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Cholangiocarcinoma (CCA) is a rare biliary tract cancer with a low five-year survival rate and high recurrence rate after surgical resection. Currently treatment approaches include systemic chemotherapeutics such as FOLFIRINOX, a chemotherapy regimen is a possible treatment for severe CCA cases. A limitation of this chemotherapy regimen is its toxicity to patients and adverse events. There exists a need for therapies to alleviate the toxicity of a FOLFIRINOX regimen while enhancing or not altering its anticancer properties. Cold Atmospheric plasma (CAP) is a technology with a promising future as a selective cancer treatment. It is critical to know the potential interactions between CAP and adjuvant chemotherapeutics. In this study the aim is to characterize the efficacy of FOLFIRINOX and CAP in combination to understand potential synergetic effect on CCA cells. FOLFIRINOX treatment alone at the highest dose tested (53.8 nM fluorouracil, 13.1 nM Leucovorin, 5.1 nM Irinotecan, and 3.7 nM Oxaliplatin) reduced CCA cell viability to below 20% while CAP treatment alone for 7 min reduced viability to 3% (p

Variable stars in the compact elliptical galaxy M32 are identified, using three epochs of photometry from the Spitzer Space Telescope at 3.6 and 4.5 $\mu$m, separated by 32 to 381 days. We present a high-fidelity catalogue of sources detected in multiple epochs at both 3.6 and 4.5 $\mu$m, which we analysed for stellar variability using a joint probability error-weighted flux difference. Of these, 83 stars are identified as candidate large-amplitude, long-period variables, with 28 considered high-confidence variables. The majority of the variable stars are classified as asymptotic giant branch star candidates using colour-magnitude diagrams. We find no evidence supporting a younger, infrared-bright stellar population in our M32 field., Comment: 11 pages, 8 figures. Accepted for publication in MNRAS

The nearby ($\sim$500 kpc) metal-poor ([Fe/H] $\approx$ -1.2; $Z$ $\approx$ 30% $Z_{\odot}$) star-forming galaxy NGC 6822 has a metallicity similar to systems at the epoch of peak star formation. Through identification and study of dusty and dust-producing stars, it is therefore a useful laboratory to shed light on the dust life cycle in the early Universe. We present a catalog of sources combining near- and mid-IR photometry from the United Kingdom Infrared Telescope (UKIRT; $J$, $H$, and $K$) and the $Spitzer$ $Space$ $Telescope$ (IRAC 3.6, 4.5, 5.8, and 8.0 $\mu$m and MIPS 24 $\mu$m). This catalog is employed to identify dusty and evolved stars in NGC 6822 utilizing three color-magnitude diagrams (CMDs). With diagnostic CMDs covering a wavelength range spanning the near- and mid-IR, we develop color cuts using kernel density estimate (KDE) techniques to identify dust-producing evolved stars, including red supergiant (RSG) and thermally-pulsing asymptotic giant branch (TP-AGB) star candidates. In total, we report 1,292 RSG candidates, 1,050 oxygen-rich AGB star candidates, and 560 carbon-rich AGB star candidates with high confidence in NGC 6822. Our analysis of the AGB stars suggests a robust population inhabiting the central stellar bar of the galaxy, with a measured global stellar metallicity of [Fe/H] = -1.286 $\pm$ 0.095, consistent with previous studies. In addition, we identify 277 young stellar object (YSO) candidates. The detection of a large number of YSO candidates within a centrally-located, compact cluster reveals the existence of an embedded, high-mass star-formation region that has eluded previous detailed study. Spitzer I appears to be younger and more active than the other prominent star-forming regions in the galaxy., Comment: Accepted for publication in The Astrophysical Journal; 27 pages, 13 figures, 12 tables (master catalog will be available from publisher)

The Mid-Infrared Instrument (MIRI) on the James Webb Space Telescope (JWST), has imaging, four coronagraphs and both low and medium resolution spectroscopic modes . Being able to simulate MIRI observations will help commissioning of the instrument, as well as get users familiar with representative data. We designed the MIRI instrument simulator (MIRISim) to mimic the on-orbit performance of the MIRI imager and spectrometers using the Calibration Data Products (CDPs) developed by the MIRI instrument team. The software encorporates accurate representations of the detectors, slicers, distortions, and noise sources along the light path including the telescope's radiative background and cosmic rays. The software also includes a module which enables users to create astronomical scenes to simulate. MIRISim is a publicly available Python package that can be run at the command line, or from within Python. The outputs of MIRISim are detector images in the same uncalibrated data format that will be delivered to MIRI users. These contain the necessary metadata for ingestion by the JWST calibration pipeline., 10 pages, 8 figures. Accepted for publication by MNRAS

