! Hubble Space Telescope Cycle 6 (1996) Phase II Proposal Template ! 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: Alice Berman ! Phone: 410-338-4462 , E-mail: aberman@stsci.edu ! ! This partially completed template was generated from a Phase I proposal. ! Proposal_Information ! Section 4 Title: Spectroscopic Study of Origin and Nature of CVs in Globular Clusters Proposal_Category: GO Scientific_Category: BINARIES AND STAR FORMATION Cycle: 6 Investigators PI_name: Jonathan Grindlay PI_Institution: Harvard University CoI_Name: Paul Callanan CoI_Institution: Harvard University Contact: ! Y or N (designate at most one contact) CoI_Name: Adrienne Cool CoI_Institution: University of California, Berkeley Contact: ! Y or N (designate at most one contact) CoI_Name: Charles Bailyn CoI_Institution: Yale University Contact: ! Y or N (designate at most one contact) CoI_Name: Haldan Cohn CoI_Institution: Indiana University Contact: ! Y or N (designate at most one contact) CoI_Name: Phyllis Lugger CoI_Institution: Indiana University Contact: ! Y or N (designate at most one contact) Abstract: ! Free format text (please update) In our revised (Phase II submission) program, we propose to determine whether H Alpha emission objects discovered in our H Alpha vs. R imaging studies of the globular cluster NGC 6397 are cataclysmic variables (CVs) and possibly magnetic CVs as suggested by our recent FOS discovery of 3 probable DQ Her systems in NGC 6397. If the two additional (fainter) H Alpha candidates in NGC 6397 are as similar as the first three, which are nearly identical, it will provide strong evidence that CVs in globulars are not only formed by capture or exchanges (as expected), but that moderately massive cluster white dwarfs (WDs) may be preferentially magnetic (totally unexpected). This would have fundamental implications for stellar and dynamical evolution on globulars. By obtaining spectra of all candidates in the visible range (c. 4500 - 6700 Angstrom), probable magnetic systems can be identified by their usually significant He II emission. By obtaining a separate uv (1300 - 2200 Angstrom) spectrum on the brightest of the original 3 CV candidates in NGC 6397, as well as a prism observation (1600 - 4800 Angstrom), we shall both obtain the complete spectrum of a cluster CV as well as measure uv line ratios (e.g. HeII(1640)/CIV(1550)) that are sensitive to whether it is a magnetic CV. The uv spectrum and complete energy distribution will also allow future comparisons with quiescent LMXB spectra, which we shall propose to obtain in future HST cycles. Questions ! Free format text (please update) Observing_Description: The goal is to obtain spectra of three faint stars in the crowded field of a globular cluster core. All are stars that were detected in a WFPC1 imaging study with the Planetary Camera. The science targets are too faint relative to nearby bright neighbors to permit peak-ups to be performed on them directly. We are therefore using blind offsets from a nearby bright star to reach the science targets. The target acquisition begins with an ACQ/BINARY on the RED side on a bright, isolated star (Target 1). This star is about 30" from the science targets, and does not appear on the PC image on which the science targets appear and from which their coordinates were measured (see note about coordinate system below). It was chosen as the nearest available star that is sufficiently isolated for the use of an ACQ/BINARY. Following the ACQ/BIN, we offset to Target 2, which is also a bright star. This star is closer to the science targets, and is on the same PC image as the science targets. We perform a series of two 3x3 ACQ/PEAK observations on the RED side on this target to refine our coordinate system, the first with 0.29" steps and the 0.5" aperture, and the second with 0.11" steps and the 0.3" aperture. Following the two peak-ups, the pointing should be accurate to 0.08" or better. We then perform a series of blind offsets to each of the three science targets, in turn. No peak-ups are planned between the three blind offsets. As we are using the 0.43" aperture on all the science targets, it is critical that the total uncertainty in the pointing be no worse than about 0.15" after the third blind offset, which will occur 4 orbits after the peak-up was done. The following estimates suggest that this should be possible. If for any reason this accuracy is not