We discuss the importance of multiwavelength (optical, infrared, millimetre, and radio), high angular resolution (arcsec to subarcsec) observations in studying star and planet formation. We provide a few illustrative examples, and briefly discuss how future observational facilities will allow a yet more detailed view of the important processes at work.

X-ray timing observations of neutron stars and black holes are among the few available probes of ultrastrong magnetic fields, strong gravity, high densities, and the propagation of thermonuclear burning. Here we review the evidence for these effects revealed with data from the Rossi Explorer in the last five years. We also discuss the exciting prospects for making the first quantitative tests of strong-gravity general relativistic predictions with a large-area X-ray timing mission.

44 VLBA observations of the 43 GHz SiO masers in the circumstellar envelope surrounding the Mira variable TX Cam reveal dramatic structural variations over the 80 week stellar cycle. The dominant dynamical mode is one of expansion although other complex motions are visible. The gravitational field of the star does not have a significant effect on the dynamics observed, these are probably governed more by the magnetic field and the effects of the shock waves resulting from the pulsation of the Mira itself.

With the advent of new correlators and dedicated arrays, spectral line VLBI is entering its ascendancy as a probe of a variety of interesting astrophysical environments. One of the most interesting environments where spectroscopic VLBI techniques are valuable are the regions directly coincident with forming stars. In these sources, water maser emission is observed when the outflowing jets of material interact with the surrounding medium. Observations of these water masers dramatically reveal the innermost regions of the star formation process at or below the 1-AU scale.

We have found that the water masers clearly trace the jets at these scales. The masers show space motions on the order of 60 to 100 kms−1 and form within a few AU of the exciting protostar. By observing the distributions and motions of the water masers associated with these objects, we may be able to address in greater detail the collimation mechanism of the jets seen in these protostars.

In this brief poster proceeding, we provide a summary image of the water masers associated with SVS13, the driving source for the HH 7-11 objects. We have also mapped the masers associated with IRAS 16293-2422, IRAS 05413-0104, IRAS 4A and IRAS 4B, both in the NGC 1333 star forming region. For further information on these sources, please contact any of the authors directly.

The fine structure of active regions in Orion KL has been studied. It is shown that accretion disks and bipolar outflows accompany star formation. The accretion disks are divided into protoplanetary rings. The H2O super maser emission is associated with the rings and bipolar outflows. The surrounding medium (VLSR=7.74 km/s) amplifies the emission within the maser window by more than two orders of magnitude.

Classical novae are interacting binary stars in which a thermonuclear runaway in material accreted onto a white dwarf from a companion red dwarf results in the ejection of around 10−4M⊙ at hundreds to thousands of kilometres per second. Recent Hubble Space Telescope and MERLIN imaging of the expanding ejecta from several classical novae are presented. In general the ejecta are clumpy but often display coherent structures, most notably equatorial rings of enhanced emission encircling prolate ellipsoidal shells. Physical mechanisms (including the common envelope phase and anisotropic irradiation of the shell) which may result in the generation of these structures are discussed.

We compare the properties of jets found in extragalactic sources with those recently discovered in the much lower luminosity microquasars in our galaxy.

The radio-jet X-ray binary SS433 was observed at five epochs in 1998 by the very long baseline interferometry (VLBI) technique at five frequencies ranging from 1.6 to 22 GHz. The innermost region of the source on milliarcsecond scales (1 mas = 5 AU) is resolved into an eastern and a western core-jet component, well separated by the Central Radio Gap (25-30 AU projected size), where the binary stellar system is located. We suggest that the radio gap is caused by local synchrotron self-absorption and external free-free absorption in an ionized medium, which has a disk-like geometry. On 100 AU scales we observe the Equatorial Emission Region, oriented roughly perpendicularly to the jets, with variable morphology at different epochs. Both of these phenomena could be interpreted with a mass outflow from the system, concentrated in the orbital plane of the binary.

The object SS433 is a well-known source of relativistic jets, which are formed in supercritical accretion disk. It is very probable that the disk has polar channels and their radiation is collimated (the photo-cones). A face-on SS433 object can appear as ultra-bright and highly variable X-ray source, Lx ˜ 1040 − 1042 erg/s. We discuss the properties of these hypothetical objects and their frequency expected in galaxies. We describe a search for such objects using the ROSAT All Sky Survey and RC3 catalog of galaxies. Among the total 418 positive correlations we find that 142 sources in S and Irr galaxies are unknown as AGNs. Nuclear sources among them still contain many AGNs. Non-nuclear (offset) sources are rather hard, their X-ray luminosities are 1039 − 1041 erg/s. Their observed frequency is about 4–5% per galaxy, that is in agreement with expected frequency of the face-on SS 433 stars. The only way to recognize such stars is their expected violent variability in X rays.

