Abstracts

M. Baldo: Microscopic theory of the neutron star inner crust

The functional method is used to calculate the structure of the neutron star crust within the Wigner-Seitz approximation. Pairing is included and the functional describes a large set of data on finite nuclei and at the same time reproduces accurately the microscopic calculations of low density neutron matter. At each average density the cell size, structure and asymmetry are determined by minimizing the total energy. Particular attention is devoted to the region near the drip point of the crust. Comparisons of the results with other methods and functionals are discussed.

F. Barranco: Microscopic Calculation of Vortex-Nucleus Interaction

We present the first microscopic quantum calculation of the vortex-nucleus interaction in the inner crust. The calculations are done in the Wigner-Seitz cell approximation, solving the HFB (De Gennes) equations, with the proper vortex condition. The resulting vortex structure is sensitive to finite-size quantum effects, and in particular to the shell structure in the continuum. This in turn leads to a very different density dependence of the pinning energy, as compared to previous models.

S. Bhattacharyya: Probing Neutron Star Physics using Thermonuclear X-ray Bursts

Many aspects of extreme physics can be studied only by observing and understanding neutron stars, as these problems cannot be addressed by doing experiments in laboratories. One such problem is the lack of knowledge of the nature of super-dense cold matter in the neutron star cores, and only the accurate measurements of the mass, radius and spin period of a neutron star can resolve this. A promising way to measure these stellar parameters is to study type I X-ray bursts, which are produced by thermonuclear burning of matter accumulated on the surfaces of accreting neutron stars. This is because, these intense bursts, which sometimes exhibit timing features (e.g., millisecond period brightness oscillations), and may show surface spectral features, contain detailed information about these stars. Moreover, X-ray bursts can be helpful for constraining the stellar atmospheric parameters, and for understanding the thermonuclear flame spreading under extreme physical conditions that exist on neutron star surfaces. I will discuss some of the diagnostic merits of these bursts.

E. Brown: Crust electron captures: Implications for superbursts and transient lightcurves

The accretion of matter from a stellar companion pushes matter in the crust of a neutron star to greater pressure and induces reactions that heat the interior. The temperature in the crust is set by balancing this heating with thermal radiation from the surface and neutrino emission from the crust and core. I review the electron capture reactions in the outer crust. These crust models incorporate electron captures into excited states, which increases the heat deposited into the crust. This heating reduces the depth at which carbon unstably ignites and thereby reduces the superburst recurrence time. The heating in the crust also depends strongly on the composition of the ashes of light element reactions.

E. Cackett: Crustal cooling in accretion heated neutron stars

Accretion onto neutron stars in low-mass X-ray binaries keeps them hot, so that they are thermal emitters of X-rays during quiescence (when accretion is minimal). When outbursts are extremely long (lasting several years), the neutron star crust gets heated significantly out of equilibrium with the rest of the star. Thus, once the outburst ends the crust cools down, back into thermal equilibrium, on a timescale set by the properties of the crust. I will review observations of crustal cooling in accretion heated neutron stars, showing that we have now measured the thermal relaxation time of the neutron star crust for 2 objects.

J. Carlson: Pairing gaps in low-density neutron matter and cold atoms

Recent experimental results in cold atoms shed light on the pairing gaps in strongly-coupled fermi systems. In both neutron matter and cold fermions at unitarity, the interaction is nearly strong enough to bind isolated pairs. In such regimes the gap is expected to be of the order of the Fermi Energy, much larger than in traditional superfluids and superconductors. I will briefly report on measurements of RF response and polarized cold atom systems at unitarity, and relate them to ongoing calculations of the pairing gap in neutron matter.

R. Cooper: Generation of Type I X-ray Burst Oscillations

Oscillations have been detected in the rising and/or decaying phases of type I X-ray bursts from 18 sources. It is currently thought that a rotationally modulated non-axisymmetric hot spot is responsible for oscillations during the burst rise, whereas surface modes are responsible for oscillations during the burst decay. Observationally, bursts exhibit oscillations during either phase only when the inferred accretion rate is high. So why do hot spots form and survive during the rise of some bursts? What drives the surface modes during the burst tails? And why do both of these mechanisms function only at high accretion rates? I will address these questions in this talk.

A. Cumming: Nuclear Burning on Accreting Neutron Stars

I discuss our current understanding of nuclear burning on accreting neutron stars, focusing on the global burst behavior as a function of accretion rate, mHz quasi-periodic oscillations, and superbursts.

