Page 1 PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID 4393c Report Date: 09-May-96:19:35 Version: ********** Check-in Date: ********** 1.Proposal Title: DISKS AROUND MAIN SEQUENCE STARS: CYCLE3 HIGH ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Proposal Type 5. Continuation ID INTERSTELLAR MEDIUM GO Sub Category CIRCUMSTELLAR MATTER ------------------------------------------------------------------------------------ 6. Principal Investigator Institution Country Telephone Christopher J. Burrows STSCI USA (410) 338-4913 ------------------------------------------------------------------------------------ 7. Abstract We propose to examine the circumstellar disk around Beta Pictoris in order to determine its radial profile, and hence (in combination with IRAS data) to fix its albedo and temperature profile. These observations will extend previous extensive ground based coronagraphic investigations, and modelling by the authors. The data will enable us to understand better the central clearing in the disk and whether it is caused by sublimation or possible planet formation. The observations will also constrain the geometric properties of the disk including its inclination angle, vertical thickness and radial profile. Such observations limit models for the dynamics of the disk, including its velocity dispersion and hence mass distribution, and radial mass transport mechanisms. If density waves or clear zones are observed, they will give indirect evidence for the presence of massive bodies (planets) in the disk. The observations involve a judicious use of roll deconvolution, polarizers, and PSF modelling in order to allow the central stellar image and associated scattered light to be subtracted. ------------------------------------------------------------------------------------ ------------------------------------------------------------------------------------ 9. Est obs time (hours) pri: 0.83 par: 0 10. Num targs pri: 4 par: 0 ------------------------------------------------------------------------------------ 11. Instruments requested: WF/PC ------------------------------------------------------------------------------------ 12. Special sched req: Time Critical obs. ------------------------------------------------------------------------------------ Page 2 I. GENERAL FORM Proposal 4393c PI: Christopher J. Burrows Proposal Title: DISKS AROUND MAIN SEQUENCE STARS: CYCLE3 HIGH ------------------------------------------------------------------------------------ 1. Proposers: Proposers Institution Country ESA ------------------------------------------------------------------------------------ Pi Christopher J. Burrows STSCI USA X Pawel Artymowicz LICK OBSERVATORY USA John E. Krist STSCI USA ------------------------------------------------------------------------------------ 3. Description of proposed observations. For Beta Pictoris, the observations are designed to give the clearest possible image of the disk. The basic observation is in reflected stellar light at 413nm with the star directly on the center of PC6. The bandpass chosen represents a best compromise between resolution and scatter. The central image is saturated, but each exposure time is limited to 1 minute in order to avoid blooming over the region beyond 1 arcsec from the target (apart from the columns that contain it). In order to penetrate within the crucial 2 arcsecond radius where the disk is expected to disappear, but which is covered by the skirt from the spherical aberration, similar exposures through polarizers will provide a differential measurement (the disk is about 30% polarized), as well as providing the first direct measurement of the polarisation of the disk from 2.5 to 5 arcsec. The total observation set is designed to take one orbit, and thus optimizes the use of HST time. The observations on Beta Pictoris are repeated a number of months later in order to allow roll deconvolution. This technique avoids unpredictable scattered light and diffraction effects caused by the focal plane masking with the pyramid used in GTO observations. After the observations are taken at the first roll angle, they will be analysed so that the exposures for the second roll angle observations can be optimised. ------------------------------------------------------------------------------------ 4. Justification of need for HST observations. HST provides an order of magnitude contrast improvement relative to the ground (Burrows et al. 1991 and see Figure 1). We believe that the reason that other protoplanetary disks have not been seen despite extensive ground based searches is probably that they are not close to edge on, as in the case of the Beta Pictoris disk. The latter has a contrast relative to a typical seeing profile of less than one, so it is clear that the other disks are likely to be unobservable from the ground. However, if they are otherwise similar to the observed disk, then they will be observable with HST. Beta Pictoris saturates 200 pixels per second through F413m, but the bleeding is predominantly along the columns. Four such exposures then yield a signal to noise of almost 20 per pixel in the disk four arcseconds from the star along the centerline, and still good signal to noise in the fainter outer regions. ------------------------------------------------------------------------------------ 5. Description of special scheduling requirements. The observations must occur when the Beta Pictoris disk is not aligned with the V3 axis of the telescope, since that is the direction of bleeding in the PC6 CCD. The observations will be repeated later at a different roll angle, so that the image of the disk will be rotated but the scattered light terms will not. Any features that rotate in the image will be associated with the target, while any that do not will be associated with the telescope. Page 3 ------------------------------------------------------------------------------------ 7. Data reduction and analysis plans. In order to supress scattered light from the central star, we propose to first subtract