More Like this

1. Chandra, HST/STIS, NICER, Swift, and TESS Detail the Flare Evolution of the Repeating Nuclear Transient ASASSN -14ko

   https://doi.org/10.3847/1538-4357/acd455  

   Payne, Anna V. ; Auchettl, Katie ; Shappee, Benjamin J. ; Kochanek, Christopher S. ; Boyd, Patricia T. ; Holoien, Thomas W. -S. ; Fausnaugh, Michael M. ; Ashall, Chris ; Hinkle, Jason T. ; Vallely, Patrick J. ; et al ( July 2023 , The Astrophysical Journal)

   ASASSN-14ko is a nuclear transient at the center of the AGN ESO 253−G003 that undergoes periodic flares. Optical flares were first observed in 2014 by the All-Sky Automated Survey for Supernovae (ASAS-SN) and their peak times are well-modeled with a period of${115.2}_{-1.2}^{+1.3}$days and period derivative of −0.0026 ± 0.0006. Here we present ASAS-SN, Chandra, HST/STIS, NICER, Swift, and TESS data for the flares that occurred on 2020 December, 2021 April, 2021 July, and 2021 November. These four flares represent flares 18–21 of the total number of flares observed by ASAS-SN so far since 2014. The HST/STIS UV spectra evolve from blueshifted broad absorption features to redshifted broad emission features over ∼10 days. The Swift UV/optical light curves peaked as predicted by the timing model, but the peak UV luminosities that varied between flares and the UV flux in Flare 20 were roughly half the brightness of the other peaks. The X-ray luminosities consistently decreased and the spectra became harder during the UV/optical rise, but apparently without changes in absorption. Finally, two high-cadence TESS light curves from Flare 18 and Flare 12 showed that the slopes during the rising and declining phases changed over time, which indicatesmore »some stochasticity in the flare’s driving mechanism. Although ASASSN-14ko remains observationally consistent with a repeating partial tidal disruption event, these rich multi-wavelength data are in need of a detailed theoretical model.

   « less
2. IFU observations of the inner 200 pc of NGC 4546: gas rotation, non-circular motions, and ionized outflows

   https://doi.org/10.1093/mnras/stac3041  

   Heckler, Kelly F. ; Ricci, Tiago V. ; Riffel, Rogemar A. ( October 2022 , Monthly Notices of the Royal Astronomical Society)

   We present a detailed analysis of the ionized gas distribution and kinematics in the inner ∼ 200 pc of NGC 4546, host of a low-luminosity active galactic nucleus (LLAGN). Using GMOS−IFU observations, with a spectral coverage of 4736–6806 Å  and an angular resolution of 0.7 arcsec, we confirm that the nuclear emission is consistent with photoionization by an AGN, while the gas in the circumnuclear region may be ionized by hot low-mass evolved stars. The gas kinematics in the central region of NGC 4546 presents three components: (i) a disc with major axis oriented along a position angle of 43° ± 3°, counter rotating relative to the stellar disc; (ii) non-circular motions, evidenced by residual velocities of up to 60 km s−1, likely associated with a previous capture of a dwarf satellite by NGC 4546; and (iii) nuclear outflows in ionized gas, identified as a broad component (σ ∼ 320 km s−1) in the line profiles, with a mass outflow rate of $\dot{M}_{\rm out} = 0.3 \pm 0.1$ M⊙ yr−1 and a total mass of Mout = (9.2 ± 0.8) × 103 M⊙ in ionized gas, corresponding to less than 3 per cent of the total mass of ionized gas in the inner 200 pc of NGC 4546. The kinetic efficiency of themore »outflow is roughly 0.1 per cent, which is smaller than the outflow coupling efficiencies predicted by theoretical studies to AGN feedback become efficient in suppressing star formation in the host galaxy.

   « less
3. The multiphase gas structure and kinematics in the circumnuclear region of NGC 5728

   https://doi.org/10.1093/mnras/stz2802  

   Shimizu, T. Taro ; Davies, R. I. ; Lutz, D. ; Burtscher, L. ; Lin, M. ; Baron, D. ; Davies, R. L. ; Genzel, R. ; Hicks, E. K. S. ; Koss, M. ; et al ( October 2019 , Monthly Notices of the Royal Astronomical Society)

