7303( 6) - 11/10/98 11:34 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 7303 Version: 6 Check-in Date: 10-Nov-1998 11:33:35 1.Proposal Title: UV Spectroscopy of Wolf-Rayet-Type Central Stars in the Magellanic Clouds ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 7 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Wolf-Rainer Hamann Universitaet Potsdam CoI: Lars Koesterke Lehrstuhl Astrophysik, Universitaet N Potsdam, Germany CoI: Grazyna Stasinska Observatoire de Paris-Meudon, France N CoI: Miriam Pena Instituto de Astronomia, UNAM, Mexico N CoI: Thomas Bloecker Institut fuer Astronomie und Astrophysik, N Univ. Kiel ------------------------------------------------------------------------------------ 5. Abstract We propose to take low-resolution UV spectra of two WC-type (subtypes WC5-6 and WC7) Central Stars of Planetary Nebulae (CSPN) in the LMC. Three spectral ranges shall be observed with STIS for each star (grisms G140L, G230L, 430L), with exposure times ranging from 26min to 62min per frame for a S/N ratio of 20-30 in the stellar continuum. Special advantage is taken from the high spatial resolution of HST which allows suppression of the nebular emission through a small slit. Together with ground-based optical spectra which we have already secured we will be able to perform quantitative spectral analyses of the central stars together with consistent nebular analyses. The decisive advantage of studying CSPN in the LMC is the knowledge of the distance. By this we will obtain definite values of the stellar parameters (especially the luminosity). This will reveal, e.g., whether WC-type CSPN are really more luminous than other CSPN, as has been suggested. A related question is why only CSPN with carbon-rich surface composition develop strong, WR-type winds. The results from the spectroscopic analyses will be used to construct post-AGB evolutionary tracks which, thanks to new physical ingredients (mixing treatment in overshoot layers), are capable now for the first time to produce WC-type abundance patterns. Metallicity effects on the evolution (LMC vs. Galaxy) will be studied. Consistent modelling of the nebulae will add further information about the evolutionary past of the central stars. ------------------------------------------------------------------------------------ 7303( 6) - 11/10/98 11:34 - [ 2] Observations Description ------------------------ The two WC-type CSPN SMP61 and MA17 in the LMC shall be observed with STIS in First Order Long Slit Spectroscopy configuration. The WR-type emission lines of these stars are broadened due to the stellar wind which reaches a terminal velocity of 700 km/s (MA17) and about 1000 km/s (SMP61), respectively. Thus the low-resolution gratings are just adequate to resolve the shape of the line profiles. Three gratings (G140L, G230L and G430L) are necessary to cover the required wavelength range. The exposure times are estimated from existing UV observations (underexposed HST spectra of SMP61, and an IUE SWP spectrum of MA17). Roughly adequate model flux distributions are fitted to these observations in order to predict the whole spectral range. Then we estimate the counts per second by multiplying the predicted stellar flux with the Point Source Sensitivity as given in Chapter 13 in the Instrument Handbook. For the observations with G230L and G430L we aim at a S/N about 30, while for the bluemost observation (G140L) a S/N about 20 is sufficient (due to the higher resolution of G140L we might smooth the data over two pixels without losing the resolution of the stellar lines). Following the example on p. 78 in the Handbook we finally apply the aperture throughput (T_A), the efficiency (epsilon_f) and the number of pixels integrated over, and obtain the total observing times given in the following Table:------------------------------ t[min] for grating Object G140L G230L G430L------------------------------ LMC- SMP61 53 60 32 LMC-MA17 53 60 32------------------------------ Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Paper