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Sample records for accreting millisecond pulsars

  1. Gravitational Radiation from Accreting Millisecond Pulsars

    CERN Document Server

    Vigelius, Matthias; Melatos, Andrew

    2008-01-01

    It is widely assumed that the observed reduction of the magnetic field of millisecond pulsars can be connected to the accretion phase during which the pulsar is spun up by mass accretion from a companion. A wide variety of reduction mechanisms have been proposed, including the burial of the field by a magnetic mountain, formed when the accreted matter is confined to the poles by the tension of the stellar magnetic field. A magnetic mountain effectively screens the magnetic dipole moment. On the other hand, observational data suggests that accreting neutron stars are sources of gravitational waves, and magnetic mountains are a natural source of a time-dependent quadrupole moment. We show that the emission is sufficiently strong to be detectable by current and next generation long-baseline interferometers. Preliminary results from fully three-dimensional magnetohydrodynamic (MHD) simulations are presented. We find that the initial axisymmetric state relaxes into a nearly axisymmetric configuration via toroidal ...

  2. Electromagnetic Spindown of a Transient Accreting Millisecond Pulsar During Quiescence

    Science.gov (United States)

    Melatos, A.; Mastrano, A.

    2016-02-01

    The measured spindown rates in quiescence of the transient accreting millisecond pulsars IGR J00291+5934, XTE J1751-305, SAX J1808.4-3658, and Swift J1756.9-2508 have been used to estimate the magnetic moments of these objects assuming standard magnetic dipole braking. It is shown that this approach leads to an overestimate if the amount of residual accretion is enough to distort the magnetosphere away from a force-free configuration through magnetospheric mass loading or crushing, so that the lever arm of the braking torque migrates inside the light cylinder. We derive an alternative spindown formula and calculate the residual accretion rates where the formula is applicable. As a demonstration we apply the alternative spindown formula to produce updated magnetic moment estimates for the four objects above. We note that based on current uncertain observations of quiescent accretion rates, magnetospheric mass loading and crushing are neither firmly indicated nor ruled out in these four objects. Because quiescent accretion rates are not measured directly (only upper limits are placed), without more data it is impossible to be confident about whether the thresholds for magnetospheric mass loading or crushing are reached or not.

  3. Durability of the accretion disk of millisecond pulsars

    Energy Technology Data Exchange (ETDEWEB)

    Michel, F.C.; Dessler, A.J.

    1985-05-01

    Pulsars with pulsation periods in the millisecond range are thought to be neutron stars that have acquired an extraordinarily short spin period through the accretion of stellar material spiraling down onto the neutron star from a nearby companion. Nearly all the angular momentum and most of the mass of the companion star is transferred to the neutron star. During this process, wherein the neutron star consumes its companion, it is required that a disk of stellar material be formed around the neutron star. In conventional models it is supposed that the disk is somehow lost when the accretion phase is finished, so that only the rapidly spinning neutron star remains. However, it is possible that, after the accretion phase, a residual disk remains in stable orbit around the neutron star. The end result of such an accretion process is an object that looks much like a miniature (about 100 kilometers), heavy version of Saturn: a central object (the neutron star) surrounded by a durable disk. 10 references.

  4. Durability of the accretion disk of millisecond pulsars.

    Science.gov (United States)

    Michel, F C; Dessler, A J

    1985-05-24

    Pulsars with pulsation periods in the millisecond range are thought to be neutron stars that have acquired an extraordinarily short spin period through the accretion of stellar material spiraling down onto the neutron star from a nearby companion. Nearly all the angular momentum and most of the mass of the companion star is transferred to the neutron star. During this process, wherein the neutron star consumes its companion, it is required that a disk of stellar material be formed around the neutron star. In conventional models it is supposed that the disk is somehow lost when the accretion phase is finished, so that only the rapidly spinning neutron star remains. However, it is possible that, after the accretion phase, a residual disk remains in stable orbit around the neutron star. The end result of such an accretion process is an object that looks much like a miniature (about 100 kilometers), heavy version of Saturn: a central object (the neutron star) surrounded by a durable disk. PMID:17797665

  5. Simulations of the magnetospheres of accreting millisecond pulsars

    CERN Document Server

    Parfrey, Kyle; Beloborodov, Andrei M

    2016-01-01

    Accreting pulsars power relativistic jets, and display a complex spin phenomenology. These behaviours may be closely related to the large-scale configuration of the star's magnetic field. The total torque experienced by the pulsar comprises spin-up and spin-down contributions from different bundles of magnetic field lines; the spin-down `braking' torque is applied both by closed stellar field lines which enter the disc beyond the corotation radius, and those which are open and not loaded with disc material. The rates of energy and angular momentum extraction on these open field lines have lower bounds in the relativistic, magnetically dominated limit, due to the effective inertia of the electromagnetic field itself. Here we present the first relativistic simulations of the interaction of a pulsar magnetosphere with an accretion flow. Our axisymmetric simulations, with the pseudospectral PHAEDRA code, treat the magnetospheric, or coronal, regions using a resistive extension of force-free electrodynamics. The m...

  6. On the connection between accreting X-ray and radio millisecond pulsars

    CERN Document Server

    Tauris, T M

    2012-01-01

    For many years it has been recognized that the terminal stages of mass transfer in a low-mass X-ray binary (LMXB) should cause the magnetosphere of the accreting neutron star to expand, leading to a braking torque acting on the spinning pulsar. After the discovery of radio millisecond pulsars (MSPs) it was therefore somewhat a paradox (e.g. Ruderman et al. 1989) how these pulsars could retain their fast spins following the Roche-lobe decoupling phase, RLDP. Here I present a solution to this so-called "turn-off problem" which was recently found by combining binary stellar evolution models with torque computations (Tauris 2012). The solution is that during the RLDP the spin equilibrium of the pulsar is broken and therefore it remains a fast spinning object. I briefly discuss these findings in view of the two observed spin distributions in the populations of accreting X-ray millisecond pulsars (AXMSPs) and radio MSPs.

  7. Timing and spectral properties of the accreting millisecond pulsar SWIFT J1756.9-2508

    NARCIS (Netherlands)

    M. Linares; R. Wijnands; M. van der Klis; H. Krimm; C.B. Markwardt; D. Chakrabarty

    2008-01-01

    SWIFT J1756.9-2508 is one of the few accreting millisecond pulsars (AMPs) discovered to date. We report here the results of our analysis of its aperiodic X-ray variability, as measured with the Rossi X-Ray Timing Explorer during the 2007 outburst of the source. We detect strong (~35%) flat-topped br

  8. Accretion, Ablation and Propeller Evolution in Close Millisecond Pulsar Binary Systems

    CERN Document Server

    Kiel, P D

    2013-01-01

    A model for the formation and evolution of binary millisecond radio pulsars in systems with low mass companions (< 0.1 Msun) is investigated using a binary population synthesis technique. Taking into account the non conservative evolution of the system due to mass loss from an accretion disk as a result of propeller action and from the companion via ablation by the pulsar, the transition from the accretion powered to rotation powered phase is investigated. It is shown that the operation of the propeller and ablation mechanisms can be responsible for the formation and evolution of black widow millisecond pulsar systems from the low mass X-ray binary phase at an orbital period of ~0.1 day. For a range of population synthesis input parameters, the results reveal that a population of black widow millisecond pulsars characterized by orbital periods as long as ~0.4 days and companion masses as low as ~0.005 Msun can be produced. The orbital periods and minimum companion mass of this radio millisecond pulsar popu...

  9. Swinging between rotation and accretion power in a binary millisecond pulsar

    CERN Document Server

    Papitto, A; Bozzo, E; Rea, N

    2013-01-01

    We present the discovery of IGR J18245-2452, the first millisecond pulsar observed to swing between a rotation-powered, radio pulsar state, and an accretion-powered X-ray pulsar state (Papitto et al. 2013, Nature, 501, 517). This transitional source represents the most convincing proof of the evolutionary link shared by accreting neutron stars in low mass X-ray binaries, and radio millisecond pulsars. It demonstrates that swings between these two states take place on the same time-scales of luminosity variations of X-ray transients, and are therefore most easily interpreted in terms of changes in the rate of mass in-flow. While accreting mass, the X-ray emission of IGR J18245-2452 varies dramatically on time-scales ranging from a second to a few hours. We interpret a state characterised by a lower flux and pulsed fraction, and by sudden increases of the hardness of the X-ray emission, in terms of the onset of a magnetospheric centrifugal inhibition of the accretion flow. Prospects of finding new members of th...

  10. The accreting millisecond X-ray pulsar IGR J00291+5934: evidence for a long timescale spin evolution

    NARCIS (Netherlands)

    A. Patruno

    2010-01-01

    Accreting millisecond X-ray pulsars like IGR J00291+5934 are important because they can be used to test theories of pulsar formation and evolution. They give also the possibility of constraining gravitational wave emission theories and the equation of state of ultra-dense matter. Particularly crucia

  11. An evolutionary channel towards the accreting millisecond pulsar SAX J1808.4-3658

    CERN Document Server

    Chen, Wen-Cong

    2016-01-01

    Recent timing analysis reveals that the orbital period of the first discovered accreting millisecond pulsar SAX J1808.4-3658 is increasing at a rate $\\dot{P}_{\\rm orb}=(3.89\\pm0.15)\\times 10^{-12}~\\rm s\\,s^{-1}$, which is at least one order of magnitude higher than the value arising from the conservative mass transfer. An ejection of mass loss rate of $10^{-9}~\\rm M_{\\odot}{\\rm yr}^{-1}$ from the donor star at the inner Lagrangian point during the quiescence state could interpret the observed orbital period derivative. However, it is unknown whether this source can offer such a high mass loss rate. In this work, we attempt to investigate an evolutionary channel towards SAX J1808.4-3658. Once the accretion disk becomes thermally and viscously unstable, the spin-down luminosity of the millisecond pulsar and the X-ray luminosity during outbursts are assumed to evaporate the donor star, and the resulting winds carry away the specific orbital angular momentum at the inner Lagrangian point. Our scenario could yield...

  12. Electromagnetic spin down of a transient accreting millisecond pulsar during quiescence

    CERN Document Server

    Melatos, Andrew

    2015-01-01

    The measured spin-down rates in quiescence of the transient accreting millisecond pulsars IGR J00291+5934, XTE J1751-305, SAX J1808.4-3658, and Swift J1756.9-2508 have been used to estimate the magnetic moments of these objects assuming standard magnetic dipole braking. It is shown that this approach leads to an overestimate, if the amount of residual accretion is enough to distort the magnetosphere away from a force-free configuration, through magnetospheric mass loading or crushing, so that the lever arm of the braking torque migrates inside the light cylinder. We derive an alternative spin-down formula and calculate the residual accretion rates where the formula is applicable. As a demonstration, we apply the alternative spin-down formula to produce updated magnetic moment estimates for the four objects above. We note that, based on current uncertain observations of quiescent accretion rates, magnetospheric mass loading and crushing are neither firmly indicated nor ruled out in these four objects. Because ...

  13. Direct formation of millisecond pulsars from rotationally delayed accretion-induced collapse of massive white dwarfs

    CERN Document Server

    Freire, Paulo C C

    2013-01-01

    Millisecond pulsars (MSPs) are believed to be old neutron stars, formed via Type Ib/c core-collapse supernovae, which have subsequently been spun up to high rotation rates via accretion from a companion star in a highly circularised low-mass X-ray binary. The recent discoveries of Galactic field binary MSPs in eccentric orbits, and mass functions compatible with that expected for helium white dwarf companions, PSR J2234+06 and PSR J1946+3417, therefore challenge this picture. Here we present a hypothesis for producing this new class of systems, where the MSPs are formed directly from a rotationally-delayed accretion-induced collapse of a super-Chandrasekhar mass white dwarf. We compute the orbital properties of the MSPs formed in such events and demonstrate that our hypothesis can reproduce the observed eccentricities, masses and orbital periods of the white dwarfs, as well as forecasting the pulsar masses and velocities. Finally, we compare this hypothesis to a triple star scenario.

  14. Evidence of Fast Magnetic Field Evolution in an Accreting Millisecond Pulsar

    CERN Document Server

    Patruno, A

    2012-01-01

    The large majority of neutron stars (NSs) in low mass X-ray binaries (LMXBs) have never shown detectable pulsations despite several decades of intense monitoring. The reason for this remains an unsolved problem that hampers our ability to measure the spin frequency of most accreting NSs. The accreting millisecond X-ray pulsar (AMXP) HETE J1900.1--2455 is an intermittent pulsar that exhibited pulsations at about 377 Hz for the first 2 months and then turned in a non-pulsating source. Understanding why this happened might help to understand why most LMXBs do not pulsate. We present a 7 year long coherent timing analysis of data taken with the Rossi X-ray Timing Explorer. We discover new sporadic pulsations that are detected on a baseline of about 2.5 years. We find that the pulse phases anti-correlate with the X-ray flux as previously discovered in other AMXPs. We place stringent upper limits of 0.05% rms on the pulsed fraction when pulsations are not detected and identify an enigmatic pulse phase drift of ~180...

  15. The long-term evolution of the accreting millisecond X-ray pulsar Swift J1756.9-2508

    CERN Document Server

    Patruno, Alessandro; Messenger, Chris

    2009-01-01

    We present a timing analysis of the 2009 outburst of the accreting millisecond X-ray pulsar Swift J1756.9-2508, and a re-analysis of the 2007 outburst. The source shows a short recurrence time of only ~2 years between outbursts. Thanks to the approximately 2 year long baseline of data, we can constrain the magnetic field of the neutron star to be 0.4x10^8 G < B < 9x10^8 G, which is within the range of typical accreting millisecond pulsars. The 2009 timing analysis allows us to put constraints on the accretion torque: the spin frequency derivative within the outburst has an upper limit of $|\\dot{\

  16. Binary and Millisecond Pulsars

    Directory of Open Access Journals (Sweden)

    Lorimer Duncan R.

    2008-11-01

    Full Text Available We review the main properties, demographics and applications of binary and millisecond radio pulsars. Our knowledge of these exciting objects has greatly increased in recent years, mainly due to successful surveys which have brought the known pulsar population to over 1800. There are now 83 binary and millisecond pulsars associated with the disk of our Galaxy, and a further 140 pulsars in 26 of the Galactic globular clusters. Recent highlights include the discovery of the young relativistic binary system PSR J1906+0746, a rejuvination in globular cluster pulsar research including growing numbers of pulsars with masses in excess of 1.5M_⊙, a precise measurement of relativistic spin precession in the double pulsar system and a Galactic millisecond pulsar in an eccentric (e = 0.44 orbit around an unevolved companion.

  17. The binary millisecond pulsar PSR J1023+0038 during its accretion state - I. Optical variability

    CERN Document Server

    Shahbaz, T; Nevado, S P; Rodríguez-Gil, P; Casares, J; Dhillon, V S; Marsh, T R; Littlefair, S; Leckngam, A; Poshyachinda, S

    2015-01-01

    We present time-resolved optical photometry of the binary millisecond `redback' pulsar PSR J1023+0038 (=AY Sex) during its low-mass X-ray binary phase. The light curves taken between 2014 January and April show an underlying sinusoidal modulation due to the irradiated secondary star and accretion disc. We also observe superimposed rapid flaring on time-scales as short as ~20 s with amplitudes of ~0.1-0.5 mag and additional large flare events on time-scales of ~5-60 min with amplitudes ~0.5-1.0 mag. The power density spectrum of the optical flare light curves is dominated by a red-noise component, typical of aperiodic activity in X-ray binaries. Simultaneous X-ray and UV observations by the Swift satellite reveal strong correlations that are consistent with X-ray reprocessing of the UV light, most likely in the outer regions of the accretion disc. On some nights we also observe sharp-edged, rectangular, flat-bottomed dips randomly distributed in orbital phase, with a median duration of ~250 s and a median ingr...

  18. New outburst of the accreting millisecond X-ray pulsar NGC 6440 X-2 and discovery of a strong 1 Hz modulation in the light-curve

    NARCIS (Netherlands)

    Patruno, A.; Yang, Y.; Altamirano, D.; Armas-Padilla, M.; Cavecchi, Y.; Degenaar, N.; Kalamkar, M.; Kaur, R.; Klis, M. Van Der; Watts, A.; Wijnands, R.; Linares, M.; Casella, P.; Rea, N.; Soleri, P.; Markwardt, C.; Strohmayer, T.; Heinke, C.

    2010-01-01

    On June 11th, 2010, RXTE/PCA galactic bulge scan observations showed an increase in activity from the globular cluster NGC 6440. Two accreting millisecond X-ray pulsars (AMXPs) and 22 other X-ray binaries are known

  19. Timing of the accreting millisecond pulsar SAX J1748.9-2021 during its 2015 outburst

    CERN Document Server

    Sanna, A; Riggio, A; Pintore, F; Di Salvo, T; Gambino, A F; Iaria, R; Matranga, M; Scarano, F

    2016-01-01

    We report on the timing analysis of the 2015 outburst of the intermittent accreting millisecond X-ray pulsar SAX J1748.9-2021 observed on March 4 by the X-ray satellite XMM-Newton. By phase-connecting the time of arrivals of the observed pulses, we derived the best-fit orbital solution for the 2015 outburst. We investigated the energy pulse profile dependence finding that the pulse fractional amplitude increases with energy while no significant time lags are detected. Moreover, we investigated the previous outbursts from this source, finding previously undetected pulsations in some intervals during the 2010 outburst of the source. Comparing the updated set of orbital parameters, in particular the value of the time of passage from the ascending node, with the orbital solutions reported from the previous outbursts, we estimated for the first time the orbital period derivative corresponding with $\\dot{P}_{orb}=(1.1\\pm0.3)\\times 10^{-10}$ s/s. We note that this value is significant at 3.5 sigma confidence level, ...

  20. Quasi-periodic X-ray brightness fluctuations in an accreting millisecond pulsar

    CERN Document Server

    Wijnands, R; Homan, J; Chakraborty, D; Markwardt, C B; Morgan, E H; Wijnands, Rudy; Klis, Michiel van der; Homan, Jeroen; Chakrabarty, Deepto; Markwardt, Craig B.; Morgan, Ed H.

    2003-01-01

    The relativistic plasma flows onto neutron stars that are accreting material from stellar companions can be used to probe strong-field gravity as well as the physical conditions in the supranuclear-density interiors of neutron stars. Plasma inhomogeneities orbiting a few kilometres above the stars are observable as X-ray brightness fluctuations on the millisecond dynamical timescale of the flows. Two frequencies in the kilohertz range dominate these fluctuations: the twin kilohertz quasi-periodic oscillations (kHz QPOs). Competing models for the origins of these oscillations (based on orbital motions) all predict that they should be related to the stellar spin frequency, but tests have been difficult because the spins were not unambiguously known. Here we report the detection of kHz QPOs from a pulsar whose spin frequency is known. Our measurements establish a clear link between kHz QPOs and stellar spin, but one not predicted by any current model. A new approach to understanding kHz QPOs is now required. We ...

  1. Timing of the accreting millisecond pulsar SAX J1748.9-2021 during its 2015 outburst

    Science.gov (United States)

    Sanna, A.; Burderi, L.; Riggio, A.; Pintore, F.; Di Salvo, T.; Gambino, A. F.; Iaria, R.; Matranga, M.; Scarano, F.

    2016-06-01

    We report on the timing analysis of the 2015 outburst of the intermittent accreting millisecond X-ray pulsar SAX J1748.9-2021 observed on March 4 by the X-ray satellite XMM-Newton. By phase connecting the time of arrivals of the observed pulses, we derived the best-fitting orbital solution for the 2015 outburst. We investigated the energy pulse profile dependence finding that the pulse fractional amplitude increases with energy while no significant time lags are detected. Moreover, we investigated the previous outbursts from this source, finding previously undetected pulsations in some intervals during the 2010 outburst of the source. Comparing the updated set of orbital parameters, in particular the value of the time of passage from the ascending node, with the orbital solutions reported from the previous outbursts, we estimated for the first time the orbital period derivative corresponding with dot{P}_{orb}=(1.1± 0.3)× 10^{-10} s s-1. We note that this value is significant at 3.5σ confidence level, because of significant fluctuations with respect to the parabolic trend and more observations are needed in order to confirm the finding. Assuming the reliability of the result, we suggest that the large value of the orbital-period derivative can be explained as a result of a highly non-conservative mass transfer driven by emission of gravitational waves, which implies the ejection of matter from a region close to the inner Lagrangian point. We also discuss possible alternative explanations.

  2. The Accreting Millisecond X-ray Pulsar IGR J00291+5934: Evidence for a Long Timescale Spin Evolution

    CERN Document Server

    Patruno, Alessandro

    2010-01-01

    Accreting Millisecond X-ray Pulsars like IGR J00291+5934 are important because it is possible to test theories of pulsar formation and evolution. They give also the possibility to constrain gravitational wave emission theories and the equation of state of ultra dense matter. Particularly crucial to our understanding is the measurement of the long term spin evolution of the accreting neutron star. An open question is whether these accreting pulsars are spinning up during an outburst and spinning down in quiescence as predicted by the recycling scenario. Until now it has been very difficult to measure torques, due to the presence of fluctuations in the pulse phases that compromise their measurements with standard coherent timing techniques. By applying a new method, I am now able to measure a spin up during an outburst and a spin down during quiescence. I ascribe the spin up (Fdot=5.1(3)x10^{-13}\\Hz/s) to accretion torques and the spin down (Fdot=-3.0(8)x10^{-15} Hz/s) to magneto dipole torques, as those observ...

  3. DISCOVERY OF BURST OSCILLATIONS IN THE INTERMITTENT ACCRETION-POWERED MILLISECOND PULSAR HETE J1900.1-2455

    International Nuclear Information System (INIS)

    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 J1808.4-3658 and XTE J1814-338. We discuss the implications for models of the burst oscillation and intermittency mechanisms.

  4. Spin frequency distributions of binary millisecond pulsars

    NARCIS (Netherlands)

    A. Papitto; D.F. Torres; N. Rea; T.M. Tauris

    2014-01-01

    Rotation-powered millisecond radio pulsars have been spun up to their present spin period by a 108−109 yr long X-ray-bright phase of accretion of matter and angular momentum in a low-to-intermediate mass binary system. Recently, the discovery of transitional pulsars that alternate cyclically between

  5. Broad-band spectral analysis of the accreting millisecond X-ray pulsar SAX J1748.9-2021

    Science.gov (United States)

    Pintore, F.; Sanna, A.; Di Salvo, T.; Del Santo, M.; Riggio, A.; D'Aì, A.; Burderi, L.; Scarano, F.; Iaria, R.

    2016-04-01

    We analysed a 115-ks XMM-Newton observation and the stacking of 8 d of INTEGRAL observations, taken during the raise of the 2015 outburst of the accreting millisecond X-ray pulsar SAX J1748.9-2021. The source showed numerous type-I burst episodes during the XMM-Newton observation, and for this reason we studied separately the persistent and burst epochs. We described the persistent emission with a combination of two soft thermal components, a cold thermal Comptonization component (˜2 keV) and an additional hard X-ray emission described by a power law (Γ ˜ 2.3). The continuum components can be associated with an accretion disc, the neutron star (NS) surface and a thermal Comptonization emission coming out of an optically thick plasma region, while the origin of the high-energy tail is still under debate. In addition, a number of broad (σ = 0.1-0.4 keV) emission features likely associated with reflection processes have been observed in the XMM-Newton data. The estimated 1.0-50 keV unabsorbed luminosity of the source is ˜5 × 1037 erg s-1, about 25 per cent of the Eddington limit assuming a 1.4 M⊙ NS. We suggest that the spectral properties of SAX J1748.9-2021 are consistent with a soft state, differently from many other accreting X-ray millisecond pulsars which are usually found in the hard state. Moreover, none of the observed type-I burst reached the Eddington luminosity. Assuming that the burst ignition and emission are produced above the whole NS surface, we estimate an NS radius of ˜7-8 km, consistent with previous results.

  6. The Quiescent X-Ray Properties of the Accreting Millisecond X-Ray Pulsar and Eclipsing binary Swift J1749.4-2807

    NARCIS (Netherlands)

    N. Degenaar; A. Patruno; R. Wijnands

    2012-01-01

    Swift J1749.4-2807 is a transient neutron star low-mass X-ray binary that contains an accreting millisecond X-ray pulsar spinning at 518 Hz. It is the first of its kind that displays X-ray eclipses, which holds significant promise to precisely constrain the mass of the neutron star. We report on a s

  7. The Luminosity and Energy Dependence of Pulse Phase Lags in the Accretion-powered Millisecond Pulsar SAX J1808.4-3658

    CERN Document Server

    Hartman, Jacob M; Chakrabarty, Deepto

    2008-01-01

    Soft phase lags, in which X-ray pulses in lower energy bands arrive later than pulses in higher energy bands, have been observed in nearly all accretion-powered millisecond pulsars, but their origin remains an open question. In a study of the 2.5 ms accretion-powered pulsar SAX J1808.4-3658, we report that the magnitude of these lags is strongly dependent on the accretion rate. During the brightest stage of the outbursts from this source, the lags increase in magnitude as the accretion rate drops; when the outbursts enter their dimmer flaring-tail stage, the relationship reverses. We evaluate this complex dependence in the context of two theoretical models for the lags, one relying on the scattering of photons by the accretion disk and the other invoking a two-component model for the photon emission. In both cases, the turnover suggests that we are observing the source transitioning into the "propeller" accretion regime.

  8. Formation of Binary Millisecond Pulsars by Accretion-Induced Collapse of White Dwarfs under Wind-Driven Evolution

    CERN Document Server

    Ablimit, Iminhaji

    2014-01-01

    Accretion-induced collapse of massive white dwarfs (WDs) has been proposed to be an important channel to form binary millisecond pulsars (MSPs). Recent investigations on thermal timescale mass transfer in WD binaries demonstrate that the resultant MSPs are likely to have relatively wide orbit periods ($\\gtrsim 10$ days). Here we calculate the evolution of WD binaries taking into account the excited wind from the companion star induced by X-ray irradiation of the accreting WD, which may drive rapid mass transfer even when the companion star is less massive than the WD. This scenario can naturally explain the formation of the strong-field neutron star in the low-mass X-ray binary 4U 1822$-$37. After AIC the mass transfer resumes when the companion star refills its Roche lobe, and the neutron star is recycled due to mass accretion. A large fraction of the binaries will evolve to become binary MSPs with a He WD companion, with the orbital periods distributed between $\\gtrsim 0.1$ day and $\\lesssim 30$ days, while...

  9. Broad-band spectral analysis of the accreting millisecond X-ray pulsar SAX J1748.9-2021

    CERN Document Server

    Pintore, Fabio; Di Salvo, Tiziana; Del Santo, Melania; Riggio, Alessandro; D'Aì, Antonino; Burderi, Luciano; Scarano, Fabiana; Iaria, Rosario

    2016-01-01

    We analyzed a 115 ks XMM-Newton observation and the stacking of 8 days of INTEGRAL observations, taken during the raise of the 2015 outburst of the accreting millisecond X-ray pulsar SAX J1748.9-2021. The source showed numerous type-I burst episodes during the XMM-Newton observation, and for this reason we studied separately the persistent and burst epochs. We described the persistent emission with a combination of two soft thermal components, a cold thermal Comptonization component (~2 keV) and an additional hard X-ray emission described by a power-law (photon index ~2.3). The continuum components can be associated with an accretion disc, the neutron star (NS) surface and a thermal Comptonization emission coming out of an optically thick plasma region, while the origin of the high energy tail is still under debate. In addition, a number of broad (~0.1-0.4 keV) emission features likely associated to reflection processes have been observed in the XMM-Newton data. The estimated 1.0-50 keV unabsorbed luminosity ...

  10. Millisecond Pulsars in Close Binaries

    CERN Document Server

    Tauris, Thomas M

    2015-01-01

    In this Habilitationsschrift (Habilitation thesis) I present my research carried out over the last four years at the Argelander Institute for Astronomy (AIfA) and the Max Planck Institute for Radio Astronomy (MPIfR). The thesis summarizes my main findings and has been written to fulfill the requirements for the Habilitation qualification at the University of Bonn. Although my work is mainly focused on the topic of millisecond pulsars (MSPs), there is a fairly broad spread of research areas ranging from the formation of neutron stars (NSs) in various supernova (SN) events, to their evolution, for example, via accretion processes in binary and triple systems, and finally to their possible destruction in merger events. The thesis is organized in the following manner: A general introduction to neutron stars and millisecond pulsars is given in Chapter 1. A selection of key papers published in 2011-2014 are presented in Chapters 2-10, ordered within five main research areas (ultra-stripped SNe in close binaries, ma...

  11. The Mass of a Millisecond Pulsar

    Science.gov (United States)

    Jacoby, B. A.; Hotan, A. W.; Bailes, M.; Ord, S. M.; Kulkarni, S. R.

    2005-12-01

    We report on two years of timing observations of the low-mass binary millisecond pulsar PSR J1909-3744 with the Caltech-Parkes-Swinburne Recorder II (CPSR2), a new instrument that gives unprecedented timing precision. Daily observations give a weighted rms residual of 74 ns. Since their discovery, the masses of the rapidly rotating millisecond pulsars have remained a mystery, with the recycling hypothesis arguing for heavy objects, and the accretion-induced collapse of a white dwarf more consistent with neutron stars less than the Chandrashkar limit. Our data have allowed the measurement of Shapiro delay in this edge-on system, giving the first precise determination of a millisecond pulsar mass, 1.438 ± 0.024 solar masses. The mass of PSR J1909-3744 is at the upper edge of the range observed in mildly recycled pulsars in double neutron star systems, consistent with the the recycling hypothesis. It appears that the production of millisecond pulsars is possible with the accretion of less than 0.2 solar masses.

  12. Orbital Evolution Measurement of the Accreting Millisecond X-ray Pulsar SAX J1808.4–3658

    Indian Academy of Sciences (India)

    Chetana Jain; Anjan Dutta; Biswajit Paul

    2007-12-01

    We present results from a pulse timing analysis of the accretion-powered millisecond X-ray pulsar SAX J1808.4–3658 using X-ray data obtained during four outbursts of this source. Extensive observations were made with the proportional counter array of the Rossi X-ray Timing Explorer (RXTE) during the four outbursts that occurred in 1998, 2000, 2002 and 2005. Instead of measuring the arrival times of individual pulses or the pulse arrival time delay measurement that is commonly used to determine the orbital parameters of binary pulsars, we have determined the orbital ephemeris during each observation by optimizing the pulse detection against a range of trial ephemeris values. The source exhibits a significant pulse shape variability during the outbursts. The technique used by us does not depend on the pulse profile evolution, and is therefore, different from the standard pulse timing analysis. Using 27 measurements of orbital ephemerides during the four outbursts spread over more than 7 years and more than 31,000 binary orbits, we have derived an accurate value of the orbital period of 7249.156862(5) s (MJD = 50915) and detected an orbital period derivative of (3.14 ± 0.21) × 10-12 s s-1. We have included a table of the 27 mid-eclipse time measurements of this source that will be valuable for further studies of the orbital evolution of the source, especially with ASTROSAT. We point out that the measured rate of orbital period evolution is considerably faster than the most commonly discussed mechanisms of orbital period evolution like mass transfer, mass loss from the companion star and gravitational wave radiation. The present time scale of orbital period change, 73 Myr is therefore likely to be a transient high value of period evolution and similar measurements during subsequent outbursts of SAX J1808.4–3658 will help us to resolve this.

  13. Modeling the Energy Dependent Pulse Profiles of the Accreting Millisecond Pulsar SAX J1808.4-3658

    CERN Document Server

    Poutanen, J; Poutanen, Juri; Gierlinski, Marek

    2002-01-01

    The pulse profiles of the accreting X-ray millisecond pulsar SAX J1808.4-3658 at different energies are studied. The two main emission component, a black body and a power-law tail, clearly identified in the time-averaged spectrum, do not vary in phase. We show that the observed variability can be easily explained if the emission patterns of the black body and the Comptonized radiation are different: a "knife" and a "fan"-like, respectively. We suggest that Comptonization in a hot slab (radiative shock) of Thomson optical depth \\~0.3 at the surface of the neutron star may be responsible for the emission. We construct a detailed model of the X-ray production accounting for the Doppler boosting, relativistic aberration and gravitational light bending. The model reproduces well the pulse profiles at different energies simultaneously, corresponding phase lags, as well as the time-averaged spectrum. By fitting the observed pulse profiles we obtain constraints on the neutron star radius (R=7.5+-1.0 km), the inclinat...

  14. On the Nature of the X-ray Emission from the Accreting Millisecond Pulsar SAX J1808.4-3658

    CERN Document Server

    Poutanen, J; Poutanen, Juri; Gierlinski, Marek

    2003-01-01

    The pulse profiles of the accreting X-ray millisecond pulsar SAX J1808.4-3658 at different energies are studied. The two main emission component, the black body and the Comptonized tail that are clearly identified in the time-averaged spectrum, show strong variability with the first component lagging the second one. The observed variability can be explained if the emission is produced by Comptonization in a hot slab (radiative shock) of Thomson optical depth ~0.3-1 at the neutron star surface. The emission patterns of the black body and the Comptonized radiation are different: a "knife"- and a "fan"-like, respectively. We construct a detailed model of the X-ray production accounting for the Doppler boosting, relativistic aberration and gravitational light bending in the Schwarzschild spacetime. We present also accurate analytical formulae for computations of the light curves from rapidly rotating neutron stars using formalism recently developed by Beloborodov (2002). Our model reproduces well the pulse profil...

  15. Formation of Millisecond Pulsars in Globular Clusters

    CERN Document Server

    Ivanova, Natalia; Rasio, Frederic A

    2007-01-01

    In this contribution we discuss how neutron stars are produced and retained in globular clusters, outlining the most important dynamical channels and evolutionary events that affect thepopulation of mass-transferring binaries with neutron stars and result in the formation of recycled pulsars. We confirm the importance of electron-capture supernovae in globular clusters as the major supplier of retained neutron stars.By comparing the observed millisecond pulsar population and the results obtained from simulations, we discuss several constraints on the evolution of mass-transferring systems.In particular, we find that in our cluster model the following mass-gaining events create populations of MSPs that do not match the observations (with respect to binary periods and companion masses or the number of produced systems) and therefore likely do not lead to NSs spun up to millisecond periods: (i) accretion during a common envelope event with a NS formed through accretion-induced collapse, and (ii) mass transfer fr...

  16. Identification of the High-Energy Gamma-Ray Source 3FGL J1544.6-1125 as a Transitional Millisecond Pulsar Binary in an Accreting State

    CERN Document Server

    Bogdanov, Slavko

    2015-01-01

    We present X-ray, ultraviolet, and optical observations of 1RXS J154439.4-112820, the most probable counterpart of the unassociated Fermi LAT source 3FGL J1544.6-1125. The optical data reveal rapid variability, which is a feature of accreting systems. The X-ray data exhibit large-amplitude flux variations in the form of fast switching (within ~10 s) between two distinct flux levels that differ by a factor of $\\approx$10. The detailed optical and X-ray behavior is virtually identical to that seen in the accretion-disk-dominated states of the transitional millisecond pulsar binaries PSR J1023+0038 and XSS J12270-4859, which are also associated with $\\gamma$-ray sources. Based on the available observational evidence, we conclude that 1RXS J154439.4-112820 and 3FGL J1544.6-1125 are the same object, with the X-rays arising from intermittent low-luminosity accretion onto a millisecond pulsar and the $\\gamma$-rays originating from an accretion-driven outflow. 1RXS J154439.4-112820 is only the fourth $\\gamma$-ray emi...

  17. Formation of millisecond pulsars with CO white dwarf companions - II. Accretion, spin-up, true ages and comparison to MSPs with He white dwarf companions

    CERN Document Server

    Tauris, Thomas M; Kramer, Michael

    2012-01-01

    Millisecond pulsars (MSPs) are mainly characterised by their spin periods, B-fields and masses - quantities which are largely affected by previous interactions with a companion star in a binary system. In this paper, we investigate the formation mechanism of MSPs by considering the pulsar recycling process in both intermediate-mass X-ray binaries (IMXBs) and low-mass X-ray binaries (LMXBs). The IMXBs mainly lead to the formation of binary MSPs with a massive carbon-oxygen (CO) or an oxygen-neon-magnesium white dwarf (ONeMg WD) companion, whereas the LMXBs form recycled pulsars with a helium white dwarf (He WD) companion. We discuss the accretion physics leading to the spin-up line in the PPdot-diagram and demonstrate that such a line cannot be uniquely defined. We derive a simple expression for the amount of accreted mass needed for any given pulsar to achieve its equilibrium spin and apply this to explain the observed differences of the spin distributions of recycled pulsars with different types of companion...

  18. Cosmic-ray positrons from millisecond pulsars

    CERN Document Server

    Venter, C; Harding, A K; Gonthier, P L; Büsching, I

    2015-01-01

    Observations by the Fermi Large Area Telescope of gamma-ray millisecond pulsar light curves imply copious pair production in their magnetospheres, and not exclusively in those of younger pulsars. Such pair cascades may be a primary source of Galactic electrons and positrons, contributing to the observed enhancement in positron flux above ~10 GeV. Fermi has also uncovered many new millisecond pulsars, impacting Galactic stellar population models. We investigate the contribution of Galactic millisecond pulsars to the flux of terrestrial cosmic-ray electrons and positrons. Our population synthesis code predicts the source properties of present-day millisecond pulsars. We simulate their pair spectra invoking an offset-dipole magnetic field. We also consider positrons and electrons that have been further accelerated to energies of several TeV by strong intrabinary shocks in black widow and redback systems. Since millisecond pulsars are not surrounded by pulsar wind nebulae or supernova shells, we assume that the p...

  19. Binary Millisecond Pulsar Discovery via Gamma-Ray Pulsations

    CERN Document Server

    Pletsch, H J; Fehrmann, H; Allen, B; Kramer, M; Aulbert, C; Ackermann, M; Ajello, M; de Angelis, A; Atwood, W B; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Bechtol, K; Bellazzini, R; Borgland, A W; Bottacini, E; Brandt, T J; Bregeon, J; Brigida, M; Bruel, P; Buehler, R; Buson, S; Caliandro, G A; Cameron, R A; Caraveo, P A; Casandjian, J M; Cecchi, C; Celik, Ö; Charles, E; Chaves, R C G; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Conrad, J; Cutini, S; D'Ammando, F; Dermer, C D; Digel, S W; Drell, P S; Drlica-Wagner, A; Dubois, R; Dumora, D; Favuzzi, C; Ferrara, E C; Franckowiak, A; Fukazawa, Y; Fusco, P; Gargano, F; Gehrels, N; Germani, S; Giglietto, N; Giordano, F; Giroletti, M; Godfrey, G; Grenier, I A; Grondin, M -H; Grove, J E; Guiriec, S; Hadasch, D; Hanabata, Y; Harding, A K; Hartog, P R den; Hayashida, M; Hays, E; Hill, A B; Hou, X; Hughes, R E; Johannesson, G; Jackson, M S; Jogler, T; Johnson, A S; Johnson, W N; Kataoka, J; Kerr, M; Knödlseder, J; Kuss, M; Lande, J; Larsson, S; Latronico, L; Lemoine-Goumard, M; Longo, F; Loparco, F; Lovellette, M N; Lubrano, P; Massaro, F; Mayer, M; Mazziotta, M N; McEnery, J E; Mehault, J; Michelson, P F; Mitthumsiri, W; Mizuno, T; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nakamori, T; Nemmen, R; Nuss, E; Ohno, M; Ohsugi, T; Omodei, N; Orienti, M; Orlando, E; de Palma, F; Paneque, D; Perkins, J S; Piron, F; Pivato, G; Porter, T A; Raino, S; Rando, R; Ray, P S; Razzano, M; Reimer, A; Reimer, O; Reposeur, T; Ritz, S; Romani, R W; Romoli, C; Sanchez, D A; Parkinson, P M Saz; Schulz, A; Sgro, C; Silva, E do Couto e; Siskind, E J; Smith, D A; Spandre, G; Spinelli, P; Suson, D J; Takahashi, H; Tanaka, T; Thayer, J B; Thayer, J G; Thompson, D J; Tibaldo, L; Tinivella, M; Troja, E; Usher, T L; Vandenbroucke, J; Vasileiou, V; Vianello, G; Vitale, V; Waite, A P; Winer, B L; Wood, K S; Wood, M; Yang, Z; Zimmer, S; 10.1126/science.1229054

    2012-01-01

    Millisecond pulsars (MSPs), old neutron stars spun-up by accreting matter from a companion star, can reach high rotation rates of hundreds of revolutions per second. Until now, all such "recycled" rotation-powered pulsars have been detected by their spin-modulated radio emission. In a computing-intensive blind search of gamma-ray data from the Fermi Large Area Telescope (with partial constraints from optical data), we detected a 2.5-millisecond pulsar, PSR J1311-3430. This unambiguously explains a formerly unidentified gamma-ray source that had been a decade-long enigma, confirming previous conjectures. The pulsar is in a circular orbit with an orbital period of only 93 minutes, the shortest of any spin-powered pulsar binary ever found.

  20. Spectral and timing properties of the accreting X-ray millisecond pulsar IGR J17498-2921

    CERN Document Server

    Falanga, M; Poutanen, J; Galloway, D K; Bozzo, E; Goldwurm, A; Hermsen, W; Stella, L

    2012-01-01

    We analyze the spectral and timing properties of IGR J17498-2921 and the characteristics of X-ray bursts to constrain the physical processes responsible for the X-ray production in this class of sources. The broad-band average spectrum is well-described by thermal Comptonization with an electron temperature of kT_e ~ 50 keV, soft seed photons of kT_bb ~ 1 keV, and Thomson optical depth \\taut ~ 1 in a slab geometry. The slab area corresponds to a black body radius of R_bb ~9 km. During the outburst, the spectrum stays remarkably stable with plasma and soft seed photon temperatures and scattering optical depth that are constant within the errors. This behavior has been interpreted as indicating that the X-ray emission originates above the neutron star (NS) surface in a hot slab (either the heated NS surface or the accretion shock). The INTEGRAL, RXTE, and Swift data reveal the X-ray pulsation at a period of 2.5 milliseconds up to ~65 keV. The pulsed fraction is consistent with being constant, i.e. energy indepe...

  1. Stokes tomography of radio pulsar magnetospheres. II. Millisecond pulsars

    CERN Document Server

    Chung, C T Y

    2011-01-01

    The radio polarization characteristics of millisecond pulsars (MSPs) differ significantly from those of non-recycled pulsars. In particular, the position angle (PA) swings of many MSPs deviate from the S-shape predicted by the rotating vector model, even after relativistic aberration is accounted for, indicating that they have non-dipolar magnetic geometries, likely due to a history of accretion. Stokes tomography uses phase portraits of the Stokes parameters as a diagnostic tool to infer a pulsar's magnetic geometry and orientation. This paper applies Stokes tomography to MSPs, generalizing the technique to handle interpulse emission. We present an atlas of look-up tables for the Stokes phase portraits and PA swings of MSPs with current-modified dipole fields, filled core and hollow cone beams, and two empirical linear polarization models. We compare our look-up tables to data from 15 MSPs and find that the Stokes phase portraits for a current-modified dipole approximately match several MSPs whose PA swings ...

  2. X-ray states of redback millisecond pulsars

    CERN Document Server

    Linares, Manuel

    2014-01-01

    Compact binary millisecond pulsars with main-sequence donors, often referred to as "redbacks", constitute the long-sought link between low-mass X-ray binaries and millisecond radio pulsars, and offer a unique probe of the interaction between pulsar winds and accretion flows. We present a systematic study of eight nearby redbacks, using more than 100 observations obtained with Swift's X-ray Telescope. We distinguish between three main states: pulsar, disk and outburst states. We find X-ray mode switching in the disk state of PSR J1023+0038 and XSS J12270-4859, similar to what was found in the other redback which showed evidence for accretion: rapid, recurrent changes in X-ray luminosity (0.5-10 keV, L$_\\mathrm{X}$), between [6-9]$\\times$10$^{32}$ erg s$^{-1}$ (disk-passive state) and [3-5]$\\times$10$^{33}$ erg s$^{-1}$ (disk-active state). This strongly suggests that mode switching $-$which has not been observed in quiescent low-mass X-ray binaries$-$ is universal among redback millisecond pulsars in the disk ...

  3. X-ray states of redback millisecond pulsars

    Energy Technology Data Exchange (ETDEWEB)

    Linares, M. [Instituto de Astrofísica de Canarias, c/Vía Láctea s/n, E-38205 La Laguna, Tenerife (Spain)

    2014-11-01

    Compact binary millisecond pulsars with main-sequence donors, often referred to as 'redbacks', constitute the long-sought link between low-mass X-ray binaries and millisecond radio pulsars and offer a unique probe of the interaction between pulsar winds and accretion flows. We present a systematic study of eight nearby redbacks, using more than 100 observations obtained with Swift's X-ray Telescope. We distinguish between three main states: pulsar, disk, and outburst states. We find X-ray mode switching in the disk state of PSR J1023+0038 and XSS J12270-4859, similar to what was found in the other redback that showed evidence for accretion: rapid, recurrent changes in X-ray luminosity (0.5-10 keV, L {sub X}), between (6-9) × 10{sup 32} erg s{sup –1} (disk-passive state) and (3-5) × 10{sup 33} erg s{sup –1} (disk-active state). This strongly suggests that mode switching—which has not been observed in quiescent low-mass X-ray binaries—is universal among redback millisecond pulsars in the disk state. We briefly explore the implications for accretion disk truncation and find that the inferred magnetospheric radius in the disk state of PSR J1023+0038 and XSS J12270-4859 lies outside the light cylinder. Finally, we note that all three redbacks that have developed accretion disks have relatively high L {sub X} in the pulsar state (>10{sup 32} erg s{sup –1}).

  4. The disturbance of a millisecond pulsar magnetosphere

    CERN Document Server

    Shannon, R M; Kerr, M; Bailes, M; Bhat, N D R; Coles, W A; Dai, S; Dempsey, J; Hobbs, G; Keith, M J; Lasky, P D; Levin, Y; Manchester, R N; Oslowski, S; Ravi, V; Reardon, D J; Rosado, P A; Spiewak, R; van Straten, W; Toomey, L; Wang, J -B; Wen, L; You, X -P; Zhu, X -J

    2016-01-01

    Pulsar timing has enabled some of the strongest tests of fundamental physics. Central to the technique is the assumption that the detected radio pulses can be used to accurately measure the rotation of the pulsar. Here we report on a broad-band variation in the pulse profile of the millisecond pulsar J1643-1224. A new component of emission suddenly appears in the pulse profile, decays over 4 months, and results in a permanently modified pulse shape. Profile variations such as these may be the origin of timing noise observed in other millisecond pulsars. The sensitivity of pulsar-timing observations to gravitational radiation can be increased by accounting for this variability.

  5. The Quiescent X-Ray Properties of the Accreting Millisecond X-Ray Pulsar and Eclipsing binary Swift J1749.4-2807

    Science.gov (United States)

    Degenaar, N.; Patruno, A.; Wijnands, R.

    2012-09-01

    Swift J1749.4-2807 is a transient neutron star low-mass X-ray binary that contains an accreting millisecond X-ray pulsar spinning at 518 Hz. It is the first of its kind that displays X-ray eclipses, which holds significant promise to precisely constrain the mass of the neutron star. We report on a ~= 105 ks long XMM-Newton observation performed when Swift J1749.4-2807 was in quiescence. We detect the source at a 0.5-10 keV luminosity of sime1 × 1033(D/6.7 kpc)2 erg s-1. The X-ray light curve displays three eclipses that are consistent in orbital phase and duration with the ephemeris derived during outburst. Unlike most quiescent neutron stars, the X-ray spectrum can be adequately described with a simple power law, while a pure-hydrogen atmosphere model does not fit the data. We place an upper limit on the 0.01-100 keV thermal luminosity of the cooling neutron star of <~ 2 × 1033 erg s-1 and constrain its temperature to be <~ 0.1 keV (for an observer at infinity). Timing analysis does not reveal evidence for X-ray pulsations near the known spin frequency of the neutron star or its first overtone with a fractional rms of <~ 34% and <~ 28%, respectively. We discuss the implications of our findings for dynamical mass measurements, the thermal state of the neutron star, and the origin of the quiescent X-ray emission.

  6. A Search for Radio Millisecond Pulsars

    Science.gov (United States)

    Sayer, Ronald Winston

    1996-01-01

    We have built a data acquisition backend for radio pulsar search observations carried out at the NRAO 140 -foot telescope in Green Bank, West Virginia. Our system sampled 512 spectral channels over 40 MHz every 256 mus, reduced samples to one-bit precision, and wrote the resulting data stream onto magnetic tape for later, off-line processing. We have completed three surveys with this backend. In the first survey, we searched most of the Northern Hemisphere for millisecond radio pulsars. Previous surveys directed towards most of the region covered had not been as sensitive to pulsars with millisecond periods. We obtained high quality data for 15,876 deg^2 of sky. Eight new pulsars were discovered and 76 previously known pulsars were detected. Two of the eight new pulsars (PSR J1022+1001 and PSR J1518+4904) are millisecond pulsars in binary systems. PSR J1518+4904 is a 41 ms radio pulsar in an eccentric (e = 0.25) 8.6 day orbit with another stellar object, probably another neutron star. It is only the fifth double neutron star system known. The system's relativistic advance of periastron has been measured to be ˙omega = 0.0112 +/- 0.0002 ^circ yr^{-1}, implying that the total mass of the pair of stars is 2.65 +/-0.07Modot. We have searched for radio pulsar companions to 40 nearby OB runaway stars. No pulsar companions to OB runaways were discovered. One previously unknown pulsar, PSR J2044+4614, was discovered while observing towards target O star BD+45,3260. However, follow-up timing observations reveal that the pulsar is not associated with the target O star. Assuming standard models for the pulsar beaming fraction and luminosity function, we conclude that most OB runaways do not have pulsar companions. We have completed a survey for pulsed radio signals towards 27 gamma-ray sources detected by the EGRET instrument of the Compton Gamma Ray Observatory. No new pulsars were discovered.

  7. The neutron star transient and millisecond pulsar in M28: from sub-luminous accretion to rotation-powered quiescence

    CERN Document Server

    Linares, Manuel; Heinke, Craig; Wijnands, Rudy; Patruno, Alessandro; Altamirano, Diego; Homan, Jeroen; Bogdanov, Slavko; Pooley, David

    2013-01-01

    The X-ray transient IGR J18245-2452 in the globular cluster M28 contains the first neutron star (NS) seen to switch between rotation-powered and accretion-powered pulsations. We analyse its 2013 March-April 25d-long outburst as observed by Swift, which had a peak bolometric luminosity of ~6% of the Eddington limit (L$_{E}$), and give detailed properties of the thermonuclear burst observed on 2013 April 7. We also present a detailed analysis of new and archival Chandra data, which we use to study quiescent emission from IGR J18245-2452 between 2002 and 2013. Together, these observations cover almost five orders of magnitude in X-ray luminosity (L$_X$, 0.5-10 keV). The Swift spectrum softens during the outburst decay (photon index $\\Gamma$ from 1.3 above L$_X$/L$_{E}$=10$^{-2}$ to ~2.5 at L$_X$/L$_{E}$=10$^{-4}$), similar to other NS and black hole (BH) transients. At even lower luminosities, deep Chandra observations reveal hard ($\\Gamma$=1-1.5), purely non-thermal and highly variable X-ray emission in quiesce...

  8. Formation of black widows and redbacks -- two distinct populations of eclipsing binary millisecond pulsars

    CERN Document Server

    Chen, Hai-Liang; Tauris, Thomas M; Han, Zhanwen

    2013-01-01

    Eclipsing binary millisecond pulsars (the so-called black widows and redbacks) can provide important information about accretion history, pulsar irradiation of their companion stars and the evolutionary link between accreting X-ray pulsars and isolated millisecond pulsars. However, the formation of such systems is not well understood, nor the difference in progenitor evolution between the two populations of black widows and redbacks. Whereas both populations have orbital periods between $0.1-1.0\\;{\\rm days}$ their companion masses differ by an order of magnitude. In this paper, we investigate the formation of these systems via evolution of converging low-mass X-ray binaries by employing the MESA stellar evolution code. Our results confirm that one can explain the formation of most of these eclipsing binary millisecond pulsars using this scenario. More notably, we find that the determining factor for producing either black widows or redbacks is the efficiency of the irradiation process, such that the redbacks ...

  9. A millisecond pulsar timing array

    Science.gov (United States)

    Hobbs, George; Manchester, Dick; Sarkissian, John; Bailes, Matthew; Bhat, Ramesh; Keith, Michael; Burke-Spolaor, Sarah; Coles, William; van Straten, Willem; Ravi, Vikram; Oslowski, Stefan; Khoo, Jonathan; Shannon, Ryan; Wang, Jingbo; Levin, Yuri

    2013-10-01

    The Parkes Pulsar Timing Array (PPTA) project has three primary goals: (a) detection of gravitational waves from astronomical sources, (b) establishment of a pulsar timescale, and (c) improvement of our understanding of Solar-system dynamics. There are many secondary goals, some astrophysical and some instrumental/technique oriented. Achievement of these ambitious primary goals requires frequent observations of at least 20 MSPs at two or preferably three widely spaced frequencies over several years. We wish to continue observing the PPTA sample at intervals of 2-3 weeks using both the 10/50cm and Multibeam receivers. The digital filterbanks (PDFB3, PDFB4) and the baseband systems (CPSR2; APSR) are used for data recording. With the new instruments and development of an efficient pipeline processing system, we have achieved the world's best pulsar timing precision. We are collaborating with the European and North American pulsar timing array groups (EPTA and NANOGrav, respectively) to obtain more frequent observations and a larger pulsar sample. Because of the high sensitivity and wide bandwidths required, RFI mitigation is an important part of the project. We request continuing status for this project.

  10. Gemini optical observations of binary millisecond-pulsars

    CERN Document Server

    Testa, V; Pallanca, C; Corongiu, A; Ferraro, F R

    2015-01-01

    Milli-second pulsars (MSPs) are rapidly spinning neutron stars, with spin periods P_s <= 10 ms, which have been most likely spun up after a phase of matter accretion from a companion star. In this work we present the results of the search for the companion stars of four binary milli-second pulsars, carried out with archival data from the Gemini South telescope. Based upon a very good positional coincidence with the pulsar radio coordinates, we likely identified the companion stars to three MSPs, namely PSRJ0614-3329 (g=21.95 +- 0.05), J1231-1411 (g=25.40 +-0.23), and J2017+0603 (g=24.72 +- 0.28). For the last pulsar (PSRJ0613-0200) the identification was hampered by the presence of a bright star (g=16 +- 0.03) at \\sim 2" from the pulsar radio coordinates and we could only set 3-sigma upper limits of g=25.0, r= 24.3, and i= 24.2 on the magnitudes of its companion star. The candidate companion stars to PSRJ0614-3329, J1231-1411, and J2017+0603 can be tentatively identified as He white dwarfs (WDs) on the bas...

  11. Giant pulses in Millisecond Pulsars

    CERN Document Server

    Joshi, B C; Lyne, A G; McLaughlin, M; Stairs, I H

    2003-01-01

    Giant pulses (GPs), occasional individual pulses with an intensity 100 times the average intensity, have been detected in four pulsars todate. Their origin is not well understood, but studies suggest a connection between the strength of magnetic field at the light cylinder B_lc and the existence of GPs. Here, we report on detection of significant Large Amplitude Pulses (LAPs) in two more pulsars with high values of B_lc, PSRs J0218+4232 and B1957+20, observed using Giant Meterwave Radio Telescope (GMRT).

  12. An active, asynchronous companion to a redback millisecond pulsar

    CERN Document Server

    van Staden, André

    2016-01-01

    PSR\\,J1723$-$2837 is a "redback" millisecond pulsar (MSP) with a low-mass companion in a 14.8\\,h orbit. The system's properties closely resemble those of "transitional" MSPs that alternate between spin-down and accretion-powered states. In this paper we report on long-term photometry of the 15.5\\,mag companion to the pulsar. We use our data to illustrate that the star experiences sporadic activity which we attribute to starspots. We also find that the companion is not tidally locked and infer $P_{\\rm s}/P_{\\rm b}= 0.9974(7)$ for the ratio between the rotational and orbital periods. We place constraints on various parameters, including the irradiation efficiency and pulsar mass. Finally, we discuss similarities with other redback MSPs and conclude that starspots provide the most likely explanation for the often seen irregular and asymmetric optical lightcurves.

  13. Phase Coherent Observations and Millisecond Pulsar Searches

    Science.gov (United States)

    Shrauner, Jay Arthur

    1997-07-01

    new pulsars and detected 14 that were previously known. One of these new pulsars, PSR J0621+1002, is a millisecond pulsar with a relatively large mass companion. This system is of special interest because the relativistic advance of periastron should be measurable within a few years.

  14. Implications of the PSR 1257+12 Planetary System for Isolated Millisecond Pulsars

    CERN Document Server

    Miller, M C; Hamilton, Douglas P.

    2000-01-01

    The first extrasolar planets were discovered in 1992 around the millisecond pulsar PSR 1257+12. We show that recent developments in the study of accretion onto magnetized stars, plus the existence of the innermost, moon-sized planet in the PSR 1257+12 system, suggest that the pulsar was born with approximately its current rotation frequency and magnetic moment. If so, this has important implications for the formation and evolution of neutron star magnetic fields as well as for the formation of planets around pulsars. In particular, it suggests that some and perhaps all isolated millisecond pulsars may have been born with high spin rates and low magnetic fields instead of having been recycled by accretion.

  15. The 2015 outburst of the accreting millisecond pulsar IGR J17511-3057 as seen by INTEGRAL, Swift and XMM-Newton

    CERN Document Server

    Papitto, A; Sanchez-Fernandez, C; Romano, P; Torres, D F; Ferrigno, C; Kajava, J J E; Kuulkers, E

    2016-01-01

    We report on INTEGRAL, Swift and XMM-Newton observations of IGR J17511-3057 performed during the outburst that occurred between March 23 and April 25, 2015. The source reached a peak flux of 0.7(2)E-9 erg/cm$^2$/s and decayed to quiescence in approximately a month. The X-ray spectrum was dominated by a power-law with photon index between 1.6 and 1.8, which we interpreted as thermal Comptonization in an electron cloud with temperature > 20 keV . A broad ({\\sigma} ~ 1 keV) emission line was detected at an energy (E = 6.9$^{+0.2}_{-0.3}$ keV) compatible with the K{\\alpha} transition of ionized Fe, suggesting an origin in the inner regions of the accretion disk. The outburst flux and spectral properties shown during this outburst were remarkably similar to those observed during the previous accretion event detected from the source in 2009. Coherent pulsations at the pulsar spin period were detected in the XMM-Newton and INTEGRAL data, at a frequency compatible with the value observed in 2009. Assuming that the so...

  16. Neutron Star Population Dynamics; 1, Millisecond Pulsars

    CERN Document Server

    Cordes, J M; Chernoff, David F.

    1997-01-01

    We study the field millisecond pulsar (MSP) population to infer its intrinsic distribution in spin period and luminosity and to determine its spatial distribution within the Galaxy. Our likelihood analysis on data from extant surveys (22 pulsars with periods 0.65 ms (99% confidence), a period distribution proportional to P^{-2.0 +- 0.33} and a pseudo-luminosity distribution proportional to L_p^{-2.0 +- 0.2} (where L_p = flux density times distance^2, for L_p >= 1.1 mJy kpc^2). We find a vertical scale height 0.65{+0.16,-0.12} kpc. We use our results to estimate the total number and birthrate of MSPs in the disk of the Galaxy. We limit the density contribution of a diffuse halo-like component to <1% of the midplane value. The MSP velocity dispersion is smaller that that of young, long-period pulsars by about a factor of 5. Our best estimate of the 1D velocity kick that is unique to MSP evolution is approximately 40 km s^-1. We discuss the evolutionary relationship of MSPs and low-mass X-ray binaries and pr...

  17. X-ray bounds on the r-mode amplitude in millisecond pulsars

    CERN Document Server

    Schwenzer, Kai; Güver, Tolga; Vurgun, Eda

    2016-01-01

    r-mode astroseismology provides a unique way to study the internal composition of compact stars. Due to their precise timing, recycled millisecond radio pulsars present a particularly promising class of sources. Although their thermal properties are still poorly constrained, X-ray data is very useful for astroseismology since r-modes could strongly heat a star. Using known and new upper bounds on the temperatures and luminosities of several non-accreting millisecond radio pulsars we derive bounds on the r-mode amplitude as low as $\\alpha\\lesssim10^{-8}$ and discuss the impact on scenarios for their internal composition.

  18. Rotation and Accretion Powered Pulsars

    International Nuclear Information System (INIS)

    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 astrophysical applications. These range from Nobel-celebrated testing of general relativity in the strong-field regime to constraining the equation-of-state of ultradense matter; from probing the winds of massive stars to globular cluster evolution. Previous notable books on the subject of pulsars have tended to focus on some particular topic in the field. The classic text Pulsars by Manchester and Taylor (1977 San Francisco, CA: Freeman) targeted almost exclusively rotation-powered radio pulsars, while the Meszaros book High-Energy Radiation from Magnetized Neutron Stars (1992 Chicago, IL: University of Chicago Press) considered both rotation- and accretion-powered neutron stars, but focused on their radiation at x-ray energies and above. The recent book Neutron Stars 1 by Haensel et al (2007 Berlin: Springer) considers only the equation of state and neutron-star structure. Into this context appears Rotation and Accretion Powered Pulsars, by Pranab Ghosh. In contrast to other books, here the author takes an encyclopedic approach and attempts to synthesize practically all of the major aspects of the two main types of neutron star. This is ambitious. The only comparable undertaking is the useful but more elementary Lyne and Graham-Smith text Pulsar Astronomy (1998 Cambridge: Cambridge University Press), or Compact Stellar X-ray Sources (eds Lewin and van der Klis, 2006 Cambridge: Cambridge University Press), an anthology of technical review articles that also includes black hole topics. Rotation and Accretion Powered Pulsars thus fills a clear void in the field, providing a readable, graduate-level book that covers nearly everything you

  19. A LOFAR Census of Millisecond Pulsars

    CERN Document Server

    Kondratiev, V I; Hessels, J W T; Bilous, A V; Stappers, B W; Kramer, M; Keane, E F; Noutsos, A; Osłowski, S; Breton, R P; Hassall, T E; Alexov, A; Cooper, S; Falcke, H; Grießmeier, J -M; Karastergiou, A; Kuniyoshi, M; Pilia, M; Sobey, C; ter Veen, S; Weltevrede, P; Bell, M E; Broderick, J W; Corbel, S; Eislöffel, J; Markoff, S; Rowlinson, A; Swinbank, J D; Wijers, R A M J; Wijnands, R; Zarka, P

    2016-01-01

    We report the detection of 48 millisecond pulsars (MSPs) out of 75 observed thus far using the LOFAR in the frequency range 110-188 MHz. We have also detected three MSPs out of nine observed in the frequency range 38-77 MHz. This is the largest sample of MSPs ever observed at these low frequencies, and half of the detected MSPs were observed for the first time at frequencies below 200 MHz. We present the average pulse profiles of the detected MSPs, their effective pulse widths and flux densities, and compare these with higher observing frequencies. The LOFAR pulse profiles will be publicly available via the EPN Database of Pulsar Profiles. We also present average values of dispersion measures (DM) and discuss DM and profile variations. About 35% of the MSPs show strong narrow profiles, another 25% exhibit scattered profiles, and the rest are only weakly detected. A qualitative comparison of the LOFAR MSP profiles with those at higher radio frequencies shows constant separation between profile components. Simi...

  20. Cosmic-ray Positrons from Millisecond Pulsars

    Science.gov (United States)

    Venter, C.; Kopp, A.; Harding, A. K.; Gonthier, P. L.; Büsching, I.

    2015-07-01

    Observations by the Fermi Large Area Telescope of γ-ray millisecond pulsar (MSP) light curves imply copious pair production in their magnetospheres, and not exclusively in those of younger pulsars. Such pair cascades may be a primary source of Galactic electrons and positrons, contributing to the observed enhancement in positron flux above ∼10 GeV. Fermi has also uncovered many new MSPs, impacting Galactic stellar population models. We investigate the contribution of Galactic MSPs to the flux of terrestrial cosmic-ray electrons and positrons. Our population synthesis code predicts the source properties of present-day MSPs. We simulate their pair spectra invoking an offset-dipole magnetic field. We also consider positrons and electrons that have been further accelerated to energies of several TeV by strong intrabinary shocks in black widow (BW) and redback (RB) systems. Since MSPs are not surrounded by pulsar wind nebulae or supernova shells, we assume that the pairs freely escape and undergo losses only in the intergalactic medium. We compute the transported pair spectra at Earth, following their diffusion and energy loss through the Galaxy. The predicted particle flux increases for non-zero offsets of the magnetic polar caps. Pair cascades from the magnetospheres of MSPs are only modest contributors around a few tens of GeV to the lepton fluxes measured by the Alpha Magnetic Spectrometer, PAMELA, and Fermi, after which this component cuts off. The contribution by BWs and RBs may, however, reach levels of a few tens of percent at tens of TeV, depending on model parameters.

  1. Search for Millisecond Pulsars for the Pulsar Timing Array project

    Science.gov (United States)

    Milia, S.

    2012-03-01

    Pulsars are rapidly rotating highly magnetised neutron stars (i.e. ultra dense stars, where about one solar mass is concentrated in a sphere with a radius of ~ 10 km), which irradiate radio beams in a fashion similar to a lighthouse. As a consequence, whenever the beams cut our line of sight we perceive a radio pulses, one (or two) per pulsar rotation, with a frequency up to hundred of times a second. Owing to their compact nature, rapid spin and high inertia, pulsars are in general fairly stable rotators, hence the Times of Arrival (TOAs) of the pulses at a radio telescope can be used as the ticks of a clock. This holds true in particular for the sub­class of the millisecond pulsars (MSPs), having a spin period smaller than the conventional limit of 30 ms, whose very rapid rotation and relatively older age provide better rotational stability than the ordinary pulsars. Indeed, some MSPs rotate so regularly that they can rival the best atomic clocks on Earth over timespan of few months or years.This feature allows us to use MSPs as tools in a cosmic laboratory, by exploiting a procedure called timing, which consists in the repeated and regular measurement of the TOAs from a pulsar and then in the search for trends in the series of the TOAs over various timespans, from fraction of seconds to decades.For example the study of pulsars in binary systems has already provided the most stringent tests to date of General Relativity in strong gravitational fields and has unambiguously showed the occurrence of the emission of gravitational waves from a binary system comprising two massive bodies in a close orbit. In last decades a new exciting perspective has been opened, i.e. to use pulsars also for a direct detection of the so far elusive gravitational waves and thereby applying the pulsar timing for cosmological studies. In fact, the gravitational waves (GWs) going across our Galaxy pass over all the Galactic pulsars and the Earth, perturbing the space­time at the

  2. A glitch in the millisecond pulsar J0613-0200

    Science.gov (United States)

    McKee, J. W.; Janssen, G. H.; Stappers, B. W.; Lyne, A. G.; Caballero, R. N.; Lentati, L.; Desvignes, G.; Jessner, A.; Jordan, C. A.; Karuppusamy, R.; Kramer, M.; Cognard, I.; Champion, D. J.; Graikou, E.; Lazarus, P.; Osłowski, S.; Perrodin, D.; Shaifullah, G.; Tiburzi, C.; Verbiest, J. P. W.

    2016-09-01

    We present evidence for a small glitch in the spin evolution of the millisecond pulsar J0613-0200, using the EPTA Data Release 1.0, combined with Jodrell Bank analogue filterbank times of arrival (TOAs) recorded with the Lovell telescope and Effelsberg Pulsar Observing System TOAs. A spin frequency step of 0.82(3) nHz and frequency derivative step of -1.6(39) × 10-19 Hz s-1 are measured at the epoch of MJD 50888(30). After PSR B1821-24A, this is only the second glitch ever observed in a millisecond pulsar, with a fractional size in frequency of Δν/ν = 2.5(1) × 10-12, which is several times smaller than the previous smallest glitch. PSR J0613-0200 is used in gravitational wave searches with pulsar timing arrays, and is to date only the second such pulsar to have experienced a glitch in a combined 886 pulsar-years of observations. We find that accurately modelling the glitch does not impact the timing precision for pulsar timing array applications. We estimate that for the current set of millisecond pulsars included in the International Pulsar Timing Array, there is a probability of ˜50 per cent that another glitch will be observed in a timing array pulsar within 10 years.

  3. An eccentric binary millisecond pulsar in the Galactic plane

    NARCIS (Netherlands)

    D.J. Champion; S.M. Ransom; P. Lazarus; F. Camilo; C. Bassa; V.M. Kaspi; D.J. Nice; P.C.C. Freire; I.H. Stairs; J. van Leeuwen; B.W. Stappers; J.M. Cordes; J.W.T. Hessels; D.R. Lorimer; Z. Arzoumanian; D.C. Backer; N.D.R. Bhat; S. Chatterjee; I. Cognard; J.S. Deneva; C.A. Faucher-Giguère; B.M. Gaensler; J. Han; F.A. Jenet; L. Kasian; V.I. Kondratiev; M. Kramer; J. Lazio; M.A. McLaughlin; A. Venkataraman; W. Vlemmings

    2008-01-01

    Binary pulsar systems are superb probes of stellar and binary evolution and the physics of extreme environments. In a survey with the Arecibo telescope, we have found PSR J1903+ 0327, a radio pulsar with a rotational period of 2.15 milliseconds in a highly eccentric ( e = 0.44) 95- day orbit around

  4. Observations of Binary and Millisecond Pulsars at Xinjiang Astronomical Observatory

    Indian Academy of Sciences (India)

    Jingbo Wang; Na Wang; Jianping Yuan; Zhiyong Liu

    2014-09-01

    We present the first results of radio timing observations of binary and millisecond pulsars in China. We have timed four binary pulsars for 9 years, using Nanshan 25-m radio telescope. The long time span has enabled us to determine their rotation and orbital parameters.

  5. On the progenitors of millisecond pulsars by the recycling evolutionary channel

    CERN Document Server

    Liu, Wei-Min

    2011-01-01

    The recycling model suggested that low-mass X-ray binaries (LMXBs) could evolve into binary millisecond pulsars (BMSPs). In this work, we attempt to investigate the progenitor properties of BMSPs formed by the recycling evolutionary channel, and if sub-millisecond pulsars can be produced by this channel. Using Eggleton's stellar evolution code, considering that the dead pulsars can be spun up to a short spin period by the accreting material and angular momentum from the donor star, we have calculated the evolution of close binaries consisting of a neutron star and a low-mass main-sequence donor star, and the spin evolution of NSs. In calculation, some physical process such as the thermal and viscous instability of a accretion disk, propeller effect, and magnetic braking are included. Our calculated results indicate that, all LMXBs with a low-mass donor star of 1.0 - 2.0 $M_\\odot$ and a short orbital period ($\\la 3-4 \\rm d$) can form millisecond pulsars with a spin period less than 10 ms. However, it is diffic...

  6. The Aid of Optical Studies in Understanding Millisecond Pulsar Binaries

    CERN Document Server

    Wadiasingh, Zorawar; Venter, Christo; Boettcher, Markus

    2016-01-01

    A large number of new "black widow" and "redback" energetic millisecond pulsars with irradiated stellar companions have been discovered through radio and optical searches of unidentified \\textit{Fermi} sources. Synchrotron emission, from particles accelerated up to several TeV in the intrabinary shock, exhibits modulation at the binary orbital period. Our simulated double-peaked X-ray light curves modulated at the orbital period, produced by relativistic Doppler-boosting along the intrabinary shock, are found to qualitatively match those observed in many sources. In this model, redbacks and transitional pulsar systems where the double-peaked X-ray light curve is observed at inferior conjunction have intrinsically different shock geometry than other millisecond pulsar binaries where the light curve is centered at superior conjunction. We discuss, and advocate, how current and future optical observations may aid in constraining the emission geometry, intrabinary shock and the unknown physics of pulsar winds.

  7. An Eccentric Binary Millisecond Pulsar in the Galactic Plane

    Science.gov (United States)

    Champion, David J.; Ransom, Scott M.; Lazarus, Patrick; Camilo, Fernando; Bassa, Cess; Kaspi, Victoria M.; Nice, David J.; Freire, Paulo C. C.; Stairs, Ingrid H.; vanLeeuwen, Joeri; Stappers, Ben W.; Cordes, James M.; Hessels, Jason W. T.; Lorimer, Duncan R.; Arzoumanian, Zaven; Backer, Don C.; Bhat, N. D. Ramesh; Chatterjee, Shami; Cognard, Ismael; Deneva, Julia S.; Faucher-Giguere, Claude-Andre; Gaensler, Bryan M.; Han, JinLin; Jenet, Fredrick A.; Kasian, Laura

    2008-01-01

    Binary pulsar systems are superb probes of stellar and binary evolution and the physics of extreme environments. In a survey with the Arecibo telescope, we have found PSR J1903+0327, a radio pulsar with a rotational period of 2.15 milliseconds in a highly eccentric (e = 0.44) 95-day orbit around a solar mass (M.) companion. Infrared observations identify a possible main-sequence companion star. Conventional binary stellar evolution models predict neither large orbital eccentricities nor main-sequence companions around millisecond pulsars. Alternative formation scenarios involve recycling a neutron star in a globular cluster, then ejecting it into the Galactic disk, or membership in a hierarchical triple system. A relativistic analysis of timing observations of the pulsar finds its mass to be 1.74 +/- 0.04 Solar Mass, an unusually high value.

  8. Statistical Analysis of I Stokes Parameter of Millisecond Pulsars

    OpenAIRE

    Panahi, Hossein; Eghdami, Issa; Monadi, Reza

    2016-01-01

    Using Detrended Fluctuation Analysis (DFA) and box counting method, we test spacial correlation and fractality of Polarization Pulse Profiles (PPPs) of 24 millisecond pulsars (MSPs) which were observed in Parkes Pulsar Timing Array (PPTA) project. DFA analysis indicates that MSPs' PPPs are persistent and the results of box counting method confirm the fractality in the majority of PPPs. A Kolmogorov-Smirnov test indicates that isolated MSPs have more complex PPPs than binary ones. Then we appl...

  9. NuSTAR Observations of the State Transition of Millisecond Pulsar Binary PSR J1023+0038

    DEFF Research Database (Denmark)

    Tendulkar, Shriharsh P.; Yang, Chengwei; An, Hongjun;

    2014-01-01

    We report NuSTAR observations of the millisecond pulsar - low mass X-ray binary (LMXB) transition system PSR J1023+0038 from June and October 2013, before and after the formation of an accretion disk around the neutron star. Between June 10-12, a few days to two weeks before the radio disappearan...

  10. NuSTAR Observations of the State Transition of Millisecond Pulsar Binary PSR J1023+0038

    DEFF Research Database (Denmark)

    Tendulkar, Shriharsh P.; Yang, Chengwei; An, Hongjun;

    2014-01-01

    We report NuSTAR observations of the millisecond pulsar-low-mass X-ray binary (LMXB) transition system PSR J1023+0038 from 2013 June and October, before and after the formation of an accretion disk around the neutron star. Between June 10 and 12, a few days to two weeks before the radio disappear...

  11. Statistical Analysis of I Stokes Parameter of Millisecond Pulsars

    CERN Document Server

    Panahi, Hossein; Monadi, Reza

    2016-01-01

    Using Detrended Fluctuation Analysis (DFA) and box counting method, we test spacial correlation and fractality of Polarization Pulse Profiles (PPPs) of 24 millisecond pulsars (MSPs) which were observed in Parkes Pulsar Timing Array (PPTA) project. DFA analysis indicates that MSPs' PPPs are persistent and the results of box counting method confirm the fractality in the majority of PPPs. A Kolmogorov-Smirnov test indicates that isolated MSPs have more complex PPPs than binary ones. Then we apply our analysis on a random sample of normal pulsars. Comparing the results of our analysis on MSPs and normal pulsars shows that MSPs have more complex PPPs which is resulted from smaller angular half-width of the emission cone and more peaks in MSPs PPPs. On the other hand, high values of Hurst exponent in MSPs confirm compact emission regions in these pulsars.

