8623( 4) - 03/21/00 13:06 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8623 Version: 4 Check-in Date: 21-Mar-2000 13:05:16 1.Proposal Title: HST, Chandra, and FUSE Studies of Interstellar Material toward HD 24534 (aka X Persei) ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 9 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Theodore Snow University of Colorado at Boulder CoI: Prof. John H. Black Chalmers University of Technology N CoI: Prof. Richard A. McCray University of Colorado N ------------------------------------------------------------------------------------ 5. Abstract We are proposing new HST/STIS high-resolution UV spectroscopic observations of the reddened star HD 24534 (aka X Persei), in order to: (1) establish accurate gas-phase column densities for elements other than carbon and oxygen (for which high- quality data already exist), for the purpose of deriving (in conjunction with FUSE and Chandra observations) absolute depletions of several key elements; and (2) further pursue molecular abundances toward this star, to supplement HST/GHRS data obtained earlier which showed that this line of sight supports a rich chemistry. The depletion work will focus on magnesium, silicon, and iron, while the molecular observations will entail searches for vibrationally excited H_2, an important indicator of cloud physical conditions; and sulfur- bearing species (such as SO, CS, and SH), which represent an important unknown in current models of interstellar cloud chemistry. HD 24534 is the best possible target for this work, because it is the brightest star available that lies behind a translucent line of sight with high molecular abundances, and because it is also an x-ray source whose spectrum is ideally suited for the measurement (through x-ray absorption and scattering) of total (gas plus dust) abundances in the line of sight. This will be the first line of sight for which depletions have been determined independent of any assumed ``cosmic'' abundance standard such as the sun or other stars. ------------------------------------------------------------------------------------ 8623( 4) - 03/21/00 13:06 - [ 2] Observations Description ------------------------ With very accurate data already in hand on oxygen and carbon, the emphasis of our proposed new depletion observations will be to determine, with comparable accuracy, the abundances of other key species thought to be important in dust and for which we will have AXAF data, such as magnesium, silicon, and iron. For magnesium we need no new observations, as the weak doublet at 1240Angstrom\ was observed by us in or previous HST program. We note that FUSE will provide additional constraints on the Mg II column density for this star, through multiplets at 1025 and 946Angstrom (but we realize that the former is likely to obliterated by H I Lyman-Beta absorption). For silicon we will measure and analyze a series of permitted Si II lines; i.e. lines at 1808, 1526, 1304, 1260, and 1190Angstrom\ (of which the 1808 and 1304Angstrom\ lines were observed previously), as well as far-UV features accessible to FUSE such as the lines at 1020 and 989Angstrom. These lines represent a range of f-values, and therefore will provide a sound measurement of the Si II column density, aided by our knowledge of the line-of-sight velocity structure. We will also attempt to detect the spin- forbidden line at 2335Angstrom, as discussed above. For iron we will observe a series of lines with a wide range of f- values, including LambdaLambda 2374, 2367, 2249, and 1608 (and several predicted, weak lines near 1600Angstrom\ as well as the very strong lines between 2500 and 2600Angstrom), which will provide an accurate column density through profile- fitting analysis (coupled with our knowledge of the b-value and of the line-of- sight velocity structure). For our molecular study, we will focus on vibrationally excited H_2 (many transitions within the short-wavelength echelle bandpass) and the compounds of sulfur described above. Following the discussion of Kaiser et al. (1998) regarding S/N levels achievable with the STIS, we find that S/N of 140 or greater in the far-UV high-resolution echelle modes and 330 or greater in the near-UV are thought to be achievable without recourse to any special procedures such as the use of FPSLIT slits. The Doppler corrections for spacecraft orbital motion are enough to ensure that +/- 12 pixel shifts and smoothing will occur for any exposures long enough to cover most of an orbit, and this provides significant smoothing of fixed-pattern noise. For HD 24534 the on-line exposure time calculator on the STScI web site indicates that S/N = 100 can be achieved in a little less than 2000 sec for both the E140H and E230H gratings, at the wavelengths of greatest interest to us (i.e. near 1300Angstrom\ in the far-UV and around 2335Angstrom\ in the near