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The first spectroscopic dust reverberation programme on active galactic nuclei: the torus in NGC 5548 (2019)
Journal Article
Landt, H., Ward, M. J., Kynoch, D., Packham, C., Ferland, G. J., Lawrence, A., …Winkler, H. (2019). The first spectroscopic dust reverberation programme on active galactic nuclei: the torus in NGC 5548. Monthly Notices of the Royal Astronomical Society, 489(2), 1572-1589. https://doi.org/10.1093/mnras/stz2212

We have recently initiated the first spectroscopic dust reverberation programme on active galactic nuclei in the near-infrared. Spectroscopy enables measurement of dust properties, such as flux, temperature, and covering factor, with higher precision... Read More about The first spectroscopic dust reverberation programme on active galactic nuclei: the torus in NGC 5548.

The relativistic jet of the γ-ray emitting narrow-line Seyfert 1 galaxy PKS J1222+0413 (2019)
Journal Article
Kynoch, D., Landt, H., Ward, M. J., Done, C., Boisson, C., Baloković, M., Angelakis, E., & Myserlis, I. (2019). The relativistic jet of the γ-ray emitting narrow-line Seyfert 1 galaxy PKS J1222+0413. Monthly Notices of the Royal Astronomical Society, 487(1), 181-197. https://doi.org/10.1093/mnras/stz1193

We present a multi-frequency study of PKS J1222+0413 (4C +04.42), currently the highest redshift γ-ray emitting narrow-line Seyfert 1 (γ-NLS1). We assemble a broad spectral energy distribution (SED) including previously unpublished datasets: X-ray da... Read More about The relativistic jet of the γ-ray emitting narrow-line Seyfert 1 galaxy PKS J1222+0413.

The ‘Big Dipper’: the nature of the extreme variability of the AGN SDSS J2232−0806 (2019)
Journal Article
Kynoch, D., Ward, M. J., Lawrence, A., Bruce, A. G., Landt, H., & MacLeod, C. L. (2019). The ‘Big Dipper’: the nature of the extreme variability of the AGN SDSS J2232−0806. Monthly Notices of the Royal Astronomical Society, 485(2), 2573-2588. https://doi.org/10.1093/mnras/stz517

SDSS J2232−0806 (the ‘Big Dipper’) has been identified as a ‘slow-blue nuclear hypervariable’: a galaxy with no previously known active nucleus, blue colours, and large-amplitude brightness evolution occurring on a time-scale of years. Subsequent obs... Read More about The ‘Big Dipper’: the nature of the extreme variability of the AGN SDSS J2232−0806.

Analyzing temporal variations of AGN emission line profiles in the context of (dusty) cloud structure formation in the broad line region (2019)
Journal Article
Esser, J., Pott, J. U., Landt, H., & Vacca, W. D. (2019). Analyzing temporal variations of AGN emission line profiles in the context of (dusty) cloud structure formation in the broad line region. Astronomy & Astrophysics, 621, https://doi.org/10.1051/0004-6361/201834291

The formation processes and the exact appearance of the dust torus and broad line region (BLR) of active galactic nuclei (AGN) are under debate. Theoretical studies show a possible connection between the dust torus and BLR through a common origin in... Read More about Analyzing temporal variations of AGN emission line profiles in the context of (dusty) cloud structure formation in the broad line region.

The relativistic jet of the γ-ray emitting narrow-line Seyfert 1 galaxy 1H 0323+342 (2017)
Journal Article
Kynoch, D., Landt, H., Ward, M. J., Done, C., Gardner, E., Boisson, C., Arrieta-Lobo, M., Zech, A., Steenbrugge, K., & Pereira Santaella, M. (2018). The relativistic jet of the γ-ray emitting narrow-line Seyfert 1 galaxy 1H 0323+342. Monthly Notices of the Royal Astronomical Society, 475(1), 404-423. https://doi.org/10.1093/mnras/stx3161

The detection of several radio-loud narrow-line Seyfert 1 (NLS1) galaxies by the Fermi Gamma-Ray Space Telescope hints at the existence of a rare, new class of γ-ray emitting active galactic nuclei with low black hole masses. Like flat spectrum radio... Read More about The relativistic jet of the γ-ray emitting narrow-line Seyfert 1 galaxy 1H 0323+342.

