Recent developments in optical interferometry data standards

A working group on interferometry data standards has been established within IAU Commission 54 (Optical/ Infrared Interferometry). The working group includes members representing the major optical interferometry projects worldwide, and aims to enhance existing standards and develop new ones to satisfy the broad interests of the optical interferometry community. We present the initial work of the group to enhance the OIFITS data exchange standard, and outline the software packages and libraries now available which implement the standard

VLTI status update: a decade of operations and beyond

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, 9146-1

Multiple star systems in the Orion nebula

This is the author accepted manuscript. The final fersion is available from EDP Sciences via the DOI in this record.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 θ1 Ori B, θ2 Ori B, and θ2 Ori C. We determined a separation for the previously suspected companion of NU Ori. We confirm four companions for θ1 Ori A, θ1 Ori C, θ1 Ori D, and θ2 Ori A, all with substantially improved astrometry and photometric mass estimates. We refined the orbit of the eccentric high-mass binary θ1 Ori C and we are able to derive a new orbit for θ1 Ori D. We find a system mass of 21.7 M⊙ 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.Marie Skłodowska-Curie Grant AgreementFCT-PortugalERC Starting Gran

PIONIER: from a Expert mode to an ESO facility instrument

<p>The PIONIER (Precision Integrated-Optics Near-infrared Imaging ExpeRiment) at the VLT Interferometer instrument was originally a visitor instrument from IPAG (Institut de Planétologie et d’Astrophysique de Grenoble). It is now offered to the ESO community as a facility instrument. As a Visitor monde instrument, it was operated on selected nights by the instrument team/consortium, the goal is now for the Paranal staff to run and monitor the instrument as any other VLT/VLTI instrument. This is done by fully integrating PIONIER in the ESO scheme. I will present here how this was done for the data reduction and the quality assurance of the science data and their related calibrations.</p

A Low Cost, High Performance, Self-Scanning Correlating White Light Fringe Tracker System

The concept of using a phased array of small, inexpensive telescopes to achieve high angular resolution of faint, distant objects is nothing new, but the practical considerations of alignment and cophasing has always limited its implementation. To be effective, the coupling of white light from these telescopes must be done in such a way as to achieve zero optical path difference (OPD) between the object being studied, the telescopes, and the point of beam recombination. In practice, this has always been very difficult due to (1.) static and time varying OPD errors from mechanical sources, (2.) large but predictable OPD shifts due to geometrical aspects of the telescopic array, and, (3.) rapid atmospheric turbulence based OPD modulations. In addition to phase errors, one must also deal with time varying mechanical and turbulence based angular misalignments of the beams.</jats:p