All Outputs (35)

AGN STORM 2. V. Anomalous Behavior of the C iv Light Curve of Mrk 817 (2024)
Journal Article
Homayouni, Y., Kriss, G. A., De Rosa, G., Plesha, R., Cackett, E. M., Goad, M. R., …Zu, Y. (2024). AGN STORM 2. V. Anomalous Behavior of the C iv Light Curve of Mrk 817. Astrophysical Journal, 963(2), Article 123. https://doi.org/10.3847/1538-4357/ad1be4

An intensive reverberation mapping campaign of the Seyfert 1 galaxy Mrk 817 using the Cosmic Origins Spectrograph on the Hubble Space Telescope revealed significant variations in the response of broad UV emission lines to fluctuations in the continuu... Read More about AGN STORM 2. V. Anomalous Behavior of the C iv Light Curve of Mrk 817.

First High-resolution Spectroscopy of X-Ray Absorption Lines in the Obscured State of NGC 5548 (2024)
Journal Article
Mehdipour, M., Kriss, G. A., Kaastra, J. S., Costantini, E., Gu, L., Landt, H., …Rogantini, D. (2024). First High-resolution Spectroscopy of X-Ray Absorption Lines in the Obscured State of NGC 5548. Astrophysical Journal, 962(2), Article 155. https://doi.org/10.3847/1538-4357/ad1bcb

Multiwavelength spectroscopy of NGC 5548 revealed remarkable changes due to the presence of an obscuring wind from the accretion disk. This broadened our understanding of obscuration and outflows in active galactic nuclei. Swift monitoring of NGC 554... Read More about First High-resolution Spectroscopy of X-Ray Absorption Lines in the Obscured State of NGC 5548.

AGN STORM 2. VI. Mapping Temperature Fluctuations in the Accretion Disk of Mrk 817 (2024)
Journal Article
Neustadt, J. M. M., Kochanek, C. S., Montano, J., Gelbord, J., Barth, A. J., De Rosa, G., …Zu, Y. (2024). AGN STORM 2. VI. Mapping Temperature Fluctuations in the Accretion Disk of Mrk 817. Astrophysical Journal, 961(2), Article 219. https://doi.org/10.3847/1538-4357/ad1386

We fit the UV/optical lightcurves of the Seyfert 1 galaxy Mrk 817 to produce maps of the accretion disk temperature fluctuations δ T resolved in time and radius. The δ T maps are dominated by coherent radial structures that move slowly (v ≪ c) inward... Read More about AGN STORM 2. VI. Mapping Temperature Fluctuations in the Accretion Disk of Mrk 817.

AGN STORM 2. IV. Swift X-Ray and Ultraviolet/Optical Monitoring of Mrk 817 (2023)
Journal Article
Cackett, E. M., Gelbord, J., Barth, A. J., De Rosa, G., Edelson, R., Goad, M. R., …Zaidouni, F. (2023). AGN STORM 2. IV. Swift X-Ray and Ultraviolet/Optical Monitoring of Mrk 817. Astrophysical Journal, 958(2), Article 195. https://doi.org/10.3847/1538-4357/acfdac

The AGN STORM 2 campaign is a large, multiwavelength reverberation mapping project designed to trace out the structure of Mrk 817 from the inner accretion disk to the broad emission line region and out to the dusty torus. As part of this campaign, Sw... Read More about AGN STORM 2. IV. Swift X-Ray and Ultraviolet/Optical Monitoring of Mrk 817.

The outer dusty edge of accretion disks in active galactic nuclei (2023)
Journal Article
Landt, H. (2023). The outer dusty edge of accretion disks in active galactic nuclei. Frontiers in Astronomy and Space Sciences, 10, 1256088. https://doi.org/10.3389/fspas.2023.1256088

Recent models for the inner structure of active galactic nuclei (AGN) aim at connecting the outer region of the accretion disk with the broad-line region and dusty torus through a radiatively accelerated, dusty outflow. Such an outflow not only requi... Read More about The outer dusty edge of accretion disks in active galactic nuclei.

