17899( 3) - 09-Jan-2025 14:21:27 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 17899 Version: 3 Check-in Time: 09-Jan-2025 14:21:27 STScI Edit Number: 0 Title Unmasking the central engine in a Cow-like transient with XMM, VLT, CXO and HST ------------------------------------------------------------------------------------ Type Cycle GO 32 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Ashley Chrimes European Space Agency - ESTEC Y CoI: Prof. Peter G. Jonker Radboud Universiteit Nijmegen N CoI: Prof. Andrew James Levan Radboud Universiteit Nijmegen N CoI: Dr. Deanne Coppejans Northwestern University N CoI: Prof. Paul J. Groot Radboud Universiteit Nijmegen N CoI: Dr. Anne Inkenhaag University of Bath N ------------------------------------------------------------------------------------ Abstract Luminous Fast Blue Optical Transients (LFBOTs, or Cow-like transients, after the prototypical AT2018cow) are characterised by luminous multi-wavelength emission, blue optical colours and rapid evolution that is inconsistent with Ni56-powered supernovae (SNe). Although the number of LFBOTs is growing thanks to high-cadence, deep and wide-field surveys, detailed studies of individual events are lacking. These are necessary to determine the central engine and progenitor. We propose a joint programme, utilising XMM- Newton, the Very Large Telescope (VLT), Chandra X-ray Observatory (CXO) and Hubble Space Telescope (HST) to firmly identify a single, low redshift LFBOT and to determine the nature of its central engine. We will monitor the long-timescale X-ray/UV light-curve, measure short-timescale X-ray variability and use environmental clues to distinguish between neutron star, stellar mass and intermediate mass black holes as the power source - placing the strongest constraints yet on the progenitors of these puzzling events. ------------------------------------------------------------------------------------ Observations Description ------------------------ Two orbits (2 epochs, non-disruptive ToOs, 1 orbit per epoch) of HST/WFC3 imaging to pinpoint the transient location, determine the host galaxy morphology, and to follow the UV light-curve up to 3-4 months post-explosion. The first epoch will be at ~25 days. The second epoch, at ~3-4 months, will enable us to follow the lightcurve as it starts to plateau (assuming AT2018cow-like behaviour). Even if not, we will obtain an unobstructed view of the environment directly under the transient. Difference imaging between epochs 1 and 2 will reveal the precise location within the host, and along with the early-time XMM/OM UV data, we will obtain a UV light-curve spanning 3-4 months and several magnitudes in luminosity. In each 20-min (half-orbit) observation we will reach m(F275W)=26 and m(F555W)=26.5 (AB) for SNR= 5 point source detections. A Cow-like event at z = 0.1 would have m(UV)~22 (26) at ~30 days (3-4 months). ------------------------------------------------------------------------------------ 17899( 3) - 09-Jan-2025 14:21:27 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 NEW-LFBOT STAR, GAMMA RAY RA=00H00M0.0000S, J2000 V = 25 BURSTER, SUPERNOVA, DEC=+00D00'0.00" SUPERNOVA TYPE IB, X-RAY TRANSIENT Reference Frame: ICRS Extended: NO Comments: Coordinates and magnitude unknown in advance. ------------------------------------------------------------------------------------------------------------------------------------ 17899( 3) - 09-Jan-2025 14:21:27 - [ 3] TARGET LIST Generic Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Selection Criteria | Flux data No | Name | Description | | ------------------------------------------------------------------------------------------------------------------------------------ 