8155( 8) - 08/29/01 13:31 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8155 Version: 8 Check-in Date: 29-Aug-2001 13:30:49 1.Proposal Title: Highly collimated strings in the nebula around Eta Carinae - a new phenomenon ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Kerstin Weis University of Minnesota - Twin Cities CoI: Prof. Wolfgang Duschl Universitaet Heidelberg, Institut fuer N Theoretische Astrophysik CoI: Prof. Kris Davidson University of Minnesota N ------------------------------------------------------------------------------------ 5. Abstract We propose to observe a set of highly collimated strings in the nebula around Eta Car with the HST/STIS in order to determine their physical nature and their relation to phenomenologically similar structures in nebulae around evolved low mass stars. Eta Car is one of the most massive stars known and a member of the class of Luminous Blue Variables. After hydrogen core burning, these stars enter a shortlived phase which is characterized by strong mass loss, part of which happens in the form of bursts. One of these bursts gave rise to the Homunculus nebula around Eta Car. The strings are faint, almost straight features outside the Homunculus. They are characterized by a linear velocity increase towards larger distances from the star. Only STIS spectroscopy will give us the required spatial resolution to investigate the ionization mechanism, the density structure, the ionizing field and the shock parameters in the strings and their changes along the strings. This will then allow us to determine the physical nature of the strings. Moreover, as there are morpologically similar features in Planetary Nebulae, the so-called FLIERS, it is of importance to investigate the relation between the strings in a nebula around an evolved high mass star and the FLIERS in a nebula around an evolved low mass star in order to understand the mass loss mechanism of the different stellar types better. We request 4 orbits to carry out these observations. ------------------------------------------------------------------------------------ 8155( 8) - 08/29/01 13:31 - [ 2] Observations Description ------------------------ We plan to observe the strings with the G750M grating in the longslit mode (52x0.5) to analyse the spatially and velocity resolved ratios of the bright diagnostic lines. (Note: The oxygen lines are most probably extremely weak due to the effects of CNO processing of the Eta Car ejecta) The spectral range optimal for our program is realized with the secondary grating setting centered at 6581 Angstrom. The flux of the approximately 0.3" wide strings in HAlpha is between 1.8 10^-15 erg cm^-2 s^-1 AA^-1 and 4.1 10^-15 erg cm^-2 s^-1 AA^-1 as derived from the HST WFPC2 images. We want to observe SII, NII, HAlpha, and get at least good upper limits for HeI Lambda6678Angstrom and maybe OI at the resolution provided by STIS in this setup. To predict reasonaby reliable integration times we use a best and a worst case scenario for the integration time estimate. The best case would be SII/HAlpha=0.5 as in the S condensation (Dufour et al. 1997). Then we need an exposure time of 800s to reach 10Sigma per resolution element at SII, which we expect to be sufficient for at least decent limits in HeI and possibly OI. Worst case would be SII/HAlpha ~ 0.1 as in the N condensation (Dufour et al. 1997). This would enforce a necessary integration time of at 5000s. Since HAlpha and NII are much brighter than SII in the Eta Carina nebula, we have not to worry about S/N in these lines. All these calculations were made with the STIS Spectroscopy Exposure Time Calculator at STScI. We conclude that under reasonable conditions we can reach our science goals with a compromize 2400s per science spectrum. Since we observe shortward of 7000Angstrom, we do not need to take fringing into account (STIS Instrument Handbook V2.0). At the declination of Eta Carina the orbital visibility lasts 56 min per orbit. During the first orbit there are the following overhead times: guide star acquisition: 6 min, target acquisition: 6 min. Since we use a relatively broad slit (52x0.5) no peakup is necessary according to the STIS Instrument Handbook (V2.0). Thus we have 44 min left in an orbit for integration on our target. This corresponds to 2640s, just what is needed to reach our science goals. We therefore require 4 orbits (one per string) to complete our program. The 0.5" slit