8294( 4) - 10/26/99 11:58 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 8294 Version: 4 Check-in Date: 26-Oct-1999 11:58:12 1.Proposal Title: Is SiO observed in the uv spectrum of Beta Gem? ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 8 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Carole Jordan University of Oxford CoI: Dr. Andrew McMurry University of Oxford Y ------------------------------------------------------------------------------------ 5. Abstract Beta Gem (HD 62509) is a K0 III star with relatively low ultraviolet (uv) emission line fluxes and X-ray emission, and is thought to be a helium core- burning `clump' giant. However, since it lies at a distance of only about 10 parsecs the fluxes at the Earth are sufficient for detailed spectral studies in the uv. Although our main interest in the star has been in modelling for the purposes of establishing and understanding the energy balance requirements, this proposal is concerned with a specific aspect of its spectrum around 2320 Angstrom to 2365 Angstrom. In Beta Gem (HD 62509) and cooler giants the strongest lines in this region are those of C II, Si II and Fe II. The spectrum of Beta Gem (HD 62509) is so far unique in that it also shows a number of narrow emission features that are not observed in the cooler stars, with an overall structure that suggests the presence of a molecular band. We wish to investigate the possibility that this is the A^1Pi - X^1Sigma (0 - 0) b an d of SiO, which has never been identified in an astrophysical spectrum. This requires the high spectral resolution of STIS. Other bands in the above system would then also be expected in the region from about 2300 Angstrom to 2500 Angstrom. Chromospheric models would be used to understand the presence of the SiO band system in Beta Gem (HD 62509) and its absence in cooler giants. ------------------------------------------------------------------------------------ 8294( 4) - 10/26/99 11:58 - [ 2] Observations Description ------------------------ We propose an exposure with E230H in the 2224 Angstrom - 2501 Angstrom tilt in order to include lines from several SiO bands in the A^1Pi - X^1Sigma system. The strongest lines in this region are those of Si II at 2334.4, 2334.6 and 2350.2 Angstrom, which are nowhere brighter than 1* 10^-11 ergs cm^-2 s^-1 A^- 1, which corresponds to 0.8 counts per second in the brightest pixel, well below the local brightness limit. Although the continuum flux at the long wavelength end of the E230H's range (3111 Angstrom) could result in a total count rate above the brightness limit, at the wavelengths to be observed the continuum is many order of magnitudes weaker. At 2500 Angstrom the continuum is < 5* 10^-12 ergs cm^-2 s^-1 A^-1. If the whole of the observed range was illuminated at this maximum brightness there would be a total count rate of < 25000 counts per second, well within the brightness limits. These flux levels are obtained from the GHRS dataset z2uz010at and the IUE dataset LW P1 5071. The observations will start with 6 minutes of guide star acquisition. To centre the star in the 0.2x0.2 arcsecond aperture, we will take an ACQ. This will require use of the neutral density filter in order not to overexpose the CCD in 0.1 seconds. To get a signal to noise level of 10 for the SiO lines with a peak flux of 3 * 10^-13 ergs cm^-2 s^-1 A^-1 we require an exposure time of at least 24 minutes and there will be an overhead on this. A single orbit allows us to make an exposure of 32 minutes, with the overhead occuring after occultation. Real Time Justification ----------------------- We have no special requirements for these observations. We have no plans for coordinated or supporting observations. Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ Data Distribution Paper Products: NO Media: ELECTRONIC Blocking Factor: 10 Ship To: PI_Address Ship Via: Email: ------------------------------------------------------------------------------------ 8294( 4) - 10/26/99 11:58 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD62509 STAR, K III-I RA=7H 45M 19.3638S +/- 0.00075", J2000 V = +3.3 V = 1.16 DEC=28D 1' 34.7171" +/- 0.00045" B-V = 0.991+/-0.005 TYPE=K0IIIB F-CONT(2500)=3.5+/-0.5e-12 F-LINE(2335.33)=2.7+/-0.4e-12 W-LINE(2335.33)=0.4+/-0.05 Comments: Coordinates from Hipparchos Output Catalogue Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1991.25 -0.0474 -0.046 0.09674 8294( 4) - 10/26/99 11:58 - [ 4] Visit: 01 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 ------------------------------------------------------------------------------------------------------------------------------------ 10 HD62509 STIS/C ACQ F25ND5 MIRROR ACQTYPE=POINT 1 0.1 S CD ------------------------------------------------------------------------------------------------------------------------------------ 20 HD62509 STIS/N ACCUM 0.2X0.2 E230H 2363 1 32 M UV-MAM A ------------------------------------------------------------------------------------------------------------------------------------ 8294( 4) - 10/26/99 11:58 - [ 5] Summary Form for Proposal 8294 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F25ND5 0.2X0.2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR E230H ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD62509 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 2363 ------------------------------------------------------------------------------------------------------------------------------------