Mid-IR AGPMs for ELT applications

The mid-infrared region is well suited for exoplanet detection thanks to the reduced contrast between the planet and its host star with respect to the visible and near-infrared wavelength regimes. This contrast may be further improved with Vector Vortex Coronagraphs (VVCs), which allow us to cancel the starlight. One flavour of the VVC is the AGPM (Annular Groove Phase Mask), which adds the interesting properties of subwavelength gratings (achromaticity, robustness) to the already known properties of the VVC. In this paper, we present the optimized designs, as well as the expected performances of mid-IR AGPMs etched onto synthetic diamond substrates, which are considered for the E-ELT/METIS instrument.Comment: 8 pages, 5 figures, Proc. of SPIE Vol. 9147 (2014

Development of a subwavelength grating vortex coronagraph of topological charge 4 (SGVC4)

One possible solution to achieve high contrast direct imaging at a small inner working angle (IWA) is to use a vector vortex coronagraph (VVC), which provides a continuous helical phase ramp in the focal plane of the telescope with a phase singularity in its center. Such an optical vortex is characterized by its topological charge, i.e., the number of times the phase accumulates 2{\pi} radians along a closed path surrounding the singularity. Over the past few years, we have been developing a charge-2 VVC induced by rotationally symmetric subwavelength gratings (SGVC2), also known as the Annular Groove Phase Mask (AGPM). Since 2013, several SGVC2s (or AGPMs) were manufactured using synthetic diamond substrate, then validated on dedicated optical benches, and installed on 10-m class telescopes. Increasing the topological charge seems however mandatory for cancelling the light of bright stars which will be partially resolved by future Extremely Large Telescopes in the near-infrared. In this paper, we first detail our motivations for developing an SGVC4 (charge 4) dedicated to the near-infrared domain. The challenge lies in the design of the pattern which is unrealistic in the theoretically perfect case, due to state-of-the-art manufacturing limitations. Hence, we propose a new realistic design of SGVC4 with minimized discontinuities and optimized phase ramp, showing conclusive improvements over previous works in this field. A preliminary validation of our concept is given based on RCWA simulations, while full 3D finite-difference time-domain simulations (and eventually laboratory tests) will be required for a final validation.Comment: 9 page

The VORTEX project: first results and perspectives

(abridged) Vortex coronagraphs are among the most promising solutions to perform high contrast imaging at small angular separations. They feature a very small inner working angle, a clear 360 degree discovery space, have demonstrated very high contrast capabilities, are easy to implement on high-contrast imaging instruments, and have already been extensively tested on the sky. Since 2005, we have been designing, developing and testing an implementation of the charge-2 vector vortex phase mask based on concentric subwavelength gratings, referred to as the Annular Groove Phase Mask (AGPM). Science-grade mid-infrared AGPMs were produced in 2012 for the first time, using plasma etching on synthetic diamond substrates. They have been validated on a coronagraphic test bench, showing broadband peak rejection up to 500:1 in the L band, which translates into a raw contrast of about $6\times 10^{-5}$ at $2 \lambda/D$. Three of them have now been installed on world-leading diffraction-limited infrared cameras (VLT/NACO, VLT/VISIR and LBT/LMIRCam). During the science verification observations with our L-band AGPM on NACO, we observed the beta Pictoris system and obtained unprecedented sensitivity limits to planetary companions down to the diffraction limit ($0.1''$). More recently, we obtained new images of the HR 8799 system at L band during the AGPM first light on LMIRCam. After reviewing these first results obtained with mid-infrared AGPMs, we will discuss the short- and mid-term goals of the on-going VORTEX project, which aims to improve the performance of our vortex phase masks for future applications on second-generation high-contrast imagers and on future extremely large telescopes (ELTs).Comment: To appear in SPIE proceedings vol. 914

