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Proposal 15886 (STScI Edit Number: 0, Created: Tuesday, December 22, 2020 at 8:00:58 AM Eastern Standard Time) - Overview

15886 - 1000 Days of GW170817: A Deep Multi-Band View of the First Merger with HST Cycle: 27, Proposal Category: GO (Availability Mode: SUPPORTED)

INVESTIGATORS Name Institution E-Mail Dr. Wen-fai Fong (PI) (Contact) Northwestern University [email protected] Prof. Edo Berger (CoI) Harvard University [email protected] Dr. Raffaella Margutti (CoI) Northwestern University [email protected] Dr. Kate Denham Alexander (CoI) Northwestern University [email protected] Prof. Ryan Chornock (CoI) Northwestern University [email protected] Dr. K Paterson (CoI) Northwestern University [email protected] Dr. Peter Blanchard (CoI) Northwestern University [email protected]

VISITS Visit Targets used in Visit Configurations used in Visit Orbits Used Last Orbit Planner Run OP Current with Visit? 01 (1) GW170817 WFC3/IR 4 22-Dec-2020 08:00:54.0 yes 02 (1) GW170817 WFC3/IR 3 22-Dec-2020 08:00:56.0 yes 03 (1) GW170817 WFC3/IR 3 22-Dec-2020 08:00:57.0 yes 04 (1) GW170817 WFC3/UVIS 3 22-Dec-2020 08:00:58.0 yes 13 Total Orbits Used

ABSTRACT

1 Proposal 15886 (STScI Edit Number: 0, Created: Tuesday, December 22, 2020 at 8:00:58 AM Eastern Standard Time) - Overview The joint detection of gravitational waves and light from the binary GW170817 has ushered in a new era of discovery. HST has played a pivotal role in characterizing the optical and near- (NIR) of GW170817, with reported detections of the and afterglow spanning ~10-350 days post-merger. In particular, at >100 days, the afterglow brightness is extremely faint at >26 mag; thus all detections or constraining upper limits at late times were enabled by HST. One major complication in measuring accurate photometry of the faint optical and NIR afterglow is contaminating light from the host , which has complex morphological structure. The only way to properly address this issue is by re-visiting the field after the afterglow has faded to obtain deep multi-band template images, against which we can subtract earlier epochs. Motivated by a case study in one of the optical filters, here we propose 13 orbits of HST/WFC3 imaging to obtain late-time template images in four filters, comprising all filters which have HST imaging beyond ~100 days and for which no adequate template images exist. These images will enable reliable and uniform photometry of the optical/NIR afterglow to GW170817 for the first time. In conjunction with ongoing radio and X-ray campaigns by the community, this will allow accurate inferred properties of relativistic outflows from the merger, and the deepest limits on a star cluster at the merger position, strongly constraining the binary progenitor's formation. Given the high-impact of GW170817, we waive all proprietary rights associated with data from this proposal.

OBSERVING DESCRIPTION This proposal is for multi-wavelength observations of the optical counterpart of GW170817 with UVIS/F814W (3 orbits), WFC3/F110W (4 orbits), WFC3/F140W (3 orbits), and WFC3/F160W (3 orbits). These observations are for a template observation of the afterglow of GW170817 and the visits may occur at any point during the cycle. These filters and apertures have been purposely chosen to match those of previous observations of this source. We note that GW170817 is a point source on the outskirts of NGC4993, a bright S0 galaxy, and that the expected brightness of GW170817 is >28 mag.