We have made multi-epoch observations of the unusual X-ray binary star LSI + 61°303 using the HALCA spacecraft in combination with a large array of ground radio telescopes. We present initial analysis of six observing epochs during a radio outburst. The images reveal an apparently stationary pattern of symmetric emission extending about 2 mas on either side of a central source. The central source is observed to expand at a rate of 0.25 mas/day. At the distance to LSI + 61°303, this corresponds to ∼ 860 km/s.

From proplyds to champagne flows, spanning 4 orders of magnitude in size and density, photoevaporation flows are ubiquitous in H II regions. Such flows are also found in planetary nebulae, in the form of cometary knots, although in this case the flows are often “advection-dominated”, unlike the “recombination-dominated” flows that predominate in H II regions.

We investigate the global stellar wind dynamics of the exciting star of the Orion Nebula by using the “proplyds” and their bowshocks as probes of the ram pressure balance conditions in the nebula. This careful analysis is only possible if high resolution data are available, since the proplyds are so small and the bowshocks are so faint.

VLA detections have been made of 8 sources in the Galactic center Arches cluster. All sources have spectra consistent with those expected for stellar wind emission. Positional correspondence between these sources and near-infrared detections of mass-losing stars confirms that we are detecting stellar wind emission from Arches cluster members.

We present high angular resolution centimeter and millimeter continuum observations of several galactic massive star formation regions. Using calibration techniques pioneered at the Very Large Array, we are able to obtain high quality images even under adverse conditions of phase stability. Techniques such as these will be essential if future millimeter arrays are to obtain high quality and high precision images. We provide a current summary of our on-going survey, and present images and a brief discussion of several of the more intriguing sources.

We report the study of ISOGAL fields in the outer galactic bulge (-1.5° < l < +1.6°, −2.6° < b < + 6.0°, area ∼ 0.42 deg2). We have combined 15 μm and 7 μm ISOCAM observations with 2MASS JHKS data to determine the nature of the sources and the interstellar extinction. Most of the ISOGAL sources show evolution of mass-loss rates in the range 3×10−8 to 1 × 10−6 (M⊙/year). Most of the detected sources are red giants above the RGB tip; a few of them show an excess in J-Ks and Ks-[15] colors. These sources are AGB stars with large mass-loss rates.

In this paper, by discussing and analyzing the observational results of near infrared imaging, optical spectroscopy and 12CO molecular line, together with IRAS and NVSS data, we conclude that WB89 520 is an UC HII region with a very young compact stellar cluster. The spectrum of the UC HII region shows that it is an extremely metal-poor nebula, which has the lowest line ratio of [NII]/Hα (∼ 1/56) discovered in the nebulae of our Galaxy until now. We give two possible explanations for the low metallicity.

In active massive star forming regions such as Orion and the Galactic center, the self-gravitational instability of a magnetized gaseous slab plays an important role as a trigger of star formation. In such high external pressure regions, the incompressible mode of self-gravitational instability (Elmegreen & Elmegreen 1978; Lubow & Pringle 1992) becomes dominant. Based on two-dimensional hydrodynamical simulations, Umekawa et al. (1999) proposed “Star formation by merging of the Jeans stable clumps” in a pressure bounded slab. In a magnetized slab confined by external pressure, Nagai et al. (1998) showed by linear analysis that the slab fragments to filaments parallel to the magnetic field lines. Here, we show by nonlinear three-dimensional MHD simulations that the filaments further fragment to Jeans stable clumps.

The advent of long-baseline optical and infrared interferometers has meant that spatially resolved studies of stellar atmospheres have now become routinely possible. While prototype arrays, which have typically operated with short baselines and limited sensitivity, have produced exciting preliminary results, it is the development of larger dedicated facility arrays, such as the CHARA, Keck, and VLT interferometers, that offer the best prospects for advancing astrophysics. In this paper I review the possibilities and limitations of interferometric studies of stellar atmospheres, and highlight some recent results from optical/IR spatial interferometry.

Lunar occultation observations at 2.2 microns of the inner dust shell of the carbon rich long period variable IRC + 10216 yield a clumpy structure with atleast four components. Comparison with concurrent and earlier speckle observations confirm the presence of these components and show that real spatial changes are taking place at the level of milli arcseconds on time scales of a few years in the inner dust shell of IRC + 10216.

We present visibility measurements of the nearby Mira-like star R Doradus taken over a wide range of wavelengths (650-990 nm). The observations were made using MAPPIT (Masked APerture-Plane Interference Telescope), an interferometer operating at the 3.9-m Anglo-Australian Telescope. We used a slit to mask the telescope aperture and prism to disperse the interference pattern in wavelength. We observed in R Dor strong decreases in visibility within the TiO absorption bands. The results are in general agreement with theory but differ in detail, suggesting that further work is needed to refine the theoretical models.