The rapid neutron capture process (r-process) is understood to be responsible for the synthesis of approximately half of all of the isotopes present in Solar System matter in the mass region from approximately zinc through the actinides. While the general features of this process were identified in the classic papers by B2FH (1957) and Cameron (1957), our current understanding of the r-process remains woefully incomplete. We have yet to cleanly identify which of the studied astrophysical sites contribute significantly to the observed abundance pattern. We have yet to reconcile the apparent duplicity of r-process sites with extant models for the operation of the r-process in diverse astronomical environments. While we may still remain theoretically challenged in our attempts to understand the r-process mechanism and to identify its site, significant clues have come from the observational side. Triggered by the first detections of the element europium (formed predominantly by the r-process) in low metallicity stars (Spite & Spite 1978), observations of heavy element abundances in halo stars have since served to provide tremendously important clues to the nature of the r-process mechanism. Identified constraints include: the utter dominance of the r-process contributions (over those of the s-process in extremely metal deficient stars; an extraordinary robustness of the r-process pattern in the mass range A[gsim ]130–140; and the demand for a second r-process site for the production of the A[lsim ]130 r-process nuclei. We will review these observational trends and theoretical models in the context of the Galactic (Cosmic) evolution of r-process abundances.

We study the application of a predictive control law based on a Kalman filter for an extreme adaptive optics system. In particular, we discuss the minimization of temporal error and show the evolution of prediction errors with the order of the model. We also discuss the choice of the optimal temporal frequency as a function of the control law and the level of noise. Finally, the gain expected with respect to a non-predictive law is presented.

We present detailed abundance measurements of neutron-capture elements for the two very metal-poor stars HD 6268 and HD 122563, based on very high-quality, near-UV spectra (S/N >140 @3100A) using Subaru/HDS. Abundances have been obtained for a total of 26 and 19 neutron-capture elements in these two stars, respectively, including Nb, Mo, Ru, Pd, Ag, Pr, and Sm. We have confirmed that the abundance pattern of neutron-capture elements in HD 6268 agrees very well with that of previously known r-process-enhanced stars. In contrast, the elemental abundances of HD 122563 are found to steeply decrease with increasing atomic number than those of HD 6268, and are much lower than than the r-process pattern in solar-system material. This result provides a new, strong constraint on models of the nucleosynthetic process that has provided light neutron-capture elements in the very early Galaxy.

We analyze the upper-end X-ray luminosity function (XLF) observed in elliptical galaxies for point sources. We propose that the observed XLF is dominated by transient BH systems in outburst and the XLF shape reflects the black hole (BH) mass spectrum among old X-ray transients. The BH mass spectrum – XLF connection depends on a weighting factor that is related to the transient duty cycle and depends on the host-galaxy age, the BH mass and the donor type (main sequence, red giant, or white dwarf). We argue that the assumption of a constant duty cycle for all systems leads to results inconsistent with current observations. The type of dominant donors in the upper-end XLF depends on what type of magnetic braking operates: in the case of “standard” magnetic braking, BH X-ray binaries with red-giant donors dominate, and in the case of weaker magnetic braking prescriptions main sequence donors dominate.

Adaptive optics (AO) systems have significantly improved astronomical imaging capabilities over the last decade, and are revolutionizing the kinds of science possible with 4-5 m class ground-based telescopes. A thorough understanding of AO system performance at the telescope can enable new frontiers of science as observations push AO systems to their performance limits. We look at the understanding we have gained from recent Lyot Project images at the Advanced Electro-Optical System (AEOS) 3.6 m telescope to show how progress made in improving WFR can be measured directly in improved science images. We describe how wave front errors affect the AO point-spread function (PSF), and model details of AEOS AO to simulate a PSF which matches the actual AO PSF in the astronomical H-band. Finally, we estimate the impact of improvements to wave front reconstruction techniques on diffraction-limited coronagraphy with the Lyot Project near-infrared coronagraph.

While the origin of r-process nuclei remains a long-standing mystery, recent spectroscopic studies of extremely metal-poor stars in the Galactic halo strongly suggest that it is associated with core-collapse supernovae. In addition, recent comprehensive analysis of such stars implies the presence of the “weak” r-process that is responsible for only lighter nuclei with A <130. In this study, we show that the weak r-process nuclei can be produced in the neutrino winds from a typical proto-neutron star of $1.4 M_\odot$. This suggests that the significant fraction of weak r-process elements (Sr, Y, Zr, etc.) originate from typical core-collapse supernovae with the progenitor mass range of ∼ 10–$20 M_\odot$

We present preliminary results from a detailed analysis of the X-ray point sources in the XMM-Newton survey of M31 (e.g. Barnard et al. 2005; Pietsch et al. 2005). These sources are expected to be mostly X-ray binaries.

