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Multi-epoch narrow-band HST images of the bipolar Hii region Sh2-106 reveal highly supersonic nebular proper motions which increase with projected distance from the massive young stellar object S106~IR, reaching over ~30 mas/year (~150 km/s at D=1.09 kpc) at a projected separation of ~1.4' (0.44 pc) from S106~IR. We propose that S106~IR experienced a $\sim10^{47}$ erg explosion ~3,500 years ago. The explosion may be the result of a major accretion burst, a recent encounter with another star, or a consequence of the interaction of a companion with the bloated photosphere of S106~IR as it grew from ~10 through ~15 Solar masses at a high accretion rate. Near-IR images reveal fingers of molecular hydrogen emission pointing away from S106~IR and an asymmetric photon-dominated region surrounding the ionized nebula. Radio continuum and Brackett-gamma emission reveal a C-shaped bend in the plasma, either indicating motion of S106~IR toward the east, or deflection of plasma toward the west by the surrounding cloud. The Hii region bends around a ~1' diameter dark bay west of S106~IR that may be shielded from direct illumination by a dense molecular clump. Herbig-Haro (HH) and Molecular Hydrogen Objects (MHOs) tracing outflows powered by stars in the Sh2-106 proto-cluster such as the Class 0 source S106 FIR are discussed., 47 pages, 24 figures

We present high-resolution $H$- and $K$-band spectroscopic observations of the archetypal T Tauri star T Tau North. Synthetic spectral modeling is used to derive the $K$-band temperature, surface gravity, magnetic field strength, and rotational velocity for this star. The $K$-band spectroscopic temperature measured is $\rm T_{K\text{-band}} = 3976 \pm 90 K$, which is $\sim 1000 \, \rm K$ cooler than the temperature measured from optical observations. Our $K$-band temperature measurement for T Tau N is confirmed using equivalent width line ratio vs. temperature relations in the $H$-band, from which a $\rm T_{H\text{-band}} = 4085 \pm 155 K$ is derived. This optical vs. IR temperature difference is interpreted as cool or hot spots, or both, covering a significant part of the surface of T Tau N. The gravity derived for T Tau N $\log{g}=3.45 \pm 0.14$ is lower than the gravity of nearly every other star in a sample of 24 classical T Tauri stars in Taurus. Combining these temperature and gravity results with magnetic stellar evolutionary models, we find the age of T Tau N to be less than 1 Myr old. These results suggest that T Tau N is in an earlier evolutionary stage than most classical T Tauri stars in Taurus, arguing that it is a protostar ejected from the embedded southern binary system shortly after its formation., 18 pages, 9 figures, 3 tables

In early 2008, the young low-mass star EX Lupi, the prototype of the EXor class of eruptive variables, optically brightened by over five magnitudes for a period of 7 months. The previous time a change of such amplitude had been observed in EX Lup was over 50 years ago. In this Letter we present new optical and near-IR high resolution spectroscopy of EX~Lup during the 2008 outburst. We investigate the physical characteristics of the outburst both soon after it began and some four months later, and consider the energetics and kinematics observed. Emission line strengths, widths, and profiles changed significantly between the two observations. Also, modeling of the 2.2935 um CO overtone bandhead emission suggests that an inner gap in the circumstellar gas disk around the star may be present and it is from the inner edge of the gas disk that the CO overtone emission probably arises. We derive a mass accretion luminosity and rate during the extreme outburst of ~2+-0.5~Lsun and ~2+-0.5x10^-7 Msun yr^-1, respectively, which suggests that this outburst was indeed one of the strongest witnessed in EX Lup, yet not as strong as those observed in FU Orionis stars., Comment: 5 pages, 4 figures

In late 2003, the young eruptive variable star V1647 Orionis optically brightened by over 5 magnitudes, stayed bright for around 26 months, and then decline to its pre-outburst level. In August 2008 the star was reported to have unexpectedly brightened yet again and we herein present the first detailed observations of this new outburst. Photometrically, the star is now as bright as it ever was following the 2003 eruption. Spectroscopically, a pronounced P Cygni profile is again seen in Halpha with an absorption trough extending to -700 km/s. In the near-infrared, the spectrum now possesses very weak CO overtone bandhead absorption in contrast to the strong bandhead emission seen soon after the 2003 event. Water vapor absorption is also much stronger than previously seen. We discuss the current outburst below and relate it to the earlier event., 6 pages, 3 figures