Within the early Universe, ‘extreme’ star formation may have been the norm rather than the exception 1,2 . Super star clusters (with masses greater than 105 solar masses) are thought to be the modern-day analogues of globular clusters, relics of a cosmic time (redshift z ≳ 2) when the Universe was filled with vigorously star-forming systems 3 . The giant H ii region 30 Doradus in the Large Magellanic Cloud is often regarded as a benchmark for studies of extreme star formation 4 . Here, we report the discovery of a massive embedded star-forming complex spanning about 500 pc in the unexplored southwest region of the Large Magellanic Cloud, which manifests itself as a younger, embedded twin of 30 Doradus. Previously known as N79, this region has a star-formation efficiency greater than that of 30 Doradus, by a factor of about 2, as measured over the past ~0.5 Myr. Moreover, at the heart of N79 lies the most luminous infrared compact source discovered with large-scale infrared surveys of the Large Magellanic Cloud and Milky Way, possibly a precursor to the central super star cluster of 30 Doradus, R136. The discovery of a nearby candidate super star cluster may provide invaluable information to understand how extreme star formation proceeds in the current and high-redshift Universe. The relatively unexplored southwestern region of the Large Magellanic Cloud is host to a massive, embedded star-forming complex that rivals the star-forming efficiency of 30 Doradus. Its most luminous object could be a super star cluster in formation.

The survey for DUST In Nearby Galaxies with Spitzer (DUSTiNGS) has identified hundreds of candidate dust-producing Asymptotic Giant Branch (AGB) stars in several nearby metal-poor galaxies. We have obtained multi-epoch follow-up observations for these candidates with the Spitzer Space Telescope and measured their infrared (IR) lightcurves. This has allowed us to confirm their AGB nature and investigate pulsation behavior at very low metallicity. We have obtained high-confidence pulsation periods for 88 sources in seven galaxies. We have confirmed DUSTiNGS variable star candidates with a 20% success rate, and determined the pulsation properties of 19 sources already identified as Thermally-Pulsing AGB (TP-AGB) stars. We find that the AGB pulsation properties are similar in all galaxies surveyed here, with no discernible difference between the DUSTiNGS galaxies (down to 1.4% solar metallicity; [Fe/H]=-1.85) and the far more metal-rich Magellanic Clouds (up to 50% solar metallicity; [Fe/H]=-0.38). These results strengthen the link between dust production and pulsation in AGB stars and establish the IR Period-Luminosity (P - L) relation as a reliable tool (+/- 4%) for determining distances to galaxies, regardless of metallicity., Comment: accepted for publication in ApJ, 26 pages, 16 figures, 7 tables

As nearby neighbors to the Milky Way, the Large and Small Magellanic Clouds (LMC and SMC) provide a unique opportunity to study star formation in the context of their galactic ecosystems. Thousands of young stellar objects (YSOs) have been characterized with large-scale Spitzer and Herschel surveys. In this paper, we present new near-IR spectroscopy of five high-mass YSOs in the LMC and one in the SMC. We detect multiple hydrogen recombination lines, as well as He I 2.058 $\mu$m, H$_2$, [Fe II], and [S III] in these highly excited sources. We estimate the internal extinction of each source and find that it is highest for sources with the youngest evolutionary classifications. Using line ratios, we assess the dominant excitation mechanism in the three sources where we detect both H$_2$ 2.12 $\mu$m and [Fe II] 1.64 $\mu$m. In each case, photoexcitation dominates over shock excitation. Finally, we detect CO bandhead absorption in one of our LMC sources. While this feature is often associated with evolved stars, this object is likely young with strong PAH and fine-structure emission lines tracing an H II region detected at longer wavelengths. Compared to high-mass YSOs in the Galaxy, our sources have higher bolometric and line luminosities, consistent with their selection as some of the brightest sources in the LMC and SMC., Comment: accepted for publication in MNRAS

