6409( 4) - 09/18/96 10:39 - [ 0] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6409 Version: 4 Check-in Date: 18-Sep-1996 10:36:14 1.Proposal Title: SPECTROPHOTOMETRY OF THE WR CENTRAL STAR OF THE LMC-PN N66 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle HOT STARS GO 6 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: Miriam Pena INSTITUTO DE ASTRONOMIA CoI: MARIA T. RUIZ DEPTO. DE ASTRONOMIA, UNIVERSIDAD DE CHILE N CoI: MANUEL PEIMBERT INSTITUTO DE ASTRONOMIA, UNIVERSIDAD N NACIONAL AUTONOMA DE MEXICO CoI: SILVIA TORRES-PEIMBERT INSTITUTO DE ASTRONOMIA, UNIVERSIDAD N NACIONAL AUTONOMA DE MEXICO CoI: JOSE MAZA DEPTO. DE ASTRONOMIA, UNIVERSIDAD DE CHILE N CoI: ROBERTO H. MENDEZ MUNCHEN UNIVERSITY N ------------------------------------------------------------------------------------ 6. Abstract This is a CONTINUATION PROPOSAL (Cycle 5 \# 6055), it was awarded 4 orbits for Cycle 5 and 4 for Cycle 6. We propose to follow the extraordinary event occurring in the central star of the LMC-PN N66. Before 1987, it showed a weak continuum with a T_eff >= 120000 K and L_bol ~eq 25000 L_\odot and in few years it developed strong WR features (P-Cygni profiles in N V Lambda1240 and C IV Lamnda1550 lines, wide He II emission, etc.) typical of a WN4.5. The continuum increased by large factors and recently it has shown large variability. The present T_eff is ~ 50000 K and its M_V is similar to that of faint Population I WR in the LMC. To explain these changes Pe\ na et al. (1994) proposed that the star is undergoing a ``final thermal pulse". The ejecta consists of highly H-deficient He- and N-rich material which is most unusual since the known PNe with WR nucleus show He- and C-rich winds. Small aperture HST observations are needed to obtain the stellar spectrum without contamination of the nebular emission. The Cycle 5 visit was already performed successfully. We used the FOS with a combination of gratings covering the wavelength range 1150-4800 A with a resolving power of 1300. The data is being analyzing to determine the present stellar parameters (mass loss, T_eff, L_bol) and the chemical composition of the wind by means of specifically developed atmosphere models. The star is undergoing dramatic changes in a timescale of months (it faded two magnitudes in Sept. 95 and re-gain some brightness from October to the present), therefore we insist that it is paramount to re-observe the object in Cycle 6 as soon as possible to follow its evolution. ------------------------------------------------------------------------------------ Observations Description ------------------------ We plan to use the FOS, with an aperture of 0sec point3 and a combination of gratings to cover the wavelength range from 1150 to 4800 Angstrom with resolution of 1300. This will allow us to obtain the important UV lines, particularly N V Lambda1240 and C IV Lambda1550 resonant lines and all the optical stellar emission lines. The 0sec point3 aperture (circular), centered in the star, will contain only a small fraction of the ionized nebula avoiding most of its emission. A S/N of about 30 is necessary to accomplish a fair analysis of the stellar continuum and emission lines. The exposure times (needed to obtain this S/N) are presented below, where we have included the time required for Guide Star acquisition, and target acquisition. The total time estimated for this proposal is about 384 min. This will be accomplished with four CVZ orbits. Cycle 6 Primary orbits: 4 (CVZ) Scientific exposures: 3 1) Guide star acquisition:..........................8 min 2) target acquisition (4 steps: 8+17+13+26):.......64 min 3) FOS/BL + G130H:....................190 min exp time + OH (23 min) 4) FOS/BL + G190H:.....................45 min exp time + OH (10 min) 5) FOS/BL + G400H:.....................35 min exp time + OH (9 min) ---------------------------------- Total time:............................384 min Real Time Justification ----------------------- We are requesting CVZ because it is the most efficient way to observe the proposed target. Besides the exposure with FOS/BL + G130H filter