Aims. We present fundamental stellar parameters, chemical abundances, and rotational velocities for a sample of 86 evolved stars with planets (56 giants; 30 subgiants), and for a control sample of 137 stars (101 giants; 36 subgiants) without planets. The analysis was based on both high signal-to-noise and resolution echelle spectra. The main goals of this work are i) to investigate chemical differences between evolved stars that host planets and those of the control sample without planets; ii) to explore potential differences between the properties of the planets around giants and subgiants; and iii) to search for possible correlations between these properties and the chemical abundances of their host stars. Implications for the scenarios of planet formation and evolution are also discussed. Methods. The fundamental stellar parameters (T eff , log g, [Fe/H], ξ t ) were computed homogeneously using the FUNDPAR code. The chemical abundances of 14 elements (Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Zn, and Ba) were obtained using the MOOG code. Rotational velocities were derived from the full width at half maximum of iron isolated lines. Results. In agreement with previous studies, we find that subgiants with planets are, on average, more metal-rich than subgiants without planets by ∼0.16 dex. The [Fe/H] distribution of giants with planets is centered at slightly subsolar metallicities and there is no metallicity enhancement relative to the [Fe/H] distribution of giants without planets. Furthermore, contrary to recent results, we do not find any clear difference between the metallicity distributions of stars with and without planets for giants with M > 1.5 M . With regard to the other chemical elements, the analysis of the [X/Fe] distributions shows differences between giants with and without planets for some elements, particularly V, Co, and Ba. Subgiants with and without planets exhibit similar behavior for most of the elements. On the other hand, we find no evidence of rapid rotation among the giants with planets or among the giants without planets. Finally, analyzing the planet properties, some interesting trends might be emerging: i) multi-planet systems around evolved stars show a slight metallicity enhancement compared with single-planet systems; ii) planets with a 0.5 AU orbit subgiants with [Fe/H] > 0 and giants hosting planets with a 1 AU have [Fe/H] < 0; iii) higher-mass planets tend to orbit more metal-poor giants with M ≤ 1.5 M , whereas planets around subgiants seem to follow the planet-mass metallicity trend observed on dwarf hosts; iv) [X/Fe] ratios for Na, Si, and Al seem to increase with the mass of planets around giants; v) planets orbiting giants show lower orbital eccentricities than those orbiting subgiants and dwarfs, suggesting a more efficient tidal circularization or the result of the engulfment of close-in planets with larger eccentricities.

We present ALMA observations of organic molecules towards five low-mass Class 0/I protostellar disk candidates in the Serpens cluster. Three sources (Ser-emb 1, Ser-emb 8, and Ser-emb 17) present emission of CH 3 OH as well as CH 3 OCH 3 , CH 3 OCHO, and CH 2 CO, while NH 2 CHO is detected in just Ser-emb 8 and Ser-emb 17. Detecting hot corino-type chemistry in three of five sources represents a high occurrence rate given the relative sparsity of these sources in the literature, and this suggests a possible link between protostellar disk formation and hot corino formation. For sources with CH 3 OH detections, we derive column densities of 10 17 -10 18 cm −2 and rotational temperatures of ∼200-250 K. The CH 3 OH-normalized column density ratios of large, oxygen-bearing COMs in the Serpens sources and other hot corinos span two orders of magnitude, demonstrating a high degree of chemical diversity at the hot corino stage. Resolved observations of a larger sample of objects are needed to understand the origins of chemical diversity in hot corinos, and the relationship between different protostellar structural elements on disk-forming scales.

