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We present MUSE deep integral-field unit spectroscopy of three planetary nebulae(PNe) with high abundance discrepancy factors (ADF > 20): NGC 6778, M 1-42 and Hf 2-2. We have constructed flux maps for more than 40 emission lines, and use them to build extinction, electron temperature (T$_e$), electron density (n$_e$), and ionic abundances maps of a number of ionic species. The effects of the contribution of recombination to the auroral [N II] and [O II] lines on T$_e$ and the abundance maps of low-ionization species are evaluated using recombination diagnostics. As a result, low T$_e$ values and a downward gradient of T$_e$ are found toward the inner zones of each PN. Spatially, this nearly coincides with the increase of abundances of heavy elements measured using recombination lines in the inner regions of PNe, and strongly supports the presence of two distinct gas phases: a cold and metal-rich and a warm one with "normal" metal content. We have simultaneously constructed, for the first time, the ADF maps of O$^+$ and O$^{2+}$ and found that they centrally peak for all three PNe under study. We show that the main issue when trying to compute realistic abundances from either ORLs or CELs is to estimate the relative contribution of each gas component to the H I emission, and we present a method to evaluate it. It is also found that, for the studied high-ADF PNe, the amount of oxygen in the cold and warm regions is of the same order., 20 pages, 10 Tables, 16 Figures. Additional material in appendix, 1 Table and 22 Figures. This article has been accepted for publication in MNRAS, Published by Oxford University Press on behalf of the Royal Astronomical Society

Aims. The project aims to understand better the role of wide brown dwarf companions on planetary systems. Methods. We obtained high-resolution spectra of six bright stars with co-moving wide substellar companions with the SONG, CARMENES, and STELLA high-resolution spectrographs. We used these spectra to derive radial velocities together with a complete set of stellar physical parameters. We then investigated radial velocities signals and discussed the fraction of planets in such systems. We also re-analyzed the ages of our targets, which were used to derive the physical parameters of wide brown dwarf companions. Finally, a compilation of systems with known planets from the literature is considered along with our sample to search for possible peculiarities in their parameter distributions. Results. Based on the derived ages of six observed systems, we re-computed the masses of the wide companions, confirming their substellar nature. We confirmed planets in the HD 3651 and HIP 70849 systems and found a new planetary candidate in the HD 46588 system. In our survey, which is sensitive mostly to Neptune-mass planets at short periods of a few days and Saturn-mass planets at longer periods of hundreds of days, we derived a frequency of planets orbiting stars with wide brown dwarf companions below 70% with the uncertainties included. Comparing the parameter distributions of our sample with single stars, we observe the enhancement of planets with short periods below six days in systems with a wide stellar companion. Finally, planets in systems with wide BD companions follow their own eccentricity distribution with a maximum at $\sim0.65$ and have periods larger than 40 days, masses larger than $0.1\,M_J$, and eccentricities larger than 0.4., 28 pages, 31 figures, accepted for publication in Astronomy & Astrophysics

56 UMa is a wide binary system that contains a chemically peculiar red giant and a faint companion. Due to its surface chemical abundances, the red giant was classified as a barium (Ba) star. This implies that the companion has to be a white dwarf, since Ba stars form when mass is transferred to them from an s-process rich Asymptotic Giant Branch (AGB) star. However, in the case of 56 UMa, the companion might be too massive to be the progeny of an AGB star that efficiently produced s-process elements such as barium. In this Letter, we revisit the orbital parameters of the system and perform a full spectral analysis with the goal of investigating the Ba-star classification of the giant and unravelling the nature of its faint companion. We combined radial-velocity and astrometric data to refine the orbital parameters of the system, including the orbital inclination and the companion mass. Then, we re-determined the stellar parameters of the giant and its chemical abundances using high-resolution HERMES spectra. Finally, we investigated the morphology of the interstellar gas in the vicinity of the system. The faint component in 56 UMa has a mass of $1.31 \pm 0.12$ M$_{\odot}$, which, together with the mixed s+r abundance profile of the red giant, confirms that the giant is not a standard barium star. Additionally, the clear identification of a cavity surrounding 56 UMa could indicate that a supernova explosion occurred about 10 5 years ago in the system, suggesting that the faint companion might be a neutron star. However, finding an evolutionary scenario that explains all the observables is not trivial, so we discuss different possible configurations of the system and their respective merits., Comment: Accepted for publication in A&AL

The evolution of young stars and disks is driven by the interplay of several processes, notably accretion and ejection of material. Critical to correctly describe the conditions of planet formation, these processes are best probed spectroscopically. About five-hundred orbits of the Hubble Space Telescope (HST) are being devoted in 2020-2022 to the ULLYSES public survey of about 70 low-mass (M, Comment: Accepted for publication on Astronomy & Astrophysics. 15 pages + appendix, language edited version