Continuum Reverberation Mapping of Mrk 876 over Three Years with Remote Robotic Observatories (2023)
Journal Article
Miller, J. A., Cackett, E. M., Goad, M. R., Horne, K., Barth, A. J., Romero-Colmenero, E., …Winkler, H. (2023). Continuum Reverberation Mapping of Mrk 876 over Three Years with Remote Robotic Observatories. Astrophysical Journal, 953(2), Article 137. https://doi.org/10.3847/1538-4357/ace342

Continuum reverberation mapping probes the size scale of the optical continuum-emitting region in active galactic nuclei (AGN). Through 3 yr of multiwavelength photometric monitoring in the optical with robotic observatories, we perform continuum rev... Read More about Continuum Reverberation Mapping of Mrk 876 over Three Years with Remote Robotic Observatories.

The SOUX AGN sample: optical/UV/X-ray SEDs and the nature of the disc (2023)
Journal Article
Mitchell, J. A. J., Done, C., Ward, M. J., Kynoch, D., Hagen, S., Lusso, E., & Landt, H. (2023). The SOUX AGN sample: optical/UV/X-ray SEDs and the nature of the disc. Monthly Notices of the Royal Astronomical Society, 524(2), 1796-1825. https://doi.org/10.1093/mnras/stad1830

We use the SOUX sample of ∼700 active galactic nucleus (AGN) to form average optical-ultraviolet (UV)-X-rays spectral energy distributions (SEDs) on a two-dimensional (2D) grid of MBH and L2500. We compare these with the predictions of a new AGN SED... Read More about The SOUX AGN sample: optical/UV/X-ray SEDs and the nature of the disc.

AGN STORM 2. II. Ultraviolet Observations of Mrk 817 with the Cosmic Origins Spectrograph on the Hubble Space Telescope* (2023)
Journal Article
Homayouni, Y., De Rosa, G., Plesha, R., Kriss, G. A., Barth, A. J., Cackett, E. M., …Zu, Y. (2023). AGN STORM 2. II. Ultraviolet Observations of Mrk 817 with the Cosmic Origins Spectrograph on the Hubble Space Telescope*. Astrophysical Journal, 948(2), Article 85. https://doi.org/10.3847/1538-4357/acc45a

We present reverberation mapping measurements for the prominent ultraviolet broad emission lines of the active galactic nucleus Mrk 817 using 165 spectra obtained with the Cosmic Origins Spectrograph on the Hubble Space Telescope. Our ultraviolet obs... Read More about AGN STORM 2. II. Ultraviolet Observations of Mrk 817 with the Cosmic Origins Spectrograph on the Hubble Space Telescope*.

AGN STORM 2. III. A NICER View of the Variable X-Ray Obscurer in Mrk 817 (2023)
Journal Article
Partington, E. R., Cackett, E. M., Kara, E., Kriss, G. A., Barth, A. J., De Rosa, G., …Zaidouni, F. (2023). AGN STORM 2. III. A NICER View of the Variable X-Ray Obscurer in Mrk 817. Astrophysical Journal, 947(1), Article 2. https://doi.org/10.3847/1538-4357/acbf44

The AGN STORM 2 Collaboration targeted the Seyfert 1 galaxy Mrk 817 for a year-long multiwavelength, coordinated reverberation mapping campaign including Hubble Space Telescope, Swift, XMM-Newton, NICER, and ground-based observatories. Early observat... Read More about AGN STORM 2. III. A NICER View of the Variable X-Ray Obscurer in Mrk 817.

A Complex Dust Morphology in the High-luminosity AGN Mrk 876 (2023)
Journal Article
Landt, H., Mitchell, J. A., Ward, M. J., Mercatoris, P., Pott, J., Horne, K., …Winkler, H. (2023). A Complex Dust Morphology in the High-luminosity AGN Mrk 876. Astrophysical Journal, 945(1), Article 62. https://doi.org/10.3847/1538-4357/acb92d

Recent models for the inner structures of active galactic nuclei (AGNs) advocate the presence of a radiatively accelerated dusty outflow launched from the outer regions of the accretion disk. Here, we present the first near-IR variable (rms) spectrum... Read More about A Complex Dust Morphology in the High-luminosity AGN Mrk 876.

