8615( 4) - 07/03/02 11:51 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8615 Version: 4 Check-in Date: 05-Jun-2001 11:04:07 1.Proposal Title: Ultraviolet Spectroscopy of R Coronae Borealis Stars -- Broad Lines from an Accretion Disc? ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 9 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: David Lambert University of Texas at Austin CoI: Prof. N. Kameswara Rao Indian Institute of Astrophysics N CoI: Assoc. Prof. Geoffrey Clayton Louisiana State University N CoI: Assoc. Prof. Peter L. Cottrell University of Canterbury N ------------------------------------------------------------------------------------ 5. Abstract STIS spectra of three R Coronae Borealis (RCB) stars will provide novel data on hot gas near these stars; such data can be obtained only from HST. RCBs are hydrogen- deficient and fade at unpredictable times as a carbon soot cloud obscures the star. Optical spectra taken when a star has faded reveal an emission line spectrum containing sharp (FWHM ~15 km s^-1) and broad (FWHM ~250 km s^-1) lines. The latter are of much higher excitation than the former. For R CrB, it has been suggested that the broad lines arise from an accretion disk around a compact secondary. These optical lines are visible only during the infrequent extreme fadings of a RCB. Although IUE spectra reveal high-excitation emission lines at maximum light, the IUE spectra lack the spectral resolution to distinguish broad from sharp lines. STIS spectra will resolve the broad-line from a sharp-line component, and, in the case, of R CrB, where repeat visits are requested, be used to search for velocity variations as the companion orbits the RCB. In addition, the line intensity ratios will provide new estimates of the physical conditions of the gas emitting the broad lines. This proposal may help to answer the question -- How are RCBs formed? And this answer may show that, although RCBs are rare, many low mass stars evolve through the RCB on their path to extinction as a white dwarf. ------------------------------------------------------------------------------------ 8615( 4) - 07/03/02 11:51 - [ 2] Observations Description ------------------------ Archived IUE spectra have been examined to estimate line and continuum fluxes. Line fluxes F_line are quoted in erg cm^-2 s^-1. All IUE spectra were at low resolution and, hence, cannot be used to separate sharp from broad emission lines. It is safe to assume from the known membership of the sharp optical lines that the C II, C IV, and C IV lines are broad lines which will be resolved with G140M and G230M. In estimating exposure times with the ETC we have assumed the lines to have a width FWHM = 250 km s^-1. A S/N = 20 is our target. Overheads of 24 min. per orbit assumed. 1. V854 Cen: Line fluxes are from Lawson et al. (1999): The C II 1335 complex has an integrated flux F_line ~1 * 10^-13. Desired S/N with G140M is reached in 30m, or 1 orbit. The C IV doublet's flux is F_line = 8 * 10^-14 at 1550 A for which S/N = 20 is closely approached in 110m or about 3 orbits. The C III lines' flux is F_line = 1 * 10^ -13 at 1909 A for which S/N = 20 requires 64m or about 2 orbits. em The C II 2326 A line has F_line = 4 * 10^-13 requiring 8m. This and the overhead can likely be squeezed into an orbit assigned to another spectral observation. 2. R CrB: Line fluxes are from our scrutiny of the many archived IUE spectra. The C IV 1550 lines are not detected. With G140M, prohibitive exposure times are needed to improve on the IUE flux limit. The C II lines are seen with an apparently variable flux at a mean flux of F_line = 1.2 * 10^-13 requiring 24m for S/N =20 or 1 orbit given the overheads. These lines are expected to be `broad' without a `sharp' component based on our observation of broad N II lines. Three observations in Cycle 9 separated by several months are requested to search for velocity differences. 3. RY Sgr: The C II 1335 lines have F_line = 2.0 * 10^-14 requiring 140m for S/N =20 or 4 orbits. The requested number of orbits is 6 for V854 Cen, 3 for R CrB, and 4 for RY Sgr for a grand total of 13 orbits. Real Time Justification ----------------------- This program can be performed equally well in decline or at maximum light. The declines happen at irregular intervals but we shall continue monitoring the stars at Mt. John Observatory, as well as continuing to sift reports from amateur observers worldwide. In deep declines, it will likely be necessary to make changes in the acquisition exposures. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 8615( 4) - 07/03/02 11:51 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD141527 STAR RA=15H 48M 34.41S +/- 0.0", J2000 V = 5.8 DEC=+28D 09' 24.3" +/- 0.0" B-V = 0.60 F(1335)=1.2e-13 Coordinate Source: HIPPARCOS/TYCHO_CATALOGUE Comments: This is an irregular variable. The V magnitude can fade by several magnitudes. The flux in the wavelength region of interest will not change significantly. 2 V854-CEN STAR RA=14H 34M 49.43S +/- 0.4", DEC= J2000 V = 7.0 -39D 33' 19.4" +/- 0.4", PLATE- B-V = 0.60 ID=0163 F(1335)=1e-13 F(1909)=1e-13 F(2326)=4e-13 Coordinate Source: GUIDE_STAR_CATALOG Comments: This is an irregular variable. The V magnitude can fade by several magnitudes. The flux in the wavelength region of interest will not change significantly. The GSC coordinates are accurate because the star was faint when the GSC plate was taken. 