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132 results on '"de Wit, Willem-Jan"'

1. Effects of the Hunga Tonga-Hunga Ha'apai Volcanic Eruption on Observations at Paranal Observatory

Author

De Rosa, Robert J., Otarola, Angel, Szeifert, Thomas, Smoker, Jonathan, Selman, Fernando, Mehner, Andrea, Bian, Fuyan, Sedaghati, Elyar, Seidel, Julia V., Smette, Alain, and de Wit, Willem-Jan

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Physics - Atmospheric and Oceanic Physics
Abstract

The Hunga Tonga-Hunga Ha'apai volcano erupted on 15 January 2022 with an energy equivalent to around 61 megatons of TNT. The explosion was bigger than any other volcanic eruption so far in the 21st century. Huge quantities of particles, including dust and water vapour, were released into the atmosphere. We present the results of a preliminary study of the effects of the explosion on observations taken at Paranal Observatory using a range of instruments. These effects were not immediately transitory in nature, and a year later stunning sunsets are still being seen at Paranal., Comment: 4 pages, 5 figures, published in ESO Messenger vol. 190

Published
2023
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2. Towards a physical understanding of the thermal background in large ground-based telescopes

Author

Burtscher, Leonard, Politopoulos, Ioannis, Fernández-Acosta, Sergio, Agocs, Tibor, Ancker, Mario van den, van Boekel, Roy, Brandl, Bernhard, Käufl, Hans Ulrich, Pantin, Eric, Pietrow, Alex G. M., Siebenmorgen, Ralf, Stuik, Remko, Tristram, Konrad R. W., and de Wit, Willem-Jan

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

Ground-based thermal-infrared observations have a unique scientific potential, but are also extremely challenging due to the need to accurately subtract the high thermal background. Since the established techniques of chopping and nodding need to be modified for observations with the future mid-infrared ELT imager and spectrograph (METIS), we investigate the sources of thermal background subtraction residuals. Our aim is to either remove or at least minimise the need for nodding in order to increase the observing efficiency for METIS. To this end we need to improve our knowledge about the origin of chop residuals and devise observing methods to remove them most efficiently, i.e. with the slowest possible nodding frequency. Thanks to dedicated observations with VLT/VISIR and GranTeCan/CanariCam, we have successfully traced the origin of three kinds of chopping residuals to (1) the entrance window, (2) the spiders and (3) other warm emitters in the pupil, in particular the VLT M3 mirror cell in its parking position. We conclude that, in order to keep chopping residuals stable over a long time (and therefore allow for slower nodding cycles), the pupil illumination needs to be kept constant, i.e. (imaging) observations should be performed in pupil-stabilised, rather than field-stabilised mode, with image de-rotation in the post-processing pipeline. This is now foreseen as the default observing concept for all METIS imaging modes., Comment: 17 pages, 9 figures, submitted to the SPIE proceedings as paper no. 11447-403

Published
2020
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3. Multiple Star Systems in the Orion Nebula

Author

GRAVITY collaboration, Karl, Martina, Pfuhl, Oliver, Eisenhauer, Frank, Genzel, Reinhard, Grellmann, Rebekka, Habibi, Maryam, Abuter, Roberto, Accardo, Matteo, Amorim, António, Anugu, Narsireddy, Ávila, Gerardo, Benisty, Myriam, Berger, Jean-Philippe, Bland, Nicolas, Bonnet, Henri, Bourget, Pierre, Brandner, Wolfgang, Brast, Roland, Buron, Alexander, Garatti, Alessio Caratti o, Chapron, Frédéric, Clénet, Yann, Collin, Claude, Foresto, Vincent Coudé du, de Wit, Willem-Jan, de Zeeuw, Tim, Deen, Casey, Delplancke-Ströbele, Françoise, Dembet, Roderick, Derie, Frédéric, Dexter, Jason, Duvert, Gilles, Ebert, Monica, Eckart, Andreas, Esselborn, Michael, Fédou, Pierre, Finger, Gert, Garcia, Paulo, Dabo, Cesar Enrique Garcia, Lopez, Rebeca Garcia, Gao, Feng, Gandron, Éric, Gillessen, Stefan, Gonté, Frédéric, Gordo, Paulo, Grözinger, Ulrich, Guajardo, Patricia, Guieu, Sylvain, Haguenauer, Pierre, Hans, Oliver, Haubois, Xavier, Haug, Marcus, Haußmann, Frank, Henning, Thomas, Hippler, Stefan, Horrobin, Matthew, Huber, Armin, Hubert, Zoltan, Hubin, Norbert, Hummel, Christian A., Jakob, Gerd, Jochum, Lieselotte, Jocou, Laurent, Kaufer, Andreas, Kellner, Stefan, Kandrew, Sarah, Kern, Lothar, Kervella, Pierre, Kiekebusch, Mario, Klein, Ralf, Köhler, Rainer, Kolb, Johan, Kulas, Martin, Lacour, Sylvestre, Lapeyrère, Vincent, Lazareff, Bernard, Bouquin, Jean-Baptiste Le, Léna, Pierre, Lenzen, Rainer, Lévêque, Samuel, Lin, Chien-Cheng, Lippa, Magdalena, Magnard, Yves, Mehrgan, Leander, Mérand, Antoine, Moulin, Thibaut, Müller, Eric, Müller, Friedrich, Neumann, Udo, Oberti, Sylvain, Ott, Thomas, Pallanca, Laurent, Panduro, Johana, Pasquini, Luca, Paumard, Thibaut, Percheron, Isabelle, Perraut, Karine, Perrin, Guy, Pflüger, Andreas, Duc, Thanh Phan, Plewa, Philipp M., Popovic, Dan, Rabien, Sebastian, Ramírez, Andrés, Ramos, Jose, Rau, Christian, Riquelme, Miguel, Rodríguez-Coira, Gustavo, Rohloff, Ralf-Rainer, Rosales, Alejandra, Rousset, Gérard, Sanchez-Bermudez, Joel, Scheithauer, Silvia, Schöller, Markus, Schuhler, Nicolas, Spyromilio, Jason, Straub, Odele, Straubmeier, Christian, Sturm, Eckhard, Suarez, Marcos, Tristram, Konrad R. W., Ventura, Noel, Vincent, Frédéric, Waisberg, Idel, Wank, Imke, Widmann, Felix, Wieprecht, Ekkehard, Wiest, Michael, Wiezorrek, Erich, Wittkowski, Markus, Woillez, Julien, Wolff, Burkhard, Yazici, Senol, Ziegler, Denis, and Zins, Gérard

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

This work presents an interferometric study of the massive-binary fraction in the Orion Trapezium Cluster with the recently comissioned GRAVITY instrument. We observe a total of 16 stars of mainly OB spectral type. We find three previously unknown companions for $\theta ^1$ Ori B, $\theta ^2$ Ori B, and $\theta ^2$ Ori C. We determine a separation for the previously suspected companion of NU Ori. We confirm four companions for $\theta ^1$ Ori A, $\theta ^1$ Ori C, $\theta ^1$ Ori D, and $\theta ^2$ Ori A, all with substantially improved astrometry and photometric mass estimates. We refine the orbit of the eccentric high-mass binary $\theta ^1$ Ori C and we are able to derive a new orbit for $\theta ^1$ Ori D. We find a system mass of 21.7 $M_{\odot}$ and a period of $53$ days. Together with other previously detected companions seen in spectroscopy or direct imaging, eleven of the 16 high-mass stars are multiple systems. We obtain a total number of 22 companions with separations up to 600 AU. The companion fraction of the early B and O stars in our sample is about 2, significantly higher than in earlier studies of mostly OB associations. The separation distribution hints towards a bimodality. Such a bimodality has been previously found in A stars, but rarely in OB binaries, which up to this point have been assumed to be mostly compact with a tail of wider companions. We also do not find a substantial population of equal-mass binaries. The observed distribution of mass ratios declines steeply with mass, and like the direct star counts, indicates that our companions follow a standard power law initial mass function. Again, this is in contrast to earlier findings of flat mass ratio distributions in OB associations. We exclude collision as a dominant formation mechanism but find no clear preference for core accretion or competitive accretion., Comment: Accepted for publication in A&A

Published
2018
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4. A sextet of clusters in the Vela OB2 region revealed by Gaia

Author

Beccari, Giacomo, Boffin, Henri M. J., Jerabkova, Tereza, Wright, Nicholas J., Kalari, Venu M., Carraro, Giovanni, De Marchi, Guido, and de Wit, Willem-Jan

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Astrophysics of Galaxies
Abstract

Using Gaia DR2 data, combined with OmegaCAM ground-based optical photometry from the AD-HOC survey, and detailed Radial Velocity measurements from ESO-Gaia, we analyse in detail a 10x5 deg region around the Wolf-Rayet star $\gamma^2$ Vel, including the previously known clusters Gamma Vel and NGC2547. Using clustering analysis that considers positions, proper motions and parallax, we discover 6 clusters or associations -- 4 of which appear new. Analysis of the colour-magnitude diagram for these clusters show that 4 of them formed coevally from the same molecular clouds 10 Myr ago, while NGC 2547 formed together with a newly discovered cluster 30 Myr ago. This study shows the incredible wealth of data provided by Gaia for the study of young stellar clusters., Comment: Accepted for publication as MNRAS letter. 5 pages and 2 figures

Published
2018
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5. Radiative transfer modelling of W33A MM1: 3-D structure and dynamics of a complex massive star forming region

Author

Izquierdo, Andrés F., Galván-Madrid, Roberto, Maud, Luke T., Hoare, Melvin G., Johnston, Katharine G., Keto, Eric R., Zhang, Qizhou, and de Wit, Willem-Jan

Subjects
Astrophysics - Astrophysics of Galaxies, Astrophysics - Solar and Stellar Astrophysics
Abstract

We present a composite model and radiative transfer simulations of the massive star forming core W33A MM1. The model was tailored to reproduce the complex features observed with ALMA at $\approx 0.2$ arcsec resolution in CH$_3$CN and dust emission. The MM1 core is fragmented into six compact sources coexisting within $\sim 1000$ au. In our models, three of these compact sources are better represented as disc-envelope systems around a central (proto)star, two as envelopes with a central object, and one as a pure envelope. The model of the most prominent object (Main) contains the most massive (proto)star ($M_\star\approx7~M_\odot$) and disc+envelope ($M_\mathrm{gas}\approx0.4~M_\odot$), and is the most luminous ($L_\mathrm{Main} \sim 10^4~L_\odot$). The model discs are small (a few hundred au) for all sources. The composite model shows that the elongated spiral-like feature converging to the MM1 core can be convincingly interpreted as a filamentary accretion flow that feeds the rising stellar system. The kinematics of this filament is reproduced by a parabolic trajectory with focus at the center of mass of the region. Radial collapse and fragmentation within this filament, as well as smaller filamentary flows between pairs of sources are proposed to exist. Our modelling supports an interpretation where what was once considered as a single massive star with a $\sim 10^3$ au disc and envelope, is instead a forming stellar association which appears to be virialized and to form several low-mass stars per high-mass object., Comment: 22 pages, 13 figures, 3 tables. Accepted for publication in MNRAS

Published
2018
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6. Science cases for a visible interferometer

