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Suppression of convection around small magnetic concentrations
Ichimoto, K.; Katsukawa, Y.; Shimojo, M. +3 more
Aims: It is well known that convective motions in the photosphere are suppressed by magnetic fields. However, it has been difficult to study the interaction between convection and small magnetic features, such as G-band bright points (GBPs) or pores with polarimetric measurements, because of the available spatial resolution (~1´´). This situation …
Detectable signatures of cosmic radiative feedback
Salvaterra, R.; Burigana, C.; Schneider, R. +3 more
We use a semi-analytical model to study the impact of reionization, and the associated radiative feedback, on galaxy formation. Two feedback models have been considered: (i) a standard prescription, according to which star formation is totally suppressed in galaxies with circular velocity below a critical threshold (model CF06) and (ii) a characte…
Time Distance Analysis of the Emerging Active Region NOAA 10790
Thompson, M. J.; Zharkov, S.
We investigate the emergence of Active Region NOAA 10790 by means of time - distance helioseismology. Shallow regions of increased sound speed at the location of increased magnetic activity are observed, with regions becoming deeper at the locations of sunspot pores. We also see a long-lasting region of decreased sound speed located underneath the…
EG And: Far Ultraviolet Spectroscopic Explorer and Hubble Space Telescope STIS Monitoring of an Eclipsing Symbiotic Binary
Espey, Brian R.; McCandliss, Stephan R.; Crowley, Cian
We present highlights and an overview of 20 FUSE and HST STIS observations of the bright symbiotic binary EG And. The main motivation behind this work is to obtain spatially resolved information on an evolved giant star in order to understand the mass-loss processes at work in these objects. The system consists of a low-luminosity white dwarf and …
A non-hydrostatic Rhea
Mackenzie, R. A.; Iess, L.; Tortora, P. +1 more
Radiometric data obtained during Cassini's close flyby of Rhea, on 26 November 2005, has been subject to several published analyses aiming to determine the satellite's mass and quadrupole gravity moments. Combining aspects of two of these analyses we present our best, unbiased estimates of the gravity field parameters and point out how the constra…
A phenomenological model of galaxy clusters
Diego, J. M.; Ascasibar, Y.
We present a simple model to describe the dark matter density, the gas density and the gas temperature profiles of galaxy clusters. Analytical expressions for these quantities are given in terms of only five free parameters with a clear physical meaning: the mass M of the dark matter halo (or the characteristic temperature T0), the char…
Optical spectroscopy of Arp220: the star formation history of the closest ULIRG
Tadhunter, C. N.; González Delgado, R. M.; Rodríguez Zaurín, J.
We present long-slit, optical spectra of the merging system Arp220, obtained using the William Herschel Telescope (WHT) on La Palma. These data were taken as a part of a large study of ultraluminous infrared galaxies (ULIRGs) with the aim of investigating the evolution and star formation histories of such objects. Spectral synthesis modelling has …
Rotational Velocities for Early-Type Stars in the Young Large Magellanic Cloud Cluster R136: Further Study of the Relationship Between Rotation Speed and Density in Star-Forming Regions
Cunha, K.; Olsen, K.; Daflon, S. +3 more
We present the results of a study aimed at assessing the distribution of rotation speeds, N(v sin i) among O- and early B-type stars located in R136, a young (t ~ 1-4 Myr) cluster in the Large Magellanic Cloud (LMC) characterized by a stellar density at least three times that of the densest Galactic clusters in which stellar rotational velocities …
A Model for the Total Solar Irradiance Based on Active Region Decay
Charbonneau, P.; Crouch, A. D.; Beaubien, G. +1 more
We present a model for the total solar irradiance. The model takes the observed location, timing, and area of emerging active regions as input and produces a time-evolving size distribution of magnetic structures over the solar surface. We assume that the bright magnetic structures (faculae), which counteract the irradiance deficit caused by sunsp…
On the Solar Origins of Open Magnetic Fields in the Heliosphere
DeRosa, Marc L.; Schrijver, Carolus J.; Rust, David M. +4 more
A combination of heliospheric and solar data was used to identify open magnetic fields stretching from the lower corona to Earth orbit. 35 near-relativistic electron beams detected at the ACE spacecraft "labeled" the heliospheric segments of the open fields. An X-ray flare occurred <20 minutes before injection of the electrons in 25 events. The…