9093( 3) - 07/13/01 07:57 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9093 Version: 3 Check-in Date: 13-Jul-2001 07:56:52 1.Proposal Title: Resolving Molecular Hydrogen Disks Around T Tauri Stars ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 10 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Christopher Johns-Krull University of California - Berkeley CoI: Dr. Jeff Valenti Space Telescope Science Institute N CoI: Dr. Jeffrey Linsky University of Colorado/JILA N ------------------------------------------------------------------------------------ 5. Abstract Molecular hydrogen is believed to be the dominant constituent of circumstellar disks at radii ~ 0.1 - 5 AU around young stars. Fluoresced UV lines pumped by Ly-Alpha are bright and offer a valuable probe of H_2 in disks around young stars, with the ultimate goal being the ability to study the structure and evolution of the planet forming regions around these stars. The limited H_2 data now available for T Tauri stars (TTS) are inadequate to isolate the location of molecular hydrogen emission, though the current data suggests emission from ~ 2 AU in the disk around DF Tau. We will use deep, high resolution (E140H) STIS-FUV spectra to resolve the distinctive spectral line signature of Keplerian rotation in disks around two nearly edge on TTS. These will be the first high resolution UV spectra of any TTS and will provide the radius in the disk at which molecular hydrogen can survive. This in turn indicates the inner boundary of the ``dead zone" in TTS accretion disks which is the likely location for the formation of planets. ------------------------------------------------------------------------------------ 9093( 3) - 07/13/01 07:57 - [ 2] Observations Description ------------------------ We require high resolution, good S/N spectra of the molecular hydrogen lines of our 3 targets. We will use the E140H grating with the 0.2 * 0.09 arcsecond slit which will provide a spectral resolution R \equiv Lambda/2DeltaLambda = 114, 000 where DeltaLambda is the dispersion (Angstrom\ pix^-1). The high resolution is required to resolve the distinctive spectral line shapes expected from a Keplerian disk in DF Tau and SU Aur. We also wish to observe TW Hya with the high resolution mode of STIS. Our E140M observations suggest that the H_2 lines in TW Hya are marginally resolved; however, these spectra were taken with the 0.5 * 0.5 arcsecond slit and the line spread function (spectral PSF) is uncertain in this mode. If the inclination is not exactly 0, some broadening may result. Thus, we require the high resolution observations to acurately determine the line broadening in TW Hya. The 0.2^ tall slit will give us limited spatial coverage (~ 3 resolution elements covering out to 28 AU) in the off chance the H_2 emission is spatially extended in any of our sources. We will also take a short (~ 100 sec) G430L spectrum of each object to obtain a flux calibrated low resolution optical spectrum which can be used to measure the mass accretion rate onto the star following the analysis of Valenti et al. (1993) or Gullbring et al. (1998) in order to place our observations in the context of the accretion variability present in these (and all) CTTS. We have used the online STIS exposure time calculator to estimate exposure times for this program. Our requirement is a S/N >= 10 per resolution element to obtain data the quality of Figure 2. Molecular hydrogen line strengths are taken from our previous GTO observations and from IUE low resolution spectra for SU Aur (Valenti et al. 2000). In the latter case we assume a broadening equal to that for DF Tau (Figure 1). For DF Tau and SU Aur, the required exposure time is ~ 180 minutes. Taking into account the visibility of the targets throughout the spacecraft orbit and various observing overheads, this results in 5 orbits giving a total exposure time of ~ 10, 890 seconds (181 minutes). This give a final S/N ~ 11.5 for DF Tau and SU Aur. TW Hya's H_2 lines are brighter, requiring only 2 orbits which will give a final S/N ~ 15. All S/N values are in given in the peak of the line. Thus, our total program requires only 12 orbits of HST time. Real Time Justification ----------------------- There are no special requirements. N/A Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9093( 3) - 07/13/01 07:57 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD283654 STAR, T TAURI STAR, K V RA=04H 27M 2.786S +/- 0.1", J2000 V = +12 V = 11.49+/-1.0 -IV DEC=25D 42' 22.559" +/- 0.1" B-V = 0.89+/-0.1 Coordinate Source: HIPPARCOS/TYCHO_CATALOGUE Comments: HIP 20777 coordinates; Proper motion from Hipparcos; RV, V, B-V from HBC Catalog Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1991.25 0.00107 -0.0264 0.007 2 HD282624 STAR, T TAURI STAR, K V RA=04H 55M 59.384S +/- 0.1", J2000 V = +16 V = 8.93+/-1.0 -IV DEC=30D 34' 1.715" +/- 0.1" B-V = 0.85+/-0.1 Coordinate Source: HIPPARCOS/TYCHO_CATALOGUE Comments: HIP 22925 coordinates; Proper motion from Hipparcos; RV, V, B-V from HBC Catalog Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1991.25 0.00001 -0.0217 0.007 3 CD-34D7151 STAR, T TAURI STAR, G V RA=11H 1M 51.954S +/- 0.1", DEC= J2000 V = +6 V = 10.94+/-1.0 -IV -34D 42' 16.912" +/- 0.1" B-V = 0.79+/-0.1 Coordinate Source: HIPPARCOS/TYCHO_CATALOGUE Comments: HIP 53911 coordinates; Proper motion from Hipparcos; RV, V, B-V from HBC Catalog Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1991.25 -0.01125 -0.0124 0.02 9093( 3) - 07/13/01 07:57 - [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 HD283654 STIS/C ACQ F28X50O MIRROR 1 30 S CD II Comments: 30 S worked in o5kc01010 S/N=125 from ETC with o5kc01010 as input spectrum; Binary with 0.1" separation ------------------------------------------------------------------------------------------------------------------------------------ 11 HD283654 STIS/C ACQ/PEA 0.2X0.0 G430L 4300 1 2 S CD K 9 Comments: 1e5 total (200 peak) electrons from ETC with o5kc01010 ------------------------------------------------------------------------------------------------------------------------------------ 12 HD283654 STIS/C ACCUM 52X0.2 G430L 4300 1 120 S MAX DUR 100% CD Comments: 30 S worked well in o5kc01010; S/N=129 from ETC with o5kc01010 as input spectrum ------------------------------------------------------------------------------------------------------------------------------------ 13 HD283654 STIS/F TIME-TA 0.2X0.0 E140H 1343 BUFFER-TIME=1800 1 1350 S UV-MAM G 9 A ------------------------------------------------------------------------------------------------------------------------------------ 14 HD283654 STIS/F TIME-TA 0.2X0.0 E140H 1343 BUFFER-TIME=1800 1 2920 S UV-MAM G 9 A ------------------------------------------------------------------------------------------------------------------------------------ 15 HD283654 STIS/F TIME-TA 0.2X0.0 E140H 1343 BUFFER-TIME=1800 1 2920 S UV-MAM G 9 A ------------------------------------------------------------------------------------------------------------------------------------ 16 HD283654 STIS/F TIME-TA 0.2X0.0 E140H 1343 BUFFER-TIME=1800 1 2920 S UV-MAM G 9 A ------------------------------------------------------------------------------------------------------------------------------------ 17 HD283654 STIS/F TIME-TA 0.2X0.0 E140H 1343 BUFFER-TIME=1800 1 2920 S UV-MAM G 9 A ------------------------------------------------------------------------------------------------------------------------------------ 9093( 3) - 07/13/01 07:57 - [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 20 HD282624 STIS/C ACQ F28X50O MIRROR 1 2 S CD II Comments: Scaling from CD-34D7151 (DeltaV=2.0) gives 2 sec ------------------------------------------------------------------------------------------------------------------------------------ 21 HD282624 STIS/C ACQ/PEA 0.2X0.0 G430L 4300 1 0.5 S CD K 9 Comments: Scaling from CD-34D7151 gives 4e5 total (920 peak) e- ------------------------------------------------------------------------------------------------------------------------------------ 22 HD282624 STIS/C ACCUM 52X0.2 G430L 4300 1 40 S MAX DUR 100% CD Comments: S/N=129 in 20 sec scaling from CD-34D7151, use 40 sec ------------------------------------------------------------------------------------------------------------------------------------ 23 HD282624 STIS/F TIME-TA 0.2X0.0 E140H 1343 BUFFER-TIME=1800 1 1545 S UV-MAM G 9 A ------------------------------------------------------------------------------------------------------------------------------------ 24 HD282624 STIS/F TIME-TA 0.2X0.0 E140H 1343 BUFFER-TIME=1800 1 2935 S UV-MAM G 9 A ------------------------------------------------------------------------------------------------------------------------------------ 25 HD282624 STIS/F TIME-TA 0.2X0.0 E140H 1343 BUFFER-TIME=1800 1 2935 S UV-MAM G 9 A ------------------------------------------------------------------------------------------------------------------------------------ 26 HD282624 STIS/F TIME-TA 0.2X0.0 E140H 1343 BUFFER-TIME=1800 1 2935 S UV-MAM G 9 A ------------------------------------------------------------------------------------------------------------------------------------ 27 HD282624 STIS/F TIME-TA 0.2X0.0 E140H 1343 BUFFER-TIME=1800 1 2935 S UV-MAM G 9 A ------------------------------------------------------------------------------------------------------------------------------------ 9093( 3) - 07/13/01 07:57 - [ 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 ------------------------------------------------------------------------------------------------------------------------------------ 30 CD-34D7151 STIS/C ACQ F28X50O MIRROR 1 12 S CD II Comments: S/N=125 from ETC with o59d01010 as input spectrum ------------------------------------------------------------------------------------------------------------------------------------ 31 CD-34D7151 STIS/C ACQ/PEA 0.2X0.0 G430L 4300 1 3 S CD K 9 Comments: 4e5 total (920 peak) electrons from ETC with o59d01010 ------------------------------------------------------------------------------------------------------------------------------------ 32 CD-34D7151 STIS/C ACCUM 52X0.2 G430L 4300 1 120 S MAX DUR 100% CD Comments: 260 S was more than enough in o59d01010; S/N=194 from ETC with o59d01010 as input spectrum ------------------------------------------------------------------------------------------------------------------------------------ 33 CD-34D7151 STIS/F TIME-TA 0.2X0.0 E140H 1343 BUFFER-TIME=1800 1 1420 S UV-MAM G 9 A ------------------------------------------------------------------------------------------------------------------------------------ 34 CD-34D7151 STIS/F TIME-TA 0.2X0.0 E140H 1343 BUFFER-TIME=1800 1 2935 S UV-MAM G 9 A ------------------------------------------------------------------------------------------------------------------------------------ 9093( 3) - 07/13/01 07:57 - [ 7] Summary Form for Proposal 9093 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50OII 0.2X0.09 52X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACQ/PEAK ACCUM TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=1800 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements MAX DUR 100% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G430L E140H ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD283654 HD282624 CD-34D7151 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 4300 1343 ------------------------------------------------------------------------------------------------------------------------------------