The SPHERE data center: a reference for high contrast imaging processing

The objective of the SPHERE Data Center is to optimize the scientific return of SPHERE at the VLT, by providing optimized reduction procedures, services to users and publicly available reduced data. This paper describes our motivation, the implementation of the service (partners, infrastructure and developments), services, description of the on-line data, and future developments. The SPHERE Data Center is operational and has already provided reduced data with a good reactivity to many observers. The first public reduced data have been made available in 2017. The SPHERE Data Center is gathering a strong expertise on SPHERE data and is in a very good position to propose new reduced data in the future, as well as improved reduction procedures.Comment: SF2A proceeding

Carbon chemistry in Galactic Bulge Planetary Nebulae

Galactic Bulge Planetary Nebulae show evidence of mixed chemistry with emission from both silicate dust and PAHs. This mixed chemistry is unlikely to be related to carbon dredge up, as third dredge-up is not expected to occur in the low mass Bulge stars. We show that the phenomenon is widespread, and is seen in 30 nebulae out of 40 of our sample, selected on the basis of their infrared flux. HST images and UVES spectra show that the mixed chemistry is not related to the presence of emission-line stars, as it is in the Galactic disk population. We also rule out interaction with the ISM as origin of the PAHs. Instead, a strong correlation is found with morphology, and the presence of a dense torus. A chemical model is presented which shows that hydrocarbon chains can form within oxygen-rich gas through gas-phase chemical reactions. The model predicts two layers, one at $A_V\sim 1.5$ where small hydrocarbons form from reactions with C$^+$, and one at $A_V\sim 4$, where larger chains (and by implication, PAHs) form from reactions with neutral, atomic carbon. These reactions take place in a mini-PDR. We conclude that the mixed chemistry phenomenon occurring in the Galactic Bulge Planetary Nebulae is best explained through hydrocarbon chemistry in an UV-irradiated, dense torus.Comment: 13 pages, 10 figue

The global gas and dust budget of the Large Magellanic Cloud: AGB stars and supernovae and the impact on the ISM evolution

‘The definitive version is available at: www3.interscience.wiley.com '. Copyright Blackwell / Royal Astronomical Society. DOI: 10.1111/j.1365-2966.2009.14743.xWe report on an analysis of the gas and dust budget in the interstellar medium (ISM) of the Large Magellanic Cloud (LMC). Recent observations from the Spitzer Space Telescope enable us to study the mid-infrared dust excess of asymptotic giant branch (AGB) stars in the LMC. This is the first time we can quantitatively assess the gas and dust input from AGB stars over a complete galaxy, fully based on observations. The integrated mass-loss rate over all intermediate and high mass-loss rate carbon-rich AGB candidates in the LMC is 8.5 × 10−3 M⊙ yr−1 , up to 2.1 × 10−2 M⊙ yr−1 . This number could be increased up to 2.7 × 10−2 M⊙ yr−1 if oxygen-rich stars are included. This is overall consistent with theoretical expectations, considering the star formation rate (SFR) when these low- and intermediate-mass stars where formed, and the initial mass functions. AGB stars are one of the most important gas sources in the LMC, with supernovae (SNe), which produces about 2–4 × 10−2 M⊙ yr−1 . At the moment, the SFR exceeds the gas feedback from AGB stars and SNe in the LMC, and the current star formation depends on gas already present in the ISM. This suggests that as the gas in the ISM is exhausted, the SFR will eventually decline in the LMC, unless gas is supplied externally. Our estimates suggest 'a missing dust-mass problem' in the LMC, which is similarly found in high-z galaxies: the accumulated dust mass from AGB stars and possibly SNe over the dust lifetime (400–800 Myr) is significant less than the dust mass in the ISM. Another dust source is required, possibly related to star-forming regions.Peer reviewe

The ALMA detection of CO rotational line emission in AGB stars in the Large Magellanic Cloud

