10931( 7) - 04/03/07 15:21 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 10931 Version: 7 Check-in Time: 03-Apr-2007 19:20:49 STScI Edit Number: 1 Title Dynamical Masses and Radii of Four White Dwarf Stars ------------------------------------------------------------------------------------ Type Cycle Parallel Pointing Tolerance GO 15 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Edmund Nelan Space Telescope Science Institute CoI: Mr. Russell Makidon Space Telescope Science Institute N CoI: Dr. Howard E. Bond Space Telescope Science Institute N CoI: Dr. Gail Schaefer Space Telescope Science Institute N ------------------------------------------------------------------------------------ Abstract add new abstract ------------------------------------------------------------------------------------ 10931( 7) - 04/03/07 15:21 - [ 2] Observations Description ------------------------ 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. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- 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. ------------------------------------------------------------------------------------ 10931( 7) - 04/03/07 15:21 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 WD1639+153 EXT-STAR, DC RA=16H41M36.7000S +/- 0.1", J2000 V = 15.7+/-0.1 DEC=+15D12'36.38" +/- 0.1" Reference Frame: Other: HST CYCLE 10 OBSERVATIONS Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000.0 0.0050 -0.736 0.0 2 WD1639-REF1 CALIBRATION, RA=16H41M39.6000S +/- 0.1", J2000 V = 10.73+/-0.1 ASTROMETRIC DEC=+15D12'1.87" +/- 0.1" Reference Frame: ICRS 3 WD1639-REF2 CALIBRATION, RA=16H41M54.1000S +/- 0.1", J2000 V = 12.1+/-0.1 ASTROMETRIC DEC=+15D11'19.20" +/- 0.1" Reference Frame: ICRS 4 WD1639-REF3 CALIBRATION, RA=16H41M49.1300S +/- 0.1", J2000 V = 14.69+/-0.0 ASTROMETRIC DEC=+15D11'1.97" +/- 0.1" Reference Frame: ICRS 5 WD1639-REF4 CALIBRATION, RA=16H41M22.8200S +/- 0.1", J2000 V = 13.25+/-0.1 ASTROMETRIC DEC=+15D11'55.82" +/- 0.1" Reference Frame: ICRS 6 WD1639-REF6 CALIBRATION, RA=16H41M22.4500S +/- 0.1", J2000 V = 13.9+/-0.1 ASTROMETRIC DEC=+15D14'11.80" +/- 0.1" Reference Frame: ICRS 7 WD1639-REF7 CALIBRATION, RA=16H41M25.9400S +/- 0.1", J2000 V = 13.26+/-0.1 ASTROMETRIC DEC=+15D15'44.39" +/- 0.1" Reference Frame: ICRS 8 WD1818+126 EXT-STAR, DC RA=18H20M30.8800S +/- 0.1", J2000 V = 16.06+/-0.1 DEC=+12D39'17.70" +/- 0.1" Reference Frame: Other: HST CYCLE 10 PROPOSAL Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000.0 0.0070 0.271 0.0 9 WD1818-GSC1- CALIBRATION, RA=18H20M23.6700S +/- 0.1", J2000 V = 10.92+/-0.2 REF1 ASTROMETRIC DEC=+12D39'43.80" +/- 0.1" Reference Frame: ICRS 10 WD1818-GSC1- CALIBRATION, RA=18H20M26.3600S +/- 0.1", J2000 V = 12.7+/-0.2 REF2 ASTROMETRIC DEC=+12D39'25.20" +/- 0.1" Reference Frame: ICRS 11 WD1818-GSC1- CALIBRATION, RA=18H20M31.9700S +/- 0.1", J2000 V = 12.97+/-0.2 REF3 ASTROMETRIC DEC=+12D38'48.12" +/- 0.1" Reference Frame: ICRS 12 WD1818-GSC2- CALIBRATION, RA=18H20M33.8600S +/- 0.1", J2000 V = 14.23+/-0.2 REF1 ASTROMETRIC DEC=+12D39'5.56" +/- 0.1" Reference Frame: ICRS Comments: position and magnitude from GSC2, using Kriss & Stys color transformations. 