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We present SCUBA-2/POL-2 850 $\mu$m polarimetric observations of the circumstellar envelope (CSE) of the carbon-rich asymptotic giant branch (AGB) star IRC+10216. Both FIR and optical polarization data indicate grains aligned with their long axis in the radial direction relative to the central star. The 850 $\mu$m polarization does not show this simple structure. The 850 $\mu$m data are indicative, albeit not conclusive, of a magnetic dipole geometry. Assuming such a simple dipole geometry, the resulting 850 $\mu$m polarization geometry is consistent with both Zeeman observations and small-scale structure in the CSE. While there is significant spectral line polarization contained within the SCUBA-2 850 $\mu$m pass-band for the source, it is unlikely that our broadband polarization results are dominated by line polarization. To explain the required grain alignment, grain mineralogy effects, due to either fossil silicate grains from the earlier oxygen-rich AGB phase of the star, or due to the incorporation of ferromagnetic inclusions in the largest grains, may play a role. We argue that the most likely explanation is due to a new alignment mechanism \citep{arXiv:2009.11304} wherein a charged grain, moving relative to the magnetic field, precesses around the induced electric field and therefore aligns with the magnetic field. This mechanism is particularly attractive as the optical, FIR, and sub-mm wave polarization of the carbon dust can then be explained in a consistent way, differing simply due to the charge state of the grains., Comment: Accepted in ApJ v2 - title update to match published manuscript

Interstellar dust grain alignment causes polarization from UV to mm wavelengths, allowing the study of the geometry and strength of the magnetic field. Over last couple of decades observations and theory have led to the establishment of the Radiative Alignment Torque (RAT) mechanism as leading candidate to explain the effect. With a quantitatively well constrained theory, polarization can be used not only to study the interstellar magnetic field, but also the dust and other environmental parameters. Photo-dissociation Regions (PDRs), with their intense, anisotropic radiation fields, consequent rapid $\rm H_{2}$ formation, and high spatial density-contrast provide a rich environment for such studies. Here we discuss an expanded optical, NIR, and mm-wave study of the IC\,63 nebula, showing strong $\rm H_{2}$ formation-enhanced alignment and the first direct empirical evidence for disalignment due to gas-grain collisions using high-resolution $\rm HCO^{+}$(J=1-0) observations. We find that relative amount of polarization is marginally anti-correlated with column density of $\rm HCO^{+}$. However, separating the lines of sight of optical polarimetry into those behind, or in front of, a dense clump as seen from $\gamma$ Cas, the distribution separates into two well defined sets, with data corresponding to \enquote{shaded} gas having a shallower slope. This is expected if the decrease in polarization is caused by collisions since collisional disalignment rate is proportional to R$_C\propto n\sqrt{T}$. Ratios of the best-fit slopes for the \enquote{illuminated} and \enquote{shaded} samples of lines of sight agrees, within the uncertainties, with the square-root of the two-temperature H$_2$ excitation in the nebula seen by Thi et al. (2009)., Comment: 14 pages, 6 figures, Accepted for publication in ApJ

How massive stars end their lives remains an open question in the field of star evolution. While the majority of stars above 9 M_sun will become red supergiants (RSGs), the terminal state of these massive stars can be heavily influenced by their mass-loss histories. Periods of enhanced circumstellar wind activity can drive stars off the RSG branch of the HR Diagram. This phase, known as post-RSG evolution, may well be tied to high mass-loss events or eruptions as seen in the Luminous Blue Variables and other massive stars. This article highlights some of the recent observational and modeling studies that seek to characterize this unique class of stars, the post-RSGs, and link them to other massive objects on the HR Diagram such as LBVs, Yellow Hypergiants, and dusty RSGs., Comment: Published in "Luminous stars in Nearby Galaxies." https://www.mdpi.com/journal/galaxies/special_issues/Luminous

