6599( 7) - 06/25/96 12:10 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6599 Version: 7 Check-in Date: 25-Jun-1996 12:01:45 1.Proposal Title: Boron in Halo Giants : A Solution to the D+3He Crisis in Big Bang Nucleosynthesis? ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle STELLAR POPULATIONS GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: CONSTANTINE DELIYANNIS YALE UNIVERSITY CoI: Douglas Duncan University of Chicago N ------------------------------------------------------------------------------------ 6. Abstract We propose to make Boron observations which can definitively distinguish between mass loss and mixing as the cause of the low ^12C/^13C ratios seen in evolved halo stars. This can help solve a long-standing problem which signals a fundamental failure of standard stellar evolution theory. As standard models evolve off the main sequence and their convection zones deepen, CN-synthesized ^13C is dredged up, lowering the ^12C/^13C ratio from ~ 90 to about 50, in agreement with observation. However, the observed C ratio in more evolved stars declines precipitously, sharply contradicting the models, and reaches the CN-cycle equilibrium value of 3 -- 4. Two proposed mechanisms remain viable to explain this: giant branch mass loss and mixing. Boron abundances will remain constant in the case of mass loss, but will decline below their maximal dilution value in the case of mixing. This allows the proposed observations to clearly discriminate between the models, possibly with important implications for cosmology. If mixing is correct, then the ^3He (including primordial ^3He) is destroyed, moving the heretofore stringent D+^3He constraint of big bang nucleosynthesis (BBN) to lower Omega_b. This could help resolve the current crisis in BBN, caused by increasingly precise observations of light element abundances which do not agree with theoretical predictions. Furthermore, mixing of freshly synthesized ^4He could lower globular cluster age estimates. ------------------------------------------------------------------------------------ 6599( 7) - 06/25/96 12:10 - [ 2] Observations Description ------------------------ A single GHRS observation will be made of each star (below), using the G270M grating centered at 2500 A, the wavelength of the B resonance lines. The same techniques (FP-SPLIT, the best vignetting corrections, etc.) used for achieving the highest S/N in our Cycle 0, 2, 3, 4, and 5 projects (section 15) will be used here. All long exposures will be broken into subexposures as is recommended. TWO OF OUR TARGETS ARE IN THE CONTINUOUS VIEWING ZONE. One would have taken 20 orbits if not in the CVZ; we can do it in 9. The other would have taken 7 orbits if not in the CVZ; we can do it in 3. We propose to observe one calibration star, and three cooler stars in the Li-depleted and C-ratio depleted region. Our first target is a calibration target, HD 6755, in which Li dilution is ending, and in which B dilution is expected to be ending. When combined with our Cycle 5 GO proposal 5857 calibrators HD 211998 (in which Li dilution has progressed significantly, but B dilution should just be starting) and HD 175305 (in which both Li and B dilution should be complete), one of which has slightly larger effective temperature and the other lower Teff, we should be able to establish empirically both the onset of B dilution as well as the critically important maximum extent of the standard Boron dilution (see Figure 1b). It is relative to this dilution level that the cooler stars will either favor mass loss (with similar levels of B depletion) or mixing (with greater B depletion). Next is HD 18907, with Li (our own data, being analyzed) at least an order of magnitude below the diluted Li plateau. This star will be compared to HD 3546 from GO proposal 5857 which is of similar Teff and metallicity. Next is HD 63791, a star of ``ideal'' metallicity at [Fe/H] = P 1.8, with ^12C/^13C ratio (at ~ 8) well below that ( ~ 50) of standard models. Finally, we wish to observe the slightly cooler HD 142691, another star of ``ideal'' metallicity ( P 1.5), which has similar Teff as the other cool star from GO proposal 5857, HD 122563. This will bring the total number of objects in the Li-depleted and C ratio- depleted region to 5 between Cycles 5 and 6. Depletion of subgiant Boron abundances will be determined by comparing to the mean B-Fe trend defined by Duncan et al 1993, and our Cycle 3 and 4 projects (section 15). Note that in