14196( 5) - 25-May-2016 12:12:14 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 14196 Version: 5 Check-in Time: 25-May-2016 12:12:14 STScI Edit Number: 0 Title The Very Low Mass Object FW Tau b: An Edge-on Brown Dwarf Disk or a Planet Caught in Formation? ------------------------------------------------------------------------------------ Type Cycle GO 23 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Gregory J. Herczeg Peking University Y CoI: Dr. Sean M Andrews Smithsonian Institution Astrophysical N Observatory CoI: Dr. Brendan Bowler University of Texas at Austin N CoI: Dr. Michael J. Ireland Australian National University N CoI: Dr. Adam L. Kraus University of Texas at Austin N ------------------------------------------------------------------------------------ Abstract Planetary mass companions to solar mass stars may form through core accretion, gravitational instabilities in the disk, or protostellar core fragmentation. Recent searches have uncovered about 15 planetary mass companions to young Sun-like stars in orbits of 50-300 AU from the central star. These objects pose significant challenges for formation theories. One particular object, FW Tau b, may be caught in the process of formation. FW Tau b has an apparent brightness and colors consistent with an early L-dwarf, bright emission lines consistent with strong accretion, heavy K-band veiling due to warm dust, and a spatially resolved jet. However, the object mass is not known because the accretion/disk signatures veil the photosphere and have prevented detection of photospheric features and along with a precise measurement of spectral type or temperature. We propose to use STIS G750L to obtain a deep red-optical spectrum of this very faint and enigmatic object to measure its spectral type and thereby infer its mass. If the photosphere is visible, an M-dwarf SpT would mean that the object is a brown dwarf obscured by an edge-on disk. An L-dwarf SpT would indicate a planetary mass object with strong accretion. If entirely veiled, this object would have a remarkably high accretion rate, consistent with it being caught either in its main formation stage or in outburst. A wealth of data, including HST optical photometry, Keck-AO near-IR spectra, and ALMA observations, all suggest that FW Tau b is a very low mass companion at an important stage of evolution. These STIS data are crucial to finally tie these observations together with a SpT and refined mass estimate of this object. ------------------------------------------------------------------------------------ Observations Description ------------------------ The goal of this program is to obtain a STIS long slit spectrum of a faint secondary located 2.28" away from the primary star. The primary star is an equal-luminosity 0.1 arcsec binary. Step 1: acquire primary star with centroid Step 2: offset to faint secondary Step 3: Integrate (2.5 orbits) Step 1: flux-weighted centroid on a 0.1 arcsec binary over 5x5 arcsec. I think 14196( 5) - 25-May-2016 12:12:14 - [ 2] that this should work well to get the centroid of the binary with an error less than the eventual slit width. There's another similar-luminosity source at 12" away, but that should be far enough to not mess up the acquisition. I put in 1.5s, which guarantees excellent S/N without coming close to saturation. Used Pickles MV as a template. Step 2: Offset. I've calculated, re-calculated, and checked several times the offset. Still, it might be useful to check that, e.g., +/- are correct. There's no "offset" button, right, I just put in the correct target coordinate offsets into the Fixed Targets list? Step 3: Integrate; Include flatfield at the end of each visit. ORIENT CONSTRAINT: As stated in the Phase I proposal, we don't want the primary falling at the same location as FW Tau in the cross dispersion direction, even with the 2" separation. The PA is 295.5. So the bad positions are 205.5 and 20.5. Then