J. Dey: Stellar and terrestrial observations from the mean field large colour QCD models

A model for large colour (Nc) QCD which could be applicable to baryons as well as quark matter with chiral symmetry restoration was developed with a Richardson potential with appropriate changes for the asymptotic freedon and the confinement scales. The model is applied to the octet and decuplet baryon energies and their magnetic moments and also compared to the many large Nc sumrules for the moments quite successfully. The application to stellar observations is interesting also and if there are strange stars as well as neutron stars in the universe one could learn a lot from the profuse data and is pouring in every day from astro-detections.

D. Eichler: What Can We Learn about Magnetar Crusts from the QPO Component of their Flare Emission?

A model is presented for the quasiperiodic component of magnetar emission during the tail phase of giant flares. The model invokes modulation of the particle number density in the magnetosphere. The magnetospheric currents are modulated by torsional motion of the surface and we calculate that the amplitude of neutron star surface oscillation should be ~1% of the NS radius in order to produce the observed features in the power spectrum. Using an axisymmetric analytical model for structure of the magnetosphere of an oscillating NS , we calculate the angular distribution of the optical depth to the resonant Compton scattering. The anisotropy of the optical depth may be why QPO are observed only at particular rotational phases.

C. Fryer: After the Shock, Magnetic Fields and Fallback on Newly Formed Neutron Stars

It is generally believed that the launch of the shock in a core-collapse supernova marks the beginning of a quiet cooling phase for the newborn neutron star. But the end of this phase may well mark a new turbulent age in the birth of many neutron stars. Strong magnetic fields may send further explosions off the surface of the neutron star. Fallback of material may drive a new phase of turbulent convection within seconds of the supernova explosion. I will present the evidence for this post-explosion activity and discuss some of the effects this activity has on studies of the neutron star.

J. Gil: X-ray pulsar radiation from hot polar caps heated by back-flow bombardment

We consider the problem of the thermal X-ray radiation from the hot polar cap of radio pulsars showing evidence of ExB subpulse drift in radio band. Using the partially screened gap (PSG) model of the inner acceleration region we derived a simple relationship between the drift rate of subpulses observed in a radio-band and the thermal X-ray luminosity from polar caps heated by the spark-associated back-flow particle bombardment. This relationship reflects the fact that both the drift rate and the polar cap heating rate are determined by the same value of the gap electric field. The theoretical formula can be tested for pulsars in which the so-called carousel rotation time P_4 of the ExB plasma drift (time interval after which sparks complete one full revolution around the polar cap), and the thermal X-ray bolometric luminosity L_x from the hot polar cap are known. They are currently four pulsars in which both quantities P_4 and L_x are measured or at least estimated: PSRs B0943+10, B1133+16, B0656+14 and B0628-28. They all seem to fully confirm the predictions of the PSG model. Other available models of the inner acceleration region fail to explain the observed relationship between radio and the X-ray data. The pure vacuum gap model predicts too high L_x and too low P_4, while the space charge limited model predicts too low L_x and the origin of the subpulse drift has no natural explanation.

E. Gotthelf: CCO Pulsars as Anti-magnetars: Evidence of Neutron Stars Weakly Magnetized at Birth

(In collaboration with Jules Halpern)
Our new study of the two Compact Central Object (CCO) pulsars leads us to conclude that they are young, isolated radio-quiet pulsars distinguished by a relatively weak natal magnetic field that shaped their unique observational properties. 1) In the dipole spin-down formalism, the 2-sigma upper-limits on their period derivative (<2E-16 s/s) for both pulsars, PSR J1210-5226 in SNR PKS 1209-51/52 (P=424-ms) and PSR J1852+0040 in SNR Kes 79 (P=105-ms) imply an unusually small surface magnetic field strength of < 3E11 G, and 2) a characteristic age that exceeds their remnant age by three orders of magnitude, requiring that the pulsar was born spinning at its present period, 3) their X-ray luminosity exceeds their respective spin-down luminosity, implying that the thermal spectra is derived from residual cooling, and perhaps partly from accretion of supernova debris. For sufficiently weak magnetic fields, an accretion disk can penetrate the light cylinder and interact with the magnetosphere while resulting torques on the neutron star remains within observable limits. We propose the following as the origin of radio-quiet CCOs: the magnetic field, derived from a turbulent dynamo, is weaker if the NS is formed spinning slowly, which enables it to accrete SN debris. Accretion excludes neutron stars born with both B < E11 G and P > 0.1 s from radio pulsar surveys, where these fields are not encountered except among very old (> 40 Myr) or recycled pulsars. We suggest that these properties define the CCO class.

