The 2002 outburst of the accretionpowered millisecond pulsar SAX J1808.43658. Askar Ibragimov and prof. Juri Poutanen. University of Oulu, Finland ...

The time variability of the x ray binary pulsars is discussed. It is found that the observed power spectral density of the aperiodic time variability of the x ray pulsar can be approximated by a power law spectrum which changes its slope at the coherent p...

This paper discusses a search for the centrifugal barrier in transient X-ray pulsars with RXTE. The RXTE observation associated with this research involved monitoring the X-ray intensities and pulse profiles of six transient x-ray pulsars on five different occasions. The goal was to determine whether the so-called "centrifugal barrier" effects exists for ...

Over 5 years of daily hard X-ray (>20 keV) monitoring of the 2 minute accretion-powered pulsar GX

Accreting high magnetic field neutron stars are observed as X-ray pulsars. ... An examination of a power spectrum of the pulsed emission shows that the peak ...

Accreting high magnetic field neutron stars are observed as X-ray pulsars. ... An examination of a power spectrum of the pulsed emission shows that the peak ...

XTE(ASM) and BATSE links to Accreting Pulsars. Last Updated: December 6, 2002 ... Undetermined Companion, Anomalous X-ray Pulsars (non-accretion objects) ...

A unified description of the properties of 14 X-ray pulsars is presented and compared with the current theoretical understanding of these systems. The sample extends over six orders of magnitude in luminosity, with the only trend in the phase averaged spe...

We investigate further a model of the accreting millisecond X-ray pulsars we proposed earlier. In this model, the X-ray-emitting regions of these pulsars are near their spin axes but move. This is to be expected if the magnetic poles of these stars are close to their spin axes, so that accreting gas is channeled ...

ries containing weakly magnetized neutron stars, and to recently suggested models of accretion-powered emission from anomalous X-ray pulsars. ...

The present conference considers topics in the fields of rotation-powered pulsars, the relationship of pulsars to SNRs, accretion-powered pulsars, neutron-star formation in theoretical SNs, neutrol stellar evolution, neutron star physics, and other manifestations of neutron stars and their ...

accreting pulsar systems. These have given new insights into the processes by ... Observations of transient pulsars with BATSE and OSSE have provided ...

A Sequence of Outbursts from the Transient X�Ray Pulsar GS 0834--430 Colleen A. Wilson, Mark H accretion�powered pulsar, has been observed in seven outbursts with the BATSE large area detectors on the Compton Gamma Ray Observatory. The first 5 outbursts observed by BATSE occurred at intervals of about 107

RXTE observations have shown that weak-field neutron stars in low-mass X-ray binary systems (LMXBs) produce three distinct types of millisecond X-ray oscillations. These are generated directly or indirectly by the star's magnetic field and rotation and can therefore be used to determine the spin rates and estimate the magnetic fields of these stars. Periodic accretion-powered ...

The formation of millisecond pulsars is addressed. Evolutionary scenarios involving the spinning up of pulsars by accretion disks are discussed, and the implications of the P(dot)-P diagram for a large sample of radio pulsars are examined. 13 references.

During the period 15 April 1997 through 15 April 2000 we have been supported in part by NASA grant NAG5-4115 to pursue a 'Search for the Centrifugal Barrier in Transient X-ray Pulsars' with the Rossi X-Ray Timing Explorer (RXTE). The RXTE observations associated with this research involved monitoring the X-ray intensities and pulse profiles of six transient X-ray ...

In the absence of accretion torques, a pulsar in a binary system will spin down due to electromagnetic dipole radiation and the spin-down power will drive a wind of relativistic electron-positron pairs. Winds from pulsars with short periods will prevent any subsequent accretion but may be ...

In the absence of accretion torques, a pulsar in a binary system will spin down due to electromagnetic dipole radiation, and the spin-down power will drive a wind of relativistic electron-position pairs. Winds from pulsars with short periods will prevent any subsequent accretion but may be ...

We report here a study of the long term properties of Quasi Periodic Oscillations (QPO) in an unusual accreting X-ray pulsar, 4U 1626-67. This is a unique accretion powered X-ray pulsar in which we have found the QPOs to be present during all sufficiently long X-ray observations with a wide ...

We report here a study of the long-term properties of quasiperiodic oscillations (QPOs) in an unusual accreting X-ray pulsar, 4U 1626-67. This is a unique accretion-powered X-ray pulsar in which we have found the QPOs to be present during all sufficiently long X-ray observations with a wide range of X-ray ...

drift is apparent in the Short High pulses showing that a re ned period can be ... Figure 5 shows a sequence of Uhuru pulses from 3] from a single Main High ...

We report the discovery of burst oscillations from the intermittent accretion-powered millisecond pulsar (AMP) HETE J1900.1-2455, with a frequency ~1 Hz below the known spin frequency. The burst oscillation properties are far more similar to those of the non-AMPs and Aql X-1 (an intermittent AMP with a far lower duty cycle), than those of the AMPs SAX ...

Jul 2, 2003 ... Caption for Animation 1: ACCRETION SPINS PULSAR TO MILLISECOND RANGE. If a pulsar -- a dense star with strong gravitational attraction -- is ...

