7348( 4) - 11/30/98 15:50 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7348 Version: 4 Check-in Date: 30-Nov-1998 15:49:10 1.Proposal Title: Boron in the extreme Pop II star HD 140283 ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Bengt Edvardsson Uppsala Astronomical Observatory CoI: Patrik Thoren Uppsala Astronomical Observatory Y ------------------------------------------------------------------------------------ 5. Abstract Using the HST and ground-based observations we have determined abundances of boron and beryllium in the extreme Pop II dwarf HD140283. These are very useful since different scenarios for the origins of Be and B in the Early Galaxy suggest different abundance ratios between the two elements. From the 2497 Angstrom B I line the boron abundance was found to be log epsilon(B) (=12 + log(N(B)/N(H))) =0.34 +/- 0.20 (Edvardsson et al. 1994, A&A 290, 176). Our abundance ratio N(B)/N(Be)~17 and similar results for other stars indicate that these elements were formed by cosmic ray spallation in the Early Galaxy. Other suggested mechanisms include inhomogeneous Big Bang nucleosynthesis, supernova boron production or photoerosion in active galactic nuclei. These mechanisms would give other abundance ratios. We now want to confirm these results by observing the 2089 Angstrom B I line. The line is expected to give an independent check of the boron abundances as well as an opportunity to examine the suitability of the line for future investigations of the ratio between the isotopes 11B/10B in Pop II stars. This isotopic ratio has never been measured in Pop II objects and provides further important information concerning the mechanism of 11B production and the conditions in the Early Galaxy. For comparison, the solar system (meteoritic) 11B/10B suggests that about 40% of the 11B in Pop I objects is not formed by ISM spallation, but probably in Supernovae of Type II. ------------------------------------------------------------------------------------ 7348( 4) - 11/30/98 15:50 - [ 2] Observations Description ------------------------ We suggest observations of the 2089 Angstrom B I line to obtain an independent boron abundance determination for the star HD140283. With the abundance determined from the 2497 Angstrom B I line, the expected strength of the 2089 Angstrom B I line is W_Lambda = 4 mAngstrom. With a S/N of ~40 and a spectral resolution of about 110, 000 this can be done with the STIS/NUV-MAMA/E230H. The F3 IV star we want to observe, HD140283, has V=7.23, Teff=5680 K, log g=3.5 and [Fe/H]=-2.6. The objects flux at 2089 A is, according to TAC (Cacciari, C. 1985, A&AS, 61, 407), 8.0 10^-13 erg/cm^2/s/Angstrom, which, according to the STIS Instrument handbook V 1.1 gives a count rate of 0.1188 counts/s/resolution element (0.059 counts/s/pixel). TAC advised us to use dithering to decrease the intrinsic noise. This was impossible with the small echelle slit, therefore we decided to use 3 wavelength settings instead of the original 2. Also we are forced to split the observation into two visits, due to the need of SAA-free orbits. With the monthly MAMA OFFSET we get another opportunity to project the spectra on different pixels, therefore we want to do the visit2 observation more than one month after the first, to be sure the MAMA has been shifted in between. Instead of the originally planned 2 different pixel position projections we will in this way get 6. With observations in 3 wavelength settings we expect a continuum S/N of ~40 per resolution element which is sufficient to determine the boron abundance from this very weak line with an accuracy of about 30% and to detect whether the line is seriously affected by any unknown line absorption. V=7.23 means that there is no risk of exceeding any bright object limit for E230H, according to table 13.24 in the August '96 update of the STIS manual. In 2 times 4 orbits we can pack 2 times 140 minutes of target integration time in the three wavelength settings. The visibility of the star is only 52 minutes per orbit, and for the first orbit we need 7 + 4 + 17 minutes for the initial guide star acquisition, the STIS target acquisition and the STIS G430M 0.2X0.09 PEAKUP, respectively. About 20 minutes exposure time remains after MAMA initialization and wavecal. In the next three orbits we can then expose the target for 41, 39 and 39 minutes, respectively if we allow for reacquisitions, MAMA, wavecals and DUMP STIS buffer overheads (Time estimates from RPS2. Our original estimates were slightly different). For the other four orbits (visit2) we use the same procedure but with a different order for the wavelength settings, to get about the same exposure time for all three settings. Real Time Justification ----------------------- None None Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 7348( 4) - 11/30/98 15:50 - [ 3] Data Distribution Paper Products: Media: ELECTRONIC Blocking Factor: 10 Ship To: Bengt Edvardsson, Uppsala Astronomical Observatory, Box 515, S-75120 Uppsala, Sweden Ship Via: Email: bengt.edvardsson@astro.uu.se ------------------------------------------------------------------------------------ 7348( 4) - 11/30/98 15:50 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD140283 STAR RA=15H 43M 03.76S +/- 0.0S, DEC= J2000 V=-171 F(2089)=8.0e-13 -10D 55' 57.9" +/- 0.0" V = 7.23 B-V = 0.49 Comments: Coordinates are from Hipparcos Catalogue(1997). Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1991.25 -0.075744 -0.30277 0.01744 7348( 4) - 11/30/98 15:50 - [ 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 HD140283 STIS/C ACQ F28X50O MIRROR ACQTYPE=POINT 1 0.2 S ONBOARD ACQ FOR 2 CD II ------------------------------------------------------------------------------------------------------------------------------------ 2 HD140283 STIS/C ACQ/PEA 0.2X0.0 G430M 4961 1 1.0 S ONBOARD ACQ FOR 3 CD K 9 ------------------------------------------------------------------------------------------------------------------------------------ 3 HD140283 STIS/N ACCUM 0.2X0.0 E230H 2113 2 870 S UV-MAM 9 A Comments: orbit 1 ------------------------------------------------------------------------------------------------------------------------------------ 4 HD140283 STIS/N ACCUM 0.2X0.0 E230H 2113 1 700 S UV-MAM 9 A Comments: orbit 2 ------------------------------------------------------------------------------------------------------------------------------------ 5 HD140283 STIS/N ACCUM 0.2X0.0 E230H 2063 1 700 S UV-MAM 9 A Comments: orbit 2 ------------------------------------------------------------------------------------------------------------------------------------ 6 HD140283 STIS/N ACCUM 0.2X0.0 E230H 2063 1 850 S UV-MAM 9 A Comments: orbit 2 ------------------------------------------------------------------------------------------------------------------------------------ 7 HD140283 STIS/N ACCUM 0.2X0.0 E230H 2063 3 800 S UV-MAM 9 A Comments: orbit 3 ------------------------------------------------------------------------------------------------------------------------------------ 8 HD140283 STIS/N ACCUM 0.2X0.0 E230H 2163 3 800 S UV-MAM 9 A Comments: orbit 4 ------------------------------------------------------------------------------------------------------------------------------------ 7348( 4) - 11/30/98 15:50 - [ 6] Visit: 02 Visit Priority: Visit Requirements: AFTER 1 BY 33D TO 57D On Hold Comments: Additional Comments: These following 4 orbits were placed in a new visit due to the need of SAA- free orbits ('Update on MAMA performance..', p 4). Visit requirement according to our need to project the spectra at different areas on the detector. It is supposed to be moved monthly. If the schedule by some reson makes our Visit2 spectra being projected on the same place as Visit1, please make the observation later, when the MAMA has been moved again. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD140283 STIS/C ACQ F28X50O MIRROR ACQTYPE=POINT 1 0.2 S ONBOARD ACQ FOR 2 CD II ------------------------------------------------------------------------------------------------------------------------------------ 2 HD140283 STIS/C ACQ/PEA 0.2X0.0 G430M 4961 1 1.0 S ONBOARD ACQ FOR 3 CD K 9 ------------------------------------------------------------------------------------------------------------------------------------ 3 HD140283 STIS/N ACCUM 0.2X0.0 E230H 2063 2 870 S UV-MAM 9 A Comments: orbit 1 ------------------------------------------------------------------------------------------------------------------------------------ 4 HD140283 STIS/N ACCUM 0.2X0.0 E230H 2113 1 700 S UV-MAM 9 A Comments: orbit 2 ------------------------------------------------------------------------------------------------------------------------------------ 5 HD140283 STIS/N ACCUM 0.2X0.0 E230H 2113 1 700 S UV-MAM 9 A Comments: orbit 2 ------------------------------------------------------------------------------------------------------------------------------------ 6 HD140283 STIS/N ACCUM 0.2X0.0 E230H 2113 1 850 S UV-MAM 9 A Comments: orbit 2 ------------------------------------------------------------------------------------------------------------------------------------ 7 HD140283 STIS/N ACCUM 0.2X0.0 E230H 2113 1 1130 S UV-MAM 9 A Comments: orbit 3 ------------------------------------------------------------------------------------------------------------------------------------ 8 HD140283 STIS/N ACCUM 0.2X0.0 E230H 2163 2 600 S UV-MAM 9 A Comments: orbit 3 ------------------------------------------------------------------------------------------------------------------------------------ 9 HD140283 STIS/N ACCUM 0.2X0.0 E230H 2163 3 800 S UV-MAM 9 A Comments: orbit 4 ------------------------------------------------------------------------------------------------------------------------------------ 7348( 4) - 11/30/98 15:50 - [ 7] Summary Form for Proposal 7348 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50OII 0.2X0.09 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 2 ONBOARD ACQ FOR 3 AFTER 1 BY 33D TO 57D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G430M E230H ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD140283 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 4961 2113 2063 2163 ------------------------------------------------------------------------------------------------------------------------------------