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Measurement of the photocentre position variations with CoRoT - further investigations

Measurement of the photocentre position variations with CoRoT - further investigations. M . Ollivier (IAS ). Summary of previous episodes. Why measuring the photocentre position ?. Accuracy of the photocentre position determination.

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Measurement of the photocentre position variations with CoRoT - further investigations

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  1. Measurement of the photocentreposition variations with CoRoT -further investigations M. Ollivier (IAS)

  2. Summary of previousepisodes CoRoT SC – 3 july 2012

  3. Why measuring the photocentre position ? CoRoT SC – 3 july 2012

  4. Accuracy of the photocentre position determination • Realistic approach : “realistic case” : Estimation of the photocenter position using the imagettes • Determination of the optimal mask for the exo target • Estimation of the photocentre position using the pixel within the mask as it is done for the sismo stars (white light) • Determination of the residual jitter thanks to the sismo stars • Correction of the jitter in the photocentre curve for the exo target • Estimation of the photocentre stability (rms of the photocentre position curve) • “clever” filtering : gain by a factor of 2 in the rms value ? • Work done for 2 targets • Star 101062850 R=15.07 • Star 102797300 R=13.68 CoRoT SC – 3 july 2012

  5. Accuracy of the photocentre position determination Star 102797300 R=13.68 : rms=0.015 px -> 0.0075 px CoRoT SC – 3 july 2012

  6. Photocentre position averaging • If we average over the transit duration + several transits: • If à 80 day run CoRoT SC – 3 july 2012

  7. Amplitude of the photocentre position variations (ΔmV=3) ΔF/F 0.6 % 2 % 3 % CoRoT SC – 3 july 2012

  8. Amplitude of the photocentre position variations (ΔmV=5) CoRoT SC – 3 july 2012

  9. Open question 1: implementation of the photocentre computation • A modification of the onboard software is costly (time, manpower, money) • Computation thanks to the imagettes • Performance of the imagettes pipeline (cf. S.B’ presentation) • Need for operations modifications : ability to change the target status during a run : (cf. S.C. O.V presentations) • How, when, how many times per run ? • How to handle different types of data for the same target • Need for the alarm mode • All the alarm in imagettes Need to be tested before generalized CoRoT SC – 3 july 2012

  10. Open question 2: Is there an alternative method ? • The use of colored photometry (about 2000 targets/run) • Differentiel effect of a contaminant eclipsing binary on the colored photometry. • Simulation : a CEB in the field : Δm=3, Δx entre +/- 10 arcsec • Utilisation du simulateur de contamination (casidéal, bruit de photon stellaire CoRoT SC – 3 july 2012

  11. Open question 2: colored photometry? CoRoT SC – 3 july 2012

  12. Open question 2: colored photometry? ΔmV=3, eclipsedepth : 10% CoRoT SC – 3 july 2012

  13. Open question 2: colored photometry? CoRoT SC – 3 july 2012

  14. Open question 2: colored photometry? ΔmV=3, eclipsedepth : 10% CoRoT SC – 3 july 2012

  15. Open question 2: colored photometry? • Ability to detect a CEB withΔx> +/- 2 arcsec (1 pixel) • Can beperformed on the coloredphotometry if sufficient S/N • Can beconsidered for mV<15 • Works onlyalong the dispersion direction CoRoT SC – 3 july 2012

  16. Proposedstrategy • Evaluation of operational impact of photocentrecalculation • Test on 2 or 3 targetswithphotometric variations • Comparisonwithactualcoloredphotometry. CoRoT SC – 3 july 2012

  17. Discussion CoRoT SC – 3 july 2012

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