width is necessary to follow the somewhat wiggly structure of the strings with one slit per string. The spectral resolution is degraded due to the wide slit by a factor of 6, but still sufficient (3 Angstrom per pix) to follow the velocity gradient of the strings and to resolve the SII doublet and the NII lines from HAlpha. Spatial resolution is determined by the width of the strings, therefore in the order of 0.3arcsec. Only HST/STIS can provide this spatial resolution, which is crucial to isolate the narrow strings from the background emission of the Eta Carinae nebula and resolve individual shock fronts. We will choose the slit positions that only the strings and no part of the bright Homunculus are inside the slits, in order ot minimize the background from to scattered light. Real Time Justification ----------------------- None None Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 8155( 8) - 08/29/01 13:31 - [ 3] Data Distribution Paper Products: NO Media: 8MM Blocking Factor: 10 Ship To: Institut fuer Theoretische Astrophysik, Tiergartenstr. 15, Heideberg, D-69121, GERMANY Ship Via: Email: kweis@ita.uni-heidelberg.de ------------------------------------------------------------------------------------ 8155( 8) - 08/29/01 13:31 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 ETA-CAR- STAR RA=10H 45M 6.0S +/- 0.3S, DEC=- J2000 V = 12.48 STRING1- 59D 41' 25.2" +/- 2", PLATE- E(B-V) = 0.41 OFFSET ID=ZZZQ B-V = 0.21 Coordinate Source: Comments: Star for acquisition and offset for string1 HST image used for coordinates: U2DH0105T 2 ETA-CAR- STAR RA=10H 45M 6.0S +/- 0.3S, DEC=- J2000 V = 12.48 STRING2- 59D 41' 25.2" +/- 2", PLATE- E(B-V) = 0.41 OFFSET ID=ZZZQ B-V = 0.21 Coordinate Source: Comments: Star for acquisition and offset for string2 HST image used for coordinates: U2DH0105T 3 ETA-CAR- STAR RA=10H 45M 3.22S +/- 0.3S, DEC=- J2000 V = 17.32 STRING3- 59D 40' 49.3" +/- 2", PLATE- E(B-V) = 0.5 OFFSET ID=ZZZQ Coordinate Source: Comments: Star for acquisition and offset for string3 HST image used for coordinates: U2DH0105T 4 ETA-CAR- STAR RA=10H 45M 3.22S +/- 0.3S, DEC=- J2000 V = 17.32 STRING4- 59D 40' 49.3" +/- 2", PLATE- E(B-V) = 0.5 OFFSET ID=ZZZQ Coordinate Source: Comments: Star for acquisition and offset for string4 HST image used for coordinates: U2DH0105T 5 ETA-CAR- STAR RA=10H 45M 3.04S +/- 0.3S, DEC=- J2000 V = 17.32 STRING4-2- 59D 40' 47.43" +/-2", PLATE- E(B-V) = 0.5 OFFSET ID=ZZZQ Coordinate Source: Comments: Star for acquisition and offset for string4_2, HST image used for coordinates: U2DH0105T 10 ETA-CAR- STAR, ETA CARINAE STAR, RA-OFF=00.15S+/- 0.003S, DEC- J2000 V = 999 STRING1 EJECTA, JET OFF=-11.199999999999999"+/- F-LINE(6563)=3+/-1e-15 0.1", FROM 1, PLATE-ID=ZZZQ Coordinate Source: Comments: Ejected string-like emission-line features Strings are not deteced in V, this V magnitude is NOT VALID ; HST image used for coordinates: U2DH0105T 20 ETA-CAR- STAR, ETA CARINAE STAR, RA-OFF=-01.44S+/- 0.003S, DEC- J2000 V = 999 STRING2 EJECTA, JET OFF=-15.199999999999999"+/- F-LINE(6563)=3+/-1e-15 0.1", FROM 2, PLATE-ID=ZZZQ Coordinate Source: Comments: Ejected string-like emission-line features Strings are not deteced in V, this V magnitude is NOT VALID ; HST image used for coordinates: U2DH0105T 30 ETA-CAR- STAR, ETA CARINAE STAR, RA-OFF=-02.42S+/- 0.003S, DEC- J2000 V = 999 STRING3 EJECTA, JET OFF=10.9"+/- 0.1", FROM 3, PLATE F-LINE(6563)=3+/-1e-15 -ID=ZZZQ Coordinate Source: Comments: Ejected string-like emission-line features Strings are not deteced in V, this V magnitude is NOT VALID ; HST image used for coordinates: U2DH0105T 40 ETA-CAR- STAR, ETA CARINAE STAR, RA-OFF=-03.15S+/- 0.003S, DEC- J2000 V = 999 STRING4 EJECTA, JET OFF=5.5999999999999996"+/- 0.1", F-LINE(6563)=3+/-1e-15 FROM 4, PLATE-ID=ZZZQ Coordinate Source: Comments: Ejected string-like emission-line features Strings are not deteced in V, this V magnitude is NOT VALID ; HST image used for coordinates: U2DH0105T 8155( 8) - 08/29/01 13:31 - [ 5] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 50 ETA-CAR- STAR, ETA CARINAE STAR, RA-OFF=-03.15S+/- 0.003S, DEC- J2000 V = 999 STRING4-2 EJECTA, JET OFF=5.5999999999999996"+/- 0.1", F-LINE(6563)=3+/-1e-15 FROM 4, PLATE-ID=ZZZQ Coordinate Source: Comments: Ejected string-like emission-line features Strings are not deteced in V, this V magnitude is NOT VALID ; HST image used for coordinates: U2DH0105T 8155( 8) - 08/29/01 13:31 - [ 6] Visit: 01 Visit