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 MAXI　15mCrab@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 Source Category Obs. Date Exposure Related information V 0332+53 X-ray binary pulsar Feb 16, 2010 32 ksec XTE J1752-223 Black hole candidate Feb 24-25, 2010 40 ksec Also proposed from the US side GX 304-1 Aug. 13, 2010 23 ksec Discovery of cyclotron features (Yamamoto et al .P-13) MAXI J1659-152 Sep 29, 30, Oct. 1-2, 2010 (3 times) 16, 24, 31 ksec

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. 2010 PASJ, Nakahira et al. P-1 ) Identified as a black hole candidate by 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 Details of observations ObservationDate　2010-02-24 04:58:00 　　　　　　　　 – 2010-02-25 04:27:24 (UT) Total exposure 41 ksec ＸＩＳ Exposure 0.5 ksec (XIS 1), 　　　　　　　　　　　 6.1 ksec (XIS 0,3) Observation direction HXD 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 MCD model Tin=0.53+/-0.01 keV Rin(cos i)1/2 /(D/10 kpc) = 117.9+/-2.0 km νFν spectra HXD/PIN 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  BH mass : 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 direction HXD 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 keV spectra 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 keV data. 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