extensive Beryllium studies underway with the Keck and other telescopes, we have found that the Be-Fe trend in normal dwarfs is very tight (e.g. Deliyannis, Boesgaard, King, and Duncan, 1995, submitted to AJ). Since it is thought that Be and B are produced together by cosmic rays interacting with the ISM, this re-inforces the tightness of the calibrating B- Fe relation. Our previous experience has verified that S/N ~ 80 P 100 is best to derive accurate abundances from the weak B lines. To determine the exposure times, we have used a) the absolute fluxes at 2500 A for our GO proposal 5857 program stars HD 175305, 3546, 122596, and 103095 observed with IUE and reported by Cacciari et al 1985, A&AS, 61, 407, b) absolute fluxes from the same source for several other stars, thus providing an empirical calibration for the dependence of the 2500 A flux on Teff, and c) we have taken into account the differences in V and Teff between these stars and our program stars. Note that we have previously calibrated the Boron region in cool stars using two (low gravity) Hyades giants, giants b Gem and Arcturus, and the (high gravity) dwarf Gmb 1830. Real Time Justification ----------------------- none Calibration Justification ------------------------- none Additional Comments ------------------- none ------------------------------------------------------------------------------------ 6599( 7) - 06/25/96 12:10 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS Email: , ------------------------------------------------------------------------------------ 6599( 7) - 06/25/96 12:10 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD6755 STAR,G V-IV RA=01H 09M 43.082S +/- 0.05", J2000 V = -325 V = 7.72+/-0.02 DEC=+61D 32' 50.14" +/- 0.07" B-V = 0.74+/-0.04 E(B-V) = 0.03+/-0.03 U-B = 0.08+/-0.04 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) J2000 0.08855 0.072 0.0 2 HD18907 STAR,G V-IV RA=03H 01M 37.653S +/- 0.04", J2000 V = +35 V = 5.88+/-0.01 DEC=-28D 05' 29.68" +/- 0.05" B-V = 0.79+/-0.01 E(B-V) = 0.05+/-0.03 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) J2000 0.0211 -0.437 0.0 3 HD63791 STAR,K V-IV RA=07H 54M 28.764S +/- 0.08", J2000 V = -108 V = 7.89+/-0.03 DEC=+62D 08' 10.48" +/- 0.08" B-V = 1.00+/-0.02 E(B-V) = 0.05+/-0.03 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) J2000 -0.0055 -0.0915 0.0 4 HD142691 STAR,K V-IV RA=15H 57M 21.332S +/- 0.06", J2000 V = -5 V = 5.80+/-0.01 DEC=-36D 11' 07.32" +/- 0.07" B-V = 1.02+/-0.04 E(B-V) = 0.06+/-0.03 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) J2000 -0.0008 -0.016 0.0 6599( 7) - 06/25/96 12:10 - [ 5] Visit: 01 Visit Requirements: CVZ 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 HD6755 HRS ACQ 2.0 MIRROR-N2 BRIGHT=RETURN,SEARCH-SIZE=5 1 5.0 S ONBOARD ACQ FOR 11-12 SEQ 10-12 NON-INT Comments: STEP-TIME=0.2S ------------------------------------------------------------------------------------------------------------------------------------ 11 HD6755 HRS ACCUM 2.0 G270M 2498.0 STEP-PATT=DEF,FP-SPLIT=STD, 5 1305.6 COMB=FOUR,DOPPLER=DEF ------------------------------------------------------------------------------------------------------------------------------------ 12 HD6755 HRS ACCUM 2.0 G270M 2498.0 STEP-PATT=DEF,FP-SPLIT=STD, 6 1414.4 COMB=FOUR,DOPPLER=DEF ------------------------------------------------------------------------------------------------------------------------------------ 6599( 7) - 06/25/96 12:10 - [ 6] Visit: 02 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 ------------------------------------------------------------------------------------------------------------------------------------ 20 HD18907 HRS ACQ 2.0 MIRROR-N2 BRIGHT=RETURN,SEARCH-SIZE=5 1 5.0 S ONBOARD ACQ FOR 21-22 Comments: STEP-TIME=0.2S ------------------------------------------------------------------------------------------------------------------------------------ 21 HD18907 HRS ACCUM 2.0 G270M 2498.0 STEP-PATT=DEF,FP-SPLIT=STD, 1 1414.4 NO SPLIT COMB=FOUR,DOPPLER=DEF Comments: expand to fill orbit ------------------------------------------------------------------------------------------------------------------------------------ 22 HD18907 HRS ACCUM 2.0 G270M 2498.0 STEP-PATT=DEF,FP-SPLIT=STD, 2 1196.8 NO SPLIT COMB=FOUR,DOPPLER=DEF Comments: expand to fill orbit ------------------------------------------------------------------------------------------------------------------------------------ 6599( 7) - 06/25/96 12:10 - [ 7] Visit: 03 Visit Requirements: CVZ 