8318( 4) - 01/24/00 14:01 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8318 Version: 4 Check-in Date: 30-Mar-1999 14:45:10 1.Proposal Title: Probing the Evolution of Massive Stars: Ejecta Ring Nebulae Abundances and Dynamics ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Linda Smith University College London CoI: Dr. Anna Pasquali Space Telescope European Coordinating N Facility CoI: Dr. Regina Schulte-Ladbeck University of Pittsburgh N CoI: Dr. Mark Clampin Space Telescope Science Institute N CoI: Dr. Stephen Hulbert Space Telescope Science Institute N CoI: Dr. Norbert Langer University of Potsdam N CoI: Dr. Antonella Nota Space Telescope Science Institute Y ------------------------------------------------------------------------------------ 5. Abstract We propose to obtain STIS spectra of the nebulae surrounding two evolved massive stars in the Magellanic Clouds. These stars represent a short but key transition phase in the evolution of an O to a Wolf-Rayet (WR) star. This phase is characterized by a sudden increase of the mass loss and the appearance of processed material at the stellar surface. The remnants of this brief period are seen as small circumstellar shells. Since the nebulae, in effect, represent the stellar surface layers during the transition phase, the stellar evolutionary history can be probed by using STIS spectra to measure the N and O abundances together with the dynamics. HST is required because the nebular radii are typically 2-4 arcsec and thus stellar contamination precludes an accurate ground-based analysis. Our previous HST/FOS observations show that one such nebula is not composed of heavily-processed wind material but material that may have originated in a RSG envelope. Since our findings direct ly challenge our understanding of the evolution of massive stars and their enrichment of the interstellar medium through extensive mass loss, we propose to undertake a systematic abundance study of nebulae around evolved massive stars. This study will allow us to understand at which evolutionary stage the major mass loss occurs in the transition from an O to a WR star, and provide new insights into the LBV mass loss mechanism. ------------------------------------------------------------------------------------ 8318( 4) - 01/24/00 14:01 - [ 2] Observations Description ------------------------ We propose to use STIS with the CCD detector to obtain long- slit spectra of the ejecta nebulae associated with two massive evolved emission-line stars. The stars will be acquired using a standard point acquisition with the [OIII] narrow-band filter in place to avoid CCD saturation. The exposure times for the acquisition process have been calculated using the STIS ACQ ETC and the observed flux calibrated spectra of the two stars. No peak-up is required since the nebulae have dimensions of several arcsec, and pointing errors of a fraction of an arcsec are not a concern. We will position the slit at the optimum position angle to cover the brightest nebular region and so maximize the nebular flux. To cover the essential diagnostic lines, and to determine the nebular reddenings from the Balmer line ratios, we will use gratings G430M and G750M at a total of four standard tilts. The `M' gratings are preferred over the `L' gratings due to the insufficient spectral resolution provi ded by the low resolution gratings . The narrow 52*0.1 aperture will be used to map the kinematics of the nebulae at HAlpha and N II. As the nebulosities will fill the apertures more or less uniformly in the dispersion direction use of this aperture/grating pair will provide a resolution of about 50 km/s at HAlpha. We will use on-board binning with the CCD to produce spectra binned spatially and spectrally over 4 and 2 bins respectively. For the 52*0.1 observations, we will not bin in the spectral direction. The wider 52*0.2 aperture will be used to determine the electron temperature and chemical abundances. Even with the reduced resolution of this aperture we will be able to resolve the necessary diagnostic features. The wavelength ranges were chosen on the basis of the wavelengths of the required essential diagnostic lines. These lines are N II Lambda5755 line (crucial for obtaining the electron temperature), S