Light Echoes from SN 2006X in M100 We propose a minimal investment of spacecraft time to discover and confirm a light echo from Supernova 2006X in M100, the closest Type Ia in many years. Our spectroscopic and photometric data indicate that this SN sits behind a large amount of interstellar dust likely to produce a strong echo signal. This is one of very few cases where we will be able to study the three-dimensional environment of a SN Ia in full detail, and begin to understand how environmental effects play into the evolutionary and observational factors which influence the utility of SN Ia as standard candles for probing cosmology. We propose an efficient program to definitively detect (or not) a light echo of reasonable signal strength, to confirm that it is an echo by demonstrating apparent superluminal motion if it exists, to map the three-dimensional geometry of the reflecting interstellar structures, and to detail the reflectance properties of the dust which can be used to constrain ! its grain size and composition distribution.
Observations consist of Visit 1 in April-June 2006, consisting of short exposures in three filters F435W, F555W and F775W, observed before the explosion in archival images, and longer exposures in Visit 2 some 4-8 months later, using the same filters. Visit 1 takes two orbits, since there is greater overhead caused by the shorter exposures, while Visit 2 takes only one orbit for comparable total exposure times. ISM IN EXTERNAL GALAXIES 0 false 0.0 false false false false false SUPPORTED STAR SUPERNOVA TYPE IA J2000 12 22 53.9600 +15 48 32.20 J2000 ACS/HRC Imaging No No F435W ACS/HRC Imaging No No F555W ACS/HRC Imaging No No F775W ACS/HRC Imaging No No F435W ACS/HRC Imaging No No F555W ACS/HRC Imaging No No F775W POS-TARG DITHER 0.15 LINE 0.098 false false 63.5 4 19.89 ACS-HRC-DITHER-BOX 1 false POS-TARG DITHER DITHER 2 0.15 LINE 0.098 false false 63.5 0.198 4 19.89 POS-TARG ACS-HRC-DITHER-BOX 44.28 2 true (Tic-Visit :proposal-id 10991 :visit-id "01" :proposal-version -1 :trans-version "20051113" :date "18-Apr-2006 16:17:55.0" :trans-errors '(:WARNINGS 0 :ERRORS 0 :HEALTH-AND-SAFETY 0 :FATAL-ERRORS 0 :CONTINUABLE-FATALS 0) :number-of-orbits 2 :saa-model "27" :si-bright-earth-limb-angle 20.0 :data-volume 588976 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 10991 :visit-id "01" :obset-id "01" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 10991 :visit-id "01" :orbit-number 1 :pcs-time 339 :si-vis-utilization 2874 :al-overhead-at-end 0 :internal-dur-at-end 0 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3257 :pcs-gap 0 ) (Tic-Orbit :proposal-id 10991 :visit-id "01" :orbit-number 2 :pcs-time 339 :si-vis-utilization 2856 :al-overhead-at-end 0 :internal-dur-at-end 360 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3257 :pcs-gap 0 ) false 2 0 /var/tmp/OPVisit7706.xml These observations take place with the same setup and filters as Visit 1, but occur 4-8 months later when the supernova is fainter, hence can be longer exposure times. (Tic-Visit :proposal-id 10991 :visit-id "02" :proposal-version -1 :trans-version "20051113" :date "18-Apr-2006 17:19:48.0" :trans-errors '(:WARNINGS 1 :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 220816 :tdrss-contact-duration 0 :coron NIL ) (Tic-Obset :proposal-id 10991 :visit-id "02" :obset-id "02" :pcs-mode "FGS" ) (Tic-Orbit :proposal-id 10991 :visit-id "02" :orbit-number 1 :pcs-time 339 :si-vis-utilization 2930 :al-overhead-at-end 0 :internal-dur-at-end 280 :dark-offset NIL :dark-utilization 0 :max-dark-utilization 1920 :low-sky "N" :pcs-visibility 3257 :pcs-gap 0 ) false 1 1 /var/tmp/OPVisit7707.xml