scispace - formally typeset
Search or ask a question

Showing papers on "Magnetar published in 2009"


BookDOI
Werner Becker1
01 Jan 2009
TL;DR: The Double Pulsar: A Unique Lab for Relativistic Plasma Physics and Tests of General Relativity as discussed by the authors, is a unique lab for experimental results on the double Pulsars.
Abstract: Radio Pulsar Statistics.- Radio Emission Properties of Pulsars.- Rotating Radio Transients.- Intermittent Pulsars.- The Double Pulsar: A Unique Lab for Relativistic Plasma Physics and Tests of General Relativity.- X-Ray Emission from Pulsars and Neutron Stars.- Isolated Neutron Stars: The Challenge of Simplicity.- Millisecond Pulsars in Globular Clusters and the Field.- Theory of Radiative Transfer in Neutron Star Atmospheres and Its Applications.- Neutron Star Interiors and the Equation of State of Superdense Matter.- Neutron Star Cooling: I.- Neutron Star Cooling: II.- Turning Points in the Evolution of Isolated Neutron Stars'Magnetic Fields.- Pulsar Spin, Magnetic Fields, and Glitches.- Pulsar Emission: Where to Go.- The Theory of Pulsar Winds and Nebulae.- Implications of HESS Observations of Pulsar.- High Energy Emission from Pulsars and Pulsar Wind Nebulae.- High-energy Emission from the Polar Cap and Slot Gap.- Physics of Drifting Sub-pulses in Radio Pulsars.- Soft Gamma-Ray Repeaters and Magnetars.- X-Ray Polarimetry and Its Potential Use for Understanding Neutron Stars.- GeV Gamma-Ray Pulsar Detection.- Gravitational Waves from Spinning Neutron Stars.

442 citations


Journal ArticleDOI
TL;DR: In this paper, the authors derived an equation describing the evolution of the magnetosphere of neutron stars and derived its solutions, and its solutions are presented. And they also discussed implications for other magnetars.
Abstract: Magnetospheres of neutron stars are anchored in the rigid crust and can be twisted by sudden crustal motions (starquakes). The twisted magnetosphere does not remain static and gradually untwists, dissipating magnetic energy and producing radiation. The equation describing this evolution is derived, and its solutions are presented. Two distinct regions coexist in untwisting magnetospheres: a potential region where ∇ × B = 0 (cavity) and a current-carrying bundle of field lines with ∇ × B ≠ 0 (j-bundle). The cavity has a sharp boundary, which expands with time and eventually erases all of the twist. In this process, the electric current of the j-bundle is sucked into the star. Observational appearance of the untwisting process is discussed. A hot spot forms at the footprints of the j-bundle. The spot shrinks with time toward the magnetic dipole axis, and its luminosity and temperature gradually decrease. As the j-bundle shrinks, the amplitude of its twist ψ can grow to the maximum possible value ψmax ~ 1. The strong twist near the dipole axis increases the spindown rate of the star and can generate a broad beam of radio emission. The model explains the puzzling behavior of magnetar XTE J1810–197, a canonical example of magnetospheric evolution following a starquake. We also discuss implications for other magnetars. The untwisting theory suggests that the nonthermal radiation of magnetars is preferentially generated on a bundle of extended closed field lines near the dipole axis.

300 citations


Journal ArticleDOI
TL;DR: Because of the collective behavior of the ions during failure found in the simulations, the neutron star crust is likely very strong and can support mountains large enough so that their gravitational wave radiation could limit the spin periods of some stars and might be detectable in large-scale interferometers.
Abstract: Mountains on rapidly rotating neutron stars efficiently radiate gravitational waves. The maximum possible size of these mountains depends on the breaking strain of the neutron star crust. With multimillion ion molecular dynamics simulations of Coulomb solids representing the crust, we show that the breaking strain of pure single crystals is very large and that impurities, defects, and grain boundaries only modestly reduce the breaking strain to around 0.1. Because of the collective behavior of the ions during failure found in our simulations, the neutron star crust is likely very strong and can support mountains large enough so that their gravitational wave radiation could limit the spin periods of some stars and might be detectable in large-scale interferometers. Furthermore, our microscopic modeling of neutron star crust material can help analyze mechanisms relevant in magnetar giant flares and microflares.

281 citations


Journal ArticleDOI
TL;DR: In this article, the authors used ideal axisymmetric relativistic magnetohydrodynamic simulations to calculate the spindown of a newly formed millisecond, B ~ 15 G, magnetar and its interaction with the surrounding stellar envelope during a core-collapse supernova (SN) explosion.
Abstract: We use ideal axisymmetric relativistic magnetohydrodynamic simulations to calculate the spindown of a newly formed millisecond, B ~ 10^{15} G, magnetar and its interaction with the surrounding stellar envelope during a core-collapse supernova (SN) explosion. The mass, angular momentum, and rotational energy lost by the neutron star are determined self-consistently given the thermal properties of the cooling neutron star's atmosphere and the wind's interaction with the surrounding star. The magnetar drives a relativistic magnetized wind into a cavity created by the outgoing SN shock. For high spindown powers (~ 10^{51}-10^{52} ergs/s), the magnetar wind is super-fast at almost all latitudes, while for lower spindown powers (~ 10^{50} erg/s), the wind is sub-fast but still super-Alfvenic. In all cases, the rates at which the neutron star loses mass, angular momentum, and energy are very similar to the corresponding free wind values (<~ 30% differences), in spite of the causal contact between the neutron star and the stellar envelope. In addition, in all cases that we consider, the magnetar drives a collimated (~5-10 deg.) relativistic jet out along the rotation axis of the star. Nearly all of the spindown power of the neutron star escapes via this polar jet, rather than being transferred to the more spherical SN explosion. The properties of this relativistic jet and its expected late-time evolution in the magnetar model are broadly consistent with observations of long duration gamma-ray bursts (GRBs) and their associated broad-lined Type Ic SN.