Although our Galactic Center harbors a black hole (Sgr A*) of a few million solar masses, it and its environments are very quiet at present. In X-rays however, the close vicinity of Sgr A* shows very unique and various phenomena mostly originated from young stellar populations. We report on the X-ray perspective on the young stellar populations which are related to our Galactic Center activities. The discussion is essentially based on the observational facts of new X-ray objects in the Galactic Center region in the $1^\circ \times 2^\circ $ area. They are;

1. Clusters of young high mass stars, which are Sgr B2, Arches, IRS 13 and Quintuplet.

2. X-ray reflections in the giant molecular clouds, such as Sgr B2, Sgr C, M0.01-0.09 and others.

3. New candidates of X-ray supernova remnants (SNRs), which are Sgr A East, G0.570-0.018 and G359.8-0.3.

4. Non-thermal Jets, Filaments and Shells, which are unique X-ray features in the GC region. These X-ray features may be closely related with each other, hence may have common origins. A unified picture is presented for the X-ray activity of our Galactic Center comparing with the X-ray spectra from other type of galaxies such as;

5. Star burst galaxy (NGC 253), low luminosity AGN (M 81) and Seyfert 2 (NGC 1068).

We present experimental results of a new procedure of measurement and pre-compensation of the non-common path aberrations in Adaptive Optics. A significant Strehl ratio increase (from 70 to 95.5 % in R band) is demonstrated.

We report on a dedicated effort to identify and study metal-poor stars that are strongly enhanced in r-process elements ($\mbox{[r/Fe]}>+1.0$dex; hereafter r-II stars), the Hamburg/ESO R-process Enhanced Star survey (HERES). In a sample of 253 confirmed metal-poor stars for which “snapshot” spectra ($R\sim 20,000$; $S/N \sim 50/1$ per pixel) were obtained with VLT/UVES, and abundances were determined in an automated fashion using the methods of Barklem et al. (2005), we identified eight new r-II stars. They are now being studied in detail by means of higher resolution and S/N spectroscopy. The new r-II stars have metallicities in the range $-3.2<\mbox{[Fe/H]}<-2.6$. Future searches for r-II stars should therefore focus on stars in this [Fe/H] range. Moderately r-process enhanced stars (i.e., $+0.3\,\mbox{dex}<\mbox{[r/Fe]}<+1.0\,\mbox{dex}$; r-I stars) were found at metallicities as high as $\mbox{[Fe/H]} = -1.5$. The [Fe/H] ranges in which r-I and r-II stars can be found may provide an important constraint for the identification of the site(s) of the r-process(es).

The Lyot Project near-infrared JHK coronagraph achieved first light on the Advanced Electro-Optical System (AEOS) in March 2004. Optical pupil plane imaging at video rates from this coronagraph provides data on atmospheric scintillation and quasi-static pupil intensity variations. We examine the effect of these variations on coronagraphic performance. Early simulations suggested Strehl ratio reductions of the order of 2–3% due to residual uncorrected phase aberrations in H-band. We find that static or quasi-static pupil illumination non-uniformity in I-band reduces Strehl by $\sim$2%. A lower bound on the effects of dynamic illumination variation over the pupil is also $\sim$2% in I-band. Some of the static intensity variations in the pupil are due to pinned deformable mirror (DM) actuators. We simulate the effects a pinned actuator has on the coronagraph. The resultant speckles in simulated coronagraphic images show similarities to some Lyot Project PSFs. This highlights the importance of knowledge of the pupil in next-generation extreme AO coronagraphs in order to realize the predicted photometric dynamic range of their images.

We compute the evolution of the abundances of barium and europium in the Milky Way with a chemical evolution model which already reproduces the majority of observational constraints, and we compared our results with the observed abundances from the recent UVES Large Program “First Stars” (Cayrel et al. 2004, François et al. 2005).

We confirm that barium is a neutron capture element mainly produced in the low mass AGB stars, during the thermal-pulsing phase, by the 13C neutron source, in a slow neutron capture process. However, in order to reproduce the [Ba/Fe] vs. [Fe/H] as well as the Ba solar abundance, Ba should be also produced as a r-process element by massive stars in the range 10-30M[odot ]. On the other hand, europium should be only a r-process element produced in the same range of masses (10-30M[odot ]), at variance with previous suggestions indicating a smaller mass range for the Eu producers. As it is well known, there is a large spread in the [Ba/Fe] and [Eu/Fe] ratios at low metallicities, although smaller in the newest data. With our model we estimate ranges in the r-process yields from massive stars for both elements which better reproduce the trend of the data. We discuss several possibilities to explain the observed spread. We suggest that a peculiar behaviour of the neutron capture elements could be the responsible for the spread instead of invoking a strongly inhomogeneous early Galactic halo. We finally underline that the production ratio of [Ba/Eu] may be almost constant in the massive stars.

Population synthesis of binary stars with relativistic component is presented.

We have performed evolutionary population synthesis calculations to investigate the nature of the faint X-ray sources in the Galactic center region detected by recent Chandra surveys. Our results show that neutron star low-mass X-ray binaries contribute significantly to the observed sources, but the majority of the sources in Wang et al. (2002) survey are still beyond our expectation. We also point out that wind-accreting neutron stars and intermediate polars play a minor role in accounting for the faint X-ray sources in Wang et al. (2002) and Muno et al. (2003) surveys, respectively.