The SOUX AGN sample: SDSS–XMM-Newton optical, ultraviolet, and X-ray selected active galactic nuclei spanning a wide range of parameter space – sample definition (2023)
Journal Article
Kynoch, D., Mitchell, J. A. J., Ward, M. J., Done, C., Lusso, E., & Landt, H. (2023). The SOUX AGN sample: SDSS–XMM-Newton optical, ultraviolet, and X-ray selected active galactic nuclei spanning a wide range of parameter space – sample definition. Monthly Notices of the Royal Astronomical Society, 520(2), 2781-2805. https://doi.org/10.1093/mnras/stad221

We assemble a sample of 696 type 1 active galactic nuclei (AGN) up to a redshift of z = 2.5, all of which have an SDSS spectrum containing at least one broad emission line (H α, H β, or Mg II) and an XMM-Newton X-ray spectrum containing at least 250... Read More about The SOUX AGN sample: SDSS–XMM-Newton optical, ultraviolet, and X-ray selected active galactic nuclei spanning a wide range of parameter space – sample definition.

The long-term broad-line responsivity in MKN 110 (2022)
Journal Article
Homan, D., Lawrence, A., Ward, M., Bruce, A., Landt, H., MacLeod, C., …Peterson, B. M. (2023). The long-term broad-line responsivity in MKN 110. Monthly Notices of the Royal Astronomical Society, 519(2), 1745-1763. https://doi.org/10.1093/mnras/stac3571

We examine the long-term history of the optical spectrum of the extremely variable Active Galactic Nucleus (AGN) MKN 110. By combining various archival data with new data, we cover an unprecedented long period of ∼30 yr (1987–2019). We find that the... Read More about The long-term broad-line responsivity in MKN 110.

Detection of an unidentified soft X-ray emission feature in NGC 5548 (2022)
Journal Article
Gu, L., Mao, J., Kaastra, J. S., Mehdipour, M., Pinto, C., Grafton-Waters, S., …Ward, M. (2022). Detection of an unidentified soft X-ray emission feature in NGC 5548. Astronomy & Astrophysics, 665, Article A93. https://doi.org/10.1051/0004-6361/202244075

Context. NGC 5548 is an X-ray bright Seyfert 1 active galaxy. It exhibits a variety of spectroscopic features in the soft X-ray band, in particular including the absorption by the active galactic nucleus (AGN) outflows of a broad range of ionization... Read More about Detection of an unidentified soft X-ray emission feature in NGC 5548.

Transient obscuration event captured in NGC 3227 III. Photoionization modeling of the X-ray obscuration event in 2019 (2022)
Journal Article
Mao, J., Kaastra, J., Mehdipour, M., Kriss, G., Wang, Y., Grafton-Waters, S., …Behar, E. (2022). Transient obscuration event captured in NGC 3227 III. Photoionization modeling of the X-ray obscuration event in 2019. Astronomy & Astrophysics, 665, Article A72. https://doi.org/10.1051/0004-6361/202142637

Context. A growing number of transient X-ray obscuration events in type I active galactic nuclei suggest that our line of sight to the central engine is not always free. Multiple X-ray obscuration events were reported in the nearby Seyfert 1.5 galaxy... Read More about Transient obscuration event captured in NGC 3227 III. Photoionization modeling of the X-ray obscuration event in 2019.

Multiple locations of near-infrared coronal lines in NGC 5548 (2022)
Journal Article
Kynoch, D., Landt, H., Dehghanian, M., Ward, M. J., & Ferland, G. J. (2022). Multiple locations of near-infrared coronal lines in NGC 5548. Monthly Notices of the Royal Astronomical Society, 516(3), https://doi.org/10.1093/mnras/stac2443

We present the first intensive study of the variability of the near-infrared coronal lines in an active galactic nucleus (AGN). We use data from a 1-yr-long spectroscopic monitoring campaign with roughly weekly cadence on NGC 5548 to study the variab... Read More about Multiple locations of near-infrared coronal lines in NGC 5548.