UV). Therefore the nominal exposure times needed for S/N = 200 and 300 are 8000 and 18, 000 sec, respectively, or 2.7 and 6 orbits (assuming a visibility period of about 3200 sec per orbit, based on the position of the star and the tabular information in the Call for Proposals). To allow for the fact that S/N does not scale directly with SQRT(N (where N is number of counts), we are assuming 4 orbits are needed when S/N = 200 is required, and 8 when we need S/N = 300. Our program consists of 6 separate wavelength settings: lambda_cent = 1343Angstrom (S/N = 200, requiring 4 orbits); lambda_cent = 1526Angstrom (S/N = 100; 1 orbit); lambda_cent = 1813Angstrom\ (S/N = 200; 4 orbits); lambda_cent = 2163Angstrom\ (S/N = 200; 4 orbits); lambda_cent = 2463Angstrom\ (S/N = 300; 8 orbits); and lambda_cent = 2962 (S/N = 100; 1 orbit). This totals 22 orbits. Real Time Justification ----------------------- We note that our longest-exposure wavelength setting requires 8 orbits, and point out that this needs to be broken into two separate exposures of 5 orbits or less, in view of the restrictions aimed at avoiding MAMA operation during spacecraft passage through the SAA. As explained in the proposal, we have upcoming observations of the HD 24534 line of sight using both the Chandra and FUSE observatories, and have already obtained ground-based ultra- high resolution spectroscopy of optical interstellar lines. The AXAF observations will provide data on the total (gas plus dust) column densities of certain elements (C, O, Mg, SI, Fe) for use in understanding depletions in this line of sight, while the FUSE spectra will provide detailed information on H_2, including an accurate total column density and rotational excitation information which will be useful in analyzing the physical conditions in the cloud. The ground-based observations were obtained through a program using the coude feed at Kitt Peak to obtain spectra at a resolving power of Lambda/DeltaLambda ~ 250, 000 in support of the FUSE H_2 analysis, and included Na I and K I profiles (helpful for interpreting UV lines due to atomic neutral species as well as molecules), as well as CH (useful in refining the molecular model of the cloud). Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 8623( 4) - 03/21/00 13:06 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD24534 STAR, OE RA=03H 55M 23.11S +/- 0.0074S, J2000 V = V = 6.51 DEC=+31D 02' 44.7" +/- 0.0051" +15.0 B-V = 0.28 Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000.0 -0.00199 -0.00451 0.00121 8623( 4) - 03/21/00 13:06 - [ 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 HD24534 STIS/C ACQ F28X50O MIRROR 1 0.1 S CD III Comments: Onboard Acq. for 2-4 ------------------------------------------------------------------------------------------------------------------------------------ 2 HD24534 STIS/C ACQ/PEA 0.2X0.0 MIRROR 1 0.1 S CD K 6 Comments: Onboard Acq. for 3-4 ------------------------------------------------------------------------------------------------------------------------------------ 3 HD24534 STIS/F ACCUM 0.2X0.0 E140H 1343 1 33 M UV-MAM 9 A Comments: The intent is to fill the first one of four orbits at this setting ------------------------------------------------------------------------------------------------------------------------------------ 4 HD24534 STIS/F ACCUM 0.2X0.0 E140H 1343 3 49 M UV-MAM 9 A Comments: The intent is to fill orbits 2-4 at this setting ------------------------------------------------------------------------------------------------------------------------------------ 8623( 4) - 03/21/00 13:06 - [ 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 HD24534 STIS/C ACQ F28X50O MIRROR 1 0.1 S CD III Comments: Onboard Acq. for 2-3 ------------------------------------------------------------------------------------------------------------------------------------ 2 HD24534 STIS/C ACQ/PEA 0.2X0.0 MIRROR 1 0.1 S CD K 6 Comments: Onboard Acq. for 3 ------------------------------------------------------------------------------------------------------------------------------------ 3 HD24534 STIS/F ACCUM 0.2X0.0 E140H 1526 1 33 M UV-MAM 9 A Comments: The intent is to fill one orbit at this setting ------------------------------------------------------------------------------------------------------------------------------------ 8623( 4) - 03/21/00 13:06 - [ 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 HD24534 STIS/C ACQ F28X50O MIRROR 1 0.1 S CD III Comments: Onboard Acq. for 2-4 ------------------------------------------------------------------------------------------------------------------------------------ 2 HD24534 STIS/C ACQ/PEA 0.2X0.0 MIRROR 1 0.1 S CD K 6 Comments: Onboard Acq. for 3-4 ------------------------------------------------------------------------------------------------------------------------------------ 3 HD24534 STIS/N ACCUM 0.2X0.0 E230H 