2 PLACEHOLDER- STAR, SUPERNOVA NEWLY DISCOVERED LFBOT V = 25 LFBOT ------------------------------------------------------------------------------------------------------------------------------------ 17899( 3) - 09-Jan-2025 14:21:27 - [ 4] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 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 ------------------------------------------------------------------------------------------------------------------------------------ 17899( 3) - 09-Jan-2025 14:21:27 - [ 5] Visit: 01 (Epoch 1) Visit Requirements: TOO RESPONSE TIME 25.0D 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 PLACEHOLDER WFC3/UVI ACCUM UVIS2-C1K F275W FLASH=16 1 354 S PATTERN 1 1 -LFBOT S 1C-SUB (1062 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 PLACEHOLDER WFC3/UVI ACCUM UVIS2-C1K F555W FLASH=7 1 354 S PATTERN 1 2 -LFBOT S 1C-SUB (1062 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 | ------------------------------------------------------------------------------------------------------------------------------------ PLACEHOLDER-LFBOT 1 WFC3/UVI ACCUM UVIS2-C1 F275W 1 none none none 1 N/A S K1C-SUB PLACEHOLDER-LFBOT 1 WFC3/UVI ACCUM UVIS2-C1 F275W 2 none none none 1 N/A S K1C-SUB PLACEHOLDER-LFBOT 1 WFC3/UVI ACCUM UVIS2-C1 F275W 3 none none none 1 N/A S K1C-SUB PLACEHOLDER-LFBOT 2 WFC3/UVI ACCUM UVIS2-C1 F555W 1 none none none 1 N/A S K1C-SUB PLACEHOLDER-LFBOT 2 WFC3/UVI ACCUM UVIS2-C1 F555W 2 none none none 1 N/A S K1C-SUB PLACEHOLDER-LFBOT 2 WFC3/UVI ACCUM UVIS2-C1 F555W 3 none none none 1 N/A S K1C-SUB 17899( 3) - 09-Jan-2025 14:21:27 - [ 6] Visit: 02 (Epoch 2) Visit Requirements: AFTER 01 BY 60.0 D TO 365.0 D; ON HOLD FOR 01; TOO RESPONSE TIME 90.0D On Hold Comments: To be excuted >~2 months after visit 01. 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 PLACEHOLDER WFC3/UVI ACCUM UVIS2-C1K F275W FLASH=16 1 354 S PATTERN 1 1 -LFBOT S 1C-SUB (1062 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 PLACEHOLDER WFC3/UVI ACCUM UVIS2-C1K F555W FLASH=7 1 354 S PATTERN 1 2 -LFBOT S 1C-SUB (1062 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 | ------------------------------------------------------------------------------------------------------------------------------------ PLACEHOLDER-LFBOT 1 WFC3/UVI ACCUM UVIS2-C1 F275W 1 none none none 1 N/A S K1C-SUB PLACEHOLDER-LFBOT 1 WFC3/UVI ACCUM UVIS2-C1 F275W 2 none none none 1 N/A S K1C-SUB PLACEHOLDER-LFBOT 1 WFC3/UVI ACCUM UVIS2-C1 F275W 3 none none none 1 N/A S K1C-SUB PLACEHOLDER-LFBOT 2 WFC3/UVI ACCUM UVIS2-C1 F555W 1 none none none 1 N/A S K1C-SUB PLACEHOLDER-LFBOT 2 WFC3/UVI ACCUM UVIS2-C1 F555W 2 none none none 1 N/A S K1C-SUB PLACEHOLDER-LFBOT 2 WFC3/UVI ACCUM UVIS2-C1 F555W 3 none none none 1 N/A S K1C-SUB 17899( 3) - 09-Jan-2025 14:21:27 - [ 7] Summary Form for Proposal 17899 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS2-C1K1C-SUB ------------------------------------------------------------------------------------------------------------------------------------ Configurations WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters FLASH=16, FLASH=7 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 01 BY 60.0 D TO 365.0 D, ON HOLD FOR 01, PATTERN 1 1, PATTERN 1 2, TOO RESPONSE TIME 25.0D, TOO RESPONSE TIME 90.0D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements F275W, F555W ------------------------------------------------------------------------------------------------------------------------------------ Target Names PLACEHOLDER-LFBOT ------------------------------------------------------------------------------------------------------------------------------------