Search Publications
Rotation speed and stellar axis inclination from p modes: how CoRoT would see other suns
García, R. A.; Ballot, J.; Lambert, P.
In the context of future space-based asteroseismic missions, we have studied the problem of extracting the rotation speed and the rotation-axis inclination of solar-like stars from the expected data. We have focused on slow rotators (at most twice solar rotation speed), first, because they constitute the most difficult case and, secondly, because …
Three-dimensional Inversion of Sound Speed below a Sunspot in the Born Approximation
Kosovichev, A. G.; Birch, A. C.; Couvidat, S.
We revise the inversion of acoustic travel times for the three-dimensional sound-speed structure below the solar NOAA Active Region 8243 of 1998 June. We benefit from recent progress in time-distance helioseismology that provides us with more reliable tools to infer subsurface solar properties. Among the improvements we implement here are the use …
Why X-Ray-selected Active Galactic Nuclei Appear Optically Dull
Rigby, J. R.; Rieke, G. H.; Pérez-González, P. G. +2 more
We investigate why half of X-ray-selected active galactic nuclei (AGNs) in deep surveys lack signs of accretion in their optical spectra. The majority of these ``optically dull'' AGNs are no more than ~6 times fainter than their host galaxies in rest-frame R band; as such, AGN lines are unlikely to be overwhelmed by stellar continuum in at least h…
Large amplitude oscillation of a polar crown filament in the pre-eruption phase
Isobe, H.; Tripathi, D.
Aims.We report observation of a large-amplitude filament oscillation followed by an eruption. This is used to probe the pre-eruption condition and the trigger mechanism of solar eruptions.Methods.We used the EUV images from the Extreme-Ultraviolet Imaging Telescope on board SOHO satellite and the Hα images from the Flare Monitoring Telescope at Hi…
Structure and scaling of the entropy in nearby galaxy clusters
Arnaud, M.; Pointecouteau, E.; Pratt, G. W.
Using XMM-Newton observations, we investigate the scaling and structural properties of the ICM entropy in a sample of 10 nearby (z < 0.2) morphologically relaxed galaxy clusters in the temperature range 2-9 keV. We derive the local entropy-temperature (S{-}T) relation at R = 0.1, 0.2, 0.3 and 0.5R200. The logarithmic slope of the rel…
The UV Scattering Halo of the Central Source Associated with η Carinae
Weis, K.; Sonneborn, G.; Smith, Nathan +8 more
We have made an extensive study of the UV spectrum of η Carinae and find that we do not directly observe the star and its wind in the UV. Because of dust along our line of sight, the UV light that we observe arises from bound-bound scattering at large impact parameters. We obtain a reasonable fit to the UV spectrum by using only the flux that orig…
Gas and stellar dynamics in NGC 1068: probing the galactic gravitational potential
Schinnerer, Eva; Emsellem, Eric; Ferruit, Pierre +3 more
We present SAURON integral field spectrography of the central 1.5 kpc of the nearby Seyfert 2 galaxy NGC 1068, encompassing the well-known near-infrared (NIR) inner bar observed in the K band. We have successively disentangled the respective contributions of the ionized gas and stars, thus deriving their two-dimensional distribution and kinematics…
Structure of the separatrix region close to a magnetic reconnection X-line: Cluster observations
Pickett, J. S.; André, M.; Khotyaintsev, Y. +9 more
We use Cluster spacecraft observations to study in detail the structure of a magnetic reconnection separatrix region on the magnetospheric side of the magnetopause about 50 ion inertial lengths away from the X-line. The separatrix region is the region between the magnetic separatrix and the reconnection jet. It is several ion inertial lengths wide…
ACS Photometry of Extended, Luminous Globular Clusters in the Outskirts of M31
Mackey, A. D.; Tanvir, N. R.; Ferguson, A. M. N. +6 more
A new population of extended, luminous globular clusters has recently been discovered in the outskirts of M31. These objects have luminosities typical of classical globular clusters, but much larger half-light radii. We report the first results from deep ACS imaging of four such clusters, one of which is a newly discovered example lying at a proje…
The radio structure of radio-quiet quasars
Falcke, H.; Hüttemeister, S.; Leipski, C. +1 more
Aims.We investigate the radio emitting structures of radio-quiet active galactic nuclei with an emphasis on radio-quiet quasars to study their connection to Seyfert galaxies.
Methods: .We present and analyse high-sensitivity VLA radio continuum images of 14 radio-quiet quasars and six Seyfert galaxies.
Results: .Many of the low redshift ra…