  12. Modelling the light curves of Fermi LAT millisecond pulsars

    CERN Document Server

    Venter, C; Harding, AK; Grove, JE

    2014-01-01

    We modelled the radio and gamma-ray light curves of millisecond pulsars using outer gap, two-pole caustic, low-altitude slot gap, and pair-starved polar cap geometric models, combined with a semi-empirical conal radio model. We find that no model fits all cases, with the outer gap and two-pole caustic models providing best fits for comparable numbers of millisecond pulsar light curves. We find a broad distribution of best-fit inclination angles as well as a clustering at large observer angles. The outer gap model furthermore seems to require relatively larger inclination angles, while the two-pole caustic model hints at an inverse trend between inclination angle and pulsar spin-down luminosity.

  13. A glitch in the millisecond pulsar J0613-0200

    CERN Document Server

    McKee, J W; Stappers, B W; Lyne, A G; Caballero, R N; Lentati, L; Desvignes, G; Jessner, A; Jordan, C A; Karuppusamy, R; Kramer, M; Cognard, I; Champion, D J; Graikou, E; Lazarus, P; Osłowski, S; Perrodin, D; Shaifullah, G; Tiburzi, C; Verbiest, J P W

    2016-01-01

    We present evidence for a small glitch in the spin evolution of the millisecond pulsar J0613$-$0200, using the EPTA Data Release 1.0, combined with Jodrell Bank analogue filterbank TOAs recorded with the Lovell telescope and Effelsberg Pulsar Observing System TOAs. A spin frequency step of 0.82(3) nHz and frequency derivative step of ${-1.6(39) \\times 10^{-19}\\,\\text{Hz} \\ \\text{s}^{-1}}$ are measured at the epoch of MJD 50888(30). After PSR B1821$-$24A, this is only the second glitch ever observed in a millisecond pulsar, with a fractional size in frequency of ${\\Delta \

  14. Three Millisecond Pulsars in FERMI LAT Unassociated Bright Sources

    CERN Document Server

    Ransom, S M; Camilo, F; Roberts, M S E; Celik, O; Wolff, M T; Cheung, C C; Kerr, M; Pennucci, T; DeCesar, M E; Cognard, I; Lyne, A G; Stappers, B W; Freire, P C C; Grove, J E; Abdo, A A; Desvignes, G; Donato, D; Ferrara, E C; Gehrels, N; Guillemot, L; Gwon, C; Harding, A K; Johnston, S; Keith, M; Kramer, M; Michelson, P F; Parent, D; Parkinson, P M Saz; Romani, R W; Smith, D A; Theureau, G; Thompson, D J; Weltevrede, P; Wood, K S; Ziegler, M

    2010-01-01

    We searched for radio pulsars in 25 of the non-variable, unassociated sources in the Fermi LAT Bright Source List with the Green Bank Telescope at 820 MHz. We report the discovery of three radio and gamma-ray millisecond pulsars (MSPs) from a high Galactic latitude subset of these sources. All of the pulsars are in binary systems, which would have made them virtually impossible to detect in blind gamma-ray pulsation searches. They seem to be relatively normal, nearby (<=2 kpc) millisecond pulsars. These observations, in combination with the Fermi detection of gamma-rays from other known radio MSPs, imply that most, if not all, radio MSPs are efficient gamma-ray producers. The gamma-ray spectra of the pulsars are power-law in nature with exponential cutoffs at a few GeV, as has been found with most other pulsars. The MSPs have all been detected as X-ray point sources. Their soft X-ray luminosities of ~10^{30-31} erg/s are typical of the rare radio MSPs seen in X-rays.

  15. A propeller model for the sub-luminous disk state of the transitional millisecond pulsar PSR J1023+0038

    CERN Document Server

    Papitto, A

    2015-01-01

    The discovery of millisecond pulsars switching between states powered either by the rotation of their magnetic field or by the accretion of matter, has recently proved the tight link shared by millisecond radio pulsars and neutron stars in low-mass X-ray binaries. Transitional millisecond pulsars also show an enigmatic intermediate state in which the neutron star is surrounded by an accretion disk, it emits coherent X-ray pulsations, but is sub-luminous in X-rays with respect to accreting neutron stars, and is brighter in gamma-rays than millisecond pulsars in the rotation-powered state. Here, we model the X-ray and gamma-ray emission observed from PSR J1023+0038 in such a state based on the assumption that most of the disk in-flow is propelled away by the rapidly rotating neutron star magnetosphere, and that electrons can be accelerated to energies of a few GeV at the turbulent disk-magnetosphere boundary. We show that the synchrotron and self-synchrotron Compton emission coming from such a region, together ...

  16. Why are millisecond pulsar magnetic fields low and how do their X-rays arise?

    Science.gov (United States)

    Webb, Natalie

    2006-10-01

    Binary millisecond pulsars (MSPs) found in the field are thought to be recycled from accreting pulsars. These MSPs have short periods, low spindown rates (Pdot) and consequently low surface magnetic fields (Bs) as Bs is proportional to (Pdot P)^0.5. It is unclear, however, how the MSP surface magnetic field can evolve from the high fields observed in pulsars to the low MSP values. Two models have been proposed to explain this. Also, the origin of the high energy emission is unclear as too few MSP X-ray observations have been made to differentiate between competing models. With these XMM-Newton observations of four MSPs previously unobserved in X-rays, we will discriminate between differing models describing the magnetic field evolution and the high energy emission origin.

  17. Discovery of a Redback Millisecond Pulsar Candidate: 3FGL J0212.1+5320

    CERN Document Server

    Li, Kwan-Lok; Hou, Xian; Mao, Jirong; Strader, Jay; Chomiuk, Laura; Tremou, Evangelia

    2016-01-01

    We present a multi-wavelength study of the unidentified Fermi object, 3FGL J0212.1+5320. Within the 95% error ellipse, Chandra detects a bright X-ray source, which has a low-mass optical counterpart (M 64% of the Roche-lobe. Spectroscopic data taken in 2015 from the Lijiang observatory show no evidence of strong emission lines, revealing the accretion is currently inactive (the pulsar state). While the X-ray luminosity and the X-ray-to-gamma-ray flux ratio are both high that are comparable to that of the two known gamma-ray transitional millisecond pulsars, 3FGL J0212.1+5320 could be a promising target to search for future transition to the accretion active state.

  18. X-ray Counterparts of Millisecond Pulsars in Globular Clusters

    CERN Document Server

    Becker, W; Prinz, T

    2010-01-01

    We have systematically studied the X-ray emission properties of globular cluster millisecond pulsars in order to evaluate their spectral properties and luminosities in a uniform way. Cross-correlating the radio timing positions of the cluster pulsars with the high resolution Chandra images revealed 31 X-ray counterparts identified in nine different globular cluster systems, including those in 47 Tuc. Timing analysis has been performed for all sources corresponding to the temporal resolution available in the archival Chandra data. Making use of unpublished data on M28, M4 and NGC 6752 allowed us to obtain further constraints for the millisecond pulsar counterparts located in these clusters. Counting rate and energy flux upper limits were computed for those 36 pulsars for which no X-ray counterparts could be detected. Comparing the X-ray and radio pulse profiles of PSR J1821-2452 in M28 and the 47 Tuc pulsars PSR J0024-7204D,O,R indicated some correspondence between both wavebands. The X-ray efficiency of the g...

  19. An eclipsing millisecond pulsar in the globular cluster Terzan 5

    International Nuclear Information System (INIS)

    We have discovered an eclipsing binary millisecond pulsar in the globular cluster Terzan 5. This, the second known eclipsing binary pulsar after PSR1957+20, has a pulse period of 11.56 ms and a very short orbital period of 1.8 hours. In contrast to PSR1957+20, where the eclipses occupy about 10 per cent of the orbital period, the eclipse duration in this pulsar is very variable and never less than one-third of the orbital period. The pulsar is in a circular orbit of radius 0.11 light seconds, which implies a minimum companion mass of 0.089 solar masses, about four times the companion mass of PSR1957+20. Timing observations suggest an identification of the pulsar with a variable continuum source located about 30 arcsec west of the cluster centre. These observations and the variable eclipse duration show that the eclipse is due to absorption or scattering in a tenuous wind which flows from the companion star. We have also detected a second pulsar in the direction of Terzan 5. This pulsar, which has a period of 442 ms, may also be a cluster member, but is more likely to be a foreground object. (author)

  20. ON DETECTING MILLISECOND PULSARS AT THE GALACTIC CENTER

    Energy Technology Data Exchange (ETDEWEB)

    Macquart, Jean-Pierre [ICRAR/Curtin University, Curtin Institute of Radio Astronomy, Perth WA 6845 (Australia); Kanekar, Nissim, E-mail: J.Macquart@curtin.edu.au [Swarnajayanti Fellow, National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Ganeshkhind, Pune-411007 (India)

    2015-06-01

    The lack of detected pulsars at the Galactic Center (GC) region is a long-standing mystery. We argue that the high stellar density in the central parsec around the GC is likely to result in a pulsar population dominated by millisecond pulsars (MSPs), similar to the situation in globular cluster environments. Earlier GC pulsar searches have been largely insensitive to such an MSP population, accounting for the lack of pulsar detections. We estimate the best search frequency for such an MSP population with present and upcoming broad-band radio telescopes for two possible scattering scenarios, the “weak-scattering” case suggested by the recent detection of a magnetar close to the GC, and the “strong-scattering” case, with the scattering screen located close to the GC. The optimal search frequencies are ≈8 GHz (weak-scattering) and ≈25 GHz (strong-scattering), for pulsars with periods 1–20 ms, assuming that GC pulsars have a luminosity distribution similar to that those in the rest of the Milky Way. We find that 10–30 hr integrations with the Very Large Array and the Green Bank Telescope would be sufficient to detect MSPs at the GC distance in the weak-scattering case. However, if the strong-scattering case is indeed applicable to the GC, observations with the full Square Kilometre Array would be needed to detect the putative MSP population.

  1. Microarcsecond VLBI pulsar astrometry with PSRPI I. Two binary millisecond pulsars with white dwarf companions

    CERN Document Server

    Deller, A T; Kaplan, D L; Goss, W M; Brisken, W F; Chatterjee, S; Cordes, J M; Janssen, G H; Lazio, T J W; Petrov, L; Stappers, B W; Lyne, A

    2016-01-01

    Model-independent distance constraints to binary millisecond pulsars (MSPs) are of great value to both the timing observations of the radio pulsars, and multiwavelength observations of their companion stars. Very Long Baseline Interferometry (VLBI) astrometry can be employed to provide these model-independent distances with very high precision via the detection of annual geometric parallax. Using the Very Long Baseline Array, we have observed two binary millisecond pulsars, PSR J1022+1001 and J2145-0750, over a two-year period and measured their distances to be 700 +14 -10 pc and 613 +16 -14 pc respectively. We use the well-calibrated distance in conjunction with revised analysis of optical photometry to tightly constrain the nature of their massive (M ~ 0.85 Msun) white dwarf companions. Finally, we show that several measurements of their parallax and proper motion obtained by pulsar timing array projects are incorrect, and investigate possible causes for the discrepancy.

  2. The implications of a companion enhanced wind on millisecond pulsar production

    Science.gov (United States)

    Smedley, Sarah L.; Tout, Christopher A.; Ferrario, Lilia; Wickramasinghe, Dayal T.

    2016-09-01

    The most frequently seen binary companions to millisecond pulsars (MSPs) are helium white dwarfs (He WDs). The standard rejuvenation mechanism, in which a low- to intermediate-mass companion to a neutron star fills its Roche lobe between central hydrogen exhaustion and core helium ignition, is the most plausible formation mechanism. We have investigated whether the observed population can realistically be formed via this mechanism. We used the Cambridge STARS code to make models of Case B RLOF with Reimers' mass loss from the donor. We find that the range of initial orbital periods required to produce the currently observed range of orbital periods of MSPs is extremely narrow. To reduce this fine tuning, we introduce a companion enhanced wind (CEW) that strips the donor of its envelope more quickly so that systems can detach at shorter periods. Our models indicate that the fine tuning can be significantly reduced if a CEW is active. Because significant mass is lost owing to a CEW we expect some binary pulsars to accrete less than the 0.1 M_{⊙} needed to spin them up to millisecond periods. This can account for mildly recycled pulsars present along the entire Mc-Porb relation. Systems with P_spin > 30 ms are consistent with this but too few of these mildly recycled pulsars have yet been observed to make a significant comparison.

  3. A millisecond pulsar in an extremely wide binary system

    CERN Document Server

    Bassa, C G; Stappers, B W; Tauris, T M; Wevers, T; Jonker, P G; Lentati, L; Verbiest, J P W; Desvignes, G; Graikou, E; Guillemot, L; Freire, P C C; Lazarus, P; Caballero, R N; Champion, D J; Cognard, I; Jessner, A; Jordan, C; Karuppusamy, R; Kramer, M; Lazaridis, K; Lee, K J; Liu, K; Lyne, A G; McKee, J; Oslowski, S; Perrodin, D; Sanidas, S; Shaifullah, G; Smits, R; Theureau, G; Tiburzi, C; Zhu, W W

    2016-01-01

    We report on 22 yrs of radio timing observations of the millisecond pulsar J1024$-$0719 by the telescopes participating in the European Pulsar Timing Array (EPTA). These observations reveal a significant second derivative of the pulsar spin frequency and confirm the discrepancy between the parallax and Shklovskii distances that has been reported earlier. We also present optical astrometry, photometry and spectroscopy of 2MASS J10243869$-$0719190. We find that it is a low-metallicity main-sequence star (K7V spectral type, $\\mathrm{[M/H]}=-1.0$, $T_\\mathrm{eff}=4050\\pm50$ K) and that its position, proper motion and distance are consistent with those of PSR J1024$-$0719. We conclude that PSR J1024$-$0719 and 2MASS J10243869$-$0719190 form a common proper motion pair and are gravitationally bound. The gravitational interaction between the main-sequence star and the pulsar accounts for the spin frequency derivatives, which in turn resolves the distance discrepancy. Our observations suggest that the pulsar and main...

  4. Three Millisecond Pulsars in Fermi LAT Unassociated Bright Sources

    Science.gov (United States)

    Ransom, S. M.; Ray, P. S.; Camilo, F.; Roberts, M. S. E.; Celik, O.; Wolff, M. T.; Cheung, C. C.; Kerr, M.; Pennucci, T.; DeCesar, M. E.; Cognard, I.; Lyne, A. G.; Stappers, B. W.; Freire, P. C. C.; Grove, J. E.; Abdo, A. A.; Desvignes, G.; Donato, D.; Ferrara, E. C.; Gehrels, N.; Guillemot, L.; Gwon, C.; Johnston, S.; Harding, A. K.; Thompson, D. J.

    2010-01-01

    We searched for radio pulsars in 25 of the non-variable, unassociated sources in the Fermi LAT Bright Source List with the Green Bank Telescope at 820 MHz. We report the discovery of three radio and gamma-ray millisecond pulsar (MSPs) from a high Galactic latitude subset of these sources. All of the pulsars are in binary systems, which would have made them virtually impossible to detect in blind gamma-ray pulsation searches. They seem to be relatively normal, nearby (<= 2 kpc) MSPs. These observations, in combination with the Fermi detection of gamma-rays from other known radio MSPs, imply that most, if not all, radio MSPs are efficient gamma-ray producers. The gamma-ray spectra of the pulsars are power law in nature with exponential cutoffs at a few Ge V, as has been found with most other pulsars. The MSPs have all been detected as X-ray point sources. Their soft X-ray luminosities of approx 10(exp 30) - 10(exp 31) erg/s are typical of the rare radio MSPs seen in X-rays.

  5. ON THE FORMATION OF ECCENTRIC MILLISECOND PULSARS WITH HELIUM WHITE-DWARF COMPANIONS

    Energy Technology Data Exchange (ETDEWEB)

    Antoniadis, John, E-mail: antoniadis@dunlap.utoronto.ca [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Dunlap Institute for Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, Ontario M5S 3H4 (Canada)

    2014-12-20

    Millisecond pulsars (MSPs) orbiting helium white dwarfs (WDs) in eccentric orbits challenge the established binary-evolution paradigm that predicts efficient orbital circularization during the mass-transfer episode that spins up the pulsar. Freire and Tauris recently proposed that these binary MSPs may instead form from the rotationally delayed accretion-induced collapse of a massive WD. However, their hypothesis predicts that eccentric systems preferably host low-mass pulsars and travel with small systemic velocities—in tension with new observational constraints. Here, I show that a substantial growth in eccentricity may alternatively arise from the dynamical interaction of the binary with a circumbinary disk. Such a disk may form from ejected donor material during hydrogen flash episodes, when the neutron star is already an active radio pulsar and tidal forces can no longer circularize the binary. I demonstrate that a short-lived (10{sup 4}-10{sup 5} yr) disk can result in eccentricities of e ≅ 0.01-0.15 for orbital periods between 15 and 50 days. Finally, I propose that, more generally, the disk hypothesis may explain the lack of circular binary pulsars for the aforementioned orbital-period range.

  6. ON THE FORMATION OF ECCENTRIC MILLISECOND PULSARS WITH HELIUM WHITE-DWARF COMPANIONS

    International Nuclear Information System (INIS)

    Millisecond pulsars (MSPs) orbiting helium white dwarfs (WDs) in eccentric orbits challenge the established binary-evolution paradigm that predicts efficient orbital circularization during the mass-transfer episode that spins up the pulsar. Freire and Tauris recently proposed that these binary MSPs may instead form from the rotationally delayed accretion-induced collapse of a massive WD. However, their hypothesis predicts that eccentric systems preferably host low-mass pulsars and travel with small systemic velocities—in tension with new observational constraints. Here, I show that a substantial growth in eccentricity may alternatively arise from the dynamical interaction of the binary with a circumbinary disk. Such a disk may form from ejected donor material during hydrogen flash episodes, when the neutron star is already an active radio pulsar and tidal forces can no longer circularize the binary. I demonstrate that a short-lived (104-105 yr) disk can result in eccentricities of e ≅ 0.01-0.15 for orbital periods between 15 and 50 days. Finally, I propose that, more generally, the disk hypothesis may explain the lack of circular binary pulsars for the aforementioned orbital-period range

  7. On the Formation of Eccentric Millisecond Pulsars with Helium White-dwarf Companions

    Science.gov (United States)

    Antoniadis, John

    2014-12-01

    Millisecond pulsars (MSPs) orbiting helium white dwarfs (WDs) in eccentric orbits challenge the established binary-evolution paradigm that predicts efficient orbital circularization during the mass-transfer episode that spins up the pulsar. Freire & Tauris recently proposed that these binary MSPs may instead form from the rotationally delayed accretion-induced collapse of a massive WD. However, their hypothesis predicts that eccentric systems preferably host low-mass pulsars and travel with small systemic velocities—in tension with new observational constraints. Here, I show that a substantial growth in eccentricity may alternatively arise from the dynamical interaction of the binary with a circumbinary disk. Such a disk may form from ejected donor material during hydrogen flash episodes, when the neutron star is already an active radio pulsar and tidal forces can no longer circularize the binary. I demonstrate that a short-lived (104-105 yr) disk can result in eccentricities of e ~= 0.01-0.15 for orbital periods between 15 and 50 days. Finally, I propose that, more generally, the disk hypothesis may explain the lack of circular binary pulsars for the aforementioned orbital-period range.

  8. High-Energy Emission at Shocks in Millisecond Pulsar Binaries

    Science.gov (United States)

    Kust Harding, Alice; Wadiasingh, Zorawar; Venter, Christo; Boettcher, Markus

    2016-04-01

    A large number of new Black Widow (BW) and Redback (RB) energetic millisecond pulsars have been discovered through radio searches of unidentified Fermi sources, increasing the known number of these systems from 4 to 28. We model the high-energy emission components from particles accelerated to several TeV in intrabinary shocks in BW and RB systems, and their predicted modulation at the binary orbital period. Synchrotron emission is expected at X-ray energies and such modulated emission has already been detected by Chandra and XMM. Inverse Compton emission from accelerated particles scattering the UV emission from the radiated companion star is expected in the Fermi and TeV bands. Detections or constraints on this emission will probe the unknown physics of pulsar winds.

  9. BOOK REVIEW: Rotation and Accretion Powered Pulsars

    Science.gov (United States)

    Kaspi, V. M.

    2008-03-01

    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 astrophysical applications. These range from Nobel-celebrated testing of general relativity in the strong-field regime to constraining the equation-of-state of ultradense matter; from probing the winds of massive stars to globular cluster evolution. Previous notable books on the subject of pulsars have tended to focus on some particular topic in the field. The classic text Pulsars by Manchester and Taylor (1977 San Francisco, CA: Freeman) targeted almost exclusively rotation-powered radio pulsars, while the Mészáros book High-Energy Radiation from Magnetized Neutron Stars (1992 Chicago, IL: University of Chicago Press) considered both rotation- and accretion-powered neutron stars, but focused on their radiation at x-ray energies and above. The recent book Neutron Stars 1 by Haensel et al (2007 Berlin: Springer) considers only the equation of state and neutron-star structure. Into this context appears Rotation and Accretion Powered Pulsars, by Pranab Ghosh. In contrast to other books, here the author takes an encyclopedic approach and attempts to synthesize practically all of the major aspects of the two main types of neutron star. This is ambitious. The only comparable undertaking is the useful but more elementary Lyne and Graham-Smith text Pulsar Astronomy (1998 Cambridge: Cambridge University Press), or Compact Stellar X-ray Sources (eds Lewin and van der Klis, 2006 Cambridge: Cambridge University Press), an anthology of technical review articles that also includes black hole topics. Rotation and Accretion Powered Pulsars thus fills a clear void in the field, providing a readable, graduate-level book that covers nearly everything you

  10. A Survey for Millisecond Pulsars and Fast Transients in the Large Magellanic Cloud

    Science.gov (United States)

    Crawford, Fronefield; Lorimer, D.; Ridley, J.; Madden, J.

    2013-01-01

    We report on a new survey for radio pulsars in the Large Magellanic Cloud (LMC) using the Parkes 64-m telescope. The survey uses the 1400 MHz multibeam receiver and the Berkeley Parkes Swinburne Recorder (BPSR) high-resolution backend. This survey has unprecedented sensitivity to millisecond pulsars and short-duration transients in the LMC. The goals of the survey include discovering new source populations (including the first extragalactic millisecond pulsar), probing the high-end of the pulsar luminosity function, and investigating how star formation differences between the LMC and the Milky Way affect the LMC pulsar population. To date about 20% of the survey area has been observed, and those data have been searched for single pulses and partially searched for accelerated pulsars over a wide range of trial dispersions. We have discovered three new pulsars in the survey so far, and we have several new millisecond pulsar candidates and transient sources that await confirmation.

  11. The birth of radio millisecond pulsars and their high-energy signature

    CERN Document Server

    Tam, P H T; Kong, A K H; Takata, J; Leung, G C K; Cheng, K S; Hui, C Y

    2014-01-01

    Millisecond pulsars (MSPs) are thought to born in low-mass X-ray binaries when the neutron star has gained enough angular momentum from the accreting materials of its companion star. It is generally believed that a radio MSP is born when the neutron star stops accreting and enters a rotation-powered state. Exactly what happens during the transition time was poorly understood until a year ago. In the past year, observations have revealed a few objects that not only switched from one state to the other (as predicted in the above picture), but also have swung between the two states within weeks to years. In this work, we present observations of two of these transition objects (PSR J1023+0038 and XSS J12270-4859) and a theoretical framework that tries to explain their high-energy radiation.

  12. On the formation of eccentric millisecond pulsars with helium white-dwarf companions

    CERN Document Server

    Antoniadis, John

    2014-01-01

    Millisecond pulsars (MSPs) orbiting helium white-dwarfs (WD) in eccentric orbits challenge the established binary-evolution paradigm that predicts efficient orbital circularization during the mass-transfer episode that spins up the pulsar. Freire and Tauris (2014) recently proposed that these binary MSPs may instead form from the rotationally-delayed accretion-induced collapse of a massive WD. This scenario predicts that eccentric systems preferably host low-mass pulsars and travel with small systemic velocities -- in tension with new observational constraints. Here, I show that a substantial growth in eccentricity may alternatively arise from the dynamical interaction of the binary with a circumbinary disk. Such a disk may form from ejected donor material during hydrogen flash episodes, when the neutron star is already an active radio pulsar and tidal forces can no longer circularize the binary. I demonstrate that a short-lived (10^4-10^5 yrs disk can result to eccentricities of e ~ 0.01-0.15 for orbital per...

  13. Cyclic spectroscopy of the millisecond pulsar, B1937+21

    Energy Technology Data Exchange (ETDEWEB)

    Walker, Mark A. [Manly Astrophysics, 3/22 Cliff Street, Manly 2095 (Australia); Demorest, Paul B. [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States); Van Straten, Willem, E-mail: Mark.Walker@manlyastrophysics.org, E-mail: pdemores@nrao.edu, E-mail: willem@swin.edu.au [Swinburne University of Technology, Astrophysics and Supercomputing, Hawthorn 3122 (Australia)

    2013-12-20

    Cyclic spectroscopy is a signal processing technique that was originally developed for engineering applications and has recently been introduced into the field of pulsar astronomy. It is a powerful technique with many attractive features, not least of which is the explicit rendering of information about the relative phases in any filtering imposed on the signal, thus making holography a more straightforward proposition. Here we present methods for determining optimum estimates of both the filter itself and the statistics of the unfiltered signal, starting from a measured cyclic spectrum. In the context of radio pulsars these quantities tell us the impulse response of the interstellar medium (ISM) and the intrinsic pulse profile. We demonstrate our techniques by application to 428 MHz Arecibo data on the millisecond pulsar B1937+21, obtaining the pulse profile free from the effects of interstellar scattering. As expected, the intrinsic profile exhibits main- and inter-pulse components that are narrower than they appear in the scattered profile; it also manifests some weak, but sharp, features that are revealed for the first time at low frequency. We determine the structure of the received electric field envelope as a function of delay and Doppler shift. Our delay Doppler image has a high dynamic range and displays some pronounced, low-level power concentrations at large delays. These concentrations imply strong clumpiness in the ionized ISM, on AU-size scales, which must adversely affect the timing of B1937+21.

  14. Timing of Five PALFA-Discovered Millisecond Pulsars

    CERN Document Server

    Stovall, K; Bogdanov, S; Brazier, A; Camilo, F; Cardoso, F; Chatterjee, S; Cordes, J M; Crawford, F; Deneva, J S; Ferdman, R; Freire, P C C; Hessels, J W T; Jenet, F; Kaplan, D L; Karako-Argaman, C; Kaspi, V M; Knispel, B; Kotulla, R; Lazarus, P; Lee, K J; van Leeuwen, J; Lynch, R; Lyne, A G; Madsen, E; McLaughlin, M A; Patel, C; Ransom, S M; Scholz, P; Siemens, X; Stairs, I H; Stappers, B W; Swiggum, J; Zhu, W W; Venkataraman, A

    2016-01-01

    We report the discovery and timing results for five millisecond pulsars (MSPs) from the Arecibo PALFA survey: PSRs J1906+0055, J1914+0659, J1933+1726, J1938+2516, and J1957+2516. Timing observations of the 5 pulsars were conducted with the Arecibo and Lovell telescopes for time spans ranging from 1.5 to 3.3 yr. All of the MSPs except one (PSR J1914+0659) are in binary systems with low eccentricities. PSR J1957+2516 is likely a redback pulsar, with a ~0.1 $M_\\odot$ companion and possible eclipses that last ~10% of the orbit. The position of PSR J1957+2516 is also coincident with a NIR source. All 5 MSPs are distant (>3.1 kpc) as determined from their dispersion measures, and none of them show evidence of $\\gamma$-ray pulsations in a search of Fermi Gamma-Ray Space Telescope data. These 5 MSPs bring the total number of MSPs discovered by the PALFA survey to 26 and further demonstrate the power of this survey in finding distant, highly dispersed MSPs deep in the Galactic plane.

  15. Timing of five millisecond pulsars discovered in the PALFA survey

    CERN Document Server

    Scholz, P; Lyne, A G; Stappers, B W; Bogdanov, S; Cordes, J M; Crawford, F; Ferdman, R D; Freire, P C C; Hessels, J W T; Lorimer, D R; Stairs, I H; Allen, B; Brazier, A; Camilo, F; Cardoso, R F; Chatterjee, S; Deneva, J S; Jenet, F A; Karako-Argaman, C; Knispel, B; Lazarus, P; Lee, K J; van Leeuwen, J; Lynch, R; Madsen, E C; McLaughlin, M A; Ransom, S M; Siemens, X; Spitler, L G; Stovall, K; Swiggum, J K; Venkataraman, A; Zhu, W W

    2015-01-01

    We present the discovery of five millisecond pulsars (MSPs) from the PALFA Galactic plane survey using Arecibo. Four of these (PSRs J0557+1551, J1850+0244, J1902+0300, and J1943+2210) are binary pulsars whose companions are likely white dwarfs, and one (PSR J1905+0453) is isolated. Phase-coherent timing solutions, ranging from $\\sim$1 to $\\sim$3 years in length, and based on observations from the Jodrell Bank and Arecibo telescopes, provide precise determinations of spin, orbital, and astrometric parameters. All five pulsars have large dispersion measures ($>100$ pc cm$^{-3}$, within the top 20% of all known Galactic field MSPs) and are faint (1.4 GHz flux density < 0.1 mJy, within the faintest 5% of all known Galactic field MSPs), illustrating PALFA's ability to find increasingly faint, distant MSPs in the Galactic plane. In particular, PSR J1850+0244 has a dispersion measure of 540 pc cm$^{-3}$, the highest of all known MSPs. Such distant, faint MSPs are important input for accurately modeling the total ...

  16. TIMING OF FIVE MILLISECOND PULSARS DISCOVERED IN THE PALFA SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Scholz, P.; Kaspi, V. M.; Ferdman, R. D.; Karako-Argaman, C. [Department of Physics, McGill University, Montreal, QC H3A 2T8 (Canada); Lyne, A. G.; Stappers, B. W. [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Bogdanov, S.; Camilo, F. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Cordes, J. M.; Brazier, A.; Chatterjee, S. [Department of Astronomy, Cornell University, Ithaca, NY 14853 (United States); Crawford, F. [Department of Physics and Astronomy, Franklin and Marshall College, Lancaster, PA 17604-3003 (United States); Freire, P. C. C. [Max-Planck-Institut für Radioastronomie, D-53121 Bonn (Germany); Hessels, J. W. T. [ASTRON, Netherlands Institute for Radio Astronomy, Postbus 2, 7990-AA Dwingeloo (Netherlands); Lorimer, D. R.; Cardoso, R. F. [Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506 (United States); Stairs, I. H. [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1 (Canada); Allen, B. [Physics Department, University of Wisconsin-Milwaukee, Milwaukee, WI 53211 (United States); Deneva, J. S. [Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375 (United States); Jenet, F. A., E-mail: pscholz@physics.mcgill.ca [Center for Gravitational Wave Astronomy, University of Texas at Brownsville, TX 78520 (United States); and others

    2015-02-20

    We present the discovery of five millisecond pulsars (MSPs) from the PALFA Galactic plane survey using Arecibo. Four of these (PSRs J0557+1551, J1850+0244, J1902+0300, and J1943+2210) are binary pulsars whose companions are likely white dwarfs, and one (PSR J1905+0453) is isolated. Phase-coherent timing solutions, ranging from ∼1 to ∼3 yr in length, and based on observations from the Jodrell Bank and Arecibo telescopes, provide precise determinations of spin, orbital, and astrometric parameters. All five pulsars have large dispersion measures (>100 pc cm{sup –3}, within the top 20% of all known Galactic field MSPs) and are faint (1.4 GHz flux density ≲0.1 mJy, within the faintest 5% of all known Galactic field MSPs), illustrating PALFA's ability to find increasingly faint, distant MSPs in the Galactic plane. In particular, PSR J1850+0244 has a dispersion measure of 540 pc cm{sup –3}, the highest of all known MSPs. Such distant, faint MSPs are important input for accurately modeling the total Galactic MSP population.

  17. Ultraviolet Emission from the Millisecond Pulsar J0437-4715

    CERN Document Server

    Kargaltsev, O; Romani, R W

    2004-01-01

    We observed PSR J0437-4715 with the FUV-MAMA detector of the Hubble Space Telescope Imaging Spectrometer (STIS) to measure the pulsar's spectrum and pulsations. For the first time, UV emission from a millisecond pulsar is detected. The measured flux, $(2.0\\pm 0.2)\\times 10^{-15}$ erg s$^{-1}$ cm$^{-2}$ in the 1150-1700 \\AA range, corresponds to the luminosity $L_{\\rm FUV}=(4.7\\pm 0.5)\\times 10^{27}$ erg s$^{-1}$, for the distance of 140 pc and negligible interstellar extinction. The shape of the observed spectrum suggests thermal emission from the neutron star surface with a surprisingly high temperature of about $1\\times 10^5$ K, above the upper limit on the surface temperature of the younger ``ordinary'' pulsar J0108-1431. For the few-Gyr-old J0437-4715, such a temperature requires a heating mechanism to operate. The spectrum of J0437-4715 shows marginal evidence of an emission line at 1372 \\AA, which might be a gravitationally redshifted Zeeman component of the Hydrogen Ly$\\alpha$ line in a magnetic field ...

  18. A Mid-Infrared Search for the Outer Companion in a Millisecond Pulsar Triple System

    NARCIS (Netherlands)

    D. Kaplan; S. Ransom; I. Stairs; J. Hessels

    2012-01-01

    Only two systems with pulsars and multiple companions are known, but they offer a wealth of information about dynamics, binary evolution, and the pulsars themselves. We have recently discovered a bright new millisecond pulsar in a very exotic stellar system: a hierarchical triple system with a low-m

  19. The Parkes multibeam pulsar survey: VII. Timing of four millisecond pulsars and the underlying spin period distribution of the Galactic millisecond pulsar population

    CERN Document Server

    Lorimer, D R; Manchester, R N; Possenti, A; Lyne, A G; McLaughlin, M A; Kramer, M; Hobbs, G; Stairs, I H; Burgay, M; Eatough, R P; Keith, M J; Faulkner, A J; D'Amico, N; Camilo, F; Corongiu, A; Crawford, F

    2015-01-01

    We present timing observations of four millisecond pulsars discovered in the Parkes 20-cm multibeam pulsar survey of the Galactic plane. PSRs J1552-4937 and J1843-1448 are isolated objects with spin periods of 6.28 and 5.47 ms respectively. PSR J1727-2946 is in a 40-day binary orbit and has a spin period of 27 ms. The 4.43-ms pulsar J1813-2621 is in a circular 8.16-day binary orbit around a low-mass companion star with a minimum companion mass of 0.2 solar masses. Combining these results with detections from five other Parkes multibeam surveys, gives a well-defined sample of 56 pulsars with spin periods below 20 ms. We develop a likelihood analysis to constrain the functional form which best describes the underlying distribution of spin periods for millisecond pulsars. The best results were obtained with a log-normal distribution. A gamma distribution is less favoured, but still compatible with the observations. Uniform, power-law and Gaussian distributions are found to be inconsistent with the data. Galactic...

  20. Rotation-induced deep crustal heating of millisecond pulsars

    CERN Document Server

    Gusakov, M E; Reisenegger, A

    2015-01-01

    The spin-down of a neutron star, e.g. due to magneto-dipole losses, results in compression of the stellar matter and induces nuclear reactions at phase transitions between different nuclear species in the crust. We show that this mechanism is effective in heating recycled pulsars, in which the previous accretion process has already been compressing the crust, so it is not in nuclear equilibrium. We calculate the corresponding emissivity and confront it with available observations, showing that it might account for the likely thermal ultraviolet emission of PSR J0437-4715.

  1. Rotochemical heating in millisecond pulsars with Cooper pairing

    CERN Document Server

    Petrovich, Cristobal

    2010-01-01

    When a rotating neutron star loses angular momentum, the reduction in the centrifugal force makes it contract. This perturbs each fluid element, raising the local pressure and originating deviations from beta equilibrium that enhance the neutrino emissivity and produce thermal energy. This mechanism is named rotochemical heating and has previously been studied for neutron stars of non-superfluid matter, finding that they reach a quasi-steady state in which the rate that the spin-down modifies the equilibrium concentrations is the same to that of the neutrino reactions restoring the equilibrium. On the other hand, the neutron star interior is believed to contain superfluid nucleons, which affect the thermal evolution of the star by suppressing the neutrino reactions and the specific heat, and opening new Cooper pairing reactions. In this work we describe the thermal effects of Cooper pairing with spatially uniform energy gaps of neutrons and protons on rotochemical heating in millisecond pulsars (MSPs) when on...

  2. Millisecond newly born pulsars as efficient accelerators of electrons

    CERN Document Server

    Osmanov, Z; Machabeli, G; Chkheidze, N

    2015-01-01

    The newly born millisecond pulsars are investigated as possible energy sources for creating ultra-high energy electrons. The transfer of energy from the star rotation to high energy electrons takes place through the Landau damping of centrifugally driven (via a two stream instability) electrostatic Langmuir waves. Generated in the bulk magnetosphere plasma, such waves grow to high amplitudes, and then damp, very effectively, on relativistic electrons driving them to even higher energies. We show that the rate of transfer of energy is so efficient that no energy losses might affect the mechanism of particle acceleration; the electrons might achieve energies of the order of 10^{18}eV for parameters characteristic of a young star.

  3. The millisecond pulsar contribution to the rising positron fraction

    CERN Document Server

    Venter, Christo; Harding, Alice K; Gonthier, Peter L; Buesching, Ingo

    2015-01-01

    Pair cascades from millisecond pulsars (MSPs) may be a primary source of Galactic electrons and positrons that contribute to the increase in positron flux above 10 GeV as observed by PAMELA and AMS-02. The Fermi Large Area Telescope (LAT) has increased the number of detected gamma-ray MSPs tremendously. Light curve modelling furthermore favours abundant pair production in MSP magnetospheres, so that models of primary cosmic-ray positrons from pulsars should include the contribution from the larger numbers of MSPs and their potentially higher positron output per source. We model the contribution of Galactic MSPs to the terrestrial cosmic-ray electron / positron flux by using a population synthesis code to predict the source properties of present-day MSPs. We simulate pair spectra assuming an offset-dipole magnetic field which boosts pair creation rates. We also consider positrons and electrons that have additionally been accelerated to very high energies in the strong intrabinary shocks in black widow (BW) and...

  4. Cool white dwarf companions to four millisecond pulsars

    CERN Document Server

    Bassa, C G; Camilo, F; Cognard, I; Koester, D; Kramer, M; Ransom, S R; Stappers, B W

    2015-01-01

    We report on photometric and spectroscopic observations of white dwarf companions to four binary radio millisecond pulsars, leading to the discovery of companions to PSRs J0614-3329, J1231-1411 and J2017+0603. We place limits on the brightness of the companion to PSR J0613-0200. Optical spectroscopy of the companion to PSR J0614-3329 identifies it as a DA type white dwarf with a temperature of Teff=6460+-80 K, a surface gravity log g=7.0+-0.2 cgs and a mass of Mwd=0.24+-0.04 Msun. We find that the distance to PSR J0614-3329 is smaller than previously estimated, removing the need for the pulsar to have an unrealistically high gamma-ray efficiency. Comparing the photometry with predictions from white dwarf cooling models allows us to estimate temperatures and cooling ages of the companions to PSRs J0613-0200, J1231-1411 and J2017+0603. We find that the white dwarfs in these systems are cool Teff5 Gyr. Thin Hydrogen envelopes are required for these white dwarfs to cool to the observed temperatures, and we sugges...

  5. Searches for millisecond pulsar candidates among the unidentified Fermi objects

    CERN Document Server

    Hui, C Y; Hu, C P; Lin, L C C; Li, K L; Kong, A K H; Tam, P H T; Takata, J; Cheng, K S; Jin, Ruolan; Yen, T -C; Kim, Chunglee

    2015-01-01

    Here we report the results of searching millisecond pulsar (MSP) candidates from the Fermi LAT second source catalog (2FGL). Seven unassociated $\\gamma-$ray sources in this catalog are identified as promising MSP candidates based on their $\\gamma$-ray properties. Through the X-ray analysis, we have detected possible X-ray counterparts, localized to an arcsecond accuracy. We have systematically estimated their X-ray fluxes and compared with the corresponding $\\gamma$-ray fluxes. The X-ray to $\\gamma$-ray flux ratios for 2FGL J1653.6-0159 and 2FGL J1946.4-5402 are comparable with the typical value for pulsars. For 2FGL J1625.2-0020, 2FGL J1653.6-0159 and 2FGL J1946.4-5402, their candidate X-ray counterparts are bright enough for performing a detailed spectral and temporal analysis to discriminate their thermal/non thermal nature and search for the periodic signal. We have also searched for possible optical/IR counterparts at the X-ray positions. For the optical/IR source coincident with the brightest X-ray obje...

  6. Five and a half roads to form a millisecond pulsar

    CERN Document Server

    Tauris, Thomas M

    2011-01-01

    In this review I discuss the characteristics and the formation of all classes of millisecond pulsars (MSPs). The main focus is on the stellar astrophysics of X-ray binaries leading to the production of fully recycled MSPs with white dwarf (WD) or substellar semi-degenerate companions. Depending on the nature of the companion star MSPs are believed to form from either low-mass X-ray binaries (LMXBs) or intermediate-mass X-ray binaries (IMXBs). For each of these two classes of X-ray binaries the evolutionary status of the donor star -- or equivalently, the orbital period -- at the onset of the Roche-lobe overflow (RLO) is the determining factor for the outcome of the mass-transfer phase and thus the nature of the MSP formed. Furthermore, the formation of binary MSPs is discussed in context of the (P,P_dot)-diagram, as well as new interpretations of the Corbet diagram. Finally, I present new models of Case A RLO of IMXBs in order to reproduce the two solar mass pulsar PSR J1614-2230.

  7. How to get the reduced B fields of millisecond pulsars: Flux expulsion by spindown before the LMXB phase

    Science.gov (United States)

    Alpar, Mehmet Ali; Gügercinoǧlu, Erbil

    2016-07-01

    The physical interaction between quantized flux lines of the Type II proton superconductor and the quantized vortex lines of the neutron superfluid is re-visited. Srinivasan et al. (1990) had proposed that this interaction led to reduction of the magnetic field to the B ˜10^9 G range as the flux lines were expelled together with vortex lines during the spindown of the neutron star in an early epoch of binary evolution. The model is discussed with reference to spindown by the wind from the companion prior to the Roche lobe filling LMXB phase. An evolutionary model for the magnetic field and the rotation rate is presented, with application to the 11 Hz accreting pulsar in the LMXB IGR J17480-2446 in Terzan 5 (Patruno et al 2012) as well as 'standard' accreting and radio millisecond pulsar evolution.

  8. High-precision baseband timing of 15 millisecond pulsars

    Science.gov (United States)

    Hotan, A. W.; Bailes, M.; Ord, S. M.

    2006-07-01

    We describe extremely precise timing experiments performed on five solitary and 10 binary millisecond pulsars during the past 3 yr, with the Caltech Parkes Swinburne Recorder (CPSR2) coherent dedispersion system at the Parkes 64-m radio telescope. 12 of our sources have rms timing residuals below 1.5μs and four are below 200ns. The quality of our data allows us to measure eight parallaxes and nine proper motions, from which we conclude that models of galactic electron density still have limited predictive power for individual objects. We derive a mean transverse velocity of 87+31/-14kms-1 for these pulsars, in good agreement with previous authors. We demonstrate that unless multifrequency observations are made, typical variations in dispersion measure (DM) could introduce an additional drift in arrival times of ~1μs per year at 20-cm wavelengths. Our high timing precision means that Shapiro delay can be used to constrain the inclination angles and component masses of all but two of the selected binary systems. The signature of annual orbital parallax is detected in the timing of PSR J0437-4715 and PSR J1713+0747, providing additional geometric constraints. The timing of PSR J1909-3744 is used to demonstrate that the DE405 ephemeris is a better model of the Solar system than the earlier DE200. In addition, we show that pulsar astrometric parameters measured using DE200 and DE405 often differ significantly. In order to use pulsars to search for a cosmological gravitational wave background, it is desirable to time them against each other to eliminate Earth-based time standards. We demonstrate that PSR J1909-3744 can be used as a reference against which we obtain a very small rms residual of 133ns for PSR J1713+0747. Although the gain of the Parkes antenna is small compared to other telescopes involved in precision timing, we obtain some of the lowest rms residuals ever measured, highlighting the importance of good instrumentation such as CPSR2 and good analysis

  9. The Contribution of Millisecond Pulsars to the Galactic Cosmic-Ray Lepton Spectrum

    CERN Document Server

    Venter, C; Gonthier, P L; Harding, A K; Büsching, I

    2014-01-01

    Pulsars are believed to be sources of relativistic electrons and positrons. The abundance of detections of gamma-ray millisecond pulsars by Fermi Large Area Telescope coupled with their light curve characteristics that imply copious pair production in their magnetospheres, motivated us to investigate this old pulsar population as a source of Galactic electrons and positrons and their contribution to the enhancement in cosmic-ray positron flux at GeV energies. We use a population synthesis code to predict the source properties (number, position, and power) of the present-day Galactic millisecond pulsars, taking into account the latest Fermi and radio observations to calibrate the model output. Next, we simulate pair cascade spectra from these pulsars using a model that invokes an offset-dipole magnetic field. We assume free escape of the pairs from the pulsar environment. We then compute the cumulative spectrum of transported electrons and positrons at Earth, following their diffusion and energy losses as they...

  10. The NANOGrav Nine-Year Data Set: Excess Noise in Millisecond Pulsar Arrival Times

    CERN Document Server

    Lam, M T; Chatterjee, S; Arzoumanian, Z; Crowter, K; Demorest, P B; Dolch, T; Ellis, J A; Ferdman, R D; Fonseca, E; Gonzalez, M E; Jones, G; Jones, M L; Levin, L; Madison, D R; McLaughlin, M A; Nice, D J; Pennucci, T T; Ransom, S M; Shannon, R M; Siemens, X; Stairs, I H; Stovall, K; Swiggum, J K; Zhu, W W

    2016-01-01

    Gravitational wave astronomy using a pulsar timing array requires high-quality millisecond pulsars, correctable interstellar propagation delays, and high-precision measurements of pulse times of arrival. Here we identify noise in timing residuals that exceeds that predicted for arrival time estimation for millisecond pulsars observed by the North American Nanohertz Observatory for Gravitational Waves. We characterize the excess noise using variance and structure function analyses. We find that 26 out of 37 pulsars show inconsistencies with a white-noise-only model based on the short timescale analysis of each pulsar and we demonstrate that the excess noise has a red power spectrum for 15 pulsars. We also decompose the excess noise into chromatic (radio-frequency-dependent) and achromatic components. Associating the achromatic red-noise component with spin noise and including additional power-spectrum-based estimates from the literature, we estimate a scaling law in terms of spin parameters (frequency and freq...

  11. Identification of candidate millisecond pulsars from Fermi LAT observations

    Science.gov (United States)

    Dai, Xue-Jie; Wang, Zhong-Xiang; Vadakkumthani, Jithesh; Xing, Yi

    2016-06-01

    We report our detailed data analysis of 39 γ-ray sources selected from the 992 unassociated sources in the third Fermi Large Area Telescope Third Source Catalog. The selection criteria, which were set for finding candidate millisecond pulsars (MSPs), are non-variables with curved spectra and >5° Galactic latitudes. From our analysis, 24 sources were found to be point-like sources not contaminated by background or nearby unknown sources. Three of them, J1544.6–1125, J1625.1–0021 and J1653.6–0158, have been previously studied, indicating that they are likely MSPs. The spectra of J0318.1+0252 and J2053.9+2922 do not have properties similar to known γ-ray MSPs, and we thus suggest that they are not MSPs. Analysis of archival X-ray data for most of the 24 sources was also conducted. Four sources were found with X-ray objects in their error circles, and 16 with no detection. The ratios between the γ-ray fluxes and X-ray fluxes or flux upper limits are generally lower than those of known γ-ray MSPs, suggesting that if the γ-ray sources are MSPs, none of the X-ray objects are their counterparts. Deep X-ray or radio observations of these sources are needed in order to identify their MSP nature.

  12. Identification of Candidate Millisecond Pulsars from Fermi LAT Observations

    CERN Document Server

    Dai, Xuejie; Jithesh, V; Xing, Yi

    2016-01-01

    We report our detailed data analysis for 39 $\\gamma$-ray sources selected from the 992 unassociated sources in the \\textit{Fermi} Large Area Telescope (LAT) third source catalog. The selection criteria, which were set for finding candidate millisecond pulsars (MSPs), are non-variables with curved spectra and $>$5$^{\\circ}$ Galactic latitudes. From our analysis, 24 sources were found to be point-like sources not contaminated by background or nearby unknown sources. Three of them, J1544.6$-$1125, J1625.1$-$0021, and J1653.6$-$0158, have been previously studied, indicating that they are likely MSPs. The spectra of J0318.1+0252 and J2053.9+2922 do not have properties similar to that of known $\\gamma$-ray MSPs, and we thus suggest that they are not MSPs. Analysis of archival X-ray data for most of the 24 sources were also conducted. Four sources were found with X-ray objects in their error circles, and 16 with no detection. The ratios between the $\\gamma$-ray fluxes and X-ray fluxes or flux upper limits are genera...

  13. Optical Identification of He White Dwarfs Orbiting Four Millisecond Pulsars in the Globular Cluster 47 Tucanae

    CERN Document Server

    Cadelano, M; Ferraro, F R; Salaris, M; Dalessandro, E; Lanzoni, B; Freire, P C C

    2015-01-01

    We used ultra-deep UV observations obtained with the Hubble Space Telescope to search for optical companions to binary millisecond pulsars (MSPs) in the globular cluster 47 Tucanae. We identified four new counterparts (to MSPs 47TucQ, 47TucS, 47TucT and 47TucY) and confirmed those already known (to MSPs 47TucU and 47TucW). In the color magnitude diagram, the detected companions are located in a region between the main sequence and the CO white dwarf cooling sequences, consistent with the cooling tracks of He white dwarfs of mass between 0.15 Msun and 0.20 Msun. For each identified companion, mass, cooling age, temperature and pulsar mass (as a function of the inclination angle) have been derived and discussed. For 47TucU we also found that the past accretion history likely proceeded in a sub-Eddington rate. The companion to the redback 47TucW is confirmed to be a non degenerate star, with properties particularly similar to those observed for black widow systems. Two stars have been identified within the 2-sig...

  14. High-precision timing of 42 millisecond pulsars with the European Pulsar Timing Array

    CERN Document Server

    Desvignes, G; Lentati, L; Verbiest, J P W; Champion, D J; Stappers, B W; Janssen, G H; Lazarus, P; Osłowski, S; Babak, S; Bassa, C G; Brem, P; Burgay, M; Cognard, I; Gair, J R; Graikou, E; Guillemot, L; Hessels, J W T; Jessner, A; Jordan, C; Karuppusamy, R; Kramer, M; Lassus, A; Lazaridis, K; Lee, K J; Liu, K; Lyne, A G; McKee, J; Mingarelli, C M F; Perrodin, D; Petiteau, A; Possenti, A; Purver, M B; Rosado, P A; Sanidas, S; Sesana, A; Shaifullah, G; Smits, R; Taylor, S R; Theureau, G; Tiburzi, C; van Haasteren, R; Vecchio, A

    2016-01-01

    We report on the high-precision timing of 42 radio millisecond pulsars (MSPs) observed by the European Pulsar Timing Array (EPTA). This EPTA Data Release 1.0 extends up to mid-2014 and baselines range from 7-18 years. It forms the basis for the stochastic gravitational-wave background, anisotropic background, and continuous-wave limits recently presented by the EPTA elsewhere. The Bayesian timing analysis performed with TempoNest yields the detection of several new parameters: seven parallaxes, nine proper motions and, in the case of six binary pulsars, an apparent change of the semi-major axis. We find the NE2001 Galactic electron density model to be a better match to our parallax distances (after correction from the Lutz-Kelker bias) than the M2 and M3 models by Schnitzeler (2012). However, we measure an average uncertainty of 80\\% (fractional) for NE2001, three times larger than what is typically assumed in the literature. We revisit the transverse velocity distribution for a set of 19 isolated and 57 bina...

  15. Einstein@Home DISCOVERY OF A PALFA MILLISECOND PULSAR IN AN ECCENTRIC BINARY ORBIT

    Energy Technology Data Exchange (ETDEWEB)

    Knispel, B.; Allen, B. [Leibniz Universität, Hannover, D-30167 Hannover (Germany); Lyne, A. G.; Stappers, B. W. [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester, M13 9PL (United Kingdom); Freire, P. C. C.; Lazarus, P. [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Aulbert, C.; Bock, O.; Eggenstein, H.-B.; Fehrmann, H. [Max-Planck-Institut für Gravitationsphysik, Callinstr. 38, D-30167 Hannover (Germany); Bogdanov, S.; Camilo, F. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Brazier, A.; Chatterjee, S.; Cordes, J. M. [Department of Astronomy and Center for Radiophysics and Space Research, Cornell University, Ithaca, NY 14853 (United States); Cardoso, F. [Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506 (United States); Crawford, F. [Department of Physics and Astronomy, Franklin and Marshall College, Lancaster, PA 17604-3003 (United States); Deneva, J. S. [National Research Council, resident at the Naval Research Laboratory, Washington, DC 20375 (United States); Ferdman, R. [Department of Physics, McGill University, Montreal, QC H3A 2T8 (Canada); Hessels, J. W. T., E-mail: benjamin.knispel@aei.mpg.de [ASTRON, Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA, Dwingeloo (Netherlands); and others

    2015-06-10

    We report the discovery of the millisecond pulsar (MSP) PSR J1950+2414 (P = 4.3 ms) in a binary system with an eccentric (e = 0.08) 22 day orbit in Pulsar Arecibo L-band Feed Array survey observations with the Arecibo telescope. Its companion star has a median mass of 0.3 M{sub ⊙} and is most likely a white dwarf (WD). Fully recycled MSPs like this one are thought to be old neutron stars spun-up by mass transfer from a companion star. This process should circularize the orbit, as is observed for the vast majority of binary MSPs, which predominantly have orbital eccentricities e < 0.001. However, four recently discovered binary MSPs have orbits with 0. 027 < e < 0.44; PSR J1950+2414 is the fifth such system to be discovered. The upper limits for its intrinsic spin period derivative and inferred surface magnetic field strength are comparable to those of the general MSP population. The large eccentricities are incompatible with the predictions of the standard recycling scenario: something unusual happened during their evolution. Proposed scenarios are (a) initial evolution of the pulsar in a triple system which became dynamically unstable, (b) origin in an exchange encounter in an environment with high stellar density, (c) rotationally delayed accretion-induced collapse of a super-Chandrasekhar WD, and (d) dynamical interaction of the binary with a circumbinary disk. We compare the properties of all five known eccentric MSPs with the predictions of these formation channels. Future measurements of the masses and proper motion might allow us to firmly exclude some of the proposed formation scenarios.

  16. DISCOVERY OF TWO MILLISECOND PULSARS IN FERMI SOURCES WITH THE NANCAY RADIO TELESCOPE

    International Nuclear Information System (INIS)

    We report the discovery of two millisecond pulsars in a search for radio pulsations at the positions of Fermi-Large Area Telescope sources with no previously known counterparts, using the Nancay Radio Telescope. The two millisecond pulsars, PSRs J2017+0603 and J2302+4442, have rotational periods of 2.896 and 5.192 ms and are both in binary systems with low-eccentricity orbits and orbital periods of 2.2 and 125.9 days, respectively, suggesting long recycling processes. Gamma-ray pulsations were subsequently detected for both objects, indicating that they power the associated Fermi sources in which they were found. The gamma-ray light curves and spectral properties are similar to those of previously detected gamma-ray millisecond pulsars. Detailed modeling of the observed radio and gamma-ray light curves shows that the gamma-ray emission seems to originate at high altitudes in their magnetospheres. Additionally, X-ray observations revealed the presence of an X-ray source at the position of PSR J2302+4442, consistent with thermal emission from a neutron star. These discoveries along with the numerous detections of radio-loud millisecond pulsars in gamma rays suggest that many Fermi sources with no known counterpart could be unknown millisecond pulsars.

  17. The accretion flow to the intermittent accreting ms pulsar, HETE J1900.1-2455, as observed by XMM-Newton and RXTE

    OpenAIRE

    Papitto, A.; D'Aì, A.; T. Di Salvo; Egron, E.; Bozzo, E.; Burderi, L.; Iaria, R.; Riggio, A.; Menna, M. T.

    2012-01-01

    We present a study of the accretion flow to the intermittent accreting millisecond pulsar, HETE J1900.1-2455, based on observations performed simultaneously by XMM-Newton and RXTE. The 0.33-50 keV spectrum is described by the sum of a hard Comptonized component originated in an optically thin {\\tau}~1 corona, a soft kTin~0.2 keV component interpreted as accretion disc emission, and of disc reflection of the hard component. Two emission features are detected at energies of 0.98(1) and 6.58(7) ...

  18. Prospects for Neutron Star Equation of State Constraints using "Recycled" Millisecond Pulsars

    CERN Document Server

    Bogdanov, Slavko

    2015-01-01

    Rotation-powered "recycled" millisecond pulsars are a variety of rapidly-spinning neutron stars that typically show thermal X-ray radiation due to the heated surface of their magnetic polar caps. Detailed numerical modeling of the rotation-induced thermal X-ray pulsations observed from recycled millisecond pulsars, including all relevant relativistic and stellar atmospheric effects, has been identified as a promising approach towards an astrophysical determination of the true neutron star mass-radius relation, and by extension the state of cold matter at densities exceeding those of atomic nuclei. Herein, I review the basic model and methodology commonly used to extract information regarding neutron star structure from the pulsed X-ray radiation observed from millisecond pulsars. I also summarize the results of past X-ray observations of these objects and the prospects for precision neutron star mass-radius measurements with the upcoming Neutron Star Interior Composition Explorer (NICER) X-ray timing mission.

  19. The noise properties of 42 millisecond pulsars from the European Pulsar Timing Array and their impact on gravitational wave searches

    CERN Document Server

    Caballero, R N; Lentati, L; Desvignes, G; Champion, D J; Verbiest, J P W; Janssen, G H; Stappers, B W; Kramer, M; Lazarus, P; Possenti, A; Tiburzi, C; Perrodin, D; Osłowski, S; Babak, S; Bassa, C G; Brem, P; Burgay, M; Cognard, I; Gair, J R; Graikou, E; Guillemot, L; Hessels, J W T; Karuppusamy, R; Lassus, A; Liu, K; McKee, J; Mingarelli, C M F; Petiteau, A; Purver, M B; Rosado, P A; Sanidas, S; Sesana, A; Shaifullah, G; Smits, R; Taylor, S R; Theureau, G; van Haasteren, R; Vecchio, A

    2015-01-01

    The sensitivity of Pulsar Timing Arrays to gravitational waves depends critically on the noise present in the individual pulsar timing data. Noise may be either intrinsic or extrinsic to the pulsar. Intrinsic sources of noise might come from rotational instabilities, for example. Extrinsic sources of noise include contributions from physical processes which are not sufficiently well modelled, for example, dispersion and scattering effects, analysis errors and instrumental instabilities. We present the results from a noise analysis for 42 millisecond pulsars (MSPs) observed with the European Pulsar Timing Array. For characterising the low-frequency, stochastic and achromatic noise component, or "timing noise", we employ two methods, based on Bayesian and frequentist statistics. For 25 MSPs, we achieve statistically significant measurements of their timing noise parameters and find that the two methods give consistent results. For the remaining 17 MSPs, we place upper limits on the timing noise amplitude at the...

  20. A population of gamma-ray millisecond pulsars seen with the Fermi Large Area Telescope.

    Science.gov (United States)

    Abdo, A A; Ackermann, M; Ajello, M; Atwood, W B; Axelsson, M; Baldini, L; Ballet, J; Barbiellini, G; Baring, M G; Bastieri, D; Baughman, B M; Bechtol, K; Bellazzini, R; Berenji, B; Bignami, G F; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Bregeon, J; Brez, A; Brigida, M; Bruel, P; Burnett, T H; Caliandro, G A; Cameron, R A; Camilo, F; Caraveo, P A; Carlson, P; Casandjian, J M; Cecchi, C; Celik, O; Charles, E; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cognard, I; Cohen-Tanugi, J; Cominsky, L R; Conrad, J; Corbet, R; Cutini, S; Dermer, C D; Desvignes, G; de Angelis, A; de Luca, A; de Palma, F; Digel, S W; Dormody, M; do Couto e Silva, E; Drell, P S; Dubois, R; Dumora, D; Edmonds, Y; Farnier, C; Favuzzi, C; Fegan, S J; Focke, W B; Frailis, M; Freire, P C C; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giebels, B; Giglietto, N; Giordano, F; Glanzman, T; Godfrey, G; Grenier, I A; Grondin, M H; Grove, J E; Guillemot, L; Guiriec, S; Hanabata, Y; Harding, A K; Hayashida, M; Hays, E; Hobbs, G; Hughes, R E; Jóhannesson, G; Johnson, A S; Johnson, R P; Johnson, T J; Johnson, W N; Johnston, S; Kamae, T; Katagiri, H; Kataoka, J; Kawai, N; Kerr, M; Knödlseder, J; Kocian, M L; Kramer, M; Kuss, M; Lande, J; Latronico, L; Lemoine-Goumard, M; Longo, F; Loparco, F; Lott, B; Lovellette, M N; Lubrano, P; Madejski, G M; Makeev, A; Manchester, R N; Marelli, M; Mazziotta, M N; McConville, W; McEnery, J E; McLaughlin, M A; Meurer, C; Michelson, P F; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nolan, P L; Norris, J P; Nuss, E; Ohsugi, T; Omodei, N; Orlando, E; Ormes, J F; Paneque, D; Panetta, J H; Parent, D; Pelassa, V; Pepe, M; Pesce-Rollins, M; Piron, F; Porter, T A; Rainò, S; Rando, R; Ransom, S M; Ray, P S; Razzano, M; Rea, N; Reimer, A; Reimer, O; Reposeur, T; Ritz, S; Rochester, L S; Rodriguez, A Y; Romani, R W; Roth, M; Ryde, F; Sadrozinski, H F W; Sanchez, D; Sander, A; Saz Parkinson, P M; Scargle, J D; Schalk, T L; Sgrò, C; Siskind, E J; Smith, D A; Smith, P D; Spandre, G; Spinelli, P; Stappers, B W; Starck, J L; Striani, E; Strickman, M S; Suson, D J; Tajima, H; Takahashi, H; Tanaka, T; Thayer, J B; Thayer, J G; Theureau, G; Thompson, D J; Thorsett, S E; Tibaldo, L; Torres, D F; Tosti, G; Tramacere, A; Uchiyama, Y; Usher, T L; Van Etten, A; Vasileiou, V; Venter, C; Vilchez, N; Vitale, V; Waite, A P; Wallace, E; Wang, P; Watters, K; Webb, N; Weltevrede, P; Winer, B L; Wood, K S; Ylinen, T; Ziegler, M

    2009-08-14

    Pulsars are born with subsecond spin periods and slow by electromagnetic braking for several tens of millions of years, when detectable radiation ceases. A second life can occur for neutron stars in binary systems. They can acquire mass and angular momentum from their companions, to be spun up to millisecond periods and begin radiating again. We searched Fermi Large Area Telescope data for pulsations from all known millisecond pulsars (MSPs) outside of globular clusters, using rotation parameters from radio telescopes. Strong gamma-ray pulsations were detected for eight MSPs. The gamma-ray pulse profiles and spectral properties resemble those of young gamma-ray pulsars. The basic emission mechanism seems to be the same for MSPs and young pulsars, with the emission originating in regions far from the neutron star surface.

  1. A Population of Gamma-Ray Millisecond Pulsars Seen with the Fermi Large Area Telescope

    International Nuclear Information System (INIS)

    Pulsars are born with sub-second spin periods and slow by electromagnetic braking for several tens of millions of years, when detectable radiation ceases. A second life can occur for neutron stars in binary systems. They can acquire mass and angular momentum from their companions, to be spun up to millisecond periods and begin radiating again. We searched Fermi Large Area Telescope data for pulsations from all known millisecond pulsars (MSPs) outside of globular clusters, using rotation parameters from radio telescopes. Strong gamma-ray pulsations were detected for eight MSPs. The gamma-ray pulse profiles and spectral properties resemble those of young gamma-ray pulsars. The basic emission mechanism seems to be the same for MSPs and young pulsars, with the emission originating in regions far from the neutron star surface. (authors)

  2. Modulated Gamma-ray emission from compact millisecond pulsar binary systems

    CERN Document Server

    Bednarek, W

    2013-01-01

    A significant amount of the millisecond pulsars has been discovered within binary systems. In several such binary systems the masses of the companion stars have been derived allowing to distinguish two classes of objects, called the Black Widow and the Redback binaries. Pulsars in these binary systems are expected to produce winds which, colliding with stellar winds, create conditions for acceleration of electrons. These electrons should interact with the anisotropic radiation from the companion stars producing gamma-ray emission modulated with the orbital period of the binary system. We consider the interaction of a millisecond pulsar (MSP) wind with a very inhomogeneous stellar wind from the companion star within binary systems of the Black Widow and Redback types. It is expected that the pulsar wind should mix efficiently with the inhomogeneous stellar wind. Electrons accelerated in such mixed, turbulent winds can interact with the magnetic field and also strong radiation from the companion star producing ...

  3. Detection and Flux Density Measurements of the Millisecond Pulsar J2145-0750 below 100 MHz

    CERN Document Server

    Dowell, J; Taylor, G B; Blythe, J N; Clarke, T; Craig, J; Ellingson, S W; Helmboldt, J F; Henning, P A; Lazio, T J W; Schinzel, F; Stovall, K; Wolfe, C N

    2013-01-01

    We present flux density measurements and pulse profiles for the millisecond pulsar PSR J2145-0750 spanning 37 to 81 MHz using data obtained from the first station of the Long Wavelength Array. These measurements represent the lowest frequency detection of pulsed emission from a millisecond pulsar to date. We find that the pulse profile is similar to that observed at 102 MHz. We also find that the flux density spectrum between ~40 MHz to 5 GHz is suggestive of a break and may be better fit by a model that includes spectral curvature with a rollover around 730 MHz rather than a single power law.

  4. A search for millisecond pulsars at high galactic latitude

    Science.gov (United States)

    Jacoby, B.; Bailes, M.; Ord, S.; Kulkarni, S.; Anderson, S.

    2002-05-01

    We are conducting a search for radio pulsars using the Parkes 64 m telescope, covering the galactic latitude range 15o Swinburne Centre for Astrophysics and Supercomputing. Analysis of ~2200 square degrees of the survey has been completed, yielding twenty new pulsars including four binary recycled pulsars. Three of these objects have great potential for ultra high precision timing experiments, and one has an unusual massive white dwarf companion. We present the current status of survey observations and analysis as well as follow-up observations of the newly discovered pulsars.

  5. Discovery of the Optical Counterparts to Four Energetic Fermi Millisecond Pulsars

    CERN Document Server

    Breton, R P; Roberts, M S E; Hessels, J W T; Camilo, F; McLaughlin, M A; Ransom, S M; Ray, P S; Stairs, I H

    2013-01-01

    In the last few years, over 43 millisecond radio pulsars have been discovered by targeted searches of unidentified gamma-ray sources found by the Fermi Gamma-Ray Space Telescope. A large fraction of these millisecond pulsars are in compact binaries with low-mass companions. These systems often show eclipses of the pulsar signal and are commonly known as black widows and redbacks because the pulsar is gradually destroying its companion. In this paper, we report on the optical discovery of four strongly irradiated millisecond pulsar companions. All four sources show modulations of their color and luminosity at the known orbital periods from radio timing. Light curve modelling of our exploratory data shows that the equilibrium temperature reached on the companion's dayside with respect to their nightside is consistent with about 10-30% of the available spin-down energy from the pulsar being reprocessed to increase the companion's dayside temperature. This value compares well with the range observed in other irra...

  6. An Eccentric Binary Millisecond Pulsar with a Helium White Dwarf Companion in the Galactic field

    Science.gov (United States)

    Antoniadis, John; Kaplan, David L.; Stovall, Kevin; Freire, Paulo C. C.; Deneva, Julia S.; Koester, Detlev; Jenet, Fredrick; Martinez, Jose G.

    2016-10-01

    Low-mass white dwarfs (LMWDs) are believed to be exclusive products of binary evolution, as the universe is not old enough to produce them from single stars. Because of the strong tidal forces operating during the binary interaction phase, the remnant systems observed today are expected to have negligible eccentricities. Here, we report on the first unambiguous identification of an LMWD in an eccentric (e = 0.13) orbit around the millisecond pulsar PSR J2234+0511, which directly contradicts this picture. We use our spectra and radio-timing solution (derived elsewhere) to infer the WD temperature ({T}{{eff}}=8600+/- 190 K), and peculiar systemic velocity relative to the local standard of rest (≃ 31 km s‑1). We also place model-independent constraints on the WD radius ({R}{{WD}}={0.024}-0.002+0.004 {R}ȯ ) and surface gravity ({log} g={7.11}-0.16+0.08 dex). The WD and kinematic properties are consistent with the expectations for low-mass X-ray binary evolution and disfavor a dynamic three-body formation channel. In the case of the high eccentricity being the result of a spontaneous phase transition, we infer a mass of ∼1.60 M ⊙ for the pulsar progenitor, which is too low for the quark-nova mechanism proposed by Jiang et al., and too high for the scenario of Freire & Tauris, in which a WD collapses into a neutron star via a rotationally delayed accretion-induced collapse. We find that eccentricity pumping via interaction with a circumbinary disk is consistent with our inferred parameters. Finally, we report tentative evidence for pulsations that, if confirmed, would transform the star into an unprecedented laboratory for WD physics.

  7. What the Timing of Millisecond Pulsars Can Teach us about Their Interior

    Science.gov (United States)

    Alford, Mark G.; Schwenzer, Kai

    2014-12-01

    The cores of compact stars reach the highest densities in nature and therefore could consist of novel phases of matter. We demonstrate via a detailed analysis of pulsar evolution that precise pulsar timing data can constrain the star's composition, through unstable global oscillations (r modes) whose damping is determined by microscopic properties of the interior. If not efficiently damped, these modes emit gravitational waves that quickly spin down a millisecond pulsar. As a first application of this general method, we find that ungapped interacting quark matter is consistent with both the observed radio and x-ray data, whereas for ordinary nuclear matter some additional enhanced damping mechanism is required.

  8. The contribution of millisecond pulsars to the Galactic cosmic-ray lepton spectrum

    Science.gov (United States)

    Venter, Christo; Kopp, Andreas; Harding, Alice K.; Gonthier, Peter L.; Büsching, Ingo

    2015-03-01

    Pulsars are believed to be sources of relativistic electrons and positrons. The abundance of detections of γ -ray millisecond pulsars by Fermi Large Area Telescope coupled with their light curve characteristics that imply copious pair production in their magnetospheres, motivated us to investigate this old pulsar population as a source of Galactic electrons and positrons and their contribution to the enhancement in cosmic-ray positron flux at GeV energies. We use a population synthesis code to predict the source properties (number, position, and power) of the present-day Galactic millisecond pulsars, taking into account the latest Fermi and radio observations to calibrate the model output. Next, we simulate pair cascade spectra from these pulsars using a model that invokes an offset-dipole magnetic field. We assume free escape of the pairs from the pulsar environment. We then compute the cumulative spectrum of transported electrons and positrons at Earth, following their diffusion and energy losses as they propagate through the Galaxy. Our results indicate that the predicted particle flux increases for non-zero offsets of the magnetic polar caps. Comparing our predicted local interstellar spectrum and positron fraction to measurements by AMS-02, PAMELA, and Fermi, we find that millisecond pulsars are only modest contributors at a few tens of GeV, after which this leptonic spectral component cuts off. The positron fraction is therefore only slightly enhanced above 10 GeV relative to a background flux model. This implies that alternative sources such as young, nearby pulsars and supernova remnants should contribute additional primary positrons within the astrophysical scenario.

  9. Optical Detection of a Variable Millisecond Pulsar Companion in 47 Tucanae

    CERN Document Server

    Edmonds, P D; Heinke, C O; Grindlay, J E; Camilo, F M; Edmonds, Peter D.; Gilliland, Ronald L.; Heinke, Craig O.; Grindlay, Jonathan E.; Camilo, Fernando

    2001-01-01

    Using results from radio and X-ray observations of millisecond pulsars in 47 Tucanae, and extensive HST U, V, I imaging of the globular cluster core, we have derived a common astrometric solution good to < 0.1". A close positional coincidence is found for 47 Tuc U, a 4.3 ms pulsar in a 0.429 day orbit, detected in radio and X-rays, with an m_V = 20.9 blue star. Analysis of extensive time series data for this optical candidate shows a 0.004 magnitude semi-amplitude variation at the period and phase expected from the radio ephemeris, and the optical variations are spatially coincident with the candidate. This provides secure optical detection of the white dwarf companion to the millisecond pulsar, the first such detection in a globular cluster, allowing for comparisons to recent models for such companions with dependencies on mass and age.

  10. A New High-Frequency Search for Galactic Center Millisecond Pulsars using DSS-43

    Science.gov (United States)

    Lemley, Cameron; Prince, Thomas Allen; Majid, Walid A.; Murchikova, Elena

    2016-01-01

    The primary 70-meter Deep Space Network antenna (DSS-43) in Canberra, Australia was equipped with a new high-frequency (18-28 GHz) receiver system in May 2015 for use in a search for Galactic Center (GC) millisecond pulsars. The primary motivation for this search is that a pulsar in the Galactic Center region (especially one that is gravitationally bound to the massive black hole at the GC) would provide unprecedented tests of gravity in the strong-field regime and would offer an entirely new tool for probing the characteristics of the Galactic Center region. Preparation for the GC pulsar search has involved the development of a single-pulse search pipeline that integrates tools from both Fortran and Python as well as the implementation of this pipeline on high performance CPUs. The original version of the search pipeline was developed using Vela Pulsar data from DSS-43, and a more refined version that relies upon chi-squared fitting techniques was ultimately developed using Crab Pulsar data. Future work will involve continued testing of the single-pulse search pipeline using data from the rotating radio transient (RRAT) J1819-1458, the characterization of RRAT pulses using high time resolution data from the new receiver system on DSS-43, and ultimately the analysis of high-frequency data using the existing pipeline to search for millisecond pulsars in the Galactic Center.

  11. A NuSTAR Observation of the Gamma-ray-emitting X-ray Binary and Transitional Millisecond Pulsar Candidate 1RXS J154439.4-112820

    Science.gov (United States)

    Bogdanov, Slavko

    2016-07-01

    I present a 40 ks Nuclear Spectroscopic Telescope Array observation of the recently identified low-luminosity X-ray binary and transitional millisecond pulsar (tMSP) candidate 1RXS J154439.4-112820, which is associated with the high-energy γ-ray source 3FGL J1544.6-1125. The system is detected up to ˜30 keV with an extension of the same power-law spectrum and rapid large-amplitude variability between two flux levels observed in soft X-rays. These findings provide further evidence that 1RXS J154439.4-112820 belongs to the same class of objects as the nearby bona fide tMSPs PSR J1023+0038 and XSS J12270-4859 and therefore almost certainly hosts a millisecond pulsar accreting at low luminosity. I also examine the long-term accretion history of 1RXS J154439.4-112820 based on archival optical, ultraviolet, X-ray, and γ-ray light curves covering approximately the past decade. Throughout this period, the source has maintained similar flux levels at all wavelengths, which is an indication that it has not experienced prolonged episodes of a non-accreting radio pulsar state but may spontaneously undergo such events in the future.

