Defocussed Transmission Spectroscopy: A potential detection of sodium in the atmosphere of WASP-12b

Abstract

We report on a pilot study of a novel observing technique, defocussed transmission spectroscopy, and its application to the study of exoplanet atmospheres using ground-based platforms. Similar to defocussed photometry, defocussed transmission spectroscopy has an added advantage over normal spectroscopy in that it reduces systematic errors due to flat-fielding, PSF variations, slit-jaw imperfections and other effects associated with ground-based observations. For one of the planetary systems studied, WASP-12b, we report a tentative detection of additional Na absorption of 0.12+/-0.03[+0.03]% during transit using a 2A wavelength mask. After consideration of a systematic that occurs mid-transit, it is likely that the true depth is actually closer to 0.15%. This is a similar level of absorption reported in the atmosphere of HD209458b (0.135+/-0.017%, Snellen et al. 2008). Finally, we outline methods that will improve the technique during future observations, based on our findings from this pilot study.

14 pages, 12 figures, 2 tables - MNRAS accepted

References in corpus (12)

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Cited by in corpus (6)

• Spectrally resolved detection of sodium in the atmosphere of HD189733b with the HARPS spectrograph
• Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS) - II. A broadened sodium feature on the ultra-hot giant WASP-76b
• A Non-isothermal Theory for Interpreting Sodium Lines in Transmission Spectra of Exoplanets
• Monitoring of the D Doublet of Neutral Sodium during Transits of Two "Evaporating" Planets
• PEPSI's non-detection of escaping hydrogen and metal lines adds to the enigma of WASP-12 b
• Investigation of the upper atmosphere in ultra-hot Jupiter WASP-76 b with high-resolution spectroscopy