what powers the brightest supernovae?

Transcription

1 what powers the brightest supernovae?

2 time-domain astronomy Palomar-48 inch a data driven revolution

3 2005ap 2008es ASASSN-15lh PTF-13ajg scp06f6 ptf09cnd 2006gy optical superluminous supernovae 2007bi type Ia ordinary core collapse supernovae

4 ultra-long duration gamma-ray bursts levan et al 2014

5 Two ways to blow up a massive star gravity powered by core collapse to neutron star or black hole thermonuclear powered by runaway nuclear burning no compact object formed hongfeng Yu Argonne NL spectral classification: Type I - no hydrogen Type II - hydrogen F. Ropke MPA

6 evolution of a core collapse supernova shock breakout light curve H envelope SN shock He core core collapse shock stall shock revival fallback accretion? C/O core Fe core bounce GW emission neutrino cooling neutron star spindown? neutron star pre-bounce

7 Core collapse supernova simulation 2D neutrino powered explosion Austin Harris (LBNL) with ORNL Chimera code

8 core collapse supernova energetics ordinary case gravitational energy released in neutron star formation E g GM 2 R ns ergs energy of supernova explosion (kinetic and thermal energy) E ke 1 2 Mv ergs total energy radiated in ordinary supernova light curve E lc L t ergs

9 credit: ASASSN Team radiated energy! super-luminous supernova ordinary supernova

10 superluminous supernova spectra Halpha Type II Smith quimby et al Type I Quimby+ 2007

11 Type I superluminous spectra SCP06f6 C/O model FeII CII CII/MgII OII/CII CIII/CII stripped envelope progenitor Howell, kasen, et al., 2013

12 supernova light curve basics debris expands at v ~ 0.03c, cools by pdv work at t ~ weeks-months r ~ cm ~ 100 AU ρ ~ g cm -3 translucent reheated to T ~ K L >~ 10 9 Lsun engine? Z Z-1 e + radioactive decay 56 Ni -> 56 Co -> 56 Fe νν Υ

13 supernova light curve basics light curve duration set by diffusion time the diffusion time of photons through optically thick remnant but since the remnant is expanding, R = vt solving for time (td ~ telapsed) e.g., arnett (1979)

14 supernova light curve basics luminosity of the light curve energy loses for adiabatically expanding radiation (pdv work) simple estimate of emergent luminosity assuming diffusion time td ~ 10 6 s

15 How to power a super-luminous supernova light curve dump in energy after the ejecta has expanded (at t ~ tdiff) so radiation can escape immediately radioactivity: decay of freshly synthesized isotopes: e.g., 56 Ni shocks: interaction of the supernova ejecta with a dense surrounding medium engines: later time energy injection from a central source (neutron star or black hole)

16 Milisecond magnetar Collapsar Pulsational Pair instability Birth star: ~30-70

17 radioactivity ~1 MeV per 56Ni need Mni >> Msun ASASSN-15lh scp06f6 2005ap ptf09cnd 2008es 2006gy MNi = Mej MNi = 0.1 Mej type Ia ordinary core collapse supernovae 2007bi

18 pair instability supernovae Rakavy, Shaviv, and Zinamon (1967), Bakrat, Rakavy, and Sack (1967) Bond, Arnett, and Carr (1984), Umeda and Nomoto (2001) Heger and Woosley (2002), Scannapeico et al 2005, Woosley (2007) H He progenitor masses M ~ Msun H He Si/Mg C/O e + /e - pairs trigger collapse and runaway thermonuclear burning Si/O 56 Ni total exposion energy: ergs radioactive 56Ni produced: 0-50 Msun

19 pair instability light curve models M = 130 helium star M = 250 red supergiant M = 250 blue supergiant type Ia type II kasen, woosley, & heger (2011) pan, kasen, & Loeb (2012)

20 ASASSN-15lh scp06f6 2004ap 2005ap 2008es ptf09cnd 2006gy He BSG RSG 2007bi type Ia ordinary core collapse supernovae pair instability supernovae

21 SN2007bi as a pair instability SN? Gal Yam et al., Nature (2009) bolometric helium stars

22 New early time observations show rise too fast Nicholl et al 2013

23 shock powered light curves from interaction with circumstellar material eta carinae

24 interacting tamped supernovae models supernova ejecta slow moving debris at ~100 AU ejection ~2 years prior