  12. Analyzing the Spectra of Accreting X-Ray Pulsars

    Science.gov (United States)

    Wolff, Michael

    This proposal seeks funding for the analysis of accretion-powered X-ray pulsar spectra from NASA/ HEASARC archived X-ray data. Spectral modeling of accreting X-ray pulsars can tell us a great deal about the physical conditions in and near high mass X-ray binary systems. Such systems have accretion flows where plasma is initially channeled from an accretion disk by the strong neutron star magnetic field, eventually falling onto the magnetic polar cap of the neutron star compact object. Many of these accreting X-ray pulsars have X-ray spectra that consist of broad power-law continua with superposed cyclotron resonant scattering features indicating magnetic field strengths above 10^12 G. The energies of these cyclotron line features have recently been shown to vary with X-ray luminosity in a number of sources such as Her X-1 and V 0332+53, a phenomenon not well understood. Another recent development is the relatively new analytic model for the spectral continuum formation in accretion-powered pulsar systems developed by Becker & Wolff. In their formalism the accretion flows are assumed to go through radiation- dominated radiative shocks and settle onto the neutron star surface. The radiation field consists of strongly Comptonized bremsstrahlung emission from the entire plasma, Comptonized cyclotron emission from the de-excitations of Landau-excited electrons in the neutron star magnetic field, and Comptonized black-body emission from a thermal mound near the neutron star surface. We seek to develop the data analysis tools to apply this model framework to the X-ray data from a wide set of sources to make progress characterizing the basic accretion properties (e.g., magnetic field strength, plasma temperatures, polar cap size, accretion rate per unit area, dominance of bulk vs. thermal Comptonization) as well as understanding the variations of the cyclotron line energies with X-ray luminosity. The three major goals of our proposed work are as follows: In the first year

  13. Low-Frequency Variability of - for Timing of Millisecond Pulsars

    Science.gov (United States)

    Blandford, R.; Narayan, R.

    Rickett, Coles and Bourgois (1984) have argued that long-term (months to years) variation in pulsar flux is caused by fluctuations in the interstellar electron density on length scales ≡1013-16cm. In this paper the authors show that there should then be correlated fluctuations in the pulse arrival time, pulse width, and angular size. PSR 1937+21 is suitable for detecting some of the new effects. The timing noise and pulse width variation in this pulsar is estimated assuming a power-law spectrum for the electron density fluctuations, normalized using scintillation data.

  14. Discovery of an unidentified Fermi object as a black widow-like millisecond pulsar

    CERN Document Server

    Kong, A K H; Cheng, K S; Takata, J; Yatsu, Y; Cheung, C C; Donato, D; Lin, L C C; Kataoka, J; Takahashi, Y; Maeda, K; Hui, C Y; Tam, P H T

    2012-01-01

    The Fermi Gamma-ray Space Telescope has revolutionized our knowledge of the gamma-ray pulsar population, leading to the discovery of almost 100 gamma-ray pulsars and dozens of gamma-ray millisecond pulsars (MSPs). Although the outer-gap model predicts different sites of emission for the radio and gamma-ray pulsars, until now all of the known gamma-ray MSPs have been visible in the radio. Here we report the discovery of a "radio-quiet" gamma-ray emitting MSP candidate by using Fermi, Chandra, Swift, and optical observations. The X-ray and gamma-ray properties of the source are consistent with known gamma-ray pulsars. We also found a 4.63-hr orbital period in optical and X-ray data. We suggest that the source is a black widow-like MSP with a ~0.1 solar-mass late-type companion star. Based on the profile of the optical and X-ray light-curves, the companion star is believed to be heated by the pulsar while the X-ray emissions originate from pulsar magnetosphere and/or from intra-binary shock. No radio detection o...

  15. Quasi-spherical accretion in X-ray pulsars

    CERN Document Server

    Postnov, K; Kochetkova, A; Hjalmarsdotter, L

    2011-01-01

    Quasi-spherical accretion in wind-fed X-ray pulsars is discussed. At X-ray luminosities <4 10^{36} erg/s, a hot convective shell is formed around the neutron star magnetosphere, and subsonic settling accretion regime sets in. In this regime, accretion rate onto neutron star is determined by the ability of plasma to enter magnetosphere via Rayleigh-Taylor instability. A gas-dynamic theory of settling accretion is constructed taking into account anisotropic turbulence. The angular momentum can be transferred through the quasi-static shell via large-scale convective motions initiating turbulence cascade. The angular velocity distribution in the shell is found depending on the turbulent viscosity prescription. Comparison with observations of long-period X-ray wind-fed pulsars shows that an almost iso-angular-momentum distribution is most likely realized in their shells. The theory explains long-term spin-down in wind- fed accreting pulsars (e.g. GX 1+4) and properties of short-term torque-luminosity correlatio...

  16. The evolution of helium white dwarfs: III. On the ages of millisecond pulsar systems

    OpenAIRE

    Schoenberner, D.; Driebe, T.; Bloecker, T.

    2000-01-01

    We employed recently computed evolutionary white-dwarf models with helium cores, supplemented by heavier models with carbon-oxygen cores, in order to investigate the ages of millisecond pulsar systems based on the cooling properties of the compact companions. Contrary to the behaviour of more massive white dwarfs, the evolutionary speed of low-mass white-dwarf models is substantially slowed down by ongoing hydrogen burning. By comparing the cooling ages of these models with the spin-down ages...

  17. Discovery of two millisecond pulsars in Fermi sources with the Nancay Radio Telescope

    CERN Document Server

    Cognard, I; Johnson, T J; Smith, D A; Venter, C; Harding, A K; Wolff, M T; Cheung, C C; Donato, D; Abdo, A A; Ballet, J; Camilo, F; Desvignes, G; Dumora, D; Ferrara, E C; Freire, P C C; Grove, J E; Keith, M; Kramer, M; Lyne, A G; Michelson, P F; Parent, D; Ransom, S M; Ray, P S; Romani, R W; Parkinson, P M Saz; Stappers, B W; Theureau, G; Thompson, D J; Weltevrede, P; Wood, K S

    2011-01-01

    We report the discovery of two millisecond pulsars in a search for radio pulsations at the positions of \\emph{Fermi Large Area Telescope} sources with no previously known counterparts, using the Nan\\c{c}ay radio telescope. The two millisecond pulsars, PSRs J2017+0603 and J2302+4442, have rotational periods of 2.896 and 5.192 ms and are both in binary systems with low-eccentricity orbits and orbital periods of 2.2 and 125.9 days respectively, suggesting long recycling processes. Gamma-ray pulsations were subsequently detected for both objects, indicating that they power the associated \\emph{Fermi} sources in which they were found. The gamma-ray light curves and spectral properties are similar to those of previously-detected gamma-ray millisecond pulsars. Detailed modeling of the observed radio and gamma-ray light curves shows that the gamma-ray emission seems to originate at high altitudes in their magnetospheres. Additionally, X-ray observations revealed the presence of an X-ray source at the position of PSR ...

  18. Rotochemical Heating in Millisecond Pulsars. Formalism and Non-superfluid case

    CERN Document Server

    Fern'andez, R; Fern\\'andez, Rodrigo; Reisenegger, Andreas

    2005-01-01

    Rotochemical heating originates in a departure from beta equilibrium due to spin-down compression in a rotating neutron star. The main consequence is that the star eventually arrives at a quasi-equilibrium state, in which the thermal photon luminosity depends only on the current value of the spin-down power, which is directly measurable. Only in millisecond pulsars the spin-down power remains high long enough for this state to be reached with a substantial luminosity. We report an extensive study of the effect of this heating mechanism on the thermal evolution of millisecond pulsars, developing a general formalism in the slow-rotation approximation of general relativity that takes the spatial structure of the star fully into account, and using a sample of realistic equations of state to solve the non-superfluid case numerically. We show that nearly all observed millisecond pulsars are very likely to be in the quasi-equilibrium state. Our predicted quasi-equilibrium temperatures for PSR J0437-4715 are only 20%...

  19. PSR J1723-2837: An Eclipsing Binary Radio Millisecond Pulsar

    CERN Document Server

    Crawford, F; Stairs, I H; Kaplan, D L; McLaughlin, M A; Freire, P C C; Burgay, M; Camilo, F; D'Amico, N; Faulkner, A; Kramer, M; Lorimer, D R; Manchester, R N; Possenti, A; Steeghs, D

    2013-01-01

    We present a study of PSR J1723-2837, an eclipsing, 1.86 ms millisecond binary radio pulsar discovered in the Parkes Multibeam survey. Radio timing indicates that the pulsar has a circular orbit with a 15 hr orbital period, a low-mass companion, and a measurable orbital period derivative. The eclipse fraction of ~15% during the pulsar's orbit is twice the Roche lobe size inferred for the companion. The timing behavior is significantly affected by unmodeled systematics of astrophysical origin, and higher-order orbital period derivatives are needed in the timing solution to account for these variations. We have identified the pulsar's (non-degenerate) companion using archival ultraviolet, optical, and infrared survey data and new optical photometry. Doppler shifts from optical spectroscopy confirm the star's association with the pulsar and indicate a pulsar-to-companion mass ratio of 3.3 +/- 0.5, corresponding to a companion mass range of 0.4 to 0.7 Msun and an orbital inclination angle range of between 30 and ...

  20. Young and Millisecond Pulsar GeV Gamma-ray Fluxes from the Galactic Center and Beyond

    CERN Document Server

    O'Leary, Ryan M; Kerr, Matthew; Dexter, Jason

    2016-01-01

    Gamma-ray observations have shown pulsars to be efficient converters of rotational energy into GeV photons and it is of wide-ranging interest to determine their contribution to the gamma-ray background. We arrive at flux predictions from both the young (<~ Myr) and millisecond (~Gyr) Galactic pulsar populations. We find that unresolved pulsars can yield both a significant fraction of the excess GeV gamma rays near the Galactic Center and an inverse Compton flux in the inner kpc similar to that inferred by Fermi. We compare models of the young pulsar population and millisecond pulsar population to constraints from gamma-ray and radio observations. Overall, we find that the young pulsars should outnumber millisecond pulsars as unassociated gamma-ray point sources in this region. The number of young radio pulsars discovered near the Galactic Center is in agreement with our model of the young pulsar population. Deeper radio observations at higher latitudes can constrain the total gamma-ray emission from both y...

  1. NuSTAR Observations of the State Transition of Millisecond Pulsar Binary PSR J1023+0038

    CERN Document Server

    Tendulkar, Shriharsh P; An, Hongjun; Kaspi, Victoria M; Archibald, Anne M; Bassa, Cees; Bellm, Eric; Bogdanov, Slavko; Harrison, Fiona A; Hessels, Jason W T; Janssen, Gemma H; Lyne, Andrew G; Patruno, Alessandro; Stappers, Benjamin; Stern, Daniel; Tomsick, John A; Boggs, Steven E; Chakrabarty, Deepto; Christensen, Finn E; Craig, William W; Hailey, Charles A; Zhang, William

    2014-01-01

    We report NuSTAR observations of the millisecond pulsar - low mass X-ray binary (LMXB) transition system PSR J1023+0038 from June and October 2013, before and after the formation of an accretion disk around the neutron star. Between June 10-12, a few days to two weeks before the radio disappearance of the pulsar, the 3-79 keV X-ray spectrum was well fit by a simple power law with a photon index of Gamma=1.17 +/-0.08 (at 90% confidence) with a 3-79 keV luminosity of 7.4+/-0.4 x 10^32 erg/s. Significant orbital modulation was observed with a modulation fraction of 36+/-10%. During the October 19-21 observation, the spectrum is described by a softer power law (Gamma=1.66+/-0.06) with an average luminosity of 5.8+/-0.2 x 10^33 erg/s and a peak luminosity of ~1.2 x 10^34 erg/s observed during a flare. No significant orbital modulation was detected. The spectral observations are consistent with previous and current multi-wavelength observations and show the hard X-ray power law extending to 79 keV without a spectra...

  2. Self consistent modeling of accretion columns in accretion powered pulsars

    Science.gov (United States)

    Falkner, Sebastian; Schwarm, Fritz-Walter; Wolff, Michael Thomas; Becker, Peter A.; Wilms, Joern

    2016-04-01

    We combine three physical models to self-consistently derive the observed flux and pulse profiles of neutron stars' accretion columns. From the thermal and bulk Comptonization model by Becker & Wolff (2006) we obtain seed photon continua produced in the dense inner regions of the accretion column. In a thin outer layer these seed continua are imprinted with cyclotron resonant scattering features calculated using Monte Carlo simulations. The observed phase and energy dependent flux corresponding to these emission profiles is then calculated, taking relativistic light bending into account. We present simulated pulse profiles and the predicted dependency of the observable X-ray spectrum as a function of pulse phase.

  3. The gamma-ray millisecond pulsar deathline, revisited - New velocity and distance measurements

    CERN Document Server

    Guillemot, L; Laffon, H; Janssen, G H; Cognard, I; Theureau, G; Desvignes, G; Ferrara, E C; Ray, P S

    2016-01-01

    Millisecond pulsars (MSPs) represent nearly half of the more than 160 currently known $\\gamma$-ray pulsars detected by the Large Area Telescope on the \\textit{Fermi} satellite, and a third of all known MSPs are seen in $\\gamma$ rays. The least energetic $\\gamma$-ray MSPs enable us to probe the so-called deathline for high-energy emission, i.e., the spin-down luminosity limit under which pulsars (PSRs) cease to produce detectable high-energy radiation. Characterizing the MSP luminosity distribution helps to determine their contribution to the Galactic diffuse $\\gamma$-ray emission. We made use of the high-quality pulsar timing data recorded at the Nan\\c{c}ay Radio Telescope over several years to characterize the properties of a selection of MSPs. For one of the pulsars, the dataset was complemented with Westerbork Synthesis Radio Telescope observations. The rotation ephemerides derived from this analysis were also used to search the LAT data for new $\\gamma$-ray MSPs. For the MSPs considered in this study, we ...

  4. Properties and Evolution of the Redback Millisecond Pulsar Binary PSR J2129-0429

    CERN Document Server

    Bellm, Eric C; Breton, Rene P; Phinney, E Sterl; Bhalerao, Varun B; Camilo, Fernando; Dahal, Sumit; Djorgovski, S G; Drake, Andrew J; Hessels, J W T; Laher, Russ R; Levitan, David B; Lewis, Fraser; Mahabal, Ashish A; Ofek, Eran O; Prince, Thomas A; Ransom, Scott M; Roberts, Mallory S E; Russell, David M; Sesar, Branimir; Surace, Jason A; Tang, Sumin

    2015-01-01

    PSR J2129-0429 is a "redback" eclipsing millisecond pulsar binary with an unusually long 15.2 hour orbit. It was discovered by the Green Bank Telescope in a targeted search of unidentified Fermi gamma-ray sources. The pulsar companion is optically bright (mean $m_R = 16.6$ mag), allowing us to construct the longest baseline photometric dataset available for such a system. We present ten years of archival and new photometry of the companion from LINEAR, CRTS, PTF, the Palomar 60-inch, and LCOGT. Radial velocity spectroscopy using the Double-Beam Spectrograph on the Palomar 200-inch indicates that the pulsar is massive: $1.74\\pm0.18 M_\\odot$. The G-type pulsar companion has mass $0.44\\pm0.04 M_\\odot$, one of the heaviest known redback companions. It is currently 95\\% Roche-lobe filling and only mildly irradiated by the pulsar. We identify a clear 13.1 mmag yr$^{-1}$ secular decline in the mean magnitude of the companion as well as smaller-scale variations in the optical lightcurve shape. This behavior may indic...

  5. Four Highly Dispersed Millisecond Pulsars Discovered in the Arecibo PALFA Galactic Plane Survey

    CERN Document Server

    Crawford, F; Lyne, A G; Stappers, B W; Nice, D J; Stairs, I H; Lazarus, P; Hessels, J W T; Freire, P C C; Allen, B; Bhat, N D R; Bogdanov, S; Brazier, A; Camilo, F; Champion, D J; Chatterjee, S; Cognard, I; Cordes, J M; Deneva, J S; Desvignes, G; Jenet, F A; Kaspi, V M; Knispel, B; Kramer, M; van Leeuwen, J; Lorimer, D R; Lynch, R; McLaughlin, M A; Ransom, S M; Scholz, P; Siemens, X; Venkataraman, A

    2012-01-01

    We present the discovery and phase-coherent timing of four highly dispersed millisecond pulsars (MSPs) from the Arecibo PALFA Galactic plane survey: PSRs J1844+0115, J1850+0124, J1900+0308, and J1944+2236. Three of the four pulsars are in binary systems with low-mass companions, which are most likely white dwarfs, and which have orbital periods on the order of days. The fourth pulsar is isolated. All four pulsars have large dispersion measures (DM > 100 pc cm-3), are distant (> 3.4 kpc), faint at 1.4 GHz (< 0.2 mJy), and are fully recycled (with spin periods P between 3.5 and 4.9 ms). The three binaries also have very small orbital eccentricities, as expected for tidally circularized, fully recycled systems with low-mass companions. These four pulsars have DM/P ratios that are among the highest values for field MSPs in the Galaxy. These discoveries bring the total number of confirmed MSPs from the PALFA survey to fifteen. The discovery of these MSPs illustrates the power of PALFA for finding weak, distant ...

  6. PSR J1723–2837: AN ECLIPSING BINARY RADIO MILLISECOND PULSAR

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, Fronefield [Department of Physics and Astronomy, Franklin and Marshall College, P.O. Box 3003, Lancaster, PA 17604 (United States); Lyne, Andrew G. [Jodrell Bank Centre for Astrophysics, University of Manchester, Manchester M13 9PL (United Kingdom); Stairs, Ingrid H. [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1 (Canada); Kaplan, David L. [Physics Department, University of Wisconsin - Milwaukee, Milwaukee, WI 53211 (United States); McLaughlin, Maura A.; Lorimer, Duncan R. [Department of Physics, West Virginia University, Morgantown, WV 26506 (United States); Freire, Paulo C. C.; Kramer, Michael [Max-Planck-Institut für Radioastronomie, auf dem Huegel 69, D-53121 Bonn (Germany); Burgay, Marta; D' Amico, Nichi; Possenti, Andrea [INAF - Osservatorio Astronomico di Cagliari, Poggio dei Pini, I-09012 Capoterra (Italy); Camilo, Fernando [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Faulkner, Andrew [Cavendish Laboratory, University of Cambridge, J. J. Thompson Avenue, Cambridge, CB3 0HE (United Kingdom); Manchester, Richard N. [CSIRO Astronomy and Space Science, Australia Telescope National Facility, P.O. Box 76, Epping, NSW 1710 (Australia); Steeghs, Danny, E-mail: fcrawfor@fandm.edu [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom)

    2013-10-10

    We present a study of PSR J1723–2837, an eclipsing, 1.86 ms millisecond binary radio pulsar discovered in the Parkes Multibeam survey. Radio timing indicates that the pulsar has a circular orbit with a 15 hr orbital period, a low-mass companion, and a measurable orbital period derivative. The eclipse fraction of ∼15% during the pulsar's orbit is twice the Roche lobe size inferred for the companion. The timing behavior is significantly affected by unmodeled systematics of astrophysical origin, and higher-order orbital period derivatives are needed in the timing solution to account for these variations. We have identified the pulsar's (non-degenerate) companion using archival ultraviolet, optical, and infrared survey data and new optical photometry. Doppler shifts from optical spectroscopy confirm the star's association with the pulsar and indicate a pulsar-to-companion mass ratio of 3.3 ± 0.5, corresponding to a companion mass range of 0.4 to 0.7 M{sub ☉} and an orbital inclination angle range of between 30° and 41°, assuming a pulsar mass range of 1.4-2.0 M{sub ☉}. Spectroscopy indicates a spectral type of G for the companion and an inferred Roche-lobe-filling distance that is consistent with the distance estimated from radio dispersion. The features of PSR J1723–2837 indicate that it is likely a 'redback' system. Unlike the five other Galactic redbacks discovered to date, PSR J1723–2837 has not been detected as a γ-ray source with Fermi. This may be due to an intrinsic spin-down luminosity that is much smaller than the measured value if the unmeasured contribution from proper motion is large.

  7. "Hiccup" accretion in the swinging pulsar IGR J18245-2452

    CERN Document Server

    Ferrigno, C; Papitto, A; Rea, N; Pavan, L; Campana, S; Wieringa, M; Filipovic, M; Falanga, M

    2013-01-01

    IGR J18245-2452 is the fifteenth discovered accreting millisecond X-ray pulsar and the first source of this class showing direct evidence for transition between accretion and rotational powered emission states. These "swings" provided the strongest confirmation of the pulsar recycling scenario available so far. During the two XMM-Newton observations that were carried out while the source was in outburst in April 2013, IGR J18245-2452 displayed a unique and peculiar variability of its X-ray emission. In this work, we report on a detailed analysis of the XMM- Newton data and focus in particular on the timing and spectral variability of the source. IGR J18245-2452 continuously switches between lower and higher intensity states, with typical variations in flux up to a factor of about 100 in time scales as short as few seconds. These variations in the source intensity are sometimes associated to a dramatic spectral hardening, during which the power-law photon index of the source changes from Gamma=1.7 to Gamma=0.7...

  8. A NuSTAR Observation of the Gamma-Ray-Emitting X-ray Binary and Transitional Millisecond Pulsar Candidate 1RXS J154439.4-112820

    CERN Document Server

    Bogdanov, Slavko

    2015-01-01

    I present a 40 kilosecond Nuclear Spectroscopic Telescope Array (NuSTAR) observation of the recently identified low-luminosity X-ray binary and transitional millisecond pulsar (tMSP) candidate 1RXS J154439.4-112820, which is associated with the high-energy gamma-ray source 3FGL J1544.6--1125. The system is detected up to ~30 keV with an extension of the same power-law spectrum and rapid large-amplitude variability between two flux levels observed in soft X-rays. These findings provide further evidence that 1RXS J154439.4-112820 belongs to the same class of objects as the nearby bona fide tMSPs PSR J1023+0038 and XSS J12270-4859 and therefore almost certainly hosts a millisecond pulsar accreting at low luminosities. I also examine the long-term accretion history of 1RXS J154439.4-112820 based on archival optical, ultraviolet, X-ray, and $\\gamma$-ray light curves covering the past $\\sim$decade. Throughout this period, the source has maintained similar flux levels at all wavelengths, which is an indication that ...

  9. Rotochemical heating of millisecond and classical pulsars with anisotropic and density-dependent superfluid gap models

    CERN Document Server

    González-Jiménez, Nicolás; Reisenegger, Andreas

    2014-01-01

    When a rotating neutron star loses angular momentum, the progressive reduction of the centrifugal force makes it contract. This perturbs each fluid element, raising the local pressure and originating deviations from beta equilibrium, inducing reactions that release heat (rotochemical heating). This effect has previously been studied by Fern\\'andez & Reisenegger (2005) for non-superfluid neutron stars and by Petrovich & Reisenegger (2010) for superfluid millisecond pulsars. Both studies found that pulsars reach a quasi-steady state in which the compression driving the matter out of beta equilibrium is balanced by the reactions trying to restore the equilibrium. We extend previous studies by considering the effect of density-dependence and anisotropy of the superfluid energy gaps, for the case in which the dominant reactions are the modified Urca processes, the protons are non-superconducting, and the neutron superfluidity is parametrized by models proposed in the literature. By comparing our prediction...

  10. PSR J1024-0719: A Millisecond Pulsar in an Unusual Long-Period Orbit

    CERN Document Server

    Kaplan, D L; Nice, D J; Irrgang, A; Heber, U; Arzoumanian, Z; Beklen, E; Crowter, K; DeCesar, M E; Demorest, P B; Dolch, T; Lynch, R S; McLaughlin, M A; Miller, A A; Ng, C; Pennucci, T T; Ellis, J A; Ferdman, R D; Ferrara, E C; Fonseca, E; Gentile, P A; Jones, G; Jones, M L; Kreuzer, S; Lam, M T; Levin, L; Lorimer, D R; Prince, T A; Ransom, S M; Ray, P S; Spiewak, R; Stairs, I H; Stovall, K; Swiggum, J; Zhu, W

    2016-01-01

    PSR J1024$-$0719 is a millisecond pulsar that was long thought to be isolated. However, puzzling results concerning its velocity, distance, and low rotational period derivative have led to reexamination of its properties. We present updated radio timing observations along with new and archival optical data that show PSR J1024$-$0719 is most likely in a long period (2$-$20 kyr) binary system with a low-mass ($\\approx 0.4\\,M_\\odot$) low-metallicity ($Z \\approx -0.9\\,$ dex) main sequence star. Such a system can explain most of the anomalous properties of this pulsar. We suggest that this system formed through a dynamical exchange in a globular cluster that ejected it into a halo orbit, consistent with the low observed metallicity for the stellar companion. Further astrometric and radio timing observations such as measurement of the third period derivative could strongly constrain the range of orbital parameters.

  11. Constraints on the R-mode oscillations from surface temperatures of millisecond pulsars

    Science.gov (United States)

    Guver, Tolga; Schwenzer, Kai

    2016-07-01

    r-modes are toroidal oscillation modes expected to occur in neutron stars and carry away energy and angular momentum in the form of gravitational waves. These modes can be unstable as long as the gravitational wave emission drives the oscillation faster than viscosity damps it. Unstable r-modes have to be saturated by a non-linear dissipative mechanism which could strongly heat the star and result in observable X-ray signatures. Using the existing spin frequency and surface temperature measurements or limits of millisecond pulsars we present our initial results constraining the physics of the r-mode oscillations.

  12. Preparing GLAST LAT studies of the millisecond pulsar PSR J0218+4232 and the blazar 3C 66A

    International Nuclear Information System (INIS)

    Millisecond pulsars have weaker magnetic fields than normal pulsars, but their rapid rotation implies open field line voltages similar to those of young pulsars and they are therefore candidates for accelerating particles to the high energies required to emit in the GeV energy domain. PSR J0218+4232 was the only millisecond pulsar detected by EGRET. Its detection was rendered difficult by the powerful BL Lacertae 3C 66A a degree away, in spite of the low background (b= -16.8 degrees). Pulsations were detected at the 4.9 σ level, reinforcing the expectation that millisecond pulsars are a promising class for detection by the forthcoming high-energy mission GLAST. To estimate the GLAST LAT performance for both PSR J0218+4232 and 3C 66A, we have simulated LAT data using predictions for the 'polar cap' and the 'outer gap' pulsar models along with spectral energy distribution estimates for the blazar, normalizing to the EGRET observed fluxes. We demonstrate that GLAST is able to separate unambiguously the two objects in a few weeks. The spectral parameters of the pulsar derived in this context could be used to discriminate between the polar cap and outer gap models

  13. HIGH-PRECISION TIMING OF FIVE MILLISECOND PULSARS: SPACE VELOCITIES, BINARY EVOLUTION, AND EQUIVALENCE PRINCIPLES

    International Nuclear Information System (INIS)

    We present high-precision timing of five millisecond pulsars (MSPs) carried out for more than seven years; four pulsars are in binary systems and one is isolated. We are able to measure the pulsars' proper motions and derive an estimate for their space velocities. The measured two-dimensional velocities are in the range 70-210 km s–1, consistent with those measured for other MSPs. We also use all the available proper motion information for isolated and binary MSPs to update the known velocity distribution for these populations. As found by earlier works, we find that the velocity distribution of binary and isolated MSPs are indistinguishable with the current data. Four of the pulsars in our observing program are highly recycled with low-mass white dwarf companions and we are able to derive accurate binary parameters for these systems. For three of these binary systems, we are able to place initial constraints on the pulsar masses with best-fit values in the range 1.0-1.6 M☉. The implications of the results presented here to our understanding of binary pulsar evolution are discussed. The updated parameters for the binary systems studied here, together with recently discovered similar systems, allowed us to update previous limits on the violation of the strong equivalence principle through the parameter |Δ| to 4.6 × 10–3 (95% confidence) and the violation of Lorentz invariance/momentum conservation through the parameter |α-hat3| to 5.5 × 10–20 (95% confidence).

  14. Probing millisecond pulsar emission geometry using light curves from the Fermi Large Area Telescope

    CERN Document Server

    Venter, C; Guillemot, L

    2009-01-01

    An interesting new high-energy pulsar sub-population is emerging following early discoveries of gamma-ray millisecond pulsars (MSPs) by the Fermi Large Area Telescope (LAT). We present results from 3D emission modeling, including the Special Relativistic effects of aberration and time-of-flight delays and also rotational sweepback of B-field lines, in the geometric context of polar cap (PC), outer gap (OG), and two-pole caustic (TPC) pulsar models. In contrast to the general belief that these very old, rapidly-rotating neutron stars (NSs) should have largely pair-starved magnetospheres due to the absence of significant pair production, we find that most of the light curves are best fit by TPC and OG models, which indicates the presence of narrow accelerating gaps limited by robust pair production -- even in these pulsars with very low spin-down luminosities. The gamma-ray pulse shapes and relative phase lags with respect to the radio pulses point to high-altitude emission being dominant for all geometries. We...

  15. Parkes radio searches of Fermi gamma-ray sources and millisecond pulsar discoveries

    CERN Document Server

    Camilo, F; Ray, P S; Ransom, S M; Sarkissian, J; Cromartie, H T; Johnston, S; Reynolds, J E; Wolff, M T; Freire, P C C; Bhattacharyya, B; Ferrara, E C; Keith, M; Michelson, P F; Parkinson, P M Saz; Wood, K S

    2015-01-01

    In a search with the Parkes radio telescope of 56 unidentified Fermi-LAT gamma-ray sources, we have detected 11 millisecond pulsars (MSPs), 10 of them discoveries, of which five were reported in Kerr et al. (2012). We did not detect radio pulsations from another six pulsars now known in these sources. We describe the completed survey, which included multiple observations of many targets done to minimize the impact of interstellar scintillation, acceleration effects in binary systems, and eclipses. We consider that 23 of the 39 remaining sources may still be viable pulsar candidates. We present timing solutions and polarimetry for five of the MSPs, and gamma-ray pulsations for PSR J1903-7051 (pulsations for five others were reported in the second Fermi-LAT catalog of gamma-ray pulsars). Two of the new MSPs are isolated and five are in >1 d circular orbits with 0.2-0.3 Msun presumed white dwarf companions. PSR J0955-6150, in a 24 d orbit with a ~0.25 Msun companion but eccentricity of 0.11, belongs to a recentl...

  16. Prospects for neutron star equation of state constraints using ''recycled'' millisecond pulsars

    Energy Technology Data Exchange (ETDEWEB)

    Bogdanov, Slavko [Columbia University, Columbia Astrophysics Laboratory, New York, NY (United States)

    2016-02-15

    ''Recycled'' millisecond pulsars are a variety of rapidly spinning neutron stars that typically show thermal X-ray radiation due to the heated surface of their magnetic polar caps. Detailed numerical modeling of the rotation-induced thermal X-ray pulsations observed from recycled millisecond pulsars, including all relevant relativistic and stellar atmospheric effects, has been identified as a promising approach towards an astrophysical determination of the true neutron star mass-radius relation, and by extension the state of cold matter at densities exceeding those of atomic nuclei. Herein, I review the basic model and methodology commonly used to extract information regarding neutron star structure from the pulsed X-ray radiation observed from millisecond pulsars. I also summarize the results of past X-ray observations of these objects and the prospects for precision neutron star mass-radius measurements with the upcoming Neutron Star Interior Composition Explorer (NICER) X-ray timing mission. (orig.)

  17. The Contribution of Millisecond Pulsars to the Local Electron / Positron Spectrum

    Science.gov (United States)

    Venter, Christo; Buesching, Ingo; Harding, Alice; Kopp, Andreas; Gonthier, Peter

    The high energies of gamma-ray photons (as well as the presence of lower-energy photons) coupled with the intense magnetic fields characterizing younger pulsars enable formation of electron-positron pair cascades which fills the pulsar magnetosphere with plasma and also feeds an outflowing particle wind that may create a surrounding pulsar wind nebula (PWN). Although this scenario was originally thought to be unique to the younger pulsar population, Fermi LAT demonstrated that the light curves of millisecond pulsars (MSPs) are generally very similar to those of younger pulsars, requiring copious pair production even for this older class with much lower surface magnetic fields and spin-down power. These pair cascades may thus be a primary source of Galactic electrons and positrons, and may present an astrophysical explanation for the observed enhancement in positron flux in the high-energy band. We investigate Galactic MSPs contribution to the flux of local cosmic-ray electrons and positrons. We use a population synthesis code to predict the source properties (number, position, and power) of the present-day Galactic MSPs, taking into account the latest Fermi observations to calibrate the model output. Next, we simulate pair cascade spectra from these MSPs using a model that invokes an offset-dipole magnetic field, as this increases the pair production rate relative to a standard dipole field geometry. The model source pair spectra may extend to several TeV, depending on pulsar properties, neutron star equation of state, and magnetic polar cap offset. Since MSPs are not surrounded by PWNe or supernova shells, we can assume that the pairs escape from the pulsar environment without energy loss and undergo losses only in the intergalactic medium. We lastly compute the spectrum of the transported electrons and positrons at Earth, following their diffusion and energy loss through the Galaxy. We will compare our results with the observed local interstellar spectrum and

  18. PSR J1738+0333: The First Millisecond Pulsar + Pulsating White Dwarf Binary

    CERN Document Server

    Kilic, Mukremin; Gianninas, A; Brown, Warren R

    2014-01-01

    We report the discovery of the first millisecond pulsar with a pulsating white dwarf companion. Following the recent discoveries of pulsations in extremely low-mass (ELM, <0.3 Msol) white dwarfs (WDs), we targeted ELM WD companions to two millisecond pulsars with high-speed Gemini photometry. We find significant optical variability in PSR J1738+0333 with periods between roughly 1790-3060 s, consistent in timescale with theoretical and empirical observations of pulsations in 0.17 Msol He-core ELM WDs. We additionally put stringent limits on a lack of variability in PSR J1909-3744, showing this ELM WD is not variable to <0.1 per cent amplitude. Thanks to the accurate distance and radius estimates from radio timing measurements, PSR J1738+0333 becomes a benchmark for low-mass, pulsating WDs. Future, more extensive time-series photometry of this system offers an unprecedented opportunity to constrain the physical parameters (including the cooling age) and interior structure of this ELM WD, and in turn, the ...

  19. Gamma-rays from millisecond pulsar population within the central stellar cluster in the Galactic Center

    CERN Document Server

    Bednarek, W

    2013-01-01

    It was proposed that the central dense stellar cluster in the Galactic Center, containing the mass of $\\sim$4 times larger than that of the central black hole, had been formed as a result of a merging of several massive globular clusters. These globular clusters are expected to provide a large number of millisecond pulsars (MSPs) within the central parsec of the Galactic Center. We propose that the GeV $\\gamma$-ray emission observed from the Galactic Center is in fact a cumulative effect of the emission from several globular clusters captured by the Galactic Center black hole. Moreover, the millisecond pulsars in globular clusters accelerate leptons in their wind zones to energies of the order of a few tens of TeV injecting them into the dense infrared and optical radiation region present within the central parsec. We calculate the expected TeV $\\gamma$-ray emission produced by these leptons by the Inverse Compton Scattering process in the soft radiation field. It is shown that this emission can be responsibl...

  20. Discovery of near-ultraviolet counterparts to millisecond pulsars in the globular cluster 47 Tucanae

    CERN Document Server

    Rivera-Sandoval, L E; Heinke, C O; Cohn, H N; Lugger, P M; Freire, P; Anderson, J; Serenelli, A M; Althaus, L G; Cool, A M; Grindlay, J E; Edmonds, P D; Wijnands, R; Ivanova, N

    2015-01-01

    We report the discovery of the likely white dwarf companions to radio millisecond pulsars 47 Tuc Q and 47 Tuc S in the globular cluster 47 Tucanae. These blue stars were found in near-ultraviolet images from the Hubble Space Telescope for which we derived accurate absolute astrometry, and are located at positions consistent with the radio coordinates to within 0.016 arcsec (0.2sigma). We present near-ultraviolet and optical colours for the previously identified companion to millisecond pulsar 47 Tuc U, and we unambiguously confirm the tentative prior identifications of the optical counterparts to 47 Tuc T and 47 Tuc Y. For the latter, we present its radio-timing solution for the first time. We find that all five near-ultraviolet counterparts have U300-B390 colours that are consistent with He white dwarf cooling models for masses ~0.16-0.3 Msun and cooling ages within ~0.1-6 Gyr. The Ha-R625 colours of 47 Tuc U and 47 Tuc T indicate the presence of a strong Ha absorption line, as expected for white dwarfs with...

  1. Probing Millisecond Pulsar Emission Geometry Using Light Curves From the Fermi Large Area Telescope

    Science.gov (United States)

    Venter, Christo; Harding, Alice; Guillemot, L.

    2009-01-01

    An interesting new high-energy pulsar sub-population is emerging following early discoveries of gamma-ray millisecond pulsars (MSPs) by the Fermi Large Area Telescope (LAT). We present results from 3D emission modeling, including the Special Relativistic effects of aberration and time-of-flight delays and also rotational sweepback of 13-field lines, in the geometric context of polar cap (PC), slot gap (SG), outer gap (OG), and two-pole caustic (TPC) pulsar models. In contrast to the general belief that these very old, rapidly-rotating neutron stars (NSs) should have largely pair-starved magnetospheres due to the absence of significant pair production, we find that most of the light curves are best fit by SG and OG models, which indicates the presence of narrow accelerating gaps limited by robust pair production -- even in these pulsars with very low spin-down luminosities. The gamma-ray pulse shapes and relative phase lags with respect to the radio pulses point to high-altitude emission being dominant for all geometries. We also find exclusive differentiation of the current gamma-ray MSP population into two MSP sub-classes: light curve shapes and lags across wavebands impose either pair-starved PC (PSPC) or SG / OG-type geometries. In the first case, the radio pulse has a small lag with respect to the single gamma-ray pulse, while the (first) gamma-ray peak usually trails the radio by a large phase offset in the latter case. Finally, we find that the flux correction factor as a function of magnetic inclination and observer angles is typically of order unity for all models. Our calculation of light curves and flux correction factor f(_, _, P) for the case of MSPs is therefore complementary to the "ATLAS paper" of Watters et al. for younger pulsars.

  2. Multi-wavelength observations of the transitional millisecond pulsar binary XSSJ12270-4859

    CERN Document Server

    de Martino, Domitilla; Belloni, Tomaso; Burgay, Marta; Wilhelmi, Emma De Ona; Li, J; Pellizzoni, Alberto; Possenti, Andrea; Rea, Nanda; Torres, Diego F

    2015-01-01

    We present an analysis of X-ray, Ultraviolet and optical/near-IR photometric data of the transitional millisecond pulsar binary XSSJ12270-4859, obtained at different epochs after the transition to a rotation-powered radio pulsar state. The observations, while confirming the large-amplitude orbital modulation found in previous studies after the state change, also reveal an energy dependence of the amplitudes as well as variations on time scale of months. The amplitude variations are anti-correlated in the X-ray and the UV/optical bands. The average X-ray spectrum is described by a power law with \\Gamma index of 1.07(8) without requiring an additional thermal component. The power law index \\Gamma varies from 1.2 to 1.0 between superior and inferior conjunction of the neutron star. We interpret the observed X-ray behaviour in terms of synchrotron radiation emitted in an extended intrabinary shock, located between the pulsar and the donor star, which is eclipsed due to the companion orbital motion. The G5 type do...

  3. Two Millisecond Pulsars Discovered by the PALFA Survey and a Shapiro Delay Measurement

    CERN Document Server

    Deneva, J S; Cordes, J M; Lyne, A G; Ransom, S M; Cognard, I; Camilo, F; Nice, D J; Stairs, I H; Allen, B; Bhat, N D R; Bogdanov, S; Brazier, A; Champion, D J; Chatterjee, S; Crawford, F; Desvignes, G; Hessels, J W T; Jenet, F A; Kaspi, V M; Knispel, B; Kramer, M; Lazarus, P; van Leeuwen, J; Lorimer, D R; Lynch, R S; McLaughlin, M A; Scholz, P; Siemens, X; Stappers, B W; Stovall, K; Venkataraman, A

    2012-01-01

    We present two millisecond pulsar discoveries from the PALFA survey of the Galactic plane with the Arecibo telescope. PSR J1955+2527 is an isolated pulsar with a period of 4.87 ms, and PSR J1949+3106 has a period of 13.14 ms and is in a 1.9-day binary system with a massive companion. Their timing solutions, based on 4 years of timing measurements with the Arecibo, Green Bank, Nan\\c{c}ay and Jodrell Bank telescopes, allow precise determination of spin and astrometric parameters, including precise determinations of their proper motions. For PSR J1949+3106, we can clearly detect the Shapiro delay. From this we measure the pulsar mass to be 1.47(+0.43/-0.31) solar masses, the companion mass to be 0.85(+0.14/-0.11) solar masses and the orbital inclination to be i = 79.9(+1.6/-1.9) degrees, where uncertainties correspond to +/- 1-\\sigma\\ confidence levels. With continued timing, we expect to also be able to detect the advance of periastron for the J1949+3106 system. This effect, combined with the Shapiro delay, wil...

  4. Five new millisecond pulsars from a radio survey of 14 unidentified Fermi-LAT gamma-ray sources

    NARCIS (Netherlands)

    M. Kerr; F. Camilo; T.J. Johnson; E.C. Ferrara; L. Guillemot; A.K. Harding; J. Hessels; S. Johnston; M. Keith; M. Kramer; S.M. Ransom; P.S. Ray; J.E. Reynolds; J. Sarkissian; K.S. Wood

    2012-01-01

    We have discovered five millisecond pulsars (MSPs) in a survey of 14 unidentified Fermi Large Area Telescope sources in the southern sky using the Parkes radio telescope. PSRs J0101-6422, J1514-4946, and J1902-5105 reside in binaries, while PSRs J1658-5324 and J1747-4036 are isolated. Using an ephem

  5. Discovery of the Millisecond Pulsar PSR J2043+1711 in a Fermi Source with the Nancay Radio Telescope

    Science.gov (United States)

    Guillemot, L.; Freire, P. C. C.; Cognard, I.; Johnson, T. J.; Takahashi, Y.; Kataoka, J.; Desvignes, G.; Camilo, F.; Ferrara, E. C.; Harding, A. K.; Janssen, G. H.; Keith, M.; Kerr, M.; Kramer, M.; Parent, D.; Ransom, S. M.; Ray, P. S.; Saz Parkinson, P. M.; Smith, D. A.; Stappers, W.; Theureau, G.

    2012-01-01

    We report the discovery of the millisecond pulsar PSR J2043+1711 in a search of a Fermi Large Area Telescope (LAT) source with no known associations, with the Nancay Radio Telescope. The new pulsar, confirmed with the Green Bank Telescope, has a spin period of 2.38 ms, is relatively nearby (d approx. < 2 kpc) and is in a 1.48-d orbit around a low-mass companion, probably an He-type white dwarf. Using an ephemeris based on Arecibo, Nancay and Westerbork timing measurements, pulsed gamma-ray emission was detected in the data recorded by the Fermi LAT. The gamma-ray light curve and spectral properties are typical of other gamma-ray millisecond pulsars seen with Fermi. X-ray observations of the pulsar with Suzaku and the Swift X-ray Telescope yielded no detection. At 1.4 GHz, we observe strong flux density variations because of interstellar diffractive scintillation; however, a sharp peak can be observed at this frequency during bright scintillation states. At 327 MHz, the pulsar is detected with a much higher signal-to-noise ratio and its flux density is far more steady. However, at that frequency the Arecibo instrumentation cannot yet fully resolve the pulse profile. Despite that, our pulse time-of-arrival measurements have a post-fit residual rms of 2 micro s. This and the expected stability of this system have made PSR J2043+1711 one of the first new Fermi-selected millisecond pulsars to be added to pulsar gravitational wave timing arrays. It has also allowed a significant measurement of relativistic delays in the times of arrival of the pulses due to the curvature of space-time near the companion, but not yet with enough precision to derive useful masses for the pulsar and the companion. Nevertheless, a mass for the pulsar between 1.7 and 2.0 solar Mass can be derived if a standard millisecond pulsar formation model is assumed. In this paper, we also present a comprehensive summary of pulsar searches in Fermi LAT sources with the Nancay Radio Telescope to date.

  6. High energy emission from the nebula around the Black Widow binary system containing millisecond pulsar B1957+20

    CERN Document Server

    Bednarek, W

    2013-01-01

    The features of pulsed $\\gamma$-ray emission from classical and millisecond pulsars indicate that the high energy radiation processes in their inner magnetospheres occur in a similar way. In the last decade several TeV $\\gamma$-ray nebulae have been discovered around classical pulsars. The above facts suggest that $\\gamma$-rays should be produced also in the surroundings of millisecond pulsars. We discuss a model for the bow shock nebula around the well known Black Widow binary system containing the millisecond pulsar B1957+20. This model predicts the existence of a synchrotron X-ray and inverse Compton $\\gamma$-ray nebula around this system. We want to find out whether $\\gamma$-ray emission from the nebula around B1957+20 could be detected by the future and present Cherenkov telescopes. Using the Monte Carlo method we followed the propagation of relativistic electrons in the vicinity of the pulsar. We calculated the very high energy radiation produced by them in the synchrotron process and the inverse Compto...

  7. XMM-Newton observations of two transient millisecond X-ray pulsars in quiescence

    CERN Document Server

    Campana, S; Stella, L; Israel, G L

    2005-01-01

    We report on XMM-Newton observations of two X-ray transient millisecond pulsars (XRTMSPs). We detected XTE J0929-314 with an unabsorbed luminosity of \\~7x10^{31} erg/s. (0.5-10 keV) at a fiducial distance of 10 kpc. The quiescent spectrum is consistent with a simple power law spectrum. The upper limit on the flux from a cooling neutron star atmosphere is about 20% of the total flux. XTE J1807-294 instead was not detected. We can put an upper limit on the source quiescent 0.5-10 keV unabsorbed luminosity <4x10^{31} erg/s at 8 kpc. These observations strenghten the idea that XRTMSPs have quiescent luminosities significantly lower than classical neutron star transients.

  8. The low-mass X-ray binary-millisecond radio pulsar birthrate problem revisited

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    We investigate the birthrate problem for low-mass X-ray binaries(LMXBs) and millisecond radio pulsars(MRPs) in this paper.We consider intermediate-mass and low-mass X-ray binaries(I/LMXBs) to be the progenitors of MRPs,and calculate their evolutionary response to the cosmic star formation rate(SFR) both semi-analytically and numerically.With a typical value(1 Gyr) of the LMXB lifetime,one may expect comparable birthrates of LMXBs and MRPs,but the calculated number of LMXBs is an order of magnitude higher than that observed in the Galaxy.Instead,we suggest that the birthrate problem could be solved if most MRPs have evolved from faint to rather than bright LMXBs.The former may have a population of-104 in the Galaxy.

  9. Rotochemical heating in millisecond pulsars: modified Urca reactions with uniform Cooper pairing gaps

    CERN Document Server

    Petrovich, Cristóbal

    2009-01-01

    Context: When a rotating neutron star loses angular momentum, the reduction in the centrifugal force makes it contract. This perturbs each fluid element, raising the local pressure and originating deviations from beta equilibrium that enhance the neutrino emissivity and produce thermal energy. This mechanism is named rotochemical heating and has previously been studied for neutron stars of nonsuperfluid matter, finding that they reach a quasi-steady configuration in which the rate at which the spin-down modifies the equilibrium concentrations is the same at which neutrino reactions restore the equilibrium. Aims: We describe the thermal effects of Cooper pairing with spatially uniform energy gaps of neutrons \\Delta_n and protons \\Delta_p on the rotochemical heating in millisecond pulsars (MSPs) when only modified Urca reactions are allowed. By this, we may determine the amplitude of the superfluid energy gaps for the neutron and protons needed to produce different thermal evolution of MSPs. Results: We find th...

  10. Properties and observability of glitches and anti-glitches in accreting pulsars

    CERN Document Server

    Ducci, L; Doroshenko, V; Santangelo, A; Mereghetti, S; Ferrigno, C

    2015-01-01

    Several glitches have been observed in young, isolated radio pulsars, while a clear detection in accretion-powered X-ray pulsars is still lacking. We use the "snowplow" model for pulsar glitches of Pizzochero (2011) and starquake models to determine for the first time the expected properties of glitches in accreting pulsars and their observability. Since some accreting pulsars show accretion-induced long-term spin-up, we also investigate the possibility that anti-glitches occur in these stars. We find that glitches caused by quakes in a slow accreting neutron star are very rare and their detection extremely unlikely. On the contrary, glitches and anti-glitches caused by a transfer of angular momentum between the superfluid neutron vortices and the non-superfluid component may take place in accreting pulsars more often. We calculate the maximum jump in angular velocity of an anti-glitch and we find that it is expected to be about 1E-5 - 1E-4 rad/s. We also note that since accreting pulsars usually have rotatio...

  11. Dynamic effects on cyclotron scattering in pulsar accretion columns

    Science.gov (United States)

    Brainerd, J. J.; Meszaros, P.

    1991-01-01

    A resonant scattering model for photon reprocessing in a pulsar accretion column is presented. The accretion column is optically thin to Thomson scattering and optically thick to resonant scattering at the cyclotron frequency. Radiation from the neutron star surface propagates freely through the column until the photon energy equals the local cyclotron frequency, at which point the radiation is scattered, much of it back toward the star. The radiation pressure in this regime is insufficient to stop the infall. Some of the scattered radiation heats the stellar surface around the base of the column, which adds a softer component to the spectrum. The partial blocking by the accretion column of X-rays from the surface produces a fan beam emission pattern. X-rays above the surface cyclotron frequency freely escape and are characterized by a pencil beam. Gravitational light bending produces a pencil beam pattern of column-scattered radiation in the antipodal direction, resulting in a strongly angle-dependent cyclotron feature.

  12. New limits on the population of normal and millisecond pulsars in the Large and Small Magellanic Clouds

    CERN Document Server

    Ridley, J P

    2010-01-01

    We model the potentially observable populations of normal and millisecond radio pulsars in the Large and Small Magellanic Clouds (LMC and SMC) where the known population currently stands at 19 normal radio pulsars. Taking into account the detection thresholds of previous surveys, and assuming optimal period and luminosity distributions based on studies of Galactic pulsars, we estimate there are (1.79 +/- 0.20) x 10^4 and (1.09 +/- 0.16) x 10^4 normal pulsars in the LMC and SMC respectively. When we attempt to correct for beaming effects, and the fraction of high-velocity pulsars which escape the clouds, we estimate birth rates in both the LMC and SMC to be comparable and in the range 0.5--1 pulsar per century. Although higher than estimates for the rate of core-collapse supernovae in the clouds, these pulsar birth rates are consistent with historical supernova observations in the past 300 yr. A substantial population of active radio pulsars (of order a few hundred thousand) have escaped the LMC and SMC and po...

  13. Formation of the planet around the millisecond pulsar J1719-1438

    CERN Document Server

    van Haaften, L M; Voss, R; Jonker, P G

    2012-01-01

    Context. Recently the discovery of PSR J1719-1438, a 5.8 ms pulsar with a companion in a 2.2 hr orbit, was reported. The combination of this orbital period and the very low mass function is unique. The discoverers, Bailes et al., proposed an ultracompact X-ray binary (UCXB) as the progenitor system. However, the standard UCXB scenario would not produce this system as the time required to reach this orbital period exceeds the current estimate of the age of the Universe. The detached state of the system aggravates the problem. Aims. We want to understand the evolutionary history of PSR J1719-1438, and determine under which circumstances it could have evolved from an UCXB. Methods. We model UCXB evolution varying the donor size and investigate the effect of a wind mass loss from the donor, and compare the results with the observed characteristics of PSR J1719-1438. Results. An UCXB can reach a 2.2 hr orbit within the age of the Universe, provided that 1) the millisecond pulsar can significantly heat and expand t...

  14. Einstein@Home Discovery of a PALFA Millisecond Pulsar in an Eccentric Binary Orbit

    CERN Document Server

    Knispel, B; Stappers, B W; Freire, P C C; Lazarus, P; Allen, B; Aulbert, C; Bock, O; Bogdanov, S; Brazier, A; Camilo, F; Cardoso, F; Chatterjee, S; Cordes, J M; Crawford, F; Deneva, J S; Eggenstein, H -B; Fehrmann, H; Ferdman, R; Hessels, J W T; Jenet, F A; Karako-Argaman, C; Kaspi, V M; van Leeuwen, J; Lorimer, D R; Lynch, R; Machenschalk, B; Madsen, E; McLaughlin, M A; Patel, C; Ransom, S M; Scholz, P; Siemens, X; Spitler, L G; Stairs, I H; Stovall, K; Swiggum, J K; Venkataraman, A; Wharton, R S; Zhu, W W

    2015-01-01

    We report the discovery of the millisecond pulsar (MSP) PSR J1950+2414 ($P=4.3$ ms) in a binary system with an eccentric ($e=0.08$) orbit in Pulsar ALFA survey observations with the Arecibo telescope. Its companion star has a median mass of 0.3 $M_\\odot$ and is most likely a white dwarf. Fully recycled MSPs like this one are thought to be old neutron stars spun-up by mass transfer from a companion star. This process should circularize the orbit, as is observed for the vast majority of binary MSPs, which predominantly have orbital eccentricities $e < 0.001$. However, four recently discovered binary MSPs have orbits with larger eccentricities ($0.03 < e < 0.4$); PSR J1950+2414 is only the fifth such system to be discovered. The upper limits for the the intrinsic spin period derivative and inferred surface magnetic field strength are comparable to those of the general MSP population. The large eccentricities of these systems are not compatible with the predictions of the standard recycling scenario: som...

  15. Exploring the intrabinary shock from the redback millisecond pulsar PSR J2129-0429

    CERN Document Server

    Hui, C Y; Park, S M; Takata, J; Li, K L; Tam, P H T; Lin, L C C; Kong, A K H; Cheng, K S; Kim, Chunglee

    2015-01-01

    We have investigated the intrabinary shock emission from the redback millisecond pulsar PSR J2129-0429 with XMM-Newton and Fermi. Orbital modulation in X-ray and UV can be clearly seen. Its X-ray modulation has a double-peak structure with a dip in between. The observed X-rays are non-thermal dominant which can be modeled by a power-law with a photon index of ~1.2. Intrabinary shock can be the origin of the observed X-rays. The UV light curve is resulted from the ellipsoidal modulation of the companion. Modeling the UV light curve prefers a large viewing angle. The heating effect of the UV light curve is found to be negligible which suggests the high energy radiation beam of PSR J2129-0429 does not direct toward its companion. On the other hand, no significant orbital modulation can be found in gamma-ray which suggests the majority of the gamma-rays come from the pulsar.

  16. Constraints on the Emission Geometries and Spin Evolution of Gamma-ray Millisecond Pulsars

    CERN Document Server

    Johnson, T J; Harding, A K; Guillemot, L; Smith, D A; Kramer, M; Celik, O; Hartog, P R den; Ferrara, E C; Hou, X; Lande, J; Ray, P S

    2014-01-01

    Millisecond pulsars (MSPs) are a growing class of gamma-ray emitters. Pulsed gamma-ray signals have been detected from more than 40 MSPs with the Fermi Large Area Telescope (LAT). The wider radio beams and more compact magnetospheres of MSPs enable studies of emission geometries over a broader range of phase space than non-recycled radio-loud gamma-ray pulsars. We have modeled the gamma-ray light curves of 40 LAT-detected MSPs using geometric emission models assuming a vacuum retarded-dipole magnetic field. We modeled the radio profiles using a single-altitude hollow-cone beam, with a core component when indicated by polarimetry; however, for MSPs with gamma-ray and radio light curve peaks occurring at nearly the same rotational phase we assume that the radio emission is co-located with the gamma rays and caustic in nature. The best-fit parameters and confidence intervals are determined using a maximum likelihood technique. We divide the light curves into three model classes, with gamma-ray peaks trailing (Cl...

  17. X-ray and $\\gamma$-ray Studies of the Millisecond Pulsar and PossibleX-ray Binary/Radio Pulsar Transition Object PSR J1723-2837

    CERN Document Server

    Bogdanov, Slavko; Crawford, Fronefield; Possenti, Andrea; McLaughlin, Maura A; Freire, Paulo

    2013-01-01

    We present X-ray observations of the ``redback'' eclipsing radio millisecond pulsar and candidate radio pulsar/X-ray binary transition object PSR J1723-2837. The X-ray emission from the system is predominantly non-thermal and exhibits pronounced variability as a function of orbital phase, with a factor of ~2 reduction in brightness around superior conjunction. Such temporal behavior appears to be a defining characteristic of this variety of peculiar millisecond pulsar binaries and is likely caused by a partial geometric occultation by the main-sequence-like companion of a shock within the binary. There is no indication of diffuse X-ray emission from a bow shock or pulsar wind nebula associated with the pulsar. We also report on a search for point source emission and $\\gamma$-ray pulsations in Fermi Large Area Telescope data using a likelihood analysis and photon probability weighting. Although PSR J1723-2837 is consistent with being a $\\gamma$-ray point source, due to the strong Galactic diffuse emission at i...

  18. The accretion flow to the intermittent accreting ms pulsar, HETE J1900.1-2455, as observed by XMM-Newton and RXTE

    CERN Document Server

    Papitto, A; Di Salvo, T; Egron, E; Bozzo, E; Burderi, L; Iaria, R; Riggio, A; Menna, M T

    2012-01-01

    We present a study of the accretion flow to the intermittent accreting millisecond pulsar, HETE J1900.1-2455, based on observations performed simultaneously by XMM-Newton and RXTE. The 0.33-50 keV spectrum is described by the sum of a hard Comptonized component originated in an optically thin {\\tau}~1 corona, a soft kTin~0.2 keV component interpreted as accretion disc emission, and of disc reflection of the hard component. Two emission features are detected at energies of 0.98(1) and 6.58(7) keV, respectively. The latter is identified as K{\\alpha} transition of Fe XXIII-XXV. A simultaneous detection in EPIC-pn, EPIC-MOS2, and RGS spectra favours an astrophysical origin also for the former, which has an energy compatible with Fe-L{\\alpha} and helium-like Ne-K{\\alpha} transitions. Broadness of the two features suggests a common origin, resulting from reflection in an accretion disc with inclination of (30+4{\\deg}), and extending down to Rin=25(+16,-11) gravitational radii from the compact object. However, the s...

  19. NuSTAR observations of the state transition of millisecond pulsar binary PSR J1023+0038

    Energy Technology Data Exchange (ETDEWEB)

    Tendulkar, Shriharsh P.; Bellm, Eric; Harrison, Fiona A. [California Institute of Technology, 1200 E California Blvd, MC 249-17, Pasadena, CA 91125 (United States); Yang, Chengwei; An, Hongjun; Kaspi, Victoria M. [Department of Physics, McGill University, 3600 University St, Montreal, QC H3A 2T8 (Canada); Archibald, Anne M.; Bassa, Cees; Hessels, Jason W. T.; Janssen, Gemma H. [ASTRON, The Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA, Dwingeloo (Netherlands); Bogdanov, Slavko [Columbia Astrophysics Laboratory, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Lyne, Andrew G.; Stappers, Benjamin [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL (United Kingdom); Patruno, Alessandro [Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden (Netherlands); Stern, Daniel [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Tomsick, John A.; Boggs, Steven E.; Craig, William W. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Chakrabarty, Deepto [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 70 Vassar Street, Cambridge, MA 02139 (United States); Christensen, Finn E., E-mail: spt@astro.caltech.edu [DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark); and others

    2014-08-20

    We report NuSTAR observations of the millisecond pulsar-low-mass X-ray binary (LMXB) transition system PSR J1023+0038 from 2013 June and October, before and after the formation of an accretion disk around the neutron star. Between June 10 and 12, a few days to two weeks before the radio disappearance of the pulsar, the 3-79 keV X-ray spectrum was well fit by a simple power law with a photon index of Γ=1.17{sub −0.07}{sup +0.08} (at 90% confidence) with a 3-79 keV luminosity of 7.4 ± 0.4 × 10{sup 32} erg s{sup –1}. Significant orbital modulation was observed with a modulation fraction of 36% ± 10%. During the October 19-21 observation, the spectrum is described by a softer power law (Γ=1.66{sub −0.05}{sup +0.06}) with an average luminosity of 5.8 ± 0.2 × 10{sup 33} erg s{sup –1} and a peak luminosity of ≈1.2 × 10{sup 34} erg s{sup –1} observed during a flare. No significant orbital modulation was detected. The spectral observations are consistent with previous and current multiwavelength observations and show the hard X-ray power law extending to 79 keV without a spectral break. Sharp-edged, flat-bottomed dips are observed with widths between 30 and 1000 s and ingress and egress timescales of 30-60 s. No change in hardness ratio was observed during the dips. Consecutive dip separations are log-normal in distribution with a typical separation of approximately 400 s. These dips are distinct from dipping activity observed in LMXBs. We compare and contrast these dips to observations of dips and state changes in the similar transition systems PSR J1824–2452I and XSS J1227.0–4859 and discuss possible interpretations based on the transitions in the inner disk.

  20. CONSTRAINTS ON THE EMISSION GEOMETRIES AND SPIN EVOLUTION OF GAMMA-RAY MILLISECOND PULSARS

    International Nuclear Information System (INIS)

    Millisecond pulsars (MSPs) are a growing class of gamma-ray emitters. Pulsed gamma-ray signals have been detected from more than 40 MSPs with the Fermi Large Area Telescope (LAT). The wider radio beams and more compact magnetospheres of MSPs enable studies of emission geometries over a broader range of phase space than non-recycled radio-loud gamma-ray pulsars. We have modeled the gamma-ray light curves of 40 LAT-detected MSPs using geometric emission models assuming a vacuum retarded-dipole magnetic field. We modeled the radio profiles using a single-altitude hollow-cone beam, with a core component when indicated by polarimetry; however, for MSPs with gamma-ray and radio light curve peaks occurring at nearly the same rotational phase, we assume that the radio emission is co-located with the gamma rays and caustic in nature. The best-fit parameters and confidence intervals are determined using a maximum likelihood technique. We divide the light curves into three model classes, with gamma-ray peaks trailing (Class I), aligned (Class II), or leading (Class III) the radio peaks. Outer gap and slot gap (two-pole caustic) models best fit roughly equal numbers of Class I and II, while Class III are exclusively fit with pair-starved polar cap models. Distinguishing between the model classes based on typical derived parameters is difficult. We explore the evolution of the magnetic inclination angle with period and spin-down power, finding possible correlations. While the presence of significant off-peak emission can often be used as a discriminator between outer gap and slot gap models, a hybrid model may be needed

  1. CONSTRAINTS ON THE EMISSION GEOMETRIES AND SPIN EVOLUTION OF GAMMA-RAY MILLISECOND PULSARS

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, T. J. [National Research Council Research Associate, National Academy of Sciences, Washington, DC 20001 (United States); Venter, C. [Centre for Space Research, North-West University, Potchefstroom Campus, Private Bag X6001, 2520 Potchefstroom (South Africa); Harding, A. K.; Çelik, Ö.; Ferrara, E. C. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Guillemot, L. [Laboratoire de Physique et Chimie de l' Environnement, LPCE UMR 6115 CNRS, F-45071 Orléans Cedex 02 (France); Smith, D. A.; Hou, X. [Centre d' Études Nucléaires de Bordeaux Gradignan, IN2P3/CNRS, Université Bordeaux 1, BP120, F-33175 Gradignan Cedex (France); Kramer, M. [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn (Germany); Den Hartog, P. R. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Lande, J. [Twitter Inc., 1355 Market Street 900, San Francisco, CA 94103 (United States); Ray, P. S., E-mail: tyrel.j.johnson@gmail.com, E-mail: Christo.Venter@nwu.ac.za, E-mail: ahardingx@yahoo.com [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States)

    2014-07-01

    Millisecond pulsars (MSPs) are a growing class of gamma-ray emitters. Pulsed gamma-ray signals have been detected from more than 40 MSPs with the Fermi Large Area Telescope (LAT). The wider radio beams and more compact magnetospheres of MSPs enable studies of emission geometries over a broader range of phase space than non-recycled radio-loud gamma-ray pulsars. We have modeled the gamma-ray light curves of 40 LAT-detected MSPs using geometric emission models assuming a vacuum retarded-dipole magnetic field. We modeled the radio profiles using a single-altitude hollow-cone beam, with a core component when indicated by polarimetry; however, for MSPs with gamma-ray and radio light curve peaks occurring at nearly the same rotational phase, we assume that the radio emission is co-located with the gamma rays and caustic in nature. The best-fit parameters and confidence intervals are determined using a maximum likelihood technique. We divide the light curves into three model classes, with gamma-ray peaks trailing (Class I), aligned (Class II), or leading (Class III) the radio peaks. Outer gap and slot gap (two-pole caustic) models best fit roughly equal numbers of Class I and II, while Class III are exclusively fit with pair-starved polar cap models. Distinguishing between the model classes based on typical derived parameters is difficult. We explore the evolution of the magnetic inclination angle with period and spin-down power, finding possible correlations. While the presence of significant off-peak emission can often be used as a discriminator between outer gap and slot gap models, a hybrid model may be needed.

  2. Constraints On the Emission Geometries and Spin Evolution Of Gamma-Ray Millisecond Pulsars

    Science.gov (United States)

    Johnson, T. J.; Venter, C.; Harding, A. K.; Guillemot, L.; Smith, D. A.; Kramer, M.; Celik, O.; den Hartog, P. R.; Ferrara, E. C.; Hou, X.; Lande, J.; Ray, P. S.

    2014-01-01

    Millisecond pulsars (MSPs) are a growing class of gamma-ray emitters. Pulsed gamma-ray signals have been detected from more than 40 MSPs with the Fermi Large Area Telescope (LAT). The wider radio beams and more compact magnetospheres of MSPs enable studies of emission geometries over a broader range of phase space than non-recycled radio-loud gamma-ray pulsars. We have modeled the gamma-ray light curves of 40 LAT-detected MSPs using geometric emission models assuming a vacuum retarded-dipole magnetic field. We modeled the radio profiles using a single-altitude hollow-cone beam, with a core component when indicated by polarimetry; however, for MSPs with gamma-ray and radio light curve peaks occurring at nearly the same rotational phase, we assume that the radio emission is co-located with the gamma rays and caustic in nature. The best-fit parameters and confidence intervals are determined using amaximum likelihood technique.We divide the light curves into three model classes, with gamma-ray peaks trailing (Class I), aligned (Class II), or leading (Class III) the radio peaks. Outer gap and slot gap (two-pole caustic) models best fit roughly equal numbers of Class I and II, while Class III are exclusively fit with pair-starved polar cap models. Distinguishing between the model classes based on typical derived parameters is difficult. We explore the evolution of the magnetic inclination angle with period and spin-down power, finding possible correlations. While the presence of significant off-peak emission can often be used as a discriminator between outer gap and slot gap models, a hybrid model may be needed.

  3. SCINTILLATION ARCS IN LOW-FREQUENCY OBSERVATIONS OF THE TIMING-ARRAY MILLISECOND PULSAR PSR J0437–4715

    Energy Technology Data Exchange (ETDEWEB)

    Bhat, N. D. R.; Ord, S. M.; Tremblay, S. E.; McSweeney, S. J.; Tingay, S. J. [International Centre for Radio Astronomy Research, Curtin University, Bentley, WA 6102 (Australia)

    2016-02-10

    Low-frequency observations of pulsars provide a powerful means for probing the microstructure in the turbulent interstellar medium (ISM). Here we report on high-resolution dynamic spectral analysis of our observations of the timing-array millisecond pulsar PSR J0437–4715 with the Murchison Widefield Array (MWA), enabled by our recently commissioned tied-array beam processing pipeline for voltage data recorded from the high time resolution mode of the MWA. A secondary spectral analysis reveals faint parabolic arcs akin to those seen in high-frequency observations of pulsars with the Green Bank and Arecibo telescopes. Data from Parkes observations at a higher frequency of 732 MHz reveal a similar parabolic feature with a curvature that scales approximately as the square of the observing wavelength (λ{sup 2}) to the MWA's frequency of 192 MHz. Our analysis suggests that scattering toward PSR J0437–4715 predominantly arises from a compact region about 115 pc from the Earth, which matches well with the expected location of the edge of the Local Bubble that envelopes the local Solar neighborhood. As well as demonstrating new and improved pulsar science capabilities of the MWA, our analysis underscores the potential of low-frequency pulsar observations for gaining valuable insights into the local ISM and for characterizing the ISM toward timing-array pulsars.

  4. Low-Mass X-Ray Binaries, Millisecond Radio Pulsars, and the Cosmic Star Formation Rate

    CERN Document Server

    White, N E; White, Nicholas E.; Ghosh, Pranab

    1998-01-01

    We report on the implications of the peak in the cosmic star-formation rate (SFR) at redshift z ~ 1.5 for the resulting population of low-mass X-ray binaries(LMXB) and for that of their descendants, the millisecond radio pulsars (MRP). Since the evolutionary timescales of LMXBs, their progenitors, and their descendants are thought be significant fractions of the time-interval between the SFR peak and the present epoch, there is a lag in the turn-on of the LMXB population, with the peak activity occurring at z ~ 0.5 - 1.0. The peak in the MRP population is delayed further, occurring at z < 0.5. We show that the discrepancy between the birthrate of LMXBs and MRPs, found under the assumption of a stead-state SFR, can be resolved for the population as a whole when the effects of a time-variable SFR are included. A discrepancy may persist for LMXBs with short orbital periods, although a detailed population synthesis will be required to confirm this. Further, since the integrated X-ray luminosity distribution of...

  5. Statistical and polarization properties of giant pulses of the millisecond pulsar B1937+21

    CERN Document Server

    Zhuravlev, V I; Soglasnov, V A; Kondrat'ev, V I; Kovalev, Y Y; Bartel, N; Ghigo, F

    2013-01-01

    We have studied the statistical and polarization properties of giant pulses (GPs) emitted by the millisecond pulsar B1937+21, with high sensitivity and time resolution. The observations were made in June 2005 with the 100-m Robert C. Byrd Green Bank Telescope at S-band (2052-2116 MHz) using the Mk5A VLBI recording system, with formal time resolution of 16 ns. The total observing time was about 4.5 hours; the rate of detection of GPs was about 130 per hour at the average longitudes of the main pulse (MPGPs) and 60 per hour at the interpulse (IPGPs). While the average profile shows well-defined polarization behavior, with regular evolution of the linear polarization position angle (PA), GPs exhibit random properties, occasionally having high linear or circular polarization. Neither MPGPs nor IPGPs show a preferred PA. The cumulative probability distribution (CPD) of GP pulse energy was constructed down to the level where GPs merge with regular pulses and noise. For both MPGPs and IPGPs, the CPD follows a power ...

  6. A millisecond pulsar candidate in a 21-hr orbit: 3FGL J0212.1+5320

    CERN Document Server

    Linares, Manuel; Rodríguez-Gil, Pablo; Shahbaz, Tariq; Casares, Jorge; Fariña, Cecilia; Karjalainen, Raine

    2016-01-01

    We present the discovery of a variable optical counterpart to the unidentified gamma-ray source 3FGL J0212.1+5320, and argue this is a new compact binary millisecond pulsar (MSP) candidate. We show 3FGL J0212.1+5320 hosts a semi-detached binary with a 0.86955$\\pm$0.00015 d orbital period and a F6-type companion star at an estimated distance of D=1.1$\\pm$0.2 kpc, with a radial velocity curve semi-amplitude K$_2$=214.1$\\pm$5.0 km s$^{-1}$ and a projected rotational velocity of Vsin(i)=73.2$\\pm$1.6 km s$^{-1}$. We find a hard X-ray source at the same location with a 0.5$-$10 keV luminosity L$_\\mathrm{X}$=2.6$\\times$10$^{32}$ (D/1.1 kpc)$^2$ erg s$^{-1}$, which strengthens the MSP identification. Our results imply a mass ratio q=M$_2$/M$_1$=0.26$^{+0.02}_{-0.03}$ if the companion star fills its Roche lobe, and q$\\gtrsim$0.23 in any case. This classifies 3FGL J0212.1+5320 as a "redback" binary MSP; if its MSP nature is confirmed, this will be the brightest compact binary MSP in the optical band (r'$\\simeq$14.3 mag...

  7. The millisecond pulsar mass distribution: Evidence for bimodality and constraints on the maximum neutron star mass

    CERN Document Server

    Antoniadis, John; Ozel, Feryal; Barr, Ewan; Champion, David J; Freire, Paulo C C

    2016-01-01

    The mass function of neutron stars (NSs) contains information about the late evolution of massive stars, the supernova explosion mechanism, and the equation-of-state of cold, nuclear matter beyond the nuclear saturation density. A number of recent NS mass measurements in binary millisecond pulsar (MSP) systems increase the fraction of massive NSs (with $M > 1.8$ M$_{\\odot}$) to $\\sim 20\\% $ of the observed population. In light of these results, we employ a Bayesian framework to revisit the MSP mass distribution. We find that a single Gaussian model does not sufficiently describe the observed population. We test alternative empirical models and infer that the MSP mass distribution is strongly asymmetric. The diversity in spin and orbital properties of high-mass NSs suggests that this is most likely not a result of the recycling process, but rather reflects differences in the NS birth masses. The asymmetry is best accounted for by a bimodal distribution with a low mass component centred at $1.393_{-0.029}^{+0.0...

  8. An eccentric binary millisecond pulsar with a helium white dwarf companion in the Galactic Field

    CERN Document Server

    Antoniadis, John; Stovall, Kevin; Freire, Paulo C; Deneva, Julia S; Koester, Detlev; Jenet, Frederick; Martinez, Jose

    2016-01-01

    Low-mass white dwarfs (LMWDs) are believed to be exclusive products of binary evolution, as the Universe is not yet old enough to produce them from single stars. Because of the strong tidal forces operating during the binary interaction phase, the remnant host systems observed today are expected to have negligible eccentricities. Here, we report on the first unambiguous identification of a LMWD in an eccentric (e=0.13) orbit with a millisecond pulsar, which directly contradicts this picture. We use our spectra and radio-timing solution (derived elsewhere) to infer the WD temperature T_eff = 8600 +/- 190 K) and 3D systemic velocity (179.5 km\\s). We also place model-independent constraints on the WD radius (R_WD = 0.024+/- 0.004/0.002 R_sun) and surface gravity (log g = 7.11 +/- 0.08/0.16 dex). The WD and kinematic properties are consistent with the expectations for low-mass X-ray binary evolution and disfavour a three-body formation channel. In the case of the high eccentricity being the result of a spontaneou...

  9. Discovery of an ultracompact gamma-ray millisecond pulsar binary candidate

    CERN Document Server

    Kong, A K H; Hui, C Y; Tam, P H T; Hu, C P; Takata, J; Lin, L C C; Cheng, K S; Yen, T -C; Park, S M; Kim, C L

    2014-01-01

    We report multi-wavelength observations of the unidentified Fermi object 2FGL J1653.6-0159. With the help of high-resolution X-ray observation, we have identified an X-ray and optical counterpart of 2FGL J1653.6-0159. The source exhibits a periodic modulation of 74.93 min in optical and possibly also in X-ray. We suggest that 2FGL J1653.6-0159 is a compact binary system with an orbital period of 74.93 min. Combining the gamma-ray and X-ray properties, 2FGL J1653.6-0159 is potentially a black widow/redback type gamma-ray millisecond pulsar (MSP). The optical and X-ray lightcurve profile shows that the companion is mildly heated by the high-energy emission and the X-rays are from intrabinary shock. Although no radio pulsation has been detected yet, we estimated that the spin period of the MSP is ~2 ms based on a theoretical model. If pulsation can be confirmed in the future, 2FGL J1653.6-0159 will become the first ultracompact rotation-powered MSP.

  10. High-fidelity radio astronomical polarimetry using a millisecond pulsar as a polarized reference source

    CERN Document Server

    van Straten, W

    2012-01-01

    A new method of polarimetric calibration is presented in which the instrumental response is derived from regular observations of PSR J0437-4715 based on the assumption that the mean polarized emission from this millisecond pulsar remains constant over time. The technique is applicable to any experiment in which high-fidelity polarimetry is required over long time scales; it is demonstrated by calibrating 7.2 years of high-precision timing observations of PSR J1022+1001 made at the Parkes Observatory. Application of the new technique followed by arrival time estimation using matrix template matching yields post-fit residuals with an uncertainty-weighted standard deviation of 880 ns, two times smaller than that of arrival time residuals obtained via conventional methods of calibration and arrival time estimation. The precision achieved by this experiment yields the first significant measurements of the secular variation of the projected semi-major axis, the precession of periastron, and the Shapiro delay; it al...

