Engineering topics

Kramer, M

Publications and source records attributed to Kramer, M.

14 records

DOE OSTI2017

Study of the wave packet treatment of neutrino oscillation at Daya Bay

The disappearance of reactor $\bar{\nu}_e$ observed by the Daya Bay experiment is examined in the framework of a model in which the neutrino is described by a wave packet with a relative intrinsic momentum dispersion $\sigma_\text{rel}$. Three pairs of nuclear reactors and eight antineutrino detectors, each with good energy resolution, distributed among three experimental halls, supply a high-statistics sample of $\bar{\nu}_e$ acquired at nine different baselines. This provides a unique platform to test the effects which arise from the wave packet treatment of neutrino oscillation. The modified survival probability formula was used to fit Daya Bay data, providing the first experimental limits: $2.38 \cdot 10^{-17} < \sigma_{\rm rel} < 0.23$. Treating the dimensions of the reactor cores and detectors as constraints, the limits are improved: $10^{-14} \lesssim \sigma_{\rm rel} < 0.23$, and an upper limit of $\sigma_{\rm rel} <0.20$ is obtained. All limits correspond to a 95\% C.L. Furthermore, the effect due to the wave packet nature of neutrino oscillation is found to be insignificant for reactor antineutrinos detected by the Daya Bay experiment thus ensuring an unbiased measurement of the oscillation parameters $\sin^22\theta_{13}$ and $\Delta m^2_{32}$ within the plane wave model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2013

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

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.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2012

A SHAPIRO DELAY DETECTION IN THE BINARY SYSTEM HOSTING THE MILLISECOND PULSAR PSR J1910-5959A

PSR J1910-5959A is a binary pulsar with a helium white dwarf (HeWD) companion located about 6 arcmin from the center of the globular cluster NGC 6752. Based on 12 years of observations at the Parkes radio telescope, the relativistic Shapiro delay has been detected in this system. We obtain a companion mass M{sub C} = 0.180 {+-} 0.018 M {sub Sun} (1{sigma}) implying that the pulsar mass lies in the range 1.1 M {sub Sun} {<=} M{sub P} {<=} 1.5 M {sub Sun }. We compare our results with previous optical determinations of the companion mass and examine prospects for using this new measurement for calibrating the mass-radius relation for HeWDs and for investigating their evolution in a pulsar binary system. Finally, we examine the set of binary systems hosting a millisecond pulsar and a low-mass HeWD for which the mass of both stars has been measured. We confirm that the correlation between the companion mass and the orbital period predicted by Tauris and Savonije reproduces the observed values but find that the predicted M{sub P} -P{sub B} correlation overestimates the neutron star mass by about 0.5 M {sub Sun} in the orbital period range covered by the observations. Moreover, a few systems do not obey the observed M{sub P} -P{sub B} correlation. We discuss these results in the framework of the mechanisms that inhibit the accretion of matter by a neutron star during its evolution in a low-mass X-ray binary.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2012

PSR J1838-0537: DISCOVERY OF A YOUNG, ENERGETIC GAMMA-RAY PULSAR

We report the discovery of PSR J1838-0537, a gamma-ray pulsar found through a blind search of data from the Fermi Large Area Telescope (LAT). The pulsar has a spin frequency of 6.9 Hz and a frequency derivative of -2.2 Multiplication-Sign 10{sup -11} Hz s{sup -1}, implying a young characteristic age of 4970 yr and a large spin-down power of 5.9 Multiplication-Sign 10{sup 36} erg s{sup -1}. Follow-up observations with radio telescopes detected no pulsations; thus PSR J1838-0537 appears radio-quiet as viewed from Earth. In 2009 September the pulsar suffered the largest glitch so far seen in any gamma-ray-only pulsar, causing a relative increase in spin frequency of about 5.5 Multiplication-Sign 10{sup -6}. After the glitch, during a putative recovery period, the timing analysis is complicated by the sparsity of the LAT photon data, the weakness of the pulsations, and the reduction in average exposure from a coincidental, contemporaneous change in LAT's sky-survey observing pattern. The pulsar's sky position is coincident with the spatially extended TeV source HESS J1841-055 detected by the High Energy Stereoscopic System (H.E.S.S.). The inferred energetics suggest that HESS J1841-055 contains a pulsar wind nebula powered by the pulsar.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2012

