Systematic effects in LOFAR data: A unified calibration strategy

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Table 1.

Type of systematic effects we isolated in LOFAR data.

Systematic effect	Type of	Ph/Amp/Both^b	Frequency	Direction	Time
	Jones matrix^a		dependency	dependent?	dependent?
Clock drift	Scalar	Ph	∝ν	No	Yes (many seconds)
Polarisation alignment	Diagonal	Ph	∝ν	No	No
Ionosphere - 1st ord. (dispersive delay)	Scalar	Ph	∝ν⁻¹	Yes	Yes (few seconds)
Ionosphere - 2sn ord. (Faraday rotation)	Rotation	Both	∝ν⁻²	Yes	Yes (few seconds)
Ionosphere - 3rd ord.	Scalar	Ph	∝ν⁻³	Yes	Yes (few seconds)
Ionosphere - scintillations	Diagonal	Amp	–	Yes	Yes (few seconds)
Dipole beam	Full-Jones	Both	–	Yes	Yes (minutes)
Bandpass	Diagonal	Amp	–	No	No

Notes. For each effect we describe the associated Jones matrix, the frequency dependency and if it is time or direction dependent.

^(a)

In linear polarisation basis.

^(b)

The matrix affects phases, amplitude or both.

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