1. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 1 Explosion, turn-off and recovery of accretion in novae revealed by X-rays Margarita Hernanz Institut de Ciències de l’Espai (CSIC-IEEC) - Barcelona (Spain)

2. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 2 OUTLINE  Classical and recurrent novae explosions: scenarios  Origin of X-ray emission  Summary of X-ray observations - Theoretical implications  Possibility to accelerate cosmic rays in novae (symbiotic recurrent) : RS Oph and V407 Cyg  Conclusions

3. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 3 White dwarfs Endpoints of stellar evolution (M< 10M  ): no E nuc available; compression until electrons become degenerate Chemical composition: He, CO, ONe; masses: typical 0.6 M , maximum: M Chandrasekhar (~1.4M  ) When isolated, they cool down to very low L (~10 -4.5 L  ): When in interacting binary systems, they can explode

4. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 4 White dwarfs in close binary systems Cataclysmic variable: WD + Main Sequence Roche lobe overflow Symbiotic system: WD + Red Giant accretion from a red giant wind Hydrogen burning in degenerate conditions on top of the white dwarf Classical novaRecurrent nova P rec ~10 4 -10 5 yr; P orb ~hr-day a~few 10 5 km~ few 10 10 cm rate ~35/yr in Galaxy P rec <100 yrs; P orb ~100’s days a ~ 10 13 -10 14 cm rate ~10 known in Galaxy Credit: David Hardy

5. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 5 In recurrent novae, initial mass of the WD should be very large (close to Chandrasekhar mass), to drive such frequent outbursts  Feasible scenario of type Ia supernova explosions, provided that less mass is ejected than accreted in each explosion  X-ray observations: way to study if WD mass grows or diminishes after each nova explosion Solve the controversy between single degenerate and double degenerate scenarios of type Ia supernovae Credit: David Hardy

6. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 6 Mass transfer from the companion star onto the white dwarf (cataclysmic variable) Hydrogen burning in degenerate conditions on top of the white dwarf Thermonuclear runaway Explosive H-burning Decay of short-lived radioactive nuclei in the outer envelope (transported by convection) Envelope expansion, L increase and mass ejection Scenario for classical novae

7. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 7 Novae observations: optical light curve apparent luminosity (m v ) time L increases very fast by factors greater than 10 4 -absolute L max ~10 4-5 L 

8. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 8 Novae observations: light curves UV satellites: L bol (L V +L UV )=ct. FH Ser 1970 - Gallagher & Code 1974 Nova Cyg 1978 – Stickland et al. 1981 IR emission dust formation L bol (L V +L UV + L IR ) =ct. V V+UV V IR UV TOT

9. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 9 Photosphere recedes as matter expands and becomes transparent Supersoft X-ray emission reveals the hot white dwarf photosphere, close to the burning shell

10. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 10 Origin of X-ray emission (I) Residual steady H-burning on top of the white dwarf: photospheric emission from the hot WD: T eff ~ (2-10)x10 5 K (L ~ 10 38 erg/s) supersoft X-rays  detected by ROSAT/PSPC in only 3 classical novae, out of 39 observed up to 10 years after explosion: GQ Mus (N Mus1983), N Cyg 1992, N LMC 1995 (Orio et al. 2001). A few more detections with BeppoSAX, Chandra, XMM-Newton; many more with Swift/XRT  duration related to H-burning turn-off time. “Old” theory: τ nuc ~ 100yr; observations: <9 - 12 yr; typically: < 2yr  new models: L-M H,rem -T eff compatible with short duration of soft X-ray phase (Tuchmann & Truran 1998; Sala & Hernanz, 2005)  very small remnant H-mass

11. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 11 Origin of X-ray emission (II) Internal (external) shocks in the ejecta: thermal plasma emission  detected early after explosion (N Her 1991, N Pup 1991, N Cyg 1992, N Vel 1999): internal shocks; recurrent nova RS Oph: external, V2491 Cyg 2008 ? Reestablished accretion: emission “as a CV” (idem)  Hard (but also soft) X-rays, depending on the thermal plasma T

12. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 12 Origin of X-ray emission (II, cont’d) Restablished accretion:  emission “CV-like” How and when? Interaction between ejecta and new accretion flow? Magnetic or non magnetic white dwarf?

13. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 13 Origin of X-ray emission (III) Compton degradation of γ- rays emitted by classical novae CAN NOT be responsible of their early hard X-ray emission: Cut-off at 20 keV (photoelectric abs.) Fast disappearence: 2days (w.r.t T max, i.e., before visual outburst) Gómez-Gomar,Hernanz,José,Isern, 1998, MNRAS

14. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 14 Observations – Supersoft X-ray emission  EXOSAT and ROSAT discoveries: GQ Mus (1983): 1st detection of X-rays in a nova, EXOSAT (Ögelman et al. 1984). One of the longest supersoft X-ray phases: 9 yr Ögelman et al.1993; Shanley et al. 1995; Orio et al. 2001; Balman & Krautter 2001 V1974 Cyg (1992): complete light curve with ROSAT- rise, plateau and decline – 1.5 yr Krautter et al. 1996, Balman et al. 1998 N LMC 1995: ROSAT & XMM-Newton – 8 yrs ROSAT discovery Orio &Greiner 1999 [XMM-Newton obs. Orio et al. 2003]

15. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 15 V1974 Cyg (1992): ROSAT’s soft X-ray light curve ONe WD atmospheres MacDonald & Vennes Balman et al. 1998, ApJ rise: until day 147 plateau: 18 months BB fits not good – too large L Krautter et al. 1996, ApJ

16. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 16 F=6x10 -10 erg/cm 2 /s kT BB =21eV, kT br =0.32keV F=3.2x10 -9 erg/cm 2 /s kT BB =30eV ( kT br =0.002keV) F=3.1x10 -9 erg/cm 2 /s kT BB =30eV (kT br =0.002keV) F=3x10 -11 erg/cm 2 /s kT BB =20 eV,kT br =0.29keV V1974 Cyg (1992): ROSAT’s soft X-ray spectra

17. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 17 Models that best explain the supersoft X-ray emission of V1974 Cyg 1992 and its evolution WD envelope models with steady H-burning (no accretion) M wd =0.9 M , 50% mixing with CO core (but V 1974Cyg 1992 was a neon nova!) or M wd =1.0 M , 25% mixing with ONe core [in goog agreement with models of the optical and UV light curve (Kato & Hachisu, 2006)] M env ~2x10 -6 M  WD properties from X-ray observation of turn-off Sala & Hernanz, A&A 2005

18. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 18  BeppoSAX V382 Vel (1999): supersoft X-ray flux not constant; model atmosphere not a good fit; emission lines from highly ionized nebula were required (Orio et al 2002) Chandra grating observations detected emission lines (Burwitz et al., 1992, Ness et al. 2005). Turn-off 7-9 months Observations – Supersoft X-ray emission

19. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 19  Chandra LETGS: V382 Vel (1999) Burwitz et al. 2002 Ness et al. 2005 Observations – Supersoft X-ray emission

20. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 20 Chandra and XMM-Newton (novae in outburst) puzzling temporal behaviours grating observations V1494 Aql (1999) - burst and pulsations Drake et al. 2003 V4743 Sgr (2002) - strong variability and complex spectra Ness et al 2003, Rauch, Orio, González Riestra et al., 2010: fits with NLTE WD atmospheric models  see Rauch’s talk – C1 Observations – Supersoft X-ray emission

21. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 21 Observations – Supersoft X- ray emission V4743 Sgr (2003) Temporal variability: P ~ 22 min. Ness et al. 2003, ApJ

22. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 22 Observations – Supersoft X- ray emission V4743 Sgr (2003) Non LTE model atmospheres Rauch, Orio, González-Riestra et al., 2010, ApJ

23. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 23 XMM-Newton Monitoring campaigns of post-outburst novae Nova LMC 1995 - Orio et al. 2003: H-burning still on in 2000  see Orio’s talk C2, about Nova LMC 2009 Galactic novae V5115 Sgr and V5116 Sgr 2005: Hernanz, Sala et al. Observations – Supersoft X-ray emission

24. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 24 TargetDiscovery date Date of observation – Time after outburst Detection N Sco 1997 V1141 Sco June 5Oct. 11, 2000 – 1224d, 3.4yr Mar. 24, 2001 – 1388d, 3.8yr Sep. 7, 2001 – 1555d, 4.3yr NO N Sgr 1998 V4633 Sgr March 22Oct. 11, 2000 – 934d, 2.6yr Mar. 9, 2001 – 1083d, 3.0yr Sep. 7, 2001 – 1265d, 3.5yr YES but no SSS N Oph 1998 V2487 Oph June 15Feb. 25, 2001 – 986d, 2.7 yr Sep. 5, 2001 – 1178d, 3.2 yr Feb. 2002 – 1352d, 3.7yr Sept. 24, 2002 – 1559d, 4.3yr YES but no SSS N Sco 1998 V1142 Sco October 21Oct. 11, 2000 – 721 d, 2.0 yr Mar. 24, 2001 – 885 d, 2.4 yr Sep. 7, 2001 – 1052 d, 2.9 yr 2.6  0.3 2.2  0.4 1.2  0.2 (10 -2 cts/s) N Mus 1998 LZ Mus December 29 Dec. 28, 2000 – 730 d, 2.0 yr Jun. 26, 2001 – 910 d, 2.5 yr Dec. 26, 2001 – 1093 d 3.0 yr NO? XMM-Newton - AO1 Cycle -Summary No supersoft X-ray emission related to residual H-burning detected No supersoft X-ray emission related to residual H-burning detected  all novae had already turned-off 3 out of 5 were emitting [thermal plasma (+ BB)] spectrum  ejecta/accretion 3 out of 5 were emitting [thermal plasma (+ BB)] spectrum  ejecta/accretion

25. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 25 TargetDiscovery date Date of observation – Time after outburst Detection N Oph 1998 V2487 Oph June 15Mar. 24, 2007 – 8.8yr AO6 long exposure YES but no SSS N Cyg 2005 V2361 Cyg February 10 May 13, 2006 - 15mo – bkg Oct. 20, 2006 - 20months AO5 -- YES marginal: (4.0  0.8)x10 -3 cts/s N Sgr 2005a V5115 Sgr March 28Sep. 27, 2006 – 18months Apr. 4, 2009 – 49 months YES supersoft source YES but no SSS N Sgr 2005b V5116 Sgr July 4Mar. 20, 2007 – 20 months Mar. 13, 2009 – 44 months YES supersoft source YES but no SSS N Cyg 2006 V2362 Cyg April 2May 5, 2007 – 13 months affected by bkg AO6 Dec. 22, 2008 – 32 months YES but no SSS N Oph 2006a V2575 Oph February 9 Sep. 4, 2007 – 19 months AO6 NO N Oph 2006b V2576 Oph April 6Oct. 3, 2007 – 18months AO6 NO Supersoft X-ray emission related to residual H-burning found in 2 novae from 2005 (V5115 Sgr & V5116 Sgr)  novae had not turned-off yet

26. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 26 partial eclipse by an asymmetric disk? Sala, Hernanz, Ferri & Greiner, ApJL 2008 Nova Sgr 2005 b – V5116 Sgr – 610 days post-outburst

27. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 27 Sala,Hernanz, Ferri, Greiner, AN (2010) Nova Sgr 2005 b – V5116 Sgr – 610 days post-outburst RGS spectra

28. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 28 Nova Sgr 2005 b – V5116 Sgr: new obs. March 2009 1348 days post-outburst Swift/XRT light light curve SSS turn-off: 2 - 3 years post- outburst compatible with Hachisu & Kato (2007) prediction L=(3-7)x10 32 erg/s (10 kpc) U filter

29. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 29 11 novae have been observed between 3 months and 5 years after outburst (9 years) Only 2, V5115 Sgr 2005a and V51116 Sgr 2005b, were still bright in supersoft X-rays, revealing remaining H- nuclear burning – one of them with a puzzling temporal behavior SSS phase absent means that either we missed it or M ejected > M accreted : M wd decreases after each nova outburst  WD can’t reach M CHANDRA and explode as SNIa SUMMARY of XMM-Newton campaign on Galactic novae

30. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 30 Swift/XRT Ness et al. 2007, Osborne (today’s talk, C1) The largest sample. Example: two extreme cases V723 Cas (1995): L and T eff not well determined (BB) Ness et al. 2008 – Still SSS 12 yrs after outburst. New XMM-Newton observations in 2010, still active V2491 Cyg (2008): duration SS phase 10 days Also observed with XMM-Newton and Suzaku: Ness et al. 2011, Takei et al. 2011 Observations – Supersoft X-ray emission

31. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 31 Observations – Supersoft X-ray emission V723 Cas (1985) Swift observations in 2007: Ness et al. 2008, MNRAS not turned-off yet XMM-Newton obs. in 2010: still on

32. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 32 Observations – Supersoft X-ray emission V2491 Cyg (2010) Page et al., 2010, MNRAS (Other interest of this nova: later)

33. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 33 Observations – Supersoft X-ray emission V2491 Cyg (2010) Ness et al. 2011

34. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 34 From Julian Osborne: see talk in C1 SUMMARY of Swift/XRT campaign

35. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 35  see talks by Henze C1 Pietsch C2 this afternoon 2007-2008 2008-2009 Novae in M31 XMM-Newton & Chandra monitoring: d and line of sight absorption known Henze et al. 2011, A&A

36. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 36 Observations of novae where H has turned off : Recovery of accretion and/or ejecta emission

37. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 37 Nova Oph 1998 = V2487 Oph - 4.3 yrs post explosion neutral Fe Kα fluorescence line 6.4 keV 6.7 keV Fe XXV 6.97 keV FeXXVI Identification of three Fe Kα emission lines: ~neutral Fe: 6.4 keV He-like Fe: 6.68 keV H-like Fe: 6.97 keV If T high ~ (10-20) keV, He-like and H-like lines well reproduced & only 6.4 keV fluorescent line added  If complex absorption - partial covering absorber- low (ISM)+ high N H  T high ~(10-20) keV Fluorescent Fe Kα line at 6.4 keV reveals reflection on cold matter (disk and/or WD): accretion

38. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 38 T low =0.3 keV T high =13 keV EM low =0.5 x10 57 cm -3 EM high =6±1 x10 57 cm -3 T bb =120 eV L bb =4±1 x10 34 erg/s N H =2x10 21 cm -2 (frozen) N H PCA =24 x10 22 cm -3 Covf=0.6±0.1 +10 -8 +0.3 -0.1 +20 -30 +0.6 -0.4 +8 -3 L unabs[0.2-10 keV] = 8.4 x10 34 erg/s +0.2 -0.4 L BB ~ 50% L TOT [0.2-10] keV - f(emitting surface/wd surface)~10 -4 (hot spots)  Luminosity, spectral shape..  Intermediate polar? need P spin vs. P orb Nova Oph 1998 = V2487 Oph 4.3 yrs post explosion d=10 kpc

39. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 39 N Oph 1998 = V2487 Oph Mar. 24, 2007 8.8yr post outburst  Spectral model: similar to previous observations  No clear periodicities in X-rays, but hint of orbital period ≈ 6.5 hrs  Optical observations seem to confirm the orbital P

40. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 40 Positional correlation with a source previously discovered by ROSAT (RASS) in 1990 suggests that the “host” of the nova explosion had been seen in X-rays before the outburst (Hernanz & Sala 2002, Science)  new case: V2491 Cyg (2008b): previous ROSAT, XMM and SWIFT detections (Ibarra et al. 2009, A&A) V2487 Oph (1998): 1 st nova seen in X-rays before its explosion (ROSAT)

41. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 41 Nova Oph 1998 = V2487 Oph Hard X-rays Detection with INTEGRAL/IBIS survey in the 20-100 keV band (Barlow et al. 2006, MNRAS): kT=25 keV ; flux compatible with our XMM-Newton results, but the IBIS spectrum has low S/N. Hints for large M WD from the optical light curve (Hachisu & Kato, 2002, ApJ)  also large M WD from large T high deduced from X-ray spectra – but T high not well constrained  The recent nova – V2491 Cyg (2008b) – has also been detected in hard X-rays with Suzaku (Takei et al. 2009)

42. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 42 Observations wih Suzaku and XMM-Newton: V2491 Cyg (2008) prompt and short duration hard X- rays Takei et al. 2009 and 2011

43. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 43 Previous outburst in 1900 June 20, discovered in the Harvard College Observatory archival photograph collection Pagnotta and Schaefer, IAUC 8951, 200; 2009 AJ)  recurrent nova - P=98 yrs  M WD very close to M CHANDRA  relevance for the SNIa scenario challenge for theory to get recurrent nova explosions with such short time scales X-ray emission CV-like ≠ RN scenario The recent nova – V2491 Cyg (2008b) – has also been claimed to be recurrent. It was also a very fast nova, expected to be massive, very luminous in X-rays (Ibarra et al. 2009, A&A), and detected in very hard X-rays (Takei et al. 2009) Nova Oph 1998=V2487 Oph - Recurrent Nova

44. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 44 Models of recurrent novae – TNR on accreting WDs Search combinations of initial conditions leading to short recurrence periods:  P rec = ΔM acc / (dM/dt) = 98 yrs (21 years for RS Oph)  ΔM acc : required accreted mass on top of the WD to power the outburst through a TNR  M wd ini ? Accretion rate? L wd ini ?  Accretion rate: related to mass loss from the red giant wind  effective dM/dt onto the WD: 2x10 -7 - 10 -8 M  /yr

45. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 45 critical accreted mass does not depend only on M wd M wd very close to M CHANDRA Accreted masses to reach H-ignition conditions L ini M=10 -8 M  /yr. Hernanz & José 2008

46. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 46 Recurrence Periods * M=2 10 -7 M  /yr & L=10 -2 L  L ini * * RS Oph: P rec =21 yr M=10 -8 M  /yr. V2487 Oph 1998: P rec =98 yr Hernanz & José 2008.

47. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 47 CONCLUSIONS (recovery of accretion) X-rays are crucial to study the recovery of accretion in post-outburst novae: type of CV, mass of the WD Magnetic WD: challenge for accretion –traditionally assumed to occur through a normal accretion disk in a non magnetic WD. But some cases of novae in magnetic CVs are known: V1500 Cyg (1975), V4633 Sgr (1998) – asynchronous polar as a consequence of the nova outburst (Lipkin & Leibowitz, 2008), V2487 Oph (1998), V2491 Cyg (2008)  see Pietsch’s talk C2: M31N 2007-12b, an IP? Massive WD: if T high (plasma) is large and/or the nova is recurrent. Novae as scenarios for type Ia supernovae  but very “ad-hoc” conditions are required to obtain a recurrent nova (P recurrence < 100 years)  but XMM spectra (V2487 Oph) looks CV-like ≠ RN scenario

48. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 48 An interesting case: the recurrent nova RS Oph, which erupted in 2006 Previous eruption in 1985 – P rec ~21 yrs Short recurrence period  large M WD close to M Chandra (deduced from models)  possible SNIa scenario (but should be CO WD!) P orb =456d; RG companion – symbiotic recurrent nova Detected as a very variable SSS by Swift/XRT (Bode et al. 2006), XMM-Newton (Nelson, Orio et al. 2008, Ness et al. 2009)

49. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 49 Supersoft X-ray light curve of the recurrent nova RS Oph (Swift observations, Bode et al. 2006) Kato & Hachisu, 2007 M wd =1.35 M  M env = 4x10 -6 M 

50. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 50 RS Oph in quiescence observed with XMM- Newton Nelson, Mukai, Orio, et al., 2011: observations in quiescence, 537 and 744 after outburst  accretion rate ≈ theoretical In previous eruptions: very faint X-ray source in quiescence, hard to reconcile with large accretion rates needed to explain frequent (every 20 yrs) outbursts

51. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 51 RS Oph grating observations with XMM-Newton and Chandra: Ness et al, Drake et al. 2009 See as well observations of U Sco (another recurrent nova, eclipsing, not of the symbiotic nova type: Ness talk C2

52. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 52 RS Oph  P rec ~21 yr: last eruptions in 1985, 2006  M WD > 1.35 M  (deduced from models; not measured)  M ejec ~ (3-4)x10 -6 M   not all accreted mass is ejected (deduced from models)  M WD increases & M close to M CHANDRA  SNIa scenario  Interaction between nova ejecta and red giant wind: expanding shock wave sweeps through the red giant wind (“mini” SN remnant)  Detected from radio to X-ray wavelengths  X-rays: reveal interaction between ejecta and wind (hard) and hot white dwarf surface with remaining nuclear burning (soft)  Acceleration of particles (Tatischeff & Hernanz 2007, ApJL)

53. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 53 RS Oph A supernova remnant-like, but faster and dimmer free expansion phase: days

54. RS Oph (2006 eruption): blast wave evolution * IR (Das+’06, Evans+’07) X-rays: RXTE & Swift (Sokoloski+’06, Bode+’06) 2 caveats Why shock cooling started at 6 days, when T s was 10 8 K and radiative cooling was not important? Particle acceleration - CRs Why v shock (X-rays) < v (IR): * (for test particle strong shock) underestimates v shock when particle accel. is efficient, because T s is lower (particle ecape and softer EOS)

55. RS Oph (2006 eruption) Non-linear diffusive shock acceleration: model of Berezhko & Ellison (1999)  accelerated proton spectrum and post shock temperatures as a funtion of η inj - the fraction of shocked protons injected into the acceleration process Tatischeff & Hernanz, ApJL 2007

56.  Good agreement with X-ray measurements of T shock for moderate CR accel. efficiency η inj ~10 -4 and Alfvén wave heating of the precursor  Energy loss rate due to particle escape ~100 times larger than L bol of postshock plasma  energy loss via accelerated particle escape much more efficient than radiative losses to cool the shock RS Oph (2006): cosmic-ray modified shock

57. RS Oph (2006): predicted gamma-ray emission π 0 production: from ε CR and (dM/dt) RG IC contribution: from non thermal synchrotron L (Kantharia et al.’07, radio 1.4 GHz), L syn ~5x10 33 t d -1.3 erg/s, and ejecta L, L ej ~L Edd = 2x10 38 erg/s: L IC = L syn x U rad /(B 2 /8π) ~ L syn  π 0 production dominates RS Oph would have been detected by Fermi!

58. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 58 V407 Cyg  Detected by Fermi/LAT 2 days after outburst: Cheung et al. 2008, Science Main differences wrt RS Oph Not a standard recurrent novae: no regular eruptions before 2010 (Munari 2010) P orb ~ 43 yr (456d in RS Oph)  a ~ 15 AU (10 times larger than for RS Oph)  shock wave needs ~7 days to reach d~a, so it propagates through the RG wind perturbed by the orbital motion in V407 Cyg (RS Oph, free exp. unperturbed wind at 1d) L syn needed to compute IC not available from early radio observations Preliminary estimation gamma-ray flux from π 0 production

59. SUMMARY (of GeV emission from symbiotic RNe) Recurrent novae in symbiotic binaries are expected to accelerate particles and emit VHE gamma-rays detectable with Fermi, because of the shock wave propagation in the dense red giant wind RS Oph would have been detected by Fermi V407 Cyg, detected by Fermi, did not behave as RS Oph, regarding X-ray and radio emission. So computing IC contribution is difficult. Other similar systems exist in the Galaxy: eventually 1-2 novae with RG companion per yr are expected (but not necessarily detected in the optical)

60. The X-Ray Universe 2011 - Berlin, 27-30 June 2011 M. Hernanz 60 Variety of behaviours of post-outburst novae: still need more observations Grating spectra are very rich, but still lack of emission models (e.g. WD expanding atmospheres) to interpret them. Blackbodies give wrong L and T eff & emission is often a mixture of photospheric and ejecta components WD Mass and envelope chemical composition (mainly H content) determine duration of SS X-ray phase Duration of SS X-ray phase observed indicates in general M env < M acc -M eject from hydro models  mass loss (wind and/or others?) Recurrent novae: very short duration of SS phase compatible with small M env. Challenging for theory: narrow parameter range: M wd extremely large & accretion rate large.  main caveat for RNe as SNIa scenario: not CO WDs but ONe Summary