model PSFs from the images. We have performed extensive PSF fitting, and have now refined the methods to the point that the models agree with the data with a mean pixel to pixel error of 15%. The models include spherical aberration, focus, other low order aberrations, spacecraft jitter, measured mirror figure errors, pixel registration, the full aperture function of the telescope, misalignemnts in the PC camera. The residual errors are correlated, and look similar from star to star, hence they can be shifted and subtracted to further improve PSF subtraction. The parameters in the models include the PSF registration relative to pixel boundaries, so this method does not require that the stars and reference exposures be identically registered with respect to the pixel boundaries. Problems with the undersampled data which can be serious with a reference star image are automatically largely overcome, as only residual images need to be resampled. Thus we would expect that a subtraction accurate to about 5% should be possible after the combination of modelling and reference image subtraction. This would give a residual contrast of about a factor of 2 where the disk turns over. The contrast outside 2.5 arcseconds is always about an order of magnitude even without subtraction. ------------------------------------------------------------------------------------ 10. Resources to be supplied by investigator's institution(s). The authors have workstations and already have written the relevant computer software to model the PSF, subtract the images, parameterize the disk, and fit it to thermal and mass equilibrium models. The authors will perform the data reduction and analysis. ------------------------------------------------------------------------------------ 11. Address Information Name: CHRISTOPHER J. BURROWS Category: PI Institution: STScI Address: SPACE TELESCOPE SCIENCE INSTITUTE 3700 SAN MARTIN DRIVE City: BALTIMORE State: MD Zip Code: 21218 Country: USA Telephone: 410-338-4913 Telex (or e-mail): ------------------------------------------------------------------------------------ TARGET LIST a) Fixed Targets ID = 4393c [ 4] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial |Acqui|FLX| Flux data No | Name | Description | Position |Eqnx | Vel. |Prblm|REF| | | | | | | | | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD39060 BETA A,124,904 RA = 5H 47M 17.1S +/- 0.1S, J2000 1 V=3.9,TYPE=A5V -PIC DEC = -51D 3' 59" +/- 0.1" 1 B-V=0.2 Comments: EXPOSURE TIMES PROVIDE FOR A S-TO-N OF 20 IN THE DISK AT FOUR ARCSECS FROM STAR USING FOUR EXPOSURES. THE STAR WILL BE SATURATED. ------------------------------------------------------------------------------------------------------------------------------------ EXPOSURE LOGSHEET ID = 4393c [ 5] ------------------------------------------------------------------------------------------------------------------------------------ 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |10 | 11 | 12 |13 |14| 15 ------------------------------------------------------------------------------------------------------------------------------------ Line | Seq | Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | S/N |Flx|Pr| Special Number | Name | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| |Rel. Time|Ref| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 HD39060 PC IMAGE PC6-FIX F413M, 2 20S 1 CYCLE 3 F8ND GROUP 1-5 NO GAP ORIENT 180D +/- 5D Comments: EXPOSURE WILL BE REPEATED ON A CONTINUATION PROPOSAL. THIS EXPOSURE USED FOR PIXEL REGISTRATION. ------------------------------------------------------------------------------------------------------------------------------------ 2 HD39060 PC IMAGE PC6-FIX F413M CLOCKS=YES 4 1M 1 ORIENT 180D +/- 5D CYCLE 3 Comments: EXPOSURE WILL BE REPEATED ON A CONTINUATION PROPOSAL ------------------------------------------------------------------------------------------------------------------------------------ 3 HD39060 PC IMAGE PC6-FIX F413M, CLOCKS=YES 2 2M 1 ORIENT 180D +/- 5D POL0 CYCLE 3 Comments: EXPOSURE WILL BE REPEATED ON A CONTINUATION PROPOSAL ------------------------------------------------------------------------------------------------------------------------------------ 4 HD39060 PC IMAGE PC6-FIX F413M, CLOCKS=YES 2 2M 1 ORIENT 180D +/- 5D POL60 CYCLE 3 Comments: EXPOSURE WILL BE REPEATED ON A CONTINUATION PROPOSAL ------------------------------------------------------------------------------------------------------------------------------------ 5 HD39060 PC IMAGE PC6-FIX F413M, CLOCKS=YES 2 2M 1 ORIENT 180D +/- 5D POL120 CYCLE 3 Comments: EXPOSURE WILL BE REPEATED ON A CONTINUATION PROPOSAL ------------------------------------------------------------------------------------------------------------------------------------ Summary Form for Proposal 4393c [ 6] Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations PC ------------------------------------------------------------------------------------------------------------------------------------ Opmodes IMAGE ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters CLOCKS=YES ------------------------------------------------------------------------------------------------------------------------------------ Proposal for GO ------------------------------------------------------------------------------------------------------------------------------------ S/C Hours 0.83 ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category INTERSTELLAR MEDIUM ------------------------------------------------------------------------------------------------------------------------------------ Scientific Sub-category CIRCUMSTELLAR MATTER ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CYCLE 3; GROUP 1-5 NO GAP; ORIENT 180D +/- 5D; CYCLE 3 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F413M, F8ND F413M F413M, POL0 F413M, POL60 F413M, POL120 ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD39060 BETA-PIC ------------------------------------------------------------------------------------------------------------------------------------