440 research outputs found
On the sensitivity of extrasolar mass-loss rate ranges: HD 209458b a case study
We present a 3D hydrodynamic study of the effects that different stellar wind
conditions and planetary wind structures have on the calculated Ly-
absorptions produced during the transit of HD 209458b. Considering a range of
stellar wind speeds [350-800] km s, coronal temperature
[3-7] K and two values of the polytropic index
[1.01-1.13], while keeping fixed the stellar mass loss rate, we found a
that a range between [3-5] g s give
account for the observational absorption in Ly- measured for the
planetary system. Also, several models with anisotropic evaporation profiles
for the planetary escaping atmosphere were carried out, showing that both, the
escape through polar regions and through the night side yields larger
absorptions than an isotropic planetary wind
Photo-ionization of planetary winds: case study HD209458b
Close-in hot Jupiters are exposed to a tremendous photon flux that ionizes
the neutral escaping material from the planet leaving an observable imprint
that makes them an interesting laboratory for testing theoretical models. In
this work we present 3D hydrodynamic simulations with radiation transfer
calculations of a close-in exoplanet in a blow-off state. We calculate the
Ly- absorption and compare it with observations of HD 209458b an
previous simplified model results.Our results show that the hydrodynamic
interaction together with a proper calculation of the photoionization proccess
are able to reproduce the main features of the observed Ly- absorption,
in particular at the blue-shifted wings of the line. We found that the ionizing
stellar flux produce an almost linear effect on the amount of absorption in the
wake. Varying the planetary mass loss rate and the radiation flux, we were able
to reproduce the absorption observed at .Comment: 9 pages, 6 figure
3D MHD simulation of polarized emission in SN 1006
We use three dimensional magnetohydrodynamic (MHD) simulations to model the
supernova remnant SN 1006. From our numerical results, we have carried out a
polarization study, obtaining synthetic maps of the polarized intensity, the
Stokes parameter , and the polar-referenced angle, which can be compared
with observational results. Synthetic maps were computed considering two
possible particle acceleration mechanisms: quasi-parallel and
quasi-perpendicular. The comparison of synthetic maps of the Stokes parameter
maps with observations proves to be a valuable tool to discern
unambiguously which mechanism is taking place in the remnant of SN 1006, giving
strong support to the quasi-parallel model.Comment: 6 pages, 4 figures, accepted by MNRA
Origin of the bilateral structure of the supernova remnant G296.5+10
In this work, we have modelled the supernova remnant (SNR) G296.5+10, by means of 3D magnetohydrodynamics (MHD) simulations. This remnant belongs to the bilateral SNR group and has an additional striking feature: the rotation measure (RM) in its eastern and western parts are very different. In order to explain both the morphology observed in radio-continuum and the RM, we consider that the remnant expands into a medium shaped by the superposition of the magnetic field of the progenitor star with a constant Galactic magnetic field. We have also carried out a polarization study from our MHD results, obtaining synthetic maps of the linearly polarized intensity and the Stokes parameters. This study reveals that both the radio morphology and the reported RM for G296.5+10 can be explained if the quasi-parallel acceleration mechanism is taking place in the shock front of this remnant.Fil: Moranchel-Basurto, A.. Universidad Nacional Autónoma de México; MéxicoFil: Velazquez, P.. Universidad Nacional Autónoma de México; MéxicoFil: Giacani, Elsa Beatriz. Universidad de Buenos Aires. Facultad de Arquitectura y Urbanismo; Argentina. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Toledo Roy, J. C.. Universidad Nacional Autónoma de México; MéxicoFil: Schneiter, E.. Universidad Nacional Autónoma de México; MéxicoFil: De Colle, F.. Universidad Nacional Autónoma de México; MéxicoFil: Esquivel, A.. Universidad Nacional Autónoma de México; Méxic
Chemical crosslinking and mass spectrometry to elucidate the topology of integral membrane proteins.
Here we made an attempt to obtain partial structural information on the topology of multispan integral membrane proteins of yeast by isolating organellar membranes, removing peripheral membrane proteins at pH 11.5 and introducing chemical crosslinks between vicinal amino acids either using homo- or hetero-bifunctional crosslinkers. Proteins were digested with specific proteases and the products analysed by mass spectrometry. Dedicated software tools were used together with filtering steps optimized to remove false positive crosslinks. In proteins of known structure, crosslinks were found only between loops residing on the same side of the membrane. As may be expected, crosslinks were mainly found in very abundant proteins. Our approach seems to hold to promise to yield low resolution topological information for naturally very abundant or strongly overexpressed proteins with relatively little effort. Here, we report novel XL-MS-based topology data for 17 integral membrane proteins (Akr1p, Fks1p, Gas1p, Ggc1p, Gpt2p, Ifa38p, Ist2p, Lag1p, Pet9p, Pma1p, Por1p, Sct1p, Sec61p, Slc1p, Spf1p, Vph1p, Ybt1p)
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