Keck Observations of Two Supernovae Hours After Explosion Shock-Breakout Flash Spectroscopy as a New Window into the Evolution and Death of Massive Stars Daniel Perley (Caltech) O. Yaron (Weizmann) A. Gal-Yam (Weizmann) E. Ofek (Weizmann) iPTF team

Palomar Transient Factory 2014-10-03

Palomar Transient Factory 2014-09-26

PTF → iPTF PTF (2009-2012): Various strategies, but typically 3-day cadence. Find large numbers of transients. Intermediate PTF (2013-present): Various strategies, but typically 1-hour cadence. (3 visits per night, every night) Find new types of fast-varying transients, and find “ordinary” supernovae very early. 2014-10-03

iPTF Nightly Scanning Scanners Palomar Keck 2014-10-03

iPTF 13ast UGC 7610 (D = 108 Mpc) 2013 May 3 04:14 UT SDSS reference image (Gal-Yam+2014, Nature 509:471) 2014-10-03

Keck Observations DEIMOS spectrum @ 0.64 days Fλ 5000 6000 7000 8000 9000 LRIS spectrum @ 6.45 days Wavelength (A) DEIMOS trigger and spectum 2014-10-03

Keck Observations DEIMOS spectrum @ 0.64 days Fλ Hβ DEIMOS spectrum @ 0.64 days N III Fλ HeII C IV, He I Hα N IV 5000 6000 7000 8000 9000 LRIS spectrum @ 6.45 days Wavelength (A) DEIMOS trigger and spectum 2014-10-03

Keck Observations DEIMOS spectrum @ 0.64 days Hβ DEIMOS spectrum @ 0.64 days N III HeII C IV, He I Hα N IV LRIS spectrum @ 6.45 days DEIMOS trigger and spectum 2014-10-03

Shock Breakout Below a Stellar Wind star X UV opt (spectrum just above stellar surface) 2014-10-03

Shock Breakout Below a Stellar Wind star shock X UV opt (spectrum just above stellar surface) 2014-10-03

Shock Breakout Below a Stellar Wind X UV opt (spectrum just above stellar surface) 2014-10-03

Shock Breakout Below a Stellar Wind X UV opt (spectrum just above stellar surface) 2014-10-03

Shock Breakout Below a Stellar Wind ionized wind X UV opt X UV opt (spectrum just above stellar surface) 2014-10-03

Shock Breakout Below a Stellar Wind ionized wind X UV opt (spectrum just above stellar surface) 2014-10-03

Shock Breakout Below a Stellar Wind X UV opt (spectrum just above stellar surface) 2014-10-03

Shock Breakout Below a Stellar Wind X UV opt (spectrum just above stellar surface) 2014-10-03

Flash Spectroscopy: Progenitor Diagnostic Flash-excited spectrum resembles a Wolf-Rayet star of type WN(h) (No oxygen: CNO-processed material is exposed in wind) IIb progenitor is a WR? Perhaps not (Groh 2014), but evolutionary link probably exists 2014-10-03

Pre-Explosion Behavior Hα luminosity constrains mass-loss rate (for inner wind; probes material emitted in last ~10 years pre-explosion) ~ 10- 2 M☉/yr Extremely rapid mass loss! Cannot be steady-state and very unlikely to be coincidental: star was highly unstable just before explosion (onset of C burning...?) 2014-10-03

iPTF 13dqy 2013 October 8 NGC 7610 (D = 51 Mpc) SDSS reference image (Yaron, Perley et al. 2014 in prep.) 2014-10-03

Early Keck Observations 0.26 d r-band light curve Swift UVW2 light curve 4000 5000 6000 7000 8000 9000 Wavelength (A) LRIS trigger and spectra time (days) 2014-10-03

Early Keck Observations 0.26 d O IV O VI Hδ He II Hγ Hβ Hα O V r-band light curve Swift UVW2 light curve 4000 5000 6000 7000 8000 9000 Wavelength (A) LRIS trigger and spectra time (days) 2014-10-03