  11. Estimating the GeV Emission of Millisecond Pulsars in Dwarf Spheroidal Galaxies

    CERN Document Server

    Winter, Miles; Bechtol, Keith; Vandenbroucke, Justin

    2016-01-01

    We estimate the conventional astrophysical emission intrinsic to dwarf spheroidal satellite galaxies (dSphs) of the Milky Way, focusing on millisecond pulsars (MSPs), and evaluate the potential for confusion with dark matter (DM) annihilation signatures at GeV energies. In low-density stellar environments, such as dSphs, the abundance of MSPs is expected to be proportional to stellar mass. Accordingly, we construct the $\\gamma$-ray luminosity function of MSPs in the Milky Way disk, where $>90$ individual MSPs have been detected with the $\\textit{Fermi}$ Large Area Telescope (LAT), and scale this luminosity function to the stellar masses of 30 dSphs to estimate the cumulative emission from their MSP populations. We predict that MSPs in the highest stellar mass dSphs, Fornax and Sculptor, produce a $\\gamma$-ray flux $>500$ MeV of $\\sim10^{-11}$~ph~cm$^{-2}$~s$^{-1}$, which is a factor $\\sim10$ below the current LAT sensitivity at high Galactic latitudes. The MSP emission in ultra-faint dSphs, including targets ...

  12. Statistical and polarization properties of giant pulses of the millisecond pulsar B1937+21

    Science.gov (United States)

    Zhuravlev, V. I.; Popov, M. V.; Soglasnov, V. A.; Kondrat'ev, V. I.; Kovalev, Y. Y.; Bartel, N.; Ghigo, F.

    2013-04-01

    We have studied the statistical and polarization properties of giant pulses (GPs) emitted by the millisecond pulsar B1937+21, with high sensitivity and time resolution. The observations were made in 2005 June with the 100-m Robert C. Byrd Green Bank Telescope at S-band (2052-2116 MHz) using the Mk5A Very Long Baseline Interferometry recording system, with formal time resolution of 16 ns. The total observing time was about 4.5 h; the rate of detection of GPs was about 130 per hour at the average longitudes of the main pulse (MPGPs) and 60 per hour at the interpulse (IPGPs). While the average profile shows well-defined polarization behaviour, with regular evolution of the linear polarization position angle (PA), GPs exhibit random properties, occasionally having high linear or circular polarization. Neither MPGPs nor IPGPs show a preferred PA. The cumulative probability distribution (CPD) of GP pulse energy was constructed down to the level where GPs merge with regular pulses and noise. For both MPGPs and IPGPs, the CPD follows a power law with a break, the power index changing from -2.4 at high energy to -1.6 for low energy. Pulse smearing due to scattering masks the intrinsic shape and duration of the detected GPs. The smearing time varied during the observing session within a range of a few hundred nanoseconds. The measured polarization and statistical properties of GPs impose strong constraints on physical models of GPs. Some of these properties support a model in which GPs are generated by the electric discharge caused by magnetic reconnection of field lines connecting the opposite magnetic poles of a neutron star.

  13. Evidence for Magneto-Levitation Accretion in Long-Period X-ray Pulsars

    CERN Document Server

    Ikhsanov, Nazar; Likh, Yury

    2014-01-01

    Study of observed spin evolution of long-period X-ray pulsars challenges quasi-spherical and Keplerian disk accretion scenarios. It suggests that the magnetospheric radius of the neutron stars is substantially smaller than Alfven radius and the spin-down torque applied to the star from accreting material significantly exceeds the value predicted by the theory. We show that these problems can be avoided if the fossil magnetic field of the accretion flow itself is incorporated into the accretion model. The initially spherical flow in this case decelerates by its own magnetic field and converts into a non-Keplerian disk (magnetic slab) in which the material is confined by its intrinsic magnetic field ("levitates") and slowly moves towards the star on a diffusion timescale. Parameters of pulsars expected within this magneto-levitation accretion scenario are evaluated.

  14. Study of frame tie between planetary ephemerids and ICRF with millisecond and young pulsars

    Science.gov (United States)

    Wang, Jingbo; Hobbs, George; Coles, William

    2016-07-01

    The positions of pulsar can be measured by pulsar timing technology and VLBI astrometry with high precision. They can be used to tie between referece frame based on solar system ephemerids and distant quasars with high accuracy. In this paper, we have collect the pulsar positions with VLBI measurement and obtain the pulsar timing position form Nanshan and Parkes data archive. We derive the rotation matrix between JPL DE and ICRF reference frame.

  15. X-ray and γ-ray studies of the millisecond pulsar and possible X-ray binary/radio pulsar transition object PSR J1723-2837

    Energy Technology Data Exchange (ETDEWEB)

    Bogdanov, Slavko [Columbia Astrophysics Laboratory, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Esposito, Paolo [INAF-IASF Milano, via East Bassini 15, I-20133 Milano (Italy); Crawford III, Fronefield [Department of Physics and Astronomy, Franklin and Marshall College, P.O. Box 3003, Lancaster, PA 17604 (United States); Possenti, Andrea [INAF-Osservatorio Astronomico di Cagliari, Loc. Poggio dei Pini, Strada 54, I-09012 Capoterra (Italy); McLaughlin, Maura A. [Department of Physics and Astronomy, West Virginia University, 210E Hodges Hall, Morgantown, WV 26506 (United States); Freire, Paulo, E-mail: slavko@astro.columbia.edu [Max-Planck-Institut für Radioastronomie, D-53121 Bonn (Germany)

    2014-01-20

    We present X-ray observations of the 'redback' eclipsing radio millisecond pulsar (MSP) and candidate radio pulsar/X-ray binary transition object PSR J1723-2837. The X-ray emission from the system is predominantly non-thermal and exhibits pronounced variability as a function of orbital phase, with a factor of ∼2 reduction in brightness around superior conjunction. Such temporal behavior appears to be a defining characteristic of this variety of peculiar MSP binaries and is likely caused by a partial geometric occultation by the main-sequence-like companion of a shock within the binary. There is no indication of diffuse X-ray emission from a bow shock or pulsar wind nebula associated with the pulsar. We also report on a search for point source emission and γ-ray pulsations in Fermi Large Area Telescope data using a likelihood analysis and photon probability weighting. Although PSR J1723-2837 is consistent with being a γ-ray point source, due to the strong Galactic diffuse emission at its position a definitive association cannot be established. No statistically significant pulsations or modulation at the orbital period are detected. For a presumed detection, the implied γ-ray luminosity is ≲5% of its spin-down power. This indicates that PSR J1723-2837 is either one of the least efficient γ-ray producing MSPs or, if the detection is spurious, the γ-ray emission pattern is not directed toward us.

  16. A LIKELY MILLISECOND PULSAR BINARY COUNTERPART FOR FERMI SOURCE 2FGL J2039.6–5620

    Energy Technology Data Exchange (ETDEWEB)

    Romani, Roger W., E-mail: rwr@astro.stanford.edu [Department of Physics, Stanford University, Stanford, CA 94305-4060 (United States)

    2015-10-20

    We have identified an optical/X-ray binary with an orbital period of P{sub b} = 5.47 hr as the likely counterpart of the Fermi source 2FGL J2039.6−5620. GROND, SOAR, and DES observations provide an accurate orbital period and allow us to compare to the light curve of an archival XMM exposure. Like many short-period optical/X-ray binaries associated with Large Area Telescope sources, this may be an interacting (black widow/redback) millisecond pulsar binary. The X-ray light curve is consistent with the emission associated with an intrabinary shock. The optical light curve shows evidence of companion heating, but has a peculiar asymmetric double peak. The nature of this optical structure is not yet clear; additional optical studies and, in particular, detection of an orbital modulation in a γ-ray pulsar are needed to elucidate the nature of this peculiar source.

  17. The NANOGrav Nine-year Data Set: Observations, Arrival Time Measurements, and Analysis of 37 Millisecond Pulsars

    CERN Document Server

    Arzoumanian, Z; Burke-Spolaor, S; Chamberlin, S; Chatterjee, S; Christy, B; Cordes, J M; Cornish, N; Crowter, K; Demorest, P B; Dolch, T; Ellis, J A; Ferdman, R D; Fonseca, E; Garver-Daniels, N; Gonzalez, M E; Jenet, F A; Jones, G; Jones, M; Kaspi, V M; Koop, M; Lazio, T J W; Lam, M T; Levin, L; Lommen, A N; Lorimer, D R; Luo, J; Lynch, R S; Madison, D; McLaughlin, M A; McWilliams, S T; Nice, D J; Palliyaguru, N; Pennucci, T T; Ransom, S M; Siemens, X; Stairs, I H; Stinebring, D R; Stovall, K; Swiggum, J K; Vallisneri, M; van Haasteren, R; Wang, Y; Zhu, W

    2015-01-01

    We present high-precision timing observations spanning up to nine years for 37 millisecond pulsars monitored with the Green Bank and Arecibo radio telescopes as part of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) project. We describe the observational and instrumental setups used to collect the data, and methodology applied for calculating pulse times of arrival; these include novel methods for measuring instrumental offsets and characterizing low signal-to-noise ratio timing results. The time of arrival data are fit to a physical timing model for each source, including terms that characterize time-variable dispersion measure and frequency-dependent pulse shape evolution. In conjunction with the timing model fit, we have performed a Bayesian analysis of a parameterized timing noise model for each source, and detect evidence for time-correlated "red" signals in 10 of the pulsars. Subsequent papers in this series will present further analysis of this data set aimed at detecting o...

  18. A Shapiro delay detection in the binary system hosting the millisecond pulsar PSR J1910-5959A

    CERN Document Server

    Corongiu, A; Possenti, A; Camilo, F; D'Amico, N; Lyne, A G; Manchester, R N; Sarkissian, J M; Bailes, M; Johnston, S; Kramer, M; van Straten, W

    2012-01-01

    PSR J1910-5959A is a binary pulsar with a helium white dwarf companion located about 6 arcmin from the center of the globular cluster NGC6752. Based on 12 years of observations at the Parkes radio telescope, the relativistic Shapiro delay has been detected in this system. We obtain a companion mass Mc = 0.180+/-0.018Msun (1sigma) implying that the pulsar mass lies in the range 1.1Msun <= Mp <= 1.5Msun. We compare our results with previous optical determinations of the companion mass, and examine prospects for using this new measurement for calibrating the mass-radius relation for helium white dwarfs and for investigating their evolution in a pulsar binary system. Finally we examine the set of binary systems hosting a millisecond pulsar and a low mass helium white dwarf for which the mass of both stars has been measured. We confirm that the correlation between the companion mass and the orbital period predicted by Tauris & Savonije reproduces the observed values but find that the predicted Mp - Pb co...

  19. Pulsed Gamma-Rays From the Millisecond Pulsar J0030+0451 with the Fermi Large Area Telescope

    International Nuclear Information System (INIS)

    We report the discovery of gamma-ray pulsations from the nearby isolated millisecond pulsar PSR J0030+0451 with the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (formerly GLAST). This discovery makes PSR J0030+0451 the second millisecond pulsar to be detected in gamma-rays after PSR J0218+4232, observed by the EGRET instrument on the Compton Gamma Ray Observatory. The spin-down power (dot E) = 3.5 x 1033 ergs s-1 is an order of magnitude lower than the empirical lower bound of previously known gamma-ray pulsars. The emission profile is characterized by two narrow peaks, respectively 0.07 ± 0.01 and 0.08 ± 0.02 wide, separated by 0.44 ± 0.02 in phase. The first gamma-ray peak falls 0.15 ± 0.01 after the main radio peak. The pulse shape is similar to that of the 'normal' gamma-ray pulsars. An exponentially cut-off power-law fit of the emission spectrum leads to an integral photon flux above 100 MeV of (6.76 ± 1.05 ± 1.35) x 10-8 cm-2 s-1 with cut-off energy (1.7 ± 0.4 ± 0.5) GeV. Based on its parallax distance of (300 ± 90) pc, we obtain a gamma-ray efficiency Lγ/(dot E) ≅ 15% for the conversion of spin-down energy rate into gamma-ray radiation, assuming isotropic emission.

  20. Pulsed Gamma-Rays From the Millisecond Pulsar J0030+0451 with the Fermi Large Area Telescope

    Energy Technology Data Exchange (ETDEWEB)

    Abdo, Aous A.; /Naval Research Lab, Wash., D.C.; Ackermann, M.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Atwood, W.B.; /UC, Santa Cruz; Axelsson, M. /Stockholm U., OKC /Stockholm U.; Baldini, L.; /INFN, Pisa; Ballet, J.; /DAPNIA, Saclay; Barbiellini, Guido; /INFN, Trieste /Trieste U.; Bastieri, Denis; /INFN, Padua /Padua U.; Battelino, M.; /Stockholm U., OKC /Royal Inst. Tech., Stockholm; Baughman, B.M.; /Ohio State U.; Bechtol, K.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bellazzini, R.; /INFN, Pisa; Berenji, B.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bloom, Elliott D.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bonamente, E.; /INFN, Perugia /Perugia U.; Borgland, A.W.; /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept.; Bregeon, J.; /INFN, Pisa; Brez, A.; /INFN, Pisa; Brigida, M.; /Bari U. /INFN, Bari; Bruel, P.; /Ecole Polytechnique; Burnett, Thompson H.; /Washington U., Seattle /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /IASF, Milan /IASF, Milan /DAPNIA, Saclay /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /George Mason U. /Naval Research Lab, Wash., D.C. /NASA, Goddard /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Perugia /Perugia U. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /LPCE, Orleans /Montpellier U. /Sonoma State U. /Stockholm U., OKC /Royal Inst. Tech., Stockholm /Stockholm U. /ASDC, Frascati /Naval Research Lab, Wash., D.C. /INFN, Trieste /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /UC, Santa Cruz /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /CENBG, Gradignan /CENBG, Gradignan /Montpellier U. /Bari U. /INFN, Bari /Stanford U., HEPL /KIPAC, Menlo Park /Stanford U., Phys. Dept. /INFN, Trieste /Hiroshima U.; /more authors..

    2011-11-17

    We report the discovery of gamma-ray pulsations from the nearby isolated millisecond pulsar PSR J0030+0451 with the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (formerly GLAST). This discovery makes PSR J0030+0451 the second millisecond pulsar to be detected in gamma-rays after PSR J0218+4232, observed by the EGRET instrument on the Compton Gamma Ray Observatory. The spin-down power {dot E} = 3.5 x 10{sup 33} ergs s{sup -1} is an order of magnitude lower than the empirical lower bound of previously known gamma-ray pulsars. The emission profile is characterized by two narrow peaks, respectively 0.07 {+-} 0.01 and 0.08 {+-} 0.02 wide, separated by 0.44 {+-} 0.02 in phase. The first gamma-ray peak falls 0.15 {+-} 0.01 after the main radio peak. The pulse shape is similar to that of the 'normal' gamma-ray pulsars. An exponentially cut-off power-law fit of the emission spectrum leads to an integral photon flux above 100 MeV of (6.76 {+-} 1.05 {+-} 1.35) x 10{sup -8} cm{sup -2} s{sup -1} with cut-off energy (1.7 {+-} 0.4 {+-} 0.5) GeV. Based on its parallax distance of (300 {+-} 90) pc, we obtain a gamma-ray efficiency L{sub {gamma}}/{dot E} {approx_equal} 15% for the conversion of spin-down energy rate into gamma-ray radiation, assuming isotropic emission.

  1. The High Time Resolution Universe Pulsar Survey X: Discovery of four millisecond pulsars and updated timing solutions of a further 12

    CERN Document Server

    Ng, C; Bates, S D; Bhat, N D R; Burgay, M; Burke-Spolaor, S; Champion, D J; Coster, P; Johnston, S; Keith, M J; Kramer, M; Levin, L; Petroff, E; Possenti, A; Stappers, B W; van Straten, W; Thornton, D; Tiburzi, C; Bassa, C G; Freire, P C C; Guillemot, L; Lyne, A G; Tauris, T M; Shannon, R M; Wex, N

    2014-01-01

    We report on the discovery of four millisecond pulsars (MSPs) in the High Time Resolution Universe (HTRU) pulsar survey being conducted at the Parkes 64-m radio telescope. All four MSPs are in binary systems and are likely to have white dwarf companions. In addition, we present updated timing solutions for 12 previously published HTRU MSPs, revealing new observational parameters such as five proper motion measurements and significant temporal dispersion measure variations in PSR J1017-7156. We discuss the case of PSR J1801-3210, which shows no significant period derivative after four years of timing data. Our best-fit solution shows a period derivative of the order of $10^{-23}$, an extremely small number compared to that of a typical MSP. However, it is likely that the pulsar lies beyond the Galactic Centre, and an unremarkable intrinsic period derivative is reduced to close to zero by the Galactic potential acceleration. Furthermore, we highlight the potential to employ PSR J1801-3210 in the strong equivale...

  2. Looking into the Theory of Pulsar Accretion: Cen X-3 and XTE J1946+274

    CERN Document Server

    Marcu, Diana M; Gottlieb, Amy M; Wolff, Michael T; Becker, Peter A; Wilms, Joern; Ferrigno, Carlo; Wood, Kent S

    2015-01-01

    This is an overview of pulsar accretion modeling. The physics of pulsar accretion, i.e., the process of plasma flow onto the neutron star surface, can be constrained from the spectral properties of the X-ray source. We discuss a new implementation of the physical continuum model developed by Becker and Wolff (2007, ApJ 654, 435). The model incorporates Comptonized blackbody, bremsstrahlung, and cyclotron emission. We discuss preliminary results of applying the new tool to the test cases of Suzaku data of Cen X-3 and XTE J1946+274. Cen X-3 is a persistent accreting pulsar with an O-star companion observed during a bright period. XTE J1946+274 is a transient accreting pulsar with a Be companion observed during a dim period. Both sources show spectra that are well described with an empirical Fermi Dirac cutoff power law model. We extend the spectral analysis by making the first steps towards a physical description of Cen X-3 and XTE J1946+274.

  3. DISCOVERY OF PSR J1227−4853: A TRANSITION FROM A LOW-MASS X-RAY BINARY TO A REDBACK MILLISECOND PULSAR

    Energy Technology Data Exchange (ETDEWEB)

    Roy, Jayanta; Bhattacharyya, Bhaswati; Stappers, Ben [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, M13 9PL (United Kingdom); Ray, Paul S.; Wolff, Michael; Wood, Kent S. [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States); Chengalur, Jayaram N. [National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune 411 007 (India); Deneva, Julia [NRC Research Associate, resident at Naval Research Laboratory, Washington, DC 20375-5352 (United States); Camilo, Fernando [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Johnson, Tyrel J. [College of Science, George Mason University, Fairfax, VA 22030, USA, resident at Naval Research Laboratory, Washington, DC 20375 (United States); Hessels, Jason W. T.; Bassa, Cees G. [ASTRON, the Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA, Dwingeloo (Netherlands); Keane, Evan F. [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Mail H30, P.O. Box 218, VIC 3122 (Australia); Ferrara, Elizabeth C.; Harding, Alice K. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2015-02-10

    XSS J12270−4859 is an X-ray binary associated with the Fermi Large Area Telescope gamma-ray source 1FGL J1227.9−4852. In 2012 December, this source underwent a transition where the X-ray and optical luminosity dropped and the spectral signatures of an accretion disk disappeared. We report the discovery of a 1.69 millisecond pulsar (MSP), PSR J1227−4853, at a dispersion measure of 43.4 pc cm{sup −3} associated with this source, using the Giant Metrewave Radio Telescope (GMRT) at 607 MHz. This demonstrates that, post-transition, the system hosts an active radio MSP. This is the third system after PSR J1023+0038 and PSR J1824−2452I showing evidence of state switching between radio MSP and low-mass X-ray binary states. We report timing observations of PSR J1227−4853 with the GMRT and Parkes, which give a precise determination of the rotational and orbital parameters of the system. The companion mass measurement of 0.17–0.46 M{sub ⊙} suggests that this is a redback system. PSR J1227−4853 is eclipsed for about 40% of its orbit at 607 MHz with additional short-duration eclipses at all orbital phases. We also find that the pulsar is very energetic, with a spin-down luminosity of ∼10{sup 35} erg s{sup −1}. We report simultaneous imaging and timing observations with the GMRT, which suggests that eclipses are caused by absorption rather than dispersion smearing or scattering.

  4. The Nearest Millisecond Pulsar Revisited with XMM-Newton: Improved Mass-Radius Constraints for PSR J0437-4715

    CERN Document Server

    Bogdanov, Slavko

    2012-01-01

    I present an analysis of the deepest X-ray exposure of a radio millisecond pulsar (MSP) to date, an X-ray Multi Mirror-Newton European Photon Imaging Camera spectroscopic and timing observation of the nearest known MSP, PSR J0437--4715. The timing data clearly reveal a secondary broad X-ray pulse offset from the main pulse by $\\sim$0.55 in rotational phase. In the context of a model of surface thermal emission from the hot polar caps of the neutron star, this can be plausibly explained by a magnetic dipole field that is significantly displaced from the stellar center. Such an offset, if commonplace in MSPs, has important implications for studies of the pulsar population, high energy pulsed emission, and the pulsar contribution to cosmic ray positrons. The continuum emission shows evidence for at least three thermal components, with the hottest radiation most likely originating from the hot magnetic polar caps and the cooler emission from the bulk of the surface. I present pulse phase-resolved X-ray spectrosco...

  5. Scintillation arcs in low-frequency observations of the timing-array millisecond pulsar J0437-4715

    CERN Document Server

    Bhat, N D R; Tremblay, S E; McSweeney, S J; Tingay, S J

    2015-01-01

    Low-frequency observations of pulsars provide a powerful means for probing the microstructure in the turbulent interstellar medium (ISM). Here we report on high-resolution dynamic spectral analysis of our observations of the timing-array millisecond pulsar J0437-4715 with the Murchison Widefield Array (MWA), enabled by our recently commissioned tied-array beam processing pipeline for voltage data recorded from the high time resolution mode of the MWA. A secondary spectral analysis reveals faint parabolic arcs, akin to those seen in high-frequency observations of pulsars with the Green Bank and Arecibo telescopes. Data from Parkes observations at a higher frequency of 732 MHz reveal a similar parabolic feature, with a curvature that scales approximately as the square of the observing wavelength ($\\lambda^2$) to the MWA's frequency of 192 MHz. Our analysis suggests that scattering toward PSR J0437-4715 predominantly arises from a compact region about 115 pc from the Earth, which matches well with the expected l...

  6. Application of a physical continuum model to recent X-ray observations of accreting pulsars

    Science.gov (United States)

    Marcu-Cheatham, Diana Monica; Pottschmidt, Katja; Wolff, Michael Thomas; Becker, Peter A.; Wood, Kent S.; Wilms, Joern; Britton Hemphill, Paul; Gottlieb, Amy; Fuerst, Felix; Schwarm, Fritz-Walter; Ballhausen, Ralf

    2016-04-01

    We present a uniform spectral analysis in the 0.5-50 keV energy range of a sample of accreting pulsars by applying an empirical broad-band continuum cut-off power-law model. We also apply the newly implemented physical continuum model developed by Becker and Wolff (2007, ApJ 654, 435) to a number of high-luminosity sources. The X-ray spectral formation process in this model consists of the Comptonization of bremsstrahlung, cyclotron, and black body photons emitted by the hot, magnetically channeled, accreting plasma near the neutron star surface. This model describes the spectral formation in high-luminosity accreting pulsars, where the dominant deceleration mechanism is via a radiation-dominated radiative shock. The resulting spectra depend on five physical parameters: the mass accretion rate, the radius of the accretion column, the electron temperature and electron scattering cross-sections inside the column, and the magnetic field strength. The empirical model is fitted to Suzaku data of a sample of high-mass X-ray binaries covering a broad luminosity range (0.3-5 x 10 37 erg/s). The physical model is fitted to Suzaku data from luminous sources: LMC X-4, Cen X-3, GX 304-1. We compare the results of the two types of modeling and summarize how they can provide new insight into the process of accretion onto magnetized neutron stars.

  7. Settling accretion onto slowly rotating X-ray pulsars

    CERN Document Server

    Shakura, N I; Kochetkova, A Yu; Hjalmarsdotter, L

    2013-01-01

    Quasi-spherical subsonic accretion onto slowly rotating magnetized NS is considered, when the accreting matter settles down subsonically onto the rotating magnetosphere, forming an extended quasi-static shell. The shell mediates the angular momentum transfer to/from the rotating NS magnetosphere by large-scale convective motions, which lead to an almost iso-angular-momentum rotation law inside the shell. The accretion rate through the shell is determined by the ability of the plasma to enter the magnetosphere due to Rayleigh-Taylor instability while taking cooling into account. The settling regime of accretion is possible for moderate X-ray luminosities L <4 10^36 erg/s. At higher luminosities a free-fall gap above the NS magnetosphere appears due to rapid Compton cooling, and accretion becomes highly non-stationary. From observations of spin-up/spin-down rates of wind accreting equilibrium XPSRs with known orbital periods (GX 301-2, Vela X-1), the main dimensionless parameters of the model and be determin...

  8. A new model for the X-ray continuum of the magnetized accreting pulsars

    CERN Document Server

    Farinelli, R; Bozzo, E; Becker, P A

    2016-01-01

    Accreting highly magnetized pulsars in binary systems are among the brightest X-ray emitters in our Galaxy. Although a number of high statistical quality broad-band (0.1-100 keV) X-ray observations are available, the spectral energy distribution of these sources is usually investigated by adopting pure phenomenological models, rather than models linked to the physics of accretion. In this paper, a detailed spectral study of the X-ray emission recorded from the high-mass X-ray binary pulsars Cen X-3, 4U 0115+63, and Her X-1 is carried out by using BeppoSAX and joined Suzaku+NuStar data, together with an advanced version of the compmag model. The latter provides a physical description of the high energy emission from accreting pulsars, including the thermal and bulk Comptonization of cyclotron and bremsstrahlung seed photons along the neutron star accretion column. The compmag model is based on an iterative method for solving second-order partial differential equations, whose convergence algorithm has been impr...

  9. The Gamma-Ray Luminosity Function of Millisecond Pulsars and Implications for the GeV Excess

    CERN Document Server

    Hooper, Dan

    2015-01-01

    It has been proposed that a large population of unresolved millisecond pulsars (MSPs) could potentially account for the excess of GeV-scale gamma-rays observed from the region surrounding the Galactic Center. The viability of this scenario depends critically on the gamma-ray luminosity function of this source population, which determines how many MSPs Fermi should have already detected as resolved point sources. In this paper, we revisit the gamma-ray luminosity function of MSPs, without relying on uncertain distance measurements. Our determination, based on a comparison of models with the observed characteristics of the MSP population, suggests that Fermi should have already detected a significant number of sources associated with such a hypothesized Inner Galaxy population. We cannot rule out a scenario in which the MSPs residing near the Galactic Center are systematically less luminous than those present in the Galactic Plane or within globular clusters.

  10. Discovery of a millisecond pulsar in the 5.4 day binary 3FGL J1417.5-4402: observing the late phase of pulsar recycling

    CERN Document Server

    Camilo, F; Ransom, S M; Halpern, J P; Bogdanov, S; Kerr, M; Ray, P S; Cordes, J M; Sarkissian, J; Barr, E D; Ferrara, E C

    2016-01-01

    In a search of the unidentified Fermi gamma-ray source 3FGL J1417.5-4402 with the Parkes radio telescope, we discovered PSR J1417-4402, a 2.66 ms pulsar having the same 5.4 day orbital period as the optical and X-ray binary identified by Strader et al. The existence of radio pulsations implies that the neutron star is currently not accreting. Substantial outflows from the companion render the radio pulsar undetectable for more than half of the orbit, and may contribute to the observed Halpha emission. Our initial pulsar observations, together with the optically inferred orbit and inclination, imply a mass ratio of 0.171+/-0.002, a companion mass of M_2=0.33+/-0.03 Msun, and a neutron star mass in the range 1.77

  11. Polynomial regression calculation of the Earth's position based on millisecond pulsar timing

    International Nuclear Information System (INIS)

    Prior to achieving high precision navigation of a spacecraft using X-ray observations, a pulsar rotation model must be built and analysis of the precise position of the Earth should be performed using ground pulsar timing observations. We can simulate time-of-arrival ground observation data close to actual observed values before using pulsar timing observation data. Considering the correlation between the Earth's position and its short arc section of an orbit, we use polynomial regression to build the correlation. Regression coefficients can be calculated using the least square method, and a coordinate component series can also be obtained; that is, we can calculate Earth's position in the Barycentric Celestial Reference System according to pulse arrival time data and a precise pulsar rotation model. In order to set appropriate parameters before the actual timing observations for Earth positioning, we can calculate the influence of the spatial distribution of pulsars on errors in the positioning result and the influence of error source variation on positioning by simulation. It is significant that the threshold values of the observation and systematic errors can be established before an actual observation occurs; namely, we can determine the observation mode with small errors and reject the observed data with big errors, thus improving the positioning result.

  12. THE NANOGRAV NINE-YEAR DATA SET: OBSERVATIONS, ARRIVAL TIME MEASUREMENTS, AND ANALYSIS OF 37 MILLISECOND PULSARS

    Energy Technology Data Exchange (ETDEWEB)

    Arzoumanian, Zaven [Center for Research and Exploration in Space Science and Technology and X-Ray Astrophysics Laboratory, NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771 (United States); Brazier, Adam; Chatterjee, Shami; Cordes, James M.; Dolch, Timothy [Department of Astronomy, Cornell University, Ithaca, NY 14853 (United States); Burke-Spolaor, Sarah; Demorest, Paul B. [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States); Chamberlin, Sydney [Center for Gravitation, Cosmology and Astrophysics, Department of Physics, University of Wisconsin-Milwaukee, P.O. Box 413, Milwaukee, WI 53201 (United States); Christy, Brian [Department of Physics and Astronomy, Franklin and Marshall College, P.O. Box 3003, Lancaster, PA 17604 (United States); Cornish, Neil [Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Crowter, Kathryn; Fonseca, Emmanuel; Gonzalez, Marjorie E. [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1 (Canada); Ellis, Justin A. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr. Pasadena CA 91109 (United States); Ferdman, Robert D.; Kaspi, Victoria M. [Department of Physics, McGill University, 3600 rue Universite, Montreal, QC H3A 2T8 (Canada); Garver-Daniels, Nathan; Jones, Megan L. [Department of Physics, West Virginia University, P.O. Box 6315, Morgantown, WV 26505 (United States); Jenet, Fredrick A. [Center for Gravitational Wave Astronomy, University of Texas at Brownsville, Brownsville, TX 78520 (United States); Jones, Glenn, E-mail: pdemores@nrao.edu [Department of Physics, Columbia University, 550 W. 120th St. New York, NY 10027 (United States); Collaboration: NANOGrav Collaboration; and others

    2015-11-01

    We present high-precision timing observations spanning up to nine years for 37 millisecond pulsars monitored with the Green Bank and Arecibo radio telescopes as part of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) project. We describe the observational and instrumental setups used to collect the data, and methodology applied for calculating pulse times of arrival; these include novel methods for measuring instrumental offsets and characterizing low signal-to-noise ratio timing results. The time of arrival data are fit to a physical timing model for each source, including terms that characterize time-variable dispersion measure and frequency-dependent pulse shape evolution. In conjunction with the timing model fit, we have performed a Bayesian analysis of a parameterized timing noise model for each source, and detect evidence for excess low-frequency, or “red,” timing noise in 10 of the pulsars. For 5 of these cases this is likely due to interstellar medium propagation effects rather than intrisic spin variations. Subsequent papers in this series will present further analysis of this data set aimed at detecting or limiting the presence of nanohertz-frequency gravitational wave signals.

  13. Multi-wavelength Observations of 3FGL J2039.6-5618: A Candidate Redback Millisecond Pulsar

    Science.gov (United States)

    Salvetti, D.; Mignani, R. P.; De Luca, A.; Delvaux, C.; Pallanca, C.; Belfiore, A.; Marelli, M.; Breeveld, A. A.; Greiner, J.; Becker, W.; Pizzocaro, D.

    2015-12-01

    We present multi-wavelength observations of the unassociated γ-ray source 3FGL J2039.6-5618 detected by the Fermi Large Area Telescope. The source γ-ray properties suggest that it is a pulsar, most likely a millisecond pulsar, for which neither radio nor γ-ray pulsations have been detected. We observed 3FGL J2039.6-5618 with XMM-Newton and discovered several candidate X-ray counterparts within/close to the γ-ray error box. The brightest of these X-ray sources is variable with a period of 0.2245 ± 0.0081 days. Its X-ray spectrum can be described by a power law with photon index ΓX = 1.36 ± 0.09, and hydrogen column density NH star. The light curve profile of the companion star, which has two asymmetric peaks, suggests that the optical emission comes from two regions with different temperatures on its tidally distorted surface. Based upon its X-ray and optical properties, we consider this source as the most likely X-ray counterpart to 3FGL J2039.6-5618, which we propose to be a new redback system.

  14. Multi-wavelength observations of 3FGL J2039.6-5618: a candidate redback millisecond pulsar

    CERN Document Server

    Salvetti, D; De Luca, A; Delvaux, C; Pallanca, C; Belfiore, A; Marelli, M; Breeveld, A A; Greiner, J; Becker, W; Pizzoccaro, D

    2015-01-01

    We present multi-wavelength observations of the unassociated gamma-ray source 3FGL J2039.6-5618 detected by the Fermi Large Area Telescope. The source gamma-ray properties suggest that it is a pulsar, most likely a millisecond pulsar, for which neither radio nor $\\gamma$-ray pulsations have been detected yet. We observed 3FGL J2039.6-5618 with XMM-Newton and discovered several candidate X-ray counterparts within/close to the gamma-ray error box. The brightest of these X-ray sources is variable with a period of 0.2245$\\pm$0.0081 d. Its X-ray spectrum can be described by a power law with photon index $\\Gamma_X =1.36\\pm0.09$, and hydrogen column density $N_{\\rm H} < 4 \\times 10^{20}$ cm$^{-2}$, which gives an unabsorbed 0.3--10 keV X-ray flux of $1.02 \\times 10^{-13}$ erg cm$^{-2}$ s$^{-1}$. Observations with the Gamma-Ray Burst Optical/Near-Infrared Detector (GROND) discovered an optical counterpart to this X-ray source, with a time-average magnitude $g'\\sim 19.5$. The counterpart features a flux modulation ...

  15. Timing and Fermi LAT Analysis of Four Millisecond Pulsars Discovered in Parkes Radio Searches of Gamma-ray Sources

    Science.gov (United States)

    Ray, Paul S.; Ransom, Scott M.; Camilo, Fernando M.; Kerr, Matthew; Reynolds, John; Sarkissian, John; Freire, Paulo; Thankful Cromartie, H.; Barr, Ewan D.

    2016-01-01

    We present phase-connected timing solutions for four binary millisecond pulsars discovered in searches of Fermi LAT gamma-ray sources using the Parkes radio telescope. Follow-up timing observations of PSRs J0955-6150, J1012-4235, J1036-8317, and J1946-5403 have yielded timing models with precise orbital and astrometric parameters. For each pulsar, we also did a gamma-ray spectral analysis using LAT Pass 8 data and generated photon probabilities for use in a weighted H-test pulsation test. In all 4 cases, we detect significant gamma-ray pulsations, confirming the identification with the gamma-ray source originally targeted in the discovery observations. We describe the results of the pulse timing and gamma-ray spectral and timing analysis and the characteristics of each of the systems. The Fermi-LAT Collaboration acknowledges support for LAT development, operation and data analysis from NASA and DOE (United States), CEA/Irfu and IN2P3/CNRS (France), ASI and INFN (Italy), MEXT, KEK, and JAXA (Japan), and the K.A. Wallenberg Foundation, the Swedish Research Council and the National Space Board (Sweden). Science analysis support in the operations phase from INAF (Italy) and CNES (France) is also gratefully acknowledged. NRL participation was funded by NASA.

  16. New millisecond pulsars detected by the Fermi Large Area Telescope and the radio/gamma-ray connection

    CERN Document Server

    Espinoza, C M; Celik, O; Weltevrede, P; Stappers, B W; Smith, D A; Kerr, M; Zavlin, V E; Cognard, I; Eatough, R P; Freire, P C C; Janssen, G H; Camilo, F; Desvignes, G; Hewitt, J W; Hou, X; Johnston, S; Keith, M; Kramer, M; Lyne, A; Manchester, R N; Ransom, S M; Ray, P S; Shannon, R; Theureau, G; Webb, N

    2012-01-01

    We report on the discovery of gamma-ray pulsations from five millisecond pulsars (MSPs) using the Fermi Large Area Telescope (LAT) and timing ephemerides provided by various radio observatories. We also present confirmation of the gamma-ray pulsations from a sixth source, PSR J2051-0827. Five of these six MSPs are in binary systems: PSRs J1713+0747, J1741+1351, J1600-3053 and the two black widow binary pulsars PSRs J0610-2100 and 2051-0827. The only isolated MSP is the nearby PSR J1024-0719, which is also known to emit X-rays. We present X-ray observations in the direction of PSRs J1600-3053 and J2051-0827. While the latter is firmly detected, we an only give upper limits for the X-ray flux of the former. There are no dedicated X-ray observations available for the other 3 objects. The MSPs mentioned above, together with most of the MSPs detected by Fermi, are used to put together a sample of 30 gamma-ray MSPs which is used to study the morphology and phase connection of radio and gamma-ray pulse profiles. We ...

  17. Constraints on the Emission Geometries of Gamma-ray Millisecond Pulsars Observed with the Fermi Large Area Telescope

    CERN Document Server

    Johnson, T J

    2012-01-01

    Millisecond pulsars (MSPs) have been established as a class of high-energy ($\\geq$0.1 GeV) emitters with the Large Area Telescope (LAT) aboard the \\emph{Fermi Gamma-ray Space Telescope}. Most MSP gamma-ray light curves display sharp peaks indicative of thin accelerating gaps, suggesting copious pair-creation in the open volume. MSP gamma-ray and radio light curves have been simulated using geometric outer-gap (OG), slot-gap/two-pole caustic (TPC), and pair-starved polar cap gamma-ray models and either a hollow-cone beam or altitude-limited, outer-magnetospheric gap radio model, all assuming a vacuum retarded dipolar magnetic field geometry. A Markov chain Monte Carlo maximum likelihood technique has been developed to find the best-fit model parameters for nineteen MSPs using data from the LAT and various radio observatories. The best-fit viewing angles follow a uniform, angular distribution. The distribution of magnetic inclination angles favors all angles equally, contrary to analyses of non-recycled pulsars...

  18. Pulsed Gamma Rays from the Original Millisecond and Black Widow Pulsars: A Case for Caustic Radio Emission?

    Science.gov (United States)

    Guillemot, L.; Johnson, T. J.; Venter, C.; Kerr, M.; Pancrazi, B.; Livingstone, M.; Janssen, G. H.; Jaroenjittichai, P.; Kramer, M.; Cognard, I.; Stappers, B. W.; Harding, A. K.; Camilo, F.; Espinoza, C. M.; Freire, P. C. C.; Gargano, F.; Grove, J. E.; Johnston, S.; Michelson, P. F.; Noutsos, A.; Parent, D.; Ransom, S. M.; Ray, P. S.; Shannon, R.; Smith, D. A.

    2011-01-01

    We report the detection of pulsed gamma-ray emission from the fast millisecond pulsars (MSPs) B1937+21 (also known as J1939+2134) and B1957+20 (J1959+2048) using 18 months of survey data recorded by the Fermi Large Area Telescope (LAT) and timing solutions based on radio observations conducted at the Westerbork and Nancay radio telescopes. In addition, we analyzed archival RXTE and XMM-Newton X-ray data for the two MSPs, confirming the X-ray emission properties of PSR B1937+21 and finding evidence (approx. 4(sigma)) for pulsed emission from PSR B1957+20 for the first time. In both cases the gamma-ray emission profile is characterized by two peaks separated by half a rotation and are in close alignment with components observed in radio and X-rays. These two pulsars join PSRs J0034..0534 and J2214+3000 to form an emerging class of gamma-ray MSPs with phase-aligned peaks in different energy bands. The modeling of the radio and gamma-ray emission pro les suggests co-located emission regions in the outer magnetosphere.

  19. The NANOGrav Nine-year Data Set: Observations, Arrival Time Measurements, and Analysis of 37 Millisecond Pulsars

    Science.gov (United States)

    The NANOGrav Collaboration; Arzoumanian, Zaven; Brazier, Adam; Burke-Spolaor, Sarah; Chamberlin, Sydney; Chatterjee, Shami; Christy, Brian; Cordes, James M.; Cornish, Neil; Crowter, Kathryn; Demorest, Paul B.; Dolch, Timothy; Ellis, Justin A.; Ferdman, Robert D.; Fonseca, Emmanuel; Garver-Daniels, Nathan; Gonzalez, Marjorie E.; Jenet, Fredrick A.; Jones, Glenn; Jones, Megan L.; Kaspi, Victoria M.; Koop, Michael; Lam, Michael T.; Lazio, T. Joseph W.; Levin, Lina; Lommen, Andrea N.; Lorimer, Duncan R.; Luo, Jing; Lynch, Ryan S.; Madison, Dustin; McLaughlin, Maura A.; McWilliams, Sean T.; Nice, David J.; Palliyaguru, Nipuni; Pennucci, Timothy T.; Ransom, Scott M.; Siemens, Xavier; Stairs, Ingrid H.; Stinebring, Daniel R.; Stovall, Kevin; Swiggum, Joseph K.; Vallisneri, Michele; van Haasteren, Rutger; Wang, Yan; Zhu, Weiwei

    2015-11-01

    We present high-precision timing observations spanning up to nine years for 37 millisecond pulsars monitored with the Green Bank and Arecibo radio telescopes as part of the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) project. We describe the observational and instrumental setups used to collect the data, and methodology applied for calculating pulse times of arrival; these include novel methods for measuring instrumental offsets and characterizing low signal-to-noise ratio timing results. The time of arrival data are fit to a physical timing model for each source, including terms that characterize time-variable dispersion measure and frequency-dependent pulse shape evolution. In conjunction with the timing model fit, we have performed a Bayesian analysis of a parameterized timing noise model for each source, and detect evidence for excess low-frequency, or “red,” timing noise in 10 of the pulsars. For 5 of these cases this is likely due to interstellar medium propagation effects rather than intrisic spin variations. Subsequent papers in this series will present further analysis of this data set aimed at detecting or limiting the presence of nanohertz-frequency gravitational wave signals.

  20. PULSED GAMMA RAYS FROM THE MILLISECOND PULSAR J0030+0451 WITH THE FERMI LARGE AREA TELESCOPE

    International Nuclear Information System (INIS)

    We report the discovery of gamma-ray pulsations from the nearby isolated millisecond pulsar (MSP) PSR J0030+0451 with the Large Area Telescope on the Fermi Gamma-ray Space Telescope (formerly GLAST). This discovery makes PSR J0030+0451 the second MSP to be detected in gamma rays after PSR J0218+4232, observed by the EGRET instrument on the Compton Gamma-Ray Observatory. The spin-down power E-dot=3.5x1033 erg s-1 is an order of magnitude lower than the empirical lower bound of previously known gamma-ray pulsars. The emission profile is characterized by two narrow peaks, 0.07 ± 0.01 and 0.08 ± 0.02 wide, respectively, separated by 0.44 ± 0.02 in phase. The first gamma-ray peak falls 0.15 ± 0.01 after the main radio peak. The pulse shape is similar to that of the 'normal' gamma-ray pulsars. An exponentially cutoff power-law fit of the emission spectrum leads to an integral photon flux above 100 MeV of (6.76 ± 1.05 ± 1.35) x 10-8 cm-2 s-1 with cutoff energy (1.7 ± 0.4 ± 0.5) GeV. Based on its parallax distance of (300 ± 90) pc, we obtain a gamma-ray efficiency Lγ/E-dot≅15 percent for the conversion of spin-down energy rate into gamma-ray radiation, assuming isotropic emission.

  1. Thermonuclear Burning on the Accreting X-Ray Pulsar GRO J1744-28

    CERN Document Server

    Bildsten, L; Bildsten, Lars; Brown, Edward F.

    1996-01-01

    We investigate the thermal stability of nuclear burning on the accreting X-ray pulsar GRO J1744-28. The neutron star's dipolar magnetic field is 50 years. We also discuss the nature of the binary and point out that a velocity measurement of the stellar companion (most likely a Roche-lobe filling giant with m_K>17) will constrain the neutron star mass.

  2. Modeling the Effect of Kick Velocity during the Accretion Induced Collapse of White Dwarfs on Binary Pulsars

    Science.gov (United States)

    Taani, Ali

    2016-07-01

    The kick velocity which arises during the binary interaction plays an important role in disruption or surviving the binary systems. This paper attempts to draw an evolutionary connection of the long-period (Porb ≥ 2 d) millisecond pulsars (MSPs) with orbits of low eccentricity (e ≤ 0.2). We propose that a kick velocity caused by dynamical effects of asymmetric collapse imparted to the companion star through an accretion induced collapse (AIC) of white dwarfs-that become unstable once they approach the Chandrasekhar limit-can account for the differences in their orbital period distributions. Furthermore, in some cases, an appropriate kick can disrupt the binary system and result in the birth of isolated MSPs. Otherwise, the binary survives and an eccentric binary MSP is formed. In this case only the binding energy equivalent (0.2M⊙) of mass is lost and the system remains intact in a symmetric collapse. Consequently, the AIC decreases the mass of the neutron star and increases the orbital period leading to orbit circularization. We present the results of our model and discuss the possible implications for the binary MSPs in galactic disk and globular clusters.

  3. The NANOGrav Nine-year Data Set: Mass and Geometric Measurements of Binary Millisecond Pulsars

    CERN Document Server

    Fonseca, Emmanuel; Ellis, Justin A; Stairs, Ingrid H; Nice, David J; Ransom, Scott M; Demorest, Paul B; Arzoumanian, Zaven; Crowter, Kathryn; Dolch, Timothy; Ferdman, Robert D; Gonzalez, Marjorie E; Jones, Glenn; Jones, Megan L; Lam, Michael T; Levin, Lina; McLaughlin, Maura A; Stovall, Kevin; Swiggum, Joseph K; Zhu, Weiwei

    2016-01-01

    We analyse 24 binary radio pulsars in the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) nine-year data set. We made fourteen significant measurements of Shapiro delay, including new detections in four pulsar-binary systems (PSRs J0613$-$0200, J2017+0603, J2302+4442, and J2317+1439), and derive estimates of the binary-component masses and orbital inclination for these MSP-binary systems. We find a wide range of binary pulsar masses, with values as low as $m_{\\rm p} = 1.18^{+0.10}_{-0.09}\\text{ M}_{\\odot}$ for PSR J1918$-$0642 and as high as $m_{\\rm p} = 1.928^{+0.017}_{-0.017}\\text{ M}_{\\odot}$ for PSR J1614$-$2230 (both 68.3\\% confidence). We make an improved measurement of the Shapiro timing delay in the PSR J1918$-$0642 and J2043+1711 systems, measuring the pulsar mass in the latter system to be $m_{\\rm p} = 1.41^{+0.21}_{-0.18}\\text{ M}_{\\odot}$ (68.3\\% confidence) for the first time. We measure secular variations of one or more orbital elements in many systems, and use these meas...

  4. Multiwavelength Observations of the Redback Millisecond Pulsar J1048+2339

    CERN Document Server

    Deneva, J S; Camilo, F; Halpern, J P; Wood, K; Cromartie, H T; Ferrara, E; Kerr, M; Ransom, S M; Wolff, M T; Chambers, K C; Magnier, E A

    2016-01-01

    We report on radio timing and multiwavelength observations of the 4.66 ms redback pulsar J1048+2339, which was discovered in an Arecibo search targeting the Fermi-LAT source 3FGLJ1048.6+2338. Two years of timing allowed us to derive precise astrometric and orbital parameters for the pulsar. PSR J1048+2339 is in a 6-hour binary, and exhibits radio eclipses over half the orbital period and rapid orbital period variations. The companion has a minimum mass of 0.3 solar masses, and we have identified a $V \\sim 20$ variable optical counterpart in data from several surveys. The phasing of its $\\sim 1$~mag modulation at the orbital period suggests highly efficient and asymmetric heating by the pulsar wind, which may be due to an intrabinary shock that is distorted near the companion, or to the companion's magnetic field channeling the pulsar wind to specific locations on its surface. We also present gamma-ray spectral analysis of the source and preliminary results from searches for gamma-ray pulsations using the radi...

  5. Timing and Spectroscopy of Accreting X-ray Pulsars: the State of Cyclotron Line Studies

    CERN Document Server

    Heindl, W A; Coburn, W; Staubert, R; Wilms, J; Kreykenbohm, I; Kretschmar, P

    2004-01-01

    A great deal of emphasis on timing in the RXTE era has been on pushing toward higher and higher frequency phenomena, particularly kHz QPOs. However, the large areas of the RXTE pointed instruments provide another capability which is key for the understanding of accreting X-ray pulsars -- the ability to accumulate high quality spectra in a limited observing time. For the accreting X-ray pulsars, with their relatively modest spin frequencies, this translates into an ability to study broad band spectra as a function of pulse phase. This is a critical tool, as pulsar spectra are strong functions of the geometry of the "accretion mound" and the observers' viewing angle to the ~10^12 G magnetic field. In particular, the appearance of "cyclotron lines" is sensitively dependent on the viewing geometry, which must change with the rotation of the star. These spectral features, seen in only a handful of objects, are quite important, as they give us our only direct measure of neutron star magnetic fields. Furthermore, th...

  6. Soft X-Ray Properties of the Binary Millisecond Pulsar J0437-4715

    Science.gov (United States)

    Halpern, Jules P.; Martin, Christopher; Marshall, Herman, L.; Oliversen, Ronald (Technical Monitor)

    2001-01-01

    We obtained a light curve for the 5.75 ms pulsar J0437-4715 in the 65-120 A range with 0.5 ms time resolution using the Deep Survey instrument on the EUVE satellite. The single-peaked profile has a pulsed fraction of 0.27 +/- 0.05, similar to the ROSAT data in the overlapping energy band. A combined analysis of the EUVE and ROSAT data is consistent with a power-law spectrum of energy index alpha = 1.2 - 1.5, intervening column density N(sub H) = (5 - 8) x 10(exp 19)/sq cm, and luminosity 5.0 x 10(exp 30) ergs/s in the 0.1 - 2.4 keV band. We also use a bright EUVE/ROSAT source only 4.2 min. from the pulsar, the Seyfert galaxy RX J0437.4-4711 (= EUVE J0437-471 = IES 0435-472), to obtain an independent upper limit on the intervening absorption to the pulsar, N(sub H) less than 1.2 x 10(exp 20)/sq cm. Although a blackbody spectrum fails to fit the ROSAT data, two-component spectral fits to the combined EUVE/ROSAT data are used to limit the temperatures and surface areas of thermal emission that might make partial contributions to the flux. A hot polar cap of radius 50 - 600 m and temperature (1.0 - 3.3) x 10(exp 6) K could be present. Alternatively, a larger region with T = (4 - 12) x 10(exp 5) K and area less than 200 sq km, might contribute most of the EUVE and soft X-ray flux, but only if a hotter component were present as well. Any of these temperatures would require some mechanism(s) of surface reheating to be operating in this old pulsar, the most plausible being the impact of accelerated electrons and positrons onto the polar caps. The kinematically corrected spin-down power of PSR J0437-4715 is only 4 x 10(exp 33) ergs/s, which is an order of magnitude less than that of the lowest-luminosity gamma-ray pulsars Geminga and PSR B1055-52. The absence of high-energy gamma-rays from PSR J0437-4715 might signify an inefficient or dead outer gap accelerator, which in turn accounts for the lack of a more luminous reheated surface such as those intermediate-age gamma

  7. Theory of quasi-spherical accretion in X-ray pulsars

    CERN Document Server

    Shakura, N; Kochetkova, A; Hjalmarsdotter, L

    2011-01-01

    A theoretical model for quasi-spherical subsonic accretion onto slowly rotating magnetized neutron stars is constructed. In this model the accreting matter subsonically settles down onto the rotating magnetosphere forming an extended quasi-static shell. This shell mediates the angular momentum removal from the rotating neutron star magnetosphere during spin-down episodes by large-scale convective motions. The accretion rate through the shell is determined by the ability of the plasma to enter the magnetosphere. The settling regime of accretion can be realized for moderate accretion rates $\\dot M< \\dot M_*\\simeq 4\\times 10^{16}$ g/s. At higher accretion rates a free-fall gap above the neutron star magnetosphere appears due to rapid Compton cooling, and accretion becomes highly non-stationary. From observations of the spin-up/spin-down rates (the angular rotation frequency derivative $\\dot \\omega^*$, and $\\partial\\dot\\omega^*/\\partial\\dot M$ near the torque reversal) of X-ray pulsars with known orbital perio...

  8. Quasi-spherical accretion in low-luminosity X-ray pulsars: Theory vs. observations

    CERN Document Server

    Postnov, K; Kochetkova, A; Hjalmarsdotter, L

    2012-01-01

    Quasi-spherical subsonic accretion can be realized in slowly rotating wind-fed X-ray pulsars (XPSRs) at X-ray luminosities <4 10^{36} erg/s. In this regime the accreting matter settles down subsonically onto the rotating magnetosphere, forming an extended quasi-static shell. The shell mediates the angular momentum removal from the rotating NS magnetosphere by shear turbulent viscosity in the boundary layer or via large-scale convective motions. In the last case the differential rotation law in the shell is close to iso-angular-momentum rotation. The accretion rate through the shell is determined by the ability of the plasma to enter the magnetosphere due to Rayleigh-Taylor instabilities while taking cooling into account. Measurements of spin-up/spin-down rates of quasi-spherically wind accreting XPSRs in equilibrium with known orbital periods (like e.g. GX 301-2 and Vela X-1) enable determination of the main dimensionless parameters of the model and the NS magnetic field. For equilibrium pulsars with indep...

  9. A new model for the X-ray continuum of the magnetized accreting pulsars

    Science.gov (United States)

    Farinelli, Ruben; Ferrigno, Carlo; Bozzo, Enrico; Becker, Peter A.

    2016-06-01

    Context. Accreting highly magnetized pulsars in binary systems are among the brightest X-ray emitters in our Galaxy. Although a number of high-quality broad-band (0.1-100 keV) X-ray observations are available, the spectral energy distribution of these sources is usually investigated by adopting pure phenomenological models rather than models linked to the physics of accretion. Aims: In this paper, a detailed spectral study of the X-ray emission recorded from the high-mass X-ray binary pulsars Cen X-3, 4U 0115+63, and Her X-1 is carried out by using BeppoSAX and joined Suzaku +NuStar data, together with an advanced version of the compmag model, which provides a physical description of the high-energy emission from accreting pulsars, including the thermal and bulk Comptonization of cyclotron and bremsstrahlung seed photons along the neutron star accretion column. Methods: The compmag model is based on an iterative method for solving second-order partial differential equations, whose convergence algorithm has been improved and consolidated during the preparation of this paper. Results: Our analysis shows that the broad-band X-ray continuum of all considered sources can be self-consistently described by the compmag model. The cyclotron absorption features (not included in the model) can be accounted for by using Gaussian components. From the fits of the compmag model to the data we inferred the physical properties of the accretion columns in all sources, finding values reasonably close to those theoretically expected according to our current understanding of accretion in highly magnetized neutron stars. Conclusions: The updated version of the compmag model has been tailored to the physical processes that are known to occur in the columns of highly magnetized accreting neutron stars and it can thus provide a better understanding of the high-energy radiation from these sources. The availability of broad-band high-quality X-ray data, such as those provided by BeppoSAX in

  10. ULX-1 in NGC5907: how bright can an accreting pulsar shine?

    CERN Document Server

    Israel, G L; Stella, L; Esposito, P; Casella, P; De Luca, A; Marelli, M; Papitto, A; Perri, M; Puccetti, S; Castillo, G A Rodriguez; Salvetti, D; Tiengo, A; Zampieri, L; D'Agostino, D; Greiner, J; Haberl, F; Novara, G; Salvaterra, R; Turolla, R; Watson, M; Wilms, J; Wolter, A

    2016-01-01

    Non-nuclear ultraluminous x-ray sources (ULXs) in nearby galaxies shine brighter than any source in our Galaxy. ULXs are usually modeled as stellar-mass black holes accreting at very high rates or intermediate-mass black-holes. We have discovered that ULX-1 in NGC 5907 is an x-ray accreting neutron star (NS) with a spin period evolving from 1.43 s in 2003 to 1.13 s in 2014. With an isotropic peak luminosity of ~500 times the Eddington limit for a NS at 17.1 Mpc, it is the most luminous and distant x-ray pulsar ever detected. Standard accretion models fail to explain its luminosity, even assuming beamed emission. We show that a strong multipolar magnetic field, similar to that of magnetars, can describe its properties. These findings suggest that other extreme ULXs might harbor NSs.

  11. Signs of Magnetic Accretion in the X-ray Pulsar Binary GX 301-2

    CERN Document Server

    Ikhsanov, N R

    2012-01-01

    Observations of the cyclotron resonance scattering feature in the X-ray spectrum of GX 301-2 suggest that the surface field of the neutron star is B_CRSF ~ 4 x 10^{12}G. The same value has been derived in modelling the rapid spin-up episodes in terms of the Keplerian disk accretion scenario. However, the spin-down rate observed during the spin-down trends significantly exceeds the value expected in currently used spin-evolution scenarios. This indicates that either the surface field of the star exceeds 50 x B_CRSF, or a currently used accretion scenario is incomplete. We show that the above discrepancy can be avoided if the accreting material is magnetized. The magnetic pressure in the accretion flow increases more rapidly than its ram pressure and, under certain conditions, significantly affects the accretion picture. The spin-down torque applied to the neutron star in this case is larger than that evaluated within a non-magnetized accretion scenario. We find that the observed spin evolution of the pulsar ca...

  12. Spectral Modeling of the Comptonized Continua of Accreting X-Ray Pulsars: Recent Progress

    Science.gov (United States)

    Wolff, Michael T.; Becker, P. A.; Marcu, D.; Pottschmidt, K.; Wilms, J.; Wood, K. S.

    2014-01-01

    We are undertaking a program to analyze the X-ray spectra of the accretion flows onto strongly magnetic neutron stars in high mass binary systems such as Her X-1, Cen X-3, and LMC X-4. These accreting pulsars typically have X-ray spectra consisting of broad Comptonized cutoff power-laws. Current theory suggests these X-ray spectra result from the impact of the high-velocity magnetically channeled plasma accretion flows onto the surfaces of the neutron stars. The flows have such high energy density that shocks developing in the plasmas can be radiation-dominated. These X-ray pulsars often, but not always, show cyclotron resonant scattering features implying neutron star surface magnetic field strengths above 10^12 G. Over the past few years a number of studies have reported both positive and negative correlations of the cyclotron line energy centroids with X-ray luminosity in a number of pulsars. However, the detailed analysis of the cyclotron line centroids suffers from the lack of a robust model for the Comptonized X-ray continuum upon which the cyclotron lines are superposed. We discuss in this presentation our progress in developing tools for the analysis of the X-ray spectra formed in these systems. The range of parameter conditions presented by the many known real accreting pulsar systems substantially exceeds that of the limited set of pulsars on which the original analytic model of Becker and Wolff (2007) was validated. In the high temperature optically thick plasmas, the processes of bremsstrahlung emission from the hot plasma, black body emission from a thermal mound near the neutron star surface, and cyclotron emission from electrons in the first Landau excited state, all contribute to the total local photon population in the shock structure. We discuss our strategy for numerically accounting for the relative contribution to the full X-ray spectrum made by each of these physical processes. Solving for the integrated spectrum involves numerical

  13. Pulsar spins from an instability in the accretion shock of supernovae

    CERN Document Server

    Blondin, J M; Blondin, John M.; Mezzacappa, Anthony

    2006-01-01

    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 pulsar spin is directly correlated with the rotation of the progenitor star. So far, however, stellar theory has not been able to explain the distribution of pulsar spins, suggesting that the birth rotation is either too slow or too fast. Here we report a robust instability of the stalled accretion shock in core-collapse supernovae that is able to generate a strong rotational flow in the vicinity of the accreting proto-neutron star. Sufficient angular momentum is deposited on the proto-neutron star to generate a final spin period consistent with observations, even beginning with spherically symmetrical initial conditions. This provides a new mechanism for the generation of neu...

  14. VizieR Online Data Catalog: ATNF Pulsar Catalogue (Manchester+, 2005)

    Science.gov (United States)

    Manchester, R. N.; Hobbs, G. B.; Teoh, A.; Hobbs, M.

    2016-05-01

    The catalogue is a compilation of the principal observed parameters of pulsars, including positions, timing parameters, pulse widths, flux densities, proper motions, distances, and dispersion, rotation, and scattering measures. It also lists the orbital elements of binary pulsars, and some commonly used parameters derived from the basic measurements. The catalogue includes all published rotation-powered pulsars, including those detected only at high energies. It also includes Anomalous X-ray Pulsars (AXPs) and Soft Gamma-ray Repeaters (SGRs) for which coherent pulsations have been detected. However, it excludes accretion-powered pulsars such as Her X-1 and the recently discovered X-ray millisecond pulsars. (2 data files).

  15. Neutron star crustal plate tectonics. I. Magnetic dipole evolution in millisecond pulsars and low-mass X-ray binaries

    International Nuclear Information System (INIS)

    Crust lattices in spinning-up or spinning-down neutron stars have growing shear stresses caused by neutron superfluid vortex lines pinned to lattice nuclei. For the most rapidly spinning stars, this stress will break and move the crust before vortex unpinning occurs. In spinning-down neutron stars, crustal plates will move an equatorial subduction zone in which the plates are forced into the stellar core below the crust. The opposite plate motion occurs in spinning-up stars. Magnetic fields which pass through the crust or have sources in it move with the crust. Spun-up neutron stars in accreting low-mass X-ray binaries LMXBs should then have almost axially symmetric magnetic fields. Spun-down ones with very weak magnetic fields should have external magnetic fields which enter and leave the neutron star surface only near its equator. The lowest field millisecond radiopulsars seem to be orthogonal rotators implying that they have not previously been spun-up in LMXBs but are neutron stars initially formed with periods near 0.001 s that subsequently spin down to their present periods. Accretion-induced white dwarf collapse is then the most plausible genesis for them. 29 refs

  16. ASTRO-H White Paper - Accreting Pulsars, Magnetars, and Related Sources

    CERN Document Server

    Kitamoto, S; Safi-Harb, S; Pottschmidt, K; Ferrigno, C; Chernyakova, M; Hayashi, T; Hell, N; Kaneko, K; Khangulyan, D; Kohmura, T; Krimm, H; Makishima, K; Nakano, T; Odaka, H; Ohno, M; Sasano, M; Sugita, S; Terada, Y; Yasuda, T; Yuasa, T

    2014-01-01

    As the endpoints of massive star evolution, neutron stars are enigmatic celestial objects characterized by extremely dense and exotic nuclear matter, magnetospheres with positrons (antimatter), rapid rotation and ultra-strong magnetic fields. Such an extreme environment has provided an accessible astrophysical laboratory to study physics under conditions unattainable on Earth and to tackle a range of fundamental questions related to: the aftermath of stellar evolution and the powerful explosions of massive stars, the equation of state and physics of some of the most exotic and magnetic stars in the Universe, the workings of the most powerful particle accelerators in our Galaxy and beyond, and the sources of gravitational waves that are yet to be detected. Recent observations revealed a great diversity of neutron stars, including ultra-strongly magnetized pulsars, referred to as "magnetars", and unusual types of accreting X-ray pulsars. In this white paper, we highlight the prospects of the upcoming X-ray miss...

  17. FIVE NEW MILLISECOND PULSARS FROM A RADIO SURVEY OF 14 UNIDENTIFIED FERMI-LAT GAMMA-RAY SOURCES

    Energy Technology Data Exchange (ETDEWEB)

    Kerr, M. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Camilo, F. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Johnson, T. J. [National Academy of Sciences, Washington, DC 20001 (United States); Ferrara, E. C.; Harding, A. K. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Guillemot, L.; Kramer, M. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn (Germany); Hessels, J. [Netherlands Institute for Radio Astronomy (ASTRON), Postbus 2, 7990 AA Dwingeloo (Netherlands); Johnston, S.; Keith, M.; Reynolds, J. E. [CSIRO Astronomy and Space Science, Australia Telescope National Facility, Epping, NSW 1710 (Australia); Ransom, S. M. [National Radio Astronomy Observatory (NRAO), Charlottesville, VA 22903 (United States); Ray, P. S.; Wood, K. S. [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States); Sarkissian, J., E-mail: kerrm@stanford.edu, E-mail: fernando@astro.columbia.edu, E-mail: tyrel.j.johnson@gmail.com [CSIRO Parkes Observatory, Parkes, NSW 2870 (Australia)

    2012-03-20

    We have discovered five millisecond pulsars (MSPs) in a survey of 14 unidentified Fermi Large Area Telescope sources in the southern sky using the Parkes radio telescope. PSRs J0101-6422, J1514-4946, and J1902-5105 reside in binaries, while PSRs J1658-5324 and J1747-4036 are isolated. Using an ephemeris derived from timing observations of PSR J0101-6422 (P = 2.57 ms, DM = 12 pc cm{sup -3}), we have detected {gamma}-ray pulsations and measured its proper motion. Its {gamma}-ray spectrum (a power law of {Gamma} = 0.9 with a cutoff at 1.6 GeV) and efficiency are typical of other MSPs, but its radio and {gamma}-ray light curves challenge simple geometric models of emission. The high success rate of this survey-enabled by selecting {gamma}-ray sources based on their detailed spectral characteristics-and other similarly successful searches indicate that a substantial fraction of the local population of MSPs may soon be known.

  18. Exploring the X-ray and gamma-ray properties of the redback millisecond pulsar PSR J1723-2837

    CERN Document Server

    Hui, C Y; Takata, J; Kong, A K H; Cheng, K S; Wu, J H K; Lin, L C C; Wu, E M H

    2013-01-01

    We have investigated the X-ray and $\\gamma$-ray properties of the redback millisecond pulsar PSR J1723-2837 with XMM-Newton, Chandra and Fermi. We have discovered the X-ray orbital modulation of this binary system with the minimum that coincides with the phases of radio eclipse. The X-ray emission is clearly non-thermal in nature which can be well described by a simple power-law with a photon index of $\\sim1.2$. The phase-averaged luminosity is $\\sim9\\times10^{31}$ erg/s in 0.3-10 keV which consumes $\\sim0.2\\%$ of the spin-down power. We have detected the $\\gamma-$ray emission in $0.1-300$ GeV from this system at a significance of $\\sim6\\sigma$ for the first time. The $\\gamma-$rays in this energy range consumes $\\sim2\\%$ of the spin-down power and can be modeled by a power-law with a photon index of $\\sim2.6$. We discuss the high energy properties of the new redback in the context of a intrabinary shock model.

  19. A radiation-hydrodynamic model of accretion columns for ultra-luminous X-ray pulsars

    CERN Document Server

    Kawashima, Tomohisa; Ohsuga, Ken; Ogawa, Takumi

    2016-01-01

    Prompted by the recent discovery of pulsed emission from an ultra-luminous X-ray source, M82 X-2 ("ULX-pulsar"), we perform a two-dimensional radiation-hydrodynamic simulation of a super-critical accretion flow onto a neutron star through a narrow accretion column. We set an accretion column with a cone shape filled with tenuous gas with density of $10^{-4} {\\rm g}~ {\\rm cm}^{-3}$ above a neutron star and solve the two dimensional gas motion and radiative transfer within the column. The side boundaries are set such that radiation can freely escape, while gas cannot. Since the initial gas layer is not in a hydrostatic balance, the column gas falls onto the neutron-star surface, thereby a shock being generated. As a result, the accretion column is composed of two regions: an upper, nearly free-fall region and a lower settling region, as was noted by Basko \\& Sunyaev (1976). The average accretion rate is very high; ${\\dot M}\\sim 10^{2-3} L_{\\rm E}/c^2$ (with $L_{\\rm E}$ being the Eddington luminosity), and s...

  20. Hard X-ray Detection and Timing of Accretion-Powered Pulsars with BATSE

    OpenAIRE

    Chakrabarty, Deepto; Prince, Thomas A.

    1996-01-01

    The BATSE all-sky monitor on the Compton Gamma Ray Observatory is a superb tool for the study of accretion-powered pulsars. In the first part of this thesis, I describe its capabilities for hard X-ray observations above 20 keV, present techniques for timing analysis of the BATSE data, and discuss general statistical issues for the detection of pulsed periodic signals in both the time and frequency domains. BATSE’s 1-day pulsed sensitivity in the 20–60 keV ...

  1. A radiation-hydrodynamics model of accretion columns for ultra-luminous X-ray pulsars

    Science.gov (United States)

    Kawashima, Tomohisa; Mineshige, Shin; Ohsuga, Ken; Ogawa, Takumi

    2016-10-01

    Prompted by the recent discovery of pulsed emission from an ultra-luminous X-ray source, M 82 X-2 ("ULX-pulsar"), we perform a two-dimensional radiation-hydrodynamics simulation of a supercritical accretion flow onto a neutron star through a narrow accretion column. We set an accretion column with a cone shape filled with tenuous gas with the density of 10-4 g cm-3 above a neutron star and solve the two-dimensional gas motion and radiative transfer within the column. The side boundaries are set such that radiation can freely escape, but gas cannot. Since the initial gas layer is not in a hydrostatic balance, the column gas falls onto the neutron-star surface, and thereby a shock is generated. As a result, the accretion column is composed of two regions: an upper, nearly free-fall region and a lower settling region, as noted by Basko and Sunyaev (1976, MNRAS, 175, 395). The average accretion rate is very high; dot{M}˜ 10^{2{-}3} L_E/c2 (with LE being the Eddington luminosity), and so radiation energy dominates over gas internal energy entirely within the column. Despite the high accretion rate, the radiation flux in the laboratory frame is kept barely below LE/(4πr2) at a distance r in the settling region so that matter can slowly accrete. This adjustment is made possible, since a large amount of photons produced via dissipation of kinetic energy of matter can escape through the side boundaries. The total luminosity can greatly exceed LE by several orders of magnitude, whereas the apparent luminosity observed from the top of the column is much less. Due to such highly anisotropic radiation fields, the observed flux should exhibit periodic variations with the rotation period, provided that the rotation and magnetic axes are misaligned.

  2. A radiation-hydrodynamics model of accretion columns for ultra-luminous X-ray pulsars

    Science.gov (United States)

    Kawashima, Tomohisa; Mineshige, Shin; Ohsuga, Ken; Ogawa, Takumi

    2016-09-01

    Prompted by the recent discovery of pulsed emission from an ultra-luminous X-ray source, M 82 X-2 ("ULX-pulsar"), we perform a two-dimensional radiation-hydrodynamics simulation of a supercritical accretion flow onto a neutron star through a narrow accretion column. We set an accretion column with a cone shape filled with tenuous gas with the density of 10-4 g cm-3 above a neutron star and solve the two-dimensional gas motion and radiative transfer within the column. The side boundaries are set such that radiation can freely escape, but gas cannot. Since the initial gas layer is not in a hydrostatic balance, the column gas falls onto the neutron-star surface, and thereby a shock is generated. As a result, the accretion column is composed of two regions: an upper, nearly free-fall region and a lower settling region, as noted by Basko and Sunyaev (1976, MNRAS, 175, 395). The average accretion rate is very high; dot{M}}˜ 10^{2-3} L_E/c2 (with LE being the Eddington luminosity), and so radiation energy dominates over gas internal energy entirely within the column. Despite the high accretion rate, the radiation flux in the laboratory frame is kept barely below LE/(4πr2) at a distance r in the settling region so that matter can slowly accrete. This adjustment is made possible, since a large amount of photons produced via dissipation of kinetic energy of matter can escape through the side boundaries. The total luminosity can greatly exceed LE by several orders of magnitude, whereas the apparent luminosity observed from the top of the column is much less. Due to such highly anisotropic radiation fields, the observed flux should exhibit periodic variations with the rotation period, provided that the rotation and magnetic axes are misaligned.

  3. The accretion-heated crust of the transiently accreting 11-Hz X-ray pulsar in the globular cluster Terzan 5

    NARCIS (Netherlands)

    N. Degenaar; R. Wijnands

    2011-01-01

    We report on a Chandra Director’s Discretionary Time observation of the globular cluster Terzan 5, carried out ∼7 weeks after the cessation of the 2010 outburst of the newly discovered transiently accreting 11-Hz X-ray pulsar. We detect a thermal spectrum that can be fitted with a neutron star atmos

  4. Fermi Study of gamma-ray Millisecond Pulsars: the Spectral Shape and Pulsed 25--200 GeV Emission from J0614-3329

    CERN Document Server

    Xing, Yi

    2016-01-01

    We report our analysis of the Fermi Large Area Telescope data for 39 millisecond pulsars (MSPs) listed in the second $\\gamma$-ray pulsar catalog. Spectra of the pulsars are obtained. We fit the spectra with a function of a power law with exponential cutoff, and find the best-fit parameters of photon index $\\Gamma = 1.54^{+0.10}_{-0.11}$ and cutoff energy $E_{c} = 3.70^{+0.95}_{-0.70}$ GeV. This spectral shape, which includes the intrinsic differences in the spectra of the MSPs, can be used for finding candidate MSPs and unidentified types of sources detected by Fermi at high Galactic latitudes. In one of the MSPs PSR J0614-3329, we find significant pulsed emission upto 200 GeV. The result has thus added this MSP to the group of the Crab and Vela pulsars that have been detected with >50 GeV pulsed emission. Comparing the $\\gamma$-ray spectrum of PSR J0614-3329 with those of the Crab and Vela pulsars, we discuss possible emission mechanisms for the very high-energy component.

  5. The Orbital Period of the Accreting Pulsar GX1+4

    CERN Document Server

    Pereira, M G; Jablonski, F J; Pereira, Marildo G.; Braga, Joao; Jablonski, Francisco J.

    1999-01-01

    We report strong evidence for a ~304-day periodicity in the spin history of the accretion-powered pulsar GX1+4 that is most probably associated with the orbital period of the system. We have used data from the Burst and Transient Source Experiment on the Compton Gamma Ray Observatory to show a clear periodic modulation of the pulsar frequency from 1991 to date, in excellent agreement with the ephemeris proposed by Cutler, Dennis & Dolan (1986). Our results indicate that the orbital period of GX1+4 is 303.8 +- 1.1 days, making it the widest known low-mass X-ray binary system by more than one order of magnitude and putting this long-standing question to rest. A likely scenario for this system is an elliptical orbit in which the neutron star decreases its spin-down rate (or even exhibits a momentary spin-up behavior) at periastron passages due to the higher torque exerted by the accretion disk onto the magnetosphere of the neutron star. These results are not inconsistent with both the X-ray pulsed flux light...

  6. The soft quiescent spectrum of the transiently accreting 11-Hz X-ray pulsar in the globular cluster Terzan 5

    NARCIS (Netherlands)

    N. Degenaar; R. Wijnands

    2011-01-01

    We report on the quiescent X-ray properties of the recently discovered transiently accreting 11-Hz X-ray pulsar in the globular cluster Terzan 5. Using two archival Chandra observations, we demonstrate that the quiescent spectrum of this neutron star low-mass X-ray binary is soft and can be fit to a

  7. A Search for Rapidly Spinning Pulsars and Fast Transients in Unidentified Radio Sources with the NRAO 43-Meter Telescope

    CERN Document Server

    Schmidt, Deborah; Langston, Glen; Gilpin, Claire

    2013-01-01

    We have searched 75 unidentified radio sources selected from the NRAO VLA Sky Survey (NVSS) catalog for the presence of rapidly spinning pulsars and short, dispersed radio bursts. The sources are radio bright, have no identifications or optical source coincidences, are more than 5% linearly polarized, and are spatially unresolved in the catalog. If these sources are fast-spinning pulsars (e.g. sub-millisecond pulsars), previous large-scale pulsar surveys may have missed detection due to instrumental and computational limitations, eclipsing effects, or diffractive scintillation. The discovery of a sub-millisecond pulsar would significantly constrain the neutron star equation of state and would have implications for models predicting a rapid slowdown of highly recycled X-ray pulsars to millisecond periods from, e.g., accretion disk decoupling. These same sources were previously searched unsuccessfully for pulsations at 610 MHz with the Lovell Telescope at Jodrell Bank. This new search was conducted at a differe...

