6055( 12) - 11/08/95 20:42 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 6055 Version: 12 Check-in Date: ********** 1.Proposal Title: SPECTROPHOTOMETRY OF THE W-R CENTRAL STAR OF THE LMC-PN N66 ------------------------------------------------------------------------------------ 2. Scientific Category 3. Proposal For 4. Cycle HOT STARS GO 5 ------------------------------------------------------------------------------------ 5. Investigators Contact? PI: MIRIAM PENA INSTITUTO DE ASTRONOMIA, UNIVERSIDAD NACIONAL AUTONOMA DE MEXICO CoI: MANUEL PEIMBERT INSTITUTO DE ASTRONOMIA, UNIVERSIDAD N NACIONAL AUTONOMA DE MEXICO CoI: SILVIA TORRES-PEIMBERT INSTITUTO DE ASTRONOMIA, UNIVERSIDAD Y NACIONAL AUTONOMA DE MEXICO CoI: MARIA T. RUIZ DEPTO. DE ASTRONOMIA, UNIVERSIDAD DE CHILE N CoI: JOSE MAZA DEPTO. DE ASTRONOMIA, UNIVERSIDAD DE CHILE N CoI: ROBERTO H. MENDEZ MUNCHEN UNIVERSITY N ------------------------------------------------------------------------------------ 6. Abstract We will study 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 solar luminosities. Recently it developed strong W-R features typical of a WN4.5 star (P -Cygni profiles in N V Lambda 1240 and C IV Lambda 1550 lines and wide He II emission lines). Simultaneously, the visual and UV continuum intensities increased by large factors. The present T(eff) is 50000 K. The ejected wind consists of highly H-deficient He- and N-rich material. This is most unusual since all the known PNe with W-R nucleus show He- and C-rich winds. To explain these changes Pena et al. (1994a) proposed that the star is undergoing a ``final thermal pulse". This is the first time that such an event is observed. The nebular emission lines have not changed in the last 20 years so the recent stellar activity has not altered the nebula yet. Small aperture observations with HST are needed to obtain the stellar spectrum without contamination of the nebular emission. We plan to use the FOS with a combination of gratings to cover the wavelength range 1150-7000 Angstrom with a resolving power of 1300. The spectrophotometric data will be used to determine the present stellar parameters (mass loss, T(eff), L(bol) and to analize the chemical composition of the atmosphere. We propose to re-observe the object in Cycle 6 since the star is undergoing important changes in time scales of 1 year or less. ------------------------------------------------------------------------------------ 6055( 12) - 11/08/95 20:42 - [ 2] Observations Description ------------------------ The FOS, with an aperture of 0.3 arcsec and a combination of gratings to cover the wavelength range from 1150 to 7000 Angstrom with resolution of 1300 will be used. This will allow us to obtain the important UV lines, particularly N V Lambda 1240 and C IV Lambda 1550 resonant lines and all the optical stellar emission lines. The 0.3 arcsec aperture (circular), centered in the star, will contain only a small fraction of the ionized nebula avoiding most of its emission. A signal-to-noise of 30 is necessary to accomplish a fair analysis of the stellar continuum and emission lines. The exposure times (needed to obtain this signal-to-noise) were calculated using the stellar fluxes of Table 1 (not corrected by reddening) and the Cycle 5 Proposal Instructions data about HST + COSTAR + FOS efficiencies, aperture throughputs and wavelength dispersion. Cycle 5 Primary orbits: 3 (CVZ) Scientific exposures: 5 1) Guide star acquisition:.............12 min 2) target acquisition:.................61 min 3) FOS/BL + G130H:.....................90 min exp. time + OH (6 min) 4) FOS/RD + G190H:......................9 min exp. time + OH (6 min) 5) FOS/RD + G270H:......................8 min exp. time + OH (6 min) 6) FOS/RD + G400H:......................7 min exp. time + OH (6 min) 7) FOS/RD + G570H:......................9 min exp. time + OH (6 min) ---------------------- ----------------------------------------------- Total time:.............................225 min Real Time Justification ----------------------- We are requesting CVZ because is the most efficient way to observe the proposed target. In this way, the target acquisition and the scientific observations will be accomplished in only 3 orbits with visibility of 96 min each. This includes a reconfiguration of 54 min from FOS Red to Blue Calibration Justification ------------------------- Additional Comments ------------------- CTIO: an observing run has been granted for December 1994 IUE - 18th cycle: 3 US1 shifts have been awarded ------------------------------------------------------------------------------------ Data Distribution Media: 8MM Blocking Factor: 10 Ship To: PI_Address Ship Via: DHL991509322 __ Email: , ------------------------------------------------------------------------------------ 6055( 12) - 11/08/95 20:42 - [ 3] 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 = 16.2+/-0.2 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) = 30 +/- 3 E-15 F-CONT(5500) = 1.3 +/- 0.3 E-15 F-LINE(1640) = 2 +/- 0.3 E-12 6055( 12) - 11/08/95 20:42 - [ 4] Visit: 01 Visit Requirements: CVZ On Hold Comments: Additional Comments: 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 SCAN-STEP- 1 20S ONBOARD ACQ FOR 12 K Y=1.23, SEARCH- SIZE-Y=3, SEARCH-SIZE-X=1 ------------------------------------------------------------------------------------------------------------------------------------ 12 LMC-N66-CS FOS/BL ACQ/PEA 1.0 G270H SCAN-STEP- 1 20S ONBOARD ACQ FOR 13 K Y=0.61, SCAN- STEP-X=0.61, SEARCH-SIZE- Y=2, SEARCH- Comments: SIZE-X=6 ------------------------------------------------------------------------------------------------------------------------------------ 13 LMC-N66-CS FOS/BL ACQ/PEA 0.5 G270H SCAN-STEP- 1 20S ONBOARD ACQ FOR 14 K Y=0.29, SCAN- STEP-X=0.29, SEARCH-SIZE- Y=3, SEARCH- Comments: SIZE-X=3 ------------------------------------------------------------------------------------------------------------------------------------ 14 LMC-N66-CS FOS/BL ACQ/PEA 0.3 G270H SCAN-STEP- 1 40S ONBOARD ACQ FOR 16-18 K Y=0.11, SCAN- STEP-X=0.11, SEARCH-SIZE- Y=4, SEARCH- Comments: SIZE-X=4 ------------------------------------------------------------------------------------------------------------------------------------ 16 LMC-N66-CS FOS/BL ACCUM 0.3 G130H 1600 1 11400S ------------------------------------------------------------------------------------------------------------------------------------ 17 LMC-N66-CS FOS/BL ACCUM 0.3 G190H 2300 1 2700S ------------------------------------------------------------------------------------------------------------------------------------ 18 LMC-N66-CS FOS/BL ACCUM 0.3 G400H 3250 1 2100S ------------------------------------------------------------------------------------------------------------------------------------ 6055( 12) - 11/08/95 20:42 - [ 5] Summary Form for Proposal 6055 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 CVZ 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 ------------------------------------------------------------------------------------------------------------------------------------