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

Alfen radius

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 theyargue is in the range between

R = 3.8 and 8.2 km!!

Nasa press release of 10 April 2002:"Cosmic x-rays reveal evidence for new form of matter"WWW.msfc.nasa.gov/news

T=7x105 K (60 eV)

R= R (1-2M/R)-1/2

f (D/120 pc) km

Star's x-ray spectrumis well represented bya black body with a temperature of

The observed x-ray fluxand temperature correspond to a stellarradius of

R=3.8 to 8.2 km

Drake et al.:

Rotationally deformed, rotating neutron star

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 1.12x106 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