89 research outputs found
K2P A photometry pipeline for the K2 mission
With the loss of a second reaction wheel, resulting in the inability to point
continuously and stably at the same field of view, the NASA Kepler satellite
recently entered a new mode of observation known as the K2 mission. The data
from this redesigned mission present a specific challenge; the targets
systematically drift in position on a ~6 hour time scale, inducing a
significant instrumental signal in the photometric time series --- this greatly
impacts the ability to detect planetary signals and perform asteroseismic
analysis. Here we detail our version of a reduction pipeline for K2 target
pixel data, which automatically: defines masks for all targets in a given
frame; extracts the target's flux- and position time series; corrects the time
series based on the apparent movement on the CCD (either in 1D or 2D) combined
with the correction of instrumental and/or planetary signals via the KASOC
filter (Handberg & Lund 2014), thus rendering the time series ready for
asteroseismic analysis; computes power spectra for all targets, and identifies
potential contaminations between targets. From a test of our pipeline on a
sample of targets from the K2 campaign 0, the recovery of data for multiple
targets increases the amount of potential light curves by a factor .
Our pipeline could be applied to the upcoming TESS (Ricker et al. 2014) and
PLATO 2.0 (Rauer et al. 2013) missions.Comment: 14 pages, 20 figures, Accepted for publication in The Astrophysical
Journal (Apj
Reuse for Research: Curating Astrophysical Datasets for Future Researchers
“Our data are going to be valuable for science for the next 50 years, so please make sure you preserve them and keep them accessible for active research for at least that period.”
These were approximately the words used by the principal investigator of the Kepler Asteroseismic Science Consortium (KASC) when he presented our task to us. The data in question consists of data products produced by KASC researchers and working groups as part of their research, as well as underlying data imported from the NASA archives.
The overall requirements for 50 years of preservation while, at the same time, enabling reuse of the data for active research presented a number of specific challenges, closely intertwining data handling and data infrastructure with scientific issues. This paper reports our work to deliver the best possible solution, performed in close cooperation between the research team and library personnel
EPIC 201585823, a rare triple-mode RR Lyrae star discovered in K2 mission data
We have discovered a new, rare triple-mode RR Lyr star, EPIC 201585823, in the Kepler K2 mission Campaign 1 data. This star pulsates primarily in the fundamental and first-overtone radial modes, and, in addition, a third non-radial mode. The ratio of the period of the non-radial mode to that of the first-overtone radial mode, 0.616 285, is remarkably similar to that seen in 11 other triple-mode RR Lyr stars, and in 260 RRc stars observed in the Galactic bulge. This systematic character promises new constraints on RR Lyr star models. We detected subharmonics of the non-radial mode frequency, which are a signature of period doubling of this oscillation; we note that this phenomenon is ubiquitous in RRc and RRd stars observed from space, and from ground with sufficient precision. The non-radial mode and subharmonic frequencies are not constant in frequency or in amplitude. The amplitude spectrum of EPIC 201585823 is dominated by many combination frequencies among the three interacting pulsation mode frequencies. Inspection of the phase relationships of the combination frequencies in a phasor plot explains the ‘upward’ shape of the light curve. We also found that raw data with custom masks encompassing all pixels with significant signal for the star, but without correction for pointing changes, is best for frequency analysis of this star, and, by implication, other RR Lyr stars observed by the K2 mission. We compare several pipeline reductions of the K2 mission data for this star
Asteroseismic properties of solar-type stars observed with the NASA K2 mission: results from Campaigns 1-3 and prospects for future observations
We present an asteroseismic analysis of 33 solar-type stars observed in short
cadence during Campaigns (C) 1-3 of the NASA K2 mission. We were able to
extract both average seismic parameters and individual mode frequencies for
stars with dominant frequencies up to ~3300{\mu}Hz, and we find that data for
some targets are good enough to allow for a measurement of the rotational
splitting. Modelling of the extracted parameters is performed by using
grid-based methods using average parameters and individual frequencies together
with spectroscopic parameters. For the target selection in C3, stars were
chosen as in C1 and C2 to cover a wide range in parameter space to better
understand the performance and noise characteristics. For C3 we still detected
oscillations in 73% of the observed stars that we proposed. Future K2 campaigns
hold great promise for the study of nearby clusters and the chemical evolution
and age-metallicity relation of nearby field stars in the solar neighbourhood.
We expect oscillations to be detected in ~388 short-cadence targets if the K2
mission continues until C18, which will greatly complement the ~500 detections
of solar-like oscillations made for short-cadence targets during the nominal
Kepler mission. For ~30-40 of these, including several members of the Hyades
open cluster, we furthermore expect that inference from interferometry should
be possible.Comment: 17 pages, 15 figures, 4 tables; accepted for publication in PAS
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