# On the Quality of Deep Representations for Kepler Light Curves Using Variational Auto-Encoders
## 3 Experimental Setup and Results
### Dataset  
Our work used the Kepler Objects of Interest (KOI, [44]) dataset described by the NASA Exoplanet Archive [45]. It is composed of 8054 light curve records ([[https://archive.stsci.edu/kepler/koi/search.php](https://archive.stsci.edu/kepler/koi/search.php)]([https://archive.stsci.edu/kepler/koi/search.php](https://archive.stsci.edu/kepler/koi/search.php)) accessed on 20 September 2019) where every KOI describes a target star in the field of view that exhibits transit-like signatures in its light curve. Primarily, a TCE that was accepted as a valid astrophysical signal based on the diagnostic tests described in [44] was designated as a KOI. According to the NASA Exoplanet Archive ([[https://exoplanetarchive.ipac.caltech.edu/](https://exoplanetarchive.ipac.caltech.edu/)]([https://exoplanetarchive.ipac.caltech.edu/](https://exoplanetarchive.ipac.caltech.edu/)) accessed on 10 July 2021), KOIs are categorized into three tags: _Confirmed_, claimed exoplanets through extensive scientific analysis and follow ups; _False Positive_, evidence indicates that they correspond to another type of behavior not associated with transit exoplanets (e.g., eclipsing binary systems), and _Candidate_, those that are still under study (unlabeled data). In some cases, multiple KOIs are obtained from the analyzed host star, where each object contains the raw flux measurements with the timestamps (in BKJD), including the instrumental error associated with each measure. The time unit Barycentric Kepler Julian Day (BKJD) corresponds to \(\text{BKJD}=\text{BJD}-2454833\), while the Barycentric Julian Day (BJD) is simply Julian days (the continuous count of days since the beginning of the Julian period) with some corrections based in the Earth's position and the barycenter of the Solar System. The _long-cadence_ sampling rate of the 4-years' worth of measurements was 0.0204 BKJD on average (i.e., half an hour); however, there is 22.98% of missing values on average in the collected and used light curves. The light curve data [46; 47; 48] described here may be obtained from the Mikulski Archive for Space Telescopes (MAST) ([[https://doi.org/10.17909/T9](https://doi.org/10.17909/T9) RP4V]([https://doi.org/10.17909/T9](https://doi.org/10.17909/T9) RP4V) accessed on 10 July 2021). The archive also provides a set of metadata values ([[https://exoplanetarchive.ipac.caltech.edu/docs/API_kepcandidate_columns.html](https://exoplanetarchive.ipac.caltech.edu/docs/API_kepcandidate_columns.html)]([https://exoplanetarchive.ipac.caltech.edu/docs/API_kepcandidate_columns.html](https://exoplanetarchive.ipac.caltech.edu/docs/API_kepcandidate_columns.html)) accessed on 10 July 2021), some of which (usually those related to the host star such as its effective temperature and metallicity) are cross-matched from other catalogs, while others are calculated following a Mandel-Aglol modeling fit [3] according to LS and MCMC. For comparing our self-generated featureswith model-based ones, we selected those that could be obtained from the light curves based on the modeling, which are: _Period; First Transit Time; Inclination; Planet Radius_ (over _Stellar Radius_); _Semi-Major Axis_ (over _Stellar Radius_); _Transit Duration_; _Impact Parameter_; and _Fitted Stellar Density_. Furthermore, we included the _Limb Darkening Coefficients_ (quadratic model) even though they are not solved -they are fixed in the fit for each star, but they are still involved in the modeling of the light curves. For data pre-processing, we used a detrending process that also normalized the stellar flux and _apriori_ removed low frequency noise. It combines ideas from the combined differential photometric precision proxy used by [49]--subtract polynomial fit and sigma-clipping, and the _Argabrightening_ detection by [50]--subtract polynomial fit and subtract median filter. This detrending process was performed over the raw flux measurements by using time.