1. 5-9 Nov 2012Tsinghua Transient Workshop Light curves and Spectra

2. 5-9 Nov 2012Tsinghua Transient Workshop SN Light Curves A SN shines for different reasons, and different types of SN may only show some of the various mechanisms Some SN classification is done on the basis of the Light curve properties The only phase common to all SNe is the radioactive phase, with 56Ni  56Co  56Fe

3. 5-9 Nov 2012Tsinghua Transient Workshop

4. 5-9 Nov 2012Tsinghua Transient Workshop SN Light Curves

5. 5-9 Nov 2012Tsinghua Transient Workshop 4 main phases 1.Shock breakout - star is hot, L~R *, rapid 2.Recombination phase (H-rich SNe) -envelope recombines, Light emitted: L, t ~ M(env), R(env) 3.Radioactive heating (long diffusion times) - 56 Ni, 56 Co decay:  ’s, deposition, optical photons L ~ M( 56 Ni), M *,  ; t ~ M *, , KE 4.Radioactive tail (short diffusion times) - 56 Co decay: prompt optical photons L ~ M( 56 Ni);t ~ M *, , KE

6. 5-9 Nov 2012Tsinghua Transient Workshop Different types of SNe have different light curves SN Type progShock Rec Rad. Heat. Rad. Tail II RSG (BSG) IIP (87A)   (small R)  Ib/c Cores (WR)  (small R)  (no H)   Ia Cores (WD)  (small R)  (no H)  

7. 5-9 Nov 2012Tsinghua Transient Workshop Type II SNe 79C: IIL (small H env. - no Rec. Phase) 93J: Ib (very small H env.: He lines) 87A: IIP-pec (BSG prog - small R) 97D: IIP (faint) (large envelope, small KE - long plateau)

8. 5-9 Nov 2012Tsinghua Transient Workshop SN 1987A : contributions to the LC Shock breakout Radioactive Heating Radioactive Tail

9. 5-9 Nov 2012Tsinghua Transient Workshop Shock breakout Explosion KE of SN ~, >> binding En of star  Expansion velocity is supersonic: Shock Wave When this reaches the surface, the star gets hot and bright Thermal En.:  If (1 ‘foe’), RSG progenitor  T~10 6 K But Very bright!

10. 5-9 Nov 2012Tsinghua Transient Workshop Shock breakout /2 But this phase is very short-lived (~1day): Adiabatic cooling: Radiation dominates:  Gas cools before it can contribute radiation to the LC

11. 5-9 Nov 2012Tsinghua Transient Workshop Adiabatic Cooling But some luminosity does escape If no other heating form, Where If E(rad) ~ 1/2 E(SN), Luminosity in this phase

12. 5-9 Nov 2012Tsinghua Transient Workshop Recombination Phase H envelope recombines when T~ 6000 K (T~12000 K for He envelope) Most opacity in H-rich SNe is Thomson scattering on free electrons When H recombines, opacity drops Recombined envelope ~ transparent to photons Photosphere follows ionization front Recombination wave moves inwards in vel space During Recombination phase, both Rph and L ~ constant: PLATEAU This is only true if H-envelope is massive

13. 5-9 Nov 2012Tsinghua Transient Workshop Plateau phase can last for months

14. 5-9 Nov 2012Tsinghua Transient Workshop Radioactive heating Adiabatic and recombination Luminosity only high if R large, E/M large (M small), H- envelope present. Otherwise, need other source of energy In SNe, 56 Ni is produced: this is radioactive  =8.8d  =111d 56 Ni  56 Co  56 Fe  e+

15. 5-9 Nov 2012Tsinghua Transient Workshop Radioactive decay/2 Energy produced: – 56 Ni: 3.9 10 10 erg/s/g – 56 Co: 6.8 10 9 erg/s/g ~96% of energy carried by  ’s, rest by e+  ’s are efficiently trapped: k  ~ 0.3 cm 2 /g Thermalisation to optical photons Optical photons must random-walk their way out in a large optical depth environment: k opt ~0.1cm 2 /g

16. 5-9 Nov 2012Tsinghua Transient Workshop Radioactive part of LC When photons escape SN becomes bright But the SN ejecta expand: density decreases and so does opacity Basic property: Maximum light occurs when heating = cooling (Arnett’s Rule) L(Max)  M( 56 Ni) Radioactive heating dominates LC if R * small, no H-envelope: Type I SNe (also SN1987A after shock breakout)

