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The well studied carbon star V Hydrae is known to exhibit a complex asymmetric environment made of a dense equatorial wind and high-velocity outflows, hinting at its transition from the AGB phase to the asymmetric planetary nebula phase. In addition, V Hydrae also exhibits a long secondary period of 17 years in its light curve, suggesting the presence of a binary companion that could shape the circumstellar environment. In this paper, we aim to confirm the binary nature of V Hydrae by deriving its orbital parameters and investigating the effect of the orbital motion on the circumbinary environment. In a first step, we used a radial-velocity monitoring performed with the HERMES spectrograph to disentangle the pulsation signal of the AGB from its orbital motion and to obtain the spectroscopic orbit. We combined the spectroscopic results with astrometric information to get the complete set of orbital parameters, including the system inclination. Next, we reported the time variations of the sodium and potassium resonance doublets. Finally, following the methods used for post-AGB stars, we carried out spatio-kinematic modelling of a conical jet to reproduce the observed spectral-line modulation. We found the orbital solution of V Hydrae for a period of 17 years. We correlated the companion passage across the line of sight with the obscuration event and the blue-shifted absorption of alkaline resonant lines. Those variations were modelled by a conical jet emitted from the companion, whose opening angle is wide and whose sky-projected orientation is found to be consistent with the axis of the large-scale bipolar outflow previously detected in the radio-emission lines of CO. We show that the periodic variation seen for V Hydrae is likely to be due to orbital motion. The presence of a conical jet offers a coherent model to explain the various features of V Hydrae environment.

Over the past decades, libraries of stellar spectra have been used in a large variety of science cases, including as sources of reference spectra for a given object or a given spectral type. Despite the existence of large libraries and the increasing number of projects of large-scale spectral surveys, there is to date only one very high-resolution spectral library offering spectra from a few hundred objects from the southern hemisphere (UVES-POP) . We aim to extend the sample, offering a finer coverage of effective temperatures and surface gravity with a uniform collection of spectra obtained in the northern hemisphere. Between 2010 and 2020, we acquired several thousand echelle spectra of bright stars with the Mercator-HERMES spectrograph located in the Roque de Los Muchachos Observatory in La Palma, whose pipeline offers high-quality data reduction products. We have also developed methods to correct for the instrumental response in order to approach the true shape of the spectral continuum. Additionally, we have devised a normalisation process to provide a homogeneous normalisation of the full spectral range for most of the objects. We present a new spectral library consisting of 3256 spectra covering 2043 stars. It combines high signal-to-noise and high spectral resolution over the entire range of effective temperatures and luminosity classes. The spectra are presented in four versions: raw, corrected from the instrumental response, with and without correction from the atmospheric molecular absorption, and normalised (including the telluric correction)., Comment: 17 pages, 18 figures Preview and access to the library: https://www.royer.se/melchiors.html

We aim to study the dust distribution in the central regions of the Keplerian disk of the Red Rectangle, the prototype of binary post-AGB stars with rotating circumbinary disks, and to compare it with the distribution of relevant molecular gas tracers We present new high-resolution (20 milliarcseconds, mas) ALMA observations of continuum and line emissions at 0.9 mm. The maps have been analyzed by means of a simple model of dust and free-free emissionn that is able to reproduce the continuum data. Resuts: i) We find that most of the dust emission in the Red Rectangle is concentrated in the inner disk regions, with a typical size of 250 AU in diameter and 50 AU in width. ii) The settlement of dust grains onto inner equatorial regions is remarkable when compared with the relatively widespread gas distribution. iii) This region is basically coincident with the warm PDR (photo-dominated region) where CI, CII, and certain molecules such as HCN are presumably formed, as well as probably PAHs (polycyclic aromatic hydrocarbons, whose emission is very strong in this source). iv) We confirm the large size of the grains, with a typical radius ~ 150 mu The opacity of dust at 0.9 mm is deduced to be relatively large, ~0.5. v) We also confirm the existence of a very compact HII region in the center, for which we measure an extent of 10 - 15 mas (~ 10 AU) and a total flux of 7 - 8 mJy at 0.9 mm., Comment: 5 pages, 4 figures, accepted by Astronomy and Astrophysics Letters

The quest for quiet or dormant black holes has been ongoing since several decades. Ellipsoidal variables possibly indicate the existence of a very high-mass invisible companion and are thought to be one of the best ways to find such dormant black holes. This, however, is not a panacea as we show here with one example. We indeed report the discovery of a new semi-detached interacting binary, V1315 Cas, discovered as an ellipsoidal variable. Using data from photometric surveys (ASAS-SN, TESS) and high-resolution spectroscopy, we derived a nearly circular orbit with an orbital period of $P_{\rm{orb}}$=34.54 d. The binary system consists of an evolved F-type star primary that is likely still filling its Roche lobe and a B-type star secondary. Using \textsc{phoebe}2, we derived the following masses and radii: for the primary, $M_p =0.84 \pm 0.03 \, M_\odot$ and $R_p =18.51^{+0.12}_{-0.07} \, R_\odot$; for the secondary, $M_s =7.3 \pm 0.3 \,M_\odot$ and $R_s =4.02^{+2.3}_{-2.0}\,R_\odot$. Modeling the evolution of the system with MESA, we found an age of $\sim$7.7e7 years. The system is at the end of a period of rapid non-conservative mass transfer that reversed its mass ratio, while significantly widening its orbit. The primary shows carbon depletion and nitrogen overabundance, indicative of CNO processed material being exposed due to mass transfer. An infrared excess as well as stationary H$\alpha$ emission suggest the presence of a circumstellar or circumbinary disc. V1315 Cas will likely become a detached stripped star binary., Comment: Accepted in MNRAS

A sample of 895 s-process-rich candidates has been found among the 454180 giant stars surveyed by LAMOST at low spectral resolution (R~1800). In a previous study, taking advantage of the higher resolution (R~86 000) offered by the the HERMES-Mercator spectrograph, we performed the re-analysis of 15 among the brightest stars of this sample. Among these 15 program stars, having close-to-solar metallicities, 11 showed mild to strong heavy element overabundances. The nucleosynthesis process(es) at the origin of these overabundances were however not questioned in our former study. We derive the abundances in s- and r-process elements of the 15 targets in order to investigate whether some stars also show an i-process signature, as sometimes found in their lower metallicity counterparts (namely, the Carbon-Enhanced Metal-Poor (CEMP)-rs stars). Abundances are derived from the high-resolution HERMES spectra for Pr, Nd, Sm, and Eu, using the TURBOSPECTRUM radiative transfer LTE code with MARCS model atmospheres. Using the new classification scheme proposed in our recent study we find that two stars show overabundances in both s- and r-process elements well above the level expected from the Galactic chemical evolution, an analogous situation to the one of CEMP-rs stars at lower metallicities. We compare the abundances of the most enriched stars with the nucleosynthetic predictions from the STAREVOL stellar evolutionary code and find abundances compatible with an i-process occurring in AGB stars. Despite a larger number of heavy elements to characterize the enrichment pattern, the limit between CEMP-s and CEMP-rs stars remains fuzzy. It is however interesting to note that an increasing number of extrinsic stars are found to have abundances better reproduced by an i-process pattern even at close-to-solar metallicities., Comment: Accepted for publication in A&A, 9 pages, 9 figures including the two in appendix

Many properties of circumbinary discs around evolved post-asymptotic giant branch (post-AGB) binary systems are similar to those of protoplanetary discs around young stars. The deficits of near-infrared (near-IR) flux in the spectral energy distributions (SEDs) of these systems hints towards large dust-free cavities that are reminiscent of transition discs as are commonly observed around young stars. We aim to assess the size of the inner rim of 6 post-AGB binary systems with lack in the near-IR like this. We used resolved mid-infrared (mid-IR) high-angular resolution observations of VLTI/MATISSE and VLTI/MIDI. We compared these inner rim sizes to 5 systems with available MATISSE data that were identified to host a disc starting at the dust sublimation radius. We used geometric ring models to estimate the inner rim sizes, the relative flux contributions of the star, the ring, and an over-resolved emission, the orientation of the ring, and the spectral dependences of the components. We find that the inner dust rims of the targets with a lack of near-IR excess in their SEDs are 2.5 to 7.5 times larger than the theoretical dust sublimation radii, and inner rim sizes of the systems that do not show this deficit are similar to those of their theoretical dust sublimation radii. The physical radii of the inner rims of these transition discs around post-AGB binaries are 3-25 au, which are larger than the disc sizes inferred for transition discs around young stars with VLTI/MIDI. With mid-IR interferometric data, we directly confirm the transition disc nature of six circumbinary discs around post-AGB binary systems. Future observational and modelling efforts are needed to progress in our understanding of the structure, origin, and evolution of these transition discs, Comment: accepted for publication in A&A. 13 pages, including appendices

