Quark Stars

1. Quark Stars Kyle Dolan Astronomy 4001 10 December 2007 NASA/Dane Berry

2. 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

3. Overview of Neutron Stars • Core of a massive star that remains after a supernova explosion • Average Density: ~1014 g/cm3 • Rotational frequency may range up to 1122 Hz (XTE J1739-285) • Magnetic field strength can be ~108-1014 times that of Earth • Exotic Physics! http://science.nasa.gov/

4. 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 1.5-1.8MSun are likely candidates http://chandra.harvard.edu

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

6. 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

7. RXJ1856.5-3754: 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

8. XTE J1739-285: 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

9. 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

10. NASA/CXC/M Weiss SN 2006gy: Possible Quark Nova • First Observed: 18 September 2006 • 100 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

11. Controversy • Possible contradiction of the QS theory: • EXO 0748-676, neutron star with possible mass ~2.1MSun, 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 MSun, 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

12. 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

13. Sources “3C58: Pulsar Gives Insight on Ultra Dense Matter and Magnetic Fields.” chandra.harvard.edu. 30 August 2006. http://chandra.harvard.edu/photo/2004/3c58/ Blaschke, D.B. et al. “Color superconducting quark matter in compact stars.”. arXiv:0712.0117v1. 2 December 2007 Drake, J. J. et al. “Is RX J185635-375 a Quark Star?” arXiv:astro-ph/0204159v1 9 Apr 2002. “Quark Stars Could Produce Biggest Bang .” spacedaily.com. 7 June, 2006. http://www.spacedaily.com/reports/Quark_Stars_Could_Produce_Biggest_Bang.html Shiga, David. “Fastest spinning star may have exotic heart.” newscientist.com. 20 February 2007. http://space.newscientist.com/article/dn11221?DCMP=NLC-nletter&nsref=dn11221 Shiga, David. “Massive neutron star rules out exotic matter.” newscientist.com. 28 June 2006. http://space.newscientist.com/article/dn9428-massive-neutron-star-rules-out-exotic-matter.html Shiga, David. “Was the brightest supernova the birth of a quark star?” newscientist.com. August 2007. http://space.newscientist.com/article/dn12514-was-the-brightest-supernova-the-birth-of-a-quark-star.html “The leader of the celestial ‘Magnificent Seven.’” scientificblogging.com. 9 March 2007. http://www.scientificblogging.com/news/the_leader_of_the_celestial_magnificent_seven Xia et al. “Thermal Evolution of Strange Stars.” arXiv:0709.0214v1. 3 September 2007. Zhang, C.M. et al. “Does Sub-millisecond Pulsar XTE J1739-285 Contain a Low Magnetic Neutron Star or Quark Star?” arXiv:0708.3566v2. 11 September 2007. Wilford, John Noble. “Stars Suggest a Quark Twist And a New Kind of Matter.” nytimes.com. 11 April, 2002. http://query.nytimes.com/gst/fullpage.html?res=9D04E7DB1F3DF932A25757C0A9649C8B63&sec=&spon=&pagewanted=print