Suzaku observations of two Galactic black hole candidates

Suzaku observations of two Galactic black hole candidates XTE J 1752 -223 and MAXI J 1659 -152 triggered by MAXI Kazutaka Yamaoka (Aoyama Gakuin University), On behalf of the MAXI and Suzaku team

Outline Coordinated MAXI and Suzaku observations of XTE J 1752 -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 J 1659 -152 Summary

Coordinated MAXI and Suzaku observations l High sensitive all-sky X-ray survery with MAXI　15 m. Crab@day + Wide-band 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 l Suzaku To. O Observations by MAXI team have been approved since AO 5. l 4 Suzaku To. O observations triggered by MAXI team so far Source Category V 0332+53 X-ray binary Feb 16, 2010 pulsar XTE J 1752 - Black hole 223 candidate Obs. Date Feb 24 -25, 2010 Exposure Related information 32 ksec 40 ksec Also proposed from the US side Discovery of cyclotron features (Yamamoto et al. P-13) GX 304 -1 X-ray binary Aug. 13, 2010 pulsar 23 ksec MAXI J 1659 -152 Black hole candidate 16, 24, 31 ksec Sep 29, 30, Oct. 12, 2010 (3 times)

BHC XTE J 1752 -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, XTEJ 1752 -223 were detected. The distance, the black hole mass, and the inclination angle are still unknown.

Suzaku observation of XTE J 1752 -223 Details of observations Suzaku observation Observation. Date　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. 1 s burst option (XIS 1) 　　 　 1/4 window 0. 3 s burst option (XIS 0. 3)　 Suzaku observed “High/Soft state” High/Soft Low/hard　

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 ke. V Hardness ratio: 　2 -10 ke. V/0. 5 -2 ke. V About 1 day

Suzaku wide-band spectra Detected up to ~ 50 ke. V with HXD/PIN. The HXD/GSO could detect no significant signals above 50 ke. V. XIS 1 XIS 0+3 HXD/PIN HXD/GSO Detection llimit Energy　(ke. V)

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) νFν spectra MCD Power law XIS 1 XIS 0+3 MCD model Tin=0. 53+/-0. 01 ke. V Rin(cos i)1/2 /(D/10 kpc) = 117. 9+/-2. 0 km Power law Γ=2. 34+/-0. 07 HXD/PIN

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. Innermost temp. Can estimate the black hole mass Flux 3 -50 ke. V Tin (ke. V) Innermost radius Rin Photon index Γ

Estimation of the black hole mass Suzaku measured innermost radius: 　　　Rin(cosi)1/2 /(D/10 kpc) =117. 9± 2. 0 (km) rin=ξκ 2 Rin (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): 3 Rs=6 GM/c 2=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 J 1659 -152 The Swift/BAT discovered a new source as GRB 100925 A on Sep. 25, 2010 (Mangano et al. GCN #11296). The MAXI/GSC independently found a new X-ray source as MAXI J 1659 -152 (Negoro et al. Atel #2873). RXTE follow-up observations reveal Sep. 24 Sep. 25 it as a black hole candidate. (Kalamkar et al. Atel # 2881) Many multi-wavelength MAXI J 1659 -152 observations were performed due to the Swift/BAT GRB trigger and its source location well above the Galactic plane.

Suzaku observations of MAXI J 1659 -152 Details of the three observations • Observation Dates　 Sep. 29, 30, Oct. 1 -2, 2010 • XIS 0/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. 3 s burst option (Oct 1 -2) 　 Suzaku observed a rare “intermediate state” in the rising phase. High/Soft MAXI/GSC Hardness. Low/hard　　　 -Intensity diagram

Preliminary results of Suzaku data The XIS+PIN spectra are explained by the disk blackbody plus power law with an exponential cutoff. Cut-off QPO features at about 3 Hz are detected in the HXD/PIN data for all the three observations. 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 AO 5 Four sources so far: V 0332+53、XTEJ 1752 -223、GX 304 -1, and MAXI J 1659 -152 Suzaku observation of XTE J 1752 -223 High/Soft state 　 The 1 -50 ke. V 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 J 1659 -152 Intermediate state in the rising phase. 0. 6 -70 ke. V 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 the 1. 3 -4. 5, 8. 0 -10. 0, 2045 ke. V 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 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`` PHA Ratio to the spectra in the Outer regions(90``<r<120``) r<30’’<r<60’’<r<90’’

MAXI light curve of V 0332+53 Suzaku observation

XIS spectra of V 0332+53 The spectrum is rather hard photon index ~1 NH= 1. 55 (-0. 17, +021)x 1022 cm-2 α= 1. 07(-0. 09, +0. 10) Flux 2 -10 ke. V 6. 4 x 10 -12 erg/cm 2/s ~0. 3 m. Crab (Crab: 2. 2 x 10 -8) χ2/dof = 320/325