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

(abridged) Stable circumbinary discs around evolved post-Asymptotic Giant branch (post-AGB) binary systems show many similarities with protoplanetary discs around young stellar objects. These discs can provide constraints on both binary evolution and the formation of macrostructures within circumstellar discs. Here we focus on one post-AGB binary system: IRAS08544-4431. We aim to refine the physical model of IRAS08544-4431 with a radiative transfer treatment and continue the near-infrared and mid-infrared interferometric analysis covering the H-, K-, L-, and N-bands. We aim to capture the previously detected amount of over-resolved flux and the radial intensity profile at and beyond the inner dust disc rim to put constraints on the physical processes in the inner disc regions. We used a Monte Carlo radiative transfer code to investigate the physical structure of the disc by reproducing both the photometry and the multi-wavelength infrared interferometric data set. We developed a strategy to identify the models which perform best to reproduce our data set. We found a family of models that successfully fit the infrared photometric and interferometric data in all bands. Some over-resolved flux component was recovered in all bands but the optimised models still fall short to explain all the over-resolved flux. This suggests that another dusty structure within the system plays a role. Multi-wavelength infrared interferometric observations of circumstellar discs allow to study the inner disc regions in unprecedented detail. The refined physical models can reproduce most of the investigated features, including the photometric characteristics, the radial extent, and the overall shape of the visibility curves. Our multi-wavelength interferometric observations combined with photometry show that the disc is similar to protoplanetary discs with similar dust masses and efficient dust growth., Comment: 18 pages, 13 figures (including apppendix), accepted for publication in A&A

The study of post asymptotic giant branch (post-AGB) stars is a valuable tool to study still poorly known aspects of the evolution of the stars through the AGB. This is due to the accurate determination of their surface chemical composition and to the peculiar shape of the SED: the emission from the central star can be easily disentangled from the contribution from the dusty shell, which can then be characterized. The goal of the present study is to reconstruct the dust formation process and more generally the late phases of the evolution of O-rich stars across the AGB phase. This is performed by studying O-rich, post-AGB stars, which are analyzed in terms of their luminosity, Teff and infrared excess. We study sources classified as single, O-rich, post-AGB stars in the Galaxy, which exhibit a double-peaked (shell-type) SED. We use results from stellar evolution modelling combined with dust formation and radiative transfer modelling to reconstruct the late AGB phases and the initial contraction to the post-AGB phase. We also determine the mass-loss and dust formation rates for stars of different mass and chemical composition. The analysis of the IR excess of the post-AGB, O-rich stars examined in this study outlines an interesting complexity, in terms of the correlation between the dust in the surroundings of the stars, the evolutionary status and the progenitor's mass. The sources descending from massive AGBs (>3Msun depending on metallicity) are generally characterized by higher IR excess than the lower mass counterparts, owing to the more intense dust formation taking place during the final AGB phases. From the determination of the location of the dusty regions we deduce that the expanding velocities of the outflow change significantly from star to star. The possibility that radiation pressure is unable to accelerate the wind in the faintest objects is also commented., Comment: 11 pages, 6 figures and 1 table. Accepted for publication in A&A

There is a class of binary post-AGB stars (binary system including a post-AGB star) that are surrounded by Keplerian disks and outflows resulting from gas escaping from the disk. To date, there are seven sources that have been studied in detail through interferometric millimeter-wave maps of CO lines (ALMA/NOEMA). For the cases of the Red Rectangle, IW Carinae, IRAS 08544-4431, and AC Herculis, it is found that around greater than 85% of the total nebular mass is located in the disk with Keplerian dynamics. The remainder of the nebular mass is located in an expanding component. This outflow is probably a disk wind consisting of material escaping from the rotating disk. These sources are the disk-dominated nebulae. On the contrary, our maps and modeling of 89 Herculis, IRAS 19125+0343, and R Scuti, which allowed us to study their morphology, kinematics, and mass distribution, suggest that, in these sources, the outflow clearly is the dominant component of the nebula (around 75% of the total nebular mass), resulting in a new subclass of nebulae around binary post-AGB stars: the outflow-dominated sources.Besides CO, the chemistry of this type of source has been practically unknown thus far. We also present a very deep single-dish radio molecular survey in the 1.3, 2, 3, 7, and 13 mm bands (around 600 h of telescope time). Our results and detections allow us to classify our sources as O- or C-rich. We also conclude that the calculated abundances of the detected molecular species other than CO are particularly low, compared with AGB stars. This fact is very significant in those sources where the rotating disk is the dominant component of the nebula., Comment: Accepted 2 August 2022 in Astronomy. 11 pages

Determining ages of stars for reconstructing the history of the Milky Way remains one of the most difficult tasks in astrophysics. This involves knowing when it is possible to relate the stellar mass with its age and when it is not. The young $\alpha-$rich (YAR) stars present such a case in which we are still not sure about their ages because they are relatively massive, implying young ages, but their abundances are $\alpha-$enhanced, which implies old ages. We report the results from new observations from a long-term radial-velocity-monitoring campaign complemented with high-resolution spectroscopy, as well as new astrometry and seismology of a sample of 41 red giants from the third version of APOKASC, which includes YAR stars. The aim is to better characterize the YAR stars in terms of binarity, mass, abundance trends, and kinematic properties.The radial velocities of HERMES, APOGEE, and Gaia were combined to determine the binary fraction among YAR stars. In combination with their mass estimate, evolutionary status, chemical composition, and kinematic properties, it allowed us to better constrain the nature of these objects. We found that stars with $\mathrm{M} < 1 \mathrm{M}_\odot$ were all single, whereas stars with $\mathrm{M} > 1 \mathrm{M}_\odot$ could be either single or binary. This is in agreement with theoretical predictions of population synthesis models. Studying their [C/N], [C/Fe], and [N/Fe], trends with mass, it became clear that many YAR stars do not follow the APOKASC stars, favoring the scenario that most of them are the product of mass transfer. Abr., Comment: Accepted in A&A

A new large sample of 895 s-process-rich candidates out of 454180 giant stars surveyed by LAMOST at low spectral resolution (R ~ 1800) has been reported by Norfolk et al. (2019; hereafter N19). We aim at confirming the s-process enrichment at the higher resolution (R ~ 86000) offered by the HERMES-Mercator spectrograph, for the 15 brightest targets of the previous study sample which consists in 13 Sr-only stars and two Ba-only stars. Abundances were derived for elements Li, C, N, O, Na, Mg, Fe, Rb, Sr, Y, Zr, Nb, Ba, La, and Ce. Binarity has been tested by comparing the Gaia DR2 radial velocity with the HERMES velocity obtained 1600 - 1800 days later. Among the 15 programme stars, four show no s-process overabundances ([X/Fe] < 0.2 dex), eight show mild s-process overabundances (at least three heavy elements with 0.2 < [X/Fe] < 0.8), and three have strong overabundances (at least three heavy elements with [X/Fe] > 0.8). Among the 13 stars classified as Sr-only by the previous investigation, four have no s-process overabundances, eight are mild barium stars, and one is a strong barium star. The two Ba-only stars turn out to be both strong barium stars and are actually dwarf barium stars. They also show clear evidence for being binaries. Among the no-s stars, there are two binaries out of four, whereas only one out of the eight mild barium stars show a clear signature of radial-velocity variations. Blending effects and saturated lines have to be considered very carefully when using machine-learning techniques, especially on low-resolution spectra. Among the Sr-only stars from the previous study sample, one may expect about 60% (8/13) of them to be true mild barium stars and about 8% to be strong barium stars, and this fraction is likely close to 100% for the previous study Ba-only stars (2/2)., Comment: Accepted for publication in A&A, 15 pages, 12 figures

