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A Chandra observation of the old open cluster M 67
Tagliaferri, G.; Belloni, T.; van den Berg, M. +1 more
We present the results of a 47-ks Chandra-ACIS observation of the old open cluster
Balltracking: An highly efficient method for tracking flow fields
Potts, H. E.; Barrett, R. K.; Diver, D. A.
We present a method for tracking solar photospheric flows that is highly efficient, and demonstrate it using high resolution MDI continuum images. The method involves making a surface from the photospheric granulation data, and allowing many small floating tracers or balls to be moved around by the evolving granulation pattern. The results are tes…
I Zw 1 observed with XMM-Newton . Low-energy spectral complexity, iron lines, and hard X-ray flares
Brandt, W. N.; Vaughan, S.; Fabian, A. C. +2 more
We present a 20 ks XMM-Newton observation of the prototypical Narrow-Line Seyfert 1 galaxy I Zw 1. The best-fit model to the data is a double blackbody plus a dominant power-law, on which complex soft absorption (possibly a blended edge or absorption lines) and/or OVII emission are superimposed, as well as strong Fe Kα emission. The iron feature i…
The complex X-ray spectrum of NGC 4507
Bianchi, S.; Matt, G.; D'Ammando, F. +1 more
XMM-Newton and Chandra/HETG spectra of the Compton-thin (NH∼4×1023 cm-2) Seyfert 2 galaxy, NGC 4507, are analyzed and discussed. The main results are: a) the soft X-ray emission is rich in emission lines; an (at least) two-zone photoionization region is required to explain the large range of ionization states; b) t…
Temporal evolution of two auroral arcs as measured by the Cluster satellite and coordinated ground-based instruments
Buchert, S.; Vaivads, A.; Dunlop, M. +7 more
The four Cluster s/c passed over Northern Scandinavia on 6 February 2001 from south-east to north-west at a radial distance of about 4.4 RE in the post-midnight sector. When mapped along geomagnetic field lines, the separation of the spacecraft in the ionosphere was confined to within 110km in latitude and 50km in longitude. This constellation all…
Probing the Evolution of the Galaxy Interaction/Merger Rate Using Collisional Ring Galaxies
Charmandaris, Vassilis; Lavery, Russell J.; Remijan, Anthony +2 more
We present the results from our program to determine the evolution of the galaxy interaction/merger rate with redshift using the unique star-forming characteristics of collisional ring galaxies. We have identified 25 distant collisional ring galaxy candidates (CRGCs) in a total of 162 deep Hubble Space Telescope (HST) Wide Field Planetary Camera 2…
Terminal Velocities of Luminous, Early-Type Stars in the Small Magellanic Cloud
Lennon, D. J.; Evans, C. J.; Heap, S. R. +2 more
Ultraviolet spectra from the Space Telescope Imaging Spectrograph (STIS) are used to determine terminal velocities for 11 O and B-type giants and supergiants in the Small Magellanic Cloud (SMC) from the Si IV and C IV resonance lines. Using archival data from observations with the Goddard High-Resolution Spectrograph and the International Ultravio…
On the Measurement of Elemental Abundance Ratios in Inner Galaxy H II Regions
Rubin, Robert H.; Haas, Michael R.; Colgan, Sean W. J. +2 more
Although variations in elemental abundance ratios in the Milky Way certainly exist, details remain uncertain, particularly in the inner Galaxy, where stars and H II regions in the Galactic plane are obscured optically. In this paper we revisit two previously studied, inner Galaxy H II regions: G333.6-0.2 and W43. We observed three new positions in…
INTEGRAL and XMM-Newton Spectral Studies of NGC 4388
Gehrels, N.; Petrucci, P. -O.; Walter, R. +4 more
We present INTEGRAL and XMM-Newton observations of a Seyfert galaxy, the type 2 active galactic nucleus (AGN) NGC 4388. Several INTEGRAL observations performed in 2003 allow us to study the spectrum in the 20-300 keV range. In addition, two XMM-Newton observations give detailed insight into the 0.2-10 keV emission. The measurements presented here …
On the Relationship between the Rotational Velocity and the Field Strength of Solar Magnetic Elements
Zhao, Junwei; Kosovichev, Alexander G.; Duvall, Thomas L., Jr.
By tracking various solar surface tracers, previous studies have found that magnetic structures, such as plages and sunspots, rotate faster than the quiet solar regions. We investigate how the rotational speed of these magnetic features is related to their magnetic field strength. By use of near-surface horizontal velocities inferred from time-dis…