1. On the formation of the peculiar LMXB IGR J17480-2446 in Terzan 5
ApJ772.6(2013)
On the formation of the peculiar LMXB IGR J in Terzan 5
Reporter: Jiang Long(姜龙) Director: Prof. Li X-D
2019/4/11

2. Outline Recycled scenario J17480-2446 Patruno’s model Our explanation
Binary-single scattering and J17480-like system formation
Reversed-to-parallel evolution history
Further discussion
2019/4/11

3. Recycled scenario of MSP
After accretion a low magnetic high rotate MSP left.

4. Known Accreting MSP SAX J1808.4-3658 401Hz 2~3*108G BD
IGR J Hz 2*108G BD
XTE J Hz 4*108G WD …

5. Cavecchi et~al. 2011;Patruno et~al. 2012J
Mass of companion M⊙
Orbit period 21.3h
Frequency derivation: 1.4*10-12HzS-1
Spin frequency: 11Hz
815Hz QPO ( B<5*108G)
Located in the core of Terzan 5
Cavecchi et~al. 2011;Patruno et~al. 2012

6. Explanation of Patruno et al. 2012
Mildly recycled pulsar
Magneto-dipole spin-down
Wind accretion spin-down
Current RLOF spin-up phase
The magnetic dipole moment decayed in proportion to the rotation rate due to flux-line vortex line coupling (Srinivasan et al. 1990).

7. Shortcomings of Patruno’s model
kHz QPO 815Hz
GX 1+4 B~3*1013G, frequency: 6*10-3
Long-period X-ray pulsar: 4U , GX301-2, SXP1062 B>1014

8. Our explanation
The current binary system is not the primordial one, the neutron star exchanged its donor during a binary-single close encounter.
The neutron star had finished its spin-up evolution and become an MSP before the encounter.
The orbit angular momentum of the later formed binary was reversed to the spin angular momentum of the neutron star

9. Heggie, Hut, McMillan, ApJ467,359(1996)
Encounter rate v 1 2 3
Heggie, Hut, McMillan, ApJ467,359(1996)

10. Anti-parallel donor binaries

11. Evolution history Spin-up to MSP Spin-down with new donor
Spin-up to current period

12. Further discussion (1)
IGR J17480−2446-like systems
Difference between two models
Magnetic field
Mass of companion

13. or Further discussion (2) Field decay: Shibazaki et al. (1989)
Kiel et al. (2008) or

14. Thank you!