9795( 3) - 04/25/03 13:32 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9795 Version: 3 Check-in Date: 25-Apr-2003 13:31:31 1.Proposal Title: A He-rich O2-3 star in the LMC: Freakish Relic or Paradigm Shifter? ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 12 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Dr. Philip Massey Lowell Observatory CoI: Dr. Knut Olsen National Optical Astronomy Observatories - N CTIO CoI: Dr. Joel W. Parker Southwest Research Institute N ------------------------------------------------------------------------------------ 5. Abstract The spectral class O2-3 is a very early, short-lived stage in the lives of the most massive stars. We recently came across a star in the LMC whose optical spectrum shows HeII and no HeI, making it a member of this group. However, there is little or no hydrogen in the spectrum of this star, suggesting it is a highly evolved object. It is as if we were looking at the spectrum of a Wolf-Rayet (WR) star (hot and with a high He/H ratio) but without the characteristic emission lines---what we would see if a WR had no stellar wind. Nothing about this makes sense. We can rule out some obvious possibilities (composite spectrum, foreground white dwarf). We are requesting here a single orbit so that we can examine its FUV spectrum and look at the critical stellar wind diagnostic lines; we will also take advantage of HST's spatial resolution and obtain narrow-slit spectra in the optical (Halpha and HeI 4471) that is free of nebular contamination. The star could simply be an oddity, perhaps the relic of the coalescence of two stars, or the result of some binary interaction, and of no greater significance. On the other hand, there are only a few dozen O2-3 stars that have ever been observed, and maybe this particular one is telling us that we don't know as much about massive star evolution as we thought. We really ought to follow this up and determine whether it's simply an intriguing peculiar star, or something more profoundly interesting. ------------------------------------------------------------------------------------ 9795( 3) - 04/25/03 13:32 - [ 2] Observations Description ------------------------ We require 1 CVZ orbit, and will make the following observations: (1) STIS/FUV- MAMA with the G140L grating and 0.2" x 0.2" aperture (2) STIS/CCD at Halpha using the G750M grating (3) STIS/CCD at 4451 with the G430M grating, dithered to improve the S/N. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9795( 3) - 04/25/03 13:32 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 LMC-054383 EXT-STAR, MAIN SEQUENCE RA=05H02M10.03S +/- 0.25", DEC=- J2000 V = 14.1+/-0.2 O 70D32'58.3" +/- 0.25", PLATE- U-B = -1.08 ID=05ZW B-V = -0.19 E(B-V) = 0.13 Coordinate Source: GSC_SURVEY_PLATE Comments: Designation and photometry from Massey 2002 ApJS 141, 81 9795( 3) - 04/25/03 13:32 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type STIS-ALONG-SLIT Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 1.1 Coordinate_Frame POS-TARG Pattern_Orient 90.0 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 9795( 3) - 04/25/03 13:32 - [ 5] Visit: 01 Visit Priority: Visit Requirements: PCS MODE FINE 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 ------------------------------------------------------------------------------------------------------------------------------------ 1 LMC-054383 STIS/C ACQ F28X50L MIRROR ACQTYPE=POINT 1 1 S CD P ------------------------------------------------------------------------------------------------------------------------------------ 2 LMC-054383 STIS/F ACCUM 0.2X0.2 G140L 1425 1 700 S UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 3 LMC-054383 STIS/C ACCUM 52X0.2 G750M 6581 CR-SPLIT=3,GAIN=1 1 900 S CD ------------------------------------------------------------------------------------------------------------------------------------ 4 LMC-054383 STIS/C ACCUM 52X0.2 G430M 4451 CR-SPLIT=2,GAIN=1 1 665 S PATTERN 1 4 CD ------------------------------------------------------------------------------------------------------------------------------------ 9795( 3) - 04/25/03 13:32 - [ 6] Summary Form for Proposal 9795 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F28X50LP 0.2X0.2 52X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/FUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT GAIN=1 CR-SPLIT=2 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE FINE CVZ PATTERN 1 4 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G140L G750M G430M ------------------------------------------------------------------------------------------------------------------------------------ Target Names LMC-054383 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 1425 6581 4451 ------------------------------------------------------------------------------------------------------------------------------------