We present a comprehensive study of massive young stellar objects (YSOs) in the metal-poor galaxy NGC 6822 using IRAC and MIPS data obtained from the {\em Spitzer Space Telescope}. We find over 500 new YSO candidates in seven massive star-formation regions; these sources were selected using six colour-magnitude cuts. Via spectral energy distribution fitting to the data with YSO radiative transfer models we refine this list, identifying 105 high-confidence and 88 medium-confidence YSO candidates. For these sources we constrain their evolutionary state and estimate their physical properties. The majority of our YSO candidates are massive protostars with an accreting envelope in the initial stages of formation. We fit the mass distribution of the Stage I YSOs with a Kroupa initial mass function and determine a global star-formation rate of 0.039 $M_{\odot} yr^{-1}$. This is higher than star-formation rate estimates based on integrated UV fluxes. The new YSO candidates are preferentially located in clusters which correspond to seven active high-mass star-formation regions which are strongly correlated with the 8 and 24 $\mu$m emission from PAHs and warm dust. This analysis reveals an embedded high-mass star-formation region, Spitzer I, which hosts the highest number of massive YSO candidates in NGC 6822. The properties of Spitzer I suggest it is younger and more active than the other prominent H\,{\sc ii} and star-formation regions in the galaxy., Comment: 16 pages, 10 figures, 9 tables; accepted for publication in MNRAS

We present the highest resolution single-dish submillimetre observations of the detached shell source U Antliae to date. The observations were obtained at $450~\micron$ and $850~\micron$ with SCUBA-2 instrument on the James Clerk Maxwell Telescope as part of the Nearby Evolved Stars Survey. The emission at $850~\micron$ peaks at $40\arcsec$ with hints of a second peak seen at $\sim 20\arcsec$. The emission can be traced out to a radius of $56\arcsec$ at a $3\sigma$ level. The outer peak observed at $850~\micron$ aligns well with the peak observed at Herschel/PACS wavelengths. With the help of spectral energy distribution fitting and radiative transfer calculations of multiple-shell models for the circumstellar envelope, we explore the various shell structures and the variation of grain sizes along the in the circumstellar envelope. We determine a total shell dust mass of $(2.0 \pm 0.3) \times 10^{-5}$ M$_{\odot}$ and established that the thermal pulse which gave rise to the detached shell occurred 3500 $\pm$ 500 years ago., Comment: Accepted for publication in MNRAS

Breast cancer is a heterogenous disease which can be classified into subtypes by the presence or absence of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor 2 receptor (HER2). Cold atmospheric plasma (CAP) has been shown to be a potential treatment for cancer. In this report, a 92–99% reduction of viability by CAP treatment was achieved across all seven tested breast cancer cell lines (p ≤ 0.05). Increasing treatment duration and power significantly reduced breast cancer cell viability (** f(2,2) ≤ 0.0176, *** f(5,14) ≤ 0.0033). The authors are the first to report that breast cancer sensitivity to CAP is based on receptor status. Cells with identical receptor status showed the least difference in CAP sensitivity (p ≤ 0.05), the difference being 33% between the two ER+/PR+/HER2- cell lines (p ≤ 0.05) and 22–44% between the three TNBC cell lines (p ≤ 0.05). HER2-negative cell lines, irrespective of ER/PR status, also showed ≤ 50% difference in CAP sensitivity (p ≤ 0.05). Moreover, demonstration of ER-/PR-/HER2+ CAP susceptibility and ER+/PR+/HER2+ CAP resistance suggests that ER/PR status is a significant factor in determining CAP sensitivity in HER2-positive cells. Our novel findings on CAP sensitivity will provide insight on how to optimize CAP treatment to better overcome CAP resistance and thus prevent tumor recurrence.

The survey for DUST in Nearby Galaxies with Spitzer (DUSTiNGS) identified several candidate Asymptotic Giant Branch (AGB) stars in nearby dwarf galaxies and showed that dust can form even in very metal-poor systems (Z ~ 0.008 $Z_\odot$). Here, we present a follow-up survey with WFC3/IR on the Hubble Space Telescope (HST), using filters that are capable of distinguishing carbon-rich (C-type) stars from oxygen-rich (M-type) stars: F127M, F139M, and F153M. We include six star-forming DUSTiNGS galaxies (NGC 147, IC 10, Pegasus dIrr, Sextans B, Sextans A, and Sag DIG), all more metal-poor than the Magellanic Clouds and spanning 1 dex in metallicity. We double the number of dusty AGB stars known in these galaxies and find that most are carbon rich. We also find 26 dusty M-type stars, mostly in IC 10. Given the large dust excess and tight spatial distribution of these M-type stars, they are most likely on the upper end of the AGB mass range (stars undergoing Hot Bottom Burning). Theoretical models do not predict significant dust production in metal-poor M-type stars, but we see evidence for dust excess around M-type stars even in the most metal-poor galaxies in our sample (12+log(O/H) = 7.26-7.50). The low metallicities and inferred high stellar masses (up to ~10 $M_\odot$) suggest that AGB stars can produce dust very early in the evolution of galaxies (~30 Myr after they form), and may contribute significantly to the dust reservoirs seen in high-redshift galaxies., 18 pages, 9 figures, accepted for publication in ApJ

