Joule heating in magnetized NS

Joule heating in the crustal layers due to Ohmic decay was thought to affect only the late photon cooling era in old NS (10^7 yr), and to be an efficient mechanism to maintain the surface temperature as high as 10^{4-5} K for a long time (Miralles & Urpin, 1998). Now we have revisited the problem and found that for strongly magnetized NS (B~10^14 G) Joule heating can be important much earlier in the evolution. The magnetic field decay energy could modify or even control the cooling of a magnetized NS, rather independently from the stellar structure or matter composition. We have performed first 2D simulations keeping the geometry of the magnetic field fixed. Coupled magneto-thermal evolution calculations are needed.

Crosstalk: Mini Workshop on Type I X-ray bursts.

Barry Davids (TRIUMF). Experimental Efforts to Determine the 15O(a,g)19Ne Reaction Rate.
To Astronomers: The 15O(a,g) reaction rate has not been measured, but upper limits are x100 above the theoretical lower limit. With present instrumentation, we can get within x10 the theoretical lower limit; to do better, we will likely need new instrumentation, to produce a high intensity 15O beam, to produce a direct measurement. This would permit pinning down the 15O(a,g)19Ne reaction rate, which is a present choke-point in the rp-process (active in type I x-ray bursts).
To Nuclear Theorists: We need reliable theoretical predictions for reaction rates, benchmarked with observables.

Chris Ruiz (TRIUMF). Nuclear Astrophysics of neutron-deficient nuclei - experimental approaches at ISAC.
To Astrophysicists: We rely on astrophysical modellers to tell us: which reactions are of astrophysical importance? It takes many years (~5 years, say) to develop a specific reaction experimental setup, so the reactions you tell us to measure must be critically important, not merely of some curiosity.


Ed Brown (MSU/JINA). The X-ray Burst-Crust Connection.
For nuclear theorists: Pay attention to all phenomena predicted by your models. It is not enough to see that it produces consistency with one phenomenon; you must also work out the implications for other phenomena as well.


Andrew Cumming (McGill). Constraints on the rp-process from X-ray bursts.
For nuclear experimentalists: There are many possible influences on the phenomena, so nuclear reaction rates are important for understanding them, but there are astronomical influences as well. At present, our uncertainties are not hung up on a single waiting point; however, our level of uncertainty does depend, for example, on
astrophysical causes, such as turbulence or spreading in the burning layer.


Randy Cooper (Harvard/CfA). Nuclear Reactions During the Onset of Type I X-ray Bursts.
The uncertainty in the Hot CNO breakout reaction rates, and in parti15O(a,g)19Ne rate is an important uncertainty in type-I x-ray burst ignition models.

Crosstalk

Zach Medin. Condensed Matter Surfaces of Neutron Stars: Applications and Tangents.
Under certain conditions the atmosphere of a neutron star is negligibly thin and a condensed matter surface forms. This is applicable for neutron stars with large surface magnetic fields and moderate surface temperatures.
For observational astronomers: Condensed matter surfaces could be used, e.g., to explain the featureless spectrum of RX J1856.5-3754, and are also a key ingredient in vacuum gap pulsar emission models.
For nuclear theorists: The strong magnetic fields of neutron stars have an important effect on matter even at low pressure/density.

Arrivals and Departures

Below is the list of arrivals and departures of those in residence at the INT, which occurred as of Monday July 9, in comparison with this previous posting.

Arrivals: Deborah Aguilera (Alicante) Ed Brown (MSU; returning), Randall Cooper (Harvard; returning), Barry Davids (TRIUMF), Huaiyu Duan (UCSD), Pawel Haensel (Copernicus), Alex Potekhin (Ioffe), Achim Schwenk (TRIUMF; returning)

Remaining: Andrew Cumming (McGill), Lirio Aparicio (UNAM), Michael Forbes (UW), Janusz Gil (Kepler Institute), Jillian Anne Henderson (UNAM), Charles Horowitz (Indiana U), Zachary Medin (Cornell), George Melikidze (University of Zielona Gora), Dany Page (UNAM), George Pavlov (PSU), Madappa Prakash (Ohio), Bob Rutledge (McGill), Nicolai Sandulescu (Institute of Atomic Physics)


Departures: Liliana Caballero (Indiana U), Sanjib Gupta (LANL), Jim Lattimer (SUNY), Kseniya Levenfish (Ioffe), Peter Moller (LANL), Jorge Piekarewicz (Florida State), Sergey Postnikov (Ohio), Sanjay Reddy (LANL), Alex Turbiner (UNAM), Roberto Turolla (INFN Padova).

