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abstract |
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1ES 1927+654 is a paradigm-defying AGN and one of the most peculiar X-ray nuclear transients. During a recent, multi-year outburst, 1ES 1927+654 underwent extreme X-ray spectral changes, including the first-observed destruction and recreation of the X-ray corona, possibly due to a TDE in an AGN accretion disk. Despite rebuilding its corona, this unique AGN still appears softer and with different variability properties than its pre-outburst state. With continued NICER monitoring, we will study the X-ray and UV variability and monitor X-ray spectral changes to assess the post-outburst nature of this NICER legacy target. We propose a one year monitoring campaign with a weekly 1 ks NICER observation and a 1 ks Swift observation every 2 weeks (totaling 52 ks with NICER and 26 ks with Swift). |
zeta Pup is a well-studied, archetypal O-type supergiant with more than one period of cyclical variability detected in multiwavelength studies. Previous Chandra and XMM-Newton observations have shown the presence of a 1.78-d period, believed to be linked to rotation, and another, longer unexplained period of around 5-6d. Monitoring this star with NICER using two separate observing cadences, we seek to probe both signals and their coherence timescales, as well as constrain the presence of possible additional stochastic variability. By combining this dataset with simultaneous BRITE space-based optical photometry, we will trace these signals back to the wind structures -- both large-scale and possibly small-scale -- that cause them, and gain a deeper understanding of the outflows of OB stars. |
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