Search Publications
Chandra unveils a binary active galactic nucleus in Mrk 463
Guainazzi, Matteo; Bianchi, Stefano; Piconcelli, Enrico +2 more
We analyse Chandra, XMM-Newton and Hubble Space Telescope (HST) data of the double-nucleus Ultraluminous Infrared Galaxy (ULIRG), Mrk 463. The Chandra detection of two luminous (L2-10keV = 1.5 × 1043 and 3.8 × 1042 erg cm-2 s-1), unresolved nuclei in Mrk 463 indicates that this galaxy hosts a …
The fraction of second generation stars in globular clusters from the analysis of the horizontal branch
D'Antona, F.; Caloi, V.
The majority of globular clusters show chemical inhomogeneities in the composition of their stars, apparently due to a second stellar generation in which the forming gas is enriched by hot-CNO cycled material processed in stars belonging to a first stellar generation. Clearly this evidence prompts questions on the modalities of formation of globul…
Mapping of molecular gas inflow towards the Seyfert nucleus of NGC4051 using Gemini NIFS
Storchi-Bergmann, Thaisa; Riffel, Rogemar A.; Winge, Cláudia +3 more
We present 2D stellar and gaseous kinematics of the inner ~130×180 pc2 of the Narrow-Line Seyfert 1 galaxy NGC4051 at a sampling of 4.5pc, from near-infrared K-band spectroscopic observations obtained with the Gemini's Near-infrared Integral Field Spectrograph (NIFS) operating with the ALTAIR adaptive optics module. We have used the CO …
On why the iron K-shell absorption in AGN is not a signature of the local warm/hot intergalactic medium
Done, Chris; Terashima, Yuichi; Hayashida, Kiyoshi +5 more
We present a comparison between the 2001 XMM-Newton and 2005 Suzaku observations of the quasar, PG1211+143, at z = 0.0809. Variability is observed in the 7 keV iron K-shell absorption line (at 7.6 keV in the quasar frame), which is significantly weaker in 2005 than during the 2001 XMM-Newton observation. From a recombination time-scale of <4 yr…
Constraints on decaying dark matter from XMM-Newton observations of M31
Boyarsky, Alexey; Ruchayskiy, Oleg; Iakubovskyi, Dmytro +1 more
We derive constraints on the parameters of the radiatively decaying dark matter (DM) particle, using the XMM-Newton EPIC spectra of the Andromeda galaxy (M31). Using the observations of the outer (5-13arcmin) parts of M31, we improve the existing constraints. For the case of sterile neutrino DM, combining our constraints with the latest computatio…
A systematic look at the very high and low/hard state of GX339-4: constraining the black hole spin with a new reflection model
Fabian, A. C.; Miller, J. M.; Miniutti, G. +3 more
We present a systematic study of GX 339-4 in both its very high and low hard states from simultaneous observations made with XMM-Newton and RXTE in 2002 and 2004. The X-ray spectra of both these extreme states exhibit strong reflection signatures, with a broad, skewed Fe Kα line clearly visible above the continuum. Using a newly developed, self-co…
The luminosities and distance scales of type II Cepheid and RR Lyrae variables
van Leeuwen, Floor; Whitelock, Patricia A.; Feast, Michael W. +2 more
Infrared and optical absolute magnitudes are derived for the type II Cepheids κ Pav and VY Pyx using revised Hipparcos parallaxes and for κ Pav, V553 Cen and SW Tau from pulsational parallaxes. Revised Hipparcos and HST parallaxes for RR Lyrae agree satisfactorily and are combined in deriving absolute magnitudes. Phase-corrected J, H and Ks
An XMM-Newton study of the environments, particle content and impact of low-power radio galaxies
Hardcastle, M. J.; Croston, J. H.; Birkinshaw, M. +2 more
We present a detailed study of the environments of a sample of nine low-power [Fanaroff-Riley type I (FRI)] radio galaxies, based on new and archival XMM-Newton observations. We report new detections of group-scale environments around three radio galaxies: 3C296, NGC1044 and 3C76.1. As with previous studies, we find that FRI radio galaxies inhabit…
Precision photometric redshift calibration for galaxy-galaxy weak lensing
Kneib, J. -P.; Cunha, C. E.; Bolzonella, M. +26 more
Accurate photometric redshifts are among the key requirements for precision weak lensing measurements. Both the large size of the Sloan Digital Sky Survey (SDSS) and the existence of large spectroscopic redshift samples that are flux-limited beyond its depth have made it the optimal data source for developing methods to properly calibrate photomet…
The type IIb SN 2008ax: the nature of the progenitor
Gal-Yam, A.; Smartt, S. J.; Maund, J. R. +9 more
A source coincident with the position of the type IIb supernova (SN) 2008ax is identified in pre-explosion Hubble Space Telescope (HST) Wide Field Planetary Camera 2 observations in three optical filters. We identify and constrain two possible progenitor systems: (i) a single massive star that lost most of its hydrogen envelope through radiatively…