Optical polarimetric observations of low-mass X-ray black hole binary MAXI J1820+070 during 2019-2021

<p>The dataset contains raw polarimetric FITS images of the low-mass X-ray black hole binary <a href="https://www.astronomerstelegram.org/?read=11399">MAXI J1820+070</a> (and surrounding field), obtained by the <a href="https://doi.org/10.3847/1538-3881/abc74f">DIPol-UF </a>optical CCD polarimeter in three (BVR) filters while mounted on the 2.56m <a href="https://www.not.iac.es">Nordic Optical Telescope</a>. The data were collected over 5 observing runs throughout 2019--2021. During each observing night, a set of calibration images were also obtained. These typically include 7 dark and 7 bias images per filter per night (sometimes more if weather conditions or instrument settings changed during observations). Bias and dark FITS files have `_bias` or `_dark` labels in their names, as well as FITS key `IMAGETYP` set to either `Bias Frame` or `Dark Frame`, respectively.</p>