requires 190 min to achieve an appropriate S/N, so "long duration" orbits are necessary for this observation. In this way, the target acquisition and the scientific observations will be accomplished in 4 orbits with visibility of 96 min each. In the non- CVZ mode, the total number of orbits required would be 6. The target has been followed in the optical each 2 or 3 months from different observatories (CTIO, ESO). IUE - 19th episode: we have been granted 16 hours of observing time, distributed along the cycle to study variability and to obtain one high resolution spectrum of the central star emission. Calibration Justification ------------------------- Additional Comments ------------------- IUE - 19th cycle: 16 hours have been awarded ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: DHL 991509322 Email: , ------------------------------------------------------------------------------------ 6409( 4) - 09/18/96 10:39 - [ 1] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 LMC-N66-CS EXT-STAR, PLANETARY RA=05H 36M 20.8S +/- 0.2S, DEC= J2000 V = 16.7+/-0.5 NEBULA CENTRAL STAR -67D 18' 08" +/-0.5", PLATE- B-V = -0.2 ID=06B0 E(B-V) = 0.1+/-0.05 TYPE=WN4.5 F-CONT(1300)=13+/-3e-15 F-CONT(5500)=6.1+/-0.3e-16 F-LINE(1640)=7+/-0.3e-13 Comments: highly variable target 6409( 4) - 09/18/96 10:39 - [ 2] Visit: 01 Visit Requirements: On Hold Comments: Additional Comments: WE REQUEST TO SCHEDULE THIS OBSERVATION IN THE FIRST OPPORTUNITY, WHICH IS NOVEMBER 96 DUE TO THE LARGE VARIABILITY OF THE TARGET. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 11 LMC-N66-CS FOS/BL ACQ/PEA 4.3 G270H 2650 SCAN-STEP-Y=1.23,SEARCH-SIZE-Y=3, 1 15 S ONBOARD ACQ FOR 12 K SEARCH-SIZE-X=1 ------------------------------------------------------------------------------------------------------------------------------------ 12 LMC-N66-CS FOS/BL ACQ/PEA 1.0 G270H 2650 SCAN-STEP-Y=0.61,SCAN-STEP-X=0.61 1 20 S ONBOARD ACQ FOR 13 K ,SEARCH-SIZE-Y=2,SEARCH-SIZE-X=6 ------------------------------------------------------------------------------------------------------------------------------------ 13 LMC-N66-CS FOS/BL ACQ/PEA 0.5 G270H 2650 SCAN-STEP-Y=0.29,SCAN-STEP-X=0.29 1 20 S ONBOARD ACQ FOR 14 K ,SEARCH-SIZE-Y=3,SEARCH-SIZE-X=3 ------------------------------------------------------------------------------------------------------------------------------------ 14 LMC-N66-CS FOS/BL ACQ/PEA 0.3 G270H 2650 SCAN-STEP-Y=0.11,SCAN-STEP-X=0.11 1 40 S ONBOARD ACQ FOR 16-18 K ,SEARCH-SIZE-Y=4,SEARCH-SIZE-X=4 ------------------------------------------------------------------------------------------------------------------------------------ 16 LMC-N66-CS FOS/BL ACCUM 0.3 G130H 1600 1 190 M ------------------------------------------------------------------------------------------------------------------------------------ 17 LMC-N66-CS FOS/BL ACCUM 0.3 G190H 2300 1 43 M ------------------------------------------------------------------------------------------------------------------------------------ 18 LMC-N66-CS FOS/BL ACCUM 0.3 G400H 3250 1 35 M ------------------------------------------------------------------------------------------------------------------------------------ 6409( 4) - 09/18/96 10:39 - [ 3] Summary Form for Proposal 6409 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Configurations FOS/BL ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/PEAK ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters SCAN-STEP-Y=1.23 SEARCH-SIZE-Y=3 SEARCH-SIZE-X=1 SEARCH-SIZE-X=6 SEARCH-SIZE-X=3 SEARCH-SIZE-X=4 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Scientific Category HOT STARS ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ONBOARD ACQ FOR 12 ONBOARD ACQ FOR 13 ONBOARD ACQ FOR 14 ONBOARD ACQ FOR 16-18 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G270H G130H G190H G400H ------------------------------------------------------------------------------------------------------------------------------------ Target Names LMC-N66-CS ------------------------------------------------------------------------------------------------------------------------------------