Bulletin of the American Physical Society
APS April Meeting 2021
Volume 66, Number 5
Saturday–Tuesday, April 17–20, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session B01: Recent Results on Pulsar Timing AstrophysicsInvited Live
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Sponsoring Units: DGRAV DAP Chair: Maura McLaughin, West Virginia University |
Saturday, April 17, 2021 10:45AM - 11:21AM Live |
B01.00001: The Search for Gravitational Waves with the NANOGrav Pulsar Timing Array Invited Speaker: Megan DeCesar Pulsar timing arrays (PTAs) are kiloparsec-scale, nanohertz-frequency gravitational wave (GW) detectors composed of millisecond pulsars (MSPs) timed over many years. Correlated variations in PTA MSPs' pulse arrival times that are consistent with a quadrupolar signature indicate the presence of a GW signal in the timing residual data. A GW background (GWB) produced by a population of coalescing supermassive binary black holes (SMBBHs) is expected to be the first GW signal detected by PTAs, with continuous-wave (CW) detections of one or more individual SMBBHs expected within the next 5-10 years; other potential sources include SMBBH mergers, cosmic strings, and inflation-era relics. Detection and characterization of GW sources by PTAs requires timing many tens of MSPs positioned across the sky, with timing precisions of tens to hundreds of nanoseconds, over timing baselines of years to decades. In this talk, I will focus primarily on the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), as well as the International Pulsar Timing Array (IPTA). I will describe the construction of these PTAs' data sets and will review recent results from their GW analyses, in particular the common spectral process detected in 12.5 years of NANOGrav data collected with the Arecibo Observatory (AO) and Green Bank Telescope (GBT). Whether this signal is the first hint of a GWB will be determined with near-future NANOGrav (15-year) and IPTA data sets. I will also describe the continual expansion of these PTAs, through instrumentation upgrades and pulsar surveys, in order to increase their GW sensitivity. Finally, I will discuss plans for the NANOGrav array in the wake of the tragic loss of Arecibo, especially the crucial role of the GBT in the coming years; the potential use of the next-generation VLA (ngVLA) for PTA observations; and the Deep Synoptic Array 2000-antenna (DSA-2000) interferometer, which will transform the field of low-frequency GW astrophysics. [Preview Abstract] |
Saturday, April 17, 2021 11:21AM - 11:57AM Live |
B01.00002: High-cadence Timing of Radio Pulsars with CHIME Invited Speaker: Emmanuel Fonseca The timing of radio pulsars -- rotating neutron stars that emit beamed radiation observed as periodic pulsations -- is a uniquely powerful technique for probing fundamental aspects of physics in extreme environments. Global pulsar-timing efforts include the eventual detection of gravitational radiation at nanohertz frequencies, observations of general-relativistic effects for testing gravitation and nuclear astrophysics, as well as monitoring the turbulent properties of the Galactic interstellar medium. Most premier single-dish observatories only observe a small fraction of the known pulsar population with several-month cadences due to limited and competitive resources. In this talk, I will describe the development and ongoing operation of a pulsar-timing backend constructed for the Canadian Hydrogen Intensity Mapping Experiment (CHIME), which observes up to 10 different sky positions at any instant in time and can observe all Northern pulsars within a several-week timespan. I will overview recent and preliminary science results made possible by the daily cadence of observations achievable with the CHIME telescope and its pulsar timing backend. [Preview Abstract] |
Saturday, April 17, 2021 11:57AM - 12:33PM Live |
B01.00003: Precision MSP Timing with MeerKAT Invited Speaker: Renee Spiewak MeerTime is a large survey project for pulsar timing using the MeerKAT telescope in South Africa, bringing together astronomers from 15 institutions on four continents. The design of the array, which consists of 64 14-metre dishes located in the South African Karoo desert, provides a sensitivity comparable to a 100-metre telescope with access to the entire sky south of $\delta\approx+40^\circ$ and high dish slew rates to maximise on-sky time. MeerTime science is divided into four themes: precision Millisecond Pulsar (MSP) timing, globular cluster pulsars, relativistic binary pulsars, and the non-recycled pulsar population. The MSP timing project utilises the sensitivity and versatility of MeerKAT to push the limits of pulsar timing precision and pave the way for MSP timing with the Square Kilometre Array. During the first two years of the MeerTime project, we conducted a census of 187 MSPs, with an emphasis on MSPs in the ``deep south'' ($\delta<-30^\circ$) which are largely inaccessible to northern observatories. Using those results, we identified $\approx80$ sources with the best timing precision for gravitational wave searches and designed projects to optimise our time allocation for the next three years. In addition, studies of interstellar scintillation in bright sources have been used to independently measure pulsar distances and velocities and binary parameters. Future timing projects include targeted campaigns to determine binary system masses, long-term timing to measure proper motions and parallaxes, and large-sample studies to refine our understanding of the MSP population and emission mechanisms. In this talk, I will provide an overview of the MSP timing project and observing strategies and discuss current and future work including wideband timing and single-pulse studies. [Preview Abstract] |
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