We report mid- to far-infrared imaging and photomety from 7 to 37 microns with SOFIA/FORCAST and 2 micron adaptive optics imaging with LBTI/LMIRCam of a large sample of red supergiants (RSGs) in four Galactic clusters; RSGC1, RSGC2=Stephenson 2, RSGC3, and NGC 7419. The red supergiants in these clusters cover their expected range in luminosity and initial mass from approximately 9 to more than 25 Solar masses. The population includes examples of very late-type RSGs such as MY Cep which may be near the end of the RSG stage, high mass losing maser sources, yellow hypergiants and post-RSG candidates. Many of the stars and almost all of the most luminous have spectral energy distributions (SEDs) with extended infrared excess radiation at the longest wavelengths. To best model their SEDs we use DUSTY with a variable radial density distribution function to estimate their mass loss rates. Our mass loss rate -- luminosity relation for 42 RSGs basically follows the classical de Jager curve, but at luminosities below 10^5 Solar luminosities we find a significant population of red supergiants with mass loss rate below the de Jager relation. At luminosities above 10^5 Solar luminosities there is a rapid transition to higher mass loss rates that approximates and overlaps the de Jager curve. We recommend that instead of using a linear relation or single curve, the empirical mass loss rate -- luminosity relation is better represented by a broad band. Interestingly, the transition to much higher mass loss rates at about 10^5 Lsun corresponds approximately to an initial mass of 18 --20 Msun which is close to the upper limit for RSGs becoming Type II SNe., Comment: Accepted for publication in the Astronomical Journal

The obscuring structure surrounding active galactic nuclei (AGN) can be explained as a dust and gas flow cycle that fundamentally connects the AGN with their host galaxies. This structure is believed to be associated with dusty winds driven by radiation pressure. However, the role of magnetic fields, which are invoked in almost all models for accretion onto a supermassive black hole and outflows, is not thoroughly studied. Here we report the first detection of polarized thermal emission by means of magnetically aligned dust grains in the dusty torus of NGC 1068 using ALMA Cycle 4 polarimetric dust continuum observations ($0.07"$, $4.2$ pc; 348.5 GHz, $860$ $\mu$m). The polarized torus has an asymmetric variation across the equatorial axis with a peak polarization of $3.7\pm0.5$\% and position angle of $109\pm2^{\circ}$ (B-vector) at $\sim8$ pc east from the core. We compute synthetic polarimetric observations of magnetically aligned dust grains assuming a toroidal magnetic field and homogeneous grain alignment. We conclude that the measured 860 $\mu$m continuum polarization arises from magnetically aligned dust grains in an optically thin region of the torus. The asymmetric polarization across the equatorial axis of the torus arises from 1) an inhomogeneous optical depth, and 2) a variation of the velocity dispersion, i.e. variation of the magnetic field turbulence at sub-pc scales, from the eastern to the western region of the torus. These observations and modeling constrain the torus properties beyond spectral energy distribution results. This study strongly supports that magnetic fields up to a few pc contribute to the accretion flow onto the active nuclei., Comment: 19 pages, 11 figures (Accepted for Publication to ApJ)

HST/STIS spectra of the small clumps and filaments closest to the central star in VY CMa reveal that the very strong K I emission and TiO and VO molecular emission, long thought to form in a dusty circumstellar shell, actually originate in a few small clumps 100's of AU from the star. The K I lines are 10 to 20 times stronger in these nearest ejecta than on the star. The observations also confirm VO as a circumstellar molecule. In this letter we discuss the spectra of the features, their motions and ages, and the identification of the molecular emission. The strength of the atomic and molecular features in the small clumps present an astrophysical problem for the excitation process. We show that the clumps must have a nearly clear line of sight to the star's radiation., Comment: To appear in the Astrophysical Journal

We present the results of spectroscopy and multi-wavelength photometry of luminous and variable star candidates in the nearby spiral galaxies NGC 2403 and M81. We discuss specific classes of stars, the Luminous Blue Variables (LBVs), B[e] supergiants (sgB[e]), and the high luminosity yellow hypergiants. We identify two new LBV candidates, and three sgB[e] stars in M81. We also find that some stars previously considered LBV candidates are actually field stars. The confirmed and candidate LBVs and sgB[e] stars together with the other confirmed members are shown on the HR Diagrams for their respective galaxies. We also present the HR Diagrams for the two "SN impostors", V37 (SN2002kg) and V12(SN1954J) in NGC 2403 and the stars in their immediate environments., Comment: To appear in the Astronomical Journal

