6058( 11) - 09/01/95 09:10 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6058 Version: 11 Check-in Date: ********** 1.Proposal Title: Direct Imaging of a Circumstellar Disk: Beta-Pictoris, a Case Study ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle Interstellar Medium GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Alfred Schultz Computer Sciences Corporation CoI: Fred Bruhweiler Catholic University of America N CoI: Mike DiSanti LEP/GSFC/NASA N CoI: Helen Hart Computer Sciences Corporation N CoI: Kent Reinhard Computer Sciences Corporation N CoI: Glenn Schneider Steward Observatory, Tucson N ------------------------------------------------------------------------------------ 6. Abstract 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. ------------------------------------------------------------------------------------ 6058( 11) - 09/01/95 09:10 - [ 2] Observations 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 ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 6058( 11) - 09/01/95 09:10 - [ 3] Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: UPS __Diagnosti Email: , ------------------------------------------------------------------------------------ 6058( 11) - 09/01/95 09:10 - [ 4] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD39060 STAR,A4-A9 III- RA=5H 47M 17.1S +/- 0.01S, DEC=- J2000.0 V=+20 SURF(V)=16.3 SURF(B)=16.6 SURF(R)=15.9 I,PROTOPLANETARY DISK 51D 03' 59.4" +/- 0.1" 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. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) J2000.0 0.001273 0.079 0.055 2 HD50241 STAR,A4-A9 V-IV RA=6H 48M 11.437S +/- 0.01S, J2000.0 V=+20.6 V=3.266+/-0.05 TYPE=A7IV B-V=0.225+/- DEC=-61D 56' 28.95" +/- 0.1" 0.19 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. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) J2000.0 -0.007319 0.269 0.046 6058( 11) - 09/01/95 09:10 - [ 5] Visit: 01 Visit Requirements: PCS MODE Fine ORIENTation 160D TO 180D On Hold Comments: Additional Comments: The first observation in this series will be used to center Beta Pic in WF3, determine the centroid of the PSF and offsets to position Beta Pic near the apex of the pyramid in WF3. The circumstellar disk will be imaged in PC1. The PCS Acquisition and INT ACQ image takes 16M for decision plus 8M for the uplink leaving 560S for PSF observations. Decision time should be shorten to allow scheduling of a third 30S observation during the first orbit. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD39060 WFPC2 IMAGE WF3 F343N 1 0.11S INT ACQ FOR 2-6 SEQ 1-4 NON-INT Comments: This is the F343N real-time acquisiton. Observaton used to determine the position of the target in WF3. Offsets will be calculated to position the target in WF3 at X=-2.0",Y=-2.0" from apex of pyramid. ------------------------------------------------------------------------------------------------------------------------------------ 2 HD39060 WFPC2 IMAGE WF3 F555W CLOCKS=YES 1 30S Comments: V image of the faint circumstellar disk about Beta Pictoris with the central star positioned in WF3 near the apex of the mirror. ------------------------------------------------------------------------------------------------------------------------------------ 3 HD39060 WFPC2 IMAGE WF3 F555W CLOCKS=YES 1 30S POS TARG -0.023,0.0; Comments: V image of the faint circumstellar disk about Beta Pictoris with the central star positioned in WF3 near the apex of the mirror. ------------------------------------------------------------------------------------------------------------------------------------ 4 HD39060 WFPC2 IMAGE WF3 F555W CLOCKS=YES 1 30S POS TARG -0.023,-0.023 END ORBIT Comments: V image of the faint circumstellar disk about Beta Pictoris with the central star positioned in WF3 near the apex of the mirror. ------------------------------------------------------------------------------------------------------------------------------------ 5 HD39060 WFPC2 IMAGE WF3 F555W CLOCKS=YES 1 1200S SAME POS AS 2 Comments: V image of the faint circumstellar disk about Beta Pictoris with the central star positioned in WF3 near the apex of the mirror. ------------------------------------------------------------------------------------------------------------------------------------ 6 HD39060 WFPC2 IMAGE WF3 F675W CLOCKS=YES 1 1200S SAME POS AS 5 Comments: This observation is used to obtain the R image of the faint circumstellar disk about Beta Pictoris with the central star positioned in WF3 near the apex of the pyramid ------------------------------------------------------------------------------------------------------------------------------------ 