13781( 8) - 29-Sep-2014 12:03:59 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 13781 Version: 8 Check-in Time: 29-Sep-2014 12:03:59 STScI Edit Number: 0 Title WO-Type Wolf-Rayet Stars: the Last Hurrah of the Most Massive Stars? ------------------------------------------------------------------------------------ Type Cycle GO 22 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Philip Massey Lowell Observatory Y CoI: Kathryn Forbes Neugent Lowell Observatory N CoI: Dr. Nidia Morrell Carnegie Institution of Washington N CoI: Dr. D. John Hillier University of Pittsburgh N ------------------------------------------------------------------------------------ Abstract WO-type Wolf-Rayet (WR) stars are considered the final evolutionary stage of the highest mass stars, immediate precursors to Type Ic (He-poor) core-collapse supernovae. These WO stars are rare, and until recently only 6 were known. Our knowledge about their physical properties is mostly based on a single object, Sand 2 in the LMC. It was the only non-binary WO star both bright and unreddened enough that its FUV and NUV spectra could be obtained by FUSE and HST/FOS. A non-LTE analysis showed that Sand 2 is very hot and its (C+O)/He abundance ratio is higher than that found in WC-type WRs, suggesting it is indeed highly evolved. However, the O VI resonance doublet in the FUV required a considerably cooler temperature (120, 000 K) model than did the optical O VI lines (170, 000 K). Further, the enhanced chemical abundances did not match the predictions of stellar evolutionary models. Another non-LTE study found a 3x higher (C+O)/He abundance ratio and a cooler temperature. We have recently discovered two other bright, single, and lightly reddened WOs in the LMC, allowing us to take a fresh look at these important objects. Our newly found WOs span a range in excitation type, from WO2 to WO4. Sand 2 is intermediate (WO3). We will use COS and STIS to obtain FUV and NUV spectra. These UV data will be combined with ground-based optical and NIR Magellan spectra for a detailed analysis with CMFGEN with the latest atomic data. Knowing the degree of chemical evolution of these WO stars is crucial to determining their evolutionary status, and thus in understanding the final stages of the most massive stars. ------------------------------------------------------------------------------------ Observations Description ------------------------ Overview: We will observe three WO-type Wolf-Rayet stars: LH41-1042, LMC195-1, and Sand2 as follows: Sand 3: 3 orbit COS with two G130M settings. All exposures take place at all four FP-POS in order to improve the signal-to-noise. LH41-1042 and LMC195-1. These stars are located in the Lucke-Hodge 41 region, and are separated from each other by 8-arcsec. (aWe will obtain a 3-orbit observation with COS G130M/1096 to obtain the critical OVI 1032, 38 line. Because of the close proximity of a B0.2 supergiant (which a F225W WFC3 exposure shows to be a 0.3" separated double) there are safety concerns with the other FUV settings, and so we then devote a 4-orbit visit with STIS to 13781( 8) - 29-Sep-2014 12:03:59 - [ 2] obtain both FUV and NUV spectra. Acqusition: The acquisition of Sand 2 is straightforward, as the region is not crowded; there are 18-19th mag stars 10" away. Sand 2 is in the GSC-II and we use those coordinates. We use the PSA and Mirror B. The field containing LH41-1042 and LMC195-1 is somewhat crowded with bright blue stars and we do the acquistion in dispersed light throught he PSA with COS on a nearby offset star (LH41-1042, a V=13.28 B1 I). Science exposures: We are fortunate that Sand 2 has been previously observed with FUSE and HST/FOS, and hence we know the observed fluxes. We use this spectrum to estimate exposure times, and scale for the other two stars using the F225W fluxes measured from our WFC3 image. Sand 2 (FOS fluxes averaged over the F225W bandpass): 1.3E-14 LH41-1042 F225W bandpass: 4.0E-14 LMC195-1 F225W bandpass: 1.4E-14 Safety concerns: the Lucke-Hodge 41 field containing LMC195-1 and LH41-1042 is crowded with bright blue stars. Fortunately, we have two excellent resources: (a) All of the potentially dangerous stars have spectral types, either published or from our own recent Magellan data. (b) We have a WFC3 F225W exposure