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 ------------------------------------------------------------------------------------------------------------------------------------ 30 HD63791 HRS ACQ 2.0 MIRROR-N2 BRIGHT=RETURN,SEARCH-SIZE=5 1 12.5 S ONBOARD ACQ FOR 31-32 SEQ 30-32 NON-INT Comments: STEP-TIME=0.5S ------------------------------------------------------------------------------------------------------------------------------------ 31 HD63791 HRS ACCUM 2.0 G270M 2498.0 STEP-PATT=DEF,FP-SPLIT=STD, 8 1305.6 COMB=FOUR,DOPPLER=DEF ------------------------------------------------------------------------------------------------------------------------------------ 32 HD63791 HRS ACCUM 2.0 G270M 2498.0 STEP-PATT=DEF,FP-SPLIT=STD, 8 1305.6 COMB=FOUR,DOPPLER=DEF ------------------------------------------------------------------------------------------------------------------------------------ 6599( 7) - 06/25/96 12:10 - [ 8] Visit: 04 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 ------------------------------------------------------------------------------------------------------------------------------------ 40 HD142691 HRS ACQ 2.0 MIRROR-N2 BRIGHT=RETURN,SEARCH-SIZE=5 1 5.0 S ONBOARD ACQ FOR 41-45 Comments: STEP-TIME=0.2S ------------------------------------------------------------------------------------------------------------------------------------ 41 HD142691 HRS ACCUM 2.0 G270M 2498.0 STEP-PATT=DEF,FP-SPLIT=STD, 1 1414.4 NO SPLIT COMB=FOUR,DOPPLER=DEF Comments: expand to fill orbit ------------------------------------------------------------------------------------------------------------------------------------ 42 HD142691 HRS ACCUM 2.0 G270M 2498.0 STEP-PATT=DEF,FP-SPLIT=STD, 2 1196.8 NO SPLIT COMB=FOUR,DOPPLER=DEF Comments: expand to fill orbit ------------------------------------------------------------------------------------------------------------------------------------ 43 HD142691 HRS ACCUM 2.0 G270M 2498.0 STEP-PATT=DEF,FP-SPLIT=STD, 2 1196.8 NO SPLIT COMB=FOUR,DOPPLER=DEF Comments: expand to fill orbit ------------------------------------------------------------------------------------------------------------------------------------ 44 HD142691 HRS ACCUM 2.0 G270M 2498.0 STEP-PATT=DEF,FP-SPLIT=STD, 2 1196.8 NO SPLIT COMB=FOUR,DOPPLER=DEF Comments: expand to fill orbit ------------------------------------------------------------------------------------------------------------------------------------ 45 HD142691 HRS ACCUM 2.0 G270M 2498.0 STEP-PATT=DEF,FP-SPLIT=STD, 2 1196.8 NO SPLIT COMB=FOUR,DOPPLER=DEF Comments: expand to fill orbit ------------------------------------------------------------------------------------------------------------------------------------ 6599( 7) - 06/25/96 12:10 - [ 9] Visit: 05 Visit Requirements: CVZ 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 ------------------------------------------------------------------------------------------------------------------------------------ 50 HD63791 HRS ACQ 2.0 MIRROR-N2 BRIGHT=RETURN,SEARCH-SIZE=5 1 12.5 S ONBOARD ACQ FOR 51-52 SEQ 50-52 NON-INT Comments: STEP-TIME=0.5S ------------------------------------------------------------------------------------------------------------------------------------ 51 HD63791 HRS ACCUM 2.0 G270M 2498.0 STEP-PATT=DEF,FP-SPLIT=STD, 10 1305.6 COMB=FOUR,DOPPLER=DEF ------------------------------------------------------------------------------------------------------------------------------------ 52 HD63791 HRS ACCUM 2.0 G270M 2498.0 STEP-PATT=DEF,FP-SPLIT=STD, 10 1305.6 COMB=FOUR,DOPPLER=DEF ------------------------------------------------------------------------------------------------------------------------------------ 6599( 7) - 06/25/96 12:10 - [ 10] Summary Form for Proposal 6599 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BRIGHT=RETURN SEARCH-SIZE=5 DOPPLER=DEF COMB=FOUR FP-SPLIT=STD STEP-PATT=DEF ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category STELLAR POPULATIONS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CVZ ONBOARD ACQ FOR 11-12 SEQ 10-12 NON-INT ONBOARD ACQ FOR 21-22 NO SPLIT ONBOARD ACQ FOR 31-32 SEQ 30-32 NON-INT ONBOARD ACQ FOR 41-45 ONBOARD ACQ FOR 51-52 SEQ 50-52 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-N2 G270M ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD6755 HD18907 HD63791 HD142691 ------------------------------------------------------------------------------------------------------------------------------------