C6H6 condensation on Titan’s stratospheric aerosols: An integrated laboratory, modeling and experimental approach

Saturn’s moon Titan was explored by the Cassini mission for nearly 13 years. Important discoveries made during the Cassini mission include the observations of stratospheric clouds in Titan’s cold polar regions in which spectral features or organic molecules were detected in the infrared (<100 μm). In particular, benzene (C6H6) ice spectral signatures were recently detected at unexpectedly high altitudes over the South Pole. The combined experimental, modeling and observational effort presented here has been devised and executed in order to interpret these high altitude benzene observations. Our multi-disciplinary approach aims to understand and characterize the microphysics of benzene clouds in Titan’s South Pole.

Tracing Cosmic Dawn

Observational effort is on the way to probe the 21-cm of neutral hydrogen from the epochs of Reionization and Cosmic Dawn. Our current poor knowledge of high redshift astrophysics results in a large uncertainty in the theoretically predicted 21-cm signal. A recent parameter study that is highlighted here explores the variety of 21-cm signals resulting from viable astrophysical scenarios. Model-independent relations between the shape of the signal and the underlying astrophysics are discussed. Finally, I briefly note on possible alternative probes of the high redshift Universe, specifically Fast Radio Bursts.

Perspectives on Galactic Structure

The Milky Way is currently the subject of great observational effort. This includes both ESA's unique Gaia mission, as well as a multitude of ground-based surveys. Several of these are already returning data of unprecedented depth and quality for large numbers of Milky Way stars. These new data are likely to lead to a quantum step in our understanding of Milky Way structure and evolution. Because the new data will allow us to study our Galaxy at much greater resolution than possible in other galaxies, we also expect to greatly improve our understanding of disk galaxy formation in general.

The Study of δ Scuti Stars in The Transition Era from Ground-Based to Space Photometry

The different research teams involved in the study of δ Sct stars have slightly changed their strategy in the past years. The observational effort to secure worldwide coverage of case studies has been continued, but the requirements have become more severe, especially about target characterization and frequency resolution.After the successful launch of the Canadian satellite MOST, which will be the pioneer of asteroseismology from space, the future missions are programmed to properly take into account the need for adequate frequency resolution: COROT will spent 30 and 150 d (additional and core programs, respectively) on the target, while EDDINGTON will spend up to 3yr. Such a requirement is a direct consequence of the observational results on δ Sct, γ Dor, SPB, and other stars obtained from ground. It should be noted that without these results (see Poretti 2000 for a review about δ Sct stars) the scientific background of the space missions would be much less defined and the risks of incomplete results (owing to inaccurate selection of targets, insufficient resolution, underestimate of the influence of the rotation) much higher.

PG 1605+072 in Wet XCov22: Support for the Multi Site Spectroscopic Telescope

The Multi-site spectroscopic telescope is a virtual instrument and the name of a collaboration that opens up a new observational window by combining continuous observations of spectroscopic variations and simultaneous photometric monitoring. This constitutes an enormous observational effort, but in return promises to finally provide access to a mode identification for and an asteroseismological analysis of the pulsating sdB star PG 1605+072. Multi-Site Spectroscopic Telescope observations for this object have been secured during a large coordinated campaign in May and June of the year 2002. The frequency resolution and coverage of the photometric time series has been noticeably enhanced by a significant contribution from the Whole Earth Telescope, which was used to observe PG 1605+072 as an alternate target during the WET XCov22 campaign, also conducted in May 2002. This paper briefly outlines the motivation for the MSST project and tries to give a first assessment of the overall quality of the data obtained, with a focus on the Whole Earth Telescope observations.

Polar Motion with Daily and Sub-daily Time Resolution

Since 1992 the IGS ACs (International GPS Service Analysis Centers) have delivered daily estimates of polar motion (PM) and length of day (LOD) to the IERS (International Earth Rotation Service). The IGS combined PM and LOD series are available since January 1, 1995. Since June 1996 the IGS rapid and the final combined orbits are accompanied with two distinct IGS combined PM series with the same time resolution of one day. Both, the IGS final and rapid combined PM series also include combined PM rate data as well as LOD, starting in March 1997.Since 1995 the CODE Analysis Center of the IGS has produced PM and LOD estimates with a two-hour time resolution on a routine basis. A study of the time series with sub-daily time resolution clearly shows the half-daily and daily tidal signals. The results correspond very well to those obtained from satellite altimetry.These sub-daily time series are based on the same observational data from the IGS tracking network as those time series with a one-day time resolution. It would thus be possible with a minor analysis effort, without additional observational effort, to come up with a long and consistent series of PM and LOD with a time resolution of about 1 to 2 hours.

Stellar chemical evolution

One of the major achievements of astrophysics has been the demonstration that most of the chemical elements have been synthesized in stars: nucleosynthesis calculations of homogeneous and inhomogeneous big bang cosmologies show that, in comparison with the most metal-poor stars currently known, essentially no elements heavier than B existed at the era of decoupling (see e.g. Wagoner, Fowler, & Hoyle 1967; Kajino, Mathews, & Fuller 1990). Following the pioneering work on stellar nucleosynthesis by Hoyle (1946), the basic precepts and the role of stars was set down in the classic papers of Burbidge et al. (1957) and Cameron (1957), and the ensuing decades have produced a vast body of theoretical and observational effort to more fully understand the details of the process.

Rapid multicolour variations of selected southern Be stars

Many previous surveys of the rapid variability of Be stars (e.g., Balona et al. 1987, Cuypers et al. 1989, Balona et al 1992) were limited to the Strömgren b-band only. We have undertaken a new observational effort with the specific aim of studying colour variations. A search for new rapidly variable stars should provide us with statistical material needed to generalize properties of the phenomenon with respect to the stellar parameters. Some preliminary results of these items are presented here.