Priority: Visit Requirements: ORIENT 195.5D TO 196.5D ORIENT 15.5D TO 16.5D 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 ETA-CAR-STR STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 0.1 S ING1-OFFSET CD P ------------------------------------------------------------------------------------------------------------------------------------ 10 ETA-CAR-STR STIS/C ACCUM 52X0.5 G750M 6581 1 2400.0 ING1 CD ------------------------------------------------------------------------------------------------------------------------------------ 8155( 8) - 08/29/01 13:31 - [ 7] Visit: 02 Visit Priority: Visit Requirements: ORIENT 218.50D TO 219.50D ORIENT 38.50D TO 39.50D 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 ------------------------------------------------------------------------------------------------------------------------------------ 15 ETA-CAR-STR STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 0.1 S ING2-OFFSET CD P ------------------------------------------------------------------------------------------------------------------------------------ 20 ETA-CAR-STR STIS/C ACCUM 52X0.5 G750M 6581 1 2400.0 ING2 CD ------------------------------------------------------------------------------------------------------------------------------------ 8155( 8) - 08/29/01 13:31 - [ 8] Visit: 03 Visit Priority: Visit Requirements: ORIENT 183.25D TO 184.25D ORIENT 3.25D TO 4.25D 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 ------------------------------------------------------------------------------------------------------------------------------------ 25 ETA-CAR-STR STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 4 S ING3-OFFSET CD P ------------------------------------------------------------------------------------------------------------------------------------ 30 ETA-CAR-STR STIS/C ACCUM 52X0.5 G750M 6581 1 2400.0 ING3 CD ------------------------------------------------------------------------------------------------------------------------------------ 8155( 8) - 08/29/01 13:31 - [ 9] Visit: 04 Visit Priority: Visit Requirements: ORIENT 171.5D TO 172.5D ORIENT 351.5D TO 352.5D 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 ------------------------------------------------------------------------------------------------------------------------------------ 35 ETA-CAR-STR STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 4 S ING4-OFFSET CD P ------------------------------------------------------------------------------------------------------------------------------------ 40 ETA-CAR-STR STIS/C ACCUM 52X0.5 G750M 6581 1 2400.0 ING4 CD ------------------------------------------------------------------------------------------------------------------------------------ 8155( 8) - 08/29/01 13:31 - [ 10] Visit: 05 Visit Priority: Visit Requirements: ORIENT 171.5D TO 172.5D ORIENT 351.5D TO 352.5D 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 ------------------------------------------------------------------------------------------------------------------------------------ 45 ETA-CAR-STR STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 4 S ING4-2-OFFS CD P ET ------------------------------------------------------------------------------------------------------------------------------------ 50 ETA-CAR-STR STIS/C ACCUM 52X0.5 G750M 6581 1 2400.0 ING4-2 CD ------------------------------------------------------------------------------------------------------------------------------------ 8155( 8) - 08/29/01 13:31 - [ 11] Summary Form for Proposal 8155 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 52X0.5 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements ORIENT 195.5D TO 196.5D ORIENT 15.5D TO 16.5D ORIENT 218.50D TO 219.50D ORIENT 38.50D TO 39.50D ORIENT 183.25D TO 184.25D ORIENT 3.25D TO 4.25D ORIENT 171.5D TO 172.5D ORIENT 351.5D TO 352.5D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G750M ------------------------------------------------------------------------------------------------------------------------------------ Target Names ETA-CAR-STRING1-OFFSET ETA-CAR-STRING1 ETA-CAR-STRING2-OFFSET ETA-CAR-STRING2 ETA-CAR-STRING3-OFFSET ETA-CAR-STRING3 ETA-CAR-STRING4-OFFSET ETA-CAR-STRING4 ETA-CAR-STRING4-2-OFFSET ETA-CAR-STRING4-2 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 6581 ------------------------------------------------------------------------------------------------------------------------------------