12303( 4) - 16-Dec-2010 20:24:19 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 12303 Version: 4 Check-in Time: 16-Dec-2010 20:24:19 STScI Edit Number: 0 Title HST/COS FUV Spectroscopy of the Nearby Solar Twin 18 Scorpii: Exploring the Last Missing Spectral Region to Probe its Chromosphere and Transition Region and to Compare Them to the Sun's ------------------------------------------------------------------------------------ Type Cycle GO 18 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Edward F. Guinan Villanova University CoI: Mr. Laurence Dewarf Villanova University N CoI: Mr. Scott G. Engle Villanova University N CoI: Dr. Graham M. Harper Trinity College Dublin N CoI: Mr. Joseph Depasquale Harvard University N CoI: Mr. Ronald Ballouz Villanova University N CoI: Mr. Jarad Coughlin Villanova University N ------------------------------------------------------------------------------------ Abstract We propose to carry out FUV spectrophotometry with COS/HST for an in-depth study of the chromosphere & transition region (TR) of the solar twin 18 Sco. This 5th mag G2 V star is an important star as a nearly perfect match to the Sun and is known as the "Closest-ever Solar Twin" (Porto de Mello & da Silva 1997). 18 Sco has nearly identical physical properties (e.g. SpType, Mass, Teff, L, R, log g, [Fe/H], Ca II HK, Lx, rotation, etc.) to the Sun. Recent studies of Ca II HK emission from Lowell Observatory (J. Hall, priv. comm.) indicate Ca II emissions are close to the Sun's and undergo a solar-like ~7-11 yr magnetic activity cycle. The proposed observations (using two consecutive HST orbits) are a crucial part of our ongoing "Sun in Time" program of solar-type stars across the electromagnetic spectra. We are proposing to utilize the enhanced FUV sensitivity of HST/COS (with the G 130M/G 160M elements) to obtain high S/N medium resolution, FUV (1150-1750??) spectrophotometry of the only remaining unexplored spectral region of this important star. The FUV region contains many crucial chromospheric and TR emission diagnostics including C III 1175A, Si III 1206A, Ly-a 1215A, N V 1240A, OI 1305A, C II 1335A, Si IV 1400A, C IV 1550A, He II 1640A, C I 1660A as well as many other weaker emissions. These line emissions originate from plasmas from 8, 000 K to 300, 000 K, and are vital for understanding the star's magnetically heated chromosphere and TR. We plan to analyze this spectrum to determine the physical properties of 18 Sco's corona, TR and chromosphere and, importantly, to compare these line strengths and ratios to the corresponding FUV line emissions of the Sun (e.g. SUSIM, SOLSTICE) at a similar magnetic activity phase. This study provides an important check on the magnetic behavior of our present Sun and solar like stars. For example, is our Sun "normal" for its age and mass? If confirmed as a precise match to our Sun (and the data obtained thus far look like it is), 18 Sco would be important for follow-up studies in asteroseismology, extrasolar planet searches, and could serve as a surrogate for the "Night-Time Sun.? In addition, as noted by Turnbull (2004), 18 Sco is one of the most promising nearby candidates for hosting life based on analysis of the HabCat list of stars. In spite of extensive observations at many other wavelengths, the best yet solar twin - 18 Sco - has not been observed in the FUV region where the most powerful diagnostic emission lines are located. With the planned COS spectroscopy, we will at long last complete the spectral coverage of this important solar twin. 12303( 4) - 16-Dec-2010 20:24:19 - [ 2] ------------------------------------------------------------------------------------ Observations Description ------------------------ We plan to observe 18 Sco with both the G140L and G130M spectral elements to provide thorough coverage of the FUV region, while at the same time returning good spectral resolution on important emission lines such as Lyman alpha and O I 1310. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 12303( 4) - 16-Dec-2010 20:24:19 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NSV-7577 STAR, G V-IV RA=16H15M37.2703S +/- 0.1", J2000 V = 5.5 DEC=-08D22'9.99" +/- 0.1" Reference Frame: ICRS Comments: General object info retrieve from Simbad. Proper Motions and Parallax obtained from "Hipparcos, the New Reduction" catalog of van Leeuwen, 2007. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.015550275472402007 -0.49552999999999997 0.07194 ------------------------------------------------------------------------------------------------------------------------------------ 12303( 4) - 16-Dec-2010 20:24:19 - [ 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| | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 NSV-7577 COS/NUV ACQ/SEA PSA G285M 2850 SCAN-SIZE=3, STEP-SIZE=1.767 1 0.1 S RCH ------------------------------------------------------------------------------------------------------------------------------------ 2 NSV-7577 COS/NUV ACQ/PEA PSA G285M 2850 1 0.1 S KXD ------------------------------------------------------------------------------------------------------------------------------------ 3 NSV-7577 COS/NUV ACQ/PEA PSA G285M 2850 NUM-POS=5, STEP-SIZE=0.9, 1 0.1 S KD CENTER=FLUX-WT-FLR ------------------------------------------------------------------------------------------------------------------------------------ 4 NSV-7577 COS/FUV TIME-TA PSA G140L 1105 FLASH=YES, FP-POS=1, 1 780 S G BUFFER-TIME=500 see below ------------------------------------------------------------------------------------------------------------------------------------ 5 NSV-7577 COS/FUV TIME-TA PSA G140L 1105 FLASH=YES, BUFFER-TIME=500, 1 766 S G FP-POS=3 see below ------------------------------------------------------------------------------------------------------------------------------------ 6 NSV-7577 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=700, FLASH=YES, 1 900 S G FP-POS=1 ------------------------------------------------------------------------------------------------------------------------------------ 7 NSV-7577 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=700, FLASH=YES, 1 900 S G FP-POS=3 ------------------------------------------------------------------------------------------------------------------------------------ 8 NSV-7577 COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=700, FLASH=YES, 1 900 S G FP-POS=4 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NSV-7577 1 COS/NUV ACQ/SEA PSA G285M 2850 none none none none 1 N/A RCH NSV-7577 2 COS/NUV ACQ/PEA PSA G285M 2850 none none none none 1 N/A KXD NSV-7577 3 COS/NUV ACQ/PEA PSA G285M 2850 none none none none 1 N/A KD NSV-7577 4 COS/FUV TIME-TA PSA G140L 1105 none none none none 1 830.0 S G NSV-7577 5 COS/FUV TIME-TA PSA G140L 1105 none none none none 1 843.0 S G NSV-7577 6 COS/FUV TIME-TA PSA G130M 1291 none none none none 2 N/A G 12303( 4) - 16-Dec-2010 20:24:19 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ NSV-7577 7 COS/FUV TIME-TA PSA G130M 1291 none none none none 2 N/A G NSV-7577 8 COS/FUV TIME-TA PSA G130M 1291 none none none none 2 N/A G 12303( 4) - 16-Dec-2010 20:24:19 - [ 6] Summary Form for Proposal 12303 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/PEAKD, ACQ/PEAKXD, ACQ/SEARCH, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=500, BUFFER-TIME=700, CENTER=FLUX-WT-FLR, FLASH=YES, FP-POS=1, FP-POS=3, FP-POS=4, NUM-POS=5, SCAN-SIZE=3, STEP-SIZE=0.9, STEP-SIZE=1.767 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G130M, G140L, G285M ------------------------------------------------------------------------------------------------------------------------------------ Target Names NSV-7577 ------------------------------------------------------------------------------------------------------------------------------------