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The variable X-ray spectrum of Markarian 766. I. Principal components analysis
Turner, T. J.; Kraemer, S. B.; Reeves, J. N. +3 more
Aims:We analyse a long XMM-Newton observation of the narrow-line Seyfert 1 galaxy Mrk 766, using the marked spectral variability on timescales >20 ks to separate components in the X-ray spectrum.
Methods: Principal components analysis is used to identify distinct emission components in the X-ray spectrum, possible alternative physical model…
Past and Present Star Formation in the SMC: NGC 346 and its Neighborhood
Tosi, M.; Sabbi, E.; Nota, A. +8 more
In the quest to understand how star formation occurs and propagates in the low-metallicity environment of the Small Magellanic Cloud (SMC), we acquired deep F555W (~V) and F814W (~I) Hubble Space Telescope ACS images of the young and massive star-forming region NGC 346. These images and their photometric analysis provide us with a snapshot of the …
Characterization of Gravitational Microlensing Planetary Host Stars
Anderson, Jay; Gaudi, B. Scott; Bennett, David P.
The gravitational microlensing light curves that reveal the presence of extrasolar planets generally yield the planet-star mass ratio and separation in units of the Einstein ring radius. The microlensing method does not require the detection of light from the planetary host star. This allows the detection of planets orbiting very faint stars, but …
Cassini observations of the variation of Saturn's ring current parameters with system size
Russell, C. T.; Dougherty, M. K.; Alexeev, I. I. +4 more
We have examined residual magnetic field vectors observed in Saturn's magnetosphere during the first 2 years of the Cassini mission and have fit them to a simple axisymmetric model of the ring current in the middle magnetosphere. We then examine the variations of the ring current parameters with size of the magnetosphere. In addition, we obtain se…
The Three-Dimensional Morphology of VY Canis Majoris. I. The Kinematics of the Ejecta
Humphreys, Roberta M.; Jones, Terry J.; Helton, L. Andrew
Images of the complex circumstellar nebula associated with the famous red supergiant VY CMa show evidence for multiple and asymmetric mass-loss events over the past 1000 yr. Doppler velocities of the arcs and knots in the ejecta show that they are not only spatially distinct but also kinematically separate from the surrounding diffuse material. In…
Nonthermal Velocities in Solar Active Regions Observed with the Extreme-Ultraviolet Imaging Spectrometer on Hinode
Young, P. R.; Mason, H. E.; Culhane, J. L. +6 more
We discuss nonthermal velocities in an active region as revealed by the Extreme-Ultraviolet Imaging Spectrometer (EIS) on the Hinode spacecraft. The velocities are derived from spectral line profiles in the extreme-ultraviolet (EUV) from a strong line of Fe XII at 195.12 Å by fitting each line profile to a Gaussian function. We compare maps of the…
Periodic Appearance of Coronal Holes and the Related Variation of Solar Wind Parameters
Veronig, Astrid M.; Temmer, Manuela; Vršnak, Bojan
We compared the variability of coronal hole (CH) areas (determined from daily GOES/SXI images) with solar wind (daily ACE data) and geomagnetic parameters for the time span 25 January 2005 until 11 September 2005 (late declining phase of solar cycle 23). Applying wavelet spectral analysis, a clear 9-day period is found in the CH time series. The G…
V arc interplanetary coronal mass ejections observed with the Solar Mass Ejection Imager
Webb, D. F.; Kahler, S. W.
Since February 2003, the Solar Mass Ejection Imager (SMEI) has been observing interplanetary coronal mass ejections (ICMEs) at solar elongation angles $\epsilon$ > 20°. The ICMEs generally appear as loops or arcs in the sky, but five show distinct outward concave shapes that we call V arcs. We expect to observe some V arcs, formed by trailing e…
The Suzaku High Resolution X-Ray Spectrometer
Ishida, Manabu; Kelley, Richard L.; Kilbourne, Caroline A. +41 more
The X-Ray Spectrometer (XRS) has been designed to provide the Suzaku Observatory with non-dispersive, high-resolution X-ray spectroscopy. As designed, the instrument covers the energy range 0.3 to 12keV, which encompasses the most diagnostically rich part of the X-ray band. The sensor consists of a 32-channel array of X-ray microcalorimeters, each…
Nuclear Spirals as Feeding Channels to the Supermassive Black Hole: The Case of the Galaxy NGC 6951
Östlin, Göran; Robinson, Andrew; Marconi, Alessandro +5 more
We report the discovery of gas streaming motions along nuclear spiral arms toward the LINER nucleus of the galaxy NGC 6951. The observations, obtained using the GMOS integral field spectrograph on the Gemini North telescope, yielded maps of the flux distributions and gas kinematics in the Hα, [N II] λ6584, and [S II] λλ6717, 6731 emission lines of…