11726( 5) - 01-Jul-2009 21:51:35 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 11726 Version: 5 Check-in Time: 01-Jul-2009 21:51:35 STScI Edit Number: 0 Title Mysteries of the North Star: HST/COS confirmation of real-time evolution and upper atmospheric heating in Polaris ------------------------------------------------------------------------------------ Type Cycle GO 17 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Edward F. Guinan Villanova University CoI: Mr. Scott G. Engle Villanova University Y CoI: Dr. Nancy R. Evans Smithsonian Institution Astrophysical N Observatory CoI: Dr. Edward L. Fitzpatrick Villanova University N ------------------------------------------------------------------------------------ Abstract The major aims of this proposal are twofold: to confirm and understand the recently observed apparent evolutionary changes of the bright (3.97-day) Cepheid Polaris ? and ? to further study the recent discovery of hot plasmas (up to 1MK) well above the photospheric temperature of the Cepheid itself. This study will have a major impact on understanding the evolution, structure, heating and dynamics of Cepheid (and related Hybrid Star) atmospheres. In our study ? the Secret Lives of Cepheids ? Polaris is noteworthy for its well-documented increase in pulsation period (+3.51 sec/year) and decrease in light amplitude over the last 100-150 years, almost ceasing pulsations in the early 1990s. Moreover, our studies of photoelectric photometry and historic visual observations have shown evidence that Polaris may have increased in brightness by almost 0.2-mag over the past century (and possibly by more than 1-mag since Ptolemy). In addition, a study of the IUE database indicates a possible increase in photospheric temperature (which the FUV region is very sensitive to) between 1978/79 and 1991/93, pointing to a change of ~35+/-12 K. More recently, FUSE and Chandra observations of Polaris indicate the presence of C III 977/1176A and O VI 1032/1038A emissions, as well as possible soft X-ray emission, respectively. The source of these hot plasmas could be related to pulsations (shock heating) and/or magnetic activity. To further investigate the evolutionary changes and upper atmospheric emissions of Polaris, we propose for HST/COS medium resolution spectrometry covering the wavelength range ~1150?2100A. This wavelength range covers both the high energy emission lines (<1600A) along with the rise in continuum of the F-supergiant photosphere (>1600A). HST/COS is the only instrument capable of carrying out the necessary FUV observations to achieve our scientific goals for Polaris ? providing a better understanding of the evolution and heating mechanisms of Cepheids. ------------------------------------------------------------------------------------ Observations Description ------------------------ For all exposure time calculations IUE spectra were originally used as input, and were then re-run with a Pickles model (F8 I) scaled to Polaris? current brightness (~1.97-mag) to ensure accuracy. To cover the shortest wavelengths (~1150?1450?), we will observe with the COS G130M (central wave. = 1291?) grating (Primary Science Aperture ? PSA) for 2591 seconds (~1 full orbit after overheads), resulting in S/N values of more than ~30 over the wavelength range. 11726( 5) - 01-Jul-2009 21:51:35 - [ 2] The G160M (1589?) grating (PSA) will then cover the ~1395?1760? region, and a 1500 second exposure will return S/N values of more than ~35. Four separate exposures with the G185M grating (PSA) will then cover ~1800?2100?. Exposure times of: (central wave. = 1913?) 200-sec, (1941?) 193-sec, (1971?) 192-sec and (1986?) 190-sec will achieve S/N values greater than ~40 for the entire wavelength range. This proposal is requesting 2 orbits each at Polaris? maximum and minimum phase. In each visit, one orbit will be used to obtain the G130M exposure, and the other orbit will obtain the G160M & G185M exposures. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- In order to further study the possible brightening of Polaris, and to better understand its chromospheric/transition region emissions, we propose for COS medium resolution observations near the maximum (phase ~ 0.0 +/- 0.05) and minimum (~0.5 +/- 0.05) of Polaris? pulsational phase. This will allow us to assess any variability in either UV continuum or emission lines fluxes, and calculate mean values for comparison with archival IUE observations. We are using the following ephemeris: 2452366.665 + 3.9726772(E) ------------------------------------------------------------------------------------ 11726( 5) - 01-Jul-2009 21:51:35 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 POLARIS STAR, CEPHEID, F3-F9, RA=02H31M49.0837S +/- 0.1", J2000 V = 1.98 +/- 0.04 PULSATING VARIABLE DEC=+89D15'50.79" +/- 0.1" Reference Frame: ICRS Comments: ------------------------------------------------------------------------------------------------------------------------------------ 11726( 5) - 01-Jul-2009 21:51:35 - [ 4] Visit: 01 Visit Requirements: Period 3.97209 D AND ZERO-PHASE HJD2454340.754 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 POLARIS COS/NUV ACQ/SEA PSA G185M 1921 STEP-SIZE=1.767, SCAN-SIZE=3 1 1 S PHASE 0.95 TO 0.05 RCH ------------------------------------------------------------------------------------------------------------------------------------ 2 POLARIS COS/NUV ACQ/PEA PSA G185M 1921 1 3 S KXD ------------------------------------------------------------------------------------------------------------------------------------ 3 POLARIS COS/NUV ACQ/PEA PSA G185M 1921 STEP-SIZE=1.2 1 1 S KD ------------------------------------------------------------------------------------------------------------------------------------ 4 POLARIS COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=302, FLASH=YES, 