The Radio Millisecond Pulsar PSR J : A Link to Low-Mass X-Ray Binaries Slavko Bogdanov
Rotation-powered millisecond pulsars Spun-up (“recycled”) by accretion of mass and angular momentum in low- mass X-ray binaries Most are in binaries with white dwarf or very low-mass (~0.03 M ) degenerate companions To date, no accreting X-ray MSP (e.g. SAX J – 3658) has been seen to turn on as a radio pulsar
SDSS J / PSR J V ~ 17.5 magnitude star with a solar-type spectrum and mild day orbital variability X-ray counterpart with non-thermal spectrum – classified as quiescent low- mass X-ray binary (Homer et al. 2005) 1.69-ms (“recycled”) rotation-powered radio pulsar in day circular binary orbit with ~0.2 M companion, discovered in Green Bank Telescope drift scan survey (Archibald et al. 2009) Deep radio eclipse near superior conjunction + random/irregular eclipses throughout orbit First known radio MSP in the field of the Galaxy with non-degenerate companion star (several similar systems in globular clusters) First radio MSP to exhibit evidence for an accretion disk (Wang et al. 2009) Archibald et al. (2009)
: Evidence for an Accretion Disk Optical observations from May Dec. 2001: blue spectrum with prominent emission lines & rapid flickering by ~1 mag Double-peaked (asymmetric) emission lines – a hot accretion disk? Simple disk model: –temperature range of 2000–34000 K, –disk inner and outer radii of 10 9 and 5.7×10 10 cm –disk mass ~10 23 g No X-ray observations during No evidence for disk or emission lines since May, 2002 Neutron star is currently a radio pulsar with a rotation-powered relativistic wind Companion may still be Roche lobe filling Optical variability due to irradiation of face of secondary star by pulsar wind. Wang et al. (2009) System transitioning between LMXB and recycled rotation-powered pulsar? HH
: X-ray Variability + Pulsations XMM-Newton EPIC pn Chandra ACIS-S keV 1.4 GHz Archibald et al. (2010) Bogdanov et al. in prep.
Or X-ray Variability at Binary Period Bogdanov, Grindlay, & van den Berg (2005) PSR J0024–7204W (47 Tuc) Bogdanov et al. (2010) PSR J1740–5340 (NGC 6397) PSR J Bogdanov et al. in prep
X-ray and Optical Variability X-ray variability due to interaction of relativistic pulsar wind and matter from secondary star – intrabinary shock X-ray pulsations due to heating of polar caps by magnetospheric return current or non-thermal magnetospheric emission
PSR J1740–5340 Credit:ESA/F.Ferraro
Summary PSR J : First radio millisecond pulsar with evidence for a past hot (accretion?) disk At present, J is a “recycled” rotation- powered millisecond pulsar ablating its companion System can offer better understanding of close binary evolution, especially transition from accretion to rotation power – e.g. does SAX J turn on as a radio MSP in quiescence? Site for studies of relativistic outflows and shocks Close optical/X-ray monitoring needed to catch system in the “disk state”