We present results of our study of the close pre-main sequence spectroscopic binary CVSO 104 in Ori OB1, based on data obtained within the PENELLOPE legacy program. We derive, for the first time, the orbital elements of the system and the stellar parameters of the two components. The system is composed of two early M-type stars and has an orbital period of about 5 days and a mass ratio of 0.92, but contrarily to expectations does not appear to have a tertiary companion. Both components have been (quasi-)synchronized, but the orbit is still very eccentric. The spectral energy distribution clearly displays a significant infrared excess compatible with a circumbinary disk. The analysis of HeI and Balmer line profiles, after the removal of the composite photospheric spectrum, reveals that both components are accreting at a similar level. We also observe excess emission in H$\alpha$ and H$\beta$, which appears redshifted or blueshifted by more than 100 km/s with respect to the mass center of the system depending on the orbital phase. This additional emission could be connected with accretion structures, such as funnels of matter from the circumbinary disk. We also analyze the optical companion located at about 2".4 from the spectroscopic binary. This companion, that we named CVSO 104B, turns out to be a background Sun-like star not physically associated with the PMS system and not belonging to Ori OB1., Comment: Accepted for publication in Astronomy and Astrophysics; 16 pages, 18 figures

The FORS Upgrade project (FORS-Up) aims at bringing a new life to the highly demanded workhorse instrument attached to ESO's Very Large Telescope (VLT). FORS2 is a multimode optical instrument, which started regular science operations in 2000 and since then, together with its twin, FORS1, has been one of the most demanded and most productive instruments of the VLT. In order to ensure that a FORS shall remain operational for at least another 15 years, an upgrade has been planned. This is required as FORS2 is using technology and software that is now obsolete and cannot be put and maintained to the standards in use at the Observatory. The project - carried out as a collaboration between ESO and INAF-Astronomical Observatory of Trieste - aims at bringing to the telescope in 2023/2024 a refurbished instrument with a new scientific detector, an upgrade of the instrument control software and electronics, a new calibration unit, as well as additional filters and grisms. The new FORS will also serve as a test bench for the Extremely Large Telescope (ELT) standard technologies (among them the use of programmable logic controllers and of the features of the ELT Control Software). The project aims at minimising the downtime of the instrument by performing the upgrade on the currently decommissioned instrument FORS1 and retrofitting the Mask Exchange Unit and polarisation optics from FORS2 to FORS1., Comment: Author version of a paper presented at SPIE Ground-based and Airborne Instrumentation for Astronomy VIII; corrected one statement

Six decades and counting, the formation of hot ~20,000-30,000 K Extreme Horizontal Branch (EHB) stars in Galactic Globular Clusters remains one of the most elusive quests in stellar evolutionary theory. Here we report on two discoveries shattering their currently alleged stable luminosity. The first EHB variability is periodic and cannot be ascribed to binary evolution nor pulsation. Instead, we here attribute it to the presence of magnetic spots: superficial chemical inhomogeneities whose projected rotation induces the variability. The second EHB variability is aperiodic and manifests itself on time-scales of years. In two cases, the six-year light curves display superflare events a mammoth several million times more energetic than solar analogs. We advocate a scenario where the two spectacular EHB variability phenomena are different manifestations of diffuse, dynamo-generated, weak magnetic fields. Ubiquitous magnetic fields, therefore, force an admittance into the intricate matrix governing the formation of all EHBs, and traverse to their Galactic field counterparts. The bigger picture is one where our conclusions bridge similar variability/magnetism phenomena in all radiative-enveloped stars: young main-sequence stars, old EHBs and defunct white dwarfs., Author's version of the main article (23 pages) and Supplementary Information (22 pages) combined into a single pdf (45 pages). Readers invited to read the Nature Astronomy Published version available at this url: https://www.nature.com/articles/s41550-020-1113-4

Motivated by the recent establishment of a connection between central star binarity and extreme abundance discrepancies in planetary nebulae, we have carried out a spectroscopic survey targeting planetary nebula with binary central stars and previously unmeasured recombination line abundances. We have discovered seven new extreme abundance discrepancies, confirming that binarity is key to understanding the abundance discrepancy problem. Analysis of all 15 objects with a binary central star and a measured abundance discrepancy suggests a cut-off period of about 1.15 days, below which extreme abundance discrepancies are found.

Variability of CzeV843 Cen was detected 31 March 2016 in the FOV of V834 Cen using Dk154 telescope at La Silla.

