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Abstract Broad absorption line quasars are actively accreting supermassive black holes that have strong outflows characterized by broad absorption lines in their rest-UV spectra. Variability in these absorption lines occurs over months to years depending on the source. WPVS 007, a low-redshift, low-luminosity narrow-line Seyfert 1 (NLS1) shows strong variability over shorter timescales, providing a unique opportunity to study the driving mechanism behind this variability that may mimic longer-scale variability in much more massive quasars. We present the first variability study using the spectral synthesis codeSimBAL, which provides velocity-resolved changes in physical conditions of the gas using constraints from multiple absorption lines. Overall, we find WPVS 007 to have a highly ionized outflow with a large mass-loss rate and kinetic luminosity. We determine the primary cause of the absorption-line variability in WPVS 007 to be a change in covering fraction of the continuum by the outflow. This study is the firstSimBALanalysis where multiple epochs of observation were fit simultaneously, demonstrating the ability ofSimBALto use the time domain as an additional constraint in spectral models. 

Abstract  We present the first results from a 100-day Swift, NICER, and ground-based X-ray–UV–optical reverberation mapping campaign of the Narrow-line Seyfert 1 Mrk 335, when it was in an unprecedented low X-ray flux state. Despite dramatic suppression of the X-ray variability, we still observe UV–optical lags as expected from disk reverberation. Moreover, the UV–optical lags are consistent with archival observations when the X-ray luminosity was >10 times higher. Interestingly, both low- and high-flux states reveal UV–optical lags that are 6–11 times longer than expected from a thin disk. These long lags are often interpreted as due to contamination from the broad line region; however theu-band excess lag (containing the Balmer jump from the diffuse continuum) is less prevalent than in other active galactic nuclei. The Swift campaign showed a low X-ray-to-optical correlation (similar to previous campaigns), but NICER and ground-based monitoring continued for another 2 weeks, during which the optical rose to the highest level of the campaign, followed ∼10 days later by a sharp rise in X-rays. While the low X-ray countrate and relatively large systematic uncertainties in the NICER background make this measurement challenging, if the optical does lead X-rays in this flare, this indicates a departure from the zeroth-order reprocessing picture. If the optical flare is due to an increase in mass accretion rate, this occurs on much shorter than the viscous timescale. Alternatively, the optical could be responding to an intrinsic rise in X-rays that is initially hidden from our line of sight. 

ABSTRACT ASASSN-18am/SN 2018gk is a newly discovered member of the rare group of luminous, hydrogen-rich supernovae (SNe) with a peak absolute magnitude of MV ≈ −20 mag that is in between normal core-collapse SNe and superluminous SNe. These SNe show no prominent spectroscopic signatures of ejecta interacting with circumstellar material (CSM), and their powering mechanism is debated. ASASSN-18am declines extremely rapidly for a Type II SN, with a photospheric-phase decline rate of ∼6.0 mag (100 d)−1. Owing to the weakening of H i and the appearance of He i in its later phases, ASASSN-18am is spectroscopically a Type IIb SN with a partially stripped envelope. However, its photometric and spectroscopic evolution shows significant differences from typical SNe IIb. Using a radiative diffusion model, we find that the light curve requires a high synthesized 56Ni mass $$M_{\rm Ni} \sim 0.4\, \rm {M_{\odot }}$$ and ejecta with high kinetic energy Ekin = (7–10) × 1051 erg. Introducing a magnetar central engine still requires $$M_{\rm Ni} \sim 0.3\, \rm {M_{\odot }}$$ and Ekin = 3 × 1051 erg. The high 56Ni mass is consistent with strong iron-group nebular lines in its spectra, which are also similar to several SNe Ic-BL with high 56Ni yields. The earliest spectrum shows ‘flash ionization’ features, from which we estimate a mass-loss rate of $$\dot{M}\approx 2\times 10^{-4} \, \rm \rm {M_{\odot }}\,yr^{-1}$$. This wind density is too low to power the luminous light curve by ejecta–CSM interaction. We measure expansion velocities as high as 17 000 $$\rm {\, km\, s^{-1}}$$ for Hα, which is remarkably high compared to other SNe II. We estimate an oxygen core mass of 1.8–3.4 M⊙ using the [O i] luminosity measured from a nebular-phase spectrum, implying a progenitor with a zero-age main-sequence mass of 19–26 M⊙.