K2 Variable Catalogue: Variable stars and eclipsing binaries in K2 campaigns 1 and 0

Armstrong, David J.; Kirk, James; Lam, K. W. F.; McCormac, J.; Walker, Simón R.; Brown, D. J. A.; Osborn, H.; Pollacco, D.; Spake, Jessica

doi:10.1051/0004-6361/201525889

Cited by 90 publications

(117 citation statements)

References 28 publications

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“…This leads to a major source of systematic noise in the lightcurve , the removal of which is the key part of our detrending method. The full method is explained in Armstrong et al (2015), but is summarised here for clarity. Initially a fixed aperture, of radius 4 pixels in this case and shape as described in Armstrong et al (2015), was centred on the brightest target pixel.…”

Section: K2mentioning

confidence: 99%

One of the closest exoplanet pairs to the 3:2 mean motion resonance: K2-19b and c

Armstrong

Santerne

Veras

et al. 2015

A&A

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Aims. The K2 mission has recently begun to discover new and diverse planetary systems. In December 2014, Campaign 1 data from the mission was released, providing high-precision photometry for ∼22 000 objects over an 80-day timespan. We searched these data with the aim of detecting more important new objects. Methods. Our search through two separate pipelines led to the independent discovery of K2-19b and c, a two-planet system of Neptune-sized objects (4.2 and 7.2 R ⊕ ), orbiting a K dwarf extremely close to the 3:2 mean motion resonance. The two planets each show transits, sometimes simultaneously owing to their proximity to resonance and the alignment of conjunctions. Results. We obtained further ground-based photometry of the larger planet with the NITES telescope, demonstrating the presence of large transit timing variations (TTVs), and used the observed TTVs to place mass constraints on the transiting objects under the hypothesis that the objects are near but not in resonance. We then statistically validated the planets through the PASTIS tool, independently of the TTV analysis.

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Section: K2mentioning

confidence: 99%

One of the closest exoplanet pairs to the 3:2 mean motion resonance: K2-19b and c

Armstrong

Santerne

Veras

et al. 2015

A&A

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“…The motion of the centroids is then fit with a polynomial and transformed into a single parameter that relates spacecraft motion to flux variations, which is then used to de-trend the data. Similar methods are employed in the K2VARCAT pipeline (Armstrong et al 2015), developed specifically for variable K2 stars, the K2P 2 pipeline (Lund et al 2015), which uses an intelligent clustering algorithm to define custom apertures, and in the pipeline of Huang et al (2015), which employs astrometric solutions to the motion of K2 targets, determining the X and Y motion of a target from the behavior of multiple stars on the same spacecraft module. Finally, the K2SC pipeline (Aigrain et al 2015(Aigrain et al , 2016 and the pipeline of Crossfield et al (2015) both employ a Gaussian process (GP) to remove instrumental noise, using the X and Y coordinates of the target star as the regressors to derive a model for the instrumental systematics.…”

Section: Introductionmentioning

confidence: 99%

Everest: Pixel Level Decorrelation of K2 Light Curves

et al. 2016

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We present EVEREST, an open-source pipeline for removing instrumental noise from K2 light curves. EVEREST employs a variant of pixel level decorrelation (PLD) to remove systematics introduced by the spacecraft's pointing error and a Gaussian process (GP) to capture astrophysical variability. We apply EVEREST to all K2 targets in campaigns 0-7, yielding light curves with precision comparable to that of the original Kepler mission for stars brighter than K p ≈ 13, and within a factor of two of the Kepler precision for fainter targets. We perform cross-validation and transit injection and recovery tests to validate the pipeline, and compare our light curves to the other de-trended light curves available for download at the MAST High Level Science Products archive. We find that EVEREST achieves the highest average precision of any of these pipelines for unsaturated K2 stars. The improved precision of these light curves will aid in exoplanet detection and characterization, investigations of stellar variability, asteroseismology, and other photometric studies. The EVEREST pipeline can also easily be applied to future surveys, such as the TESS mission, to correct for instrumental systematics and enable the detection of low signal-to-noise transiting exoplanets. The EVEREST light curves and the source code used to generate them are freely available online.

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“…To correct these systematics in the K2 data, several methods have been developed, all presenting two main steps: a photometric extraction with a variety of aperture shapes and positions and a "correction of systematics". Vanderburg & Johnson (2014) and later on Armstrong et al (2015) used normal aperture photometry and corrected the systematics decorrelating the flux and the position variations of the target on the CCD. However, while Vanderburg & Johnson (2014) used the fact that the main motion of the line of sight was along one direction (the roll direction), which reduced the decorrelation to 1D, Armstrong et al (2015) opted for a 2D decorrelation.…”

Section: Introductionmentioning

confidence: 99%

New planetary and eclipsing binary candidates from campaigns 1−6 of the K2 mission

Barros

Deleuil

2016

A&A

104

122

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Context. With only two functional reaction wheels, Kepler cannot maintain stable pointing at its original target field and has entered a new mode of observation called K2. Aims. We describe a new pipeline to reduce K2 pixel files into light curves that are later searched for transit like features. Methods. Our method is based on many years of experience in planet hunting for the CoRoT mission. Owing to the unstable pointing, K2 light curves present systematics that are correlated with the target position in the charge coupled device (CCD). Therefore, our pipeline also includes a decorrelation of this systematic noise. Our pipeline is optimised for bright stars for which spectroscopic follow-up is possible. We achieve a maximum precision on 6 hours of 6 ppm. The decorrelated light curves are searched for transits with an adapted version of the CoRoT alarm pipeline. Results. We present 172 planetary candidates and 327 eclipsing binary candidates from campaigns 1, 2, 3, 4, 5, and 6 of K2. Both the planetary candidates and eclipsing binary candidates lists are made public to promote follow-up studies. The light curves will also be available to the community.

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K2 Variable Catalogue: Variable stars and eclipsing binaries in K2 campaigns 1 and 0

Cited by 90 publications

References 28 publications

One of the closest exoplanet pairs to the 3:2 mean motion resonance: K2-19b and c

One of the closest exoplanet pairs to the 3:2 mean motion resonance: K2-19b and c

Everest: Pixel Level Decorrelation of K2 Light Curves

New planetary and eclipsing binary candidates from campaigns 1−6 of the K2 mission

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