! File: 4393C.PROP ! Database: PEPDB ! Date: 22-FEB-1994:09:56:59 coverpage: title_1: DISKS AROUND MAIN SEQUENCE STARS: CYCLE3 HIGH sci_cat: INTERSTELLAR MEDIUM sci_subcat: CIRCUMSTELLAR MATTER proposal_for: GO pi_fname: CHRISTOPHER pi_mi: J. pi_lname: BURROWS pi_inst: STSCI pi_country: USA pi_phone: (410) 338-4913 hours_pri: 0.83 num_pri: 4 wf_pc: Y time_crit: Y off_fname: HERVEY off_mi: S. off_lname: STOCKMAN off_title: DEPUTY DIRECTOR off_inst: 3470 off_addr_1: SPACE TELESCOPE SCIENCE INSTITUTE off_addr_2: 3700 SAN MARTIN DRIVE off_city: BALTIMORE off_state: MD off_zip: 21218 off_country: USA off_phone: 410-338-4730 ! end of coverpage abstract: line_1: We propose to examine the circumstellar disk around Beta Pictoris in line_2: order to determine its radial profile, and hence (in combination with line_3: IRAS data) to fix its albedo and temperature profile. These line_4: observations will extend previous extensive ground based coronagraphic line_5: investigations, and modelling by the authors. The data will enable us line_6: to understand better the central clearing in the disk and whether it is line_7: caused by sublimation or possible planet formation. The observations will line_8: also constrain the geometric properties of the disk including its line_9: inclination angle, vertical thickness and radial profile. Such line_10: observations limit models for the dynamics of the disk, including its line_11: velocity dispersion and hence mass distribution, and radial mass line_12: transport mechanisms. If density waves or clear zones are observed, they line_13: will give indirect evidence for the presence of massive bodies (planets) line_14: in the disk. The observations involve a judicious use of roll line_15: deconvolution, polarizers, and PSF modelling in order to allow the line_16: central stellar image and associated scattered light to be subtracted. ! ! end of abstract general_form_proposers: lname: BURROWS fname: CHRISTOPHER title: PI mi: J. inst: STSCI country: USA esa: Y ! lname: ARTYMOWICZ fname: PAWEL inst: LICK OBSERVATORY country: USA ! lname: KRIST fname: JOHN mi: E. inst: STSCI country: USA ! ! end of general_form_proposers block general_form_text: question: 3 section: 1 line_1: For Beta Pictoris, the observations are designed to give the clearest possible line_2: image of the disk. The basic observation is in reflected stellar light at 413nm line_3: with the star directly on the center of PC6. The bandpass chosen represents a line_4: best compromise between resolution and scatter. The central image is line_5: saturated, but each exposure time is limited to 1 minute in order to avoid line_6: blooming over the region beyond 1 arcsec from the target (apart from the line_7: columns that contain it). line_8: In order to penetrate within the crucial 2 arcsecond radius where the disk is line_9: expected to disappear, but which is covered by the skirt from the spherical line_10: aberration, similar exposures through polarizers will provide a differential line_11: measurement (the disk is about 30% polarized), as well as providing the first line_12: direct measurement of the polarisation of the disk from 2.5 to 5 arcsec. The line_13: total observation set is designed to take one orbit, and thus optimizes the line_14: use of HST time. The observations on Beta Pictoris are repeated a number of line_15: months later in order to allow roll deconvolution. line_16: This technique avoids unpredictable scattered light and diffraction effects line_17: caused by the focal plane masking with the pyramid used in GTO observations. ! question: 3 section: 2 line_1: After the observations are taken at the first roll angle, they will be line_2: analysed so that the exposures for the second roll angle observations can be line_3: optimised. ! question: 4 section: 1 