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Suzaku discovery of a transient ultra-luminous X-ray source,

Hard Soft. Suzaku discovery of a transient ultra-luminous X-ray source, Suzaku J1305-4931 , in a nearby Seyfert II galaxy NGC 4945 Naoki Isobe (RIKEN, isobe@crab.riken.jp ), and Suzaku SWG team of NGC 4945. 1. Suzaku X-ray image of NGC 4945. 2. X-ray Spectrum.

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Suzaku discovery of a transient ultra-luminous X-ray source,

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  1. Hard Soft Suzaku discovery of a transient ultra-luminous X-ray source, Suzaku J1305-4931, in a nearby Seyfert II galaxy NGC 4945 Naoki Isobe (RIKEN, isobe@crab.riken.jp), and Suzaku SWG team of NGC 4945 1. Suzaku X-ray image of NGC 4945 2. X-ray Spectrum • Emission from the galaxy at the SRC region XIS FI (0+2+3) The spectrum is descried with a power law (PL) + MEKAL model. • August 22-23, 2005 (23 ks) PL : integration of point sources G = 2.16 – 0.28 + 0.17 FX = 2.03 x 10-13 erg s-1 cm-2 Color : X-ray Image Contour : IR K-band image (Jarrett et al. 2003) ★ : Center of NGC 4945 ＋: Point sources detected with XMM-Newton BGD PL MEKAL MEKAL : thermal plasma in galaxy kT = 0.34 – 0.06 + 0.26 keV FX = 0.64 x 10-13 erg s-1 cm-2 SRC c2 = 1.2 • Suzaku J1305-4931 The spectrum is descried with a multi-color disk model (MCD) or a PL model. • January 15-17, 2006 (80 ks) MCD MCD: c2 = 1.06 NH = (2.14 -0.26 +0.27) x 1021cm-2 Tin = 1.70 ± 0.06 keV Rin = 76 - 4.7 + 4.9 km Lbol = 4.4 x 1039 erg s-1 (The disk inclination of i = 60o is assumed) Emission from the galaxy A new bright transient source has emerged ! The position of the source is determined to be (13h05m05s.5, -49o31’39”). We named the source as Suzaku J1305-4931. We found no counterpart for the source, in X-rays or other wavelength. BGD MCD PL PL : c2 = 1.09 NH = (5.78 -0.42 +0.43) x 1021cm-2 G = 1.88 ± 0.05 SRC kerrBB We adopt the MCD model. 4. Relation between Lbol and Tin 3. X-ray light curve of Suzaku J1305-4931 ULXs : Lbol ∝ Tin2 Slim Disk Suzaku J1305-4931 shows a factor-of-two variation in the soft (0.5-2 keV) and hard (2-10 keV) band, in a timescale of ～ 10 ks. The hardness of the source tends to be larger, when the source is righter. Soft • Suzaku J1305-4931 • Lbol∝Tin4 • Lbol > LEdd (i.e. ULX) Hard Eddington limit BHs : Lbol ∝ Tin4 Standard Disk We divided the exposure into 4 phases, and fitted the spectrum of each phase with MCD model. Black : Galactic Black Holes (BHs) Blue : Ultra luminous X-ray sources (ULXs) (Makishima et al. 2000, Mizuno et al. 2001, Miyawaki et al. 2004, Tanaka et al. 2005) 5. The nature of Suzaku J1305-4931 : Kerr BH interpretation. • M and Mdot with kerrbb model In the MCD model ; Assuming the disc inclination of i = 60o(40O < i < 85 O), the nature of Suzaku J1305-4931 is successfully interpreted by the Kerr BH model, with a specific angular momentum of a ～ 1. • Lbol ∝ Tin4 : Standard (not Slim) Disk ? • Rin is constant during the observation Rin～ 80 km ⇒ M～ 9.1 M◎ • But, Lbol / LEdd～ 3 for M～ 9.1 M◎ We try to investigate the behavior of Suzaku J1305-4931 with Kerr BH. We fit the X-ray spectrum of Suzaku J1305-4931 with Kerr BH model (kerrbb in XSPEC; Li et al. 2005), to evaluate M and accretion rate Mdot. Mass required to meed the Eddington limit.

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