9130( 3) - 08/22/01 13:55 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9130 Version: 3 Check-in Date: 22-Aug-2001 13:54:44 1.Proposal Title: The iron abundance in the Magellanic Clouds and Bridge ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 10 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Philip Dufton The Queen's University of Belfast CoI: Dr. Stephen Smartt Institute of Astronomy, Cambridge N CoI: Dr. Danny Lennon Isaac Newton Group N CoI: Dr. Robert Rolleston Queen's University of Belfast Y CoI: Prof. Francis Keenan Queen's University of Belfast N ------------------------------------------------------------------------------------ 5. Abstract The spectra of early-type main-sequence stars provide excellent probes of the current chemical composition of galaxies. The physics of their atmospheres are well understood, while their surfaces will normally be unaffected by the products of interior nuclear reactions. We have previously used optical spectra of such targets to map the abundances of light metals (such as C, N, O, Mg, Si) in our Galaxy, in the Magellanic Clouds and in a Bridge of material connecting the latter. However, we have been unable to obtain iron group abundances for the Magellanic System due to the intrinsic weakness of the optical Fe II/III spectra and the system's low metallicity. Here we propose observations of strong Fe III ultraviolet lines for two Bridge stars, plus an LMC target. These will be supplemented by AAT and ESO optical spectroscopy plus HST spectra for two previously observed targets in the middle of the Bridge and in the SMC. Using non-LTE model atmosphere and careful differential methods, relative abundances accurate to 0.1 dex should be achievable. These five stars will allow us to determine key element abundances and ratios (eg. O/Fe) in both Clouds and across the Bridge. As well as providing the first detailed comparison of the Bridge's metallicity with those of its parent Clouds, it will clarify the evolutionary history of this system. ------------------------------------------------------------------------------------ 9130( 3) - 08/22/01 13:55 - [ 2] Observations Description ------------------------ We will observe our 3 targets using STIS and the moderate resolution grating G230M (resolution ~ 15kms) in the spectral region 1890-1980Angstrom (central wavelength 1933Angstrom). This grating was chosen instead of, for example the E230M, as it has a higher throughput; additionally the observational setup will be identical to that used for the SMC star, AV304, by Dr. G. Peters, which will simplify comparisons. The spectral region contains the strong Fe III multiplet near 1910Angstrom\ that we have previously used to estimate iron abundances from IUE spectra of B-type stars. Count rates and exposure times have been estimated from a Kurucz low metallicity model atmosphere with the appropriate effective temperature and gravity using the STIS Exposure Time Calculator on the WWW. Our low resolution IUE observations of a cooler supergiant, DI1194, implies that reddening in the Magellanic Bridge is very small; indeed, Demers and Battinelli (1998) reported reddenings of E(B-V)~0.08 towards the associations containing DI 1239 and DGIK 975. For the LMC star LH 10-3270, this object is associated with the H II region LH 10. We have adopted the reddening value of E(B-V)~0.20 -- reported by Parker et al. (1992) for this object. In Figure 2, a synthetic spectrum is shown for the atmospheric parameters of our targets and an iron underabundance of 1.0 dex; the spectrum has been convolved with a projected rotational velocity profile of 70 km/s (our estimated value for DGIK 975 and larger than that for LH 10-3270). Also plotted is the spectrum degraded to a s/n ratio of 30 and to the appropriate spectral resolution and pixel size of the proposed observations. The components of the Fe III multiplet are clearly visible. Exposure times of 274 min, 300 min & 284 min have been calculated for DI 1239, DGIK 975 and LH 10-3270 respectively, so as to provide a S/N~30 per resolution element in the stellar continuua. Orbit estimates have been determined from the exposure time estimates using the procedures outlined in the STIS manual and from our experience of Phase II submissions, and including the relevant overhead requirements. Thus, we require 7 orbits per star to complete the observations using the standard orbital visibility. Real Time Justification ----------------------- None. None. Calibration Justification ------------------------- No special requirements for this program. Additional Comments ------------------- ------------------------------------------------------------------------------------ 9130( 3) - 08/22/01 13:55 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 DI1239 STAR, B0-B2 V-IV RA=02H 30M 40.84S +/- 0.3", DEC= J2000 V = +152 V = 15.24+/-0.10 -74D 4' 45.7" +/- 0.3", PLATE- B-V = -0.2+/-0.1 ID=04BU E(B-V) = 0.08+/-0.05 TYPE=B1IV Coordinate Source: GUIDE_STAR_CATALOG 2 DGIK975 STAR, B0-B2 V-IV RA=04H 19M 58.63S +/- 0.3", DEC= J2000 V = +210 