1 European Southern Observatory, Alonso de Cordova 3107, Casilla 19, Santiago, Chile e-mail: janderso@eso.org 2 Millennium Institute of Astrophysics, Casilla 36-D, Santiago, Chile 3 Departamento de Astronomia, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Chile 4 Laboratoire Lagrange, Universite Cote d’Azur, Observatoire de la Cote d’Azur, CNRS, Boulevard de l’Observatoire, CS 34229, 06304 Nice Cedex 4, France 5 Carnegie Observatories, Las Campanas Observatory, Casilla 601, La Serena, Chile 6 Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark 7 Instituto de Astrofisica de La Plata, Facultad de Ciencias Astronomicas y Geofisicas, Universidad Nacional de La Plata, CONICET, Paseo del Bosque S/N, B1900FWA, La Plata, Argentina 8 Nucleo de Astronomia de la Facultad de Ingenieria, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile

In anticipation of the Gaia astrometric mission, a sample of spectroscopic binaries is being observed since 2010 with the Sophie spectrograph at the Haute--Provence Observatory. Our aim is to derive the orbital elements of double-lined spectroscopic binaries (SB2s) with an accuracy sufficient to finally obtain the masses of the components with relative errors as small as 1 % when combined with Gaia astrometric measurements. In order to validate the masses derived from Gaia, interferometric observations are obtained for three SB2s in our sample with F-K components: HIP 14157, HIP 20601 and HIP 117186. The masses of the six stellar components are derived. Due to its edge-on orientation, HIP 14157 is probably an eclipsing binary. We note that almost all the derived masses are a few percent larger than the expectations from the standard spectral-type-mass calibration and mass-luminosity relation. Our calculation also leads to accurate parallaxes for the three binaries, and the Hipparcos parallaxes are confirmed., 10 pages, 3 figures, accepted by MNRAS

CCD photometry of the newly discovered eclipsing dwarf nova IY Ursae Majoris is used to study the physical properties of the accretion disc in the late decline and quiescence stages. Eclipse mapping analysis shows that in these stages the accretion disc is cool with approximately flat radial brightness temperature distribution and $T_{\rm BR}\sim5000-5500$ K. The hot spot is found to lie close along the stream trajectory at distance $0.36a$ and $0.25a$ from the disc center in February and March. The orbital hump strength decreases by ∼ 30% in a month. Taking the smallest possible size of the hot spot, we derive an upper limit for its brightness temperature, ∼ 15 900 K and ∼ 13 800 K, respectively.

It is expected that an average protostar will undergo at least one impulsive interaction with a neighbouring protostar whilst a large fraction of its mass is still in a massive, extended disc. If protostars are formed individually within a cluster before falling together and interacting, there should be no preferred orientation for such interactions. As star formation within clusters is believed to be coeval, it is probable that during interactions, both protostars possess massive, extended discs. We have used an SPH code to carry out a series of simulations of non-colpanar disc-disc interactions. We find that non-coplanar interactions trigger gravitational instabilities in the discs, which may then fragment to form new companions to the existing stars. (This is different from coplanar interactions, in which most of the new companion stars form after material in the discs has been swept up into a shock layer, and this then fragments.) The original stars may also capture each other, leading to the formation of a small-N cluster. If every star undergoes a randomly oriented disc-disc interaction, then the outcome will be the birth of many new stars. Approximately two-thirds of the stars will end up in multiple systems., 12 pages, submitted to MNRAS; low resolution figures only

Aims. The role of episodic mass loss is one of the outstanding questions in massive star evolution. The structural inhomogeneities and kinematics of their nebulae are tracers of their mass-loss history. We conduct a three-dimensional morpho-kinematic analysis of the ejecta of η Car outside its famous Homunculus nebula. Methods. We carried out the first large-scale integral field unit observations of η Car in the optical, covering a field of view of 1′× 1′ centered on the star. Observations with the Multi Unit Spectroscopic Explorer (MUSE) at the Very Large Telescope (VLT) reveal the detailed three-dimensional structure of η Car’s outer ejecta. Morpho-kinematic modeling of these ejecta is conducted with the code SHAPE. Results. The largest coherent structure in η Car’s outer ejecta can be described as a bent cylinder with roughly the same symmetry axis as the Homunculus nebula. This large outer shell is interacting with the surrounding medium, creating soft X-ray emission. Doppler velocities of up to 3000 km s-1 are observed. We establish the shape and extent of the ghost shell in front of the southern Homunculus lobe and confirm that the NN condensation can best be modeled as a bowshock in the orbital/equatorial plane. Conclusions. The SHAPE modeling of the MUSE observations provides a significant gain in the study of the three-dimensional structure of η Car’s outer ejecta. Our SHAPE modeling indicates that the kinematics of the outer ejecta measured with MUSE can be described by a spatially coherent structure, and that this structure also correlates with the extended soft X-ray emission associated with the outer debris field. The ghost shell immediately outside the southern Homunculus lobe hints at a sequence of eruptions within the time frame of the Great Eruption from 1837–1858 or possibly a later shock/reverse shock velocity separation. Our 3D morpho-kinematic modeling and the MUSE observations constitute an invaluable dataset to be confronted with future radiation-hydrodynamics simulations. Such a comparison may shed light on the yet elusive physical mechanism responsible for η Car-like eruptions.

