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N. Isobe (Kyoto University; n-isobe@kusuastro.kyoto-u.ac.jp ) K. Ohsuga (NAOJ), K. Makishima, P. Gandhi (RIKEN), T. Mizuno (Hiroshima University), A. Kubota (Shibaura Institute of Technology) July 24, 2009 1 The Energetic Cosmos: from Suzaku to ASTRO-H
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Non-nuclear X-ray sources in nearby galaxies L X >>10 39 ergs s -1 L X >>10 39 ergs s -1 (significantly higher than L Edd of stellar mass BH) Originally discovered with Einstein (Fabbiano 1989) Extensively studied with ASCA (e.g., Makishima et al. 2000, Mizuno et al. 2001), Chandra (e.g., Swartz et al. 2004) and Newton (e.g., Stobbart et al. 2006). Their nature remains unsolved. Possible interpretations Intermediate mass BHs Intermediate mass BHs (M >> 10 M ◎ ) at ~ L Edd Stellar mass BHs with a super critical accretion rates They exhibit two spectral states PL-like and Multi-color-disk (MCD)-like <- similar to Galctic BHs Luminosity-dependent spectral changes provide an important clue July 24, 2009The Energetic Cosmos: from Suzaku to ASTRO-H 2
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Slim disk state Extension of MCD (p-free disk) : T ∝ r –p p = 0.75 for MCD 0.5 < p < 0.75 for Slim disk (e.g., Watarai et al. 2001) Very High state Cool MCD + PL (2 < < 3) Comptonization of disk photons by hot coronae High/soft state MCD (T in < 1 keV) + PL Standard accretion disk Low/hard state PL ( < 1.5) July 24, 2009The Energetic Cosmos: from Suzaku to ASTRO-H 3 110 100 Energy [keV] L X /L Edd XIS 1 0.1 0.01 HXD/PIN (e.g., Kubota & Makishima 2004, Kubota & Done 2004) Slim disk and Very high states are important for ULXs
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NGC 2403 Src 3 (Isobe et al. 2009) Transition between the Slim disk and Very High states were detected, using Suzaku, Chandra and XMM-Newton M ~ 15 M ◎ at ~ L Edd ⇒ M ~ 15 M ◎ at ~ L Edd 2 ULXs in IC 342 (Kubota et al. 2001) and several ULXs July 24, 2009The Energetic Cosmos: from Suzaku to ASTRO-H 4 Suzaku : MCD-like Chandra (ObsID = 4628) : MCD-like Newton : p ~ 0.6 Chandra (ObsID = 4630) : PL-like ( = 2.37) L X =2 x 10 39 ergs/s Unfolded spectra of NGC 2403 Src3
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NGC 1313 a nearby galaxy at 4.13 Mpc (Mendez et al. 2002) X1 and X2 hosts two ULXs, X1 and X2 X1 and X2 one of the most extensively studied ULXs with ASCA (Mizuno et al. 2001), Chandra, and XMM-Newton (Feng & Kaaret 2005, 2006 ). observed with Suzaku on Oct. 15, 2005, during the SWG Phase (Mizuno et al. 2007) A follow up Suzaku AO3 observation, to investigate their spectral changes. July 24, 2009The Energetic Cosmos: from Suzaku to ASTRO-H 5 XIS Image of NGC 1313 SN 1978K X1 X2 Suzaku DSS Dec. 05 – 08, 2008 (AO3), 76.7 ks 6 arcmin
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July 24, 2009The Energetic Cosmos: from Suzaku to ASTRO-H 6 SWG Bright Phase : Extension of MCD (p-free) T in = 1.84 -0.39 + 0.40 keV R in = 75.2 -17.8 +21.2 km p = 0.64 ± 0.04 SWG Faint Phase : MCD T in = 1.34 -0.36 +0.40 keV R in = 170.1 -16.0 + 19.8 km (Consistent with Mizuno et al.2007) AO3 : cool MCD + PL T in = 0.27 -0.08 + 0.11 keV R in = (1.48 -0.90 + 2.38 ) x 10 3 km = 1.8 ± 0.2 MCD PL Suzaku spectra of NGC 1313 X2 2.0 x 10 39 ergs s -1 8.0 x 10 39 ergs s -1 4.4 x 10 39 ergs s -1 Frequent transitions between the Very High and Slim disk states Transitions at L T = 4 x 10 39 ergs s -1 (in 0.5 – 10 keV) p = 0.6 – 0.75 T in = 1.8 – 2.5 keV T in = 0.2 – 0.3 keV = 1.8 – 2.3 0.512510 Energy [keV]
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SWG Bright Phase Cool MCD + cutoff PL T in = 0.19 -0.03 +0.05 keV R in = (10.3 -6.5 + 9.7) x 10 3 km = 0.91 -0.18 +0.16 E cut = 3.4 ± 0.5 keV Extension of MCD (p-free) T in = 2.08 ± 0.09 keV R in = 98.8 -11.6 +12.6 km p = 0.602 -0.012 +0.013 SWG Faint Phase : cutoff PL = 1.69 -0.30 +0.28 E cut = 6.9 -2.6 + 10.3 keV AO3 : cool MCD + PL T in = 0.18 -0.02 +0.04 keV R in = (7.0 -3.6 + 5.3) x 10 3 km = 1.73 -0.05 +0.04 July 24, 2009The Energetic Cosmos: from Suzaku to ASTRO-H 7 Suzaku spectra of NGC 1313 X1 MCD PL 7.3 x 10 39 ergs s -1 2.7 x 10 40 ergs s -1 Complicated
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July 24, 2009The Energetic Cosmos: from Suzaku to ASTRO-H 8 Cutoff PL + MCDPL + MCD 0.5x10 40 ergs s -1 2x10 40 ergs s -1 (cf. Feng & Kaaret 2006) Physical condition in the coronae (T e and ) significantly changed (Kubota & Done 2004) Accretion disk Truncated Relatively stable Suzaku Newton
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BHs usually make transitions between the Slim Disk and Very High states at L T = (0.3 – 1) L Edd (e.g. Kubota & Makishima 2004, Abe et al. 2005) NGC 1313 X2 The transition luminosity : L T = 4 x 10 39 ergs s -1. The mass of X2: M 2 = 30 -1 M ◎ ( = L T /L Edd ). NGC 1313 X1 We have not yet confirmed the state transition. The transition luminosity : L T > 2 x 10 40 ergs s -1. The mass of X1 : M 1 > 150 -1 M ◎. (Cf. M X1 ~ 200M ◎ ; Dewangan et al. 2009) July 24, 2009The Energetic Cosmos: from Suzaku to ASTRO-H 9 ULXs = intermediate mass black holes
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We made a Suzaku follow up observation of two ULXs in NGC 1313, during the AO3 phase. X2 NGC 1313 X2 made a clear transition from the slim disk to very high stats, between the SWG and AO3 observations. X1 The spectral shape of NGC 1313 X1 in the AO3 (MCD + PL) was different from that in the SWG (cutoff PL + MCD or Extended MCD). By comparing the Suzaku and Newton spectra, we conclude that X1 resided in the very high state. Referring to the transition luminosity of Galactic BHBs, the mass of X1 and X2 is estimated as M 1 > 150 -1 M ◎, and M 2 = 30 -1 M ◎, respectively ( = L T / L Edd ). July 24, 2009The Energetic Cosmos: from Suzaku to ASTRO-H 10
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