25 Mass loss from late stage nuclear burning? oxygen burning lasts ~1 year releases ~10 52 ergs! Tap that energy somehow: convectively driven waves, burning instabilitiies, pair instability Quataert & Shiode (2012) Quataert, Fernandez, Kasen, et al (2016) Smith & Arnett (2014) Arnett & Meakin (2011) Woosley et al (2007)

26 density colliding shell toy model velocity

27 colliding shell supernovae ~30% efficiency of conversion of kinetic energy to light shell colliding shell model Esn = ergs Rsh = cm pair instability (100 Msun He star)

28 signatures of interaction narrow line emission as in Type II SLSNe smith et al., 2006, 2008

29 central crab pulsar engine wind nebula power from gaenslar and slane (2006) from neutron star spindown crab nebula pulsar B ~ 5x10 12 g from gaenslar and slane (2006) P ~ 20 ms

30 neutron star spindown magnetized neutron stars release their rotational energy by magnetic dipole emission see Ostriker & Gunn (1974), Bodenheimer & Ostriker (1974), Gaffet (1977) rotational energy spindown timescale

31 ultra-luminous supernovae from magnetars to dump in energy at the right time ( months) requires the right magnetic field B and period P pulsar wind nebula (e.g., the Crab nebula) B ~ 5 x g; P ~ 20 ms Em ~ 5 x ergs; tm ~ 2,000 years too slow... magnetar model of gamma-ray bursts B ~ 3 x10 15 g; P ~ 1 ms Em ~ 2 x ergs; tm ~ 1 minute too fast... magnetar powered super-luminous supernovae B ~ 1x10 14 g; P ~ 4 ms Em ~ ergs; tm ~ months just right... e.g., Thompson et al., (2004) Bucciantini et al., (2007, 2008) Uzdensky and MacFadyen (2007)

32 dynamics of magnetar energy injection chen et al 2016

33 magnetar energy deposition magnetic dipole spindown in vacuum: mechanism and thermalization efficiency magnetized pulsar wind particle acceleration geometry hard photon production (inverse compton/synchrotron) x-ray absorption thermal optical radiation spherical or bipolar? Metzger et al 2015, Kasen, Metzger, & Bildsten (2016)

34 1D dynamics of magnetar powered supernova Kasen & Bildsten (2010)

35 P = 1 ms theoretical maximum 2-3 x ergs/s P = 2 ms P = 5 ms longer spindown time

36 magnetar theoretical maximum ~ 2x10 45 ergs/s ASASSN-15lh 2005ap 2008es scp06f6 ptf09cnd 2006gy P =1 ms MNi = Mej 2007bi P =5 ms MNi = 0.1 Mej

37 bolometric magnetar models kasen and bildsten (2010)

38 an early signature of the engine? nicholl+ (2015) c.f. leloudas+ (2012) (2012) > bright supernova + magnetar? > CSM + CSM (moriya+ 2012) > CSM interaction + magnetar? (piro 2015)

39 two types of magnetar heating

40 shell structure, t = 10 days density temperature velocity

41 double peaked light curves from magnetar driven shock breakout kasen, metzger, bildsten 2016

42 double peaked light curves from magnetar driven shock breakout kasen, metzger, bildsten 2016 with inefficient pulsar nebula thermalization at early times

43 kasen, metzger, bildsten 2016

44 Early peaks are common in SLSNe smith+ 2016

45 black hole central engines an inefficiently cooled disk blows energetic winds MacFadyen and Woosley (1999)

46 rotating core collapse and disk formation rodrigo fernandez (UCB)

47 C/O core He core H envelope 1D core collapse explosion model dexter and kasen (2013) lower explosion energy and/or strong reverse shocks give continuous fallback and black hole feeding at later times escape speed

48 fallback accretion rate from low energy explosions of massive stars red supergiant (Type II) dexter and kasen (2013) quataert and kasen (2014) blue supergiant (Type II) Mdot ~ t -5/3 He star (Type Ib) L BH = Ṁc ergs s 1 Ṁ M s 1

49 10 44 sn2008es sn1998bw sn2008d sn2010x simple toy light curve models comparison Luminosity (ergs s -1 ) to observed supernova light curves Days since explosion

50 diversity of outcomes dexter and kasen (2013)

51 ultra-long duration gamma-ray bursts levan et al 2014

52 an ultra-long (10 4 s) GRB with a luminous supernova Greiner et al 2015

53 diversity of transients from magnetars metzger, margalit, kasen & quataert (2015)