A5033874437- Radio Astronomy Observations and Technology
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Antenna Design and Optimization
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Precipitation Measurement and Analysis
- Soil Moisture and Remote Sensing
- Radio Wave Propagation Studies
- Electromagnetic Compatibility and Measurements
- GNSS positioning and interference
- Advanced Frequency and Time Standards
- Scientific Research and Discoveries
- Satellite Communication Systems
- Galaxies: Formation, Evolution, Phenomena
- Planetary Science and Exploration
- Superconducting and THz Device Technology
- Network Time Synchronization Technologies
- High-pressure geophysics and materials
- Advancements in PLL and VCO Technologies
- Spacecraft Design and Technology
- Astronomy and Astrophysical Research
- Photonic and Optical Devices
- Embedded Systems Design Techniques
- Optical Network Technologies
University of California, Berkeley
2020-2025
California Institute of Technology
2016-2020
Center for Astrophysics Harvard & Smithsonian
2009-2018
Jet Propulsion Laboratory
2014-2016
Harvard University
2012-2014
Swinburne University of Technology
2010-2013
Australian National University
2005-2011
Curtin University
2010
Harvard University Press
2010
The University of Melbourne
2010
A "pulsar timing array" (PTA), in which observations of a large sample pulsars spread across the celestial sphere are combined, allows investigation "global" phenomena such as background gravitational waves or instabilities atomic timescales that produce correlated residuals array. The Parkes Pulsar Timing Array (PPTA) is an implementation PTA concept based on with 64-m radio telescope. 20 millisecond being observed at three radio-frequency bands, 50cm (~700 MHz), 20cm (~1400 MHz) and 10cm...
The Murchison Widefield Array (MWA) is a dipole-based aperture array synthesis telescope designed to operate in the 80-300 MHz frequency range. It capable of wide range science investigations, but initially focused on three key projects. These are detection and characterization 3-dimensional brightness temperature fluctuations 21cm line neutral hydrogen during Epoch Reionization (EoR) at redshifts from 6 10, solar imaging remote sensing inner heliosphere via propagation effects signals...
Fast radio bursts (FRBs) are one of the most tantalizing mysteries sky; their progenitors and origins remain unknown until now no rapid multiwavelength follow-up an FRB has been possible. New instrumentation decreased time between observation discovery from years to seconds, enables polarimetry be performed on FRBs for first time. We have discovered (FRB 140514) in real-time 14 May, 2014 at 17:14:11.06 UTC Parkes telescope triggered other wavelengths within hours event. 140514 was found with...
Signals from radio pulsars show a wavelength-dependent delay due to dispersion in the interstellar plasma. At typical observing wavelength, this can vary by tens of microseconds on five-year time scales, far excess signals interest pulsar timing arrays, such as that induced gravitational-wave background. Measurement these variations is not only crucial for detection signals, but also provides an unparallelled measurement turbulent plasma at au scales. In paper we demonstrate without...
Using observations of pulsars from the Parkes Pulsar Timing Array (PPTA) project we develop first pulsar-based timescale that has a precision comparable to uncertainties in international atomic timescales.Our ensemble provides an Ensemble Scale (EPS) analogous free Échelle Atomique Libre (EAL).The EPS can be used detect fluctuations timescales and therefore lead new realisation Terrestrial Time, TT(PPTA11).We successfully follow features known affect frequency International Atomic Timescale...
The Large-aperture Experiment to Detect the Dark Age (LEDA) was designed detect predicted O(100) mK sky-averaged absorption of cosmic microwave background by hydrogen in neutral pre- and intergalactic medium just after cosmological Age. spectral signature would be associated with emergence a diffuse Lyα from starlight during 'Cosmic Dawn'. Recently, Bowman et al. have reported detection this feature, an unexpectedly large amplitude 530 mK, centred at 78 MHz. Verification result independent...
The birth of the first luminous sources and ensuing epoch reionization are best studied via redshifted 21-cm emission line, signature two imprinting last. In this work we present a fully-Bayesian method, \textsc{hibayes}, for extracting faint, global (sky-averaged) signal from much brighter foreground emission. We show that simplified (but plausible), Gaussian model Cosmic Dawn ($15 \lesssim z 30$), parameterized by an amplitude $A_{\rm HI}$, frequency peak $\nu_{\rm HI}$ width $\sigma_{\rm...
The 21\,cm transition of neutral hydrogen is opening an observational window into the cosmic dawn universe---the epoch first star formation. We use 28\,hr data from Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA) to place upper limits on spatial power spectrum emission at $z \approx 18.4$ ($\Delta_{21} \lesssim 10^4\,\text{mK}$), and within absorption feature reported by EDGES experiment (Bowman et al. 2018). In process we demonstrate application double Karhunen-Lo\`{e}ve...
Abstract A host of new low-frequency radio telescopes seek to measure the 21 cm transition neutral hydrogen from early universe. These have potential directly probe star and galaxy formation at redshifts 20 ≳ z 7 but are limited by dynamic range they can achieve against foreground sources emission. Consequently, there is a growing demand for modern, high-fidelity maps sky frequencies below 200 MHz use in modeling removal. We describe wide-field imaging technique drift-scanning...
