This poster advertizes the Jean-Marie Mariotti Center software tools, databases and services aimed at facilitating the use of optical interferometry worldwide such as preparation of observations, data reduction and data analysis. Its mission and organization are presented before listing the current software suite. Finally some facts and perspectives are mentioned.
The JMMC1 Calibrator Workgroup has long developed methods to ascertain the angular diameter of stars, and provides
this expertise in the SearchCal2 software. SearchCal dynamically finds calibrators near science objects by querying CDS3
hosted catalogs according to observational parameters. Initially limited to bright objects (K magnitude ≤ 5.5), it has been
upgraded with a new method providing calibrators without any magnitude limit but those of queried catalogs. We
introduce here a new static catalog of stellar diameters, containing more than 38000 entries, obtained from SearchCal
results aggregation on the whole celestial sphere, complete for all stars with HIPPARCOS4 parallaxes. We detail the
methods and tools used to produce and study this catalog, and compare the static catalog approach with the dynamical
querying provided by SearchCal engine. We also introduce a new Virtual Observatory service, enabling the reporting of,
and querying about, stars flagged as "bad calibrators" by astronomers, adding this ever-growing database to our
SearchCal service.
This paper presents the current status of the VEGA (Visible spEctroGraph and polArimeter) instrument installed
at the coherent focus of the CHARA Array, Mount Wilson CA. Installed in september 2007, the first science
programs have started during summer 2008 and first science results are now published. Dedicated to high angular (0.3mas) and high spectral (R=30000) astrophysical studies, VEGA main objectives are the study of circumstellar environments of hot active stars or interactive binary systems and a large palette of new programs dedicated to fundamental stellar parameters. We will present successively the main characteristics of the instrument and its current performances in the CHARA environment, a short summary of two science programs and finally we will develop some studies showing the potential and difficulties of the 3 telescopes mode of VEGA/CHARA.
Massive stars deeply influence their surroundings by their luminosity and the injection of kinetic energy. So
far, they have mostly been studied with spatially unresolved observations, although evidence of geometrical
complexity of their wind are numerous. Interferometry can provide spatially resolved observations of massive
stars and their immediate vicinity. Specific geometries (disks, jets, latitude-dependent winds) can be probed by
this technique.
The first observation of a Wolf-Rayet (WR) star (γ2 Vel) with the AMBER/VLTI instrument yielded to a
re-evaluation of its distance and an improved characterization of the stellar components, from a very limited
data-set. This motivated our team to increase the number of WR targets observed with AMBER. We present
here new preliminary results that encompass several spectral types, ranging from early WN to evolved dusty
WC.
We present unpublished data on WR79a, a massive star probably at the boundary between the O and Wolf-Rayet type, evidencing some
Wolf-Rayet broad emission lines from an optically thin wind. We also present new data obtained on γ2 Vel that can be compared to the up-to-date interferometry-based orbital parameters from North et al. (2007). We discuss the presence of a wind-wind collision zone in the system and provide preliminary analysis suggesting the presence of such a structure in the data. Then, we present data obtained on 2 dusty Wolf-Rayet stars: WR48a-b and WR118, the latter exhibiting some clues of a pinwheel-like structure from the
visibility variations.
The VEGA spectrograph and polarimeter has been recently integrated on the visible beams of the CHARA
Array. With a spectral resolution up to 35000 and thanks to operation at visible wavelengths, VEGA brings
unique capabilities in terms of spatial and spectral resolution to the CHARA Array. We will present the main
characteristics of VEGA on CHARA, some results concerning the performance and a preliminary analysis of the
first science run.
Interferometry has been intensively done at long wavelengths, starting with the radio interferometers in the years 50 since it was easier to guide radio wavelengths in cable while keeping the phase information or using a local oscillator and a correlator to recombine "a posteriori" the beams over intercontinental distances. In the optical a lot of work as been done at IR and near-IR wavelengths since it was technically easier, or we must say, less difficult to recombine directly the optical beams since the coherence length is larger and the turbulence slower than at shorter wavelengths.
Therefore, the visible domain of the electromagnetic spectrum is not covered at the same level than near or mid infrared.
