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Bas Nefs

Publications and source records attributed to Bas Nefs.

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Exoplanet-atmospheres at high spectral resolution: A CRIRES survey of hot-Jupiters

Recently, we presented the detection of carbon monoxide in the transmission spectrum of extrasolar planet HD209458b, using CRIRES, the Cryogenic high-resolution Infrared Echelle Spectrograph at ESO's Very Large Telescope (VLT). The high spectral resolution observations (R=100,000) provide a wealth of information on the planet's orbit, mass, composition, and even on its atmospheric dynamics. The new observational strategy and data analysis techniques open up a whole world of opportunities. We therefore started an ESO large program using CRIRES to explore these, targeting both transiting and non-transiting planets in carbon monoxide, water vapour, and methane. Observations of the latter molecule will also serve as a test-bed for METIS, the proposed mid-infrared imager and spectrograph for the European Extremely Large Telescope.

astro-ph.EP

The Mid-Infrared [SIV]/[NeII] versus [NeIII]/[NeII] Correlation

The mid-infrared ratio [NeIII]15.6mum/[NeII]12.8mum is a strong diagnostic of the ionization state of emission line objects, due to its use of only strong neon emission lines only weakly affected by extinction. However this ratio is not available to ground-based telescopes as only a few spectroscopic windows are available in the MIR. To deal with this problem we aimed to verify if there exists a conversion law between ground-accessible, strong MIR line ratio [SIV]/[NeII] and the diagnostic [NeIII]/[NeII] ratio that can serve as a reference for future ground-based observations. We collated the [SIV]10.5mum, [NeII]12.8mum, [NeIII]15.6\mum and [SIII]18.7mum emission line fluxes from a wide range of sources in the rich Spitzer and ISO archives, and compared the [NeIII]/[NeII], [SIV]/[SIII], and [SIV]/[NeII] ratios. We find a strong correlation between the [SIV]/[NeII] and [\neiii]/[\neii] ratio, with a linear fit of log([NeIII]/[NeII]) = 0.81log([SIV]/[NeII])+0.36, accurate to a factor of ~2 over four orders of magnitude in the line ratios. This demonstrates clearly the ability of ground-based infrared spectrographs to do ionization studies of nebulae.

astro-ph