Sample records for double neutron star

  1. Double Neutron Star Systems and Natal Neutron Star Kicks

    Microsoft Academic Search

    Chris Fryer; Vassiliki Kalogera

    1997-01-01

    We study the four double neutron star systems found in the Galactic disk in terms of the orbital characteristics of their immediate progenitors and the natal kicks imparted to neutron stars. Analysis of the effect of the second supernova explosion on the orbital dynamics, combined with recent results from simulations of rapid accretion onto neutron stars, lead us to conclude

  2. Double Neutron Star Binaries: Implications for LIGO

    E-print Network

    Chang-Hwan Lee; Gerald E. Brown

    2005-10-13

    Double neutrons are especially important because they give most accurate informations on the masses of neutron stars. Observations on double neutron stars show that all masses of the neutron stars are below 1.5$\\msun$. Furthermore, two neutron stars in a given double pulsar are nearly equal in mass. With hypercritical accretion, we found that the probability of having companion mass $>1.5\\msun$ is larger than 90%, while there is no observations on such systems. We believe that those companions with masses higher than $1.5\\msun$ went into black holes, which is consistent with our preferred maximum neutron star mass $M_{NS}^{max} \\approx 1.5\\msun$ due to the kaon condensation. In this work, we point out that the black-hole neutron star binaries are 10 times more dominant than double neutron star binaries. As a result, black-hole, neutron star binaries can increase the LIGO detection rate by a factor 20.

  3. Double Neutron Star Systems and Natal Neutron Star Kicks

    E-print Network

    Chris Fryer; Vassiliki Kalogera

    1997-06-03

    We study the four double neutron star systems found in the Galactic disk in terms of the orbital characteristics of their immediate progenitors and the natal kicks imparted to neutron stars. Analysis of the effect of the second supernova explosion on the orbital dynamics, combined with recent results from simulations of rapid accretion onto neutron stars lead us to conclude that the observed systems could not have been formed had the explosion been symmetric. Their formation becomes possible if kicks are imparted to the radio-pulsar companions at birth. We identify the constraints imposed on the immediate progenitors of the observed double neutron stars and calculate the ranges within which their binary characteristics (orbital separations and masses of the exploding stars) are restricted. We also study the dependence of these limits on the magnitude of the kick velocity and the time elapsed since the second explosion. For each of the double neutron stars, we derive a minimum kick magnitude required for their formation, and for the two systems in close orbits we find it to exceed 200km/s. Lower limits are also set to the center-of-mass velocities of double neutron stars, and we find them to be consistent with the current proper motion observations.

  4. Stochastic background from inspiralling double neutron stars

    E-print Network

    Tania Regimbau

    2006-12-30

    We review the contribution of extra galactic inspiralling double neutron stars, to the LISA astrophysical gravitational wave foreground. Using recent fits of the star formation rate, we show that sources beyond $z_*=0.005$ contribute to a truly continuous background, which may dominate the LISA instrumental noise in the range $3 \\simeq 10^{-4}$ - $1 \\times 10^{-2}$ Hz and overwhelm the galactic WD-WD confusion noise at frequencies larger than $\

  5. Population Synthesis of Double Neutron Stars

    NASA Astrophysics Data System (ADS)

    Tenney, Craig; Lorimer, D.; Bagchi, M.

    2014-01-01

    Globular clusters in our galaxy provide a fertile ground for stars to undergo supernova which leads to the creation of neutron stars. A population synthesis was created to study the population of double neutron stars (DNS) in our Galaxy that originated in globular clusters. The rate of DNS formation is proportional to the cluster's luminosity and the resulting kick from the supernova at birth ejects the DNS from the cluster. Initial conditions are given to the DNS after being ejected and allowed to evolve throughout the galaxy to the present time. With a simulated population of DNS we test to see how many of them are detectable from Earth with radio telescopes. DNS are being used as a way to detect gravitation waves when the two neutron stars spiral into each other. A better constraint on their formation and existence will lead to more accurate predictions for gravitational wave detectors.

  6. THE ROLE OF HELIUM STARS IN THE FORMATION OF DOUBLE NEUTRON STARS N. Ivanova,1

    E-print Network

    Rasio, Frederic A.

    THE ROLE OF HELIUM STARS IN THE FORMATION OF DOUBLE NEUTRON STARS N. Ivanova,1 K. Belczynski,1,2 V:5 6 M with a 1.4 M neutron star companion to investigate the formation of double neutron star systems phase) leads to the formation of extremely short-period double neutron star systems (with Pd0:1 days

  7. Coalescence Rates of Double Neutron Stars

    E-print Network

    Vassiliki Kalogera

    1999-04-17

    Merger events of close double neutron stars (DNS) lie at the basis of a number of current issues in relativistic astrophysics, such as the indirect and possible direct detection of gravitational waves, the production of gamma-ray bursts at cosmological distances, and the origin of r-process elements in the universe. In assessing the importance or relevance of DNS coalescence to these issues, knowledge of the rate of coalescence in our Galaxy is required. In this paper, I review the current estimates of the DNS merger rate (theoretical and empirical) and discuss new ways to obtain limits on this rate using all information available at present.

  8. Merger Sites of Double Neutron Stars and their Host Galaxies

    E-print Network

    Krzysztof Belczynski; Tomasz Bulik; Vassiliki Kalogera

    2002-04-24

    Using the StarTrack population synthesis code we analyze the formation channels possibly available to double neutron star binaries and find that they can be richer than previously thought. We identify a group of short lived, tight binaries, which do not live long enough to escape their host galaxies, despite their large center-of-mass velocities. We present our most recent results on all possible evolutionary paths leading to the formation of double neutron stars, calculate their coalescence rates, and also revisit the question of the distribution of merger sites around host galaxies. For a wide variety of binary evolution models and galaxy potentials, we find that most of neutron star mergers take place within galaxies. Our results stem from allowing for radial and common envelope evolution of helium-rich stars (testable in the future with detailed stellar-structure and hydrodynamic calculations) and indicate that double neutron star binaries may not be excluded as Gamma-Ray Burst (GRB) progenitors solely on the basis of their spatial distribution around host galaxies. We also find, in contrast to Bethe & Brown (1998), that in a significant fraction of common envelope (CE) phases neutron stars do not accrete enough material to become black holes, and thus the channels involving CEs are still open for the formation of double neutron stars.

  9. Double Neutron Stars: Evidence For Two Different Neutron-Star Formation Mechanisms

    E-print Network

    E. P. J. van den Heuvel

    2007-04-26

    Six of the eight double neutron stars known in the Galactic disk have low orbital eccentricities (stars received only very small velocity kicks at birth. This is similar to the case of the B-emission X-ray binaries, where a sizable fraction of the neutron stars received hardly any velocity kick at birth (Pfahl et al. 2002). The masses of the second-born neutron stars in five of the six low-eccentricity double neutron stars are remarkably low (between 1.18 and 1.30 Msun). It is argued that these low-mass, low-kick neutron stars were formed by the electron-capture collapse of the degenerate O-Ne-Mg cores of helium stars less massive than about 3.5 Msun, whereas the higher-mass, higher kick-velocity neutron stars were formed by the collapses of the iron cores of higher initial mass. The absence of low-velocity single young radio pulsars (Hobbs et al. 2005) is consistent with the model proposed by Podsiadlowski et al. (2004), in which the electron-capture collapse of degenerate O-Ne-Mg cores can only occur in binary systems, and not in single stars.

  10. The late stages of evolution of helium star-neutron star binaries and the formation of double neutron star systems

    Microsoft Academic Search

    J. D. M. Dewi; O. R. Pols

    2003-01-01

    With a view to understanding the formation of double neutron-stars (DNS), we\\u000ainvestigate the late stages of evolution of helium stars with masses of 2.8 -\\u000a6.4 Msun in binary systems with a 1.4 Msun neutron-star companion. We found\\u000athat mass transfer from 2.8 - 3.3 Msun helium stars and from 3.3 - 3.8 Msun in\\u000avery close orbits (P_orb

  11. Evolutionary Channels for the Formation of Double Neutron Stars

    NASA Astrophysics Data System (ADS)

    Andrews, Jeff J.; Farr, W. M.; Kalogera, V.; Willems, B.

    2015-03-01

    We analyze binary population models of double-neutron stars and compare results to the accurately measured orbital periods and eccentricities of the eight known such systems in our Galaxy. In contrast to past similar studies, we especially focus on the dominant evolutionary channels (we identify three); for the first time, we use a detailed understanding of the evolutionary history of three double neutron stars as actual constraints on the population models. We find that the evolutionary constraints derived from the double pulsar are particularly tight, and less than half of the examined models survive the full set of constraints. The top-likelihood surviving models yield constraints on the key binary evolution parameters, but most interestingly reveal (1) the need for electron-capture supernovae from relatively low-mass degenerate, progenitor cores, and (2) the most likely evolutionary paths for the rest of the known double neutron stars. In particular, we find that J1913+16 likely went through a phase of Case BB mass transfer, and J1906+0746 and J1756-2251 are consistent with having been formed in electron-capture supernovae.

  12. The Cosmic Coalescence Rates for Double Neutron Star Binaries

    Microsoft Academic Search

    V. Kalogera; C. Kim; D. R. Lorimer; M. Burgay; N. D'Amico; A. Possenti; R. N. Manchester; A. G. Lyne; B. C. Joshi; M. A. McLaughlin; M. Kramer; J. M. Sarkissian; F. Camilo

    2004-01-01

    We report on the newly increased event rates due to the recent discovery of the highly relativistic binary pulsar J0737-3039. Using a rigorous statistical method, we present the calculations reported by Burgay et al., which produce a coalescence rate for Galactic double neutron star (DNS) systems that is higher by a factor of 6-7 compared to estimates made prior to

  13. Stochastic background from extra-galactic double neutron stars

    E-print Network

    T. Regimbau; B. Chauvineau

    2007-07-30

    We present Monte Carlo simulations of the extra galactic population of inspiralling double neutron stars, and estimate its contribution to the astrophysical gravitational wave background, in the frequency range of ground based interferometers, corresponding to the last thousand seconds before the last stable orbit when more than 96 percent of the signal is released. We show that sources at redshift z>0.5 contribute to a truly continuous background which may be detected by correlating third generation interferometers.

  14. The Role of Helium Stars in the Formation of Double Neutron Stars

    Microsoft Academic Search

    N. Ivanova; K. Belczynski; V. Kalogera; F. A. Rasio; R. E. Taam

    2003-01-01

    We have calculated the evolution of 60 model binary systems consisting of helium stars in the mass range of MHe=2.5-6Msolar with a 1.4 Msolar neutron star companion to investigate the formation of double neutron star systems. Orbital periods ranging from 0.09 to 2 days are considered, corresponding to Roche lobe overflow starting from the helium main sequence to after the

  15. The Role of Helium Stars in the Formation of Double Neutron Stars

    E-print Network

    N. Ivanova; K. Belczynski; V. Kalogera; F. A. Rasio; R. E. Taam

    2003-07-13

    We have calculated the evolution of 60 model binary systems consisting of helium stars in the mass range of M_He= 2.5-6Msun with a 1.4Msun neutron star companion to investigate the formation of double neutron star systems.Orbital periods ranging from 0.09 to 2 days are considered, corresponding to Roche lobe overflow starting from the helium main sequence to after the ignition of carbon burning in the core. We have also examined the evolution into a common envelope phase via secular instability, delayed dynamical instability, and the consequence of matter filling the neutron star's Roche lobe. The survival of some close He-star neutron-star binaries through the last mass transfer episode (either dynamically stable or unstable mass transfer phase) leads to the formation of extremely short-period double neutron star systems (with Pstar masses (~ 2.6-3.3Msun). The existence of a short-period population of double neutron stars increases the predicted detection rate of inspiral events by ground-based gravitational-wave detectors and impacts their merger location in host galaxies and their possible role as gamma-ray burst progenitors. We use a set of population synthesis calculations and investigate the implications of the mass-transfer results for the orbital properties of DNS populations.

  16. Millisecond Pulsar Searches and Double Neutron Star Binaries

    E-print Network

    John Middleditch

    2004-05-06

    A unified strategy is developed that can be used to search for millisecond pulsars (MSPs) with ~solar mass companions (including neutron star companions in double neutron star binaries [DNSBs]) belonging to both very short period binaries, and those with periods so long that they could be appropriate targets for acceleration searches, and to bridge the gap between these two extremes. In all cases, the orbits are assumed to be circular. Applications to searches for binary pulsars similar to PSR J0737-3039 are discussed. The most likely candidates for more DNSBs consist of weakly magnetized neutron stars, spinning only moderately fast, like J0737-3039A, with periods generally longer than 15 ms, though this issue is not yet settled. Because of the similarity between the MSP components of DNSBs, and the longer period MSP population specific to massive condensed or core collapsed globular clusters, as well as the uncertainties about accretion-driven spinup, doubts linger about the standard models of DNSB formation.

  17. Complex orbital dynamics of a double neutron star system revolving around a massive black hole

    E-print Network

    Grant N. Remmen; Kinwah Wu

    2013-01-14

    We investigate the orbital dynamics of hierarchical three-body systems containing a double neutron star system orbiting around a massive black hole. These systems show complex dynamical behaviour because of relativistic coupling between orbits of the neutron stars in the double neutron star system and the orbit of the double neutron star system around the black hole. The orbital motion of the neutron stars around each other drives a loop mass current, which gives rise to gravito-magnetism. Generally, gravito-magnetism involves a rotating black hole. The hierarchical three-body system that we consider is an unusual situation in which black hole rotation is not required. Using a gravito-electromagnetic formulation, we calculate the orbital precession and nutation of the double neutron star system. These precession and nutation effects are observable, thus providing probes to the spacetime around black holes as well as tests of gravito-electromagnetism in the framework of general relativity.

  18. CONSTRAINTS ON NATAL KICKS IN GALACTIC DOUBLE NEUTRON STAR SYSTEMS

    SciTech Connect

    Wong, Tsing-Wai; Willems, Bart; Kalogera, Vassiliki, E-mail: TsingWong2012@u.northwestern.ed, E-mail: b-willems@northwestern.ed, E-mail: vicky@northwestern.ed [Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States)

    2010-10-01

    Since the discovery of the first double neutron star (DNS) system in 1975 by Hulse and Taylor, there are currently eight confirmed DNS in our galaxy. For every system, the masses of both neutron stars, the orbital semimajor axis, and eccentricity are measured, and proper motion is known for half of the systems. Using the orbital parameters and kinematic information, if available, as constraints for all systems, we investigate the immediate progenitor mass of the second-born neutron star (NS2) and the magnitude of the supernova kick it received at birth, with the primary goal to understand the core-collapse mechanism leading to neutron star formation. Compared to earlier studies, we use a novel method to address the uncertainty related to the unknown radial velocity of the observed systems. For PSR B1534+12 and PSR B1913+16, the kick magnitudes are 150-270 km s{sup -1} and 190-450 km s{sup -1} (with 95% confidence), respectively, and the progenitor masses of the NS2 are 1.3-3.4 M{sub sun} and 1.4-5.0 M{sub sun} (95%), respectively. These suggest that the NS2 was formed by an iron core-collapse supernova in both systems. For PSR J0737 - 3039, on the other hand, the kick magnitude is only 5-120 km s{sup -1} (95%), and the progenitor mass of the NS2 is 1.3-1.9 M{sub sun} (95%). Because of the relatively low progenitor mass and kick magnitude, the formation of the NS2 in PSR J0737 - 3039 is potentially connected to an electron capture supernova of a massive O-Ne-Mg white dwarf. For the remaining five Galactic DNS, the kick magnitude ranges from several tens to several hundreds of km s{sup -1}, and the progenitor mass of the NS2 can be as low as {approx}1.5 M{sub sun} or as high as {approx}8 M{sub sun}. Therefore, in these systems it is not clear which type of supernova is more likely to form the NS2.

  19. The late stages of evolution of helium star-neutron star binaries and the formation of double neutron star systems

    E-print Network

    J. D. M. Dewi; O. R. Pols

    2003-06-03

    With a view to understanding the formation of double neutron-stars (DNS), we investigate the late stages of evolution of helium stars with masses of 2.8 - 6.4 Msun in binary systems with a 1.4 Msun neutron-star companion. We found that mass transfer from 2.8 - 3.3 Msun helium stars and from 3.3 - 3.8 Msun in very close orbits (P_orb > 0.25d) will end up in a common-envelope (CE) and spiral-in phase due to the development of a convective helium envelope. If the neutron star has sufficient time to complete the spiraling-in process before the core collapses, the system will produce very tight DNSs (P_orb ~ 0.01d) with a merger timescale of the order of 1 Myr or less. These systems would have important consequences for the detection rate of GWR and for the understanding of GRB progenitors. On the other hand, if the time left until the explosion is shorter than the orbital-decay timescale, the system will undergo a SN explosion during the CE phase. Helium stars with masses 3.3 - 3.8 Msun in wider orbits (P_orb > 0.25d) and those more massive than 3.8 Msun do not go through CE evolution. The remnants of these massive helium stars are DNSs with periods in the range of 0.1 - 1 d. This suggests that this range of mass includes the progenitors of the galactic DNSs with close orbits (B1913+16 and B1534+12). A minimum kick velocity of 70 km/s and 0 km/s (for B1913+16 and B1534+12, respectively) must have been imparted at the birth of the pulsar's companion. The DNSs with wider orbits (J1518+4904 and probably J1811-1736) are produced from helium star-neutron star binaries which avoid RLOF, with the helium star more massive than 2.5 Msun. For these systems the minimum kick velocities are 50 km/s and 10 km/s (for J1518+4904 and J1811-1736, respectively).

  20. Polar kicks and the spin period - eccentricity relation in double neutron stars

    E-print Network

    B. Willems; J. Andrews; V. Kalogera; K. Belczynski

    2007-10-01

    We present results of a population synthesis study aimed at examining the role of spin-kick alignment in producing a correlation between the spin period of the first-born neutron star and the orbital eccentricity of observed double neutron star binaries in the Galactic disk. We find spin-kick alignment to be compatible with the observed correlation, but not to alleviate the requirements for low kick velocities suggested in previous population synthesis studies. Our results furthermore suggest low- and high-eccentricity systems may form through two distinct formation channels distinguished by the presence or absence of a stable mass transfer phase before the formation of the second neutron star. The presence of highly eccentric systems in the observed sample of double neutron stars may furthermore support the notion that neutron stars accrete matter when moving through the envelope of a giant companion.

  1. The Cosmic Coalescence Rates for Double Neutron Star Binaries

    E-print Network

    V. Kalogera; C. Kim; D. R. Lorimer; M. Burgay; N. D'Amico; A. Possenti; R. N. Manchester; A. G. Lyne; B. C. Joshi; M. A. McLaughlin; M. Kramer; J. M. Sarkissian; F. Camilo

    2004-08-11

    This manuscript is an updated version of Kalogera et al. (2004) published in ApJ Letters to correct our calculation of the Galactic DNS in-spiral rate. The details of the original erratum submitted to ApJ Letters are given in page 6 of this manuscript. We report on the newly increased event rates due to the recent discovery of the highly relativistic binary pulsar J0737--3039 (Burgay et al. 2003). Using a rigorous statistical method, we present the calculations reported by Burgay et al., which produce a in-spiral rate for Galactic double neutron star (DNS) systems that is higher by a factor of 5-7 compared to estimates made prior to the new discovery. Our method takes into account known pulsar-survey selection effects and biases due to small-number statistics. This rate increase has dramatic implications for gravitational wave detectors. For the initial Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors, the most probable detection rates for DNS in-spirals are one event per 10-630 yr; at 95% confidence, we obtain rates up to one per 3 yr. For the advanced LIGO detectors, the most probable rates are 10-500 events per year. These predictions, for the first time, bring the expectations for DNS detections by the initial LIGO detectors to the astrophysically relevant regime. We also use our models to predict that the large-scale Parkes Multibeam pulsar survey with acceleration searches could detect an average of four binary pulsars similar to those known at present.

  2. Members of the double pulsar system PSR J0737-3039 : neutron stars or strange stars ?

    E-print Network

    Manjari Bagchi; Jishnu Dey; Sushan Konar; Gour Bhattacharya; Mira Dey

    2008-04-29

    One interesting method of constraining the dense matter Equations of State is to measure the advancement of the periastron of the orbit of a binary radio pulsar (when it belongs to a double neutron star system). There is a great deal of interest on applicability of this procedure to the double pulsar system PSR J0737-3039 (A/B). Although the above method can be applied to PSR A in future within some limitations, for PSR B this method can not be applied. On the other hand, the study of genesis of PSR B might be useful in this connection and its low mass might be an indication that it could be a strange star.

  3. A New Formation Channel for Double Neutron Stars Without Recycling: Implications for Gravitational Wave Detection

    Microsoft Academic Search

    Krzysztof Belczynski; Vassiliki Kalogera

    2001-01-01

    We report on a new evolutionary path leading to the formation of close double neutron stars (NSs), with the unique characteristic that none of the two NSs ever had the chance to be recycled by accretion. The existence of this channel stems from the evolution of helium-rich stars (cores of massive NS progenitors), which has been neglected in most previous

  4. The spin period - eccentricity relation of double neutron stars: evidence for weak supernova kicks?

    Microsoft Academic Search

    J. D. M. Dewi; Ph. Podsiadlowski; O. R. Pols

    2005-01-01

    Double neutron stars (DNSs), binary systems consisting of a radio pulsar and\\u000aa generally undetected second neutron star (NS), have proven to be excellent\\u000alaboratories for testing the theory of general relativity. The seven systems\\u000adiscovered in our Galaxy exhibit a remarkably well-defined relation between the\\u000apulsar spin period and the orbital eccentricity. Here we show, using a simple\\u000amodel

  5. The Coalescence Rate of Double Neutron Star Systems

    Microsoft Academic Search

    V. Kalogera; R. Narayan; D. N. Spergel; J. H. Taylor

    2000-01-01

    We estimate the coalescence rate of close binaries with two neutron stars\\u000a(NS) and discuss the prospects for the detection of NS-NS inspiral events by\\u000aground-based gravitational-wave observatories, such as LIGO. We derive the\\u000aGalactic coalescence rate using the observed sample of close NS-NS binaries\\u000a(PSR B1913+16 and PSR B1534+12) and examine in detail each of the sources of\\u000auncertainty

  6. High space velocities of single radio pulsars versus low orbital eccentricities and masses of double neutron stars: Evidence for two different neutron star formation mechanisms

    NASA Astrophysics Data System (ADS)

    van den Heuvel, Edward P. J.

    2010-03-01

    Radio pulsars tend to be high-velocity objects, which implies that the majority of them received a velocity kick of several hundreds of km s -1 at birth. However, six of the eight known double neutron stars in the galactic disk have quite low orbital eccentricities (0.085-0.27), indicating - taking into account the eccentricity induced by the mass-loss effects in the second supernova - that their second-born neutron stars received hardly any velocity kick at birth. The second-born neutron stars in these systems tend to have low masses (1.25 ± 0.07 M ?) and the same is true for the neutron star in the close white dwarf-neutron star system PSRJ 1145-6545, which also is the second-born star in a system of low eccentricity ( e = 0.17). Such a low mass would fit well with the formation of the second-born neutron stars by the electron-capture collapse of a Chandrasekhar-mass degenerate O-Ne-Mg core of stars of initial main-sequence mass between 8 and about 12 M ?. Podsiadlowski et al. (2004) have pointed out that neutron-star formation in this mass range is possible only if the star is in a close binary, following loss of the hydrogen envelope, while single stars can leave neutron stars only if they started out with masses above about 12 M ?; in the latter case a neutron star forms by the final collapse of an iron core. We point out here that the low masses of the second-born neutron stars in the low-eccentricity double neutron stars, together with the high space velocities of the single radio pulsars find a consistent explanation if one postulates, following ( Van den Heuvel, 2004; Podsiadlowski et al., 2004; Dewi et al., 2005) that neutron stars formed by electron-capture collapse of a degenerate O-Ne-Mg core receive hardly any kick velocity at birth, whereas neutron stars formed by iron-core collapse receive a large space velocity at birth. The existence of a population of low-kick neutron stars in binaries has important implications for understanding the formation of the neutron star population of globular clusters and for the origin of low-mass X-ray binaries and their descendants, the wide circular-orbit binary radio pulsars.

  7. Double-core evolution and the formation of neutron-star binaries with compact companions

    E-print Network

    J. D. M. Dewi; Ph. Podsiadlowski; A. Sena

    2006-02-23

    We present the results of a systematic exploration of an alternative evolutionary scenario to form double neutron-star binaries, first proposed by Brown (1995), which does not involve a neutron star passing through a common envelope. In this scenario, the initial binary components have very similar masses, and both components have left the main sequence before they evolve into contact; preferably the primary has already developed a CO core. We have performed population synthesis simulations to study the formation of double neutron star binaries via this channel and to predict the orbital properties and system velocities of such systems. We obtain a merger rate for DNSs in this channel in the range of 0.1 - 12/Myr. These rates are still subject to substantial uncertainties such as the modelling of the contact phase.

  8. Double stars

    Microsoft Academic Search

    J. Dommanget

    1989-01-01

    The work devoted to the identification of double and multiple stars for the Hipparcos input catalog is presented. Ground based observations, and photometric and astrometric aspects are included. The aim of the work is to improve the main stream of the data reduction. The tasks performed by the input catalog (INCA) double star working groups are reported. The contents of

  9. Constraints on Supernova Kicks from the Double Neutron Star System PSR B1913+16

    Microsoft Academic Search

    N. Wex; V. Kalogera; M. Kramer

    2000-01-01

    We use recent information on geodetic precession of the binary pulsar B1913+16 along with measurements of its orbital parameters and proper motion to derive new constraints on the immediate progenitor of this double neutron star system. As part of our analysis, we model the motion of the binary in the Galaxy after the second supernova explosion, and we derive constraints

  10. The Coalescence Rate of Double Neutron Star Systems

    E-print Network

    V. Kalogera; R. Narayan; D. N. Spergel; J. H. Taylor

    2001-03-21

    We estimate the coalescence rate of close binaries with two neutron stars (NS) and discuss the prospects for the detection of NS-NS inspiral events by ground-based gravitational-wave observatories, such as LIGO. We derive the Galactic coalescence rate using the observed sample of close NS-NS binaries (PSR B1913+16 and PSR B1534+12) and examine in detail each of the sources of uncertainty associated with the estimate. Specifically, we investigate (i) the dynamical evolution of NS-NS binaries in the Galactic potential and the vertical scale height of the population, (ii) the pulsar lifetimes, (iii) the effects of the faint end of the radio pulsar luminosity function and their dependence on the small number of observed objects, (iv) the beaming fraction, and (v) the extrapolation of the Galactic rate to extragalactic distances expected to be reachable by LIGO. We find that the dominant source of uncertainty is the correction factor (up to about 200) for faint (undetectable) pulsars. All other sources are much less important, each with uncertainty factors smaller than 2. Despite the relatively large uncertainty, the derived coalescence rate is approximately consistent with previously derived upper limits, and is more accurate than rates obtained from population studies. We obtain a most conservative lower limit for the LIGO II detection rate of 2 events per year. Our upper limit on the detection rate lies between 300 to more than 1000 events per year.

  11. The formation of the double neutron star pulsar J0737--3039

    E-print Network

    J. D. M. Dewi; E. P. J. van den Heuvel

    2003-12-05

    We find that the orbital period (2.4 hours), eccentricity (0.09), dipole magnetic field strength (6.9 x 10^9 Gauss) and spin period (22 ms) of the new highly relativistic double neutron star system PSR J0737-3039 can all be consistently explained if this system originated from a close helium star plus neutron star binary (HeS-NS) in which at the onset of the evolution the helium star had a mass in the range 4.0 to 6.5 M_sun and an orbital period in the range 0.1 to 0.2 days. Such systems are the post-Common-Envelope remnants of wide Be/X-ray binaries (orbital period ~ 100 to 1000 days) which consist of a normal hydrogen-rich star with a mass in the range 10 - 20 M_sun and a neutron star. The close HeS-NS progenitor system went through a phase of mass transfer by Roche-lobe overflow at a high rate lasting a few times 10^4 years; assuming Eddington-limited disk accretion onto the neutron star this star was spun up to its present rapid spin rate. At the moment of the second supernova explosion the He star had a mass in the range 2.3 to 3.3 M_sun and in order to obtain the present orbital parameters of PSR J0737-3039 a kick velocity in the range 70 - 230 km/s must have been imparted to the second neutron star at its birth.

  12. Accretion onto neutron stars with the presence of a double layer

    NASA Technical Reports Server (NTRS)

    Williams, A. C.; Weisskopf, M. C.; Elsner, R. F.; Darbro, W.; Sutherland, P. G.

    1987-01-01

    It is known, from laboratory experiments, that double layers will form in plasmas, usually in the presence of an electric current. It is argued that a double layer may be present in the accretion column of a neutron star in a binary system. It is suggested that the double layer may be the predominant deceleration mechanism for the accreting ions, especially for sources with X-ray luminosities of less than about 10 to the 37th erg/s. Previous models have involved either a collisionless shock or an assumed gradual deceleration of the accreting ions to thermalize the energy of the infalling matter.

  13. Accretion onto neutron stars with the presence of a double layer

    NASA Technical Reports Server (NTRS)

    Williams, A. C.; Weisskopf, M. C.; Elsner, R. F.; Darbro, W.; Sutherland, P. G.

    1986-01-01

    It is known from laboratory experiments that double layers can form in plasmas, usually in the presence of an electric current. It is argued that a double layer may be present in the accretion column of a neutron star in a binary system. It is suggested that the double layer may be the predominant deceleration mechanism for the accreting ions, especially for sources with X-ray luminosities of less than about 10 to the 37th erg/s. Previous models have involved either a collisionless shock or an assumed gradual deceleration of the accreting ions to thermalize the energy of the infalling matter.

  14. The spin period - eccentricity relation of double neutron stars: evidence for weak supernova kicks?

    E-print Network

    J D M Dewi; Ph Podsiadlowski; O R Pols

    2005-07-27

    Double neutron stars (DNSs), binary systems consisting of a radio pulsar and a generally undetected second neutron star (NS), have proven to be excellent laboratories for testing the theory of general relativity. The seven systems discovered in our Galaxy exhibit a remarkably well-defined relation between the pulsar spin period and the orbital eccentricity. Here we show, using a simple model where the pulsar is spun up by mass transfer from a helium-star companion, that this relation can only be produced if the second neutron star received a kick that is substantially smaller (with a velocity dispersion of less than 50 km/s) than the standard kick received by a single radio pulsar. This demonstrates that the kick mechanism depends on the evolutionary history of the NS progenitor and that the orbital parameters of DNSs are completely determined by the evolution in the preceding helium star - neutron star phase. This has important implications for estimating the rates of NS-NS mergers, one of the major potential astrophysical sources for the direct detection of gravitational waves, and for short-period gamma-ray bursts.

  15. An increased estimate of the merger rate of double neutron stars from observations of a highly relativistic system

    Microsoft Academic Search

    M. Burgay; N. D'Amico; A. Possenti; R. N. Manchester; A. G. Lyne; B. C. Joshi; M. A. McLaughlin; M. Kramer; J. M. Sarkissian; F. Camilo; V. Kalogera; C. Kim; D. R. Lorimer

    2003-01-01

    The merger of close binary systems containing two neutron stars should produce a burst of gravitational waves, as predicted by the theory of general relativity. A reliable estimate of the double-neutron-star merger rate in the Galaxy is crucial in order to predict whether current gravity wave detectors will be successful in detecting such bursts. Present estimates of this rate are

  16. PSR J1756-2251: a new relativistic double neutron star system

    E-print Network

    A. J. Faulkner; M. Kramer; A. G. Lyne; R. N. Manchester; M. A. McLaughlin; I. H. Stairs; G. Hobbs; A. Possenti; D. R. Lorimer; N. D'Amico; F. Camilo; M. Burgay

    2004-11-30

    We report the discovery during the Parkes Multibeam Pulsar Survey of PSR J1756-2251, a 28.5 ms pulsar in a relativistic binary system. Subsequent timing observations showed the pulsar to have an orbital period of 7.67 hrs and an eccentricity of 0.18. They also revealed a significant advance of periastron, 2.585+/-0.002 deg./yr. Assuming this is entirely due to general relativity implies a total system mass (pulsar plus companion) of 2.574+/-0.003 solar mass. This mass and the significant orbital eccentricity suggest that this is a double neutron star system. Measurement of the gravitational redshift, gamma, and an evaluation of the Shapiro delay shape, s, indicate a low companion mass of double neutron star systems.

  17. Pulsar Timing Observations and Tests of General Relativity in Double-Neutron-Star Binaries

    E-print Network

    I. H. Stairs

    2001-05-04

    We describe the techniques used in pulsar timing observations, and show how these observations may be applied to tests of strong-field general relativity for double-neutron-star binary systems. We describe the tests of GR resulting from the PSRs B1913+16 and B1534+12 systems. For the latter pulsar, 5 "Post-Keplerian" timing parameters are measurable, including the orbital period derivative and the two Shapiro delay parameters.

  18. THE DOUBLE PULSAR: EVIDENCE FOR NEUTRON STAR FORMATION WITHOUT AN IRON CORE-COLLAPSE SUPERNOVA

    SciTech Connect

    Ferdman, R. D.; Kramer, M.; Stappers, B. W.; Lyne, A. G. [School of Physics and Astronomy, University of Manchester, Jodrell Bank Centre for Astrophysics, Alan Turing Building, Oxford Road, Manchester M13 9PL (United Kingdom)] [School of Physics and Astronomy, University of Manchester, Jodrell Bank Centre for Astrophysics, Alan Turing Building, Oxford Road, Manchester M13 9PL (United Kingdom); Stairs, I. H. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1 (Canada)] [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC V6T 1Z1 (Canada); Breton, R. P. [School of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom)] [School of Physics and Astronomy, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); McLaughlin, M. A. [Department of Physics, West Virginia University, Morgantown, WV 26505 (United States)] [Department of Physics, West Virginia University, Morgantown, WV 26505 (United States); Freire, P. C. C. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany)] [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, D-53121 Bonn (Germany); Possenti, A. [INAF-Osservatorio Astronomico di Cagliari, Loc. Poggio dei Pini, I-09012 Capoterra (Italy)] [INAF-Osservatorio Astronomico di Cagliari, Loc. Poggio dei Pini, I-09012 Capoterra (Italy); Kaspi, V. M. [Department of Physics, McGill University, Ernest Rutherford Physics Building, 3600 University Street, Montreal, QC H3A 2T8 (Canada)] [Department of Physics, McGill University, Ernest Rutherford Physics Building, 3600 University Street, Montreal, QC H3A 2T8 (Canada); Manchester, R. N., E-mail: ferdman@jb.man.ac.uk [CSIRO Astronomy and Space Science, Australia Telescope National Facility, Epping, NSW 1710 (Australia)

    2013-04-10

    The double pulsar system PSR J0737-3039A/B is a double neutron star binary, with a 2.4 hr orbital period, which has allowed measurement of relativistic orbital perturbations to high precision. The low mass of the second-formed neutron star, as well as the low system eccentricity and proper motion, point to a different evolutionary scenario compared to most other known double neutron star systems. We describe analysis of the pulse profile shape over 6 years of observations and present the resulting constraints on the system geometry. We find the recycled pulsar in this system, PSR J0737-3039A, to be a near-orthogonal rotator with an average separation between its spin and magnetic axes of 90 Degree-Sign {+-} 11 Degree-Sign {+-} 5 Degree-Sign . Furthermore, we find a mean 95% upper limit on the misalignment between its spin and orbital angular momentum axes of 3. Degree-Sign 2, assuming that the observed emission comes from both magnetic poles. This tight constraint lends credence to the idea that the supernova that formed the second pulsar was relatively symmetric, possibly involving electron capture onto an O-Ne-Mg core.

  19. Neutron Stars

    NASA Technical Reports Server (NTRS)

    Cottam, J.

    2007-01-01

    Neutron stars were discovered almost 40 years ago, and yet many of their most fundamental properties remain mysteries. There have been many attempts to measure the mass and radius of a neutron star and thereby constrain the equation of state of the dense nuclear matter at their cores. These have been complicated by unknown parameters such as the source distance and burning fractions. A clean, straightforward way to access the neutron star parameters is with high-resolution spectroscopy. I will present the results of searches for gravitationally red-shifted absorption lines from the neutron star atmosphere using XMM-Newton and Chandra.

  20. Is the Bursting Radio-source GCRT J1745-3009 a Double Neutron Star Binary ?

    E-print Network

    R. Turolla; A. Possenti; A. Treves

    2005-06-18

    GCRT J1745-3009 is a peculiar transient radio-source in the direction of the Galactic Center. It was observed to emit a series of ~ 1 Jy bursts at 0.33 GHz, with typical duration ~ 10 min and at apparently regular intervals of ~ 77 min. If the source is indeed at the distance of the Galactic Center as it seems likely, we show that its observational properties are compatible with those expected from a double neutron star binary, similar to the double pulsar system J0737-3039. In the picture we propose the (coherent) radio emission comes from the shock originating in the interaction of the wind of the more energetic pulsar with the magnetosphere of the companion. The observed modulation of the radio signal is the consequence of an eccentric orbit, along which the separation between the two stars varies. This cyclically drives the shock inside the light cylinder radius of the less energetic pulsar.

  1. On the Eccentricities and Merger Rates of Double Neutron Star Binaries and the Creation of "Double Supernovae"

    E-print Network

    H. K. Chaurasia; M. Bailes

    2005-04-01

    We demonstrate that a natural consequence of an asymmetric kick imparted to neutron stars at birth is that the majority of double neutron star binaries should possess highly eccentric orbits. This leads to greatly accelerated orbital decay, due to the enormous increase in the emission of gravitational radiation at periastron as originally demonstrated by Peters (1964). A uniform distribution of kick velocities constrained to the orbital plane would result in ~24% of surviving binaries coalescing at least 10,000 times faster than an unperturbed circular system. Even if the planar kick constraint is lifted, ~6% of bound systems still coalesce this rapidly. In a non-negligible fraction of cases it may even be possible that the system could coalesce within 10 years of the final supernova, resulting in what we might term a "double supernova''. For systems resembling the progenitor of PSR J0737-3039A, this number is as high as \\~9% (in the planar kick model). Whether the kick velocity distribution extends to the range required to achieve this is still unclear. We do know that the observed population of binary pulsars has a deficit of highly eccentric systems at small orbital periods. In contrast, the long-period systems favour large eccentricities, as expected. We argue that this is because the short-period highly eccentric systems have already coalesced and are thus selected against by pulsar surveys. This effect needs to be taken into account when using the scale-factor method to estimate the coalescence rate of double neutron star binaries. We therefore assert that the coalesence rate of such binaries is underestimated by a factor of several.

  2. An increased estimate of the merger rate of double neutron stars from observations of a highly relativistic system

    E-print Network

    M. Burgay; N. D'Amico; A. Possenti; R. N. Manchester; A. G. Lyne; B. C. Joshi; M. A. McLaughlin; M. Kramer; J. M. Sarkissian; F. Camilo; V. Kalogera; C. Kim; D. R. Lorimer

    2003-12-02

    The merger of close binary systems containing two neutron stars should produce a burst of gravitational waves, as predicted by the theory of general relativity. A reliable estimate of the double-neutron-star merger rate in the Galaxy is crucial in order to predict whether current gravity wave detectors will be successful in detecting such bursts. Present estimates of this rate are rather low, because we know of only a few double-neutron-star binaries with merger times less than the age of the Universe. Here we report the discovery of a 22-ms pulsar, PSR J0737-3039, which is a member of a highly relativistic double-neutron-star binary with an orbital period of 2.4 hours. This system will merge in about 85 Myr, a time much shorter than for any other known neutron-star binary. Together with the relatively low radio luminosity of PSR J0737-3039, this timescale implies an order-of-magnitude increase in the predicted merger rate for double-neutron-star systems in our Galaxy (and in the rest of the Universe).

  3. An increased estimate of the merger rate of double neutron stars from observations of a highly relativistic system.

    PubMed

    Burgay, M; D'Amico, N; Possenti, A; Manchester, R N; Lyne, A G; Joshi, B C; McLaughlin, M A; Kramer, M; Sarkissian, J M; Camilo, F; Kalogera, V; Kim, C; Lorimer, D R

    2003-12-01

    The merger of close binary systems containing two neutron stars should produce a burst of gravitational waves, as predicted by the theory of general relativity. A reliable estimate of the double-neutron-star merger rate in the Galaxy is crucial in order to predict whether current gravity wave detectors will be successful in detecting such bursts. Present estimates of this rate are rather low, because we know of only a few double-neutron-star binaries with merger times less than the age of the Universe. Here we report the discovery of a 22-ms pulsar, PSR J0737-3039, which is a member of a highly relativistic double-neutron-star binary with an orbital period of 2.4 hours. This system will merge in about 85 Myr, a time much shorter than for any other known neutron-star binary. Together with the relatively low radio luminosity of PSR J0737-3039, this timescale implies an order-of-magnitude increase in the predicted merger rate for double-neutron-star systems in our Galaxy (and in the rest of the Universe). PMID:14654834

  4. Hunting for Gravitational Waves with Massive Gravitons from Inspiralling Double Neutron Star Systems with Pulsar Clocks

    E-print Network

    Joan Jing Wang; Hsiang-Kuang Chang

    2014-12-09

    Pulsars, especially millisecond pulsars, are intrinsically very stable celestial clocks, and their great pulse period stability open up a wide range of potential applications to astronomical phenomena, such as a natural detector for very low frequency ($10^{-7}-10^{-9}$ Hz) gravitational waves (GWs) background from supermassive black hole binaries. Double neutron star (DNS) binary systems, containing one or two radio pulsars, lose orbital energy by gravitational radiation, which leads to the orbital shrink. As a result, two neutron stars get closer and closer, during which it contributes to the emission of high frequency GWs of $1-10^4$ Hz. In this paper, we investigate the frequency shift of pulse signal for radio pulsars in DNS system that is induced by the emission of GWs from the system. We point out that the pulse frequency shift of radio signal in these systems can be a potential tool to hunt for the high-frequency GWs, with massive gravitons, from DNS systems, which resorts to a temporal shift of gravitational constant $\\delta G(t)/G$. The sensitivity to high-frequency GWs from DNS by radio pulse frequency shift is discussed. The correlation between timing residuals of pulsar pair in double radio pulsars, such as the system PSR 0737-3039 A(B), is also considered.

  5. Observation time to first detection of double neutron star mergers by gravitational wave observatories

    E-print Network

    D. M. Coward

    2008-06-15

    We constrain the uncertainty in waiting times for detecting the first double-neutron-star (DNS) mergers by gravitational wave observatories. By accounting for the Poisson fluctuations in the rate density of DNS mergers and galaxy space density inhomogeneity in the local Universe, we define a detection `zone' as a region in a parameter space constrained by the double neutron star merger rate and two LIGO operations parameters: an observation horizon distance and science run duration. Assuming a mean rate of about 80 DNS mergers per Milky Way galaxy Myr^{-1}, we find a 1/20 chance of observing a merger by Enhanced LIGO in only 1 yr of observation. The minimum waiting time and temporal zone width for an Advanced LIGO sensitivity are much shorter and imply that there is a 95% probability of detecting a DNS merger in less than 60 days and a 1/20 chance of a first detection in about 1 day. At the 5% probability threshold for a first detection, we find that the effect of galaxy clusters on detection is smoothed out and may only influence detection rates after 5-10 years observation time.

  6. CXOU J121538.2+361921 in the galaxy NGC 4214: a double neutron star in the making?

    E-print Network

    J. Dewi

    2006-07-05

    CXOU J121538.2+361921 is the brightest X-ray source in the galaxy NGC 4214, with an X-ray luminosity of up to 0.7 x 10^39 erg/s. The observed periodicity of 3.62 hr is interpreted as the orbital period of the system. It has been suggested that the system is a low-mass helium star with a lower-mass compact companion. If this idea is correct, then CXOU J121538.2+361921 will evolve into a double neutron star, a binary consisting of a radio pulsar and another neutron star. In this study we investigate further this possibility. We find that the X-ray luminosity is consistent with super-Eddington accretion in a helium star-neutron star binary. The binary is in a state of mass transfer phase which is initiated when the helium-star donor is on the helium shell burning stage. A donor star with a current mass in the range of around 2.2 - 3.6 Msun is required to explain the observed orbital period. Helium stars in this mass range are massive enough to collapse in a supernova explosion, making CXOU J121538.2+361921 the immediate progenitor of a double neutron star.

  7. The gravitational-wave signal generated by a galactic population of double neutron-star binaries

    E-print Network

    Yu, Shenghua

    2015-01-01

    We investigate the gravitational wave (GW) signal generated by a population of double neutron-star binaries (DNS) with eccentric orbits caused by kicks during supernova collapse and binary evolution. The DNS population of a standard Milky-Way type galaxy has been studied as a function of star formation history, initial mass function (IMF) and metallicity and of the binary-star common-envelope ejection process. The model provides birth rates, merger rates and total numbers of DNS as a function of time. The GW signal produced by this population has been computed and expressed in terms of a hypothetical space GW detector (eLISA) by calculating the number of discrete GW signals at different confidence levels, where `signal' refers to detectable GW strain in a given frequency-resolution element. In terms of the parameter space explored, the number of DNS-originating GW signals is greatest in regions of recent star formation, and is significantly increased if metallicity is reduced from 0.02 to 0.001, consistent wi...

  8. A New Formation Channel for Double Neutron Stars Without Recycling: Implications for Gravitational Wave Detection

    E-print Network

    K. Belczynski; V. Kalogera

    2001-02-12

    We report on a new evolutionary path leading to the formation of close double neutron stars (NS), with the unique characteristic that none of the two NS ever had the chance to be recycled by accretion. The existence of this channel stems from the evolution of helium-rich stars (cores of massive NS progenitors), which has been neglected in most previous studies of double compact object formation. We find that these non-recycled NS-NS binaries are formed from bare carbon-oxygen cores in tight orbits, with formation rates comparable to or maybe even higher than those of recycled NS-NS binaries. On the other hand, their detection probability as binary pulsars is greatly reduced (by about 1000) relative to recycled pulsars, because of their short lifetimes. We conclude that, in the context of gravitational-wave detection of NS-NS inspiral events, this new type of binaries calls for an increase of the rate estimates derived from the observed NS-NS with recycled pulsars, typically by factors of 1.5-3 or even higher.

  9. Erratum: ``The Cosmic Coalescence Rates for Double Neutron Star Binaries''(ApJ, 601, L179 [2004])

    Microsoft Academic Search

    V. Kalogera; C. Kim; D. R. Lorimer; M. Burgay; N. D'Amico; A. Possenti; R. N. Manchester; A. G. Lyne; B. C. Joshi; M. A. McLaughlin; M. Kramer; J. M. Sarkissian; F. Camilo

    2004-01-01

    In our original Letter, we calculated the likely size of the Galactic double neutron star (DNS) population in two stages. First, we simulated the DNS distribution in the Galaxy. At this stage, in addition to storing the spatial properties and luminosities of the model pulsars, we also computed their expected dispersion measures and pulse scatter broadening times using a model

  10. Demagnified gravitational waves from cosmological double neutron stars and gravitational wave foreground cleaning around 1 Hz

    NASA Astrophysics Data System (ADS)

    Seto, Naoki

    2009-11-01

    Gravitational waves (GWs) from cosmological double neutron star binaries (NS+NS) can be significantly demagnified by the strong gravitational lensing effect, and the proposed future missions such as the Big Bang Observer or Deci-hertz Interferometer Gravitational Wave Observatory might miss some of the demagnified GW signals below a detection threshold. The undetectable binaries would form a GW foreground, which might hamper detection of a very weak primordial GW signal. We discuss the outlook of this potential problem, using a simple model based on the singular isothermal sphere lens profile. Fortunately, it is expected that, for a presumable merger rate of NS+NSs, the residual foreground would be below the detection limit ?GW,lim˜10-16 realized with the Big Bang Observer/Deci-hertz Interferometer Gravitational Wave Observatory by correlation analysis.

  11. Demagnified GWs from Cosmological Double Neutron Stars and GW Foreground Cleaning Around 1Hz

    E-print Network

    Naoki Seto

    2009-10-26

    Gravitational waves from cosmological double neutron star binaries can be significantly demagnified by strong gravitational lensing effect, and the proposed future missions such as BBO or DECIGO might miss some of the demagnified GW signals below a detection threshold. The undetectable binaries would form a GW foreground which might hamper detection of a very weak primordial GW signal. We discuss the outlook of this potential problem, using a simple model based on the singular-isothermal-sphere lens profile. Fortunately, it is expected that, for presumable merger rate of NS+NSs, the residual foreground would be below the detection limit Omega_{GW} ~ 10^{-16} realized with BBO/DECIGO by correlation analysis.

  12. Demagnified gravitational waves from cosmological double neutron stars and gravitational wave foreground cleaning around 1 Hz

    SciTech Connect

    Seto, Naoki [Department of Physics, Kyoto University, Kyoto 606-8502 (Japan)

    2009-11-15

    Gravitational waves (GWs) from cosmological double neutron star binaries (NS+NS) can be significantly demagnified by the strong gravitational lensing effect, and the proposed future missions such as the Big Bang Observer or Deci-hertz Interferometer Gravitational Wave Observatory might miss some of the demagnified GW signals below a detection threshold. The undetectable binaries would form a GW foreground, which might hamper detection of a very weak primordial GW signal. We discuss the outlook of this potential problem, using a simple model based on the singular isothermal sphere lens profile. Fortunately, it is expected that, for a presumable merger rate of NS+NSs, the residual foreground would be below the detection limit {omega}{sub GW,lim}{approx}10{sup -16} realized with the Big Bang Observer/Deci-hertz Interferometer Gravitational Wave Observatory by correlation analysis.

  13. Cyg X-3: a Galactic double black hole or black hole-neutron star progenitor

    E-print Network

    Krzysztof Belczynski; Tomasz Bulik; Ilya Mandel; B. S. Sathyaprakash; Andrzej Zdziarski; Joanna Mikolajewska

    2012-09-12

    There are no known double black hole (BH-BH) or black hole-neutron star (BH-NS) systems. We argue that Cyg X-3 is a very likely BH-BH or BH-NS progenitor. This Galactic X-ray binary consists of a compact object, wind-fed by a Wolf-Rayet (WR) type companion. Based on a comprehensive analysis of observational data, it was recently argued that Cyg X-3 harbors a 2-4.5 Msun BH and a 7.5-14.2 Msun WR companion. We find that the fate of such a binary leads to the prompt (13 Msun). For the low- to mid-mass range of the WR star (M_WR=7-10 Msun) Cyg X-3 is most likely (probability 70%) disrupted when WR ends up as a supernova. However, with smaller probability, it may form a wide (15%) or a close (15%) BH-NS system. The advanced LIGO/VIRGO detection rate for mergers of BH-BH systems from the Cyg X-3 formation channel is 10 per year, while it drops down to 0.1 per year for BH-NS systems. If Cyg X-3 in fact hosts a low mass BH and massive WR star, it lends additional support for the existence of BH-BH/BH-NS systems.

  14. The gravitational-wave signal generated by a galactic population of double neutron-star binaries

    NASA Astrophysics Data System (ADS)

    Yu, Shenghua; Jeffery, C. Simon

    2015-04-01

    We investigate the gravitational wave (GW) signal generated by a population of double neutron-star (DNS) binaries with eccentric orbits caused by kicks during supernova collapse and binary evolution. The DNS population of a standard Milky Way-type galaxy has been studied as a function of star formation history, initial mass function (IMF) and metallicity and of the binary-star common-envelope ejection process. The model provides birthrates, merger rates and total number of DNS as a function of time. The GW signal produced by this population has been computed and expressed in terms of a hypothetical space GW detector (eLISA) by calculating the number of discrete GW signals at different confidence levels, where `signal' refers to detectable GW strain in a given frequency-resolution element. In terms of the parameter space explored, the number of DNS-originating GW signals is greatest in regions of recent star formation, and is significantly increased if metallicity is reduced from 0.02 to 0.001, consistent with Belczynski et al. Increasing the IMF power-law index (from -2.5 to -1.5) increases the number of GW signals by a large factor. This number is also much higher for models where the common-envelope ejection is treated using the ?-mechanism (energy conservation) than when using the ?-mechanism (angular-momentum conservation). We have estimated the total number of detectable DNS GW signals from the Galaxy by combining contributions from thin disc, thick disc, bulge and halo. The most probable numbers for an eLISA-type experiment are 0-1600 signals per year at S/N ? 1, 0-900 signals per year at S/N ? 3, and 0-570 at S/N ? 5, coming from about 0-65, 0-60 and 0-50 resolved DNS, respectively.

