Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 4573c Report Date: 09-May-96:19:43 Version: ********** Check-in Date: ********** 1.Proposal Title: BORON IN ORION: CYCLE 3 MEDIUM ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID HOT STARS GO Sub Category CHEMICAL ABUNDANCES ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Douglas R. Gies GEORGIA STATE UNIVERSITY USA ------------------------------------------------------------------------------------ 7. Abstract The abundance of Boron will be derived from the B II 1362A resonance line for a sample of massive (8-9 Msun) stars. Stars near the Trapezium in Orion are enriched in Oxygen. This enrichment is presumed to be due to enrichment of the parental molecular cloud with Oxygen from SNeII. If B is synthesized by neutrino-induced spallation in SNeII, the O-rich Orion stars will be overabundant in Boron. This prediction will be tested by measuring the 1362A line in the most O-rich Orion star, and by comparing the Boron abundance with that for other O-normal Orion stars. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 4.50 par: 0 10. Num targs pri: 3 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: HRS ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 4573c PI: Douglas R. Gies Proposal Title: BORON IN ORION: CYCLE 3 MEDIUM ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Pi Douglas R. Gies GEORGIA STATE UNIVERSITY USA David L. Lambert UNIVERSITY OF TEXAS USA Kimberly Venn UNIVERSITY OF TEXAS USA Katia Cunha UNIVERSITY OF TEXAS USA ------------------------------------------------------------------------------------ 2. Scientific Justification. INTRODUCTION. The abundance of boron in early type stars was discussed in the late 1970s using spectra at 1360A from the Copernicus satellite. The seminal paper is Boesgaard and Heacox (1978 ApJ 226 888 [BH]). To our knowledge no new information has been provided by the IUE satellite. We propose to return to B to investigate its synthesis. BH showed through synthetic spectra and analysis of Copernicus spectra that the B abundance was obtainable from the B II resonance (singlet) line in early-A to early-B stars. The B abundance from 16 normal stars having temperatures of 9000 to 25000K was independent of temperature and close to the meteoritic value. Above 25000K, the B II line is weak and blended with a much stronger Si III line. In short, BH's study shows that the 1362A line is a useful monitor of the stellar B abundance for B stars. We shall improve upon BH's study principally by acquiring spectra of higher S/N at a resolution comparable to that of Copernicus, and by using nearby Si III lines to better gauge the strength of the Si III blended with the B II. We expect also to be able to establish more securely the continuum level, and to provide more complete synthetic spectra. LOCAL ENRICHMENT OF THE ORION ASSOCIATION. Large molecular clouds may produce several successive stellar generations and possibly the first stars to die may pollute the portions of a cloud that later forms stars. The Orion OB association consists of 4 major pieces of different ages (Blaauw 1964 ARAA 2 213). Olive and Schramm (1982 ApJ 257 276) suggested that the younger subgroups could be enriched in products of SNeII from massive stars. Our search for this enrichment shows that the region of the Trapezium, the region now forming stars, is enriched in oxygen: our principal target HD36285's O abundance is about 60% higher than the well-defined abundance of the older stars (Cunha and Lambert 1992 ApJ 399 586). (HD36285's N abundance is not distinctive.) Since O is a principal product of SNeII from massive stars, we identify the enrichment with that hypothesized by Olive and Schramm. This identification offers a chance to test the proposal that B is synthesised in SNeII by neutrino-induced spallation (Woosley et al. 1990 ApJ 356 272): v + 12C --> 11B, in short, where the 12C is in the C-shell of the star. Calculations (Woosley 1991 "Supernovae", Springer-Verlag p.206) show that the O enrichment of HD36285 could be accompanied by a similar enrichment of B. We plan to observe the most O-rich star and 2 O-normal stars that bracket the temperature of the O-rich star in order to search for a B enrichment of the O-rich star. Detection of excess B would be the first direct evidence that 11B is made in SNeII. Production of 11B by SNeII would resolve a longstanding problem concerning the synthesis of 11B and 10B. Synthesis of the light