1. Wild Stars in the Old West – Tucson –16-19 March 2009 M. Hernanz (CSIC-IEEC) 1 The recovery of accretion in classical 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)

2. Wild Stars in the Old West – Tucson –16-19 March 2009 M. Hernanz (CSIC-IEEC) 2 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

3. Wild Stars in the Old West – Tucson –16-19 March 2009 M. Hernanz (CSIC-IEEC) 3 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 bol  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 (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”: t nuc  100yr (>>observed) – based on estimated remnant H-mass after nova explosion “new”: L-M H,rem -T eff compatible with short duration of soft X-ray phase (Sala & Hernanz, 2005)  very small remnant H-mass

4. Wild Stars in the Old West – Tucson –16-19 March 2009 M. Hernanz (CSIC-IEEC) 4 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?

5. Wild Stars in the Old West – Tucson –16-19 March 2009 M. Hernanz (CSIC-IEEC) 5 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), M WD, accretion rate… Observations with XMM-Newton

6. Wild Stars in the Old West – Tucson –16-19 March 2009 M. Hernanz (CSIC-IEEC) 6 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 no supersoft 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 no supersoft 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 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 (H-burning) 2-3 out of 5 were emitting[thermal plasma(+BB)] spectrum  ejecta/accretion 2-3 out of 5 were emitting[thermal plasma(+BB)] spectrum  ejecta/accretion XMM- Newton AO1 cycle summary

7. Wild Stars in the Old West – Tucson –16-19 March 2009 M. Hernanz (CSIC-IEEC) 7 see Gloria Sala’s talk TargetDiscovery date Date of observation – Time after outburst Detection N Oph 1998 V2487 Oph June 15Mar. 24, 2007 – 8.8yr AO6 long exposure YES no supersoft N Cyg 2005 V2361 Cyg February 10 May 13, 2006 - 15mo – bkg October 20, 2006 - 20months AO5 -- YES marginal: (4.0  0.8)x10 -3 cts/s N Sgr 2005a V5115 Sgr March 28Sep. 27, 2006 – 18months AO5 YES supersoft N Sgr 2005b V5116 Sgr July 4March 20, 2007 – 20 months AO5 YES supersoft N Cyg 2006 V2362 Cyg April 2May 5, 2007 – 13 months affected by bkg AO6 YES no supersoft 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 X-ray emission related to residual H-burning found in novae from 2005 (V5115 Sgr & V5116 Sgr)  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 XMM- Newton AO5 & AO6

8. Wild Stars in the Old West – Tucson –16-19 March 2009 M. Hernanz (CSIC-IEEC) 8 Nova Sgr 1998 – V4633 Sgr Hernanz & Sala, ApJ 2007 3.5 yrs 2.6 yrs post explosion 3.0 yrs Thermal plasma only, no BB T (keV): 0.1, 1, >(3-5) EM (10 55 cm -3 ):  0.3-7 if nova ejecta abundances  0.4-600 if solar accretion ab. L unabs (0.2-10)keV (erg/s):  (2-8)x10 33 / (2-32) x10 33 ejecta/accr.

9. Wild Stars in the Old West – Tucson –16-19 March 2009 M. Hernanz (CSIC-IEEC) 9 2.7 yrs post explosion 3.2 yrs 3.7 yrs 4.3 yrs L unabs[0.2-10 keV] = 8.4 x10 34 erg/s +0.2 -0.4 L unabs[0.2-10 keV] = 7.8  0.4 x10 34 erg/s L unabs[0.2-10 keV] = 8.3 x10 34 erg/s +0.2 L unabs[0.2-10 keV] = 8.0 x10 34 erg/s +0.2 -0.4 BB (WD heated by accretion) + Thermal Plasma (2T) + Fe line complex Restablishment of accretion in < 3 years - Hernanz & Sala (2002), Science Nova Oph 1998 = V2487 Oph d=10 kpc

10. Wild Stars in the Old West – Tucson –16-19 March 2009 M. Hernanz (CSIC-IEEC) 10 Nova Oph 1998 = V2487 Oph - 4.3 yrs post explosion neutral Fe K  fluorescence line 6.4 keV 6.7 keV Fe XXV 6.97 keV FeXXVI 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 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 K  line at 6.4 keV reveals reflection on cold matter (disk and/or WD): accretion

11. Wild Stars in the Old West – Tucson –16-19 March 2009 M. Hernanz (CSIC-IEEC) 11 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

12. Wild Stars in the Old West – Tucson –16-19 March 2009 M. Hernanz (CSIC-IEEC) 12 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

13. Wild Stars in the Old West – Tucson –16-19 March 2009 M. Hernanz (CSIC-IEEC) 13 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)

14. Wild Stars in the Old West – Tucson –16-19 March 2009 M. Hernanz (CSIC-IEEC) 14 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 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. poster)

15. Wild Stars in the Old West – Tucson –16-19 March 2009 M. Hernanz (CSIC-IEEC) 15 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  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

16. Wild Stars in the Old West – Tucson –16-19 March 2009 M. Hernanz (CSIC-IEEC) 16 critical accreted mass does not depend only on M wd Accreted masses to reach H-ignition conditions L ini M=10 -8 M  /yr. Hernanz & José 2008

17. Wild Stars in the Old West – Tucson –16-19 March 2009 M. Hernanz (CSIC-IEEC) 17 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. N Oph 98: P rec =98 yr Hernanz & José 2008.

18. Wild Stars in the Old West – Tucson –16-19 March 2009 M. Hernanz (CSIC-IEEC) 18 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 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