K2 Observations of Open Clusters Ann Marie Cody NPP fellow at NASA Ames November 2, 2015

Acknowledgm ents Ames collaborators: Steve Howell, Tom Barclay, Fergal Mullally, Susan Thompson, Geert Barentsen, Jason Rowe, student interns: Bryan Mann, Shishir Dholakia, Shashank Dholakia External collaborators: Lynne Hillenbrand, Trevor David, John Stauffer, Luisa Rebull, Kevin Covey, Adam Kraus, Michael Ireland, Stephanie Douglas, Suzanne Aigrain

K2 is ideally suited to monitor star clusters  Large field of view  High precision  Long time baseline  Continuous time series  Bright, nearby targets – great for follow-up

M35

Ground vs. K2 A. Vanderburg Nardiello et al. (2015)

K2 is Contributing Enormously to Young Star Science

Taurus!! (300+ known members)

K2 has a number of photometric pipelines  Official K2 pipeline: Light curves for Campaigns 3, 4, 5 with PDC detrending  A. Vanderburg pipeline: Light curves for Campaigns 0-4 with SFF detrending  Other approaches- C. Huang et al. (2015); Libralato et al. (2015); S. Aigrain in prep.  My pipeline: operates on both regular and superstamp images

Superstamp Photometry: M35

Superstamp WCS solution  Track X,Y movement of individual sources Measure fluxes with range of moving circular apertures Decorrelate flux vs. X,Y position

Star clusters in the time domain: Science  Eclipsing binaries  Starspot properties and stellar rotation  Exploration of accretion and disk- related variability  Search for young planets

~50 EBs in the M35 Superstamp …but which are cluster members?

M35 Candidates Field stars Bouy et al. (2015)

Eclipsing Binaries are Yielding Clues to Early Stellar Evolution David, Hillenbrand, Cody+ subm. David poster

Star clusters in the time domain: Science  Eclipsing binaries  Starspot properties and stellar rotation  Exploration of accretion and disk- related variability  Search for young planets

K2 reveals spot evolution and/or differential rotation M35 USco Pleiades Hyades

K2 reveals spot evolution and differential rotation  Can be difficult to differentiate the two phenomena (Aigrain et al. 2015)  ~20-30% of intermediate age stars show multiple light curve frequencies  Spot evolution appears on ~week timescales, if at all.  Currently comparing long-term spot behavior on the pre main sequence vs. in older clusters. Mass dependence unclear. Rebull poster

The mass dependence of rotation at young ages Covey poster

Star clusters in the time domain: Science  Eclipsing binaries  Starspot properties and stellar rotation  Exploration of accretion and disk- related variability  Search for young planets

Hartmann 1999

The space based photometry revolution on young stars CoRoT: NGC 2264 MOST: Taurus- Auriga/ Lupus/ TW Hya K2: Sco-Cen/ ρ Oph/ Lagoon/ Taurus? Sub-1% precision days of continuous photometric monitoring

A Zoo of Young Star Light Curves

Stochastic stars Quasi-periodic stars Purely periodic Flux Asymmetry Stochasticity Light Curve Classification Scheme Eclipsing binaries Bursters Dippers Cody+ 2014

Classes can now be selected statistically! Cody et al. 2014

~20-30%: Quasi-periodic flux dips: Circumstellar dust obscuration

New classes of young star behavior! “Bursters” [Embargoed slide.]

Bursters display a spatial spread on the sky

Star clusters in the time domain: Science  Eclipsing binaries  Starspot properties and stellar rotation  Exploration of accretion and disk- related variability  Search for young planets

Many False Positives to Sort Through!

A candidate – but unclear whether it is a cluster member Found by high school students Shashank & Shishir Dholakia!

Summary  K2 is an excellent platform for photometric monitoring of young to intermediate age star clusters.  The resulting time series are being used to contrain stellar parameters, understand angular momentum evolution, as well as magnetic spot properties.  More cluster data to come!  By the end of the mission, we may have a significant enough sample to constraint planet occurrence rates at young ages.