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10-05-2018
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First observations through a tied-array beam of Apertif

Submitter: Yogesh Maan and Joeri van Leeuwen
Description: Exploiting the collective sensitivity of WSRT, by in-phase adding the voltage streams from individual dishes, is at the heart of time-domain science goals with Apertif. Thanks to the Apertif team, particularly Menno and Boudewijn, for calibrating out various instrumental phase-offsets, time-domain observations in the form of a tied-array beam (TAB) are now possible. The plots here show some of the first TAB observations of a bright pulsar B1933+16 using various combinations of different WSRT dishes. The top panels show 5 minutes long observations of the pulsar using a single dish (left), and coherently added 3 (middle) and 10 dishes (right). The increase in sensitivity as we add more dishes is glaringly evident. The bottom panel shows the increase in observed S/N as a function of number of dishes for several combinations. The straight line fit indicates that the sensitivity scales very close to linearly with the number of dishes.

The observations above used a single TAB. The real-time survey for fast radio bursts (FRBs) and pulsars will utilize hundreds of such TABs, filling the complete field of view facilitated by Apertif. The firmware that is being developed for this massively multi-TAB observing was recently successfully synthesized for the final chip for the first time. Together with these first TAB observations, the full sensitivity FRB and pulsar survey with Apertif seems to enter reality in very near future.
Copyright: Yogesh Maan and the ARTS team
 
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