1 3000 S G FP-POS=3 see below ------------------------------------------------------------------------------------------------------------------------------------ 5 POLARIS COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=302, FLASH=YES, 1 3000 S G FP-POS=4 see below ------------------------------------------------------------------------------------------------------------------------------------ 6 POLARIS COS/FUV TIME-TA PSA G160M 1589 FLASH=YES, BUFFER-TIME=230, 1 1500 S G FP-POS=AUTO see below ------------------------------------------------------------------------------------------------------------------------------------ 7 POLARIS COS/NUV ACCUM PSA G185M 1913 1 200 S see below ------------------------------------------------------------------------------------------------------------------------------------ 8 POLARIS COS/NUV ACCUM PSA G185M 1941 1 200 S see below ------------------------------------------------------------------------------------------------------------------------------------ 9 POLARIS COS/NUV ACCUM PSA G185M 1882 1 200 S see below ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ POLARIS 1 COS/NUV ACQ/SEA PSA G185M 1921 none none none none 1 N/A RCH POLARIS 2 COS/NUV ACQ/PEA PSA G185M 1921 none none none none 1 N/A KXD POLARIS 3 COS/NUV ACQ/PEA PSA G185M 1921 none none none none 1 N/A KD POLARIS 4 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 1184.0 S G 11726( 5) - 01-Jul-2009 21:51:35 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ POLARIS 5 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 1180.0 S G POLARIS 6 COS/FUV TIME-TA PSA G160M 1589 none none none 1 2 350.0 S G POLARIS 6 COS/FUV TIME-TA PSA G160M 1589 none none none 2 2 350.0 S G POLARIS 6 COS/FUV TIME-TA PSA G160M 1589 none none none 3 2 350.0 S G POLARIS 6 COS/FUV TIME-TA PSA G160M 1589 none none none 4 2 350.0 S G POLARIS 7 COS/NUV ACCUM PSA G185M 1913 none none none none 2 243.0 S POLARIS 8 COS/NUV ACCUM PSA G185M 1941 none none none none 2 244.0 S POLARIS 9 COS/NUV ACCUM PSA G185M 1882 none none none none 2 243.0 S 11726( 5) - 01-Jul-2009 21:51:35 - [ 6] Visit: 02 Visit Requirements: Period 3.97209 D AND ZERO-PHASE HJD2454340.754 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 POLARIS COS/NUV ACQ/SEA PSA G185M 1921 STEP-SIZE=1.767, SCAN-SIZE=3 1 1 S PHASE 0.45 TO 0.55 RCH ------------------------------------------------------------------------------------------------------------------------------------ 2 POLARIS COS/NUV ACQ/PEA PSA G185M 1921 1 3 S KXD ------------------------------------------------------------------------------------------------------------------------------------ 3 POLARIS COS/NUV ACQ/PEA PSA G185M 1921 STEP-SIZE=1.2 1 1 S KD ------------------------------------------------------------------------------------------------------------------------------------ 4 POLARIS COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=302, FLASH=YES, 1 3000 S G FP-POS=3 see below ------------------------------------------------------------------------------------------------------------------------------------ 5 POLARIS COS/FUV TIME-TA PSA G130M 1291 BUFFER-TIME=302, FLASH=YES, 1 3000 S G FP-POS=4 see below ------------------------------------------------------------------------------------------------------------------------------------ 6 POLARIS COS/FUV TIME-TA PSA G160M 1589 FLASH=YES, BUFFER-TIME=230, 1 1500 S G FP-POS=AUTO see below ------------------------------------------------------------------------------------------------------------------------------------ 7 POLARIS COS/NUV ACCUM PSA G185M 1913 1 200 S see below ------------------------------------------------------------------------------------------------------------------------------------ 8 POLARIS COS/NUV ACCUM PSA G185M 1941 1 200 S see below ------------------------------------------------------------------------------------------------------------------------------------ 9 POLARIS COS/NUV ACCUM PSA G185M 1882 1 200 S see below ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ POLARIS 1 COS/NUV ACQ/SEA PSA G185M 1921 none none none none 1 N/A RCH POLARIS 2 COS/NUV ACQ/PEA PSA G185M 1921 none none none none 1 N/A KXD POLARIS 3 COS/NUV ACQ/PEA PSA G185M 1921 none none none none 1 N/A KD POLARIS 4 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 1184.0 S G 11726( 5) - 01-Jul-2009 21:51:35 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ POLARIS 5 COS/FUV TIME-TA PSA G130M 1291 none none none none 1 1180.0 S G POLARIS 6 COS/FUV TIME-TA PSA G160M 1589 none none none 1 2 350.0 S G POLARIS 6 COS/FUV TIME-TA PSA G160M 1589 none none none 2 2 350.0 S G POLARIS 6 COS/FUV TIME-TA PSA G160M 1589 none none none 3 2 350.0 S G POLARIS 6 COS/FUV TIME-TA PSA G160M 1589 none none none 4 2 350.0 S G POLARIS 7 COS/NUV ACCUM PSA G185M 1913 none none none none 2 243.0 S POLARIS 8 COS/NUV ACCUM PSA G185M 1941 none none none none 2 244.0 S POLARIS 9 COS/NUV ACCUM PSA G185M 1882 none none none none 2 243.0 S 11726( 5) - 01-Jul-2009 21:51:35 - [ 8] Summary Form for Proposal 11726 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ/PEAKD, ACQ/PEAKXD, ACQ/SEARCH, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=230, BUFFER-TIME=302, FLASH=YES, FP-POS=3, FP-POS=4, FP-POS=AUTO, SCAN-SIZE=3, STEP-SIZE=1.2, STEP-SIZE=1.767 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements PHASE 0.45 TO 0.55, PHASE 0.95 TO 0.05, Period 3.97209 D AND ZERO-PHASE HJD2454340.754 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G130M, G160M, G185M ------------------------------------------------------------------------------------------------------------------------------------ Target Names POLARIS ------------------------------------------------------------------------------------------------------------------------------------