11607( 6) - 23-Nov-2009 16:39:53 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 11607 Version: 6 Check-in Time: 23-Nov-2009 16:39:53 STScI Edit Number: 4 Title Ly-alpha propagation in the planet-forming region of a circumstellar disk ------------------------------------------------------------------------------------ Type Cycle GO 17 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Thomas John Bethell University of Michigan CoI: Dr. Edwin Anthony Bergin University of Michigan N CoI: Dr. Gregory J. Herczeg California Institute of Technology N ------------------------------------------------------------------------------------ Abstract We propose using STIS to spectrally image the radial profile of resonantly scattered Lyman-alpha from the protoplanetary disk of TW Hya. Recent HST results have demonstrated that strong Lyman-alpha emission dominates the FUV radiation field of TW Hya. This has significant consequences for the chemical equilibrium of key species such as water within the planet-forming zone. Exploratory radiative transfer modeling predicts that the dominant Lyman-alpha component should resonantly scatter from the atomic layers of such disks at levels easily detectable with STIS. Using careful PSF subtraction, S/N ratios greater than 5 should be obtainable between 6-25AU from the central star. A detection of extended, resonantly scattered Lyman-alpha will reveal new information about the disk properties that cannot be obtained directly from other methods of observation. This includes constraining the morphology of the upper layers of the gas disk and possibly revealing the existence of a puffed-up inner disk. We will also be able to place limits on the Lyman-alpha flux driving chemistry in the disk interior. ------------------------------------------------------------------------------------ Observations Description ------------------------ We require high SNR, spatially resolved spectra of the Ly-alphga emission in the vicinity of the star TW Hya. To extract the Ly-alpha excess above the stellar PSF we use PSF subtraction by obtaining the instrument PSF from a WD. The basic observations employ long slit spectroscopy using STIS FUV-MAMA, the 52x0.2" slit, and the G140M grating which will select the Ly-alpha spectrum (that must be subsequently separated from the continuum emission in the case of TW Hya). This requires an identical sequence of exposures for TW Hya and the WD. Long slit observation will be made at offset -0.4, -0.2, 0, 0.2, 0.4" relative 11607( 6) - 23-Nov-2009 16:39:53 - [ 2] to each star. This is achieved by defining a single perpendicular-to-slit pattern. In general the exposures are limited by available orbits, although the SNR will be enhanced by integrating over wavelength space. Regardless, the Ly-alpha line of TW Hya is sufficiently broad (~400km/s) to be resolved by the G140M grating. The most important exposure is the 0 offset, which has the longest exposure times. The other offsets are provided to reveal (albeit crudely) any 2D asymmetries in TW Hya's emission. The Peak-up exposure for TW Hya employs the G430L and may provide usual scientific information regarding the accretion rate. Real Time Justification ----------------------- None. Calibration Justification ------------------------- None. Additional Comments ------------------- ------------------------------------------------------------------------------------ 11607( 6) - 23-Nov-2009 16:39:53 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 V-TW-HYA STAR, CIRCUMSTELLAR RA=11H01M51.9063S +/- 0.1", J2000 V = 11.1 B=11.8 MATTER, EXTRA-SOLAR DEC=-34D42'17.02" +/- 0.1" PLANETARY SYSTEM, PROTOPLANETARY DISK, T TAURI STAR Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Proper motions and fluxes from Simbad entry. Proper motion RA has been transformed from arsec/yr to sec/yr Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1997 -0.0054 -0.01236 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 2 WD-1056-384 STAR, DA RA=10H58M20.1100S +/- 0.1", J2000 V = 14.0 DEC=-38D44'25.10" +/- 0.1" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Coordinates were updated to more accurate and recent (2006-2007 epoch observations) J2000/ICRS coordinates to meet STIS accuracy requirements. Coordinates and proper motions taken from Landolt 2007 AJ. Proper motion RA has been converted from arcsec/yr to sec/yr. Chosen for its proximity to Target 1 (TW Hya). This object is used primarily to obtain the instrument PSF. