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Sample records for isolated radio millisecond

  1. Millisecond radio pulsars in globular clusters

    NASA Technical Reports Server (NTRS)

    Verbunt, Frank; Lewin, Walter H. G.; Van Paradijs, Jan

    1989-01-01

    It is shown that the number of millisecond radio pulsars, in globular clusters, should be larger than 100, applying the standard scenario that all the pulsars descend from low-mass X-ray binaries. Moreover, most of the pulsars are located in a small number of clusters. The prediction that Teran 5 and Liller 1 contain at least about a dozen millisecond radio pulsars each is made. The observations of millisecond radio pulsars in globular clusters to date, in particular the discovery of two millisecond radio pulsars in 47 Tuc, are in agreement with the standard scenario, in which the neutron star is spun up during the mass transfer phase.

  2. Millisecond solar radio spikes observed at 1420 MHz

    NASA Astrophysics Data System (ADS)

    Dabrowski, B. P.; Kus, A. J.

    We present results from observations of narrowband solar millisecond radio spikes at 1420 MHz. Observing data were collected between February 2000 and December 2001 with the 15-m radio telescope at the Centre for Astronomy Nicolaus Copernicus University in Torun, Poland, equipped with a radio spectrograph that covered the 1352-1490 MHz frequency band. The radio spectrograph has 3 MHz frequency resolution and 80 microsecond time resolution. We analyzed the individual radio spike duration, bandwidth and rate of frequency drift. A part of the observed spikes showed well-outlined subtle structures. On dynamic radio spectrograms of the investigated events we notice complex structures formed by numerous individual spikes known as chains of spikes and distinctly different structure of columns. Positions of active regions connected with radio spikes emission were investigated. It turns out that most of them are located near the center of the solar disk, suggesting strong beaming of the spikes emission.

  3. Spin-down of radio millisecond pulsars at genesis.

    PubMed

    Tauris, Thomas M

    2012-02-01

    Millisecond pulsars are old neutron stars that have been spun up to high rotational frequencies via accretion of mass from a binary companion star. An important issue for understanding the physics of the early spin evolution of millisecond pulsars is the impact of the expanding magnetosphere during the terminal stages of the mass-transfer process. Here, I report binary stellar evolution calculations that show that the braking torque acting on a neutron star, when the companion star decouples from its Roche lobe, is able to dissipate >50% of the rotational energy of the pulsar. This effect may explain the apparent difference in observed spin distributions between x-ray and radio millisecond pulsars and help account for the noticeable age discrepancy with their young white dwarf companions. PMID:22301314

  4. Spin-down of radio millisecond pulsars at genesis.

    PubMed

    Tauris, Thomas M

    2012-02-01

    Millisecond pulsars are old neutron stars that have been spun up to high rotational frequencies via accretion of mass from a binary companion star. An important issue for understanding the physics of the early spin evolution of millisecond pulsars is the impact of the expanding magnetosphere during the terminal stages of the mass-transfer process. Here, I report binary stellar evolution calculations that show that the braking torque acting on a neutron star, when the companion star decouples from its Roche lobe, is able to dissipate >50% of the rotational energy of the pulsar. This effect may explain the apparent difference in observed spin distributions between x-ray and radio millisecond pulsars and help account for the noticeable age discrepancy with their young white dwarf companions.

  5. RADIO AND GAMMA-RAY PULSED EMISSION FROM MILLISECOND PULSARS

    SciTech Connect

    Du, Y. J.; Chen, D.; Qiao, G. J.

    2013-01-20

    Pulsed {gamma}-ray emission from millisecond pulsars (MSPs) has been detected by the sensitive Fermi space telescope, which sheds light on studies of the emission region and its mechanism. In particular, the specific patterns of radio and {gamma}-ray emission from PSR J0101-6422 challenge the popular pulsar models, e.g., outer gap and two-pole caustic models. Using the three-dimensional annular gap model, we have jointly simulated radio and {gamma}-ray light curves for three representative MSPs (PSR J0034-0534, PSR J0101-6422, and PSR J0437-4715) with distinct radio phase lags, and present the best simulated results for these MSPs, particularly for PSR J0101-6422 with complex radio and {gamma}-ray pulse profiles, and for PSR J0437-4715 with a radio interpulse. We have found that both the {gamma}-ray and radio emission originate from the annular gap region located in only one magnetic pole, and the radio emission region is not primarily lower than the {gamma}-ray region in most cases. In addition, the annular gap model with a small magnetic inclination angle instead of an 'orthogonal rotator' can account for the MSPs' radio interpulse with a large phase separation from the main pulse. The annular gap model is a self-consistent model not only for young pulsars but also MSPs, and multi-wavelength light curves can be fundamentally explained using this model.

  6. Catching the rebirth of a radio millisecond pulsar

    NASA Astrophysics Data System (ADS)

    Patruno, Alessandro

    2012-09-01

    On 2013 Dec 10 we have discovered with a Swift/XRT observation, that the low mass X-ray binary (LMXB) XSS J12270-4859 has recently changed state from a quiescent-LMXB into a new anomalous faint state with no signatures of accretion (ATel #5647). An NTT optical observation suggests a transition around December 2012 in the opposite direction to that of the "missing link" PSR J1023+0038 (that switched from a radio millisecond pulsar (MSP), into an LMXB, Stappers et al.2013, Patruno et al. 2013). A MSP may therefore be now active in XSS J12270. We are currently completing the analysis of Parkes data to search for the putative MSP. The Swift/XRT shows a faint source (1e32-1e33 erg/s). We want now to characterize the spectral behaviour with a 30 ks Chandra pointing. If we do not detect radio pulsations Chandra can potentially tell us if the pulsar (and pulsar wind) are on even if the radio pulsar is undetectable (as our preliminary Parkes analysis seems to suggest).

  7. Inconsistency of Ulysses Millisecond Langmuir Spikes with Wave Collapse in Type 3 Radio Sources

    NASA Technical Reports Server (NTRS)

    Cairns, Iver H.; Robinson, P. A.

    1995-01-01

    Recent Ulysses observations of millisecond spikes superposed on broader Langmuir wave packets in type 3 radio sources are compared quantitatively with constraints from the theory of wave collapse. It is found that both the millisecond spikes and the wave packets have fields at least 10 times too small to be consistent with collapse, contrary to previous interpretations in terms of this process. Several alternative explanations are considered and it is argued that the spikes should be interpreted as either non-collapse phenomena or observational artifacts. To the extent the observations are representative, this rules out theories for type 3 bursts at approx. 1 - 4 AU that rely on collapse.

  8. Radio Detection of the Fermi-LAT Blind Search Millisecond Pulsar J1311-3430

    NASA Technical Reports Server (NTRS)

    Ray, P. S.; Ransom, S. M.; Cheung, C. C.; Giroletti, M.; Cognard, I.; Camilo, F.; Bhattacharyya, B.; Roy, J.; Romani, R. W.; Ferrara, E. C.; Guillemot, L.; Johnston, S.; Keith, M.; Kerr, M.; Kramer, M.; Pletsch, H. J.; Parkinson, P. M. Saz

    2013-01-01

    We report the detection of radio emission from PSR J1311.3430, the first millisecond pulsar (MSP) discovered in a blind search of Fermi Large Area Telescope (LAT) gamma-ray data. We detected radio pulsations at 2 GHz, visible for less than 10% of approximately 4.5 hr of observations using the Green Bank Telescope (GBT). Observations at 5 GHz with the GBT and at several lower frequencies with Parkes, Nan cay, and the Giant Metrewave Radio Telescope resulted in non-detections. We also report the faint detection of a steep spectrum continuum radio source (0.1 mJy at 5 GHz) in interferometric imaging observations with the Jansky Very Large Array. These detections demonstrate that PSR J1311.3430 is not radio quiet and provide additional evidence that radio-quiet MSPs are rare. The radio dispersion measure of 37.8 pc cm(exp -3) provides a distance estimate of 1.4 kpc for the system, yielding a gamma-ray efficiency of 30%, typical of LAT-detected MSPs. We see apparent excess delay in the radio pulses as the pulsar appears from eclipse and we speculate on possible mechanisms for the non-detections of the pulse at other orbital phases and observing frequencies.

  9. RADIO DETECTION OF THE FERMI-LAT BLIND SEARCH MILLISECOND PULSAR J1311-3430

    SciTech Connect

    Ray, P. S.; Wood, K. S.; Ransom, S. M.; Cheung, C. C.; Giroletti, M.; Cognard, I.; Camilo, F.; Bhattacharyya, B.; Roy, J.; Romani, R. W.; Kerr, M.; Ferrara, E. C.; Guillemot, L.; Kramer, M.; Johnston, S.; Keith, M.; Pletsch, H. J.; Saz Parkinson, P. M.

    2013-01-20

    We report the detection of radio emission from PSR J1311-3430, the first millisecond pulsar (MSP) discovered in a blind search of Fermi Large Area Telescope (LAT) gamma-ray data. We detected radio pulsations at 2 GHz, visible for <10% of {approx}4.5 hr of observations using the Green Bank Telescope (GBT). Observations at 5 GHz with the GBT and at several lower frequencies with Parkes, Nancay, and the Giant Metrewave Radio Telescope resulted in non-detections. We also report the faint detection of a steep spectrum continuum radio source (0.1 mJy at 5 GHz) in interferometric imaging observations with the Jansky Very Large Array. These detections demonstrate that PSR J1311-3430 is not radio quiet and provide additional evidence that radio-quiet MSPs are rare. The radio dispersion measure of 37.8 pc cm{sup -3} provides a distance estimate of 1.4 kpc for the system, yielding a gamma-ray efficiency of 30%, typical of LAT-detected MSPs. We see apparent excess delay in the radio pulses as the pulsar appears from eclipse and we speculate on possible mechanisms for the non-detections of the pulse at other orbital phases and observing frequencies.

  10. Discovery of millisecond pulsars in radio searches of southern Fermi Large Area Telescope sources

    NASA Astrophysics Data System (ADS)

    Keith, M. J.; Johnston, S.; Ray, P. S.; Ferrara, E. C.; Saz Parkinson, P. M.; Çelik, Ö.; Belfiore, A.; Donato, D.; Cheung, C. C.; Abdo, A. A.; Camilo, F.; Freire, P. C. C.; Guillemot, L.; Harding, A. K.; Kramer, M.; Michelson, P. F.; Ransom, S. M.; Romani, R. W.; Smith, D. A.; Thompson, D. J.; Weltevrede, P.; Wood, K. S.

    2011-06-01

    Using the Parkes Radio Telescope, we have carried out deep observations of 11 unassociated gamma-ray sources. Periodicity searches of these data have discovered two millisecond pulsars, PSR J1103-5403 (1FGL J1103.9-5355) and PSR J2241-5236 (1FGL J2241.9-5236), and a long-period pulsar, PSR J1604-44 (1FGL J1604.7-4443). In addition, we searched for but did not detect any radio pulsations from six gamma-ray pulsars discovered by the Fermi satellite to a level of ˜0.04 mJy (for pulsars with a 10 per cent duty cycle). The timing of the millisecond pulsar PSR J1103-5403 has shown that its position is 9 arcmin from the centroid of the gamma-ray source. Since these observations were carried out, independent evidence has shown that 1FGL J1103.9-5355 is associated with the flat spectrum radio source PKS 1101-536. It appears certain that the pulsar is not associated with the gamma-ray source, despite the seemingly low probability of a chance detection of a radio millisecond pulsar. We consider that PSR J1604-44 is a chance discovery of a weak, long-period pulsar and is unlikely to be associated with 1FGL J1604.7-4443. PSR J2241-5236 has a spin period of 2.2 ms and orbits a very low mass companion with a 3.5-h orbital period. The relatively high flux density and low dispersion measure of PSR J2241-5236 make it an excellent candidate for high precision timing experiments. The gamma rays of 1FGL J2241.9-5236 have a spectrum that is well modelled by a power law with an exponential cut-off, and phase binning with the radio ephemeris results in a multipeaked gamma-ray pulse profile. Observations with Chandra have identified a coincident X-ray source within 0.1 arcsec of the position of the pulsar obtained by radio timing.

  11. Birth and Evolution of Isolated Radio Pulsars

    NASA Astrophysics Data System (ADS)

    Faucher-Giguère, Claude-André; Kaspi, Victoria M.

    2008-02-01

    We investigate the birth and evolution of isolated radio pulsars using a population synthesis method, modeling the birth properties of the pulsars, their time evolution, and their detection in the Parkes and Swinburne Multibeam (MB) surveys. Together, the Parkes and Swinburne MB surveys [1, 2] have detected nearly 2/3 of the known pulsars and provide a remarkably homogeneous sample to compare with simulations. New proper motion measurements [3, 4] and an improved model of the distribution of free electrons in the interstellar medium, NE2001 [5], also make revisiting these issues particularly worthwhile. We present a simple population model that reproduces the actual observations well, and consider others that fail. We conclude that: pulsars are born in the spiral arms, with the birthrate of 2.8+/-0.5 pulsars/century peaking at a distance ~3 kpc from the Galactic centre, and with mean initial speed of 380-60+40 km s-1 the birth spin period distribution extends to several hundred milliseconds, with no evidence of multimodality, implying that characteristic ages overestimate the true ages of the pulsars by a median factor >2 for true ages <30,000 yr models in which the radio luminosities of the pulsars are random generically fail to reproduce the observed P-Ṗ diagram, suggesting a relation between intrinsic radio luminosity and (P,Ṗ) radio luminosities L~Ė provides a good match to the observed P-Ṗ diagram; for this favored radio luminosity model, we find no evidence for significant magnetic field decay over the lifetime of the pulsars as radio sources (~100 Myr).

  12. The evolutionary link between low-mass X-ray binaries and millisecond radio pulsars

    NASA Astrophysics Data System (ADS)

    Degenaar, Nathalie

    2014-10-01

    Low-mass X-ray binaries (LMXBs) and millisecond radio pulsars (MSRPs) are two different manifestations of neutron stars in binary systems. They are thought to be evolutionary linked, but many questions about their connection remain. Recent discoveries have opened up a new vista to investigate the LMXB/MSRP link. The neutron star XSS J12270-4859 was recently observed to switch between the two different manifestations. Here, we propose to exploit the unique UV capabilities of the HST to search for the presence of a quiescent accretion disk and to test if the neutron star is hot. This will give insight into its accretion history and the mechanism driving its metamorphosis, which will have direct implications for our understanding of the LMXB/MSRP evolutionary link.

  13. Population synthesis of radio and gamma-ray millisecond pulsars using Markov Chain Monte Carlo techniques

    NASA Astrophysics Data System (ADS)

    Gonthier, Peter L.; Koh, Yew-Meng; Kust Harding, Alice

    2016-04-01

    We present preliminary results of a new population synthesis of millisecond pulsars (MSP) from the Galactic disk using Markov Chain Monte Carlo techniques to better understand the model parameter space. We include empirical radio and gamma-ray luminosity models that are dependent on the pulsar period and period derivative with freely varying exponents. The magnitudes of the model luminosities are adjusted to reproduce the number of MSPs detected by a group of thirteen radio surveys as well as the MSP birth rate in the Galaxy and the number of MSPs detected by Fermi. We explore various high-energy emission geometries like the slot gap, outer gap, two pole caustic and pair starved polar cap models. The parameters associated with the birth distributions for the mass accretion rate, magnetic field, and period distributions are well constrained. With the set of four free parameters, we employ Markov Chain Monte Carlo simulations to explore the model parameter space. We present preliminary comparisons of the simulated and detected distributions of radio and gamma-ray pulsar characteristics. We estimate the contribution of MSPs to the diffuse gamma-ray background with a special focus on the Galactic Center.We express our gratitude for the generous support of the National Science Foundation (RUI: AST-1009731), Fermi Guest Investigator Program and the NASA Astrophysics Theory and Fundamental Program (NNX09AQ71G).

  14. Five New Millisecond Pulsars from a Radio Survey of 14 Unidentified Fermi-LAT Gamma-Ray Sources

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    We have discovered five millisecond pulsars (MSPs) in a survey of 14 unidentified Ferm;'LAT sources in the southern sky using the Parkes radio telescope. PSRs J0101-6422, J1514-4946, and J1902-5105 reside in binaries, while PSRs J1658-5324 and J1747-4036 are isolated. Using an ephemeris derived from timing observations of PSR JOl01-6422 (P=2.57ms, DH=12pc/cubic cm ), we have detected gamma-ray pulsations and measured its proper motion. Its gamma-ray spectrum (a power law of Gamma = 0.9 with a cutoff at 1.6 GeV) and efficiency are typical of other MSPs, but its radio and gamma-ray light curves challenge simple geometric models of emission. The high success rate of this survey -- enabled by selecting gamma-ray sources based on their detailed spectral characteristics -- and other similarly successful searches indicate that a substantial fraction of the local population of MSPs may soon be known.

  15. Birth and Evolution of Isolated Radio Pulsars

    NASA Astrophysics Data System (ADS)

    Faucher-Giguère, Claude-André; Kaspi, Victoria M.

    2006-05-01

    We investigate the birth and evolution of Galactic isolated radio pulsars. We begin by estimating their birth space velocity distribution from proper-motion measurements of Brisken and coworkers. We find no evidence for multimodality of the distribution and favor one in which the absolute one-dimensional velocity components are exponentially distributed and with a three-dimensional mean velocity of 380+40-60 km s-1. We then proceed with a Monte Carlo-based population synthesis, modeling the birth properties of the pulsars, their time evolution, and their detection in the Parkes and Swinburne Multibeam surveys. We present a population model that appears generally consistent with the observations. Our results suggest that pulsars are born in the spiral arms, with a galactocentric radial distribution that is well described by the functional form proposed by Yusifov & Küçük, in which the pulsar surface density peaks at radius ~3 kpc. The birth spin period distribution extends to several hundred milliseconds, with no evidence of multimodality. Models that assume the radio luminosities of pulsars to be independent of the spin periods and period derivatives are inadequate, as they lead to the detection of too many old simulated pulsars in our simulations. Dithered radio luminosities proportional to the square root of the spin-down luminosity accommodate the observations well and provide a natural mechanism for the pulsars to dim uniformly as they approach the death line, avoiding an observed pileup on the latter. There is no evidence for significant torque decay (due to magnetic field decay or otherwise) over the lifetime of the pulsars as radio sources (~100 Myr). Finally, we estimate the pulsar birthrate and total number of pulsars in the Galaxy.

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

    SciTech Connect

    Crawford, Fronefield; Lyne, Andrew G.; Stairs, Ingrid H.; Kaplan, David L.; McLaughlin, Maura A.; Lorimer, Duncan R.; Freire, Paulo C. C.; Kramer, Michael; Burgay, Marta; D'Amico, Nichi; Possenti, Andrea; Camilo, Fernando; Faulkner, Andrew; Manchester, Richard N.; Steeghs, Danny

    2013-10-10

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

  17. MODELING PHASE-ALIGNED GAMMA-RAY AND RADIO MILLISECOND PULSAR LIGHT CURVES

    SciTech Connect

    Venter, C.; Johnson, T. J.; Harding, A. K.

    2012-01-01

    Since the discovery of the first eight gamma-ray millisecond pulsars (MSPs) by the Fermi Large Area Telescope, this population has been steadily expanding. Four of the more recent detections, PSR J0034-0534, PSR J1939+2134 (B1937+21; the first MSP ever discovered), PSR J1959+2048 (B1957+20; the first discovery of a black widow system), and PSR J2214+3000, exhibit a phenomenon not present in the original discoveries: nearly phase-aligned radio and gamma-ray light curves (LCs). To account for the phase alignment, we explore models where both the radio and gamma-ray emission originate either in the outer magnetosphere near the light cylinder or near the polar caps. Using a Markov Chain Monte Carlo technique to search for best-fit model parameters, we obtain reasonable LC fits for the first three of these MSPs in the context of 'altitude-limited' outer gap (alOG) and two-pole caustic (alTPC) geometries (for both gamma-ray and radio emission). These models differ from the standard outer gap (OG)/two-pole caustic (TPC) models in two respects: the radio emission originates in caustics at relatively high altitudes compared to the usual conal radio beams, and we allow both the minimum and maximum altitudes of the gamma-ray and radio emission regions to vary within a limited range (excluding the minimum gamma-ray altitude of the alTPC model, which is kept constant at the stellar radius, and that of the alOG model, which is set to the position-dependent null charge surface altitude). Alternatively, phase-aligned solutions also exist for emission originating near the stellar surface in a slot gap scenario ('low-altitude slot gap' (laSG) models). We find that the alTPC models provide slightly better LC fits than the alOG models, and both of these give better fits than the laSG models (for the limited range of parameters considered in the case of the laSG models). Thus, our fits imply that the phase-aligned LCs are likely of caustic origin, produced in the outer magnetosphere

  18. Modeling Phase-Aligned Gamma-Ray and Radio Millisecond Pulsar Light Curves

    NASA Technical Reports Server (NTRS)

    Venter, C.; Johnson, T.; Harding, A.

    2012-01-01

    Since the discovery of the first eight gamma-ray millisecond pulsars (MSPs) by the Fermi Large Area Telescope, this population has been steadily expanding. Four of the more recent detections, PSR J00340534, PSR J1939+2134 (B1937+21; the first MSP ever discovered), PSR J1959+2048 (B1957+20; the first discovery of a black widow system), and PSR J2214+3000, exhibit a phenomenon not present in the original discoveries: nearly phase-aligned radio and gamma-ray light curves (LCs). To account for the phase alignment, we explore models where both the radio and gamma-ray emission originate either in the outer magnetosphere near the light cylinder or near the polar caps. Using a Markov Chain Monte Carlo technique to search for best-fit model parameters, we obtain reasonable LC fits for the first three of these MSPs in the context of altitude-limited outer gap (alOG) and two-pole caustic (alTPC) geometries (for both gamma-ray and radio emission). These models differ from the standard outer gap (OG)/two-pole caustic (TPC) models in two respects: the radio emission originates in caustics at relatively high altitudes compared to the usual conal radio beams, and we allow both the minimum and maximum altitudes of the gamma-ray and radio emission regions to vary within a limited range (excluding the minimum gamma-ray altitude of the alTPC model, which is kept constant at the stellar radius, and that of the alOG model, which is set to the position-dependent null charge surface altitude). Alternatively, phase-aligned solutions also exist for emission originating near the stellar surface in a slot gap scenario (low-altitude slot gap (laSG) models). We find that the alTPC models provide slightly better LC fits than the alOG models, and both of these give better fits than the laSG models (for the limited range of parameters considered in the case of the laSG models). Thus, our fits imply that the phase-aligned LCs are likely of caustic origin, produced in the outer magnetosphere, and

  19. Modeling and Maximum Likelihood Fitting of Gamma-Ray and Radio Light Curves of Millisecond Pulsars Detected with Fermi

    NASA Technical Reports Server (NTRS)

    Johnson, T. J.; Harding, A. K.; Venter, C.

    2012-01-01

    Pulsed gamma rays have been detected with the Fermi Large Area Telescope (LAT) from more than 20 millisecond pulsars (MSPs), some of which were discovered in radio observations of bright, unassociated LAT sources. We have fit the radio and gamma-ray light curves of 19 LAT-detected MSPs in the context of geometric, outermagnetospheric emission models assuming the retarded vacuum dipole magnetic field using a Markov chain Monte Carlo maximum likelihood technique. We find that, in many cases, the models are able to reproduce the observed light curves well and provide constraints on the viewing geometries that are in agreement with those from radio polarization measurements. Additionally, for some MSPs we constrain the altitudes of both the gamma-ray and radio emission regions. The best-fit magnetic inclination angles are found to cover a broader range than those of non-recycled gamma-ray pulsars.

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

  2. PULSED GAMMA RAYS FROM THE ORIGINAL MILLISECOND AND BLACK WIDOW PULSARS: A CASE FOR CAUSTIC RADIO EMISSION?

    SciTech Connect

    Guillemot, L.; Kramer, M.; Freire, P. C. C.; Noutsos, A.; Johnson, T. J.; Harding, A. K.; Venter, C.; Kerr, M.; Michelson, P. F.; Pancrazi, B.; Livingstone, M.; Janssen, G. H.; Jaroenjittichai, P.; Stappers, B. W.; Espinoza, C. M.; Cognard, I.; Camilo, F.; Gargano, F.; Grove, J. E.; Johnston, S. E-mail: tyrel.j.johnson@gmail.com E-mail: kerrm@stanford.edu; and others

    2012-01-01

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

  3. HIGH-FIDELITY RADIO ASTRONOMICAL POLARIMETRY USING A MILLISECOND PULSAR AS A POLARIZED REFERENCE SOURCE

    SciTech Connect

    Van Straten, W.

    2013-01-15

    A new method of polarimetric calibration is presented in which the instrumental response is derived from regular observations of PSR J0437-4715 based on the assumption that the mean polarized emission from this millisecond pulsar remains constant over time. The technique is applicable to any experiment in which high-fidelity polarimetry is required over long timescales; it is demonstrated by calibrating 7.2 years of high-precision timing observations of PSR J1022+1001 made at the Parkes Observatory. Application of the new technique followed by arrival time estimation using matrix template matching yields post-fit residuals with an uncertainty-weighted standard deviation of 880 ns, two times smaller than that of arrival time residuals obtained via conventional methods of calibration and arrival time estimation. The precision achieved by this experiment yields the first significant measurements of the secular variation of the projected semimajor axis, the precession of periastron, and the Shapiro delay; it also places PSR J1022+1001 among the 10 best pulsars regularly observed as part of the Parkes Pulsar Timing Array (PPTA) project. It is shown that the timing accuracy of a large fraction of the pulsars in the PPTA is currently limited by the systematic timing error due to instrumental polarization artifacts. More importantly, long-term variations of systematic error are correlated between different pulsars, which adversely affects the primary objectives of any pulsar timing array experiment. These limitations may be overcome by adopting the techniques presented in this work, which relax the demand for instrumental polarization purity and thereby have the potential to reduce the development cost of next-generation telescopes such as the Square Kilometre Array.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  5. An interpretation on the millisecond- and second-scale time structures in the radio spike radiation

    NASA Astrophysics Data System (ADS)

    Shi, Jian-Kui; Zhao, Ren-Yang

    1993-03-01

    In the present paper, the time structures in solar radio spike radiation have been studied. We suggest that during the oscillations of the nonlinear MHD 'sausage' wave modes, the energetic electron beams are reflected to and fro between each two adjacent magnetic mirror points, thereby forming the loss-cone distributions in which the upward moving electron beams drive the growth of the wave modes of electron cyclotron maser instabilities, and generate the millisec-scale spike radiation. In the meanwhile, the sausage wave modes modulate the millisec-spike radiation with a period of the scale of a second. This modulation period is consistent with the evolution period of the electron beams in the loss-cone distributions.

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

    SciTech Connect

    Bogdanov, Slavko; Esposito, Paolo; Crawford III, Fronefield; Possenti, Andrea; McLaughlin, Maura A.; Freire, Paulo

    2014-01-20

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  8. SDSS J102347.6+003841: A MILLISECOND RADIO PULSAR BINARY THAT HAD A HOT DISK DURING 2000-2001

    SciTech Connect

    Wang Zhongxiang; Archibald, Anne M.; Kaspi, Victoria M.; Thorstensen, John R.; Lorimer, Duncan R.; Stairs, Ingrid; Ransom, Scott M.

    2009-10-01

    The Sloan Digital Sky Survey (SDSS) source J102347.6+003841 was recently revealed to be a binary 1.69 ms radio pulsar with a 4.75 hr orbital period and a approx0.2 M {sub sun} companion. Here, we analyze the SDSS spectrum of the source in detail. The spectrum was taken on 2001 February 1, when the source was in a bright state and showed broad, double-peaked hydrogen and helium lines-dramatically different from the G-type absorption spectrum seen from 2002 May onward. The lines are consistent with emission from a disk around the compact primary. We derive properties of the disk by fitting the SDSS continuum with a simple disk model, and find a temperature range of 2000-34,000 K from the outer to inner edge of the disk. The disk inner and outer radii were approximately 10{sup 9} and 5.7x10{sup 10} cm, respectively. These results further emphasize the unique feature of the source: it is a system likely at the end of its transition from an X-ray binary to a recycled radio pulsar. The disk mass is estimated to have been approx10{sup 23} g, most of which would have been lost due to pulsar wind ablation (or due to the propeller effect if the disk had extended inside the light cylinder of the pulsar) before the final disk disruption event. The system could undergo repeated episodes of disk formation. Close monitoring of the source is needed to catch the system in its bright state again, so that this unusual example of a pulsar-disk interaction can be studied in much finer detail.

  9. The Velocity Distribution of Isolated Radio Pulsars

    NASA Technical Reports Server (NTRS)

    Arzoumanian, Z.; Chernoff, D. F.; Cordes, J. M.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    We infer the velocity distribution of radio pulsars based on large-scale 0.4 GHz pulsar surveys. We do so by modelling evolution of the locations, velocities, spins, and radio luminosities of pulsars; calculating pulsed flux according to a beaming model and random orientation angles of spin and beam; applying selection effects of pulsar surveys; and comparing model distributions of measurable pulsar properties with survey data using a likelihood function. The surveys analyzed have well-defined characteristics and cover approx. 95% of the sky. We maximize the likelihood in a 6-dimensional space of observables P, dot-P, DM, absolute value of b, mu, F (period, period derivative, dispersion measure, Galactic latitude, proper motion, and flux density). The models we test are described by 12 parameters that characterize a population's birth rate, luminosity, shutoff of radio emission, birth locations, and birth velocities. We infer that the radio beam luminosity (i) is comparable to the energy flux of relativistic particles in models for spin-driven magnetospheres, signifying that radio emission losses reach nearly 100% for the oldest pulsars; and (ii) scales approximately as E(exp 1/2) which, in magnetosphere models, is proportional to the voltage drop available for acceleration of particles. We find that a two-component velocity distribution with characteristic velocities of 90 km/ s and 500 km/ s is greatly preferred to any one-component distribution; this preference is largely immune to variations in other population parameters, such as the luminosity or distance scale, or the assumed spin-down law. We explore some consequences of the preferred birth velocity distribution: (1) roughly 50% of pulsars in the solar neighborhood will escape the Galaxy, while approx. 15% have velocities greater than 1000 km/ s (2) observational bias against high velocity pulsars is relatively unimportant for surveys that reach high Galactic absolute value of z distances, but is severe for

  10. Birth of millisecond pulsars in globular clusters

    NASA Technical Reports Server (NTRS)

    Grindlay, J. E.; Bailyn, C. D.

    1988-01-01

    It is argued here that accretion-induced collapse of white dwarfs in binaries can form millisecond pulsars directly without requiring a precursor low-mass X-ray binary stage. Ablation of the precollapse binary companion by the millisecond pulsar's radiation field, a process invoked to explain some of the characteristics of the recently discovered eclipsing millisecond pulsar, can then yield isolated neutron stars witout requiring an additional stellar encounter.

  11. The Disturbance of a Millisecond Pulsar Magnetosphere

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  12. The Disturbance of a Millisecond Pulsar Magnetosphere

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  13. Millisecond Oxidation of Alkanes

    SciTech Connect

    Scott Han

    2011-09-30

    This project was undertaken in response to the Department of Energy's call to research and develop technologies 'that will reduce energy consumption, enhance economic competitiveness, and reduce environmental impacts of the domestic chemical industry.' The current technology at the time for producing 140 billion pounds per year of propylene from naphtha and Liquified Petroleum Gas (LPG) relied on energy- and capital-intensive steam crackers and Fluidized Catalytic Cracking (FCC) units. The propylene is isolated from the product stream in a costly separation step and subsequently converted to acrylic acid and other derivatives in separate production facilities. This project proposed a Short Contact Time Reactor (SCTR)-based catalytic oxydehydrogenation process that could convert propane to propylene and acrylic acid in a cost-effective and energy-efficient fashion. Full implementation of this technology could lead to sizeable energy, economic and environmental benefits for the U. S. chemical industry by providing up to 45 trillion BTUs/year, cost savings of $1.8 billion/year and a combined 35 million pounds/year reduction in environmental pollutants such as COx, NOx, and SOx. Midway through the project term, the program directive changed, which approval from the DOE and its review panel, from direct propane oxidation to acrylic acid at millisecond contact times to a two-step process for making acrylic acid from propane. The first step was the primary focus, namely the conversion of propane to propylene in high yields assisted by the presence of CO2. The product stream from step one was then to be fed directly into a commercially practiced propylene-to-acrylic acid tandem reactor system.

  14. Search for millisecond pulsars at the GMRT and the exotic discoveries

    NASA Astrophysics Data System (ADS)

    Bhaswati Bhattacharyya, Bhaswati

    There are, arguably, no other astronomical object whose discovery and subsequent studies provides more insight in such a rich variety of physics and astrophysics than the millisecond pulsars (MSPs). MSPs are a small sub-class of pulsars, rotating with periods of only a few milliseconds and due to their extraordinary rotational stability, MSPs can be considered as astrophysical clocks. The search for such exotic objects will not only enhance the MSP population, but will also allow much wider probe to explore their evolutionary history. We have discovered six MSPs with much diverse characteristics at the positions of Fermi LAT unassociated sources using the GMRT. Being the first galactic disk millisecond pulsars discovered at the GMRT, these discoveries are very important scientific achievement from India and illustrate the importance of low-frequency search for nearby millisecond pulsars. The discovery of these precise astrophysical clocks demands much finer grid in search phase space, which is completely driven by the number crunching capability of the High Performance Compute engine. The discoveries of binary MSPs in exotic evolutionary phases demands complete 3-D search. For example, 7.5 Tflops of compute power is used for the discovery of a very compact binary MSP, a Black Widow pulsar. This pulsar eclipses for about 13% of its orbit by a very low-mass companion (0.017 M_{⊙}). Such Black Widow pulsars are missing link between the isolated and fully recycled pulsars, where the pulsar is ablating its companion creating significant amount of intra-binary material to obscure the pulsar emission. Radio timing ephemeris allowed us to detect the gamma-ray pulsations from this millisecond pulsar. The details of the GMRT discoveries, the interesting results from our observations and the possible scientific impact of the discoveries of such exotic systems will be illustrated in this presentation.

  15. Acute isolated volar dislocation of the distal radio-ulnar joint: case report and literature review.

    PubMed

    Werthel, J-D; Masmejean, E; Silvera, J; Boyer, P; Schlur, C

    2014-10-01

    The acute isolated distal radio-ulnar (DRU) dislocation is a rare traumatic pathology and no consensus concerning its management has been established. This case report describes an acute isolated volar DRU dislocation in a 26-year-old patient. The authors propose, based on this case and after an exhaustive review of the literature, a non-operative management for these isolated and non-complicated dislocations.

  16. Millisecond pulsars - Nature's most stable clocks

    NASA Astrophysics Data System (ADS)

    Taylor, Joseph H., Jr.

    1991-07-01

    The author describes the role pulsars might play in time and frequency technology. Millisecond pulsars are rapidly rotating neutron stars: spherical flywheels some 20 km in diameter, 1.4 times as massive as the Sun, and spinning as fast as several thousand radians per second. Radio noise generated in a pulsar's magnetosphere by a highly beamed process is detectable over interstellar distances, as a periodic sequence of pulses similar to the ticks of an excellent clock. High-precision comparisons between pulsar time and terrestrial atomic time show that over intervals of several years, some millisecond pulsars have fractional stabilities comparable to those of the best atomic clocks. The author briefly reviews the physics of pulsars, discusses the techniques of pulsar timing measurements, and summarizes the results of careful studies of pulsar stabilities.

  17. Ten Years Timing of Millisecond Pulsars at Kalyazin

    NASA Astrophysics Data System (ADS)

    Ilyasov, Yu. P.; Oreshko, V. V.

    2006-08-01

    Precise timing of millisecond binary pulsars has been started at Kalyazin radio astronomical observatory since 1995. (Tver' region, Russia). Binary pulsars: J0613-02, J1020+10, J1640+22, J1643-12, J1713+07, J2145-07 and isolated millisecond pulsar B1937+21 have been included among the Kalayazin Pulsar Timing Array (KPTA). The Backer's pulsar B1937+21 is being monitored at Kalyazin observatory (0.6 GHz) and Kashima space research centre of the National Institute of Communication Technology (NICT, Japan) (2.2 GHz) simultaneously from 1996, as well. .At Kalyazin pulsars are observed at 0.6 GHz by a full steerable 64-m dish radio telescope RT-64 of the Special Research Bureau of the Moscow Power Engineering Institute. Filter-bank receiver of PRAO Lebedev Physical Institute is used for observations in two circular polarizations by 80 channels per each. Bandwidth per channel is 40 kHz, so total band is 3.2 MHz and time resolution is about 10 μs per channel. Now a perfect data base of pulses Time of Arrival (TOA) are collected with refer to the Solar system barycenter for about 10 years period. Main aim is: a) to study Pulsar Time and to establish a long-term standard of time based on pulsars ensemble as space long life clock alternative to atomic standards; b) to detect gravitational waves extremely low frequency belong to the Gravity Wave Background - GWB. After ten years monitoring of B1937+21 its timing noise is looking as "white phase noise" with RMS about 1.8 μs.( Fractional instability is about 6.10^-15). After these data and timing results of binary pulsar J1640+22 gravitational natural GWB upper limit should be reduced till to less than Ω[g]h^2 <10^-7-10^ -9 . Secular changes of DM toward millisecond pulsar B1937+21 was revealed after long time two frequency timing observations (Kalyazin -0,6 and Kashima -2.3).

  18. PSR J1024–0719: A Millisecond Pulsar in an Unusual Long-period Orbit

    NASA Astrophysics Data System (ADS)

    Kaplan, David L.; Kupfer, Thomas; Nice, David J.; Irrgang, Andreas; Heber, Ulrich; Arzoumanian, Zaven; Beklen, Elif; Crowter, Kathryn; DeCesar, Megan E.; Demorest, Paul B.; Dolch, Timothy; Ellis, Justin A.; Ferdman, Robert D.; Ferrara, Elizabeth C.; Fonseca, Emmanuel; Gentile, Peter A.; Jones, Glenn; Jones, Megan L.; Kreuzer, Simon; Lam, Michael T.; Levin, Lina; Lorimer, Duncan R.; Lynch, Ryan S.; McLaughlin, Maura A.; Miller, Adam A.; Ng, Cherry; Pennucci, Timothy T.; Prince, Tom A.; Ransom, Scott M.; Ray, Paul S.; Spiewak, Renee; Stairs, Ingrid H.; Stovall, Kevin; Swiggum, Joseph; Zhu, Weiwei

    2016-07-01

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

  19. High-Energy Emission From Millisecond Pulsars

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.; Usov, Vladimir V.; Muslimov, Alex G.

    2004-01-01

    The X-ray and gamma-ray spectrum of rotation-powered millisecond pulsars is investigated in a model for acceleration and pair cascades on open field lines above the polar caps. Although these pulsars have low surface magnetic fields, their short periods allow them to have large magnetospheric potential drops, but the majority do not produce sufficient pairs to completely screen the accelerating electric field. In these sources, the primary and secondary electrons continue to accelerate to high altitude and their Lorentz factors are limited by curvature and synchrotron radiation reaction. The accelerating particles maintain high Lorentz factors and undergo cyclotron resonant absorption of radio emission, that produces and maintains a large pitch angle, resulting in a strong synchrotron component. The resulting spectra consist of several distinct components: curvature radiation from primary electrons dominating from 1 - 100 GeV, synchrotron radiation from primary and secondary electrons dominating up to about 100 MeV, and much weaker inverse-Compton radiation from primary electrons a t 0.1 - 1 TeV. We find that the relative size of these components depends on pulsar period, period derivative, and neutron star mass and radius with the level of the synchrotron component also depending sensitively on the radio emission properties. This model is successful in describing the observed X-ray and gamma-ray spectrum of PSR J0218+4232 as synchrotron radiation, peaking around 100 MeV and extending up to a turnover around several GeV. The predicted curvature radiation components from a number of millisecond pulsars, as well as the collective emission from the millisecond pulsars in globular clusters, should be detectable with AGILE and GLAST. We also discuss a hidden population of X-ray-quiet and radio-quiet millisecond pulsars which have evolved below the pair death line, some of which may be detectable by telescopes sensitive above 1 GeV. Subject headings: pulsars: general

  20. Quark nova model for fast radio bursts

    NASA Astrophysics Data System (ADS)

    Shand, Zachary; Ouyed, Amir; Koning, Nico; Ouyed, Rachid

    2016-05-01

    Fast radio bursts (FRBs) are puzzling, millisecond, energetic radio transients with no discernible source; observations show no counterparts in other frequency bands. The birth of a quark star from a parent neutron star experiencing a quark nova - previously thought undetectable when born in isolation - provides a natural explanation for the emission characteristics of FRBs. The generation of unstable r-process elements in the quark nova ejecta provides millisecond exponential injection of electrons into the surrounding strong magnetic field at the parent neutron star's light cylinder via β-decay. This radio synchrotron emission has a total duration of hundreds of milliseconds and matches the observed spectrum while reducing the inferred dispersion measure by approximately 200 cm‑3 pc. The model allows indirect measurement of neutron star magnetic fields and periods in addition to providing astronomical measurements of β-decay chains of unstable neutron rich nuclei. Using this model, we can calculate expected FRB average energies (˜ 1041 erg) and spectral shapes, and provide a theoretical framework for determining distances.

  1. Quark nova model for fast radio bursts

    NASA Astrophysics Data System (ADS)

    Shand, Zachary; Ouyed, Amir; Koning, Nico; Ouyed, Rachid

    2016-05-01

    Fast radio bursts (FRBs) are puzzling, millisecond, energetic radio transients with no discernible source; observations show no counterparts in other frequency bands. The birth of a quark star from a parent neutron star experiencing a quark nova - previously thought undetectable when born in isolation - provides a natural explanation for the emission characteristics of FRBs. The generation of unstable r-process elements in the quark nova ejecta provides millisecond exponential injection of electrons into the surrounding strong magnetic field at the parent neutron star's light cylinder via β-decay. This radio synchrotron emission has a total duration of hundreds of milliseconds and matches the observed spectrum while reducing the inferred dispersion measure by approximately 200 cm‑3 pc. The model allows indirect measurement of neutron star magnetic fields and periods in addition to providing astronomical measurements of β-decay chains of unstable neutron rich nuclei. Using this model, we can calculate expected FRB average energies (∼ 1041 erg) and spectral shapes, and provide a theoretical framework for determining distances.

  2. String theories and millisecond pulsars

    NASA Astrophysics Data System (ADS)

    Sanchez, N.; Signore, M.

    1988-11-01

    We discuss the two ways of connecting string theories (cosmic, fundamental and the connection between them) to the observational reality: (i) radioastronomy observations (millisecond pulsar timing), and (ii) elementary particle phenomenology (compactification schemes). We study the limits imposed on the string parameter Gμ by recent millisecond pulsar timings. Cosmic strings derived from GUTs agree with (i). For cosmic strings derived from fundamental strings themselves there is contradiction between (i) and (ii). One of these scenarios connecting string theory to reality must be revised (or the transition from fundamental into cosmic strings rejected). Meanwhile, millisecond pulsar can select one scenario, or reject both of them. UA 336 Laboratoire Associé au CNRS, Observatoire de Meudon et Ecole Normale Supérieure, 24 rue Lhomond, F-75231 Paris Cedex 05, France.

  3. Swings between rotation and accretion power in a binary millisecond pulsar.

    PubMed

    Papitto, A; Ferrigno, C; Bozzo, E; Rea, N; Pavan, L; Burderi, L; Burgay, M; Campana, S; Di Salvo, T; Falanga, M; Filipović, M D; Freire, P C C; Hessels, J W T; Possenti, A; Ransom, S M; Riggio, A; Romano, P; Sarkissian, J M; Stairs, I H; Stella, L; Torres, D F; Wieringa, M H; Wong, G F

    2013-09-26

    It is thought that neutron stars in low-mass binary systems can accrete matter and angular momentum from the companion star and be spun-up to millisecond rotational periods. During the accretion stage, the system is called a low-mass X-ray binary, and bright X-ray emission is observed. When the rate of mass transfer decreases in the later evolutionary stages, these binaries host a radio millisecond pulsar whose emission is powered by the neutron star's rotating magnetic field. This evolutionary model is supported by the detection of millisecond X-ray pulsations from several accreting neutron stars and also by the evidence for a past accretion disc in a rotation-powered millisecond pulsar. It has been proposed that a rotation-powered pulsar may temporarily switch on during periods of low mass inflow in some such systems. Only indirect evidence for this transition has hitherto been observed. Here we report observations of accretion-powered, millisecond X-ray pulsations from a neutron star previously seen as a rotation-powered radio pulsar. Within a few days after a month-long X-ray outburst, radio pulses were again detected. This not only shows the evolutionary link between accretion and rotation-powered millisecond pulsars, but also that some systems can swing between the two states on very short timescales.

  4. Swings between rotation and accretion power in a binary millisecond pulsar.

    PubMed

    Papitto, A; Ferrigno, C; Bozzo, E; Rea, N; Pavan, L; Burderi, L; Burgay, M; Campana, S; Di Salvo, T; Falanga, M; Filipović, M D; Freire, P C C; Hessels, J W T; Possenti, A; Ransom, S M; Riggio, A; Romano, P; Sarkissian, J M; Stairs, I H; Stella, L; Torres, D F; Wieringa, M H; Wong, G F

    2013-09-26

    It is thought that neutron stars in low-mass binary systems can accrete matter and angular momentum from the companion star and be spun-up to millisecond rotational periods. During the accretion stage, the system is called a low-mass X-ray binary, and bright X-ray emission is observed. When the rate of mass transfer decreases in the later evolutionary stages, these binaries host a radio millisecond pulsar whose emission is powered by the neutron star's rotating magnetic field. This evolutionary model is supported by the detection of millisecond X-ray pulsations from several accreting neutron stars and also by the evidence for a past accretion disc in a rotation-powered millisecond pulsar. It has been proposed that a rotation-powered pulsar may temporarily switch on during periods of low mass inflow in some such systems. Only indirect evidence for this transition has hitherto been observed. Here we report observations of accretion-powered, millisecond X-ray pulsations from a neutron star previously seen as a rotation-powered radio pulsar. Within a few days after a month-long X-ray outburst, radio pulses were again detected. This not only shows the evolutionary link between accretion and rotation-powered millisecond pulsars, but also that some systems can swing between the two states on very short timescales. PMID:24067710

  5. Isolation of radio-iodinated apical and basal-lateral plasma membranes of toad bladder epithelium.

    PubMed

    Rodriguez, H J; Edelman, I S

    1979-04-01

    The apical and basal-lateral plasma membranes of toad bladder epithelium were radio-iodinated with the glucose-glucose oxidase-lactoperoxidase system. The covalently bound radio iodine was used as a marker during subcellular fractionation and membrane isolation. Homogenization conditions that ensured rupture of more than 80% of the cells without substantial nuclear damage were defined by Normarski optics. The nuclei were separated by differential centrifugation and the apical and basal-lateral components were resolved by differential and sucrose density gradient centrifugation. The apical components yielded two radioactive bands that were identified as glycocalyx and plasma membrane labeled with 125I. The basal-lateral components yielded a hetero-disperse pattern made up of at least 3 radioactive bands, but the bulk of the activity of ouabain-sensitive ATPase comigrated with only one of these bands. The mitochondia, identified by assays for cytochrome oxidase and NADH cytochrome c reductase activities, were separated from the radio-iodine labeled by centrifugation in sucrose density gradients under isokinetic conditions. The labeled glycocalyx and the slowly migrating components of basal-lateral labeling were separated from the radio-iodinated membranes by centrifugation at 100,000 x g x 1 hr after removal of the mitochrondria by the isokinetic method. The labeled membranes were then subjected to ultracentrifugation in sucrose density gradients under isopycnic conditions; the basal-lateral membranes containing ouabain-sensitive ATP-ase were well resolved from the apical membranes by this method. These results provide a relatively rapid method of attaining partial purification of the apical and basal-lateral plasma membranes of toad bladder epithelium. PMID:222911

  6. Binary millisecond pulsar discovery via gamma-ray pulsations.

    PubMed

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

    2012-12-01

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

  7. An eccentric binary millisecond pulsar in the galactic plane.

    PubMed

    Champion, David J; Ransom, Scott M; Lazarus, Patrick; Camilo, Fernando; Bassa, Cees; Kaspi, Victoria M; Nice, David J; Freire, Paulo C C; Stairs, Ingrid H; van Leeuwen, Joeri; Stappers, Ben W; Cordes, James M; Hessels, Jason W T; Lorimer, Duncan R; Arzoumanian, Zaven; Backer, Don C; Bhat, N D Ramesh; Chatterjee, Shami; Cognard, Ismaël; Deneva, Julia S; Faucher-Giguère, Claude-André; Gaensler, Bryan M; Han, Jinlin; Jenet, Fredrick A; Kasian, Laura; Kondratiev, Vlad I; Kramer, Michael; Lazio, Joseph; McLaughlin, Maura A; Venkataraman, Arun; Vlemmings, Wouter

    2008-06-01

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

  8. An Eccentric Binary Millisecond Pulsar in the Galactic Plane

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

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

  9. Binary millisecond pulsar discovery via gamma-ray pulsations.

    PubMed

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

    2012-12-01

    Millisecond pulsars, old neutron stars spun up by accreting matter from a companion star, can reach high rotation rates of hundreds of revolutions per second. Until now, all such "recycled" rotation-powered pulsars have been detected by their spin-modulated radio emission. In a computing-intensive blind search of gamma-ray data from the Fermi Large Area Telescope (with partial constraints from optical data), we detected a 2.5-millisecond pulsar, PSR J1311-3430. This unambiguously explains a formerly unidentified gamma-ray source that had been a decade-long enigma, confirming previous conjectures. The pulsar is in a circular orbit with an orbital period of only 93 minutes, the shortest of any spin-powered pulsar binary ever found. PMID:23112297

  10. An eccentric binary millisecond pulsar in the galactic plane.

    PubMed

    Champion, David J; Ransom, Scott M; Lazarus, Patrick; Camilo, Fernando; Bassa, Cees; Kaspi, Victoria M; Nice, David J; Freire, Paulo C C; Stairs, Ingrid H; van Leeuwen, Joeri; Stappers, Ben W; Cordes, James M; Hessels, Jason W T; Lorimer, Duncan R; Arzoumanian, Zaven; Backer, Don C; Bhat, N D Ramesh; Chatterjee, Shami; Cognard, Ismaël; Deneva, Julia S; Faucher-Giguère, Claude-André; Gaensler, Bryan M; Han, Jinlin; Jenet, Fredrick A; Kasian, Laura; Kondratiev, Vlad I; Kramer, Michael; Lazio, Joseph; McLaughlin, Maura A; Venkataraman, Arun; Vlemmings, Wouter

    2008-06-01

    Binary pulsar systems are superb probes of stellar and binary evolution and the physics of extreme environments. In a survey with the Arecibo telescope, we have found PSR J1903+0327, a radio pulsar with a rotational period of 2.15 milliseconds in a highly eccentric (e = 0.44) 95-day orbit around a solar mass (M(middle dot in circle)) companion. Infrared observations identify a possible main-sequence companion star. Conventional binary stellar evolution models predict neither large orbital eccentricities nor main-sequence companions around millisecond pulsars. Alternative formation scenarios involve recycling a neutron star in a globular cluster, then ejecting it into the Galactic disk, or membership in a hierarchical triple system. A relativistic analysis of timing observations of the pulsar finds its mass to be 1.74 +/- 0.04 M solar symbol, an unusually high value. PMID:18483399

  11. A distinct class of isolated intracloud lightning discharges and their associated radio emissions

    NASA Astrophysics Data System (ADS)

    Smith, D. A.; Shao, X. M.; Holden, D. N.; Rhodes, C. T.; Brook, M.; Krehbiel, P. R.; Stanley, M.; Rison, W.; Thomas, R. J.

    1999-02-01

    Observations of radio emissions from thunderstorms were made during the summer of 1996 using two arrays of sensors located in northern New Mexico. The first array consisted of three fast electric field change meters separated by distances of 30 to 230 km. The second array consisted of three broadband (3 to 30 MHz) HF data acquisition systems separated by distances of 6 to 13 km. Differences in signal times of arrival at multiple stations were used to locate the sources of received signals. Relative times of arrival of signal reflections from the ionosphere and Earth were used to determine source heights. A distinct class of short-duration electric field change emissions was identified and characterized. The emissions have previously been termed narrow positive bipolar pulses (NPBPs). NPBPs were emitted from singular intracloud discharges that occurred in the most active regions of three thunderstorms located in New Mexico and west Texas. The discharges occurred at altitudes between 8 and 11 km above mean sea level. NEXRAD radar images show that the NPBP sources were located in close proximity to high reflectivity storm cores where reflectivity values were in excess of 40 dBZ. NPBP electric field change waveforms were isolated, bipolar, initially positive pulses with peak amplitudes comparable to those of return stroke field change waveforms. The mean FWHM (full width at half maximum) of initial NPBP field change pulses was 4.7 μs. The HF emissions associated with NPBPs were broadband noise-like radiation bursts with a mean duration of 2.8 μs and amplitudes 10 times larger than emissions from typical intracloud and cloud-to-ground lightning processes. Calculations indicate that the events represent a distinct class of singular, isolated lightning discharges that have limited spatial extents of 300 to 1000 m and occur in high electric field regions. The unique radio emissions produced by these discharges, in combination with their unprecedented physical

  12. Microwave millisecond spike emission and its associated phenomena during the impulsive phase of large flares

    NASA Technical Reports Server (NTRS)

    Li, Chunsheng; Jiang, Shuying; Li, Hongwei; Fu, Qi-Jun

    1986-01-01

    A tentative model is proposed to account for some features of the microwave millisecond spike emission and its links with the physical processes of associated phenomena during the impulsive phase of large flares by comparing the optical, radio, and X-ray observations on May 16, 1981 to those on October 12, 1981.

  13. X-Ray States of Redback Millisecond Pulsars

    NASA Astrophysics Data System (ADS)

    Linares, M.

    2014-11-01

    Compact binary millisecond pulsars with main-sequence donors, often referred to as "redbacks," constitute the long-sought link between low-mass X-ray binaries and millisecond radio pulsars and offer a unique probe of the interaction between pulsar winds and accretion flows. We present a systematic study of eight nearby redbacks, using more than 100 observations obtained with Swift's X-ray Telescope. We distinguish between three main states: pulsar, disk, and outburst states. We find X-ray mode switching in the disk state of PSR J1023+0038 and XSS J12270-4859, similar to what was found in the other redback that showed evidence for accretion: rapid, recurrent changes in X-ray luminosity (0.5-10 keV, L X), between (6-9) × 1032 erg s-1 (disk-passive state) and (3-5) × 1033 erg s-1 (disk-active state). This strongly suggests that mode switching—which has not been observed in quiescent low-mass X-ray binaries—is universal among redback millisecond pulsars in the disk state. We briefly explore the implications for accretion disk truncation and find that the inferred magnetospheric radius in the disk state of PSR J1023+0038 and XSS J12270-4859 lies outside the light cylinder. Finally, we note that all three redbacks that have developed accretion disks have relatively high L X in the pulsar state (>1032 erg s-1).

  14. Case studies of pre-engineered and manufactured sound isolation rooms for music practice and radio broadcast

    NASA Astrophysics Data System (ADS)

    Probst, Ron N.; Rypka, Dann

    2005-09-01

    Pre-engineered and manufactured sound isolation rooms were developed to ensure guaranteed sound isolation while offering the unique ability to be disassembled and relocated without loss of acoustic performance. Case studies of pre-engineered sound isolation rooms used for music practice and various radio broadcast purposes are highlighted. Three prominent universities wrestle with the challenges of growth and expansion while responding to the specialized acoustic requirements of these spaces. Reduced state funding for universities requires close examination of all options while ensuring sound isolation requirements are achieved. Changing curriculum, renovation, and new construction make pre-engineered and manufactured rooms with guaranteed acoustical performance good investments now and for the future. An added benefit is the optional integration of active acoustics to provide simulations of other spaces or venues along with the benefit of sound isolation.

  15. Search for pairs of isolated radio pulsars—Components in disrupted binary systems

    NASA Astrophysics Data System (ADS)

    Chmyreva, E. G.; Beskin, G. M.; Biryukov, A. V.

    2010-02-01

    We have developed a method for analyzing the kinematic association of isolated relativistic objects-possible remnants of disrupted close binary systems. We investigate pairs of fairly young radio pulsars with known proper motions and estimated distances (dispersion measures) that are spaced no more than 2-3 kpc apart. Using a specified radial velocity distribution for these objects, we have constructed 100-300 thousand trajectories of their possible motion in the Galactic gravitational field on a time scale of several million years. The probabilities of their close encounters at epochs consistent with the age of the younger pulsar in the pair are analyzed. When these probabilities exceed considerably their reference values obtained by assuming a purely random encounter between the pulsars under consideration, we conclude that the objects may have been gravitationally bound in the past. As a result, we have detected six pulsar pairs (J0543+2329/J0528+2200, J1453-6413/J1430-6623, J2354+6155/J2321+6024, J1915+1009/J1909+1102, J1832-0827/J1836-1008, and J1917+1353/J1926+1648) that are companions in disrupted binary systems with a high probability. Estimates of their kinematic ages and velocities at binary disruption and at the present epoch are provided.

  16. Three Millisecond Pulsars in Fermi LAT Unassociated Bright Sources

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

  17. THREE MILLISECOND PULSARS IN FERMI LAT UNASSOCIATED BRIGHT SOURCES

    SciTech Connect

    Ransom, S. M.; Ray, P. S.; Wolff, M. T.; Grove, J. E.; Camilo, F.; Roberts, M. S. E.; Celik, Oe.; DeCesar, M. E.; Ferrara, E. C.; Gehrels, N.; Cheung, C. C.; Abdo, A. A.; Kerr, M.; Pennucci, T.; Cognard, I.; Freire, P. C. C.; Desvignes, G.; Donato, D. E-mail: Paul.Ray@nrl.navy.mil

    2011-01-20

    We searched for radio pulsars in 25 of the non-variable, unassociated sources in the Fermi LAT Bright Source List with the Green Bank Telescope at 820 MHz. We report the discovery of three radio and {gamma}-ray millisecond pulsars (MSPs) from a high Galactic latitude subset of these sources. All of the pulsars are in binary systems, which would have made them virtually impossible to detect in blind {gamma}-ray pulsation searches. They seem to be relatively normal, nearby ({<=}2 kpc) MSPs. These observations, in combination with the Fermi detection of {gamma}-rays from other known radio MSPs, imply that most, if not all, radio MSPs are efficient {gamma}-ray producers. The {gamma}-ray spectra of the pulsars are power law in nature with exponential cutoffs at a few GeV, as has been found with most other pulsars. The MSPs have all been detected as X-ray point sources. Their soft X-ray luminosities of {approx}10{sup 30}-10{sup 31} erg s{sup -1} are typical of the rare radio MSPs seen in X-rays.

  18. A LOFAR census of millisecond pulsars

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    We report the detection of 48 millisecond pulsars (MSPs) out of 75 observed thus far using the LOw-Frequency ARray (LOFAR) in the frequency range 110-188 MHz. We have also detected three MSPs out of nine observed in the frequency range 38-77 MHz. This is the largest sample of MSPs ever observed at these low frequencies, and half of the detected MSPs were observed for the first time atfrequencies below 200 MHz. We present the average pulse profiles of the detected MSPs, their effective pulse widths, and flux densities and compare these with higher observing frequencies. The flux-calibrated, multifrequency LOFAR pulse profiles are publicly available via the European Pulsar Network Database of Pulsar Profiles. We also present average values of dispersion measures (DM) and discuss DM and profile variations. About 35% of the MSPs show strong narrow profiles, another 25% exhibit scattered profiles, and the rest are only weakly detected. A qualitative comparison of the LOFAR MSP profiles with those at higher radio frequencies shows constant separation between profile components. Similarly, the profile widths are consistent with those observed at higher frequencies, unless scattering dominates at the lowest frequencies. This is very different from what is observed for normal pulsars and suggests a compact emission region in the MSP magnetosphere. The amplitude ratio of the profile components, on the other hand, can dramatically change towards low frequencies, often with the trailing component becoming dominant. As previously demonstrated this can be caused by aberration and retardation. This data set enables high-precision studies of pulse profile evolution with frequency, dispersion, Faraday rotation, and scattering in the interstellar medium. Characterising and correcting these systematic effects may improve pulsar-timing precision at higher observing frequencies, where pulsar timing array projects aim to directly detect gravitational waves.

  19. COHERENTLY DEDISPERSED GATED IMAGING OF MILLISECOND PULSARS

    SciTech Connect

    Roy, Jayanta; Bhattacharyya, Bhaswati

    2013-03-10

    Motivated by the need for rapid localization of newly discovered faint millisecond pulsars (MSPs), we have developed a coherently dedispersed gating correlator. This gating correlator accounts for the orbital motions of MSPs in binaries while folding the visibilities with a best-fit topocentric rotational model derived from a periodicity search in a simultaneously generated beamformer output. Unique applications of the gating correlator for sensitive interferometric studies of MSPs are illustrated using the Giant Metrewave Radio Telescope (GMRT) interferometric array. We could unambiguously localize five newly discovered Fermi MSPs in the on-off gated image plane with an accuracy of {+-}1''. Immediate knowledge of such a precise position enables the use of sensitive coherent beams of array telescopes for follow-up timing observations which substantially reduces the use of telescope time ({approx}20 Multiplication-Sign for the GMRT). In addition, a precise a priori astrometric position reduces the effect of large covariances in the timing fit (with discovery position, pulsar period derivative, and an unknown binary model), which in-turn accelerates the convergence to the initial timing model. For example, while fitting with the precise a priori position ({+-}1''), the timing model converges in about 100 days, accounting for the effect of covariance between the position and pulsar period derivative. Moreover, such accurate positions allow for rapid identification of pulsar counterparts at other wave bands. We also report a new methodology of in-beam phase calibration using the on-off gated image of the target pulsar, which provides optimal sensitivity of the coherent array removing possible temporal and spacial decoherences.

  20. A Chandra look at the X-ray faint millisecond pulsars in the globular cluster NGC 6752

    NASA Astrophysics Data System (ADS)

    Forestell, L. M.; Heinke, C. O.; Cohn, H. N.; Lugger, P. M.; Sivakoff, G. R.; Bogdanov, S.; Cool, A. M.; Anderson, J.

    2014-06-01

    We combine new and archival Chandra observations of the globular cluster NGC 6752 to create a deeper X-ray source list, and study the faint radio millisecond pulsars (MSPs) of this cluster. We detect four of the five MSPs in NGC 6752, and present evidence for emission from the fifth. The X-rays from these MSPs are consistent with thermal emission from the neutron star surfaces, with significantly higher fitted blackbody temperatures than other globular cluster MSPs (though we cannot rule out contamination by non-thermal emission or other X-ray sources). NGC 6752 E is one of the lowest-LX MSPs known, with LX(0.3-8 keV) = 1.0^{+0.9}_{-0.5}× 10^{30} erg s-1. We check for optical counterparts of the three isolated MSPs in the core using new Hubble Space Telescope Advanced Camera for Surveys images, finding no plausible counterparts, which is consistent with their lack of binary companions. We compile measurements of LX and spin-down power for radio MSPs from the literature, including errors where feasible. We find no evidence that isolated MSPs have lower LX than MSPs in binary systems, omitting binary MSPs showing emission from intrabinary wind shocks. We find weak evidence for an inverse correlation between the estimated temperature of the MSP X-rays and the known MSP spin period, consistent with the predicted shrinking of the MSP polar cap size with increasing spin period.

  1. Genesis stories for the millisecond pulsar

    NASA Technical Reports Server (NTRS)

    Ruderman, M. A.; Shaham, J.