183 citations


Journal ArticleDOI
TL;DR: In this paper, the authors used ideal axisymmetric relativistic magnetohydrodynamic simulations to calculate the spin-down of a newly formed millisecond, B ∼ 10 15 G, magnetar and its interaction with the surrounding stellar envelope during a core-collapse supernova (SN) explosion.
Abstract: We use ideal axisymmetric relativistic magnetohydrodynamic simulations to calculate the spin-down of a newly formed millisecond, B ∼ 10 15 G, magnetar and its interaction with the surrounding stellar envelope during a core-collapse supernova (SN) explosion. The mass, angular momentum and rotational energy lost by the neutron star are determined self-consistently given the thermal properties of the cooling neutron star's atmosphere and the wind's interaction with the surrounding star. The magnetar drives a relativistic magnetized wind into a cavity created by the outgoing SN shock. For high spin-down powers (∼10 51 ―10 52 erg s ―1 ), the magnetar wind is superfast at almost all latitudes, while for lower spin-down powers (∼10 50 erg s ―1 ), the wind is subfast but still super-Alfvenic. In all cases, the rates at which the neutron star loses mass, angular momentum and energy are very similar to the corresponding free wind values (≤30 per cent differences), in spite of the causal contact between the neutron star and the stellar envelope. In addition, in all cases that we consider, the magnetar drives a collimated (∼5―10°) relativistic jet out along the rotation axis of the star. Nearly all of the spin-down power of the neutron star escapes via this polar jet, rather than being transferred to the more spherical SN explosion. The properties of this relativistic jet and its expected late-time evolution in the magnetar model are broadly consistent with observations of long duration gamma-ray bursts (GRBs) and their associated broad-lined Type Ic SN.

182 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated the possibility that the formation of a highly magnetized millisecond pulsar, pumping energy into the fireball on timescales longer than the prompt emission, could explain the existence of a shallow decay phase in early X-ray afterglows of gamma-ray bursts.
Abstract: The existence of a shallow decay phase in the early X-ray afterglows of gamma-ray bursts is a common feature. Here we investigate the possibility that this is connected to the formation of a highly magnetized millisecond pulsar, pumping energy into the fireball on timescales longer than the prompt emission. In this scenario, the nascent neutron star could undergo a secular bar-mode instability, leading to gravitational wave losses which would affect the neutron star spin-down. In this case, nearby gamma-ray bursts with isotropic energies of the order of 1050 ergs would produce a detectable gravitational wave signal emitted in association with an observed X-ray light-curve plateau, over relatively long timescales of minutes to about an hour. The peak amplitude of the gravitational wave signal would be delayed with respect to the gamma-ray burst trigger, offering gravitational wave interferometers such as the advanced LIGO and Virgo the challenging possibility of catching its signature on the fly.

166 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the possibility that the formation of a highly magnetized millisecond pulsar, pumping energy into the fireball on timescales longer than the prompt emission, could explain the existence of a shallow decay phase in the early X-ray afterglows of gamma-ray bursts.
Abstract: The existence of a shallow decay phase in the early X-ray afterglows of gamma-ray bursts is a common feature. Here we investigate the possibility that this is connected to the formation of a highly magnetized millisecond pulsar, pumping energy into the fireball on timescales longer than the prompt emission. In this scenario the nascent neutron star could undergo a secular bar-mode instability, leading to gravitational wave losses which would affect the neutron star spin-down. In this case, nearby gamma-ray bursts with isotropic energies of the order of 1e50 ergs would produce a detectable gravitational wave signal emitted in association with an observed X-ray light-curve plateau, over relatively long timescales of minutes to about an hour. The peak amplitude of the gravitational wave signal would be delayed with respect to the gamma-ray burst trigger, offering gravitational wave interferometers such as the advanced LIGO and Virgo the challenging possibility of catching its signature on the fly.

156 citations


Journal ArticleDOI
TL;DR: In this article, the authors present multi-wavelength (radio through X-ray) observations of GRBs 050820A, 060418, and 080319B, and construct afterglow models to extract the opening angle and beaming-corrected energy release for all three events.
Abstract: Long-duration gamma-ray bursts (GRBs) are widely believed to be highly-collimated explosions (opening angle theta ~ 1-10 deg). As a result of this beaming factor, the true energy release from a GRB is usually several orders of magnitude smaller than the observed isotropic value. Measuring this opening angle, typically inferred from an achromatic steepening in the afterglow light curve (a "jet" break), has proven exceedingly difficult in the Swift era. Here we undertake a study of five of the brightest (in terms of the isotropic prompt gamma-ray energy release, E(gamma, iso)) GRBs in the Swift era to search for jet breaks and hence constrain the collimation-corrected energy release. We present multi-wavelength (radio through X-ray) observations of GRBs 050820A, 060418, and 080319B, and construct afterglow models to extract the opening angle and beaming-corrected energy release for all three events. Together with results from previous analyses of GRBs 050904 and 070125, we find evidence for an achromatic jet break in all five events, strongly supporting the canonical picture of GRBs as collimated explosions. The most natural explanation for the lack of observed jet breaks from most Swift GRBs is therefore selection effects. However, the opening angles for the events in our sample are larger than would be expected if all GRBs had a canonical energy release of ~ 10e51 erg. The total energy release we measure for those "hyper-energetic" (E(total) >~ 10e52 erg) events in our sample is large enough to start challenging models with a magnetar as the compact central remnant.

