Extended Data Fig. 4: XMM-Newton/EPIC-pn soft X-ray (0.25-2.5 keV) PDS of AT2018cow to assess noise continuum at low frequencies.
From: Evidence for a compact object in the aftermath of the extragalactic transient AT2018cow
The PDS was derived by averaging 15 1024 s light curve segments sampled at 1/16 Hz. The frequency resolution is 1/2048 Hz. The error bars represent the 1-σ uncertainties. The red horizontal line is the Poisson noise level of 2. The 224 Hz QPO in NICER data is outside of this band pass, that is, beyond EPIC-pn’s Nyquist frequency.