  15. Physics of gamma-ray bursts and multi-messenger signals from double neutron star mergers

    NASA Astrophysics Data System (ADS)

    Gao, He

    My dissertation includes two parts: Physics of Gamma-Ray Bursts (GRBs): Gamma-ray bursts are multi-wavelength transients, with both prompt gamma-ray emission and late time afterglow emission observed by telescopes in different wavelengths. I have carried out three investigations to understand GRB prompt emission and afterglow. Chapter 2 develops a new method, namely, "Stepwise Filter Correlation" method, to decompose the variability components in a light curve. After proving its reliability through simulations, we apply this method to 266 bright GRBs and find that the majority of the bursts have clear evidence of superposition of fast and slow variability components. Chapter 3 gives a complete presentation of the analytical approximations for synchrotron self-compton emission for all possible orders of the characteristic synchrotron spectral breaks (nua, nu m, and nuc). We identify a "strong absorption" regime whennua > nuc, and derive the critical condition for this regime. The external shock theory is an elegant theory to model GRB afterglows. It invokes a limit number of model parameters, and has well predicted spectral and temporal properties. Chapter 4 gives a complete reference of all the analytical synchrotron external shock afterglow models by deriving the temporal and spectral indices of all the models in all spectral regimes. This complete reference will serve as a useful tool for afterglow observers to quickly identify relevant models to interpret their data and identify new physics when the models fail. Milti-messenger signals from double neutron star merger: As the multi-messenger era of astronomy ushers in, the second part of the dissertation studies the possible electromagnetic (EM) and neutrino emission counterparts of double neutron star mergers. Chapter 6 suggests that if double neutron star mergers leave behind a massive magnetar rather than a black hole, the magnetar wind could push the ejecta launched during the merger process, and under certain conditions, accelerates it to a relativistic speed. Such a magnetar-powered ejecta, when interacting with the ambient medium, would develop a bright broad-band afterglow due to external shock synchrotron radiation. We study this physical scenario in detail, and present the predicted X-ray, optical and radio light curves for a range of magnetar and ejecta parameters. Chapter 7 applies the model to interpret one optical transient discovered recently. In chapter 8, we show that protons accelerated in the external shock would interact with photons generated in the dissipating magnetar wind and emit high energy neutrinos and photons. We find that PeV neutrinos could be emitted from the shock front as long as the ejecta could be accelerated to a relativistic speed. These events would contribute to the diffuse Pev neutrino background and sub-Tev gamma-ray background.

  16. CYG X-3: A GALACTIC DOUBLE BLACK HOLE OR BLACK-HOLE-NEUTRON-STAR PROGENITOR

    SciTech Connect

    Belczynski, Krzysztof; Bulik, Tomasz [Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, 00-478 Warsaw (Poland)] [Astronomical Observatory, University of Warsaw, Al. Ujazdowskie 4, 00-478 Warsaw (Poland); Mandel, Ilya [School of Physics and Astronomy, University of Birmingham, Edgbaston B15 2TT (United Kingdom)] [School of Physics and Astronomy, University of Birmingham, Edgbaston B15 2TT (United Kingdom); Sathyaprakash, B. S. [School of Physics and Astronomy, Cardiff University, 5, The Parade, Cardiff CF24 3YB (United Kingdom)] [School of Physics and Astronomy, Cardiff University, 5, The Parade, Cardiff CF24 3YB (United Kingdom); Zdziarski, Andrzej A.; Mikolajewska, Joanna [Centrum Astronomiczne im. M. Kopernika, Bartycka 18, PL-00-716 Warszawa (Poland)] [Centrum Astronomiczne im. M. Kopernika, Bartycka 18, PL-00-716 Warszawa (Poland)

    2013-02-10

    There are no known stellar-origin double black hole (BH-BH) or black-hole-neutron-star (BH-NS) systems. We argue that Cyg X-3 is a very likely BH-BH or BH-NS progenitor. This Galactic X-ray binary consists of a compact object, wind-fed by a Wolf-Rayet (W-R) type companion. Based on a comprehensive analysis of observational data, it was recently argued that Cyg X-3 harbors a 2-4.5 M {sub Sun} black hole (BH) and a 7.5-14.2 M {sub Sun} W-R companion. We find that the fate of such a binary leads to the prompt ({approx}< 1 Myr) formation of a close BH-BH system for the high end of the allowed W-R mass (M {sub W-R} {approx}> 13 M {sub Sun }). For the low- to mid-mass range of the W-R star (M {sub W-R} {approx} 7-10 M {sub Sun }) Cyg X-3 is most likely (probability 70%) disrupted when W-R ends up as a supernova. However, with smaller probability, it may form a wide (15%) or a close (15%) BH-NS system. The advanced LIGO/VIRGO detection rate for mergers of BH-BH systems from the Cyg X-3 formation channel is {approx}10 yr{sup -1}, while it drops down to {approx}0.1 yr{sup -1} for BH-NS systems. If Cyg X-3 in fact hosts a low-mass black hole and massive W-R star, it lends additional support for the existence of BH-BH/BH-NS systems.

  17. The Probability Distribution of the Double Neutron Star Coalescence Rate and Predictions for More Detections

    E-print Network

    Vassiliki Kalogera; Chunglee Kim; Duncan R. Lorimer

    2002-12-02

    We present an analysis method that allows us to estimate the Galactic formation of radio pulsar populations based on their observed properties and our understanding of survey selection effects. More importantly, this method allows us to assign a statistical significance to such rate estimates and calculate the allowed ranges of values at various confidence levels. Here, we apply the method to the question of the double neutron star (NS-NS) coalescence rate using the current observed sample, and we find calculate the most likely value for the total Galactic coalescence rate to lie in the range 3-22 Myr^{-1}, for different pulsar population models. The corresponding range of expected detection rates of NS--NS inspiral are (1-9)x10^{-3} yr^{-1} for the initial LIGO, and 6-50 yr^{-1} for the advanced LIGO. Based on this newly developed statistical method, we also calculate the probability distribution for the expected number of pulsars that could be observed by the Parkes Multibeam survey, when acceleration searches will alleviate the effects of Doppler smearing due to orbital motions. We suggest that the Parkes survey will probably detect 1-2 new binary pulsars like PSRs B1913+16 and/or B1534+12.

  18. Evolution of the double neutron star merging rate and the cosmological origin of gamma-ray burst sources

    Microsoft Academic Search

    V. M. Lipunov; K. A. Postnov; M. E. Prokhorov; I. E. Panchenko; H. E. Jorgensen

    1995-01-01

    Evolution of the coalescence rate of double neutron stars (NS) and neutron\\u000astar -- black hole (BH) binaries are computed for model galaxies with different\\u000astar formation rates. Assuming gamma-ray bursts (GRB) to originate from NS+NS\\u000aor NS+BH merging in distant galaxies, theoretical logN--logS distributions and\\u000a tests of gamma-ray bursts (GRB) are calculated for the first time\\u000ataking the

  19. An Upper Limit on the Coalescence Rate of Double Neutron-Star Binaries in the Galaxy

    Microsoft Academic Search

    Vassiliki Kalogera; Duncan R. Lorimer

    2000-01-01

    In the context of assessing the detectability of the coalescence of two neutron stars (NS) by currently built gravitational wave experiments, we present a way of obtaining an upper limit to the coalescence rate in the Galaxy. We consider the NS\\/NS progenitors just before the second supernova explosion. We combine the theoretical understanding of orbital dynamics at NS formation with

  20. Evolution of the double neutron star merging rate and the cosmological origin of gamma-ray burst sources

    E-print Network

    V. M. Lipunov; K. A. Postnov; M. E. Prokhorov; I. E. Panchenko

    1995-04-13

    Evolution of the coalescence rate of double neutron stars (NS) and neutron star -- black hole (BH) binaries are computed for model galaxies with different star formation rates. Assuming gamma-ray bursts (GRB) to originate from NS+NS or NS+BH merging in distant galaxies, theoretical logN--logS distributions and tests of gamma-ray bursts (GRB) are calculated for the first time taking the computed merging rates into account. We use a flat cosmological model (Omega=1) with different values of the cosmological constant Lambda and under various assumptions about the star formation history in galaxies. The calculated source evolution predicts a 5-10 times increase of the source statistics at count rates 3-10 times lower than the exising BATSE sensitivity limit. The most important parameter in fitting the 2nd BATSE catalogue is the initial redshift of star formation, which is found to be z_*=2-5 depending on a poorly determined average spectral index of GRB.

  1. Double core evolution. 7: The infall of a neutron star through the envelope of its massive star companion

    NASA Technical Reports Server (NTRS)

    Terman, James L.; Taam, Ronald E.; Hernquist, Lars

    1995-01-01

    Binary systems with properties similar to those of high-mass X-ray binaries are evolved through the common envelope phase. Three-dimensional simulations show that the timescale of the infall phase of the neutron star depends upon the evolutionary state of its massive companion. We find that tidal torques more effectively accelerate common envelope evolution for companions in their late core helium-burning stage and that the infall phase is rapid (approximately several initial orbital periods). For less evolved companions the decay of the orbit is longer; however, once the neutron star is deeply embedded within the companion's envelope the timescale for orbital decay decreases rapidly. As the neutron star encounters the high-density region surrounding the helium core of its massive companion, the rate of energy loss from the orbit increases dramatically leading to either partial or nearly total envelope ejection. The outcome of the common envelope phase depends upon the structure of the evolved companion. In particular, it is found that the entire common envelope can be ejected by the interaction of the neutron star with a red supergiant companion in binaries with orbital periods similar to those of long-period Be X-ray binaries. For orbital periods greater than or approximately equal to 0.8-2 yr (for companions of mass 12-24 solar mass) it is likely that a binary will survive the common envelope phase. For these systems, the structure of the progenitor star is characterized by a steep density gradient above the helium core, and the common envelope phase ends with a spin up of the envelope to within 50%-60% of corotation and with a slow mass outflow. The efficiency of mass ejection is found to be approximately 30%-40%. For less evolved companions, there is insufficient energy in the orbit to unbind the common envelope and only a fraction of it is ejected. Since the timescale for orbital decay is always shorter than the mass-loss timescale from the common envelope, the two cores will likely merge to form a Thorne-Zytkow object. Implications for the origin of Cyg X-3, an X-ray source consisting of a Wolf-Rayet star and a compact companion, and for the fate of the remnant binary consisting of a helium star and a neutron star are briefly discussed.

  2. Neutron-Capture Elements in the Double-Enhanced Star HE 1305-0007: a New s- and r-Process Paradigm

    E-print Network

    Wen-Yuan Cui; D. N. Cui; Y. S. Du; B. Zhang

    2007-04-04

    The star HE 1305-0007 is a metal-poor double-enhanced star with metallicity [Fe/H] $=-2.0$, which is just at the upper limit of the metallicity for the observed double-enhanced stars. Using a parametric model, we find that almost all s-elements were made in a single neutron exposure. This star should be a member of a post-common-envelope binary. After the s-process material has experienced only one neutron exposure in the nucleosynthesis region and is dredged-up to its envelope, the AGB evolution is terminated by the onset of common-envelope evolution. Based on the high radial-velocity of HE 1305-0007, we speculate that the star could be a runaway star from a binary system, in which the AIC event has occurred and produced the r-process elements.

  3. Neutron skins and neutron stars

    SciTech Connect

    Piekarewicz, J. [Department of Physics, Florida State University, Tallahassee, FL 32306-4350 (United States)

    2013-11-07

    The neutron-skin thickness of heavy nuclei provides a fundamental link to the equation of state of neutron-rich matter, and hence to the properties of neutron stars. The Lead Radius Experiment ('PREX') at Jefferson Laboratory has recently provided the first model-independence evidence on the existence of a neutron-rich skin in {sup 208}Pb. In this contribution we examine how the increased accuracy in the determination of neutron skins expected from the commissioning of intense polarized electron beams may impact the physics of neutron stars.

  4. An Upper Limit on the Coalescence Rate of Double Neutron-Star Binaries in the Galaxy

    E-print Network

    Vassiliki Kalogera; Duncan Lorimer

    1999-09-30

    In the context of assessing the detectability of the coalescence of two neutron stars (NS) by currently built gravitational-wave experiments, we present a way of obtaining an upper limit to the coalescence rate in the Galaxy. We consider the NS/NS progenitors just before the second supernova explosion. By combining our theoretical understanding of orbital dynamics at NS formation with methods of empirically estimating pulsar birth rates we derive an upper limit of a few mergers every 100,000 yr. Such a Galactic rate implies a possible detection by the ``enhanced'' LIGO of up to a few to ten mergers per year.

  5. Dibaryons in neutron stars

    NASA Technical Reports Server (NTRS)

    Olinto, Angela V.; Haensel, Pawel; Frieman, Joshua A.

    1991-01-01

    The effects are studied of H-dibaryons on the structure of neutron stars. It was found that H particles could be present in neutron stars for a wide range of dibaryon masses. The appearance of dibaryons softens the equations of state, lowers the maximum neutron star mass, and affects the transport properties of dense matter. The parameter space is constrained for dibaryons by requiring that a 1.44 solar mass neutron star be gravitationally stable.

  6. Expected Coalescence Rate of Double Neutron Stars for Ground Based Interferometers

    E-print Network

    T. Regimbau; J. A. de Freitas Pacheco; A. Spallicci; S. Vincent

    2005-06-14

    In this paper we present new estimates of the coalescence rate of neutron star binaries in the local universe and we discuss its consequences for the first generations of ground based interferometers. Our approach based on both evolutionary and statistical methods gives a galactic merging rate of 1.7 10$^{-5}$ yr$^{-1}$, in the range of previous estimates 10$^{-6}$ - 10$^{-4}$ yr$^{-1}$. The local rate which includes the contribution of elliptical galaxies is two times higher, in the order of 3.4 10$^{-5}$ yr$^{-1}$. We predict one detection every 148 and 125 years with initial VIRGO and LIGO, and up to 6 events per year with their advanced configuration. Our recent detection rate estimates from investigations on VIRGO future improvements are quoted.

  7. Hadron star models. [neutron stars

    NASA Technical Reports Server (NTRS)

    Cohen, J. M.; Boerner, G.

    1974-01-01

    The properties of fully relativistic rotating hadron star models are discussed using models based on recently developed equations of state. All of these stable neutron star models are bound with binding energies as high as about 25%. During hadron star formation, much of this energy will be released. The consequences, resulting from the release of this energy, are examined.

  8. ORBITAL VARIATION OF THE X-RAY EMISSION FROM THE DOUBLE NEUTRON STAR BINARY J1537+1155

    SciTech Connect

    Durant, Martin; Kargaltsev, Oleg [Department of Astronomy, University of Florida, Gainesville, FL 32611-2055 (United States); Volkov, Igor; Pavlov, George G., E-mail: martin.durant@astro.ufl.edu, E-mail: oyk100@astro.ufl.edu, E-mail: pavlov@astro.psu.edu [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States)

    2011-11-01

    We observed the double neutron star binary (DNSB) containing PSR J1537+1155 (also known as B1534+12) with the Chandra X-Ray Observatory. This is one of the two DNSBs detected in X-rays and the only one where a hint of variability with orbital phase was found (in the previous Chandra observation). Our follow-up observation supports the earlier result: the distribution of photon arrival times with orbital phase again shows a deficit around apastron. The significance of the deficit in the combined data set exceeds 99%. Such an orbital light curve suggests that the X-ray emission is seen only when neutron star (NS) B passes through the equatorial pulsar wind of NS A. We describe statistical tests that we used to determine the significance of the deficit, and conclusions that can be drawn from its existence, such as interaction of the pulsar wind with the NS companion. We also provide better constrained spectral model parameters obtained from the joint spectral fits to the data from both observations. A power law successfully fits the data, with best-fit photon index {Gamma} = 3.1 {+-} 0.4 and unabsorbed flux f = (3.2 {+-} 0.8) Multiplication-Sign 10{sup -15} erg s{sup -1} cm{sup -2} (0.3-8 keV range).

  9. A Double Neutron Star Merger Origin for the Cosmological Relativistic Fading Source PTF11agg?

    NASA Astrophysics Data System (ADS)

    Wu, Xue-Feng; Gao, He; Ding, Xuan; Zhang, Bing; Dai, Zi-Gao; Wei, Jian-Yan

    2014-01-01

    The Palomar Transient Factory (PTF) team recently reported the discovery of a rapidly fading optical transient source, PTF11agg. A long-lived scintillating radio counterpart was identified, but the search for a high-energy counterpart showed negative results. The PTF team speculated that PTF11agg may represent a new class of relativistic outbursts. Here we suggest that a neutron star (NS)-NS merger system with a supra-massive magnetar central engine could be a possible source to power such a transient, if our line of sight is not on the jet axis direction of the system. These systems are also top candidates for gravitational wave sources to be detected in the advanced LIGO/Virgo era. We find that the PTF11agg data could be explained well with such a model, suggesting that at least some gravitational wave bursts due to NS-NS mergers may be associated with such a bright electromagnetic counterpart without a ?-ray trigger.

  10. Introduction to neutron stars

    NASA Astrophysics Data System (ADS)

    Lattimer, James M.

    2015-02-01

    Neutron stars contain the densest form of matter in the present universe. General relativity and causality set important constraints to their compactness. In addition, analytic GR solutions are useful in understanding the relationships that exist among the maximum mass, radii, moments of inertia, and tidal Love numbers of neutron stars, all of which are accessible to observation. Some of these relations are independent of the underlying dense matter equation of state, while others are very sensitive to the equation of state. Recent observations of neutron stars from pulsar timing, quiescent X-ray emission from binaries, and Type I X-ray bursts can set important constraints on the structure of neutron stars and the underlying equation of state. In addition, measurements of thermal radiation from neutron stars has uncovered the possible existence of neutron and proton superfluidity/superconductivity in the core of a neutron star, as well as offering powerful evidence that typical neutron stars have significant crusts. These observations impose constraints on the existence of strange quark matter stars, and limit the possibility that abundant deconfined quark matter or hyperons exist in the cores of neutron stars.

  11. Neutron Star Collision

    NSDL National Science Digital Library

    Dave Bock

    1999-01-21

    Systems of orbiting neutron stars are born when the cores of two old stars collapse in supernova explosions. Neutron stars have the mass of our Sun but are the size of a city, so dense that boundaries between atoms disappear. Einsteins theory of general relativity predicts that the orbit shrinks from ripples of space-time called gravitational waves. After about 1 billion simulation years, the two neutron stars closely circle each other at 60,000 revolutions per minute. The stars finally merge in a few milliseconds, sending out a burst of gravitational waves.

  12. The Double Star mission

    Microsoft Academic Search

    Z. X. Liu; C. P. Escoubet; Z. Pu; H. Laakso; J. K. Shi; C. Shen; M. Hapgood

    2005-01-01

    The Double Star Programme (DSP) was first proposed by China in March, 1997 at the Fragrant Hill Workshop on Space Science, Beijing, organized by the Chinese Academy of Science. It is the first mission in collaboration between China and ESA. The mission is made of two spacecraft to investigate the magnetospheric global processes and their response to the interplanetary disturbances

  13. Sonoluminescence in Neutron Stars

    E-print Network

    Walter Simmons; John Learned; Sandip Pakvasa; Xerxes Tata

    1996-02-27

    After a brief discussion of a possible relationship between the electroweak phase transition in highly compressed matter and gravitational collapse, we examine the speculative possibility that the electroweak phase transition might be contemporarily occurring in processes in neutron stars. We conjecture that adiabatic compression of neutron star matter due to focusing of the energy from a supernova bounce into a very small volume could result in extreme densities, and Fermi levels or temperature above $\\cal{O}$ (100 GeV). We propose a qualitative scenario for sonoluminescence in neutron stars and discuss possible observable consequences.

  14. Sonoluminescence in neutron stars

    E-print Network

    Simmons, W; Pakvasa, S; Tata, Xerxes; Simmons, Walter; Learned, John; Pakvasa, Sandip; Tata, Xerxes

    1998-01-01

    After a brief discussion of a possible relationship between the electroweak phase transition in highly compressed matter and gravitational collapse, we examine the speculative possibility that the electroweak phase transition might be contemporarily occurring in processes in neutron stars. We conjecture that adiabatic compression of neutron star matter due to focusing of the energy from a supernova bounce into a very small volume could result in extreme densities, and Fermi levels or temperature above \\cal{O} (100 GeV). We propose a qualitative scenario for sonoluminescence in neutron stars and discuss possible observable consequences.

  15. Hyperons in neutron stars

    E-print Network

    Tetsuya Katayama; Koichi Saito

    2015-01-22

    Using the Dirac-Brueckner-Hartree-Fock approach, the properties of neutron-star matter including hyperons are investigated. In the calculation, we consider both time and space components of the vector self-energies of baryons as well as the scalar ones. Furthermore, the effect of negative-energy states of baryons is partly taken into account. We obtain the maximum neutron-star mass of $2.08\\,M_{\\odot}$, which is consistent with the recently observed, massive neutron stars. We discuss a universal, repulsive three-body force for hyperons in matter.

  16. Cooling of neutron stars

    NASA Technical Reports Server (NTRS)

    Pethick, C. J.

    1992-01-01

    It is at present impossible to predict the interior constitution of neutron stars based on theory and results from laboratory studies. It has been proposed that it is possible to obtain information on neutron star interiors by studying thermal radiation from their surfaces, because neutrino emission rates, and hence the temperature of the central part of a neutron star, depend on the properties of dense matter. The theory predicts that neutron stars cool relatively slowly if their cores are made up of nucleons, and cool faster if the matter is in an exotic state, such as a pion condensate, a kaon condensate, or quark matter. This view has recently been questioned by the discovery of a number of other processes that could lead to copious neutrino emission and rapid cooling.

  17. The Double Star mission

    NASA Astrophysics Data System (ADS)

    Liu, Z. X.; Escoubet, C. P.; Pu, Z.; Laakso, H.; Shi, J. K.; Shen, C.; Hapgood, M.

    2005-11-01

    The Double Star Programme (DSP) was first proposed by China in March, 1997 at the Fragrant Hill Workshop on Space Science, Beijing, organized by the Chinese Academy of Science. It is the first mission in collaboration between China and ESA. The mission is made of two spacecraft to investigate the magnetospheric global processes and their response to the interplanetary disturbances in conjunction with the Cluster mission. The first spacecraft, TC-1 (Tan Ce means "Explorer"), was launched on 29 December 2003, and the second one, TC-2, on 25 July 2004 on board two Chinese Long March 2C rockets. TC-1 was injected in an equatorial orbit of 570x79000 km altitude with a 28° inclination and TC-2 in a polar orbit of 560x38000 km altitude. The orbits have been designed to complement the Cluster mission by maximizing the time when both Cluster and Double Star are in the same scientific regions. The two missions allow simultaneous observations of the Earth magnetosphere from six points in space. To facilitate the comparison of data, half of the Double Star payload is made of spare or duplicates of the Cluster instruments; the other half is made of Chinese instruments. The science operations are coordinated by the Chinese DSP Scientific Operations Centre (DSOC) in Beijing and the European Payload Operations Service (EPOS) at RAL, UK. The spacecraft and ground segment operations are performed by the DSP Operations and Management Centre (DOMC) and DSOC in China, using three ground station, in Beijing, Shanghai and Villafranca.

  18. The evolution and birth properties of the most massive stars as progenitors of double neutron stars and black holes

    NASA Astrophysics Data System (ADS)

    De Mink, Selma

    Improving our understanding of the evolution of most massive stars from their birth marked by the onset of nuclear burning until their death marked by their final explosions is crucial for predicting an understanding the nature and rate of detectable gravitational wave sources. I will highlight several recent advancements in this area triggered by the combination of theoretical work and new large spectroscopic surveys of massive stars. I will discuss (a) new constraints on the initial conditions: the binary frequency, distribution of separations, mass ratios, eccentricities and rotation rates, (b) ongoing attempts to understand the potentially drastic effects of mixing induced by stellar rotation and its consequences for the final core masses and (c) attempts to find observational constraints for stars with 100-500 solar masses.

  19. The Probability Distribution of Binary Pulsar Coalescence Rates. I. Double Neutron Star Systems in the Galactic Field

    Microsoft Academic Search

    C. Kim; V. Kalogera; D. R. Lorimer

    2003-01-01

    Estimates of the Galactic coalescence rate (R) of close binaries with two neutron stars (NS-NS) are known to be uncertain by large factors (about 2 orders of magnitude) mainly because of the small number of systems detected as binary radio pulsars. We present an analysis method that allows us to estimate the Galactic NS-NS coalescence rate using the current observed

  20. Neutron rich nuclei and neutron stars

    E-print Network

    C. J. Horowitz

    2013-03-01

    The PREX experiment at Jefferson Laboratory measures the neutron radius of 208Pb with parity violating electron scattering in a way that is free from most strong interaction uncertainties. The 208Pb radius has important implications for neutron rich matter and the structure of neutron stars. We present first PREX results, describe future plans, and discuss a follow on measurement of the neutron radius of 48Ca. We review radio and X-ray observations of neutron star masses and radii. These constrain the equation of state (pressure versus density) of neutron rich matter. We present a new energy functional that is simultaneously fit to both nuclear and neutron star properties. In this approach, neutron star masses and radii constrain the energy of neutron matter. This avoids having to rely on model dependent microscopic calculations of neutron matter. The functional is then used to predict the location of the drip lines and the properties of very neutron rich heavy nuclei.

  1. Atmospheres around Neutron Stars

    NASA Astrophysics Data System (ADS)

    Fryer, Chris L.; Benz, Willy

    1994-12-01

    Interest in the behavior of atmospheres around neutron stars has grown astronomically in the past few years. Some of this interest arrived in the wake of the explosion of Supernova 1987A and its elusive remnant; spawning renewed interest in a method to insure material ``fall-back'' onto the adolescent neutron star in an effort to transform it into a silent black hole. However, the bulk of the activity with atmospheres around neutron stars is concentrated in stellar models with neutron star, rather than white dwarf, cores; otherwise known as Thorne-Zytkow objects. First a mere seed in the imagination of theorists, Thorne-Zytkow objects have grown into an observational reality with an ever-increasing list of formation scenarios and observational prospects. Unfortunately, the analytic work of Chevalier on supernova fall-back implies that, except for a few cases, the stellar simulations of Thorne-Zytkow objects are missing an important aspect of physics: neutrinos. Neutrino cooling removes the pressure support of these atmospheres, allowing accretion beyond the canonical Eddington rate for these objects. We present here the results of detailed hydrodynamical simulations in one and two dimensions with the additional physical effects of neutrinos, advanced equations of state, and relativity over a range of parameters for our atmosphere including entropy and chemical composition as well as a range in the neutron star size. In agreement with Chevalier, we find, under the current list of formation scenarios, that the creature envisioned by Thorne and Zytkow will not survive the enormous appetite of a neutron star. However, neutrino heating (a physical effect not considered in Chevalier's analysis) can play an important role in creating instabilities in some formation schemes, leading to an expulsion of matter rather than rapid accretion. By placing scrutiny upon the formation methods, we can determine the observational prospects for each.

  2. The neutron star zoo

    NASA Astrophysics Data System (ADS)

    Harding, Alice K.

    2013-12-01

    Neutron stars are a very diverse population, both in their observational and their physical properties. They prefer to radiate most of their energy at X-ray and gamma-ray wavelengths. But whether their emission is powered by rotation, accretion, heat, magnetic fields or nuclear reactions, they are all different species of the same animal whose magnetic field evolution and interior composition remain a mystery. This article will broadly review the properties of inhabitants of the neutron star zoo, with emphasis on their high-energy emission.

  3. Neutrinos from neutron stars

    NASA Technical Reports Server (NTRS)

    Helfand, D. J.

    1979-01-01

    A calculation of the flux of ultra-high energy neutrinos from galactic neutron stars is presented. The calculation is used to determine the number of point sources detectable at the sensitivity threshold of a proposed deep underwater muon and neutrino detector array. The detector array would have a point source detection threshold of about 100 eV/sq cm-sec. Analysis of neutrino luminosities and the number of detectable sources suggests that the deep underwater detector may make a few discoveries. In particular, a suspected neutron star in the Cyg X-3 source seems a promising target for the deep underwater array.

  4. Planets Around Neutron Stars

    NASA Technical Reports Server (NTRS)

    Wolszczan, Alexander; Kulkarni, Shrinivas R; Anderson, Stuart B.

    2003-01-01

    The objective of this proposal was to continue investigations of neutron star planetary systems in an effort to describe and understand their origin, orbital dynamics, basic physical properties and their relationship to planets around normal stars. This research represents an important element of the process of constraining the physics of planet formation around various types of stars. The research goals of this project included long-term timing measurements of the planets pulsar, PSR B1257+12, to search for more planets around it and to study the dynamics of the whole system, and sensitive searches for millisecond pulsars to detect further examples of old, rapidly spinning neutron stars with planetary systems. The instrumentation used in our project included the 305-m Arecibo antenna with the Penn State Pulsar Machine (PSPM), the 100-m Green Bank Telescope with the Berkeley- Caltech Pulsar Machine (BCPM), and the 100-m Effelsberg and 64-m Parkes telescopes equipped with the observatory supplied backend hardware.

  5. Quaking Neutron Stars

    E-print Network

    Lucia M. Franco; Bennett Link; Richard I. Epstein

    1999-11-06

    Gravitational, magnetic and superfluid forces can stress the crust of an evolving neutron star. Fracture of the crust under these stresses could affect the star's spin evolution and generate high-energy emission. We study the growth of strain in the crust of a spinning down, magnetized neutron star and examine the initiation of crust cracking (a {\\em starquake}). In preliminary work (Link, Franco & Epstein 1998), we studied a homogeneous model of a neutron star. Here we extend this work by considering a more realistic model of a solid, homogeneous crust afloat on a liquid core. In the limits of astrophysical interest, our new results qualitatively agree with those from the simpler model: the stellar crust fractures under shear stress at the rotational equator, matter moves to higher latitudes and the star's oblateness is reduced. Magnetic stresses favor faults directed toward the magnetic poles. Thus our previous conclusions concerning the star's spin response still hold; namely, asymmetric redistribution of matter excites damped precession which could ultimately lead to an increase in the spin-down torque. Starquakes associated with glitches could explain the permanent {\\em offsets} in period derivative observed to follow glitches in at least three pulsars.

  6. Neutron Star Phenomena

    NASA Technical Reports Server (NTRS)

    Ruderman, Malvin

    1998-01-01

    Various phenomena involving neutron stars are addressed. Electron-positron production in the near magnetosphere of gamma-ray pulsars is discussed along with magnetic field evolution in spun-up and spinning-down pulsars. Glitches and gamma-ray central engines are also discussed.

  7. Hyperons and neutron stars

    NASA Astrophysics Data System (ADS)

    Vidaña, Isaac

    2015-02-01

    In this lecture I will briefly review some of the effects of hyperons on the properties of neutron and proto-neutron stars. In particular, I will revise the problem of the strong softening of the EoS, and the consequent reduction of the maximum mass, induced by the presence of hyperons, a puzzle which has become more intringuing and difficult to solve due the recent measurements of the unusually high masses of the millisecond pulsars PSR J1903+0327 (1.667±0.021M?), PSR J1614-2230 (1.97±0.04M?), and PSR J0348+0432 (2.01±0.04M?). Finally, I will also examine the role of hyperons on the cooling properties of newly born neutron stars and on the so-called r-mode instability.

  8. Neutron Stars and NuSTAR

    NASA Astrophysics Data System (ADS)

    Bhalerao, Varun

    2012-05-01

    My thesis centers around the study of neutron stars, especially those in massive binary systems. To this end, it has two distinct components: the observational study of neutron stars in massive binaries with a goal of measuring neutron star masses and participation in NuSTAR, the first imaging hard X-ray mission, one that is extremely well suited to the study of massive binaries and compact objects in our Galaxy. The Nuclear Spectroscopic Telescope Array (NuSTAR) is a NASA Small Explorer mission that will carry the first focusing high energy X-ray telescope to orbit. NuSTAR has an order-of-magnitude better angular resolution and has two orders of magnitude higher sensitivity than any currently orbiting hard X-ray telescope. I worked to develop, calibrate, and test CdZnTe detectors for NuSTAR. I describe the CdZnTe detectors in comprehensive detail here - from readout procedures to data analysis. Detailed calibration of detectors is necessary for analyzing astrophysical source data obtained by the NuSTAR. I discuss the design and implementation of an automated setup for calibrating flight detectors, followed by calibration procedures and results. Neutron stars are an excellent probe of fundamental physics. The maximum mass of a neutron star can put stringent constraints on the equation of state of matter at extreme pressures and densities. From an astrophysical perspective, there are several open questions in our understanding of neutron stars. What are the birth masses of neutron stars? How do they change in binary evolution? Are there multiple mechanisms for the formation of neutron stars? Measuring masses of neutron stars helps answer these questions. Neutron stars in high-mass X-ray binaries have masses close to their birth mass, providing an opportunity to disentangle the role of "nature" and "nurture" in the observed mass distributions. In 2006, masses had been measured for only six such objects, but this small sample showed the greatest diversity in masses among all classes of neutron star binaries. Intrigued by this diversity - which points to diverse birth masses - we undertook a systematic survey to measure the masses of neutron stars in nine high-mass X-ray binaries. In this thesis, I present results from this ongoing project. While neutron stars formed the primary focus of my work, I also explored other topics in compact objects. Appendix A describes the discovery and complete characterization of a 1RXS J173006.4+033813, a polar cataclysmic variable. Appendix B describes the discovery of a diamond planet orbiting a millisecond pulsar, and our search for its optical counterpart.

  9. Neutron Star Mass Measurements. I. Radio Pulsars

    Microsoft Academic Search

    S. E. Thorsett; Deepto Chakrabarty

    1999-01-01

    There are now about 50 known radio pulsars in binary systems, including at least five in double neutron star binaries. In some cases, the stellar masses can be directly determined from measurements of relativistic orbital effects. In others, only an indirect or statistical estimate of the masses is possible. We review the general problem of mass measurement in radio pulsar

  10. Hubble Sees a Neutron Star Alone in Space Nearest Known Neutron Star

    E-print Network

    Barnes, Joshua Edward

    Hubble Sees a Neutron Star Alone in Space Nearest Known Neutron Star #12;Birth of a Neutron Star & neutrinos. The birth temperature of a neutron star is ~5Ã?1011 K, but neutrino emission cools it to `only' 106 to 107 K. #12;Sizes of Neutron Stars Google Maps: Oahu #12;Sizes of Neutron Stars Artist

  11. Superfluidity of $?$ hyperons in neutron stars

    E-print Network

    Y. N. Wang; H. Shen

    2010-02-01

    We study the $^1S_0$ superfluidity of $\\Lambda$ hyperons in neutron star matter and neutron stars. We use the relativistic mean field (RMF) theory to calculate the properties of neutron star matter. In the RMF approach, the meson-hyperon couplings are constrained by reasonable hyperon potentials that include the updated information from recent developments in hypernuclear physics. To examine the $^1S_0$ pairing gap of $\\Lambda$ hyperons, we employ several $\\Lambda\\Lambda$ interactions based on the Nijmegen models and used in double-$\\Lambda$ hypernuclei studies. It is found that the maximal pairing gap obtained is a few tenths of a MeV. The magnitude and the density region of the pairing gap are dependent on the $\\Lambda\\Lambda$ interaction and the treatment of neutron star matter. We calculate neutron star properties and find that whether the $^1S_0 $ superfluidity of $\\Lambda$ hyperons exists in the core of neutron stars mainly depends on the $\\Lambda\\Lambda$ interaction used.

  12. Keepers of the double stars

    NASA Astrophysics Data System (ADS)

    Tenn, Joseph S.

    2013-03-01

    Astronomers have long tracked double stars in efforts to find those that are gravitationally-bound binaries and then to determine their orbits. Early catalogues by the Herschels, Struves, and others began with their own discoveries. In 1906 court reporter and amateur astronomer Sherburne Wesley Burnham published a massive double star catalogue containing data from many observers on more than 13,000 systems. Lick Observatory astronomer Robert Grant Aitken produced a much larger catalogue in 1932 and coordinated with Robert Innes of Johannesburg, who catalogued the southern systems. Aitken maintained and expanded Burnham's records of observations on handwritten file cards, and eventually turned them over to the Lick Observatory, where astrometrist Hamilton Jeffers further expanded the collection and put all the observations on punched cards. With the aid of Frances M. "Rete" Greeby he made two catalogues: an Index Catalogue with basic data about each star, and a complete catalogue of observations, with one observation per punched card. He enlisted Willem van den Bos of Johannesburg to add southern stars, and together they published the Index Catalogue of Visual Double Stars, 1961.0. As Jeffers approached retirement he became greatly concerned about the disposition of the catalogues. He wanted to be replaced by another "double star man," but Lick Director Albert E. Whitford had the new 120-inch reflector, the world's second largest telescope, and he wanted to pursue modern astrophysics instead. Jeffers was vociferously opposed to turning over the card files to another institution, and especially against their coming under the control of Kaj Strand of the United States Naval Observatory. In the end the USNO got the files and has maintained the records ever since, first under Charles Worley, and, since 1997, under Brian Mason. Now called the Washington Double Star Catalog (WDS), it is completely online and currently contains more than 1,200,000 measures of more than 125,000 star systems.

  13. Theory of neutron star magnetospheres

    Microsoft Academic Search

    F. C. Michel

    1991-01-01

    The theory of neutron star magnetospheres is presented with reference to the most important observational data on neutron stars available to date. In particular, attention is given to the nature of pulsars and pulsar properties and statistics; phenomenological models; the aligned rotator and oblique rotator models; the disk models; alternative models; and radio emission models. The discussion also covers winds

  14. Precession of Isolated Neutron Stars

    E-print Network

    Bennett Link

    2002-11-08

    I summarize the evidence for precession of isolated neutron stars and theoretical effort to understand the observations. I discuss factors that might set the precession period, describe constraints on the material properties of the crust, and conclude with a brief discussion of possible sources of stress that would deform a neutron star to the extent required.

  15. Physics of Neutron Star Crusts

    E-print Network

    N. Chamel; P. Haensel

    2008-12-20

    The physics of neutron star crusts is vast, involving many different research fields, from nuclear and condensed matter physics to general relativity. This review summarizes the progress, which has been achieved over the last few years, in modeling neutron star crusts, both at the microscopic and macroscopic levels. The confrontation of these theoretical models with observations is also briefly discussed.

  16. Structure of neutron star cores

    NASA Technical Reports Server (NTRS)

    Canuto, V.; Datta, B.; Lodenquai, J.

    1975-01-01

    After reviewing the outer and central regions of a neutron star, we discuss the central region and the possibility that the core has a solid structure. We present the work of different groups on the solidification problem, suggesting that the neutron star-cores are indeed solid.

  17. The Probability Distribution of Binary Pulsar Coalescence Rates. I. Double Neutron Star Systems in the Galactic Field

    E-print Network

    C. Kim; V. Kalogera; D. R. Lorimer

    2002-10-21

    Estimates of the Galactic coalescence rate (R) of close binaries with two neutron stars (NS-NS) are known to be uncertain by large factors (about two orders of magnitude) mainly due to the small number of systems detected as binary radio pulsars. We present an analysis method that allows us to estimate the Galactic NS-NS coalescence rate using the current observed sample and, importantly, to assign a statistical significance to these estimates and to calculate the allowed ranges of values at various confidence levels. The method involves the simulation of selection effects inherent in all relevant radio pulsar surveys and a Bayesian statistical analysis for the probability distribution of the rate. The most likely values for the total Galactic coalescence rate (R_peak) lie in the range 2-60 per Myr depending on different pulsar population models. For our reference model 1, where the most likely estimates of pulsar population properties are adopted, we obtain R_tot = 8_{-5}^{+9} per Myr at a 68% statistical confidence level. The corresponding range of expected detection rates of NS-NS inspiral are 3_{-2}^{+4}x10^{-3} per yr for the initial LIGO and 18_{-11}^{+21} per yr for the advanced LIGO.

  18. Grand unification of neutron stars

    PubMed Central

    Kaspi, Victoria M.

    2010-01-01

    The last decade has shown us that the observational properties of neutron stars are remarkably diverse. From magnetars to rotating radio transients, from radio pulsars to isolated neutron stars, from central compact objects to millisecond pulsars, observational manifestations of neutron stars are surprisingly varied, with most properties totally unpredicted. The challenge is to establish an overarching physical theory of neutron stars and their birth properties that can explain this great diversity. Here I survey the disparate neutron stars classes, describe their properties, and highlight results made possible by the Chandra X-Ray Observatory, in celebration of its 10th anniversary. Finally, I describe the current status of efforts at physical “grand unification” of this wealth of observational phenomena, and comment on possibilities for Chandra’s next decade in this field. PMID:20404205

  19. QPO Constraints on Neutron Stars

    NASA Technical Reports Server (NTRS)

    Miller, M. Coleman

    2005-01-01

    The kilohertz frequencies of QPOs from accreting neutron star systems imply that they are generated in regions of strong gravity, close to the star. This suggests that observations of the QPOs can be used to constrain the properties of neutron stars themselves, and in particular to inform us about the properties of cold matter beyond nuclear densities. Here we discuss some relatively model-insensitive constraints that emerge from the kilohertz QPOs, as well as recent developments that may hint at phenomena related to unstable circular orbits outside neutron stars.

  20. Hiding a neutron star inside a wormhole

    E-print Network

    Vladimir Dzhunushaliev; Vladimir Folomeev; Burkhard Kleihaus; Jutta Kunz

    2014-04-12

    We consider neutron-star-plus-wormhole configurations supported by a massless ghost scalar field. The neutron fluid is modeled by an anisotropic equation of state. When the central energy density of the fluid is of comparable magnitude to the one of the scalar field, configurations with an equator at the center and a double throat arise. These double-throat wormholes can be either partially or completely filled by the neutron fluid. In the latter case, the passage of light - radiated by the neutron matter - through these wormholes is studied. A stability analysis indicates that all considered configurations are unstable with respect to linear perturbations, independent of whether the fluid is isotropic or anisotropic.

  1. Children's Literature on Neutron Stars

    NASA Astrophysics Data System (ADS)

    Struck, James

    Children's literature is simple discussion of complicated issues. Neutron stars are discussed in several children's books. Using libraries in Chicago, I will review children's books on neutron stars and compare the literature to literature from scientific discussions of neutron stars on sites like the Chandra site, Hubble Space Telescope site and NASA site. The result will be a discussion of problems and issues involved in discussion of neutron stars. Do children's books leave material out? Do children's books discuss recent observations? Do children's books discuss anything discredited or wrong? How many children's books are in resources like World Cat, the Library of Congress catalog, and the Chicago Public Library catalog? Could children's books be useful to present some of your findings or observations or projects? Children's books are useful for both children and scientist as they present simplified discussion of topics, although sometimes issues are simplified too much.

  2. The Neutron Star Zoo

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.

    2014-01-01

    Neutron stars are a very diverse population, both in their observational and their physical properties. They prefer to radiate most of their energy at X-ray and gamma-ray wavelengths. But whether their emission is powered by rotation, accretion, heat, magnetic fields or nuclear reactions, they are all different species of the same animal whose magnetic field evolution and interior composition remain a mystery. This article will broadly review the properties of inhabitants of the neutron star zoo, with emphasis on their high-energy emission. XXX Neutron stars are found in a wide variety of sources, displaying an amazing array of behavior. They can be isolated or in binary systems, accreting, heating, cooling, spinning down, spinning up, pulsing, flaring and bursting. The one property that seems to determine their behavior most strongly is their magnetic field strength, structure and evolution. The hot polar caps, bursts and flares of magnetars are likely due to the rapid decay and twisting of their superstrong magnetic fields, whose very existence requires some kind of early dynamo activity. The intermediate-strength magnetic fields of RPPs determines their spin-down behavior and radiation properties. However, the overlap of the magnetar and RPP populations is not understood at present. Why don't high-field RPPs burst or flare? Why don't lower-field magnetars sometimes behave more like RPPs? INS may be old magnetars whose high fields have decayed, but they do not account for the existence of younger RPPs with magnetar-strength fields. Not only the strength of the magnetic field but also its configuration may be important in making a NS a magnetar or a RPP. Magnetic field decay is a critical link between other NS populations as well. "Decay" of the magnetic field is necessary for normal RPPs to evolve into MSPs through accretion and spin up in LMXBs. Some kind of accretion-driven field reduction is the most likely mechanism, but it is controversial since it is not clear how effective it is or on what timescale a buried field might re-emerge. One piece of evidence in favor of accretion-driven field reduction is the fact that NSs in LMXBs, which are older systems (> 108 yr), have mostly low fields and NSs in HMXBs, which are younger systems (107 - 108 yr), have higher fields. This may be an indication that accretion-driven field reduction or decay has not had enough time to operate in HMXBs but has in LMXBs. However, there does not seem to be any evidence of decaying fields in either the LMXB or HMXB populations; e.g. smaller magnetic fields in older systems. On the other hand, CCOs are very young so if they acquired their low fields through mass fallback accretion, the field submergence would have had to operate on much faster timescales than it apparently does in LMXBs. But as we continue to find new species in the NS zoo, one of these may someday be the "Rosetta Stone" that will give us the clues for solving these puzzles.

  3. Complexity and neutron star structure

    NASA Astrophysics Data System (ADS)

    Chatzisavvas, K. Ch.; Psonis, V. P.; Panos, C. P.; Moustakidis, Ch. C.

    2009-10-01

    We apply the statistical measure of complexity introduced by López-Ruiz, Mancini and Calbet (1995) [1] to neutron star structure. We continue the recent application of Sañudo and Pacheco (2009) [2] to white dwarfs. The interplay of gravity, the short-range nuclear force and the very short-range weak interaction shows that neutron stars, under the current theoretical framework, are ordered (low complexity) systems.

  4. Neutron Stars in Supernova Remnants

    Microsoft Academic Search

    Franco Pacini

    1999-01-01

    I briefly summarize some facts and ideas concerning the presence of neutron\\u000astars in Supernova remnants. While sources similar to the Crab Nebula require\\u000athe presence of a central energetic object, shell-type remnants such as Cas A\\u000aare compatible with the presence of neutron stars releasing a weak relativistic\\u000awind.

  5. Binary Neutron Star Mergers

    NASA Astrophysics Data System (ADS)

    Faber, Joshua A.; Rasio, Frederic A.

    2012-07-01

    We review the current status of studies of the coalescence of binary neutron star systems. We begin with a discussion of the formation channels of merging binaries and we discuss the most recent theoretical predictions for merger rates. Next, we turn to the quasi-equilibrium formalisms that are used to study binaries prior to the merger phase and to generate initial data for fully dynamical simulations. The quasi-equilibrium approximation has played a key role in developing our understanding of the physics of binary coalescence and, in particular, of the orbital instability processes that can drive binaries to merger at the end of their lifetimes. We then turn to the numerical techniques used in dynamical simulations, including relativistic formalisms, (magneto-)hydrodynamics, gravitational-wave extraction techniques, and nuclear microphysics treatments. This is followed by a summary of the simulations performed across the field to date, including the most recent results from both fully relativistic and microphysically detailed simulations. Finally, we discuss the likely directions for the field as we transition from the first to the second generation of gravitational-wave interferometers and while supercomputers reach the petascale frontier.

  6. WIMP Annihilation and Cooling of Neutron Stars

    E-print Network

    Chris Kouvaris

    2007-08-17

    We study the effect of WIMP annihilation on the temperature of a neutron star. We shall argue that the released energy due to WIMP annihilation inside the neutron stars, might affect the temperature of stars older than 10 million years, flattening out the temperature at $\\sim 10^4$ K for a typical neutron star.

  7. The nuclear physics of neutron stars

    SciTech Connect

    Piekarewicz, J. [Department of Physics, Florida State University, Tallahassee, FL 32306-4350 (United States)

    2014-05-09

    We explore the unique and fascinating structure of neutron stars. Although neutron stars are of interest in many areas of Physics, our aim is to provide an intellectual bridge between Nuclear Physics and Astrophysics. We argue against the naive perception of a neutron star as a uniform assembly of neutrons packed to enormous densities. Rather, by focusing on the many exotic phases that are speculated to exist in a neutron star, we show how the reality is different and far more interesting.

  8. Old and new neutron stars

    SciTech Connect

    Ruderman, M.

    1984-09-01

    The youngest known radiopulsar in the rapidly spinning magnetized neutron star which powers the Crab Nebula, the remnant of the historical supernova explosion of 1054 AD. Similar neutron stars are probably born at least every few hundred years, but are less frequent than Galactic supernova explosions. They are initially sources of extreme relativistic electron and/or positron winds (approx.10/sup 38/s/sup -1/ of 10/sup 12/ eV leptons) which greatly decrease as the neutron stars spin down to become mature pulsars. After several million years these neutron stars are no longer observed as radiopulsars, perhaps because of large magnetic field decay. However, a substantial fraction of the 10/sup 8/ old dead pulsars in the Galaxy are the most probable source for the isotropically distributed ..gamma..-ray burst detected several times per week at the earth. Some old neutron stars are spun-up by accretion from companions to be resurrected as rapidly spinning low magnetic field radiopulsars. 52 references, 6 figures, 3 tables.

  9. Neutron Star Oscillations from Starquakes

    NASA Astrophysics Data System (ADS)

    Keer, L. C.; Jones, D. I.

    2015-01-01

    Glitches - sudden increases in spin rate - are observed in many pulsars. One mechanism that has been proposed to account for these is the starquake model, in which glitches are triggered by a loss of strain in the solid crust of the star. Starquakes can be expected to excite some of the oscillation modes of the neutron star, which means that they are of interest as a source of gravitational waves. We describe a model that we are developing to calculate the change in the properties of the star during a starquake, in order to work out how the star oscillates after the glitch.

  10. Neutron stars and black holes

    NASA Technical Reports Server (NTRS)

    Lamb, F. K.

    1991-01-01

    The radiation of neutron stars is powered by accretion, rotation, or internal heat; accreting black holes are thought to be the central engines of AGNs and of a handful of binary X-ray sources in the Galaxy. The evolution of a neutron star depends on the coupling between the rotating neutron and proton fluids in the interior, and between these fluids and the crust; it also depends on the magnetic and thermal properties of the star. Significant progress has been made in recent years in the understanding of radial and disk accretion by black holes. Radiation from pair plasmas may make an important contribution to the X- and gamma-ray spectra of AGNs and black holes in binary systems.

  11. BPS Skyrmions as neutron stars

    E-print Network

    C. Adam; C. Naya; J. Sanchez-Guillen; R. Vazquez; A. Wereszczynski

    2015-02-26

    The BPS Skyrme model has been demonstrated already to provide a physically intriguing and quantitatively reliable description of nuclear matter. Indeed, the model has both the symmetries and the energy-momentum tensor of a perfect fluid, and thus represents a field theoretic realization of the "liquid droplet" model of nuclear matter. In addition, the classical soliton solutions together with some obvious corrections (spin-isospin quantization, Coulomb energy, proton-neutron mass difference) provide an accurate modeling of nuclear binding energies for heavier nuclei. These results lead to the rather natural proposal to try to describe also neutron stars by the BPS Skyrme model coupled to gravity. We find that the resulting self-gravitating BPS Skyrmions provide excellent results as well as some new perspectives for the description of bulk properties of neutron stars when the parameter values of the model are extracted from nuclear physics. Specifically, the maximum possible mass of a neutron star before black-hole formation sets in is a few solar masses, the precise value depending on the precise values of the model parameters, and the resulting neutron star radius is of the order of 10 km.

  12. BPS Skyrmions as neutron stars

    NASA Astrophysics Data System (ADS)

    Adam, C.; Naya, C.; Sanchez-Guillen, J.; Vazquez, R.; Wereszczynski, A.

    2015-03-01

    The BPS Skyrme model has been demonstrated already to provide a physically intriguing and quantitatively reliable description of nuclear matter. Indeed, the model has both the symmetries and the energy-momentum tensor of a perfect fluid, and thus represents a field theoretic realization of the "liquid droplet" model of nuclear matter. In addition, the classical soliton solutions together with some obvious corrections (spin-isospin quantization, Coulomb energy, proton-neutron mass difference) provide an accurate modeling of nuclear binding energies for heavier nuclei. These results lead to the rather natural proposal to try to describe also neutron stars by the BPS Skyrme model coupled to gravity. We find that the resulting self-gravitating BPS Skyrmions provide excellent results as well as some new perspectives for the description of bulk properties of neutron stars when the parameter values of the model are extracted from nuclear physics. Specifically, the maximum possible mass of a neutron star before black-hole formation sets in is a few solar masses, the precise value of which depends on the precise values of the model parameters, and the resulting neutron star radius is of the order of 10 km.

  13. Nuclear Physics of Neutron Stars

    E-print Network

    J. Piekarewicz

    2009-01-28

    Understanding the equation of state (EOS) of cold nuclear matter, namely, the relation between the pressure and energy density, is a central goal of nuclear physics that cuts across a variety of disciplines. Indeed, the limits of nuclear existence, the collision of heavy ions, the structure of neutron stars, and the dynamics of core-collapse supernova, all depend critically on the equation of state of hadronic matter. In this contribution I will concentrate on the special role that nuclear physics plays in constraining the EOS of cold baryonic matter and its impact on the properties of neutron stars.

  14. Supernova remnants containing neutron stars

    NASA Technical Reports Server (NTRS)

    Seward, F. D.

    1985-01-01

    X-ray observations of Crab Nebula-like supernova remnants are summarized. Five remnants are found to contain internal neutron stars - four isolated and one in a binary system. Another five remnants have central unresolved X-ray sources which are probably neutron stars. Thus approximately 10 remnants are now known to have their origin in gravitational collapse. Another 22 remnants show some Crab-like properties, but the existence of a central compact object or pulsar is doubtful or unconfirmed. The four fast isolated pulsars in SNR are also compared with five X-ray detected radio pulsars.

  15. Structure of neutron star envelopes

    NASA Technical Reports Server (NTRS)

    Gudmundsson, E. H.; Pethick, C. J.; Epstein, R. I.

    1983-01-01

    The envelopes of nonmagnetic neutron stars are studied using the best available opacities and equation of state. The general relativistic equations of the structure and evolution of nonmagnetic neutron stars are discussed, and it is shown that they can be reduced to a single equation for calculating the thermal structure of neutron star envelopes. The physical input needed to solve the thermal structure equation is investigated and the numerical results of envelope model calculations are presented. It is shown that the thermal structure of neutron star envelopes is determined by the single parameter T(s) to the 4th/g(s), where T(s) is the effective surface temperature and g(s) the surface gravity of the star. This result is used to derive a number of other scaling relations, and the effects of general relativity on the envelope thermal structure are examined in detail. The results of a sensitivity analysis of the regional opacity needed to obtain a reliable relationship between the temperatures of the inner and outer boundaries of the envelope is presented.

