15346( 11) - 06-Dec-2018 13:49:39 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15346 Version: 11 Check-in Time: 06-Dec-2018 13:49:39 STScI Edit Number: 0 Title Verifying a candidate counterpart to gravitational waves ------------------------------------------------------------------------------------ Type Cycle GO 25 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Mansi Kasliwal California Institute of Technology Y CoI: Dr. Stephen Bradley Cenko NASA Goddard Space Flight Center N CoI: Prof. Varun Bhalerao Indian Institute of Technology Bombay N CoI: Dr. Daniel Perley Liverpool John Moores University N CoI: Prof. David L. Kaplan University of Wisconsin - Milwaukee N CoI: Prof. Ariel Goobar Stockholm University N CoI: Dr. Leo Singer NASA Goddard Space Flight Center N ------------------------------------------------------------------------------------ Abstract With advances in sensitivity of gravitational wave interferometers, the direct detection of neutron star mergers should be imminent. Identification of an electromagnetic counterpart would enable a wealth of astrophysics and answer the long-standing question of whether neutron star mergers are the missing cosmic mines of heavy elements synthesized by the r-process. We will be searching for a fast-fading optical counterpart with the new Zwicky Transient Facility at Palomar Observatory. Here, we propose to use HST/WFC3 to look for infrared emission from a single, most-promising candidate optical counterpart. The infrared emission would serve as a direct diagnostic of the radioactive decay of heavy elements. ------------------------------------------------------------------------------------ Observations Description ------------------------ We request one disruptive ToO with HST/WFC3. With GROWTH network follow-up of ZTF candidates, we expect to identify a promising candidate (if any) and submit the ToO trigger within 36 hours of the neutron star merger. With HST, we request the first epoch within one week and the second epoch at three weeks (Figure 2). We need two epochs to determine the rate at which the emission fades. Given current models, we expect a non-detection in the second non-disruptive epoch but it would serve as an invaluable reference to subtract any host galaxy light. Each epoch would comprise one orbit in each of two filters: F606W and F160W. We choose F160W as it is the reddest available infrared filter. We choose F606W as that would be closest to the discovery filter for ZTF. We run the ETC assuming 50 min of integration per orbit given overheads on account of target acquisition and multiple dithers. With F606W, we would reach a depth of 26.8 mag in 1 orbit and with H-band, we would reach a depth of 26.1 mag AB with S/N=10. With this depth, the F606W filter would be sensitive to opacity < 3 cm^2 / gm and neutron star mass > 3 x 10^(-5) Msun (see Figure 2). With this depth, the F160W filter would be sensitive to ejecta mass > 0.0001 Msun and a ejecta velocity > 0.05 c. We emphasize that HST is more sensitive in H-band 15346( 11) - 06-Dec-2018 13:49:39 - [ 2] than a ground-based telescope due to the strong OH airglow one has to look through from the ground. The sky background from space is 6-10 mag darker at H than from a good ground-based site (e.g., Sullivan & Simcoe 2012). We request long-term status for both Cycles 25 and Cycles 26 for the following reasons: (i) The duration of the third advanced LIGO run is expected to be approximately 9-12 months between Summer 2018 and Spring 2019. This schedule spans both cycles 25 and cycles 26. (ii) The rates of neutron star mergers is uncertain by an order of magnitude. Assuming the realistic rate, we expect one trigger per month out to 150Mpc. Given the challenges in follow-up where we need the sun, moon and weather to co-operate, we conservatively only request one disruptive ToO trigger for our most promising candidate (see trigger criterion in next section). Our total request is 4 HST orbits. ------------------------------------------------------------------------------------ 15346( 11) - 06-Dec-2018 13:49:39 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC4993OT STAR, T RA=13H09M48.0890S, J2000 V = 20.0 DEC=-23D22'53.35" Reference Frame: ICRS Extended: NO ------------------------------------------------------------------------------------------------------------------------------------ 15346( 11) - 06-Dec-2018 13:49:39 - [ 4] TARGET LIST Generic Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Selection Criteria | Flux data No | Name | Description | | ------------------------------------------------------------------------------------------------------------------------------------ 1 GROWTH-EMGW UNIDENTIFIED, INFRARED OTHER: CANDIDATE ELECTROMAGNETIC V = 26 +/- 4 EMITTER, OPTICAL COUNTERPART TO GRAVITATIONAL WAVES EMITTER Comments: This is a disruptive ToO proposal. We will only trigger on targets that are spatially and temporally coincident with a gravitational wave trigger. Our trigger criterion to identify the most promising counterpart is to utilize all available information to reject common, unrelated classes of transients (e.g., Supernovae, Active Galactic Nuclei, M-dwarf flares). For example: (i) Spectra dissimilar to any known type of transient and/or (ii) Photometric evolution that is so fast and/or so red that it is most consistent with a neutron star merger and/or (iii) Spatially consistent with a nearby host galaxy known to have a distance within LIGO's sensitivity