Next Week's Talks

Monday, July 9
10:30. C421. Zach Medin (Cornell)
Condensed Matter Surfaces of Neutron Stars: Applications and Tangents

Tuesday, July 10
10:30. C421. A. Potekhin (Ioffe)
Thermal structure of magnetized neutron star envelopes

Wednesday, July 11
10:30. C421. Pawel Haensel (Copernicus)
Deep crustal heating in accreting neutron stars


Thursday, July 12.
Mini-Workshop: Nuclear Reactions in Type I X-ray Bursts. C421.
10:30. Barry Davids (TRIUMF). Experimental Efforts to Determine the 15O(a,g)19Ne Reaction Rate
11:15. Chris Ruiz (TRIUMF). Nuclear Astrophysics of neutron-deficient nuclei - experimental
2:00. Ed Brown (MSU, JINA). The X-ray Burst—Crust Connection
2:30. Andrew Cumming (McGill). Constraints on the rp-process from X-ray Bursts
3:00. Randall Cooper (Harvard/CfA). Nuclear Reactions During the Onset of Type I X-ray Bursts
3:30-5:00 Coffee & Discussion


Friday, July 12.
10:30. C421. Madappa Prakash (Ohio U.)
Discussion: Hot Topics in The Neutron Star Crust and Surface

Crosstalk

O.L. Caballero. Transport Properties of Dense Plasmas. We are calculating transport properties of the ions in the Neutron star crust using MD simulations. In our model the ions interact via a Yukawa potential. We obtained the thermal conductivity, diffusion coefficient and shear viscosity for a density range between 10^9 to 10^13 gm/cm^3. We expect to match results coming from quantum calculations by Prakash and Postnikov for the dilute gas. In the future we expect to generate results for the nuclear pasta phase.

Neutrino Emission due to Cooper Pair Breaking and Formation (PBF): Clarification

One of the conclusions of my talk during the workshop was that the PBF rate in the vector channel is highly suppressed by a factor of V_F^4 (about 10_as described in the paper by Leinson and Perez (2006). Sedrakian and collaborators have revisted the problem. They also find the rate is suppressed relative to the calculation by Flowers, Sutherland and Ruderman by a factor of about 4 *10^-3 at densities of relevance to the crust.

Crosstalk

From Friday, June 29th:

Jean in' t Zand. Observations of Rare and Peculiar X-ray Bursts.
Many of the details of X-ray bursts are not understood, and many of these may have nuclear physics explanations.

Randy Cooper. Generation of Type 1 X-ray Burst Oscillations.
For nuclear theorists: These oscillations are exciting for nuclear theorists, because they can constrain neutron star compactness, and so contain information about the nuclear EOS, in a way which is complementary and independent of methods heard this week.

Erik Kuulkers. INTEGRAL Galactic Bulge Monitoring Program.
For nuclear theorists: the high energy sky changes from time to time.


Fang Peng. Weak Hydrogen-Powered Explosions on Accreting Neutron Stars.
For Nuclear theorists: X-ray burst modeling depends on the heating from the crust.
For Astronomical observers: Observations of the following phenomena would be useful in constraining burst models: X-ray bursts in low-luminosity sources, search for long bursts, weak H flashes, or peculiar bursts, need high resolution light curves.


Andrew Cumming. Nuclear Burning on Accreting Nuetron Stars.
For nuclear theorists: people working the proton rich side, particularly on rp-processes, we need to understand the timescales for the different processes in rp-process burning. Also on the neutron rich side, we need to understand the crustal processes which produce the heat flux at the base of the crust, to help us explain KS 1731-260.


A problem: H and He is clearly burning stably at 0.1-0.2 of the Eddington accretion rate (i.e., at low temperature in the atmosphere); but we expect to only burn stably at accretion rates at the Eddington rate (at a much higher temperature in the atmosphere). How is it able to burn stably at such a low accretion rate?