Author

Stee, Philippe, Allard, France, Benisty, Myriam, Bigot, Lionel, Blind, Nicolas, Boffin, Henri, Fernandes, Marcelo Borges, Carciofi, Alex, Chiavassa, Andrea, Creevey, Orlagh, Cruzalebes, Pierre, de Wit, Willem-Jan, de Souza, Armando Domiciano, Elvis, Martin, Fabas, Nicolas, Faes, Daniel, Gallenne, Alexandre, Pena, Carlos Guerrero, Hillen, Michel, Hoenig, Sebastian, Ireland, Michael, Kervella, Pierre, Kishimoto, Makoto, Kostogryz, Nadia, Kraus, Stefan, Labeyrie, Antoine, Bouquin, Jean-Baptiste Le, Lebre, Agnès, Ligi, Roxanne, Marconi, Alessandro, Marsh, Thomas, Meilland, Anthony, Millour, Florentin, Monnier, John, Mourard, Denis, Nardetto, Nicolas, Ohnaka, Keiichi, Paladini, Claudia, Perraut, Karine, Perrin, Guy, Petit, Pascal, Petrov, Romain, Rakshit, Suvendu, Schaefer, Gail, Schneider, Jean, Shulyak, Denis, Simon, Michal, Soulez, Ferreol, Steeghs, Danny, Tallon-Bosc, Isabelle, Tallon, Michel, Brummelaar, Theo ten, Thiebaut, Eric, Thévenin, Frédéric, Van Winckel, Hans, Wittkowski, Markus, and Zorec, Juan

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

High spatial resolution is the key for the understanding various astrophysical phenomena. But even with the future E-ELT, single dish instruments are limited to a spatial resolution of about 4 mas in the visible. For the closest objects within our Galaxy most of the stellar photosphere remains smaller than 1 mas. With the success of long baseline interferometry these limitations were soom overcome. Today low and high resolution interferometric instruments on the VLTI and CHARA offer an immense range of astrophysical studies. Combining more telescopes and moving to visible wavelengths broadens the science cases even more. With the idea of developing strong science cases for a future visible interferometer, we organized a science group around the following topics: pre-main sequence and main sequence stars, fundamental parameters, asteroseismology and classical pulsating stars, evolved stars, massive stars, active galactic nuclei (AGNs) and imaging techniques. A meeting was organized on the 15th and 16th of January, 2015 in Nice with the support of the Action Specific in Haute Resolution Angulaire (ASHRA), the Programme National en Physique Stellaire (PNPS), the Lagrange Laboratory and the Observatoire de la Cote d'Azur, in order to present these cases and to discuss them further for future visible interferometers. This White Paper presents the outcome of the exchanges. This book is dedicated to the memory of our colleague Olivier Chesneau who passed away at the age of 41., Comment: White Paper prospective. This book is dedicated to the memory of our colleague Olivier Chesneau who passed away at the age of 41. v2 includes some corrections to text

Published
2017

7. A high-mass protobinary system with spatially resolved circumstellar accretion disks and circumbinary disk

Author

Kraus, Stefan, Kluska, Jacques, Kreplin, Alexander, Bate, Matthew, Harries, Tim J., Hofmann, Karl-Heinz, Hone, Edward, Monnier, John D., Weigelt, Gerd, Anugu, Narsireddy, de Wit, Willem-Jan, and Wittkowski, Markus

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

High-mass multiples might form via fragmentation of self-gravitational disks or alternative scenarios such as disk-assisted capture. However, only few observational constraints exist on the architecture and disk structure of high-mass protobinaries and their accretion properties. Here we report the discovery of a close ($57.9\pm0.2$mas=170au) high-mass protobinary, IRAS17216-3801, where our VLTI/GRAVITY+AMBER near-infrared interferometry allows us to image the circumstellar disks around the individual components with 3 milliarcsecond resolution. We estimate the component masses to $\sim20$ and $\sim18 M_{\odot}$ and find that the radial intensity profiles can be reproduced with an irradiated disk model, where the inner regions are excavated of dust, likely tracing the dust sublimation region in these disks. The circumstellar disks are strongly misaligned with respect to the binary separation vector, which indicates that the tidal forces did not have time to realign the disks, pointing towards a young dynamical age of the system. We constrain the distribution of the Br$\gamma$ and CO-emitting gas using VLTI/GRAVITY spectro-interferometry and VLT/CRIRES spectro-astrometry and find that the secondary is accreting at a higher rate than the primary. VLT/NACO imaging shows $L'$-band emission on 3-4 times larger scales than the binary separation, matching the expected dynamical truncation radius for the circumbinary disk. The IRAS17216-3801 system is $\sim3\times$ more massive and $\sim5\times$ more compact than other high-mass multiplies imaged at infrared wavelengths and the first high-mass protobinary system where circumstellar and circumbinary dust disks could be spatially resolved. This opens exciting new opportunities for studying star-disk interactions and the role of multiplicity in high-mass star formation., Comment: 9 pages, 4 figures, accepted for publication in The Astrophysical Journal Letters

Published
2016
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8. The 2nd Generation VLTI path to performance

Author

Woillez, Julien, Alonso, Jaime, Berger, Jean-Philippe, Bonnet, Henri, de Wit, Willem-Jan, Egner, Sebastian, Eisenhauer, Frank, Gonté, Frédéric, Guieu, Sylvain, Haguenauer, Pierre, Mérand, Antoine, Pettazzi, Lorenzo, Poupar, Sébastien, Schöller, Markus, and Schuhler, Nicolas

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

The upgrade of the VLTI infrastructure for the 2nd generation instruments is now complete with the transformation of the laboratory, and installation of star separators on both the 1.8-m Auxiliary Telescopes (ATs) and the 8-m Unit Telescopes (UTs). The Gravity fringe tracker has had a full semester of commissioning on the ATs, and a first look at the UTs. The CIAO infrared wavefront sensor is about to demonstrate its performance relative to the visible wavefront sensor MACAO. First astrometric measurements on the ATs and astrometric qualification of the UTs are on-going. Now is a good time to revisit the performance roadmap for VLTI that was initiated in 2014, which aimed at coherently driving the developments of the interferometer, and especially its performance, in support to the new generation of instruments: Gravity and MATISSE., Comment: 9 pages, 6 figures, 1 table, Proc. SPIE 2016

Published
2016
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9. Planet Formation Imager (PFI): science vision and key requirements

Author

Kraus, Stefan, Monnier, John D., Ireland, Michael J., Duchene, Gaspard, Espaillat, Catherine, Hoenig, Sebastian, Juhasz, Attila, Mordasini, Chris, Olofsson, Johan, Paladini, Claudia, Stassun, Keivan, Turner, Neal, Vasisht, Gautam, Harries, Tim J., Bate, Matthew R., Gonzalez, Jean-Francois, Matter, Alexis, Zhu, Zhaohuan, Panic, Olja, Regaly, Zsolt, Morbidelli, Alessandro, Meru, Farzana, Wolf, Sebastian, Ilee, John, Berger, Jean-Philippe, Zhao, Ming, Kral, Quentin, Morlok, Andreas, Bonsor, Amy, Ciardi, David, Kane, Stephen R., Kratter, Kaitlin, Laughlin, Greg, Pepper, Joshua, Raymond, Sean, Labadie, Lucas, Nelson, Richard P., Weigelt, Gerd, Brummelaar, Theo ten, Pierens, Arnaud, Oudmaijer, Rene, Kley, Wilhelm, Pope, Benjamin, Jensen, Eric L. N., Bayo, Amelia, Smith, Michael, Boyajian, Tabetha, Quiroga-Nunez, Luis Henry, Millan-Gabet, Rafael, Chiavassa, Andrea, Gallenne, Alexandre, Reynold, Mark, de Wit, Willem-Jan, Wittkowski, Markus, Millour, Florentin, Gandhi, Poshak, Almeida, Cristina Ramos, Herrero, Almudena Alonso, Packham, Chris, Kishimoto, Makoto, Tristram, Konrad R. W., Pott, Joerg-Uwe, Surdej, Jean, Buscher, David, Haniff, Chris, Lacour, Sylvestre, Petrov, Romain, Ridgway, Steve, Tuthill, Peter, van Belle, Gerard, Armitage, Phil, Baruteau, Clement, Benisty, Myriam, Bitsch, Bertram, Paardekooper, Sijme-Jan, Pinte, Christophe, Masset, Frederic, and Rosotti, Giovanni P.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Earth and Planetary Astrophysics
Abstract

The Planet Formation Imager (PFI) project aims to provide a strong scientific vision for ground-based optical astronomy beyond the upcoming generation of Extremely Large Telescopes. We make the case that a breakthrough in angular resolution imaging capabilities is required in order to unravel the processes involved in planet formation. PFI will be optimised to provide a complete census of the protoplanet population at all stellocentric radii and over the age range from 0.1 to about 100 Myr. Within this age period, planetary systems undergo dramatic changes and the final architecture of planetary systems is determined. Our goal is to study the planetary birth on the natural spatial scale where the material is assembled, which is the "Hill Sphere" of the forming planet, and to characterise the protoplanetary cores by measuring their masses and physical properties. Our science working group has investigated the observational characteristics of these young protoplanets as well as the migration mechanisms that might alter the system architecture. We simulated the imprints that the planets leave in the disk and study how PFI could revolutionise areas ranging from exoplanet to extragalactic science. In this contribution we outline the key science drivers of PFI and discuss the requirements that will guide the technology choices, the site selection, and potential science/technology tradeoffs., Comment: 13 pages, 5 figures, Proceedings of SPIE 2016

Published
2016
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10. The LBV HR Car has a partner: Discovery of a companion with the VLTI

Author

Boffin, Henri M. J., Rivinius, Thomas, Merand, Antoine, Mehner, Andrea, LeBouquin, Jean-Baptiste, Pourbaix, Dimitri, de Wit, Willem-Jan, Martayan, Christophe, and Guieu, Sylvain

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

Luminous Blue Variables (LBVs) are massive stars caught in a post-main sequence phase, during which they are losing a significant amount of mass. As, on one hand, it is thought that the majority of massive stars are close binaries that will interact during their lifetime, and on the other, the most dramatic example of an LBV, Eta Car, is a binary, it would be useful to find other binary LBVs. We present here interferometric observations of the LBV HR Car done with the AMBER and PIONIER instruments attached to ESO's Very Large Telescope Interferometer (VLTI). Our observations, spanning two years, clearly reveal that HR Car is a binary star. It is not yet possible to constrain fully the orbit, and the orbital period may lie between a few years and several hundred years. We derive a radius for the primary in the system and possibly resolve as well the companion. The luminosity ratio in the H-band between the two components is changing with time, going from about 6 to 9. We also tentatively detect the presence of some background flux which remained at the 2% level until January 2016, but then increased to 6% in April 2016. Our AMBER results show that the emission line forming region of Br gamma is more extended than the continuum emitting region as seen by PIONIER and may indicate some wind-wind interaction. Most importantly, we constrain the total masses of both components, with the most likely range being 33.6 and 45 solar masses. Our results show that the LBV HR Car is possibly an Eta Car analog binary system with smaller masses, with variable components, and further monitoring of this object is definitively called for., Comment: A&A, in press

Published
2016
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11. Training telescope operators and support astronomers at Paranal

Author

Boffin, Henri M. J., Gadotti, Dimitri A., Anderson, Joe, Pino, Andres, de Wit, Willem-Jan, and Girard, Julien H. V.

