Search Publications
Discovery of the first τ Sco analogues: HD 66665 and HD 63425
Wade, G. A.; Ignace, R.; Marcolino, W. L. F. +3 more
The B0.2 V magnetic star τ Sco stands out from the larger population of massive OB stars due to its high X-ray activity, peculiar wind diagnostics and highly complex magnetic field. This Letter presents the discovery of the first two τ Sco analogues - HD 66665 and HD 63425, identified by the striking similarity of their ultraviolet (UV) spectra to…
The PEP survey: clustering of infrared-selected galaxies and structure formation at z ∼ 2 in GOODS-South
Berta, S.; Magnelli, B.; Lutz, D. +23 more
This paper presents the first direct estimate of the 3D clustering properties of far-infrared sources up to z∼ 3. This has been possible thanks to the PACS Evolutionary Probe (PEP) survey of the GOODS-South field performed with the PACS instrument on board the Herschel satellite. 550 and 502 sources were detected respectively in the 100- and 160-&…
Hoag's Object: evidence for cold accretion on to an elliptical galaxy
Brosch, Noah; Moiseev, Alexei; Finkelman, Ido +1 more
We present new photometric and spectroscopic observations of the famous Hoag's Object, a peculiar ring galaxy with a central roundish core. The nature of Hoag's Object is still under controversy. Previous studies demonstrated that a major accretion event that took place at least 2-3 Gyr ago can account for the observational evidence. However, the …
Infrared two-colour diagrams for AGB stars using AKARI, MSX, IRAS and near-infrared data
Suh, Kyung-Won; Kwon, Young-Joo
Using a revised version of the catalogue of asymptotic giant branch (AGB) stars by Suh & Kwon, we present various infrared two-colour diagrams (2CDs) for 3003 O-rich, 1168 C-rich, 362 S-type and 35 silicate carbon stars in our Galaxy. For each object in the new catalogue, we cross-identify the AKARI, Midcourse Space Experiment (MSX) and Two-Mi…
Modelling the broad-band spectra of MCG-6-30-15 with a relativistic reflection model
Fabian, A. C.; Chiang, Chia-Ying
The spectrum of the bright Seyfert I galaxy MCG-6-30-15 shows a broad Fe Kα emission line, generally interpreted to originate very close to the central black hole which must then have a high spin. The observed X-ray variability is driven by a power-law component, with little variability found in the iron line energy band. The disconnection of cont…
Large-scale nested stellar discs in NGC 7217
Chilingarian, Igor V.; Sil'Chenko, Olga K.; Sotnikova, Natalia Ya. +1 more
NGC 7217 is an unbarred early-type spiral galaxy having a multisegment exponential light profile and a system of star-forming rings of the unknown origin; it also possesses a circumnuclear gaseous polar disc. We analysed new long-slit spectroscopic data for NGC 7217 and derived the radial distributions of its stellar population parameters, and ste…
The nature of X-ray-absorbed quasi-stellar objects
Ebrero, J.; Page, M. J.; Stevens, J. A. +2 more
There exists a significant population of broad line, z∼ 2 quasi-stellar objects (QSOs) which have heavily absorbed X-ray spectra. Follow-up observations in the submillimetre show that these QSOs are embedded in ultraluminous starburst galaxies, unlike most unabsorbed QSOs at the same redshifts and luminosities. Here we present X-ray spectra from X…
Black hole accretion rings revealed by future X-ray spectroscopy
Dovčiak, M.; Karas, V.; Svoboda, J. +1 more
Spectral features can arise by reflection of coronal X-rays on a black hole accretion disc. The resulting profile bears various imprints of a strong gravitational field acting on the light-emitting gas. The observed shape of the reflection line is formed by integrating contributions over a range of radii across the accretion disc plane, where the …
Compton-thick active galactic nuclei inside local ultraluminous infrared galaxies
Nardini, E.; Risaliti, G.
We present an X-ray analysis of the most luminous obscured active galactic nuclei (AGN) inside local ultraluminous infrared galaxies (ULIRGs). Our sample consists of 10 sources, harbouring AGN components with estimated luminosity in excess of ∼1012 L⊙ and yet unidentified at optical wavelengths because of their large obscurat…
Comparing spectral models for ultraluminous X-ray sources with NGC 4517 ULX1
Done, C.; Fabian, A. C.; Roberts, T. P. +4 more
We present the previously unanalysed high-quality XMM-Newton spectrum of an ultraluminous X-ray source (ULX) candidate in NGC 4517. As with other high-quality ULX spectra, a downturn in the spectrum is observed at ∼6 keV. Both of the recent disc reflection and Comptonization interpretations of this feature are applied, in order to present a direct…