The LOFAR Tied-Array All-Sky Survey (LOTAAS): Survey overview and initial pulsar discoveries

Abstract

We present an overview of the LOFAR Tied-Array All-Sky Survey (LOTAAS) for radio pulsars and fast transients. The survey uses the high-band antennas of the LOFAR Superterp, the dense inner part of the LOFAR core, to survey the northern sky (δ > 0 • ) at a central observing frequency of 135 MHz. A total of 219 tied-array beams (coherent summation of station signals, covering 12 square degrees), as well as three incoherent beams (covering 67 square degrees) are formed in each survey pointing. For each of the 222 beams, total intensity is recorded at 491.52 µs time resolution. Each observation integrates for 1 hr and covers 2592 channels from 119 to 151 MHz. This instrumental setup allows LOTAAS to reach a detection threshold of 1 to 5 mJy for periodic emission. Thus far, the LOTAAS survey has resulted in the discovery of 73 radio pulsars. Among these are two mildly recycled binary millisecond pulsars (P = 13 and 33 ms), as well as the slowest-spinning radio pulsar currently known (P = 23.5 s). The survey has thus far detected 311 known pulsars, with spin periods ranging from 4 ms to 5.0 s and dispersion measures from 3.0 to 217 pc cm −3 . Known pulsars are detected at flux densities consistent with literature values. We find that the LOTAAS pulsar discoveries have, on average, longer spin periods than the known pulsar population. This may reflect different selection biases between LOTAAS and previous surveys, though it is also possible that slower-spinning pulsars preferentially have steeper radio spectra. LOTAAS is the deepest all-sky pulsar survey using a digital aperture array; we discuss some of the lessons learned that can inform the approach for similar surveys using future radio telescopes such as the Square Kilometre Array.

The LOFAR Tied-Array All-Sky Survey (LOTAAS): Characterization of 20 pulsar discoveries and their single-pulse behavior

“…We are using this telescope in the frequency range 119 − 151 MHz to perform the LO-FAR Tied-Array All-Sky Survey (LOTAAS, Coenen et al 2014) 2 for pulsars and fast transients in the Northern sky. A detailed description of the survey is presented in Sanidas et al (2019). Among the LOTAAS discoveries presented in this paper, PSR J0815+4611 has been first presented by Jelić et al (2015), who identified a steep spectrum, unresolved and polarized point source in continuum images of the 3C 196 field observed by the LOFAR Epoch of Reionization project (Candi2, Ger de Bruyn, priv.…”

Synthesising the intrinsic FRB population using frbpoppy

“…Such parent populations can be used to optimise the strategies for such pulsar surveys as using LOFAR (van Leeuwen & Stappers 2010) and the Square Kilometre Array (SKA; Smits et al 2009), and predict the outcomes to within a factor of a few (cf. Sanidas et al 2019).…”

LOFAR radio search for single and periodic pulses from M 31

“…All data were blindly searched on the Dutch supercomputer Cartesius. We used the LOTAAS single-pulse search pipeline (Sanidas et al, 2019), which is based on PRESTO, to remove RFI and identify individual pulses up to widths of 100 ms. We inspected the single-pulse and periodic output both by eye, and with the LOTAAS single-pulse (Michilli & Hessels, 2018;Michilli et al, 2018) and periodic (Lyon et al, 2016) No single pulses were found that appeared in both the initial search of the 50−60 pc cm −3 dispersion-measure range, and the full search. Of the noteworthy periodic candidates seen in the 2011 data (cf.…”