On 2011 February 1 the Kepler mission released data for 156,453 stars observed from the beginning of the science observations on 2009 May 2 through September 16. There are 1235 planetary candidates with transit-like signatures detected in this period. These are associated with 997 host stars. Distributions of the characteristics of the planetary candidates are separated into five class sizes: 68 candidates of approximately Earth-size (R p

ABSTRACT. With the unprecedented photometric precision of the Kepler spacecraft, significant systematic and stochastic errors on transit signal levels are observable in the Kepler photometric data. These errors, which include discontinuities, outliers, systematic trends, and other instrumental signatures, obscure astrophysical signals. The presearch data conditioning (PDC) module of the Kepler data analysis pipeline tries to remove these errors while preserving planet transits and other astrophysically interesting signals. The completely new noise and stellar variability regime observed in Kepler data poses a significant problem to standard cotrending methods. Variable stars are often of particular astrophysical interest, so the preservation of their signals is of significant importance to the astrophysical community. We present a Bayesian maximum a posteriori (MAP) approach, where a subset of highly correlated and quiet stars is used to generate a cotrending basis vector set, which is in turn used to establish a range of "reasonable" robust fit parameters. These robust fit parameters are then used to generate a Bayesian prior and a Bayesian posterior probability distribution function (PDF) which, when maximized, finds the best fit that simultaneously removes systematic effects while reducing the signal distortion and noise injection that commonly afflicts simple least-squares (LS) fitting. A numerical and empirical approach is taken where the Bayesian prior PDFs are generated from fits to the light-curve distributions themselves.Online material: color figures AN OVERVIEW OF THE KEPLER DATA PIPELINEKepler's primary science objective is to determine the frequency of Earth-size planets transiting their Sun-like host stars in the habitable zone. 6 This daunting task demands an instrument capable of measuring the light output from each of over 100,000 stars simultaneously with an unprecedented photometric precision of 20 parts per million (ppm) at 6.5-hr intervals. The large number of stars is required because the probability of the geometrical alignment of planetary orbits that permit observation of transits is the ratio of the size of the star to the size of the planetary orbit. For Earth-like planets in 1 AU orbits about Sun-like stars, only ∼0:5% will exhibit transits. By observing such a large number of stars, Kepler is guaranteed to produce a robust result in the happy event that many Earth-size planets are detected in or near the habitable zone.The Kepler data pipeline is divided into several components in order to allow for efficient management and parallel processing of data (Jenkins 2010a). Raw pixel data downlinked from the Kepler photometer are calibrated by the calibration module (CAL) to produce calibrated target and background pixels (Quintana 2010) and their associated uncertainties (Clarke 2010). The calibrated pixels are then processed by the photometric analysis module (PA) to fit and remove sky background and extract simple aperture photometry from the backgroundcorrected, calibrated target pixel...

ABSTRACT. Kepler provides light curves of 156,000 stars with unprecedented precision. However, the raw data as they come from the spacecraft contain significant systematic and stochastic errors. These errors, which include discontinuities, systematic trends, and outliers, obscure the astrophysical signals in the light curves. To correct these errors is the task of the Presearch Data Conditioning (PDC) module of the Kepler data analysis pipeline. The original version of PDC in Kepler did not meet the extremely high performance requirements for the detection of miniscule planet transits or highly accurate analysis of stellar activity and rotation. One particular deficiency was that astrophysical features were often removed as a side effect of the removal of errors. In this article we introduce the completely new and significantly improved version of PDC which was implemented in Kepler SOC version 8.0. This new PDC version, which utilizes a Bayesian approach for removal of systematics, reliably corrects errors in the light curves while at the same time preserving planet transits and other astrophysically interesting signals. We describe the architecture and the algorithms of this new PDC module, show typical errors encountered in Kepler data, and illustrate the corrections using real light curve examples.

The Chandra X-Ray Observatory observed the Crab Nebula and pulsar during orbital calibration. Zeroth-order images with the High-Energy Transmission Grating (HETG) readout by the Advanced CCD Imaging Spectrometer spectroscopy array (ACIS-S) show a striking richness of X-ray structure at a resolution comparable to that of the best ground-based visible-light observations. The HETG-ACIS-S images reveal, for the first time, an X-ray inner ring within the X-ray torus, the suggestion of a hollow-tube structure for the torus, and X-ray knots along the inner ring and (perhaps) along the inward extension of the X-ray jet. Although complicated by instrumental effects and the brightness of the Crab Nebula, the spectrometric analysis shows systematic variations of the Xray spectrum throughout the nebula.

Main TextKepler is a NASA Discovery-class mission designed to determine the frequency of Earth-radius planets in and near the HZ of solar-like stars (1-6). Planets are detected as "transits" that cause the host star to appear periodically fainter when the planets pass in front it along the observer's line of sight. Kepler-62 (KIC 9002278, KOI 701) is one of approximately 170,000 stars observed by the Kepler spacecraft. Based on an analysis of long-cadence photometric observations from Kepler taken in Quarters 1 through 12 (May 13, 2009 through March 28, 2012, we report the detection of five planets including two super-Earth-size planets in the HZ and a hot Mars-size planet orbiting Kepler-62 ( Fig. 1 and Table 1). Prior to validation, three of these objects were designated as planetary candidates 701.02, and 701.03 in the Kepler 2011 catalog (7) and the Kepler 2012 catalog (8). KOI-701.04 and 701.05 were identified subsequently using a larger data sample (9).Analysis of high-resolution spectra indicates that Kepler-62 is a K2V spectral type with an estimated mass and radius (in solar units) of 0.69 ± 0.02 Mʘ and 0.63 ± 0.02 Rʘ (9). Examination of the sky close to Kepler-62 showed the presence of only one additional star that contributed as much as 1% to the total flux (figs. S3-S4)(9). Warm-Spitzer observations ( fig. S9) and the analysis of centroid motion (Table S1) were consistent with the target star as the source of the transit signals ( Fig. 1 and fig. S1). We computed the radius, semi-major axis, and radiative equilibrium 3 temperature of each planet (Table 1) based on light curve modeling given the derived stellar parameters (Table S3). Fig. 1. Kepler-62 light curves after the data were detrended to remove the stellar variability. Composite of phase-folded transit light curves (dots), data binned in ½ hour intervals (blue error bars), and model fits (colored curves) for Kepler-62b through -62f. Model parameters are provided in Table 1. The error bars get larger as the period becomes larger because there are fewer points to bin together. For the shortest periods, the bars are too small to see. Notes: 1) T 0 is the epoch in mid-transit in Barycentric Julian Days, P is the period, duration is the transit duration, "depth" is the percent reduction of the flux during the transits determined from the model fit to the data, R p /R * is the ratio of the radius of the planet to the radius of the star, a/R * is the ratio of the planet's semi-major axis to the stellar radius, b is the impact parameter in units of stellar radius, i is the orbital inclination, ecosω is the product of the orbital eccentricity e with the cosine of the periapse angle ω, a is the semi-major axis, and R p is the radius of the planet, and Maximum Mass is the upper limit to the mass based on transiting timing and RV observations, M⊕ is the mass of the Earth, and Teq is the radiative equilibrium temperature.2) The values of the uncertainties are ±1 standard deviation unless otherwise noted.3) Values for the maximum mass are for the 95 th p...