coverpage: title_1: THE DISKS AROUND YOUNG STELLAR OBJECTS - HL TAU sci_cat: INTERSTELLAR MEDIUM sci_subcat: CIRCUMSTELLAR MATTER proposal_for: GTO/WF2 cont_id: 5204 pi_title: DR. pi_fname: JOHN pi_mi: T. pi_lname: TRAUGER pi_inst: JPL pi_country: USA pi_phone: (818) 354-9594 hours_pri: 2.82 num_pri: 3 wf_pc: Y time_crit: Y pi_position: PROJECT SCIENTIST off_fname: JOHN off_mi: T. off_lname: TRAUGER off_title: DR. off_inst: JET PROPULSION LABORATORY off_addr_1: 4800 OAK GROVE DRIVE off_addr_2: MAIL STOP 179-225 off_city: PASADENA off_state: CA off_zip: 91109 off_country: USA off_phone: (818) 354-9594 ! end of coverpage abstract: line_1: Circumstellar material has been detected at 1.3 mm around about 50% of the line_2: young (T<10^6 yr) stellar objects in the Taurus-Auriga molecular cloud. The line_3: observations permit an estimate of the material's spatial extent, mass and line_4: temperature, which are usually of sizes compatible with estimates of the line_5: conditions in the nebula which surrounded our sun prior to and during our line_6: planetary system formation (M of order 0.1 solar, T of order 100- 200 degrees line_7: and R of order 10 AU.). In the case of HL-Tau, a circumstellar disk has been line_8: resolved and shown to be in Keplerian rotation around the star. We propose to line_9: resolve the largest disks in scattered visible radiation with WFPC2. This line_10: will allow us to determine physical properties of the solid material line_11: such as its albedo, particle sizes, and spatial distribution. ! ! end of abstract general_form_proposers: lname: TRAUGER fname: JOHN title: DR. mi: T. inst: JPL country: USA esa: N ! lname: BURROWS fname: CHRISTOPHER title: DR. mi: J. inst: STSCI country: USA esa: Y ! lname: CLARKE fname: JOHN inst: UNIV. OF MICHIGAN country: USA ! lname: CRISP fname: DAVID inst: JPL country: USA ! lname: HOESSEL fname: JOHN inst: UNIV. OF WISCONSIN country: USA ! lname: GALLAGHER fname: JAY inst: UNIV. OF WISCONSIN country: USA ! lname: GRIFFITHS fname: RICHARD inst: JOHNS HOPKINS UNIV country: USA ! lname: HESTER fname: JEFF inst: ARIZONA STATE UNIV. country: USA ! lname: HOLTZMAN fname: JOHN inst: LOWELL OBSERVATORY country: USA ! lname: MOULD fname: JEREMY inst: CALTECH country: USA ! lname: WESTPHAL fname: JAMES inst: CALTECH country: USA ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: The same observational techniques as those used in the Beta Pictoris proposal line_2: are applied to a search for optical disks around nearby (<120pc) protostars in line_3: the Taurus molecular cloud. Rather than propose a full survey at this stage line_4: we choose to perform a limited set of observations on the 3 best targets. line_5: We propose to observe the following objects: line_6: NAME Sp Av Log t L* M* 04h DEC Mdisk T R(AU) Ldisk line_7: T Tau K1 2.1 5.27 14. 1.91 19m04.21 19d25'05.4" 0.016 390 7 17. line_8: HL Tau Co 3.2 5.98 0.9 0.55 28m44.42 18d07'36.2" 0.10 307 25 6.7 line_9: Naked T-Tauri stars: line_10: SAO76411A G1 0.0 6.8 0.71 1.5 -1m55.10 21d59'59.0" line_11: We do not know the particle sizes in these disks, but they are expected to have line_12: a larger population of small particles, and so they should be brighter than the line_13: Beta Pictoris disk. If we assume that extinction to the star is the same as line_14: extinction to the brightest parts of the disk, we can scale the Beta Pictoris line_15: disk in order to get a reasonable estimate of exposure times. These stars are line_16: above the main sequence, but later type and heavily reddened. They have ! question: 3 section: 2 line_1: absolute V magnitudes 1.8 and 5.2 more than Beta Pic. In order line_2: to get a peak count rate of 400 electrons/pixel, through a V filter we need line_3: exposure times of 0.25 and 6.0 minutes through V respectively. line_4: For CY-Tau, for example a M1V star dereddened V=11.9, E(B-V) is about 0.45. line_5: The following table indicates approximate count rates to be expected for line_6: various amounts of redenning. Exposure times in the R and I bandpasses have line_7: been scaled from this table. Counts per second through the HST aperture for line_8: a V=11.9 M1V star (from XCAL). line_9: ---------------------------------------------------------------------------- line_10: Filter f569w f675w f791w line_11: Name V R I line_12: Wavelength 5657.29 6736.12 7869.69 line_13: FWHM 977.79 879.47 1224.52 line_14: ---------------------------------------------------------------------------- line_15: E(B-V)= 0.00 98797.30 230639.60 337731.30 line_16: E(B-V)= 0.25 49878.53 133174.90 215033.80 line_17: E(B-V)= 0.50 25299.54 77012.18 137116.70 line_18: E(B-V)= 0.75 12892.59 44600.08 87563.46 line_19: E(B-V)= 1.00 6600.68 25866.67 56002.09 line_20: ! question: 4 section: 1 line_1: HST provides an order of magnitude contrast improvement relative to the ground line_2: as well