ABSTRACT The Deep Synoptic Array 10-dish prototype (DSA-10) is an instrument designed to detect and localize fast radio bursts with arcsecond accuracy in real time. Deployed at Owens Valley Radio Observatory, it consists of ten 4.5-m diameter dishes, equipped a 250-MHz bandwidth dual polarization receiver, centred 1.4 GHz. 20 input signals are digitized field programmable gate arrays used transform the data frequency domain transmit over ethernet. A series computer servers buffer both raw...
We present the first spectroscopic images of solar radio transients from prototype for Murchison Widefield Array (MWA), observed on 2010 March 27. Our observations span instantaneous frequency band 170.9-201.6 MHz. Though our observing period is characterized as a `low' to `medium' activity, one broadband emission feature and numerous short-lived, narrowband, non-thermal features are evident. data represent significant advance in low imaging, enabling us follow spatial, spectral, temporal...
A “large-N” correlator that makes use of Field Programmable Gate Arrays and Graphics Processing Units has been deployed as the digital signal processing system for Long Wavelength Array station at Owens Valley Radio Observatory (LWA-OV), to enable Large Aperture Experiment Detect Dark Ages (LEDA). The samples a [Formula: see text][Formula: text]MHz baseband processes signals from 512 antennas (256 dual polarization) over instantaneous sub-band, achieving 16.8[Formula: text]Tops[Formula:...
Experiments were performed with prototype antenna tiles for the Mileura Widefield Array Low Frequency Demonstrator (MWA LFD) to better understand wide-field, wide-band properties of their design and characterize radio-frequency interference (RFI) between 80 300 MHz at site in Western Australia. Observations acquired during 6 month deployment confirmed predicted sensitivity antennas, sky-noise-dominated system temperatures, phase-coherent interferometric measurements. The radio spectrum is...
We have carried out high frequency radio observations of the magnetic field pulsar PSR J1119-6127 following its recent X-ray outburst. While initial showed no evidence significant emission, subsequent detected pulsed emission across a large band. In this letter, we report on disappearance and prompt reactivation dramatic evolution over several months observation. The periodic pulse profile at S-band (2.3 GHz) after exhibits multi-component structure, while simultaneous X-band (8.4 shows...
We report on simultaneous radio and X-ray observations of the repeating fast burst source FRB 180916.J0158+65 using Canadian Hydrogen Intensity Mapping Experiment (CHIME), Effelsberg, Deep Space Network (DSS-14 DSS-63) telescopes Chandra Observatory. During 33 ks observations, we detect no bursts in overlapping Effelsberg or a single during CHIME/FRB transits. events excess background observations. These non-detections imply 5-$\sigma$ limit $<5\times10^{-10}$ erg cm$^{-2}$ for 0.5--10 keV...
Abstract The astrophysical origins of fast radio bursts (FRBs) are still unknown, but magnetars a strong candidate for producing at least some FRBs. To investigate the magnetar progenitor model, we conducted deep search M77 and M82, two nearby galaxies with high star formation rates that could potentially harbor large populations. Using one 34 m dishes in Deep Space Network, observed 8.4 GHz about 100 hr each. At this observing frequency, unaffected by extreme temporal broadening caused...
The Murchison Wide-field Array (MWA) is a low frequency radio telescope, currently under construction, intended to search for the spectral signature of epoch re-ionisation (EOR) and probe structure solar corona. Sited in Western Australia, full MWA will comprise 8192 dipoles grouped into 512 tiles, be capable imaging sky south 40 degree declination, from 80 MHz 300 with an instantaneous field view that tens degrees wide resolution few arcminutes. A 32-station prototype has been recently...
This paper addresses the first practical application of spatial filtering techniques to data taken with a multibeam receiver. Spatial filters make use relative arrival times signal at multiple sensors identify and separate signals from different directions. The method is consequence Karhunen–Loève theorem relies on eigen decomposition covariance matrix formed paths. effectiveness demonstrated observations Vela pulsar Parkes 20 cm Multibeam experiment was highly successful, results show...
Single pixel feeds on large aperture radio telescopes have the ability to detect weak (∼10 mJy) impulsive bursts of emission and sub-mJy pulsars. Unfortunately, in large-scale blind surveys, frequency interference (RFI) mimics both pulsars, greatly reducing sensitivity new discoveries as real signals astronomical origin get lost among millions false candidates. In this paper a technique that takes advantage multipixel use eigenvector decomposition common is used facilitate burst pulsar...
Abstract We have conducted the most sensitive low-frequency (below 100 MHz) search to date for prompt, radio emission associated with short-duration gamma-ray bursts (GRBs), using Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA). The OVRO-LWA’s nearly full-hemisphere field of view (∼20,000 square degrees) allows us (sub-100 counterparts a large sample subset GRB events which prompt has been predicted. Following detection short 170112A by Swift , we used all-sky OVRO-LWA images...
Abstract We present results from observations of the Galactic Center magnetar, PSR J1745–2900, at 2.3 and 8.4 GHz with NASA Deep Space Network 70 m antenna, DSS-43. study magnetar’s radio profile shape, flux density, spectrum, single pulse behavior over a ∼1 year period between MJDs 57233 57621. In particular, magnetar exhibits significantly negative average spectral index <?CDATA $\langle \alpha \rangle =-1.86\pm 0.02$?> when is single-peaked, which flattens considerably double-peaked. have...