13dqy Spectra 0.26 d 0.30 d 0.37 d 0.42 d 0.88 d 1.4d 2.0d 5.3d 8.8d 10.9d 20.2d 22.4d 27.1d 31.3d 43.3d 2014-10-03

13dqy Spectra 0.26 d 0.30 d Flash-excited narrow lines 0.37 d 0.42 d Hot continuum II-P supernova 2014-10-03

Line Profiles O IV, O V: No narrow core, Continuum-subtracted spectrum O IV, O V: No narrow core, Broad component only (all material is inner; t >> 1) but, O VI has a weak narrow component? H I, He II: Narrow core (recombination of outer material) + Broad wings (Thomson scattering of inner material) 2014-10-03

Line Flux Evolution Hydrogen peaks at ~1.5 d; disappears between 6-8 d He II peaks at ~1.0 d, disappears between 2-5 d O V, O VI peak at <0.3 d and disappear by 2 d 2014-10-03

Flash-Ionization and Light Travel Time 106 breakout Unflashed wind EUV-flashed wind EUV flash: ~ hour 105 EUV flash NUV flash cooling to Keck NUV flash: ~day 104 NUV-flashed wind pre-explosion time 8 light-days (=1360 AU, =2.1 × 101 6 cm) surface temperature (K) 2014-10-03

13dqy Preliminary Results Shock-breakout flash: Flash temperature ~105 K, lasting ~1 hour Mass-loss history: Emitting region ~ few light days Recent mass-loss rate ~10- 4 M☉/yr (Again not steady-state – late instability?) Slow wind velocity (< 100 km/s) Red supergiant progenitor, exploding during a period of greatly enhanced mass loss. Wind/surface composition: H/O-rich. (Possibly N-poor?) 2014-10-03

Stellar Wind Flash Tomography 2014-10-03

The Future This is only the beginning! Every core-collapse SN may very well behave this way. 2 out of 2 with <1 day observations Search of PTF archive finds several more transient H/He signatures in early (~few days) spectra. Early SN Ia spectra taken so far do not show these features. ~1 SN at <100 Mpc per day A few <1 day detections per year with iPTF A few <1 day detections per month with ZTF HIRES monitoring of a SN over first few days would provide detailed tomography of the spatially resolved wind Approved HST UV spectroscopy proposal starting next year (PI Gal-Yam) 2014-10-03

Summary iPTF 13ast (II-b): H, He, N lines disappearing in <5 days Progenitor was oxygen-depleted Enhanced mass loss / ejection in final years iPTF 13dqy (II-P): H, He, O lines disappearing in 1-5 days Progenitor wind oxygen-rich RSG progenitor, with enhanced mass loss All cc-SNe may show flash-excited early spectra, and All cc-SNe may undergo enhanced mass loss shortly before exploding. 2014-10-03

2014-10-03

Three Supernova Spectra Fλ 5000 6000 7000 8000 9000 2014-10-03

Three Supernova Spectra N IV He II Hβ C IV N IV He I Fλ very hot SN IIn 5000 6000 7000 8000 9000 Wavelength (A) Fλ featureless hot continuum featureless hot continuum Fe II H Ca II Fλ SN IIb He I He I 5000 6000 7000 8000 9000 2014-10-03

Three Supernova Spectra N IV He II Hβ C IV N IV He I very hot SN IIn Fλ featureless hot continuum featureless hot continuum 5000 6000 7000 8000 9000 Fe II Wavelength (A) H Ca II Fλ SN IIb He I He I 5000 6000 7000 8000 9000 2014-10-03

Three Supernova Spectra N IV He II Hβ C IV N IV He I very hot SN IIn Fλ featureless hot continuum featureless hot continuum Fe II H Ca II SN IIb He I He I 5000 6000 7000 8000 9000 2014-10-03

Three Supernova Spectra t = 0.64 days N IV He II Hβ C IV N IV He I very hot SN IIn t = 3.1 days Fλ featureless hot continuum featureless hot continuum t = 69 days Fe II H Ca II SN IIb He I He I 5000 6000 7000 8000 9000 2014-10-03