ar X iv : 0 90 6 . 15 95 v 1 [ as tr o - ph . S R ] 8 Ju n 20 09 2 - D simulations of FU Orionis disk outbursts

ar X iv : 0 80 2 . 40 99 v 2 [ as tr o - ph ] 1 8 D ec 2 00 8 Planet Formation by Concurrent Collapse

After reviewing the difficulties faced by the conventional theory of planet formation (based upon the aggregation of microscopic dust particles), we describe an alternative hypothesis. We propose that planets form by gravitational collapse at the same time as the star about which they orbit. This concurrent collapse hypothesis avoids theoretical difficulties associated with the conventional mod...

ar X iv : 0 90 6 . 48 35 v 1 [ m at h . O C ] 2 6 Ju n 20 09 The Complex Gradient Operator and the CR - Calculus

ar X iv : 0 90 1 . 39 43 v 1 [ as tr o - ph . S R ] 2 6 Ja n 20 09 Solar analogues in open clusters : The case of M 67

Solar analogues are fundamental targets for a better understanding of our Sun and our Solar System. Usually, this research is limited to field stars, which offer several advantages and limitations. In this work, we present the results of a research of solar twins performed for the first time in a open cluster, namely M67. Our analysis allowed us to find five solar twins and also to derive a sol...

ar X iv : a st ro - p h / 06 05 36 5 v 1 15 M ay 2 00 6 Spitzer - IRS Observations of FU Orionis Objects

We present 5-35 µm spectra, taken with the Infrared Spectrograph (IRS) on the Spitzer Space Telescope, of five FU Orionis objects: FU Ori, V1515 Cyg, V1057 Cyg, BBW 76, and V346 Nor. All but V346 Nor reveal amorphous silicate grains in emission at 10 µm and 20 µm, and show water-vapor absorption bands at 5.8 and 6.8 µm and SiO or possibly methane absorption at 8 µm. These absorption features cl...

ar X iv : 0 90 6 . 43 48 v 1 [ as tr o - ph . C O ] 2 3 Ju n 20 09 Computer Simulations of Cosmic Reionization Hy Trac

The cosmic reionization of hydrogen was the last major phase transition in the evolution of the universe, which drastically changed the ionization and thermal conditions in the cosmic gas. To the best of our knowledge today, this process was driven by the ultra-violet radiation from young, star-forming galaxies and from first quasars. We review the current observational constraints on cosmic re...