No problems at all with the phase II forms - assuming I've got it all right, the documentation was superb. If I've got anything totally wrong then I guess it wasn't as clear as I thought! ----- Submission 1 (Thu Jun 29 19:16:33 GMT 2006) ----- ----- Attempting Submission 2 (Tue Feb 27 20:40:43 GMT 2007) ----- The error message doesn't seem to be connected to anything - I have re-run all the tools, and the diagnostics tool isn't giving me any more information. We obtained high time-resolution photometry using the high speed CCD camera ULTRACAM between 2002 and 2004, which revealed a gradual reduction in the orbital period of the pre- cataclysmic variable NN Serpentis. There are three possible explanations for this period change: firstly, we may have been successful in obtaining the first and only direct measurement of the braking rate of a close binary system, in which case our measured values are approximately 2 orders of magnitude greater than predicted, and pose serious problems for the theory of close binary evolution. Secondly, the unusually high braking rate may be caused by the presence of a circumbinary disk, which would help to answer two of the outstanding problems with current CV theory - namely the high mass-transfer rates seen in some CVs, and the fact that the minimum observed value in the CV period distribution is approximately 15% longer than expected. Finally, our observations could be explained by a light travel-time effect caused by a third body in orbit around the binary, which would raise major questions about the evolutionary history of the system, in particular how a third body has managed to remain in a stable orbit throughout periods of intense mass-loss in the central binary. We intend to use IRAC observations to search for a mid-infrared excess in the spectral energy distribution of NN Ser, which would confirm the presence of either a disk or a third body. We then propose to use HST imaging to attempt to resolve a third body, allowing us to discriminate between the two possibilities. If both methods fail to reveal any extra system components, we will have ruled out our only remaining alternatives to a genuinely high angular momentum loss rate in this system, with profound implications for CV evolution.

We will use the WFPC2 with both the F555W and F814W filters to obtain deep images of NN Ser. The goal is to detect a tertiary red dwarf companion, therefore we require the colour information to differentiate between the known central binary components and any third body. In order to remove cosmic rays, hot pixels and detector blemishes, minimise flat-fielding errors, and, most importantly, oversample the PSF, we will utilise an 4-point box dither pattern. To be certain that we image deeply enough, we have estimated the likely V- and I-band brightness of the central system and the tertiary companion. We used the WFPC2 ETC to obtain total- and sub-exposure times required to obtain a S/N of 30 for V=22 and I=20 respectively, while ensuring that the brighter central binary system is never over-exposed. 12 false 0.0 false false false false false false SUPPORTED STAR CIRCUMSTELLAR MATTER DA M V-IV LOW MASS COMPANION I=17+/10.5 J2000 15 52 56.2000 +12 54 47.20 J2000 ACS/HRC Imaging No No F555W ACS/HRC Imaging No No F814W POS-TARG DITHER 0.559017 LINE 0.559017 false false 143.130096 4 26.56505 WFPC2-BOX 1 false /private/tmp/OPVisit49937.xml 1172608639610 (Tic-Visit :proposal-id 10999 :visit-id "01" :proposal-version -1 :trans-version "20070108" :date "27-Feb-2007 12:37:19.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "26" :si-bright-earth-limb-angle 20.0 :data-volume 358528 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 10999 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 10999 :visit-id "01" :orbit-number 1 :pcs-time 355 :si-vis-utilization 2760 :al-overhead-at-end 120 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3137 :pcs-gap 0 ) true 1 0 /private/tmp/OPVisit65232.xml 1151606351570