Quark Stars Kyle Dolan Astronomy December 2007 NASA/Dane Berry

Outline Introduction to Quark Stars (QS) Significance of QS Characteristics of QS Possible examples of QS Controversy over the existence of QS Possible future observations

Overview of Neutron Stars Core of a massive star that remains after a supernova explosion Average Density: ~10 14 g/cm 3 Rotational frequency may range up to 1122 Hz (XTE J ) Magnetic field strength can be ~ times that of Earth Exotic Physics!

Quark Stars (QS) Stellar core composed of free quarks (strange matter) Would form through neutron deconfinement Neutron Star (NS) collapses inward after spinning down, losing centrifugal force Strange matter would be “softer”, more compressible than neutrons Smaller, denser than a NS NS massing from M Sun are likely candidates

Significance of Quark Stars Opportunity to study strange matter in nature, and its unique behavior Quark novae may explain gamma ray bursts. NASA/CXC/M Weiss

Quark Star Characteristics Smaller Size, indicating densities significantly greater than an atomic nucleus High Rotational Frequency –Conservation of angular momentum allows more compact star to spin faster Faster Cooling –Higher-density matter allows production of more cooling particles (neutrinos) to carry energy away

RXJ : Possible QS Discovered in 1996 Diameter of ≤10km. Data suggests that the star is too small to be made of normal neutrons, and could be made of strange matter. ESO/VLT

XTE J : Record-Setting Pulsar Previously known as a normal neutron star, accreting matter from a companion star Brightness variations of frequency 1122 Hz observed Previous record for rotational frequency was ~700Hz High frequency indicates a more compact star, possibly made of strange matter May contradict theories of gravitational waves braking rotational speeds NASA/Dana Berry

3C58 – Possible Quark Nova Remnant Pulsar, possibly the remnant core of SN 1181 First observed by Chinese and Japanese Astronomers Remnant cools by internal collisions that release neutrinos to carry away thermal energy Cooling rate is too fast for matter made only of neutrons 3C58 would have to be ~5 times as dense as a normal neutron star for this cooling rate to make sense Chandra X-Ray Observatory

SN 2006gy: Possible Quark Nova First Observed: 18 September times brighter than typical Type II novae Neutron deconfinement would blow the outer layers of the NS away at near light speed, to collide with the original supernova debris. Observation of elements with A>130 in the debris could confirm 2006gy as a quark nova NASA/CXC/M Weiss

Controversy Possible contradiction of the QS theory: –EXO , neutron star with possible mass ~2.1M Sun, indicates too much rigidity for strange matter –Strange matter is too compressible not to collapse in a mass this large –Mass could be as low as 1.8 M Sun, however, which would still fit QS models More observations of XTE are needed to confirm its frequency 3C58 may be older than the SN 1181 remnant, due to the lack of variation in its radio emissions

Conclusions Quark Stars still theoretical, but evidence continues to accumulate to support them Quark Stars would offer unique opportunities to study exotic matter Helpful Observations for the Future: –Search for exotic elements in nova remnants –Precise determinations of NS radii and rotational frequency –Close observations of new Supernovae/Quark Novae

Sources “3C58: Pulsar Gives Insight on Ultra Dense Matter and Magnetic Fields.” chandra.harvard.edu. 30 August Blaschke, D.B. et al. “Color superconducting quark matter in compact stars.”. arXiv: v1. 2 December 2007 Drake, J. J. et al. “Is RX J a Quark Star?” arXiv:astro-ph/ v1 9 Apr “Quark Stars Could Produce Biggest Bang.” spacedaily.com. 7 June, Shiga, David. “Fastest spinning star may have exotic heart.” newscientist.com. 20 February Shiga, David. “Massive neutron star rules out exotic matter.” newscientist.com. 28 June Shiga, David. “Was the brightest supernova the birth of a quark star?” newscientist.com. August “The leader of the celestial ‘Magnificent Seven.’” scientificblogging.com. 9 March Xia et al. “Thermal Evolution of Strange Stars.” arXiv: v1. 3 September Zhang, C.M. et al. “Does Sub-millisecond Pulsar XTE J Contain a Low Magnetic Neutron Star or Quark Star?” arXiv: v2. 11 September Wilford, John Noble. “Stars Suggest a Quark Twist And a New Kind of Matter.” nytimes.com. 11 April, ed=print