We will use HST+FGS to measure the parallax of the transiting planet host star XO-3. The resulting accurate distance measurement will provide the most accurate radius determination to date for this massive extrasolar planet (XO-3b), allowing us to critically test current giant extrasolar planet structure models. These observations will also constrain the amount of heating that may be produced inside XO-3b by tides raised on the planet as it moves through its 3.2 d eccentric (e ~ 0.22) orbit.

For this proposed study we will obtain 11 orbits of astrometric data with FGS 1r for XO-3 and associated reference stars, spread over 2 years. The pattern will be two orbits near the four maximum parallax factors, and one orbit at each of the first, second, and third intervening minimum parallax factors. The two orbits at each maximum parallax factor phase will bracket the epoch of maximum parallax factor and be spread out over 15 days. Each orbit will include 3-4 measures of the primary target and several measures of each reference star, completely filling the 40-50 minute visibility period. This approach will guarantee a parallax precision of ~0.2 mas. Each visit will include multiple POS mode (fringe tracking) observations of XO-3 and ~5 astrometric reference stars. EXTRA-SOLAR PLANETS 12 false 0.0 0.0 false false false false false SUPPORTED STAR EXTRA-SOLAR PLANET EXTRA-SOLAR PLANETARY SYSTEM K V-IV This object was generated by the targetselector and retrieved from the SIMBAD database. GSC-03727-01064 J2000 04 21 52.7050 +57 49 1.89 J2000 STAR G V-IV J2000 00 00 0.0000 +00 00 0.00 J2000 STAR G V-IV J2000 00 00 0.0000 +00 00 0.00 J2000 STAR G V-IV J2000 00 00 0.0000 +00 00 0.00 J2000 STAR G V-IV J2000 00 00 0.0000 +00 00 0.00 J2000 STAR G V-IV J2000 00 00 0.0000 +00 00 0.00 J2000 STAR G V-IV J2000 00 00 0.0000 +00 00 0.00 J2000 STAR G V-IV J2000 00 00 0.0000 +00 00 0.00 J2000 FGS POS No F583W The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. XO-3 intermediate parallax (Tic-Visit :proposal-id 11706 :visit-id "01" :proposal-version -1 :trans-version "20080609" :date "18-Jun-2008 12:03:38.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "05" :si-bright-earth-limb-angle 15.5 :data-volume 0 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11706 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11706 :visit-id "01" :orbit-number 1 :pcs-time 241 :si-vis-utilization 2885 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3222 :pcs-gap 0 ) false 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. XO-3 at max parallax 1234323264000 76.5 (Tic-Visit :proposal-id 11706 :visit-id "02" :proposal-version -1 :trans-version "20080609" :date "18-Jun-2008 11:43:32.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "05" :si-bright-earth-limb-angle 15.5 :data-volume 0 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11706 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11706 :visit-id "02" :orbit-number 1 :pcs-time 241 :si-vis-utilization 3261 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3517 :pcs-gap 0 ) false 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. XO-3 at max parallax 1234828800000 76.5 (Tic-Visit :proposal-id 11706 :visit-id "03" :proposal-version -1 :trans-version "20080624" :date "02-Jul-2008 11:25:07.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "05" :si-bright-earth-limb-angle 15.5 :data-volume 0 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11706 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11706 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2996 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3517 :pcs-gap 0 ) false 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. XO-3 at max parallax (Tic-Visit :proposal-id 11706 :visit-id "04" :proposal-version -1 :trans-version "20080609" :date "18-Jun-2008 15:01:35.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "05" :si-bright-earth-limb-angle 15.5 :data-volume 0 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11706 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11706 :visit-id "04" :orbit-number 1 :pcs-time 241 :si-vis-utilization 2940 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3222 :pcs-gap 0 ) false 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. XO-3 at max parallax (Tic-Visit :proposal-id 11706 :visit-id "05" :proposal-version -1 :trans-version "20080609" :date "18-Jun-2008 15:01:39.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "05" :si-bright-earth-limb-angle 15.5 :data-volume 0 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11706 :visit-id "05" :obset-id "05" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11706 :visit-id "05" :orbit-number 1 :pcs-time 241 :si-vis-utilization 2940 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3222 :pcs-gap 0 ) false 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. XO-3 intermediate parallax 1249147551000 282.1 (Tic-Visit :proposal-id 11706 :visit-id "06" :proposal-version -1 :trans-version "20080624" :date "01-Jul-2008 15:44:38.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "05" :si-bright-earth-limb-angle 15.5 :data-volume 0 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11706 :visit-id "06" :obset-id "06" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11706 :visit-id "06" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2944 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3517 :pcs-gap 0 ) false 1 0