A Multi-band Study of the Remarkable Jet in Quasar 4C+19.44 (2017)
Journal Article
Harris, D. E., Lee, N. P., Schwartz, D. A., Siemiginowska, A., Massaro, F., Birkinshaw, M., Worrall, D. M., Cheung, C. C., Gelbord, J. M., Jorstad, S. G., Marscher, A. P., Landt, H., Marshall, H., Perlman, E. S., Stawarz, L., Uchiyama, Y., & Urry, C. M. (2017). A Multi-band Study of the Remarkable Jet in Quasar 4C+19.44. Astrophysical Journal, 846(2), Article 119. https://doi.org/10.3847/1538-4357/aa845c

We present arcsecond-resolution data in the radio, IR, optical, and X-ray for 4C+19.44 (=PKS 1354+195), the longest and straightest quasar jet with deep X-ray observations. We report results from radio images with half to one arcsecond angular resolu... Read More about A Multi-band Study of the Remarkable Jet in Quasar 4C+19.44.

The infrared to X-ray correlation spectra of unobscured type 1 active galactic nuclei (2017)
Journal Article
García-Bernete, I., Ramos Almeida, C., Landt, H., Ward, M. .., Baloković, M., & Acosta-Pulido, J. A. (2017). The infrared to X-ray correlation spectra of unobscured type 1 active galactic nuclei. Monthly Notices of the Royal Astronomical Society, 469(1), 110-126. https://doi.org/10.1093/mnras/stx795

We use new X-ray data obtained with the Nuclear Spectroscopic Telescope Array (NuSTAR), near-infrared (NIR) fluxes and mid-infrared (MIR) spectra of a sample of 24 unobscured type 1 active galactic nuclei (AGN) to study the correlation between variou... Read More about The infrared to X-ray correlation spectra of unobscured type 1 active galactic nuclei.

BAT AGN Spectroscopic Survey - IV: Near-Infrared Coronal Lines, Hidden Broad Lines, and Correlation with Hard X-ray Emission (2017)
Journal Article
Lamperti, I., Koss, M., Trakhtenbrot, B., Schawinski, K., Ricci, C., Oh, K., …Veilleux, S. (2017). BAT AGN Spectroscopic Survey - IV: Near-Infrared Coronal Lines, Hidden Broad Lines, and Correlation with Hard X-ray Emission. Monthly Notices of the Royal Astronomical Society, 467(1), 540-572. https://doi.org/10.1093/mnras/stx055

We provide a comprehensive census of the near-infrared (NIR, 0.8–2.4 μm) spectroscopic properties of 102 nearby (z < 0.075) active galactic nuclei (AGN), selected in the hard X-ray band (14–195 keV) from the Swift-Burst Alert Telescope survey. With t... Read More about BAT AGN Spectroscopic Survey - IV: Near-Infrared Coronal Lines, Hidden Broad Lines, and Correlation with Hard X-ray Emission.

Reaching the peak of the quasar spectral energy distribution – II. Exploring the accretion disc, dusty torus and host galaxy (2016)
Journal Article
Collinson, J. S., Ward, M. J., Landt, H., Done, C., Elvis, M., & McDowell, J. C. (2017). Reaching the peak of the quasar spectral energy distribution – II. Exploring the accretion disc, dusty torus and host galaxy. Monthly Notices of the Royal Astronomical Society, 465(1), 358-382. https://doi.org/10.1093/mnras/stw2666

We continue our study of the spectral energy distributions (SEDs) of 11 active galactic nuclei (AGN) at 1.5 < z < 2.2, with optical–near-infrared (NIR) spectra, X-ray data and mid-IR photometry. In a previous paper, we presented the observations and... Read More about Reaching the peak of the quasar spectral energy distribution – II. Exploring the accretion disc, dusty torus and host galaxy.