Neutron Stars, Pulsars, Millisecond Pulsars, and Gravitational Radiation: GLOSSARY. Accretion disk: The flattened, pancake-like structure formed by matter ...

X-ray timing of the accretion-powered pulsations during the 2003 outburst of the accreting millisecond pulsar XTE J1814-338 has revealed variation in the pulse time of arrival residuals. These can be interpreted in several ways, including spin-down and wandering of the fuel impact point around the magnetic pole. In this Letter we show ...

Therefore it is commonly referred to as "the Bursting Pulsar". The X-rays observed by RXTE come from accretion onto a pulsar with a spin period of 0.467 s ...

The heating associated with the deposition of ?-rays in an accretion disk is proposed as a mechanism to facilitate the transformation of a low-mass X-ray binary to the radio millisecond pulsar (MSP) phase. The ?-ray emission produced in the outer gap accelerator in the pulsar magnetosphere likely irradiates the surrounding disk, ...

The BATSE all-sky monitor on the Compton Gamma Ray Observatory is a superb tool for the study of accretion-powered pulsars. In the #rst part of this thesis, I describe its capabilities for hard X-ray observations above20keV, present techniques for timing analysis of the BATSE data, and discuss general statistical issues for the detection of pulsed periodic ...

GS 0834-430, a 12.3 s accretion-powered pulsar, has been observed in seven outbursts with the BATSE large-area detectors on the Compton Gamma Ray Observatory. The first five outbursts observed by BATSE occurred at intervals of about 107 days, while the fi...

Pulsar astrophysics has come a long way in the 40 years since the discovery of the first pulsar by Bell and Hewish. From humble beginnings as bits of 'scruff' on the Cambridge University group's chart recorder paper, the field of pulsars has blossomed into a major area of mainstream astrophysics, with an unparalleled diversity of ...

We present a theoretical model for the thermal X-ray emission properties and cooling behaviors of isolated pulsars, assuming that pulsars are solid quark stars. We calculate the heat capacity for such a quark star, including the component of the crystalline lattice and that of the extremely relativistic electron gas. The results show that the residual ...

Rotation-powered radio pulsars are born with inferred initial rotation periods of order 300 ms (some as short as 20 ms) in core-collapse supernovae. In the traditional picture, this fast rotation is the result of conservation of angular momentum during the collapse of a rotating stellar core. This leads to the inevitable conclusion that ...

Nuclear-powered oscillations during Type-I X-ray bursts have so far revealed the spin of about twenty accreting millisecond pulsars in low-mass X-ray binaries. We study the properties of such burst oscillations by means of numerical computations of hot spots on the neutron star surface. We use adaptive mesh refinement hydrodynamical ...

This thesis consists of two parts. In the first hart, we present the development of instruments for high-speed infrared and optical photometry optimized for pulsar observations. In the second part, we present observational studies of pulsars, mainly on accretion- powered pulsars but also on ...

The energy source of the anomalous X-ray pulsars (AXPs) is not understood, hence their designation as anomalous. Unlike binary X-ray pulsars, no companions are seen, so the energy cannot be supplied by accretion of matter from a companion star. The loss of rotational energy, which powers radio ...

In binary systems containing an X-ray pulsar, the X-ray flux shows aperiodic noise components in addition to the neutron star rotation signal. In the power spectra of their light curves, the noise variability appears in the form of continuum components underlying the discrete peaks arising from the coherent periodic signals. The study of these continuum ...

The nature of pulsars that exhibit quasi-periodic oscillations (QPOs) is discussed. It is shown how QPOs are produced by an interaction between the accretion disk surrounding a neutron star with the neutron star's magnetic field. The possible relationship between pulsars that exhibit QPOs and millisecond ...

An optical, intensified CCD observation of the field of the 3.49 s X-ray pulsar lE 2259+586 is discussed. Two stars with B = 22.0 and B = 21.3 are found to lie 4.''9 and 6.''3 away from the nominal X-ray position determined by the High Resolution Imager (HRI) camera of the Einstein Observatory. The fainter star is identified as the optical ...

The spectrum of the X-ray binary pulsars is usually described by a power-law model, but several sources exhibit a significant excess at low energies. This feature has been described with different models (both thermal and non-thermal), and various physical processes have been invoked to produce it. The study of this feature is essential in order to cast ...

The population of radio pulsars in the Galactic globular cluster system has nearly quadrupled in the last five years largely due to advances in observing equipment and increased computational power There are currently 130 sources known many of which can be used to study the physics of neutron stars globular clusters binary systems ...

We will describe a Thomson X-ray polarimeter developed for a small satellite mission. The instrument works in the 5-30 keV band and will be suitable for X-ray polarisation measurement in about 50 hard X-ray sources. The accretion powered X-ray pulsars, black hole X-ray binaries, rotation powered ...

The illumination of companion stars in very low mass X-ray binaries by various kinds of radiation from the neighborhood of the neutron star after accretion has terminated or during accretion is considered. If a neutron star's spun-up period approaches 0.001 s, pulsar kHz radiation can quench accretion by ...

Millisecond pulsars are neutron stars that are thought to have been spun-up by mass accretion from a stellar companion. It is not known whether there is a natural brake for this process, or if it continues until the centrifugal breakup limit is reached at submillisecond periods. Many neutron stars that are accreting mass from a ...

