We report the systematic analysis of the durations for Swift gamma-ray bursts (GRBs) and compare the results with those of pre-Swift data. We show that the durations of Swift bursts also have two log-normal distributions that are clearly divided at T90 = 2 s. Their intrinsic durations also show a bimodal distribution but shift systematically toward the smaller value compared with the observed one. This study confirms the spectra of short GRBs are in general harder than the long GRBs and shows that this trend becomes weak in the source frame.

Several dynamical processes may induce considerable Lorentz forces in atmospheres of mCP stars, thus modifying the hydrostatic structure of their atmospheres. This modification can be seen as characteristic rotational variability of certain spectral features such as hydrogen Balmer lines. In this work we present the first results of modeling the magnetic pressure effects in atmospheres of mCP stars in the framework of model atmosphere analysis with accurate treatment of microscopic properties of atmospheric plasma. We show that at least part of the rotational variability of hydrogen lines seen in high-resolution spectra of mCP stars could be attributed to the non-zero electrical currents flowing along stellar surfaces.

The activities of the Commission have continued to focus on controlling unwanted light and radio emissions at observatory sites, monitoring of conditions at observatory sites, and education and outreach. Commission members have been active in securing new legislation in several locations to further the protection of observatory sites.

Searches for extrasolar planets using the periodic Doppler shift of stellar spectral lines have recently achieved a precision better than 60cm/s. To find a 1-Earth mass planet in an Earth-like orbit, a precision of 5cm/s is necessary. The combination of a laser frequency comb with a Fabry-Perot filtering cavity has been suggested as a promising approach to achieve such Doppler shift resolution via improved spectrograph wavelength calibration. Here we report the fabrication of such a filtered laser comb with up to 40 GHz (~1 Angstrom) line spacing, generated from a 1 GHz repetition-rate source, without compromising long-term stability, reproducibility or spectral resolution. This wide-line-spacing comb (astro-comb) is well matched to the resolving power of high-resolution astrophysical spectrographs. The astrocomb should allow a precision as high as 1cm/s in astronomical readial velocity measurements.

The present work shows the proportion of interstellar meteors from different mass ranges (exceeding 20 orders of mass scale) detected by various observational techniques. Having analysed the IAU Meteor Data Center, we find that the mass index of interstellar particles continuously increases towards higher masses, but there is a significant change between 10−10 − 10−11 kg. This break is possibly caused by different physical processes leading to different populations of interstellar particles and might be connected with their origin.

The atmospheres of magnetic chemically peculiar (mCP) stars display the presence of magnetic fields of different geometry and strength, ranging from a few hundred G up to tens of kG. Except several very approximate attempts there were no detailed studies of magnetic field effects on model atmospheres structure, possibly leading to errors in the stellar parameter determination and abundance analysis routines. We present the magnetic model atmospheres based on LLmodels code which accounts for the detailed treatment of anomalous Zeeman splitting and polarized radiative transfer.

The properties of W UMa binary stars are studied based on the well-determined physical parameters of 132 W UMa systems. It is found that the energy transfer rate has a maximum value at q ~ 0.58. The relation between the energy transfer rate and the temperature deviation is also investigated, and the temperature of the secondary component is related to the energy transfer rate.

The HARPS search for low-mass extrasolar planets has been ongoing for more than 4 years, targeting originally about 400 bright FGK dwarfs in the solar neighbourhood. The published low-mass planetary systems coming from this survey are fully confirmed by subsequent observations, which demonstrate the sub-m/s long-term stability reached by HARPS. The complex RV curves of these systems have led us to focus on a smaller sample of stars, accumulating more data points per star. We perform a global search in our data to assess the existence of the large population of ice giants and super-Earths predicted by numerical simulations of planet formation. We indeed detect about 45 candidates having minimum masses below 30 M⊕ and orbital periods below 50 days. These numbers are preliminary since the existence of these objects has to be confirmed by subsequent observations. However, they indicate that about 30% of solar-type stars may have such close-in, low-mass planets. Some emerging properties of this low-mass population are presented. We finally discuss the prospects for finding transiting objects among these candidates, which may possibly yield the first nearby, transiting super-Earth.