as an order of magnitude resolution improvement (Burrows et al. 1991). line_3: Both of these attributes are necessary in order to image these disks the line_4: largest of which are known to have sizes of order 20 AU (0.2 arcsec). This is line_5: the same scale as the peak in the Beta Pictoris disk. ! question: 5 section: 1 line_1: The basic observation set is repeated at 3 month interval. In this time, line_2: the spacecraft will roll around the target by about 90 degrees, so the image of line_3: the disk will be rotated on the detector by the same angle. On the other hand line_4: all scattered light terms will be unrotated, so that any feature that rotates line_5: in the image is associated with the target, while any feature that doesn't is line_6: associated with the telescope. ! question: 7 section: 1 line_1: In order to supress scattered light from the central star, we propose to first line_2: subtract model PSFs from the images. We have performed extensive PSF fitting, line_3: and have now refined the methods to the point that the models agree with the line_4: data with a mean pixel to pixel error of 15%. The models include spherical line_5: aberration, focus, other low order aberrations, spacecraft jitter, measured line_6: mirror figure errors, pixel registration, the full aperture function of the line_7: telescope, misalignemnts in the PC camera. The residual errors are correlated, line_8: and look similar from star to star, hence they can be shifted and subtracted line_9: to further improve PSF subtraction. The parameters in the models include the line_10: PSF registration relative to pixel boundaries, so this method does not require line_11: that the stars and reference exposures be identically registered with respect line_12: to the pixel boundaries. Problems with the undersampled data which can be line_13: serious with a reference star image are automatically largely overcome, as line_14: only residual images need to be resampled. line_15: Thus we would expect that a subtraction accurate to about 5% should be possible line_16: after the combination of modelling and reference image subtraction. This would line_17: give a residual contrast of about a factor of 2 where the disk turns over. The line_18: contrast outside 2.5 arcseconds is always about an order of magnitude even line_19: without subtraction. ! question: 10 section: 1 line_1: The authors have workstations and already have written the relevant computer line_2: software to model the PSF, subtract the images, parameterize the disk, and fit line_3: it to thermal and mass equilibrium models. The authors will perform the data line_4: reduction and analysis. ! !end of general form text general_form_address: lname: TRAUGER fname: JOHN mi: T. title: DR. category: PI inst: JPL addr_1: Mail stop 179-225 addr_2: 4800 Oak Grove Drive city: Pasadena state: CA zip: 91109 country: USA phone: (818) 354-9594 ! lname: BURROWS fname: CHRISTOPHER mi: J. title: DR. category: CON inst: STScI addr_1: 3700 San Martin Drive city: Baltimore state: MD zip: 21218 country: USA phone: (410) 338-4935 ! lname: KRIST fname: JOHN mi: E. category: CON inst: STScI addr_1: 3700 San Martin Drive city: Baltimore state: MD zip: 21218 country: USA phone: (410) 338-5030 ! ! end of general_form_address records fixed_targets: targnum: 1 name_1: HL-TAU-OFF descr_1: A,156 pos_1: RA = 4H 28M 45.2S +/- 0.1S, pos_2: DEC = 18D 07' 36" +/- 0.1" equinox: J1950 fluxnum_1: 1 fluxval_1: V=13.4 fluxnum_2: 2 fluxval_2: B-V=+1.7 comment_1: shifted 11.4 arcsec E of HL Tau comment_2: so that reference star will also comment_3: be on the PC ! end of fixed targets ! No solar system records found ! No generic target records found exposure_logsheet: linenum: 4.100 sequence_1: DEFINE sequence_2: IMAGE4 targname: HL-TAU-OFF config: WFPC2 opmode: IMAGE aperture: PC1 sp_element: F675W num_exp: 1 time_per_exp: 14.0M s_to_n: 1 fluxnum_1: 1 priority: 1 param_1: ATD-GAIN=7 param_2: CLOCKS=YES param_3: CR-SPLIT= 0.5 comment_1: STAR WILL BE SATURATED. ! linenum: 4.200 sequence_1: DEFINE sequence_2: IMAGE4 targname: HL-TAU-OFF config: WFPC2 opmode: IMAGE aperture: PC1 sp_element: F814W num_exp: 1 time_per_exp: 3.0S s_to_n: 1 fluxnum_1: 1 priority: 1 param_1: ATD-GAIN=15 param_2: CLOCKS=YES ! linenum: 4.300 sequence_1: DEFINE sequence_2: IMAGE4 targname: HL-TAU-OFF config: WFPC2 opmode: IMAGE aperture: PC1 sp_element: F814W num_exp: 1 time_per_exp: 20.0M s_to_n: 1 fluxnum_1: 1 priority: 1 param_1: ATD-GAIN=15 param_2: CLOCKS=YES param_3: CR-SPLIT=0.5 comment_1: STAR WILL BE SATURATED. ! linenum: 21.000 sequence_1: USE sequence_2: IMAGE4 req_1: CYCLE 4; req_2: SEQ 4.1-4.3 NO GAP; req_3: ORIENT 85D +/- 7D comment_1: CAN ALTERNATIVELY BE AT: comment_2: ORIENT 302D +/- 7D comment_3: CAN ALTERNATIVELY BE AT: comment_4: ORIENT 14D +/- 22D ! ! end of exposure logsheet ! No scan data records found