A Review of Recent Hard X-ray Studies of Classical Novae (CNe)

2010/11/30-2010/12/22010/11/30-2010/12/2 4th International MAXI Workshop4th International MAXI Workshop 11

A Review ofA Review of Recent Hard X-ray Studies Recent Hard X-ray Studies of Classical Novae (CNe)of Classical Novae (CNe)

M. Tsujimoto (ISAS) & D. Takei (Rikkyo M. Tsujimoto (ISAS) & D. Takei (Rikkyo U.)U.)


Scope & GoalScope & Goal

Scope : Scope : Recent observational results in hard (1-10 Recent observational results in hard (1-10 keV) and super-hard (10-100 keV) X-rays.keV) and super-hard (10-100 keV) X-rays.

An emphasis on Suzaku results.An emphasis on Suzaku results. Results in other wavelengths not included.Results in other wavelengths not included.

Goal :Goal : To convey To convey three ideas.three ideas. Swift changed the game completely.Swift changed the game completely.

– – Expanded opportunities for hard X-ray obs. from CNe.Expanded opportunities for hard X-ray obs. from CNe. Hard X-rays have potential to address Hard X-rays have potential to address

important questions.important questions.– – Non-thermal processes in CNe, WD mass and evolution.Non-thermal processes in CNe, WD mass and evolution.

MAXI has some roles to play in future outlook.MAXI has some roles to play in future outlook.


Talk planTalk plan

1.1. Historical context.Historical context.

2.2. Recent results.Recent results.

3.3. Future outlook.Future outlook.

Further reading:Further reading: ““Classical Novae 2Classical Novae 2ndnd edition” M. F. Bode and A. edition” M. F. Bode and A.

Evans (2008), Cambridge Astrophysics Series Vol. 43Evans (2008), Cambridge Astrophysics Series Vol. 43 ““X-ray Observations of Classical Novae” D. Takei X-ray Observations of Classical Novae” D. Takei

(2010), Astronomical Herald ((2010), Astronomical Herald ( 天文月報天文月報 ), 2010-07.), 2010-07.

1 2 3

1 2 3 4 5 6 7

1 2


1 2 3 1 2 3 4 5 6 7 1 21-1. CNe and hard X-1-1. CNe and hard X-raysrays Classical Novae (CNe)Classical Novae (CNe)

– Binary of WD and late-type dwarf/giant.Binary of WD and late-type dwarf/giant.– TNR on WD surface.TNR on WD surface.– MMejectaejecta~10~10-5-5-10-10-6 -6 MMoo

– VVejectaejecta=10=1033-10-1044 km/s km/s– ~10/yr discovered.~10/yr discovered.

Soft (< 1 keV) X-raysSoft (< 1 keV) X-rays– Emission from heated WD atmosphere; a.k.a. SSS.Emission from heated WD atmosphere; a.k.a. SSS.

Hard (>1 keV) X-raysHard (>1 keV) X-rays– Early appearance.Early appearance.– Different flux evolution.Different flux evolution.

V2491 Cyg

Page et al. (2010, MNRAS)Soft (0.3-1.5 keV)

Hard (1.5-10 keV)


1 2 3 1 2 3 4 5 6 7 1 21-2. Discovery: V838 1-2. Discovery: V838 HerHer Hard X-rays discovered by ROSAT ToO Hard X-rays discovered by ROSAT ToO

observation on day 5 of V838 Her in 1991.observation on day 5 of V838 Her in 1991.– Lloyd et al. (1992, Nature)Lloyd et al. (1992, Nature)

Distinctive from SSS emission in early Distinctive from SSS emission in early appearance & spectral hardness.appearance & spectral hardness.

Interpreted as plasma by ejecta shocks.Interpreted as plasma by ejecta shocks.– O’Brien+ (1994, MNRAS), Mukai & Ishida (2001, ApJ), etc.O’Brien+ (1994, MNRAS), Mukai & Ishida (2001, ApJ), etc.

Hard X-rays in post CN explosions are rare; Hard X-rays in post CN explosions are rare; faint and disappear quickly.faint and disappear quickly.– Orio+ (A&A, 2001), Ness+ (ApJ, 2007), etc.Orio+ (A&A, 2001), Ness+ (ApJ, 2007), etc.

ToO observations risky.ToO observations risky.

Lloyd et al. (1992)


1 2 3 1 2 3 4 5 6 7 1 21-3. Advent of Swift 1-3. Advent of Swift eraera Swift (2004-) changed the game completely.Swift (2004-) changed the game completely. X-ray snapshots for optically-discovered X-ray snapshots for optically-discovered

bright CNe at a high cadence from day >1.bright CNe at a high cadence from day >1. Observations by “observatory-type” satellites Observations by “observatory-type” satellites

(Chandra, XMM-Newton, Suzaku) planned (Chandra, XMM-Newton, Suzaku) planned when most needed.when most needed.

