16212( 10) - 16-Feb-2021 14:37:10 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 16212 Version: 10 Check-in Time: 16-Feb-2021 14:37:10 STScI Edit Number: 4 Title HST Spectroscopy of a Fast-Rising Luminous Ultraviolet Transient ------------------------------------------------------------------------------------ Type Cycle GO 28 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Daniel Perley Liverpool John Moores University Y CoI: Anna Yen Qin Ho California Institute of Technology N CoI: Prof. Shrinivas R. Kulkarni California Institute of Technology N CoI: Dr. Lin Yan California Institute of Technology N CoI: Prof. Robert M. Quimby San Diego State University N CoI: Dr. Ragnhild Lunnan Stockholm University N CoI: Dr. Christoffer Fremling California Institute of Technology N ------------------------------------------------------------------------------------ Abstract The extremely luminous, fast, hot transient AT2018cow has provoked a reconsideration in our view of the transient sky. This event, by far the nearest example of the class of fast-rising luminous transients (sometimes referred to as FBOTs or FELTs), displayed an array of peculiar properties that highly strain theoretical models for what is possible in a supernova explosion. For all their peculiarities, however, fast-rising transients are not rare in a volumetric sense - and with ZTF and ATLAS both obtaining high-cadence observations of wide areas of the northern sky it is probable that another such event will be observed in the coming year. These are primarily ultraviolet phenomena, and UV spectroscopy has the power to reveal similarities or differences betwen this event and other known varieties of transient (including young CCSNe, superluminous SNe, and TDEs) that are not apparent in optical observations alone, and to discover (or rule out) the presence of a dense stellar wind around the progenitor. We propose to obtain target-of-opportunity UV spectroscopy of another event of this type in Cycle 28 to critically evaluate these links and secure the physical origins of this class while HST's unique UV spectroscopic resource is still available. ------------------------------------------------------------------------------------ Observations Description ------------------------ This is a target of opportunity UV spectroscopy proposal that requires as fast turnaround as possible (but not an ultra-rapid response). Selection will be based on ground-based observations and we will supply a precise coordinate for the target as soon as possible. Observations will be requested in the COS/G140L and STIS/G230L grisms. Our nominal plan is to obtain two epochs separated by 1-2 week, although this may depend on the actual brightness and evolution of the target. ------------------------------------------------------------------------------------ 16212( 10) - 16-Feb-2021 14:37:10 - [ 2] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 2 ZTF21AAKILYD EXT-STAR, SUPERNOVA RA=14H26M22.1220S +/- 0.3", J2000 Z = V = 18 u=17.5 DEC=+05D51'33.26" +/- 0.3" 0.081 Reference Frame: ICRS Extended: NO ------------------------------------------------------------------------------------------------------------------------------------ 16212( 10) - 16-Feb-2021 14:37:10 - [ 3] TARGET LIST Generic Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Selection Criteria | Flux data No | Name | Description | | ------------------------------------------------------------------------------------------------------------------------------------ 1 TOO EXT-STAR, SUPERNOVA A FAST-RISING, VERY LUMINOUS, HOT V = 18.5 +/- 1.5 THERMAL TRANSIENT. Comments: The target is unknown and will be discovered shortly before we request the observations. We will know the optical brightness and will have strong constraints (and by the time of observation, measurements) on the UV brightness as well. Our selection criteria are a fast rise (less than about 3 days from half-peak to peak), a high luminosity (M_UV ~< -20 in the UV), and a very high temperature (>15000 from UV/optical colors). ------------------------------------------------------------------------------------------------------------------------------------ 16212( 10) - 16-Feb-2021 14:37:10 - [ 4] Visit: 01 (COS spectrum visit 1) Visit Requirements: ON HOLD ; TOO RESPONSE TIME 4.0D On Hold Comments: Target of opportunity awaiting a suitable trigger from ZTF or another survey. The prototypical event of this class faded by 0.25 mag/day, so sooner is always better. A response slower than 4 days may be acceptable depending on the initial brightness of the event. This observation should take place as close in time as possible to the STIS observation. Additional Comments: Exposure times will need to be changed depending on the visibility duration of the actual target at the time of trigger. 