Jeremiah presented a model for the production of gravitational wave emission during a core collapse supernova, with which the detection of gravitational waves can be interpreted.
Thursday, January 28, 2010
Jeremiah Murphy - A Model for Gravitational Waves for Supernova Explosions
Jeremiah presented a model for the production of gravitational wave emission during a core collapse supernova, with which the detection of gravitational waves can be interpreted.
Wednesday, January 27, 2010
Afternoon Discussion
During afternoon discussion, some of the topics which were covered included the following.
Flow measurments. Danielewicz et al 2002 Science 298, 1592. K=167-210.
Mass, Radius and Temperature. Sanjay Reddy would like multiple measurements of compact object mass (to 10%), radius (10%) and the temperature.
Multi-object Monte Carlo. Ed Brown showed the recent analysis results of himself and Steiner, in which measurements of RXJ 1856, three globular cluster qLMXBs, are all used to constrain the dEOS.
Quark Matter Star Observables. Predictable observables: two branches in the mass radius realtionship of compact stars: there is the Hadronic branch, and quark star branch, and these are separated by about 2 km in radius, which means that radius measurements of precision better than 0.5 km are important.
Pasta Phases: how are we going to detect them? Nobody seems to know.
Flow measurments. Danielewicz et al 2002 Science 298, 1592. K=167-210.
Mass, Radius and Temperature. Sanjay Reddy would like multiple measurements of compact object mass (to 10%), radius (10%) and the temperature.
Multi-object Monte Carlo. Ed Brown showed the recent analysis results of himself and Steiner, in which measurements of RXJ 1856, three globular cluster qLMXBs, are all used to constrain the dEOS.
Quark Matter Star Observables. Predictable observables: two branches in the mass radius realtionship of compact stars: there is the Hadronic branch, and quark star branch, and these are separated by about 2 km in radius, which means that radius measurements of precision better than 0.5 km are important.
Pasta Phases: how are we going to detect them? Nobody seems to know.
Ed Brown -- Nuclear Astrophysics in the Neutron Star Crust
Ed reviewed the entire crustal nuclear processes theory, showing the ability of analytic models to explain even more detailed theoretical predictions for the processes which take place in the crusts of neutron stars.
One of the important conclusions of this work is that the final quiescent luminosity of the qLMXB, following thermal relaxation of the crust, is related to the temperature of the core, and the theoretical uncertainty is due to uncertainty in the composition of the crust (iron? or solar metalicity?), but this is only about a factor of two in temperature. Thus, the quiescent luminosities tell us the temperature of the neutron star core. Of course, if you know how much energy is deposited in the crust, and the heat capacity of the core, you can then calculate the neutrino losses in the neutron star.
Tuesday, January 26, 2010
M. Shibata -- Merger of binary neutron stars
Most interesting to me about Shibata-san's talk: low mass ratio neutron star binaries (~1, such as we see in our galaxy) will not produce an outflow if they produce a black hole after spiraling together due to gravitational wave radiation.
If we assume a black hole horizon is needed to produce a gamma ray burst (GRB), then this implies that the GRBs we see must involve a NS-BH inspiral, or a neutron star-neutron star inspiral of extreme mass ratio, but which nonetheless the masses add up to above the highest possible mass for a neutron star.
Inescapably, this implies that the neutron star binaries we see in our galaxy --- all of which have low mass ratios (~1) -- do not produce the observed gamma ray bursts.
Thus, the gamma ray burst rate is due to binaries which we have not yet observed in our own galaxy.
If we assume a black hole horizon is needed to produce a gamma ray burst (GRB), then this implies that the GRBs we see must involve a NS-BH inspiral, or a neutron star-neutron star inspiral of extreme mass ratio, but which nonetheless the masses add up to above the highest possible mass for a neutron star.
Inescapably, this implies that the neutron star binaries we see in our galaxy --- all of which have low mass ratios (~1) -- do not produce the observed gamma ray bursts.
Thus, the gamma ray burst rate is due to binaries which we have not yet observed in our own galaxy.
