Romain Petrov

... mastery related to the operation of a complex interferometric system at Dome C during polar winter, includ-ing: logistics chain, maintenance, tuning ... Elhalkouj, T., Ziad, A., Petrov, RG, et al., 2008, A&A, 477, 337 Elhalkouj, T., Petrov, RG, Lazrek, M., & Benkhaldoun, Z., 2006, IAU ...

ABSTRACT We propose a spectro-astrometric observing mode for the Japanese/European SPICA mission. It is expected to offer an additional detecting/characterizing capability to the SPICA coronagraph (see Haze et al., this conference). Indeed the spectro-astrometric technique will be sensitive to very close-in giant planets orbiting at a typical distance from 0.01 to a few AUs. It is capable in principle to recover astrometric parameters as well as spectra from a host planet. In this poster, we summarize the main aspects of this observing technique, and we present the current status of our on-going laboratory experiment. Our goal is to demonstrate the capabilty to measure differential photocentre displacements down to at least 10-3 pixels, thus validating our spectro-astometric measurement model. We discuss the various instrumental and astrophysical effects that we expect to hamper the exo-planetary spectro-astrometric signature.

ABSTRACT We investigate the general constraints that differential interferometry (DI) can yield on BLRs and discuss the signatures of different BLR parameters, such as black hole mass, BLR size, thickness, distribution of clouds, local micro or macroturbulence versus global velocity, rotation versus inflow and outflow, and cloud optical thickness, on both DI and reverberation mapping (RM) observables, describing a 3D geometrical and kinematic BLR model that can simulate all DI and RM observables. Combination of DI and RM not only constrain the BLR geometry and kinematics, but also provide a way to use BLRs as standard candles. It appears that DI can constrain the RM projection factor and decrease the number of fixed model parameters. We use a SNR analysis of DI, updated and calibrated on our actual 3C273 data, to evaluate the number of targets accessible to current (AMBER+), upcoming (GRAVITY) and possible VLTI instruments, that suggest the full potential of the VLTI exceeds 60 targets with known improvements of instruments and fringe trackers. Using a MCMC algorithm on simulated data we found that DI under RM constraints yields mass accuracies between 0.06 and 0.13 dex that is better than the 0.44 dex in the current mass-luminosity fits. The combination of DI and RM on such a target set, that covers a $10^{4}$ to $10^{5}$ luminosity range, should allow a decisive improvement in RM mass-luminosity and size-luminosity laws and permit to evaluate a larger unification scheme relating the main BLR characteristics to the luminosity of the central source.

ABSTRACT We want to study a polychromatic inverse problem method with nulling interferometers to obtain information on the structures of the exozodiacal light. For this reason, during the first semester of 2013, thanks to the support of the consortium PERSEE, we launched a campaign of laboratory measurements with the nulling interferometric test bench PERSEE, operating with 9 spectral channels between J and K bands. Our objective is to characterise the transfer function, i.e. the map of the null as a function of wavelength for an off-axis source, the null being optimised on the central source or on the source photocenter. We were able to reach on-axis null depths better than 10^{-4}. This work is part of a broader project aiming at creating a simulator of a nulling interferometer in which typical noises of a real instrument are introduced. We present here our first results.

ABSTRACT 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.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The SPICA coronagraph will be dedicated to detecting and observing extra-solar planets. How-ever, the limited angular resolution of SPICA in the Near/Mid Infrared (0.2 arcsec at 3.5 mi-cron) will prevent the study of very close-in planets, closer than a few A.U. from their parent star. We propose to implement Color Differential Astrometry (originally proposed by Petrov), a complementary observing mode for the coronagraph. It is a spectro-astrometric method which would push the detection range to very close-in planets and up to a few AUs, thus nicely com-plementing the imaging coronagraph. We describe the CDA method and show that it could directly recover the planet orbital elements and low resolution spectrum. The analysis of the fundamental contributions to the SNR (source and background noise, detector noise) give a substantial range of application to the technique provided that certain characteristics of instru-ment stability or calibration methods are met. These instrumental req...

... 1 Laboratoire Universitaire d'Astrophysique de Nice, Laboratoire d'Astrophysique de Grenoble, Obser-vatoire de Nice in France, Max-Planck Institute for ... dis-play showing three telescope fringes, in medium resolution between 2 090 and 2 200 nm, on the bright Be star αArae. ...