Spin-Powered Pulsars: A Census. Data from ATNF Pulsar Catalogue, .... 2010). � For high Edot pulsars, it is probable that the radio ...

LS I +61 303 is a puzzling Be/X-ray binary with variable gamma-ray emission at up TeV energies. The nature of the compact object and the origin of the high-energy emission are unclear. One family of models invokes particle acceleration in shocks from the collision between the B-star wind and a relativistic pulsar wind, while another centers on a relativistic jet ...

Isolated (solitary or non-accreting) millisecond pulsars with observed X-ray emission can be divided

... Hamilton 2001; Hansen 2002), but all generally rely on an accretion disk around the pulsar within which the planets form. Millisecond pulsars are a ...

The Cygnus X-3 source might represent a long-period accreting pulsar, a companion to a red supergiant in a binary system with an orbital period of several years.

We review recent results from the X-ray timing of accreting millisecond pulsars in LMXBs. This is the first time a timing analysis is performed on accreting millisecond pulsars, and for the first time we can obtain information on the behavior of a very fast pulsar subject to ...

Accretion-powered millisecond pulsars (AMPs) are very interesting astrophysical objects. Mat-ter from accretion disk is captured by star's magnetic field and falls along the field lines, creating "hotspots" near magnetic poles of the star. Typical spectrum of an AMP contains a disk emis-sion, blackbody emission of a hotspot and a ...

The formation of 'photon bubbles' in a convectively stable scattering atmosphere supported against gravity entirely by radiation pressure is studied by means of linear stability theory. A simple model is developed for the 2D structure of a plasma mound formed by laminar accretion onto the magnetic poles of a neutron star, in which upward photon diffusion ...

been considered a critical test of accretion torque theory (x 3). We have observed _ and 20{50keV pulsed. ux, F pulsed , in outbursts of two transients, ...

Anomalous X-ray pulsars (AXPs) are a class of rare X-ray emitting pulsars whose energy source has been perplexing for some 20 years. Unlike other X-ray emitting pulsars, AXPs cannot be powered by rotational energy or by accretion of matter from a binary companion star, hence the designation ...

Nuclear-powered oscillations during Type-I X-ray bursts have so far revealed the spin of about twenty accreting millisecond pulsars in low-mass X-ray binaries. Constraining strong gravity through the emission from the hot spots on the neutron star surface requires understanding of the properties of such burst oscillations. We use ...

Several neutron stars associated with the accretion-powered long-period X-ray pulsars are observed to experience rapid spin-down years-long trends. Modeling of these trends in terms of the canonical spin-down scenario for accretionpowered compact stars in close binaries suggests that the surface field of these neutron stars is supercritical. This ...

The accreting pulsar GX 301-2 (P = 680 s) has been observed continuously by the large-area detectors

We report on a Chandra/ACIS-S observation of the eclipsing accretion-powered millisecond pulsar SWIFT J1749.4-2807, which has recently been reported in a fading outburst during 2010 April 11-21 (ATels #2548, #2561, #2565, #2569, #2576, #2579). Our 1080 s observation was made on April 25 (12:25 TT). Using the pulsar orbital parameters ...

May 31, 1996 ... The Pulsar Powered Crab Credit: J. Hester and P. Scowen (ASU), ... The core of the star collapsed to form a rotating neutron star or pulsar, ...

Pulsar spindown forms a reliable yet enigmatic prototype for the energy loss processes in many astrophysical objects including accretion disks and back holes. In this paper we review the physics of pulsar magnetospheres, concentrating on recent developmen...

We have shown previously that many of the properties of persistent accretion-powered millisecond pulsars can be understood if their X-ray emitting areas are near their spin axes and move as the accretion rate and structure of the inner disk vary. Here, we show that this 'nearly aligned moving spot model' may also ...

4U 2206+54 is a high-mass X-ray binary which has been suspected to contain a neutron star accreting from the wind of its companion, BD +53{sup 0} 2790. Reig et al. have recently detected 5560 s period pulsations in both Rossi X-ray Timing Explorer (RXTE) and International Gamma-ray Astrophysics Laboratory observations which they conclude are due to the spin of the neutron ...

The key contribution of the discovery of nuclear-powered pulsations from the accretion-powered millisecond pulsars (AMPs) has been the establishment of burst oscillation frequency as a reliable proxy for stellar spin rate. This has doubled the sample of rapidly-rotating accreting neutron stars and revealed the ...

The Rossi X-ray Timing Explorer has observed a wide range of sources and is producing valuable science. Its broad-band sensitivity has been key in the observations of both compact, stellar, and nebular objects. RXTE is ideally suited for observing X-rays from both galactic and extragalactic black holes. The range of accretion rates, masses, and possibly angular momenta of ...

We observed PSR B1259-63, a young non-accreting pulsar orbiting around a Be star SS 2883, eight times with the Suzaku satellite from July to September 2007, to characterize the X-ray emission arising from the interaction between a pulsar relativistic wind and Be star outflows. The X-ray spectra showed a featureless continuum in 0.6-10 ...

