15834( 5) - 16-Jul-2020 22:22:25 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 15834 Version: 5 Check-in Time: 16-Jul-2020 22:22:25 STScI Edit Number: 0 Title UV Spectroscopic Signatures from Type Ibn Supernovae Strongly Interacting with a Circumstellar Medium ------------------------------------------------------------------------------------ Type Cycle GO 27 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Ori Dosovitz Fox Space Telescope Science Institute Y CoI: Dr. Jennifer Andrews University of Arizona N CoI: Dr. Thomas G Brink University of California - Berkeley N CoI: Dr. Peter J. Brown Texas A & M University N CoI: Dr. Roger A. Chevalier The University of Virginia N CoI: Dr. Geoffrey C. Clayton Louisiana State University and A & M N College CoI: Prof. Alex V. Filippenko University of California - Berkeley N CoI: Prof. Claes Fransson Stockholm University N CoI: Dr. Jose Groh University of Dublin, Trinity College N CoI: Dr. Griffin Hosseinzadeh Harvard University N CoI: Dr. Patrick Kelly University of Minnesota - Twin Cities N CoI: Dr. Jon Mauerhan University of California - Berkeley N CoI: Dr. Adam Miller Northwestern University N CoI: Dr. Nathan Smith University of Arizona N CoI: Dr. Tamas Szalai University of Szeged N CoI: Dr. Schuyler D. Van Dyk California Institute of Technology N CoI: Dr. WeiKang Zheng University of California - Berkeley N ------------------------------------------------------------------------------------ Abstract Type Ibn supernovae (SNe Ibn) are a rare (<1%) core-collapse SN subclass that exhibits hydrogen-poor (e.g., stripped-envelope Type Ib) spectra dominated by narrow helium features that arise from a slow-moving, pre-existing, dense circumstellar medium (CSM). Compared to other SN subclasses, the light curves tend to be brighter and rise/decline faster. These unique properties leave a number of outstanding unknowns, such as progenitor system and powering mechanism. Increasing the intrigue, SNe Ibn are now linked to an even lesser well-known set of explosions known as Fast Blue Optical Transients (FBOTs), which have been suggested to harbor tidal disruption events and/or magnetars. The UV offers an opportunity to determine the true nature of the SN Ibn subclass given its sensitivity to spectral line diagnostics that can constrain the progenitor mass-loss history and CNO processing. Yet given the low rates and fast decline of SNe Ibn (and FBOTs), UV spectroscopy is limited to just two SNe Ibn (and zero FBOTs), and these spectra are of limited use because they (a) do not extend into the far-UV and (b) are either low-resolution or low signal-to-noise ratio. Here we propose a disruptive ToO with HST/STIS to obtain 2 epochs of UV spectra of a SN Ibn within 250 Mpc. This program will not only distinguish between the Type Ibn progenitors and powering mechanisms, but will also provide clues about the nature of FBOTs. Coinciding with Cycle 27's UV Initiative, this program opens up new phase space in our study of the progenitor and explosion characteristics of the SN Ibn subclass. ------------------------------------------------------------------------------------ 15834( 5) - 16-Jul-2020 22:22:25 - [ 2] Observations Description ------------------------ We propose to obtain 2 epochs (3 orbits each) of STIS-MAMA spectra of a single Type Ibn supernova. The brightness is really the most important factor, but SNe Ibn can vary in brightness substantially (magnitudes). We offer rough guidelines of a target within 250 Mpc and as close to light-curve maximum as possible (preferably pre-max). The goal is to detect UV signatures that can distinguish between progenitor scenarios. These observations will also trace circumstellar interaction, constrain the progenitor mass loss, and identify late-time heating mechanisms for potential warm dust. The initial spectrum will be triggered as a *disruptive* ToO, and observations should be scheduled as soon as