Context. Low- and intermediate-mass stars lose most of their stellar mass at the end of their lives on the asymptotic giant branch (AGB). Determining gas and dust mass-loss rates (MLRs) is important in quantifying the contribution of evolved stars to the enrichment of the interstellar medium. Aims: This study attempts to spectrally resolve CO thermal line emission in a small sample of AGB stars in the Large Magellanic Cloud (LMC). Methods: The Atacama Large Millimeter Array was used to observe two OH/IR stars and four carbon stars in the LMC in the CO J = 2-1 line. Results: We present the first measurement of expansion velocities in extragalactic carbon stars. All four C stars are detected and wind expansion velocities and stellar velocities are directly measured. Mass-loss rates are derived from modelling the spectral energy distribution and Spitzer/IRS spectrum with the DUSTY code. The derived gas-to-dust ratios allow the predicted velocities to agree with the observed gas-to-dust ratios. The expansion velocities and MLRs are compared to a Galactic sample of well-studied relatively low MLRs stars supplemented with extreme C stars with properties that are more similar to the LMC targets. Gas MLRs derived from a simple formula are significantly smaller than those derived from dust modelling, indicating an order of magnitude underestimate of the estimated CO abundance, time-variable mass loss, or that the CO intensities in LMC stars are lower than predicted by the formula derived for Galactic objects. This could be related to a stronger interstellar radiation field in the LMC. Conclusions: Although the LMC sample is small and the comparison to Galactic stars is non-trivial because of uncertainties in their distances (hence luminosities), it appears that for C stars the wind expansion velocities in the LMC are lower than in the solar neighbourhood, while the MLRs appear to be similar. This is in agreement with dynamical dust-driven wind models

VLT/SPHERE deep insight of NGC 3603's core: Segregation or confusion?

We present new near-infrared photometric measurements of the core of the young massive cluster NGC 3603 obtained with extreme adaptive optics. The data were obtained with the SPHERE instrument mounted on ESO Very Large Telescope, and cover three fields in the core of this cluster. We applied a correction for the effect of extinction to our data obtained in the J and K broadband filters and estimated the mass of detected sources inside the field of view of SPHERE/IRDIS, which is 13.5"x13.5". We derived the mass function (MF) slope for each spectral band and field. The MF slope in the core is unusual compared to previous results based on Hubble space telescope (HST) and very large telescope (VLT) observations. The average slope in the core is estimated as -1.06^{+0.26}_{-0.26} for the main sequence stars with 3.5 Msun < M < 120 Msun.Thanks to the SPHERE extreme adaptive optics, 814 low-mass stars were detected to estimate the MF slope for the pre-main sequence stars with 0.6 Msun< M < 3.5 Msun , Gamma = -0.54^{+0.11}_{-0.11} in the K-band images in two fields in the core of the cluster. For the first time, we derive the mass function of the very core of the NGC 3603 young cluster for masses in the range 0.6 - 120 Msun. Previous studies were either limited by crowding, lack of dynamic range, or a combination of both

SPHERE: the exoplanet imager for the Very Large Telescope

Observations of circumstellar environments to look for the direct signal of exoplanets and the scattered light from disks has significant instrumental implications. In the past 15 years, major developments in adaptive optics, coronagraphy, optical manufacturing, wavefront sensing and data processing, together with a consistent global system analysis have enabled a new generation of high-contrast imagers and spectrographs on large ground-based telescopes with much better performance. One of the most productive is the Spectro-Polarimetic High contrast imager for Exoplanets REsearch (SPHERE) designed and built for the ESO Very Large Telescope (VLT) in Chile. SPHERE includes an extreme adaptive optics system, a highly stable common path interface, several types of coronagraphs and three science instruments. Two of them, the Integral Field Spectrograph (IFS) and the Infra-Red Dual-band Imager and Spectrograph (IRDIS), are designed to efficiently cover the near-infrared (NIR) range in a single observation for efficient young planet search. The third one, ZIMPOL, is designed for visible (VIR) polarimetric observation to look for the reflected light of exoplanets and the light scattered by debris disks. This suite of three science instruments enables to study circumstellar environments at unprecedented angular resolution both in the visible and the near-infrared. In this work, we present the complete instrument and its on-sky performance after 4 years of operations at the VLT.Comment: Final version accepted for publication in A&