2 Proposal 15886-Visit011000DaysofGW170817:ADeepMulti-BandViewtheFirst NeutronStarMergerwithHST Exposures Fixed Targets Patterns Visit 2 1 # Extended=NO Description=[GAMMA RAYBURSTER] Category=EXT-STAR Comments: (1) # (1) # Comments: 4-orbitobservationwithIR/F110W.WerestricttheORIENTrangestoavoidabrightstarpositionedatedgeofchip(whichhas previouslycausedcontaminationinotherobservations). Special Requirements:ORIENT345DTO76D;84D164174D248274D326D Scientific Instruments:WFC3/IR Diagnostic Status:NoDiagnostics Proposal 15886,Visit01 Label GW170817 Name Line Spacing=0.365 Point Spacing=0.572 Number OfPoints=4 Purpose=DITHER BOX-MIN Pattern Type=WFC3-IR-DITHER- Primary Pattern (1) GW170817 Target (1) GW170817 Equinox: J2000 Dec: -232253.35(-23.38149d) RA: 130948.0900(197.4503750d) Target Coordinates WFC3/IR, MULTIACCUM,IR WFC3/IR, MULTIACCUM,IR Config,Mode,Aperture Center Pattern=false Angle BetweenSides=74.653 Pattern Orientation=18.528 Coordinate Frame=POS-TARG F110W F110W Spectral Els. Targ. Coord.Corrections Secondary Pattern S100 SAMP-SEQ=SPAR NSAMP=14; S100 SAMP-SEQ=SPAR NSAMP=14; Opt. Params. 3 1 POS TARG0.68,0.6 Special Reqs. V=27 Fluxes n Visit01(1) Pattern 1,Exps2-2i n Visit01(1) Pattern 1,Exps1-1i Groups [==>(Pattern 4)] [==>(Pattern 3)] [==>(Pattern 2)] [==>(Pattern 1)] 1302.93649 Secs(5211.746Secs) [==>(Pattern 4)] [==>(Pattern 3)] [==>(Pattern 2)] [==>(Pattern 1)] 1302.93649 Secs(5211.746Secs) Exp. Time(Total)/[ActualDur.] Reference Frame:SIMBAD Miscellaneous (1), (2) Exposures Tue Dec2213:00:58GMT2020 Orbit [4] [3] [2] [1] Proposal 15886-Visit011000DaysofGW170817:ADeepMulti-BandViewtheFirst NeutronStarMergerwithHST Orbit Structure 4 Proposal 15886 - Visit 01 - 1000 Days of GW170817: A Deep Multi-Band View of the First Neutron Star Merger with HST

5 Proposal 15886-Visit021000DaysofGW170817:ADeepMulti-BandViewtheFirst NeutronStarMergerwithHST Exposures Fixed Targets Patterns Diagnostics Visit 3 2 1 # Extended=NO Description=[GAMMA RAYBURSTER] Category=EXT-STAR Comments: (1) # (2) (1) # (Visit 02)Warning(OrbitPlanner):ORBITALVISIBILITYOVERRUN We employasmallPOS-TARGoffsetbetweenditherpatterns.add small exposureattheendofvisittofilloutorbit. Comments: 3-orbitobservationwithIR/F140W.WerestricttheORIENTrangestoavoidabrightstarpositionedatedgeofchip(whichhas previouslycausedcontaminationinotherobservations). Special Requirements:ORIENT345DTO76D;84D164174D248274D326D Scientific Instruments:WFC3/IR Diagnostic Status:Warning Proposal 15886,Visit02 Label GW170817 Name Line Spacing= Point Spacing=0.605 Number OfPoints=3 Purpose=DITHER LINE-3PT Pattern Type=WFC3-IR-DITHER- Line Spacing=0.365 Point Spacing=0.572 Number OfPoints=4 Purpose=DITHER BOX-MIN Pattern Type=WFC3-IR-DITHER- Primary Pattern (1) GW170817 (1) GW170817 (1) GW170817 Target Equinox: J2000 Dec: -232253.35(-23.38149d) RA: 130948.0900(197.4503750d) Target Coordinates WFC3/IR, MULTIACCUM, IR WFC3/IR, MULTIACCUM, IR WFC3/IR, MULTIACCUM,IR Config,Mode,Aperture Center Pattern=false Angle BetweenSides= Pattern Orientation=41.788 Coordinate Frame=POS-TARG Center Pattern=false Angle BetweenSides=74.653 Pattern Orientation=18.528 Coordinate Frame=POS-TARG F140W F140W F140W Spectral Els. Targ. Coord.Corrections Secondary Pattern S25 SAMP-SEQ=SPAR NSAMP=9; S100 SAMP-SEQ=SPAR NSAMP=9; S100 SAMP-SEQ=SPAR NSAMP=14; Opt. Params. 6 1 POS TARG0.68,0.6 1 POS TARG0.68,0.6 POS TARG0.67,0.2 Special Reqs. V=27 Fluxes n Visit02(2) Pattern 2,Exps2-2 i n Visit02(1) Pattern 1,Exps1-1i Groups [==>] 202.936411 Secs (202.936 Secs) [==>(Pattern 3)] [==>(Pattern 2)] [==>(Pattern 1)] 802.934875 Secs (2408.805 Secs) [==>(Pattern 4)] [==>(Pattern 3)] [==>(Pattern 2)] [==>(Pattern 1)] 1302.93649 Secs(5211.746Secs) Exp. Time(Total)/[ActualDur.] Reference Frame:SIMBAD Miscellaneous (2) (1) Exposures Tue Dec2213:00:59GMT2020 Orbit [3] [3] [2] [1] Proposal 15886-Visit021000DaysofGW170817:ADeepMulti-BandViewtheFirst NeutronStarMergerwithHST Orbit Structure 7 Proposal 15886 - Visit 02 - 1000 Days of GW170817: A Deep Multi-Band View of the First Neutron Star Merger with HST

