Variability of the High-velocity Outflow in the Quasar PDS 456

Reeves, J.N.; Braito, V.; Gofford, J.; Sim, S.A.; Behar, E.; Costa, M.; Kaspi, S.; Matzeu, G.; Miller, L.; O'Brien, P.; Turner, T.J.; Ward, M.

doi:10.1088/0004-637x/780/1/45

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., …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.

The broad-band SEDs of four ‘hypervariable’ AGN (2017)
Journal Article
Collinson, J. S., Ward, M. J., Lawrence, A., Bruce, A., MacLeod, C. L., Elvis, M., …Done, C. (2018). The broad-band SEDs of four ‘hypervariable’ AGN. Monthly Notices of the Royal Astronomical Society, 474(3), 3565-3575. https://doi.org/10.1093/mnras/stx2992

We present an optical-to-X-ray spectral analysis of four ‘hypervariable’ AGN (HVAs) discovered by comparing Pan-STARRS data to that from the Sloan Digital Sky Survey over a 10 yr baseline (Lawrence et al.). There is some evidence that these objects a... Read More about The broad-band SEDs of four ‘hypervariable’ AGN.

A population of highly energetic transient events in the centres of active galaxies (2017)
Journal Article
Kankare, E., Kotak, R., Mattila, S., Lundqvist, P., Ward, M., Fraser, M., …Waters, C. (2017). A population of highly energetic transient events in the centres of active galaxies. Nature Astronomy, 1(12), 865-871. https://doi.org/10.1038/s41550-017-0290-2

Recent all-sky surveys have led to the discovery of new types of transients. These include stars disrupted by the central supermassive black hole, and supernovae that are 10–100 times more energetic than typical ones. However, the nature of even more... Read More about A population of highly energetic transient events in the centres of active galaxies.

Determining the torus covering factors for a sample of type 1 AGN in the local Universe (2017)
Journal Article
Ezhikode, S. H., Gandhi, P., Done, C., Ward, M., Dewangan, G. C., Misra, R., & Philip, N. S. (2017). Determining the torus covering factors for a sample of type 1 AGN in the local Universe. Monthly Notices of the Royal Astronomical Society, 472(3), 3492-3511. https://doi.org/10.1093/mnras/stx2160

In the unified scheme of active galactic nuclei, a dusty torus absorbs and then reprocesses a fraction of the intrinsic luminosity which is emitted at longer wavelengths. Thus, subject to radiative transfer corrections, the fraction of the sky covere... Read More about Determining the torus covering factors for a sample of type 1 AGN in the local Universe.

Super-Eddington QSO RX J0439.6-5311 – II. Multiwavelength constraints on the global structure of the accretion flow (2017)
Journal Article
Jin, C., Done, C., Ward, M., & Gardner, E. (2017). Super-Eddington QSO RX J0439.6-5311 – II. Multiwavelength constraints on the global structure of the accretion flow. Monthly Notices of the Royal Astronomical Society, 471(1), 706-721. https://doi.org/10.1093/mnras/stx1634

We present a detailed multiwavelength study of an unobscured, highly super-Eddington Type-1 QSO RX J0439.6-5311. We combine the latest XMM–Newton observation with all archival data from infrared to hard X-rays. The optical spectrum is very similar to... Read More about Super-Eddington QSO RX J0439.6-5311 – II. Multiwavelength constraints on the global structure of the accretion flow.

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. (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.

Spectral analysis of four ‘hypervariable’ AGN: a micro-needle in the haystack? (2017)
Journal Article
Bruce, A., Lawrence, A., MacLeod, C., Elvis, M., Ward, M., Collinson, J., …Waters, C. (2017). Spectral analysis of four ‘hypervariable’ AGN: a micro-needle in the haystack?. Monthly Notices of the Royal Astronomical Society, 467(2), 1259-1280. https://doi.org/10.1093/mnras/stx168

We analyse four extreme active galactic nuclei (AGN) transients to explore the possibility that they are caused by rare, high-amplitude microlensing events. These previously unknown type-I AGN are located in the redshift range 0.6–1.1 and show change... Read More about Spectral analysis of four ‘hypervariable’ AGN: a micro-needle in the haystack?.

Reaching the peak of the quasar spectral energy distribution – II. Exploring the accretion disc, dusty torus and host galaxy (2016)
Journal Article
Collinson, J., Ward, M., Landt, H., Done, C., Elvis, M., & McDowell, J. (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., Baloković, M., Kynoch, D., Storchi-Bergmann, T., Boisson, C., …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.

