object and identify possible chemical peculiarities in the star. Methods. HD 235349 was observed using the long-slit spectrograph at Tartu Observatory, as well as photometrically by the TESS mission. The spectra were modeled to determine stellar parameters and chemical abundances. The photometric light curve was then analyzed in the context of the stellar parameters to determine properties of the transiting object. Results. We find the transiting object is a low-mass stellar companion, not a planet. However, the primary of this eclipsing binary is a rare type of chemically peculiar star. A strong overabundance of P is found with overabundances of Ne and Nd and mild overabundances of Ti and Mn, while He is mildly underabundant. There is also clear evidence for vertical stratification of P in the atmosphere of the star. The lack of Hg and the weak Mn overabundance suggests that this is not a typical HgMn star. It may be in the class of helium-weak phosphorus-gallium (He-weak PGa) stars or an intermediate between these two classes. Conclusions. We show that HD 235349 is a rare type of chemically peculiar star (He-weak PGa) in an eclipsing binary system with a low-mass stellar companion. This appears to be the first He-weak PGa star discovered in an eclipsing binary.
Modern astronomy has finally been able to observe protoplanetary disks in reasonable resolution and detail, unveiling the processes happening during planet formation. These observed processes are understood under the framework of disk-planet interaction, a process studied analytically and modeled numerically for over 40 years. Long a theoreticians' game, the wealth of observational data has been allowing for increasingly stringent tests of the theoretical models. Modeling efforts are crucial to support the interpretation of direct imaging analyses, not just for potential detections but also to put meaningful upper limits on mass accretion rates and other physical quantities in current and future large-scale surveys. This white paper addresses the questions of what efforts on the computational side are required in the next decade to advance our theoretical understanding, explain the observational data, and guide new observations. We identified the nature of accretion, ab initio planet formation, early evolution, and circumplanetary disks as major fields of interest in computational planet formation. We recommend that modelers relax the approximations of alpha-viscosity and isothermal equations of state, on the grounds that these models use flawed assumptions, even if they give good visual qualitative agreement with observations. We similarly recommend that population synthesis move away from 1D hydrodynamics. The computational resources to reach these goals should be developed during the next decade, through improvements in algorithms and the hardware for hybrid CPU/GPU clusters. Coupled with high angular resolution and great line sensitivity in ground based interferometers, ELTs and JWST, these advances in computational efforts should allow for large strides in the field in the next decade.
Abstract The elemental carbon-to-oxygen ratio (C/O) in the atmosphere of a giant planet is a promising diagnostic of that planet’s formation history in a protoplanetary disk. Alongside efforts in the exoplanet community to measure C/O in planetary atmospheres, observational and theoretical studies of disks are increasingly focused on understanding how the gas-phase C/O varies both with radial location and between disks. This is mostly tied to the icelines of major volatile carriers such as CO and H2O. Using ALMA observations of CS and SO, we have unearthed evidence for an entirely novel type of C/O variation in the protoplanetary disk around HD 100546: an azimuthal variation from a typical, oxygen-dominated ratio (C/O 0.5) to a carbon-dominated ratio (C/O&1.0). We show that the spatial distribution and peculiar line kinematics of both CS and SO molecules can be well explained by azimuthal variations in the C/O ratio. We propose a shadowing mechanism that could lead to such a chemical dichotomy. Our results imply that tracing the formation history of giant exoplanets using their atmospheric C/O ratios will need to take into account time-dependent azimuthal C/O variations in a planet’s accretion zone.
Abstract We present high-resolution millimeter continuum imaging of the disk surrounding the young star CI Tau, a system hosting the first hot Jupiter candidate in a protoplanetary disk system. The system has extended mm emission on which are superposed three prominent annular gaps at radii ∼13, 39, and 100 au. We argue that these gaps are most likely to be generated by massive planets so that, including the hot Jupiter, the system contains four gas giant planets at an age of only 2 Myr. Two of the new planets are similarly located to those inferred in the famous HL Tau protoplanetary disk; in CI Tau, additional observational data enables a more complete analysis of the system properties than was possible for HL Tau. Our dust and gas dynamical modeling satisfies every available observational constraint and points to the most massive ensemble of exoplanets ever detected at this age, with its four planets spanning a factor 1000 in orbital radius. Our results show that the association between hot Jupiters and gas giants on wider orbits, observed in older stars, is apparently in place at an early evolutionary stage.
Of the roughly 3000 neutron stars known, only a handful have sub-stellar companions. The most famous of these are the low-mass planets around the millisecond pulsar B1257+12. New evidence indicates that observational biases could still hide a wide variety of planetary systems around most neutron stars. We consider the environment and physical processes relevant to neutron star planets, in particular the effect of X-ray irradiation and the relativistic pulsar wind on the planetary atmosphere. We discuss the survival time of planet atmospheres and the planetary surface conditions around different classes of neutron stars, and define a neutron star habitable zone. Depending on as-yet poorly constrained aspects of the pulsar wind, both Super-Earths around B1257+12 could lie within its habitable zone.
KELT-9b is an ultra-hot Jupiter observed to be undergoing extreme mass loss. Its A0-type host star has a radiative envelope, which makes its surface layers prone to retaining recently accreted material. To search for potential signs of planetary material polluting the stellar surface, we carry out the most comprehensive chemical characterisation of KELT-9 to-date. New element detections include Na and Y, which had previously been detected in the ultra-hot Jupiter but not studied in the star; these detections complete the set of nine elements measured in both star and planet. In comparing KELT-9 with similar open cluster stars we find no strong anomalies. This finding is consistent with calculations of photospheric pollution accounting for stellar mixing and using observationally estimated KELT-9b mass loss rates. We also rule out recent, short-lived intensive mass transfer such as the stellar ingestion of an Earth-mass exomoon.
High resolution line spectra of star-forming regions are mines of information: they provide unique clues to reconstruct the chemical, dynamical, and physical structure of the observed source. We present the first results from the Herschel key project "Chemical HErschel Surveys of Star forming regions", CHESS. We report and discuss observations towards five CHESS targets, one outflow shock spot and four protostars with luminosities bewteen 20 and 2 × 105 : L1157-B1, IRAS 16293-2422, OMC2-FIR4, AFGL 2591, and NGC 6334I. The observations were obtained with the heterodyne spectrometer HIFI on board Herschel, with a spectral resolution of 1 MHz. They cover the frequency range 555–636 GHz, a range largely unexplored before the launch of the Herschel satellite. A comparison of the five spectra highlights spectacular differences in the five sources, for example in the density of methanol lines, or the presence/absence of lines from S-bearing molecules or deuterated species. We discuss how these differences can be attributed to the different star-forming mass or evolutionary status.
