13433( 5) - 14-Jul-2014 18:44:10 - [ 1] HUBBLE SPACE TELESCOPE OBSERVING PROGRAM 13433 Version: 5 Check-in Time: 14-Jul-2014 18:44:10 STScI Edit Number: 0 Title Stellar Forensics V: A post-explosion view of the progenitor of SN 2011dh ------------------------------------------------------------------------------------ Type Cycle GO 21 ------------------------------------------------------------------------------------ Investigators Contact? PI: Dr. Justyn Maund The Queen's University of Belfast Y CoI: Ms. Emma Reilly The Queen's University of Belfast N CoI: Dr. Stephen J. Smartt The Queen's University of Belfast N CoI: Dr. Morgan Fraser University of Cambridge N CoI: Dr. John J. Eldridge The University of Auckland N CoI: Dr. Seppo Mattila University of Turku N CoI: Dr. Richard Stancliffe Universitat Bonn, Argelander Institute for N Astronomy CoI: Mattias Ergon Stockholm University N ------------------------------------------------------------------------------------ Abstract 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 and ACS WFC of the site of the Type IIb supernova 2011dh. The nature of the observed yellow supergiant progenitor conflicts with the predictions of stellar evolution models and our understanding of the optical and radio light curves of the subsequent supernova. We aim to: 1) Confirm our original identification, made in pre-explosion images, by confirming that the yellow supergiant 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; 3) conduct a deep search for the hypothesised hot binary companion; and 4) 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 UV/optical imaging at very faint magnitudes that will facilitate this study. ------------------------------------------------------------------------------------ Observations Description ------------------------ We require deep 5 colour imaging of the site of the Type IIb SN 2011dh 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 WFPC2 F336W and ACS F435W, F555W and F814W images has disappeared. In addition, we wish to ascertain the presence of a possible binary companion (either hot or cool) that may have been blended with the pre-explosion source, such that we also request an observation with the F225W 13433( 5) - 14-Jul-2014 18:44:10 - [ 2] filter (to probe a hot companion). This late-time imaging consists of a series of deep observations at the site of SN 2011dh, using WFC3 UVIS and the 1kx1k subarray and ACS and the 1kx1k subarry (to reduce readout times, since only a small area around the SN is actually required). The WFC3 UVIS observations are to be conducted in the F225W and F336W filters, while the ACS/WFC observations will use the F435W, F555W and F814W filters. We use these filter combinations to accurately 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_F225W~25.5, m_F336W~26., m_F435W~27, m_F555W~27, m_F814W~27 (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, any nearby bright sources should not saturate (which we have confirmed with our previous photometry of the position of this SN and the BOT). The F225W and F336W observations 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 F225W, 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, for the WFC3 observation and 40e- following Smith et al. 2013. Post-flash is not required for the F555W and F814W observations. The 2 orbits per instrument have been broken into separate visits; however it will be useful to have them conducted at approximately similar times. This will enable us to evaluate any residual SN flux at UV and optical wavelength, using colour terms to derive the likely SN parameters and, hence, calculate the relative contamination at different wavelengths. In order to enable this science we require the SN to be as faint as possible, and loosely constrain the time window for the two visits to be in the second half of Cycle 21 (and loosely constrain Visit 2 to be conducted within 28 days of Visit 1). ------ Calibration Justification ------- A series of 26 ACS bias frames in the WFC1-1K subarray mode have been inserted directly into this program for the purpose of calibration of the ACS subarray images in visit 02. This subarray mode is fully supported, so the two internal orbits required to obtain these 26 frames should be charged to the Cycle 21 ACS Calibration Program. Contact David Golimowski (x4808) for more information. --------- Additional Comments ---------- We note that there are previous observations of the site of SN 2011dh in the HST archive. These observations were either taken before the SN exploded (i.e. with the progenitor still present) or post-explosion (i.e. with the SN still 13433( 5) - 14-Jul-2014 18:44:10 - [ 3] bright). We aim to make the authoritative study of this progenitor system by probing the disappearance of the putative