INSTRUMENT PERFORMANCE IN KEPLER 's FIRST MONTHS

Abstract

The Kepler Mission relies on precise differential photometry to detect the 80 parts per million (ppm) signal from an Earth-Sun equivalent transit. Such precision requires superb instrument stability on time scales up to ∼2 days and systematic error removal to better than 20 ppm. To this end, the spacecraft and photometer underwent 67 days of commissioning, which included several data sets taken to characterize the photometer performance. Because Kepler has no shutter, we took a series of dark images prior to the dust cover ejection, from which we measured the bias levels, dark current, and read noise. These basic detector properties are essentially unchanged from ground-based tests, indicating that the photometer is working as expected. Several image artifacts have proven more complex than when observed during ground testing, as a result of their interactions with starlight and the greater thermal stability in flight, which causes the temperature-dependent artifact variations to be on the timescales of transits. Because of Kepler's unprecedented sensitivity and stability, we have also seen several unexpected systematics that affect photometric precision. We are using the first 43 days of science data to characterize these effects and to develop detection and mitigation methods that will be implemented in the calibration pipeline. Based on early testing, we expect to attain Kepler's planned photometric precision over 80%-90% of the field of view.

Kepler-423b: a half-Jupiter mass planet transiting a very old solar-like star

“…To account for the current surface metallicity of Kepler-423 ([M/H] = −0.10 ± 0.05 dex) and microscopic diffusion of heavy elements towards the centre of the star, we computed evolutionary tracks assuming an initial metal content of Z = 0.010, Z = 0.011, Z = 0.012, Z = 0.013, Z = 0.014, and Z = 0.015. The corresponding initial helium abundances, i.e., Y = 0.268, 0.271, 0.273, 0.275, 0.277, and 0.279, were determined assuming a helium-to-metal enrichment ratio ∆Y/∆Z=2 (Jimenez et al 2003;Casagrande 2007;Gennaro et al 2010) and a cosmological 4 He abundance Y p = 0.2485 (Cyburt 2004;Peimbert et al 2007a,b). For each chemical composition, we generated a very fine grid of evolutionary tracks in the mass domain M = 0.70-1.10 M , with step of ∆M = 0.01 M , leading to a total of 246 stellar tracks.…”

KEPLERMONITORING OF AN L DWARF I. THE PHOTOMETRIC PERIOD AND WHITE LIGHT FLARES

“…Excluding the small number of outliers, whose nature are discussed in Section 4, the standard deviation about the fit is 0.65%, or 7 mmag. We adopt this as the noise level of the measurements, as it is only a slight increase over the expected value (0.5%) and there are other possible noise sources in the Kepler instrument (Caldwell et al 2010), though real intrinsic variations may contribute. Figure 2 shows four days of Kepler data as an example of unphased data including a possible flare (Section 4.2); our radio observations (Section 2.3) were in this time period.…”

THE APOGEE SPECTROSCOPIC SURVEY OFKEPLERPLANET HOSTS: FEASIBILITY, EFFICIENCY, AND FIRST RESULTS

“…In addition, the high precision photometry (∼80 ppm over 6 hr timescales for the brightest (K p  15) dwarfs, Caldwell et al 2010;Gilliland et al 2011;Christiansen et al 2012) enables studies of giant exoplanets and a wide variety of variable stars. Its photometric band K p covers 423-897 nm and is similar to, but broader than, a combined V and R band .…”