possible. The second epoch should be obtained again within 10 days (the goal is to maximize the time between the two epochs, so there may be some wiggle room depending on the brightness and evolution timeline of the SN). We will use the data to trace circumstellar interaction, constrain the progenitor mass loss, and measure the CNO processing. Comparisons to other SN and FBOT subclasses will also help distinguish between progenitor systems and central engine powering mechanisms. The first epoch will include observations in both the G140 and G230L bandpasses. The second epoch will include observations in only the G230L bandpass. We choose STIS over COS for several reasons. Most importantly, STIS offers spatially resolved spectra that exploit the intrinsically high resolution of HST over a large spectral range (accommodating both the C III] 1909 Ang and Mg II 2800 Ang lines). The long slit length will allow us to subtract contamination from zodiacal light, earthshine, the host galaxy, and H II regions. STIS also has superior sensitivity to COS in the NUV. While COS is optimized for isolated, faint point sources in the FUV with medium resolution, we would suffer from less wavelength coverage and require more integrations. We would also lose the advantages of the slit described above. ------------------------------------------------------------------------------------ 15834( 5) - 16-Jul-2020 22:22:25 - [ 3] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 2 AT2020NXT STAR, SUPERNOVA TYPE IB RA=22H37M36.2350S, J2000 V = 17 DEC=+35D00'7.66" Reference Frame: ICRS Extended: NO ------------------------------------------------------------------------------------------------------------------------------------ 15834( 5) - 16-Jul-2020 22:22:25 - [ 4] TARGET LIST Generic Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Selection Criteria | Flux data No | Name | Description | | ------------------------------------------------------------------------------------------------------------------------------------ 1 SN1 TYPE IBN WITHIN ABOUT 250 MPC AND V = 15 NEAR MAXIMUM (PREFERABLY 2 DAYS PRE-MAX). WE WOULD IDEALLY USE SWIFT TO JUSTIFY A UMVM2 (APPROXIMATELY F218W BANDPASS) OF BRIGHTER THAN -21 (OR APPARENT MAGNITUDE AROUND 16). Comments: In the case where we may not have swift observations but the Type Ibn apppears very bright in ground-based optical observations (v~15), we may also decide to trigger. ------------------------------------------------------------------------------------------------------------------------------------ 15834( 5) - 16-Jul-2020 22:22:25 - [ 5] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 1 Primary_Pattern Secondary_Pattern Pattern_Type STIS-ALONG-SLIT Pattern_Purpose DITHER Number_Of_Points 2 Point_Spacing 0.264 Line_Spacing Coordinate_Frame POS-TARG Pattern_Orient 90.0 Angle_Between_Sides Center_Pattern YES ------------------------------------------------------------------------------------------------------------------------------------ 15834( 5) - 16-Jul-2020 22:22:25 - [ 6] Visit: 01 (STIS-SNIbn1-Epoch1(FUV)) Visit Requirements: ON HOLD ; TOO RESPONSE TIME 2.0D On Hold Comments: Target-of-Opportunity. The initial spectrum will be triggered as a disruptive ToO, and observations should be scheduled as soon as possible (2-5 days as stated in the CfP). Less than 2 days could be possible since PI Fox works at STScI and has worked on ultra-rapid responses with HST planners in the past. The main goal, however, is to make sure the observations are obtained around peak, which typically happens about 3 days post-discovery. Additional Comments: Likely to acquire on bright SN. 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 AT2020NXT STIS/CCD ACQ 50CCD MIRROR 1 10 S (10 S) Comments: Used 10, 000K Blackbody normalized to V=16. SN should be bright during initial acquisition. ------------------------------------------------------------------------------------------------------------------------------------ 2 AT2020NXT STIS/NUV ACCUM 52X0.2 G230L 2376 1 2000 S -MAMA see below (1800 S) Comments: Assuming a 10, 000K Blackbody around peak. ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ AT2020NXT 1 STIS/CCD ACQ 50CCD MIRROR none none none none 1 N/A AT2020NXT 2 STIS/NUV ACCUM 52X0.2 G230L 2376 none none none none 1 1800 S -MAMA 15834( 5) - 16-Jul-2020 22:22:25 - [ 7] Visit: 02 (STIS-SNIbn1-Epoch1(FUV)) Visit Requirements: AFTER 01 BY 0 Orbits TO 1 Orbits; ON HOLD ; TOO RESPONSE TIME 2.0D On Hold Comments: Target-of-Opportunity. The initial spectrum will be triggered as a disruptive ToO, and observations should be scheduled as soon as possible (2-5 days as stated in the CfP). Less than 2 days could be possible since PI Fox works at STScI and has worked on ultra-rapid responses with HST planners in the past. The main goal, however, is to make sure the observations are obtained around peak, which typically happens about 3 days post-discovery. Additional Comments: Likely to acquire on bright SN. 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 AT2020NXT STIS/CCD ACQ 50CCD MIRROR 1 10 S (10 S) Comments: Used 10, 000K Blackbody normalized to V=16. SN should be bright during initial acquisition. ------------------------------------------------------------------------------------------------------------------------------------ 2 AT2020NXT STIS/FUV ACCUM 52X0.2D1 G140L 1425 1 2000 S -MAMA see below (1800 S) Comments: Assuming a 10, 000K Blackbody around peak. ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ AT2020NXT 1 STIS/CCD ACQ 50CCD MIRROR none none none none 1 N/A AT2020NXT 2 STIS/FUV ACCUM 52X0.2D1 G140L 1425 none none none none 1 1800 S -MAMA 15834( 5) - 16-Jul-2020 22:22:25 - [ 8] Visit: 03 (STIS-SNIbn1-Epoch1(FUV)) Visit Requirements: AFTER 02 BY 0 Orbits TO 1 Orbits; ON HOLD ; TOO RESPONSE TIME 2.0D On Hold Comments: Target-of-Opportunity. The initial spectrum will be triggered as a disruptive ToO, and observations should be scheduled as soon as possible (2-5 days as stated in the CfP). Less than 2 days could be possible since PI Fox works at STScI and has worked on ultra-rapid responses with HST planners in the past. The main goal, however, is to make sure the observations are obtained around peak, which typically happens about 3 days post-discovery. Additional Comments: Likely to acquire on bright SN. 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 AT2020NXT STIS/CCD ACQ 50CCD MIRROR 1 10 S (10 S) Comments: Used 10, 000K Blackbody normalized to V=16. SN should be bright during initial acquisition. ------------------------------------------------------------------------------------------------------------------------------------ 2 AT2020NXT STIS/FUV ACCUM 52X0.2D1 G140L 1425 1 2000 S -MAMA see below (1800 S) Comments: Assuming a 10, 000K Blackbody around peak. ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ AT2020NXT 1 STIS/CCD ACQ 50CCD MIRROR none none none none 1 N/A AT2020NXT 2 STIS/FUV ACCUM 52X0.2D1 G140L 1425 none none none none 1 1800 S -MAMA 15834( 5) - 16-Jul-2020 22:22:25 - [ 9] Visit: 04 (STIS-SNIbn1-Epoch2(FUV)) Visit Requirements: AFTER 01 BY 6 D TO 12 D; ON HOLD On Hold Comments: Target-of-Opportunity. This visit will be scheduled for 6-12 days following the first visit (as specified in the Timing Requirements), ideally aiming for 10 days. But we'd like to have some flexibility with our final submission to account for the brightness and light-curve evolution. Additional Comments: Likely to acquire on bright SN. 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 AT2020NXT STIS/CCD ACQ F28X50LP MIRROR 1 40 S (40 S) Comments: Used 10, 000K Blackbody normalized to V=16. SN should be bright during initial acquisition. ------------------------------------------------------------------------------------------------------------------------------------ 2 AT2020NXT STIS/NUV ACCUM 52X0.2 G230L 2376 1 2000 S -MAMA see below (2100 S) Comments: Assuming a 7, 000K Blackbody around 10 days post-max. ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ AT2020NXT 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A AT2020NXT 2 STIS/NUV ACCUM 52X0.2 G230L 2376 none none none none 1 2100.0 S -MAMA 15834( 5) - 16-Jul-2020 22:22:25 - [ 10] Visit: 05 (STIS-SNIbn1-Epoch2(FUV)) Visit Requirements: AFTER 04 BY 0 Orbits TO 1 Orbits; ON HOLD On Hold Comments: Target-of-Opportunity. This visit will be scheduled for 6-12 days following the first visit (as specified in the Timing Requirements), ideally aiming for 10 days. But we'd like to have some flexibility with our final submission to account for the brightness and light-curve evolution. Additional Comments: Likely to acquire on bright SN. 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 AT2020NXT STIS/CCD ACQ F28X50LP MIRROR 1 40 S (40 S) Comments: Used 10, 000K Blackbody normalized to V=16. SN should be bright during initial acquisition. ------------------------------------------------------------------------------------------------------------------------------------ 2 AT2020NXT STIS/NUV ACCUM 52X0.2 G230L 2376 1 2000 S -MAMA see below (2100 S) Comments: Assuming a 7, 000K Blackbody around 10 days post-max. ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ AT2020NXT 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A AT2020NXT 2 STIS/NUV ACCUM 52X0.2 G230L 2376 none none none none 1 2100.0 S -MAMA 15834( 5) - 16-Jul-2020 22:22:25 - [ 11] Visit: 06 (STIS-SNIbn1-Epoch2(FUV)) Visit Requirements: AFTER 05 BY 0 Orbits TO 1 Orbits; ON HOLD On Hold Comments: Target-of-Opportunity. This visit will be scheduled for 6-12 days following the first visit (as specified in the Timing Requirements), ideally aiming for 10 days. But we'd like to have some flexibility with our final submission to account for the brightness and light-curve evolution. Additional Comments: Likely to acquire on bright SN. 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 AT2020NXT STIS/CCD ACQ F28X50LP MIRROR 1 40 S (40 S) Comments: Used 10, 000K Blackbody normalized to V=16. SN should be bright during initial acquisition. ------------------------------------------------------------------------------------------------------------------------------------ 2 AT2020NXT STIS/NUV ACCUM 52X0.2 G230L 2376 1 2000 S -MAMA see below (2100 S) Comments: Assuming a 7, 000K Blackbody around 10 days post-max. ------------------------------------------------------------------------------------------------------------------------------------ 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 | ------------------------------------------------------------------------------------------------------------------------------------ AT2020NXT 1 STIS/CCD ACQ F28X50LP MIRROR none none none none 1 N/A AT2020NXT 2 STIS/NUV ACCUM 52X0.2 G230L 2376 none none none none 1 2100.0 S -MAMA 15834( 5) - 16-Jul-2020 22:22:25 - [ 12] Summary Form for Proposal 15834 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures 50CCD, 52X0.2, 52X0.2D1, F28X50LP ------------------------------------------------------------------------------------------------------------------------------------ Configurations STIS/CCD, STIS/FUV-MAMA, STIS/NUV-MAMA ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM, ACQ ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 01 BY 0 Orbits TO 1 Orbits, AFTER 01 BY 6 D TO 12 D, AFTER 02 BY 0 Orbits TO 1 Orbits, AFTER 04 BY 0 Orbits TO 1 Orbits, AFTER 05 BY 0 Orbits TO 1 Orbits, ON HOLD , TOO RESPONSE TIME 2.0D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements G140L, G230L, MIRROR ------------------------------------------------------------------------------------------------------------------------------------ Target Names AT2020NXT ------------------------------------------------------------------------------------------------------------------------------------