... Blanc, Alain Blazit, Jean-Lucien Boit, Daniel Bonneau, Olivier Chesneau, Jean M. Clausse, JM Corneloup, Robert Dalla, Michel Dugue, Andre Glentzlin, L. Hill, Antoine Labeyrie, Joel Le Merrer,Serge Menardi, Guy Merlin, Gabriel Moreaux, Romain G. Petrov, Sylvestre Rebattu ...

MATISSE is foreseen as a mid-infrared spectro-interferometric instrument combining the beams of up to four UTs/ATs of the Very Large Telescope Interferometer (VLTI). MATISSE will measure closure phase relations and thus offer an efficient capability for image reconstruction. In addition to this, MATISSE will open 2 new observing windows at the VLTI: the L and M band in addition to

ABSTRACT A variety of instrumental effects can corrupt the observable quantities in optical or nulling stellar interferometry. One such effect is parasitic interference, which can occur inside an interferometric instrument. Because of diffraction effects related to beam propagation along finite size optics, or parasitic reflections inside transmitting optics, a coherent crosstalk may occur between the beams and create a parasitic interference pattern superimposed on the genuine one. We developed an analytical approach to describe the impact of this effect on the observables of classical and nulling stellar interferometers. Considering classical interferometry, we show that differential phase and closure phase are both corrupted, depending on the crosstalk level and the residual piston between the beams. Considering typical specifications of piston correction of ground-based interferometers (≍ 100 nm), the detection of hot Jupiter-like planets by differential phase implies a tolerance on the parasitic flux to about 5% of the incident intensity. Also, we show that the closure phase relation does not remove this parasitic contribution. The corresponding corrupted closure phase is not zero for an unresolved source, and depends on the residual piston. Considering nulling interferometry, we show that parasitic effects modify the transmission map level, depending on the crosstalk level and the phase shift between primary and secondary beams. In the extreme case of a pi-phase shift, the crosstalk effect implies a decrease of the final output signal-to-noise ratio. Numerical simulations, adapted to handle consistently crosstalk, are then performed to estimate this degradation and validate our theoretical study.

AMBER is the first general user near infrared VLTI focal instrument. It combines low and middle resolution spectroscopy with some imaging capability thanks to the measure of phase closures between three telescopes. It is optimized for high accuracy measurements thanks to a spatial filtering of each beam using single mode fibers. The poster presents AMBER main characteristics, discusses its potential

AMBER is the General User near infrared focal instrument of the Very Large Telescope Interferometer. Its a single mode, dispersed fringes, three telescopes instrument. A limiting magnitude of the order of H=13 will allow to tackle a fair sample of extra galactic targets. A very high accuracy, in particular in color differential phase and closure phase modes gives good hope

ABSTRACT MATISSE (Multi AperTure mid-Infrared SpectroScopic Experiment) is the future spectro-interferometer of the European Southern Observatory VLT operating in the spectral bands L, M and N, and combining four beams from the telescopes UTs or ATs. This paper describes the concept, the specifications and the expected performances of the instrument. The requirements have been established including transmission and contrast degradation budgets. An assessment of the performances is given in this paper taking into account the instrument and VLTI characteristics.

Our objective is the development of mid-infrared imaging at the VLTI. The related science case study demonstrates the enormous capability of a new generation mid-infrared beam combiner. MATISSE will constitute an evolution of the two-beam interferometric instrument MIDI by increasing the number of recombined beams up to four. MIDI is a very successful instrument which offers a perfect combination of

A first generation of VLTI (Very Large Telescopes Interferometer) focal instruments, AMBER in the near-infrared and MIDI in the mid-infrared, has been already integrated and tested. New and important science results have been obtained. These instruments combine two (for MIDI) or three (for AMBER) beams coming from the eight telescopes installed at Cerro Paranal (four 8-meters and four 1.8-meters telescopes).

ABSTRACT MATISSE is a mid-infrared spectro-interferometer combining the beams of up to four Unit Telescopes or Auxiliary Telescopes of the Very Large Telescope Interferometer (VLTI) of the European Southern Observatory. MATISSE will constitute an evolution of the two-beam interferometric instrument MIDI. New characteristics present in MATISSE will give access to the mapping and the distribution of the material, the gas and essentially the dust, in the circumstellar environments by using the mid-infrared band coverage extended to L, M and N spectral bands. The four beam combination of MATISSE provides an efficient uv-coverage: 6 visibility points are measured in one set and 4 closure phase relations which can provide aperture synthesis images in the mid-infrared spectral regime. We give an overview of the instrument including the expected performances and a view of the Science Case. We present how the instrument would be operated. The project involves the collaborations of several agencies and institutes: the Observatoire de la Co te d'Azur of Nice and the INSU-CNRS in Paris, the Max Planck Institut fur Astronomie of Heidelberg; the University of Leiden and the NOVA-ASTRON Institute of Dwingeloo, the Max Planck Institut fur Radioastronomie of Bonn, the Institut fur Theoretische Physik und Astrophysik of Kiel, the Vienna University and the Konkoly Observatory.

