This is a resubmission of the current program after approval of Program Change Request 1334 ----- Submission 1 (Sun May 07 17:52:50 GMT 2006) ----- Phase II Proposal 10791 (1E1207) successfully submitted. ----- Attempting Submission 3 (Fri Mar 09 15:06:29 GMT 2007) ----- Assigned ID: 261 ----- Submission 1 (Fri Jan 27 16:43:00 GMT 2006) ----- Phase I Proposal 261 (1E1207) successfully submitted. ----- Submission 1 (Fri Jan 27 16:43:42 GMT 2006) ----- Unable to contact STScI submission server ----- Submission 3 (Fri Jan 27 18:05:53 GMT 2006) ----- Phase I Proposal 261 (1E1207) successfully submitted. 1E 1207.4-5209 is one of the most puzzling X-ray compact sources in the Galaxy. Long known to be a radio-quiet Neutron Star (NS) embedded in a young (~7000 y) supernova remnant, it displays a unique phenomenology, including multiple cyclotron absorption features in its thermal X-ray spectrum, as well as a possible non-monotonous evolution of its 424 ms rotational period. A candidate optical counterpart (I~23.4) with very red colours (not consistent with the expected emission of a NS, but rather with a low-mass stellar companion, or a fossil disk) was singled out with HST/ACS in 2003, at the margin of the Chandra error box. In order to test the reality of such an association, we propose to take advantage of the high space velocities characteristics of NSs to search for the expected displacement (~150 mas in the NE direction) of the candidate counterpart over a 3 years time span. One orbit observation, either unveiling the displacement or ruling it out, will settle the problem of the optical identification of 1E1207.4-5209. We stress that a null result would also be important for the understanding of this source.

We plan to performaccurate positioning of the pulsar 1E1207-5209 accurate counterpart with the ACS/WFC HOT STARS 12 false 0.0 false false false false false false SUPPORTED STAR PULSAR J2000 12 10 0.8260 -52 26 28.43 J2000 ACS/WFC Imaging No No F814W C:\Documents and Settings\roberto mignani\Impostazioni locali\Temp\OPVisit42844.xml 1173452318406 (Tic-Visit :proposal-id 10791 :visit-id "01" :proposal-version -1 :trans-version "20061109" :date "09-Mar-2007 14:58:38.0" :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 179264 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 10791 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 10791 :visit-id "01" :orbit-number 1 :pcs-time 355 :si-vis-utilization 2820 :al-overhead-at-end 180 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3200 :pcs-gap 0 ) true 1 0