17. 5-9 Nov 2012Tsinghua Transient Workshop Radioactive Tail At late times,  opt <1,   <1 Only e+ deposit: ke+ ~ 7cm 2 /g,  e+ >>1 LC follows 56 Co decay rate (optical photons immediately emitted)  m = 0.98 mag/100d

18. 5-9 Nov 2012Tsinghua Transient Workshop Radioactive Tail/2 If envelope not massive, eventually even e+ may not fully deposit, and LC will decline faster

19. 5-9 Nov 2012Tsinghua Transient Workshop Radioactive Tail/3 For massive envelope (eg SN1987A) 56Co decay effective for a long time (2-3 yr), then other radioactive species with long decay times (eg 44Ti, 57Co) take over

20. 5-9 Nov 2012Tsinghua Transient Workshop SN Light Curves Peak Lum: 56Ni Plateau: H-envelope, R * (SNe IIL: small H-envelope SN 1987A: small R * ) Tail: 56Ni, M, E

21. 5-9 Nov 2012Tsinghua Transient Workshop SN Spectra Formation, Observables

22. 5-9 Nov 2012Tsinghua Transient Workshop Early-time spectrum Homologous expansion (v ≈ R) Ejecta are dense “Photospheric Epoch” τ =1 continuum absorption

23. 5-9 Nov 2012Tsinghua Transient Workshop Ejecta are dense  pseudo-photosphere Lines have P-Cygni profiles with But velocities are high: many lines overlap: “Line Blanketing” Early-time spectrum

24. 5-9 Nov 2012Tsinghua Transient Workshop Montecarlo approach SN envelope expands like Hubble flow: Photons continously redshifted They can only interact with the next red line Easy to treat in MC

25. 5-9 Nov 2012Tsinghua Transient Workshop Montecarlo spectra Treatment of ionization/excitation includes approximate NLTE (nebular approx.) Excited states Ground/metastable states: LTE Ionization: modified Saha

26. 5-9 Nov 2012Tsinghua Transient Workshop Photon Travel in Montecarlo scheme Abbott & Lucy 1985

27. 5-9 Nov 2012Tsinghua Transient Workshop Treatment of Opacities in MC Mazzali & Lucy 1993

28. 5-9 Nov 2012Tsinghua Transient Workshop Photon Branching in MC Mazzali 2000

29. 5-9 Nov 2012Tsinghua Transient Workshop The effect of Photon Branching Mazzali 2000

30. 5-9 Nov 2012Tsinghua Transient Workshop Testing different distances

31. 5-9 Nov 2012Tsinghua Transient Workshop Testing different risetimes

32. 5-9 Nov 2012Tsinghua Transient Workshop Late-time spectra Ejecta are thin: “Nebular Epoch” Gas heated by deposition of γ ’s and cooled by forbidden line emission Spectrum: no continuum. Emission line profiles depend on velocity, abundance distribution. Homologous expansion, homogenous density and abundance: parabolic profiles τ < 1

33. 5-9 Nov 2012Tsinghua Transient Workshop Late-time spectra Solve gamma-ray deposition, NLTE equations for state of gas Emission in mostly forbidden lines

34. 5-9 Nov 2012Tsinghua Transient Workshop Supernova Classification Maximum light spectra H / no H SNe II SNe I | | Light Curve shape Si / no Si SNe IIL SNe IIP SNe Ia He / no He SNe Ib SNe Ic

35. 5-9 Nov 2012Tsinghua Transient Workshop Spectral Classification

36. 5-9 Nov 2012Tsinghua Transient Workshop Supernova Classification Late-time spectra (6mo-1yr) H / no H SNe II SNe I | | O, H Fe, no O / O SNe Ia SNe Ib/c

37. 5-9 Nov 2012Tsinghua Transient Workshop Properties of SNe earlylateradiogalaxylightcurveM (Ni) (M  ) H HeSiHO E Speak tail~0.6 Ia         nar fast~0.1 Ib         nar fast~0.1 Ic         nar fast~0.1 II       brd slow-IIP nar-IIL

38. 5-9 Nov 2012Tsinghua Transient Workshop SNe II H lines dominate at all times HH Ca II

39. 5-9 Nov 2012Tsinghua Transient Workshop Properties of SNe from spectra: SNe II

40. 5-9 Nov 2012Tsinghua Transient Workshop Properties of SNe from spectra: SNe II

41. 5-9 Nov 2012Tsinghua Transient Workshop SNe II: spectral evolution reflects structure of massive star Early times: outer layers visible Late times: inner part exposed

