Assigned ID: 691 ----- Attempting Submission 1 (Fri Feb 24 20:49:44 GMT 2012) ----- The Phase 2 has been updated such that: 1) the F336W and F438W observations now include postflash 2) the F336W observation uses a larger box dither pattern more details are included in the observing description section ----- Attempting Submission 1 (Mon Jul 09 16:02:14 GMT 2012) ----- HST Phase II Proposal 12968 (go12968_phase2.apt) successfully submitted. ----- Attempting Submission 2 (Wed Oct 03 15:37:05 GMT 2012) ----- Recent studies have used high spatial resolution HST observations of supernova (SN) sites to directly identify the progenitors of core-collapse SNe on pre-explosion images. These studies have set constraints about the nature of massive stars and their evolution just prior to their explosion as SNe. Now, at late-times when the SNe have faded sufficiently, it is possible to return to the sites of these core-collapse supernovae to search for clues about the nature of their progenitors. We request time to conduct deep, late-time, high-resolution imaging with WFC3 UVIS of the site of the core-collapse SN 2009hd. We aim to: 1) Confirm our original identification, made in pre-explosion images, by confirming that the progenitor is now missing; 2) Apply image subtraction techniques for the pre-explosion images with this late-time imaging to determine accurate photometry of the progenitor to constrain its temperature and luminosity; and 3) use the stellar population in the immediate vicinity of the SN to determine the reddening and extinction that affected the progenitor. HST provides the unique combination of high-resolution optical/IR imaging at very faint magnitudes that will facilitate this study. We require deep 4 colour imaging of the site of the Type II SN 2009hd at late-times. A progenitor object was identified in deep pre-explosion WFPC2 and ACS imaging; we wish to see if the object that was identified in the pre-explosion F555W and F814W images has disappeared (and determine if the progenitor was also part of the background in pre-explosion F336W and F439W images, but not resolved as an individual source). This late-time imaging consists of a series of deep observations at the site of SN 2009hd, using WFC3 UVIS and a 1kx1k subarray (to reduce readout times, since only a small area around the SN is actually required). The observations are to be conducted in the F336W, F438W, F555W and F814W filters, to match the corresponding pre-explosion HST observations. A standard 4-point box dither pattern is employed to aid the rejection of cosmic rays and hotpixels, as well as improve the sampling of the PSF. The observations are designed to go down to levels of m_F336W~26.5, m_F438W~27, m_F555W~27, m_F814W~26.5 (to a S/N of 3) to probe the nature of the faint background. Given the duration of the four individual exposures that make up the dither pattern, nearby bright sources should not saturate. As we require as little as possible flux from the SN in these late-time images (to facilitate image subtraction analysis), we make a general requirement that the observation take place sometime towards the end of Cycle 20 (and have placed a requirement in this phase 2, such that the observations take place in the second half of cycle 20). 03-Oct-2012 - UPDATE The F336W observation has been updated to use a larger box dither pattern to overcome the effects of local droplets in the UVIS field. The pattern A4 (from ISR WFC3-2010-09, Dahlen et al.) has been adopted, and I have calculated the values of the point spacing, line spacing, pattern orientation and angles between sides using their prescription - the resulting positions for the fovs for the individual pointings in this dither pattern (checked using Aladin) seem consistent with what I would expect for this pattern, but a check of my calculations would be useful. The F336W and F438W observations have been updated to include a postflash - which has been set to 12e- per pixel in accordance with Anderson et al. 2012 No special calibrations are required for these observations HOT STARS 12 false 0.0 0.0 false false false false SUPPORTED EXT-STAR SUPERNOVA TYPE II This object was generated by the targetselector and retrieved from the SIMBAD database. J2000 J2000 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 0.119 LINE 4.312 false false 80.735 4 33.715 WFC3-UVIS-DITHER-BOX 2 false POS-TARG DITHER 0.173 LINE 0.112 false false 81.785 4 23.884 WFC3-UVIS-DITHER-BOX 3 false 1349278587634 /private/var/folders/8l/g53807596tg1q5kw0j9dnvqr0000gn/T/OPVisit6461719486736056942.xml The scheduling data was generated by CASM 20.2. CASM was run in Phase II mode. 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