Mid-IR AGPMs for ELT applications

The mid-infrared region is well suited for exoplanet detection thanks to the reduced contrast between the planet and its host star with respect to the visible and near-infrared wavelength regimes. This contrast may be further improved with Vector Vortex Coronagraphs (VVCs), which allow us to cancel the starlight. One flavour of the VVC is the AGPM (Annular Groove Phase Mask), which adds the interesting properties of subwavelength gratings (achromaticity, robustness) to the already known properties of the VVC. In this paper, we present the optimized designs, as well as the expected performances of mid-IR AGPMs etched onto synthetic diamond substrates, which are considered for the E-ELT/METIS instrument

Three years of harvest with the vector vortex coronagraph in the thermal infrared

For several years, we have been developing vortex phase masks based on sub-wavelength gratings, known as Annular Groove Phase Masks. Etched onto diamond substrates, these AGPMs are currently designed to be used in the thermal infrared (ranging from 3 to 13 {\mu}m). Our AGPMs were first installed on VLT/NACO and VLT/VISIR in 2012, followed by LBT/LMIRCam in 2013 and Keck/NIRC2 in 2015. In this paper, we review the development, commissioning, on-sky performance, and early scientific results of these new coronagraphic modes and report on the lessons learned. We conclude with perspectives for future developments and applications.Comment: To appear in SPIE proceedings vol. 990

A population of gamma-ray emitting globular clusters seen with the Fermi Large Area Telescope

Globular clusters with their large populations of millisecond pulsars (MSPs) are believed to be potential emitters of high-energy gamma-ray emission. Our goal is to constrain the millisecond pulsar populations in globular clusters from analysis of gamma-ray observations. We use 546 days of continuous sky-survey observations obtained with the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope to study the gamma-ray emission towards 13 globular clusters. Steady point-like high-energy gamma-ray emission has been significantly detected towards 8 globular clusters. Five of them (47 Tucanae, Omega Cen, NGC 6388, Terzan 5, and M 28) show hard spectral power indices $(0.7 < \Gamma <1.4)$ and clear evidence for an exponential cut-off in the range 1.0-2.6 GeV, which is the characteristic signature of magnetospheric emission from MSPs. Three of them (M 62, NGC 6440 and NGC 6652) also show hard spectral indices $(1.0 < \Gamma < 1.7)$, however the presence of an exponential cut-off can not be unambiguously established. Three of them (Omega Cen, NGC 6388, NGC 6652) have no known radio or X-ray MSPs yet still exhibit MSP spectral properties. From the observed gamma-ray luminosities, we estimate the total number of MSPs that is expected to be present in these globular clusters. We show that our estimates of the MSP population correlate with the stellar encounter rate and we estimate 2600-4700 MSPs in Galactic globular clusters, commensurate with previous estimates. The observation of high-energy gamma-ray emission from a globular cluster thus provides a reliable independent method to assess their millisecond pulsar populations that can be used to make constraints on the original neutron star X-ray binary population, essential for understanding the importance of binary systems in slowing the inevitable core collapse of globular clusters.Comment: Accepted for publication in A&A. Corresponding authors: J. Kn\"odlseder, N. Webb, B. Pancraz

Direct exoplanet imaging with small-angle Vortex coronagraphs

Vortex coronagraphs are among the most promising solutions to perform high contrast imaging at small angular separations from bright stars. They enhance the dynamic range at very small inner working angle (down to the diffraction limit of the telescope) and provide a clear 360 degree discovery space for high-contrast direct imaging of exoplanets. In this talk, we will report on the first scientific results obtained with Vortex coronagraphs installed on 10-m class telescopes (i.e., the VLT and the LBT) and on the recent installation of one Vortex at Keck. We will describe the in-lab and on-sky performance of the Vortex, and describe the lessons learned after a few years of operation. Finally, we will discuss the prospects of our vortices for future extremely large telescopes and space missions.VORTE

Etude in vitro des mécanismes d'action impliqués dans la réponse cellulaire à une radioimmunothérapie à l'iode 125