V = 15.05+/-0.1 -73D 52' 25.8" +/- 0.3", PLATE- B-V = -0.19+/-0.1 ID=00RF E(B-V) = 0.12+/-0.05 TYPE=B2IV Coordinate Source: GUIDE_STAR_CATALOG 3 LH10-3270 STAR, B0-B2 V-IV RA=04H 57M 21.23S +/- 0.3", DEC= J2000 V = +215 V = 14.90+/-0.1 -66D 25' 1.2" +/- 0.3", PLATE- B-V = -0.20+/-0.1 ID=06AF E(B-V) = 0.20+/-0.05 TYPE=B0.5V Coordinate Source: GUIDE_STAR_CATALOG 9130( 3) - 08/22/01 13:55 - [ 4] Visit: 01 Visit Priority: Visit Requirements: 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 DI1239 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 2.0 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 DI1239 STIS/C ACQ/PEA 52X0.1 MIRROR 1 2.0 S CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 DI1239 STIS/N ACCUM 52X0.1 G230M 1933 1 2450 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 DI1239 STIS/N ACCUM 52X0.1 G230M 1933 1 3235 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 5 DI1239 STIS/N ACCUM 52X0.1 G230M 1933 1 3235 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 6 DI1239 STIS/N ACCUM 52X0.1 G230M 1933 1 3235 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9130( 3) - 08/22/01 13:55 - [ 5] Visit: 02 Visit Priority: Visit Requirements: 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 DI1239 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 2.0 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 DI1239 STIS/C ACQ/PEA 52X0.1 MIRROR 1 2.0 S CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 DI1239 STIS/N ACCUM 52X0.1 G230M 1933 1 2450 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 DI1239 STIS/N ACCUM 52X0.1 G230M 1933 1 3235 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 5 DI1239 STIS/N ACCUM 52X0.1 G230M 1933 1 3235 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9130( 3) - 08/22/01 13:55 - [ 6] Visit: 03 Visit Priority: Visit Requirements: 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 DGIK975 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 2.0 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 DGIK975 STIS/C ACQ/PEA 52X0.1 MIRROR 1 2.0 S CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 DGIK975 STIS/N ACCUM 52X0.1 G230M 1933 1 2450 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 DGIK975 STIS/N ACCUM 52X0.1 G230M 1933 1 3235 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 5 DGIK975 STIS/N ACCUM 52X0.1 G230M 1933 1 3235 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 6 DGIK975 STIS/N ACCUM 52X0.1 G230M 1933 1 3235 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9130( 3) - 08/22/01 13:55 - [ 7] Visit: 04 Visit Priority: Visit Requirements: 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 DGIK975 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 2.0 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 DGIK975 STIS/C ACQ/PEA 52X0.1 MIRROR 1 2.0 S CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 DGIK975 STIS/N ACCUM 52X0.1 G230M 1933 1 2450 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 DGIK975 STIS/N ACCUM 52X0.1 G230M 1933 1 3235 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 5 DGIK975 STIS/N ACCUM 52X0.1 G230M 1933 1 3235 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9130( 3) - 08/22/01 13:55 - [ 8] Visit: 05 Visit Priority: Visit Requirements: 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 LH10-3270 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 1.5 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 LH10-3270 STIS/C ACQ/PEA 52X0.1 MIRROR 1 1.5 S CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 LH10-3270 STIS/N ACCUM 52X0.1 G230M 1933 1 2365 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 LH10-3270 STIS/N ACCUM 52X0.1 G230M 1933 1 3150 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 5 LH10-3270 STIS/N ACCUM 52X0.1 G230M 1933 1 3150 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 6 LH10-3270 STIS/N ACCUM 52X0.1 G230M 1933 1 3150 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9130( 3) - 08/22/01 13:55 - [ 9] Visit: 06 Visit Priority: Visit Requirements: 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 LH10-3270 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 1.5 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 LH10-3270 STIS/C ACQ/PEA 52X0.1 MIRROR 1 1.5 S CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 LH10-3270 STIS/N ACCUM 52X0.1 G230M 1933 1 2365 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 LH10-3270 STIS/N ACCUM 52X0.1 G230M 1933 1 3150 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 5 LH10-3270 STIS/N ACCUM 52X0.1 G230M 1933 1 3150 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 9130( 3) - 08/22/01 13:55 - [ 10] Summary Form for Proposal 9130 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G230M ------------------------------------------------------------------------------------------------------------------------------------ Target Names DI1239 DGIK975 LH10-3270 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1933 ------------------------------------------------------------------------------------------------------------------------------------