MATISSE is foreseen as a mid-infrared spectro-interferometer combining the beams of up to four UTs/ATs of the Very Large Telescope Interferometer (VLTI). MATISSE will measure closure phase relations and thus offer an efficient capability for image reconstruction in the L, M and N bands of the mid-infrared domain.

We present interferometric near-infrared observations of the Luminous Blue Variable (LBV) eta Car using the Very Large Telescope Interferometer (VLTI) and the AMBER instrument of the European Southern Observatory (ESO). A high spatial resolution of 5 mas (~11.5 AU) and a high spectral resolution R = lambda/Deltalambda=1500 and 12000 were obtained. Some of the data was recorded using the fringe

ABSTRACT MATISSE (Multi AperTure mid-Infrared SpectroScopic Experiment) is the spectro-interferometer of the European Southern Observatory VLT operating in the spectral bands L, M and N, and, combining four beams from the unit or auxiliary telescopes. The concept constitutes an evolution of the two-beam interferometric instrument MIDI operating on the VLTI. It will give access to the mapping and the distribution of the material, the gas and essentially the dust, in the circumstellar environments and will provide aperture synthesis images in the mid-infrared spectral regime. The Warm OPtics (WOP) of the instrument provides the functions of spectral band separation, optical path equalization and modulation, pupil positioning, beam anamorphosis, beam positioning, and beam commutation. It also allows the alignment function of the beams with the Cold Optics contained in two separate cryostats. This sub-system is presently aligned and tested at the Observatoire de la Côte d'Azur in Nice, France, to validate accuracy and stability. The present paper gives the results of the Warm OPtics laboratory tests.

ABSTRACT We present the first interferometric NIR observations of the LBV η Carinae with high spectral resolution. The observations were carried out with three 8.2 m VLTI Unit Telescopes in the K-band. The raw data are spectrally dispersed interferograms obtained with spectral resolutions of 1,500 (MR-K mode) and 12,000 (HR-K mode). The observations were performed in the wavelength range around both the He I 2.059 μm and the Brγ 2.166 μm emission lines. The spectrally dispersed AMBER interferograms allow the investigation of the wavelength dependence of the visibility, differential phase, and closure phase of η Car. In the K-band continuum, a diameter of 4.0+/-0.2 mas (Gaussian FWHM) was measured for η Car's optically thick wind region, whereas the Brγ and He I emission line regions are larger. If we fit Hillier et al. model visibilities to the observed AMBER visibilities, we obtain 50% encircled-energy diameters of 4.3, 6.5 and 9.6 mas in the 2.17 μm continuum, the He I, and the Brγemission lines, respectively. In the continuum near the Brγ line, an elongation along a position angle of 128° +/- 15° was found, consistent with previous VLTI/VINCI measurements. We find good agreement between the measured visibilities and the predictions of the radiative transfer model of Hillier et al. For the interpretation of the non-zero differential and closure phases measured within the Brγ line, we present a simple geometric model of an inclined, latitude-dependent wind zone. Our observations support theoretical models of anisotropic winds from fast-rotating, luminous hot stars with enhanced high-velocity mass loss near the polar regions.

We evaluate the potential of differential interferometry using the AMBER and MIDI instruments of the VLT interferometer for the direct detection and the study of atmospheric characteristics of hot giant extrasolar planets around nearby stars. Differential interferometry has been ...

The differential phase yields high dynamics and/or super resolution information. This mode will be available with AMBER at VLTI in autumn 2003 and has a wide range of scientific applications. The goal of our study is to keep the instrumental effects under the level of ...

ABSTRACT AMBER is the first general user near infrared VLTI focal instrument. It combines low and middle resolution spectroscopy with some imaging capability thanks to the measure of phase closures between three telescopes. It is optimized for high accuracy measurements thanks to a spatial filtering of each beam using single mode fibers. The poster presents AMBER main characteristics, discusses its potential and lists some of its scientific programs.