YSG progenitor and probe any hot/cool companion star remaining at the SN position (with minimal contribution from SN). ------------------------------------------------------------------------------------ 13433( 5) - 14-Jul-2014 18:44:10 - [ 4] TARGET LIST Fixed Targets ------------------------------------------------------------------------------------------------------------------------------------ Tar| Target | Target | Target |Coord | Radial | Flux data No | Name | Description | Position |Eqnx | Vel. | ------------------------------------------------------------------------------------------------------------------------------------ 1 SN-2011DH EXT-STAR, SUPERGIANT O, RA=13H30M5.1200S, J2000 V = 27 +/- 0.2 SUPERNOVA, SUPERNOVA DEC=+47D10'11.00" TYPE II Reference Frame: Other: SIMBAD Comments: This object was generated by the targetselector and retrieved from the SIMBAD database. ------------------------------------------------------------------------------------------------------------------------------------ 13433( 5) - 14-Jul-2014 18:44:10 - [ 5] Patterns ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 2 Primary_Pattern Secondary_Pattern Pattern_Type ACS-WFC-DITHER-BOX Pattern_Purpose DITHER Number_Of_Points 4 Point_Spacing 0.265 Line_Spacing 0.187 Coordinate_Frame POS-TARG Pattern_Orient 20.67 Angle_Between_Sides 69.05 Center_Pattern NO ------------------------------------------------------------------------------------------------------------------------------------ Pattern_Number: 3 Primary_Pattern Secondary_Pattern Pattern_Type LINE WFC3-UVIS-DITHER-LINE Pattern_Purpose DITHER DITHER Number_Of_Points 2 2 Point_Spacing 4.26 0.145 Line_Spacing Coordinate_Frame POS-TARG POS-TARG Pattern_Orient 47.616 46.84 Angle_Between_Sides Center_Pattern NO NO ------------------------------------------------------------------------------------------------------------------------------------ 13433( 5) - 14-Jul-2014 18:44:10 - [ 6] Visit: 01 Visit Requirements: AFTER 15-MAR-2014:00:00:00 On Hold Comments: Additional Comments: 2 orbits to acquire WFC3/UVIS F225W and F336W imaging of the site of SN 2011dh Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 SN-2011DH WFC3/UVI ACCUM UVIS2-C1K F225W FLASH=12 1 943 S PATTERN 3 1 S 1C-SUB (3772 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SN-2011DH WFC3/UVI ACCUM UVIS2-C1K F336W FLASH=12 1 446 S PATTERN 3 2 S 1C-SUB (1784 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ SN-2011DH 1 WFC3/UVI ACCUM UVIS2-C1 F225W 1 1 none none 1 N/A S K1C-SUB SN-2011DH 1 WFC3/UVI ACCUM UVIS2-C1 F225W 1 2 none none 1 N/A S K1C-SUB SN-2011DH 1 WFC3/UVI ACCUM UVIS2-C1 F225W 2 1 none none 1 N/A S K1C-SUB SN-2011DH 1 WFC3/UVI ACCUM UVIS2-C1 F225W 2 2 none none 2 N/A S K1C-SUB SN-2011DH 2 WFC3/UVI ACCUM UVIS2-C1 F336W 1 1 none none 2 N/A S K1C-SUB SN-2011DH 2 WFC3/UVI ACCUM UVIS2-C1 F336W 1 2 none none 2 N/A S K1C-SUB SN-2011DH 2 WFC3/UVI ACCUM UVIS2-C1 F336W 2 1 none none 2 N/A S K1C-SUB SN-2011DH 2 WFC3/UVI ACCUM UVIS2-C1 F336W 2 2 none none 2 N/A S K1C-SUB 13433( 5) - 14-Jul-2014 18:44:10 - [ 7] Visit: 02 Visit Requirements: AFTER 01 BY 0 D TO 28 D On Hold Comments: Additional Comments: 2 orbits to acquire ACS/WFC F435W, F555W and F814W imaging of the site of SN 2011dh Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 SN-2011DH ACS/WFC ACCUM WFC1-1K F435W FLASH=60 1 268 S PATTERN 2 1 (1072 S) ------------------------------------------------------------------------------------------------------------------------------------ 2 SN-2011DH ACS/WFC ACCUM WFC1-1K F555W 1 308 S PATTERN 2 2 (1232 S) ------------------------------------------------------------------------------------------------------------------------------------ 3 SN-2011DH ACS/WFC ACCUM WFC1-1K F814W 1 544 S PATTERN 2 3 (2176 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ SN-2011DH 1 ACS/WFC ACCUM WFC1-1K F435W 1 none none none 1 N/A SN-2011DH 1 ACS/WFC ACCUM WFC1-1K F435W 2 none none none 1 N/A SN-2011DH 1 ACS/WFC ACCUM WFC1-1K F435W 3 none none none 1 N/A SN-2011DH 1 ACS/WFC ACCUM WFC1-1K F435W 4 none none none 1 N/A SN-2011DH 2 ACS/WFC ACCUM WFC1-1K F555W 1 none none none 1 N/A SN-2011DH 2 ACS/WFC ACCUM WFC1-1K F555W 2 none none none 1 N/A SN-2011DH 2 ACS/WFC ACCUM WFC1-1K F555W 3 none none none 1 N/A SN-2011DH 2 ACS/WFC ACCUM WFC1-1K F555W 4 none none none 2 N/A SN-2011DH 3 ACS/WFC ACCUM WFC1-1K F814W 1 none none none 2 N/A SN-2011DH 3 ACS/WFC ACCUM WFC1-1K F814W 2 none none none 2 N/A SN-2011DH 3 ACS/WFC ACCUM WFC1-1K F814W 3 none none none 2 N/A SN-2011DH 3 ACS/WFC ACCUM WFC1-1K F814W 4 none none none 2 N/A 13433( 5) - 14-Jul-2014 18:44:10 - [ 8] Visit: A1 Visit Requirements: SEQ A1, A2 WITHIN 1 D On Hold Comments: Additional Comments: This orbit is charged to the Cycle 21 ACS Subarray Bias Calibration Program. