Search Publications
The nature of X-ray spectral variability in MCG-6-30-15
Papadakis, I. E.; Kammoun, E. S.
The flux-flux plot (FFP) method can provide model-independent clues regarding the X-ray variability of active galactic nuclei. To use it properly, the bin size of the light curves should be as short as possible, provided the average counts in the light-curve bins are larger than ∼200. We apply the FFP method, performed in 2013, to the simultaneous…
Ultraviolet spectroscopy of the blue supergiant SBW1: the remarkably weak wind of a SN 1987A analogue
Smith, Nathan; France, Kevin; Groh, Jose H. +1 more
The Galactic blue supergiant SBW1 with its circumstellar ring nebula represents the best known analogue of the progenitor of SN 1987A. High-resolution imaging has shown Hα and infrared structures arising in an ionized flow that partly fills the ring's interior. To constrain the influence of the stellar wind on this structure, we obtained an ultrav…
Diffuse interstellar bands carriers and cometary organic material★
Bertaux, Jean-Loup; Lallement, Rosine
We suggest that the large organic molecules found in the dust of comet 67P/CG originated from the interstellar medium (ISM), and that this material is the source of absorption features in stellar spectra known as diffuse interstellar bands (DIBs). These large organic molecules were present in the ISM prior to the emergence of the pre-solar nebula …
Suzaku analysis of the supernova remnant G306.3-0.9 and the gamma-ray view of its neighbourhood
Sezer, A.; Yamazaki, R.; Ergin, T.
We present an investigation of the supernova remnant (SNR) G306.3-0.9, using archival multiwavelength data. The Suzaku spectra are well described by two-component thermal plasma models: the soft component is in ionization equilibrium and has a temperature ∼0.59 keV, while the hard component has temperature ∼3.2 keV and ionization time-scale ∼2.6 ×…
AGNs with discordant optical and X-ray classification are not a physical family: diverse origin in two AGNs
Barcons, X.; Carrera, F. J.; Braito, V. +7 more
Approximately 3-17 per cent of active galactic nuclei (AGNs) without detected rest-frame UV/optical broad emission lines (type-2 AGN) do not show absorption in X-rays. The physical origin behind the apparently discordant optical/X-ray properties is not fully understood. Our study aims at providing insight into this issue by conducting a detailed a…
AKARI near-infrared background fluctuations arise from normal galaxy populations
Komatsu, E.; Helgason, K.
We show that measurements of the fluctuations in the near-infrared background (NIRB) from the AKARI satellite can be explained by faint galaxy populations at low redshifts. We demonstrate this using reconstructed images from deep galaxy catalogues (Hawk-I UDS/GOODS Survey and S-Cosmic Assembly Deep Near-Infrared Extragalactic Legacy Survey) and tw…
DDO 161 and UGCA 319: an isolated pair of nearby dwarf galaxies
Rizzi, L.; Karachentsev, I. D.; Makarova, L. N. +3 more
We report Hubble Space Telescope/Advanced Camera for Surveys observations of two nearby gas-rich dwarf galaxies: DDO 161 and UGCA 319. Their distances determined via the tip of the red giant branch are 6.03_{-0.21}^{+0.29} and 5.75 ± 0.18 Mpc, respectively. The galaxies form an isolated pair dynamically well separated from the nearest neighbours: …
Do water fountain jets really indicate the onset of the morphological metamorphosis of circumstellar envelopes?
Hsia, Chih-Hao; Yung, Bosco H. K.; Nakashima, Jun-ichi +1 more
Small-scale bipolar jets with short dynamical ages from 'water-fountain' (WF) sources are regarded as an indication of the onset of circumstellar envelope morphological metamorphosis of intermediate-mass stars. Such a process usually happens at the end of the asymptotic giant branch (AGB) phase. However, recent studies found that WFs could be AGB …
New ATCA, ALMA and VISIR observations of the candidate LBV SK -67 266 (S61): the nebular mass from modelling 3D density distributions
Paladini, R.; Umana, G.; Agliozzo, C. +10 more
We present new observations of the nebula around the Magellanic candidate Luminous Blue Variable S61. These comprise high-resolution data acquired with the Australia Telescope Compact Array (ATCA), the Atacama Large Millimetre/Submillimetre Array (ALMA), and the VLT Imager and Spectrometer for mid Infrared (VISIR) at the Very Large Telescope. The …
Modelling of the outburst on 2015 July 29 observed with OSIRIS cameras in the Southern hemisphere of comet 67P/Churyumov-Gerasimenko
Jorda, L.; Lamy, P. L.; Lara, L. M. +60 more
Images of the nucleus and the coma (gas and dust) of comet 67P/Churyumov- Gerasimenko have been acquired by the OSIRIS (Optical, Spectroscopic and Infrared Remote Imaging System) cameras since 2014 March using both the wide-angle camera and the narrow-angle camera (NAC). We use images from the NAC camera to study a bright outburst observed in the …