Some very nice and important results have been however obtained with the GI2T interferometer in south of France, the
Mark III interferometer on the Mount Wilson, USA, the NPOI array in Flagstaff, USA or the SUSI interferometer in Australia. We will present in this paper the science cases of a new but already existing and tested instrument: the
REGAIN focal instrument which was designed and built for the GI2T. This instrument, in his CHARA adaptation, called VEGA will open new fields in a wide range of Astrophysical topics only addressable in the visible domain. It will provide a spectral resolution up to 30000 within the spectral range 0.4-0.9 micron and a spatial resolution of less than 1mas for up to 4 telescopes in its X-lambda special configuration. A polarimetric device (SPIN) measuring simultaneously the polarization in 2 directions either circular or linear is also implemented in this instrument. Since VEGA was already tested on the sky on 1.5 m telescopes it is also very well suited for the 1m CHARA array and will only need minor adaptations for the injection of the CHARA beams. This paper will focus on some of the most promising science drivers only possible with this visible instrument.
We describe a project for the installation of a visible focal instrument at the CHARA Array, named VEGA for Visible spEctroGraph and polArimeter. This new instrument will further open the visible domain and offer both spectral and polarimetric capabilities at the CHARA Array. It will create a new and unique scientific niche for the CHARA Array, especially in the context of international competition. The combination of the visible domain and high spectral resolution mode combined with a good sensitivity will allow VEGA/CHARA to carve out a new piece of observational phase space and compliment many existing or planned near-infrared interferometers. VEGA will help make CHARA the interferometer with the largest spectral and spatial resolution worldwide.
We present a test bench designed to study the performances of interferometric recombination systems, mainly for direct imaging applications (hypertelescope principle). It aims at comparing the aperture synthesis, Fizeau and densified pupils beam combination schemes. It allows identification of the technical requirements like photometry and cophasing correction of the future imaging recombiners for large arrays. A densified assembly has been designed in the visible wavelengths, using a multi-apertures mask associated with a wavefront sensor. It allows pupil rearrangement and spatial filtering by using single mode fibers. The technical specifications and the conception of the fiber densifier are described here, with a particular attention to the correction of the differential chromatic dispersion.
We give an overview of recent results obtained with the GI2T interferometer. On the technical side, great improvements have been obtained on photon counting detectors, especially in terms of quantum efficiency and of photon centroiding algorithms. Piston measurements with the GI2T dispersed fringes have been made during
coordinate observations with the Generalized Seeing Monitor GSM. These observations have lead to wavefront outer scale determinations. The last topic we will present concerns the polarimetric measurements done with the SPIN device on the GI2T spectrograph. We conclude this paper by a summary of the results obtained with the GI2T during its scientific life.
In stellar interferometry, the raw fringe visibilities must be calibrated to obtain the intrinsic object visibilities and then object parameters which can be interpreted in term of astrophysical parameters. The selection of suitable calibration stars is crucial to reach the ultimate precision of the interferometric instruments like VLTI. So, we have developed a user-dedicated software to create an evolutive catalog of such calibration stars. This gives useful information for the selection of calibrators with respect to the requirements of the astrophysical program and of the instrumental configuration. A list of potential calibrators is obtained from a set of catalogs available at the Centre de Donnees Astronomiques de Strasbourg (CDS). The CDS request is based on some selection criteria like the maximum angular distance and the range of magnitude around the scientific target. This calibrator selection tool is integrated into ASPRO the interferometric observing preparation software developed by the Jean-Marie Marriotti Center (JMMC), and which is accessible at http://mariotti.ujf-grenoble.fr/~aspro/
The GI2T interferometer has been recently equipped with a new beam combiner called REGAIN, including a dedicated visible spectrograph for enhanced spectral capabilities. The control system, the fringe tracking processor, the photon counting detectors as well as the data reduction pipeline have been refurbished or changed. After a long phase of qualification, the whole system is now ready for scientific operations. We will describe the main new features of the system.