The faint star next to FU Orionis recently discovered by Wang et al. has been observed with adaptive optics at the Subaru Telescope. Infrared JHK'L' photometry shows clear infrared excess, indicating that the object is a pre-main-sequence star. Its infrared K-band spectrum is very different from that of FU Orionis and suggests a star of spectral type K. We discuss these observations in light of the hypothesis that FUors may be newborn binaries that have become bound when a small nonhierarchical multiple system breaks up. This scenario predicts that FU Orionis must be a close binary (

We present a study of McNeil's Nebula, a newly appeared reflection nebula in the L1630 cloud, together with photometry and spectroscopy of its source. New IR photometry compared to earlier 2MASS data shows that the star has brightened by about 3 magnitudes in the near-infrared, changing its location in a J-H/H-K diagram precisely along a reddening vector. A Gemini NIRI K-band spectrum shows strong CO-bandhead emission and Br-gamma is in emission, indicative of strong accretion. A Gemini GMOS optical spectrum shows only a red, heavily veiled continuum, with H-alpha strongly in emission and displaying a pronounced P Cygni profile, with an absorption trough reaching velocities up to 600 km s-1. This implies significant mass loss in a powerful wind. However, no evidence is found for any shocks, as commonly seen in collimated outflows from young stars. Apparently the eruption has dispersed a layer of extinction and this, together with the intrinsic brightening of the IRAS source, has allowed an earlier outflow cavity to be flooded with light, thus creating McNeil's Nebula., 9 pages, 5 figures

We have identified a major Herbig-Haro flow, HH 777, that is bursting out of the IC 1396N cometary cloud core. Near- and mid-infrared images reveal a very red object embedded in the center of the core, located on the symmetry axis of the large HH 777 flow, suggesting that this is likely the driving source. The projected separation of the working surface from the source is 0.6 pc. Additionally, 0.4 pc to the east of the source and on the flow axis, there is a faint, previously known HH object (HH 594) that may be part of the counterflow. It thus appears that we are seeing a blowout of a parsec-scale flow into the surrounding H II region. We study numerical simulations of a jet breaking out of a neutral cloud into a photoionized medium, and we reproduce the main features of the HH 777 flow.

We present new Chandra X-Ray Observatory observations of the L1551 molecular cloud in Taurus. We find a compact, but slightly resolved, X-ray source, displaced westward from the IRS 5 binary protostar by about 50-100 AU, which coincides with the base of the HH 154 protostellar jet. The column density of material lying in front of the X-ray source is more than an order of magnitude lower than the column density toward L1551 IRS 5. Thus, it is highly improbable that the X-rays come directly from the embedded protobinary. It is possible, however, that X-rays produced by one or both members of the IRS 5 binary escape through the outflow cavity and are scattered into the line of sight by a dense infalling envelope or material in the outflow. Constraints on the physical properties of the scattering medium are discussed. It is also possible that the X-rays are produced in situ by fast shocks at the base of the HH 154 jet. We consider several possible geometries for such shocks. The radiating plasma may be located behind standing shocks, where a wide-angle wind from one member of the IRS 5 binary is collimated into a jet, or behind shocks formed on the axis of the outflow, where winds from each member of the binary collide or where these winds impact a tilted circumbinary disk. To produce the observed X-ray luminosity and plasma temperature, shock velocities larger than 350 km s-1 are required, with a preshock hydrogen density of (1–10) × 103 cm-3. The implied postshock cooling length is around 800 AU, close to the observed length of the bright near-infrared [Fe II] emission in the inner portion of the HH 154 jet.

We report the discovery of a 4 pc long bipolar Herbig-Haro outflow driven by a 10 L☉ class I source, IRAS 05399-0121, which is deeply embedded within a submillimeter dust condensation in the LBS 30 cloud core in the Orion B molecular cloud north of NGC 2024. A highly collimated low-excitation jet, HH 92, emerges from an asymmetric infrared reflection nebula and breaks into a cluster of well-resolved Hα-bright bow shocks about 25 northwest of the source. We propose that the well-known objects HH 90 and 91, and some previously uncataloged shocks that lie along the axis of the HH 92 jet, trace a single giant outflow lobe ~3 pc in length. The object HH 93, which lies about 10' southeast of HH 92, traces the counterflow.

