! Proposal 6772, submission 3 ! PI: Mark Clampin ! Received Thu Mar 20 16:55:30 EST 1997 ! From: clampin@stsci.edu ! +====================+ ! | PED OUTPUT PRODUCT | ! +====================+ ! ! /islay/data3/prop6772/6772.prop ! Generated by PREPROCESSOR, version 6.0e ! Date: Mon Feb 26 06:17:18 EST 1996 Proposal_Information Title: Dust properties in the Beta Pictoris Proposal_Category: GO Scientific_Category: INTERSTELLAR MEDIUM Cycle: 6 Investigators PI_Name: Mark Clampin PI_Institution: Space Telescope Science Institute CoI_Name: Pawel Artymowicz CoI_Institution: University of Stockholm Contact: CoI_Name: Francesco Paresce CoI_Institution: European Southern Observatory Contact: CoI_Name: Sebastiano Ligori CoI_Institution: University of Turin Contact: Abstract: Multicolor imaging polarimetry is an excellent diagnostic of dust grain properties and scattering geometries. We propose to obtain U, B and V band imaging polarimetry of the Beta Pictoris disk to probe the dust grain distribution and composition over the region of the disk extending 4"--15" (65 AU--245 AU) from the central star. This region has been chosen so we can study the transition at 100 AU, reported from coronographic observations, which cannot be explained by current disk models. We plan to use the polarization data to compare grain size distribution and composition in the inner (65 AU--100 AU) and outer (>100 AU) regions of the disk. In addition, we will confirm the polarization asymmetries possibly measured at distances >165 AU, by previous ground- based polarization observations. We will use Mie-theory dust grain modelling to investigate the variations in grain size distribution and composition responsible for these asymmetries. The angular resolution of HST is essential to this program, as polarimetric observations cannot be made this close to the star from the ground. Circumstellar disks around main-sequence stars are generally interpreted as evidence of planetary-system formation: the characterization of their properties is a step towards an understanding of the formation and evolution of planetary systems. Questions Observing_Description: Polarimetric observations with WFPC2 require careful design in order to avoid constraints imposed by the design of the quadrant polarizer filter. In order to achieve our stated science goals, we have adopted an observing strategy recommended by STScI (Biretta and Sparks, WFPC2 ISR 95-01). Observations of the target are made at relative polarization angles of 0^o, 60^o and 120^o using a combination of partial filter rotations and telescope roll angles. The proposed strategy offers several advantages: beginitemize em The required roll angles are small and minimize scheduling constraints by allowing all three sets of observations ( 0^o, 60^o and 120^o) to be made during consecutive orbits. em In each case the target is placed on WF2, so the same flat field is applied to all three polarimetric observations. The main element which dominates precision of polarimetric measurements with WFPC2 is the calibration of the flat field which is currently uncertain to ~2-3% over the field of view of each CCD. We have chosen to conduct all of our observations on WF2 to avoid the further complication of calibrating CCD-to-CCD flat field and zero point effects which would compound the overall uncertainty of our polarimetric calibration. By adopting this strategy we aim to keep the absolute uncertainty of our measurements to