The Jean-Marie Mariotti Center is a network of 11 French Institutes,
Laboratories or Observatories, appointed by CNRS in 2000. It coordinates the efforts of the member institutes to offer all the potential users of interferometric facilities the best operational environment, providing software, academic formation and stimulating the prospective on new interferometric developments. At present,
besides academic formation, the major effort is focused on the
development of the software to prepare the observations, to reduce the data and to interpret the results in terms of models or reconstructed images. In this contribution, we describe the achievements and the future plans of the Mariotti Center.
After five years of development, the REGAIN project has obtained its first light during summer 1999. The main goals were improving the quality and quantity of data through a complete re-designing and re-building of the central beam combiner. The REGAIN interferometric bonnette delivers two coherent foci, one at visible wavelengths and one in the IR bands (J, H and K). The visible focus is equipped with a dedicated visible spectrograph and two photon counting detectors. The infrared focus can be equipped with different instruments. I will discuss the main technical issues that have been chosen.
We have initiated an observational program to investigate evolved stars from high spatial and spectral resolution observations with GI2T (Grand Interferometre a 2 Telescopes) in the visible and near-infrared wavelengths. The scientific objectives are: measuring limb darkening, resolving small- scale structures and understanding stellar pulsation. The target selection and model fitting procedure are discussed here. Also presented are the limiting magnitude of GI2T/REGAIN for our program and simulated visibility curves. Actual observations are planned during coming months.
KEYWORDS: Stars, Visibility, Interferometry, Beryllium, Spectroscopy, Spatial resolution, Interferometers, Systems modeling, Modeling, Signal to noise ratio
The capabilities of GI2T-REGAIN (Grand Interferometre a 2 Telescopes-REcombinateur du GrAnd INterferometre) interferometer are well suited for studying and understanding the morphology and physical processes of multiple systems. Thus we present the observing program we intend to carry out with this instrument. It will lead to an accurate determination of their fundamental parameters such as masses and sizes. Our program on interacting binaries will be coupled to a mass transfer model which can benefit from these observations.
This paper presents the optical layout of the REGAIN beam combiner including the optical delay line LAROCA with its variable curvature mirror, the field rotator devices, the image and pupil tracking systems and the dedicated visible spectrography. Preliminary studies of foreseen improvements, such as adaptive optics, IR spectrograph and addition of a third telescope, will be discussed.
This paper reviews the scientific results obtained with the Grand Interferometre a 2 Telescopes (the GI2T interferometer) from 1990 to 1996. During this epoch, accurate spectroscopy coupled to interferometry were achieved on luminous and multiple stars. Subtle structures in circumstellar environments such as: jets in the binary system β Lyrae, dumpiness in the wind of P Cygni, a rotating arm in ζTau have been discovered. Measurements of angular diameter variability versus time and wavelength provide fundamental parameters which constraint δ Cephei and γCas models. In addition to GI2T results, we develop in our group hydrodynamic and radiative transfert models dedicated to the interpretation of interferometry results. These models can directly constrain luminous star physics through their observable parameters.
This paper describes the present status of the Grand Interferometre a 2 Telescopes (GI2T). We review the general features of this instrument and present the scientific programs pursued by our group. Attention is given here to procedures of instrumental and visibility calibration, including the response of both the detector and spectrometer. We discuss the method of data analysis and the attainable accuracy of astrophysical parameters. The current limitations of the GI2T and development of our new optical table are presented.
A new focal instrumentation for the Grand Interferometre a 2 Telescopes (GI2T) called REGAIN (REcombinaison pour GrAnd INterferometre) is under study at the Observatoire de la Cote d'Azur (OCA) and the Laboratoire d'Astronomie Spatiale (LAS) in Marseille, France. The objectives of the REGAIN project are multiple. Priority number 1 is a more efficient astrophysical exploitation of the GI2T. Next is the possibility for observing simultaneously at visible and near-infrared wavelengths. Finally REGAIN should ensure the test of the OVLA prototype telescope added to the present GI2T. Therefore, the resulting GI3T could be used for phase-closure imaging with 1.5-m apertures. At the same time reservations will be made for implementing adaptive optics units for each telescope whilst the VLT interferometer fringe- sensor currently studied at the OCA, should be tested on the GI3T.
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