The presence of stable, compact circumbinary discs of gas and dust around post-asymptotic giant branch (post-AGB) binary systems has been well established. We focus on one such system: IRAS 08544-4431. We present an interferometric multi-wavelength analysis of the circumstellar environment of IRAS 08544-4431. The aim is to constrain different contributions to the total flux in the H, K, L, and N-bands in the radial direction. The data from VLTI/PIONIER, VLTI/GRAVITY, and VLTI/MATISSE range from the near-infrared, where the post-AGB star dominates, to the mid-infrared, where the disc dominates. We fitted two geometric models to the visibility data to reproduce the circumbinary disc: a ring with a Gaussian width and a flat disc model with a temperature gradient. The flux contributions from the disc, the primary star (modelled as a point-source), and an over-resolved component are recovered along with the radial size of the emission, the temperature of the disc as a function of radius, and the spectral dependencies of the different components. The trends of all visibility data were well reproduced with the geometric models. The near-infrared data were best fitted with a Gaussian ring model while the mid-infrared data favoured a temperature gradient model. This implies that a vertical structure is present at the disc inner rim, which we attribute to a rounded puffed-up inner rim. The N-to-K size ratio is 2.8, referring to a continuous flat source, analogues to young stellar objects. By combining optical interferometric instruments operating at different wavelengths we can resolve the complex structure of circumstellar discs and study the wavelength-dependent opacity profile. A detailed radial, vertical, and azimuthal structural analysis awaits a radiative transfer treatment in 3D to capture all non-radial complexity., Comment: 8 pages, 5 figures, accepted for publication in A&A Letters

Despite being the best studied red supergiant star in our Galaxy, the physics behind the photometric variability and mass loss of Betelgeuse is poorly understood. Moreover, recently the star has experienced an unusual fading with its visual magnitude reaching a historical minimum. We investigate the nature of this event with the help of a recently developed tomographic technique. Tomography allows us to probe different depths in the stellar atmosphere and to recover the corresponding disk-averaged velocity field. We apply the tomographic method to a few-year time-series high-resolution spectroscopic observations of Betelgeuse in order to relate its atmospheric dynamics to the photometric variability. Our results show that a sudden increase of the molecular opacity in the cooler upper atmosphere of Betelgeuse is likely the reason of the observed unusual decrease of the star's brightness., Comment: A&A Letters, accepted for publication

There is a class of binary post-AGB stars with a remarkable near-infrared excess that are surrounded by Keplerian or quasi-Keplerian disks and extended outflows composed of gas escaping from the disk. The Keplerian dynamics had been well identified in four cases, namely the Red Rectangle, AC Her, IW Car, and IRAS 08544-4431. In these objects, the mass of the outflow represents ~ 10 % of the nebular mass, the disk being the dominant component of the nebula. We present interferometric NOEMA maps of 12CO and 13CO J=2-1 in 89 Her and 12CO J=2-1 in AC Her, IRAS 19125+0343, and R Sct. Several properties of the nebula are obtained from the data and model fitting, including the structure, density, and temperature distributions, as well as the dynamics. We also discuss the uncertainties on the derived values. The presence of an expanding component in AC Her is doubtful, but thanks to new maps and models, we estimate an upper limit to the mass of this outflow of < 3 10^-5 Mo, that is, the mass of the outflow is < 5 % of the total nebular mass. For 89 Her, we find a total nebular mass of 1.4 10^-2 Mo, of which ~ 50 % comes from an hourglass-shaped extended outflow. In the case of IRAS 19125+0343, the nebular mass is 1.1 10^-2 Mo, where the outflow contributes ~ 70 % of the total mass. The nebular mass of R Sct is 3.2 10^-2 Mo, of which ~ 75 % corresponds to a very extended outflow that surrounds the disk. Our results for IRAS 19125+0343 and R Sct lead us to introduce a new subclass of binary post-AGB stars, for which the outflow is the dominant component of the nebula. Moreover, the outflow mass fraction found in AC Her is smaller than those found in other disk-dominated binary post-AGB stars. 89 Her would represent an intermediate case between both subclasses., Comment: Accepted 4 March 2021 in Astronomy & Astrophysics. 26 pages

With the advent of interferometric instruments with 4 telescopes at the VLTI and 6 telescopes at CHARA, the scientific possibility arose to routinely obtain milli-arcsecond scale images of the observed targets. Such an image reconstruction process is typically performed in a Bayesian framework where the function to minimize is made of two terms: the datalikelihood and the Bayesian prior. This prior should be based on our prior knowledge of the observed source. Up to now,this prior was chosen from a set of generic and arbitrary functions, such as total variation for example. Here, we present an image reconstruction framework using generative adversarial networks where the Bayesian prior is defined using state-of-the-art radiative transfer models of the targeted objects. We validate this new image reconstruction algorithm on synthetic data with added noise. The generated images display a drastic reduction of artefacts and allow a more straight forward astrophysical interpretation. The results can be seen as a first illustration of how neural networks can provide significant improvements to the image reconstruction of a variety of astrophysical sources., Comment: SPIE Astronomical Telescopes + Instrumentation 2020 conference Paper No. 11446-110

Context: The observed orbital characteristics of post-asymptotic giant branch (post-AGB) and post-red giant branch (post-RGB) binaries are not understood. We suspect that the missing ingredients to explain them probably lie in the continuous interaction of the central binary with its circumstellar environment. Aims: We aim at studying the circumbinary material in these complex systems by investigating the connection between the innermost and large-scale structures. Methods: We perform high-angular resolution observations in the near-infrared continuum of HD101584, which has a complex structure as seen at millimeter wavelengths with a disk-like morphology and a bipolar outflow due to an episode of strong binary interaction. To account for the complexity of the target we first perform an image reconstruction and use this result to fit a geometrical model to extract the morphological and thermal features of the environment. Results: The image reveals an unexpected double-ring structure. We interpret the inner ring to be produced by emission from dust located in the plane of the disk and the outer ring to be produced by emission from dust that is located 1.6[D/1kpc] au above the disk plane. The inner ring diameter (3.94[D/1kpc] au), and temperature (T=1540$\pm$10K) are compatible with the dust sublimation front of the disk. The origin of the out-of-plane ring (with a diameter of 7.39[D/1kpc] au and a temperature of 1014$\pm10$K) could be due to episodic ejection or a dust condensation front in the outflow. Conclusion: The observed outer ring is possibly linked with the blue-shifted side of the large scale outflow seen by ALMA and is tracing its launching location to the central star. Such observations give morphological constraints on the ejection mechanism. Additional observations are needed to constrain the origin of the out-of-plane structure., Comment: Accepted to A&A. 14 pages, 13 figures

The origin of the Li-rich K giants is still highly debated. Here, we investigate the incidence of binarity among this family from a nine-year radial-velocity monitoring of a sample of 11 Li-rich K giants using the HERMES spectrograph attached to the 1.2m Mercator telescope. A sample of 13 non-Li-rich giants (8 of them being surrounded by dust according to IRAS, WISE, and ISO data) was monitored alongside. When compared to the binary frequency in a reference sample of 190 K giants (containing 17.4% of definite spectroscopic binaries -- SB -- and 6.3% of possible spectroscopic binaries -- SB?), the binary frequency appears normal among the Li-rich giants (2/11 definite binaries plus 2 possible binaries, or 18.2% SB + 18.2% SB?), after taking account of the small sample size through the hypergeometric probability distribution. Therefore, there appears to be no causal relationship between Li enrichment and binarity. Moreover, there is no correlation between Li enrichment and the presence of circumstellar dust, and the only correlation that could be found between Li enrichment and rapid rotation is that the most Li-enriched K giants appear to be fast-rotating stars. However, among the dusty K giants, the binary frequency is much higher (4/8 definite binaries plus 1 possible binary). The remaining 3 dusty K giants suffer from a radial-velocity jitter, as is expected for the most luminous K giants, which these are.

