This proposal uses the FGS1r in TRANS mode to resolve a pair of double degenerate binary systems (WD1639+153 and WD 1818+26) in order to determine their orbital elements. In addition, the binaries and several nearby field stars are observed by FGS1r in POS mode to establish the local inertial reference frame of each binary, as well as its parallax and proper motion. This will allow for a direct measurement of the distance, which yields the instrinsic luminosity, and when combined with the spectroscopic estimates of the T_eff, the radius of each of the four WD stars. When combined with the orbital elements, this leads to a dynamical mass measurement for each WD, and a four calibration points of the WD mass-radius relation.

We will use FGS1r in its high angular resolution observing mode (TRANS) to resolve the white dwarf binary systems. Each exposure will be comprised of about 20 scans. The interferograms derived from each scan will be cross-correlated and co-added to yield a high SNR. To further surpress the noise (these targets are near the FGS's faint limiting magnitude), the co-added inteferograms will be carefully smoothed by being represented as a piece-wise smooth segmanted polynomial. These observations will yield the separation and position angle of the binary components, as well as the brightness of each. In addition, the binary and field stars simultaneously in the FGS FOV will be observed in POS mode to accurately determine the relative positions of the stars. This will facilitate the construction of an inertial reference frame for the binary, thereby allowing the relative orbit that will be ultimately determined from the TRANS data to be converted into a physical orbit. This will allow us to determine the relative mass of each white dwarf in the binarty system. In addition, the POS mode data will give the proper motion and parallax of the binary, which will allow us to compute the mass and radius of each white dwarf. The observations should be scheduled to occur at times of maximum parallax factor to allow us to determine the distance to each of these two white dwarf binary systems. 12 false 0.0 0.0 false false false false false false SUPPORTED EXT-STAR DC Maximum parallax factor occurs Feb 27 & Aug 30. J2000 00 00 0.0000 +00 00 0.00 J2000 CALIBRATION ASTROMETRIC GSC1520.00549 J2000 00 00 0.0000 +00 00 0.00 J2000 CALIBRATION ASTROMETRIC GSC1520.00514 J2000 00 00 0.0000 +00 00 0.00 J2000 CALIBRATION ASTROMETRIC GSC1520.00496 J2000 00 00 0.0000 +00 00 0.00 J2000 CALIBRATION ASTROMETRIC GSC1520.00555 J2000 00 00 0.0000 +00 00 0.00 J2000 CALIBRATION ASTROMETRIC GSC1520.00628 J2000 00 00 0.0000 +00 00 0.00 J2000 CALIBRATION ASTROMETRIC GSC1520.00612 J2000 00 00 0.0000 +00 00 0.00 J2000 EXT-STAR DC maximum parallax factor occurs Sep 29 and March 29 J2000 00 00 0.0000 +00 00 0.00 J2000 CALIBRATION ASTROMETRIC GSC1018.02189 J2000 00 00 0.0000 +00 00 0.00 J2000 CALIBRATION ASTROMETRIC GSC1018.02278 J2000 00 00 0.0000 +00 00 0.00 J2000 CALIBRATION ASTROMETRIC GSC1018.01251 J2000 00 00 0.0000 +00 00 0.00 J2000 CALIBRATION ASTROMETRIC position and magnitude from GSC2, using Kriss & Stys color transformations. N020230030828 J2000 00 00 0.0000 +00 00 0.00 J2000 CALIBRATION ASTROMETRIC position and magnitude from GSC2, using Kriss & Stys color transformations N020230030566 J2000 00 00 0.0000 +00 00 0.00 J2000 CALIBRATION ASTROMETRIC position and magnitude from GSC2, using Kriss & Stys color transformation N020230031910 J2000 00 00 0.0000 +00 00 0.00 J2000 CALIBRATION ASTROMETRIC position and magnitude from GSC2, color transformation using Kriss & Stys N020230031978 J2000 00 00 0.0000 +00 00 0.00 J2000 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. 1233700138000 290.0 (Tic-Visit :proposal-id 11787 :visit-id "01" :proposal-version -1 :trans-version "20080624" :date "04-Aug-2008 22:45:10.0" :trans-errors '(:WARNINGS 8 :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 11787 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11787 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2908 :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 3257 :pcs-gap 0 ) false 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. 1251448567000 110.0 (Tic-Visit :proposal-id 11787 :visit-id "02" :proposal-version -1 :trans-version "20080624" :date "04-Aug-2008 23:06:31.0" :trans-errors '(:WARNINGS 8 :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 11787 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11787 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2907 :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 3257 :pcs-gap 0 ) false 1 0 The scheduling data was generated by CASM 17.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 11787 :visit-id "04" :proposal-version -1 :trans-version "20080624" :date "04-Aug-2008 23:10:01.0" :trans-errors '(:WARNINGS 1 :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 11787 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11787 :visit-id "04" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2798 :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 3137 :pcs-gap 0 ) false 1 0