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Chandra spectroscopy of the hot star βCrucis and the discovery of a pre-main-sequence companion
Miller, Nathan A.; Cohen, David H.; Jensen, Eric L. N. +2 more
In order to test the O star wind-shock scenario for X-ray production in less luminous stars with weaker winds, we made a pointed 74-ks observation of the nearby early B giant, βCrucis (βCru B0.5III), with the Chandra High Energy Transmission Grating Spectrometer. We find that the X-ray spectrum is quite soft, with a dominant thermal component near…
Surface Brightness Profiles of Composite Images of Compact Galaxies at z ≃ 4-6 in the Hubble Ultra Deep Field
Hathi, N. P.; Keel, W. C.; Jansen, R. A. +4 more
The Hubble Ultra Deep Field (HUDF) contains a significant number of B-, V-, and i'-band dropout objects, many of which were recently confirmed to be young star-forming galaxies at z ≃ 4-6. These galaxies are too faint individually to accurately measure their radial surface-brightness profiles. Their average light profiles are potentially of great …
Sputtering of ice grains and icy satellites in Saturn's inner magnetosphere
Johnson, R. E.; Sittler, E. C.; Smith, H. T. +3 more
Icy grains and satellites orbiting in Saturn's magnetosphere are immersed in a plasma that sputters their surfaces. This limits the lifetime of the E-ring grains and ejects neutrals that orbit Saturn until they are ionized and populate its magnetosphere. Here we re-evaluate the sputtering rate of ice in Saturn's inner magnetosphere using the recen…
Solar wind excitation of Pc5 fluctuations in the magnetosphere and on the ground
Kessel, R. L.
The primary purpose of this paper is to show the importance of solar wind excitation as a source of magnetospheric and ground Pc5 fluctuations. In particular, we show that pressure fluctuations, a nearly ubiquitous feature of the solar wind, drive magnetospheric compressional Pc5, whose amplitude and power increase in direct proportion to the ampl…
Deep Chandra Monitoring Observations of NGC 3379: Catalog of Source Properties
Zezas, A.; Gallagher, J.; King, A. R. +11 more
We present the properties of the discrete X-ray sources detected in our monitoring program of the 'typical' elliptical galaxy, NGC 3379, observed with Chandra ACIS-S in five separate pointings, resulting in a co-added exposure of 324 ks. From this deep observation, 132 sources have been detected within the region overlapped by all observations, 98…
High Spatial Velocity Features in the Orion Nebula,
O'Dell, C. R.; Henney, W. J.
We have used widely spaced in time Hubble Space Telescope images to determine tangential velocities of features associated with outflows from young stars. These observations were supplemented by ground-based telescope spectroscopy, and from the resultant radial velocities, space velocities were determined for many outflows. Numerous new moving fea…
The fundamental parameters of the roAp star α Circini
Tuthill, P. G.; Davis, J.; Kurtz, D. W. +12 more
We have used the Sydney University Stellar Interferometer to measure the angular diameter of α Cir. This is the first detailed interferometric study of a rapidly oscillating A (roAp) star, α Cir being the brightest member of its class. We used the new and more accurate Hipparcos parallax to determine the radius to be 1.967 ± 0.066 R⊙. W…
Atmospheric Electricity at Saturn
Dyudina, Ulyana A.; Gurnett, Donald A.; Fischer, Georg +5 more
The Cassini mission provides a great opportunity to enlarge our knowledge of atmospheric electricity at the gas giant Saturn. Following Voyager studies, the RPWS (Radio and Plasma Wave Science) instrument has measured again the so-called SEDs (Saturn Electrostatic Discharges) which are the radio signature of lightning flashes. Observations by Cass…
Mg II h+k emission lines as stellar activity indicators of main sequence F-K stars
Buccino, A. P.; Mauas, P. J. D.
Context: The largest dataset of stellar activity measurements available at present is the one obtained at the Mount Wilson Observatory, where high-precision Ca II H+K fluxes have been measured from 1966 for about 2200 stars. Since the Mg II h and k lines at λ2800 Å are formed in a similar way to the Ca II H+K emission lines, they are also good ind…
XMM-Newton X-ray study of early type stars in the Carina OB1 association
van der Hucht, K. A.; Rauw, G.; Vreux, J. -M. +2 more
Aims:X-ray properties of the stellar population in the Carina OB1 association are examined with special emphasis on early-type stars. Their spectral characteristics provide some clues to understanding the nature of X-ray formation mechanisms in the winds of single and binary early-type stars.
Methods: A timing and spectral analysis of five obs…