15893( 4) - 24-Jun-2020 22:12:33 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15893 Version: 4 Check-in Time: 24-Jun-2020 22:12:33 STScI Edit Number: 1 Title Observing Changes in the Primary Shock Front of the Cygnus Loop: An HST 20+ Year Perspective ------------------------------------------------------------------------------------ Type Cycle GO 27 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Ravi Sankrit Space Telescope Science Institute Y CoI: Dr. John Charles Raymond Smithsonian Institution Astrophysical N Observatory CoI: Dr. William P. Blair The Johns Hopkins University N ------------------------------------------------------------------------------------ Abstract We propose to re-observe the faint, primary blast wave of the Cygnus Loop supernova remnant with WFC3, a region that has been observed twice before with WFPC2, in 1997 and 2001. The region contains a delicate rippled sheet of plasma visible in H-alpha, that represents a section of the primary non-radiative supernova shock, and an adjacent [O III] 5007-emitting filament that is a shock in transition to becoming radiative. This would be the third epoch in H-alpha, and the second in [O III] 5007. With the recent accurate GAIA DR2-derived distance to the Cygnus Loop (735 +/- 25 pc), and the proper motion in H-alpha from epochs 1 and 2, the derived shock velocity is 245 km/s. The epoch 3 H-alpha data and long time baseline will permit a sensitive search for signs of deceleration of the filament, either globally or locally along portions of the filament structure. The two epochs of [O III] will measure or constrain any changes in the filament structure over ~20 years due to catastrophic cooling, thermal instabilities, or density variations that are predicted to occur as SN remnant shocks turn radiative. The Cygnus Loop provides a unique target to test for these changes since the densities and shock velocities involved provide for the possibility of observable changes on a reasonable timescale. ------------------------------------------------------------------------------------ Observations Description ------------------------ Two WFC3/UVIS filters, F656N and F502N, will be used to image a single field in the Cygnus Loop supernova remnant, targeting a narrow, extended H-alpha emitting filament, with portions of it emitting in [OIII]. There are two visits, each with three orbits. The first visit uses F656N, and the second visit uses F502N. For each visit, a dither pattern to cover the chip gap, plus a subpattern to remove cosmic rays and bad pixels have been specified. This results in two sub-exposures per orbit. Orientation requirements have been specified in order to get the entire filament on a single UVIS detector, with the second detector covering a region towards the interior of the remnant (i.e. southwest of the filament). The range for the allowed orientation is such that the exact target co-ordinates (specified in the proposal for the UVIS CENTER aperture) will need to be tweaked after the visits have been scheduled in the long-range plan. Therefore we request that once we the target is scheduled we are given the opportunity to 15893( 4) - 24-Jun-2020 22:12:33 - [ 2] update the target co-ordinates in the Phase II proposal before execution. We have also specified that visit 02 be obtained at the same orientation as visit 01, to best match the relative locations of the H-alpha and [OIII] emission. Also, we have specified that the two visits be obtained within 60 days of each other, so they are included in the same visibility window, and there is no significant temporal evolution of the shock between them. ------------------------------------------------------------------------------------ 15893( 4) - 24-Jun-2020 22:12:33 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 CYGLOOP-NENR ISM, EMISSION LINE RA=20H56M1.6044S, J2000 V = 35 +/- 0 H-alpha surface brightness 1 NEBULA, FILAMENT, SHOCK DEC=+31D56'9.91" 6.0 +/- 0.5 E-16 erg/s/cm2/arcsec2 FRONT, SNR Reference Frame: ICRS ------------------------------------------------------------------------------------------------------------------------------------ 15893( 4) - 24-Jun-2020 22:12:33 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-GAP-LINE WFC3-UVIS-DITHER-LINE-3PT Pattern_Purpose MOSAIC DITHER Number_Of_Points 2 3 Point_Spacing 2.414 1.485 Line_Spacing Coordinate_Frame POS-TARG POS-TARG Pattern_Orient 85.759 46.84 Angle_Between_Sides Center_Pattern YES NO ------------------------------------------------------------------------------------------------------------------------------------ 15893( 4) - 24-Jun-2020 22:12:33 - [ 5] Visit: 01 (F656N) Visit Requirements: SCHED 100%; ORIENT 330D TO 15 D; ORIENT 150D TO 195 D 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| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 CYGLOOP-NEN WFC3/UVI ACCUM UVIS-CENT F656N FLASH=20 1 1200 S PATTERN 1 1 R1 S ER see below (7414 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 | ------------------------------------------------------------------------------------------------------------------------------------ CYGLOOP-NENR1 1 WFC3/UVI ACCUM UVIS-CEN F656N 1 1 none none 1 1225.0 S S TER CYGLOOP-NENR1 1 WFC3/UVI ACCUM UVIS-CEN F656N 1 2 none none 1 1225.0 S S TER CYGLOOP-NENR1 1 WFC3/UVI ACCUM UVIS-CEN F656N 1 3 none none 2 1241.0 S S TER CYGLOOP-NENR1 1 WFC3/UVI ACCUM UVIS-CEN F656N 2 1 none none 2 1241.0 S S TER CYGLOOP-NENR1 1 WFC3/UVI ACCUM UVIS-CEN F656N 2 2 none none 3 1241.0 S S TER CYGLOOP-NENR1 1 WFC3/UVI ACCUM UVIS-CEN F656N 2 3 none none 3 1241.0 S S TER 15893( 4) - 24-Jun-2020 22:12:33 - [ 6] Visit: 02 (F502N) Visit Requirements: SCHED 100%; SAME ORIENT AS 01; GROUP 02, 01 WITHIN 60D 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| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 CYGLOOP-NEN WFC3/UVI ACCUM UVIS-CENT F502N FLASH=20 1 1200 S PATTERN 1 1 R1 S ER see below (7414 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 | ------------------------------------------------------------------------------------------------------------------------------------ CYGLOOP-NENR1 1 WFC3/UVI ACCUM UVIS-CEN F502N 1 1 none none 1 1225.0 S S TER CYGLOOP-NENR1 1 WFC3/UVI ACCUM UVIS-CEN F502N 1 2 none none 1 1225.0 S S TER CYGLOOP-NENR1 1 WFC3/UVI ACCUM UVIS-CEN F502N 1 3 none none 2 1241.0 S S TER CYGLOOP-NENR1 1 WFC3/UVI ACCUM UVIS-CEN F502N 2 1 none none 2 1241.0 S S TER CYGLOOP-NENR1 1 WFC3/UVI ACCUM UVIS-CEN F502N 2 2 none none 3 1241.0 S S TER CYGLOOP-NENR1 1 WFC3/UVI ACCUM UVIS-CEN F502N 2 3 none none 3 1241.0 S S TER 15893( 4) - 24-Jun-2020 22:12:33 - [ 7] Summary Form for Proposal 15893 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS-CENTER ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=20 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements GROUP 02, 01 WITHIN 60D, ORIENT 150D TO 195 D, ORIENT 330D TO 15 D, PATTERN 1 1, SAME ORIENT AS 01, SCHED 100% ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F502N, F656N ------------------------------------------------------------------------------------------------------------------------------------ Target Names CYGLOOP-NENR1 ------------------------------------------------------------------------------------------------------------------------------------