Search

High-contrast observations in optical and infrared astronomy are defined as any observation requiring a technique to reveal a celestial object of interest that is in such close angular proximity to another source brighter by a factor of at least 105 that optical effects hinder or prevent the collection of photons directly from the target of observation. This is a relatively new type of observation that enables research on previously obscured parts of the Universe. In particular, it is most applicable to comparative planetary science, a field that directly attacks such questions as "how common are planetary systems? What types of planets exist, and are there planets other than Earth that are capable of supporting life as we know it?" We survey the scientific motivations for high-contrast observations, provide an overview of the techniques currently being used or developed, and discuss some ideas and studies for future prospects. [ABSTRACT FROM AUTHOR]

Abstract: We present a retrospective on, and some new imaging data from The Lyot Project JHK coronagraph which is used behind the 3.6 m AEOS 941-channel AO telescope on Mt. Haleakala, on the island of Maui in Hawaii. This instrument is the first ‘extreme adaptive optics’ (ExAO) coronagraph ever; it opens up new scientific search spaces in direct imaging of faint companions of nearby stars. It also blazed a trail for current ExAO systems being developed for ESO-VLT and Gemini telescopes. Amongst other things, the Lyot Project has been used to demonstrate a device for precision coronagraphic astrometry and photometry using the novel technique of placing a wire grid over the pupil to create stable fiducial ghost images, to show the effects of frozen actuators on a deformable mirror, to refine angular differential imaging for use on the Coudé focus of Alt-Az telescopes, and to develop a coronagraphic data reduction pipeline. To cite this article: A. Sivaramakrishnan et al., C. R. Physique 8 (2007). [Copyright &y& Elsevier]

κ Andromedae is a B9IVn star at 52 pc for which a faint substellar companion separated by 55 ± 2 AU was recently announced. In this work, we present the first spectrum of the companion, “κ And B,” using the Project 1640 high-contrast imaging platform. Comparison of our low-resolution YJH-band spectra to empirical brown dwarf spectra suggests an early-L spectral type. Fitting synthetic spectra from PHOENIX model atmospheres to our observed spectrum allows us to constrain the effective temperature to ∼2000 K as well as place constraints on the companion surface gravity. Further, we use previously reported log(g) and Teff measurements of the host star to argue that the κ And system has an isochronal age of 220 ± 100 Myr, older than the 30 Myr age reported previously. This interpretation of an older age is corroborated by the photometric properties of κ And B, which appear to be marginally inconsistent with other 10-100 Myr low-gravity L-dwarfs for the spectral type range we derive. In addition, we use Keck aperture masking interferometry combined with published radial velocity measurements to rule out the existence of any tight stellar companions to κ And A that might be responsible for the system's overluminosity. Further, we show that luminosity enhancements due to a nearly “pole-on” viewing angle coupled with extremely rapid rotation is unlikely. κ And A is thus consistent with its slightly evolved luminosity class (IV), and we propose here that κ And, with a revised age of 220 ± 100 Myr, is an interloper to the 30 Myr Columba association with which it was previously associated. The photometric and spectroscopic evidence for κ And B combined with our reassessment of the system age implies a substellar companion mass of 50 MJup, consistent with a brown dwarf rather than a planetary-mass companion. [ABSTRACT FROM AUTHOR]

We report low-resolution near-infrared spectroscopic observations of the eruptive star FU Orionis using the Integral Field Spectrograph (IFS) Project 1640 installed at the Palomar Hale telescope. This work focuses on elucidating the nature of the faint source, located 0.″5 south of FU Ori, and identified in 2003 as FU Ori S. We first use our observations in conjunction with published data to demonstrate that the two stars are indeed physically associated and form a true binary pair. We then proceed to extract J- and H-band spectro-photometry using the damped LOCI algorithm, a reduction method tailored for high contrast science with IFS. This is the first communication reporting the high accuracy of this technique, pioneered by the Project 1640 team, on a faint astronomical source. We use our low-resolution near-infrared spectrum in conjunction with 10.2 μm interferometric data to constrain the infrared excess of FU Ori S. We then focus on estimating the bulk physical properties of FU Ori S. Our models lead to estimates of an object heavily reddened, AV = 8-12, with an effective temperature of ∼4000-6500 K. Finally, we put these results in the context of the FU Ori N-S system and argue that our analysis provides evidence that FU Ori S might be the more massive component of this binary system. [ABSTRACT FROM AUTHOR]