We present Suzaku and XMM observations of the high-mass X-ray pulsar LMC X-4 at different phases in its superorbital cycle, which is due to the precession of a warped accretion disk. The superorbital period and phase for each observation is determined accurately using RXTE ASM data. At all superorbital phases, the broadband X-ray spectra are described by a ...

We study the physical processes in the system containing the 47 ms radio pulsar PSR B1259{minus}63 orbiting around a Be star in a highly eccentric orbit. This system is the only known binary where a radio pulsar is observed to interact with gaseous material from a Be star. A rapidly rotating radio pulsar such as PSR B1259{minus}63 is ...

We present X-ray observations of the transient accretion-powered millisecond pulsar IGR J00291+5934 during quiescence. IGR J00291+5934 is the first source among accretion-powered millisecond pulsars to show signs of a thermal component in its quiescent spectrum. Fitting this component with a neutron star atmosphere ...

This presentation describes the behavior of matter in environments with extreme magnetic and gravitational fields, explains the instability/stability of accretion disks in certain systems, and discusses how emergent radiation affects accretion flow. Magne...

Gamma-ray loud X-ray binaries are binary systems that show non-thermal broadband emission from radio to gamma rays. If the system comprises a massive star and a young non-accreting pulsar, their winds will collide producing broadband non-thermal emission, most likely originated in the shocked pulsar wind. Thermal X-ray emission is ...

We review recent results from the X-ray timing of accreting millisecond pulsars in LMXBs. This is the first time a timing analysis is performed on accreting millisecond pulsars, and for the first time we can obtain information on the behavior of a very fast pulsar subject to ...

We review recent results from the X-ray timing of accreting millisecond pulsars in LMXBs. This is the first time a timing analysis is performed on accreting millisecond pulsars, and for the first time we can obtain information on the behavior of a very fast pulsar subject to ...

Population of Rotation-powered Pulsars and Magnetars ... Normal and millisecond pulsars. - Review Emission Models, Comparison with. Observations ...

We define and study a simple dynamical model for accretion systems, the "dripping handrail" (DHR). The time evolution of this spatially extended system is a mixture of periodic and apparently random (but actually deterministic) behavior. The nature of this mixture depends on the values of its physical parameters the accretion rate, diffusion coefficient, ...

Observations of millisecond pulsars are discussed, taking into account a review of millisecond pulsars, arrival time observations of the 1.6 millisecond pulsar 1937 + 214, a 6.1 millisecond binary pulsar, polarimetry of the two fastest pulsars, an optical synchrotron nebula around the X-ray ...

Pulsar spindown forms a reliable yet enigmatic prototype for the energy loss processes in many astrophysical objects including accretion disks and back holes. In this paper we review the physics of pulsar magnetospheres, concentrating on recent developments in force-free modeling of the magnetospheric structure. In particular, we ...

Thanks to its high throughput and good spatial, timing and spectral resolution, the XMM-Newton X-ray space telescope is well suited to perform detailed studies also of faint X-ray sources. Here we report the results we obtained on the persistent Be binaries, a sub-class of the accreting X-ray binary pulsars which are characterized by non-transient ...

It is now ten years ago that the first accreting millisecond X-ray pulsar (AMP) was discovered in the low-mass X-ray binary SAX J1808.4-3658. This RXTE discovery confirmed long-standing predictions that low magnetic field neutron stars can be spun up to high spin frequencies by accretion in X-ray binaries. AMPs have since been ...

This thesis presents quantitative models of the magnetosphere of a magnetic star surrounded by a thin plasma disk. The model is motivated by the currently accepted picture of many accretion-powered pulsars as strongly magnetic neutron stars accreting from disks. It may also be relevant to the luminous galactic bulge X-ray sources that ...

The twelfth accretion-powered millisecond pulsar, IGR J17511-3057, was discovered in 2009 September. In this work we study its spectral and timing properties during the 2009 outburst based on Swift and RXTE data. Our spectral analysis of the source indicates only slight spectral shape evolution during the entire outburst. The equivalent width of the iron ...

The spectra of many X-ray pulsars show a low-energy component in addition to the main power-law, which can be described with different models (both thermal and non-thermal). The study of this feature is essential in order to cast light on the physical processes on-going in accreting sources. Due to the low absorption in its direction, ...

Millisecond pulsars are believed to descend from low-mass X-ray binaries. Observable parameters of binary millisecond pulsars, e.g. mass of the pulsar, mass of the companion, spin period of the pulsar, orbital period, orbital eccentricity, etc., are used to probe the past accretion history of ...

Pulsars inside binary systems can accrete matter that arrives up to the pulsar surface provided that its period is long enough. During the accretion process, matter has to be accelerated to the rotational velocity of the pulsar magnetosphere at the distance where the balance between the ...

I review the basic observational properties of accreting millisecond pulsars that are important for understanding the physics involved in formation of their pulse profiles. I then discuss main effects responsible for shaping these profiles. Some analytical results that help to understand the results of simulations are presented. Constraints on the ...

The problem of spectral formation in accretion-powered X-ray pulsars was solved for the first time using an analytical model in 2007. Based on fundamental physics, the resulting model spectra were shown to agree closely with those observed from several of the most luminous X-ray pulsars. However, to derive the analytical solutions, ...

