11294( 4) - 05/08/07 16:15 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 11294 Version: 4 Check-in Time: 08-May-2007 20:15:04 STScI Edit Number: 2 Title The orbit of the most massive known astrometric binary ------------------------------------------------------------------------------------ Type Cycle Parallel Pointing Tolerance GO 16 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Jesus Maiz Apellaniz Instituto de Astrofisica de Andalucia (IAA) CoI: Dr. Edmund Nelan Space Telescope Science Institute N CoI: Dr. Nolan R. Walborn Space Telescope Science Institute N CoI: Dr. Nidia Morrell Carnegie Institution of Washington N CoI: Dr. Virpi S. Niemela Universidad Nacional de La Plata (UNLP) N CoI: Dr. Paula Benaglia Universidad Nacional de La Plata (UNLP) N CoI: Mr. Alfredo Sota Space Telescope Science Institute N ------------------------------------------------------------------------------------ Abstract We have recently used FGS and HRC observations to (a) resolve HD 93129A into two components with very similar optical/UV colors and a magnitude difference of 1.3 and to (b) detect their relative orbital motion over a span of 8 years. HD 93129Aa is the prototype O2 If* star, with an evolutionary mass near 100 M_Sun, while Ab is likely to be a very early O main-sequence star with a similar or only slightly smaller mass. Our HST astrometric measurements yield a total mass above 100 M_Sun, thus confirming the extremely high mass of the binary, and indicate that the system appears to be approaching periastron. We request new FGS observations to (a) calculate the mass ratio of the system by measuring the orbit of each of the components with respect to the nearby stars, (b) obtain the periastron epoch, and (c) start measuring the orbit in order to produce an estimate of the total mass. These measurements are crucial to shed light on the value of the stellar upper mass limit. ------------------------------------------------------------------------------------ 11294( 4) - 05/08/07 16:15 - [ 2] Observations Description ------------------------ We propose observing HD 93129 at three different epochs using ACS/HRC and FGS. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 11294( 4) - 05/08/07 16:15 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD93129A STAR, OF, SUPERGIANT O, RA=10H43M57.5000S +/- 0.1", J2000 V = 7.3+/-0.1 WIND DEC=-59D32'53.00" +/- 0.1" O2 If* Reference Frame: ICRS 2 REF1 CALIBRATION, RA=10H43M57.3000S +/- 0.1", J2000 V = 12.8+/-0.2 ASTROMETRIC DEC=-59D32'8.40" +/- 0.1" Reference Frame: ICRS 3 REF2 CALIBRATION, RA=10H43M56.2600S +/- 0.1", J2000 V = 13.34+/-0.2 ASTROMETRIC DEC=-59D32'28.20" +/- 0.1" Reference Frame: ICRS 4 REF3 CALIBRATION, RA=10H44M2.7800S +/- 0.1", DEC=- J2000 V = 12.59+/-0.2 ASTROMETRIC 59D32'28.80" +/- 0.1" Reference Frame: ICRS 5 REF4 CALIBRATION, RA=10H44M3.8500S +/- 0.1", DEC=- J2000 V = 13.21+/-0.2 ASTROMETRIC 59D33'10.90" +/- 0.1" Reference Frame: ICRS 6 REF5 CALIBRATION, RA=10H43M59.1200S +/- 0.1", J2000 V = 12.71+/-0.2 ASTROMETRIC DEC=-59D33'20.10" +/- 0.1" Reference Frame: ICRS 7 REF6 CALIBRATION, RA=10H43M57.6600S +/- 0.1", J2000 V = 12.34+/-0.2 ASTROMETRIC DEC=-59D33'38.80" +/- 0.1" Reference Frame: ICRS 8 REF7 CALIBRATION, RA=10H43M53.7000S +/- 0.1", J2000 V = 12.42+/-0.2 ASTROMETRIC DEC=-59D33'28.70" +/- 0.1" Reference Frame: ICRS 9 REF8 CALIBRATION, RA=10H43M46.6900S +/- 0.1", J2000 V = 9.5+/-0.2 ASTROMETRIC DEC=-59D32'54.50" +/- 0.1" Reference Frame: ICRS 11294( 4) - 05/08/07 16:15 - [ 4] Visit: 02 Visit Priority: Visit Requirements: PCS MODE FINE; SCHED 70%; ORIENT 144.0D TO 145.0 D; BETWEEN 01-JUL- 