The Mid-Infrared Instrument (MIRI) for the {\em James Webb Space Telescope} (JWST) will revolutionize our understanding of infrared stellar populations in the Local Volume. Using the rich {\em Spitzer}-IRS spectroscopic data-set and spectral classifications from the Surveying the Agents of Galaxy Evolution (SAGE)-Spectroscopic survey of over a thousand objects in the Magellanic Clouds, the Grid of Red supergiant and Asymptotic giant branch star ModelS ({\sc grams}), and the grid of YSO models by Robitaille et al. (2006), we calculate the expected flux-densities and colors in the MIRI broadband filters for prominent infrared stellar populations. We use these fluxes to explore the {\em JWST}/MIRI colours and magnitudes for composite stellar population studies of Local Volume galaxies. MIRI colour classification schemes are presented; these diagrams provide a powerful means of identifying young stellar objects, evolved stars and extragalactic background galaxies in Local Volume galaxies with a high degree of confidence. Finally, we examine which filter combinations are best for selecting populations of sources based on their JWST colours., Comment: 16 pages, 7 figures, 2 online tables; accepted for publication in ApJ

We present new SOFIA-FORCAST observations obtained in Feburary 2016 of the archetypal outbursting low mass young stellar object FU Orionis, and compare the continuum, solid state, and gas properties with mid-IR data obtained at the same wavelengths in 2004 with Spitzer-IRS. In this study, we conduct the first mid-IR spectroscopic comparison of an FUor over a long time period. Over a 12 year period, UBVR monitoring indicates that FU Orionis has continued its steady decrease in overall brightness by ~ 14%. We find that this decrease in luminosity occurs only at wavelengths < 20 microns. In particular, the continuum short ward of the silicate emission complex at 10 microns exhibits a ~ 12% (~ 3 sigma) drop in flux density, but no apparent change in slope; both the Spitzer and SOFIA spectra are consistent with a 7200 K blackbody. Additionally, the detection of water absorption is consistent with the Spitzer spectrum. The silicate emission feature at 10 microns continues to be consistent with unprocessed grains, unchanged over 12 years. We conclude that either the accretion rate in FU Orionis has decreased by ~ 12-14% over this time baseline, or that the inner disk has cooled, but the accretion disk remains in a superheated state outside of the innermost region., 12 pages, 7 figures

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: Attempt to, for the first time, spectrally resolve CO thermal line emission in a small sample of AGB stars in the Large Magellanic Cloud. Methods: ALMA was used to observe 2 OH/IR stars and 4 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. Gas-to-dust ratios are derived that make the predicted velocities agree with the observed ones. The expansion velocities and MLRs are compared to a Galactic sample of well-studied relatively low MLRs stars supplemented with "extreme" C-stars that have properties more similar to the LMC targets. Gas MLRs derived from a simple formula are significantly smaller than derived from the 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 it appears that for C stars the wind expansion velocities in the LMC are lower than in the solar neighbourhood, while the MLRs appear similar. This is in agreement with dynamical dust-driven wind models., Accepted for publication by A&A

We explore the wind-driving mechanism of giant stars through the nearby (117 pc), intermediate-luminosity ($L \approx 1600$ L$_\odot$) star EU Del (HIP 101810, HD 196610). APEX observations of the CO (3--2) and (2--1) transitions are used to derive a wind velocity of 9.51 $\pm$ 0.02 km s$^{-1}$, a $^{12}$C/$^{13}$C ratio of 14 $^{+9}_{-4}$, and a mass-loss rate of a few $\times$ 10$^{-8}$ M$_\odot$ yr$^{-1}$. From published spectra, we estimate that the star has a metallicity of [Fe/H] = --0.27 $\pm$ $\sim$0.30 dex. The star's dusty envelope lacks a clear 10-$\mu$m silicate feature, despite the star's oxygen-rich nature. Radiative transfer modelling cannot fit a wind acceleration model which relies solely on radiation pressure on condensing dust. We compare our results to VY Leo (HIP 53449), a star with similar temperature and luminosity, but different pulsation properties. We suggest the much stronger mass loss from EU Del may be driven by long-period stellar pulsations, due to its potentially lower mass. We explore the implications for the mass-loss rate and wind velocities of other stars., Comment: 11 pages, 3 figures

