Serendipitous Discovery of Three Millisecond Pulsars with the GMRT in Fermi-directed Survey and Follow-up Radio Timing

We report the discovery of three millisecond pulsars (MSPs): PSRs J1120-3618, J1646-2142, and J1828+0625 with the Giant Metrewave Radio Telescope (GMRT) at a frequency of 322 MHz using a 32 MHz observing bandwidth. These sources were discovered serendipitously while conducting the deep observations to search for millisecond radio pulsations in the directions of unidentified Fermi Large Area Telescope (LAT) γ-ray sources. We also present phase coherent timing models for these MSPs using ∼5 yr of observations with the GMRT. PSR J1120-3618 has a 5.5 ms spin period and is in a binary system with an orbital period of 5.6 days and minimum companion mass of 0.18 M, PSR J1646-2142 is an isolated object with a spin period of 5.8 ms, and PSR J1828+0625 has a spin period of 3.6 ms and is in a binary system with an orbital period of 77.9 days and minimum companion mass of 0.27 M. The two binaries have very low orbital eccentricities, in agreement with expectations for MSP-helium white dwarf systems. Using the GMRT 607 MHz receivers having a 32 MHz bandwidth, we have also detected PSR J1646-2142 and PSR J1828+0625, but not PSR J1120-3618. PSR J1646-2142 has a wide profile, with significant evolution between 322 and 607 MHz, whereas PSR J1120-3618 exhibits a single peaked profile at 322 MHz and PSR J1828+0625 exhibits a single peaked profile at both the observing frequencies. These MSPs do not have γ-ray counterparts, indicating that these are not associated with the target Fermi LAT pointing emphasizing the significance of deep blind searches for MSPs. © 2022. The Author(s). Published by the American Astronomical Society

Relic Gravitational Waves and Their Detection

The range of expected amplitudes and spectral slopes of relic (squeezed) gravitational waves, predicted by theory and partially supported by observations, is within the reach of sensitive gravity-wave detectors. In the most favorable case, the detection of relic gravitational waves can be achieved by the cross-correlation of outputs of the initial laser interferometers in LIGO, VIRGO, GEO600. In the more realistic case, the sensitivity of advanced ground-based and space-based laser interferometers will be needed. The specific statistical signature of relic gravitational waves, associated with the phenomenon of squeezing, is a potential reserve for further improvement of the signal to noise ratio.Comment: 25 pages, 9 figures included, revtex. Based on a talk given at "Gyros, Clocks, and Interferometers: Testing General Relativity in Space" (Germany, August 99

What can we learn about GW Physics with an elastic spherical antenna?

A general formalism is set up to analyse the response of an arbitrary solid elastic body to an arbitrary metric Gravitational Wave perturbation, which fully displays the details of the interaction antenna-wave. The formalism is applied to the spherical detector, whose sensitivity parameters are thereby scrutinised. A multimode transfer function is defined to study the amplitude sensitivity, and absorption cross sections are calculated for a general metric theory of GW physics. Their scaling properties are shown to be independent of the underlying theory, with interesting consequences for future detector design. The GW incidence direction deconvolution problem is also discussed, always within the context of a general metric theory of the gravitational field.Comment: 21 pages, 7 figures, REVTeX, enhanced Appendix B with numerical values and mathematical detail. See also gr-qc/000605

Detecting a stochastic background of gravitational radiation: Signal processing strategies and sensitivities

We analyze the signal processing required for the optimal detection of a stochastic background of gravitational radiation using laser interferometric detectors. Starting with basic assumptions about the statistical properties of a stochastic gravity-wave background, we derive expressions for the optimal filter function and signal-to-noise ratio for the cross-correlation of the outputs of two gravity-wave detectors. Sensitivity levels required for detection are then calculated. Issues related to: (i) calculating the signal-to-noise ratio for arbitrarily large stochastic backgrounds, (ii) performing the data analysis in the presence of nonstationary detector noise, (iii) combining data from multiple detector pairs to increase the sensitivity of a stochastic background search, (iv) correlating the outputs of 4 or more detectors, and (v) allowing for the possibility of correlated noise in the outputs of two detectors are discussed. We briefly describe a computer simulation which mimics the generation and detection of a simulated stochastic gravity-wave signal in the presence of simulated detector noise. Numerous graphs and tables of numerical data for the five major interferometers (LIGO-WA, LIGO-LA, VIRGO, GEO-600, and TAMA-300) are also given. The treatment given in this paper should be accessible to both theorists involved in data analysis and experimentalists involved in detector design and data acquisition.Comment: 81 pages, 30 postscript figures, REVTE

