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Origin of X-ray emission (I)

The recovery of accretion in c lassical novae as seen in X-rays Margarita Hernanz Carlo Ferri, Glòria Sala * , Institut de Ciències de l’Espai (CSIC-IEEC), Barcelona (Spain) * Departament Física i Enginyeria Nuclear, UPC, Barcelona (Spain). Origin of X-ray emission (I).

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Origin of X-ray emission (I)

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  1. The recovery of accretion in classical novae as seen in X-raysMargarita Hernanz Carlo Ferri,Glòria Sala*, Institut de Ciències de l’Espai (CSIC-IEEC), Barcelona (Spain) *Departament Física i Enginyeria Nuclear, UPC, Barcelona (Spain)

  2. Origin of X-ray emission (I) Residual steady H-burning on top of the white dwarf: photospheric emission from the hot WD: Teff(2-10)x105K (Lbol1038erg/s) supersoft X-rays • detected by ROSAT/PSPCin only 3 classical novae, out of 39 observed up to 10 years after explosion (Orio et al. 2001). A few more detections with BeppoSAX, Chandra, XMM-Newton, Swift Julian Osborne’s talk • duration related to turn-off time of H-burning • “old”: tnuc100yr (>>observed) – based on estimated remnant H-mass after nova explosion • “new”: L-MH,rem-Teff compatible with short durationof soft X-ray phase (Sala & Hernanz, 2005)  very small remnant H-mass

  3. Origin of X-ray emission (II) • Shocks in the ejecta produce hard X-rays • sometimes detected early after explosion (N Her 1991, N Pup 1991, N Cyg 1992, N Vel 1999, ...): internal shocks • Restablished accretion: emission “CV-like” • How and when? • Magnetic or non magnetic white dwarf? • Interaction between ejecta and new accretion flow?

  4. Observations with XMM-Newton Monitoring campaign of X-ray emission from “young” post-outburst novae with XMM-Newton (started pre-Swift launch) • Original aim: study turn-off of H-nuclear burning on top of accreting WDs after their explosion as classical novae, and of the ejecta properties • Additional interest :restablishment of accretion properties of the cataclysmic variable hosting the exploding WD: non magnetic or magnetic (IP, Polar), MWD, accretion rate…

  5. XMM-Newton AO1 cycle summary • No supersoft X-ray emission related to residual H-burning detected •  all novae had already turned-off (H-burning) • 2-3 out of 5 were emitting[thermal plasma(+BB)] spectrum  ejecta/accretion

  6. XMM-Newton AO5 & AO6 see Gloria Sala’s talk SupersoftX-ray emission related to residual H-burning found in 2novae from 2005 (V5115 Sgr & V5116 Sgr) novae had not turned-off yet

  7. Nova Sgr 1998 – V4633 Sgr 3.5 yrs 2.6 yrs post explosion • Thermal plasma only, no BB • T (keV): 0.1, 1, >(3-5) • EM (1055cm-3): • 0.3-7 if nova ejecta abundances • 0.4-600 if solar accretion ab. • Lunabs(0.2-10)keV (erg/s): • (2-8)x1033/ (2-32) x1033 ejecta/accr. 3.0 yrs Hernanz & Sala, ApJ 2007

  8. Nova Oph 1998 = V2487 Oph +0.2 -0.4 +0.2 -1.0 +0.2 -0.4 Lunabs[0.2-10 keV]= 8.4 x1034 erg/s Lunabs[0.2-10 keV]= 8.3 x1034 erg/s Lunabs[0.2-10 keV]= 8.0 x1034 erg/s 3.7 yrs 2.7 yrs post explosion Lunabs[0.2-10 keV]= 7.8  0.4 x1034 erg/s d=10 kpc 3.2 yrs 4.3 yrs BB (WD heated by accretion) + Thermal Plasma (2T) + Fe line complex Restablishment of accretion in < 3 years - Hernanz & Sala (2002), Science

  9. 6.7 keV Fe XXV neutral Fe K fluorescence line 6.4 keV 6.97 keV FeXXVI Nova Oph 1998 = V2487 Oph - 4.3 yrs post explosion • Identification of three Fe Kemission lines: ~neutral Fe: 6.4 keV He-like Fe: 6.68 keV H-like Fe: 6.97 keV • If Thigh ~ (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 NH Thigh~(10-20) keV Fluorescent Fe K line at 6.4 keVreveals reflection on cold matter (disk and/or WD): accretion

  10. Lunabs[0.2-10 keV]= 8.4 x1034 erg/s +0.2 -0.4 NH=2x1021 cm-2 (frozen) +0.3 -0.1 +20 -30 Tbb=120 eV +0.6 -0.4 Covf=0.6±0.1 +8 -3 Lbb=4±1 x1034 erg/s +10 -8 NHPCA=24 x1022 cm-3 Tlow=0.3 keV EMlow=0.5 x1057 cm-3 Thigh=13 keV EMhigh=6±1 x1057 cm-3 Nova Oph 1998 = V2487 Oph 4.3 yrs post explosion d=10 kpc • LBB ~ 50% LTOT[0.2-10] keV - f(emitting surface/wd surface)~10-4 (hot spots) • Luminosity, spectral shape .. Intermediate polar? need Pspinvs. Porb

  11. N Oph 1998 = V2487 Oph Mar. 24, 2007 8.8yr post outburst • Spectral model: similar to previous observations • No clear periodicities in X-rays • Ongoing optical observations in collaboration with Rodríguez-Gil, Casares, Steeghs

  12. V2487 Oph (1998):1st nova seen in X-rays before its explosion (ROSAT) 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)

  13. 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 is poor. Is there Compton reflection and with which properties? • Hints for large MWDfrom the optical light curve (Hachisu & Kato, 2002, ApJ) • also large MWDfrom large Thighdeduced from X-ray spectra – but Thigh not well constrained • The recent nova – V2491 Cyg (2008b) – has also been detected in hard X-rays with Suzaku (Takei et al. poster)

  14. Nova Oph 1998=V2487 Oph - Recurrent Nova • Previous outburst in 1900 June 20, discovered in the Harvard College Observatory archival photograph collection Pagnotta and Schaefer, IAUC 8951, 2008) – talk today • recurrent nova - P=98 yrs • MWD very close to MCHANDRA  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)

  15. . M=10-8 M/yr Accreted masses to reach H-ignition conditions critical accreted mass does not depend only on Mwd Lini Hernanz & José 2008

  16. . M=10-8 M/yr Recurrence Periods N Oph 98: Prec=98 yr Lini * RS Oph: Prec=21 yr . * M=2 10-7 M/yr & L=10-2L * Hernanz & José 2008

  17. CONCLUSIONS • 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) • Massive WD: if Thigh(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 (Precurrence < 100 years) • but XMM spectra (V2487 Oph) looks CV-like  RN scenario

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