N. Isobe (Kyoto University; ) K. Ohsuga (NAOJ), K. Makishima, P. Gandhi (RIKEN), T. Mizuno (Hiroshima University), A. Kubota (Shibaura Institute of Technology) July 24, The Energetic Cosmos: from Suzaku to ASTRO-H

 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

 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 Energy [keV] L X /L Edd XIS HXD/PIN (e.g., Kubota & Makishima 2004, Kubota & Done 2004) Slim disk and Very high states are important for ULXs

 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 ergs/s Unfolded spectra of NGC 2403 Src3

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

July 24, 2009The Energetic Cosmos: from Suzaku to ASTRO-H 6  SWG Bright Phase : Extension of MCD (p-free)  T in = keV  R in = km  p = 0.64 ± 0.04  SWG Faint Phase : MCD  T in = keV  R in = km (Consistent with Mizuno et al.2007)  AO3 : cool MCD + PL  T in = keV  R in = ( ) x 10 3 km   = 1.8 ± 0.2 MCD PL Suzaku spectra of NGC 1313 X2 2.0 x ergs s x ergs s x ergs s -1 Frequent transitions between the Very High and Slim disk states Transitions at L T = 4 x 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 – Energy [keV]

 SWG Bright Phase  Cool MCD + cutoff PL  T in = keV  R in = ( ) x 10 3 km   =  E cut = 3.4 ± 0.5 keV  Extension of MCD (p-free)  T in = 2.08 ± 0.09 keV  R in = km  p =  SWG Faint Phase : cutoff PL   =  E cut = keV  AO3 : cool MCD + PL  T in = keV  R in = ( ) x 10 3 km   = July 24, 2009The Energetic Cosmos: from Suzaku to ASTRO-H 7 Suzaku spectra of NGC 1313 X1 MCD PL 7.3 x ergs s x ergs s -1 Complicated

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

 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 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 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

 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