    1983-01-01

    Theoretical models proposed to explain the origin of the millisecond pulsar (MP) PSR 1937+214 are reviewed, examining their ability to explain its low surface dipole magnetic field (B), its low birth temperature (less than 10 to the 8th K), the absence of a companion or remnant, and its low velocity perpendicular to the Galactic plane. The models discussed are a single isolated explosion forming a rapidly spinning neutron star, spin-up of a dead pulsar by accretion from a companion, collapse of an accreting spinning white dwarf, and fusion of a tight binary composed of two old neutron stars. Although all of the models have difficulties in explaining one or more of the MP characteristics, the second model is found to be most probable in the light of present knowledge. The lack of a companion is explained by its tidal disruption after it had fed the accreting pre-pulsar for 1 Gyr or more and its mass had decreased to about 0.01 solar mass. Neutron stars accreting in this way have been observed in Galactic-bulge X-ray sources.

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

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

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

  3. What is causing the eclipse in the millisecond binary pulsar

    SciTech Connect

    Rasio, F.A.; Shapiro, S.L.; Teukolsky, S.A. )

    1989-07-01

    Possible physical mechanisms for explaining the radio eclipses in the millisecond binary pulsar PSR 1957 + 20 are discussed. If, as recent observations suggest, the duration of the eclipses depends on the observing frequency, a plausible mechanism is free-free absorption of the radio pulses by a low-density ionized wind surrounding the companion. Detailed numerical calculations are performed for this case, and it is found that all of the observations made at 430 MHz can be reliably reproduced, including the asymmetry in the excess time delay of the pulses. The model leads to definite predictions for the duration of the eclipse at other observing frequencies, as well as the radio intensity and excess time delay of the pulses as a function of orbital phase. If the duration of the eclipses were found to be independent of frequency, then the likely mechanism would be reflection of the radio signal at a contact discontinuity between a high-density wind and the pulsar radiation. In this case, however, it is difficult to explain the observed symmetry of the eclipse. 12 refs.

  4. X-ray states of redback millisecond pulsars

    SciTech Connect

    Linares, M.

    2014-11-01

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

  5. FORMATION OF BLACK WIDOWS AND REDBACKS—TWO DISTINCT POPULATIONS OF ECLIPSING BINARY MILLISECOND PULSARS

    SciTech Connect

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

    2013-09-20

    Eclipsing binary millisecond pulsars (MSPs; the so-called black widows and redbacks) can provide important information about accretion history, pulsar irradiation of their companion stars, and the evolutionary link between accreting X-ray pulsars and isolated MSPs. However, the formation of such systems is not well understood, nor the difference in progenitor evolution between the two populations of black widows and redbacks. Whereas both populations have orbital periods between 0.1 and 1.0 days, their companion masses differ by an order of magnitude. In this paper, we investigate the formation of these systems via the evolution of converging low-mass X-ray binaries by employing the MESA stellar evolution code. Our results confirm that one can explain the formation of most of these eclipsing binary MSPs using this scenario. More notably, we find that the determining factor for producing either black widows or redbacks is the efficiency of the irradiation process, such that the redbacks absorb a larger fraction of the emitted spin-down energy of the radio pulsar (resulting in more efficient mass loss via evaporation) compared to that of the black widow systems. We argue that geometric effects (beaming) are responsible for the strong bimodality of these two populations. Finally, we conclude that redback systems do not evolve into black widow systems with time.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  7. Millisecond Pulsars at Gamma-Ray Energies: Fermi Detections and Implications

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.

    2011-01-01

    The Fermi Gamma-Ray Space Telescope has revolutionized the study of pulsar physics with the discovery of new populations of radio quiet and millisecond gamma-ray pulsars. The Fermi Large Area Telescope has so far discovered approx.20 new gamma-ray millisecond pulsars (MSPs) by both folding at periods of known radio MSPs or by detecting them as gamma-ray sources that are followed up by radio pulsar searches. The second method has resulted in a phenomenally successful synergy, with -30 new radio MSPs (to date) having been discovered at Fermi unidentified source locations and the gamma-ray pulsations having then been detected in a number of these using the radio timing solutions. Many of the newly discovered MSPs may be suitable for addition to the collection of very stable MSPs used for gravitational wave detection. Detection of such a large number of MSPs was surprising, given that most have relatively low spin-down luminosity and surface field strength. I will discuss their properties and the implications for pulsar particle acceleration and emission, as well as their potential contribution to gamma-ray backgrounds and Galactic cosmic rays.

  8. Population synthesis of isolated neutron stars with magneto-rotational evolution - II. From radio-pulsars to magnetars

    NASA Astrophysics Data System (ADS)

    Gullón, M.; Pons, J. A.; Miralles, J. A.; Viganò, D.; Rea, N.; Perna, R.

    2015-11-01

    Population synthesis studies constitute a powerful method to reconstruct the birth distribution of periods and magnetic fields of the pulsar population. When this method is applied to populations in different wavelengths, it can break the degeneracy in the inferred properties of initial distributions that arises from single-band studies. In this context, we extend previous works to include X-ray thermal emitting pulsars within the same evolutionary model as radio-pulsars. We find that the cumulative distribution of the number of X-ray pulsars can be well reproduced by several models that, simultaneously, reproduce the characteristics of the radio-pulsar distribution. However, even considering the most favourable magneto-thermal evolution models with fast field decay, lognormal distributions of the initial magnetic field overpredict the number of visible sources with periods longer than 12 s. We then show that the problem can be solved with different distributions of magnetic field, such as a truncated lognormal distribution, or a binormal distribution with two distinct populations. We use the observational lack of isolated neutron stars (NSs) with spin periods P > 12 s to establish an upper limit to the fraction of magnetars born with B > 1015 G (less than 1 per cent). As future detections keep increasing the magnetar and high-B pulsar statistics, our approach can be used to establish a severe constraint on the maximum magnetic field at birth of NSs.

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

    SciTech Connect

    Abdo, Aous A.; Ackermann, M.; Atwood, W.B.; Axelsson, M. Baldini, L.; Ballet, J.; Barbiellini, Guido; Bastieri, Denis; Battelino, M.; Baughman, B.M.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Bloom, Elliott D.; Bonamente, E.; Borgland, A.W.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Burnett, Thompson H.; /more authors..

    2011-11-17

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

  10. The Mass of a Millisecond Pulsar

    NASA Astrophysics Data System (ADS)

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

    2005-12-01

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

  11. Millisecond Timescale Synchrony among Hippocampal Neurons

    PubMed Central

    Amarasingham, Asohan; Mizuseki, Kenji; Buzsáki, György

    2014-01-01

    Inhibitory neurons in cortical circuits play critical roles in composing spike timing and oscillatory patterns in neuronal activity. These roles in turn require coherent activation of interneurons at different timescales. To investigate how the local circuitry provides for these activities, we applied resampled cross-correlation analyses to large-scale recordings of neuronal populations in the cornu ammonis 1 (CA1) and CA3 regions of the hippocampus of freely moving rats. Significant counts in the cross-correlation of cell pairs, relative to jittered surrogate spike-trains, allowed us to identify the effective couplings between neurons in CA1 and CA3 hippocampal regions on the timescale of milliseconds. In addition to putative excitatory and inhibitory monosynaptic connections, we uncovered prominent millisecond timescale synchrony between cell pairs, observed as peaks in the central 0 ms bin of cross-correlograms. This millisecond timescale synchrony appeared to be independent of network state, excitatory input, and γ oscillations. Moreover, it was frequently observed between cells of differing putative interneuronal type, arguing against gap junctions as the sole underlying source. Our observations corroborate recent in vitro findings suggesting that inhibition alone is sufficient to synchronize interneurons at such fast timescales. Moreover, we show that this synchronous spiking may cause stronger inhibition and rebound spiking in target neurons, pointing toward a potential function for millisecond synchrony of interneurons in shaping and affecting timing in pyramidal populations within and downstream from the circuit. PMID:25378164

  12. The coevolution of decimetric millisecond spikes and hard X-ray emission during solar flares

    NASA Technical Reports Server (NTRS)

    Aschwanden, Markus J.; Guedel, Manuel

    1992-01-01

    Results are presented of an analysis of a comprehensive data set of 27 solar flares with decimetric millisecond spikes between 1980 and 1989, simultaneously observed with the Zuerich radio spectrometers and the Hard X-ray Burst Spectrometer on the SMM spacecraft. Two contradictory relationships of the coevolution of hard X-ray and spiky radio emissions during flares are found: the temporal evolution of both emissions reveals a close functional dependence, but there is a substantial time delay between the two emissions. Five possible scenarios for the hard-X-ray-associated radio spike emission which may account for both their detailed coevolution and their substantial intervening time delay are discussed. All five scenarios are able to explain both the close coevolution of hard X-ray and radio emission as well as their mutual delay to some degree, but none of them can explain all observational aspects in a simple way.

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

    NASA Astrophysics Data System (ADS)

    Rivera Sandoval, Liliana E.

    2016-07-01

    Up to date 144 radio millisecond pulsars have been found in Galactic globular clusters, of which about two-thirds are in a binary. However, until recently only for 10 of those binary millisecond pulsars the companion has been firmly identified at optical wavelengths. We present the discovery of 2 likely He white dwarf companions to millisecond pulsars in the globular cluster 47 Tucanae, as well as the confirmation of 2 tentative identifications in the same cluster, using near-ultraviolet images obtained with the Hubble Space Telescope. This represents an important contribution to the total number of optical counterparts known in Galactic globular clusters so far. We have also analyzed optical observations taken with Hubble. From these images, we obtained H_α results for some of the counterparts. Based on our UV photometry and He WD cooling models we derived the ages, the masses and the bolometric luminosities for all the He WD companions. I will discuss our results and their implications in the context of the standard millisecond pulsar formation scenario.

  14. XMM-Newton Observations of Four Millisecond Pulsars

    NASA Technical Reports Server (NTRS)

    Zavlin, Vyacheslav E.

    2005-01-01

    I present an analysis of the XMM-Newton observations of four millisecond pulsars, J0437-4715, J2124-3358, J1024-0719, and J0034-0534. The new data provide strong evidence of thermal emission in the X-ray flux detected from the first three objects. This thermal component is best interpreted as radiation from pulsar polar caps covered with a nonmagnetic hydrogen atmosphere. A nonthermal power-law component, dominating at energies E greater than or equal to 3 keV, can also be present in the detected X-ray emission. For PSR J0437-4715, the timing analysis reveals that the shape and pulsed fraction of the pulsar light curves are energy dependent. This, together with the results obtained from the phase-resolved spectroscopy, supports the two-component (thermal plus nonthermal) interpretation of the pulsar's X-ray radiation. Highly significant pulsations have been found in the X-ray flux of PSRs 52124-3358 and 51024-0719. For PSR 50034-0534, a possible X-ray counterpart of the radio pulsar has been suggested. The inferred properties of the detected thermal emission are compared with predictions of radio pulsar models.

  15. The High Time Resolution Radio Sky

    NASA Astrophysics Data System (ADS)

    Thornton, D.

    2013-11-01

    each orbit, PSR J1729-2117 which is an unusual isolated recycled pulsar, and PSR J2322-2650 which has a companion of very low mass - just 7 × 10^{-4} {M}_{⊙}, amongst others. I begin this thesis with the study of these pulsars and discuss their histories. In addition, I demonstrate that optical observations of the companions to some of the newly discovered pulsars in the High Time Resolution Universe survey may result in a measurement of their age and that of the pulsar. I have discovered five new extragalactic single radio bursts, confirming them as an astronomical population. These appear to occur frequently, with a rate of 1.0^{+0.6}_{-0.5} × 10^4 sky^{-1} day^{-1}. The sources are likely at cosmological distances - with redshifts between 0.45 and 1.45, making them more than half way to the Big Bang in the most distant case. This implies their luminosities must be enormous, 10^{31} to 10^{33} J emitted in just a few milliseconds. Their source is unknown but I present an analysis of the options. I also perform a population simulation of the bursts which demonstrates how their intrinsic spectrum could be measured, even for unlocalised FRBs: early indications are that the spectral index of FRBs < 0.

  16. A millisecond pulsar in a stellar triple system.

    PubMed

    Ransom, S M; Stairs, I H; Archibald, A M; Hessels, J W T; Kaplan, D L; van Kerkwijk, M H; Boyles, J; Deller, A T; Chatterjee, S; Schechtman-Rook, A; Berndsen, A; Lynch, R S; Lorimer, D R; Karako-Argaman, C; Kaspi, V M; Kondratiev, V I; McLaughlin, M A; van Leeuwen, J; Rosen, R; Roberts, M S E; Stovall, K

    2014-01-23

    Gravitationally bound three-body systems have been studied for hundreds of years and are common in our Galaxy. They show complex orbital interactions, which can constrain the compositions, masses and interior structures of the bodies and test theories of gravity, if sufficiently precise measurements are available. A triple system containing a radio pulsar could provide such measurements, but the only previously known such system, PSR B1620-26 (refs 7, 8; with a millisecond pulsar, a white dwarf, and a planetary-mass object in an orbit of several decades), shows only weak interactions. Here we report precision timing and multiwavelength observations of PSR J0337+1715, a millisecond pulsar in a hierarchical triple system with two other stars. Strong gravitational interactions are apparent and provide the masses of the pulsar M[Symbol: see text](1.4378(13), where M[Symbol: see text]is the solar mass and the parentheses contain the uncertainty in the final decimal places) and the two white dwarf companions (0.19751(15)M[Symbol: see text] and 0.4101(3))M[Symbol: see text], as well as the inclinations of the orbits (both about 39.2°). The unexpectedly coplanar and nearly circular orbits indicate a complex and exotic evolutionary past that differs from those of known stellar systems. The gravitational field of the outer white dwarf strongly accelerates the inner binary containing the neutron star, and the system will thus provide an ideal laboratory in which to test the strong equivalence principle of general relativity. PMID:24390352

  17. A millisecond pulsar in an extremely wide binary system

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    We report on 22 yr of radio timing observations of the millisecond pulsar J1024-0719 by the telescopes participating in the European Pulsar Timing Array (EPTA). These observations reveal a significant second derivative of the pulsar spin frequency and confirm the discrepancy between the parallax and Shklovskii distances that has been reported earlier. We also present optical astrometry, photometry and spectroscopy of 2MASS J10243869-0719190. We find that it is a low-metallicity main-sequence star (K7V spectral type, [M/H] = -1.0, Teff = 4050 ± 50 K) and that its position, proper motion and distance are consistent with those of PSR J1024-0719. We conclude that PSR J1024-0719 and 2MASS J10243869-0719190 form a common proper motion pair and are gravitationally bound. The gravitational interaction between the main-sequence star and the pulsar accounts for the spin frequency derivatives, which in turn resolves the distance discrepancy. Our observations suggest that the pulsar and main-sequence star are in an extremely wide (Pb > 200 yr) orbit. Combining the radial velocity of the companion and proper motion of the pulsar, we find that the binary system has a high spatial velocity of 384 ± 45 km s-1 with respect to the local standard of rest and has a Galactic orbit consistent with halo objects. Since the observed main-sequence companion star cannot have recycled the pulsar to millisecond spin periods, an exotic formation scenario is required. We demonstrate that this extremely wide-orbit binary could have evolved from a triple system that underwent an asymmetric supernova explosion, though find that significant fine-tuning during the explosion is required. Finally, we discuss the implications of the long period orbit on the timing stability of PSR J1024-0719 in light of its inclusion in pulsar timing arrays.

  18. A millisecond pulsar in a stellar triple system.

    PubMed

    Ransom, S M; Stairs, I H; Archibald, A M; Hessels, J W T; Kaplan, D L; van Kerkwijk, M H; Boyles, J; Deller, A T; Chatterjee, S; Schechtman-Rook, A; Berndsen, A; Lynch, R S; Lorimer, D R; Karako-Argaman, C; Kaspi, V M; Kondratiev, V I; McLaughlin, M A; van Leeuwen, J; Rosen, R; Roberts, M S E; Stovall, K

    2014-01-23

    Gravitationally bound three-body systems have been studied for hundreds of years and are common in our Galaxy. They show complex orbital interactions, which can constrain the compositions, masses and interior structures of the bodies and test theories of gravity, if sufficiently precise measurements are available. A triple system containing a radio pulsar could provide such measurements, but the only previously known such system, PSR B1620-26 (refs 7, 8; with a millisecond pulsar, a white dwarf, and a planetary-mass object in an orbit of several decades), shows only weak interactions. Here we report precision timing and multiwavelength observations of PSR J0337+1715, a millisecond pulsar in a hierarchical triple system with two other stars. Strong gravitational interactions are apparent and provide the masses of the pulsar M[Symbol: see text](1.4378(13), where M[Symbol: see text]is the solar mass and the parentheses contain the uncertainty in the final decimal places) and the two white dwarf companions (0.19751(15)M[Symbol: see text] and 0.4101(3))M[Symbol: see text], as well as the inclinations of the orbits (both about 39.2°). The unexpectedly coplanar and nearly circular orbits indicate a complex and exotic evolutionary past that differs from those of known stellar systems. The gravitational field of the outer white dwarf strongly accelerates the inner binary containing the neutron star, and the system will thus provide an ideal laboratory in which to test the strong equivalence principle of general relativity.

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

    NASA Astrophysics Data System (ADS)

    Milia, S.

    2012-03-01

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

  20. Transformation of a star into a planet in a millisecond pulsar binary.

    PubMed

    Bailes, M; Bates, S D; Bhalerao, V; Bhat, N D R; Burgay, M; Burke-Spolaor, S; D'Amico, N; Johnston, S; Keith, M J; Kramer, M; Kulkarni, S R; Levin, L; Lyne, A G; Milia, S; Possenti, A; Spitler, L; Stappers, B; van Straten, W

    2011-09-23

    Millisecond pulsars are thought to be neutron stars that have been spun-up by accretion of matter from a binary companion. Although most are in binary systems, some 30% are solitary, and their origin is therefore mysterious. PSR J1719-1438, a 5.7-millisecond pulsar, was detected in a recent survey with the Parkes 64-meter radio telescope. We show that this pulsar is in a binary system with an orbital period of 2.2 hours. The mass of its companion is near that of Jupiter, but its minimum density of 23 grams per cubic centimeter suggests that it may be an ultralow-mass carbon white dwarf. This system may thus have once been an ultracompact low-mass x-ray binary, where the companion narrowly avoided complete destruction. PMID:21868629

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

    PubMed

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

    2009-08-14

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

  2. Search for Gamma-Ray Millisecond Pulsars with the Fermi LAT

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.

    2009-01-01

    Prior to the launch of Fermi, only weak gamma-ray pulsations from a single millisecond pulsar, PSR J0218+4232, had been reported. A firm detection of gamma rays from a member of this class of pulsar having periods near neutron star break-up and magnetic dipole moments well below those of normal pulsars would provide new insights into pulsar acceleration and emission. Using accurate ephemerides obtained from several radio telescopes as well as the unprecedented accuracy of the GPS-derived clocks used by Fermi and the LAT, we have searched for gamma-ray pulsations from known pulsars over a broad range of timing parameters. We will present some results from our search for pulsed gamma rays from millisecond pulsars.

  3. Transformation of a star into a planet in a millisecond pulsar binary.

    PubMed

    Bailes, M; Bates, S D; Bhalerao, V; Bhat, N D R; Burgay, M; Burke-Spolaor, S; D'Amico, N; Johnston, S; Keith, M J; Kramer, M; Kulkarni, S R; Levin, L; Lyne, A G; Milia, S; Possenti, A; Spitler, L; Stappers, B; van Straten, W

    2011-09-23

    Millisecond pulsars are thought to be neutron stars that have been spun-up by accretion of matter from a binary companion. Although most are in binary systems, some 30% are solitary, and their origin is therefore mysterious. PSR J1719-1438, a 5.7-millisecond pulsar, was detected in a recent survey with the Parkes 64-meter radio telescope. We show that this pulsar is in a binary system with an orbital period of 2.2 hours. The mass of its companion is near that of Jupiter, but its minimum density of 23 grams per cubic centimeter suggests that it may be an ultralow-mass carbon white dwarf. This system may thus have once been an ultracompact low-mass x-ray binary, where the companion narrowly avoided complete destruction.

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

    PubMed

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

    2009-08-14

    Pulsars are born with subsecond spin periods and slow by electromagnetic braking for several tens of millions of years, when detectable radiation ceases. A second life can occur for neutron stars in binary systems. They can acquire mass and angular momentum from their companions, to be spun up to millisecond periods and begin radiating again. We searched Fermi Large Area Telescope data for pulsations from all known millisecond pulsars (MSPs) outside of globular clusters, using rotation parameters from radio telescopes. Strong gamma-ray pulsations were detected for eight MSPs. The gamma-ray pulse profiles and spectral properties resemble those of young gamma-ray pulsars. The basic emission mechanism seems to be the same for MSPs and young pulsars, with the emission originating in regions far from the neutron star surface. PMID:19574349

  5. The Mass of a Millisecond Pulsar

    NASA Astrophysics Data System (ADS)

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

    2005-08-01

    We report on nearly 2 years of timing observations of the low-mass binary millisecond pulsar PSR J1909-3744 with the Caltech-Parkes-Swinburne Recorder II, a new instrument that gives unprecedented timing precision. Daily observations give a weighted rms residual of 74 ns, indicating an extremely low level of systematic error. We have greatly improved on the previous parallax and proper motion measurements of PSR J1909-3744, yielding a distance of 1.14+0.04-0.03 kpc and transverse velocity of 200+7-6 km s-1. The system's orbital eccentricity is just (1.35+/-12)×10-7, the smallest yet recorded. Since their discovery, the masses of the rapidly rotating millisecond pulsars have remained a mystery, with the recycling hypothesis arguing for heavy objects, and the accretion-induced collapse of a white dwarf more consistent with neutron stars less than the Chandrashkar limit. Fortuitously, PSR J1909-3744 is an edge-on system, and our data have allowed the measurement of the range and shape of the Shapiro delay to high accuracy, giving the first precise determination of a millisecond pulsar mass to date, mp=1.438+/-0.024 Msolar. The mass of PSR J1909-3744 is at the upper edge of the range observed in mildly recycled pulsars in double neutron star systems, consistent with the recycling hypothesis. It appears that the production of millisecond pulsars is possible with the accretion of <0.2 Msolar.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    We report on the high-precision timing of 42 radio millisecond pulsars (MSPs) observed by the European Pulsar Timing Array (EPTA). This EPTA Data Release 1.0 extends up to mid-2014 and baselines range from 7-18 yr. It forms the basis for the stochastic gravitational-wave background, anisotropic background, and continuous-wave limits recently presented by the EPTA elsewhere. The Bayesian timing analysis performed with TEMPONEST yields the detection of several new parameters: seven parallaxes, nine proper motions and, in the case of six binary pulsars, an apparent change of the semimajor axis. We find the NE2001 Galactic electron density model to be a better match to our parallax distances (after correction from the Lutz-Kelker bias) than the M2 and M3 models by Schnitzeler. However, we measure an average uncertainty of 80 per cent (fractional) for NE2001, three times larger than what is typically assumed in the literature. We revisit the transverse velocity distribution for a set of 19 isolated and 57 binary MSPs and find no statistical difference between these two populations. We detect Shapiro delay in the timing residuals of PSRs J1600-3053 and J1918-0642, implying pulsar and companion masses m_p=1.22_{-0.35}^{+0.5} M_{⊙}, m_c = 0.21_{-0.04}^{+0.06} M_{⊙} and m_p=1.25_{-0.4}^{+0.6} M_{⊙}, m_c = 0.23_{-0.05}^{+0.07} M_{⊙}, respectively. Finally, we use the measurement of the orbital period derivative to set a stringent constraint on the distance to PSRs J1012+5307 and J1909-3744, and set limits on the longitude of ascending node through the search of the annual-orbital parallax for PSRs J1600-3053 and J1909-3744.

  7. Isolation and analysis of UV and radio-resistant bacteria from Chernobyl.

    PubMed

    Zavilgelsky, G B; Abilev, S K; Sukhodolets, V V; Ahmad, S I

    1998-05-15

    The accident at the Chernobyl nuclear power station in 1986 led to the dispersal of large amounts of a variety of radioactive materials, most importantly uranium, plutonium, 137Cs, 131I and 90Sr, over very large distances estimated to reach as far as Sweden, Norway, Turkey and possibly the USA. As a consequence, the soil on which the radioactive materials fell was contaminated and the degree of contamination varied with distance from the station, the direction and strength of the wind and the amount of atmospheric scavenging by rainfall at that time. Some of the radioactive materials have left a significant impact on mankind in the form of chromosomal aberrations including trisomy, various forms of cancers and death, whilst others are still in the ground where they will remain for a prolonged period to continue to exert their effects. Likewise, microbes living in the soil and exposed to radioactive materials may have been affected in a number of ways; some perished, and others survived due to the acquisition of advantageous mutation. Six years after the accident, soil samples contaminated with different levels of radioactivity were obtained from five regions within a 30 km radius of the nuclear power plant. From these soil samples spore-forming bacilli were isolated, quantified, identified and tested for resistance to X-rays, UVC and 4-nitroquinoline 1-oxide (4NQO). As a control, spore-forming bacilli were obtained from 'Zeleny mys' (an area 50 km south-east of the power station and emitting basal levels of radioactivity). A mutant of Escherichia coli hyper-resistant to a variety of DNA-damaging agents and its parent strain were also included in the study. Analysis of results reveals that a proportion of isolates of the same species from near the power station and the E. coli mutant SA236 were more resistant to X-rays, UVC and 4NQO compared with isolates from the control site and the E. coli parent strain, KL14, respectively. PMID:9679315

  8. Isolation and analysis of UV and radio-resistant bacteria from Chernobyl.

    PubMed

    Zavilgelsky, G B; Abilev, S K; Sukhodolets, V V; Ahmad, S I

    1998-05-15

    The accident at the Chernobyl nuclear power station in 1986 led to the dispersal of large amounts of a variety of radioactive materials, most importantly uranium, plutonium, 137Cs, 131I and 90Sr, over very large distances estimated to reach as far as Sweden, Norway, Turkey and possibly the USA. As a consequence, the soil on which the radioactive materials fell was contaminated and the degree of contamination varied with distance from the station, the direction and strength of the wind and the amount of atmospheric scavenging by rainfall at that time. Some of the radioactive materials have left a significant impact on mankind in the form of chromosomal aberrations including trisomy, various forms of cancers and death, whilst others are still in the ground where they will remain for a prolonged period to continue to exert their effects. Likewise, microbes living in the soil and exposed to radioactive materials may have been affected in a number of ways; some perished, and others survived due to the acquisition of advantageous mutation. Six years after the accident, soil samples contaminated with different levels of radioactivity were obtained from five regions within a 30 km radius of the nuclear power plant. From these soil samples spore-forming bacilli were isolated, quantified, identified and tested for resistance to X-rays, UVC and 4-nitroquinoline 1-oxide (4NQO). As a control, spore-forming bacilli were obtained from 'Zeleny mys' (an area 50 km south-east of the power station and emitting basal levels of radioactivity). A mutant of Escherichia coli hyper-resistant to a variety of DNA-damaging agents and its parent strain were also included in the study. Analysis of results reveals that a proportion of isolates of the same species from near the power station and the E. coli mutant SA236 were more resistant to X-rays, UVC and 4NQO compared with isolates from the control site and the E. coli parent strain, KL14, respectively.

  9. New Neighbours: Modelling the Growing Population of gamma-ray Millisecond Pulsars

    NASA Technical Reports Server (NTRS)

    Venter, C.; Harding, A. K.; Johnson, T. J.

    2010-01-01

    The Fermi Large Area Telescope, in collaboration with several groups from the radio community. have had marvelous success at uncovering new gamma-ray millisecond pulsars (MSPs). In fact, MSPs now make up a sizable fraction of the total number of known gamma-ray pulsars. The MSP population is characterized by a variety of pulse profile shapes, peak separations, and radio-to-gamma phase lags, with some members exhibiting nearly phase-aligned radio and gamma-ray light curves (LCs). The MSPs' short spin periods underline the importance of including special relativistic effects in LC calculations, even for emission originating from near the stellar surface. We present results on modelling and classification of MSP LCs using standard pulsar model geometries.

  10. New Millisecond Isomer Lifetime Measurements at LANSCE

    SciTech Connect

    Devlin, M. Nelson, R.O.; Fotiades, N.; O'Donnell, J.M.

    2014-06-15

    New half-life measurements have been made of the millisecond isomers {sup 71m}Ge, {sup 114m2}I, {sup 208m}Bi, {sup 88m1}Y, {sup 88m2}Y, and {sup 75m}As populated in neutron-induced reactions. These measurements were made using the unique time structure of the LANSCE/WNR neutron source, by observing the γ-ray decays of the isomers during the time between the LANSCE proton macropulses. Two different LANSCE proton beam time structures were used. The GEANIE array of HPGe detectors was used to detect the γ-ray decays.

  11. ON DETECTING MILLISECOND PULSARS AT THE GALACTIC CENTER

    SciTech Connect

    Macquart, Jean-Pierre

    2015-06-01

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

  12. Cool white dwarf companions to four millisecond pulsars

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    We report on photometric and spectroscopic observations of white dwarf companions to four binary radio millisecond pulsars, leading to the discovery of companions to PSRs J0614-3329, J1231-1411 and J2017+0603. We place limits on the brightness of the companion to PSR J0613-0200. Optical spectroscopy of the companion to PSR J0614-3329 identifies it as a DA-type white dwarf with a temperature of Teff = 6460 ± 80 K, a surface gravity log g = 7.0 ± 0.2 cgs and a mass of MWD = 0.24 ± 0.04 M⊙. We find that the distance to PSR J0614-3329 is smaller than previously estimated, removing the need for the pulsar to have an unrealistically high γ-ray efficiency. Comparing the photometry with predictions from white dwarf cooling models allows us to estimate temperatures and cooling ages of the companions to PSRs J0613-0200, J1231-1411 and J2017+0603. We find that the white dwarfs in these systems are cool Teff < 4000 K and old ≳ 5 Gyr. Thin hydrogen envelopes are required for these white dwarfs to cool to the observed temperatures, and we suggest that besides hydrogen shell flashes, irradiation driven mass loss by the pulsar may have been important.

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

    SciTech Connect

    Walker, Mark A.; Van Straten, Willem E-mail: pdemores@nrao.edu

    2013-12-20

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

  14. High-energy emission of the first millisecond pulsar

    SciTech Connect

    Ng, C.-Y.; Takata, J.; Leung, G. C. K.; Cheng, K. S.; Philippopoulos, P.

    2014-06-01

    We report on X-ray and gamma-ray observations of the millisecond pulsar (MSP) B1937+21 taken with the Chandra X-ray Observatory, XMM-Newton, and the Fermi Large Area Telescope. The pulsar X-ray emission shows a purely non-thermal spectrum with a hard photon index of 0.9 ± 0.1, and is nearly 100% pulsed. We found no evidence of varying pulse profile with energy as previously claimed. We also analyzed 5.5 yr of Fermi survey data and obtained much improved constraints on the pulsar's timing and spectral properties in gamma-rays. The pulsed spectrum is adequately fitted by a simple power-law with a photon index of 2.38 ± 0.07. Both the gamma-ray and X-ray pulse profiles show similar two-peak structure and generally align with the radio peaks. We found that the aligned profiles and the hard spectrum in X-rays seem to be common properties among MSPs with high magnetic fields at the light cylinder. We discuss a possible physical scenario that could give rise to these features.

  15. Identification of candidate millisecond pulsars from Fermi LAT observations

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  16. Millisecond Pulsars: The Gifts that Keep on Giving

    NASA Astrophysics Data System (ADS)

    Ransom, Scott M.

    2011-01-01

    There are about 2000 pulsars known, and while all of them as neutron stars are fascinating objects, the best and most exciting science comes from a very small percentage ( 1%) of exotic objects, most of which are millisecond pulsars (MSPs). These systems are notoriously hard to detect, yet their numbers have bloomed in the past 5-6 years via surveys using the world's largest radio telescopes and the Fermi Gamma-ray Space Telescope. Timing observations of these new MSPs as well as much improved monitoring of previously known MSPs are providing a wealth of science. In this talk I'll briefly cover 3 main areas in basic physics where systems like these are making an impact: strong-field tests of general relativity, the nature of matter at supra-nuclear densities, and the direct detection of gravitational waves (e.g. NANOGrav). In addition, several of the systems exhibit some very interesting astrophysics as well, including a transition from X-ray binary to MSP and a likely triple system that turned into an eccentric MSP binary.

  17. MILLISECOND PULSAR SCINTILLATION STUDIES WITH LOFAR: INITIAL RESULTS

    SciTech Connect

    Archibald, Anne M.; Kondratiev, Vladislav I.; Hessels, Jason W. T.; Stinebring, Daniel R. E-mail: kondratiev@astron.nl E-mail: dan.stinebring@oberlin.edu

    2014-08-01

    High-precision timing of millisecond pulsars (MSPs) over years to decades is a promising technique for direct detection of gravitational waves at nanohertz frequencies. Time-variable, multi-path scattering in the interstellar medium is a significant source of noise for this detector, particularly as timing precision approaches 10 ns or better for MSPs in the pulsar timing array. For many MSPs, the scattering delay above 1 GHz is at the limit of detectability; therefore, we study it at lower frequencies. Using the LOw-Frequency ARray (LOFAR) radio telescope, we have analyzed short (5-20 minutes) observations of 3 MSPs in order to estimate the scattering delay at 110-190 MHz, where the number of scintles is large and, hence, the statistical uncertainty in the scattering delay is small. We used cyclic spectroscopy, still relatively novel in radio astronomy, on baseband-sampled data to achieve unprecedented frequency resolution while retaining adequate pulse-phase resolution. We detected scintillation structure in the spectra of the MSPs PSR B1257+12, PSR J1810+1744, and PSR J2317+1439 with diffractive bandwidths of 6 ± 3, 2.0 ± 0.3, and ∼7 kHz, respectively, where the estimate for PSR J2317+1439 is reliable to about a factor of two. For the brightest of the three pulsars, PSR J1810+1744, we found that the diffractive bandwidth has a power-law behavior Δν{sub d}∝ν{sup α}, where ν is the observing frequency and α = 4.5 ± 0.5, consistent with a Kolmogorov inhomogeneity spectrum. We conclude that this technique holds promise for monitoring the scattering delay of MSPs with LOFAR and other high-sensitivity, low-frequency arrays like the low-frequency component of the Square Kilometre Array.

  18. Millisecond Pulsar Scintillation Studies with LOFAR: Initial Results

    NASA Astrophysics Data System (ADS)

    Archibald, Anne M.; Kondratiev, Vladislav I.; Hessels, Jason W. T.; Stinebring, Daniel R.

    2014-08-01

    High-precision timing of millisecond pulsars (MSPs) over years to decades is a promising technique for direct detection of gravitational waves at nanohertz frequencies. Time-variable, multi-path scattering in the interstellar medium is a significant source of noise for this detector, particularly as timing precision approaches 10 ns or better for MSPs in the pulsar timing array. For many MSPs, the scattering delay above 1 GHz is at the limit of detectability; therefore, we study it at lower frequencies. Using the LOw-Frequency ARray (LOFAR) radio telescope, we have analyzed short (5-20 minutes) observations of 3 MSPs in order to estimate the scattering delay at 110-190 MHz, where the number of scintles is large and, hence, the statistical uncertainty in the scattering delay is small. We used cyclic spectroscopy, still relatively novel in radio astronomy, on baseband-sampled data to achieve unprecedented frequency resolution while retaining adequate pulse-phase resolution. We detected scintillation structure in the spectra of the MSPs PSR B1257+12, PSR J1810+1744, and PSR J2317+1439 with diffractive bandwidths of 6 ± 3, 2.0 ± 0.3, and ~7 kHz, respectively, where the estimate for PSR J2317+1439 is reliable to about a factor of two. For the brightest of the three pulsars, PSR J1810+1744, we found that the diffractive bandwidth has a power-law behavior Δνdvpropνα, where ν is the observing frequency and α = 4.5 ± 0.5, consistent with a Kolmogorov inhomogeneity spectrum. We conclude that this technique holds promise for monitoring the scattering delay of MSPs with LOFAR and other high-sensitivity, low-frequency arrays like the low-frequency component of the Square Kilometre Array.

  19. What the timing of millisecond pulsars can teach us about their interior.

    PubMed

    Alford, Mark G; Schwenzer, Kai

    2014-12-19

    The cores of compact stars reach the highest densities in nature and therefore could consist of novel phases of matter. We demonstrate via a detailed analysis of pulsar evolution that precise pulsar timing data can constrain the star's composition, through unstable global oscillations (r modes) whose damping is determined by microscopic properties of the interior. If not efficiently damped, these modes emit gravitational waves that quickly spin down a millisecond pulsar. As a first application of this general method, we find that ungapped interacting quark matter is consistent with both the observed radio and x-ray data, whereas for ordinary nuclear matter some additional enhanced damping mechanism is required. PMID:25554870

  20. Millisecond laser machining of transparent materials assisted by nanosecond laser.

    PubMed

    Pan, Yunxiang; Zhang, Hongchao; Chen, Jun; Han, Bing; Shen, Zhonghua; Lu, Jian; Ni, Xiaowu

    2015-01-26

    A new form of double pulse composed of a nanosecond laser and a millisecond laser is proposed for laser machining transparent materials. To evaluate its advantages and disadvantages, experimental investigations are carried out and the corresponding results are compared with those of single millisecond laser. The mechanism is discussed from two aspects: material defects and effects of modifications induced by nanosecond laser on thermal stress field during millisecond laser irradiation. It is shown that the modifications of the sample generated by nanosecond laser improves the processing efficiency of subsequent millisecond laser, while limits the eventual size of modified region.

  1. Radio Galaxies.

    ERIC Educational Resources Information Center

    Downes, Ann

    1986-01-01

    Provides background information on radio galaxies. Topic areas addressed include: what produces the radio emission; radio telescopes; locating radio galaxies; how distances to radio galaxies are found; physics of radio galaxies; computer simulations of radio galaxies; and the evolution of radio galaxies with cosmic time. (JN)

  2. Serial Millisecond Crystallography of Membrane Proteins.

    PubMed

    Jaeger, Kathrin; Dworkowski, Florian; Nogly, Przemyslaw; Milne, Christopher; Wang, Meitian; Standfuss, Joerg

    2016-01-01

    Serial femtosecond crystallography (SFX) at X-ray free-electron lasers (XFELs) is a powerful method to determine high-resolution structures of pharmaceutically relevant membrane proteins. Recently, the technology has been adapted to carry out serial millisecond crystallography (SMX) at synchrotron sources, where beamtime is more abundant. In an injector-based approach, crystals grown in lipidic cubic phase (LCP) or embedded in viscous medium are delivered directly into the unattenuated beam of a microfocus beamline. Pilot experiments show the application of microjet-based SMX for solving the structure of a membrane protein and compatibility of the method with de novo phasing. Planned synchrotron upgrades, faster detectors and software developments will go hand-in-hand with developments at free-electron lasers to provide a powerful methodology for solving structures from microcrystals at room temperature, ligand screening or crystal optimization for time-resolved studies with minimal or no radiation damage. PMID:27553240

  3. Discovery of the optical counterparts to four energetic Fermi millisecond pulsars

    SciTech Connect

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

    2013-06-01

    In the last few years, over 43 millisecond radio pulsars have been discovered by targeted searches of unidentified γ-ray sources found by the Fermi Gamma-Ray Space Telescope. A large fraction of these millisecond pulsars are in compact binaries with low-mass companions. These systems often show eclipses of the pulsar signal and are commonly known as black widows and redbacks because the pulsar is gradually destroying its companion. In this paper, we report on the optical discovery of four strongly irradiated millisecond pulsar companions. All four sources show modulations of their color and luminosity at the known orbital periods from radio timing. Light curve modeling of our exploratory data shows that the equilibrium temperature reached on the companion's dayside with respect to their nightside is consistent with about 10%-30% of the available spin-down energy from the pulsar being reprocessed to increase the companion's dayside temperature. This value compares well with the range observed in other irradiated pulsar binaries and offers insights about the energetics of the pulsar wind and the production of γ-ray emission. In addition, this provides a simple way of estimating the brightness of irradiated pulsar companions given the pulsar spin-down luminosity. Our analysis also suggests that two of the four new irradiated pulsar companions are only partially filling their Roche lobe. Some of these sources are relatively bright and represent good targets for spectroscopic follow-up. These measurements could enable, among other things, mass determination of the neutron stars in these systems.

  4. Discovery of an Unidentified Fermi Object as a Black Widow-Like Millisecond Pulsar

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    The Fermi Gamma-ray Space Telescope has revolutionized our knowledge of the gamma-ray pulsar population, leading to the discovery of almost 100 gamma-ray pulsars and dozens of gamma-ray millisecond pulsars (MSPs). Although the outer-gap model predicts different sites of emission for the radio and gamma-ray pulsars, until now all of the known gamma-ray MSPs have been visible in the radio. Here we report the discovery of a radio-quiet" gamma-ray emitting MSP candidate by using Fermi, Chandra, Swift, and optical observations. The X-ray and gamma-ray properties of the source are consistent with known gamma-ray pulsars. We also found a 4.63-hr orbital period in optical and X-ray data. We suggest that the source is a black widow-like MSP with a approx. 0.1 Stellar Mass late-type companion star. Based on the profile of the optical and X-ray light-curves, the companion star is believed to be heated by the pulsar while the X-ray emissions originate from pulsar magnetosphere and/or from intra-binary shock. No radio detection of the source has been reported yet and although no gamma-ray/radio pulsation has been found, we estimated that the spin period of the MSP is approx. 3-5 ms based on the inferred gamma-ray luminosity.

  5. DISCOVERY OF AN UNIDENTIFIED FERMI OBJECT AS A BLACK WIDOW-LIKE MILLISECOND PULSAR

    SciTech Connect

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

    2012-03-15

    The Fermi {gamma}-ray Space Telescope has revolutionized our knowledge of the {gamma}-ray pulsar population, leading to the discovery of almost 100 {gamma}-ray pulsars and dozens of {gamma}-ray millisecond pulsars (MSPs). Although the outer-gap model predicts different sites of emission for the radio and {gamma}-ray pulsars, until now all of the known {gamma}-ray MSPs have been visible in the radio. Here we report the discovery of a 'radio-quiet' {gamma}-ray-emitting MSP candidate by using Fermi, Chandra, Swift, and optical observations. The X-ray and {gamma}-ray properties of the source are consistent with known {gamma}-ray pulsars. We also found a 4.63 hr orbital period in optical and X-ray data. We suggest that the source is a black widow-like MSP with a {approx}0.1 M{sub Sun} late-type companion star. Based on the profile of the optical and X-ray light curves, the companion star is believed to be heated by the pulsar while the X-ray emissions originate from pulsar magnetosphere and/or from intrabinary shock. No radio detection of the source has been reported yet, and although no {gamma}-ray/radio pulsation has been found we estimate that the spin period of the MSP is {approx}3-5 ms based on the inferred {gamma}-ray luminosity.

  6. Pulsar searches: From radio to gamma-rays

    NASA Astrophysics Data System (ADS)

    Chandler, Adam M.

    2003-08-01

    We report the results of four different pulsar searches, covering radio, X-ray, and gamma-ray wavelengths. These searches targeted pulsars in virtually all of their guises: young and old, long-period and short-period, accretion-powered and rotation-powered. Ten new pulsars were discovered. There are very few known gamma-ray pulsars, all of which were found by folding gamma-ray data with a pulse period known from other wavelengths. Some emission models indicate that there may be a large number of gamma-ray pulsars that are undetectable at lower energies. We searched several of the brightest unidentified gamma-ray sources for pulsations. This was the first attempt to identify gamma-ray pulsars by directly searching gamma- ray data. No new identifications resulted; we report upper limits. Even more rare than gamma-ray pulsars are accreting millisecond pulsars. We searched for coherent pulsations from Aql X-1, a low-mass X-ray binary suspected of harboring such an object. No pulsations were detected, and we argue that the quiescent emission of this system has a thermal origin. The two radio searches included here were both designed to detect millisecond pulsars. First, we report the results of a large area survey from Arecibo. Five new slow pulsars were discovered, including an apparent orthogonal rotator and an extremely unusual bursting radio pulsar. No short-period pulsars were discovered and we place some of the first useful observational constraints on the limiting spin period of a neutron star. We also performed pointed searches of several globular clusters using the new Green Bank Telescope. Three new binary millisecond pulsars were found in M62. These were the first new objects found with the GBT, and they bring the total pulsar population in M62 to six. We also discovered two isolated pulsars, one each in NGC 6544 and NGC 6624. Many of the methods we developed will be relevant to future searches. Perhaps the most significant contribution is a dynamic power

  7. Physics of radio emission in gamma-ray pulsars

    NASA Astrophysics Data System (ADS)

    Petrova, S. A.

    2016-04-01

    > Propagation of radio emission in a pulsar magnetosphere is reviewed. The effects of polarization transfer, induced scattering and reprocessing to high energies are analysed with a special emphasis on the implications for the gamma-ray pulsars. The possibilities of the pulsar plasma diagnostics based on the observed radio pulse characteristics are also outlined. As an example, the plasma number density profiles obtained from the polarization data for the Vela and the gamma-ray millisecond pulsars J1446-4701, J1939+2134 and J1744-1134 are presented. The number densities derived tend to be the highest/lowest when the radio pulse leads/lags the gamma-ray peak. In the PSR J1939+2134, the plasma density profiles for the main pulse and interpulse appear to fit exactly the same curve, testifying to the origin of both radio components above the same magnetic pole and their propagation through the same plasma flow in opposite directions. The millisecond radio pulse components exhibiting flat position angle curves are suggested to result from the induced scattering of the main pulse by the same particles that generate gamma rays. This is believed to underlie the wide-sense radio/gamma-ray correlation in the millisecond pulsars. The radio quietness of young gamma-ray pulsars is attributed to resonant absorption, whereas the radio loudness to the radio beam escape through the periphery of the open field line tube.

  8. Millisecond accuracy video display using OpenGL under Linux.

    PubMed

    Stewart, Neil

    2006-02-01

    To measure people's reaction times to the nearest millisecond, it is necessary to know exactly when a stimulus is displayed. This article describes how to display stimuli with millisecond accuracy on a normal CRT monitor, using a PC running Linux. A simple C program is presented to illustrate how this may be done within X Windows using the OpenGL rendering system. A test of this system is reported that demonstrates that stimuli may be consistently displayed with millisecond accuracy. An algorithm is presented that allows the exact time of stimulus presentation to be deduced, even if there are relatively large errors in measuring the display time.

  9. Solar microwave millisecond spike at 2.84 GHz

    NASA Technical Reports Server (NTRS)

    Fu, Qi-Jun; Jin, Sheng-Zhen; Zhao, Ren-Yang; Zheng, Le-Ping; Liu, Yu-Ying; Li, Xiao-Cong; Wang, Shu-Lan; Chen, Zhi-Jun; Hu, Chu-Min

    1986-01-01

    Using the high time resolution of 1 ms, the data of solar microwave millisecond spike (MMS) event was recorded more than two hundred times at the frequency of 2.84 GHz at Beijing (Peking) Observatory since May 1981. A preliminary analysis was made. It can be seen from the data that the MMS-events have a variety of the fast activities such as the dispersed and isolated spikes, the clusters of the crowded spikes, the weak spikes superimposed on the noise background, and the phenomena of absorption. The marked differences from that observed with lower time resolution are presented. Using the data, a valuable statistical analysis was made. There are close correlations between MMS-events and hard X-ray bursts, and fast drifting bursts. The MMS events are highly dependent on the type of active regions and the magnetic field configuration. It seems to be crucial to find out the accurate positions on the active region where the MMS-events happen and to make co-operative observations at different bands during the special period when specific active regions appear on the solar disk.

  10. The Transient Radio Sky

    NASA Astrophysics Data System (ADS)

    Keane, E. F.

    2010-11-01

    The high time-resolution radio sky represents unexplored astronomical territory where the discovery potential is high. In this thesis I have studied the transient radio sky, focusing on millisecond scales. As such, this work is concerned primarily with neutron stars, the mostpopulous member of the radio transient parameter space. In particular, I have studied the well known radio pulsars and the recently identified group of neutron stars which show erratic radio emission, known as RRATs, which show radio bursts every few minutes to every few hours. When RRATs burst onto the scene in 2006, it was thought that they represented a previously unknown, distinct class of sporadically emitting sources. The difficulty in their identification implies a large underlying population, perhaps larger than the radio pulsars. The first question investigated in this thesis was whether the large projected population of RRATs posed a problem, i.e. could the observed supernova rate account for so many sources. In addition to pulsars and RRATs, the various other known neutron star manifestations were considered, leading to the conclusion that distinct populations would result in a `birthrate problem'. Evolution between the classes could solve this problem -- the RRATs are not a distinct population ofneutron stars.Alternatively, perhaps the large projected population of RRATs is an overestimate. To obtain an improved estimate, the best approach is to find more sources. The Parkes Multi-beam Pulsar Survey, wherein the RRATs were initially identified, offered an opportunity to do just this. Abouthalf of the RRATs showing bursts during the survey were thought to have been missed, due to the deleterious effects of impulsive terrestrial interference signals. To remove these unwanted signals, so that we could identify the previously shrouded RRATs, we developed newinterference mitigation software and processing techniques. Having done this, the survey was completely re-processed, resulting in

  11. Observations of the Eclipsing Millisecond Pulsar

    NASA Astrophysics Data System (ADS)

    Bookbinder, Jay

    1990-12-01

    FRUCHTER et al. (1988a) HAVE RECENTLY DISCOVERED a 1.6 MSEC PULSAR (PSR 1957+20) IN A 9.2 HOUR ECLIPSING BINARY SYSTEM. THE UNUSUAL BEHAVIOR OF THE DISPERSION MEASURE AS A FUNCTION OF ORBITAL PHASE, AND THE DISAPPEARANCE OF THE PULSAR SIGNAL FOR 50 MINUTES DURING EACH ORBIT, IMPLIES THAT THE ECLIPSES ARE DUE TO A PULSAR-INDUCED WIND FLOWING OFF OF THE COMPANION. THE OPTICAL COUNTERPART IS A 21ST MAGNITUDE OBJECT WHICH VARIES IN INTENSITY OVER THE BINARY PERIOD; ACCURATE GROUND-BASED OBSERVATIONS ARE PREVENTED BY THE PROXIMITY (0.7") OF A 20TH MAGNITUDE K DWARF. WE PROPOSE TO OBSERVE THE OPTICAL COUNTERPART IN A TWO-PART STUDY. FIRST, THE WF/PC WILL PROVIDE ACCURATE MULTICOLOR PHOTOMETRY, ENABLING US TO DETERMINE UNCONTAMINATED MAGNITUDES AND COLORS BOTH AT MAXIMUM (ANTI-ECLIPSE) AS WELL AS AT MINIMUM (ECLIPSE). SECOND, WE PROPOSE TO OBSERVE THE EXPECTED UV LINE EMISSION WITH FOS, ALLOWING FOR AN INTIAL DETERMINATION OF THE TEMPERATURE AND DENSITY STRUCTURE AND ABUNDANCES OF THE WIND THAT IS BEING ABLATED FROM THE COMPANION. STUDY OF THIS UNIQUE SYSTEM HOLDS ENORMOUS POTENTIAL FOR THE UNDERSTANDING OF THE RADIATION FIELD OF A MILLISECOND PULSAR AND THE EVOLUTION OF LMXRBs AND MSPs IN GENERAL. WE EXPECT THESE OBSERVATIONS TO PLACE VERY SIGNIFICANT CONTRAINTS ON MODELS OF THIS UNIQUE OBJECT.

  12. Probing the Birth of Post-merger Millisecond Magnetars with X-Ray and Gamma-Ray Emission

    NASA Astrophysics Data System (ADS)

    Wang, Ling-Jun; Dai, Zi-Gao; Liu, Liang-Duan; Wu, Xue-Feng

    2016-05-01

    There is growing evidence that a stable magnetar could be formed from the coalescence of double neutron stars. In previous papers, we investigated the signature of formation of stable millisecond magnetars in radio and optical/ultraviolet bands by assuming that the central rapidly rotating magnetar deposits its rotational energy in the form of a relativistic leptonized wind. We found that the optical transient PTF11agg could be the first evidence for the formation of post-merger millisecond magnetars. To enhance the probability of finding more evidence for the post-merger magnetar formation, it is better to extend the observational channel to other photon energy bands. In this paper, we propose to search the signature of post-merger magnetar formation in X-ray and especially gamma-ray bands. We calculate the synchrotron self-Compton (SSC) emission of the reverse shock powered by post-merger millisecond magnetars. We find that the SSC component peaks at 1 {GeV} in the spectral energy distribution and extends to ≳ 10 {TeV} for typical parameters. These energy bands are quite suitable for Fermi Large Area Telescope and Cherenkov Telescope Array (CTA), which, with their current observational sensitivities, can detect the SSC emission powered by post-merger magnetars up to 1 {Gpc}. NuSTAR, which is sensitive in X-ray bands, can detect the formation of post-merger millisecond magnetars at redshift z˜ 1. Future improvements in the sensitivity of CTA can also allow us to probe the birth of post-merger millisecond magnetars at redshift z˜ 1. However, because of the γ-γ collisions, strong high-energy emission is clearly predicted only for ejecta masses lower than {10}-3 {M}⊙ .

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

    SciTech Connect

    Johnson, T. J.; Venter, C.; Harding, A. K.; Çelik, Ö.; Ferrara, E. C.; Guillemot, L.; Smith, D. A.; Hou, X.; Den Hartog, P. R.; Lande, J.; Ray, P. S. E-mail: Christo.Venter@nwu.ac.za

    2014-07-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

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

  15. In vitro stemness characterization of radio-resistant clones isolated from a medulloblastoma cell line ONS-76

    PubMed Central

    Sun, Lue; Moritake, Takashi; Zheng, Yun-Wen; Suzuki, Kenshi; Gerelchuluun, Ariungerel; Hong, Zhengshan; Zenkoh, Junko; Taniguchi, Hideki; Tsuboi, Koji

    2013-01-01

    One-third of patients with medulloblastoma die due to recurrence after various treatments including radiotherapy. Although it has been postulated that cancer stem-like cells are radio-resistant and play an important role in tumor recurrence, the “stemness” of medulloblastoma cells surviving irradiation has not yet been elucidated. Using a medulloblastoma cell line ONS-76, cells that survived gamma irradiation were investigated on their “stemness” in vitro. From 10 500 cells, 20 radio-resistant clones were selected after gamma ray irradiation (5 Gy × two fractions) using the replica micro-well technique. These 20 resistant clones were screened for CD133 positivity by flow cytometry followed by side population assay, tumor sphere formation assay and clonogenic survival assay. Results revealed CD133 fractions were significantly elevated in three clones, which also exhibited significantly increased levels of tumor sphere formation ability and side population fraction. Clonogenic survival assay demonstrated that their radio-resistance was significantly higher than the parental ONS-76. This may support the hypothesis that a small number of cancer stem-like cells (CSCs) are the main culprits in local recurrence after radiotherapy, and disruption of the resistance mechanism of these CSCs is a critical future issue in improving the outcome of patients with medulloblastoma. PMID:22951319

  16. AN ASTEROID BELT INTERPRETATION FOR THE TIMING VARIATIONS OF THE MILLISECOND PULSAR B1937+21

    SciTech Connect

    Shannon, R. M.; Cordes, J. M.; Metcalfe, T. S.; Lazio, T. J. W.; Jessner, A.; Kramer, M.; Lazaridis, K. E-mail: cordes@astro.cornell.edu

    2013-03-20

    Pulsar timing observations have revealed companions to neutron stars that include other neutron stars, white dwarfs, main-sequence stars, and planets. We demonstrate that the correlated and apparently stochastic residual times of arrival from the millisecond pulsar B1937+21 are consistent with the signature of an asteroid belt having a total mass {approx}< 0.05 M{sub Circled-Plus }. Unlike the solar system's asteroid belt, the best fit pulsar asteroid belt extends over a wide range of radii, consistent with the absence of any shepherding companions. We suggest that any pulsar that has undergone accretion-driven spin-up and subsequently evaporated its companion may harbor orbiting asteroid mass objects. The resulting timing variations may fundamentally limit the timing precision of some of the other millisecond pulsars. Observational tests of the asteroid belt model include identifying periodicities from individual asteroids, which are difficult; testing for statistical stationarity, which becomes possible when observations are conducted over a longer observing span; and searching for reflected radio emission.

  17. Detection of Pulsed Emission from the Millisecond Pulsar PSR J2145-0750 Below 100 MHz

    NASA Astrophysics Data System (ADS)

    Taylor, Gregory B.; Dowell, J.; Wavelength Array, Long

    2014-01-01

    Millisecond pulsars (MPSs) are distinguished from normal pulsars by faster rotation periods, weaker magnetic fields, and flux density spectra that are well fit by a single power law down to 100 MHz. Below 100 MHz some MSPs show a break in the power law, however, additional observations, particularly of the pulse profile, are needed in this frequency range to provide better constraints on emission mechanisms. The first station of the Long Wavelength Array, LWA1, is a low frequency telescope that is ideally suited to address these questions. We present recent results from LWA1 on the millisecond pulsar PSR J2145-0750. Using coherent dedispersion we detected pulsed emission between 37 and 85 MHz. From this we derive flux densities and pulse profiles at 41, 57, 65, 73, and 81 MHz. We find that the flux density spectrum of PSR J2145-0750 appears to flatten below 100 MHz relative to the spectral index of ~-1.6 found in the literature. We also find that the pulse profile shows little evolution over this frequency range and is similar to profiles found at 102 MHz. We also discuss the prospects for precision dispersion measure monitoring at these frequencies. Construction of the LWA has been supported by the Office of Naval Research under Contract N00014-07-C-0147. Support for operations and continuing development of the LWA1 is provided by the National Science Foundation under grants AST-1139963 and AST-1139974 of the University Radio Observatory program.

  18. A PARALLAX DISTANCE AND MASS ESTIMATE FOR THE TRANSITIONAL MILLISECOND PULSAR SYSTEM J1023+0038

    SciTech Connect

    Deller, A. T.; Archibald, A. M.; Kaspi, V. M.; Brisken, W. F.; Chatterjee, S.; Janssen, G. H.; Lyne, A. G.; Stappers, B.; Lorimer, D.; McLaughlin, M. A.; Ransom, S.; Stairs, I. H.

    2012-09-10

    The recently discovered transitional millisecond pulsar system J1023+0038 exposes a crucial evolutionary phase of recycled neutron stars for multiwavelength study. The system, comprising the neutron star itself, its stellar companion, and the surrounding medium, is visible across the electromagnetic spectrum from the radio to X-ray/gamma-ray regimes and offers insight into the recycling phase of millisecond pulsar evolution. Here, we report on multiple-epoch astrometric observations with the Very Long Baseline Array (VLBA) which give a system parallax of 0.731 {+-} 0.022 milliarcseconds (mas) and a proper motion of 17.98 {+-} 0.05 mas yr{sup -1}. By combining our results with previous optical observations, we are able to use the parallax distance of 1368{sup +42}{sub -{sub 39}} pc to estimate the mass of the pulsar to be 1.71 {+-} 0.16 M{sub Sun }, and we are also able to measure the three-dimensional space velocity of the system to be 126 {+-} 5 km s{sup -1}. Despite the precise nature of the VLBA measurements, the remaining {approx}3% distance uncertainty dominates the 0.16 M{sub Sun} error on our mass estimate.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  20. High-precision baseband timing of 15 millisecond pulsars

    NASA Astrophysics Data System (ADS)

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

    2006-07-01

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

  1. On the magnetization and origin of the millisecond pulsar 1937 + 214

    NASA Astrophysics Data System (ADS)

    Arons, J.

    1983-03-01

    The structure of the millisecond pulsar PSR1937 + 214 is shown to include a magnetosphere compatible with other radio pulsars, although no synchrotron radiation-emitting bright nebula has been observed. It is suggested that interstellar extinction lowers the nebular energy to below the detection threshold level for the Einstein Observatory. Constraints on the pulsars magnetic dipole moment indicate a minimum spin-down rate of 10 to the -19th. The low magnetization detected may arise from initially low magnetic fields or field decay. Models of an expanding gas bubble are described for the case of supersonic expansion if the object is less than 1000 yr old and subsonic expansion if older. A scenario of a groupe of short period, weakly magnetized neutron stars is discussed.

  2. Confirmation of Earth-Mass Planets Orbiting the Millisecond Pulsar PSR B1257 + 12.

    PubMed

    Wolszczan, A

    1994-04-22

    The discovery of two Earth-mass planets orbiting an old ( approximately 10(9) years), rapidly spinning neutron star, the 6.2-millisecond radio pulsar PSR B1257+12, was announced in early 1992. It was soon pointed out that the approximately 3:2 ratio of the planets' orbital periods should lead to accurately predictable and possibly measurable gravitational perturbations of their orbits. The unambiguous detection of this effect, after 3 years of systematic timing observations of PSR B1257+12 with the 305-meter Arecibo radiotelescope, as well as the discovery of another, moon-mass object in orbit around the pulsar, constitutes irrefutable evidence that the first planetary system around a star other than the sun has been identified.

  3. A PROPELLER MODEL FOR THE SUB-LUMINOUS STATE OF THE TRANSITIONAL MILLISECOND PULSAR PSR J1023+0038

    SciTech Connect

    Papitto, A.; Torres, D. F.

    2015-07-01

    The discovery of millisecond pulsars switching between states powered either by the rotation of their magnetic field or by the accretion of matter has recently proved the tight link shared by millisecond radio pulsars and neutron stars in low-mass X-ray binaries. Transitional millisecond pulsars also show an enigmatic intermediate state in which the neutron star is surrounded by an accretion disk and emits coherent X-ray pulsations, but is sub-luminous in X-rays with respect to accreting neutron stars, and is brighter in gamma-rays than millisecond pulsars in the rotation-powered state. Here, we model the X-ray and gamma-ray emission observed from PSR J1023+0038 in such a state based on the assumptions that most of the disk in-flow is propelled away by the rapidly rotating neutron star magnetosphere, and that electrons can be accelerated to energies of a few GeV at the turbulent disk–magnetosphere boundary. We show that the synchrotron and self-synchrotron Compton emission coming from such a region, together with the hard disk emission typical of low states of accreting compact objects, is able to explain the radiation observed in the X-ray and gamma-ray bands. The average emission observed from PSR J1023+0038 is modeled by a disk in-flow with a rate of 1–3 × 10{sup −11} M{sub ⊙} yr{sup −1}, truncated at a radius ranging between 30 and 45 km, compatible with the hypothesis of a propelling magnetosphere. We compare the results we obtained with models that assume that a rotation-powered pulsar is turned on, showing how the spin-down power released in similar scenarios is hardly able to account for the magnitude of the observed emission.

  4. Radio Journalism.

    ERIC Educational Resources Information Center

    Bittner, John R.; Bittner, Denise A.

    This book, a how-to-do-it guide for the novice and the professional alike, deals with several aspects of radio journalism: producing documentaries, preparing and announcing radio news, ethics and responsibility, regulation of radio journalism, and careers. It traces the history and growth of radio news, shows its impact on the public, and…

  5. ATCA radio observations of Swift J1756.9-2508 in outburst

    NASA Astrophysics Data System (ADS)

    Tudose, V.; Tzioumis, A.; Patruno, A.; Linares, M.; Soleri, P.; Russell, D.

    2009-07-01

    Swift J1756.9-2508 was discovered by the X-ray satellite Swift during an outburst in 2007 (ATEL #1105) and recognized immediately as an accretion-driven millisecond X-ray pulsar (ATEL #1108). No radio pulsations (ATEL #1129) and no continuum radio emission (ATEL #1128) were detected then. While the radio pulsation search was performed during the outburst, the continuum observations were carried out when the X-ray flux levels already decreased below the detection limit of Swift.

  6. [Radio Frequency Electromagnetic Field Effect on the State of Na+/Ca2+ Exchange in the Isolated Rat Heart].

    PubMed

    Alabovsky, V V; Kudryshov, Yu B; Vinokurov, A A; Bogacheva, E V; Maslov, O V; Perov, S Yu

    2016-01-01

    It has been shown that a single exposure to 171 MHz electromagnetic field with 180 V/m electric field strength and 0.04 mW/kg specific absorption rate significantly alters the Na+/Ca2+ exchange in the isolated rat heart. It is assumed that enhancement of the Na+/Ca2+ exchange towards removing Ca2+ from the cardiomyocytes electromagnetic field exposure is a result of Ca2+ extraction from the sarcoplasmic reticulum and the increase of its intracellular level. PMID:27534068

  7. The Annular Gap: Gamma-Ray & Radio Emission of Pulsars

    NASA Astrophysics Data System (ADS)

    Qiao, G. J.; Du, Y. J.; Han, J. L.; Xu, R. X.