horizon and/or (iv) No past history of variability. ------------------------------------------------------------------------------------------------------------------------------------ 15346( 11) - 06-Dec-2018 13:49:39 - [ 5] 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 NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-IR-DITHER-BOX-MIN Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.572 Line_Spacing 0.365 Coordinate_Frame POS-TARG Pattern_Orient 18.528 Angle_Between_Sides 74.653 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 3 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-IR-DITHER-LINE-3PT Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 0.605 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 41.788 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 4 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE-3PT Pattern_Purpose DITHER Number_Of_Points 3 Point_Spacing 0.135 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 15346( 11) - 06-Dec-2018 13:49:39 - [ 6] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 5 Primary_Pattern Secondary_Pattern Pattern_Type WFC3-UVIS-DITHER-LINE Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.145 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 46.84 Angle_Between_Sides Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ 15346( 11) - 06-Dec-2018 13:49:39 - [ 7] Visit: 01 Visit Requirements: ON HOLD ; TOO RESPONSE TIME 5.0D On Hold Comments: We request the first epoch within 1 week of merger. 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 NGC4993OT WFC3/UVI ACCUM UVIS2-C1K F336W FLASH=12 1 363 S PATTERN 4 1 S 1C-CTE (1089 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC4993OT WFC3/UVI ACCUM UVIS2-C1K F225W FLASH=12 1 363 S PATTERN 4 2 S 1C-CTE (1089 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC4993OT 1 WFC3/UVI ACCUM UVIS2-C1 F336W 1 none none none 1 N/A S K1C-CTE NGC4993OT 1 WFC3/UVI ACCUM UVIS2-C1 F336W 2 none none none 1 N/A S K1C-CTE NGC4993OT 1 WFC3/UVI ACCUM UVIS2-C1 F336W 3 none none none 1 N/A S K1C-CTE NGC4993OT 2 WFC3/UVI ACCUM UVIS2-C1 F225W 1 none none none 1 N/A S K1C-CTE NGC4993OT 2 WFC3/UVI ACCUM UVIS2-C1 F225W 2 none none none 1 N/A S K1C-CTE NGC4993OT 2 WFC3/UVI ACCUM UVIS2-C1 F225W 3 none none none 1 N/A S K1C-CTE 15346( 11) - 06-Dec-2018 13:49:39 - [ 8] Visit: 02 Visit Requirements: ON HOLD ; TOO RESPONSE TIME 5.0D; VISIBILITY INTERVAL 49 M On Hold Comments: We request the first epoch within 1 week of merger. 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 NGC4993OT WFC3/UVI ACCUM UVIS2-C1K F336W FLASH=12 1 473 S (946 PATTERN 5 1 S 1C-CTE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 NGC4993OT WFC3/UVI ACCUM UVIS2-C1K F275W FLASH=12 1 363 S PATTERN 4 2 S 1C-CTE (1089 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC4993OT 1 WFC3/UVI ACCUM UVIS2-C1 F336W 1 none none none 1 N/A S K1C-CTE NGC4993OT 1 WFC3/UVI ACCUM UVIS2-C1 F336W 2 none none none 1 N/A S K1C-CTE NGC4993OT 2 WFC3/UVI ACCUM UVIS2-C1 F275W 1 none none none 1 N/A S K1C-CTE NGC4993OT 2 WFC3/UVI ACCUM UVIS2-C1 F275W 2 none none none 1 N/A S K1C-CTE NGC4993OT 2 WFC3/UVI ACCUM UVIS2-C1 F275W 3 none none none 1 N/A S K1C-CTE 15346( 11) - 06-Dec-2018 13:49:39 - [ 9] Visit: 03 Visit Requirements: BETWEEN 01-DEC-2017:00:00:00 AND 10-DEC-2017:00:00:00 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 NGC4993OT WFC3/IR MULTIAC IR F160W NSAMP=7, SAMP-SEQ=SPARS100 1 DEF PATTERN 2 1 CUM (2411.737 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC4993OT 1 WFC3/IR MULTIAC IR F160W 1 none none none 1 N/A CUM NGC4993OT 1 WFC3/IR MULTIAC IR F160W 2 none none none 1 N/A CUM NGC4993OT 1 WFC3/IR MULTIAC IR F160W 3 none none none 1 N/A CUM NGC4993OT 1 WFC3/IR MULTIAC IR F160W 4 none none none 1 N/A CUM 15346( 11) - 06-Dec-2018 13:49:39 - [ 10] Visit: 04 Visit Requirements: AFTER 03 BY 30 D TO 120 D; ON HOLD On Hold Comments: would like the data for visit 03 before refining visit 04 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 NGC4993OT WFC3/IR MULTIAC IR F160W NSAMP=7, SAMP-SEQ=SPARS100 1 DEF PATTERN 2 1 CUM (2411.737 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 | ------------------------------------------------------------------------------------------------------------------------------------ NGC4993OT 1 WFC3/IR MULTIAC IR F160W 1 none none none 1 N/A CUM NGC4993OT 1 WFC3/IR MULTIAC IR F160W 2 none none none 1 N/A CUM NGC4993OT 1 WFC3/IR MULTIAC IR F160W 3 none none none 1 N/A CUM NGC4993OT 1 WFC3/IR MULTIAC IR F160W 4 none none none 1 N/A CUM 15346( 11) - 06-Dec-2018 13:49:39 - [ 11] Summary Form for Proposal 15346 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures IR, UVIS2-C1K1C-CTE ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/IR, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, MULTIACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=12, NSAMP=7, SAMP-SEQ=SPARS100 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 03 BY 30 D TO 120 D, BETWEEN 01-DEC-2017:00:00:00 AND 10-DEC-2017:00:00:00, ON HOLD , PATTERN 2 1, PATTERN 4 1, PATTERN 4 2, PATTERN 5 1, TOO RESPONSE TIME 5.0D, VISIBILITY INTERVAL 49 M ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F160W, F225W, F275W, F336W ------------------------------------------------------------------------------------------------------------------------------------ Target Names NGC4993OT ------------------------------------------------------------------------------------------------------------------------------------