A long-term study of Mrk 50: appearance and disappearance of soft excess

Abstract

We present an extensive temporal and spectral study of the Seyfert 1 AGN Mrk 50 using 15 yr (2007–2022) of multiwavelength observations from XMM-Newton, Swift, and NuSTAR for the first time. From the timing analysis, we found that the source exhibited variability of ∼20% during the 2007 observation, which reduced to below 10% in the subsequent observations and became nonvariable in the observations from 2010 onward. From the spectral study, we found that the spectra are nearly featureless. Nondetection of absorption in the low-energy domain during the 15 yr of observation infers the absence of obscuration around the central engine, rendering the nucleus a "bare" type. A prominent soft X-ray excess below 2 keV was detected in the source spectrum during the observations between 2007 and 2010, which vanished during the later observations. To describe the nature of the soft excess, we use two physical models, such as warm Comptonization and blurred reflection from the ionized accretion disk. Both of the physical models explain the nature and origin of the soft excess in this source. Our analysis found that Mrk 50 accretes at a sub-Eddington accretion rate (λEdd = 0.13–0.02) during all of the observations used in this work.