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics, Physics - Physics Education
Abstract

The operations model of the Paranal Observatory relies on the work of efficient staff to carry out all the daytime and nighttime tasks. This is highly dependent on adequate training. The Paranal Science Operations department (PSO) has a training group that devises a well-defined and continuously evolving training plan for new staff, in addition to broadening and reinforcing courses for the whole department. This paper presents the training activities for and by PSO, including recent astronomical and quality control training for operators, as well as adaptive optics and interferometry training of all staff. We also present some future plans., Comment: Paper 9910-123 presented at SPIE 2016

Published
2016
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12. Star Formation at milli-arcsecond resolution

Author

Oudmaijer, Rene and de Wit, Willem-Jan

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

This chapter discusses the use and possibilities of optical and infrared interferometry to study star formation. The chapter starts with a brief overview of the star formation process and highlights the open questions from an observational point of view. These are found at the smallest scales, as this is, inevitably, where all the action such as accretion and outflows, occurs. We then use basic astrophysical concepts to assess which scales and conditions can be probed with existing interferometric set-ups for which we use the ESO/VLTI instrument suite as example. We will concentrate on the more massive stars observed at high resolution with continuum interferometry. Throughout, some of the most recent interferometric results are used as examples of the various processes discussed., Comment: Chapter in the proceedings of "What can the highest angular resolution bring to stellar astrophysics?", Eds Millour et al.. The chapter is based on lectures given at the 2013 VLTI School held in Barcelonnette (France). 13 pages, 4 figures

Published
2015
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13. A multi-wavelength interferometric study of the massive young stellar object IRAS 13481-6124

Author

Boley, Paul A., Kraus, Stefan, de Wit, Willem-Jan, Linz, Hendrik, van Boekel, Roy, Henning, Thomas, Lacour, Sylvestre, Monnier, John D., Stecklum, Bringfried, and Tuthill, Peter G.

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

We present new mid-infrared interferometric observations of the massive young stellar object IRAS 13481-6124, using VLTI/MIDI for spectrally-resolved, long-baseline measurements (projected baselines up to $\sim120$ m) and GSO/T-ReCS for aperture-masking interferometry in five narrow-band filters (projected baselines of $\sim1.8-6.4$ m) in the wavelength range of $7.5-13$ $\mu$m. We combine these measurements with previously-published interferometric observations in the $K$ and $N$ bands in order to assemble the largest collection of infrared interferometric observations for a massive YSO to date. Using a combination of geometric and radiative-transfer models, we confirm the detection at mid-infrared wavelengths of the disk previously inferred from near-infrared observations. We show that the outflow cavity is also detected at both near- and mid-infrared wavelengths, and in fact dominates the mid-infrared emission in terms of total flux. For the disk, we derive the inner radius ($\sim1.8$ mas or $\sim6.5$ AU at 3.6 kpc), temperature at the inner rim ($\sim1760$ K), inclination ($\sim48$ deg) and position angle ($\sim107$ deg). We determine that the mass of the disk cannot be constrained without high-resolution observations in the (sub-)millimeter regime or observations of the disk kinematics, and could be anywhere from $\sim10^{-3}$ to $20$ M$_\odot$. Finally, we discuss the prospects of interpreting the spectral energy distributions of deeply-embedded massive YSOs, and warn against attempting to infer disk properties from the SED., Comment: Accepted to Astronomy and Astrophysics

Published
2015
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15. VLTI status update: a decade of operations and beyond

Author

Merand, Antoine, Abuter, Roberto, Aller-Carpentier, Emmanuel, Andolfato, Luigi, Alonso, Jaime, Berger, Jean-Philippe, Blanchard, Guillaume, Boffin, Henri, Bourget, Pierre, Bristow, Paul, Cid, Claudia, de Wit, Willem-Jan, del Valle, Diego, Delplancke-Stroebele, Franccoise, Derie, Frederic, Faundez, Lorena, Ertel, Steve, Grellmann, Rebekka, Gitton, Philippe, Glindemann, Andreas, Guajardo, Patricia, Guieu, Sylvain, Guisard, Stephane, Guniat, Serge, Haguenauer, Pierre, Herrera, Christian, Hummel, Christian, La Fuente, Carlos, Lopez, Marcelo, Mardones, Pedro, Morel, Sebastien, Mueller, Andre, Percheron, Isabelle, Duc, Than Phan, Pino, Andres, Poupar, Sebastien, Pozna, Eszter, Ramirez, Andres, Rengaswamy, Sridharan, Rivas, Lionel, Rivinius, Thomas, Segovia, Alex, Schmid, Christian, Schoeller, Markus, Schuhler, Nicolas, Woillez, Julien, and Wittkowski, Markus

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

We present the latest update of the European Southern Observatory's Very Large Telescope interferometer (VLTI). The operations of VLTI have greatly improved in the past years: reduction of the execution time; better offering of telescopes configurations; improvements on AMBER limiting magnitudes; study of polarization effects and control for single mode fibres; fringe tracking real time data, etc. We present some of these improvements and also quantify the operational improvements using a performance metric. We take the opportunity of the first decade of operations to reflect on the VLTI community which is analyzed quantitatively and qualitatively. Finally, we present briefly the preparatory work for the arrival of the second generation instruments GRAVITY and MATISSE., Comment: 10 pages, 7 figures, Proceedings of the SPIE, 9146-19

Published
2014
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16. Dusty Blue Supergiants: News from High-Angular Resolution Observations

Author

de Wit, Willem-Jan, Oudmaijer, Rene, and Vink, Jorick

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

An overview is presented of the recent advances in understanding the B[e] phenomenon among blue supergiant stars in light of high-angular resolution observations and with an emphasis on the results obtained by means of long baseline optical stellar interferometry. The focus of the review is on the circumstellar material and evolutionary phase of B[e] supergiants, but recent results on dust production in regular blue supergiants are also highlighted., Comment: 8 pages, 2 figures. Published in "Advances in Astronomy" by Hindawi Publishing Corporation

Published
2014
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17. Speckle Imaging with VLT/NACO No-AO Mode

Author

Rengaswamy, Sridharan, Girard, Julien, de Wit, Willem-Jan, and Boffin, Henri

Subjects
Astrophysics - Instrumentation and Methods for Astrophysics
Abstract

Long-exposure stellar images recorded with large ground-based telescopes are blurred due to the turbulent nature of the atmosphere. The VLT employs active and adaptive optics (AO) systems to compensate for the deleterious effects of the atmosphere in real time. The speckle imaging technique provides an alternative way to achieve diffraction-limited imaging by post-processing a series of short-exposure images. The use of speckle imaging with the no-AO mode of NACO at the VLT is demonstrated. Application of this technique is particularly suited to the J-band and it provides versatile high angular resolution imaging under mediocre conditions and/or in imaging extended objects. The implementation of this mode underlines the continuing attractiveness of NACO at the VLT., Comment: 5 pages, 6 figures

Published
2014

18. Near-Infrared Evidence for a Sudden Temperature Increase in Eta Carinae

Author

Mehner, Andrea, Ishibashi, Kazunori, Whitelock, Patricia, Nagayama, Takahiro, Feast, Michael, van Wyk, Francois, and de Wit, Willem-Jan

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

Aims. Eta Car's ultra-violet, optical, and X-ray light curves and its spectrum suggest a physical change in its stellar wind over the last decade. It was proposed that the mass-loss rate decreased by a factor of about 2 in the last 15 years. We complement these recent results by investigating the past evolution and the current state of eta Car in the near-infrared (IR). Methods. We present JHKL photometry of eta Car obtained at SAAO Sutherland from 2004-2013 with the Mk II photometer at the 0.75-m telescope and JHKs photometry with SIRIUS at the 1.4-m IRSF telescope from 2012-2013. The near-IR light curves since 1972 are analyzed. Results. The long-term brightening trends in eta Car's JHKL light curves were discontinuous around the 1998 periastron passage. After 1998, the star shows excess emission above the extrapolated trend from earlier dates, foremost in J and H, and the blueward, cyclical progression in its near-IR colors is accelerated. The near-IR color evolution is strongly correlated with the periastron passages. After correcting for the secular trend we find that the color evolution matches an apparent increase in blackbody temperature of an optically thick near-IR emitting plasma component from about 3500 to 6000 K over the last 20 years. Conclusions. We suggest that the changing near-IR emission may be caused by variability in optically thick bremsstrahlung emission. Periastron passages play a key role in the observed excess near-IR emission after 1998 and the long-term color evolution. We thus propose as a hypothesis that angular momentum transfer (via tidal acceleration) during periastron passages leads to sudden changes in eta Car's atmosphere resulting in a long-term decrease in the mass-loss rate., Comment: 11 pages, 5 figures, accepted in A&A

Published
2014
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19. Neutral and ionized gas around the post-Red Supergiant IRC+10420 at au size scales

Author

Oudmaijer, Rene and de Wit, Willem-Jan

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

IRC +10420 is one of the few known massive stars in rapid transition from the Red Supergiant phase to the Wolf-Rayet or Luminous Blue Variable phase. The star has an ionised wind and using the Br gamma hydrogen recombination emission we assess the mass-loss on spatial scales of order 1 au. We present new VLT Interferometer AMBER data which are combined with all other AMBER data in the literature. The final dataset covers a position angle range of 180 degrees and baselines up to 110 meters. The spectrally dispersed visibilities, differential phases and line flux are conjointly analyzed and modelled. We also present AMBER/FINITO observations which cover a larger wavelength range and allow us to observe the Na I doublet at 2.2 micron. The data are complemented by X-Shooter data, which provide a higher spectral resolution view. The Brackett gamma line and the Na I doublet are both spatially resolved. After correcting the AMBER data for the fact that the lines are not spectrally resolved, we find that Br gamma traces a ring with a diameter of 4.18 milli-arcseconds. We consider a geometric model in which the Br gamma emission emerges from the top and bottom rings of an hour-glass shaped structure, viewed almost pole-on. It provides satisfactory fits to most visibilities and differential phases. The fact that we detect line emission from a neutral metal like Na I within the ionized region, a very unusual occurrence, suggests the presence of a dense pseudo-photosphere. The ionized wind can be reproduced with a polar wind, which could well have the shape of an hour-glass. The resolved Na I emission is found to occur on scales barely larger than the continuum. This fact and that many Yellow Hypergiants exhibit this comparatively rare emission hints at the presence of a "Yellow" or even "White Wall" in the Hertzsprung-Russell diagram, preventing them from visibly evolving to the blue., Comment: Accepted for publication in A&A. 12 pages, 11 figures

Published
2012
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20. Molecular emission from GG Car's circumbinary disk

Author

Kraus, Michaela, Oksala, Mary, Nickeler, Dieter, Muratore, Florencia, Fernandes, Marcelo Borges, Aret, Anna, Cidale, Lydia, and de Wit, Willem-Jan

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

The appearance of the B[e] phenomenon in evolved massive stars such as B[e] supergiants is still a mystery. While these stars are generally found to have disks that are cool and dense enough for efficient molecule and dust condensation, the origin of the disk material is still unclear. We aim at studying the kinematics and origin of the disk in the eccentric binary system GG Car, whose primary component is proposed to be a B[e] supergiant. Based on medium- and high-resolution near-infrared spectra we analyzed the CO-band emission detected from GG Car. The complete CO-band structure delivers information on the density and temperature of the emitting region, and the detectable 13CO bands allow us to constrain the evolutionary phase. In addition, the kinematics of the CO gas can be extracted from the shape of the first 12CO band head. We find that the CO gas is located in a ring surrounding the eccentric binary system, and its kinematics agrees with Keplerian rotation with a velocity, projected to the line of sight, of (80\pm 1) km/s. The CO ring has a column density of (5\pm 3)x10^21 cm^-2 and a temperature of 3200\pm 500 K. In addition, the material is chemically enriched in 13CO, which agrees with the primary component being slightly evolved off the main sequence. We discuss two possible scenarios for the origin of the circumbinary disk: (i) non-conservative Roche lobe overflow, and (ii) the possibility that the progenitor of the primary component could have been a classical Be star. Neither can be firmly excluded, but for Roche lobe overflow to occur, a combination of stellar and orbital parameter extremawould be required., Comment: 8 pages, 5 figures, accepted to Astronomy and Astrophysics

