13369( 8) - 04-Jun-2014 18:12:51 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 13369 Version: 8 Check-in Time: 04-Jun-2014 18:12:51 STScI Edit Number: 5 Title The Dynamical Mass of Polaris, the Nearest Cepheid ------------------------------------------------------------------------------------ Type Cycle GO 21 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Nancy R. Evans Smithsonian Institution Astrophysical Y Observatory CoI: Dr. Howard E. Bond The Pennsylvania State University N CoI: Prof. Giuseppe Bono Universita di Roma Tor Vergata N CoI: Dr. Margarita Karovska Smithsonian Institution Astrophysical N Observatory CoI: Dr. Edmund Nelan Space Telescope Science Institute N CoI: Dr. Kailash C. Sahu Space Telescope Science Institute N CoI: Dr. Gail Schaefer Georgia State University Research N Foundation CoI: Evan Tingle Smithsonian Institution Astrophysical N Observatory ------------------------------------------------------------------------------------ Abstract Cepheid variables are the primary standard candles for measuring extragalactic distances, and they provide critical tests of stellar-evolution theory. Thus it is important to understand them astrophysically. Polaris (alpha UMi) is the nearest and brightest of all Cepheids. It offers a unique opportunity to measure the dynamical mass of a Cepheid, because it is in a 30-year binary system for which a single-lined spectroscopic orbit is already available. In Cycle 14, we resolved the system for the first time, using ACS/HRC in the UV, and followed up in Cycle 15. These observations established the sense of the orbital motion, as well as a first approximation to the dynamical mass. An observation with WFC3 in Cycle 17 again revealed the companion, in spite of the larger pixels than ACS/HRC, after deconvolution. This further refined our mass determination. We propose an additional WFC3 observation in Cycle 21, which will extend the coverage of the orbit substantially. We estimate that this new observation will reduce the uncertainty in the mass of Polaris from 26% to 10%. The window for this observation is rapidly closing since the two stars are heading for periastron. This is a UV Initiative proposal since making the observations in the UV enhances the relative brightness of the companion, which is warmer than Polaris, by about 2 magnitudes relative to the visible. Because of the degradation of the PSF in short WFC3 exposures due to "shutter jitter, " we also request one orbit to observe a nearby bright single star, Beta Cas, using identical exposure times, to serve as a PSF reference star in the specialized FQ232N filter that we will use. ------------------------------------------------------------------------------------ Observations Description ------------------------ The aim of the observations is to resolve the very close, faint companion of Polaris, and measure its separation and position angle as part of a solution 13369( 8) - 04-Jun-2014 18:12:51 - [ 2] for the dynamical mass of Polaris. We will take a series of dithered 1.4-sec exposures on Polaris in the FQ232N filter, which makes unsaturated images of Polaris possible, and reduces the magnitude difference between the two stars. We will also take a set of identical exposures on Gamma Cas, in order to determine the PSF in this very rarely used WFC3 filter for a single star, observed with the same amount of shutter jitter as for Polaris. For all of the exposures, because of very faint backgrounds, we added FLASH=12. Real Time Justification ----------------------- Calibration Justification ------------------------- Additional Comments ------------------- ------------------------------------------------------------------------------------ 13369( 8) - 04-Jun-2014 18:12:51 - [ 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=02H31M49.0950S +/- 0.1", J2000 V = 1.98 +/- 0.1 PULSATING VARIABLE DEC=+89D15'50.79" +/- 0.1" Reference Frame: ICRS Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.23088419644378155 -0.01185 0.00754 ------------------------------------------------------------------------------------------------------------------------------------ 3 GAMMA-CYG STAR, F3-F9 RA=20H22M13.7018S +/- 0.1", J2000 V = 2.237 DEC=+40D15'24.04" +/- 0.1" Reference Frame: ICRS Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 2.087818103769164E-4 -9.1E-4 0.00178 ------------------------------------------------------------------------------------------------------------------------------------ 13369( 8) - 04-Jun-2014 18:12:51 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.173 Line_Spacing 0.112 Coordinate_Frame POS-TARG Pattern_Orient 23.884 Angle_Between_Sides 81.785 Center_Pattern YES ------------------------------------------------------------------------------------------------------------------------------------ 13369( 8) - 04-Jun-2014 18:12:51 - [ 5] Visit: 01 Visit Requirements: ORIENT 322D TO 352 D; ORIENT 19.13D TO 26 D; BEFORE 15-JUN-2014:00:00:00 On Hold Comments: Additional Comments: ORIENT is chosen to place the faint companion Polaris Ab at between "noon" and "1 o'clock" in the image frame relative to Polaris A, which appears to be the optimal location for the FQ232N PSF to avoid diffraction spikes and filter ghosts. A small window around "2 o'clock" is also allowed. The BEFORE 15-jun-2014 is included to assure that the observation is done in Cycle 21, so as to cover this important part of the binary orbit. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 POLARIS WFC3/UVI ACCUM UVIS-QUAD FQ232N CR-SPLIT=NO, FLASH=12, BLADE=A 3 1.4 S GS ACQ SCENARIO BASE1B3; S -SUB (16.8 S) PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 POLARIS WFC3/UVI ACCUM UVIS-QUAD FQ232N CR-SPLIT=NO, FLASH=12, BLADE=A 2 1.4 S (2.8 POS TARG 0, 0 S -SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 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 WFC3/UVI ACCUM UVIS-QUA FQ232N 1 none 1 none 1 N/A S D-SUB POLARIS 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 1 none 2 none 1 N/A S D-SUB POLARIS 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 1 none 3 none 1 N/A S D-SUB POLARIS 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 2 none 1 none 1 N/A S D-SUB POLARIS 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 2 none 2 none 1 N/A S D-SUB POLARIS 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 2 none 3 none 1 N/A S D-SUB POLARIS 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 3 none 1 none 1 N/A S D-SUB POLARIS 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 3 none 2 none 1 N/A S D-SUB POLARIS 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 3 none 3 none 1 N/A S D-SUB POLARIS 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 4 none 1 none 1 N/A S D-SUB POLARIS 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 4 none 2 none 1 N/A S D-SUB POLARIS 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 4 none 3 none 1 N/A S D-SUB POLARIS 2 WFC3/UVI ACCUM UVIS-QUA FQ232N none none 1 none 1 N/A S D-SUB 13369( 8) - 04-Jun-2014 18:12:51 - [ 6] 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 2 WFC3/UVI ACCUM UVIS-QUA FQ232N none none 2 none 1 N/A S D-SUB 13369( 8) - 04-Jun-2014 18:12:51 - [ 7] Visit: 02 Visit Requirements: GROUP 02, 01 WITHIN 2D On Hold Comments: Additional Comments: This is a PSF reference star for the analysis of the Polaris images. Set of exposures is identical to those for Polaris. Should be taken within a few HST orbits of the Polaris observation. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GAMMA-CYG WFC3/UVI ACCUM UVIS-QUAD FQ232N CR-SPLIT=NO, FLASH=12, BLADE=A 3 1.4 S GS ACQ SCENARIO BASE1B3; S -SUB (16.8 S) PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ GAMMA-CYG 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 1 none 1 none 1 N/A S D-SUB GAMMA-CYG 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 1 none 2 none 1 N/A S D-SUB GAMMA-CYG 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 1 none 3 none 1 N/A S D-SUB GAMMA-CYG 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 2 none 1 none 1 N/A S D-SUB GAMMA-CYG 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 2 none 2 none 1 N/A S D-SUB GAMMA-CYG 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 2 none 3 none 1 N/A S D-SUB GAMMA-CYG 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 3 none 1 none 1 N/A S D-SUB GAMMA-CYG 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 3 none 2 none 1 N/A S D-SUB GAMMA-CYG 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 3 none 3 none 1 N/A S D-SUB GAMMA-CYG 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 4 none 1 none 1 N/A S D-SUB GAMMA-CYG 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 4 none 2 none 1 N/A S D-SUB GAMMA-CYG 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 4 none 3 none 1 N/A S D-SUB 13369( 8) - 04-Jun-2014 18:12:51 - [ 8] Visit: 03 Visit Requirements: ORIENT 300D TO 352 D; ORIENT 19.13D TO 26 D; ORIENT 142D TO 172 D; ORIENT 199.13D TO 206 D; BEFORE 15-JUL-2014:00:00:00 On Hold Comments: Additional Comments: ORIENT is chosen to place the faint companion Polaris Ab at between "noon" and "1 o'clock" in the image frame relative to Polaris A, which appears to be the optimal location for the FQ232N PSF to avoid diffraction spikes and filter ghosts. A small window around "2 o'clock" is also allowed. The BEFORE 15-Oct-2014 is included to assure that the observation is done in Cycle 21, so as to cover this important part of the binary orbit. Note that this is a repeat of Visit 01 which failed in March 2014. We also added orients differing by 180 deg from the originals, and changed the exposure times from 1.4 to 1.5 sec. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 POLARIS WFC3/UVI ACCUM UVIS-QUAD FQ232N CR-SPLIT=NO, FLASH=12, BLADE=A 3 1.5 S (18 GS ACQ SCENARIO BASE1B3; S -SUB S) SEQ 1-2 NON-INT; PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 2 POLARIS WFC3/UVI ACCUM UVIS-QUAD FQ232N CR-SPLIT=NO, FLASH=12, BLADE=A 2 1.5 S (3 POS TARG 0, 0 S -SUB S) ------------------------------------------------------------------------------------------------------------------------------------ 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 WFC3/UVI ACCUM UVIS-QUA FQ232N 1 none 1 none 1 N/A S D-SUB POLARIS 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 1 none 2 none 1 N/A S D-SUB POLARIS 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 1 none 3 none 1 N/A S D-SUB POLARIS 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 2 none 1 none 1 N/A S D-SUB POLARIS 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 2 none 2 none 1 N/A S D-SUB POLARIS 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 2 none 3 none 1 N/A S D-SUB POLARIS 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 3 none 1 none 1 N/A S D-SUB POLARIS 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 3 none 2 none 1 N/A S D-SUB POLARIS 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 3 none 3 none 1 N/A S D-SUB POLARIS 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 4 none 1 none 1 N/A S D-SUB 13369( 8) - 04-Jun-2014 18:12:51 - [ 9] 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 WFC3/UVI ACCUM UVIS-QUA FQ232N 4 none 2 none 1 N/A S D-SUB POLARIS 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 4 none 3 none 1 N/A S D-SUB POLARIS 2 WFC3/UVI ACCUM UVIS-QUA FQ232N none none 1 none 1 N/A S D-SUB POLARIS 2 WFC3/UVI ACCUM UVIS-QUA FQ232N none none 2 none 1 N/A S D-SUB 13369( 8) - 04-Jun-2014 18:12:51 - [ 10] Visit: 04 Visit Requirements: GROUP 04, 03 WITHIN 2D On Hold Comments: Additional Comments: This is a PSF reference star for the analysis of the Polaris images. Set of exposures is identical to those for Polaris. Should be taken within a few HST orbits of the Polaris observation. Note that this is a repeat of Visit 02 which failed in March 2014. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 GAMMA-CYG WFC3/UVI ACCUM UVIS-QUAD FQ232N CR-SPLIT=NO, FLASH=12, BLADE=A 3 1.5 S (18 GS ACQ SCENARIO BASE1B3; S -SUB S) SEQ 1 NON-INT; PATTERN 1 1 ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ GAMMA-CYG 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 1 none 1 none 1 N/A S D-SUB GAMMA-CYG 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 1 none 2 none 1 N/A S D-SUB GAMMA-CYG 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 1 none 3 none 1 N/A S D-SUB GAMMA-CYG 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 2 none 1 none 1 N/A S D-SUB GAMMA-CYG 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 2 none 2 none 1 N/A S D-SUB GAMMA-CYG 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 2 none 3 none 1 N/A S D-SUB GAMMA-CYG 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 3 none 1 none 1 N/A S D-SUB GAMMA-CYG 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 3 none 2 none 1 N/A S D-SUB GAMMA-CYG 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 3 none 3 none 1 N/A S D-SUB GAMMA-CYG 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 4 none 1 none 1 N/A S D-SUB GAMMA-CYG 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 4 none 2 none 1 N/A S D-SUB GAMMA-CYG 1 WFC3/UVI ACCUM UVIS-QUA FQ232N 4 none 3 none 1 N/A S D-SUB 13369( 8) - 04-Jun-2014 18:12:51 - [ 11] Summary Form for Proposal 13369 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS-QUAD-SUB ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BLADE=A, CR-SPLIT=NO, FLASH=12 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements BEFORE 15-JUL-2014:00:00:00, BEFORE 15-JUN-2014:00:00:00, GROUP 02, 01 WITHIN 2D, GROUP 04, 03 WITHIN 2D, GS ACQ SCENARIO BASE1B3, ORIENT 142D TO 172 D, ORIENT 19.13D TO 26 D, ORIENT 199.13D TO 206 D, ORIENT 300D TO 352 D, ORIENT 322D TO 352 D, PATTERN 1 1, POS TARG 0, 0, SEQ 1 NON-INT, SEQ 1-2 NON-INT ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements FQ232N ------------------------------------------------------------------------------------------------------------------------------------ Target Names GAMMA-CYG, POLARIS ------------------------------------------------------------------------------------------------------------------------------------