8206( 4) - 10/09/00 11:00 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8206 Version: 4 Check-in Date: 09-Oct-2000 10:59:17 1.Proposal Title: The Structure of the Accretion Flow on pre-main-sequence stars ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Erik Gullbring Stockholm University CoI: Dr. Lee Hartmann Smithsonian Astrophysical Observatory N CoI: Mr. James Muzerolle Smithsonian Astrophysical Observatory N CoI: Erik Gullbring Stockholm Observatory N ------------------------------------------------------------------------------------ 5. Abstract We propose to test an essential prediction of the magnetospheric accretion model for T Tauri stars. STIS echelle spectra will be used to search for the relatively narrow high-temperature emission lines that must result from the magnetospheric accretion shock, but are not expected in the previous, alternative boundary layer model. By combining the results from high temperature (10^5 K) lines, accessible only with HST, with optical lines and optical-UV continuum emission, we will develop physically self-consistent models of accretion shock structure. The geometrically distribution of the emitting gas as derived from our results will test theories of mass-loading of magnetic field lines at the magnetosphere-disk interface. Analysis of the UV emission lines will also provide improved calibrations between ultraviolet continuum emission and accretion luminosities, and thus improve estimates of mass accretion rates for T Tauri stars. ------------------------------------------------------------------------------------ 8206( 4) - 10/09/00 11:00 - [ 2] Observations Description ------------------------ We propose to use the the echelle mode on the STIS-instrument with the 0.2*0.2 slit using the gratings E230M and E140M. This instrument setting will provide us with enough spectral resolution and signal-to-noise (S/N) ratio within a reasonable exposure time. We have estimated integration times from what is known of the flux-level in the ultraviolet wavelengths region, which is not necessarily reflected in the optical brightness of the T Tauri stars. We have estimated the UV-level from MMT spectra down to 3200 Angstrom, obtained by us, and from IUE-spectra extracted from the NEWSIPS archive. These data, together with calculated spectra for wavelengths that are not covered by previous observations, were used as intrinsic flux-levels for the STIS Spectroscopic ETC. Values for the interstellar reddening for the individual objects were adopted from Gullbring et al. (1998). It is important to note that T Tauri stars show intrinsic variability i their UV-flux, making it difficult t o a priori know the flux-level of a star at the time of observation. For an accreting TTS, that have a high emission level in the UV a S/N of 15 in the continuum at 2800 Angstrom with the E230M grating is achieved in 30 - 40 minutes. In addition to guide star acquisition (6 minutes), the 0.2x0.2 slit requires target acquisition including peak-up aquisition with a total of 5 + 6.5 minutes for the first orbit in each visit. We estimate from the target aquisition ETC that a S/N of more than 40 is reached in 6 seconds with a OIII filter for the ccd. Five minutes re-aquistion for each orbit will then follow. For the E140M grating 40 - 90 min scientific integration is required to obtain a S/N of 3 in the continuum at 1550 Angstrom\ (close to the C IV line) for the accreting T Tauri stars. Therefore, it will take 3 orbits to collect a spectrum covering 1150 to 3100 Angstrom\ of an accreting T Tauri star. The line-to- continuum values for the emission lines are typically in the range f ro m 2 to 10, which then provides a good enough S/N to analyze the l ine-profiles. For the non- accreting WTTS, an integration time of 80 minutes for the E230M grating is required to obtain a S/N of 3 in the continuum. This implies 2 orbits. We do not propose to observe the WTTS with the E140M grating, since not enough S/N can be gained within reasonable integration times. Real Time Justification ----------------------- scheduling, Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 8206( 4) - 10/09/00 11:00 - [ 3] Data Distribution Paper Products: NO Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8206( 4) - 10/09/00 11:00 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 DS-TAU STAR, T TAURI STAR RA=4H 47M 48.45S +/- 0.4", J2000 V = 12+/-0.5 DEC=29D 25' 12.4" +/- 0.4", TYPE=K5V PLATE-ID=02TR A(V) = 0.3+/-0.1 2 DR-TAU STAR, T TAURI STAR RA=04H 47M 6.22S +/- 0.2", J2000 V = 11.1+/-0.6 DEC=16D 58' 43.4" +/- 0.2", A(V) = 1.6+/-0.4 PLATE-ID=00FI 3 CY-TAU STAR, T TAURI STAR RA=04H 17M 33.83S +/- 0.3", J2000 V = 13+/-0.7 DEC=28D 20' 47.3" +/- 0.3", A(V) = 0.3+/-0.05 PLATE-ID=0051 TYPE=M1V 4 V819-TAU STAR, T TAURI STAR RA=04H 19M 26.34S +/- 0.3", J2000 V = 13+/-0.2 DEC=28D 26' 14.7" +/- 0.3", A(V) = 0.9+/-0.1 PLATE-ID=0051 TYPE=K7V 8206( 4) - 10/09/00 11:00 - [ 5] 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 DS-TAU STIS/C ACQ F28X50O MIRROR ACQTYPE=POINT 1 6 S CD III ------------------------------------------------------------------------------------------------------------------------------------ 20 DS-TAU STIS/N ACCUM 0.2X0.2 E230M 1978 1 19 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 30 DS-TAU STIS/N ACCUM 0.2X0.2 E230M 2707 1 15 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 40 DS-TAU STIS/F ACCUM 0.2X0.2 E140M 1425 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 50 DS-TAU STIS/F ACCUM 0.2X0.2 E140M 1425 1 50 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8206( 4) - 10/09/00 11:00 - [ 6] 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 DR-TAU STIS/C ACQ F28X50O MIRROR ACQTYPE=POINT 1 5 S CD III ------------------------------------------------------------------------------------------------------------------------------------ 20 DR-TAU STIS/N ACCUM 0.2X0.2 E230M 1978 1 18 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 30 DR-TAU STIS/N ACCUM 0.2X0.2 E230M 2707 1 14 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 40 DR-TAU STIS/F ACCUM 0.2X0.2 E140M 1425 1 42 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 50 DR-TAU STIS/F ACCUM 0.2X0.2 E140M 1425 1 42 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8206( 4) - 10/09/00 11:00 - [ 7] 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 CY-TAU STIS/C ACQ F28X50O MIRROR ACQTYPE=POINT 1 11 S CD III ------------------------------------------------------------------------------------------------------------------------------------ 20 CY-TAU STIS/N ACCUM 0.2X0.2 E230M 1978 1 21 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 30 CY-TAU STIS/N ACCUM 0.2X0.2 E230M 2707 1 17 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 40 CY-TAU STIS/F ACCUM 0.2X0.2 E140M 1425 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 50 CY-TAU STIS/F ACCUM 0.2X0.2 E140M 1425 1 50 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8206( 4) - 10/09/00 11:00 - [ 8] 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 V819-TAU STIS/C ACQ F28X50O MIRROR ACQTYPE=POINT 1 11 S CD III ------------------------------------------------------------------------------------------------------------------------------------ 20 V819-TAU STIS/N ACCUM 0.2X0.2 E230M 2707 1 41 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 30 V819-TAU STIS/N ACCUM 0.2X0.2 E230M 1978 1 45 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8206( 4) - 10/09/00 11:00 - [ 9] Summary Form for Proposal 8206 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50OIII 0.2X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/NUV-MAMA STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR E230M E140M ------------------------------------------------------------------------------------------------------------------------------------ Target Names DS-TAU DR-TAU CY-TAU V819-TAU ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1978 2707 1425 ------------------------------------------------------------------------------------------------------------------------------------