10 Yr Transformation of the Obscuring Wind in NGC 5548 (2022)
Journal Article
Mehdipour, M., Kriss, G. A., Costantini, E., Gu, L., Kaastra, J. S., Landt, H., & Mao, J. (2022). 10 Yr Transformation of the Obscuring Wind in NGC 5548. Astrophysical Journal Letters, 934(2), https://doi.org/10.3847/2041-8213/ac822f

A decade ago, the archetypal Seyfert-1 galaxy NGC 5548 was discovered to have undergone major spectral changes. The soft X-ray flux had dropped by a factor of 30 while new broad and blueshifted UV absorption lines appeared. This was explained by the... Read More about 10 Yr Transformation of the Obscuring Wind in NGC 5548.

AGN STORM 2. I. First results: A Change in the Weather of Mrk 817 (2021)
Journal Article
Kara, E., Mehdipour, M., Kriss, G. A., Cackett, E. M., Arav, N., Barth, A. J., …Zu, Y. (2021). AGN STORM 2. I. First results: A Change in the Weather of Mrk 817. Astrophysical Journal, 922(2), Article 151. https://doi.org/10.3847/1538-4357/ac2159

We present the first results from the ongoing, intensive, multiwavelength monitoring program of the luminous Seyfert 1 galaxy Mrk 817. While this active galactic nucleus was, in part, selected for its historically unobscured nature, we discovered tha... Read More about AGN STORM 2. I. First results: A Change in the Weather of Mrk 817.

Broad He i 1.08-µm absorption from the obscurer in the active galaxy NGC 5548 (2020)
Journal Article
Wildy, C., Landt, H., Ward, M. J., Czerny, B., & Kynoch, D. (2021). Broad He i 1.08-µm absorption from the obscurer in the active galaxy NGC 5548. Monthly Notices of the Royal Astronomical Society: Letters, 500(2), 2063-2075. https://doi.org/10.1093/mnras/staa3301

The nucleus of the active galaxy NGC 5548 was the target of two intensive spectroscopic monitoring campaigns at X-ray, ultraviolet (UV), and optical frequencies in 2013/2014. These campaigns detected the presence of a massive obscuration event. In 20... Read More about Broad He i 1.08-µm absorption from the obscurer in the active galaxy NGC 5548.

State-of-the-art AGN SEDs for Photoionization Models: BLR Predictions Confront the Observations (2020)
Journal Article
Ward, M. J., Landt, H., Jin, C., Done, C., & Ferland, G. J. (2020). State-of-the-art AGN SEDs for Photoionization Models: BLR Predictions Confront the Observations. Monthly Notices of the Royal Astronomical Society, 494(4), 5917-5922. https://doi.org/10.1093/mnras/staa1207

The great power offered by photoionization models of Active Galactic Nuclei (AGN) emission line regions has long been mitigated by the fact that very little is known about the spectral energy distribution (SED) between the Lyman limit, where interven... Read More about State-of-the-art AGN SEDs for Photoionization Models: BLR Predictions Confront the Observations.

The spectral energy distributions of active galactic nuclei (2019)
Journal Article
Brown, M. J. I., Duncan, K. J., Landt, H., Kirk, M., Ricci, C., Kamraj, N., …Ananna, T. (2019). The spectral energy distributions of active galactic nuclei. Monthly Notices of the Royal Astronomical Society, 489(3), 3351-3367. https://doi.org/10.1093/mnras/stz2324

We present spectral energy distributions (SEDs) of 41 active galactic nuclei, derived from multiwavelength photometry and archival spectroscopy. All of the SEDs span at least 0.09 to 30 μm, but in some instances wavelength coverage extends into the X... Read More about The spectral energy distributions of active galactic nuclei.