  16. Superconducting Superfluids in Neutron Stars

    E-print Network

    Brandon Carter

    2000-10-05

    For treatment of the layers below the crust of a neutron star it is useful to employ a relativistic model involving three independently moving constituents, representing superfluid neutrons, superfluid protons, and degenerate negatively charged leptons. A Kalb Ramond type formulation is used here to develop such a model for the specific purpose of application at the semi macroscopic level characterised by lengthscales that are long compared with the separation between the highly localised and densely packed proton vortices of the Abrikosov type lattice that carries the main part of the magnetic flux, but that are short compared with the separation between the neutron vortices.

  17. Chandra Observations of Neutron Stars: An Overview

    NASA Technical Reports Server (NTRS)

    Weisskopf, M. C.; Six, N. Frank (Technical Monitor)

    2002-01-01

    We present a brief review of Chandra observations of neutron stars, with a concentration on neutron stars in supernova remnants. The early Chandra results clearly demonstrate how critical the angular resolution has been in order to separate the neutron star emission from the surrounding nebulosity.

  18. Holographic Neutron Stars

    E-print Network

    Jan de Boer; Kyriakos Papadodimas; Erik Verlinde

    2009-07-23

    We construct in the context of the AdS/CFT correspondence degenerate composite operators in the conformal field theory that are holographically dual to degenerate stars in anti de Sitter space. We calculate the effect of the gravitational back-reaction using the Tolman-Oppenheimer-Volkoff equations, and determine the "Chandrasekhar limit" beyond which the star undergoes gravitational collapse towards a black hole.

  19. Photovisual Magnitude Differences of double Stars

    Microsoft Academic Search

    K. Aa. Strand

    1971-01-01

    Differences in magnitudes between the components of 874 double stars have been derived from visual estimates on several series of multi-exposure photographic plates. The plates were obtained with long focus refractors primarily for the purpose of determining the relative positions of double stars according to the well-known Hertzsprung method. Except for binaries with magnitude differences less than half a magnitude,

  20. The Nuclear Physics of Neutron Stars

    E-print Network

    J. Piekarewicz

    2008-02-27

    A remarkable fact about spherically-symmetric neutron stars in hydrostatic equilibrium - the so-called Schwarzschild stars - is that the only physics that they are sensitive to is the equation of state of neutron-rich matter. As such, neutron stars provide a myriad of observables that may be used to constrain poorly known aspects of the nuclear interaction under extreme conditions of density. After discussing many of the fascinating phases encountered in neutron stars, I will address how powerful theoretical, experimental, and observational constraints may be used to place stringent limits on the equation of state of neutron-rich matter.

  1. Neutron Stars in Supernova Remnants

    NASA Technical Reports Server (NTRS)

    Slane, Patrick; Kaluzienski, Lou (Technical Monitor)

    2002-01-01

    The grant provided funds for a conference entitled 'Neutron Stars in Supernova Remnants' held in Boston on 14-17 August 2001, in part to support invited speakers and students attending the meeting. The conference was completed on the specified dates and was a considerable success, attracting over 100 scientists from around the world. The conference included talks and papers on the most recent work in this field, including results from the Chandra X-ray Observatory, XMM-Newton, the Parkes Multibeam Pulsar Survey, the Very Large Array, and many other facilities. Theoretical work based on the latest results was also highlighted. The Proceedings of the conference have now been published as 'Neutron Stars in Supernova Remnants'. In addition, a large fraction of the papers from the conference have been submitted to astro-ph, and the volume in indexed through the Astronomical Data System.

  2. Neutron Stars in the News

    NSDL National Science Digital Library

    In this science literacy extension students read and analyze two different articles about XMM-Newton discoveries involving neutron stars and their magnetic fields. This is Activity 4 of the Supernova Guide developed by the XMM-Newton and GLAST E/PO programs. The guide features extensive background information, assessment rubrics, student worksheets, extension and transfer activities, and detailed information about physical science and mathematics content standards. Note: In 2008, GLAST was renamed Fermi, for the physicist Enrico Fermi.

  3. Birth accelerations of neutron stars

    NASA Astrophysics Data System (ADS)

    Heras, Ricardo

    2013-03-01

    We suggest that neutron stars experienced at birth three related physical changes, which may originate in magneto-rotational instabilities: (i) an increase in period from the initial value P 0 to the current value Ps , implying a change of rotational energy ? E rot; (ii) an exponential decay of its magnetic field from the initial value B 0 to the current surface value Bs , implying a change of radiative energy ? E rad; and (iii) an increase of space velocity from the initial value v 0 to the current value v, implying a change of kinetic energy ? E kin. These changes are assumed to be connected by ? E rad + ? E kin = ? E rot. This means that the radiation loss and increase of kinetic energy are both at the expense of a rotational energy loss. It is shown that this energy conversion occurs during times of order of 10-4 s if the neutron stars are born with magnetic fields in the range of 1015-1016 G and initial periods in range 1-20 ms. It is shown that the birth accelerations of neutron stars are of the order of 108g.

  4. Astrometric observations of neutron stars

    NASA Astrophysics Data System (ADS)

    Chatterjee, Shami

    2013-02-01

    Astrometric observations of neutron stars have been conducted with a variety of techniques and over a wide range of wavelengths, ranging from radio-pulse timing and Very Long Baseline Interferometry to optical and X-ray imaging. Here I review the techniques and scientific goals behind recent high-precision neutron-star astrometry. Such measurements can yield model-independent distances and velocities that can be exploited, for example, to locate neutron-star birth sites, establish reference-frame ties, model the Galactic electron-density distribution, and constrain the astrophysics of supernova explosions. Recently, the Fermi gamma-ray space telescope has identified several highly luminous recycled pulsars, and precise measurement of their distances is of paramount importance to understand their energetics and astrophysics. The ongoing science returns from precision astrometry will continue in the long term with improvements in technology such as focal-plane arrays and synergies with new telescopes such as Gaia and the Square Kilometer Array.

  5. Neutron stars as cosmic hadron physics laboratories

    NASA Technical Reports Server (NTRS)

    Pines, D.

    1985-01-01

    Extensive observations of Her-1 with the Exosat satellite have led to a new understanding of both the dynamics of neutron-star superfluids and the free precession of neutron stars. Detailed microscopic calculations on neutron matter and the properties of the pinned crustal superfluid are provided to serve as a basis for comparing theory with observation on neutron stars. Topics discussed include the Hadron matter equation of state, neutron star structure, Hadron superfluids, the vortex creep theory, Vela pulsar glitches, astrophysical constraints on neutron matter energy gaps, the 35 day periodicity of Her-1, and the neutron matter equation of state. It is concluded that since the post-glitch fits and the identification of the 35th periodicity in Her X-1 as stellar wobble require a rigid neutron matter equation of state, the astrophysical evidence for such an equation seems strong, as well as that for an intermediate Delta(rho) curve.

  6. Neutron star structure and the neutron radius of 208Pb.

    PubMed

    Horowitz, C J; Piekarewicz, J

    2001-06-18

    We study relationships between the neutron-rich skin of a heavy nucleus and the properties of neutron-star crusts. Relativistic effective field theories with a thicker neutron skin in 208Pb have a larger electron fraction and a lower liquid-to-solid transition density for neutron-rich matter. These properties are determined by the density dependence of the symmetry energy which we vary by adding nonlinear couplings between isoscalar and isovector mesons. An accurate measurement of the neutron radius in 208Pb-via parity violating electron scattering-may have important implications for the structure of the crust of neutron stars. PMID:11415324

  7. Accreting Neutron Stars as Astrophysical Laboratories

    NASA Technical Reports Server (NTRS)

    Chakrabarty, Deepto

    2004-01-01

    In the last year, we have made an extremely important breakthrough in establishing the relationship between thermonuclear burst oscillations in accreting neutron stars and the stellar spin. More broadly, we have continued t o make significant scientific progress in all four of the key focus areas identified in our original proposal: (1) the disk-magnetosphere interaction in neutron stars, (2) rapid variability in accreting neutron stars, (3) physics of accretion flows, and (4) fundamental properties of neutron stars. A list of all publications that have arising from this work since the start of our program is given.

  8. Burst Oscillations: Watching Neutron Stars Spin

    NASA Technical Reports Server (NTRS)

    Strohmayer, Tod

    2010-01-01

    It is now almost 15 years since the first detection of rotationally modulated emission from X-ray bursting neutron stars, "burst oscillations," This phenomenon enables us to see neutron stars spin, as the X-ray burst flux asymmetrically lights up the surface. It has enabled a new way to probe the neutron star spin frequency distribution, as well as to elucidate the multidimensional nature of nuclear burning on neutron stars. I will review our current observational understanding of the phenomenon, with an eye toward highlighting some of the interesting remaining puzzles, of which there is no shortage.

  9. White Dwarfs, Neutron Stars and Black Holes

    ERIC Educational Resources Information Center

    Szekeres, P.

    1977-01-01

    The three possible fates of burned-out stars: white dwarfs, neutron stars and black holes, are described in elementary terms. Characteristics of these celestial bodies, as provided by Einstein's work, are described. (CP)

  10. Photovisual magnitude differences of double stars

    Microsoft Academic Search

    K. Aa. Strand

    1971-01-01

    Differences in magnitudes between the components of 874 double stars have been derived from visual estimates on several series\\u000a of multi-exposure photographic plates. The plates were obtained with long focus refractors primarily for the purpose of determining\\u000a the relative positions of double stars according to the well-known Hertzsprung method.\\u000a \\u000a Except for binaries with magnitude differences less than half a magnitude,

  11. A New Double Star in Cepheus

    NASA Astrophysics Data System (ADS)

    Bryant, T. V.

    2015-04-01

    A new double star has been found in Cepheus, at 21:55:22.8 +65:01:40.8, J2000. A measurement made with the Aladin tool1 of the new double gives 15.6 arc seconds of separation and a position angle of 27°. The APASS2 visual magnitudes, as reported by the UCAC43 are 11.1 and 11.35. Historical data from the stars are listed, as are distance estimates to the pair.

  12. Double Planet Meets Triple Star

    NASA Astrophysics Data System (ADS)

    2002-08-01

    High-Resolution VLT Image of Pluto Event on July 20, 2002 A rare celestial phenomenon involving the distant planet Pluto has occurred twice within the past month. Seen from the Earth, this planet moved in front of two different stars on July 20 and August 21, respectively, providing observers at various observatories in South America and in the Pacific area with a long awaited and most welcome opportunity to learn more about the tenuous atmosphere of that cold planet. On the first date, a series of very sharp images of a small sky field with Pluto and the star was obtained with the NAOS-CONICA (NACO) adaptive optics (AO) camera mounted on the ESO VLT 8.2-m YEPUN telescope at the Paranal Observatory. With a diameter of about 2300 km, Pluto is about six times smaller than the Earth. Like our own planet, it possesses a relatively large moon, Charon , measuring 1200 km across and circling Pluto at a distance of about 19,600 km once every 6.4 days. In fact, because of the similarity of the two bodies, the Pluto-Charon system is often referred to as a double planet . At the current distance of nearly 4,500 million km from the Earth, Pluto's disk subtends a very small angle in the sky, 0.107 arcsec. It is therefore very seldom that Pluto - during its orbital motion - passes exactly in front of a comparatively bright star. Such events are known as "occultations" , and it is difficult to predict exactly when and where on the Earth's surface they are visible. Stellar occultations When Pluto moves in front of a star, it casts a "shadow" on the Earth's surface within which an observer cannot see the star, much like the Earth's Moon hides the Sun during a total solar eclipse. During the occultation event, Pluto's "shadow" also moves across the Earth's surface. The width of this shadow is equal to Pluto's diameter, i.e. about 2300 km. One such occultation event was observed in 1988, and two others were expected to occur in 2002, according to predictions published in 2000 by American astronomers Steve W. McDonald and James L. Elliot (Massachussetts Institute of Technology [MIT], Cambridge, USA). Further refinements provided by other observers later showed that the first event would be visible from South America on July 20, 2002 , while a second one on August 21 was expected to be observable in the Pacific basin, from the western coast of North America down to Hawaii and New Zealand. A stellar occultation provides a useful opportunity to study the planetary atmosphere, by means of accurate photometric measurements of the dimming of the stellar light, as the planet moves in front of the star. The observed variation of the light intensity and colour provides crucial information about the structure (atmospheric layers) and composition of different gases and aerosols. More information is available in the Appendix below. The July 20 occultation ESO PR Photo 21a/02 ESO PR Photo 21a/02 [Preview - JPEG: 400 x 477 pix - 65k] [Normal - JPEG: 800 x 953 pix - 224k] Caption : PR Photo 21c/02 shows the path of Pluto's shadow (grey region) during the July 20, 2002 occultation. The shadow has a diameter of about 2300 km and moves from right to left; the timings along the central line are indicated in one-minute intervals (Universal Time - UT). The width of the gray area corresponds to the regions where more than 50% of the light from the star P126 A was attenuated by Pluto's atmosphere. The dotted lines indicate where the stellar flux was attenuated by more than 10%. The maximum duration of the occultation (for observers located at the middle of the shadow track) was about 3 min. The plot is based on astrometric measurements posted at the MIT site. Once completely analyzed, the VLT NACO images will provide significantly better accuracy on the location of this track and therefore a solid basis for the interpretation of the photometric observations obtained with other telescopes. In order to profit from the rare opportunity to learn more about Pluto and its atmosphere, a large campaign involving more than twenty scientists a

  13. Magnetic fields in Neutron Stars

    E-print Network

    Viganò, Daniele; Miralles, Juan A; Rea, Nanda

    2015-01-01

    Isolated neutron stars show a diversity in timing and spectral properties, which has historically led to a classification in different sub-classes. The magnetic field plays a key role in many aspects of the neutron star phenomenology: it regulates the braking torque responsible for their timing properties and, for magnetars, it provides the energy budget for the outburst activity and high quiescent luminosities (usually well above the rotational energy budget). We aim at unifying this observational variety by linking the results of the state-of-the-art 2D magneto-thermal simulations with observational data. The comparison between theory and observations allows to place two strong constraints on the physical properties of the inner crust. First, strong electrical currents must circulate in the crust, rather than in the star core. Second, the innermost part of the crust must be highly resistive, which is in principle in agreement with the presence of a novel phase of matter so-called nuclear pasta phase.

  14. Dynamics of Rotating, Magnetized Neutron Stars

    E-print Network

    Steven L. Liebling

    2010-02-10

    Using a fully general relativistic implementation of ideal magnetohydrodynamics with no assumed symmetries in three spatial dimensions, the dynamics of magnetized, rigidly rotating neutron stars are studied. Beginning with fully consistent initial data constructed with Magstar, part of the Lorene project, we study the dynamics and stability of rotating, magnetized polytropic stars as models of neutron stars. Evolutions suggest that some of these rotating, magnetized stars may be minimally unstable occurring at the threshold of black hole formation.

  15. ON THE MASS DISTRIBUTION AND BIRTH MASSES OF NEUTRON STARS

    SciTech Connect

    Oezel, Feryal; Psaltis, Dimitrios; Santos Villarreal, Antonio [Department of Astronomy, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Narayan, Ramesh [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138,USA (United States)

    2012-09-20

    We investigate the distribution of neutron star masses in different populations of binaries, employing Bayesian statistical techniques. In particular, we explore the differences in neutron star masses between sources that have experienced distinct evolutionary paths and accretion episodes. We find that the distribution of neutron star masses in non-recycled eclipsing high-mass binaries as well as of slow pulsars, which are all believed to be near their birth masses, has a mean of 1.28 M{sub Sun} and a dispersion of 0.24 M{sub Sun }. These values are consistent with expectations for neutron star formation in core-collapse supernovae. On the other hand, double neutron stars, which are also believed to be near their birth masses, have a much narrower mass distribution, peaking at 1.33 M{sub Sun }, but with a dispersion of only 0.05 M{sub Sun }. Such a small dispersion cannot easily be understood and perhaps points to a particular and rare formation channel. The mass distribution of neutron stars that have been recycled has a mean of 1.48 M{sub Sun} and a dispersion of 0.2 M{sub Sun }, consistent with the expectation that they have experienced extended mass accretion episodes. The fact that only a very small fraction of recycled neutron stars in the inferred distribution have masses that exceed {approx}2 M{sub Sun} suggests that only a few of these neutron stars cross the mass threshold to form low-mass black holes.

  16. Star products, duality and double Lie algebras

    E-print Network

    Olga V. Man'ko; Vladimir I. Man'ko; Giuseppe Marmo; Patrizia Vitale

    2006-09-06

    Quantization of classical systems using the star-product of symbols of observables is discussed. In the star-product scheme an analysis of dual structures is performed and a physical interpretation is proposed. At the Lie algebra level duality is shown to be connected to double Lie algebras. The analysis is specified to quantum tomography. The classical tomographic Poisson bracket is found.

  17. Astrometry of double stars with HIPPARCOS

    Microsoft Academic Search

    F. Mignard; S. Söderhjelm; H.-H. Bernstein; R. Pannunzio; J. Kovalevsky; M. Froeschle; J. L. Falin; L. Lindegren; C. Martin; M. Badiali; D. Cardini; A. Emanuele; A. Spagna; P. L. Bernacca; L. Borriello; G. Prezioso

    1995-01-01

    After the processing of 30 months of the observations carried out by HIPPARCOS it is possible to provide reliable statistics on the number of double and multiple stars to be detected at the mission completion and on the quality of the astrometric and photometric results on these objects. About 21000 stars have been recognized as non-single, including 12000 already known

  18. Planetary Systems Around Neutron Stars

    NASA Technical Reports Server (NTRS)

    Wolszczan, Alexander

    1997-01-01

    This project was initiated in 1993, about one year after the announcement of two planets around PSR B1257+12. Its goal was to investigate planetary systems around neutron stars using high precision timing of radio pulsars as a tool. A microsecond precision of the pulse timing analysis, which is equivalent to a millimeter-per-second radial velocity resolution, makes it possible to detect asteroid-mass bodies in orbit around pulsars and to study the dynamics of pulsar planetary systems. The project originally consisted of two longterm efforts: (i) routine observations and timing analysis of the millisecond pulsar PSR B1257+12 which was found to be orbited by at least two earth-mass bodies (Wolszczan and Frail, Nature, 355, 145) and (ii) a sensitive all-sky search for millisecond pulsars to detect further examples of neutron stars with planetary systems. In the third year of the project, it was expanded to include long-term timing observations of slow pulsars in search for planetary systems around these younger neutron stars. The instrumentation used to conduct these investigations included the 305-m Arecibo antenna with the Penn State Pulsar Machine (PSPM-1), the 100-m Effelsberg telescope with the local pulse timing hardware, and the 32-m paraboloid of the Torun Centre for Astronomy in Torun, Poland (TCFA) with the PSPM-2, the second pulsar machine built at Penn State. The PI's collaborators included pulsar groups led by D. Backer (Berkeley), R. Foster (NRL), S. Kulkarni (Caltech), J. Taylor (Princeton) and R. Wielebinski (Bonn). One postdoc (Stuart Anderson), one graduate student (Brian Cadwell) and several undergraduates have been engaged in various aspects of research related to this project.

  19. Electrodynamics of disk-accreting magnetic neutron stars

    NASA Technical Reports Server (NTRS)

    Miller, M. Coleman; Lamb, Frederick K.; Hamilton, Russell J.

    1994-01-01

    We have investigated the electrodynamics of magnetic neutron stars accreting from Keplerian disks and the implications for particle acceleration and gamma-ray emission by such systems. We argue that the particle density in the magnetospheres of such stars is larger by orders of magnitude than the Goldreich-Julian density, so that the formation of vacuum gaps is unlikely. We show that even if the star rotates slowly, electromotive forces (EMFs) of order 10(exp 15) V are produced by the interaction of plasma in the accretion disk with the magnetic field of the neutron star. The resistance of the disk-magnetosphere-star circuit is small, and hence these EMFs drive very large conduction currents. Such large currents are likely to produce magnetospheric instabilities, such as relativistic double layers and reconnection events, that can accelerate electrons or ions to very high energies.

  20. Observing quantum vacuum lensing in a neutron star binary system.

    PubMed

    Dupays, Arnaud; Robilliard, Cécile; Rizzo, Carlo; Bignami, Giovanni F

    2005-04-29

    In this Letter we study the propagation of light in the neighborhood of magnetized neutron stars. Because of the optical properties of quantum vacuum in the presence of a magnetic field, the light emitted by background astronomical objects is deviated, giving rise to a phenomenon of the same kind as the gravitational one. We give a quantitative estimation of this effect, and we discuss the possibility of its observation. We show that this effect could be detected by monitoring the evolution of the recently discovered double neutron star system J0737-3039. PMID:15904205

  1. Hamilton Jeffers and the Double Star Catalogues

    NASA Astrophysics Data System (ADS)

    Tenn, Joseph S.

    2013-01-01

    Astronomers have long tracked double stars in efforts to find those that are gravitationally-bound binaries and then to determine their orbits. Court reporter and amateur astronomer Shelburne Wesley Burnham (1838-1921) published a massive double star catalogue containing more than 13,000 systems in 1906. The next keeper of the double stars was Lick Observatory astronomer Robert Grant Aitken (1864-1951), who produced a much larger catalogue in 1932. Aitken maintained and expanded Burnham’s records of observations on handwritten file cards, eventually turning them over to Lick Observatory astrometrist Hamilton Moore Jeffers (1893-1976). Jeffers further expanded the collection and put all the observations on punched cards. With the aid of Frances M. "Rete" Greeby (1921-2002), he made two catalogues: an Index Catalogue with basic data about each star, and a complete catalogue of observations, with one observation per punched card. He enlisted Willem van den Bos of Johannesburg to add southern stars, and they published the Index Catalogue of Visual Double Stars, 1961.0. As Jeffers approached retirement he became greatly concerned about the disposition of the catalogues. He wanted to be replaced by another "double star man," but Lick Director Albert E. Whitford (1905-2002) had the new 120-inch reflector, the world’s second largest telescope, and he wanted to pursue modern astrophysics instead. Jeffers was vociferously opposed to turning over the card files to another institution, and especially against their coming under the control of Kaj Strand of the U.S. Naval Observatory. In the end the USNO got the files and has maintained the records ever since, first under Charles Worley (1935-1997), and, since 1997, under Brian Mason. Now called the Washington Double Star Catalog (WDS), it is completely online and currently contains more than 1,000,000 measures of more than 100,000 pairs.

  2. Rotating Neutron Stars, Pulsars and Supernova Remnants

    Microsoft Academic Search

    F. Pacini

    1968-01-01

    I SHALL discuss here some problems connected with theories linking the pulsars to the rotation of neutron stars (ref. 1 and a preprint by L. Woltjer). Because neutron stars can be formed during a supernova explosion, their rotation could be coupled with the surrounding gaseous remnant2,3: the following considerations will therefore also refer to the problem of the activity observed

  3. Neutron Star Interior Composition Explorer (NICE)

    NASA Technical Reports Server (NTRS)

    Gendreau, Keith C.; Arzoumanian, Zaven

    2008-01-01

    This viewgraph presentation contains an overview of the mission of the Neutron Star Interior Composition Explorer (NICE), a proposed International Space Station (ISS) payload dedicated ot the study of neutron stars. There are also reviews of the Science Objectives of the payload,the science measurements, the design and the expected performance for the instruments for NICE,

  4. Reaction rates in accreting neutron stars

    Microsoft Academic Search

    Mary Beard; Michael Wiescher

    2002-01-01

    Temperature conditions in the deep layers of neutron star crusts can be affected by the occurence of pycnonuclear reaction processes. To simulate the fate of accreted matter in neutron star binary systems, we have calculated pycnonuclear reactions for the ashes of rp-process nucleosynthesis at extreme density conditions. Building on the work of Salpeter and Van Horn, nuclear reactions between very

  5. Hydromagnetic stability of differentially rotating neutron stars

    NASA Astrophysics Data System (ADS)

    Urpin, V.

    2003-11-01

    The stability properties of differentially rotating magnetic neutron stars are considered, and the instability criteria are obtained. The influence of the magnetic field is twofold: it may stabilize a fluid against some instabilities, on the one hand, and it can lead to new branches of instabilities, on the other hand. It turns out that some of the instability criteria of magnetic neutron stars can be satisfied at smaller departures from the uniform rotation than the criteria of non-magnetic stars. Interaction of hydrodynamic motions caused by instabilities in the core with the neutron star crust can result in small irregularities in the measured spin period of pulsars.

  6. Electron-neutron scattering and transport properties of neutron stars

    NASA Astrophysics Data System (ADS)

    Bertoni, Bridget; Reddy, Sanjay; Rrapaj, Ermal

    2015-02-01

    We show that electrons can couple to the neutron excitations in neutron stars, and find that this can limit their contribution to the transport properties of dense matter, especially the shear viscosity. The coupling between electrons and neutrons is induced by protons in the core, and by ions in the crust. We calculate the effective electron-neutron interaction for the kinematics of relevance to the scattering of degenerate electrons at high density. We use this interaction to calculate the electron thermal conductivity, electrical conductivity, and shear viscosity in the neutron star inner crust, and in the core where we consider both normal and superfluid phases of neutron-rich matter. In some cases, particularly when protons are superconducting and neutrons are in their normal phase, we find that electron-neutron scattering can be more important than the other scattering mechanisms considered previously.

  7. Electron-neutron scattering and transport properties of neutron stars

    E-print Network

    Bridget Bertoni; Sanjay Reddy; Ermal Rrapaj

    2014-09-27

    We show that electrons can couple to the neutron excitations in neutron stars and find that this can limit their contribution to the transport properties of dense matter, especially the shear viscosity. The coupling between electrons and neutrons is induced by protons in the core, and by ions in the crust. We calculate the effective electron-neutron interaction for the kinematics of relevance to the scattering of degenerate electrons at high density. We use this interaction to calculate the electron thermal conductivity, electrical conductivity, and shear viscosity in the neutron star inner crust, and in the core where we consider both normal and superfluid phases of neutron-rich matter. In some cases, particularly when protons are superconducting and neutrons are in their normal phase, we find that electron-neutron scattering can be more important than the other scattering mechanisms considered previously.

  8. Untwisting magnetospheres of neutron stars

    E-print Network

    Andrei M. Beloborodov

    2009-07-05

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

  9. The maximum mass of a neutron star.

    NASA Astrophysics Data System (ADS)

    Bombaci, I.

    1996-01-01

    The concept of neutron star maximum mass is revisited. In particular we show that when the dynamical processes occuring in the first few seconds after the neutron star birth are considered, the concept of neutron star maximum mass, as introduced by Oppenheimer and Volkoff, is partially inadequate. We show that both the maximum mass concept and the final stages of the evolution of massive stars depend on the composition of the neutron star material. In particular, we find two different scenarios depending on the absence or presence of negatively charged hadrons among the constituents. In the first scenario, we show that the Oppenheimer Volkoff mass M_OV_ does not represent the boundary between the value of the masses of neutron stars and black holes. In fact, we find a mass range in which both a neutron star and a black hole may exist. In the second scenario we show that, contrary to the standard view, it is possible to have a supernova explosion (accompained by nucleosynthesis and neutrino emission) followed by the delayed formation of a black hole. The latter mechamism could explain the lack of any observational evidence for a neutron star in the remnant of the supernova 1987A.

  10. Gravitational waves from low mass neutron stars

    NASA Astrophysics Data System (ADS)

    Horowitz, C. J.

    2010-05-01

    Low mass neutron stars may be uniquely strong sources of gravitational waves. The neutron star crust can support large deformations for low mass stars. This is because of the star’s weaker gravity. We find maximum ellipticities ? (fractional difference in moments of inertia) that are 1000 times larger, and maximum quadrupole moments Q22 over 100 times larger, for low mass stars than for 1.4M? neutron stars. Indeed, we calculate that the crust can support an ? as large as 0.005 for a minimum mass neutron star. A 0.12M? star, that is maximally strained and rotating at 100 Hz, will produce a characteristic gravitational wave strain of h0=2.1×10-24 at a distance of 1 kpc. The gravitational wave detector Advanced LIGO should be sensitive to such objects through out the Milky Way Galaxy. A low mass neutron star could be uniquely identified from a large observed spin down rate and its discovery would have important implications for general relativity, supernova mechanisms, and possibly nucleosynthesis.

  11. Holographic indeterminacy and neutron stars

    E-print Network

    Scott Funkhouser

    2009-02-16

    The holographic indeterminacy resulting from the quantization of spacetime leads to an inherent uncertainty (lpL)1/2 in the relative positions of two events, separated by a distance L, in a direction transverse to a null ray connecting the events, where lP is the Planck length. The new indeterminacy principle leads to a critical condition in which the holographic uncertainty in the relative transverse positions of two diametrically opposed particles on the surface a body becomes greater than the average distance between particles in the body. The Chandrasekhar mass and the characteristic nuclear density emerge as the minimum mass and density of a baryonic body that could meet the critical criteria. Neutron stars are therefore identified as a class of bodies in which holographic indeterminacy may have physical consequences.

  12. Isolated Neutron Stars: Accretors and Coolers

    E-print Network

    Aldo Treves; Roberto Turolla; Silvia Zane; Monica Colpi

    1999-11-23

    As many as $10^9$ neutron stars populate the Galaxy, but only $\\approx 10^3$ are directly observed as pulsars or as accreting sources in X-ray binaries. In principle also the accretion of the interstellar medium may make isolated neutron stars shine, and their weak luminosity could be detected in soft X-rays. Recent ROSAT observations have convincingly shown that neutron stars accreting from the interstellar medium are extremely rare, if observed at all, in contrast with earlier theoretical predictions. Until now two possible explanations for their elusiveness have been proposed: their velocity distribution may peak at $\\sim 200-400 {\\rm km s}^{-1}$, as inferred from pulsar statistics, and this would severely choke accretion; the magnetic field may decay on timescales $\\sim 10^8-10^9$ yr, preventing a large fraction of neutron stars from entering the accretor stage. The search for accreting neutron stars has produced up to now a handful of promising candidates. While little doubt is left that these objects are indeed isolated neutron stars, the nature of their emission is still controversial. In particular accreting objects can be confused with much younger, cooling neutron stars. However, a combination of observations and theoretical modeling may help in discriminating between the two classes.

  13. Anisotropic pressure and hyperons in neutron stars

    E-print Network

    A. Sulaksono

    2014-12-23

    We study the effects of anisotropic pressure on properties of the neutron stars with hyperons inside its core within the framework of extended relativistic mean field. It is found that the main effects of anisotropic pressure on neutron star matter is to increase the stiffness of the equation of state, which compensates for the softening of the EOS due to the hyperons. The maximum mass and redshift predictions of anisotropic neutron star with hyperonic core are quite compatible with the result of recent observational constraints if we use the parameter of anisotropic pressure model $h \\le 0.8$[1] and $\\Lambda \\le -1.15$ [2]. The radius of the corresponding neutron star at $M$=1.4 $M_\\odot$ is more than 13 km, while the effect of anisotropic pressure on the minimum mass of neutron star is insignificant. Furthermore, due to the anisotropic pressure in the neutron star, the maximum mass limit of higher than 2.1 $M_\\odot$ cannot rule out the presence of hyperons in the neutron star core.

  14. The HIPPARCOS Double and Multiple Star Solutions

    NASA Astrophysics Data System (ADS)

    Mignard, F.

    The Hipparcos catalogue provides general astrometric and photometric information on double and multiple stars in specific fields of the main catalogue and detailed data on the components in the various sections of a dedicated annex: the Double and Multiple Systems Annex (DMSA). Overall statistics of these solutions are presented for the 13,211 entries of this annex and the different types of solutions are outlined.

  15. The breaking strain of neutron star crust

    SciTech Connect

    Kadau, Kai [Los Alamos National Laboratory; Horowitz, C J [INDIANA UNIV

    2009-01-01

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

  16. Double neutron capture in62Ni

    NASA Astrophysics Data System (ADS)

    Harder, A.; Michaelsen, S.; Jungclaus, A.; Lieb, K. P.; Williams, A. P.; Börner, H. G.; Trautmannsheimer, M.

    1992-03-01

    The ?-radiation following single and double neutron capture in isotopically enriched62Ni was studied at the high flux reactor of the Institut Laue-Langevin, using a pair and Compton suppressed germanium detector. Measurements before and after 170 d of breeding were performed. The ?-ray fluxes through63Ni and64Ni are discussed; several new levels and spin-parity assignments were found. On the basis of the known discrete levels and the low-energy neutron resonances, level density parameters were determined within the Constant Temperature Fermi Gas model. The neutron binding energies were measured as B n (63Ni)=6837.92(18) keV and B n (64Ni)=9657.64(24) keV. The63Ni ( n, ?) cross section for reactor neutrons was measured to be ?=20{-2/+5} b.

  17. Experimental approach to neutron stars

    SciTech Connect

    Leifels, Yvonne [GSI Helmholtzzentrum für Schwerionenforschung, Planckstr. 1, 64291 Darmstadt (Germany)

    2014-05-09

    The equation of state (EOS) of nuclear matter is of fundamental importance in many areas of nuclear physics and astrophysics In the laboratory, there are different means to study the nuclearmatter equation of state and its density dependence in particular: nuclear masses, neutron skins, pygmy resonance, and nuclear structure at the drip line give access to nuclear matter properties at densities lower than and at saturation density ?0. Heavy ion reactions at energies above 0.1 AGeV are the only means to study nuclear matter at densities larger than normal nuclear matter density ?0. In the beamenergy range of 0.1 to 2A GeV nuclear matter is compressed upto three times ?0. Access to nuclear matter properties is achieved by simulating nuclear collisions by means of microscopic transport codes, or statistical or hydrodynamicalmodels. Characteristics of heavy-ion collisions are discussed, and experimental observables which allow to constrain nuclear matter properties by comparing experimental results with those of transport codes are presented. Special emphasis will be given to the density dependence of the symmetry energy which is the most relevant connection between neutron stars and heavy ion collisions.

  18. Neutron Stars and Thermonuclear X-ray Bursts

    NASA Technical Reports Server (NTRS)

    Bhattacharyya, Supid

    2007-01-01

    This viewgraph presentation describes neutron stars and thermonuclear x ray bursts. The contents include: 1) Neutron Stars: why do we care?; 2) Thermonuclear Bursts: why do we care?; 3) Neutron Stars: Mass, Radius and Spin: a. Continuum Spectroscopy of Bursts b. Spectral Lines from Bursts c. Timing Properties of Bursts; 4) Neutron Star Atmosphere: Thermonuclear Flame Spreading; and 5) Future Prospects and Conclusions.

  19. DYNAMICAL CAPTURE BINARY NEUTRON STAR MERGERS

    SciTech Connect

    East, William E.; Pretorius, Frans [Department of Physics, Princeton University, Princeton, NJ 08544 (United States)

    2012-11-20

    We study dynamical capture binary neutron star mergers as may arise in dense stellar regions such as globular clusters. Using general-relativistic hydrodynamics, we find that these mergers can result in the prompt collapse to a black hole or in the formation of a hypermassive neutron star, depending not only on the neutron star equation of state but also on impact parameter. We also find that these mergers can produce accretion disks of up to a tenth of a solar mass and unbound ejected material of up to a few percent of a solar mass. We comment on the gravitational radiation and electromagnetic transients that these sources may produce.

  20. Color Ferromagnetic Quark Matter in Neutron Stars

    E-print Network

    Aiichi Iwazaki; Osamu Morimatsu; Tetsuo Nishikawa; Munehisa Ohtani

    2005-12-16

    We show that color ferromagnetic phase of quark matter is energetically more favored than color superconducting phases in neutron stars. Namely, increasing baryon density in neutron stars transforms nuclear matter into the quark matter of the color ferromagnetic phase. Further increase of the density makes the quark matter take the color superconducting phases. We find that a critical mass of the neutron star with such an internal structure is about $1.6M_{\\odot}$. We stress that analysis of gluon dynamics is crucial for exploring dense quark matter.

  1. Pulsar observations and neutron star models

    NASA Technical Reports Server (NTRS)

    Boerner, G.; Cohen, J. M.

    1974-01-01

    Information about the physical parameters of neutron stars is obtained from pulsar observations. The energy balance of the Crab Nebula and the Vela X remnant allows one to derive limits for the masses of the Crab and Vela pulsars. Glitch observations provide further clues on the masses of these two pulsars. The degree of confidence with which one should believe the derived numbers is pointed out. The possibility of observing neutron stars in binary systems as pulsating X-ray sources is discussed. Finally, the importance of observing redshifted gamma ray lines from the surface of neutron stars, and thus directly measuring either individual or statistical properties of these objects, is pointed out.

  2. Pulsar observations and neutron star models

    NASA Technical Reports Server (NTRS)

    Boerner, G.; Cohen, J. M.

    1972-01-01

    Information about the physical parameters of neutron stars is obtained from pulsar observations. The energy balance of the Crab nebula and the Vela X remnant allows derivation of limits for the masses of the Crab and Vela pulsars. Glitch observations provide further clues on the masses of these two pulsars. The degree of confidence in the derived numbers is pointed out. The possibility of observing neutron stars in binary systems as pulsating X-ray sources is discussed. The importance of observing redshifted gamma ray lines from the surface of neutron stars, and thus directly measuring either individual or statistical properties of these objects is pointed out.

  3. Constraining the neutron star equation of state with gravitational wave signals from coalescing binary neutron stars

    E-print Network

    Agathos, Michalis; Del Pozzo, Walter; Li, Tjonnie G F; Tompitak, Marco; Veitch, John; Vitale, Salvatore; Broeck, Chris Van Den

    2015-01-01

    Recently exploratory studies were performed on the possibility of constraining the neutron star equation of state (EOS) using signals from coalescing binary neutron stars, or neutron star-black hole systems, as they will be seen in upcoming advanced gravitational wave detectors such as Advanced LIGO and Advanced Virgo. In particular, it was estimated to what extent the combined information from multiple detections would enable one to distinguish between different equations of state through hypothesis ranking or parameter estimation. Under the assumption of zero neutron star spins both in signals and in template waveforms and considering tidal effects to 1PN order, it was found that O(20) sources would suffice to distinguish between a hard, moderate, and soft equation of state. Here we revisit these results, this time including neutron star tidal effects to the highest order currently known, termination of gravitational waveforms at the contact frequency, neutron star spins, and the resulting quadrupole-monopo...

  4. Stellar Wind Disruption by an Orbiting Neutron Star: Neutron Star Close-up

    NSDL National Science Digital Library

    Alan McConnell

    1990-07-10

    A tiny neutron star orbits incessantly around a massive star with a diameter a million times larger than its own. The high luminosity of the massive star drives a strong wind from its surface. The neutron star crashes through this wind at over 300 kilometers per second. The gravity and X-ray luminosity of the neutron star act to disrupt the wind, producing an extended wake of dense gas trailing behind the neutron star. The large scale structure seen in the accretion wake is powered by the release of gravitational potential energy near the surface of the neutron star. The numerical simulations depicted here were computed using the Cray X-MP 48 at the National Center for Supercomputing Applications, University of Illinois, Urbana-Champaign.

  5. Neutron-star matter within the energy-density functional theory and neutron-star structure

    NASA Astrophysics Data System (ADS)

    Fantina, A. F.; Chamel, N.; Pearson, J. M.; Goriely, S.

    2015-02-01

    In this lecture, we will present some nucleonic equations of state of neutron-star matter calculated within the nuclear energy-density functional theory using generalized Skyrme functionals developed by the Brussels-Montreal collaboration. These equations of state provide a consistent description of all regions of a neutron star. The global structure of neutron stars predicted by these equations of state will be discussed in connection with recent astrophysical observations.

  6. Plasma physics of accreting neutron stars

    NASA Technical Reports Server (NTRS)

    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.

  7. Magnetic properties in double star induction machine

    Microsoft Academic Search

    H. Hammache; D. Moussaoui; K. Marouani; T. Hamdouche

    2008-01-01

    Multiphase machines are getting increasingly common in electric traction. The prediction of the losses in multiphase machine is a fundamental step for the optimization of its design. The present paper deals with an experimental study of the behavior of the losses observed in double star induction machines (DSIM). We suggest a study of the losses through the measurements of the

  8. Apsidal Motion in Double Stars. I. Catalog

    Microsoft Academic Search

    A. V. Petrova; V. V. Orlov

    1999-01-01

    A catalog of 128 double stars with measured periods of apsidal motion is compiled. Besides the apsidal periods, the orbital elements of binaries and physical parameters of components (masses, radii, effective temperatures, surface gravities) are given. The agreement of the apsidal periods found by various authors is discussed.

  9. Spacecraft potential control for Double Star

    Microsoft Academic Search

    K. Torkar; H. Arends; W. Baumjohann; C. P. Escoubet; A. Fazakerley; M. Fehringer; G. Fremuth; H. Jeszenszky; G. Laky; B. T. Narheim; W. Riedler; F. Rüdenauer; W. Steiger; K. Svenes; H. Zhao

    2005-01-01

    The spacecraft potential of Double Star TC-1 is positive in large parts of the orbits due to the photo-effect from solar EUV irradiation. These positive potentials typically disturb low energy plasma measurements on board. The potential can be reduced, and thereby the particle measurements improved, by emitting a positive ion beam. This method has successfully been applied on several other

  10. Neutron Star Compared to Manhattan - Duration: 0:11.

    NASA Video Gallery

    A pulsar is a neutron star, the crushed core of a star that has exploded. Neutron stars crush half a million times more mass than Earth into a sphere no larger than Manhattan, as animated in this s...

  11. Optical Observations of Isolated Neutron Stars

    E-print Network

    R. Mignani

    1998-10-02

    Only 1% of the Isolated Neutron Star (INS) population has been identified in the optical, albeit with different degrees of confidence. Optical observations of INSs are reviewed and their emission properties discussed in an evolutionary framework.

  12. Electromagnetic damping of neutron star oscillations

    NASA Technical Reports Server (NTRS)

    Mcdermott, P. N.; Savedoff, M. P.; Van Horn, H. M.; Zweibel, E. G.; Hansen, C. J.

    1984-01-01

    A simple model of magnetic field perturbations driven by neutron star oscillations is used to estimate the electromagnetic power radiated by g-modes and torsional oscillations. The calculation assumes that the neutron star has a frozen-in magnetic field which is perturbed by the oscillatory motions of the surface. The disturbances propagate into the vacuum as outgoing electromagnetic waves. The relative effectiveness of Joule heating of the neutron star crust by pulsation-induced electric currents is estimated. It is concluded that electromagnetic damping is the dominant energy dissipation mechanism for quadrupole g-mode oscillations of neutron stars. For dipole spheroidal modes, both electromagnetic radiation and Joule heating are important, and there is no gravitational radiation emitted by these modes.

  13. The Neutron Star Interior Composition Explorer

    NASA Technical Reports Server (NTRS)

    Gendreau, Keith C.

    2008-01-01

    The Neutron star Interior Composition Explorer (NICE) will be a Mission of Opportunity dedicated to the study of neutron stars, the only places in the universe where all four fundamental forces of nature are simultaneously in play. NICE will explore the exotic states of matter within neutron stars, revealing their interior and surface compositions through rotation resolved X-ray spectroscopy. Absolute time-referenced data will allow NICE to probe the extreme physical environments associated with neutron stars, leveraging observations across the electromagnetic spectrum to answer decades-old questions about one of the most powerful cosmic accelerators known. Finally, NICE will definitively measure stabilities of pulsars as clocks, with implications for navigation, a pulsar-based timescale, and gravitational-wave detection. NICE will fly on the International Space Station, while GLAST is on orbit and post-RXTE, and will allow for the discovery of new high-energy pulsars and provide continuity in X-ray timing astrophysics.

  14. On the Collapse of Neutron Stars

    E-print Network

    Jose N. Pecina-Cruz

    2006-10-03

    This paper reviews the Oppenheimer, Volkoff and Snyder's arguments about the formation of black holes from the collapse of Neutron Stars. It is found that such a collapse is inconsistent with microscopic causality and Heisenberg uncertainty principle.

  15. Neutron stars in Einstein-aether theory

    E-print Network

    Christopher Eling; Ted Jacobson; M. Coleman Miller

    2009-12-06

    As current and future experiments probe strong gravitational regimes around neutron stars and black holes, it is desirable to have theoretically sound alternatives to general relativity against which to test observations. Here we study the consequences of one such generalization, Einstein-aether theory, for the properties of non-rotating neutron stars. This theory has a parameter range that satisfies all current weak-field tests. We find that within this range it leads to lower maximum neutron star masses, as well as larger surface redshifts at a particular mass, for a given nuclear equation of state. For non-rotating black holes and neutron stars, the innermost stable circular orbit is only slightly modified in this theory.

  16. pi-condensation and neutron star cooling

    Microsoft Academic Search

    J. Kogut; J. T. Manassah

    1972-01-01

    We show, within the context of an independent particle model, that pi- condensation should occur in neutron stars having baryon densities exceeding~0.4 - 0.5 fm-3. This high concentration of pi- implies a very fast cooling rate for `hot' neutron stars. Work supported by the Air Force Office of Scientific Research, Office of Aerospace Research, United States Air Force, under AFOSR

  17. Chandra Observations of Isolated Neutron Stars

    NASA Technical Reports Server (NTRS)

    Weisskopf, Martin

    2006-01-01

    We present a review of the first six years of Chandra X-ray Observatory observations of isolated neutron stars. The outstanding spatial and spectral resolution of this great observatory have allowed for observations of unprecedented clarity and accuracy. Many of these observations have provided new insights into neutron star physics. We present a (biased) overview of six years of these observations, highlighting new discoveries made possible by the Observatory's unique capabilities.

  18. Hydrodynamical evolution of coalescing binary neutron stars

    NASA Technical Reports Server (NTRS)

    Rasio, Frederic A.; Shapiro, Stuart L.

    1992-01-01

    The hydrodynamics of the final merging of two neutron stars and the corresponding gravitational wave emission is studied in detail. Various test calculations are presented, including the compressible Roche and Darwin problems and the head-on collision of two polytropes. A complete coalescence calculation is presented for the simplest case of two identical neutron stars, represented by Gamma = 2 polytropes, in a circular orbit, with their spins aligned and synchronized with the orbital rotation.

  19. Direct URCA process in neutron stars

    NASA Technical Reports Server (NTRS)

    Lattimer, James M.; Prakash, Madappa; Pethick, C. J.; Haensel, Pawel

    1991-01-01

    It is shown that the direct URCA process can occur in neutron stars if the proton concentration exceeds some critical value in the range 11-15 percent. The proton concentration, which is determined by the poorly known symmetry energy of matter above nuclear density, exceeds the critical value in many current calculations. If it occurs, the direct URCA process enhances neutrino emission and neutron star cooling rates by a large factor compared to any process considered previously.

  20. Neutron star cooling: effects of envelope physics

    SciTech Connect

    Van Riper, K.A.

    1982-01-01

    Neutron star cooling calculations are reported which employ improved physics in the calculation of the temperature drop through the atmosphere. The atmosphere microphysics is discussed briefly. The predicted neutron star surface temperatures, in the interesting interval 200 less than or equal to t (yr) less than or equal to 10/sup 5/, do not differ appreciably from the earlier results of Van Riper and Lamb (1981) for a non-magnetic star; for a magnetic star, the surface temperature is lower than in the previous work. Comparison with observational limits show that an exotic cooling mechanism, such as neutrino emission from a pion condensate or in the presence of percolating quarks, is not required unless the existence of a neutron star in the Tycho or SN1006 SNRs is established.

  1. Plasma magnetosphere of deformed magnetized neutron star

    NASA Astrophysics Data System (ADS)

    Rayimbaev, J. R.; Ahmedov, B. J.; Juraeva, N. B.; Rakhmatov, A. S.

    2015-04-01

    The plasma magnetosphere surrounding a rotating magnetized neutron star described by non-Kerr spacetime metric in slow rotation approximation has been studied. First we have studied the vacuum solutions of the Maxwell equations in spacetime of slowly rotating magnetized non-Kerr star with dipolar magnetic configuration. Then for the magnetospheric model we have derived second-order differential equation for electrostatic potential from the system of Maxwell equations in spacetime of slowly rotating magnetized non-Kerr star. Analytical solutions of Goldreich-Julian (GJ) charge density along open field lines of slowly rotating magnetized non-Kerr neutron star have been obtained which indicate the modification of an accelerating electric field, charge density along the open field lines and radiating losses of energy of the neutron star by the deformation parameter.

  2. Theoretical Studies of Accreting Neutron Stars

    NASA Technical Reports Server (NTRS)

    Taam, Ronald E.

    2003-01-01

    Among the newly discovered classes of X-ray sources which have attracted wide attention are close binary systems in which mass is transferred via Roche lobe overflow from a low mass donor star to its neutron star companion. Many of these sources exhibit intense bursts of X-ray radiation as well as periodic and quasi-periodic phenomena. Intensive analysis of these sources as a class has provided insight into the accretion process in binary star systems and into the magnetic field, rotational, and nuclear evolution of the underlying neutron star. In this proposal we have focused on theoretical studies of the hydrodynamical and nuclear processes that take place on the surface of accreting neutron stars in these systems. The investigation of these processes is critical for providing an understanding of a number of outstanding problems related to their transient behavior and evolution.

  3. Neutron stars as laboratories for gravity physics

    SciTech Connect

    Deliduman, Cemsinan [Department of Physics, Mimar Sinan Fine Arts University, Bomonti 34380, ?stanbul (Turkey)

    2014-06-24

    We study the structure of neutron stars in R+?R{sup 2} gravity model with perturbative method. We obtain mass-radius relations for four representative equations of state (EoS). We find that, for |?|?10{sup 9} cm{sup 2}, the results differ substantially from the results of general relativity. The effects of modified gravity are seen as mimicking a stiff or soft EoS for neutron stars depending upon whether ? is negative or positive, respectively. Some of the soft EoS that are excluded within the framework of general relativity can be reconciled for certain values of ? of this order with the 2 solar mass neutron star recently observed. Indeed, if the EoS is ever established to be soft, modified gravity of the sort studied here may be required to explain neutron star masses as large as 2 M{sub ?}. The associated length scale ?(?)?10{sup 5} cm is of the order of the the typical radius of neutron stars implying that this is the smallest value we could find by using neutron stars as a probe. We thus conclude that the true value of ? is most likely much smaller than 10{sup 9} cm{sup 2}.

  4. The decompression of cold neutron star matter

    NASA Technical Reports Server (NTRS)

    Lattimer, J. M.; Mackie, F.; Ravenhall, D. G.; Schramm, D. N.

    1977-01-01

    The ejection of cold neutron-star matter is examined, and an attempt is made to determine whether the final composition of this matter may be similar to that normally associated with the hot high-neutron-flux r-process. A semiempirical liquid-drop model is used for the nucleus, and the equilibrium composition of the matter is determined by assuming it to be in its absolute ground state at a given density. Physical mechanisms operating during the expansion are analyzed, and the composition of the ejected matter is found as a function of its density during expansion. The results indicate that it is virtually impossible for deuterium to form, that neutrons can be captured only after beta decay increases the atomic numbers of nuclei, and that no free neutrons can escape. It is concluded that neutron-star ejecta can produce heavy neutron-rich nuclei and may produce somewhat heavier nuclei than a standard r-process.

  5. Carbon Atmosphere Discovered On Neutron Star

    NASA Astrophysics Data System (ADS)

    2009-11-01

    Evidence for a thin veil of carbon has been found on the neutron star in the Cassiopeia A supernova remnant. This discovery, made with NASA's Chandra X-ray Observatory, resolves a ten-year mystery surrounding this object. "The compact star at the center of this famous supernova remnant has been an enigma since its discovery," said Wynn Ho of the University of Southampton and lead author of a paper that appears in the latest issue of Nature. "Now we finally understand that it can be produced by a hot neutron star with a carbon atmosphere." By analyzing Chandra's X-ray spectrum - akin to a fingerprint of energy - and applying it to theoretical models, Ho and his colleague Craig Heinke, from the University of Alberta, determined that the neutron star in Cassiopeia A, or Cas A for short, has an ultra-thin coating of carbon. This is the first time the composition of an atmosphere of an isolated neutron star has been confirmed. The Chandra "First Light" image of Cas A in 1999 revealed a previously undetected point-like source of X-rays at the center. This object was presumed to be a neutron star, the typical remnant of an exploded star, but researchers were unable to understand its properties. Defying astronomers' expectations, this object did not show any X-ray or radio pulsations or any signs of radio pulsar activity. By applying a model of a neutron star with a carbon atmosphere to this object, Ho and Heinke found that the region emitting X-rays would uniformly cover a typical neutron star. This would explain the lack of X-ray pulsations because -- like a lightbulb that shines consistently in all directions -- this neutron star would be unlikely to display any changes in its intensity as it rotates. Scientists previously have used a neutron star model with a hydrogen atmosphere giving a much smaller emission area, corresponding to a hot spot on a typical neutron star, which should produce X-ray pulsations as it rotates. Interpreting the hydrogen atmosphere model without pulsations would require a tiny size, consistent only with exotic stars made of strange quark matter. "Our carbon veil solves one of the big questions about the neutron star in Cas A," said Craig Heinke. "People have been willing to consider some weird explanations, so it's a relief to discover a less peculiar solution." Unlike most astronomical objects, neutron stars are small enough to understand on a human scale. For example, neutron stars typically have a diameter of about 14 miles, only slightly longer than a half-marathon. The atmosphere of a neutron star is on an even smaller scale. The researchers calculate that the carbon atmosphere is only about 4 inches thick, because it has been compressed by a surface gravity that is 100 billion times stronger than on Earth. "For people who are used to hearing about immense sizes of things in space, it might be a surprise that we can study something so small," said Ho. "It's also funny to think that such a thin veil over this star played a key role in frustrating researchers." In Earth's time frame, the estimated age of the neutron star in Cas A is only several hundred years, making it about ten times younger than other neutron stars with detected surface emission. Therefore, the Cas A neutron star gives a unique window into the early life of a cooling neutron star. The carbon itself comes from a combination of material that has fallen back after the supernova, and nuclear reactions on the hot surface of the neutron star which convert hydrogen and helium into carbon. The X-ray spectrum and lack of pulsar activity suggest that the magnetic field on the surface of this neutron star is relatively weak. Similarly low magnetic fields are implied for several other young neutron stars by study of their weak X-ray pulsations. It is not known whether these neutron stars will have low magnetic fields for their entire lives, and never become radio pulsars, or whether processes in their interior will lead to the development of stronger magnetic fields as

  6. Microscopic magnetic dipole radiation in neutron stars

    E-print Network

    Hao Tong; Qiu-he Peng; Hua Bai

    2008-01-03

    There is ${}^3P_2$ neutron superfluid region in NS (neutron star) interior. For a rotating NS, the ${}^3P_2$ superfluid region is like a system of rotating magnetic dipoles. It will give out electromagnetic radiation, which may provides a new heating mechanism of NSs. This heating mechanism plus some cooling agent may give sound explanation to NS glitches.