    2013-01-01

    Pulsars have been found more than 40 years. Observations from radio to gamma-rays present abundant information. However, the radiation mechanism is still an open question. It is found that the annular gap could be formed in the magnetosphere of pulsars (neutron stars or quark stars), which combines the advantages of the polar cap, slot gap and outer gap models. It is emphasized that observations of some radio pulsars, normal and millisecond gamma-ray pulsars (MSGPs) show that the annular gap would play a very important role. Here we show some observational and theoretical evidences about the annular gap. For example, bi-drifting sub-pulses; radio and gamma-ray millisecond pulsars and so on.

  8. Fast radio burst discovered in the Arecibo pulsar ALFA survey

    SciTech Connect

    Spitler, L. G.; Freire, P. C. C.; Lazarus, P.; Lee, K. J.; Cordes, J. M.; Chatterjee, S.; Wharton, R. S.; Brazier, A.; Hessels, J. W. T.; Lorimer, D. R.; McLaughlin, M. A.; Crawford, F.; Deneva, J. S.; Kaspi, V. M.; Karako-Argaman, C.; Allen, B.; Bogdanov, S.; Camilo, F.; Jenet, F. A.; Knispel, B.; and others

    2014-08-01

    Recent work has exploited pulsar survey data to identify temporally isolated, millisecond-duration radio bursts with large dispersion measures (DMs). These bursts have been interpreted as arising from a population of extragalactic sources, in which case they would provide unprecedented opportunities for probing the intergalactic medium; they may also be linked to new source classes. Until now, however, all so-called fast radio bursts (FRBs) have been detected with the Parkes radio telescope and its 13-beam receiver, casting some concern about the astrophysical nature of these signals. Here we present FRB 121102, the first FRB discovery from a geographic location other than Parkes. FRB 121102 was found in the Galactic anti-center region in the 1.4 GHz Pulsar Arecibo L-band Feed Array (ALFA) survey with the Arecibo Observatory with a DM = 557.4 ± 2.0 pc cm{sup –3}, pulse width of 3.0 ± 0.5 ms, and no evidence of interstellar scattering. The observed delay of the signal arrival time with frequency agrees precisely with the expectation of dispersion through an ionized medium. Despite its low Galactic latitude (b = –0.°2), the burst has three times the maximum Galactic DM expected along this particular line of sight, suggesting an extragalactic origin. A peculiar aspect of the signal is an inverted spectrum; we interpret this as a consequence of being detected in a sidelobe of the ALFA receiver. FRB 121102's brightness, duration, and the inferred event rate are all consistent with the properties of the previously detected Parkes bursts.

  9. MILLISECOND PULSAR AGES: IMPLICATIONS OF BINARY EVOLUTION AND A MAXIMUM SPIN LIMIT

    SciTech Connect

    Kiziltan, Buelent; Thorsett, Stephen E.

    2010-05-20

    In the absence of constraints from the binary companion or supernova remnant, the standard method for estimating pulsar ages is to infer an age from the rate of spin-down. While the generic spin-down age may give realistic estimates for normal pulsars, it can fail for pulsars with very short periods. Details of the spin-up process during the low-mass X-ray binary (LMXB) phase pose additional constraints on the period (P) and spin-down rates ( P-dot ) that may consequently affect the age estimate. Here, we propose a new recipe to estimate millisecond pulsar (MSP) ages that parametrically incorporates constraints arising from binary evolution and limiting physics. We show that the standard method can be improved by this approach to achieve age estimates closer to the true age while the standard spin-down age may overestimate or underestimate the age of the pulsar by more than a factor of {approx}10 in the millisecond regime. We use this approach to analyze the population on a broader scale. For instance, in order to understand the dominant energy loss mechanism after the onset of radio emission, we test for a range of plausible braking indices. We find that a braking index of n = 3 is consistent with the observed MSP population. We demonstrate the existence and quantify the potential contributions of two main sources of age corruption: the previously known 'age bias' due to secular acceleration and 'age contamination' driven by sub-Eddington progenitor accretion rates. We explicitly show that descendants of LMXBs that have accreted at very low rates ( m-dot << M-dot{sub Edd}) will exhibit ages that appear older than the age of the Galaxy. We further elaborate on this technique, the implications and potential solutions it offers regarding MSP evolution, the underlying age distribution, and the post-accretion energy loss mechanism.

  10. tpipe: Searching radio interferometry data for fast, dispersed transients

    NASA Astrophysics Data System (ADS)

    Law, Casey J.

    2016-03-01

    Visibilities from radio interferometers have not traditionally been used to study the fast transient sky. Millisecond transients (e.g., fast radio bursts) and periodic sources (e.g., pulsars) have been studied with single-dish radio telescopes and a software stack developed over the past few decades. tpipe is an initial attempt to develop the fast transient algorithms for visibility data. Functions exist for analysis of visibilties, such as reading data, flagging data, applying interferometric gain calibration, and imaging. These functions are given equal footing as time-domain techniques like filters and dedispersion.

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

    NASA Technical Reports Server (NTRS)

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

    2009-01-01

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

  12. Registration of Neutrons Within 2 Milliseconds after EAS

    NASA Astrophysics Data System (ADS)

    JȨDRZEJCZAK, K.; Karczmarczyk, J.; Kasztelan, M.; Petrochenkov, S. A.; Polański, A.; Swarzyński, J.; Szabelski, J.; Wibig, T.

    We register an excess of signals from neutron detectors within a few milliseconds after passage of EAS front in Łódź EAS array. The most probable explanation is that neutrons are produced in EAS hadron interactions with lead block of muon detector. These neutrons diffuse and are thermalized before the detection. We present experimental data and results of simulations using MCNP code. This "new EAS observable" can be used as inexpensive hadron detector in EAS.

  13. A repeating fast radio burst.

    PubMed

    Spitler, L G; Scholz, P; Hessels, J W T; Bogdanov, S; Brazier, A; Camilo, F; Chatterjee, S; Cordes, J M; Crawford, F; Deneva, J; Ferdman, R D; Freire, P C C; Kaspi, V M; Lazarus, P; Lynch, R; Madsen, E C; McLaughlin, M A; Patel, C; Ransom, S M; Seymour, A; Stairs, I H; Stappers, B W; van Leeuwen, J; Zhu, W W

    2016-03-10

    Fast radio bursts are millisecond-duration astronomical radio pulses of unknown physical origin that appear to come from extragalactic distances. Previous follow-up observations have failed to find additional bursts at the same dispersion measure (that is, the integrated column density of free electrons between source and telescope) and sky position as the original detections. The apparent non-repeating nature of these bursts has led to the suggestion that they originate in cataclysmic events. Here we report observations of ten additional bursts from the direction of the fast radio burst FRB 121102. These bursts have dispersion measures and sky positions consistent with the original burst. This unambiguously identifies FRB 121102 as repeating and demonstrates that its source survives the energetic events that cause the bursts. Additionally, the bursts from FRB 121102 show a wide range of spectral shapes that appear to be predominantly intrinsic to the source and which vary on timescales of minutes or less. Although there may be multiple physical origins for the population of fast radio bursts, these repeat bursts with high dispersion measure and variable spectra specifically seen from the direction of FRB 121102 support an origin in a young, highly magnetized, extragalactic neutron star. PMID:26934226

  14. A repeating fast radio burst.

    PubMed

    Spitler, L G; Scholz, P; Hessels, J W T; Bogdanov, S; Brazier, A; Camilo, F; Chatterjee, S; Cordes, J M; Crawford, F; Deneva, J; Ferdman, R D; Freire, P C C; Kaspi, V M; Lazarus, P; Lynch, R; Madsen, E C; McLaughlin, M A; Patel, C; Ransom, S M; Seymour, A; Stairs, I H; Stappers, B W; van Leeuwen, J; Zhu, W W

    2016-03-10

    Fast radio bursts are millisecond-duration astronomical radio pulses of unknown physical origin that appear to come from extragalactic distances. Previous follow-up observations have failed to find additional bursts at the same dispersion measure (that is, the integrated column density of free electrons between source and telescope) and sky position as the original detections. The apparent non-repeating nature of these bursts has led to the suggestion that they originate in cataclysmic events. Here we report observations of ten additional bursts from the direction of the fast radio burst FRB 121102. These bursts have dispersion measures and sky positions consistent with the original burst. This unambiguously identifies FRB 121102 as repeating and demonstrates that its source survives the energetic events that cause the bursts. Additionally, the bursts from FRB 121102 show a wide range of spectral shapes that appear to be predominantly intrinsic to the source and which vary on timescales of minutes or less. Although there may be multiple physical origins for the population of fast radio bursts, these repeat bursts with high dispersion measure and variable spectra specifically seen from the direction of FRB 121102 support an origin in a young, highly magnetized, extragalactic neutron star.

  15. Millisecond measurement of transport during and after an electroporation pulse.

    PubMed Central

    Prausnitz, M R; Corbett, J D; Gimm, J A; Golan, D E; Langer, R; Weaver, J C

    1995-01-01

    Electroporation involves the application of an electric field pulse that creates transient aqueous pathways in lipid bilayer membranes. Transport through these pathways can occur by different mechanisms during and after a pulse. To determine the time scale of transport and the mechanism(s) by which it occurs, efflux of a fluorescent molecule, calcein, across erythrocyte ghost membranes was measured with a fluorescence microscope photometer with millisecond time resolution during and after electroporation pulses several milliseconds in duration. One of four outcomes was typically observed. Ghosts were: (1) partially emptied of calcein, involving efflux primarily after the pulse; (2) completely emptied of calcein, involving efflux primarily after the pulse; (3) completely emptied of calcein, involving efflux both during and after the pulse; or (4) completely emptied of calcein, involving efflux primarily during the pulse. Partial emptying, involving significant efflux during the pulse, was generally not observed. We conclude that under some conditions transport caused by electroporation occurs predominantly by electrophoresis and/or electroosmosis during a pulse, although under other conditions transport occurs in part or almost completely by diffusion within milliseconds to seconds after a pulse. PMID:7612828

  16. A glitch in the millisecond pulsar J0613-0200

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  17. The importance of Radio Quiet Zone (RQZ) for radio astronomy

    NASA Astrophysics Data System (ADS)

    Umar, Roslan; Abidin, Zamri Zainal; Ibrahim, Zainol Abidin

    2013-05-01

    Most of radio observatories are located in isolated areas. Since radio sources from the universe is very weak, astronomer need to avoid radio frequency interference (RFI) from active spectrum users and radio noise produced by human made (telecommunication, mobile phone, microwave user and many more. There are many observatories around the world are surrounded by a Radio Quiet Zone (RQZ), which is it was set up using public or state laws. A Radio Quiet Zone normally consists of two areas: an exclusive area in which totally radio emissions are forbidden, with restrictions for residents and business developments, and a larger (radius up to 100 km above) coordination area where the power of radio transmission limits to threshold levels. Geographical Information System (GIS) can be used as a powerful tool in mapping large areas with varying RQZ profiles. In this paper, we report the initial testing of the usage of this system in order to identify the areas were suitable for Radio Quiet Zone. Among the important parameters used to develop the database for our GIS are population density, information on TV and telecommunication (mobile phones) transmitters, road networks (highway), and contour shielding. We will also use other information gathered from on-site RFI level measurements on selected 'best' areas generated by the GIS. The intention is to find the best site for the purpose of establishing first radio quiet zones for radio telescope in Malaysia.

  18. K-ART (Korea Array Radio Telescope) and Monitoring of Radio Transients

    NASA Astrophysics Data System (ADS)

    Kim, Jeong-Sook; Lim, Soon-Wook; Park, Yong-Sun

    2010-12-01

    Korea Array Radio Telescope (K-ART), a proto-type radio array telescope, is designed for 300-450 MHz wavebands. The system is located in the Jeju Island of the South Korea, and is currently in its testing mode since last mid-October 2010. It is primarily designed for monitoring solar activity and radio transients. K-ART has a capacity to monitor transients for about 2 hours per day, with a spatial resolution of about 10 minutes and a timing resolution of milliseconds. The sensitivity is expected to be a few mJy or less. We propose to monitor radio transients such as X-ray binaries, cataclysmic variables and quasars, on the target-of-opportunity mode, in addition to the scheduled observation.

  19. Chemicals from heavy fuels in millisecond catalytic reactors

    NASA Astrophysics Data System (ADS)

    Krummenacher, Jakob Jose

    The role that millisecond catalytic reactors play on the development of the hydrogen economy is crucial because they have higher throughputs and smaller volumes than their traditional counter parts. Issues with the storage and production of hydrogen give an advantage to these reactors because their compact and small size makes them highly portable. As with the development of any new technology challenges that threaten the operation of the millisecond catalytic reactor with liquid fuels were encountered. First, the autoignition of linear alkanes is higher than their boiling points. This makes it impossible to simply vaporize the fuel and mix it with air. Second, analyzing such a diverse range of products using gas chromatography is not possible with conventional equipment. The first results of the especially engineered reactor show the successful partial oxidation of linear alkanes. Decane and hexadecane over rhodium catalysts produce synthesis gas with selectivities exceeding 80%. Experiments confirmed the highly tunable nature of the reactor. A fuel concentrated feed produces ethylene and alpha-olefins with high selectivities. A proposed mechanism and experimental results obtained suggest that these olefins are formed by homogeneous endothermic cracking. A single fuel, decane, was used to study further the millisecond catalytic reactor versatility. Several operating conditions such as catalyst porosity, effect of wash-coat, addition of steam, and addition of hydrogen were studied. Rhodium, platinum, and platinum-rhodium mixtures were coated on supports of different porosity to determine the differences in metal reactivities. The results show that rhodium is the best catalyst for making hydrogen or synthesis gas and that adding steam improves its performance. The highest yields of ethylene and a-olefins were obtained using a platinum catalyst coated with a small amount of rhodium on the front face. A rough economic analysis gives a sound idea of the potential that

  20. Observing and Modeling the Optical Counterparts of Short-Period Binary Millisecond Pulsars

    NASA Astrophysics Data System (ADS)

    Schroeder, Joshua

    In this dissertation, I explore the subject of short-period binary millisecond pulsars discovered by the Fermi Gamma-ray Space Telescope and radio follow-up teams, and present observations of fields containing eight recently discovered short-period (Porb < 1 d) binary millisecond pulsars using the telescopes at MDM Observatory. The goal of these observations was to detect the optical counterparts of the binaries and, for the best-suited counterparts detected, to observe the photometric variation of the companion that happens over the course of the orbit in various filters. The hope was to then use the light curves to model the systems and obtain constraints on the mass of the neutron stars which are likely to be some of the most massive neutron stars in the galaxy. Optical counterparts to four of these systems are detected, one of which, PSR J2214+3000, is a novel detection. Additionally, I present the fully orbital phase-resolved B, V , and R light curves of the optical counterparts to two objects, PSR J1810+1744 and PSR J2215+5135, for which I employ the ELC model of Orosz & Hauschildt (2000) to measure the unknown system parameters. For PSR J1810+1744 I find that the system parameters cannot be fit even assuming that 100% of the spin-down luminosity of the pulsar is irradiating the secondary, and so radial velocity measurements of this object will be required for the complete solution. However, PSR J2215+5135 exhibits light curves that are extremely well constrained using the ELC model and we find that the mass of the neutron star is constrained by these and the radio observations to be MNS > 1.75 solar masses; at the 3-sigma level. I also find a discrepancy between the model temperature and the measured colors of this object which I interpret as possible evidence for an additional high-temperature source such as a quiescent disk. Given this and the fact that PSR J2215+5135 contains a relatively high mass companion (Mc > 0.1 solar masses), I propose that similar

  1. Radio wave.

    PubMed

    Elkin, V

    1992-01-01

    In developing countries with high rates of poverty and illiteracy, radio is emerging as an excellent medium for delivering information on health issues, family planning, nutrition, and agricultural development. Since radio does not require wired electricity, it can reach remote rural populations. Surveys have found that between 50-75% of poor rural households in developing countries own radios, and the majority listen to educational radio at least once a week. A program that reaches the urban poor outside of Lima, Peru, has been instrumental in controlling the spread of cholera. A Bolivian station broadcasts 8 hours of literacy, health, agricultural, and cultural programming a day to an audience of more than 2 million Aymara Indians. Small village radio stations with a broadcast range of 15 miles can be established for under US$400 and can generally achieve sustainability through local fundraising events such as raffles. In many cases, listeners have become broadcasters at their local radio stations.

  2. The source location of Jovian millisecond radio bursts with respect to Jupiter's magnetic field

    NASA Technical Reports Server (NTRS)

    Genova, Francoise; Calvert, Wynne

    1988-01-01

    The location of the source of the Jovian S bursts was studied by comparing the high-frequency limit of these emissions, recorded in Nancay, to the surface gyrofrequency at the foot of the magnetic field lines which intersect Io's orbit, according to the O4 magnetic field model. For this purpose, the statistical occurrence of the S bursts was examined, both in central meridian longitude versus Io phase and as a function of the relative phase of Io with respect to Jupiter. The S bursts and the Io-dependent L emissions were found to originate from approximately the same locations at Jupiter, and probably under similar conditions of excitation by Io, although the beaming of these S emissions, which is indicated by the compactness of the occurrence patterns, was somewhat narrower than for the corresponding L emissions. Also, like the L emissions, an apparent delay of up to 70 deg was found to occur between the predicted instanteneous Io flux tube and the apparent source field line. The possible origin of this 70 deg delay is discussed.

  3. Radio sociology

    NASA Astrophysics Data System (ADS)

    Swenson, George W., Jr.

    1996-04-01

    A work was conducted, using radio telemetry, to locate a migrating, radio-tagged, sharp-shinned hawk. The hawk was monitored through the noise radiation it created. The hawk was found. During this study, it was found that the concentration of population corresponds with areas of increased noise temperature. Through this study, a bigger study was planned. The study would involved the relationship between a place's radiation signature and its other attributes, such as economic type, population, geographic concentration. The method of radio sociology would be used to track the sources of radio noise.

  4. A single source femtosecond-millisecond broadband spectrometer

    NASA Astrophysics Data System (ADS)

    Carroll, E. C.; Hill, M. P.; Madsen, D.; Malley, K. R.; Larsen, D. S.

    2009-02-01

    Time-resolved measurement of population dynamics extending over femtosecond to millisecond time scales typically requires a combination of transient absorption techniques involving different laser systems and detection schemes. The spectrometer design presented here facilitates transient absorption measurements over 12 decades with a single ultrafast laser system by picking pump and probe pulses independently from the laser oscillator pulse train. Unamplified pulses seed a photonic crystal fiber to a supercontinuum probe source for spectrally resolved measurements. The utility of the system is demonstrated by measuring triplet state dynamics following photoexcitation of vitamin B6 in aqueous solution.

  5. Microarcsecond VLBI Pulsar Astrometry with PSRπ. I. Two Binary Millisecond Pulsars with White Dwarf Companions

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    Model-independent distance constraints to binary millisecond pulsars (MSPs) are of great value to both the timing observations of the radio pulsars and multiwavelength observations of their companion stars. Astrometry using very long baseline interferometry (VLBI) can be employed to provide these model-independent distances with very high precision via the detection of annual geometric parallax. Using the Very Long Baseline Array, we have observed two binary MSPs, PSR J1022+1001 and J2145–0750, over a two-year period and measured their distances to be {700}-10+14 pc and {613}-14+16 pc respectively. We use the well-calibrated distance in conjunction with revised analysis of optical photometry to tightly constrain the nature of their massive (M˜ 0.85 {M}ȯ ) white dwarf companions. Finally, we show that several measurements of the parallax and proper motion of PSR J1022+1001 and PSR J2145–0750 obtained by pulsar timing array projects are incorrect, differing from the more precise VLBI values by up to 5σ. We investigate possible causes for the discrepancy, and find that imperfect modeling of the solar wind is a likely candidate for the errors in the timing model given the low ecliptic latitude of these two pulsars.

  6. Multi-wavelength modeling of globular clusters–the millisecond pulsar scenario

    SciTech Connect

    Kopp, A.; Venter, C.; Büsching, I.; De Jager, O. C.

    2013-12-20

    The potentially large number of millisecond pulsars (MSPs) in globular cluster (GC) cores makes these parent objects ideal laboratories for studying the collective properties of an ensemble of MSPs. Such a population is expected to radiate several spectral components in the radio through γ-ray waveband. First, pulsed emission is expected via curvature and synchrotron radiation (CR and SR) and possibly even via inverse Compton (IC) scattering inside the pulsar magnetospheres. Second, unpulsed emission should transpire through the continuous injection of relativistic leptons by the MSPs into the ambient region, which in turn produce SR and IC emission when they encounter the cluster magnetic field, as well as several background photon components. In this paper we continue to develop the MSP scenario for explaining the multi-wavelength properties of GCs by considering the entire modeling chain, including the full transport equation, refined emissivities of stellar and Galactic background photons, integration of the flux along the line of sight, and comparison with observations. As an illustration, we apply the model to Terzan 5, where we can reasonably fit both the (line-of-sight-integrated) X-ray surface flux and spectral energy density data, using the first to constrain the leptonic diffusion coefficient within the GC. We lastly discuss possible future extensions to and applications of this maturing model.

  7. OPTICAL IDENTIFICATION OF He WHITE DWARFS ORBITING FOUR MILLISECOND PULSARS IN THE GLOBULAR CLUSTER 47 TUCANAE

    SciTech Connect

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

    2015-10-10

    We used ultra-deep UV observations obtained with the Hubble Space Telescope to search for optical companions to binary millisecond pulsars (MSPs) in the globular cluster 47 Tucanae. We identified four new counterparts (to MSPs 47TucQ, 47TucS, 47TucT, and 47TucY) and confirmed those already known (to MSPs 47TucU and 47TucW). In the color–magnitude diagram, the detected companions are located in a region between the main sequence and the CO white dwarf (WD) cooling sequences, consistent with the cooling tracks of He WDs with masses between 0.15 M{sub ⊙} and 0.20 M{sub ⊙}. For each identified companion, mass, cooling age, temperature, and pulsar mass (as a function of the inclination angle) have been derived and discussed. For 47TucU we also found that the past accretion history likely proceeded at a sub-Eddington rate. The companion to the redback 47TucW is confirmed to be a non-degenerate star, with properties particularly similar to those observed for black widow systems. Two stars have been identified within the 2σ astrometric uncertainty from the radio positions of 47TucH and 47TucI, but the available data prevent us from firmly assessing whether they are the true companions of these two MSPs.

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

    SciTech Connect

    Antoniadis, John

    2014-12-20

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

  9. Microarcsecond VLBI Pulsar Astrometry with PSRπ. I. Two Binary Millisecond Pulsars with White Dwarf Companions

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    Model-independent distance constraints to binary millisecond pulsars (MSPs) are of great value to both the timing observations of the radio pulsars and multiwavelength observations of their companion stars. Astrometry using very long baseline interferometry (VLBI) can be employed to provide these model-independent distances with very high precision via the detection of annual geometric parallax. Using the Very Long Baseline Array, we have observed two binary MSPs, PSR J1022+1001 and J2145-0750, over a two-year period and measured their distances to be {700}-10+14 pc and {613}-14+16 pc respectively. We use the well-calibrated distance in conjunction with revised analysis of optical photometry to tightly constrain the nature of their massive (M˜ 0.85 {M}⊙ ) white dwarf companions. Finally, we show that several measurements of the parallax and proper motion of PSR J1022+1001 and PSR J2145-0750 obtained by pulsar timing array projects are incorrect, differing from the more precise VLBI values by up to 5σ. We investigate possible causes for the discrepancy, and find that imperfect modeling of the solar wind is a likely candidate for the errors in the timing model given the low ecliptic latitude of these two pulsars.

  10. DISCOVERY OF AN ULTRACOMPACT GAMMA-RAY MILLISECOND PULSAR BINARY CANDIDATE

    SciTech Connect

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

    2014-10-20

    We report multi-wavelength observations of the unidentified Fermi object 2FGL J1653.6-0159. With the help of high-resolution X-ray observations, we have identified an X-ray and optical counterpart to 2FGL J1653.6-0159. The source exhibits a periodic modulation of 75 minutes in the optical and possibly also in the X-ray. We suggest that 2FGL J1653.6-0159 is a compact binary system with an orbital period of 75 minutes. Combining the gamma-ray and X-ray properties, 2FGL J1653.6-0159 is potentially a black-widow-/redback-type gamma-ray millisecond pulsar (MSP). The optical and X-ray light curve profiles show that the companion is mildly heated by the high-energy emission and that the X-rays are from intrabinary shock. Although no radio pulsation has yet been detected, we estimated that the spin period of the MSP is ∼ 2 ms based on a theoretical model. If pulsation can be confirmed in the future, 2FGL J1653.6-0159 will become the first ultracompact rotation-powered MSP.

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

    NASA Astrophysics Data System (ADS)

    Antoniadis, John

    2014-12-01

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

  12. Multiwavelength observations of the transitional millisecond pulsar binary XSS J12270-4859

    NASA Astrophysics Data System (ADS)

    de Martino, D.; Papitto, A.; Belloni, T.; Burgay, M.; De Ona Wilhelmi, E.; Li, J.; Pellizzoni, A.; Possenti, A.; Rea, N.; Torres, D. F.

    2015-12-01

    We present an analysis of X-ray, ultraviolet and optical/near-IR photometric data of the transitional millisecond pulsar binary XSS J12270-4859, obtained at different epochs after the transition to a rotation-powered radio pulsar state. The observations, while confirming the large-amplitude orbital modulation found in previous studies after the state change, also reveal an energy dependence of the amplitudes as well as variations on time-scale of months. The amplitude variations are anticorrelated in the X-ray and the UV/optical bands. The average X-ray spectrum is described by a power law with Γ index of 1.07(8) without requiring an additional thermal component. The power-law index Γ varies from ˜1.2 to ˜1.0 between superior and inferior conjunction of the neutron star. We interpret the observed X-ray behaviour in terms of synchrotron radiation emitted in an extended intrabinary shock, located between the pulsar and the donor star, which is eclipsed due to the companion orbital motion. The G5-type donor dominates the UV/optical and near-IR emission and is similarly found to be heated up to ˜6500 K as in the disc state. The analysis of optical light curves gives a binary inclination 46° ≲ i ≲ 65° and a mass ratio 0.11 ≲ q ≲ 0.26. The donor mass is found to be 0.15 ≲ M2 ≲ 0.36 M⊙ for a neutron star mass of 1.4 M⊙. The variations in the amplitude of the orbital modulation are interpreted in terms of small changes in the mass-flow rate from the donor star. The spectral energy distribution from radio to gamma-rays is composed by multiple contributions that are different from those observed during the accretion-powered state.

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

    NASA Astrophysics Data System (ADS)

    Alpar, Mehmet Ali; Gügercinoǧlu, Erbil

    2016-07-01

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

  14. Advances in solar radio astronomy

    NASA Technical Reports Server (NTRS)

    Kundu, M. R.

    1982-01-01

    The status of the observations and interpretations of the sun's radio emission covering the entire radio spectrum from millimeter wavelengths to hectometer and kilometer wavelengths is reviewed. Emphasis is given to the progress made in solar radio physics as a result of recent advances in plasma and radiation theory. It is noted that the capability now exists of observing the sun with a spatial resolution of approximately a second of arc and a temporal resolution of about a millisecond at centimeter wavelengths and of obtaining fast multifrequency two-dimensional pictures of the sun at meter and decameter wavelengths. A summary is given of the properties of nonflaring active regions at millimeter, centimeter, and meter-decameter wavelengths. The properties of centimeter wave bursts are discussed in connection with the high spatial resolution observations. The observations of the preflare build-up of an active region are reviewed. High spatial resolution observations (a few seconds of arc to approximately 1 arcsec) are discussed, with particular attention given to the one- and two-dimensional maps of centimeter-wavelength burst sources.

  15. Radio Astronomical Polarimetry and Point-Source Calibration

    NASA Astrophysics Data System (ADS)

    van Straten, W.

    2004-05-01

    A mathematical framework is presented for use in the experimental determination of the polarimetric response of observatory instrumentation. Elementary principles of linear algebra are applied to model the full matrix description of the polarization measurement equation by least-squares estimation of nonlinear, scalar parameters. The formalism is applied to calibrate the center element of the Parkes Multibeam receiver using observations of the millisecond pulsar PSR J0437-4715 and the radio galaxy 3C 218 (Hydra A).

  16. DISCOVERY OF THE OPTICAL/ULTRAVIOLET/GAMMA-RAY COUNTERPART TO THE ECLIPSING MILLISECOND PULSAR J1816+4510

    SciTech Connect

    Kaplan, D. L.; Kotulla, R.; Biwer, C. M.; Day, D. F.; Stovall, K.; Dartez, L.; Ford, A. J.; Garcia, A.; Jenet, F. A.; Ransom, S. M.; Roberts, M. S. E.; Archibald, A. M.; Karako, C.; Kaspi, V. M.; Lynch, R. S.; Boyles, J.; Lorimer, D. R.; McLaughlin, M. A.; Hessels, J. W. T.; Kondratiev, V. I.; and others

    2012-07-10

    The energetic, eclipsing millisecond pulsar J1816+4510 was recently discovered in a low-frequency radio survey with the Green Bank Telescope. With an orbital period of 8.7 hr and a minimum companion mass of 0.16 M{sub Sun }, it appears to belong to an increasingly important class of pulsars that are ablating their low-mass companions. We report the discovery of the {gamma}-ray counterpart to this pulsar and present a likely optical/ultraviolet counterpart as well. Using the radio ephemeris, we detect pulsations in the unclassified {gamma}-ray source 2FGL J1816.5+4511, implying an efficiency of {approx}25% in converting the pulsar's spin-down luminosity into {gamma}-rays and adding PSR J1816+4510 to the large number of millisecond pulsars detected by Fermi. The likely optical/UV counterpart was identified through position coincidence (<0.''1) and unusual colors. Assuming that it is the companion, with R = 18.27 {+-} 0.03 mag and effective temperature {approx}> 15,000 K, it would be among the brightest and hottest of low-mass pulsar companions and appears qualitatively different from other eclipsing pulsar systems. In particular, current data suggest that it is a factor of two larger than most white dwarfs of its mass but a factor of four smaller than its Roche lobe. We discuss possible reasons for its high temperature and odd size, and suggest that it recently underwent a violent episode of mass loss. Regardless of origin, its brightness and the relative unimportance of irradiation make it an ideal target for a mass, and hence a neutron star mass, determination.

  17. Radio stars.

    PubMed

    Hjellming, R M; Wade, C M

    1971-09-17

    Up to the present time six classes of radio stars have been established. The signals are almost always very faint and drastically variable. Hence their discovery has owed as much to serendipity as to the highly sophisticated equipment and techniques that have been used. When the variations are regular, as with the pulsars, this characteristic can be exploited very successfully in the search for new objects as well as in the detailed study of those that are already known. The detection of the most erratically variable radio stars, the flare stars and the x-ray stars, is primarily a matter of luck and patience. In the case of the novas, one at least knows where and oughly when to look for radio emission. A very sensitive interferometer is clearly the best instrument to use in the initial detection of a radio star. The fact that weak background sources are frequently present makes it essential to prove that the position of a radio source agrees with that of a star to within a few arc seconds. The potential of radio astronomy for the study of radio stars will not be realized until more powerful instruments than those that are available today can be utilized. So far, we have been able to see only the most luminous of the radio stars. PMID:17836594

  18. College Radio.

    ERIC Educational Resources Information Center

    Sauls, Samuel J.

    As with commercial stations, the underlying premise of the college radio station is to serve the community, whether it be the campus community or the community at large, but in unique ways often geared to underserved niches of the population. Much of college radio's charm lies in its unpredictable nature and constant mutations. The stations give…

  19. Radio Astronomy

    NASA Technical Reports Server (NTRS)

    Shaffer, R. D.; Wolken, P. R.; Niell, A. E.

    1981-01-01

    The activities of the DSN in support of Radio and Radar Astronomy Operations during September through December 1980 are described. Emphasis is on a report of an experiment selected for use of the DSN by the radio Astronomy Experiment Selection Panel: that of VLBI observations of the energetic galactic object SS-433.

  20. Radio astronomy

    NASA Technical Reports Server (NTRS)

    Wolken, P. R.; Schaffer, R. D.; Gorenstein, M. V.

    1981-01-01

    The activities of the Deep Space Network in support of Radio Astronomy Operations during April and May 1981 are reported. Work in progres in support of an experiment selected for use of the DSN by the Radio Astronomy Experiment Selection Panel, Twin Quasi-Stellar Object VLBI, is reported.

  1. Radio astronomy

    NASA Technical Reports Server (NTRS)

    Shaffer, R. D.; Wolken, P. R.; Gulkis, S.

    1981-01-01

    The activities of the Deep Space Network in support of radio astronomy operations during the first quarter of 1981 are reported. Results of the use of a low noise maser are presented, as well as updates in DSN support of experiments sanctioned by the Radio Astronomy Experiment Selection Panel.

  2. Radio astronomy

    NASA Technical Reports Server (NTRS)

    Taylor, R. M.; Manchester, R. N.

    1980-01-01

    The activities of the Deep Space Network in support of radio and radar astronomy operations during July and August 1980 are reported. A brief update on the OSS-sponsored planetary radio astronomy experiment is provided. Also included are two updates, one each from Spain and Australia on current host country activities.

  3. Radio stars.

    PubMed

    Hjellming, R M; Wade, C M

    1971-09-17

    Up to the present time six classes of radio stars have been established. The signals are almost always very faint and drastically variable. Hence their discovery has owed as much to serendipity as to the highly sophisticated equipment and techniques that have been used. When the variations are regular, as with the pulsars, this characteristic can be exploited very successfully in the search for new objects as well as in the detailed study of those that are already known. The detection of the most erratically variable radio stars, the flare stars and the x-ray stars, is primarily a matter of luck and patience. In the case of the novas, one at least knows where and oughly when to look for radio emission. A very sensitive interferometer is clearly the best instrument to use in the initial detection of a radio star. The fact that weak background sources are frequently present makes it essential to prove that the position of a radio source agrees with that of a star to within a few arc seconds. The potential of radio astronomy for the study of radio stars will not be realized until more powerful instruments than those that are available today can be utilized. So far, we have been able to see only the most luminous of the radio stars.

  4. Millisecond burning of confined energetic materials during cookoff

    SciTech Connect

    Schmitt, R.G.; Baer, T.A.

    1997-11-01

    The response of a system containing an energetic material (EM) to an abnormal thermal environment is termed cookoff. To predict the violence of reaction of confined energetic materials during cookoff requires a description of the relevant physical processes that occur on time scales Ranging from days to submicroseconds. The time-to-ignition can be characterized accurately using heat transfer with chemistry and quasistatic mechanics. After ignition the energetic material deflagrates on a millisecond time scale. During this time the mechanical processes become dynamic. If the confinement survives burning then accelerated deflagration can lead to shock formation and deflagration to detonation transition. The focus of this work is the dynamic combustion regime in the millisecond time domain. Due to the mathematical stiffness of the chemistry equations and the prohibitively fine spatial resolution requirements needed to resolve the structure of the flame, an interface tracking approach is used to propagate the burn front. Demonstrative calculations are presented that illustrate the dynamic interaction of the deflagrating energetic material with its confinement.

  5. On neutron star structure and the millisecond pulsar

    NASA Technical Reports Server (NTRS)

    Harding, A. K.

    1983-01-01

    The recently discovered millisecond pulsar (PSR1937-214) is observed to be rotating close to the limit of dynamical instability for a neutron star. Despite its extremely rapid rotation, measurements of the period derivative put a stringent upper limit on the energy loss from gravitational radiation, thus requiring that the quadrupole moment be quite small. The pulsar must also be rotating below the critical frequency at which its equilibrium configuration would become non-axisymmetric, since the lifetime of this configuration against decay by gravitational radiation is very short. This critical frequency, given by the theory of rotating ellipsoids, imposes a restriction on the rotation rate more severe than the break-up frequency and may be used to set a lower limit, rho 2 x 10 to the 14th power g/cu cm, on the density of the star. If the mass is 0.5 - 1.5 solar mass, several of the stiffer neutron star equations of state may be ruled out, and the radius should be less than 16 km. The condition for axisymmetry also imposes an upper limit on the rotation rate to which neutron stars may be spun up by accretion disks in binary systems, a model recently proposed for the evolution of the millisecond pulsar.

  6. Radio Telescopes

    NASA Astrophysics Data System (ADS)

    Ekers, Ron; Wilson, Thomas L.

    ``Radio Telescopes" starts with a brief historical introduction from Jansky's1931 discovery of radio emission from the Milky Way through the development ofradio telescope dishes and arrays to aperture synthesis imaging. It includessufficient basics of electromagnetic radiation to provide some understanding of thedesign and operation of radio telescopes. The criteria such as frequencyrange, sensitivity, survey speed, angular resolution, and field of view thatdetermine the design of radio telescopes are introduced. Because it is soeasy to manipulate the electromagnetic waves at radio frequencies, radiotelescopes have evolved into many different forms, sometimes with "wire"structures tuned to specific wavelengths, which look very different from anykind of classical telescope. To assist astronomers more familiar with otherwavelength domains, the appendix A.1. includes a comparison of radioand optical terminology. Some of the different types of radio telescopesincluding the filled aperture dishes, electronically steered phased arrays, andaperture synthesis radio telescopes are discussed, and there is a sectioncomparing the differences between dishes and arrays. Some of the morerecent developments including hierarchical beam forming, phased arrayfeeds, mosaicing, rotation measure synthesis, digital receivers, and longbaseline interferometers are included. The problem of increasing radiofrequency interference is discussed, and some possible mitigation strategies areoutlined.

  7. Application of Millisecond Pulsar Timing to the Long-Term Stability of Clock Ensembles

    NASA Technical Reports Server (NTRS)

    Foster, Roger S.; Matsakis, Demetrios N.

    1996-01-01

    We review the application of millisecond pulsars to define a precise long-term standard and positional reference system in a nearly inertial reference frame. We quantify the current timing precision of the best millisecond pulsars and define the required precise time and time interval (PTTI) accuracy and stability to enable time transfer via pulsars. Pulsars may prove useful as independent standards to examine decade-long timing stability and provide an independent natural system within which to calibrate any new, perhaps vastly improved atomic time scale. Since pulsar stability appears to be related to the lifetime of the pulsar, the new millisecond pulsar J173+0747 is projected to have a 100-day accuracy equivalent to a single HP5071 cesium standard. Over the last five years, dozens of new millisecond pulsars have been discovered. A few of the new millisecond pulsars may have even better timing properties.

  8. Challenges in explaining the Galactic Center gamma-ray excess with millisecond pulsars

    SciTech Connect

    Cholis, Ilias; Hooper, Dan; Linden, Tim E-mail: dhooper@fnal.gov

    2015-06-01

    Millisecond pulsars have been discussed as a possible source of the gamma-ray excess observed from the region surrounding the Galactic Center. With this in mind, we use the observed population of bright low-mass X-ray binaries to estimate the number of millisecond pulsars in the Inner Galaxy. This calculation suggests that only ∼ 1–5% of the excess is produced by millisecond pulsars. We also use the luminosity function derived from local measurements of millisecond pulsars, along with the number of point sources resolved by Fermi, to calculate an upper limit for the diffuse emission from such a population. While this limit is compatible with the millisecond pulsar population implied by the number of low-mass X-ray binaries, it strongly excludes the possibility that most of the excess originates from such objects.

  9. Lipidic cubic phase serial millisecond crystallography using synchrotron radiation

    PubMed Central

    Nogly, Przemyslaw; James, Daniel; Wang, Dingjie; White, Thomas A.; Zatsepin, Nadia; Shilova, Anastasya; Nelson, Garrett; Liu, Haiguang; Johansson, Linda; Heymann, Michael; Jaeger, Kathrin; Metz, Markus; Wickstrand, Cecilia; Wu, Wenting; Båth, Petra; Berntsen, Peter; Oberthuer, Dominik; Panneels, Valerie; Cherezov, Vadim; Chapman, Henry; Schertler, Gebhard; Neutze, Richard; Spence, John; Moraes, Isabel; Burghammer, Manfred; Standfuss, Joerg; Weierstall, Uwe

    2015-01-01

    Lipidic cubic phases (LCPs) have emerged as successful matrixes for the crystallization of membrane proteins. Moreover, the viscous LCP also provides a highly effective delivery medium for serial femtosecond crystallography (SFX) at X-ray free-electron lasers (XFELs). Here, the adaptation of this technology to perform serial millisecond crystallography (SMX) at more widely available synchrotron microfocus beamlines is described. Compared with conventional microcrystallography, LCP-SMX eliminates the need for difficult handling of individual crystals and allows for data collection at room temperature. The technology is demonstrated by solving a structure of the light-driven proton-pump bacteriorhodopsin (bR) at a resolution of 2.4 Å. The room-temperature structure of bR is very similar to previous cryogenic structures but shows small yet distinct differences in the retinal ligand and proton-transfer pathway. PMID:25866654

  10. Millisecond optical photometry of the DQ Herculis objects

    NASA Technical Reports Server (NTRS)

    Imamura, James N.; Steiman-Cameron, Thomas Y.

    1988-01-01

    The results of millisecond optical photometry of the DQ Herculis stars EX Hya, H2252-035, V1223 Sgr, and AE Aqr obtained at the Las Campanas Observatory and Cerro Tololo Inter-American Observatory during the years 1985, 1986, and 1987 are reported. The data for coherent and incoherent features are searched for. Coherent features (other than those previously known) were not detected for frequencies between 0.1 and 250 Hz at 4-sigma upper limits of 0.05-0.4 percent. Evidence is not found for 1-3 s, quasi-coherent features. Such features have been detected in the optical emission of the AM Her objects AN UMa, EF Eri, and E1405-451. Because of the similarities between AM Her and DQ Her objects, it was suggested that such quasi-coherent features might also be found in the DQ Her objects.

  11. Millisecond newly born pulsars as efficient accelerators of electrons.

    PubMed

    Osmanov, Zaza; Mahajan, Swadesh; Machabeli, George; Chkheidze, Nino

    2015-01-01

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

  12. On neutron star structure and the millisecond pulsar

    NASA Technical Reports Server (NTRS)

    Harding, A. K.

    1983-01-01

    The millisecond pulsar is the first observed example of a neutron star spinning rapidly enough to approach the Jacobi bifurcation point and thus affords the possibility of constraining neutron star physics. The pulsar must be rotating below the critical frequency at which its equilibrium configuration would become nonaxisymmetric, since the lifetime of this configuration against decay by gravitational radiation is very short. This critical frequency may be used to set a lower limit of 2 x 10 to the 14th g/cu cm on the density of the star. If the mass is 0.5-1.5 solar mass, several of the stiffer neutron star equations of state may be ruled out, and the radius should be less than 16 km. The condition for axisymmetry also imposes an upper limit on the rotation rate to which neutron stars may be spun up by accretion disks in binary systems.

  13. Millisecond newly born pulsars as efficient accelerators of electrons

    NASA Astrophysics Data System (ADS)

    Osmanov, Zaza; Mahajan, Swadesh; Machabeli, George; Chkheidze, Nino

    2015-09-01

    The newly born millisecond pulsars are investigated as possible energy sources for creating ultra-high energy electrons. The transfer of energy from the star rotation to high energy electrons takes place through the Landau damping of centrifugally driven (via a two stream instability) electrostatic Langmuir waves. Generated in the bulk magnetosphere plasma, such waves grow to high amplitudes, and then damp, very effectively, on relativistic electrons driving them to even higher energies. We show that the rate of transfer of energy is so efficient that no energy losses might affect the mechanism of particle acceleration; the electrons might achieve energies of the order of 1018 eV for parameters characteristic of a young star.

  14. Millisecond newly born pulsars as efficient accelerators of electrons

    PubMed Central

    Osmanov, Zaza; Mahajan, Swadesh; Machabeli, George; Chkheidze, Nino

    2015-01-01

    The newly born millisecond pulsars are investigated as possible energy sources for creating ultra-high energy electrons. The transfer of energy from the star rotation to high energy electrons takes place through the Landau damping of centrifugally driven (via a two stream instability) electrostatic Langmuir waves. Generated in the bulk magnetosphere plasma, such waves grow to high amplitudes, and then damp, very effectively, on relativistic electrons driving them to even higher energies. We show that the rate of transfer of energy is so efficient that no energy losses might affect the mechanism of particle acceleration; the electrons might achieve energies of the order of 1018 eV for parameters characteristic of a young star. PMID:26403155

  15. Quantum memory with millisecond coherence in circuit QED

    NASA Astrophysics Data System (ADS)

    Reagor, Matthew; Pfaff, Wolfgang; Axline, Christopher; Heeres, Reinier W.; Ofek, Nissim; Sliwa, Katrina; Holland, Eric; Wang, Chen; Blumoff, Jacob; Chou, Kevin; Hatridge, Michael J.; Frunzio, Luigi; Devoret, Michel H.; Jiang, Liang; Schoelkopf, Robert J.

    2016-07-01

    Significant advances in coherence render superconducting quantum circuits a viable platform for fault-tolerant quantum computing. To further extend capabilities, highly coherent quantum systems could act as quantum memories for these circuits. A useful quantum memory must be rapidly addressable by Josephson-junction-based artificial atoms, while maintaining superior coherence. We demonstrate a superconducting microwave cavity architecture that is highly robust against major sources of loss that are encountered in the engineering of circuit QED systems. The architecture allows for storage of quantum superpositions in a resonator on the millisecond scale, while strong coupling between the resonator and a transmon qubit enables control, encoding, and readout at MHz rates. This extends the maximum available coherence time attainable in superconducting circuits by almost an order of magnitude compared to earlier hardware. Our design is an ideal platform for studying coherent quantum optics and marks an important step towards hardware-efficient quantum computing in Josephson-junction-based quantum circuits.

  16. Millisecond newly born pulsars as efficient accelerators of electrons.

    PubMed

    Osmanov, Zaza; Mahajan, Swadesh; Machabeli, George; Chkheidze, Nino

    2015-01-01

    The newly born millisecond pulsars are investigated as possible energy sources for creating ultra-high energy electrons. The transfer of energy from the star rotation to high energy electrons takes place through the Landau damping of centrifugally driven (via a two stream instability) electrostatic Langmuir waves. Generated in the bulk magnetosphere plasma, such waves grow to high amplitudes, and then damp, very effectively, on relativistic electrons driving them to even higher energies. We show that the rate of transfer of energy is so efficient that no energy losses might affect the mechanism of particle acceleration; the electrons might achieve energies of the order of 10(18) eV for parameters characteristic of a young star. PMID:26403155

  17. XSS J12270-4859: A Transformation from an X-ray Binary to a Rotation-Powered Millisecond Pulsar System

    NASA Astrophysics Data System (ADS)

    Bogdanov, Slavko; Bassa, Cees; Archibald, Anne M; Patruno, Alessandro; Hessels, Jason; Janssen, Gemma H; Stappers, Benjamin; Tendulkar, Shriharsh P.

    2014-08-01

    XSS J12270-4859 has been previously suggested to be a low-mass X-ray binary, and until recently the only such system to be seen at MeV-GeV energies. We present radio, optical and X-ray observations that demonstrate that XSS J12270-4859 has undergone a sudden decline in optical and X-ray brightness and no longer shows evidence for an accretion disk. Along with the recent detection of radio pulsations, these findings indicate that XSS J12270-4859 transformed to a full-fledged eclipsing "redback" system between 2012 November 14 and December 21 and presently hosts an active rotation-powered millisecond pulsar.

  18. Radio Astronomy

    NASA Technical Reports Server (NTRS)

    Wolken, P. R.; Shaffer, R. D.

    1983-01-01

    Deep Space Network (DSN) 26- and 64-meter antenna stations were utilized in support of Radio Astronomy Experiment Selection Panel experiments. Within a time span of 10 days, in May 1983 (267.75 hours total), nine RAES experiments were supported. Most of these experiments involved multifacility interferometry using Mark 3 data recording terminals and as many as six non-DSN observatories. Investigations of black holes, quasars, galaxies, and radio sources are discussed.

  19. Radio-quiet Fast Coronal Mass Ejections

    NASA Astrophysics Data System (ADS)

    Gopalswamy, N.; Aguilar-Rodriguez, E.; Kaiser, M. L.; Howard, R. A.

    2004-12-01

    Coronal mass ejections (CMEs) drive shocks in the interplanetary medium that produce type II radio emission. These CMEs are faster and wider on the average, than the general population of CMEs. However, when we start from fast (speed > 900 km/s) and wide (angular width > 60 degrees), more than half of them are not associated with radio bursts. In order to understand why these CMEs are radio quiet, we collected all the fast and wide (FW) CMEs detected by the Solar and Heliospheric Observatory (SOHO) mission's Large Angle and Spectrometric Coronagraph (LASCO) and isolated those without associated type II radio bursts. The radio bursts were identified in the dynamic spectra of the Radio and Plasma Wave (WAVES) Experiment on board the Wind spacecraft. We also checked the list against metric type II radio bursts reported in Solar Geophysical Data and isolated those without any radio emission. This exercise resulted in about 140 radio-quiet FW CMEs. We identified the source regions of these CMEs using the Solar Geophysical Data listings, cross-checked against the eruption regions in the SOHO/EIT movies. We explored a number of possibilities for the radio-quietness: (i) Source region being too far behind the limb, (ii) flare size, (iii) brightness of the CME, and (iv) the density of the ambient medium. We suggest that a combination of CME energy and the Alfven speed profile of the ambient medium is primarily responsible for the radio-quietness of these FW CMEs.

  20. A 24 hr global campaign to assess precision timing of the millisecond pulsar J1713+0747

    SciTech Connect

    Dolch, T.; Lam, M. T.; Cordes, J.; Chatterjee, S.; Bassa, C.; Hessels, J. W. T.; Janssen, G.; Kondratiev, V.; Bhattacharyya, B.; Jordan, C.; Keith, M.; Champion, D. J.; Karuppusamy, R.; Kramer, M.; Lazarus, P.; Cognard, I.; Demorest, P. B.; Jenet, F. A.; Jones, G.; and others

    2014-10-10

    The radio millisecond pulsar J1713+0747 is regarded as one of the highest-precision clocks in the sky and is regularly timed for the purpose of detecting gravitational waves. The International Pulsar Timing Array Collaboration undertook a 24 hr global observation of PSR J1713+0747 in an effort to better quantify sources of timing noise in this pulsar, particularly on intermediate (1-24 hr) timescales. We observed the pulsar continuously over 24 hr with the Arecibo, Effelsberg, GMRT, Green Bank, LOFAR, Lovell, Nançay, Parkes, and WSRT radio telescopes. The combined pulse times-of-arrival presented here provide an estimate of what sources of timing noise, excluding DM variations, would be present as compared to an idealized √N improvement in timing precision, where N is the number of pulses analyzed. In the case of this particular pulsar, we find that intrinsic pulse phase jitter dominates arrival time precision when the signal-to-noise ratio of single pulses exceeds unity, as measured using the eight telescopes that observed at L band/1.4 GHz. We present first results of specific phenomena probed on the unusually long timescale (for a single continuous observing session) of tens of hours, in particular interstellar scintillation, and discuss the degree to which scintillation and profile evolution affect precision timing. This paper presents the data set as a basis for future, deeper studies.

  1. A 24 Hr Global Campaign to Assess Precision Timing of the Millisecond Pulsar J1713+0747

    NASA Astrophysics Data System (ADS)

    Dolch, T.; Lam, M. T.; Cordes, J.; Chatterjee, S.; Bassa, C.; Bhattacharyya, B.; Champion, D. J.; Cognard, I.; Crowter, K.; Demorest, P. B.; Hessels, J. W. T.; Janssen, G.; Jenet, F. A.; Jones, G.; Jordan, C.; Karuppusamy, R.; Keith, M.; Kondratiev, V.; Kramer, M.; Lazarus, P.; Lazio, T. J. W.; Lee, K. J.; McLaughlin, M. A.; Roy, J.; Shannon, R. M.; Stairs, I.; Stovall, K.; Verbiest, J. P. W.; Madison, D. R.; Palliyaguru, N.; Perrodin, D.; Ransom, S.; Stappers, B.; Zhu, W. W.; Dai, S.; Desvignes, G.; Guillemot, L.; Liu, K.; Lyne, A.; Perera, B. B. P.; Petroff, E.; Rankin, J. M.; Smits, R.

    2014-10-01

    The radio millisecond pulsar J1713+0747 is regarded as one of the highest-precision clocks in the sky and is regularly timed for the purpose of detecting gravitational waves. The International Pulsar Timing Array Collaboration undertook a 24 hr global observation of PSR J1713+0747 in an effort to better quantify sources of timing noise in this pulsar, particularly on intermediate (1-24 hr) timescales. We observed the pulsar continuously over 24 hr with the Arecibo, Effelsberg, GMRT, Green Bank, LOFAR, Lovell, Nançay, Parkes, and WSRT radio telescopes. The combined pulse times-of-arrival presented here provide an estimate of what sources of timing noise, excluding DM variations, would be present as compared to an idealized \\sqrt{N} improvement in timing precision, where N is the number of pulses analyzed. In the case of this particular pulsar, we find that intrinsic pulse phase jitter dominates arrival time precision when the signal-to-noise ratio of single pulses exceeds unity, as measured using the eight telescopes that observed at L band/1.4 GHz. We present first results of specific phenomena probed on the unusually long timescale (for a single continuous observing session) of tens of hours, in particular interstellar scintillation, and discuss the degree to which scintillation and profile evolution affect precision timing. This paper presents the data set as a basis for future, deeper studies.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

    We used ultra-deep UV observations obtained with the Hubble Space Telescope to search for optical companions to binary millisecond pulsars (MSPs) in the globular cluster 47 Tucanae. We identified four new counterparts (to MSPs 47TucQ, 47TucS, 47TucT, and 47TucY) and confirmed those already known (to MSPs 47TucU and 47TucW). In the color-magnitude diagram, the detected companions are located in a region between the main sequence and the CO white dwarf (WD) cooling sequences, consistent with the cooling tracks of He WDs with masses between 0.15 M⊙ and 0.20 M⊙. For each identified companion, mass, cooling age, temperature, and pulsar mass (as a function of the inclination angle) have been derived and discussed. For 47TucU we also found that the past accretion history likely proceeded at a sub-Eddington rate. The companion to the redback 47TucW is confirmed to be a non-degenerate star, with properties particularly similar to those observed for black widow systems. Two stars have been identified within the 2σ astrometric uncertainty from the radio positions of 47TucH and 47TucI, but the available data prevent us from firmly assessing whether they are the true companions of these two MSPs. Based on observations collected with the NASA/ESA HST (Prop. 12950), obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555.

  4. TWO MILLISECOND PULSARS DISCOVERED BY THE PALFA SURVEY AND A SHAPIRO DELAY MEASUREMENT

    SciTech Connect

    Deneva, J. S.; Camilo, F.; Freire, P. C. C.; Champion, D. J.; Desvignes, G.; Cordes, J. M.; Brazier, A.; Chatterjee, S.; Lyne, A. G.; Ransom, S. M.; Cognard, I.; Nice, D. J.; Stairs, I. H.; Allen, B.; Bhat, N. D. R.; Bogdanov, S.; Crawford, F.; Hessels, J. W. T.; Jenet, F. A.; Kaspi, V. M.; and others

    2012-09-20

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

  5. The Millisecond Magnetar Central Engine in Short GRBs

    NASA Astrophysics Data System (ADS)

    Lü, Hou-Jun; Zhang, Bing; Lei, Wei-Hua; Li, Ye; Lasky, Paul D.

    2015-06-01

    One favored progenitor model for short duration gamma-ray bursts (GRBs) is the coalescence of two neutron stars (NS-NS). One possible outcome of such a merger would be a rapidly spinning, strongly magnetized neutron star (known as a millisecond magnetar). These magnetars may be “supra-massive,” implying that they would collapse to black holes after losing centrifugal support due to magnetic dipole spin down. By systematically analyzing the Burst Alert Telescope (BAT)-XRT light curves of all short GRBs detected by Swift, we test how consistent the data are with this central engine model of short GRBs. We find that the so-called “extended emission” feature observed with BAT in some short GRBs is fundamentally the same component as the “internal X-ray plateau” observed in many short GRBs, which is defined as a plateau in the light curve followed by a very rapid decay. Based on how likely a short GRB is to host a magnetar, we characterize the entire Swift short GRB sample into three categories: the “internal plateau” sample, the “external plateau” sample, and the “no plateau” sample. Based on the dipole spin-down model, we derive the physical parameters of the putative magnetars and check whether these parameters are consistent with expectations from the magnetar central engine model. The derived magnetar surface magnetic field {{B}p} and the initial spin period P0 fall into a reasonable range. No GRBs in the internal plateau sample have a total energy exceeding the maximum energy budget of a millisecond magnetar. Assuming that the beginning of the rapid fall phase at the end of the internal plateau is the collapse time of a supra-massive magnetar to a black hole, and applying the measured mass distribution of NS-NS systems in our Galaxy, we constrain the neutron star equation of state (EOS). The data suggest that the NS EOS is close to the GM1 model, which has a maximum non-rotating NS mass of {{M}TOV}˜ 2.37 {{M}⊙ }.

  6. Radio astronomy

    NASA Technical Reports Server (NTRS)

    Kellermann, Kenneth I.; Heeschen, David; Backer, Donald C.; Cohen, Marshall H.; Davis, Michael; Depater, Imke; Deyoung, David; Dulk, George A.; Fisher, J. R.; Goss, W. Miller

    1991-01-01

    The following subject areas are covered: (1) scientific opportunities (millimeter and sub-millimeter wavelength astronomy; meter to hectometer astronomy; the Sun, stars, pulsars, interstellar masers, and extrasolar planets; the planets, asteroids, and comets; radio galaxies, quasars, and cosmology; and challenges for radio astronomy in the 1990's); (2) recommendations for new facilities (the millimeter arrays, medium scale instruments, and small-scale projects); (3) continuing activities and maintenance, upgrading of telescopes and instrumentation; (4) long range programs and technology development; and (5) social, political, and organizational considerations.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    Context. Millisecond pulsars (MSPs) represent nearly half of the more than 160 currently known γ-ray pulsars detected by the Large Area Telescope on the Fermi satellite, and a third of all known MSPs are seen in γ rays. The least energetic γ-ray MSPs enable us to probe the so-called deathline for high-energy emission, i.e., the spin-down luminosity limit under which pulsars (PSRs) cease to produce detectable high-energy radiation. Characterizing the MSP luminosity distribution helps to determine their contribution to the Galactic diffuse γ-ray emission. Aims: Because of the Shklovskii effect, precise proper motion and distance measurements are key ingredients for determining the spin-down luminosities of MSPs accurately. Our aim is to obtain new measurements of these parameters for γ-ray MSPs when possible, and clarify the relationship between the γ-ray luminosity of pulsars and their spin-down luminosity. Detecting low spin-down luminosity pulsars in γ rays and characterizing their spin properties is also particularly interesting for constraining the deathline for high-energy emission. Methods: We made use of the high-quality pulsar timing data recorded at the Nançay Radio Telescope over several years to characterize the properties of a selection of MSPs. For one of the pulsars, the dataset was complemented with Westerbork Synthesis Radio Telescope observations. The rotation ephemerides derived from this analysis were also used to search the LAT data for new γ-ray MSPs. Results: For the MSPs considered in this study, we obtained new transverse proper motion measurements or updated the existing ones, and placed new distance constraints for some of them, with four new timing parallax measurements. We discovered significant GeV γ-ray signals from four MSPs, i.e., PSRs J0740+6620, J0931-1902, J1455-3330, and J1730-2304. The latter is now the least energetic γ-ray pulsar found to date. Despite the improved Ė and Lγ estimates, the relationship between these

  8. The host galaxy of a fast radio burst.

    PubMed

    Keane, E F; Johnston, S; Bhandari, S; Barr, E; Bhat, N D R; Burgay, M; Caleb, M; Flynn, C; Jameson, A; Kramer, M; Petroff, E; Possenti, A; van Straten, W; Bailes, M; Burke-Spolaor, S; Eatough, R P; Stappers, B W; Totani, T; Honma, M; Furusawa, H; Hattori, T; Morokuma, T; Niino, Y; Sugai, H; Terai, T; Tominaga, N; Yamasaki, S; Yasuda, N; Allen, R; Cooke, J; Jencson, J; Kasliwal, M M; Kaplan, D L; Tingay, S J; Williams, A; Wayth, R; Chandra, P; Perrodin, D; Berezina, M; Mickaliger, M; Bassa, C

    2016-02-25

    In recent years, millisecond-duration radio signals originating in distant galaxies appear to have been discovered in the so-called fast radio bursts. These signals are dispersed according to a precise physical law and this dispersion is a key observable quantity, which, in tandem with a redshift measurement, can be used for fundamental physical investigations. Every fast radio burst has a dispersion measurement, but none before now have had a redshift measurement, because of the difficulty in pinpointing their celestial coordinates. Here we report the discovery of a fast radio burst and the identification of a fading radio transient lasting ~6 days after the event, which we use to identify the host galaxy; we measure the galaxy's redshift to be z = 0.492 ± 0.008. The dispersion measure and redshift, in combination, provide a direct measurement of the cosmic density of ionized baryons in the intergalactic medium of ΩIGM = 4.9 ± 1.3 per cent, in agreement with the expectation from the Wilkinson Microwave Anisotropy Probe, and including all of the so-called 'missing baryons'. The ~6-day radio transient is largely consistent with the radio afterglow of a short γ-ray burst, and its existence and timescale do not support progenitor models such as giant pulses from pulsars, and supernovae. This contrasts with the interpretation of another recently discovered fast radio burst, suggesting that there are at least two classes of bursts. PMID:26911781

  9. The host galaxy of a fast radio burst.

    PubMed

    Keane, E F; Johnston, S; Bhandari, S; Barr, E; Bhat, N D R; Burgay, M; Caleb, M; Flynn, C; Jameson, A; Kramer, M; Petroff, E; Possenti, A; van Straten, W; Bailes, M; Burke-Spolaor, S; Eatough, R P; Stappers, B W; Totani, T; Honma, M; Furusawa, H; Hattori, T; Morokuma, T; Niino, Y; Sugai, H; Terai, T; Tominaga, N; Yamasaki, S; Yasuda, N; Allen, R; Cooke, J; Jencson, J; Kasliwal, M M; Kaplan, D L; Tingay, S J; Williams, A; Wayth, R; Chandra, P; Perrodin, D; Berezina, M; Mickaliger, M; Bassa, C

    2016-02-25

    In recent years, millisecond-duration radio signals originating in distant galaxies appear to have been discovered in the so-called fast radio bursts. These signals are dispersed according to a precise physical law and this dispersion is a key observable quantity, which, in tandem with a redshift measurement, can be used for fundamental physical investigations. Every fast radio burst has a dispersion measurement, but none before now have had a redshift measurement, because of the difficulty in pinpointing their celestial coordinates. Here we report the discovery of a fast radio burst and the identification of a fading radio transient lasting ~6 days after the event, which we use to identify the host galaxy; we measure the galaxy's redshift to be z = 0.492 ± 0.008. The dispersion measure and redshift, in combination, provide a direct measurement of the cosmic density of ionized baryons in the intergalactic medium of ΩIGM = 4.9 ± 1.3 per cent, in agreement with the expectation from the Wilkinson Microwave Anisotropy Probe, and including all of the so-called 'missing baryons'. The ~6-day radio transient is largely consistent with the radio afterglow of a short γ-ray burst, and its existence and timescale do not support progenitor models such as giant pulses from pulsars, and supernovae. This contrasts with the interpretation of another recently discovered fast radio burst, suggesting that there are at least two classes of bursts.

  10. FAST RADIO BURSTS AND RADIO TRANSIENTS FROM BLACK HOLE BATTERIES

    SciTech Connect

    Mingarelli, Chiara M. F.; Levin, Janna; Lazio, T. Joseph W.