  8. The quiescent state of the accreting X-ray pulsar SAX J2103.5+4545

    CERN Document Server

    Reig, P; Zezas, A

    2014-01-01

    We present an X-ray timing and spectral analysis of the Be/X-ray binary SAX J2103.5+4545 at a time when the Be star's circumstellar disk had disappeared and thus the main reservoir of material available for accretion had extinguished. In this very low optical state, pulsed X-ray emission was detected at a level of L_X~10^{33} erg/s. This is the lowest luminosity at which pulsations have ever been detected in an accreting pulsar. The derived spin period is 351.13 s, consistent with previous observations. The source continues its overall long-term spin-up, which reduced the spin period by 7.5 s since its discovery in 1997. The X-ray emission is consistent with a purely thermal spectrum, represented by a blackbody with kT=1 keV. We discuss possible scenarios to explain the observed quiescent luminosity and conclude that the most likely mechanism is direct emission resulting from the cooling of the polar caps, heated either during the most recent outburst or via intermittent accretion in quiescence.

  9. Accretion regimes in the X-ray pulsar 4U 1901+03

    CERN Document Server

    Reig, P

    2016-01-01

    The source 4U 1901+03 is a high-mass X-ray pulsar than went into outburst in 2003. Observation performed with the Rossi X-ray Timing Explorer showed spectral and timing variability, including the detection of flares, quasi-periodic oscillations, complex changes in the pulse profiles, and pulse phase dependent spectral variability. We re-analysed the data covering the 2003 X-ray outburst and focused on several aspects of the variability that have not been discussed so far. These are the 10 keV feature and the X-ray spectral states and their association with accretion regimes, including the transit to the propeller state at the end of the outburst. We find that 4U 1901+03 went through three accretion regimes over the course of the X-ray outburst. At the peak of the outburst and for a very short time, the X-ray flux may have overcome the critical limit that marks the formation of a radiative shock at a certain distance above the neutron star surface. Most of the time, however, the source is in the subcritical re...

  10. Contrasting Behaviour from Two Be/X-ray Binary Pulsars: Insights into Differing Neutron Star Accretion Modes

    Science.gov (United States)

    Townsend, L. J.; Drave, S. P.; Hill, A. B.; Coe, M. J.; Corbet, R. H. D.; Bird, A. J.

    2013-01-01

    In this paper we present the identification of two periodic X-ray signals coming from the direction of the Small Magellanic Cloud (SMC). On detection with the Rossi X-ray Timing Explorer (RXTE), the 175.4 s and 85.4 s pulsations were considered to originate from new Be/X-ray binary (BeXRB) pulsars with unknown locations. Using rapid follow-up INTEGRAL and XMM-Newton observations, we show the first pulsar (designated SXP175) to be coincident with a candidate high-mass X-ray binary (HMXB) in the northern bar region of the SMC undergoing a small Type II outburst. The orbital period (87d) and spectral class (B0-B0.5IIIe) of this system are determined and presented here for the first time. The second pulsar is shown not to be new at all, but is consistent with being SXP91.1 - a pulsar discovered at the very beginning of the 13 year long RXTE key monitoring programme of the SMC. Whilst it is theoretically possible for accreting neutron stars to change spin period so dramatically over such a short time, the X-ray and optical data available for this source suggest this spin-up is continuous during long phases of X-ray quiescence, where accretion driven spin-up of the neutron star should be minimal.

  11. NuSTAR discovery of a cyclotron line in the accreting X-ray pulsar IGR J16393-4643

    DEFF Research Database (Denmark)

    Bodaghee, Arash; Tomsick, John A.; Fornasini, Francesca A.;

    2016-01-01

    The high-mass X-ray binary and accreting X-ray pulsar IGR J16393-4643 was observed by NuSTAR in the 3-79 keV energy band for a net exposure time of 50 ks. We present the results of this observation which enabled the discovery of a cyclotron resonant scattering feature with a centroid energy of 29...

  12. FORMATION OF THE GALACTIC MILLISECOND PULSAR TRIPLE SYSTEM PSR J0337+1715—A NEUTRON STAR WITH TWO ORBITING WHITE DWARFS

    International Nuclear Information System (INIS)

    The millisecond pulsar in a triple system (PSR J0337+1715, recently discovered by Ransom et al.) is an unusual neutron star with two orbiting white dwarfs. The existence of such a system in the Galactic field poses new challenges to stellar astrophysics for understanding evolution, interactions, and mass transfer in close multiple stellar systems. In addition, this system provides the first precise confirmation for a very wide-orbit system of the white dwarf mass-orbital period relation. Here, we present a self-consistent, semi-analytical solution to the formation of PSR J0337+1715. Our model constrains the peculiar velocity of the system to be less than 160 km s–1 and brings novel insight to, for example, common envelope evolution in a triple system, for which we find evidence for in-spiral of both outer stars. Finally, we briefly discuss our scenario in relation to alternative models

  13. Latest results of pulse phase resolved spectroscopy of cyclotron lines in accretion powered pulsars

    CERN Document Server

    Maitra, Chandreyee

    2013-01-01

    We have performed pulse phase resolved spectroscopy of the Cyclotron Resonance Scattering Features (CRSF) of some bright accretion powered X-ray pulsars like 1A 1118-61, Vela X-1, A0535+26, XTE J1946+274, 4U 1907+09, 4U 1626-67 and GX 301-2 using Suzaku observations with long exposures. We have performed the study using different spectral models for the continuum and have obtained similar patterns of variations of the CRSF in all the cases, thus demonstrating the robustness of our results. Pulse phase dependence of the CRSF in XTE J1946+274 has been obtained for the first time, and phase resolved variations of the CRSF in 4U 1907+09 has been compared at factor of ~ 2 difference in luminosity. We have also studied the pulse profiles of these objects near the CRSF energy, and have noticed an increased pulse fraction and/or a change in the pulse shape near the CRSF energy for some sources. The implications of the results are discussed.

  14. Latest results of pulse phase resolved spectroscopy of cyclotron lines in accretion powered pulsars

    Directory of Open Access Journals (Sweden)

    Maitra Chandreyee

    2014-01-01

    Full Text Available We have performed pulse phase resolved spectroscopy of the Cyclotron Resonance Scattering Features (CRSF of some bright accretion powered X-ray pulsars like 1A 1118-61, Vela X-1, A0535+26, XTE J1946+274, 4U 1907+09, 4U 1626-67 and GX 301-2 using Suzaku observations with long exposures. We have performed the study using different spectral models for the continuum and have obtained similar patterns of variations of the CRSF in all the cases, thus demonstrating the robustness of our results. Pulse phase dependence of the CRSF in XTE J1946+274 has been obtained for the first time, and phase resolved variations of the CRSF in 4U 1907+09 has been compared at factor of ~ 2 difference in luminosity. We have also studied the pulse profiles of these objects near the CRSF energy, and have noticed an increased pulse fraction and/or a change in the pulse shape near the CRSF energy for some sources. The implications of the results are discussed.

  15. New H.E.S.S. diffuse emission from the Galactic center: a combination of heavy dark matter and millisecond pulsars?

    CERN Document Server

    Lacroix, Thomas; Moulin, Emmanuel; Boehm, Celine

    2016-01-01

    In this letter, we show that the newly detected H.E.S.S. gamma-ray diffuse emission from the Galactic center below 0.45 deg can be accounted for by inverse Compton emission from millisecond pulsars and heavy (~ 100 TeV) dark matter annihilating to electrons or muons with a thermal or sub-thermal cross-section, provided that the dark matter density profile features a supermassive black hole-induced spike on sub-pc scales. We discuss the impact of the interstellar radiation field, magnetic field and diffusion set-up on the spectral and spatial morphology of the resulting emission. For well-motivated parameters, we show that the DM-induced emission reproduces the spatial morphology of the H.E.S.S. signal above ~ 10 TeV, while we obtain a more extended component from pulsars at lower energies, which could be used as a prediction for future H.E.S.S. observations.

  16. The optical companion to the intermediate mass millisecond pulsar J1439-5501 in the Galactic field

    OpenAIRE

    Pallanca C.; Lanzoni B.; Dalessandro E.; Ferraro F. R.; Possenti A.; Salaris M.; Burgay M.

    2013-01-01

    We present the identification of the companion star to the intermediate mass binary pulsar J1439-5501 obtained by means of ground-based deep images in the B, V and I bands, acquired with FORS2 mounted at the ESO-VLT. The companion is a massive white dwarf (WD) with B=23.57+-0.02, V=23.21+-0.01 and I=22.96+-0.01, located at only ~0.05" from the pulsar radio position. Comparing the WD location in the (B, B-V) and (V, V-I) Color-Magnitude diagrams with theoretical cooling sequences we derived a ...

  17. Different twins in the millisecond pulsar recycling scenario: optical polarimetry of PSR J1023+0038 and XSS J12270-4859

    CERN Document Server

    Baglio, M C; Campana, S; Zelati, F Coti; Covino, S; Russell, D M

    2016-01-01

    We present the first optical polarimetric study of the two transitional pulsars PSR J1023+0038 and XSS J12270-4859. This work is focused on the search for intrinsical linear polarisation (LP) in the optical emission from the two systems. We carried out multiband optical and NIR photo-polarimetry of the two systems using the ESO NTT at La Silla (Chile), equipped with the EFOSC2 and the SOFI instruments. XSS J12270-4859 was observed during its radio-pulsar state; we did not detect LP in all bands, with 3 sigma upper limits of, e.g., 1.4% in the R-band. We built the NIR-optical averaged spectral energy distribution (SED) of the system, that could be well described by an irradiated black body with radius $R_{*} = 0.33\\pm0.03\\,R_{\\odot}$ and albedo $\\eta=0.32\\pm0.05$, without the need of further components (thus excluding the visible presence of an extended accretion disc and/or of relativistic jets). The case was different for PSR J1023+0038, that was in its accretion phase during our campaign. We measured a LP o...

  18. Radio Detection Prospects for a Bulge Population of Millisecond Pulsars as Suggested by Fermi-LAT Observations of the Inner Galaxy

    Science.gov (United States)

    Calore, F.; Di Mauro, M.; Donato, F.; Hessels, J. W. T.; Weniger, C.

    2016-08-01

    The dense stellar environment of the Galactic center has been proposed to host a large population of as-yet undetected millisecond pulsars (MSPs). Recently, this hypothesis has found support in an analysis of gamma-rays detected using the Large Area Telescope onboard the Fermi satellite, which revealed an excess of diffuse GeV photons in the inner 15 deg about the Galactic center. The excess can be interpreted as the collective emission of thousands of MSPs in the Galactic bulge, with a spherical distribution strongly peaked toward the Galactic center. In order to fully establish the MSP interpretation, it is essential to find corroborating evidence in multi-wavelength searches, most notably through the detection of radio pulsations from individual bulge MSPs. Based on globular cluster observations and gamma-ray emission from the inner Galaxy, we investigate the prospects for detecting MSPs in the Galactic bulge. While previous pulsar surveys failed to identify this population, we demonstrate that upcoming large-area surveys of this region should lead to the detection of dozens of bulge MSPs. Additionally, we show that deep targeted searches of unassociated Fermi sources should be able to detect the first few MSPs in the bulge. The prospects for these deep searches are enhanced by a tentative gamma-ray/radio correlation that we infer from high-latitude gamma-ray MSPs. Such detections would constitute the first clear discoveries of field MSPs in the Galactic bulge, with far-reaching implications for gamma-ray observations, the formation history of the central Milky Way, and strategy optimization for future deep radio pulsar surveys.

  19. Contrasting behaviour from two Be/X-ray binary pulsars: insights into differing neutron star accretion modes

    CERN Document Server

    Townsend, L J; Hill, A B; Coe, M J; Corbet, R H D; Bird, A J

    2013-01-01

    In this paper we present the identification of two periodic X-ray signals coming from the direction of the Small Magellanic Cloud (SMC). On detection with the Rossi X-ray Timing Explorer (RXTE), the 175.4s and 85.4s pulsations were considered to originate from new Be/X-ray binary (BeXRB) pulsars with unknown locations. Using rapid follow-up INTEGRAL and XMM-Newton observations, we show the first pulsar (designated SXP175) to be coincident with a candidate high-mass X-ray binary (HMXB) in the northern bar region of the SMC undergoing a small Type II outburst. The orbital period (87d) and spectral class (B0-B0.5IIIe) of this system are determined and presented here for the first time. The second pulsar is shown not to be new at all, but is consistent with being SXP91.1 - a pulsar discovered at the very beginning of the 13 year long RXTE key monitoring programme of the SMC. Whilst it is theoretically possible for accreting neutron stars to change spin period so dramatically over such a short time, the X-ray and ...

  20. Probing neutron star physics using accreting neutron stars

    Directory of Open Access Journals (Sweden)

    Patruno A.

    2010-10-01

    Full Text Available We give an obervational overview of the accreting neutron stars systems as probes of neutron star physics. In particular we focus on the results obtained from the periodic timing of accreting millisecond X-ray pulsars in outburst and from the measurement of X-ray spectra of accreting neutron stars during quiescence. In the first part of this overview we show that the X-ray pulses are contaminated by a large amount of noise of uncertain origin, and that all these neutron stars do not show evidence of spin variations during the outburst. We present also some recent developments on the presence of intermittency in three accreting millisecond X-ray pulsars and investigate the reason why only a small number of accreting neutron stars show X-ray pulsations and why none of these pulsars shows sub-millisecond spin periods. In the second part of the overview we introduce the observational technique that allows the study of neutron star cooling in accreting systems as probes of neutron star internal composition and equation of state. We explain the phenomenon of the deep crustal heating and present some recent developments on several quasi persistent X-ray sources where a cooling neutron star has been observed.

  1. On the dependence of the X-ray continuum variations with luminosity in accreting X-ray pulsars

    CERN Document Server

    Postnov, K A; Klochkov, D; Laplace, E; Lukin, V V; Shakura, N I

    2015-01-01

    Using RXTE/ASM archival data, we investigate the behaviour of the spectral hardness ratio as a function of X-ray luminosity in a sample of six transient X-ray pulsars (EXO 2030+375, GX 304-1, 4U 0115+63, V 0332+63, A 0535+26 and MXB 0656-072). In all sources we find that the spectral hardness ratio defined as $F_{5-12\\mathrm{keV}}/ F_{1.33-3\\mathrm{keV}}$ increases with the ASM flux (1.33--12 keV) at low luminosities and then saturates or even slightly decreases above some critical X-ray luminosity falling into the range $\\sim(3-7)\\times10^{37}$~erg~s$^{-1}$. Two-dimensional structure of accretion columns in the radiation-diffusion limit is calculated for two possible geometries (filled and hollow cylinder) for mass accretion rates $\\dot M$ ranging from $10^{17}$ to 1.2$\\times 10^{18}$~g s$^{-1}$. The observed spectral behaviour in the transient X-ray pulsars with increasing $\\dot M$ can be reproduced by a Compton saturated sidewall emission from optically thick magnetized accretion columns with taking into a...

  2. Luminosity-dependent spectral and timing properties of the accreting pulsar GX 304-1 measured with INTEGRAL

    CERN Document Server

    Malacaria, Christian; Santangelo, Andrea; Staubert, Rüdiger

    2015-01-01

    Context: Be/X-ray binaries show outbursts with peak luminosities up to a few times $10^{37}\\,$erg/s, during which they can be observed and studied in detail. Most (if not all) Be/X-ray binaries harbour accreting pulsars, whose X-ray spectra in many cases contain cyclotron resonant scattering features related to the magnetic field of the sources. Spectral variations as a function of luminosity and of the rotational phase of the neutron star are observed in many accreting pulsars. Aims: We explore X-ray spectral and timing properties of the Be/X-ray binary GX 304-1 during an outburst episode. Specifically, we investigate the behavior of the cyclotron resonant scattering feature, the continuum spectral parameters, the pulse period, and the energy- and luminosity-resolved pulse profiles. We combine the luminosity-resolved spectral and timing analysis to probe the accretion geometry and the beaming patterns of the rotating neutron star. Methods: We analyze the INTEGRAL data from the two JEM-X modules, ISGRI and SP...

  3. THE OPTICAL COMPANION TO THE INTERMEDIATE-MASS MILLISECOND PULSAR J1439-5501 IN THE GALACTIC FIELD

    Energy Technology Data Exchange (ETDEWEB)

    Pallanca, C.; Lanzoni, B.; Dalessandro, E.; Ferraro, F. R. [Dipartimento di Fisica e Astronomia, Universita degli Studi di Bologna, Viale Berti Pichat 6/2, I-40127 Bologna (Italy); Possenti, A.; Burgay, M. [INAF-Osservatorio Astronomico di Cagliari, localita Poggio dei Pini, strada 54, I-09012 Capoterra (Italy); Salaris, M. [Astrophysics Research Institute, Liverpool John Moores University (United Kingdom)

    2013-08-20

    We present the identification of the companion star to the intermediate-mass binary pulsar (PSR) J1439-5501 obtained by means of ground-based deep images in the B, V, and I bands, acquired with FORS2 mounted at the European Southern Observatory (ESO)-Very Large Telescope (VLT). The companion is a massive white dwarf (WD) with B = 23.57 {+-} 0.02, V = 23.21 {+-} 0.01, and I = 22.96 {+-} 0.01, located at only {approx}0.''05 from the pulsar radio position. Comparing the WD location in the (B, B-V) and (V, V-I) color-magnitude diagrams with theoretical cooling sequences, we derived a range of plausible combinations of companion masses (1 M{sub Sun} {approx}< M{sub COM} {approx}< 1.3 M{sub Sun }), distances (d {approx}< 1200 pc), radii ({approx}< 7.810{sup -3} R{sub Sun }), and temperatures (T=31350{sup +21500}{sub -7400}). From the PSR mass function and the estimated mass range we also constrained the inclination angle i {approx}> 55 Degree-Sign and the pulsar mass (M{sub PSR} {approx}< 2.2 M{sub Sun }). The comparison between the WD cooling age and the spin-down age suggests that the latter is overestimated by a factor of about 10.

  4. Luminosity-dependent spectral and timing properties of the accreting pulsar GX 304-1 measured with INTEGRAL

    Science.gov (United States)

    Malacaria, C.; Klochkov, D.; Santangelo, A.; Staubert, R.

    2015-09-01

    Context. Be/X-ray binaries show outbursts with peak luminosities up to a few times 1037 erg/s, during which they can be observed and studied in detail. Most (if not all) Be/X-ray binaries harbor accreting pulsars, whose X-ray spectra in many cases contain cyclotron resonant scattering features related to the magnetic field of the sources. Spectral variations as a function of luminosity and of the rotational phase of the neutron star are observed in many accreting pulsars. Aims: We explore X-ray spectral and timing properties of the Be/X-ray binary GX 304-1 during an outburst episode. Specifically, we investigate the behavior of the cyclotron resonant scattering feature, the continuum spectral parameters, the pulse period, and the energy- and luminosity-resolved pulse profiles. Methods: We analyze the INTEGRAL data from the two JEM-X modules, ISGRI and SPI, covering the 2012 January-February outburst, divided into six observations. We obtain pulse profiles in two energy bands, phase-averaged and phase-resolved spectra for each observation. We combine the luminosity-resolved spectral and timing analysis to probe the accretion geometry and the beaming patterns of the rotating neutron star. Results: We confirm the positive luminosity dependence of the cyclotron line energy in GX 304-1 and report a dependence of the photon index on luminosity. Using a pulse-phase connection technique, we find a pulse period solution valid for the entire outburst. Our pulse-phase resolved analysis shows that the centroid energy of the cyclotron line varies only slightly with pulse phase, while other spectral parameters show more pronounced variations. Our results are consistent with a scenario in which, as the pulsar rotates, we are exploring only a small portion of its beam pattern. Appendix A is available in electronic form at http://www.aanda.org

  5. A Possible 55-day X-ray Period of the Ultraluminous Accreting Pulsar M82 X-2

    OpenAIRE

    Kong, A. K. H.; Hu, C. -P.; Lin, L. C. -C.; Li, K. L.; Jin, R.; Liu, C.Y.; Yen, D. C. -C.

    2016-01-01

    We report a possible detection of a 55-day X-ray modulation for the ultraluminous accreting pulsar M82 X-2 from archival Chandra observations. Because M82 X-2 is known to have a 2.5-day orbital period, if the 55-day period is real, it will be the superorbital period of the system. We also investigated variabilities of other three nearby ultraluminous X-ray sources in the central region of M82 with the Chandra data and did not find any evidence of periodicities. Furthermore, we re-examined the...

  6. On the dependence of the X-ray continuum variations with luminosity in accreting X-ray pulsars

    Science.gov (United States)

    Postnov, K. A.; Gornostaev, M. I.; Klochkov, D.; Laplace, E.; Lukin, V. V.; Shakura, N. I.

    2015-09-01

    Using RXTE/ASM archival data, we investigate the behaviour of the spectral hardness ratio as a function of X-ray luminosity in a sample of six transient X-ray pulsars (EXO 2030+375, GX 304-1, 4U 0115+63, V 0332+63, A 0535+26 and MXB 0656-072). In all sources we find that the spectral hardness ratio defined as F5-12 keV/F1.33-3 keV increases with the ASM flux (1.33-12 keV) at low luminosities and then saturates or even slightly decreases above some critical X-ray luminosity falling into the range ˜(3-7) × 1037 erg s-1. Two-dimensional structure of accretion columns in the radiation-diffusion limit is calculated for two possible geometries (filled and hollow cylinder) for mass accretion rates dot{M} ranging from 1017 to 1.2 × 1018 g s-1. The observed spectral behaviour in the transient X-ray pulsars with increasing dot{M} can be reproduced by a Compton-saturated sidewall emission from optically thick magnetized accretion columns with taking into account the emission reflected from the neutron star atmosphere. At dot{M} above some critical value dot{M}_cr˜ (6-8)× 10^{17} g s-1, the height of the column becomes such that the contribution of the reflected component to the total emission starts decreasing, which leads to the saturation and even slight decrease of the spectral hardness. Hollow-cylinder columns have a smaller height than the filled-cylinder ones, and the contribution of the reflected component in the total emission does not virtually change with dot{M} (and hence the hardness of the continuum monotonically increases) up to higher mass accretion rates than dot{M}_cr for the filled columns.

  7. Constraining the Relative Inclinations of the Planets B and C of the Millisecond Pulsar PSR B1257+12

    Indian Academy of Sciences (India)

    Lorenzo Iorio

    2010-09-01

    We investigate on the relative inclination of the planets B and C orbiting the pulsar PSR B1257+12. First, we show that the third Kepler’s law does represent an adequate model for the orbital periods of the planets, because other Newtonian and Einsteinian corrections are orders of magnitude smaller than the accuracy in measuring B/C. Then, on the basis of available timing data, we determine the ratio sin C/ sin B = 0.92 ± 0.05 of the orbital inclinations B and C independently of the pulsar’s mass . It turns out that coplanarity of the orbits of B and C would imply a violation of the equivalence principle. Adopting a pulsar mass range 1 ≲ ≲ 3, in solar masses (supported by present-day theoretical and observational bounds for pulsar’s masses), both face-on and edge-on orbital configurations for the orbits of the two planets are ruled out; the acceptable inclinations for B span the range 36 deg ≲ B ≲ 66 deg, with a corresponding relative inclination range 6 deg ≲ (C − B) ≲ 13 deg.

  8. Pulsar spins from an instability in the accretion shock of supernovae

    OpenAIRE

    Blondin, John M.; Mezzacappa, Anthony

    2006-01-01

    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 pulsar spin is directly correlated with the rotation of the progenitor star. So far, however, stellar theory has not been able to explain the distribution of ...

  9. NuSTAR Discovery of a Cyclotron Line in the Accreting X-Ray Pulsar IGR J16393-4643

    Science.gov (United States)

    Bodaghee, Arash; Tomsick, John A.; Fornasini, Francesca M.; Krivonos, Roman; Stern, Daniel; Mori, Kaya; Rahoui, Farid; Boggs, Steven E.; Christensen, Finn E.; Craig, William W.; Hailey, Charles J.; Harrison, Fiona A.; Zhang, William W.

    2016-06-01

    The high-mass X-ray binary and accreting X-ray pulsar IGR J16393-4643 was observed by the Nuclear Spectroscope Telescope Array in the 3–79 keV energy band for a net exposure time of 50 ks. We present the results of this observation which enabled the discovery of a cyclotron resonant scattering feature with a centroid energy of {29.3}-1.3+1.1 keV. This allowed us to measure the magnetic field strength of the neutron star for the first time: B = (2.5 ± 0.1) × 1012 G. The known pulsation period is now observed at 904.0 ± 0.1 s. Since 2006, the neutron star has undergone a long-term spin-up trend at a rate of \\dot{P}=-2× {10}-8 s s‑1 (‑0.6 s per year, or a frequency derivative of \\dot{ν }=3× {10}-14 Hz s‑1). In the power density spectrum, a break appears at the pulse frequency which separates the zero slope at low frequency from the steeper slope at high frequency. This addition of angular momentum to the neutron star could be due to the accretion of a quasi-spherical wind, or it could be caused by the transient appearance of a prograde accretion disk that is nearly in corotation with the neutron star whose magnetospheric radius is around 2 × 108 cm.

  10. NuSTAR discovery of a cyclotron line in the accreting X-ray pulsar IGR J16393-4643

    CERN Document Server

    Bodaghee, Arash; Fornasini, Francesca A; Krivonos, Roman; Stern, Daniel; Mori, Kaya; Rahoui, Farid; Boggs, Steven E; Christensen, Finn E; Craig, William W; Hailey, Charles J; Harrison, Fiona A; Zhang, William W

    2016-01-01

    The high-mass X-ray binary and accreting X-ray pulsar IGR J16393-4643 was observed by NuSTAR in the 3-79 keV energy band for a net exposure time of 50 ks. We present the results of this observation which enabled the discovery of a cyclotron resonant scattering feature with a centroid energy of 29.3(+1.1/-1.3) keV. This allowed us to measure the magnetic field strength of the neutron star for the first time: B = (2.5+/-0.1)e12 G. The known pulsation period is now observed at 904.0+/-0.1 s. Since 2006, the neutron star has undergone a long-term spin-up trend at a rate of P' = -2e-8 s/s (-0.6 s per year, or a frequency derivative of nu' = 3e-14 Hz/s ). In the power density spectrum, a break appears at the pulse frequency which separates the zero slope at low frequency from the steeper slope at high frequency. This addition of angular momentum to the neutron star could be due to the accretion of a quasi-spherical wind, or it could be caused by the transient appearance of a prograde accretion disk that is nearly i...

  11. Interplanetary spacecraft navigation using pulsars

    OpenAIRE

    Deng, X. P.; Hobbs, G.; You, X. P.; M. T. Li; Keith, M. J.; Shannon, R. M.; Coles, W.; Manchester, R. N.; J.H. Zheng; Yu, X. Z.; Gao, D.; Wu, X; Chen, D.

    2013-01-01

    We demonstrate how observations of pulsars can be used to help navigate a spacecraft travelling in the solar system. We make use of archival observations of millisecond pulsars from the Parkes radio telescope in order to demonstrate the effectiveness of the method and highlight issues, such as pulsar spin irregularities, which need to be accounted for. We show that observations of four millisecond pulsars every seven days using a realistic X-ray telescope on the spacecraft throughout a journe...

  12. A Possible 55-day X-ray Period of the Ultraluminous Accreting Pulsar M82 X-2

    CERN Document Server

    Kong, A K H; Lin, L C -C; Li, K L; Jin, R; Liu, C Y; Yen, D C -C

    2016-01-01

    We report a possible detection of a 55-day X-ray modulation for the ultraluminous accreting pulsar M82 X-2 from archival Chandra observations. Because M82 X-2 is known to have a 2.5-day orbital period, if the 55-day period is real, it will be the superorbital period of the system. We also investigated variabilities of other three nearby ultraluminous X-ray sources in the central region of M82 with the Chandra data and did not find any evidence of periodicities. Furthermore, we re-examined the previously reported 62-day periodicity near the central region of M82 by performing a systematic timing study with all the archival Rossi X-Ray Timing Explorer and Swift data. Using various dynamic timing analysis methods, we confirmed that the 62-day period is not stable, suggesting that it is not the orbital period of M82 X-1 in agreement with previous work.

  13. NuSTAR detection of 4s Hard X-ray Lags from the Accreting Pulsar GS 0834-430

    Directory of Open Access Journals (Sweden)

    Bachetti Matteo

    2014-01-01

    Full Text Available The NuSTAR hard X-ray telescope observed the transient Be/X-ray binary GS 0834–430 during its 2012 outburst. The source is detected between 3 – 79 keV with high statistical significance, and we were able to perform very accurate spectral and timing analysis. The phase-averaged spectrum is consistent with that observed in many other magnetized accreting pulsars. We fail to detect cyclotron resonance scattering features in either phase-averaged nor phase-resolved spectra that would allow us to constrain the pulsar’s magnetic field. We detect a pulse period of ~ 12:29 s in all energy bands. The pulse profile can be modeled with a double Gaussian and shows a strong and smooth hard lag of up to 0.3 cycles in phase, or about 4s between the pulse at ~ 3 and ≳ 30 keV. This is the first report of such a strong lag in high-mass X-ray binary (HMXB pulsars. Previously reported lags have been significantly smaller in phase and restricted to low-energies (E<10 keV. We investigate the possible mechanisms that might produce such lags. We find the most likely explanation for this effect to be a complex beam geometry.

  14. Different twins in the millisecond pulsar recycling scenario: Optical polarimetry of PSR J1023+0038 and XSS J12270-4859

    Science.gov (United States)

    Baglio, M. C.; D'Avanzo, P.; Campana, S.; Coti Zelati, F.; Covino, S.; Russell, D. M.

    2016-06-01

    We present the first optical polarimetric study of the two transitional pulsars PSR J1023+0038 and XSS J12270-4859. This work is focused on the search for intrinsically linearly polarised optical emission from the two systems. To this aim, we carried out multiband optical (BVRi) and near-infrared (NIR; JHK) photo-polarimetric observations of the two systems using the ESO New Technology Telescope (NTT) at La Silla (Chile), equipped with the EFOSC2 and the SOFI instruments. The system XSS J12270-4859 was observed during its radio-pulsar state; we did not detect a significant degree of polarisation in any of the bands, with 3σ upper limits, for example, of 1.4% in the R-band. We built the NIR-optical averaged spectral energy distribution (SED) of the system, which could be described well by an irradiated black body with radius R∗ = 0.33 ± 0.03 R⊙ and albedo η = 0.32 ± 0.05, without the need for further components. Thus, we excluded the visible presence of an extended accretion disc and/or of relativistic jets. The case was different for PSR J1023+0038, which was in its accretion phase during our campaign. We measured a linear polarisation of 1.09 ± 0.27% and 0.90 ± 0.17% in the V and R bands, respectively. The phase-resolved polarimetric curve of the source in the R band reveals a hint of a sinusoidal modulation at the source 4.75 h orbital period, peaked at the same orbital phase as the light curve. The measured optical polarisation of PSR J1023+0038 could, in principle, be interpreted as electron scattering with free electrons, which can be found in the accretion disc of the system or even in the hot corona that sorrounds the disc itself, or as synchrotron emission from a jet of relativistic particles or an outflow. However, the NIR-optical SED of the system built from our dataset did not suggest the presence of a jet. We conclude that the optical linear polarisation observed for PSR J1023+0038 is possibly due to Thomson scattering with electrons in the

  15. X-ray pulsar rush in 1998

    Energy Technology Data Exchange (ETDEWEB)

    Imanishi, K.; Tsujimoto, K.; Nishiuchi, Mamiko; Yokogawa, J.; Koyama, K. [Kyoto Univ., Faculty of Science, Kyoto (Japan)

    1999-08-01

    We present recent remarkable topics about discoveries of X-ray pulsars. 1. Pulsations from two Soft Gamma-ray Repeaters: These pulsars have enormously strong magnetic field (B {approx} 10{sup 15} G), thus these are called as 'magnetar', new type of X-ray pulsars. 2. New Crab-like pulsars: These discoveries lead to suggesting universality of Crab-like pulsars. 3. An X-ray bursting millisecond pulsar: This is strong evidence for the recycle theory of generating radio millisecond pulsars. 4. X-ray pulsar rush in the SMC: This indicates the younger star formation history in the SMC. (author)

  16. On pulsar-driven mass ejection in low-mass X-ray binaries

    Institute of Scientific and Technical Information of China (English)

    Lei Fu; Xiang-Dong Li

    2011-01-01

    There is accumulating evidence for mass ejection in low-mass X-ray binaries (LMXBs) driven by radio pulsar activity during X-ray quiescence.We consider the condition for mass ejection by comparing the radiation pressure from a millisecond pulsar,and the gas pressure at the inner Lagrange point or at the surrounding accretion disk.We calculate the critical spin period of the pulsar below which mass ejection is allowed.Combining with the evolution of the mass transfer rate,we present constraints on the orbital periods of the systems.We show that mass ejection could happen in both wide and compact LMXBs.It may be caused by transient accretion due to thermal instability in the accretion disks in the former,and irradiation-driven mass-transfer cycles in the latter.

  17. Comptonization in the accretion column of the X-ray pulsar GX~1+4

    OpenAIRE

    Galloway, D. K.

    2000-01-01

    X-ray observations of the binary pulsar GX 1+4 made using the Rossi X-ray Timing Explorer (RXTE) satellite between February 1996 and May 1997 were analysed to quantify source spectral variation with luminosity. Mean Proportional Counter Array (PCA) spectra over the range 2-40 keV are best fitted with a Comptonization model, with source spectrum temperature T_0 approx 1-1.3 keV, plasma temperature T_e approx 6-10 keV, and optical depth tau approx 2-6. The range of fitted T_0 was consistent wit...

  18. NuSTAR discovery of a cyclotron line in the accreting X-ray pulsar IGR J16393-4643

    DEFF Research Database (Denmark)

    Bodaghee, Arash; Tomsick, John A.; Fornasini, Francesca A.;

    2016-01-01

    The high-mass X-ray binary and accreting X-ray pulsar IGR J16393-4643 was observed by NuSTAR in the 3-79 keV energy band for a net exposure time of 50ks. We present the results of this observation which enabled the discovery of acyclotron resonant scattering feature with a centroid energy of 29.3...

  19. Pulsars in Globular Clusters with the SKA

    CERN Document Server

    Hessels, J W T; Bailes, M; Bassa, C G; Freire, P C C; Lorimer, D R; Lynch, R; Ransom, S M; Stairs, I H

    2015-01-01

    Globular clusters are highly efficient radio pulsar factories. These pulsars can be used as precision probes of the clusters' structure, gas content, magnetic field, and formation history; some of them are also highly interesting in their own right because they probe exotic stellar evolution scenarios as well as the physics of dense matter, accretion, and gravity. Deep searches with SKA1-MID and SKA1-LOW will plausibly double to triple the known population. Such searches will only require one to a few tied-array beams, and can be done during early commissioning of the telescope - before an all-sky pulsar survey using hundreds to thousands of tied-array beams is feasible. With SKA2 it will be possible to observe most of the active radio pulsars within a large fraction of the Galactic globular clusters, an estimated population of 600 - 3700 observable pulsars (those beamed towards us). This rivals the total population of millisecond pulsars that can be found in the Galactic field; fully characterizing it will p...

  20. Search for VHE γ-ray emission from the direction of the two millisecond pulsars PSR J0437-4715 and PSR J1824-2452 and the composite supernova remnant Kes 75 with H.E.S.S

    International Nuclear Information System (INIS)

    This work reports on the search for pulsed and steady very-high energy (VHE) gamma-ray emission in the energy range extending from 100 GeV up to 100 TeV from the direction of three pulsars with the High Energy Stereoscopic System (H.E.S.S.). Pulsed gamma-ray radiation from pulsars with energies beyond 100 GeV was found thus far only for the young and energetic Crab pulsar. A special class of pulsar wind nebulae (PWNe) is associated with composite supernova remnants (SNRs) where the PWN is centered in an expanding SNR shell. In the first part of this thesis, the results on the search for pulsed and steady VHE gamma-ray emission from the two millisecond pulsars, PSR J0437-4715 and PSR J1824-2452, are presented. Parts of the observations were conducted in a special trigger setup (the topological trigger with convergent pointing) to reduce the energy threshold of the instrument. No signal of pulsed or steady emission is found and upper limits on the pulsed and steady gamma-ray flux are derived. The upper limits on the pulsed gamma-ray flux are compared to existing model predictions and, in the case of PSR J1824-2452, allow the range of possible viewing geometries in some models to be constrained. In the second part of this work, results on the search for pulsed and steady VHE gamma-ray emission from the direction of the composite SNR Kes 75 are presented. The PWN in the center of Kes 75 is powered by a very young and powerful pulsar, PSR J1846-0258, that has an exceptionally high magnetic field. While no hint for pulsed emission is found, steady VHE gamma-ray emission is detected with a statistical significance of 10 sigma from a point-like source. The VHE gamma-ray emission is spatially coincident with the PWN and the SNR shell. Both are discussed as a possible origin for the observed emission. The pulsar of Kes 75 would be the youngest pulsar known to date to power a VHE PWN.

  1. Long-Term Monitoring of the Accreting Pulsar GX 1+4

    OpenAIRE

    Chakrabarty, Deepto; Bildsten, L.; Chiu, J.; Grunsfeld, J. M.; Koh, T; Prince, Thomas A.; Finger, Mark H.; Wilson, Robert B.

    1993-01-01

    We present preliminary results from two years of GRO/BATSE hard X‐ray (20–100 keV) monitoring of the ∼120 s accretion‐powered pulsar GX 1+4. Daily pulse frequency measurements from 1991 April to 1993 September show an average spin‐down of ḟ≊−5×10^(−12) s^(−2), with increases in the spin‐down rate during high‐luminosity intervals. The 20–100 keV pulsed flux spectrum for the interval TJD 8393–8406 is fit by a power‐law index of 2.56±0.04. Optical spectroscopy of the suggested red giant compani...

  2. A 16 Millisecond X-Ray Pulsar in the Crab-Like SNR N157B Fast Times at 30 Doradus

    CERN Document Server

    Gotthelf, E V; Marshall, F E; Middleditch, J; Wang, Q D

    1998-01-01

    The supernova remnant N157B (30 Dor B, SNR 0539-69.1, NGC 2060), located in the Tarantula Nebula of the Large Magellanic Cloud, has long been considered a possible Crab-like remnant. This hypothesis has been confirmed, quite spectacularly, with the discovery of PSR J0537-6910, the remarkable 16 ms X-ray pulsar in N157B. PSR J0537-6910 is the most rapidly spinning pulsar found to be associated with a supernova remnant. Here we report our discovery and summarize the properties of this pulsar and its supernova remnant.

  3. IGR J17252-3616: an accreting pulsar observed by INTEGRAL and XMM-Newton

    CERN Document Server

    Heras, J A Z; Walter, R; Bodaghee, A; Bélanger, G; Courvoisier, T; Shaw, S E; Stephen, J B

    2005-01-01

    The discovery of the X-ray source IGR J17252-3616 by INTEGRAL was reported on 9 February 2004. Regular monitoring by INTEGRAL shows that IGR J17252-3616 is a persistent hard X-ray source with an average count rate of 0.96 counts/s (~6.4 mCrab) in the 20-60 keV energy band. A follow-up observation with XMM-Newton, which was performed on 21 March 21 2004, showed that the source is located at R.A.(2000.0)=17h25m11.4 and Dec.=-36degr16'58.6" with an uncertainty of 4". The only infra-red counterpart to be found within the XMM-Newton error circle was 2MASS J17251139-3616575, which has a Ks-band magnitude of 10.7 and is located 1" away from the XMM-Newton position. The analysis of the combined INTEGRAL and XMM-Newton observations shows that the source is a binary X-ray pulsar with a spin period of 413.7 s and an orbital period of 9.72 days. The spectrum can be fitted with a flat power law plus an energy cut off (Gamma~0.02,Ecut~8.2 keV) or a Comptonized model (kTe~5.5 keV, tau~7.8). The spectrum also indicates a lar...

  4. Positive correlation between the cyclotron line energy and luminosity in sub-critical X-ray pulsars: Doppler effect in the accretion channel

    CERN Document Server

    Mushtukov, Alexander A; Serber, Alexander V; Suleimanov, Valery F; Poutanen, Juri

    2015-01-01

    Cyclotron resonance scattering features observed in the spectra of some X-ray pulsars show significant changes of the line centroid energy with the pulsar luminosity. Whereas for bright sources above the so called critical luminosity these variations are established to be connected with the appearance of the high accretion column above the neutron star surface, at low, sub-critical luminosities the nature of the variations (but with the opposite sign) has not been discussed widely. We argue here that the cyclotron line is formed when the radiation from a hotspot propagates through the plasma falling with a mildly relativistic velocity onto the neutron star surface. The position of the cyclotron resonance is determined by the Doppler effect. The change of the cyclotron line position in the spectrum with luminosity is caused by variations of the velocity profile in the line-forming region affected by the radiation pressure force. The presented model has several characteristic features: (i) the line centroid ene...

  5. Recycling Pulsars: spins, masses and ages

    CERN Document Server

    Tauris, T M; Langer, N

    2012-01-01

    Although the first millisecond pulsars (MSPs) were discovered 30 years ago we still do not understand all details of their formation process. Here, we present new results from Tauris, Langer & Kramer (2012) on the recycling scenario leading to radio MSPs with helium or carbon-oxygen white dwarf companions via evolution of low- and intermediate mass X-ray binaries (LMXBs, IMXBs). We discuss the location of the spin-up line in the (P,Pdot)-diagram and estimate the amount of accreted mass needed to obtain a given spin period and compare with observations. Finally, we constrain the true ages of observed recycled pulsars via calculated isochrones in the (P,Pdot)-diagram.

  6. The slowest spinning X-ray pulsar in an extragalactic globular cluster

    CERN Document Server

    Zolotukhin, Ivan; Sartore, Nicola; Chilingarian, Igor; Webb, Natalie A

    2016-01-01

    Neutron stars are thought to be born rapidly rotating and then exhibit a phase of a rotation-powered pulsations as they slow down to 1-10 s periods. The significant population of millisecond pulsars observed in our Galaxy is explained by the recycling concept: during an epoch of accretion from a donor star in a binary system, the neutron star is spun up to millisecond periods. However, only a few pulsars are observed during this recycling process, with relatively high rotational frequencies. Here we report the detection of an X-ray pulsar with $P_{\\rm spin} = 1.20$ s in the globular cluster B091D in the Andromeda galaxy, the slowest pulsar ever found in a globular cluster. This bright (up-to 30% of the Eddington luminosity), high spin-up rate pulsar, persistent over the 12 years of observations, must have started accreting less than 1 Myr ago and has not yet had time to accelerate to hundreds of Hz. The neutron star in this unique wide binary with an orbital period $P_{\\rm orb} = 30.5$ h in a 12 Gyr old, meta...

  7. Ensemble Pulsar Time Scale

    Science.gov (United States)

    Yin, D. S.; Gao, Y. P.; Zhao, S. H.

    2016-05-01

    Millisecond pulsars can generate another type of time scale that is totally independent of the atomic time scale, because the physical mechanisms of the pulsar time scale and the atomic time scale are quite different from each other. Usually the pulsar timing observational data are not evenly sampled, and the internals between data points range from several hours to more than half a month. What's more, these data sets are sparse. And all these make it difficult to generate an ensemble pulsar time scale. Hence, a new algorithm to calculate the ensemble pulsar time scale is proposed. Firstly, we use cubic spline interpolation to densify the data set, and make the intervals between data points even. Then, we employ the Vondrak filter to smooth the data set, and get rid of high-frequency noise, finally adopt the weighted average method to generate the ensemble pulsar time scale. The pulsar timing residuals represent clock difference between the pulsar time and atomic time, and the high precision pulsar timing data mean the clock difference measurement between the pulsar time and atomic time with a high signal to noise ratio, which is fundamental to generate pulsar time. We use the latest released NANOGRAV (North American Nanohertz Observatory for Gravitational Waves) 9-year data set to generate the ensemble pulsar time scale. This data set is from the newest NANOGRAV data release, which includes 9-year observational data of 37 millisecond pulsars using the 100-meter Green Bank telescope and 305-meter Arecibo telescope. We find that the algorithm used in this paper can lower the influence caused by noises in timing residuals, and improve long-term stability of pulsar time. Results show that the long-term (> 1 yr) frequency stability of the pulsar time is better than 3.4×10-15.

  8. Ensemble Pulsar Time Scale

    CERN Document Server

    Rodin, Alexander E

    2010-01-01

    The algorithm of the ensemble pulsar time scale (PT$_{\\rm ens}$) based on the optimal Wiener filtration method has been proposed. This algorithm allows the separation of the contributions to the post-fit pulsar timing residuals of the atomic clock and pulsar itself. Filters were designed with the use of the cross-spectra of the timing residuals. The method has been applied to the timing data of six millisecond pulsars. Direct comparison with the classical method of the weighted average showed that use of the optimal Wiener filters before averaging allows noticeably to improve the fractional instability of the ensemble time scale. Application of the proposed method to the most stable millisecond pulsars with the fractional instability $\\sigma_z < 10^{-15}$ may improve the fractional instability of PT$_{\\rm ens}$ up to the level $\\sim 10^{-16}$.

  9. Interplanetary spacecraft navigation using pulsars

    CERN Document Server

    Deng, X P; You, X P; Li, M T; Keith, M J; Shannon, R M; Coles, W; Manchester, R N; Zheng, J H; Yu, X Z; Gao, D; Wu, X; Chen, D

    2013-01-01

    We demonstrate how observations of pulsars can be used to help navigate a spacecraft travelling in the solar system. We make use of archival observations of millisecond pulsars from the Parkes radio telescope in order to demonstrate the effectiveness of the method and highlight issues, such as pulsar spin irregularities, which need to be accounted for. We show that observations of four millisecond pulsars every seven days using a realistic X-ray telescope on the spacecraft throughout a journey from Earth to Mars can lead to position determinations better than approx. 20km and velocity measurements with a precision of approx. 0.1m/s.

  10. Impact of accretion on the statistics of neutron star masses

    CERN Document Server

    Cheng, Z; Zhao, Y H; 10.1017/S1743921312019588

    2013-01-01

    We have collected the parameter of 38 neutron stars (NSs) in binary systems with spin periods and measured masses. By adopting the Boot-strap method, we reproduced the procedure of mass calculated for each system separately, to determine the truly mass distribution of the NS that obtained from observation. We also applied the Monte-Carlo simulation and introduce the characteristic spin period 20 ms, in order to distinguish between millisecond pulsars (MSPs) and less recycled pulsars. The mass distributions of MSPs and the less recycled pulsars could be fitted by a Gaussian function as $\\rm 1.45\\pm0.42 M_{\\odot}$ and $\\rm 1.31\\pm0.17 M_{\\odot} (\\rm with ~ 1\\sigma)$ respectively. As such, the MSP masses are heavier than those in less recycled systems by factor of $\\rm \\sim 0.13M_{\\odot}$, since the accretion effect during the recycling process.

  11. Pulsars and quark stars

    CERN Document Server

    Xu, R

    2005-01-01

    Members of the family of pulsar-like stars are distinguished by their different manifestations observed, i.e., radio pulsars, accretion-driven X-ray pulsars, X-ray bursts, anomalous X-ray pulsars/soft gamma-ray repeaters, compact center objects, and dim thermal neutron stars. Though one may conventionally think that these stars are normal neutron stars, it is still an open issue whether they are actually neutron stars or quark stars, as no convincing work, either theoretical from first principles or observational, has confirmed Baade-Zwicky's original idea that supernovae produce neutron stars. After introducing briefly the history of pulsars and quark stars, the author summarizes the recent achievements in his pulsar group, including quark matter phenomenology at low temperature, starquakes of solid pulsars, low-mass quark stars, and the pulsar magnetospheric activities.

  12. GBM Accreting Pulsar Histories

    Data.gov (United States)

    National Aeronautics and Space Administration — For each source we plot the history of pulse frequency and pulsed flux measured using the Fermi Gamma-Ray Burst Monitor (GBM) NaI detectors. For these measurements...

  13. Pulsars and Gravity

    CERN Document Server

    Manchester, R N

    2015-01-01

    Pulsars are wonderful gravitational probes. Their tiny size and stellar mass give their rotation periods a stablility comparable to that of atomic frequency standards. This is especially true of the rapidly rotating "millisecond pulsars" (MSPs). Many of these rapidly rotating pulsars are in orbit with another star, allowing pulsar timing to probe relativistic perturbations to the orbital motion. Pulsars have provided the most stringent tests of theories of relativistic gravitation, especially in the strong-field regime, and have shown that Einstein's general theory of relativity is an accurate description of the observed motions. Many other gravitational theories are effectively ruled out or at least severely constrained by these results. MSPs can also be used to form a "Pulsar Timing Array" (PTA). PTAs are Galactic-scale interferometers that have the potential to directly detect nanohertz gravitational waves from astrophysical sources. Orbiting super-massive black holes in the cores of distant galaxies are t...

  14. Current Flows in Pulsar Magnetospheres

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The global structure of .current flows in pulsar magnetosphere is investigated, with rough calculations of the circuit elements. It is emphasized that the potential of the critical field lines (the field lines that intersect the null surface at the light cylinder radius) should be the same as that of interstellar medium, and that pulsars whose rotation axes and magnetic dipole axes are parallel should be positively charged, in order to close the pulsar's current flows. The statistical relation between the radio luminosity and pulsar's electric charge (or the spindown power) may hint that the millisecond pulsars could be low-mass bare strange stars.

  15. IMPLICATIONS OF BURST OSCILLATIONS FROM THE SLOWLY ROTATING ACCRETING PULSAR IGR J17480-2446 IN THE GLOBULAR CLUSTER TERZAN 5

    International Nuclear Information System (INIS)

    The recently discovered accreting X-ray pulsar IGR J17480-2446 spins at a frequency of ∼11 Hz. We show that Type I X-ray bursts from this source display oscillations at the same frequency as the stellar spin. IGR J17480-2446 is the first secure case of a slowly rotating neutron star (NS) which shows Type I burst oscillations (BOs), all other sources featuring such oscillations spin at hundreds of Hertz. This means that we can test BO models in a completely different regime. We explore the origin of Type I BOs in IGR J17480-2446 and conclude that they are not caused by global modes in the NS ocean. We also show that the Coriolis force is not able to confine an oscillation-producing hot spot on the stellar surface. The most likely scenario is that the BOs are produced by a hot spot confined by hydromagnetic stresses.

  16. Positive correlation between the cyclotron line energy and luminosity in sub-critical X-ray pulsars: Doppler effect in the accretion channel

    Science.gov (United States)

    Mushtukov, Alexander A.; Tsygankov, Sergey S.; Serber, Alexander V.; Suleimanov, Valery F.; Poutanen, Juri

    2015-12-01

    Cyclotron resonance scattering features observed in the spectra of some X-ray pulsars show significant changes of the line centroid energy with the pulsar luminosity. Whereas for bright sources above the so-called critical luminosity, these variations are established to be connected with the appearance of the high-accretion column above the neutron star surface, at low, sub-critical luminosities the nature of the variations (but with the opposite sign) has not been discussed widely. We argue here that the cyclotron line is formed when the radiation from a hotspot propagates through the plasma falling with a mildly relativistic velocity on to the neutron star surface. The position of the cyclotron resonance is determined by the Doppler effect. The change of the cyclotron line position in the spectrum with luminosity is caused by variations of the velocity profile in the line-forming region affected by the radiation pressure force. The presented model has several characteristic features: (i) the line centroid energy is positively correlated with the luminosity; (ii) the line width is positively correlated with the luminosity as well; (iii) the position and the width of the cyclotron absorption line are variable over the pulse phase; (iv) the line has a more complicated shape than widely used Lorentzian or Gaussian profiles; (v) the phase-resolved cyclotron line centroid energy and the width are negatively and positively correlated with the pulse intensity, respectively. The predictions of the proposed theory are compared with the variations of the cyclotron line parameters in the X-ray pulsar GX 304-1 over a wide range of sub-critical luminosities as seen by the INTEGRAL observatory.

  17. Formation of redbacks via accretion induced collapse

    CERN Document Server

    Smedley, Sarah L; Ferrario, Lilia; Wickramasinghe, Dayal T

    2014-01-01

    We examine the growing class of binary millisecond pulsars known as redbacks. In these systems the pulsar's companion has a mass between 0.1 and about 0.5 solar masses in an orbital period of less than 1.5 days. All show extended radio eclipses associated with circumbinary material. They do not lie on the period-companion mass relation expected from the canonical intermediate-mass X-ray binary evolution in which the companion filled its Roche lobe as a red giant and has now lost its envelope and cooled as a white dwarf. The redbacks lie closer to, but usually at higher period than, the period-companion mass relation followed by cataclysmic variables and low-mass X-ray binaries. In order to turn on as a pulsar mass accretion on to a neutron star must be sufficiently weak, considerably weaker than expected in systems with low-mass main-sequence companions driven together by magnetic braking or gravitational radiation. If a neutron star is formed by accretion induced collapse of a white dwarf as it approaches th...

  18. NuSTAR observations of the supergiant X-ray pulsar IGR J18027-2016: accretion from the stellar wind and possible cyclotron absorption line

    CERN Document Server

    Lutovinov, A; Postnov, K; Krivonos, R; Molkov, S; Tomsick, J

    2016-01-01

    We report on the first focused hard X-ray view of the absorbed supergiant system IGRJ18027-2016 performed with the NuSTAR observatory. The pulsations are clearly detected with a period of P_{spin}=139.866(1) s and a pulse fraction of about 50-60% at energies from 3 to 80 keV. The source demonstrates an approximately constant X-ray luminosity on a time scale of more than dozen years with an average spin-down rate of dP/dt~6x10^{-10} s/s. This behaviour of the pulsar can be explained in terms of the wind accretion model in the settling regime. The detailed spectral analysis at energies above 10 keV was performed for the first time and revealed a possible cyclotron absorption feature at energy ~23 keV. This energy corresponds to the magnetic field B~3x10^{12} G at the surface of the neutron star, which is typical for X-ray pulsars.

  19. The Pulsar Population in Globular Clusters and in the Galaxy

    CERN Document Server

    Freire, Paulo C C

    2012-01-01

    In this paper, I review some of the basic properties of the pulsar population in globular clusters (GCs) and compare it with the the Galactic disk population. The neutron stars (NSs) in GCs were likely formed - and appear to continue forming - in highly symmetric supernovae (SNe), likely from accretion-induced collapse (AIC). I review the many pulsar finds and discuss some particularly well populated GCs and why they are so. I then discuss some particularly interesting objects, like millisecond pulsars (MSPs) with eccentric orbits, which were heavily perturbed by passing stars. Some of these systems, like NGC 1851A and NGC 6544B, are almost certainly the result of exchange interactions, i.e., they are witnesses to the very same processes that created the large population of MSPs in the first place. I also review briefly the problem posed by the presence of young pulsars in GCs (with a special emphasis on a sub-class of young pulsars, the super-energetic MSPs), which suggest continuing formation of NSs in low-...

  20. "Missing Link" Revealing Fast-Spinning Pulsar Mysteries

    Science.gov (United States)

    2009-05-01

    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 process in action," said Anne Archibald, of McGill University in Montreal, Canada. Pulsar and Companion Neutron star with accretion disk (left) drawing material from companion star (right). CREDIT:Bill Saxton, NRAO/AUI/NSF Animations of this system and its evolution. Pulsars are superdense neutron stars, the remnants left after massive stars have exploded as supernovae. Their powerful magnetic fields generate lighthouse-like beams of light and radio waves that sweep around as the star rotates. Most rotate a few to tens of times a second, slowing down over thousands of years. However, some, dubbed millisecond pulsars, rotate hundreds of times a second. Astronomers believe the fast rotation is caused by a companion star dumping material onto the neutron star and spinning it up. The material from the companion would form a flat, spinning disk around the neutron star, and during this period, the radio waves characteristic of a pulsar would not be seen coming from the system. As the amount of matter falling onto the neutron star decreased and stopped, the radio waves could emerge, and the object would be recognized as a pulsar. This sequence of events is apparently what happened with a binary-star system some 4000 light-years from Earth. The millisecond pulsar in this system, called J1023, was discovered by the National Science Foundation's (NSF) Robert C. Byrd Green Bank Telescope (GBT) in West Virginia in 2007 in a survey led by astronomers at West Virginia University and the National Radio Astronomy Observatory (NRAO). The astronomers then found that the object had been detected by NSF's Very Large Array (VLA) radio

  1. Ejector and propeller spin-down: How might a superluminous supernova millisecond magnetar become the 6.67 hr pulsar in RCW103

    CERN Document Server

    Ho, Wynn C G

    2016-01-01

    The X-ray source 1E 161348-5055 in the supernova remnant RCW 103 recently exhibited X-ray activity typical of magnetars, i.e., neutron stars with magnetic fields > 10^14-10^15 G. However, 1E 161348-5055 has an observed period of 6.67 hr, in contrast to magnetars which have a spin period of seconds. Here we describe a simple model which can explain the spin evolution of 1E 161348-5055, as well as other magnetars, from an initial period of milliseconds that would be required for dynamo generation of magnetar-strength magnetic fields. We propose that the key difference between 1E 161348-5055 and other magnetars is the persistence of a remnant disk of small total mass. This disk caused 1E 161348-5055 to undergo ejector and propeller phases in its life, during which strong torques caused a rapid increase of its spin period. By matching its observed spin period and ~1-3 kyr age, we find that 1E 161348-5055 has the (slightly) highest magnetic field of all known magnetars, with B~5x10^15 G, and that its disk had a ma...

  2. Spectra of Southern Pulsars

    CERN Document Server

    Toscano, M; Manchester, R N; Sandhu, J S

    1998-01-01

    We compare the spectral properties of the millisecond and slow pulsars detected in the Parkes 70 cm survey. The mean spectral index for the millisecond pulsars (MSPs) is -1.9 +/- 0.1 whereas the mean spectral index for the slow pulsars is a surprisingly steep -1.72 +/- 0.04. A Kolmogorov-Smirnov test indicates that there is only a 72% probability that the two distributions differ. As a class, MSPs are therefore only fractionally steeper-spectrum objects than slow pulsars, as recent literature would suggest. We then model the expected distribution of millisecond pulsars in the Galaxy and find that high-frequency surveys, with sensitivities similar to the current Parkes multibeam survey, are likely to detect MSPs in large numbers. The observed distribution of MSPs will be much less isotropic than that resulting from low-frequency surveys, with 50% of detectable MSPs residing within 11 degrees of the Galactic plane in an all-sky survey.

  3. Evidence for crust cooling in the transiently accreting 11-Hz X-ray pulsar in the globular cluster Terzan 5

    NARCIS (Netherlands)

    N. Degenaar; E.F. Brown; R. Wijnands

    2011-01-01

    The temporal heating and subsequent cooling of the crusts of transiently accreting neutron stars carries unique information about their structure and a variety of nuclear reaction processes. We report on a new Chandra Director’s Discretionary Time observation of the globular cluster Terzan 5, aimed

  4. NuSTAR discovers a cyclotron line and reveals the spinning up of the accreting X-ray pulsar IGR J16393-4643

    Science.gov (United States)

    Bodaghee, Arash; Tomsick, John; Fornasini, Francesca; Krivonos, Roman; Stern, Daniel; Mori, Kaya; Rahoui, Farid; Boggs, Steven E.; Christensen, Finn; Craig, William W.; Hailey, Charles James; Harrison, Fiona; Zhang, William

    2016-04-01

    After several misclassifications, IGR J16393-4643 is now known to be a high-mass X-ray binary consisting of a heavily-absorbed pulsar that is likely paired with a massive and distant B star. It was observed for 50-ks by NuSTAR in the 3--79 keV energy band, complemented by a contemporaneous 2-ks observation with Swift-XRT. These observations enabled the discovery of a cyclotron resonant scattering feature with a centroid energy of 29.3(+1.1/-1.3) keV. This allowed us to measure the magnetic field strength of the neutron star for the first time: B = (2.5±0.1)×1012 G. The known pulsation period is now observed at 904.0±0.1 s. Since 2006, the neutron star has undergone a long-term spin-up trend at a rate of dP/dt = -2×10-8 s s-1 (-0.6 s per year, or a frequency derivative of dν/dt = 3×10-14 Hz s-1). In the power density spectrum, a break appears at the pulse frequency which separates the zero slope at low frequency from the steeper slope at high frequency. This addition of angular momentum to the neutron star could be due to the accretion of a quasi-spherical wind, or it could be caused by the transient appearance of a prograde accretion disk that is nearly in corotation with the neutron star whose magnetospheric radius is around 2×108 cm.

  5. Search for Orbital Motion of the Pulsar 4U 1626-67: Candidate for a Neutron Star with a Supernova Fall-back Accretion Disk

    Indian Academy of Sciences (India)

    Chetana Jain; Biswajit Paul; Kaustubh Joshi; Anjan Dutta; Harsha Raichur

    2007-12-01

    We report here results from a new search for orbital motion of the accretion powered X-ray pulsar 4U 1626-67 using two different analysis techniques. X-ray light curve obtained with the Proportional Counter Array of the Rossi X-ray Timing Explorer during a long observation carried out in February 1996, was used in this work. The spin period and the local period derivative were first determined from the broad 2–60 keV energy band light curve and these were used for all subsequent timing analysis. In the first technique, the orbital phase dependent pulse arrival times were determined for different trial orbital periods in the range of 500 to 10,000 s. We have determined a 3 upper limit of 13 lt-ms on the projected semimajor axis of the orbit of the neutron star for most of the orbital period range, while in some narrow orbital period ranges, covering about 10% of the total orbital period range, it is 20 lt-ms. In the second method, we have measured the pulse arrival times at intervals of 100 s over the entire duration of the observation. The pulse arrival time data were used to put an upper limit on any periodic arrival time delay using the Lomb–Scargle periodogram. We have obtained a similar upper limit of 10 lt-ms using the second method over the orbital period range of 500–10,000 s. This puts very stringent upper limits for the mass of the compact object except for the unlikely case of a complete face-on orientation of the binary system with respect to our line-of-sight. In the light of this measurement and the earlier reports, we discuss the possibility of this system being a neutron star with a supernovae fall-back accretion disk.

  6. Engulfing a radio pulsar: the case of PSR J1023+0038

    OpenAIRE

    Zelati, F. Coti; Baglio, M. C.; S. Campana; D'Avanzo, P.; Goldoni, P.; Masetti, N.; Muñoz-Darias, T.; Covino, S.; Fender, R. P.; Bailón, E. Jiménez; Otí-Floranes, H.; Palazzi, E.; F. G. Ramón-Fox

    2014-01-01

    The binary millisecond radio pulsar PSR J1023+0038 has been recently the subject of multiwavelength monitoring campaigns which revealed that an accretion disc has formed around the neutron star (since 2013 June). We present here the results of X-ray and UV observations carried out by the Swift satellite between 2013 October and 2014 May, and of optical and NIR observations performed with the REM telescope, the Liverpool Telescope, the 2.1-m telescope at the San Pedro M\\'artir Observatory and ...

  7. Pulsar disk systems

    Energy Technology Data Exchange (ETDEWEB)

    Michel, F.C.; Dessler, A.J.

    1981-12-15

    We argue that the radio pulsars and the X-ray pulsars differ mainly in the fact that the latter are surrounded by an accretion disk, while the former are surrounded by a fossil collapse disk presumably left over from the formation event. We attribute the difference between these two types of pulsars to a strong interaction (enforced accretion) of the X-ray pulsars with their disks as opposed to a relatively weak interaction (and negligible accretion) in the case of the radio pulsars. A number of observational problems (e.g., role of alignment, ion confinement, nulling, drifting subpulses, braking index, residuals, and the supernova association) are readily addressed in terms of the disk model. Moreover, the model is consistent with a ''hollow cone'' type of emission pattern. Rough estimates here suggest that pulsars with disks could function with magnetic fields at the neutron star surface as low as 10/sup 9/ gauss, far below that often assumed; conventional field strengths of 10/sup 12/ gauss are not excluded, however.

  8. Torque Enhancement, Spin Equilibrium, and Jet Power from Disk-Induced Opening of Pulsar Magnetic Fields

    CERN Document Server

    Parfrey, Kyle; Beloborodov, Andrei M

    2015-01-01

    The interaction of a rotating star's magnetic field with a surrounding plasma disk lies at the heart of many questions posed by neutron stars in X-ray binaries. We consider the opening of stellar magnetic flux due to differential rotation along field lines coupling the star and disk, using a simple model for the disk-opened flux, the torques exerted on the star by the magnetosphere, and the power extracted by the electromagnetic wind. We examine the conditions under which the system enters an equilibrium spin state, in which the accretion torque is instantaneously balanced by the pulsar wind torque alone. For magnetic moments, spin frequencies, and accretion rates relevant to accreting millisecond pulsars, the spin-down torque from this enhanced pulsar wind can be substantially larger than that predicted by existing models of the disk-magnetosphere interaction, and is in principle capable of maintaining spin equilibrium at frequencies less than 1 kHz. We speculate that this mechanism may account for the non-d...

  9. MHD Simulations of Magnetized Stars in the Propeller Regime of Accretion

    Directory of Open Access Journals (Sweden)

    Lii Patrick

    2014-01-01

    Full Text Available Accreting magnetized stars may be in the propeller regime of disc accretion in which the angular velocity of the stellar magnetosphere exceeds that of the inner disc. In these systems, the stellar magnetosphere acts as a centrifugal barrier and inhibits matter accretion onto the rapidly rotating star. Instead, the matter accreting through the disc accumulates at the disc-magnetosphere interface where it picks up angular momentum and is ejected from the system as a wide-angled outflow which gradually collimates at larger distances from the star. If the ejection rate is lower than the accretion rate, the matter will accumulate at the boundary faster than it can be ejected; in this case, accretion onto the star proceeds through an episodic accretion instability in which the episodes of matter accumulation are followed by a brief episode of simultaneous ejection and accretion of matter onto the star. In addition to the matter dominated wind component, the propeller outflow also exhibits a well-collimated, magnetically-dominated Poynting jet which transports energy and angular momentum away from the star. The propeller mechanism may explain some of the weakly-collimated jets and winds observed around some T Tauri stars as well as the episodic variability present in their light curves. It may also explain some of the quasi-periodic variability observed in cataclysmic variables, millisecond pulsars and other magnetized stars.

  10. Ion-proton pulsars

    OpenAIRE

    Jones, P. B.

    2016-01-01

    Evidence derived with minimal assumptions from existing published observations is presented to show that an ion-proton plasma is the source of radio-frequency emission in millisecond and in normal isolated pulsars. There is no primary involvement of electron-positron pairs. This conclusion has also been reached by studies of the plasma composition based on well-established particle-physics processes in neutron stars with positive polar-cap corotational charge density. This work has been publi...

  11. Aquila X-1 from outburst to quiescence: the onset of the propeller effect and signs of an awaken rotation powered pulsar

    Energy Technology Data Exchange (ETDEWEB)

    Campana, S.; Stella, L.; Mereghetti, S.; Colpi, M.; Tavani, M.; Ricci, D.; Dal Fiume, D.; Belloni, T

    1999-01-01

    According to current evolutionary scenarios, neutron stars in Low Mass X-Ray Binaries (LMXRBs) are spun-up by accretion torques to limiting periods in the millisecond range and give rise to 'recycled' millisecond radio pulsars once accretion stops{sup 1-3}. In addition to persistent sources, the X-ray sky is populated by a number of transient sources. Among them, Soft X-Ray Transients (SXRTs), when in outburst, show properties similar to those of LMXRBs{sup 4-6}. SXRTs are characterised by luminosities, and therefore mass accretion rates, that vary over many decades: while it is clear that when in outburst their emission is powered by accretion onto the neutron star surface, the origin of the low-level emission detected during quiescence remained uncertain{sup 7,8}. Here we report on BeppoSAX pointed observations of Aql X-1, the first to follow the decay of a SXRT outburst down to quiescence. The fast X-ray flux decay that leads to quiescence is most readily interpreted in terms of the propeller effect arising from the very fast rotation of the neutron star magnetosphere. The hard X-ray spectrum that characterises the quiescent emission is probably due to shock emission powered by a turned-on radio pulsar.

  12. X-ray Pulsars

    CERN Document Server

    Walter, Roland

    2016-01-01

    X-ray pulsars shine thanks to the conversion of the gravitational energy of accreted material to X-ray radiation. The accretion rate is modulated by geometrical and hydrodynamical effects in the stellar wind of the pulsar companions and/or by instabilities in accretion discs. Wind driven flows are highly unstable close to neutron stars and responsible for X-ray variability by factors $10^3$ on time scale of hours. Disk driven flows feature slower state transitions and quasi periodic oscillations related to orbital motion and precession or resonance. On shorter time scales, and closer to the surface of the neutron star, X-ray variability is dominated by the interactions of the accreting flow with the spinning magnetosphere. When the pulsar magnetic field is large, the flow is confined in a relatively narrow accretion column, whose geometrical properties drive the observed X-ray emission. In low magnetized systems, an increasing accretion rate allows the ignition of powerful explosive thermonuclear burning at t...

  13. Testing Gravity with Pulsars in the SKA Era

    CERN Document Server

    Shao, Lijing; Antoniadis, John; Deller, Adam T; Freire, Paulo C C; Hessels, Jason W T; Janssen, Gemma H; Kramer, Michael; Kunz, Jutta; Lämmerzahl, Claus; Perlick, Volker; Possenti, Andrea; Ransom, Scott; Stappers, Benjamin W; van Straten, Willem

    2015-01-01

    The Square Kilometre Array (SKA) will use pulsars to enable precise measurements of strong gravity effects in pulsar systems, which yield tests of gravitational theories that cannot be carried out anywhere else. The Galactic census of pulsars will discover dozens of relativistic pulsar systems, possibly including pulsar -- black hole binaries which can be used to test the "cosmic censorship conjecture" and the "no-hair theorem". Also, the SKA's remarkable sensitivity will vastly improve the timing precision of millisecond pulsars, allowing probes of potential deviations from general relativity (GR). Aspects of gravitation to be explored include tests of strong equivalence principles, gravitational dipole radiation, extra field components of gravitation, gravitomagnetism, and spacetime symmetries.

  14. Pulsars, PTAs, and PALFA: Highlights and Opportunities

    Science.gov (United States)

    Scholz, Paul A.

    2015-08-01

    The detection of gravitational waves with nanohertz frequencies from SMBHs in merging galaxies, either a single source or a background, is greatly aided by increasing the sensitivity of pulsar timing arrays (PTAs). Increasing the number of millisecond pulsars in PTAs is one of the best ways to enhance their sensitivity. Therefore searches for new millisecond pulsars are absolutely essential to the detection of gravitational waves from merging galaxies. I will review the status of current pulsar search efforts and how they have contributed to PTAs. I will then present some of the recent highlights of the PALFA survey. Using the PALFA survey as a case study, I will outline the current challenges faced by pulsar searches, including RFI and a large number of false positives, and potential solutions to those issues.

  15. Circular Polarization in Pulsar Integrated Profiles: Updates

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    We update the systematic studies of circular polarization in integrated pulse profiles by Han et al. Data of circular polarization profiles are compiled. Sense reversals can occur in core or cone components, or near the intersection between components. The correlation between the sense of circular polarization and the sense of position angle variation for conal-double pulsars is confirmed with a much large database. Circular polarization of some pulsars has clear changes with frequency.Circular polarization of millisecond pulsars is marginally different from that of normal pulsars.

  16. Detecting Dark Matter with Imploding Pulsars in the Galactic Center

    CERN Document Server

    Bramante, Joseph

    2014-01-01

    The paucity of old millisecond pulsars observed at the galactic center of the Milky Way could be the result of dark matter accumulating in and destroying neutron stars. In regions of high dark matter density, dark matter clumped in a pulsar can exceed the Schwarzschild limit and collapse into a natal black hole which destroys the pulsar. We examine what dark matter models are consistent with this hypothesis and find regions of parameter space where dark matter accumulation can significantly degrade the neutron star population within the galactic center while remaining consistent with observations of old millisecond pulsars in globular clusters and near the solar position. We identify what dark matter couplings and masses might cause a young pulsar at the galactic center to unexpectedly extinguish. Finally, we find that pulsar collapse age scales inversely with the dark matter density and linearly with the dark matter velocity dispersion. This implies that maximum pulsar age is spatially dependent on position ...

  17. Radio Searches for Pulsars and Short-Duration Transients

    CERN Document Server

    McLaughlin, Maura

    2011-01-01

    I discuss methods and current software packages for radio searches for pulsars and short-duration transients. I then describe the properties of the current pulsar population and the status of and predictions for ongoing and future surveys. The presently observed pulsar population numbers around 2000 and is expected to roughly double over the next five years, with the number of millisecond pulsars expected to more than triple. Finally, I discuss individual objects discovered in the Green Bank Telescope 350-MHz Drift-Scan Survey and the Arecibo Pulsar ALFA Survey.

  18. Gravitational wave detection and data analysis for pulsar timing arrays

    NARCIS (Netherlands)

    Haasteren, Rutger van

    2011-01-01

    Long-term precise timing of Galactic millisecond pulsars holds great promise for measuring long-period (months-to-years) astrophysical gravitational waves. In this work we develop a Bayesian data analysis method for projects called pulsar timing arrays; projects aimed to detect these gravitational w

  19. The Fastest Rotating Pulsar: a Strange Star?

    Institute of Scientific and Technical Information of China (English)

    徐仁新; 徐轩彬; 吴鑫基

    2001-01-01

    According to the observational limits on the radius and mass, the fastest rotating pulsar (PSR 1937+21) is probably a strange star, or at least some neutron star equations of state should be ruled out, if we suggest that a dipole magnetic field is relevant to its radio emission. We presume that the millisecond pulsar is a strange star with much low mass, small radius and weak magnetic moment.

  20. The Parkes Pulsar Timing Array

    Science.gov (United States)

    Manchester, Richard N.

    2015-08-01

    The Parkes Pulsar Timing Array (PPTA) project uses the Parkes 64-m radio telescope to observe 22 millisecond pulsars in three bands: 40cm (band centre 732 MHz), 20cm (1369 MHz) and 10cm (3100 MHz). Coherent de-dispersion systems are used for the 40cm and 20cm bands and digital polyphase filterbanks are used for the 20cm and 10cm bands. Observations are made at intervals of two to three weeks and observations times for each pulsar in each band are typically one hour. Regular PPTA observations commenced in early 2005 but earlier timing data, primarily in the 20cm band, exist for many of the pulsars back to 1994. Pipeline processing scripts are based on PSRCHIVE routines and take into account instrumental offsets. Timing analyses include modelling of dispersion variations and red and white noise in the data. The primary scientific goal of the PPTA project is the detection of gravitational waves, either a stochastic background from supermassive black-hole binary systems in distant galaxies or from individual binary systems. The PPTA data sets have many other applications including establishment of a pulsar-based timescale, improvement of solar-system ephemerides and studies of the individual pulsars. PPTA data sets have been made available to the International Pulsar Timing Array consortium and analysis of the combined data sets is progressing. Recent developments, both instrumental and science-related, will be described.

  1. The hunt for new pulsars with the Green Bank Telescope

    CERN Document Server

    Lynch, Ryan S; Banaszak, Shawn; Becker, Alison; Berndsen, Aaron; Biwer, Chris; Boyles, Jason; Cardoso, Rogerio F; Cherry, Angus; Dartez, Louis P; Day, David; Epstein, Courtney R; Flanigan, Joe; Ford, Anthony; Garcia, Alejandro; Hessels, Jason W T; Jenet, Fredrick A; Kaplan, David L; Karako-Argaman, Chen; Kaspi, Victoria M; Kondratiev, Vladislav I; Lorimer, Duncan R; Lunsford, Grady; Martinez, Jose; McLaughlin, Maura A; McPhee, Christie A; Pennucci, Tim; Ransom, Scott M; Roberts, Mallory S E; Rohr, Matt; Siemens, Xavi; Stairs, Ingrid H; Stovall, Kevin; van Leeuwen, Joeri; Walker, Arielle; Wells, Brad

    2013-01-01

    The Green Bank Telescope (GBT) is the largest fully steerable radio telescope in the world and is one of our greatest tools for discovering and studying radio pulsars. Over the last decade, the GBT has successfully found over 100 new pulsars through large-area surveys. Here I discuss the two most recent---the GBT 350 MHz Drift-scan survey and the Green Bank North Celestial Cap survey. The primary science goal of both surveys is to find interesting individual pulsars, including young pulsars, rotating radio transients, exotic binary systems, and especially bright millisecond pulsars (MSPs) suitable for inclusion in Pulsar Timing Arrays, which are trying to directly detect gravitational waves. These two surveys have combined to discover 85 pulsars to date, among which are 14 MSPs and many unique and fascinating systems. I present highlights from these surveys and discuss future plans. I also discuss recent results from targeted GBT pulsar searches of globular clusters and Fermi sources.