II Lambda6717/6731 (electron density), O II Lambda3727 (O abundance), N II Lambda6584 (N abun dance), and HAlpha/HBeta (extincti o n determination). The nebulae have a low T_e of 6000-7000 K and thus measurement of the strengths of the O II and N II lines, together with a T_e and N_e measurement, directly give the O and N abundances. No correction for unseen ionization stages are necessary e.g. O III is absent in the similar R127 and S119 nebulae. With our previous FOS observations of the R127 nebula we were able to determine E(B-V), T_e, and N_e to an accuracy of +/-0.03, +/-300 K and +/-100 cm^-3. With this precision, we obtained N and O abundances to +/-0.1 and +/-0.2 dex. These errors are typical of PNe and H II region abundance analyses and thus we wish to obtain STIS spectra of similar quality to the R127 FOS spectra in order for us to determine accurate abundances. Analysis of this spectrum shows that we need to detect the essential diagnostic lines at a S/N of 15. This requirement has therefore determined our exposure times. The exposure times have been calculated using the H alpha fluxes fr om WFPC2 images of the two targets R143 and S61, and scaling the WFPC2 H alpha fluxes and FOS spectrum of R127. We have assumed that the relative line intensities in the R127 FOS spectrum will be the same in the R143 and S61 nebulae but have allowed for the different reddenings. The observed WFPC2 H alpha fluxes (erg/s/cm^2/arcsec^2) for R127, R143 and S61 are 8.60E-13, 1.61E-12 and 9.76E-13. Thus R143 and S61 are 1.9 and 1.1 times brighter. Exposure times have been calculated with the STIS ETC using the intrinsic R127 peak line fluxes, assuming an LMC reddening of E(B-V)=0.50 (R143) and E(B-V)=0.21 (S61) and scaling by the factors given above. For the G750M grating, we assumed the lines were unresolved (FWHM=1A) and divided the fluxes by a factor of 2. For the wavelength settings, the exposure times given in Table 1 produce a S/N of 15 at the peak of the line except for [NII] 5755 which corresponds to 3. These spectra will be binned spatially over the 3 arcsec nebular extent to improve the S/N. The long exposure times and loss of spatia l information is quite reasonable in this case as this line is a critical diagnostic feature for determining the electron temperature. The exposure times for the dynamical data were obtained assuming a S/N of 20 at the peak of the H alpha line. Three positions in the nebulae have been chosen to measure the dynamics. Table 1 - Exposure times Nebula G750M G750M G750M G430M G430M 6768 6768 5734 4961 3680 52x0.1 52x0.2 52x0.2 52x0.2 52x0.2 R143-POS1 140 s 650 s 7000 s 275 s 4700 s-POS2 140 s-POS3 140 s S61-POS1 225 s 1150 s 10500 s 400 s 5240 s-POS2 225 s-POS3 225 s Real Time Justification ----------------------- In order to observe the brightest area of each nebula, the STIS long slit must be oriented at a particular position angle to maximize the nebula flux. We have determined the maximum range in ORIENT as detailed below. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 8318( 4) - 01/24/00 14:01 - [ 3] Data Distribution Paper Products: NO Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8318( 4) - 01/24/00 14:01 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD269929- EXT-STAR, LUMINOUS BLUE RA=05H 38M 51.68S +/- 0.2S, DEC= J2000 V = 11.9+/-0.5 OFFSET VARIABLE, EMISSION LINE -69D 8' 7.5" +/- 0.2", PLATE- B-V = 0.41 STAR ID=05ZW F-CONT(5000)=7.00e-14 E(B-V) = 0.5+/-0.1 TYPE=B3I 2 HD269929-NEB EXT-MEDIUM, HII REGION XI-OFF=-1.2"+/- 0.1", ETA- J2000 SURF-LINE(6563)=1.61e-12 -POS1 OFF=0.0"+/- 0.1", FROM 1 F-LINE(6717)=4.94e-15 F-LINE(4861)=1.96e-14 W-LINE(6717)=1 W-LINE(4861)=1 SIZE=3 E(B-V) = 0.50 Comments: Offset is measured to be 0.22S W of star F-LINE refers to peak line flux and is /arcsec^2 3 HD269929-NEB EXT-MEDIUM, HII REGION XI-OFF=-1.8"+/- 0.1", ETA- J2000 SURF-LINE(6563)=1.61e-12 -POS2 OFF=0.0"+/- 0.1", FROM 1 F-LINE(6563)=7.46e-14 W-LINE(6563)=1 SIZE=3 E(B-V) = 0.50 Comments: Offset is measured to be 1.8" W of star F-LINE refers to peak line flux and is /arcsec^2 4 HD269929-NEB EXT-MEDIUM, HII REGION XI-OFF=-0.6"+/- 0.1", ETA- J2000 SURF-LINE(6563)=1.61e-12 -POS3 OFF=0.0"+/- 0.1", FROM 1 F-LINE(6563)=7.46e-14 W-LINE(6563)=1 SIZE=3 E(B-V) = 0.50 Comments: