! Hubble Space Telescope Cycle 5 (1995) Phase II Proposal Template ! $Id: 6058,v 11.1 1995/09/01 13:04:36 pepsa Exp $ ! ! Refer to the HST Phase II Proposal Instructions to fill this out ! ! Anything after a "!" is ignored, and may be deleted ! ! All keywords with multiple entries are comma delimited except the ! Visit_Requirements and Special_Requirements keywords which can be ! delimited with carriage returns or semi-colons, but not commas ! ! For help call your Program Coordinator: Denise Taylor ! Phone: 410 338-4824 , E-mail: dctaylor@stsci.edu ! ! This partially completed template was generated from a Phase I proposal. ! Date generated: Sun Dec 18 11:49:35 EST 1994 ! Proposal_Information ! Section 4 Title: Direct Imaging of a Circumstellar Disk: Beta-Pictoris, a Case Study Proposal_Category: GO Scientific_Category: Interstellar Medium Cycle: 5 Investigators PI_name: Alfred Schultz PI_Institution: Computer Sciences Corporation CoI_Name: Fred Bruhweiler CoI_Institution: Catholic University of America Contact: ! Y or N (designate at most one contact) CoI_Name: Mike DiSanti CoI_Institution: LEP/GSFC/NASA Contact: ! Y or N (designate at most one contact) CoI_Name: Helen Hart CoI_Institution: Computer Sciences Corporation Contact: ! Y or N (designate at most one contact) CoI_Name: Kent Reinhard CoI_Institution: Computer Sciences Corporation Contact: ! Y or N (designate at most one contact) CoI_Name: Glenn Schneider CoI_Institution: Steward Observatory, Tucson Contact: ! Y or N (designate at most one contact) Abstract: ! Free format text (please update) We propose to employ the unique imaging capabilities of WFPC2 onboard HST to obtain high resolution PC1 images of the dust disk about Beta Pictoris. Our goal is to obtain accurate photometry of the disk and to investigate the reported morphology (gaps) and variable disk thickness. The diffraction limited image resolution of WFPC2 will provide information needed to delineate more clearly the optical properties and size distribution of the circumstellar dust. The Beta Pic circumstellar disk currently represents our best candidate for an extrasolar proto-planetary system or possibly a massive Kuiper Belt. It is the only circumstellar disk that is detectable with optical imaging techniques. Due to the large differences in brightness between the central star (V ~3.9) and the disk (V ~16 mag/sq. arcsec), it is only possible to obtain ground-based resolution with a coronagraph. We propose to position the core of the stellar PSF for Beta Pic in WF3, isolating the blooming and saturation from overexposure to this frame. Details of the dust disk normally masked by the extended halo of the PSF core will be revealed in the adjacent CCD frame PC1. This method of imaging the disk is only possible with WFPC2 onboard the Hubble Space Telescope. No other telescope has this imaging capability. Questions ! Free format text (please update) Observing_Description: We propose high resolution PC1 observations (with the F555W and F675W filters) of Alpha and Beta Pictoris that will be used to investigate the extent and morphology of the circumstellar disk around Beta Pictoris. The stellar PSF for each target star will be positioned near the apex in WF3, isolating the effects of overexposure (saturation and blooming) from adjacent CCD frames. A total of 28 images, 14 each of Alpha and Beta Pictoris, will be obtained during 4 visits. Each visit to a target star will consist of a real-time acquisition image (0.11 sec), two exposures at the end of the first target of visibility window, and four exposures during the second orbit. The first image with the F343N filter will be used for centroiding. We estimate that a 0.11 second exposure of Beta Pictoris with the F343N filter will yield ~30,000 electrons, which is about half the dynamic range of the WFPC2 A-to-D converter using a gain of 15 electrons/DN. The second (30.0 sec). third (30.0 sec), and fourth (30.0 sec) exposures of each visit will be used for PSF fitting. Two observations will be dithered slightly in position to smaple the change in the PSF near the apex of the pyramid. The slight differences in pointing of the three images will be usd to help define the subtraction of the Alpha Pic images from the images of Beta Pic. During the second oribt, two 20 minute exposures, one each using the F555W and F675W filters will be obtained. Due to the CR-SPLIT, this will result in two 10 minute exposures in the two filters. We assumed the surface brightness of the circumstellar disk was ~16.6, ~16.3, ~15.9, and ~15.9 mag/sq. arcsecond for the B, V, R, and I bands as reported by Paresce and Burrows (1987). Each pixel in the PC1 subtends 0.046 arcseconds. Therefore, the disk would have a magnitude of ~22.68 mag/pixel. The detected PC1 signal (electrons) in F555W during a 1200 second integration will be: 11 -0.4(22.68 mag/pix) N_el = 2.5 x 10 x (exposure) x (QT) x 10 = 211.8 x (QT) x (exposure) where (QT) = 0.0250 for F555W and 0.0216 for F675W. The noise will be: 2 Noise = sqrt( N_el + dark * (exposure) + sky * (exposure) + (RN) ) The sky brightness contributes ~ 0.03 electrons/sec, dark will contribute ~ 2.1 x 10**2 electrons/sec/pixel at 90 degrees point , and the Read Noise is ~ 5.2 e^-. Therefore, for 1200 sec exposures (including the CR-SPLIT), the S/N becomes ~ 79. In the F675W passband, the S/N for a 1200 second exposure becomes ~ 73 in the disk. However, due to light scatter within the telescope plus subtracting the scaled PSF of Alpha Pic, we do not expect to achieve such high S/N. Based on a brief examination of saturated images of bright stars, we expect a more conservative range for the S/N across the disk of ~10 to ~20. But, the exposure calculation does demonstrate that PC1 is the detector of choice, with the star positioned in WF3. Variations in surface brightness across the disk that are significantly greater than 2-sigma will be detectable. Each visit to a target star will follow a 2-orbit sequence. First orbit: 12 minutes for guide star acquisition one 0.11 second exposure with F343N INTACQ Second orbit: 6 minutes for guide star reacquisition two 600 sec exposures (CR-SPLIT) with F555W two 600 sec exposures (CR -SPLIT) with F675W 10 minutes of overhead Cycle 5 Primary Orbits= 8 Exposures= 16 Real_Time_Justification: Two requests must be met to accomplish the imaging of the circumstellar disk: 1) positioning of the bright star Beta Pictoris within ~2" of the apex of the pyramid, and 2) the orientation (ORIENT) to be used should be +180 degrees, or - 180 degrees. A real-time acquisition (INTACQ) is required to correctly position the core of the stellar PSF in the CCD frame. Positioning in the CCD frame is critical so as not to cause overexposure effects in adjacent frames in which the dust disk is imaged. Unlike WFPC1, WFPC2 CCDs are clocked in Multi-Phased Pinning (MPP) mode, greatly reducing the effects of charge migration which can lead to column bleeding. This is an added advantage that was not available with WFPC1. The orientation (ORIENT) should be such that the dust disk appears diagonally in opposing CCD chips according to the geometry of Figure 1. From discussions with a STScI scientist, using an updated set of coordinates obtained during the first set of INTACQs, it should be possible to position Alpha & Beta Pic in WF3 without the need for a second set of INTACQs. We want to position the targets the second time without an INTACQ. We will investigate updating the target coordinates based upon the analysis of the first set of observations. This may require reuse of the same guide star pair for the second epoch set of observations. Calibration_Justification: ! Move appropriate text from Real_Time_Justification Additional_Comments: Fixed_Targets ! Section 5.1 Target_Number: 1 Target_Name: HD39060 Alternate_Names: BETA-PICTORIS Description: STAR,A4-A9 III-I,PROTOPLANETARY DISK Position: RA=5H 47M 17.1S +/- 0.01S, ! Most common specification format is DEC=-51D 03' 59.4" +/- 0.1" ! RA=0H 0M 0.00S +/- 0S, ! DEC=0D 0' 0.0" +/- 0", ! PLATE-ID=0000 Equinox: J2000.0 RV_or_Z: V=+20 RA_PM: 0.001273 ! Units are seconds of time per year Dec_PM: 0.079 ! Units are seconds of arc per year Epoch: J2000.0 Annual_Parallax: 0.055 Flux: SURF(V)=16.3 ! Include at least V and B-V SURF(B)=16.6 SURF(R)=15.9 SURF(I)=15.9 Comments: Beta Pic proper motion, parallax, V-magnitude=3.85, color index B-V=0.171, spectral type=A5III, and radial velocity obtained from The Hipparcos Input catalogue, EAS SP-1136, 1992. Surface brightness/sq. arcsecond for the circumstellar disk obtained from Paresce and Burrows 1989, Ap.J., 319, L23-L25. Target_Number: 2 Target_Name: HD50241 Alternate_Names: ALPHA-PICTORIS Description: STAR,A4-A9 V-IV Position: RA=6H 48M 11.437S +/- 0.01S, ! Most common specification format is DEC=-61D 56' 28.95" +/- 0.1" ! RA=0H 0M 0.00S +/- 0S, ! DEC=0D 0' 0.0" +/- 0", ! PLATE-ID=0000 Equinox: J2000.0 RV_or_Z: V=+20.6 RA_PM: -0.007319 ! Units are seconds of time per year Dec_PM: 0.269 ! Units are seconds of arc per year Epoch: J2000.0 Annual_Parallax: 0.046 Flux: V=3.266+/-0.05 TYPE=A7IV B-V=0.225+/-0.19 ! Include at least V and B-V Comments: Alpha Pic proper motion, parallax, V-magnitude=3.266, color index B-V=0.225, spectral type=A7IV, and radial velocity obtained from The Hipparcos Input catalogue, EAS SP-1136, 1992. ! This is a template for a single visit containing a single exposure ! Repeat exposure and visit blocks as needed Visits ! Section 6 Visit_Number: 1 Visit_Requirements: ! Section 7.1 ! Uncomment or copy visit level special requirements needed ! Most of these requirements (including ORIENT) will limit scheduling PCS MODE Fine ! GUIDing TOLerance ORIENTation 160D TO 180D ! ORIENTation TO FROM ! ORIENTation TO FROM NOMINAL ! SAME ORIENTation AS ! CVZ ! PARallel ! AFTER [BY [TO ]] ! AFTER ! BEFORE ! BETWEEN AND ! GROUP WITHIN