Data by advanced technologies (CCD & Data by advanced technologies (CCD & grating spectroscopy, high-resolution grating spectroscopy, high-resolution imaging, super-hard band detectors, ...) imaging, super-hard band detectors, ...) accumulated.accumulated.

V2491 Cyg

V2491 Cyg

Page et al. (2010, MNRAS)

Suzaku XMM-Newton


1 2 3 1 2 3 4 5 6 7 1 2

2. Recent results2. Recent results

1.1. Evidence for shocks for X-ray plasma.Evidence for shocks for X-ray plasma.

2.2. Non-solar elemental abundance in Non-solar elemental abundance in plasma.plasma.

3.3. Reestablished accretion after nova.Reestablished accretion after nova.

4.4. Non-thermal processes.Non-thermal processes.


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Accumulating evidence for the shock origin of the Accumulating evidence for the shock origin of the hard X-ray plasma.hard X-ray plasma.

Emission lines from optically-thin thermal Emission lines from optically-thin thermal plasma.plasma.

Blue-shifted absorption.Blue-shifted absorption.

Shocks:Shocks: Internal shocks: collision among nova winds at Internal shocks: collision among nova winds at

different velocities.different velocities. External shocks: collision of winds by nova and External shocks: collision of winds by nova and

companion (recurrent novae, symbiotic novae)companion (recurrent novae, symbiotic novae)

2-1. Evidence for 2-1. Evidence for shocksshocks

Tsujimoto et al. (2009, PASJ)V458 Vul

Ne X Mg XI Si XIII S XV

Ness. (2010, AN)

V2491 Cyg

Companion

WD

Internal

External


1 2 3 1 2 3 4 5 6 7 1 22-2. Elemental 2-2. Elemental abundanceabundance Metal abundances (N, O, Ne, Mg, Si, S, Ar, Fe) : Metal abundances (N, O, Ne, Mg, Si, S, Ar, Fe) :

[m/H][m/H]CNCN/[m/H]/[m/H]solar solar (assuming [He/H](assuming [He/H]CNCN=[He/H]=[He/H]solarsolar).). Plasma abundance reflects WD core composition Plasma abundance reflects WD core composition

and nuclear products. An indicator of Mand nuclear products. An indicator of MWDWD.. V458 Vul speculated to be ONe-type by X-ray. V458 Vul speculated to be ONe-type by X-ray.

Confirmed to be CO-type by optical.Confirmed to be CO-type by optical.

Fe deficiency.Fe deficiency. Reason unknown; Non-equilibrium ionization, Reason unknown; Non-equilibrium ionization,

dust condensation, sinking deep into WD?dust condensation, sinking deep into WD?

Takei et al. (in prep., PASJ)V2672 Oph

Si XIII, Si XIV

Mukai & Ishida (2001, ApJ)V382 Vel

ONeCO

M(i)WD<~1.1Mo M(i)

WD>~1.1Mo

RWD

1. Accretion2. Mixing3. Synthesizing

g=GMWD/RWD

Si SMg

OC

N


1 2 3 1 2 3 4 5 6 7 1 22-3. Rekindled 2-3. Rekindled accretionaccretion Accretion process stops after a CN. How early Accretion process stops after a CN. How early

does it resume?does it resume?

Some CNe occur in magnetized WDs (~10 Some CNe occur in magnetized WDs (~10 IPs; BIPs; BWDWD~10~1066 gauss, 1 Polar; B gauss, 1 Polar; BWDWD>10>1077 gauss). gauss).

IPs = Strong emitters of Fe lines (Fe I, Fe IPs = Strong emitters of Fe lines (Fe I, Fe XXV, & Fe XXVI) powered by accretion.XXV, & Fe XXVI) powered by accretion.

Reestablished accretion probed w. Fe lines.Reestablished accretion probed w. Fe lines.

Fe XXV, Fe XXVIFe I

WD


1 2 3 1 2 3 4 5 6 7 1 22-3. Rekindled 2-3. Rekindled accretionaccretion

V2491 Cyg

Page et al. (2010, MNRAS)

Suzaku XMM-Newton

1

2 3 4 5 6

Take

i et a

l. (Subm

itted, P

ASJ)

V2491 Cyg1

2

3

4

5

6

Fe I Fe XXV Fe XXVI


1 2 3 1 2 3 4 5 6 7 1 22-4. Non-thermal 2-4. Non-thermal processprocess Particle acceleration in CN explosions (analogy Particle acceleration in CN explosions (analogy

to SNe and SNRs).to SNe and SNRs). Super-hard (10-100 keV) band X-rays.Super-hard (10-100 keV) band X-rays.

