Transcript 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.

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)
Wild Stars in the Old West – Tucson –16-19 March 2009
M. Hernanz (CSIC-IEEC)
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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 (Lbol1038erg/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”: tnuc100yr (>>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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Observations with XMM-Newton
Monitoring campaign of X-ray emission from “young”
post-outburst novae with XMM-Newton (started preSwift 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…
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XMMNewton
AO1 cycle
summary
Target
Discovery
date
N Sco 1997
V1141 Sco
June 5
N Sgr 1998
V4633 Sgr
March 22
N Oph 1998
V2487 Oph
June 15
N Sco 1998
V1142 Sco
N Mus 1998
LZ Mus
Date of observation – Time
after outburst
Oct. 11, 2000 – 1224d, 3.4yr
Mar. 24, 2001 – 1388d, 3.8yr
Sep. 7, 2001 – 1555d, 4.3yr
Oct. 11, 2000 – 934d, 2.6yr
Mar. 9, 2001 – 1083d, 3.0yr
Sep. 7, 2001 – 1265d, 3.5yr
Detection
NO
YES
no supersoft
Feb. 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
October 21
Oct. 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)
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
• 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
Wild Stars in the Old West – Tucson –16-19 March 2009
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Discovery
date
N Oph 1998
V2487 Oph
June 15
Mar. 24, 2007 – 8.8yr
AO6 long exposure
N Cyg 2005
V2361 Cyg
February
10
May 13, 2006 - 15mo – bkg
October 20, 2006 - 20months
AO5
March 28
Sep. 27, 2006 – 18months
AO5
YES
supersoft
YES
supersoft
XMMNewton
AO5 &
AO6
N Sgr 2005a
V5115 Sgr
see
Gloria
Sala’s
talk
Date of observation – Time
after outburst
Target
Detection
YES
no supersoft
-YES
marginal:
(4.00.8)x10-3 cts/s
N Sgr 2005b
V5116 Sgr
July 4
March 20, 2007 – 20 months
AO5
N Cyg 2006
V2362 Cyg
April 2
May 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 6
Oct. 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
Wild Stars in the Old West – Tucson –16-19 March 2009
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Nova Sgr 1998 – V4633 Sgr
2.6 yrs post explosion
3.5 yrs
Thermal plasma only, no BB
• T (keV): 0.1, 1, >(3-5)
• EM (1055cm-3):
3.0 yrs
 0.3-7 if nova ejecta abundances
 0.4-600 if solar
accretion ab.
• Lunabs(0.2-10)keV (erg/s):
Hernanz & Sala, ApJ 2007
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(2-8)x1033/ (2-32) x1033 ejecta/accr.
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Nova Oph 1998 = V2487 Oph
3.7 yrs
2.7 yrs post explosion
Lunabs[0.2-10 keV]= 7.8  0.4 x1034 erg/s
+0.2
Lunabs[0.2-10 keV]= 8.3 -1.0 x1034 erg/s
d=10 kpc
3.2 yrs
Lunabs[0.2-10 keV]=
+0.2
8.0 -0.4
4.3 yrs
+0.2
x1034 erg/s
Lunabs[0.2-10 keV]= 8.4 -0.4 x1034 erg/s
BB (WD heated by accretion) + Thermal Plasma (2T) + Fe line complex
Restablishment of accretion in < 3 years - Hernanz & Sala (2002), Science
Wild Stars in the Old West – Tucson –16-19 March 2009
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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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Nova Oph 1998 = V2487 Oph 4.3 yrs post explosion
+0.2
Lunabs[0.2-10 keV]= 8.4-0.4 x1034 erg/s
NH=2x1021 cm-2 (frozen)
Tbb=120 +20
-30
d=10 kpc
eV
Tlow=0.3+0.3
-0.1 keV
57
-3
EMlow=0.5+0.6
-0.4 x10 cm
Covf=0.6±0.1
+8
Lbb=4±1 x1034 erg/s Thigh=13-3 keV
NHPCA=24 +10
x1022 cm-3
-8
EMhigh=6±1 x1057 cm-3
• LBB ~ 50% LTOT[0.2-10] keV - f(emitting surface/wd surface)~10-4 (hot spots)
 Luminosity, spectral shape .. Intermediate polar? need Pspinvs. Porb
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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
Wild Stars in the Old West – Tucson –16-19 March 2009
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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)
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Nova Oph 1998 = V2487 Oph Hard X-rays
• Detection with INTEGRAL/IBIS survey in the 20100 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 Xray 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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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)
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Accreted masses to reach H-ignition conditions
.
M=10-8 M/yr
Lini
critical accreted
mass does not
depend only on
Mwd
Hernanz & José 2008
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Recurrence Periods
.
M=10-8 M/yr
N Oph 98: Prec=98 yr
Lini
*
RS Oph: Prec=21 yr
.
*
-7 M /yr
M=2
10

*
& L=10-2 L
Hernanz & José 2008
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CONCLUSIONS
• X-rays are crucial to study the recovery of accretion in postoutburst 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
Wild Stars in the Old West – Tucson –16-19 March 2009
M. Hernanz (CSIC-IEEC)
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