    2015-12-01

    Most black holes (BHs) will absorb a neutron star (NS) companion fully intact without tidal disruption, suggesting the pair will remain dark to telescopes. Even without tidal disruption, electromagnetic (EM) luminosity is generated from the battery phase of the binary when the BH interacts with the NS magnetic field. Originally, the luminosity was expected to be in high-energy X-rays or gamma-rays, however, we conjecture that some of the battery power is emitted in the radio bandwidth. While the luminosity and timescale are suggestive of fast radio bursts (FRBs; millisecond-scale radio transients) NS–BH coalescence rates are too low to make these a primary FRB source. Instead, we propose that the transients form a FRB sub-population, distinguishable by a double peak with a precursor. The rapid ramp-up in luminosity manifests as a precursor to the burst which is 20%–80% as luminous given 0.5 ms timing resolution. The main burst arises from the peak luminosity before the merger. The post-merger burst follows from the NS magnetic field migration to the BH, causing a shock. NS–BH pairs are especially desirable for ground-based gravitational wave (GW) observatories since the pair might not otherwise be detected, with EM counterparts greatly augmenting the scientific leverage beyond the GW signal. The EM signal’s ability to break degeneracies in the parameters encoded in the GW and probe the NS magnetic field strength is quite valuable, yielding insights into open problems in NS magnetic field decay.

  11. Fast Radio Bursts and Radio Transients from Black Hole Batteries

    NASA Astrophysics Data System (ADS)

    Mingarelli, Chiara M. F.; Levin, Janna; Lazio, T. Joseph W.

    2015-12-01

    Most black holes (BHs) will absorb a neutron star (NS) companion fully intact without tidal disruption, suggesting the pair will remain dark to telescopes. Even without tidal disruption, electromagnetic (EM) luminosity is generated from the battery phase of the binary when the BH interacts with the NS magnetic field. Originally, the luminosity was expected to be in high-energy X-rays or gamma-rays, however, we conjecture that some of the battery power is emitted in the radio bandwidth. While the luminosity and timescale are suggestive of fast radio bursts (FRBs; millisecond-scale radio transients) NS–BH coalescence rates are too low to make these a primary FRB source. Instead, we propose that the transients form a FRB sub-population, distinguishable by a double peak with a precursor. The rapid ramp-up in luminosity manifests as a precursor to the burst which is 20%–80% as luminous given 0.5 ms timing resolution. The main burst arises from the peak luminosity before the merger. The post-merger burst follows from the NS magnetic field migration to the BH, causing a shock. NS–BH pairs are especially desirable for ground-based gravitational wave (GW) observatories since the pair might not otherwise be detected, with EM counterparts greatly augmenting the scientific leverage beyond the GW signal. The EM signal’s ability to break degeneracies in the parameters encoded in the GW and probe the NS magnetic field strength is quite valuable, yielding insights into open problems in NS magnetic field decay.

  12. THE NEAREST MILLISECOND PULSAR REVISITED WITH XMM-NEWTON: IMPROVED MASS-RADIUS CONSTRAINTS FOR PSR J0437-4715

    SciTech Connect

    Bogdanov, Slavko

    2013-01-10

    I present an analysis of the deepest X-ray exposure of a radio millisecond pulsar (MSP) to date, an X-ray Multi Mirror-Newton European Photon Imaging Camera spectroscopic and timing observation of the nearest known MSP, PSR J0437-4715. The timing data clearly reveal a secondary broad X-ray pulse offset from the main pulse by {approx}0.55 in rotational phase. In the context of a model of surface thermal emission from the hot polar caps of the neutron star, this can be plausibly explained by a magnetic dipole field that is significantly displaced from the stellar center. Such an offset, if commonplace in MSPs, has important implications for studies of the pulsar population, high energy pulsed emission, and the pulsar contribution to cosmic-ray positrons. The continuum emission shows evidence for at least three thermal components, with the hottest radiation most likely originating from the hot magnetic polar caps and the cooler emission from the bulk of the surface. I present pulse phase-resolved X-ray spectroscopy of PSR J0437-4715, which for the first time properly accounts for the system geometry of a radio pulsar. Such an approach is essential for unbiased measurements of the temperatures and emission areas of polar cap radiation from pulsars. Detailed modeling of the thermal pulses, including relativistic and atmospheric effects, provides a constraint on the redshift-corrected neutron star radius of R > 11.1 km (at 3{sigma} conf.) for the current radio timing mass measurement of 1.76 M {sub Sun }. This limit favors 'stiff' equations of state.

  13. Disentangling sub-millisecond processes within an auditory transduction chain.

    PubMed

    Gollisch, Tim; Herz, Andreas M V

    2005-01-01

    Every sensation begins with the conversion of a sensory stimulus into the response of a receptor neuron. Typically, this involves a sequence of multiple biophysical processes that cannot all be monitored directly. In this work, we present an approach that is based on analyzing different stimuli that cause the same final output, here defined as the probability of the receptor neuron to fire a single action potential. Comparing such iso-response stimuli within the framework of nonlinear cascade models allows us to extract the characteristics of individual signal-processing steps with a temporal resolution much finer than the trial-to-trial variability of the measured output spike times. Applied to insect auditory receptor cells, the technique reveals the sub-millisecond dynamics of the eardrum vibration and of the electrical potential and yields a quantitative four-step cascade model. The model accounts for the tuning properties of this class of neurons and explains their high temporal resolution under natural stimulation. Owing to its simplicity and generality, the presented method is readily applicable to other nonlinear cascades and a large variety of signal-processing systems.

  14. Registration of neutrons within 2 milliseconds after EAS impact

    NASA Astrophysics Data System (ADS)

    Jȩdrzejczak, K.; Karczmarczyk, J.; Kasztelan, M.; Petrochenkov, S. A.; Polański, A.; Swarzyński, J.; Szabelski, J.; Wibig, T.

    2006-01-01

    We register an excess of signals from neutron detectors within a few milliseconds after passage of EAS front in Lodz EAS array. The most probable explanation is that neutrons are produced in EAS hadron interactions with lead block of muon detector. These neutrons diffuse and are thermalized before the detection in the Geiger-Müller counters, the boron counter and other detectors registering time structure of the impulses (10 MHz FADC, 8-bit converters, 32 kB memory). We performed computer simulations of neutron diffusion in the vicinity of the array. We used MCNP program and introduced the detailed geometry of the array and its surroundings. Simulated neutrons started their diffusion in the lead block or in the ground near the detector. The obtained time distributions of slow neutrons are consistent with the registrations in the boron counter. The only problem is the requirement of a great number of neutrons produced at the shower arrival. This "new EAS observable" can be used as inexpensive hadron detector in EAS.

  15. Millisecond-Scale Biochemical Response to Change in Strain

    PubMed Central

    Bickham, Dale C.; West, Timothy G.; Webb, Martin R.; Woledge, Roger C.; Curtin, Nancy A.; Ferenczi, Michael A.

    2011-01-01

    Muscle fiber contraction involves the cyclical interaction of myosin cross-bridges with actin filaments, linked to hydrolysis of ATP that provides the required energy. We show here the relationship between cross-bridge states, force generation, and Pi release during ramp stretches of active mammalian skeletal muscle fibers at 20°C. The results show that force and Pi release respond quickly to the application of stretch: force rises rapidly, whereas the rate of Pi release decreases abruptly and remains low for the duration of the stretch. These measurements show that biochemical change on the millisecond timescale accompanies the mechanical and structural responses in active muscle fibers. A cross-bridge model is used to simulate the effect of stretch on the distribution of actomyosin cross-bridges, force, and Pi release, with explicit inclusion of ATP, ADP, and Pi in the biochemical states and length-dependence of transitions. In the simulation, stretch causes rapid detachment and reattachment of cross-bridges without release of Pi or ATP hydrolysis. PMID:22098743

  16. Electron-cyclotron maser and solar microwave millisecond spike emission

    NASA Technical Reports Server (NTRS)

    Li, Hong-Wei; Li, Chun-Sheng; Fu, Qi-Jun

    1986-01-01

    An intense solar microwave millisecond spike emission (SMMSE) event was observed on May 16, 1981 by Zhao and Jin at Beijing Observatory. The peak flux density of the spikes is high to 5 x 100,000 s.f.u. and the corresponding brightness temperature (BT) reaches approx. 10 to the 15th K. In order to explain the observed properties of SMMSE, it is proposed that a beam of electrons with energy of tens KeV injected from the acceleration region downwards into an emerging magnetic arch forms so-called hollow beam distribution and causes electron-cyclotron maser (ECM) instability. The growth rate of second harmonic X-mode is calculated and its change with time is deduced. It is shown that the saturation time of ECM is t sub s approx. equals 0.42 ms and only at last short stage (delta t less than 0.2 t sub s) the growth rate decreases to zero rather rapidly. So a SMMSE with very high BT will be produced if the ratio of number density of nonthermal electrons to that of background electrons, n sub s/n sub e, is larger than 4 x .00001.

  17. Mediating millisecond reaction time around particles and cells.

    PubMed

    Dudani, Jaideep S; Go, Derek E; Gossett, Daniel R; Tan, Andrew P; Di Carlo, Dino

    2014-02-01

    Precise spatiotemporal control of how particles and cells interact with reagents is critical for numerous laboratory and industrial processes. Novel tools for exerting this control at shorter time scales will enable development of new chemical processes and biomedical assays. Previously, we have developed a generalized approach to manipulate cells and particles across fluid streams termed rapid inertial solution exchange (RInSE), which utilizes inertial lift forces at finite Reynolds number and high Peclet number to transfer particles from an initial solution to another within a millisecond. Here, we apply these principles toward developing a continuous flow microfluidic platform that enables transient chemical treatments of cells and particles (on the order of 1 ms). We also demonstrate how the reactant stream can be employed as a diffusion barrier, preventing adverse reactions between coflowing solutions. In order to demonstrate the utility of the method, we applied it to various operations in molecular biology and automated cell staining including cell permeabilization, fluorescent staining, and molecular delivery to viable cells. We expect this method will enable previously unexplored studies of the dynamics of molecular events, improve uniformity of reactions carried on the surface of beads, and increase uniformity in cell-based assays through automation.

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

    NASA Astrophysics Data System (ADS)

    Melatos, A.; Mastrano, A.

    2016-02-01

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

  19. SEARCHES FOR MILLISECOND PULSAR CANDIDATES AMONG THE UNIDENTIFIED FERMI OBJECTS

    SciTech Connect

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

    2015-08-10

    Here we report the results of searching millisecond pulsar (MSP) candidates from the Fermi LAT second source catalog (2FGL). Seven unassociated γ-ray sources in this catalog are identified as promising MSP candidates based on their γ-ray properties. Through the X-ray analysis, we have detected possible X-ray counterparts, localized to an arcsecond accuracy. We have systematically estimated their X-ray fluxes and compared them with the corresponding γ-ray fluxes. The X-ray to γ-ray flux ratios for 2FGL J1653.6-0159 and 2FGL J1946.4-5402 are comparable with the typical value for pulsars. For 2FGL J1625.2-0020, 2FGL J1653.6-0159, and 2FGL J1946.4-5402, their candidate X-ray counterparts are bright enough to perform a detailed spectral and temporal analysis to discriminate their thermal/non-thermal nature and search for the periodic signal. We have also searched for possible optical/IR counterparts at the X-ray positions. For the optical/IR source coincident with the brightest X-ray object associated with 2FGL J1120.0-2204, its spectral energy distribution is comparable with a late-type star. Evidence for the variability has also been found by examining its optical light curve. All the aforementioned 2FGL sources resemble a pulsar in one or more aspects, making them promising targets for follow-up investigations.

  20. Durability of the accretion disk of millisecond pulsars.

    PubMed

    Michel, F C; Dessler, A J

    1985-05-24

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

  1. Independent Population Coding of Speech with Sub-Millisecond Precision

    PubMed Central

    Garcia-Lazaro, Jose A.; Belliveau, Lucile A. C.

    2013-01-01

    To understand the strategies used by the brain to analyze complex environments, we must first characterize how the features of sensory stimuli are encoded in the spiking of neuronal populations. Characterizing a population code requires identifying the temporal precision of spiking and the extent to which spiking is correlated, both between cells and over time. In this study, we characterize the population code for speech in the gerbil inferior colliculus (IC), the hub of the auditory system where inputs from parallel brainstem pathways are integrated for transmission to the cortex. We find that IC spike trains can carry information about speech with sub-millisecond precision, and, consequently, that the temporal correlations imposed by refractoriness can play a significant role in shaping spike patterns. We also find that, in contrast to most other brain areas, the noise correlations between IC cells are extremely weak, indicating that spiking in the population is conditionally independent. These results demonstrate that the problem of understanding the population coding of speech can be reduced to the problem of understanding the stimulus-driven spiking of individual cells, suggesting that a comprehensive model of the subcortical processing of speech may be attainable in the near future. PMID:24305831

  2. DNA/Fusogenic Lipid Nanocarrier Assembly: Millisecond Structural Dynamics.

    PubMed

    Angelov, Borislav; Angelova, Angelina; Filippov, Sergey K; Narayanan, Theyencheri; Drechsler, Markus; Štěpánek, Petr; Couvreur, Patrick; Lesieur, Sylviane

    2013-06-01

    Structural changes occurring on a millisecond time scale during uptake of DNA by cationic lipid nanocarriers are monitored by time-resolved small-angle X-ray scattering (SAXS) coupled to a rapid-mixing stopped-flow technique. Nanoparticles (NPs) of nanochannel organization are formed by PEGylation, hydration, and dispersion of a lipid film of the fusogenic lipid monoolein in a mixture with positively charged (DOMA) and PEGylated (DOPE-PEG2000) amphiphiles and are characterized by the inner cubic structure of very large nanochannels favorable for DNA upload. Ultrafast structural dynamics of complexation and assembly of these cubosome particles with neurotrophic plasmid DNA (pDNA) is revealed thanks to the high brightness of the employed synchrotron X-ray beam. The rate constant of the pDNA/lipid NP complexation is estimated from dynamic roentgenograms recorded at 4 ms time resolution. pDNA upload into the vastly hydrated channels of the cubosome carriers leads to a fast nanoparticle-nanoparticle structural transition and lipoplex formation involving tightly packed pDNA. PMID:26283134

  3. Oscillations millisecondes des binaires X : La révolution de RXTE

    NASA Astrophysics Data System (ADS)

    Olive, Jean-Francois

    2001-01-01

    In this lecture for the ``23ieme Ecole CNRS de Goutelas'' on binary systems, I review the RXTE observations of new neutron- star phenomena, namely the coherent pulsations from the first accreting millisecond pulsar, the coherent oscillations during X-ray bursts and kiloHertz quasi-periodic oscillations. I describe the ways in which study these millisecond phenomena could help to distinguish between models of dense matter and advance our understanding of general relativity in strong gravitational fields.

  4. ASSESSING THE ROLE OF SPIN NOISE IN THE PRECISION TIMING OF MILLISECOND PULSARS

    SciTech Connect

    Shannon, Ryan M.; Cordes, James M. E-mail: cordes@astro.cornell.ed

    2010-12-20

    We investigate rotational spin noise (referred to as timing noise) in non-accreting pulsars: millisecond pulsars, canonical pulsars, and magnetars. Particular attention is placed on quantifying the strength and non-stationarity of timing noise in millisecond pulsars because the long-term stability of these objects is required to detect nanohertz gravitational radiation. We show that a single scaling law is sufficient to characterize timing noise in millisecond and canonical pulsars while the same scaling law underestimates the levels of timing noise in magnetars. The scaling law, along with a detailed study of the millisecond pulsar B1937+21, leads us to conclude that timing noise is latent in most millisecond pulsars and will be measurable in many objects when better arrival time estimates are obtained over long data spans. The sensitivity of a pulsar timing array to gravitational radiation is strongly affected by any timing noise. We conclude that detection of proposed gravitational wave backgrounds will require the analysis of more objects than previously suggested over data spans that depend on the spectra of both the gravitational wave background and of the timing noise. It is imperative to find additional millisecond pulsars in current and future surveys in order to reduce the effects of timing noise.

  5. Shortwave Radio: A Tool for Integrating the Curriculum.

    ERIC Educational Resources Information Center

    King, Irvin L.

    Because of their geographical isolation from major population centers, many of the islands of Micronesia are without live television or daily newspapers. However, the skies of the Pacific are alive with radio broadcasts that can be received with shortwave radios. This presentation explains the nature of shortwave radio and describes how teachers…

  6. Fast Radio Bursts: The Search for Their Origins

    NASA Astrophysics Data System (ADS)

    Burke Spolaor, Sarah

    2015-08-01

    Fast Radio Bursts (FRBs) are millisecond-duration radio signals whose swept-frequency signals indicate a non-local origin.FRB science has been building rapidly since the first discovery of an FRB in 2007; proof of an FRB population in 2013 (Thornton et al.) was quickly followed by further evidence of their likely, although not yet definite, extragalactic origin (e.g. Kulkarni et al. 2014, Burke-Spolaor & Bannister 2014). Until recently, only circumstantial evidence allowed statements on what progenitors FRBs might arise from, and whether they are local, Galactic, or extragalactic. However, we are now able to detect FRB events in real-time, and have the capability to detect FRBs with radio interferometers. This has opened up the possibility to understand their origins through arcsecond localization and the identification of multi-wavelength counterparts. I will describe what we currently know about FRBs, and the status of the FRB hunt for their enigmatic origins.

  7. The Radio JOVE Project - Shoestring Radio Astronomy

    NASA Technical Reports Server (NTRS)

    Thieman, J.; Flagg, R.; Greenman, W.; Higgins, C.; Reyes, F.; Sky, J.

    2010-01-01

    Radio JOVE is an education and outreach project intended to give students and other interested individuals hands-on experience in learning radio astronomy. They can do this through building a radio telescope from a relatively inexpensive kit that includes the parts for a receiver and an antenna as well as software for a computer chart recorder emulator (Radio Skypipe) and other reference materials

  8. Space Telecommunications Radio System STRS Cognitive Radio

    NASA Technical Reports Server (NTRS)

    Briones, Janette C.; Handler, Louis M.

    2013-01-01

    Radios today are evolving from awareness toward cognition. A software defined radio (SDR) provides the most capability for integrating autonomic decision making ability and allows the incremental evolution toward a cognitive radio. This cognitive radio technology will impact NASA space communications in areas such as spectrum utilization, interoperability, network operations, and radio resource management over a wide range of operating conditions. NASAs cognitive radio will build upon the infrastructure being developed by Space Telecommunication Radio System (STRS) SDR technology. This paper explores the feasibility of inserting cognitive capabilities in the NASA STRS architecture and the interfaces between the cognitive engine and the STRS radio. The STRS architecture defines methods that can inform the cognitive engine about the radio environment so that the cognitive engine can learn autonomously from experience, and take appropriate actions to adapt the radio operating characteristics and optimize performance.

  9. Fast Radio Bursts and Their Gamma-Ray or Radio Afterglows as Kerr-Newman Black Hole Binaries

    NASA Astrophysics Data System (ADS)

    Liu, Tong; Romero, Gustavo E.; Liu, Mo-Lin; Li, Ang

    2016-07-01

    Fast radio bursts (FRBs) are radio transients lasting only about a few milliseconds. They seem to occur at cosmological distances. We propose that these events can originate in the collapse of the magnetospheres of Kerr-Newman black holes (KNBHs). We show that the closed orbits of charged particles in the magnetospheres of these objects are unstable. After examining the dependencies on the specific charge of the particle and the spin and charge of the KNBH, we conclude that the resulting timescale and radiation mechanism fit well with extant observations of FRBs. Furthermore, we argue that the merger of a KNBH binary is a plausible central engine for the potential gamma-ray or radio afterglow following certain FRBs and can also account for gravitational wave (GW) events like GW 150914. Our model leads to predictions that can be tested by combined multi-wavelength electromagnetic and GW observations.

  10. Fast Radio Bursts and Their Gamma-Ray or Radio Afterglows as Kerr–Newman Black Hole Binaries

    NASA Astrophysics Data System (ADS)

    Liu, Tong; Romero, Gustavo E.; Liu, Mo-Lin; Li, Ang

    2016-07-01

    Fast radio bursts (FRBs) are radio transients lasting only about a few milliseconds. They seem to occur at cosmological distances. We propose that these events can originate in the collapse of the magnetospheres of Kerr–Newman black holes (KNBHs). We show that the closed orbits of charged particles in the magnetospheres of these objects are unstable. After examining the dependencies on the specific charge of the particle and the spin and charge of the KNBH, we conclude that the resulting timescale and radiation mechanism fit well with extant observations of FRBs. Furthermore, we argue that the merger of a KNBH binary is a plausible central engine for the potential gamma-ray or radio afterglow following certain FRBs and can also account for gravitational wave (GW) events like GW 150914. Our model leads to predictions that can be tested by combined multi-wavelength electromagnetic and GW observations.

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

    NASA Astrophysics Data System (ADS)

    Bogdanov, Slavko

    2016-07-01

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

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

    NASA Astrophysics Data System (ADS)

    Bogdanov, Slavko

    2016-07-01

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

  13. RADIO ALTIMETERS

    DOEpatents

    Bogle, R.W.

    1960-11-22

    A radio ranging device is described which utilizes a superregenerative oscillator having alternate sending and receiving phases with an intervening ranging interval between said phases, means for varying said ranging interval, means responsive to an on-range noise reduction condition for stopping said means for varying the ranging interval and indicating means coupled to the ranging interval varying means and calibrated in accordance with one-half the product of the ranging interval times the velocity of light whereby the range is indicated.

  14. Discovery of a 1.69 ms radio pulsar associated with the X-ray binary XSS J12270-4859

    NASA Astrophysics Data System (ADS)

    Ray, Paul S.; Roy, Jayanta; Bhattacharyya, Bhaswati; Stappers, Benjamin; Chengalur, Jayaram N.; Deneva, Julia S.; Camilo, Fernando M.

    2015-01-01

    XSS J12270-4859 is an X-ray binary associated with the Fermi LAT gamma-ray source 1FGL J1227.9-4852 (Hill et al. 2011). In 2012 December, the source underwent a transition where the X-ray and optical luminosity dropped suddenly and spectral signatures of an accretion disk disappeared (Bassa et al. 2014). We report the discovery of a 1.69 millisecond pulsar using the Giant Metrewave Radio Telescope at 607 MHz associated with this source, confirming that system is now an active radio millisecond pulsar. We report on radio timing observations of the source with the GMRT and Parkes Telescope that allow precise determination of the orbital parameters of the system. In addition, using simultaneous radio imaging and timing observations with the GMRT, we are able to study the eclipse behavior.

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

    SciTech Connect

    Arzoumanian, Zaven; Brazier, Adam; Chatterjee, Shami; Cordes, James M.; Dolch, Timothy; Burke-Spolaor, Sarah; Demorest, Paul B.; Chamberlin, Sydney; Christy, Brian; Cornish, Neil; Crowter, Kathryn; Fonseca, Emmanuel; Gonzalez, Marjorie E.; Ellis, Justin A.; Ferdman, Robert D.; Kaspi, Victoria M.; Garver-Daniels, Nathan; Jones, Megan L.; Jenet, Fredrick A.; Jones, Glenn; Collaboration: NANOGrav Collaboration; and others

    2015-11-01

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

  16. Multi-wavelength emissions from the millisecond pulsar binary PSR J1023+0038 during an accretion active state

    SciTech Connect

    Takata, J.; Leung, Gene C. K.; Wu, E. M. H.; Cheng, K. S.; Li, K. L.; Kong, A. K. H.; Tam, P. H. T.; Hui, C. Y.; Xing, Yi; Wang, Zhongxiang; Cao, Yi; Tang, Sumin E-mail: akong@phys.nthu.edu.tw

    2014-04-20

    Recent observations strongly suggest that the millisecond pulsar binary PSR J1023+0038 has developed an accretion disk since 2013 June. We present a multi-wavelength analysis of PSR J1023+0038, which reveals that (1) its gamma-rays suddenly brightened within a few days in 2013 June/July and has remained at a high gamma-ray state for several months; (2) both UV and X-ray fluxes have increased by roughly an order of magnitude; and (3) the spectral energy distribution has changed significantly after the gamma-ray sudden flux change. Time variabilities associated with UV and X-rays are on the order of 100-500 s and 50-100 s, respectively. Our model suggests that a newly formed accretion disk, due to the sudden increase of the stellar wind, could explain the changes of all these observed features. The increase of UV is emitted from the disk, and a new component in gamma-rays is produced by inverse Compton scattering between the new UV component and pulsar wind. The increase of X-rays results from the enhancement of injection pulsar wind energy into the intra-binary shock due to the increase of the stellar wind. We also predict that the radio pulses may be blocked by the evaporated winds from the disk, and the pulsar is still powered by rotation.

  17. Optical counterparts of two Fermi millisecond pulsars: PSR J1301+0833 and PSR J1628–3205

    SciTech Connect

    Li, Miao; Halpern, Jules P.; Thorstensen, John R.

    2014-11-10

    Using the 1.3 m and 2.4 m Telescopes of the MDM Observatory, we identified the close companions of two eclipsing millisecond radio pulsars that were discovered by the Green Bank Telescope in searches of Fermi Gamma-ray Space Telescope sources, and measured their light curves. PSR J1301+0833 is a black widow pulsar in a 6.5 hr orbit whose companion star is strongly heated on the side facing the pulsar. It varies from R = 21.8 to R > 24 around the orbit. PSR J1628–3205 is a 'redback', a nearly Roche-lobe-filling system in a 5.0 hr orbit whose optical modulation in the range 19.0 < R < 19.4 is dominated by strong ellipsoidal variations, indicating a large orbital inclination angle. PSR J1628–3205 also shows evidence for a long-term variation of about 0.2 mag, and an asymmetric temperature distribution possibly due to either off-center heating by the pulsar wind, or large starspots. Modeling of its light curve restricts the inclination angle to i > 55°, the mass of the companion to 0.16 < M{sub c} < 0.30 M {sub ☉}, and the effective temperature to 3560 < T {sub eff} < 4670 K. As is the case for several redbacks, the companion of PSR J1628–3205 is less dense and hotter than a main-sequence star of the same mass.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  19. The End of Accretion: The X-Ray Binary/Millisecond Pulsar Transition Object PSR J1023+0038

    NASA Astrophysics Data System (ADS)

    Archibald, Anne

    2015-04-01

    Millisecond radio pulsars (MSRPs), those spinning hundreds of times per second, have long been understood to be old pulsars that have been spun up by the accretion of matter from a companion in a low-mass X-ray binary (LMXB) phase. Yet the details of this transformation, particularly the end of the accretion process and the birth of a radio pulsar, remain mysterious. I will describe the discovery and detailed study of the first object known to transition between MSRP and LMXB states, PSR J1023+0038. By dint of a multiwavelength campaign of observations in the RMSP state, we are able to measure all the key system parameters and show the existence of an X-ray shock close to the pulsar-facing side of the companion. Since the discovery of PSR J1023+0038, two more objects (XSS J12270-4859 and M28I) have been found to make the same transition, and the study of these transitioning objects has become an active field of research. Most interestingly, PSR J1023+0038 has transitioned back into an LMXB state, with an active accretion disk and a puzzling increase in gamma-ray flux. Our detailed picture of the system allows us to test models of accretion against the phenomena we observe in PSR J1023+0038, and in fact these observations challenge current models: in spite of the low luminosity of the system (and low inferred accretion rate) some material is penetrating the centrifugal barrier and falling on the neutron-star surface. Key evidence for explaining this puzzling behaviour will come when PSR J1023+0038 returns to an MSRP state and we are able to compare pulsar timing models from after the LMXB state with those we obtained in this work.

  20. Exploring the Progenitors of Fast Radio Bursts

    NASA Astrophysics Data System (ADS)

    Burke-Spolaor, Sarah; Kramer, Michael; Bhat, Ramesh; Kulkarni, S. R.; Keller, Stefan; Champion, David; Flynn, Chris; Kasliwal, Mansi

    2014-10-01

    Fast Radio Bursts (FRBs) are millisecond bursts that are broadly evidenced to arise from extragalactic, but yet unknown, progenitors. They have presented a true mystery in that so far no progenitor theory can adequately account for their observed properties. We request observations that will glean basic information on FRB progenitors. Our observations will execute a specific test of whether FRBs originate in nearby galaxies. We have also designed our target field and time request to enable a thorough exploration of optical counterparts before, during, and after any detected FRB episode. Additionally, with a number depending on the typical distance to FRBs, our observations will raise the running list of total FRB discoveries by 10-60%.

  1. Multi-Timescale Radio Observations of Multi-Wavelength GRBs

    NASA Astrophysics Data System (ADS)

    Van der Horst, Alexander

    2016-07-01

    Gamma-ray bursts are a broadband phenomenon, with emission detected across the electromagnetic spectrum from low-frequency radio waves to high-energy gamma-rays. Besides this extremely broad spectral range, they are also observed over a very large range of timescales, from millisecond variability in gamma-rays to the afterglows at radio frequencies that can sometimes be observed for years after the initial gamma-ray trigger. Our current understanding of gamma-ray bursts is based on these multi-frequency and multi-timescale observations. In this talk I will show the role that radio observations have played and will play in putting together a broadband picture of the physics behind the observed emission, the progenitors, and their environment. I will highlight some recent discoveries and developments, in particular the searches for early radio emission within the first minutes after gamma-ray triggers; the increasing number of radio-detected, optically dark bursts; and the possibilities that several new and upgraded radio observatories offer to obtain a better understanding of the macro- and microphysics behind these enigmatic phenomena.

  2. Radio Jove: Jupiter Radio Astronomy for Citizens

    NASA Astrophysics Data System (ADS)

    Higgins, Charles; Thieman, J. R.; Flagg, R.; Reyes, F. J.; Sky, J.; Greenman, W.; Brown, J.; Typinski, D.; Ashcraft, T.; Mount, A.

    2014-01-01

    Radio JOVE is a hands-on educational activity that brings the radio sounds of the Sun, Jupiter, the Milky Way Galaxy, and terrestrial radio noise to students, teachers, and the general public. Participants may build a simple radio telescope kit, make scientific observations, and interact with professional radio observatories in real-time over the Internet. Our website (http://radiojove.gsfc.nasa.gov) includes science information, construction manuals, observing guides, and education resources for teachers and students. Radio Jove is continually expanding its participants with over 1800 kits sold to more than 70 countries worldwide. Recently some of our most dedicated observers have upgraded their Radio Jove antennas to semi-professional observatories. We have spectrographs and wide band antennas, some with 8 MHz bandwidth and some with dual polarization capabilities. In an effort to add to the science literature, these observers are coordinating their efforts to pursue some basic questions about Jupiter’s radio emissions (radio source locations, spectral structure, long term changes, etc.). We can compare signal and ionosphere variations using the many Radio Jove observers at different locations. Observers are also working with members of the Long Wavelength Array Station 1 (LWA1) radio telescope to coordinate observations of Jupiter; Radio Jove is planning to make coordinated observations while the Juno Mission is active beginning in 2015. The Radio Jove program is overviewed, its hardware and software are highlighted, recent sample observations are shown, and we demonstrate that we are capable of real citizen science.

  3. Learning radio astronomy by doing radio astronomy

    NASA Astrophysics Data System (ADS)

    Vaquerizo Gallego, J. A.

    2011-11-01

    PARTNeR (Proyecto Académico con el Radio Telescopio de NASA en Robledo, Academic Project with the NASA Radio Telescope at Robledo) is an educational program that allows high school and undergraduate students to control a 34 meter radio telescope and conduct radio astronomical observations via the internet. High-school teachers who join the project take a course to learn about the science of radio astronomy and how to use the antenna as an educational resource. Also, teachers are provided with learning activities they can do with their students and focused on the classroom implementation of the project within an interdisciplinary framework. PARTNeR provides students with firsthand experience in radio astronomy science. Thus, remote radio astronomical observations allow students to learn with a first rate scientific equipment the basics of radio astronomy research, aiming to arouse scientific careers and positive attitudes toward science. In this contribution we show the current observational programs and some recent results.

  4. DETECTION AND FLUX DENSITY MEASUREMENTS OF THE MILLISECOND PULSAR J2145–0750 BELOW 100 MHz

    SciTech Connect

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

    2013-09-20

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

  5. Millisecond temporal structure in Cyg X-1. [including X ray variability

    NASA Technical Reports Server (NTRS)

    Rothschild, R. E.; Boldt, E. A.; Holt, S. S.; Serlemitsos, P. J.

    1973-01-01

    Evidence is presented for the X-ray variability of Cyg X-1 on time scales down to a millisecond. Several bursts of millisecond duration are observed. The duty cycle for bursting is estimated to be approximately greater than. 0002 averaged over the entire 49. second exposure, although the maximum burst activity is associated with a region of enhanced emission lasting about 1/3 second. Such bursts may be associated with turbulence in disk accretion at the innermost orbits for a black hole.

  6. A SEARCH FOR RAPIDLY SPINNING PULSARS AND FAST TRANSIENTS IN UNIDENTIFIED RADIO SOURCES WITH THE NRAO 43 METER TELESCOPE

    SciTech Connect

    Schmidt, Deborah; Crawford, Fronefield; Gilpin, Claire; Langston, Glen

    2013-04-15

    We have searched 75 unidentified radio sources selected from the NRAO VLA Sky Survey catalog for the presence of rapidly spinning pulsars and short, dispersed radio bursts. The sources are radio bright, have no identifications or optical source coincidences, are more than 5% linearly polarized, and are spatially unresolved in the catalog. If these sources are fast-spinning pulsars (e.g., sub-millisecond pulsars), previous large-scale pulsar surveys may have missed detection due to instrumental and computational limitations, eclipsing effects, or diffractive scintillation. The discovery of a sub-millisecond pulsar would significantly constrain the neutron star equation of state and would have implications for models predicting a rapid slowdown of highly recycled X-ray pulsars to millisecond periods from, e.g., accretion disk decoupling. These same sources were previously searched unsuccessfully for pulsations at 610 MHz with the Lovell Telescope at Jodrell Bank. This new search was conducted at a different epoch with a new 800 MHz backend on the NRAO 43 m Telescope at a center frequency of 1200 MHz. Our search was sensitive to sub-millisecond pulsars in highly accelerated binary systems and to short transient pulses. No periodic or transient signals were detected from any of the target sources. We conclude that diffractive scintillation, dispersive smearing, and binary acceleration are unlikely to have prevented detection of the large majority of the sources if they are pulsars, though we cannot rule out eclipsing, nulling or intermittent emission, or radio interference as possible factors for some non-detections. Other (speculative) possibilities for what these sources might include radio-emitting magnetic cataclysmic variables or older pulsars with aligned magnetic and spin axes.

  7. A search for millisecond pulsars at high galactic latitude

    NASA Astrophysics Data System (ADS)

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

    2002-05-01

    We are conducting a search for radio pulsars using the Parkes 64 m telescope, covering the galactic latitude range 15o < | b | < 25o from l=260o to l=50o. Each pointing is observed for 265 s with the 13-beam multibeam system at a frequency of 1374 MHz. The signal from each beam is processed by a 2 x 96 channel filterbank sampled every 125 μ s, with a bandwidth of 288 MHz. These observing parameters afford rapid sky coverage and good sensitivity to pulsars with periods as short as ~1 ms, whose existence would constrain the neutron star equation of state. Data are analyzed offline using the workstation cluster at the Swinburne Centre for Astrophysics and Supercomputing. Analysis of ~2200 square degrees of the survey has been completed, yielding twenty new pulsars including four binary recycled pulsars. Three of these objects have great potential for ultra high precision timing experiments, and one has an unusual massive white dwarf companion. We present the current status of survey observations and analysis as well as follow-up observations of the newly discovered pulsars.

  8. Radio pulsar disk electrodynamics

    SciTech Connect

    Michel, F.C.

    1983-03-01

    We outline the macroscopic physics of a disk close to an isolated, magnetized, rotating neutron star. It seems likely that such systems are formed from time to time in the universe. The neutron star acts as a Faraday disk dynamo, and the disk acts as both a load and a neutral sheet, permitting the polar cap current to return to the neutron star and also splitting a dipolar magnetic field into two monopolar halves. Michel and Dessler have proposed that such systems are radio pulsars. The dominant energy loss is from the stellar wind torque (giving a deceleration index n = 7/3), and the next contribution is dissipation in the ''auroral'' zones, where the current returns to the star in a sheet about 5 cm thick. The latter is comparable to the observed radio luminosities and is in reasonable accord with the data. The disk itself may be a source of visible radiation comparable to that in pulsed radiofrequency emission. As the pulsar ages, the disk expands and narrows into a ring, the plausible consequence of which could be cessation of pulsed emission at periods of a few seconds.

  9. Neutron stars and millisecond pulsars from accretion-induced collapse in globular clusters

    NASA Technical Reports Server (NTRS)

    Bailyn, Charles D.; Grindlay, Jonathan E.

    1990-01-01

    This paper examines the limits on the number of millisecond pulsars which could be formed in globular clusters by the generally accepted scenario (in which a neutron star is created by the supernova of an initially massive star and subsequently captures a companion to form a low-mass X-ray binary which eventually becomes a millisecond pulsar). It is found that, while the number of observed low-mass X-ray binaries can be adequately explained in this way, the reasonable assumption that the pulsar luminosity function in clusters extends below the current observational limits down to the luminosity of the faintest millisecond pulsars in the field suggests a cluster population of millisecond pulsars which is substantially larger than the standard model can produce. Alleviating this problem by postulating much shorter lifetimes for the X-ray binaries requires massive star populations sufficiently large that the mass loss resulting from their evolution would be likely to unbind the cluster. It is argued that neutron star formation in globular clusters by accretion-induced collapse of white dwarfs may resolve the discrepancy in birthrates.

  10. Extremely rapid radio spikes in flares: A review

    NASA Technical Reports Server (NTRS)

    Benz, A. O.

    1986-01-01

    Radio spikes of a few to tens of milliseconds of the solar radio emission have recently seen a surge of interest of theoreticians who are fascinated by their high brightness temperature of up to 10 to the 15th power K, their association with hard X-ray bursts, and a possibly very intimate relation to electron acceleration. Their bandwidth and global distribution in frequency were quantitatively measured only recently. This review is intended to emphasize the considerable extend of old and new observational knowledge which is hardly touched upon by theory. The wide range of spike observations is summarized and brought into perspective of recent models. It is concluded that spikes yield a considerable potential for the diagnostics of energetic particles, their origin, and history in astrophysical plasmas.

  11. SHORT-LIVED RADIO BURSTS FROM THE CRAB PULSAR

    SciTech Connect

    Crossley, J. H.; Eilek, J. A.; Hankins, T. H.; Kern, J. S.

    2010-10-20

    Our high-time-resolution observations reveal that individual main pulses from the Crab pulsar contain one or more short-lived microbursts. Both the energy and duration of bursts measured above 1 GHz can vary dramatically in less than a millisecond. These fluctuations are too rapid to be caused by propagation through turbulence in the Crab Nebula or in the interstellar medium; they must be intrinsic to the radio emission process in the pulsar. The mean duration of a burst varies with frequency as {nu}{sup -2}, significantly different from the broadening caused by interstellar scattering. We compare the properties of the bursts to some simple models of microstructure in the radio emission region.

  12. A follow-up campaign for fast radio bursts

    NASA Astrophysics Data System (ADS)

    Petroff, Emily; Possenti, Andrea; Johnston, Simon; Kramer, Michael; Bailes, Matthew; Burke-Spolaor, Sarah; van Straten, Willem; Keane, Evan; Champion, David; Jameson, Andrew; Ng, Cherry; Barr, Ewan; Flynn, Chris; Caleb, Manisha

    2014-04-01

    Fast Radio Bursts (FRBs) are bright, millisecond-duration radio pulses hypothesized to originate at cosmological distances. To date, no counterpart sources have been associated with FRBs and their origins remain a puzzling mystery. Some have proposed FRBs come from Crab-like pulsar giant pulses or rare bursts from main sequence flare stars in our Galaxy. Both mechanisms would generate observable subsequent FRB-like events. In this proposal we directly test this hypothesis by conducting several follow-up observations on the eight FRBs from the High Time Resolution Universe Survey. This sample represents the majority of the dozen or so known FRB sources. With these observations we will set strict limits on any repetition of FRBs while using the 12 off-source beams of the multi-beam receiver as real-time FRB and transient detectors.

  13. How Else Can We Detect Fast Radio Bursts?

    NASA Astrophysics Data System (ADS)

    Lyutikov, Maxim; Lorimer, Duncan R.

    2016-06-01

    We discuss possible electromagnetic signals accompanying Fast Radio Bursts (FRBs) that are expected in the scenario where FRBs originate in neutron star magnetospheres. For models involving Crab-like giant pulses, no appreciable contemporaneous emission is expected at other wavelengths. However, magnetar giant flares, driven by the reconfiguration of the magnetosphere, can produce both contemporaneous bursts at other wavelengths as well as afterglow-like emission. We conclude that the best chances are: (i) prompt short GRB-like emission, (ii) a contemporaneous optical flash that can reach naked eye peak luminosity (but only for a few milliseconds), and (iii) a high-energy afterglow emission. Case (i) could be tested by coordinated radio and high-energy experiments. Case (ii) could be seen in a coordinated radio-optical surveys, e.g., by the Palomar Transient Factory in a 60 s frame as a transient object of m = 15–20 mag with an expected optical detection rate of about 0.1 hr‑1, an order of magnitude higher than in radio. Shallow, but large-area sky surveys such as ASAS-SN and EVRYSCOPE could also detect prompt optical flashes from the more powerful Lorimer-burst clones. The best constraints on the optical to radio power for this kind of emission could be provided by future observations with facilities like Large Synoptic Survey Telescope. Case (iii) might be seen in relatively rare cases that the relativistically ejected magnetic blob is moving along the line of sight.

  14. How Else Can We Detect Fast Radio Bursts?

    NASA Astrophysics Data System (ADS)

    Lyutikov, Maxim; Lorimer, Duncan R.

    2016-06-01

    We discuss possible electromagnetic signals accompanying Fast Radio Bursts (FRBs) that are expected in the scenario where FRBs originate in neutron star magnetospheres. For models involving Crab-like giant pulses, no appreciable contemporaneous emission is expected at other wavelengths. However, magnetar giant flares, driven by the reconfiguration of the magnetosphere, can produce both contemporaneous bursts at other wavelengths as well as afterglow-like emission. We conclude that the best chances are: (i) prompt short GRB-like emission, (ii) a contemporaneous optical flash that can reach naked eye peak luminosity (but only for a few milliseconds), and (iii) a high-energy afterglow emission. Case (i) could be tested by coordinated radio and high-energy experiments. Case (ii) could be seen in a coordinated radio-optical surveys, e.g., by the Palomar Transient Factory in a 60 s frame as a transient object of m = 15-20 mag with an expected optical detection rate of about 0.1 hr-1, an order of magnitude higher than in radio. Shallow, but large-area sky surveys such as ASAS-SN and EVRYSCOPE could also detect prompt optical flashes from the more powerful Lorimer-burst clones. The best constraints on the optical to radio power for this kind of emission could be provided by future observations with facilities like Large Synoptic Survey Telescope. Case (iii) might be seen in relatively rare cases that the relativistically ejected magnetic blob is moving along the line of sight.

  15. Extended Corbet Diagram of HMXBs, LMXBs and radio pulsar binaries

    NASA Astrophysics Data System (ADS)

    Yan, Yan; Ali, Esamdin; Yin, Hongxing

    2010-09-01

    The evolutionary scenario of neutron star binaries is still an essential enigma in both stellar astrophysics and high energy astrophysics. In order to explore the scenario, we include the accumulation of data on the orbits and spins of compact binaries in multi-wavelength ranging from radio to X-ray, such as radio pulsar binaries, HMXBs, and LMXBs, filling them into the so called “Corbet Diagram” which initially investigated the period of orbit ( P orb)˜ the period of spin ( P spin) correlation of HMXBs. We find that the evolutionary scenario comes more clearly and makes strong confirmation of the connection between LMXBs and radio pulsar binaries, predicted by the recycle process. However, the origins of radio pulsar binaries sre still unknown. Accretion Induced Collapse (AIP) process may be a mechanism which can explain the origin of the binary millisecond pulsars with relatively longer orbital periods. A correlation of P {orb/1/3} ˜ P {spin/-1} of LMXBs and radio pulsar binaries may exist.

  16. The host galaxy of a fast radio burst

    NASA Astrophysics Data System (ADS)

    Keane, E. F.; Johnston, S.; Bhandari, S.; Barr, E.; Bhat, N. D. R.; Burgay, M.; Caleb, M.; Flynn, C.; Jameson, A.; Kramer, M.; Petroff, E.; Possenti, A.; van Straten, W.; Bailes, M.; Burke-Spolaor, S.; Eatough, R. P.; Stappers, B. W.; Totani, T.; Honma, M.; Furusawa, H.; Hattori, T.; Morokuma, T.; Niino, Y.; Sugai, H.; Terai, T.; Tominaga, N.; Yamasaki, S.; Yasuda, N.; Allen, R.; Cooke, J.; Jencson, J.; Kasliwal, M. M.; Kaplan, D. L.; Tingay, S. J.; Williams, A.; Wayth, R.; Chandra, P.; Perrodin, D.; Berezina, M.; Mickaliger, M.; Bassa, C.

    2016-02-01

    In recent years, millisecond-duration radio signals originating in distant galaxies appear to have been discovered in the so-called fast radio bursts. These signals are dispersed according to a precise physical law and this dispersion is a key observable quantity, which, in tandem with a redshift measurement, can be used for fundamental physical investigations. Every fast radio burst has a dispersion measurement, but none before now have had a redshift measurement, because of the difficulty in pinpointing their celestial coordinates. Here we report the discovery of a fast radio burst and the identification of a fading radio transient lasting ~6 days after the event, which we use to identify the host galaxy; we measure the galaxy’s redshift to be z = 0.492 ± 0.008. The dispersion measure and redshift, in combination, provide a direct measurement of the cosmic density of ionized baryons in the intergalactic medium of ΩIGM = 4.9 ± 1.3 per cent, in agreement with the expectation from the Wilkinson Microwave Anisotropy Probe, and including all of the so-called ‘missing baryons’. The ~6-day radio transient is largely consistent with the radio afterglow of a short γ-ray burst, and its existence and timescale do not support progenitor models such as giant pulses from pulsars, and supernovae. This contrasts with the interpretation of another recently discovered fast radio burst, suggesting that there are at least two classes of bursts.

  17. Radio frequency detection assembly and method for detecting radio frequencies

    DOEpatents

    Cown, Steven H.; Derr, Kurt Warren

    2010-03-16

    A radio frequency detection assembly is described and which includes a radio frequency detector which detects a radio frequency emission produced by a radio frequency emitter from a given location which is remote relative to the radio frequency detector; a location assembly electrically coupled with the radio frequency detector and which is operable to estimate the location of the radio frequency emitter from the radio frequency emission which has been received; and a radio frequency transmitter electrically coupled with the radio frequency detector and the location assembly, and which transmits a radio frequency signal which reports the presence of the radio frequency emitter.

  18. A Day in the Life of Millisecond Pulsar J1713+0747: Limits on Timing Precision Over 24 Hours and Implications for Gravitational Wave Detection

    NASA Astrophysics Data System (ADS)

    Dolch, Timothy; Bailes, M.; Bassa, C.; Bhat, R.; Bhattacharyya, B.; Champion, D.; Chatterjee, S.; Cognard, I.; Cordes, J. M.; Crowter, K.; Demorest, P.; Finn, L. S.; Fonseca, E.; Hessels, J.; Hobbs, G.; Janssen, G.; Jones, G.; Jordan, C.; Karuppusamy, R.; Keith, M.; Kramer, M.; Kraus, A.; Lam, M. T.; Lazarus, P.; Lazio, J.; Lee, K.; Levin, L.; Liu, K.; Lorimer, D.; Manchester, R. N.; McLaughlin, M.; Palliyaguru, N.; Perrodin, D.; Petroff, E.; Rajwade, K.; Rankin, J. M.; Ransom, S. M.; Rosenblum, J.; Roy, J.; Shannon, R.; Stappers, B.; Stinebring, D.; Stovall, K.; Teixeira, M.; van Leeuwen, J.; van Straten, W.; Verbiest, J.; Zhu, W.

    2014-01-01

    A 24-hour global observation of millisecond radio pulsar J1713+0747 was undertaken by the International Pulsar Timing Array (IPTA) collaboration as an effort to better quantify sources of noise in this object, which is regularly timed for the purpose of detecting gravitational waves (GWs). Given an 8-year timing RMS of 30ns, it is regarded as one of the best precision clocks in the PTA. However, sources of timing noise visible on timescales longer than the usual 20-30min biweekly observation may nonetheless be present. Data from the campaign were taken contiguously with the Parkes, Arecibo, Green Bank, GMRT, LOFAR, Effelsberg, WSRT, Lovell, and Nancay radio telescopes. The combined pulse times-of-arrival provide an estimate of the absolute noise floor, in other words, what unaccounted sources of timing noise impede an otherwise simple sqrt(N) improvement in timing precision, where N is the number of pulses in a single observing session. We present first results of specific phenomena probed on the unusual timescale of tens of hours, in particular interstellar scattering (ISS), and discuss the degree to which ISS affects precision timing. Finally, we examine single pulse information during selected portions of the observation and determine the degree to which the pulse jitter of J1713+0747 varies throughout the course of the day-long dataset.

  19. EGRET upper limits to the high-energy gamma-ray emission from the millisecond pulsars in nearby globular clusters

    NASA Technical Reports Server (NTRS)

    Michelson, P. F.; Bertsch, D. L.; Brazier, K.; Chiang, J.; Dingus, B. L.; Fichtel, C. E.; Fierro, J.; Hartman, R. C.; Hunter, S. D.; Kanbach, G.

    1994-01-01

    We report upper limits to the high-energy gamma-ray emission from the millisecond pulsars (MSPs) in a number of globular clusters. The observations were done as part of an all-sky survey by the energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (CGRO) during Phase I of the CGRO mission (1991 June to 1992 November). Several theoretical models suggest that MSPs may be sources of high-energy gamma radiation emitted either as primary radiation from the pulsar magnetosphere or as secondary radiation generated by conversion into photons of a substantial part of the relativistic e(+/-) pair wind expected to flow from the pulsar. To date, no high-energy emission has been detected from an individual MSP. However, a large number of MSPs are expected in globular cluster cores where the formation rate of accreting binary systems is high. Model predictions of the total number of pulsars range in the hundreds for some clusters. These expectations have been reinforced by recent discoveries of a substantial number of radio MSPs in several clusters; for example, 11 have been found in 47 Tucanae (Manchester et al.). The EGRET observations have been used to obtain upper limits for the efficiency eta of conversion of MSP spin-down power into hard gamma rays. The upper limits are also compared with the gamma-ray fluxes predicted from theoretical models of pulsar wind emission (Tavani). The EGRET limits put significant constraints on either the emission models or the number of pulsars in the globular clusters.

  20. Observations and modeling of the companions of short period binary millisecond pulsars: evidence for high-mass neutron stars

    SciTech Connect

    Schroeder, Joshua; Halpern, Jules

    2014-10-01

    We present observations of fields containing eight recently discovered binary millisecond pulsars using the telescopes at MDM Observatory. Optical counterparts to four of these systems are detected, one of which, PSR J2214+3000, is a novel detection. Additionally, we present the fully phase-resolved B, V, and R light curves of the optical counterparts to two objects, PSR J1810+1744 and PSR J2215+5135 for which we employ model fitting using the eclipsing light curve (ELC) model of Orosz and Hauschildt to measure the unknown system parameters. For PSR J1810+1744, we find that the system parameters cannot be fit even assuming that 100% of the spin-down luminosity of the pulsar is irradiating the secondary, and so radial velocity measurements of this object will be required for the complete solution. However, PSR J2215+5135 exhibits light curves that are extremely well constrained using the ELC model and we find that the mass of the neutron star is constrained by these and the radio observations to be M {sub NS} > 1.75 M {sub ☉} at the 3σ level. We also find a discrepancy between the model temperature and the measured colors of this object, which we interpret as possible evidence for an additional high-temperature source such as a quiescent disk. Given this and the fact that PSR J2215+5135 contains a relatively high mass companion (M {sub c} > 0.1 M {sub ☉}), we propose that similar to the binary pulsar systems PSR J1023+0038 and IGR J18245–2452, the pulsar may transition between accretion- and rotation-powered modes.

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    We report 3-79 keV NuSTAR observations of the remarkable millisecond pulsar-low mass X-ray binary (LMXB) transition system PSR J1023+0038 from June and October 2013, before and after the formation of an accretion disk around the neutron star. Between June 10-12, shortly before the radio disappearance of the pulsar, the 3-79 keV X-ray spectrum was well fit by a simple power law with a photon index of Γ = 1.17±0.08 with a 3-79 keV luminosity of 7.4±0.4×1032 erg/s. Significant orbital modulation was observed with a modulation fraction of 36±10%. During the October 19-21 observation, the spectrum is described by a softer power law (Γ = 1.66±0.06) with an average luminosity of 5.8±0.2×1033 erg/s and a peak luminosity of ≈ 1.2×1034 erg/s observed during a flare. No significant orbital modulation was detected. The spectral observations are consistent with previous and current multi-wavelength observations and show the hard X-ray power law extending to 79 keV without a spectral break. Unusual, sharp edged, flat bottomed ‘dips’ are observed with widths between 30-1000 s and ingress and egress time-scales of 30-60 s. These dips are distinct from dipping activity observed in LMXBs. We compare and contrast these dips to observations of dips and state changes in the similar transition systems PSR J1824-2452I and XSS J1227.0-4859 and discuss possible interpretations based on the transitions in the inner disk.

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    We report NuSTAR observations of the millisecond pulsar-low-mass X-ray binary (LMXB) transition system PSR J1023+0038 from 2013 June and October, before and after the formation of an accretion disk around the neutron star. Between June 10 and 12, a few days to two weeks before the radio disappearance of the pulsar, the 3-79 keV X-ray spectrum was well fit by a simple power law with a photon index of Γ =1.17+0.08-0.07 (at 90% confidence) with a 3-79 keV luminosity of 7.4 ± 0.4 × 1032 erg s-1. Significant orbital modulation was observed with a modulation fraction of 36% ± 10%. During the October 19-21 observation, the spectrum is described by a softer power law (Γ =1.66+0.06-0.05) with an average luminosity of 5.8 ± 0.2 × 1033 erg s-1 and a peak luminosity of ≈1.2 × 1034 erg s-1 observed during a flare. No significant orbital modulation was detected. The spectral observations are consistent with previous and current multiwavelength observations and show the hard X-ray power law extending to 79 keV without a spectral break. Sharp-edged, flat-bottomed dips are observed with widths between 30 and 1000 s and ingress and egress timescales of 30-60 s. No change in hardness ratio was observed during the dips. Consecutive dip separations are log-normal in distribution with a typical separation of approximately 400 s. These dips are distinct from dipping activity observed in LMXBs. We compare and contrast these dips to observations of dips and state changes in the similar transition systems PSR J1824-2452I and XSS J1227.0-4859 and discuss possible interpretations based on the transitions in the inner disk.

  3. Wideband Observations of Radio Pulsars

    NASA Astrophysics Data System (ADS)

    Pennucci, Timothy T.

    2015-08-01

    Pulsars are exotic objects which have yielded a bounty of important astrophysical results. As rapidly rotating, highly magnetized neutron stars, pulsars' stable rotation and beamed radio emission enables their use as interstellar laboratory clocks. The extraordinary timing regularity of the millisecond pulsar (MSP) population permits some of the most precise measurements in astronomy. The discovery of MSPs raised the probability of directly detecting gravitational waves for the first time. Ongoing efforts by several pulsar timing array (PTA) collaborations compliment the ground- and space-based efforts of laser interferometers. One such PTA is the North American Nanohertz Observatory for Gravitational Waves (NANOGrav). NANOGrav has recently employed a new set of wideband instruments to increase the sensitivity of their PTA, and the future of pulsar astronomy is moving towards progressively larger bandwidths. In this dissertation, we address the benefits and issues from adopting the new instrumentation, particularly for the scientific motivations of NANOGrav. We first develop a measurement technique for simultaneously obtaining pulse times-of-arrival (TOAs) and dispersion measures (DMs) using 2D models of evolving Gaussian components. We then apply the methodology broadly to a variety of pulsars, including a bright, test MSP in a globular cluster, the Galactic Center magnetar, and the entire suite of 37 MSPs from the NANOGrav 9-year data set. For a subset of these MSPs, we make targeted observations at specific orbital phases aimed at improving the timing models and constraining the Shapiro delay. With a few exceptions, we find positive or consistent timing results from the implementation of our first generation wideband timing protocol. Some highlights include: improved measurement uncertainties, mitigation of chromatic ISM effects, a reduction in the number of timing parameters and TOAs, signs of chromatic DMs, and at least one new pulsar mass.

  4. ALL TRANSIENTS, ALL THE TIME: REAL-TIME RADIO TRANSIENT DETECTION WITH INTERFEROMETRIC CLOSURE QUANTITIES

    SciTech Connect

    Law, Casey J.; Bower, Geoffrey C.

    2012-04-20

    We demonstrate a new technique for detecting radio transients based on interferometric closure quantities. The technique uses the bispectrum, the product of visibilities around a closed loop of baselines of an interferometer. The bispectrum is calibration independent, resistant to interference, and computationally efficient, so it can be built into correlators for real-time transient detection. Our technique could find celestial transients anywhere in the field of view and localize them to arcsecond precision. At the Karl G. Jansky Very Large Array (VLA), such a system would have a high survey speed and a 5{sigma} sensitivity of 38 mJy on 10 ms timescales with 1 GHz of bandwidth. The ability to localize dispersed millisecond pulses to arcsecond precision in large volumes of interferometer data has several unique science applications. Localizing individual pulses from Galactic pulsars will help find X-ray counterparts that define their physical properties, while finding host galaxies of extragalactic transients will measure the electron density of the intergalactic medium with a single dispersed pulse. Exoplanets and active stars have distinct millisecond variability that can be used to identify them and probe their magnetospheres. We use millisecond timescale visibilities from the Allen Telescope Array and VLA to show that the bispectrum can detect dispersed pulses and reject local interference. The computational and data efficiency of the bispectrum will help find transients on a range of timescales with next-generation radio interferometers.

  5. Resonance and Radio

    ERIC Educational Resources Information Center

    Starrett, Malin J.

    2008-01-01

    The science and technology of radio receives little attention in contemporary education. This article discusses ways to explore the basic operating principles of radio. (Contains 4 figures, 3 footnotes, and 2 notes.)

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

    SciTech Connect

    Roy, Jayanta; Bhattacharyya, Bhaswati; Stappers, Ben; Ray, Paul S.; Wolff, Michael; Wood, Kent S.; Chengalur, Jayaram N.; Deneva, Julia; Camilo, Fernando; Johnson, Tyrel J.; Hessels, Jason W. T.; Bassa, Cees G.; Keane, Evan F.; Ferrara, Elizabeth C.; Harding, Alice K.

    2015-02-10

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

  7. Discovery of Psr J1227-4853: A Transition from a Low-mass X-Ray Binary to a Redback Millisecond Pulsar

    NASA Astrophysics Data System (ADS)

    Roy, Jayanta; Ray, Paul S.; Bhattacharyya, Bhaswati; Stappers, Ben; Chengalur, Jayaram N.; Deneva, Julia; Camilo, Fernando; Johnson, Tyrel J.; Wolff, Michael; Hessels, Jason W. T.; Bassa, Cees G.; Keane, Evan F.; Ferrara, Elizabeth C.; Harding, Alice K.; Wood, Kent S.

    2015-02-01

    XSS J12270-4859 is an X-ray binary associated with the Fermi Large Area Telescope gamma-ray source 1FGL J1227.9-4852. In 2012 December, this source underwent a transition where the X-ray and optical luminosity dropped and the spectral signatures of an accretion disk disappeared. We report the discovery of a 1.69 millisecond pulsar (MSP), PSR J1227-4853, at a dispersion measure of 43.4 pc cm-3 associated with this source, using the Giant Metrewave Radio Telescope (GMRT) at 607 MHz. This demonstrates that, post-transition, the system hosts an active radio MSP. This is the third system after PSR J1023+0038 and PSR J1824-2452I showing evidence of state switching between radio MSP and low-mass X-ray binary states. We report timing observations of PSR J1227-4853 with the GMRT and Parkes, which give a precise determination of the rotational and orbital parameters of the system. The companion mass measurement of 0.17-0.46 M⊙ suggests that this is a redback system. PSR J1227-4853 is eclipsed for about 40% of its orbit at 607 MHz with additional short-duration eclipses at all orbital phases. We also find that the pulsar is very energetic, with a spin-down luminosity of ˜1035 erg s-1. We report simultaneous imaging and timing observations with the GMRT, which suggests that eclipses are caused by absorption rather than dispersion smearing or scattering.

  8. The spin period formation of millisecond pulsar by the torques of accretion and gravitational wave emission

    NASA Astrophysics Data System (ADS)

    Guo, Y. Q.; Zhang, C. M.; Pan, Y. Y.

    2016-11-01

    We investigated the spin period evolution of the accreting neutron star (NS) in binary systems, based on the accretion-induced magnetic decay model, while both the accretion spin-up torque and the gravitational wave (GW) emission induced spin-down torque are taken into account. We found that the spin period of millisecond pulsar (MSP) can stop at the value of several milliseconds, if the accretion spin-up torque balances the spin-down torque by the GW radiation. Furthermore, we obtained the minimum spin period of MSP and its relation to the deformation ellipticity of NS that accounts for the NS mass quadrupole moment. The comparisons between the pulsar observations and the model results are discussed in the diagram of magnetic field versus spin period, and the consistency can be obtained.

  9. Multicompartment lipid cubic nanoparticles with high protein upload: millisecond dynamics of formation.

    PubMed

    Angelov, Borislav; Angelova, Angelina; Filippov, Sergey K; Drechsler, Markus; Štěpánek, Petr; Lesieur, Sylviane

    2014-05-27

    Membrane shapes, produced by dynamically assembled lipid/protein architectures, are crucial for both physiological functions and the design of therapeutic nanotechnologies. Here we investigate the dynamics of lipid membrane-neurotrophic BDNF protein complexes formation and ordering in nanoparticles, with the purpose of innovation in nanostructure-based neuroprotection and biomimetic nanoarchitectonics. The kinetic pathway of membrane states associated with rapidly occurring nonequilibrium self-assembled lipid/protein nanoarchitectures was determined by millisecond time-resolved small-angle X-ray scattering (SAXS) at high resolution. The neurotrophin binding and millisecond trafficking along the flexible membranes induced an unusual overlay of channel-network architectures including two coexisting cubic lattices epitaxially connected to lamellar membrane stacks. These time-resolved membrane processes, involving intercalation of discrete stiff proteins in continuous soft membranes, evidence stepwise curvature control mechanisms. The obtained three-phase liquid-crystalline nanoparticles of neurotrophic composition put forward important advancements in multicompartment soft-matter nanostructure design.

  10. The saturation of the electron-cyclotron maser instability and the interpretation of solar millisecond spikes

    NASA Technical Reports Server (NTRS)

    Aschwanden, M. J.

    1990-01-01

    A self-consistent numeric two-dimensional code of the kinetic wave-particle equations developed to investigate the maser dynamics in the solar context is applied to solar millisecond-spike observations in order to improve the diagnostic capabilities of the theory of the electron-cyclotron maser instablitity. Attention is given to the inhomogeneity of the magnetic field selecting magneto-ionic modes with relatively short saturation lengths and suppressing mechanisms such as collisional deflection, free-free absorption, and gyroresonance absorption. The time scales of maser saturation in respect to time scales of global particle changes in a magnetic loop are covered, relevant observations of solar millisecond spikes are described, and the interpretation in terms of physical parameters deduced from the quasi-linear maser simulations are presented. It is demonstrated that the quasi-linear simulations make it possible to constrain the physical parameters from the observed time scale and frequency.