Offset is measured to be 0.6"W of star F-LINE refers to peak line flux and is /arcsec^2 5 S61-OFFSET EXT-STAR, LUMINOUS BLUE RA=05H 45M 52.05S +/- 0.1S, DEC= J2000 V = 12.00 VARIABLE, EMISSION LINE -67D 14' 26.0" +/- 0.4", PLATE- B-V = -0.09 STAR ID=06B0 E(B-V) = 0.10 F-CONT(5000)=7.84e-14 TYPE=OFPE/WN9 Comments: Coordinates are from GSC 6 S61-NEB-POS1 EXT-MEDIUM, HII REGION, XI-OFF=0.0"+/- 0.1", ETA- J2000 SURF-LINE(6563)=9.76e-13 RING NEBULA OFF=1.3"+/- 0.1", FROM 5 F-LINE(6717)=2.83e-15 F-LINE(4861)=1.37e-14 W-LINE(6717)=1 W-LINE(4861)=1 SIZE=3 E(B-V) = 0.21 Comments: Offset is measured to be 1.3" N of star F-LINE refers to peak line fluxes and is /arcsec^2 7 S61-NEB-POS2 EXT-MEDIUM, HII REGION, XI-OFF=0.0"+/- 0.1", ETA- J2000 SURF-LINE(6563)=9.76e-13 RING NEBULA OFF=0.8"+/- 0.1", FROM 5 F-LINE(6563)=4.50e-14 W-LINE(6563)=1 SIZE=3 E(B-V) = 0.21 Comments: Offset is measured to be 0.8" N of star F-LINE refers to peak line fluxes and is /arcsec^2 8318( 4) - 01/24/00 14:01 - [ 5] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 8 S61-NEB-POS3 EXT-MEDIUM, HII REGION, XI-OFF=0.0"+/- 0.1", ETA- J2000 SURF-LINE(6563)=9.76e-13 RING NEBULA OFF=0.4"+/- 0.1", FROM 5 F-LINE(6563)=4.50e-14 W-LINE(6563)=1 SIZE=3 E(B-V) = 0.21 Comments: Offset is measured to be 0.4"N of star F-LINE refers to peak line fluxes and is /arcsec^2 8318( 4) - 01/24/00 14:01 - [ 6] Visit: 01 Visit Priority: Visit Requirements: ORIENT 60D TO 77D ORIENT 240D TO 257D On Hold Comments: Additional Comments: Sky PA range 15D to 32D and 180D flip Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 HD269929-OF STIS/C ACQ F28X50O MIRROR ACQTYPE=POINT 1 100.0 S ONBOARD ACQ FOR 20-110 FSET CD III ------------------------------------------------------------------------------------------------------------------------------------ 20 HD269929-NE STIS/C ACCUM 52X0.2 G430M 3680 BINAXIS1=2,BINAXIS2=4,CR-SPLIT=2, 1 1060 S END ORBIT B-POS1 CD PATTERN=ALONG-SLIT,NUM-POS=2, STEP-SIZE=0.25 ------------------------------------------------------------------------------------------------------------------------------------ 30 HD269929-NE STIS/C ACCUM 52X0.2 G430M 3680 BINAXIS1=2,BINAXIS2=4,CR-SPLIT=2, 1 1490 S END ORBIT B-POS1 CD PATTERN=ALONG-SLIT,NUM-POS=2, STEP-SIZE=0.25 ------------------------------------------------------------------------------------------------------------------------------------ 40 HD269929-NE STIS/C ACCUM 52X0.2 G430M 4961 BINAXIS1=2,BINAXIS2=4 1 275 S B-POS1 CD ------------------------------------------------------------------------------------------------------------------------------------ 50 HD269929-NE STIS/C ACCUM 52X0.1 G750M 6768 BINAXIS1=1,BINAXIS2=4 1 140 S B-POS1 CD ------------------------------------------------------------------------------------------------------------------------------------ 60 HD269929-NE STIS/C ACCUM 52X0.1 G750M 6768 BINAXIS1=1,BINAXIS2=4 1 140 S B-POS2 CD ------------------------------------------------------------------------------------------------------------------------------------ 70 HD269929-NE STIS/C ACCUM 52X0.1 G750M 6768 BINAXIS1=1,BINAXIS2=4 1 140 S B-POS3 CD ------------------------------------------------------------------------------------------------------------------------------------ 80 HD269929-NE STIS/C ACCUM 52X0.2 G750M 6768 BINAXIS1=2,BINAXIS2=4 1 650 S B-POS1 CD ------------------------------------------------------------------------------------------------------------------------------------ 90 HD269929-NE STIS/C ACCUM 52X0.2 G750M 5734 BINAXIS1=2,BINAXIS2=4 1 1000 S END ORBIT B-POS1 CD ------------------------------------------------------------------------------------------------------------------------------------ 100 HD269929-NE STIS/C ACCUM 52X0.2 G750M 5734 BINAXIS1=2,BINAXIS2=4,CR-SPLIT=2, 1 1490 S END ORBIT B-POS1 CD PATTERN=ALONG-SLIT,NUM-POS=2, STEP-SIZE=0.25 ------------------------------------------------------------------------------------------------------------------------------------ 110 HD269929-NE STIS/C ACCUM 52X0.2 G750M 5734 BINAXIS1=2,BINAXIS2=4,CR-SPLIT=2, 1 1490 S END ORBIT B-POS1 CD PATTERN=ALONG-SLIT,NUM-POS=2, STEP-SIZE=0.25 ------------------------------------------------------------------------------------------------------------------------------------ 8318( 4) - 01/24/00 14:01 - [ 7] Visit: 02 Visit Priority: Visit Requirements: ORIENT 118D TO 140D ORIENT 298D TO 320D On Hold Comments: Additional Comments: Sky PA range 73D to 95D and 180D flip Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exposure| Target |Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Number | Name |Config| Mode |or FOV |Element |Waveln.