We present high spatial resolution LBTI/NOMIC $9-12$ $\mu m$ images of VY CMa and its massive outflow feature, the Southwest (SW) Clump. Combined with high-resolution imaging from HST ($0.4-1$ $\mu m$) and LBT/LMIRCam ($1-5$ $\mu m$), we isolate the spectral energy distribution (SED) of the clump from the star itself. Using radiative-transfer code DUSTY, we model both the scattered light from VY CMa and the thermal emission from the dust in the clump to estimate the optical depth, mass, and temperature of the SW Clump. The SW Clump is optically thick at 8.9 $\mu m$ with a brightness temperature of $\sim$200 K. With a dust chemistry of equal parts silicates and metallic iron, as well as assumptions on grain size distribution, we estimate a dust mass of $5.4\times10^{-5}\,M_\odot$. For a gas--to--dust ratio of 100, this implies a total mass of $5.4\times10^{-3}\,M_\odot$. Compared to the typical mass-loss rate of VY CMa, the SW Clump represents an extreme, localized mass-loss event from $\lesssim300$ years ago., Comment: Published in AJ, February 2019. 14 pages, 5 figures, 2 tables

We describe new results on two supernova impostors in NGC 2403, SN 1954J(V12) and SN 2002kg(V37). For the famous object SN 1954J we combine four critical observations: its current SED, its Halpha emission line profile, the Ca II triplet in absorption in its red spectrum, and the brightness compared to its pre-event state. Together these strongly suggest that the survivor is now a hot supergiant with T ~ 20000 K, a dense wind, substantial circumstellar extinction, and a G-type supergiant companion. The hot star progenitor of V12's giant eruption was likely in the post-red supergiant stage and had already shed a lot of mass. V37 is a classical LBV/S Dor variable. Our photometry and spectra observed during and after its eruption show that its outburst was an apparent transit on the HR Diagram due to enhanced mass loss and the formation of a cooler, dense wind. V37 is an evolved hot supergiant at ~10^6 Lsun with a probable initial mass of 60 -80 Msun., Comment: To appear in the Astrophysical Journal

New MMT/MIRAC (9-11 {\mu}m), SOFIA/FORCAST (11-37 {\mu}m), and Herschel/PACS (70 and 160 {\mu}m) infrared (IR) imaging and photometry is presented for three famous OH/IR red supergiants (NML Cyg, VX Sgr, and S Per) and two normal red supergiants (RS Per and T Per). We model the observed spectral energy distributions (SEDs) using radiative transfer code DUSTY. Azimuthal average profiles from the SOFIA/FORCAST imaging, in addition to dust mass distribution profiles from DUSTY, constrain the mass-loss histories of these supergiants. For all of our observed supergiants, the DUSTY models suggest that constant mass-loss rates do not produce enough dust to explain the observed infrared emission in the stars' SEDs. Combining our results with Shenoy et al. (2016) (Paper I) we find mixed results with some red supergiants showing evidence for variable and high mass-loss events while others have constant mass loss over the past few thousand years., Comment: 29 pages, 15 figures, 3 tables. Accepted to AJ

We present images and spectral energy distributions (SEDs) of massive young stellar objects (YSOs) in three star-forming H II regions of the Large Magellanic Cloud: N159A, N159 Papillon, and N160. We use photometry from SOFIA/FORCAST at 25.3--37.1 um to constrain model fits to the SEDs and determine luminosities, ages, and dust content of the embedded YSOs and their local environments. By placing these sources on mid-infrared color-magnitude and color-color diagrams, we analyze their dust properties and consider their evolutionary status. Since each object in the FORCAST images has an obvious bright near-infrared counterpart in Spitzer Space Telescope images, we do not find any evidence for new, very cool, previously-undiscovered Class 0 YSOs. Additionally, based on its mid-infrared colors and model parameters, N159A is younger than N160 and the Papillon. The nature of the first extragalactic protostars in N159, P1 and P2, is also discussed., Comment: 31 pages, 8 figures, 3 tables. Accepted for publication in ApJ, November 2016