TeV γ-ray observations of the young synchrotron-dominated SNRs G1.9+0.3 and G330.2+1.0 with H.E.S.S (2014)
Journal Article
Abramowski, A., Aharonian, F., Ait Benkhali, F., Akhperjanian, A., Angüner, E., Anton, G., …Zechlin, H. (2014). TeV γ-ray observations of the young synchrotron-dominated SNRs G1.9+0.3 and G330.2+1.0 with H.E.S.S. Monthly Notices of the Royal Astronomical Society, 441(1), 790-799. https://doi.org/10.1093/mnras/stu459

The non-thermal nature of the X-ray emission from the shell-type supernova remnants (SNRs) G1.9+0.3 and G330.2+1.0 is an indication of intense particle acceleration in the shock fronts of both objects. This suggests that the SNRs are prime candidates... Read More about TeV γ-ray observations of the young synchrotron-dominated SNRs G1.9+0.3 and G330.2+1.0 with H.E.S.S.

Search for TeV Gamma-ray emission from GRB 100621A, an extremely bright GRB in X-rays, with H.E.S.S (2014)
Journal Article
Abramowski, A., Aharonian, F., Ait Benkhali, F., Akhperjanian, A., Angüner, E., Anton, G., …Zechlin, H. (2014). Search for TeV Gamma-ray emission from GRB 100621A, an extremely bright GRB in X-rays, with H.E.S.S. Astronomy & Astrophysics, 565, Article A16. https://doi.org/10.1051/0004-6361/201322984

The long gamma-ray burst (GRB) 100621A, at the time the brightest X-ray transient ever detected by Swift-XRT in the 0.3–10 keV range, has been observed with the H.E.S.S. imaging air Cherenkov telescope array, sensitive to gamma radiation in the very-... Read More about Search for TeV Gamma-ray emission from GRB 100621A, an extremely bright GRB in X-rays, with H.E.S.S.

HESS J1640-465 - an exceptionally luminous TeV γ-ray supernova remnant (2014)
Journal Article
Abramowski, A., Aharonian, F., Benkhali, F., Akhperjanian, A., Angüner, E., Anton, G., …Zechlin, H. (2014). HESS J1640-465 - an exceptionally luminous TeV γ-ray supernova remnant. Monthly Notices of the Royal Astronomical Society, 439(3), 2828-2836. https://doi.org/10.1093/mnras/stu139

The results of follow-up observations of the TeV γ-ray source HESS J1640−465 from 2004 to 2011 with the High Energy Stereoscopic System (HESS) are reported in this work. The spectrum is well described by an exponential cut-off power law with photon i... Read More about HESS J1640-465 - an exceptionally luminous TeV γ-ray supernova remnant.

Flux upper limits for 47 AGN observed with H.E.S.S. in 2004-2011 (2014)
Journal Article
Collaboration, H., Abramowski, A., Aharonian, F., Ait Benkhali, F., Akhperjanian, A., Angüner, E., …Zechlin, H. (2014). Flux upper limits for 47 AGN observed with H.E.S.S. in 2004-2011. Astronomy & Astrophysics, 564, Article A9. https://doi.org/10.1051/0004-6361/201322897

Context. About 40% of the observation time of the High Energy Stereoscopic System (H.E.S.S.) is dedicated to studying active galactic nuclei (AGN), with the aim of increasing the sample of known extragalactic very-high-energy (VHE, E > 100 GeV) sourc... Read More about Flux upper limits for 47 AGN observed with H.E.S.S. in 2004-2011.

Revealing the Location and Structure of the Accretion Disk Wind in PDS 456 (2014)
Journal Article
Gofford, J., Reeves, J., Braito, V., Nardini, E., Costa, M., Matzeu, G., …Miller, L. (2014). Revealing the Location and Structure of the Accretion Disk Wind in PDS 456. Astrophysical Journal, 784(1), Article 77. https://doi.org/10.1088/0004-637x/784/1/77

We present evidence for the rapid variability of the high-velocity iron K-shell absorption in the nearby (z = 0.184) quasar PDS 456. From a recent long Suzaku observation in 2013 (~1 Ms effective duration), we find that the equivalent width of iron K... Read More about Revealing the Location and Structure of the Accretion Disk Wind in PDS 456.

