17477( 6) - 07-Oct-2024 18:25:53 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17477 Version: 6 Check-in Time: 07-Oct-2024 18:25:53 STScI Edit Number: 1 Title HST Spectroscopy of a Fast-Rising Luminous Ultraviolet Transient ------------------------------------------------------------------------------------ Type Cycle GO 31 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Daniel Perley Liverpool John Moores University Y CoI: Dr. Lin Yan California Institute of Technology N CoI: Anna Yen Qin Ho Cornell University N CoI: Prof. Shrinivas R. Kulkarni California Institute of Technology N CoI: Dr. Christoffer Fremling California Institute of Technology N CoI: Dr. Ragnhild Lunnan Stockholm University N ------------------------------------------------------------------------------------ Abstract High-cadence time-domain surveys have unveiled a population of fast-evolving, luminous extragalactic transients with SEDs that remain dominated by ultraviolet emission for long after peak and also exhibit luminous X-ray and radio counterparts. While they show some observational similarities with strongly-interacting supernovae, optical follow-up has failed to identify any recognizable supernova features and the extreme properties of these events strain theoretical models for what is possible in a supernova explosion. Ultraviolet spectroscopy has the power to reveal similarities or differences betwen this event and other supernova classes not apparent from optical observations alone, and offers a means of identifying the progenitor star via transmission spectroscopy of the dense stellar wind before the explosion sweeps it up. We propose to obtain target-of-opportunity UV spectroscopy of a new event of this type in Cycle 31 or 32 to secure the physical origins of this class while HST's unique UV spectroscopic resource is still available. ------------------------------------------------------------------------------------ Observations Description ------------------------ Our objective is to carry out low-resolution FUV and NUV spectroscopy of a fast-luminous UV transient with COS (G140L) and STIS (G230L). Fast turnaround is helpful for many reasons - both to optimize the S/N (the target will not be bright) and to decrease the risk of acquisition failure if the target's UV flux evolution is different than expected. A turnaround of up to 1 week is acceptable, although for a sufficiently nearby event we may accept a longer delay. Using fewer guide stars may be acceptable to achieve faster turnaround. It is desirable in principle to obtain the COS and STIS observations close in time to each other but observing sooner in one band will almost always be preferred if the option is available. Rapid two-way communication with STScI will be necessary to correctly configure the observations and perform all safety checks to ensure a successful acquisition. The PI's mobile number is +44 745 6339330 and can be contacted 24 hours a day. ------------------------------------------------------------------------------------ 17477( 6) - 07-Oct-2024 18:25:53 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 2 AT2024WPP STAR, SUPERNOVA, X-RAY RA=02H42M5.4850S +/- 0.35", J2000 Z = V = 19 UVM2 = 19.8 (AB, expected) TRANSIENT DEC=-16D57'23.04" +/- 0.35" 0.0868 Reference Frame: ICRS Extended: NO Comments: This is a projection of the magnitude based on information available as of October 4th. The source is evolving, and updated/improved estimates can be provided later. Epoch of Position RA proper motion (seconds of time/yr) DEC Proper Motion (arcsec/yr) Annual Parallax (arcsec) 2000 0.0 0.0 0.0 ------------------------------------------------------------------------------------------------------------------------------------ 17477( 6) - 07-Oct-2024 18:25:53 - [ 3] TARGET LIST Generic Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Selection Criteria | Flux data No | Name | Description | | ------------------------------------------------------------------------------------------------------------------------------------ 1 TOO STAR, SUPERNOVA FAST RISE (<3 DAYS) TO HIGH V = 19 +/- 2 LUMINOSITY (M ~ -20) WITHOUT COOLING Comments: The target will be identified from ZTF or potentially another high-cadence optical survey. The trigger will be submitted at or after peak and there will be a clear upper limit on the flux of the target based on this. The source will probably be close to V=18.5, UV=17.5 mag at peak (AB). The source is expected to fade rapidly after