42. 5-9 Nov 2012Tsinghua Transient Workshop SN1987A - confirmation of core collapse Core-collapse of massive star Catalogued star SK-69 202 M=17M  T eff =17000 Log L/ L  = 5.0 Star has disappeared Neutrinos confirm neutron star formation No pulsar or neutron star yet seen

43. 5-9 Nov 2012Tsinghua Transient Workshop Red supergiant progenitor - SN2003gd SN1987A progenitor was a blue supergiant. Progenitor detection difficult. Only one example of a red supergiant of a normal Type II supernova

44. 5-9 Nov 2012Tsinghua Transient Workshop SNe IIL: small H-envelope These are rare events, showing a rapid (Linear) decline with no plateau: e.g. SN1980K

45. 5-9 Nov 2012Tsinghua Transient Workshop SNe IIL: small H-envelope Spectra show weak absorptions, often emission lines, indicative of interaction with surrounding CSM gas Early time: small H- envelope + CSM CSMLate time: core

46. 5-9 Nov 2012Tsinghua Transient Workshop SNe IIn: extreme case of interaction Similar to IIL: early signs of interaction, but interaction luminosity sustains LC for a long time: e.g. SN1995G These can be among the brightest SNe

47. 5-9 Nov 2012Tsinghua Transient Workshop SNe IIn spectra Dominated by interaction: narrow H lines indicate massive CSM

48. 5-9 Nov 2012Tsinghua Transient Workshop SNe IIn spectra Dominated by interaction: massive CSM

49. 5-9 Nov 2012Tsinghua Transient Workshop SNe IIn: massive H-envelope Star collapsed while H-envelope was being shedded, SN strongly interacts with surrounding CSM gas Early time: small H- envelope + CSM CSM Late time: core

50. 5-9 Nov 2012Tsinghua Transient Workshop SNe IIn: ejecta-CSM interaction Two shock are launched at the contact discontinuity

51. 5-9 Nov 2012Tsinghua Transient Workshop SNe IIn: ejecta-CSM interaction Wind may be clumpy Narrow (few 100 km/s): clumpy wind Intermediate (~1000 km/s) : shocked wind Broad (few 100 km/s): : shocked ejecta

52. 5-9 Nov 2012Tsinghua Transient Workshop SNe IIb: an intermediate class? Early times: Both H and He present

53. 5-9 Nov 2012Tsinghua Transient Workshop SNe IIb: an intermediate class? Late times: O dominates, some weak H  also present, with flat-top profile: H in a shell H-envelope partially stripped early late

54. 5-9 Nov 2012Tsinghua Transient Workshop A binary progenitor? Detect hot star (B1 Ia) spectrum in spectum of SN1993J

55. 5-9 Nov 2012Tsinghua Transient Workshop SN1993J had lost most of its H-envelope to a companion Now companion is more massive New evolutionary track of companion after mass accretion

56. 5-9 Nov 2012Tsinghua Transient Workshop SNe Ib Early: optical: He, Ca, Si, some O IR: characteristic He lines He lines require non-thermal excitation by fast particles

57. 5-9 Nov 2012Tsinghua Transient Workshop SNe Ib Late: O, Ca, Mg Early times: see He H-envelope lost Late times: see CO core, as in SNe II Stripped star

58. 5-9 Nov 2012Tsinghua Transient Workshop SNe Ic Early: optical: Fe, Ca, Si, O IR: evidence of He lines unclear

59. 5-9 Nov 2012Tsinghua Transient Workshop SNe Ib/c Early: He (Ib), Ca, Si, some OLate: O dominates, Ca He lines require non-thermal excitation by fast particles

60. 5-9 Nov 2012Tsinghua Transient Workshop SNe Ic Late: O, Ca, Mg Early times: see CO core H- and H envelopes lost Late times: see CO core, as in SNe II, Ib Star more stripped

61. 5-9 Nov 2012Tsinghua Transient Workshop A Wolf-Rayet progenitor ?- SN2002ap Progenitor detection difficult. Probably a Wolf-Rayet star (stripped massive star)

62. 5-9 Nov 2012Tsinghua Transient Workshop An evolutionary sequence among core-collapse SNe earlylate

63. 5-9 Nov 2012Tsinghua Transient Workshop Btw, SNe Ib v. Ic: Helium Ib Ic 2.058µm 1.083µm (Taubenberger et al. 2006) Strongest HeI lines in IR. 1  can cause confusion, 2  line unique

64. 5-9 Nov 2012Tsinghua Transient Workshop Most nearby long-soft GRBs come with type Ic SNe stripped stars are more fun