In this series of papers we have presented the results of a spectroscopic survey of luminous and variable stars in the nearby spirals M31 and M33. In this paper, we present spectroscopy of 132 additional luminous stars, variables, and emission line objects. Most of the stars have emission line spectra, including LBVs and candidate LBVs, Fe II emission line stars and the B[e] supergiants, and the warm hypergiants. Many of these objects are spectroscopically similar and are often confused with each other. With this large spectroscopic data set including various types of emission line stars, we examine their similarities and differences and propose the following criteria that can be used to help distinguish these stars in future work: 1. The B[e] supergiants have emission lines of [O I] and [Fe II] in their spectra. Most of the spectroscopically confirmed sgB[e] stars also have warm circumstellar dust in their SEDs. 2. Confirmed LBVs do not have the [O I] emission lines in their spectra. Some LBVs have [Fe II] emission lines, but not all. Their SEDS shows free-free emission in the near-infrared but no evidence for warm dust. Their most important and defining characteristic is the S Dor-type variability. 3. The warm hypergiants spectroscopically resemble both the LBVs in their eruption or dense wind state and the B[e] supergiants. However, they are very dusty. Some have [Fe II] and [O I] emission in their spectra like the sgB[e] stars, but can be distinguished by their absorption line spectra characteristic of A and F-type supergiants. In contrast, the B[e] supergiant spectra have strong continua and few if any apparent absorption lines., Comment: 42 pages, 6 figures, 7 tables. Submitted to ApJ for publication, November 2016

The supernova impostor PSN J09132750+7627410 in NGC 2748 reached a maximum luminosity of approximately -14 mag. It was quickly realized that its was not a true supernova, but another example of a non-terminal giant eruption. PSN J09132750+7627410 is distinguished by multiple P Cygni absorption minima in the Balmer emission lines that correspond to outflow velocities of -400, -1100, and -1600 km/s. Multiple outflows have been observed in only a few other objects. In this paper we describe the evolution of the spectrum and the P Cygni profiles for three months past maximum, the post-maximum formation of a cool, dense wind, and the identification of a possible progenitor. One of the possible progenitors is an infrared source. Its pre-eruption spectral energy distribution suggests a bolometric luminosity of -8.3 mag and a dust temperature of 780 degrees K. If it is the progenitor it is above the AGB limit unlike the intermediate luminosity red transients. The three P Cygni profiles could be due to ejecta from the current eruption, the wind of the progenitor, or previous mass loss events. We suggest that they were all formed as part of the same high mass loss event and are due to material ejected at different velocities or energies. We also suggest that multiple outflows during giant eruptions may be more common than reported., Comment: To appear in the Astrophysical Journal

Recent supernova and transient surveys have revealed an increasing number of non-terminal stellar eruptions. Though the progenitor class of these eruptions includes the most luminous stars, little is known of the pre-supernova mechanics of massive stars in their most evolved state, thus motivating a census of possible progenitors. From surveys of evolved and unstable luminous star populations in nearby galaxies, we select a sample of yellow and red supergiant candidates in M31 and M33 for review of their spectral characteristics and spectral energy distributions. Since the position of intermediate and late-type supergiants on the color-magnitude diagram can be heavily contaminated by foreground dwarfs, we employ spectral classification and multi-band photometry from optical and near-infrared surveys to confirm membership. Based on spectroscopic evidence for mass loss and the presence of circumstellar dust in their SEDs, we find that $30-40\%$ of the yellow supergiants are likely in a post-red supergiant state. Comparison with evolutionary tracks shows that these mass-losing, post-RSGs have initial masses between $20-40\,M_{\odot}$. More than half of the observed red supergiants in M31 and M33 are producing dusty circumstellar ejecta. We also identify two new warm hypergiants in M31, J004621.05+421308.06 and J004051.59+403303.00, both of which are likely in a post-RSG state., Comment: Accepted for publication in ApJ. 34 pages, 11 figures