S stars are late-type giants with overabundances of s-process elements. They come in two flavours depending on the presence or not of technetium (Tc), an element without stable isotopes. Intrinsic S stars are Tc-rich and genuine asymptotic giant branch (AGB)stars while extrinsic S stars owe their s-process overabundances to the pollution from a former AGB companion, now a white dwarf(WD). In addition to Tc, another distinctive feature between intrinsic and extrinsic S stars is the overabundance of niobium (Nb) in the latter class. We discuss the case of the S stars BD+79 156 and o1Ori whose specificity is to share the distinctive features of both intrinsic and extrinsic S stars, namely the presence of Tc along with a Nb overabundance. BD+79 156 is the first clear case of a bitrinsic star, i.e. a doubly s-process-enriched object, first through mass transfer in a binary system, and then through internal nucleosynthesis (responsible for the Tc-enrichment in BD+79 156 which must therefore have reached the AGB phase of its evolution). This hybrid nature of the s-process pattern in BD+79 156 is supported by its binary nature and its location in the HR diagram just beyond the onset of the third dredge-up on the AGB. The Tc-rich, binary S-star o1Ori with a WD companion was another long-standing candidate for a similar hybrid s-process enrichment. However the marginal overabundance of Nb derived ino1Ori does not allow to trace unambiguously the evidence of a large pollution coming from the AGB progenitor of its current WD companion. As a side product, the current study offers a new way of detecting binary AGB stars with WD companions by identifying their Tc-rich nature along with a Nb overabundance., Comment: A & A Letters, accepted for publication

Context. The fate of a massive star during the latest stages of its evolution is highly dependent on its mass-loss rate/geometry and therefore knowing the geometry of the circumstellar material close to the star and its surroundings is crucial. Aims. We aim to study the nature (i.e. geometry, rates) of mass-loss episodes. In this context, yellow hypergiants are great targets. Methods. We analyse a large set of optical/near-infrared data, in spectroscopic and photometric (X-shooter/VLT), spectropolarimetric (ISIS/WHT), and interferometric GRAVITY-AMBER/VLTI) modes, toward the yellow hypergiant IRAS 17163-3907. We present the first model-independent reconstructed images of IRAS 17163-3907 at these wavelengths at milli-arcsecond scales. Lastly, we apply a 2D radiative transfer model to fit the dereddened photometry and the radial profiles of published VISIR images at 8.59 {\mu}m, 11.85 {\mu}m and 12.81 {\mu}m simultaneously, adopting the revised Gaia distance (DR2). Results. The interferometric observables around 2 {\mu}m show that the Br{\gamma} emission is more extended and asymmetric than the Na i and the continuum emission. In addition to the two known shells surrounding IRAS 17163-3907 we report on the existence of a third hot inner shell with a maximum dynamical age of only 30 yr. Conclusions. The interpretation of the presence of Na i emission at closer distances to the star compared to Br{\gamma} has been a challenge in various studies. We argue that the presence of a pseudophotosphere is not needed, but it is rather an optical depth effect. The three observed distinct mass-loss episodes are characterised by different mass-loss rates and can inform the theories on mass-loss mechanisms, which is a topic still under debate. We discuss these in the context of photospheric pulsations and wind bi-stability mechanisms., Comment: 26 pages, 22 Figures, 6 tables, accepted for publication in A&A. Original abstract will be available after publication

Post-AGB binaries are surrounded by circumbinary disks of gas and dust that are similar to protoplanetary disks found around young stars. We aim to understand the structure of these disks and identify the physical phenomena at play in their very inner regions. We want to understand the disk-binary interaction and to further investigate the comparison with protoplanetary disks. We have conducted an interferometric snapshot survey of 23 post-AGB binaries in the near-infrared (H-band) using VLTI/PIONIER. We have fitted the multiwavelength visibilities and closure phases with purely geometrical models with an increasing complexity in order to retrieve the sizes, temperatures and flux ratios of the different components All sources are resolved and the different components contributing to the H-band flux are dissected. The environment of these targets is very complex: 13/23 targets need models with thirteen or more parameters to fit the data. We find that the inner disk rims follow and extend the size-luminosity relation established for disks around young stars with an offset toward larger sizes. The measured temperature of the near-infrared circumstellar emission of post-AGB binaries is lower (Tsub~1200K) than for young stars, probably due to a different dust mineralogy and/or gas density in the dust sublimation region. The dusty inner rims of the circumbinary disks around post-AGB binaries are ruled by dust sublimation physics. Additionally, a significant amount of the circumstellar H-band flux is over-resolved (14 targets have more than 10% of their non-stellar flux over-resolved) hinting for more structure from a yet unknown origin (disk structure or outflow). The amount of over-resolved flux is larger than around young stars. Due to the complexity of these targets, interferometric imaging is a necessary tool to reveal the interacting inner regions in a model-independent way., Comment: Accepted for publication in A&A, 40 pages

The substantial number of binary central stars of planetary nebulae (CSPNe) now known ($\sim$50) has revealed a strong connection between binarity and some morphological features including jets and low-ionisation structures. However, some features and asymmetries might be too complex or subtle to ascribe to binary interactions alone. A tertiary component, i.e. a triple nucleus, could be the missing ingredient required to produce these features. The only proven triple, NGC 246, is insufficient to investigate the shaping role of triple nuclei, but one straight-forward way to identify more triples is to search for binaries in nuclei with known visual companions. Here we report on the SALT HRS discovery of a 4.81 d orbital period in the CSPN of Sp 3 which has a visual companion 0.31" away. The spectroscopic distance of the visual companion agrees with distance estimates to the nebula, the GAIA DR2 parallax of the central star, and the gravity distance of the central star. This supports a physical association between the visual companion and the 4.81 d binary, making the nucleus of Sp 3 a likely triple. We determine $T_\mathrm{eff}=68^{+12}_{-6}$ kK, $\log g=4.6\pm0.2$ cm s$^{-2}$ and $v_\mathrm{rot}=80\pm20$ km s$^{-1}$ for the primary from NLTE model atmosphere analysis. The peculiar nebula presents an apparent bipolar morphology, jets and an unexpected `extreme' oxygen abundance discrepancy factor (adf) of 24.6$^{+4.1}_{-3.4}$. The adf is inconsistent with the purported trend for longer orbital period post-CE PNe to exhibit normal adfs, further highlighting selection effects in post-CE PNe. The Type-I nebular abundances of Sp 3, whose origin is often tied to more massive progenitors, are incongruous with the likely Galactic Thick Disk membership of Sp 3, possibly suggesting that rotation and binarity may play an important role in the AGB nucleosynthesis of PNe. (abridged), Comment: Accepted for publication in PASA. 23 pages, 17 figures

We performed a photometric and spectroscopic analysis of two RV Tauri stars GK Car and GZ Nor. Both objects are surrounded by hot circumstellar dust. Their pulsation periods, derived from ASAS photometric time series, have been used to derive their luminosities and distances via the PLC relation. In addition, for both objects, GAIA distances are available. The Gaia distances and luminosities are consistent with the values obtained from the PLC relationship. GK Car is at distance of 4.5$\pm{1.3}$ kpc and has a luminosity of 1520$\pm{840}$ L$_{\odot}$, while GZ Nor is at distance of 8.4$\pm{2.3}$ kpc and has a luminosity of 1240 $\pm{690}$ L$_{\odot}$. Our abundance analysis reveals that both stars show depletion of refractory elements with [Fe/H]=$-$1.3 and [Zn/Ti]=$+$1.2 for GK Car and [Fe/H]=$-$2.0 and [Zn/Ti]=$+$0.8 for GZ Nor. In the WISE colour-colour diagram, GK Car is located in the RV Tauri box as originally defined by \cite{evans85} and updated by \cite{gezer15}, while GZ Nor is not. Despite this, we argue that both objects are surrounded by a gravitationally bound disc. As depletion is observed in binaries, we postulate that both stars are binaries as well. RV Tauri stars are generally acknowledged to be post$-$AGB stars. Recent studies show that they might be either indeed post$-$AGB or post$-$RGB objects depending on their luminosity. For both objects, the derived luminosities are relatively low for post-AGB objects, however, the uncertainties are quite large. We conclude that they could be either post-RGB or post-AGB objects., Comment: Accepted for publication in MNRAS. 9 pages, 8 figures, 8 tables

The orbital period distribution of close binary stars consisting of a white dwarf and a main-sequence star (WDMS) is a powerful observational constraint on population synthesis models of the poorly understood common-envelope (CE) interaction. Models have often struggled to reproduce the small number of post-CE WDMS binaries with anomalously long orbital periods greater than $\sim$4 d, though recent studies suggest that in longer period systems recombination energy may help contribute to the efficient ejection of the CE. Planetary nebulae (PNe) are an emerging source of rare long period post-CE binaries which can act as powerful complementary constraints on population synthesis models to more traditional post-CE binary populations. A tentative 9.0 d orbital period was recently proposed for the central star of the PN IC~4776, potentially one of the longest periods observed in post-CE WDMS binaries. Here we present SALT HRS observations of IC~4776 that rule out a 9.0 d orbital period, as well as the previously suggested Wolf-Rayet classification of the primary. The SALT HRS data establish a 3.11 d orbital period and rule out Of and Wolf-Rayet primary spectral types. Assuming a mass of 0.6 $M_\odot$ for the primary and an orbital inclination matching the nebula orientation, we find a companion mass of $0.22\pm0.03$ $M_\odot$, most likely corresponding to an M4V companion. The orbital period of IC~4776 is still consistent with findings of abundance discrepancy factor (ADF) studies of post-CE PNe, but any trends in the ADF distribution derived from the sample remain significantly biased by selection effects., Comment: 7 pages, 5 figures, 3 tables. Accepted for publication in MNRAS

