Étienne Artigau

A NEAR-INFRARED SURVEY OF THE INNER GALACTIC PLANE FOR WOLF-RAYET STARS. II. GOING FAINTER: 71 MORE NEW W-R STARS

We are continuing a J, K and narrowband imaging survey of 300 deg2 of the plane of the Galaxy, searching for new Wolf-Rayet (W-R) stars. Our survey spans 150° in Galactic longitude and reaches 1° above and below the Galactic plane. The survey has a useful limiting magnitude of K = 15 over most of the observed Galactic plane, and K = 14 (due to severe crowding) within a few degrees of the Galactic center. Thousands of emission-line candidates have been detected. In spectrographic follow-ups of 146 relatively bright W-R star candidates, we have re-examined 11 previously known WC and WN stars and discovered 71 new W-R stars, 17 of type WN and 54 of type WC. Our latest image analysis pipeline now picks out W-R stars with a 57% success rate. Star subtype assignments have been confirmed with the K-band spectra and distances approximated using the method of spectroscopic parallax. Some of the new W-R stars are among the most distant known in our Galaxy. The distribution of these new W-R stars is beginning to trace the locations of massive stars along the distant spiral arms of the Milky Way.

H4RG characterization for high-resolution infrared spectroscopy

Large-format infrared arrays are enablers for a variety of astronomical applications, from wide-field imaging to very high-resolution spectroscopy over a wide range of wavelength. We present the optimization of the science-grade H4RG array used in the SPIRou high-resolution spectrograph designed for high-precision velocity measurements. In SPIRou nominal science operation, the array is used in a relatively low flux regime, well below the full-well of the arrays and, for some applications, the readout noise is a major contributor to the overall signal-to-noise budget. We describe the detector fine-tuning process as well as the derived properties and their impact on performances. We identify persistence as potentially problematic under certain circumstances for infrared m/s velocimetry.

Preliminary characterization results of a large format 4k x 4k EMCCD

Scientific EMCCD cameras have demonstrated excellent imaging performance under extreme low light conditions. Photon counting capability combined with a very low dark current offered by the CCD technology have made EMCCDs the detector of choice for high-performance applications such as time resolved spectroscopy and low light imaging. However, future astronomical instrumentation requires high spatial resolution while commercially available EMCCD devices are limited by a relatively modest area format of (1kx1k). To address this requirement, the Universitė de Montrėal and Teledyne-e2v have jointly developed a 4kx4k EMCCD, the CCD282. This paper presents the results of cryogenic characterization of the CCD282 operated with Nüvü Camēras’ CCD Controller for Counting Photons version 3. The advantages of a novel large format EMCCD over existing technology for high resolution spectroscopy are discussed.

SPIRou @CFHT: full in-lab and on-sky performances

SPIRou is the new high resolution echelle spectropolarimeter and high-precision velocimeter, in the near infra- red, for the 3.6m Canada-France-Hawaii Telescope (CFHT Mauna Kea). This next generation instrument aims at detecting and characterizing Earth-like planets in the habitable zone of low-mass dwarfs and at investigating how magnetic fields impact star and planet formation. SPIRou consists of an achromatic polarimetric module coupled with a fluoride fiber link to a thermally-controlled cryogenic echelle spectrograph, and a Calibration Unit which can fed the light of hollow-cathod lamps, a radial velocity reference (Fabry-Pérot), or a cold source to the polarimeter and/or the spectrograph. Here we present a summary of the full performances obtained in laboratory tests carried in Toulouse (France), and the first results of the on-going commissioning at the CFHT. SPIRou covers a spectral range from 0.96 to 2.48 μm (YJHK domain) in one single exposure at a resolving power of 70 K, providing unpolarized and polarized spectra (with sensitivity 10 ppm) of stars, with a 10 15% peak throughput. Lab tests demonstrate that SPIRou is capable of achieving a relative radial velocity precision better than 0.2 m/s rms on timescales of 24 hr. Science operations of SPIRou are expected to start in 2018 S2, enabling significant synergies with major space and ground instruments such as the JWST, TESS, ALMA and later-on PLATO and the ELT.

Experimental test of a 40 cm-long R=100 000 spectrometer for exoplanet characterisation

High-resolution spectroscopy is a key element for present and future astronomical instrumentation. In particular, coupled to high contrast imagers and coronagraphs, high spectral resolution enables higher contrast and has been identified as a very powerful combination to characterise exoplanets, starting from giant planets now, up to Earth-like planet eventually for the future instruments. In this context, we propose the implementation of an innovative echelle spectrometer based on the use of VIPA (Virtually Imaged Phased Array, Shirasaki 1996). The VIPA itself is a particular kind of Fabry-P´erot interferometer, used as an angular disperser with much greater dispersive power than common diffraction grating. The VIPA is an efficient, small component (3 cm × 2.4 cm), that takes the very advantage of single mode injection in a versatile design. The overall instrument presented here is a proof-of-concept of a compact, high-resolution (R > 80 000) spectrometer, dedicated to the H and K bands, in the context of the project “High-Dispersion Coronograhy“ developed at IPAG. The optical bench has a foot-print of 40 cm × 26 cm ; it is fed by two Single-Mode Fibers (SMF), one dedicated to the companion, and one to the star and/or to a calibration channel, and is cooled down to 80 K. This communication first presents the scientific and instrumental context of the project, and the principal merit of single-mode operations in high-resolution spectrometry. After recalling the physical structure of the VIPA and its implementation in an echelle-spectrometer design, it then details the optical design of the spectrometer. In conclusion, further steps (integration, calibration, coupling with adaptive optics) and possible optimization are briefly presented.