10931( 7) - 04/03/07 15:21 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 13 WD1818-GSC2- CALIBRATION, RA=18H20M35.3400S +/- 0.1", J2000 V = 14.49+/-0.2 REF2 ASTROMETRIC DEC=+12D38'50.74" +/- 0.1" Reference Frame: ICRS Comments: position and magnitude from GSC2, using Kriss & Stys color transformations 14 WD1818-GSC2- CALIBRATION, RA=18H20M33.6100S +/- 0.1", J2000 V = 14.43+/-0.3 REF3 ASTROMETRIC DEC=+12D40'16.29" +/- 0.1" Reference Frame: ICRS Comments: position and magnitude from GSC2, using Kriss & Stys color transformation 15 WD1818-GSC2- CALIBRATION, RA=18H20M29.4800S +/- 0.1", J2000 V = 15.01+/-0.2 REF4 ASTROMETRIC DEC=+12D40'21.03" +/- 0.1" Reference Frame: ICRS Comments: position and magnitude from GSC2, color transformation using Kriss & Stys 10931( 7) - 04/03/07 15:21 - [ 5] Visit: 01 Visit Priority: Visit Requirements: PCS MODE FINE; SCHED 70%; ORIENT 135.0D TO 135.0 D; BETWEEN 06-JUL- 2006:00:00:00 AND 15-JUL-2006:00:00:00 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 WD1639+153 FGS TRANS 1 F583W STEP-SIZE=0.5,SCANS=25 1 800 S POS TARG 0,-17; SEQ 1-11 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 2 WD1639+153 FGS POS 1 F583W 1 25 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 3 WD1639-REF1 FGS POS 1 F583W 1 5 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 4 WD1639-REF3 FGS POS 1 F583W 1 10 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 5 WD1639-REF7 FGS POS 1 F583W 1 5 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 6 WD1639-REF1 FGS POS 1 F583W 1 5 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 7 WD1639+153 FGS POS 1 F583W 1 25 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 8 WD1639-REF7 FGS POS 1 F583W 1 10 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 9 WD1639-REF3 FGS POS 1 F583W 1 5 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 10 WD1639-REF1 FGS POS 1 F583W 1 5 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 11 WD1639+153 FGS POS 1 F583W 1 5 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ WD1639+153 1 FGS TRANS 1 F583W none none none none 1 N/A WD1639+153 2 FGS POS 1 F583W none none none none 1 N/A WD1639-REF1 3 FGS POS 1 F583W none none none none 1 N/A WD1639-REF3 4 FGS POS 1 F583W none none none none 1 N/A WD1639-REF7 5 FGS POS 1 F583W none none none none 1 N/A WD1639-REF1 6 FGS POS 1 F583W none none none none 1 N/A WD1639+153 7 FGS POS 1 F583W none none none none 1 N/A WD1639-REF7 8 FGS POS 1 F583W none none none none 1 N/A WD1639-REF3 9 FGS POS 1 F583W none none none none 1 N/A WD1639-REF1 10 FGS POS 1 F583W none none none none 1 N/A WD1639+153 11 FGS POS 1 F583W none none none none 1 N/A 10931( 7) - 04/03/07 15:21 - [ 6] Visit: 02 Visit Priority: Visit Requirements: PCS MODE FINE; SCHED 70%; ORIENT 308.0D TO 308.0 D; BETWEEN 15-JAN- 2007:00:00:00 AND 30-JAN-2007:00:00:00 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 WD1639+153 FGS TRANS 1 F583W STEP-SIZE=0.5,SCANS=25 1 800 S POS TARG 0,-17; SEQ 1-11 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 2 WD1639+153 FGS POS 1 F583W 1 25 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 3 WD1639-REF1 FGS POS 1 F583W 1 5 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 4 WD1639-REF2 FGS POS 1 F583W 1 10 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 5 WD1639-REF3 FGS POS 1 F583W 1 5 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 6 WD1639+153 FGS POS 1 F583W 1 25 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 7 WD1639-REF1 FGS POS 1 F583W 1 5 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 8 WD1639-REF7 FGS POS 1 F583W 1 25 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 9 WD1639+153 FGS POS 1 F583W 1 10 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 10 WD1639-REF1 FGS POS 1 F583W 1 5 