In the context of extrasolar planet direct detection, we evaluated the performance of differential imaging with ground-based telescopes. This study was carried out in the framework of the VLT-Planet Finder project and is further extended to the case of Extremely Large Telescopes. Our analysis is providing critical specifications for future instruments mostly in terms of phase aberrations but also regarding alignments of the instrument optics or offset pointing on the coronagraph. It is found that Planet Finder projects on 8m class telescopes can be successful at detecting Extrasolar Giant Planets providing phase aberrations, alignments and pointing are accurately controlled. The situation is more pessimistic for the detection of terrestrial planets with Extremely Large Telescopes for which phase aberrations must be lowered at a very challenging level.

Areas surveyed for ELT projects using satellite data are described. A synopsis of the methodology used is given and selected results from recent studies are presented.

Ground and space based coronagraphs have been proposed to suppress the light of the star so a planet nearby can be imaged. But even when starlight has been suppressed by $10^{10}$, the residual starlight is as bright as the planet, and must be subtracted to $2*10^{-11}$ for a 5 sigma detection of the planet. For a ground based AO coronagraph, the problem is even more severe. Typically suppression of starlight to $10^{-5}$ of the star is possible and the residual speckle pattern must not have any “bumps” that mimic a planet at $10^{-7}-10^{-8}$. This paper describes a speckle calibration approach that measures the electric field of the light after it exits the coronagraph, in order to estimate the speckle pattern in the image plane. This technique makes use of the coherence of star light or rather the incoherence of starlight to planet light, and has very significant advantages compared to other techniques.

For a space based coronagraph, an alternative approach is to rotate the telescope /coronagraph and subtract two images. The calibration interferometer described here has the advantage that the temporal stability of the system can be relaxed by several orders of magnitude. For a ground based AO coronagraph system this approach has none of the serious limitations of the techniques based on the radial expansion of the speckle pattern with wavelength and enables ground based AO coronagraphs to approach the photon limit rather than the atmospheric limit. The calibration interferometer is being built for a NASA sounding rocket experiment by BU, JPL, MIT, and GSFC (PICTURE) with a 50cm telescope and a nulling coronagraph to be launched in 2007. It is also part of a design study for an extreme AO coronagraph for the Gemini Telescope, and a conceptual study of an extreme AO coronagraph for the TMT.

INTEGRAL is the first gamma-ray astronomy mission with a sufficient sensitivity and angular resolution combination appropriate to the detection and identification of considerable numbers of gamma-ray emitting sources. The large field of view enables INTEGRAL to survey the Galactic Plane on a regular ($\sim$weekly) basis as part of the core programme. The first source catalogue, based on the 1st year of core programme data ($\sim$5 Msec) has been completed and published (Bird et al. 2004). It contained 123 $\gamma$-ray sources (24 HMXB, 54 LMXB, 28 “unknown”, plus 17 others) - sufficient numbers for a reasonable statistical analysis of their global properties. The detection of previously unknown $\gamma$-ray emitting sources generally exhibiting high intrinsic absorption, which do not have readily identifiable counterparts at other wavelengths, is intriguing. The substantial fraction of unclassified $\gamma$-ray sources suggests they must constitute a significant family of objects. In this paper we review the global characteristics of the known galactic sources as well as the unclassified objects.

Accurate relative abundances of light elements (C to Ca) have been obtained in a sample of mildly metal-poor stars (Decauwer et al. 2005). Combined with the results of a previous study (Jehin et al. 1999), we find different slopes in the correlations between the different α-elements. These results can be explained by postulating that the stars exhibiting lower than average α/Fe form in low mass clouds, unable to sustain the formation of very massive stars.

We present the first results of our X-ray monitoring campaign using the X-ray satellites XMM-Newton and Chandra on the 1.7 square degree region centered on Sgr A*. The purpose of this campaign is to monitor the X-ray behavior of X-ray sources (both persistent and transient ones) which are too faint to be detected by monitoring instruments aboard other satellites currently in orbit (e.g., RXTE, Integral, Swift). Our first observations were obtained on June 5, 2005, using the HRC-I detector aboard Chandra. Here we briefly discuss our results on the very faint X-ray transients we detected during these observations. We detected new outbursts (with peak luminosities close to $10^{36}$ erg s$^{-1}$) of the two very faint transients GRS 1741.9–2853 and XMM J174457-2850.3, as well as a potential new very faint X-ray transient with an outburst luminosity of a few times $10^{34}$ erg s$^{-1}$.