– Upper limit in V382 Vel (SAX; Orio et al. 2001, Upper limit in V382 Vel (SAX; Orio et al. 2001, MNRAS).MNRAS).

– Detection in V2491 Cyg (Suzaku; Takei et al. 2010, Detection in V2491 Cyg (Suzaku; Takei et al. 2010, ApJL)ApJL)

GeV gamma-raysGeV gamma-rays– Detection in V407 Cyg (Fermi; Abdo et al. 2010, Sci).Detection in V407 Cyg (Fermi; Abdo et al. 2010, Sci).– Talk by Dr. Hays [O-12].Talk by Dr. Hays [O-12].

Takei et al. (2009, ApJL)

V2491 Cyg


GeV emission from V407 Cyg.GeV emission from V407 Cyg.– Radiation: IC or Radiation: IC or 00 decay. decay.– Acceleration: Shock acceleration at ext. Acceleration: Shock acceleration at ext.

shock.shock.

Superhard X-ray emission from V2491 Superhard X-ray emission from V2491 Cyg.Cyg.– Radiation: Synchrotron, IC, brems, ?Radiation: Synchrotron, IC, brems, ?– Acceleration: DSA inconsistent w. observed Acceleration: DSA inconsistent w. observed

=0.1. Some exotic mechanims?=0.1. Some exotic mechanims?

1 2 3 1 2 3 4 5 6 7 1 22-4. Non-thermal 2-4. Non-thermal processprocess

Abdo et al. (2010, Sci)

V407 CygNe X Mg XI Si XIII S XV

Companion

WDExternal

Hachisu & Kato (2010, ApJL)

Suzaku


1 2 3 1 2 3 4 5 6 7 1 2

3. Future outlook3. Future outlook

Unique capabilities of hard X-rays.Unique capabilities of hard X-rays.1.1. Penetrating power through the Galactic plane.Penetrating power through the Galactic plane.2.2. Coverage of both thermal & non-thermal features.Coverage of both thermal & non-thermal features.3.3. Diagnoses of MDiagnoses of MWDWD (still immature). (still immature).

Problems within reach of hard X-rays.Problems within reach of hard X-rays.1.1. Abundance pattern to distinguish C-O/O-Ne type WDs.Abundance pattern to distinguish C-O/O-Ne type WDs.2.2. Mass distribution of Galactic CNe. How many WDs Mass distribution of Galactic CNe. How many WDs

close to Mclose to Mchch? Do they gain or lose mass?? Do they gain or lose mass?3.3. Post-nova evolution of non-thermal emission.Post-nova evolution of non-thermal emission.4.4. Differences in hard X-rays between magnetic & non- Differences in hard X-rays between magnetic & non-

magnetic WDs.magnetic WDs.5.5. Cause for the Fe deficiency.Cause for the Fe deficiency.


1 2 3 1 2 3 4 5 6 7 1 2

3. Possible MAXI utility3. Possible MAXI utility

Post-nova evolution of non-thermal emission.Post-nova evolution of non-thermal emission.– Any relation with curious optical behavior?Any relation with curious optical behavior?– Super-hard non-thermal emission detected from one Super-hard non-thermal emission detected from one

source (V2491 Cyg) only once.source (V2491 Cyg) only once.– RS Oph by RXTE (Sokoloski et al. 2006, Nature).RS Oph by RXTE (Sokoloski et al. 2006, Nature).

Unbiased survey of CNe.Unbiased survey of CNe.– Histogram of MHistogram of MWDWD. . – Current survey (only in optical) biased for low MCurrent survey (only in optical) biased for low MWDWD..– MAXI sensitivity is insufficient, but attempt exists MAXI sensitivity is insufficient, but attempt exists

(Shimanoe et al. [P-35]).(Shimanoe et al. [P-35]).

SuperMAXI?SuperMAXI?– 2x102x103434 erg/s @8.5 kpc ~ 0.1 mCrab. erg/s @8.5 kpc ~ 0.1 mCrab.– CNe obs.CNe obs. initiated by X-rays, similarly to BH/NS binaries.initiated by X-rays, similarly to BH/NS binaries.

Sokoloski et al. (2006, Nature)

RS Oph

Courtesy: T. Yoshida

MAXI/GSC spectrum(1 day integration)


ENENDD

1.1. Swift changed the game completely.Swift changed the game completely.2.2. Hard X-rays have potential to address Hard X-rays have potential to address

important questions.important questions.3.3. MAXI has roles to play in future MAXI has roles to play in future

outlook.outlook.

Documents

A Review of Recent Hard X-ray Studies of Classical Novae (CNe)