The role of episodic mass loss in evolved massive stars is one of the outstanding questions in stellar evolution theory. Integral field spectroscopy of nebulae around massive stars provide information on their recent mass-loss history. η Car is one of the most massive evolved stars and is surrounded by a complex circumstellar environment. We have conducted a three-dimensional morpho-kinematic analysis of η Car’s ejecta outside its famous Homunculus nebula. SHAPE modelling of VLT MUSE data establish unequivocally the spatial cohesion of the outer ejecta and the correlation of ejecta with the soft X-ray emission.

We simulate numerically the surface flow of a gas-supplying companion star in a semi-detached binary system. Calculations are carried out for a region including only the mass-losing star, thus not the mass accreting star. The equation of state is that of an ideal gas characterized by a specific heat ratio gamma, and the case with gamma=5/3 is mainly studied. A system of eddies appears on the surface of the companion star: an eddy in the low pressure region near the L1 point, one around the high pressure at the north pole, and one or two eddies around the low pressure at the opposite side of the L1 point. Gas elements starting near the pole region rotate clockwise around the north pole (here the binary system rotates counter-clockwise as seen from the north pole). Because of viscosity, the gas drifts to the equatorial region, switches to the counter-clockwise eddy near the L1 point and flows through the L1 point to finally form the L1 stream. The flow field in the L1 region and the structure of the L1 stream are also considered., Comment: 10 pages, 22 figures, Accepted for publication in A&A

The well-known recurrent nova T Pyx has brightened by 7 magnitudes, starting on 2011 April 14, its first eruption since 1966. T Pyx is unique amongst recurrent novæ in being surrounded by a nebula formed of material ejected during previous eruptions. The latest eruption therefore offers the rare opportunity to observe a light echo sweeping through the existing shell, and a new one forming. The sudden exposure of the existing shell to high-energy light is expected to result in a change of the dust morphology as well as in the part destruction of molecules. We observe this process in the near- and mid-IR during several epochs using ESO's VLT instruments Sinfoni, Visir and Isaac. Unfortunately, in the data analysed so far we only have a tentative detection in Brα from the shell, so might in the end have to be content with upper limits for the emission from the various molecular bands and ionised lines.

We numerically simulate the surface flow of a gas-supplying companion star in a semi-detached binary system and construct the Doppler map. Our numerical results indicate an eddy configuration composed of a Heddy, a L1-eddy, and a L2-eddy associated with high/low pressures on the surface of the companion star. We find that the formation of these eddies can be explained in terms of the astrostrophic wind. We apply our calculations to the Galactic supersoft X-ray source RX J0019.8+2156. This object is very attractive for the present study since the observed Doppler map might reflect the surface flow on the companion star. We have constructed the Doppler map of RX J0019.8+2156 and compare it with observations.

Ba II stars are red giants showing an enhancement of carbon and s-process elements. The elucidation of their nature seems to require a mass transfer, either by wind or Roche lobe overflow, during their past evolution. Were it really the case, all Ba II stars would be binaries with a white dwarf as companion. To better understand the exact role of their binarity, more orbits are definitely needed. They can be obtained by monitoring the radial velocity variations of those stars. However, a quicker way to find new Ba II stars with orbital elements would be to search for their existence among known spectroscopic binaries. This would also crucially test whether mass transfer is a necessary and sufficient condition to explain Ba II stars. If it is indeed the case, then all spectroscopic binaries, made of a giant and a white dwarf, in a reasonable range of periods, would exhibit the Ba II pecularity. However, the discovery of a peculiar giant+main sequence binary system would imply a revision of our ideas about Ba II stars. To this end have we begun a systematic spectral survey of spectroscopic binaries with orbital periods in the range characteristic of known Ba II stars and containing a red giant. The realization that some stars of the catalogue we compiled were already identified as semibariium stars encourages us to pursue our investigation. Coude spectra were taken with the 152 cm telescope, at a dispersion of 12 Å mm−1 . Until now, 2 stars out of a sample of 31 present a slight enhancement of s-process elements (their anomaly being in the range Ba 0.3 to 0.5), and 2 more appear to be good candidates. The study of a larger sample is currently in progress. A discussion of the nature of the companion to the 2 newly discovered semibarium stars is presented on grounds of their mass function and photometric indices.