On the black hole mass of the γ-ray emitting narrow-line Seyfert 1 galaxy 1H 0323+342 (2016)
Journal Article
Landt, H., Ward, M. J., Baloković, M., Kynoch, D., Storchi-Bergmann, T., Boisson, C., Done, C., Schimoia, J., & Stern, D. (2017). On the black hole mass of the γ-ray emitting narrow-line Seyfert 1 galaxy 1H 0323+342. Monthly Notices of the Royal Astronomical Society, 464(3), 2565-2576. https://doi.org/10.1093/mnras/stw2447

Narrow-line Seyfert 1 galaxies have been identified by the Fermi Gamma-Ray Space Telescope as a rare class of γ-ray emitting active galactic nuclei. The lowest redshift candidate among them is the source 1H 0323+342. Here we present quasi-simultaneou... Read More about On the black hole mass of the γ-ray emitting narrow-line Seyfert 1 galaxy 1H 0323+342.

The near-infrared broad emission line region of active galactic nuclei – II. The 1-μm continuum (2011)
Journal Article
Landt, H., Martin, E., Ward, M., Bentz, M., Korista, K., & Karovska, M. (2011). The near-infrared broad emission line region of active galactic nuclei – II. The 1-μm continuum. Monthly Notices of the Royal Astronomical Society, 414(1), 218-240. https://doi.org/10.1111/j.1365-2966.2011.18383.x

We use quasi-simultaneous near-infrared (near-IR) and optical spectroscopy from four observing runs to study the continuum around 1 μm in 23 well-known broad emission line active galactic nuclei (AGN). We show that, after correcting the optical spect... Read More about The near-infrared broad emission line region of active galactic nuclei – II. The 1-μm continuum.

On the dust geometry in radio-loud active galactic nuclei. (2010)
Journal Article
Landt, H., Buchanan, C., & Barmby, P. (2010). On the dust geometry in radio-loud active galactic nuclei. Monthly Notices of the Royal Astronomical Society, 408(4), 1982-1997. https://doi.org/10.1111/j.1365-2966.2010.17264.x

We use photometric and spectroscopic infrared observations obtained with the Spitzer Space Telescope of 12 radio-loud active galactic nuclei to investigate the dust geometry. Our approach is to look at the change of the infrared spectral energy distr... Read More about On the dust geometry in radio-loud active galactic nuclei..

On the relationship between BL Lacertae objects and radio galaxies. (2008)
Journal Article
Landt, H., & Bignall, H. (2008). On the relationship between BL Lacertae objects and radio galaxies. Monthly Notices of the Royal Astronomical Society, 391(2), 967-985. https://doi.org/10.1111/j.1365-2966.2008.13967.x

We present deep radio images at 1.4 GHz of a large and complete sample of BL Lacertae objects (BL Lacs) selected from the Deep X-ray Radio Blazar Survey (DXRBS). We have observed 24 northern (δ≳− 30°) sources with the Very Large Array (VLA) in both i... Read More about On the relationship between BL Lacertae objects and radio galaxies..

A Search for Synchrotron X-Ray Emission in Radio Quasars (2008)
Journal Article
Landt, H., Padovani, P., Giommi, P., Perri, M., & Cheung, C. (2008). A Search for Synchrotron X-Ray Emission in Radio Quasars. Astrophysical Journal, 676(1), 87-100. https://doi.org/10.1086/527531

This paper presents XMM-Newton and Chandra X-ray spectroscopy of 10 flat-spectrum radio quasars (FSRQ) that are candidates to have an X-ray spectrum dominated by jet synchrotron emission. In all these FSRQ, which are less strongly relativistically be... Read More about A Search for Synchrotron X-Ray Emission in Radio Quasars.