Barium (Ba) dwarfs and CH subgiants are the less-evolved analogues of Ba and CH giants. They are F- to G-type main-sequence stars polluted with heavy elements by a binary companion when the latter was on the Asymptotic Giant Branch (AGB). This companion is now a white dwarf that in most cases cannot be directly detected. We present a large systematic study of 60 objects classified as Ba dwarfs or CH subgiants. Combining radial-velocity measurements from HERMES and SALT high-resolution spectra with radial-velocity data from CORAVEL and CORALIE, we determine the orbital parameters of 27 systems. We also derive their masses by comparing their location in the Hertzsprung-Russell diagram with evolutionary models. We confirm that Ba dwarfs and CH subgiants are not at different evolutionary stages and have similar metallicities, despite their different names. Additionally, Ba giants appear significantly more massive than their main-sequence analogues. This is likely due to observational biases against the detection of hotter main-sequence post-mass-transfer objects. Combining our spectroscopic orbits with the Hipparcos astrometric data, we derive the orbital inclinations and the mass of the WD companion for four systems. Since this cannot be done for all systems in our sample yet (but should be with upcoming Gaia data releases), we also analyse the mass-function distribution of our binaries. We can model this distribution with very narrow mass distributions for the two components and random orbital orientation on the sky. Finally, based on BINSTAR evolutionary models, we suggest that the orbital evolution of low-mass Ba systems can be affected by a second phase of interaction along the Red Giant Branch of the Ba star, impacting on the eccentricities and periods of the giants., Comment: Accepted for publication in A&A on the 5th of April, 2019

This paper provides long-period and revised orbits for barium and S stars adding to previously published ones. The sample of barium stars with strong anomalies comprise all such stars present in the Lu et al. catalogue. We find orbital motion for all barium and extrinsic S stars monitored. We obtain the longest period known so far for a spectroscopic binary involving an S star, namely 57 Peg with a period of the order of 100 - 500 yr. We present the mass distribution for the barium stars, which ranges from 1 to 3 Msun, with a tail extending up to 5 Msun in the case of mild barium stars. This high-mass tail comprises mostly high-metallicity objects ([Fe/H] >= -0.1). Mass functions are compatible with WD companions and we derive their mass distribution which ranges from 0.5 to 1 Msun. Using the initial - final mass relationship established for field WDs, we derived the distribution of the mass ratio q' = MAGB,ini / MBa (where MAGB, ini is the WD progenitor initial mass, i.e., the mass of the system former primary component) which is a proxy for the initial mass ratio. It appears that the distribution of q' is highly non uniform, and significantly different for mild and strong barium stars, the latter being characterized by values mostly in excess of 1.4, whereas mild barium stars occupy the range 1 - 1.4. We investigate as well the correlation between abundances, orbital periods, metallicities, and masses (barium star and WD companion). The 105 orbits of post-mass-transfer systems presented in this paper pave the way for a comparison with binary-evolution models., Comment: This version 2 is the one accepted by A&A, after language edition. Paper II about dwarf-Ba and subgiant-CH orbits by Escorza et al. is arXiv:1904.04095

Circumbinary disks are common around post-asymptotic giant branch (post-AGB) stars with a stellar companion on orbital time scales of a few 100 to few 1000 days. The presence of a disk is usually inferred from the system's spectral energy distribution (SED), and confirmed, for a sub-sample, by interferometric observations. We used the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument on the Very Large Telescope to obtain extreme adaptive optics assisted scattered light images of the post-AGB binary system AR Puppis. Data have been obtained in the V, I, and H bands. Our observations have produced the first resolved images of AR Puppis' circumbinary disk and confirm its edge-on orientation. In our high angular-resolution and high dynamic-range images we identify several structural components such as a dark mid-plane, the disk surface, and arc-like features. We discuss the nature of these components and use complementary photometric monitoring to relate them to the orbital phase of the binary system. Because the star is completely obscured by the disk at visible wavelengths, we conclude that the long-term photometric variability of the system must be caused by variable scattering, not extinction, of star light by the disk over the binary orbit. Finally, we discuss how the short disk life times and fast evolution of the host stars compared to the ages at which protoplanetary disks are typically observed make systems like AR Puppis valuable extreme laboratories to study circumstellar disk evolution and constrain the time scale of dust grain growth during the planet formation process., Comment: 17 pages, 9 figures, accepted for publication in AJ

We report on our search for spectroscopic binaries among a sample of AGB stars. Observations were carried out in the framework of the monitoring of radial velocities of (candidate) binary stars performed at the Mercator 1.2m telescope, using the HERMES spectrograph. We found evidence for duplicity in UV Cam, TU Tau, BL Ori, VZ Per, T Dra, and V Hya. This short communication focus on V Hya, found to behave like RV Tau of the b subtype, which are binaries surrounded by a disc., Comment: Poster presented at IAU Symp. 343 "Why Galaxies Care About AGB Stars", Vienna, august 2018

Context: Post-Asymptotic Giant Branch (AGB) binaries are surrounded by stable dusty and gaseous disks similar to the ones around young stellar objects. Whereas significant effort is spent on modeling observations of disks around young stellar objects, the disks around post-AGB binaries receive significantly less attention, even though they pose significant constraints on theories of disk physics and binary evolution. Aims: We want to examine the structure of and phenomena at play in circumbinary disks around post-AGB stars. We continue the analysis of our near-infrared interferometric image of the inner rim of the circumbinary disk around IRAS08544-4431. We want to understand the physics governing this inner disk rim. Methods: We use a radiative transfer model of a dusty disk to reproduce simultaneously the photometry as well as the near-infrared interferometric dataset on IRAS08544-4431. The model assumes hydrostatic equilibrium and takes dust settling self-consistently into account. Results: The best-fit radiative transfer model shows excellent agreement with the spectral energy distribution up to mm wavelengths as well as with the PIONIER visibility data. It requires a rounded inner rim structure, starting at a radius of 8.25 au. However, the model does not fully reproduce the detected over-resolved flux nor the azimuthal flux distribution of the inner rim. While the asymmetric inner disk rim structure is likely to be the consequence of disk-binary interactions, the origin of the additional over-resolved flux remains unclear. Conclusions: As in young stellar objects, the disk inner rim of IRAS08544-4431 is ruled by dust sublimation physics. Additional observations are needed to understand the origin of the extended flux and the azimuthal perturbation at the inner rim of the disk., Comment: Accepted for publication in A&A, 13 figures, 13 pages

We are studying a class of binary post-AGB stars that seem to be systematically surrounded by equatorial disks and slow outflows. Although the rotating dynamics had only been well identified in three cases, the study of such structures is thought to be fundamental to the understanding of the formation of nebulae around evolved stars. We present ALMA maps of 12CO and 13CO J=3-2 lines in one of these sources, IRAS08544-4431. We analyzed the data by means of nebula models, which account for the expectedly composite source and can reproduce the data. From our modeling, we estimated the main nebula parameters, including the structure and dynamics and the density and temperature distributions. We discuss the uncertainties of the derived values and, in particular, their dependence on the distance. Our observations reveal the presence of an equatorial disk in rotation; a low-velocity outflow is also found, probably formed of gas expelled from the disk. The main characteristics of our observations and modeling of IRAS08544-4431 are similar to those of better studied objects, confirming our interpretation. The disk rotation indicates a total central mass of about 1.8 Mo, for a distance of 1100 pc. The disk is found to be relatively extended and has a typical diameter of ~ 4 10^16 cm. The total nebular mass is ~ 2 10^-2 Mo, of which ~ 90% corresponds to the disk. Assuming that the outflow is due to mass loss from the disk, we derive a disk lifetime of ~ 10000 yr. The disk angular momentum is found to be comparable to that of the binary system at present. Assuming that the disk angular momentum was transferred from the binary system, as expected, the high values of the disk angular momentum in this and other similar disks suggest that the size of the stellar orbits has significantly decreased as a consequence of disk formation., Comment: 10 pages, 7 figures, accepted by A&A