  11. Time-resolved temperature measurement and numerical simulation of millisecond laser irradiated silicon

    SciTech Connect

    Li Zewen; Zhang Hongchao; Shen Zhonghua; Ni Xiaowu

    2013-07-21

    Thermal process of 1064 nm millisecond pulsed Nd:YAG laser irradiated silicon was time-resolved temperature measured by an infrared radiation pyrometer, temperature evolutions of the spot center for wide range of laser energy densities were presented. The waveforms of temperature evolution curves contained much information about phase change, melting, solidification and vaporization. An axisymmetric numerical model was established for millisecond laser heating silicon. The transient temperature fields were obtained by using the finite element method. The numerical results of temperature evolutions of the spot center are in good agreement with the experimental results. Furthermore, the axial temperature distributions of the numerical results give a better understanding of the waveforms in the experimental results. The melting threshold, vaporizing threshold, melting duration, and melting depth were better identified by analyzing two kinds of results.

  12. Miniaturized thermocontrol devices enable analysis of biomolecular behavior on their timescales, second to millisecond.

    PubMed

    Arata, Hideyuki F; Fujita, Hiroyuki

    2009-06-01

    To establish general-purpose methods and tools for biological experiments on a short time scale is an essential requirement for future research in molecular biology because most of the functions of living organisms at the molecular level take place on a time scale from 1-second to millisecond. Thermal control with on-chip micro-thermodevices is one of the strongest and most useful ways to realize biological experiments at molecular level on these time scales. Novel biological phenomena revealed by the experiments using micro-thermodevices on a 1-second and millisecond time scale will be shown for the proof. Finally, the advantages and impact of this methodology in molecular biology will be discussed.

  13. Millisecond analysis of double stranded DNA with fluorescent intercalator by micro-thermocontrol-device.

    PubMed

    Arata, Hideyuki F; Gillot, Frederic; Collard, Dominique; Fujita, Hiroyuki

    2009-08-15

    Study of interaction between DNA and intercalator at molecular level is important to understand the mechanisms of DNA replication and repair. A micro-fabricated local heating thermodevice was adapted to perform denaturation experiments of DNA with fluorescent intercalator on millisecond time scale. Response time of complete unzipping of double stranded DNA, 16 microm in length, was measured to be around 5 min by commercial thermocycler. Response time of quenching of double stranded DNA with fluorescent intercalator SYBR Green was measured to be 10 ms. Thus, quenching properties owing to strand unzipping and denaturation at base pair level were distinguished. This method has provided easy access to measure this parameter and may be a powerful methodology in analyzing biomolecules on millisecond time scale.

  14. A PC parallel port button box provides millisecond response time accuracy under Linux.

    PubMed

    Stewart, Neil

    2006-02-01

    For psychologists, it is sometimes necessary to measure people's reaction times to the nearest millisecond. This article describes how to use the PC parallel port to receive signals from a button box to achieve millisecond response time accuracy. The workings of the parallel port, the corresponding port addresses, and a simple Linux program for controlling the port are described. A test of the speed and reliability of button box signal detection is reported. If the reader is moderately familiar with Linux, this article should provide sufficient instruction for him or her to build and test his or her own parallel port button box. This article also describes how the parallel port could be used to control an external apparatus.

  15. ZnO nanorods prepared via ablation of Zn with millisecond laser in liquid media.

    PubMed

    Honda, Mitsuhiro; Goto, Taku; Owashi, Tatsuki; Rozhin, Alex G; Yamaguchi, Shigeru; Ito, Tsuyohito; Kulinich, Sergei A

    2016-09-14

    ZnO nanomaterials with controlled size, shape and surface chemistry are required for applications in diverse areas, such as optoelectronics, photocatalysis, biomedicine and so on. Here, we report on ZnO nanostructures with rod-like and spherical shapes prepared via laser ablation in liquid using a laser with millisecond-long pulses. By changing laser parameters (such as pulse width and peak power), the size or aspect ratio of such nanostructures could be tuned. The surface chemistry and defects of the products were also strongly affected by applied laser conditions. The preparation of different structures is explained by the intense heating of liquid media caused by millisecond-long pulses and secondary irradiation of already-formed nanostructures. PMID:27507010

  16. Extragalactic Radio Sources

    ERIC Educational Resources Information Center

    Kellerman, Kenneth I.

    1973-01-01

    Discusses new problems arising from the growing observational data through radio telescope arrays, involving the origin of radio sources, apparent superluminal velocities, conversion of radio sources to relativistic particles, and the nature of compact opaque and extended transparent sources. New physics may be needed to answer these cosmological…

  17. Orbit Solution for the Millisecond Pulsar IGR J00291+5934

    NASA Astrophysics Data System (ADS)

    Markwardt, C. B.; Galloway, D. K.; Chakrabarty, D.; Morgan, E. H.; Strohmayer, T. E.

    2004-12-01

    The INTEGRAL Transient IGR J00291+5934 (ATEL #352), now known to be a 1.67 millisecond X-ray pulsar (ATEL #353), was observed by the RXTE PCA on Dec 5 and 6. The source has decayed to approximately 27 mCrab (2-10 keV). The data were barycentered using the Fox & Kulkarni optical counterpart position (ATEL #354). Pulsations with a sinusoidal frequency modulation are clearly detected in each observation.

  18. Milli-second optical observations of V 404 Cyg with SiFAP

    NASA Astrophysics Data System (ADS)

    Ambrosino, F.; Bruni, I.; Cretaro, P.; Meddi, F.; Rossi, C.; Giovannelli, F.

    2015-07-01

    SiFAP: A simple sub-millisecond astronomical photometer (Ambrosino et al.: 2013, J. Astron. Instrum. Vol. 2 (01), 1350006; Ambrosino et al.: 2014, Proc of the SPIE, 9147, 91478R) has been used at the Cassegrain focus of the G.D. Cassini 152 cm Loiano telescope in order to detect possible short term periodicities and/or QPOs of the black hole X-ray binary V 404 Cyg.

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

    NASA Astrophysics Data System (ADS)

    González-Jiménez, Nicolás; Petrovich, Cristobal; Reisenegger, Andreas

    2015-03-01

    When a rotating neutron star loses angular momentum, the progressive reduction of the centrifugal force makes it contract. This perturbs each fluid element, raising the local pressure and originating deviations from beta equilibrium, inducing reactions that release heat (`rotochemical heating'). This effect has previously been studied by Fernández & Reisenegger for non-superfluid neutron stars and by Petrovich & Reisenegger for superfluid millisecond pulsars. Both studies found that pulsars reach a quasi-steady state in which the compression driving the matter out of beta equilibrium is balanced by the reactions trying to restore the equilibrium. We extend previous studies by considering the effect of density-dependence and anisotropy of the superfluid energy gaps, for the case in which the dominant reactions are the modified Urca processes, the protons are non-superconducting, and the neutron superfluidity is parametrized by models proposed in the literature. By comparing our predictions with the surface temperature of the millisecond pulsar PSR J0437-4715 and upper limits for 21 classical pulsars, we find the millisecond pulsar can be only explained by the models with the effectively largest energy gaps (type B models), the classical pulsars require with the gap models that vanish for some angle (type C) and two different envelope compositions. Thus, no single model for neutron superfluidity can simultaneously account for the thermal emission of all available observations of non-accreting neutron stars, possibly due to our neglect of proton superconductivity.

  20. Millisecond Kinetics of Nanocrystal Cation Exchange UsingMicrofluidic X-ray Absorption Spectroscopy

    SciTech Connect

    Chan, Emory M.; Marcus, Matthew A.; Fakra, Sirine; Elnaggar,Mariam S.; Mathies, Richard A.; Alivisatos, A. Paul

    2007-05-07

    We describe the use of a flow-focusing microfluidic reactorto measure the kinetics of theCdSe-to-Ag2Se nanocrystal cation exchangereaction using micro-X-ray absorption spectroscopy (mu XAS). The smallmicroreactor dimensions facilitate the millisecond mixing of CdSenanocrystal and Ag+ reactant solutions, and the transposition of thereaction time onto spatial coordinates enables the in situ observation ofthe millisecond reaction with mu XAS. XAS spectra show the progression ofCdSe nanocrystals to Ag2Se over the course of 100 ms without the presenceof long-lived intermediates. These results, along with supporting stoppedflow absorption experiments, suggest that this nanocrystal cationexchange reaction is highly efficient and provide insight into how thereaction progresses in individual particles. This experiment illustratesthe value and potential of in situ microfluidic X-ray synchrotrontechniques for detailed studies of the millisecond structuraltransformations of nanoparticles and other solution-phase reactions inwhich diffusive mixing initiates changes in local bond structures oroxidation states.

  1. What's in your buffer? Solute altered millisecond motions detected by solution NMR.

    PubMed

    Wong, Madeline; Khirich, Gennady; Loria, J Patrick

    2013-09-17

    To date, little work has been conducted on the relationship between solute and buffer molecules and conformational exchange motion in enzymes. This study uses solution NMR to examine the effects of phosphate, sulfate, and acetate in comparison to MES- and HEPES-buffered references on the chemical shift perturbation and millisecond, chemical, or conformational exchange motions in the enzyme ribonuclease A (RNase A), triosephosphate isomerase (TIM) and HisF. The results indicate that addition of these solutes has a small effect on (1)H and (15)N chemical shifts for RNase A and TIM but a significant effect for HisF. For RNase A and TIM, Carr-Purcell-Meiboom-Gill relaxation dispersion experiments, however, show significant solute-dependent changes in conformational exchange motions. Some residues show loss of millisecond motions relative to the reference sample upon addition of solute, whereas others experience an enhancement. Comparison of exchange parameters obtained from fits of dispersion data indicates changes in either or both equilibrium populations and chemical shifts between conformations. Furthermore, the exchange kinetics are altered in many cases. The results demonstrate that common solute molecules can alter observed enzyme millisecond motions and play a more active role than what is routinely believed.

  2. Novel microfabricated device to measure hormone/neurotransmitter release with millisecond temporal resolution

    NASA Astrophysics Data System (ADS)

    Gillis, Kevin D.; Chen, Peng; Xu, Bai; Tokranova, Natalya; Feng, Xiaojun; Castracane, James

    2002-06-01

    We are developing a novel readout for secretion of hormones and neurotransmitter on micro/nanofabricated chips. Traditional biochemical assays of signaling molecules secreted from cells are slow, cumbersome and have at best, a temporal resolution of several seconds. On the other hand, electrochemical measurement of hormone or transmitter secretion can obtain millisecond temporal resolution if the diffusion distance between the release site on the cell and the working electrode is within 1 micron. Carbon fiber microelectrodes can have millisecond time resolution, but can only measure release form a small fraction of the cell surface. We have fabricated arrays of Au electrodes in wells micromachined on the surface of silicon microchips. Each well/microelectrode roughly conforms to the shape of a single cell in order to capture release forma large fraction of the surface area of each cell with minimal diffusional delays. This paper will present details of the microfabrication process flow as well a initial results demonstrating millisecond-resolution measurement of catecholamine secretion form adrenal chromaffin cells. Our goal for this project is to develop enabling technology for massively parallel systems on a chip such as cell-based biosensors to detect neurotoxins and high-throughput assays of drugs that affect neurotransmitter release.

  3. Single-pulse study of radio pulsars

    NASA Astrophysics Data System (ADS)

    Bilous, Anna V.

    Single pulses provide valuable information about the pulsar magnetosphere, giving more spatial and time resolution than the integrated pulse profiles. Clearly, there are several different types of single pulse emission, however it is still unknown what is the nature or even strict definition of each type. This work aims to shed some light on different kinds of single pulses, making an attempt to constrain some emission theories and trace the possible connection between different types. The thesis consists of following case studies: 1. No apparent correlation was found between giant pulses (GPs) from the Crab pulsar (9 GHz, Green Bank Telescope) and its gamma-ray photons (100 MeV - 5 GeV, Fermi). This result suggests that GPs, at least the ones detected at high radio frequencies, are due to changes in coherence of radio emission rather than an overall increase in the magnetospheric particle density. Also, no apparent correlation was found between Crab GPs (1.5 GHz, Green Bank Telescope) and X-ray photons (1.5 - 4.5 keV, Chandra). 2. We show that single pulses from the millisecond pulsar B182-24A fall into two distinct categories — broad faint pulses, coincident with the peaks of integrated pulse profile and bright narrow GPs on the trailing edges of profile components. Owing to our large fractional bandwidth we were able to prove the hypothesis that the spectra of these GPs consist of separate substantially polarized patches. 3. We present a LOFAR study of single pulses from pulsars B0809+74 and B1133+16 below 90 MHz. We show that the spectral width of bright, low-frequency pulses scales with increasing frequency as Δ f/f ˜ 0.15, at least in the case of PSR B0809+74. This behaviour is consistent with predictions of strong plasma turbulence model. 4. Millisecond pulsar B1744-24A belongs to "windy" binary systems, with unbound material escaping from the companion star and interacting with the pulsar's magnetosphere. B1744-24A appears to emit strong wide single

  4. On the correlation between exciter duration and decay constant of solar decameter Type III radio bursts

    NASA Astrophysics Data System (ADS)

    Subramanian, K. R.; Krishan, V.; Sastry, Ch. V.

    1981-04-01

    It is observed that while there exists a strong correlation between the decay constant and the exciter duration for isolated Type III radio bursts, it is absent for those Type III radio bursts which are preceded by Type IIIb radio bursts. A possible theoretical explanation for the presence of correlation in one case and lack of it in the other is proposed.

  5. Search for Pulsations from a Nearby Millisecond Pulsar and Wasilewski 49: Mirror for a Hidden Seyfert 1 Nucleus

    NASA Technical Reports Server (NTRS)

    Halpern, Jules P.

    1999-01-01

    Five studies are reported in this final report. The recently discovered 5.3 ms pulsar J1012+5307 at a distance of 520 pc is in an area of the sky which is particularly deficient in absorbing gas. The column density along the line of sight is less than 7.5 x 10(exp 19) CM(exp -2) which facilitates soft X-ray observations. Halpern reported a possible ROSAT Position Sensitive Proportional Counter (PSPC) detection of the pulsar in a serendipitous, off-axis observation. We have now confirmed the X-ray emission of PSR J1012+,5307 in a 23 ksec observation with the ROSAT High Resolution Imager (HRI). A point source is detected within 3" of the radio position. Its count rate of 1.6 +/- 0.3 x 10(exp -3) s(exp -1) corresponds to an unabsorbed 0. 1-2.4 keV flux of 6.4 x 10(exp -14) ergs cm(exp -2) s(exp -1), similar to that reported previously. This counts-to-flux conversion is valid for N(sub H) = 5 x 10(exp 19) cm(exp -2), and either a power-law spectrum of photon index 2.5 or a blackbody of kT = 0.1 keV. The implied X-ray luminosity of 2.0 x 10(exp 30) ergs s(exp -1) is 5 X 10(exp -4) of the pulsar's spin-down power dot-E, and similar to that of the nearest millisecond pulsar J0437-4715, which is nearly a twin of J1012+5307 in P dot-E. We subjected the 37 photons (and 13 background counts) within the source region to a pulsar search, but no evidence for pulsation was found. The pulsar apparently emits over a large fraction of its rotation cycle, and the absence of sharp modulation can be taken as evidence for surface thermal emission, as is favored for PSR J0437-4715, rather than magnetospheric X-ray emission which is apparent in the sharp pulses of the much more energetic millisecond pulsar B1821-24. A further test of this interpretation will be made with a longer ROSAT observation, which will increase the number of photons collected by a factor of 5, and permit a more sensitive examination of the light curve for modulation due to emission from heated polar caps. If found

  6. Search for Pulsations from a Nearby Millisecond Pulsar and Wasilewski 49: Mirror for a Hidden Seyfert 1 Nucleus

    NASA Astrophysics Data System (ADS)

    Halpern, Jules P.

    1999-03-01

    Five studies are reported in this final report. The recently discovered 5.3 ms pulsar J1012+5307 at a distance of 520 pc is in an area of the sky which is particularly deficient in absorbing gas. The column density along the line of sight is less than 7.5 x 1019 CM-2 which facilitates soft X-ray observations. Halpern reported a possible ROSAT Position Sensitive Proportional Counter (PSPC) detection of the pulsar in a serendipitous, off-axis observation. We have now confirmed the X-ray emission of PSR J1012+,5307 in a 23 ksec observation with the ROSAT High Resolution Imager (HRI). A point source is detected within 3" of the radio position. Its count rate of 1.6 +/- 0.3 x 10-3 s-1 corresponds to an unabsorbed 0. 1-2.4 keV flux of 6.4 x 10-14 ergs cm-2 s-1, similar to that reported previously. This counts-to-flux conversion is valid for NH = 5 x 1019 cm-2, and either a power-law spectrum of photon index 2.5 or a blackbody of kT = 0.1 keV. The implied X-ray luminosity of 2.0 x 1030 ergs s-1 is 5 X 10-4 of the pulsar's spin-down power dot-E, and similar to that of the nearest millisecond pulsar J0437-4715, which is nearly a twin of J1012+5307 in P dot-E. We subjected the 37 photons (and 13 background counts) within the source region to a pulsar search, but no evidence for pulsation was found. The pulsar apparently emits over a large fraction of its rotation cycle, and the absence of sharp modulation can be taken as evidence for surface thermal emission, as is favored for PSR J0437-4715, rather than magnetospheric X-ray emission which is apparent in the sharp pulses of the much more energetic millisecond pulsar B1821-24. A further test of this interpretation will be made with a longer ROSAT observation, which will increase the number of photons collected by a factor of 5, and permit a more sensitive examination of the light curve for modulation due to emission from heated polar caps. If found, such modulation will be further evidence that surface reheating by the impact

  7. Fast radio bursts — A brief review: Some questions, fewer answers

    NASA Astrophysics Data System (ADS)

    Katz, J. I.

    2016-04-01

    Fast radio bursts (FRBs) are millisecond bursts of radio radiation at frequencies of about 1 GHz, recently discovered in pulsar surveys. They have not yet been definitively identified with any other astronomical object or phenomenon. The bursts are strongly dispersed, indicating passage through a high column density of low density plasma. The most economical interpretation is that this is the intergalactic medium, indicating that FRB are at “cosmological” distances with redshifts in the range 0.3-1.3. Their inferred brightness temperatures are as high as 1037 K, implying coherent emission by “bunched” charges, as in radio pulsars. I review the astronomical sites, objects and emission processes that have been proposed as the origin of FRB, with particular attention to soft gamma repeaters (SGRs) and giant pulsar pulses.

  8. Radio source evolution

    NASA Astrophysics Data System (ADS)

    Perucho, M.

    2016-02-01

    Baldwin (1982) wrote that {``the distribution of sources in the radio luminosity, P, overall physical size, D, diagram''} could be considered as {``the radio astronomer's H-R diagram''}. However, unlike the case of stars, not only the intrinsic properties of the jets, but also those of the host galaxy and the intergalactic medium are relevant to explain the evolutionary tracks of radio radio sources. In this contribution I review the current status of our understanding of the evolution of radio sources from a theoretical and numerical perspective, using the P-D diagram as a framework. An excess of compact (linear size {≤ 10} kpc) sources could be explained by low-power jets being decelerated within the host galaxy, as shown by recent numerical simulations. Finally, I discuss the possible tracks that radio sources may follow within this diagram, and the physical processes that can explain the different tracks.

  9. The Sardinia Radio Telescope

    NASA Astrophysics Data System (ADS)

    Grueff, G.; Alvito, G.; Ambrosini, R.; Bolli, P.; D'Amico, N.; Maccaferri, A.; Maccaferri, G.; Morsiani, M.; Mureddu, L.; Natale, V.; Olmi, L.; Orfei, A.; Pernechele, C.; Poma, A.; Porceddu, I.; Rossi, L.; Zacchiroli, G.

    We describe the Sardinia Radio Telescope (SRT), a new general purpose, fully steerable antenna of the National Institute for Astrophysics. The radio telescope is under construction near Cagliari (Sardinia). With its large aperture (64m diameter) and its active surface, SRT is capable of operations up to ˜100GHz, it will contribute significantly to VLBI networks and will represent a powerful single-dish radio telescope for many science fields. The radio telescope has a Gregorian optical configuration with a supplementary beam-waveguide (BWG), which provides additional focal points. The Gregorian surfaces are shaped to minimize the spill-over and standing wave. After the start of the contract for the radio telescope structural and mechanical fabrication in 2003, in the present year the foundation construction will be completed. The schedule foresees the radio telescope inauguration in late 2006.

  10. Ligand Binding Enhances Millisecond Conformational Exchange in Xylanase B2 from Streptomyces lividans.

    PubMed

    Gagné, Donald; Narayanan, Chitra; Nguyen-Thi, Nhung; Roux, Louise D; Bernard, David N; Brunzelle, Joseph S; Couture, Jean-François; Agarwal, Pratul K; Doucet, Nicolas

    2016-08-01

    Xylanases catalyze the hydrolysis of xylan, an abundant carbon and energy source with important commercial ramifications. Despite tremendous efforts devoted to the catalytic improvement of xylanases, success remains limited because of our relatively poor understanding of their molecular properties. Previous reports suggested the potential role of atomic-scale residue dynamics in modulating the catalytic activity of GH11 xylanases; however, dynamics in these studies was probed on time scales orders of magnitude faster than the catalytic time frame. Here, we used nuclear magnetic resonance titration and relaxation dispersion experiments ((15)N-CPMG) in combination with X-ray crystallography and computational simulations to probe conformational motions occurring on the catalytically relevant millisecond time frame in xylanase B2 (XlnB2) and its catalytically impaired mutant E87A from Streptomyces lividans 66. Our results show distinct dynamical properties for the apo and ligand-bound states of the enzymes. The apo form of XlnB2 experiences conformational exchange for residues in the fingers and palm regions of the catalytic cleft, while the catalytically impaired E87A variant displays millisecond dynamics only in the fingers, demonstrating the long-range effect of the mutation on flexibility. Ligand binding induces enhanced conformational exchange of residues interacting with the ligand in the fingers and thumb loop regions, emphasizing the potential role of residue motions in the fingers and thumb loop regions for recognition, positioning, processivity, and/or stabilization of ligands in XlnB2. To the best of our knowledge, this work represents the first experimental characterization of millisecond dynamics in a GH11 xylanase family member. These results offer new insights into the potential role of conformational exchange in GH11 enzymes, providing essential dynamic information to help improve protein engineering and design applications. PMID:27387012

  11. Ligand Binding Enhances Millisecond Conformational Exchange in Xylanase B2 from Streptomyces lividans.

    PubMed

    Gagné, Donald; Narayanan, Chitra; Nguyen-Thi, Nhung; Roux, Louise D; Bernard, David N; Brunzelle, Joseph S; Couture, Jean-François; Agarwal, Pratul K; Doucet, Nicolas

    2016-08-01

    Xylanases catalyze the hydrolysis of xylan, an abundant carbon and energy source with important commercial ramifications. Despite tremendous efforts devoted to the catalytic improvement of xylanases, success remains limited because of our relatively poor understanding of their molecular properties. Previous reports suggested the potential role of atomic-scale residue dynamics in modulating the catalytic activity of GH11 xylanases; however, dynamics in these studies was probed on time scales orders of magnitude faster than the catalytic time frame. Here, we used nuclear magnetic resonance titration and relaxation dispersion experiments ((15)N-CPMG) in combination with X-ray crystallography and computational simulations to probe conformational motions occurring on the catalytically relevant millisecond time frame in xylanase B2 (XlnB2) and its catalytically impaired mutant E87A from Streptomyces lividans 66. Our results show distinct dynamical properties for the apo and ligand-bound states of the enzymes. The apo form of XlnB2 experiences conformational exchange for residues in the fingers and palm regions of the catalytic cleft, while the catalytically impaired E87A variant displays millisecond dynamics only in the fingers, demonstrating the long-range effect of the mutation on flexibility. Ligand binding induces enhanced conformational exchange of residues interacting with the ligand in the fingers and thumb loop regions, emphasizing the potential role of residue motions in the fingers and thumb loop regions for recognition, positioning, processivity, and/or stabilization of ligands in XlnB2. To the best of our knowledge, this work represents the first experimental characterization of millisecond dynamics in a GH11 xylanase family member. These results offer new insights into the potential role of conformational exchange in GH11 enzymes, providing essential dynamic information to help improve protein engineering and design applications.

  12. STEM on the radio

    NASA Astrophysics Data System (ADS)

    Showstack, Randy

    2011-10-01

    Looking for an Internet radio station focusing on programing about science, technology, engineering, and math (STEM)? The U.S. National Science Foundation (NSF) announced on 26 September the launch of Science360 Radio, which it says is the first Internet radio stream dedicated to STEM programing. Science360 includes more than 100 radio shows and podcasts that are available on the Web as well as on iPhone and Android devices. The shows originate from a variety of sources, including NSF, other U.S. government agencies, science organizations, universities, and media outlets. For more information, see http://science360.gov/files/.

  13. Radio data transmission for SCADA

    SciTech Connect

    Frasier, W.E. )

    1989-09-01

    Enron has used such wireless systems as meteor burst radio, 952 MHz multiple address radio, VSAT and L-band satellite, cellular radio and ACSB radio. The company's experience with meteor burst radio communications is discussed in this paper. It indicates good system reliability and consequently all back-up telephone lines have been removed from sites using this system.

  14. MULTI-WAVELENGTH OBSERVATIONS OF 3FGL J2039.6–5618: A CANDIDATE REDBACK MILLISECOND PULSAR

    SciTech Connect

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

    2015-12-01

    We present multi-wavelength observations of the unassociated γ-ray source 3FGL J2039.6−5618 detected by the Fermi Large Area Telescope. The source γ-ray properties suggest that it is a pulsar, most likely a millisecond pulsar, for which neither radio nor γ-ray pulsations have been detected. We observed 3FGL J2039.6−5618 with XMM-Newton and discovered several candidate X-ray counterparts within/close to the γ-ray error box. The brightest of these X-ray sources is variable with a period of 0.2245 ± 0.0081 days. Its X-ray spectrum can be described by a power law with photon index Γ{sub X} = 1.36 ± 0.09, and hydrogen column density N{sub H} < 4 × 10{sup 20} cm{sup −2}, which gives an unabsorbed 0.3–10 keV X-ray flux of 1.02 × 10{sup −13} erg cm{sup −2} s{sup −1}. Observations with the Gamma-Ray Burst Optical/Near-Infrared Detector discovered an optical counterpart to this X-ray source, with a time-averaged magnitude g′ ∼ 19.5. The counterpart features a flux modulation with a period of 0.22748 ± 0.00043 days that coincides, within the errors, with that of the X-ray source, confirming the association based on the positional coincidence. We interpret the observed X-ray/optical periodicity as the orbital period of a close binary system where one of the two members is a neutron star. The light curve profile of the companion star, which has two asymmetric peaks, suggests that the optical emission comes from two regions with different temperatures on its tidally distorted surface. Based upon its X-ray and optical properties, we consider this source as the most likely X-ray counterpart to 3FGL J2039.6−5618, which we propose to be a new redback system.

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

    SciTech Connect

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

    2014-08-20

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

  16. Powerful Radio Burst Indicates New Astronomical Phenomenon

    NASA Astrophysics Data System (ADS)

    2007-09-01

    . "It was a bit of luck that the survey included some observations of the sky surrounding the clouds," Narkevic said. It was from those "flanking" observations that the mysterious radio burst appeared in the data. The burst of radio waves was strong by astronomical standards, but lasted less than five milliseconds. The signal was spread out, with higher frequencies arriving at the telescope before the lower frequencies. This effect, called dispersion, is caused by the signal passing through ionized gas in interstellar and intergalactic space. The amount of this dispersion, the astronomers said, indicates that the signal likely originated about three billion light-years from Earth. No previously-detected cosmic radio burst has the same set of characteristics. "This burst represents an entirely new astronomical phenomenon," Bailes said. The astronomers estimate on the basis of their results that hundreds of similar events should occur over the sky each day. "Few radio surveys have the necessary sensitivity to such short-duration bursts, which makes them notoriously difficult to detect with current instruments," added Crawford. The next generation of radio telescopes currently under development should be able to detect many of these bursts across the sky. Although the nature of the mysterious new object is unclear, the astronomers have some ideas of what may cause such a burst. One idea is that it may be part of the energy released when a pair of superdense neutron stars collide and merge. Such an event is thought by some scientists to be the cause of one type of gamma-ray burst, but the only radio emission seen so far from these has been from the long-lived "afterglow" that follows the original burst. Another, more exotic, candidate is a burst of energy from an evaporating black hole. Black holes, concentrations of mass so dense that not even light can escape their powerful gravity, can lose mass and energy through a process proposed by famed British physicist Stephen

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

    NASA Astrophysics Data System (ADS)

    Guver, Tolga; Schwenzer, Kai

    2016-07-01

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

  18. Millisecond laser machining of transparent materials assisted by a nanosecond laser with different delays.

    PubMed

    Pan, Yunxiang; Lv, Xueming; Zhang, Hongchao; Chen, Jun; Han, Bing; Shen, Zhonghua; Lu, Jian; Ni, Xiaowu

    2016-06-15

    A millisecond laser combined with a nanosecond laser was applied to machining transparent materials. The influences of delay between the two laser pulses on processing efficiencies and modified sizes were studied. In addition, a laser-supported combustion wave (LSCW) was captured during laser irradiation. An optimal delay corresponding to the highest processing efficiency was found for cone-shaped cavities. The modified size as well as the lifetime and intensity of the LSCW increased with the delay decreasing. Thermal cooperation effects of defects, overlapping effects of small modified sites, and thermal radiation from LSCW result in all the phenomena. PMID:27304294

  19. Magnetic fields generated by r-modes in accreting millisecond pulsars

    SciTech Connect

    Cuofano, Carmine; Drago, Alessandro

    2010-10-15

    In rotating neutron stars the existence of the Coriolis force allows the presence of the so-called Rossby oscillations (r-modes) which are known to be unstable to emission of gravitational waves. Here, for the first time, we introduce the magnetic damping rate in the evolution equations of r-modes. We show that r-modes can generate very strong toroidal fields in the core of accreting millisecond pulsars by inducing differential rotation. We shortly discuss the instabilities of the generated magnetic field and its long time-scale evolution in order to clarify how the generated magnetic field can stabilize the star.

  20. Twenty-one millisecond pulsars in Terzan 5 using the Green Bank Telescope.

    PubMed

    Ransom, Scott M; Hessels, Jason W T; Stairs, Ingrid H; Freire, Paulo C C; Camilo, Fernando; Kaspi, Victoria M; Kaplan, David L

    2005-02-11

    We have identified 21 millisecond pulsars (MSPs) in globular cluster Terzan 5 by using the Green Bank Telescope, bringing the total of known MSPs in Terzan 5 to 24. These discoveries confirm fundamental predictions of globular cluster and binary system evolution. Thirteen of the new MSPs are in binaries, of which two show eclipses and two have highly eccentric orbits. The relativistic periastron advance for the two eccentric systems indicates that at least one of these pulsars has a mass 1.68 times greater than the mass of the Sun at 95% confidence. Such large neutron star masses constrain the equation of state of matter at or beyond the nuclear equilibrium density.

  1. Millisecond laser machining of transparent materials assisted by a nanosecond laser with different delays.

    PubMed

    Pan, Yunxiang; Lv, Xueming; Zhang, Hongchao; Chen, Jun; Han, Bing; Shen, Zhonghua; Lu, Jian; Ni, Xiaowu

    2016-06-15

    A millisecond laser combined with a nanosecond laser was applied to machining transparent materials. The influences of delay between the two laser pulses on processing efficiencies and modified sizes were studied. In addition, a laser-supported combustion wave (LSCW) was captured during laser irradiation. An optimal delay corresponding to the highest processing efficiency was found for cone-shaped cavities. The modified size as well as the lifetime and intensity of the LSCW increased with the delay decreasing. Thermal cooperation effects of defects, overlapping effects of small modified sites, and thermal radiation from LSCW result in all the phenomena.

  2. Predictions of Gamma-ray Emission from Globular Cluster Millisecond Pulsars Above 100 MeV

    NASA Technical Reports Server (NTRS)

    Venter, C.; de Jaker, O.C.; Clapson, A.C.

    2009-01-01

    The recent Fermi detection of the globular cluster (GC) 47 Tucanae highlighted the importance of modeling collective gamma-ray emission of millisecond pulsars (MSPs) in GCs. Steady flux from such populations is also expected in the very high energy (VHE) domain covered by ground-based Cherenkov telescopes. We present pulsed curvature radiation (CR) as well as unpulsed inverse Compton (IC) calculations for an ensemble of MSPs in the GCs 47 Tucanae and Terzan 5. We demonstrate that the CR from these GCs should be easily detectable for Fermi, while constraints on the total number of MSps and the nebular B-field may be derived using the IC flux components.

  3. Astrometry of the Planetary-System Millisecond Pulsar B1257+12

    NASA Astrophysics Data System (ADS)

    Nunes, N. V.; Bartel, N.

    We present the VLBI determined position of the millisecond pulsar PSR B1257+12 which has been shown to have a planetary system (Wolszczan & Frail 1992). The position determination for epoch June 20, 1992 is: alphaJ2000 = \\ra[13 0 3.05005](5), deltaJ2000 = + \\dec[12 40 56.7043] (34). We indicate how the combination of such pulsar observations along with timing observations can be used to directly tie the solar-system dynamic reference frames and the extragalactic reference frame.

  4. X-ray coherent pulsations during a sub-luminous accretion disc state of the transitional millisecond pulsar XSS J12270-4859

    NASA Astrophysics Data System (ADS)

    Papitto, A.; de Martino, D.; Belloni, T. M.; Burgay, M.; Pellizzoni, A.; Possenti, A.; Torres, D. F.

    2015-04-01

    We present the first detection of X-ray coherent pulsations from the transitional millisecond pulsar XSS J12270-4859, while it was in a sub-luminous accretion disc state characterized by a 0.5-10 keV luminosity of 5 × 1033 erg s-1 (assuming a distance of 1.4 kpc). Pulsations were observed by XMM-Newton at an rms amplitude of (7.7 ± 0.5) per cent with a second harmonic stronger than the fundamental frequency, and were detected when the source is neither flaring nor dipping. The most likely interpretation of this detection is that matter from the accretion disc was channelled by the neutron star magnetosphere and accreted on to its polar caps. According to standard disc accretion theory, for pulsations to be observed the mass inflow rate in the disc was likely larger than the amount of plasma actually reaching the neutron star surface; an outflow launched by the fast rotating magnetosphere then probably took place, in agreement with the observed broad-band spectral energy distribution. We also report about the non-detection of X-ray pulsations during a recent observation performed while the source behaved as a rotationally-powered radio pulsar.

  5. Micro-arcing in radio frequency plasmas

    NASA Astrophysics Data System (ADS)

    Yin, Y.; Bilek, M. M. M.; McKenzie, D. R.; Boswell, R. W.; Charles, C.

    2004-10-01

    Micro-arcing and breakdown of the wall plasma sheath in radio frequency (RF) plasmas is studied in a hollow cathode system, using a Langmuir probe to measure the floating potential. Micro-arcing was induced reproducibly by controlling the floating potential. By dc grounding the hollow cathode, a negative current can flow to ground resulting in a higher voltage sheath between the plasma and the earthed vacuum vessel. The wall arcing threshold of the plasma potential in this system is in the vicinity of 50 V. In the present system, the charging process to rebuild the plasma potential, which is about a few tens of milliseconds, is much slower than the microsecond discharge. The arcing frequency was found to depend strongly on the plasma potential and the pressure. We propose a mechanism for the dependence of the frequency of periodic micro-arcing based on the development of electron field emission sites. The measurement of floating potential is suggested as a useful parameter to monitor and prevent micro-arcing in RF plasmas.

  6. A population of fast radio bursts at cosmological distances.

    PubMed

    Thornton, D; Stappers, B; Bailes, M; Barsdell, B; Bates, S; Bhat, N D R; Burgay, M; Burke-Spolaor, S; Champion, D J; Coster, P; D'Amico, N; Jameson, A; Johnston, S; Keith, M; Kramer, M; Levin, L; Milia, S; Ng, C; Possenti, A; van Straten, W

    2013-07-01

    Searches for transient astrophysical sources often reveal unexpected classes of objects that are useful physical laboratories. In a recent survey for pulsars and fast transients, we have uncovered four millisecond-duration radio transients all more than 40° from the Galactic plane. The bursts' properties indicate that they are of celestial rather than terrestrial origin. Host galaxy and intergalactic medium models suggest that they have cosmological redshifts of 0.5 to 1 and distances of up to 3 gigaparsecs. No temporally coincident x- or gamma-ray signature was identified in association with the bursts. Characterization of the source population and identification of host galaxies offers an opportunity to determine the baryonic content of the universe.

  7. Transcontinental baselines and the rotation of the Earth measured by radio interferometry.

    PubMed

    Shapiro, I I; Robertson, D S; Knight, C A; Counselman, C C; Rogers, A E; Hinteregger, H F; Lippincott, S; Whitney, A R; Clark, T A; Niell, A E; Spitzmesser, D J

    1974-12-01

    Nine separate very-long-baseline interferometry (VLBI) experiments, carried out in 1972 and 1973 with radio telescopes 3900 kilometers apart, yielded values for the baseline length with a root-mean-square deviation about the mean of less than 20 centitneters. The corresponding fractional spread is about five parts in 10(8). Changes in universal time and in polar motion were also detertnined accurately from these data; the root-mean-square scatter of these results with respect to those based on optical methods were 2.9 milliseconds and 1.3 meters, respectively. Solid-earth tides were apparently detected, but no useful estimate of their amplituide was extracted.

  8. Characteristics of radio-frequency atmospheric pressure dielectric-barrier discharge with dielectric electrodes

    SciTech Connect

    Hussain, S. E-mail: shussainuos@yahoo.com; Qazi, H. I. A.; Badar, M. A.

    2014-03-15

    An experimental investigation to characterize the properties and highlight the benefits of atmospheric pressure radio-frequency dielectric-barrier discharge (rf DBD) with dielectric electrodes fabricated by anodizing aluminium substrate is presented. The current-voltage characteristics and millisecond images are used to distinguish the α and γ modes. This atmospheric rf DBD is observed to retain the discharge volume without constriction in γ mode. Optical emission spectroscopy demonstrates that the large discharge current leads to more abundant reactive species in this plasma source.

  9. The Radio Jove Project

    NASA Technical Reports Server (NTRS)

    Thieman, J. R.

    2010-01-01

    The Radio love Project is a hands-on education and outreach project in which students, or any other interested individuals or groups build a radio telescope from a kit, operate the radio telescope, transmit the resulting signals through the internet if desired, analyze the results, and share the results with others through archives or general discussions among the observers. Radio love is intended to provide an introduction to radio astronomy for the observer. The equipment allows the user to observe radio signals from Jupiter, the Sun, the galaxy, and Earth-based radiation both natural and man-made. The project was started through a NASA Director's Discretionary Fund grant more than ten years ago. it has continued to be carried out through the dedicated efforts of a group of mainly volunteers. Dearly 1500 kits have been distributed throughout the world. Participation can also be done without building a kit. Pre-built kits are available. Users can also monitor remote radio telescopes through the internet using free downloadable software available through the radiosky.com website. There have been many stories of prize-winning projects, inspirational results, collaborative efforts, etc. We continue to build the community of observers and are always open to new thoughts about how to inspire the observers to still greater involvement in the science and technology associated with Radio Jove.

  10. Film, Radio, and Television.

    ERIC Educational Resources Information Center

    Hardesty, Carolyn, Ed.

    1990-01-01

    This journal issue covers the history of film, radio, and television in Iowa. The first article, "When Pictures and Sound Came to Iowa," summarizes the origin of movies and radio and their early beginnings in Iowa. Using old photographs and measurement charts, the viewing, reading, and listening habits of young people in 1950 and 1958 are…

  11. Writing for Radio.

    ERIC Educational Resources Information Center

    Tupper, Marianna S.

    1995-01-01

    Describes a 24-hour commercial radio station simulation class project for eighth-grade language arts. Students wrote their own scripts, chose music and were disc jockeys on their own music and talk shows, and prepared news and traffic reports. Guest speakers from actual commercial radio came in to discuss issues such as advertising, censorship,…

  12. Frequencies for radio astronomy.

    PubMed

    Smith, F G

    1970-10-31

    At present the scope of research in radio astronomy is limited by the allocation of frequencies, some of which have to be shared with other radio services. When the International Telecommunications Union reconsiders all frequency allocations next year, astronomers are hoping for an improvement.

  13. Stabilized radio frequency quadrupole

    DOEpatents

    Lancaster, H.D.; Fugitt, J.A.; Howard, D.R.

    1984-12-25

    Disclosed is a long-vane stabilized radio frequency resonator for accelerating charged particles and including means defining a radio frequency resonator cavity, a plurality of long vanes mounted in the defining means for dividing the cavity into sections, and means interconnecting opposing ones of the plurality of vanes for stabilizing the resonator. 5 figs.

  14. Stabilized radio frequency quadrupole

    DOEpatents

    Lancaster, Henry D.; Fugitt, Jock A.; Howard, Donald R.

    1984-01-01

    A long-vane stabilized radio frequency resonator for accelerating charged particles and including means defining a radio frequency resonator cavity, a plurality of long vanes mounted in the defining means for dividing the cavity into sections, and means interconnecting opposing ones of the plurality of vanes for stabilizing the resonator.

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

    NASA Astrophysics Data System (ADS)

    Liu, Wei-Min; Chen, Wen-Cong

    2011-09-01

    The recycling model suggested that low-mass X-ray binaries (LMXBs) could evolve into binary millisecond pulsars (BMSPs). In this work, we attempt to investigate the progenitor properties of BMSPs formed by the recycling evolutionary channel, and if submillisecond pulsars can be produced by this channel. Using Eggleton's stellar evolution code, considering that the dead pulsars can be spun up to a short spin period by the accreting material and angular momentum from the donor star, we have calculated the evolution of close binaries consisting of a neutron star (NS) and a low-mass main-sequence donor star, and the spin evolution of NSs. In the calculation, some physical processes, such as the thermal and viscous instability of an accretion disc, propeller effect and magnetic braking, are included. Our calculated results indicate that all LMXBs with a low-mass donor star of 1.0-2.0 M⊙ and a short orbital period (≲ 3-4 d) can form millisecond pulsars with a spin period less than 10 ms. However, it is difficult to produce submillisecond pulsars by this evolutionary channel. In addition, our evolutionary scenario cannot account for the existence of BMSPs with a long orbital period (Porb≳ 70-80 d).

  16. Reengineering Rate-Limiting, Millisecond Enzyme Motions by Introduction of an Unnatural Amino Acid

    PubMed Central

    Watt, Eric D.; Rivalta, Ivan; Whittier, Sean K.; Batista, Victor S.; Loria, J. Patrick

    2011-01-01

    Rate-limiting millisecond motions in wild-type (WT) Ribonuclease A (RNase A) are modulated by histidine 48. Here, we incorporate an unnatural amino acid, thia-methylimidazole, at this site (H48C-4MI) to investigate the effects of a single residue on protein motions over multiple timescales and on enzyme catalytic turnover. Molecular dynamics simulations reveal that H48C-4MI retains some crucial WT-like hydrogen bonding interactions but the extent of protein-wide correlated motions in the nanosecond regime is decreased relative to WT. NMR Carr-Purcell-Meiboom-Gill relaxation dispersion experiments demonstrate that millisecond conformational motions in H48C-4MI are present over a similar pH range compared to WT. Furthermore, incorporation of this nonnatural amino acid allows retention of WT-like catalytic activity over the full pH range. These studies demonstrate that the complexity of the protein energy landscape during the catalytic cycle can be maintained using unnatural amino acids, which may prove useful in enzyme design efforts. PMID:21767494

  17. Active Learning Approaches by Visualizing ICT Devices with Milliseconds Resolution for Deeper Understanding in Physics

    NASA Astrophysics Data System (ADS)

    Kobayashi, Akizo; Okiharu, Fumiko

    2010-07-01

    We are developing various modularized materials in physics education to overcome students' misconceptions by use of ICT, i.e. video analysis software and ultra-high-speed digital movies, motion detector, force sensors, current and voltage probes, temperature sensors etc. Furthermore, we also present some new modules of active learning approaches on electric circuit using high speed camera and voltage probes with milliseconds resolution. We are now especially trying to improve conceptual understanding by use of ICT devices with milliseconds resolution in various areas of physics education We give some modules of mass measurements by video analysis of collision phenomena by using high speed cameras—Casio EX-F1(1200 fps), EX-FH20(1000 fps) and EX-FC100/150(1000 fps). We present several new modules on collision phenomena to establish deeper understanding of conservation laws of momentum. We discuss some effective results of trial on a physics education training courses for science educators, and those for science teachers during the renewal years of teacher's license after every ten years in Japan. Finally, we discuss on some typical results of pre-test and post-test in our active learning approaches based on ICT, i.e. some evidence on improvements of physics education (increasing ratio of correct answer are 50%-level).

  18. Strong Support for the Millisecond Pulsar Origin of the Galactic Center GeV Excess.

    PubMed

    Bartels, Richard; Krishnamurthy, Suraj; Weniger, Christoph

    2016-02-01

    Using γ-ray data from the Fermi Large Area Telescope, various groups have identified a clear excess emission in the Inner Galaxy, at energies around a few GeV. This excess resembles remarkably well a signal from dark-matter annihilation. One of the most compelling astrophysical interpretations is that the excess is caused by the combined effect of a previously undetected population of dim γ-ray sources. Because of their spectral similarity, the best candidates are millisecond pulsars. Here, we search for this hypothetical source population, using a novel approach based on wavelet decomposition of the γ-ray sky and the statistics of Gaussian random fields. Using almost seven years of Fermi-LAT data, we detect a clustering of photons as predicted for the hypothetical population of millisecond pulsar, with a statistical significance of 10.0σ. For plausible values of the luminosity function, this population explains 100% of the observed excess emission. We argue that other extragalactic or Galactic sources, a mismodeling of Galactic diffuse emission, or the thick-disk population of pulsars are unlikely to account for this observation.

  19. Strong Support for the Millisecond Pulsar Origin of the Galactic Center GeV Excess.

    PubMed

    Bartels, Richard; Krishnamurthy, Suraj; Weniger, Christoph

    2016-02-01

    Using γ-ray data from the Fermi Large Area Telescope, various groups have identified a clear excess emission in the Inner Galaxy, at energies around a few GeV. This excess resembles remarkably well a signal from dark-matter annihilation. One of the most compelling astrophysical interpretations is that the excess is caused by the combined effect of a previously undetected population of dim γ-ray sources. Because of their spectral similarity, the best candidates are millisecond pulsars. Here, we search for this hypothetical source population, using a novel approach based on wavelet decomposition of the γ-ray sky and the statistics of Gaussian random fields. Using almost seven years of Fermi-LAT data, we detect a clustering of photons as predicted for the hypothetical population of millisecond pulsar, with a statistical significance of 10.0σ. For plausible values of the luminosity function, this population explains 100% of the observed excess emission. We argue that other extragalactic or Galactic sources, a mismodeling of Galactic diffuse emission, or the thick-disk population of pulsars are unlikely to account for this observation. PMID:26894696

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  1. Reverse shock emission driven by post-merger millisecond magnetar winds: Effects of the magnetization parameter

    NASA Astrophysics Data System (ADS)

    Liu, L. D.; Wang, L. J.; Dai, Z. G.

    2016-08-01

    The study of short-duration gamma-ray bursts provides growing evidence that a good fraction of double neutron star mergers lead to the formation of stable millisecond magnetars. The launch of Poynting flux by the millisecond magnetars could leave distinct electromagnetic signatures that reveal the energy dissipation processes in the magnetar wind. In previous studies, we assume that the magnetar wind becomes completely lepton-dominated so that electrons/positrons in the magnetar wind are accelerated by a diffusive shock. However, theoretical modeling of pulsar wind nebulae shows that in many cases the magnetic field energy in the pulsar wind may be strong enough to suppress diffusive shock acceleration. In this paper, we investigate the reverse shock emission and the forward shock emission with an arbitrary magnetization parameter σ of a magnetar wind. We find that the reverse shock emission strongly depends on σ, and in particular that σ ~ 0.3 leads to the strongest reverse shock emission. Future observations would be helpful to diagnose the composition of the magnetar wind.

  2. Songbird Respiration is Controlled by Multispike Patterns at Millisecond Temporal Resolution

    NASA Astrophysics Data System (ADS)

    Holmes, Caroline; Srivastava, Kyle; Vellema, Michiel; Elemans, Coen; Nemenman, Ilya; Sober, Samuel

    Although the importance of precise timing of neural action potentials (spikes) is well known in sensory systems, approaches to motor control have focused almost exclusively on firing rates. Here we examined whether precise timing of spikes in multispike patterns has an effect on the motor output in the respiratory system of the Bengalese finch, a songbird. By recording from single motor neurons and the muscle fibers they innervate in freely behaving birds, we find that the spike trains are significantly non-Poisson, suggesting that the precise timing of spikes is tightly controlled. We further find that even a one millisecond shift of an individual spike in a multispike pattern predicts a significantly different air sac pressure. Finally, we provide evidence for the causal relation between precise spike timing and the motor output in this organism by stimulating the motor system with precisely timed patterns of electrical impulses. We observe that shifting a single pulse by as little as two milliseconds elicits differences in resulting air sac pressure. These results demonstrate that the precise timing of spikes does play a role in motor control. This work was partially supported by NSF Grant IOS/1208126, NIH Grant 5R90DA033462 , NIH Grant R01NS084844, and NIH Grant F31DC013753.

  3. Numerical and experimental study of the thermal stress of silicon induced by a millisecond laser

    SciTech Connect

    Wang Xi; Qin Yuan; Wang Bin; Zhang Liang; Shen Zhonghua; Lu Jian; Ni Xiaowu

    2011-07-20

    A spatial axisymmetric finite element model of single-crystal silicon irradiated by a 1064 nm millisecond laser is used to investigate the thermal stress damage induced by a millisecond laser. The transient temperature field and the thermal stress field for 2 ms laser irradiation with a laser fluence of 254 J/cm{sup 2} are obtained. The numerical simulation results indicate that the hoop stresses along the r axis on the front surface are compressive stress within the laser spot and convert to tensile stress outside the laser spot, while the radial stresses along the r axis on the front surface and on the z axis are compressive stress. The temperature of the irradiated center is the highest temperature obtained, yet the stress is not always highest during laser irradiation. At the end of the laser irradiation, the maximal hoop stress is located at r=0.5 mm and the maximal radial stress is located at r=0.76 mm. The temperature measurement experiments are performed by IR pyrometer. The numerical result of the temperature field is consistent with the experimental result. The damage morphologies of silicon under the action of a 254 J/cm{sup 2} laser are inspected by optical microscope. The cracks are observed initiating at r=0.5 mm and extending along the radial direction.

  4. Numerical and experimental study of the thermal stress of silicon induced by a millisecond laser.

    PubMed

    Wang, Xi; Qin, Yuan; Wang, Bin; Zhang, Liang; Shen, Zhonghua; Lu, Jian; Ni, Xiaowu

    2011-07-20

    A spatial axisymmetric finite element model of single-crystal silicon irradiated by a 1064 nm millisecond laser is used to investigate the thermal stress damage induced by a millisecond laser. The transient temperature field and the thermal stress field for 2 ms laser irradiation with a laser fluence of 254 J/cm(2) are obtained. The numerical simulation results indicate that the hoop stresses along the r axis on the front surface are compressive stress within the laser spot and convert to tensile stress outside the laser spot, while the radial stresses along the r axis on the front surface and on the z axis are compressive stress. The temperature of the irradiated center is the highest temperature obtained, yet the stress is not always highest during laser irradiation. At the end of the laser irradiation, the maximal hoop stress is located at r=0.5 mm and the maximal radial stress is located at r=0.76 mm. The temperature measurement experiments are performed by IR pyrometer. The numerical result of the temperature field is consistent with the experimental result. The damage morphologies of silicon under the action of a 254 J/cm(2) laser are inspected by optical microscope. The cracks are observed initiating at r=0.5 mm and extending along the radial direction. PMID:21772353

  5. Millisecond direct measurement of the magnetocaloric effect of a Fe2P-based compound by the mirage effect

    NASA Astrophysics Data System (ADS)

    Cugini, F.; Porcari, G.; Viappiani, C.; Caron, L.; dos Santos, A. O.; Cardoso, L. P.; Passamani, E. C.; Proveti, J. R. C.; Gama, S.; Brück, E.; Solzi, M.

    2016-01-01

    We present direct measurements of the magnetocaloric effect on a Fe2P-based compound induced by a milliseconds pulsed magnetic field of 1 T to test their possible use in high frequency (up to 100 Hz) thermomagnetic cycles. The reported measurements were performed with an innovative and versatile non-contact set up based on the mirage effect. The adiabatic temperature change of a MnFeP0.45As0.55 sample is presented and compared with measurements performed varying the same magnetic field in a time interval of 1 s and 100 ms. These results demonstrate the absence of kinetic constraints in the first-order phase transition of this sample induced on the milliseconds time scale. The study of the materials' response to millisecond magnetic field pulses represents a fundamental test for the development of more powerful and efficient magnetic refrigerators.

  6. Radio efficiency of pulsars

    SciTech Connect

    Szary, Andrzej; Melikidze, George I.; Gil, Janusz; Zhang, Bing; Xu, Ren-Xin E-mail: zhang@physics.unlv.edu

    2014-03-20

    We investigate radio emission efficiency, ξ, of pulsars and report a near-linear inverse correlation between ξ and the spin-down power, E-dot , as well as a near-linear correlation between ξ and pulsar age, τ. This is a consequence of very weak, if any, dependences of radio luminosity, L, on pulsar period, P, and the period derivative, P-dot , in contrast to X-ray or γ-ray emission luminosities. The analysis of radio fluxes suggests that these correlations are not due to a selection effect, but are intrinsic to the pulsar radio emission physics. We have found that, although with a large variance, the radio luminosity of pulsars is ≈10{sup 29} erg s{sup –1}, regardless of the position in the P-- P-dot diagram. Within such a picture, a model-independent statement can be made that the death line of radio pulsars corresponds to an upper limit in the efficiency of radio emission. If we introduce the maximum value for radio efficiency into the Monte Carlo-based population syntheses we can reproduce the observed sample using the random luminosity model. Using the Kolmogorov-Smirnov test on a synthetic flux distribution reveals a high probability of reproducing the observed distribution. Our results suggest that the plasma responsible for generating radio emission is produced under similar conditions regardless of pulsar age, dipolar magnetic field strength, and spin-down rate. The magnetic fields near the pulsar surface are likely dominated by crust-anchored, magnetic anomalies, which do not significantly differ among pulsars, leading to similar conditions for generating electron-positron pairs necessary to power radio emission.

  7. ORIGIN OF INTERMITTENT ACCRETION-POWERED X-RAY OSCILLATIONS IN NEUTRON STARS WITH MILLISECOND SPIN PERIODS

    SciTech Connect

    Lamb, Frederick K.; Boutloukos, Stratos; Van Wassenhove, Sandor; Chamberlain, Robert T.; Lo, Ka Ho; Coleman Miller, M.

    2009-11-01

    We have shown previously that many of the properties of persistent accretion-powered millisecond pulsars can be understood if their X-ray emitting areas are near their spin axes and move as the accretion rate and structure of the inner disk vary. Here, we show that this 'nearly aligned moving spot model' may also explain the intermittent accretion-powered pulsations that have been detected in three weakly magnetic accreting neutron stars. We show that movement of the emitting area from very close to the spin axis to approx10 deg. away can increase the fractional rms amplitude from approx<0.5%, which is usually undetectable with current instruments, to a few percent, which is easily detectable. The second harmonic of the spin frequency usually would not be detected, in agreement with observations. The model produces intermittently detectable oscillations for a range of emitting area sizes and beaming patterns, stellar masses and radii, and viewing directions. Intermittent oscillations are more likely in stars that are more compact. In addition to explaining the sudden appearance of accretion-powered millisecond oscillations in some neutron stars with millisecond spin periods, the model explains why accretion-powered millisecond oscillations are relatively rare and predicts that the persistent accretion-powered millisecond oscillations of other stars may become undetectable for brief intervals. It suggests why millisecond oscillations are frequently detected during the X-ray bursts of some neutron stars but not others and suggests mechanisms that could explain the occasional temporal association of intermittent accretion-powered oscillations with thermonuclear X-ray bursts.

  8. Radio broadcasting via satellite

    NASA Astrophysics Data System (ADS)

    Helm, Neil R.; Pritchard, Wilbur L.

    1990-10-01

    Market areas offering potential for future narrowband broadcast satellites are examined, including international public diplomacy, government- and advertising-supported, and business-application usages. Technical issues such as frequency allocation, spacecraft types, transmission parameters, and radio receiver characteristics are outlined. Service and system requirements, advertising revenue, and business communications services are among the economic issues discussed. The institutional framework required to provide an operational radio broadcast service is studied, and new initiatives in direct broadcast audio radio systems, encompassing studies, tests, in-orbit demonstrations of, and proposals for national and international commercial broadcast services are considered.

  9. Millisecond autothermal catalytic reforming of carbohydrates for synthetic fuels by reactive flash volatilization

    NASA Astrophysics Data System (ADS)

    Dauenhauer, Paul Jakob

    Carbohydrates including glucose, cellulose, starch and polyols including glycerol, ethylene glycol and methanol produced in large quantities from biomass are considered as a carbon-based feedstock for high temperature catalytic reforming by catalytic partial oxidation. Autothermal catalytic partial oxidation of methanol, ethylene glycol, and glycerol with Rh and Pt-based catalysts with ceria on alumina foam supports at residence times less than ten milliseconds produced equilibrium selectivity to synthesis gas. The addition of steam at S/C>4 produced selectivity to H2 higher than 80% with little or no selectivity to minor products. In a new process referred to as 'reactive flash volatilization,' catalytic partial oxidation was combined with pyrolysis of biomass by directly impinging particles of cellulose, starch, polyethylene, soy oil, or Aspen (Populous Tremuloides) on an operating Rh-based reforming catalyst at 700-800°C. Solid particles endothermically pyrolyzed to volatile organic compounds which mixed with air and reformed on the catalyst exothermically generating heat to drive the overall process. Particles of ˜250 mum microcrystalline cellulose processed at the conditions of C/O=1.0 on a RhCe/gamma-Al2O3/alpha-Al 2O3 at a residence time of ˜70 milliseconds produced a gaseous effluent stream selecting for 50% H2 and 50% CO with no observable side products other than H2O and CO2, and <1% CH4. To obtain a more optimal synthesis gas stream, the reforming of ˜400 mum microcrystalline particles was examined over a fixed bed of RhCe/gamma-Al2O3/alpha-Al2O 3 spheres by varying the feed ratio of N2/O2, the temperature of the feed gas, the total particle feed rate, and the addition of steam permitting cellulose conversion with ˜75% fuel efficiency. Cellulose, sucrose, and glycerol particle conversion was examined with high-speed photography (1000 frames/second) revealing the formation of a liquid intermediate from cellulose permitting extremely high heat flux (

  10. A theory for narrow-banded radio bursts at Uranus - MHD surface waves as an energy driver

    NASA Technical Reports Server (NTRS)

    Farrell, W. M.; Curtis, S. A.; Desch, M. D.; Lepping, R. P.

    1992-01-01

    A possible scenario for the generation of the narrow-banded radio bursts detected at Uranus by the Voyager 2 planetary radio astronomy experiment is described. In order to account for the emission burstiness which occurs on time scales of hundreds of milliseconds, it is proposed that ULF magnetic surface turbulence generated at the frontside magnetopause propagates down the open/closed field line boundary and mode-converts to kinetic Alfven waves (KAW) deep within the polar cusp. The oscillating KAW potentials then drive a transient electron stream that creates the bursty radio emission. To substantiate these ideas, Voyager 2 magnetometer measurements of enhanced ULF magnetic activity at the frontside magnetopause are shown. It is demonstrated analytically that such magnetic turbulence should mode-convert deep in the cusp at a radial distance of 3 RU.

  11. The VLBA Fast Radio Transient Experiment: Progress and Early Results

    NASA Astrophysics Data System (ADS)

    Wayth, Randall B.; Brisken, Walter F.; Deller, Adam T.; Majid, Walid A.; Thompson, David R.; Tingay, Steven J.; Wagstaff, Kiri L.

    2012-04-01

    Motivated by recent discoveries of isolated, dispersed radio pulses of possible extragalactic origin, we are performing a commensal search for short-duration (ms) continuum radio pulses using the Very Long Baseline Array (VLBA). The geographically separated antennæ of the VLBA make the system robust to local RFI and allow events to be verified and localised on the sky with milli-arcsec accuracy. We report sky coverage and detection limits from the experiment to date.

  12. Eratosthenes via Ham Radio

    ERIC Educational Resources Information Center

    Koser, John F.

    1975-01-01

    A secondary geology class used Eratosthenes' method for measuring the circumference of the earth by comparing their measurements of the shadow of a vertical rod to the measurements made by another person contacted by ham radio. (MLH)

  13. The Sardinia Radio Telescope

    NASA Astrophysics Data System (ADS)

    D'Amico, Nichi

    2011-08-01

    We present the status of the Sardinia Radio Telescope (SRT) project, a new general purpose, fully steerable 64 m diameter parabolic radio telescope under construction in Sardinia. The instrument is funded by Italian Ministry of University and Research (MIUR), by the Sardinia Regional Government (RAS), and by the Italian Space Agency (ASI), and it is charge to three research structures of the National Institute for Astrophysics (INAF): the Institute of Radio Astronomy of Bologna, the Cagliari Astronomical Observatory (in Sardinia), and the Arcetri Astrophysical Observatory in Florence. The radio telescope has a shaped Gregorian optical configuration with a 8 m diameter secondary mirror and additional Beam-Wave Guide (BWG) mirrors. One of the most challenging feature of SRT is the active surface of the primary reflector which provides good efficiency up to about 100 GHz. This paper reports on the most recent advances of the construction.

  14. Mechanical crack propagation drives millisecond daughter cell separation in Staphylococcus aureus

    PubMed Central

    Zhou, Xiaoxue; Halladin, David K.; Rojas, Enrique R.; Koslover, Elena F.; Lee, Timothy K.; Huang, Kerwyn Casey; Theriot, Julie A.

    2016-01-01

    When Staphylococcus aureus undergoes cytokinesis, it builds a septum generating two hemispherical daughters whose cell walls are only connected via a narrow peripheral ring. We found that resolution of this ring occurred within milliseconds (“popping”), without detectable changes in cell volume. The likelihood of popping depended on cell wall stress, and the separating cells split open asymmetrically leaving the daughters connected by a hinge. An elastostatic model of the wall indicated high circumferential stress in the peripheral ring before popping. Finally, we observed small perforations in the peripheral ring that are likely initial points of mechanical failure. Thus, the ultrafast daughter cell separation in S. aureus appears to be driven by accumulation of stress in the peripheral ring, and exhibits hallmarks of mechanical crack propagation. PMID:25931560

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

    NASA Astrophysics Data System (ADS)

    Campana, S.; Ferrari, N.; Stella, L.; Israel, G. L.

    2005-05-01

    We report on XMM-Newton observations of two X-ray transient millisecond pulsars (XRTMSPs). We detected XTE J0929-314 with an unabsorbed luminosity of ˜ 7× 1031 erg s-1 (0.5-10 keV) at a fiducial distance of 10 kpc. The quiescent spectrum is consistent with a simple power law spectrum. The upper limit on the flux from a cooling neutron star atmosphere is about 20% of the total flux. XTE J1807-294 instead was not detected. We can put an upper limit on the source quiescent 0.5-10 keV unabsorbed luminosity ⪉ 4×1031 erg s-1 at 8 kpc. These observations strenghten the idea that XRTMSPs have quiescent luminosities significantly lower than classical neutron star transients.