C. Heinke: Constraints on Neutron Star Physics from Transiently Accreting Neutron Stars in Quiescence

Transiently accreting neutron stars remain hot during intervals of quiescence, due to deep crustal heating (e.g. Brown et al. 1998). Studying X-ray emission from the hot neutron star surface can provide constraints upon neutron star properties. I will briefly review constraints upon the neutron star radius (partly degenerate with the neutron star mass), and constraints on the rate of cooling of the neutron star core, from observations of transiently accreting neutron stars with well-determined distances.

J. Heyl: QED can explain the non-thermal emission from SGRs and AXPs

Owing to effects arising from quantum electrodynamics (QED), magnetohydrodynamical fast modes of sufficient strength will break down to form electron-positron pairs while traversing the magnetospheres of strongly magnetised neutron stars. The bulk of the energy of the fast mode fuels the development of an electron-positron fireball. However, a small, but potentially observable, fraction of the energy (~ 10^33} ergs) can generate a non-thermal distribution of electrons and positrons far from the star. This paper examines the cooling and radiative output of these particles. Small-scale waves may produce only the non-thermal emission. The properties of this non-thermal emission in the absence of a fireball match those of the quiescent, non-thermal radiation recently observed non-thermal emission from several anomalous X-ray pulsars and soft-gamma repeaters. Initial estimates of the emission as a function of angle indicate that the non-thermal emission should be beamed and therefore one would expect this emission to be pulsed as well. According to this model the pulsation of the non-thermal emission should be between 90 and 180 degrees out of phase from the thermal emission from the stellar surface.

C. Horowitz: Neutron rich matter and neutron star crusts

We review neutron rich matter with an emphasis on understanding it well enough to predict transport properties such as the thermal conductivity or sheer viscosity. We start with low density warm matter near the neutrinosphere of a supernova. Here, the Virial expansion makes model independent predictions for the equation of state, composition, and neutrino response. Next we review relationships between crust properties and the density dependence of the symmetry energy. This allows measurements of neutron skins in heavy nuclei to have many implications for neutron star crusts. We update the status of the Pb Radius Experiment (PREX), including a recent target test. The complex pasta phases, that are expected in the inner crust, are described with large scale molecular dynamics simulations. These show that Coulomb interactions suppress density fluctuations. Finally, the role of impurities in the outer crust is highlighted. Molecular dynamics simulations of freezing show that impurities can significantly reduce the melting temperature and lead to chemical separation, with the liquid ocean of accreting stars greatly enriched in low Z elements compared to the composition of the solid crust.

A. Hungerford: Neutrino Scattering in Proto-Neutron Stars

Neutrino transport in and above proto-neutron stars appears to play a critical role in determining the strength of explosion in computational core-collapse supernova models. Several approximations are employed in the numerical treatments for transport physics. In this presentation, I will review aspects of neutrino scattering approximations used in a core-collapse code and discuss their validity. I will discuss the impact that relaxing these approximations has on the integral properties of the proto-neutron star.

J. in 't Zand: Observations of rare and peculiar X-ray bursts

Three decades after the discovery of the first case an estimated five thousand X-ray bursts have been detected. Particular the large databases gathered with BeppoSAX and RXTE have resulted in the detections of rare kinds of X-ray bursts, most notably intermediately long X-ray bursts and superbursts, and of rare phenomena in X-ray bursts such as mHz oscillations, multiple peaks and delayed photospheric radius expansion. The dependencies of these phenomena on the inner conditions of the neutron stars and the nature of the accompanying fuel-donating star present interesting opportunities to learn more about neutron stars. A discussion of these observations will be presented as well as of prospects of future observations with existing and proposed facilities.

D. Kaplan: Nearby, Thermally Emitting Neutron Stars

Over the last decade, astronomers have identified a sample of 7 nearby, cooling neutron stars that do not appear to show any other emission. I will discuss what we currently know and understand about these objects, as well as what the major open questions are.

V. Kaspi: Magnetars

I review the observational properties of Soft Gamma Ray Repeaters and Anomalous X-ray Pulsars, two source classes now commonly thought to be magnetars -- young, isolated pulsars powered by the decay of a large internal magnetic field. I will focus on recent interesting developments of greatest relevance to the workshop, namely topics that involve, in some way, the dense matter equation of state, such as glitches.

