! Proposal 6520, submission 1 ! PI: Dr. Verne V. Smith ! Received Wed Feb 14 16:11:06 EST 1996 ! From: verne@maxwell.as.utexas.edu ! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! $Id: 6520,v 5.1 1996/02/15 19:19:11 pepsa Exp $ ! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! $Id: 6520,v 5.1 1996/02/15 19:19:11 pepsa Exp $ ! ! Refer to the HST Phase II Proposal Instructions to fill this out ! ! Anything after a "!" is ignored, and may be deleted ! ! All keywords with multiple entries are comma delimited except the ! Visit_Requirements and Special_Requirements keywords which can be ! delimited with carriage returns or semi-colons, but not commas ! ! For help call your Program Coordinator: Manning ! Phone: 410-338-4456 , E-mail: manning@stsci.edu ! ! This partially completed template was generated from a Phase I proposal. ! Name of Phase I Proposal: archive-0351.v._smith.prop ! Date generated: Fri Dec 22 16:49:27 EST 1995 ! Proposal_Information ! Section 4 Title: The Origins of Boron Proposal_Category: GO Scientific_Category: COOL STARS Cycle: 6 Investigators PI_name: Dr. Verne V. Smith PI_Institution: University of Texas at El Paso CoI_Name: Dr. Katia Cunha CoI_Institution: University of Texas Contact: ! Y or N (designate at most one contact) CoI_Name: Dr. David L. Lambert CoI_Institution: University of Texas Contact: ! Y or N (designate at most one contact) Abstract: ! Free format text (please update) 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. Questions ! Free format text (please update) Observing_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 3.4.5.1 in the GHRS Handbook, assuming Case 2 where the dark count must be considered. We used a dark count rate, as listed for Side 2 of the GHRS, of 0.011 counts s^-1 diode^-1 and set the number of binned pixels to 2, as this is sufficient to analyze the B I feature as found in tests of our noisy synthetic spectra. Orbits were calculated using the overhead times described in the Cycle 6 Phase I Proposal Instructions. 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. Our two high- priority stars are P1455 and BD-05 1317, which show undepleted lithium and different oxygen abundances. Both BD- 06 1250 and HD294297 show modest depletions of Li, so they are of interest in order to see if these rather small Li depletions are accompanied by any B depletion (recall that Li is destroyed at temperatures lower than B). begintabularlcclcr Target & V & V sini & Li & O & Flux (2500 Angstrom) & Exposure (min.), P1455 & 10.92 & 21. & 3.5 & 8.9 & 8.3 * 10^-15 & 400 , BD-05 1317 & 9.87 & 40. & 3.3 & 9.2 & 2.1 * 10^-14 & 180 , 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 is in-press in the Ap.J. (20 October 1995 issue), while a paper on the oxygen abundances, as well as the detailed abundance distribution of many elements, is in preparation. We have observing time at McDonald Observatory in November 1995 to obtain spectra of the low- mass members of the oldest Orion subgroup (Ia) in order to further investigate, in particular, the Li and O abundances in these oldest 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: Fixed_Targets Target_Number: 1 Target_Name: BD-05D1317 Alternate_Names: Description: STAR, F3-F9 Position: RA=05H 32M 53.495S +/-0.1S, DEC=-05D 11' 08.56" +/-0.5" Equinox: 1950.0 RV_or_Z: V= +30.8 RA_PM: +0.000 Dec_PM: +0.001 Epoch: 1950.0 Annual_Parallax: Flux: V=9.87 +/-0.03 B-V=+0.71 +/-0.05 F-CONT(2500)=2.1+/-0.1E-14 Comments: Target_Number: 2 Target_Name: BD-06D1250 Alternate_Names: Description: STAR, F3-F9 Position: RA=05H 33M 39.662S +/-0.1S, DEC=-06D 21' 28.17" +/-0.5" Equinox: 1950.0 RV_or_Z: V= +19.4 RA_PM: +0.000 Dec_PM: +0.006 Epoch: 1950.0 Annual_Parallax: Flux: V=9.96 +/-0.03 B-V=+0.53 +/-0.05 F-CONT(2500)=2.0+/-0.1E-14 Comments: Target_Number: 3 Target_Name: HD294297 Alternate_Names: Description: STAR, F3-F9 Position: RA=05H 37M 56.547S +/-0.1S, DEC=-02D 27' 13.88" +/-0.5" Equinox: 1950.0 RV_or_Z: V= +10.5 RA_PM: +0.001 Dec_PM: -0.002 Epoch: 1950.0 Annual_Parallax: Flux: V=10.12 +/-0.03 B-V=+0.58 +/-0.05 F-CONT(2500)=1.7+/-0.1E-14 Comments: ! This is a template for a single visit containing a single exposure ! Repeat exposure and visit blocks as needed Visits ! Section 6 Visit_Number:1 Visit_Requirements: ! Section 7.1 ! Uncomment or copy visit level special requirements needed ! Most of these requirements (including ORIENT) will limit scheduling ! PCS MODE [Fine | Gyro] ! GUIDing TOLerance ! DROP TO GYRO IF NECESSARY [NO REACQuisition] ! ORIENTation TO ! ORIENTation TO FROM ! ORIENTation TO FROM NOMINAL ! SAME ORIENTation AS ! CVZ ! PARallel ! SCHEDulability ! AFTER [BY [TO ]] ! AFTER ! BEFORE ! BETWEEN AND ! GROUP WITHIN