the same order of magnitude as the flat field error, i.e., ~2-3%, although the relative accuracy should be higher. em The partial filter rotations required permit a maximum field of view of 30", which is adequate to observe the Beta Pictoris disk out to ~15" (245 AU). em It has also been shown (WFPC2 Handbook 1995) that bright objects should be observed in the wide field cameras, as the PC suffers from an elevated level of scattered light. em We have employed the same strategy in our cycle 4 HST program, imaging polarimetry of another bright object, the Eta Carinae homunucleus. enditemize To study the polarization of the Beta Pictoris disk, at distances of 4 "-15" from the star, we will make the following set of observations, which require a total of 3 orbits. , 6pt begintabularllll Filter & Integration time & Relative Polarization angle , F300W+POLQ & 2x550 secs & 0^o, 60^o , 120^o , F450W+POLQ & 2x200 secs & 0^o, 60^o, 120^o , F555W+POLQ & 2x200 secs & 0^o, 60^o, 120^o , endtabular 6pt Our choice of filters is designed to produce observations with bandpasses located close to the U, B, and V bands. WFPC2 has a U band filter, F336W, but it has a large redleak, so we have chosen F300W which has been used in other WFPC2 GO polarimetry programs. While desirable an I band observations is not feasible with the WFPC2 polarizer. The exposure times are designed to yield a minimum S/N of at least 40 pixel^-1 for a surface brightness of 16 mag/arcsec^2, which corresponds to a distance of 100 AU from Beta Pictoris. Beta Pictoris is a bright object (V=3.8) and so the feasibility of the proposed observations must be addressed. Since it has now been observed in two different WFPC2 imaging programs, it is clear that Beta Pictoris can be observed by WFPC2. In addition, we are avoiding the technically challenging region very close to the star within 40 AU, where uncertainties in the HST PSF wings dominate the observational errors, even with HST. The observations we have proposed are not feasible without HST. Ground-based imaging polarimetry of the Beta Pictoris disk is not possible in the 4-10" region of the disk (see Wolstencroft 1995), which is crucial to our scientific goals. Equally important, we require excellent spatial sampling across the width of the disk, which is only just resolved from the ground, in order to map the polarization vectors as a function of distance from the midplane. In summary, we require a total of 3 orbits on Beta Pictoris to obtain sufficient observations for our theoretical analysis. Real_Time_Justification: See above. This program will have to be carried out at two pre-selected telescope rolls, which can be scheduled sequentially. None. Calibration_Justification: Additional_Comments: Fixed_Targets Target_Number: 1 Target_Name: HD39060 Alternate_Names: Beta-Pictoris Description: ISM,PROTOPLANETARY DISK, Position: RA=05H 46M 5.935S +/- 0.1S,DEC=-51D 5' 1.75" +/- 0.1" Equinox: B1950 RV_or_Z: RA_PM: 0.0005 Dec_PM: 0.087 Epoch: B1950 Annual_Parallax: 0.0 Flux: V = 3.9 Comments: Visits Visit_Number: 01 Visit_Requirements: ORIENTation 88D to 92D On_Hold_Comments: Visit_Comments: Exposure_Number: 10 Target_Name: HD39060 Config: WFPC2 Opmode: IMAGE Aperture: WF3 Sp_Element: POLQ,F555W Wavelength: Optional_Parameters: CR-SPLIT=NO,CLOCKS=YES,ATD-GAIN=15,READ=3 Number_of_Iterations: 1 Time_Per_Exposure: 260S Special_Requirements: POS TARG -33,0 Comments: Exposure_Number: 20 Target_Name: HD39060 Config: WFPC2 Opmode: IMAGE Aperture: WF3 Sp_Element: POLQ,F336W Wavelength: Optional_Parameters: ATD-GAIN=15,CLOCKS=YES,CR-SPLIT=NO,READ=3 Number_of_Iterations: 1 Time_Per_Exposure: 600S Special_Requirements: SAME POS AS 10 Comments: Exposure_Number: 30 Target_Name: HD39060 Config: WFPC2 Opmode: IMAGE Aperture: WF3 Sp_Element: POLQ,F555W Wavelength: Optional_Parameters: CR-SPLIT=NO,CLOCKS=YES,ATD-GAIN=15,READ=3 Number_of_Iterations: 1 Time_Per_Exposure: 260S Special_Requirements: POS TARG 33,0 Comments: Exposure_Number: 40 Target_Name: HD39060 Config: WFPC2 Opmode: IMAGE Aperture: WF3 Sp_Element: POLQ,F336W Wavelength: Optional_Parameters: ATD-GAIN=15,CLOCKS=YES,CR-SPLIT=NO,READ=3 Number_of_Iterations: 1 Time_Per_Exposure: 600S Special_Requirements: SAME POS AS 30 Comments: Visit_Number: 02 Visit_Requirements: ORIENTation 58D TO 62D FROM 1 On_Hold_Comments: Visit_Comments: Exposure_Number: 10 Target_Name: HD39060 Config: WFPC2 Opmode: IMAGE Aperture: WF3 Sp_Element: POLQ,F555W Wavelength: Optional_Parameters: CR-SPLIT=NO,CLOCKS=YES,ATD-GAIN=15,READ=3 Number_of_Iterations: 1 Time_Per_Exposure: 260S Special_Requirements: POS TARG -33,0 Comments: Exposure_Number: 20 Target_Name: HD39060 Config: WFPC2 Opmode: IMAGE Aperture: WF3 Sp_Element: POLQ,F336W Wavelength: Optional_Parameters: ATD-GAIN=15,CLOCKS=YES,CR-SPLIT=NO,READ=3 Number_of_Iterations: 1 Time_Per_Exposure: 600S Special_Requirements: SAME POS AS 10 Comments: Exposure_Number: 30 Target_Name: HD39060 Config: WFPC2 Opmode: IMAGE Aperture: WF3 Sp_Element: POLQ,F555W Wavelength: Optional_Parameters: CR-SPLIT=NO,CLOCKS=YES,ATD-GAIN=15,READ=3 Number_of_Iterations: 1 Time_Per_Exposure: 260S Special_Requirements: POS TARG 33,0 Comments: Exposure_Number: 40 Target_Name: HD39060 Config: WFPC2 Opmode: IMAGE Aperture: WF3 Sp_Element: POLQ,F336W Wavelength: Optional_Parameters: ATD-GAIN=15,CLOCKS=YES,CR-SPLIT=NO,READ=3 Number_of_Iterations: 1 Time_Per_Exposure: 600S Special_Requirements: SAME POS AS 30 Comments: Visit_Number: 03 Visit_Requirements: ORIENTation 118D TO 122D FROM 1 On_Hold_Comments: Visit_Comments: Exposure_Number: 10 Target_Name: HD39060 Config: WFPC2 Opmode: IMAGE Aperture: WF3 Sp_Element: POLQ,F555W Wavelength: Optional_Parameters: CR-SPLIT=NO,CLOCKS=YES,ATD-GAIN=15,READ=3 Number_of_Iterations: 1 Time_Per_Exposure: 260S Special_Requirements: POS TARG -33,0 Comments: Exposure_Number: 20 Target_Name: HD39060 Config: WFPC2 Opmode: IMAGE Aperture: WF3 Sp_Element: POLQ,F336W Wavelength: Optional_Parameters: ATD-GAIN=15,CLOCKS=YES,CR-SPLIT=NO,READ=3 Number_of_Iterations: 1 Time_Per_Exposure: 600S Special_Requirements: SAME POS AS 10 Comments: Exposure_Number: 30 Target_Name: HD39060 Config: WFPC2 Opmode: IMAGE Aperture: WF3 Sp_Element: POLQ,F555W Wavelength: Optional_Parameters: CR-SPLIT=NO,CLOCKS=YES,ATD-GAIN=15,READ=3 Number_of_Iterations: 1 Time_Per_Exposure: 260S Special_Requirements: POS TARG 33,0 Comments: Exposure_Number: 40 Target_Name: HD39060 Config: WFPC2 Opmode: IMAGE Aperture: WF3 Sp_Element: POLQ,F336W Wavelength: Optional_Parameters: ATD-GAIN=15,CLOCKS=YES,CR-SPLIT=NO,READ=3 Number_of_Iterations: 1 Time_Per_Exposure: 600S Special_Requirements: SAME POS AS 30 Comments: Data_Distribution ! Defaults indicated; change if desired Medium: 8MM Blocking_Factor: 10 Ship_To: STSCI Ship_Via: Recipient_Email: clampin@stsci.edu ! Let us know what you think of this template and software! ! Please send a list of your likes and dislikes to your Program Coordinator !num_orbits: 3