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2006 -0.013 0.0324 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 11607( 6) - 23-Nov-2009 16:39:53 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type STIS-PERP-TO-SLIT Pattern_Purpose DITHER Number_Of_Points 5 Point_Spacing 0.2 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 0.0 Angle_Between_Sides Center_Pattern YES ------------------------------------------------------------------------------------------------------------------------------------ 11607( 6) - 23-Nov-2009 16:39:53 - [ 5] Visit: 01 Visit Requirements: On Hold Comments: Additional Comments: TW Hya visit. Acquisition followed by Peak-up followed by series of five offset science exposures from -0.4 to +0.4" Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 V-TW-HYA STIS/CCD ACQ F28X50OII MIRROR 1 6 S I Comments: ACQ ETC used to calculate ACQ exposure time. Trebled time required for SNR=40, as recommended. ------------------------------------------------------------------------------------------------------------------------------------ 2 V-TW-HYA STIS/CCD ACQ/PEA 52X0.05 G430L 4300 1 15 S K Comments: STIS Spectroscopic ETC used. Exposure time treble that required for SNR=40. ------------------------------------------------------------------------------------------------------------------------------------ 3 V-TW-HYA STIS/FUV ACCUM 52X0.2 G140M 1222 1 1000 S PATTERN 1 3 -MAMA see below ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ V-TW-HYA 1 STIS/CCD ACQ F28X50OI MIRROR none none none none 1 N/A II V-TW-HYA 2 STIS/CCD ACQ/PEA 52X0.05 G430L 4300 none none none none 1 N/A K V-TW-HYA 3 STIS/FUV ACCUM 52X0.2 G140M 1222 1 none none none 1 788.0 S -MAMA V-TW-HYA 3 STIS/FUV ACCUM 52X0.2 G140M 1222 2 none none none 1 788.0 S -MAMA V-TW-HYA 3 STIS/FUV ACCUM 52X0.2 G140M 1222 3 none none none 2 3058 S -MAMA V-TW-HYA 3 STIS/FUV ACCUM 52X0.2 G140M 1222 4 none none none 3 1504.0 S -MAMA V-TW-HYA 3 STIS/FUV ACCUM 52X0.2 G140M 1222 5 none none none 3 1504.0 S -MAMA 11607( 6) - 23-Nov-2009 16:39:53 - [ 6] Visit: 02 Visit Requirements: SAME ORIENT AS 01 On Hold Comments: Additional Comments: Visit WD 1056-384. Same sequence of exposures as visit 1, although the acquisition filters/gratings differ. This visit uses a special requirement on the orientation. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 WD-1056-384 STIS/CCD ACQ F28X50LP MIRROR 1 0.4 S Comments: Exposure time calculated using ACQ ETC. ------------------------------------------------------------------------------------------------------------------------------------ 2 WD-1056-384 STIS/CCD ACQ/PEA 52X0.05 MIRROR 1 1.5 S K Comments: ACQ PEAK ETC used. Exposure time (for SNR=40) multiplied by five. ------------------------------------------------------------------------------------------------------------------------------------ 3 WD-1056-384 STIS/FUV ACCUM 52X0.2 G140M 1222 1 10 S PATTERN 1 3 -MAMA see below ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ WD-1056-384 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A WD-1056-384 2 STIS/CCD ACQ/PEA 52X0.05 MIRROR none none none none 1 N/A K WD-1056-384 3 STIS/FUV ACCUM 52X0.2 G140M 1222 1 none none none 1 977 S -MAMA WD-1056-384 3 STIS/FUV ACCUM 52X0.2 G140M 1222 2 none none none 1 977 S -MAMA WD-1056-384 3 STIS/FUV ACCUM 52X0.2 G140M 1222 3 none none none 2 3085 S -MAMA WD-1056-384 3 STIS/FUV ACCUM 52X0.2 G140M 1222 4 none none none 3 1517 S -MAMA WD-1056-384 3 STIS/FUV ACCUM 52X0.2 G140M 1222 5 none none none 3 1517 S -MAMA 11607( 6) - 23-Nov-2009 16:39:53 - [ 7] Summary Form for Proposal 11607 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 52X0.05, 52X0.2, F28X50LP, F28X50OIII ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ, ACQ/PEAK ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PATTERN 1 3, SAME ORIENT AS 01 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140M, G430L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names V-TW-HYA, WD-1056-384 ------------------------------------------------------------------------------------------------------------------------------------