2007:00:00:00 AND 31-AUG-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 HD93129A FGS TRANS 1 F5ND SCANS=1,STEP-SIZE=2 1 75 S SEQ 1-17 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 2 HD93129A FGS TRANS 1 F5ND SCANS=16,STEP-SIZE=0.5 1 992 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 3 HD93129A FGS POS 1 F5ND 1 6 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 4 REF1 FGS POS 1 F583W 1 6 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 5 REF2 FGS POS 1 F583W 1 6 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 6 REF3 FGS POS 1 F583W 1 6 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 7 REF4 FGS POS 1 F583W 1 6 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 8 REF1 FGS POS 1 F583W 1 6 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 9 HD93129A FGS POS 1 F5ND 1 6 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 10 REF8 FGS POS 1 F583W 1 6 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 11 REF7 FGS POS 1 F583W 1 6 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 12 REF6 FGS POS 1 F583W 1 6 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 13 REF4 FGS POS 1 F583W 1 6 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 14 REF5 FGS POS 1 F583W 1 6 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 15 HD93129A FGS POS 1 F5ND 1 6 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 16 REF1 FGS POS 1 F583W 1 6 S SAME POS AS 1 ------------------------------------------------------------------------------------------------------------------------------------ 17 REF4 FGS POS 1 F583W 1 6 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 | ------------------------------------------------------------------------------------------------------------------------------------ 11294( 4) - 05/08/07 16:15 - [ 5] 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 | ------------------------------------------------------------------------------------------------------------------------------------ HD93129A 1 FGS TRANS 1 F5ND none none none none 1 N/A HD93129A 2 FGS TRANS 1 F5ND none none none none 1 N/A HD93129A 3 FGS POS 1 F5ND none none none none 1 N/A REF1 4 FGS POS 1 F583W none none none none 1 N/A REF2 5 FGS POS 1 F583W none none none none 1 N/A REF3 6 FGS POS 1 F583W none none none none 1 N/A REF4 7 FGS POS 1 F583W none none none none 1 N/A REF1 8 FGS POS 1 F583W none none none none 1 N/A HD93129A 9 FGS POS 1 F5ND none none none none 1 N/A REF8 10 FGS POS 1 F583W none none none none 1 N/A REF7 11 FGS POS 1 F583W none none none none 1 N/A REF6 12 FGS POS 1 F583W none none none none 1 N/A REF4 13 FGS POS 1 F583W none none none none 1 N/A REF5 14 FGS POS 1 F583W none none none none 1 N/A HD93129A 15 FGS POS 1 F5ND none none none none 1 N/A REF1 16 FGS POS 1 F583W none none none none 1 N/A REF4 17 FGS POS 1 F583W none none none none 1 N/A 11294( 4) - 05/08/07 16:15 - [ 6] Summary Form for Proposal 11294 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations FGS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes TRANS POS ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SCANS=1 STEP-SIZE=2 SCANS=16 STEP-SIZE=0.5 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE FINE; SCHED 70%; ORIENT 144.0D TO 145.0 D; BETWEEN 01-JUL-2007 00 00 00 AND 31-AUG-2007 00 00 00; SEQ 1-17 NON-INT; SAME POS AS 1; ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F5ND F583W ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD93129A REF1 REF2 REF3 REF4 REF8 REF7 REF6 REF5 ------------------------------------------------------------------------------------------------------------------------------------