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The discovery that Vega is a rapidly rotating pole-on star has raised a number of questions about this fundamental standard, including such issues as its composition, and in turn its mass and age. We report here a reanalysis of Vegas composition. A full spectral synthesis based on the Roche model derived earlier from NPOI interferometry is used. We find the line shapes in Vegas spectrum to be more complex than just flat-bottomed, which have been previously reported; profiles range from slightly self-reversed to simple ``V shapes. A high SNR spectrum, obtained by stacking spectra from the ELODIE archive, shows excellent agreement with the calculations, provided we add about 10 km/s of macroturbulence to the predicted spectra. From the abundance analysis, we find that Vega shows the peculiar abundance pattern of a W Bootis star as previously suggested. We investigate the effects of rotation on the deduced abundances and show that the dominant ionization states are only slightly affected compared to analyses using non-rotating models. We argue that the rapid rotation requires the star be fully mixed. The composition leads to masses and particularly ages that are quite different compared to what are usually assumed.
In a laboratory experiment, water-ice aggregates are trapped in a vacuum chamber at a pressure of 2 mbar due to photophoresis and thermophoresis. The particles are located between a Peltier element at the bottom at 250 K and a reservoir of liquid nit
While it is well known that constant rotation induces linear dispersive effects in various fluid models, we study here its effect on long time nonlinear dynamics in the inviscid setting. More precisely, we investigate stability in the 3d rotating Eul
We study the effects of rotation on the growth and saturation of the double-diffusive fingering (thermohaline) instability at low Prandtl number. Using direct numerical simulations, we estimate the compositional transport rates as a function of the r
Brightness inhomogeneities in the stellar photosphere (dark spots or bright regions) affect the measurements of the planetary transmission spectrum. To investigate the star spots of the M dwarf GJ 1214, we conducted a multicolor photometric monitorin
Short period (<50 days) low-mass (<10Mearth) exoplanets are abundant and the few of them whose radius and mass have been measured already reveal a diversity in composition. Some of these exoplanets are found on eccentric orbits and are subjected to s