Initial Characteristics of Kepler Short Cadence Data

TL;DR

This paper characterizes the short cadence data from Kepler's first quarter, highlighting its high precision, artifacts, and differences from long cadence data, crucial for asteroseismology and exoplanet studies.

Contribution

It provides the first detailed analysis of Kepler's short cadence data, including noise levels, artifacts, and comparison with long cadence observations.

Findings

Per-point measurement errors of 200 ppm at 11th magnitude

High precision achieved even for saturated stars near 7th magnitude

Identified two types of artifacts affecting the data

Abstract

The Kepler Mission offers two options for observations -- either Long Cadence (LC) used for the bulk of core mission science, or Short Cadence (SC) which is used for applications such as asteroseismology of solar-like stars and transit timing measurements of exoplanets where the 1-minute sampling is critical. We discuss the characteristics of SC data obtained in the 33.5-day long Quarter 1 (Q1) observations with Kepler which completed on 15 June 2009. The truly excellent time series precisions are nearly Poisson limited at 11th magnitude providing per-point measurement errors of 200 parts-per-million per minute. For extremely saturated stars near 7th magnitude precisions of 40 ppm are reached, while for background limited measurements at 17th magnitude precisions of 7 mmag are maintained. We note the presence of two additive artifacts, one that generates regularly spaced peaks in frequency, and one that involves additive offsets in the time domain inversely proportional to stellar brightness. The difference between LC and SC sampling is illustrated for transit observations of TrES-2.