Evidence for Pre-Existing Dust in the Bright Type IIn SN 2010jl

SN 2010jl was an extremely bright, Type IIn SNe which showed a significant IR excess no later than 90 days after explosion. We have obtained Spitzer 3.6 and 4.5 \mum and JHK observations of SN 2010jl \sim90 days post explosion. Little to no reddening in the host galaxy indicated that the circumstellar material lost from the progenitor must lie in a torus inclined out of the plane of the sky. The likely cause of the high mid-IR flux is the reprocessing of the initial flash of the SN by pre-existing circumstellar dust. Using a 3D Monte Carlo Radiative Transfer code, we have estimated that between 0.03-0.35 Msun of dust exists in a circumstellar torus around the SN located 6 \times 10 ^17 cm away from the SN and inclined between 60-80\cdot to the plane of the sky. On day 90, we are only seeing the illumination of approximately 5% of this torus, and expect to see an elevated IR flux from this material up until day \sim 450. It is likely this dust was created in an LBV-like mass loss event of more than 3 Msun, which is large but consistent with other LBV progenitors such as {\eta} Carinae.Comment: Accepted in A

Expanding the set of rhodococcal Baeyer–Villiger monooxygenases by high-throughput cloning, expression and substrate screening

To expand the available set of Baeyer–Villiger monooxygenases (BVMOs), we have created expression constructs for producing 22 Type I BVMOs that are present in the genome of Rhodococcus jostii RHA1. Each BVMO has been probed with a large panel of potential substrates. Except for testing their substrate acceptance, also the enantioselectivity of some selected BVMOs was studied. The results provide insight into the biocatalytic potential of this collection of BVMOs and expand the biocatalytic repertoire known for BVMOs. This study also sheds light on the catalytic capacity of this large set of BVMOs that is present in this specific actinomycete. Furthermore, a comparative sequence analysis revealed a new BVMO-typifying sequence motif. This motif represents a useful tool for effective future genome mining efforts.

Cold Dust in Three Massive Evolved Stars in the LMC

Massive evolved stars can produce large amounts of dust, and far-infrared (IR) data are essential for determining the contribution of cold dust to the total dust mass. Using Herschel, we search for cold dust in three very dusty massive evolved stars in the Large Magellanic Cloud: R71 is a Luminous Blue Variable, HD36402 is a Wolf-Rayet triple system, and IRAS05280-6910 is a red supergiant. We model the spectral energy distributions using radiative transfer codes and find that these three stars have mass-loss rates up to 10^-3 solar masses/year, suggesting that high-mass stars are important contributors to the life-cycle of dust. We found far-IR excesses in two objects, but these excesses appear to be associated with ISM and star-forming regions. Cold dust (T < 100 K) may thus not be an important contributor to the dust masses of evolved stars.Comment: accepted to A&A as part of the Herschel first results special issu

The ALMA detection of CO rotational line emission in AGB stars in the Large Magellanic Cloud

Context. Low- and intermediate-mass stars lose most of their stellar mass at the end of their lives on the asymptotic giant branch (AGB). Determining gas and dust mass-loss rates (MLRs) is important in quantifying the contribution of evolved stars to the enrichment of the interstellar medium. Aims: This study attempts to spectrally resolve CO thermal line emission in a small sample of AGB stars in the Large Magellanic Cloud (LMC). Methods: The Atacama Large Millimeter Array was used to observe two OH/IR stars and four carbon stars in the LMC in the CO J = 2-1 line. Results: We present the first measurement of expansion velocities in extragalactic carbon stars. All four C stars are detected and wind expansion velocities and stellar velocities are directly measured. Mass-loss rates are derived from modelling the spectral energy distribution and Spitzer/IRS spectrum with the DUSTY code. The derived gas-to-dust ratios allow the predicted velocities to agree with the observed gas-to-dust ratios. The expansion velocities and MLRs are compared to a Galactic sample of well-studied relatively low MLRs stars supplemented with extreme C stars with properties that are more similar to the LMC targets. Gas MLRs derived from a simple formula are significantly smaller than those derived from dust modelling, indicating an order of magnitude underestimate of the estimated CO abundance, time-variable mass loss, or that the CO intensities in LMC stars are lower than predicted by the formula derived for Galactic objects. This could be related to a stronger interstellar radiation field in the LMC. Conclusions: Although the LMC sample is small and the comparison to Galactic stars is non-trivial because of uncertainties in their distances (hence luminosities), it appears that for C stars the wind expansion velocities in the LMC are lower than in the solar neighbourhood, while the MLRs appear to be similar. This is in agreement with dynamical dust-driven wind models