8 Proposal 15886-Visit031000DaysofGW170817:ADeepMulti-BandViewtheFirst NeutronStarMergerwithHST Exposures Fixed Targets Patterns Diagnostics Visit 3 2 1 # Extended=NO Description=[GAMMA RAYBURSTER] Category=EXT-STAR Comments: (1) # (2) (1) # (Visit 03)Warning(OrbitPlanner):ORBITALVISIBILITYOVERRUN We employasmallPOS-TARGoffsetbetweenditherpatterns.add small exposureattheendofvisittofilloutorbit. Comments: 3-orbitobservationwithIR/F160W.WerestricttheORIENTrangestoavoidabrightstarpositionedatedgeofchip(whichhas previouslycausedcontaminationinotherobservations). Special Requirements:ORIENT345DTO76D;84D164174D248274D326D Scientific Instruments:WFC3/IR Diagnostic Status:Warning Proposal 15886,Visit03 Label GW170817 Name Line Spacing= Point Spacing=0.605 Number OfPoints=3 Purpose=DITHER LINE-3PT Pattern Type=WFC3-IR-DITHER- Line Spacing=0.365 Point Spacing=0.572 Number OfPoints=4 Purpose=DITHER BOX-MIN Pattern Type=WFC3-IR-DITHER- Primary Pattern (1) GW170817 (1) GW170817 (1) GW170817 Target Equinox: J2000 Dec: -232253.35(-23.38149d) RA: 130948.0900(197.4503750d) Target Coordinates WFC3/IR, MULTIACCUM, IR WFC3/IR, MULTIACCUM, IR WFC3/IR, MULTIACCUM,IR Config,Mode,Aperture Center Pattern=false Angle BetweenSides= Pattern Orientation=41.788 Coordinate Frame=POS-TARG Center Pattern=false Angle BetweenSides=74.653 Pattern Orientation=18.528 Coordinate Frame=POS-TARG F160W F160W F160W Spectral Els. Targ. Coord.Corrections Secondary Pattern S25 SAMP-SEQ=SPAR NSAMP=9; S100 SAMP-SEQ=SPAR NSAMP=9; S100 SAMP-SEQ=SPAR NSAMP=14; Opt. Params. 9 1 POS TARG0.68,0.6 1 POS TARG0.68,0.6 Special Reqs. V=27 Fluxes n Visit03(2) Pattern 2,Exps2-2 i n Visit03(1) Pattern 1,Exps1-1i Groups [==>] 202.936411 Secs (202.936 Secs) [==>(Pattern 3)] [==>(Pattern 2)] [==>(Pattern 1)] 802.934875 Secs (2408.805 Secs) [==>(Pattern 4)] [==>(Pattern 3)] [==>(Pattern 2)] [==>(Pattern 1)] 1302.93649 Secs(5211.746Secs) Exp. Time(Total)/[ActualDur.] Reference Frame:SIMBAD Miscellaneous (2) (1) Exposures Tue Dec2213:00:59GMT2020 Orbit [3] [3] [2] [1] Proposal 15886-Visit031000DaysofGW170817:ADeepMulti-BandViewtheFirst NeutronStarMergerwithHST Orbit Structure 10 Proposal 15886 - Visit 03 - 1000 Days of GW170817: A Deep Multi-Band View of the First Neutron Star Merger with HST