line_1: HST provides an order of magnitude contrast improvement relative to the ground line_2: (Burrows et al. 1991 and see Figure 1). We believe that the reason that other line_3: protoplanetary disks have not been seen despite extensive ground based searches line_4: is probably that they are not close to edge on, as in the case of the Beta line_5: Pictoris disk. The latter has a contrast relative to a typical seeing profile line_6: of less than one, so it is clear that the other disks are likely to be line_7: unobservable from the ground. However, if they are otherwise similar to the line_8: observed disk, then they will be observable with HST. line_9: Beta Pictoris saturates 200 pixels per second through F413m, but the bleeding line_10: is predominantly along the columns. Four such exposures then yield a signal to line_11: noise of almost 20 per pixel in the disk four arcseconds from the star along line_12: the centerline, and still good signal to noise in the fainter outer regions. ! question: 5 section: 1 line_1: The observations must occur when the Beta Pictoris disk is not aligned with line_2: the V3 axis of the telescope, since that is the direction of bleeding in the line_3: PC6 CCD. The observations will be repeated later at a different roll angle, line_4: so that the image of the disk will be rotated but the scattered light terms line_5: will not. Any features that rotate in the image will be associated with the line_6: target, while any that do not will be 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: BURROWS fname: CHRISTOPHER mi: J. category: PI inst: STScI addr_1: SPACE TELESCOPE SCIENCE INSTITUTE addr_2: 3700 SAN MARTIN DRIVE city: BALTIMORE state: MD zip: 21218 country: USA phone: 410-338-4913 ! ! end of general_form_address records fixed_targets: targnum: 1 name_1: HD39060 name_2: BETA-PIC descr_1: A,124,904 pos_1: RA = 5H 47M 17.1S +/- 0.1S, pos_2: DEC = -51D 3' 59" +/- 0.1" equinox: J2000 comment_1: EXPOSURE TIMES PROVIDE FOR A S-TO-N comment_2: OF 20 IN THE DISK AT FOUR ARCSECS comment_3: FROM STAR USING FOUR EXPOSURES. THE comment_4: STAR WILL BE SATURATED. fluxnum_1: 1 fluxval_1: V=3.9,TYPE=A5V fluxnum_2: 1 fluxval_2: B-V=0.2 ! ! end of fixed targets ! No solar system records found ! No generic target records found exposure_logsheet: linenum: 1.000 targname: HD39060 config: PC opmode: IMAGE aperture: PC6-FIX sp_element: F413M, F8ND num_exp: 2 time_per_exp: 20S priority: 1 req_1: CYCLE 3; req_2: GROUP 1-5 NO GAP; req_3: ORIENT 180D +/- 5D; comment_1: EXPOSURE WILL BE REPEATED comment_2: ON A CONTINUATION PROPOSAL. comment_3: THIS EXPOSURE USED FOR comment_4: PIXEL REGISTRATION. ! linenum: 2.000 targname: HD39060 config: PC opmode: IMAGE aperture: PC6-FIX sp_element: F413M num_exp: 4 time_per_exp: 1M priority: 1 param_1: CLOCKS=YES req_1: ORIENT 180D +/- 5D; req_2: CYCLE 3 comment_1: EXPOSURE WILL BE REPEATED comment_2: ON A CONTINUATION PROPOSAL ! linenum: 3.000 targname: HD39060 config: PC opmode: IMAGE aperture: PC6-FIX sp_element: F413M, POL0 num_exp: 2 time_per_exp: 2M priority: 1 param_1: CLOCKS=YES req_1: ORIENT 180D +/- 5D; req_2: CYCLE 3 comment_1: EXPOSURE WILL BE REPEATED comment_2: ON A CONTINUATION PROPOSAL ! linenum: 4.000 targname: HD39060 config: PC opmode: IMAGE aperture: PC6-FIX sp_element: F413M, POL60 num_exp: 2 time_per_exp: 2M priority: 1 param_1: CLOCKS=YES req_1: ORIENT 180D +/- 5D; req_2: CYCLE 3 comment_1: EXPOSURE WILL BE REPEATED comment_2: ON A CONTINUATION PROPOSAL ! linenum: 5.000 targname: HD39060 config: PC opmode: IMAGE aperture: PC6-FIX sp_element: F413M, POL120 num_exp: 2 time_per_exp: 2M priority: 1 param_1: CLOCKS=YES req_1: ORIENT 180D +/- 5D; req_2: CYCLE 3 comment_1: EXPOSURE WILL BE REPEATED comment_2: ON A CONTINUATION PROPOSAL ! ! end of exposure logsheet ! No scan data records found