3 HD180093 STAR RA=19H 16M 32.77S +/- 0.0", DEC= J2000 V = 6.5 -33D 31' 20.3" +/- 0.0" B-V = 0.60 F(1335)=2e-14 Coordinate Source: HIPPARCOS/TYCHO_CATALOGUE Comments: This is an irregular variable. The V magnitude can fade by several magnitudes. The flux in the wavelength region of interest will not change significantly. 8615( 4) - 07/03/02 11:51 - [ 4] Visit: 01 Visit Priority: Visit Requirements: BETWEEN 1-JUN-2000 AND 30-SEP-2000 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 HD141527 STIS/C ACQ F25ND3 MIRROR ACQTYPE=POINT 1 0.1 S CD ------------------------------------------------------------------------------------------------------------------------------------ 2 HD141527 STIS/F ACCUM 52X0.2 G140M 1321 1 30 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8615( 4) - 07/03/02 11:51 - [ 5] Visit: 02 Visit Priority: Visit Requirements: BETWEEN 1-DEC-2000 AND 28-FEB-2001 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 HD141527 STIS/C ACQ F25ND3 MIRROR ACQTYPE=POINT 1 9.0 S CD ------------------------------------------------------------------------------------------------------------------------------------ 2 HD141527 STIS/F ACCUM 52X0.2 G140M 1321 1 30 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8615( 4) - 07/03/02 11:51 - [ 6] Visit: 03 Visit Priority: Visit Requirements: BETWEEN 1-APR-2001 AND 30-JUN-2001 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 HD141527 STIS/C ACQ F25ND3 MIRROR ACQTYPE=POINT 1 0.1 S CD ------------------------------------------------------------------------------------------------------------------------------------ 2 HD141527 STIS/F ACCUM 52X0.2 G140M 1321 1 30 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8615( 4) - 07/03/02 11:51 - [ 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 V854-CEN STIS/C ACQ F25ND3 MIRROR ACQTYPE=POINT 1 0.1 S CD ------------------------------------------------------------------------------------------------------------------------------------ 2 V854-CEN STIS/F ACCUM 52X0.2 G140M 1321 1 37 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 3 V854-CEN STIS/N ACCUM 52X0.2 G230M 1933 1 49 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 V854-CEN STIS/N ACCUM 52X0.2 G230M 1933 1 25 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 5 V854-CEN STIS/N ACCUM 52X0.2 G230M 2338 1 9 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8615( 4) - 07/03/02 11:51 - [ 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 V854-CEN STIS/C ACQ F25ND3 MIRROR ACQTYPE=POINT 1 0.1 S CD ------------------------------------------------------------------------------------------------------------------------------------ 2 V854-CEN STIS/F ACCUM 52X0.2 G140M 1567 3 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8615( 4) - 07/03/02 11:51 - [ 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 HD180093 STIS/C ACQ F25ND3 MIRROR ACQTYPE=POINT 1 0.1 S CD ------------------------------------------------------------------------------------------------------------------------------------ 2 HD180093 STIS/F ACCUM 52X0.2 G140M 1321 2 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8615( 4) - 07/03/02 11:51 - [ 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 HD180093 STIS/C ACQ F25ND3 MIRROR ACQTYPE=POINT 1 0.1 S CD ------------------------------------------------------------------------------------------------------------------------------------ 2 HD180093 STIS/F ACCUM 52X0.2 G140M 1321 2 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8615( 4) - 07/03/02 11:51 - [ 11] Visit: 53 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 HD141527 STIS/C ACQ F25ND3 MIRROR ACQTYPE=POINT 1 0.1 S CD ------------------------------------------------------------------------------------------------------------------------------------ 2 HD141527 STIS/F ACCUM 52X0.2 G140M 1321 1 30 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8615( 4) - 07/03/02 11:51 - [ 12] Visit: 54 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 V854-CEN STIS/C ACQ F25ND3 MIRROR ACQTYPE=POINT 1 0.1 S CD ------------------------------------------------------------------------------------------------------------------------------------ 2 V854-CEN STIS/F ACCUM 52X0.2 G140M 1321 1 37 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 3 V854-CEN STIS/N ACCUM 52X0.2 G230M 1933 1 49 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 4 V854-CEN STIS/N ACCUM 52X0.2 G230M 1933 1 25 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 5 V854-CEN STIS/N ACCUM 52X0.2 G230M 2338 1 9 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8615( 4) - 07/03/02 11:51 - [ 13] Summary Form for Proposal 8615 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F25ND3 52X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BETWEEN 1-JUN-2000 AND 30-SEP-2000 BETWEEN 1-DEC-2000 AND 28-FEB-2001 BETWEEN 1-APR-2001 AND 30-JUN-2001 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G140M G230M ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD141527 V854-CEN HD180093 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1321 1933 2338 1567 ------------------------------------------------------------------------------------------------------------------------------------