  7. Neutron stars and the fermionic Casimir effect

    E-print Network

    Piotr Magierski; Aurel Bulgac; Paul-Henri Heenen

    2001-12-03

    The inner crust of neutron stars consists of nuclei of various shapes immersed in a neutron gas and stabilized by the Coulomb interaction in the form of a crystal lattice. The scattering of neutrons on nuclear inhomegeneities leads to the quantum correction to the total energy of the system. This correction resembles the Casimir energy and turns out to have a large influence on the structure of the crust.

  8. Neutron Stars and the Discovery of Pulsars.

    ERIC Educational Resources Information Center

    Greenstein, George

    1985-01-01

    Part one recounted the story of the discovery of pulsars and examined the Crab Nebula, supernovae, and neutron stars. This part (experts from the book "Frozen Star") shows how an understanding of the nature of pulsars allowed astronomers to tie these together. (JN)

  9. Equilibrium Models of Strongly Magnetized Neutron Stars

    NASA Astrophysics Data System (ADS)

    Hirschmann, Eric W.

    2015-01-01

    We consider equilibrium configurations of strongly magnetized neutron stars. Within full general relativity and assuming axisymmetry, we construct rotating stars with both poloidal and toroidal fields. Using a self-consistent field approach, we investigate the relative contributions from both magnetic components.

  10. Measurements of Neglected Double Stars Report of September 2014

    NASA Astrophysics Data System (ADS)

    Carro, Joseph

    2015-01-01

    This article presents measurements of 25 neglected double stars. The stars were selected from the Northern List I of Neglected Double Stars published by the United States Naval Observatory. While, the photographs were obtained with a remote telescope, the astrometric reductions were done by the author. This report is part of a project to measure all of the neglected northern stars.

  11. Constraining Hadronic Superfluidity with Neutron Star Precession

    E-print Network

    Bennett Link

    2003-08-28

    I show that the standard picture of the neutron star core containing coexisting neutron and proton superfluids, with the proton component forming a type II superconductor threaded by flux tubes, is inconsistent with observations of long-period (~1 yr) precession in isolated pulsars. I conclude that either the two superfluids coexist nowhere in the stellar core, or the core is a type I superconductor rather than type II. Either possibility would have interesting implications for neutron star cooling and theories of spin jumps (glitches).

  12. Constraining hadronic superfluidity with neutron star precession.

    PubMed

    Link, Bennett

    2003-09-01

    I show that the standard picture of the neutron star core containing coexisting neutron and proton superfluids, with the proton component forming a type II superconductor threaded by flux tubes, is inconsistent with observations of long-period (approximately 1 yr) precession in isolated pulsars. I conclude that either the two superfluids coexist nowhere in the stellar core, or the core is a type I superconductor rather than type II. Either possibility would have interesting implications for neutron star cooling and theories of spin jumps (glitches). PMID:14525469

  13. Which Stars Form Black Holes and Neutron Stars?

    E-print Network

    Michael P. Muno

    2006-11-18

    I describe the current state of our knowledge of the mapping between the initial masses of stars and the compact objects -- particularly neutron stars and black holes -- that they produce. Most of that knowledge is theoretical in nature, and relies on uncertain assumptions about mass loss through winds, binary mass transfer, and the amount of mass ejected during a supernovae. Observational constraints on the initial masses of stars that produce neutron stars and black holes is scarce. They fall into three general categories: (1) models of the stars that produced the supernova remnants associated with known compact objects, (2) scenarios through with high mass X-ray binaries were produced, and (3) associations between compact objects and coeval clusters of stars for which the minimum masses of stars that have undergone supernovae are known. I focus on the last category as the most promising in the near term. I describe three highly-magnetized neutron stars that have been associated with progenitors that had initial masses of $>$30\\msun, and evaluate the prospects of finding further associations between star clusters and compact objects.

  14. From nuclear matter to Neutron Stars

    E-print Network

    T. K. Jha

    2009-02-02

    Neutron stars are the most dense objects in the observable Universe and conventionally one uses nuclear theory to obtain the equation of state (EOS) of dense hadronic matter and the global properties of these stars. In this work, we review various aspects of nuclear matter within an effective Chiral model and interlink fundamental quantities both from nuclear saturation as well as vacuum properties and correlate it with the star properties.

  15. Forecasting neutron star temperatures: predictability and variability.

    PubMed

    Page, Dany; Reddy, Sanjay

    2013-12-13

    It is now possible to model thermal relaxation of neutron stars after bouts of accretion during which the star is heated out of equilibrium by nuclear reactions in its crust. Major uncertainties in these models can be encapsulated in modest variations of a handful of control parameters that change the fiducial crustal thermal conductivity, specific heat, and heating rates. Observations of thermal relaxation constrain these parameters and allow us to predict longer term variability in terms of the neutron star core temperature. We demonstrate this explicitly by modeling ongoing thermal relaxation in the neutron star XTE J1701-462. Its future cooling, over the next 5 to 30 years, is strongly constrained and depends mostly on its core temperature, uncertainties in crust physics having essentially been pinned down by fitting to the first three years of observations. PMID:24483640

  16. Cluster and Double Star observations of dipolarization

    Microsoft Academic Search

    R. Nakamura; W. Baumjohann; T. L. Zhang; C. M. Carr; A. Balogh; K.-H. Fornacon; E. Georgescu; H. Rème; I. Dandouras; T. Takada; M. Volwerk; Y. Asano; A. Runov; H. Eichelberger; B. Klecker; C. Mouikis; L. M. Kistler; O. Amm

    2005-01-01

    We studied two types of dipolarization events with different IMF conditions when Cluster and Double Star (TC-1) were located in the same local time sector: 7 August 2004, 18:00-24:00 UT, during a disturbed southward\\/northward IMF interval, and 14 August 2004, 21:00-24:00 UT, when the IMF was stably northward. Cluster observed dipolarization as well as fast flows during both intervals, but

  17. Neutron Stars Opacity and Proton Fraction

    E-print Network

    P. N. Alcain; C. O. Dorso

    2015-02-03

    Background: In neutron stars the nucleons are submitted to extreme conditions. The study of this natural occurring objects can lead to further understanding of the behaviour of nuclear matter in highly asymmetric nuclei. Among the characteristics of neutron stars, its neutrino absorption - associated to structural inhomoegeneities - stands out as one of the possible magnitudes linked to an observable. Purpose: We have carried out a systematic study of this neutrino absorption for different thermodynamic conditions in order to assess the impact that the structure has on it. Method: We study the dynamics of nucleons in conditions according to the neutron star crust with a semiclassical molecular dynamics model, for different densities, proton fractions and temperature, we calculate the long range opacity and the cluster distribution. Results: The neutrino absorption, the main mechanism for neutron stars cooldown, takes its highest value for temperatures and densities low compared with the inner crust, and a proton fraction is close to the symmetric case $x=0.5$. Conclusions: Within the used model the neutrinos are absorbed mostly close to the surface of the neutron star. Also, for high temperatures, a large cluster still exists, but the appearance of several small-sized clusters smears out the very long range order needed for neutrino absorption.

  18. Dissipative processes in superfluid neutron stars

    SciTech Connect

    Mannarelli, Massimo [Departament d'Estructura i Constituents de la Materia and Institut de Ciencies del Cosmos (ICCUB), Universitat de Barcelona, Marti i Franques 1, 08028 Barcelona (Spain); Colucci, Giuseppe [Universita di Bari, I-70126 Bari, Italia and .N.F.N., Sezione di Bari, I-70126 Bari (Italy); Manuel, Cristina [Instituto de Ciencias del Espacio (IEEC/CSIC), Campus Universitat Autonoma de Barcelona, Facultat de Ciencies, Torre C5 E-08193 Bellaterra (Barcelona) (Spain)

    2011-05-23

    We present some results about a novel damping mechanism of r-mode oscillations in neutron stars due to processes that change the number of protons, neutrons and electrons. Deviations from equilibrium of the number densities of the various species lead to the appearance in the Euler equations of the system of a dissipative mechanism, the so-called rocket effect. The evolution of the r-mode oscillations of a rotating neutron star are influenced by the rocket effect and we present estimates of the corresponding damping timescales. In the description of the system we employ a two-fluid model, with one fluid consisting of all the charged components locked together by the electromagnetic interaction, while the second fluid consists of superfluid neutrons. Both components can oscillate however the rocket effect can only efficiently damp the countermoving r-mode oscillations, with the two fluids oscillating out of phase. In our analysis we include the mutual friction dissipative process between the neutron superfluid and the charged component. We neglect the interaction between the two r-mode oscillations as well as effects related with the crust of the star. Moreover, we use a simplified model of neutron star assuming a uniform mass distribution.

  19. Neutronic effects on tungsten-186 double neutron capture

    NASA Astrophysics Data System (ADS)

    Garland, Marc Alan

    Rhenium-188, a daughter product of tungsten-188, is an isotope of great interest in therapeutic nuclear medicine, being used in dozens of laboratory and clinical investigations worldwide. Applications include various cancer therapy strategies, treatment of rheumatoid arthritis, prevention of restenosis following coronary artery angioplasty, and palliation of bone pain associated with cancer metastases. With its half-life of 17 hours, 2.12 MeV (maximum) beta-particle emission, chemical similarity to technetium-99m (the most widely used diagnostic radioisotope), and its availability in a convenient tungsten-188/rhenium-188 generator system, rhenium-188 is a superb candidate for a broad range of applications. Production of 188W is typically via double neutron capture by 186W in a high flux nuclear reactor, predominantly the High Flux Isotope Reactor at the Oak Ridge National Laboratory in Tennessee. Experience at HFIR has shown that production yields (measured in Ci of 188W produced per g of 186W target) decrease considerably as target size increases. While the phenomenon of neutron resonance self-shielding would be expected to produce such an effect, temperature effects on neutron flux distribution and neutron capture rates may also be involved. Experimental investigations of these phenomena have not been previously performed. The work presented in this thesis evaluates the factors that contribute to the decrease in 188W yield from both theoretical and experimental standpoints. Neutron self-shielding and temperature effects were characterized to develop a strategy for target design that would optimize production yield, an important factor in minimizing health care costs. It was determined that decrease in yield due to neutron self-shielding can be attributed to depletion of epithermal neutrons at resonant energies, most significantly within the initial 0.4 mm depth of the target. The results from these studies further show that 188W yield in the interior of the target (beyond 0.4 mm depth) does not decrease as would be expected due to neutron attenuation. This observation was explained by the fact elevated temperatures in the interior of the target result in an increase in the 188W yield through Doppler broadening of cross sections, compensating for reduced yield due to neutron attenuation. Finally, this work supports earlier analyses that questioned the accuracy of the 187W thermal cross section and resonance integral.

  20. Neutron-capture elements in the s- and r-process-rich stars: Constraints on neutron-capture nucleosynthesis processes

    E-print Network

    Bo Zhang; Kun Ma; Guide Zhou

    2006-05-14

    The chemical abundances of the very metal-poor double-enhanced stars are excellent information for setting new constraints on models of neutron-capture processes at low metallicity. These stars are known as s+r stars, since they show enhancements of both s-process and r-process elements. The observed abundance ratios for the double-enhanced stars can be explained by those of stars that were polluted by an AGB star and subsequently accreted very significant amounts of r-process material out of an AIC (accretion-induced collapse) or Type 1.5 supernova. In this paper we present for the first time an attempt to fit the elemental abundances observed in the s- and r-rich, very metal-poor stars using a parametric model and suggest a new concept of component coefficients to describe the contributions of the individual neutron-capture processes to double-enhanced stars. We find that the abundance ratios of these stars are best fitted by enrichments of s- and r-process material. The overlap factor in the AGB stars where the observed s-process elements were produced lies between 0.1 and 0.81. Taking into account the dependence of the initial-final mass relations on metallicity, this wide range of values could possibly be explained by a wide range of core-mass values of AGB stars at low metallicity. The component coefficient of the r-process is strongly correlated with the component coefficient of the s-process for the double-enhanced stars. This is significant evidence that the r-process material in double-enhanced stars comes from an AIC or Type 1.5 supernova.

  1. The Mystery of the Lonely Neutron Star

    NASA Astrophysics Data System (ADS)

    2000-09-01

    The VLT Reveals Bowshock Nebula around RX J1856.5-3754 Deep inside the Milky Way, an old and lonely neutron star plows its way through interstellar space. Known as RX J1856.5-3754 , it measures only ~ 20 km across. Although it is unusually hot for its age, about 700,000 °C, earlier observations did not reveal any activity at all, contrary to all other neutron stars known so far. In order to better understand this extreme type of object, a detailed study of RX J1856.5-3754 was undertaken by Marten van Kerkwijk (Institute of Astronomy of the University of Utrecht, The Netherlands) and Shri Kulkarni (California Institute of Technology, Pasadena, California, USA). To the astronomers' delight and surprise, images and spectra obtained with the ESO Very Large Telescope (VLT) now show a small nearby cone-shaped ("bowshock") nebula. It shines in the light from hydrogen atoms and is obviously a product of some kind of interaction with this strange star. Neutron stars - remnants of supernova explosions Neutron stars are among the most extreme objects in the Universe. They are formed when a massive star dies in a "supernova explosion" . During this dramatic event, the core of the star suddenly collapses under its own weight and the outer parts are violently ejected into surrounding space. One of the best known examples is the Crab Nebula in the constellation Taurus (The Bull). It is the gaseous remnant of a star that exploded in the year 1054 and also left behind a pulsar , i.e., a rotating neutron star [1]. A supernova explosion is a very complex event that is still not well understood. Nor is the structure of a neutron star known in any detail. It depends on the extreme properties of matter that has been compressed to incredibly high densities, far beyond the reach of physics experiments on Earth [2]. The ultimate fate of a neutron star is also unclear. From the observed rates of supernova explosions in other galaxies, it appears that several hundred million neutron stars must have formed in our own galaxy, the Milky Way. However, most of these are now invisible, having since long cooled down and become completely inactive while fading out of sight. An unsual neutron star - RX J1856.5-3754 Some years ago, the X-ray source RX J1856.5-3754 was found by the German ROSAT X-ray satellite observatory. Later observations with the Hubble Space Telescope (cf. STScI-PR97-32 ) detected extremely faint optical emission from this source and conclusively proved that it is an isolated neutron star [3]. There is no sign of the associated supernova remnant and it must therefore be at least 100,000 years "old". Most interestingly, and unlike younger isolated neutron stars or neutron stars in binary stellar systems, RX J1856.5-3754 does not show any sign of activity whatsoever, such as variability or pulsations. As a unique member of its class, RX J1856.5-3754 quickly became the centre of great interest among astronomers. It apparently presented the first, very welcome opportunity to perform detailed studies of the structure of a neutron star, without the disturbing influence of ill-understood activity. One particular question arose immediately. The emission of X-rays indicates a very high temperature of RX J1856.5-3754 . However, from the moment of their violent birth, neutron stars are thought to lose energy and to cool down continuously. But then, how can an old neutron star like this one be so hot? One possible explanation is that some interstellar material, gas and/or dust grains, is being captured by its strong gravitational field. Such particles would fall freely towards the surface of the neutron star and arrive there with about half the speed of light. Since the kinetic energy of these particles is proportionate to the second power of the velocity, even small amounts of matter would deposit much energy upon impact, thereby heating the neutron star. The spectrum of RX J1856.5-3754 The new VLT study by van Kerkwijk and Kulkarni of RX J1856.5-3754 was first aimed at taking optical spectra, in order to study its s

  2. Neutron source, neutron density and the origin of barium stars

    Microsoft Academic Search

    Robert A. Malaney; David L. Lambert

    1988-01-01

    The authors present new high resolution spectra of the MgH profiles in nine barium stars, and determine, by spectral synthesis techniques, the magnesium isotopic ratios in each star. When compared with recent AGB nucleosynthesis calculations, they can emphatically rule out the operation of the 22Ne(alpha, n)25Mg reaction as the neutron source responsible for the s-process enhancements observed in these barium

  3. The Neutron Star Interior Composition Explorer (NICER)

    NASA Technical Reports Server (NTRS)

    Wilson-Hodge, Colleen A.; Gendreau, K.; Arzoumanian, Z.

    2014-01-01

    The Neutron Star Interior Composition Explorer (NICER) is an approved NASA Explorer Mission of Opportunity dedicated to the study of the extraordinary gravitational, electromagnetic, and nuclear-physics environments embodied by neutron stars. Scheduled to be launched in 2016 as an International Space Station payload, NICER will explore the exotic states of matter, using rotation-resolved spectroscopy of the thermal and non-thermal emissions of neutron stars in the soft (0.2-12 keV) X-ray band. Grazing-incidence "concentrator" optics coupled with silicon drift detectors, actively pointed for a full hemisphere of sky coverage, will provide photon-counting spectroscopy and timing registered to GPS time and position, with high throughput and relatively low background. The NICER project plans to implement a Guest Observer Program, which includes competitively selected user targets after the first year of flight operations. I will describe NICER and discuss ideas for potential Be/X-ray binary science.

  4. Interpreting QPOs from Accreting Neutron Stars

    E-print Network

    M. Coleman Miller

    2003-12-17

    The high time resolution and large area of the Rossi X-ray Timing Explorer have been essential in the detection and characterization of high-frequency quasi-periodic variability in the flux from neutron stars in low-mass X-ray binaries. An unknown phenomenon prior to RXTE, kilohertz quasi-periodic oscillations (QPOs) have now been detected from more than twenty systems. Their high frequencies (up to 1330 Hz) imply that they are generated close to the neutron star, where general relativistic effects are expected to play an important role. I summarize current models for the kilohertz QPO phenomenon. In particular, I show that there is a significant domain of agreement among the models that can be used to constrain neutron star structure and look for signatures of highly curved spacetime in the properties of the QPOs.

  5. Magnetic Field Evolution During Neutron Star Recycling

    E-print Network

    Andrew Cumming

    2004-04-27

    I describe work on two aspects of magnetic field evolution relevant for the "recycling" scenario for making millisecond radio pulsars. First, many of the theoretical ideas for bringing about accretion-induced field decay rely on dissipation of currents in the neutron star crust. I discuss field evolution in the crust due to the Hall effect, and outline when it dominates Ohmic decay. This emphasises the importance of understanding the impurity level in the crust. Second, I briefly discuss the progress that has been made in understanding the magnetic fields of neutron stars currently accreting matter in low mass X-ray binaries. In particular, thermonuclear X-ray bursts offer a promising probe of the magnetic field of these neutron stars.

  6. Magnetosphere of Oscillating Neutron Star. Nonvacuum Treatment

    E-print Network

    A. N. Timokhin; G. S. Bisnovatyi-Kogan; H. C. Spruit

    2000-03-02

    We generalize a formula for the Goldreich-Julian charge density (\\rho), originally derived for rotating neutron star, for arbitrary oscillations of a neutron star with arbitrary magnetic field configuration under assumption of low current density in the inner parts of the magnetosphere. As an application we consider toroidal oscillation of a neutron star with dipole magnetic field and calculate energy losses. For some oscillation modes the longitudinal electric field can not be canceled by putting charged particles in the magnetosphere without a presence of strong electric current j = (c/(\\omega r))\\rho c. It is shown that the energy losses are strongly affected by plasma in the magnetosphere, and cannot be described by vacuum formulas.

  7. Ultrahigh energy neutrinos from galactic neutron stars

    NASA Technical Reports Server (NTRS)

    Helfand, D. J.

    1979-01-01

    An attempt is made to estimate the production rate of ultrahigh energy (UHE) neutrinos from galactic neutron stars. The statistics of various stellar populations are reviewed as well as an evolutionary scheme linking several neutron star environments. An observational test for predicting stellar evolution is made using two mass ratio intervals of less than 0.3 and greater than or approximately equal to 0.3, which is supported by kinematical evidence. Attention is given to the problem of the target material that is required by UHE protons accelerated from the pulsar's surface to their rotational kinetic energy, and to the detectability of neutron stars in the UHE neutrinos by employing the deep underwater muon and neutrino detector (DUMAND) array.

  8. r-Process in Neutron Star Mergers.

    PubMed

    Freiburghaus; Rosswog; Thielemann

    1999-11-10

    The production site of the neutron-rich heavy elements that are formed by rapid neutron capture (the r-process) is still unknown despite intensive research. Here we show detailed studies of a scenario that has been proposed earlier by Lattimer & Schramm, Symbalisty & Schramm, Eichler et al., and Davies et al., namely the merger of two neutron stars. The results of hydrodynamic and full network calculations are combined in order to investigate the relevance of this scenario for r-process nucleosynthesis. Sufficient material is ejected to explain the amount of r-process nuclei in the Galaxy by decompression of neutron star material. Provided that the ejecta consist of matter with a proton-to-nucleon ratio of Ye approximately 0.1, the calculated abundances fit the observed solar r-pattern excellently for nuclei that include and are heavier than the A approximately 130 peak. PMID:10525469

  9. Towards a metallurgy of neutron star crusts.

    PubMed

    Kobyakov, D; Pethick, C J

    2014-03-21

    In the standard picture of the crust of a neutron star, matter there is simple: a body-centered-cubic lattice of nuclei immersed in an essentially uniform electron gas. We show that, at densities above that for neutron drip (? 4 × 1 0(11)? g cm(-3) or roughly one-thousandth of nuclear matter density), the interstitial neutrons give rise to an attractive interaction between nuclei that renders the lattice unstable. We argue that the likely equilibrium structure is similar to that in displacive ferroelectric materials such as BaTiO3. As a consequence, the properties of matter in the inner crust are expected to be much richer than previously appreciated, and we mention possible consequences for observable neutron star properties. PMID:24702357

  10. Towards a Metallurgy of Neutron Star Crusts

    NASA Astrophysics Data System (ADS)

    Kobyakov, D.; Pethick, C. J.

    2014-03-01

    In the standard picture of the crust of a neutron star, matter there is simple: a body-centered-cubic lattice of nuclei immersed in an essentially uniform electron gas. We show that, at densities above that for neutron drip (˜4×1011 g cm-3 or roughly one-thousandth of nuclear matter density), the interstitial neutrons give rise to an attractive interaction between nuclei that renders the lattice unstable. We argue that the likely equilibrium structure is similar to that in displacive ferroelectric materials such as BaTiO3. As a consequence, the properties of matter in the inner crust are expected to be much richer than previously appreciated, and we mention possible consequences for observable neutron star properties.

  11. Neutron stars as type-I superconductors.

    PubMed

    Buckley, Kirk B W; Metlitski, Max A; Zhitnitsky, Ariel R

    2004-04-16

    In a recent paper by Link, it was pointed out that the standard picture of the neutron star core composed of a mixture of a neutron superfluid and a proton type-II superconductor is inconsistent with observations of a long period precession in isolated pulsars. In the following we will show that an appropriate treatment of the interacting two-component superfluid (made of neutron and proton Cooper pairs), when the structure of proton vortices is strongly modified, may dramatically change the standard picture, resulting in a type-I superconductor. In this case the magnetic field is expelled from the superconducting regions of the neutron star, leading to the formation of the intermediate state when alternating domains of superconducting matter and normal matter coexist. PMID:15169277

  12. Probabilistic star discrepancy bounds for double infinite random matrices

    E-print Network

    Aistleitner, Christoph

    Probabilistic star discrepancy bounds for double infinite random matrices Christoph Aistleitner;Probabilistic star discrepancy bounds for double infinite random matrices 3 and the integral of a function f can their results were generalized by Dick to the case of double infinite random matrices. In the present paper we

  13. Measurements of 16th Hour Northern Neglected Double Stars

    NASA Astrophysics Data System (ADS)

    Vander Haagen, Gary A.

    2008-10-01

    CCD images were taken of 16 neglected double stars from the United States Naval Observatory (USNO) northern list of neglected double stars. The star group's positional data were all measured using the software measurement utility, MPO Canopus. All CCD images were made at Stonegate Observatory Ann Arbor, Michigan, June 20, 2008 at 42:17:48N and 83:50:14W.

  14. Integral trees homeomorphic to a double star A. E. Brouwer

    E-print Network

    Brouwer, Andries E.

    Integral trees homeomorphic to a double star A. E. Brouwer 2009-09-17 Abstract Trees with two of degree larger than two. They write We would now like to examine the trees homeomorphic to a double star, that is, to a tree obtained by joining the centers of two stars with an edge. Unfortunately, the details

  15. Measurements of Neglected Double Stars: November 2014 Report

    NASA Astrophysics Data System (ADS)

    Carro, Joseph

    2015-04-01

    This article presents measurements of 30 neglected double stars. The stars were selected from the Washington Double Star Catalog published by the United States Naval Observatory. The photographs were taken by a remote telescope. The measurements were done by the author.

  16. Physics in Strong Magnetic Fields Near Neutron Stars.

    ERIC Educational Resources Information Center

    Harding, Alice K.

    1991-01-01

    Discussed are the behaviors of particles and energies in the magnetic fields of neutron stars. Different types of possible research using neutron stars as a laboratory for the study of strong magnetic fields are proposed. (CW)

  17. Neutron stars and strong-field effects of general relativity

    E-print Network

    W. Kluzniak

    2000-12-29

    The basic observed properties of neutron stars are reviewed. I suggest that neutron stars in low-mass X-ray binaries are the best of all known sites for testing strong-field effects of general relativity.

  18. Neutron Stars and Quantum Billiards

    E-print Network

    Aurel Bulgac; Piotr Magierski

    2000-08-21

    Homogeneous neutron matter at subnuclear densities becomes unstable towards the formation of inhomogeneities. Depending on the average value of the neutron density one can observe the appearance of either bubbles, rods, tubes or plates embeded in a neutron gas. We estimate the quantum corrections to the ground state energy (which could be termed either shell correction or Casimir energy) of such phases of neutron matter. The calculations are performed by evaluating the contribution of the shortest periodic orbits in the Gutzwiller trace formula for the density of states. The magnitude of the quantum corrections to the ground state energy of neutron matter are of the same order as the energy differences between various phases.

  19. Quark matter core in neutron star

    NASA Astrophysics Data System (ADS)

    Anand, J. D.; Bhattacharjee, P.; Biswas, S. N.

    1980-09-01

    The possible phase transition to quark matter in a neutron star is considered using the neutron matter equation of state proposed recently by Canuto, Datta, and Kalman which involves spin-2 meson interaction among nucleons. The corresponding equation of state for quark matter is taken from quantum chromodynamics. The Oppenheimer-Volkoff equation is then numerically solved to investigate the stability of a superdense system with quarkion cores.

  20. The Outcome of Neutron Star Mergers

    NASA Astrophysics Data System (ADS)

    Foucart, Francois

    2014-10-01

    Black hole-neutron star and neutron star-neutron star mergers are among the main sources of gravitational waves which will be detected in the coming years by the Advanced LIGO/VIRGO/KAGRA observatories. In some cases, these mergers can also power bright electromagnetic emissions: they are the most likely progenitors of short gamma-ray bursts, and the radioactive decay of neutron-rich material ejected by the merger can power optical/infrared transients days after the merger. Finally, they may provide important constraints on the equation of state of cold dense matter, and on the source of heavy elements in the universe. I will discuss the general relativistic simulations which are required to properly model these events, and what they have told us so far about the outcome of neutron star mergers. I will also discuss efforts to improve the physical realism of the simulations by improving the treatment of the most important effects beyond general relativistic hydrodynamics: magnetic fields, neutrinos, and the properties of nuclear matter.

  1. Chandra Observations of Neutron Stars: An Overview

    NASA Technical Reports Server (NTRS)

    Weisskopf, Martin C.; Karovska, M.; Pavlov, G. G.; Zavlin, V. E.; Clarke, Tracy

    2006-01-01

    We present a brief review of Chandra X-ray Observatory observations of neutron stars. The outstanding spatial and spectral resolution of this great observatory have allowed for observations of unprecedented clarity and accuracy. Many of these observations have provided new insights into neutron star physics. We present an admittedly biased and overly brief overview of these observations, highlighting some new discoveries made possible by the Observatory's unique capabilities. We also include our analysis of recent multiwavelength observations of the putative pulsar and its pulsar-wind nebula in the IC 443 SNR.

  2. An instability in neutron stars at birth

    NASA Technical Reports Server (NTRS)

    Burrows, Adam; Fryxell, Bruce A.

    1992-01-01

    Calculations with a two-dimensional hydrodynamic simulation show that a generic Raleigh-Taylor-like instability occurs in the mantles of nascent neutron stars, that it is possibly violent, and that the standard spherically symmetric models of neutron star birth and supernova explosion may be inadequate. Whether this 'convective' instability is pivotal to the supernova mechanism, pulsar nagnetic fields, or a host of other important issues that attend stellar collapse remains to be seen, but its existence promises to modify all questions concerning this most energetic of astronomical phenomena.

  3. Bulk viscosity of superfluid neutron stars

    SciTech Connect

    Gusakov, Mikhail E. [Ioffe Physical Technical Institute, Politekhnicheskaya 26, 194021 St. Petersburg (Russian Federation)

    2007-10-15

    The hydrodynamics describing dynamical effects in superfluid neutron stars essentially differs from the standard one-fluid hydrodynamics. In particular, we have four bulk viscosity coefficients in the theory instead of one. In this paper we calculate these coefficients, for the first time, assuming they are due to nonequilibrium beta processes (such as modified or direct Urca process). The results of our analysis are used to estimate characteristic damping times of sound waves in superfluid neutron stars. It is demonstrated that all four bulk viscosity coefficients lead to comparable dissipation of sound waves and should be considered on the same footing.

  4. Dark-Matter Admixed Neutron Stars

    E-print Network

    S. -C. Leung; M. -C. Chu; L. -M. Lin

    2011-11-08

    We study the hydrostatic equilibrium configuration of an admixture of degenerate dark matter and normal nuclear matter by using a general relativistic two-fluid formalism. We consider non- self-annihilating dark matter particles of mass ~ 1 GeV. The mass-radius relations and moments of inertia of these dark-matter admixed neutron stars are investigated and the stability of these stars is demonstrated by performing a radial perturbation analysis. We find a new class of compact stars which consists of a small normal matter core with radius of a few km embedded in a ten-kilometer- sized dark matter halo. These stellar objects may be observed as extraordinarily small neutron stars that are incompatible with realistic nuclear matter models.

  5. Young Neutron Stars and Their Wind Nebulae

    E-print Network

    Patrick Slane

    2005-05-24

    With Teragauss magnetic fields, surface gravity sufficiently strong to significantly modify light paths, central densities higher than that of a standard nucleus, and rotation periods of only hundredths of a second, young neutron stars are sites of some of the most extreme physical conditions known in the Universe. They generate magnetic winds with particles that are accelerated to energies in excess of a TeV. These winds form synchrotron-emitting bubbles as the particle stream is eventually decelerated to match the general expansion caused by the explosion that formed the neutron stars. The structure of these pulsar wind nebulae allow us to infer properties of the winds and the pulsating neutron stars themselves. The surfaces of the the stars radiate energy from the rapidly cooling interiors where the physical structure is basically unknown because of our imprecise knowledge of the strong interaction at ultrahigh densities. Here I present a summary of recent measurements that allow us to infer the birth properties of neutron stars and to probe the nature of their winds, the physics of their atmospheres, and the structure of their interiors.

  6. Neutron Star Observations and the Equation of State

    SciTech Connect

    Lattimer, James M. [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States)

    2009-05-07

    This talk reviews limits to the properties of neutron stars established from physical considerations such as causality and stability. In addition, it summarizes recent attempts to determine realistic bounds to the equation of state (EOS) from a simultaneous measurement of a neutron star's mass and radius. Observational constraints on the neutron star radius from thermal emission, seismology, spin-orbit coupling, and tidal effects in mergers are discussed. Possible constraints from neutron star cooling, including neutrino emissions, are discussed.

  7. Neutron degeneracy and plasma physics effects on radiative neutron captures in neutron star crust

    E-print Network

    P. S. Shternin; M. Beard; M. Wiescher; D. G. Yakovlev

    2012-07-25

    We consider the astrophysical reaction rates for radiative neutron capture reactions ($n,\\gamma$) in the crust of a neutron star. The presence of degenerate neutrons at high densities (mainly in the inner crust) can drastically affect the reaction rates. Standard rates assuming a Maxwell-Boltzmann distribution for neutrons can underestimate the rates by several orders of magnitude. We derive simple analytical expressions for reaction rates at a variety of conditions with account for neutron degeneracy. We also discuss the plasma effects on the outgoing radiative transition channel in neutron radiative capture reactions and show that these effects can also increase the reaction rates by a few orders of magnitude. In addition, using detailed balance, we analyze the effects of neutron degeneracy and plasma physics on reverse ($\\gamma,n$) photodisintegration. We discuss the dependence of the reaction rates on temperature and neutron chemical potential and outline the efficiency of these reactions in the neutron star crust.

  8. Neutron stars - A cosmic hadron physics laboratory

    NASA Technical Reports Server (NTRS)

    Pines, David

    1989-01-01

    A progress report is given on neutron stars as a cosmic hadron physics laboratory. Particular attention is paid to the crustal neutron superfluid, and to the information concerning its properties which may be deduced from observations of pulsar glitches and postglitch behavior. Current observational evidence concerning the softness or stiffness of the high density neutron matter equation of state is reviewed briefly, and the (revolutionary) implications of a confirmation of the existence of a 0.5 ms pulsar at the core of (Supernova) SN1987A are discussed.

  9. Neutron stars: A cosmic hadron physics laboratory

    NASA Technical Reports Server (NTRS)

    Pines, David

    1989-01-01

    A progress report is given on neutron stars as a cosmic hadron physics laboratory. Particular attention is paid to the crustal neutron superfluid, and to the information concerning its properties which may be deduced from observations of pulsar glitches and postglitch behavior. Current observational evidence concerning the softness or stiffness of the high density neutron matter equation of state is reviewed briefly, and the (revolutionary) implications of a confirmation of the existence of a 0.5 ms pulsar at the core of (Supernova) SN1987A are discussed.

  10. Transition density and pressure in hot neutron stars

    E-print Network

    Xu, Jun; Chen, Lie-Wen; Ko, Che Ming; Li, Bao-An.

    2010-01-01

    in neutrino-trapped neutron stars than in neutrino-free neutron stars. Furthermore, both are found to decrease with increasing temperature of a neutron star as well as increasing slope parameter of the nuclear symmetry energy, except that the transition...

  11. Vibrating neutron stars, quakes, and gamma-ray bursts

    Microsoft Academic Search

    S. E. Woosley

    1995-01-01

    In order to explore the observational consequences a sudden adjustments in neutron star structure, a number of numerical simulations of sound wave propagation in the neutron star crust have been carried out using a one dimensional implicit hydrodynamics code with appropriate, though simplified physics. A neutron star is constructed in hydrostatic equilibrium and its natural oscillation frequency determined empirically, 0.34

  12. Hot neutron star in generalized thermo-statistics

    E-print Network

    Hot neutron star in generalized thermo-statistics K. Miyazaki E-mail: miyazakiro@rio.odn.ne.jp Abstract The hot neutron star (NS) is investigated for the ...rst time in the generalized thermo-statistics. The study of neutron star (NS) is an important subject in nuclear physics and astro- physics. The equation

  13. Neutron Stars and Pulsar: Three Years of Chandra Operations

    NASA Technical Reports Server (NTRS)

    Weisskopf, M. C.; Six, N. Frank (Technical Monitor)

    2002-01-01

    We present a brief review of Chandra Observations of neutron stars, with a concentration on neutron stars in supernova remnants. Three years of Chandra results clearly demonstrate how critical the angular resolution has been in order to separate the neutron star emission from the surrounding nebulosity.

  14. Chandra Observations of Supernova Remnants and Neutron Stars: An Overview

    NASA Technical Reports Server (NTRS)

    Weisskopf, Martin C.

    2002-01-01

    We present a brief overview of Chandra observations of supernova remnants and neutron stars, with emphasis on neutron stars in supernova remnants. The Chandra images demonstrate the importance of angular resolution in separating the neutron star emission from the surrounding nebulosity.

  15. Generalized equation of state for cold superfluid neutron stars

    SciTech Connect

    Chamel, N.; Goriely, S. [Institut d'Astronomie et d'Astrophysique, Universite Libre de Bruxelles, B-1050 Brussels (Belgium); Pearson, J. M. [Departement de Physique, Universite de Montreal, Montreal (Quebec), H3C 3J7 (Canada)

    2011-09-21

    Mature neutron stars are expected to contain various kinds of superfluids in their interiors. Modeling such stars requires the knowledge of the mutual entrainment couplings between the different condensates. We present a unified equation of state describing the different regions of a neutron star with superfluid neutrons and superconducting protons in its core.

  16. Nice observatory measurements of double stars (3rd series)

    NASA Astrophysics Data System (ADS)

    Thorel, J.-C.

    2000-12-01

    We present recent measurements of visual double stars made at the Nice Observatory (3rd series). We also report the discovery of a new double star: JCT 4. Moreover we give a more precise position of the double star DOO 35. Table 1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html

  17. Life Extinction Due To Neutron Star Mergers

    E-print Network

    Arnon Dar; Ari Laor; Nir J. Shaviv

    1996-11-24

    Cosmic ray bursts (CRBs) from mergers or accretion induced collapse of neutron stars that hit an Earth-like planet closer than $\\sim 1 kpc$ from the explosion produce lethal fluxes of atmospheric muons at ground level, underground and underwater. These CRBs also destroy the ozone layer and radioactivate the environment. The mean rate of such life devastating CRBs is one in 100 million years (Myr), consistent with the observed 5 ``great'' extinctions in the past 600 Myr. Unlike the previously suggested extraterrestrial extinction mechanisms the CRBs explain massive life extinction on the ground, underground and underwater and the higher survival levels of radiation resistant species and of terrain sheltered species. More distant mergers can cause smaller extinctions. Biological mutations caused by ionizing radiation produced by the CRB may explain a fast appearance of new species after mass extinctions. The CRB extinction predicts detectable enrichment of rock layers which formed during the extinction periods with cosmogenically produced radioactive nucleides such as $^{129}$I, $^{146}$Sm, $^{205}$Pb with and $^{244}$Pu. Tracks of high energy particles in rock layers on Earth and on the moon may also contain records of intense CRBs. An early warning of future extinctions due to neutron star mergers can be obtained by identifying, mapping and timing all the nearby binary neutron stars systems. A final warning of an approaching CRB from a nearby neutron stars merger will be provided by a gamma ray burst a few days before the arrival of the CRB.

  18. Hydromagnetic stability of differentially rotating neutron stars

    Microsoft Academic Search

    V. Urpin

    2003-01-01

    The stability properties of differentially rotating magnetic neutron stars are considered, and the instability criteria are obtained. The influence of the magnetic field is twofold: it may stabilize a fluid against some instabilities, on the one hand, and it can lead to new branches of instabilities, on the other hand. It turns out that some of the instability criteria of

  19. Relativistic Hydrodynamics in Close Neutron Star Binaries

    Microsoft Academic Search

    G. J. Mathews; P. Marronetti; J. R. Wilson

    1997-01-01

    We discuss several new physical processes which occur in close neutron star binaries. These processes are purely relativistic effects which can be directly traced to terms in our formulation of general relativistic hydrodynamics. In addition to the well known orbit instability, we show that these systems may also be subject to relativistically induced compression, heating and collapse. The neutrino emission

  20. Nuclear physics problems for accreting neutron stars

    SciTech Connect

    Wallace, R.K.; Woosley, S.E.

    1983-01-01

    The importance of p(e/sup -/nu)n and of (p,..gamma..) reactions on /sup 56/Ni during a thermonuclear runaway on a neutron star surface is pointed out. A fast 16-isotope approximate nuclear reaction network is developed that is suitable for use in hydrodynamic calculations of such events.

  1. Neutron Star Superfluidity, Dynamics and Precession

    E-print Network

    M. Ali Alpar

    2005-05-04

    Basic rotational and magnetic properties of neutron superfluids and proton superconductors in neutron stars are reviewed. The modes of precession of the neutron superfluid are discussed in detail. We emphasize that at finite temperature, pinning of superfluid vortices does not offer any constraint on the precession. Any pinning energies can be surmounted by thermal activation and there exists a dynamical steady state in which the superfluid follows the precession of the crust at a small lag angle between the crust and superfluid rotation velocity vectors. At this small lag the system is far from the critical conditions for unpinning, even if the observed precession of the crust may entail a large angle between the figure axis and the crust's rotation velocity vector. We conclude that if long period modulations of pulse arrival times and pulse shapes observed in a pulsar like the PSR B1828-11 are due to the precession of the neutron star, this does not have any binding implications about the existence of pinning by flux lines or the existence of Type II superconductivity in the neutron star.

  2. Quasiuniversal properties of neutron star mergers

    E-print Network

    Sebastiano Bernuzzi; Alessandro Nagar; Simone Balmelli; Tim Dietrich; Maximiliano Ujevic

    2014-06-06

    Binary neutron star mergers are studied using nonlinear 3+1 numerical relativity simulations and the analytical effective-one-body (EOB) model. The EOB model predicts quasiuniversal relations between the mass-rescaled gravitational wave frequency and the binding energy at the moment of merger, and certain dimensionless binary tidal coupling constants depending on the stars Love numbers, compactnesses and the binary mass ratio. These relations are quasiuniversal in the sense that, for a given value of the tidal coupling constant, they depend significantly neither on the equation of state nor on the mass ratio, though they do depend on stars spins. The spin dependence is approximately linear for small spins aligned with the orbital angular momentum. The quasiuniversality is a property of the conservative dynamics; nontrivial relations emerge as the binary interaction becomes tidally dominated. This analytical prediction is qualitatively consistent with new, multi-orbit numerical relativity results for the relevant case of equal-mass irrotational binaries. Universal relations are thus expected to characterize neutron star mergers dynamics. In the context of gravitational wave astronomy, these universal relations may be used to constrain the neutron star equation of state using waveforms that model the merger accurately.

  3. Quasiuniversal Properties of Neutron Star Mergers

    NASA Astrophysics Data System (ADS)

    Bernuzzi, Sebastiano; Nagar, Alessandro; Balmelli, Simone; Dietrich, Tim; Ujevic, Maximiliano

    2014-05-01

    Binary neutron star mergers are studied using nonlinear 3+1 numerical relativity simulations and the analytical effective-one-body model. The effective-one-body model predicts quasiuniversal relations between the mass-rescaled gravitational wave frequency and the binding energy at the moment of merger and certain dimensionless binary tidal coupling constants depending on the stars' Love numbers, compactnesses, and the binary mass ratio. These relations are quasiuniversal in the sense that, for a given value of the tidal coupling constant, they depend significantly neither on the equation of state nor on the mass ratio, though they do depend on stars spins. The spin dependence is approximately linear for small spins aligned with the orbital angular momentum. The quasiuniversality is a property of the conservative dynamics; nontrivial relations emerge as the binary interaction becomes tidally dominated. This analytical prediction is qualitatively consistent with new, multiorbit numerical relativity results for the relevant case of equal-mass irrotational binaries. Universal relations are, thus, expected to characterize neutron star mergers dynamics. In the context of gravitational wave astronomy, these universal relations may be used to constrain the neutron star equation of state using waveforms that model the merger accurately.

  4. General relativistic neutron stars with twisted magnetosphere

    NASA Astrophysics Data System (ADS)

    Pili, A. G.; Bucciantini, N.; Del Zanna, L.

    2015-03-01

    Soft gamma-ray repeaters and anomalous X-ray pulsars are extreme manifestations of the most magnetized neutron stars: magnetars. The phenomenology of their emission and spectral properties strongly support the idea that the magnetospheres of these astrophysical objects are tightly twisted in the vicinity of the star. Previous studies on equilibrium configurations have so far focused on either the internal or the external magnetic field configuration, without considering a real coupling between the two fields. Here, we investigate numerical equilibrium models of magnetized neutron stars endowed with a confined twisted magnetosphere, solving the general relativistic Grad-Shafranov equation both in the interior and in the exterior of the compact object. A comprehensive study of the parameters space is provided, to investigate the effects of different current distributions on the overall magnetic field structure.

  5. General relativistic neutron stars with twisted magnetosphere

    E-print Network

    Pili, A G; Del Zanna, L

    2014-01-01

    Soft Gamma-Ray Repeaters and Anomalous X-Ray Pulsars are extreme manifestations of the most magnetized neutron stars: magnetars. The phenomenology of their emission and spectral properties strongly support the idea that the magnetospheres of these astrophysical objects are tightly twisted in the vicinity of the star. Previous studies on equilibrium configurations have so far focused on either the internal or the external magnetic field configuration, without considering a real coupling between the two fields. Here we investigate numerical equilibrium models of magnetized neutron stars endowed with a confined twisted magnetosphere, solving the general relativistic Grad-Shafranov equation both in the interior and in the exterior of the compact object. A comprehensive study of the parameters space is provided to investigate the effects of different current distributions on the overall magnetic field structure.

  6. General relativistic neutron stars with twisted magnetosphere

    E-print Network

    A. G. Pili; N. Bucciantini; L. Del Zanna

    2014-12-12

    Soft Gamma-Ray Repeaters and Anomalous X-Ray Pulsars are extreme manifestations of the most magnetized neutron stars: magnetars. The phenomenology of their emission and spectral properties strongly support the idea that the magnetospheres of these astrophysical objects are tightly twisted in the vicinity of the star. Previous studies on equilibrium configurations have so far focused on either the internal or the external magnetic field configuration, without considering a real coupling between the two fields. Here we investigate numerical equilibrium models of magnetized neutron stars endowed with a confined twisted magnetosphere, solving the general relativistic Grad-Shafranov equation both in the interior and in the exterior of the compact object. A comprehensive study of the parameters space is provided to investigate the effects of different current distributions on the overall magnetic field structure.

  7. Fallback Disks, Magnetars and Other Neutron Stars

    NASA Astrophysics Data System (ADS)

    Alpar, M. Ali; Çal??kan, ?.; Ertan, Ü.

    2013-02-01

    The presence of matter with angular momentum, in the form of a fallback disk around a young isolated neutron star will determine its evolution. This leads to an understanding of many properties of different classes of young neutron stars, in particular a natural explanation for the period clustering of AXPs, SGRs and XDINs. The spindown or spinup properties of a neutron star are determined by the dipole component of the magnetic field. The natural possibility that magnetars and other neutron stars may have different strengths of the dipole and higher multipole components of the magnetic field is now actually required by observations on the spindown rates of some magnetars. This talk gives a broad overview and some applications of the fallback disk model to particular neutron stars. Salient points are: (i) A fallback disk has already been observed around the AXP 4U 0142+61 some years ago. (ii) The low observed spindown rate of the SGR 0418+5729 provides direct evidence that the dipole component of the field is in the 1012 G range. All properties of the SGR 0418+5729 at its present age can be explained by spindown under torques from a fallback disk. (iii) The anomalous braking index of PSR J1734-3333 can also be explained by the fallback disk model which gives the luminosity, period, period derivative and the period second derivative at the present age. (iv) These and all applications to a variety of other sources employ the same disk physics and evolution, differing only in the initial conditions of the disk.

  8. Shear viscosity in neutron star cores

    E-print Network

    P. S. Shternin; D. G. Yakovlev

    2008-08-21

    We calculate the shear viscosity $\\eta = \\eta_{e\\mu}+\\eta_{n}$ in a neutron star core composed of nucleons, electrons and muons ($\\eta_{e\\mu}$ being the electron-muon viscosity, mediated by collisions of electrons and muons with charged particles, and $\\eta_{n}$ the neutron viscosity, mediated by neutron-neutron and neutron-proton collisions). Deriving $\\eta_{e\\mu}$, we take into account the Landau damping in collisions of electrons and muons with charged particles via the exchange of transverse plasmons. It lowers $\\eta_{e\\mu}$ and leads to the non-standard temperature behavior $\\eta_{e\\mu}\\propto T^{-5/3}$. The viscosity $\\eta_{n}$ is calculated taking into account that in-medium effects modify nucleon effective masses in dense matter. Both viscosities, $\\eta_{e\\mu}$ and $\\eta_{n}$, can be important, and both are calculated including the effects of proton superfluidity. They are presented in the form valid for any equation of state of nucleon dense matter. We analyze the density and temperature dependence of $\\eta$ for different equations of state in neutron star cores, and compare $\\eta$ with the bulk viscosity in the core and with the shear viscosity in the crust.

  9. Oscillations of dissipative superfluid neutron stars

    SciTech Connect

    Andersson, N.; Haskell, B. [School of Mathematics, University of Southampton, Southampton SO17 1BJ (United Kingdom); Glampedakis, K. [SISSA, via Beirut 2-4, 34014 Trieste (Italy); Theoretical Astrophysics, Auf der Morgenstelle 10, University of Tuebingen, Tuebingen D-72076 (Germany)

    2009-05-15

    We investigate the oscillations of slowly rotating superfluid stars, taking into account the vortex-mediated mutual friction force that is expected to be the main damping mechanism in mature neutron star cores. Working to linear order in the rotation of the star, we consider both the fundamental f-modes and the inertial r-modes. In the case of the (polar) f-modes, we work out an analytic approximation of the mode which allows us to write down a closed expression for the mutual friction damping time scale. The analytic result is in good agreement with previous numerical results obtained using an energy integral argument. We extend previous work by considering the full range of permissible values for the vortex drag, e.g. the friction between each individual vortex and the electron fluid. This leads to the first ever results for the f-mode in the strong drag regime. Our estimates provide useful insight into the dependence on, and relevance of, various equation of state parameters. In the case of the (axial) r-modes, we confirm the existence of two classes of modes. However, we demonstrate that only one of these sets remains purely axial in more realistic neutron star models. Our analysis lays the foundation for companion studies of the mutual friction damping of the r-modes at second order in the slow-rotation approximation, the first time evolutions for superfluid neutron star perturbations and also the first detailed attempt at studying the dynamics of superfluid neutron stars with both a relative rotation between the components and mutual friction.

  10. The lowest-mass stellar black holes: catastrophic death of neutron stars in gamma-ray bursts

    E-print Network

    Belczynski, K; Kalogera, V; Rasio, F; Taam, R; Bulik, T

    2007-01-01

    Mergers of double neutron stars are considered the most likely progenitors for short gamma-ray bursts. Indeed such a merger can produce a black hole with a transient accreting torus of nuclear matter and the conversion of the torus mass-energy to radiation can power a gamma-ray burst. Using available binary pulsar observations supported by our extensive evolutionary calculations of double neutron star formation, we demonstrate that the fraction of mergers that can form a black hole -- torus system depends very sensitively on the (largely unknown) maximum neutron star mass. We show that the available observations and models put a very stringent constraint on this maximum mass under the assumption that a majority of short gamma-ray bursts originate in double neutron star mergers. Specifically, we find that the maximum neutron star mass must be within 2--2.5 Msun. Moreover, a single unambiguous measurement of a neutron star mass above 2.5 Msun would exclude double neutron star mergers as short gamma-ray burst pr...

  11. General Relativistic Decompression of Binary Neutron Stars During Dynamic Inspiral

    E-print Network

    Mark Miller

    2007-01-03

    We investigate the dynamic stability of inspiraling neutron stars by performing multiple-orbit numerical relativity simulations of the binary neutron star inspiral process. By introducing eccentricities in the orbits of the neutron stars, significant changes in orbital separation are obtained within orbital timescales. We find that as the binary system evolves from apastron to periastron (as the binary separation decreases), the central rest mass density of each star decreases, thus stabilizing the stars against individual prompt collapse. As the binary system evolves from periastron to apastron, the central rest mass density increases; the neutron stars re-compress as the binary separation increases.

  12. Stellar Wind Disruption by an Orbiting Neutron Star

    NSDL National Science Digital Library

    Alan McConnell

    1990-07-10

    A tiny neutron star orbits incessantly around a massive star with a diameter a million times larger than its own. The high luminosity of the massive star drives a strong wind from its surface. The neutron star crashes through this wind at over 300 kilometers per second. The gravity and X-ray luminosity of the neutron star act to disrupt the wind, producing an extended wake of dense gas trailing behind the neutron star. The numerical simulations depicted here were computed using the Cray X-MP 48 at the National Center for Supercomputing Applications, University of Illinois, Urbana-Champaign.

  13. Neutron stars and quark stars: Two coexisting families of compact stars?

    E-print Network

    J. Schaffner-Bielich

    2006-12-29

    The mass-radius relation of compact stars is discussed with relation to the presence of quark matter in the core. The existence of a new family of compact stars with quark matter besides white dwarfs and ordinary neutron stars is outlined.

  14. Confirming a substellar companion candidate around a neutron star

    NASA Astrophysics Data System (ADS)

    Posselt, Bettina; Luhman, Kevin

    2014-08-01

    In a search for substellar companions around young neutron stars, we found an indication for a very faint near-infrared source at the position of the isolated neutron star RXJ0806.4-4123. The suspected near-IR source cannot be the neutron star itself because the latter is much too faint to be detected. Recent Herschel 160 microm observations of the field point to an additional dusty belt around the neutron star. The outer location of the dusty belt could be explained by the presence of a substellar companion around the neutron star. We propose deeper near-infrared observations with FLAMINGOS-2 to confirm that the near-infrared source is real. The observation could provide the first direct detection of a substellar companion around a neutron star. However, even a non-detection would be interesting to constrain evolution models of the dusty belt around the neutron star.

