1. In this lecture we look at: 1) Neutron stars in x-ray binaries 2) Mass-radius relationship 3) Strange star candidates 4) Quark deconfinement at T=0 5) Astrophysical signals of quark matter

2. Alfen radius

8. RXJ 1856.5-3754 Drake et al. point out that this NS may in fact be a quark star (astro-ph/0204159) because of its small radius, which they argue is in the range between R ' = 3.8 and 8.2 km!! ÄÄ Nasa press release of 10 April 2002: "Cosmic x-rays reveal evidence for new form of matter" WWW.msfc.nasa.gov/news

9. T ' =7x10 5 K (X60 eV) R ' = R (1-2M/R) -1/2 Y f (D/120 pc) km Star's x-ray spectrum is well represented by a black body with a temperature of The observed x-ray flux and temperature correspond to a stellar radius of R ' =3.8 to 8.2 km Drake et al.:

18. Rotationally deformed, rotating neutron star

26. Pulsar 3C58  A 65 ms pulsar (J0205+6449) was discovered by Murray et al. (to appear in the ApJ, 2002).  This pulsar is at the center of 3C58, a young Crab-like supernova remnant (SN 1181).  Thus 3C58 is somewhat younger than Crab.  The pulsar's surface temperature is 1.12x10 6 K (Slane, Helfand, Murray, astro-ph/0204151, to appear in the ApJ) Nasa press release of 10 April 2002: "Cosmic x-rays reveal evidence for new form of matter" www.msfc.nasa.gov/news