We present results from long-term optical photometric observations of the Pre-Main Sequence (PMS) stars, located in the star formation region around the bright nebula NGC 7129. Using the long-term light curves and spectroscopic data, we tried to classify the PMS objects in the field and to define the reasons for the observed brightness variations. Our main goal is to explore the known PMS stars and discover new, young, variable stars. The new variable PMS star 2MASS J21403576+6635000 exhibits unusual brightness variations for very short time intervals (few minutes or hours) with comparatively large amplitudes (ΔI = 2.65 mag).

Two-dimensional emission line images of the HH30 jet were recently used (De Colle et al. 2010) to recover the three-dimensional structure of the jet by applying standard tomographic technique (“Tikhonov regularization techniques”). In this paper I show that it is possible to determine the ejection history of the HH30 jet by directly comparing the outcome of numerical simulations with the results of the tomographic inversion. In particular, it is shown that the HH30 jet electron density map is best reproduced by assuming a velocity variation at the base of the jet with a large scale periodicity (with a period of ~3 yrs) added to small scales velocity variation (with periods ≲months).

Jet formation MHD simulations are presented considering a variety of model setups. The first approach investigates the interrelation between the disk magnetisation profile and jet collimation. Our results suggest (and quantify) that outflows launched from a very concentrated region at the inner disk tend to be weakly collimated. In the second approach, jet formation is investigated from a magnetic field configuration consisting of a stellar dipole superposed by a strong disk field. We find that the central dipole considerably de-collimates the disk wind. In addition, reconnection flares are launched in the interaction region of disk and stellar magnetic field, subsequently changing the outflow mass flux by factors of two. The time interval between flare ejection is about 1000 Keplerian periods - surprisingly similar to the observed time lag between jet knots. The third approach considers radiative pressure effects on jet collimation - an environment which is interesting mainly for outflows from massive young stars (but also for relativistic jets). Finally we present relativistic MHD simulations of jet formation from accretion disks extenting the previous non-relativistic approaches.

Protostellar outflows can inject sufficient mass, momentum, and kinetic energy into their parent star-forming clumps to dramatically alter their structure, generate turbulence, and even to disrupt them. Outflows represent the lowest rung on a ‘feedback ladder’ consisting of increasingly powerful mechanisms which kick-in if star formation escalates towards the production of more massive stars, higher efficiency, and larger clusters. Outflow feedback may dominate turbulence generation and cloud disruption on the scale of cluster-forming clumps having dimensions up to a few parsecs. Outflows inject energy and momentum on a wide-range of length-scales from less than 0.01 pc to over 30 pc. However, they fail by several orders of magnitude to inject sufficient momentum and kinetic energy to drive turbulent motions on the size and mass-scales of GMCs. Injection from higher rungs on the feedback ladder or momentum injected by Galactic-scale processes are needed to power the observed turbulence on the 10 to 100 pc scales of GMCs.

The birth of a young star is accompanied not only by accretion but by the expulsion of matter as well in the form of a collimated outflow. These outflows are seen at various wavelengths from X-rays to the radio band, but ultimately the driving mechanism appears to be a highly collimated supersonic jet that contains not only atomic but molecular components as well. These jets may also play a key role in the star formation process itself since they could be one of the primary mechanism for removing angular momentum from the accretion disk thereby allowing accretion to occur. Whereas much is known about their propagation on large-scales (i.e., hundreds of AU to several parsecs) from both observations and simulations, we must explore the “central engine” in order to understand how they are generated. While this is particularly challenging, high spatial resolution studies are beginning to reveal interesting data from which we can confront the various models. In this review, I will summarise what these studies suggest and note how they already favour certain models over others. I will also describe some of the results from spectro-astrometry and interferometry that are revealing details of outflows on milliarcsecond scales from the source.

Jets from newly-formed stars plow into the surrounding ISM, creating nebulous regions known as Herbig-Haro (HH) objects. Signatures of C-type shocks have been found in many HH objects. Models of shock-excited 1720-MHz OH masers associated with SNRs suggest that the masers could be signposts of C-type shocks. We have conducted a 1720MHz survey towards a number of HH objects to see if any shock-excited masers occur in association with these objects. Some results of our search are reported. When present, the 1720-MHz OH line can occur as emission, absorption or as P Cygni profiles. OH mainline emission is found in many of our sources. We have identified several potential 1720-, 1665- and 1667-MHz OH masers.