Search Publications
Using principal component analysis to understand the variability of PDS 456
Fabian, A. C.; Buisson, D. J. K.; Reeves, J. N. +2 more
We present a spectral-variability analysis of the low-redshift quasar PDS 456 using principal component analysis. In the XMM-Newton data, we find a strong peak in the first principal component at the energy of the Fe absorption line from the highly blueshifted outflow. This indicates that the absorption feature is more variable than the continuum,…
A new powerful and highly variable disc wind in an AGN-star-forming galaxy, the case of MCG-03-58-007
Campana, S.; Turner, T. J.; Ballo, L. +7 more
We present the discovery of a new candidate for a fast disc wind, in the nearby Seyfert 2 galaxy MCG-03-58-007. This wind is discovered in a deep Suzaku observation that was performed in 2010. Overall the X-ray spectrum of MCG-03-58-007 is highly absorbed by a neutral column density of NH ∼1023 cm-2, in agreement w…
Study of a sample of faint Be stars in the exofield of CoRoT. II. Pulsation and outburst events: Time series analysis of photometric variations
Eggenberger, P.; Frémat, Y.; Zorec, J. +5 more
Context. The class of Be stars are the epitome of rapid rotators in the main sequence. These stars are privileged candidates for studying the incidence of rotation on the stellar internal structure and on non-radial pulsations. Pulsations are considered possible mechanisms to trigger mass-ejection phenomena required to build up the circumstellar d…
Meter-scale thermal contraction crack polygons on the nucleus of comet 67P/Churyumov-Gerasimenko
Jorda, L.; Lamy, P. L.; Lara, L. M. +48 more
We report on the detection and characterization of more than 6300 polygons on the surface of the nucleus of comet 67P/Churyumov-Gerasimenko, using images acquired by the OSIRIS camera onboard Rosetta between August 2014 and March 2015. They are found in consolidated terrains and grouped in localized networks. They are present at all latitudes (fro…
The Gaia-ESO Survey: The N/O abundance ratio in the Milky Way
Gilmore, G.; Bayo, A.; Franciosini, E. +31 more
Context. The abundance ratio N/O is a useful tool to study the interplay of galactic processes, for example star formation efficiency, timescale of infall, and outflow loading factor.
Aims: We aim to trace log(N/O) versus [Fe/H] in the Milky Way and to compare this ratio with a set of chemical evolution models to understand the role of infall…
Flux rope breaking and formation of a rotating blowout jet
Joshi, Navin Chandra; Nishizuka, Naoto; Filippov, Boris +2 more
We analysed a small flux rope eruption converted into a helical blowout jet in a fan-spine configuration using multiwavelength observations taken by Solar Dynamics Observatory, which occurred near the limb on 2016 January 9. In our study, first, we estimated the fan-spine magnetic configuration with the potential-field calculation and found a sini…
The Arches cluster revisited. II. A massive eclipsing spectroscopic binary in the Arches cluster
Crowther, P. A.; Evans, C. J.; Najarro, F. +3 more
We have carried out a spectroscopic variability survey of some of the most massive stars in the Arches cluster, using K-band observations obtained with SINFONI on the VLT. One target, F2, exhibits substantial changes in radial velocity (RV); in combination with new KMOS and archival SINFONI spectra, its primary component is found to undergo RV var…
Is there a UV/X-ray connection in IRAS 13224-3809?
Fabian, A. C.; Pinto, C.; Miniutti, G. +16 more
We present results from the optical, ultraviolet, and X-ray monitoring of the NLS1 galaxy IRAS 13224-3809 taken with Swift and XMM-Newton during 2016. IRAS 13224-3809 is the most variable bright AGN in the X-ray sky and shows strong X-ray reflection, implying that the X-rays strongly illuminate the inner disc. Therefore, it is a good candidate to …
Observations of the Kelvin-Helmholtz Instability Driven by Dynamic Motions in a Solar Prominence
Polito, Vanessa; Hillier, Andrew
Prominences are incredibly dynamic across the whole range of their observable spatial scales, with observations revealing gravity-driven fluid instabilities, waves, and turbulence. With all of these complex motions, it would be expected that instabilities driven by shear in the internal fluid motions would develop. However, evidence of these have …
The X-ray/UV ratio in active galactic nuclei: dispersion and variability
Paolillo, M.; Tombesi, F.; Vagnetti, F. +1 more
Context. The well established negative correlation between the αOX spectral slope and the optical/ultraviolet (UV) luminosity, a by-product of the relation between X-rays and optical/UV luminosity, is affected by relatively large dispersion. The main contributors to this dispersion can be variability in the X-ray/UV ratio and/or changes…