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Star Formation at z ~ 6: The Hubble Ultra Deep Parallel Fields
van Dokkum, P.; Bouwens, R. J.; Illingworth, G. D. +8 more
We report on the i-dropouts detected in two exceptionally deep Advanced Camera for Surveys fields (B435, V606, i775, and z850 with 10σ limits of 28.8, 29.0, 28.5, and 27.8, respectively) taken in parallel with the Ultra Deep Field Near-Infrared Camera and Multi-Object Spectrometer observations. Using an …
The Homogeneity of Interstellar Oxygen in the Galactic Disk
Meyer, David M.; Cartledge, Stefan I. B.; Lauroesch, J. T. +1 more
We present an analysis of high-resolution Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) observations of O I λ1356 and H I Lyα absorption in 36 sight lines that probe a variety of Galactic disk environments and include paths that range over nearly 4 orders of magnitude in f(H2), over 2 orders of magnitude in &l…
Hubble Space Telescope Observations of the White Dwarf Cooling Sequence of M4
Currie, Thayne; Rich, R. Michael; Gibson, Brad K. +7 more
We investigate in detail the white dwarf cooling sequence of the globular cluster Messier 4. In particular, we study the influence of various systematic uncertainties, both observational and theoretical, on the determination of the cluster age from the white dwarf cooling sequence. These include uncertainties in the distance to the cluster and the…
Orientation and propagation of current sheet oscillations
Sauvaud, J. -A.; Balogh, A.; Zhang, T. L. +6 more
Using the four-spacecraft Cluster system, we analyze rapid neutral sheet crossings near the Cluster apogee at about -18RE. In case studies of multiple oscillations of the locally quiet plasma sheet as well as in a statistical study of oscillations in dawn and dusk near-flank plasma sheet portions we typically obtain that locally these d…
Do We Know of Any Maunder Minimum Stars?
Wright, J. T.
Most stars previously identified as Maunder minimum stars are old and evolved off the main sequence. Analysis of activity measurements from the California and Carnegie Planet Search program stars and Hipparcos parallaxes implies that the canonical relation between age and chromospheric activity breaks down for stars older than ~6 Gyr when activity…
An X-ray Baldwin effect for the narrow Fe Kα lines observed in active galactic nuclei
O'Brien, P. T.; Reeves, J. N.; Page, K. L. +1 more
The majority of active galactic nuclei (AGN) observed by XMM-Newton reveal narrow Fe Kα lines at ~6.4 keV, due to emission from cold (neutral) material. There is an X-ray Baldwin effect in type I AGN, in that the equivalent width (EW) of the line decreases with increasing luminosity, with weighted linear regression giving EW~L-0.17+/-0.08
A microscopic and nanoscopic view of storm-time chorus on 31 March 2001
Gurnett, D. A.; Pickett, J. S.; Santolík, O. +2 more
We investigate intense whistler-mode chorus emissions which occurred during the geomagnetic storm on 31 March 2001. We use multipoint measurements obtained by the Cluster spacecraft in the premidnight equatorial region outside the plasmasphere at a radial distance of 4 Earth radii (L = 4.0 - 4.2). Observed spatio-temporal variations of the directi…
Chandra and XMM-Newton Observations of RDCS 1252.9-2927, A Massive Cluster at z=1.24
Demarco, R.; Lidman, C.; Tozzi, P. +10 more
We present deep Chandra and XMM-Newton observations of the galaxy cluster RDCS 1252.9-2927, which was selected from the ROSAT Deep Cluster Survey (RDCS) and confirmed by extensive spectroscopy with the Very Large Telescope at redshift z=1.237. With the Chandra data, the X-ray emission from the intracluster medium is well resolved and traced out to…
The ACS Virgo Cluster Survey. III. Chandra and Hubble Space Telescope Observations of Low-Mass X-Ray Binaries and Globular Clusters in M87
Jordán, Andrés; Tonry, John L.; Côté, Patrick +7 more
The ACIS instrument on board the Chandra X-Ray Observatory has been used to carry out the first systematic study of low-mass X-ray binaries (LMXBs) in M87, the giant elliptical galaxy near the dynamical center of the Virgo Cluster. These images-with a total exposure time of 154 ks-are the deepest X-ray observations yet obtained of M87. We identify…
A Hard X-ray Survey of the Galactic-Center Region with the IBIS Telescope of the INTEGRAL Observatory: A Catalog of Sources
Gilfanov, M. R.; Sunyaev, R. A.; Cherepashchuk, A. M. +6 more
From August 23 through September 24, 2003, the INTEGRAL Observatory conducted a deep survey of the Galactic-Center region with a record-breaking sensitivity at energies above 20 keV. We have analyzed the images of the Galactic-Center region obtained with the ISGRI detector of the IBIS telescope (15-200 keV) and give a catalog of detected sources. …