The discovery of a new transient X-ray pulsar, EXO 2030+375, that is associated with a Be star companion, is reported. The results of a series of EXOSAT observations, where the evolution of the pulsar's properties over two orders of magnitude in luminosity was monitored. The dependence of the change in pulsar period on ...

This grant was in support of a guest observation using the ASCA satellite of the young, spin-powered pulsar PSR B 1706-44. The pulsar is interesting for several reasons: (1) it is young and shares many similar characteristics with te Vela pulsar, (2) it i...

The pulsar jet is significant in explaining how the Vela pulsar's rotational energy is transported outward to the rest of the SNR, since direct radiation from the pulsar only accounts for a small percentage of the total power. Our previous ROSAT observati...

Millisecond pulsars, both during and after accretion, stand a class apart from the general pulsar population due to the much weaker field strength at their surface. The prevailing view is that accretion of matter on to a neutron star causes a decay of its magnetic field strength, as viewed by an external observer. ...

The only known accretion-powered millisecond X-ray pulsar SAX J1808.4-3658 exhibited an outburst in January and Februay of this year. The exact starting date is unknown because the source was unobservable by RXTE until 2000 Jan. 21, due to its proximity to the sun. The 401 Hz X-ray pulsations were detected in several short observations. The source also ...

Re-analysis of a Swift/XRT ToO observation of IGR J01572-7259 in the Magellanic Bridge (=IGR J015712-7259, c.f. Coe et al., 2008, ATel #1882) has enabled us to establish the first soft X-ray spectrum for this 11.6-s X-ray pulsar and suspected high-mass X-ray binary. Observation-ID 00031313001 was taken on December 20, 2008, for an effective exposure time of 1950 s. The ...

OAO 1657-415 is an accreting pulsar in an eclipsing binary system. We analyzed the INTEGRAL core program observations of this object and obtained the eclipse light curve in the soft gamma-ray band between 15 keV and 40 keV. We note that the gamma rays from the pulsar allow to probe the density profile of the outer layers of the B super ...

Topics covered include young rapidly spinning pulsars; static gaps in outer magnetospheres; dynamic gaps in pulsar outer magnetospheres; pulse structure of energetic radiation sustained by outer gap pair production; outer gap radiation, Crab pulsar; outer gap radiation, the Vela pulsar; radioemission; and high ...

The maximum acceleration of the rotation of an accreting star is found. A comparison with observations of x-ray pulsars shows that they are neutron stars but not white dwarfs. It is found that the experimentally determined rates of deceleration of x-ray pulsars correlate with their luminosities and periods. This indicates that x-ray ...

Astronomers have discovered a unique double-star system that represents a "missing link" stage in what they believe is the birth process of the most rapidly-spinning stars in the Universe -- millisecond pulsars. "We've thought for some time that we knew how these pulsars get 'spun up' to rotate so swiftly, and this system looks like it's showing us the ...

The Rossi X-ray Timing Explorer has observed five outbursts from the transient 2.5 ms accretion-powered pulsar SAX J1808.4-3658 during 1998-2008. We present a pulse timing study of the most recent outburst and compare it with the previous timing solutions. The spin frequency of the source continues to decrease at a rate of (-5.5 {+-} 1.2) x 10{sup -18} Hz ...

A neutron star in a binary system whose other component is a Wolf--Rayet star will undergo distinctive accretion. In such a system an x-ray pulsar could develop only under highly special conditions.

Mar 25, 1998 ... This one of 12 known transient accreting X-ray pulsars with no visible companion . Pulsars - rotating neutron stars - are among the most ...

Oct 25, 2005 ... GOF, RXTE Finds the First Millisecond Pulsar in an Accreting X-ray ... the times at which the signals from the pulsar arrival at the Earth. ...

An analytic model of magnetic torques applied to an accreting neutron star is employed to evaluate the magnetic dipole moments of x-ray pulsars. A new type of close binary system containing a neutron star is suggested.

In contrast with bipolar jets from the magnetic rotating bodies with accretion flows, it is expected for pulsar winds that high energy outflow is in a ring-like shape. It is also suggested that the kinetic energy flux is comparable with the Poynting flux.

By careful measurements of the fluctuations in pulsar pulse periods on time scales of days and longer, researchers determined that these fluctuations are caused by changes in the rotation rate of the stellar crust apparently arising from matter accretion....

Dec 15, 2009 ... detected with the GBM pulsar monitoring technique ..... Accreting Pulsars with GBM Earth Occultation. Vela X-1. GX301-2. A0535+26. A0535+262 ...

Relativistic one and two photon Compton scattering in a strong magnetic field was calculated. X-ray pulsar model calculations are presented for the phase-dependent spectrum, pulse shape, cyclotron line profile, degree and angle of linear polarization for ...

Context. The burst-only source Swift J1749.4-2807 was discovered in a high X-ray-active state, during an INTEGRAL observations of the Galactic bulge on 2010 April 10. Pulsations at 518 Hz were discovered in the RXTE data, confirming previous suggestions of possible associations between burst-only sources and accreting millisecond X-ray pulsars. The ...

