Rene Racine

Speckle Noise and the Detection of Faint Companions

ABSTRACT Speckles dominate shot noise within the halo of adaptively corrected bright star images and, consequently, impose severe limits on ground‐based attempts to directly detect planets around nearby stars. The effect is orders of magnitude greater than conventional photon noise. It depends on the dwell time of the speckle pattern, the brightness of the star, and the fraction \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

Efficient Speckle Noise Attenuation in Faint Companion Imaging

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TRIDENT: An Infrared Differential Imaging Camera Optimized for the Detection of Methanated Substellar Companions

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THE TELESCOPE POINT SPREAD FUNCTION

ABSTRACT Numerical simulations are used to evaluate a technique to attenuate speckle noise and enhance faint companion images buried in a bright‐star point‐spread function (PSF). It is shown that when frames taken simultaneously at two different wavelengths are subtracted from one another, the general evolution of the PSF profile with wavelength limits the attenuation to \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

Globular clusters in the halo of M31

A_{2}\sim 2\sigma ^{2}_{\phi }\Delta \lambda / \lambda

Differential Imaging with a Multicolor Detector Assembly: A New Exoplanet Finder Concept

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Fifth image and photometric variability in 2237+0305 («Einstein cross»)

ABSTRACT We describe a near‐infrared camera in use at the Canada‐France‐Hawaii Telescope (CFHT) and at the 1.6 m telescope of the Observatoire du mont Megantic (OMM). The camera is based on a Hawaii‐1 1024 × 1024 HgCdTe array detector. Its main feature is the acquisition of three simultaneous images at three wavelengths across the methane absorption bandhead at 1.6 μm, enabling, in theory, an accurate subtraction of the stellar point‐spread function (PSF) and the detection of faint close, methanated companions. The instrument has no coronagraph and features fast data acquisition, yielding high observing efficiency on bright stars. The performance of the instrument is described, and it is illustrated by laboratory tests and CFHT observations of the nearby stars GL 526, υ And, and χ And. TRIDENT can detect (6 σ) a methanated companion with \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \use...

Altitude. Elevation, and Seeing

New observations are used to accurately define the stellar point spread function produced by atmospheric turbulence at the focus of large telescopes and to compare its profile to those computed from wavefronts characterized by various structure functions. Excellent agreement is found with the PSF expected from Kolmogorov statistics, except for the presence of an extended aureole of light which appears to results from a combination of instrumental and atmospheric light scattering. Simple yet accurate analytic fits are developed to represent the PSF profile over a range of 15 magnitudes in surface brightness. The relation between the Strehl ratio S of the PSF and the value of the parameter D/r0 is re-discussed, both for a natural wavefront and for a wavefront whose variance DeltaN is reduced by an adaptive optics systems. A simple expression for S(D/r0, DeltaN) is proposed and shown to yield essentially correct Strehl ratios for any value of the parameters.

Continuum and semiforbidden C III microlensing in Q2237 + 0305 and the quasar geometry

The CFHT was used to obtain high-resolution CCD images of 82 cluster candidates in the halo of M31. These data, combined with radial velocities which cover an additional 27 candidates, are used to compile a catalog of 51 bona fide M31 halo globulars. The other candidates are found to be background galaxies (54) and field stars (4). The cluster sample appears to be incomplete for V greater than 18. The projected distribution of globulars follows an 1/r-squared law for r(kpc) between values of 6 and 22 and then drops faster, suggesting a cutoff at about 40 kpc. These trends are similar to those for globular clusters in the Milky Way halo. The total populaton of globulars in M31 is estimated to be larger than in the Milky Way by a factor of 1.8 + or - 0.3. 30 refs.

Globular clusters and the distance to the Galactic center

Simultaneous spectral differential imaging is a high-contrast technique by which subtraction of simultaneous images reduces noise from atmospheric speckles and optical aberrations. Small non-common-wave-front errors between channels can seriously degrade its performance. We present a new concept, a multicolor detector assembly, which can eliminate this problem. The device consists of an infrared detector and a microlens array onto the flat side of which a checkerboard pattern of narrowband microfilters is deposited, each microfilter coinciding with a microlens. Practical considerations for successful implementation of the technique are mentioned. Numerical simulations predict a noise attenuation of 10-3 at 05 for a 105 s integration on a mH = 5 star of Strehl ratio 0.9 taken with an 8 m telescope. This reaches a contrast of 10-7 at an angular distance of 05 from the center of the star image.