Direct Ultraviolet Imaging and Spectroscopy of Betelgeuse

Direct images of Betelgeuse were obtained over a span of 4 years with the Faint Object Camera on the Hubble Space Telescope. These images reveal the extended ultraviolet continuum emission (about 2 times the optical diameter), the varying overall ultraviolet flux levels and a pattern of bright surface continuum features that change in position and appearance over several months or less. Concurrent photometry and radial velocity measures support the model of a pulsating star, first discovered in the ultraviolet from IUE. Spatially resolved HST spectroscopy reveals a larger extention in chromospheric emissions of Mg II as well as the rotation of the supergiant. Changing localized subsonic flows occur in the low chromosphere that can cover a substantial fraction of the stellar disk and may initiate the mass outflow.Comment: 9 pages, 5 figures, Betelgeuse Workshop, November 2012, Paris. To be published in the European Astronomical Society Publications Series, 2013, Editors: Pierre Kervella, Thibaut Le Bertre & Guy Perri

Particle Dark Energy

We explore the physics of a gas of particles interacting with a condensate that spontaneously breaks Lorentz invariance. The equation of state of this gas varies from 1/3 to less than -1 and can lead to the observed cosmic acceleration. The particles are always stable. In our particular class of models these particles are fermions with a chiral coupling to the condensate. They may behave as relativistic matter at early times, produce a brief period where they dominate the expansion with w<0 today, and behave as matter at late time. There are no small parameters in our models, which generically lead to dark energy clustering and, depending on the choice of parameters, smoothing of small scale power.Comment: 8 pages, 5 figures; minor update with added refs; version appearing in Phys. Rev.

Theoretical and experimental analysis of the backward extrusion process with a rotational die of AZ31 alloy

In this work theoretical and experimental analysis of the backward extrusion with a rotary die of the AZ31 alloy has been performed. The modification of the classical extrusion was based on the use of a rotary die. The results of theoretical research have confirmed that the use of the modified backward extrusion causes the appearance of shear stress in deformed material, which could affects the activation of additional mechanisms of deformation. The numerical modelling of the rotating extrusion of AZ31 alloy has been conducted by using the computer program Forge®. The experimental tests were carried out in the conditions of the STD 810 torsion plastometer using newly designed tools

Line Broadening in Field Metal-poor Red Giant and Red Horizontal Branch Stars

We report 349 radial velocities for 45 metal-poor field red giant and red horizontal branch stars. We have have identified one new spectroscopic binary, HD 4306, and one possible such system, HD 184711. We also report 57 radial velocities for 11 of the 91 stars reported on previously by Carney et al. (2003). As was found in the previous study, radial velocity "jitter" is present in many of the most luminous stars. Excluding stars showing spectroscopic binary orbital motion, all 7 of the red giants with M(V) <= -2.0 display jitter, as well as 3 of the 14 stars with -2.0 <= M(V) <= -1.4. We have also measured line broadening in all of the new spectra, using synthetic spectra as templates. The most luminous red giants show significant line broadening, as do many of the red horizontal branch stars, and we discuss briefly possible causes.Comment: To appear in the Astronomical Journa

HAT-P-3b: A heavy-element rich planet transiting a K dwarf star

We report the discovery of a Jupiter-size planet transiting a relatively bright (V = 11.56) and metal-rich early K dwarf star with a period of about 2.9 days. On the basis of follow-up photometry and spectroscopy we determine the mass and radius of the planet, HAT-P-3b, to be M_p = 0.599 +/- 0.026 M_Jup and R_p = 0.890 +/- 0.046 R_Jup. The relatively small size of the object for its mass implies the presence of about 75 Earth masses worth of heavy elements (1/3 of the total mass) based on current theories of irradiated extrasolar giant planets, similar to the mass of the core inferred for the transiting planet HD 149026b. The bulk density of HAT-P-3b is found to be rho_p = 1.06 +/- 0.17 g/cm^3, and the planet orbits the star at a distance of 0.03894 AU. Ephemerides for the transit centers are T_c = 2,454,218.7594 +/- 0.0029 + N (2.899703 +/- 0.000054) (HJD).Comment: To appear in ApJ

HAT-P-4b: A metal-rich low-density transiting hot Jupiter

We describe the discovery of HAT-P-4b, a low-density extrasolar planet transiting BD+36 2593, a V = 11.2 mag slightly evolved metal-rich late F star. The planet's orbital period is 3.056536+/-0.000057 d with a mid-transit epoch of 2,454,245.8154 +/- 0.0003 (HJD). Based on high-precision photometric and spectroscopic data, and by using transit light curve modeling, spectrum analysis and evolutionary models, we derive the following planet parameters: Mp= 0.68 +/- 0.04 MJ, Rp= 1.27 +/- 0.05 RJ, rho = 0.41 +/- 0.06 g cm-3 and a = 0.0446 +/- 0.0012 AU. Because of its relatively large radius, together with its assumed high metallicity of that of its parent star, this planet adds to the theoretical challenges to explain inflated extrasolar planets.Comment: 5 pages, accepted for publication in ApJ