148 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present a state-of-the-art scenario for newly born magnetars as strong sources of gravitational waves in the early days after formation, which is consistent with recent studies of supernova remnant surrounding Anomalous X-ray Pulsars (AXPs) and Soft Gamma-Ray Repeaters (SGRs) in the Galaxy that constrains the electromagnetic energy input from the central NS to be ≤ 10 51 erg.
Abstract: We present a state-of-the-art scenario for newly born magnetars as strong sources of gravitational waves (GWs) in the early days after formation. We address several aspects of the astrophysics of rapidly rotating, ultra-magnetized neutron stars (NSs), including early cooling before transition to superfluidity, the effects of the magnetic field on the equilibrium shape of NSs, the internal dynamical state of a fully degenerate, oblique rotator and the strength of the electromagnetic torque on the newly born NS. We show that our scenario is consistent with recent studies of supernova remnant surrounding Anomalous X-ray Pulsars (AXPs) and Soft Gamma-Ray Repeaters (SGRs) in the Galaxy that constrains the electromagnetic energy input from the central NS to be ≤ 10 51 erg. We further show that if this condition is met, then the GW signal from such sources is potentially detectable with the forthcoming generation of GW detectors up to Virgo cluster distances where an event rate ∼ 1 yr ―1 can be estimated. Finally, we point out that the decay of an internal magnetic field in the 10 16 G range couples strongly with the NS cooling at very early stages, thus significantly slowing down both processes: the field can remain this strong for at least 10 3 yr, during which the core temperature stays higher than several times 10 8 K.

146 citations


Journal ArticleDOI
TL;DR: In this paper, the authors used the X-ray lightcurves of all gamma-ray bursts observed by the Swift satellite to identify a subset of bursts which have a feature in their light curves which they call an internal plateau, which may be powered by a magnetar.
Abstract: Long duration gamma-ray bursts (GRBs) are thought to be produced by the core-collapse of a rapidly-rotating massive star. This event generates a highly relativistic jet and prompt gamma-ray and X-ray emission arises from internal shocks in the jet or magnetised outflows. If the stellar core does not immediately collapse to a black hole, it may form an unstable, highly magnetised millisecond pulsar, or magnetar. As it spins down, the magnetar would inject energy into the jet causing a distinctive bump in the GRB light curve where the emission becomes fairly constant followed by a steep decay when the magnetar collapses. We assume that the collapse of a massive star to a magnetar can launch the initial jet. By automatically fitting the X-ray lightcurves of all GRBs observed by the Swift satellite we identified a subset of bursts which have a feature in their light curves which we call an internal plateau -- unusually constant emission followed by a steep decay -- which may be powered by a magnetar. We use the duration and luminosity of this internal plateau to place limits on the magnetar spin period and magnetic field strength and find that they are consistent with the most extreme predicted values for magnetars.

138 citations


Journal ArticleDOI
TL;DR: In this paper, the authors studied the phase-resolved spectral evolution of the soft gamma-ray repeater SGR 0501+4516 with XMM-Newton observations for a 3-month period and found that the source flux decreased exponentially with a time-scale of t(c) = 23.8 d.
Abstract: We report here on the outburst onset and evolution of the new soft gamma-ray repeater SGR 0501+4516. We monitored the new SGR with XMM- Newton starting on 2008 August 23, 1 day after the source became burst active, and continuing with four more observations in the following month, with the last one on 2008 September 30. Combining the data with the Swift X-ray telescope (Swift-XRT) and Suzaku data, we modelled the outburst decay over a 3-month period, and we found that the source flux decreased exponentially with a time-scale of t(c) = 23.8 d. In the first XMM-Newton observation, a large number of short X-ray bursts were observed, the rate of which decayed drastically in the following observations. We found large changes in the spectral and timing behaviour of the source during the first month of the outburst decay, with softening emission as the flux decayed, and the non-thermal soft X-ray spectral component fading faster than the thermal one. Almost simultaneously to our second and fourth XMM-Newton observations (on 2008 August 29 and September 2), we observed the source in the hard X-ray range with INTEGRAL, which clearly detected the source up to similar to 100 keV in the first pointing, while giving only upper limits during the second pointing, discovering a variable hard X-ray component fading in less than 10 days after the bursting activation. We performed a phase-coherent X-ray timing analysis over about 160 days starting with the burst activation and found evidence of a strong second derivative period component [(sic) = -1.6(4) x 10(-19) s s(-2)]. Thanks to the phase connection, we were able to study the phase-resolved spectral evolution of SGR 0501+ 4516 in great detail. We also report on the ROSAT quiescent source data, taken back in 1992 when the source exhibits a flux similar to 80 times lower than that measured during the outburst, and a rather soft, thermal spectrum.