Monday, January 25, 2010
David Blaschke -- Color superconductivity and compact star phenomenology
David discussed predictions of the properties of compact stars in the presence of a color-flavor-locked phase. Of the most interest to me is the fact that he has been able to construct a model in which the cooling still takes place over a million year timescale, but that the surface temperature becomes mass dependent (on timescales longer than ~100 years). If so, this would remove one of the strong observational distinctions with non-quark matter.
Wednesday, January 20, 2010
Sanjay Reddy -- Physics of Neutron Stars: A Nuclear Theory Perspective
Sanjay provided a broadly interesting overview of the nuclear physics properties of neutron stars. I'll focus here on one aspect which Sanjay has been championing, and which is very interesting:
A high nuclear symmetry energy can favor large proton fraction at and above nuclear density, and allow direct URCA cooling -- which is extremely efficient. A large symmetry energy will also produce neutron stars with larger radii (>12 km). However, a small symmetry energy will produce a low proton fraction, and will not permit direct URCA cooling, requiring that cooling be dominated by the slow process called "modified URCA"; this will also permit small radius neutron stars (<12 km).
Thus, neutron star radius measurements, cooling, and the symmetry energy are all related. "It is difficult to reconcile a rapid cooling neutron star with mass of 1.4 solar masses, and a radius of < 12 km." This, Sanjay tells us, would require some new physics.
A high nuclear symmetry energy can favor large proton fraction at and above nuclear density, and allow direct URCA cooling -- which is extremely efficient. A large symmetry energy will also produce neutron stars with larger radii (>12 km). However, a small symmetry energy will produce a low proton fraction, and will not permit direct URCA cooling, requiring that cooling be dominated by the slow process called "modified URCA"; this will also permit small radius neutron stars (<12 km).
Thus, neutron star radius measurements, cooling, and the symmetry energy are all related. "It is difficult to reconcile a rapid cooling neutron star with mass of 1.4 solar masses, and a radius of < 12 km." This, Sanjay tells us, would require some new physics.
Tuesday, January 19, 2010
Toshiki Maruyama -- Structured Mixed Phase of Nuclear Matter
The phase transitions in nuclear matter include: Liquid-gas, neutron drip, meson condensation, hyperon mixture, quark deconfinement, color super-conductivity, and others. Some of these are first order transitions, which means that near the transition, there will be mixed phases. This makes studying the dense matter equation of state (EOS) and thermodynamic properties of mixed phases interesting. This harkens back to "nuclear pasta", as proposed by Ravenhall et al (1983). and Hashimoto et al (1984, in PTP 71 320).
This has modest implications for the structure of neutron stars, but more importantly, it has strong implications for supernovae. These structures of mixed phases occur at below nuclear saturation density, and so are going to be important in determining how supernovae explosions proceed.
At present, many researches who use the EOS, or perform calculations of EOS properties, do so without considering the effects of pasta structure; what Toshiki underlined is, these structures are sometimes is important, and should not be neglected. More importantly, he presented the result that including coulomb screening in the calculations of pressure as a function of density makes the more complex bulk Gibbs calculation have a result which is more similar to the Maxwell construction in the region of the phase transition (which is the result of a more simple calculation).
This has modest implications for the structure of neutron stars, but more importantly, it has strong implications for supernovae. These structures of mixed phases occur at below nuclear saturation density, and so are going to be important in determining how supernovae explosions proceed.
At present, many researches who use the EOS, or perform calculations of EOS properties, do so without considering the effects of pasta structure; what Toshiki underlined is, these structures are sometimes is important, and should not be neglected. More importantly, he presented the result that including coulomb screening in the calculations of pressure as a function of density makes the more complex bulk Gibbs calculation have a result which is more similar to the Maxwell construction in the region of the phase transition (which is the result of a more simple calculation).
Jim Lattimer -- The equation of state and neutron stars
Jim gave a great review of the equation of state of dense matter, and what can be (and has been) learned from neutron star observations.
The room was very interested in PSR J1903, which was reported discovered by Champion et al (2008). Jim mentioned more recent observations by Freire, in which with 95% confidence limits the mass to be above 1.65 solar masses.
