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K2 Observations of Open Clusters
Ann Marie CodyNPP fellow at NASA Ames
November 2, 2015
Acknowledgments
•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+ knownmembers)
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
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 M35
USco USco
Pleiades Pleiades
Hyades 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 2264MOST:
Taurus-Auriga/ Lupus/TW Hya
K2:Sco-Cen/
ρ Oph/Lagoon/Taurus?
• Sub-1% precision• 20-80 days of continuous photometric monitoring
A Zoo of Young Star Light Curves
Stochasticstars
Quasi-periodicstars
Purelyperiodic
Flux Asymmetry
Stochasticity
Light Curve Classification Scheme
Eclipsingbinaries
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.
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