Journal ArticleDOI
TL;DR: In this article, phase-connected timing of the 105 ms X-ray pulsar PSR J1852+0040 was obtained for the first measurement of the spin-down rate of a member of the class of Central Compact Objects (CCOs) in supernova remnants.
Abstract: Using XMM-Newton and Chandra, we achieved phase-connected timing of the 105 ms X-ray pulsar PSR J1852+0040 that provides the first measurement of the spin-down rate of a member of the class of Central Compact Objects (CCOs) in supernova remnants. We measure P-dot = 8.68(9)E-18, and find no evidence for timing noise or variations in X-ray flux over 4.8 yr. In the dipole spin-down formalism, this implies a surface magnetic field strength B_s = 3.1E10 G, the smallest ever measured for a young neutron star, and consistent with being a fossil field. In combination with upper limits on B_s from other CCO pulsars, this is strong evidence in favor of the "anti-magnetar" explanation for their low luminosity and lack of magnetospheric activity or synchrotron nebulae. While this dipole field is small, it can prevent accretion of sufficient fall-back material so that the observed X-ray luminosity of L_x = 5.3E33(d/7.1 kpc)^2 erg/s must instead be residual cooling. The spin-down luminosity of PSR J1852+0040, E-dot = 3.0E32 erg/s, is an order-of-magnitude smaller than L_x. Fitting of the X-ray spectrum to two blackbodies finds small emitting radii, R_1 = 1.9 km and R_2 = 0.45 km, for components of kT_1 = 0.30 keV and kT_2 = 0.52 keV, respectively. Such small, hot regions are ubiquitous among CCOs, and are not yet understood in the context of the anti-magnetar picture because anisotropic surface temperature is usually attributed to the effects of strong magnetic fields.

Journal ArticleDOI
TL;DR: In this article, the authors used the star formation history map of the Large Magellanic Cloud (LMC) to study the sites of the eight smallest (and presumably youngest) supernova remnants in the Cloud: SN 1987A, N158A and N49, and N63A.
Abstract: We use the star formation history map of the Large Magellanic Cloud recently published by Harris & Zaritsky to study the sites of the eight smallest (and presumably youngest) supernova remnants in the Cloud: SN 1987A, N158A, N49, and N63A (core collapse remnants), 0509 67.5, 0519 69.0, N103B, and DEM L71 (Type Ia remnants). The local star formation histories provide unique insights into the nature of the supernova progenitors, which we compare with the properties of the supernova explosions derived from the remnants themselves and from supernova light echoes. We find that all the core collapse supernovae that we have studied are associated with vigorous star formation in the recent past. In the case of SN 1987A, the time of the last peak of star formation (12 Myr) matches the lifetime of a star with the known mass of its blue supergiant progenitor (� 20M⊙). More recent peaks of star formation can lead to supernovae with more massive progenitors, which opens the possibility of a Type Ib/c origin for SNRs N158A and N63A. Stars more massive than 21.5M⊙ are very scarce around SNR N49, implying that the magnetar SGR 0526 66 in this SNR was either formed elsewhere or came from a progenitor with a mass well below the 30M⊙ threshold suggested in the literature. Three of our four Ia SNRs are associated with old, metal poor stellar populations. This includes SNR 0509 67.5, which is known to have been originated by an extremely bright Type Ia event, and yet is located very far away from any sites of recent star formation, in a population with a mean age of 7.9 Gyr. The Type Ia SNR N103B, on the other hand, is associated with recent star formation, and might have had a relatively younger and more massive progenitor with substantial mass loss before the explosion. We discuss these results in the context of our present understanding of core collapse and Type Ia supernova progenitors.

Journal ArticleDOI
TL;DR: In this paper, a phase-coherent X-ray timing analysis of the SGR 0501+4516 was performed over 160 days starting with the burst activation and found evidence of a strong second derivative period component (\ddot{P} = -1.6(4)x10-19} s/s^{-2}).
Abstract: We report here on the outburst onset and evolution of the new Soft Gamma Repeater SGR 0501+4516. We monitored the new SGR with XMM-Newton starting on 2008 August 23, one day after the source became burst-active, and continuing with 4 more observations, with the last one on 2008 September 30. Combining the data with the Swift-XRT and Suzaku data, we modelled the outburst decay over 160 days, and we found that the source flux decreased exponentially with a timescale of t_c=23.8 days. In the first XMM-Newton observation a large number of short X-ray bursts were observed, the rate of which decayed drastically in the following observations. We found large changes in the spectral and timing behavior of the source during the outburst, with softening emission as the flux decayed, and the non-thermal soft X-ray spectral component fading faster than the thermal one. Almost simultaneously to our XMM-Newton observations (on 2008 August 29 and September 2), we observed the source in the hard X-ray range with INTEGRAL, which clearly detected the source up to ~100keV in the first pointing, while giving only upper limits during the second pointing, discovering a variable hard X-ray component fading in less than 10 days after the bursting activation. We performed a phase-coherent X-ray timing analysis over about 160 days starting with the burst activation and found evidence of a strong second derivative period component (\ddot{P} = -1.6(4)x10^{-19} s/s^{-2}). Thanks to the phase-connection, we were able to study the the phase-resolved spectral evolution of SGR 0501+4516 in great detail. We also report on the ROSAT quiescent source data, taken back in 1992 when the source exhibits a flux ~80 times lower than that measured during the outburst, and a rather soft, thermal spectrum.

