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

Astrophysics, abstract
astro-ph/0504652

From: Christian Marois [view email]

Date: Thu, 28 Apr 2005 23:50:18 GMT   (372kb)

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 is described.
The camera is based on a Hawaii-1 1024×1024 HgCdTe array detector. Its main
feature is to acquire three simultaneous images at three wavelengths across the
methane absorption bandhead at 1.6 microns, 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 GL526, Ups And and
Chi And. TRIDENT can detect (6 sigma) a methanated companion with delta H = 9.5
at 0.5" separation from the star in one hour of observing time. Non-common path
aberrations and amplitude modulation differences between the three optical
paths are likely to be the limiting factors preventing further PSF attenuation.
Instrument rotation and reference star subtraction improve the detection limit
by a factor of 2 and 4 respectively. A PSF noise attenuation model is presented
to estimate the non-common path wavefront difference effect on PSF subtraction
performance.

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