The discovery of about 0.2 Hz quasi-periodic oscillations (QPOs) in the 1-15 keV X-ray flux of the transient 42 s pulsar EXO 2030 + 375 is reported. The detection of QPOs in the power spectra of this pulsar was made possible by the application of a newly developed technique to decouple the power spectrum peaks. ...

We report the detection of a recent torque reversal to spin-up in 4U 1626-67. This is an accretion powered X-ray pulsar and shows slow gradual intensity and pulse period variation on a few years of timescale. Recently, a significant increase in the X-ray flux was observed in the long term RXTE-ASM and Swift-BAT light curve (Krimm et ...

The accretion-powered millisecond pulsar IGR J00291+5934 underwent two ~10 day long outbursts during 2008, separated by 30 days in quiescence. Such a short quiescent period between outbursts has never been seen before from a neutron star X-ray transient. X-ray pulsations at the 599 Hz spin frequency are detected throughout both outbursts. For the first ...

Dramatic torque reversals between spin-up and spin-down have been observed in half of the persistent

The discovery of orbitally-modulated, periodic X-ray pulsations from Cen ...... Ariel 5 discovered 103 s pulsations from A 0535+26 in 1975 (Rosenberg et al. ...

Aug 17, 2010... in the universe and test a key prediction of Einstein's relativity theory. ... "Like many accreting binary systems, J1749 undergoes outbursts ...

We review recent results of our group on X-ray timing of accreting millisecond pulsars in LMXBs. The good quality of the RXTE data allow us to obtain information on the behavior of a very fast pulsar subject to accretion torques. We find both spin-up and spin-down behaviors, from which, using available models for ...

After more than 40 years of studies, surprisingly little is known on the emission of accreting pulsars at low-luminosity. It was suggested that already at 10^{35} ergs/s the onset of a centrifugal barrier should inhibit the accretion. On the other hand, pulsations during quiescence were reported for three transient ...

The exchange of angular momentum between accreting matter and the magnetosphere of a neutron star is studied as a possible explanation for the soft X-ray emission of X-ray pulsars. The flux of soft X-radiation from Her X-1 may be related to dissipation of rotational energy of accreting matter into a layer of the disk at the radial ...

The broadened iron lines observed from accreting compact objects are most easily interpreted in terms of reflection onto the accretion disc of the hard X-ray photons emitted by the central source. In this context, such a broadness is due to the relativistic motion of the reflecting plasma, in the deep gravitational well of the compact object, and can thus ...

Very recently the discovery of an intermittent radio pulsar was reported on Science (Kramer et al.2006,astro-ph/0604605). PSR B1931+24 has the surprising peculiarity of being a 813ms radio-pulsar for ~5d and being radio quiet for the following 25-35d, periodically. The pulsar spin slows down 50% faster when the ...

We have phase-connected a sequence of Rossi X-Ray Timing Explorer Proportional Counter Array observations of SGR 1806-20 covering 178 days. We find that a simple secular spin-down model does not adequately fit the data. The period derivative varies gradually during the observations between 8.1x10-11 and 11.7x10-11 s s(-1) (at its highest, approximately 40% larger than the long-term trend), while ...

We report on observations of the unusual neutron-star binary system FIRST J102347.6+003841 carried out using the XMM-Newton satellite. This system consists of a radio millisecond pulsar (PSR J1023+0038) in a 0.198 day orbit with a ~0.2 M sun Roche-lobe-filling companion and appears to have had an accretion disk in 2001. We observe a hard ...

We report on observations of the unusual neutron-star binary system FIRST J102347.6+003841 carried out using the XMM-Newton satellite. This system consists of a radio millisecond pulsar (PSR J1023+0038) in a 0.198 day orbit with a {approx}0.2 M{sub sun} Roche-lobe-filling companion and appears to have had an accretion disk in 2001. We observe a hard ...

Timing noise in the data on accretion-powered millisecond pulsars (AMP) appears as irregular pulse phase jumps on timescales from hours to weeks. A large systematic phase drift is also observed in the first discovered AMP SAX J1808.4 - 3658. To study the origin of these timing features, we use here the data of the well studied 2002 outburst of SAX J1808.4 ...

An eigenfunction expansion method involving hypergeometric functions is used to solve the partial differential equation governing the transport of radiation in an x-ray pulsar accretion column containing a radiative shock. The procedure yields the exact solution for the Green's function, which describes the scattering of monochromatic radiation ...

) #12;IV: Fueling AGN: Hot vs. Cold Gas Accretion #12;Hot vs. Cold Accretion Bondi accretion vs. jet power: accretion flow or jet? � The 3CRR sample of radio galaxies � An accretion-flow mode dichotomy in RL AGN � Fueling AGN: Cold vs. hot gas ...

The influence of the hot spot that very likely forms at the base of the accretion column of X-ray pulsars with X-ray luminosities not much larger than ?1030W onto emitted spectra and angle dependent fluxes is discussed.

It is now more than eleven years since the discovery of the first accreting millisecond X-ray pulsar. Since then, eleven additional systems have been found, two of them during the last year. Here I briefly discuss the most recent developments with respect to these systems.

We investigate the role of the compact object in the production of jets from neutron star X-ray binaries. The goal is to quantify the effect of the neutron star spin, if any, in powering the jet. We compile all the available measures or estimates of the neutron star spin frequency in jet-detected neutron star X-ray binaries. We use as an estimate of the ranking jet ...

