On the Compatibility of Ground-based and Space-based Data: WASP-96 b, an Example

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On the Compatibility of Ground-based and Space-based Data: WASP-96 b, an Example

Yip, KH; Changeat, Q; Edwards, B; Morvan, M; Chubb, KL; Tsiaras, A; Waldmann, IP; (2021) On the Compatibility of Ground-based and Space-based Data: WASP-96 b, an Example. The Astronomical Journal , 161 (1) , Article 4. 10.3847/1538-3881/abc179. Green open access

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Abstract

The study of exoplanetary atmospheres relies on detecting minute changes in the transit depth at different wavelengths. To date, a number of ground- and space-based instruments have been used to obtain transmission spectra of exoplanets in different spectral bands. One common practice is to combine observations from different instruments in order to achieve a broader wavelength coverage. We present here two inconsistent observations of WASP-96 b, one by the Hubble Space Telescope (HST) and the other by the Very Large Telescope (VLT). We present two key findings in our investigation: (1) a strong water signature is detected via the HST WFC3 observations and (2) a notable offset in transit depth (>1100 ppm) can be seen when the ground-based and space-based observations are combined. The discrepancy raises the question of whether observations from different instruments could indeed be combined. We attempt to align the observations by including an additional parameter in our retrieval studies but are unable to definitively ascertain that the aligned observations are indeed compatible. The case of WASP-96 b signals that compatibility of instruments should not be assumed. While wavelength overlaps between instruments can help, it should be noted that combining data sets remains risky business. The difficulty of combining observations also strengthens the need for next-generation instruments that possess broader spectral coverage.

Type:	Article
Title:	On the Compatibility of Ground-based and Space-based Data: WASP-96 b, an Example
Open access status:	An open access version is available from UCL Discovery
DOI:	10.3847/1538-3881/abc179
Publisher version:	https://doi.org/10.3847/1538-3881/abc179
Language:	English
Additional information:	This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords:	Exoplanet atmospheres; Exoplanet atmospheric composition; Observational astronomy; Bayesian statistics
UCL classification:	UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI:	https://discovery.ucl.ac.uk/id/eprint/10117029