Published
2012
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21. The circumstellar disk, envelope, and bi-polar outflow of the Massive Young Stellar Object W33A

Author

Davies, Ben, Lumsden, Stuart L., Hoare, Melvin G., Oudmaijer, Rene D., and de Wit, Willem-Jan

Subjects
Astrophysics - Solar and Stellar Astrophysics
Abstract

The Young Stellar Object (YSO) W33A is one of the best known examples of a massive star still in the process of forming. Here we present Gemini North ALTAIR/NIFS laser-guide star adaptive-optics assisted K-band integral-field spectroscopy of W33A and its inner reflection nebula. In our data we make the first detections of a rotationally-flattened outer envelope and fast bi-polar jet of a massive YSO at near-infrared wavelengths. The predominant spectral features observed are Br-gamma, H_2, and a combination of emission and absorption from CO gas. We perform a 3-D spectro-astrometric analysis of the line emission, the first study of its kind. We find that the object's Br-gamma emission reveals evidence for a fast bi-polar jet on sub-milliarcsecond scales, which is aligned with the larger-scale outflow. The hybrid CO features can be explained as a combination of hot CO emission arising in a disk close to the central star, while cold CO absorption originates in the cooler outer envelope. Kinematic analysis of these features reveals that both structures are rotating, and consistent with being aligned perpendicularly to both the ionised jet and the large-scale outflow. Assuming Keplerian rotation, we find that the circumstellar disk orbits a central mass of >10Msun, while the outer envelope encloses a mass of ~15Msun. Our results suggest a scenario of a central star accreting material from a circumstellar disk at the centre of a cool extended rotating torus, while driving a fast bi-polar wind. These results therefore provide strong supporting evidence for the hypothesis that the formation mechanism for high-mass stars is qualitatively similar to that of low-mass stars., Comment: 13 pages, 18 figs. Accepted for publication in MNRAS

Published
2009
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22. Post-Red Supergiants

Author

Oudmaijer, Rene, Davies, Ben, de Wit, Willem-Jan, and Patel, Mitesh

Subjects
Astrophysics
Abstract

The yellow hypergiants are found in a stage between the massive Red Supergiants and the Wolf-Rayet stars. This review addresses current issues concerning the evolution of massive stars, concentrating on the transitional post-Red Supergiant phase. Few yellow hypergiants are known and even fewer show direct evidence for having evolved off the Red Supergiant branch. Indeed, only two such rare objects with clear evidence for having gone through of a previous mass losing phase are known, IRC +10420 and HD 179821. We will review their properties and present recent results employing near-infrared interferometry, integral field spectroscopy and polarimetry. Finally, their real-time evolution is discussed., Comment: 16 pages. This is an updated and slightly expanded version of a Keynote Talk given at ``Biggest, Baddest, Coolest Stars'' (ASP Conf Series) eds. D. Luttermoser, B. Smith, and R. Stencel

Published
2008

25. VISIR - operations, calibrations, upgrades

Author

de Wit, Willem-Jan

Abstract

ESO's VISIR instrument aims to provide diffraction-limited observations at high sensitivity in three mid-infrared atmospheric windows: the M-band, the N-band, and the Q-band for both imaging and spectroscopy. The instrument has been in near continuous operations since 2005, undergoing a few game-changing upgrades over the years. In particular the major VISIR upgrade project lasting about two years until 2015. In ths presentation, I will present VISIR's operational model its versatility and limitations and describe the instrument's performance improvements over the years.

Published
2020
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26. Unveiling substructures in disks around massive young stellar objects

Author

Frost, Abigail, Oudmaijer, René, Lumsden, Stuart, and de Wit, Willem-Jan

Subjects
Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

Protostellar disks play key roles in the accretion process and formation of planetesimals for low-mass stars, and form various substructures, as different physical processes occur within them. Massive stars (M>8Mdot) form from the same clouds of dust and gas as low-mass stars and affect the both their own stellar environment and galaxies as a whole. Despite their importance, the formation of massive stars is poorly understood as they are deeply embedded, distant and rare, which introduces more observational challenges. While disks have recently been found around massive protostars massive disk evolution is yet to be constrained. In my talk, I will discuss our recent work which has, using a multi-scale analysis on a sample of massive young stellar objects (MYSOs), detected inner holes and gap-like substructures within the MYSO disks. I will also tie these geometrical traits to an independently determined evolutionary sequence and discuss what this means for disk evolution around MYSOs.

Published
2020
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27. Towards a physical understanding of the thermal background in large ground-based telescopes

Author

Burtscher, Leonard, primary, Politopoulos, Ioannis, additional, Fernández-Acosta, Sergio, additional, Agocs, Tibor, additional, van den Ancker, Mario, additional, van Boekel, Roy, additional, Brandl, Bernhard, additional, Käufl, Hans-Ulrich, additional, Pantin, Eric, additional, Pietrow, Alexander, additional, Siebenmorgen, Ralf, additional, Stuik, Remko, additional, Tristram, Konrad R., additional, and de Wit, Willem-Jan, additional

Published
2020
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31. Precision Monitoring of Cool Evolved Stars: Constraining Effects of Convection and Pulsation

Author

Wittkowski, Markus, Bladh, Sara, Chiavassa, Andrea, De Wit, Willem-Jan, Eriksson, Kjell, Freytag, Bernd, Haubois, Xavier, Höfner, Susanne, Kravchenko, Kateryna, Paladini, Claudia, Paumard, Thibaut, Rau, Gioia, and Wood, Peter R.

Subjects
Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

Mass loss from cool evolved stars is an important ingredient of the cosmic matter cycle, enriching the Universe with newly formed elements and dust. However, physical processes that are not considered in current models represent uncertainties in our general understanding of mass loss. Time-series of interferometric data provide the strongest tests of dynamical processes in the atmospheres of these stars. Here, we present a pilot study of such measurements obtained with the GRAVITY instrument on the Very Large Telescope Interferometer., Published in The Messenger vol. 178, pp. 34-35, December 2019.

Published
2019
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32. Imagerie spectro-interférométrique du noyau de η Car avec l'instrument GRAVITY : images de la zone de collision de vent dans les raies Br γ et He I avec une résolution de la milli-seconde d'arc

Author

Sanchez-Bermudez, Joel, Weigelt, Gerd, Bestenlehner, Joachim M., Kervella, Pierre, Brandner, Wolfgang, Henning, Thomas, Müller, André, Perrin, Guy, Pott, Jorg-Uwe, Schöller, Markus, Van Boekel, Roy, Abuter, Roberto, Accardo, Matteo, Amorim, Antonio, Anugu, Narsireddy, Avila, Gerardo, Benisty, Myriam, Berger, Jean-Philippe, Blind, Nicolas, Bonnet, Henri, Bourget, Pierre, Brast, Roland, Buron, Alexander, Cantalloube, Faustine, Caratti O Garatti, Alessio, Cassaing, Frederic, Chapron, Frédéric, Choquet, Élodie, Clenet, Yann, Collin, Claude, Coude Du Foresto, Vincent, de Wit, Willem-Jan, De Zeeuw, Tim, Deen, Casey, Delplancke-Ströbele, Françoise, Dembet, Roderick, Derie, Frédéric, Dexter, Jason, Duvert, Gilles, Ebert, Monica, Eckart, Andreas, Eisenhauer, Frank, Esselborn, Michael, Fédou, Pierre, Garcia, Paulo J. V., Garcia-Dabo, Cesar Enrique, Garcia Lopez, Rebeca, Gao, Feng, Gendron, Eric, Genzel, Reinhard, Gillessen, Stefan, Haubois, Xavier, Haug, Marcus, Haussmann, Frank, Hippler, Stefan, Horrobin, Matthew, Huber, Armin, Huber, Zoltan, Hubin, Norbert, Hummel, Christian A., Jakob, Gerd, Jochum, Lieselotte, Jocou, Laurent, Karl, Martina, Kaufer, Andreas, Kellner, Stefan, Kendrew, Sarah, Kern, Lothar, Kiekebusch, Mario, Klein, Ralf, Kolb, Johann, Kulas, Martin, Lacour, Sylvestre, Lapeyrère, Vincent, Lazareff, Bernard, Le Bouquin, Jean-Baptiste, Léna, Pierre, Lenzen, Rainer, Lévêque, Samuel, Lippa, Magdalena, Magnard, Yves, Mehrgan, Leander, Mellein, Marcus, Mérand, Antoine, Moreno-Ventas, Javier, Moulin, Thibaut, Muller, Ewald, Muller, Friedrich, Neumann, Udo, Oberti, Sylvain, Ott, Thomas, Pallanca, Laurent, Panduro, Johana, Pasquini, Luca, Paumard, Thibaut, Percheron, Isabelle, Perraut, Karine, Petrucci, Pierre-Olivier, Pflüger, Andreas, Pfuhl, Oliver, Duc, Thanh Phan, Plewa, Philipp M., Popovic, Dan, Rabien, Sebastian, Ramirez, Andres, Ramos, Jose Ricardo, Rau, Christian, Riquelme, Miguel, Rodríguez-Coira, Gustavo, Rohloff, Ralf-Rainer, Rosales, Alejandra, Rousset, Gérard, Scheithauer, Silvia, Schuhler, Nicolas, Spyromilio, Jason, Straub, Odele, Straubmeier, Christian, Sturm, Eckhard, Suarez, Marco, Tristram, Konrad R. W., Ventura, Noel, Vincent, Frédéric, Waisberg, Idel, Wank, Imke, Widmann, Felix, Wieprecht, Ekkehard, Wiest, Michael, Wiezorrek, Erich, Wittkowski, Markus, Woillez, Julien, Wolff, Burkhard, Yazici, Senol, Ziegler, Denis, Zins, Gerard, Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, European Southern Observatory [Santiago] (ESO), European Southern Observatory (ESO), Max-Planck-Institut für Radioastronomie (MPIFR), University of Sheffield [Sheffield], Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Universidad de Santiago de Chile [Santiago] (USACH), CENTRA Instituto Superior Tecnico, Universidade de Lisboa (ULISBOA), University of Exeter, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève (UNIGE), Max Planck Institute for Extraterrestrial Physics (MPE), Dublin Institute for Advanced Studies (DIAS), DOTA, ONERA, Université Paris Saclay [Châtillon], ONERA-Université Paris-Saclay, Leiden University, Physikalisches Institut [Köln], Universität zu Köln, Max Planck Institute for Radio Astronomy, Universidade do Porto [Porto], Instituto Superior Técnico, Technical University of Lisbon, Lawrence Berkeley National Laboratory [Berkeley] (LBNL), European Space Agency (Baltimore) Space Telescope Science Institute (ESA), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), DOTA, ONERA, Université Paris Saclay (COmUE) [Châtillon], ONERA-Université Paris Saclay (COmUE), Universidade do Porto, Franche-Comté Électronique Mécanique, Thermique et Optique - Sciences et Technologies (UMR 6174) (FEMTO-ST), Université de Technologie de Belfort-Montbeliard (UTBM)-Ecole Nationale Supérieure de Mécanique et des Microtechniques (ENSMM)-Université de Franche-Comté (UFC), and Université Bourgogne Franche-Comté [COMUE] (UBFC)-Université Bourgogne Franche-Comté [COMUE] (UBFC)-Centre National de la Recherche Scientifique (CNRS)