We present JHK$_{s}$ observations of the metal-poor ([Fe/H] $10^{-11}$ $M_\odot \,{\rm yr}^{-1}$, confirming that metal-poor stars can form substantial amounts of dust. We also find tentative evidence for oxygen-rich dust formation at low metallicity, contradicting previous models that suggest oxygen-rich dust production is inhibited in metal-poor environments. The total rates of dust injection into the interstellar medium of Leo A and Sextans A are (8.2 $\pm$ 1.8) $\times 10^{-9}$ $M_\odot \,{\rm yr}^{-1}$ and (6.2 $\pm$ 0.2) $\times 10^{-7}$ $M_\odot \,{\rm yr}^{-1}$, respectively. The majority of this dust is produced by a few very dusty evolved stars, and does not vary strongly with metallicity., Comment: 21 pages, 11 figures, 10 tables; accepted for publication in ApJ

ALMA observations show a non-detection of carbon monoxide around the four most luminous asymptotic giant branch (AGB) stars in the globular cluster 47 Tucanae. Stellar evolution models and star counts show that the mass-loss rates from these stars should be ~1.2-3.5 x 10^-7 solar masses per year. We would naively expect such stars to be detectable at this distance (4.5 kpc). By modelling the ultraviolet radiation field from post-AGB stars and white dwarfs in 47 Tuc, we conclude CO should be dissociated abnormally close to the stars. We estimate that the CO envelopes will be truncated at a few hundred stellar radii from their host stars and that the line intensities are about two orders of magnitude below our current detection limits. The truncation of CO envelopes should be important for AGB stars in dense clusters. Observing the CO (3-2) and higher transitions and targeting stars far from the centres of clusters should result in the detections needed to measure the outflow velocities from these stars., Comment: 14 pages, 4 figures, accepted MNRAS

We used Spitzer's Infrared Spectrograph (IRS) to observe stars in the Small Magellanic Cloud (SMC) selected from the Midcourse Space Experiment (MSX) Point Source Catalog. We concentrate on the dust properties of oxygen-rich evolved stars, which show less alumina than Galactic stars. This difference may arise from the SMC's lower metallicity, but it could be a selection effect: the SMC sample includes more stars which are brighter and thus more massive. The distribution of SMC stars along the silicate sequence looks more like that of Galactic red supergiants than asymptotic giant branch stars (AGBs). While many are definitively AGBs, several SMC stars show evidence of hot bottom burning. Other sources show mixed chemistry (oxygen-rich and carbon-rich features), including supergiants with PAH emission. MSX SMC 134 may be the first confirmed silicate/carbon star in the SMC, and MSX SMC 049 is a post-AGB candidate. MSX SMC 145, previously a candidate OH/IR star, is actually an AGB star with a background galaxy at z=0.16 along the same line-of-sight. We consider the overall characteristics of all the {\em MSX} sources, the most infrared-bright objects in the SMC, in light of {\em Spitzer}'s higher sensitivity and resolution, and compare them with the object types expected from the original selection criteria. This population represents what will be seen in more distant galaxies by the James Webb Space Telescope (JWST). Color-color diagrams using the IRS spectra and JWST mid-infrared filters show how one can separate evolved stars from young stellar objects (YSOs) and distinguish among different YSO classes., Comment: Accepted for publication in ApJ

We study the evolved stellar population of the galaxy Sextans A. This galaxy is one of the lowest metallicity dwarfs in which variable asymptotic giant branch stars have been detected, suggesting that little metal enrichment took place during the past history. The analysis consists in the characterization of a sample of evolved stars, based on evolutionary tracks of asymptotic giant branch and red super giant stars, which include the description of dust formation in their winds. Use of mid-infrared and near-infrared data allowed us to identify carbon-rich sources, stars undergoing hot bottom burning and red super giants. The dust production rate, estimated as $6\times 10^{-7} M_{\odot}/$yr, is dominated by $\sim 10$ carbon stars, with a small contribution of higher mass M-stars, of the order of $4\times 10^{-8} M_{\odot}/$yr. The importance of this study to understand how dust production works in metal-poor environments is also evaluated., 13 pages, 5 figures, accepted for publication in MNRAS