Periodic Variables and Gyrochronology in NGC2301

Periodic Variables and Gyrochronology in NGC2301Tuguldur Sukhbold Dr.Steve Howell NOAOHowell et. al. (2005) , Tonry et.al.(2005)Search for Planetary Occultation in Open Cluster NGC2301

Open Cluster Formed in the same Gas cloudLoosely Gravitationaly BoundFew 1000 starsFew Hundred My

Why Open?

NGC2301

Howell et.al.(2005)

University of Hawaii 88 (2.2m)

14 daysPlanetary Occultation

Light Curve

Light CurveWhy non-continuous?

Phase PlotRaw Light Curve

Phased Light Curve

Stat.Analysis of 4078starsTonry et.al.(2005)Prob.periodicity ; Prob.exoplanet.

Goal 1: Find Eclipsing Binaries (EBs)So that I can measure the distance

What is EB

Contact EB

How can I measure the Distance?Take Spectra => Measure Doppler Shifts => Derive Radial Velocity Curve => Find Mass, Radius of Component Stars => DistanceRadial Velocity CurveM=m-5(logDL-1)

Berg et.al.(2001)Pool of data of 4078

EBs are periodic variables =>

find Periodic Variables first and then look for EBs in the listUsed prob.periodicityP=1-PfDecreasing Probability of Periodicity ------------------------------->2 Rejected StarsVariables, but not periodic on the time-sclale of 14day observing runEB ~ Unequal Minima

Found 5 candidates!!! :DSE292 Notice!

Periods are Extremely short!!!0.24-0.34days ~ 6-8hours!

Same Mass, Circular Orbit:

Crude Radial Velocity Estimation: ~200km/sec!!!Assuming real EBs are they real Members?

CMD isochrones, Yi et.al.(2003)

CMD of NGC 2301Yale Isochrones, Yi et.al.(2003)Grubissich & Prugathofer (1962) Cluster Apparent Radius ~18 arcminutesGoal 2: GyrochronologyHow old is the cluster?

How well does Gyrochronology work?

Skumanich LawAndrew Skumanich, 1972

Sydney Barnes (2003)

Empirical IsochronesI sequence

C sequence

Population (time)

Meibom et.al.(2008) M35

Color Conversion (B-V) (B-R)Values from Cox (2000)

Period Color Plane for NGC2301200My

Filtering:7 stars (B-R) < 1.00

5 stars EBs

10 stars PulsatorsLeft with 116 stars:Still messPreviously Determined Ages~164My Unknown Method /WEBDA/

250+/-45My Kim et.al.(2001)

~205My Kharchenko et.al.(2006)Isochrones of Previous ages:What can I do?1) Fit Isochrones on subjectively defined sequence regions

2) Direct application of Skumanich Relation1. Isochrone FitsOnly on I sequence, because contamination in C sequencePNyquist------------------------------P=5.5(B-R)-4.5P=6.5(B-R)-4.5PNGrubissich & Prugathofer (1962) Cluster Apparent Radius ~18 arcminutesCentral Region on CMDPeriod-Color diagram Central RegionSame Criteria linesP=6.5(B-R)-4.5P=3220My96My2. Direct Application of Skumanich

Meibom et.al.(2008)Hyades Cluster ~625My------------------------------------------------------------------------------------------------------------------------------------------------------------

So how old is this cluster?I dont know??196My177My205My164My96My250My220MySame Criteria Lines,

Contamination about ~ 12% ~8stars, but in the interval of only What I didFrom the data set of Howell et.al.(2005) and Tonry et.al.(2005): found 138 periodic variables including 5 EB candidates in the field of NGC2301Analysis of Period-Color diagram Gyro-age isochrone fits on available dataProposed a direct application of Skumanich LawRoughly estimated contamination in the data set

FutureWith Dr.Steve around ~November, WYIN 3.5m Telescope, HYDRA Spectrograph

This summer with Dr.Meakin, 3D Hydrodynamical simulations, TYCHOcode

ReferencesBarnes, S. A. 2003, ApJ, 586, 464Cox, A.N. 2000, in Allens Astrophysical Quantities, 4th Edition,(Springer, AIP Press)Grubissich, G. and Purgathofer, A., 1962, Z. Astrophys. 54, 41Howell, S. B., VanOutryve, C., Tonry, J., et al., 2005, PASP, 117, 1187Kharchenko N. V., Piskunov A. E., Roeser S.,et al. R.-D., 2005, A&A, 438, 1163Kim, S. L., Chun, M.Y., Park, B. G., et al., 2001, A&A, 371, 571Meibom S., Mathieu R. D., Stassun K. G., 2008, ApJ,Skumanich, A. 1972, ApJ, 171, 565Tonry, J. L., Howell, S. B., Everett, M. E., et al., 2005, PASP, 117, 281Yi, S. K., Kim, Y., & Demarque, P. 2003, ApJS, 144, 259