that allows us to measure the NUV flux of potential hazards. Full details have been forward to Dr. Nolan Walborn on July 14th, along with a figure. Using a the combined flux of 4.27E-13 for this B0.2I composite, an effective wavelength of 2374A, adopting the B1V Kurucz model (which should have a similar temperature to that of a B0.2 supergiant), and using E(B-V)=0.13 with an LMC reddening law, we find that the G130M/1096 exposures should be safe (ETC 620478) but that other COS FUV exposures would not be. There are no safety concerns with this star with STIS using the 0.2"x0.2" aperture as only one of the two components could fall into the aperture at a given time. ------------------------------------------------------------------------------------ 13781( 8) - 29-Sep-2014 12:03:59 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 LH41-1042 EXT-STAR, WOLF RAYET, RA=05H18M10.8680S +/- 0.02", J2000 V = 13.95 +/- 0.1 Flux in F225W filter WOLF RAYET - WC DEC=-69D13'10.89" +/- 0.02" is 4.0E-14 Reference Frame: ICRS Comments: Coordinates measured from WFC3 image iby705010_drz.fits[SCI] ------------------------------------------------------------------------------------------------------------------------------------ 2 LMC195-1 EXT-STAR, WOLF RAYET, RA=05H18M10.3060S +/- 0.02", J2000 V = 14.80 +/- 0.1 Flux in F225W filter WOLF RAYET - WC DEC=-69D13'1.95" +/- 0.02" is 1.4E-14 Reference Frame: ICRS Comments: Coordinates measured from WFC3 image iby705010_drz.fits[SCI] ------------------------------------------------------------------------------------------------------------------------------------ 3 SAND2 EXT-STAR, WOLF RAYET, RA=05H39M34.3300S +/- 0.2", J2000 V = 15.20 +/- 0.05 B-V=+0.42, WOLF RAYET - WC DEC=-68D44'9.33" +/- 0.2" U-B=-1.17. Flux averaged over F225W bandpass is 1.3E-14 Reference Frame: ICRS Comments: Coordinates are from the GSC-II. ------------------------------------------------------------------------------------------------------------------------------------ 4 LH41-44OFFSE EXT-STAR, B0-B2 III-I RA=05H18M6.3070S +/- 0.02", J2000 V = 13.28 +/- 0.05 B-V=-0.16, T DEC=-69D12'35.87" +/- 0.02" E(B-V)=0.13, Flux in F225W is 1.4E-13 Reference Frame: ICRS Comments: Coordinates measured from WFC3 image iby705010_drz.fits ------------------------------------------------------------------------------------------------------------------------------------ 13781( 8) - 29-Sep-2014 12:03:59 - [ 4] Visit: 01 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 LH41-44OFFS COS/NUV ACQ/PEA PSA G230L 3000 1 0.3 S (0.3 ET KXD S) Comments: Exposure time is 0.3sec using a Kurucz B1V model normalized to a V magnitude of (13.28 (ETC 631143), and is 0.2 sec when normalized to a F225W flux of 1.4E-14. ------------------------------------------------------------------------------------------------------------------------------------ 2 LH41-44OFFS COS/NUV ACQ/PEA PSA G230L 3000 NUM-POS=5, STEP-SIZE=0.9, 1 0.3 S (0.3 ET KD CENTER=FLUX-WT-FLR S) ------------------------------------------------------------------------------------------------------------------------------------ 3 LH41-1042 COS/FUV TIME-TA PSA G130M 1096 BUFFER-TIME=1000, FP-POS=ALL 1 500 S G see below (2272 S) Comments: Expect a S/N of 8 per spectral resolution element at 1035A. ------------------------------------------------------------------------------------------------------------------------------------ 4 LMC195-1 COS/FUV TIME-TA PSA G130M 1096 BUFFER-TIME=2000, FP-POS=ALL 1 1200 S G see below (6228 S) Comments: Expect a SN of 7.7 per spectral resolution element at 1035A. ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ LH41-44OFFSET 1 COS/NUV ACQ/PEA PSA G230L 3000 none none none none 1 N/A KXD LH41-44OFFSET 2 COS/NUV ACQ/PEA PSA G230L 3000 none none none none 1 N/A KD LH41-1042 3 COS/FUV TIME-TA PSA G130M 1096 none none none 1 1 568.0 S G LH41-1042 3 COS/FUV TIME-TA PSA G130M 1096 none none none 2 1 568.0 S G LH41-1042 3 COS/FUV TIME-TA PSA G130M 1096 none none none 3 1 568.0 S G LH41-1042 3 COS/FUV TIME-TA PSA G130M 1096 none none none 4 1 568.0 S G LMC195-1 4 COS/FUV TIME-TA PSA G130M 1096 none none none 1 2 1557.0 S G 13781( 8) - 29-Sep-2014 12:03:59 - [ 5] Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ LMC195-1 4 COS/FUV TIME-TA PSA G130M 1096 none none none 2 2 