Commission 55 was approved at the IAU XXVI General Assembly in Prague, 2006, following the great success of the Working Group Communicating Astronomy, which had been set up in 2003.

If interstellar meteors are present among the registered meteor orbits, the distribution of the excesses of their heliocentric velocities should correspond to the distribution of radial velocities of close stars. Hence, for the velocity vi = 20 kms−1 of an interstellar meteor (with respect to the Sun) we obtain a heliocentric velocity vH = 46.6 kms−1 of an interstellar meteor arriving at the Earth. Moreover, a concentration of radiants to the Sun's apex should be observed. An analysis of the hyperbolic meteors among the 4581 photographic orbits of the IAU Meteor Data Center showed that the identification of the vast majority of the hyperbolic orbits in these catalogues has been caused by an erroneous determination of their heliocentric velocity and/or other parameters. Any error in the determination of vH, especially near the parabolic limit, can create an artificial hyperbolic orbit that does not really exist. On the basis of photographic meteors from the IAU MDC, the proportion of possible interstellar meteors decreased significantly (greater than 1 order of magnitude) after error analysis and does not exceed the value 2.5 × 10−4. Neither any concentration of radiants to the Sun's apex, nor any distribution following the motion of interstellar material has been found.

We report 2D time-dependent non-linear magneto-hydrodynamical simulations of waves in the atmospheres of roAp stars. We explore a grid of simulations in a wide parameter space. The aim of our study is to understand the influence of the atmosphere and the magnetic field on the propagation and reflection properties of magneto-acoustic waves, formation of shocks and node layers.

The possibility of an extraterrestrial origin of biomolecule building blocks has been a subject of intense discussions for many years. The detection of amino acids in meteorites opens the possibility of a delivery of biomolecules synthesized in the interstellar medium or star-forming regions to the primeval Earth. Whereas it can be doubted if more complex species like amino acids can survive the strong UV radiation in the early Solar System, this does not necessary hold for more primitive precursor molecules like nitriles. These compounds can also be synthesized very efficiently in methane-nitrogen dominated atmospheres like the one present on Titan and the early ages of Earth. This Contribution focuses on the formation and degradation processes of nitriles in interstellar clouds and planetary atmospheres and on their possible role in the generation of biomolecules.

While expecting a huge increase of interest in the IAU as a result of the planet definition issue on the agenda of the IAU XXVI General Assembly, Prague, Czech Republic, August 2006, the Executive Committee appointed Lars Lindberg Christensen as Press Officer in June 2006. He will stay on the job till at least the IAU XXVII General Assembly in Rio de Janeiro, Brazil, August 2009.

We present the integrated J, H, K, L, M and N magnitudes and the colours involving infrared bands, for an extensive set of instantaneous-burst binary stellar populations (BSPs) by using evolutionary population synthesis (EPS). By comparing the results for BSPs WITH and WITHOUT binary interactions we show that the inclusion of binary interactions makes the magnitudes of populations larger (fainter) and the integrated colours smaller (bluer) for τ ≥ 1 Gyr. Also, we compare our model magnitudes and colours with those of Bruzual & Charlot (2003, hereafter BC03) and Maraston (2005, hereafter M05). At last, we compare these model broad colours with Magellanic Clouds globular clusters (GCs) and Milky Way GCs. In (V − R)−[Fe/H] and (V − I)−[Fe/H] diagrams it seems that our models match the observations better than those of BC03 and M05.

