18387( 3) - 17-Aug-2026 15:22:44 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 18387 Version: 3 Check-in Time: 17-Aug-2026 15:22:44 STScI Edit Number: 0 Title The origin of superluminous supernovae and their role in galaxy evolution from the first progenitor iron abundance measurements ------------------------------------------------------------------------------------ Type Cycle GO 34 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Matt Nicholl Queen's University Belfast Y CoI: Dr. Ting-Wan Chen National Central University N CoI: Dr. Fergus Cullen University of Edinburgh, Institute for N Astronomy CoI: Dr. Ryan Anthony Begley Armagh Observatory and Planetarium N CoI: Dr. Sean L. McGee University of Birmingham N CoI: Dr. Thomas Moore Space Telescope Science Institute N CoI: Mr. Dylan Magill Queen's University Belfast N CoI: Adam Smith Queen's University Belfast N CoI: Dr. Charlotte Rebecca Angus Queen's University Belfast N ------------------------------------------------------------------------------------ Abstract It is a remarkable fact of our Universe that "superluminous" supernovae (SLSNe) occur preferentially in low-luminosity galaxies, but the reason for this is not well understood. Metallicity is likely to play a role, as it effects stellar evolution directly through the wind-driving efficiency. However, all metallicity constraints to date in SLSN host galaxies have been oxygen abundances measured via gas-phase emission lines, rather than the stellar iron abundances needed for detailed progenitor modelling. This program will provide the first direct iron abundances in a pilot sample of carefully selected SLSN hosts using far-UV spectroscopy with the Cosmic Origins Spectrograph. Established methods allow us to extract the iron abundance directly from the FUV continuum between 1200-2000 Angstroms. We will combine the HST FUV spectra with ground-based oxygen abundances to measure the alpha/Fe ratio in these galaxies. We can then test a clear prediction: since it is the iron, rather than oxygen, that primarily affects stellar evolution, if metallicity is the key ingredient in forming SLSNe these galaxies should show a strong preference for low iron abundance and would appear alpha-enhanced relative to other galaxies of a similar mass. With a modest time request, this proposal provides an entirely new approach to resolve the question of why SLSNe favour dwarf galaxies, and will provide a crucial input to stellar evolution models of SLSN progenitors. ------------------------------------------------------------------------------------ Observations Description ------------------------ COS UV spectroscopy of four low-redshift SLSN host galaxies with GALEX detections. Three orbits per galaxy using G140L. Expected SNR~5-10 per pixel. Acquisition requirements for extended sources: For PTF12dam, SN2020tcw and SN2018bsz, we target the UV-brightest part of the galaxy, centering on the GALEX coordinates. For this ACQ/IMAGE should be the most effective method 18387( 3) - 17-Aug-2026 15:22:44 - [ 2] For SN2017egm, the explosion did not occur in the brightest part of the galaxy. In this case we do not want to recentre to point at the brightest UV pixels. However, the light profile is relatively smooth around the SN location, and obtaining a spectrum centred with ~1 arcsecond of the quoted coordinates is sufficient. ------------------------------------------------------------------------------------ 18387( 