   We report on our combined analysis of HST, VLT/MUSE, VLT/SINFONI, and ALMA observations of the local Seyfert 2 galaxy, NGC 5728 to investigate in detail the feeding and feedback of the active galactic nucleus (AGN). The data sets simultaneously probe the morphology, excitation, and kinematics of the stars, ionized gas, and molecular gas over a large range of spatial scales (10 pc to 10 kpc). NGC 5728 contains a large stellar bar that is driving gas along prominent dust lanes to the inner 1 kpc where the gas settles into a circumnuclear ring. The ring is strongly star forming and contains a substantial population of young stars as indicated by the lowered stellar velocity dispersion and gas excitation consistent with H ii regions. We model the kinematics of the ring using the velocity field of the CO (2–1) emission and stars and find it is consistent with a rotating disc. The outer regions of the disc, where the dust lanes meet the ring, show signatures of inflow at a rate of 1 M$\odot$ yr−1. Inside the ring, we observe three molecular gas components corresponding to the circular rotation of the outer ring, a warped disc, and the nuclear stellar bar. The AGN is driving an ionized gasmore »outflow that reaches a radius of 250 pc with a mass outflow rate of 0.08 M$\odot$ yr−1 consistent with its luminosity and scaling relations from previous studies. While we observe distinct holes in CO emission which could be signs of molecular gas removal, we find that largely the AGN is not disrupting the structure of the circumnuclear region.

   « less
4. The Close AGN Reference Survey (CARS): Tracing the circumnuclear star formation in the super-Eddington NLS1 Mrk 1044

   https://doi.org/10.1051/0004-6361/202243697  

   Winkel, N. ; Husemann, B. ; Davis, T. A. ; Smirnova-Pinchukova, I. ; Bennert, V. N. ; Combes, F. ; Gaspari, M. ; Jahnke, K. ; Neumann, J. ; O’Dea, C. P. ; et al ( July 2022 , Astronomy & Astrophysics)

   Context. The host galaxy conditions for rapid supermassive black hole growth are poorly understood. Narrow-line Seyfert 1 (NLS1) galaxies often exhibit high accretion rates and are hypothesized to be prototypes of active galactic nuclei (AGN) at an early stage of their evolution. Aims. We present adaptive optics (AO) assisted VLT MUSE NFM observations of Mrk 1044, the nearest super-Eddington accreting NLS1. Together with archival MUSE WFM data, we aim to understand the host galaxy processes that drive Mrk 1044’s black hole accretion. Methods. We extracted the faint stellar continuum emission from the AGN-deblended host and performed spatially resolved emission line diagnostics with an unprecedented resolution. Combining both MUSE WFM and NFM-AO observations, we used a kinematic model of a thin rotating disk to trace the stellar and ionized gas motion from 10 kpc galaxy scales down to ∼30 pc around the nucleus. Results. Mrk 1044’s stellar kinematics follow circular rotation, whereas the ionized gas shows tenuous spiral features in the center. We resolve a compact star-forming circumnuclear ellipse (CNE) that has a semi-minor axis of 306 pc. Within this CNE, the gas is metal-rich and its line ratios are entirely consistent with excitation by star formation. With an integrated star formation rate ofmore »0.19 ± 0.05  M ⊙  yr −1 , the CNE contributes 27% of the galaxy-wide star formation. Conclusions. We conclude that Mrk 1044’s nuclear activity has not yet affected the circumnuclear star formation. Thus, Mrk 1044 is consistent with the idea that NLS1s are young AGN. A simple mass budget consideration suggests that the circumnuclear star formation and AGN phase are connected and the patterns in the ionized gas velocity field are a signature of the ongoing AGN feeding.« less
5. The Rapid X-Ray and UV Evolution of ASASSN-14ko

   https://doi.org/10.3847/1538-4357/ac480c  

   Payne, Anna V. ; Shappee, Benjamin J. ; Hinkle, Jason T. ; Holoien, Thomas W. -S. ; Auchettl, Katie ; Kochanek, Christopher S. ; Stanek, K. Z. ; Thompson, Todd A. ; Tucker, Michael A. ; Armstrong, James D. ; et al ( February 2022 , The Astrophysical Journal)

   ASASSN-14ko is a recently discovered periodically flaring transient at the center of the active galactic nucleus (AGN) ESO 253−G003 with a slowly decreasing period. Here, we show that the flares originate from the northern, brighter nucleus in this dual-AGN, post-merger system. The light curves for the two flares that occurred in 2020 May and September are nearly identical over all wavelengths. For both events, Swift observations showed that the UV and optical wavelengths brightened in unison. The effective temperature of the UV/optical emission rises and falls with the increase and subsequent decline in the luminosity. The X-ray flux, by contrast, first rapidly drops over ∼2.6 days, rises for ∼5.8 days, drops again over ∼4.3 days, and then recovers. The X-ray spectral evolution of the two flares differ, however. During the 2020 May peak the spectrum softened with increases in the X-ray luminosity, while we observed the reverse for the 2020 September peak. We found a small change in the period derivative, which seems to indicate that the system does not have a static period derivative and there is some stochasticity in its evolution.