  15. Nucleosynthesis in decompressing neutron star matter

    E-print Network

    Jaikumar, P; Otsuki, K; Ouyed, R; Jaikumar, Prashanth; Meyer, Bradley S.; Otsuki, Kaori; Ouyed, Rachid

    2006-01-01

    We explore heavy-element nucleosynthesis by rapid neutron capture (r-process) in the decompressing ejecta from the surface of a neutron star. The decompression is triggered by a violent phase transition to strange quark matter (quark-nova scenario). The presence of neutron-rich large Z nuclei (40,95)decompressing ejecta present favorable conditions for the r-process. We perform network calculations that are adapted to the quark-nova conditions, and which mimic usual (n-\\gamma) equilibrium r-process calculations during the initially cold decompression phase. They match to dynamical r-process calculations at densities below neutron drip (4x10^11 g/cc). We present results for the final element abundance distribution with and without heating from nuclear reactions, and compare to the solar abundance pattern of r-process elements. We highlight the distinguishing features of quark-novae by contrasting it with conv...

  16. FURTHER EVIDENCE FOR THE BIMODAL DISTRIBUTION OF NEUTRON-STAR MASSES

    SciTech Connect

    Schwab, J.; Rappaport, S. [37-602B, M.I.T., Department of Physics and Kavli Institute for Astrophysics and Space Research, 70 Vassar St., Cambridge, MA, 02139 (United States); Podsiadlowski, Ph., E-mail: sar@mit.ed, E-mail: jschwab@mit.ed, E-mail: jwschwab@berkeley.ed, E-mail: podsi@astro.ox.ac.u [Department of Astrophysics, University of Oxford, Oxford OX1 3RH (United Kingdom)

    2010-08-10

    We use a collection of 14 well-measured neutron-star masses to strengthen the case that a substantial fraction of these neutron stars were formed via electron-capture (e-capture) supernovae (SNe) as opposed to Fe core-collapse SNe. The e-capture SNe are characterized by lower resultant gravitational masses and smaller natal kicks, leading to lower orbital eccentricities when the e-capture SN has led to the formation of the second neutron star in a binary system. Based on the measured masses and eccentricities, we identify four neutron stars, which have a mean post-collapse gravitational mass of {approx}1.25 M {sub sun}, as the product of e-capture SNe. We associate the remaining 10 neutron stars, which have a mean mass of {approx}1.35 M {sub sun}, with Fe core-collapse SNe. If the e-capture SN occurs during the formation of the first neutron star, then this should substantially increase the formation probability for double neutron stars, given that more systems will remain bound with the smaller kicks. However, this does not appear to be the case for any of the observed systems and we discuss possible reasons for this.

  17. Instabilities in Very Young Neutron Stars: Temperature

    NSDL National Science Digital Library

    Pamela ONeil

    1994-02-12

    This simulation shows the first 20 milliseconds in the life of a neutron star which is formed in a Type II supernova. After an initial collapse phase, the neutron star becomes unstable to convection. The resulting convective motions destroy the spherical symmetry of the star and rapidly mix the inner regions. In addition, the neutrino flux from the neutron star will be non-spherical and will be significantly enhanced by the convective motions. This may have major implications for the Type II supernova mechanism. The calculation was performed using the Piecewise-Parabolic Method for hydrodynamics. The computational grid contained 300 zones in radius and 200 zones in angle. The inner 200 zones in radius were uniformly spaced, ranging from the inner boundary at 25 km to 175 km. The outer 100 zones were non-uniformly spaced and stretched to 2000 km. Only the inner 200 zones are plotted. The inner boundary was treated as a hard sphere. At the outer boundary, zero gradients for all the variables were assumed. Periodic boundary conditions were used along the sides of the grid. The following sequence shows the temperature structure for 20 milliseconds after the shock stalls. The minimum temperature is approximately 1.35 MeV. The maximum temperature varies from 6 MeV at the beginning of the calculation to 10 MeV at the later times.

  18. Instabilities in Very Young Neutron Stars: Density

    NSDL National Science Digital Library

    Pamela ONeil

    1994-02-12

    This simulation shows the first 20 milliseconds in the life of a neutron star which is formed in a Type II supernova. After an initial collapse phase, the neutron star becomes unstable to convection. The resulting convective motions destroy the spherical symmetry of the star and rapidly mix the inner regions. In addition, the neutrino flux from the neutron star will be non-spherical and will be significantly enhanced by the convective motions. This may have major implications for the Type II supernova mechanism. The calculation was performed using the Piecewise-Parabolic Method for hydrodynamics. The computational grid contained 300 zones in radius and 200 zones in angle. The inner 200 zones in radius were uniformly spaced, ranging from the inner boundary at 25 km to 175 km. The outer 100 zones were non-uniformly spaced and stretched to 2000 km. Only the inner 200 zones are plotted. The inner boundary was treated as a hard sphere. At the outer boundary, zero gradients for all the variables were assumed. Periodic boundary conditions were used along the sides of the grid. The following sequence shows the density evolution for 20 milliseconds after the shock stalls. The density is plotted on a log scale. Values range from 10^9 gm-cm^3 at the outer boundary to 1.4 x 10^12 gm-cm^3 at the inner boundary.

  19. Attenuation of Beaming Oscillations Near Neutron Stars

    E-print Network

    M. Coleman Miller

    2000-07-17

    Observations with RXTE have revealed kilohertz quasi-periodic brightness oscillations (QPOs) from nearly twenty different neutron-star low-mass X-ray binaries (LMXBs). These frequencies often appear as a pair of kilohertz QPOs in a given power density spectrum. In many models the higher-frequency of these QPOs is a beaming oscillation at the frequency of a nearly circular orbit at some radius near the neutron star. In such models it is expected that there will also be beaming oscillations at the stellar spin frequency and at overtones of the orbital frequency, but no strong QPOs have been detected at these frequencies. We therefore examine the processes that can attenuate beaming oscillations near neutron stars, and in doing so extend the work on this subject that was initiated by the discovery of lower-frequency QPOs from LMXBs. Among our main results are (1)in a spherical scattering cloud, all overtones of rotationally modulated beaming oscillations are attenuated strongly, not just the even harmonics, and (2)it is possible to have a relatively high-amplitude modulation near the star at, e.g., the stellar spin frequency, even if no peak at that frequency is detectable in a power density spectrum taken at infinity. We discuss the application of these results to modeling of kilohertz QPOs.

  20. How bright planets became dim stars: planetary speculations in John Herschel's double star astronomy.

    PubMed

    Case, Stephen

    2014-03-01

    Previous research on the origins of double star astronomy in the early nineteenth century emphasized the role mathematical methods and instrumentation played in motivating early observations of these objects. The work of the British astronomer John Herschel, however, shows that questions regarding the physical nature of double stars were also important. In particular, an analysis of John Herschel's early work on double stars illustrates the way in which speculations regarding these objects were shaped by assumptions of the properties of stars themselves. For Herschel, a major consideration in double star astronomy was distinguishing between types of double stars. Optical doubles were useful in determining parallax while binary doubles were not. In practice, classification of a specific double star pair into one of these categories was based on the assumption that stars were of approximately the same luminosity and thus differences in relative brightness between stars were caused by difference in distances. Such assumptions, though ultimately abandoned, would lead Herschel in the 1830s to advance the possibility that the dim companion stars in certain double star pairs were not stars at all but in fact planets. PMID:24508199

  1. Magnetic neutron stars in f( R) gravity

    NASA Astrophysics Data System (ADS)

    Astashenok, Artyom V.; Capozziello, Salvatore; Odintsov, Sergei D.

    2015-02-01

    Neutron stars with strong magnetic fields are considered in the framework of f( R) gravity. In order to describe dense matter in magnetic field, the model with baryon octet interacting through ???-fields is used. The hyperonization process results in softening the equation of state (EoS) and in decreasing the maximal mass. We investigate the effect of strong magnetic field in models involving quadratic and cubic corrections in the Ricci scalar R to the Hilbert-Einstein action. For large fields, the Mass-Radius relation differs considerably from that of General Relativity only for stars with masses close to the maximal one. Another interesting feature is the possible existence of more compact stable stars with extremely large magnetic fields (˜6×1018 G instead of ˜4×1018 G as in GR) in the central regions of the stars. Due to cubic terms, a significant increasing of the maximal mass is possible.

  2. Neutron degeneracy and plasma physics effects on radiative neutron captures in neutron star crust

    E-print Network

    Shternin, P S; Wiescher, M; Yakovlev, D G; 10.1103/PhysRevC.86.015808

    2012-01-01

    We consider the astrophysical reaction rates for radiative neutron capture reactions ($n,\\gamma$) in the crust of a neutron star. The presence of degenerate neutrons at high densities (mainly in the inner crust) can drastically affect the reaction rates. Standard rates assuming a Maxwell-Boltzmann distribution for neutrons can underestimate the rates by several orders of magnitude. We derive simple analytical expressions for reaction rates at a variety of conditions with account for neutron degeneracy. We also discuss the plasma effects on the outgoing radiative transition channel in neutron radiative capture reactions and show that these effects can also increase the reaction rates by a few orders of magnitude. In addition, using detailed balance, we analyze the effects of neutron degeneracy and plasma physics on reverse ($\\gamma,n$) photodisintegration. We discuss the dependence of the reaction rates on temperature and neutron chemical potential and outline the efficiency of these reactions in the neutron s...

  3. The Double Star Plasma Electron and Current Experiment

    Microsoft Academic Search

    A. N. Fazakerley; P. J. Carter; G. Watson; A. Spencer; Y. Q. Sun; J. Coker; P. Coker; D. O. Kataria; D. Fontaine; Z. X. Liu; L. Gilbert; L. He; A. D. Lahiff; B. Mihalcic; S. Szita; M. G. G. T. Taylor; R. J. Wilson; M. Dedieu; S. J. Schwartz

    2005-01-01

    The Double Star Project is a collaboration between Chinese and European space agencies, in which two Chinese magnetospheric research spacecraft, carrying Chinese and European instruments, have been launched into equatorial (on 29 December 2003) and polar (on 25 July 2004) orbits designed to enable complementary studies with the Cluster spacecraft. The two Double Star spacecraft TC-1 and TC-2 each carry

  4. Coordinated Cluster\\/Double Star observations of dayside reconnection signatures

    Microsoft Academic Search

    M. W. Dunlop; M. G. G. T. Taylor; J. A. Davies; C. J. Owen; F. Pitout; A. N. Fazakerley; Z. Pu; H. Laakso; Y. V. Bogdanova; Q.-G. Zong; C. Shen; K. Nykyri; B. Lavraud; S. E. Milan; T. D. Phan; H. Rème; C. P. Escoubet; C. M. Carr; P. Cargill; M. Lockwood; B. Sonnerup

    2005-01-01

    The recent launch of the equatorial spacecraft of the Double Star mission, TC-1, has provided an unprecedented opportunity to monitor the southern hemisphere dayside magnetopause boundary layer in conjunction with northern hemisphere observations by the quartet of Cluster spacecraft. We present first results of one such situation where, on 6 April 2004, both Cluster and the Double Star TC-1 spacecraft

  5. Rotational parameters of strange stars in comparison with neutron stars

    E-print Network

    Manjari Bagchi

    2009-07-03

    I study stellar structures $i.e.$ the mass, the radius, the moment of inertia and the oblateness parameter at different spin frequencies for strange stars and neutron stars in a comparative manner. I also calculate the values of the radii of the marginally stable orbits and Keplerian orbital frequencies. By equating kHz QPO frequencies to Keplerian orbital frequencies, I find corresponding orbital radii. Knowledge about these parameters might be useful in further modeling of the observed features from LMXBs with advanced and improved future techniques for observations and data analysis.

  6. Second Double Star satellite successfully launched

    NASA Astrophysics Data System (ADS)

    2004-07-01

    Tan Ce ("Explorer") 2 was launched from the Taiyuan spaceport west of Beijing (Zhangye province) using a Long March 2C rocket. The launch, initially scheduled for today 26 July, took place one day earlier in order to avoid adverse weather conditions expected in the days to come. The spacecraft will join Tan Ce 1, which was launched on 29 December 2003, to complete the Double Star configuration. About 8 hours after launch the two solid booms holding the magnetometers were successfully deployed. In the next few weeks, all spacecraft sub-systems will be checked out and the commissioning of the on-board scientific instrument will follow. Double Star will operate alongside ESA’s quartet of Cluster satellites to closely study the interaction between the solar wind and the Earth’s magnetic field. Together, these missions will provide the most detailed view to date. TC-1 is already returning a wealth of scientific data. Back in January, both missions tracked a coronal mass ejection from the Sun and gathered valuable data about the Earth's bow shock. Tan Ce 2 reached its nominal orbit, with perigee at 682 km, apogee at 38279 km and inclination of 90.1 deg. The positions and orbit of the Double Star satellites have been carefully defined to enable exploration of the magnetosphere on a larger scale than is possible with Cluster alone. One example of this coordinated activity is the study of the substorms that produce aurorae. The exact region where these emissions of brightness form is still unclear, but the simultaneous high-resolution measurements combined under these two missions are expected to provide an answer. ESA is contributing eight scientific instruments to the mission, seven of which are Cluster-derived units. These are the first ever European experiments to fly on a Chinese satellite. ESA will also be providing ground segment support, four hours each day, via its Villafranca satellite tracking station in Spain. Scientific cooperation between China and ESA goes back quite a long way. A first Agreement signed back in 1980 facilitated the exchange of scientific information. Thirteen years later, the collaboration focused on a specific mission, Cluster, to study the Earth's magnetosphere. Then, in 1997, came a big step forward. The CNSA invited ESA to participate in the Double Star dual-satellite mission to study the Earth’s magnetic field, from a perspective different but complementary to Cluster's. The Agreement to carry out this joint mission was signed on 9 July 2001 by ESA’s then Director General Antonio Rodotà and CNSA Administrator Luan Enjie. For Professor David Southwood, ESA’s Science Programme Director: “Today’s successful launch marks the culmination of these joint efforts and a further important step forward in this historic collaboration between China and Europe.”

  7. Gamma Ray Bursts from Baryon Decay in Neutron Stars

    E-print Network

    Ue-Li Pen; Abraham Loeb; Neil Turok

    1997-12-15

    The standard unbroken electroweak theory is known to erase baryon number. The baryon number symmetry can be restored in the core of a neutron star as its density diverges via gravitational instability due to a binary merger event. We argue that for certain double Higgs models with discrete symmetries, this process may result in an expanding self-sustained burning front which would convert the entire neutron matter into radiation. This process would release ~10^{54} ergs in electromagnetic radiation over ~10^{-4} sec, with negligible baryonic contamination. The resulting fireball would have all the properties necessary to produce a gamma-ray burst as a result of its interaction with ambient interstellar gas. The subsequent Higgs decay would produce a millisecond burst of ~10^{52} ergs in ~100 GeV neutrinos which might be observable. The above mechanism may have also caused electroweak baryogenesis in the early universe, giving rise to the observed matter-antimatter asymmetry today.

  8. Constraining decaying dark matter with neutron stars

    E-print Network

    M. Angeles Perez-Garcia; J. Silk

    2014-07-18

    The amount of decaying dark matter, accumulated in the central regions in neutron stars together with the energy deposition rate from decays, may set a limit on the neutron star survival rate against transitions to more compact objects and, correspondingly, on the dark matter particle decay time, $\\tau_{\\chi}$. We find that for masses $(m_{\\chi}/ \\rm TeV) \\gtrsim 9 \\times 10^{-4}$ or $(m_{\\chi}/ \\rm TeV) \\gtrsim 5 \\times 10^{-2}$ in the bosonic or fermionic decay cases respectively, lifetimes ${\\tau_{\\chi}}\\lesssim 10^{55}$ s and ${\\tau_{\\chi}}\\lesssim 10^{53}$ s can be excluded. Our result significantly improves on other current constraints if nuclear matter is metastable to percolation.

  9. 'Tertiary' nuclear burning - Neutron star deflagration?

    NASA Technical Reports Server (NTRS)

    Michel, F. Curtis

    1988-01-01

    A motivation is presented for the idea that dense nuclear matter can burn to a new class of stable particles. One of several possibilities is an 'octet' particle which is the 16 baryon extension of alpha particle, but now composed of a pair of each of the two nucleons, (3Sigma, Delta, and 2Xi). Such 'tertiary' nuclear burning (here 'primary' is H-He and 'secondary' is He-Fe) may lead to neutron star explosions rather than collapse to a black hole, analogous to some Type I supernovae models wherein accreting white dwarfs are pushed over the Chandrasekhar mass limit but explode rather than collapse to form neutron stars. Such explosions could possibly give gamma-ray bursts and power quasars, with efficient particle acceleration in the resultant relativistic shocks. The new stable particles themselves could possibly be the sought-after weakly interacting, massive particles (WIMPs) or 'dark' matter.

  10. Fast Fossil Rotation of Neutron Star Cores

    NASA Astrophysics Data System (ADS)

    Melatos, A.

    2012-12-01

    It is argued that the superfluid core of a neutron star super-rotates relative to the crust, because stratification prevents the core from responding to the electromagnetic braking torque, until the relevant dissipative (viscous or Eddington-Sweet) timescale, which can exceed ~103 yr and is much longer than the Ekman timescale, has elapsed. Hence, in some young pulsars, the rotation of the core today is a fossil record of its rotation at birth, provided that magnetic crust-core coupling is inhibited, e.g., by buoyancy, field-line topology, or the presence of uncondensed neutral components in the superfluid. Persistent core super-rotation alters our picture of neutron stars in several ways, allowing for magnetic field generation by ongoing dynamo action and enhanced gravitational wave emission from hydrodynamic instabilities.

  11. Magnetized Iron Atmospheres for Neutron Stars

    E-print Network

    Mohan Rajagopal; Roger W. Romani; M. Coleman Miller

    1996-10-24

    Using a Hartree-Fock formalism, we estimate energy levels and photon cross sections for atomic iron in magnetic fields B ~ 10^13 G. Computing ionization equilibrium and normal mode opacities with these data, we construct LTE neutron star model atmospheres at 5.5 < Log(T_eff) < 6.5 and compute emergent spectra. We examine the dependence of the emergent spectra on T_eff and B. We also show the spectral variation with the angle between the magnetic field and the atmosphere normal and describe the significant limb darkening in the X-ray band. These results are compared with recent detailed computations of neutron star H model atmospheres in high fields and with low field Fe and H model atmospheres constructed from detailed opacities. The large spectral differences for different surface compositions may be discernible with present X-ray data; we also note improvements needed to allow comparison of Fe models with high quality spectra.

  12. FAST FOSSIL ROTATION OF NEUTRON STAR CORES

    SciTech Connect

    Melatos, A., E-mail: amelatos@unimelb.edu.au [School of Physics, University of Melbourne, Parkville, VIC 3010 (Australia)

    2012-12-10

    It is argued that the superfluid core of a neutron star super-rotates relative to the crust, because stratification prevents the core from responding to the electromagnetic braking torque, until the relevant dissipative (viscous or Eddington-Sweet) timescale, which can exceed {approx}10{sup 3} yr and is much longer than the Ekman timescale, has elapsed. Hence, in some young pulsars, the rotation of the core today is a fossil record of its rotation at birth, provided that magnetic crust-core coupling is inhibited, e.g., by buoyancy, field-line topology, or the presence of uncondensed neutral components in the superfluid. Persistent core super-rotation alters our picture of neutron stars in several ways, allowing for magnetic field generation by ongoing dynamo action and enhanced gravitational wave emission from hydrodynamic instabilities.

  13. Supergiant Pulses from Extragalactic Neutron Stars

    E-print Network

    Cordes, J M

    2015-01-01

    We evaluate the hypothesis that extragalactic radio bursts originate from neutron stars. These could be active pulsars or dormant, slowly spinning objects, but the different population distances for these two classes require correspondingly different contributions to burst dispersion measures from any host or intervening galaxies combined with the intergalactic medium. The large, apparent burst rate $\\sim 10^4~$ sky$^{-1}~$ day$^{-1}$ is comparable to the core-collapse supernova rate in a Hubble volume and can be accommodated by a single burst per object in the resulting large reservoir of $\\sim 10^{17}~$ neutron stars. A smaller population distance requires more bursts per object but the likelihood of seeing repeated bursts from any single object is extremely low on human timescales. Gravitational microlensing could play a role for high redshift sources. Extrapolation of the Crab pulsar's giant pulses --- exemplars of coherent, high brightness temperature radiation --- to a rate of one per $10^3~$yr yields a...

  14. General Relativistic Decompression of Binary Neutron Stars During Inspiral

    E-print Network

    Miller, M

    2005-01-01

    We investigate the dynamic stability of inspiraling neutron stars by performing multiple-orbit numerical relativity simulations of the binary neutron star inspiral process. We find that as the separation between the stars decreases during the inspiral induced by gravitational wave emission, the central rest mass density of each star decreases, thus stabilizing each star against collapse. We compare the amount of decompression observed in our numerical relativity simulations with the amount predicted by post-Newtonian approximations.

  15. Disorder resistivity of solid neutron-star matter.

    PubMed

    Jones, P B

    2004-11-26

    Lower limits are found for the disorder electrical resistivity of solid neutron-star matter in the neutron-drip region which is amorphous and heterogeneous in nuclear charge. This temperature-independent resistivity, large compared with that produced by phonon scattering, has direct consequences for theories of neutron-star magnetic field generation and evolution. PMID:15601078

  16. Hydrodynamics of neutron star interiors and laboratory superfluids

    Microsoft Academic Search

    Tassilo Andreas Reisenegger

    1993-01-01

    This thesis contains the following papers: (1) A new class of g-modes in neutron stars. In the fluid core of a neutron star, the ratio of the number densities of charged particles (protons and electrons) to neutrons is an increasing function of the mass density. This composition gradient stably stratifies the matter, giving rise to g-modes with periods ranging upward

  17. Particle acceleration in axisymmetric, magnetized neutron stars

    NASA Technical Reports Server (NTRS)

    Baker, K. B.; Sturrock, P. A.

    1977-01-01

    The potential drop in the polar cap region of a rotating, magnetized neutron star is found assuming that the magnetic field is dipolar, with the field aligned (or anti-aligned) with the rotation axis. The curvature of the field lines is of critical importance. Charge flow is assumed to be along magnetic field lines. The electric field has a maximum at radius 1.5 R and the magnitude and functional form of the current is determined.

  18. Neutron Stars in Supernova Remnants and Beyond

    E-print Network

    V. V. Gvaramadze

    2002-12-26

    We discuss a concept of off-centred cavity supernova explosion as applied to neutron star/supernova remnant associations and show how this concept could be used to preclude the anti-humane decapitating the Duck (G5.4-1.2 + G5.27-0.9) and dismembering the Swan (Cygnus Loop), as well as to search for a stellar remnant associated with the supernova remnant RCW86.

  19. Physics of systems containing neutron stars

    NASA Technical Reports Server (NTRS)

    Shaham, Jacob

    1989-01-01

    The following is a summary of work done during the period of Mar. to Oct. 1989. Three major topics were extensively looked into during this time: the reported 2,000 Hz optical signal from the direction of SNR1987A, the possibility that neutron stellar surface magnetic fields do not decay except when the star is accreting, and the 6 Hz QPOs of LMXBs.

  20. Gravitational Radiation from Accreting Neutron Stars

    Microsoft Academic Search

    Andrew Melatos; D. J. Payne; C. Peralta

    2006-01-01

    Accreting neutron stars spinning at near-kHz frequencies are thought to be strong gravitational wave (GW) emitters. X-ray timing experiments reveal a dearth of such objects spinning near break up, suggesting that GW emission stalls recycling by accretion. We present recent numerical modeling of two new GW emission mechanisms in this class of sources: (i) hydromagnetic oscillations of a magnetically confined

  1. Magnetorotational instability in relativistic hypermassive neutron stars

    NASA Astrophysics Data System (ADS)

    Siegel, Daniel M.; Ciolfi, Riccardo; Harte, Abraham I.; Rezzolla, Luciano

    2013-06-01

    A differentially rotating hypermassive neutron star (HMNS) is a metastable object which can be formed in the merger of neutron-star binaries. The eventual collapse of the HMNS into a black hole is a key element in generating the physical conditions expected to accompany the launch of a short gamma-ray burst. We investigate the influence of magnetic fields on HMNSs by performing three-dimensional simulations in general-relativistic magnetohydrodynamics. In particular, we provide direct evidence for the occurrence of the magnetorotational instability (MRI) in HMNS interiors. For the first time in simulations of these systems, rapidly-growing and spatially-periodic structures are observed to form with features like those of the channel flows produced by the MRI in other systems. Moreover, the growth time and wavelength of the fastest-growing mode are extracted and compared successfully with analytical predictions. The MRI emerges as an important mechanism to amplify magnetic fields over the lifetime of the HMNS, whose collapse to a black hole is accelerated. The evidence provided here that the MRI can actually develop in HMNSs could have a profound impact on the outcome of the merger of neutron-star binaries and on its connection to short gamma-ray bursts.

  2. Magneto--thermal evolution of neutron stars

    E-print Network

    Pons, J A; Geppert, U

    2008-01-01

    We study the mutual influence of thermal and magnetic evolution in a neutron star's crust in axial symmetry. Taking into account realistic microphysical inputs, we find the heat released by Joule effect consistent with the circulation of currents in the crust, and we incorporate its effects in 2D cooling calculations. We solve the induction equation numerically using a hybrid method (spectral in angles, but a finite--differences scheme in the radial direction), coupled to the thermal diffusion equation. We present the first long term 2D simulations of the coupled magneto-thermal evolution of neutron stars. This substantially improves previous works in which a very crude approximation in at least one of the parts (thermal or magnetic diffusion) has been adopted. Our results show that the feedback between Joule heating and magnetic diffusion is strong, resulting in a faster dissipation of the stronger fields during the first million years of a NS's life. As a consequence, all neutron stars born with fields larg...

  3. Quasi-static winds from neutron stars

    SciTech Connect

    Joss, P.C.; Melia, F.

    1987-01-01

    A series of numerical models is constructed for radiatively driven, quasi-static winds from the surfaces of hot neutron stars. A mathematical technique is devised that in many cases facilitates the integration of the fluid equations in the vicinity of the sonic point, and an improved treatment of radiative transfer is developed that is appropriate to the exotic physical conditions encountered in the models. Boundary conditions which are more realistic than previous ones are used in these models. In agreement with earlier studies, it is found that radiatively driven winds are likely to be directly relevant to the existence of precursors in fast X-ray transients and to apparent radius variations during the course of some type I bursts, and that the presence of such a wind should prevent the bolometric luminosity of a neutron star from exceeding the Eddington limit by more than a small fractional amount. Formulas describing the wind models are presented which are usable as boundary conditions for calculations of the evolution of the deeper, hydrostatic layers of a neutron-star envelope. 23 references.

  4. Quasi-static winds from neutron stars

    NASA Technical Reports Server (NTRS)

    Joss, Paul C.; Melia, Fulvio

    1987-01-01

    A series of numerical models is constructed for radiatively driven, quasi-static winds from the surfaces of hot neutron stars. A mathematical technique is devised that in many cases facilitates the integration of the fluid equations in the vicinity of the sonic point, and an improved treatment of radiative transfer is developed that is appropriate to the exotic physical conditions encountered in the models. Boundary conditions which are more realistic than previous ones are used in these models. In agreement with earlier studies, it is found that radiatively driven winds are likely to be directly relevant to the existence of precursors in fast X-ray transients and to apparent radius variations during the course of some type I bursts, and that the presence of such a wind should prevent the bolometric luminosity of a neutron star from exceeding the Eddington limit by more than a small fractional amount. Formulas describing the wind models are presented which are usable as boundary conditions for calculations of the evolution of the deeper, hydrostatic layers of a neutron-star envelope.

  5. Magnetically driven crustquakes in neutron stars

    NASA Astrophysics Data System (ADS)

    Lander, S. K.; Andersson, N.; Antonopoulou, D.; Watts, A. L.

    2015-05-01

    Crustquake events may be connected with both rapid spin-up `glitches' within the regular slowdown of neutron stars, and high-energy magnetar flares. We argue that magnetic-field decay builds up stresses in a neutron star's crust, as the elastic shear force resists the Lorentz force's desire to rearrange the global magnetic-field equilibrium. We derive a criterion for crust-breaking induced by a changing magnetic-field configuration, and use this to investigate strain patterns in a neutron star's crust for a variety of different magnetic-field models. Universally, we find that the crust is most liable to break if the magnetic field has a strong toroidal component, in which case the epicentre of the crustquake is around the equator. We calculate the energy released in a crustquake as a function of the fracture depth, finding that it is independent of field strength. Crust-breaking is, however, associated with a characteristic local field strength of 2.4 × 1014 G for a breaking strain of 0.001, or 2.4 × 1015 G at a breaking strain of 0.1. We find that even the most luminous magnetar giant flare could have been powered by crustal energy release alone.

  6. Physics of Strongly Magnetized Neutron Stars

    E-print Network

    Alice K. Harding; Dong Lai

    2006-07-11

    There has recently been growing evidence for the existence of neutron stars possessing magnetic fields with strengths that exceed the quantum critical field strength of $4.4 \\times 10^{13}$ G, at which the cyclotron energy equals the electron rest mass. Such evidence has been provided by new discoveries of radio pulsars having very high spin-down rates and by observations of bursting gamma-ray sources termed magnetars. This article will discuss the exotic physics of this high-field regime, where a new array of processes becomes possible and even dominant, and where familiar processes acquire unusual properties. We review the physical processes that are important in neutron star interiors and magnetospheres, including the behavior of free particles, atoms, molecules, plasma and condensed matter in strong magnetic fields, photon propagation in magnetized plasmas, free-particle radiative processes, the physics of neutron star interiors, and field evolution and decay mechanisms. Application of such processes in astrophysical source models, including rotation-powered pulsars, soft gamma-ray repeaters, anomalous X-ray pulsars and accreting X-ray pulsars will also be discussed. Throughout this review, we will highlight the observational signatures of high magnetic field processes, as well as the theoretical issues that remain to be understood.

  7. CD Double Star Measures: Jack Jones Memorial Observatory Report #3

    NASA Astrophysics Data System (ADS)

    Jones, James L.

    2010-10-01

    This paper submits 114 CCD measurements of 92 multiple star systems for inclusion in the WDS. Observations were made during the calendar year 2007. Measurements were obtained using either an SBIG ST-7 CCD camera or an SBIG ST-8 CCD camera and an 11-inch SCT. Selected double stars are discussed. Negative findings are included for certain stars.

  8. A New Double Star from Lunar Occultations: HIP 87306

    NASA Astrophysics Data System (ADS)

    Herald, Dave; Kashiwagura, M.; Loader, Brian; Messner, Steve; Sandy, Robert; Togashi, H.

    2010-04-01

    A lunar occultation of HIP 87306 (= ZC2564, star #2564 in Robertson's Zodiacal Catalog of 1940) observed on 2009 Aug 2 showed this star to be a double star with a separation of 0.086^2. Two video observations made in 2003 were subsequently identified and retrieved, enabling a measurement for that epoch to also be made.

  9. The lowest-mass stellar black holes: catastrophic death of neutron stars in gamma-ray bursts

    E-print Network

    K. Belczynski; R. O'Shaughnessy; V. Kalogera; F. Rasio; R. Taam; T. Bulik

    2008-04-16

    Mergers of double neutron stars are considered the most likely progenitors for short gamma-ray bursts. Indeed such a merger can produce a black hole with a transient accreting torus of nuclear matter (Lee & Ramirez-Ruiz 2007, Oechslin & Janka 2006), and the conversion of a fraction of the torus mass-energy to radiation can power a gamma-ray burst (Nakar 2006). Using available binary pulsar observations supported by our extensive evolutionary calculations of double neutron star formation, we demonstrate that the fraction of mergers that can form a black hole -- torus system depends very sensitively on the (largely unknown) maximum neutron star mass. We show that the available observations and models put a very stringent constraint on this maximum mass under the assumption that a black hole formation is required to produce a short gamma-ray burst in a double neutron star merger. Specifically, we find that the maximum neutron star mass must be within 2 - 2.5 Msun. Moreover, a single unambiguous measurement of a neutron star mass above 2.5 Msun would exclude a black hole -- torus central engine model of short gamma-ray bursts in double neutron star mergers. Such an observation would also indicate that if in fact short gamma-ray bursts are connected to neutron star mergers, the gamma-ray burst engine is best explained by the lesser known model invoking a highly magnetized massive neutron star (e.g., Usov 1992; Kluzniak & Ruderman 1998; Dai et al. 2006; Metzger, Quataert & Thompson 2007).

  10. Evolution of Close Neutron Star Binaries

    E-print Network

    W. Ogawaguchi; Y. Kojima

    1996-10-17

    We have calculated evolution of neutron star binaries towards the coalescence driven by gravitational radiation. The hydrodynamical effects as well as the general relativistic effects are important in the final phase. All corrections up to post$^{2.5}$-Newtonian order and the tidal effect are included in the orbital motion. The star is approximated by a simple Newtonian stellar model called affine star model. Stellar spins and angular momentum are assumed to be aligned. We have showed how the internal stellar structure affects the stellar deformation, variations of the spins, and the orbital motion of the binary just before the contact. The gravitational wave forms from the last a few revolutions significantly depend on the stellar structure.

  11. Activities and Achievements of the Double Star Committee of the Socié té Astronomique de France

    Microsoft Academic Search

    Jean-Louis Agati; Sébastien Caille; André Debackère; Pierre Durand; Florent Losse; René Manté; Florence Mauroy; Pascal Mauroy; Guy Morlet; Claude Pinlou; Maurice Salaman; Edgar Soulié; Yvonne Thorel; Jean-Claude Thorel

    2007-01-01

    In a synthesis article (see ref. below), the double star expert Paul COUTEAU put the work of French pioneers of double stars observation in the perspective of the double star work carried in the world. After Antoine Yvon VILLARCEAU and Camille FLAMMARION, one prominent pioneer of double stars was Robert JONCKHEERE (1888toiles Doubles, Maurice DURUY (1894le with a 40-cm and

  12. Neutron stars and strange stars in the chiral SU(3) quark mean field model

    E-print Network

    P. Wang; S. Lawley; D. B. Leinweber; A. W. Thomas; A. G. Williams

    2005-06-06

    We investigate the equations of state for pure neutron matter and strange hadronic matter in $\\beta$-equilibrium, including $\\Lambda$, $\\Sigma$ and $\\Xi$ hyperons. The masses and radii of pure neutron stars and strange hadronic stars are obtained. For a pure neutron star, the maximum mass is about $1.8 M_{\\mathrm{sun}}$, while for a strange hadronic star, the maximum mass is around $1.45 M_{\\mathrm{sun}}$. The typical radii of pure neutron stars and strange hadronic stars are about 11.0-12.3 km and 10.7-11.7 km, respectively.

  13. Reduced coherence in double-slit diffraction of neutrons

    E-print Network

    R. Tumulka; A. Viale; N. Zanghi

    2007-03-28

    In diffraction experiments with particle beams, several effects lead to a fringe visibility reduction of the interference pattern. We theoretically describe the intensity one can measure in a double-slit setup and compare the results with the experimental data obtained with cold neutrons. Our conclusion is that for cold neutrons the fringe visibility reduction is due not to decoherence, but to initial incoherence.

  14. Isolated neutron stars in the galaxy: from magnetars to antimagnetars

    SciTech Connect

    Boldin, P. A., E-mail: boldin.pavel@gmail.com [Moscow Engineering Physics Institute (State University) (Russian Federation); Popov, S. B., E-mail: polar@sai.msu.ru [Moscow State University, Sternberg Astronomical Institute (Russian Federation)

    2012-07-15

    Using the model with decaying magnetic fields it is possible to describe with one smooth (log-Gaussian) initial magnetic field distribution three types of isolated neutron stars: radiopulsar, magnetars, and cooling close-by compact objects. The same model is used here to make predictions for old accreting isolated neutron stars. It is shown that using the updated field distribution we predict a significant fraction of isolated neutron stars at the stage of accretion despite long subsonic propeller stage.

  15. Towards a consistent model for Neutron-Star Sources

    E-print Network

    W. Kundt

    2002-08-30

    We are still far from understanding how pulsars pulse, how neutron stars are born, what neutron stars can emit, and in which way they do this. In this short communication, I list 18 alternatives -- several of them old, a few of them new -- which are handled differently by different authors but all of which are crucial for a model of neutron stars to be viable.

  16. Gamma-ray bursts from extinct neutron stars

    NASA Technical Reports Server (NTRS)

    Michel, F. C.

    1990-01-01

    The paper concentrates on disks around old extinct pulsars, that can produce gamma-ray bursts owing to viscous evolution of the disk bringing it into the near vicinity of the neutron star, with runaway ionization of the disk and simultaneous precipitation of this plasma onto the neutron star. An old extinct pulsar is modeled as a magnetized neutron star circled by a ring of cold dense matter with an orbital period approximately equal to the rotational period of the neutron star. The numerical estimates produced are found to be consistent with the observed properties of gamma-ray bursters.

  17. Neutron Stars in f(R) Gravity with Perturbative Constraints

    E-print Network

    Alan Cooney; Simon DeDeo; Dimitrios Psaltis

    2010-09-08

    We study the structure of neutron stars in f(R) gravity theories with perturbative constraints. We derive the modified Tolman-Oppenheimer-Volkov equations and solve them for a polytropic equation of state. We investigate the resulting modifications to the masses and radii of neutron stars and show that observations of surface phenomena alone cannot break the degeneracy between altering the theory of gravity versus choosing a different equation of state of neutron-star matter. On the other hand, observations of neutron-star cooling, which depends on the density of matter at the stellar interior, can place significant constraints on the parameters of the theory.

  18. Burst Oscillations: A New Spin on Neutron Stars

    NASA Technical Reports Server (NTRS)

    Strohmayer, Tod

    2007-01-01

    Observations with NASA's Rossi X-ray Timing Explorer (RXTE) have shown that the X-ray flux during thermonuclear X-ray bursts fr-om accreting neutron stars is often strongly pulsed at frequencies as high as 620 Hz. We now know that these oscillations are produced by spin modulation of the thermonuclear flux from the neutron star surface. In addition to revealing the spin frequency, they provide new ways to probe the properties and physics of accreting neutron stars. I will briefly review our current observational and theoretical understanding of these oscillations and discuss what they are telling us about neutron stars.

  19. Neutron stars in f(R) gravity with perturbative constraints

    SciTech Connect

    Cooney, Alan; DeDeo, Simon; Psaltis, Dimitrios [Department of Physics, University of Arizona, Tucson, Arizona 85721 (United States); Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, New Mexico 87501 (United States); Departments of Astronomy and Physics, University of Arizona, Tucson, Arizona 85721 (United States)

    2010-09-15

    We study the structure of neutron stars in f(R) gravity theories with perturbative constraints. We derive the modified Tolman-Oppenheimer-Volkov equations and solve them for a polytropic equation of state. We investigate the resulting modifications to the masses and radii of neutron stars and show that observations of surface phenomena alone cannot break the degeneracy between altering the theory of gravity versus choosing a different equation of state of neutron-star matter. On the other hand, observations of neutron-star cooling, which depends on the density of matter at the stellar interior, can place significant constraints on the parameters of the theory.

  20. Plasmon excitations in homogeneous neutron star matter

    E-print Network

    Marcello Baldo; Camille Ducoin

    2009-07-01

    We study the possible collective plasma modes which can affect neutron-star thermodynamics and different elementary processes in the baryonic density range between nuclear saturation ($\\rho_0$) and $3\\rho_0$. In this region, the expected constituents of neutron-star matter are mainly neutrons, protons, electrons and muons ($npe\\mu$ matter), under the constraint of beta equilibrium. The elementary plasma excitations of the $pe\\mu$ three-fluid medium are studied in the RPA framework. We emphasize the relevance of the Coulomb interaction among the three species, in particular the interplay of the electron and muon screening in suppressing the possible proton plasma mode, which is converted into a sound-like mode. The Coulomb interaction alone is able to produce a variety of excitation branches and the full spectral function shows a rich structure at different energy. The genuine plasmon mode is pushed at high energy and it contains mainly an electron component with a substantial muon component, which increases with density. The plasmon is undamped for not too large momentum and is expected to be hardly affected by the nuclear interaction. All the other branches, which fall below the plasmon, are damped or over-damped.

  1. Mutual Friction in Superfluid Neutron Stars

    E-print Network

    N. Andersson; T. Sidery; G. L. Comer

    2005-10-03

    We discuss vortex-mediated mutual friction in the two-fluid model for superfluid neutron star cores. Our discussion is based on the general formalism developed by Carter and collaborators, which makes due distinction between transport velocity and momentum for each fluid. This is essential for an implementation of the so-called entrainment effect, whereby the flow of one fluid imparts momentum in the other and vice versa. The mutual friction follows by balancing the Magnus force that acts on the quantised neutron vortices with a resistive force due to the scattering of electrons off of the magnetic field with which each vortex core is endowed. We derive the form of the macroscopic mutual friction force which is relevant for a model based on smooth-averaging over a collection of vortices. We discuss the coefficients that enter the expression for this force, and the timescale on which the two interpenetrating fluids in a neutron star core are coupled. This discussion confirms that our new formulation accords well with previous work in this area.

  2. Gravitational Waves from Rapidly Rotating Neutron Stars

    NASA Astrophysics Data System (ADS)

    Haskell, Brynmor; Andersson, Nils; D'Angelo, Caroline; Degenaar, Nathalie; Glampedakis, Kostas; Ho, Wynn C. G.; Lasky, Paul D.; Melatos, Andrew; Oppenoorth, Manuel; Patruno, Alessandro; Priymak, Maxim

    Rapidly rotating neutron stars in Low Mass X-ray Binaries have been proposed as an interesting source of gravitational waves. In this chapter we present estimates of the gravitational wave emission for various scenarios, given the (electromagnetically) observed characteristics of these systems. First of all we focus on the r-mode instability and show that a "minimal" neutron star model (which does not incorporate exotica in the core, dynamically important magnetic fields or superfluid degrees of freedom), is not consistent with observations. We then present estimates of both thermally induced and magnetically sustained mountains in the crust. In general magnetic mountains are likely to be detectable only if the buried magnetic field of the star is of the order of B ? 10^{12} G. In the thermal mountain case we find that gravitational wave emission from persistent systems may be detected by ground based interferometers. Finally we re-asses the idea that gravitational wave emission may be balancing the accretion torque in these systems, and show that in most cases the disc/magnetosphere interaction can account for the observed spin periods.

  3. Gravitational waves from rapidly rotating neutron stars

    E-print Network

    Brynmor Haskell; Nils Andersson; Caroline D`Angelo; Nathalie Degenaar; Kostas Glampedakis; Wynn C. G. Ho; Paul D. Lasky; Andrew Melatos; Manuel Oppenoorth; Alessandro Patruno; Maxim Priymak

    2014-07-31

    Rapidly rotating neutron stars in Low Mass X-ray Binaries have been proposed as an interesting source of gravitational waves. In this chapter we present estimates of the gravitational wave emission for various scenarios, given the (electromagnetically) observed characteristics of these systems. First of all we focus on the r-mode instability and show that a 'minimal' neutron star model (which does not incorporate exotica in the core, dynamically important magnetic fields or superfluid degrees of freedom), is not consistent with observations. We then present estimates of both thermally induced and magnetically sustained mountains in the crust. In general magnetic mountains are likely to be detectable only if the buried magnetic field of the star is of the order of $B\\approx 10^{12}$ G. In the thermal mountain case we find that gravitational wave emission from persistent systems may be detected by ground based interferometers. Finally we re-asses the idea that gravitational wave emission may be balancing the accretion torque in these systems, and show that in most cases the disc/magnetosphere interaction can account for the observed spin periods.

  4. Statistical theory of thermal evolution of neutron stars

    NASA Astrophysics Data System (ADS)

    Beznogov, M. V.; Yakovlev, D. G.

    2015-02-01

    Thermal evolution of neutron stars is known to depend on the properties of superdense matter in neutron star cores. We suggest a statistical analysis of isolated cooling middle-aged neutron stars and old transiently accreting quasi-stationary neutron stars warmed up by deep crustal heating in low-mass X-ray binaries. The method is based on simulations of the evolution of stars of different masses and on averaging the results over respective mass distributions. This gives theoretical distributions of isolated neutron stars in the surface temperature-age plane and of accreting stars in the photon thermal luminosity-mean mass accretion rate plane to be compared with observations. This approach permits to explore not only superdense matter but also the mass distributions of isolated and accreting neutron stars. We show that the observations of these stars can be reasonably well explained by assuming the presence of the powerful direct Urca process of neutrino emission in the inner cores of massive stars, introducing a slight broadening of the direct Urca threshold (for instance, by proton superfluidity), and by tuning mass distributions of isolated and accreted neutron stars.

  5. Rotational and magnetic field instabilities in neutron stars

    SciTech Connect

    Kokkotas, Kostas D. [Theoretical Astrophysics, IAAT, Eberhard Karls University of Tübingen, Tübingen 72076 (Germany)

    2014-01-14

    In this short review we present recent results on the dynamics of neutron stars and their magnetic fields. We discuss the progress that has been made, during the last 5 years, in understanding the rotational instabilities with emphasis to the one due to the f-mode, the possibility of using gravitational wave detection in constraining the parameters of neutron stars and revealing the equation of state as well as the detectability of gravitational waves produced during the unstable phase of a neutron star’s life. In addition we discuss the dynamics of extremely strong magnetic fields observed in a class of neutron stars (magnetars). Magnetic fields of that strength are responsible for highly energetic phenomena (giant flares) and we demonstrate that the analysis of the emitted electromagnetic radiation can lead in constraining the parameters of neutron stars. Furthermore, we present our results from the study of such violent phenomena in association with the emission of gravitational radiation.

  6. Dark matter transport properties and rapidly rotating neutron stars

    E-print Network

    C. J. Horowitz

    2012-05-16

    Neutron stars are attractive places to look for dark matter because their high densities allow repeated interactions. Weakly interacting massive particles (WIMPs) may scatter efficiently in the core or in the crust of a neutron star. In this paper we focus on WIMP contributions to transport properties, such as shear viscosity or thermal conductivity, because these can be greatly enhanced by long mean free paths. We speculate that WIMPs increase the shear viscosity of neutron star matter and help stabilize r-mode oscillations. These are collective oscillations where the restoring force is the Coriolis force. At present r-modes are thought to be unstable in many observed rapidly rotating stars. If WIMPs stabilize the r-modes, this would allow neutron stars to spin rapidly. This likely requires WIMP-nucleon cross sections near present experimental limits and an appropriate density of WIMPs in neutron stars.

  7. Relativistic superfluid models for rotating neutron stars

    E-print Network

    Brandon Carter

    2001-01-16

    This article starts by providing an introductory overview of the theoretical mechanics of rotating neutron stars as developped to account for the frequency variations, and particularly the discontinuous glitches, observed in pulsars. The theory suggests, and the observations seem to confirm, that an essential role is played by the interaction between the solid crust and inner layers whose superfluid nature allows them to rotate independently. However many significant details remain to be clarified, even in much studied cases such as the Crab and Vela. The second part of this article is more technical, concentrating on just one of the many physical aspects that needs further development, namely the provision of a satisfactorily relativistic (local but not microscopic) treatment of the effects of the neutron superfluidity that is involved.

  8. Magneto--thermal evolution of neutron stars

    E-print Network

    J. A. Pons; J. A. Miralles; U. Geppert

    2008-12-16

    We study the mutual influence of thermal and magnetic evolution in a neutron star's crust in axial symmetry. Taking into account realistic microphysical inputs, we find the heat released by Joule effect consistent with the circulation of currents in the crust, and we incorporate its effects in 2D cooling calculations. We solve the induction equation numerically using a hybrid method (spectral in angles, but a finite--differences scheme in the radial direction), coupled to the thermal diffusion equation. We present the first long term 2D simulations of the coupled magneto-thermal evolution of neutron stars. This substantially improves previous works in which a very crude approximation in at least one of the parts (thermal or magnetic diffusion) has been adopted. Our results show that the feedback between Joule heating and magnetic diffusion is strong, resulting in a faster dissipation of the stronger fields during the first million years of a NS's life. As a consequence, all neutron stars born with fields larger than a critical value (about 5 10^13 G) reach similar field strengths (approximately 2-3 10^{13} G) at late times. Irrespectively of the initial magnetic field strength, after $10^6$ years the temperature becomes so low that the magnetic diffusion timescale becomes longer than the typical ages of radio--pulsars, thus resulting in apparently no dissipation of the field in old NS. We also confirm the strong correlation between the magnetic field and the surface temperature of relatively young NSs discussed in preliminary works. The effective temperature of models with strong internal toroidal components are systematically higher than those of models with purely poloidal fields, due to the additional energy reservoir stored in the toroidal field that is gradually released as the field dissipates.

  9. EQUATION OF STATE FOR MASSIVE NEUTRON STARS

    SciTech Connect

    Katayama, Tetsuya; Saito, Koichi; Miyatsu, Tsuyoshi, E-mail: koichi.saito@rs.tus.ac.jp [Department of Physics, Faculty of Science and Technology, Tokyo University of Science (TUS), Noda 278-8510 (Japan)

    2012-12-15

    Using the relativistic Hartree-Fock approximation, we investigate the properties of neutron-star matter in detail. In the present calculation, we consider not only the tensor coupling of vector mesons to octet baryons and the form factors at interaction vertices but also the change in the internal (quark) structure of baryons in dense matter. The relativistic Hartree-Fock calculations are performed in two ways: one with coupling constants determined by SU(6) (quark model) symmetry and the other with coupling constants based on SU(3) (flavor) symmetry. For the latter case, we use the latest Nijmegen (ESC08) model. Then, it is very remarkable that the particle composition of the core matter in SU(3) symmetry is completely different from that in SU(6) symmetry. In SU(6) symmetry, all octet baryons appear in the density region below {approx}1.2 fm{sup -3}, while in the ESC08 model only the {Xi}{sup -} hyperon is produced. Furthermore, the medium modification of the internal baryon structure hardens the equation of state for the core matter. Taking all these effects into account, we can obtain the maximum neutron-star mass which is consistent with the recently observed mass, 1.97 {+-} 0.04 M{sub Sun} (PSR J1614-2230). We therefore conclude that the extension from SU(6) symmetry to SU(3) symmetry in meson-baryon couplings and the internal baryon structure variation in matter considerably enhance the mass of neutron stars. Furthermore, the effects of the form factor at the vertex and the Fock contribution, including the tensor coupling due to vector mesons, are indispensable for describing the core matter.

  10. The Washington Double Star Catalog (WDS, 1996.0)

    Microsoft Academic Search

    C. E. Worley; G. G. Douglass

    1997-01-01

    A major revision of the Washington Double Star (WDS) catalog containing data for the components of 78 100 systems is now available from the data centers and via the World Wide Web (http:\\/\\/aries.usno.navy.mil\\/ad\\/wds\\/).

  11. Washington Double Star Catalog Cross Index (1950 position sort)

    NASA Technical Reports Server (NTRS)

    1993-01-01

    A machine-readable version of the Washington Catalog of Visual Double Stars (WDS) was prepared in 1984 on the basis of a data file that was collected and maintained for more than a century by a succession of double-star observers. Although this catalog is being continually updated, a new copy for distribution is not expected to be available for a few years. The WDS contains DM numbers, but many of these are listed only in the notes, which makes it difficult to search for double-star information, except by position. Hence, a cross index that provides complete DM identifications is desirable, and it appears useful to add HD numbers for systems in that catalog. Aitken Double Star (ADS) numbers were retained from the WDS, but no attempt was made to correct these except for obvious errors.

  12. Sound velocity bound and neutron stars

    E-print Network

    Paulo F. Bedaque; Andrew W. Steiner

    2015-01-25

    It has been conjectured that the velocity of sound in any medium is smaller than the velocity of light in vacuum divided by $\\sqrt{3}$. Simple arguments support this bound in non-relativistic and/or weakly coupled theories. The bound has been demonstrated in several classes of strongly coupled theories with gravity duals and is saturated only in conformal theories. We point out that the existence of neutron stars with masses around two solar masses combined with the knowledge of the equation of state of hadronic matter at "low" densities is in strong tension with this bound.

  13. Sound velocity bound and neutron stars.

    PubMed

    Bedaque, Paulo; Steiner, Andrew W

    2015-01-23

    It has been conjectured that the velocity of sound in any medium is smaller than the velocity of light in vacuum divided by sqrt[3]. Simple arguments support this bound in nonrelativistic and/or weakly coupled theories. The bound has been demonstrated in several classes of strongly coupled theories with gravity duals and is saturated only in conformal theories. We point out that the existence of neutron stars with masses around two solar masses combined with the knowledge of the equation of state of hadronic matter at "low" densities is in strong tension with this bound. PMID:25658990

  14. Nonthermal accretion disk models around neutron stars

    NASA Technical Reports Server (NTRS)

    Tavani, M.; Liang, Edison P.

    1994-01-01

    We consider the structure and emission spectra of nonthermal accretion disks around both strongly and weakly magnetized neutron stars. Such disks may be dissipating their gravitational binding energy and transferring their angular momentum via semicontinuous magnetic reconnections. We consider specifically the structure of the disk-stellar magnetospheric boundary where magnetic pressure balances the disk pressure. We consider energy dissipation via reconnection of the stellar field and small-scale disk turbulent fields of opposite polarity. Constraints on the disk emission spectrum are discussed.

  15. Sound Velocity Bound and Neutron Stars

    NASA Astrophysics Data System (ADS)

    Bedaque, Paulo; Steiner, Andrew W.

