!-------------- GO 6475, slightly revised ("final" version?) ----- ! (KD, 6 Feb 1996) Here I've changed exposures 130 and 250 somewhat ! from the version that Rob Landis made. (130 is slightly shorter, ! 250 is slightly longer.) !------------------------------------------------------------------ ! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! $Id: 6475,v 6.1 1996/02/13 21:01:23 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: Landis ! Phone: 410-338-4560 , E-mail: landis@stsci.edu ! ! Name of Phase I Proposal: archive-0244.humphreys.prop Proposal_Information ! Section 4 Title: High Resolution Imaging of Unstable Massive Stars at the Top of the HR Diagram Proposal_Category: GO Scientific_Category: HOT STARS Cycle: 6 Investigators PI_name: Roberta Humphreys PI_Institution: University of Minnesota CoI_Name: Kris Davidson CoI_Institution: University of Minnesota Contact: Y ! Y or N (designate at most one contact) CoI_Name: Terry Jones CoI_Institution: University of Minnesota Contact: ! Y or N (designate at most one contact) CoI_Name: Robert Gehrz CoI_Institution: University of Minnesota Contact: ! Y or N (designate at most one contact) CoI_Name: Joachim Krautter CoI_Institution: Landessternwarte,Heidelberg Contact: ! Y or N (designate at most one contact) ! New abstract prepared by Roberta 2/96 (diff from Phase 1) Abstract: A few highly unstable, very massive stars lie on or near the empirical upper luminosity boundary in the HR diagram. These include the Luminous Blue Variables, the cool hypergiants and other even rarer objects, all related by the violent mass-loss phenomena responsible for the upper boundary. We propose to obtain high-spatial resolution WFPC2/BV images of IRC+10420 a cool hypergiant and OH/IR star with visible nebulosity. Our groundbased optical nad infrared observations, including polarimetry and spectroscopy, revealed a rich and complex circumstellar environment with an equatorial disk surrounded by diffuse and clumpy gas and dust. Recent 10micron imaging shows an extended bipolar structure. The HST images are needed for studies of the morphology of the ejecta and for comparison with our infrared and radio observations. Questions ! Free format text (please update) ! New observing description (diff from Phase 1) Observing_Description: Reasons for the observing plan are described here, as well as the plan itself. ----- (1. GENERAL INFORMATION:) IRC+10420 is a bright hypergiant star with detectable ejecta and nebulosity. In our ground-based optical and near-IR images the object is extended 1--2 arcsec in the N-S direction, and a recent 10-micron image shows probable bipolar structure as much as 8 arcsec across. At a distance of 5 kpc for IRC+10420, the PC resolution of about 0.001 pc will allow us to resolve the complex structures that we have good reason to believe are present. At WFPC2 wavelengths we expect this to be mainly reflection nebulosity plus perhaps some emission lines; there is a limited analogy with the Homunculus nebula of Eta Car, ----- (2. BASIC PLAN:) A large dynamic range is needed, because the central star is bright while the outlying nebulosity may be quite faint. We plan to obtain this by using a wide range of WFPC2 integration times. The shortest exposure times will be short enough to image the star without data-saturation; the longest will be determined by the amount of time available; and intermediate exposure times will also be used in order to obtain maximum S/N for intermediate brightness levels. More than one filter is needed, in order to get color information. Of course we use the PC quadrant of the WFPC2. ----- (3. CHOICE OF FILTERS:) IRC+10420 is very red (B-V ~ 2.7 magn) because of interstellar reddening. Therefore we choose filters in the B-to-V wavelength range. Violet filters would require long exposure times. Red filters are inappropriate because the (nebulosity/star) brightness ratio is small for reflection nebulosity at red wavelengths, and because the star is awkwardly bright at such wavelengths. We do NOT use wide filters such as F439W, F555W, and F569W, because their effective wavelengths would be uncertain and position-dependent