We present a long-slit spectrum of the Herbig-Haro object HH 111, obtained with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. This spectrum has a spectral resolution of ≈50 km s-1, so it gives a good picture of the kinematical properties of the observed object at very high angular resolution. We find that some of the knots along the jet are associated with sudden drops in the radial velocity (modulus), confirming that the emission from the knots is formed in shocks. We interpret the observed position-velocity diagrams in terms of a model of a jet from a variable source, and we attempt to carry out a reconstruction of the ejection velocity variability necessary for reproducing the observed kinematical structure.

New Hα and [S II] images of the HH 111 jet taken with the Hubble Space Telescope reveal marked proper motions and morphological changes when compared with similar images obtained 4 years earlier. Knots in the jet, which are dominated by emission from nested bow shocks, generally move ballistically, with no evidence for turbulent motions even in regions where the emission has a complex morphology. These bow shocks sometimes overtake one another; the new images show this occurred in knot L about 80 years ago. Photometric variability, clearly visible for the first time at subarcsecond scales, can confuse ground-based measurements that require many years between epochs to detect reliable proper motions. With the exception of the bow shock L, whose wings expand laterally, the jet moves mainly along its long axis. Because HH 111 lies nearly in the plane of the sky, the proper motions translate accurately to space velocities, which range from 220 to 330 km s-1 with a typical uncertainty of ±5 km s-1. The fastest knots are associated with object E at the base of the visible jet, where a cooling layer is in the process of forming behind one of the shocks. Velocity differences between adjacent knots within the optically bright part of the jet are typically 40 km s-1, in line with predictions of nonmagnetic shock models based on emission-line fluxes. This agreement limits the component of the magnetic field perpendicular to the axis of the jet to be 1 mG.

We have observed the Orion Molecular Clouds 2 and 3 (OMC-2 and OMC-3) with the Chandra X-ray Observatory (CXO). The northern part of OMC-3 is found to be particularly rich in new X-ray features; four hard X-ray sources are located in and along the filament of cloud cores. Two sources coincide positionally with the sub$mm$-$mm$ dust condensations of MMS 2 and 3 or an outflow radio source VLA 1, which are in a very early phase of star formation. The X-ray spectra of these sources show an absorption column of (1-3) x 10^23 H cm-2. Assuming a moderate temperature plasma, the X-ray luminosity in the 0.5-10 keV band is estimated to be ~10^30 erg s^-1 at a distance of 450 pc. From the large absorption, positional coincidence and moderate luminosity, we infer that the hard X-rays are coming from very young stellar objects embedded in the molecular cloud cores. We found another hard X-ray source near the edge of the dust filament. The extremely high absorption of 3 x 10^23 H cm^-2 indicates that the source must be surrounded by dense gas, suggesting that it is either a YSO in an early accretion phase or a Type II AGN (e.g. a Seyfert 2), although no counterpart is found at any other wavelength. In contrast to the hard X-ray sources, soft X-ray sources are found spread around the dust filaments, most of which are identified with IR sources in the T Tauri phase., Comment: 9 pages, To be appeared in ApJ v554 n2 Jun 20, 2001 issue, related press release is available at http://science.psu.edu/alert/Tsuboi11-2000.htm, Figure 1 and figure 2 with the best resolution is available at ftp.astro.psu.edu/pub/tsuboi/OMC/010205/

The Bok globule B175, located toward a giant region of patchy extinction 10° above the Galactic plane known as the Cepheus Flare, is currently engaged in a chance encounter with a B9.5 V star, producing a prominent reflection nebula, Ced 201. Partly owing to the presence of this star, a fairly accurate distance estimate of 400 pc can be derived for B175. An imaging and spectroscopic study of B175 led to the discovery of a new Herbig-Haro (HH) object, HH 450, emerging from a deeply embedded and cold IRAS source, 22129+7000. Furthermore, we find several parsec-scale filaments of emission that trace the rim of a new supernova remnant, G110.3+11.3, which appears to be approaching the globule. This remnant is located near the edge of a large, 6° radius H I and CO cavity that coincides with a bright diffuse soft X-ray enhancement, probably due to several recent supernova explosions. At 400 pc, G110.3+11.3 is one of the closer known supernova remnants. The supernova remnant and the HH flow appear to be heading toward a frontal collision in about 1000 yr.

