7748( 8) - 06/02/98 15:21 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7748 Version: 8 Check-in Date: 14-May-1998 13:52:40 1.Proposal Title: The Origins of Boron ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO/CAR 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: VERNE SMITH UNIVERSITY OF TEXAS EL PASO CoI: Dr. Katia Cunha University of Texas at El Paso N CoI: Dr. David L. Lambert University of Texas at Austin N ------------------------------------------------------------------------------------ 5. Abstract The Orion OB1 association comprises four subgroups of differing ages. The youngest stars show higher oxygen abundances than the oldest stars. This enrichment has been shown to be due to contamination of the original gas in Orion by oxygen-rich ejecta from supernovae. Boron abundances will be derived from the B I 2497 Angstrom line in four lower-mass stars in the Orion association having different oxygen and lithium abundances. Two of the target stars have undepleted Li abundances, as determined by us based upon ground-based optical spectra, which indicates that the boron observed in these stars will be untouched by internal stellar astration, and will thus represent an unambiguous measurement of the current boron abundance in young Galactic gas. The target stars also exhibit a real variation in their oxygen abundances, such that a positive correlation of the boron and oxygen abundances will, if present, indicate that boron, as ^11B, is synthesized by the supernovae responsible for the oxygen abundances. The boron abundances derived from the HST spectra, in conjunction with oxygen, iron, and especially lithium abundances derived from the ground-based spectra, will yield our clearest look at the current behavior of boron in the Milky Way. ------------------------------------------------------------------------------------ 7748( 8) - 06/02/98 15:21 - [ 2] Observations Description ------------------------ The B, i resonance line at 2496.76 Angstrom\ will be observed in four F/G dwarf stars in Orion using the GHRS, with G270M centered at 2500 Angstrom in the Small Science Aperture (for best spectral definition) and the N2 mirror for target acquisition. With this arrangement we cover about 46 Angstrom\ of spectra. We are aiming to achieve a signal-to- noise ~ 25-30 per pixel. We deem this sufficient for determining reasonably accurate boron abundances. This is illustrated in the bottom panel of Figure 1, where the filled dots represent a synthetic spectrum of the B I region generated using a model atmosphere which corresponds to a late F dwarf (similar to the types of stars we are proposing to observe) to which noise has been added, corresponding to a S/N = 30, and which has been sampled at the G270M resolution. The continous curves represent noiseless synthetic spectra with boron abundances corresponding to log Epsilon(B) = 2.8, 2.4 and 2.0. The noisy synthesis was generated with log Epsilon (B) = 2.4, corresponding to the middle value of the continous curves. These synthetic spectra were computed for a stellar Vsin(i)= 25kms. This demonstrates that boron abundances with internal accuracies of 0.2 dex are feasible with this quality of data. Exposure times (below) were calculated from the V magnitudes for the stars. We assumed a reddening of E(B-V) = 0.05, which is typical of the Orion association, i.e. the reddening is small and does not vary significantly (Warren & Hesser, 1978, ApJS, 36, 497). This unreddened V- magnitude was used to calculate a flux at 5500 Angstrom, and an unreddened flux at 2500 Angstrom was estimated by using the apropriate Kurucz (1979, ApJS, 40, 1) model flux ratios (these models reproduce UV flux distributions of solar- like stars quite well at this wavelength). This unreddened UV flux was then attenuated with our typical reddening of E(B-V) = 0.05, using the ultraviolet extinction law as given in Table 8.4 of the GHRS Handbook. The exposure times were calculated using Section 13 in the STIS Handbook. Orbits were calculated using the overhead times described in the Cycle 7 STIS Manual. A list of the target stars with their respective V magnitudes, V sin i, lithium and oxygen abundances, as well as the flux at 2500 Angstrom (in units of erg-cm^-2-s^-1- AA^- 1) and exposure times are presented in Table 1. begintabularlcclcr Target & V & V sini & Li & O & Flux (2500 Angstrom) & Exposure (min.), BD-06 1250 & 9.96 & 15. & 2.8 & 8.8 & 2.0 * 10^-14 & 200 , HD294297 & 10.12 & 5. & 2.6 & 8.7 & 1.7 * 10^-14 & 240 , endtabular Real Time Justification ----------------------- No special requirements. We continue to observe and study the lower-mass stars of the Orion association: a paper concerning the Li abundances and details of membership has appeared (1995, Ap.J., xxx, xxx), while a paper on the oxygen abundances, as well as the detailed abundance distribution of many elements, is in press in the Ap.J.. We continue to observe, at McDonald, low- mass members of the Orion Association in order to further investigate, in particular, the Li and O abundances in the Orion members. The addition of the key element boron to our continuing work will allow us to probe stellar astration and possible neutrino nucleosynthesis in more detail. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 7748( 8) - 06/02/98 15:21 - [ 3] Data Distribution Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: --753e_1fd2-3813_f96-2b8d_2485-- ------------------------------------------------------------------------------------ 7748( 8) - 06/02/98 15:21 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 BD-06D1250 STAR, F3-F9 RA=05H 36M 05.96S +/-0.05S, DEC= J2000.0 V= +19.4 V = 9.96+/-0.03 -06D 19' 38.6" +/-0.2", PLATE- B-V = +0.53+/-0.05 ID=06EL F-CONT(2500)=2.0+/-0.1e-14 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1986.132 0.000 0.006 0.0 2 HD294297 STAR, F3-F9 RA=05H 40M 27.40S +/-0.05S, DEC= J2000.0 V= +10.5 V = 10.12+/-0.03 -02D 25' 43.2" +/-0.2", PLATE- B-V = +0.58+/-0.05 ID=06EN F-CONT(2500)=1.7+/-0.1e-14 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1986.132 0.001 -0.002 0.0 7748( 8) - 06/02/98 15:21 - [ 5] 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 BD-06D1250 STIS/C ACQ F25ND3 MIRROR 1 10 S ONBOARD ACQ FOR 2 CD ------------------------------------------------------------------------------------------------------------------------------------ 2 BD-06D1250 STIS/C ACQ/PEA 52X0.1 G430M 5471 1 10 S ONBOARD ACQ FOR 3-7 CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 BD-06D1250 STIS/N ACCUM 52X0.1 G230M 2499 1 1560 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 BD-06D1250 STIS/N ACCUM 52X0.1 G230M 2499 1 2460 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 5 BD-06D1250 STIS/N ACCUM 52X0.1 G230M 2499 1 2460 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 6 BD-06D1250 STIS/N ACCUM 52X0.1 G230M 2499 1 2460 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7 BD-06D1250 STIS/N ACCUM 52X0.1 G230M 2499 1 2460 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7748( 8) - 06/02/98 15:21 - [ 6] 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 BD-06D1250 STIS/C ACQ F25ND3 MIRROR 1 10 S ONBOARD ACQ FOR 2 CD ------------------------------------------------------------------------------------------------------------------------------------ 2 BD-06D1250 STIS/C ACQ/PEA 52X0.1 G430M 5471 1 10 S ONBOARD ACQ FOR 3-7 CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 BD-06D1250 STIS/N ACCUM 52X0.1 G230M 2499 1 1560 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 BD-06D1250 STIS/N ACCUM 52X0.1 G230M 2499 1 2460 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 5 BD-06D1250 STIS/N ACCUM 52X0.1 G230M 2499 1 2460 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 6 BD-06D1250 STIS/N ACCUM 52X0.1 G230M 2499 1 2460 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7 BD-06D1250 STIS/N ACCUM 52X0.1 G230M 2499 1 2460 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7748( 8) - 06/02/98 15:21 - [ 7] 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 HD294297 STIS/C ACQ F25ND3 MIRROR 1 10 S ONBOARD ACQ FOR 2 CD ------------------------------------------------------------------------------------------------------------------------------------ 2 HD294297 STIS/C ACQ/PEA 52X0.1 G430M 5471 1 10 S ONBOARD ACQ FOR 3 CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 HD294297 STIS/N ACCUM 52X0.1 G230M 2499 1 1560 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 HD294297 STIS/N ACCUM 52X0.1 G230M 2499 1 2460 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 5 HD294297 STIS/N ACCUM 52X0.1 G230M 2499 1 2460 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 6 HD294297 STIS/N ACCUM 52X0.1 G230M 2499 1 2460 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7 HD294297 STIS/N ACCUM 52X0.1 G230M 2499 1 2460 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7748( 8) - 06/02/98 15:21 - [ 8] 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 HD294297 STIS/C ACQ F25ND3 MIRROR 1 10 S ONBOARD ACQ FOR 2 CD ------------------------------------------------------------------------------------------------------------------------------------ 2 HD294297 STIS/C ACQ/PEA 52X0.1 G430M 5471 1 10 S ONBOARD ACQ FOR 3 CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 HD294297 STIS/N ACCUM 52X0.1 G230M 2499 1 1560 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 HD294297 STIS/N ACCUM 52X0.1 G230M 2499 1 2460 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 5 HD294297 STIS/N ACCUM 52X0.1 G230M 2499 1 2460 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 6 HD294297 STIS/N ACCUM 52X0.1 G230M 2499 1 2460 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7 HD294297 STIS/N ACCUM 52X0.1 G230M 2499 1 2460 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7748( 8) - 06/02/98 15:21 - [ 9] 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 HD294297 STIS/C ACQ F25ND3 MIRROR 1 10 S ONBOARD ACQ FOR 2 CD ------------------------------------------------------------------------------------------------------------------------------------ 2 HD294297 STIS/C ACQ/PEA 52X0.1 G430M 5471 1 10 S ONBOARD ACQ FOR 3 CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 HD294297 STIS/N ACCUM 52X0.1 G230M 2499 1 1560 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7748( 8) - 06/02/98 15:21 - [ 10] Summary Form for Proposal 7748 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F25ND3 52X0.1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO/CAR ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2 ONBOARD ACQ FOR 3-7 ONBOARD ACQ FOR 3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G430M G230M ------------------------------------------------------------------------------------------------------------------------------------ Target Names BD-06D1250 HD294297 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 5471 2499 ------------------------------------------------------------------------------------------------------------------------------------