25th CoRoT Scientific Council : 24-25 sept 2007 - M.O. - L.J.

Evaluation of exo N1 data

M.Ollivier - L Jorda

25th CoRoT Scientific Council : 24-25 sept 2007 - M.O. - L.J.

Goal of the evaluation

• Check if N1 data are compliant with N1 specifications

• Global noise not larger than 1.5 times the photon noise for a K0 star of mag 14 (photon noise = 700 ppm over 512 seconds, 250 ppm over 1hour)

25th CoRoT Scientific Council : 24-25 sept 2007 - M.O. - L.J.

Conclusion of first evaluation (june 2007)

• White photometry– Pb with outliers (SAA)– Pb with hot pixels, particularly when present in a

background window – When outliers are flagged and kept away, specification is

reached whatever the magnitude is

• Colored photometry– Drift (red : positive slope, green and blue : negative

slope)– As a consequence, specification in term of stability is not

reached (even if OK fter slope correction).

Conclusion : not far from N1 requirements

25th CoRoT Scientific Council : 24-25 sept 2007 - M.O. - L.J.

What has changed in the pipeline ?

• Optimisation of parameters for cosmics detection

• Flag of the SAA input / output (not implemented in tested data)

• How to correct hot pixels (cf. VL and MA presentations)

25th CoRoT Scientific Council : 24-25 sept 2007 - M.O. - L.J.

Method

• Starting from N1 data (LRc01 in this case, IR01 in previous evaluation)

• Use of unflagged data only• 512 second sampling• Removal of low frequencies (substraction of a fit

over 16 samples)• Removal of outliers (only unflagged points)• Evaluation of mean and variance of residuals

25th CoRoT Scientific Council : 24-25 sept 2007 - M.O. - L.J.

White photometry1 hour White photometry

0

0,5

1

1,5

2

2,5

3

3,5

4

11,8 12 12,2 12,4 12,6 12,8 13 13,2 13,4 13,6

Magnitude

S/N (photon noise unit)

25th CoRoT Scientific Council : 24-25 sept 2007 - M.O. - L.J.

White photometry (2)

• Very few outliers that have not been detected and flagged

• The hot pixels are very present and really need to be treated.

25th CoRoT Scientific Council : 24-25 sept 2007 - M.O. - L.J.

Colored photometry• Real pb of color correction in quite all LRc01 LCs.

25th CoRoT Scientific Council : 24-25 sept 2007 - M.O. - L.J.

Colored photometry (2)Colored photometry

0

2

4

6

8

10

12

11,8 12 12,2 12,4 12,6 12,8 13 13,2 13,4 13,6

Magnitude

S/N (photo noise unit)

25th CoRoT Scientific Council : 24-25 sept 2007 - M.O. - L.J.

Colored photometry (3)

• Intra color correction not optimized

• Pb of drift not corrected

• S/N requirement not compliant with the specification

Colored photometry processing must be improved (by the project or by users ?)

25th CoRoT Scientific Council : 24-25 sept 2007 - M.O. - L.J.

Conclusions

• White photometry is OK (from S/N requirement point of view)

• A processing for of hot pixels should be implemented

• Colored photometry is still not at the required level.

25th CoRoT Scientific Council : 24-25 sept 2007 - M.O. - L.J.

“nice” LCs

25th CoRoT Scientific Council : 24-25 sept 2007 - M.O. - L.J.

“nice” LCs