6040( 6) - 11/10/95 09:48 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6040 Version: 6 Check-in Date: ********** 1.Proposal Title: Ultra--high angular resolution of O3 stars in the Carina Nebula and in the LMC ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Hot Stars GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: R. Burg Johns Hopkins University CoI: M. G. Lattanzi Space Telescope Science Institute Y CoI: N. R. Walborn Space Telescope Science Institute N CoI: J. E. Pringle Institute of Astronomy N CoI: J.L. Hershey Space Telescope Science Institute N CoI: B.J. McLean Space Telescope Science Institute N CoI: I.N. Evans Space Telescope Science Institute N ------------------------------------------------------------------------------------ 6. Abstract The upper mass limit for individual stars remains an open question of great importance in astronomy. Theory is not currently capable of placing a firm upper mass limit and, therefore, the problem is an observational one. O3 stars in giant HII regions are the hottest and presumably the most massive Population I stars. Of the 70 definite and possible members of this class, 59 are in the Magellanic Clouds (Walborn 1994). The Carina Nebula has the highest concentration of these stars in the Milky Way and hence provides the most accessible laboratory for the investigation of the most massive stars. The LMC has the most extreme examples; i.e., those objects which are candidates for the most massive star. We propose to use the Fine Guidance Sensor (FGS) in its interferometric mode to investigate a complete sample of six O3 stars in Carina and three extreme objects in the LMC in order to establish if these stars are massive single stars or if, like R136a in the LMC, they are multiple star systems. ------------------------------------------------------------------------------------ 6040( 6) - 11/10/95 09:48 - [ 2] Observations Description ------------------------ All of our proposed exposures use the TRANS mode of the astrometer FGS (FGS 3). As described in the FGS Instrument Handbook (Version 4.0), and in recently published papers (Bernacca et al. 1993, Lattanzi et al. 1994) this mode samples the interference fringe produced by the Koester's prism interferometer, the ``heart'' of the Fine Guidance Sensor. There are two Koester's prism interferometers in each FGS. These are fed by a beam--splitter to give sensitivity in two orthogonal directions, usually referred to as X and Y axes. Therefore, each FGS3 TRANS scan produces two fringes which can then be independently analyzed for signatures other than those characteristic of the FGS3 standard single star UP69. Indeed, deviations from the single star fringes are used to measure double, or multiple, stars projected separations. On--sky separation and position angle are easily derived from these measurements and telescope attitude data (Bernacca et al. 1993 and references therein). Accurate V magnitudes are also derived from the same counts used to construct the fringes and provided by the 4 photomultipliers (two per axis) which detect the photons from the Koester's prisms (Bucciarelli et al. 1994; Bernacca et al. 1994). Experience with observations very similar to those proposed here (Bernacca et al. 1993 and 1994; Lattanzi et al. 1994, and references therein) indicate that the FGS interferometers are capable of measuring separations smaller than 0.015 arcsec and position angles to better than 1 deg. We request one visit per target. Following the procedure for the calculation of the number of orbits given in the Cycle 5 Phase I Proposal Instructions volume, each visit comprises a guide star acquisition (12 min), the set--up time (including the selected filter) for TRANS mode (3 min), then the science exposure. Our science exposure consists of 30 TRANS scans of 2sec point1 on the sky each (i.e., 1sec point5 per FGS axis) sampled every 0sec point0008 (the pixel size per axis is 0sec point0006). Since each sample takes a fixed 0.025 sec, the 30 scans take 31.3 min, for a total of 12+3+31.3 = 46.3 min per visit. This is less than the visibility period per orbit. Therefore, we request one orbit per target. Recent observations (Lattanzi et al. 1994 and references therein) show that scans with the same pixel size, and through the PUPIL element give optimal resolution with minimum scan time. Consecutive scans are required for three reasons. First, spacecraft jitter can corrupt fringes. With multiple scans one can identify jitter--corrupted fringes and reject them. Second, analysis of multiple scans is the only reliable way to check on the repeatibility of a detection. Finally, multiple scans are co--added to increase the signal--to-- noise ratio (S/N). This is crucial for best resolution during the reductions and to allow for any star variability, and higher background due to diffuse light emission from nebulosity around the stars. Successful exposures should yield co--added fringes with typical S/N > 60. Two of our targets are too bright to be observed with the PUPIL element and the neutral density filter (F5ND) is required. This filter as been very little used with TRANS observations and some degradation of the fringes is expected. Also, it is necessary to have F5ND fringes of the FGS single star standard UP69. Routine TRANS mode calibration observations on UP69 run by the STScI do not foresee the F5ND filter. We have therefore added one calibration orbit on UP69. Length, pixel size, and number of scans in the calibration visit are the same as for the science observations. This calibration should be placed as close in time as possible to the F5ND science observations. Should the STScI Cycle 5 calibration plan for TRANS mode include the F5ND filter, the calibrations orbit requested would not be necessary. Real Time Justification ----------------------- None. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 6040( 6) - 11/10/95 09:48 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: __Diagnostic-Sum-Section__ Software-Version (Contro, ------------------------------------------------------------------------------------ 6040( 6) - 11/10/95 09:48 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HDE269810 EXT-STAR, Giant O RA = 05H 35M 13.93S +/- 0.1S, 2000 V=12.3 +/- 0.1 DEC = -67D 33' 26.7" +/- 1", B-V=-0.23 PLATE-ID=06B0 TYPE=O3III 2 LMC-053705- EXT-STAR, Giant O RA = 05H 37M 05.57S +/- 0.1S, 2000 V=13.1 +/- 0.1 662136 DEC = -66D 21' 35.4" +/- 1", B-V=-0.12 PLATE-ID=06B0 TYPE=O3III 3 LMC-045659- EXT-STAR, Giant O RA= 04H 56M 58.92S +/- 0.1S, DEC 2000 V=12.66 +/- 0.01 662438 = -66D 24' 39.0" +/- 1", PLATE- B-V=-0.11 +/- 0.01 ID=06AF TYPE=O3III 4 HD93129A STAR, Supergiant O RA = 10H 43M 57.30S +/- 0.1S, 2000 V=7.3 +/- 0.1 DEC = -59D 32' 51.2" +/- 1", B-V=0.22 PLATE-ID=ZZZQ Comments: Target HD93129B is TRANSed together with HD93129A 5 HD93205 STAR, Main Sequence O RA = 10H 44M 33.90S +/- 0.1S, 2000 V=7.8 +/- 0.1 DEC = -59D 44' 15.2" +/- 1", B-V=0.05 PLATE-ID=ZZZQ 6 HD93250 STAR, Main Sequence O RA = 10H 44M 45.13S +/- 0.1S, 2000 V=7.4 +/- 0.1 DEC = -59D 33' 55.0" +/- 1", B-V=0.15 PLATE-ID=ZZZQ 7 HD303308 STAR, Main Sequence O RA = 10H 45M 06.05S +/- 0.1S, 2000 V=8.2 +/- 0.1 DEC = -59D 40' 06.1" +/- 1", B-V=0.13 PLATE-ID=ZZZQ 8 HD93128 STAR, Main Sequence O RA = 10H 43M 54.00S +/- 0.1S, 2000 V=8.8 +/- 0.1 DEC = -59D 32' 56.0" +/- 1", B-V=0.24 PLATE-ID=ZZZQ 9 Mk42 EXT-STAR, Supergiant O RA=05H 38M 42.22S +/- 0.05S, J2000 V=12.7 +/- 0.1 DEC=-69D 05' 55.3" +/- 0.1" B-V=0.0 +/- 0.1 6040( 6) - 11/10/95 09:48 - [ 5] Visit: 01 Visit Requirements: PCS MODE F On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HDE269810 FGS TRANS 3 PUPIL STEP-SIZE=0.6, 1 1875S SCANS=30 ------------------------------------------------------------------------------------------------------------------------------------ 6040( 6) - 11/10/95 09:48 - [ 6] Visit: 02 Visit Requirements: PCS MODE F ORIENT 355D TO 5D ON HOLD On Hold Comments: Waiting for non-HST data Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 LMC-053705- FGS TRANS 3 PUPIL STEP-SIZE=0.6, 1 1625S 662136 SCANS=26 ------------------------------------------------------------------------------------------------------------------------------------ 6040( 6) - 11/10/95 09:48 - [ 7] Visit: 03 Visit Requirements: PCS MODE F On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 LMC-045659- FGS TRANS 3 PUPIL STEP-SIZE=0.6, 1 1875S 662438 SCANS=30 ------------------------------------------------------------------------------------------------------------------------------------ 6040( 6) - 11/10/95 09:48 - [ 8] Visit: 04 Visit Requirements: PCS MODE F ORIENTation 101D TO 107D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD93129A FGS TRANS 3 F5ND STEP-SIZE=1.2, 1 2004.3S SCANS=17 ------------------------------------------------------------------------------------------------------------------------------------ 2 HD93129A FGS TRANS 3 F5ND STEP-SIZE=1.2, 1 2240.1S SCANS=19 ------------------------------------------------------------------------------------------------------------------------------------ 6040( 6) - 11/10/95 09:48 - [ 9] Visit: 05 Visit Requirements: PCS MODE F On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD93205 FGS TRANS 3 F5ND STEP-SIZE=0.6, 1 1812.5S SCANS=29 ------------------------------------------------------------------------------------------------------------------------------------ 6040( 6) - 11/10/95 09:48 - [ 10] Visit: 06 Visit Requirements: PCS MODE F On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD93250 FGS TRANS 3 F5ND STEP-SIZE=0.6, 1 1812.5S SCANS=29 ------------------------------------------------------------------------------------------------------------------------------------ 6040( 6) - 11/10/95 09:48 - [ 11] Visit: 07 Visit Requirements: PCS MODE F On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD303308 FGS TRANS 3 PUPIL STEP-SIZE=0.6, 1 1812.5S SCANS=29 ------------------------------------------------------------------------------------------------------------------------------------ 6040( 6) - 11/10/95 09:48 - [ 12] Visit: 08 Visit Requirements: PCS MODE F On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD93128 FGS TRANS 3 PUPIL STEP-SIZE=0.6, 1 1812.5S SCANS=29 ------------------------------------------------------------------------------------------------------------------------------------ 6040( 6) - 11/10/95 09:48 - [ 13] Visit: 09 Visit Requirements: ORIENT 297D TO 307D On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 Mk42 FGS TRANS 3 PUPIL STEP-SIZE=2, 1 1769.63 SCANS=13 ------------------------------------------------------------------------------------------------------------------------------------ 6040( 6) - 11/10/95 09:48 - [ 14] Summary Form for Proposal 6040 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FGS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes TRANS ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters STEP-SIZE=0.6 SCANS=30 SCANS=26 SCANS=17 SCANS=19 SCANS=29 SCANS=13 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Hot Stars ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE F PCS MODE F ORIENT 355D TO 5D ON HOLD PCS MODE F ORIENTation 101D TO 107D ORIENT 297D TO 307D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements PUPIL F5ND ------------------------------------------------------------------------------------------------------------------------------------ Target Names HDE269810 LMC-053705-662136 LMC-045659-662438 HD93129A HD93205 HD93250 HD303308 HD93128 Mk42 ------------------------------------------------------------------------------------------------------------------------------------