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 11 WD1639-REF7 FGS POS 1 F583W 1 5 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ WD1639+153 1 FGS TRANS 1 F583W none none none none 1 N/A WD1639+153 2 FGS POS 1 F583W none none none none 1 N/A WD1639-REF1 3 FGS POS 1 F583W none none none none 1 N/A WD1639-REF2 4 FGS POS 1 F583W none none none none 1 N/A WD1639-REF3 5 FGS POS 1 F583W none none none none 1 N/A WD1639+153 6 FGS POS 1 F583W none none none none 1 N/A WD1639-REF1 7 FGS POS 1 F583W none none none none 1 N/A WD1639-REF7 8 FGS POS 1 F583W none none none none 1 N/A WD1639+153 9 FGS POS 1 F583W none none none none 1 N/A WD1639-REF1 10 FGS POS 1 F583W none none none none 1 N/A WD1639-REF7 11 FGS POS 1 F583W none none none none 1 N/A 10931( 7) - 04/03/07 15:21 - [ 7] Visit: 03 Visit Priority: Visit Requirements: PCS MODE FINE; SCHED 70%; ORIENT 274.0D TO 275.0 D; BETWEEN 01-MAR- 2007:00:00:00 AND 16-MAR-2007:00:00:00 On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 WD1639+153 FGS TRANS 1 F583W STEP-SIZE=0.5,SCANS=25 1 770 S POS TARG 0,-17; GS ACQ SCENARIO ONEB1T; SEQ 1-11 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 2 WD1639+153 FGS POS 1 F583W 1 25 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 3 WD1639-REF1 FGS POS 1 F583W 1 5 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 4 WD1639-REF2 FGS POS 1 F583W 1 10 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 5 WD1639-REF3 FGS POS 1 F583W 1 5 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 6 WD1639+153 FGS POS 1 F583W 1 25 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 7 WD1639-REF4 FGS POS 1 F583W 1 5 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 8 WD1639+153 FGS POS 1 F583W 1 25 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 9 WD1639-REF1 FGS POS 1 F583W 1 10 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 10 WD1639+153 FGS POS 1 F583W 1 5 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 11 WD1639-REF4 FGS POS 1 F583W 1 5 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ WD1639+153 1 FGS TRANS 1 F583W none none none none 1 N/A WD1639+153 2 FGS POS 1 F583W none none none none 1 N/A WD1639-REF1 3 FGS POS 1 F583W none none none none 1 N/A WD1639-REF2 4 FGS POS 1 F583W none none none none 1 N/A WD1639-REF3 5 FGS POS 1 F583W none none none none 1 N/A WD1639+153 6 FGS POS 1 F583W none none none none 1 N/A WD1639-REF4 7 FGS POS 1 F583W none none none none 1 N/A WD1639+153 8 FGS POS 1 F583W none none none none 1 N/A WD1639-REF1 9 FGS POS 1 F583W none none none none 1 N/A WD1639+153 10 FGS POS 1 F583W none none none none 1 N/A 10931( 7) - 04/03/07 15:21 - [ 8] Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ WD1639-REF4 11 FGS POS 1 F583W none none none none 1 N/A 10931( 7) - 04/03/07 15:21 - [ 9] Visit: 04 Visit Priority: Visit Requirements: PCS MODE FINE; SCHED 70%; ORIENT 265.0D TO 270.0 D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 WD1818+126 FGS TRANS 1 F583W STEP-SIZE=0.4,SCANS=20 1 830 S POS TARG 0, 0; SEQ 1-12 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 2 WD1818+126 FGS POS 1 F583W 1 25 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 3 WD1818-GSC1 FGS POS 1 F583W 1 10 S SAME POS AS 1 -REF1 ------------------------------------------------------------------------------------------------------------------------------------ 4 WD1818-GSC1 FGS POS 1 F583W 1 10 S SAME POS AS 1 -REF2 ------------------------------------------------------------------------------------------------------------------------------------ 