Subjects
INSTRUMENTATION: HAUTE RESOLUTION ANGULAIRE, IMAGERIE STELLAIRE, BINARY STAR, MASS LOSS, [SPI.OPTI]Engineering Sciences [physics]/Optics / Photonic, HIGH ANGULAR RESOLUTION, INSTRUMENTATION: INTERFEROMETRES, ETOILE: PERTE DE MASSE, STAR IMAGING, INTERFEROMETER, ETOILES BINAIRES, MASSIVE STAR, ETOILES MASSIVES
Abstract

International audience; Context. η Car is one of the most intriguing luminous blue variables in the Galaxy. Observations and models of the X-ray, ultraviolet, optical, and infrared emission suggest a central binary in a highly eccentric orbit with a 5.54 yr period residing in its core. 2D and 3D radiative transfer and hydrodynamic simulations predict a primary with a dense and slow stellar wind that interacts with the faster and lower density wind of the secondary. The wind-wind collision scenario suggests that the secondary’s wind penetrates the primary’s wind creating a low-density cavity in it, with dense walls where the two winds interact. However, the morphology of the cavity and its physical properties are not yet fully constrained.Aims. We aim to trace the inner ∼5–50 au structure of η Car’s wind-wind interaction, as seen through Brγ and, for the first time, through the He I 2s-2p line.Methods. We have used spectro-interferometric observations with the K-band beam-combiner GRAVITY at the VLTI. The analyses of the data include (i) parametrical model-fitting to the interferometric observables, (ii) a CMFGEN model of the source’s spectrum, and (iii) interferometric image reconstruction.Results. Our geometrical modeling of the continuum data allows us to estimate its FWHM angular size close to 2 mas and an elongation ratio ϵ = 1.06 ± 0.05 over a PA = 130° ± 20°. Our CMFGEN modeling of the spectrum helped us to confirm that the role of the secondary should be taken into account to properly reproduce the observed Brγ and He I lines. Chromatic images across the Brγ line reveal a southeast arc-like feature, possibly associated to the hot post-shocked winds flowing along the cavity wall. The images of the He I 2s-2p line served to constrain the 20 mas (∼50 au) structure of the line-emitting region. The observed morphology of He I suggests that the secondary is responsible for the ionized material that produces the line profile. Both the Brγ and the He I 2s-2p maps are consistent with previous hydrodynamical models of the colliding wind scenario. Future dedicated simulations together with an extensive interferometric campaign are necessary to refine our constraints on the wind and stellar parameters of the binary, which finally will help us predict the evolutionary path of η Car.; Contexte : η Car est une des étoiles brillantes bleues variables les plus intrigante de notre galaxie. Les observations et les modèles des émissions X, UV et optique et IR suggèrent qu'une étoile binaire avec une orbite fortement excentrique de période 5,54 ans réside au centre de son coeur. Les simulations hydrodynamiques et de transfert radiatif 2D et 3D prédisent la présence d'une étoile primaire avec vent stellaire dense et lent, qui interagit avec le vent de densité moindre et plus rapide de l'étoile secondaire. Ce scénario de collision vent-vent suggère que le vent de l'étoile secondaire pénètre dans le vent de l'étoile primaire, créant dans ce dernier une cavité de faible densité, avec des murs denses où les deux vents interagissent. Cependant, la morphologie de cette cavité et ses propriétés physiques ne sont pas encore pleinement contraints.Objectifs. Nous visons à déterminer la structure interne de l’interaction vent-vent de Car dans une zone allant de 5 à 50 Unités Astronomiques, telle que vue à travers Br γ et, pour la première fois, à travers la transition 2s-2p de He I.Méthodes : Nous avons utilisé des observations spectro-interférométriques du combineur de faisceaux en bande K de GRAVITY au VLTI. Les analyses des données comprennent: (i) un ajustement de modèle paramétrique aux observables interférométriques, (ii) un modèle CMFGEN du spectre de la source, et (iii) des reconstructions d'image interférométriques.Résultats : Notre modélisation géométrique des données du continuum nous permet d'estimer sa taille angulaire FWHM proche de 2 mas et son coefficient d'allongement de 1,06 ± 0,05 sur un PA = 130° ± 20°. Notre modélisation CMFGEN du spectre nous a permis de confirmer que le rôle de l'étoile secondaire devrait être pris en compte pour reproduire correctement les émissions Br γ et He I observées. Les images spectrales dans la bande Br γ révèle une caractéristique semblable à un arc au sud-est, peut-être associé aux vents chauds post-choc circulant le long du mur de la cavité. Les images dans la bande He I 2s-2p ont servi à contraindre la structure de la région d'émission de la transition, avec une résolution de 20 millisecondes d'arc (50 UA). La morphologie observée de He I suggère que l'étoile secondaire est responsable de l'ionisationproduisant le profil de raie. Les deux images (en Br γ et He I 2s-2p) sont compatibles avec les modèles hydrodynamiques précédents du scénario de vent en collision. De futures simulations dédiées ainsi qu’une vaste campagne interférométrique sont nécessaires pour affiner nos contraintes sur le vent et les paramètres stellaires de la binaire, ce qui nous aidera enfin à prédire le chemin évolutif de η Car.

Published
2018
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33. The Accretion Dicsc in Halfa with OmegaCAM (ADHOC) Survey

Author

Beccari, Giacomo, Petr-Gotzens, Monika G., Boffin, Henri M. J., Jerabkova, Tereza, Romaniello, Martino, Areal, María Belén, Carraro, Giovanni, Celis, Mariela, De Marchi, Guido De, De Wit, Willem-Jan, Drew, Janet E., Fedele, Davide, Ferrero, Leticia V., Kalari, Venu M., Manara, Carlo F., Mardones, Diego, Martin, Eduardo L., Meza, Erick, Mieske, Steffen, Panagia, Nino, Testi, Leonardo, Vink, Jorick S., Walsh, Jeremy R., and Wright, Nick J.

Subjects
OMEGACAM, Astrophysics::High Energy Astrophysical Phenomena, Ciencias Físicas, STAR-FORMING REGION, Astrophysics::Cosmology and Extragalactic Astrophysics, purl.org/becyt/ford/1.3 [https], Astronomía, purl.org/becyt/ford/1 [https], Astrophysics::Solar and Stellar Astrophysics, PHOTOMETRY, Astrophysics::Earth and Planetary Astrophysics, ACCRETION DISC, Astrophysics::Galaxy Astrophysics, CIENCIAS NATURALES Y EXACTAS
Abstract

We present the first results of the Accretion Discs in Hα with OmegaCAM (ADHOC) survey, which aims to perform a deep and homogeneous photometric study of pre-main sequence (PMS) stars in a number of nearby star-forming regions. We took advantage of the exquisite image quality and wide-field capabilities of OmegaCAM at the VLT Survey Telescope (VST) to perform multi-band (ugri and Hα), deep (iSDSS < 22 mag), homogeneous and wide-field (covering tens of parsecs) observations of eight star-forming regions: the Orion Nebula Cluster, Lupus, Sco-Cen, Haffner 18, Vela OB2, Eta Cha, Chamaeleon and Ophiuchus. Using a robust method to identify PMS stars through their photometric excess in the Hα band, we aim to measure physical parameters (including mass accretion rates) for over 10 000 PMS stars. Direct comparison with low-resolution spectroscopy confirms that the objects with Hα excess emission that are detected photometrically are bona-fide PMS stars. The first results from this study clearly demonstrate the validity of the observational approach to unveiling complex stellar populations in young clusters., Published in The Messenger vol. 173, pp. 17-21, September 2018.

Published
2018

34. Paranal instrumentation for star formation studies

Author

De Wit, Willem-Jan

Subjects
Astrophysics::Instrumentation and Methods for Astrophysics, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

We will present the capabilities for star formation studies of some appropriate current, and future instruments at ESO's Paranal Observatory. In particular, we will discuss results by means of the the mid-infrared imager and spectrograph VISIR, the soon to be re-installed and cross-dispersed, high resolution, near-IR spectrograph CRIRES, the extreme AO instrument SPHERE, and the spectro-interferometric instruments Gravity (K-band) and MATISSE (M-, L-, N-band).

Published
2017
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35. Increased understanding of accretion in massive YSOs

Author

De Wit, Willem-Jan, Caratti, A., and Kraus, S.

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Earth and Planetary Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Galaxy Astrophysics
Abstract

That massive stars up to 20Msol form by disk accretion is by now reasonably well established. We will present the latest observational results for the formation of single and multiple massive YSOs. By means of optical interferometry using the newly commissioned instrument Gravity at the VLT-I, we show the discovery of a young, embedded, 170AU-wide binary and is the most massive and most compact accreting young binary to date. We will also present the results of a multi-site multi-epoch follow-up campaign of the first well studied accretion outburst in a massive YSO.

Published
2017
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37. VLTI status update: three years into the second generation

Author

Abad, José Antonio, primary, Abuter, Roberto, primary, Aller-Carpentier, Emmanuel, primary, Alonso, Jaime, primary, Andolfato, Luigi, primary, Barriga, Pablo José, primary, Beltran, Juan, primary, Berger, Jean-Philippe, primary, Fuentaseca, Eloy, primary, Woillez, Julien, primary, Gonté, Frédéric, primary, Egner, Sébastien, primary, Mérand, Antoine, primary, Haubois, Xavier, primary, Schuhler, Nicolas, primary, Darré, Pascaline, primary, Bourget, Pierre, primary, Brast, Roland, primary, Bristow, Paul, primary, Caniguante, Luis, primary, Conzelmann, Ralf, primary, Cortes, Angela, primary, Delboulbé, Alain, primary, Delplancke-Ströbele, Françoise, primary, Del Valle, Diego, primary, Dembet, Roderick, primary, Derie, Frédéric, primary, Donoso, Reinaldo, primary, Duhoux, Philippe, primary, Dupuy, Christophe, primary, Föster, Andreas, primary, Frahm, Robert, primary, Gaytan, Daniel, primary, Glindemann, Andreas, primary, Gonzales, Jaime, primary, Guerlet, Thibaut, primary, Guieu, Sylvain, primary, Guisard, Stéphane, primary, Gutierrez, Pablo, primary, Haguenauer, Pierre, primary, Haimerl, Andreas, primary, van der Heyden, Pierre, primary, Huber, Stefan, primary, Hubin, Norbert, primary, Jochum, Lieselotte, primary, Jocou, Laurent, primary, Jolley, Paul, primary, Kirchbauer, Jean-Paul, primary, Kolb, Johann, primary, Kosmalski, Johan, primary, Krempl, Peter, primary, Le Bouquin, Jean-Baptiste, primary, Lévêque, Samuel, primary, Lilley, Paul, primary, Lizon, Jean-Louis, primary, Magnard, Yves, primary, Mardones, Pedro, primary, Meister, Alexandre, primary, Moulin, Thibaut, primary, Osorio, Juan, primary, Ott, Jürgen, primary, Pallanca, Laurent, primary, Paufique, Jérôme, primary, Pavez, Marcus, primary, Pasquini, Luca, primary, Percheron, Isabelle, primary, Pettazzi, Lorenzo, primary, Duc, Thanh Phan, primary, Pirard, Jean-François, primary, Pino, Andres, primary, Poupar, Sébastien, primary, Quentin, Juta, primary, Ramírez, Andrés, primary, Reyes, Javier, primary, Ridings, Robert, primary, Rochat, Sylvain, primary, Rivinius, Thomas, primary, Salgado, Fernando, primary, Schöller, Markus, primary, Shchekaturov, Pavel, primary, Stephan, Christian, primary, Suarez, Marcos, primary, Tamblay, Richard, primary, Tapia, mario, primary, Tristram, Konrad, primary, Valdes, Guillermo, primary, Verinaud, Christophe, primary, de Wit, Willem-Jan, primary, and Zins, Gérard, primary