3) - 17-Aug-2026 15:22:44 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 PTF12DAM-HOS GALAXY, DWARF COMPACT, RA=14H24M46.2129S +/- 0.05", J2000 V = 19 GALEX FUV = 20.1 T STARBURST DEC=+46D13'48.66" +/- 0.05" Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 2 SN2020TCW-HO GALAXY, DWARF COMPACT, RA=15H28M17.1792S +/- 0.05", J2000 V = 19 GALEX FUV = 19.2 ST STARBURST DEC=+39D56'50.57" +/- 0.05" Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 3 SN2017EGM-HO GALAXY, SPIRAL, STAR RA=10H19M5.6201S +/- 0.05", J2000 V = 14.3 GALEX FUV = 16.2 (integrated) ST FORMING REGION DEC=+46D27'14.08" +/- 0.05" Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 4 SN2018BSZ-HO GALAXY, DWARF COMPACT, RA=16H09M38.9189S +/- 0.05", J2000 V = 16 GALEX FUV = 19.2 ST STAR FORMING REGION DEC=-32D03'42.48" +/- 0.05" Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 5 SN2017EGM-HO GALAXY, NUCLEUS RA=10H19M5.1274S +/- 0.01", J2000 V = 14.3 GALEX FUV = 16.2 (integrated) ST-OFFSET DEC=+46D27'14.69" +/- 0.01" Reference Frame: ICRS Extended: YES ------------------------------------------------------------------------------------------------------------------------------------ 18387( 3) - 17-Aug-2026 15:22:44 - [ 4] Visit: 01 Visit Requirements: 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 PTF12DAM-HO COS/NUV ACQ/IMA PSA MIRRORA 1 100 S (100 ST GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 PTF12DAM-HO COS/FUV TIME-TA PSA G140L 1105 FP-POS=1, LIFETIME-POS=LP11, 1 1000 S ST G BUFFER-TIME=9500 see below (1591 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 PTF12DAM-HO COS/FUV TIME-TA PSA G140L 1105 FP-POS=2, LIFETIME-POS=LP11, 1 300 S ST G BUFFER-TIME=9500 see below (391 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 PTF12DAM-HO COS/FUV TIME-TA PSA G140L 1105 FP-POS=2, LIFETIME-POS=LP11, 1 1300 S ST G BUFFER-TIME=9500 see below (1226 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 PTF12DAM-HO COS/FUV TIME-TA PSA G140L 1105 FP-POS=3, LIFETIME-POS=LP11, 1 1300 S ST G BUFFER-TIME=9500 see below (1226 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 PTF12DAM-HO COS/FUV TIME-TA PSA G140L 1105 FP-POS=3, LIFETIME-POS=LP11, 1 500 S ST G BUFFER-TIME=9500 see below (631 S) ------------------------------------------------------------------------------------------------------------------------------------ 7 PTF12DAM-HO COS/FUV TIME-TA PSA G140L 1105 FP-POS=4, LIFETIME-POS=LP11, 1 1200 S ST G BUFFER-TIME=9500 see below (1831 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 | ------------------------------------------------------------------------------------------------------------------------------------ PTF12DAM-HOST 1 COS/NUV ACQ/IMA PSA MIRRORA none none none none 1 N/A GE PTF12DAM-HOST 2 COS/FUV TIME-TA PSA G140L 1105 none none none none 1 1591.0 S G PTF12DAM-HOST 3 COS/FUV TIME-TA PSA G140L 1105 none none none none 1 391.0 S G PTF12DAM-HOST 4 COS/FUV TIME-TA PSA G140L 1105 none none none none 2 1226.0 S G 18387( 3) - 17-Aug-2026 15:22:44 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ PTF12DAM-HOST 5 COS/FUV TIME-TA PSA G140L 1105 none none none none 2 1226.0 S G PTF12DAM-HOST 6 COS/FUV TIME-TA PSA G140L 1105 none none none none 3 631.0 S G PTF12DAM-HOST 7 COS/FUV TIME-TA PSA G140L 1105 none none none none 3 1831.0 S G 18387( 3) - 17-Aug-2026 15:22:44 - [ 6] Visit: 02 Visit Requirements: 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 SN2020TCW-H COS/NUV ACQ/IMA PSA MIRRORA 