Search Publications
He II Lyβ Gunn-Peterson Absorption: New HST Observations and Theoretical Expectations
Anderson, Scott F.; Pieri, Matthew; Schneider, Donald P. +7 more
Observations of He II Lyα Gunn-Peterson troughs have proved to be a valuable probe of the epoch of helium reionization at z ~ 3. Since this optical depth can become unmeasurably large even for modest He II fractions, various alternate techniques have been proposed to push to higher redshift, and among the more promising is looking at higher-order …
Detailed study of the X-ray and optical/UV orbital ephemeris of X1822-371
Robba, N. R.; Papitto, A.; Burderi, L. +4 more
Aims: Recent studies of the optical/UV and X-ray ephemerides of X1822-371 have found some discrepancies in the value of the orbital period derivative. Because of the importance of this value in constraining the system evolution, we comprehensively analyse all the available optical/UV/X eclipse times of this source to investigate the origin of…
Removal of Titan's Atmospheric Noble Gases by Their Sequestration in Surface Clathrates
Mousis, Olivier; Lunine, Jonathan I.; Mandt, Kathleen E. +3 more
A striking feature of the atmosphere of Titan is that no heavy noble gases other than argon were detected by the Gas Chromatograph Mass Spectrometer aboard the Huygens probe during its descent to Titan's surface in 2005 January. Here we provide an explanation of the mysterious absence or rarity of these noble gases in Titan's atmosphere: the therm…
Radio Evidence of Break-out Reconnection?
Mann, G.; Karlický, M.; Aurass, H. +1 more
We reconsider the 2003 October 28 X17 flare/coronal mass ejection (CME), studying the five minutes immediately before the impulsive flare phase (not discussed in previous work). To this aim we examine complementary dynamic radio spectrograms, single frequency polarimeter records, radio images, space-based longitudinal field magnetograms, and ultra…
High-resolution spectroscopy of the blue compact dwarf galaxy Haro 15 - I. Internal kinematics
Morrell, Nidia; Díaz, Ángeles I.; Firpo, Verónica +2 more
Using echelle spectroscopy, obtained at Las Campanas Observatory, we present a detailed study of the internal kinematics of the nebular material in multiple knots of the blue compact dwarf galaxy Haro 15. A detailed analysis of the complex emission-line profiles shows the presence of an underlying broad component in almost all knots, and the brigh…
X-ray detected infrared excess AGN in the Chandra deep fields: a moderate fraction of Compton-thick sources
Comastri, A.; Georgantopoulos, I.; Rovilos, E. +2 more
We examine the properties of the X-ray-detected infrared excess AGN or dust obscured galaxies (DOGs) in the Chandra deep fields (CDFs). We find 26 X-ray-detected sources that obey the 24 µm to R-band flux ratio criterion f24/fR > 1000. These are at a median redshift of 2.3, while their IR luminosities are above 10
The two components of the evolved massive binary LZ Cephei. Testing the effects of binarity on stellar evolution
Bouret, J. -C.; Martins, F.; Donati, J. -F. +2 more
Aims: We present an in-depth study of the two components of the binary system LZ Cep to constrain the effects of binarity on the evolution of massive stars.
Methods: We analyzed a set of high-resolution, high signal-to-noise ratio optical spectra obtained over the orbital period of the system to perform a spectroscopic disentangling and …
Neutral H2 and H2+ ions in the Saturnian magnetosphere
Johnson, Robert E.; Thomsen, Michelle F.; Tseng, Wei-Ling +2 more
The Saturnian system is immersed in an extended cloud of neutrals. Although water vapor ejected from Enceladus' south pole is the dominant neutral source, photolysis and radiolysis of ices can release H2O, O2, and H2 from the icy ring particles and the icy satellites, and Titan's atmosphere is a source of H2
Spectral and Timing Studies of Cyg X-1 in the Low/Hard State with Suzaku
Done, Chris; Gandhi, Poshak; Makishima, Kazuo +6 more
From 2005 to 2009, 25 observations of Cyg X-1 were performed with Suzaku, achieving a total exposure of 446 ks. In all observations, the source was found in the low/hard state, while the 1.5-12.0 keV count rate of the All-Sky Monitor onboard RXTE varied by a factor of
Testing Stellar Population Synthesis Models with Sloan Digital Sky Survey Colors of M31's Globular Clusters
Kundu, Arunav; Zepf, Stephen E.; Maccarone, Thomas J. +1 more
Accurate stellar population synthesis models are vital in understanding the properties and formation histories of galaxies. In order to calibrate and test the reliability of these models, they are often compared with observations of star clusters. However, relatively little work has compared these models in the ugriz filters, despite the recent wi…