  2. Arecibo Pulsar and Transient Surveys Using ALFA

    Science.gov (United States)

    Cordes, J. M.

    2008-02-01

    A large scale survey for pulsars and transients is being conducted at the Arecibo Observatory using the Arecibo L-band Feed Array (ALFA). Data acquisition so far has been with correlation spectrometers that analyze a 0.1 GHz bandwidth at 1.4 GHz. The 256 frequency channels limit dispersion smearing to 1.2 ms at DMmax = 103 pc cm-3 while the sampling interval of 64 μs equals the dispersion smearing at DM~54 pc cm-3, providing high sensitivity to millisecond pulsars with standard periods out to implied distances of several kpc at low Galactic latitudes. In early 2008, we will use a new set of polyphase filter bank systems that provide the same time and frequency resolutions but over ALFA's full 0.3 GHz bandwidth. Currently the survey covers sky positions within 5° of the Galactic plane that are reachable with Arecibo. Preliminary results are given for some of the discoveries made so far, which include millisecond pulsars, a relativistic binary pulsar, a likely counterpart of a Compton GRO/EGRET gamma-ray source, and transient pulsars (including `RRATs''). We discuss the methodology of the survey, which includes archival of raw survey data at the Cornell Center for Advanced Computing and processing at distributed sites. The survey and follow up observations, which include timing observations, multiwavelength searches for orbital companions in the case of binary pulsars, etc. are organized through the Pulsar-ALFA (PALFA) Consortium. We expect the Galactic plane survey to continue until at least 2010, most likely involving multiple passes on each sky position to optimize detection of variable sources. The ALFA system will also be used to survey intermediate Galactic latitudes for millisecond pulsars, relativistic binaries with large systemic velocities, and runaway pulsars that will escape the Galaxy.

  3. Theory of wind accretion

    Directory of Open Access Journals (Sweden)

    Shakura N.I.

    2014-01-01

    Full Text Available A review of wind accretion in high-mass X-ray binaries is presented. We focus attention to different regimes of quasi-spherical accretion onto the neutron star: the supersonic (Bondi accretion, which takes place when the captured matter cools down rapidly and falls supersonically toward NS magnetospghere, and subsonic (settling accretion which occurs when plasma remains hot until it meets the magnetospheric boundary. Two regimes of accretion are separated by an X-ray luminosity of about 4 × 1036 erg/s. In the subsonic case, which sets in at low luminosities, a hot quasi-spherical shell must be formed around the magnetosphere, and the actual accretion rate onto NS is determined by ability of the plasma to enter the magnetosphere due to Rayleigh-Taylor instability. We calculate the rate of plasma entry the magnetopshere and the angular momentum transfer in the shell due to turbulent viscosity appearing in the convective differentially rotating shell. We also discuss and calculate the structure of the magnetospheric boundary layer where the angular momentum between the rotating magnetosphere and the base of the differentially rotating quasi-spherical shell takes place. We show how observations of equilibrium X-ray pulsars Vela X-1 and GX 301-2 can be used to estimate dimensionless parameters of the subsonic settling accretion theory, and obtain the width of the magnetospheric boundary layer for these pulsars.

  4. Theory of wind accretion

    Science.gov (United States)

    Shakura, N. I.; Postnov, K. A.; Kochetkova, A. Yu.; Hjalmarsdotter, L.

    2014-01-01

    A review of wind accretion in high-mass X-ray binaries is presented. We focus attention to different regimes of quasi-spherical accretion onto the neutron star: the supersonic (Bondi) accretion, which takes place when the captured matter cools down rapidly and falls supersonically toward NS magnetospghere, and subsonic (settling) accretion which occurs when plasma remains hot until it meets the magnetospheric boundary. Two regimes of accretion are separated by an X-ray luminosity of about 4 × 1036 erg/s. In the subsonic case, which sets in at low luminosities, a hot quasi-spherical shell must be formed around the magnetosphere, and the actual accretion rate onto NS is determined by ability of the plasma to enter the magnetosphere due to Rayleigh-Taylor instability. We calculate the rate of plasma entry the magnetopshere and the angular momentum transfer in the shell due to turbulent viscosity appearing in the convective differentially rotating shell. We also discuss and calculate the structure of the magnetospheric boundary layer where the angular momentum between the rotating magnetosphere and the base of the differentially rotating quasi-spherical shell takes place. We show how observations of equilibrium X-ray pulsars Vela X-1 and GX 301-2 can be used to estimate dimensionless parameters of the subsonic settling accretion theory, and obtain the width of the magnetospheric boundary layer for these pulsars.

  5. Parkes Observations of Globular Cluster Pulsars

    Science.gov (United States)

    Bailes, M.; Zhu, J.; Richter, S.

    2005-07-01

    Follow-up observations of pulsars from the Swinburne intermediate latitude survey with the Parkes radio telescope have caused us to question the association of PSR B1718-19 with the globular cluster NGC 6342 given the proximity of PSR J1721-1939 to the cluster. We have also found that the millisecond pulsar near the core of NGC 6624 has a large period second derivative, which would change the sign of the first derivative in about 6000 years. This is consistent with the pulsar experiencing a large gravitational perturbation from the cluster core.

  6. Dark matter vs. Pulsars: Catching the impostor

    CERN Document Server

    Mirabal, N

    2013-01-01

    Evidence of excess GeV emission nearly coinciding with the Galactic Centre has been interpreted as a possible signature of annihilating dark matter. In this paper, we argue that it seems too early to discard pulsars as a viable explanation for the observed excess. On the heels of the recently released Second Fermi LAT Pulsar Catalogue (2FPC), it is still possible that a population of hard (Gamma < 1) millisecond pulsars (MSPs) either endemic to the innermost region or part of a larger nascent collection of hard MSPs that appears to be emerging in the 2FPC could explain the GeV excess near the Galactic Centre.

  7. X-ray observations and the search for Fermi-LAT gamma-ray pulsars

    OpenAIRE

    Saz Parkinson, PM; Belfiore, A.; Caraveo, P.; De Luca, A; Marelli, M.

    2013-01-01

    The Large Area Telescope (LAT) on Fermi has detected ~150 gamma-ray pulsars, about a third of which were discovered in blind searches of the $\\gamma$-ray data. Because the angular resolution of the LAT is relatively poor and blind searches for pulsars (especially millisecond pulsars, MSPs) are very sensitive to an error in the position, one must typically scan large numbers of locations. Identifying plausible X-ray counterparts of a putative pulsar drastically reduces the number of trials, th...

  8. Stability of pulsar rotational and orbital periods

    CERN Document Server

    Kopeikin, Sergei

    2009-01-01

    Millisecond and binary pulsars are the most stable astronomical standards of frequency. They can be applied to solving a number of problems in astronomy and time-keeping metrology including the search for a stochastic gravitational wave background in the early universe, testing general relativity, and establishing a new time-scale. The full exploration of pulsar properties requires that proper unbiased estimates of spin and orbital parameters of the pulsar be obtained. These estimates depend essentially on the random noise components present in pulsar timing residuals. The instrumental white noise has predictable statistical properties and makes no harm for interpretation of timing observations, while the astrophysical/geophysical low-frequency noise corrupts them, thus, reducing the quality of tests of general relativity and decreasing the stability of the pulsar time scale.

  9. Arecibo and the ALFA Pulsar Survey

    CERN Document Server

    Van Leeuwen, J; Lorimer, D R; Freire, P C C; Camilo, F; Stairs, I H; Nice, D J; Champion, D J; Ramachandran, R; Faulkner, A J; Lyne, A G; Ransom, S M; Arzoumanian, Z; Manchester, R N; McLaughlin, M A; Hessels, J W T; Vlemmings, W; Deshpande, A A; Bhat, N D R; Chatterjee, S; Han, J L; Gaensler, B M; Kasian, L; Deneva, J S; Reid, B; Lazio, T J W; Kaspi, V M; Crawford, F; Lommen, A N; Backer, D C; Krämer, M; Stappers, B W; Hobbs, G B; Possenti, A; D'Amico, N; Faucher-Gigu`ere, C A; Burgay, M

    2006-01-01

    The recently started Arecibo L-band Feed Array (ALFA) pulsar survey aims to find ~1000 new pulsars. Due to its high time and frequency resolution the survey is especially sensitive to millisecond pulsars, which have the potential to test gravitational theories, detect gravitational waves and probe the neutron-star equation of state. Here we report the results of our preliminary analysis: in the first months we have discovered 21 new pulsars. One of these, PSR J1906+0746, is a young 144-ms pulsar in a highly relativistic 3.98-hr low-eccentricity orbit. The 2.61 +- 0.02 solar-mass system is expected to coalesce in ~300 Myr and contributes significantly to the computed cosmic inspiral rate of compact binary systems.

  10. Arecibo pulsar survey using ALFA. III. Precursor survey and population synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Swiggum, J. K.; Lorimer, D. R.; McLaughlin, M. A.; Bates, S. D.; Senty, T. R. [Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506 (United States); Champion, D. J.; Lazarus, P. [Max-Planck-Institut für Radioastronomie, D-53121 Bonn (Germany); Ransom, S. M. [NRAO, Charlottesville, VA 22903 (United States); Brazier, A.; Chatterjee, S.; Cordes, J. M. [Astronomy Department, Cornell University, Ithaca, NY 14853 (United States); Hessels, J. W. T. [ASTRON, Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA, Dwingeloo (Netherlands); Nice, D. J. [Department of Physics, Lafayette College, Easton, PA 18042 (United States); Ellis, J.; Allen, B. [Physics Department, University of Wisconsin-Milwaukee, Milwaukee WI 53211 (United States); Bhat, N. D. R. [Center for Astrophysics and Supercomputing, Swinburne University, Hawthorn, Victoria 3122 (Australia); Bogdanov, S.; Camilo, F. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Crawford, F. [Department of Physics and Astronomy, Franklin and Marshall College, Lancaster, PA 17604-3003 (United States); Deneva, J. S. [Arecibo Observatory, HC3 Box 53995, Arecibo, PR 00612 (United States); and others

    2014-06-01

    The Pulsar Arecibo L-band Feed Array (PALFA) Survey uses the ALFA 7-beam receiver to search both inner and outer Galactic sectors visible from Arecibo (32° ≲ ℓ ≲ 77° and 168° ≲ ℓ ≲ 214°) close to the Galactic plane (|b| ≲ 5°) for pulsars. The PALFA survey is sensitive to sources fainter and more distant than have previously been seen because of Arecibo's unrivaled sensitivity. In this paper we detail a precursor survey of this region with PALFA, which observed a subset of the full region (slightly more restrictive in ℓ and |b| ≲ 1°) and detected 45 pulsars. Detections included 1 known millisecond pulsar and 11 previously unknown, long-period pulsars. In the surveyed part of the sky that overlaps with the Parkes Multibeam Pulsar Survey (36° ≲ ℓ ≲ 50°), PALFA is probing deeper than the Parkes survey, with four discoveries in this region. For both Galactic millisecond and normal pulsar populations, we compare the survey's detections with simulations to model these populations and, in particular, to estimate the number of observable pulsars in the Galaxy. We place 95% confidence intervals of 82,000 to 143,000 on the number of detectable normal pulsars and 9000 to 100,000 on the number of detectable millisecond pulsars in the Galactic disk. These are consistent with previous estimates. Given the most likely population size in each case (107,000 and 15,000 for normal and millisecond pulsars, respectively), we extend survey detection simulations to predict that, when complete, the full PALFA survey should have detected 1000{sub −230}{sup +330} normal pulsars and 30{sub −20}{sup +200} millisecond pulsars. Identical estimation techniques predict that 490{sub −115}{sup +160} normal pulsars and 12{sub −5}{sup +70} millisecond pulsars would be detected by the beginning of 2014; at the time, the PALFA survey had detected 283 normal pulsars and 31 millisecond pulsars, respectively. We attribute the deficiency in normal pulsar

  11. Fate of the companion stars of ultra-rapid pulsars

    International Nuclear Information System (INIS)

    A millisecond pulsar that is formed by spin-up 'recycling' in a binary system will, once the mass transfer becomes temporarily interrupted, start to evaporate its companion star as a consequence of the large impinging pulsar energy flux. This evaporation is easiest if the pulsar has a short pulse period, the companion star has a relatively large radius and is therefore hydrogen-rich, and the orbital period is short. Evaporation of companion stars induced by millisecond pulsars could account for the lack of low-mass X-ray binaries with short orbital periods below the period gap of the cataclysmic variables, and for the statistics of new-born radio pulsars and their space velocities. (author)

  12. Detecting stochastic backgrounds of gravitational waves with pulsar timing arrays

    Science.gov (United States)

    Siemens, Xavier

    2016-03-01

    For the past decade the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) has been using the Green Bank Telescope and the Arecibo Observatory to monitor millisecond pulsars. NANOGrav, along with two other international collaborations, the European Pulsar Timing Array and the Parkes Pulsar Timing Array in Australia, form a consortium of consortia: the International Pulsar Timing Array (IPTA). The goal of the IPTA is to directly detect low-frequency gravitational waves which cause small changes to the times of arrival of radio pulses from millisecond pulsars. In this talk I will discuss the work of NANOGrav and the IPTA, as well as our sensitivity to stochastic backgrounds of gravitational waves. I will show that a detection of the background produced by supermassive black hole binaries is possible by the end of the decade. Supported by the NANOGrav Physics Frontiers Center.

  13. Pulsar Magnetospheres and Pulsar Winds

    CERN Document Server

    Beskin, Vasily S

    2016-01-01

    Surprisingly, the chronology of nearly 50 years of the pulsar magnetosphere and pulsar wind research is quite similar to the history of our civilization. Using this analogy, I have tried to outline the main results obtained in this field. In addition to my talk, the possibility of particle acceleration due to different processes in the pulsar magnetosphere is discussed in more detail.

  14. EINSTEIN-HOME DISCOVERY OF 24 PULSARS IN THE PARKES MULTI-BEAM PULSAR SURVEY

    International Nuclear Information System (INIS)

    We have conducted a new search for radio pulsars in compact binary systems in the Parkes multi-beam pulsar survey (PMPS) data, employing novel methods to remove the Doppler modulation from binary motion. This has yielded unparalleled sensitivity to pulsars in compact binaries. The required computation time of ≈17, 000 CPU core years was provided by the distributed volunteer computing project Einstein-Home, which has a sustained computing power of about 1 PFlop s–1. We discovered 24 new pulsars in our search, 18 of which were isolated pulsars, and 6 were members of binary systems. Despite the wide filterbank channels and relatively slow sampling time of the PMPS data, we found pulsars with very large ratios of dispersion measure (DM) to spin period. Among those is PSR J1748–3009, the millisecond pulsar with the highest known DM (≈420 pc cm–3). We also discovered PSR J1840–0643, which is in a binary system with an orbital period of 937 days, the fourth largest known. The new pulsar J1750–2536 likely belongs to the rare class of intermediate-mass binary pulsars. Three of the isolated pulsars show long-term nulling or intermittency in their emission, further increasing this growing family. Our discoveries demonstrate the value of distributed volunteer computing for data-driven astronomy and the importance of applying new analysis methods to extensively searched data

  15. Pulsar observations with European telescopes for testing gravity and detecting gravitational waves

    CERN Document Server

    Perrodin, D; Janssen, G H; Karuppusamy, R; Kramer, M; Lee, K; Liu, K; McKee, J; Purver, M; Sanidas, S; Smits, R; Stappers, B W; Zhu, W; Concu, R; Melis, A; Burgay, M; Casu, S; Corongiu, A; Egron, E; Iacolina, N; Pellizzoni, A; Pilia, M; Trois, A

    2016-01-01

    A background of nanohertz gravitational waves from supermassive black hole binaries could soon be detected by pulsar timing arrays, which measure the times-of-arrival of radio pulses from millisecond pulsars with very high precision. The European Pulsar Timing Array uses five large European radio telescopes to monitor high-precision millisecond pulsars, imposing in this way strong constraints on a gravitational wave background. To achieve the necessary precision needed to detect gravitational waves, the Large European Array for Pulsars (LEAP) performs simultaneous observations of pulsars with all five telescopes, which allows us to coherently add the radio pulses, maximize the signal-to-noise of pulsar signals and increase the precision of times-of-arrival. We report on the progress made and results obtained by the LEAP collaboration, and in particular on the addition of the Sardinia Radio Telescope to the LEAP observations during its scientific validation phase. In addition, we discuss how LEAP can be used t...

  16. Observing peculiar γ-ray pulsars with AGILE

    Science.gov (United States)

    Pilia, M.; Pellizzoni, A.

    2011-08-01

    The AGILE γ-ray satellite provides large sky exposure levels (>=109 cm2 s per year on the Galactic Plane) with sensitivity peaking at E ~100 MeV where the bulk of pulsar energy output is typically released. Its ~1 μs absolute time tagging capability makes it perfectly suited for the study of γ-ray pulsars. AGILE collected a large number of γ-ray photons from EGRET pulsars (>=40,000 pulsed counts for Vela) in two years of observations unveiling new interesting features at sub-millisecond level in the pulsars' high-energy light-curves, γ-ray emission from pulsar glitches and Pulsar Wind Nebulae. AGILE detected about 20 nearby and energetic pulsars with good confidence through timing and/or spatial analysis. Among the newcomers we find pulsars with very high rotational energy losses, such as the remarkable PSR B1509-58 with a magnetic field in excess of 1013 Gauss, and PSR J2229+6114 providing a reliable identification for the previously unidentified EGRET source 3EG2227+6122. Moreover, the powerful millisecond pulsar B1821-24, in the globular cluster M28, is detected during a fraction of the observations.

  17. The "Perseus Arm" Multibeam pulsar survey

    Science.gov (United States)

    Lyne, Andrew; Possenti, Andrea; Manchester, Dick; Kramer, Michael; Hobbs, George; McLaughlin, Maura; Burgay, Marta; D'Amico, Nichi; Camilo, Fernando; Stairs, Ingrid; Keith, Michael; Lorimer, Duncan Ross

    2007-10-01

    Given the extremely fruitful results of the completed Parkes Multibeam Pulsar Survey, Parkes Multibeam High Latitude Pulsar Survey, and Parkes Multibeam Intermediate Latitude Swinburne Survey, we have undertaken a new deep search for pulsars, sampling the galactic plane in the direction of the Perseus Arm at galactic coordinates 200 deg pulsar population and in particular improving the knowledge of the poorly known radial distribution of the pulsars in the outer regions of the Galaxy disk. Given the survey parameters and the sky coverage, this search will lead to the discovery of few tens of sources, with a good discovery rate (twice higher than for the two most recent large-scale searches performed at Parkes) and with a favorable ratio of millisecond over longer period pulsars. The requested range of Sidereal Time is complementary to other pulsar projects. We propose to continue this project, concluding the survey observations during this OCT07 semester and timing the discovered pulsars.

  18. The Transient Accreting X-Ray Pulsar XTE J1946+274: Stability of X-Ray Properties at Low Flux and Updated Orbital Solution

    Science.gov (United States)

    Marcu-Cheatham, Diana M.; Pottschmidt, Katja; Kühnel, Matthias; Müller, Sebastian; Falkner, Sebastian; Caballero, Isabel; Finger, Mark H.; Jenke, Peter J.; Wilson-Hodge, Colleen A.; Fürst, Felix; Grinberg, Victoria; Hemphill, Paul B.; Kreykenbohm, Ingo; Klochkov, Dmitry; Rothschild, Richard E.; Terada, Yukikatsu; Enoto, Teruaki; Iwakiri, Wataru; Wolff, Michael T.; Becker, Peter A.; Wood, Kent S.; Wilms, Jörn

    2015-12-01

    We present a timing and spectral analysis of the X-ray pulsar XTE J1946+274 observed with Suzaku during an outburst decline in 2010 October and compare with previous results. XTE J1946+274 is a transient X-ray binary consisting of a Be-type star and a neutron star with a 15.75 s pulse period in a 172 days orbit with 2-3 outbursts per orbit during phases of activity. We improve the orbital solution using data from multiple instruments. The X-ray spectrum can be described by an absorbed Fermi-Dirac cut-off power-law model along with a narrow Fe Kα line at 6.4 keV and a weak Cyclotron Resonance Scattering Feature (CRSF) at ˜35 keV. The Suzaku data are consistent with the previously observed continuum flux versus iron line flux correlation expected from fluorescence emission along the line of sight. However, the observed iron line flux is slightly higher, indicating the possibility of a higher iron abundance or the presence of non-uniform material. We argue that the source most likely has only been observed in the subcritical (non-radiation dominated) state since its pulse profile is stable over all observed luminosities and the energy of the CRSF is approximately the same at the highest (˜5 × 1037 erg s-1) and lowest (˜5 × 1036 erg s-1) observed 3-60 keV luminosities.

  19. A Measurement Model for Precision Pulsar Timing

    CERN Document Server

    Cordes, J M

    2010-01-01

    This paper describes a comprehensive measurement model for the error budget of pulse arrival times with emphasis on intrinsic pulse jitterand plasma propagation effects (particularly interstellar scattering), which are stochastic in time and have diverse dependences on radio frequency. To reduce their contribution, timing measurements can be made over a range of frequencies that depends on a variety of pulsar and instrumentation-dependent factors that we identify. A salient trend for high signal-to-noise measurements of millisecond pulsars is that time-of-arrival precision is limited either by irreducible interstellar scattering or by pulse-phase jitter caused by variable emission within pulsar magnetospheres. A cap on timing errors implies that pulsars must be confined to low dispersion measures (DMs) and observed at high frequencies. Use of wider bandwidths that increase signal-to-noise ratios will degrade timing precision if nondispersive chromatic effects are not mitigated. The allowable region in the DM-...

  20. Gamma radiation from pulsar magnetospheric gaps

    Science.gov (United States)

    Chiang, James; Romani, Roger W.

    1992-01-01

    We investigate the production of gamma rays in two pulsar emission models: the 'polar cap' model and the 'outer cap' model. For the former, we have performed detailed simulations of energetic electrons flowing in the vacuum dipole open field line region. In the outer gap case, we generate light curves for various magnetosphere geometries. Using data from radio and optical observations, we construct models for specific viewing angles appropriate to the Crab and Vela pulsars. Phase-resolved spectra are also computed in the polar cap case and provide signatures for testing the models. The calculations have been extended to include millisecond pulsars, and we have been able to predict fluxes and spectra for populations of recycled pulsars, which are compared to COS B data for globular cluster populations.

  1. Be/X-Ray Pulsar Binary Science with LOFT

    Science.gov (United States)

    Wilson-Hodge, Colleen A.

    2011-01-01

    Accretion disks are ubiquitous in astronomical sources. Accretion powered pulsars are a good test bed for accretion disk physics, because unlike for other objects, the spin of the neutron star is directly observable allowing us to see the effects of angular momentum transfer onto the pulsar. The combination of a sensitive wide-field monitor and the large area detector on LOFT will enable new detailed studies of accretion powered pulsars which I will review. RXTE observations have shown an unusually high number of Be/X-ray pulsar binaries in the SMC. Unlike binaries in the Milky Way, these systems are all at the same distance, allowing detailed population studies using the sensitive LOFT WFM, potentially providing connections to star formation episodes. For Galactic accreting pulsar systems, LOFT will allow measurement of spectral variations within individual pulses, mapping the accretion column in detail for the first time. LOFT will also provide better constraints on magnetic fields in accreting pulsars, allowing measurements of cyclotron features, observations of transitions into the centrifugal inhibition regime, and monitoring of spin-up rate vs flux correlations. Coordinated multi-wavelength observations are crucial to extracting the best science from LOFT from these and numerous other objects.

  2. A Large-Area Survey for Radio Pulsars at High Galactic Latitudes

    Science.gov (United States)

    Jacoby, B. A.; Bailes, M.; Ord, S. M.; Edwards, R. T.; Kulkarni, S. R.

    2009-07-01

    We have completed a survey for pulsars at high Galactic latitudes with the 64 m Parkes radio telescope. Observing with the 13 beam multibeam receiver at a frequency of 1374 MHz, we covered ~4150 square degrees in the region -100° Swinburne Intermediate Latitude Pulsar Survey a further 15° on either side of the Galactic plane. The signal from each beam was processed by a 96 channel × 3 MHz × 2 polarization filterbank, with the detected power in the two polarizations of each frequency channel summed and digitized with 1 bit sampling every 125 μs, giving good sensitivity to millisecond pulsars with low or moderate dispersion measure. The resulting 2.4 TB data set was processed using standard pulsar search techniques with the workstation cluster at the Swinburne Centre for Astrophysics and Supercomputing. This survey resulted in the discovery of 26 new pulsars including seven binary and/or millisecond pulsars, and redetected 36 previously known pulsars. We describe the survey methodology and results, and present timing solutions for the 19 newly discovered slow pulsars, as well as for nine slow pulsars discovered the Swinburne Intermediate Latitude Pulsar Survey that had no previous timing solutions. Even with a small sampling interval, 1374 MHz center frequency, and a large mid-latitude survey volume we failed to detect any very rapidly spinning pulsars. Evidently, such "submillisecond" pulsars are rare.

  3. Ion-proton pulsars

    Science.gov (United States)

    Jones, P. B.

    2016-07-01

    Evidence derived with minimal assumptions from existing published observations is presented to show that an ion-proton plasma is the source of radio-frequency emission in millisecond and in normal isolated pulsars. There is no primary involvement of electron-positron pairs. This conclusion has also been reached by studies of the plasma composition based on well-established particle-physics processes in neutron stars with positive polar-cap corotational charge density. This work has been published in a series of papers which are also summarized here. It is now confirmed by simple analyses of the observed radio-frequency characteristics, and its implications for the further study of neutron stars are outlined.

  4. Ion-proton pulsars

    CERN Document Server

    Jones, P B

    2016-01-01

    Evidence derived with minimal assumptions from existing published observations is presented to show that an ion-proton plasma is the source of radio-frequency emission in millisecond and in normal isolated pulsars. There is no primary involvement of electron-positron pairs. This conclusion has also been reached by studies of the plasma composition based on well-established particle-physics processes in neutron stars with positive polar-cap corotational charge density. This work has been published in a series of papers which are also summarized here. It is now confirmed by simple analyses of the observed radio-frequency characteristics, and its implications for the further study of neutron stars are outlined.

  5. Central compact objects, superslow X-ray pulsars, gamma-ray bursts: do they have anything to do with magnetars?

    CERN Document Server

    Tong, H

    2014-01-01

    Magnetars and many of the magnetar-related objects are summarized together and discussed. It is shown that there is an abuse of language in the use of "magnetar". Anomalous X-ray pulsars and soft gamma-ray repeaters are well-known magnetar candidates. The current so called anti-magnetar (for central compact objects), accreting magnetar (for superslow X-ray pulsars in high mass X-ray binaries), and millisecond magnetar (for the central engine of some gamma-ray bursts), they may not be real magnetars in present understandings. Their observational behaviors are not caused by the magnetic energy. Many of them are just neutron stars with strong surface dipole field. A neutron star plus strong dipole field is not a magnetar. The characteristic parameters of the neutron stars for the central engine of some gamma-ray bursts are atypical from the neutron stars in the Galaxy. Possible signature of magnetic activities in accreting systems are discussed, including repeated bursts and a hard X-ray tail. China's future har...

  6. The Second Fermi Large Area Telescope Catalog of Gamma-Ray Pulsars

    OpenAIRE

    Abdo, A A; et al, .; Hessels, J.

    2013-01-01

    This catalog summarizes 117 high-confidence ≥0.1 GeV gamma-ray pulsar detections using three years of data acquired by the Large Area Telescope (LAT) on the Fermi satellite. Half are neutron stars discovered using LAT data through periodicity searches in gamma-ray and radio data around LAT unassociated source positions. The 117 pulsars are evenly divided into three groups: millisecond pulsars, young radio-loud pulsars, and young radio-quiet pulsars. We characterize the pulse profiles and ener...

  7. Detecting dark matter with imploding pulsars in the galactic center.

    Science.gov (United States)

    Bramante, Joseph; Linden, Tim

    2014-11-01

    The paucity of old millisecond pulsars observed at the galactic center of the Milky Way could be the result of dark matter accumulating in and destroying neutron stars. In regions of high dark matter density, dark matter clumped in a pulsar can exceed the Schwarzschild limit and collapse into a natal black hole which destroys the pulsar. We examine what dark matter models are consistent with this hypothesis and find regions of parameter space where dark matter accumulation can significantly degrade the neutron star population within the galactic center while remaining consistent with observations of old millisecond pulsars in globular clusters and near the solar position. We identify what dark matter couplings and masses might cause a young pulsar at the galactic center to unexpectedly extinguish. Finally, we find that pulsar collapse age scales inversely with the dark matter density and linearly with the dark matter velocity dispersion. This implies that maximum pulsar age is spatially dependent on position within the dark matter halo of the Milky Way. In turn, this pulsar age spatial dependence will be dark matter model dependent.

  8. THE PECULIAR PULSAR POPULATION OF THE CENTRAL PARSEC

    Energy Technology Data Exchange (ETDEWEB)

    Dexter, Jason; O' Leary, Ryan M., E-mail: jdexter@berkeley.edu, E-mail: oleary@berkeley.edu [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States)

    2014-03-01

    Pulsars orbiting the Galactic center black hole, Sgr A*, would be potential probes of its mass, distance, and spin, and may even be used to test general relativity. Despite predictions of large populations of both ordinary and millisecond pulsars in the Galactic center, none have been detected within 25 pc by deep radio surveys. One explanation has been that hyperstrong temporal scattering prevents pulsar detections, but the recent discovery of radio pulsations from a highly magnetized neutron star (magnetar) within 0.1 pc shows that the temporal scattering is much weaker than predicted. We argue that an intrinsic deficit in the ordinary pulsar population is the most likely reason for the lack of detections to date: a ''missing pulsar problem'' in the Galactic center. In contrast, we show that the discovery of a single magnetar implies efficient magnetar formation in the region. If the massive stars in the central parsec form magnetars rather than ordinary pulsars, their short lifetimes could explain the missing pulsars. Efficient magnetar formation could be caused by strongly magnetized progenitors, or could be further evidence of a top-heavy initial mass function. Furthermore, current high-frequency surveys should already be able to detect bright millisecond pulsars, given the measured degree of temporal scattering.

  9. Detecting Dark Matter with Imploding Pulsars in the Galactic Center

    Science.gov (United States)

    Bramante, Joseph; Linden, Tim

    2014-11-01

    The paucity of old millisecond pulsars observed at the galactic center of the Milky Way could be the result of dark matter accumulating in and destroying neutron stars. In regions of high dark matter density, dark matter clumped in a pulsar can exceed the Schwarzschild limit and collapse into a natal black hole which destroys the pulsar. We examine what dark matter models are consistent with this hypothesis and find regions of parameter space where dark matter accumulation can significantly degrade the neutron star population within the galactic center while remaining consistent with observations of old millisecond pulsars in globular clusters and near the solar position. We identify what dark matter couplings and masses might cause a young pulsar at the galactic center to unexpectedly extinguish. Finally, we find that pulsar collapse age scales inversely with the dark matter density and linearly with the dark matter velocity dispersion. This implies that maximum pulsar age is spatially dependent on position within the dark matter halo of the Milky Way. In turn, this pulsar age spatial dependence will be dark matter model dependent.

  10. The Peculiar Pulsar Population of the Central Parsec

    Science.gov (United States)

    Dexter, Jason; O'Leary, Ryan M.

    2014-03-01

    Pulsars orbiting the Galactic center black hole, Sgr A*, would be potential probes of its mass, distance, and spin, and may even be used to test general relativity. Despite predictions of large populations of both ordinary and millisecond pulsars in the Galactic center, none have been detected within 25 pc by deep radio surveys. One explanation has been that hyperstrong temporal scattering prevents pulsar detections, but the recent discovery of radio pulsations from a highly magnetized neutron star (magnetar) within 0.1 pc shows that the temporal scattering is much weaker than predicted. We argue that an intrinsic deficit in the ordinary pulsar population is the most likely reason for the lack of detections to date: a "missing pulsar problem" in the Galactic center. In contrast, we show that the discovery of a single magnetar implies efficient magnetar formation in the region. If the massive stars in the central parsec form magnetars rather than ordinary pulsars, their short lifetimes could explain the missing pulsars. Efficient magnetar formation could be caused by strongly magnetized progenitors, or could be further evidence of a top-heavy initial mass function. Furthermore, current high-frequency surveys should already be able to detect bright millisecond pulsars, given the measured degree of temporal scattering.

  11. The population of black widow pulsars

    CERN Document Server

    King, A R; Rolfe, D J; Schenker, K; Skipp, J M

    2005-01-01

    We consider the population of black widow pulsars (BWPs). The large majority of these are members of globular clusters. For minimum companion masses 0.1 Msun are systems relaxing to equilibrium after a relatively recent capture event. We point out that all binary millisecond pulsars (MSPs) with orbital periods P < 10 h are BWPs (our line of sight allows us to see the eclipses in 10 out of 16 cases). This implies that recycled MSPs emit either in a wide fan beam or a pencil beam close to the spin plane. Simple evolutionary ideas favour a fan beam.

  12. Searches for Gravitational Waves from Known Pulsars With Science Run 5 Ligo Data

    OpenAIRE

    Abbott, B.; Abbott, R.; Acernese, F.; Adhikari, R.; Ajith, P.; Allen, B.; Allen, G; Alshourbagy, M.; Amin, R.; Anderson, S.; Anderson, W.; Antonucci, F.; Aoudia, S.; Arain, M; Araya, M.

    2010-01-01

    We present a search for gravitational waves from 116 known millisecond and young pulsars using data from the fifth science run of the LIGO detectors. For this search, ephemerides overlapping the run period were obtained for all pulsars using radio and X-ray observations. We demonstrate an updated search method that allows for small uncertainties in the pulsar phase parameters to be included in the search. We report no signal detection from any of the targets and therefore interpret our result...

  13. X-ray pulsars: a review

    CERN Document Server

    Caballero, I

    2012-01-01

    Accreting X-ray pulsars are among the most luminous objects in the X-ray sky. In highly magnetized neutron stars (B~10^12 G), the flow of matter is dominated by the strong magnetic field. The general properties of accreting X-ray binaries are presented, focusing on the spectral characteristics of the systems. The use of cyclotron lines as a tool to directly measure a neutron star's magnetic field and to test the theory of accretion are discussed. We conclude with the current and future prospects for accreting X-ray binary studies.

  14. Einstein@Home Discovery of 24 Pulsars in the Parkes Multi-beam Pulsar Survey

    CERN Document Server

    Knispel, B; Kim, H; Keane, E F; Allen, B; Anderson, D; Aulbert, C; Bock, O; Crawford, F; Eggenstein, H -B; Fehrmann, H; Hammer, D; Kramer, M; Lyne, A G; Machenschalk, B; Miller, R B; Papa, M A; Rastawicki, D; Sarkissian, J; Siemens, X; Stappers, B W

    2013-01-01

    We have conducted a new search for radio pulsars in compact binary systems in the Parkes multi-beam pulsar survey (PMPS) data, employing novel methods to remove the Doppler modulation from binary motion. This has yielded unparalleled sensitivity to pulsars in compact binaries. The required computation time of approximately 17 000 CPU core years was provided by the distributed volunteer computing project Einstein@Home, which has a sustained computing power of about one PFlop/s. We discovered 24 new pulsars in our search, of which 18 were isolated pulsars, and six were members of binary systems. Despite the wide filterbank channels and relatively slow sampling time of the PMPS data, we found pulsars with very large ratios of dispersion measure (DM) to spin period. Among those is PSR J1748-3009, the millisecond pulsar with the highest known DM (420 pc cm^{-3}). We also discovered PSR J1840-0643, which is in a binary system with an orbital period of 937 days, the fourth largest known. The new pulsar J1750-2531 li...

  15. Radio Searches of Fermi LAT Sources and Blind Search Pulsars: The Fermi Pulsar Search Consortium

    CERN Document Server

    Ray, P S; Parent, D; Bhattacharya, D; Bhattacharyya, B; Camilo, F; Cognard, I; Theureau, G; Ferrara, E C; Harding, A K; Thompson, D J; Freire, P C C; Guillemot, L; Gupta, Y; Roy, J; Hessels, J W T; Johnston, S; Keith, M; Shannon, R; Kerr, M; Michelson, P F; Romani, R W; Kramer, M; McLaughlin, M A; Ransom, S M; Roberts, M S E; Parkinson, P M Saz; Ziegler, M; Smith, D A; Stappers, B W; Weltevrede, P; Wood, K S

    2012-01-01

    We present a summary of the Fermi Pulsar Search Consortium (PSC), an international collaboration of radio astronomers and members of the Large Area Telescope (LAT) collaboration, whose goal is to organize radio follow-up observations of Fermi pulsars and pulsar candidates among the LAT gamma-ray source population. The PSC includes pulsar observers with expertise using the world's largest radio telescopes that together cover the full sky. We have performed very deep observations of all 35 pulsars discovered in blind frequency searches of the LAT data, resulting in the discovery of radio pulsations from four of them. We have also searched over 300 LAT gamma-ray sources that do not have strong associations with known gamma-ray emitting source classes and have pulsar-like spectra and variability characteristics. These searches have led to the discovery of a total of 43 new radio millisecond pulsars (MSPs) and four normal pulsars. These discoveries greatly increase the known population of MSPs in the Galactic disk...

  16. Physics of radio emission in gamma-ray pulsars

    Science.gov (United States)

    Petrova, S. A.

    2016-04-01

    > Propagation of radio emission in a pulsar magnetosphere is reviewed. The effects of polarization transfer, induced scattering and reprocessing to high energies are analysed with a special emphasis on the implications for the gamma-ray pulsars. The possibilities of the pulsar plasma diagnostics based on the observed radio pulse characteristics are also outlined. As an example, the plasma number density profiles obtained from the polarization data for the Vela and the gamma-ray millisecond pulsars J1446-4701, J1939+2134 and J1744-1134 are presented. The number densities derived tend to be the highest/lowest when the radio pulse leads/lags the gamma-ray peak. In the PSR J1939+2134, the plasma density profiles for the main pulse and interpulse appear to fit exactly the same curve, testifying to the origin of both radio components above the same magnetic pole and their propagation through the same plasma flow in opposite directions. The millisecond radio pulse components exhibiting flat position angle curves are suggested to result from the induced scattering of the main pulse by the same particles that generate gamma rays. This is believed to underlie the wide-sense radio/gamma-ray correlation in the millisecond pulsars. The radio quietness of young gamma-ray pulsars is attributed to resonant absorption, whereas the radio loudness to the radio beam escape through the periphery of the open field line tube.

  17. Developing Precision Pulsar Timing Capability for the DSN

    Science.gov (United States)

    Majid, Walid A.; Kuiper, T. B.; Lazio, J.; Monroe, R.; Preston, R. A.; Spolaor, S.; Teitelbaum, L.; Trinh, J.

    2014-01-01

    Millisecond pulsars are a class of radio pulsars with extremely stable rotations. The excellent timing stability of millisecond pulsars can be used to study a wide variety of astrophysical phenomena. In particular, observations of a large sample of these pulsars can be used to detect the presence of low-frequency gravitational waves. We are currently developing a precision pulsar timing backend for the Deep Space Network (DSN), which will allow the use of short gaps in tracking schedules to observe and time pulses from an ensemble of millisecond pulsars. The NASA Deep Space Network (DSN) operates clusters of large dish antennas (up to 70-m in diameter), located roughly equi-distant around the Earth, for communication and tracking of deep-space spacecraft. The backend system will be capable of removing entirely the dispersive effects of propagation of radio waves through the interstellar medium in real-time. We will describe our development work, initial results, and prospects for pilot observations scheduled later this year. This research was performed at the Jet Propulsion Laboratory, California Institute of Technology, under the Research and Technology Development Program, under a contract with the National Aeronautics and Space Administration.

  18. THE SECOND FERMI LARGE AREA TELESCOPE CATALOG OF GAMMA-RAY PULSARS

    International Nuclear Information System (INIS)

    This catalog summarizes 117 high-confidence ≥0.1 GeV gamma-ray pulsar detections using three years of data acquired by the Large Area Telescope (LAT) on the Fermi satellite. Half are neutron stars discovered using LAT data through periodicity searches in gamma-ray and radio data around LAT unassociated source positions. The 117 pulsars are evenly divided into three groups: millisecond pulsars, young radio-loud pulsars, and young radio-quiet pulsars. We characterize the pulse profiles and energy spectra and derive luminosities when distance information exists. Spectral analysis of the off-peak phase intervals indicates probable pulsar wind nebula emission for four pulsars, and off-peak magnetospheric emission for several young and millisecond pulsars. We compare the gamma-ray properties with those in the radio, optical, and X-ray bands. We provide flux limits for pulsars with no observed gamma-ray emission, highlighting a small number of gamma-faint, radio-loud pulsars. The large, varied gamma-ray pulsar sample constrains emission models. Fermi's selection biases complement those of radio surveys, enhancing comparisons with predicted population distributions

  19. THE SECOND FERMI LARGE AREA TELESCOPE CATALOG OF GAMMA-RAY PULSARS

    Energy Technology Data Exchange (ETDEWEB)

    Abdo, A. A. [Center for Earth Observing and Space Research, College of Science, George Mason University, Fairfax, VA 22030 (United States); Ajello, M. [Space Sciences Laboratory, 7 Gauss Way, University of California, Berkeley, CA 94720-7450 (United States); Allafort, A.; Bloom, E. D.; Bottacini, E. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Baldini, L. [Università di Pisa and Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Ballet, J. [Laboratoire AIM, CEA-IRFU/CNRS/Université Paris Diderot, Service d' Astrophysique, CEA Saclay, F-91191 Gif sur Yvette (France); Barbiellini, G. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, I-34127 Trieste (Italy); Baring, M. G. [Rice University, Department of Physics and Astronomy, MS-108, P.O. Box 1892, Houston, TX 77251 (United States); Bastieri, D. [Istituto Nazionale di Fisica Nucleare, Sezione di Padova, I-35131 Padova (Italy); Belfiore, A. [Santa Cruz Institute for Particle Physics, Department of Physics and Department of Astronomy and Astrophysics, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Bellazzini, R.; Bregeon, J. [Istituto Nazionale di Fisica Nucleare, Sezione di Pisa, I-56127 Pisa (Italy); Bhattacharyya, B. [National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune 411 007 (India); Bissaldi, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, and Università di Trieste, I-34127 Trieste (Italy); Bonamente, E. [Istituto Nazionale di Fisica Nucleare, Sezione di Perugia, I-06123 Perugia (Italy); Brandt, T. J. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Brigida, M., E-mail: hartog@stanford.edu [Dipartimento di Fisica ' ' M. Merlin' ' dell' Università e del Politecnico di Bari, I-70126 Bari (Italy); and others

    2013-10-01

    This catalog summarizes 117 high-confidence ≥0.1 GeV gamma-ray pulsar detections using three years of data acquired by the Large Area Telescope (LAT) on the Fermi satellite. Half are neutron stars discovered using LAT data through periodicity searches in gamma-ray and radio data around LAT unassociated source positions. The 117 pulsars are evenly divided into three groups: millisecond pulsars, young radio-loud pulsars, and young radio-quiet pulsars. We characterize the pulse profiles and energy spectra and derive luminosities when distance information exists. Spectral analysis of the off-peak phase intervals indicates probable pulsar wind nebula emission for four pulsars, and off-peak magnetospheric emission for several young and millisecond pulsars. We compare the gamma-ray properties with those in the radio, optical, and X-ray bands. We provide flux limits for pulsars with no observed gamma-ray emission, highlighting a small number of gamma-faint, radio-loud pulsars. The large, varied gamma-ray pulsar sample constrains emission models. Fermi's selection biases complement those of radio surveys, enhancing comparisons with predicted population distributions.

  20. The second FERMI large area telescope catalog of gamma-ray pulsars

    Energy Technology Data Exchange (ETDEWEB)

    Abdo, A. A.; Ajello, M.; Allafort, A.; Baldini, L.; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; Belfiore, A.; Bellazzini, R.; Bhattacharyya, B.; Bissaldi, E.; Bloom, E. D.; Bonamente, E.; Bottacini, E.; Brandt, T. J.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Burgay, M.; Burnett, T. H.; Busetto, G.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Camilo, F.; Caraveo, P. A.; Casandjian, J. M.; Cecchi, C.; Çelik, Ö.; Charles, E.; Chaty, S.; Chaves, R. C. G.; Chekhtman, A.; Chen, A. W.; Chiang, J.; Chiaro, G.; Ciprini, S.; Claus, R.; Cognard, I.; Cohen-Tanugi, J.; Cominsky, L. R.; Conrad, J.; Cutini, S.; D' Ammando, F.; de Angelis, A.; DeCesar, M. E.; De Luca, A.; den Hartog, P. R.; de Palma, F.; Dermer, C. D.; Desvignes, G.; Digel, S. W.; Di Venere, L.; Drell, P. S.; Drlica-Wagner, A.; Dubois, R.; Dumora, D.; Espinoza, C. M.; Falletti, L.; Favuzzi, C.; Ferrara, E. C.; Focke, W. B.; Franckowiak, A.; Freire, P. C. C.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Germani, S.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Gotthelf, E. V.; Grenier, I. A.; Grondin, M. -H.; Grove, J. E.; Guillemot, L.; Guiriec, S.; Hadasch, D.; Hanabata, Y.; Harding, A. K.; Hayashida, M.; Hays, E.; Hessels, J.; Hewitt, J.; Hill, A. B.; Horan, D.; Hou, X.; Hughes, R. E.; Jackson, M. S.; Janssen, G. H.; Jogler, T.; Jóhannesson, G.; Johnson, R. P.; Johnson, A. S.; Johnson, T. J.; Johnson, W. N.; Johnston, S.; Kamae, T.; Kataoka, J.; Keith, M.; Kerr, M.; Knödlseder, J.; Kramer, M.; Kuss, M.; Lande, J.; Larsson, S.; Latronico, L.; Lemoine-Goumard, M.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Lyne, A. G.; Manchester, R. N.; Marelli, M.; Massaro, F.; Mayer, M.; Mazziotta, M. N.; McEnery, J. E.; McLaughlin, M. A.; Mehault, J.; Michelson, P. F.; Mignani, R. P.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakamori, T.; Nemmen, R.; Nuss, E.; Ohno, M.; Ohsugi, T.; Orienti, M.; Orlando, E.; Ormes, J. F.; Paneque, D.; Panetta, J. H.; Parent, D.; Perkins, J. S.; Pesce-Rollins, M.; Pierbattista, M.; Piron, F.; Pivato, G.; Pletsch, H. J.; Porter, T. A.; Possenti, A.; Rainò, S.; Rando, R.; Ransom, S. M.; Ray, P. S.; Razzano, M.; Rea, N.; Reimer, A.; Reimer, O.; Renault, N.; Reposeur, T.; Ritz, S.; Romani, R. W.; Roth, M.; Rousseau, R.; Roy, J.; Ruan, J.; Sartori, A.; Saz Parkinson, P. M.; Scargle, J. D.; Schulz, A.; Sgrò, C.; Shannon, R.; Siskind, E. J.; Smith, D. A.; Spandre, G.; Spinelli, P.; Stappers, B. W.; Strong, A. W.; Suson, D. J.; Takahashi, H.; Thayer, J. G.; Thayer, J. B.; Theureau, G.; Thompson, D. J.; Thorsett, S. E.; Tibaldo, L.; Tibolla, O.; Tinivella, M.; Torres, D. F.; Tosti, G.; Troja, E.; Uchiyama, Y.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Venter, C.; Vianello, G.; Vitale, V.; Wang, N.; Weltevrede, P.; Winer, B. L.; Wolff, M. T.; Wood, D. L.; Wood, K. S.; Wood, M.; Yang, Z.

    2013-09-19

    This catalog summarizes 117 high-confidence ≥0.1 GeV gamma-ray pulsar detections using three years of data acquired by the Large Area Telescope (LAT) on the Fermi satellite. Half are neutron stars discovered using LAT data through periodicity searches in gamma-ray and radio data around LAT unassociated source positions. The 117 pulsars are evenly divided into three groups: millisecond pulsars, young radio-loud pulsars, and young radio-quiet pulsars. We characterize the pulse profiles and energy spectra and derive luminosities when distance information exists. Spectral analysis of the off-peak phase intervals indicates probable pulsar wind nebula emission for four pulsars, and off-peak magnetospheric emission for several young and millisecond pulsars. We compare the gamma-ray properties with those in the radio, optical, and X-ray bands. We provide flux limits for pulsars with no observed gamma-ray emission, highlighting a small number of gamma-faint, radio-loud pulsars. The large, varied gamma-ray pulsar sample constrains emission models. Fermi's selection biases complement those of radio surveys, enhancing comparisons with predicted population distributions.

  1. Fermi Observation of the transitional pulsar binary XSS J12270-4859

    CERN Document Server

    Xing, Yi

    2014-01-01

    Because of the disappearance of its accretion disk since the time period around 2012 November--December, XSS J12270-4859 has recently been identified as, in addition to PSR J1023+0038, another transitional millisecond pulsar binary. We have carried out detailed analysis of the Fermi Large Area Telescope data for the binary. While both spectra before and after the disk-disappearance transition are well described by an exponentially cut-off power law, typical for pulsars' emission in the Fermi's 0.2-300 GeV, a factor of 2 flux decrease related to the transition is detected. A weak orbital modulation is seen, but only detectable in the after-transition data, same to that found at X-rays. In the long-term light curve of the source before the transition, a factor of 3 flux variations are seen. Comparing to the properties of J1023+0038, we disucss the implications from these results. We suggest that since the modulation is aligned with that at X-rays in orbital phase, it possibly arises due to the occultation of th...

  2. Star Cluster Buzzing With Pulsars

    Science.gov (United States)

    2005-01-01

    A dense globular star cluster near the center of our Milky Way Galaxy holds a buzzing beehive of rapidly-spinning millisecond pulsars, according to astronomers who discovered 21 new pulsars in the cluster using the National Science Foundation's 100-meter Robert C. Byrd Green Bank Telescope (GBT) in West Virginia. The cluster, called Terzan 5, now holds the record for pulsars, with 24, including three known before the GBT observations. Pulsar Diagram Pulsar Diagram: Click on image for more detail. "We hit the jackpot when we looked at this cluster," said Scott Ransom, an astronomer at the National Radio Astronomy Observatory in Charlottesville, VA. "Not only does this cluster have a lot of pulsars -- and we still expect to find more in it -- but the pulsars in it are very interesting. They include at least 13 in binary systems, two of which are eclipsing, and the four fastest-rotating pulsars known in any globular cluster, with the fastest two rotating nearly 600 times per second, roughly as fast as a household blender," Ransom added. Ransom and his colleagues reported their findings to the American Astronomical Society's meeting in San Diego, CA, and in the online journal Science Express. The star cluster's numerous pulsars are expected to yield a bonanza of new information about not only the pulsars themselves, but also about the dense stellar environment in which they reside and probably even about nuclear physics, according to the scientists. For example, preliminary measurements indicate that two of the pulsars are more massive than some theoretical models would allow. "All these exotic pulsars will keep us busy for years to come," said Jason Hessels, a Ph.D student at McGill University in Montreal. Globular clusters are dense agglomerations of up to millions of stars, all of which formed at about the same time. Pulsars are spinning, superdense neutron stars that whirl "lighthouse beams" of radio waves or light around as they spin. A neutron star is what is

  3. Imprints of relic gravitational waves on pulsar timing

    International Nuclear Information System (INIS)

    Relic gravitational waves (RGWs), a background originating during inflation, would leave imprints on pulsar timing residuals. This makes RGWs an important source for detection of RGWs using the method of pulsar timing. In this paper, we discuss the effects of RGWs on single pulsar timing, and quantitatively analyze the timing residuals caused by RGWs with different model parameters. In principle, if the RGWs are strong enough today, they can be detected by timing a single millisecond pulsar with high precision after the intrinsic red noises in pulsar timing residuals are understood, even though simultaneously observing multiple millisecond pulsars is a more powerful technique for extracting gravitational wave signals. We correct the normalization of RGWs using observations of the cosmic microwave background (CMB), which leads to the amplitudes of RGWs being reduced by two orders of magnitude or so compared to our previous works. We obtained new constraints on RGWs using recent observations from the Parkes Pulsar Timing Array, employing the tensor-to-scalar ratio r = 0.2 due to the tensor-type polarization observations of CMB by BICEP2 as a reference value, even though its reliability has been brought into question. Moreover, the constraints on RGWs from CMB and Big Bang nucleosynthesis will also be discussed for comparison. (paper)

  4. Advection of magnetic flux by accretion disks around neutron stars

    Science.gov (United States)

    Flores-Tulian, S.; Reisenegger, A.

    The aim of our research is to address why millisecond pulsars have relatively weak surface magnetic fields, of about 10^8 G, with a narrow spread. We propose that the accretion of plasma from the companion star fully screens the original neutron star field, but the accretion disk carries additional magnetic flux from the companion star, or itself can generate field by means of dynamo processes. For a strongly magnetized star, the field prevents the disk from approaching the star. The accretion is along the field lines and deposits the matter on the polar cap. Then, the accreted plasma flows, dragging with itself the magnetic field lines, from the pole to the equator (Payne & Melatos 2004). In a following stage, when the star becomes non-magnetic, because the field has been buried, the disk touches the star. We suggest that some effective mechanism of magnetic flux transport such as that proposed by Spruit & Uzdensky 2005 (or Bisnovatyi-Kogan & Lovelace 2007), operates and necessarily leads to a "strongly magnetized disk''. It becomes laminar because the magneto-rotational instability saturates (it is considered to be responsible for turbulence in the disk), and the magnetic difussivity is negligible. Then, the loss of angular momentum allowing the accretion is only caused by the magneto-centrifugal disk-wind (Blandford & Payne 1982). Meanwhile, the wind-driven transport of the magnetic flux by the disk re-magnetizes the star. This process continues until the Lorentz force due to the star's magnetic field forbids any further accretion of matter and magnetic flux, in the Ideal Magneto-Hydro-Dynamics approach. Additional of material can fall onto the star (but at lower rate) if some instability process sets in, allowing the diffusion of mass through the magnetic field lines (e.g the Interchange Instability, Spruit & Taam 1990). All these processes might lead to an asymptotic magnetic field of 10^8 G,as is inferred from observations. We are developing a self

  5. The Parkes Pulsar Timing Array Project

    CERN Document Server

    Manchester, R N; Bailes, M; Coles, W A; van Straten, W; Keith, M J; Shannon, R M; Bhat, N D R; Brown, A; Burke-Spolaor, S G; Champion, D J; Chaudhary, A; Edwards, R T; Hampson, G; Hotan, A W; Jameson, A; Jenet, F A; Kesteven, M J; Khoo, J; Kocz, J; Maciesiak, K; Oslowski, S; Ravi, V; Reynolds, J R; Sarkissian, J M; Verbiest, J P W; Wen, Z L; Wilson, W E; Yardley, D; Yan, W M; You, X P

    2012-01-01

    A "pulsar timing array" (PTA), in which observations of a large sample of pulsars spread across the celestial sphere are combined, allows investigation of "global" phenomena such as a background of gravitational waves or instabilities in atomic timescales that produce correlated timing residuals in the pulsars of the array. The Parkes Pulsar Timing Array (PPTA) is an implementation of the PTA concept based on observations with the Parkes 64-m radio telescope. A sample of 20 millisecond pulsars is being observed at three radio-frequency bands, 50cm (~700 MHz), 20cm (~1400 MHz) and 10cm (~3100 MHz), with observations at intervals of 2 - 3 weeks. Regular observations commenced in early 2005. This paper describes the systems used for the PPTA observations and data processing, including calibration and timing analysis. The strategy behind the choice of pulsars, observing parameters and analysis methods is discussed. Results are presented for PPTA data in the three bands taken between 2005 March and 2011 March. For...

  6. Gravitational Radiation from Compact Binary Pulsars

    CERN Document Server

    Antoniadis, John

    2014-01-01

    An outstanding question in modern Physics is whether general relativity (GR) is a complete description of gravity among bodies at macroscopic scales. Currently, the best experiments supporting this hypothesis are based on high-precision timing of radio pulsars. This chapter reviews recent advances in the field with a focus on compact binary millisecond pulsars with white-dwarf (WD) companions. These systems - if modeled properly - provide an unparalleled test ground for physically motivated alternatives to GR that deviate significantly in the strong-field regime. Recent improvements in observational techniques and advances in our understanding of WD interiors have enabled a series of precise mass measurements in such systems. These masses, combined with high-precision radio timing of the pulsars, result to stringent constraints on the radiative properties of gravity, qualitatively very different from what was available in the past.

  7. Constraint on the internal structure of a neutron star from Vela pulsar glitches

    CERN Document Server

    Chamel, N

    2016-01-01

    Pulsars are spinning extremely rapidly with periods as short as about $1.4$ milliseconds and delays of a few milliseconds per year at most, thus providing the most accurate clocks in the Universe. Nevertheless, sudden spin ups have been detected in some pulsars like the emblematic Vela pulsar. These abrupt changes in the pulsar's rotation period have long been thought to be the manifestation of a neutron superfluid permeating the inner crust of neutron stars. However, the neutron superfluid has been recently found to be so strongly coupled to the crust that it does not carry enough angular momentum to explain the Vela data. We explore the extent to which pulsar-timing observations can be reconciled with the standard glitch theory considering the lack of knowledge of the dense-matter equation of state.

  8. Radio Pulsars

    CERN Document Server

    Beskin, V S; Gwinn, C R; Tchekhovskoy, A

    2015-01-01

    Almost 50 years after radio pulsars were discovered in 1967, our understanding of these objects remains incomplete. On the one hand, within a few years it became clear that neutron star rotation gives rise to the extremely stable sequence of radio pulses, that the kinetic energy of rotation provides the reservoir of energy, and that electromagnetic fields are the braking mechanism. On the other hand, no consensus regarding the mechanism of coherent radio emission or the conversion of electromagnetic energy to particle energy yet exists. In this review, we report on three aspects of pulsar structure that have seen recent progress: the self-consistent theory of the magnetosphere of an oblique magnetic rotator; the location, geometry, and optics of radio emission; and evolution of the angle between spin and magnetic axes. These allow us to take the next step in understanding the physical nature of the pulsar activity.

  9. Astronomers Discover Fastest-Spinning Pulsar

    Science.gov (United States)

    2006-01-01

    discovered in 1982. For reference, the fastest speeds of common kitchen blenders are 250-500 Hz. The scientists say the object's fast rotation speed means that it cannot be any larger than about 20 miles across. According to Hessels, "If it were any larger, material from the surface would be flung into orbit around the star." The scientists' calculation assumed that the neutron star contains less than two times the mass of the Sun, an assumption that is consistent with the masses of all known neutron stars. The spinning pulsar has a companion star that orbits it once every 26 hours. The companion passes in front of the pulsar, eclipsing the pulsar about 40 percent of the time. The long eclipse period, probably due to bloating of the companion, makes it difficult for the astronomers to learn details of the orbital configuration that would allow them to precisely measure the masses of the pulsar and its companion. "If we could pin down these masses more precisely, we could then get a better limit on the size of the pulsar. That, in turn, would then give us a better figure for the true density inside the neutron star," explained Ingrid Stairs, an assistant professor at the University of British Columbia and another collaborator on the work. Competing theoretical models for the types and distributions of elementary particles inside neutron stars make widely different predictions about the pressure and density of such an object. "We want observational data that shows which models fit the reality of nature," Hessels said. If the scientists can't use PSR J1748-2446ad to do that, they are hopeful some of its near neighbors will yield the data they seek. Using the GBT, the astronomers so far have found 30 new fast "millisecond pulsars" in the cluster Terzan 5, making 33 pulsars known in the cluster in total. This is the largest number of such pulsars ever found in a single globular cluster. Dense globular clusters of stars are excellent places to find fast-rotating millisecond

  10. Birth and Evolution of Isolated Radio Pulsars

    Science.gov (United States)

    Faucher-Giguère, Claude-André; Kaspi, Victoria M.

    2008-02-01

    We investigate the birth and evolution of isolated radio pulsars using a population synthesis method, modeling the birth properties of the pulsars, their time evolution, and their detection in the Parkes and Swinburne Multibeam (MB) surveys. Together, the Parkes and Swinburne MB surveys [1, 2] have detected nearly 2/3 of the known pulsars and provide a remarkably homogeneous sample to compare with simulations. New proper motion measurements [3, 4] and an improved model of the distribution of free electrons in the interstellar medium, NE2001 [5], also make revisiting these issues particularly worthwhile. We present a simple population model that reproduces the actual observations well, and consider others that fail. We conclude that: pulsars are born in the spiral arms, with the birthrate of 2.8+/-0.5 pulsars/century peaking at a distance ~3 kpc from the Galactic centre, and with mean initial speed of 380-60+40 km s-1 the birth spin period distribution extends to several hundred milliseconds, with no evidence of multimodality, implying that characteristic ages overestimate the true ages of the pulsars by a median factor >2 for true ages <30,000 yr models in which the radio luminosities of the pulsars are random generically fail to reproduce the observed P-Ṗ diagram, suggesting a relation between intrinsic radio luminosity and (P,Ṗ) radio luminosities L~Ė provides a good match to the observed P-Ṗ diagram; for this favored radio luminosity model, we find no evidence for significant magnetic field decay over the lifetime of the pulsars as radio sources (~100 Myr).

  11. Pulsar Results with the Fermi Large Area Telescope

    CERN Document Server

    Ray, Paul S

    2010-01-01

    The launch of the Fermi Gamma-ray Space Telescope has heralded a new era in the study of gamma-ray pulsars. The population of confirmed gamma-ray pulsars has gone from 6-7 to more than 60, and the superb sensitivity of the Large Area Telescope (LAT) on Fermi has allowed the detailed study of their spectra and light curves. Twenty-four of these pulsars were discovered in blind searches of the gamma-ray data, and twenty-one of these are, at present, radio quiet, despite deep radio follow-up observations. In addition, millisecond pulsars have been confirmed as a class of gamma-ray emitters, both individually and collectively in globular clusters. Recently, radio searches in the direction of LAT sources with no likely counterparts have been highly productive, leading to the discovery of a large number of new millisecond pulsars. Taken together, these discoveries promise a great improvement in the understanding of the gamma-ray emission properties and Galactic population of pulsars. We summarize some of the result...

  12. Millisecond Oxidation of Alkanes

    Energy Technology Data Exchange (ETDEWEB)

    Scott Han

    2011-09-30

    This project was undertaken in response to the Department of Energy's call to research and develop technologies 'that will reduce energy consumption, enhance economic competitiveness, and reduce environmental impacts of the domestic chemical industry.' The current technology at the time for producing 140 billion pounds per year of propylene from naphtha and Liquified Petroleum Gas (LPG) relied on energy- and capital-intensive steam crackers and Fluidized Catalytic Cracking (FCC) units. The propylene is isolated from the product stream in a costly separation step and subsequently converted to acrylic acid and other derivatives in separate production facilities. This project proposed a Short Contact Time Reactor (SCTR)-based catalytic oxydehydrogenation process that could convert propane to propylene and acrylic acid in a cost-effective and energy-efficient fashion. Full implementation of this technology could lead to sizeable energy, economic and environmental benefits for the U. S. chemical industry by providing up to 45 trillion BTUs/year, cost savings of $1.8 billion/year and a combined 35 million pounds/year reduction in environmental pollutants such as COx, NOx, and SOx. Midway through the project term, the program directive changed, which approval from the DOE and its review panel, from direct propane oxidation to acrylic acid at millisecond contact times to a two-step process for making acrylic acid from propane. The first step was the primary focus, namely the conversion of propane to propylene in high yields assisted by the presence of CO2. The product stream from step one was then to be fed directly into a commercially practiced propylene-to-acrylic acid tandem reactor system.

  13. A Pulsar Eases Off the Brakes

    Science.gov (United States)

    Kohler, Susanna

    2015-10-01

    In 2006, pulsar PSR 18460258 unexpectedly launched into a series of energetic X-ray outbursts. Now a study has determined that this event may have permanently changed the behavior of this pulsar, raising questions about our understanding of how pulsars evolve.Between CategoriesA pulsar a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation can be powered by one of three mechanisms:Rotation-powered pulsars transform rotational energy into radiation, gradually slowing down in a predictable way.Accretion-powered pulsars convert the gravitational energy of accreting matter into radiation.Magnetars are powered by the decay of their extremely strong magnetic fields.Astronomical classification often results in one pesky object that doesnt follow the rules. In this case, that object is PSR 18460258, a young pulsar categorized as rotation-powered. But in 2006, PSR 18460258 suddenly emitted a series of short, hard X-ray bursts and underwent a flux increase behavior that is usually only exhibited by magnetars. After this outburst, it returned to normal, rotation-powered-pulsar behavior.Since the discovery of this event, scientists have been attempting to learn more about this strange pulsar that seems to straddle the line between rotation-powered pulsars and magnetars.Unprecedented DropOne way to examine whats going on with PSR 18460258 is to evaluate whats known as its braking index, a measure of how quickly the pulsars rotation slows down. For a rotation-powered pulsar, the braking index should be roughly constant. The pulsar then slows down according to a fixed power law, where the slower it rotates, the slower it slows down.In a recent study, Robert Archibald (McGill University) and collaborators report on 7 years worth of timing observations of PSR 18460258 after its odd magnetar-like outburst. They then compare these observations to 6.5 years of data from before the outburst. The team finds that the braking index for this bizarre

  14. Timing Noise Analysis of NANOGrav Pulsars

    CERN Document Server

    Perrodin, Delphine; Lommen, Andrea; Finn, Lee; Demorest, Paul; Ferdman, Robert; Gonzalez, Marjorie; Nice, David; Ransom, Scott; Stairs, Ingrid

    2013-01-01

    We analyze timing noise from five years of Arecibo and Green Bank observations of the seventeen millisecond pulsars of the North-American Nanohertz Observatory for Gravitational Waves (NANOGrav) pulsar timing array. The weighted autocovariance of the timing residuals was computed for each pulsar and compared against two possible models for the underlying noise process. The first model includes red noise and predicts the autocovariance to be a decaying exponential as a function of time lag. The second model is Gaussian white noise whose autocovariance would be a delta function. We also perform a ``nearest-neighbor" correlation analysis. We find that the exponential process does not accurately describe the data. Two pulsars, J1643-1224 and J1910+1256, exhibit weak red noise, but the rest are well described as white noise. The overall lack of evidence for red noise implies that sensitivity to a (red) gravitational wave background signal is limited by statistical rather than systematic uncertainty. In all pulsars...

  15. Discovery of Two New Pulsars in 47 Tucanae (NGC 104)

    CERN Document Server

    Pan, Zhichen; Li, Di; Ridolfi, Alessandro; Wang, Pei; Freire, Paulo

    2016-01-01

    We report the discovery of two new millisecond pulsars (PSRs J0024$-$7204aa and J0024$-$7204ab) in the globular cluster 47\\,Tucanae (NGC 104). Our results bring the total number of pulsars in 47\\,Tucanae to 25. These pulsars were discovered by reprocessing archival observations from the Parkes radio telescope. We reprocessed the data using a standard search procedure based on the PRESTO software package as well as using a new method in which we incoherently added the power spectra corresponding to $\\sim$1100\\,hr of observations. The newly discovered PSR~J0024$-$7204aa, has a pulse frequency of $\\rm \\sim$541\\,Hz (corresponding to a $\\rm \\sim$1.84 ms period), which is higher than any other pulsars currently known in the cluster and ranks 12$^{\\rm{th}}$ amongst all the currently known pulsars. The dispersion measure of this pulsar, 24.941(7)\\,cm$^{-3}$ pc, is the highest in the cluster. The second discovered pulsar, PSR~J0024$-$7204ab, is an isolated pulsar with a pulse frequency of $\\rm \\sim$270\\,Hz (correspond...

  16. Prospects for Pulsar Studies with the GLAST Large Area Telescope

    Science.gov (United States)

    Harding, Alice K.

    2007-01-01

    The Large Area Telescope (LAT) on the Gamma-ray Large Area Space Telescope (GLAST), due to launch in November 2007, will have unprecedented sensitivity and energy resolution for gamma-rays in the range of 30 MeV to 200 GeV. GLAST is therefore expected to provide major advances in the understanding of high-energy emission from rotation-powered pulsars. As the only presently known galactic GeV source class; pulsars will be one of the most important sources for study with GLAST. The main science goals of the LAT for pulsar studies include an increase in the number of detected radio-loud and radio-quiet gamma-ray pulsars, including millisecond pulsars, giving much better statistics for elucidating population characteristics, measurement of the high-energy spectrum and the shape of spectral cutoffs and determining pulse profiles for a variety of pulsars of different age. Further, measurement of phase-resolved spectra and energy dependent pulse profiles of the brighter pulsars should allow detailed tests of magnetospheric particle acceleration and radiation mechanisms, by comparing data with theoretical models that have been developed. Additionally, the LAT will have the sensitivity to allow blind pulsation searches of nearly all unidentified EGRET sources, to possibly uncover more radio-quiet Geminga-like pulsars.

  17. Reverse Shock Emission Driven By Post-Merger Millisecond Magnetar Winds: Effects of the Magnetization Parameter

    CERN Document Server

    Liu, L D; Dai, Z G

    2016-01-01

    The study of short-duration gamma-ray bursts provides growing evidence that a good fraction of double neutron star mergers lead to the formation of stable millisecond magnetars. The launch of Poynting flux by the millisecond magnetars could leave distinct electromagnetic signatures that reveal the energy dissipation processes in the magnetar wind. In previous studies (Wang & Dai 2013b; Wang et al. 2015), we assume that the magnetar wind becomes completely lepton-dominated so that electrons/positrons in the magnetar wind are accelerated by a diffusive shock. However, theoretical modeling of pulsar wind nebulae shows that in many cases the magnetic field energy in the pulsar wind may be strong enough to suppress diffusive shock acceleration. In this paper, we investigate the reverse shock emission as well as the forward shock emission with an arbitrary magnetization parameter $\\sigma$ of a magnetar wind. We find that the reverse shock emission strongly depends on $\\sigma$, and in particular, $\\sigma \\sim 0....

  18. The pulsar planet production process

    Science.gov (United States)

    Phinney, E. S.; Hansen, B. M. S.

    1993-01-01

    Most plausible scenarios for the formation of planets around pulsars end with a disk of gas around the pulsar. The supplicant author then points to the solar system to bolster faith in the miraculous transfiguration of gas into planets. We here investigate this process of transfiguration. We derive analytic sequences of quasi-static disks which give good approximations to exact solutions of the disk diffusion equation with realistic opacity tables. These allow quick and efficient surveys of parameter space. We discuss the outward transfer of mass in accretion disks and the resulting timescale constraints, the effects of illumination by the central source on the disk and dust within it, and the effects of the widely different elemental compositions of the disks in the various scenarios, and their extensions to globular clusters. We point out where significant uncertainties exist in the appropriate grain opacities, and in the effect of illumination and winds from the neutron star.

  19. Intrinsic Instrumental Polarization and High-Precision Pulsar Timing

    CERN Document Server

    Foster, Griffin; Paulin, Remi; Carozzi, Tobia; Johnston, Simon; van Straten, Willem

    2015-01-01

    Radio telescopes are used to accurately measure the time of arrival (ToA) of radio pulses in pulsar timing experiments that target mostly millisecond pulsars (MSPs) due to their high rotational stability. This allows for detailed study of MSPs and forms the basis of experiments to detect gravitational waves. Apart from intrinsic and propagation effects, such as pulse-to-pulse jitter and dispersion variations in the interstellar medium, timing precision is limited in part by the following: polarization purity of the telescope's orthogonally polarized receptors, the signal-to-noise ratio (S/N) of the pulsar profile, and the polarization fidelity of the system. Using simulations, we present how fundamental limitations in recovering the true polarization reduce the precision of ToA measurements. Any real system will respond differently to each source observed depending on the unique pulsar polarization profile. Using the profiles of known MSPs we quantify the limits of observing system specifications that yield s...

  20. Upper limits for pulsars with MAGIC (2005/2006 observations)

    CERN Document Server

    Reyes, R De los; Camara, M; López, M

    2009-01-01

    During the last 4 years the MAGIC collaboration has searched for high-energy gamma-ray emission of some of the most promising pulsar candidates. The low energy threshold of MAGIC offered the opportunity for a high sensitivity search just above 50-100 GeV (since 2008 a new trigger system has decreased the energy threshold to 25 GeV), an energy region up to now not reachable to ground based instruments and past satellite borne detectors. No pulsed gamma-ray emission has been detected from any pulsar observed during the observation campaigns of 2005-2006. Here we present the upper limits obtained for tow canonical pulsars (PSR J0205+6449 and PSR J2229+6114) and their host nebulae (3C 58 and Boomerang, respectively) and the millisecond pulsar PSR J0218+4232. Physics implications will be discussed.

  1. Constraining Binary Stellar Evolution With Pulsar Timing

    Science.gov (United States)

    Ferdman, Robert D.; Stairs, I. H.; Backer, D. C.; Burgay, M.; Camilo, F.; D'Amico, N.; Demorest, P.; Faulkner, A.; Hobbs, G.; Kramer, M.; Lorimer, D. R.; Lyne, A. G.; Manchester, R.; McLaughlin, M.; Nice, D. J.; Possenti, A.

    2006-06-01

    The Parkes Multibeam Pulsar Survey has yielded a significant number of very interesting binary and millisecond pulsars. Two of these objects are part of an ongoing timing study at the Green Bank Telescope (GBT). PSR J1756-2251 is a double-neutron star (DNS) binary system. It is similar to the original Hulse-Taylor binary pulsar system PSR B1913+16 in its orbital properties, thus providing another important opportunity to test the validity of General Relativity, as well as the evolutionary history of DNS systems through mass measurements. PSR J1802-2124 is part of the relatively new and unstudied "intermediate-mass" class of binary system, which typically have spin periods in the tens of milliseconds, and/or relatively massive (> 0.7 solar masses) white dwarf companions. With our GBT observations, we have detected the Shapiro delay in this system, allowing us to constrain the individual masses of the neutron star and white dwarf companion, and thus the mass-transfer history, in this unusual system.

  2. X-ray observations and the search for Fermi-LAT gamma-ray pulsars

    CERN Document Server

    Parkinson, P M Saz; Caraveo, P; De Luca, A; Marelli, M

    2013-01-01

    The Large Area Telescope (LAT) on Fermi has detected ~150 gamma-ray pulsars, about a third of which were discovered in blind searches of the $\\gamma$-ray data. Because the angular resolution of the LAT is relatively poor and blind searches for pulsars (especially millisecond pulsars, MSPs) are very sensitive to an error in the position, one must typically scan large numbers of locations. Identifying plausible X-ray counterparts of a putative pulsar drastically reduces the number of trials, thus improving the sensitivity of pulsar blind searches with the LAT. I discuss our ongoing program of Swift, XMM-Newton, and Chandra observations of LAT unassociated sources in the context of our blind searches for gamma-ray pulsars.

  3. Radiation dosimetry of binary pulsars

    CERN Document Server

    Eichler, D; Eichler, David; Nath, Biman B

    1995-01-01

    Companion stars exposed to high energy radiation from a primary neutron star or accreting black hole can experience significant spallation of their heavy elements, so that their atmospheres would be extremely rich in lithium, beryllium, and especially boron. In this paper we note that the detection or non-detection of these elements, and their relative abundances if detected, would provide a diagnostic of the high energy output of the primary, and possibly the shock acceleration of particles at the companion's bow shock in a pulsar wind.

  4. Pulsar statistics: a study of pulsar luminosities

    International Nuclear Information System (INIS)

    A statistically significant correlation between pulsar luminosity at 400 MHz and both pulsar period and period derivative is found. Fitting a phenomenological power-law model L/sub model/(P,P) approx. P/sup α/P/sup β/ (where P is pulsar period, P - period derivative and L - radio luminosity) to the pulsar luminosity data, we obtain α = -1.04 +- 0.15 and β = 0.35 +- 0.06. The above values suggest that pulsar radio luminosity varies roughly as the cube root of the total loss of rotational energy. 16 references, 5 figures

  5. Special Purpose Pulsar Telescope for the Detection of Cosmic Gravitational Waves

    OpenAIRE

    Wang, Shou-Guan; Zhu, Zong-Hong; Zou, Zhen-Long; Zhang, Yuan-Zhong

    2002-01-01

    Pulsars can be used to search for stochastic backgrounds of gravitational waves of cosmological origin within the very low frequency band (VLF), $10^{-7}$ to $10^{-9}$ Hz. We propose to construct a special 50 m radio telescope. Regular timing measurements of about 10 strong millisecond pulsars will perhaps allow the detection of gravitational waves within VLF or at least will give a more stringent upper limits.

