We present the results of a Chandra observation made of the nearby spiral galaxy NGC 7793: the effective exposure time of this observation was 49094 seconds. Twenty-two discrete sources were identified at a minimum of a 3$\sigma$ level to an estimated limiting luminosity of ∼$2\times10^{36}$ ergs sec$^{-1}$. We have performed a spectral analysis of the known ultraluminous X-ray source (ULX) in this galaxy: statistically-acceptable fits to the spectrum can be obtained with either a power law model, a bremsstrahlung model or a DISKBB model. We have also searched for counterparts at multiple wavelengths to these sources: based on this search, we have classified two supernova remnants, one HII region and two foreground stars.

We present results from an ongoing program to map the spatial distribution of ices in dark cloud cores with the Spitzer Space Telescope and VLT-ISAAC. The ice maps are used to directly trace the freeze-out of CO and the formation of H2O, CH3OH and CO2.

We present the results of an on-going program for the identification and characterization of optical counterparts of Ultra-Luminous X-ray (ULX) sources. The targets have been selected from the catalogues by Colbert & Ptak (2002) and Swartz et al. (2004). A clear identification based on unambiguous optical spectral features was possible for 26 objects. A large number of objects result to be QSOs at higher redshift than the putative parent galaxy, and other ULXs seem to be associated to HII regions. In a few cases the optical counterpart results a foreground star in our galaxy. The observational program will continue to obtain a representative sample for statistical studies.

An asteroid family is a group of asteroids with similar orbits and spectra that was produced by a collisional breakup of a large parent body. To identify asteroid families, researchers look for clusters of asteroid positions in the space of proper orbital elements. These elements, being more constant over time than osculating orbital elements, provide a dynamical criterion of whether a group of bodies has a common ancestor. More than fifty asteroid families have been identified to date. Their analysis produced several important insights into the physics of large scale collisions, dynamical processes affecting small bodies in the Solar System, and surface and interior properties of asteroids.

The Gamma-ray Large Area Space Telescope (GLAST) is an international and multi-agency space mission that will study the cosmos in the energy range 10 keV – 300 GeV. The GLAST Science Support Center (GSSC) is the scientific community's interface with GLAST. The GSSC will provide data, analysis software and documentation. In addition, the GSSC will administer the guest investigator program for NASA HQ. Consequently, the GSSC will provide proposal preparation tools to assist proposers in assessing the feasibility of observing sources of interest.

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.

We present results of optical follow-up observations of candidate ultra-luminous X-ray sources (ULXs). Using Keck optical spectroscopy, 17 of the candidates from the Colbert & Ptak (2002) catalog have been identified; this is one of the largest sets of optical identifications of such objects thus far. 15 are background active galactic nuclei (AGN); 2 are foreground stars in our Galaxy. These findings are compared with background and foreground object expectations, as derived from log $N$-log $S$ relations. Also, the results are briefly discussed in terms of the spiral-galaxy/ULX connection.

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.

Outer satellites of the planets have distant, eccentric orbits that can be highly inclined or even retrograde relative to the equatorial planes of their planets. These irregular orbits cannot have formed by circumplanetary accretion and are likely products of early capture from heliocentric orbit. The irregular satellites may be the only small bodies remaining which are still relatively near their formation locations within the giant planet region. The study of the irregular satellites provides a unique window on processes operating in the young solar system and allows us to probe possible planet formation mechanisms and the composition of the solar nebula between the rocky objects in the main asteroid belt and the very volatile rich objects in the Kuiper Belt. The gas and ice giant planets all appear to have very similar irregular satellite systems irrespective of their mass or formation timescales and mechanisms. Water ice has been detected on some of the outer satellites of Saturn and Neptune whereas none has been observed on Jupiter's outer satellites.

Recent years have seen substantial progresses in our understanding of solar type protostellar structure, and particularly of the chemical structure of the protostellar envelopes. On the one hand, the cold outer regions keep intact the memory of the previous pre-collapse phase, when the dust is so cold and dense that almost all molecules freeze out onto the dust grain mantles. The gas-phase chemical composition undergoes dramatic changes, the most spectacular aspect of which is the huge increase of the molecular deuteration degree, which can reach 13 orders of magnitude with respect to the elemental D/H ratio. On the other hand, in the innermost regions of the envelope – the so-called hot corinos – the grain mantles evaporate when the dust temperatures exceed 100 K, injecting into the gas phase hydrogenated molecules, such as formaldehyde and methanol. Those molecules probably undergo chemical reactions that form more complex organic molecules, which have now also been observed in low-mass hot corinos. In this contribution, I review what we have and have not recently understood concerning both the cold envelopes and the hot corinos of solar-type protostars.