Published
2018
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38. Planet formation imager: project update

Author

Monnier, John D., primary, Ireland, Michael, primary, Kraus, Stefan, primary, Bonsor, Amy, primary, Baron, Fabien, primary, Berger, Jean-Philippe, primary, Boyajian, Tabetha, primary, Chiavassa, Andrea, primary, Ciardi, David, primary, Creech-Eakman, Michelle, primary, de Wit, Willem-Jan, primary, Dong, Ruobing, primary, Espaillat, Catherine, primary, Gallenne, Alexandre, primary, Gandhi, Poshak, primary, Gonzalez, Jean-Francois, primary, Haniff, Chris, primary, Hoenig, Sebastian, primary, Ilee, John, primary, Isella, Andrea, primary, Jensen, Eric, primary, Juhasz, Attila, primary, Kane, Stephen, primary, Kishimoto, Makoto, primary, Kley, Wilhelm, primary, Kral, Quentin, primary, Kratter, Kaitlin, primary, Labadie, Lucas, primary, Lacour, Sylvestre, primary, Laughlin, Greg, primary, Le Bouquin, Jean-Baptiste, primary, Michael, Ernest, primary, Meru, Farzana, primary, Millan-Gabet, Rafael, primary, Millour, Florentin, primary, Minardi, Stefano, primary, Morbidelli, Alessandro, primary, Mordasini, Chris, primary, Morlok, Andreas, primary, Mozurkewich, Dave, primary, Nelson, Richard, primary, Oudmaijer, Rene, primary, Packham, Chris, primary, Paladini, Claudia, primary, Panic, Olja, primary, Petrov, Romain, primary, Pope, Benjamin, primary, Pott, Joerg-Uwe, primary, Quiroga-Nuñez, Luis Henry, primary, Ramos Almeida, Cristina, primary, Raymond, Sean, primary, Regaly, Zsolt, primary, Reynolds, Mark, primary, Ridgway, Stephen, primary, Rinehart, Stephen, primary, Smith, Michael, primary, Stassun, Keivan, primary, Surdej, Jean, primary, Turner, Neal, primary, Tuthill, Peter, primary, van Belle, Gerard T., primary, Vasisht, Gautum, primary, Weigelt, Gerd, primary, Wishnow, Edward, primary, Wolf, Sebastian, primary, Zhao, Ming, primary, Zhu, Zhaohuan, primary, Schreiber, Matthias, primary, Duchêne, Gaspard, primary, Bayo, Amelia, primary, Olofsson, Johan, primary, ten Brummelaar, Theo, primary, Tristram, Konrad, primary, Wittkowski, Markus, primary, Young, John, primary, Wallace, Alexander, primary, Defrere, Denis, primary, Alonso-Herrero, Almudena, primary, and Z\'u\~niga-Fern\'andez, Sebasti\'an, primary

Published
2018
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40. Multiple star systems in the Orion nebula

Author

Karl, Martina, Pfuhl, Oliver, Eisenhauer, Frank, Genzel, Reinhard, Grellmann, Rebekka, Habibi, Maryam, Abuter, Roberto, Accardo, Matteo, Amorim, Antonio, Anugu, Narsireddy, Avila, Gerardo, Benisty, Myriam, Berger, Jean-Philippe, Blind, Nicolas, Bonnet, Henri, Bourget, Pierre, Brandner, Wolfgang, Brast, Roland, Buron, Alexander, Garatti, Alessio Caratti O., Chapron, Frederic, Clenet, Yann, Collin, Claude, du Foresto, Vincent Coude, de Wit, Willem-Jan, de Zeeuw, Tim, Deen, Casey, Delplancke-Stroebele, Francoise, Dembet, Roderick, Derie, Frederic, Dexter, Jason, Duvert, Gilles, Ebert, Monica, Eckart, Andreas, Esselborn, Michael, Fedou, Pierre, Finger, Gert, Garcia, Paulo, Dabo, Cesar Enrique Garcia, Lopez, Rebeca Garcia, Gao, Feng, Gendron, Eric, Gillessen, Stefan, Gonte, Frederic, Gordo, Paulo, Groezinger, Ulrich, Guajardo, Patricia, Guieu, Sylvain, Haguenauer, Pierre, Hans, Oliver, Haubois, Xavier, Haug, Marcus, Haussmann, Frank, Henning, Thomas, Hippler, Stefan, Horrobin, Matthew, Huber, Armin, Hubert, Zoltan, Hubin, Norbert, Jakob, Gerd, Jochum, Lieselotte, Jocou, Laurent, Kaufer, Andreas, Kellner, Stefan, Kendrew, Sarah, Kern, Lothar, Kervella, Pierre, Kiekebusch, Mario, Klein, Ralf, Koehler, Rainer, Kolb, Johan, Kulas, Martin, Lacour, Sylvestre, Lapeyrere, Vincent, Lazareff, Bernard, Le Bouquin, Jean-Baptiste, Lena, Pierre, Lenzen, Rainer, Leveque, Samuel, Lin, Chien-Cheng, Lippa, Magdalena, Magnard, Yves, Mehrgan, Leander, Merand, Antoine, Moulin, Thibaut, Mueller, Eric, Mueller, Friedrich, Neumann, Udo, Oberti, Sylvain, Ott, Thomas, Pallanca, Laurent, Panduro, Johana, Pasquini, Luca, Paumard, Thibaut, Percheron, Isabelle, Perraut, Karine, Perrin, Guy, Pflueger, Andreas, Plewa, Philipp M., Popovic, Dan, Rabien, Sebastian, Ramirez, Andres, Ramos, Jose, Rau, Christian, Riquelme, Miguel, Rodriguez-Coira, Gustavo, Rohloff, Ralf-Rainer, Rosales, Alejandra, Rousset, Gerard, Sanchez-Bermudez, Joel, Scheithauer, Silvia, Schoeller, Markus, Schuhler, Nicolas, Spyromilio, Jason, Straub, Odele, Straubmeier, Christian, Sturm, Eckhard, Suarez, Marcos, Tristram, Konrad R. W., Ventura, Noel, Vincent, Frederic, Waisberg, Idel, Wank, Imke, Widmann, Felix, Wieprecht, Ekkehard, Wiest, Michael, Wiezorrek, Erich, Wittkowski, Markus, Woillez, Julien, Wolff, Burkhard, Yazici, Senol, Ziegler, Denis, Zins, Gerard, Karl, Martina, Pfuhl, Oliver, Eisenhauer, Frank, Genzel, Reinhard, Grellmann, Rebekka, Habibi, Maryam, Abuter, Roberto, Accardo, Matteo, Amorim, Antonio, Anugu, Narsireddy, Avila, Gerardo, Benisty, Myriam, Berger, Jean-Philippe, Blind, Nicolas, Bonnet, Henri, Bourget, Pierre, Brandner, Wolfgang, Brast, Roland, Buron, Alexander, Garatti, Alessio Caratti O., Chapron, Frederic, Clenet, Yann, Collin, Claude, du Foresto, Vincent Coude, de Wit, Willem-Jan, de Zeeuw, Tim, Deen, Casey, Delplancke-Stroebele, Francoise, Dembet, Roderick, Derie, Frederic, Dexter, Jason, Duvert, Gilles, Ebert, Monica, Eckart, Andreas, Esselborn, Michael, Fedou, Pierre, Finger, Gert, Garcia, Paulo, Dabo, Cesar Enrique Garcia, Lopez, Rebeca Garcia, Gao, Feng, Gendron, Eric, Gillessen, Stefan, Gonte, Frederic, Gordo, Paulo, Groezinger, Ulrich, Guajardo, Patricia, Guieu, Sylvain, Haguenauer, Pierre, Hans, Oliver, Haubois, Xavier, Haug, Marcus, Haussmann, Frank, Henning, Thomas, Hippler, Stefan, Horrobin, Matthew, Huber, Armin, Hubert, Zoltan, Hubin, Norbert, Jakob, Gerd, Jochum, Lieselotte, Jocou, Laurent, Kaufer, Andreas, Kellner, Stefan, Kendrew, Sarah, Kern, Lothar, Kervella, Pierre, Kiekebusch, Mario, Klein, Ralf, Koehler, Rainer, Kolb, Johan, Kulas, Martin, Lacour, Sylvestre, Lapeyrere, Vincent, Lazareff, Bernard, Le Bouquin, Jean-Baptiste, Lena, Pierre, Lenzen, Rainer, Leveque, Samuel, Lin, Chien-Cheng, Lippa, Magdalena, Magnard, Yves, Mehrgan, Leander, Merand, Antoine, Moulin, Thibaut, Mueller, Eric, Mueller, Friedrich, Neumann, Udo, Oberti, Sylvain, Ott, Thomas, Pallanca, Laurent, Panduro, Johana, Pasquini, Luca, Paumard, Thibaut, Percheron, Isabelle, Perraut, Karine, Perrin, Guy, Pflueger, Andreas, Plewa, Philipp M., Popovic, Dan, Rabien, Sebastian, Ramirez, Andres, Ramos, Jose, Rau, Christian, Riquelme, Miguel, Rodriguez-Coira, Gustavo, Rohloff, Ralf-Rainer, Rosales, Alejandra, Rousset, Gerard, Sanchez-Bermudez, Joel, Scheithauer, Silvia, Schoeller, Markus, Schuhler, Nicolas, Spyromilio, Jason, Straub, Odele, Straubmeier, Christian, Sturm, Eckhard, Suarez, Marcos, Tristram, Konrad R. W., Ventura, Noel, Vincent, Frederic, Waisberg, Idel, Wank, Imke, Widmann, Felix, Wieprecht, Ekkehard, Wiest, Michael, Wiezorrek, Erich, Wittkowski, Markus, Woillez, Julien, Wolff, Burkhard, Yazici, Senol, Ziegler, Denis, and Zins, Gerard

Abstract

This work presents an interferometric study of the massive-binary fraction in the Orion Trapezium cluster with the recently comissioned GRAVITY instrument. We observed a total of 16 stars of mainly OB spectral type. We find three previously unknown companions for theta(1) Ori B, theta(2) Ori B, and theta(2) Ori C. We determined a separation for the previously suspected companion of NU Ori. We confirm four companions for theta(1) Ori A, theta(1) Ori C, theta(1) Ori D, and theta(2) Ori A, all with substantially improved astrometry and photometric mass estimates. We refined the orbit of the eccentric high-mass binary theta(1) Ori C and we are able to derive a new orbit for theta(1) Ori D. We find a system mass of 21.7 M-circle dot and a period of 53 days. Together with other previously detected companions seen in spectroscopy or direct imaging, eleven of the 16 high-mass stars are multiple systems. We obtain a total number of 22 companions with separations up to 600 AU. The companion fraction of the early B and O stars in our sample is about two, significantly higher than in earlier studies of mostly OB associations. The separation distribution hints toward a bimodality. Such a bimodality has been previously found in A stars, but rarely in OB binaries, which up to this point have been assumed to be mostly compact with a tail of wider companions. We also do not find a substantial population of equal-mass binaries. The observed distribution of mass ratios declines steeply with mass, and like the direct star counts, indicates that our companions follow a standard power law initial mass function. Again, this is in contrast to earlier findings of flat mass ratio distributions in OB associations. We excluded collision as a dominant formation mechanism but find no clear preference for core accretion or competitive accretion.