CHANGES IN POLARIZATION POSITION ANGLE ACROSS THE ECLIPSE IN THE DOUBLE PULSAR SYSTEM

We investigate the changes in polarization position angle in radiation from pulsar A around the eclipse in the Double Pulsar system PSR J0737-3039A/B at the 20 cm and 50 cm wavelengths using the Parkes 64 m telescope. The changes are {approx}2{sigma} during and shortly after the eclipse at 20 cm but less significant at 50 cm. We show that the changes in position angle during the eclipse can be modeled by differential synchrotron absorption in the eclipse regions. Position angle changes after the eclipse are interpreted as Faraday rotation in the magnetotail of pulsar B. Implied charge densities are consistent with the Goldreich-Julian density, suggesting that the particle energies in the magnetotail are mildly relativistic.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2012

CONSTRAINING THE OPTICAL EMISSION FROM THE DOUBLE PULSAR SYSTEM J0737-3039

We present the first optical observations of the unique system J0737-3039 (composed of two pulsars, hereafter PSR-A and PSR-B). Ultra-deep optical observations, performed with the High Resolution Camera of the Advanced Camera for Surveys on board the Hubble Space Telescope, could not detect any optical emission from the system down to m{sub F435W} = 27.0 and m{sub F606W} = 28.3. The estimated optical flux limits are used to constrain the three-component (two thermal and one non-thermal) model recently proposed to reproduce the XMM-Newton X-ray spectrum. They suggest the presence of a break at low energies in the non-thermal power-law component of PSR-A and are compatible with the expected blackbody emission from the PSR-B surface. The corresponding efficiency of the optical emission from PSR-A's magnetosphere would be comparable to that of other Myr-old pulsars, thus suggesting that this parameter may not dramatically evolve over a timescale of a few Myr.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2012

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

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

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2012

THE DOUBLE PULSAR ECLIPSES. I. PHENOMENOLOGY AND MULTI-FREQUENCY ANALYSIS

The double pulsar PSR J0737-3039A/B displays short, 30 s eclipses that arise around conjunction when the radio waves emitted by pulsar A are absorbed as they propagate through the magnetosphere of its companion pulsar B. These eclipses offer a unique opportunity to directly probe the magnetospheric structure and the plasma properties of pulsar B. We have performed a comprehensive analysis of the eclipse phenomenology using multi-frequency radio observations obtained with the Green Bank Telescope. We have characterized the periodic flux modulations previously discovered at 820 MHz by McLaughlin et al. and investigated the radio frequency dependence of the duration and depth of the eclipses. Based on their weak radio frequency evolution, we conclude that the plasma in pulsar B's magnetosphere requires a large multiplicity factor ({approx}10{sup 5}). We also found that, as expected, flux modulations are present at all radio frequencies in which eclipses can be detected. Their complex behavior is consistent with the confinement of the absorbing plasma in the dipolar magnetic field of pulsar B as suggested by Lyutikov and Thompson and such a geometric connection explains that the observed periodicity is harmonically related to pulsar B's spin frequency. We observe that the eclipses require a sharp transition region beyond which the plasma density drops off abruptly. Such a region defines a plasmasphere that would be well inside the magnetospheric boundary of an undisturbed pulsar. It is also two times smaller than the expected standoff radius calculated using the balance of the wind pressure from pulsar A and the nominally estimated magnetic pressure of pulsar B.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2012

PROSPECTS FOR PROBING THE SPACETIME OF Sgr A* WITH PULSARS

The discovery of radio pulsars in compact orbits around Sgr A* would allow an unprecedented and detailed investigation of the spacetime of this supermassive black hole. This paper shows that pulsar timing, including that of a single pulsar, has the potential to provide novel tests of general relativity, in particular its cosmic censorship conjecture and no-hair theorem for rotating black holes. These experiments can be performed by timing observations with 100 {mu}s precision, achievable with the Square Kilometre Array for a normal pulsar at frequency above 15 GHz. Based on the standard pulsar timing technique, we develop a method that allows the determination of the mass, spin, and quadrupole moment of Sgr A*, and provides a consistent covariance analysis of the measurement errors. Furthermore, we test this method in detailed mock data simulations. It seems likely that only for orbital periods below {approx}0.3 yr is there the possibility of having negligible external perturbations. For such orbits, we expect a {approx}10{sup -3} test of the frame dragging and a {approx}10{sup -2} test of the no-hair theorem within five years, if Sgr A* is spinning rapidly. Our method is also capable of identifying perturbations caused by distributed mass around Sgr A*, thus providing high confidence in these gravity tests. Our analysis is not affected by uncertainties in our knowledge of the distance to the Galactic center, R{sub 0}. A combination of pulsar timing with the astrometric results of stellar orbits would greatly improve the measurement precision of R{sub 0}.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2012

PSR J2030+3641: RADIO DISCOVERY AND GAMMA-RAY STUDY OF A MIDDLE-AGED PULSAR IN THE NOW IDENTIFIED FERMI-LAT SOURCE 1FGL J2030.0+3641