... Accession Number : ADP001669. Title : Mechanisms for Ice Bonding in Wet Snow Accretions on Power Lines,. Corporate ...

that this is already greater than one Earth mass, this may mean that isolated millisecond pulsars either have planetary MILLISECOND PULSARS M. COLEMAN MILLER AND DOUGLAS P. HAMILTON Department of Astronomy, University of Maryland the millisecond pulsar PSR 1257]12. We show that recent developments in the study of ...

We present an evolutionary scenario for the spin-up and evolution of binary millisecond pulsars, according to which the companion of the pulsar PSR J1740-5340 , recently discovered as a binary with orbital period of 32.5 hrs in the Globular Cluster NGC 6397, is presently in a phase of `radio--ejection' mass loss from the system.

Over the past decade our understanding of accreting neutron stars has been revolutionized. Observations with NASA's Rossi X-ray Timing Explorer (RXTE) have resulted in the discovery of fast, coherent X-ray intensity oscillations (hereafter, ``burst oscillations'') during thermonuclear X-ray bursts from 13 low mass X-ray binaries (LMXBs). Although many of their detailed ...

The problem of spectral formation in accretion-powered X-ray pulsars was solved for the first time using an analytical model based on the fundamental physics in 2007, and the resulting spectra were shown to agree rather closely with those observed from several of the most luminous sources. However, in order to derive the analytical solutions, simplifying ...

At the center of this image made by NASA's Chandra X-ray Observatory is a very young and powerful pulsar, known as PSR B1509-58, or B1509 for short. ...

A central pulsar presumably powers each filled-center supernova remnant. Thus, the inner nebula of a plerion is particularly interesting, since it is the ...

We present here the high-resolution X-ray spectrum of the accreting binary X-ray pulsar GX 1+4, obtained with the High Energy Transmission Grating (HETG) instrument of the Chandra X-Ray Observatory. This was supplemented by a simultaneous observation with the Proportional Counter Array (PCA) of the Rossi X-Ray Timing Explorer (RXTE). During this ...

Long gamma-ray bursts (GRBs) could be emitted from rapidly spinning black-hole-torus systems, resulting from either hypernovae or black-hole-neutron-star coalescence. We show that a nonaxisymmetric torus may also radiate gravitational radiation, powered by the spin energy of the black hole. The coupling to the spin energy of the black hole operates by equivalence in poloidal ...

Long gamma-ray bursts (GRBs) could be emitted from rapidly spinning black-hole--torus systems, resulting from either hypernovae or black-hole--neutron-star coalescence. We show that a nonaxisymmetric torus may also radiate gravitational radiation, powered by the spin energy of the black hole. The coupling to the spin energy of the black hole operates by equivalence in poloidal ...

We report on possible orbit solutions of the new accretion powered millisecond pulsar IGR J17498-2921 (ATEL #3551, #3555, #3556, #3558, #3559, #3560). We used RXTE PCA observations from 2011-08-13 (Papitto et al., ATEL #3556) and 2011-08-15 at 20:20 for 3.8 ks exposure. The pulsation signal is strongly detected in both observations. ...

A Search for Radio�Quiet Gamma�Ray Pulsars in the EGRET Archive T. Koh 1 , R. C. Lamb 2 , D. J�ray pulsars in the EGRET database is presented. The search technique utilizes sig� nificant computational identified, and these are all young, rotation powered pulsars. Of the 6 pulsars, 5 ...

Anomalous X-ray pulsars (AXPs) are slowly rotating neutron stars with very bright and highly variable X-ray emission that are believed to be powered by ultra-strong magnetic fields of >10(14) G, according to the 'magnetar' model. The radio pulsations that have been observed from more than 1,700 neutron stars with weaker magnetic fields have never been ...

High Energy Astrophysics: Accretion Disks I 1/60 Accretion Disks I References: Accretion Power in Astrophysics, J. Frank, A. King and D. Raine. High Energy Astrophysics, Vol. 2, M.S. Longair, Cambridge Astrophysics: Accretion Disks I 2/60 1 Overview Accretion disks are ...

The violent birth of black holes and neutron stars during core- collapse supernovae and merging events probes the fundamental nature of gravity, neutrinos, high-density equations of state, and beyond-QED-strength magnetic fields. Post-birth these compact objects continue to be of significant interest by powering pulsar wind nebulae, active galactic nuclei, ...

We study accretion-induced collapse of magnetized white dwarfs as an origin of millisecond pulsars. We apply magnetized accretion disk models to the precollapse accreting magnetic white dwarfs and calculate the white dwarf spin evolution. If the pulsar magnetic field results solely from the ...

Recent work suggests that rotating magnetized neutron stars (i.e., pulsar models) trap plasma instead of emitting it. The trapping arises because nonneutral plasma can be stably trapped within such a magnetosphere provided the overall system charge is nonzero. It has been argued that particles from the interstellar medium would discharge this system, thereby presumably ...