We report the discovery of a dozen Herbig-Haro jets illuminated by the Lyman continuum and/or softer far-ultraviolet radiation fields of nearby high mass stars. Five irradiated outflows lie in the outer parts of the Orion Nebula and seven lie near the reflection nebula NGC 1333 in the Perseus molecular cloud. We propose that the UV radiation field has eroded residual material left over from the formation of these young source stars. Many of the irradiated jets exhibit unusual C-shaped bending. In the outskirts of the Orion Nebula, most irradiated jets bend away from the core of the nebula. On the other hand, in NGC 1333, the C-shaped jets bend back towards the cluster center. Jet bending in the Orion Nebula may be dominated by either the outflow of material from the nebular core or by the rocket effect pushing on the irradiated portion of a mostly neutral jet beam. But in NGC 1333, jet bending may indicate that the source stars have been ejected from the cluster core. Many irradiated jets are asymmetric with one beam much brighter than the other. When fully photo-ionized, irradiated jets may provide unique insights into the physical conditions within outflows powered by young stars, permitting the determination of the density and location of stellar ejecta even in the absence of shocks. We present a model for the photo-ionization of these outflows by external radiation fields and discuss possible mechanisms for producing the observed asymmetries. We demonstrate that the UV radiation field may alter the amount of cloud material entrained by the jet. We also report the discovery of some large scale bow shocks which face the core of the Orion Nebula and which surround visible young stars. These wind-wind collision fronts provide further evidence for a large scale mass flow originating near the nebular core., Comment: 36 pages, 15 figures

We have mapped the CO J = 1-0 emission from molecular outflows associated with five young stellar systems of class 0 to class II/III using the BIMA array and the FCRAO 14 m antenna. The systems, VLA 05487, HH 212, HH 240/241, HH 111, and RNO 91, are all relatively nearby and of low luminosity, and the majority have H2 emission or optical jet features. The CO outflow generally forms a shell structure around the outflow axis with the higher velocity emission further out from the source. Two distinctive kinematic features are evident in position-velocity (PV) diagrams: a parabolic structure originating at the driving source (e.g., VLA 05487 and HH 111) and a convex spur structure with the high-velocity tip near known H2 bow shocks (e.g., HH 212, HH 240/241 and HH 111). The parabolic PV structure can be produced by a wide-angle-wind model, while the velocity spur structure can be modeled with a jet-driven bow shock model. VLA 05487, which is not associated with any H2 bow shocks, shows only the parabolic structure and kinematics consistent with the wide-angle wind-driven model. HH 212, which is associated with a series of H2 bow shock structures, shows a striking morphological coincidence between the H2 and CO emission and velocity spurs in the PV diagram. It is our best example of the jet-driven bow shock model, and its kinematics can be qualitatively explained in that context. HH 240/241 is similar to HH 212 and shows a close relationship between the H2 and CO emission. The kinematics of its western lobe can also be explained with the jet-driven model. The kinematics of RNO 91 are similar to VLA 05487 and are broadly consistent with a wide-angle wind-driven model. HH 111 has both parabolic and spur PV structures, a combination that is not easily explained in the simplest version of either model. Thus, these observations provide examples of systems that support either the wide-angle wind-driven or jet-driven model in the simplest interpretation. More detailed calculations are needed to understand whether one model might be able to fit all systems. It is crucial to know if time-dependent or long-lived jet-driven bow shock models can produce the observed outflow widths and parabolic PV structures, or if a wide-angle wind can produce the shock features and velocity spur structures in our observations.