6058( 11) - 09/01/95 09:10 - [ 6] Visit: 02 Visit Requirements: PCS MODE Fine SAME ORIENT AS 1 On Hold Comments: Additional Comments: The first observation in this series will be used to center Alpha Pic in WF3, determine the centroid of the PSF and offsets to position Beta Pic near the apex of the pyramid in WF3. These observations will be used to model the PSF, light scatter, and will be scaled and subtracted from the images of Beta Pic to reveal the circumstellar disk. The PCS Acquisition and INT ACQ image takes 16M for decision plus 8M for the uplink leaving 560S for PSF observations. Decision time should be shorten to allow scheduling of a third 30S observation during the first orbit. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD50241 WFPC2 IMAGE WFALL F343N 1 0.11S INT ACQ FOR 2-6 SEQ 1-4 NON-INT Comments: This is the F343N real-time acquisition Observation used to determine the position of the target in WF3. Offsets will be calculated to position the target in WF3 at X=-2.0",Y=-2.0" from apex of pyramid. ------------------------------------------------------------------------------------------------------------------------------------ 2 HD50241 WFPC2 IMAGE WF3 F555W CLOCKS=YES 1 30S Comments: V image of Alpha Pic with the center of the PSF positioned in WF3 near the apex of pyramid. ------------------------------------------------------------------------------------------------------------------------------------ 3 HD50241 WFPC2 IMAGE WF3 F555W CLOCKS=YES 1 30S POS TARG -0.023,0.0; Comments: V image of Alpha Pic with the center of the PSF positioned in WF3 near the apex of pyramid. ------------------------------------------------------------------------------------------------------------------------------------ 4 HD50241 WFPC2 IMAGE WF3 F555W CLOCKS=YES 1 30S POS TARG -0.023,-0.023 END ORBIT Comments: V image of Alpha Pic with the center of the PSF positioned in WF3 near the apex of pyramid. ------------------------------------------------------------------------------------------------------------------------------------ 5 HD50241 WFPC2 IMAGE WF3 F555W CLOCKS=YES 1 1200S SAME POS AS 2 Comments: V image of Alpha Pic with the center of the PSF positioned in WF3 near the apex of pyramid. ------------------------------------------------------------------------------------------------------------------------------------ 6 HD50241 WFPC2 IMAGE WF3 F675W CLOCKS=YES 1 1200S SAME POS AS 5 Comments: This observation is used to obtain the R image of Alpha Pic with the center of the PSF positioned in WF3 near the apex of the pyramid. ------------------------------------------------------------------------------------------------------------------------------------ 6058( 11) - 09/01/95 09:10 - [ 7] Visit: 03 Visit Requirements: PCS MODE Fine ORIENT 335D TO 355D On Hold Comments: Pending updated target coordinates as determined from visit 1. The second series of INT ACQ observations may not be necessary. Additional Comments: The first observation in this series will be used to center Beta Pic in WF3, determine the centroid of the PSF and offsets to position Beta Pic near the apex of the pyramid in WF3. The circumstellar disk will be imaged in PC1. The PCS Acquisition and INT ACQ image takes 16M for decision plus 8M for the uplink leaving 560S for PSF observations. Decision time should be shorten to allow scheduling of a third 30S observation during the first orbit. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD39060 WFPC2 IMAGE PC1 F343N 1 0.7S INT ACQ FOR 2-6 SEQ 1-4 NON-INT Comments: This is the F343N real-time acquisiton. Observaton used to determine the position of the target in WF3. Offsets will be calculated to position the target in WF3 at X=-2.0",Y=-2.0" from apex of pyramid. ------------------------------------------------------------------------------------------------------------------------------------ 2 HD39060 WFPC2 IMAGE PC1 F555W CLOCKS=YES 1 30S Comments: V image of the faint circumstellar disk about Beta Pictoris with the central star positioned in WF3 near the apex of the mirror. ------------------------------------------------------------------------------------------------------------------------------------ 3 HD39060 WFPC2 IMAGE PC1 F555W CLOCKS=YES 1 30S POS TARG -0.023,0.0; Comments: V image of the faint circumstellar disk about Beta Pictoris with the central star positioned in WF3 near the apex of the mirror. ------------------------------------------------------------------------------------------------------------------------------------ 4 HD39060 WFPC2 IMAGE PC1 F555W CLOCKS=YES 1 30S POS TARG -0.023,-0.023 END ORBIT Comments: V image of the faint circumstellar disk about Beta Pictoris with the central star positioned in WF3 near the apex of the mirror. ------------------------------------------------------------------------------------------------------------------------------------ 5 HD39060 WFPC2 IMAGE PC1 F555W CLOCKS=YES 1 1200S SAME POS AS 2 Comments: V image of the faint circumstellar disk about Beta Pictoris with the central star positioned in WF3 near the apex of the mirror. ------------------------------------------------------------------------------------------------------------------------------------ 6 HD39060 WFPC2 IMAGE PC1 F675W CLOCKS=YES 1 1200S SAME POS AS 5 Comments: This observation is used to obtain the R image of the faint circumstellar disk about Beta Pictoris with the central star positioned in WF3 near the apex of the pyramid ------------------------------------------------------------------------------------------------------------------------------------ 6058( 11) - 09/01/95 09:10 - [ 8] Visit: 04 Visit Requirements: PCS MODE Fine SAME ORIENT AS 3 On Hold Comments: Pending updated target coordinates as determined from visit 2. The second series of INT ACQ observations may not be necessary. Additional Comments: The first observation in this series will be used to center Alpha Pic in WF3, determine the centroid of the PSF and offsets to position Beta Pic near the apex of the pyramid in WF3. These observations will be used to model the PSF, light scatter, and will be scaled and subtracted from the images of Beta Pic to reveal the circumstellar disk. The PCS Acquisition and INT ACQ image takes 16M for decision plus 8M for the uplink leaving 560S for PSF observations. Decision time should be shorten to allow scheduling of a third 30S observation during the first orbit. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD50241 WFPC2 IMAGE PC1 F343N 1 0.7S INT ACQ FOR 2-6 SEQ 1-4 NON-INT Comments: This is the F343N real-time acquisition Observation used to determine the position of the target in WF3. Offsets will be calculated to position the target in WF3 at X=-2.0",Y=-2.0" from apex of pyramid. ------------------------------------------------------------------------------------------------------------------------------------ 2 HD50241 WFPC2 IMAGE PC1 F555W CLOCKS=YES 1 30S Comments: V image of Alpha Pic with the center of the PSF positioned in WF3 near the apex of pyramid. ------------------------------------------------------------------------------------------------------------------------------------ 3 HD50241 WFPC2 IMAGE PC1 F555W CLOCKS=YES 1 30S POS TARG -0.023,0.0; Comments: V image of Alpha Pic with the center of the PSF positioned in WF3 near the apex of pyramid. ------------------------------------------------------------------------------------------------------------------------------------ 4 HD50241 WFPC2 IMAGE PC1 F555W CLOCKS=YES 1 30S POS TARG -0.023,-0.023 END ORBIT Comments: V image of Alpha Pic with the center of the PSF positioned in WF3 near the apex of pyramid. ------------------------------------------------------------------------------------------------------------------------------------ 5 HD50241 WFPC2 IMAGE PC1 F555W CLOCKS=YES 1 1200S SAME POS AS 2 Comments: V image of Alpha Pic with the center of the PSF positioned in WF3 near the apex of pyramid. ------------------------------------------------------------------------------------------------------------------------------------ 6 HD50241 WFPC2 IMAGE PC1 F675W CLOCKS=YES 1 1200S SAME POS AS 5 Comments: This observation is used to obtain the R image of Alpha Pic with the center of the PSF positioned in WF3 near the apex of the pyramid. ------------------------------------------------------------------------------------------------------------------------------------ 6058( 11) - 09/01/95 09:10 - [ 9] Summary Form for Proposal 6058 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFPC2 ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CLOCKS=YES ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category Interstellar Medium ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE Fine ORIENTation 160D TO 180D INT ACQ FOR 2-6 SEQ 1-4 NON-INT POS TARG -0.023,0.0; POS TARG -0.023,-0.023 END ORBIT SAME POS AS 2 SAME POS AS 5 PCS MODE Fine SAME ORIENT AS 1 PCS MODE Fine ORIENT 335D TO 355D PCS MODE Fine SAME ORIENT AS 3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F343N F555W F675W ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD39060 HD50241 ------------------------------------------------------------------------------------------------------------------------------------