Context. In August 2008, the accreting milli-second X-ray pulsar (AMXP), IGR J00291+5934, underwent an outburst lasting ~100 days, the first since its discovery in 2004. Aims: We present data from the 2008 double-peaked outburst of IGR J00291+5934 from Faulkes Telescope North, the Isaac Newton Telescope, the Keck Telescope, PAIRITEL, the Westerbork ...

It has been clear for many years now that the process of accretion on to a compact object is largely dominated by magnetic fields. The magnetic field channels the accretion flow onto strongly magnetized stars such as magnetic white dwarfs (cataclysmic variables), and neutron stars (accreting X-ray pulsars). ...

SAX J1808.4-3658 is a unique source being the first Low Mass X-ray Binary showing coherent pulsations at a spin period comparable to that of millisecond radio pulsars. Here we present an XMM-Newton observation of SAX J1808.4-3658 in quiescence, the first which assessed its quiescent luminosity and spectrum with good signal to noise. XMM-Newton did not reveal other sources in ...

We report on time-resolved optical imaging of the X-ray binary SAX J1808.4-3658 during its quiescent state and 2008 outburst. The binary, containing an accretion-powered millisecond pulsar, has a large sinusoidal-like modulation in its quiescent optical emission. We employ a Markov chain Monte Carlo technique to fit our multi-band light curve data in ...

We present an analysis of archival X-ray observations of the Type IIL supernova SN 1979C. We find that its X-ray luminosity is remarkably constant at (6.5 � 0.1) � 1038 erg s-1 over a period of 12 years between 1995 and 2007. The high and steady luminosity is considered as possible evidence for a stellar-mass (�5-10 M?) black hole accreting material from either a ...

We have photometrically monitored the optical transient associated with the accretion-powered millisecond pulsar IGRJ00291+5934 (ATEL352,353,354,363) during the period of December 11, 2004 - January 13, 2005, with Russian-Turkish 1.5-m optical telescope (RTT150) at Bakirlitepe (Antalya, Turkey). The R-band light curve is shown at ...

The accreting millisecond pulsar SAX J1808.4-3658 may be a transition object between accreting X-ray binaries and millisecond radio pulsars. We have constrained the thermal radiation from its surface through XMM-Newton X-ray observations, providing strong evidence for neutrino cooling processes from the neutron ...

SMC X-1 is a short period (0.71 s) X-ray pulsar accreting from a B0 supergiant companion. It is unusual in that it has exhibited one probable Type II X-ray burst, possibly putting it in a class with GRO J1744-28 (`` The Bursting Pulsar''). It has also shown smooth spinup since its discovery, despite varying in luminosity from 1037 to ...

Context: LS 5039 is one of the few TeV emitting X-ray binaries detected so far. The powering source of its multiwavelength emission can be accretion in a microquasar scenario or wind interaction in a young nonaccreting pulsar scenario. Aims: To present new high-resolution radio images and compare them with the expected behavior in the ...

The Gravity and Extreme Magnetism Small explorer (GEMS) was recently selected for flight in 2014 by NASA and will make the first sensitive search for X-ray polarization across a wide set of source classes including stellar black holes, Seyfert galaxies and quasars, blazars, rotation and accretion-powered pulsars, magnetars, shell supernova remnants and ...

The Gravity and Extreme Magnetism Small explorer (GEMS) was recently selected for flight in 2014 by NASA and will make the first sensitive search for X-ray polarization across a wide set of source classes including stellar black holes, Seyfert galaxies and quasars, blazars, rotation and accretion-powered pulsars, magnetars, shell supernova remnants and ...

The Gravity and Extreme Magnetism Small explorer (GEMS) was recently selected for flight in 2014 by NASA and will make the first sensitive search for X-ray polarization across a wide set of source classes including stellar black holes, Seyfert galaxies and quasars, blazars, rotation and accretion-powered pulsars, magnetars, shell supernova remnants and ...

The youngest known radiopulsar in the rapidly spinning magnetized neutron star which powers the Crab Nebula, the remnant of the historical supernova explosion of 1054 AD. Similar neutron stars are probably born at least every few hundred years, but are less frequent than Galactic supernova explosions. They are initially sources of extreme relativistic electron and/or positron ...

Anomalous x-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs) are believed to be candidates for magnetars, and they are powered by the decay of ultra-strong magnetic fields of > 1014 G. From the modified spin-down relation of pulsars dot P propto P2-n, we find that the Vela pulsar would evolve into the ...

We discuss the problems of formation and evolution of pulsars in close binaries. The first discovered binary pulsar called Hulse-Taylor pulsar, on the name of discoverers. Observations indicate to existence of single recycled pulsars, and disruption of pulsar pairs. by the mechanism of enhanced ...

CONSTRAINTS ON ACCRETION AND MAGNETAR MODELS D. L. KAPLAN,1 S. R. KULKARNI,1 M. H. VAN KERKWIJK,2 R. E strong new constraints on both accretion disk and magnetar models and suggest that the spectral energy, and a magnetar would require a D1015�1016 G �eld. Subject headings : accretion, accretion disks � ...

An initial study of the evolution of a neutron star in a close-binary orbit of high eccentricity discloses a special class of systems that will never achieve a state of pure, steady accretion: the neutron star will continually oscillate between an accreting state and a propeller state. This may be what is happening in the rapid-spin ...