Journal ArticleDOI
TL;DR: The Rossi X-ray Pulsar 1E 1048.1 - 5937 (RXTE) was reactivated in 2007 March 26 (MJD 54185.9), contemporaneous with the onset of a pulsed-flux flare.
Abstract: After three years of no unusual activity, Anomalous X-ray Pulsar 1E 1048.1 - 5937 reactivated in 2007 March. We report on the detection of a large glitch ({delta}{nu}/{nu} = 1.63(2) x 10{sup -5}) on 2007 March 26 (MJD 54185.9), contemporaneous with the onset of a pulsed-flux flare, the third flare observed from this source in 10 years of monitoring with the Rossi X-ray Timing Explorer (RXTE). Additionally, we report on a detailed study of the evolution of the timing properties, the pulsed flux, and the pulse profile of this source as measured by RXTE from 1996 July to 2008 January. In our timing study, we attempted phase-coherent timing of all available observations. We show that in 2001 a timing anomaly of uncertain nature occurred near the rise of the first pulsed flux flare; we show that a likely glitch ({delta}{nu}/{nu} = 2.91(9) x 10{sup -6}) occurred in 2002, near the rise of the second flare, and we present a detailed description of the variations in the spin down. In our pulsed flux study, we compare the decays of the three flares and discuss changes in the hardness ratio. In our pulse profile study, we show that the profile exhibited large more » variations near the peak of the first two flares, and several small short-term profile variations during the most recent flare. Finally, we report on the discovery of a small burst 27 days after the peak of the last flare, the fourth burst discovered from this source. We discuss the relationships between the observed properties in the framework of the magnetar model. « less

Journal ArticleDOI
TL;DR: In this article, the authors presented adaptive-optics assisted Keck/NIRC2 imaging and NIRSPEC spectroscopy of the cluster associated with the magnetar SGR 1900+14, and reported that the initial progenitor star mass was a factor of 2 lower than this limit, M = 17 ± 2 M_⊙.
Abstract: Magnetars are young neutron stars with extreme magnetic fields (B ≳ 10^(14)-10^(15) G). How these fields relate to the properties of their progenitor stars is not yet clearly established. However, from the few objects associated with young clusters it has been possible to estimate the initial masses of the progenitors, with results indicating that a very massive progenitor star (M_(prog) > 40 M_⊙) is required to produce a magnetar. Here, we present adaptive-optics assisted Keck/NIRC2 imaging and Keck/NIRSPEC spectroscopy of the cluster associated with the magnetar SGR 1900+14, and report that the initial progenitor star mass of the magnetar was a factor of 2 lower than this limit, M_(prog) = 17 ± 2 M_⊙. Our result presents a strong challenge to the concept that magnetars can only result from very massive progenitors. Instead, we favor a mechanism which is dependent on more than just initial stellar mass for the production of these extreme magnetic fields, such as the "fossil-field" model or a process involving close binary evolution.

Journal ArticleDOI
TL;DR: In this paper, a detailed study of the evolution of the timing properties, the pulsed flux, and the pulse profile of anomalous X-ray Pulsar 1E 1048.1-5937 was presented.
Abstract: After three years of no unusual activity, Anomalous X-ray Pulsar 1E 1048.1-5937 reactivated in 2007 March. We report on the detection of a large glitch (deltav/v = 1.63(2) x 10(exp -5)) on 2007 March 26 (MJD 54185.9), contemporaneous with the onset of a pulsed-flux flare, the third flare observed from this source in 10 years of monitoring with the Rossi X-ray Timing Explorer. Additionally, we report on a detailed study of the evolution of the timing properties, the pulsed flux, and the pulse profile of this source as measured by RXTE from 1996 July to 2008 January. In our timing study, we attempted phase coherent timing of all available observations. We show that in 2001, a timing anomaly of uncertain nature occurred near the rise of the first pulsed flux flare; we show that a likely glitch (deltav/v = 2.91(9) x 10(exp -6)) occurred in 2002, near the rise of the second flare, and we present a detailed description of the variations in the spin-down. In our pulsed flux study, we compare the decays of the three flares and discuss changes in the hardness ratio. In our pulse profile study, we show that the profile exhibited large variations near the peak of the first two flares, and several small short-term profile variations during the most recent flare. Finally, we report on the discovery of a small burst 27 days after the peak of the last flare, the fourth burst discovered from this source. We discuss the relationships between the observed properties in the framework of the magnetar model.

Book ChapterDOI
01 Jan 2009
TL;DR: In this article, the main observational properties of the Magnificent seven are reviewed, and the current status of theoretical modeling presented, focusing on the main challenge these objects pose to theorists, namely how can a cooling neutron star emit a nearly perfect blackbody spectrum.
Abstract: The seven soft, thermal sources discovered by ROSAT offer an unprecedented opportunity to unveil the temperature and magnetic field surface distribution of isolated neutron stars. This makes a direct measurement of the star radius and mass within reach and will allow to place tight constraints on matter equation of state at nuclear densities. In this chapter the main observational properties of the Magnificent Seven are reviewed, and the current status of theoretical modeling presented. Emphasis is placed on the main challenge these objects pose to theorists, namely how can a cooling neutron star emit a nearly perfect blackbody spectrum. Open issues concern the origin of the broad absorption features (or lack thereof) detected around a few hundred electron volts, the search for new candidates and the (possible) links of the Magnificent Seven with other classes of Galactic neutron star sources, the newly discovered rotating radio transients and the magnetar candidates in particular. First hypothesised in the 1930s, neutron stars have been for more than 40 years a theoretician’s dainty, until the discovery of the first radio pulsar [27]. Since then, neutron stars have been mostly detected at radio wavelengths, and the number of known radio pulsars exceeds now 1,800.1 This vast success contributed to spread the general belief that isolated (i.e. those not in binary systems) neutron stars are with no exception active radio pulsars. It was thanks to X-ray telescopes flown in the last 20 years that our picture of isolated neutron stars gradually started to change. Search for the soft X-ray radiation given off by the cooling surface of aging neutron stars has been already one of the goals of the EINSTEIN mission. However, its limited spatial resolution and low-energy sensitivity made it difficult to