11 Proposal 15886-Visit041000DaysofGW170817:ADeepMulti-BandViewtheFirst NeutronStarMergerwithHST Exposures Fixed Targets Patterns Diagnostics Visit 2 1 # Extended=NO Description=[GAMMA RAYBURSTER] Category=EXT-STAR Comments: (1) # (4) (3) # (Visit 04)Warning(OrbitPlanner):ORBITALVISIBILITYOVERRUN (Visit 04)Warning(OrbitPlanner):ORBITALVISIBILITYOVERRUN (Visit 04)Warning(OrbitPlanner):ORBITALVISIBILITYOVERRUN Comments: 3-orbitobservationwithUVIS/F814W.WerestricttheORIENTrangestoavoidabrightstarpositionedatedgeofchip(which haspreviouslycausedcontaminationinotherobservations). Special Requirements:ORIENT338DTO81D;150D265287D318D Scientific Instruments:WFC3/UVIS Diagnostic Status:Warning Proposal 15886,Visit04 Label Name GW170817 Line Spacing= Point Spacing=0.135 Number OfPoints=3 Purpose=DITHER LINE-3PT Pattern Type=WFC3-UVIS-DITHER- Line Spacing=0.112 Point Spacing=0.173 Number OfPoints=4 Purpose=DITHER BOX Pattern Type=WFC3-UVIS-DITHER- Primary Pattern (1) GW170817 (1) GW170817 Target Equinox: J2000 Dec: -232253.35(-23.38149d) RA: 130948.0900(197.4503750d) Target Coordinates WFC3/UVIS, ACCUM,UVIS2 WFC3/UVIS, ACCUM,UVIS2 Config,Mode,Aperture Center Pattern=false Angle BetweenSides= Pattern Orientation=46.84 Coordinate Frame=POS-TARG Center Pattern=false Angle BetweenSides=81.785 Pattern Orientation=23.884 Coordinate Frame=POS-TARG F814W F814W Spectral Els. Targ. Coord.Corrections Secondary Pattern Opt. Params. 12 1 POS TARG0.68,0.2 Special Reqs. V=27 Fluxes n Visit04(4) Pattern 4,Exps2-2i n Visit04(3) Pattern 3,Exps1-1i Groups [==>(Pattern 3)] [==>(Pattern 2)] [==>(Pattern 1)] 860 Secs(2580Secs) [==>(Pattern 4)] [==>(Pattern 3)] [==>(Pattern 2)] [==>(Pattern 1)] 1340 Secs(5360Secs) Exp. Time(Total)/[ActualDur.] Reference Frame:SIMBAD Miscellaneous (2) (1) Exposures Tue Dec2213:00:59GMT2020 Orbit [3] [2] [1] Proposal 15886-Visit041000DaysofGW170817:ADeepMulti-BandViewtheFirst NeutronStarMergerwithHST Orbit Structure 13 Proposal 15886 - Visit 04 - 1000 Days of GW170817: A Deep Multi-Band View of the First Neutron Star Merger with HST

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