for such a reddened object, and because we want to minimize emission-line contributions so that we're sure of what we're looking at. Therefore we choose to use filters F467M (pseudo-B) and F547M (V). Assuming magnitudes B = 13.7 and V = 11.0, the central star will produce roughly 4000 and 110000 counts per second with F467M and F547M respectively (i.e., CCD electrons per second in the entire star image). ----- (4. IMAGING WITH F467M:) First we do a single 12-second exposure to get the star itself without any data-saturation. Then, two 30-second exposures at slightly different positions (what STScI calls "dithering") in order to image bright stuff close to the star. The two different positions are chosen to get maximum possible effective resolution, i.e., they are separated by half-integer numbers of pixels to make the sampling very good. These two different positions will also be helpful for patching over instrument defects. Then, two long exposures, each at least 140 seconds, to detect fainter outlying material. These are taken at slightly different positions ("dithering" again, if one insists on calling it that), separated by integer numbers of pixels this time, to help patch over CR hits and instrument defects. ----- (5. IMAGING WITH F547M:) Our data with this filter can be used in combination with the F467M data to make a color map, but the observing plan is optimized differently. We don't have enough time to "dither" the F547M observations. F547M will be more useful for detecting the faintest outlying stuff (because the interstellar reddening is high), but F467M is better adapted to small-scale details (because this is a reflection nebula). The range in exposure times is much larger for F547M: An exposure time of less than a second is needed to image the star itself without data saturation, while we use an integration time longer than 100 seconds for the deepest exposure. Intermediate exposure times are used so that every intermediate brightness level has an exposure that gives excellent S/N. Note that our longest specified F547M exposure time, 2 140-second integrations, should be increased if time available in the orbit permits it. Real_Time_Justification: None, but note the following---- R. D. Gehrz and J. Krautter have initiated a series of supporting IR imaging studies of IRC +10420 and VY CMa at ESO using the IRAC-2 near-IR camera on the 2.3-meter and the TIMMI mid-IR camera on the 3.6-meter. The first images of IRC +10420 at 2.3 and 10 microns were recorded in May, 1995, and have been analyzed, showing evidence for a bipolar dust nebula. Additional observations are scheduled for April and May 1996. Since this is a variable target object, it is highly desirable not to delay the HST observations more than necessary after that time. Calibration_Justification: ! Move appropriate text from Real_Time_Justification Additional_Comments: Fixed_Targets ! Section 5.1 Target_Number: 100 Target_Name: IRC+10420 Alternate_Names: V1302-AQL Description: STAR, F0-F2, LUMINOUS BLUE VARIABLE, IRREGULAR VARIABLE Position: RA=19H 26M 48.09S +/- 0.1S, DEC=+11D 21' 17.7" +/- 1.5", PLATE-ID=02V0 ! Most common specification format is ! RA=0H 0M 0.00S +/- 0S, ! DEC=0D 0' 0.0" +/- 0", ! PLATE-ID=0000 Equinox: 2000 ! RV_or_Z: ! RA_PM: ! Units are seconds of time per year ! Dec_PM: ! Units are seconds of arc per year ! Epoch: !Annual_Parallax: Flux: V=11.0+/-0.5, B-V=2.7+/-0.5, E(B-V)=2.5+/-0.7 Comments: Brightness of the ejecta/halo is not known but probably spans a large range of surface brightness, in radius several arcsec. !Solar_System_Targets ! Section 5.2 ! (several lines omitted here) !Generic_Targets ! Section 5.3 ! (several lines omitted here) !Scan_Data ! Appendix B ! (several lines omitted here) ! ===-=== observing plan begins here; only 1 orbit for this project 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 | Gyro] ! GUIDing TOLerance ! DROP TO GYRO IF NECESSARY [NO REACQuisition] ! ORIENTation TO ! ORIENTation TO FROM ! ORIENTation TO FROM NOMINAL ! SAME ORIENTation AS ! CVZ ! PARallel ! SCHEDulability ! AFTER [BY [TO ]] ! AFTER ! BEFORE BETWEEN 01-APR-96 AND 05-MAY-96 ! GROUP WITHIN