TAOS photometry using IRAF

1. 2002 ASIAA Summer Student Program TAOS photometry using IRAF Shao-Er Chuang Department of Earth sciences, National Taiwan Normal University, Supervisor Jen-Hung Wang, Sun-Kun King Institute of Astronomy and Astrophysics, Academia Sinica

2. Outlines • Introduction • Data reduction • Preliminary result • Conclusion • future

3. Introduction • TAOS project To detect occultations cause by Kuiper Belt Objects. The observation will help us to understand the planets formation and dynamical evolution of the outer solar system.

5. Introduction • Unique observation technique zipper mode So require special analysis method. • What’s Zipper mode?

7. Illustration • A simple illustration for occultation event

8. 4 3 2 1 Illustration shift Readout

9. TAOS Zipper mode imageRowblocks GIF animation Y X 0 256 512 512 768 1024 Row block size : 2048 x 32 pixels Exposure time : 0.2 sec

10. TAOS Zipper mode image Partial of original image size : 1024 x 768 pixels Original image size : 2048 x 18048 pixels File name : 020508_zipper_3002.fit

11. TAOS Zipper mode image Partial of original image size : 1024 x 768 pixels Original image size : 2048 x 18048 pixels File name : 020508_zipper_3002.fit

12. Low signal to noise ratio

13. Data reduction • IRAF Aperture Photometry Package • IRAF Scripts • Fortran 90

14. Photometry flowchart Input Image & set parameter Calculate Mag StdDev Find Alarm Daofind Phot Row block image input Produce report Append data to file continue Recheck stop

15. Preliminary result • Zipper mode stars light curve

16. Preliminary result • Zipper mode mag & mag error StdDev relation

17. Suspected occultation event criteria • Magnitude are missing in IRAF phot result The mag of the star is shown as INDEF • Magnitude fluctuation greater than 4 times of magnitude standard deviation

18. Some false alarms

19. Some false alarms

20. Some false alarms

21. Some false alarms

22. Some false alarms

23. Some false alarms

24. Some false alarms

25. Some false alarms

26. Some false alarms

27. Some false alarms

28. Some false alarms

29. Some false alarms

30. Summery

31. Conclusion • Sky background is too bright A source exposes 0.2 sec, but the sky background exposes 12.8 sec . Using zipper mode will lower S/N ratio of data. • Tracking error • How to reduce ? (1) Enlarge Zipper mode shift pixel length, may use 128 pixels or 256 pixels . But it will cause the data will expand to 4 times or 8 times large. (2) Put a mask in front of CCD, just allow target stars light go through. It needs lots of masks, and lots tiny holes on those masks.

32. No re-find center stars light curve

33. Re-find center stars light curve

34. Sky background getting brighter and brighter Source expose 0.2sec Sky background expose 0.2 x 64 = 12.8sec

35. Future works • To identify zipper mode field stars To estimate limit magnitude & calibrate by reference stars. Create a database of TAOS. • Image process to improve S/N Subtract dark current and bias . • To make photometry more efficient To achieve real-time analyze. • Decide all criteria for TAOS image

36. Acknowledgements I would like to thank the members in IAA who gave me instructions ,precious opinions and helps. Especially, thanks to Jen-Hung Wang, Sun-Kun King, Shiang-Yu Wang, Bau-Ching Hsieh, Frank, Joshua, Tony.