An Adaptive Optics Survey for Close Protostellar Binaries

In order to test the hypothesis that Class I protostellar binary stars are a product of ejections during the dynamical decay of non-hierarchical multiple systems, we combined the results of new adaptive optics (AO) observations of Class I protostars with our previously published AO data to investigate whether Class I protostars with a widely separated companion (r>200 AU) are more likely to also have a close companion (r<200 AU). In total, we observed 47 embedded young stellar objects (YSOs) with either the Subaru natural guide star AO system or the Keck laser guide star AO system. We found that targets with a widely separated companion within 5,000 AU are not more likely to have a close companion. However, targets with another YSO within a projected separation of 25,000 AU are much more likely to have a close companion. Most importantly, every target with a close companion has another YSO within a projected separation of 25,000 AU. We came to the same conclusions after considering a restricted sample of targets within 500 pc and close companions wider than 50 AU to minimize incompleteness effects. The Orion star forming region was found to have an excess of both close binaries and YSOs within 25,000 AU compared to other star forming regions. We interpret these observations as strong evidence that many close Class I binary stars form via ejections and that many of the ejected stars become unbound during the Class I phase.Comment: 22 pages, 3 figures, 2 table

Immunodominance, clonal composition and TCRß repertoire of the bovine CD8⁺ T-cell response to Theileria parva

In view of the evidence that CD8+ T-cells are involved in mediating immunity against Theileria parva, the antigens recognised by these cells are obvious candidates for inclusion in a subunit vaccine. Results from previous studies have inferred that the CD8+ T-cell response to T. parva is focused on a limited number of immunodominant antigens that exhibit polymorphism between different parasite strains. This could pose a major challenge to the design of a broadly effective subunit vaccine. The recent identification of CTL target antigens has provided the opportunity to characterise immunodominance within the T. parva systemThe objective of this study was to quantitatively assess immunodominance in the CD8+ T-cell response to T. parva and to characterise the clonal composition and TCRp repertoires ofthe epitope-specific T-cell populations. The results from four animals presented in this study have demonstrated that the CDS T-cell response restricted by two MHC class I haplotypes is reproducibly dominated by single polymorphic epitopes. Using a suite of molecular tools developed during this study it was determined that the T-cell populations specific for both these epitopes were polyclonal but dominated by a limited number of large clonal expansions and the TCRP repertoires expressed by these populations was diverse.During the course of this work several novel bovine TCRp genes were identified. Further examination ofTCRp cDNA transcripts and the bovine genome assembly substantially expanded the known bovine TCRP repertoire, which is now the largest characterised for any species. Notably several VP subfamilies, especially Vpi and 13 have undergone extensive duplication and contain large numbers of genes. By annotating the available genomic data it has been shown that the bovine TCRB locus has a highly conserved synteny with the human TCRB locus. Furthermore, this annotation has demonstrated that prodigious duplication of a cassette containing a Vpi and Vpi3 gene has contributed to the large membership of these two subfamilies and that there are three D-J-Cp clusters in the bovine TCRB locus rather than the two seen in the other mammalian TCRB loci described

Simultaneous monitoring of the photometric and polarimetric activity of the young star PV Cep in the optical/near-infrared bands

We present the results of a simultaneous monitoring, lasting more than 2 years, of the optical and near-infrared photometric and polarimetric activity of the variable protostar PV Cep. During the monitoring period, an outburst has occurred in all the photometric bands, whose declining phase ($\Delta$J $\approx$ 3 mag) lasted about 120 days. A time lag of $\sim$ 30 days between optical and infrared light curves has been measured and interpreted in the framework of an accretion event. This latter is directly recognizable in the significant variations of the near-infrared colors, that appear bluer in the outburst phase, when the star dominates the emission, and redder in declining phase, when the disk emission prevails. All the observational data have been combined to derive a coherent picture of the complex morphology of the whole PV Cep system, that, in addition to the star and the accretion disk, is composed also by a variable biconical nebula. In particular, the mutual interaction between all these components is the cause of the high value of the polarization ($\approx$ 20%) and of its fluctuations. The observational data concur to indicate that PV Cep is not a genuine EXor star, but rather a more complex object; moreover the case of PV Cep leads to argue about the classification of other recently discovered young sources in outburst, that have been considered, maybe over-simplifying, as EXor.Comment: Accepted for publication on Ap

\u3cem\u3eMontana Envtl Info. Ctr. v. Montana Dept. of Envtl Quality\u3c/em\u3e: Stream Classification and Water Quality

This case presents the following issues: 1) whether the Montana Department of Environmental Quality (MDEQ) acted unlawfully when it allowed a strip mine to renew its permit with far lower pollution control requirements by recognizing receiving waters as ephemeral streams; and 2) whether the monitoring program MDEQ did require was too lenient and not representative of the total discharges. This appeal presents an opportunity to clarify MDEQ powers and has ramifications sounding in both agency powers and potential environmental quality consequences for Montana’s waters and mining industry

The Evolution of the Multiplicity of Embedded Protostars II: Binary Separation Distribution & Analysis