  6. The Peculiar Pulsar Population of the Central Parsec

    CERN Document Server

    Dexter, Jason

    2013-01-01

    Pulsars orbiting the Galactic center black hole, Sgr A*, would be potential probes of its mass, distance and spin, and may even be used to test general relativity. Despite predictions of large populations of both ordinary and millisecond pulsars in the Galactic center, none have been detected within 25 pc by deep radio surveys. One explanation has been that hyperstrong temporal scattering prevents pulsar detections, but the recent discovery of radio pulsations from a magnetar within 0.1 pc shows that the temporal scattering is much weaker than predicted. We argue that an intrinsic deficit in the ordinary pulsar population is the most likely reason for the lack of detections to date: a "missing pulsar problem" in the Galactic center. In contrast, we show that the discovery of a single magnetar implies efficient magnetar formation in the region. If the massive stars in the central parsec form magnetars rather than ordinary pulsars, their short lifetimes could explain the missing pulsars. Efficient magnetar form...

  7. Towards Robust Gravitational Wave Detection with Pulsar Timing Arrays

    CERN Document Server

    Cornish, Neil J

    2015-01-01

    Precision timing of highly stable milli-second pulsars is a promising technique for the detection of very low frequency sources of gravitational waves. In any single pulsar, a stochastic gravitational wave signal appears as an additional source of timing noise that can be absorbed by the noise model, and so it is only by considering the coherent response across a network of pulsars that the signal can be distinguished from other sources of noise. In the limit where there are many gravitational wave sources in the sky, or many pulsars in the array, the signals produce a unique tensor correlation pattern that depends only on the angular separation between each pulsar pair. It is this distinct fingerprint that is used to search for gravitational waves using pulsar timing arrays. Here we consider how the prospects for detection are diminished when the statistical isotropy of the timing array or the gravitational wave signal is broken by having a finite number of pulsars and a finite number of sources. We find the...

  8. Magnetically Accreting Isolated Old Neutron Stars

    CERN Document Server

    Rutledge, R E

    2001-01-01

    Previous work on the emission from isolated old neutron stars (IONS) accreting the inter-stellar medium (ISM) focussed on gravitational capture - Bondi accretion. We propose a new class of sources which accrete via magnetic interaction with the ISM. While for the Bondi mechanism, the accretion rate decreases with increasing NS velocity, in magnetic accretors (MAGACs="magics") the accretion rate increases with increasing NS velocity. MAGACs will be produced among high velocity (~> 100 km s-1) high magnetic field (B> 1e14 G) radio pulsars - the ``magnetars'' - after they have evolved first through magnetic dipole spin-down, followed by a ``propeller'' phase (when the object sheds angular momentum on a timescale ~1e14 G; minimum velocities relative to the ISM of >25-100 km s-1, depending on B, well below the median in the observed radio-pulsar population; spin-periods of >days to years; accretion luminosities of 1e28- 1e31 ergs s-1 ; and effective temperatures kT=0.3 - 2.5 keV if they accrete onto the magnetic p...

  9. Spectral Properties of Anomalous X-ray Pulsars

    Institute of Scientific and Technical Information of China (English)

    Ye Lu; Wei Wang; Yong-Heng Zhao

    2003-01-01

    We examine the spectra of the persistent emission from anomalous X-ray pulsars (AXPs) and their variation with the spin-down rate Ω. Based on an accretion-powered model, the influences of both the magnetic field and the mass accretion rate on the spectral properties of AXPs are addressed. We then investigate the relation between the spectral property of AXPs and mass accretion rate M. The result shows that there exists a linear correlation between the photon index and the mass accretion rate: the spectral hardness increases with increasing M. A possible emission mechanism for the explanation of the spectral properties of AXPs is also discussed.

  10. The Gamma-Ray Pulsar Population of Globular Clusters: Implications for the GeV Excess

    CERN Document Server

    Hooper, Dan

    2016-01-01

    It has been suggested that the GeV excess, observed from the region surrounding the Galactic Center, might originate from a population of millisecond pulsars that formed in globular clusters. With this in mind, we employ the publicly available Fermi data to study the gamma-ray emission from 157 globular clusters, identifying a statistically significant signal from 25 of these sources (ten of which are not found in existing gamma-ray catalogs). We combine these observations with the predicted pulsar formation rate based on the stellar encounter rate of each globular cluster to constrain the gamma-ray luminosity function of millisecond pulsars in the Milky Way's globular cluster system. We find that this pulsar population exhibits a luminosity function that is quite similar to those millisecond pulsars observed in the field of the Milky Way (i.e. the thick disk). After pulsars are expelled from a globular cluster, however, they continue to lose rotational kinetic energy and become less luminous, causing their l...

  11. Pulsars at the Center of the Galaxy

    Science.gov (United States)

    Majid, Walid

    2016-07-01

    Over the past few years, a number of groups using data from NASA's space-borne Fermi LAT instrument have identified excess gamma-ray flux toward the inner 1º of the Galactic Center (GC), with an even larger significant excess within 0.2º degrees. At present there are two leading candidates for this excess: dark matter annihilation and a population of unresolved millisecond pulsars (MSPs). We are currently developing dedicated instrumentation to carry out a sensitive search for the pulsars in this region of the galaxy using a newly developed front end and receiver on a Deep Space Network large diameter antenna in Australia. In this presentation, we will provide an overview of the challenges encountered with pulsar searches at the GC region and a summary of previous and ongoing efforts to survey this region with radio telescopes. We will also provide preliminary results from our recent observations of the GC region at 2 and 8 GHz and will conclude with prospects for detection of perhaps hundreds of pulsars in this region with new generations of radio telescopes now under construction.

  12. Pulsar population synthesis using palfa detections and pulsar search collaboratory discoveries including a wide DNS system and a nearby MSP

    Science.gov (United States)

    Swiggum, Joseph Karl

    Using the ensemble of detections from pulsar surveys, we can learn about the sizes and characteristics of underlying populations. In this thesis, I analyze results from the Pulsar Arecibo L-band Feed Array (PALFA) precursor and Green Bank Telescope 350 MHz Drift Scan surveys; I examine survey sensitivity to see how detections can inform pulsar population models, I look at new ways of including young scientists -- high school students -- in the discovery process and I present timing solutions for students' discoveries (including a nearby millisecond pulsar and a pulsar in a wide-orbit double neutron star system). The PALFA survey is on-going and uses the ALFA 7-beam receiver at 1400 MHz to search both inner and outer Galactic sectors visible from Arecibo (32° ?£? 77° and 168° ?£? 214°) close to the Galactic plane (|b| ? 5°) for pulsars. The PALFA precursor survey observed a subset of this region, (|b| ? 1°) and detected 45 pulsars, including one known millisecond pulsar (MSP) and 11 previously unknown, long-period (normal) pulsars. I assess the sensitivity of the PALFA precursor survey and use the number of normal pulsar and MSP detections to infer the size of each underlying Galactic population. Based on 44 normal pulsar detections and one MSP, we constrain each population size to 107,000+36,000-25,000 and 15,000 +85,000-6,000 respectively with 95% confidence. Based on these constraints, we predict yields for the full PALFA survey and find a deficiency in normal pulsar detections, possibly due to radio frequency interference and/or scintillation, neither of which are currently accounted for in population simulations. The GBT 350 MHz Drift Scan survey collected data in the summer of 2007 while the GBT was stationary, undergoing track replacement. Results discussed here come from ~20% of the survey data, which were processed and donated to the Pulsar Search Collaboratory (PSC). The PSC is a joint outreach program between WVU and NRAO, involving high school

  13. PulsarPlane: a feasibility study for millisecond radio pulsar navigation

    NARCIS (Netherlands)

    Buist, Peter; Hesselink, Henk; Gibbs, Alex; Keuning, Michel; Gaubitch, Nikolay; Noroozi, Arash; Verhoeven, Chris; Heusdens, Richard; Fernandes, Jorge; Kabakchiev, Hristo; Bentum, Mark; Kestilä, Antti

    2014-01-01

    Stars have been used -in what is called celestial navigation- since thousands of years by mankind. Celestial navigation was used extensively in aviation until the 1960s, and in marine navigation until recently. It has been investigated for agriculture applications, utilized for military aircraft and

  14. A Pulsar and a Disk

    Science.gov (United States)

    Kohler, Susanna

    2016-07-01

    V appeared.Hong and collaborators were then left with the task of piecing together this strange behavior into a picture of what was happening with this binary system.The authors proposed model for SXP 214. Here the binary has a ~30-day orbit tilted at 15 to the circumstellar disk. The pulsar passes through the circumstellar disk of its companion once per orbit. The interval marked A (orange line) is suggested as the period of time corresponding to the Chandra observations in this study: just as the neutron star is emerging from the disk after passing through it. [Hong et al. 2016]Passing Through a DiskIn the model the authors propose, the pulsar is on a ~30-day eccentric orbit that takes it through the circumstellar disk of its companion once per orbit.In this picture, the authors Chandra detections must have been made just as the pulsar was emerging from the circumstellar disk. The disk had initially hidden the soft X-ray emission from the pulsar, but as the pulsar emerged, that component became brighter, causing both the overall rise in X-ray counts and the shift in the spectrum to lower energies.Since the pulsars accretion is fueled by material picked up as it passes through the circumstellar disk, the accretion from a recent passage through the disk likely also caused the observed spin-up to the shorter period.If the authors model is correct, this series of observations of the pulsar as it emerges from the disk provides a rare opportunity to examine what happens to X-ray emission during this passage. More observations of this intriguing system can help us learn about the properties of the disk and the emission geometry of the neutron star surface.CitationJaeSub Hong et al 2016 ApJ 826 4. doi:10.3847/0004-637X/826/1/4

  15. Arecibo Pulsar Survey Using ALFA. III. Precursor Survey and Population Synthesis

    CERN Document Server

    Swiggum, J K; McLaughlin, M A; Bates, S D; Champion, D J; Ransom, S M; Lazarus, P; Brazier, A; Hessels, J W T; Nice, D J; Ellis, J; Senty, T R; Allen, B; Bhat, N D R; Bogdanov, S; Camilo, F; Chatterjee, S; Cordes, J M; Crawford, F; Deneva, J S; Freire, P C C; Jenet, F A; Karako-Argaman, C; Kaspi, V M; Knispel, B; Lee, K J; Van Leeuwen, J; Lynch, R; Lyne, A G; Scholz, P; Siemens, X; Stairs, I H; Stappers, B W; Stovall, K; Venkataraman, A; Zhu, W W

    2014-01-01

    The Pulsar Arecibo L-band Feed Array (PALFA) Survey uses the ALFA 7-beam receiver to search both inner and outer Galactic sectors visible from Arecibo ($32^{\\circ}\\lesssim \\ell \\lesssim 77^{\\circ}$ and $168^{\\circ}\\lesssim \\ell \\lesssim 214^{\\circ}$) close to the Galactic plane ($|b|\\lesssim5^{\\circ}$) for pulsars. In this paper we detail a precursor survey of this region with PALFA, which observed a subset of the full region (slightly more restrictive in $\\ell$ and $|b|\\lesssim1^{\\circ}$) and detected 45 pulsars. For both Galactic millisecond and normal pulsar populations, we compare the survey's detections with simulations to model these populations and, in particular, to estimate the number of observable pulsars in the Galaxy. We place 95\\% confidence intervals of 82,000 to 143,000 on the number of detectable normal pulsars and 9,000 to 100,000 on the number of detectable millisecond pulsars in the Galactic disk. These are consistent with previous estimates. Given the most likely population size in each ca...

  16. Searches for gravitational waves from known pulsars with S5 LIGO data

    CERN Document Server

    Abbott, B P; Acernese, F; Adhikari, R; Ajith, P; Allen, B; Allen, G; Alshourbagy, M; Amin, R S; Anderson, S B; Anderson, W G; Antonucci, F; Aoudia, S; Arain, M A; Araya, M; Armandula, H; Armor, P; Arun, K G; Aso, Y; Aston, S; Astone, P; Aufmuth, P; Aulbert, C; Babak, S; Baker, P; Ballardin, G; Ballmer, S; Barker, C; Barker, D; Barone, F; Barr, B; Barriga, P; Barsotti, L; Barsuglia, M; Barton, M A; Bartos, I; Bassiri, R; Bastarrika, M; Bauer, Th S; Behnke, B; Beker, M; Benacquista, M; Betzwieser, J; Beyersdorf, P T; Bigotta, S; Bilenko, I A; Billingsley, G; Birindelli, S; Biswas, R; Bizouard, M A; Black, E; Blackburn, J K; Blackburn, L; Blair, D; Bland, B; Boccara, C; Bodiya, T P; Bogue, L; Bondu, F; Bonelli, L; Bork, R; Boschi, V; Bose, S; Bosi, L; Braccini, S; Bradaschia, C; Brady, P R; Braginsky, V B; Brau, J E; Bridges, D O; Brillet, A; Brinkmann, M; Brisson, V; Broeck, C Van Den; Brooks, A F; Brown, D A; Brummit, A; Brunet, G; Budzynski, R; Bulik, T; Bullington, A; Bulten, H J; Buonanno, A; Burmeister, O; Buskulic, D; Byer, R L; Cadonati, L; Cagnoli, G; Calloni, E; Camp, J B; Campagna, E; Cannizzo, J; Cannon, K C; Canuel, B; Cao, J; Carbognani, F; Cardenas, L; Caride, S; Castaldi, G; Caudill, S; Cavaglià, M; Cavalier, F; Cavalieri, R; Cella, G; Cepeda, C; Cesarini, E; Chalermsongsak, T; Chalkley, E; Charlton, P; Chassande-Mottin, E; Chatterji, S; Chelkowski, S; Chen, Y; Chincarini, A; Christensen, N; Chung, C T Y; Clark, D; Clark, J; Clayton, J H; Cleva, F; Coccia, E; Cokelaer, T; Colacino, C N; Colas, J; Colla, A; Colombini, M; Conte, R; Cook, D; Corbitt, T R C; Corda, C; Cornish, N; Corsi, A; Coulon, J -P; Coward, D; Coyne, D C; Creighton, J D E; Creighton, T D; Cruise, A M; Culter, R M; Cumming, A; Cunningham, L; Cuoco, E; Danilishin, S L; D'Antonio, S; Danzmann, K; Dari, A; Dattilo, V; Daudert, B; Davier, M; Davies, G; Daw, E J; Day, R; De Rosa, R; DeBra, D; Degallaix, J; del Prete, M; Dergachev, V; Desai, S; DeSalvo, R; Dhurandhar, S; Di Fiore, L; Di Lieto, A; Emilio, M Di Paolo; Di Virgilio, A; Díaz, M; Dietz, A; Donovan, F; Dooley, K L; Doomes, E E; Drago, M; Drever, R W P; Dueck, J; Duke, I; Dumas, J -C; Dwyer, J G; Echols, C; Edgar, M; Effler, A; Ehrens, P; Espinoza, E; Etzel, T; Evans, M; Evans, T; Fafone, V; Fairhurst, S; Faltas, Y; Fan, Y; Fazi, D; Fehrmann, H; Ferrante, I; Fidecaro, F; Finn, L S; Fiori, I; Flaminio, R; Flasch, K; Foley, S; Forrest, C; Fotopoulos, N; Fournier, J -D; Franc, J; Franzen, A; Frasca, S; Frasconi, F; Frede, M; Frei, M; Frei, Z; Freise, A; Frey, R; Fricke, T; Fritschel, P; Frolov, V V; Fyffe, M; Galdi, V; Gammaitoni, L; Garofoli, J A; Garufi, F; Gemme, G; Genin, E; Gennai, A; Gholami, I; Giaime, J A; Giampanis, S; Giardina, K D; Giazotto, A; Goda, K; Goetz, E; Goggin, L M; González, G; Gorodetsky, M L; Goßler, S; Gouaty, R; Granata, M; Granata, V; Grant, A; Gras, S; Gray, C; Gray, M; Greenhalgh, R J S; Gretarsson, A M; Greverie, C; Grimaldi, F; Grosso, R; Grote, H; Grünewald, S; Günther, M; Guidi, G; Gustafson, E K; Gustafson, R; Hage, B; Hallam, J M; Hammer, D; Hammond, G D; Hanna, C; Hanson, J; Harms, J; Harry, G M; Harry, I W; Harstad, E D; Haughian, K; Hayama, K; Heefner, J; Heitmann, H; Hello, P; Heng, I S; Heptonstall, A; Hewitson, M; Hild, S; Hirose, E; Hoak, D; Hodge, K A; Holt, K; Hosken, D J; Hough, J; Hoyland, D; Huet, D; Hughey, B; Huttner, S H; Ingram, D R; Isogai, T; Ito, M; Ivanov, A; Jaranowski, P; Johnson, B; Johnson, W W; Jones, D I; Jones, G; Jones, R; de la Jordana, L Sancho; Ju, L; Kalmus, P; Kalogera, V; Kandhasamy, S; Kanner, J; Kasprzyk, D; Katsavounidis, E; Kawabe, K; Kawamura, S; Kawazoe, F; Kells, W; Keppel, D G; Khalaidovski, A; Khalili, F Ya; Khan, R; Khazanov, E; King, P; Kissel, J S; Klimenko, S; Kokeyama, K; Kondrashov, V; Kopparapu, R; Koranda, S; Kowalska, I; Kozak, D; Krishnan, B; Królak, A; Kumar, R; Kwee, P; La Penna, P; Lam, P K; Landry, M; Lantz, B; Lazzarini, A; Lei, H; Lei, M; Leindecker, N; Leonor, I; Leroy, N; Letendre, N; Li, C; Lin, H; Lindquist, P E; Littenberg, T B; Lockerbie, N A; Lodhia, D; Longo, M; Lorenzini, M; Loriette, V; Lormand, M; Losurdo, G; Lu, P; Lubinski, M; Lucianetti, A; Lück, H; Machenschalk, B; MacInnis, M; Mackowski, J -M; Mageswaran, M; Mailand, K; Majorana, E; Man, N; Mandel, I; Mandic, V; Mantovani, M; Marchesoni, F; Marion, F; Márka, S; Márka, Z; Markosyan, A; Markowitz, J; Maros, E; Marque, J; Martelli, F; Martin, I W; Martin, R M; Marx, J N; Mason, K; Masserot, A; Matichard, F; Matone, L; Matzner, R A; Mavalvala, N; McCarthy, R; McClelland, D E; McGuire, S C; McHugh, M; McIntyre, G; McKechan, D J A; McKenzie, K; Mehmet, M; Melatos, A; Melissinos, A C; Mendell, G; Menéndez, D F; Menzinger, F; Mercer, R A; Meshkov, S; Messenger, C; Meyer, M S; Michel, C; Milano, L; Miller, J; Minelli, J; Minenkov, Y; Mino, Y; Mitrofanov, V P; Mitselmakher, G; Mittleman, R; Miyakawa, O; Moe, B; Mohan, M; Mohanty, S D; Mohapatra, S R P; Moreau, J; Moreno, G; Morgado, N; Morgia, A; Morioka, T; Mors, K; Mosca, S; Moscatelli, V; Mossavi, K; Mours, B; MowLowry, C; Müller, G; Muhammad, D; Mühlen, H zur; Mukherjee, S; Mukhopadhyay, H; Mullavey, A; Müller-Ebhardt, H; Munch, J; Murray, P G; Myers, E; Myers, J; Nash, T; Nelson, J; Neri, I; Newton, G; Nishizawa, A; Nocera, F; Numata, K; Ochsner, E; O'Dell, J; Ogin, G H; O'Reilly, B; O'Shaughnessy, R; Ottaway, D J; Ottens, R S; Overmier, H; Owen, B J; Pagliaroli, G; Palomba, C; Pan, Y; Pankow, C; Paoletti, F; Papa, M A; Parameshwaraiah, V; Pardi, S; Pasqualetti, A; Passaquieti, R; Passuello, D; Patel, P; Pedraza, M; Penn, S; Perreca, A; Persichetti, G; Pichot, M; Piergiovanni, F; Pierro, V; Pietka, M; Pinard, L; Pinto, I M; Pitkin, M; Pletsch, H J; Plissi, M V; Poggiani, R; Postiglione, F; Prato, M; Principe, M; Prix, R; Prodi, G A; Prokhorov, L; Puncken, O; Punturo, M; Puppo, P; Quetschke, V; Raab, F J; Rabaste, O; Rabeling, D S; Radkins, H; Raffai, P; Raics, Z; Rainer, N; Rakhmanov, M; Rapagnani, P; Raymond, V; Re, V; Reed, C M; Reed, T; Regimbau, T; Rehbein, H; Reid, S; Reitze, D H; Ricci, F; Riesen, R; Riles, K; Rivera, B; Roberts, P; Robertson, N A; Robinet, F; Robinson, C; Robinson, E L; Rocchi, A; Roddy, S; Rolland, L; Rollins, J; Romano, J D; Romano, R; Romie, J H; Rosinska, D; Röver, C; Rowan, S; Rüdiger, A; Ruggi, P; Russell, P; Ryan, K; Sakata, S; Salemi, F; Sandberg, V; Sannibale, V; Santamaría, L; Saraf, S; Sarin, P; Sassolas, B; Sathyaprakash, B S; Sato, S; Satterthwaite, M; Saulson, P R; Savage, R; Savov, P; Scanlan, M; Schilling, R; Schnabel, R; Schofield, R; Schulz, B; Schutz, B F; Schwinberg, P; Scott, J; Scott, S M; Searle, A C; Sears, B; Seifert, F; Sellers, D; Sengupta, A S; Sentenac, D; Sergeev, A; Shapiro, B; Shawhan, P; Shoemaker, D H; Sibley, A; Siemens, X; Sigg, D; Sinha, S; Sintes, A M; Slagmolen, B J J; Slutsky, J; Van der Sluys, M V; Smith, J R; Smith, M R; Smith, N D; Somiya, K; Sorazu, B; Stein, A; Stein, L C; Steplewski, S; Stochino, A; Stone, R; Strain, K A; Strigin, S; Stroeer, A; Sturani, R; Stuver, A L; Summerscales, T Z; Sun, K -X; Sung, M; Sutton, P J; Swinkels, B; Szokoly, G P; Talukder, D; Tang, L; Tanner, D B; Tarabrin, S P; Taylor, J R; Taylor, R; Terenzi, R; Thacker, J; Thorne, K A; Thorne, K S; Thüring, A; Tokmakov, K V; Toncelli, A; Tonelli, M; Torres, C; Torrie, C; Tournefier, E; Travasso, F; Traylor, G; Trias, M; Trummer, J; Ugolini, D; Ulmen, J; Urbanek, K; Vahlbruch, H; Vajente, G; Vallisneri, M; Brand, J F J van den; van der Putten, S; Vass, S; Vaulin, R; Vavoulidis, M; Vecchio, A; Vedovato, G; van Veggel, A A; Veitch, J; Veitch, P; Veltkamp, C; Verkindt, D; Vetrano, F; Viceré, A; Villar, A; Vinet, J -Y; Vocca, H; Vorvick, C; Vyachanin, S P; Waldman, S J; Wallace, L; Ward, R L; Was, M; Weidner, A; Weinert, M; Weinstein, A J; Weiss, R; Wen, L; Wen, S; Wette, K; Whelan, J T; Whitcomb, S E; Whiting, B F; Wilkinson, C; Willems, P A; Williams, H R; Williams, L; Willke, B; Wilmut, I; Winkelmann, L; Winkler, W; Wipf, C C; Wiseman, A G; Woan, G; Wooley, R; Worden, J; Wu, W; Yakushin, I; Yamamoto, H; Yan, Z; Yoshida, S; Yvert, M; Zanolin, M; Zhang, J; Zhang, L; Zhao, C; Zotov, N; Zucker, M E; Zweizig, J; Bégin, S; Corongiu, A; D'Amico, N; Freire, P C C; Hessels, J; Hobbs, G B; Krämer, M; Lyne, A G; Manchester, R N; Marshall, F E; Middleditch, J; Possenti, A; Ransom, S M; Stairs, I H; Stappers, B

    2009-01-01

    We present a search for gravitational waves from 116 known millisecond and young pulsars using data from the fifth science run of the LIGO detectors. For this search ephemerides overlapping the run period were obtained for all pulsars using radio and X-ray observations. We demonstrate an updated search method that allows for small uncertainties in the pulsar phase parameters to be included in the search. We report no signal detection from any of the targets and therefore interpret our results as upper limits on the gravitational wave signal strength. Our best (lowest) upper limit on gravitational wave amplitude is 2.3x10^-26 for J1603-7202 and our best (lowest) limit on the inferred pulsar ellipticity is 7.0x10^-8 for J2124-3358. Of the recycled millisecond pulsars several of the measured upper limits are only about an order of magnitude above their spin-down limits. For the young pulsars J1913+1011 and J1952+3252 we are only a factor of a few above the spin-down limit, and for the X-ray pulsar J0537-6910 we ...

  17. Wind accretion: Theory and observations

    Science.gov (United States)

    Shakura, N. I.; Postnov, K. A.; Kochetkova, A. Yu.; Hjalmarsdotter, L.; Sidoli, L.; Paizis, A.

    2015-07-01

    A review of wind accretion in high-mass X-ray binaries is presented. We focus on different regimes of quasi-spherical accretion onto the neutron star (NS): the supersonic (Bondi) accretion, which takes place when the captured matter cools down rapidly and falls supersonically towards the NS magnetosphere, and subsonic (settling) accretion which occurs when plasma remains hot until it meets the magnetospheric boundary. These two regimes of accretion are separated by an X-ray luminosity of about 4 × 1036 erg s-1. In the subsonic case, which sets in at lower luminosities, a hot quasi-spherical shell must form around the magnetosphere, and the actual accretion rate onto NS is determined by the ability of the plasma to enter the magnetosphere due to Rayleigh-Taylor instability. In turn, two regimes of subsonic accretion are possible, depending on plasma cooling mechanism (Compton or radiative) near the magnetopshere. The transition from the high-luminosity with Compton cooling to the lowluminosity (Lx ≲ 3 × 1035 erg s-1) with radiative cooling can be responsible for the onset of the off states repeatedly observed in several low-luminosity slowly accreting pulsars, such as Vela X-1, GX 301-2, and 4U 1907+09. The triggering of the transitionmay be due to a switch in the X-ray beam pattern in response to a change in the optical depth in the accretion column with changing luminosity. We also show that in the settling accretion theory, bright X-ray flares (~1038-1040 erg) observed in supergiant fast X-ray transients (SFXT) can be produced by sporadic capture of magnetized stellar wind plasma. At sufficiently low accretion rates, magnetic reconnection can enhance the magnetospheric plasma entry rate, resulting in copious production of X-ray photons, strong Compton cooling and ultimately in unstable accretion of the entire shell. A bright flare develops on the free-fall time scale in the shell, and the typical energy released in an SFXT bright flare corresponds to the mass

  18. Strong-Field Tests of Gravity Using Pulsars and Black Holes

    CERN Document Server

    Krämer, M; Cordes, J M; Lazio, T J W; Stappers, B W; Johnston, S

    2004-01-01

    The sensitivity of the SKA enables a number of tests of theories of gravity. A Galactic Census of pulsars will discover most of the active pulsars in the Galaxy beamed toward us. In this census will almost certainly be pulsar-black hole binaries as well as pulsars orbiting the super-massive black hole in the Galactic centre. These systems are unique in their capability to probe the ultra-strong field limit of relativistic gravity. These measurements can be used to test the Cosmic Censorship Conjecture and the No-Hair theorem. The large number of millisecond pulsars discovered with the SKA will also provide a dense array of precision clocks on the sky. These clocks will act as the multiple arms of a huge gravitational wave detector, which can be used to detect and measure the stochastic cosmological gravitational wave background that is expected from a number of sources.

  19. The Velocity Distribution of Isolated Radio Pulsars

    Science.gov (United States)

    Arzoumanian, Z.; Chernoff, D. F.; Cordes, J. M.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    spatially bounded surveys; (3) an important low-velocity population exists that increases the fraction of neutron stars retained by globular clusters and is consistent with the number of old objects that accrete from the interstellar medium; (4) under standard assumptions for supernova remnant expansion and pulsar spin-down, approx. 10% of pulsars younger than 20 kyr will appear to lie outside of their host remnants. Finally, we comment on the ramifications of our birth velocity distribution for binary survival and the population of inspiraling binary neutron stars relevant to some GRB models and potential sources for LIGO.

  20. An Estimation of the Initial Period of Pulsars

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The initial period of a pulsar is an important factor in our understandingof the formation of neutron stars and of the nature of the equation of state of neutronstar matter. Up to now this quantity can only be obtained for a few pulsars forwhich accurate age and braking index are known. Based on the theory of the off-center dipole emission, in which pulsars obtain their high velocities depending onthe initial periods, we calculate the initial period using the proper motion data.Because the orbital velocity of the progenitor and asymmetric kick in the supernovaexplosion may also contribute to the observed velocity of the pulsar, the derivedvalues of initial periods are lower limits. For normal pulsars, the initial periodsare in the range of 0.6 ~ 2.6 ms. For the millisecond pulsars, the initial periods arecomparable to their current periods, and the ratio between the initial period and thecurrent period increases with the decrease of the current period. For PSR B1937+21with the shortest period of 1.56 ms, the ratio is 0.77.

  1. High energy signatures of quasi-spherical accretion onto rotating, magnetized neutron star in the ejector-accretor intermediate state

    CERN Document Server

    Bednarek, W

    2015-01-01

    We consider a simple scenario for the accretion of matter onto a neutron star in order to understand processes in the inner pulsar magnetosphere during the transition stage between different accretion modes. A simple quasi-spherical accretion process onto rotating, magnetized compact object is analyzed in order to search for the radiative signatures which could appear during transition between ejecting and accreting modes. It is argued that different accretion modes can be present in a single neutron star along different magnetic field lines for specific range of parameters characterising the pulsar (rotational period, surface magnetic field strength) and the density of surrounding medium. The radiation processes characteristic for the ejecting pulsar, i.e. curvature and synchrotron radiation produced by primary electrons in the pulsar outer gap, are expected to be modified by the presence of additional thermal radiation from the neutron star surface. We predict that during the transition from the pure ejecto...

  2. Probing Binary Evolution Using the Pulsar Fossil Record

    Science.gov (United States)

    Ferdman, Robert D.; Stairs, I. H.; Kramer, M.; McLaughlin, M. A.; Faulkner, A.; Backer, D. C.; Demorest, P.; Nice, D. J.; Burgay, M.; Camilo, F.; D'Amico, N.; Hobbs, G.; Lorimer, D. R.; Lyne, A. G.; Manchester, R.; Possenti, A.

    2006-12-01

    The Parkes Multibeam Pulsar Survey has yielded a significant number of very interesting binary and millisecond pulsars. Two of these objects are part of an ongoing timing study at the Green Bank Telescope (GBT). PSR J1756-2251 is a double-neutron star (DNS) binary system. Its orbital properties show it to be a similar system to PSR B1913+16, the original binary pulsar system discovered by Hulse and Taylor. Mass measurements of this system thus provide another important opportunity to test the validity of General Relativity, and to study the evolutionary history of DNS systems. PSR J1802-2124 is part of the relatively new and unstudied "intermediate-mass" class of binary pulsars. These typically spin with periods in the tens of milliseconds, and often have relatively massive (> 0.7 solar masses) white dwarf companions. GBT observations over the past two years have enabled us to detect the Shapiro delay in this system. This has led to the determination of the individual masses of the neutron star and white dwarf companion, providing constraints on the mass-transfer history in this unusual system.

  3. Physics of radio emission in gamma-ray pulsars

    CERN Document Server

    Petrova, S A

    2016-01-01

    Propagation of radio emission in pulsar magnetosphere is reviewed. The effects of polarization transfer, induced scattering and reprocessing to high energies are analysed with an especial emphasis on the implications for the gamma-ray pulsars. The possibilities of the pulsar plasma diagnostics based on the observed radio pulse characteristics are outlined as well. As an example, the plasma number density profiles obtained from the polarization data for the Vela and the gamma-ray millisecond pulsars J1446-4701, J1939+2134 and J1744-1134 are presented. The number densities derived tend to be the highest/lowest when the radio pulse leads/lags the gamma-ray peak. In the PSR J1939+2134, the plasma density profiles for the main pulse and interpulse appear to fit exactly the same curve, testifying to the origin of both radio components above the same magnetic pole and their propagation through the same plasma flow in opposite directions. The millisecond radio pulse components exhibiting flat position angle curves ar...

  4. Scattering of pulsar radio emission by the interstellar plasma

    CERN Document Server

    Coles, W A; Gao, J J; Hobbs, G; Verbiest, J P W

    2010-01-01

    We present simulations of scattering phenomena which are important in pulsar observations, but which are analytically intractable. The simulation code, which has also been used for solar wind and atmospheric scattering problems, is available from the authors. These simulations reveal an unexpectedly important role of dispersion in combination with refraction. We demonstrate the effect of analyzing observations which are shorter than the refractive scale. We examine time-of-arrival fluctuations in detail: showing their correlation with intensity and dispersion measure; providing a heuristic model from which one can estimate their contribution to pulsar timing observations; and showing that much of the effect can be corrected making use of measured intensity and dispersion. Finally, we analyze observations of the millisecond pulsar J0437$-$4715, made with the Parkes radio telescope, that show timing fluctuations which are correlated with intensity. We demonstrate that these timing fluctuations can be corrected,...

  5. Observations of transients and pulsars with LOFAR international stations

    CERN Document Server

    Serylak, Maciej; Williams, Chris; Armour, Wes

    2012-01-01

    The LOw FRequency ARray - LOFAR is a new radio telescope that is moving the science of radio pulsars and transients into a new phase. Its design places emphasis on digital hardware and flexible software instead of mechanical solutions. LOFAR observes at radio frequencies between 10 and 240 MHz where radio pulsars and many transients are expected to be brightest. Radio frequency signals emitted from these objects allow us to study the intrinsic pulsar emission and phenomena such as propagation effects through the interstellar medium. The design of LOFAR allows independent use of its stations to conduct observations of known bright objects, or wide field monitoring of transient events. One such combined software/hardware solution is called the Advanced Radio Transient Event Monitor and Identification System (ARTEMIS). It is a backend for both targeted observations and real-time searches for millisecond radio transients which uses Graphical Processing Unit (GPU) technology to remove interstellar dispersion and d...

  6. What flashes of pulsars can teach us about their interior

    CERN Document Server

    Alford, Mark G

    2013-01-01

    The cores of compact stars reach the highest densities in nature and therefore could consist of novel phases of matter. They can be probed seismologically via mechanical oscillation modes. One example is unstable r-modes which, if not efficiently damped, emit gravitational waves that would quickly spin down a millisecond pulsar. The damping is determined by microscopic properties of the dense interior. We demonstrate via a detailed analysis of the pulsar evolution how precise pulsar timing data can constrain the star's composition. We find that interacting quark matter is consistent with both the observed radio and x-ray data, whereas for ordinary nuclear matter some additional enhanced damping mechanism will be required.

  7. Particle Emission-Dependent Timing Noise of Pulsars

    Institute of Scientific and Technical Information of China (English)

    LIU Xiong-Wei; NA Xue-Sen; XU Ren-Xin; QIAO Guo-Jun

    2011-01-01

    Though pulsars spin regularly, the differences between the observed and predicted ToA (time of arrival), known as "timing noise", can still reach a few milliseconds or more. We try to understand the noise in this study. As proposed by Xu and Qiao in 2001, both dipole radiation and particle emission would result in pulsar braking. Accordingly, possible fluctuation of particle current Sow is suggested here to contribute significant ToA variation of pulsars. We find that the particle emission fluctuation could lead to timing noise which cannot be eliminated in timing process and that a longer period fluctuation would arouse a stronger noise. The simulated timing noise proGle and amplitude are in agreement with the observed timing behaviors on the timescale of years.

  8. The High Time Resolution Universe Pulsar Survey XII : Galactic plane acceleration search and the discovery of 60 pulsars

    CERN Document Server

    Ng, C; Bailes, M; Barr, E D; Bates, S D; Bhat, N D R; Burgay, M; Burke-Spolaor, S; Flynn, C M L; Jameson, A; Johnston, S; Keith, M J; Kramer, M; Levin, L; Petroff, E; Possenti, A; Stappers, B W; van Straten, W; Tiburzi, C; Eatough, R P; Lyne, A G

    2015-01-01

    We present initial results from the low-latitude Galactic plane region of the High Time Resolution Universe pulsar survey conducted at the Parkes 64-m radio telescope. We discuss the computational challenges arising from the processing of the terabyte-sized survey data. Two new radio interference mitigation techniques are introduced, as well as a partially-coherent segmented acceleration search algorithm which aims to increase our chances of discovering highly-relativistic short-orbit binary systems, covering a parameter space including potential pulsar-black hole binaries. We show that under a constant acceleration approximation, a ratio of data length over orbital period of ~0.1 results in the highest effectiveness for this search algorithm. From the 50 per cent of data processed thus far, we have re-detected 435 previously known pulsars and discovered a further 60 pulsars, two of which are fast-spinning pulsars with periods less than 30ms. PSR J1101-6424 is a millisecond pulsar whose heavy white dwarf (WD)...

  9. The effect of small inter-pulsar distance variations in stochastic gravitational wave background searches with Pulsar Timing Arrays

    CERN Document Server

    Mingarelli, Chiara M F

    2014-01-01

    One of the primary objectives for Pulsar Timing Arrays (PTAs) is to detect a stochastic background generated by the incoherent superposition of gravitational waves (GWs), in particular from the cosmic population of supermassive black hole binaries. Current stochastic background searches assume that pulsars in a PTA are separated from each other and the Earth by many GW wavelengths. As more millisecond pulsars are discovered and added to PTAs, some may be separated by only a few radiation wavelengths or less, resulting in correlated GW phase changes between close pulsars in the array. Here we investigate how PTA overlap reduction functions (ORFs), up to quadrupole order, are affected by these additional correlated phase changes, and how they are in turn affected by relaxing the assumption that all pulsars are equidistant from the solar system barycenter. We find that in the low frequency GW background limit of $f\\sim10^{-9}$~Hz, and for pulsars at varying distances from the Earth, that these additional correla...

  10. Radio Timing and Analysis of Black Widow Pulsar J2256-1024

    Science.gov (United States)

    Crowter, Kathryn; Stairs, Ingrid H.; McPhee, Christie A.; Archibald, Anne M.; Boyles, Jason; Hessels, Jason; Kaspi, Victoria M.; Kondratiev, Vlad I.; Lorimer, Duncan; Lynch, Ryan S.; McLaughlin, Maura; Pennucci, Timothy; Ransom, Scott M.; Roberts, Mallory; Stovall, Kevin; van Leeuwen, Joeri

    2015-01-01

    Pulsar J2256-1024, discovered in a 350MHz GBT drift-scan survey and subsequently detected by Fermi-LAT, is a black widow millisecond pulsar in an eclipsing binary system. Black widow pulsars have a rather interesting history. They started life in a binary system, were then spun up by their companions into millisecond pulsars but at some point started ablating those companions, slowly destroying them - thus the moniker "black widow". They are characterized by relatively short orbital periods, in this case 5.1 hours, a low companion mass and, if the inclination angle is right, eclipses. For J2256-1024 we see very clear radio eclipses. Black widow systems used to be few and far between but are now more common with at least 18 currently known. Black widows are interesting for a variety of reasons. They provide potential insight into the formation of isolated millisecond pulsars which must have formed in a binary but are now seen alone, and in eclipsing systems pulses travel through the magnetosphere of the companion providing a probe of that region. Here we present timing and polarization results for J2256-1024 based on radio observations with the GBT.

  11. The Green Bank Telescope 350 MHz Drift-scan Survey II: Data Analysis and the Timing of 10 New Pulsars, Including a Relativistic Binary

    CERN Document Server

    Lynch, Ryan S; Ransom, Scott M; Stairs, Ingrid H; Lorimer, Duncan R; McLaughlin, Maura A; Hessels, Jason W T; Kaspi, Victoria M; Kondratiev, Vladislav I; Archibald, Anne M; Berndsen, Aaron; Cardoso, Rogerio F; Cherry, Angus; Karako-Argaman, Chen; van Leeuwen, Joeri; McPhee, Christie A; Pennucci, Tim; Roberts, Mallory S E

    2012-01-01

    We have completed a 350 MHz drift scan survey using the Robert C. Byrd Green Bank Telescope with the goal of finding new radio pulsars, especially millisecond pulsars that can be timed to high precision. This survey covered ~10300 square degrees and all of the data have now been fully processed. We have discovered a total of 31 new pulsars, seven of which are recycled pulsars. A companion paper by Boyles et al. (2012) describes the survey strategy, sky coverage, and instrumental set-up, and presents timing solutions for the first 13 pulsars. Here we describe the data analysis pipeline, survey sensitivity, and follow-up observations of new pulsars, and present timing solutions for 10 other pulsars. We highlight several sources---two interesting nulling pulsars, an isolated millisecond pulsar with a measurement of proper motion, and a partially recycled pulsar, PSR J0348+0432, which has a white dwarf companion in a relativistic orbit. PSR J0348+0432 will enable unprecedented tests of theories of gravity.

  12. THE GREEN BANK TELESCOPE 350 MHz DRIFT-SCAN SURVEY II: DATA ANALYSIS AND THE TIMING OF 10 NEW PULSARS, INCLUDING A RELATIVISTIC BINARY

    International Nuclear Information System (INIS)

    We have completed a 350 MHz Drift-scan Survey using the Robert C. Byrd Green Bank Telescope with the goal of finding new radio pulsars, especially millisecond pulsars that can be timed to high precision. This survey covered ∼10,300 deg2 and all of the data have now been fully processed. We have discovered a total of 31 new pulsars, 7 of which are recycled pulsars. A companion paper by Boyles et al. describes the survey strategy, sky coverage, and instrumental setup, and presents timing solutions for the first 13 pulsars. Here we describe the data analysis pipeline, survey sensitivity, and follow-up observations of new pulsars, and present timing solutions for 10 other pulsars. We highlight several sources—two interesting nulling pulsars, an isolated millisecond pulsar with a measurement of proper motion, and a partially recycled pulsar, PSR J0348+0432, which has a white dwarf companion in a relativistic orbit. PSR J0348+0432 will enable unprecedented tests of theories of gravity.

  13. Known Pulsars Identified in the GMRT 150 MHz All-Sky Survey

    CERN Document Server

    Frail, D A; Mooley, K P; Intema, H T

    2016-01-01

    We have used the 150 MHz radio continuum survey (TGSS ADR) from the Giant Metrewave Radio Telescope (GMRT) to search for phase-averaged emission toward all well-localized radio pulsars north of -53deg Declination. We detect emission toward 200 pulsars with high confidence (>=5-sigma) and another 88 pulsars at fainter levels. We show that most of our identifications are likely from pulsars, except for a small number where the measured flux density is confused by an associated supernova or pulsar-wind nebula, or a globular cluster. We investigate the radio properties of the 150 MHz sample and we find an unusually high number of gamma-ray binary millisecond pulsars with very steep spectral indices. We also note a discrepancy in the measured flux densities between GMRT and LOFAR pulsar samples, suggesting that the flux density scale for the LOFAR pulsar sample may be in error by approximately a factor two. We carry out a separate search of 30 well-localized gamma-ray, radio-quiet pulsars in an effort to detect a ...

  14. Millisecond extragalactic radio bursts as magnetar flares

    CERN Document Server

    Popov, S B

    2013-01-01

    Properties of the population of millisecond extragalactic radio bursts discovered by Thornton et al. (2013) are in good correspondence with the hypothesis that such events are related to hyperflares of magnetars, as was proposed by us after the first observation of an extragalactic millisecond radio burst by Lorimer et al. (2007). We also point that some of multiple millisecond radio bursts from M31 discovered by Rubio-Herrera et al. (2013) also can be related to weaker magnetar bursts.

  15. Plasma physics of accreting neutron stars

    Science.gov (United States)

    Ghosh, Pranab; Lamb, Frederick K.

    1991-01-01

    Plasma concepts and phenomena that are needed to understand X- and gamma-ray sources are discussed. The capture of material from the wind or from the atmosphere or envelope of a binary companion star is described and the resulting types of accretion flows discussed. The reasons for the formation of a magnetosphere around the neutron star are explained. The qualitative features of the magnetospheres of accreting neutron stars are then described and compared with the qualitative features of the geomagnetosphere. The conditions for stable flow and for angular and linear momentum conservation are explained in the context of accretion by magnetic neutron stars and applied to obtain rough estimates of the scale of the magnetosphere. Accretion from Keplerian disks is then considered in some detail. The radial structure of geometrically thin disk flows, the interaction of disk flows with the neutron star magnetosphere, and models of steady accretion from Keplerian disks are described. Accretion torques and the resulting changes in the spin frequencies of rotating neutron stars are considered. The predicted behavior is then compared with observations of accretion-powered pulsars. Magnetospheric processes that may accelerate particles to very high energies, producing GeV and, perhaps, TeV gamma-rays are discussed. Finally, the mechanisms that decelerate and eventually stop accreting plasma at the surfaces of strongly magnetic neutron stars are described.

  16. Towards robust gravitational wave detection with pulsar timing arrays

    Science.gov (United States)

    Cornish, Neil J.; Sampson, Laura

    2016-05-01

    Precision timing of highly stable millisecond pulsars is a promising technique for the detection of very low frequency sources of gravitational waves. In any single pulsar, a stochastic gravitational wave signal appears as an additional source of timing noise that can be absorbed by the noise model, and so it is only by considering the coherent response across a network of pulsars that the signal can be distinguished from other sources of noise. In the limit where there are many gravitational wave sources in the sky, or many pulsars in the array, the signals produce a unique tensor correlation pattern that depends only on the angular separation between each pulsar pair. It is this distinct fingerprint that is used to search for gravitational waves using pulsar timing arrays. Here we consider how the prospects for detection are diminished when the statistical isotropy of the timing array or the gravitational wave signal is broken by having a finite number of pulsars and a finite number of sources. We find the standard tensor-correlation analysis to be remarkably robust, with a mild impact on detectability compared to the isotropic limit. Only when there are very few sources and very few pulsars does the standard analysis begin to fail. Having established that the tensor correlations are a robust signature for detection, we study the use of "sky scrambles" to break the correlations as a way to increase confidence in a detection. This approach is analogous to the use of "time slides" in the analysis of data from ground-based interferometric detectors.

  17. Pulsar Observations with Radio Telescope FAST

    Science.gov (United States)

    Nan, Ren-Dong; Wang, Qi-Ming; Zhu, Li-Chun; Zhu, Wen-Bai; Jin, Cheng-Jin; Gan, Heng-Qian

    2006-12-01

    FAST, Five hundred meter Aperture Spherical Telescope, is the Chinese effort for the international project SKA, Square Kilometer Array. An innovative engineering concept and design pave a new road to realizing huge single dish in the most effective way. Three outstanding features of the telescope are the unique karst depressions as the sites, the active main reflector which corrects spherical aberration on the ground to achieve full polarization and wide band without involving complex feed system, and the light focus cabin driven by cables and servomechanism plus a parallel robot as secondary adjustable system to carry the most precise parts of the receivers. Besides a general coverage of those critical technologies involved in FAST concept, the progresses in demonstrating model being constructed at the Miyun Radio Observatory of the NAOC is introduced. Being the most sensitive radio telescope, FAST will enable astronomers to jumpstart many of science goals, for example, the natural hydrogen line surveying in distant galaxies, looking for the first generation of shining objects, hearing the possible signal from other civilizations, etc. Among these subjects, the most striking one could be pulsar study. Large scale survey by FAST will not only improve the statistics of the pulsar population, but also may offer us a good fortune to pick up more of the most exotic, even unknown types like a sub-millisecond pulsar or a neutron star -- black hole binary as the telescope is put into operation.

  18. Shallow Decay of X-ray Afterglows in Short GRBs: Energy Injection from a Millisecond Magnetar?

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    With the successful launch of Swift satellite, more and more data of early X-ray afterglows from short gamma-ray bursts have been collected. Some interesting features such as unusual afterglow light curves and unexpected X-ray flares are revealed. Especially, in some cases, there is a flat segment in the X-ray afterglow light curve. Here we present a simplified model in which we believe that the flattening part is due to energy injection from the central engine. We assume that this energy injection arises from the magnetic dipole radiation of a millisecond pulsar formed after the merger of two neutron stars. We check this model with the short GRB 060313. Our numerical results suggest that energy injection from a millisecond magnetar could make part of the X-ray afterglow light curve flat.

  19. Are pulsars born with a hidden magnetic field?

    CERN Document Server

    Torres-Forné, Alejandro; Pons, José A; Font, José A

    2015-01-01

    The observation of several neutron stars in the center of supernova remnants and with significantly lower values of the dipolar magnetic field than the average radio-pulsar population has motivated a lively debate about their formation and origin, with controversial interpretations. A possible explanation requires the slow rotation of the proto-neutron star at birth, which is unable to amplify its magnetic field to typical pulsar levels. An alternative possibility, the hidden magnetic field scenario, considers the accretion of the fallback of the supernova debris onto the neutron star as responsible for the submergence (or screening) of the field and its apparently low value. In this paper we study under which conditions the magnetic field of a neutron star can be buried into the crust due to an accreting, conducting fluid. For this purpose, we consider a spherically symmetric calculation in general relativity to estimate the balance between the incoming accretion flow and the magnetosphere. Our study analyse...

  20. Pulsar Ephemerides for Timing LAT Pulsars

    Data.gov (United States)

    National Aeronautics and Space Administration — Timing pulsars with the LAT requires the use of an ephemeris that covers the time period being analyzed. Below are several resources to provide this useful input to...

  1. Pulsars in Globular Clusters

    CERN Document Server

    Camilo, F; Camilo, Fernando; Rasio, Frederic A.

    2005-01-01

    More than 100 radio pulsars have been detected in 24 globular clusters. The largest observed samples are in Terzan 5 and 47 Tucanae, which together contain 45 pulsars. Accurate timing solutions, including positions in the cluster, are known for many of these pulsars. Here we provide an observational overview of some properties of pulsars in globular clusters, as well as properties of the globular clusters with detected pulsars. The many recent detections also provide a new opportunity to re-examine theoretically the formation and evolution of recycled pulsars in globular clusters. Our brief review considers the most important dynamical interaction and binary evolution processes: collisions, exchange interactions, mass transfer, and common-envelope phases.

  2. An ultraluminous X-ray source powered by an accreting neutron star

    DEFF Research Database (Denmark)

    Bachetti, M.; Harrison, F. A.; Walton, D. J.;

    2014-01-01

    the Eddington limit for a 1.4-solar-mass object, or more than ten times brighter than any known accreting pulsar. This implies that neutron stars may not be rare in the ultraluminous X-ray population, and it challenges physical models for the accretion of matter onto magnetized compact objects....

  3. Pulsars and Gravitational Waves

    CERN Document Server

    Lee, K J; Qiao, G J

    2011-01-01

    The relationship between pulsar-like compact stars and gravitational waves is briefly reviewed. Due to regular spins, pulsars could be useful tools for us to detect ~nano-Hz low-frequency gravitational waves by pulsar-timing array technique; besides, they would also be ~kilo-Hz high-frequency gravitational wave radiators because of their compactness. The wave strain of an isolate pulsar depends on the equation state of cold matter at supra-nuclear densities. Therefore, a real detection of gravitational wave should be very meaningful in gravity physics, micro-theory of elementary strong interaction, and astronomy.

  4. Arecibo Pulsar Survey Using ALFA. IV. Mock Spectrometer Data Analysis, Survey Sensitivity, and the Discovery of 41 Pulsars

    CERN Document Server

    Lazarus, P; Hessels, J W T; Karako-Argaman, C; Kaspi, V M; Lynch, R; Madsen, E; Patel, C; Ransom, S M; Scholz, P; Swiggum, J; Zhu, W W; Allen, B; Bogdanov, S; Camilo, F; Cardoso, F; Chatterjee, S; Cordes, J M; Crawford, F; Deneva, J S; Ferdman, R; Freire, P C C; Jenet, F A; Knispel, B; Lee, K J; van Leeuwen, J; Lorimer, D R; Lyne, A G; McLaughlin, M A; Siemens, X; Spitler, L G; Stairs, I H; Stovall, K; Venkataraman, A

    2015-01-01

    The on-going PALFA survey at the Arecibo Observatory began in 2004 and is searching for radio pulsars in the Galactic plane at 1.4 GHz. Observations since 2009 have been made with new wider-bandwidth spectrometers than were previously employed in this survey. A new data reduction pipeline has been in place since mid-2011 which consists of standard methods using dedispersion, searches for accelerated periodic sources, and search for single pulses, as well as new interference-excision strategies and candidate selection heuristics. This pipeline has been used to discover 41 pulsars, including 8 millisecond pulsars (MSPs; P = 100 ms that gradually becomes up to a factor of ~10 worse for P > 4 s at DM < 150 pc/cc. This degradation of sensitivity at long periods is largely due to red noise. We find that 35 +- 3% of pulsars are missed despite being bright enough to be detected in the absence of red noise. This reduced sensitivity could have implications on estimates of the number of long-period pulsars in the Gal...

  5. Detectability of rotation-powered pulsars in future hard X-ray surveys

    Institute of Scientific and Technical Information of China (English)

    Wei Wang

    2009-01-01

    Recent INTEGRAL/IBIS hard X-ray surveys have detected about 10 young pulsars.We show hard X-ray properties of these 10 young pulsars,which have a luminosity of 10~(33)-10~(37) erg s~(-1) and a photon index of 1.6-2.1 in the energy range of 20-100 keV.The correlation between X-ray luminosity and spin-down power of L_X∝ L_(sd)~(1.31) suggests that the hard X-ray emission in rotation-powered pulsars is dominated by the pulsar wind nebula (PWN) component.Assuming spectral properties are similar in 20-100keV and 2-10 keV for both the pulsar and PWN components,the hard X-ray luminosity and flux of 39 known young X-ray pulsars and 8 millisecond pulsars are obtained,and a correlation of L_X ∝ L_(sd)~(1.5) is derived.About 20 known young X-ray pulsars and 1 millisecond pulsars could be detected with future INTEGRAL and HXMT surveys.We also carry out Monte Carlo simulations of hard X-ray pulsars in the Galaxy and the Gould Belt,assuming values for the pulsar birth rate,initial position,proper motion velocity,period,and magnetic field distribution and evolution based on observational statistics and the L_X - L_(sd) relations: L_X∝ L_(sd)~(1.31) and L_X∝ L_(sd)~(1.5).More than 40 young pulsars (mostly in the Galactic plane) could be detected after ten years of INTEGRAL surveys and the launch of HXMT.So,the young pulsars would be a significant part of the hard X-ray source population in the sky,and will contribute to unidentified hard X-ray sources in present and future hard X-ray surveys by INTEGRAL and HXMT.

  6. Spectroscopic Studies of X-Ray Binary Pulsars

    Indian Academy of Sciences (India)

    F. Nagase

    2002-03-01

    Several new features of X-ray binary pulsars are revealed from recent observations with ASCA, RXTE, BeppoSAX and other X-ray observatories. Among these, I will review in this paper some recent progress in spectroscopic studies of accreting X-ray pulsars in binary systems (XBPs). First, I will discuss soft excess features observed in the energy spectra of XBPs and propose that it is a common feature for various subclasses of XBPs. Next I will present some recent results of high resolution spectroscopy with ASCA and Chandra.

  7. Newly Commissioned Green Bank Telescope Bags New Pulsars

    Science.gov (United States)

    2002-01-01

    Astronomers using the National Science Foundation's newly commissioned Robert C. Byrd Green Bank Telescope (GBT) have discovered a windfall of three previously undetected millisecond pulsars in a dense cluster of stars in the Milky Way Galaxy. The Green Bank Telescope The Robert C. Byrd Green Bank Telescope "This globular cluster, known as Messier 62, has been very well studied, and it would have been an exciting discovery to find just one new pulsar. The fact that we were able to detect three new pulsars at one time is simply remarkable," said Bryan Jacoby, a graduate student at the California Institute of Technology who led the research team. Results of the discovery were recently announced in an International Astronomical Union Circular. Jacoby and his colleague Adam Chandler, also a graduate student at Caltech, used the GBT to search for new pulsars in addition to the three already known in this cluster. Their research was part of the GBT's Early Science Program, which allows scientific investigations during the testing and commissioning of the telescope. The researchers used the Berkeley-Caltech Pulsar Machine, a new instrument whose development was overseen by Donald Backer at the University of California at Berkeley, to process the signals from the GBT and record them for later analysis. After their data were analyzed, the researchers discovered the telltale signatures of three additional pulsars and their white dwarf companion stars. Pulsars are rapidly rotating neutron stars that emit intense beams of radio waves along their misaligned magnetic axes. When these beams intersect the Earth, we see the pulsar flash on and off. Due to their exquisitely steady rotation, pulsars allow astronomers to study the basic laws of physics and the ways in which these dense clusters and exotic stellar systems are formed. Astronomers study globular clusters because they are among the oldest building blocks of our Galaxy. With their very dense stellar populations, these

  8. Reverse shock emission driven by post-merger millisecond magnetar winds: Effects of the magnetization parameter

    Science.gov (United States)

    Liu, L. D.; Wang, L. J.; Dai, Z. G.

    2016-08-01

    The study of short-duration gamma-ray bursts provides growing evidence that a good fraction of double neutron star mergers lead to the formation of stable millisecond magnetars. The launch of Poynting flux by the millisecond magnetars could leave distinct electromagnetic signatures that reveal the energy dissipation processes in the magnetar wind. In previous studies, we assume that the magnetar wind becomes completely lepton-dominated so that electrons/positrons in the magnetar wind are accelerated by a diffusive shock. However, theoretical modeling of pulsar wind nebulae shows that in many cases the magnetic field energy in the pulsar wind may be strong enough to suppress diffusive shock acceleration. In this paper, we investigate the reverse shock emission and the forward shock emission with an arbitrary magnetization parameter σ of a magnetar wind. We find that the reverse shock emission strongly depends on σ, and in particular that σ ~ 0.3 leads to the strongest reverse shock emission. Future observations would be helpful to diagnose the composition of the magnetar wind.

  9. The Unusual Binary Pulsar PSR J1744-3922: Radio Flux Variability, Near-Infrared Observation, and Evolution

    Science.gov (United States)

    Breton, R. P.; Roberts, M. S. E.; Ransom, S. M.; Kaspi, V. M.; Durant, M.; Bergeron, P.; Faulkner, A. J.

    2007-06-01

    PSR J1744-3922 is a binary pulsar exhibiting highly variable pulsed radio emission. We report on a statistical multifrequency study of the pulsed radio flux variability which suggests that this phenomenon is extrinsic to the pulsar and possibly tied to the companion, although not strongly correlated with orbital phase. The pulsar has an unusual combination of characteristics compared to typical recycled pulsars: a long spin period (172 ms); a relatively high magnetic field strength (1.7×1010 G); a very circular, compact orbit of 4.6 hr; and a low-mass companion (0.08 Msolar). These spin and orbital properties are likely inconsistent with standard evolutionary models. We find similarities between the properties of the PSR J1744-3922 system and those of several other known binary pulsar systems, motivating the identification of a new class of binary pulsars. We suggest that this new class could result from: a standard accretion scenario of a magnetar or a high magnetic field pulsar; common envelope evolution with a low-mass star and a neutron star, similar to what is expected for ultracompact X-ray binaries; or accretion induced collapse of a white dwarf. We also report the detection of a possible K'=19.30(15) infrared counterpart at the position of the pulsar, which is relatively bright if the companion is a helium white dwarf at the nominal distance, and discuss its implications for the pulsar's companion and evolutionary history.

  10. The PALFA Survey: Going to great depths to find radio pulsars

    CERN Document Server

    Lazarus, P; Bhat, N D R; Bogdanov, S; Bouchard, A; Brazier, A; Camilo, F; Cardoso, F; Chatterjee, S; Cordes, J M; Crawford, F; Deneva, J S; Desvignes, G; Freire, P C C; Hessels, J W T; Jenet, F A; Kaspi, V M; Knispel, B; van Leeuwen, J; Lorimer, D R; Lynch, R; Lyne, A G; McLaughlin, M A; Nice, D J; Ransom, S M; Scholz, P; Siemens, X; Stairs, I H; Stappers, B W; Stovall, K; Swiggum, J

    2012-01-01

    The on-going PALFA survey is searching the Galactic plane (|b| < 5 deg., 32 < l < 77 deg. and 168 < l < 214 deg.) for radio pulsars at 1.4 GHz using ALFA, the 7-beam receiver installed at the Arecibo Observatory. By the end of August 2012, the PALFA survey has discovered 100 pulsars, including 17 millisecond pulsars (P < 30 ms). Many of these discoveries are among the pulsars with the largest DM/P ratios, proving that the PALFA survey is capable of probing the Galactic plane for millisecond pulsars to a much greater depth than any previous survey. This is due to the survey's high sensitivity, relatively high observing frequency, and its high time and frequency resolution. Recently the rate of discoveries has increased, due to a new more sensitive spectrometer, two updated complementary search pipelines, the development of online collaborative tools, and access to new computing resources. Looking forward, focus has shifted to the application of artificial intelligence systems to identify puls...

  11. The High Time Resolution Universe surveys for pulsars and fast transients

    CERN Document Server

    Keith, Michael J

    2012-01-01

    The High Time Resolution Universe survey for pulsars and transients is the first truly all-sky pulsar survey, taking place at the Parkes Radio Telescope in Australia and the Effelsberg Radio Telescope in Germany. Utilising multibeam receivers with custom built all-digital recorders the survey targets the fastest millisecond pulsars and radio transients on timescales of 64 us to a few seconds. The new multibeam digital filter-bank system at has a factor of eight improvement in frequency resolution over previous Parkes multibeam surveys, allowing us to probe further into the Galactic plane for short duration signals. The survey is split into low, mid and high Galactic latitude regions. The mid-latitude portion of the southern hemisphere survey is now completed, discovering 107 previously unknown pulsars, including 26 millisecond pulsars. To date, the total number of discoveries in the combined survey is 135 and 29 MSPs. These discoveries include the first magnetar to be discovered by it's radio emission, unusua...

  12. High sensitivity pulsar search

    International Nuclear Information System (INIS)

    The planning, implementation, and results from a highly sensitive, automated search for new pulsars are discussed. This research effort was begun with a study of the relevant signal detection theory, and the conclusions reached are presented. The general procedures developed were specifically tailored for use on a high speed minicomputer, and produced a search relatively free from observational selection effects. The actual computer coding of these procedures is also described, with emphasis on how the required speed and efficiency of these routines was obtained. The final system applied over half a million different matched digital filters to the data obtained from each successive telescope beam area. Use of this search system at the 1000 foot telescope of the Arecibo Observatory resulted in the detection of 50 pulsars, 40 of which were not previously known. Parameters are presented for these new pulsars. The relatively limited range in dispersion measure exhibited by this pulsar sample is used, along with other evidence, to infer a reduced number density of pulsars at distances beyond approximately 10 kpc from the galactic center. By far the most interesting individual pulsar discovered in the course of this search was PSR 1913+16. Large periodic variations in the observed pulsation period of this pulsar are interpreted in terms of doppler shifts associated with its orbital motion about some companion object. The data analysis methods employed to arrive at the current observational description of this system are discussed, along with a review of the theoretical conclusions that are based on this description

  13. The Scaling of the RMS with Dwell Time in NANOGrav Pulsars

    CERN Document Server

    Handzo, Emma; Lommen, Andrea N; Perrodin, Delphine

    2015-01-01

    Pulsar Timing Arrays (PTAs) are collections of well-timed millisecond pulsars that are being used as detectors of gravitational waves (GWs). Given current sensitivity, projected improvements in PTAs and the predicted strength of the GW signals, the detection of GWs with PTAs could occur within the next decade. One way we can improve a PTA is to reduce the measurement noise present in the pulsar timing residuals. If the pulsars included in the array display uncorrelated noise, the root mean square (RMS) of the timing residuals is predicted to scale as $\\mathrm{T}^{-1/2}$, where T is the dwell time per observation. In this case, the sensitivity of the array can be increased by increasing T. We studied the 17 pulsars in the five year North American Nanohertz Observatory for Gravitational Waves (NANOGrav) data set to determine if the noise in the timing residuals of the pulsars observed was consistent with this property. For comparison, we performed the same analysis on PSR B1937+21, a pulsar that is known to dis...

  14. Gravitational Waves from Known Pulsars: Results from the Initial Detector Era

    Science.gov (United States)

    Aasi, J.; Abadie, J.; Abbott, B. P.; Abbott, R.; Abbott, T.; Abernathy, M. R.; Accadia, T.; Acernese, F.; Adams, C.; Adams, T.; Adhikari, R. X.; Affeldt, C.; Agathos, M.; Aggarwal, N.; Aguiar, O. D.; Ajith, P.; Allen, B.; Allocca, A.; Ceron, E. A.; Blackburn, L.; Camp, J. B.; Gehrels, N.; Graff, P. B.; Kanner, J. B.; Hobbs, G. B.

    2014-01-01

    We present the results of searches for gravitational waves from a large selection of pulsars using data from the most recent science runs (S6, VSR2 and VSR4) of the initial generation of interferometric gravitational wave detectors LIGO (Laser Interferometric Gravitational-wave Observatory) and Virgo. We do not see evidence for gravitational wave emission from any of the targeted sources but produce upper limits on the emission amplitude. We highlight the results from seven young pulsars with large spin-down luminosities. We reach within a factor of five of the canonical spin-down limit for all seven of these, whilst for the Crab and Vela pulsars we further surpass their spin-down limits. We present new or updated limits for 172 other pulsars (including both young and millisecond pulsars). Now that the detectors are undergoing major upgrades, and, for completeness, we bring together all of the most up-to-date results from all pulsars searched for during the operations of the first-generation LIGO, Virgo and GEO600 detectors. This gives a total of 195 pulsars including the most recent results described in this paper.

  15. The Parkes Pulsar Timing Array and detection of gravitational waves

    Science.gov (United States)

    Manchester, R.

    Gravitational waves are an important prediction of Einstein s general theory of relativity Evidence for their existence has come from observations of orbit decay in double-neutron-star binary systems but up to now despite huge efforts there has been no direct detection of these waves In collaboration with groups from the Swinburne University of Technology Melbourne and the University of Texas Brownsville we have embarked on a major project to establish the Parkes Pulsar Timing Array PPTA with the principal goal of making a direct detection of gravitational waves of astronomical origin The project involves making precision timing observations of 20 millisecond pulsars at intervals of 2 -- 3 weeks using the Parkes 64-m radio telescope Observations are made at three radio frequencies 685 1400 and 3100 MHz to allow correction for interstellar propagation effects The PPTA is most sensitive to gravitational waves with frequencies in the nanoHertz range and hence is complementary to ground- and space-based laser interferometer systems Simulations suggest that if timing precisions of order 100 nanoseconds can be reached for most of the observed sample over a 5-year data span the stochastic background of gravitational waves from super-massive binary black holes in the cores of galaxies should be detectable Currently we have achieved this level of precision for 3 or 4 pulsars and sub-microsecond precision for a further 8 or 9 pulsars Improved hardware and software systems under development will hopefully allow us to reach our goal The PPTA

  16. Versatile directional searches for gravitational waves with Pulsar Timing Arrays

    Science.gov (United States)

    Madison, D. R.; Zhu, X.-J.; Hobbs, G.; Coles, W.; Shannon, R. M.; Wang, J. B.; Tiburzi, C.; Manchester, R. N.; Bailes, M.; Bhat, N. D. R.; Burke-Spolaor, S.; Dai, S.; Dempsey, J.; Keith, M.; Kerr, M.; Lasky, P.; Levin, Y.; Osłowski, S.; Ravi, V.; Reardon, D.; Rosado, P.; Spiewak, R.; van Straten, W.; Toomey, L.; Wen, L.; You, X.

    2016-02-01

    By regularly monitoring the most stable millisecond pulsars over many years, pulsar timing arrays (PTAs) are positioned to detect and study correlations in the timing behaviour of those pulsars. Gravitational waves (GWs) from supermassive black hole binaries (SMBHBs) are an exciting potentially detectable source of such correlations. We describe a straightforward technique by which a PTA can be `phased-up' to form time series of the two polarization modes of GWs coming from a particular direction of the sky. Our technique requires no assumptions regarding the time-domain behaviour of a GW signal. This method has already been used to place stringent bounds on GWs from individual SMBHBs in circular orbits. Here, we describe the methodology and demonstrate the versatility of the technique in searches for a wide variety of GW signals including bursts with unmodelled waveforms. Using the first six years of data from the Parkes Pulsar Timing Array, we conduct an all-sky search for a detectable excess of GW power from any direction. For the lines of sight to several nearby massive galaxy clusters, we carry out a more detailed search for GW bursts with memory, which are distinct signatures of SMBHB mergers. In all cases, we find that the data are consistent with noise.

  17. Versatile Directional Searches for Gravitational Waves with Pulsar Timing Arrays

    CERN Document Server

    Madison, D R; Hobbs, G; Coles, W; Shannon, R M; Wang, J; Tiburzi, C; Manchester, R N; Bailes, M; Bhat, N D R; Burke-Spolaor, S; Dai, S; Dempsey, J; Keith, M; Kerr, M; Lasky, P; Levin, Y; Oslowski, S; Ravi, V; Reardon, D; Rosado, P; Spiewak, R; van Straten, W; Toomey, L; Wen, L; You, X

    2015-01-01

    By regularly monitoring the most stable millisecond pulsars over many years, pulsar timing arrays (PTAs) are positioned to detect and study correlations in the timing behaviour of those pulsars. Gravitational waves (GWs) from supermassive black hole binaries (SMBHBs) are an exciting potentially detectable source of such correlations. We describe a straight-forward technique by which a PTA can be "phased-up" to form time series of the two polarisation modes of GWs coming from a particular direction of the sky. Our technique requires no assumptions regarding the time-domain behaviour of a GW signal. This method has already been used to place stringent bounds on GWs from individual SMBHBs in circular orbits. Here, we describe the methodology and demonstrate the versatility of the technique in searches for a wide variety of GW signals including bursts with unmodeled waveforms. Using the first six years of data from the Parkes Pulsar Timing Array, we conduct an all-sky search for a detectable excess of GW power fr...

  18. Geriatric Pulsar Still Kicking

    Science.gov (United States)

    2009-02-01

    The oldest isolated pulsar ever detected in X-rays has been found with NASA's Chandra X-ray Observatory. This very old and exotic object turns out to be surprisingly active. The pulsar, PSR J0108-1431 (J0108 for short) is about 200 million years old. Among isolated pulsars -- ones that have not been spun-up in a binary system -- it is over 10 times older than the previous record holder with an X-ray detection. At a distance of 770 light years, it is one of the nearest pulsars known. Pulsars are born when stars that are much more massive than the Sun collapse in supernova explosions, leaving behind a small, incredibly weighty core, known as a neutron star. At birth, these neutron stars, which contain the densest material known in the Universe, are spinning rapidly, up to a hundred revolutions per second. As the rotating beams of their radiation are seen as pulses by distant observers, similar to a lighthouse beam, astronomers call them "pulsars". Astronomers observe a gradual slowing of the rotation of the pulsars as they radiate energy away. Radio observations of J0108 show it to be one of the oldest and faintest pulsars known, spinning only slightly faster than one revolution per second. The surprise came when a team of astronomers led by George Pavlov of Penn State University observed J0108 in X-rays with Chandra. They found that it glows much brighter in X-rays than was expected for a pulsar of such advanced years. People Who Read This Also Read... Chandra Data Reveal Rapidly Whirling Black Holes Milky Way’s Giant Black Hole Awoke from Slumber 300 Years Ago Erratic Black Hole Regulates Itself Celebrate the International Year of Astronomy Some of the energy that J0108 is losing as it spins more slowly is converted into X-ray radiation. The efficiency of this process for J0108 is found to be higher than for any other known pulsar. "This pulsar is pumping out high-energy radiation much more efficiently than its younger cousins," said Pavlov. "So, although it

  19. Pulsars and Extreme Physics

    Science.gov (United States)

    Bell-Burnell, Jocelyn

    2004-10-01

    Pulsars were discovered 35 years ago. What do we know about them now, and what have they taught us about the extremes of physics? With an average density comparable to that of the nucleus, magnetic fields around 108 T and speeds close to c these objects have stretched our understanding of the behaviour of matter. They serve as extrememly accurate clocks with which to carry out precision experiments in relativity. Created in cataclysmic explosions, pulsars are a (stellar) form of life after death. After half a billion revolutions most pulsars finally die, but amazingly some are born again to yet another, even weirder, afterlife. Pulsar research continues lively, delivering exciting, startling and almost unbelievable results!

  20. Detection of Gravitational Waves through Observations of a Group of Pulsars

    CERN Document Server

    Rodin, Alexander E

    2011-01-01

    We suggest a new approach to the detection of gravitational waves using observations of a group of millisecond pulsars. In contrast to the usual method, based on increasing the accuracy of the arrival times of pulses by excluding possible distorting factors, our method supposes that the additive phase noise that is inevitably present even in the most accurate observational data has various spectral components, which have characteristic amplitudes and begin to appear on different time scales. We use the "Caterpillar" (Singular Spectral Analysis, SSA) method to decompose the signal into its components. Our initial data are the residuals of the pulse arrival times for six millisecond pulsars. We constructed the angular correlation function for components of the decomposition of a given number, whose theoretical form for the case of an isotropic and homogeneous gravitational-wave background is known. The individual decomposition components show a statistically significant agreement with the theoretical expectatio...

  1. Elementary Wideband Timing of Radio Pulsars

    Science.gov (United States)

    Pennucci, Timothy T.; Demorest, Paul B.; Ransom, Scott M.

    2014-08-01

    We present an algorithm for the simultaneous measurement of a pulse time-of-arrival (TOA) and dispersion measure (DM) from folded wideband pulsar data. We extend the prescription from Taylor's 1992 work to accommodate a general two-dimensional template "portrait," the alignment of which can be used to measure a pulse phase and DM. We show that there is a dedispersion reference frequency that removes the covariance between these two quantities and note that the recovered pulse profile scaling amplitudes can provide useful information. We experiment with pulse modeling by using a Gaussian-component scheme that allows for independent component evolution with frequency, a "fiducial component," and the inclusion of scattering. We showcase the algorithm using our publicly available code on three years of wideband data from the bright millisecond pulsar J1824-2452A (M28A) from the Green Bank Telescope, and a suite of Monte Carlo analyses validates the algorithm. By using a simple model portrait of M28A, we obtain DM trends comparable to those measured by more standard methods, with improved TOA and DM precisions by factors of a few. Measurements from our algorithm will yield precisions at least as good as those from traditional techniques, but is prone to fewer systematic effects and is without ad hoc parameters. A broad application of this new method for dispersion measure tracking with modern large-bandwidth observing systems should improve the timing residuals for pulsar timing array experiments, such as the North American Nanohertz Observatory for Gravitational Waves.

  2. Pulse Portraiture: Pulsar timing

    Science.gov (United States)

    Pennucci, Timothy T.; Demorest, Paul B.; Ransom, Scott M.

    2016-06-01

    Pulse Portraiture is a wideband pulsar timing code written in python. It uses an extension of the FFTFIT algorithm (Taylor 1992) to simultaneously measure a phase (TOA) and dispersion measure (DM). The code includes a Gaussian-component-based portrait modeling routine. The code uses the python interface to the pulsar data analysis package PSRCHIVE (ascl:1105.014) and also requires the non-linear least-squares minimization package lmfit (ascl:1606.014).

  3. Why study pulsars optically?

    OpenAIRE

    Shearer, A.; Golden, A

    2002-01-01

    Observations of the five confirmed optical pulsars indicate that the peak emission scales according to the magnetic field strength at the light cylinder. To the accuracy that such low number allows we show that this gives further confirmation that a straightforward synchrotron model such as Pacini & Salvati (1987) still has validity. The derived relationships indicates that the emission mechanism is common across all of the pulsars and towards the edge of the light cylinder. In the future obs...