The radial velocity technique is commonly used to classify transiting exoplanet candidates. However, stars are intrinsically noisy in radial velocity. No good description of this noise has yet been proffered, although activity in general has been suggested as the source, making it impossible to evaluate its effect on signal detection. In this poster, we propose an activity-based model that incorporates both light and dark stellar spots, capable of producing both photometric and radial velocity time series. We demonstrate its consistency with both SOHO/VIRGO photometry and SOHO/GOLF radial velocities. We then use this model to establish lower and upper limits on the effects of intrinsic stellar noise on the metal lines used to follow up transit candidates, making use of Monte Carlo simulations. Based on these results, we can suggest an optimal observational sampling rate.

The SOPHIE Consortium started a large program of exoplanets search and characterization in the Northern hemisphere with the new spectrograph SOPHIE at the 1.93-m telescope of Haute-Provence Observatory, France. The objectives of this program are to characterize the zoo of exoplanets and to bring strong constraints on their processes of formation and evolution using the radial velocity technique. We present here new SOPHIE measurements of the transiting planet host star XO-3. This allowed us to observe the Rossiter-McLaughlin effect and to refine the parameters of the planet. The unusual shape of the radial velocity anomaly during the transit provides a hint for a nearly transverse Rossiter-McLaughlin effect. The sky-projected angle between the planetary orbital axis and the stellar rotation axis should be λ = 70° ± 15° to be compatible with our observations. This suggests that some close-in planets might result from gravitational interaction between planets and/or stars rather than migration. This result requires confirmation by additional observations.

The long-term orbital period changes of detached chromospheric active binaries were surveyed. 17 of such systems are found to be undergoing secular period decreasing with the rates (dP/dt) of −3.05 × 10−9 to −3.77 × 10−5 days per year. The longer the orbital period, the more rapidly the period decreases. Following Stepien (1995), the period decreasing rate due to the angular momentum loss (AML) caused by magnetic wind is computed for each system. A comparison shows that the observed dP/dt's are obviously higher than that of the theoretical predictions by 1-3 orders of magnitude. It suggests that the magnetic wind is not likely the determinant mechanism driving the AML in close binaries.

Carbonaceous materials play an important role in space. Polycyclic Aromatic Hydrocarbons (PAHs) are a ubiquitous component of organic matter in space. Their contribution is invoked in a broad spectrum of astronomical observations that range from the ultraviolet to the far-infrared and cover a wide variety of objects and environments from meteorites and interplanetary dust particles to outer Solar System bodies to the interstellar medium in the local Milky Way and in other galaxies. Extensive efforts have been devoted in the past two decades to experimental, theoretical, and observational studies of PAHs. A brief review is given here of the evidence obtained so far for the contribution of PAHs to the phenomena aforementioned. An attempt is made to distinguish the cases where solid evidence is available from cases where reasonable assumptions can be made to the cases where the presence - or the absence - of PAHs is purely speculative at this point.

We report the observed systematic differences in longitudinal magnetic field values, obtained from measurements of metal lines and the core of the Hβ line for a number of Ap stars, having strong global magnetic fields. In overwhelming majority of cases the magnetic field values, obtained from measurements of hydrogen lines cores, is smaller then the ones obtained from metal lines. We discuss some possible explanations of this effect, the most probable of which is the existence of the gradient of the magnetic field in stellar atmospheres.

In 2004 a deep sequence of HST images of the Bulge was used to identify sixteen transiting extrasolar planet candidates (the SWEEPS candidates; Sahu et al. 2006), of which at least seven are likely to be true planets. Of these, SWEEPS-4 is almost certainly in the disk, and was shown through radial velocity followup to contain a planetary companion; the identification of the remaining fifteen candidates was left undetermined.

We have used a repeat visit in 2006 to attach proper motions to some 180,000 objects, including all sixteen SWEEPS candidates. This has allowed us to build a sample of bulge stars to unprecedented purity. A population of more than 13,000 bulge objects is kinematically isolated, with fewer than thirty disk contaminants. We use the mean bulge and disk populations to test the balance of kinematic associations for the sixteen SWEEPS candidates. Assuming both the detectability and the astrophysical false-positive fraction to be similar for disk and bulge, we find the fraction of stars with planets in the bulge to be consistent with that in the disk.