We present new Hubble Space Telescope (HST ) NICMOS images of the source region of the HH 1/2 —ow. The HH 1 jet is traced in the (Fe II) 1.64 km and the 2.12 km lines to about of the deeply H 2 2A.5 embedded VLA source. In general, the structure of the jet is similar in and (Fe II), with all the H 2 features having comparable brightness in both species. However, there is a gradient in the II) H 2 /(Fe ratio which increases with distance from the source. We also compare our infrared images with almost contemporary HST WFPC2 images in Ha and (S II). The ratio of (Fe II )t o (SII), both low-excitation tracers of weak shocks, is almost constant along the visible part of the jet but then increases by an order of magnitude where the optical jet disappears. If this is due to reddening, then the extinction, A V , increases by at least 4 mag in a space of corresponding to 420 AU. Beyond this obscuring ridge, we 0A.9, detect —ve more infrared knots. Less than 2A now separate the infrared jet and the tip of the compact 3.6 cm radio continuum jet centered on the VLA source. The heavy extinction which obscures the base of the IR jet is probably due to the compact cloud core recently detected in HCO'. The jet is observed to steadily increase in width, and we argue that this is either due to sideways ejection of shocked material from internal working surfaces or a sonic expansion of the hot jet beam. Surprisingly, the width of the jet is the same to within measurement errors in and (Fe II), contrary to the expectations of some H 2 models. Two small, previously detected oU-axis knots appear to form an independent HH —ow, which we call HH 501. An infrared cometary nebula (dubbed the X nebula) is found next to the HH 1 jet, along a line through the HH 501 knots, possibly supporting earlier speculations that yet one more source exists in the region. However, new proper motions of the HH 501 —ow suggest an origin of these knots near VLA 1, and it is therefore possible that the VLA 1 source itself may be a close binary, thus forming a triple system with the more distant VLA 2. Subject headings: infrared: ISM: lines and bandsISM: jets and out—owsstars: formation ¨ stars: mass loss

We report multi-epoch interferometric radio observations of the IRAS source 18162-2048 that drives the thermal radio jet in the HH 80-81/GGD 27 complex. Our main goal was to follow the proper motion and flux density decay of the two inner young jet condensations N4 and S4, discovered by Mart? et al., on their way out from the driving source. The tangential velocity estimated for the condensations amounts to ~60 mas yr-1, equivalent to ~500 km s-1 at the distance of the complex. The brightness decay can be fitted by a power law of the time elapsed since ejection, yielding power law exponents of about -2 and -3 for the northern and southern condensations, respectively. We also discuss our observations in the context of simple biconical jet models, suggesting that both condensations are consistent with relatively weak density enhancements in the otherwise steady jet flow. Their fade in brightness seems to be in agreement with the density decay expected in a freely expanding jet.

We have mapped the 1300 μm dust emission of a 6' × 16' field in the OMC-2 and -3 region and detected an extended filamentary structure with at least 11 embedded condensations in OMC-2 and 10 in OMC-3. Six have been observed previously at 1300 μm, and two were also detected by IRAS. We observed eight of the new sources at six wave bands from 350 to 2000 μm and derived upper limits for their far-infrared (FIR) emission from the IRAS raw data. The millimeter/submillimeter emission originates from cold dust (Td ~ 20 K), and the individual components have gas masses of 5 M☉ < Mgas < 36 M☉. The ratio Lbol/Lsmm is below 70 for six sources associated with OMC-3, indicating that they are class 0-type objects. Condensations in the OMC-2 region have Lbol/Lsmm ≤ 360, suggesting an evolutionary effect from north to south. We report the discovery of a highly collimated bipolar CO outflow, most likely driven by the source OMC-3 MMS 8. The flow is over 5' (0.7 pc) long and less than 1' (0.15 pc) wide and is oriented nearly east-west. Less prominent outflows are associated with OMC-2 FIR 2/3 and OMC-3 MMS 6. The 1300 μm continuum emission is confined to a ridge less than 1' wide while the emission in J = 2-113CO, C18O, and CS is between 5' and 10' wide. The continuum emission is displaced toward the eastern side of the molecular ridge that contains it. Most 1300 μm sources lie in or close to line emission peaks. However, not all line emission peaks contain prominent 1300 μm continuum sources. The curved filamentary structure of the large-scale dust and molecular emission is likely the result of compression by the superbubble centered ~25-70 pc further north, plus the impact of energy from the younger 1c subgroup of the Orion OB association, which lies 10-50 pc in front of our mapped region, and by the very recent expansion of the NGC 1977 and M42 H II regions.