1557.0 S G LMC195-1 4 COS/FUV TIME-TA PSA G130M 1096 none none none 3 3 1557.0 S G LMC195-1 4 COS/FUV TIME-TA PSA G130M 1096 none none none 4 3 1557.0 S G 13781( 8) - 29-Sep-2014 12:03:59 - [ 6] Visit: 02 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 SAND2 COS/FUV ACQ/PEA PSA G130M 1300 1 2.0 S (2 KXD S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SAND2 COS/FUV ACQ/PEA PSA G130M 1300 STEP-SIZE=0.9, NUM-POS=5, 1 2.0 S (2 KD CENTER=FLUX-WT-FLR S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SAND2 COS/FUV TIME-TA PSA G130M 1300 FP-POS=ALL, BUFFER-TIME=1000 1 50 S G see below (656 S) Comments: Expect to reach a SN of 2.5 per FP at 1170 assuming a continuum flux of 2E-14 ------------------------------------------------------------------------------------------------------------------------------------ 4 SAND2 COS/FUV TIME-TA PSA G130M 1096 BUFFER-TIME=2400, FP-POS=ALL 1 1500 S G see below (8032 S) Comments: Expect to reach a SN of 2 in 4000 sec (total) of integration at 1032A. ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ SAND2 1 COS/FUV ACQ/PEA PSA G130M 1300 none none none none 1 N/A KXD SAND2 2 COS/FUV ACQ/PEA PSA G130M 1300 none none none none 1 N/A KD SAND2 3 COS/FUV TIME-TA PSA G130M 1300 none none none 1 1 164.0 S G SAND2 3 COS/FUV TIME-TA PSA G130M 1300 none none none 2 1 164.0 S G SAND2 3 COS/FUV TIME-TA PSA G130M 1300 none none none 3 1 164.0 S G SAND2 3 COS/FUV TIME-TA PSA G130M 1300 none none none 4 1 164.0 S G SAND2 4 COS/FUV TIME-TA PSA G130M 1096 none none none 1 1 1614.0 S G SAND2 4 COS/FUV TIME-TA PSA G130M 1096 none none none 2 2 1566.0 S G SAND2 4 COS/FUV TIME-TA PSA G130M 1096 none none none 3 2 1566.0 S G 13781( 8) - 29-Sep-2014 12:03:59 - [ 7] Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ SAND2 4 COS/FUV TIME-TA PSA G130M 1096 none none none 4 3 3286.0 S G 13781( 8) - 29-Sep-2014 12:03:59 - [ 8] Visit: 03 Visit Requirements: On Hold Comments: Additional Comments: Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 LH41-44OFFS STIS/CCD ACQ F28X50LP MIRROR ACQTYPE=POINT 1 0.1 S (0.1 ET S) ------------------------------------------------------------------------------------------------------------------------------------ 2 LH41-1042 STIS/FUV ACCUM 0.2X0.2 G140L 1425 1 1120 S -MAMA see below (1141 S) Comments: Expect a S/N of approx 70 at 1400A ------------------------------------------------------------------------------------------------------------------------------------ 3 LH41-1042 STIS/NUV ACCUM 0.2X0.2 G230L 2376 1 1120 S -MAMA see below (1141 S) Comments: Expect a S/N of about 60 at 2200A ------------------------------------------------------------------------------------------------------------------------------------ 4 LMC195-1 STIS/FUV ACCUM 0.2X0.2 G140L 1425 1 2500 S -MAMA see below (3308 S) Comments: Expected S/N of 70 at 1400A ------------------------------------------------------------------------------------------------------------------------------------ 5 LMC195-1 STIS/NUV ACCUM 0.2X0.2 G230L 2376 1 2500 S -MAMA see below (3266 S) Comments: Expected S/N of 60 at 2200A ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ LH41-44OFFSET 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A LH41-1042 2 STIS/FUV ACCUM 0.2X0.2 G140L 1425 none none none none 1 1141.0 S -MAMA LH41-1042 3 STIS/NUV ACCUM 0.2X0.2 G230L 2376 none none none none 1 1141.0 S -MAMA LMC195-1 4 STIS/FUV ACCUM 0.2X0.2 G140L 1425 none none none none 2 3308.0 S -MAMA LMC195-1 5 STIS/NUV ACCUM 0.2X0.2 G230L 2376 none none none none 3 3266.0 S -MAMA 13781( 8) - 29-Sep-2014 12:03:59 - [ 9] Summary Form for Proposal 13781 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 0.2X0.2, F28X50LP, PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV, STIS/CCD, STIS/FUV-MAMA, STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ, ACQ/PEAKD, ACQ/PEAKXD, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT, BUFFER-TIME=1000, BUFFER-TIME=2000, BUFFER-TIME=2400, CENTER=FLUX-WT-FLR, FP-POS=ALL, NUM-POS=5, STEP-SIZE=0.9 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G130M, G140L, G230L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names LH41-1042, LH41-44OFFSET, LMC195-1, SAND2 ------------------------------------------------------------------------------------------------------------------------------------