We present the Class I protostellar binary separation distribution based on the data tabulated in the companion paper. We verify the excess of Class I binary stars over solar-type main-sequence stars, especially at separations beyond 500 AU. Although our sources are in nearby star forming regions distributed across the entire sky (including Orion), none of our objects are in a high stellar density environment. The binary separation distribution changes significantly during the Class I phase, and the binary frequency at separations greater than 1000 AU declines steadily with respect to spectral index. Despite these changes, the binary frequency remains constant until the end of the Class I phase, when it drops sharply. We propose a scenario to account for the changes in the Class I binary separation distribution. This scenario postulates that companions with a separation greater than ~1000 AU were ejected during the Class 0 phase, but remain gravitationally bound due to the mass of the envelope. As the envelope dissipates, these companions become unbound and the binary frequency at wide separations declines. This scenario predicts that a large number of Class 0 objects should be non-hierarchical multiple systems, and that many Class I YSOs with a widely separated companion should also have a very close companion. We also find that Class I protostars are not dynamically pristine, and have experienced dynamical evolution before they are visible as Class I objects. For the first time, evidence is presented showing that the Class I binary frequency and the binary separation distribution strongly depend on the star forming environment. The reason for this dependence remains unclear.Comment: 33 pages, 16 figures, accepted by the Astronomical Journa

A Near-Infrared Spectroscopic Survey of Class I Protostars

We present the results of a near-IR spectroscopic survey of 110 Class I protostars observed from 0.80 microns to 2.43 microns at a spectroscopic resolution of R=1200. We find that Class I objects exhibit a wide range of lines and the continuum spectroscopic features. 85% of Class I protostars exhibit features indicative of mass accretion, and we found that the veiling excess, CO emission, and Br Gamma emission are closely related. We modeled the spectra to estimate the veiling excess (r_k) and extinction to each target. We also used near-IR colors and emission line ratios, when available, to also estimate extinction. In the course of this survey, we observed the spectra of 10 FU Orionis-like objects, including 2 new ones, as well as 3 Herbig Ae type stars among our Class I YSOs. We used photospheric absorption lines, when available, to estimate the spectral type of each target. Although most targets are late type stars, there are several A and F-type stars in our sample. Notably, we found no A or F class stars in the Taurus-Auriga or Perseus star forming regions. There are several cases where the observed CO and/or water absorption bands are deeper than expected from the photospheric spectral type. We find a correlation between the appearance of the reflection nebula, which traces the distribution of material on very large scales, and the near-IR spectrum, which probes smaller scales. The spectra of the components of spatially resolved protostellar binaries tend to be very similar. In particular both components tend to have similar veiling and H_2 emission, inconsistent with random selection from the sample as a whole. There is a strong correlation between [Fe II] and H_2 emission, supporting previous results showing that H_2 emission in the spectra of young stars is usually shock excited by stellar winds.Comment: 89 pages, 13 figures, 7 Table

A Photometrically and Morphologically Variable Infrared Nebula in L483

We present narrow and broad K-band observations of the Class 0/I source IRAS 18148-0440 that span 17 years. The infrared nebula associated with this protostar in the L483 dark cloud is both morphologically and photometrically variable on a time scale of only a few months. This nebula appears to be an infrared analogue to other well-known optically visible variable nebulae associated with young stars, such as Hubble's Variable Nebula. Along with Cepheus A, this is one of the first large variable nebulae to be found that is only visible in the infrared. The variability of this nebula is most likely due to changing illumination of the cloud rather than any motion of the structure in the nebula. Both morphological and photometric changes are observed on a time scale only a few times longer than the light crossing time of the nebula, suggesting very rapid intrinsic changes in the illumination of the nebula. Our narrow-band observations also found that H_2 knots are found nearly twice as far to the east of the source as to its west, and that H_2 emission extends farther east of the source than the previously known CO outflow.Comment: 19 pages, 6 figures, 1 tabl

Orphaned Protostars

We explore the origin of a population of distant companions (~1000 - 5000 AU) to Class I protostellar sources recently found by Connelley and co-workers, who noted that the companion fraction diminished as the sources evolved. Here we present N-body simulations of unstable triple systems embedded in dense cloud cores. Many companions are ejected into unbound orbits and quickly escape, but others are ejected with insufficient momentum to climb out of the potential well of the cloud core and associated binary. These loosely bound companions reach distances of many thousands of AU before falling back and eventually being ejected into escapes as the cloud cores gradually disappear. We use the term orphans to denote protostellar objects that are dynamically ejected from their placental cloud cores, either escaping or for a time being tenuously bound at large separations. Half of all triple systems are found to disintegrate during the protostellar stage, so if multiple systems are a frequent outcome of the collapse of a cloud core, then orphans should be common. Bound orphans are associated with embedded close protostellar binaries, but escaping orphans can travel as far as ~0.2 pc during the protostellar phase. The steep climb out of a potential well ensures that orphans are not kinematically distinct from young stars born with a less violent pre-history. The identification of orphans outside their heavily extincted cloud cores will allow the detailed study of protostars high up on their Hayashi tracks at near-infrared and in some cases even at optical wavelengths.Comment: 16 pages, 5 figure