Search Publications
Discovery of Probable Relativistic Fe Emission and Absorption in the Cloverleaf Quasar H 1413+117
Agol, E.; Dai, X.; Chartas, G. +2 more
We present results from Chandra and XMM-Newton observations of the low-ionization broad absorption line (LoBAL) quasar H 1413+117. Our spatial and spectral analysis of a recent deep Chandra observation confirms a microlensing event in a previous Chandra observation performed about five years earlier. We present constraints on the structure of the …
On the Metallicity Dependence of the 24 µm Luminosity as a Star Formation Tracer
Battaner, E.; Relaño, M.; Vílchez, J. M. +2 more
We investigate the use of the rest-frame 24 µm luminosity as an indicator of the star formation rate (SFR) in galaxies with different metallicities by comparing it to the (extinction-corrected) Hα luminosity. We carry out this analysis in two steps: First, we compare the emission from H II regions in different galaxies with metallicities bet…
Observations of O I and Ca II Emission Lines in Quasars: Implications for the Site of Fe II Line Emission
Kawara, K.; Oyabu, S.; Tsuzuki, Y. +1 more
We present results of the near-infrared (IR) spectroscopy of six quasars whose redshifts range from 0.158 to 1.084. Combined with the satellite ultraviolet data, the relative line strengths of O I λ1304, O I λ8446, O I λ11287, and the near-IR Ca II triplet are given. In addition, the corresponding O I line strengths measured in normal Seyfert 1s a…
Density and Magnetic Field Signatures of Interplanetary 1/f Noise
Romoli, M.; Bemporad, A.; Poletto, G. +4 more
We investigate the occurrence of 1/f noise in the interplanetary density and the magnetic field at varying heliocentric latitudes. The characteristic spectral amplitudes can be found in Ulysses density and magnetic data in the expected frequency ranges at all available latitudes, ranging from the ecliptic plane to more than 80°. Average spectra in…
Encounter of the Ulysses Spacecraft with the Ion Tail of Comet MCNaught
Geiss, J.; McComas, D. J.; Smith, E. J. +12 more
Comet McNaught was the brightest comet observed from Earth in the last 40 years. For a period of five days in early 2007 February, four instruments on the Ulysses spacecraft directly measured cometary ions and key properties of the interaction of the comet's ion tail with the high-speed solar wind from the polar regions of the Sun. Because of the …
The Coronal-dimming Footprint of a Streamer-Puff Coronal Mass Ejection: Confirmation of the Magnetic-Arch-Blowout Scenario
Moore, Ronald L.; Sterling, Alphonse C.
A streamer puff is a recently identified variety of coronal mass ejection (CME) of narrow to moderate width. It (1) travels out along a streamer, transiently inflating the streamer but leaving it largely intact, and (2) occurs in step with a compact ejective flare in an outer flank of the base of the streamer. These aspects suggest the following m…
The Galaxy Luminosity Function at z ~= 1 in the HUDF: Probing the Dwarf Population
Panagia, N.; di Serego Alighieri, S.; Moustakas, L. A. +10 more
We present a catalog of spectrophotometric redshifts for 1308 galaxies from the Grism ACS Program for Extragalactic Science (GRAPES) observations with the Hubble Space Telescope. These low-resolution spectra between 6000 Å and 9500 Å are supplemented with U, J, H, and Ks data from various facilities, resulting in redshifts computed with…
New Physical Insight on the Changes in Magnetic Topology during Coronal Mass Ejections: Case Studies for the 2002 April 21 and August 24 Events
Lugaz, Noé; Roussev, Ilia I.; Sokolov, Igor V.
In order to investigate the dynamics of the coronal mass ejections on 2002 April 21 and August 24, we performed a series of numerical simulations with an ad hoc driver for the eruptions. The resulting evolution of the solar corona for each event was followed by means of three-dimensional MHD simulations. We used SOHO MDI data to set realistic boun…
Low-Mass X-Ray Binaries and Globular Clusters in Centaurus A
Sarazin, Craig L.; Jordán, Andrés; Raychaudhury, Somak +19 more
We present results of Hubble Space Telescope and Chandra X-Ray Observatory observations of globular clusters (GCs) and low-mass X-ray binaries (LMXBs) in the central regions of Centaurus A. Out of 440 GC candidates, we find 41 host X-ray point sources that are most likely LMXBs. We fit King models to our GC candidates in order to measure their str…
Color, Rotation, Age, and Chromospheric Activity Correlations in Late-Type Main-Sequence Stars
Cassatella, Angelo; Cardini, Daniela
A study of the rotation-activity-age relationships in a large sample of single late-type main-sequence stars is carried out, based on rotation period data from the literature, on our measurements of the Mg II k line chromospheric flux in IUE high-resolution spectra, and on Hipparcos parallaxes. The analysis of the rotation period data of open clus…