Published
2018

41. First light for GRAVITY: Phase referencing optical interferometry for the Very Large Telescope Interferometer

Author

Abuter, Roberto, Accardo, Matteo, Antonio, Amorim, Narsireddy, Anugu, Avila, Gerardo, Azouaoui, N., Benisty, Myriam, Berger, Jean-Philippe, Blind, Nicolas, Bonnet, Henri, Bourget, Pierre, Brandner, Wolfgang, Brast, Roland, Buron, Alexander, Burtscher, L., Cassaing, Frederic, Chapron, Frédéric, Choquet, Elodie, Clénet, Yann, Collin, Claude, Coudé du Forestol, Vincent, de Wit, Willem-Jan, De Zeeuw, Tim, Casey, Deen, Delplancke-Ströbele, Françoise, Dembet, Roderick, Derie, Frédéric, Dexter, Jason, Duvert, Gilles, Ebert, Monica, Eckart, Andreas, Eisenhauer, Frank, Michael, Esselborn, Fédou, Pierre, Finger, Gert, Garcia, Paulo, Garcia Dabo, Cesar Enrique, Garcia Lopez, Rebeca, Gendron, Eric, Genzel, Reinhard, Gillessen, Stefan, Conté, Frédéric, Gordo, Paulo, Grould, Marion, Groözinger, Ulrich, Guieu, Sylvain, Haguenauer, Pierre, Hans, Olivier, Haubois, Xavier, Haug, Marcus, Haussmann, Frank, Henning, Thomas, Hippler, Stefan, Horrobin, Matthew, Huber, Armin, Hubert, Zoltan, Hubin, Norbert, Hummel, Christian, Jakob, Gerd, Janssen, A., Jochum, Lieselotte, Jocou, Laurent, Kaufer, Andreas, Kellner, Stefan, Kendrew, Sarah, Kern, Lothar, Kervella, Pierre, Kiekebusch, Mario, Klein, Ralf, Kok, Y., Kolb, Johan, Kulas, Martin, Lacour, Sylvestre, Lapeyrère, Vincent, Lazareff, Bernard, Le Bouquin, Jean-Baptiste, Léna, Pierre, Lenzen, Rainer, Levêque, Samuel, Lippa, Magdalena, Magnard, Yves, Mehrgan, Leander, Mellein, Marcus, Merand, Antoine, Moreno-Ventas, Javier, Moulin, Thibaut, Müller, Eric, Müller, Fredrich, Neumann, Udo, Oberti, Sylvain, Ott, Thomas, Pallanca, Laurent, Panduro, Johana, Pasquini, Luca, Paumard, Thibaut, Percheron, Isabelle, Perraut, Karine, Perrin, Guy, Pflüger, Andreas, Pfuhl, Olivier, Duc, Thanh Phan, Plewa, Philipp, Popovic, Dan, Rabien, Sebastian, Ramirez, Andres, Ramos, Jose, Rau, Christian, Riquelme, Miguel, Rohloff, Ralf-Rainer, Rousset, Gérard, Sanchez-Bermudez, Joel, Scheithauer, Sylvia, Schöller, Marcus, Schuhler, Nicolas, Spyromilio, Jason, Straubmeier, Christian, Sturm, Eckhard, Suarez, Marco, Tristram, Konrad, Ventura, Noel, Vincent, Frédéric, Waisberg, Idel, Wank, Imke, Weber, J., Wieprecht, Ekkehard, Wiest, Michael, Wiezorrek, Erich, Wittkowski, Markus, Woillez, Julien, Wolff, Burkhard, Yazici, Senol, Ziegler, Denis, Zins, Gérard, Amorim, A., Anugu, N., Ávila, G., Clenet, Y., Coudé Du Foresto, V., de Zeeuw, P., Deen, C., Esselborn, M., Dabo, C, Gonte, F., Grözinger, U., Henning, Th, Le Bouquin, J.-B, Lèna, P., Lévêque, S., Mérand, A., Muller, E., Muller, F., Phan Duc, T., Ramírez, A., Garcia Dabo, E., Henning, Th., Le Bouquin, B., Plewa, M., European Southern Observatory (ESO), CENTRA, Universidade de Lisboa, CENTRA, Universidade do Porto, Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève (UNIGE), Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, Max Planck Institute for Extraterrestrial Physics (MPE), Leiden Observatory [Leiden], Universiteit Leiden [Leiden], ONERA - The French Aerospace Lab [Châtillon], ONERA, Physikalisches Institut [Köln], Universität zu Köln, Max Planck Institute for Radio Astronomy, Department of Physics [Berkeley], University of California [Berkeley], University of California-University of California, European Space Agency (ESA), European Southern Observatory [Santiago] (ESO), Institute Patology and Imunology Molecular, Fac Ciencias, Universidade do Porto [Porto], Brain Mind Institute (BMI - EPFL), Ecole Polytechnique Fédérale de Lausanne (EPFL), Technische Universität Dresden (TUD), Departamento de Control Automático (CINVESTAV-IPN), Center for Research and Advanced Studies of the National Polytechnic Institute (CINVESTAV-IPN), Universidade do Porto, Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), ONERA-Université Paris Saclay (COmUE), GRAVITY Collaboration, European Southern Observatory ( ESO ), Laboratoire d'études spatiales et d'instrumentation en astrophysique ( LESIA ), Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université Paris Diderot - Paris 7 ( UPD7 ) -Centre National de la Recherche Scientifique ( CNRS ), Institut de Planétologie et d'Astrophysique de Grenoble ( IPAG ), Observatoire des Sciences de l'Univers de Grenoble ( OSUG ), Université Joseph Fourier - Grenoble 1 ( UJF ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Université Grenoble Alpes ( UGA ) -Université Joseph Fourier - Grenoble 1 ( UJF ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Centre National de la Recherche Scientifique ( CNRS ) -Université Grenoble Alpes ( UGA ) -Centre National de la Recherche Scientifique ( CNRS ), Observatoire Astronomique de l'Université de Genève ( ObsGE ), Université de Genève ( UNIGE ), Max-Planck-Institut für Astronomie ( MPIA ), Max Planck Institute for Extraterrestrial Physics ( MPE ), ONERA - The French Aerospace Lab ( Chatillon ), Max Planck Institute for Radio Astronomy, Bonn, European Space Agency ( ESA ), Universidad de Santiago de Chile [Santiago] ( USACH ), European Southern Observatory [Santiago] ( ESO ), University of Porto, Center for Brain Simulation, Ecole Polytechnique Fédérale de Lausanne, Technische Universität Dresden ( TUD ), Departamento de Control Automático ( CINVESTAV-IPN ), Center for Research and Advanced Studies of the National Polytechnic Institute ( CINVESTAV-IPN ), Universidade do Porto = University of Porto, Université de Genève = University of Geneva (UNIGE), Universiteit Leiden, Universität zu Köln = University of Cologne, University of California [Berkeley] (UC Berkeley), University of California (UC)-University of California (UC), and Agence Spatiale Européenne = European Space Agency (ESA)

Subjects
[ SPI.SIGNAL ] Engineering Sciences [physics]/Signal and Image processing, Astrophysics, ÉTOILE DOUBLE, OPTIQUE ADAPTATIVE, 01 natural sciences, law.invention, law, Astrophysics::Solar and Stellar Astrophysics, INSTRUMENTATION OPTIQUE, INSTRUMENTATION, instrumentation: interferometers, 010303 astronomy & astrophysics, Physics, Galaxy: center, Galactic Center, Astrophysics::Instrumentation and Methods for Astrophysics, Astrometry, [PHYS.PHYS.PHYS-SPACE-PH]Physics [physics]/Physics [physics]/Space Physics [physics.space-ph], [ PHYS.PHYS.PHYS-SPACE-PH ] Physics [physics]/Physics [physics]/Space Physics [physics.space-ph], quasars: emission lines, Interferometry, EMISSION LINE, Closure phase, binaries: symbiotic, Astrophysics::Earth and Planetary Astrophysics, [ SPI.OPTI ] Engineering Sciences [physics]/Optics / Photonic, Astrophysics - Instrumentation and Methods for Astrophysics, [SPI.SIGNAL]Engineering Sciences [physics]/Signal and Image processing, CENTER, INTERFEROMETRIE GRANDE BASE, FOS: Physical sciences, stars: pre-main sequence, instrumentation: adaptive optics, QUASAR, 010309 optics, Telescope, 0103 physical sciences, Angular resolution, INTERFEROMETERS, Instrumentation and Methods for Astrophysics (astro-ph.IM), CENTRE GALACTIQUE, Astrophysics::Galaxy Astrophysics, ADAPTIVE OPTICS, Very Large Telescope, Astronomy and Astrophysics, First light, GALAXY, Space and Planetary Science, [SPI.OPTI]Engineering Sciences [physics]/Optics / Photonic, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

GRAVITY is a new instrument to coherently combine the light of the European Southern Observatory Very Large Telescope Interferometer to form a telescope with an equivalent 130 m diameter angular resolution and a collecting area of 200 m$^2$. The instrument comprises fiber fed integrated optics beam combination, high resolution spectroscopy, built-in beam analysis and control, near-infrared wavefront sensing, phase-tracking, dual beam operation and laser metrology [...]. This article gives an overview of GRAVITY and reports on the performance and the first astronomical observations during commissioning in 2015/16. We demonstrate phase tracking on stars as faint as m$_K$ ~ 10 mag, phase-referenced interferometry of objects fainter than m$_K$ ~ 15 mag with a limiting magnitude of m$_K$ ~ 17 mag, minute long coherent integrations, a visibility accuracy of better than 0.25 %, and spectro-differential phase and closure phase accuracy better than 0.5{\deg}, corresponding to a differential astrometric precision of better than 10 microarcseconds ({\mu}as). The dual-beam astrometry, measuring the phase difference of two objects with laser metrology, is still under commissioning. First observations show residuals as low as 50 {\mu}as when following objects over several months. We illustrate the instrument performance with the observations of archetypical objects for the different instrument modes. Examples include the Galactic Center supermassive black hole and its fast orbiting star S2 for phase referenced dual beam observations and infrared wavefront sensing, the High Mass X-Ray Binary BP Cru and the Active Galactic Nucleus of PDS 456 for few {\mu}as spectro-differential astrometry, the T Tauri star S CrA for a spectro-differential visibility analysis, {\xi} Tel and 24 Cap for high accuracy visibility observations, and {\eta} Car for interferometric imaging with GRAVITY., Comment: Accepted for publication in A&A, 23 pages, 23 figures, corresponding author: F. Eisenhauer

Published
2017
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42. First Light for GRAVITY: A New Era for Optical Interferometry

