We present here a short review of the calibration processes that are currently applied to the instruments AMBER and MIDI of the VLTI (Very Large Telescope Interferometer) at Paranal. We first introduce the general principles to calibrate... more
We present here a short review of the calibration processes that are currently applied to the instruments AMBER and MIDI of the VLTI (Very Large Telescope Interferometer) at Paranal. We first introduce the general principles to calibrate the raw data (the “visibilities”) that have been measured by long-baseline optical interferometry. Then, we focus on the specific case of the scientific
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The Phase Referenced Imaging and Microarcsecond Astrometry (PRIMA) instrument was recently delivered to the summit of Cerro Paranal and installed as part of the Very Large Telescope Interferometer (VLTI) infrastructure. PRIMA is designed... more
The Phase Referenced Imaging and Microarcsecond Astrometry (PRIMA) instrument was recently delivered to the summit of Cerro Paranal and installed as part of the Very Large Telescope Interferometer (VLTI) infrastructure. PRIMA is designed to (i) provide phase-referenced interferometric imaging at milliarcsecond scales, (ii) enable faint star science several magnitudes fainter than the current atmospheric limits of the VLTI, and (iii) provide astrometric measurements at the tens of micro-arcsecond level. PRIMA has successfully seen first fringes and is currently (as of late 2008) undergoing initial commissioning tests.
The ESO Very Large Telescope Interferometer (VLTI) offers the unique access to the combination of the four 8-meter Unit Telescopes (UT) of Cerro Paranal. The quality of the scientific observations in interferometric mode is strongly... more
The ESO Very Large Telescope Interferometer (VLTI) offers the unique access to the combination of the four 8-meter Unit Telescopes (UT) of Cerro Paranal. The quality of the scientific observations in interferometric mode is strongly related to the stability of the optical path difference (OPD) between the telescopes. Vibrations at the level of the telescopes and affecting the mirrors were shown to be an important source of perturbation for the OPD. ESO has thus started an important effort on the UTs and VLTI to tackle this effect. Active controls based on accelerometers and phase measurements have been developed to provide real-time correction of the variation of OPD introduced by vibrations. Systematic studies and measurement of the sources of vibration (instruments, wind, telescope altitude, ...) have been performed. Solutions to reduce the vibrations via design modification and/or new operation configurations are studied and implemented. To ensure good operational conditions, the...
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Brown dwarfs are important objects because they may provide a missing link between stars and planets, two populations that have dramatically different formation history. In this paper, we present the candidate binaries with brown dwarf... more
Brown dwarfs are important objects because they may provide a missing link between stars and planets, two populations that have dramatically different formation history. In this paper, we present the candidate binaries with brown dwarf companions that are found by analyzing binary microlensing events discovered during 2004 - 2011 observation seasons. Based on the low mass ratio criterion of q < 0.2, we found 7 candidate events, including OGLE-2004-BLG-035, OGLE-2004-BLG-039, OGLE-2007-BLG-006, OGLE-2007-BLG-399/MOA-2007-BLG-334, MOA-2011-BLG-104/OGLE-2011-BLG-0172, MOA-2011-BLG-149, and MOA-201-BLG-278/OGLE-2011-BLG-012N. Among them, we are able to confirm that the companions of the lenses of MOA-2011-BLG-104/OGLE-2011-BLG-0172 and MOA-2011-BLG-149 are brown dwarfs by determining the mass of the lens based on the simultaneous measurement of the Einstein radius and the lens parallax. The measured mass of the brown dwarf companions are (0.02 +/- 0.01) M_Sun and (0.019 +/- 0.002) M_...