Stars in globular clusters exhibit abundance patterns such as the well-known O-Na and Mg-Al anticorrelations which have no counterpart among halo stars. Whereas winds from AGB stars have been proposed as the primordial sources for these anomalies, the impact of rotation in these stars has not been studied in the GC context. To address this issue we present a model of a rotating AGB star with an initial mass of 7 M[odot ] and a metallicity Z = 10−5. We discuss the effect of rotation on the evolutionary features, and focus on the surface abundances which can be modified by rotation, dredge-up events and hot bottom burning.

We describe the rationale and requirements for an integral-field spectrograph aboard NASA's Terrestrial Planet Finder Coronagraph.

Following the tracks of Malbet, Yu, & Shao (1995) on dark hole algorithms, we present analytical methods to measure and correct the speckle noise behind an ideal coronagraph. We show that, in a low aberration regime, wavefront sensing can be accomplished with only three images, the next image being fully corrected (no iterative process needed). The only hardware required is the coronagraph deformable mirror and an imaging detector in the focal plane, thus there are no non-common path errors to correct. Our first method, speckle field nulling, is a fast FFT-based algorithm requiring the deformable mirror influence functions to have identical shapes. Our second method, speckle energy minimization is more general and based on matrix inversion. Numerical simulations show that these methods can improve the contrast by several orders of magnitude.

As part of a program of abundance studies of old open clusters, we present an analysis of high-dispersion echelle spectra of three giant stars in the 10 Gyr old cluster Berkeley 17. Abundances were determined relative to the disk giant Arcturus. Be 17 is found to have a mean [Fe/H] = −0.10 ±0.05 (mean error). Oxygen abundances, determined from the forbidden [O I] lines, show solar abundance ratios. The α-elements Mg, Ca, and Ti also show scaled solar abundance ratios, with suggestions that the Si abundance is slightly enhanced. The odd-Z elements Na and Al are significantly enhanced relative to scaled solar abundances. These abundance patterns are similar to those in two other 8-10 Gyr old open clusters, Cr261 and NGC 6791, and suggest that the Galactic disk was enriched to solar abundance levels at very early times.

Shell-like supernova remnants (SNRs) are primary candidates for the origin of Galactic cosmic rays. However, among the known SNRs (about 220), only a small fraction has been known to exhibit the synchrotron X-ray spectrum, that is considered to be a piece of evidence for high energy particle acceleration. Synchrotron X-ray emitting SNRs are known to be systematically radio-quiet compared to the SNRs that do not emit synchrotron X-rays. Therefore, most synchrotron X-ray emitting SNR candidates may have escaped detection in the previous systematic radio surveys. On the other hand, hard X-ray surveys are effective to search for synchrotron X-ray emitting SNRs, because of its penetration power. Thus we have searched for SNRs in the ASCA Galactic Plane Survey data, the first Galactic imaging survey in $>$2 keV, and discovered 14 candidates. Deep follow-up observations with ASCA, XMM, or Chandra on 5 of them revealed 2 sources to be synchrotron X-ray emitting SNRs. Furthermore we confirmed non-thermal X-ray spectra from the other 3 sources, though the origin is yet unknown. We report the observational results and discuss the X-ray origin.

Fundamental parameters and lithium abundances, ALi, have been derived for a sample of evolved stars in the globular cluster 47 Tuc (from GIRAFFE spectra and MARCS models of atmosphere). These data sample a complete evolutionary sequence from subgiant stage to the tip of the Asymptotic Giant Branch. With this unique observational data set we have analyzed the evolution of ALi along the Red Giant Branch (RGB) using non-standard stellar evolution models, so as to explore the occurence and the efficiency of extra-mixing processes in low mass stars at the so-called Red Giant bump.

Recent studies suggested that there might be a correlation between unidentified $\gamma$-ray sources from the third EGRET catalogue and OB associations. Moreover, when extrapolating the fluxes measured by EGRET at energies above 100 MeV with a power-law down to the energy range of ISGRI, the expected count rates should be large enough to be detectable with INTEGRAL. Most of those OB associations being located in the Galactic plane, they are monitored by INTEGRAL as part of the Core Program during both the Galactic Plane Scans and the Galactic Center Deep Exposure. Combining public and CP data, we have performed a search for gamma-ray emission from OB associations and the first results are presented.

