The featureless and non-variable optical spectral energy distribution of AXP 4U 0142+61
The featureless and non-variable optical spectral energy distribution of AXP 4U 0142+61
Abstract We present GTC-10.4 m spectroscopy and multiband photometry of the faint (r ∼ 26) optical counterpart of the anomalous X-ray pulsar 4U 0142+61. The 5000–9000 Å spectrum – the first obtained for a magnetar – is featureless, allowing us to set an equivalent width upper limit EW < 25 …