peak, but this is difficult to project. The target is a point source and we expect it will be brighter than its host galaxy (in UV) but will confirm at the time of triggering. ------------------------------------------------------------------------------------------------------------------------------------ 17477( 6) - 07-Oct-2024 18:25:53 - [ 4] Visit: 01 (COS FUV spectrum) Visit Requirements: TOO RESPONSE TIME 4.0D 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 AT2024WPP COS/NUV ACQ/IMA PSA MIRRORB 1 280 S (280 GE S) Comments: MirrorB acquisition strategy. ------------------------------------------------------------------------------------------------------------------------------------ 2 AT2024WPP COS/FUV TIME-TA PSA G140L 1105 FLASH=YES, BUFFER-TIME=6400, 1 1000 S G FP-POS=ALL see below (4104 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 | ------------------------------------------------------------------------------------------------------------------------------------ AT2024WPP 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE AT2024WPP 2 COS/FUV TIME-TA PSA G140L 1105 none none none 1 1 820.0 S G AT2024WPP 2 COS/FUV TIME-TA PSA G140L 1105 none none none 2 1 820.0 S G AT2024WPP 2 COS/FUV TIME-TA PSA G140L 1105 none none none 3 2 1232.0 S G AT2024WPP 2 COS/FUV TIME-TA PSA G140L 1105 none none none 4 2 1232.0 S G 17477( 6) - 07-Oct-2024 18:25:53 - [ 5] Visit: 02 (COS FUV spectrum) Visit Requirements: TOO RESPONSE TIME 4.0D 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 AT2024WPP COS/NUV ACQ/IMA PSA MIRRORA 1 180 S (180 GE S) Comments: MirrorA acquisition strategy. ------------------------------------------------------------------------------------------------------------------------------------ 2 AT2024WPP COS/FUV TIME-TA PSA G140L 1105 FLASH=YES, BUFFER-TIME=6400, 1 1000 S G FP-POS=ALL see below (4304 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 | ------------------------------------------------------------------------------------------------------------------------------------ AT2024WPP 1 COS/NUV ACQ/IMA PSA MIRRORA none none none none 1 N/A GE AT2024WPP 2 COS/FUV TIME-TA PSA G140L 1105 none none none 1 1 920.0 S G AT2024WPP 2 COS/FUV TIME-TA PSA G140L 1105 none none none 2 1 920.0 S G AT2024WPP 2 COS/FUV TIME-TA PSA G140L 1105 none none none 3 2 1232.0 S G AT2024WPP 2 COS/FUV TIME-TA PSA G140L 1105 none none none 4 2 1232.0 S G 17477( 6) - 07-Oct-2024 18:25:53 - [ 6] Visit: 03 (STIS NUV spectrum) Visit Requirements: TOO RESPONSE TIME 4.0D 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 AT2024WPP STIS/CCD ACQ 50CCD MIRROR 1 60 S (60 S) Comments: Updated to use 50CCD acquisition aperture in case the target is fainter than anticipated. ------------------------------------------------------------------------------------------------------------------------------------ 2 AT2024WPP STIS/NUV TIME-TA 52X0.2 G230L 2376 BUFFER-TIME=663 1 2100 S -MAMA G see below (1859 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 AT2024WPP STIS/NUV TIME-TA 52X0.2 G230L 2376 BUFFER-TIME=663 1 2100 S -MAMA G see below (2615 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 | ------------------------------------------------------------------------------------------------------------------------------------ AT2024WPP 1 STIS/CCD ACQ 50CCD MIRROR none none none none 1 N/A AT2024WPP 2 STIS/NUV TIME-TA 52X0.2 G230L 2376 none none none none 1 1859.0 S -MAMA G AT2024WPP 3 STIS/NUV TIME-TA 52X0.2 G230L 2376 none none none none 2 2615.0 S -MAMA G 17477( 6) - 07-Oct-2024 18:25:53 - [ 7] Summary Form for Proposal 17477 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 50CCD, 52X0.2, PSA ------------------------------------------------------------------------------------------------------------------------------------ Configurations COS/FUV, COS/NUV, STIS/CCD, STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACQ, ACQ/IMAGE, TIME-TAG ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters BUFFER-TIME=6400, BUFFER-TIME=663, FLASH=YES, FP-POS=ALL ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements TOO RESPONSE TIME 4.0D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140L, G230L, MIRROR, MIRRORA, MIRRORB ------------------------------------------------------------------------------------------------------------------------------------ Target Names AT2024WPP ------------------------------------------------------------------------------------------------------------------------------------