On 4 July 2005 at 5:52 UT the Deep Impact mission successfully completed its goal to hit the nucleus of 9P/Tempel 1 with an impactor, forming a crater on the nucleus and ejecting material into the coma of the comet (A'Hearn et al. 2005). The 370 kg impactor collided with the sunlit side of the nucleus with a relative velocity of 10.2 km s$^{-1}$. NASA's Submillimeter Wave Astronomy Satellite (SWAS) observed the $1_{10}-1_{01}$ ortho-water ground-state rotational transition in comet 9P/Tempel 1 before, during, and after the impact. No excess emission from the impact was detected by SWAS. However, the water production rate of the comet showed large natural variations of more than a factor of three during the weeks before the impact.

We report the first astronomical detection of the CF$^+$ (fluoromethylidynium) ion, obtained by recent observations of its $J = 1-0$ (102.6 GHz), $J = 2-1$ (205.2 GHz), and $J = 3-2$ (307.7 GHz) pure rotational emissions toward the Orion Bar. Our search for CF$^+$ — carried out using the IRAM 30m and APEX 12m telescopes—was motivated by recent theoretical models that predict CF$^+$ abundances of a $\rm few \times 10^{-10}$ in UV-irradiated molecular regions where C$^+$ is present. The measurements confirm the predictions. They provide support for our current theories of interstellar fluorine chemistry, which suggest that hydrogen fluoride should be ubiquitous in interstellar gas clouds.

We present a new analysis of the light curve of the secondary star in the PSR B1957+20 system. Combining previous data and new data points at minimum from the Hubble Space Telescope, we have 100% coverage in the R-band. We also have a number of new K$_s$ band data points, which we use to constrain the IR magnitude of the system. We model this with the Eclipsing Light Curve code. From the modeling we obtain colour information about the secondary at minimum in BVRI & K. For our best fit model we are able to constrain the system inclination to 66.6 $\pm$ 2.1$^o$ for pulsar masses ranging from 1.35 – 1.9 M$_{\odot}$. The pulsar mass is unconstrained. We also find that the secondary is not filling its Roche lobe, which has important consequences for evolutionary models of this system. The temperature of the un-irradiated side of the companion is in agreement with previous estimates.

We present a study of the variable X-ray source populations in the Antennae galaxies and a small sample of nearby star-forming galaxies. We find that source variability does not affect the shape of their X-ray luminosity functions. Several of the sources detected in the Antennae exhibit a wide range of spectral variability patterns. Finally, from our study of a small sample of nearby star-forming galaxies, we find a weak indication for variations of the shape of their luminosity functions.

We have investigated 136 Chandra extragalactic sources without broad emission lines, including 93 NELG and 43 ALG. Based on $f_X/f_O$, $L_X$, X-ray spectral hardness and optical emission line diagnostics, we have conservatively classified 36 normal galaxies (20 spirals and 16 ellipticals) and 71 AGNs. Their redshift ranges from 0.01 to 1.2, while normal galaxies are at z=0.01–0.3. Our sample galaxies appear to share similar characteristics with local galaxies in terms of X-ray luminosities and spectral properties, as expected from the X-ray binary populations and the hot ISM. In conjunction with normal galaxies found in other surveys, we found no statistically significant evolution in $L_X/L_B$, within the limited z range ($<$0.1). We have built our log(N)-log(S) relationship of normal galaxies in the flux range, $f_X$ (0.5–8.0) = $10^{-15}$–$10^{-13}$ erg sec$^{-1}$ cm$^{-2}$, after correcting completeness by a series of simulations. The best-fit slope is −1.5 for both soft (0.5–2.0 KeV) and broad (0.5–8.0 KeV) energy bands, which is considerably steeper than that of AGN-dominated cosmic background sources at faint fluxes, but slightly flatter than the previous estimate, indicating normal galaxies will exceed in number over the AGN population at $f_X<10^{-18}$ erg sec$^{-1}$ cm$^{-2}$.