elements is largely the responsibility of spallation reactions between the galactic cosmic rays and interstellar nuclei (e.g., p + O --> 10B etc.) These reactions predict 11B/10B = 2.5 but the meteoritic value (the only available measurement) is 11B/10B = 4.05. SNeII may have contributed the additional 11B. (Spallation can provide a higher isotopic ratio if low energy CRs are invoked.) Page 3 ------------------------------------------------------------------------------------ 3. Description of proposed observations. The B II 1362A line will be observed with GHRS/G160M/SSA to a S/N of 400. The targets are local, visually bright B-type stars of luminosity classes V: Star Teff log g vsini Comment HD35039 20600 3.7 16 Orion member, normal N and O abundance HD35299 24000 4.3 5 Orion member, normal N and O abundance HD36285 22000 4.4 5 Orion member, O 60% above normal ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. Boron is a trace element with no detectable transitions in the visible or infra- red spectra of hot stars. IUE, while providing about the same spectral resolution of G160M, lacks the capability to provide adequate S/N to measure the B II line accurately. Several of our stars have temperatures such that the B II line is weak and high S/N is needed to define it accurately. This is well shown by the synthetic spectra computed by Boesgaard and Heacox (1978 ApJ 226 888) and by the fact that, after more than a decade, IUE has yet to provide a B abundance for a hot (or a cool) star. The desired S/N is achievable with GHRS, as we have demonstrated with our GTO observations of interstellar CO in Zeta Oph where S/N = 900 was achieved with a strategy of substepping and exposures at slightly different carrousel positions. Leckrone and Adelman (1989 ApJS 71 387) have given an extensive discussion of the S/N ratio of high-dispersion IUE spectra and the gains that result from co- addition of spectra. They show that "the average signal-to-noise ratio (S/N) at the continuum level in well exposed stellar spectra varies from 10 to 20" and "The co-addition procedure yields an improvement in S/N by factors ranging from 2.3 to 2.9". In other words, a S/N of about 50 may be achievable. A S/N >100 is certainly not possible. Boesgaard and Heacox's spectra have generally S/N of about 100. We need the more accurate spectra from HST/GHRS to search for what are possibly small star-to-star differences in the B abundance. Boron abundances for A and B-type stars were derived by Boesgaard and Heacox from their Copernicus spectra. Their sample is inadequate to meet our goals, e.g., no stars from Orion. Exposure times were calculated for GHRS/G160M/SSA using observed 1360A fluxes, as given by the TD-1 satellite (1976 ESA SR-27) or the IUE Spectral Atlas. A S/N = 400 was the target but some minor compromises were made. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. None. ------------------------------------------------------------------------------------ 6. Description of special calibration exposures. None. ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. Spectra will be reduced in Atlanta. The PI with Dr D Lambert and Katia Cunha will analyse the Orion stars; chemical evolution of the Orion Association forms Cunha's Ph.D. dissertation. Calculations will be done with Kurucz model atmospheres. Synthetic spectra at 1360A have already been computed. All participants have extensive experience in model atmospheres/synthetic spectra analysis. ------------------------------------------------------------------------------------ 8. Additional comments or special requests. None. Page 4 ------------------------------------------------------------------------------------ 9. Description of previous HST work. DLL is PI on all these GTO proposals and a Co-I on the GO proposals: GTO1064 Boron in Main Sequence Stars, not related GTO1065 Isotopic Abundances of Carbon and Oxygen and Fractionation of Interstellar Carbon Monoxide, not related GTO1066 Carbon Chemistry in Interstellar Diffuse Clouds, not related GTO1067 Old Novae and Cataclysmic Variables - DQ Her, not related GTO1068 Epsilon Aurigae- A Search for the Secondary, not related GO3824 A Search for Silicon and Carbon in GP Com, not related GO3479 Boron in Pop. II Dwarfs - Primeval or Spallated?, not related Note: GTO1064 and GO3479 refer to Boron and its chemical evolution over the lifetime of the Galaxy, and not to the problems of B in hot stars. First Results from the GHRS: C I, S I, and CO toward Xi Persei and the Physical Conditions of the Diffuse Clouds. A M Smith, F C Bruhweiler, D L Lambert, B D Savage, J A Cardelli, D C Ebbets, C-H Lyu, & Y Sheffer, ApJ, 377, L61, 1991. Fractionation of CO in the Diffuse Clouds toward Zeta Oph, Y Sheffer, S R Federman, D L Lambert, & J A Cardelli, ApJ, 397, 482, 1992. The Abundance of Boron in three Halo Stars, D K Duncan, D L Lambert, & M Lemke, ApJ, 401, 584, 1992. