Formation of Redback and Black Widow Binary Millisecond

Formation of Redback and Black Widow Binary Millisecond Pulsars Kun Jia and Xiang-Dong Li Department of Astronomy Nanjing University 2015 -9 -25 KIAA-WAP 1

Millisecond Pulsar (MSP)-Low-mass Xray Binary (LMXB) Relation Recycling Scenario (Alpar 1982; Radakrishnan & Srinivasan 1982) – Spin up to ms periods – Magnetic field decay High mass star 2015 -9 -25 PSR LMXB KIAA-WAP MSP 2

Observational evidence for the recycling scenario n Millisecond X-ray pulsations from LMXBs SAX J 1808. 4 -3658 Wijnands & van der Klis 1998 Patruno & Watts 2012 2015 -9 -25 2013 -04 -25 KIAA-WAP KIAA 3

Observational evidence for the recycling scenario n Transitions between rotation and accretion power in MSPs q q q 2015 -9 -25 PSR J 1023+ 0038 (Archibald et al. 2009) IGR J 18245 -2452/PSR J 1824– 2452 I (Papitto et al. 2013) XSS J 12270 -4859 (Bogdanov et al. 2014) X-ray KIAA-WAP radio 4

The three transitional pulsars are also eclipsing MSPs Roberts 2013 n Black widows q 2015 -9 -25 n (semi)-degenerate companion (~0. 02 M⊙-0. 05 M⊙) Redbacks q KIAA-WAP non-degenerate companion (~0. 2 M⊙-0. 4 M⊙) 5

n The eclipsing material possibly originates from the companions evaporated by the high-energy particles from the MSPs 2015 -9 -25 KIAA-WAP 6

Gamma-ray MSPs n n n > ⅓ of known MSPs are Gamma-ray MSPs For Ė>5× 1033 erg/s is >¾ (!) Most Fermi MSPs are black widows and redbacks 2015 -9 -25 KIAA-WAP 7

n A significant variation in the accretion rate is required to explain the transitional behavior in LMXBs. Linares 2014 2015 -9 -25 KIAA-WAP 8

The disrupted magnetic braking (MB) model (Chen et al. 2013) n MB 2015 -9 -25 KIAA-WAP GR 9

The irradiation-induced cyclic mass transfer model (Benvenuto et al. 2014, 2015) n 2015 -9 -25 KIAA-WAP 10

The accretion-induced collapse (AIC) model (Smedley et al. 2015) n n Collapse of an accreting white dwarf (WD) to form a MSP The companion star becomes detached from its Roche lobe because of sudden orbital expansion Formation rates uncertain Difficult or impossible for the occurrence of AIC in traditional CVs 2015 -9 -25 KIAA-WAP 11

Transient LMXBs n Outburst 2015 -9 -25 Quiescence KIAA-WAP 12

The parameter space for the disk instability n n Covers the distribution of known redbacks If the MSP activity switches on during the quiescent phase of LMXBs, they may evolve to be redbacks 2015 -9 -25 KIAA-WAP 13

Evolution with evaporation n Evaporative wind mass loss rate v 2, esc - escape velocity at the surface of the companion star Lp - NS’s spin-down luminosity f - efficiency of evaporation 2015 -9 -25 KIAA-WAP 14

Cases with f = 0. 1 2015 -9 -25 KIAA-WAP 15

Changing f and angular momettum 2015 -9 -25 KIAA-WAP 16

Results n n Binary evolution sensitively depends on the angular momentum of the evaporative wind and f The redback companions The redback orbital periods Redback - black widow relation 2015 -9 -25 KIAA-WAP 17

Conclusions n n n Almost all LMXBs are subject to thermal and viscous instability during their evolution The resultant redbacks can possess main-sequence, evolved, and (proto-)WD companions with either Roche lobe filling or under-filling Part of redbacks may become black widows, while others form MSP/He WD binaries 2015 -9 -25 KIAA-WAP 18