Journal ArticleDOI
TL;DR: In this paper, it was shown that energy deposited into an expanding supernova remnant by a highly magnetic (B ~ 5 x 10^14 G) neutron star spinning at an initial period of P ~ 2-20 ms can substantially brighten the light curve.
Abstract: We show that energy deposited into an expanding supernova remnant by a highly magnetic (B ~ 5 x 10^14 G) neutron star spinning at an initial period of P ~ 2-20 ms can substantially brighten the light curve. For magnetars with parameters in this range, the rotational energy is released on a timescale of days to weeks, which is comparable to the effective diffusion time through the supernova remnant. The late time energy injection can then be radiated without suffering overwhelming adiabatic expansion losses. The magnetar input also produces a central bubble which sweeps ejecta into an internal dense shell, resulting in a prolonged period of nearly constant photospheric velocity in the observed spectra. We derive analytic expressions for the light curve rise time and peak luminosity as a function of B, P and the properties of the supernova ejecta that allow for direct inferences about the underlying magnetar in bright supernovae. We perform numerical radiation hydrodynamical calculations of a few specific instances and compare the resulting light curves to observed events. Magnetar activity is likely to impact more than a few percent of all core collapse supernovae, and may naturally explain some of the brightest events ever seen (e.g., SN 2005ap and SN 2008es) at L > 10^44 ergs/s.

Journal ArticleDOI
TL;DR: In this paper, a three-blackbody model was proposed to reproduce the spectral properties of XTE J1810-197 over the entire outburst statistically better than the two blackbodies model previously used in the literature.
Abstract: Aims. XTE J1810-197 is the first transient anomalous X-ray pulsar ever discovered. Its highly variable X-ray flux allowed us to study the timing and spectral emission properties of a magnetar candidate over a flux range of about two orders of magnitude. Methods. We analyzed nine XMM-Newton observations of XTE J1810-197 collected over a four year baseline (September 2003– September 2007). EPIC PN and MOS data were reduced and used for detailed timing and spectral analysis. Pulse-phase spectroscopic studies were also carried out for observations with a high enough signal-to-noise. Results. We find that (i) a three-blackbody model reproduces the spectral properties of XTE J1810-197 over the entire outburst statistically better than the two blackbodies model previously used in the literature, (ii) the coldest blackbody is consistent with the thermal emission from the whole surface and has temperature and radius similar to those inferred from ROSAT observations before the outburst onset, (iii) there is a spectral feature around 1.1 keV during six consecutive observations (since March 2005). If this stems from proton resonant cyclotron scattering, it would imply a magnetic field of ∼2 × 10 14 G. This closely agrees with the value from the spin period measurements.

Journal ArticleDOI
TL;DR: In this paper, the role of neutron star superfluidity for magnetar oscillations was investigated using a plane-wave analysis, and it was shown that the superfluid imprint is likely to be more significant than the effects of the crustal magnetic field.
Abstract: We investigate the role of neutron star superfluidity for magnetar oscillations. Using a plane-wave analysis, we estimate the effects of a neutron superfluid in the elastic crust region. We demonstrate that the superfluid imprint is likely to be more significant than the effects of the crustal magnetic field. We also consider the region immediately beneath the crust, where superfluid neutrons are thought to coexist with a type II proton superconductor. Since the magnetic field in the latter is carried by an array of fluxtubes, the dynamics of this region differ from standard magnetohydrodynamics. We show that the presence of the neutron superfluid (again) leaves a clear imprint on the oscillations of the system. Taken together, our estimates show that the superfluid components cannot be ignored in efforts to carry out 'magnetar seismology'. This increases the level of complexity of the modelling problem, but also points to the possibility of using observations to probe the superfluid nature of supranuclear matter.

Journal ArticleDOI
TL;DR: In this article, the authors analyzed nine XMM-Newton observations of XTE J1810-197 collected over a four-year baseline (September 2003 - September 2007).
Abstract: XTE J1810-197 is the first transient Anomalous X-ray Pulsar ever discovered. Its highly variable X-ray flux allowed us to study the timing and spectral emission properties of a magnetar candidate over a flux range of about two orders of magnitude. We analyzed nine XMM-Newton observations of XTE J1810-197 collected over a four years baseline (September 2003 - September 2007). EPIC PN and MOS data were reduced and used for detailed timing and spectral analysis. Pulse phase spectroscopic studies were also carried out for observations with sufficiently high signal to noise. We find that: (i) a three blackbodies model reproduces the spectral properties of the source over the entire outburst statistically better than the two blackbodies model previously used in the literature, (ii) the coldest blackbody is consistent with the thermal emission from the whole surface, and has temperature and radius similar to those inferred from ROSAT observations before the outburst onset, (iii) there is a spectral feature around 1.1 keV during six consecutive observations (since March 2005); if due to proton resonant cyclotron scattering, it would imply a magnetic field of around 2E14 G. This is in a very good agreement with the value from the spin period measurements.