Jim also mentioned that, from chiral EFT, Hebeler and Schwenk (2009) determine that a 1.4 solar mass star will have a radius of 11.5 +/1.5 km.
The distance to the INS RXS J1856 has been a long standing question, since this affects the interpretation of observations of its thermal spectrum. In an updated work, Walter Eisenbeiss, Kim and Lattimer (2010) find a distance to the isolated neutron star 1RXS J1856 of 115 +/- 8 pc with 2002-2004 HST data. They conclude that the results in conference proceedings (van Kerkwijk & Kaplan 2007) find D=167 +/- 16 pc must be flawed.
Jim also presented a Bayesian analyses performed by Steiner, Lattimer and Brown (2010), using existing constraints on measurements of neutron star masses, radii and redshifts (qLMXBs M13, Omega Cen, and 47 Tuc X7; INS RXS j1856; and constraings on EXO 1745-248, 4U 182-30, and 4U 1608-522), and this places interesting constraints on the nuclear properties of the equation of state (such as the symmetry energy; the compressibility, for example, is constrained as well as it is with nuclear experiments. A factor of 10 increase on the number of such objects observed would surpass nuclear constraints on these equations. The group was particulary interested on the joing constraings due to 47 Tuc X7 and M13, since those qLMXBs are extremely disparate in their radiation radii.
The room was very interested in PSR J1903, which was reported discovered by Champion et al (2008). Jim mentioned more recent observations by Freire, in which with 95% confidence limits the mass to be above 1.65 solar masses.
Jim also mentioned that, from chiral EFT, Hebeler and Schwenk (2009) determine that a 1.4 solar mass star will have a radius of 11.5 +/1.5 km.
The distance to the INS RXS J1856 has been a long standing question, since this affects the interpretation of observations of its thermal spectrum. In an updated work, Walter Eisenbeiss, Kim and Lattimer (2010) find a distance to the isolated neutron star 1RXS J1856 of 115 +/- 8 pc with 2002-2004 HST data. They conclude that the results in conference proceedings (van Kerkwijk & Kaplan 2007) find D=167 +/- 16 pc must be flawed.
Jim also presented a Bayesian analyses performed by Steiner, Lattimer and Brown (2010), using existing constraints on measurements of neutron star masses, radii and redshifts (qLMXBs M13, Omega Cen, and 47 Tuc X7; INS RXS j1856; and constraings on EXO 1745-248, 4U 182-30, and 4U 1608-522), and this places interesting constraints on the nuclear properties of the equation of state (such as the symmetry energy; the compressibility, for example, is constrained as well as it is with nuclear experiments. A factor of 10 increase on the number of such objects observed would surpass nuclear constraints on these equations. The group was particulary interested on the joing constraings due to 47 Tuc X7 and M13, since those qLMXBs are extremely disparate in their radiation radii.
Welcome!
Welcome to blog for "New Frontiers in QCD 2010"! I will be present at this 2 month workshop, held at the Yukawa Center for Theoretical Physics in Kyoto, Japan (Jan 18-March 19 2010) for the Nuclear Astrophysics portion of (Jan 18-Feb 5th), and will be following the proceedings here.
We begin this morning with a talk from Jim Lattimer (on the Equation of State, Neutron Stars and Supernovae) -- at 10:30 in Y206 (the Yukawa Memorial Hall). This is followed by a talk by Toshiki Maruyama, "Structure Mixed Phase of Nuclear Matter". I'm looking forward to both -- Toshiki will be talking on quark pasta, which is a subject I'm unfamiliar with.
Cheers!
We begin this morning with a talk from Jim Lattimer (on the Equation of State, Neutron Stars and Supernovae) -- at 10:30 in Y206 (the Yukawa Memorial Hall). This is followed by a talk by Toshiki Maruyama, "Structure Mixed Phase of Nuclear Matter". I'm looking forward to both -- Toshiki will be talking on quark pasta, which is a subject I'm unfamiliar with.
Cheers!
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