Context. The structure and composition of emerging planetary systems are likely strongly influenced by their natal environment within the protoplanetary disc at the time when the star is still gaining mass. It is therefore essential to identify and study the physical processes at play in the gas and dust close to young protostars and investigate the chemical composition of the material that is inherited from the parental cloud. Aims. The purpose of this paper is to explore and compare the physical and chemical structure of Class I low-mass protostellar sources on protoplanetary disc scales. Methods. We present a study of the dust and gas emission towards a representative sample of 12 Class I protostars from the Ophiuchus molecular cloud with the Atacama Large Millimeter/submillimeter Array (ALMA). The continuum at 0.87 mm and molecular transitions from C 17 O, C 34 S, H 13 CO + , CH 3 OH, SO 2 , and C 2 H were observed at high angular resolution (0 . 4, ∼60 au diameter) towards each source. The spectrally and spatially resolved maps reveal the kinematics and the spatial distribution of each species. Moreover, disc and stellar masses are estimated from the continuum flux and position-velocity diagrams, respectively. Results. Six of the sources show disc-like structures in C 17 O, C 34 S , or H 13 CO + emission. Towards the more luminous sources, compact emission and large line widths are seen for transitions of SO 2 that probe warm gas (E u ∼200 K). In contrast, C 17 O emission is detected towards the least evolved and less luminous systems. No emission of CH 3 OH is detected towards any of the continuum peaks, indicating an absence of warm CH 3 OH gas towards these sources. Conclusions. A trend of increasing stellar mass is observed as the envelope mass decreases. In addition, a power-law relation is seen between the stellar mass and the bolometric luminosity, corresponding to a mass accretion rate of (2.4 ± 0.6) × 10 −7 M year −1 for the Class I sources, with a minimum and maximum value of 7.5 × 10 −8 and 7.6 × 10 −7 M year −1 , respectively. This mass accretion rate is lower than the expected value if the accretion is constant in time and rather points to a scenario of accretion occurring in bursts. The differentiation between C 17 O and SO 2 suggests that they trace different physical components: C 17 O traces the densest and colder regions of the disc-envelope system, while SO 2 may be associated with regions of higher temperature, such as accretion shocks. The lack of warm CH 3 OH emission suggests that there is no hot-core-like region around any of the sources and that the CH 3 OH column density averaged over the disc is low. Finally, the combination of bolometric temperature and luminosity may indicate an evolutionary trend of chemical composition during these early stages.

Context. Astronomers recently started discovering exoplanets around binary systems. Therefore, understanding the formation and evolution of circumbinary disks and their environment is crucial for a complete scenario of planet formation. Aims. The purpose of this paper is to present the detection of a circumbinary disk around the system Oph-IRS67 and analyse its chemical and physical structure. Methods. We present high-angular-resolution (0 . 4, ∼60 AU) observations of C 17 O, H 13 CO + , C 34 S, SO 2 , C 2 H and c−C 3 H 2 molecular transitions with the Atacama Large Millimeter/submillimeter Array (ALMA) at wavelengths of 0.8 mm. The spectrally and spatially resolved maps reveal the kinematics of the circumbinary disk as well as its chemistry. Molecular abundances are estimated using the non-local thermodynamic equilibrium (LTE) radiative-transfer tool RADEX. Results. The continuum emission agrees with the position of Oph-IRS67 A and B, and reveals the presence of a circumbinary disk around the two sources. The circumbinary disk has a diameter of ∼620 AU and is well traced by C 17 O and H 13 CO + emission. Two further molecular species, C 2 H and c−C 3 H 2 , trace a higher-density region which is spatially offset from the sources (∼430 AU). Finally, SO 2 shows compact and broad emission around only one of the sources, Oph-IRS67 B. The molecular transitions which trace the circumbinary disk are consistent with a Keplerian profile on smaller disk scales ( 200 AU) and an infalling profile for larger envelope scales ( 200 AU). The Keplerian fit leads to an enclosed mass of 2.2 M . Inferred CO abundances with respect to H 2 are comparable to the canonical ISM value of 2.7 × 10 −4 , reflecting that freeze-out of CO in the disk midplane is not significant. Conclusions. Molecular emission and kinematic studies prove the existence and first detection of the circumbinary disk associated with the system Oph-IRS67. The high-density region shows a different chemistry than the disk, being enriched in carbon chain molecules. The lack of methanol emission agrees with the scenario where the extended disk dominates the mass budget in the innermost regions of the protostellar envelope, generating a flat density profile where less material is exposed to high temperatures, and thus, complex organic molecules would be associated with lower column densities. Finally, Oph-IRS67 is a promising candidate for proper motion studies and the detection of both circumstellar disks with higher-angular-resolution observations.