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 ZTF21AAKILY COS/NUV ACQ/IMA PSA MIRRORB 1 120 S (120 D GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ZTF21AAKILY COS/FUV TIME-TA PSA G140L 1105 FLASH=YES, BUFFER-TIME=6400, 1 460 S D G FP-POS=ALL see below (1872 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 ZTF21AAKILY COS/FUV TIME-TA PSA G140L 1105 FLASH=YES, BUFFER-TIME=6400, 1 460 S D G FP-POS=ALL see below (2372 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 | ------------------------------------------------------------------------------------------------------------------------------------ ZTF21AAKILYD 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE ZTF21AAKILYD 2 COS/FUV TIME-TA PSA G140L 1105 none none none 1 1 468.0 S G ZTF21AAKILYD 2 COS/FUV TIME-TA PSA G140L 1105 none none none 2 1 468.0 S G ZTF21AAKILYD 2 COS/FUV TIME-TA PSA G140L 1105 none none none 3 1 468.0 S G ZTF21AAKILYD 2 COS/FUV TIME-TA PSA G140L 1105 none none none 4 1 468.0 S G ZTF21AAKILYD 3 COS/FUV TIME-TA PSA G140L 1105 none none none 1 2 593.0 S G ZTF21AAKILYD 3 COS/FUV TIME-TA PSA G140L 1105 none none none 2 2 593.0 S G ZTF21AAKILYD 3 COS/FUV TIME-TA PSA G140L 1105 none none none 3 2 593.0 S G ZTF21AAKILYD 3 COS/FUV TIME-TA PSA G140L 1105 none none none 4 2 593.0 S G 16212( 10) - 16-Feb-2021 14:37:10 - [ 5] Visit: 02 (STIS spectrum visit 1) Visit Requirements: ON HOLD ; TOO RESPONSE TIME 4.0D On Hold Comments: Target of opportunity awaiting a suitable trigger from ZTF or another survey. The prototypical event of this class faded by 0.25 mag/day, so sooner is always better. A response slower than 4 days may be acceptable depending on the initial brightness of the event. This observation should take place as close in time as possible to the COS observation. Additional Comments: Exposure times will need to be changed depending on the visibility duration of the actual target at the time of trigger. 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 ZTF21AAKILY STIS/CCD ACQ F28X50LP MIRROR 1 30 S (30 GS ACQ SCENARIO SINGLE D S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ZTF21AAKILY STIS/NUV TIME-TA 52X0.2 G230L 2376 BUFFER-TIME=663 1 2100 S D -MAMA G (2100 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 | ------------------------------------------------------------------------------------------------------------------------------------ ZTF21AAKILYD 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A ZTF21AAKILYD 2 STIS/NUV TIME-TA 52X0.2 G230L 2376 none none none none 1 N/A -MAMA G 16212( 10) - 16-Feb-2021 14:37:10 - [ 6] Visit: 03 (COS spectrum visit 2) Visit Requirements: AFTER 01 BY 2 D TO 16 D; ON HOLD ; TOO RESPONSE TIME 4.0D On Hold Comments: Target of opportunity awaiting a suitable trigger from ZTF or another survey. This is a follow-up spectrum to be executed approximately 1-2 weeks after the first. Depending on the brightness and nature of evolution of the actual target we may wish to change the timescale. 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 ZTF21AAKILY COS/NUV ACQ/IMA PSA MIRRORB 1 240 S (240 D GE S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ZTF21AAKILY COS/FUV TIME-TA PSA G140L 1105 FLASH=YES, BUFFER-TIME=6400, 1 460 S D G FP-POS=ALL see below (1632 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 ZTF21AAKILY COS/FUV TIME-TA PSA G140L 1105 FLASH=YES, BUFFER-TIME=6400, 1 460 S D G FP-POS=ALL see below (2372 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 | ------------------------------------------------------------------------------------------------------------------------------------ ZTF21AAKILYD 1 COS/NUV ACQ/IMA PSA MIRRORB none none none none 1 N/A GE ZTF21AAKILYD 2 COS/FUV TIME-TA PSA G140L 1105 none none none 1 1 408.0 S G ZTF21AAKILYD 2 COS/FUV TIME-TA PSA G140L 1105 none none none 2 1 408.0 S G ZTF21AAKILYD 2 COS/FUV TIME-TA PSA G140L 1105 none none none 3 1 408.0 S G ZTF21AAKILYD 2 COS/FUV TIME-TA PSA G140L 1105 none none none 4 1 408.0 S G ZTF21AAKILYD 3 COS/FUV TIME-TA PSA G140L 1105 none none none 1 2 593.0 S G ZTF21AAKILYD 3 COS/FUV TIME-TA PSA G140L 1105 none none none 2 2 593.0 S G ZTF21AAKILYD 3 COS/FUV TIME-TA PSA G140L 1105 none none none 3 2 593.0 S G ZTF21AAKILYD 3 COS/FUV TIME-TA PSA G140L 1105 none none none 4 2 593.0 S G 16212( 10) - 16-Feb-2021 14:37:10 - [ 7] Visit: 04 (STIS spectrum visit 2) Visit Requirements: SCHED 70%; AFTER 02 BY 2 D TO 16 D; ON HOLD ; TOO RESPONSE TIME 4.0D On Hold Comments: Target of opportunity awaiting a suitable trigger from ZTF or another survey. This is a follow-up spectrum to be executed approximately 1-2 weeks after the first. Depending on the brightness and nature of evolution of the actual target we may wish to change the timescale. 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 ZTF21AAKILY STIS/CCD ACQ F28X50LP MIRROR 1 45 S (45 GS ACQ SCENARIO SINGLE D S) ------------------------------------------------------------------------------------------------------------------------------------ 2 ZTF21AAKILY STIS/NUV TIME-TA 52X0.2 G230L 2376 BUFFER-TIME=663 1 2100 S D -MAMA G see below (2030 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 | ------------------------------------------------------------------------------------------------------------------------------------ ZTF21AAKILYD 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A ZTF21AAKILYD 2 STIS/NUV TIME-TA 52X0.2 G230L 2376 none none none none 1 2030.0 S -MAMA G 16212( 10) - 16-Feb-2021 14:37:10 - [ 8] Summary Form for Proposal 16212 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 52X0.2, F28X50LP, 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 AFTER 01 BY 2 D TO 16 D, AFTER 02 BY 2 D TO 16 D, GS ACQ SCENARIO SINGLE, ON HOLD , SCHED 70%, TOO RESPONSE TIME 4.0D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140L, G230L, MIRROR, MIRRORB ------------------------------------------------------------------------------------------------------------------------------------ Target Names ZTF21AAKILYD ------------------------------------------------------------------------------------------------------------------------------------