  4. Eclipsing Binary Pulsars

    CERN Document Server

    Freire, P C C

    2004-01-01

    The first eclipsing binary pulsar, PSR B1957+20, was discovered in 1987. Since then, 13 other eclipsing low-mass binary pulsars have been found, 12 of these are in globular clusters. In this paper we list the known eclipsing binary pulsars and their properties, with special attention to the eclipsing systems in 47 Tuc. We find that there are two fundamentally different groups of eclipsing binary pulsars; separated by their companion masses. The less massive systems (M_c ~ 0.02 M_sun) are a product of predictable stellar evolution in binary pulsars. The systems with more massive companions (M_c ~ 0.2 M_sun) were formed by exchange encounters in globular clusters, and for that reason are exclusive to those environments. This class of systems can be used to learn about the neutron star recycling fraction in the globular clusters actively forming pulsars. We suggest that most of these binary systems are undetectable at radio wavelengths.

  5. Revised Pulsar Spindown

    CERN Document Server

    Contopoulos, I; Contopoulos, Ioannis; Spitkovsky, Anatoly

    2005-01-01

    We address the issue of electromagnetic pulsar spindown by combining our experience from the two limiting idealized cases which have been studied in great extent in the past: that of an aligned rotator where ideal MHD conditions apply, and that of a misaligned rotator in vacuum. We construct a spindown formula that takes into account the misalignment of the magnetic and rotation axes, and the magnetospheric particle acceleration gaps. We show that near the death line aligned rotators spin down much slower than orthogonal ones. In order to test this approach, we use a simple Monte Carlo method to simulate the evolution of pulsars and find a good fit to the observed pulsar distribution in the P-Pdot diagram without invoking magnetic field decay. Our model may also account for individual pulsars spinning down with braking index n 3, and that the older pulsar population has preferentially smaller magnetic inclination angles. We discuss possible signatures of such alignment in the existing pulsar data.

  6. Detection of Gravitational Waves through Observations of a Group of Pulsars

    OpenAIRE

    Rodin, Alexander E.

    2010-01-01

    We suggest a new approach to the detection of gravitational waves using observations of a group of millisecond pulsars. In contrast to the usual method, based on increasing the accuracy of the arrival times of pulses by excluding possible distorting factors, our method supposes that the additive phase noise that is inevitably present even in the most accurate observational data has various spectral components, which have characteristic amplitudes and begin to appear on different time scales. ...

  7. The Green Bank Telescope 350 MHz Drift-scan Survey I: Survey Observations and the Discovery of 13 Pulsars

    CERN Document Server

    Boyles, Jason; Ransom, Scott M; Stairs, Ingrid H; Lorimer, Duncan R; McLaughlin, Maura A; Hessels, Jason W T; Kaspi, Vicky M; Kondratiev, Vlad I; Archibald, Anne; Berndsen, Aaron; Cardoso, Rogerio F; Cherry, Angus; McPhee, Christie A; Pennucci, Tim; Roberts, Mallory S E; Stovall, Kevin; van Leeuwen, Joeri

    2012-01-01

    Over the summer of 2007, we obtained 1191 hours of `drift-scan' pulsar search observations with the Green Bank Telescope at a radio frequency of 350 MHz. Here we describe the survey setup, search procedure, and the discovery and follow-up timing of thirteen pulsars. Among the new discoveries, one (PSR J1623-0841) was discovered only through its single pulses, two (PSRs J1327-0755 and J1737-0814) are millisecond pulsars, and another (PSR J2222-0137) is a mildly recycled pulsar. PSR J1327-0755 is a 2.7 ms pulsar at a DM of 27.9 pc cm^{-3} in a 8.7 day orbit with a minimum companion mass of 0.22$ solar mass. PSR J1737-0814 is a 4.2 ms pulsar at a DM of 55.3 pc cm^{-3} in a 79.3 day orbit with a minimum companion mass of 0.06 solar mass. PSR J2222$-$0137 is a 32.8 ms pulsar at a very low DM of 3.27 pc cm^{-3} in a 2.4 day orbit with a minimum companion mass of 1.11 solar mass. It is most likely a white dwarf-neutron star system or an unusual low-eccentricity double neutron star system. Ten other pulsars discovere...

  8. The formation of low-mass helium white dwarfs orbiting pulsars: Evolution of low-mass X-ray binaries below the bifurcation period

    CERN Document Server

    Istrate, Alina; Langer, Norbert

    2014-01-01

    Millisecond pulsars (MSPs) are generally believed to be old neutron stars (NSs) which have been spun up to high rotation rates via accretion of matter from a companion star in a low-mass X-ray binary (LMXB). However, many details of this recycling scenario remain to be understood. Here we investigate binary evolution in close LMXBs to study the formation of radio MSPs with low-mass helium white dwarf companions (He WDs) in tight binaries with orbital periods P_orb = 2-9 hr. In particular, we examine: i) if such observed systems can be reproduced from theoretical modelling using standard prescriptions of orbital angular momentum losses (i.e. with respect to the nature and the strength of magnetic braking), ii) if our computations of the Roche-lobe detachments can match the observed orbital periods, and iii) if the correlation between WD mass and orbital period (M_WD, P_orb) is valid for systems with P_orb < 2 days. Numerical calculations with a detailed stellar evolution code were used to trace the mass-tra...

  9. A Search for Very High-Energy Gamma Rays from the Missing Link Binary Pulsar J1023+0038 with VERITAS

    CERN Document Server

    Aliu, E; Archer, A; Benbow, W; Bird, R; Biteau, J; Buchovecky, M; Buckley, J H; Bugaev, V; Byrum, K; Cardenzana, J V; Cerruti, M; Chen, X; Ciupik, L; Connolly, M P; Cui, W; Dickinson, H J; Eisch, J D; Falcone, A; Feng, Q; Finley, J P; Fleischhack, H; Flinders, A; Fortin, P; Fortson, L; Furniss, A; Gillanders, G H; Griffin, S; Grube, J; Gyuk, G; Hütten, M; Håkansson, N; Holder, J; Humensky, T B; Johnson, C A; Kaaret, P; Kar, P; Kelley-Hoskins, N; Kertzman, M; Kieda, D; Krause, M; Lang, M J; Loo, A; Maier, G; McArthur, S; McCann, A; Meagher, K; Moriarty, P; Mukherjee, R; Nguyen, T; Nieto, D; de Bhróithe, A O'Faoláin; Ong, R A; Otte, A N; Pandel, D; Park, N; Pelassa, V; Petrashyk, A; Pohl, M; Popkow, A; Pueschel, E; Quinn, J; Ragan, K; Reynolds, P T; Richards, G T; Roache, E; Rulten, C; Santander, M; Sembroski, G H; Shahinyan, K; Smith, A W; Staszak, D; Telezhinsky, I; Tucci, J V; Tyler, J; Varlotta, A; Vincent, S; Wakely, S P; Weiner, O M; Weinstein, A; Wilhelm, A; Williams, D A; Zitzer, B; Chernyakova, M; Roberts, M

    2016-01-01

    The binary millisecond radio pulsar PSR J1023+0038 exhibits many characteristics similar to the gamma-ray binary system PSR B1259--63/LS 2883, making it an ideal candidate for the study of high-energy non-thermal emission. It has been the subject of multi-wavelength campaigns following the disappearance of the pulsed radio emission in 2013 June, which revealed the appearance of an accretion disk around the neutron star. We present the results of very high-energy gamma-ray observations carried out by VERITAS before and after this change of state. Searches for steady and pulsed emission of both data sets yield no significant gamma-ray signal above 100 GeV, and upper limits are given for both a steady and pulsed gamma-ray flux. These upper limits are used to constrain the magnetic field strength in the shock region of the PSR J1023+0038 system. Assuming that very high-energy gamma rays are produced via an inverse-Compton mechanism in the shock region, we constrain the shock magnetic field to be greater than $\\si...

  10. Prospects for high-precision pulsar timing with the new Effelsberg PSRIX backend

    Science.gov (United States)

    Lazarus, P.; Karuppusamy, R.; Graikou, E.; Caballero, R. N.; Champion, D. J.; Lee, K. J.; Verbiest, J. P. W.; Kramer, M.

    2016-05-01

    The PSRIX backend is the primary pulsar timing instrument of the Effelsberg 100 m radio telescope since early 2011. This new ROACH-based system enables bandwidths up to 500 MHz to be recorded, significantly more than what was possible with its predecessor, the Effelsberg-Berkeley Pulsar Processor (EBPP). We review the first four years of PSRIX timing data for 33 pulsars collected as part of the monthly European Pulsar Timing Array (EPTA) observations. We describe the automated data analysis pipeline, COASTGUARD, that we developed to reduce these observations. We also introduce TOASTER, the EPTA timing data base, used to store timing results, processing information and observation metadata. Using these new tools, we measure the phase-averaged flux densities at 1.4 GHz of all 33 pulsars. For seven of these pulsars, our flux density measurements are the first values ever reported. For the other 26 pulsars, we compare our flux density measurements with previously published values. By comparing PSRIX data with EBPP data, we find an improvement of ˜2-5 times in signal-to-noise ratio, which translates to an increase of ˜2-5 times in pulse time-of-arrival (TOA) precision. We show that such an improvement in TOA precision will improve the sensitivity to the stochastic gravitational wave background. Finally, we showcase the flexibility of the new PSRIX backend by observing several millisecond-period pulsars (MSPs) at 5 and 9 GHz. Motivated by our detections, we discuss the potential for complementing existing pulsar timing array data sets with MSP monitoring campaigns at these higher frequencies.

  11. SAX J1808.4-3657 in quiescence: A keystone for neutron star science

    NARCIS (Netherlands)

    C.O. Heinke; C.J. Deloye; P.G. Jonker; R.E. Taam; R. Wijnands

    2007-01-01

    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

  12. Gamma-rays from nebulae around binary systems containing energetic rotation powered pulsars

    CERN Document Server

    Bednarek, W

    2013-01-01

    We consider nebulae which are created around binary systems containing rotation powered pulsars and companion stars with strong stellar winds. It is proposed that the stellar and pulsar winds have to mix at some distance from the binary system, defined by the orbital period of the companion stars and the velocity of the stellar wind. The mixed pulsar-stellar wind expands with a specific velocity determined by the pulsar power and the mass loss rate of the companion star. Relativistic particles, either from the inner pulsar magnetosphere and/or accelerated at the shocks between stellar and pulsar winds, are expected to be captured and isotropized in the reference frame of the mixed wind. Therefore, they can efficiently comptonize stellar radiation producing GeV-TeV $\\gamma$-rays in the inverse Compton process. We calculate the $\\gamma$-ray spectra expected in such scenario for the two example binary systems: J1816+4510 which is the redback type millisecond binary and LS 5039 which is supposed to contain energe...

  13. Gravitational-waves from known pulsars: results from the initial detector era

    CERN Document Server

    Aasi, J; Abbott, B P; Abbott, R; Abbott, T; Abernathy, M R; Accadia, T; Acernese, F; Adams, C; Adams, T; Adhikari, R X; Agathos, M; Affeldt, C; Aggarwal, N; Aguiar, O D; Ajith, P; Allen, B; Allocca, A; Ceron, E Amador; Amariutei, D; Anderson, R A; Anderson, S B; Anderson, W G; Arai, K; Araya, M C; Arceneaux, C; Areeda, J; Ast, S; Aston, S M; Astone, P; Aufmuth, P; Aulbert, C; Austin, L; Aylott, B E; Babak, S; Baker, P T; Ballardin, G; Ballmer, S W; Barayoga, J C; Barker, D; Barnum, S H; Barone, F; Barr, B; Barsotti, L; Barsuglia, M; Barton, M A; Bartos, I; Bassiri, R; Basti, A; Batch, J; Bauchrowitz, J; Bauer, Th S; Bebronne, M; Behnke, B; Bejger, M; Beker, M G; Bell, A S; Bell, C; Belopolski, I; Bergmann, G; Berliner, J M; Bertolini, A; Bessis, D; Betzwieser, J; Beyersdorf, P T; Bhadbhade, T; Bilenko, I A; Billingsley, G; Birch, J; Bitossi, M; Bizouard, M A; Black, E; Blackburn, J K; Blackburn, L; Blair, D; Blom, M; Bock, O; Bodiya, T P; Boer, M; Bogan, C; Bond, C; Bondu, F; Bonelli, L; Bonnand, R; Bork, R; Born, M; Boschi, V; Bose, S; Bosi, L; Bowers, J; Bradaschia, C; Brady, P R; Braginsky, V B; Branchesi, M; Brannen, C A; Brau, J E; Breyer, J; Briant, T; Bridges, D O; Brillet, A; Brinkmann, M; Brisson, V; Britzger, M; Brooks, A F; Brown, D A; Brown, D D; Brüeckner, F; Bulik, T; Buonanno, A; Bulten, H J; Buskulic, D; Buy, C; Byer, R L; Cadonati, L; Cagnoli, G; Bustillo, J Calderón; Calloni, E; Camp, J B; Campsie, P; Cannon, K C; Canuel, B; Cao, J; Capano, C D; Carbognani, F; Carbone, L; Caride, S; Castiglia, A; Caudill, S; Cavaglià, M; Cavalier, F; Cavalieri, R; Cella, G; Cepeda, C; Cesarini, E; Chakraborty, R; Chalermsongsak, T; Chao, S; Charlton, P; Chassande-Mottin, E; Chen, X; Chen, Y; Chincarini, A; Chiummo, A; Cho, H S; Chow, J; Christensen, N; Chu, Q; Chua, S S Y; Chung, S; Ciani, G; Clara, F; Clark, D E; Clark, J A; Cleva, F; Coccia, E; Cohadon, P -F; Colla, A; Colombini, M; Constancio, M; Conte, A; Conte, R; Cook, D; Corbitt, T R; Cordier, M; Cornish, N; Corsi, A; Costa, C A; Coughlin, M W; Coulon, J -P; Countryman, S; Couvares, P; Coward, D M; Cowart, M; Coyne, D C; Craig, K; Creighton, J D E; Creighton, T D; Crowder, S G; Cumming, A; Cuoco, E; Cunningham, L; D'Antonio, S; Dahl, K; Canton, T Dal; Damjanic, M; Danilishin, S L; Danzmann, K; Dattilo, V; Daudert, B; Daveloza, H; Davier, M; Davies, G S; Daw, E J; Day, R; Dayanga, T; De Rosa, R; Debreczeni, G; Degallaix, J; Del Pozzo, W; Deleeuw, E; Deléglise, S; Denker, T; Dent, T; Dereli, H; Dergachev, V; DeRosa, R; DeSalvo, R; Dhurandhar, S; Di Fiore, L; Di Lieto, A; Di Palma, I; Di Virgilio, A; Díaz, M; Dietz, A; Dmitry, K; Donovan, F; Dooley, K L; Doravari, S; Drago, M; Drever, R W P; Driggers, J C; Du, Z; Dumas, J -C; Dwyer, S; Eberle, T; Edwards, M; Effler, A; Ehrens, P; Eichholz, J; Eikenberry, S S; Endrőczi, G; Essick, R; Etzel, T; Evans, K; Evans, M; Evans, T; Factourovich, M; Fafone, V; Fairhurst, S; Fang, Q; Farr, B; Farr, W; Favata, M; Fazi, D; Fehrmann, H; Feldbaum, D; Ferrante, I; Ferrini, F; Fidecaro, F; Finn, L S; Fiori, I; Fisher, R; Flaminio, R; Foley, E; Foley, S; Forsi, E; Forte, L A; Fotopoulos, N; Fournier, J -D; Franco, S; Frasca, S; Frasconi, F; Frede, M; Frei, M; Frei, Z; Freise, A; Frey, R; Fricke, T T; Fritschel, P; Frolov, V V; Fujimoto, M -K; Fulda, P; Fyffe, M; Gair, J; Gammaitoni, L; Garcia, J; Garufi, F; Gehrels, N; Gemme, G; Genin, E; Gennai, A; Gergely, L; Ghosh, S; Giaime, J A; Giampanis, S; Giardina, K D; Giazotto, A; Gil-Casanova, S; Gill, C; Gleason, J; Goetz, E; Goetz, R; Gondan, L; González, G; Gordon, N; Gorodetsky, M L; Gossan, S; Goßler, S; Gouaty, R; Graef, C; Graff, P B; Granata, M; Grant, A; Gras, S; Gray, C; Greenhalgh, R J S; Gretarsson, A M; Griffo, C; Groot, P; Grote, H; Grover, K; Grunewald, S; Guidi, G M; Guido, C; Gushwa, K E; Gustafson, E K; Gustafson, R; Hall, B; Hall, E; Hammer, D; Hammond, G; Hanke, M; Hanks, J; Hanna, C; Hanson, J; Harms, J; Harry, G M; Harry, I W; Harstad, E D; Hartman, M T; Haughian, K; Hayama, K; Heefner, J; Heidmann, A; Heintze, M; Heitmann, H; Hello, P; Hemming, G; Hendry, M; Heng, I S; Heptonstall, A W; Heurs, M; Hild, S; Hoak, D; Hodge, K A; Holt, K; Holtrop, M; Hong, T; Hooper, S; Horrom, T; Hosken, D J; Hough, J; Howell, E J; Hu, Y; Hua, Z; Huang, V; Huerta, E A; Hughey, B; Husa, S; Huttner, S H; Huynh, M; Huynh-Dinh, T; Iafrate, J; Ingram, D R; Inta, R; Isogai, T; Ivanov, A; Iyer, B R; Izumi, K; Jacobson, M; James, E; Jang, H; Jang, Y J; Jaranowski, P; Jiménez-Forteza, F; Johnson, W W; Jones, D; Jones, D I; Jones, R; Jonker, R J G; Ju, L; K, Haris; Kalmus, P; Kalogera, V; Kandhasamy, S; Kang, G; Kanner, J B; Kasprzack, M; Kasturi, R; Katsavounidis, E; Katzman, W; Kaufer, H; Kaufman, K; Kaw, P; Kawabe, K; Kawamura, S; Kawazoe, F; Kéfélian, F; Keitel, D; Kelley, D B; Kells, W; Keppel, D G; Khalaidovski, A; Khalili, F Y; Khazanov, E A; Kim, B K; Kim, C; Kim, K; Kim, N; Kim, W; Kim, Y -M; King, E; King, P J; Kinzel, D L; Kissel, J S; Klimenko, S; Kline, J; Koehlenbeck, S; Kokeyama, K; Kondrashov, V; Koranda, S; Korth, W Z; Kowalska, I; Kozak, D; Kremin, A; Kringel, V; Królak, A; Krishnan, B; Kucharczyk, C; Kudla, S; Kuehn, G; Kumar, A; Kumar, P; Kumar, R; Kurdyumov, R; Kwee, P; Landry, M; Lantz, B; Larson, S; Lasky, P D; Lawrie, C; Lazzarini, A; Roux, A Le; Leaci, P; Lebigot, E O; Lee, C -H; Lee, H K; Lee, H M; Lee, J; Leonardi, M; Leong, J R; Leroy, N; Letendre, N; Levine, B; Lewis, J B; Lhuillier, V; Li, T G F; Lin, A C; Littenberg, T B; Litvine, V; Liu, F; Liu, H; Liu, Y; Liu, Z; Lloyd, D; Lockerbie, N A; Lockett, V; Lodhia, D; Loew, K; Logue, J; Lombardi, A L; Lorenzini, M; Loriette, V; Lormand, M; Losurdo, G; Lough, J; Luan, J; Lubinski, M J; Lück, H; Lundgren, A P; Macarthur, J; Macdonald, E; Machenschalk, B; MacInnis, M; Macleod, D M; Magana-Sandoval, F; Mageswaran, M; Mailand, K; Majorana, E; Maksimovic, I; Malvezzi, V; Man, N; Manca, G M; Mandel, I; Mandic, V; Mangano, V; Mantovani, M; Marchesoni, F; Marion, F; Márka, S; Márka, Z; Markosyan, A; Marque, J; Maros, E; Martelli, F; Martin, I W; Martin, R M; Martinelli, L; Martynov, D; Marx, J N; Mason, K; Masserot, A; Massinger, T J; Matichard, F; Matone, L; Matzner, R A; Mavalvala, N; May, G; Mazumder, N; Mazzolo, G; McCarthy, R; McClelland, D E; McGuire, S C; McIntyre, G; McIver, J; Meacher, D; Meadors, G D; Meidam, J; Mehmet, M; Meier, T; Melatos, A; Mendell, G; Mercer, R A; Meshkov, S; Messenger, C; Meyer, M S; Miao, H; Michel, C; Mikhailov, E; Milano, L; Miller, J; Minenkov, Y; Mingarelli, C M F; Mishra, C; Mitra, S; Mitrofanov, V P; Mitselmakher, G; Mittleman, R; Moe, B; Mohan, M; Mohapatra, S R P; Mokler, F; Moraru, D; Moreno, G; Morgado, N; Mori, T; Morriss, S R; Mossavi, K; Mours, B; Mow-Lowry, C M; Mueller, C L; Mueller, G; Mukherjee, S; Mullavey, A; Munch, J; Murphy, D; Murray, P G; Mytidis, A; Nagy, M F; Kumar, D Nanda; Nardecchia, I; Nash, T; Naticchioni, L; Nayak, R; Necula, V; Nelemans, G; Neri, I; Neri, M; Newton, G; Nguyen, T; Nishida, E; Nishizawa, A; Nitz, A; Nocera, F; Nolting, D; Normandin, M E; Nuttall, L K; Ochsner, E; O'Dell, J; Oelker, E; Ogin, G H; Oh, J J; Oh, S H; Ohme, F; Oppermann, P; O'Reilly, B; Larcher, W Ortega; O'Shaughnessy, R; Osthelder, C; Ottaway, D J; Ottens, R S; Ou, J; Overmier, H; Owen, B J; Padilla, C; Pai, A; Palomba, C; Pan, Y; Pankow, C; Paoletti, F; Paoletti, R; Papa, M A; Paris, H; Pasqualetti, A; Passaquieti, R; Passuello, D; Patel, P; Pedraza, M; Peiris, P; Penn, S; Perreca, A; Phelps, M; Pichot, M; Pickenpack, M; Piergiovanni, F; Pierro, V; Pinard, L; Pindor, B; Pinto, I M; Pitkin, M; Poeld, J; Poggiani, R; Poole, V; Poux, C; Predoi, V; Prestegard, T; Price, L R; Prijatelj, M; Principe, M; Privitera, S; Prix, R; Prodi, G A; Prokhorov, L; Puncken, O; Punturo, M; Puppo, P; Quetschke, V; Quintero, E; Quitzow-James, R; Raab, F J; Rabeling, D S; Rácz, I; Radkins, H; Raffai, P; Raja, S; Rajalakshmi, G; Rapagnani, P; Rakhmanov, M; Ramet, C; Raymond, V; Re, V; Reed, C M; Reed, T; Regimbau, T; Reid, S; Reitze, D H; Ricci, F; Riesen, R; Riles, K; Robertson, N A; Robinet, F; Rocchi, A; Roddy, S; Rodriguez, C; Rodruck, M; Roever, C; Rolland, L; Rollins, J G; Romano, J D; Romano, R; Romanov, G; Romie, J H; Rosińska, D; Rowan, S; Rüdiger, A; Ruggi, P; Ryan, K; Salemi, F; Sammut, L; Sandberg, V; Sanders, J; Sannibale, V; Santiago-Prieto, I; Saracco, E; Sassolas, B; Sathyaprakash, B S; Saulson, P R; Savage, R; Schilling, R; Schnabel, R; Schofield, R M S; Schreiber, E; Schuette, D; Schulz, B; Schutz, B F; Schwinberg, P; Scott, J; Scott, S M; Seifert, F; Sellers, D; Sengupta, A S; Sentenac, D; Sergeev, A; Shaddock, D; Shah, S; Shahriar, M S; Shaltev, M; Shapiro, B; Shawhan, P; Shoemaker, D H; Sidery, T L; Siellez, K; Siemens, X; Sigg, D; Simakov, D; Singer, A; Singer, L; Sintes, A M; Skelton, G R; Slagmolen, B J J; Slutsky, J; Smith, J R; Smith, M R; Smith, R J E; Smith-Lefebvre, N D; Soden, K; Son, E J; Sorazu, B; Souradeep, T; Sperandio, L; Staley, A; Steinert, E; Steinlechner, J; Steinlechner, S; Steplewski, S; Stevens, D; Stochino, A; Stone, R; Strain, K A; Straniero, N; Strigin, S; Stroeer, A S; Sturani, R; Stuver, A L; Summerscales, T Z; Susmithan, S; Sutton, P J; Swinkels, B; Szeifert, G; Tacca, M; Talukder, D; Tang, L; Tanner, D B; Tarabrin, S P; Taylor, R; ter Braack, A P M; Thirugnanasambandam, M P; Thomas, M; Thomas, P; Thorne, K A; Thorne, K S; Thrane, E; Tiwari, V; Tokmakov, K V; Tomlinson, C; Toncelli, A; Tonelli, M; Torre, O; Torres, C V; Torrie, C I; Travasso, F; Traylor, G; Tse, M; Ugolini, D; Unnikrishnan, C S; Vahlbruch, H; Vajente, G; Vallisneri, M; Brand, J F J van den; Broeck, C Van Den; van der Putten, S; van der Sluys, M V; van Heijningen, J; van Veggel, A A; Vass, S; Vasúth, M; Vaulin, R; Vecchio, A; Vedovato, G; Veitch, J; Veitch, P J; Venkateswara, K; Verkindt, D; Verma, S; Vetrano, F; Viceré, A; Vincent-Finley, R; Vinet, J -Y; Vitale, S; Vlcek, B; Vo, T; Vocca, H; Vorvick, C; Vousden, W D; Vrinceanu, D; Vyachanin, S P; Wade, A; Wade, L; Wade, M; Waldman, S J; Walker, M; Wallace, L; Wan, Y; Wang, J; Wang, M; Wang, X; Wanner, A; Ward, R L; Was, M; Weaver, B; Wei, L -W; Weinert, M; Weinstein, A J; Weiss, R; Welborn, T; Wen, L; Wessels, P; West, M; Westphal, T; Wette, K; Whelan, J T; Whitcomb, S E; White, D J; Whiting, B F; Wibowo, S; Wiesner, K; Wilkinson, C; Williams, L; Williams, R; Williams, T; Willis, J L; Willke, B; Wimmer, M; Winkelmann, L; Winkler, W; Wipf, C C; Wittel, H; Woan, G; Worden, J; Yablon, J; Yakushin, I; Yamamoto, H; Yancey, C C; Yang, H; Yeaton-Massey, D; Yoshida, S; Yum, H; Yvert, M; Zadrożny, A; Zanolin, M; Zendri, J -P; Zhang, F; Zhang, L; Zhao, C; Zhu, H; Zhu, X J; Zotov, N; Zucker, M E; Zweizig, J; Buchner, S; Cognard, I; Corongiu, A; D'Amico, N; Espinoza, C M; Freire, P C C; Gotthelf, E V; Guillemot, L; Hessels, J W T; Hobbs, G B; Kramer, M; Lommen, A N; Lyne, A G; Marshall, F E; Possenti, A; Ransom, S M; Ray, P S; Roy, J; Stappers, B W

    2013-01-01

    We present the results of searches for gravitational-waves from a large selection of pulsars using data from the most recent science runs (S6, VSR2 and VSR4) of the initial generation of interferometric gravitational-wave detectors LIGO (Laser Interferometric Gravitational-wave Observatory) and Virgo. We do not see evidence for gravitational-wave emission from any of the targeted sources but produce upper limits on the emission amplitude. We highlight the results from seven young pulsars with large spin-down luminosities. We reach within a factor of five of the canonical spin-down limit for all seven of these, whilst for the Crab and Vela pulsars we further surpass their spin-down limits. We present new or updated limits for 172 other pulsars (including both young and millisecond pulsars). Now that the detectors are undergoing major upgrades, and, for completeness, we bring together all of the most up-to-date results from all pulsars searched for during the operations of the first-generation LIGO, Virgo and G...

  14. The GBT350 Survey of the Northern Galactic Plane for Radio Pulsars and Transients

    CERN Document Server

    Hessels, J W T; Kaspi, V M; Roberts, M S E; Champion, D J; Stappers, B W

    2007-01-01

    Using the Green Bank Telescope (GBT) and Pulsar Spigot at 350MHz, we have surveyed the Northern Galactic Plane for pulsars and radio transients. This survey covers roughly 1000 square degrees of sky within 75 deg < l < 165 deg and |b| < 5.5 deg, a region of the Galactic Plane inaccessible to both the Parkes and Arecibo multibeam surveys. The large gain of the GBT along with the high time and frequency resolution provided by the Spigot make this survey more sensitive by factors of about 4 to slow pulsars and more than 10 to millisecond pulsars (MSPs), compared with previous surveys of this area. In a preliminary, reduced-resolution search of all the survey data, we have discovered 33 new pulsars, almost doubling the number of known pulsars in this part of the Galaxy. While most of these sources were discovered by normal periodicity searches, 5 of these sources were first identified through single, dispersed bursts. We discuss the interesting properties of some of these new sources. Data processing usi...

  15. Alternancia entre el estado de emisión de Rayos-X y Pulsar en Sistemas Binarios Interactuantes

    Science.gov (United States)

    De Vito, M. A.; Benvenuto, O. G.; Horvath, J. E.

    2015-08-01

    Redbacks belong to the family of binary systems in which one of the components is a pulsar. Recent observations show redbacks that have switched their state from pulsar - low mass companion (where the accretion of material over the pulsar has ceased) to low mass X-ray binary system (where emission is produced by the mass accretion on the pulsar), or inversely. The irradiation effect included in our models leads to cyclic mass transfer episodes, which allow close binary systems to switch between one state to other. We apply our results to the case of PSR J1723-2837, and discuss the need to include new ingredients in our code of binary evolution to describe the observed state transitions.

  16. Flares from Galactic Centre pulsars: a new class of X-ray transients?

    Science.gov (United States)

    Giannios, Dimitrios; Lorimer, Duncan R.

    2016-06-01

    Despite intensive searches, the only pulsar within 0.1 pc of the central black hole in our Galaxy, Sgr A*, is a radio-loud magnetar. Since magnetars are rare among the Galactic neutron star population, and a large number of massive stars are already known in this region, the Galactic Centre (GC) should harbour a large number of neutron stars. Population syntheses suggest several thousand neutron stars may be present in the GC. Many of these could be highly energetic millisecond pulsars which are also proposed to be responsible for the GC gamma-ray excess. We propose that the presence of a neutron star within 0.03 pc from Sgr A* can be revealed by the shock interactions with the disc around the central black hole. As we demonstrate, these interactions result in observable transient non-thermal X-ray and gamma-ray emission over time-scales of months, provided that the spin-down luminosity of the neutron star is Lsd ˜ 1035 erg s-1. Current limits on the population of normal and millisecond pulsars in the GC region suggest that a number of such pulsars are present with such luminosities.

  17. Fast radio bursts as giant pulses from young rapidly rotating pulsars

    Science.gov (United States)

    Lyutikov, Maxim; Burzawa, Lukasz; Popov, Sergei B.

    2016-10-01

    We discuss possible association of fast radio bursts (FRBs) with supergiant pulses emitted by young pulsars (ages ˜ tens to hundreds of years) born with regular magnetic field but very short - few milliseconds - spin periods. We assume that FRBs are extra-Galactic events coming from distances d ≲ 100 Mpc and that most of the dispersion measure (DM) comes from the material in the freshly ejected SNR shell. We then predict that for a given burst the DM should decrease with time and that FRBs are not expected to be seen below ˜300 MHz due to free-free absorption in the expanding ejecta. A supernova might have been detected years before the burst; FRBs are mostly associated with star-forming galaxies. The model requires that some pulsars are born with very fast spins, of the order of few milliseconds. The observed distribution of spin-down powers dot{E} in young energetic pulsars is consistent with equal birth rate per decade of dot{E}. Accepting this injection distribution and scaling the intrinsic brightness of FRBs with dot{E}, we predict the following properties of a large sample of FRBs: (i) the brightest observed events come from a broad distribution in distances; (ii) for repeating bursts brightness either remains nearly constant (if the spin-down time is longer than the age of the pulsar) or decreases with time otherwise; in the latter case DM ∝ dot{E}.

  18. 1FGL J0523.5-2529: A New Probable Gamma-ray Pulsar Binary

    CERN Document Server

    Strader, Jay; Sonbas, Eda; Sokolovsky, Kirill; Sand, David J; Moskvitin, Alexander S; Cheung, C C

    2014-01-01

    We report optical photometric and SOAR spectroscopic observations of an X-ray source found within the localization error of the Fermi-LAT unidentified gamma-ray source J0523.5-2529. The optical data show periodic flux modulation and radial velocity variations indicative of a binary with a 16.5-hr period. The data suggest a massive non-degenerate secondary (~> 0.8 M_sun), and we argue the source is likely a pulsar binary. The radial velocities have good phase coverage and show evidence for a measurable eccentricity (e=0.04). There is no clear sign of irradiation of the secondary in either photometry or spectroscopy. The spatial location out of the Galactic plane and gamma-ray luminosity of the source are more consistent with classification as a recycled millisecond pulsar than as a young pulsar. Future radio timing observations can confirm the identity of the primary and further characterize this interesting system.

  19. 2FGL J1653.6-0159: A New Low in Evaporating Pulsar Binary Periods

    CERN Document Server

    Romani, Roger W; Cenko, S Bradley

    2014-01-01

    We have identified an optical binary with orbital period P_b=4488s as the probable counterpart of the Fermi source 2FGL J1653.6-0159. Although pulsations have not yet been detected, the source properties are consistent with an evaporating millisecond pulsar binary; this P_b=75min is the record low for a spin-powered system. The heated side of the companion shows coherent radial velocity variations, with amplitude K=666.9+/-7.5 km/s for a large mass function of f(M)=1.60+/-0.05 M_sun. This heating suggests a pulsar luminosity ~3x10^34 erg/s. The colors and spectra show additional hard emission dominating at binary minimum. This system is similar to PSR J1311-3430, with a low mass H-depleted companion, a dense shrouding wind and, likely, a large pulsar mass.

  20. Theory of wind accretion

    OpenAIRE

    Shakura N.I.; Postnov K.A.; Kochetkova A.Yu.; Hjalmarsdotter L.

    2013-01-01

    A review of wind accretion in high-mass X-ray binaries is presented. We focus attention to different regimes of quasi-spherical accretion onto the neutron star: the supersonic (Bondi) accretion, which takes place when the captured matter cools down rapidly and falls supersonically toward NS magnetospghere, and subsonic (settling) accretion which occurs when plasma remains hot until it meets the magnetospheric boundary. Two regimes of accretion are separated by an X-ray luminosity of about $4\\...

  1. Pulsars: Gigantic Nuclei

    CERN Document Server

    Xu, Renxin

    2011-01-01

    What is the real nature of pulsars? This is essentially a question of the fundamental strong interaction between quarks at low-energy scale and hence of the non-perturbative quantum chromo-dynamics, the solution of which would certainly be meaningful for us to understand one of the seven millennium prize problems (i.e., "Yang-Mills Theory") named by the Clay Mathematical Institute. After a historical note, it is argued here that a pulsar is very similar to an extremely big nucleus, but is a little bit different from the {\\em gigantic nucleus} speculated 80 years ago by L. Landau. The paper demonstrates the similarity between pulsars and gigantic nuclei from both points of view: the different manifestations of compact stars and the general behavior of the strong interaction.

  2. Pulsar lensing geometry

    CERN Document Server

    Liu, Siqi; Macquart, J-P; Brisken, Walter; Deller, Adam

    2015-01-01

    Our analysis of archival VLBI data of PSR 0834+06 revealed that its scintillation properties can be precisely modelled using the inclined sheet model (Pen & Levin 2014), resulting in two distinct lens planes. These data strongly favour the grazing sheet model over turbulence as the primary source of pulsar scattering. This model can reproduce the parameters of the observed diffractive scintillation with an accuracy at the percent level. Comparison with new VLBI proper motion results in a direct measure of the ionized ISM screen transverse velocity. The results are consistent with ISM velocities local to the PSR 0834+06 sight-line (through the Galaxy). The simple 1D structure of the lenses opens up the possibility of using interstellar lenses as precision probes for pulsar lens mapping, precision transverse motions in the ISM, and new opportunities for removing scattering to improve pulsar timing. We describe the parameters and observables of this double screen system. While relative screen distances can i...

  3. Particle acceleration by pulsars

    International Nuclear Information System (INIS)

    The evidence that pulsars accelerate relativistic particles is reviewed, with emphasis on the γ-ray observations. The current state of knowledge of acceleration in strong waves is summarized, with emphasis on the inability of consistent theories to accelerate very high energy particles without converting too much energy into high energy photons. The state of viable models for pair creation by pulsars is summarized, with the conclusion that pulsars very likely lose rotational energy in winds instead of in superluminous strong waves. The relation of the pair creation models to γ-ray observations and to soft X-ray observations of pulsars is outlined, with the conclusion that energetically viable models may exist, but none have yet yielded useful agreement with the extant data. Some paths for overcoming present problems are discussed. The relation of the favored models to cosmic rays is discussed. It is pointed out that the pairs made by the models may have observable consequences for observation of positrons in the local cosmic ray flux and for observations of the 511 keV line from the interstellar medium. Another new point is that asymmetry of plasma supply from at least one of the models may qualitatively explain the gross asymmetry of the X-ray emission from the Crab nebula. It is also argued that acceleration of cosmic ray nuclei by pulsars, while energetically possible, can occur only at the boundary of the bubbles blown by the pulsars, if the cosmic ray composition is to be anything like that of the known source spectrum

  4. A cold neutron star in the transient low-mass X-ray binary HETE J1900.1-2455 after 10 years of active accretion

    CERN Document Server

    Degenaar, N; Reynolds, M T; Wijnands, R; Page, D

    2016-01-01

    The neutron star low-mass X-ray binary and intermittent millisecond X-ray pulsar HETE J1900.1-2455 returned to quiescence in late 2015, after a prolonged accretion outburst of ~10 yr. Using a Chandra observation taken ~180 d into quiescence we detect the source at a luminosity of ~4.5E31 (D/4.7 kpc)^2 erg/s (0.5-10 keV). The X-ray spectrum can be described by a neutron star atmosphere model with a temperature of ~54 eV for an observer at infinity. We perform thermal evolution calculations based on the 2016 quiescent data and a <98 eV temperature upper limit inferred from a Swift observation taken during an unusually brief (<2 weeks) quiescent episode in 2007. We find no evidence in the present data that the thermal properties of the crust, such as the heating rate and thermal conductivity, are different than those of non-pulsating neutron stars. Finding this neutron star so cold after its long outburst imposes interesting constraints on the heat capacity of the stellar core; these become even stronger i...

  5. The Pulsar Search Collaboratory

    CERN Document Server

    Rosen, Rachel; McLaughlin, Maura A; Lynch, Ryan; Kondratiev, Vlad I; Boyles, Jason R; Wilson, M Terry; Lorimer, Duncan R; Ransom, Scott; 10.3847/AER2010004

    2010-01-01

    The Pulsar Search Collaboratory [PSC, NSF #0737641] is a joint project between the National Radio Astronomy Observatory (NRAO) and West Virginia University (WVU) designed to interest high school students in science, technology, engineering, and mathematics [STEM] related career paths by helping them to conduct authentic scientific research. The 3- year PSC program, which began in summer 2008, teaches students to analyze astronomical radio data acquired with the 100-m Robert C. Byrd Green Bank Telescope for the purpose of discovering new pulsars. We present the results of the first complete year of the PSC, which includes two astronomical discoveries.

  6. Pulsars in FIRST Observations

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    We identify 16 pulsars from the Survey of Faint Images of the Radio Sky at Twenty-cm (FIRST) at 1.4 GHz. Their positions and total flux densities are extracted from the FIRST catalog. By comparing the source positions with those in the PSR catalog, we obtain better determined positions of PSR J1022+1001,J1518+4904, J1652+2651, and proper motion upper limits of PSR J0751+1807,J1012+5307, and J1640+2224. The proper motions of the other ten pulsars are consistent with the catalog values.

  7. Pulsars: Cosmic Permanent 'Neutromagnets'?

    CERN Document Server

    Hansson, Johan

    2011-01-01

    We argue that pulsars may be spin-polarized neutron stars, i.e. cosmic permanent magnets. This would simply explain several observational facts about pulsars, including the 'beacon effect' itself i.e. the static/stable misalignment of rotational and magnetic axes, the extreme temporal stability of the pulses and the existence of an upper limit for the magnetic field strength - coinciding with the one observed in "magnetars". Although our model admittedly is speculative, this latter fact seems to us unlikely to be pure coincidence.

  8. Goals, Strategies and First Discoveries of AO327, the Arecibo All-Sky 327 MHz Drift Pulsar Survey

    CERN Document Server

    Deneva, J S; McLaughlin, M A; Bates, S D; Freire, P C C; Martinez, J G; Jenet, F; Bagchi, M

    2013-01-01

    We report initial results from AO327, a drift survey for pulsars with the Arecibo telescope at 327 MHz. The first phase of AO327 will cover the sky at declinations of -1 to 28 degrees, excluding the region within 5 degrees of the Galactic plane, where high scattering and dispersion make low-frequency surveys sub-optimal. We record data from a 57 MHz bandwidth with 1024 channels and 125 us sampling time. The 60 s transit time through the AO327 beam means that the survey is sensitive to very tight relativistic binaries even with no acceleration searches. To date we have detected 44 known pulsars with periods ranging from 3 ms to 2.21 s and discovered 24 new pulsars. The new discoveries include three millisecond pulsars, three objects with periods of a few tens of milliseconds typical of young as well as mildly recycled pulsars, a nuller, and a rotating radio transient. Five of the new discoveries are in binary systems. The second phase of AO327 will cover the sky at declinations of 28 to 38 degrees. We compare ...

  9. Millisecond Oscillations During Thermonuclear X-ray Bursts

    CERN Document Server

    Muno, M P

    2004-01-01

    I review the basic phenomenology and theory of the millisecond brightness oscillations observed during thermonuclear X-ray bursts from 13 of approximately 70 accreting neutron stars in low-mass X-ray binaries. Compelling observations indicate that the oscillations are produced by surface brightness patterns on the rapidly rotating neutron stars. However, it remains to be understood (1) why the brightness patterns producing them persist for up to 15 s during an X-ray burst, whereas the burning should cover the entire surface in less than 1 s, and (2) why the frequencies drift upward by about 5 Hz during the course of the burst. These peculiarities can probably be explained by taking into account the expansion of the surface layers caused by the burning, zonal flows that form due to pressure gradients between the equator and poles, and Rossby-Alfven modes that are excited in the surface ocean. Further progress toward understanding how burning progresses on the surface of the neutron star can be made with a next...

  10. THE ELECTROMAGNETIC MODEL OF SHORT GRBs, THE NATURE OF PROMPT TAILS, SUPERNOVA-LESS LONG GRBs, AND HIGHLY EFFICIENT EPISODIC ACCRETION

    Energy Technology Data Exchange (ETDEWEB)

    Lyutikov, Maxim [Department of Physics, Purdue University, 525 Northwestern Avenue, West Lafayette, IN 47907-2036 (United States)

    2013-05-01

    Many short gamma-ray bursts (GRBs) show prompt tails lasting up to hundreds of seconds that can be energetically dominant over the initial sub-second spike. In this paper we develop an electromagnetic model of short GRBs that explains the two stages of the energy release, the prompt spike and the prompt tail. The key ingredient of the model is the recent discovery that an isolated black hole can keep its open magnetic flux for times much longer than the collapse time and thus can spin down electromagnetically, driving the relativistic wind. First, the merger is preceded by an electromagnetic precursor wind with total power L{sub p} Almost-Equal-To (((GM{sub NS}){sup 3}B{sub NS}{sup 2})/c{sup 5}R){proportional_to}(-t){sup - Vulgar-Fraction-One-Quarter }, reaching 3 Multiplication-Sign 10{sup 44} erg s{sup -1} for typical neutron star masses of 1.4 M{sub Sun} and magnetic fields B {approx} 10{sup 12} G. If a fraction of this power is converted into pulsar-like coherent radio emission, this may produce an observable radio burst of a few milliseconds (like the Lorimer burst). At the active stage of the merger, two neutron stars produce a black hole surrounded by an accretion torus in which the magnetic field is amplified to {approx}10{sup 15} G. This magnetic field extracts the rotational energy of the black hole and drives an axially collimated electromagnetic wind that may carry of the order of 10{sup 50} erg, limited by the accretion time of the torus, a few hundred milliseconds. For observers nearly aligned with the orbital normal this is seen as a classical short GRB. After the accretion of the torus, the isolated black hole keeps the open magnetic flux and drives the equatorially (not axially) collimated outflow, which is seen by an observer at intermediate polar angles as a prompt tail. The tail carries more energy than the prompt spike, but its emission is de-boosted for observers along the orbital normal. Observers in the equatorial plane miss the prompt spike

  11. The dynamic of stellar wind accretion and the HMXB zoo

    Science.gov (United States)

    Walter, Roland; Manousakis, Antonios

    2016-07-01

    The dynamic of the accretion of stellar wind on the pulsar in Vela X-1 is dominated by unstable hydrodynamical flows. Off-states, 10^{37} erg/s flares, quasi-periodic oscillations and log normal flux distribution can all be reproduced by hydrodynamical simulations and reveal the complex motion of bow shocks moving either towards or away from the neutron star. These behaviors are enlightening the zoo of HMXB and suggest new phenomenology to be detected.

  12. Review of overall parameters of giant radio pulses from the Crab pulsar and B1937+21

    CERN Document Server

    Bilous, A V; Popov, M V; Soglasnov, V A

    2007-01-01

    We present a review of observed parameters of giant radio pulses, based on the observations conducted by our group during recent years. The observations cover a broad frequency range of about 3 octaves, concentrating between 600 and 4850 MHz. Giant pulses of both the Crab pulsar and the millisecond pulsar B1937+21 were studied with the 70-m Tidbinbilla, the 100-m GBT, 64-m Kalyazin and Westerbork radio telescopes. We discuss pulse energy distribution, dependence of peak flux density from the pulse width, peculiarities of radio spectra, and polarization properties of giant radio pulses.

  13. The Pulsar Search Collaboratory

    Science.gov (United States)

    Rosen, R.; Heatherly, S.; McLaughlin, M. A.; Kondratiev, V. I.; Boyles, J. R.; Wilson, M.; Lorimer, D. R.; Lynch, R.; Ransom, S.

    2010-01-01

    The Pulsar Search Collaboratory (PSC) (NSF #0737641) is a joint project between the National Radio Astronomy Observatory and West Virginia University designed to interest high school students in science, technology, engineering, and mathematics related career paths by helping them to conduct authentic scientific research. The 3 year PSC program,…

  14. Student Discovers New Pulsar

    Science.gov (United States)

    2010-01-01

    A West Virginia high-school student has discovered a new pulsar, using data from the giant Robert C. Byrd Green Bank Telescope (GBT). Shay Bloxton, 15, a participant in a project in which students analyze data from the radio telescope, spotted evidence of the pulsar on October 15. Bloxton, along with NRAO astronomers observed the object again one month later. The new observation confirmed that the object is a pulsar, a rotating, superdense neutron star. Bloxton is a sophomore at Nicholas County High School in Summersville, West Virginia. "I was very excited when I found out I had actually made a discovery," Bloxton said. She went to Green Bank in November to participate in the follow-up observation. She termed that visit "a great experience." "It also helped me learn a lot about how observations with the GBT are actually done," she added. The project in which she participated, called the Pulsar Search Collaboratory (PSC), is a joint project of the National Radio Astronomy Observatory (NRAO) and West Virginia University, funded by a grant from the National Science Foundation. Pulsars are known for their lighthouse-like beams of radio waves that sweep through space as the neutron star rotates, creating a pulse as the beam sweeps by the Earth. First discovered in 1967, pulsars serve as valuable natural "laboratories" for physicists studying exotic states of matter, quantum mechanics and General Relativity. The GBT, dedicated in 2000, has become one of the world's leading tools for discovering and studying pulsars. The PSC, led by NRAO Education Officer Sue Ann Heatherly and Project Director Rachel Rosen, includes training for teachers and student leaders, and provides parcels of data from the GBT to student teams. The project involves teachers and students in helping astronomers analyze data from 1500 hours of observing with the GBT. The 120 terabytes of data were produced by 70,000 individual pointings of the giant, 17-million-pound telescope. Some 300 hours of the

  15. A new look at Anomalous X-ray Pulsars

    CERN Document Server

    Bisnovatyi-Kogan, G S

    2014-01-01

    We explore a possibility to explain the phenomenon of the Anomalous X-ray Pulsars (AXP) and Soft Gamma-ray Repeaters (SGR) within the scenario of fall-back magnetic accretion onto a young isolated neutron star. The X-ray emission of the pulsar in this case is originated due to accretion of matter onto the surface of the neutron star from the magnetic slab surrounding its magnetosphere. The expected spin-down rate of the neutron star within this approach is close to the observed value. We show that these neutron stars are relatively young and are going through a transition from the propeller state to the accretor state. The pulsars activity in the gamma-rays is connected with their relative youth and is provided by the energy stored in the non-equilibrium layer located in the crust of low-mass neutron stars. This energy can be released due to mixing of matter in the neutron star crust with super heavy nuclei approaching its surface and getting unstable. The nuclei fission in the low-density region initiates ch...

  16. The Optimization of GBT Pulsar Data for the GBNCC Pulsar Survey

    Science.gov (United States)

    Gordon, Ashlee Nicole; Green Bank NRAO, GBNCC

    2016-01-01

    The Green Bank Telescope collects data from the Green Bank Northern Celestial Cap (GBNCC) pulsar survey in order to find new pulsars within its sensitivity and also, to confirm previously found pulsars within its sensitivity range. The collected data is then loaded into the CyberSKA website database where astronomers are tasked with rating the data sets based on its potential to be a pulsar from 0(unclassified), 1(class 1 pulsar), 2(class 2 pulsar), 3(class 3 pulsar), 4(radio frequency interference), 5(not a pulsar), 6(know pulsar), 7(harmonic of a known pulsar). This specific research done was to use previously classified pulsars to create a python script that will automatically identify the data set as a pulsar or a non-pulsar. After finding the recurring frequencies of radio frequency interference (RFI), the frequencies were then added to a pipeline to further discern pulsars from RFI.

  17. Hunting for Orphaned Central Compact Objects among Radio Pulsars

    CERN Document Server

    Luo, J; Ho, W C G; Bogdanov, S; Kaspi, V M; He, C

    2015-01-01

    Central compact objects (CCOs) are a handful of young neutron stars found at the center of supernova remnants (SNRs). They show high thermal X-ray luminosities but no radio emission. Spin-down rate measurements of the three CCOs with X-ray pulsations indicate surface dipole fields much weaker than those of typical young pulsars. To investigate if CCOs and known radio pulsars are objects at different evolutionary stages, we carried out a census of all weak-field (<1e11 G) isolated radio pulsars in the Galactic plane to search for CCO-like X-ray emission. None of the 12 candidates is detected at X-ray energies, with luminosity limits of 1e32-1e34 erg/s. We consider a scenario in which the weak surface fields of CCOs are due to rapid accretion of supernova materials and show that as the buried field diffuses back to the surface, a CCO descendant is expected to leave the P-Pdot parameter space of our candidates at a young age of a few times 10kyr. Hence, the candidates are likely to be just old ordinary pulsar...

  18. Time-dependent models of accretion discs with nuclear burning following the tidal disruption of a white dwarf by a neutron star

    Science.gov (United States)

    Margalit, Ben; Metzger, Brian D.

    2016-09-01

    We construct time-dependent one-dimensional (vertically averaged) models of accretion discs produced by the tidal disruption of a white dwarf (WD) by a binary neutron star (NS) companion. Nuclear reactions in the disc mid-plane burn the WD matter to increasingly heavier elements at sequentially smaller radii, releasing substantial energy which can impact the disc dynamics. A model for disc outflows is employed, by which cooling from the outflow balances other sources of heating (viscous, nuclear) in regulating the Bernoulli parameter of the mid-plane to a fixed value ≲0. We perform a comprehensive parameter study of the compositional yields and velocity distributions of the disc outflows for WDs of different initial compositions. For C/O WDs, the radial composition profile of the disc evolves self-similarly in a quasi-steady-state manner, and is remarkably robust to model parameters. The nucleosynthesis in helium WD discs does not exhibit this behaviour, which instead depends sensitively on factors controlling the disc mid-plane density (e.g. the strength of the viscosity, α). By the end of the simulation, a substantial fraction of the WD mass is unbound in outflows at characteristic velocities of ˜109 cm s-1. The outflows from WD-NS merger discs contain 10-4-3 × 10-3 M⊙ of radioactive 56Ni, resulting in fast (˜ week long) dim (˜1040 erg s-1) optical transients; shock heating of the ejecta by late-time outflows may increase the peak luminosity to ˜1043 erg s-1. The accreted mass on to the NS is probably not sufficient to induce gravitational collapse, but may be capable of spinning up the NS to periods of ˜10 ms, illustrating the feasibility of this channel in forming isolated millisecond pulsars.

  19. Why are pulsar planets rare?

    CERN Document Server

    Martin, Rebecca G; Palaniswamy, Divya

    2016-01-01

    Pulsar timing observations have revealed planets around only a few pulsars. We suggest that the rarity of these planets is due mainly to two effects. First, we show that the most likely formation mechanism requires the destruction of a companion star. Only pulsars with a suitable companion (with an extreme mass ratio) are able to form planets. Second, while a dead zone (a region of low turbulence) in the disk is generally thought to be essential for planet formation, it is most probably rare in disks around pulsars because of the irradiation from the pulsar. The irradiation strongly heats the inner parts of the disk pushing the inner boundary of the dead zone out. We suggest that the rarity of pulsar planets can be explained by the low probability for these two requirements - a very low-mass companion and a dead zone - to be satisfied.

  20. Magneto-Levitation Accretion in High Mass X-ray Binaries

    Science.gov (United States)

    Pustilnik, Lev; Beskrovnaya, Nina; Ikhsanov, Nazar; Kim, Vitally; Likh, Yuri

    A wind-fed accretion by a neutron star in a High Mass X-ray Binary is discussed. We show that the structure and physical parameters of the accretion flow onto the neutron star strongly depends on the magnetic field strength in the stellar wind of its massive companion. A neutron star accreting material from a magnetized wind is expected to be surrounded by a dense non-Keplerian disk (magnetic slab) in which the material is confined by the magnetic field of the accretion flow itself. The accretion process in this case is governed by anomalous (Bohm) diffusion. We find that spin evolution and equilibrium period of the pulsar within this magneto-levitation accretion scenario are consistent with the observed values.

  1. Astrophysical Mechanisms for Pulsar Spindown

    OpenAIRE

    Addison, Eric

    2011-01-01

    Pulsars are astrophysical sources of pulsed electromagnetic radiation. The pulses have a variety of shapes in the time-domain, and the pulse energy generally peaks in the radio spectrum. The accepted models theorize that pulsars are rapidly rotating neutron stars with strong dipolar magnetic fields. Current models predict that rotational kinetic energy is extracted from the pulsar in the form of electromagnetic and gravitational radiation, causing it to slowly lose rotational speed, or “spin ...

  2. Gamma radiation from radio pulsars

    Science.gov (United States)

    Ruderman, Malvin

    1990-01-01

    The probable magnetospheric location and source of the gamma ray emission from some young radiopulsars is discussed. The suggested evolution of this emission as a function of pulsar period gives a diminished gamma-ray luminosity for a more rapidly spinning pre-Crab pulsar. A greatly enhanced one, similar to that of unidentified Cos B sources, is predicted for a slightly slower post-Vela pulsar, followed by a relatively rapid quenching of the gamma-ray luminosity at still longer periods. Possible anomalous exo-magnetospheric pulsed MeV and TeV-PeV radiation from the Crab pulsar is considered.

  3. Pulsar Pair Cascades in Magnetic Fields with Offset Polar Caps

    Science.gov (United States)

    Harding, Alice K.; Muslimov, Alex G.

    2012-01-01

    Neutron star magnetic fields may have polar caps (PC) that are offset from the dipole axis, through field-line sweepback near the light cylinder or non-symmetric currents within the star. The effects of such offsets on electron-positron pair cascades are investigated, using simple models of dipole magnetic fields with small distortions that shift the PCs by different amounts or directions. Using a Monte Carlo pair cascade simulation, we explore the changes in the pair spectrum, multiplicity and energy flux across the PC, as well as the trends in pair flux and pair energy flux with spin-down luminosity, L(sub sd). We also give an estimate of the distribution of heating flux from returning positrons on the PC for different offsets. We find that even modest offsets can produce significant increases in pair multiplicity, especially for pulsars that are near or beyond the pair death lines for centered PCs, primarily because of higher accelerating fields. Pair spectra cover several decades in energy, with the spectral range of millisecond pulsars (MSPs) two orders of magnitude higher than for normal pulsars, and PC offsets allow significant extension of all spectra to lower pair energies. We find that the total PC pair luminosity L(sub pair) is proportional to L(sub sd), with L(sub pair) approximates 10(exp -3) L(sub sd) for normal pulsars and L(sub pair) approximates 10(exp -2) L(sub sd) for MSPs. Remarkably, the total PC heating luminosity for even large offsets increases by less than a factor of two, even though the PC area increases by much larger factors, because most of the heating occurs near the magnetic axis.

  4. Models of Pulsar Glitches

    CERN Document Server

    Haskell, Brynmor

    2015-01-01

    Radio pulsars provide us with some of the most stable clocks in the universe. Nevertheless several pulsars exhibit sudden spin-up events, known as glitches. More than forty years after their first discovery, the exact origin of these phenomena is still open to debate. It is generally thought that they an observational manifestation of a superfluid component in the stellar interior and provide an insight into the dynamics of matter at extreme densities. In recent years there have been several advances on both the theoretical and observational side, that have provided significant steps forward in our understanding of neutron star interior dynamics and possible glitch mechanisms. In this article we review the main glitch models that have been proposed and discuss our understanding, in the light of current observations.

  5. Generative pulsar timing analysis

    CERN Document Server

    Lentati, L; Hobson, M P

    2014-01-01

    A new Bayesian method for the analysis of folded pulsar timing data is presented that allows for the simultaneous evaluation of evolution in the pulse profile in either frequency or time, along with the timing model and additional stochastic processes such as red spin noise, or dispersion measure variations. We model the pulse profiles using `shapelets' - a complete ortho-normal set of basis functions that allow us to recreate any physical profile shape. Any evolution in the profiles can then be described as either an arbitrary number of independent profiles, or using some functional form. We perform simulations to compare this approach with established methods for pulsar timing analysis, and to demonstrate model selection between different evolutionary scenarios using the Bayesian evidence. %s The simplicity of our method allows for many possible extensions, such as including models for correlated noise in the pulse profile, or broadening of the pulse profiles due to scattering. As such, while it is a marked...

  6. The Extended Pulsar Magnetosphere

    CERN Document Server

    Kalapotharakos, Constantinos; Kazanas, Demos

    2011-01-01

    We present the structure of the 3D ideal MHD pulsar magnetosphere to a radius ten times that of the light cylinder, a distance about an order of magnitude larger than any previous such numerical treatment. Its overall structure exhibits a stable, smooth, well-defined undulating current sheet which approaches the kinematic split monopole solution of Bogovalov 1999 only after a careful introduction of diffusivity even in the highest resolution simulations. It also exhibits an intriguing spiral region at the crossing of two zero charge surfaces on the current sheet, which shows a destabilizing behavior more prominent in higher resolution simulations. We discuss the possibility that this region is physically (and not numerically) unstable. Finally, we present the spiral pulsar antenna radiation pattern.

  7. The Pulsar Search Collaboratory

    OpenAIRE

    Rosen, Rachel; Heatherly, Sue Ann; McLaughlin, Maura A.; Lynch, Ryan; Kondratiev, Vlad I.; Boyles, Jason R.; Wilson, M. Terry; Lorimer, Duncan R.; Ransom, Scott

    2010-01-01

    The Pulsar Search Collaboratory [PSC, NSF #0737641] is a joint project between the National Radio Astronomy Observatory (NRAO) and West Virginia University (WVU) designed to interest high school students in science, technology, engineering, and mathematics [STEM] related career paths by helping them to conduct authentic scientific research. The 3- year PSC program, which began in summer 2008, teaches students to analyze astronomical radio data acquired with the 100-m Robert C. Byrd Green Bank...

  8. Pulsar Polar Cap Heating and Surface Thermal X-ray Emission. 2; Inverse Compton Radiation Pair Fronts

    Science.gov (United States)

    Harding, Alice K.; Muslimov, Alexander G.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    We investigate the production of electron-positron pairs by inverse Compton scattered (ICS) photons above a pulsar polar cap (PC) and calculate surface heating by returning positrons. This paper is a continuation of our self-consistent treatment of acceleration, pair dynamics, and electric field screening above pulsar PCs. We calculate the altitude of the inverse Compton pair-formation fronts, the flux of returning positrons, and present the heating efficiencies and X-ray luminosities. We revise pulsar death lines implying cessation of pair formation, and present them in surface magnetic field-period space. We find that virtually all known radio pulsars are capable of producing pairs by resonant and nonresonant ICS photons radiated by particles accelerated above the PC in a pure star-centered dipole field, so that our ICS pair death line coincides with empirical radio pulsar death. Our calculations show that ICS pairs are able to screen the accelerating electric field only for high PC surface temperatures and magnetic fields. We argue that such screening at ICS pair fronts occurs locally, slowing but not turning off acceleration of particles until screening can occur at a curvature radiation (CR) pair front at higher altitude. In the case where no screening occurs above the PC surface, we anticipate that the pulsar gamma-ray luminosity will be a substantial fraction of its spin-down luminosity. The X-ray luminosity resulting from PC heating by ICS pair fronts is significantly lower than the PC heating luminosity from CR pair fronts, which dominates for most pulsars. PC heating from ICS pair fronts is highest in millisecond pulsars, which cannot produce CR pairs, and may account for observed thermal X-ray components in the spectra of these old pulsars.

  9. Nature of eclipsing pulsars

    CERN Document Server

    Khechinashvili, D; Gil, J; Khechinashvili, David; Melikidze, George; Gil, Janusz

    2000-01-01

    We present a model for pulsar radio eclipses in some binary systems, and test this model for PSRs B1957+20 and J2051-0827. We suggest that in these binaries the companion stars are degenerate dwarfs with strong surface magnetic fields. The magnetospheres of these stars are permanently infused by the relativistic particles of the pulsar wind. We argue that the radio waves emitted by the pulsar split into the eigenmodes of the electron-positron plasma as they enter the companion's magnetosphere and are then strongly damped due to cyclotron resonance with the ambient plasma particles. Our model explains in a natural way the anomalous duration and behavior of radio eclipses observed in such systems. In particular, it provides stable, continuous, and frequency-dependent eclipses, in agreement with the observations. We predict a significant variation of linear polarization both at eclipse ingress and egress. In this paper we also suggest several possible mechanisms of generation of the optical and $X$-ray emission ...

  10. Pulsar Wind Nebulae Modeling

    CERN Document Server

    Bucciantini, N

    2013-01-01

    Pulsar Wind Nebulae (PWNe) are ideal astrophysical laboratories where high energy relativistic phenomena can be investigated. They are close, well resolved in our observations, and the knowledge derived in their study has a strong impact in many other fields, from AGNs to GRBs. Yet there are still unresolved issues, that prevent us from a full clear understanding of these objects. The lucky combination of high resolution X-ray imaging and numerical codes to handle the outflow and dynamical properties of relativistic MHD, has opened a new avenue of investigation that has lead to interesting progresses in the last years. Despite all of this, we do not understand yet how particles are accelerated, and the functioning of the pulsar wind and pulsar magnetosphere, that power PWNe. I will review what is now commonly known as the MHD paradigm, and in particular I will focus on various approaches that have been and are currently used to model these systems. For each I will highlight its advantages, limitations, and de...

  11. a Surprise from the Pulsar in the Crab Nebula

    Science.gov (United States)

    1995-11-01

    New observations of the spectrum of the rapidly spinning neutron star (the `pulsar') in the Crab Nebula have been carried out with the ESO 3.5-metre New Technology Telescope (NTT) by a group of Italian astronomers [1]. Because of greatly improved spectral resolution which allows to register even very fine details in the pulsar's spectrum, they are able to determine for the first time with high accuracy the overall dependance of the emission on wavelength, i.e. the `shape' of the spectrum. Quite unexpectedly, they also detect a hitherto unknown 100 A (10 nm) broad `absorption dip', which can be securely attributed to the pulsar. These results open an exciting new window for the study of the extreme physical processes close to a pulsar. The Nature of Pulsars It is estimated that there may be as many as 100 million neutron stars in our Galaxy. A neutron star is the superdense remnant of the extremely violent supernova explosion that occurs at the end of the life of a comparatively massive star. In fact, all stars that are more than about 6 times heavier than the Sun are believed to end their lives as supernovae. During the explosion, the central core of the dying star collapses in a few milliseconds and the matter at the centre is compressed to a density comparable to that of an atomic nucleus. Due to the enormous inward pressure, the atomic particles are squeezed together into a kind of neutron jam. The outcome is the formation of a neutron star with a diameter of 10-15 kilometres, weighing as much as the Sun. In accordance with the physical law that implies that the rotation momentum of the exploding star must be conserved, newborn neutron stars will rotate very rapidly around their axis, in some cases as fast as 100 times per second. In the same way, the new neutron star is expected to possess a strong magnetic field. Of these myriads of neutron stars, about 700 have been observed to emit radio pulses (hence the name `pulsar'). A few of these can also be detected

  12. Pulsar polarisation below 200 MHz: Average profiles and propagation effects

    Science.gov (United States)

    Noutsos, A.; Sobey, C.; Kondratiev, V. I.; Weltevrede, P.; Verbiest, J. P. W.; Karastergiou, A.; Kramer, M.; Kuniyoshi, M.; Alexov, A.; Breton, R. P.; Bilous, A. V.; Cooper, S.; Falcke, H.; Grießmeier, J.-M.; Hassall, T. E.; Hessels, J. W. T.; Keane, E. F.; Osłowski, S.; Pilia, M.; Serylak, M.; Stappers, B. W.; ter Veen, S.; van Leeuwen, J.; Zagkouris, K.; Anderson, K.; Bähren, L.; Bell, M.; Broderick, J.; Carbone, D.; Cendes, Y.; Coenen, T.; Corbel, S.; Eislöffel, J.; Fender, R.; Garsden, H.; Jonker, P.; Law, C.; Markoff, S.; Masters, J.; Miller-Jones, J.; Molenaar, G.; Osten, R.; Pietka, M.; Rol, E.; Rowlinson, A.; Scheers, B.; Spreeuw, H.; Staley, T.; Stewart, A.; Swinbank, J.; Wijers, R.; Wijnands, R.; Wise, M.; Zarka, P.; van der Horst, A.

    2015-04-01

    Aims: We present the highest-quality polarisation profiles to date of 16 non-recycled pulsars and four millisecond pulsars, observed below 200 MHz with the LOFAR high-band antennas. Based on the observed profiles, we perform an initial investigation of expected observational effects resulting from the propagation of polarised emission in the pulsar magnetosphere and the interstellar medium. Methods: The polarisation data presented in this paper have been calibrated for the geometric-projection and beam-shape effects that distort the polarised information as detected with the LOFAR antennas. We have used RM Synthesis to determine the amount of Faraday rotation in the data at the time of the observations. The ionospheric contribution to the measured Faraday rotation was estimated using a model of the ionosphere. To study the propagation effects, we have compared our low-frequency polarisation observations with archival data at 240, 400, 600, and 1400 MHz. Results: The predictions of magnetospheric birefringence in pulsars have been tested using spectra of the pulse width and fractional polarisation from multifrequency data. The derived spectra offer only partial support for the expected effects of birefringence on the polarisation properties, with only about half of our sample being consistent with the model's predictions. It is noted that for some pulsars these measurements are contaminated by the effects of interstellar scattering. For a number of pulsars in our sample, we have observed significant variations in the amount of Faraday rotation as a function of pulse phase, which is possibly an artefact of scattering. These variations are typically two orders of magnitude smaller than that observed at 1400 MHz by Noutsos et al. (2009), for a different sample of southern pulsars. In this paper we present a possible explanation for the difference in magnitude of this effect between the two frequencies, based on scattering. Finally, we have estimated the magnetospheric

  13. Millisecond laser machining of transparent materials assisted by nanosecond laser.

    Science.gov (United States)

    Pan, Yunxiang; Zhang, Hongchao; Chen, Jun; Han, Bing; Shen, Zhonghua; Lu, Jian; Ni, Xiaowu

    2015-01-26

    A new form of double pulse composed of a nanosecond laser and a millisecond laser is proposed for laser machining transparent materials. To evaluate its advantages and disadvantages, experimental investigations are carried out and the corresponding results are compared with those of single millisecond laser. The mechanism is discussed from two aspects: material defects and effects of modifications induced by nanosecond laser on thermal stress field during millisecond laser irradiation. It is shown that the modifications of the sample generated by nanosecond laser improves the processing efficiency of subsequent millisecond laser, while limits the eventual size of modified region.

  14. Flares from Galactic centre pulsars: a new class of X-ray transients?

    CERN Document Server

    Giannios, Dimitrios

    2016-01-01

    Despite intensive searches, the only pulsar within 0.1 pc of the central black hole in our Galaxy, Sgr A*, is a radio-loud magnetar. Since magnetars are rare among the Galactic neutron star population, and a large number of massive stars are already known in this region, the Galactic centre (GC) should harbor a large number of neutron stars. Population syntheses suggest several thousand neutron stars may be present in the GC. Many of these could be highly energetic millisecond pulsars which are also proposed to be responsible for the GC gamma-ray excess. We propose that the presence of a neutron star within 0.03~pc from Sgr~A* can be revealed by the shock interactions with the disk around the central black hole. As we demonstrate, these interactions result in observable transient non-thermal X-ray and gamma-ray emission over timescales of months, provided that the spin down luminosity of the neutron star is L_{sd}~10^{35} erg/s. Current limits on the population of normal and millisecond pulsars in the GC regi...

  15. Fast radio bursts as giant pulses from young rapidly rotating pulsars

    CERN Document Server

    Lyutikov, Maxim; Popov, Sergei B

    2016-01-01

    We discuss possible association of fast radio bursts (FRBs) with supergiant pulses emitted by young pulsars (ages $\\sim$ tens to hundreds of years) born with regular magnetic field but very short -- few milliseconds -- spin periods. FRBs are extra-Galactic events coming from distances $d \\lesssim 100$ Mpc. Most of the dispersion measure (DM) comes from the material in the freshly ejected SNR shell; for a given burst the DM should decrease with time. FRBs are not expected to be seen below $\\sim 300 $ MHz due to free-free absorption in the expanding ejecta. A supernova might have been detected years before the burst; FRBs are mostly associated with star forming galaxies. The model requires that some pulsars are born with very fast spins, of the order of few milliseconds. The observed distribution of spin-down powers $\\dot{E}$ in young energetic pulsars is consistent with equal birth rate per decade of $\\dot{E}$. Accepting this injection spectrum and scaling the intrinsic brightness of FRBs with $\\dot{E}$, we pr...

  16. The discovery of an eccentric millisecond pulsar in the Galactic plane

    NARCIS (Netherlands)

    D.J. Champion; S.M. Ransom; P. Lazarus; F. Camilo; V.M. Kaspi; D.J. Nice; P.C.C. Freire; J.M. Cordes; J.W.T. Hessels; C. Bassa; D.R. Lorimer; I.H. Stairs; J. van Leeuwen; Z. Arzoumnian; D.C. Backer; N.D.R. Bhat; S. Chatterjee; F. Crawford; J.S. Deneva; C.A. Faucher-Giguère; B.M. Gaensler; J. Han; F.A. Jenet; L. Kasian; V.I. Kondratiev; M. Kramer; J. Lazio; M.A. McLaughlin; B.W. Stappers; A. Venkataraman; W. Vlemmings

    2007-01-01

    The evolution of binary systems is governed by their orbital properties and the stellar density of the local environment. Studies of neutron stars in binary star systems offer unique insights into both these issues. In an Arecibo survey of the Galactic disk, we have found PSR J1903+0327, a radio emi

  17. Long-term observations of the pulsars in 47 Tucanae. I. A study of four elusive binary systems

    CERN Document Server

    Ridolfi, A; Torne, P; Heinke, C O; Berg, M van den; Jordan, C; Kramer, M; Bassa, C G; Sarkissian, J; D'Amico, N; Lorimer, D; Camilo, F; Manchester, R N; Lyne, A

    2016-01-01

    For the past couple of decades, the Parkes radio telescope has been regularly observing the millisecond pulsars in 47 Tucanae (47 Tuc). This long-term timing program was designed to address a wide range of scientific issues related to these pulsars and the globular cluster where they are located. In this paper, the first of a series, we address one of these objectives: the characterization of four previously known binary pulsars for which no precise orbital parameters were known, namely 47 Tuc P, V, W and X (pulsars 47 Tuc R and Y are discussed elsewhere). We determined the previously unknown orbital parameters of 47 Tuc V and X and greatly improved those of 47 Tuc P and W. For pulsars W and X we obtained, for the first time, full coherent timing solutions across the whole data span, which allowed a much more detailed characterization of these systems. 47 Tuc W, a well-known tight eclipsing binary pulsar, exhibits a large orbital period variability, as expected for a system of its class. 47 Tuc X turns out to...

  18. The LOFAR Known Pulsar Data Pipeline

    NARCIS (Netherlands)

    A. Alexov; J.W.T. Hessels; J.D. Mol; B. Stappers; J. van Leeuwen

    2010-01-01

    Abstract: Transient radio phenomena and pulsars are one of six LOFAR Key Science Projects (KSPs). As part of the Transients KSP, the Pulsar Working Group (PWG) has been developing the LOFAR Pulsar Data Pipelines to both study known pulsars as well as search for new ones. The pipelines are being deve

  19. Probing the presence of a single or binary black hole in the globular cluster NGC 6752 with pulsar dynamics

    CERN Document Server

    Colpi, M; Possenti, A; Colpi, Monica; Mapelli, Michela; Possenti, Andrea

    2003-01-01

    The five millisecond pulsars that inhabit NGC 6752 display locations or accelerations that are quite unusual compared to all other pulsars known in globular clusters. In particular PSR-A, a binary pulsar, lives in the cluster halo, while PSR-B and PSR-E, located in the core, show remarkably high negative spin derivatives. This is suggestive that some uncommon dynamical process is at play in the cluster core that we attribute to the presence of a massive perturber. We here investigate whether a single intermediate-mass black hole, lying on the extrapolation of the Mass versus Sigma relation observed in galaxy spheroids, or a less massive binary consisting of two black holes could play the requested role. To this purpose we simulated binary-binary encounters involving PSR-A, its companion star, and the black hole(s). Various scenarios are discussed in detail. In our close 4-body encounters, a black hole-black hole binary may attract on a long-term stable orbit a millisecond pulsar. Timing measurements on the ca...

  20. On the magnetic fields of Be/X-ray pulsars in the Small Magellanic Cloud

    Science.gov (United States)

    Ikhsanov, N. R.; Mereghetti, S.

    2015-12-01

    We explore the possibility of explaining the properties of the Be/X-ray pulsars observed in the Small Magellanic Cloud (SMC) within the magnetic levitation accretion scenario. This implies that their X-ray emission is powered by a wind-fed accretion on to a neutron star (NS) which captures matter from a magnetized stellar wind. The NS in this case is accreting matter from a non-Keplerian magnetically levitating disc which is surrounding its magnetosphere. This allows us to explain the observed periods of the pulsars in terms of spin equilibrium without the need of invoking dipole magnetic fields outside the usual range ˜1011-1013 G inferred from cyclotron features of Galactic high-mass X-ray binaries. We find that the equilibrium period of a NS, under certain conditions, depends strongly on the magnetization of the stellar wind of its massive companion and, correspondingly, on the magnetic field of the massive companion itself. This may help to explain why similar NSs in binaries with similar properties rotate with different periods yielding a large scatter of periods of the accretion-powered pulsar observed in SMC and our galaxy.