Author

Abuter, Roberto, Accardo, Matteo, Antonio, Amorim, Narsireddy, Anugu, Avila, Gerardo, Benisty, Myriam, Berger, Jean-Philippe, Blind, Nicolas, Bonnet, Henri, Bourget, Pierre, Brandner, Wolfgang, Brast, Roland, Buron, Alexander, Cassaing, Frederic, Chapron, Frédéric, Choquet, Elodie, Clénet, Yann, Collin, Claude, Coudé du Forestol, Vincent, de Wit, Willem-Jan, De Zeeuw, Tim, Casey, Deen, Delplancke-Ströbele, Françoise, Dembet, Roderick, Derie, Frédéric, Dexter, Jason, Duvert, Gilles, Ebert, Monica, Eckart, Andreas, Eisenhauer, Frank, Michael, Esselborn, Fédou, Pierre, Finger, Gert, Garcia, Paulo, Garcia Dabo, Cesar Enrique, Garcia Lopez, Rebeca, Gao, Feng, Gendron, Eric, Genzel, Reinhard, Gillessen, Stefan, Conté, Frédéric, Gordo, Paulo, Grould, Marion, Groözinger, Ulrich, Guieu, Sylvain, Haguenauer, Pierre, Hans, Olivier, Haubois, Xavier, Haug, Marcus, Haussmann, Frank, Henning, Thomas, Hippler, Stefan, Horrobin, Matthew, Huber, Armin, Hubert, Zoltan, Hubin, Norbert, Hummel, Christian, Jakob, Gerd, Jochum, Lieselotte, Jocou, Laurent, Karl, Martina, Kaufer, Andreas, Kellner, Stefan, Kendrew, Sarah, Kern, Lothar, Kervella, Pierre, Kiekebusch, Mario, Klein, Ralf, Kolb, Johan, Kulas, Martin, Lacour, Sylvestre, Lapeyrère, Vincent, Lazareff, Bernard, Le Bouquin, Jean-Baptiste, Léna, Pierre, Lenzen, Rainer, Levêque, Samuel, Lippa, Magdalena, Magnard, Yves, Mehrgan, Leander, Mellein, Marcus, Merand, Antoine, Moreno-Ventas, Javier, Moulin, Thibaut, Müller, Eric, Müller, Friedrich, Neumann, Udo, Oberti, Sylvain, Ott, Thomas, Pallanca, Laurent, Panduro, Johana, Pasquini, Luca, Paumard, Thibaut, Percheron, Isabelle, Perraut, Karine, Perrin, Guy, Petrucci, Pierre-Olivier, Pflüger, Andreas, Pfuhl, Olivier, Duc, Thanh Phan, Plewa, Philipp, Popovic, Dan, Rabien, Sebastian, Ramirez, Andres, Ramos, Jose, Rau, Christian, Riquelme, Miguel, Rodriguez-Coira, Gustavo, Rohloff, Ralf-Rainer, Rosales, Alejandra, Rousset, Gérard, Sanchez-Bermudez, Joel, Scheithauer, Sylvia, Schöller, Marcus, Schuhler, Nicolas, Spyromilio, Jason, Straub, Odele, Straubmeier, Christian, Sturm, Eckhard, Suarez, Marco, Tristram, Konrad, Ventura, Noel, Vincent, Frédéric, Waisberg, Idel, Wank, Imke, Widmann, Felix, Wieprecht, Ekkehard, Wiest, Michael, Wiezorrek, Erich, Wittkowski, Markus, Woillez, Julien, Wolff, Burkhard, Yazici, Senol, Ziegler, Denis, Zins, Gérard, European Southern Observatory (ESO), CENTRA, Universidade de Lisboa, Universidade do Porto = University of Porto, Institut de Planétologie et d'Astrophysique de Grenoble (IPAG), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG ), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national des sciences de l'Univers (INSU - CNRS)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Observatoire Astronomique de l'Université de Genève (ObsGE), Université de Genève = University of Geneva (UNIGE), Max-Planck-Institut für Astronomie (MPIA), Max-Planck-Gesellschaft, Max Planck Institute for Extraterrestrial Physics (MPE), ONERA - The French Aerospace Lab [Châtillon], ONERA-Université Paris Saclay (COmUE), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Leiden Observatory [Leiden], Universiteit Leiden, Physikalisches Institut [Köln], Universität zu Köln = University of Cologne, Max Planck Institute for Radio Astronomy, Department of Physics [Berkeley], University of California [Berkeley] (UC Berkeley), University of California (UC)-University of California (UC), Agence Spatiale Européenne = European Space Agency (ESA), Universidad de Santiago de Chile [Santiago] (USACH), European Southern Observatory [Santiago] (ESO), CENTRA, Universidade do Porto, Centre National d'Études Spatiales [Toulouse] (CNES)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers de Grenoble (OSUG), Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)-Université Joseph Fourier - Grenoble 1 (UJF)-Centre National de la Recherche Scientifique (CNRS), Université de Genève (UNIGE), ONERA, Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Universiteit Leiden [Leiden], Universität zu Köln, University of California [Berkeley], University of California-University of California, European Space Agency (ESA), and Universidade do Porto

Subjects
COPHASAGE, 010308 nuclear & particles physics, INTERFEROMETRIE GRANDE BASE, LONG-BASELINE INTERFEROMETRY, IMAGERIE INTERFEROMETRIQUE, 01 natural sciences, INTERFEROMETRIC IMAGING, VLTI, PHASE TRACKING, ASTROMETRY, 0103 physical sciences, [SPI.OPTI]Engineering Sciences [physics]/Optics / Photonic, ASTROMETRIE, 010303 astronomy & astrophysics, [SPI.SIGNAL]Engineering Sciences [physics]/Signal and Image processing
Abstract

With the arrival of the second generation instrument GRAVITY, the Very Large Telescope Interferometer (VLTI) has entered a new era of optical interferometry. This instrument pushes the limits of accuracy and sensitivity by orders of magnitude. GRAVITY has achieved phase-referenced imaging at approximately milliarcsecond (mas) resolution and down to ~ 100-microarcsecond astrometry on objects that are several hundred times fainter than previously observable. The cutting-edge design presented in Eisenhauer et al. (2011) has become reality. This article sketches out the basic principles of the instrument design and illustrates its performance with key science results obtained during commissioning: phase-tracking on stars with K ~ 10 mag, phase-referenced interferometry of objects fainter than K ≳ 17 mag, minute-long coherent integrations, a visibility accuracy of better than 0.25 %, and spectro-differential phase and closure phase accuracy better than 0.5 degrees, corresponding to a differential astrometric precision of a few microarcseconds (μas)., Published in The Messenger vol. 170, pp. 10-15, December 2017.

Published
2017
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43. VLTI Imaging of a High-Mass Protobinary System: Unveiling the Dynamical Processes in High-Mass Star Formation

Author

Kraus, Stefan, Kluska, Jacques, Kreplin, Alexander, Bate, Matthew, Harries, Timothy, Hofmann, Karl-Heinz, Hone, Edward, Monnier, John, Weigelt, Gerd, Anugu, Narsireddy, De Wit, Willem-Jan, and Wittkowski, Markus

Subjects
010504 meteorology & atmospheric sciences, 0103 physical sciences, Astrophysics::Solar and Stellar Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Astrophysics::Earth and Planetary Astrophysics, 010303 astronomy & astrophysics, 01 natural sciences, Astrophysics::Galaxy Astrophysics, 0105 earth and related environmental sciences
Abstract

High-mass stars exhibit a significantly higher multiplicity frequency than low-mass stars, likely reflecting differences in how they formed. Theory suggests that high-mass binaries may form by the fragmentation of self-gravitational discs or by alternative scenarios such as disc-assisted capture. Near-infrared interferometric observations reveal the high-mass young stellar object IRAS 17216-3801 to be a close high-mass protobinary with a separation of 0.058 arcseconds (~ 170 au). This is the closest high-mass protobinary system imaged to date. We also resolve near- infrared excess emission around the individual stars, which is associated with hot dust in circumstellar discs. These discs are strongly misaligned with respect to the binary separation vector, indicating that tidal forces have not yet had time to realign. We measure a higher accretion rate towards the circumsecondary disc, confirming a hydrodynamic effect where the secondary star disrupts the primary star’s accretion stream and effectively limits the mass that the primary star can accrete. NACO L′-band imaging may also have resolved the circumbinary disc that feeds the accretion onto the circumstellar discs. This discovery demonstrates the unique capabilities of the VLTI, creating exciting new opportunities to study the dynamical processes that govern the architecture of close multiple systems., Published in The Messenger vol. 170, pp. 45-49, December 2017.

Published
2017
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44. GRAVITY Science Verification

Author

Mérand, Antoine, Berger, Jean-Philippe, De Wit, Willem-Jan, Eisenhauer, Frank, Haubois, Xavier, Paumard, Thibaut, Schoeller, Markus, Wittkowski, Markus, Woillez, Julien, and Wolff, Burkhard

Abstract

In the time between successfully commissioning an instrument and before offering it in the Call for Proposals for the first time, ESO gives the community at large an opportunity to apply for short Science Verification (SV) programmes. In 2016, ESO offered SV time for the second-generation Very Large Telescope Interferometer instrument GRAVITY. In this article we describe the selection process, outline the range of science cases covered by the approved SV programmes, and highlight some of the early scientific results., Published in The Messenger vol. 170, pp. 16-19, December 2017.

Published
2017
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48. Not so lonely: The LBV binary HR Car

Author

Rivinius, T., Boffin, Henri, Mérand, Antoine, Mehner, Andrea, LeBouquin, J.-B., Pourbaix, Dimitri, De Wit, Willem Jan, Martayan, C., Rivinius, T., Boffin, Henri, Mérand, Antoine, Mehner, Andrea, LeBouquin, J.-B., Pourbaix, Dimitri, De Wit, Willem Jan, and Martayan, C.

Abstract

info:eu-repo/semantics/published

Published
2017

49. The luminous blue variable HR Carinae has a partner. Discovery of a companion with the VLTI

Author

Boffin, Henri, Rivinius, T., Mérand, Antoine, Mehner, Andrea, LeBouquin, J.-B., Pourbaix, Dimitri, De Wit, Willem Jan, Martayan, C., Guieu, Sylvain, Boffin, Henri, Rivinius, T., Mérand, Antoine, Mehner, Andrea, LeBouquin, J.-B., Pourbaix, Dimitri, De Wit, Willem Jan, Martayan, C., and Guieu, Sylvain

Abstract

Luminous blue variables (LBVs) are massive stars caught in a post-main sequence phase, during which they lose a significant amount of mass. Since, on one hand, it is thought that the majority of massive stars are close binaries that will interact during their lifetime, and on the other, the most dramatic example of an LBV, η Car, is a binary, it would be useful to find other binary LBVs. We present here interferometric observations of the LBV HR Car done with the AMBER and PIONIER instruments attached to ESO's Very Large Telescope Interferometer (VLTI). Our observations, spanning two years, clearly reveal that HR Car is a binary star. It is not yet possible to fully constrain the orbit, and the orbital period may lie between a few years and several hundred years. We derive a radius for the primary in the system and possibly also resolve the companion. The luminosity ratio in the H-band between the two components is changing with time, going from about 6 to 9. We also tentatively detect the presence of some background flux which remained at the 2% level until January 2016, but then increased to 6% in April 2016. Our AMBER results show that the emission line-forming region of Brγ is more extended than the continuum-emitting region as seen by PIONIER and may indicate some wind-wind interaction. Most importantly, we constrain the total masses of both components, with the most likely range being 33.6 MȮ and 45 MȮ. Our results show that the LBV HR Car is possibly an η Car analog binary system with smaller masses, with variable components, and further monitoring of this object is definitively called for., SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2016

50. A multi-wavelength interferometric study of the massive young stellar object IRAS 13481-6124

Author

Boley, Paul A., Kraus, Stefan, de Wit, Willem-Jan, Linz, Hendrik, van Boekel, Roy, Henning, Thomas, Lacour, Sylvestre, Monnier, John D., Stecklum, Bringfried, Tuthill, Peter G., Boley, Paul A., Kraus, Stefan, de Wit, Willem-Jan, Linz, Hendrik, van Boekel, Roy, Henning, Thomas, Lacour, Sylvestre, Monnier, John D., Stecklum, Bringfried, and Tuthill, Peter G.

Published
2016

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