Theoretical as well as observational aspects of the s-process nucleosynthesis are reviewed. The classical site-independent s-process model as well as the s-process in massive stars are shortly described. A special attention is paid to the nucleosynthesis taking place in AGB stars and the extra-mixing invoked to explain the production of neutrons in the C-rich layers during the interpulse. We also discuss the nucleosynthesis found in hot AGB stars for which the s-process during the interpulse phase is inhibited, but the one resulting from the large temperatures in the thermal pulse is boosted. We comment on the uncertainties affecting our understanding of the physical mechanisms responsible for a successful s-process. Finally, various types of spectroscopic observations of s-process elements are discussed.

In principle, band-limited coronagraphic image masks are capable of removing all on-axis starlight providing infinite dynamic range for the direct imaging of exoplanets. In practice, optical aberrations left uncorrected by the adaptive optics system and practical limitations on mask alignment prevent band-limited masks from reaching contrast levels necessary for exoplanet imaging. So-called, “high-order” band-limited masks reduce the coronagraph's sensitivity to low order aberrations, and have been measured to reach contrast levels of $10^{-7}$ at $4\, \lambda/D$ without the aid of a deformable mirror. In this work, we simulate the performance of high-order band-limited coronagraphic image masks in a variety of adaptive optics systems. We compare their performance with that of hard-edge stops, soft-edge Gaussian masks, and traditional (4th-order) band-limited coronagraphs.

TPF-I capability for planetary signal extraction, including both detection and spectral characterization, can be optimized by taking proper account of instrumental characteristics and astrophysical prior information. We have developed the Point Process Algorithm (PPA), a Bayesian technique for extracting planetary signals using the sine/cosine chopped outputs of a dual nulling interferometer. It is so-called because it represents the system being observed as a set of points in a suitably defined state space, thus providing a natural way of incorporating our prior knowledge of the compact nature of the targets of interest. It can also incorporate the spatial covariance of the exozodi as prior information which could help mitigate against false detections. Data at multiple wavelengths are used simultaneously, taking into account possible spectral variations of the planetary signals. Input parameters include the sigma of measurement noise and the a priori probability of the presence of a planet. The output can be represented as an image of the intensity distribution on the sky, optimized for the detection of point sources. Previous approaches by others to the problem of planet detection for TPF-I have relied on the potentially non-robust identification of peaks in a “dirty” image, usually a correlation map. Tests with synthetic data suggest that the PPA provides greater sensitivity to fainter sources than does the standard approach (correlation map + CLEAN), and will be a useful tool for optimizing the design of TPF-I.

The classical analysis of the s-process is commonly used to predict the s percentage contribution to the solar system abundance of a given isotope, and by default of the r-process residual (calculated as 1. - s). We discuss the advantages and the disadvantages of this first-order prediction, by comparing stellar model calculations at various metallicities in AGB stars and in massive stars exploding as SNII, with spectroscopic observations of different stellar populations. Observations of short-lived r-process isotopes in the early solar system help to characterize at least three different r-process components.

We propose that the observed difference in the formation rates of bright low-mass X-ray binaries in metal-rich and metal-poor globular clusters can be explained by taking into account the difference in the stellar structure of main sequence donors with masses between ${\sim}0.85 M_\odot$ and ${\sim}1.25 M_\odot$ at different metallicities. This difference is caused by the absence of an outer convective zone in metal-poor main sequence stars in this mass range. In the result, magnetic braking, a powerful mechanism of orbital shrinkage, does not operate and dynamically formed main sequence – neutron star binaries fail to start mass transfer or appear as bright low-mass X-ray binaries.

Chemical abundances and upper limits of three dozen elements have been derived for the binary blue metal-poor, extremely lead-rich star CS29497-030. The findings include a large contribution of s-process material (e.g., [Pb/Fe] >3.5) and a large contribution of r-process material (e.g, [Eu/Fe] ∼2), abundances which place it in the class of objects known as r+s stars. The ratio of [Zr/Nb] ∼0, along with its stellar parameters, indicates that it is not an intrinsic AGB star. Modelling the abundance distribution (which includes the first Bi abundance determination for any metal-poor star) with s-process calculations employing FRANEC models, there is excellent agreement with the observations by adopting a 1.3 M[odot ] AGB model with an enhanced 13C-pocket and a pre-enrichment of r-process material. In this scenario, the initial abundances of CS29497-030 and its binary partner arose from a parent cloud with an extreme r-process abundance, in which star formation was triggered by a core-collapse supernova which polluted, snowplowed, and clumped a nearby molecular cloud. Pollution from the former AGB star's dredged-up material subsequently enriched the envelope composition of CS29497-030 (Ivans et al. 2005). Critical tests of this model and scenario include the dependence of abundance ratios on systematics due to non-LTE effects, the choice of stellar parameters and model atmospheres, and the assumed abundance pattern of the protostellar cloud out of which the CS29497-030 binary system formed.