He star evolutionary channel to intermediate-

mass binarypulsars with a short-

orbital-period Chen Wen-Cong School of Physics, Peking University

Department of Physics, Shangqiu Normal University

Normal Radio Pulsars and Millisecond pulsars

Normal radio pulsars

MSPs

Recycled Scenario of MSPs

X-ray pulsarsSpin Periods

death line

Binary pulsars Low mass binary pulsars (LMBPs) millisecond pulsar + He WD

Intermediate mass binary pulsars (IMBPs) mildly recycled pulsar + CO/ONeMg WD

spin periods, magnetic field, and orbital eccentricities of IMBPs are considerably greater than those of LMBPs

PSR J1802-2124 circular orbit, Porb=16.8 hr Ps=12.6 ms Mp=1.24+/-0.11 Msun M2=0.78+/-0.04 Msun, CO white dwarf

(Ferdman et al. 2010, ApJ)

Light pulsar, heavy WD, short orbital period, moderate long spin period imply that it experiences a peculiar evolutionary history

Previous works L/IMXB, Roche lobe overflow, common envelope, spiral in, s

hort timescale super-Eddington accretion (van den Heuvel 1994)

thermal-viscous instability of the accretion disks in IMXBs may result in the birth of a mildly recycled pulsar (Li 2002)

Tauris et al (2000) found that IMBPs with wide orbit (> 3 d) can be formed through a short-lived highly super-Eddington mass transfer phase

We propose that NS+He star system may be the progenitor of IMBPs with a short-orbital-period like PSR J1802-2124

Our work

Population synthesis Results:

CC: core collapse AIC: accretion induced collapse

Initial distribution of NS + He star systems

An evolutionary example to PSRJ1802-2124 Eggleton stellar code NS + He star system Eddington accretion limit Orbital angular momentum loss Gravitational wave radiation magnetic braking isotropic winds

Evolutionary results

(Chen, Li & Xu 2011, A&A, in press)

Observed parameters of PSR J1802-2124:

Summary There exist sufficient IMBPs with a short-orbital-period (SOP) in the Galaxy NS + He star channel may be responsible for the formation of most IMBPs with a SOP. AIC process makes a main contribution in forming SOP IMBPs

Thank you!