ORIENT=PA+45, so the bad ORIENT positions are 250 and 65. We have set the VISIT constraints to rule out those slit orientations. The ORIENT constraint is also set so that the slit is not placed along the diffraction spikes from the primary (within 10 degrees). ------------------------------------------------------------------------------------ 14196( 5) - 25-May-2016 12:12:14 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 FW-TAU-B STAR, PRE-MAIN SEQUENCE RA-OFF=-0.153S, DEC-OFF=+0.981", J2000 V = 23.0 +/- 0.3 primary for STAR FROM 2 acquisition is R=15.9 Extended: NO Comments: Position is 2.278 arcsec from primary, PA=295.5, so it's N and W of the primary. ------------------------------------------------------------------------------------------------------------------------------------ 2 V-FW-TAU STAR, M V-IV, T TAURI RA=04H29M29.7080S +/- 0.01S, J2000 V = 16.1 STAR DEC=+26D16'52.92" +/- 0.1" Reference Frame: ICRS Extended: NO Comments: Position is from: ibsm24070_drz.fit Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2012.044 6.17125280099059E-4 -0.0155 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 14196( 5) - 25-May-2016 12:12:14 - [ 4] Visit: 01 Visit Requirements: ORIENT 180D TO 235 D; ORIENT 265D TO 320 D; ORIENT 0D TO 55 D; ORIENT 85D TO 140 D On Hold Comments: Additional Comments: ORIENT set so that primary does not fall parallel to secondary on the slit. 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 V-FW-TAU STIS/CCD ACQ F28X50LP MIRROR 1 1.5 S (1.5 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 FW-TAU-B STIS/CCD ACCUM 52X0.2 G750L 7751 CR-SPLIT=2 1 2382 S (2382 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 CCDFLAT STIS/CCD ACCUM 0.3X0.09 G750L 7751 2 DEF (0 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 FW-TAU-B STIS/CCD ACCUM 52X0.2 G750L 7751 CR-SPLIT=2 1 2896 S (2896 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 CCDFLAT STIS/CCD ACCUM 0.3X0.09 G750L 7751 2 DEF (0 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 FW-TAU-B STIS/CCD ACCUM 52X0.2 G750L 7751 CR-SPLIT=2 1 2896 S (2896 S) ------------------------------------------------------------------------------------------------------------------------------------ 7 CCDFLAT STIS/CCD ACCUM 0.3X0.09 G750L 7751 2 DEF (0 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 | ------------------------------------------------------------------------------------------------------------------------------------ V-FW-TAU 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A FW-TAU-B 2 STIS/CCD ACCUM 52X0.2 G750L 7751 none none none 1 1 N/A FW-TAU-B 2 STIS/CCD ACCUM 52X0.2 G750L 7751 none none none 2 1 N/A CCDFLAT 3 STIS/CCD ACCUM 0.3X0.09 G750L 7751 none none 1 none 1 N/A CCDFLAT 3 STIS/CCD ACCUM 0.3X0.09 G750L 7751 none none 2 none 1 N/A FW-TAU-B 4 STIS/CCD ACCUM 52X0.2 G750L 7751 none none none 1 2 N/A FW-TAU-B 4 STIS/CCD ACCUM 52X0.2 G750L 7751 none none none 2 2 N/A CCDFLAT 5 STIS/CCD ACCUM 0.3X0.09 G750L 7751 none none 1 none 2 N/A CCDFLAT 5 STIS/CCD ACCUM 0.3X0.09 G750L 7751 none none 2 none 2 N/A FW-TAU-B 6 STIS/CCD ACCUM 52X0.2 G750L 7751 none none none 1 3 N/A FW-TAU-B 6 STIS/CCD ACCUM 52X0.2 G750L 7751 none none none 2 3 N/A CCDFLAT 7 STIS/CCD ACCUM 0.3X0.09 G750L 7751 none none 1 none 3 N/A CCDFLAT 7 STIS/CCD ACCUM 0.3X0.09 G750L 7751 none none 2 none 3 N/A 14196( 5) - 25-May-2016 12:12:14 - [ 5] Summary Form for Proposal 14196 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 0.3X0.09, 52X0.2, F28X50LP ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CR-SPLIT=2 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 0D TO 55 D, ORIENT 180D TO 235 D, ORIENT 265D TO 320 D, ORIENT 85D TO 140 D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G750L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names CCDFLAT, FW-TAU-B, V-FW-TAU ------------------------------------------------------------------------------------------------------------------------------------