| Parameters |Exp| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 10 S61-OFFSET STIS/C ACQ F28X50O MIRROR ACQTYPE=POINT 1 30 S ONBOARD ACQ FOR 30-120 CD III ------------------------------------------------------------------------------------------------------------------------------------ 20 S61-NEB-POS STIS/C ACCUM 52X0.2 G430M 4961 BINAXIS1=2,BINAXIS2=4 1 400 S 1 CD ------------------------------------------------------------------------------------------------------------------------------------ 30 S61-NEB-POS STIS/C ACCUM 52X0.2 G430M 3680 BINAXIS1=2,BINAXIS2=4, 1 890 S END ORBIT 1 CD PATTERN=ALONG-SLIT,NUM-POS=2, STEP-SIZE=0.25 ------------------------------------------------------------------------------------------------------------------------------------ 40 S61-NEB-POS STIS/C ACCUM 52X0.2 G430M 3680 BINAXIS1=2,BINAXIS2=4,CR-SPLIT=2, 1 1490 S END ORBIT 1 CD PATTERN=ALONG-SLIT,NUM-POS=2, STEP-SIZE=0.25 ------------------------------------------------------------------------------------------------------------------------------------ 50 S61-NEB-POS STIS/C ACCUM 52X0.1 G750M 6768 BINAXIS1=1,BINAXIS2=4 1 190 S 1 CD ------------------------------------------------------------------------------------------------------------------------------------ 60 S61-NEB-POS STIS/C ACCUM 52X0.1 G750M 6768 BINAXIS1=1,BINAXIS2=4 1 190 S 2 CD ------------------------------------------------------------------------------------------------------------------------------------ 70 S61-NEB-POS STIS/C ACCUM 52X0.1 G750M 6768 BINAXIS1=1,BINAXIS2=4 1 190 S 3 CD ------------------------------------------------------------------------------------------------------------------------------------ 80 S61-NEB-POS STIS/C ACCUM 52X0.2 G750M 6768 BINAXIS1=2,BINAXIS2=4 1 1000 S 1 CD ------------------------------------------------------------------------------------------------------------------------------------ 90 S61-NEB-POS STIS/C ACCUM 52X0.2 G750M 5734 BINAXIS1=2,BINAXIS2=4 1 1090 S END ORBIT 1 CD ------------------------------------------------------------------------------------------------------------------------------------ 100 S61-NEB-POS STIS/C ACCUM 52X0.2 G750M 5734 BINAXIS1=2,BINAXIS2=4,CR-SPLIT=2, 1 1490 S END ORBIT 1 CD PATTERN=ALONG-SLIT,NUM-POS=2, STEP-SIZE=0.25 ------------------------------------------------------------------------------------------------------------------------------------ 110 S61-NEB-POS STIS/C ACCUM 52X0.2 G750M 5734 BINAXIS1=2,BINAXIS2=4,CR-SPLIT=2, 1 1490 S END ORBIT 1 CD PATTERN=ALONG-SLIT,NUM-POS=2, STEP-SIZE=0.25 ------------------------------------------------------------------------------------------------------------------------------------ 120 S61-NEB-POS STIS/C ACCUM 52X0.2 G750M 5734 BINAXIS1=2,BINAXIS2=4,CR-SPLIT=2, 1 1490 S END ORBIT 1 CD PATTERN=ALONG-SLIT,NUM-POS=2, STEP-SIZE=0.25 ------------------------------------------------------------------------------------------------------------------------------------ 8318( 4) - 01/24/00 14:01 - [ 8] Summary Form for Proposal 8318 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50OIII 52X0.2 52X0.1 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT STEP-SIZE=0.25 NUM-POS=2 BINAXIS2=4 BINAXIS1=1 BINAXIS1=2 PATTERN=ALONG-SLIT CR-SPLIT=2 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 60D TO 77D ORIENT 240D TO 257D ONBOARD ACQ FOR 20-110 END ORBIT ORIENT 118D TO 140D ORIENT 298D TO 320D ONBOARD ACQ FOR 30-120 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G430M G750M ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD269929-OFFSET HD269929-NEB-POS1 HD269929-NEB-POS2 HD269929-NEB-POS3 S61-OFFSET S61-NEB-POS1 S61-NEB-POS2 S61-NEB-POS3 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 3680 4961 6768 5734 ------------------------------------------------------------------------------------------------------------------------------------