Detecting and Characterizing Exomoons and Exorings

Heller, René

doi:10.1007/978-3-319-30648-3_35-1

Cited by 2 publications

(4 citation statements)

References 77 publications

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“…In the latest report of the HEK team, Teachey et al (2018) find evidence for an exomoon candidate around the roughly Jupiter-sized exoplanet candidate Kepler-1625 b, which they provisionally refer to as Kepler-1625 b-i. Kepler-1 For reviews see and Heller (2017). 1625 is a slightly evolved G-type star with a mass of M = 1.079 +0.100 −0.138 M (M being the solar mass), a radius of R = 1.793 +0.263 −0.488 R (with R as the solar radius), and an effective temperature of T eff, = 5548 +83 −72 K (Mathur et al 2017). Its Kepler magnitude of 15.756 makes it a relatively dim Kepler target.…”

Section: Introductionmentioning

confidence: 99%

Revisiting the exomoon candidate signal around Kepler-1625 b

Rodenbeck

Heller

Hippke

et al. 2018

A&A

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Context. Transit photometry of the Jupiter-sized exoplanet candidate Kepler-1625 b has recently been interpreted to show hints of a moon. This exomoon, the first of its kind, would be as large as Neptune and unlike any moon we know from the solar system. Aims. We aim to clarify whether the exomoon-like signal is indeed caused by a large object in orbit around Kepler-1625 b, or whether it is caused by stellar or instrumental noise or by the data detrending procedure. Methods. To prepare the transit data for model fitting, we explore several detrending procedures using second-, third-, and fourthorder polynomials and an implementation of the Cosine Filtering with Autocorrelation Minimization (CoFiAM). We then supply a light curve simulator with the co-planar orbital dynamics of the system and fit the resulting planet-moon transit light curves to the Kepler data. We employ the Bayesian Information Criterion (BIC) to assess whether a single planet or a planet-moon system is a more likely interpretation of the light curve variations. We carry out a blind hare-and-hounds exercise using many noise realizations by injecting simulated transits into different out-of-transit parts of the original Kepler-1625 light curve: (1) 100 sequences with three synthetic transits of a Kepler-1625 b-like Jupiter-size planet and (2) 100 sequences with three synthetic transits of a Kepler-1625 b-like planet with a Neptune-sized moon. Results. The statistical significance and characteristics of the exomoon-like signal strongly depend on the detrending method (polynomials versus cosines), the data chosen for detrending, and on the treatment of gaps in the light curve. Our injection-retrieval experiment shows evidence of moons in about 10 % of those light curves that do not contain an injected moon. Strikingly, many of these false-positive moons resemble the exomoon candidate, i.e. a Neptune-sized moon at about 20 Jupiter radii from the planet. We recover between about a third and half of the injected moons, depending on the detrending method, with radii and orbital distances broadly corresponding to the injected values. Conclusions. A ∆BIC of −4.9 for the CoFiAM-based detrending is indicative of an exomoon in the three transits of Kepler-1625 b. This solution, however, is only one out of many and we find very different solutions depending on the details of the detrending method. We find it concerning that the detrending is so clearly key to the exomoon interpretation of the available data of Kepler-1625 b. Further high-accuracy transit observations may overcome the effects of red noise but the required amount of additional data might be large.

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Section: Introductionmentioning

confidence: 99%

Revisiting the exomoon candidate signal around Kepler-1625 b

Rodenbeck

Heller

Hippke

et al. 2018

A&A

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“…We note that extending observation time from 1 hour to 10 days does not improve the situation of O 2 retrieval. Kaltenegger et al (2007) suggests that atmospheres with O 2 concentration lower than 10 –3 cannot be observed. Because the best wavelengths to detect O 2 are 0.69 and 0.76 micron, which are outside of the wavelength range analyzed in this work, our conclusion regarding O 2 detection is more conservative than that in Kaltenegger et al (2007).…”

Section: Resultsmentioning

confidence: 99%

“…This problem is caused by the weakness of O 2 absorption feature, which could be easily mixed up with other species. This conclusion is consistent with the findings in Kaltenegger et al (2007).…”

Section: Discussionmentioning

confidence: 99%

“…Before introducing the results, it is important to point out the difference between our method and those in previous exomoon detection efforts, most of which propose to analyze transit photometry or transit timing/duration variations (Heller et al, 2016;Heller, 2017, and references therein). Several works have been published on exomoon detection through analyzing phase-dependent thermal emission variability of exoplanet-exomoon system during a full exomoon orbit.…”

Section: Methodsmentioning

confidence: 99%

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Simultaneous characterization of the atmospheres, surfaces, and exomoons of nearby rocky exoplanets

Cui¹,

Zhang²,

Cui³

et al. 2018

Earth and Planetary Physics

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Atmospheric composition is an important indicator of habitability and life. The presence or absence of a large exomoon around an Earth‐size exoplanet could have important consequences for planet climate stability. Thus the detection of exomoons and retrieval of information regarding atmospheric composition of Earth‐size exoplanets are important goals of future exoplanet observations. Here a data analysis method is developed to achieve both goals simultaneously, based on reflection spectra of exoplanet‐exomoon systems. We show that the existence of exomoons, the size of exomoons, and the concentrations of some atomic and molecular species in the atmospheres of their hosting Earth‐like exoplanets can be retrieved with high levels of reliability. In addition, the method can provide well‐constrained fractions of basic surface types on the targets because of the characteristic spectral features of atmospheric species and surface types in the analyzed spectral range.

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Detecting and Characterizing Exomoons and Exorings

Cited by 2 publications

References 77 publications

Revisiting the exomoon candidate signal around Kepler-1625 b

Revisiting the exomoon candidate signal around Kepler-1625 b

Simultaneous characterization of the atmospheres, surfaces, and exomoons of nearby rocky exoplanets

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