Dust to Dust: Monitoring the Evolution of a New Class of Self-Obscured Transients

Science Keywords: Select from 2 to 5 items. Science Keywords is a required field. 0 Assigned ID: 1232 ----- Attempting Submission 1 (Wed Sep 07 14:08:32 GMT 2016) ----- Joint Spitzer/Hst added orient constraints recommeded by Dr. Momcheva (program contact scientist) 444761312 ----- Attempting Submission 1 (Tue Sep 20 15:24:31 GMT 2016) ----- HST Phase II Proposal 14844 (sn2008snew.apt) successfully submitted. Receipt: # 14844-1 ----- Attempting Submission 2 (Fri Oct 28 17:34:33 GMT 2016) ----- Dust to Dust: Monitoring the Evolution of a New Class of Self-Obscured Transients The goal of this proposal is to understand a new class of explosive transients associated with the most massive AGB stars. Today these sources are true creatures of the mid-IR, being optically invisible and very faint in the near-IR. By coarsely monitoring them with Spitzer and HST we can examine the evolution of the luminosity, dust optical depth and dust radius/temperature at a key time when their observed fluxes are approaching those of the two known progenitors. At its very simplest, if they do not stop fading in the mid-IR or start to brighten in the near-IR, then they are almost certainly examples of the theoretically expected but observationally missing electron capture supernovae (ecSNe). The exciting result from the last set of HST/Spitzer observations is that the sources continued to fade and two are clearly substantially fainter than their progenitors. If this continues, the ecSNe interpretation becomes far stronger. The newly recognized SN2008S class of transients consists of some form of explosive transient, possibly an electron capture supernova, on heavily self-obscured ~10Msun extreme AGB stars. After the transient they again cloak themselves with dust to be almost invisible in the near-IR while remaining very luminous in the mid-IR. The only way to determine their true natures is to continue following their evolution. We have allocated Spitzer time to follow their evolution, but the mid-IR data is not sensitive to the evolution of the dust optical depth. We propose observing 2 of these systems with WFC3/IR in the YJ (F110W) and H (F160W) bands. The near-IR emission comes from the underlying source (an expanding shock and/or a surviving star) and is absorbed by the surrounding dust, so the near-IR fluxes are exponentially sensitive to the evolution of the dust optical depth. For example, the optical depth from the observer through a dusty wind down to an expanding shock drops inversely with time, so we should begin to see these sources become brighter in the near-IR. Stellar Physics 12 false false false false false false SUPPORTED STAR SUPERNOVA copied from previous HST observation phase 2 APT J2000 J2000 STAR SUPERNOVA copied from previous HST observation phase 2 APT J2000 J2000 WFC3/IR Imaging No No F110W WFC3/IR Imaging No No F160W WFC3/IR Imaging No No F110W WFC3/IR Imaging No No F160W POS-TARG DITHER 0.605 LINE false false 3 41.788 WFC3-IR-DITHER-LINE-3PT 1

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