Journal ArticleDOI
TL;DR: In this article, the authors reported a large spin-up glitch in PSR J1846-0258 which coincided with the onset of magnetar-like behavior on 2006 May 31, and showed that the pulsar experienced an unusually large glitch recovery, with a recovery fraction of Q=8.7+/- 2.5.
Abstract: We report a large spin-up glitch in PSR J1846-0258 which coincided with the onset of magnetar-like behavior on 2006 May 31. We show that the pulsar experienced an unusually large glitch recovery, with a recovery fraction of Q=8.7+/- 2.5, resulting in a net decrease of the pulse frequency. Such a glitch recovery has never before been observed in a rotation-powered pulsar, however, similar but smaller glitch over-recovery has been recently reported in the magnetar AXP 4U~0142+61 and may have occurred in the SGR 1900+14. We also report a large increase in the timing noise of the source. We discuss the implications of the unusual timing behavior in PSR J1846-0258 on its status as the first identified magnetically active rotation-powered pulsar.

Journal ArticleDOI
TL;DR: In this article, it was shown that the initial progenitor star mass of the magnetar was a factor of two lower than this limit, M_prog=17 \pm 2 Msun.
Abstract: Magnetars are young neutron stars with extreme magnetic fields (B > 10^{14}-10^{15}G). How these fields relate to the properties of their progenitor stars is not yet clearly established. However, from the few objects associated with young clusters it has been possible to estimate the initial masses of the progenitors, with results indicating that a very massive progenitor star (M_prog >40Msun) is required to produce a magnetar. Here we present adaptive-optics assisted Keck/NIRC2 imaging and Keck/NIRSPEC spectroscopy of the cluster associated with the magnetar SGR 1900+14, and report that the initial progenitor star mass of the magnetar was a factor of two lower than this limit, M_prog=17 \pm 2 Msun. Our result presents a strong challenge to the concept that magnetars can only result from very massive progenitors. Instead, we favour a mechanism which is dependent on more than just initial stellar mass for the production of these extreme magnetic fields, such as the "fossil-field" model or a process involving close binary evolution.

Journal ArticleDOI
TL;DR: In this article, a 3D Monte Carlo code for solving radiation transport as soft, thermal photons emitted by the star surface are resonantly upscattered by the magnetospheric particles is presented.
Abstract: Within the magnetar scenario, the ‘twisted magnetosphere’ model appears very promising in explaining the persistent X-ray emission from soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs). In the first two papers of the series, we have presented a 3D Monte Carlo code for solving radiation transport as soft, thermal photons emitted by the star surface are resonantly upscattered by the magnetospheric particles. A spectral model archive has been generated and implemented in xspec. Here, we report on the systematic application of our spectral model to different XMM-Newton and INTEGRAL observations of SGRs and AXPs. We find that the synthetic spectra provide a very good fit to the data for the nearly all the source (and source states) we have analysed.

Journal ArticleDOI
TL;DR: In this paper, a rotating magnetar radiating according to the classic dipole formula could power a very luminous supernova and the peak luminosity would be most sensitive to the dipole field strength of the magnetar.
Abstract: Following an initial explosion that might be launched either by magnetic interactions or neutrinos, a rotating magnetar radiating according to the classic dipole formula could power a very luminous supernova. While some 56Ni might be produced in the initial explosion, the peak of the light curve in a Type I supernova would not be directly related to its mass. In fact, the peak luminosity would be most sensitive to the dipole field strength of the magnetar. The tail of the light curve could resemble radioactive decay for some time but, assuming complete trapping of the pulsar emission, would eventually be brighter. Depending on the initial explosion energy, both high and moderate velocities could accompany a very luminous light curve.

Journal ArticleDOI
TL;DR: In this article, the authors used the Lovell, 94m equivalent Westerbork Synthesis Radio Telescope (WSRT) and 100m Effelsberg radio telescopes to investigate the simultaneous single-pulse properties of the radio emitting magnetar XTE J1810-197 at frequencies of 1.4, 4.8 and 8.35 GHz during 2006 May and July.
Abstract: We have used the 76-m Lovell, 94-m equivalent Westerbork Synthesis Radio Telescope (WSRT) and 100-m Effelsberg radio telescopes to investigate the simultaneous single-pulse properties of the radio emitting magnetar Anomalous X-ray Pulsar (AXP) XTE J1810-197 at frequencies of 1.4, 4.8 and 8.35 GHz during 2006 May and July. We study the magnetar's pulse-energy distributions which are found to be very peculiar as they are changing on time-scales of days and cannot be fit by a single statistical model. The magnetar exhibits strong spiky single giant-pulse-like subpulses, but they do not fit the definition of the giant pulse or giant micropulse phenomena. Measurements of the longitude-resolved modulation index reveal a high degree of intensity fluctuations on day-to-day time-scales and dramatic changes across pulse phase. We find the frequency evolution of the modulation index values differs significantly from what is observed in normal radio pulsars. We find that no regular drifting subpulse phenomenon is present at any of the observed frequencies at any observing epoch. However, we find a quasi-periodicity of the subpulses present in the majority of the observing sessions. A correlation analysis indicates a relationship between components from different frequencies. We discuss the results of our analysis in light of the emission properties of normal radio pulsars and a recently proposed model which takes radio emission from magnetars into consideration.