  16. Characterizing millisecond intermediates in hemoproteins using rapid-freeze-quenched resonance Raman spectroscopy

    PubMed Central

    Matsumura, Hirotoshi; Moënne-Loccoz, Pierre

    2014-01-01

    Summary The combination of rapid-freeze-quenching (RFQ) technique and resonance Raman (RR) spectroscopy represents a unique tool to investigate the nature of short-lived intermediates formed during the enzymatic reaction of metalloproteins. Commercially available equipment allows trapping of intermediates within the millisecond to second timescale for low-temperature RR analysis and direct detection of metal-ligand vibrations and porphyrin skeletal vibrations in hemoproteins. This chapter briefly discusses previous RFQ-RR studies carried-out in our laboratory, and presents as a practical example protocols for the preparation of RFQ samples of the reaction of metmyoglobin with nitric oxide (NO) which requires anaerobic conditions. We also describe important controls and practical procedure for the analysis of these samples by low-temperature RR spectroscopy. PMID:24639256

  17. Twenty-one millisecond pulsars in Terzan 5 using the Green Bank Telescope.

    PubMed

    Ransom, Scott M; Hessels, Jason W T; Stairs, Ingrid H; Freire, Paulo C C; Camilo, Fernando; Kaspi, Victoria M; Kaplan, David L

    2005-02-11

    We have identified 21 millisecond pulsars (MSPs) in globular cluster Terzan 5 by using the Green Bank Telescope, bringing the total of known MSPs in Terzan 5 to 24. These discoveries confirm fundamental predictions of globular cluster and binary system evolution. Thirteen of the new MSPs are in binaries, of which two show eclipses and two have highly eccentric orbits. The relativistic periastron advance for the two eccentric systems indicates that at least one of these pulsars has a mass 1.68 times greater than the mass of the Sun at 95% confidence. Such large neutron star masses constrain the equation of state of matter at or beyond the nuclear equilibrium density. PMID:15653465

  18. Sub-millisecond Transient Absorption Frequency Comb Spectroscopy in the Mid-Infrared Spectral Region

    NASA Astrophysics Data System (ADS)

    Bjork, Bryce; Fleisher, Adam; Bui, Thinh; Cossel, Kevin; Okumura, Mitchio; Ye, Jun

    2013-05-01

    The study of highly-reactive transient reaction intermediates is fundamental to understanding chemical dynamics and is particularly relevant to applications such as atmospheric chemistry. Their study often poses a significant challenge for traditional spectrometers, which typically provide broad bandwidth or fast temporal resolution, but not both without long acquisition times. We introduce a cavity-enhanced frequency-comb solution that allows for high-resolution, sensitive spectra to be captured at millisecond intervals in the mid-infrared spectral region using a VIPA dispersive etalon. Once individual comb teeth are resolved, the spectral resolution of the system is limited by the comb linewidth (<40 kHz) while the temporal resolution is limited by the minimum integration time of the InSb detector array (10 μs). In this presentation, I will present the application of this real-time spectroscopic system to small molecule photodissociation.

  19. Scanning transmission electron microscopy strain measurement from millisecond frames of a direct electron charge coupled device

    SciTech Connect

    Mueller, Knut; Rosenauer, Andreas; Ryll, Henning; Ordavo, Ivan; Ihle, Sebastian; Soltau, Heike; Strueder, Lothar; Volz, Kerstin; Zweck, Josef

    2012-11-19

    A high-speed direct electron detection system is introduced to the field of transmission electron microscopy and applied to strain measurements in semiconductor nanostructures. In particular, a focused electron probe with a diameter of 0.5 nm was scanned over a fourfold quantum layer stack with alternating compressive and tensile strain and diffracted discs have been recorded on a scintillator-free direct electron detector with a frame time of 1 ms. We show that the applied algorithms can accurately detect Bragg beam positions despite a significant point spread each 300 kV electron causes during detection on the scintillator-free camera. For millisecond exposures, we find that strain can be measured with a precision of 1.3 Multiplication-Sign 10{sup -3}, enabling, e.g., strain mapping in a 100 Multiplication-Sign 100 nm{sup 2} region with 0.5 nm resolution in 40 s.

  20. Millisecond precision psychological research in a world of commodity computers: new hardware, new problems?

    PubMed

    Plant, Richard R; Turner, Garry

    2009-08-01

    Since the publication of Plant, Hammond, and Turner (2004), which highlighted a pressing need for researchers to pay more attention to sources of error in computer-based experiments, the landscape has undoubtedly changed, but not necessarily for the better. Readily available hardware has improved in terms of raw speed; multi core processors abound; graphics cards now have hundreds of megabytes of RAM; main memory is measured in gigabytes; drive space is measured in terabytes; ever larger thin film transistor displays capable of single-digit response times, together with newer Digital Light Processing multimedia projectors, enable much greater graphic complexity; and new 64-bit operating systems, such as Microsoft Vista, are now commonplace. However, have millisecond-accurate presentation and response timing improved, and will they ever be available in commodity computers and peripherals? In the present article, we used a Black Box ToolKit to measure the variability in timing characteristics of hardware used commonly in psychological research.

  1. IDENTIFICATION OF THE OPTICAL COUNTERPART OF FERMI BLACK WIDOW MILLISECOND PULSAR PSR J1544+4937

    SciTech Connect

    Tang, Sumin; Phinney, E. Sterl; Prince, Thomas A.; Bellm, Eric; Cao, Yi; Perley, Daniel A.; Kaplan, David L.; Breton, Rene P.; Bildsten, Lars; Kong, Albert K. H.; Yen, T.-C.; Sesar, Branimir; Wolf, William M.

    2014-08-10

    We report the optical identification of the companion to the Fermi black widow millisecond pulsar PSR J1544+4937. We find a highly variable source on Keck Low Resolution Imaging Spectrometer images at the nominal pulsar position, with 2 mag variations over orbital period in the B, g, R, and I bands. The nearly achromatic light curves are difficult to explain with a simply irradiated hemisphere model, and suggest that the optical emission is dominated by a nearly isothermal hot patch on the surface of the companion facing the pulsar. We roughly constrain the distance to PSR J1544+4937 to be between 2 and 5 kpc. A more reliable distance measurement is needed in order to constrain the composition of the companion.

  2. Searches for millisecond pulsations in low-mass X-ray binaries

    NASA Technical Reports Server (NTRS)

    Wood, K. S.; Hertz, P.; Norris, J. P.; Vaughan, B. A.; Michelson, P. F.; Mitsuda, K.; Lewin, W. H. G.; Van Paradijs, J.; Penninx, W.; Van Der Klis, M.

    1991-01-01

    High-sensitivity search techniques for millisecond periods are presented and applied to data from the Japanese satellite Ginga and HEAO 1. The search is optimized for pulsed signals whose period, drift rate, and amplitude conform with what is expected for low-class X-ray binary (LMXB) sources. Consideration is given to how the current understanding of LMXBs guides the search strategy and sets these parameter limits. An optimized one-parameter coherence recovery technique (CRT) developed for recovery of phase coherence is presented. This technique provides a large increase in sensitivity over the method of incoherent summation of Fourier power spectra. The range of spin periods expected from LMXB phenomenology is discussed, the necessary constraints on the application of CRT are described in terms of integration time and orbital parameters, and the residual power unrecovered by the quadratic approximation for realistic cases is estimated.

  3. Scanning transmission electron microscopy strain measurement from millisecond frames of a direct electron charge coupled device

    NASA Astrophysics Data System (ADS)

    Müller, Knut; Ryll, Henning; Ordavo, Ivan; Ihle, Sebastian; Strüder, Lothar; Volz, Kerstin; Zweck, Josef; Soltau, Heike; Rosenauer, Andreas

    2012-11-01

    A high-speed direct electron detection system is introduced to the field of transmission electron microscopy and applied to strain measurements in semiconductor nanostructures. In particular, a focused electron probe with a diameter of 0.5 nm was scanned over a fourfold quantum layer stack with alternating compressive and tensile strain and diffracted discs have been recorded on a scintillator-free direct electron detector with a frame time of 1 ms. We show that the applied algorithms can accurately detect Bragg beam positions despite a significant point spread each 300 kV electron causes during detection on the scintillator-free camera. For millisecond exposures, we find that strain can be measured with a precision of 1.3 × 10-3, enabling, e.g., strain mapping in a 100×100 nm2 region with 0.5 nm resolution in 40 s.

  4. Sub-millisecond closed-loop feedback stimulation between arbitrary sets of individual neurons

    PubMed Central

    Müller, Jan; Bakkum, Douglas J.; Hierlemann, Andreas

    2012-01-01

    We present a system to artificially correlate the spike timing between sets of arbitrary neurons that were interfaced to a complementary metal–oxide–semiconductor (CMOS) high-density microelectrode array (MEA). The system features a novel reprogrammable and flexible event engine unit to detect arbitrary spatio-temporal patterns of recorded action potentials and is capable of delivering sub-millisecond closed-loop feedback of electrical stimulation upon trigger events in real-time. The relative timing between action potentials of individual neurons as well as the temporal pattern among multiple neurons, or neuronal assemblies, is considered an important factor governing memory and learning in the brain. Artificially changing timings between arbitrary sets of spiking neurons with our system could provide a “knob” to tune information processing in the network. PMID:23335887

  5. Millisecond precision psychological research in a world of commodity computers: new hardware, new problems?

    PubMed

    Plant, Richard R; Turner, Garry

    2009-08-01

    Since the publication of Plant, Hammond, and Turner (2004), which highlighted a pressing need for researchers to pay more attention to sources of error in computer-based experiments, the landscape has undoubtedly changed, but not necessarily for the better. Readily available hardware has improved in terms of raw speed; multi core processors abound; graphics cards now have hundreds of megabytes of RAM; main memory is measured in gigabytes; drive space is measured in terabytes; ever larger thin film transistor displays capable of single-digit response times, together with newer Digital Light Processing multimedia projectors, enable much greater graphic complexity; and new 64-bit operating systems, such as Microsoft Vista, are now commonplace. However, have millisecond-accurate presentation and response timing improved, and will they ever be available in commodity computers and peripherals? In the present article, we used a Black Box ToolKit to measure the variability in timing characteristics of hardware used commonly in psychological research. PMID:19587169

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

    NASA Astrophysics Data System (ADS)

    Webb, Natalie

    2006-10-01

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

  7. Conceptual Background to Radio

    NASA Astrophysics Data System (ADS)

    Ponsonby, J. E. B.

    2004-06-01

    The International Telecommunications Union (ITU) conceives the radio spectrum as primarily a resource for telecommunications. Indeed most applications of radio are for communications and other radio services, particularly the Radio Astronomy Service, are deemed to be `pretend'communication serviceas for spectrum amnagement purposes. The language of Radio Spectrum Management is permeated by the terminology ofcommunications, some derived from the physics of radio and some from aspects of information theory. This contribution touches on all the essential concepts of radiocommunications which the author thinks should be the common mental equipment of the Spectrum Manager. The fundamental capacity of a communication channel is discussed in terms of the degrees of freedom and bandwidth of a signal, and the signal to noise ratio. It is emphasized that an information bearing signal is inherently unpredictable, and must, at some level, be discontinuous. This has important consequences for the form of its power spectrum. The effect of inserting filters is discussed particularly with regard to constant amplitude signals and, in the context of non-linear power amplifiers, the phenomenon of`sideband recovery'. All the common generic forms of modulation are discussed including the very different case of `no-modulation' which applies in all forms of passive remote sensing. Whilst all are agreed that the radio spectrum should be used `efficiently', there is no quantitative measure of spectral efficiency which embraces all relevant aspects of spectral usage. These various aspects are dicussed. Finally a brief outline of some aspects of antennae are reviewed. It is pointed out that the recent introduction of so-called `active antennnae', which have properties unlike traditional passive antennae, has confused the interpretation of those ITU Radio Regulations which refer to antennae.

  8. The Radio JOVE Project

    NASA Astrophysics Data System (ADS)

    Garcia, L.; Thieman, J.; Higgins, C.

    1999-09-01

    Radio JOVE is an interactive educational activity which brings the radio sounds of Jupiter and the Sun to students, teachers, and the general public. This is accomplished through the construction of a simple radio telescope kit and the use of a real-time radio observatory on the Internet. Our website (http://radiojove.gsfc.nasa.gov/) will contain science information, instruction manuals, observing guides, and education resources for students and teachers. Our target audience is high school science classes, but subjects can be tailored to college undergraduate physics and astronomy courses or even to middle school science classes. The goals of the project are: 1) Educate people about planetary and solar radio astronomy, space physics, and the scientific method 2) Provide teachers and students with a hands-on radio astronomy exercise as a science curriculum support activity by building and using a simple radio telescope receiver/antenna kit 3) Create the first ever online radio observatory which provides real-time data for those with internet access 4) Allow interactions among participating schools by facilitating exchanges of ideas, data, and observing experiences. Our current funding will allow us to impact 100 schools by partially subsidizing their participation in the program. We expect to expand well beyond this number as publicity and general interest increase. Additional schools are welcome to fully participate, but we will not be able to subsidize their kit purchases. We hope to make a wide impact among the schools by advertising through appropriate newsletters, space grant consortia, the INSPIRE project (http://image.gsfc.nasa.gov/poetry/inspire/), electronic links, and science and education meetings. We would like to acknoledge support from the NASA/GSFC Director's Discretionary Fund, the STScI IDEAS grant program and the NASA/GSFC Space Science Data Operations Office.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    We present time-resolved optical photometry of the binary millisecond `redback' pulsar PSR J1023+0038 (=AY Sex) during its low-mass X-ray binary phase. The light curves taken between 2014 January and April show an underlying sinusoidal modulation due to the irradiated secondary star and accretion disc. We also observe superimposed rapid flaring on time-scales as short as ˜20 s with amplitudes of ˜0.1-0.5 mag and additional large flare events on time-scales of ˜5-60 min with amplitudes of ˜0.5-1.0 mag. The power density spectrum of the optical flare light curves is dominated by a red-noise component, typical of aperiodic activity in X-ray binaries. Simultaneous X-ray and UV observations by the Swift satellite reveal strong correlations that are consistent with X-ray reprocessing of the UV light, most likely in the outer regions of the accretion disc. On some nights we also observe sharp-edged, rectangular, flat-bottomed dips randomly distributed in orbital phase, with a median duration of ˜250 s and a median ingress/egress time of ˜20 s. These rectangular dips are similar to the mode-switching behaviour between disc `active' and `passive' luminosity states, observed in the X-ray light curves of other redback millisecond pulsars. This is the first time that the optical analogue of the X-ray mode-switching has been observed. The properties of the passive- and active-state light curves can be explained in terms of clumpy accretion from a trapped inner accretion disc near the corotation radius, resulting in rectangular, flat-bottomed optical and X-ray light curves.

  10. Gravitational-wave Constraints on the Progenitors of Fast Radio Bursts

    NASA Astrophysics Data System (ADS)

    Callister, Thomas; Kanner, Jonah; Weinstein, Alan

    2016-07-01

    The nature of fast radio bursts (FRBs) remains enigmatic. Highly energetic radio pulses of millisecond duration, FRBs are observed with dispersion measures consistent with an extragalactic source. A variety of models have been proposed to explain their origin. One popular class of theorized FRB progenitor is the coalescence of compact binaries composed of neutron stars and/or black holes. Such coalescence events are strong gravitational-wave emitters. We demonstrate that measurements made by the LIGO and Virgo gravitational-wave observatories can be leveraged to severely constrain the validity of FRB binary coalescence models. Existing measurements constrain the binary black hole rate to approximately 5% of the FRB rate, and results from Advanced LIGO’s O1 and O2 observing runs may place similarly strong constraints on the fraction of FRBs due to binary neutron star and neutron star-black hole progenitors.

  11. Are the distributions of fast radio burst properties consistent with a cosmological population?

    NASA Astrophysics Data System (ADS)

    Caleb, M.; Flynn, C.; Bailes, M.; Barr, E. D.; Hunstead, R. W.; Keane, E. F.; Ravi, V.; van Straten, W.

    2016-05-01

    High time resolution radio surveys over the last few years have discovered a population of millisecond-duration transient bursts called fast radio bursts (FRBs), which remain of unknown origin. FRBs exhibit dispersion consistent with propagation through a cold plasma and dispersion measures indicative of an origin at cosmological distances. In this paper, we perform Monte Carlo simulations of a cosmological population of FRBs, based on assumptions consistent with observations of their energy distribution, their spatial density as a function of redshift and the properties of the interstellar and intergalactic media. We examine whether the dispersion measures, fluences, derived redshifts, signal-to-noise ratios and effective widths of known FRBs are consistent with a cosmological population. Statistical analyses indicate that at least 50 events at Parkes are required to distinguish between a constant comoving FRB density, and an FRB density that evolves with redshift like the cosmological star formation rate density.

  12. Dense magnetized plasma associated with a fast radio burst

    NASA Astrophysics Data System (ADS)

    Masui, Kiyoshi; Lin, Hsiu-Hsien; Sievers, Jonathan; Anderson, Christopher J.; Chang, Tzu-Ching; Chen, Xuelei; Ganguly, Apratim; Jarvis, Miranda; Kuo, Cheng-Yu; Li, Yi-Chao; Liao, Yu-Wei; McLaughlin, Maura; Pen, Ue-Li; Peterson, Jeffrey B.; Roman, Alexander; Timbie, Peter T.; Voytek, Tabitha; Yadav, Jaswant K.

    2015-12-01

    Fast radio bursts are bright, unresolved, non-repeating, broadband, millisecond flashes, found primarily at high Galactic latitudes, with dispersion measures much larger than expected for a Galactic source. The inferred all-sky burst rate is comparable to the core-collapse supernova rate out to redshift 0.5. If the observed dispersion measures are assumed to be dominated by the intergalactic medium, the sources are at cosmological distances with redshifts of 0.2 to 1 (refs 10 and 11). These parameters are consistent with a wide range of source models. One fast burst revealed circular polarization of the radio emission, but no linear polarization was detected, and hence no Faraday rotation measure could be determined. Here we report the examination of archival data revealing Faraday rotation in the fast radio burst FRB 110523. Its radio flux and dispersion measure are consistent with values from previously reported bursts and, accounting for a Galactic contribution to the dispersion and using a model of intergalactic electron density, we place the source at a maximum redshift of 0.5. The burst has a much higher rotation measure than expected for this line of sight through the Milky Way and the intergalactic medium, indicating magnetization in the vicinity of the source itself or within a host galaxy. The pulse was scattered by two distinct plasma screens during propagation, which requires either a dense nebula associated with the source or a location within the central region of its host galaxy. The detection in this instance of magnetization and scattering that are both local to the source favours models involving young stellar populations such as magnetars over models involving the mergers of older neutron stars, which are more likely to be located in low-density regions of the host galaxy.

  13. Dense magnetized plasma associated with a fast radio burst.

    PubMed

    Masui, Kiyoshi; Lin, Hsiu-Hsien; Sievers, Jonathan; Anderson, Christopher J; Chang, Tzu-Ching; Chen, Xuelei; Ganguly, Apratim; Jarvis, Miranda; Kuo, Cheng-Yu; Li, Yi-Chao; Liao, Yu-Wei; McLaughlin, Maura; Pen, Ue-Li; Peterson, Jeffrey B; Roman, Alexander; Timbie, Peter T; Voytek, Tabitha; Yadav, Jaswant K

    2015-12-24

    Fast radio bursts are bright, unresolved, non-repeating, broadband, millisecond flashes, found primarily at high Galactic latitudes, with dispersion measures much larger than expected for a Galactic source. The inferred all-sky burst rate is comparable to the core-collapse supernova rate out to redshift 0.5. If the observed dispersion measures are assumed to be dominated by the intergalactic medium, the sources are at cosmological distances with redshifts of 0.2 to 1 (refs 10 and 11). These parameters are consistent with a wide range of source models. One fast burst revealed circular polarization of the radio emission, but no linear polarization was detected, and hence no Faraday rotation measure could be determined. Here we report the examination of archival data revealing Faraday rotation in the fast radio burst FRB 110523. Its radio flux and dispersion measure are consistent with values from previously reported bursts and, accounting for a Galactic contribution to the dispersion and using a model of intergalactic electron density, we place the source at a maximum redshift of 0.5. The burst has a much higher rotation measure than expected for this line of sight through the Milky Way and the intergalactic medium, indicating magnetization in the vicinity of the source itself or within a host galaxy. The pulse was scattered by two distinct plasma screens during propagation, which requires either a dense nebula associated with the source or a location within the central region of its host galaxy. The detection in this instance of magnetization and scattering that are both local to the source favours models involving young stellar populations such as magnetars over models involving the mergers of older neutron stars, which are more likely to be located in low-density regions of the host galaxy. PMID:26633633

  14. Dense magnetized plasma associated with a fast radio burst.

    PubMed

    Masui, Kiyoshi; Lin, Hsiu-Hsien; Sievers, Jonathan; Anderson, Christopher J; Chang, Tzu-Ching; Chen, Xuelei; Ganguly, Apratim; Jarvis, Miranda; Kuo, Cheng-Yu; Li, Yi-Chao; Liao, Yu-Wei; McLaughlin, Maura; Pen, Ue-Li; Peterson, Jeffrey B; Roman, Alexander; Timbie, Peter T; Voytek, Tabitha; Yadav, Jaswant K

    2015-12-24

    Fast radio bursts are bright, unresolved, non-repeating, broadband, millisecond flashes, found primarily at high Galactic latitudes, with dispersion measures much larger than expected for a Galactic source. The inferred all-sky burst rate is comparable to the core-collapse supernova rate out to redshift 0.5. If the observed dispersion measures are assumed to be dominated by the intergalactic medium, the sources are at cosmological distances with redshifts of 0.2 to 1 (refs 10 and 11). These parameters are consistent with a wide range of source models. One fast burst revealed circular polarization of the radio emission, but no linear polarization was detected, and hence no Faraday rotation measure could be determined. Here we report the examination of archival data revealing Faraday rotation in the fast radio burst FRB 110523. Its radio flux and dispersion measure are consistent with values from previously reported bursts and, accounting for a Galactic contribution to the dispersion and using a model of intergalactic electron density, we place the source at a maximum redshift of 0.5. The burst has a much higher rotation measure than expected for this line of sight through the Milky Way and the intergalactic medium, indicating magnetization in the vicinity of the source itself or within a host galaxy. The pulse was scattered by two distinct plasma screens during propagation, which requires either a dense nebula associated with the source or a location within the central region of its host galaxy. The detection in this instance of magnetization and scattering that are both local to the source favours models involving young stellar populations such as magnetars over models involving the mergers of older neutron stars, which are more likely to be located in low-density regions of the host galaxy.

  15. Powerful Radio Burst Indicates New Astronomical Phenomenon

    NASA Astrophysics Data System (ADS)

    2007-09-01

    . "It was a bit of luck that the survey included some observations of the sky surrounding the clouds," Narkevic said. It was from those "flanking" observations that the mysterious radio burst appeared in the data. The burst of radio waves was strong by astronomical standards, but lasted less than five milliseconds. The signal was spread out, with higher frequencies arriving at the telescope before the lower frequencies. This effect, called dispersion, is caused by the signal passing through ionized gas in interstellar and intergalactic space. The amount of this dispersion, the astronomers said, indicates that the signal likely originated about three billion light-years from Earth. No previously-detected cosmic radio burst has the same set of characteristics. "This burst represents an entirely new astronomical phenomenon," Bailes said. The astronomers estimate on the basis of their results that hundreds of similar events should occur over the sky each day. "Few radio surveys have the necessary sensitivity to such short-duration bursts, which makes them notoriously difficult to detect with current instruments," added Crawford. The next generation of radio telescopes currently under development should be able to detect many of these bursts across the sky. Although the nature of the mysterious new object is unclear, the astronomers have some ideas of what may cause such a burst. One idea is that it may be part of the energy released when a pair of superdense neutron stars collide and merge. Such an event is thought by some scientists to be the cause of one type of gamma-ray burst, but the only radio emission seen so far from these has been from the long-lived "afterglow" that follows the original burst. Another, more exotic, candidate is a burst of energy from an evaporating black hole. Black holes, concentrations of mass so dense that not even light can escape their powerful gravity, can lose mass and energy through a process proposed by famed British physicist Stephen

  16. Astrometry of southern radio sources.

    PubMed

    White, G L; Jauncey, D L; Harvey, B R; Savage, A; Gulkis, S; Preston, R A; Peterson, B A; Reynolds, J E; Nicolson, G D; Malin, D F

    1991-01-01

    An overview is presented of a number of astrometry and astrophysics programs based on radio sources from the Parkes 2.7 GHz catalogues. The programs cover the optical identification and spectroscopy of flat-spectrum Parkes sources and the determination of their milliarc-second radio structures and positions. Work is also in progress to tie together the radio and Hipparcos positional reference frames. A parallel program of radio and optical astrometry of southern radio stars is also under way.

  17. Pilot study of the radio-emitting AGN population: the emerging new class of FR 0 radio-galaxies

    NASA Astrophysics Data System (ADS)

    Baldi, Ranieri D.; Capetti, Alessandro; Giovannini, Gabriele

    2015-04-01

    We present the results of a pilot JVLA project aimed at studying the bulk of the radio-emitting AGN population, that was unveiled by the NVSS/FIRST and SDSS surveys. The key questions are related to the origin of their radio-emission and to its connection with the properties of their hosts. We obtained A-array observations at the JVLA at 1.4, 4.5, and 7.5 GHz for 12 sources, a small but representative subsample. The radio maps reveal compact unresolved or only slightly resolved radio structures on a scale of 1-3 kpc, with the one exception of a hybrid FR I/FR II source extended over ~40 kpc. Thanks to either the new high-resolution maps or to the radio spectra, we isolated the radio core component in most of them. We split the sample into two groups. Four sources have low black hole (BH) masses (mostly ~107 M⊙) and are hosted by blue galaxies, often showing evidence of a contamination from star formation to their radio emission, and are associated with radio-quiet (RQ) AGN. The second group consists in seven radio-loud (RL) AGN, which are located in red massive (~1011 M⊙) early-type galaxies, have high BH masses (≳108 M⊙), and are spectroscopically classified as low excitation galaxies (LEG). These are all characteristics typical of FR I radio galaxies. They also lie on the correlation between radio core power and [O III] line luminosity defined by FR Is. However, they are more core-dominated (by a factor of ~30) than FR Is and show a deficit of extended radio emission. We dub these sources "FR 0" to emphasize their lack of prominent extended radio emission, which is their single distinguishing feature with respect to FR Is. The differences in radio properties between FR 0s and FR Is might be ascribed to an evolutionary effect, with the FR 0 sources undergoing rapid intermittency that prevents the growth of large-scale structures. However, this contrasts with the scenario in which low-luminosity radio-galaxies are fed by continuous accretion of gas from

  18. Radio emission from supernovae.

    NASA Astrophysics Data System (ADS)

    Weiler, K. W.; Panagia, N.; Sramek, R. A.; Van Dyk, S. D.; Stockdale, C. J.; Williams, C. L.

    Study of radio supernovae over the past 30 years includes more than three dozen detected objects and more than 150 upper limits. From this work it is possible to identify classes of radio properties, demonstrate conformance to and deviations from existing models, estimate the density and structure of the circumstellar material and, by inference, the evolution of the presupernova stellar wind, and reveal the last stages of stellar evolution before explosion. Along with reviewing these general properties of the radio emission from supernovae, we present our extensive observations of the radio emission from supernova (SN) 1993J in M 81 (NGC 3031) made with the Very Large Array and other radio telescopes. The SN 1993J radio emission evolves regularly in both time and frequency, and the usual interpretation in terms of shock interaction with a circumstellar medium (CSM) formed by a pre-supernova stellar wind describes the observations rather well considering the complexity of the phenomenon. However: 1) The highest frequency measurements at 85 - 110 GHz at early times (<40 days) are not well fitted by the parameterization which describes the cm wavelength measurements. 2) At a time ˜3100 days after shock breakout, the decline rate of the radio emission steepens from (t+beta ) beta ˜ -0.7 to beta ˜ -2.7 without change in the spectral index (nu +alpha ; alpha ˜ -0.81). This decline is best described not as a power-law, but as an exponential decay with an e-folding time of ˜ 1100 days. 3) The best overall fit to all of the data is a model including both non-thermal synchrotron self-absorption (SSA) and a thermal free-free absorbing (FFA) components at early times, evolving to a constant spectral index, optically thin decline rate, until a break in that decline rate at day ˜3100, as mentioned above.

  19. The Fluence and Distance Distributions of Fast Radio Bursts

    NASA Astrophysics Data System (ADS)

    Vedantham, H. K.; Ravi, V.; Hallinan, G.; Shannon, R. M.

    2016-10-01

    Fast radio bursts (FRB) are millisecond-duration radio pulses with apparent extragalactic origins. All but two of the FRBs have been discovered using the Parkes dish, which employs multiple beams formed by an array of feed horns on its focal plane. In this paper, we show that (i) the preponderance of multiple-beam detections and (ii) the detection rates for varying dish diameters can be used to infer the index α of the cumulative fluence distribution function (the logN–logF function: α = 1.5 for a non-evolving population in a Euclidean universe). If all detected FRBs arise from a single progenitor population, multiple-beam FRB detection rates from the Parkes telescope yield the constraint 0.52 < α < 1.0 with 90% confidence. Searches at other facilities with different dish sizes refine the constraint to 0.5 < α < 0.9. Our results favor FRB searches with smaller dishes, because for α < 1 the gain in field of view for a smaller dish is more important than the reduction in sensitivity. Further, our results suggest that (i) FRBs are not standard candles, and (ii) the distribution of distances to the detected FRBs is weighted toward larger distances. If FRBs are extragalactic, these results are consistent with a cosmological population, which would make FRBs excellent probes of the baryonic content and geometry of the universe.

  20. VERY LONG BASELINE INTERFEROMETRY MEASURED PROPER MOTION AND PARALLAX OF THE γ-RAY MILLISECOND PULSAR PSR J0218+4232

    SciTech Connect

    Du, Yuanjie; Chen, Ding; Yang, Jun; Campbell, Robert M.; Janssen, Gemma; Stappers, Ben

    2014-02-20

    PSR J0218+4232 is a millisecond pulsar (MSP) with a flux density ∼0.9 mJy at 1.4 GHz. It is very bright in the high-energy X-ray and γ-ray domains. We conducted an astrometric program using the European VLBI Network (EVN) at 1.6 GHz to measure its proper motion and parallax. A model-independent distance would also help constrain its γ-ray luminosity. We achieved a detection of signal-to-noise ratio S/N >37 for the weak pulsar in all five epochs. Using an extragalactic radio source lying 20 arcmin away from the pulsar, we estimate the pulsar's proper motion to be μ{sub α}cos δ = 5.35 ± 0.05 mas yr{sup –1} and μ{sub δ} = –3.74 ± 0.12 mas yr{sup –1}, and a parallax of π = 0.16 ± 0.09 mas. The very long baseline interferometry (VLBI) proper motion has significantly improved upon the estimates from long-term pulsar timing observations. The VLBI parallax provides the first model-independent distance constraints: d=6.3{sub −2.3}{sup +8.0} kpc, with a corresponding 3σ lower-limit of d = 2.3 kpc. This is the first pulsar trigonometric parallax measurement based solely on EVN observations. Using the derived distance, we believe that PSR J0218+4232 is the most energetic γ-ray MSP known to date. The luminosity based on even our 3σ lower-limit distance is high enough to pose challenges to the conventional outer gap and slot gap models.

  1. An Introduction to Radio Astronomy

    NASA Astrophysics Data System (ADS)

    Burke, Bernard F.; Graham-Smith, Francis

    2009-09-01

    Preface; 1. Introduction; 2. The nature of the radio signal; 3. Signals, noise, radiometers and spectrometers; 4. Single-aperture radio telescopes; 5. The two-element interferometer; 6. Aperture synthesis; 7. Radiation, propagation and absorption of radio waves; 8. The local universe; 9. The interstellar medium; 10. Galactic dynamics; 11. Stars; 12. Pulsars; 13. Radio galaxies and quasars; 14. Cosmology fundamentals; 15. The angular structure of the CMB; 16. Cosmology: discrete radio sources and gravitational lensing; 17. The future of radio astronomy; Appendixes; References; Index.

  2. An Introduction to Radio Astronomy

    NASA Astrophysics Data System (ADS)

    Burke, Bernard F.; Graham-Smith, Francis

    2014-02-01

    Preface; 1. Introduction; 2. The nature of the radio signal; 3. Signals, noise, radiometers and spectrometers; 4. Single-aperture radio telescopes; 5. The two-element interferometer; 6. Aperture synthesis; 7. Radiation, propagation and absorption of radio waves; 8. The local universe; 9. The interstellar medium; 10. Galactic dynamics; 11. Stars; 12. Pulsars; 13. Radio galaxies and quasars; 14. Cosmology fundamentals; 15. The angular structure of the CMB; 16. Cosmology: discrete radio sources and gravitational lensing; 17. The future of radio astronomy; Appendixes; References; Index.

  3. Saturn's variable radio period

    NASA Astrophysics Data System (ADS)

    Kurth, W. S.; Lecacheux, A.; Zarka, P.; Gurnett, D. A.; Cecconi, B.

    Temporal modulations in radio emissions are often used to determine the rotation rate of the emitting body. The rotation period (presumably) of Jupiter's interior was established in this way [Burke et al., 1962] and has recently been refined by Higgins et al. [1997]. Rotation periods for the remainder of the outer planet gas giants were determined from Voyager planetary radio astronomy observations. Similar techniques have been applied to astrophysical objects, including pulsars, for which the radio period is assumed to be the rotation period of the neutron star. In 2001, however, this simple relation between the radio period and rotation period became suspect, at least for the case of Saturn. Galopeau and Lecacheux [2001] reported that the radio period of Saturn had changed by as much as 1% from that determined by Voyager and, further, exhibited variations on time scales of years. More recently, Cassini observations indicate that the Saturn kilometric radiation is modulated with a period longer than that observed by Voyager and that this period is variable on a time scale of a year or less. The recent Higgins et al. result suggests that Jupiter's period is steady, within measurement accuracy. There are no additional measurements from Uranus or Neptune with which to look for time variations in their radio periods. For conservation of energy and angular momentum reasons, true variations of the rotation period of Saturn's deep interior are not believed to be a viable explanation for the variation in radio period, hence, it would appear that there is some disconnection of the radio period from the rotation period in the case of Saturn. One possible contributing factor may be that since Saturn's magnetic field is very accurately aligned with its rotational axis, there is no first-order beaming effect caused by the wobbling of the magnetic field, contrary to the situation at the other magnetized planets. Another explanation suggested by Galopeau and Lecacheux [2001] and

  4. Planetary radio waves

    NASA Technical Reports Server (NTRS)

    Goertz, C. K.

    1986-01-01

    Three planets, the earth, Jupiter and Saturn are known to emit nonthermal radio waves which require coherent radiation processes. The characteristic features (frequency spectrum, polarization, occurrence probability, radiation pattern) are discussed. Radiation which is externally controlled by the solar wind is distinguished from internally controlled radiation which only originates from Jupiter. The efficiency of the externally controlled radiation is roughly the same at all three planets (5 x 10 to the -6th) suggesting that similar processes are active there. The maser radiation mechanism for the generation of the radio waves and general requirements for the mechanism which couples the power generator to the region where the radio waves are generated are briefly discussed.

  5. Comets at radio wavelengths

    NASA Astrophysics Data System (ADS)

    Crovisier, Jacques; Bockelée-Morvan, Dominique; Colom, Pierre; Biver, Nicolas

    2016-11-01

    Comets are considered as the most primitive objects in the Solar System. Their composition provides information on the composition of the primitive solar nebula, 4.6 Gyr ago. The radio domain is a privileged tool to study the composition of cometary ices. Observations of the OH radical at 18 cm wavelength allow us to measure the water production rate. A wealth of molecules (and some of their isotopologues) coming from the sublimation of ices in the nucleus have been identified by observations in the millimetre and submillimetre domains. We present an historical review on radio observations of comets, focusing on the results from our group, and including recent observations with the Nançay radio telescope, the IRAM antennas, the Odin satellite, the Herschel space observatory, ALMA, and the MIRO instrument aboard the Rosetta space probe. xml:lang="fr"

  6. Radio coverage statistics.

    PubMed

    Lynn, W

    1984-01-01

    The Clearinghouse on Development Communication surveyed 135 countries in Asia, Africa, Europe, North and South America, for U.S.A.I.D., to determine the number of radio and television broadcast stations and receivers. Some of the data were obtained from the World Factbook, the World Radio and TV Handbook, and the World Radio and T.V. Facts and Figures, from 1979 to 1981. In those countries where stations are privately owned, audience surveys are often available. In 2 out of 3 developing countries, however, stations are government owned, and no such information is available. Numbers of receivers can sometimes be ascertained from receiver license applications. There is a need for more complete information on broadcast demographics, listening and viewing patterns by the community of world development program personnel.

  7. High redshift radio galaxies

    NASA Technical Reports Server (NTRS)

    Mccarthy, Patrick J.

    1993-01-01

    High redshift galaxies that host powerful radio sources are examined. An overview is presented of the content of radio surveys: 3CR and 3CRR, 4C and 4C/USS, B2/1 Jy, MG, MRC/1Jy, Parkes/PSR, B3, and ESO Key-Project. Narrow-line radio galaxies in the visible and UV, the source of ionization and excitation of the emission lines, emission-line luminosities, morphology of the line-emitting gas, physical properties and energetics, kinematics of the line-emitting gas, and implications from the emission lines are discussed. The morphologies and environments of the host galaxies, the alignment effect, and spectral energy distributions and ages are also examined.

  8. Sensors Locate Radio Interference

    NASA Technical Reports Server (NTRS)

    2009-01-01

    After receiving a NASA Small Business Innovation Research (SBIR) contract from Kennedy Space Center, Soneticom Inc., based in West Melbourne, Florida, created algorithms for time difference of arrival and radio interferometry, which it used in its Lynx Location System (LLS) to locate electromagnetic interference that can disrupt radio communications. Soneticom is collaborating with the Federal Aviation Administration (FAA) to install and test the LLS at its field test center in New Jersey in preparation for deploying the LLS at commercial airports. The software collects data from each sensor in order to compute the location of the interfering emitter.

  9. Radio astronomy with microspacecraft

    NASA Technical Reports Server (NTRS)

    Collins, D.

    2001-01-01

    A dynamic constellation of microspacecraft in lunar orbit can carry out valuable radio astronomy investigations in the frequency range of 30kHz--30MHz, a range that is difficult to explore from Earth. In contrast to the radio astronomy ivestigations that have flown on individual spacecraft, the four microspacecraft together with a carrier spacecraft, which transported them to lunar orbit, form an interferometer with far superior angular resolution. Use of microspacecraft allows the entire constellation to be launched with a Taurus-class vehicle. Also distinguishing this approach is that the Moon is used as needed to shield the constellation from RF interference from the Earth and Sun.

  10. Radio Emission from Supernovae

    NASA Astrophysics Data System (ADS)

    Weiler, Kurt W.; Panagia, Nino; Sramek, Richard A.; van Dyk, Schuyler D.; Williams, Christopher L.; Stockdale, Christopher J.; Kelley, Matthew T.

    2007-10-01

    Study of radio supernovae over the past 27 years includes more than three dozen detected objects and more than 150 upper limits. From this work it is possible to identify classes of radio properties, demonstrate conformance to and deviations from existing models, estimate the density and structure of the circumstellar material and, by inference, the evolution of the presupernova stellar wind, and reveal the last stages of stellar evolution before explosion. It is also possible to detect ionized hydrogen along the line of sight, to demonstrate binary properties of the presupernova stellar system, and to detect clumpiness of the circumstellar material. Along with reviewing these general properties of the radio emission from supernovae, we present our extensive observations of the radio emission from supernova (SN) 1993J in M 81 (NGC 3031) made with the Very Large Array and other radio telescopes. The SN 1993J radio emission evolves regularly in both time and frequency, and the usual interpretation in terms of shock interaction with a circumstellar medium (CSM) formed by a pre-supernova stellar wind describes the observations rather well considering the complexity of the phenomenon. However: 1) The highest frequency measurements at 85-110 GHz at early times (<40 days) are not well fitted by the parameterization which describes the cm wavelength measurements rather well. 2) At mid-cm wavelengths there is often deviation from the fitted radio light curves, particularly near the peak flux density, and considerable shorter term deviations in the declining portion when the emission has become optically thin. 3) At a time ~3100 days after shock breakout, the decline rate of the radio emission steepens from (t+β)β~-0.7 to β~-2.7 without change in the spectral index (ν+αα~-0.81). However, this decline is best described not as a power-law, but as an exponential decay starting at day ~3100 with an e-folding time of ~1100 days. 4) The best overall fit to all of the data is

  11. Radio Emission from Supernovae

    SciTech Connect

    Weiler, Kurt W.; Panagia, Nino; Sramek, Richard A.; Van Dyk, Schuyler D.; Stockdale, Christopher J.; Kelley, Matthew T.

    2009-05-03

    Study of radio supernovae over the past 27 years includes more than three dozen detected objects and more than 150 upper limits. From this work it is possible to identify classes of radio properties, demonstrate conformance to and deviations from existing models, estimate the density and structure of the circumstellar material and, by inference, the evolution of the presupernova stellar wind, and reveal the last stages of stellar evolution before explosion. It is also possible to detect ionized hydrogen along the line of sight, to demonstrate binary properties of the presupernova stellar system, and to detect dumpiness of the circumstellar material.

  12. Ordinary X-Rays from Three Extraordinary Millisecond Pulsars: XMM-Newton Observations of PSRs J0337+1715, J0636+5129, and J0645+5158

    NASA Astrophysics Data System (ADS)

    Spiewak, Renée; Kaplan, David L.; Archibald, Anne; Gentile, Peter; Hessels, Jason; Lorimer, Duncan; Lynch, Ryan; McLaughlin, Maura; Ransom, Scott; Stairs, Ingrid; Stovall, Kevin

    2016-05-01

    We present the first X-ray observations of three recently discovered millisecond pulsars (MSPs) with interesting characteristics: PSR J0337+1715, PSR J0636+5129, and PSR J0645+5158. PSR J0337+1715 is a fast-spinning, bright, and so-far unique MSP in a hierarchical triple system with two white dwarf companions. PSR J0636+5129 is an MSP in a very tight 96-minute orbit with a low-mass, 8 M J companion. PSR J0645+5158 is a nearby, isolated MSP with a very small duty cycle (1%–2%), which has led to its inclusion in high-precision pulsar timing programs. Using data from XMM-Newton, we have analyzed X-ray spectroscopy for these three objects, as well as optical/ultraviolet photometry for PSR J0337+1715. The X-ray data for each are largely consistent with expectations for most MSPs with regards to the ratios of thermal and non-thermal emission. We discuss the implications of these data on the pulsar population, and prospects for future observations of these pulsars.

  13. Very-Long-Baseline Radio Interferometry: The Mark III System for Geodesy, Astrometry, and Aperture Synthesis.

    PubMed

    Rogers, A E; Cappallo, R J; Hinteregger, H F; Levine, J I; Nesman, E F; Webber, J C; Whitney, A R; Clark, T A; Ma, C; Ryan, J; Corey, B E; Counselman, C C; Herring, T A; Shapiro, I I; Knight, C A; Shaffer, D B; Vandenberg, N R; Lacasse, R; Mauzy, R; Rayhrer, B; Schupler, B R; Pigg, J C

    1983-01-01

    The Mark III very-long-baseline interferometry (VLBI) system allows recording and later processing of up to 112 megabits per second from each radio telescope of an interferometer array. For astrometric and geodetic measurements, signals from two radio-frequency bands (2.2 to 2.3 and 8.2 to 8.6 gigahertz) are sampled and recorded simultaneously at all antenna sites. From these dual-band recordings the relative group delays of signals arriving at each pair of sites can be corrected for the contributions due to the ionosphere. For many radio sources for which the signals are sufficiently intense, these group delays can be determined with uncertainties under 50 picoseconds. Relative positions of widely separated antennas and celestial coordinates of radio sources have been determined from such measurements with 1 standard deviation uncertainties of about 5 centimeters and 3 milliseconds of arc, respectively. Sample results are given for the lengths of baselines between three antennas in the United States and three in Europe as well as for the arc lengths between the positions of six extragalactic radio sources. There is no significant evidence of change in any of these quantities. For mapping the brightness distribution of such compact radio sources, signals of a given polarization, or of pairs of orthogonal polarizations, can be recorded in up to 28 contiguous bands each nearly 2 megahertz wide. The ability to record large bandwidths and to link together many large radio telescopes allows detection and study of compact sources with flux densities under 1 millijansky.

  14. 75 FR 10439 - Cognitive Radio Technologies and Software Defined Radios

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-08

    ... Order 1. On March 17, 2005, the Commission adopted the Cognitive Radio Report and Order, 70 FR 23032... Memorandum Opinion and Order (MO&O), 72 FR 31190, June 6, 2007, which responded to two petitions filed in... COMMISSION 47 CFR Part 2 Cognitive Radio Technologies and Software Defined Radios AGENCY:...

  15. e-POP Radio Science Using Amateur Radio Transmissions

    NASA Astrophysics Data System (ADS)

    Frissell, N. A.; Perry, G. W.; Miller, E. S.; Shovkoplyas, A.; Moses, M. L.; James, H. G.; Yau, A. W.

    2015-12-01

    A major component of the enhanced Polar Outflow Probe (e-POP) Radio Receiver Instrument (RRI) mission is to utilize artificially generated radio emissions to study High Frequency (HF) radio wave propagation in the ionosphere. In the North American and European sectors, communications between amateur radio operators are a persistent and abundant source source of HF transmissions. We present the results of HF radio wave propagation experiments using amateur radio transmissions as an HF source for e-POP RRI. We detail how a distributed and autonomously operated amateur radio network can be leveraged to study HF radio wave propagation as well as the structuring and dynamics of the ionosphere over a large geographic region. In one case, the sudden disappearance of nearly two-dozen amateur radio HF sources located in the midwestern United States was used to detect a enhancement in foF2 in that same region. We compare our results to those from other more conventional radio instruments and models of the ionosphere to demonstrate the scientific merit of incorporating amateur radio networks for radio science at HF.

  16. Prism beamswitch for radio telescopes.

    PubMed

    Payne, J M; Ulich, B L

    1978-12-01

    A dielectric prism and switching mechanism have been constructed for beamswitching a Cassegrain radio telescope. Spatially extended radio sources may be mapped without significant confusion utilizing the sensitivity and stability inherent in the conventional Dicke radiometer.

  17. Community Radio in Canada.

    ERIC Educational Resources Information Center

    Canadian Broadcasting Corp., Ottawa (Ontario).

    Results are presented of a survey of 20 community radio organizations operating in Canada. For each of the 20 agencies, information is provided relating to: (1) the name and address of the organization; (2) the name and population of the community served; (3) the station's call letters, frequency, and power; (4) the date of the station's license;…

  18. RADIO RANGING DEVICE

    DOEpatents

    Nieset, R.T.

    1961-05-16

    A radio ranging device is described. It utilizes a super regenerative detector-oscillator in which echoes of transmitted pulses are received in proper phase to reduce noise energy at a selected range and also at multiples of the selected range.

  19. Educational Broadcasting--Radio.

    ERIC Educational Resources Information Center

    Ahamed, Uvais; Grimmett, George

    This manual is intended for those who must conduct educational radio broadcasting training courses in Asia-Pacific countries without the resources of experienced personnel, as well as for individuals to use in self-learning situations. The selection of material has been influenced by the need to use broadcasting resources effectively in programs…

  20. Radio Channel Simulator (RCSM)

    2007-01-31

    This is a simulation package for making site specific predictions of radio signal strength. The software computes received power at discrete grid points as a function of the transmitter location and propagation environment. It is intended for use with wireless network simulation packages and to support wireless network deployments.

  1. Zelenchukskaya Radio Astronomical Observatory

    NASA Technical Reports Server (NTRS)

    Smolentsev, Sergey; Dyakov, Andrei

    2013-01-01

    This report summarizes information about Zelenchukskaya Radio Astronomical Observatory activities in 2012. Last year a number of changes took place in the observatory to improve some technical characteristics and to upgrade some units to the required status. The report provides an overview of current geodetic VLBI activities and gives an outlook for the future.

  2. Svetloe Radio Astronomical Observatory

    NASA Technical Reports Server (NTRS)

    Smolentsev, Sergey; Rahimov, Ismail

    2013-01-01

    This report summarizes information about the Svetloe Radio Astronomical Observatory activities in 2012. Last year, a number of changes took place in the observatory to improve some technical characteristics and to upgrade some units to their required status. The report provides an overview of current geodetic VLBI activities and gives an outlook for the future.

  3. Telling It by Radio

    ERIC Educational Resources Information Center

    Milander, Henry M.

    1975-01-01

    Olympic College purchased eight one-minute advertising spots per day for use seven days a week at a local independent radio station. Ten sample spots are presented. This economical approach was successful in increasing over-all enrollment and the number of FTE students; it also attracted many adults to the college. (DC)

  4. A Radio Station Project.

    ERIC Educational Resources Information Center

    Geva, Edna

    2002-01-01

    Describes a radio program in an English-as-a-Foreign-Language classroom in Israel. Classrooms of English students listen carefully to daily broadcasts, waiting to solve the brain teaser. Personal messages and catchy music follow the program. The project has encouraged students to use English actively and purposefully. Evaluation of the broadcasts…

  5. Japanese Radio Exercises. Revised.

    ERIC Educational Resources Information Center

    Young, Jocelyn

    This unit focuses on Japanese radio exercises which became popular in Japan just after World War II and are still used among students and workers in companies to help raise morale and form group unity. The exercises reflect the general role of exercise in Japanese culture--to serve as a symbol of unity and cooperation among the Japanese, as well…

  6. Torun Radio Astronomy Observatory

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    Torun Center for Astronomy is located at Piwnice, 15 km north of Torun, Poland. A part of the Faculty of Physics and Astronomy of the Nicolaus Copernicus University, it was created by the union of Torun Radio Astronomy Observatory (TRAO) and the Institute of Astronomy on 1 January 1997....

  7. A reminder on millisecond timing accuracy and potential replication failure in computer-based psychology experiments: An open letter.

    PubMed

    Plant, Richard R

    2016-03-01

    There is an ongoing 'replication crisis' across the field of psychology in which researchers, funders, and members of the public are questioning the results of some scientific studies and the validity of the data they are based upon. However, few have considered that a growing proportion of research in modern psychology is conducted using a computer. Could it simply be that the hardware and software, or experiment generator, being used to run the experiment itself be a cause of millisecond timing error and subsequent replication failure? This article serves as a reminder that millisecond timing accuracy in psychology studies remains an important issue and that care needs to be taken to ensure that studies can be replicated on current computer hardware and software. PMID:25761394

  8. Large interdomain rearrangement triggered by suppression of micro- to millisecond dynamics in bacterial Enzyme I

    PubMed Central

    Venditti, Vincenzo; Tugarinov, Vitali; Schwieters, Charles D.; Grishaev, Alexander; Clore, G. Marius

    2014-01-01

    Enzyme I (EI), the first component of the bacterial phosphotransfer signal transduction system, undergoes one of the largest substrate-induced interdomain rearrangements documented to date. Here, we characterize the perturbations generated by two small molecules, the natural substrate phosphoenolpyruvate (PEP) and the inhibitor α-ketoglutarate (αKG), on the structure and dynamics of EI using NMR, small-angle X-ray scattering (SAXS) and biochemical techniques. The results indicate unambiguously that the open-to-closed conformational switch of EI is triggered by complete suppression of micro- to millisecond dynamics within the C-terminal domain of EI. Indeed, we show that a ligand-induced transition from a dynamic to a more rigid conformational state of the C-terminal domain stabilizes the interface between the N- and C-terminal domains observed in the structure of the closed state, thereby promoting the resulting conformational switch and autophosphorylation of EI. The mechanisms described here may be common to several other multidomain proteins and allosteric systems. PMID:25581904

  9. Formation of Millisecond Pulsars with Heavy White Dwarf Companions: Extreme Mass Transfer on Subthermal Timescales.

    PubMed

    Tauris; van Den Heuvel EP; Savonije

    2000-02-20

    We have performed detailed numerical calculations of the nonconservative evolution of close X-ray binary systems with intermediate-mass (2.0-6.0 M middle dot in circle) donor stars and a 1.3 M middle dot in circle accreting neutron star. We calculated the thermal response of the donor star to mass loss in order to determine its stability and follow the evolution of the mass transfer. Under the assumption of the "isotropic reemission model," we demonstrate that in many cases it is possible for the binary to prevent a spiral-in and survive a highly super-Eddington mass transfer phase (1millisecond pulsars with heavy CO white dwarfs and relatively short orbital periods (3-50 days). However, we conclude that to produce a binary pulsar with a O-Ne-Mg white dwarf or Porb approximately 1 day (e.g., PSR B0655+64) the above scenario does not work, and a spiral-in phase is still considered the most plausible scenario for the formation of such a system. PMID:10655173

  10. A massive neutron star in the millisecond pulsar PSR J2215+5135

    NASA Astrophysics Data System (ADS)

    Shahbaz, Tariq

    2016-07-01

    Binary evolution may increase neutron masses via accretion. Hence the most massive neutron stars (NSs) are expected to be located amongst the binary millisecond pulsars (MSPs) spun-up within X-ray binaries. Most MSPs are found with brown dwarf lookalikes or ˜0.2 M stars in systems called "black widows" and "redbacks", respectively, because these companions are ablated by the pulsar wind. These systems offer some advantages over white dwarf-pulsar binaries: they are typically brighter, they present strongly irradiated hemispheres, and they fill significant fractions of their Roche lobes. As a result, their optical light curves exhibit variability due to a combination of their ellipsoidal shape and irradiation, which can be modelled in order to determine orbital parameters such as the mass ratio and inclination. Combining these with optical spectroscopy and/or pulsar timing enables one to determine a reliable NS masses. Here we present the results of our detailed modelling of the optical lightcurves and radial velocity curves of J2215+5135, which allows us to determine various ystem parameters, including the NS mass.

  11. Following Molecular Transitions with Single Residue Spatial and Millisecond Time Resolution

    SciTech Connect

    Shcherbakova,I.; Mitra, S.; Beer, R.; Brenowitz, M.

    2008-01-01

    'Footprinting' describes assays in which ligand binding or structure formation protects polymers such as nucleic acids and proteins from either cleavage or modification; footprinting allows the accessibility of individual residues to be mapped in solution. Equilibrium and time-dependent footprinting links site-specific structural information with thermodynamic and kinetic transitions, respectively. The hydroxyl radical ({center_dot}OH) is a uniquely insightful footprinting probe by virtue of it being among the most reactive chemical oxidants; it reports the solvent accessibility of reactive sites on macromolecules with as fine as a single residue resolution. A novel method of millisecond time-resolved {center_dot}OH footprinting is presented based on the Fenton reaction, Fe(II) + H2O2 {yields} Fe(III) + {center_dot}OH + OH-. It is implemented using a standard three-syringe quench-flow mixer. The utility of this method is demonstrated by its application to the studies on RNA folding. Its applicability to a broad range of biological questions involving the function of DNA, RNA, and proteins is discussed.

  12. Searches for millisecond pulsations in low-mass X-ray binaries, 2

    NASA Technical Reports Server (NTRS)

    Vaughan, B. A.; Van Der Klis, M.; Wood, K. S.; Norris, J. P.; Hertz, P.; Michelson, P. F.; Paradijs, J. Van; Lewin, W. H. G.; Mitsuda, K.; Penninx, W.

    1994-01-01

    Coherent millisecond X-ray pulsations are expected from low-mass X-ray binaries (LMXBs), but remain undetected. Using the single-parameter Quadratic Coherence Recovery Technique (QCRT) to correct for unknown binary orbit motion, we have performed Fourier transform searches for coherent oscillations in all long, continuous segments of data obtained at 1 ms time resolution during Ginga observations of LMXB. We have searched the six known Z sources (GX 5-1, Cyg X-2, Sco X-1, GX 17+2, GX 340+0, and GX 349+2), seven of the 14 known atoll sources (GX 3+1. GX 9+1, GX 9+9, 1728-33. 1820-30, 1636-53 and 1608-52), the 'peculiar' source Cir X-1, and the high-mass binary Cyg X-3. We find no evidence for coherent pulsations in any of these sources, with 99% confidence limits on the pulsed fraction between 0.3% and 5.0% at frequencies below the Nyquist frequency of 512 Hz. A key assumption made in determining upper limits in previous searches is shown to be incorrect. We provide a recipe for correctly setting upper limits and detection thresholds. Finally we discuss and apply two strategies to improve sensitivity by utilizing multiple, independent, continuous segments of data with comparable count rates.

  13. EVOLUTION OF TRANSIENT LOW-MASS X-RAY BINARIES TO REDBACK MILLISECOND PULSARS

    SciTech Connect

    Jia, Kun; Li, Xiang-Dong

    2015-11-20

    Redback millisecond pulsars (MSPs; hereafter redbacks) are a subpopulation of eclipsing MSPs in close binaries. The formation processes of these systems are not clear. The three pulsars showing transitions between rotation- and accretion-powered states belong to both redbacks and transient low-mass X-ray binaries (LMXBs), suggesting a possible evolutionary link between them. Through binary evolution calculations, we show that the accretion disks in almost all LMXBs are subject to the thermal-viscous instability during certain evolutionary stages, and the parameter space for the disk instability covers the distribution of known redbacks in the orbital period—companion mass plane. We accordingly suggest that the abrupt reduction of the mass accretion rate during quiescence of transient LMXBs provides a plausible way to switch on the pulsar activity, leading to the formation of redbacks, if the neutron star has been spun up to be an energetic MSP. We investigate the evolution of redbacks, taking into account the evaporation feedback, and discuss its possible influence on the formation of black widow MSPs.

  14. A STRANGE STAR SCENARIO FOR THE FORMATION OF ECCENTRIC MILLISECOND PULSAR/HELIUM WHITE DWARF BINARIES

    SciTech Connect

    Jiang, Long; Li, Xiang-Dong; Dey, Jishnu; Dey, Mira

    2015-07-01

    According to the recycling scenario, millisecond pulsars (MSPs) have evolved from low-mass X-ray binaries (LMXBs). Their orbits are expected to be circular due to tidal interactions during binary evolution, as observed in most binary MSPs. There are some peculiar systems that do not fit this picture. Three recent examples are the PSRs J2234+06, J1946+3417, and J1950+2414, all of which are MSPs in eccentric orbits but with mass functions compatible with expected He white dwarf (WD) companions. It has been suggested these MSPs may have formed from delayed accretion-induced collapse of massive WDs, or the eccentricity may be induced by dynamical interaction between the binary and a circumbinary disk. Assuming that the core density of accreting neutron stars (NSs) in LMXBs may reach the density of quark deconfinement, which can lead to phase transition from NSs to strange quark stars, we show that the resultant MSPs are likely to have an eccentric orbit, due to the sudden loss of the gravitational mass of the NS during the transition. The eccentricities can be reproduced with a reasonable estimate of the mass loss. This scenario might also account for the formation of the youngest known X-ray binary Cir X–1, which also possesses a low-field compact star in an eccentric orbit.

  15. Formation of Millisecond Pulsars with Heavy White Dwarf Companions: Extreme Mass Transfer on Subthermal Timescales.

    PubMed

    Tauris; van Den Heuvel EP; Savonije

    2000-02-20

    We have performed detailed numerical calculations of the nonconservative evolution of close X-ray binary systems with intermediate-mass (2.0-6.0 M middle dot in circle) donor stars and a 1.3 M middle dot in circle accreting neutron star. We calculated the thermal response of the donor star to mass loss in order to determine its stability and follow the evolution of the mass transfer. Under the assumption of the "isotropic reemission model," we demonstrate that in many cases it is possible for the binary to prevent a spiral-in and survive a highly super-Eddington mass transfer phase (1millisecond pulsars with heavy CO white dwarfs and relatively short orbital periods (3-50 days). However, we conclude that to produce a binary pulsar with a O-Ne-Mg white dwarf or Porb approximately 1 day (e.g., PSR B0655+64) the above scenario does not work, and a spiral-in phase is still considered the most plausible scenario for the formation of such a system.

  16. Formation of millisecond pulsars with low-mass helium white dwarf companions in very compact binaries

    SciTech Connect

    Jia, Kun; Li, X.-D.

    2014-08-20

    Binary millisecond pulsars (BMSPs) are thought to have evolved from low-mass X-ray binaries (LMXBs). If the mass transfer in LMXBs is driven by nuclear evolution of the donor star, the final orbital period is predicted to be well correlated with the mass of the white dwarf (WD), which is the degenerate He core of the donor. Here we show that this relation can be extended to very small WD mass (∼0.14-0.17 M {sub ☉}) and narrow orbital period (about a few hours), depending mainly on the metallicities of the donor stars. There is also discontinuity in the relation, which is due to the temporary contraction of the donor when the H-burning shell crosses the hydrogen discontinuity. BMSPs with low-mass He WD companions in very compact binaries can be accounted for if the progenitor binary experienced very late Case A mass transfer. The WD companion of PSR J1738+0333 is likely to evolve from a Pop II star. For PSR J0348+0432, to explain its extreme compact orbit in the Roche-lobe-decoupling phase, even lower metallicity (Z = 0.0001) is required.

  17. Sub-millisecond ligand probing of cell receptors with multiple solution exchange

    PubMed Central

    Sylantyev, Sergiy; Rusakov, Dmitri A

    2013-01-01

    The accurate knowledge of receptor kinetics is crucial to our understanding of cell signal transduction in general and neural function in particular. The classical technique of probing membrane receptors on a millisecond scale involves placing a recording micropipette with a membrane patch in front of a double-barrel (θ-glass) application pipette mounted on a piezo actuator. Driven by electric pulses, the actuator can rapidly shift the θ-glass pipette tip, thus exposing the target receptors to alternating ligand solutions. However, membrane patches survive for only a few minutes, thus normally restricting such experiments to a single-application protocol. In order to overcome this deficiency, we have introduced pressurized supply microcircuits in the θ-glass channels, thus enabling repeated replacement of application solutions within 10–15 s. this protocol, which has been validated in our recent studies and takes 20–60 min to implement, allows the characterization of ligand-receptor interactions with high sensitivity, thereby also enabling a powerful paired-sample statistical design. PMID:23744290

  18. Integrated analysis of millisecond laser irradiation of steel by comprehensive optical diagnostics and numerical simulation

    NASA Astrophysics Data System (ADS)

    Doubenskaia, M.; Smurov, I.; Nagulin, K. Yu.

    2016-04-01

    Complimentary optical diagnostic tools are applied to provide comprehensive analysis of thermal phenomena in millisecond Nd:YAG laser irradiation of steel substrates. The following optical devices are employed: (a) infrared camera FLIR Phoenix RDASTM equipped by InSb sensor with 3 to 5 µm band pass arranged on 320 × 256 pixels array, (b) ultra-rapid camera Phantom V7.1 with SR-CMOS monochrome sensor in the visible spectral range, up to 105 frames per second for 64 × 88 pixels array, (c) original multi-wavelength pyrometer in the near-infrared range (1.370-1.531 µm). The following laser radiation parameters are applied: variation of energy per pulse in the range 15-30 J at a constant pulse duration of 10 ms with and without application of protective gas (Ar). The evolution of true temperature is restored based on the method of multi-colour pyrometry; by this way, melting/solidification dynamics is analysed. Emissivity variation with temperature is studied, and hysteresis type functional dependence is found. Variation of intensity of surface evaporation visualised by the camera Phantom V7.1 is registered and linked with the surface temperature evolution, different surface roughness and influence of protective gas atmosphere. Determination of the vapour plume temperature based on relatively intensities of spectral lines is done. The numerical simulation is carried out applying the thermal model with phase transitions taken into account.

