Nipuni Palliyaguru

Nipuni Palliyaguru
West Virginia University | WVU · Department of Physics

Doctor of Philosophy

About

26
Publications
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1,622
Citations

Publications

Publications (26)
Preprint
Full-text available
After a decade of great progress in understanding gas flow into, out of, and through the Milky Way, we are poised to merge observations with simulations to build a comprehensive picture of the multi-scale magnetized interstellar medium (ISM). These insights will also be crucial to four bold initiatives in the 2020s: detecting nanohertz gravitationa...
Preprint
The discovery of Fast Radio Bursts (FRBs) at cosmological distances has opened a powerful window on otherwise unseen matter in the Universe. In the 2020s, observations of $>10^{4}$ FRBs will assess the baryon contents and physical conditions in the hot/diffuse circumgalactic, intracluster, and intergalactic medium, and test extant compact-object da...
Article
The discovery of Fast Radio Bursts (FRBs) at cosmological distances has opened a powerful window on otherwise unseen matter in the Universe. In the 2020s, observations of >10^4 FRBs will assess the baryon contents and physical conditions in the hot/diffuse circumgalactic, intracluster, and intergalactic medium, and test extant compact-object dark m...
Article
The intermediate Palomar Transient Factory (iPTF) autonomously responded to and promptly tiled the error region of the first gravitational wave event GW150914 to search for an optical counterpart. Only a small fraction of the total localized region was immediately visible in the Northern night sky, due both to sun-angle and elevation constraints. H...
Article
The highly stable spin of neutron stars can be exploited for a variety of (astro-)physical investigations. In particular arrays of pulsars with rotational periods of the order of milliseconds can be used to detect correlated signals such as those caused by gravitational waves. Three such “Pulsar Timing Arrays” (PTAs) have been set up around the wor...
Article
We report on an effort to extract and monitor interstellar scintillation parameters in regular timing observations collected for the NANOGrav pulsar timing array. Scattering delays are measured by creating dynamic spectra for each pulsar and observing epoch of wide-band observations centered near 1500 MHz and carried out at the Green Bank Telescope...
Article
Full-text available
Long duration y-ray bursts are thought to be a rare subclass of stripped-envelope core-collapse supernovae that launch collimated relativistic out ows (jets). All y-ray-burst-associated supernovae are spectroscopically of Type Ic with broad lines, but the fraction of broad-lined Type Ic supernovae harboring low-luminosity y-ray-bursts remains larg...
Article
Light travel time changes due to gravitational waves may be detected within the next decade through precision timing of millisecond pulsars. Removal of frequency-dependent interstellar medium (ISM) delays due to dispersion and scattering is a key issue in the detection process. Current timing algorithms routinely correct pulse times of arrival (TOA...
Article
Full-text available
Dense, continuous pulsar timing observations over a 24-hr period provide a method for probing intermediate gravitational wave (GW) frequencies from 10 microhertz to 20 millihertz. The European Pulsar Timing Array (EPTA), the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), the Parkes Pulsar Timing Array (PPTA), and the combi...
Article
Full-text available
We compute upper limits on the nanohertz-frequency isotropic stochastic gravitational wave background (GWB) using the 9-year data release from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) collaboration. We set upper limits for a GWB from supermassive black hole binaries under power law, broken power law, and free spec...
Article
Full-text available
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...
Article
Full-text available
Among efforts to detect gravitational radiation, pulsar timing arrays are uniquely poised to detect "memory" signatures, permanent perturbations in spacetime from highly energetic astrophysical events such as mergers of supermassive black hole binaries. The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) observes dozens of t...
Article
Full-text available
We perform a search for continuous gravitational waves from individual supermassive black hole binaries using robust frequentist and Bayesian techniques. We augment standard pulsar timing models with the addition of time-variable dispersion measure and frequency variable pulse shape terms. We apply our techniques to the Five Year Data Release from...
Article
Full-text available
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-hour global observation of PSR J1713+0747 in an effort to better quantify sources of timing noise in this p...
Article
Full-text available
The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) project currently observes 43 pulsars using the Green Bank and Arecibo radio telescopes. In this work we use a subset of 17 pulsars timed for a span of roughly five years (2005--2010). We analyze these data using standard pulsar timing models, with the addition of time-vari...
Article
J1713+0747, a radio pulsar with a period of ~4.5ms, is routinely monitored by NANOGrav (the North American Nanohertz Observatory for Gravitational waves) because of a stable timing RMS of ~30ns that makes it a significant contributor to NANOGrav's gravitational wave (GW) detection campaign with Arecibo Observatory and the Green Bank Telescope. Othe...
Article
Density fluctuations in the interstellar medium affect pulsar signals by scattering the pulses on their way to Earth, which causes a delay of the pulses’ time of arrival at the telescope. The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) uses an array of millisecond pulsars in an effort to directly detect gravitational wav...
Article
The rotating radio transients are sporadic pulsars which are difficult to detect through periodicity searches. By using a single-pulse search method, we can discover these sources, measure their periods, and determine timing solutions. Here we introduce our results on six RRATs based on Parkes and Green Bank Telescope (GBT) observations, along with...
Conference Paper
Precision pulsar timing observations are subject to many effects from the interstellar medium (ISM) which corrupt the signal and reduce the achievable timing precision. The largest effect, dispersion, is now routinely corrected for using the technique of coherent dedispersion, where a digital filter is used to invert the linear transfer function of...
Article
Full-text available
The rotating radio transients are sporadic pulsars which are difficult to detect through periodicity searches. By using a single-pulse search method, we can discover these sources, measure their periods, and determine timing solutions. Here we introduce our results on six RRATs based on Parkes and Green Bank Telescope(GBT) observations, along with...
Article
Full-text available
We observed the Crab pulsar with the 43-m telescope in Green Bank, WV over a timespan of 15 months. In total we obtained 100 hours of data at 1.2 GHz and seven hours at 330 MHz, resulting in a sample of about 95000 giant pulses (GPs). This is the largest sample, to date, of GPs from the Crab pulsar taken with the same telescope and backend and anal...
Article
Full-text available
We present an analysis of high-precision pulsar timing data taken as part of the North American Nanohertz Observatory for Gravitational waves (NANOGrav) project. We have observed 17 pulsars for a span of roughly five years using the Green Bank and Arecibo radio telescopes. We analyze these data using standard pulsar timing models, with the addition...
Article
We have analysed the long- and short-term time dependence of the pulse arrival times and the pulse detection rates for eight rotating radio transient (RRAT) sources from the Parkes Multibeam Pulsar Survey. We find significant periodicities in the individual pulse arrival times from six RRATs. These periodicities range from ∼30 min to 2100 d, and fr...
Article
In searching for gravitational waves with high-precision pulsar timing, we have analyzed the possibility of applying the method of cyclic spectroscopy (CS) to correct for the arrival time fluctuations of the signals. The main causes of these delays are interstellar medium effects such as electron density variations and multi-path scattering, timing...
Article
We request continuing timing observations of eight rotating radio transients. Since the last observing semester, we have achieved phase-connected solutions for additional sources and published three papers which make use of the Parkes data from this program. The observations proposed here are crucial to obtain new solutions and search for timing ab...
Article
We present an analysis of regular timing observations of the high magnetic field Rotating Radio Transient (RRAT) J1819−1458 obtained using the 64-m Parkes and 76-m Lovell radio telescopes over the past 5 years. During this time, the RRAT has suffered two significant glitches with fractional frequency changes of 0.6 × 10−6 and 0.1 × 10−6. Glitches o...

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