Post conjunction detection of β\beta Pictoris b with VLT/SPHERE

With an orbital distance comparable to that of Saturn in the solar system, \bpic b is the closest (semi-major axis $\simeq$\,9\,au) exoplanet that has been imaged to orbit a star. Thus it offers unique opportunities for detailed studies of its orbital, physical, and atmospheric properties, and of disk-planet interactions. With the exception of the discovery observations in 2003 with NaCo at the Very Large Telescope (VLT), all following astrometric measurements relative to \bpic have been obtained in the southwestern part of the orbit, which severely limits the determination of the planet's orbital parameters. We aimed at further constraining \bpic b orbital properties using more data, and, in particular, data taken in the northeastern part of the orbit. We used SPHERE at the VLT to precisely monitor the orbital motion of beta \bpic b since first light of the instrument in 2014. We were able to monitor the planet until November 2016, when its angular separation became too small (125 mas, i.e., 1.6\,au) and prevented further detection. We redetected \bpic b on the northeast side of the disk at a separation of 139\,mas and a PA of 30$^{\circ}$ in September 2018. The planetary orbit is now well constrained. With a semi-major axis (sma) of $a = 9.0 \pm 0.5$ au (1 $\sigma$), it definitely excludes previously reported possible long orbital periods, and excludes \bpic b as the origin of photometric variations that took place in 1981. We also refine the eccentricity and inclination of the planet. From an instrumental point of view, these data demonstrate that it is possible to detect, if they exist, young massive Jupiters that orbit at less than 2 au from a star that is 20 pc away.Comment: accepted by A&

Discovery of a brown dwarf companion to the star HIP 64892

We report the discovery of a bright, brown dwarf companion to the star HIP 64892, imaged with VLT/SPHERE during the SHINE exoplanet survey. The host is a B9.5V member of the Lower-Centaurus-Crux subgroup of the Scorpius Centaurus OB association. The measured angular separation of the companion ($1.2705\pm0.0023$") corresponds to a projected distance of $159\pm12$ AU. We observed the target with the dual-band imaging and long-slit spectroscopy modes of the IRDIS imager to obtain its SED and astrometry. In addition, we reprocessed archival NACO L-band data, from which we also recover the companion. Its SED is consistent with a young (<30 Myr), low surface gravity object with a spectral type of M9$_{\gamma}\pm1$. From comparison with the BT-Settl atmospheric models we estimate an effective temperature of $T_{\textrm{eff}}=2600 \pm 100$ K, and comparison of the companion photometry to the COND evolutionary models yields a mass of $\sim29-37$ M$_{\text{J}}$ at the estimated age of $16^{+15}_{-7}$ Myr for the system. HIP 64892 is a rare example of an extreme-mass ratio system ($q\sim0.01$) and will be useful for testing models relating to the formation and evolution of such low-mass objects.Comment: 12 pages, 11 figures, accepted for publication in A&

A dusty veil shading Betelgeuse during its Great Dimming

This is the author accepted manuscript. The final version is available from Springer Nature via the DOI in this record.Data availability: Raw data were generated at the ESO under programs 0102.D-0240(A), 0102.D-0240(D), 104.20UZ and 104.20V6.004. Derived data that support the findings of this study are available at the Centre de Données Astronomiques de Strasbourg (CDS) via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/other/Nat (for the VLT/SPHERE–ZIMPOL images) and at the Optical Interferometry Database (OiDB; for the VLTI/GRAVITY and VLT/SPHERE–IRDIS SAM observations). Source data are provided with this paper.The SPHERE and GRAVITY pipelines are available on the ESO website: http://www.eso.org/sci/software/ pipelines/index.html. The RADMC3D code is publicly available online: https://github.com/dullemond/ radmc3d-2.0Code availability: The SPHERE and GRAVITY pipelines are available on the ESO website (http://www.eso.org/sci/software/pipelines/index.html). The PyRAF implementation of the Richardson–Lucy deconvolution algorithm is publicly available at https://astroconda.readthedocs.io/en/latest/. The RADMC3D code is publicly available at https://github.com/dullemond/radmc3d-2.0.Red supergiants represent the most common final stage of the evolution of stars with initial masses between 8 and 30-35 times the mass of the Sun. During this phase of lifetime lasting ≈ 105 yrs, they experience substantial mass loss of unknown mechanism. This mass loss can affect their evolutionary path, collapse, future supernova light curve, and ultimate fate as a neutron star or a black hole. From November 2019 to March 2020, the second closest red supergiant (RSG, 222+48 −34 pc) Betelgeuse experienced a historic dimming of its visible brightness, witnessed worldwide. Usually between 0.1 and 1.0 mag, it went down to 1.614±0.008 mag around 7-13 February 2020. Here we report high angular resolution observations showing that the southern hemisphere of the star was ten times darker than usual in the visible. Observations and modeling support the scenario of a dust clump recently formed in the vicinity of the star due to a local temperature decrease in a cool patch appearing on the photosphere. The directly imaged brightness variations of Betelgeuse evolved on a timescale of weeks. This event suggests that an inhomogeneous component of red supergiant mass loss is linked to a very contrasted and rapidly changing photosphere.European Research Council (ERC)European Union Horizon 2020Foundation FlandersKU LeuvenNAS