Search Publications
The Connection between X-Ray Binaries and Star Clusters in NGC 4449
Chandar, Rupali; Rangelov, Blagoy; Prestwich, Andrea H.
We present 23 candidate X-ray binaries with luminosities down to 1.8 × 1036 erg s-1, in the nearby starburst galaxy NGC 4449, from observations totaling 105 ks taken with the ACIS-S instrument on the Chandra Space Telescope. We determine count rates, luminosities, and colors for each source, and perform spectral fits for sour…
Implications for the structure of the relativistic jet from multiwavelength observations of NGC 6251
Gargano, F.; Giordano, F.; Giroletti, M. +8 more
NGC 6251 is a luminous radio galaxy ≈104 Mpc away that was detected significantly with the Fermi Gamma-ray Space Telescope, and before that with EGRET (onboard the Compton Gamma-ray Observatory). Different observational constraints favor a nuclear origin for the γ-ray emission. Here we present a study of the spectral energy distribution of the cor…
Dynamics of Jupiter’s equatorial region at cloud top level from Cassini and HST images
Hueso, R.; Sánchez-Lavega, A.; Rojas, J. F. +6 more
We present a study of the equatorial region of Jupiter, between latitudes ∼15°S and ∼15°N, based on Cassini ISS images obtained during the Jupiter flyby at the end of 2000, and HST images acquired in May and July 2008. We examine the structure of the zonal wind profile and report the detection of significant longitudinal variations in the intensit…
Lensed arc statistics: comparison of Millennium simulation galaxy clusters to Hubble Space Telescope observations of an X-ray selected sample
Maoz, Dan; Bartelmann, Matthias; Hilbert, Stefan +1 more
It has been debated for a decade whether there is a large overabundance of strongly lensed arcs in galaxyclusters, compared to expectations from Λ cold dark matter cosmology. We perform ray tracing through the most massive haloes of the Millennium simulation at several redshifts in their evolution, using the Hubble Ultra Deep Field as a source ima…
Abundances in planetary nebulae: NGC 1535, NGC 6629, He2-108, and Tc1
Pottasch, S. R.; Bernard-Salas, J.; Surendiranath, R.
Context. Models have been made of stars of a given mass that produce planetary nebulae that usually begin on the AGB (although they may begin earlier) and run to the white dwarf stage. While these models cover the so-called dredge-up phases when nuclear reactions occur and the newly formed products are brought to the surface, it is important to co…
Magnetic signatures of a tenuous atmosphere at Dione
Dougherty, Michele K.; Saur, Joachim; Simon, Sven +2 more
We present Cassini magnetic field observations from the only two close flybys (16DI and 129DI) of Saturn's icy satellite Dione which have been carried out so far. Data from 16DI show a weak field perturbation in the upstream region, indicative of a tenuous atmosphere around the satellite. By applying an analytical model of the perturbations caused…
Constraints on the origin and evolution of Iani Chaos, Mars
Muller, Jan-Peter; Warner, Nicholas H.; Gupta, Sanjeev +5 more
The origin mechanisms and geologic evolution of chaotic terrain on Mars are poorly constrained. Iani Chaos, located at the head Ares Vallis, is among the most geomorphologically complex of the chaotic terrains. Its morphology is defined by (1) multiple, 1 to 2 km deep basins, (2) flat-topped, fractured plateaus that are remnants of highland terrai…
Probing general relativistic effects during active galactic nuclei X-ray eclipses
Elvis, M.; Brenneman, L.; Nardini, E. +2 more
Long X-ray observations of bright active galactic nuclei (AGN) show that X-ray eclipses, with durations from a few hours to a few days, are rather common. This opens up a new window of opportunity in the search for signatures of relativistic effects in AGN: an obscuring cloud covers/uncovers different parts of the accretion disc at different times…
Further deep imaging of HR 7329 A (η Tel A) and its brown dwarf companion B
Neuhäuser, R.; Schmidt, T. O. B.; Ginski, C. +1 more
About 4 arcsec south of the young A0-type star HR 7329, a faint companion candidate was found by Lowrance et al. Its spectral type of M7-8 is consistent with a young brown dwarf companion. Here we report 10 new astrometric imaging observations of the pair HR 7329 A and B, obtained with the Hubble Space Telescope and the Very Large Telescope, aimed…
A Temporal Study of the Oxygen-rich Pulsating Variable Asymptotic Giant Branch Star, T Cep: Investigation on Dust Formation and Dust Properties
Onaka, Takashi; Speck, Angela K.; Guha Niyogi, Suklima
Pulsation is believed to be the leading cause of dusty mass loss from asymptotic giant branch stars. We present a temporal study of T Cep, a long-period Mira variable, using seven Infrared Space Observatory Short Wavelength Spectrometer spectra, covering a 16 month period over a single pulsation cycle. The observed spectral dust features change ov…