E. Kuulkers: INTEGRAL Galactic bulge monitoring program

The Galactic Bulge region is a rich host of variable high-energy X-ray and gamma-ray point sources. These sources include bright and relatively faint X-ray transients, X-ray bursters, persistent neutron star and black-hole candidate binaries, high-mass X-ray binaries, etc.. We have a program to monitor the Galactic Bulge region regularly and frequently with the gamma-ray observatory INTEGRAL. As a service to the scientific community the high-energy light curves of sources present are made available through the WWW at http://isdc.unige.ch/Science/BULGE/. We show the ongoing results of this exciting program.

D. Lai: Surfaces of Magnetic Neutron Stars

I'll discuss recent works on the physics of magnetized neutron star surfaces, and their implications for neutron star astrophysics (e.g., surface emission and magnetospheres).

J. Lattimer: Observational Constraints on the Neutron Star Crust and Their Implications for the Dense Matter Equation of State

Recent observations of explosions on neutron star surfaces, including giant flares and superbursts, can be used to investigate the size and thermal properties of neutron star crusts. Inferences from these observations can be coupled with other observational probes of neutron star masses and radii to place constraints on nuclear matter properties at high densities. These limits will be discussed in general terms, in anticipation of detailed analyses to be presented during this workshop. Special emphasis will be placed on the role of the nuclear symmetry energy and its density dependence in the comparison of theory and observations. Calculations of the composition of the crust and its size using a variety of approaches will be presented to show their dependences on the parameters of the nuclear equation of state.

K. Levenfish: Thermal steady-states of neutron stars in SXTs vs deep crustal heating

Deep crustal heating (owing to nuclear transformations in the accreted matter) may uphold hot thermal states of transiently accreting neutron stars in SXTs. A realistic theory of deep crustal heating is still to be built. Up to date, few models of the matter transformations have been suggested. They differ in distributions of heat-release reactions through the crust and, most important, in total amount of heat released per accreted nucleon. We show how sensitive are thermal steady-states of neutron stars in SXTs to uncertainties of deep crustal heating.

B. Link: The Dynamics of Vortex Pinning in the Neutron Star Crust

The energetically-preferred rotational state of the inner-crust superfluid involves pinning of the neutron vortices to the lattice through a vortex-nucleus interaction. The question of whether or not vortices actually reach this state is crucial toward understanding the rotational modes of a neutron star. I will describe the physics of relaxation of unpinned vortices to the pinned state and show that vortices can pin only if the differential velocity between the superfluid and the solid is very low, less than about 10 cm/s. I will argue that the pinned state, though energetically favored, is quite possibly dynamically inaccessible in a typical neutron star. I will discuss the implications for understanding neutron star spin jumps and long-period precession (nutation).

J. Margueron: Equation of state in the inner crust of neutron matter: discussion of the finite size effects

I will discuss of the equation of state in dense stellar objects and focus on the shell effects in the treatment of unbound neutrons. In describing better and better the nuclear cluster, one may get a poor description of the unbound neutrons, which are indeed mainly responsible of the major physical effects. A method is proposed to remove partially those spurious shell effects, the finite size effects, and is applyed in the search for the more stable wigner-Seitz cell. It will be shown that those finite size effects favor the compact cells. The new EoS will be compared with other calculations and discussed.

G. Melikidze: Partially Screened Polar Gap and its Observational Consequences

Thermal X-ray emission seems to be a quite common feature of the radio pulsars. On the other hand characteristics of such radiation allow us to get a lot of information about the polar cap region of the pulsars. Observations suggest the assumption that the pulsar magnetic field at the stellar surface essentially differs from the pure dipole field. We discuss the model of the pulsar polar gap which implies that the temperature of the polar cap surface is almost equal to the critical temperature which is defined by the strength of the magnetic field at the neutron star surface. Observations of thermal X-ray emission point out an important correlation between the bolometric area and the temperature derived from the blackbody fit. We believe that, major characteristics of the pulsar radiation, including correlation between observed features of X-ray and radio emissions can be naturally explained in the frame of this model. We model various possible configurations of the surface magnetic field and demonstrate that the curvature and structure of the field lines can be of the kind that naturally allows interpretation of observations. In some cases the curvature photons can be absorbed in the region of the closed field lines. The created pairs propagate along the closed field lines and heat the stellar surface near the local poles. Then the estimated area of the X-ray emitting hot spot can be even bigger then the conventional dipolar polar cap surface, which are the cases of PSR J1119-6127 and B0656+14.

