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Direct Detection of the Close Companion of Polaris with the Hubble Space Telescope
Schaefer, Gail H.; Bond, Howard E.; Evans, Nancy Remage +5 more
Polaris, the nearest and brightest classical Cepheid, is a single-lined spectroscopic binary with an orbital period of 30 yr. Using the High Resolution Channel of the Advanced Camera for Surveys on board the Hubble Space Telescope (HST) at a wavelength of ~2255 Å, we have directly detected the faint companion at a separation of 0farcs17. A second …
Gemini Imaging of Mid-Infrared Emission from the Nuclear Region of Centaurus A
Levenson, N. A.; Perlman, Eric; De Buizer, James M. +7 more
We present high spatial resolution mid-IR images of the nuclear region of NGC 5128 (Centaurus A). Images were obtained at 8.8 µm, N band (10.4 µm), and 18.3 µm using the mid-IR imager/spectrometer T-ReCS on Gemini South. These images show a bright unresolved core surrounded by low-level extended emission. We place an upper limit …
On the nature of unabsorbed Seyfert 2 galaxies
Nandra, Kirpal; Brightman, Murray
We present an analysis of six 12µm selected Seyfert 2 galaxies that have been reported to be unabsorbed in the X-ray. By comparing the luminosities of these galaxies in the mid-infrared (12µm), optical ([OIII]) and hard X-ray (2-10keV), we show that they are all underluminous in the 2-10keV X-ray band. Four of the objects exhibit X-ray…
A New Approach to the Study of Stellar Populations in Early-Type Galaxies: K-Band Spectral Indices and an Application to the Fornax Cluster
Kuntschner, Harald; Lyubenova, Mariya; Silva, David R.
The strong spectral features near 2.2 µm in early-type galaxies remain relatively unexplored. Yet, they open a tightly focused window on the coolest giant stars in these galaxies—a window that can be used to explore both age and metallicity effects. Here, new measurements of K-band spectral features are presented for 11 early-type galaxies i…
Geological context of water-altered minerals in Valles Marineris, Mars
Hynek, Brian M.; Chojnacki, Matthew
Greater than 15,000 km2 of the layered deposits within Valles Marineris are associated with water-altered minerals, yet their origin and history of alteration remain a mystery. There are numerous competing hypotheses for the formation of the interior layered deposits including aeolian, lacustrine, and volcanic. Recent orbiter spectrosco…
The relationship between EUV dimming and coronal mass ejections. I. Statistical study and probability model
Harrison, R. A.; Brown, D. S.; Bewsher, D.
Aims:There have been many studies of extreme-ultraviolet (EUV) dimming in association with coronal mass ejection (CME) onsets. However, there has never been a thorough statistical study of this association, covering appropriate temperature ranges. Thus, we make use of a large campaign database utilising the Coronal Diagnostic Spectrometer (CDS) an…
First results from the Cassini radio occultations of the Titan ionosphere
French, Richard G.; Flasar, F. Michael; Marouf, Essam A. +10 more
The first four sets of radio occultations of the Titan's ionosphere were obtained by the Cassini spacecraft between March 2006 and May 2007. These occultations occurred at middle and high latitudes, at solar zenith angles from about 86° to 96°. The main ionospheric peak was seen, as expected from modeling and previous observations, near 1200 km, w…
Multifractal Properties of Evolving Active Regions
Maguire, K.; Gallagher, P. T.; Young, C. A. +5 more
Magnetohydrodynamic turbulence is thought to be responsible for producing complex, multiscale magnetic field distributions in solar active regions. Here we explore the multiscale properties of a number of evolving active regions using magnetograms from the Michelson Doppler Imager (MDI) on the Solar and Heliospheric Observatory (SOHO). The multifr…
ENA periodicities at Saturn
Krimigis, S. M.; Mitchell, D. G.; Paranicas, C. +2 more
The Magnetospheric Imaging Instrument (MIMI) on the Cassini spacecraft has observed energetic neutral atoms (ENA) at Saturn for three years from 2004 to 2007. The 20-50 keV hydrogen and 64-144 keV oxygen neutrals were examined for periodic behavior by projecting their images onto a plane perpendicular to Saturn's equatorial plane and summing the e…
The Globular Cluster System of M60 (NGC 4649). II. Kinematics of the Globular Cluster System
Rey, Soo-Chang; Lee, Myung Gyoon; Hwang, Ho Seong +7 more
We present a kinematic analysis of the globular cluster (GC) system in the giant elliptical galaxy (gE) M60 in the Virgo Cluster, using a photometric and spectroscopic database of 121 GCs (83 blue and 38 red GCs). We have found that the M60 GC system shows a significant overall rotation. The rotation amplitude of the blue GCs is slightly smaller t…