Storms or systematics? The changing secondary eclipse depth of WASP-12b. Issue 2 (5th April 2019)

• Record Type: Journal Article
• Authors: Hooton, Matthew J; de Mooij, Ernst J W; Watson, Christopher A; Gibson, Neale P; Galindo-Guil, Francisco J; Clavero, Rosa; Merritt, Stephanie R
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 486:Issue 2(2019)
• Page Start: 2397
• Page End: 2406
• Publication Date: 2019-04-05
• Subjects: techniques: photometric -- stars: individual: WASP-12 -- planetary systems; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stz966
• Languages: English
• ISSNs: 0035-8711

Abstract

Abstract: WASP-12b is one of the most well-studied transiting exoplanets, as its highly inflated radius and its 1.1 d orbit around a G0-type star make it an excellent target for atmospheric categorization through observation during its secondary eclipse. We present two new secondary eclipse observations of WASP-12b, acquired an year apart with the Wide Field Camera on the Isaac Newton Telescope (INT) and the IO:O instrument on the Liverpool Telescope (LT). These observations were conducted in the i ′ band, a window expected to be dominated by titanium oxide features if present in appreciable quantities in the upper atmosphere. We measured eclipse depths that disagree with each other by ∼3σ (0.97 ± 0.14 mmag on the INT and 0.44 ± 0.21 mmag on the LT), a result that is mirrored in previous z ′ band secondary eclipse measurements for WASP-12b. We explore explanations for these disagreements, including systematic errors and variable thermal emission in the dayside atmosphere of WASP-12b caused by temperature changes of a few hundred Kelvin: a possibility we cannot rule out from our analysis. Full-phase curves observed with TESS and CHEOPS have the potential to detect similar atmospheric variability for WASP-12b and other optimal targets, and a strategic, multitelescope approach to future ground-based secondary eclipse observations is required to discriminate between explanations involving storms and systematics.