The evolutionary state of Miras with changing pulsation periods

Context: Miras are long-period variables thought to be in the asymptotic giant branch (AGB) phase of evolution. In about one percent of known Miras, the pulsation period is changing. It has been speculated that this changing period is the consequence of a recent thermal pulse in these stars. Aims: We aim to clarify the evolutionary state of these stars, and to determine in particular whether or not they are in the thermally-pulsing (TP-)AGB phase. Methods: One important piece of information that has been neglected so far when determining the evolutionary state is the presence of the radio-active s-process element technetium (Tc). We obtained high-resolution, high signal-to-noise-ratio optical spectra of a dozen prominent Mira variables with changing pulsation period to search for this indicator of TPs and dredge-up. We also use the spectra to measure lithium (Li) abundances. Furthermore, we establish the evolutionary states of our sample stars by means of their present-day periods and luminosities. Results: Among the twelve sample stars observed in this programme, five were found to show absorption lines of Tc. BH Cru is found to be a carbon-star, its period increase in the past decades possibly having stopped by now. We report a possible switch in the pulsation mode of T UMi from Mira-like to semi-regular variability in the past two years. R Nor, on the other hand, is probably a fairly massive AGB star, which could be true for all meandering Miras. Finally, we assign RU Vul to the metal-poor thick disk with properties very similar to the short-period, metal-poor Miras. Conclusions: We conclude that there is no clear correlation between period change class and Tc presence. The stars that are most likely to have experienced a recent TP are BH Cru and R Hya, although their rates of period change are quite different.Comment: 11 pages, 7 figures, 2 tables; accepted for publication in A&

Satori 2023

The Satori is a student literary publication that expresses the artistic spirit of the students of Winona State University. Student poetry, prose, and graphic art are published in the Satori every spring since 1970. The Satori 2023 editors are Gabriel Hathaway, Van Herman, Madeline Schonitzer, Brianna Strohbehn, Page Sutton, Willow Swinbank, and Emily Venné. The Satori 2023 faculty advisor is Dr. Jim Armstrong, Professor of English.https://openriver.winona.edu/satori/1010/thumbnail.jp

Long Period Variables in the Large Magellanic Cloud from the EROS-2 survey

Context. The EROS-2 survey has produced a database of millions of time series from stars monitored for more than six years, allowing to classify some of their sources into different variable star types. Among these, Long Period Variables (LPVs), known to follow sequences in the period-luminosity diagram, include long secondary period variables whose variability origin is still a matter of debate. Aims.We use the 856 864 variable stars available from the Large Magellanic Cloud (LMC) in the EROS-2 database to detect, classify and characterize LPVs. Methods. Our method to extract LPVs is based on the statistical Abbe test. It investigates the regularity of the light curve with respect to the survey duration in order to extract candidates with long-term variability. The period search is done by Deeming, Lomb-Scargle and generalized Lomb-Scargle methods, combined with Fourier series fit. Color-magnitude, period-magnitude and period-amplitude diagrams are used to characterize our candidates. Results. We present a catalog of 43 551 LPV candidates for the Large Magellanic Cloud. For each of them, we provide up to five periods, mean magnitude in EROS-2, 2MASS and Spitzer bands, BE-RE color, RE amplitude and spectral type.We use infrared data to make the distinction between RGB, O-rich, C-rich and extreme AGB stars. Properties of our LPV candidates are investigated by analyzing period-luminosity and period-amplitude diagrams.Comment: Accepted for publication in A&

Comparing call-based versus subunit-based methods for categorizing Norwegian killer whale, Orcinus orca, vocalizations

Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Animal Behaviour 81 (2011): 377-386, doi:10.1016/j.anbehav.2010.09.020.Students of animal communication face significant challenges when deciding how to categorise calls into subunits, calls, and call series. Here, we use algorithms designed to parse human speech to test different approaches for categorising calls of killer whales. Killer whale vocalisations have traditionally been categorised by humans into discrete call types. These calls often contain internal spectral shifts, periods of silence, and synchronously produced low and high frequency components, suggesting that they may be composed of subunits. We describe and compare three different approaches for modelling Norwegian killer whale calls. The first method considered the whole call as the basic unit of analysis. Inspired by human speech processing techniques, the second and third methods represented the calls in terms of subunits. Subunits may provide a more parsimonious approach to modelling the vocal stream since (1) there were fewer subunits than call types; (2) nearly 75% of all call types shared at least one subunit. We show that contour traces from stereotyped Norwegian killer whale calls yielded similar automatic classification performance using either whole calls or subunits. We also demonstrate that subunits derived from Norwegian stereotyped calls were detected in some Norwegian variable (non-stereotyped) calls as well as the stereotyped calls of other killer whale populations. Further work is required to test whether killer whales use subunits to generate and categorize their vocal repertoire.The undergraduate students were supported by the Massachusetts Institute of Technology Undergraduate Research Opportunities Program office and the Ocean Life Institute (OLI) at the Woods Hole Oceanographic Institution (WHOI). Field work was financed by the OLI, National Geographic Society and WWF Sweden. A. D. Shapiro was funded by a National Defense Science and Engineering Graduate Fellowship and the WHOI Academic Programs Office