Bo Reipurth

HH 80-81 : a highly collimated Herbig-Haro complex powered by a massive young star

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

THE 2008 EXTREME OUTBURST OF THE YOUNG ERUPTIVE VARIABLE STAR EX LUPI

In early 2008, the young low-mass star EX Lupi, the prototype of the EXor class of eruptive variables, optically brightened by over 5 mag for a period of seven 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 observed energetics and kinematics. Emission line strengths, widths, and profiles significantly changed between the two observations. Also, modeling of the 2.2935 μm CO overtone band head emission suggests that an inner gap in the circumstellar gas disk around the star may be present and that 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 L_⊙ and ~(2 ± 0.5) × 10^(–7) M_⊙ 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.

Infrared Nebulae around Young Stellar Objects

We present a K-band atlas of 106 reflection nebulae, 41 of which are new discoveries. We observed these nebulae with the University of Hawaii 2.2 m telescope in the course of an imaging survey of 197 objects that were selected as nearby young Class I sources. K-band images and flux-calibrated surface brightness contour plots of each nebula are presented. We found that the near-IR luminosities and physical sizes of the nebulae increase with the bolometric luminosity of the illuminating sources. Only 22 nebulae, about 10% of these candidate Class I sources, have indications of shocked H2 emission. The great variety of nebulae that we observed prevented us from classifying them based on morphology. However, we note that as the spectral index decreases, the central star is more frequently visible at K band, and the flux from the central star tends to be dominant over the flux from the nebula. For objects that have a higher spectral index, most of the K-band flux is from the reflection nebula, and the central star is less frequently visible. The nebula around IRAS 05450+0019 has a unique morphology, and we speculate that it may be an example of a disk shadow being projected into the surrounding cloud. We present J-, H-, and K-band images of this object with surface brightness contours, as well as its spectral energy distribution from 1.2 to 100 μm.

The Structure of the Inner HH 34 Jet from Optical Integral Field Spectroscopy

We present high spatial resolution optical integral field spectroscopy of a collimated Herbig-Haro jet viewed nearly edge-on. Maps of the line emission, velocity centroid, and velocity dispersion were generated for the H? and [S?II] emission features from the inner collimated jet and exciting source region of the HH 34 outflow. The kinematic structure of the jet shows several maxima and minima in both velocity centroid value and velocity dispersion along the jet axis. Perpendicular to the flow direction the velocity decreases outward from the axis to the limb of the jet, but the velocity dispersion increases. Maps of the electron density structure were derived from the line ratio of [S?II] ?6731/?6716 emission. We have found that the jet exhibits a pronounced striped pattern in electron density; the high ne regions are at the leading side of each of the emission knots in the collimated jet, and low ne regions in the downflow direction. On average, the measured electron density decreases outward from the inner regions of the jet, but the highest ne found in the outflow is spatially offset from the nominal position of the exciting star. The results of our high spatial resolution optical integral field spectroscopy show very good agreement with the kinematics and electron density structure predicted by the existing internal working surface models of the HH 34 outflow.

V733 Cep (Persson's Star): A New FU Orionis Object in Cepheus

Persson recently found that a faint star had appeared in a cloud in Cepheus. A CCD image shows a R ~ 17.3 nebulous star, now known as V733 Cep, located in the L1216 = Cep F cloud at the apex of a cavity in the cloud. Infrared photometry indicates a modest infrared excess. Optical spectroscopy shows a well-defined Li I λ6707 line, and blueshifted absorption troughs at the Hα and Na I D lines extending to at least 200 km s-1, indicative of a massive fast wind. An infrared 1-4 μm spectrum of V733 Cep shows the presence of strong water vapor features, and is almost identical to a similar IR spectrum of FU Ori that is reddened by AV = 8 mag. Assuming an intrinsic energy distribution similar to that of FU Ori, V733 Cep has a luminosity of about 135 L⊙ at the assumed distance of 800 pc. The star was detected by the Midcourse Space Experiment satellite at 8.3 μm, but not by IRAS. Nor is it detected at 850 μm, indicating that while the star possesses circumstellar material it is not surrounded by a significant cool envelope. A 12CO(3-2) map shows what appears to be a small molecular outflow along the same axis as the cavity seen in optical images. There is evidence for a limited amount of other low- and medium-mass star formation in the Cep F cloud. The totality of the evidence strongly indicates that V733 Cep is a new FU Ori-type object that must have erupted sometime between 1953 and 1984.

HIGH-ANGULAR-RESOLUTION OBSERVATIONS AT 7 MM OF THE CORE OF THE QUADRUPOLAR HH 111/121 OUTFLOW

We present sensitive, high-angular-resolution (005) Very Large Array continuum observations made at 7 mm of the core of the HH 111/121 quadrupolar outflow. We estimate that, at this wavelength, the continuum emission is dominated by dust, although a significant free-free contribution (~30%) is still present. The observed structure is formed by two overlapping, elongated sources approximately perpendicular to each other as viewed from the Earth. We interpret this structure as either tracing two circumstellar disks that exist around each of the protostars of the close binary source at the core of this quadrupolar outflow, or a disk with a jet perpendicular to it. Both interpretations have advantages and disadvantages, and future high-angular-resolution spectroscopic millimeter observations are required to favor one of them in a more conclusive way.

MULTIPLE OUTFLOWS AND PROTOSTARS IN BARNARD 1. II. DEEP OPTICAL AND NEAR-INFRARED IMAGES ∗,†

We have used deep optical (Hα and [S II]) and near-IR (H2 and KS ) images and catalogs of protostars based on optical and infrared data to follow up our previous observations and examine the protostellar outflow population in the Barnard 1 (B1) dark cloud. The deep images presented here link shocks at the low extinction periphery of the cloud to an outflow system that bisects the confused core of B1. In addition, we find that a deeply embedded infrared shock, previously identified as a protostar, is likely the impact of a flow on a submillimeter clump. In all, we detail nine outflow systems in this cloud, eight of which have clearly identified source protostars.