LoTr 5 is a planetary nebula with an unusual long-period binary central star. As far as we know, the pair consists of a rapidly rotating G-type star and a hot star, which is responsible for the ionization of the nebula. The rotation period of the G-type star is 5.95 days and the orbital period of the binary is now known to be $\sim$2700 days, one of the longest in central star of planetary nebulae. The spectrum of the G central star shows a complex H$\alpha$ double-peaked profile which varies with very short time scales, also reported in other central stars of planetary nebulae and whose origin is still unknown. We present new radial velocity observations of the central star which allow us to confirm the orbital period for the long-period binary and discuss the possibility of a third component in the system at $\sim$129 days to the G star. This is complemented with the analysis of archival light curves from SuperWASP, ASAS and OMC. From the spectral fitting of the G-type star, we obtain a effective temperature of $T_{\rm eff}$ = 5410$\pm$250 K and surface gravity of $\log g$ = 2.7$\pm$0.5, consistent with both giant and subgiant stars. We also present a detailed analysis of the H$\alpha$ double-peaked profile and conclude that it does not present correlation with the rotation period and that the presence of an accretion disk via Roche lobe overflow is unlikely., Comment: 12 pages, 12 figures, accepted for publication in MNRAS

To understand the scientific imaging capability, one must characterize the intra-pixel sensitivity variation (IPSV) of the CMOS image sensor. Extracting an IPSV map contributes to an improved detector calibration that allows to eliminate some of the uncertainty in the spatial response of the system. This paper reports the measurement of the sub-pixel sensitivity variation and the extraction of the 2D IPSV map of a front-side illuminated CMOS image sensor with a pixel pitch of 6 {\mu}m. Our optical measurement setup focuses a collimated beam onto the imaging surface with a microscope objective. The spot was scanned in a raster over a single pixel and its immediate neighbors in order to probe its response at selected (sub-pixel) positions. In this work we introduced a novel technique to extract the IPSV map by fitting (forward modeling) the measured data to a mathematical model of the image, generated in a single pixel that allows for a spatially varying sensitivity.

Post-asymptotic giant branch (post-AGB) stars are known to be chemically diverse. In this paper we present the first observational evidence of a star that has failed the third dredge-up (TDU). J005252.87-722842.9 is a A-type ($T_{\rm eff}$ = 8250 $\pm$ 250K) luminous (8200 $\pm$ 700 $\rm L_{\odot}$), metal-poor ($\textrm{[Fe/H]}$ = $- 1.18 \pm$ 0.10), low-mass (M$_{\rm initial}$ $\approx$ 1.5 $-$ 2.0 $\rm M_{\odot}$) post-AGB star in the Small Magellanic Cloud. Through a systematic abundance study, using high-resolution optical spectra from UVES, we found that this likely post-AGB object shows an intriguing photospheric composition with no confirmed carbon-enhancement (upper limit of [C/Fe] $<$ 0.50) nor enrichment of $s$-process elements. We derived an oxygen abundance of [O/Fe] = 0.29 $\pm$ 0.1. For Fe and O, we took into account the effects of non-local thermodynamic equilibrium (NLTE). We could not derive an upper limit for the nitrogen abundance as there are no useful nitrogen lines within our spectral coverage. The chemical pattern displayed by this object has not been observed in single or binary post-AGBs. Based on its derived stellar parameters and inferred evolutionary state, single star nucleosynthesis models predict that this star should have undergone TDU episodes while on the AGB and be carbon-enriched. However, our observations are in contrast with these predictions. We identify two possible Galactic analogues which are likely to be post-AGB stars, but the lack of accurate distances (hence luminosities) to these objects does not allow us to confirm their post-AGB status. If they have low luminosities then they are likely to be dusty post-RGB stars. The discovery of J005252.87-722842.9 reveals a new stellar evolutionary channel whereby a star evolves without any third dredge-up episodes., Comment: 15 pages, 13 figures, 6 tables

With the availability of parallaxes provided by the Tycho-Gaia Astrometric Solution, it is possible to construct the Hertzsprung-Russell diagram (HRD) of barium and related stars with unprecedented accuracy. A direct result from the derived HRD is that subgiant CH stars occupy the same region as barium dwarfs, contrary to what their designations imply. By comparing the position of barium stars in the HRD with STAREVOL evolutionary tracks, it is possible to evaluate their masses, provided the metallicity is known. We used an average metallicity [Fe/H] = -0.25 and derived the mass distribution of barium giants. The distribution peaks around 2.5 Msun with a tail at higher masses up to 4.5 Msun. This peak is also seen in the mass distribution of a sample of normal K and M giants used for comparison and is associated with stars located in the red clump. When we compare these mass distributions, we see a deficit of low-mass (1 - 2 Msun) barium giants. This is probably because low-mass stars reach large radii at the tip of the red giant branch, which may have resulted in an early binary interaction. Among barium giants, the high-mass tail is however dominated by stars with barium indices of less than unity, based on a visual inspection of the barium spectral line; that is, these stars have a very moderate barium line strength. We believe that these stars are not genuine barium giants, but rather bright giants, or supergiants, where the barium lines are strengthened because of a positive luminosity effect. Moreover, contrary to previous claims, we do not see differences between the mass distributions of mild and strong barium giants., Comment: 14 pages, 17 figures

We aim at describing and understanding binary interaction processes in systems with very evolved companions. Here, we focus on understanding the origin and determining the properties of the high-velocity outflow observed in one such system. We present a quantitative analysis of BD+46$^{\circ}$442, a post-AGB binary which shows active mass transfer that leads to the creation of a disk-driven outflow or jet. We obtained high-resolution optical spectra from the HERMES spectrograph, mounted on the 1.2m Flemish Mercator Telescope. By performing a time-series analysis of the Halpha profile, we dissected the different components of the system. We deduced the jet geometry by comparing the orbital phased data with our jet model. In order to image the accretion disk around the companion of BD+46$^{\circ}$442, we applied the technique of Doppler tomography. The orbital phase-dependent variations in the Halpha profile can be related to an accretion disk around the companion, from which a high-velocity outflow or jet is launched. Our model shows that there is a clear correlation between the inclination angle and the jet opening angle. The latitudinally dependent velocity structure of our jet model shows a good correspondence to the data, with outflow velocities at least higher than 400km/s. We show that BD+46$^{\circ}$442, is a result of a binary interaction channel. The origin of the fast outflow in this system can be attributed to a gaseous disk around the secondary component, which is most likely a main sequence star. Our analysis suggests the outflow to have a rather wide opening angle instead of being strongly collimated. Similar orbital phase-dependent Halpha profiles are commonly observed in post-AGB binaries. Post-AGB binaries provide ideal test bets to study jet formation and launching mechanisms over a wide range of orbital conditions., Comment: 18 pages, 18 figures, 3 tables, accepted for publication in A&A

We report the discovery of MASCARA-1 b, the first exoplanet discovered with the Multi-site All-Sky CAmeRA (MASCARA). It is a hot Jupiter orbiting a bright $m_V=8.3$, rapidly rotating ($v\sin i_\star > 100~\rm{km~s}^{-1}$) A8 star with a period of $2.148780\pm8\times10^{-6} ~\rm{days}$. The planet has a mass and radius of $3.7\pm0.9~\rm{M}_{\rm{Jup}}$ and $1.5\pm0.3~\rm{R}_{\rm{Jup}}$, respectively. As with most hot Jupiters transiting early-type stars we find a misalignment between the planet orbital axis and the stellar spin axis, which may be signature of the formation and migration histories of this family of planets. MASCARA-1 b has a mean density of $1.5\pm0.9~\rm{g~cm^{-3}}$ and an equilibrium temperature of $2570^{+50}_{-30}~\rm{K}$, one of the highest temperatures known for a hot Jupiter to date. The system is reminiscent of WASP-33, but the host star lacks apparent delta-scuti variations, making the planet an ideal target for atmospheric characterization. We expect this to be the first of a series of hot Jupiters transiting bright early-type stars that will be discovered by MASCARA., Comment: 7 pages, 5 figures, Published in A&A. A typo in the value of the spectroscopic impact parameter was corrected

Whether planetary nebulae (PNe) are predominantly the product of binary stellar evolution as some population synthesis models (PSM) suggest remains an open question. Around 50 short period binary central stars ($P\sim1$ d) are known, but with only four with measured orbital periods over 10 d, our knowledge is severely incomplete. Here we report on the first discovery from a systematic SALT HRS survey for long period binary central stars. We find a 142 d orbital period from radial velocities of the central star of NGC~1360, HIP~16566. NGC~1360 appears to be the product of common-envelope (CE) evolution, with nebula features similar to post-CE PNe, albeit with an orbital period considerably longer than expected to be typical of post-CE PSM. The most striking feature is a newly-identified ring of candidate low-ionisation structures (LIS). Previous spatio-kinematic modelling of the nebula gives a nebula inclination of $30\pm10$ deg, and assuming the binary nucleus is coplanar with the nebula, multi-wavelength observations best fit a more massive, evolved WD companion. A WD companion in a 142 d orbit is not the focus of many PSM, making NGC~1360 a valuable system with which to improve future PSM work. HIP~16566 is amongst many central stars in which large radial velocity variability was found by low-resolution surveys. The discovery of its binary nature may indicate long period binaries may be more common than PSM models predict., Comment: 15 pages, 10 figures, 6 tables. Accepted for publication in MNRAS