5 WD1818-GSC1 FGS POS 1 F583W 1 10 S SAME POS AS 1 -REF3 ------------------------------------------------------------------------------------------------------------------------------------ 6 WD1818-GSC2 FGS POS 1 F583W 1 15 S SAME POS AS 1 -REF1 ------------------------------------------------------------------------------------------------------------------------------------ 7 WD1818-GSC2 FGS POS 1 F583W 1 15 S SAME POS AS 1 -REF2 ------------------------------------------------------------------------------------------------------------------------------------ 8 WD1818-GSC1 FGS POS 1 F583W 1 10 S SAME POS AS 1 -REF2 ------------------------------------------------------------------------------------------------------------------------------------ 9 WD1818-GSC2 FGS POS 1 F583W 1 15 S SAME POS AS 1 -REF3 ------------------------------------------------------------------------------------------------------------------------------------ 10 WD1818-GSC2 FGS POS 1 F583W 1 15 S SAME POS AS 1 -REF4 ------------------------------------------------------------------------------------------------------------------------------------ 11 WD1818+126 FGS POS 1 F583W 1 25 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 12 WD1818-GSC1 FGS POS 1 F583W 1 10 S SAME POS AS 1 -REF1 ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ WD1818+126 1 FGS TRANS 1 F583W none none none none 1 N/A 10931( 7) - 04/03/07 15:21 - [ 10] Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ WD1818+126 2 FGS POS 1 F583W none none none none 1 N/A WD1818-GSC1-REF1 3 FGS POS 1 F583W none none none none 1 N/A WD1818-GSC1-REF2 4 FGS POS 1 F583W none none none none 1 N/A WD1818-GSC1-REF3 5 FGS POS 1 F583W none none none none 1 N/A WD1818-GSC2-REF1 6 FGS POS 1 F583W none none none none 1 N/A WD1818-GSC2-REF2 7 FGS POS 1 F583W none none none none 1 N/A WD1818-GSC1-REF2 8 FGS POS 1 F583W none none none none 1 N/A WD1818-GSC2-REF3 9 FGS POS 1 F583W none none none none 1 N/A WD1818-GSC2-REF4 10 FGS POS 1 F583W none none none none 1 N/A WD1818+126 11 FGS POS 1 F583W none none none none 1 N/A WD1818-GSC1-REF1 12 FGS POS 1 F583W none none none none 1 N/A 10931( 7) - 04/03/07 15:21 - [ 11] Summary Form for Proposal 10931 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations FGS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes TRANS POS ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters STEP-SIZE=0.5 SCANS=25 STEP-SIZE=0.4 SCANS=20 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE FINE; SCHED 70%; ORIENT 135.0D TO 135.0 D; BETWEEN 06-JUL-2006 00 00 00 AND 15-JUL-2006 00 00 00; POS TARG 0,-17; SEQ 1-11 NON-INT; SAME POS AS 1; ORIENT 308.0D TO 308.0 D; BETWEEN 15-JAN-2007 00 00 00 AND 30-JAN-2007 00 00 00; ORIENT 274.0D TO 275.0 D; BETWEEN 01-MAR-2007 00 00 00 AND 16-MAR-2007 00 00 00; GS ACQ SCENARIO ONEB1T; ORIENT 265.0D TO 270.0 D; POS TARG 0, 0; SEQ 1-12 NON-INT; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F583W ------------------------------------------------------------------------------------------------------------------------------------ Target Names WD1639+153 WD1639-REF1 WD1639-REF3 WD1639-REF7 WD1639-REF2 WD1639-REF4 WD1818+126 WD1818-GSC1-REF1 WD1818-GSC1-REF2 WD1818-GSC1-REF3 WD1818-GSC2-REF1 WD1818-GSC2-REF2 WD1818-GSC2-REF3 WD1818-GSC2-REF4 ------------------------------------------------------------------------------------------------------------------------------------