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 ( \delta > 0 \degr ) 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 \upmu s 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 .