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Suzaku observations of two Galactic black hole candidates XTE J1752-223 and MAXI J1659-152 triggered by MAXI. Kazutaka Yamaoka (Aoyama Gakuin University), On behalf of the MAXI and Suzaku team. Outline. Coordinated MAXI and Suzaku observations Suzaku observations of XTE J1752-223
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Suzaku observations of two Galactic black hole candidates XTE J1752-223 and MAXI J1659-152 triggered by MAXI Kazutaka Yamaoka (Aoyama Gakuin University), On behalf of the MAXI and Suzaku team
Outline • Coordinated MAXI and Suzaku observations • Suzaku observations of XTE J1752-223 with MAXI results Please also see Nakahira et al. P-1 (MAXI) and Koyama et al. P-2 (Suzaku) • Very preliminary results from Suzaku observations of MAXI J1659-152 • Summary
Coordinated MAXI and Suzaku observations • High sensitive all-sky X-ray survery with MAXI15mCrab@day + Wide-band and high-sensitive X-ray observations with Suzaku Very powerful collaboration for studying X-ray transients. e.x. Discovery of a new MAXI source Identify the nature of the source with Suzaku • Suzaku ToO Observations by MAXI team have been approved since AO5. • 4 Suzaku ToO observations triggered by MAXI team so far
BHC XTE J1752-223 • Discovered by the RXTE/PCA Galactic-Center scan observations (Markwardt et al. 2009) • MAXI confirms this new transient and monitor the entire outburst. (Nakahira et al. 2010PASJ, Nakahira et al. P-1 ) • Identified as a black hole candidateby RXTE. • Displayed Hard –to-soft, and Soft-to-hard transitions. Bipolar plasma ejection events, i.e. jets, were detected. • The distance, the black hole mass, and the inclination angle are still unknown. XTEJ1752-223
Suzaku observation of XTE J1752-223 Suzaku observation Details of observations • ObservationDate2010-02-24 04:58:00 – 2010-02-25 04:27:24 (UT) • Total exposure 41 ksec • XIS Exposure0.5 ksec (XIS 1), 6.1 ksec (XIS 0,3) • Observation directionHXD nominal • XIS mode • Full window 0.1s burst option (XIS 1) 1/4 window 0.3s burst option (XIS 0.3) Suzaku observed “High/Soft state” Low/hard High/Soft
The Suzaku/XIS light curve During the obs., the XIS intensity and spectral shape do not change significantly. Produce the XIS spectra by averaging over the whole observation. XIS count rate : 0.5-10 keV Hardness ratio:2-10 keV/0.5-2 keV About 1 day
Suzaku wide-band spectra XIS1 Detected up to ~ 50 keV with HXD/PIN. The HXD/GSO could detect no significant signals above 50 keV. HXD/PIN XIS0+3 HXD/GSO Detection llimit Energy(keV)
Spectral modeling of wide-band spectra Modeling with the Multi-Color Disk model (Mitsuda et al. 1984) plus a power-law (χ2 /dof = 508/339) XIS1 XIS0+3 Power law Γ=2.34+/-0.07 MCDmodel Tin=0.53+/-0.01 keV Rin(cos i)1/2 /(D/10 kpc) = 117.9+/-2.0 km HXD/PIN νFνspectra Power law MCD
Results from RXTE and MAXI observations RXTE and MAXI monitoring observations show that the innermost radii are almost constant at 110~130 km, which is independent of X-ray flux. This value is almost consistent with Suzaku measured one. Can estimate the black hole mass Innermost temp. Tin (keV) Innermost radius Rin Photon index Γ Flux 3-50 keV
Estimation of the black hole mass Suzaku measured innermost radius: Rin(cosi)1/2 /(D/10 kpc) =117.9±2.0 (km) • rin=ξκ2Rin(Kubota et al. 1998) κ=1.7:Spectral hardening factor (Shimura & Takahara 1995) ξ=0.412: boundary condition near the inner edge of the disk = 198.5±3.4 x(D/10 kpc) x (cosi /cos 60°)-1/2 (km) If we assume a Schwartzchild black hole, the innermost stable circular orbit (ISCO): 3Rs=6GM/c2=8.86 (M/M◎) km BHmass : M= 22.4±0.4 x (D/10 kpc) x (cosi /cos 60°)-1/2(M◎) Precise determination of a distance and an inclination angle will be desired in a future.
BHC MAXI J1659-152 • The Swift/BAT discovered a new source as GRB 100925A on Sep. 25, 2010 (Mangano et al. GCN #11296). • The MAXI/GSC independently found a new X-ray source as MAXI J1659-152 (Negoro et al. Atel #2873). • RXTE follow-up observations reveal it as a black hole candidate. (Kalamkar et al. Atel # 2881) • Many multi-wavelength observations were performed due to the Swift/BAT GRB trigger and its source location well above the Galactic plane. Sep. 24 Sep. 25 MAXI J1659-152
Suzaku observations of MAXI J1659-152 • Details of the three observations • Observation Dates • Sep. 29, 30, Oct. 1-2, 2010 • XIS0/HXD exposure • 1.6 k / 16.3 ksec • 15.0 k / 23.5 ksec • 4.9 k / 30.7 ksec • Observation directionHXD nominal • XIS mode • ¼ window with no burst option (Sep. 29, 30) • 0.3s burst option (Oct 1-2) • Suzaku observed a rare “intermediate state”in the rising phase. High/Soft MAXI/GSC Hardness-Intensity diagram Low/hard
Preliminary results of Suzaku data The XIS+PIN spectra are explained by the disk blackbody plus power law with an exponential cutoff. QPO features at about 3 Hz are detected in the HXD/PIN data for all the three observations. Cut-off LF QPO The intermediate observations with Suzaku might reveal a disk-corona-jet geometry around the BH during the state transition.
Summary • MAXI and Suzaku coordinated observations since AO5 • Four sources so far: V0332+53、XTEJ1752-223、GX304-1, and MAXI J1659-152 • Suzaku observation of XTE J1752-223 • High/Soft state • The 1-50 keVspectra are explained by MCD model plus power law. • Suzaku and RXTE observation suggests a constancy of innermost radius at 120~130 km Estimation of the black hole mass 22.4+/-0.4 M◎for i=60°, D=10 kpc • Further examination of the “ disk-line feature” • Suzaku observation of MAXI J1659-152 • Intermediate state in the rising phase. • 0.6-70 keV spectra are explained by MCD model plus cutoff power law. • The QPO features are present in the HXD/PIN power spectrum.
Presence of a disk line? Reis et al. (2010) suggested a presence of a disk line using the same Suzaku data. They fitted the continuum using the1.3-4.5, 8.0-10.0, 20-45 keVdata. We can reproduce the same feature with the same procedures, but using all the energy bands, we can see a reflection feature instead. Suzaku RXTE/PCA
Pile-up effects PHA Ratio to the spectra in the Outer regions(90``<r<120``) • For bright sources, the XIS spectra were affected by pile-up effects。 • In the central region, the spectra get harder. • Need to exclude • at least the • region with • r<60`` r<30’’ 30’’<r<60’’ 60’’<r<90’’
MAXI light curve of V0332+53 Suzaku observation
XIS spectra of V0332+53 The spectrum is rather hard photon index ~1 NH= 1.55 (-0.17,+021)x1022 cm-2 α= 1.07(-0.09, +0.10) Flux 2-10 keV 6.4x10-12 erg/cm2/s ~0.3 mCrab (Crab:2.2x10-8) χ2/dof = 320/325