This submission is for mid-cycle consideration. -702374868 Assigned ID: 1230 ----- Attempting Submission 1 (Wed Sep 30 18:15:30 GMT 2020) ----- HST Phase I Proposal 1230 successfully submitted. Receipt: # 1230-1 ----- Attempting Submission 2 (Wed Sep 30 22:53:07 GMT 2020) ----- HST Phase I Proposal 1230 successfully submitted. Receipt: # 1230-2 1) The first epoch (quienscence), was rescheduled to the next oppurtunity before the April outburst as discuessed with Elizabeth Nance and Amy Jones. -762917129 ----- Attempting Submission 1 (Sat Nov 28 21:01:58 GMT 2020) ----- HST Phase II Proposal 16451 successfully submitted. Receipt: # 16451-1 ----- Attempting Submission 2 (Tue Dec 15 20:25:53 GMT 2020) ----- A STIS view of ASASSN-14ko: uncovering the nature of the recently discovered periodic nuclear transient ASASSN-14ko is a recently discovered, periodically flaring, nuclear transient within known AGN ESO 253-G003. The flares have a mean period of ~114 days and a nonzero, negative period derivative. The exact origin of these UV/optical flares is currently unknown. Here we propose a four epoch STIS UV set of observations of the next predicted flare in December 2020. The prior 6+ years of seventeen observed flares seen in ASAS-SN tightly constrains the predicted times of pre-flare quiescence, rise, peak, and decline. These observations will be part of a much larger followup effort but the UV spectroscopy is pivotal. We will measure the evolution of UV absorption and emission lines from elements (e.g., C, N, Si) and ionization states/potentials not seen in optical spectra, which will directly help distinguish whether or not these flares are caused by a partial TDE, AGN disk accretion, or another high energy phenomenon. The impact of reduced-gyro operations on this project are uncertain, but, given that the epochs of these observations are highly constrained it is likely that the effect will be to further constrain or eliminate some of the epochs. This is a proposal by the ASAS-SN team to observe the UV bright, repeating nuclear transient ASASSN-14ko. We believe this source is a repeating TDE although it might be a new form of AGN variability. ASAS-SN has revolutionized the TDE field through its discovery and characterization of bright, nearby TDEs. This includes the discoveries of ASASSN-14ae (Holoien et al. 2014, Brown et al. 2016), ASASSN-14li (Holoien et al. 2016, Brown et al. 2017a), ASASSN-15oi (Holoien et al. 2016, 2018) and ASASSN-18jd (Neustadt et al. 2020). We have also carried out studies of iPTF16fnl (Brown et al. 2017b) and PS18kh (Holoien et al. 2018), which were first identified by iPTF and PanSTARRS, respectively. The paper on iPTF16fnl includes our STIS UV spectra from a previous proposal, although the campaign was halted after three observations because the source faded so rapidly. The paper on ASASSN-18jd contains a sequence of STIS spectra we obtained. The PI and CoIs have extensive experience with both AGN and TDE science. Supermassive Black Holes and Active Galaxies 6 false false true false false false false SUPPORTED GALAXY ACCRETION DISK MULTIPLE NUCLEI NUCLEUS QUASAR Note, this is the nucleaus of a galaxy, but, it is a complex galaxy. Please see submission notes. J2000 J2000 at peak: W1=15.69(0.04), M2=15.66(0.07), and W2=15.64(0.04) STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/NUV-MAMA Spectroscopic No No G230L 2376 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/NUV-MAMA Spectroscopic No No G230L 2376 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/NUV-MAMA Spectroscopic No No G230L 2376 STIS/FUV-MAMA Spectroscopic No No G140L 1425 STIS/NUV-MAMA Spectroscopic No No G230L 2376 POS-TARG DITHER 0.3829 LINE false false 2 90.0 STIS-ALONG-SLIT 1 false POS-TARG DITHER 0.3829 LINE false false 3 90.0 STIS-ALONG-SLIT 2 false /Users/shappee/GoogleHawaii/Proposals/HST/Cycle28-mid/OP-cache/14ko-mid-phaseII-v01.xml The scheduling data was generated by CASM 28.2. CASM was run in Phase II mode. Quiescence before ASASSN-14ko Dec 2020 outburst (Tic-Visit :proposal-id 16451 :visit-id "01" :proposal-version -1 :trans-version "20200619" :date "28-Nov-2020 10:59:19.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 887680 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 16451 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 16451 :visit-id "01" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2892 :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 3285 :pcs-gap 0 ) (Tic-Orbit :proposal-id 16451 :visit-id "01" :orbit-number 2 :pcs-time 392 :si-vis-utilization 2893 :al-overhead-at-end 0 :internal-dur-at-end 375 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3285 :pcs-gap 0 ) true 2 0 /Users/shappee/GoogleHawaii/Proposals/HST/Cycle28-mid/OP-cache/14ko-mid-phaseII-v02.xml The scheduling data was generated by CASM 28.2. CASM was run in Phase II mode. Rise of ASASSN-14ko Dec 2020 outburst 1608295254000 5.074351405637913 (Tic-Visit :proposal-id 16451 :visit-id "02" :proposal-version -1 :trans-version "20200619" :date "28-Nov-2020 10:59:22.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 887680 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 16451 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 16451 :visit-id "02" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2580 :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 2973 :pcs-gap 0 ) (Tic-Orbit :proposal-id 16451 :visit-id "02" :orbit-number 2 :pcs-time 392 :si-vis-utilization 2581 :al-overhead-at-end 85 :internal-dur-at-end 394 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 2973 :pcs-gap 0 ) true 2 0 The scheduling data was generated by CASM 28.2. CASM was run in Phase II mode. /Users/shappee/GoogleHawaii/Proposals/HST/Cycle28-mid/OP-cache/14ko-mid-phaseII-v03.xml Peak of the ASASSN-14ko Dec 2020 outburst 1608642671000 9.41427810171919 (Tic-Visit :proposal-id 16451 :visit-id "03" :proposal-version -1 :trans-version "20200619" :date "28-Nov-2020 10:59:25.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 591920 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 16451 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 16451 :visit-id "03" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2688 :al-overhead-at-end 0 :internal-dur-at-end 450 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3081 :pcs-gap 0 ) true 1 0 /Users/shappee/GoogleHawaii/Proposals/HST/Cycle28-mid/OP-cache/14ko-mid-phaseII-v04.xml The scheduling data was generated by CASM 28.2. CASM was run in Phase II mode. Decline of the ASASSN-14ko Dec 2020 outburst (Tic-Visit :proposal-id 16451 :visit-id "04" :proposal-version -1 :trans-version "20200619" :date "28-Nov-2020 10:59:28.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "24" :si-bright-earth-limb-angle 20.0 :data-volume 887680 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 16451 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 16451 :visit-id "04" :orbit-number 1 :pcs-time 393 :si-vis-utilization 2892 :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 3285 :pcs-gap 0 ) (Tic-Orbit :proposal-id 16451 :visit-id "04" :orbit-number 2 :pcs-time 392 :si-vis-utilization 2893 :al-overhead-at-end 0 :internal-dur-at-end 375 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3285 :pcs-gap 0 ) true 2 0