The VLTI has been operating for about 5 years using the VINCI instrument first, and later MIDI. In October 2005 (Period 76) the first Science Operations with the AMBER instrument started, with 14 Open Time proposals in the observing... more
The VLTI has been operating for about 5 years using the VINCI instrument first, and later MIDI. In October 2005 (Period 76) the first Science Operations with the AMBER instrument started, with 14 Open Time proposals in the observing queues submitted by the astronomical community. AMBER, the near-infrared/red focal instrument of the VLTI, operates in the bands J, H, and,
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Abstract. PLANET, the Probing Lensing Anomaly NETwork, is an international team conducting observations of on-going gravitational microlensing events from five sites in the southern hemisphere. Our primary goal is to detect or to put... more
Abstract. PLANET, the Probing Lensing Anomaly NETwork, is an international team conducting observations of on-going gravitational microlensing events from five sites in the southern hemisphere. Our primary goal is to detect or to put constraints on sub-stellar companions ...
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ABSTRACT This paper presents the recent changes undergone by the Science Operations department of the ESO Paranal Observatory. This revised science operations model, named SciOps2, aims at improving operations efficiency and quality of... more
ABSTRACT This paper presents the recent changes undergone by the Science Operations department of the ESO Paranal Observatory. This revised science operations model, named SciOps2, aims at improving operations efficiency and quality of the data delivered to our community of users. The changes regarding the new department structure, its staffing, and the distribution of tasks and responsibilities, are described in details, as well as the measured impact of these changes.
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The ESO Very Large Telescope Interferometer (VLTI) offers the unique access to the combination of the four 8-meter Unit Telescopes (UT) of Cerro Paranal. The quality of the scientific observations in interferometric mode is strongly... more
The ESO Very Large Telescope Interferometer (VLTI) offers the unique access to the combination of the four 8-meter Unit Telescopes (UT) of Cerro Paranal. The quality of the scientific observations in interferometric mode is strongly related to the stability of the optical path difference (OPD) between the telescopes. Vibrations at the level of the telescopes and affecting the mirrors were shown to be an important source of perturbation for the OPD. ESO has thus started an important effort on the UTs and VLTI to tackle this effect. Active controls based on accelerometers and phase measurements have been developed to provide real-time correction of the variation of OPD introduced by vibrations. Systematic studies and measurement of the sources of vibration (instruments, wind, telescope altitude, ...) have been performed. Solutions to reduce the vibrations via design modification and/or new operation configurations are studied and implemented. To ensure good operational conditions, the levels of vibrations are regularly monitored to control any environmental change. This document will describe the modifications implemented and foreseen and give a status of the VLTI-UT vibrations evolution.
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ABSTRACT The ESO Very Large Telescope Interferometer (VLTI) using the Unit Telescope (UT) was strongly affected by vibrations since the first observations. Investigation by ESO on that subject had started in 2007, with a considerable... more
ABSTRACT The ESO Very Large Telescope Interferometer (VLTI) using the Unit Telescope (UT) was strongly affected by vibrations since the first observations. Investigation by ESO on that subject had started in 2007, with a considerable effort since mid 2008. An important number of investigations on various sub-systems (On telescope: Guiding, Passive supports, Train Coude, insulation of electronics cabinets; On Instruments: dedicated campaign on each instruments with a special attention on the ones equipped with Close Cycle Cooler) were realized. Vibrations were not only recorded and analyzed using the usual accelerometers but also using on use sub-systems as InfRared Image Sensor (IRIS) and Multiple Applications Curvature Adaptive Optics (MACAO) and using a specific tool developed for vibrations measurements Mirror vibrAtion Metrology systeM for the Unit Telescope (MAMMUT). Those tools and systems have been used in order to improve the knowledge on telescope by finding sources. The sources whenever it was possible were damped. As known for years, instruments are still the principal sources of vibrations, for the majority of the UT. A special test in which 2 UTs instruments were completely shut down was realized to determine the minimum Optical Path Length (OPL) achievable. Vibrations is now a part of the instruments interface document and during the installation of any new instrument (KMOS) or system (AOF) a test campaign is realized. As a result some modifications (damping of CCC) can be asked in case of non-compliance. To ensure good operational conditions, levels of vibrations are regularly recorded to control any environmental change.