A new look at Spitzer primary transit observations of the exoplanet HD 189733b

Journal Article · Thu May 01 04:00:00 EDT 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/786/1/22· OSTI ID:22357041

Morello, G.; Waldmann, I. P.; Tinetti, G.; Howarth, I. D. ^[1]; Peres, G. ^[2]

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1. Department of Physics and Astronomy, University College London, Gower Street, WC1E6BT (United Kingdom)
2. Dipartimento di Fisica, Università degli Studi di Palermo, via Archirafi I-90123, Italy. (Italy)

Blind source separation techniques are used to reanalyze two exoplanetary transit light curves of the exoplanet HD 189733b recorded with the IR camera IRAC on board the Spitzer Space Telescope at 3.6 μm during the 'cold' era. These observations, together with observations at other IR wavelengths, are crucial to characterize the atmosphere of the planet HD 189733b. Previous analyses of the same data sets reported discrepant results, hence the necessity of the reanalyses. The method we used here is based on the Independent Component Analysis (ICA) statistical technique, which ensures a high degree of objectivity. The use of ICA to detrend single photometric observations in a self-consistent way is novel in the literature. The advantage of our reanalyses over previous work is that we do not have to make any assumptions on the structure of the unknown instrumental systematics. Such 'admission of ignorance' may result in larger error bars than reported in the literature, up to a factor 1.6. This is a worthwhile tradeoff for much higher objectivity, necessary for trustworthy claims. Our main results are (1) improved and robust values of orbital and stellar parameters, (2) new measurements of the transit depths at 3.6 μm, (3) consistency between the parameters estimated from the two observations, (4) repeatability of the measurement within the photometric level of ∼2 × 10{sup –4} in the IR, and (5) no evidence of stellar variability at the same photometric level within one year.

• OSTI ID: 22357041
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 786; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
DATA ANALYSIS
INFRARED RADIATION
PLANETS
SATELLITE ATMOSPHERES
SATELLITES
SPACE
TELESCOPES
VISIBLE RADIATION
WAVELENGTHS