NUV Monitoring of a SNIa with Late-Onset CSM Interaction

0 Assigned ID: 1606 ----- Attempting Submission 1 (Tue Oct 24 23:51:53 GMT 2017) ----- HST Phase I Proposal 1606 (apt_proposal.apt) successfully submitted. Receipt: # 1606-1 This target is not used in this proposal. Phase II Submission Attempt #3. Changes from attempt #2: We have fixed the coordinates of PS15DPQ-AS-OFFSET, which are with respect to our offset star SDSSJ03. Remaining minor second concerns: How can we confirm that two guide stars will be used, and that we will not have to reacquire after 2-3 orbits in order to keep the target centered on the slit? Dan had a question about emission lines in our spectral region that remains open. 616527543 ----- Attempting Submission 1 (Wed Nov 01 00:22:14 GMT 2017) ----- HST Phase II Proposal 15407 (apt_proposal.apt) successfully submitted. Receipt: # 15407-1 ----- Attempting Submission 2 (Wed Nov 01 05:57:20 GMT 2017) ----- HST Phase II Proposal 15407 (apt_proposal.apt) successfully submitted. Receipt: # 15407-2 ----- Attempting Submission 3 (Wed Nov 01 20:00:56 GMT 2017) ----- We've kept the original Fixed Target for PS15DPQ which has the actual RA and Dec, but are now using PS15DPQ-AS-OFFSET in the visit, which has the coordinates specified as an offset with respect to a nearby star, which we use for acquisition. NUV Monitoring of a SNIa with Late-Onset CSM Interaction We propose for Director's Discretionary Time to monitor the first-ever Type Ia supernova (SN Ia) found to be experiencing late-onset interaction between its ejecta and circumstellar material. Very few SNe Ia have been observed to interact with CSM, and always within a month or two of peak brightness, which indicates that their CSM was relatively nearby. Based on observations of time-varying and/or blueshifted sodium absorption, more distant CSM is predicted to exist in about 20% of all SN Ia systems, but has never been directly confirmed. This motivated our Cycle 24 Snapshot program to search for late-onset interaction in a sample of 80 nearby SNe Ia with NUV imaging at 1 to 3 years after exposion. In September 2017 we discovered PanSTARRS 15dpq to have a F275W apparent magnitude of 24.3 mag, ~2 years after its explosion. An optical spectrum in October 2017 showed a broad hydrogen emission line, confirming that the emission is associated with CSM interaction. At early-times, PS15dpq did not exhibit any sodium absorption or CSM interaction, making it the first and only example of SN Ia surrounded by a cleared-out inner volume and distant CSM. We propose for one epoch of STIS spectroscopy to constrain the NUV emission features (i.e., continuum- or line-emission), followed by six epochs of time-series NUV photometry to monitor the luminosity evolution. These data will allow us to place direct physical constraints on the amount and distribution of the CSM surrounding PS15dpq and will provide unique insight into the diversity of SN Ia progenitor systems, which is important because they are commonly used as standardizable candles for dark-energy cosmology. A single visit, 5 orbit STIS spectrum of our target with the NUV-MAMA detector and the G230L grating. Stellar Physics 0 SUPPORTED EXT-STAR SUPERNOVA TYPE IA NO This target is not used but kept for now in case we decide to go for direct acquisition. J2000 J2000 F275W 24.3 mag on 2017-09-12 STAR F0-F2 J2000 F275W 20.0 mag EXT-STAR SUPERNOVA TYPE IA Same as target PS15DPQ, but with location defined in reference to star SDSSJ03... F275W 24.3 mag on 2017-09-12 STIS/NUV-MAMA Spectroscopic No No G230L 2376 WFC3/UVIS Imaging No No F275W WFC3/UVIS Imaging No No F225W WFC3/UVIS Imaging No No F275W WFC3/UVIS Imaging No No F275W WFC3/UVIS Imaging No No F275W WFC3/UVIS Imaging No No F275W WFC3/UVIS Imaging No No F275W 1509566283435 /private/var/folders/yb/dlzzyh3117lft3f339cw0v2m0000gn/T/OPVisit5398004194358862172.xml The scheduling data was generated by CASM 25.2. CASM was run in Phase II mode. (Tic-Visit :proposal-id 15407 :visit-id "01" :proposal-version -1 :trans-version "20170613" :date "01-Nov-2017 12:58:02.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 5 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 435392 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 15407 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 15407 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2643 :al-overhead-at-end 0 :internal-dur-at-end 113 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2988 :pcs-gap 0 ) (Tic-Orbit :proposal-id 15407 :visit-id "01" :orbit-number 2 :pcs-time 222 :si-vis-utilization 2766 :al-overhead-at-end 104 :internal-dur-at-end 132 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2988 :pcs-gap 0 ) (Tic-Orbit :proposal-id 15407 :visit-id "01" :orbit-number 3 :pcs-time 222 :si-vis-utilization 2766 :al-overhead-at-end 104 :internal-dur-at-end 132 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2988 :pcs-gap 0 ) (Tic-Orbit :proposal-id 15407 :visit-id "01" :orbit-number 4 :pcs-time 222 :si-vis-utilization 2766 :al-overhead-at-end 104 :internal-dur-at-end 132 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2988 :pcs-gap 0 ) (Tic-Orbit :proposal-id 15407 :visit-id "01" :orbit-number 5 :pcs-time 222 :si-vis-utilization 2766 :al-overhead-at-end 104 :internal-dur-at-end 394 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2988 :pcs-gap 0 ) true 5 0 Would like to execute as soon as possible. We are not entirely sure of this star's spectral type. I've used Pickles F2 since it appears quite blue. In our HST image it is F275W 20 mag, and in the SDSS photometry it has a ugriz of 17.0/15.2/14.3/16.4/13.7 mag. The object is PS15DPQ-OFFSET, whose coordinates are defined as offsets from star SDSSJ0...