    2015-01-01

    It has been conjectured that the velocity of sound in any medium is smaller than the velocity of light in vacuum divided by ?{3 }. Simple arguments support this bound in nonrelativistic and/or weakly coupled theories. The bound has been demonstrated in several classes of strongly coupled theories with gravity duals and is saturated only in conformal theories. We point out that the existence of neutron stars with masses around two solar masses combined with the knowledge of the equation of state of hadronic matter at "low" densities is in strong tension with this bound.

  16. Quark matter droplets in neutron stars

    NASA Technical Reports Server (NTRS)

    Heiselberg, H.; Pethick, C. J.; Staubo, E. F.

    1993-01-01

    We show that, for physically reasonable bulk and surface properties, the lowest energy state of dense matter consists of quark matter coexisting with nuclear matter in the presence of an essentially uniform background of electrons. We estimate the size and nature of spatial structure in this phase, and show that at the lowest densities the quark matter forms droplets embedded in nuclear matter, whereas at higher densities it can exhibit a variety of different topologies. A finite fraction of the interior of neutron stars could consist of matter in this new phase, which would provide new mechanisms for glitches and cooling.

  17. On neutron star/supernova remnant associations

    E-print Network

    V. V. Gvaramadze

    2001-04-01

    It is pointed out that a cavity supernova (SN) explosion of a moving massive star could result in a significant offset of the neutron star (NS) birth-place from the geometrical centre of the supernova remnant (SNR). Therefore: a) the high implied transverse velocities of a number of NSs (e.g. PSR B1610-50, PSR B1757-24, SGR0525-66) could be reduced; b) the proper motion vector of a NS should not necessarily point away from the geometrical centre of the associated SNR; c) the circle of possible NS/SNR associations could be enlarged. An observational test is discussed, which could allow to find the true birth-places of NSs associated with middle-aged SNRs, and thereby to get more reliable estimates of their transverse velocities.

  18. Coalescence of Magnetized Binary Neutron Star Systems

    NASA Astrophysics Data System (ADS)

    Motl, Patrick M.; Anderson, Matthew; Lehner, Luis; Liebling, Steven L.; Neilsen, David; Palenzuela, Carlos; Ponce, Marcelo

    2015-01-01

    We present simulations of the merger of binary neutron star systems calculated with full general relativity and incorporating the global magnetic field structure for the stars evolved with resistive magnetohydrodynamics. Our simulation tools have recently been improved to incorporate the effects of neutrino cooling and have been generalized to allow for tabular equations of state to describe the degenerate matter. Of particular interest are possible electromagnetic counterparts to the gravitational radiation that emerges from these systems. We focus on magnetospheric interactions that ultimately tap into the gravitational potential energy of the binary to power a Poynting flux and deposition of energy through Joule heating and magnetic reconnection. We gratefully acknowledge the support of NASA through the Astrophysics Theory Program grant NNX13AH01G.

  19. A SECOND NEUTRON STAR IN M4?

    SciTech Connect

    Kaluzny, J.; Rozanska, A.; Rozyczka, M.; Krzeminski, W. [Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw (Poland); Thompson, Ian B. [Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)

    2012-05-01

    We show that the optical counterpart of the X-ray source CX 1 in M4 is a {approx}20th magnitude star, located in the color-magnitude diagram on (or very close to) the main sequence of the cluster, and exhibiting sinusoidal variations of the flux. We find the X-ray flux to be also periodically variable, with X-ray and optical minima coinciding. Stability of the optical light curve, lack of UV-excess, and unrealistic mean density resulting from period-density relation for semidetached systems speak against the original identification of CX 1 as a cataclysmic variable. We argue that the X-ray active component of this system is a neutron star (probably a millisecond pulsar).

  20. 3D MHD Simulations of accreting neutron stars: evidence of QPO emission from the surface

    SciTech Connect

    Bachetti, Matteo; Burderi, Luciano [Universita degli Studi di Cagliari (Italy); Romanova, Marina M.; Kulkarni, Akshay [Cornell University (United States); Salvo, Tiziana di [Universita degli Studi di Palermo (Italy)

    2010-07-15

    3D Magnetohydrodynamic simulations show that when matter accretes onto neutron stars, in particular if the misalignment angle is small, it does not constantly fall at a fixed spot. Instead, the location at which matter reaches the star moves. These moving hot spots can be produced both during stable accretion, where matter falls near the magnetic poles of the star, and unstable accretion, characterized by the presence of several tongues of matter which fall on the star near the equator, due to Rayleigh-Taylor instabilities. Precise modeling with Monte Carlo simulations shows that those movements could be observed as high frequency Quasi Periodic Oscillations. We performed a number of new simulation runs with a much wider set of parameters, focusing on neutron stars with a small misalignment angle. In most cases we observe oscillations whose frequency is correlated with the mass accretion rate M. Moreover, in some cases double QPOs appear, each of them showing the same correlation with M.

  1. Theory of Radiation Transfer in Neutron Star Atmospheres

    NASA Technical Reports Server (NTRS)

    Zavlin, Vyacheslav

    2006-01-01

    The possibility for direct investigation of thermal emission from isolated neutron stars opened about a quarter of century ago with the launch of the first X-ray observatories Einstein and EXOSAT stimulated developing models of the neutron star surface radiation which began at the end of 80's. Confronting observational data with theoretical models of thermal emission allows one to infer the surface temperatures, magnetic fields, chemical composition, and neutron star masses and radii. This information, supplemented with the model equations of state and neutron star cooling models, provides an opportunity to understand the fundamental properties of the superdense matter in the stars' interiors. Almost all available models are based on the assumption that thermal radiation emitted by a neutron star is formed in the superficial star's layers--atmosphere. The neutron star atmospheres are very different from those of usual stars due to the immense gravity and huge magnetic fields. In this presentation we review the current status of the neutron star atmosphere modeling, present most important results, discuss problems and possible future developments.

  2. TeV mu Neutrinos from Young Neutron Stars

    E-print Network

    B. Link; Fiorella Burgio

    2005-05-19

    Neutron stars are efficient accelerators for bringing charges up to relativistic energies. We show that if positive ions are accelerated to ~1 PeV near the surface of a young neutron star (t_age star's radiation field will produce beamed mu neutrinos with energies of ~50 TeV that could produce the brightest neutrino sources at these energies yet proposed. These neutrinos would be coincident with the radio beam, so that if the star is detected as a radio pulsar, the neutrino beam will sweep the Earth; the star would be a ``neutrino pulsar''. Looking for muon neutrino emission from young neutron stars will provide a valuable probe of the energetics of the neutron star magnetosphere.

  3. TeV mu neutrinos from young neutron stars.

    PubMed

    Link, Bennett; Burgio, Fiorella

    2005-05-13

    Neutron stars are efficient accelerators for bringing charges up to relativistic energies. We show that if positive ions are accelerated to approximately 1 PeV near the surface of a young neutron star (t(age) less than or nearly 10(5) yr), protons interacting with the star's radiation field produce beamed mu neutrinos with energies of approximately 50 TeV that could produce the brightest neutrino sources at these energies yet proposed. These neutrinos would be coincident with the radio beam, so that, if the star is detected as a radio pulsar, the neutrino beam will sweep the Earth; the star would be a "neutrino pulsar." Looking for nu(mu) emission from young neutron stars will provide a valuable probe of the energetics of the neutron star magnetosphere. PMID:15904352

  4. Spectral Models of Neutron Star Magnetospheres

    NASA Technical Reports Server (NTRS)

    Romani, Roger W.

    1997-01-01

    We revisit the association of unidentified Galactic plane EGRET sources with tracers of recent massive star formation and death. Up-to-date catalogs of OB associations, SNR's, young pulsars, H2 regions and young open clusters were used in finding counterparts for a recent list of EGRET sources. It has been argued for some time that EGRET source positions are correlated with SNR's and OB associations as a class; we extend such analyses by finding additional counterparts and assessing the probability of individual source identifications. Among the several scenarios relating EGRET sources to massive stars, we focus on young neutron stars as the origin of the gamma-ray emission. The characteristics of the candidate identifications are compared to the known gamma-ray pulsar sample and to detailed Galactic population syntheses using our outer gap pulsar model of gamma-ray emission. Both the spatial distribution and luminosity function of the candidates are in good agreement with the model predictions; we infer that young pulsars can account for the bulk of the excess low latitude EGRET sources. We show that with this identification, the gamma-ray point sources provide an important new window into the history of recent massive star death in the solar neighborhood.

  5. BD +46o664 - A "New" Double Star

    NASA Astrophysics Data System (ADS)

    Vollman, Wolfgang

    2014-10-01

    The pair of stars BD+46o664p and BD+46o664s was found as a visual double star. Using modern astrometrical and astrophysical catalogs it is not ruled out that this is a physical pair with small but similar proper motion, spectral type and spectroscopic parallax.

  6. Slowly rotating general relativistic superfluid neutron stars with relativistic entrainment

    Microsoft Academic Search

    G. L. Comer

    2004-01-01

    Neutron stars that are cold enough should have two or more superfluids or supercondutors in their inner crusts and cores. The implication of superfluidity or superconductivity for equilibrium and dynamical neutron star states is that each individual particle species that forms a condensate must have its own, independent number density current and equation of motion that determines that current. An

  7. Neutron star dynamos and the origins of pulsar magnetism

    Microsoft Academic Search

    Christopher Thompson; Robert C. Duncan

    1993-01-01

    Neutron star convection is a transient phenomenon and has an extremely high magnetic Reynolds number. In this sense, a neutron star dynamo is the quintessential fast dynamo. The convective motions are only mildly turbulent on scales larger than the approximately 100 cm neutrino mean free path, but the turbulence is well developed on smaller scales. Several fundamental issues in the

  8. Physics of neutron star surface layers and their thermal radiation

    E-print Network

    , Thermodynamic processes, conduction, convection, equations of state PACS: 97.60.Jd, 95.30.Tg INTRODUCTIONPhysics of neutron star surface layers and their thermal radiation Alexander Y. Potekhin Ioffe radiation, taking into consideration the effects of strong magnetic fields. Keywords: Neutron stars

  9. Nuclear Equation of State and Neutron Star Cooling

    E-print Network

    Yeunhwan Lim; Chang Ho Hyun; Chang-Hwan Lee

    2015-01-19

    We investigate the effects of the nuclear equation of state (EoS) to the neutron star cooling. New era for nuclear EoS has begun after the discovery of $\\sim 2\\msun$ neutron stars PSR J1614$-$2230 and PSR J0348$+$0432 [1, 2]. Also recent works on the mass and radius of neutron stars from low-mass X-ray binaries [3] strongly constrain the EoS of nuclear matter. On the other hand, observations of the neutron star in Cassiopeia A (Cas A) more than 10 years confirmed the existence of nuclear superfluidity [4, 5]. Nuclear superfluidity reduces the heat capacities as well as neutrino emissivities. With nuclear superfluidity the neutrino emission processes are highly suppressed, and the existence of superfluidity makes the cooling path quite different from that of the standard cooling process. Superfluidity also allows new neutrino emission process, which is called `Pair Breaking and Formation'(PBF). PBF is a fast cooling process and can explain the fast cooling rate of neutron star in Cas A. Therefore, it is essential to add the superfluidity effect in the neutron star cooling process. In this work, we simulate neutron star cooling curves using both non-relativistic and relativistic nuclear models. The existence of too early direct Urca process shows that some of nuclear models do not fit for the cooling simulation. After this first selection process, the nuclear pairing gaps are searched using the observational neutron star's age and temperature data.

  10. Neutron Star Structure in the Presence of Scalar Fields

    NASA Technical Reports Server (NTRS)

    Kazanas, Demosthenes

    2004-01-01

    Motivated by the possible presence of scalar fields on astrophysical scales, suggested by the apparent acceleration of the universe implied by the supernovae surveys, we present models of neutron star structure including the contribution of a (massless) scalar field to the stress energy momentum tensor, in addition to that made by the normal matter. To that end we solve the coupled Einstein -- scalar field -- hydrostatic balance equations to compute the effect of the presence of the scalar field on the neutron star structure. We find that the presence of the scalar field does change the structure of the neutron star, especially in cases of strong coupling between the scalar field and the matter density. We present the neutron star radius as a function of the matter--scalar field coupling constant for different values of the neutron star central density. The presence of the scalar field affects both the maximum neutron star mass and Its radius, the latter increasing with the value of the above coupling constant. We also compute particle and photon geodesics in the geometry of these neutron stars as well as to the geometry of black holes with different values of the scalar field. Our results may be testable with timing observations of accreting neutron stars.

  11. Physics of systems containing neutron stars

    NASA Technical Reports Server (NTRS)

    Ruderman, Malvin

    1996-01-01

    This grant dealt with several topics related to the dynamics of systems containing a compact object. Most of the research dealt with systems containing Neutron Stars (NS's), but a Black Hole (BH) or a White Dwarf (WD) in situations relevant to NS systems were also addressed. Among the systems were isolated regular pulsars, Millisecond Pulsars (MSP's) that are either Single (SMP's) or in a binary (BMP's), Low Mass X-Ray Binaries (LMXB's) and Cataclysmic Variables (CV's). Also dealt with was one aspect of NS structure, namely NS superfluidity. A large fraction of the research dealt with irradiation-driven winds from companions which turned out to be of importance in the evolution of LMXB's and MSP's, be they SMP's or BMP's. While their role during LMXB evolution (i.e. during the accretion phase) is not yet clear, they may play an important role in turning BMP's into SMP's and also in bringing about the formation of planets around MSP's. Work was concentrated on the following four problems: The Windy Pulsar B197+20 and its Evolution; Wind 'Echoes' in Tight Binaries; Post Nova X-ray Emission in CV's; and Dynamics of Pinned Superfluids in Neutron Stars.

  12. Anisotropic pressure and hyperons in neutron stars

    NASA Astrophysics Data System (ADS)

    Sulaksono, A.

    2015-01-01

    We study the effects of anisotropic pressure (AI-P) on properties of the neutron stars (NSs) with hyperons inside its core within the framework of extended relativistic mean field. It is found that the main effects of AI-P on NS matter is to increase the stiffness of the equation of state EOS, which compensates for the softening of the EOS due to the hyperons. The maximum mass and redshift predictions of anisotropic neutron star with hyperonic core are quite compatible with the result of recent observational constraints if we use the parameter of AI-P model h ? 0.8 [L. Herrera and W. Barreto, Phys. Rev. D88 (2013) 084022.] and ? ? -1.15 [D. D. Doneva and S. S. Yazadjiev, Phys. Rev. D85 (2012) 124023.]. The radius of the corresponding NS at M = 1.4 M? is more than 13 km, while the effect of AI-P on the minimum mass of NS is insignificant. Furthermore, due to the AI-P in the NS, the maximum mass limit of higher than 2.1 M? cannot rule out the presence of hyperons in the NS core.

  13. Tidal effects in binary neutron star coalescence

    E-print Network

    Sebastiano Bernuzzi; Alessandro Nagar; Marcus Thierfelder; Bernd Bruegmann

    2012-05-15

    We compare dynamics and waveforms from binary neutron star coalescence as computed by new long-term ($\\sim 10 $ orbits) numerical relativity simulations and by the tidal effective-one-body (EOB) model including analytical tidal corrections up to second post-Newtonian order (2PN). The current analytical knowledge encoded in the tidal EOB model is found to be sufficient to reproduce the numerical data up to contact and within their uncertainties. Remarkably, no calibration of any tidal EOB free parameters is required, beside those already fitted to binary black holes data. The inclusion of 2PN tidal corrections minimizes the differences with the numerical data, but it is not possible to significantly distinguish them from the leading-order tidal contribution. The presence of a relevant amplification of tidal effects is likely to be excluded, although it can appear as a consequence of numerical inaccuracies. We conclude that the tidally-completed effective-one-body model provides nowadays the most advanced and accurate tool for modelling gravitational waveforms from binary neutron star inspiral up to contact. This work also points out the importance of extensive tests to assess the uncertainties of the numerical data, and the potential need of new numerical strategies to perform accurate simulations.

  14. Proto-Neutron and Neutron Stars in a Chiral SU(3) Model

    E-print Network

    V. Dexheimer; S. Schramm

    2008-07-16

    A hadronic chiral SU(3) model is applied to neutron and proto-neutron stars, taking into account trapped neutrinos, finite temperature and entropy. The transition to the chirally restored phase is studied and global properties of the stars like minimum and maximum masses and radii are calculated for different cases. In addition, the effects of rotation on neutron star masses are included and the conservation of baryon number and angular momentum determine the maximum frequencies of rotation during the cooling.

  15. NARROW ATOMIC FEATURES FROM RAPIDLY SPINNING NEUTRON STARS

    SciTech Connect

    Bauboeck, Michi; Psaltis, Dimitrios; Oezel, Feryal, E-mail: mbaubock@email.arizona.edu, E-mail: dpsaltis@email.arizona.edu, E-mail: fozel@email.arizona.edu [Astronomy Department, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)] [Astronomy Department, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)

    2013-04-01

    Neutron stars spinning at moderate rates ({approx}300-600 Hz) become oblate in shape and acquire a nonzero quadrupole moment. In this paper, we calculate the profiles of atomic features from such neutron stars using a ray-tracing algorithm in the Hartle-Thorne approximation. We show that line profiles acquire cores that are much narrower than the widths expected from pure Doppler effects for a large range of observer inclinations. As a result, the effects of both the oblateness and the quadrupole moments of neutron stars need to be taken into account when aiming to measure neutron-star radii from rotationally broadened lines. Moreover, the presence of these narrow cores substantially increases the likelihood of detecting atomic lines from rapidly spinning neutron stars.

  16. Constraints on Neutron Star Masses and Radii from Kilohertz QPOs

    E-print Network

    Frederick K. Lamb; M. Coleman Miller; Dimitrios Psaltis

    1997-12-19

    The frequencies of the highest-frequency kilohertz QPOs recently discovered in some sixteen neutron stars in low-mass X-ray binary systems are most likely orbital frequencies. If so, these QPOs provide tight upper bounds on the masses and radii of these neutron stars and interesting new constraints on the equation of state of neutron star matter. If the frequency of a kilohertz QPO can be established as the orbital frequency of the innermost stable circular orbit, this would confirm one of the key predictions of general relativity in the strong-field regime. If the spin frequency of the neutron star can also be determined, the frequency of the QPO would fix the mass of the neutron star for each assumed equation of state. Here we describe how bounds on the stellar mass and radius can be derived and how these bounds are affected by the stellar spin. We also discuss detection of the innermost stable circular orbit.

  17. Intriguing triple-mode RR Lyrae star with period doubling

    E-print Network

    Smolec, R; Udalski, A; Szyma?ski, M K; Pietrukowicz, P; Skowron, J; Koz?owski, S; Poleski, R; Moskalik, P; Skowron, D; Pietrzy?ski, G; Wyrzykowski, ?; Ulaczyk, K; Mróz, P

    2014-01-01

    We report the discovery of an intriguing triple-mode RR Lyrae star found in the OGLE Galactic bulge collection, OGLE-BLG-RRLYR-24137. In the OGLE catalog the star was identified as RRd star - double-mode pulsator, pulsating simultaneously in the fundamental and in the first overtone modes. We find that third mode is excited and firmly detect its period doubling. Period ratios are not far from that expected for triple-mode - fundamental, first and third overtone - pulsation. Unfortunately, we cannot reproduce period ratios of the three modes with a consistent set of pulsation models. Therefore the other interpretation, that additional mode is non-radial, is also likely.

  18. Discovery of 4 New Double Stars in Constellation Serpens

    NASA Astrophysics Data System (ADS)

    Schlimmer, Joerg

    2015-01-01

    During observations in the constellation Serpens, four new double stars could be found: USNO B1.0 1007-0241735, USNO B1.0 1004-0244945, USNO B1.0 0950-0252685 and USNO B1.0 0949-0248260. All these double stars are listed as single stars in USNO catalog but can be separated into two components. Separations are between 4 and 10 arc seconds. In 3 cases proper motions are known and comply with Halbwachs' criteria for possible common proper motion pairs.

  19. Gravitational and Electromagnetic Emission from Binary Neutron Star Mergers

    NASA Astrophysics Data System (ADS)

    Motl, Patrick M.; Palenzuela, C.; Lehner, L.; Ponce, M.; Liebling, S. L.; Anderson, M.; Neilsen, D.

    2013-06-01

    The inspiral of a neutron star - neutron star binary is a leading candidate for strong emission of gravitational waves. The interaction between the stellar magnetospheres may also give rise to electromagnetic emissions accompanying the gravity waves as the neutron stars inspiral and merge. We present results from a set of resistive magnetohydrodynamic simulations of mergers computed with full general relativity. We vary the initial magnetic field of the neutron stars including cases where the fields are initially aligned, anit-aligned and where one star’s field dominates over its companion. This presentation is based upon work supported by the National Aeronautics and Space Administration under grant No. NNX13AH01G through the astrophysics theory program.

  20. DOUBLE STARS IN THE USNO CCD ASTROGRAPHIC CATALOG

    SciTech Connect

    Hartkopf, William I.; Mason, Brian D.; Finch, Charlie T.; Zacharias, Norbert; Wycoff, Gary L.; Hsu, Danley, E-mail: wih@usno.navy.mil, E-mail: bdm@usno.navy.mil, E-mail: finch@usno.navy.mil, E-mail: nz@usno.navy.mil [US Naval Observatory, Washington, DC 20392 (United States)

    2013-10-01

    The newly completed Fourth USNO CCD Astrographic Catalog (UCAC4) has proven to be a rich source of double star astrometry and photometry. Following initial comparisons of UCAC4 results against those obtained by speckle interferometry, the UCAC4 catalog was matched against known double stars in the Washington Double Star Catalog in order to provide additional differential astrometry and photometry for these pairs. Matches to 58,131 pairs yielded 61,895 astrometric and 68,935 photometric measurements. Finally, a search for possible new common proper motion (CPM) pairs was made using new UCAC4 proper motion data; this resulted in 4755 new potential CPM doubles (and an additional 27,718 astrometric and photometric measures from UCAC and other sources)

  1. Energy Density Functional for Nuclei and Neutron Stars

    SciTech Connect

    Erler, J. [UTK/ORNL/German Cancer Research Center-Heidelberg; Horowitz, C. J. [UTK/ORNL/Indiana University; Nazarewicz, Witold [UTK/ORNL/University of Warsaw; Rafalski, M. [UTK/ORNL; Reinhard, P.-G. [Universitat Erlangen, Germany

    2013-01-01

    Background: Recent observational data on neutron star masses and radii provide stringent constraints on the equation of state of neutron rich matter [ Annu. Rev. Nucl. Part. Sci. 62 485 (2012)]. Purpose: We aim to develop a nuclear energy density functional that can be simultaneously applied to finite nuclei and neutron stars. Methods: We use the self-consistent nuclear density functional theory (DFT) with Skyrme energy density functionals and covariance analysis to assess correlations between observables for finite nuclei and neutron stars. In a first step two energy functionals a high density energy functional giving reasonable neutron properties, and a low density functional fitted to nuclear properties are matched. In a second step, we optimize a new functional using exactly the same protocol as in earlier studies pertaining to nuclei but now including neutron star data. This allows direct comparisons of performance of the new functional relative to the standard one. Results: The new functional TOV-min yields results for nuclear bulk properties (energy, rms radius, diffraction radius, and surface thickness) that are of the same quality as those obtained with the established Skyrme functionals, including SV-min. When comparing SV-min and TOV-min, isoscalar nuclear matter indicators vary slightly while isovector properties are changed considerably. We discuss neutron skins, dipole polarizability, separation energies of the heaviest elements, and proton and neutron drip lines. We confirm a correlation between the neutron skin of 208Pb and the neutron star radius. Conclusions: We demonstrate that standard energy density functionals optimized to nuclear data do not carry information on the expected maximum neutron star mass, and that predictions can only be made within an extremely broad uncertainty band. For atomic nuclei, the new functional TOV-min performs at least as well as the standard nuclear functionals, but it also reproduces expected neutron star data within assumed error bands. This functional is expected to yield more reliable predictions in the region of very neutron rich heavy nuclei.

  2. Mass and radius formulas for low-mass neutron stars

    E-print Network

    Hajime Sotani; Kei Iida; Kazuhiro Oyamatsu; Akira Ohnishi

    2014-03-31

    Neutron stars, produced at the death of massive stars, are often regarded as giant neutron-rich nuclei. This picture is especially relevant for low-mass (below about solar mass) neutron stars, where non-nucleonic components are not expected to occur. Due to the saturation property of nucleonic matter, leading to the celebrated liquid-drop picture of atomic nuclei, empirical nuclear masses and radii can be approximately expressed as function of atomic mass number. It is, however, not straightforward to express masses and radii of neutron stars even in the low-mass range where the structure is determined by a balance between the pressure of neutron-rich nucleonic matter and the gravity. Such expressions would be of great use given possible simultaneous mass and radius measurements. Here we successfully construct theoretical formulas for the masses and radii of low-mass neutron stars from various models that are consistent with empirical masses and radii of stable nuclei. In this process, we discover a new equation-of-state parameter that characterizes the structure of low-mass neutron stars. This parameter, which plays a key role in connecting the mass-radius relation of the laboratory nuclei to that of the celestial objects, could be constrained from future observations of low-mass neutron stars.

  3. Mass and radius formulas for low-mass neutron stars

    NASA Astrophysics Data System (ADS)

    Sotani, Hajime; Iida, Kei; Oyamatsu, Kazuhiro; Ohnishi, Akira

    2014-05-01

    Neutron stars, produced at the death of massive stars, are often regarded as giant neutron-rich nuclei. This picture is especially relevant for low-mass (below about solar mass, M_?) neutron stars, where non-nucleonic components are not expected to occur. Due to the saturation property of nucleonic matter, leading to the celebrated liquid-drop picture of atomic nuclei, empirical nuclear masses and radii can be approximately expressed as a function of atomic mass number. It is, however, not straightforward to express masses and radii of neutron stars even in the low-mass range where the structure is determined by a balance between the pressure of neutron-rich nucleonic matter and gravity. Such expressions would be of great use given possible simultaneous mass and radius measurements. Here we successfully construct theoretical formulas for the masses and radii of low-mass neutron stars from various models that are consistent with empirical masses and radii of stable nuclei. In this process, we discover a new equation-of-state parameter that characterizes the structure of low-mass neutron stars. This parameter, which plays a key role in connecting the mass-radius relation of the laboratory nuclei to that of the celestial objects, could be constrained from future observations of low-mass neutron stars.

  4. Differences in the Cooling Behavior of Strange Quark Matter Stars and Neutron Stars

    E-print Network

    Christoph Schaab; Bernd Hermann; Fridolin Weber; Manfred K. Weigel

    1997-02-21

    The general statement that hypothetical strange (quark matter) stars cool more rapidly than neutron stars is investigated in greater detail. It is found that the direct Urca process could be forbidden not only in neutron stars but also in strange stars. In this case, strange stars are slowly cooling, and their surface temperatures are more or less indistinguishable from those of slowly cooling neutron stars. Furthermore the case of enhanced cooling is reinvestigated. It shows that strange stars cool significantly more rapidly than neutron stars within the first $\\sim 30$ years after birth. This feature could become particularly interesting if continued observation of SN 1987A would reveal the temperature of the possibly existing pulsar at its center.

  5. Journey to the Center of a Neutron Star

    NASA Technical Reports Server (NTRS)

    Wanjek, Christopher

    2003-01-01

    A neutron star is not a place most would want to visit. This dense remnant of a collapsed star has a magnetic field billions of times stronger than Earth's, enough to shuffle your body's molecules long before you even land. The featureless surface is no fun either. Crushing gravity ensures that the star is a near perfect sphere, compressing all matter so that a sand-grain-sized scoop of neutron star material would weigh as much as a battleship on Earth. At least black holes offer the promise of funky singularity, time warps, and the Odyssean temptation to venture beyond a point of no return. What s a journey to a neutron star good for, one might ask? Well, for starters, it offers the possibility of confirming a theorized state of matter called quark-gluon plasma, which likely existed for a moment after the Big Bang and now might only exist in the superdense interiors of neutron stars. Beneath the neutron star crust, a kilometer-thick plate of crystalline matter, lies the great unknown. The popular theory is that the neutron star interior is made up of a neutron superfluid - a fluid without friction. With the help of two NASA satellites - the Rossi X-Ray Timing Explorer and the Chandra X-Ray Observatory - scientists are journeying to the center of a neutron star. Matter might be so compressed there that it breaks down into quarks, the building blocks of protons and neutrons, and gluons, the carrier of the strong nuclear force. To dig inside a neutron star, no simple drill bit will do. Scientists gain insight into the interior through events called glitches, a sudden change in the neutron star s precise spin rate. 'Glitches are one of the few ways we have to study the neutron star interior,' says Frank Marshall of NASA s Goddard Space Flight Center, who has used the Rossi Explorer to follow the escapades of the glitchiest of all neutron stars, dubbed the Big Glitcher and known scientifically as PSR J0537-6910.

  6. The NASA Neutron Star Grand Challenge: The coalescences of Neutron Star Binary System

    Microsoft Academic Search

    Wai-Mo Suen

    1998-01-01

    NASA funded a Grand Challenge Project (9\\/1996-1999) for the development of a multi-purpose numerical treatment for relativistic astrophysics and gravitational wave astronomy. The coalescence of binary neutron stars is chosen as the model problem for the code development. The institutes involved in it are the Argonne Lab, Livermore lab, Max-Planck Institute at Potsdam, StonyBrook, U of Illinois and Washington U.

  7. Towards real neutron star seismology: Accounting for elasticity and superfluidity

    E-print Network

    A. Passamonti; N. Andersson

    2011-05-24

    We study the effects of an elastic crust on the oscillation spectrum of superfluid neutron stars. Within the two fluid formalism, we consider Newtonian stellar models that include the relevant constituents of a mature neutron stars. The core is formed by a mixture of superfluid neutrons and a conglomerate of charged particles, while the inner crust is described by a lattice of nuclei permeated by superfluid neutrons. We linearise the Poisson and the conservation equations of nonrotating superfluid stars and study the effects of elasticity, entrainment and composition stratification on the shear and acoustic modes. In both the core and the crust, the entrainment is derived from recent results for the nucleon effective mass. Solving the perturbation equations as an eigenvalue problem, we find that the presence of superfluid neutrons in the crust and their large effective mass may have significant impact on the star's oscillation spectrum.

  8. Superfluid heat conduction and the cooling of magnetized neutron stars

    SciTech Connect

    Cirigliano, Vincenzo [Los Alamos National Laboratory; Reddy, Sanjay [Los Alamos National Laboratory; Sharma, Rishi [Los Alamos National Laboratory; Aguilera, Deborah N [BUENOS AIRES

    2008-01-01

    We report on a new mechanism for heat conduction in the neutron star crust. We find that collective modes of superftuid neutron matter, called superfiuid phonons (sPhs), can influence heat conduction in magnetized neutron stars. They can dominate the heat conduction transverse to magnetic field when the magnetic field B {approx}> 10{sup 13} C. At density p {approx_equal} 10{sup 12}--10{sup 14} g/cm{sup 3} the conductivity due to sPhs is significantly larger than that due to lattice phonons and is comparable to electron conductivity at when temperature {approx_equal} 10{sup 8} K. This new mode of heat conduction can limit the surface anisotropy in highly magnetized neutron stars. Cooling curves of magnetized neutron stars with and without superfluid heat conduction show observationally discernible differences.

  9. Cyclotron line features from neutron star atmospheres

    NASA Technical Reports Server (NTRS)

    Wang, John C. L.; Wasserman, Ira M.; Salpeter, Edwin E.

    1989-01-01

    Cyclotron line features from the polar cap plasmas of accreting magnetized neutron stars are modeled. The polar cap environment is modeled by a homogeneous isothermal plane-parallel slab threaded by a uniform superstrong magnetic field oriented orthogonal to the slab. Two physical cyclotron photon source functions are used. For conventional stopping depths, the emergent line spectra are fairly independent of the source functions. For hot atmospheres the details of the line transfer using relativistic kinematics differ substantially from those using nonrelativistic kinematics. Aside from finite recoil, both a finite natural linewidth and conventional stopping depths suppress the escape of photons blueward of line center and potential line features tend to be smeared out into the low-energy continuum. The formation of a line features is most favorable in low-field high-temperature atmospheres where cyclotron photon production is confined to a layer of small column density.

  10. Europium production: neutron star mergers versus core-collapse supernovae

    E-print Network

    Matteucci, F; Arcones, A; Korobkin, O; Rosswog, S

    2013-01-01

    We have explored the Eu production in the Milky Way by means of a very detailed chemical evolution model. In particular, we have assumed that Eu is formed in merging neutron star (or neutron star black hole) binaries as well as in type II supernovae. We have tested the effects of several important parameters influencing the production of Eu during the merging of two neutron stars, such as: i) the time scale of coalescence, ii) the Eu yields and iii) the range of initial masses for the progenitors of the neutron stars. The yields of Eu from type II supernovae are very uncertain, more than those from coalescing neutron stars, so we have explored several possibilities. We have compared our model results with the observed rate of coalescence of neutron stars, the solar Eu abundance, the [Eu/Fe] versus [Fe/H] relation in the solar vicinity and the [Eu/H] gradient along the Galactic disc. Our main results can be summarized as follows: i) neutron star mergers can be entirely responsible for the production of Eu in t...

  11. Neutron Star Structure In The Presence of Scalar Fields

    NASA Technical Reports Server (NTRS)

    Crawford, James P.; Kazanas, Demosthenes

    2004-01-01

    Motivated by the possible presence of scalar fields on astrophysical scales, suggested by the recent measurement of the deceleration parameter by supernovae surveys, we present models of neutron star structure under the assumption that a scalar field makes a significant contribution to the stress energy momentum tensor, in addition to that made by the normal matter. To that end we solve the coupled Einstein - scalar field - hydrostatic balance equations to compute the effect of the presence of the scalar field on the neutron star structure. We find that the presence of the scalar field does change the structure of the neutron star, especially in cases of strong coupling between the scalar field and the matter density. We present the neutron star radius as a function of the matter-scalar field coupling constant for different values of the neutron star central density. The presence of the scalar field does affect both the maximum neutron star mass and its radius, the latter increasing with the value of the above coupling constant. Our results may be testable with the recent timing observations of accreting neutron stars.

  12. Breaking strain of neutron star crust and gravitational waves.

    PubMed

    Horowitz, C J; Kadau, Kai

    2009-05-15

    Mountains on rapidly rotating neutron stars efficiently radiate gravitational waves. The maximum possible size of these mountains depends on the breaking strain of the neutron star crust. With multimillion ion molecular dynamics simulations of Coulomb solids representing the crust, we show that the breaking strain of pure single crystals is very large and that impurities, defects, and grain boundaries only modestly reduce the breaking strain to around 0.1. Because of the collective behavior of the ions during failure found in our simulations, the neutron star crust is likely very strong and can support mountains large enough so that their gravitational wave radiation could limit the spin periods of some stars and might be detectable in large-scale interferometers. Furthermore, our microscopic modeling of neutron star crust material can help analyze mechanisms relevant in magnetar giant flares and microflares. PMID:19518937

  13. Neutron star dynamos and the origins of pulsar magnetism

    NASA Technical Reports Server (NTRS)

    Thompson, Christopher; Duncan, Robert C.

    1993-01-01

    Neutron star convection is a transient phenomenon and has an extremely high magnetic Reynolds number. In this sense, a neutron star dynamo is the quintessential fast dynamo. The convective motions are only mildly turbulent on scales larger than the approximately 100 cm neutrino mean free path, but the turbulence is well developed on smaller scales. Several fundamental issues in the theory of fast dynamos are raised in the study of a neutron star dynamo, in particular the possibility of dynamo action in mirror-symmetric turbulence. It is argued that in any high magnetic Reynolds number dynamo, most of the magnetic energy becomes concentrated in thin flux ropes when the field pressure exceeds the turbulent pressure at the smallest scale of turbulence. In addition, the possibilities for dynamo action during the various (pre-collapse) stages of convective motion that occur in the evolution of a massive star are examined, and the properties of white dwarf and neutron star progenitors are contrasted.

  14. Electromagnetic and Radiative Properties of Neutron Star Magnetospheres

    NASA Astrophysics Data System (ADS)

    Li, Jason G.

    2014-05-01

    Magnetospheres of neutron stars are commonly modeled as either devoid of plasma in "vacuum'' models or filled with perfectly conducting plasma with negligible inertia in "force-free'' models. While numerically tractable, neither of these idealized limits can simultaneously account for both the plasma currents and the accelerating electric fields that are needed to explain the morphology and spectra of high-energy emission from pulsars. In this work we improve upon these models by considering the structure of magnetospheres filled with resistive plasma. We formulate Ohm's Law in the minimal velocity fluid frame and implement a time-dependent numerical code to construct a family of resistive solutions that smoothly bridges the gap between the vacuum and force-free magnetosphere solutions. We further apply our method to create a self-consistent model for the recently discovered intermittent pulsars that switch between two distinct states: an "on'', radio-loud state, and an "off'', radio-quiet state with lower spin-down luminosity. Essentially, we allow plasma to leak off open field lines in the absence of pair production in the "off'' state, reproducing observed differences in spin-down rates. Next, we examine models in which the high-energy emission from gamma-ray pulsars comes from reconnecting current sheets and layers near and beyond the light cylinder. The reconnected magnetic field provides a reservoir of energy that heats particles and can power high-energy synchrotron radiation. Emitting particles confined to the sheet naturally result in a strong caustic on the skymap and double peaked light curves for a broad range of observer angles. Interpulse bridge emission likely arises from interior to the light cylinder, along last open field lines that traverse the space between the polar caps and the current sheet. Finally, we apply our code to solve for the magnetospheric structure of merging neutron star binaries. We find that the scaling of electromagnetic luminosity with orbital angular velocity varies between the power 4 for nonspinning stars and the power 1.5 for rapidly spinning millisecond pulsars near contact. Our derived scalings and magnetospheres can be used to help understand electromagnetic signatures from merging neutron stars to be observed by Advanced LIGO.

  15. Comment on "Three-dimensional hydrodynamic simulations of the combustion of a neutron star into a quark star"

    E-print Network

    M. I. Krivoruchenko; B. V. Martemyanov

    2015-03-04

    If strange matter is absolutely stable, the ordinary nuclei decay to strangelets, while neutron stars convert into strange stars. Lifetimes of the ordinary nuclei are constrained experimentally to be above $\\sim 10^{33}$ years, while lifetimes of the metastable neutron stars depend on the neutron star masses and can exceed the age of the Universe. As a consequence, the neutron stars and the strange stars can coexist in the Universe. We point out that numerical simulations of the conversion of neutron stars to strange stars, performed by M. Herzog and F. K. Roepke in Phys. Rev. D 84, 083002 (2011) [arXiv:1109.0539], are focused on a region in the parameter space of strange matter, in which low-mass neutron stars and strange stars are coexistent, whereas massive neutron stars are unstable and short lived on an astronomical timescale.

  16. A Second Neutron Star in M4?

    NASA Astrophysics Data System (ADS)

    Kaluzny, J.; Rozanska, A.; Rozyczka, M.; Krzeminski, W.; Thompson, Ian B.

    2012-05-01

    We show that the optical counterpart of the X-ray source CX 1 in M4 is a ~20th magnitude star, located in the color-magnitude diagram on (or very close to) the main sequence of the cluster, and exhibiting sinusoidal variations of the flux. We find the X-ray flux to be also periodically variable, with X-ray and optical minima coinciding. Stability of the optical light curve, lack of UV-excess, and unrealistic mean density resulting from period-density relation for semidetached systems speak against the original identification of CX 1 as a cataclysmic variable. We argue that the X-ray active component of this system is a neutron star (probably a millisecond pulsar). Based on observations made with the NASA/ESA Hubble Space Telescope, and obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European Coordinating Facility (ST-ECF/ESA) and the Canadian Astronomy Data Centre (CADC/NRC/CSA).

  17. Resonant Shattering of Neutron Star Crusts

    NASA Astrophysics Data System (ADS)

    Tsang, David; Read, Jocelyn; Piro, Anthony; Hinderer, Tanja

    2014-08-01

    The resonant excitation of neutron star (NS) modes by tides is investigated as a source of short gamma-ray burst (sGRB) precursors. We find that the driving of a crust-core interface mode can lead to shattering of the NS crust, liberating ~10^46-10^47 erg of energy secondsbefore the merger of a NS-NS or NS-black hole binary. Such properties are consistent with Swift/BAT detections of sGRB precursors, and we use the timing of the observed precursors to place weak constraints on the crust equation of state. We describe how a larger sample of precursor detections could be used alongside coincident gravitational wave detections of the inspiral by Advanced LIGO class detectors to probe the NS structure. These two types of observations nicely complement one another, since the former constrains the equation of state and structure near the crust-core boundary, while the latter is more sensitive to the core equation of state. I will also discuss shattering flares as electromagnetic counterparts to gravitational wave bursts during parabolic and elliptic encounters in dense star clusters.

  18. Neutron Stars and Thermonuclear X-ray Bursts

    NASA Technical Reports Server (NTRS)

    Bhattacharyya, Sudip

    2007-01-01

    Studies of thermonuclear X-ray bursts can be very useful to constrain the spin rate, mass and radius of a neutron star approaching EOS model of high density cold matter in the neutron star cores. +k Extensive observation and analysis of the data from the rising portions of the bursts - modeling of burst oscillations and thermonuclear flame spreading. +k Theoretical study of thermonuclear flame spreading on the rapidly spinning neutron stars should be done considering all the main physical effects (including magnetic field, nuclear energy generation, Coriolis effect, strong gravity, etc.).

  19. Understanding Neutron Stars using Thermonuclear X-ray Bursts

    NASA Technical Reports Server (NTRS)

    Bhattacharyya, S.

    2007-01-01

    Studies of thermonuclear X-ray bursts can be very useful to constrain the spin rate, mass and radius of a neutron star = EOS model of high density cold matter in the neutron star cores. Extensive observation and analysis of the data from the rising portions of the bursts = modeling of burst oscillations and thermonuclear flame spreading. Theoretical study of thermonuclear flame spreading on the rapidly spinning neutron stars should be done considering all the main physical effects (including magnetic field, nuclear energy generation, Coriolis effect, strong gravity, etc.).

  20. Does mass accretion lead to field decay in neutron stars

    NASA Technical Reports Server (NTRS)

    Shibazaki, N.; Murakami, T.; Shaham, Jacob; Nomoto, K.

    1989-01-01

    The recent discovery of cyclotron lines from gamma-ray bursts indicates that the strong magnetic fields of isolated neutron stars might not decay. The possible inverse correlation between the strength of the magnetic field and the mass accreted by the neutron star suggests that mass accretion itself may lead to the decay of the magnetic field. The spin and magnetic field evolution of the neutron star was calculated under the hypothesis of the accretion-induced field decay. It is shown that the calculated results are consistent with the observations of binary and millisecond radio pulsars.

  1. On the maximum mass of hyperonic neutron stars

    E-print Network

    Elisabeth Massot; Jérôme Margueron; G. Chanfray

    2012-01-13

    Chiral Lagrangian and quark-meson coupling models of hyperon matter are used to estimate the maximum mass of neutron stars. Our relativistic calculations include, for the first time, both Hartree and Fock contributions in a consistent manner. Being related to the underlying quark structure of baryons, these models are considered to be good candidates for describing the dense core of neutron stars. Taking account of the known experimental constraints at saturation density, the equations of state deduced from these relativistic approaches cannot sustain a neutron star with a mass larger than 1.6-1.66 $M_\\odot$.

  2. MUFFINS: Metallurgy Uncovers Forced Fractures Inside Neutron Stars

    NASA Astrophysics Data System (ADS)

    Hoffman, Kelsey L.; Heyl, J. S.

    2011-01-01

    As a result of nuclear reactions within the neutron star crust, even neutron stars that have not accreted matter can have impurities in their crust. These impurities would have an effect on the mechanical properties of the crust, possibly creating a more brittle structure. In order to investigate the properties of an impure crust we are performing molecular dynamic simulations using the Large scale Atomic/Molecular Massively Parallel Simulator (LAMMPS). The simulations are run at fixed energy and volume with the isotopes interacting via a repulsive Yukawa potential. Here we present effects of impurities with respect the the breaking strain in a non-accreting neutron star crust.

  3. Probing neutron-star superfluidity with gravitational-wave data.

    PubMed

    Andersson, N; Comer, G L

    2001-12-10

    We discuss the possibility that future gravitational-wave detectors may be able to detect various modes of oscillation of old, cold neutron stars. We argue that such detections would provide unique insights into the superfluid nature of neutron-star cores, and could also lead to a much improved understanding of pulsar glitches. Our estimates are based on a detector configuration with several narrow-band (cryogenic) interferometers operating as a "xylophone" which could lead to high sensitivity at high frequencies. We also draw on recent advances in our understanding of the dynamics of pulsating superfluid neutron-star cores. PMID:11736491

  4. Light Curves for Rapidly-Rotating Neutron Stars

    E-print Network

    Coire Cadeau; Sharon M. Morsink; Denis Leahy; Sheldon S. Campbell

    2006-09-12

    We present raytracing computations for light emitted from the surface of a rapidly-rotating neutron star in order to construct light curves for X-ray pulsars and bursters. These calculations are for realistic models of rapidly-rotating neutron stars which take into account both the correct exterior metric and the oblate shape of the star. We find that the most important effect arising from rotation comes from the oblate shape of the rotating star. We find that approximating a rotating neutron star as a sphere introduces serious errors in fitted values of the star's radius and mass if the rotation rate is very large. However, in most cases acceptable fits to the ratio M/R can be obtained with the spherical approximation.

  5. MAGNETIC INTERACTIONS IN COALESCING NEUTRON STAR BINARIES

    SciTech Connect

    Piro, Anthony L., E-mail: piro@caltech.edu [Theoretical Astrophysics, California Institute of Technology, 1200 E California Blvd., M/C 350-17, Pasadena, CA 91125 (United States)

    2012-08-10

    It is expected on both evolutionary and empirical grounds that many merging neutron star (NS) binaries are composed of a highly magnetized NS in orbit with a relatively low magnetic field NS. I study the magnetic interactions of these binaries using the framework of a unipolar inductor model. The electromotive force generated across the non-magnetic NS as it moves through the magnetosphere sets up a circuit connecting the two stars. The exact features of this circuit depend on the uncertain resistance in the space between the stars R{sub space}. Nevertheless, I show that there are interesting observational and/or dynamical effects irrespective of its exact value. When R{sub space} is large, electric dissipation as great as {approx}10{sup 46} erg s{sup -1} (for magnetar-strength fields) occurs in the magnetosphere, which would exhibit itself as a hard X-ray precursor in the seconds leading up to merger. With less certainty, there may also be an associated radio transient. When R{sub space} is small, electric dissipation largely occurs in the surface layers of the magnetic NS. This can reach {approx}10{sup 49} erg s{sup -1} during the final {approx}1 s before merger, similar to the energetics and timescales of short gamma-ray bursts. In addition, for dipole fields greater than Almost-Equal-To 10{sup 12} G and a small R{sub space}, magnetic torques spin up the magnetized NS. This drains angular momentum from the binary and accelerates the inspiral. A faster coalescence results in less orbits occurring before merger, which would impact matched-filtering gravitational-wave searches by ground-based laser interferometers and could create difficulties for studying alternative theories of gravity with compact inspirals.

  6. Accuracy of measurement of photographic plates with double stars taken with 26-inch refractor in Pulkovo observatory

    E-print Network

    Boyer, Edmond

    191 Accuracy of measurement of photographic plates with double stars taken with 26-inch refractor of the measurements. The plates contain the images of more than 300 double and multiple stars from Pulkovo double star reliable in the case of double stars, where we measure the relative positions of double star components

  7. Gamow's calculation of the neutron star's critical mass revised

    NASA Astrophysics Data System (ADS)

    Ludwig, Hendrik; Ruffini, Remo

    2014-09-01

    It has at times been indicated that Landau introduced neutron stars in his classic paper of 1932. This is clearly impossible because the discovery of the neutron by Chadwick was submitted more than one month after Landau's work. Therefore, and according to his calculations, what Landau really did was to study white dwarfs, and the critical mass he obtained clearly matched the value derived by Stoner and later by Chandrasekhar. The birth of the concept of a neutron star is still today unclear. Clearly, in 1934, the work of Baade and Zwicky pointed to neutron stars as originating from supernovae. Oppenheimer in 1939 is also well known to have introduced general relativity (GR) in the study of neutron stars. The aim of this note is to point out that the crucial idea for treating the neutron star has been advanced in Newtonian theory by Gamow. However, this pioneering work was plagued by mistakes. The critical mass he should have obtained was 6.9 M ?, not the one he declared, namely, 1.5 M ?. Probably, he was taken to this result by the work of Landau on white dwarfs. We revise Gamow's calculation of the critical mass regarding calculational and conceptual aspects and discuss whether it is justified to consider it the first neutron-star critical mass. We compare Gamow's approach to other early and modern approaches to the problem.

  8. Eccentric mergers of black holes with spinning neutron stars

    E-print Network

    East, William E; Pretorius, Frans

    2015-01-01

    We study dynamical capture binary black hole-neutron star mergers focusing on the effects of the neutron star spin. These events may arise in dense stellar regions, such as globular clusters, where the majority of neutron stars are expected to be rapidly rotating. Using general-relativistic hydrodynamical simulations, we find that even moderate spins can significantly increase the amount of mass in unbound material. In some of the more extreme cases, there can be up to a third of a solar mass in unbound matter. Similarly, large amounts of tidally stripped material can remain bound and eventually accrete onto the black hole --- as much as a tenth of a solar mass in some cases. These simulations demonstrate that it is important to treat neutron star spin in order to make reliable predictions of the gravitational wave and electromagnetic transient signals accompanying these sources.

  9. Effects of superfluidity on spheroidal oscillations of neutron stars

    SciTech Connect

    Collins, T.J.B.; Van Horn, H.M. (Univ. of Rochester, NY (United States)); Epstein, R.I. (Los Alamos National Lab., New Mexico (United States))

    1992-01-01

    The cores and crusts of neutron stars contain neutron superfluid. A short wavelength analysis of the effects of superfluidity on neutron star oscillations (Epstein 1988) revealed greatly changed sound speeds. Subsequently, Van Horn and Epstein (1990) examined the global toroidal oscillation modes and found the effects of superfluidity to be significant for them as well. In this paper the authors report some preliminary results of an investigation of the effects of superfluidity on the global spheroidal oscillations of neutron stars. Specifically they consider the effects of coupling between the superfluid and the lattice in the crust of the star. They find that the s-modes, which are spheroidal shear-wave oscillations of the crust, and the p-modes, or pressure modes, are affected by superfluidity in much the same way as the toroidal modes.

  10. Galactic neutron stars and gamma-ray bursts

    NASA Technical Reports Server (NTRS)

    Hartmann, Dieter; Woosley, S. E.; Epstein, Richard I.

    1990-01-01

    The association of the gamma-ray burst phenomenon with Galactic neutron stars is investigated statistically, and the distance to presently observable gamma-ray bursts is constrained. This is done by calculating the spatial distribution and kinematic properties of a sample of Population I neutron stars and comparing their properties to those of observed gamma-ray bursts. Both brightness distribution and angular distribution on the celestial sphere are employed. Current observations suggest negligible correlation on small angular scales, large-scale isotropy, and a radial distribution that is approximately uniform to the distances currently observed. It is concluded that the distribution of Population I neutron stars is consistent with current observations if gamma-ray bursts occur continuously throughout the neutron star lifetime and if the current sampling depth is at least about 150 pc but not more than roughly 2 kpc.

  11. Chandra Captures Neutron Star Action - Duration: 1:01.

    NASA Video Gallery

    This movie from NASA's Chandra X-ray Observatory shows a fast moving jet of particles produced by a rapidly rotating neutron star, and may provide new insight into the nature of some of the densest...

  12. Molecular Dynamics Simulations of Non-accreting Neutron Star Crusts

    NASA Astrophysics Data System (ADS)

    Hoffman, Kelsey L.; Heyl, J. S.

    2010-02-01

    Neutron stars which do not accrete material can still have impurities in their crust, due to nuclear reactions in the crust. These impurities in the crust could affect the mechanical properties of the neutron star crust. In order to investigate the properties of the crust of a non-accreting neutron star we are performing molecular dynamic simulations of the crust. We are using the Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS), where simulations are run at fixed energy and volume, with the isotopes interacting via a repulsive Yukawa potential. Here we are presenting the preliminary results of the equilibrium structure of the solid neutron star crust using abundances of a non-accreting source.

  13. Properties of nuclei in the neutron star crust

    E-print Network

    Piotr Magierski; Aurel Bulgac; Paul-Henri Heenen

    2001-12-03

    In the present study we investigate the static properties of nuclei in the inner crust of neutron stars. Using the Hartree-Fock method in coordinate space, together with the semiclassical approximation, we examine the patterns of phase transitions.

  14. Calculation of Thermal Conductivity Coefficients for Magnetized Neutron Star

    NASA Astrophysics Data System (ADS)

    Glushikhina, M. V.; Bisnovatyi-Kogan, G. S.

    2015-01-01

    The coefficients that determine the electron heat transfer and diffusion in the crust of neutron stars are calculated on the basis of a solution of the Boltzmann equation with allowance for degeneracy.

  15. Crust cooling of accretion-heated neutron stars

    NASA Astrophysics Data System (ADS)

    Wijnands, Rudy

    2014-09-01

    We propose to continue our successful program to use the observed cooling of the crusts in accreting neutron star systems to probe the properties of ultra-dense matter. Those crusts are heated due to the accretion of matter onto neutron stars during the X-ray outburst and after the outbursts are over the crusts should cool down until they are in equilibrium with the core again. Following this cooling processes in several systems has already given us new insights in the structure of neutron stars (i.e., the crust but also the core and hence in ultra dense matter), but many uncertainties remain. Therefore it is needed to enlarge our sample of well studied sources to obtain better insights in the behavior of how neutron stars react to the accretion of matter.

