Search Publications
Recycling of the Solar Corona's Magnetic Field
Longcope, D. W.; Priest, E. R.; Parnell, C. E. +1 more
Magnetic fields play a dominant role in the atmospheres of the Sun and other Sun-like stars. Outside sunspot regions, the photosphere of the so-called quiet Sun contains myriads of small-scale magnetic concentrations, with strengths ranging from the detection limit of ~1016 Mx up to ~3×1020 Mx. The tireless motion of these ma…
Unraveling the Helix Nebula: Its Structure and Knots
O'Dell, C. R.; Meixner, Margaret; McCullough, Peter R.
Through Hubble Space Telescope (HST) imaging of the inner part of the main ring of the Helix Nebula, together with CTIO 4 m images of the fainter outer parts, we have a view of unprecedented quality of the nearest bright planetary nebula. These images have allowed us to determine that the main ring of the nebula is composed of an inner disk of abo…
ESO 3060170: A Massive Fossil Galaxy Group with a Heated Gas Core?
Hornstrup, A.; Vikhlinin, A.; Forman, W. +3 more
We present a detailed study of the ESO 3060170 galaxy group, combining Chandra, XMM-Newton, and optical observations. The system is found to be a fossil galaxy group. The group X-ray emission is composed of a central, dense, cool core (10 kpc in radius) and an isothermal medium beyond the central 10 kpc. The region between 10 and 50 kpc (the cooli…
EUVE observations of the helium glow: Interstellar and solar parameters
Lallement, R.; Lemoine, M.; Vallerga, J. +2 more
We present new observations of the diffuse He I 58.4 nm background recorded in 1998 and 2000 by the Extreme Ultraviolet Explorer (EUVE). This emission is due to resonant scattering of the solar EUV radiation by interstellar and geocoronal helium. Depending on the geometry and relative velocity, a fraction of the interstellar helium glow can be abs…
Arrival time of halo coronal mass ejections in the vicinity of the Earth
Gopalswamy, N.; Lara, A.; Manoharan, P. K. +1 more
We describe an empirical model to predict the 1-AU arrival time of halo CMEs. This model is based on the effective acceleration described by Gopalswamy et al. (\cite{Gopalswamy00}a, Geophys. Res. Lett., 27, 145). We verify the Helios/Pioneer Venus Orbiter(PVO) estimation of the effective acceleration profile (Gopalswamy et al. \cite{Gopalswamy01}a…
Fe II/Mg II Emission-Line Ratios of QSOs. II. z > 6 Objects
Doi, Mamoru; Yoshii, Yuzuru; Motohara, Kentaro +4 more
Near-infrared spectra of four QSOs located at z>6 are obtained with the OH-airglow suppressor mounted on the Subaru telescope. The Fe II/Mg II emission-line ratios of these QSOs are examined by the same fitting algorithm as in our previous study of z<5.3 QSOs. The fitting results show that two out of the four z>6 QSOs have significant Fe …
Direct Measurement of the Size of the Large Kuiper Belt Object (50000) Quaoar
Brown, Michael E.; Trujillo, Chadwick A.
We imaged the recently discovered bright Kuiper belt object (50000) Quaoar with the Hubble Space Telescope High Resolution Camera to directly determine its size. The point-spread function (PSF) of each of 16 images was carefully measured from a field star 13" from Quaoar, and the expected PSF at the location of Quaoar was convolved with Quaoar's m…
Spectral types and masses of white dwarfs in globular clusters
Heber, U.; Zoccali, M.; Koester, D. +4 more
White dwarfs in globular clusters offer additional possibilities to determine distances and ages of globular clusters, provided their spectral types and masses are known. We therefore started a project to obtain spectra of white dwarfs in the globular clusters NGC 6397 and NGC 6752. All observed white dwarfs show hydrogen-rich spectra and are ther…
A Survey for Water Maser Emission toward Planetary Nebulae: New Detection in IRAS 17347-3139
Miranda, Luis F.; Anglada, Guillem; de Gregorio-Monsalvo, Itziar +4 more
We report on a water maser survey toward a sample of 27 planetary nebulae (PNe) using the Robledo de Chavela and Medicina single-dish antennas, as well as the Very Large Array (VLA). Two detections have been obtained: the already known water maser emission in K3-35, and a new cluster of masers in IRAS 17347-3139. This low rate of detections is com…
A Study of Quasar Evolution in the X-Ray Band with the Aid of Gravitational Lensing
Eracleous, Michael; Garmire, Gordon P.; Dai, Xinyu +1 more
We present results from a minisurvey of relatively high redshift (1.7<z<4), gravitationally lensed, radio-quiet quasars observed with the Chandra X-Ray Observatory and with XMM-Newton. The lensing magnification effect allows us to search for changes with redshift in quasar spectroscopic and flux variability properties, ranging over 3 orders …