Outputs (38)

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., Horne, K., Kara, E. A., Landt, H., Arav, N., Boizelle, B. D., Bentz, M. C., Brink, T. G., Brotherton, M. S., Chelouche, D., Dalla Bontà, E., Dehghanian, M., Du, P., Ferland, G. J., Ferrarese, L., …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., Homayouni, Y., Horne, K., Landt, H., Zoghbi, A., Edelson, R., Arav, N., Boizelle, B. D., Bentz, M. C., Brotherton, M. S., Byun, D., Dalla Bontà, E., Dehghanian, M., Du, P., Fian, C., …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.-U., Horne, K., Hernández Santisteban, J. V., Malhotra, D., Cackett, E. M., Goad, M. R., Romero Colmenero, E., & 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., Bianchi, S., Landt, H., Branduardi-Raymont, G., Costantini, E., Ebrero, J., Petrucci, P.-O., Behar, E., di Gesu, L., De Marco, B., Matt, G., Mitchell, J. A., Peretz, U., Ursini, F., & 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., Branduardi-Raymont, G., Pinto, C., Landt, H., Walton, D., Costantini, E., Di Gesu, L., Bianchi, S., Petrucci, P.-O., De Marco, B., Ponti, G., Fukazawa, Y., Ebrero, J., & 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., Byun, D., Brotherton, M. S., De Rosa, G., Gelbord, J., Hernández Santisteban, J. V., Hu, C., Kaastra, J., Landt, H., Li, Y.-R., Miller, J. A., Montano, J., Partington, E., Aceituno, J., Bai, J.-M., …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.