Lithium abundance A(Li) and surface rotation are good diagnostic tools to probe the internal mixing and angular momentum transfer in stars. We explore the relation between surface rotation, A(Li) and age in a sample of seismic solar-analogue (SA) stars and study their possible binary nature. We select a sample of 18 SA observed by the NASA Kepler satellite for an in-depth analysis. Their seismic properties and surface rotation are well constrained from previous studies. About 53 hours of high-resolution spectroscopy were obtained to derive fundamental parameters and A(Li). These values were combined and confronted with seismic masses, radii and ages, as well as surface rotation periods. We identify a total of 6 binary systems. A well-defined relation between A(Li) and rotation was obtained. With models constrained by the characterisation of the individual mode frequencies for single stars, we identify a sequence of three SA with similar mass (~1.1Mo) and stellar ages ranging between 1 to 9 Gyr. Within the realistic estimate of ~7% for the mass uncertainty, we find a good agreement between the measured A(Li) and the predicted A(Li) evolution from a grid of models calculated with the Toulouse-Geneva stellar evolution code, which includes rotational internal mixing, calibrated to reproduce solar chemical properties. We present A(Li) for a consistent spectroscopic survey of SA with a mass of 1.00+/-0.15Mo, and characterised through asteroseismology and surface rotation rates based on Kepler observations. The correlation between A(Li) and P_rot supports the gyrochronological concept for stars younger than the Sun. The consensus between measured A(Li) for solar analogues with model grids, calibrated onto the Sun's chemical properties suggests that these targets share the same internal physics. In this light, the solar Li and rotation rate appear to be normal for a star like the Sun., Comment: Accepted for publications in A&A, 11 pages, 6 figures

We aim to study the presence of both rotation and expansion in post-AGB nebulae, in particular around IW Car, a binary post-AGB star that was suspected to be surrounded by a Keplerian disk. We obtained high-quality ALMA observations of 12CO and 13CO J=3-2 lines in IW Car. The maps were analyzed by means of a simplified model of CO emission, based on those used for similar objects. Our observations clearly show the presence of gas components in rotation, in an equatorial disk, and expansion, which shows an hourglass-like structure with a symmetry axis perpendicular to the rotation plane and is probably formed of material extracted from the disk. Our modeling can reproduce the observations and shows moderate uncertainties. The rotation velocity corresponds to a central stellar mass of approximately 1 Mo. We also derive the total mass of the molecule-rich nebula, found to be of ~ 4 10e-3 Mo; the outflow is approximately eight times less massive than the disk. From the kinematical age of the outflow and the mass values derived for both components, we infer a (future) lifetime of the disk of approximately 5000--10000 yr., Comment: 7 pages, 9 figures. Accepted as a Letter in Astronomy and Astrophysics

Yellow hypergiants are rare and represent a fast evolutionary stage of massive evolved stars. That evolutionary phase is characterised by a very intense mass loss, the understanding of which is still very limited. Here we report ALMA Compact Array observations of a 50$"$-mosaic toward the Fried Egg nebula, around one of the few Galactic yellow hypergiants IRAS 17163-3907. The emission from the $^{12}$CO J=2-1 line, H30$\alpha$ recombination line, and continuum is imaged at a resolution of $\sim$8$"$, revealing the morphology of the molecular environment around the star. The continuum emission is unresolved and peaks at the position of the star. The radio recombination line H30$\alpha$ shows unresolved emission at the star, with an approximately gaussian spectrum centered on a velocity of 21$\pm$3~km/s with a width of 57$\pm$6~km/s. In contrast, the CO 2-1 emission is complex and decomposes into several components beyond the contamination from interstellar gas in the line of sight. The CO spectrum toward the star is a broad plateau, centered at the systemic velocity of +18 km/s and with an expansion velocity of 100$\pm$10 km/s. Assuming isotropic and constant mass-loss, we estimate a mass-loss rate of 8$\pm$1.5 $\times10^{-5}$~M$_\odot$ yr$^{-1}$. At a radius of 25$"$ from the star, we detect CO emission associated with the dust ring previously imaged by {\it Herschel}. The kinematics of this ring, however, is not consistent with an expanding shell, but show a velocity gradient of $v_{sys} \pm$20 km/s. In addition, we find a puzzling bright feature radially connecting the star to the CO ring, at a velocity of +40 km/s relative to the star. This spur feature may trace a unidirectional ejection event from the star. Our ACA observations reveal the complex morphology around IRAS 17163 and illustrate the breakthroughs that ALMA will bring to the field of massive stellar evolution., Comment: Accepted for publication in A&A. 8 pages, 7 figures, plus appendix

Stars similar to the Sun, known as solar analogues, provide an excellent opportunity to study the preceding and following evolutionary phases of our host star. The unprecedented quality of photometric data collected by the \Kepler NASA mission allows us to characterise solar-like stars through asteroseismology and study diagnostics of stellar evolution, such as variation of magnetic activity, rotation and the surface lithium abundance. In this project, presented in a series of papers by Salabert et al. (2016a,b) and Beck et al (2016a,b), we investigate the link between stellar activity, rotation, lithium abundance and oscillations in a group of 18 solar-analogue stars through space photometry, obtained with the NASA Kepler space telescope and from currently 50+ hours of ground-based, high-resolution spectroscopy with the Hermes instrument. In these proceedings, we first discuss the selection of the stars in the sample, observations and calibrations and then summarise the main results of the project. By investigating the chromospheric and photospheric activity of the solar analogues in this sample, it was shown that for a large fraction of these stars the measured activity levels are compatible to levels of the 11-year solar activity cycle 23. A clear correlation between the lithium abundance and surface rotation was found for rotation periods shorter than the solar value. Comparing the lithium abundance measured in the solar analogues to evolutionary models with the Toulouse-Geneva Evolutionary Code (TGEC), we found that the solar models calibrated to the Sun also correctly describe the set of solar/stellar analogs showing that they share the same internal mixing physics. Finally, the star KIC 3241581 and KIC 10644353 are discussed in more detail., Comment: Proceedings of "The 19th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun"; 8 pages, 4 Figures

We present a mid-IR interferometric survey of the circumstellar environment of a specific class of post-Asymptotic Giant Branch (post-AGB) binaries. For this class the presence of a compact dusty disk has been postulated on the basis of various spatially unresolved measurements. Our interferometric survey was performed with the MIDI instrument on the VLTI. In total 19 different systems were observed using variable baseline configurations. Combining all the visibilities at a single wavelength at 10.7 micron, we fitted two parametric models to the data: a uniform disk (UD) and a ring model mimicking a temperature gradient. We compared our observables of the whole sample, with synthetic data computed from a grid of radiative transfer models of passively irradiated disks in hydrostatic equilibrium. These models are computed with a Monte Carlo code that has been widely applied to describe the structure of protoplanetary disks around young stellar objects (YSO). The spatially resolved observations show that the majority of our targets cluster closely together in the distance-independent size-colour diagram, and have extremely compact N-band emission regions. The typical uniform disk diameter of the N-band emission region is about 40 mass which corresponds to a typical brightness temperature of 400-600~K. The resolved objects display very similar characteristics in the interferometric observables and in the spectral energy distributions. Therefore, the physical properties of the disks around our targets must be similar. The grid of protoplanetary disk models covers very well the observed objects. Much like for young stars, the spatially resolved N-band emission region is determined by the hot inner rim of the disk. Continued comparisons between post-AGB and protoplanetary disks will help to understand grain growth and disk evolution processes, Comment: 30 pages, 21 figures, in press in Astronomy and Astrophysics

