4 Examples of Persistence

Dafydd Wyn Evans

29 March 2006

Interleaving and stacking

Filename Extension X YType
w20051008_00441.fit Ext 1 538 972Single
w20051008_00442.fit Ext 1 538 972Single
w20051008_00442_sf.fit Ext 110761964Interleaved
w20051008_00442_sf_st.fitExt 110761979Interleaved and Stacked

This data was taken on 8 October 2005 and is from the UKIDSS GPS survey. The individual frames are 10 second exposures taken in J. Frame 00441 is the final frame from the previous stack. About 15 seconds elapse from the end of that exposure and the start of the next exposure (00442) as the telescope moves to the target of the next series of 8 exposures. Between each exposure of this series there is a gap of about 3 seconds. The first four frames (00442-00445) are interleaved to form w20051008_00442_sf.fit. The next four frames (00446-00449) are then interleaved to form w20051008_00446_sf.fit and then this frame stacked with w20051008_00442_sf.fit to form w20051008_00442_sf_st.fit.

The perturbing source in frame 00441 is at 21h 22m 20.3s +48° 31' 40" and has a 2MASS J magnitude of 8.79.

Bright H perturbing source

Filename Extension X YType
w20051014_02353.fit Ext 316841479Single
w20051014_02354.fit Ext 316841479Single

This data was taken on 14 October 2005 and is from the UKIDSS GCS survey. The individual frames are 10 second exposures taken in H. About 15 seconds elapse from the end of 02353 and the start of 02354.

The perturbing source in frame 02353 is at 4h 8m 28.7s +21° 34' 40" and has a 2MASS H magnitude of 6.07.

Faint H perturbing source

Filename Extension X YType
w20051014_02353.fit Ext 31195985Single
w20051014_02354.fit Ext 31195985Single

This data was taken on 14 October 2005 and is from the UKIDSS GCS survey. The individual frames are 10 second exposures taken in H. About 15 seconds elapse from the end of 02353 and the start of 02354. The noise in this frame is about 55 counts and compares with the measured persistence effect of 76 counts.

The perturbing source in frame 02353 is at 4h 8m 14.5s +21° 37' 56" and has a 2MASS H magnitude of 8.84.

Faint Z perturbing source

Filename Extension X YType
w20051008_01867.fit Ext 310082003Single
w20051008_01868.fit Ext 310082003Single

This data was taken on 8 October 2005 and is from the UKIDSS GCS survey. The individual frames are 20 second exposures taken in Z. About 20 seconds elapse from the end of 01867 and the start of 01868. The noise is only 8 counts and compares with the measured persistence of 111 counts.

Note that the second frame has two persistent images on it (red and green circles) due to the 2 point jitter pattern of the previous pair of exposures. The red circled image is the decaying remnant of the blue circled persistent image in the first frame

The perturbing source in frame 01867 is at 3h 48m 13.5s +22° 18' 51" and has a 2MASS J magnitude of 9.81. The measured Z magnitude is 10.46, but will be underestimated since the image is saturated.


Dafydd Wyn Evans (dwe @ ast.cam.ac.uk)
Last modified: 29 March 2006