We report the discovery of over 20 groups of new Herbig-Haro (HH) objects in the NGC 1333 region of the Perseus molecular cloud, including some highly collimated jets. Our images contain over 30 groups of HH objects driven by over a dozen active outflow sources. Several of the new jets appear to be driven by optically visible stars, including HH 333, HH 334, and possibly HH 335 and HH 336. A spectacular jet, HH 333, lies nearly in the plane of the sky and has a length-to-width ratio exceeding 100 and may exhibit S-shaped point symmetry about a faint Hα emission-line star. HH 336 is located toward the cloud edge and is also centered on a visible star. A large number of new HH objects lie to the south of the concentration of known young stellar objects near SVS 13. We use published millimeter-wavelength CO and near-infrared H2 maps and images to associate HH objects, H2 emitting shocks, and CO outflows with more than a dozen potential driving sources. The high density of objects results in source confusion that limits the extent to which this can be done. Some HH objects are seen toward low-extinction regions far from the opaque cloud cores and may trace parts of parsec scale outflows from embedded sources. The large number of collisionally excited nebulae in this young stellar cluster requires a nearly coeval microburst of star formation.

We present Hubble Space Telescope Hα and [S II] images of HH 29. The proximity of HH 29 (140 pc) and the high resolution of the Planetary Camera has resulted in the most detailed images obtained so far of any Herbig-Haro object. The most prominent feature is a linear Hα ridge leading the working surface of a bow shock with a chaotic trailing [S II] bright region. The high-excitation ridge is perpendicular to a line extending toward the class 0 protostar L1551-NE, supporting its recent identification as the driving source. Previous studies have identified several low-velocity features within the working surface. Our images reveal them to be miniature bow shocks facing upstream. Evidently a cluster of dense quasi-stationary clumps have been overrun by a faster, lower density flow. The shock front impacted the front of the largest clump several decades ago, and during the 1990s, a prominent gap appeared in the advancing bow shock in the wake of the obstacle. The Hubble Space Telescope images show that by 1998 the shock front had wrapped around the back of the clump, closing the shock shadow it produced.

We present new Hα and Hβ images of the HH 1/2 system, and we find that the Hα/Hβ ratio has high values in ridges along the leading edges of the HH 1 bow shock and of the brighter condensations of HH 2. These ridges have Hα/Hβ = 4 → 6, which is consistent with collisional excitation from the n = 1 to the n = 3 and 4 levels of hydrogen in a gas of temperatures T = 1.5 → 10 × 10{sup 4} K. This is therefore the first direct evidence that the collisional excitation/ionization region of hydrogen just behind Herbig-Haro shock fronts is detected.

We have carried out high spatial resolution, 12'', CO J = 2-1 observations at the IRAM 30 m telescope of the molecular outflow in the HH 111 jet complex. The Herbig-Haro jet is found to coincide with a highly collimated CO flow, with two distinct velocities, possibly providing kinematic evidence that the CO flow surrounds the HH jet. A second well-defined bipolar molecular flow, at large angles to the principal flow axis, coincides with the HH 121 infrared flow that emanates from the (presumably binary) VLA driving source; the region thus harbors one of the rare quadrupolar molecular flows. Extremely high velocity CO is found toward the principal HH working surface at the same velocity as the optically emitting gas, whereas this emission is weak toward the Herbig-Haro jet. Since the inclination of the HH jet is known from optical observations to be 10° to the plane of the sky, we conclude that there is CO in the flow with space velocities of up to 500 km s-1! Further out, and precisely along the flow axis, we have discovered three equidistant CO bullets with space velocities of about 240 km s-1, which are not detected in the optical. We interpret these bullets as the result of earlier eruptions from the energy source that are now moving through an ambient medium so tenuous that no observable shock interaction takes place. Finally, we discuss the physical relation between the Herbig-Haro jet, the CO bullets, and the low-velocity molecular outflow. We favor the view that HH jets and CO bullets, which represent different manifestations of the same physical phenomena, are driving the low-velocity molecular outflow.