We report on the discovery of a planetary companion candidate with a minimum mass Msini = 4.6 M_J orbiting the K2 III giant star HD 175370 (KIC 007940959). This star was a target in our program to search for planets around a sample of 95 giant stars observed with Kepler. This detection was made possible using precise stellar radial velocity measurements of HD 175370 taken over five years and four months using the coude echelle spectrograph of the 2-m Alfred Jensch Telescope and the fibre-fed echelle spectrograph HERMES of the 1.2-m Mercator Telescope. Our radial velocity measurements reveal a periodic (349.5 days) variation with a semi-amplitude K = 133 m/s, superimposed on a long-term trend. A low-mass stellar companion with an orbital period of ~88 years in a highly eccentric orbit and a planet in a Keplerian orbit with an eccentricity e = 0.22 are the most plausible explanation of the radial velocity variations. However, we cannot exclude the existence of stellar envelope pulsations as a cause for the low-amplitude radial velocity variations and only future continued monitoring of this system may answer this uncertainty. From Kepler photometry we find that HD 175370 is most likely a low-mass red-giant branch or asymptotic-giant branch star., Comment: 12 pages, 10 figures. This is a pre-copyedited, author-produced PDF of an article accepted for publication in MNRAS following peer review. The version of record DOI=10.1093/mnras/stw2379 is available online at: http://mnras.oxfordjournals.org/cgi/reprint/stw2379?ijkey=TaJttgdCtBDXV36&keytype=ref

CMOS imagers are becoming increasingly popular in astronomy. A very low noise level is required to observe extremely faint targets and to get high-precision flux measurements. Although CMOS technology offers many advantages over CCDs, a major bottleneck is still the read noise. To move from an industrial CMOS sensor to one suitable for scientific applications, an improved design that optimizes the noise level is essential. Here, we study the 1/f and thermal noise performance of the source follower (SF) of a CMOS pixel in detail. We identify the relevant design parameters, and analytically study their impact on the noise level using the BSIM3v3 noise model with an enhanced model of gate capacitance. Our detailed analysis shows that the dependence of the 1/f noise on the geometrical size of the source follower is not limited to minimum channel length, compared to the classical approach to achieve the minimum 1/f noise. We derive the optimal gate dimensions (the width and the length) of the source follower that minimize the 1/f noise, and validate our results using numerical simulations. By considering the thermal noise or white noise along with 1/f noise, the total input noise of the source follower depends on the capacitor ratio CG/CFD and the drain current (Id). Here, CG is the total gate capacitance of the source follower and CFD is the total floating diffusion capacitor at the input of the source follower. We demonstrate that the optimum gate capacitance (CG) depends on the chosen bias current but ranges from CFD/3 to CFD to achieve the minimum total noise of the source follower. Numerical calculation and circuit simulation with 180nm CMOS technology are performed to validate our results., Comment: SPIE Astronomical Telescopes and Instrumentation, 2016

We present new high-quality ALMA observations of the Red Rectangle (a well known post-AGB object) in C17O J=6-5 and H13CN J=4-3 line emission and results from a new reduction of already published 13CO J=3-2 data. A detailed model fitting of all the molecular line data, including previous maps and single-dish spectra, was performed using a sophisticated code. These observations and the corresponding modeling allowed us to deepen the analysis of the nebular properties. We also stress the uncertainties in the model fitting. We confirm the presence of a rotating equatorial disk and an outflow, which is mainly formed of gas leaving the disk. The mass of the disk is ~ 0.01 Mo, and that of the CO-rich outflow is ~ 10 times smaller. High temperatures of ~ 100 K are derived for most components. From comparison of the mass values, we roughly estimate the lifetime of the rotating disk, which is found to be of about 10000 yr. Taking data of a few other post-AGB composite nebulae into account, we find that the lifetimes of disks around post-AGB stars typically range between 5000 and more than 20000 yr. The angular momentum of the disk is found to be high, ~ 9 Mo AU km/s, which is comparable to that of the stellar system at present. Our observations of H13CN show a particularly wide velocity dispersion and indicate that this molecule is only abundant in the inner Keplerian disk, at ~ 60 AU from the stellar system. We suggest that HCN is formed in a dense photodissociation region (PDR) due to the UV excess known to be produced by the stellar system, following chemical mechanisms that are well established for interstellar medium PDRs and disks orbiting young stars. We further suggest that this UV excess could lead to the efficient formation and excitation of PAHs and other C-bearing macromolecules, whose emission is very intense in the optical counterpart., Comment: Astronomy & Astrohysics, in press; 17 pages, 18 figures, 1 table

Classical novae are the product of thermonuclear runaway-initiated explosions occurring on accreting white dwarfs. V339 Del (Nova Delphinus 2013) was one of the brightest classical novae of the last hundred years. Spectroscopy and photometry are available from $\gamma$-rays through infrared at stages that have frequently not been well observed. The complete data set is intended to provide a benchmark for comparison with modeling and for understanding more sparsely monitored historical classical and recurrent novae. This paper is the first in the series of reports on the development of the nova. We report here on the early stages of the outburst, through the X-ray active stage. A time sequence of optical, flux calibrated high resolution spectra was obtained with the Nordic Optical Telescope (NOT) using FIES simultaneously, or contemporaneously, with the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope during the early stages of the outburst. These were supplemented with MERCATOR/HERMES optical spectra. High resolution IUE ultraviolet spectra of OS And 1986, taken during the Fe curtain phase, served as a template for the distance determination. We used standard plasma diagnostics (e.g., [O III] and [N II] line ratios, and the H$\beta$ line flux) to constrain electron densities and temperatures of the ejecta. Using Monte Carlo modeling of the ejecta, we derived the structure, filling factor, and mass from comparisons of the optical and ultraviolet line profiles., Comment: 14 pages, 18 figures

We present the first near-IR milli-arcsecond-scale image of a post-AGB binary that is surrounded by hot circumbinary dust. A very rich interferometric data set in six spectral channels was acquired of IRAS08544-4431 with the new RAPID camera on the PIONIER beam combiner at the Very Large Telescope Interferometer (VLTI). A broadband image in the \textit{H} band was reconstructed by combining the data of all spectral channels using the SPARCO method. We spatially separate all the building blocks of the IRAS08544-4431 system in our milliarcsecond-resolution image. Our dissection reveals a dust sublimation front that is strikingly similar to that expected in early-stage protoplanetary disks, as well as an unexpected flux signal of $\sim$4\% from the secondary star. The energy output from this companion indicates the presence of a compact circum-companion accretion disk, which is likely the origin of the fast outflow detected in H$\alpha$. Our image provides the most detailed view into the heart of a dusty circumstellar disk to date. Our results demonstrate that binary evolution processes and circumstellar disk evolution can be studied in detail in space and over time., Comment: PR @ http://www.eso.org/public/news/eso1608/

Context: We present a newly discovered class of low-luminosity, dusty, evolved objects in the Magellanic Clouds. These objects have dust excesses, stellar parameters, and spectral energy distributions similar to those of dusty post-asymptotic giant branch (post-AGB) stars. However, they have lower luminosities and hence lower masses. We suggest that they have evolved off the red giant branch (RGB) instead of the AGB as a result of binary interaction. Aims: In this study we aim to place these objects in an evolutionary context and establish an evolutionary connection between RGB binaries (such as the sequence E variables) and our new sample of objects. Methods: We compared the theoretically predicted birthrates of the progeny of RGB binaries to the observational birthrates of the new sample of objects. Results: We find that there is order-of-magnitude agreement between the observed and predicted birthrates of post-RGB stars. The sources of uncertainty in the birthrates are discussed; the most important sources are probably the observational incompleteness factor and the post-RGB evolution rates. We also note that mergers are relatively common low on the RGB and that stars low on the RGB with mid-IR excesses may recently have undergone a merger. Conclusions: Our sample of dusty post-RGB stars most likely provides the first observational evidence for a newly discovered phase in binary evolution: post-RGB binaries with circumstellar dust., Comment: Accepted for publication in Astronomy and Astrophysics Letters

Solar-analog stars provide an excellent opportunity to study the Sun's evolution, i.e. the changes with time in stellar structure, activity, or rotation for solar-like stars. The unparalleled photometric data from the NASA space telescope Kepler allows us to study and characterise solar-like stars through asteroseismology. We aim to spectroscopically investigate the fundamental parameter and chromospheric activity of solar analogues and twins, based on observations obtained with the HERMES spectrograph and combine them with asteroseismology. Therefore, we need to build a solar atlas for the spectrograph, to provide accurate calibrations of the spectroscopically determined abundances of solar and late type stars observed with this instrument and thus perform differential spectral comparisons. We acquire high-resolution and high signal-to-noise spectroscopy to construct three solar reference spectra by observing the reflected light of Vesta and Victoria asteroids and Europa (100