Attached is our Phase II submission for HST observations of nearby supernova 2019ehk in M100. We have been allocated 2 orbits: 1 for WFC3/UVIS imaging and 1 of WFC3/IR imaging. Please direct all inquiries to me, Wynn Jacobson-Galan, if any additional information is needed. Thank you! Best, Wynn Jacobson-Galan -93754568 ----- Attempting Submission 1 (Wed Mar 18 21:37:45 GMT 2020) ----- Supernova (SN) 2019ehk in M100 is the closest known Calcium-rich (Ca-rich) transient and the only object in this class with an X-ray detection. Prompt, high-cadence follow-up of this transient across the EM spectrum, in addition to pre-explosion HST imaging, has indicated that the progenitor star was likely low mass and surrounded by dense circumstellar material (CSM) whose geometry/density was capable of producing luminous X-ray emission as well as a double-peaked light curve. The close proximity of SN 2019ehk provides the first opportunity to track the photometric evolution of a Ca-rich transient at late phases (>300 days) when the SN luminosity is governed by radioactive decay and/or additional power sources e.g., CSM, and is too faint for ground-based observatories. These objects typically decrease in magnitude rapidly and thus their late-time decline rate and power source is unknown. Here we propose multi-color imaging of SN 2019ehk in order to understand its late-time bolometric behavior and to constrain the total mass of Ni-56 synthesized in the explosion. This will allow us to test whether SN 2019ehk is powered solely by radioactive decay or by additional CSM at large distances from the progenitor system. We propose to observe nearby supernova 2019ehk with WFC3/IR in F110W and F160W filters in the first of our two allocated orbits. In the second orbit, we will observe SN 2019ehk with WFC3/UVIS in filters F555W and F814W. Our optimal observing window is between 06-May-2020 and 01-June-2020. We have requested that IR imaging be taken within 3 days of the UVIS imaging orbit. Below is our observing plan for each filter in each orbit: Orbit 1: F555W: Total Exposure time = 1500s; Split into two 750s exposures using WFC3-UVIS-DITHER-LINE pattern F814W: Total Exposure time = 900s; Split into two 450s exposures using WFC3-UVIS-DITHER-LINE pattern Orbit 2: F110W/F160W: Four ~300s individual exposures for each filter using the WFC3-IR-DILTER-BOX-MIN pattern. Mr. Wynn Jacobson-Galan has extensive experience analyzing and reducing WFC3/UVIS data, the instrument proposed for this program. Mr. Jacobson-Galan is a graduate student with burgeoning expertise on the late-time light curves of thermonuclear supernovae observed with HST (1 refereed paper) and calcium-rich transients (1 paper in press). Mr. Jacobson-Galan has completed analysis on the early-time, multi-wavelength observations of the proposed target, SN 2019ehk, and all data on this object will be included in a journal article planned to be submitted within the month. Prof. Raffaella Margutti is a leading expert on x-ray and radio observations of exotic transients such as SN 2019ehk. Prof. Dan Milisavljevic has 1 refereed paper on calcium-rich transients and has compreheisve experience with HST observations. Dr. Peter Blanchard has published 5 papers using HST data, including both archival and new observations led by Dr. Blanchard. Dr. Charles Kilpatrick has significant experience in reduction and analysis of HST/WFC3, ACS, and WFPC2 imaging data, including the prime instruments used in these proposed observations. Prof. Ryan Foley is an expert in transient surveys and follow up of all types of explosive transients. Mr. Sebastian Gomez and Dr. Griffin Hosseinzadeh are assisting with the ground-based observations of the proposed target. Stellar Physics and Stellar Types 3 false false false false false false false SUPPORTED STAR SUPERNOVA NO J2000 J2000 g ~ 28, r ~ 26.5, i/z ~ 24.2 WFC3/UVIS Imaging No No F475W WFC3/UVIS Imaging No No F625W WFC3/UVIS Imaging No No F814W WFC3/IR Imaging No No F110W WFC3/IR Imaging No No F160W POS-TARG DITHER 0.145 LINE false false 2 46.84 WFC3-UVIS-DITHER-LINE 1 false POS-TARG DITHER 0.572 LINE 0.365 false false 74.653 4 18.528 WFC3-IR-DITHER-BOX-MIN 2 false 1584567304285 /private/var/folders/mw/ypvmkj2s06zc1tvhvrnx3flm0000gn/T/OPVisit8351869119645882428.xml The scheduling data was generated by CASM 28.0. CASM was run in Phase II mode. Orbit 1: Filters: F110W, F160W Orbit 2: Filters: F555W, F814W (Tic-Visit :proposal-id 16075 :visit-id "01" :proposal-version -1 :trans-version "20191203" :date "18-Mar-2020 16:35:03.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "29" :si-bright-earth-limb-angle 20.0 :data-volume 3104800 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 16075 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 16075 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2776 :al-overhead-at-end 0 :internal-dur-at-end 65 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3156 :pcs-gap 0 ) (Tic-Orbit :proposal-id 16075 :visit-id "01" :orbit-number 2 :pcs-time 302 :si-vis-utilization 2833 :al-overhead-at-end 116 :internal-dur-at-end 352 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3156 :pcs-gap 0 ) true 2 0