9368( 2) - 01/30/02 09:12 - [ 1] PROPOSAL FOR HUBBLE SPACE TELESCOPE OBSERVATIONS ST ScI Use Only ID: 9368 Version: 2 Check-in Date: 30-Jan-2002 09:11:50 1.Proposal Title: Spectrophotometry of Procyon A: Testing Metal Opacities ------------------------------------------------------------------------------------ 2. Proposal For 3. Cycle GO 11 ------------------------------------------------------------------------------------ 4. Investigators Contact? PI: Carlos Allende-Prieto University of Texas at Austin CoI: Prof. David Lambert University of Texas N CoI: Dr. Ivan Hubeny Laboratory for Astronomy and Solar Physics N CoI: Dr. Thierry Lanz Laboratory for Astronomy and Solar Physics N CoI: Dr. Ramon J. Garc'\i a-Lopez Instituto de Astrof'\i sica de Canarias N ------------------------------------------------------------------------------------ 5. Abstract Metal opacity shapes the near-UV spectrum of late-type stars, which dominate intermediate and old stellar populations. Learning the details of how metal opacity blocks the light in this spectral region is of capital importance to understanding the energy balance in the atmosphere of these stars and, ultimately, building reliable models to interpret observed fluxes. The model atmospheres most used in spectroscopic analyses of individual stars and at the core of population synthesis codes are based on calculations of photoionization cross-sections from the 70's, when better data have been available for a long time. We implement modern cross- sections in our calculations of synthetic fluxes and model atmospheres, but the models need to be confronted with observations. Detailed absolute fluxes for stars of known effective temperatures and angular diameters can constrain the opacities directly from observations. So far, such high-quality UV observations are available only for the Sun, and this leaves some room for ambiguity between line and continuum opacity. Observations with identical quality are possible with STIS for a second nearby late-type star: Procyon A. This star is indeed the only relatively unevolved late-type star for which an extremely precise determination of its angular diameter is available. ------------------------------------------------------------------------------------ 9368( 2) - 01/30/02 09:12 - [ 2] Observations Description ------------------------ We plan to use gratings G230MB and G430M to carry out medium- resolution observations of our only target: Procyon. Six tilts of G230MB (prime settings at central wavelengths: 2276, 2416, 2557, 2697, 2836, and 2976 Angstrom) will provide coverage between 2200 and 3050 Angstrom, approximately, and four tilts of G430M (prime settings centered at 3165, 3423, 3680, and 3936 Angstrom) will cover the spectrum from about 3022 to slightly above 4000 Angstrom. We expect that the high count level will make CTE problems negligible. In order to make sure that we do not lose flux, ensuring an accurate flux calibration, we plan to observe with a 2 arcsec slit. We request ACCUM mode with CCDGAIN=4, to avoid saturation. CR-SPLIT would always be 3, as even for short exposure times the high CR impact rate in space would cause problems. Dithering in two different positions is used with the pattern STIS-ALONG-SLIT, to ensure cleaning of persistently hot pixels. The exposure times for each of the settings has been calculated using the spectroscopic ETC. The flux predicted by a Kurucz's model atmosphere for a F5V star, scaled to match Procyon's V=0.36 mag, was used. The interstellar extinction is neglected for a star at only 3.5 pc from the Sun, and average background levels were adopted for the Earth shine and the zodiacal light. The dark current, and readout noise are negligible for short exposures of bright objects. Considering also that measurements of angular diameters and the pipeline calibration of the STIS data are likely to improve in the future, we aim at a very high SNR, about 500, practically limited by the flat-field correction. In flight, broadband flat-field exposures spanning a month constrain changes in the pixel-to-pixel response to be less than 0.2 per cent rms (Kimble et al. 1998). The observations would be made over two orbits. The target acquisition will not present problems related to saturation in the CCD, as the neutral density filter with the highest blocking factor (F25ND5) satisfactorily reduces the signal. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 9368( 2) - 01/30/02 09:12 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 HD61421 STAR, F3-F9 RA=114.82724194D +/- J2000 V = - V = 0.36+/-0.01 0.00000023D, DEC=5.22750767D +/- 3.15 B-V = 0.42+/-0.01 0.00000014D TYPE=F5IV F-CONT(3000)=10+/-3e-10 Coordinate Source: HIPPARCOS/TYCHO_CATALOGUE Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 1991.25 -0.0475 -1.023 0.28593 9368( 2) - 01/30/02 09:12 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type STIS-ALONG-SLIT Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 1.0 Coordinate_Frame POS-TARG Pattern_Orient 90 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 9368( 2) - 01/30/02 09:12 - [ 5] Visit: 01 Visit Priority: Visit Requirements: PCS MODE FINE 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 HD61421 STIS/C ACQ F25ND5 MIRROR ACQTYPE=POINT 1 0.1 S CD ------------------------------------------------------------------------------------------------------------------------------------ 10 HD61421 STIS/C ACCUM 52X2 G230MB 2276 GAIN=4,CR-SPLIT=3,SIZEAXIS2=200 1 66.7 S PATTERN 1 10 CD ------------------------------------------------------------------------------------------------------------------------------------ 20 HD61421 STIS/C ACCUM 52X2 G230MB 2416 GAIN=4,CR-SPLIT=3,SIZEAXIS2=200 1 88.3 S PATTERN 1 20 CD ------------------------------------------------------------------------------------------------------------------------------------ 30 HD61421 STIS/C ACCUM 52X2 G230MB 2557 GAIN=4,CR-SPLIT=3,SIZEAXIS2=200 1 37.4 S PATTERN 1 30 CD ------------------------------------------------------------------------------------------------------------------------------------ 40 HD61421 STIS/C ACCUM 52X2 G230MB 2697 GAIN=4,CR-SPLIT=3,SIZEAXIS2=200 1 19.4 S PATTERN 1 40 CD ------------------------------------------------------------------------------------------------------------------------------------ 50 HD61421 STIS/C ACCUM 52X2 G230MB 2836 GAIN=4,CR-SPLIT=3,SIZEAXIS2=200 1 12.9 S PATTERN 1 50 CD ------------------------------------------------------------------------------------------------------------------------------------ 60 HD61421 STIS/C ACCUM 52X2 G230MB 2976 GAIN=4,CR-SPLIT=3,SIZEAXIS2=200 1 6.6 S PATTERN 1 60 CD ------------------------------------------------------------------------------------------------------------------------------------ 70 HD61421 STIS/C ACCUM 52X2 G430M 3165 CR-SPLIT=3,GAIN=4,SIZEAXIS2=200 1 1.5 S PATTERN 1 70 CD ------------------------------------------------------------------------------------------------------------------------------------ 80 HD61421 STIS/C ACCUM 52X2 G430M 3423 CR-SPLIT=3,GAIN=4,SIZEAXIS2=200 1 1.2 S PATTERN 1 80 CD ------------------------------------------------------------------------------------------------------------------------------------ 90 HD61421 STIS/C ACCUM 52X2 G430M 3680 CR-SPLIT=3,GAIN=4,SIZEAXIS2=200 1 0.9 S PATTERN 1 90 CD ------------------------------------------------------------------------------------------------------------------------------------ 100 HD61421 STIS/C ACCUM 52X2 G430M 3936 CR-SPLIT=3,GAIN=4,SIZEAXIS2=200 1 0.6 S PATTERN 1 100 CD ------------------------------------------------------------------------------------------------------------------------------------ 9368( 2) - 01/30/02 09:12 - [ 6] Summary Form for Proposal 9368 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures F25ND5 52X2 ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ACQTYPE=POINT SIZEAXIS2=200 CR-SPLIT=3 GAIN=4 ------------------------------------------------------------------------------------------------------------------------------------ Proposal Category GO ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PCS MODE FINE PATTERN 1 10 PATTERN 1 20 PATTERN 1 30 PATTERN 1 40 PATTERN 1 50 PATTERN 1 60 PATTERN 1 70 PATTERN 1 80 PATTERN 1 90 PATTERN 1 100 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements MIRROR G230MB G430M ------------------------------------------------------------------------------------------------------------------------------------ Target Names HD61421 ------------------------------------------------------------------------------------------------------------------------------------ Wavelengths 2276 2416 2557 2697 2836 2976 3165 3423 3680 3936 ------------------------------------------------------------------------------------------------------------------------------------