F. Paerels: Photospheric Spectroscopy and the Fundamental Stellar Parameters of Neutron Stars

The hot photospheres of bursting neutron stars contain trace heavy elements from accretion, and offer the prospect for detailed atomic line spectroscopy. They are probably unique in this respect, for a variety of reasons. The line spectra are sensitive to the stellar parameters, just as you are used to for ordinary stars, except that the line spectra are in the X-ray band. When combined with the gravitational redshift (easy to measure for a NS), the line profiles and contrasts will yield direct and independent measurements for the mass and radius of the star. We have one possible detection of a significant atomic absorption spectrum in a burster, the now-notorious EXO0748-676. I will discuss the spectroscopic data, their interpretation, and prospects for progress.

F. Peng: Weak Hydrogen-Powered Explosions on Accreting Neutron Stars

Many observed neutron stars accrete gas from a companion star. Once enough gas has piled up on the neutron star surface, nuclear reactions ignite and trigger an explosion known to astronomers as an X-ray burst. For systems where gas is transferred slowly, the ignition of hydrogen is not violent enough to trigger a strong X-ray burst. As a result, there is only a weak flash, which just burns the accumulated hydrogen to helium. When this deep helium layer finally ignites, the unstable fusion reactions would create a large energetic flare. This pattern of numerous weak hydrogen flashes followed by a large helium explosion might account for the unusually energetic X-ray bursts observed from some slowly accreting neutron stars. If the rate at which gas is transferred from the companion were further decreased, the hydrogen layer would become deep enough at ignition that it could not cool as easily. In this case the hydrogen fusion would then trigger helium fusion, and a "normal" X-ray burst ensues.

J. Piekarewicz: The Impact of Terrestrial Facilities on the Structure of the Neutron Star Crust

The outer crust of a neutron star is speculated to consist of a Wigner crystal of neutron-rich nuclei. At densities of about 4x10^11 g/cm^3, the neutron-drip line is reached and the system evolves into a Coulomb crystal immersed in a vapor of free neutrons. At even higher densities, Coulomb "frustration" sets in fueling the speculation that the inner crust is composed of nearly-degenerate exotic structures known as "pasta" phases. In this presentation I will focus on the impact that terrestrial facilities, such as the Jefferson Laboratory and the proposed facility for rare-isotope beams (FRIB, formerly known as RIA), will have on the structure of the neutron star crust. I will conclude with a few remarks on the similarities of this problem to the two-dimensional electron gas.

S. Price: Time-correlated Structure in Spin Fluctuations of an Isolated Neutron Star

We show that stochastic variations in the spin rate ( "timing noise") of an ordinary radio pulsar contain correlated structure; a fluctuation in rotational phase at a given time is correlated with past fluctuations over a correlation time of ~10 d; over longer times, the fluctuations are uncorrelated. We interpret this result as the signature of a damped rotational mode in the star, excited by the noise process, and likely due to friction between the crust and the interior liquid.

S. Reddy: Weak interactions in superfluids and cooling rates in the inner crust

We discuss the microphysics of relevance to neutrino pair production in superfluid neutron matter. We begin with a brief introduction to superfluids and their excitation spectrum, and discuss in detail the pair breaking and formation processes in the 1S0 neutron superfluid.

N. Sandulescu: Nuclear Superfluidity and Cooling Time of Neutron-Star Crust

We shall discuss the effect of neutron superfluidity on the cooling time of inner crust matter in neutron stars, in the case of a rapid cooling of the core. The specific heat of the inner crust, which determines the thermal response of the crust, is calculated in the framework of HFB approach at finite temperature. The calculations are performed with two paring forces chosen to simulate the pairing properties of uniform neutron matter corresponding respectively to Gogny-BCS approximation and to many-body techniques including polarisation effects. Using a simple model for the heat transport across the inner crust, it is shown that the two pairing forces give very different values for the cooling time.

K. Sato: Nuclear "pasta" phases by Quantum Molecular Dynamics

More than two decades ago, nuclear "pasta" phases, phases consist of non-spherical nuclei with rod-like and slab-like shapes, were predicted to exist in neutron star crusts and supernova inner cores. However, their dynamical formation process including its possibility had been an open problem until recently. We have approached this problem using a semiclassical and dynamical method, Quantum Molecular Dynamics. Our results strongly support the existence of the pasta phases in neutron stars and supernovae. I this talk, we shall start with a historical overview of study of the pasta phases and then we will review our works including a brief introduction to our method. We will also discuss astrophysical consequences of the pasta phases, especially, their effects on neutrino opacity.

H.-J. Schulze: Pairing Gaps in Neutron Star Matter

I review the current theoretical status regarding superfluid properties of low-density neutron star matter, including a recent calculation of proton 1S0 pairing involving a complete set of medium effects.

