1. The Radio Millisecond Pulsar PSR J1023+0038: A Link to Low-Mass X-Ray Binaries Slavko Bogdanov

2. 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 J1808.4 – 3658) has been seen to turn on as a radio pulsar

3. SDSS J102347.6+003841 / PSR J1023+0038  V ~ 17.5 magnitude star with a solar-type spectrum and mild 0.198-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 0.198 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)

4. 2000-2001: Evidence for an Accretion Disk  Optical observations from May 2000 - 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 2000-2001  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? HH

5. 2009-2010: X-ray Variability + Pulsations XMM-Newton EPIC pn Chandra ACIS-S 0.25-2.5 keV 1.4 GHz Archibald et al. (2010) Bogdanov et al. in prep.

6. 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 J1023+0038 Bogdanov et al. in prep

7. 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

8. PSR J1740–5340 Credit:ESA/F.Ferraro

9. Summary PSR J1023+0038: First radio millisecond pulsar with evidence for a past hot (accretion?) disk At present, J1023+0038 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 J1808.4-3658 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”