  16. Temperature-dependent pulsations of superfluid neutron stars

    E-print Network

    M. E. Gusakov; N. Andersson

    2006-11-01

    We examine radial oscillations of superfluid neutron stars at finite internal temperatures. For this purpose we generalize the description of relativistic superfluid hydrodynamics to the case of superfluid mixtures. We show that in a neutron star at hydrostatic and beta-equilibrium the red-shifted temperature gradient is smoothed out by neutron superfluidity (but not by proton superfluidity). We calculate radial oscillation modes of neutron stars assuming "frozen" nuclear composition in the pulsating matter. The resulting pulsation frequencies show a strong temperature dependence in the temperature range (0.1-1) T_cn, where T_cn is the critical temperature of neutron superfluidity. Combining our results with thermal evolution, we obtain a significant evolution of the pulsation spectrum, associated with highly efficient Cooper pairing neutrino emission, for 20 years after superfluidity onset.

  17. Phase transitions in nucleonic matter and neutron-star cooling.

    PubMed

    Khodel, V A; Clark, J W; Takano, M; Zverev, M V

    2004-10-01

    A new scenario for neutron-star cooling is suggested by the correspondence between pion condensation, induced by critical spin-isospin fluctuations, and the metal-insulator phase transition in a 2D electron gas. Above the threshold density for pion condensation, the neutron single-particle spectrum acquires an insulating gap that quenches neutron contributions to neutrino production. In the liquid phase just below the transition, the fluctuations play dual roles by (i) creating a multisheeted neutron Fermi surface that extends to low momenta and activates the normally forbidden direct Urca cooling mechanism, and (ii) amplifying the nodeless P-wave neutron superfluid gap while suppressing S-wave pairing. Lighter stars without a pion-condensed core undergo slow cooling, whereas enhanced cooling occurs in heavier stars via direct Urca emission from a thin shell of the interior. PMID:15524862

  18. Double Star Measurements for 2011 Part 2

    NASA Astrophysics Data System (ADS)

    Smith, Frank

    2015-04-01

    I report 65 measurements of binary systems from 2011.772 to 2011.774. The observations were conducted with the T11 robotic telescope located at the iTelescope Observatory, Mayhill, NM, USA . Discussion includes notes on a number of the observed doubles. Information about instrumentation and methodology and results are included.

  19. Slowly rotating general relativistic superfluid neutron stars with relativistic entrainment

    Microsoft Academic Search

    G. L. Comer

    2004-01-01

    Neutron stars that are cold enough should have two or more\\u000asuperfluids\\/supercondutors in their inner crusts and cores. The implication of\\u000asuperfluidity\\/superconductivity for equilibrium and dynamical neutron star\\u000astates is that each individual particle species that forms a condensate must\\u000ahave its own, independent number density current and equation of motion that\\u000adetermines that current. An important consequence of the

  20. Do pions condense in neutron-star matter

    SciTech Connect

    Wheeler, J W; Gleeson, A M

    1983-04-01

    Pion condensates in neutron-star matter, formed either as new modes, or on states identifiable with those of the free pion are studied. A description of neutron-star matter at finite temperature is formulated upon a suitable basis of realistic interactions in a modified background field description, and leads to the onset of a pion condensate between the density of nuclear matter and the density of free hadrons. This condensate, however, is blocked when strange hadrons are incorporated in the description.

  1. Color Superconductivity and Blinking Proto-Neutron Stars

    E-print Network

    G. W. Carter

    2001-11-27

    If quark matter exists in the cores of neutron stars, it is most likely color superconducting. Thus a phase transition from free to paired quark matter might occur during the first minute of proto-neutron star evolution. In this talk I discuss how critical behavior of the medium will modify neutrino diffusion, possibly leading to a short temporal variation in the neutrino signal detected on Earth.

  2. Neutrino emission from triplet pairing of neutrons in neutron stars

    SciTech Connect

    Leinson, L. B. [Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation RAS, RU-142190 Troitsk, Moscow Region (Russian Federation)

    2010-02-15

    Neutrino emission resulting from the pair breaking and formation processes in the bulk triplet superfluid in neutron stars is investigated taking into account anomalous weak interactions. I consider the problem in the BCS approximation discarding Fermi-liquid effects. By this approach I derive self-consistent equations for anomalous vector and axial-vector vertices of weak interactions taking into account {sup 3}P{sub 2}-{sup 3}F{sub 2} mixing. Further, I simplify the problem and consider pure {sup 3}P{sub 2} pairing with m{sub j}=0, as is adopted in the minimal-cooling paradigm. As was expected because of current conservation, I have obtained a large suppression of neutrino emissivity in the vector channel. More exactly, the neutrino emission through the vector channel vanishes in the nonrelativistic limit V{sub F}=0. The axial channel is also found to be moderately suppressed. Total neutrino emissivity is suppressed by a factor of 1.9x10{sup -1} relative to original estimates using bare weak vertices.

  3. The Origin of Kilohertz QPOs and Implications for Neutron Stars

    E-print Network

    Frederick K. Lamb; M. Coleman Miller; Dimitrios Psaltis

    1998-03-23

    One of the most dramatic discoveries made with the Rossi X-Ray Timing Explorer is that many accreting neutron stars in low-mass binary systems produce strong, remarkably coherent, high-frequency X-ray brightness oscillations. The 325-1200 Hz quasi-periodic oscillations (QPOs) observed in the accretion-powered emission are thought to be produced by gas orbiting very close to the neutron star, whereas the 360-600 Hz brightness oscillations seen during thermonuclear X-ray bursts are produced by one or two hot spots rotating with the star and have frequencies equal to the stellar spin frequency or its first overtone. The oscillations constrain the masses and radii of these neutron stars, which are thought to be the progenitors of the millisecond pulsars. Modeling indicates that the stars have spin frequencies 250-350 Hz and magnetic fields 1e7-5e9 G.

  4. Neutron star formation in theoretical supernovae. Low mass stars and white dwarfs

    SciTech Connect

    Nomoto, K.

    1986-01-01

    The presupernova evolution of stars that form semi-degenerate or strongly degenerate O + Ne + Mg cores is discussed. For the 10 to 13 Msub solar stars, behavior of off-center neon flashes is crucial. The 8 to 10 m/sub solar stars do not ignite neon and eventually collapse due to electron captures. Properties of supernova explosions and neutron stars expected from these low mass progenitors are compared with the Crab nebula. The conditions for which neutron stars form from accretion-induced collapse of white dwarfs in clsoe binary systems is also examined.

  5. Slowly rotating neutron stars and hadronic stars in chiral SU(3) quark mean field model

    E-print Network

    Shaoyu Yin; Jiadong Zang; Ru-Keng Su

    2009-12-31

    The equations of state for neutron matter, strange and non-strange hadronic matter in a chiral SU(3) quark mean field model are applied in the study of slowly rotating neutron stars and hadronic stars. The radius, mass, moment of inertia, and other physical quantities are carefully examined. The effect of nucleon crust for the strange hadronic star is exhibited. Our results show the rotation can increase the maximum mass of compact stars significantly. For big enough mass of pulsar which can not be explained as strange hadronic star, the theoretical approaches to increase the maximum mass are addressed.

  6. Instability windows and evolution of rapidly rotating neutron stars.

    PubMed

    Gusakov, Mikhail E; Chugunov, Andrey I; Kantor, Elena M

    2014-04-18

    We consider an instability of rapidly rotating neutron stars in low-mass x-ray binaries (LMXBs) with respect to excitation of r modes (which are analogous to Earth's Rossby waves controlled by the Coriolis force). We argue that finite temperature effects in the superfluid core of a neutron star lead to a resonance coupling and enhanced damping (and hence stability) of oscillation modes at certain stellar temperatures. Using a simple phenomenological model we demonstrate that neutron stars with high spin frequency may spend a substantial amount of time at these "resonance" temperatures. This finding allows us to explain puzzling observations of hot rapidly rotating neutron stars in LMXBs and to predict a new class of hot, nonaccreting, rapidly rotating neutron stars, some of which may have already been observed and tentatively identified as quiescent LMXB candidates. We also impose a new theoretical limit on the neutron star spin frequency, which can explain the cutoff spin frequency ?730??Hz, following from the statistical analysis of accreting millisecond x-ray pulsars. In addition to explaining the observations, our model provides a new tool to constrain superdense matter properties by comparing measured and theoretically predicted resonance temperatures. PMID:24785021

  7. Spin-up/spin-down of neutron star in Be-X-ray binary system GX 304-1

    NASA Astrophysics Data System (ADS)

    Postnov, K. A.; Mironov, A. I.; Lutovinov, A. A.; Shakura, N. I.; Kochetkova, A. Yu.; Tsygankov, S. S.

    2015-01-01

    We analyse spin-up/spin-down of the neutron star in Be-X-ray binary system GX 304-1 observed by Swift/X-ray telescope (XRT) and Fermi/gamma-ray burst monitor (GBM) instruments in the period of the source activity from 2010 April to 2013 January and discuss possible mechanisms of angular momentum transfer to/from the neutron star. We argue that the neutron star spin-down at quiescent states of the source with an X-ray luminosity of Lx ˜ 1034 erg s-1 between a series of Type I outbursts and spin-up during the outbursts can be explained by quasi-spherical settling accretion on to the neutron star. The outbursts occur near the neutron star periastron passages, where the density is enhanced due to the presence of an equatorial Be-disc tilted to the orbital plane. We also propose an explanation to the counterintuitive smaller spin-up rate observed at higher luminosity in a double-peak Type I outburst due to lower value of the specific angular momentum of matter captured from the quasi-spherical wind from the Be-star by the neutron star moving in an elliptical orbit with eccentricity e ? 0.5.

  8. CCD Double Star Measures: Jack Jones Memorial Observatory Report #1

    NASA Astrophysics Data System (ADS)

    Jones, James

    2008-01-01

    This paper reports on 63 CCD measurements of 58 multiple star systems observed between 2003 and 2007. It also reports on delta mag(V) measurements of selected doubles. Measurements were made using a CCD camera and 8" or 11" SCT. A brief description of methods used is provided.

  9. On the analytic calculation of visual double star orbits

    Microsoft Academic Search

    J. A. Docobo; RamOn Maria Aller

    1985-01-01

    This article studies the existence of periodic Keplerian orbits for visual double stars whose corresponding apparent orbits are to pass through three selected points. The analytical results provide the basis for a new method of calculating orbits which does not require prior calculation of the areal constant. This method is applied to the binary 04404 N 4313.

  10. Numerical experiments on planetary orbits in double stars

    Microsoft Academic Search

    R. Dvorak

    1984-01-01

    This is a numerical study of orbits in the elliptic restricted three-body problem concerning the dependence of the critical orbits on the eccentricity of the primaries. They are defined as being the separatrix between stable and unstable single periodic orbits. As our results are adapted to the existence of planetary orbits in double stars we concentrated first on the P-orbits

  11. Cluster and Double Star multipoint observations of a plasma bubble

    Microsoft Academic Search

    A. P. Walsh; A. N. Fazakerley; A. D. Lahiff; M. Volwerk; A. Grocott; M. W. Dunlop; A. T. Y. Lui; L. M. Kistler; M. Lester; C. Mouikis; Z. Pu; C. Shen; J. Shi; M. G. G. T. Taylor; E. Lucek; T. L. Zhang; I. Dandouras

    2009-01-01

    Depleted flux tubes, or plasma bubbles, are one possible explanation of bursty bulk flows, which are transient high speed flows thought to be responsible for a large proportion of flux transport in the magnetotail. Here we report observations of one such plasma bubble, made by the four Cluster spacecraft and Double Star TC-2 around 14:00 UT on 21 September 2005,

  12. On the eigenvalues of generalized and double generalized stars

    Microsoft Academic Search

    Francesco Barioli; Shaun Fallat

    2005-01-01

    We consider describing all possible spectra of symmetric matrices associated with certain graphs by characterizing all possible ordered multiplicity lists. For generalized and double generalized stars we provide a complete description of all possible eigenvalue sequences. This result is obtained by first verifying all possible multiplicity lists for these graphs which, in fact, turns out to be necessary and sufficient

  13. Double Star Measurements with a Three Inch Tasco Telescope

    NASA Astrophysics Data System (ADS)

    Grisham, Darrell R.; Johnson, Jolyon M.; Genet, Russell M.; Arnold, David L.

    2008-01-01

    Observations were made of three double stars with known separations and position angles using a three inch 1960's Tasco telescope equipped with a Meade astrometric eyepiece. After these observations were completed, their mean values were compared with cataloged values. It was concluded that, under appropriate conditions, a modest aperture Tasco telescope can provide remarkably accurate and precise results.

  14. Searching for New Double Stars with a Computer

    NASA Astrophysics Data System (ADS)

    Bryant, T. V.

    2015-04-01

    The advent of computers with large amounts of RAM memory and fast processors, as well as easy internet access to large online astronomical databases, has made computer searches based on astrometric data practicable for most researchers. This paper describes one such search that has uncovered hitherto unrecognized double stars.

  15. The Equation of State for Supernovae and Neutron Stars

    E-print Network

    Yamamoto, Hirosuke

    The Equation of State for Supernovae and Neutron Stars James M. Lattimer lattimer & Pethick (1971) · Formation of Elements in Neutron Rich Ejected Matter of Supernovae (Sato, Nakazawa & Ikeuchi 1973) · First discussion that matter becomes opaque to electron neutrinos · Supernova Explosion

  16. Measuring neutron-star properties via gravitational waves from neutron-star mergers.

    PubMed

    Bauswein, A; Janka, H-T

    2012-01-01

    We demonstrate by a large set of merger simulations for symmetric binary neutron stars (NSs) that there is a tight correlation between the frequency peak of the postmerger gravitational-wave (GW) emission and the physical properties of the nuclear equation of state (EoS), e.g., expressed by the radius of the maximum-mass Tolman-Oppenheimer-Volkhoff configuration. Therefore, a single measurement of the peak frequency of the postmerger GW signal will constrain the NS EoS significantly. For optimistic merger-rate estimates a corresponding detection with Advanced LIGO is expected to happen within an operation time of roughly a year. PMID:22304250

  17. Resonant shattering of neutron star crusts.

    PubMed

    Tsang, David; Read, Jocelyn S; Hinderer, Tanja; Piro, Anthony L; Bondarescu, Ruxandra

    2012-01-01

    The resonant excitation of neutron star (NS) modes by tides is investigated as a source of short gamma-ray burst (SGRB) precursors. We find that the driving of a crust-core interface mode can lead to shattering of the NS crust, liberating ?10{46}-10{47}??erg of energy seconds before the merger of a NS-NS or NS-black-hole binary. Such properties are consistent with Swift/BAT detections of SGRB precursors, and we use the timing of the observed precursors to place weak constraints on the crust equation of state. We describe how a larger sample of precursor detections could be used alongside coincident gravitational wave detections of the inspiral by Advanced LIGO class detectors to probe the NS structure. These two types of observations nicely complement one another, since the former constrains the equation of state and structure near the crust-core boundary, while the latter is more sensitive to the core equation of state. PMID:22304251

  18. HYDRODYNAMICAL NEUTRON STAR KICKS IN THREE DIMENSIONS

    SciTech Connect

    Wongwathanarat, Annop; Janka, Hans-Thomas; Mueller, Ewald, E-mail: annop@mpa-garching.mpg.d [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching (Germany)

    2010-12-10

    Using three-dimensional (3D) simulations of neutrino-powered supernova explosions, we show that the hydrodynamical kick scenario proposed by Scheck et al. on the basis of two-dimensional (2D) models can yield large neutron star (NS) recoil velocities also in 3D. Although the shock stays relatively spherical, standing accretion-shock and convective instabilities lead to a globally asymmetric mass and energy distribution in the post-shock layer. An anisotropic momentum distribution of the ejecta is built up only after the explosion sets in. Total momentum conservation implies the acceleration of the NS on a timescale of 1-3 s, mediated mainly by long-lasting, asymmetric accretion downdrafts and the anisotropic gravitational pull of large inhomogeneities in the ejecta. In a limited set of 15 M{sub sun} models with an explosion energy of about 10{sup 51} erg, this stochastic mechanism is found to produce kicks from <100 km s{sup -1} to {approx}>500 km s{sup -1}, and kicks {approx}>1000 km s{sup -1} seem possible. Strong rotational flows around the accreting NS do not develop in our collapsing, non-rotating progenitors. The NS spins therefore remain low with estimated periods of {approx}500-1000 ms and no alignment with the kicks.

  19. Magnetically Accreting Isolated Old Neutron Stars

    E-print Network

    Robert E. Rutledge

    2001-01-31

    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 polar cap. We find no examples of MAGACs among previously observed source classes (anomalous X-ray pulsars, soft-gamma-ray repeaters or known IONS). However, MAGACs may be more prevelant in flux-limited X-ray catalogs than their gravitationally accreting counterparts.

  20. Simulations of Axisymmetric Magnetospheres of Neutron Stars

    E-print Network

    S. S. Komissarov

    2005-11-28

    In this paper we present the results of time-dependent simulations of dipolar axisymmetric magnetospheres of neutron stars carried out both within the framework of relativistic magnetohydrodynamics and within the framework of resistive force-free electrodynamics. The results of force-free simulations reveal the inability of our numerical method to accommodate the equatorial current sheets of pulsar magnetospheres and raise a question mark over the robustness of this approach. On the other hand, the MHD approach allows to make a significant progress. We start with a nonrotating magnetically dominated dipolar magnetospheres and follow its evolution as the stellar rotation is switched on. We find that the time-dependent solution gradually approaches the steady state that is very close to the stationary solution of the Pulsar Equation found by Contopoulos et al.(1999). This result suggests that other stationary solutions that have the y-point located well inside the light cylinder are unstable. The role of the particle inertia and pressure on the structure and dynamics of MHD magnetospheres is studied in details, as well as the potential implications of the dissipative processes in the equatorial current sheet. We argue that pulsars may have differentially rotating magnetospheres which develop noticeable structural oscillations and that this may help to explain the nature of the sub-pulse phenomena.

  1. Intriguing triple-mode RR Lyrae star with period doubling

    NASA Astrophysics Data System (ADS)

    Smolec, R.; Soszy?ski, I.; Udalski, A.; Szyma?ski, M. K.; Pietrukowicz, P.; Skowron, J.; Koz?owski, S.; Poleski, R.; Moskalik, P.; Skowron, D.; Pietrzy?ski, G.; Wyrzykowski, ?.; Ulaczyk, K.; Mróz, P.

    2015-03-01

    We report the discovery of an intriguing triple-mode RR Lyrae star found in the Optical Gravitational Lensing Experiment (OGLE) Galactic bulge collection, OGLE-BLG-RRLYR-24137. In the OGLE catalogue, the star was identified as RRd star - double-mode pulsator, pulsating simultaneously in the fundamental and in the first overtone modes. We find that third mode is excited and firmly detect its period doubling. Period ratios are not far from that expected for triple-mode - fundamental, first and third overtone - pulsation. Unfortunately, we cannot reproduce period ratios of the three modes with a consistent set of pulsation models. Therefore the other interpretation, that additional mode is non-radial, is also likely.

  2. Gravitational radiation from rapidly rotating nascent neutron stars

    NASA Technical Reports Server (NTRS)

    Lai, Dong; Shapiro, Stuart L.

    1995-01-01

    We study the secular evolution and gravitational wave signature of a newly formed, rapidly rotating neutron star. The neutron star may arise from core collapse in a massive star or from the accretion-induced collapse of a white dwarf. After a brief dynamical phase, the nascent neutron star settles into an axisymmetric, secularly unstable state. Gravitational radiation drives the star to a nonaxisymmetric, stationary equilibrium configuration via the bar-mode instability. The emitted quasi-periodic gravitational waves have a unique signature: the wave frequency sweeps downward from a few hundred Hertz to zero, while the wave amplitude increase from zero to a maximum and then decays back to zero. Such a wave signal could detected by broadband gravitational wave interferometers currently being constructed. We also characterize two other types of gravitational wave signals that could arise in principle from a rapidly rotating, secularly unstable neutron star: a high-frequency (f greater than or approximately = 1000 Hz) wave which increases the pattern-speed of the star, and a wave that actually increases the angular momentum of the star.

  3. Neutron-Capture Element Abundances in Halo Stars

    E-print Network

    John J. Cowan; Christopher Sneden

    2004-09-22

    We present new abundance observations of neutron-capture elements in Galactic stars. These include new Hubble Space Telescope (HST) detections of the elements Ge, Zr and Pt in a group of 11 halo stars. Correlations between these elements and Eu (obtained with ground-based observations), and with respect to metallicity, are also presented.

  4. Neutron Stars Join The Black Hole Jet Set

    NASA Astrophysics Data System (ADS)

    2007-06-01

    NASA's Chandra X-ray Observatory has revealed an X-ray jet blasting away from a neutron star in a binary system. This discovery may help astronomers understand how neutron stars as well as black holes can generate powerful beams of relativistic particles. The jet was found in Circinus X-1, a system where a neutron star is in orbit around a star several times the mass of the Sun, about 20,000 light years from Earth. A neutron star is an extremely dense remnant of an exploded star consisting of tightly packed neutrons. Many jets have been found originating near black holes - both the supermassive and stellar-mass variety - but the Circinus X-1 jet is the first extended X-ray jet associated with a neutron star in a binary system. This detection shows that the unusual properties of black holes - such as presence of an event horizon and the lack of an actual surface - may not be required to form powerful jets. "Gravity appears to be the key to creating these jets, not some trick of the event horizon," said Sebastian Heinz of the University of Wisconsin at Madison, who led the study. The discovery of this jet with Chandra also reveals how efficient neutron stars can be as cosmic power factories. Heinz and his colleagues estimate that a surprisingly high percentage of the energy available from material falling onto the neutron star is converted into powering the jet. "In terms of energy efficiency across the Universe, this result shows that neutron stars are near the top of the list," said Norbert Schulz, a coauthor from the Massachusetts Institute of Technology in Cambridge. "This jet is almost as efficient as one from a black hole." The Chandra results also help to explain the origin of diffuse lobes of radio emission previously detected around Circinus X-1. The team found the X-ray jets of high-energy particles are powerful enough to create and maintain these balloons of radio-emitting gas. "We've seen enormous radio clouds around supermassive black holes at the centers of galaxies," said Heinz. "What's unusual here is that this pocket-sized version, relatively speaking, is being powered by a neutron star, not a black hole." The main evidence for the newly found jet comes in two extended features in the Chandra data. These two fingers of X-ray emission are separated by about 30 degrees and may represent the outer walls of a wide jet. When overlapped with radio images, these X-ray features, which are at least five light years from the neutron star, closely trace the outline of the radio jet. Another interpretation is that these two features represent two separate, highly collimated jets produced at different times by a precessing neutron star. That is, the neutron star wobbles like a top as it spins and the jet fires at different angles at different times. Jet precession is also consistent with radio observations taken at different times, which show varying orientation angles of the jet. If the precession scenario is correct, Circinus X-1 would possess one of the longest, narrowest jets found in X-ray binary systems to date, representing yet another way in which neutron stars can rival and even outdo their larger black hole relatives. These results will appear in an upcoming issue of The Astrophysical Journal Letters. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the agency's Science Mission Directorate. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass.

  5. Nuclear hydrodynamics in the inner crust of neutron stars

    E-print Network

    Piotr Magierski; Aurel Bulgac

    2003-12-30

    In the inner crust of a neutron star, due to the high density and pressure, nuclei which are still present, are immersed in a neutron superfluid. One then expects that the dynamical properties of nuclei are significantly affected. In order to estimate the magnitude of the effect associated with the presence of a superfluid medium, we formulate the hydrodynamical approach to the nuclear dynamics in the inner crust of neutron stars. We calculate the renormalized nuclear mass and the strength of the medium-induced interaction between nuclei. We argue that these effects noticeably modify the properties of the Coulomb crystal in the inner crust.

  6. Nuclear Matter and Neutron stars in a Parity Doublet Model

    E-print Network

    V. Dexheimer; S. Schramm; D. Zschiesche

    2007-10-23

    We investigate the properties of isospin-symmetric nuclear matter and neutron stars in a chiral model approach adopting the SU(2) parity doublet formulation. This ansatz explicitly incorporates chiral symmetry restoration with the limit of degenerate masses of the nucleons and their parity partners. Instead of searching for an optimized parameter set we explore the general parameter dependence of nuclear matter and star properties in the model. We are able to get a good description of ground state nuclear matter as well as large values of mass for neutron stars in agreement with observation.

  7. Mass and radius formulas for low-mass neutron stars

    E-print Network

    Sotani, Hajime; Oyamatsu, Kazuhiro; Ohnishi, Akira

    2014-01-01

    Neutron stars, produced at the death of massive stars, are often regarded as giant neutron-rich nuclei. This picture is especially relevant for low-mass (below about solar mass) neutron stars, where non-nucleonic components are not expected to occur. Due to the saturation property of nucleonic matter, leading to the celebrated liquid-drop picture of atomic nuclei, empirical nuclear masses and radii can be approximately expressed as function of atomic mass number. It is, however, not straightforward to express masses and radii of neutron stars even in the low-mass range where the structure is determined by a balance between the pressure of neutron-rich nucleonic matter and the gravity. Such expressions would be of great use given possible simultaneous mass and radius measurements. Here we successfully construct theoretical formulas for the masses and radii of low-mass neutron stars from various models that are consistent with empirical masses and radii of stable nuclei. In this process, we discover a new equat...

  8. Decomposition of Odd-hole-free Graphs by Double Star Cutsets and 2-Joins

    E-print Network

    Cornuejols, Gerard P.

    Decomposition of Odd-hole-free Graphs by Double Star Cutsets and 2-Joins Michele Conforti #3; G#19-hole-free graphs, even-signable graphs, decomposition, 2-join, double star cutset. #3; Dipartimento di Matematica as an induced subgraph a chordless cycle of odd length greater than three) with double star cutsets and 2-joins

  9. Adversary degree-associated reconstruction number of double-stars , Huangping Shi

    E-print Network

    West, Douglas B.

    Adversary degree-associated reconstruction number of double-stars Meijie Ma , Huangping Shi,n be the double- star with central vertices having m and n leaf neighbors. For 1 m n, we prove that always adrn: degree-associated reconstruction number, double-star 1 Introduction The Reconstruction Conjecture

  10. VizieR Online Data Catalog: Double stars measurements at Nice Obs. III. (Thorel, 2000)

    NASA Astrophysics Data System (ADS)

    Thorel, J.-C.

    2000-10-01

    We present recent measurements of visual double stars made at the Nice Observatory (3rd series). We also report the discovery of a new double star: JCT 4. Moreover we give a more precise position of the double star DOO 35. (1 data file).

  11. The companion candidate near Fomalhaut - a background neutron star?

    NASA Astrophysics Data System (ADS)

    Neuhäuser, R.; Hohle, M. M.; Ginski, C.; Schmidt, J. G.; Hambaryan, V. V.; Schmidt, T. O. B.

    2015-03-01

    The directly detected planetary mass companion candidate close to the young, nearby star Fomalhaut is a subject of intense discussion. While the detection of common proper motion led to the interpretation as Jovian-mass companion, later non-detections in the infrared raised doubts. Recent astrometric measurements indicate a belt crossing or highly eccentric orbit for the object, if a companion, making the planetary interpretation potentially even more problematic. In this study we discuss the possibility of Fomalhaut b being a background object with a high proper motion. By analysing the available photometric and astrometric data of the object, we show that they are fully consistent with a neutron star: neutron stars are faint, hot (blue), and fast moving. Neutron stars with an effective temperature of the whole surface area being 112 000-126 500 K (with small to negligible extinction) at a distance of roughly 11 pc (best fit) would be consistent with all observables, namely with the photometric detections in the optical, with the upper limits in the infrared and X-rays, as well as with the astrometry (consistent with a distances of 11 pc or more and high proper motion as typical for neutron stars) and non-detection of pulsation (not beamed). We consider the probability of finding an unrelated object or even a neutron star nearby and mostly co-aligned in proper motion with Fomalhaut A and come to the conclusion that this is definitely well possible.

  12. The Nonradial Oscillation Node Precession of Neutron Stars

    E-print Network

    Haochen Li

    2005-06-28

    The standing wave nodes of nonradial oscillations on a neutron star crust will drift with a definite angle velocity around rotational pole due to the rotation of neutron stars. This is called the nonradial oscillation node precession of neutron stars. This article estimated the precession velocity and pointed out that it merely lies on the star's rotation velocity and the angular order of spherical harmonic $l$ by one order approximation. If we suppose that oscillations effect the particles' escaping from the polar cap of a neutron star, so that the antinode and node areas of the standing waves have different radiative intensity, several unusual conclusions are acquired by reviewing the observation of pulsars which had already been taken as neutron stars. For example, the drifting subpulse period $P_{3}$ can be gotten from the width of subpulses and order $l$; the larger velocity drift may produce the peak structure of average pulse profiles; the dissimilar radiation phenomena between neighboring periods generated from drift provide a reasonable explanation of interpulses which have been found on some pulsars.

  13. HUBBLE SEES A NEUTRON STAR ALONE IN SPACE

    NASA Technical Reports Server (NTRS)

    2002-01-01

    his is the first direct look, in visible light, at a lone neutron star, as seen by NASA's Hubble Space Telescope. The Hubble results show the star is very hot (1.2 million degrees Fahrenheit at the surface), and can be no larger than 16.8 miles (28 kilometers) across. These results prove that the object must be a neutron star, because no other known type of object can be this hot, small, and dim (below 25th magnitude). The first clue that there was a neutron star at this location came in 1992, when the ROSAT (the Roentgen Satellite) found a bright X-ray source without any optical counterpart in optical sky surveys. Hubble's Wide Field Planetary Camera 2 was used in October 1996 to undertake a sensitive search for the optical object, and found a stellar pinpoint of light within only 2 arc seconds (1/900th the diameter of the Moon) of the X-ray position. Astronomers haven't directly measured the neutron star's distance, but fortunately the neutron star lies in front of a molecular cloud known to be about 400 light-years away in the southern constellation Corona Australis. Credit: Fred Walter (State University of New York at Stony Brook), and NASA

  14. Self-similarity relations for cooling superfluid neutron stars

    NASA Astrophysics Data System (ADS)

    Shternin, P. S.; Yakovlev, D. G.

    2015-02-01

    We consider models of cooling neutron stars with nucleon cores which possess moderately strong triplet-state superfluidity of neutrons. When the internal temperature drops below the maximum of the critical temperature over the core, TC, this superfluidity sets in. It produces a neutrino outburst due to Cooper pairing of neutrons which greatly accelerates the cooling. We show that the cooling of the star with internal temperature T within 0.6 TC ? T ? TC is described by analytic self-similar relations. A measurement of the effective surface temperature of the star and its decline, supplemented by assumptions on star's mass, radius and composition of heat-blanketing envelope, allows one to construct a family of cooling models parametrized by the value of TC. Each model reconstructs cooling history of the star including its neutrino emission level before neutron superfluidity onset and the intensity of Cooper pairing neutrinos. The results are applied to interpret the observations of the neutron star in the Cassiopeia A supernova remnant.

  15. Will black hole-neutron star binary inspirals tell us about the neutron star equation of state?

    Microsoft Academic Search

    Francesco Pannarale; Luciano Rezzolla; Frank Ohme; Jocelyn S. Read

    2011-01-01

    The strong tidal forces that arise during the last stages of the life of a black hole-neutron star binary may severely distort, and possibly disrupt, the star. Both phenomena will imprint signatures about the stellar structure in the emitted gravitational radiation. The information from the disruption, however, is confined to very high frequencies, where detectors are not very sensitive. We

  16. High energy gamma rays from old accreting neutron stars

    E-print Network

    P. Blasi

    1996-06-28

    We consider a magnetized neutron star with accretion from a companion star or a gas cloud around it, as a possible source of gamma rays with energy between $100$ $MeV$ and $10^{14}-10^{16}~eV$. The flow of the accreting plasma is terminated by a shock at the Alfv\\'en surface. Such a shock is the site for the acceleration of particles up to energies of $\\sim 10^{15}-10^{17}~eV$; gamma photons are produced in the inelastic $pp$ collisions between shock-accelerated particles and accreting matter. The model is applied to old neutron stars both isolated or in binary systems. The gamma ray flux above $100~MeV$ is not easily detectable, but we propose that gamma rays with very high energy could be used by Cherenkov experiments as a possible signature of isolated old neutron stars in dense clouds in our galaxy.

  17. Limits on self-interacting dark matter from neutron stars.

    PubMed

    Kouvaris, Chris

    2012-05-11

    We impose new severe constraints on the self-interactions of fermionic asymmetric dark matter based on observations of nearby old neutron stars. Weakly interacting massive particle (WIMP) self-interactions mediated by Yukawa-type interactions can lower significantly the number of WIMPs necessary for gravitational collapse of the WIMP population accumulated in a neutron star. Even nearby neutron stars located at regions of low dark matter density can accrete a sufficient number of WIMPs that can potentially collapse, form a mini black hole, and destroy the host star. Based on this, we derive constraints on the WIMP self-interactions which in some cases are by several orders of magnitude stricter than the ones from the bullet cluster. PMID:23003023

  18. Improved Universality in the Neutron Star Three-Hair Relations

    E-print Network

    Majumder, Barun; Yunes, Nicolas

    2015-01-01

    No-hair like relations between the multipole moments of the exterior gravitational field of neutron stars have recently been found to be approximately independent of the star's internal structure. This approximate, equation-of-state universality arises after one adimensionalizes the multipole moments appropriately, which then begs the question of whether there are better ways to adimensionalize the moments to obtain stronger universality. We here investigate this question in detail by considering slowly-rotating neutron stars both in the non-relativistic limit and in full General Relativity. We find that there exist normalizations that lead to stronger equation-of-state universality in the relations among the moment of inertia and the quadrupole, octopole and hexadecapole moments of neutron stars. We determine the optimal normalization that minimizes the equation-of-state dependence in these relations. The results found here may have applications in the modeling of X-ray pulses and atomic line profiles from m...

  19. Fast radio bursts: the last sign of supramassive neutron stars

    NASA Astrophysics Data System (ADS)

    Falcke, Heino; Rezzolla, Luciano

    2014-02-01

    Context. Several fast radio bursts have been discovered recently, showing a bright, highly dispersed millisecond radio pulse. The pulses do not repeat and are not associated with a known pulsar or gamma-ray burst. The high dispersion suggests sources at cosmological distances, hence implying an extremely high radio luminosity, far larger than the power of single pulses from a pulsar. Aims: We suggest that a fast radio burst represents the final signal of a supramassive rotating neutron star that collapses to a black hole due to magnetic braking. The neutron star is initially above the critical mass for non-rotating models and is supported by rapid rotation. As magnetic braking constantly reduces the spin, the neutron star will suddenly collapse to a black hole several thousand to million years after its birth. Methods: We discuss several formation scenarios for supramassive neutron stars and estimate the possible observational signatures making use of the results of recent numerical general-relativistic calculations. Results: While the collapse will hide the stellar surface behind an event horizon, the magnetic-field lines will snap violently. This can turn an almost ordinary pulsar into a bright radio "blitzar": accelerated electrons from the travelling magnetic shock dissipate a significant fraction of the magnetosphere and produce a massive radio burst that is observable out to z > 0.7. Only a few per cent of the neutron stars need to be supramassive in order to explain the observed rate. Conclusions: We suggest the intriguing possibility that fast radio bursts might trace the solitary and almost silent formation of stellar mass black holes at high redshifts. These bursts could be an electromagnetic complement to gravitational-wave emission and reveal a new formation and evolutionary channel for black holes and neutron stars that are not seen as gamma-ray bursts. If supramassive neutron stars are formed at birth and not by accretion, radio observations of these bursts could trace the core-collapse supernova rate throughout the universe.

  20. Double mode RR Lyrae stars in Omega Centauri

    E-print Network

    A. Olech; P. Moskalik

    2008-12-22

    Aim: The aim of this work was to search for double mode pulsators among RR Lyr variables of globular cluster Omega Cen. Methods: We conducted a systematic frequency analysis of CASE photometry of Omega Cen RR Lyr stars. We searched for periodicities using Fourier and ANOVA periodograms, combined with consecutive prewhitening technique. Results: We discovered six double mode pulsators, with the first overtone and a secondary mode of higher frequency simultaneously excited. These are the first double mode RR Lyr stars identified in Omega Cen. In variable V10 period ratio of the two modes is 0.80, which corresponds to pulsations in the first and second radial overtones. In V19 and V105 we found unexpected period ratio of 0.61. Three other stars display period ratios of either ~0.80 or ~0.61, depending on the choice of aliases. Conclusions: While the period ratio of ~0.80 is easy to interpret in terms of two lowest radial overtones, the value of ~0.61 cannot be explained by any two radial modes. Thus, V19 and V105 are the first members of a new class of double mode RR Lyr pulsators.

  1. "Doublet", Neutron and Neutron stars --- An essay on Landau and Neutron stars

    E-print Network

    Renxin Xu

    2011-03-02

    The concept of extremely dense matter at supra-nuclear density was first speculated by L. Landau in the beginning of 1930s when neutron was just discovered. A historical review on these issues not only explains the interaction between micro and cosmic physics, but also has profound implications for scientific innovation. It is surely meaningful in realistic physics education to look back to this history. (The review was published in Chinese.)

  2. Axisymmetric oscillations of magnetic neutron stars

    E-print Network

    Umin Lee

    2006-10-06

    We calculate axisymmetric oscillations of rotating neutron stars composed of the surface fluid ocean, solid crust, and fluid core, taking account of a dipole magnetic field as strong as $B_S\\sim 10^{15}$G at the surface. The adiabatic oscillation equations for the solid crust threaded by a dipole magnetic field are derived in Newtonian dynamics, on the assumption that the axis of rotation is aligned with the magnetic axis so that perturbations on the equilibrium can be represented by series expansions in terms of spherical harmonic functions $Y_l^m(\\theta,\\phi)$ with different degrees $l$ for a given azimuthal wave number $m$ around the the magnetic axis. Although the three component models can support a rich variety of oscillation modes, axisymmetric ($m=0$) toroidal $_{l}t_n$ and spheroidal $_ls_n$ shear waves propagating in the solid crust are our main concerns, where $l$ and $n$ denote the harmonic degree and the radial order of the modes, respectively. In the absence of rotation, axisymmetric spheroidal and toroidal modes are completely decoupled, and we consider the effects of rotation on the oscillation modes only in the limit of slow rotation. We find that the oscillation frequencies of the fundamental toroidal torsional modes $_{l}t_n$ in the crust are hardly affected by the magnetic field as strong as $B_S\\sim 10^{15}$G at the surface. As the radial order $n$ of the shear modes in the crust becomes higher, however, both spheroidal and toroidal modes become susceptible to the magnetic field and their frequencies in general get higher with increasing $B_S$. We also find that the surface $g$ modes and the crust/ocean interfacial modes are suppressed by a strong magnetic field, and that there appear magnetic modes in the presence of a strong magnetic field.

  3. Neutron Stars in a Varying Speed of Light Theory

    E-print Network

    A. W. Whinnett

    2003-05-21

    We study neutron stars in a varying speed of light (VSL) theory of gravity in which the local speed of light depends upon the value of a scalar field $\\phi$. We find that the masses and radii of the stars are strongly dependent on the strength of the coupling between $\\phi$ and the matter field and that for certain choices of coupling parameters, the maximum neutron star mass can be arbitrarily small. We also discuss the phenomenon of cosmological evolution of VSL stars (analogous to the gravitational evolution in scalar-tensor theories) and we derive a relation showing how the fractional change in the energy of a star is related to the change in the cosmological value of the scalar field.

  4. The mass ratio distribution of short period double degenerate stars

    Microsoft Academic Search

    P. F. L. Maxted; T. R. Marsh; C. K. J. Moran

    2002-01-01

    Short period double degenerates (DDs) are close white dwarf - white dwarf\\u000abinary stars which are the result of the evolution of interacting binary stars.\\u000aWe present the first definitive measurements of the mass ratio for two DDs,\\u000aWD0136+768 and WD1204+450, and an improved measurement of the mass ratio for\\u000aWD0957-666. We compare the properties of the 6 known DDs

  5. Neutron-capture Nucleosynthesis in the First Stars

    NASA Astrophysics Data System (ADS)

    Roederer, Ian U.; Preston, George W.; Thompson, Ian B.; Shectman, Stephen A.; Sneden, Christopher

    2014-04-01

    Recent studies suggest that metal-poor stars enhanced in carbon but containing low levels of neutron-capture elements may have been among the first to incorporate the nucleosynthesis products of the first generation of stars. We have observed 16 stars with enhanced carbon or nitrogen using the MIKE Spectrograph on the Magellan Telescopes at Las Campanas Observatory and the Tull Spectrograph on the Smith Telescope at McDonald Observatory. We present radial velocities, stellar parameters, and detailed abundance patterns for these stars. Strontium, yttrium, zirconium, barium, europium, ytterbium, and other heavy elements are detected. In four stars, these heavy elements appear to have originated in some form of r-process nucleosynthesis. In one star, a partial s-process origin is possible. The origin of the heavy elements in the rest of the sample cannot be determined unambiguously. The presence of elements heavier than the iron group offers further evidence that zero-metallicity rapidly rotating massive stars and pair instability supernovae did not contribute substantial amounts of neutron-capture elements to the regions where the stars in our sample formed. If the carbon- or nitrogen-enhanced metal-poor stars with low levels of neutron-capture elements were enriched by products of zero-metallicity supernovae only, then the presence of these heavy elements indicates that at least one form of neutron-capture reaction operated in some of the first stars. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile, and The McDonald Observatory of The University of Texas at Austin.

  6. Mergers of binary neutron stars with realistic spin

    E-print Network

    Sebastiano Bernuzzi; Tim Dietrich; Wolfgang Tichy; Bernd Bruegmann

    2014-06-06

    Simulations of binary neutron stars have seen great advances in terms of physical detail and numerical quality. However, the spin of the neutron stars, one of the simplest global parameters of binaries, remains mostly unstudied. We present the first, fully nonlinear general relativistic dynamical evolutions of the last three orbits for constraint satisfying initial data of spinning neutron star binaries, with astrophysically realistic spins aligned and anti-aligned to the orbital angular momentum. The initial data is computed with the constant rotational velocity approach. The dynamics of the systems is analyzed in terms of gauge-invariant binding energy vs. orbital angular momentum curves. By comparing to a binary black hole configuration we can estimate the different tidal and spin contributions to the binding energy for the first time. First results on the gravitational wave forms are presented. The phase evolution during the orbital motion is significantly affected by spin-orbit interactions, leading to delayed or early mergers. Furthermore, a frequency shift in the main emission mode of the hyper massive neutron star is observed. Our results suggest that a detailed modeling of merger waveforms requires the inclusion of spin, even for the moderate magnitudes observed in binary neutron star systems.

  7. Shapiro delay measurement of a two solar mass neutron star

    E-print Network

    Paul Demorest; Tim Pennucci; Scott Ransom; Mallory Roberts; Jason Hessels

    2010-10-27

    Neutron stars are composed of the densest form of matter known to exist in our universe, and thus provide a unique laboratory for exploring the properties of cold matter at super-nuclear density. Measurements of the masses or radii of these objects can strongly constrain the neutron-star matter equation of state, and consequently the interior composition of neutron stars. Neutron stars that are visible as millisecond radio pulsars are especially useful in this respect, as timing observations of the radio pulses provide an extremely precise probe of both the pulsar's motion and the surrounding space-time metric. In particular, for a pulsar in a binary system, detection of the general relativistic Shapiro delay allows us to infer the masses of both the neutron star and its binary companion to high precision. Here we present radio timing observations of the binary millisecond pulsar PSR J1614-2230, which show a strong Shapiro delay signature. The implied pulsar mass of 1.97 +/- 0.04 M_sun is by far the highest yet measured with such certainty, and effectively rules out the presence of hyperons, bosons, or free quarks at densities comparable to the nuclear saturation density.

  8. Neutron resonances in few-body systems and the EOS of neutron star crust

    E-print Network

    N. Takibayev; K. Kato; M. Takibayeva; A. Sarsembayeva; D. Nasirova

    2012-12-03

    The effective interactions formed by neutron rescattering between the nuclei fixed in nodes of the crystalline lattice of neutron star crusts have been considered. In the case of two-body resonances in neutron-nucleus subsystems new neutron resonances of few-body nature come into existence in the overdense crystal under certain conditions. The energies and widths of new resonances get additional dependence on the lattice parameters. The effective interactions result in nonlinear correction to the equation of state determined by the balance of gravitational, Coulomb and nuclear resonance forces. This leads to resonant oscillations of density in the accordant layers of crusts that are accompanied by oscillations of gamma radiation. The phenomena may clarify some processes connected with few-body neutron resonances in neutron star crusts, that have influence on the microstructure of pulsar impulses.

  9. Plasma magnetosphere of rotating magnetized neutron star in the braneworld

    NASA Astrophysics Data System (ADS)

    Morozova, V. S.; Ahmedov, B. J.; Abdujabbarov, A. A.; Mamadjanov, A. I.

    2010-12-01

    Plasma magnetosphere surrounding rotating magnetized neutron star in the braneworld has been studied. For the simplicity of calculations Goldreich-Julian charge density is analyzed for the aligned neutron star with zero inclination between magnetic field and rotation axis. From the system of Maxwell equations in spacetime of slowly rotating star in braneworld, second-order differential equation for electrostatic potential is derived. Analytical solution of this equation indicates the general relativistic modification of an accelerating electric field and charge density along the open field lines by brane tension. The implication of this effect to the magnetospheric energy loss problem is underlined. It was found that for initially zero potential and field on the surface of a neutron star, the amplitude of the plasma mode created by Goldreich-Julian charge density will increase in the presence of the negative brane charge. Finally we derive the equations of motion of test particles in magnetosphere of slowly rotating star in the braneworld. Then we analyze particle motion in the polar cap and show that brane tension can significantly change conditions for particle acceleration in the polar cap region of the neutron star.

  10. Plasma Magnetosphere of Rotating Magnetized Neutron Star in the Braneworld

    E-print Network

    V. S. Morozova; B. J. Ahmedov; A. A. Abdujabbarov; A. I. Mamadjanov

    2010-04-23

    Plasma magnetosphere surrounding rotating magnetized neutron star in the braneworld has been studied. For the simplicity of calculations Goldreich-Julian charge density is analyzed for the aligned neutron star with zero inclination between magnetic field and rotation axis. From the system of Maxwell equations in spacetime of slowly rotating star in braneworld, second-order differential equation for electrostatic potential is derived. Analytical solution of this equation indicates the general relativistic modification of an accelerating electric field and charge density along the open field lines by brane tension. The implication of this effect to the magnetospheric energy loss problem is underlined. It was found that for initially zero potential and field on the surface of a neutron star, the amplitude of the plasma mode created by Goldreich-Julian charge density will increase in the presence of the negative brane charge. Finally we derive the equations of motion of test particles in magnetosphere of slowly rotating star in the braneworld. Then we analyze particle motion in the polar cap and show that brane tension can significantly change conditions for particle acceleration in the polar cap region of the neutron star.

  11. A debris disk around an isolated young neutron star.

    PubMed

    Wang, Zhongxiang; Chakrabarty, Deepto; Kaplan, David L

    2006-04-01

    Pulsars are rotating, magnetized neutron stars that are born in supernova explosions following the collapse of the cores of massive stars. If some of the explosion ejecta fails to escape, it may fall back onto the neutron star or it may possess sufficient angular momentum to form a disk. Such 'fallback' is both a general prediction of current supernova models and, if the material pushes the neutron star over its stability limit, a possible mode of black hole formation. Fallback disks could dramatically affect the early evolution of pulsars, yet there are few observational constraints on whether significant fallback occurs or even the actual existence of such disks. Here we report the discovery of mid-infrared emission from a cool disk around an isolated young X-ray pulsar. The disk does not power the pulsar's X-ray emission but is passively illuminated by these X-rays. The estimated mass of the disk is of the order of 10 Earth masses, and its lifetime (> or = 10(6) years) significantly exceeds the spin-down age of the pulsar, supporting a supernova fallback origin. The disk resembles protoplanetary disks seen around ordinary young stars, suggesting the possibility of planet formation around young neutron stars. PMID:16598251

  12. Sensitivity of neutron star properties to the equation of state

    NASA Astrophysics Data System (ADS)

    Fattoyev, Farrooh

    2011-01-01

    The subject of this doctoral dissertation is to study the equations of state of nuclear and neutron-star matter. We tackle this problem by employing several models of the relativistic effective interactions. The relativistic effective interactions and their applications to the ground-state properties of medium to heavy nuclei have enjoyed enormous success for the past three decades. With just a few model parameters calibrated to the ground state properties of the closed-shell nuclei, these models exhibit and encode a great amount of physics. However, theses models are untested far away from their narrow window of applicability. In particular, while these models tend to agree on the saturation properties of symmetric nuclear matter, they largely disagree on its density and isospin dependence, especially in the region of high densities and large proton-neutron asymmetries. In order to better understand the properties of nuclear matter at these extreme regions of isospin asymmetry and high-densities, we will apply these models to predict several neutron star properties. Since the matter in the neutron stars are very neutron-rich, while the density of matter in neutron stars spans over a wide range of magnitudes, these compact objects remain unique laboratories for probing the equation of state of neutron-rich matter under conditions unattainable by terrestrial experiments. Thus it is expected that at least the following neutron star properties must be sensitive to the underlying equation of state: maximum mass, typical radii, moments of inertia (both total and crustal), redshifts, and cooling mechanism. We present numerical solutions and in some cases also analytical solutions to each of the properties above. In particular, the sensitivity of the stellar moment of inertia to the neutron-star matter equation of state is examined using accurately-calibrated relativistic mean-field models. We probe this sensitivity by tuning both the density dependence of the symmetry energy and the high density component of the equation of state, properties that are at present poorly constrained by existing laboratory data. Particularly attractive is the study of the fraction of the moment of inertia contained in the solid crust. Analytic treatments of the crustal moment of inertia reveal a high sensitivity to the transition pressure at the core-crust interface. Motivated by a recent astrophysical measurement of the pressure of cold matter above nuclear-matter saturation density, we compute the equation of state of neutron-star matter using various accurately calibrated relativistic models. We found the predictions of these models to be in fairly good agreement with the measured equation of state. In the effort to explain the observational data we introduce a new relativistic effective interaction that is simultaneously constrained by the properties of finite nuclei, their collective excitations, and neutron-star properties. By adjusting two of the empirical parameters of the theory, one can efficiently tune the neutron skin thickness of 208Pb and the maximum neutron star mass. The new effective interaction is moderately soft at intermediate densities and relatively stiff at high densities. It is fitted to a neutron skin thickness in 208Pb of only Rn--Rp = 0.16 fm and a moderately large maximum neutron star mass of 1.94 MSun consistent with the latest observation. Last, theoretical uncertainties in the predictions of relativistic mean-field models are estimated using a chi-square minimization procedure that is implemented by studying the small oscillations around the chi-square minimum. It is shown that such statistical analysis provides access to a wealth of information that would normally remain hidden. The power of covariance analysis is illustrated in two relativistic mean field models. By performing this analysis one obtains meaningful theoretical uncertainties for both model parameters and predicted observables. Moreover, it is shown, how covariance analysis is able to establish robust correlations between physical observables.

  13. Discontinuous SVPWM Techniques for Double Star Induction Motor Drive Control

    Microsoft Academic Search

    Khoudir Marouani; Lotfi Baghli; Djafar Hadiouche; Abdelaziz Kheloui; Abderrezak Rezzoug

    2006-01-01

    In this paper, we present SVPWM control techniques suitable for a double-star induction motor drive (DSIM). The induction machine has two sets of three-phase stator windings spatially shifted by 30 electrical degrees. Each set of three-phase stator windings is fed by a three-phase inverter. Continuous and discontinuous space vector PWM techniques are presented. Implementation on a DSP controller board is

  14. Neutron Star Kinematics: Pulsar Parallaxes, Bow Shock Nebulae and the Interstellar Medium

    NASA Astrophysics Data System (ADS)

    Chatterjee, S.

    2003-12-01

    The measurement of distances is a fundamental problem in astronomy. Parallaxes and proper motions of pulsars provide model-independent estimates of their distances and velocities, allowing us to probe the physics of neutron stars, constrain core collapse phenomena in supernovae, and investigate the distribution of matter in the interstellar medium. Here we present high-precision measurements of the trigonometric parallaxes and proper motions of three radio pulsars using the NRAO Very Long Baseline Array, and discuss how they have been used to investigate the interstellar medium, as well as the birth sites, cooling curves, and velocity distribution of neutron stars. Bow shocks and pulsar wind nebulae probe the interaction of neutron star relativistic winds with the interstellar medium. We utilize scaling laws derived for bow shock nebulae, in combination with estimates of neutron star distances and velocities, to extract information about the interstellar medium. The spectacular Guitar nebula, produced by a high velocity but otherwise unremarkable neutron star, was observed at two epochs with the Hubble Space Telescope. We report time evolution in the position and morphology of the nebula, and infer the existence of small scale density fluctuations in the interstellar medium. Increases in the sample of precise astrometric measurements will enable many such scientific applications: we introduce an ongoing project with the Very Long Baseline Array, which is expected to at least double the number of measured pulsar parallaxes in the next two years. This work was supported in part by NSF grants AST 9819931 and AST 0206036 to Cornell University. NRAO is a facility of the NSF operated under cooperative agreement by Associated Universities, Inc. Observations made with the NASA/ESA Hubble Space Telescope were obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc.

  15. Universality in quasi-normal modes of neutron stars

    NASA Astrophysics Data System (ADS)

    Tsui, L. K.; Leung, P. T.