La radioimmunothérapie (RIT) consiste à associer la spécificité de ciblage d'un anticorps monoclonal à la forte toxicité d'un atome radioactif. Afin d'évaluer l'efficacité d'une RIT à l' 125 I, émetteur d'électrons Auger, les lignées cellulaires de carcinome colique HCT 116 p53 (+/+) et p53 (-/-) exprimant les récepteurs HER1 et CEA ont été exposées pendant 48h à des activités croissantes d'anticorps radiomarqué permettant d'obtenir une localisation finale de l'émetteur cytoplasmique (anticorps internalisant anti-HER1) ou membranaire (anticorps non-internalisant anti-CEA). L'évaluation rigoureuse de l'efficacité de cette RIT a nécessité de déterminer la dose d'irradiation moyenne délivrée au noyau par le formalisme du MIRD cellulaire. Nos résultats montrent qu'un taux de survie cellulaire similaire (40%) est observé pour les 2 localisations alors qu'une dose moyenne d'irradiation au noyau beaucoup plus faible (1,2 versus 42,9 Gy) est délivrée dans le cas de l'anticorps non-internalisant. Cette toxicité plus importante associée à une localisation membranaire de l'125I est observée quel que soit le statut p53. Ces résultats suggèrent que la membrane est une cible sensible aux forts dépôts d'énergie associés aux électrons Auger. Afin d'étudier l'origine de cette toxicité accrue, la formation des lésions au niveau de l'ADN en fonction de la dose délivrée au noyau a d'abord été évaluée. Les résultats montrent, qu'en dépit de doses d'irradiation au noyau très différentes, un niveau similaire de cassures de brins de l'ADN et de micronoyaux est observé quel que soit la localisation finale de l'125I, dans les deux lignées cellulaires. Rapportée au Gy, la formation des lésions est plus importante lorsque le débit de dose est plus faible. Nous avons aussi observé une accumulation de la protéïne p53 et une activation de la protéïne p21 dans la lignée HCT 116 p53 (+/+), accompagnée d'un arrêt du cycle cellulaire en G2/M et d'une induction d'apoptose. Ces données suggèrent que les lésions de l'ADN produites sont bien détectées par la cellule et que la mort par apoptose ne joue pas un rôle majeur dans la toxicité de l'125I au niveau membranaire. L'autophagie semble toutefois être impliquée dans la réponse à la RIT à l'125I et reste à déterminer dans de futurs travauxRadioimmunotherapy (RIT) results from the combinaison between a monoclonal antibody (mAb) directed against tumor associated antigen and the strong toxicity of a radioactive isotope. In order to assess the efficiency of RIT based on 125I, an Auger electron emitter, carcinoma colic cell lines HCT 116 p53 (+/+) and p53 (-/-) expressing HER1 and CEA antigens were exposed to increasing activities of either internalizing 125I-mAbs (anti-HER1, cytoplasmic localization) or of non-internalizing 125I-mAbs (anti CEA, cell membrane localization). In order to truly compare efficiency of both 125I final localizations, mean nucleus irradiation dose was determined using MIRD cellular approach. Similar cell survival (40%) was observed while much lower irradiation doses were delivered to the nucleus (1,2 versus 42,9 Gy) using the non-internalizing mAb. The latter toxicity due to cell membrane 125I decays was observed whatever p53 status. These results suggest thet cell membrane is a sensitive target to 125I decays. In order to investigate the mechanisms involved, the level of DNA damage was measured. Although strongly different irradiation doses were delivered, we observed that levels in DNA breaks, together with micronuclei formation was similar for the two final localizations of 125I and for the two cell lines. Expressed as a function of delivered Gy, DNA damge yield was much higher for low dose-rate irradiation (membrane localization). We also observed p53 accumulation and subsequent p21 activation in HCT 116 p53 (+/+) cell line. Cell cycle arrest in G2/M and radio-induced apoptosis were also measured in the latter cell line. These data suggest that low level of radiation-induced DNA damage are properly detected by the cells and that apoptotic death is not involved in the toxicity of 125I at the cell membrane level. However, autophagy might be involved but further studies are required to assess its involvement in the observed biological effectsMONTPELLIER-BU Médecine UPM (341722108) / SudocMONTPELLIER-BU Médecine (341722104) / SudocSudocFranceF