Constraints on the outer radius of the broad emission line region of active galactic nuclei (2014)
Journal Article
Landt, H., Ward, M., Elvis, M., & Karovska, M. (2014). Constraints on the outer radius of the broad emission line region of active galactic nuclei. Monthly Notices of the Royal Astronomical Society, 439(1), 1051-1062. https://doi.org/10.1093/mnras/stu031

Here we present observational evidence that the broad emission line region (BELR) of active galactic nuclei (AGN) generally has an outer boundary. This was already clear for sources with an obvious transition between the broad and narrow components o... Read More about Constraints on the outer radius of the broad emission line region of active galactic nuclei.

HESS J1818–154, a new composite supernova remnant discovered in TeV gamma rays and X-rays (2014)
Journal Article
Abramowski, A., Aharonian, F., Ait Benkhali, F., Akhperjanian, A., Angüner, E., Anton, G., …Zechlin, H. (2014). HESS J1818–154, a new composite supernova remnant discovered in TeV gamma rays and X-rays. Astronomy & Astrophysics, 562, Article A40. https://doi.org/10.1051/0004-6361/201322914

Composite supernova remnants (SNRs) constitute a small subclass of the remnants of massive stellar explosions where non-thermal radiation is observed from both the expanding shell-like shock front and from a pulsar wind nebula (PWN) located inside of... Read More about HESS J1818–154, a new composite supernova remnant discovered in TeV gamma rays and X-rays.

Search for extended γ-ray emission around AGN with H.E.S.S. and Fermi-LAT (2014)
Journal Article
Abramowski, A., Aharonian, F., Ait Benkhali, F., Akhperjanian, A., Angüner, E., Anton, G., …Malyshev, D. (2014). Search for extended γ-ray emission around AGN with H.E.S.S. and Fermi-LAT. Astronomy & Astrophysics, 562, Article A145. https://doi.org/10.1051/0004-6361/201322510

Context. Very-high-energy (VHE; E > 100 GeV) γ-ray emission from blazars inevitably gives rise to electron-positron pair production through the interaction of these γ-rays with the extragalactic background light (EBL). Depending on the magnetic field... Read More about Search for extended γ-ray emission around AGN with H.E.S.S. and Fermi-LAT.

H.E.S.S. observations of the Crab during its March 2013 GeV gamma- ray flare (2014)
Journal Article
Abramowski, A., Aharonian, F., Ait Benkhali, F., Akhperjanian, A., Angüner, E., Anton, G., …Zechlin, H. (2014). H.E.S.S. observations of the Crab during its March 2013 GeV gamma- ray flare. Astronomy & Astrophysics, 562, Article L4. https://doi.org/10.1051/0004-6361/201323013

Context. On March 4, 2013 the Fermi-LAT and AGILE reported a flare from the direction of the Crab nebula in which the high-energy (HE; E > 100 MeV) flux was six times above its quiescent level. Simultaneous observations in other energy bands give us... Read More about H.E.S.S. observations of the Crab during its March 2013 GeV gamma- ray flare.

Long-term TeV and X-Ray Observations of the Gamma-Ray Binary HESS J0632+057 (2014)
Journal Article
Aliu, E., Archambault, S., Aune, T., Behera, B., Beilicke, M., Benbow, W., …Zechlin, H. (2014). Long-term TeV and X-Ray Observations of the Gamma-Ray Binary HESS J0632+057. Astrophysical Journal, 780(2), Article 168. https://doi.org/10.1088/0004-637x/780/2/168

HESS J0632+057 is the only gamma-ray binary known so far whose position in the sky allows observations with ground-based observatories in both the northern and southern hemispheres. Here we report on long-term observations of HESS J0632+057 conducted... Read More about Long-term TeV and X-Ray Observations of the Gamma-Ray Binary HESS J0632+057.

Variability of the High-velocity Outflow in the Quasar PDS 456 (2014)
Journal Article
Reeves, J., Braito, V., Gofford, J., Sim, S., Behar, E., Costa, M., …Ward, M. (2014). Variability of the High-velocity Outflow in the Quasar PDS 456. Astrophysical Journal, 780(1), Article 45. https://doi.org/10.1088/0004-637x/780/1/45

We present a comparison of two Suzaku X-ray observations of the nearby (z = 0.184), luminous (L bol ~ 1047 erg s–1) type I quasar, PDS 456. A new 125 ks Suzaku observation in 2011 caught the quasar during a period of low X-ray flux and with a hard X-... Read More about Variability of the High-velocity Outflow in the Quasar PDS 456.

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