In a recent paper, Smith and Tombleson (2015) state that the Luminous Blue Variables (LBVs) in the Milky Way and the Magellanic Clouds are isolated; that they are not spatially associated with young O-type stars. They propose a novel explanation that would overturn the standard view of LBVs. In this paper we test their hypothesis for the LBVs in M31 and M33 as well as the LMC and SMC. In M31 and M33, the LBVs are associated with luminous young stars and supergiants appropriate to their luminosities and positions on the HR Diagram. Moreover, in the Smith and Tombleson scenario most of the LBVs should be runaway stars, but the stars' velocities are consistent with their positions in the respective galaxies. In the Magellanic Clouds, those authors' sample was a mixed population. We reassess their analysis, removing seven stars that have no clear relation to LBVs. When we separate the more massive classical and the less luminous LBVs, the classical LBVs have a distribution similar to the late O-type stars, while the less luminous LBVs have a distribution like the red supergiants. None of the confirmed LBVs have high velocities or are candidate runaway stars. These results support the accepted description of LBVs as evolved massive stars that have shed a lot of mass, and are now close to their Eddington limit., Comment: To appear in the Astrophysical Journal With an expanded discussion of statistical errors

We report the fifth confirmed Luminous Blue Variable/S Doradus variable in M31. In 2006, J004526.62+415006.3 had the spectrum of hot Fe II emission line star with strong P Cygni profiles in the Balmer lines. In 2010, its absorption line spectrum resembled an early A-type supergiant with H and Fe II emission lines with strong P Cygni profiles, and in 2013 the spectrum had fully transitioned to an F-type supergiant due to the formation of the optically thick, cool wind which characterizes LBVs at maximum light. The photometric record supports the LBV/S Dor nature of the variability. Its bolometric luminosity ~ -9.65 mag places it on the HR Diagram near the known LBVs, AE And, Var C in M33 and S Dor.

We present constraints on cosmological and astrophysical parameters from high-resolution microwave background maps at 148 GHz and 218 GHz made by the Atacama Cosmology Telescope (ACT) in three seasons of observations from 2008 to 2010. A model of primary cosmological and secondary foreground parameters is fit to the map power spectra and lensing deflection power spectrum, including contributions from both the thermal Sunyaev-Zeldovich (tSZ) effect and the kinematic Sunyaev-Zeldovich (kSZ) effect, Poisson and correlated anisotropy from unresolved infrared sources, radio sources, and the correlation between the tSZ effect and infrared sources. The power ell^2 C_ell/2pi of the thermal SZ power spectrum at 148 GHz is measured to be 3.4 +\- 1.4 muK^2 at ell=3000, while the corresponding amplitude of the kinematic SZ power spectrum has a 95% confidence level upper limit of 8.6 muK^2. Combining ACT power spectra with the WMAP 7-year temperature and polarization power spectra, we find excellent consistency with the LCDM model. We constrain the number of effective relativistic degrees of freedom in the early universe to be Neff=2.79 +\- 0.56, in agreement with the canonical value of Neff=3.046 for three massless neutrinos. We constrain the sum of the neutrino masses to be Sigma m_nu < 0.39 eV at 95% confidence when combining ACT and WMAP 7-year data with BAO and Hubble constant measurements. We constrain the amount of primordial helium to be Yp = 0.225 +\- 0.034, and measure no variation in the fine structure constant alpha since recombination, with alpha/alpha0 = 1.004 +/- 0.005. We also find no evidence for any running of the scalar spectral index, dns/dlnk = -0.004 +\- 0.012., Comment: 26 pages, 22 figures. This paper is a companion to Das et al. (2013) and Dunkley et al. (2013). Matches published JCAP version

We conduct a search for radio stars by combining radio and optical data from the Faint Images of the Radio Sky at Twenty cm survey (FIRST) and the Sloan Digital Sky Survey (SDSS). The faint limit of SDSS makes possible a homogeneous search for radio emission from stars of low optical luminosity. We select a sample of 112 candidate radio stars in the magnitude range $15