16290( 4) - 27-Jun-2020 22:07:50 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 16290 Version: 4 Check-in Time: 27-Jun-2020 22:07:50 STScI Edit Number: 2 Title UV Spectroscopy of PDS 70: A T Tauri Star Hosting a Newborn Planetary System ------------------------------------------------------------------------------------ Type Cycle GO 28 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Stephen L. Skinner University of Colorado at Boulder Y CoI: Dr. Marc Audard Observatoire de Geneve N ------------------------------------------------------------------------------------ Abstract Observational studies of planet-hosting T Tauri stars (TTS) provide crucial insight into the earliest evolutionary stages of planet formation at ages of a few Myr. In a exciting new discovery, two giant protoplanets have been directly imaged orbiting in the disk gap of the nearby (113 pc) TTS PDS 70. The gap is gas-depleted, directly exposing the protoplanets to UV and X-ray irradiation from the star. PDS 70 is the closest planet-hosting TTS discovered so far and viewed through very low extinction, making it an exceptional target for UV spectroscopy with HST. We propose to obtain the first UV spectra of PDS 70 using STIS FUV (G140L) and NUV (G230L) gratings. Our main objectives are to determine the star's accretion rate (which remains controversial) and use the UV spectra, along with existing X-ray spectra, to assess the impact of UV/X-ray irradiation on disk and protoplanet atmosphere ionization and heating. Stellar UV and X-ray emission influence disk dissipation and mass-loss, thus affecting the timescale for planet-formation, a key constraint for planet-formation models. ------------------------------------------------------------------------------------ Observations Description ------------------------ We propose to obtain STIS/MAMA long-slit (52 x 0.2 arcsec aperture) spectra of the T Tauri star PDS 70 with G140L (1 orbit) and G230L (1 orbit). We prefer that the two spectra be obtained contemporaneously and we have thus packaged them into one Visit (2 orbits) in Phase II. There are no Orient or explicit Timing constraints. In Phase II, we have used G140L and G230L exposure times of 887 and 739 s respectively with 3 iterations to fill the orbits. We want to use these shorter exposures to check for possible spectral variability across exposures, which may be present in our target since T Tauri stars often vary in the UV. We have requested the G140L exposure to be placed in the second orbit since it provides more usable exposure time and 16290( 4) - 27-Jun-2020 22:07:50 - [ 2] we anticipate lower fluxes in the FUV than in NUV. For the representative STIS ETC G230L simulation (number entered in APT template) we have assumed a Pickles K7V spectral type normalized to B = 13.42 mag (Simbad), and have added a representative Mg II doublet line (2799 A.) using a line flux of 1.0e-13 erg/cm2/s (sum of the doublet components) typical of T Tauri stars. For the G140L ETC simulation we have assumed a faint flat continuum and have added a C IV doublet line (1549 A.) using a typical T Tauri star doublet line flux of 1.65e-14 erg/cm2/s (sum of the doublet components). We will perform a target ACQ but since we are using a 0.2 arcsec slit width we have not inserted a PEAK-up in the Phase II observing plan. We have selected the STIS LP filter (F28X50LP) for ACQ. We have set the ACQ exposure time to 0.4 s which ETC simulations indicate will provide SNR = 178 - 289, depending on what input values we use to normalize the target flux for Pickles K7V spectral template , i.e. B=13.42, V = 12.18, R = 11.71, or F_lambda = 2.2e-15 ergs/cm2/s/A from Swift U-filter (center=3465 A.) flux density. Using B=13.42 gives SNR=289 in 0.4 s (t_sat = 1.6 s), V = 12.18 gives SNR = 270 (t_sat= 1.83 s), R=11.71 gives SNR=204 (t_sat = 3.21 s), and the Swift U-filter flux density gives SNR=178 (t_sat = 4.17 s). ------------------------------------------------------------------------------------ 16290( 4) - 27-Jun-2020 22:07:50 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 PDS70 STAR, K V-IV, T TAURI RA=14H08M10.1540S +/- J2000 V = 3.13 V = 12.18 +/- 0.13 B=13.42 (Simbad); STAR 0.0000397", DEC=-41D23'52.58" Swift uvw2 (1599-2256 A.) = 1.5e-13 +/- 0.0000284" ergs/cm^2/s; uvwI (2253-2946 A.) = 2.7e-13 ergs/cm^2/s (ref. Joyce et al. 2020) Reference Frame: ICRS Comments: RA, Dec are from Simbad (referenced to Gaia DR2). RA, Dec errors, Proper Motion, Radial Velocity are from Gaia DR2. V mag and uncertainty are from range given in Simbad. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 -0.002636059339522487 -0.023823 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 16290( 4) - 27-Jun-2020 22:07:50 - [ 4] Visit: 01 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 PDS70 STIS/CCD ACQ F28X50LP MIRROR 1 0.4 S (0.4 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 PDS70 STIS/NUV ACCUM 52X0.2 G230L 2376 3 739 S -MAMA (2217 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 PDS70 STIS/FUV ACCUM 52X0.2 G140L 1425 3 887 S -MAMA (2661 S) ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ PDS70 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A PDS70 2 STIS/NUV ACCUM 52X0.2 G230L 2376 none none 1 none 1 N/A -MAMA PDS70 2 STIS/NUV ACCUM 52X0.2 G230L 2376 none none 2 none 1 N/A -MAMA PDS70 2 STIS/NUV ACCUM 52X0.2 G230L 2376 none none 3 none 1 N/A -MAMA PDS70 3 STIS/FUV ACCUM 52X0.2 G140L 1425 none none 1 none 2 N/A -MAMA PDS70 3 STIS/FUV ACCUM 52X0.2 G140L 1425 none none 2 none 2 N/A -MAMA PDS70 3 STIS/FUV ACCUM 52X0.2 G140L 1425 none none 3 none 2 N/A -MAMA 16290( 4) - 27-Jun-2020 22:07:50 - [ 5] Summary Form for Proposal 16290 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 52X0.2, F28X50LP ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/FUV-MAMA, STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140L, G230L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names PDS70 ------------------------------------------------------------------------------------------------------------------------------------