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). Adequate computing facilities are available at both participating institutions. Although the program stars have already be extensively analysed by us on the basis of their visual spectra, additional spectra, if required, can be readily obtained at the McDonald Observatory in west Texas. ------------------------------------------------------------------------------------ 11. Address Information Name: DOUGLAS R. GIES Category: PI Institution: Georgia State University Address: DEPARTMENT OF PHYSICS AND ASTRONOMY GEORGIA STATE UNIVERSITY City: ATLANTA State: GA Zip Code: 30303 Country: USA Telephone: 404-651-2932 Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 4573c [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial |Acqui|FLX| Flux data No | Name | Description | Position |Eqnx | Vel. |Prblm|REF| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD35039 BD- A,110 RA = 5H 19M 12.47S +/- 1950 V=28.2 1 V=4.73, TYPE=B2IV 00D930 0.02S, 1 B-V=-0.17, E(B-V)=0.07 DEC = -00D 25' 49.03" +/- 2 F(1360)=1.3E-9 0.06" ------------------------------------------------------------------------------------------------------------------------------------ 2 HD35299 BD- A,110 RA = 5H 21M 8.75S +/- 0.09S, 1950 V=21.0 1 V=5.70, TYPE=B1.5V 00D936 DEC = -00D 12' 18.70" +/- 1 B-V=-0.21, E(B-V)=0.04 0.09" 2 F(1360)=7.3E-10 ------------------------------------------------------------------------------------------------------------------------------------ 3 HD36285 BD- A,110 RA = 5H 27M 55.63S +/- 1950 V=11.3 1 V=6.33, TYPE=B2V 07D1099 0.15S, 1 B-V=-0.19, E(B-V)=0.05 DEC = -07D 28' 20.03" +/- 2 F(1360)=3.0E-10 0.15" ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 4573c [ 6] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 DEFINE # HRS ACQ 2.0 MIRROR-A2 SEARCH-SIZE=3 1 1.8S 100 2 # B2-ACQ BRIGHT=RETURN ------------------------------------------------------------------------------------------------------------------------------------ 2 DEFINE # HRS ACCUM 0.25 G160M 1362.0 FP-SPLIT=STD # 10M 500 1 # BORON2 STEP-PATT=5 ------------------------------------------------------------------------------------------------------------------------------------ 4 USE B2- HD35039 X1 1 ONBOARD ACQ FOR 5 ACQ CYCLE 3 / 4-5 ------------------------------------------------------------------------------------------------------------------------------------ 5 USE HD35039 2 X1 1 CYCLE 3 BORON2 ------------------------------------------------------------------------------------------------------------------------------------ 6 USE B2- HD35299 X1 1 ONBOARD ACQ FOR 7 ACQ CYCLE 3 / 6-7 ------------------------------------------------------------------------------------------------------------------------------------ 7 USE HD35299 3 X1 1 CYCLE 3 BORON2 ------------------------------------------------------------------------------------------------------------------------------------ 8 USE B2- HD36285 X1 1 ONBOARD ACQ FOR 9 ACQ CYCLE 3 / 8-9 ------------------------------------------------------------------------------------------------------------------------------------ 9 USE HD36285 8 X1.1 1 CYCLE 3 BORON2 ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 4573c [ 7] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations HRS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SEARCH-SIZE=3 BRIGHT=RETURN FP-SPLIT=STD STEP-PATT=5 ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 4.50 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category HOT STARS ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category CHEMICAL ABUNDANCES ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 5; CYCLE 3 / 4-5 CYCLE 3 ONBOARD ACQ FOR 7; CYCLE 3 / 6-7 ONBOARD ACQ FOR 9; CYCLE 3 / 8-9 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR-A2 G160M ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD35039 BD-00D930 HD35299 BD-00D936 HD36285 BD-07D1099 ------------------------------------------------------------------------------------------------------------------------------------