65. 5-9 Nov 2012Tsinghua Transient Workshop Significance of spectrum Broad lines  Large Kinetic Energy  “Hypernovae” (only SN1998bw was associated with a GRB) Narrow lines  “normal” KE (1 foe)  Normal SN Ic Mazzali et al. 2002

66. 5-9 Nov 2012Tsinghua Transient Workshop SNe Ib/c cover a range of Lum SN1998bw was as bright as a SN Ia It produced much more 56Ni than `normal’ core- collapse SNe (~ 0.5 M  )

67. 5-9 Nov 2012Tsinghua Transient Workshop SNe span a range of KE GRB/SNe have very high expansion velocities (optical velocities up to 0.1c track relativistic properties) XRF/SNe have lower velocities after Pian et al. 2006, Nature

68. 5-9 Nov 2012Tsinghua Transient Workshop Iwamoto et al. 1998 SN 1998bw: modelling

69. 5-9 Nov 2012Tsinghua Transient Workshop GRB/SNe are highly aspherical Evidence in nebular spectrum (Oxygen line broader than Fe lines, Mazzali et al. 2001 ) but also in light curve

70. 5-9 Nov 2012Tsinghua Transient Workshop 56 Fe 16 O Spherical Aspherical FeII] 5200A [OI] 6300A Observed Aspherical explosion: aspect-dep line shape Orientation 15 deg Maeda et al. 2002

71. 5-9 Nov 2012Tsinghua Transient Workshop Was SN 2003jd = 98bw off-axis? It was almost as bright at peak as SN1998bw (Mv = -18.7) Early-time spectra had broad lines, but closer to SN2002ap

72. 5-9 Nov 2012Tsinghua Transient Workshop Prediction from asphericity: off-axis GRB/SNe Double-peaked [O I] line indicates edge-on SN SN Ic 2003jd had broad lines was luminous, and showed a double-peaked [O I] line but the presence of an off-axis GRB seems ruled out by radio limits (Soderberg et al. 2006) So, something’s missing Mazzali et al. (2005)

73. 5-9 Nov 2012Tsinghua Transient Workshop Which stars become which SNe? SN types of nonrotating massive single stars as a function of initial metallicity and initial mass. Green horizontal hatching indicates the domain where SNe IIp occur. At the high-mass end of the regime they may be weak and observationally faint because of fallback of 56Ni. These weak SNe IIp should preferentially occur at low metallicity. At the upper right-hand edge of the SN II regime, close to the green line of loss of the hydrogen envelope, SNe IIL/b that have a H-envelope of ~2 Mo; are made (purple cross-hatching). In the upper right-hand quarter of the figure, above both the lines of H-envelope loss and direct black hole formation, SNe Ib/c occur; in the lower part of their regime (middle of the right half of the figure) they may be weak and observationally faint because of fallback of 56Ni, similar to the weak SNe IIp. In the direct black hole regime no "normal" (non–jet-powered) SNe occur since no SN shock is launched. An exception are pulsational pair-instability SNe (lower right-hand corner; brown diagonal hatching) that launch their ejection before the core collapses. Below and to the right of this we find the (nonpulsational) pair-instability SNe (red cross-hatching), making no remnant, and finally another domain where black hole are formed promptly at the lowest metallicities and highest masses (white) where no SNe are made. Single WDs also do not make SNe (white strip at the very left).

74. 5-9 Nov 2012Tsinghua Transient Workshop Spectra of SNe: SNe Ia Early phase: absorption linesLate phase: nebular lines

75. 5-9 Nov 2012Tsinghua Transient Workshop The case of SNe Ia ASTRO: Calibration of SN luminosity –Brighter SNe have broader LCs (Phillips 93) PHYS: What causes Lum-light curve relation? Observednormalised

76. 5-9 Nov 2012Tsinghua Transient Workshop The case of SNe Ia Observations near maximum –Composition of outer layers, energetics Importance of late, nebular phase –Properties of inner layers, dominated by 56 Ni Mazzali et al. 1998 EarlyLate

77. 5-9 Nov 2012Tsinghua Transient Workshop The case of SNe Ia Abundance tomography –Model time series of spectra –Montecarlo and NLTE techniques –Complete description of SN (Mazzali et al. 2008)

78. 5-9 Nov 2012Tsinghua Transient Workshop The case of SNe Ia Mazzali et al. (2007) 56 Ni Si stable Fe The key to understanding Zorro diagram SN Ia behaviour –Study many SNe –Mass (Ni + Si) ~ const Mass burned ~ const KE ~ const Lum  M( 56 Ni) LC width  opacity  M(Fe group) –Links to progenitor/ explosion