High contrast imaging from space must overcome photon noise of the diffracted star light and scattered light from optical components defects. The very high contrast required (up to $10^{-10}$ for terrestrial planets) puts severe requirements on the wavefront control system, as the achievable contrast is limited by the quality of the wavefront. In this paper we present a closed loop correction method for the shaped pupil coronagraph to minimize the energy in a pre-defined region in the image where terrestrial planets would be found. The reconstruction part uses three intensity measurements in the image plane with a pinhole added to the shaped pupil for diversity. This method has been shown in simulations to be effective in the presence of photon noise, deformable mirror modeling errors and overcoming defective actuators in the deformable mirror.

Nulling interferometers such as Darwin or TPF will require a rather sophisticated data processing in order to perform a reliable planet detection and characterization. We propose a Bayesian method, which follows the maximum a posteriori (MAP) approach, to solve this problem. Our method accounts for the noise statistics and optimally combines the data from a nulling interferometer at all observed wavelengths to perform reliable planet detection. The problem to be solved is however multi-modal. We show how, in practice, the global optimum of the MAP criterion can be found by our method; the latter also provides the most likely spectral energy distributions of all planets. Additionally, we show that a proper regularization allows us to achieve an improved robustness of the detection and could lead to shorter observation times.

We study high mass X-ray binaries (HMXBs) in the Galaxy using data of the INTEGRAL observatory. High sensitivity survey of the whole Galaxy with a possibility to detect absorbed sources significantly enlarged our sample of HMXBs in a comparison with the previous studies. Large fraction of detected high mass X-ray binaries is highly photoabsorbed. We investigated the HMXBs distribution along the Galactic plane and found their strong concentrations toward Galactic spiral arms, confirming previous results of Grimm et al. (2002) obtained using smaller sample of sources. We conclude that the mapping of Galactic HMXBs should be important tool to trace the star formation regions at the opposite side of the Galaxy.

We present elemental abundance ratios for red giant stars in 9 old halo globular clusters based on the homogeneous data sample and analysis method. Our result suggests that [Si/Ti] ratios in old globular clusters decrease with Galactocentric distances, confirming the previous result by Lee & Carney (2002). We propose that contributions from different masses of the Type II suprenovae progenitors that enriched proto-globular clusters' clouds are responsible for this gradient.

We have observed seven giants in the metal-poor globular cluster M15 using Subaru/HDS. We confirmed that there are significant star-to-star variations in the neutron-capture elemental abundances. This abundance variation means there were primordial chemical inhomogeneities in the proto-globular cluster cloud of M15. This result implies that there was insufficient time for complete mixing after r-process nucleosynthesis. It suggests that the main r-process occurs probably in supernovae which explode in later stages of globular cluster formation.

An analysis of the high-energy emission from IGR J16393–4643 is presented using data from INTEGRAL and XMM-Newton. The source is persistent in the 20–40 keV band at an average flux of $5.1\times10^{-11}$ergs cm$^{-2}$ s$^{-1}$, with variations in intensity by at least an order of magnitude. A pulse period of 912$\,{\pm}\,$3 s was discovered in the ISGRI and EPIC light curves. The source spectrum is a strongly-absorbed ($N_{\mathrm{H}}=(2.5\,{\pm}\,0.2)\times10^{23}$ cm$^{-2}$) power law that features a high-energy cutoff above 15 keV. Two iron emission lines at 6.4 and 7.1 keV, an iron absorption edge $\gtrsim$7.1 keV, and a soft excess emission of $7\times10^{-15}$ergs cm$^{-2}$ s$^{-1}$ between 0.5–2 keV, are detected in the EPIC spectrum. The shape of the spectrum does not change with the pulse. Its persistence, pulsation, and spectrum place IGR J16393–4643 among the class of heavily-absorbed HMXBs. The improved position from EPIC is R.A. (J2000)$=16^{\mathrm{h}}39^{\mathrm{m}}05.4^{\mathrm{s}}$ and Dec.$=-46^{\circ}42'12''$ ($4''$ uncertainty) which is compatible with that of 2MASS J16390535–4642137.

The performance of high contrast imaging systems is very often limited by the presence of static speckles in the point-spread function of the central source. Several techniques have already been proposed to discriminate a faint companion from these residual speckles. These techniques used different criteria to separate a speckle from a companion: polarization, spectral information or coherence. Here, we propose a new imaging device, the Self-Coherent Camera (SCC), that is based on the lack of coherence between the stellar light and the planet that is searched for. This SCC is a simple instrument that allows us to reach the fundamental limitation of the photon noise by calibrating the speckles in the recorded images. After the description of the general problem of discriminating speckles from planets, we will explain the principle of the SCC. Then, we will analyze the different limitations of this technique as well as the performance that can be reached with current telescopes.