The VLBA Imaging and Polarimetry Survey at 5 GHz

We present the first results of the VLBA Imaging and Polarimetry Survey (VIPS), a 5 GHz VLBI survey of 1,127 sources with flat radio spectra. Through automated data reduction and imaging routines, we have produced publicly available I, Q, and U images and have detected polarized flux density from 37% of the sources. We have also developed an algorithm to use each source's I image to automatically classify it as a point-like source, a core-jet, a compact symmetric object (CSO) candidate, or a complex source. The mean ratio of the polarized to total 5 GHz flux density for VIPS sources with detected polarized flux density ranges from 1% to 20% with a median value of about 5%. We have also found significant evidence that the directions of the jets in core-jet systems tend to be perpendicular to the electric vector position angles (EVPAs). The data is consistent with a scenario in which ~24% of the polarized core-jets have EVPAs that are anti-aligned with the directions of their jet components and which have a substantial amount of Faraday rotation. In addition to these initial results, plans for future follow-up observations are discussed.Comment: 36 pages, 3 tables, 13 figures; accepted for publication in Ap

Detection methods for non-Gaussian gravitational wave stochastic backgrounds

We address the issue of finding an optimal detection method for a discontinuous or intermittent gravitational wave stochastic background. Such a signal might sound something like popcorn popping. We derive an appropriate version of the maximum likelihood detection statistic, and compare its performance to that of the standard cross-correlation statistic both analytically and with Monte Carlo simulations. The maximum likelihood statistic performs better than the cross-correlation statistic when the background is sufficiently non-Gaussian. For both ground and space based detectors, this results in a gain factor, ranging roughly from 1 to 3, in the minimum gravitational-wave energy density necessary for detection, depending on the duty cycle of the background. Our analysis is exploratory, as we assume that the time structure of the events cannot be resolved, and we assume white, Gaussian noise in two collocated, aligned detectors. Before this detection method can be used in practice with real detector data, further work is required to generalize our analysis to accommodate separated, misaligned detectors with realistic, colored, non-Gaussian noise.Comment: 25 pages, 12 figures, submitted to physical review D, added revisions in response to reviewers comment

GALPROP WebRun: an internet-based service for calculating galactic cosmic ray propagation and associated photon emissions

GALPROP is a numerical code for calculating the galactic propagation of relativistic charged particles and the diffuse emissions produced during their propagation. The code incorporates as much realistic astrophysical input as possible together with latest theoretical developments and has become a de facto standard in astrophysics of cosmic rays. We present GALPROP WebRun, a service to the scientific community enabling easy use of the freely available GALPROP code via web browsers. In addition, we introduce the latest GALPROP version 54, available through this service.Comment: Accepted for publication in Computer Physics Communications. Version 2 includes improvements suggested by the referee. Metadata completed in version 3 (no changes to the manuscript

On the Detection of a Scalar Stochastic Background of Gravitational Waves

In the near future we will witness the coming to a full operational regime of laser interferometers and resonant mass detectors of spherical shape. In this work we study the sensitivity of pairs of such gravitational wave detectors to a scalar stochastic background of gravitational waves. Our computations are carried out both for minimal and non minimal coupling of the scalar fields.Comment: 25 pages, 3 figure

SO(2,1) conformal anomaly: Beyond contact interactions

The existence of anomalous symmetry-breaking solutions of the SO(2,1) commutator algebra is explicitly extended beyond the case of scale-invariant contact interactions. In particular, the failure of the conservation laws of the dilation and special conformal charges is displayed for the two-dimensional inverse square potential. As a consequence, this anomaly appears to be a generic feature of conformal quantum mechanics and not merely an artifact of contact interactions. Moreover, a renormalization procedure traces the emergence of this conformal anomaly to the ultraviolet sector of the theory, within which lies the apparent singularity.Comment: 11 pages. A few typos corrected in the final versio