In a radio search with the Green Bank Telescope of three unidentified low Galactic latitude Fermi Large Area Telescope (LAT) sources, we have discovered the middle-aged pulsar J2030+3641 associated with 1FGL J2030.0+3641 (2FGL J2030.0+3640). Following the detection of gamma-ray pulsations using a radio ephemeris, we have obtained a phase-coherent timing solution based on gamma-ray and radio pulse arrival times which spans the entire Fermi mission. With a rotation period of 0.2 s, a spin-down luminosity of 3 Multiplication-Sign 10{sup 34} erg s{sup -1}, and a characteristic age of 0.5 Myr, PSR J2030+3641 is a middle-aged neutron star with spin parameters similar to those of the exceedingly gamma-ray-bright and radio-undetected Geminga. Its gamma-ray flux is 1% that of Geminga, primarily because of its much larger distance, as suggested by the large integrated column density of free electrons, DM = 246 pc cm{sup -3}. We fit the gamma-ray light curve, along with limited radio polarimetric constraints, to four geometrical models of magnetospheric emission, and while none of the fits have high significance some are encouraging and suggest that further refinements of these models may be worthwhile. We argue that not many more non-millisecond radio pulsars may be detected along the Galactic plane that are responsible for LAT sources, but that modified methods to search for gamma-ray pulsations should be productive-PSR J2030+3641 would have been found blindly in gamma rays if only {approx}> 0.8 GeV photons had been considered, owing to its relatively flat spectrum and location in a region of high soft background.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2012

DISCOVERY OF NINE GAMMA-RAY PULSARS IN FERMI LARGE AREA TELESCOPE DATA USING A NEW BLIND SEARCH METHOD

We report the discovery of nine previously unknown gamma-ray pulsars in a blind search of data from the Fermi Large Area Telescope (LAT). The pulsars were found with a novel hierarchical search method originally developed for detecting continuous gravitational waves from rapidly rotating neutron stars. Designed to find isolated pulsars spinning at up to kHz frequencies, the new method is computationally efficient and incorporates several advances, including a metric-based gridding of the search parameter space (frequency, frequency derivative, and sky location) and the use of photon probability weights. The nine pulsars have spin frequencies between 3 and 12 Hz, and characteristic ages ranging from 17 kyr to 3 Myr. Two of them, PSRs J1803-2149 and J2111+ 4606, are young and energetic Galactic-plane pulsars (spin-down power above 6 Multiplication-Sign 10{sup 35} erg s{sup -1} and ages below 100 kyr). The seven remaining pulsars, PSRs J0106+4855, J0622+3749, J1620-4927, J1746-3239, J2028+3332, J2030+4415, and J2139+4716, are older and less energetic; two of them are located at higher Galactic latitudes (|b| > 10 Degree-Sign ). PSR J0106+4855 has the largest characteristic age (3 Myr) and the smallest surface magnetic field (2 Multiplication-Sign 10{sup 11} G) of all LAT blind-search pulsars. PSR J2139+4716 has the lowest spin-down power (3 Multiplication-Sign 10{sup 33} erg s{sup -1}) among all non-recycled gamma-ray pulsars ever found. Despite extensive multi-frequency observations, only PSR J0106+4855 has detectable pulsations in the radio band. The other eight pulsars belong to the increasing population of radio-quiet gamma-ray pulsars.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1938

A New Spinning-test Method

This report contains a description of a new spinning-test arrangement wherein the otherwise customary rotation of the model about a fixed axis is abandoned in favor of a corresponding rotation of the air stream. The advantage of this method lies in the fact that the model is at rest while the spin is recorded. In this manner it is possible to secure systematic results with little loss of time while employing 3- or 6-component wind-tunnel balances. The troublesome equalization of the mass forces is eliminated and the flow phenomena are accessible to direct observation.

Kramer, M↗

NASA NTRS1938

Systematic Airfoil Tests in the Large Wind Tunnel of the DVL

The present report is a description of systematic tests at maximum lift on airfoils with and without split flap and of profile drag at low lift. In order to obtain an opinion as to the suitability of the airfoils with flaps, the maximum-lift measurements were repeated on airfoils with split flaps. The profile drag at low lift was arrived at by direct weighing and momentum measurements and, since the profiles were of unusual depth, extended to large Reynolds numbers.

Doetsch, H↗

NASA NTRS1936

The 5- by 7-meter Wind Tunnel of the DVL

The report contains a description of the DVL wind tunnel. According to the cones fixed, an elliptical stream with axes 5 by 7 meters and length 9 meters, or a stream 6 by 8 meters in cross section and 11 meters in length is available. The top speed with the smaller cone is 65 meters per second. The testing equipment consists of an automatic six-component balance and a test rig for propellers and engines up to 650 horsepower.

Kramer, M↗