Uncovering the Putative B-Star Binary Companion of the SN 1993J Progenitor

0 Assigned ID: 294 ----- Attempting Submission 1 (Thu Apr 10 23:20:47 GMT 2014) ----- HST Phase I Proposal 294 (fox_hst_93j_v2.apt) successfully submitted. ----- Attempting Submission 2 (Fri Apr 11 22:38:50 GMT 2014) ----- HST Phase I Proposal 294 (fox_hst_93j_v2.apt) successfully submitted. ----- Attempting Submission 3 (Fri Apr 11 23:20:06 GMT 2014) ----- At the suggestion of our WFC3 CS, adding a y pos-targ of -4 and changing FLASH from 8 to 12 -1439399446 ----- Attempting Submission 1 (Thu Jul 24 04:29:41 GMT 2014) ----- ----- Attempting Submission 2 (Wed Jul 30 19:07:06 GMT 2014) ----- Uncovering the Putative B-Star Binary Companion of the SN 1993J Progenitor The stripped-envelope Type IIb supernova (SN IIb) is a unique subclass of core-collapse explosions that result when a massive star loses most, but not all, of its outer envelope. Theoretical models suggest progenitor systems consist of low-mass stars that lose their envelopes during mass transfer to a binary companion, which becomes UV bright in the process. Although four stripped-envelope supernovae have progenitor stars identified in pre-explosion images, not a single progenitor companion star has been directly detected to date. In other words, the Type IIb progenitor system remains observationally unconfirmed. The nearby Type IIb SN 1993J in M81, at a distance of only 3.6 Mpc, offers one of the best opportunities to detect the putative companion and test the progenitor model. Indeed, evidence has been mounting over the past decade for a hot companion, but the dominating SN flux and contamination from nearby stars has made a confirmation difficult. In 2012, our team obtained HST/COS spectra and detected a far-UV (FUV) excess flux consistent with a hot B-star. This spectrum, however, is limited by a low signal-to-noise ratio and poor spatial resolution. Now that the SN has sufficiently faded, we propose FUV and NUV imaging of SN 1993J and the surrounding stars to disentangle the source of the FUV excess flux once and for all. Coinciding with Cycle 22's UV initiative, we can shed light on the binary nature of Type IIb progenitors in just 3 orbits. WFC3: - Use the C512C subarray - Near amp C - mitigate CTE - low flat field gradient - 512 pix = 20 arcsec - plenty of room to dither and get all of surrounding stars - short readout --> get almost all of our planned exposure time - amp C has ~20 droplet, but we arent going to worry about the droplets - Don't have to use POSTARGs to put target near amplifier - EXPTIME (actual/ planned): - F218W - 3000s/3000s - F275 - 2260s/2300s - F336W - 640s/700s - FLASH = 9 - Based on 12531 observations, background is ~2.5, we want 12 e-/pix --> FLASH of 9 e-/pix - 1 WFC3 visit: - putting all WFC3 observations in one 2 orbit visit. We want everything relatively close in time anyways, why not? - 4 pt box dither - sub pixel dither to maximize PSF sampling and therefore spatial sampling - remove CR and hot pixels ACS: - ETC Calc for binary companion: http://etc.stsci.edu/etc/results/ACS.im.573826/ - F140LP - remove airglow lines - EXPTIME (actual/planned) = 3150s/3000s - Use SBC aperture HOT STARS Default false true false false false SUPPORTED EXT-STAR SUPERNOVA This object was generated by the targetselector and retrieved from the NED database. J2000 J2000 ACS/SBC Imaging No No F140LP WFC3/UVIS Imaging No No F218W WFC3/UVIS Imaging No No F275W WFC3/UVIS Imaging No No F336W POS-TARG DITHER 0.173 LINE 0.112 false false 81.785 4 23.884 WFC3-UVIS-DITHER-BOX 5

false

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