Sudip Bhattacharyya. Probing Neutron Star Physics Using Thermonuclear X-ray Bursts. For nuclear theorists: produce mass-radius relationships using only up-to-date physics for neutron stars, strange stars and hybrid stars (quark cores, normal matter in the atmosphere/crust). In other words, please specify which models have outlived their assumptions.

That's the question

If you suddenly find yourself awake at night and
frantically try to remember what that crucial question
(or quest in my opinion) was, well, now you can
here it over and over again, and you'll never
forget: Bob's quest.
Enjoy!

July 4th Party

Prakash and Dany Page invite program participants to a July 4th party at their place:

July 4th Party and BBQ.
3pm-
Madappa Prakash and Dany Page
4227 Dayton Ave.
(Intersecton of 42nd St. & Fremont Ave, leads to Daton Ave).
Ph: (206) 632-5055 CORRECTION 634 0515.
Please feel free to bring: whatever you like, though basic BBQ meats and beer will be present (check with Dany and Prakash).

Directions.
Bus #44 on 45th St. is useful, but it will follow the Sunday schedule due to the holiday.

Crosstalk

J. Henderson - Solving the Mysteries of Ultra-Magnetized Neutron Stars - Heat Transport inside the Crust.
The addition of a toroidal component to the crustal field can sufficiently reduce the radius of the hot emitting areas on the NS surface to possibly explain some observations (i.e. "The Magnificent Seven").
To Observational Astronomers: Keep doing what you're doing.


Alexandros Gezerlis - Neutron Star Matter Superfluidity: from BCS to QMC.
Microscopic simulations of the 1S0 zero-temperature neutron-matter pairing gap show it to be larger than that calculated within all the previous formalisms.
To Observational Astronomers: to quote Chuck Horowitz, "Astronomers should ask nuclear physicists two questions: (1) Are your results model dependent, and (2) What are your theoretical error bars?"

Talks This Week

Monday July 2
10:30. C421. J. Henderson (UAM). Solving the Mysteries of Ultra-Magnetized Neutron Stars?
and A. Gezerlis (LANL). Neutron Star Matter Superfluidity: from BCS to QMC. Each 30 min + 15 min for questions.

Tuesday, July 3
10:30. C421. P. Moller (LANL) Large-scale calculations of nuclear-structure data for simulation data bases
and Sanjib Gupta (LANL). Composition dependence of Neutron Star Deep Crust Crustal Heating.

Wednesday, July 4
Holiday. INT Closed.

Thursday, July 5
10:30. C421. Sergey Postnikov (Ohio). Thermal and Transport Properties of a Non-Relativistic Quantum System
and Liliana Caballero (Indiana U). Transport Properties of Dense Plasmas


Friday, July 6
10:30. C421. George Melikidze (University of Zielona Gora). Partially Screened Polar Gap and its Observational Consequences
and Janusz Gil (J. Kepler Institute of Astronomy). X-ray Pulsar Radiation from Hot Polar Caps Heated by Back-Flow Bombardment.

Arrivals and Departures

Below is the list of arrivals and departures of those in residence at the INT, which occurred as of Monday July 2, in comparison with this previous posting.

Arrivals: Lirio Aparicio (UNAM), Liliana Caballero (Indiana U), Andrew Cumming (McGill), Alex Gezerlis (LANL), Janusz Gil (Kepler Institute), Sanjib Gupta (LANL), Jillian Anne Henderson (UNAM), Charles Horowitz (Indiana U), Jim Lattimer (SUNY Stony Brook), Kseniya Levenfish (Ioffe), Zachary Medin (Cornell), George Mlikidze (University of Zielona Gora), Peter Moller (LANL), George Pavlov (PSU), Jorge Piekarewicz (Florida State), Sergey Postnikov (Ohio), Madappa Prakash (Ohio), Sanjay Reddy (LANL), Nikolai Sandulescu (Institute of Atomic Physics), Alex Turbiner (UNAM), Roberto Turolla (INFN Padova).

Departures: Werner Becker, Chris Fryer, Aimee Hungerford, Jerome Margueron, Vyatcheslav Zavlin, Joseph Carlson.