We review processes leading to the orbital migration of bodies ranging from dust particles up to protoplanets in the earth mass range in protoplanetary disks. The objects most at risk of being lost from the disk have dimensions of the order of metres. To retain these it may be necessary to invoke either strong turbulence or trapping due to special flow features such as vortices. Migration also becomes important for protoplanets with mass exceeding $0.1M_{\oplus}$. In this case it can also lead to the attainment of commensurabilities for pairs of protoplanets. Such pairs could be left behind after disk dispersal. We review some recent work on the attainment of commensurabilities for protoplanets in the earth mass range.

The conventional picture of disk accretion onto magnetized neutron stars has been challenged by the spin changes observed in a few X-ray pulsars, and by theoretical results from numerical simulations of disk-magnetized star interactions. Here we present a model for the torque exerted by accretion disks on magnetized neutron stars, assuming accretion continues even for fast rotators.

The discovery of binaries in each of the major populations of minor bodies in the solar system is propelling a rapid growth of heretofore unattainable physical information. The availability of mass and density constraints for minor bodies opens the door to studies of internal structure, comparisons with meteorite samples, and correlations between bulk-physical and surface-spectral properties. The number of known binaries is now more than 70 and is growing rapidly. A smaller number have had the extensive followup observations needed to derive mass and albedo information, but this list is growing as well. It will soon be the case that we will know more about the physical parameters of objects in the Kuiper Belt than has been known about asteroids in the Main Belt for the last 200 years. Another important aspect of binaries is understanding the mechanisms that lead to their formation and survival. The relative sizes and separations of binaries in the different minor body populations point to more than one mechanism for forming bound pairs. Collisions appear to play a major role in the Main Belt. Rotational and/or tidal fission may be important in the Near Earth population. For the Kuiper Belt, capture in multi-body interactions may be the preferred formation mechanism. However, all of these conclusions remain tentative and limited by observational and theoretical incompleteness. Observational techniques for identifying binaries are equally varied. High angular resolution observations from space and from the ground are critical for detection of the relatively distant binaries in the Main Belt and the Kuiper Belt. Radar has been the most productive method for detection of Near Earth binaries. Lightcurve analysis is an independent technique that is capable of exploring phase space inaccessible to direct observations. Finally, spacecraft flybys have played a crucial paradigm-changing role with discoveries that unlocked this now-burgeoning field.

Since its launch in October 2002, ESA's INTEGRAL observatory has enabled significant advances to be made in the study of Galactic nucleosynthesis. In particular, the imaging Ge spectrometer SPI combines for the first time the diagnostic powers of high resolution gamma-ray line spectroscopy and moderate spatial resolution. This review summarizes the major nucleosynthesis results obtained with INTEGRAL so far. Positron annihilation in our Galaxy is being studied in unprecented detail. SPI observations yield the first sky maps in both the 511 keV annihilation line and the positronium continuum emission, and the most accurate spectrum at 511 keV to date, thereby imposing new constraints on the source(s) of Galactic positrons which still remain(s) unidentified. For the first time, the imprint of Galactic rotation on the centroid and shape of the 1809 keV gamma-ray line due to the decay of $^{26}$Al has been seen, confirming the Galactic origin of this emission. SPI also provided the most accurate determination of the gamma-ray line flux due to the decay of $^{60}$Fe. The combined results for $^{26}$Al and $^{60}$Fe have important implications for nucleosynthesis in massive stars, in particular Wolf-Rayet stars. Both IBIS and SPI are searching the Galactic plane for young supernova remnants emitting the gamma-ray lines associated with radioactive $^{44}$Ti. None have been found so far, which raises important questions concerning the production of $^{44}$Ti in supernovae, the Galactic supernova rate, and the Galaxy's chemical evolution.

Low-frequency ($f \leq 10^{-6}$ Hz) quasi-periodic variability observed from radioloud, jet-emitting Active Galactic Nuclei (AGNs) can provide substantial inductive support for the presence of close ($d \lesssim 0.1$ pc) supermassive binary black holes in their centers. Such periodic variability may arise, for example, due to differential Doppler boosting along helical jet paths driven by the orbital motion or jet precession. If the jet path is non-ballistic, travel time effects can lead to a strong reduction of the observable period by up to a factor of $\gamma_b^{-2}$. Here we suggest a binary model where the optical periodicity with timescale of several years is related to accretion disk interactions, radio periodicity to Newtonian jet precession and periodicities in the high energy bands to the orbital motion of the jet. We analyze the explanatory potential of such a framework and comment on the possible origin of periodicities in AO 0235+16.