Products: Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 7303( 6) - 11/10/98 11:34 - [ 3] TARGET LIST a) Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 LMC-MA17- EXT-STAR, Wolf Rayet - RA=05H 55M 13.68S +/- 0.5", DEC= J2000.0 V = 19 CENTRAL-STAR WC, Planetary Nebula -65D 28' 24.0" +/- 0.5", PLATE- F-CONT(1400)=3.4e-15 Central Star ID=02I7 F-CONT(2300)=9.6e-16 F-CONT(4300)=1.7e-16 TYPE=WC7 Comments: Flux predicted from model, reddened with E(B-V)=0.1 (LMC reddening law), and scaled to the visual magnitude of 19 2 LMC-SMP61- EXT-STAR, Wolf Rayet - RA=05H 24M 35.98S +/- 0.5", DEC= J2000.0 V = 19 CENTRAL-STAR WC, Planetary Nebula -73D 40' 39.4" +/- 0.5", PLATE- F-CONT(1400)=3.4e-15 Central Star ID=00RG F-CONT(2300)=9.6e-16 F-CONT(4300)=1.7e-16 TYPE=WC5-6 Comments: Flux predicted from model, reddened with E(B-V)=0.1 (LMC reddening law), and scaled to the visual magnitude of 19 7303( 6) - 11/10/98 11:34 - [ 4] Visit: 01 Visit Priority: 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-MA17-CE STIS/C ACQ 50CCD MIRROR 1 100 S ONBOARD ACQ FOR 13, 14, NTRAL-STAR CD 15 ------------------------------------------------------------------------------------------------------------------------------------ 13 LMC-MA17-CE STIS/C ACCUM 52X0.2 G430L 4300 1 30 M NTRAL-STAR CD ------------------------------------------------------------------------------------------------------------------------------------ 14 LMC-MA17-CE STIS/F ACCUM 52X0.2 G140L 1425 1 55 M NTRAL-STAR UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 15 LMC-MA17-CE STIS/N ACCUM 52X0.2 G230L 2376 1 60 M NTRAL-STAR UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7303( 6) - 11/10/98 11:34 - [ 5] Visit: 02 Visit Priority: Visit Requirements: 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 ------------------------------------------------------------------------------------------------------------------------------------ 21 LMC-SMP61-C STIS/C ACQ 50CCD MIRROR 1 100 S ONBOARD ACQ FOR 23, 24, ENTRAL-STAR CD 25, 26 SEQ 21, 23 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ 23 LMC-SMP61-C STIS/F ACCUM 52X0.2 G140L 1425 1 40 M ENTRAL-STAR UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 24 LMC-SMP61-C STIS/F ACCUM 52X0.2 G140L 1425 1 22 M ENTRAL-STAR UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 25 LMC-SMP61-C STIS/N ACCUM 52X0.2 G230L 2376 1 22 M ENTRAL-STAR UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 26 LMC-SMP61-C STIS/N ACCUM 52X0.2 G230L 2376 1 45 M ENTRAL-STAR UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 7303( 6) - 11/10/98 11:34 - [ 6] Visit: 03 Visit Priority: Visit Requirements: On Hold Comments: Additional Comments: Same target as Visit 02, but extra CCD visit following the new MAMA policy Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 31 LMC-SMP61-C STIS/C ACQ 50CCD MIRROR 1 100 S ONBOARD ACQ FOR 33 ENTRAL-STAR CD ------------------------------------------------------------------------------------------------------------------------------------ 33 LMC-SMP61-C STIS/C ACCUM 52X0.2 G430L 4300 1 35 M ENTRAL-STAR CD ------------------------------------------------------------------------------------------------------------------------------------ 7303( 6) - 11/10/98 11:34 - [ 7] Summary Form for Proposal 7303 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 50CCD 52X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements CVZ ONBOARD ACQ FOR 13, 14, 15 ONBOARD ACQ FOR 23, 24, 25, 26 SEQ 21, 23 NON-INT ONBOARD ACQ FOR 33 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G430L G140L G230L ------------------------------------------------------------------------------------------------------------------------------------ Target Names LMC-MA17-CENTRAL-STAR LMC-SMP61-CENTRAL-STAR ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 4300 1425 2376 ------------------------------------------------------------------------------------------------------------------------------------