Search Publications
Constraints on Helium Enhancement in the Globular Cluster M4 (NGC 6121): The Horizontal Branch Test
Catelan, M.; Cortés, C.; Alonso-García, J. +2 more
Recent pieces of evidence have revealed that most, and possibly all, globular star clusters are composed of groups of stars that formed in multiple episodes with different chemical compositions. In this sense, it has also been argued that variations in the initial helium abundance (Y) from one population to the next are also the rule, rather than …
A Comprehensive X-Ray and Multiwavelength Study of the Colliding Galaxy Pair NGC 2207/IC 2163
Homan, J.; Rappaport, S.; Levine, A. +3 more
We present a comprehensive study of the total X-ray emission from the colliding galaxy pair NGC 2207/IC 2163, based on Chandra, Spitzer, and GALEX data. We detect 28 ultraluminous X-ray sources (ULXs), 7 of which were not detected previously because of X-ray variability. Twelve sources show significant long-term variability, with no correlated spe…
Modeling the SAR backscatter of linear dunes on Earth and Titan
Le Gall, A.; Bernard, D.; Radebaugh, J. +3 more
We modeled the Synthetic Aperture Radar (SAR) response of linear dunes of the Great Sand Sea in Egypt using a single surface scattering term, based on Integral Equation and Physical Optics Models. Using multi-frequency SIR-C/X-SAR radar scenes and topography obtained from the Shuttle Radar Topography Mission (SRTM), we were able to estimate reason…
Saturn's elusive nightside polar arc
Jackman, C. M.; Milan, S. E.; Fear, R. C. +5 more
Nightside polar arcs are some of the most puzzling auroral emissions at Earth. They are features which extend from the nightside auroral oval into the open magnetic field line region (polar cap), and they represent optical signatures of magnetotail dynamics. Here we report the first observation of an arc at Saturn, which is attached at the nightsi…
X- and γ-Ray Pulsations of the Nearby Radio-faint PSR J1741-2054
Belfiore, A.; Camilo, F.; Marelli, M. +6 more
We report the results of a deep XMM-Newton observation of the radio-faint γ-ray pulsar J1741-2054 and its nebula together with the analysis of five years of Fermi Large Area Telescope (LAT) data. The X-ray spectrum of the pulsar is consistent with an absorbed power law plus a blackbody, originating at least partly from the neutron star cooling. Th…
Detailed modelling of a large sample of Herschel sources in the Lockman Hole: identification of cold dust and of lensing candidates through their anomalous SEDs★
Valtchanov, Ivan; Oliver, Seb; Vaccari, Mattia +12 more
We have studied in detail a sample of 967 SPIRE sources with 5σ detections at 350 and 500 µm and associations with Spitzer-SWIRE 24 µm galaxies in the HerMES-Lockman survey area, fitting their mid- and far-infrared, and submillimetre, spectral energy distributions (SEDs) in an automatic search with a set of six infrared templates. For …
Probing the accretion scheme of the dipping X-ray binary 4U 1915-05 with Suzaku
Makishima, Kazuo; Zhang, Zhongli; Sasano, Makoto +2 more
The dipping low-mass X-ray binary 4U 1915-05 was observed by Suzaku on 2007 November 8 for a net exposure of 39 ks. It was detected by the XIS with a 0.8-10 keV signal rate of 9.84 ± 0.01 cts s-1 per camera, and HXD-PIN with a 12-45 keV signal rate of 0.29 ± 0.01 cts s-1. After removing the periodic dips and an X-ray burst, t…
The Lutz-Kelker paradox.
Francis, C.
The Lutz-Kelker correction is intended to give an unbiased estimate for stellar parallaxes and magnitudes, but it is shown explicitly that it does not. This paradox results from the application of an argument about sample statistics to the treatment of individual stars, and involves the erroneous use of a frequency distribution in the manner of a …
VLT observations of the asymmetric Etched Hourglass Nebula, MyCn 18
Redman, M. P.; Matsuura, M.; Meaburn, J. +3 more
Context. The mechanisms that form extreme bipolar planetary nebulae remain unclear.
Aims: The physical properties, structure, and dynamics of the bipolar planetary nebula, MyCn 18, are investigated in detail with the aim of understanding the shaping mechanism and evolutionary history of this object.
Methods: VLT infrared images, VLT ISAA…
Statistically anisotropic Gaussian simulations of the CMB temperature field
Souradeep, Tarun; Mukherjee, Suvodip
Although theoretically expected to be statistically isotropic (SI), the observed cosmic microwave background (CMB) temperature and polarization field would exhibit SI violation due to various inevitable effects like weak lensing, Doppler boost, and practical limitations of observations like noncircular beam, masking, etc. However, the presence of …