Journal ArticleDOI
TL;DR: In this article, the authors reported the discovery of a 4.5μm counterpart to the anomalous X-ray pulsar (magnetar) 1E 2259+586 with the Spitzer Space Telescope.
Abstract: We report the discovery of a 4.5μm counterpart to the anomalous X-ray pulsar (magnetar) 1E 2259+586 with the Spitzer Space Telescope. The mid-infrared flux density is 6.3 ± 1.0μJy at 4.5μm and <20 μJy (at 95% confidence) at 8μm, or 0.02% of the 2–10 keV X-ray flux (corrected for extinction). Combining our Spitzer measurements with previously published near-infrared data, we show that the overall infrared emission from 1E 2259+586 is qualitatively similar to that from the magnetar 4U 0142+61. Therefore, the passive X-ray-heated dust disk model originally developed for 4U 0142+61 might also apply to 1E 2259+586. However, the IR data from this source can also be fitted by a simple power-law spectrum as might be expected from magnetospheric emission.

Journal ArticleDOI
TL;DR: In this article, the temporal and spectral characteristics of PSR J1846−0258 over a broad ∼3-300 keV energy range were studied to derive constraints on theoretical scenarios aiming to explain this schizophrenic behaviour.
Abstract: Aims. PSR J1846−0258 is a young rotation-powered pulsar with one of the highest surface magnetic field strengths, located in the centre of SN-remnant Kes-75. In June 2006 a magnetar-like outburst took place. Using multi-year RXTE and INTEGRAL observations covering the epoch of the outburst, we aim to study the temporal and spectral characteristics of PSR J1846−0258 over a broad ∼3–300 keV energy range to derive constraints on theoretical scenarios aiming to explain this schizophrenic behaviour. Methods. We explored all publically available RXTE observations of PSR J1846−0258 to generate accurate ephemerides over the period January 30, 2000–November 7, 2007. Phase-folding procedures yielded pulse profiles for RXTE PCA (∼3–30 keV), RXTE HEXTE (∼15–250 keV) and INTEGRAL ISGRI (∼20–300 keV). The pulsed spectrum over the full ∼3–300 keV energy range was derived, as well as the total spectrum (including the pulsar wind nebula) over the 20–300 keV band with the ISGRI. The timing, spatial, and spectral analyses were applied for epochs before, during, and after the magnetar-like outburst to study the evolution of the high-energy characteristics. Results. ISGRI detected PSR J1846−0258/Kes-75 before outburst during 2003–2006 with a power-law-shape spectrum over the 20– 300 keV energy range with photon index Γ= 1.80 ± 0.06 and energy flux (20–300 keV) of (6.62 ± 0.35) × 10 −11 erg/cm 2 s. More than 90 days after the onset of the outburst, still during the decay phase, the same spectral shape was measured ( Γ= 1.75 +0.27 −0.31 ) with an indication for a 52% (2.3σ) enhanced total emission, while one year after the outburst the hard X-ray non-thermal emission of PSR J1846−0258/Kes-75 was found to be back to its pre-outburst values. PCA monitoring of PSR J1846−0258 before the outburst yielded phase-coherent ephemerides confirming the earlier derived breaking index of the spindown. During the outburst, incoherent solutions have been derived. We show that the radiative outburst was triggered by a major spin-up glitch near MJD 53 883 ± 3 with a glitch size Δν/ν in the range (2.0−4.4) × 10 −6 . Using all pre-outburst observations of ISGRI and HEXTE for the first time pulse profiles have been obtained up to 150 keV with a broad single asymmetric pulse. The pulse shape did not vary with energy over the 2.9–150 keV energy range, nor did it change during the magnetar-like outburst. The time-averaged pre-outburst ∼3–300 keV pulsed spectrum measured with the PCA, HEXTE, and ISGRI was fitted with a power-law model with Γ= 1.20 ± 0.01. A fit with a curved power-law model gives an improved fit. Around 150 keV the pulsed fraction approaches 100%. For the first 32 days of the magnetarlike outburst, the 3–30 keV pulsed spectrum can be represented with two power laws, a soft component with index Γs = 2.96 ± 0.06 and a hard component with the pre-outburst value Γh ∼ 1.2. Above ∼9 keV, all spectra during outburst are consistent with the latter single power-law shape with index ∼1.2. The 2–10 keV flux increased by a factor ∼5 and the 10–30 keV flux increased with only 35%. After ∼120 days the soft outburst and the enhancement of the hard non-thermal component both vanish. Conclusions. The varying temporal and spectral characteristics of PSR J1846−0258 can be explained in a scenario of a young high-Bfield pulsar in which a major glitch triggered a sudden release of energy. Resonant cyclotron upscattering could subsequently generate the decaying/cooling soft pulsed component measured during outburst between 3 and 10 keV. The (variation in the) non-thermal hard X-ray component can be explained with synchrotron emission in a slot-gap or outer-gap pulsar model.

Journal ArticleDOI
TL;DR: In this article, a 3D Monte Carlo code for solving radiation transport as soft, thermal photons emitted by the star surface are resonantly upscattered by the magnetospheric particles is presented.
Abstract: Within the magnetar scenario, the "twisted magnetosphere" model appears very promising in explaining the persistent X-ray emission from the Soft Gamma Repeaters and the Anomalous X-ray Pulsars (SGRs and AXPs). In the first two papers of the series, we have presented a 3D Monte Carlo code for solving radiation transport as soft, thermal photons emitted by the star surface are resonantly upscattered by the magnetospheric particles. A spectral model archive has been generated and implemented in XSPEC. Here we report on the systematic application of our spectral model to different XMM-Newton and Integral observations of SGRs and AXPs. We find that the synthetic spectra provide a very good fit to the data for the nearly all the source (and source states) we have analyzed.