1 100 S (100 OST GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SN2020TCW-H COS/FUV TIME-TA PSA G140L 1105 FP-POS=1, LIFETIME-POS=LP11, 1 1000 S OST G BUFFER-TIME=9500 see below (1582 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SN2020TCW-H COS/FUV TIME-TA PSA G140L 1105 FP-POS=2, LIFETIME-POS=LP11, 1 300 S OST G BUFFER-TIME=9500 see below (382 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 SN2020TCW-H COS/FUV TIME-TA PSA G140L 1105 FP-POS=2, LIFETIME-POS=LP11, 1 1300 S OST G BUFFER-TIME=9500 see below (1216 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 SN2020TCW-H COS/FUV TIME-TA PSA G140L 1105 FP-POS=3, LIFETIME-POS=LP11, 1 1300 S OST G BUFFER-TIME=9500 see below (1216 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 SN2020TCW-H COS/FUV TIME-TA PSA G140L 1105 FP-POS=3, LIFETIME-POS=LP11, 1 500 S OST G BUFFER-TIME=9500 see below (621 S) ------------------------------------------------------------------------------------------------------------------------------------ 7 SN2020TCW-H COS/FUV TIME-TA PSA G140L 1105 FP-POS=4, LIFETIME-POS=LP11, 1 1200 S OST G BUFFER-TIME=9500 see below (1821 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN2020TCW-HOST 1 COS/NUV ACQ/IMA PSA MIRRORA none none none none 1 N/A GE SN2020TCW-HOST 2 COS/FUV TIME-TA PSA G140L 1105 none none none none 1 1582.0 S G SN2020TCW-HOST 3 COS/FUV TIME-TA PSA G140L 1105 none none none none 1 382.0 S G SN2020TCW-HOST 4 COS/FUV TIME-TA PSA G140L 1105 none none none none 2 1216.0 S G 18387( 3) - 17-Aug-2026 15:22:44 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN2020TCW-HOST 5 COS/FUV TIME-TA PSA G140L 1105 none none none none 2 1216.0 S G SN2020TCW-HOST 6 COS/FUV TIME-TA PSA G140L 1105 none none none none 3 621.0 S G SN2020TCW-HOST 7 COS/FUV TIME-TA PSA G140L 1105 none none none none 3 1821.0 S G 18387( 3) - 17-Aug-2026 15:22:44 - [ 8] Visit: 03 Visit Requirements: 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 SN2017EGM-H COS/NUV ACQ/IMA PSA MIRRORB 1 100 S (100 OST-OFFSET GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SN2017EGM-H COS/FUV TIME-TA PSA G140L 1105 FP-POS=1, LIFETIME-POS=LP11, 1 1000 S OST G BUFFER-TIME=9500 see below (1591 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SN2017EGM-H COS/FUV TIME-TA PSA G140L 1105 FP-POS=2, LIFETIME-POS=LP11, 1 300 S OST G BUFFER-TIME=9500 see below (391 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 SN2017EGM-H COS/FUV TIME-TA PSA G140L 1105 FP-POS=2, LIFETIME-POS=LP11, 1 1300 S OST G BUFFER-TIME=9500 see below (1226 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 SN2017EGM-H COS/FUV TIME-TA PSA G140L 1105 FP-POS=3, LIFETIME-POS=LP11, 1 1300 S OST G BUFFER-TIME=9500 see below (1226 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 SN2017EGM-H COS/FUV TIME-TA PSA G140L 1105 FP-POS=3, LIFETIME-POS=LP11, 1 500 S OST G BUFFER-TIME=9500 see below (631 S) ------------------------------------------------------------------------------------------------------------------------------------ 7 SN2017EGM-H COS/FUV TIME-TA PSA G140L 1105 FP-POS=4, LIFETIME-POS=LP11, 1 1200 S OST G BUFFER-TIME=9500 see below (1831 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN2017EGM-HOST-OFFS 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A ET GE SN2017EGM-HOST 2 COS/FUV TIME-TA PSA G140L 1105 none none none none 1 1591.0 S G SN2017EGM-HOST 3 COS/FUV TIME-TA PSA G140L 1105 none none none none 1 391.0 S G SN2017EGM-HOST 4 COS/FUV TIME-TA