Everest: Pixel Level Decorrelation of K2 Light Curves

Luger, Rodrigo; Agol, Eric; Kruse, Ethan; Barnes, Rory; Becker, A. C.; Foreman-Mackey, Daniel; Deming, Drake

doi:10.3847/0004-6256/152/4/100

Cited by 291 publications

(287 citation statements)

References 22 publications

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“…After we had begun writing this paper, two other light-curve reductions became publicly available for Campaign 2, the Vanderburg reduction (Vanderburg & Johnson 2014) and the EVEREST reduction (Luger et al 2016). We downloaded light curves for each of the stars that we considered as possibly relevant to this paper.…”

Section: K2 Light Curvesmentioning

confidence: 99%

Orbiting Clouds of Material at the Keplerian Co-rotation Radius of Rapidly Rotating Low-mass WTTs in Upper Sco

et al. 2017

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Using K2 data, we identified 23 very-low-mass members of the ρ Oph and Upper Scorpius star-forming region as having periodic photometric variability not easily explained by well-established physical mechanisms such as star spots, eclipsing binaries, or pulsation. All of these unusual stars are mid-to-late M dwarfs without evidence of active accretion, and with photometric periods generally <1 day. Often the unusual light-curve signature takes the form of narrow flux dips; when we also have rotation periods from star spots, the two periods agree, suggesting that the flux dips are due to material orbiting the star at the Keplerian co-rotation radius. We sometimes see "statechanges" in the phased light-curve morphologies where ∼25% of the waveform changes shape on timescales less than a day; often, the "state-change" takes place immediately after a strong flare. For the group of stars with these sudden light-curve morphology shifts, we attribute their flux dips as most probably arising from eclipses of warm coronal gas clouds, analagous to the slingshot prominences postulated to explain transient Hα absorption features in AB Doradus and other rapidly rotating late-type stars. For another group of stars with somewhat longer periods, we find the short-duration flux dips to be highly variable on both short and long timescales, with generally asymmetric flux-dip profiles. We believe that these flux dips are due to particulate clouds possibly associated with a close-in planet or resulting from a recent collisional event.

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Section: K2 Light Curvesmentioning

confidence: 99%

Orbiting Clouds of Material at the Keplerian Co-rotation Radius of Rapidly Rotating Low-mass WTTs in Upper Sco

et al. 2017

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“…To this, late in the process, we added (5) the LCs from the EVEREST pipeline (Luger et al 2016), which uses pixel level decorrelation. We removed any data points corresponding to thruster firings and any others with bad data flags set in the corresponding data product.…”

Section: K2 Datamentioning

confidence: 99%

Rotation of Late-type Stars in Praesepe with K2

Rebull

Stauffer

Hillenbrand

et al. 2017

ApJ

105

133

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We have Fourier-analyzed 941 K2 light curves (LCs) of likely members of Praesepe, measuring periods for 86% and increasing the number of rotation periods (P) by nearly a factor of four. The distribution of P versus -( ) V K s , a mass proxy, has three different regimes:, where the rotation rate rapidly slows as mass decreases; 1.3< -( ) V K s <4.5, where the rotation rate slows more gradually as mass decreases; andwhere the rotation rate rapidly increases as mass decreases. In this last regime, there is a bimodal distribution of periods, with few between ∼2 and ∼10 days. We interpret this to mean that once M stars start to slow down, they do so rapidly. The K2 period-color distribution in Praesepe (∼790 Myr) is much different than that in the Pleiades (∼125 Myr) for late F, G, K, and early-M stars; the overall distribution moves to longer periods and is better described by two line segments. For mid-M stars, the relationship has a similarly broad scatter and is steeper in Praesepe. The diversity of LCs and of periodogram types is similar in the two clusters; about a quarter of the periodic stars in both clusters have multiple significant periods. Multi-periodic stars dominate among the higher masses, starting at a bluer color in Praesepe ( -( ) V K s ∼1.5) than in the Pleiades ( -( ) V K s ∼2.6). In Praesepe, there are relatively more LCs that have two widely separated periods, D > P 6 days. Some of these could be examples of M star binaries where one star has spun down but the other has not.

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“…Another possibility is a nonlinear response of pixels to increasing incident flux due to saturation. Saturation effects in Kepler data have been encountered and discussed by Lurie et al (2015); Luger et al (2016). Our target star is significantly fainter than the Kp = 11.3 mag which is believed to be the saturation threshold (Gilliland et al 2010).…”

Section: Vim Detectionsmentioning

confidence: 74%

Kepler Data on KIC 7341653: A Nearby M Dwarf with Monster Flares and a Phase-coherent Variability

Макаров

Goldin²

2017

ApJ

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KIC 7341653 is one of several late-type M dwarfs observed in the main mission of Kepler with peculiar infrared colors placing them in the domain of suspected young stellar objects (YSO). It is likely associated with a powerful X-ray emitter with X-ray flares. Kepler light curves reveal two distinct types of activity: frequent flares lasting from less than 30 min to a few hours and a periodic variability with a period of 0.5463441(7) d. The largest flare detected increased the flux in the Kepler passband by a factor of 2.8 and released an estimated 4×10 34 erg of energy in the Kepler band. Segmented periodogram analysis reveals that the amplitude of the periodic variation was subject to secular changes, dropping from peak values around 20 ppt to below 5 ppt toward the end of the mission, while the phase varied periodically with an amplitude of 0.15 radians and period 362(3) d. Two possible interpretations of the phase periodicity are discussed: a migrating longlived photospheric spot and a Doppler frequency shift generated by a solar-mass faint companion, such as a white dwarf.

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Everest: Pixel Level Decorrelation of K2 Light Curves

Cited by 291 publications

References 22 publications

Orbiting Clouds of Material at the Keplerian Co-rotation Radius of Rapidly Rotating Low-mass WTTs in Upper Sco

Orbiting Clouds of Material at the Keplerian Co-rotation Radius of Rapidly Rotating Low-mass WTTs in Upper Sco

Rotation of Late-type Stars in Praesepe with K2

Kepler Data on KIC 7341653: A Nearby M Dwarf with Monster Flares and a Phase-coherent Variability

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