  19. Mechanisms of allosteric gene regulation by NMR quantification of microsecond-millisecond protein dynamics.

    PubMed

    Kleckner, Ian R; Gollnick, Paul; Foster, Mark P

    2012-01-13

    The trp RNA-binding attenuation protein (TRAP) is a paradigmatic allosteric protein that regulates the tryptophan biosynthetic genes associated with the trp operon in bacilli. The ring-shaped 11-mer TRAP is activated for recognition of a specific trp-mRNA target by binding up to 11 tryptophan molecules. To characterize the mechanisms of tryptophan-induced TRAP activation, we have performed methyl relaxation dispersion (MRD) nuclear magnetic resonance (NMR) experiments that probe the time-dependent structure of TRAP in the microsecond-to-millisecond "chemical exchange" time window. We find significant side chain flexibility localized to the RNA and tryptophan binding sites of the apo protein and that these dynamics are dramatically reduced upon ligand binding. Analysis of the MRD NMR data provides insights into the structural nature of transiently populated conformations sampled in solution by apo TRAP. The MRD data are inconsistent with global two-state exchange, indicating that conformational sampling in apo TRAP is asynchronous. These findings imply a temporally heterogeneous population of structures that are incompatible with RNA binding and substantiate the study of TRAP as a paradigm for probing and understanding essential dynamics in allosteric, regulatory proteins. PMID:22115774

  20. Interfacial tension measured at high expansion rates and within milliseconds using microfluidics.

    PubMed

    Muijlwijk, Kelly; Hinderink, Emma; Ershov, Dmitry; Berton-Carabin, Claire; Schroën, Karin

    2016-05-15

    To understand droplet formation and stabilisation, technologies are needed to measure interfacial tension at micrometer range and millisecond scale. In this paper, microtechnology is used, and that allows us to access these ranges and derive a model for surfactant free systems. The predicting power of the model was tested, and we found that it can be used to accurately (validated with >60 experiments) describe droplet size for a wide range of flow rates, interfacial tensions, and continuous phase viscosities. The model was used next to determine interfacial tensions in a system with hexadecane and sodium dodecylsulfate (SDS) solutions, and it was found that the model can be used for droplet formation times ranging from 0.4 to 9.4ms while using a wide range of process conditions. The method described here differs greatly from standard dynamic interfacial tension methods that use quiescent, mostly diffusion-limited situations. The effects that we measured are much faster due to enhanced mass transfer; this allows us to assess the typical time scales used in industrial emulsification devices.

  1. Hierarchical Conformational Analysis of Native Lysozyme Based on Sub-Millisecond Molecular Dynamics Simulations

    PubMed Central

    Wang, Kai; Long, Shiyang; Tian, Pu

    2015-01-01

    Hierarchical organization of free energy landscape (FEL) for native globular proteins has been widely accepted by the biophysics community. However, FEL of native proteins is usually projected onto one or a few dimensions. Here we generated collectively 0.2 milli-second molecular dynamics simulation trajectories in explicit solvent for hen egg white lysozyme (HEWL), and carried out detailed conformational analysis based on backbone torsional degrees of freedom (DOF). Our results demonstrated that at micro-second and coarser temporal resolutions, FEL of HEWL exhibits hub-like topology with crystal structures occupying the dominant structural ensemble that serves as the hub of conformational transitions. However, at 100ns and finer temporal resolutions, conformational substates of HEWL exhibit network-like topology, crystal structures are associated with kinetic traps that are important but not dominant ensembles. Backbone torsional state transitions on time scales ranging from nanoseconds to beyond microseconds were found to be associated with various types of molecular interactions. Even at nanoseconds temporal resolution, the number of conformational substates that are of statistical significance is quite limited. These observations suggest that detailed analysis of conformational substates at multiple temporal resolutions is both important and feasible. Transition state ensembles among various conformational substates at microsecond temporal resolution were observed to be considerably disordered. Life times of these transition state ensembles are found to be nearly independent of the time scales of the participating torsional DOFs. PMID:26057625

  2. Multiple-Beam Detection of Fast Transient Radio Sources

    NASA Technical Reports Server (NTRS)

    Thompson, David R.; Wagstaff, Kiri L.; Majid, Walid A.

    2011-01-01

    A method has been designed for using multiple independent stations to discriminate fast transient radio sources from local anomalies, such as antenna noise or radio frequency interference (RFI). This can improve the sensitivity of incoherent detection for geographically separated stations such as the very long baseline array (VLBA), the future square kilometer array (SKA), or any other coincident observations by multiple separated receivers. The transients are short, broadband pulses of radio energy, often just a few milliseconds long, emitted by a variety of exotic astronomical phenomena. They generally represent rare, high-energy events making them of great scientific value. For RFI-robust adaptive detection of transients, using multiple stations, a family of algorithms has been developed. The technique exploits the fact that the separated stations constitute statistically independent samples of the target. This can be used to adaptively ignore RFI events for superior sensitivity. If the antenna signals are independent and identically distributed (IID), then RFI events are simply outlier data points that can be removed through robust estimation such as a trimmed or Winsorized estimator. The alternative "trimmed" estimator is considered, which excises the strongest n signals from the list of short-beamed intensities. Because local RFI is independent at each antenna, this interference is unlikely to occur at many antennas on the same step. Trimming the strongest signals provides robustness to RFI that can theoretically outperform even the detection performance of the same number of antennas at a single site. This algorithm requires sorting the signals at each time step and dispersion measure, an operation that is computationally tractable for existing array sizes. An alternative uses the various stations to form an ensemble estimate of the conditional density function (CDF) evaluated at each time step. Both methods outperform standard detection strategies on a test

  3. The Nicaragua Radio Mathematics Project.

    ERIC Educational Resources Information Center

    Searle, Barbara

    The Radio Mathematics Project was funded by the Agency for International Development to design, implement, and evaluate, in conjunction with personnel of a developing country, a system for teaching primary-grade mathematics by radio. In July 1974, a project in Nicaragua began with a series of radio presentations, each followed by 20 minutes of…

  4. Ham Radio is Mir Magic.

    ERIC Educational Resources Information Center

    Evans, Gary

    1997-01-01

    Presents a classroom activity in which students communicated with U.S. and Russian astronauts via ham radio while they were in orbit on the space station Mir. Gives suggestions for other ham radio classroom activities as well as names of organizations, publications, and grant programs that teachers can access to help in bring ham radio into their…

  5. Writing the Instructional Radio Script.

    ERIC Educational Resources Information Center

    de Fossard, Esta

    This guide was developed for script writers on the Radio Language Arts Project, which was designed to develop, implement, and test the effectiveness of an instructional radio system to teach English as a second language at the primary school level in Kenya. The project was planned to produce a radio-based, English language program with…

  6. Radio jet refraction in galactic atmospheres with static pressure gradients

    NASA Technical Reports Server (NTRS)

    Henriksen, R. N.; Vallee, J. P.; Bridle, A. H.

    1981-01-01

    A theory based on the refraction of radio jets in the extended atmosphere of an elliptical galaxy, is proposed for double radio sources with a Z or S morphology. The model describes a collimated jet of supersonic material that bends self-consistently under the influence of external static pressure gradients, and may alternatively be seen as a continuous-jet version of the buoyancy model proposed by Gull (1973). Emphasis is placed on (1) S-shaped radio sources identified with isolated galaxies, such as 3C 293, whose radio structures should be free of distortions resulting from motion relative to a cluster medium, and (2) small-scale, galaxy-dominated rather than environment-dominated S-shaped sources such as the inner jet structure of Fornax A.

  7. Collaborative Beamfocusing Radio (COBRA)

    NASA Astrophysics Data System (ADS)

    Rode, Jeremy P.; Hsu, Mark J.; Smith, David; Husain, Anis

    2013-05-01

    A Ziva team has recently demonstrated a novel technique called Collaborative Beamfocusing Radios (COBRA) which enables an ad-hoc collection of distributed commercial off-the-shelf software defined radios to coherently align and beamform to a remote radio. COBRA promises to operate even in high multipath and non-line-of-sight environments as well as mobile applications without resorting to computationally expensive closed loop techniques that are currently unable to operate with significant movement. COBRA exploits two key technologies to achieve coherent beamforming. The first is Time Reversal (TR) which compensates for multipath and automatically discovers the optimal spatio-temporal matched filter to enable peak signal gains (up to 20 dB) and diffraction-limited focusing at the intended receiver in NLOS and severe multipath environments. The second is time-aligned buffering which enables TR to synchronize distributed transmitters into a collaborative array. This time alignment algorithm avoids causality violations through the use of reciprocal buffering. Preserving spatio-temporal reciprocity through the TR capture and retransmission process achieves coherent alignment across multiple radios at ~GHz carriers using only standard quartz-oscillators. COBRA has been demonstrated in the lab, aligning two off-the-shelf software defined radios over-the-air to an accuracy of better than 2 degrees of carrier alignment at 450 MHz. The COBRA algorithms are lightweight, with computation in 5 ms on a smartphone class microprocessor. COBRA also has low start-up latency, achieving high accuracy from a cold-start in 30 ms. The COBRA technique opens up a large number of new capabilities in communications, and electronic warfare including selective spatial jamming, geolocation and anti-geolocation.

  8. The LOFAR radio environment

    NASA Astrophysics Data System (ADS)

    Offringa, A. R.; de Bruyn, A. G.; Zaroubi, S.; van Diepen, G.; Martinez-Ruby, O.; Labropoulos, P.; Brentjens, M. A.; Ciardi, B.; Daiboo, S.; Harker, G.; Jelić, V.; Kazemi, S.; Koopmans, L. V. E.; Mellema, G.; Pandey, V. N.; Pizzo, R. F.; Schaye, J.; Vedantham, H.; Veligatla, V.; Wijnholds, S. J.; Yatawatta, S.; Zarka, P.; Alexov, A.; Anderson, J.; Asgekar, A.; Avruch, M.; Beck, R.; Bell, M.; Bell, M. R.; Bentum, M.; Bernardi, G.; Best, P.; Birzan, L.; Bonafede, A.; Breitling, F.; Broderick, J. W.; Brüggen, M.; Butcher, H.; Conway, J.; de Vos, M.; Dettmar, R. J.; Eisloeffel, J.; Falcke, H.; Fender, R.; Frieswijk, W.; Gerbers, M.; Griessmeier, J. M.; Gunst, A. W.; Hassall, T. E.; Heald, G.; Hessels, J.; Hoeft, M.; Horneffer, A.; Karastergiou, A.; Kondratiev, V.; Koopman, Y.; Kuniyoshi, M.; Kuper, G.; Maat, P.; Mann, G.; McKean, J.; Meulman, H.; Mevius, M.; Mol, J. D.; Nijboer, R.; Noordam, J.; Norden, M.; Paas, H.; Pandey, M.; Pizzo, R.; Polatidis, A.; Rafferty, D.; Rawlings, S.; Reich, W.; Röttgering, H. J. A.; Schoenmakers, A. P.; Sluman, J.; Smirnov, O.; Sobey, C.; Stappers, B.; Steinmetz, M.; Swinbank, J.; Tagger, M.; Tang, Y.; Tasse, C.; van Ardenne, A.; van Cappellen, W.; van Duin, A. P.; van Haarlem, M.; van Leeuwen, J.; van Weeren, R. J.; Vermeulen, R.; Vocks, C.; Wijers, R. A. M. J.; Wise, M.; Wucknitz, O.

    2013-01-01

    Aims: This paper discusses the spectral occupancy for performing radio astronomy with the Low-Frequency Array (LOFAR), with a focus on imaging observations. Methods: We have analysed the radio-frequency interference (RFI) situation in two 24-h surveys with Dutch LOFAR stations, covering 30-78 MHz with low-band antennas and 115-163 MHz with high-band antennas. This is a subset of the full frequency range of LOFAR. The surveys have been observed with a 0.76 kHz/1 s resolution. Results: We measured the RFI occupancy in the low and high frequency sets to be 1.8% and 3.2% respectively. These values are found to be representative values for the LOFAR radio environment. Between day and night, there is no significant difference in the radio environment. We find that lowering the current observational time and frequency resolutions of LOFAR results in a slight loss of flagging accuracy. At LOFAR's nominal resolution of 0.76 kHz and 1 s, the false-positives rate is about 0.5%. This rate increases approximately linearly when decreasing the data frequency resolution. Conclusions: Currently, by using an automated RFI detection strategy, the LOFAR radio environment poses no perceivable problems for sensitive observing. It remains to be seen if this is still true for very deep observations that integrate over tens of nights, but the situation looks promising. Reasons for the low impact of RFI are the high spectral and time resolution of LOFAR; accurate detection methods; strong filters and high receiver linearity; and the proximity of the antennas to the ground. We discuss some strategies that can be used once low-level RFI starts to become apparent. It is important that the frequency range of LOFAR remains free of broadband interference, such as DAB stations and windmills.

  9. Accurate radio and optical positions for southern radio sources

    NASA Technical Reports Server (NTRS)

    Harvey, Bruce R.; Jauncey, David L.; White, Graeme L.; Nothnagel, Axel; Nicolson, George D.; Reynolds, John E.; Morabito, David D.; Bartel, Norbert

    1992-01-01

    Accurate radio positions with a precision of about 0.01 arcsec are reported for eight compact extragalactic radio sources south of -45-deg declination. The radio positions were determined using VLBI at 8.4 GHz on the 9589 km Tidbinbilla (Australia) to Hartebeesthoek (South Africa) baseline. The sources were selected from the Parkes Catalogue to be strong, flat-spectrum radio sources with bright optical QSO counterparts. Optical positions of the QSOs were also measured from the ESO B Sky Survey plates with respect to stars from the Perth 70 Catalogue, to an accuracy of about 0.19 arcsec rms. These radio and optical positions are as precise as any presently available in the far southern sky. A comparison of the radio and optical positions confirms the estimated optical position errors and shows that there is overall agreement at the 0.1-arcsec level between the radio and Perth 70 optical reference frames in the far south.

  10. Nonreciprocal Radio Frequency Transduction in a Parametric Mechanical Artificial Lattice

    NASA Astrophysics Data System (ADS)

    Huang, Pu; Zhang, Liang; Zhou, Jingwei; Tian, Tian; Yin, Peiran; Duan, Changkui; Du, Jiangfeng

    2016-07-01

    Generating nonreciprocal radio frequency transduction plays important roles in a wide range of research and applications, and an aspiration is to integrate this functionality into microcircuits without introducing a magnetic field, which, however, remains challenging. By designing a 1D artificial lattice structure with a neighbor interaction engineered parametrically, we predicted a nonreciprocity transduction with a large unidirectionality. We then experimentally demonstrated the phenomenon on a nanoelectromechanical chip fabricated by conventional complementary metal-silicon processing. A unidirectionality with isolation as high as 24 dB is achieved, and several different transduction schemes are realized by programing the control voltage topology. Apart from being used as a radio frequency isolator, the system provides a way to build a practical on-chip programmable device for broad research and applications in the radio frequency domain.

  11. Nonreciprocal Radio Frequency Transduction in a Parametric Mechanical Artificial Lattice.

    PubMed

    Huang, Pu; Zhang, Liang; Zhou, Jingwei; Tian, Tian; Yin, Peiran; Duan, Changkui; Du, Jiangfeng

    2016-07-01

    Generating nonreciprocal radio frequency transduction plays important roles in a wide range of research and applications, and an aspiration is to integrate this functionality into microcircuits without introducing a magnetic field, which, however, remains challenging. By designing a 1D artificial lattice structure with a neighbor interaction engineered parametrically, we predicted a nonreciprocity transduction with a large unidirectionality. We then experimentally demonstrated the phenomenon on a nanoelectromechanical chip fabricated by conventional complementary metal-silicon processing. A unidirectionality with isolation as high as 24 dB is achieved, and several different transduction schemes are realized by programing the control voltage topology. Apart from being used as a radio frequency isolator, the system provides a way to build a practical on-chip programmable device for broad research and applications in the radio frequency domain. PMID:27419591

  12. Quasars: Millisecond-of-Arc Structure Revealed by Very-Long-Baseline Interferometry.

    PubMed

    Knight, C A; Robertson, D S; Rogers, A E; Shapiro, I I; Whitney, A R; Clark, T A; Goldstein, R M; Marandino, G E; Vandenberg, N R

    1971-04-01

    Observations with the Goldstone-Haystack radio interferometer of the quasars 3C 279 and 3C 273 have disclosed the presence of fine structure in their radio emissions. Although the interpretation is not unique, the fringe-amplitude data for quasar 3C 279 are quite consistent with emissions from two points, each contributing equally to the correlated flux. The separation of the two points is estimated to be (1.55 +/- 0.05) x 10(-3) arc second, or about 20 light years at the distance of 3 x 10(9) light years inferred from optical red-shift data. The formal uncertainty in the right-ascension component of the separation is about 6 x 10(-6) arc second; differential proper motion in this direction at half the speed of light could be discerned within a year. The fringe-amplitude data of quasar 3C 273 allow similar, but less definitive, interpretations.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  14. High stability radio links

    NASA Technical Reports Server (NTRS)

    Kursinski, E. Robert

    1989-01-01

    Radio telecommunication links are used for communication with deep space probes. These links consist of sinusoidal carrier signals at radio frequencies (RF) modulated with information sent between the spacecraft and the earth. This carrier signal is a very pure and stable sinusoid, typically derived from an atomic frequency standard whose frequency and phase are used to measure the radial velocity of the probe and from this and other data types derive its trajectory. This same observable can be used to search for space-time distortions cased by low frequency (0.1 to 100 MHz) gravitation radiation. How such a system works, what its sensitivity limitations are, and what potential future improvements can be made are discussed.

  15. Are isolated wetlands isolated?

    USGS Publications Warehouse

    Smith, Loren M.; Euliss, Ned H.; Haukos, David A.

    2011-01-01

    While federal regulations during the past 10 years have treated isolated wetlands as unconnected to aquatic resources protected by the Clean Water Act, they provide critical ecosystem services to society that extend well beyond their wetland boundaries. The authors offer well-documented examples from the scientific literature on some of the ecosystem services provided by isolated wetlands to society and other ecosystems.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    PSR J2129‑0429 is a “redback” eclipsing millisecond pulsar binary with an unusually long 15.2 hr orbit. It was discovered by the Green Bank Telescope in a targeted search of unidentified Fermi gamma-ray sources. The pulsar companion is optically bright (mean mR = 16.6 mag), allowing us to construct the longest baseline photometric data set available for such a system. We present 10 years of archival and new photometry of the companion from the Lincoln Near-Earth Asteroid Research Survey, the Catalina Real-time Transient Survey, the Palomar Transient Factory, the Palomar 60 inch, and the Las Cumbres Observatory Global Telescope. Radial velocity spectroscopy using the Double-Beam Spectrograph on the Palomar 200 inch indicates that the pulsar is massive: 1.74 ± 0.18 {M}ȯ . The G-type pulsar companion has mass 0.44 ± 0.04 {M}ȯ , one of the heaviest known redback companions. It is currently 95 ± 1% Roche-lobe filling and only mildly irradiated by the pulsar. We identify a clear 13.1 mmag yr‑1 secular decline in the mean magnitude of the companion as well as smaller-scale variations in the optical light curve shape. This behavior may indicate that the companion is cooling. Binary evolution calculations indicate that PSR J2129‑0429 has an orbital period almost exactly at the bifurcation period between systems that converge into tighter orbits as black widows and redbacks and those that diverge into wider pulsar–white dwarf binaries. Its eventual fate may depend on whether it undergoes future episodes of mass transfer and increased irradiation.

  17. Millisecond timescale disinhibition mediates fast information transmission through an avian basal ganglia loop.

    PubMed

    Leblois, Arthur; Bodor, Agnes L; Person, Abigail L; Perkel, David J

    2009-12-01

    Avian song learning shares striking similarities with human speech acquisition and requires a basal ganglia (BG)-thalamo-cortical circuit. Information processing and transmission speed in the BG is thought to be limited by synaptic architecture of two serial inhibitory connections. Propagation speed may be critical in the avian BG circuit given the temporally precise control of musculature during vocalization. We used electrical stimulation of the cortical inputs to the BG to study, with fine time resolution, the functional connectivity within this network. We found that neurons in thalamic and cortical nuclei that are not directly connected with the stimulated area can respond to the stimulation with extremely short latencies. Through pharmacological manipulations, we trace this property back to the BG and show that the cortical stimulation triggers fast disinhibition of the thalamic neurons. Surprisingly, feedforward inhibition mediated by striatal inhibitory neurons onto BG output neurons sometimes precedes the monosynaptic excitatory drive from cortical afferents. The fast feedforward inhibition lengthens a single interspike interval in BG output neurons by just a few milliseconds. This short delay is sufficient to drive a strong, brief increase in firing probability in the target thalamic neurons, evoking short-latency responses. By blocking glutamate receptors in vivo, we show that thalamic responses do not appear to rely on excitatory drive, and we show in a theoretical model that they could be mediated by postinhibitory rebound properties. Such fast signaling through disinhibition and rebound may be a crucial specialization for learning of rapid and temporally precise motor acts such as vocal communication. PMID:20007467

  18. Mechanism of substrate translocation by a ring-shaped ATPase motor at millisecond resolution

    PubMed Central

    Ma, Wen

    2015-01-01

    Ring-shaped, hexameric ATPase motors fulfill key functions in cellular processes, such as genome replication, transcription or protein degradation, by translocating a long substrate through their central pore powered by ATP hydrolysis. Despite intense research efforts, the atomic-level mechanism transmitting chemical energy from hydrolysis into mechanical force that translocates the substrate is still unclear. Here we employ all-atom molecular dynamics simulations combined with advanced path sampling techniques and milestoning analysis to characterize how mRNA substrate is translocated by an exemplary homo-hexameric motor, the transcription termination factor Rho. We find that the release of hydrolysis product (ADP+Pi) triggers the force-generating process of Rho through a 0.1 millisecond-long conformational transition, the time scale seen also in experiment. The calculated free energy profiles and kinetics show that Rho unidirectionally translocates the single-stranded RNA substrate via a population shift of the conformational states of Rho; upon hydrolysis product release, the most favorable conformation shifts from the pre-translocation state to the post-translocation state. Via two previously unidentified intermediate states, the RNA chain is seen to be pulled by six K326 side chains, whose motions are induced by highly coordinated relative translation and rotation of Rho’s six subunits. The present study not only reveals in new detail the mechanism employed by ring-shaped ATPase motors, for example the use of loosely bound and tightly bound hydrolysis reactant and product states to coordinate motor action, but also provides an effective approach to identify allosteric sites of multimeric enzymes in general. PMID:25646698

  19. A CHANDRA X-RAY OBSERVATION OF THE BINARY MILLISECOND PULSAR PSR J1023+0038

    SciTech Connect

    Bogdanov, Slavko; Archibald, Anne M.; Kaspi, Victoria M.; Hessels, Jason W. T.; Lorimer, Duncan; McLaughlin, Maura A.; Ransom, Scott M.; Stairs, Ingrid H.

    2011-12-01

    We present a Chandra X-Ray Observatory ACIS-S variability, spectroscopy, and imaging study of the peculiar binary containing the millisecond pulsar J1023+0038. The X-ray emission from the system exhibits highly significant (12.5{sigma}) large-amplitude (factor of two to three) orbital variability over the five consecutive orbits covered by the observation, with a pronounced decline in the flux at all energies at superior conjunction. This can be naturally explained by a partial geometric occultation by the secondary star of an X-ray-emitting intrabinary shock, produced by the interaction of outflows from the two stars. The depth and duration of the eclipse imply that the intrabinary shock is localized near or at the surface of the companion star and close to the inner Lagrangian point. The energetics of the shock favor a magnetically dominated pulsar wind that is focused into the orbital plane, requiring close alignment of the pulsar spin and orbital angular momentum axes. The X-ray spectrum consists of a dominant non-thermal component and at least one thermal component, likely originating from the heated pulsar polar caps, although a portion of this emission may be from an optically thin 'corona'. We find no evidence for extended emission due to a pulsar wind nebula or bow shock down to a limiting luminosity of L{sub X} {approx}< 3.6 Multiplication-Sign 10{sup 29} erg s{sup -1} (0.3-8 keV), {approx}< 7 Multiplication-Sign 10{sup -6} of the pulsar spin-down luminosity, for a distance of 1.3 kpc and an assumed power-law spectrum with photon index {Gamma} = 1.5.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  1. Millisecond denaturation dynamics of fluorescent proteins revealed by femtoliter container on micro-thermodevice.

    PubMed

    Arata, Hideyuki F; Gillot, Frederic; Nojima, Takahiko; Fujii, Teruo; Fujita, Hiroyuki

    2008-09-01

    Real-time observation of biomolecular behavior focusing on high speed temperature response is an essential endeavor for further biological study at the molecular level. This is because most of the important biological functions at the molecular level happen at the sub-second time scale. We used our own on-chip microheaters and microcontainers to observe the denaturation dynamics of fluorescent proteins at the millisecond time scale. The microheater controls the temperature in 1 ms under the microscope. Fluorescent proteins were contained in 28 fL PDMS microcontainers to prevent them from diffusing into the solution. The proteins were denatured by high temperatures and observed by a high speed CCD camera with 5 ms per frame. Hence, denaturation speeds of red fluorescent proteins (rDsRed and rHcRed) were measured to be 5-10 ms. Green fluorescent proteins (rAcGFP and rGFPuv) denatured with bi-exponential decay. rAcGFP denatured with time constants of 5 ms and 75 ms while rGFPuv denatured with 10 ms and 130 ms. This may be the reverse process of a two step renaturation of GFP observed in a previous report. This micro-thermodevice is applicable to other biomaterials such as nucleic acids or other proteins. It does not require any chemical treatment nor mutation to the biomaterial itself. Therefore, the methodology using this general purpose device gives access to biomolecular studies in short time scales and acts as a powerful tool in molecular biology.

  2. A METAL-RICH LOW-GRAVITY COMPANION TO A MASSIVE MILLISECOND PULSAR

    SciTech Connect

    Kaplan, D. L.; Bhalerao, V. B.; Van Kerkwijk, M. H.; Koester, D.; Kulkarni, S. R.; Stovall, K. E-mail: mhvk@astro.utoronto.ca

    2013-03-10

    Most millisecond pulsars with low-mass companions are in systems with either helium-core white dwarfs or non-degenerate (''black widow'' or ''redback'') stars. A candidate counterpart to PSR J1816+4510 was identified by Kaplan et al. whose properties were suggestive of both types of companions although identical to neither. We have assembled optical spectroscopy of the candidate companion and confirm that it is part of the binary system with a radial velocity amplitude of 343 {+-} 7 km s{sup -1}, implying a high pulsar mass, M{sub psr}sin {sup 3} i = 1.84 {+-} 0.11 M{sub Sun }, and a companion mass M{sub c} sin {sup 3} i = 0.193 {+-} 0.012 M{sub Sun }, where i is the inclination of the orbit. The companion appears similar to proto-white dwarfs/sdB stars, with a gravity log{sub 10}(g) = 4.9 {+-} 0.3, and effective temperature 16, 000 {+-} 500 K. The strongest lines in the spectrum are from hydrogen, but numerous lines from helium, calcium, silicon, and magnesium are present as well, with implied abundances of roughly 10 times solar (relative to hydrogen). As such, while from the spectrum the companion to PSR J1816+4510 is superficially most similar to a low-mass white dwarf, it has much lower gravity, is substantially larger, and shows substantial metals. Furthermore, it is able to produce ionized gas eclipses, which had previously been seen only for low-mass, non-degenerate companions in redback or black widow systems. We discuss the companion in relation to other sources, but find that we understand neither its nature nor its origins. Thus, the system is interesting for understanding unusual stellar products of binary evolution, as well as, independent of its nature, for determining neutron-star masses.

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

    SciTech Connect

    Knispel, B.; Allen, B.; Lyne, A. G.; Stappers, B. W.; Freire, P. C. C.; Lazarus, P.; Aulbert, C.; Bock, O.; Eggenstein, H.-B.; Fehrmann, H.; Bogdanov, S.; Camilo, F.; Brazier, A.; Chatterjee, S.; Cordes, J. M.; Cardoso, F.; Crawford, F.; Deneva, J. S.; Ferdman, R.; Hessels, J. W. T.; and others

    2015-06-10

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  5. Solar radio continuum storms

    NASA Technical Reports Server (NTRS)

    Sakurai, K.

    1976-01-01

    The paper reviews the current status of research on solar radio continuum emissions from metric to hectometric wave frequencies, emphasizing the role of energetic electrons in the 10-100 keV range in these emissions. It is seen that keV-energy electrons generated in active sunspot groups must be the sources of radio continuum storm emissions for wide frequency bands. These electrons excite plasma oscillations in the medium, which in turn are converted to electromagnetic radiation. The radio noise continuum sources are usually associated with type III burst activity observed above these sources. Although the mechanism for the release of the energetic electrons is not known, it seems they are ejected from storm source regions in association with rapid variation of associated sunspot magnetic fields due to their growth into complex types. To explain some of the observed characteristics, the importance of two-stream instability and the scattering of ambient plasma ions on energetic electron streams is pointed out.

  6. Workshop on Radio Transients

    NASA Astrophysics Data System (ADS)

    Croft, Steve; Gaensler, Bryan

    2012-04-01

    abstract-type="normal">SummaryWe are entering a new era in the study of variable and transient radio sources. This workshop discussed the instruments and the strategies employed to study those sources, how they are identified and classified, how results from different surveys can be compared, and how radio observations tie in with those at other wavelengths. The emphasis was on learning what common ground there is between the plethora of on-going projects, how methods and code can be shared, and how best practices regarding survey strategy could be adopted. The workshop featured the four topics below. Each topic commenced with a fairly brief introductory talk, which then developed into discussion. By way of preparation, participants had been invited to upload and discuss one slide per topic to a wiki ahead of the workshop. 1. Telescopes, instrumentation and survey strategy. New radio facilities and on-going projects (including upgrades) are both studying the variability of the radio sky, and searching for transients. The discussion first centred on the status of those facilities, and on projects with a time-domain focus, both ongoing and planned, before turning to factors driving choices of instrumentation, such as phased array versus single pixel feeds, the field of view, spatial and time resolution, frequency and bandwidth, depth, area, and cadence of the surveys. 2. Detection, pipelines, and classification. The workshop debated (a) the factors that influence decisions to study variability in the (u,v) plane, in images, or in catalogues, (b) whether, and how much, pipeline code could potentially be shared between one project and another, and which software packages are best for different approaches, (c) how data are stored and later accessed, and (d) how transients and variables are defined and classified. 3. Statistics, interpretation, and synthesis. It then discussed how (i) the choice of facility and strategy and (ii) detection and classification schemes

  7. PHYSICAL CONSTRAINTS ON FAST RADIO BURSTS

    SciTech Connect

    Luan, Jing; Goldreich, Peter

    2014-04-20

    Fast radio bursts (FRBs) are isolated, ms radio pulses with dispersion measure (DM) of order 10{sup 3} pc cm{sup –3}. Galactic candidates for the DM of high latitude bursts detected at GHz frequencies are easily dismissed. DM from bursts emitted in stellar coronas are limited by free-free absorption and those from H II regions are bounded by the nondetection of associated free-free emission at radio wavelengths. Thus, if astronomical, FRBs are probably extragalactic. FRB 110220 has a scattering tail of ∼5.6 ± 0.1 ms. If the electron density fluctuations arise from a turbulent cascade, the scattering is unlikely to be due to propagation through the diffuse intergalactic plasma. A more plausible explanation is that this burst sits in the central region of its host galaxy. Pulse durations of order ms constrain the sizes of FRB sources implying high brightness temperatures that indicates coherent emission. Electric fields near FRBs at cosmological distances would be so strong that they could accelerate free electrons from rest to relativistic energies in a single wave period.

  8. Sampling Studies Of Quasars, Radio-loud Galaxies, & Radio-quiet Galaxies -- Searching For The Cause Of Radio Emission

    NASA Astrophysics Data System (ADS)

    Coldwell, G.; Salois, Amee; Soechting, I.; Smith, M.

    2011-01-01

    Comparing the environments of Radio-Loud Galaxies, Radio-Quiet Galaxies, and Quasars offers an opportunity to study the evolution of these objects. Our samples have been carefully chosen from Data Release 7 of the Sloan Digital Sky Survey, which also includes samples studied in the FIRST survey, and have been cut to determine the best possible results. Our study includes three samples. The Quasar sample currently contains 69 objects, the Radio-Loud Galaxy (RLG) sample has 1,335 objects, and the Radio-Quiet Galaxy (RQG) sample contains 2,436 objects (any updates will be given at the meeting). A number of trims were made to produce (smaller) samples with characteristics suited for precise results. By comparing the environments of these three samples we will be able to see any similarities or differences between them. If similarities are detected it suggests that the central object has evolved according to 'nature' - in an isolated manner with little environmental feedback, which may or may not have an effect on its evolution, as supposed by Coldwell et al. (2009). If differences are detected it suggests that the central object has evolved according to `nurture’ and that the environment may have played an important role in the development of their properties. We employ similar procedures used by Coldwell et al. (2009) in their study of blue and red AGNs. Upon the completion of an accurate sample, future work will be pursued studying a number of properties of the environments including studies of: the stellar masses, star formation rates, sersic morphologies, as well as densities and ages of the environments.

  9. Radio emision from supernova remnants

    NASA Astrophysics Data System (ADS)

    Dubner, G.

    2016-06-01

    The vast majority of supernova remnants (SNRs) in our Galaxy and nearby galaxies have been discovered through radio observations, and only a very small number of the SNRs catalogued in the Milky Way have not been detected in the radio band, or are poorly defined by current radio observations. The study of the radio emission from SNRs is an excellent tool to investigate morphological characteristics, marking the location of shock fronts and contact discontinuities; the presence, orientation and intensity of the magnetic field; the energy spectrum of the emitting particles; and the dynamical consequences of the interaction with the circumstellar and interstellar medium. I will review the present knowledge of different important aspects of radio remnants and their impact on the interstellar gas. Also, new radio studies of the Crab Nebula carried out with the Karl Jansky Very Large Array (JVLA) at 3 GHz and with ALMA at 100 GHz, will be presented.

  10. Fast radio bursts as giant pulses from young rapidly rotating pulsars

    NASA Astrophysics Data System (ADS)

    Lyutikov, Maxim; Burzawa, Lukasz; Popov, Sergei B.

    2016-10-01

    We discuss possible association of fast radio bursts (FRBs) with supergiant pulses emitted by young pulsars (ages ˜ tens to hundreds of years) born with regular magnetic field but very short - few milliseconds - spin periods. We assume that FRBs are extra-Galactic events coming from distances d ≲ 100 Mpc and that most of the dispersion measure (DM) comes from the material in the freshly ejected SNR shell. We then predict that for a given burst the DM should decrease with time and that FRBs are not expected to be seen below ˜300 MHz due to free-free absorption in the expanding ejecta. A supernova might have been detected years before the burst; FRBs are mostly associated with star-forming galaxies. The model requires that some pulsars are born with very fast spins, of the order of few milliseconds. The observed distribution of spin-down powers dot{E} in young energetic pulsars is consistent with equal birth rate per decade of dot{E}. Accepting this injection distribution and scaling the intrinsic brightness of FRBs with dot{E}, we predict the following properties of a large sample of FRBs: (i) the brightest observed events come from a broad distribution in distances; (ii) for repeating bursts brightness either remains nearly constant (if the spin-down time is longer than the age of the pulsar) or decreases with time otherwise; in the latter case DM ∝ dot{E}.

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

    NASA Astrophysics Data System (ADS)

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

    2009-07-01

    We have completed a survey for pulsars at high Galactic latitudes with the 64 m Parkes radio telescope. Observing with the 13 beam multibeam receiver at a frequency of 1374 MHz, we covered ~4150 square degrees in the region -100° <= l <= 50°, 15° <= |b| <= 30° with 7232 pointings of 265 s each, thus extending the Swinburne Intermediate Latitude Pulsar Survey a further 15° on either side of the Galactic plane. The signal from each beam was processed by a 96 channel × 3 MHz × 2 polarization filterbank, with the detected power in the two polarizations of each frequency channel summed and digitized with 1 bit sampling every 125 μs, giving good sensitivity to millisecond pulsars with low or moderate dispersion measure. The resulting 2.4 TB data set was processed using standard pulsar search techniques with the workstation cluster at the Swinburne Centre for Astrophysics and Supercomputing. This survey resulted in the discovery of 26 new pulsars including seven binary and/or millisecond pulsars, and redetected 36 previously known pulsars. We describe the survey methodology and results, and present timing solutions for the 19 newly discovered slow pulsars, as well as for nine slow pulsars discovered the Swinburne Intermediate Latitude Pulsar Survey that had no previous timing solutions. Even with a small sampling interval, 1374 MHz center frequency, and a large mid-latitude survey volume we failed to detect any very rapidly spinning pulsars. Evidently, such "submillisecond" pulsars are rare.

  12. Locating Radio Noise from Sprites

    NASA Astrophysics Data System (ADS)

    Fullekrug, M.; Mezentsev, A.; Watson, R.; Gaffet, S.; Astin, I.; Evans, A.

    2014-12-01

    Sprites are composed of individual streamer discharges (e.g., Pasko, 2010) which split into exponentially growing streamer tips (McHarg et al., 2010). The acceleration of the electrons to a few eV results in the radiation of a small amount of electromagnetic energy. The incoherent superposition of many streamers causes the low frequency radio noise from sprites near ~40 km height (Qin et al., 2012). The presence of this theoretically predicted radiation was recently confirmed by low frequency radio noise measurements during dancing sprites with a very sensitive radio receiver (Fullekrug et al., 2013). To locate the radio noise from sprites in the sky, an interferometric network of low frequency radio receivers was developed (Mezentsev and Fullekrug, JGR, 2013). The key parameter for the interferometric signal processing is the frequency dependent wave propagation velocity of the radio waves within the Earth's atmosphere. This wave propagation velocity is determined by the wave number vector which needs to be inferred from the measurements. Here we adapt and subsequently apply array analyses which have been developed for seismic and infrasound arrays to determine the horizontal wave number vectors of ~20-24 kHz radio waves measured with an array of ten radio receivers distributed over an area of ~1 km × 1 km. It is found that the horizontal slowness of ~20-24 kHz radio waves ranges from ~2.7 ns/m to ~4.1 ns/m depending on the arrival azimuth of the radio wave. For comparison, an electromagnetic wave in vacuum has a slowness of ~3.34 ns/m. A larger slowness indicates an apparent velocity which is smaller than the speed of light and a smaller slowness indicates that the radio wave arrives at the array from an elevation angle. The observed variability of the observed slowness almost certainly results from the distance dependent superposition of the transverse electric and magnetic TEn and TMn radio wave propagation modes.

  13. Origins of Canadian Radio Astronomy

    NASA Astrophysics Data System (ADS)

    Covington, A. E.

    1988-08-01

    Radar technology after World War II was rapidly applied to the radio astronomy founded by Jansky and Reber. The first post-war discoveries in various countries from 1945 to 1950 were made with instruments built from surplus parts, and quickly led to the design of specialized equipment. The development in Ottawa at the Laboratories of the National Research Council is outlined, initially for solar radio observations and then for the early galactic observations at the Goth Hill Radio Observatory, near Ottawa.

  14. An observational overview of the millisecond magnetar scenario for long and short gamma-ray bursts

    NASA Astrophysics Data System (ADS)

    O'Brien, Paul; Gompertz, Ben

    2016-07-01

    The standard model for GRBs involves either the collapse of a massive star or the merger of a compact binary system resulting in a black hole which accretes for a brief period of time. An alternative model is to form a magnetar, which survives for a while at least powering the emission. I will discuss some recent attempts to fit a magnetar model, including the effects of spindown and propellering, to the high-energy data for some GRBs. I will also show how energy injection from a magnetar could be tested using radio observations

  15. Decimetric radio dot emissions

    NASA Astrophysics Data System (ADS)

    Mészárosová, H.; Karlický, M.; Sawant, H. S.; Fernandes, F. C. R.; Cecatto, J. R.; de Andrade, M. C.

    2008-11-01

    Context: We study a rare type of solar radio bursts called decimetric dot emissions. Aims: In the period 1999-2001, 20 events of decimetric dot emissions observed by the Brazilian Solar Spectroscope (BSS) in the frequency range 950-2640 MHz are investigated statistically and compared with radio fine structures of zebras and fibers. Methods: For the study of the spectral characteristics of the dot emissions we use specially developed Interactive Data Language (IDL) software called BSSView and basic statistical methods. Results: We have found that the dm dot emissions, contrary to the fine structures of the type IV bursts (i.e. zebras, fibers, lace bursts, spikes), are not superimposed on any background burst emission. In the radio spectrum, in most cases the dot emissions form chains that appear to be arranged in zebra patterns or fibers. Because some zebras and fibers, especially those observed with high time and high spectral resolutions, also show emission dots (but superimposed on the background burst emission), we compared the spectral parameters of the dot emissions with the dots being the fine structure of zebras and fibers. For both these dots, similar spectral characteristics were found. Some similarities of the dot emissions can be found also with the lace bursts and spikes. For some events the dot emissions show structural evolution from patterns resembling fibers to patterns resembling zebras and vice versa, or they evolve into fully chaotic patterns. Conclusions: For the first time, we present decimetric dot emissions that appear to be arranged in zebra patterns or fibers. We propose that these emissions are generated by the plasma emission mechanism at the locations in the solar atmosphere where the double resonance condition is fulfilled.

  16. Observations of Solar Radio Transients

    NASA Astrophysics Data System (ADS)

    Paige, Giorla

    2011-05-01

    A low frequency radio telescope has been recently been constructed on the campus of the The College of New Jersey (TCNJ) and has begun conducting observations at 20MHz as part of NASA'a Radio Jove program. This instrument is capable of observations of solar radio emission including strong prompt radio emission associated with solar burst events. We will discuss solar observations conducted with this instrument as well as an effort to conduct coincident observations with the Eight-meter-wavelength Transient Array (ETA) and the Long Wavelength Array (LWA).

  17. Radio Loud AGNs are Mergers

    NASA Astrophysics Data System (ADS)

    Chiaberge, Marco; Gilli, Roberto; Lotz, Jennifer M.; Norman, Colin

    2015-06-01

    We measure the merger fraction of Type 2 radio-loud and radio-quiet active galactic nuclei (AGNs) at z\\gt 1 using new samples. The objects have Hubble Space Telescope (HST) images taken with Wide Field Camera 3 (WFC3) in the IR channel. These samples are compared to the 3CR sample of radio galaxies at z\\gt 1 and to a sample of non-active galaxies. We also consider lower redshift radio galaxies with HST observations and previous generation instruments (NICMOS and WFPC2). The full sample spans an unprecedented range in both redshift and AGN luminosity. We perform statistical tests to determine whether the different samples are differently associated with mergers. We find that all (92%-14%+8%) radio-loud galaxies at z\\gt 1 are associated with recent or ongoing merger events. Among the radio-loud population there is no evidence for any dependence of the merger fraction on either redshift or AGN power. For the matched radio-quiet samples, only 38%-15+16 are merging systems. The merger fraction for the sample of non-active galaxies at z\\gt 1 is indistinguishable from radio-quiet objects. This is strong evidence that mergers are the triggering mechanism for the radio-loud AGN phenomenon and the launching of relativistic jets from supermassive black holes (SMBHs). We speculate that major black hole (BH)-BH mergers play a major role in spinning up the central SMBHs in these objects.

  18. Internet Resources for Radio Astronomy

    NASA Astrophysics Data System (ADS)

    Andernach, H.

    A subjective overview of Internet resources for radio-astronomical information is presented. Basic observing techniques and their implications for the interpretation of publicly available radio data are described, followed by a discussion of existing radio surveys, their level of optical identification, and nomenclature of radio sources. Various collections of source catalogues and databases for integrated radio source parameters are reviewed and compared, as well as the web interfaces to interrogate the current and ongoing large-area surveys. Links to radio observatories with archives of raw (uv-) data are presented, as well as services providing images, both of individual objects or extracts (``cutouts'') from large-scale surveys. While the emphasis is on radio continuum data, a brief list of sites providing spectral line data, and atomic or molecular information is included. The major radio telescopes and surveys under construction or planning are outlined. A summary is given of a search for previously unknown optically bright radio sources, as performed by the students as an exercise, using Internet resources only. Over 200 different links are mentioned and were verified, but despite the attempt to make this report up-to-date, it can only provide a snapshot of the situation as of mid-1998.

  19. A CHANDRA OBSERVATION OF THE BURSTING MILLISECOND X-RAY PULSAR IGR J17511-3057

    SciTech Connect

    Paizis, A.; Nowak, M. A.; Rodriguez, J.; Chaty, S.; Del Santo, M.; Ubertini, P. E-mail: mnowak@space.mit.edu

    2012-08-10

    IGR J17511-3057 is a low-mass X-ray binary hosting a neutron star and is one of the few accreting millisecond X-ray pulsars with X-ray bursts. We report on a 20 ks Chandra grating observation of IGR J17511-3057, performed on 2009 September 22. We determine the most accurate X-ray position of IGR J17511-3057, {alpha}{sub J2000} = 17{sup h}51{sup m}08.{sup s}66, {delta}{sub J2000} = -30 Degree-Sign 57'41.''0 (90% uncertainty of 0.''6). During the observation, a {approx}54 s long type-I X-ray burst is detected. The persistent (non-burst) emission has an absorbed 0.5-8 keV luminosity of 1.7 Multiplication-Sign 10{sup 36} erg s{sup -1} (at 6.9 kpc) and can be well described by a thermal Comptonization model of soft, {approx}0.6 keV, seed photons upscattered by a hot corona. The type-I X-ray burst spectrum, with average luminosity over the 54 s duration L{sub 0.5-8{sub keV}} = 1.6 Multiplication-Sign 10{sup 37} erg s{sup -1}, can be well described by a blackbody with kT{sub bb} {approx} 1.6 keV and R{sub bb} {approx} 5 km. While an evolution in temperature of the blackbody can be appreciated throughout the burst (average peak kT{sub bb} = 2.5{sup +0.8}{sub -0.4} keV to tail kT{sub bb} = 1.3{sup +0.2}{sub -0.1} keV), the relative emitting surface shows no evolution. The overall persistent and type-I burst properties observed during the Chandra observation are consistent with what was previously reported during the 2009 outburst of IGR J17511-3057.

  20. Study of millisecond laser annealing on ion implanted soi and application to scaled finfet technology

    NASA Astrophysics Data System (ADS)

    Michalak, Tyler J.

    The fabrication of metal-oxide-semiconductor field effect transistors (MOSFET) requires the engineering of low resistance, low leakage, and extremely precise p-n junctions. The introduction of finFET technology has introduced new challenges for traditional ion implantation and annealing techniques in junction design as the fin widths continue to decrease for improved short channel control. This work investigates the use of millisecond scanning laser annealing in the formation of n-type source/drain junctions in next generation MOSFET. We present a model to approximate the true thermal profile for a commercial laser annealing process which allows us to represent more precisely specific thermal steps using Technology Computer Aided Design (TCAD). Sheet resistance and Hall Effect measurements for blanket films are used to correlate dopant activation and mobility with the regrowth process during laser anneal. We show the onset of high conductivity associated with completion of solid phase epitaxial regrowth (SPER) in the films. The Lattice Kinetic Monte Carlo (LKMC) model shows excellent agreement with cross section transmission electron microscopy (TEM), correlating the increase of conductivity with completion of crystal regrowth, increased activation, and crystal quality at various temperatures. As scaled devices move into the non-planar geometries and possibly adopt silicon-on-insulator (SOI) substrates, the crystal regrowth and dopant activation of amorphizing implants becomes more complicated and doping methods must adapt accordingly. Following the concept of the more recently proposed hot ion implantation and the benefits of laser anneal, we investigate a possible process flow for a 10/14 nm node SOI finFET by utilizing process and device TCAD. Device simulation parameters for the 10/14 nm node device are taken from a calibrated model based on fabricated non-planar 40 nm gate length device finFET. The implications on device performance are considered for the

  1. Partial accretion in the propeller stage of accreting millisecond X-ray pulsars

    NASA Astrophysics Data System (ADS)

    Gungor, Can; Gogus, Ersin; Eksi, Kazim Yavuz; Guver, Tolga

    2016-07-01

    Accreting millisecond X-ray pulsars (AMXPs) are very important objects for studying the stages of disk - magnetosphere interaction as these objects may show different stages in an observable duration. A typical X-ray light curve of an outburst of AMXP has a fast rise and an exponential decay phases. Most of the outbursts have a knee where the flux goes from the slow decay stage to the rapid decay stage. This knee may be linked to the transition from accretion to propeller stage. Since, after the knee, the X-ray luminosity of the source is still higher than its quiescent level, the accretion from inner disc must be continuing in the propeller stage with a lower fraction than in the accretion stage. The X-ray does not only come from accretion onto the poles but the inner parts of the disk may also contribute to the total X-ray luminosity. To infer what fraction (f) of the inflowing matter accretes onto the star the light curve in the propeller stage, one should first separate the emission originating from the disk and obtain a light curve of X-ray emission only from the magnetic poles. We provide a new method to infer from the observational data the fraction of accreting matter onto the neutron star pole to the mass transferring from outer layers of the disc to the inner disc (f), as a function of the fastness parameter (ω_{*}), assuming the knee is due to the transition from accretion to the propeller stage. We transform X-ray luminosities to the mass fraction, f, and the time scale of outburst to fastness parameter, ω_*. It allows us to compare different types of outbursts of an AMXP in f - ω_* space which is universal for a unique system. We analysed the Rossi X-ray Timing Explorer/Proportional Counter Array (RXTE/PCA) observations of the 2000 and the 2011 outbursts and the Swift Gamma-Ray Burst Mission/X-ray Telescope (SWIFT/XRT) data of the 2013 outburst of the most known AMXP, Aql X-1 using a combination of blackbody representing hot spot, disk blackbody

  2. Evidence for a Millisecond Pulsar in 4U 1636-53 During a Superburst

    NASA Technical Reports Server (NTRS)

    Strohmayer, Tod E.; Markwardt, Craig B.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    We report the discovery with the Proportional Counter Array on board the Rossi X-ray Timing Explorer of highly coherent 582 Hz pulsations during the February 22, 2001 (UT) 'superburst' from 4U 1636-53. The pulsations are detected during an 800 s interval spanning the flux maximum of the burst. Within this interval the barycentric oscillation frequency increases in a monotonic fashion from 581.89 to 581.93 Hz. The predicted orbital motion of the neutron star during this interval is consistent with such an increase as long as optical maximum corresponds roughly with superior conjunction of V801 Arae, the optical companion to the neutron star in 4U 1636-53. We show that a range of circular orbits with 90 < v(sub ns) sin i < 175 km/s and 0.336 > phi(sub 0) > 0.277 for the neutron star can provide an excellent description of the frequency and phase evolution. The brevity of the observed pulse train with respect to the 3.8 hour orbital period unfortunately does not allow more precise constraints. The average pulse profile is sinusoidal and the time averaged pulsation amplitude, as inferred from the half amplitude of the sinusoid is 1%, smaller than typical for burst oscillations observed in normal thermonuclear bursts. We do not detect any higher harmonics nor the putative subharmonic near 290 Hz. The 90% upper limits on signal amplitude at the subharmonic and first harmonic are 0.1 and 0.06%, respectively. The highly coherent pulsation, with a Q = v(sub 0)/delta-v > 4.5 x 10(exp 5) provides compelling evidence for a rapidly rotating neutron star in 4U 1636-53, and further supports the connection of burst oscillation frequencies with the spin frequencies of neutron stars. Our results provide further evidence that some millisecond pulsars are spun up via accretion in LMXBs. We also discuss the implications of our orbital velocity constraint for the masses of the components of 4U 1636-53.

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

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Astrophysics Data System (ADS)

    Bednarek, W.; Sitarek, J.

    2013-02-01

    Context. The features of pulsed γ-ray emission from classical and millisecond pulsars indicate that the high energy radiation processes in their inner magnetospheres occur in a similar way. In the past decade several TeV γ-ray nebulae have been discovered around classical pulsars. The above facts suggest that γ-rays should be produced also in the surroundings of millisecond pulsars. Aims: We discuss a model for the bow shock nebula around the well known Black Widow binary system containing the millisecond pulsar B1957+20. This model predicts the existence of a synchrotron X-ray and inverse Compton γ-ray nebula around this system. We want to find out whether γ-ray emission from the nebula around B1957+20 could be detected by the future and present Cherenkov telescopes. Methods: Using the Monte Carlo method we followed the propagation of relativistic electrons in the vicinity of the pulsar. We calculated the very high energy radiation produced by them in the synchrotron process and the inverse Compton scattering of the microwave background radiation and of the infrared radiation from the galactic disk. We also computed the X-ray emission produced by the electrons in the synchrotron process. Results: We show that the hard X-ray tail emission observed from the vicinity of B1957+20 can be explained by our model. Moreover, we predict that the TeV γ-ray emission produced by the electrons in the inverse Compton process should be detectable by the future Cherenkov Telescope Array and possibly by the long term observations with the present Cherenkov arrays such as MAGIC and VERITAS. The γ-ray emission from B1957+20 is expected to be extended, inhomogeneous, and shifted from the present location of the binary system by a distance comparable to the radius of the nebula.

  5. Solar radio emission

    NASA Technical Reports Server (NTRS)

    Goldman, M. V.; Smith, D. F.

    1981-01-01

    Active areas of both observational and theoretical research in which rapid progress is being made are discussed. These include: (1) the dynamic spectrum or frequency versus time plot; (2) physical mechanisms in the development of various types of bursts; (3) microwave type 1, 2, 3, and moving type 4 bursts; (4) bursts caused by trapped electrons; (5) physics of type 3bursts; (6) the physics of type 2 bursts and their related shocks; (7) the physics of both stationary and moving traps and associated type 1 and moving type 4 bursts; and (8) the status of the field of solar radio emission.

  6. RADIO FREQUENCY ATTENUATOR

    DOEpatents

    Giordano, S.

    1963-11-12

    A high peak power level r-f attenuator that is readily and easily insertable along a coaxial cable having an inner conductor and an outer annular conductor without breaking the ends thereof is presented. Spaced first and second flares in the outer conductor face each other with a slidable cylindrical outer conductor portion therebetween. Dielectric means, such as water, contact the cable between the flares to attenuate the radio-frequency energy received thereby. The cylindrical outer conductor portion is slidable to adjust the voltage standing wave ratio to a low level, and one of the flares is slidable to adjust the attenuation level. An integral dielectric container is also provided. (AFC)

  7. Lunar Farside Radio Lab

    NASA Astrophysics Data System (ADS)

    Maccone, Claudio

    2005-03-01

    It is proposed that the Farside of the Moon should be protected legally against man-made radio pollution and uncontrolled exploitation. In fact, only by establishing a radiotelescope on the Farside of the Moon it will finally be possible to cope with the Radio Frequency Interference (RFI) that is now increasingly plaguing all of Radioastronomy, Bioastronomy and Search for Extraterrestrial Intelligence (SETI) Searches done from the surface of the Earth. It is suggested to partition the Farside into 3 sectors, each 60°wide, to ensurethe creation of a future “Lunar Farside Radio Lab” inside crater Daedalus (at 180°E) with our planned Radiotelescope (in practice a Phased Array),complete freedom to exploit the Nearside as well as the four Lagrangian points L1, L3, L4 and L5 of the Earth Moon system by allowing even some International Space Stations to be located there. It is also claimed, however, thatthe “opposite” Lagrangian point L2 should possibly be kept free of spacecrafts that would flood the Farside by the RFI they produce. Realistically, it might be difficult to comply with the latter request in view of the far-future development of a Space Base located there in order to depart towards the Asteroids and the Outer Planets at very reduced fuel consumption. A more reasonable request about any future space station located at the Earth Moon L2 point is thus that this future space station should be shielded to prevent its RFI from reaching the Farside of the Moon.A number of further astrophysical, astronautical and technical issues could just be highlighted in this study and deserve much more elaboration. To mention a few:the precise size of the “Quiet Cone” extending into space above the Farside of the Moon. Also, the experimental measurement of how quiet this Cone actually is by letting a radiometer orbit the Moon (see the web site www.rli.it);the mathematical modelling of the weak ionosphere of the Moon and its possible diffraction effects at very

  8. Investigation on laser-assisted tissue repair with NIR millisecond-long light pulses and Indocyanine Green-biopolymeric patches

    NASA Astrophysics Data System (ADS)

    Matteini, Paolo; Banchelli, Martina; Cottat, Maximilien; Osticioli, Iacopo; de Angelis, Marella; Rossi, Francesca; Pini, Roberto

    2016-03-01

    In previous works a minimally invasive laser-assisted technique for vascular repair was presented. The technique rests on the photothermal adhesion of a biocompatible and bioresorbable patch containing Indocyanine Green that is brought into contact with the site to be repaired. Afterward the use of NIR millisecond-long light pulses generates a strong welding effect between the patch and the underlying tissue and in turn the repair of the wound. This technique was shown to be effective in animal model and provides several advantages over conventional suturing methods. Here we investigate and discuss the optical stability of the ICG-biopolymeric patches and the photothermal effects induced to the irradiated tissue.

  9. SOLAR RADIO BURSTS WITH SPECTRAL FINE STRUCTURES IN PREFLARES

    SciTech Connect

    Zhang, Yin; Tan, Baolin; Huang, Jing; Tan, Chengming; Karlický, Marian; Mészárosová, Hana; Simões, Paulo J.A.

    2015-01-20

    Good observations of preflare activities are important for us to understand the origin and triggering mechanism of solar flares, and to predict the occurrence of solar flares. This work presents the characteristics of microwave spectral fine structures as preflare activities of four solar flares observed by the Ondřejov radio spectrograph in the frequency range of 0.8-2.0 GHz. We found that these microwave bursts which occurred 1-4 minutes before the onset of flares have spectral fine structures with relatively weak intensities and very short timescales. They include microwave quasi-periodic pulsations with very short periods of 0.1-0.3 s and dot bursts with millisecond timescales and narrow frequency bandwidths. Accompanying these microwave bursts are filament motions, plasma ejection or loop brightening in the EUV imaging observations, and non-thermal hard X-ray emission enhancements observed by RHESSI. These facts may reveal certain independent, non-thermal energy releasing processes and particle acceleration before the onset of solar flares. They may help us to understand the nature of solar flares and to predict their occurrence.

  10. The Extragalactic Radio Background

    NASA Technical Reports Server (NTRS)

    Kogut, A.; Fixsen, D. J.; Levin, S. M.; Limon, M.; Lubin, P. M.; Seiffert, M.; Singal, J.; Villela, T.; Wollack, E.; Wuensche, C. A.

    2011-01-01

    The existence of an isotropic component of the high-latitude radio sky has been recognized for nearly fifty years, but has typically been assumed to be Galactic in origin. We use recent radio observations to test whether the observed high-latitude component could originate within either an extended Galactic halo or a more local "bubble" structure. The lack of significant polarization from the isotropic component, combined with the lack of significant correlation with the Galactic far-infrared emission, rule out an origin within the Galaxy. We conclude that an extragalactic origin is the only viable alternative for the bulk of the isotropic high-latitude emission. The extragalactic component is 2-3 times brighter than local (Galactic) emission towards the Galactic poles and is consistent with a power law in frequency with amplitude T(sub r) = 24.1 plus or minus 2.1 K and spectral index beta = -2.599 plus or minus 0.036 evaluated at reference frequency 310 MHz.

  11. Solar and stellar radio spikes - Limits on the saturation of the electron-cyclotron maser

    NASA Technical Reports Server (NTRS)

    Wentzel, Donat G.; Aschwanden, Markus J.

    1991-01-01

    The solar millisecond radio 'spikes' have been explained in terms of X-mode radiation generated by a maser near the electron gyrofrequency, acting on fast coronal electrons with a loss cone. This maser is a phenomenon described by quasi-linear theory. It is sensitive to the small first-relativistic correction to the gyrofrequency. Thus, it might be disrupted rather easily by nonlinear effects. The maximum radiation density that can be reached before the radiation entrains (phase-locks) the electrons and saturates the maser is discussed. If the observed durations of solar radio spikes are a measure of the rate of scattering into the loss-cone, then the inferred energy density is at least two orders of magnitude less than the energy density at which entrainment sets in. Also, maser emission from auroral kilometric radiation does not reach wave energies critical for electron entrainment. Maser emissions from flare stars, however, show 3-4 orders of magnitude higher radio fluxes and brightness temperatures than for the solar case and are likely to be saturated by entrainment.

  12. Frequency Allocation; The Radio Spectrum.

    ERIC Educational Resources Information Center

    Federal Communications Commission, Washington, DC.

    The Federal Communications Commission (FCC) assigns segments of the radio spectrum to categories of users, and specific frequencies within each segment to individual users. Since demand for channel space exceeds supply, the process is complex. The radio spectrum can be compared to a long ruler: the portion from 10-540 kiloHertz has been set aside…

  13. The future for radio astronomy

    NASA Astrophysics Data System (ADS)

    Breton, Rene P.; Hassall, Tom

    2013-12-01

    THE TRANSIENT UNIVERSE Rene P Breton and Tom Hassall argue that, while radio astronomy has always involved transient phenomena, exploration of this part of the electromagnetic spectrum has been falling behind because of the lack of data. But the advent of a new generation of radio telescopes such as LOFAR, could change that.

  14. Safety and Special Radio Services.

    ERIC Educational Resources Information Center

    Federal Communications Commission, Washington, DC.

    Numerous radio stations across the nation perform nonbroadcast services in areas ranging from aviation, forestry protection, and telephone maintenance to amateur and citizen radio. These services can be grouped in four general categories: (1) safety, (2) industry, (3) land transportation, and (4) miscellaneous purposes. This bulletin briefly…

  15. Stabilized radio-frequency quadrupole

    DOEpatents

    Lancaster, H.D.; Fugitt, J.A.; Howard, D.R.

    1982-09-29

    A long-vane stabilized radio frequency resonator for accelerating charged particles and including means defining a radio frequency resonator cavity, a plurality of long vanes mounted in the defining means for dividing the cavity into sections, and means interconnecting opposing ones of the plurality of vanes for stabilizing the resonator.

  16. Space Telecommunications Radio Architecture (STRS)

    NASA Technical Reports Server (NTRS)

    Reinhart, Richard C.

    2006-01-01

    A software defined radio (SDR) architecture used in space-based platforms proposes to standardize certain aspects of radio development such as interface definitions, functional control and execution, and application software and firmware development. NASA has charted a team to develop an open software defined radio hardware and software architecture to support NASA missions and determine the viability of an Agency-wide Standard. A draft concept of the proposed standard has been released and discussed among organizations in the SDR community. Appropriate leveraging of the JTRS SCA, OMG's SWRadio Architecture and other aspects are considered. A standard radio architecture offers potential value by employing common waveform software instantiation, operation, testing and software maintenance. While software defined radios offer greater flexibility, they also poses challenges to the radio development for the space environment in terms of size, mass and power consumption and available technology. An SDR architecture for space must recognize and address the constraints of space flight hardware, and systems along with flight heritage and culture. NASA is actively participating in the development of technology and standards related to software defined radios. As NASA considers a standard radio architecture for space communications, input and coordination from government agencies, the industry, academia, and standards bodies is key to a successful architecture. The unique aspects of space require thorough investigation of relevant terrestrial technologies properly adapted to space. The talk will describe NASA s current effort to investigate SDR applications to space missions and a brief overview of a candidate architecture under consideration for space based platforms.

  17. SETI radio spectrum surveillance system

    NASA Technical Reports Server (NTRS)

    Crow, B.; Lokshin, A.; Marina, M.; Ching, L.

    1985-01-01

    The SETI Radio Spectrum Surveillance System (SRSSS) will provide a data base for assessing the radio frequency interference (RFI) environment for SETI and minimizing RFI disruptions during the search. The system's hardware and software are described and the sensitivity of the system is discussed.

  18. Audiences for Contemporary Radio Formats.

    ERIC Educational Resources Information Center

    Lull, James T.; And Others

    A radio audience survey of 110 sample geographic clusters in the Santa Barbara, California, area served a twofold purpose: the construction of a demographic profile of audience types according to radio format choices, and the identification and analysis of various audience subgroups. A skip interval technique of these geographic clusters resulted…

  19. Numerical simulation of melt ejection during the laser drilling process on aluminum alloy by millisecond pulsed laser

    NASA Astrophysics Data System (ADS)

    Wei, Zhang; Jin, Guangyong; Wang, Yibin

    2016-01-01

    In this paper, established a physical model to simulate the melt ejection induced by millisecond pulsed laser on aluminum alloy and use the finite element method to simulate the whole process. A semi-infinite axisymmetric model was established according to the experiment and the analytical solution of temperature in a solid phase was derived based on the thermal conduction equation. Mean while, by assuming that material was removed from the hole once it was melted, the function describing the hole's shape was obtained with the energy balance theory. This simulation is based on the interaction between single pulsed laser with different pulse-width and different peak energy and aluminum alloy material, the result of numerical simulation is that the hole's depth increases with the increase of laser energy and the hole's depth increases with the increase of laser pulse width, the keyhole depth is linearly increased with the increase of laser energy, respectively; the growth of the keyhole radius is in the trend to be gentle. By comparing the theoretical simulation data and the actual test data, we discover that: we discover that: the relative error between the theoretical values and the actual values is about 8.8%, the theoretical simulation curve is well consistent with the actual experimental curve. This research may provide the theoretical references to the understanding of the interaction between millisecond pulsed laser and many kinds of materials, as well as be beneficial to the application of the laser materials processing and military field.

