Supernovae (SNe) have a profound effect on galaxies, and have been used recently as precise cosmological probes, resulting in the discovery of the accelerating Universe. They are clearly very important events deserving of intense study. Yet, even with nearly 4000 known SNe, we know relatively little about the stars which give rise to these powerful explosions. The main limitation has been the lack of spatial resolution in pre-SN imaging data. However, since 1999 our team has been at the vanguard of directly identifying SN progenitor stars in HST images. From this exciting new line of study, the emerging trend from 5 detections for Type II-Plateau SNe is that their progenitors appear to be relatively low mass (8 to 20 Msun) red supergiants, although more cases are needed. Nonetheless, the nature of the progenitors of Type Ib/c SNe, a subset of which are associated with the amazing gamma-ray bursts, remains ambiguous. Furthermore, we remain in the continually embarrassing situation that we still do not yet know which progenitor systems explode as Type Ia SNe, which are currently being used for precision cosmology. In Cycle 16 we have triggered on the Type Ic SN 2007gr and Type IIb SN 2008ax so far. We propose to determine the identities of the progenitors of 4 SNe within 17 Mpc, which we expect to occur during Cycle 17, through ToO observations using ACS/HRC.

We plan for four ToO triggers during Cycle 17. If we detect one or more candidate stellar objects within a 1-sigma positional uncertainty in ACS or WFPC2 pre-supernova archival image(s), we will request a trigger to confirm the progenitor candidate. Our original plan was to image with ACS/HRC, however, with its unavailability, we are using ACS/WFC, instead, to provide the highest possible spatial resolution. Our strategy, generally, is to acquire a series of short-exposure (20-s) dithered images in one band, V (F555W), for the 3 core-collapse visits (which will likely best match with the available archival image data), and in B (F435W) for a putative, nearby (< ~ 6 Mpc) SN Ia visit, since these SNe will likely be too bright in redder bands, but fade more rapidly in the blue. We will likely request triggers when the SN is still fairly bright, depending on its age at discovery, but limit this, generally, to m>~13 mag. The ToOs are not intended to be high-impact, and the SNe can be imaged weeks after explosion, so there should be no disruption of normal scheduling. HOT STARS 0 false 0.0 0.0 false false false false false false SUPPORTED STAR SUPERNOVA TYPE II J2000 00 00 0.0000 +00 00 0.00 J2000 STAR SUPERNOVA TYPE II J2000 00 00 0.0000 +00 00 0.00 J2000 STAR SUPERNOVA TYPE IB J2000 00 00 0.0000 +00 00 0.00 J2000 STAR SUPERNOVA TYPE II J2000 00 00 0.0000 +00 00 0.00 J2000 ACS/HRC Imaging No No F435W ACS/HRC Imaging No No F555W ACS/HRC Imaging No No F814W ACS/HRC Imaging No No F435W ACS/HRC Imaging No No F555W ACS/HRC Imaging No No F814W ACS/HRC Imaging No No F435W ACS/HRC Imaging No No F555W ACS/HRC Imaging No No F814W ACS/HRC Imaging No No F330W ACS/HRC Imaging No No F435W ACS/HRC Imaging No No F555W POS-TARG DITHER 3.011 LINE false false 2 85.28 ACS-WFC-DITHER-LINE 1 false POS-TARG DITHER 0.265 LINE 0.187 false false 69.05 4 20.67 ACS-WFC-DITHER-BOX 2 false The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. 1260754591000 302.9397170446436 (Tic-Visit :proposal-id 11575 :visit-id "01" :proposal-version -1 :trans-version "20100505" :date "30-Aug-2010 09:13:49.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 1136896 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11575 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11575 :visit-id "01" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2839 :al-overhead-at-end 0 :internal-dur-at-end 349 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3245 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. 1285014442000 276.45878954625636 (Tic-Visit :proposal-id 11575 :visit-id "02" :proposal-version -1 :trans-version "20100505" :date "30-Aug-2010 09:15:42.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 1136896 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11575 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11575 :visit-id "02" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2681 :al-overhead-at-end 0 :internal-dur-at-end 349 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3021 :pcs-gap 0 ) true 1 0 The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. 1285870721000 113.05874341438857 (Tic-Visit :proposal-id 11575 :visit-id "03" :proposal-version -1 :trans-version "20100505" :date "30-Aug-2010 09:13:51.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 1136896 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11575 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11575 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2839 :al-overhead-at-end 0 :internal-dur-at-end 349 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3245 :pcs-gap 0 ) true 1 0 HOPR repeat of visit 3. Visit 3 lost due to ACS suspend. (Tic-Visit :proposal-id 11575 :visit-id "03" :proposal-version -1 :trans-version "20100505" :date "30-Aug-2010 09:13:51.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 1136896 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11575 :visit-id "03" :obset-id "03" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11575 :visit-id "03" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2839 :al-overhead-at-end 0 :internal-dur-at-end 349 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3245 :pcs-gap 0 ) false 1 0 The scheduling data was generated by CASM 18.3.1. CASM was run in Phase II mode. 1286613901000 42.0 (Tic-Visit :proposal-id 11575 :visit-id "04" :proposal-version -1 :trans-version "20100505" :date "30-Aug-2010 09:13:53.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 1 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 1705344 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 11575 :visit-id "04" :obset-id "04" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 11575 :visit-id "04" :orbit-number 1 :pcs-time 333 :si-vis-utilization 2821 :al-overhead-at-end 0 :internal-dur-at-end 349 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3275 :pcs-gap 0 ) true 1 0