    2005-03-01

    We study universality in gravitational waves emitted from non-rotating neutron stars characterized by different equations of state (EOSs). We find that the quasi-normal mode frequencies of such waves, including the w-modes and the f-mode, display similar universal scaling behaviours that hold for most EOSs. Such behaviours are shown to stem from the mathematical structure of the axial and the polar gravitational wave equations, and the fact that the mass distribution function can be approximated by a cubic-quintic polynomial in the radius. As a benchmark for other realistic neutron stars, a simple model of neutron stars is adopted here to reproduce the pulsation frequencies and the generic scaling behaviours mentioned above with good accuracy.

  16. Gamma-ray bursts and neutron star field decay

    NASA Technical Reports Server (NTRS)

    Hartmann, Dieter; Blumenthal, George; Chuang, Kuan-Wen; Hurley, Kevin; Kargatis, Vincent; Liang, Edison; Linder, Eric

    1992-01-01

    Assuming a Galactic origin of gamma-ray bursts, we use pulsar data to calculate the spatial distribution of neutron stars and determine the sampling depths of current detectors. Based on these distance limits, we calculate the corresponding age distribution of Galactic neutron stars and apply an exponential field decay model to test whether the observed high incidence rate of cyclotron lines is consistent with suggested field decay time scales of order 10 exp 7 years. We find that the properties of the observed population of gamma-ray bursts are inconsistent with the idea that bursts originate at arbitrary times on neutron stars whose fields decay on time scales shorter than about 10 exp 9 years. Possible interpretations of this inconsistency are discussed.

  17. Rapidly rotating neutron stars in $R$-squared gravity

    E-print Network

    Yazadjiev, Stoytcho S; Kokkotas, Kostas D

    2015-01-01

    $f(R)$ theories of gravity are one of the most popular alternative explanations for dark energy and therefore studying the possible astrophysical implications of these theories is an important task. In the present paper we make a substantial advance in this direction by considering rapidly rotating neutron stars in $R^2$ gravity. The results are obtained numerically and the method we use is non-perturbative and self-consistent. The neutron star properties, such as mass, radius and moment of inertia, are studied in detail and the results show that rotation magnifies the deviations from general relativity and the maximum mass and moment of inertia can reach very high values. This observation is similar to previous studies of rapidly rotating neutron stars in other alternative theories of gravity, such as the scalar-tensor theories, and it can potentially lead to strong astrophysical manifestations.

  18. Determining the properties of accretion-gap neutron stars

    NASA Technical Reports Server (NTRS)

    Kluzniak, Wlodzimierz; Michelson, Peter; Wagoner, Robert V.

    1990-01-01

    If neutron stars have radii as small as has been argued by some, observations of accretion-powered X-rays could verify the existence of innermost stable circular orbits (predicted by general relativity) around weakly magnetized neutron stars. This may be done by detecting X-ray emission from clumps of matter before and after they cross the gap (where matter cannot be supported by rotation) between the inner accretion disk and the stellar surface. Assuming the validity of general relativity, it would then be possible to determine the masses of such neutron stars independently of any knowledge of binary orbital parameters. If an accurate mass determination were already available through any of the methods conventionally used, the new mass determination method proposed here could then be used to quantitatively test strong field effects of gravitational theory.

  19. Persistent crust-core spin lag in neutron stars

    E-print Network

    Glampedakis, Kostas

    2015-01-01

    It is commonly believed that the magnetic field threading a neutron star provides the ultimate mechanism (on top of fluid viscosity) for enforcing long-term corotation between the slowly spun down solid crust and the liquid core. We show that this argument fails for axisymmetric magnetic fields with closed field lines in the core, the commonly used `twisted torus' field being the most prominent example. The failure of such magnetic fields to enforce global crust-core corotation leads to the development of a persistent spin lag between the core region occupied by the closed field lines and the rest of the crust and core. We discuss the repercussions of this spin lag for the evolution of the magnetic field, suggesting that, in order for a neutron star to settle to a stable state of crust-core corotation, the bulk of the toroidal field component should be deposited into the crust soon after the neutron star's birth.

  20. Thermonuclear Burning as a Probe of Neutron Star

    NASA Technical Reports Server (NTRS)

    Strohmayer, Tod

    2008-01-01

    Thermonuclear fusion is a fundamental process taking place in the matter transferred onto neutron stars in accreting binary systems. The heat deposited by nuclear reactions becomes readily visible in the X-ray band when the burning is either unstable or marginally stable, and results in the rich phenomenology of X-ray bursts, superbursts, and mHz quasiperiodic oscillations. Fast X-ray timing observations with NASA's Rossi X-ray Timing Explorer (RXTE) over the past decade have revealed a wealth of new phenomena associated with thermonuclear burning on neutron stars, including the discovery of nuclear powered pulsations during X-ray bursts and superbursts. I will briefly review our current observational and theoretical understanding of these new phenomena, with an emphasis on recent findings, and discuss what they are telling us about the structure of neutron stars.

  1. Physics in strong magnetic fields near neutron stars

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.

    1991-01-01

    Electromagnetic phenomena occurring in the strong magnetic fields of neutron stars are currently of great interest in high-energy astrophysics. Observations of rotation rate changes and cyclotron lines in pulsars and gamma-ray bursts indicate that surface magnetic fields of neutron stars often exceed a trillion gauss. In fields this strong, where electrons behave much as if they were in bound atomic states, familiar processes undergo profound changes, and exotic processes become important. Strong magnetic fields affect the physics in several fundamental ways: energies perpendicular to the field are quantized, transverse momentum is not conserved, and electron-positron spin is important. Neutron stars therefore provide a unique laboratory for the study of physics in extremely high fields that cannot be generated on earth.

  2. Stringent neutron-star limits on large extra dimensions.

    PubMed

    Hannestad, Steen; Raffelt, Georg G

    2002-02-18

    Supernovae (SNe) are copious sources for Kaluza-Klein (KK) gravitons which are generic for theories with large extra dimensions. These massive particles are produced with average velocities approximately 0.5c so that many of them are gravitationally retained by the SN core. Every neutron star thus has a halo of KK gravitons which decay into nu(nu), e(+)e(-), and gammagamma on time scales approximately 10(9) years. The EGRET gamma-flux limits (E(gamma) approximately 100 MeV) for nearby neutron stars constrain the compactification scale for n = 2 extra dimensions to M > or = 500 TeV, and M > or = 30 TeV for n = 3. The requirement that neutron stars are not excessively heated by KK decays implies M > or = 1700 TeV for n = 2, and M > or = 60 TeV for n = 3. PMID:11863879

  3. Accreting Millisecond Pulsars: Neutron Star Masses and Radii

    NASA Technical Reports Server (NTRS)

    Strohmayer, Tod

    2004-01-01

    High amplitude X-ray brightness oscillations during thermonuclear X-ray bursts were discovered with the Rossi X-ray Timing Explorer (RXTE) in early 1996. Spectral and timing evidence strongly supports the conclusion that these oscillations are caused by rotational modulation of the burst emission and that they reveal the spin frequency of neutron stars in low mass X-ray binaries. The recent discovery of X-ray burst oscillations from two accreting millisecond pulsars has confirmed this basic picture and provided a new route to measuring neutron star properties and constraining the dense matter equation of state. I will briefly summarize the current observational understanding of accreting millisecond pulsars, and describe recent attempts to determine the mass and radius of the neutron star in XTE J1814-338.

  4. Effects of hyperons in binary neutron star mergers.

    PubMed

    Sekiguchi, Yuichiro; Kiuchi, Kenta; Kyutoku, Koutarou; Shibata, Masaru

    2011-11-18

    Numerical simulations for the merger of binary neutron stars are performed in full general relativity incorporating both nucleonic and hyperonic finite-temperature equations of state (EOS) and neutrino cooling. It is found that even for the hyperonic EOS, a hypermassive neutron star is first formed after the merger for the typical total mass ?2.7M(?), and subsequently collapses to a black hole (BH). It is shown that hyperons play a substantial role in the postmerger dynamics, torus formation around the BH, and emission of gravitational waves (GWs). In particular, the existence of hyperons is imprinted in GWs. Therefore, GW observations will provide a potential opportunity to explore the composition of neutron star matter. PMID:22181867

  5. Magnetized neutron stars with superconducting cores: Effect of entrainment

    E-print Network

    Palapanidis, K; Lander, S K

    2015-01-01

    We construct equilibrium configurations of magnetized, two-fluid neutron stars using an iterative numerical method. We assume that the neutron star has two regions: the core, which is modelled as a two-component fluid consisting of type-II superconducting protons and superfluid neutrons, and the crust, a region composed of normal matter. Taking a new step towards more complete equilibrium models, we include the effect of entrainment, which implies that a magnetic force acts on neutrons, too. We consider purely poloidal field cases and present improvements to an earlier numerical scheme for solving equilibrium equations, by introducing new convergence criteria. We find that entrainment results in qualitative differences in the structure of field lines across the crust-core boundary and along the magnetic axis.

  6. Rapid Cooling of the Neutron Star in Cassiopeia A Triggered by Neutron Superfluidity in Dense Matter

    E-print Network

    Dany Page; Madappa Prakash; James M. Lattimer; Andrew W. Steiner

    2011-01-19

    We propose that the observed cooling of the neutron star in Cassiopeia A is due to enhanced neutrino emission from the recent onset of the breaking and formation of neutron Cooper pairs in the 3P2 channel. We find that the critical temperature for this superfluid transition is ~0.5x10^9 K. The observed rapidity of the cooling implies that protons were already in a superconducting state with a larger critical temperature. Our prediction that this cooling will continue for several decades at the present rate can be tested by continuous monitoring of this neutron star.

  7. The Magnetosphere of Oscillating Neutron Stars in General Relativity

    E-print Network

    Ernazar B. Abdikamalov; Bobomurat J. Ahmedov; John C. Miller

    2009-01-28

    Just as a rotating magnetised neutron star has material pulled away from its surface to populate a magnetosphere, a similar process can occur as a result of neutron-star pulsations rather than rotation. This is of interest in connection with the overall study of neutron star oscillation modes but with a particular focus on the situation for magnetars. Following a previous Newtonian analysis of the production of a force-free magnetosphere in this way Timokhin et al. (2000), we present here a corresponding general-relativistic analysis. We give a derivation of the general relativistic Maxwell equations for small-amplitude arbitrary oscillations of a non-rotating neutron star with a generic magnetic field and show that these can be solved analytically under the assumption of low current density in the magnetosphere. We apply our formalism to toroidal oscillations of a neutron star with a dipole magnetic field and find that the low current density approximation is valid for at least half of the oscillation modes, similarly to the Newtonian case. Using an improved formula for the determination of the last closed field line, we calculate the energy losses resulting from toroidal stellar oscillations for all of the modes for which the size of the polar cap is small. We find that general relativistic effects lead to shrinking of the size of the polar cap and an increase in the energy density of the outflowing plasma. These effects act in opposite directions but the net result is that the energy loss from the neutron star is significantly smaller than suggested by the Newtonian treatment.

  8. Spin-up/spin-down of neutron star in Be-X-ray binary system GX 304-1

    E-print Network

    Postnov, K A; Lutovinov, A A; Shakura, N I; Kochetkova, A Yu; Tsygankov, S S

    2014-01-01

    We analyze spin-up/spin-down of the neutron star in Be X-ray binary system GX\\,304-1 observed by \\textit{Swift}/XRT and \\textit{Fermi}/GBM instruments in the period of the source activity from April 2010 to January 2013 and discuss possible mechanisms of angular momentum transfer to/from the neutron star. We argue that the neutron star spin-down at quiescent states of the source with an X-ray luminosity of $L_x\\sim 10^{34}$~erg s$^{-1}$ between a series of Type I outbursts and spin-up during the outbursts can be explained by quasi-spherical settling accretion onto the neutron star. The outbursts occur near the neutron star periastron passages where the density is enhanced due to the presence of an equatorial Be-disc tilted to the orbital plane. We also propose an explanation to the counterintuitive smaller spin-up rate observed at higher luminosity in a double-peak Type I outburst due to lower value of the specific angular momentum of matter captured from the quasi-spherical wind from the Be-star by the neutr...

  9. PROSPECTS FOR MEASURING NEUTRON-STAR MASSES AND RADII WITH X-RAY PULSE PROFILE MODELING

    E-print Network

    Psaltis, Dimitrios

    Modeling the amplitudes and shapes of the X-ray pulsations observed from hot, rotating neutron stars provides a direct method for measuring neutron-star properties. This technique constitutes an important part of the science ...

  10. Neutron star natal kicks and the long-term survival of star clusters

    E-print Network

    Contenta, Filippo; Heggie, Douglas C

    2015-01-01

    We investigate the dynamical evolution of a star cluster in an external tidal field by using N-body simulations, with focus on the effects of the presence or absence of neutron star natal velocity kicks.We show that, even if neutron stars typically represent less than 2% of the total bound mass of a star cluster, their primordial kinematic properties may affect the lifetime of the system by up to almost a factor of four. We interpret this result in the light of two known modes of star cluster dissolution, dominated by either early stellar evolution mass loss or two-body relaxation. The competition between these effects shapes the mass loss profile of star clusters, which may either dissolve abruptly ("jumping"), in the pre-core-collapse phase, or gradually ("skiing"), after having reached core collapse.

  11. Neutron star natal kicks and the long-term survival of star clusters

    NASA Astrophysics Data System (ADS)

    Contenta, Filippo; Varri, Anna Lisa; Heggie, Douglas C.

    2015-04-01

    We investigate the dynamical evolution of a star cluster in an external tidal field by using N-body simulations, with focus on the effects of the presence or absence of neutron star natal velocity kicks. We show that, even if neutron stars typically represent less than 2 per cent of the total bound mass of a star cluster, their primordial kinematic properties may affect the lifetime of the system by up to almost a factor of 4. We interpret this result in the light of two known modes of star cluster dissolution, dominated by either early stellar evolution mass-loss or two-body relaxation. The competition between these effects shapes the mass-loss profile of star clusters, which may either dissolve abruptly (`jumping'), in the pre-core-collapse phase, or gradually (`skiing'), after having reached core collapse.

  12. Neutron stars and the distance to gamma-ray bursters

    NASA Technical Reports Server (NTRS)

    Dermer, Charles D.; Hurley, Kevin C.

    1991-01-01

    Assuming that gamma-ray bursts originate from galactic neutron stars, an analytic method for studying their statistical properties is outlined. If a significant fraction of all neutron stars are born with space velocities of less than approximately 100 km/s, as suggested by studies of pulsar statistics, then the sampling distance to gamma-ray burst sources should be less than about several hundred pc. These results have important implications on theories of radio-pulsar evolution and magnetic-field decay.

  13. Hyperons and nuclear symmetry energy in neutron star matter

    SciTech Connect

    Ryu, Chung-Yeol [Department of Physics, Hanyang University, Seoul 133-791 (Korea, Republic of); Hyun, Chang Ho [Department of Physics Education, Daegu University, Gyeongsan 712-714 (Korea, Republic of); Lee, Chang-Hwan [Department of Physics, Pusan National University, Busan 609-735 (Korea, Republic of)

    2011-09-15

    In this work, masses and radii of neutron stars are considered to investigate the effect of nuclear symmetry energy on astrophysical observables. A relativistic mean-field model with density-dependent meson-baryon coupling constants is employed in describing the equation of state of dense nuclear matter, and the density dependencies of the symmetry energies are quoted from the recent phenomenological formulas obtained from heavy-ion data at subnuclear saturation densities. Since hyperons can take part in the {beta}-equilibrium of the dense matter inside neutron stars, we include hyperons in our estimation and their roles are discussed in combination with that of the nuclear symmetry energy.

  14. Gravitational radiation from dual neutron star elliptical binaries

    NASA Technical Reports Server (NTRS)

    Hils, Dieter

    1991-01-01

    General expressions are derived for the gravitational radiation incident on earth due to elliptical binary systems in the Galaxy. These results are applied to dual neutron star elliptical binaries. Calculations show that eccentric dual neutron star binaries lead to a moderate increase in gravitational flux density compared with circular systems for frequencies above approximately 0.0001 Hz. Tables of various quantities such as average gravitational luminosity, number of sources per unit bandwidth, energy spectral flux density, and gravitational wave strain density are given.

  15. Isospin-dependent clusterization of Neutron-Star Matter

    E-print Network

    Camille Ducoin; Philippe Chomaz; Francesca Gulminelli

    2007-04-19

    Because of the presence of a liquid-gas phase transition in nuclear matter, compact-star matter can present a region of instability against the formation of clusters. We investigate this phase separation in a matter composed of neutrons, protons and electrons, within a Skyrme-Lyon mean-field approach. Matter instability and phase properties are characterized through the study of the free-energy curvature. The effect of beta-equilibrium is also analyzed in detail, and we show that the opacity to neutrinos has an influence on the presence of clusterized matter in finite-temperature proto-neutron stars.

  16. Binary Evolution and Neutron Stars in Globular Clusters

    E-print Network

    Natalia Ivanova; John M. Fregeau; Frederic A. Rasio

    2004-05-20

    We investigate the dynamical formation and evolution of binaries containing neutron stars in dense globular clusters. Our numerical simulations combine a simple Monte Carlo prescription for stellar dynamics, a sophisticated binary population synthesis code, and a small-N-body integrator for computing 3-body and 4-body interactions. Our results suggest that there is no ``retention problem,'' i.e., that, under standard assumptions, globular clusters can retain enough neutron stars to produce the observed numbers of millisecond pulsars. We also identify the dominant evolutionary and dynamical channels through which globular clusters produce their two main types of binary millisecond pulsars

  17. Thermal emission from low-field neutron stars

    E-print Network

    B. T. Gaensicke; T. M. Braje; R. W. Romani

    2002-03-04

    We present a new grid of LTE model atmospheres for weakly magnetic (B<=10e10G) neutron stars, using opacity and equation of state data from the OPAL project and employing a fully frequency- and angle-dependent radiation transfer. We discuss the differences from earlier models, including a comparison with a detailed NLTE calculation. We suggest heating of the outer layers of the neutron star atmosphere as an explanation for the featureless X-ray spectra of RX J1856.5-3754 and RX J0720.4-3125 recently observed with Chandra and XMM.

  18. Nuclear Superfluidity in Exotic Nuclei and Neutron Stars

    E-print Network

    Nicolae Sandulescu

    2006-12-11

    Nuclear superfludity in exotic nuclei close to the drip lines and in the inner crust matter of neutron stars have common features which can be treated with the same theoretical tools. In the first part of my lecture I discuss how two such tools, namely the HFB approach and the linear response theory can be used to describe the pairing correlations in weakly bound nuclei, in which the unbound part of the energy spectrum becomes important. Then, using the same models, I shall discuss how the nuclear superfluidity can affect the thermal properties of the inner crust of neutron stars.

  19. GRAVITATIONAL WAVES AND THE MAXIMUM SPIN FREQUENCY OF NEUTRON STARS

    SciTech Connect

    Patruno, Alessandro; Haskell, Brynmor; D'Angelo, Caroline [Astronomical Institute 'Anton Pannekoek', University of Amsterdam, Postbus 94249, NL-1090 GE Amsterdam (Netherlands)

    2012-02-10

    In this paper, we re-examine the idea that gravitational waves are required as a braking mechanism to explain the observed maximum spin frequency of neutron stars. We show that for millisecond X-ray pulsars, the existence of spin equilibrium as set by the disk/magnetosphere interaction is sufficient to explain the observations. We show as well that no clear correlation exists between the neutron star magnetic field B and the X-ray outburst luminosity L{sub X} when considering an enlarged sample size of millisecond X-ray pulsars.

  20. Producing ultrastrong magnetic fields in neutron star mergers.

    PubMed

    Price, D J; Rosswog, S

    2006-05-01

    We report an extremely rapid mechanism for magnetic field amplification during the merger of a binary neutron star system. This has implications for the production of the short class of gamma-ray bursts, which recent observations suggest may originate in such mergers. In detailed magnetohydrodynamic simulations of the merger process, the fields are amplified by Kelvin-Helmholtz instabilities beyond magnetar field strength and may therefore represent the strongest magnetic fields in the universe. The amplification occurs in the shear layer that forms between the neutron stars and on a time scale of only 1 millisecond, that is, long before the remnant can collapse into a black hole. PMID:16574823

  1. Neutron stars within pseudo-complex general relativity

    NASA Astrophysics Data System (ADS)

    Rodríguez, Isaac; Hess, Peter O.; Schramm, Stefan; Greiner, Walter

    2014-10-01

    The properties of neutron stars within the theory of pseudo-complex general relativity are studied. The pc-Tolman-Oppenheimer-Volkoff equations are numerically integrated in order to understand the structure of these objects. The interior ?-term energy density {{\\varepsilon }_{\\Lambda i}} has been linearly coupled to the respective baryonic quantity ?m. Two models for the exterior region have been analyzed attending the continuity of the energy density at the boundary. Energy conditions have been studied for both regions. Solutions have been presented for different values of the coupling parameter. It is shown that accumulation of the ?-term component allows the theoretical existence of larger and more massive neutron stars.

  2. Diagnostics of disk-magnetosphere interaction in neutron star binaries

    NASA Technical Reports Server (NTRS)

    Ghosh, Pranab; Lamb, Frederick K.

    1992-01-01

    The interaction between the magnetospheres of accreting neutron stars and accretion disks plays at key role in determining the properties of many accretion-powered neutron star X-ray sources and the recycled binary and millisecond rotation-powered pulsars. Here we show that the behavior of the horizontal branch quasi-periodic intensity oscillations in low mass X-ray binaries and the correlation between the magnetic fields and periods of binary and millisecond pulsars are sensitive probes of the state of the inner disk.

  3. X-ray spectra from convective photospheres of neutron stars

    SciTech Connect

    Zavlin, V.E. [Max-Planck-Institut fuer Extraterrestrische Physik, Garching (Germany); Pavlov, G.G. [Pennsylvania State Univ., PA (United States)]|[Ioffe Institute of Physics and Technology, St. Petersburg, RU (United States); Shibanov, Yu.A. [Ioffe Institute of Physics and Technology, St. Petersburg (Russian Federation); Rogers, F.J.; Iglesias, C.A. [Lawrence Livermore National Lab., CA (United States)

    1996-01-17

    We present first results of modeling convective photospheres of neutron stars. We show that in photospheres composed of the light elements convection arises only at relatively low effective temperatures ({le}3 - 5 x 10{sup 4} K), whereas in the case of iron composition it arises at T{sub eff}{le} 3 x 10{sup 5}K. Convection changes the depth dependence of the photosphere temperature and the shapes of the emergent spectra. Thus, it should be taken into account for the proper interpretation of EUV/soft-X-ray observations of the thermal radiation from neutron stars.

  4. The effects of strong magnetic fields on the neutron star structure: lowest order constrained variational calculations

    E-print Network

    Gholam Hossein Bordbar; Zeinab Rezaei

    2012-12-08

    We investigate the effects of strong magnetic fields upon the gross properties of neutron and protoneutron stars. In our calculations, the neutron star matter was approximated by the pure neutron matter. Using the lowest order constrained variational approach at zero and finite temperatures, and employing $AV_{18}$ potential, we present the effects of strong magnetic fields on the gravitational mass, radius, and gravitational redshift of the neutron and protoneutron stars. It is found that the equation of state of neutron star becomes stiffer with increase of the magnetic field and temperature. This leads to larger values of the maximum mass and radius for the neutron stars.

  5. Neutron star matter in an effective model

    E-print Network

    T. K. Jha; P. K. Raina; P. K. Panda; S. K. Patra

    2007-11-13

    We study the equation of state (EOS) for dense matter in the core of the compact star with hyperons and calculate the star structure in an effective model in the mean field approach. With varying incompressibility and effective nucleon mass, we analyse the resulting EOS with hyperons in beta equilibrium and its underlying effect on the gross properties of the compact star sequences. The results obtained in our analysis are compared with predictions of other theoretical models and observations. The maximum mass of the compact star lies in the range $1.21-1.96 ~M_{\\odot}$ for the different EOS obtained, in the model.

  6. Quark matter in high-mass neutron stars?

    E-print Network

    Lastowiecki, R; Fischer, T; Klahn, T

    2015-01-01

    The recent measurements of the masses of the pulsars PSR J1614-2230 and PSR J0348-0432 provide independent proof for the existence of neutron stars with masses in range of 2 $M_\\odot$. This fact has significant implications for the physics of high density matter and it challenges the hypothesis that the cores of NS can be composed of deconfined quark matter. In this contribution we study a description of quark matter based on the Nambu--Jona-Lasinio effective model and construct the equation of state for matter in beta equilibrium. This equation of state together with the hadronic Dirac-Brueckner-Hartree-Fock equation of state is used here to describe neutron star and hybrid star configurations. We show that compact stars masses of 2 $M_\\odot$ are compatible with the possible existence of deconfined quark matter in their core.

  7. Rapid cooling of the neutron star in Cassiopeia A triggered by neutron superfluidity in dense matter.

    PubMed

    Page, Dany; Prakash, Madappa; Lattimer, James M; Steiner, Andrew W

    2011-02-25

    We propose that the observed cooling of the neutron star in Cassiopeia A is due to enhanced neutrino emission from the recent onset of the breaking and formation of neutron Cooper pairs in the (3)P(2) channel. We find that the critical temperature for this superfluid transition is ?0.5×10(9) K. The observed rapidity of the cooling implies that protons were already in a superconducting state with a larger critical temperature. This is the first direct evidence that superfluidity and superconductivity occur at supranuclear densities within neutron stars. Our prediction that this cooling will continue for several decades at the present rate can be tested by continuous monitoring of this neutron star. PMID:21405561

  8. Role of isospin physics in supernova matter and neutron stars

    E-print Network

    Bharat K. Sharma; Subrata Pal

    2010-10-28

    We investigate the liquid-gas phase transition of hot protoneutron stars shortly after their birth following supernova explosion and the composition and structure of hyperon-rich (proto)neutron stars within a relativistic mean-field model where the nuclear symmetry energy has been constrained from the measured neutron skin thickness of finite nuclei. Light clusters are abundantly formed with increasing temperature well inside the neutrino-sphere for an uniform supernova matter. Liquid-gas phase transition is found to suppress the cluster yield within the coexistence phase as well as decrease considerably the neutron-proton asymmetry over a wide density range. We find symmetry energy has a modest effect on the boundaries and the critical temperature for the liquid-gas phase transition, and the composition depends more sensitively on the number of trapped neutrinos and temperature of the protoneutron star. The influence of hyperons in the dense interior of stars makes the overall equation of state soft. However, neutrino trapping distinctly delays the appearance of hyperons due to abundance of electrons. We also find that a softer symmetry energy further makes the onset of hyperon less favorable. The resulting structures of the (proto)neutron stars with hyperons and with liquid-gas phase transition are discussed.

  9. A Hot Water Bottle for Aging Neutron Stars

    E-print Network

    Alford, M; Kouvaris, C; Kundu, J; Rajagopal, K; Alford, Mark; Jotwani, Pooja; Kouvaris, Chris; Kundu, Joydip; Rajagopal, Krishna

    2004-01-01

    The gapless color-flavor locked (gCFL) phase is the second-densest phase of matter in the QCD phase diagram, making it a plausible constituent of the core of neutron stars. We show that even a relatively small region of gCFL matter in a star will dominate both the heat capacity C_V and the heat loss by neutrino emission L_\

  10. A Hot Water Bottle for Aging Neutron Stars

    E-print Network

    Mark Alford; Pooja Jotwani; Chris Kouvaris; Joydip Kundu; Krishna Rajagopal

    2005-04-01

    The gapless color-flavor locked (gCFL) phase is the second-densest phase of matter in the QCD phase diagram, making it a plausible constituent of the core of neutron stars. We show that even a relatively small region of gCFL matter in a star will dominate both the heat capacity C_V and the heat loss by neutrino emission L_\

  11. Extreme neutron stars from Extended Theories of Gravity

    E-print Network

    Artyom V. Astashenok; Salvatore Capozziello; Sergei D. Odintsov

    2014-11-24

    We discuss neutron stars with strong magnetic mean fields in the framework of Extended Theories of Gravity. In particular, we take into account models derived from $f(R)$ and $f(\\cal G)$ extensions of General Relativity where functions of the Ricci curvature invariant $R$ and the Gauss-Bonnet invariant ${\\cal G}$ are respectively considered. Dense matter in magnetic mean field, generated by magnetic properties of particles, is described by assuming a model with three meson fields and baryons octet. As result, the considerable increasing of maximal mass of neutron stars can be achieved by cubic corrections in $f(R)$ gravity. In principle, massive stars with $M> 4 M_{\\odot}$ can be obtained. On the other hand, stable stars with high strangeness fraction (with central densities $\\rho_{c}\\sim 1.5-2.0$ GeV/fm$^{3}$) are possible considering quadratic corrections of $f(\\cal {G})$ gravity. The magnetic field strength in the star center is of order $6-8\\times 10^{18}$ G. In general, we can say that other branches of massive neutron stars are possible considering the extra pressure contributions coming from gravity extensions. Such a feature can constitute both a probe for alternative theories and a way out to address anomalous self-gravitating compact systems.

  12. Bounds on the Compactness of Neutron Stars from Brightness Oscillations

    E-print Network

    M. Coleman Miller; Frederick K. Lamb

    1997-11-26

    The discovery of high-amplitude brightness oscillations at the spin frequency or its first overtone in six neutron stars in low-mass X-ray binaries during type~1 X-ray bursts provides a powerful new way to constrain the compactness of these stars, and hence to constrain the equation of state of the dense matter in all neutron stars. Here we present the results of general relativistic calculations of the maximum fractional rms amplitudes that can be observed during bursts. In particular, we determine the dependence of the amplitude on the compactness of the star, the angular dependence of the emission from the surface, the rotational velocity at the stellar surface, and whether there are one or two emitting poles. We show that if two poles are emitting, as is strongly indicated by independent evidence in 4U 1636-536 and KS 1731-26, the resulting limits on the compactness of the star can be extremely restrictive. We also discuss the expected amplitudes of X-ray color oscillations and the observational signatures necessary to derive convincing constraints on neutron star compactness from the amplitudes of burst oscillations.

  13. Extreme neutron stars from Extended Theories of Gravity

    NASA Astrophysics Data System (ADS)

    Astashenok, Artyom V.; Capozziello, Salvatore; Odintsov, Sergei D.

    2015-01-01

    We discuss neutron stars with strong magnetic mean fields in the framework of Extended Theories of Gravity. In particular, we take into account models derived from f(R) and f(Script G) extensions of General Relativity where functions of the Ricci curvature invariant R and the Gauss-Bonnet invariant Script G are respectively considered. Dense matter in magnetic mean field, generated by magnetic properties of particles, is described by assuming a model with three meson fields and baryons octet. As result, the considerable increasing of maximal mass of neutron stars can be achieved by cubic corrections in f(R) gravity. In principle, massive stars with M > 4M? can be obtained. On the other hand, stable stars with high strangeness fraction (with central densities ?c ~ 1.5-2.0 GeV/fm3) are possible considering quadratic corrections of f(Script G) gravity. The magnetic field strength in the star center is of order 6-8 × 1018 G. In general, we can say that other branches of massive neutron stars are possible considering the extra pressure contributions coming from gravity extensions. Such a feature can constitute both a probe for alternative theories and a way out to address anomalous self-gravitating compact systems.

  14. Lightning Stars: Anomalous Photoproduction in Neutron Stars via Parametric Resonance Mechanism

    E-print Network

    S. D. Campos; A. Maia Jr

    2005-07-04

    In this work we propose a new mechanism for photoproduction inside a neutron star based on Parametric Resonance phenomenon as firstly applied to Inflationary Cosmology. Our assumptions are based on the pion condensation model by Harrington and Shepard. We show that a huge number of photons are created which, on turns, reheats the matter in the star's core. Thus, we argue that Parametric Resonance can be effective during a brief period out of an neutron star lifetime leading to an anomalous uprising variation of its brightness departing from the black body radiation at regularly spaced frequencies. In adition, a time periodic signal is obtained in moderate (not exponential) regimes. We argue also that our PR mechanism offers a simple and feasible explanation for some recent observations of giant flares from neutron stars.

  15. Neutron stars, strange stars, and the nuclear equation of state

    SciTech Connect

    Weber, F.; Glendenning, N.K.

    1992-11-02

    This article consists of three parts. In part one we review the present status of dense nuclear matter calculations, and introduce a representative collection of realistic nuclear equations of state which are derived for different assumptions about the physical behavior of dense matter (baryon population, pion condensation,.possible transition of baryon matter to quark matter). In part two we review recently performed non-rotating and rotating compact star calculations performed for these equations of state. The minimum stable rotational periods of compact stars, whose knowledge is of decisive importance for the interpretation of rapidly rotating pulsars, axe determined. For this purpose two different limits on stable rotation are studied: rotation at the general relativistic Kepler period (below which mass shedding at the star`s equator sets in), and, secondly, rotation at the gravitational radiation-reaction instability (at which emission of gravitational waves set in which slows the star down). Part three of this article deals with the properties of hypothetical strange stars. Specifically we investigate the amount of nuclear solid crust that can be carried by a rotating strange star, and answer the question whether such objects can give rise to the observed phenomena of pulsar glitches, which is at the present time the only astrophysical test of the strange-quark-matter hypothesis.

  16. Neutron Star Matter Including Delta Isobars Guang-Zhou Liu1,2

    E-print Network

    Xu, Ren-Xin

    Neutron Star Matter Including Delta Isobars Guang-Zhou Liu1,2 , Wei Liu1 and En-Guang Zhao2 1 a new phase structure of neutron star matter including nucleons and delta isobars is presented. Particle fractions populated and pion condensations in neutron star matter are investgated in this model

  17. Neutron stars in Einstein-aether theory Christopher Eling,1,* Ted Jacobson,1,

    E-print Network

    Miller, Cole

    , Einstein-aether theory, for the properties of nonrotating neutron stars. This theory has a parameter range such as LISA [12]. A third source of strong field tests could exploit neutron star masses and surface redNeutron stars in Einstein-aether theory Christopher Eling,1,* Ted Jacobson,1, and M. Coleman Miller

  18. ccsd00004644, Observing Quantum Vacuum Lensing in a Neutron Star Binary System

    E-print Network

    of magnetised neutron stars. Thanks to the optical properties of quantum vacuum in the presence of a magnetic speculations that neutron stars could be a source of very intense magnetic #12;elds. Since then, most authorsccsd­00004644, version 1 ­ 6 Apr 2005 Observing Quantum Vacuum Lensing in a Neutron Star Binary

  19. Effects of the symmetry energy on properties of neutron star crusts near the neutron drip density

    E-print Network

    S. S. Bao; J. N. Hu; Z. W. Zhang; H. Shen

    2014-10-19

    We study the effects of the symmetry energy on the neutron drip density and properties of nuclei in neutron star crusts. The nonuniform matter around the neutron drip point is calculated by using the Thomas--Fermi approximation with the relativistic mean-field model. The neutron drip density and the composition of the crust are found to be correlated with the symmetry energy and its slope. We compare the self-consistent Thomas--Fermi approximation with other treatments of surface and Coulomb energies and find that these finite-size effects play an essential role in determining the equilibrium state at low density.

  20. Bare Quark Stars or Naked Neutron Stars ? The Case of RX J1856.5-3754

    E-print Network

    Roberto Turolla; Silvia Zane; Jeremy J. Drake

    2003-11-21

    In a cool neutron star (T 1.e13 G), a phase transition may occur in the outermost layers. As a consequence the neutron star becomes `bare', i.e. no gaseous atmosphere sits on the top of the crust. The surface of a cooling, bare neutron star does not necessarily emit a blackbody spectrum because the emissivity is strongly suppressed at energies below the electron plasma frequency, omega_p. Since omega_p ~ 1 keV under the conditions typical of the denseelectron gas in the condensate, the emission from a T ~ 100 eV bare neutron star will be substantially depressed with respect to that of a perfect Planckian radiator at most energies. Here we present a detailed analysis of the emission properties of a bare neutron star. In particular, we derive the surface emissivity for a Fe composition in a range of magnetic fields and temperatures representative of cooling isolated neutron stars, like RX J1856.5-3754. We find that the emitted spectrum is strongly dependent on the electron conductivity in the solid surface layers. In the cold electron gas approximation (no electron-lattice interactions), the spectrum turns out to be a featureless depressed blackbody in the 0.1-2 keV band with a steeper low-energy distribution. When damping effects due to collisions between electrons and the ion lattice (mainly due to electron-phonon interactions) are accounted for, the spectrum is more depressed depending on the magnetic field strength. Details of the emitted spectrum are found, however, to be strongly dependent of the assumed treatment of the transition from the external vacuum to the metallic surface. The implications of out results to RX J1856.5-3754 and other isolated neutron stars are discussed.

  1. Pairing and superfluidity of nucleons in neutron stars

    E-print Network

    A. Gezerlis; C. J. Pethick; A. Schwenk

    2015-04-13

    We survey the current status of understanding of pairing and superfluidity of neutrons and protons in neutron stars from a theoretical perspective, with emphasis on basic physical properties. During the past two decades, the blossoming of the field of ultracold atomic gases and the development of quantum Monte Carlo methods for solving the many-body problem have been two important sources of inspiration, and we shall describe how these have given insight into neutron pairing gaps. The equilibrium properties and collective oscillations of the inner crust of neutron stars, where neutrons paired in a $^1$S$_0$ state coexist with a lattice of neutron-rich nuclei, are also described. While pairing gaps are well understood at densities less than one tenth of the nuclear saturation density, significant uncertainties exist at higher densities due to the complicated nature of nucleon-nucleon interactions, the difficulty of solving the many-body problem under these conditions, and the increasing importance of many-nucleon interactions. We also touch more briefly on the subject of pairing of neutrons in other angular momentum states, specifically the $^3$P$_2$ state, as well as pairing of protons.

  2. Many-particle theory of nuclear systems with application to neutron star matter

    NASA Technical Reports Server (NTRS)

    Chakkalakal, D. A.; Yang, C. H.

    1974-01-01

    The energy-density relation was calculated for pure neutron matter in the density range relevant for neutron stars, using four different hard-core potentials. Calculations are also presented of the properties of the superfluid state of the neutron component, along with the superconducting state of the proton component and the effects of polarization in neutron star matter.

  3. Electron correlation from path resummations: the double-excitation star Alex J. W. Thom,

    E-print Network

    Alavi, Ali

    Electron correlation from path resummations: the double-excitation star Alex J. W. Thom, George H evaluation of a N-electron path-integral. In particular, we show that the double excitation star graph. In this paper, we concentrate on the case of the star graph, whose form allows its weight to be calculated

  4. Oscillations and surface physics of neutron stars

    NASA Astrophysics Data System (ADS)

    Piro, Anthony L.

    Accreting neutron stars (NSs) show recurrent nuclear flashes, called type IX- ray bursts. An exciting recent discovery is millisecond oscillations seen in the rise and tail of the X-ray burst light curves, or burst oscillations. If these oscillations are confirmed as resulting from an oscillatory mode of the NS, they would allow a powerful investigation into the interior layers of NSs in a way analogous to what has been done with seismology for the earth and sun. This has inspired us to make a detailed study of accreting NS oscillation modes, so as to understand how the modes reflect the NS structure and also to try to explain the burst oscillations. Burst oscillations clearly show that the bursting properties of NSs are not spherically symmetric. This motivates a study of non-spherical perturbations on the surfaces of NSs accreting helium-rich fuel. We find that a shallow surface wave in the hot upper burning layers is driven unstably by an increase in the nuclear reactions during the oscillation. Our discovery of an unstable mode in a thermally stable atmosphere shows that non-radial perturbations have a different stability criterion than the spherically symmetric thermal perturbations that generate type I X-ray bursts. We next study a wave associated with the interface between the NS ocean and crust, the crustal interface wave. It is shown to act like a shallow ocean wave, but with a large radial displacement at the ocean/crust boundary due to flexing of the crust, which lowers its frequency. We then consider the properties of oscillations on a NS cooling from an X-ray burst. Our calculations show that a surface wave in the shallow burning layer transitions into a crustal interface wave as the envelope cools, a new and previously uninvestigated phenomenon. When we include rotational modifications, the mode frequencies and drifts are consistent with those observed for burst oscillations. The large NS spin ( [approximate] 270--620 Hz) needed to make this match implies that accreting NSs are spinning at frequencies [approximate] 4 Hz above the burst oscillation. The most exciting implication of this result is that the observed drifts can be used to learn about the composition and temperature of NS crusts. Finally, we calculate the photon energy dependence of the pulsed amplitude of surface modes. Simple approximations demonstrate that it depends most strongly on the bursting NS surface temperature. This result compares well with full integrations that include Doppler shifts from rotation and general relativistic corrections to photon propagation. We show that it agrees with the energy dependence of burst oscillations, lending further support to the hypothesis that burst oscillations originate from surface waves. The critical test of the mode hypothesis for burst oscillations would be a measurement of their energy dependence from an accreting millisecond pulsar. x

  5. Envelope calculations for a low temperature neutron star

    E-print Network

    McCoy, Robert Paul

    1976-01-01

    includes electron degeneracy. The calculations are performed for three model neutron stars and a range of surface temperatures from gx10 OK to Sx10 CK. Estimates of the total stored thermal energy and characteristic cooling times due to photon... of density at different values of temperature 22 Temperature-pressure dependence of the Model I star at different values of Te 26 Temperature-pressure dependence of all three star models S, I and II at T = 10 oK e 27 Pressure variation with distance...

  6. Dark matter, neutron stars and strange quark matter

    E-print Network

    M. Angeles Perez-Garcia; Joseph Silk; Jirina R. Stone

    2010-09-04

    We show that self-annihilating neutralino WIMP dark matter accreted onto neutron stars may provide a mechanism to seed compact objects with long-lived lumps of strange quark matter, or strangelets, for WIMP masses above a few GeV. This effect may trigger a conversion of most of the star into a strange star. We use an energy estimate for the long-lived strangelet based on the Fermi gas model combined with the MIT bag model to set a new limit on the possible values of the WIMP mass that can be especially relevant for subdominant species of massive neutralinos.

  7. Gamma-burst emission from neutron-star accretion

    NASA Technical Reports Server (NTRS)

    Colgate, S. A.; Petschek, A. G.; Sarracino, R.

    1983-01-01

    A model for emission of the hard photons of gamma bursts is presented. The model assumes accretion at nearly the Eddington limited rate onto a neutron star without a magnetic field. Initially soft photons are heated as they are compressed between the accreting matter and the star. A large electric field due to relatively small charge separation is required to drag electrons into the star with the nuclei against the flux of photons leaking out through the accreting matter. The photon number is not increased substantially by Bremsstrahlung or any other process. It is suggested that instability in an accretion disc might provide the infalling matter required.

  8. Neutron stars, strange stars, and the nuclear equation of state

    SciTech Connect

    Weber, F.; Glendenning, N.K.

    1992-11-02

    This article consists of three parts. In part one we review the present status of dense nuclear matter calculations, and introduce a representative collection of realistic nuclear equations of state which are derived for different assumptions about the physical behavior of dense matter (baryon population, pion condensation,.possible transition of baryon matter to quark matter). In part two we review recently performed non-rotating and rotating compact star calculations performed for these equations of state. The minimum stable rotational periods of compact stars, whose knowledge is of decisive importance for the interpretation of rapidly rotating pulsars, axe determined. For this purpose two different limits on stable rotation are studied: rotation at the general relativistic Kepler period (below which mass shedding at the star's equator sets in), and, secondly, rotation at the gravitational radiation-reaction instability (at which emission of gravitational waves set in which slows the star down). Part three of this article deals with the properties of hypothetical strange stars. Specifically we investigate the amount of nuclear solid crust that can be carried by a rotating strange star, and answer the question whether such objects can give rise to the observed phenomena of pulsar glitches, which is at the present time the only astrophysical test of the strange-quark-matter hypothesis.

  9. Developing a model for neutron star oscillations following starquakes

    NASA Astrophysics Data System (ADS)

    Keer, L.; Jones, D. I.

    2015-01-01

    Glitches - sudden increases in spin rate - are observed in many pulsars. One mechanism advanced to explain glitches in the youngest pulsars is that they are caused by a starquake, a sudden rearrangement of the crust of the neutron star. Starquakes have the potential to excite some of the oscillation modes of the neutron star, which means that they are of interest as a source of gravitational waves. These oscillations could also have an impact on radio emission. In this paper, we make upper estimates of the amplitude of the oscillations produced by a starquake, and the corresponding gravitational wave emission. We then develop a more detailed framework for calculating the oscillations excited by the starquake, using a toy model of a solid, incompressible star where all strain is lost instantaneously from the star at the glitch. For this toy model, we give plots of the amplitudes of the modes excited, as the shear modulus and rotation rate of the star are varied. We find that for our specific model, the largest excitation is generally of a mode similar to the f-mode of an incompressible fluid star, but that other modes of the star are excited to a significant degree over small parameter ranges of the rotation rate.

  10. Constraints on perturbative f(R) gravity via neutron stars

    SciTech Connect

    Arapo?lu, Sava?; Ek?i, K. Yavuz [?stanbul Technical University, Faculty of Science and Letters, Physics Engineering Department, Maslak 34469, ?stanbul (Turkey); Deliduman, Cemsinan, E-mail: arapoglu@itu.edu.tr, E-mail: cemsinan@msgsu.edu.tr, E-mail: eksi@itu.edu.tr [Mimar Sinan Fine Arts University, Department of Physics, Be?ikta? 34349, ?stanbul (Turkey)

    2011-07-01

    We study the structure of neutron stars in perturbative f(R) gravity models with realistic equations of state. We obtain mass-radius relations in a gravity model of the form f(R) = R+?R{sup 2}. We find that deviations from the results of general relativity, comparable to the variations due to using different equations of state (EoS'), are induced for |?| ? 10{sup 9} cm{sup 2}. Some of the soft EoS' that are excluded within the framework of general relativity can be reconciled with the 2 solar mass neutron star recently observed for certain values of ? within this range. For some of the EoS' we find that a new solution branch, which allows highly massive neutron stars, exists for values of ? greater than a few 10{sup 9} cm{sup 2}. We find constraints on ? for a variety of EoS' using the recent observational constraints on the mass-radius relation. These are all 5 orders of magnitude smaller than the recent constraint obtained via Gravity Probe B for this gravity model. The associated length scale ?(alpha)approx 10{sup 5} cm is only an order of magnitude smaller than the typical radius of a neutron star, the probe used in this test. This implies that real deviations from general relativity can be even smaller.

  11. Inhomogeneous seeding of quark bubbles in Neutron Stars

    E-print Network

    Perez-Garcia, M A

    2015-01-01

    In this proceedings contribution we briefly discuss about the consequences of the presence of Majorana dark matter in a dense neutron star environment focusing on a particularly interesting possible indirect effect, namely that of bubble nucleation. This is somewhat similar to current techniques developed for direct detection using bubble chamber or superheated droplet detectors.

  12. Bulk viscosity and r-modes of neutron stars

    E-print Network

    Debarati Chatterjee; Debades Bandyopadhyay

    2008-08-08

    The bulk viscosity due to the non-leptonic process involving hyperons in $K^-$ condensed matter is discussed here. We find that the bulk viscosity is modified in a superconducting phase. Further, we demonstrate how the exotic bulk viscosity coefficient influences $r$-modes of neutron stars which might be sources of detectable gravitational waves.

  13. NEUTRON STAR BIRTH RATES D.R. LORIMER

    E-print Network

    Lorimer, Dunc

    NEUTRON STAR BIRTH RATES D.R. LORIMER National Astronomy and Ionospheric Center Arecibo Observatory. Abstract. A crucial test any proposed evolutionary scenario must pass is can the birth rate of the sources used to determine the birth rates of normal and millisecond radio pulsars and sum­ marise recent

  14. Simulations of Coalescing Neutron Star and Black Hole Binaries

    Microsoft Academic Search

    Maximilian Ruffert; H.-Thomas Janka

    1999-01-01

    We investigate the dynamics and evolution of merging neutronstars, of neutron stars coalescing with stellar-mass black holes, and the formation and properties of accretion tori around the (remnant) black holes. The three-dimensional Newtonian hydrodynamics equations are integrated by a Eulerian PPM code on four nested Cartesian grids. The code includes the emission and backreaction of gravitational waves as well as

  15. General Relativistic Hydrodynamic Processes in Close Neutron Star Binaries

    Microsoft Academic Search

    Grant J. Mathews; Pedro Marronetti; James R. Wilson

    1997-01-01

    We discuss several new physical processes which occur in close neutron star binaries. These processes are purely relativistic effects which can be directly traced to terms in our formulation of general relativistic hydrodynamics. In addition to the well known orbit instability, we show that these systems are also subject to relativistically induced compression, heating and collapse. The neutrino emission associated

  16. Supernova Explosions and the Birth of Neutron Stars

    Microsoft Academic Search

    H.-Thomas Janka; Andreas Marek; Bernhard Mueller; Leonhard Scheck

    2008-01-01

    We report here on recent progress in understanding the birth conditions of neutron stars and the way how supernovae explode. More sophisticated numerical models have led to the discovery of new phenomena in the supernova core, for example a generic hydrodynamic instability of the stagnant supernova shock against low-mode nonradial deformation and the excitation of gravity-wave activity in the surface

  17. Equation-of-state-independent relations in neutron stars

    NASA Astrophysics Data System (ADS)

    Maselli, Andrea; Cardoso, Vitor; Ferrari, Valeria; Gualtieri, Leonardo; Pani, Paolo

    2013-07-01

    Neutron stars are extremely relativistic objects which abound in our universe and yet are poorly understood, due to the high uncertainty on how matter behaves in the extreme conditions which prevail in the stellar core. It has recently been pointed out that the moment of inertia I, the Love number ?, and the spin-induced quadrupole moment Q of an isolated neutron star, are related through functions which are practically independent of the equation of state. These surprising universal I-?-Q relations pave the way for a better understanding of neutron stars, most notably via gravitational-wave emission. Gravitational-wave observations will probe highly dynamical binaries and it is important to understand whether the universality of the I-?-Q relations survives strong-field and finite-size effects. We apply a post-Newtonian-affine approach to model tidal deformations in compact binaries and show that the I-? relation depends on the inspiral frequency, but is insensitive to the equation of state. We provide a fit for the universal relation, which is valid up to a gravitational wave frequency of ˜900Hz and accurate to within a few percent. Our results strengthen the universality of I-?-Q relations, and are relevant for gravitational-wave observations with advanced ground-based interferometers. We also discuss the possibility of using the Love-compactness relation to measure the neutron-star radius with an uncertainty ?10% from gravitational-wave observations.

  18. Quark deconfinement in high-mass neutron stars

    NASA Astrophysics Data System (ADS)

    Orsaria, M.; Rodrigues, H.; Weber, F.; Contrera, G. A.

    2014-01-01

    In this paper, we explore whether or not quark deconfinement may occur in high-mass neutron stars such as J1614 - 2230 (1.97±0.04M?) and J0348 + 0432 (2.01±0.04M?). Our study is based on a nonlocal extension of the SU(3) Nambu-Jona-Lasinio (n3NJL) model with repulsive vector interactions among the quarks. This model goes beyond the frequently used local version of the Nambu-Jona-Lasinio (NJL) model by accounting for several key features of QCD which are not part of the local model. Confined hadronic matter is treated in the framework of nonlinear relativistic mean field theory. We find that both the local as well as the nonlocal NJL model predict the existence of extended regions of mixed quark-hadron (quark-hybrid) matter in high-mass neutron stars with masses of 2.1 to 2.4M?. Pure quark matter in the cores of neutron stars is obtained for certain parametrizations of the hadronic lagrangian and choices of the vector repulsion among quarks. The radii of high-mass neutron stars with quark-hybrid matter and/or pure quark matter cores in their centers are found to lie in the canonical range of 12 to 13 km.

  19. Magnetar activity mediated by plastic deformations of neutron star crust

    NASA Astrophysics Data System (ADS)

    Lyutikov, Maxim

    2015-02-01

    We advance a `solar flare' model of magnetar activity, whereas a slow evolution of the magnetic field in the upper crust, driven by electron magnetohydrodynamic flows, twists the external magnetic flux tubes, producing persistent emission, bursts, and flares. At the same time, the neutron star crust plastically relieves the imposed magnetic field stress, limiting the strain ?t to values well below the critical strain ?crit of a brittle fracture, ?t ˜ 10-2?crit. Magnetar-like behaviour, occurring near the magnetic equator, takes place in all neutron stars, but to a different extent. The persistent luminosity is proportional to cubic power of the magnetic field (at a given age), and hence is hardly observable in most rotationally powered neutron stars. Giant flares can occur only if the magnetic field exceeds some threshold value, while smaller bursts and flares may take place in relatively small magnetic fields. Bursts and flares are magnetospheric reconnection events that launch Alfvén shocks which convert into high-frequency whistlers upon hitting the neutron star surface. The resulting whistler pulse induces a strain that increases with depth both due to the increasing electron density (and the resulting slowing of the waves), and due to the increasing coherence of a whistler pulse with depth. The whistler pulse is dissipated on a time-scale of approximately a day at shallow depths corresponding to ? ˜ 1010 g cm-3; this energy is detected as enhanced post-flare surface emission.

  20. The study of neutron star magnetospheres with LOFT

    E-print Network

    Mignani, R P; Bucciantini, N; Burgay, M; Cusumano, G; De Luca, A; Esposito, P; Gouiffes, C; Hermsen, W; Kanbach, G; Kuiper, L; Israel, G L; Marelli, M; Mereghetti, S; Mineo, T; Motch, C; Pellizzoni, A; Possenti, A; Ray, P S; Rea, N; Rudak, B; Salvetti, D; Shearer, A; S?owikowska, A; Tiengo, A; Turolla, R; Webb, N

    2015-01-01

    This is a White Paper in support of the mission concept of the Large Observatory for X-ray Timing (LOFT), proposed as a medium-sized ESA mission. We discuss the potential of LOFT for the study of magnetospheres of isolated neutron stars. For a summary, we refer to the paper.