  20. PULSE AMPLITUDE DEPENDS ON kHz QPO FREQUENCY IN THE ACCRETING MILLISECOND PULSAR SAX J1808.4-3658

    SciTech Connect

    Bult, Peter; Van der Klis, Michiel

    2015-01-10

    We study the relation between the 300-700 Hz upper kHz quasi-periodic oscillation (QPO) and the 401 Hz coherent pulsations across all outbursts of the accreting millisecond X-ray pulsar SAX J1808.4-3658 observed with the Rossi X-ray Timing Explorer. We find that the pulse amplitude systematically changes by a factor of ∼2 when the upper kHz QPO frequency passes through 401 Hz: it halves when the QPO moves to above the spin frequency and doubles again on the way back. This establishes for the first time the existence of a direct effect of kHz QPOs on the millisecond pulsations and provides a new clue to the origin of the upper kHz QPO. We discuss several scenarios and conclude that while more complex explanations can not formally be excluded, our result strongly suggests that the QPO is produced by azimuthal motion at the inner edge of the accretion disk, most likely orbital motion. Depending on whether this azimuthal motion is faster or slower than the spin, the plasma then interacts differently with the neutron-star magnetic field. The most straightforward interpretation involves magnetospheric centrifugal inhibition of the accretion flow that sets in when the upper kHz QPO becomes slower than the spin.

  1. SPIN EVOLUTION OF MILLISECOND MAGNETARS WITH HYPERACCRETING FALLBACK DISKS: IMPLICATIONS FOR EARLY AFTERGLOWS OF GAMMA-RAY BURSTS

    SciTech Connect

    Dai, Z. G.; Liu Ruoyu E-mail: ryliu@nju.edu.cn

    2012-11-01

    The shallow decay phase or plateau phase of early afterglows of gamma-ray bursts (GRBs), discovered by Swift, is currently understood as being due to energy injection to a relativistic blast wave. One natural scenario for energy injection invokes a millisecond magnetar as the central engine of GRBs because the conventional model of a pulsar predicts a nearly constant magnetic-dipole-radiation luminosity within the spin-down timescale. However, we note that significant brightening occurs in some early afterglows, which apparently conflicts with the above scenario. Here we propose a new model to explain this significant brightening phenomena by considering a hyperaccreting fallback disk around a newborn millisecond magnetar. We show that for typical values of the model parameters, sufficient angular momentum of the accreted matter is transferred to the magnetar and spins it up. It is this spin-up that leads to a dramatic increase of the magnetic-dipole-radiation luminosity with time and thus significant brightening of an early afterglow. Based on this model, we carry out numerical calculations and fit well early afterglows of 12 GRBs assuming sufficiently strong fallback accretion. If the accretion is very weak, our model turns out to be the conventional energy-injection scenario of a pulsar. Therefore, our model can provide a unified explanation for the shallow decay phase, plateaus, and significant brightening of early afterglows.

  2. Spike Timing Regulation on the Millisecond Scale by Distributed Synaptic Plasticity at the Cerebellum Input Stage: A Simulation Study

    PubMed Central

    Garrido, Jesús A.; Ros, Eduardo; D’Angelo, Egidio

    2013-01-01

    The way long-term synaptic plasticity regulates neuronal spike patterns is not completely understood. This issue is especially relevant for the cerebellum, which is endowed with several forms of long-term synaptic plasticity and has been predicted to operate as a timing and a learning machine. Here we have used a computational model to simulate the impact of multiple distributed synaptic weights in the cerebellar granular-layer network. In response to mossy fiber (MF) bursts, synaptic weights at multiple connections played a crucial role to regulate spike number and positioning in granule cells. The weight at MF to granule cell synapses regulated the delay of the first spike and the weight at MF and parallel fiber to Golgi cell synapses regulated the duration of the time-window during which the first-spike could be emitted. Moreover, the weights of synapses controlling Golgi cell activation regulated the intensity of granule cell inhibition and therefore the number of spikes that could be emitted. First-spike timing was regulated with millisecond precision and the number of spikes ranged from zero to three. Interestingly, different combinations of synaptic weights optimized either first-spike timing precision or spike number, efficiently controlling transmission and filtering properties. These results predict that distributed synaptic plasticity regulates the emission of quasi-digital spike patterns on the millisecond time-scale and allows the cerebellar granular layer to flexibly control burst transmission along the MF pathway. PMID:23720626

  3. Planetary radio astronomy from Voyager

    NASA Technical Reports Server (NTRS)

    Alexander, J. K.

    1983-01-01

    The technique of radio astronomy makes it possible for a remote observer to detect the presence of magnetic fields and plasmas in planetary environments. Prior to the flights of the Voyager spacecraft, radio astronomical studies of Jupiter from earth and from earth orbit had correctly predicted the strength and orientation of Jupiter's magnetic field and trapped radiation belts. The Voyager Planetary Radio Astronomy investigations have now provided measurements of the complete spectrum of low frequency radio emissions from both planets. Each Voyager instrument consists of a pair of orthogonal, 10-m, electric monopole antennas which are connected to a step-tuned, superheterodyne receiver operating over the frequency range from 1.2 kHz to 40.5 MHz. The Voyager trajectory provided observations from above both the sunlit and nightside hemispheres of Jupiter. Saturn's nonthermal radio emission has been observed at frequencies as low as 3 kHz and as high as 1.2 MHz.

  4. CONSTRAINING RADIO EMISSION FROM MAGNETARS

    SciTech Connect

    Lazarus, P.; Kaspi, V. M.; Dib, R.; Champion, D. J.; Hessels, J. W. T.

    2012-01-10

    We report on radio observations of five magnetars and two magnetar candidates carried out at 1950 MHz with the Green Bank Telescope in 2006-2007. The data from these observations were searched for periodic emission and bright single pulses. Also, monitoring observations of magnetar 4U 0142+61 following its 2006 X-ray bursts were obtained. No radio emission was detected for any of our targets. The non-detections allow us to place luminosity upper limits of L{sub 1950} {approx}< 1.60 mJy kpc{sup 2} for periodic emission and L{sub 1950,single} {approx}< 7.6 Jy kpc{sup 2} for single pulse emission. These are the most stringent limits yet for the magnetars observed. The resulting luminosity upper limits together with previous results are discussed, as is the importance of further radio observations of radio-loud and radio-quiet magnetars.

  5. Radio outburst of BL Lacertae

    NASA Astrophysics Data System (ADS)

    Buemi, C. S.; Leto, P.; Trigilio, C.; Umana, G.; Giroletti, M.; Orienti, M.; Raiteri, C. M.; Villata, M.; Bach, U.

    2013-04-01

    We report on extremely high radio flux of BL Lacertae at 43 and 8 GHz. Observations at 43 GHz with the 32 m radio telescope in Noto (Italy) revealed a flux density of 10.5 +/- 0.2 Jy on 2013 April 10.65, while observations at 8 GHz with the 32 m radio telescope in Medicina (Italy) detected a flux density of 8.2 +/- 0.7 Jy on April 12.22. These extremely high radio fluxes show that the radio activity likely correlated to the strong optical, near-infrared, and gamma-ray activity of 2011-2012 (see ATels #4028, #4031, #4155, #4271, #4277, #4349, #4565, #4600), and X-ray activity of late 2012 (ATels #4557, #4627), is far to be exhausted.

  6. A Multiwavelength View of Isolated Galaxies

    NASA Astrophysics Data System (ADS)

    Verdes-Montenegro, L.

    2014-03-01

    In the last few years interest in isolated galaxies has been renewed within a context regarding secular evolution. This adds to their value as a control sample for environmental studies of galaxies. This presentation will review important results from recent studies of isolated galaxies. I will emphasize work involving statistically significant samples of isolated galaxies culminating with refinement of the CIG in the AMIGA program. The AMIGA project (Analysis of the interstellar Medium of Isolated Galaxies, http://amiga.iaa.es) has identified a significant sample of the most isolated (Tcc(nearest-neighbor) ˜ 2-3Gyr) galaxies in the local Universe and revealed that they have different properties than galaxies in richer environments. Our analysis of a multiwavelength database includes quantification of degree of isolation, morphologies, as well as FIR and radio line/continuum properties. Properties usually regarded as susceptible to interaction enhancement show lower averages in AMIGA-lower than any galaxy sample yet identified. We find lower MIR/ FIR measures, low levels of radio continuum emission, no radio excess above the radio-FIR correlation, a small number of AGN, and lower molecular gas content. The late-type spiral majority in our sample show very small bulge/total ratios (largely < 0.1) and Sersic indices consistent with an absence of classical bulges. They have redder g-r colors and lower color dispersion for AMIGA subtypes and larger disks, and present the narrowest (Gaussian) distribution of HI profile asymmetries of any sample yet studied.

  7. Optical Observations of the Millisecond Pulsars PSR 1937+214 and PSR 1953+29

    NASA Astrophysics Data System (ADS)

    Loredo, T.; Ricker, G.; Rappaport, S.; Middleditch, J.

    The authors report here the results of photometric and time-resolved optical observations of the fields of the recently discovered ultra-fast radio pulsars, PSR 1937+214 and PSR 1953+29. Deep images of the fields reveal no conspicuous optical counterpart for PSR 1937+214, though a star with mv ≡ 20.5 is coincident with the position of PSR 1953+29. Time-resolved images of the fields of both objects, obtained with a new stroboscopic technique, have yielded upper limits on the pulsed near-infrared emission from each object. The authors briefly discuss constraints on the physical models for these systems derived from their optical studies.

  8. Exploring the Dynamic Radio Sky

    NASA Astrophysics Data System (ADS)

    Mooley, Kunal P.; Hallinan, Gregg; Frail, Dale A.; Myers, Steven T.; Kulkarni, Shrinivas R.; Bourke, Stephen; Horesh, Assaf

    2015-01-01

    Most of what is currently known about slow radio transients (supernovae, gamma-ray bursts, tidal disruption events, stellar flares, etc.) has come via radio follow-up of objects identified by synoptic telescopes at optical, X-ray or gamma-ray wavelengths. However, with the ability to capture obscured, unbeamed and magnetically-driven phenomena, radio surveys offer unique discovery strong diagnostic for cosmic transients. For the first time, we are systematically exploring the dynamic radio sky on timescales between one day to several years using multi-epoch large surveys with the Karl G. Jansky Array (VLA). We have carried out surveys in the COSMOS deep field as well as wide fields like Stripe 82. I have developed a unique infrastructure for near-real-time calibration, imaging, transient search, transient vetting, rapid multiwavelength follow-up, and contemporaneous optical surveys to better characterize radio transient phenomena. A large part of my thesis includes the commissioning of a new observing mode at the VLA: On-The-Fly Mosaicking. This mode has significantly improved the survey efficiency of the VLA, and it is a driver for VLASS, the future all-sky survey planned with this telescope. Through our radio surveys we have discovered several fascinating transients that are unique to the radio. These surveys have established the VLA as an efficient transient discovery machine. My thesis has enormous implications for how to design efficient transient surveys for the next generation of radio interferometer facilities like ASKAP, MeerKAT, WSRT/Apertif and LOFAR. My work has also provided answers to key problems such as the rates of transients, demographics of variability of radio sources including AGN, and false-positive foreground for future searches for the radio counterparts of gravitational-wave (GW) sources.

  9. Modulated gamma-ray emission from compact millisecond pulsar binary systems

    NASA Astrophysics Data System (ADS)

    Bednarek, W.

    2014-01-01

    Context. A significant number of the millisecond pulsars (MSPs) have been discovered within binary systems. Tens of these MSPs emit γ-rays that are modulated with the pulsar period since this emission is produced in the inner pulsar magnetosphere. In several such binary systems, the masses of the companion stars have been derived allowing two classes of objects to be distinguished, which are called the black widow and the redback binaries. Pulsars in these binary systems are expected to produce winds that create conditions for acceleration of electrons, when colliding with stellar winds. These electrons should interact with the anisotropic radiation from the companion stars producing γ-ray emission modulated with the orbital period of the binary system, similar to what is observed in the massive TeV γ-ray binary systems. Aims: We consider the interaction of a MSP wind with a very inhomogeneous stellar wind from the companion star within binary systems of the black widow and redback types. Our aim is to determine the features of γ-ray emission produced in the collision region of the winds from a few typical MSP binary systems. Methods: It is expected that the pulsar wind should mix efficiently with the inhomogeneous stellar wind. The mixed winds move outside the binary with relatively low velocity. Electrons accelerated in such mixed, turbulent winds can interact with the magnetic field and strong radiation from the companion star, producing not only synchrotron radiation but also γ-rays in the inverse Compton process, fluxes of which are expected to be modulated on the periods of the binary systems. Applying numerical methods, we calculated the GeV-TeV gamma-ray spectra and the light curves expected from some MSP binary systems. Results: Gamma-ray emission, produced within the binary systems, is compared with the sensitivities of the present and future gamma-ray telescopes. It is concluded that energetic MSP binary systems create a new class of TeV

  10. The faint radio sky: radio astronomy becomes mainstream

    NASA Astrophysics Data System (ADS)

    Padovani, Paolo

    2016-09-01

    Radio astronomy has changed. For years it studied relatively rare sources, which emit mostly non-thermal radiation across the entire electromagnetic spectrum, i.e. radio quasars and radio galaxies. Now, it is reaching such faint flux densities that it detects mainly star-forming galaxies and the more common radio-quiet active galactic nuclei. These sources make up the bulk of the extragalactic sky, which has been studied for decades in the infrared, optical, and X-ray bands. I follow the transformation of radio astronomy by reviewing the main components of the radio sky at the bright and faint ends, the issue of their proper classification, their number counts, luminosity functions, and evolution. The overall "big picture" astrophysical implications of these results, and their relevance for a number of hot topics in extragalactic astronomy, are also discussed. The future prospects of the faint radio sky are very bright, as we will soon be flooded with survey data. This review should be useful to all extragalactic astronomers, irrespective of their favourite electromagnetic band(s), and even stellar astronomers might find it somewhat gratifying.

  11. The Radio Language Arts Project: adapting the radio mathematics model.

    PubMed

    Christensen, P R

    1985-01-01

    Kenya's Radio Language Arts Project, directed by the Academy for Educational Development in cooperation with the Kenya Institute of Education in 1980-85, sought to teach English to rural school children in grades 1-3 through use of an intensive, radio-based instructional system. Daily 1/2 hour lessons are broadcast throughout the school year and supported by teachers and print materials. The project further was aimed at testing the feasibility of adaptation of the successful Nicaraguan Radio Math Project to a new subject area. Difficulties were encountered in articulating a language curriculum with the precision required for a media-based instructional system. Also a challenge was defining the acceptable regional standard for pronunciation and grammar; British English was finally selected. An important modification of the Radio Math model concerned the role of the teacher. While Radio Math sought to reduce the teacher's responsibilities during the broadcast, Radio Language Arts teachers played an important instructional role during the English lesson broadcasts by providing translation and checks on work. Evaluations of the Radio language Arts Project suggest significant gains in speaking, listening, and reading skills as well as high levels of satisfaction on the part of parents and teachers.

  12. Radio frequency coaxial feedthrough

    DOEpatents

    Owens, Thomas L.

    1989-01-17

    An improved radio frequency coaxial transmission line vacuum feed-through provided based on the use of a half-wavelength annular dielectric pressure barrier disk, or multiple disks comprising an effective half wavelength structure to eliminate reflections from the barrier surfaces. Gas-tight seals are formed about the outer and inner diameter surfaces of the barrier disk using a sealing technique which generates radial forces sufficient to form seals by forcing the conductor walls against the surfaces of the barrier disks in a manner which does not deform the radii of the inner and outer conductors, thereby preventing enhancement of the electric field at the barrier faces which limits voltage and power handling capabilities of a feedthrough.

  13. Division X: Radio Astronomy

    NASA Astrophysics Data System (ADS)

    Nan, Ren-Dong; Taylor, Russ; Rodriguez, Luis F.; Chapman, Jessica; Dubner, Gloria; Garrett, Michael; Goss, W. Miller; Torrelles, Jose M.; Hirabayashi, Hisashi; Carilli, Chris; Hills, Richard; Shastri, Prajval

    2010-05-01

    The business meeting of Division X in the IAU 2009GA took place in three sessions during the day of August 6, 2009. The meeting, being well attended, started with the approval for the meeting agenda. Then the triennium reports were made in the first session by the president of Division X, Ren-Dong Nan, and by the chairs of three working groups: “Historic Radio Astronomy WG” by Wayne Orchiston, “Astrophysically Important Lines WG” by Masatoshi Ohishi, and “Global VLBI WG” by Tasso Tzioumis (proxy chair appointed by Steven Tingay). Afterwards, a dozen reports from observatories and worldwide significant projects have been presented in the second session. Business meeting of “Interference Mitigation WG” was located in the third session.

  14. Radio frequency distribution assembly

    NASA Astrophysics Data System (ADS)

    Culley, K. M.

    The Naval Research Laboratory (NRL) Radio Frequency Distribution Assembly (RFDA) is an interface between the Sperry four-channel, fast-switching synthesizer and the EF-111 jamming system antenna ports. The RFDS is a sophisticated, high-speed RF interface designed to convert the banded outputs of the four-channel synthesizer (16 ports) to 36 ports which represent six ordinal directions of arrival (DOA) for the EF-111 jamming system. The RFDS will distribute the RF signals while providing controlled RF amplitudes to simulate the antenna patterns of the EF-111 Electronic Warfare (EW) system. The simulation of the arrival angles which appear between the ordinal directions is performed by controlling the amplitude of the RF signal from the DOA channels. The RFDA is capable of operating over the frequency range of 500MHz to 18GHz, and can rapidly switch between varying frequencies and attenuation levels.

  15. Teaching radio astronomy with Affordable Small Radio Telescope (ASRT)

    NASA Astrophysics Data System (ADS)

    Joshi, Bhal Chandra

    A simple, easy to build and portable radio telescope, called Affordable Small Radio Telescope (ASRT), has been developed by the Radio Physics Laboratory (RPL), a radio astronomy teaching unit associated with the National Centre for Radio Astrophysics (TIFR) and Inter-University Centre for Astronomy and Astrophysics (IUCAA), which are two premier astronomy institutes in India. ASRT consists of off-the-shelf available Direct to Home television dishes and is easy to assemble. Our design is scalable from simple very low cost telescope to more complex yet moderately costing instrument. ASRT provides a platform for demonstrating radio physics concepts through simple hands-on experiment as well as for carrying out solar monitoring by college/University students. The presentation will highlight the concept of ASRT and the different experiments that can be carried out using it. The solar monitoring observations will be discussed along-with details of methods for calibrating these measurements. The pedagogical usefulness of ASRT in introducing undergraduatephysics students to astrophysics, measurements and analysis methods used in radio astronomy will also be discussed. Use of ASRT in the last three years in the programs of RPL, namely the annual Radio Astronomy Winter School for College students (RAWSC) and Pulsar Observing for Students (POS) is also presented. This year a new program was initiated to form a virtual group of an ASRT community, which will not only share their measurements, but also think of improving the pedagogical usefulness of ASRT by innovative experiments. This initiative is presented with the best practices drawn from our experience in using ASRT as a tool for student training in space sciences. The talk will also point out future ideas in involving a larger body of students in simple radio astronomy experiments with the ASRT, which RPL is likely to nucleate as part of its mandate.

  16. Radio halos in future surveys in the radio continuum

    NASA Astrophysics Data System (ADS)

    Cassano, R.; Brunetti, G.; Norris, R. P.; Röttgering, H. J. A.; Johnston-Hollitt, M.; Trasatti, M.

    2012-12-01

    Aims: Giant radio halos are Mpc-scale synchrotron sources detected in a significant fraction of massive and merging galaxy clusters. The statistical properties of radio halos can be used to discriminate among various models for the origin of non-thermal particles in galaxy clusters. Therefore, theoretical predictions are important as new radio telescopes are about to begin to survey the sky at low and high frequencies with unprecedented sensitivity. Methods: We carry out Monte Carlo simulations to model the formation and evolution of radio halos in a cosmological framework and extend previous calculations based on the hypothesis of turbulent-acceleration. We adopt a phenomenological approach by assuming that radio halos are either generated in turbulent merging clusters, or are purely hadronic sources generated in more relaxed clusters, "off-state" halos. Results: The models predict that the luminosity function of radio halos at high radio luminosities is dominated by the contribution of halos generated in turbulent clusters. The generation of these halos becomes less efficient in less massive systems causing a flattening of the luminosity function at lower radio luminosities, as also pointed out in previous studies. However, we find that potentially this can be more than compensated for by the intervening contribution of "off-state" halos that dominate at lower radio luminosities. We derive the expected number of halos to explore the potential of the EMU+WODAN surveys that will be carried out with ASKAP and Aperitif, respectively, in the near future. By restricting to clusters at redshifts ≤ 0.6, we show that the planned EMU+WODAN surveys at 1.4 GHz have the potential to detect up to about 200 new radio halos, increasing their number by one order of magnitude. A fraction of these sources will be "off-state" halos that should be found at flux level f1.4 ≤ 10 mJy, presently accessible only to deep pointed observations. We also explore the synergy between surveys

  17. A blind search for prompt gamma-ray counterparts of fast radio bursts with Fermi-LAT data

    NASA Astrophysics Data System (ADS)

    Yamasaki, Shotaro; Totani, Tomonori; Kawanaka, Norita

    2016-08-01

    Fast radio bursts (FRBs) are a mysterious flash phenomenon detected in radio wavelengths with a duration of only a few milliseconds, and they may also have prompted gamma-ray flashes. Here, we carry out a blind search for ms-duration gamma-ray flashes using the 7-yr Fermi Large Area Telescope all-sky gamma-ray data. About 100 flash candidates are detected, but after removing those associated with bright steady point sources, we find no flash events at high Galactic latitude region (|b| > 20°). Events at lower latitude regions are consistent with statistical flukes originating from the diffuse gamma-ray background. From these results, we place an upper limit on the GeV gamma-ray to radio flux ratio of FRBs as ξ ≡ (νLν)γ/(νLν)radio ≲ (4.2-12) × 107, depending on the assumed FRB rate evolution index β = 0-4 [cosmic FRB rate ΦFRB ∝ (1 + z)β]. This limit is comparable with the largest value found for pulsars, though ξ of pulsars is distributed in a wide range. We also compare this limit with the spectral energy distribution of the 2004 giant flare of the magnetar SGR 1806-20.

  18. Properties of the observed recycle radio pulsars

    NASA Astrophysics Data System (ADS)

    Johnston, Simon

    1994-04-01

    Recent searches for pulsars have been highly successful in discovering recycle and binary pulsars, and we now know of approximately 25 recycled pulsars in the Galaxy and approximately 30 in globular cluster systems. These pulsars fall into four classes; those with high-mass stellar companions, with neutron star companions, with low-mass companions, and those whose evolutionary history has been affected by a companion since lost. There are two pulsars known to have high-mass stellar companions. Both systems contain approximately 10 solar mass B-star companions and have high eccentricities (e approximately 0.85). PSR B1259-63 has a spin period of 47 ms and an orbital period in excess of three years. In constrast, PSR J0045-7319 has a spin period close to 1 s and an orbital period of only 50 days. These systems originated from a binary system containing two massive stars. The supernova explosion (SN) creates the pulsar and is also responsible for the observed high eccentricity. There are five pulsars thought to have neutron star companions. All these systems have orbital eccentricities in excess of 0.2, and they fall into two classes. The first class contain the pulsars formed after the first SN, and which have been spun-up to approximately 50 ms periods during the giant phase of their companion star. This also reduces the orbital peirod to 0.3 day and the second SN induces the high eccentricity. The pulsars observed in the second class were born after the second SN and thus have periods more typical of the bulk of pulsars (greater than 250 ms). The bulk of the recycled pulsars have low-mass (probably white dwarf) companions. In general, these pulsars have very fast spin-rates (the 'millisecond' pulsars) and large apparent ages. The observed eccentricities are extremely small (less than 10-5). These pulsars are re-born as millisecond pulsars after accreting matter and angular momentum from their companion stars in their giant phase. The orbit is circularized during

  19. Local area networking in a radio quiet environment

    NASA Astrophysics Data System (ADS)

    Childers, Edwin L.; Hunt, Gareth; Brandt, Joseph J.

    2002-11-01

    The Green Bank facility of the National Radio Astronomy Observatory is spread out over 2,700 acres in the Allegheny Mountains of West Virginia. Good communication has always been needed between the radio telescopes and the control buildings. The National Radio Quiet Zone helps protect the Green Bank site from radio transmissions that interfere with the astronomical signals. Due to stringent Radio Frequency Interference (RFI) requirements, a fiber optic communication system was used for Ethernet transmissions on the site and coaxial cable within the buildings. With the need for higher speed communications, the entire network has been upgraded to use optical fiber with modern Ethernet switches. As with most modern equipment, the implementation of the control of the newly deployed Green Bank Telescope (GBT) depends heavily on TCP/IP. In order to protect the GBT from the commodity Internet, the GBT uses a non-routable network. Communication between the control building Local Area Network (LAN) and the GBT is implemented using a Virtual LAN (VLAN). This configuration will be extended to achieve isolation between trusted local user systems, the GBT, and other Internet users. Legitimate access to the site, for example by remote observers, is likely to be implemented using a virtual private network (VPN).

  20. Radio studies of extragalactic supernovae.

    PubMed

    Weiler, K W; Sramek, R A; Panagia, N

    1986-03-14

    Some exploding stars (supernovae) are powerful emitters of centimeter radio radiation. Detailed observations have shown that these supernovae quickly become detectable in the radio range, first at shorter wavelengths (higher frequencies) and later at progressively longer and longer wavelengths (lower frequencies). This part of the phenomenon appears to be well explained by a monotonic decrease in the amount of ionized material surrounding the radio-emitting regions as the shock from the explosion travels outward. The radio emission itself is of a nonthermal, synchrotron origin, as is the case in most bright cosmic radio sources. Once the absorption effects become negligible, the radio intensity declines with time until reaching the detection limit of the telescope. Models suggest that the absorbing material originates in a dense wind of matter lost by the supernova progenitor star, or by its companion if it is in a binary system, in the last stages of evolution before the explosion. The synchrotron radio emission can be generated either externally by the shock wave from the explosion propagating through this same high density stellar wind or internally by a rapidly rotating neutron star, which is the collapsed core of the exploded star. Present results appear to favor the former model for at least the first several years after the supernova explosion, although the latter model remains viable.

  1. Radio emission in Mercury magnetosphere

    NASA Astrophysics Data System (ADS)

    Varela, J.; Reville, V.; Brun, A. S.; Pantellini, F.; Zarka, P.

    2016-10-01

    Context. Active stars possess magnetized wind that has a direct impact on planets that can lead to radio emission. Mercury is a good test case to study the effect of the solar wind and interplanetary magnetic field (IMF) on radio emission driven in the planet magnetosphere. Such studies could be used as proxies to characterize the magnetic field topology and intensity of exoplanets. Aims: The aim of this study is to quantify the radio emission in the Hermean magnetosphere. Methods: We use the magnetohydrodynamic code PLUTO in spherical coordinates with an axisymmetric multipolar expansion for the Hermean magnetic field, to analyze the effect of the IMF orientation and intensity, as well as the hydrodynamic parameters of the solar wind (velocity, density and temperature), on the net power dissipated on the Hermean day and night side. We apply the formalism derived by Zarka et al. (2001, Astrophys. Space Sci., 277, 293), Zarka (2007, Planet. Space Sci., 55, 598) to infer the radio emission level from the net dissipated power. We perform a set of simulations with different hydrodynamic parameters of the solar wind, IMF orientations and intensities, that allow us to calculate the dissipated power distribution and infer the existence of radio emission hot spots on the planet day side, and to calculate the integrated radio emission of the Hermean magnetosphere. Results: The obtained radio emission distribution of dissipated power is determined by the IMF orientation (associated with the reconnection regions in the magnetosphere), although the radio emission strength is dependent on the IMF intensity and solar wind hydro parameters. The calculated total radio emission level is in agreement with the one estimated in Zarka et al. (2001, Astrophys. Space Sci., 277, 293) , between 5 × 105 and 2 × 106 W.

  2. Radio Loud AGNs are Mergers

    NASA Astrophysics Data System (ADS)

    Chiaberge, Marco; Gilli, Roberto; Lotz, Jennifer M.; Norman, Colin

    2015-06-01

    We measure the merger fraction of Type 2 radio-loud and radio-quiet active galactic nuclei (AGNs) at z\\gt 1 using new samples. The objects have Hubble Space Telescope (HST) images taken with Wide Field Camera 3 (WFC3) in the IR channel. These samples are compared to the 3CR sample of radio galaxies at z\\gt 1 and to a sample of non-active galaxies. We also consider lower redshift radio galaxies with HST observations and previous generation instruments (NICMOS and WFPC2). The full sample spans an unprecedented range in both redshift and AGN luminosity. We perform statistical tests to determine whether the different samples are differently associated with mergers. We find that all (92%-14%+8%) radio-loud galaxies at z\\gt 1 are associated with recent or ongoing merger events. Among the radio-loud population there is no evidence for any dependence of the merger fraction on either redshift or AGN power. For the matched radio-quiet samples, only 38%-15+16 are merging systems. The merger fraction for the sample of non-active galaxies at z\\gt 1 is indistinguishable from radio-quiet objects. This is strong evidence that mergers are the triggering mechanism for the radio-loud AGN phenomenon and the launching of relativistic jets from supermassive black holes (SMBHs). We speculate that major black hole (BH)–BH mergers play a major role in spinning up the central SMBHs in these objects.

  3. Recurrent Activity in Radio Galaxies

    SciTech Connect

    Jamrozy, Marek; Konar, Chiranjib; Machalski, Jerzy; Mack, Karl-Heinz; Saikia, Dhruba; Siemiginowska, Aneta; Stawarz, Lukasz; /KIPAC, Menlo Park /Jagiellonian U.

    2007-10-15

    One of the outstanding issues concerning extragalactic radio sources is the total duration of their active phase and the possible existence of duty cycles of their nuclear activity. A duty cycle can be recognized if there is a mechanism which preserves the information of past activity for a sufficiently long time after a new activity has started up. If a new cycle starts before the radio lobes created during a former activity period have faded, we can recognize this by the observations of a young radio source embedded in an old relic structure.

  4. The Helios radio astronomy experiment

    NASA Technical Reports Server (NTRS)

    Kayser, S.; Stone, R.

    1984-01-01

    Radio bursts traveling between the Sun and the Earth were tracked by radio astronomy experiments on Helios 1 and 2. A relatively short dipole antenna with a well-defined toroidal reception pattern was flown. The antenna spins in the ecliptic at 60.3 rpm and 2 frequencies are measured in each revolution. The signal analysis determines the strength of the signal, the direction of the source in the ecliptic, and the degree of modulation, and estimates source size. The experiments provide three-dimensional direction finding in space. They extend the radio frequency window beyond what is observable on Earth, and offer a long triangulation baseline.

  5. Four-Sector Cylindrical Radio-Frequency Ion Trap

    NASA Technical Reports Server (NTRS)

    Melbourne, Ruthann K.; Prestage, John D.; Maleki, Lutfollah

    1992-01-01

    Proposed linear radio-frequency ion trap consists of closed metal cylinder partitioned into four equal cylindrical-sector electrodes and two circular end electrodes. Features include relatively large ion-storage capacity and shielding against external fields. Used in frequency-standard laboratories to confine 199Hg+ ions electrodynamically in isolation from external environment. Similar to device described in "Linear Ion Trap for Atomic Clock" (NPO-17758).

  6. Observations of Rotating Radio Transients Using the Long Wavelength Array

    NASA Astrophysics Data System (ADS)

    Miller, Rossina B.; McLaughlin, M.

    2014-01-01

    Rotating radio transients (RRATs) are a type of pulsar discovered through their isolated single pulses. Currently over 80 of these objects are known, but less than half have timing solutions as their sporadic nature makes obtaining solutions difficult. We present the first observations of RRATS with the Long Wavelength Array (LWA), the properties of these objects, and the potential for long-term timing at very low frequencies.

  7. Gamma-ray bursts from extragalactic radio pulsars

    NASA Technical Reports Server (NTRS)

    Melia, Fulvio; Fatuzzo, Marco

    1992-01-01

    It is argued here that the recent BATSE results on the distribution of gamma-ray bursts (GRBs) does not require the abandonment of the isolated neutron stars model in which most of the bursts have a magnetospheric origin. It is demonstrated that GRBs may be produced on relatively young radio pulsars residing in galaxies out to a redshift of about 2.5, consistent with the cosmological hypothesis. These sources may therefore be beacons that trace galactic evolution.

  8. REVERSE SHOCK EMISSION AND IONIZATION BREAKOUT POWERED BY POST-MERGER MILLISECOND MAGNETARS

    SciTech Connect

    Wang, Ling-Jun; Dai, Zi-Gao; Yu, Yun-Wei E-mail: yuyw@mail.ccnu.edu.cn

    2015-02-20

    There is accumulating evidence that at least a fraction of binary neutron star (BNS) mergers result in rapidly spinning magnetars, with subrelativistic neutron-rich ejecta as massive as a small fraction of a solar mass. The ejecta could be heated continuously by the Poynting flux emanated from the central magnetars. Such a Poynting flux could become lepton dominated so that a reverse shock develops. It was demonstrated that such a picture is capable of accounting for the optical transient PTF11agg. In this paper we investigate the X-ray and ultraviolet (UV) radiation, as well as the optical and radio radiation studied by Wang and Dai. UV emission is particularly important because it has the right energy to ionize the hot ejecta at times t ≲ 600 s. It is thought that the ejecta of BNS mergers are a remarkably pure sample of r-process material, about which our understanding is still incomplete. In this paper we evaluate the possibility of observationally determining the bound-bound and bound-free opacities of the r-process material by timing the X-ray, UV, and optical radiation. It is found that these timings depend on the opacities weakly, and therefore only loose constraints on the opacities can be obtained.

  9. 46 CFR 15.830 - Radio officers.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 1 2010-10-01 2010-10-01 false Radio officers. 15.830 Section 15.830 Shipping COAST... Computations § 15.830 Radio officers. Radio officers are required on certain merchant vessels of the United States. The determination of when a radio officer is required is based on the Federal...

  10. PARTNeR: Radio astromony for students

    NASA Astrophysics Data System (ADS)

    Blasco, C.; Vaquerizo, J. A.

    2008-06-01

    PARTNeR stands for Proyecto Academico con el Radiotelescopio de NASA en Robledo (the Academic Project with NASA's radio telescope at Robledo), and allows students to perform radio astronomy observations. High school and university students can access the PARTNeR radio telescope via the internet. The students can operate the antenna from their own school or university and perform radio astronomy observations.

  11. 46 CFR 15.830 - Radio officers.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 1 2013-10-01 2013-10-01 false Radio officers. 15.830 Section 15.830 Shipping COAST... Computations § 15.830 Radio officers. Radio officers are required on certain merchant vessels of the United States. The determination of when a radio officer is required is based on the Federal...

  12. 46 CFR 15.830 - Radio officers.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 1 2012-10-01 2012-10-01 false Radio officers. 15.830 Section 15.830 Shipping COAST... Computations § 15.830 Radio officers. Radio officers are required on certain merchant vessels of the United States. The determination of when a radio officer is required is based on the Federal...

  13. 46 CFR 15.830 - Radio officers.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 1 2011-10-01 2011-10-01 false Radio officers. 15.830 Section 15.830 Shipping COAST... Computations § 15.830 Radio officers. Radio officers are required on certain merchant vessels of the United States. The determination of when a radio officer is required is based on the Federal...

  14. Radio astronomy - The next decade

    SciTech Connect

    Kellermann, K.I. )

    1991-09-01

    Discoveries made over the past several decades by radio astronomers include radio galaxies, quasars, pulsars, gravitational lenses, energetic bursts from the sun and Jupiter, the greenhouse effect on Venus, the rotation of Mercury, giant molecular clouds, violent activity in galactic nuclei, and cosmic background radiation. This paper discusses the development of ever more powerful radio telescopes, which include the VLA operated by NRAO near Socorro (New Mexico); the new NRAO's 100-m Green Bank Telescope being constructed in Green Bank (West Virginia); and the proposed Millimeter Array, which will consist of 40 antennas, each 8-m across, arranged in any of four different ways depending on the size of the region under study. Consideration is also given to methods for increasing the resolving power and image quality of radio telescopes, with special attention given to very-long-baseline interferometry.

  15. Radio: The Other Public Medium.

    ERIC Educational Resources Information Center

    Mullally, Donald P.

    1980-01-01

    Four problems affecting the growth of public radio are discussed: the inability to pay the salaries to attract the talent required to produce quality programing; programing directed to limited audiences; the use of block programing; and poor promotional campaigns. (JMF)

  16. EVA Radio DRATS 2011 Report

    NASA Technical Reports Server (NTRS)

    Swank, Aaron J.; Bakula, Casey J.

    2012-01-01

    In the Fall of 2011, National Aeronautics and Space Administration (NASA) Glenn Research Center (GRC) participated in the Desert Research and Technology Studies (DRATS) field experiments held near Flagstaff, Arizona. The objective of the DRATS outing is to provide analog mission testing of candidate technologies for space exploration, especially those technologies applicable to human exploration of extra- terrestrial rocky bodies. These activities are performed at locations with similarities to extra-terrestrial conditions. This report describes the Extravehicular Activity (EVA) Dual-Band Radio Communication System which was demonstrated during the 2011 outing. The EVA radio system is designed to transport both voice and telemetry data through a mobile ad hoc wireless network and employs a dual-band radio configuration. Some key characteristics of this system include: 1. Dual-band radio configuration. 2. Intelligent switching between two different capability wireless networks. 3. Self-healing network. 4. Simultaneous data and voice communication.

  17. SETI and International Radio Law

    NASA Astrophysics Data System (ADS)

    Lyall, F.

    2010-04-01

    The use of radio in SETI is subject to international rules agreed through the International Telecommunication Union. These are summarised. An opportunity for their revision will arise in 2012. Suggestions may be made.

  18. A BROADBAND RADIO STUDY OF THE AVERAGE PROFILE AND GIANT PULSES FROM PSR B1821-24A

    SciTech Connect

    Bilous, A. V.; Demorest, P.; Ransom, S. M.

    2015-04-20

    We present the results of a wideband (720–2400 MHz) study of PSR B1821–24A (J1824–2452A, M28A), an energetic millisecond pulsar (MSP) visible in radio, X-rays and γ-rays. In radio, the pulsar has a complex average profile that spans ≳85% of the spin period and exhibits strong evolution with observing frequency. For the first time we measure phase-resolved polarization properties and spectral indices of radio emission throughout almost all of the on-pulse window. We synthesize our findings with high-energy information to compare M28A to other known γ-ray MSPs and to speculate that M28A’s radio emission originates in multiple regions within its magnetosphere (i.e., both in the slot or outer gaps near the light cylinder and at lower altitudes above the polar cap). M28A is one of a handful of pulsars that are known to emit giant radio pulses (GRPs)—short, bright radio pulses of unknown nature. We report a drop in the linear polarization of the average profile in both windows of GRP generation and also a “W”-shaped absorption feature (resembling a double notch), partly overlapping with one of the GRP windows. The GRPs themselves have broadband spectra consisting of multiple patches with Δν/ν ∼ 0.07. Although our time resolution was not sufficient to resolve the GRP structure on the μs scale, we argue that GRPs from this pulsar most closely resemble the GRPs from the main pulse of the Crab pulsar, which consist of a series of narrowband nanoshots.

  19. A zero-power radio receiver.

    SciTech Connect

    Brocato, Robert Wesley

    2004-09-01

    This report describes both a general methodology and some specific examples of passive radio receivers. A passive radio receiver uses no direct electrical power but makes sole use of the power available in the radio spectrum. These radio receivers are suitable as low data-rate receivers or passive alerting devices for standard, high power radio receivers. Some zero-power radio architectures exhibit significant improvements in range with the addition of very low power amplifiers or signal processing electronics. These ultra-low power radios are also discussed and compared to the purely zero-power approaches.

  20. Study on the mechanism of a charge-coupled device detector irradiated by millisecond pulse laser under functional loss.

    PubMed

    Li, Mingxin; Jin, Guangyong; Tan, Yong; Guo, Ming; Zhu, Pengbo

    2016-02-20

    The damage mechanism of a CCD detector was studied by building an experimental system containing a millisecond pulse laser irradiating a CCD detector. The experimental results show that the damage on the CCD detector was mainly thermal damage, along with mechanical damage. A melting phenomenon was caused by the thermal damage, so that a crater was observed on the surface of the CCD detector. Caused by melting of the polysilicon electrodes and a temperature rise in the silicon dioxide, the shift register impedance values were sharply reduced. Most of the substrate clock signals were broken and disappeared due to melting of channels in the silicon substrate layer, which caused a functional loss for the CCD detector. The mechanical damage on the melting edge of the CCD detector created heave; the temperature gradient caused this damage. In this paper, the decrease in vertical shift register impedance values was consistent with previous test results. PMID:26906576

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

    SciTech Connect

    Romani, Roger W.

    2015-10-20

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

  2. The gamma-ray luminosity function of millisecond pulsars and implications for the GeV excess

    DOE PAGES

    Hooper, Dan; Mohlabeng, Gopolang

    2016-03-29

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

  3. Progress of Systematic Hands on Devices for Active Learning Methods by Visualizing ICT Tools in Physics with Milliseconds Resolution

    NASA Astrophysics Data System (ADS)

    Kobayashi, Akizo; Okiharu, Fumiko

    We are developing various systematic hands on devices for progress of active learning (AL) to improve students' conceptual understanding in physics laws. We are promoting AL methods in physics education for getting deeper conceptual understanding by using various ICT-based hands on devices and using visualizing ICT tools with milliseconds resolution. Here we investigate AL modules on collisions of big balloon pendulum with another known mass pendulum to get directly the air mass in the big balloon. We also discuss on Newton's laws of blowgun darts systems by using tapioca straws where we get definite works and energy just proportional to the length of the pipes of connected tapioca straws. These AL plans by using modules of big balloon system and blowgun-darts system are shown to be very effective for deeper conceptual understanding of Newton's Laws in almost frictionless worlds.

  4. Time-temperature-transformation measurements of FePt thin films in the millisecond regime using pulse laser processing

    NASA Astrophysics Data System (ADS)

    Inaba, Yuki; Zana, Iulica; Swartz, Caleb; Kubota, Yukiko; Klemmer, Tim; Harrell, J. W.; Thompson, Gregory B.

    2010-11-01

    A section of the time-temperature-transformation (TTT) curve has been measured in the millisecond regime to describe the A1 to L10 transformation of 10 nm FePt thin films. Short time annealing was accomplished using a pulsed neodymium-doped yttrium aluminum garnet laser operating at a wavelength of 1064 nm. The temperature-time profile of the films was measured using an optical pyrometer and a platinum thin film resistor and it was numerically modeled. Effective thermal pulse widths were determined from the time dependence of the atomic diffusion coefficient calculated from the measured temperature profile. The measured TTT diagram involving average order parameter is consistent with theoretical predictions of TTT diagrams involving ordered volume fraction and shows that partial ordering can be obtained with a single effective thermal pulse as short as 1.1 ms.

  5. Line width roughness reduction by rational design of photoacid generator for sub-millisecond laser post-exposure bake

    NASA Astrophysics Data System (ADS)

    Jiang, Jing; Thompson, Michael O.; Ober, Christopher K.

    2014-03-01

    Sub-millisecond laser post-exposure bake (PEB) is an alternative technology to address the excessive acid diffusion for chemically amplified photoresist systems. By rationally designing the resist, laser post-exposure bake is able to improve the resolution and reduce the line width roughness (LWR) compared to patterns exposed under the same conditions but using conventional hotplate PEB. It was found that only the resist with high deprotection activation energy and low diffusion activation energy showed improved performance using laser PEB. Accordingly, a PAG was designed to have low acid diffusivity by binding the counter ions to a molecular glass core while keeping photophysical properties and processing conditions similar to a conventional PAG. By reducing the diffusivity of the counter ions, the PAG was able to further reduce LWR by 60% using laser PEB.

  6. Radio emission from supernova remnants

    NASA Astrophysics Data System (ADS)

    Dubner, Gloria; Giacani, Elsa

    2015-09-01

    The explosion of a supernova releases almost instantaneously about 10^{51} ergs of mechanic energy, changing irreversibly the physical and chemical properties of large regions in the galaxies. The stellar ejecta, the nebula resulting from the powerful shock waves, and sometimes a compact stellar remnant, constitute a supernova remnant (SNR). They can radiate their energy across the whole electromagnetic spectrum, but the great majority are radio sources. Almost 70 years after the first detection of radio emission coming from an SNR, great progress has been achieved in the comprehension of their physical characteristics and evolution. We review the present knowledge of different aspects of radio remnants, focusing on sources of the Milky Way and the Magellanic Clouds, where the SNRs can be spatially resolved. We present a brief overview of theoretical background, analyze morphology and polarization properties, and review and critically discuss different methods applied to determine the radio spectrum and distances. The consequences of the interaction between the SNR shocks and the surrounding medium are examined, including the question of whether SNRs can trigger the formation of new stars. Cases of multispectral comparison are presented. A section is devoted to reviewing recent results of radio SNRs in the Magellanic Clouds, with particular emphasis on the radio properties of SN 1987A, an ideal laboratory to investigate dynamical evolution of an SNR in near real time. The review concludes with a summary of issues on radio SNRs that deserve further study, and analysis of the prospects for future research with the latest-generation radio telescopes.

  7. Radio astronomy. [principles and observations

    NASA Technical Reports Server (NTRS)

    Alexander, J.; Clark, T.

    1974-01-01

    The origins, generation, detection, and interpretation of radio signals are discussed for signals with an assumed random polarization. After defining the basic parameters, the discussion moves to such topics as synchrotron radiation, plasma effects, changes in the electron energy spectrum in the radiating regions, energy loss to ionization, bremsstrahlung, radio astronomical observations of high-energy particles, emission by energetic particles, observation of supernova remnants and pulsars, galactic background continuum radiation, and others.

  8. Radio astrometry from the Moon

    NASA Technical Reports Server (NTRS)

    Linfield, R. P.

    1992-01-01

    An array of three radio telescopes on the Moon, separated by 100-1000 km, could measure the positions of compact radio sources 50-100 times more accurately than can be done on Earth. These measurements would form an all-sky reference frame of extreme precision (5-10 micro-arcsec) and stability, with applications to the dynamics of the solar system, our galaxy, and nearby galaxies.

  9. Evaluation of number concentration quantification by single-particle inductively coupled plasma mass spectrometry: microsecond vs. millisecond dwell times.

    PubMed

    Abad-Álvaro, Isabel; Peña-Vázquez, Elena; Bolea, Eduardo; Bermejo-Barrera, Pilar; Castillo, Juan R; Laborda, Francisco

    2016-07-01

    The quality of the quantitative information in single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS) depends directly on the number concentration of the nanoparticles in the sample analyzed, which is proportional to the flux of nanoparticles through the plasma. Particle number concentrations must be selected in accordance with the data acquisition frequency, to control the precision from counting statistics and the bias, which is produced by the occurrence of multiple-particle events recorded as single-particle events. With quadrupole mass spectrometers, the frequency of data acquisition is directly controlled by the dwell time. The effect of dwell times from milli- to microseconds (10 ms, 5 ms, 100 μs, and 50 μs) on the quality of the quantitative data has been studied. Working with dwell times in the millisecond range, precision figures about 5 % were achieved, whereas using microsecond dwell times, the suitable fluxes of nanoparticles are higher and precision was reduced down to 1 %; this was independent of the dwell time selected. Moreover, due to the lower occurrence of multiple-nanoparticle events, linear ranges are wider when dwell times equal to or shorter than 100 μs are used. A calculation tool is provided to determine the optimal concentration for any instrument or experimental conditions selected. On the other hand, the use of dwell times in the microsecond range reduces significantly the contribution of the background and/or the presence of dissolved species, in comparison with the use of millisecond dwell times. Although the use of dwell times equal to or shorter than 100 μs offers improved performance working in single-particle mode, the use of conventional dwell times (3-10 ms) should not be discarded, once their limitations are known.

  10. Ionization break-out from millisecond pulsar wind nebulae: an X-ray probe of the origin of superluminous supernovae

    NASA Astrophysics Data System (ADS)

    Metzger, Brian D.; Vurm, Indrek; Hascoët, Romain; Beloborodov, Andrei M.

    2014-01-01

    Magnetic spin-down of a rapidly rotating (millisecond) neutron star has been proposed as the power source of hydrogen-poor `superluminous' supernovae (SLSNe-I). However, producing an unambiguous test that can distinguish this model from alternatives, such as circumstellar interaction, has proven challenging. After the supernova explosion, the pulsar wind inflates a hot cavity behind the expanding stellar ejecta: the nascent millisecond pulsar wind nebula. Electron/positron pairs injected by the wind cool through inverse Compton scattering and synchrotron emission, producing a pair cascade and hard X-ray spectrum inside the nebula. These X-rays ionize the inner exposed side of the ejecta, driving an ionization front that propagates outwards with time. Under some conditions this front can breach the ejecta surface within months after the optical supernova peak, allowing ˜0.1-1 keV photons to escape the nebula unattenuated with a characteristic luminosity LX ˜ 1043-1045 erg s-1. This `ionization break-out' may explain the luminous X-ray emission observed from the transient SCP 06F, providing direct evidence that this SLSN was indeed engine powered. Luminous break-out requires a low ejecta mass and that the spin-down time of the pulsar be comparable to the photon diffusion time-scale at optical maximum, the latter condition being similar to that required for a supernova with a high optical fluence. These relatively special requirements may explain why most SLSNe-I are not accompanied by detectable X-ray emission. Global asymmetry of the supernova ejecta increases the likelihood of an early break-out along the direction of lowest density. Atomic states with lower threshold energies are more readily ionized at earlier times near optical maximum, allowing `UV break-out' across a wider range of pulsar and ejecta properties than X-ray break-out, possibly contributing to the blue/UV colours of SLSNe-I.

  11. Probing the Time Scale of FPOP (Fast Photochemical Oxidation of Proteins): Radical Reactions Extend Over Tens of Milliseconds

    NASA Astrophysics Data System (ADS)

    Vahidi, Siavash; Konermann, Lars

    2016-07-01

    Hydroxyl radical (ṡOH) labeling with mass spectrometry detection reports on protein conformations and interactions. Fast photochemical oxidation of proteins (FPOP) involves ṡOH production via H2O2 photolysis by UV laser pulses inside a flow tube. The experiments are conducted in the presence of a scavenger (usually glutamine) that shortens the ṡOH lifetime. The literature claims that FPOP takes place within 1 μs. This ultrafast time scale implies that FPOP should be immune to labeling-induced artifacts that may be encountered with other techniques. Surprisingly, the FPOP time scale has never been validated in direct kinetic measurements. Here we employ flash photolysis for probing oxidation processes under typical FPOP conditions. Bleaching of the reporter dye cyanine-5 (Cy5) served as readout of the time-dependent radical milieu. Surprisingly, Cy5 oxidation extends over tens of milliseconds. This time range is four orders of magnitude longer than expected from the FPOP literature. We demonstrate that the glutamine scavenger generates metastable secondary radicals in the FPOP solution, and that these radicals lengthen the time frame of Cy5 oxidation. Cy5 and similar dyes are widely used for monitoring the radical dose experienced by proteins in solution. The measured Cy5 kinetics thus strongly suggest that protein oxidation in FPOP extends over a much longer time window than previously thought (i.e., many milliseconds instead of one microsecond). The optical approach developed here should be suitable for assessing the performance of future FPOP-like techniques with improved temporal labeling characteristics.

  12. An approach to probe some neural systems interaction by functional MRI at neural time scale down to milliseconds

    PubMed Central

    Ogawa, Seiji; Lee, Tso-Ming; Stepnoski, Ray; Chen, Wei; Zhu, Xiao-Hong; Ugurbil, Kamil

    2000-01-01

    In this paper, we demonstrate an approach by which some evoked neuronal events can be probed by functional MRI (fMRI) signal with temporal resolution at the time scale of tens of milliseconds. The approach is based on the close relationship between neuronal electrical events and fMRI signal that is experimentally demonstrated in concurrent fMRI and electroencephalographic (EEG) studies conducted in a rat model with forepaw electrical stimulation. We observed a refractory period of neuronal origin in a two-stimuli paradigm: the first stimulation pulse suppressed the evoked activity in both EEG and fMRI signal responding to the subsequent stimulus for a period of several hundred milliseconds. When there was an apparent site–site interaction detected in the evoked EEG signal induced by two stimuli that were primarily targeted to activate two different sites in the brain, fMRI also displayed signal amplitude modulation because of the interactive event. With visual stimulation using two short pulses in the human brain, a similar refractory phenomenon was observed in activated fMRI signals in the primary visual cortex. In addition, for interstimulus intervals shorter than the known latency time of the evoked potential induced by the first stimulus (≈100 ms) in the primary visual cortex of the human brain, the suppression was not present. Thus, by controlling the temporal relation of input tasks, it is possible to study temporal evolution of certain neural events at the time scale of their evoked electrical activity by noninvasive fMRI methodology. PMID:11005873

  13. Probing the Time Scale of FPOP (Fast Photochemical Oxidation of Proteins): Radical Reactions Extend Over Tens of Milliseconds.

    PubMed

    Vahidi, Siavash; Konermann, Lars

    2016-07-01

    Hydroxyl radical (⋅OH) labeling with mass spectrometry detection reports on protein conformations and interactions. Fast photochemical oxidation of proteins (FPOP) involves ⋅OH production via H2O2 photolysis by UV laser pulses inside a flow tube. The experiments are conducted in the presence of a scavenger (usually glutamine) that shortens the ⋅OH lifetime. The literature claims that FPOP takes place within 1 μs. This ultrafast time scale implies that FPOP should be immune to labeling-induced artifacts that may be encountered with other techniques. Surprisingly, the FPOP time scale has never been validated in direct kinetic measurements. Here we employ flash photolysis for probing oxidation processes under typical FPOP conditions. Bleaching of the reporter dye cyanine-5 (Cy5) served as readout of the time-dependent radical milieu. Surprisingly, Cy5 oxidation extends over tens of milliseconds. This time range is four orders of magnitude longer than expected from the FPOP literature. We demonstrate that the glutamine scavenger generates metastable secondary radicals in the FPOP solution, and that these radicals lengthen the time frame of Cy5 oxidation. Cy5 and similar dyes are widely used for monitoring the radical dose experienced by proteins in solution. The measured Cy5 kinetics thus strongly suggest that protein oxidation in FPOP extends over a much longer time window than previously thought (i.e., many milliseconds instead of one microsecond). The optical approach developed here should be suitable for assessing the performance of future FPOP-like techniques with improved temporal labeling characteristics. Graphical Abstract ᅟ. PMID:27067899

  14. Sub-millisecond time-resolved SAXS using a continuous-flow mixer and X-ray microbeam.

    PubMed

    Graceffa, Rita; Nobrega, R Paul; Barrea, Raul A; Kathuria, Sagar V; Chakravarthy, Srinivas; Bilsel, Osman; Irving, Thomas C

    2013-11-01

    Small-angle X-ray scattering (SAXS) is a well established technique to probe the nanoscale structure and interactions in soft matter. It allows one to study the structure of native particles in near physiological environments and to analyze structural changes in response to variations in external conditions. The combination of microfluidics and SAXS provides a powerful tool to investigate dynamic processes on a molecular level with sub-millisecond time resolution. Reaction kinetics in the sub-millisecond time range has been achieved using continuous-flow mixers manufactured using micromachining techniques. The time resolution of these devices has previously been limited, in part, by the X-ray beam sizes delivered by typical SAXS beamlines. These limitations can be overcome using optics to focus X-rays to the micrometer size range providing that beam divergence and photon flux suitable for performing SAXS experiments can be maintained. Such micro-SAXS in combination with microfluidic devices would be an attractive probe for time-resolved studies. Here, the development of a high-duty-cycle scanning microsecond-time-resolution SAXS capability, built around the Kirkpatrick-Baez mirror-based microbeam system at the Biophysics Collaborative Access Team (BioCAT) beamline 18ID at the Advanced Photon Source, Argonne National Laboratory, is reported. A detailed description of the microbeam small-angle-scattering instrument, the turbulent flow mixer, as well as the data acquisition and control and analysis software is provided. Results are presented where this apparatus was used to study the folding of cytochrome c. Future prospects for this technique are discussed.

  15. Sub-millisecond time-resolved SAXS using a continuous-flow mixer and X-ray microbeam

    PubMed Central

    Graceffa, Rita; Nobrega, R. Paul; Barrea, Raul A.; Kathuria, Sagar V.; Chakravarthy, Srinivas; Bilsel, Osman; Irving, Thomas C.

    2013-01-01

    Small-angle X-ray scattering (SAXS) is a well established technique to probe the nanoscale structure and interactions in soft matter. It allows one to study the structure of native particles in near physiological environments and to analyze structural changes in response to variations in external conditions. The combination of microfluidics and SAXS provides a powerful tool to investigate dynamic processes on a molecular level with sub-millisecond time resolution. Reaction kinetics in the sub-millisecond time range has been achieved using continuous-flow mixers manufactured using micromachining techniques. The time resolution of these devices has previously been limited, in part, by the X-ray beam sizes delivered by typical SAXS beamlines. These limitations can be overcome using optics to focus X-rays to the micrometer size range providing that beam divergence and photon flux suitable for performing SAXS experiments can be maintained. Such micro-SAXS in combination with microfluidic devices would be an attractive probe for time-resolved studies. Here, the development of a high-duty-cycle scanning microsecond-time-resolution SAXS capability, built around the Kirkpatrick–Baez mirror-based microbeam system at the Biophysics Collaborative Access Team (BioCAT) beamline 18ID at the Advanced Photon Source, Argonne National Laboratory, is reported. A detailed description of the microbeam small-angle-scattering instrument, the turbulent flow mixer, as well as the data acquisition and control and analysis software is provided. Results are presented where this apparatus was used to study the folding of cytochrome c. Future prospects for this technique are discussed. PMID:24121320

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  17. Limits on fast radio bursts at 145 MHz with ARTEMIS, a real-time software backend

    NASA Astrophysics Data System (ADS)

    Karastergiou, A.; Chennamangalam, J.; Armour, W.; Williams, C.; Mort, B.; Dulwich, F.; Salvini, S.; Magro, A.; Roberts, S.; Serylak, M.; Doo, A.; Bilous, A. V.; Breton, R. P.; Falcke, H.; Grießmeier, J.-M.; Hessels, J. W. T.; Keane, E. F.; Kondratiev, V. I.; Kramer, M.; van Leeuwen, J.; Noutsos, A.; Osłowski, S.; Sobey, C.; Stappers, B. W.; Weltevrede, P.

    2015-09-01

    Fast radio bursts (FRBs) are millisecond radio signals that exhibit dispersion larger than what the Galactic electron density can account for. We have conducted a 1446 h survey for FRBs at 145 MHz, covering a total of 4193 deg2 on the sky. We used the UK station of the low frequency array (LOFAR) radio telescope - the Rawlings Array - accompanied for a majority of the time by the LOFAR station at Nançay, observing the same fields at the same frequency. Our real-time search backend, Advanced Radio Transient Event Monitor and Identification System - ARTEMIS, utilizes graphics processing units to search for pulses with dispersion measures up to 320 cm-3 pc. Previous derived FRB rates from surveys around 1.4 GHz, and favoured FRB interpretations, motivated this survey, despite all previous detections occurring at higher dispersion measures. We detected no new FRBs above a signal-to-noise threshold of 10, leading to the most stringent upper limit yet on the FRB event rate at these frequencies: 29 sky-1 d-1 for five ms-duration pulses above 62 Jy. The non-detection could be due to scatter-broadening, limitations on the volume and time searched, or the shape of FRB flux density spectra. Assuming the latter and that FRBs are standard candles, the non-detection is compatible with the published FRB sky rate, if their spectra follow a power law with frequency (∝ να), with α ≳ +0.1, demonstrating a marked difference from pulsar spectra. Our results suggest that surveys at higher frequencies, including the low frequency component of the Square Kilometre Array, will have better chances to detect, estimate rates and understand the origin and properties of FRBs.

  18. Mathematical modeling of radio systems and devices

    NASA Astrophysics Data System (ADS)

    Borisov, Iu. P.; Tsvetnov, V. V.

    Methods for developing mathematical models of radio systems and devices are presented with emphasis on the functional approach to the modeling of radio systems. In particular, attention is given to the formal description of radio systems, computer-aided modeling of radio systems, a classification of methods of radio system modeling, and methods of mathematical description of signals and noise. Specific methods discussed include the carrier method, the complex envelope method, the method of statistical equivalents, and the information parameter method.

  19. Information Content in Radio Waves: Student Investigations in Radio Science

    NASA Astrophysics Data System (ADS)

    Jacobs, K.; Scaduto, T.

    2013-12-01

    We describe an inquiry-based instructional unit on information content in radio waves, created in the summer of 2013 as part of a MIT Haystack Observatory (Westford, MA) NSF Research Experiences for Teachers (RET) program. This topic is current and highly relevant, addressing science and technical aspects from radio astronomy, geodesy, and atmospheric research areas as well as Next Generation Science Standards (NGSS). Projects and activities range from simple classroom demonstrations and group investigations, to long term research projects incorporating data acquisition from both student-built instrumentation as well as online databases. Each of the core lessons is applied to one of the primary research centers at Haystack through an inquiry project that builds on previously developed units through the MIT Haystack RET program. In radio astronomy, students investigate the application of a simple and inexpensive software defined radio chip (RTL-SDR) for use in systems implementing a small and very small radio telescope (SRT and VSRT). Both of these systems allow students to explore fundamental principles of radio waves and interferometry as applied to radio astronomy. In ionospheric research, students track solar storms from the initial coronal mass ejection (using Solar Dynamics Observatory images) to the resulting variability in total electron density concentrations using data from the community standard Madrigal distributed database system maintained by MIT Haystack. Finally, students get to explore very long-baseline interferometry as it is used in geodetic studies by measuring crustal plate displacements over time. Alignment to NextGen standards is provided for each lesson and activity with emphasis on HS-PS4 'Waves and Their Applications in Technologies for Information Transfer'.

  20. The Radio JOVE Project - An Inexpensive Introduction to Radio Astronomy

    NASA Astrophysics Data System (ADS)

    Thieman, J. R.; Higgins, C.

    2004-12-01

    The Radio JOVE project began over six years ago as an education-centered program to inspire secondary school students' interest in space science through hands-on radio astronomy. The project was begun on small grants from the Goddard Space Flight Center Director's Discretionary Fund, the Initiative to Develop Education through Astronomy and Space Science (IDEAS) program, and the American Astronomical Society. Students build a radio receiver and antenna kit capable of receiving Jovian, solar, and galactic emissions at a frequency of 20.1 MHz. More than 600 of these kits have been distributed to students and interested observers (ages 10 through adult) in over 30 countries. For those who are not comfortable building their own kit, the Radio JOVE project has made it possible to monitor real-time data and streaming audio online from professional radio telescopes in Florida (http://jupiter.kochi-ct.jp) and Hawaii http://jupiter.wcc.hawaii.edu/newradiojove/main.html). Freely downloadable software called Radio-Skypipe (http://radiosky.com) emulates a chart recorder to monitor ones own radio telescope or the telescopes of other observers worldwide who send out their data over the Internet. Inexpensive spectrographs have been developed for the professional telescopes in Hawaii and Florida and freely downloadable spectrograph display software is available to receive this research-quality data. We believe the amateur network data to be of value to the research community and would like to have students more directly connected to ongoing research projects to enhance their interest in participating. Results of the project and plans for the future will be highlighted.