possible, we can modify our program to include peak-ups between science targets. Blind offsets are said to be accurate to 0.08" for a 1 arcmin offset, and proportional to the offset angle. Each of our blind offsets will be no more than 16", and the maximum distance from the offset star (Target 2) is no more than 16". We thus expect that the cumulative pointing error due to the blind offset will be no more than 0.02"-0.03". Combining this in quadrature with the 0.08" accuracy following the second peak-up on Target 2, the overall pointing should be no worse than 0.09". This accuracy is sufficient to insure that the science targets will fall well inside the 0.43" aperture that we are using. These peak-ups, blind offsets, and observations of the three science targets will occupy 5 of the program's 7 orbits. Spectra of the first two science targets (Targets 4 and 5) will be taken with the G570H grating on the RED side. For the third science target (Target 3), we will obtain a spectrum with the PRISM on the RED side. The last 2 orbits will be devoted to taking a UV spectrum of Target 3 on the BLUE side with the G160L grating. We will switch to the BLUE side during occultation after the 5th orbit, and begin the 6th orbit with a peak-up on on Target 2. This peak-up will insure a pointing accuracy of 0.08" following the switch to the BLUE side. We then perform a blind offset to Target 3, less than 2" away, and again use the 0.43" aperture for the observation. Please note that in our Fixed_Targets list, we have specified the coordinates of all the Targets relative to Target 1, for convenience. Target 1 was successfully acquired in our Cycle 4 FOS observation of this cluster, and we are using the identical RA and DEC for this star that we used in that program. However, the coordinates of the science targets (Targets 3, 4, and 5) are best determined relative to Target 2, which is the offset star that appears on the Planetary Camera image on which the science targets also appear. The coordinates are significantly less certain relative to Target 1, and are insufficiently accurate relative to that star for the purposes of this program. Thus our final peak-ups are always done on Target 2. Our understanding is that the final peak-up on Target 2 will determine the coordinate system, and that, in effect, all the offsets will be done relative to the final peak-up position on that star. Exposure times were computed based on data supplied in the FOS Handbook and/or by scaling from our Cycle 4 FOS observations of other faint stars in this cluster. Real_Time_Justification: Calibration_Justification: ! Move appropriate text from Real_Time_Justification Additional_Comments: Fixed_Targets ! Section 5.1 Target_Number: 1 Target_Name: NGC6397-174041-534001-OFFSET Alternate_Names: NGC6397-STAR1-OFFSET Description: STAR Position: RA = 17H 40M 40.570S +/- 0.020S, DEC = -53D 40' 01.10" +/- 0.20", PLATE-ID=0688 Equinox: J2000 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 = 14 B-V=0.85 E(B-V) = 0.2 Comments: Target_Number: 2 Target_Name: NGC6397-174041-534021-OFFSET Alternate_Names: NGC6397-STAR2-OFFSET Description: STAR Position: RA-OFF = 0.910S +/- 0.010S, DEC-OFF = -20.00" +/- 0.10", FROM 1, PLATE-ID=0688 Equinox: J2000 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 = 14 B-V=0.85 E(B-V) = 0.2 Comments: Target_Number: 3 Target_Name: NGC6397-174042-534020 Alternate_Names: NGC6397-STAR3 Description: STAR, DC Position: RA-OFF = 0.932S +/- 0.005S, DEC-OFF = -18.71" +/- 0.05", FROM 1, PLATE-ID=0688 Equinox: J2000 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 = 18 B-V=0.5 E(B-V) = 0.2 Comments: Target_Number: 4 Target_Name: NGC6397-174041-534028 Alternate_Names: Description: STAR Position: RA-OFF = 0.416S +/- 0.005S, DEC-OFF = -26.46" +/- 0.05", FROM 1, PLATE-ID=0688 Equinox: J2000 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 = 20 B-V=0.5 E(B-V) = 0.2 Comments: Target_Number: 5 Target_Name: NGC6397-174042-534022 Alternate_Names: Description: STAR, DC Position: RA-OFF = 1.164S +/- 0.005S, DEC-OFF = -20.77" +/- 0.05", FROM 1, PLATE-ID=0688 Equinox: J2000 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 = 20 B-V=0.5 E(B-V) = 0.2 Comments: ! This is a template for a single visit containing a single exposure ! Repeat exposure and visit blocks as needed Visits ! Section 6 Visit_Number: 01 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 AND ! GROUP WITHIN