Suzaku X-ray Observations of Classical Novae

Transcription

1 Suzaku X-ray Observations of Classical Novae Physics of Accreting Compact Binaries, Dai Takei 1, Masahiro Tsujimoto 2, Jan-Uwe Ness 3, Shunji Kitamoto 1, and Jeremy J. Drake 4 1 Rikkyo Univ., 2 ISAS/JAXA, 3 ESAC/ESA, 4 SAO

2 Novae late-type dwarf or giant (IR ~ Optical) white dwarf (X-rays) accretion disc (Optical ~ UV) 2/23

3 3/23

4 photosphere (Optical (Optical) ~ UV) 4/23

5 1 photosphere (super-soft (Optical ~X-ray) UV) 5/23

6 1 photosphere (super-soft X-ray) 2 shock? (thermal X-ray) 6/23 3 unknown? (non-thermal X-ray)

7 7/23 SSX VS Hard Emission 1SSX 2&3 Hard emission 2&3 Hard emission

8 Point of Views : Classical Novae Hard X-ray emission - Fast evolution - Weak source - Emission lines in the spectra Behavior unpredictable - Observations are difficult to schedule!! - Only a hand full of novae have been studied We planned deep and systematic X-ray spectroscopy of classical novae!! 8/23

9 9/ X-ray Satellite Suzaku ( すざく )

10 10/ Suzaku Detectors of Suzaku XRS XIS HXD (0,1, 2,3) (PIN,GSO) Bandpass 0.2 ~ 12 kev 15 ~ 600 kev Spatial Resolution Not-Working... ~2 arcm. (HPD) N/A Energy Resolution ~130 6 kev ~4.0 kev (PIN) Time Resolution 8 sec 61μsec

11 11/23 Point of Views : Suzaku Advantages of Suzaku... - Wide energy range (0.2 ~ 600 kev) - High sensitivity above 10 kev - Moderately good energy resolution Suzaku is a well-suited tool... - to study line emission of hard X-ray - to examine non-thermal emission We conducted some ToO observations of classical novae using Suzaku!!

12 12/23 ROSAT ALL-Sky X-ray Background Survey ( kev) Suzaku View : Classical Novae 3 V2491 Cyg ( ) - Takei et al. (2009), ApJL, 697, 54 - Takei et al. (2010), AN, 331, Takei et al., in prep. 5 U Sco ( ) - Takei et al., in prep. 2 V458 Vul ( ) - Tsujimoto et al. (2009), PASJ, 61, S69 4 V2672 Oph ( ) - Takei et al., in prep. 1 Suzaku J ( ) - Takei et al. (2008), PASJ, 60, S231

13 13/23 ROSAT ALL-Sky X-ray Background Survey ( kev) Suzaku View : Classical Novae 3 V2491 Cyg ( ) - Takei et al. (2009), ApJL, 697, 54 - Takei et al. (2010), AN, 331, Takei et al., in prep. 5 U Sco ( ) - Takei et al., in prep. 2 V458 Vul ( ) - Tsujimoto et al. (2009), PASJ, 61, S69 4 V2672 Oph ( ) - Takei et al., in prep. 1 Suzaku J ( ) - Takei et al. (2008), PASJ, 60, S231

14 14/23 Classical Nova V2491 Cygni - Discovery on 2008 April (UT) (Nakano et al. 2008, IAUC, 8934, 1) - Swift detected X-rays on day 5 (Page et al. 2009, MNRAS, submitted.) - XMM-Newton observed on day 40 and 50 (Ness et al. 2009, in prep.; Takei et al. 2009, in prep.) - X-rays were detected in the pre-nova phase (Ibarra et al. 2009, A&A, 497, L5)

15 15/23 The optical data were provided by the variable star observations from the AAVSO International Database and the VSOLJ Observation Database contributed by observers worldwide and used in this research. V2491 Cygni : Light Curve Day 9 Day 29

16 16/23 Takei et al.,2009, ApJL, 697, 54 V2491 Cygni : Spectra (Day 9) The highest energy X-rays up to 70 kev ever detected from a nova!! (Takei et al. 2009, ApJL, 697, 54)

17 V2491 Cygni : Spectra (Day 9) Flux (photons cm -2 s -1 kev -1 ) XIS HXD Power-Law (Γ = 0.1) Thin-thermal Plasma 17/23 Energy (kev) Takei et al.,2009, ApJL, 697, 54

18 18/23 Takei et al.,2009, ApJL, 697, 54 V2491 Cygni : Spectra (Day 29)

19 Discussion Photon X-ray 19/23 What is the origin of the power-law spectra...? Non-thermal origin is a straight-forward approach Non-thermal particles - Theoretical works (e.g., Tatischeff & Hernanz 2007) - RS Oph, radio synchrotron (e.g., Rupen et al. 2008) - V407 Cyg, gamma-ray obs. (Cheung et al. 2010) Magnetic Field + Proton - Electron - Electron Electron - X-ray X-ray 1 2 3

20 Discussion Photon X-ray 20/23 Power-law Spectrum - Photon Index - Energy Index - Photon Flux - Energy Flux Electron Population - Distribution - 1 IC, 2 Sync. - 3 Bremss. - Number Index : Γ = 0.1 : α =Γ- 1 : F P (E) E -Γ : F E (E) E -α : N e (E) E -P : P 2Γ- 1 : P Γ- (1/2) : P -0.4 Let s compare the value with that of acceleration models!! Magnetic Field + Proton - Electron - Electron Electron - X-ray X-ray 1 2 3

21 21/ Standard Acceleration Model Diffusive Shock Acceleration model (P 2.0) (e.g., Blandford & Ostriker 1980, ApJ, 237, 793) Flat population cannot be explained... (Takei et al. 2009, ApJL, 697, L54) SNR (SN1006) Shock Wave Upstream Downstream Diffusive Shock Acceleration

22 22/23 New Developments!!! Compton degradation of Gamma-ray emission lines from radioactive isotope 22 Na can explain the spectra!! (Suzuki & Shigeyama 2010, ApJ, Submitted) 2 days ago in astro-ph!!

23 23/23 Summary Five recent classical novae were observed with the Suzaku X-ray satellite Super-Hard X-ray (SHX) emission was discovered from V2491 Cyg We got a new view of classical novae from hard X-ray observations