July. 22, 2004 Glast Lunch 1

Santa Cruz Institute for Particle Physics

Unidentified Galactic gamm-ray sources and microquasrs

Mutsumi SugizakiUCSC/SCIPP, SLAC

i. Introduction: X-ray binaries, Microquasars, Unidentified galactic gamma-ray sources

ii. A microquasar candidate AX J1639.0-4642 = IGR J16393-4643 (appear soon in A&A)

iii. Summary and future

July. 22, 2004 Glast Lunch 2

Santa Cruz Institute for Particle Physics EGRET Unidentified sources

Population IGalactic plane

Population IIGalactic halo

+Gould Belt+Extragalactic

3 groups

July. 22, 2004 Glast Lunch 3

Santa Cruz Institute for Particle Physics X-ray binaries and Microquasars

• X-ray binary (280)– Binary system containing a compact object, either a neutron

star or a stellar-mass black hole– Accretion powered

• Categories of X-ray binaries– HMXBs: High Mass companion star system (131)

They are distributed very close to the Galactic plane. – LMXBs: Low Mass companion star system (149)

Their distribution has a longer scale height than the HMXB.

• Microquasars– X-ray binary with non-thermal radio emission (REXB: 43) in

our Galaxy showing relativistic jet activity (16) – Are all REXBs Microquasars?– Are all XRBs Microquasars?

July. 22, 2004 Glast Lunch 4

Santa Cruz Institute for Particle Physics Example of microquasars

Observation by Chandra

(S. Migliari et al. 2002)(S. Corbel et al. 2002)

July. 22, 2004 Glast Lunch 5

Santa Cruz Institute for Particle Physics

Unidentified gamm-ray sources and Microquasars

• Gamma-ray emission from microquasers

Inverse Compton up-scattering of stellar photons from companion stars by relativistic jets.

• Population I:

-> Microquasars with massive companion stars (HMXBs)• Population II:

-> Microquasars with low-mass companion stars (LMXBs)• The gamma-ray spectrum of the HMXBs would be harder than

that of the LMXBs because of the initial seed photon spectrum from companion stars.

Does It explain everything of unidentified galactic gamma-ray sources?

July. 22, 2004 Glast Lunch 6

Santa Cruz Institute for Particle Physics

A microquasar candidateAX J1639.0-4642 = IGR J16393-4643

• The unidentified X-ray source was discovered by the ASCA

Galactic plane survey. ID= AX J1639.0-4642 – The source was quite faint in a soft X-ray bad (<2 keV)

– A significant time variability was observed.

• The source was detected by INTEGRAL ISGRI in 15-40 keV band. ID= IGR J16393-4643

(R. Walter et al. 2003)(Sugizaki et al. 2001)

July. 22, 2004 Glast Lunch 7

Santa Cruz Institute for Particle Physics

A microquasar candidateAX J1639.0-4642 = IGR J16393-4643

• ASCA GIS X-ray spectrum (0.7-10 keV)

• ASCA GIS X-ray light curve

July. 22, 2004 Glast Lunch 8

Santa Cruz Institute for Particle Physics

A microquasar candidateAX J1639.0-4642 = IGR J16393-4643

• As a result of search for possible counterparts in other wavelength data, we found a radio source in 843 MHz and an unidentified gamma-ray source with good position coincidence.

• Conclusion: The source has to be observed more. (XMM was scheduled. Done?)

July. 22, 2004 Glast Lunch 9

Santa Cruz Institute for Particle Physics Summary and future

• Study of microquaser/unidentified galactic gamma-ray sources would be very important to solve the problem of the origin of jets in a connection with those of extragalactic sources.

• GLAST can give us much more information about them and make the situation much clearer.

• To do these analysis, study of source detection method, careful modeling of diffuse galactic gamma-ray emission would be necessary.

• INTEGRAL / XMM will increase the number of candidates. Combined analysis of multi-wavelength data would be helpful. (Data of ASCA might be still useful)