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)

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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 (Lbol1038erg/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”: tnuc100yr (>>observed) – based on estimated remnant

H-mass after nova explosion • “new”: L-MH,rem-Teff compatible with short duration of soft X-ray

phase (Sala & Hernanz, 2005) very small remnant H-mass

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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?

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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…

Observations with XMM-Newton

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Target Discovery date

Date of observation – Time after outburst

Detection

N Sco 1997V1141 Sco

June 5 Oct. 11, 2000 – 1224d, 3.4yrMar. 24, 2001 – 1388d, 3.8yrSep. 7, 2001 – 1555d, 4.3yr

NO

N Sgr 1998V4633 Sgr

March 22 Oct. 11, 2000 – 934d, 2.6yrMar. 9, 2001 – 1083d, 3.0yrSep. 7, 2001 – 1265d, 3.5yr

YESno supersoft

N Oph 1998 V2487 Oph

June 15 Feb. 25, 2001 – 986d, 2.7 yrSep. 5, 2001 – 1178d, 3.2 yrFeb. 2002 – 1352d, 3.7yrSept. 24, 2002 – 1559d, 4.3yr

YESno supersoft

N Sco 1998V1142 Sco

October 21 Oct. 11, 2000 – 721 d, 2.0 yrMar. 24, 2001 – 885 d, 2.4 yrSep. 7, 2001 – 1052 d, 2.9 yr

2.60.3 2.20.4 1.20.2

(10-2 cts/s)

N Mus 1998LZ Mus

December 29

Dec. 28, 2000 – 730 d, 2.0 yrJun. 26, 2001 – 910 d, 2.5 yrDec. 26, 2001 – 1093 d 3.0 yr

NO

• No supersoft X-ray emission related to residual H-burning detected 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 2-3 out of 5 were emitting[thermal plasma(+BB)] spectrum ejecta/accretion ejecta/accretion

XMM-Newton

AO1 cycle summary

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see Gloria Sala’s talk

Target Discovery date

Date of observation – Time after outburst

Detection

N Oph 1998 V2487 Oph

June 15 Mar. 24, 2007 – 8.8yrAO6 long exposure

YESno supersoft

N Cyg 2005V2361 Cyg

February 10

May 13, 2006 - 15mo – bkg October 20, 2006 - 20monthsAO5

--YES

marginal: (4.00.8)x10-3 cts/s

N Sgr 2005aV5115 Sgr

March 28 Sep. 27, 2006 – 18monthsAO5

YESsupersoft

N Sgr 2005bV5116 Sgr

July 4 March 20, 2007 – 20 monthsAO5

YESsupersoft

N Cyg 2006V2362 Cyg

April 2 May 5, 2007 – 13 monthsaffected by bkg AO6

YESno supersoft

N Oph 2006aV2575 Oph

February 9 Sep. 4, 2007 – 19 monthsAO6

NO

N Oph 2006bV2576 Oph

April 6 Oct. 3, 2007 – 18monthsAO6

NO

Supersoft X-ray emission related to residual H-burning found in X-ray emission related to residual H-burning found in 2 novae novae from 2005 (V5115 Sgr & V5116 Sgr)from 2005 (V5115 Sgr & V5116 Sgr) novae had not turned-off yet

XMM-Newton AO5 & AO6

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Nova Sgr 1998 – V4633 Sgr

Hernanz & Sala, ApJ 2007

3.5 yrs2.6 yrs post explosion

3.0 yrs

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.

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2.7 yrs post explosion

3.2 yrs

3.7 yrs

4.3 yrs

Lunabs[0.2-10 keV]= 8.4 x1034 erg/s+0.2-0.4

Lunabs[0.2-10 keV]= 7.8 0.4 x1034 erg/sLunabs[0.2-10 keV]= 8.3 x1034 erg/s+0.2-1.0

Lunabs[0.2-10 keV]= 8.0 x1034 erg/s+0.2-0.4

BB (WD heated by accretion) + Thermal Plasma (2T) + Fe line complexRestablishment of accretion in < 3 years - Hernanz & Sala (2002), Science

Nova Oph 1998 = V2487 Oph

d=10 kpc

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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 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 keV reveals reflection on cold matter (disk and/or WD): accretion

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Tlow=0.3 keV

Thigh=13 keV

EMlow=0.5 x1057 cm-3

EMhigh=6±1 x1057 cm-3

Tbb=120 eV

Lbb=4±1 x1034 erg/s

NH=2x1021 cm-2 (frozen)

NHPCA=24 x1022 cm-3

Covf=0.6±0.1 +10-8

+0.3-0.1+20

-30 +0.6-0.4

+8-3

Lunabs[0.2-10 keV]= 8.4 x1034 erg/s +0.2-0.4

• LBB ~ 50% LTOT[0.2-10] keV - f(emitting surface/wd surface)~10-4 (hot spots)

Luminosity, spectral shape .. Intermediate polar? need Pspinvs. Porb

Nova Oph 1998 = V2487 Oph 4.3 yrs post explosion

d=10 kpc

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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

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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):1st nova seen in X-rays before its explosion (ROSAT)

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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 MWD from the optical light curve (Hachisu & Kato, 2002, ApJ)

also large MWD from large Thigh deduced 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)

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• 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)

Nova Oph 1998=V2487 Oph - Recurrent Nova

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critical accreted mass does not depend only on Mwd

Accreted masses to reach H-ignition conditions

Lini

M=10-8 M/yr.

Hernanz & José 2008

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Recurrence Periods

* M=2 10-7 M/yr

& L=10-2 L

Lini

*

*

RS Oph: Prec=21 yr

M=10-8 M/yr.

N Oph 98: Prec=98 yr

Hernanz & José 2008

.

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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