Detailed observations of a recently recognized eruptive variable, V900 Mon, are presented. The star is located in the small cloud L1656, a little-studied region of modest star formation activity in Monoceros, and is presently at a magnitude of r ~ 16, surrounded by a bright compact reflection nebula, where only a 20th magnitude star was seen on the red first-epoch POSS plate. Optical spectra show a red absorption-line spectrum not later than mid-K, and the Hα line and the Na I D 12 doublet display prominent P Cygni profiles with massive absorption troughs indicating a cool outflowing wind. Near-infrared spectra show deep CO bandhead absorption and pronounced molecular bands of water vapor indicative of a much cooler object. This spectral appearance is very similar to that of FU Orionis, except that V900 Mon has a much higher reddening of AV ~ 13 mag. The energy distribution of V900 Mon, compiled from non-simultaneous observations and thus dependent on possible luminosity changes, shows that V900 Mon is a Class I protostar with a massive cool envelope. At a distance of about 1100 pc, V900 Mon has a luminosity of 106 L ☉ in the range of 0.55-160 μm. These data identify V900 Mon as a new member of the rare class of FU Orionis variables.

We present multifrequency, matching-beam VLA continuum observations of the HH 80-81 system as well as high-resolution observations of its central exciting source. A highly collimated bipolar jet emanates from this central source along a line between the source and HH 80-81. The jet consists of a multitude of knots, with a spacing of about 1400 AU and widths of less than 500 AU. This is strikingly similar to the structure of HH jets emanating from young stars more than a thousand times less luminous. The southern lobe terminates in the visible HH objects HH 80-81 at a projected distance of 2.3 pc from the central source

We report the discovery of new faint Herbig-Haro knots in the vicinity of the well-known HH 1-2 bipolar flow. HH 144 forms a well-collimated structure 83″ long with numerous faint knots, while HH 145 is a more disorganized group of knots further to the west. Proper motion measurements of the two brightest knots in HH 144 show a large motion away from the vicinity of VLA 1, the source of the HH 1-2 flow. The alignment of the HH 144 knots suggests, however, that a faint previously known VLA source, VLA 2, located 3″ from VLA 1, is the source of the new flow. This is confirmed by a very deep infrared K-band image, which shows reflection nebulae fanning out from VLA 1 toward HH 1 and from VLA 2 toward HH 144

We have obtained near-infrared K-band images of the HH 111 region, and detected, besides the HH 111 jet itself, a new optically invisible bipolar jet here called HH 121, from the source region of HH 111, but at large angles to the HH 111 flow axis. Near-infrared long-slit spectra of both jets confirm their emission-line nature. Radial velocities derived from H 2 lines show that the northern lobe of HH 121 is approaching and the southern is receding, but the velocities are so low that the system is likely to lie almost in the plane of the sky. There is a considerable angle between the two lobes of HH 121

Narrow-band CCD images of the HH 111 optical jet complex obtained at the ESO 3.5 m New Technology Telescope under conditions of excellent seeing are presented. These new images reveal the existence of a faint counterjet in the redshifted lobe of this bipolar outflow. The knot at the tip of the main jet is also identified as a further bow shock, in addition to the three already known in this system. By performing a partial deconvolution of the seeing profile, we have been able to resolve the knots in the trunk of the jet, which are found to have widths of about 0.8″-1.1″, and separation-to-width rations of 2-4. The first bright knot at the base of the jet is split in two, perpendicular to the jet. It is suggested that this structure is a ring of enhanced emission, viewed edge-on, such as might result from the passage of a puff of enhanced density through an oblique shock in the jet

The discovery of what appears to be a supernova remnant at unusually high latitude near the Galactic anticenter is reported. CCD images in the light of both [S II] and Hα show patchy filaments scattered over a 3' region, but with relative strengths in the two lines which vary by a factor of 20 from one filament to another. Spectra confirm the line identifications and variable intensities. The most extreme filaments have line flux ratios [S II]/Hα ∼ 5, among the highest observed in remnants. The position of G203.2-12.3 coincides with that of a «guest star» recorded by Chinese astronomers in A.D. 483