1813 1 33 M UV-MAM 9 A Comments: The intent is to fill the first one of four orbits at this setting ------------------------------------------------------------------------------------------------------------------------------------ 4 HD24534 STIS/N ACCUM 0.2X0.0 E230H 1813 3 49 M UV-MAM 9 A Comments: The intent is to fill orbits 2-4 at this setting ------------------------------------------------------------------------------------------------------------------------------------ 8623( 4) - 03/21/00 13:06 - [ 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 HD24534 STIS/C ACQ F28X50O MIRROR 1 0.1 S CD III Comments: Onboard Acq. for 2-4 ------------------------------------------------------------------------------------------------------------------------------------ 2 HD24534 STIS/C ACQ/PEA 0.2X0.0 MIRROR 1 0.1 S CD K 6 Comments: Onboard Acq.for 3-4 ------------------------------------------------------------------------------------------------------------------------------------ 3 HD24534 STIS/N ACCUM 0.2X0.0 E230H 2163 1 33 M UV-MAM 9 A Comments: The intent is to fill the first one of four orbits at this setting ------------------------------------------------------------------------------------------------------------------------------------ 4 HD24534 STIS/N ACCUM 0.2X0.0 E230H 2163 3 49 M UV-MAM 9 A Comments: The intent is to fill orbits 2-4 at this setting ------------------------------------------------------------------------------------------------------------------------------------ 8623( 4) - 03/21/00 13:06 - [ 8] 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 HD24534 STIS/C ACQ F28X50O MIRROR 1 0.1 S CD III Comments: Onboard Acq. for 2-4 ------------------------------------------------------------------------------------------------------------------------------------ 2 HD24534 STIS/C ACQ/PEA 0.2X0.0 MIRROR 1 0.1 S CD K 6 Comments: Onboard Acq. for 3-4 ------------------------------------------------------------------------------------------------------------------------------------ 3 HD24534 STIS/N ACCUM 0.2X0.0 E230H 2463 1 33 M UV-MAM 9 A Comments: The intent is to fill the first one of eight orbits at this setting ------------------------------------------------------------------------------------------------------------------------------------ 4 HD24534 STIS/N ACCUM 0.2X0.0 E230H 2463 3 49 M UV-MAM 9 A Comments: The intent is to fill orbits 2-4 of eight orbits at this setting ------------------------------------------------------------------------------------------------------------------------------------ 8623( 4) - 03/21/00 13:06 - [ 9] Visit: 06 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 HD24534 STIS/C ACQ F28X50O MIRROR 1 0.1 S CD III Comments: Onboard Acq. for 2-4 ------------------------------------------------------------------------------------------------------------------------------------ 2 HD24534 STIS/C ACQ/PEA 0.2X0.0 MIRROR 1 0.1 S CD K 6 Comments: Onboard cq. for 3-4 ------------------------------------------------------------------------------------------------------------------------------------ 3 HD24534 STIS/N ACCUM 0.2X0.0 E230H 2463 1 33 M UV-MAM 9 A Comments: The intent is to fill orbit 5 of eight orbits at this setting ------------------------------------------------------------------------------------------------------------------------------------ 4 HD24534 STIS/N ACCUM 0.2X0.0 E230H 2463 3 49 M UV-MAM 9 A Comments: The intent is to fill orbits 6-8 of eight orbits at this setting ------------------------------------------------------------------------------------------------------------------------------------ 8623( 4) - 03/21/00 13:06 - [ 10] Visit: 07 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 HD24534 STIS/C ACQ F28X50O MIRROR 1 0.1 S CD III Comments: Onboard Acq. for 2-3 ------------------------------------------------------------------------------------------------------------------------------------ 2 HD24534 STIS/C ACQ/PEA 0.2X0.0 MIRROR 1 0.1 S CD K 6 Comments: Onboard Acq. for 3 ------------------------------------------------------------------------------------------------------------------------------------ 3 HD24534 STIS/N ACCUM 0.2X0.0 E230H 2962 1 33 M UV-MAM 9 A Comments: The intent is to fill one orbit at this setting ------------------------------------------------------------------------------------------------------------------------------------ 8623( 4) - 03/21/00 13:06 - [ 11] Summary Form for Proposal 8623 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50OIII 0.2X0.06 0.2X0.09 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR E140H E230H ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD24534 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1343 1526 1813 2163 2463 2962 ------------------------------------------------------------------------------------------------------------------------------------