A. Schwenk: Superfluidity in neutron stars

I will discuss S- and P-wave superfluidity in neutron matter including induced interactions. Using an effective field theory (EFT) for large scattering length and large effective range, we present results for the S-wave gaps at low densities. At next-to-leading order, the existing (reliable) S-wave gaps are consistent with our EFT results within errors.

A. Steiner: Symmetry energy, crust thicknesses, and KS 1731

KS 1731 produced a superburst before going into quiescence. The superburst observation provides a lower limit on the temperature of the inner crust, and the crust cooling observations during quiescence provide an upper limit of the temperature near the saturation density. The nature of the cooling requires a knowledge of the thickness of the crust, which depends crucially on the symmetry energy. We examine how the thickness of the crust depends on the symmetry energy We compute the cooling of KS 1731 for various models of the size of the crust and discuss the implications.

A. Turbiner: One-two electrons atomic-molecular systems in a strong magnetic field

A brief review of the Coulomb systems made from one/two electrons and several protons and/or alpha-particles placed to a strong magnetic field is presented. For the 1-e case a complete classification is given with special emphasis on the H2+ and H3++ molecular ions which are the most bound systems. For the 2-e case, the H3+ and He2++ molecular ions will be discussed in details. A possibility to have 1-2 -e charged hydrogenic and helium chains is mentioned.

R. Turolla: X-ray Spectra from Magnetar Candidates

The twisted magnetosphere model (Thompson, Lyutikov & Kulkarni 2002) appears very promising in explaining the observed properties of AXPs and SGRs persistent emission in the 0.1-10 keV range. In this talk I shall present model spectra computed in the framework of the twisted magnetosphere scenario by means of a new montecarlo code. A library of models for different values of the model parameters has been produced and implemented in XSPEC. Preliminary fits of synthetic spectra to selected sources will be presented.

E. Vigezzi: Pairing calculations beyond Mean Field in the Inner Crust

Finite-size and proximity effects play an important role in the study of pairing correlations in the inhomogeneous inner crust, where the sea of free neutrons coexists with the nuclei which form the Coulomb lattice. We first review some results at the mean-field level, and then consider the way they are renormalized by medium fluctuations. Such renormalization effects are very different (even opposite) in uniform matter and in finite nuclei, and it is an open question how to deal with them in the crust, where the two phases coexist.

A. Watts: Magnetar seismology

The detection of seismic vibrations in the afterglow of giant flares from two magnetars has opened up the prospect of using seismological techniques to study the neutron star crust and interior. I will review recent theoretical progress in our understanding of magnetar vibrations, focusing on the complex issues of crust/core coupling, the emission mechanism, and the fracture process. I will also discuss the results of a recent theoretical study showing that magnetar vibrations pose major challenges for strange star models. On the observational side, I will present preliminary results from deeper searches for magnetar vibrations triggered by intermediate and regular flares.

S. Zane: SGRs long term spectral variability

I will discuss a few examples of long/medium term spectral variability observed in SGRs over a time scale of months/years. In particular, I will present a possible interpretation for the spectral variations observed from SGR1806-20 before and after the Giant Flare of 27 Dec 2004, in terms of evolution of a twisted magnetosphere. During periods of enhanced bursting/flaring activity, a large amount of energy can also be released in the inner crust of the neutron star and later re-emitted by the cooling surface. I will review the XMM-Netwon observations of SGR1900+14 and SGR1627-41 in a low luminosity state, and discuss the long term fading observed in the quiescent luminosity of these sources in view of present models of crustal cooling.

V. Zavlin: X-ray emission from the young pulsar J1357-6429 and similar objects

The first Chandra and XMM-Newton observations of the young and energetic pulsar J1357-6429 provided strong indications of a tail-like pulsar-wind nebula associated with this object, as well as pulsations of its X-ray flux with a pulsed fraction above 50% and a thermal component dominating at lower photon energies (below 2 keV). The elongated nebula is very compact in size and may be interpreted as evidence for a pulsar jet. The thermal radiation is most plausibly emitted from the entire neutron star surface of an effective temperature about 1 MK covered with a magnetized hydrogen atmosphere. At higher energies the pulsar's emission is of a nonthermal (magnetospheric) origin, with a power-law spectrum of a photon index of 1.1-1.3. This makes the X-ray properties of PSR J1357-6429 very similar to those of the youngest pulsars J1119-6127, Vela and several others with a detected thermal radiation.