0 Assigned ID: 1086 ----- Attempting Submission 1 (Fri Apr 10 23:50:02 GMT 2015) ----- HST Phase I Proposal 1086 (sn13ej_echo_apt) successfully submitted. Receipt: # 1086-1 ----- Attempting Submission 2 (Fri Apr 10 23:52:30 GMT 2015) ----- HST Phase I Proposal 1086 (sn13ej_echo_apt) successfully submitted. Receipt: # 1086-2 ----- Attempting Submission 3 (Fri Apr 10 23:54:16 GMT 2015) ----- HST Phase I Proposal 1086 (sn13ej_echo_apt) successfully submitted. Receipt: # 1086-3 ----- Attempting Submission 4 (Fri Apr 10 23:58:16 GMT 2015) ----- FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser FLASH level may be too low for this exposure or a short subexposure. See extended explanation in the diagnostic browser 0 ----- Attempting Submission 1 (Mon Jul 20 23:27:40 GMT 2015) ----- ----- Attempting Submission 2 (Tue Dec 08 19:18:18 GMT 2015) ----- Still getting warning from APT about FLASH level in F555W and F814W. Ignoring Light echoes from supernovae are fascinating phenomena and can probe both the circumstellar and interstellar structures, the size distribution and chemical composition of the scattering dust, and the detailed history of the outburst giving rise to the echo. Although light echoes from recent extragalactic supernovae could well be a common occurrence, observations which spatially resolve echoes are relatively rare. The main obstacle to resolving the echo is that the SN host galaxies must be relatively nearby, although, even then, the structures can only be revealed by the superior angular resolution of HST. The light echo of a SN results from the luminous ultraviolet (UV)/optical pulse scattered by dust in the SN environment. In particular, we can witness a record of the bright, rapid, elusive flash of X-ray/UV emission emerging as the SN shock breaks through the massive envelope around the progenitor star. We propose to search for a light echo around the recent Type II-Plateau Supernova 2013ej in the nearby, nearly face-on spiral host galaxy Messier 74. Previous HST imaging since the explosion has not revealed an echo. However, those observations were too soon, when the SN was still on the plateau and quite bright. The WFC3/UVIS multi-band imaging we propose will be late enough, near day 900 of the SN age, and sensitive enough to detect a possible light echo. There are very few other supernovae this nearby, at an old enough age, where adequately resolving the echo is possible. Cycle 23 is the time to do this for SN 2013ej, taking particular advantage of the UV. We will image the site of SN 2013ej in M74 with WFC3/UVIS in F275W, F336W, F438W, F555W, and F814W, using the subarray UVIS2-C1K1C-SUB. We will be able to precisely pinpoint the SN's location in the new images. Any echo around SN 2013ej could be appreciably fainter, given that there is apparently less internal host dust at the site than for the site of SN 2012aw. We have estimated that we can include 1280 sec total exposures in F275W and F336W in one full orbit, including overheads (guide star acquisition, dither, filter changes). With the subarray we save substantially in the need for buffer dumps. We can obtain 720-s total exposures in F438W and F555W, plus a 820-sec total exposure in F814W, into a second full orbit. The total exposures consist of equal pairs of exposures, which will be line-dithered and post-flashed, to mitigate against CR hits and improve overall sensitivity. In each of the bands we should be able to detect the integrated light of an echo around SN 2013ej at 5-sigma to the following magnitudes: 22.0 (F275W), 22.7 (F336W), 22.6 (F438W), 23.5 (F555W), and 22.2 (F814W). The SN itself should be extremely faint in all bands and should not therefore pose a problem; we should be able to detect any residual point source at the SN site, though, to, e.g., ~26.4 mag at 3-sigma in F814W. We would, then, potentially be able to determine that the identified red supergiant has vanished, confirming it as SN progenitor. We will also be able to characterize stars in the immediate SN environment as well. We should be able to fully and successfully model the flux from an observed SN 2013ej light echo. ISM IN EXTERNAL GALAXIES 12 false false false false SUPPORTED EXT-STAR SUPERNOVA TYPE II J2000 J2000 WFC3/UVIS Imaging No No F275W WFC3/UVIS Imaging No No F336W WFC3/UVIS Imaging No No F438W WFC3/UVIS Imaging No No F555W WFC3/UVIS Imaging No No F814W POS-TARG DITHER 0.145 LINE false false 2 46.84 WFC3-UVIS-DITHER-LINE 1 false 1449601827083 /private/var/folders/6g/xnmzjq6x4gqg_99lmrhmn4pm0000gq/T/OPVisit9035627198573675912.xml The scheduling data was generated by CASM 23.2. CASM was run in Phase II mode. 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