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Taiwan America Occultation Survey TAOS 2002/8/28 TAOS photometry using IRAF Shao-Er Chuang Department of Earth sciences, National Taiwan Normal University,

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Presentation on theme: "Taiwan America Occultation Survey TAOS 2002/8/28 TAOS photometry using IRAF Shao-Er Chuang Department of Earth sciences, National Taiwan Normal University,"— Presentation transcript:

1 Taiwan America Occultation Survey TAOS 2002/8/28 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 2002 ASIAA Summer Student Program

2 Taiwan America Occultation Survey TAOS 2002/8/28 Outlines  Introduction  Data reduction  Preliminary result  Conclusion  future

3 Taiwan America Occultation Survey TAOS 2002/8/28 Introduction  TAOS project To detect occultations cause by Kuiper Belt Objects. 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. The observation will help us to understand the planets formation and dynamical evolution of the outer solar system.

4 Taiwan America Occultation Survey TAOS 2002/8/28

5 Taiwan America Occultation Survey TAOS 2002/8/28  Unique observation technique zipper mode zipper mode So require special analysis method. So require special analysis method.  What ’ s Zipper mode? Introduction

6 Taiwan America Occultation Survey TAOS 2002/8/28

7 Taiwan America Occultation Survey TAOS 2002/8/28 Illustration  A simple illustration for occultation event A simple illustration for occultation event A simple illustration for occultation event

8 Taiwan America Occultation Survey TAOS 2002/8/28 Illustration Readout shift

9 Taiwan America Occultation Survey TAOS 2002/8/28 TAOS Zipper mode image Rowblocks GIF animation X Y Row block size : 2048 x 32 pixels Exposure time : 0.2 sec

10 Taiwan America Occultation Survey TAOS 2002/8/28 TAOS Zipper mode image Partial of original image size : 1024 x 768 pixels Original image size : 2048 x pixels File name : _zipper_3002.fit

11 Taiwan America Occultation Survey TAOS 2002/8/28 TAOS Zipper mode image Partial of original image size : 1024 x 768 pixels Original image size : 2048 x pixels File name : _zipper_3002.fit

12 Taiwan America Occultation Survey TAOS 2002/8/28 Low signal to noise ratio

13 Taiwan America Occultation Survey TAOS 2002/8/28 Data reduction  IRAF Aperture Photometry Package  IRAF Scripts  Fortran 90

14 Taiwan America Occultation Survey TAOS 2002/8/28 Photometry flowchart Input Image & set parameter Daofind Phot Produce report Calculate Mag StdDev Row block image input Append data to file continue Find Alarm stop Recheck

15 Taiwan America Occultation Survey TAOS 2002/8/28 Preliminary result  Zipper mode stars light curve

16 Taiwan America Occultation Survey TAOS 2002/8/28 Preliminary result  Zipper mode mag & mag error StdDev relation

17 Taiwan America Occultation Survey TAOS 2002/8/28 Suspected occultation event criteria  Magnitude are missing in IRAF phot result The mag of the star is shown as INDEF The mag of the star is shown as INDEF  Magnitude fluctuation greater than 4 times of magnitude standard deviation 4 times of magnitude standard deviation

18 Taiwan America Occultation Survey TAOS 2002/8/28 Some false alarms

19 Taiwan America Occultation Survey TAOS 2002/8/28 Some false alarms

20 Taiwan America Occultation Survey TAOS 2002/8/28 Some false alarms

21 Taiwan America Occultation Survey TAOS 2002/8/28 Some false alarms

22 Taiwan America Occultation Survey TAOS 2002/8/28 Some false alarms

23 Taiwan America Occultation Survey TAOS 2002/8/28 Some false alarms

24 Taiwan America Occultation Survey TAOS 2002/8/28 Some false alarms

25 Taiwan America Occultation Survey TAOS 2002/8/28 Some false alarms

26 Taiwan America Occultation Survey TAOS 2002/8/28 Some false alarms

27 Taiwan America Occultation Survey TAOS 2002/8/28 Some false alarms

28 Taiwan America Occultation Survey TAOS 2002/8/28 Some false alarms

29 Taiwan America Occultation Survey TAOS 2002/8/28 Some false alarms

30 Taiwan America Occultation Survey TAOS 2002/8/28 Image Photometry times Suspected Occultation eventsFalsealarmratio MagINDEF Mag>4 _zipper1_3002.fit85x % _zipper1_3003.fit89x % _zipper1_3004.fit82x % _zipperc_a020.fit141x % _zipperc_a021.fit144x % _zipperc_a025.fit139x % _zipperc_a030.fit132x % Summery

31 Taiwan America Occultation Survey TAOS 2002/8/28 Conclusion  Sky background is too bright A source exposes 0.2 sec, but the sky background exposes 12.8 sec. A source exposes 0.2 sec, but the sky background exposes 12.8 sec. Using zipper mode will lower S/N ratio of data. 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 (1) Enlarge Zipper mode shift pixel length, may use 128 pixels or 256 pixels. 256 pixels. But it will cause the data will expand to 4 times or 8 times large. 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 (2) Put a mask in front of CCD, just allow target stars light go through. through. It needs lots of masks, and lots tiny holes on those masks. It needs lots of masks, and lots tiny holes on those masks.

32 Taiwan America Occultation Survey TAOS 2002/8/28 No re-find center stars light curve

33 Taiwan America Occultation Survey TAOS 2002/8/28 Re-find center stars light curve

34 Taiwan America Occultation Survey TAOS 2002/8/28 Sky background getting brighter and brighter Source expose 0.2sec Sky background expose 0.2 x 64 = 12.8sec

35 Taiwan America Occultation Survey TAOS 2002/8/28 Future works  To identify zipper mode field stars To estimate limit magnitude & calibrate by To estimate limit magnitude & calibrate by reference stars. reference stars. Create a database of TAOS. Create a database of TAOS.  Image process to improve S/N Subtract dark current and bias. Subtract dark current and bias.  To make photometry more efficient To achieve real-time analyze. To achieve real-time analyze.  Decide all criteria for TAOS image

36 Taiwan America Occultation Survey TAOS 2002/8/28 Acknowledgements I would like to thank the members in IAA who gave me instructions,precious opinions and helps. 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. Especially, thanks to Jen-Hung Wang, Sun-Kun King, Shiang-Yu Wang, Bau-Ching Hsieh, Frank, Joshua, Tony.

37 Taiwan America Occultation Survey TAOS 2002/8/28


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