Aris Karastergiou

Abstract:

Fast radio bursts (FRBs) constitute an emerging class of fast radio transient whose origin continues to be a mystery. Realizing the importance of increasing coverage of the search parameter space, we have designed, built, and deployed a realtime monitor for FRBs at the 305-m Arecibo radio telescope. Named `ALFABURST', it is a commensal instrument that is triggered whenever the 1.4 GHz seven-beam Arecibo L-Band Feed Array (ALFA) receiver commences operation. The ongoing commensal survey we are conducting using ALFABURST has an instantaneous field of view of 0.02 sq. deg. within the FWHM of the beams, with the realtime software configurable to use up to 300 MHz of bandwidth. We search for FRBs with dispersion measure up to 2560 cm^-3 pc and pulse widthsranging from 0.128 ms to 16.384 ms. Commissioning observations performed over the past few months have demonstrated the capability of the instrument in detecting single pulses from known pulsars. In this paper, I describe the instrument and the associated survey.

Abstract:

Radio astronomy has traditionally depended on observatories allocating time to observers for exclusive use of their telescopes. The disadvantage of this scheme is that the data thus collected is rarely used for other astronomy applications, and in many cases, is unsuitable. For example, properly calibrated pulsar search data can, with some reduction, be used for spectral line surveys. A backend that supports plugging in multiple applications to a telescope to perform commensal data analysis will vastly increase the science throughput of the facility. In this paper, we present "SETIBURST," a robotic, commensal, realtime multi-science backend for the 305 m Arecibo Telescope. The system uses the 1.4 GHz, seven-beam Arecibo L-band Feed Array (ALFA) receiver whenever it is operated. SETIBURST currently supports two applications: SERENDIP VI, a SETI spectrometer that is conducting a search for signs of technological life, and ALFABURST, a fast transient search system that is conducting a survey of fast radio bursts (FRBs). Based on the FRB event rate and the expected usage of ALFA, we expect 0-5 FRB detections over the coming year. SETIBURST also provides the option of plugging in more applications. We outline the motivation for our instrumentation scheme and the scientific motivation of the two surveys, along with their descriptions and related discussions.

Abstract:

In this paper, we present a framework for assessing the effect of non-stationary Gaussian noise and radio frequency interference (RFI) on the signal to noise ratio, the number of false positives detected per true positive and the sensitivity of standard pulsar search pipelines. The results highlight the necessity to develop algorithms that are able to identify and remove non-stationary variations from the data before RFI excision and searching is performed in order to limit false positive detections. The results also show that the spectrum whitening algorithms currently employed, severely affect the efficiency of pulsar search pipelines by reducing their sensitivity to long period pulsars.