Mass Loss and Evolution of LowMass Xray Binaries

Mass Loss and Evolution of Low-Mass X-ray Binaries Xiang-Dong Li Department of Astronomy Nanjing University 2009 -5 -20

Low-Mass X-ray Binaries (LMXBs)

LMXBs and BMSPs Magnetic fields Radio PSRs Spin-up line MS PSRs LMXBs Spin Periods

From Deloye (2008)

Stability of Mass Transfer • Two mass-radius exponents • Stability requires that after mass loss the star is still contained by its Roche lobe. From Soberman et al. (1997)

Stable Mass Transfer • Driving mechanisms – Loss of orbital angular momentum • Gravitational radiation • Magnetic braking – Nuclear evolution of the companion star From Deloye (2008)

Bifurcation Period in L/IMXB Evolution 1. 5 M⊙ + 1. 0 M⊙ From Pylyser & Savonije (1988)

Porb-Mwd Relation in Wide Binary Pulsars From Rappaport et al. (1995)

Thermal Timescale Mass Transfer • Mass transfer is dynamically stable but occurs on a thermal timescale if • This requires that the donor star has a radiative envelope, or the convective envelope is not too deep. From Deloye (2008)

Evolution of IMXBs From Podsiadlowski et al. (2001) From Li (2002)

Dynamically Unstable Mass Transfer • Massive donors with a convective envelope Common envelope evolution Ultracompact LMXBs From Deloye (2008)

RGB/AGB TTMT CV-like UC-LMXBs

Angular Momentum Loss by Magnetic Braking Standard MB Saturated MB From Andronov et al. (2001)

Radio Pulsar Mass Measurements PSR J 1911 -5958: 1. 4 (+0. 16, -0. 10) 2 S 0921 -630: 1. 44 (± 0. 10) PSR J 1909 -3744: 1. 438 (± 0. 024) PSR J 0437 -4715: 1. 58 (± 0. 18) PSR J 1012+5307: 1. 6 (± 0. 20) Mass transfer is highly non-conservative during I/LMXB evolution M = 1. 35± 0. 04 M⊙ Thorsett & Chakrabarty 1999

Mass and Angular Momentum Loss Outflow Circumbinary disk Wind

Bifurcation Periods • Model 1: conservative mass transfer + traditional MB law • Model 2: conservative mass transfer + saturated MB law • Model 3: non-conservative mass transfer + mass loss from L 1 point + saturated MB law • Model 4: non-conservative mass transfer + mass loss from the NS + saturated MB law

From Ma & Li (2009 a)

Magnetic Capture Model for the Formation of UCXBs From van der Sluys et al. (2005)

A CB Disk in Work From Ma & Li (2009 b)

From Ma & Li (2009 b)

Conclusions • The standard model for L/IMXBs still fails to reproduce some of the main features of the observed LMXBs and MS PSRs. • An unknown mechanism that mimics the features of a CB disk may be an important ingredient for understanding the overall evolution of I/LMXBs and CVs.