PSA G140L 1105 none none none none 2 1226.0 S G 18387( 3) - 17-Aug-2026 15:22:44 - [ 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN2017EGM-HOST 5 COS/FUV TIME-TA PSA G140L 1105 none none none none 2 1226.0 S G SN2017EGM-HOST 6 COS/FUV TIME-TA PSA G140L 1105 none none none none 3 631.0 S G SN2017EGM-HOST 7 COS/FUV TIME-TA PSA G140L 1105 none none none none 3 1831.0 S G 18387( 3) - 17-Aug-2026 15:22:44 - [ 10] Visit: 04 Visit Requirements: 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 SN2018BSZ-H COS/NUV ACQ/IMA PSA MIRRORA 1 100 S (100 OST GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SN2018BSZ-H COS/FUV TIME-TA PSA G140L 1105 FP-POS=1, LIFETIME-POS=LP11, 1 1000 S OST G BUFFER-TIME=9500 see below (1579 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SN2018BSZ-H COS/FUV TIME-TA PSA G140L 1105 FP-POS=2, LIFETIME-POS=LP11, 1 300 S OST G BUFFER-TIME=9500 see below (379 S) ------------------------------------------------------------------------------------------------------------------------------------ 4 SN2018BSZ-H COS/FUV TIME-TA PSA G140L 1105 FP-POS=2, LIFETIME-POS=LP11, 1 1300 S OST G BUFFER-TIME=9500 see below (1214 S) ------------------------------------------------------------------------------------------------------------------------------------ 5 SN2018BSZ-H COS/FUV TIME-TA PSA G140L 1105 FP-POS=3, LIFETIME-POS=LP11, 1 1300 S OST G BUFFER-TIME=9500 see below (1214 S) ------------------------------------------------------------------------------------------------------------------------------------ 6 SN2018BSZ-H COS/FUV TIME-TA PSA G140L 1105 FP-POS=3, LIFETIME-POS=LP11, 1 500 S OST G BUFFER-TIME=9500 see below (619 S) ------------------------------------------------------------------------------------------------------------------------------------ 7 SN2018BSZ-H COS/FUV TIME-TA PSA G140L 1105 FP-POS=4, LIFETIME-POS=LP11, 1 1200 S OST G BUFFER-TIME=9500 see below (1819 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN2018BSZ-HOST 1 COS/NUV ACQ/IMA PSA MIRRORA none none none none 1 N/A GE SN2018BSZ-HOST 2 COS/FUV TIME-TA PSA G140L 1105 none none none none 1 1579.0 S G SN2018BSZ-HOST 3 COS/FUV TIME-TA PSA G140L 1105 none none none none 1 379.0 S G SN2018BSZ-HOST 4 COS/FUV TIME-TA PSA G140L 1105 none none none none 2 1214.0 S G 18387( 3) - 17-Aug-2026 15:22:44 - [ 11] 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 | ------------------------------------------------------------------------------------------------------------------------------------ SN2018BSZ-HOST 5 COS/FUV TIME-TA PSA G140L 1105 none none none none 2 1214.0 S G SN2018BSZ-HOST 6 COS/FUV TIME-TA PSA G140L 1105 none none none none 3 619.0 S G SN2018BSZ-HOST 7 COS/FUV TIME-TA PSA G140L 1105 none none none none 3 1819.0 S G 18387( 3) - 17-Aug-2026 15:22:44 - [ 12] Summary Form for Proposal 18387 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ/IMAGE, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=9500, FP-POS=1, FP-POS=2, FP-POS=3, FP-POS=4, LIFETIME-POS=LP11 ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140L, MIRRORA, MIRRORB ------------------------------------------------------------------------------------------------------------------------------------ Target Names PTF12DAM-HOST, SN2017EGM-HOST, SN2017EGM-HOST-OFFSET, SN2018BSZ-HOST, SN2020TCW-HOST ------------------------------------------------------------------------------------------------------------------------------------