8612( 2) - 03/02/00 13:13 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8612 Version: 2 Check-in Date: 02-Mar-2000 13:12:44 1.Proposal Title: Boron in the Lithium-Rich K-Giants: A Critical Test of Deep Stellar Mixing Versus Brown-Dwarf Ingestion ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 9 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Ramiro de la Reza Observatorio Nacional CoI: Dr. Katia Cunha University of Texas El Paso N CoI: Dr. Verne V. Smith University of Texas El Paso N ------------------------------------------------------------------------------------ 5. Abstract We will observe the B I 2500Angstrom\ lines in four Li-rich K- giants using HST with STIS/G230M in order to test two different evolutionary scenarios invoked to explain the high Li abundances: the cool bottom process (CBP) versus the possible accretion of brown dwarfs/planets. This test utilizes the two following properties of boron: among the three light elements (Li, Be, and B) which are easily destroyed in stars by (p, Alpha) reactions, B is the least fragile to nuclear destruction. In addition, unlike Li which can be created under certain conditions in stellar mixing, B can only be destroyed. The hypothetical mixing mechanism, CBP, produces Li by introducing deeper mixing to hotter layers such that ^7Li is created via ^3He(alpha, Gamma)^7Be(e^-, anti- Nu)^7Li. A by-product of CBP is the total destruction of pre- existing Be and B. If B I is absent from the spectra, we will prove that deep mixing has occurred. In an accretion scenario, the increase in the Li abundance caused by the deposition of fresh material onto the red giant from a substellar mass companion will also result in an increase in the Be and B abundances. Because B is more robust to nuclear burning than Be, as well as initially being 20 times more abundant, spectroscopy of the B I lines will provide a solid and definitive test of whether the process that creates these chemically peculiar giants is a new type of internal mixing, or the ingestion of a substellar mass companion. ------------------------------------------------------------------------------------ 8612( 2) - 03/02/00 13:13 - [ 2] Observations Description ------------------------ The two B I resonance lines near 2497Angstrom\ will be observed in four Li-rich K-giants. STIS with G230M, centered at 2499Angstrom, and the 52x0.1 slit will be used. With this set-up, we cover 90Angstrom\ of spectra at a resolution of about R=Lambda/DeltaLambda=13, 000. We plan to achieve a signal-to-noise of (square)uig 50 per resolution element. This is sufficiently accurate to derive reliable boron abundances. We illustrate in Figure 1 synthetic spectra, including predictions from CBP and brown dwarf/giant planet ingestion, demonstrating that STIS with G230M can do the job. Exposure times (below) were calculated using the STIS Time Estimator on the World-Wide-Web. To estimate 2500Angstrom fluxes for our target stars, we first used the IUE archive to access measured 2500Angstrom\ fluxes for a sample of K-giants spanning the color range of our targets. Using the V- magnitudes of these K-giants, a ratio of F_V/F_2500 fluxes can be calculated and this plotted versus (B-V). Quite a tight trend is defined: most of these K-giants, as well as our targets here, are relatively bright and suffer little reddening. We can now use our target K- giant (B-V) colors to define the expected flux ratio of F_V/F_2500 and, with the target V-magnitudes, can compute the expected 2500Angstrom flux. This procedure will predict the flux to within 50 quite good. We present the exposure times in the table below for the our 4 targets. Orbits were calculated based upon aquisition, peakup, instrument overhead, and reaquisition as described for STIS in the Phase I Handbook. All four targets have some of the largest Li abundances found for the Li-rich K-giants, which tend to cluster at about log Epsilon(Li)~ 2.7-2.9. This is near what is expected if a K-giant, with a convective envelope mass of sim0.4M_\odot, ingested a maximum-mass brown dwarf with 0.08M_\odot. To enhance the contrast in the B abundances expected from CBP versus ingestion, we want targets with the largest Li abundances; these either represent the most mixing, in the CBP picture and, hence the largest B depletions, or accretion of the most massive sub-stellar mass objects, in which case they will have relatively large B abundances. begintabularlcclc Target & V & Flux (2500 Angstrom) & Exposure (min.) & Orbits, HD787 & 5.25 & 9.0 * 10^-14 & 80 & 2 , HD9746 & 5.92 & 9.7 * 10^-14 & 74 & 2 , HD39853 & 5.66 & 5.9 * 10^- 14 & 123 & 3 , HD112127 & 6.91 & 3.3 * 10^-14 & 223 & 5 , endtabular Real Time Justification ----------------------- No special requirements. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 8612( 2) - 03/02/00 13:13 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD787 STAR RA=00H 12M 09.95S +/-0.5", DEC=- J2000 V = 5.25+/-0.03 17D 56' 17.6" +/-0.5" F-CONT(2500)=9.0+/-1.0e-14 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1991.25 0.0042 -0.0247 0.005 2 HD9746 STAR RA=01H 36M 27.21S +/-0.5", J2000 V = 5.92+/-0.03 DEC=+48D 43' 22.2" +/-0.5" F-CONT(2500)=9.7+/-1.0e-14 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1991.25 -0.0016 -0.0187 0.008 3 HD39853 STAR RA=05H 54M 43.59S +/-0.5", DEC=- J2000 V = 5.66+/-0.03 11D 46' 27.3" +/-0.5" F-CONT(2500)=5.9+/-1.0e-14 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1991.25 0.0052 0.0282 0.004 4 HD112127 STAR RA=12H 53M 55.74S +/-0.5", J2000 V = 6.91+/-0.03 DEC=+26D 46' 48.0" +/-0.5" F-CONT(2500)=3.3+/-1.0e-14 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1991.25 0.0001 -0.0041 0.008 8612( 2) - 03/02/00 13:13 - [ 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 HD787 STIS/C ACQ F28X50O MIRROR ACQTYPE=POINT 1 0.1 S CD II ------------------------------------------------------------------------------------------------------------------------------------ 2 HD787 STIS/C ACQ/PEA 52X0.1 MIRROR 1 0.1 S CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 HD787 STIS/N ACCUM 52X0.1 G230M 2499 1 2110 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 HD787 STIS/N ACCUM 52X0.1 G230M 2499 1 2897 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8612( 2) - 03/02/00 13:13 - [ 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 HD9746 STIS/C ACQ F28X50O MIRROR ACQTYPE=POINT 1 0.1 S CD II ------------------------------------------------------------------------------------------------------------------------------------ 2 HD9746 STIS/C ACQ/PEA 52X0.1 MIRROR 1 0.1 S CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 HD9746 STIS/N ACCUM 52X0.1 G230M 2499 1 2246 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 HD9746 STIS/N ACCUM 52X0.1 G230M 2499 1 3054 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8612( 2) - 03/02/00 13:13 - [ 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 HD39853 STIS/C ACQ F28X50O MIRROR ACQTYPE=POINT 1 0.1 S CD II ------------------------------------------------------------------------------------------------------------------------------------ 2 HD39853 STIS/C ACQ/PEA 52X0.1 MIRROR 1 0.1 S CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 HD39853 STIS/N ACCUM 52X0.1 G230M 2499 1 2112 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 HD39853 STIS/N ACCUM 52X0.1 G230M 2499 1 2899 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 5 HD39853 STIS/N ACCUM 52X0.1 G230M 2499 1 2899 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8612( 2) - 03/02/00 13:13 - [ 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 HD112127 STIS/C ACQ F28X50O MIRROR ACQTYPE=POINT 1 0.1 S CD II ------------------------------------------------------------------------------------------------------------------------------------ 2 HD112127 STIS/C ACQ/PEA 52X0.1 MIRROR 1 0.1 S CD K ------------------------------------------------------------------------------------------------------------------------------------ 3 HD112127 STIS/N ACCUM 52X0.1 G230M 2499 1 2136 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 HD112127 STIS/N ACCUM 52X0.1 G230M 2499 1 2923 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 5 HD112127 STIS/N ACCUM 52X0.1 G230M 2499 1 2923 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 6 HD112127 STIS/N ACCUM 52X0.1 G230M 2499 1 2923 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7 HD112127 STIS/N ACCUM 52X0.1 G230M 2499 1 2923 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8612( 2) - 03/02/00 13:13 - [ 8] Summary Form for Proposal 8612 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50OII 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 HD787 HD9746 HD39853 HD112127 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 2499 ------------------------------------------------------------------------------------------------------------------------------------