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 BIAS ACS/WFC ACCUM WFC1-1K DEF GAIN=2.0, COMPRESSION=NONE 13 0 S (0 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 1 none 1 N/A BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 2 none 1 N/A BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 3 none 1 N/A BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 4 none 1 N/A BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 5 none 1 N/A BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 6 none 1 N/A BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 7 none 1 N/A BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 8 none 1 N/A BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 9 none 1 N/A BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 10 none 1 N/A BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 11 none 1 N/A BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 12 none 1 N/A BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 13 none 1 N/A 13433( 5) - 14-Jul-2014 18:44:10 - [ 9] Visit: A2 Visit Requirements: GROUP A2, 02 WITHIN 14D On Hold Comments: Additional Comments: This orbit is charged to the Cycle 21 ACS Subarray Bias Calibration Program. Exposures ------------------------------------------------------------------------------------------------------------------------------------ Exp | Target | Instr | Oper. | Aper |Spectral|Central| Optional |Num| Time | Special Num | Name | Config | Mode | or FOV |Element |Waveln.| Parameters |Exp| (Total) | Requirements ------------------------------------------------------------------------------------------------------------------------------------ 1 BIAS ACS/WFC ACCUM WFC1-1K DEF GAIN=2.0, COMPRESSION=NONE 13 0 S (0 S) ------------------------------------------------------------------------------------------------------------------------------------ Sub Exposures ------------------------------------------------------------------------------------------------------------------------------------ Target | Exp |Instr | Oper. | Aper |Spectral|Cent.|Primary |Secondary |Iteration |CR-SPLIT |Orbit |Duration Name | Num |Config | Mode | or FOV |Element |Wave.|Pattern Pos |Pattern Pos |Num |Num |Number | ------------------------------------------------------------------------------------------------------------------------------------ BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 1 none 1 N/A BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 2 none 1 N/A BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 3 none 1 N/A BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 4 none 1 N/A BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 5 none 1 N/A BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 6 none 1 N/A BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 7 none 1 N/A BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 8 none 1 N/A BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 9 none 1 N/A BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 10 none 1 N/A BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 11 none 1 N/A BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 12 none 1 N/A BIAS 1 ACS/WFC ACCUM WFC1-1K DEF none none 13 none 1 N/A 13433( 5) - 14-Jul-2014 18:44:10 - [ 10] Summary Form for Proposal 13433 Item Used in this proposal ------------------------------------------------------------------------------------------------------------------------------------ Apertures UVIS2-C1K1C-SUB, WFC1-1K ------------------------------------------------------------------------------------------------------------------------------------ Configurations ACS/WFC, WFC3/UVIS ------------------------------------------------------------------------------------------------------------------------------------ Opmodes ACCUM ------------------------------------------------------------------------------------------------------------------------------------ Optional Parameters COMPRESSION=NONE, FLASH=12, FLASH=60, GAIN=2.0 ------------------------------------------------------------------------------------------------------------------------------------ Special Requirements AFTER 01 BY 0 D TO 28 D, AFTER 15-MAR-2014:00:00:00, GROUP A2, 02 WITHIN 14D, PATTERN 2 1, PATTERN 2 2, PATTERN 2 3, PATTERN 3 1, PATTERN 3 2, SEQ A1, A2 WITHIN 1 D ------------------------------------------------------------------------------------------------------------------------------------ Spectral Elements DEF, F225W, F336W, F435W, F555W, F814W ------------------------------------------------------------------------------------------------------------------------------------ Target Names BIAS, SN-2011DH ------------------------------------------------------------------------------------------------------------------------------------