0 Assigned ID: 5580 ----- Attempting Submission 1 (Tue Mar 26 19:31:37 GMT 2024) ----- HST Phase I Proposal 5580 successfully submitted. Receipt: # 5580-1 This target is not used in this proposal. This pattern is not used in this proposal. This pattern is not used in this proposal. This pattern is not used in this proposal. I did my best to try to fit within 13 min per orbit. I will be available at any time for clarifications or if you have suggestions to make this work. Please do not hesitate to contact me. Major change is the inclusion of IR filters. At this time, this is the most compelling need of the community for confirming this as a kilonova. Ground based imaging is failing due to avariety of reasons (bad visibility, bad weather, etc) All five visits should be planned, 1 per orbit. No need for the orbits to be one after the other one. -849152205 ----- Attempting Submission 1 (Sun Jul 28 17:21:04 GMT 2024) ----- ----- Attempting Submission 2 (Thu Aug 21 21:26:48 GMT 2025) ----- n/a Ultra-rapid observations of a gravitational wave source The discovery of GW170817 ushered in a new era of multi-messenger astrophysics, in which gravitational waves and light are used to explore the most extreme phenomena, such as gamma-ray bursts and kilonovae. We propose to use the unique sensitivity and spectral UV coverage of HST to probe the earliest phases of a young kilonova, promptly (< 4 hr) localized through gravitational waves and light. A similar event, although rare, would offer us the unique opportunity to open a new window into the physics of kilonovae and probe an unexplored stage of their life. These observations would constrain the physical properties of the emitting ejecta (e.g. temperature, expansion velocity) and critically distinguish between competing models (e.g. radioactivity, shock interactions, magnetar) to power the luminous blue kilonova. For events at > 100 Mpc, we request 5 orbits of UV imaging (F336W, F275W, F225W) split in two visits, one (2 orbits) as soon as possible (IMA V1) and the second one (3 orbits) within 1 day (IMA V2) since V1. For an event <100 Mpc, we would instead opt for spectroscopic observations using the WFC3/G280 grism and the same number of orbits. Depending on the reaction time and information available at the time of the trigger, a hybrid configuration (spectroscopy followed by imaging) may be adopted. Our team has decades-long experience in the field of GRBs and transient follow-up. Our experience includes follow-up observations of the kilonova AT2017gfo, including HST imaging and spectroscopy, as well as the discovery of kilonova candidates in the nearby short GRBs. Our team includes key members of the Swift (Dichiara, Troja) and Einstein Probe (Troja) mission, which will be used in synergy with HST to guide the UV follow-up. Co-Is Fryer and Wollager are expert in kilonova modeling and will help with the theoretical interpretation. Co-Is O'Connor, Becerra-Gonzalez and Becerra are experienced observers and will help providing the ground-based dataset. Stellar Physics and Stellar Types Stellar Populations and the Interstellar Medium 3 false true false false false false SUPPORTED STAR EJECTA NEUTRON STAR NO J2000 GW counterpart WFC3/UVIS Imaging No No F225W WFC3/UVIS Imaging No No F275W WFC3/UVIS Imaging No No F336W WFC3/UVIS Imaging No No F438W WFC3/UVIS Spectroscopic No No G280 WFC3/UVIS Imaging No No F225W WFC3/UVIS Imaging No No F275W WFC3/UVIS Imaging No No F336W WFC3/UVIS Imaging No No F438W WFC3/UVIS Spectroscopic No No G280 POS-TARG DITHER 0.173 LINE 0.112 false false 81.785 4 23.884 WFC3-UVIS-DITHER-BOX 1 false POS-TARG DITHER 0.135 LINE false false 3 46.84 WFC3-UVIS-DITHER-LINE-3PT 2 false POS-TARG DITHER 0.145 LINE false false 2 46.84 WFC3-UVIS-DITHER-LINE 3 false POS-TARG DITHER 0.605 LINE false false 3 41.788 WFC3-IR-DITHER-LINE-3PT 5 false POS-TARG DITHER DITHER 4 1 WFC3-IR-DITHER-BOX-MIN false 74.653 false 0.365 0.572 2 5 POS-TARG LINE 18.528 6 true The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. /Users/eleonora/Downloads/OP-cache/17805-v01.xml Imaging, single filter F225W, 1 orbit Recommended post-flash of 20 e/pixels Aperture chosen to target near the C amplifier to reduce CTE losses If you need to reduce the FOV, use UVIS2-C1K1C-SUB (Tic-Visit :proposal-id 17805 :visit-id "01" :proposal-version -1 :trans-version "20250624" :date "21-Aug-2025 17:15:34.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 577488 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17805 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17805 :visit-id "01" :orbit-number 1 :pcs-time 380 :si-vis-utilization 270 :al-overhead-at-end 128 :internal-dur-at-end 668 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2987 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. /Users/eleonora/Downloads/OP-cache/17805-v02.xml (Tic-Visit :proposal-id 17805 :visit-id "02" :proposal-version -1 :trans-version "20250624" :date "21-Aug-2025 17:16:40.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 417808 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17805 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17805 :visit-id "02" :orbit-number 1 :pcs-time 380 :si-vis-utilization 540 :al-overhead-at-end 0 :internal-dur-at-end 538 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2867 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. /Users/eleonora/Downloads/OP-cache/17805-v03.xml (Tic-Visit :proposal-id 17805 :visit-id "03" :proposal-version -1 :trans-version "20250624" :date "21-Aug-2025 17:16:40.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 417808 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17805 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17805 :visit-id "03" :orbit-number 1 :pcs-time 380 :si-vis-utilization 540 :al-overhead-at-end 0 :internal-dur-at-end 538 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2867 :pcs-gap 0 ) true 1 0 Awaiting GW trigger The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. /Users/eleonora/Downloads/OP-cache/17805-v04.xml (Tic-Visit :proposal-id 17805 :visit-id "04" :proposal-version -1 :trans-version "20250624" :date "21-Aug-2025 17:16:41.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 417808 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17805 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17805 :visit-id "04" :orbit-number 1 :pcs-time 380 :si-vis-utilization 540 :al-overhead-at-end 0 :internal-dur-at-end 538 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2867 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 33.1. CASM was run in Phase II mode. /private/var/folders/q4/7fyr1y1j2xjccb5nzdvfrpxr0000gn/T/OPVisit18087098664278575721.xml (Tic-Visit :proposal-id 17805 :visit-id "05" :proposal-version -1 :trans-version "20250624" :date "21-Aug-2025 17:16:42.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "30" :si-bright-earth-limb-angle 20.0 :data-volume 417808 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 17805 :visit-id "05" :obset-id "05" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 17805 :visit-id "05" :orbit-number 1 :pcs-time 380 :si-vis-utilization 540 :al-overhead-at-end 0 :internal-dur-at-end 538 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2867 :pcs-gap 0 ) true 1 0 Awaiting GW trigger