arXiv subjects

D. John Hillier

Publications and source records attributed to D. John Hillier.

At least 73 records · Page 4Linked to original sources

arXiv2017

The Evolution and Physical Parameters of WN3/O3s: a New Type of Wolf-Rayet Star

As part of a search for Wolf-Rayet (WR) stars in the Magellanic Clouds, we have discovered a new type of WR star in the Large Magellanic Cloud (LMC). These stars have both strong emission lines, as well as He ii and Balmer absorption lines and spectroscopically resemble a WN3 and O3V binary pair. However, they are visually too faint to be WN3+O3V binary systems. We have found nine of these WN3/O3s, making up ~6% of the population of LMC WRs. Using CMFGEN, we have successfully modeled their spectra as single stars and have compared the physical parameters with those of more typical LMC WNs. Their temperatures are around 100,000 K, a bit hotter than the majority of WN stars (by around 10,000 K) although a few hotter WNs are known. The abundances are what you would expect for CNO equilibrium. However, most anomalous are their mass-loss rates which are more like that of an O-type star than a WN star. While their evolutionary status is uncertain, their low mass-loss rates and wind velocities suggest that they are not products of homogeneous evolution. It is possible instead that these stars represent an intermediate stage between O stars and WNs. Since WN3/O3 stars are unknown in the Milky Way, we suspect that their formation depends upon metallicity, and we are investigating this further by a deep survey in M33, which posses a metallicity gradient.

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arXiv2017

Explosion of red-supergiant stars: influence of the atmospheric structure on shock breakout and the early-time supernova radiation

Early-time observations of the Type II supernovae (SNe) 2013cu and 2013fs have revealed an interaction of ejecta with material near the star surface. Unlike the Type IIn SN2010jl, which interacts with a dense wind for ~1yr, the interaction ebbs after 2-3d, suggesting a dense and compact circumstellar envelope. Here, we use multi-group radiation-hydrodynamics and non-local-thermodynamic-equilibrium radiative transfer to explore the properties of red supergiant (RSG) star explosions embedded in a variety of dense envelopes. We consider the cases of an extended static atmosphere or a steady-state wind, adopting a range of mass loss rates. The shock-breakout signal, the SN radiation up to 10d, and the ejecta dynamics are strongly influenced by the properties of this nearby environment. This compromises the use of early-time observations to constrain Rstar. The presence of narrow lines for 2-3d in 2013fs and 2013cu require a cocoon of material of ~0.01Msun out to 5-10Rstar. Spectral lines evolve from electron-scattering to Doppler broadened, with a growing blueshift of their emission peaks. Recent studies propose a super-wind phase with a mass loss rate from 0.001 up to 1Msun/yr in the last months/years of the RSG life, although there is no observational constraint that this external material is a steady-state outflow. Alternatively, observations may be explained by the explosion of a RSG star inside its complex atmosphere. Indeed, spatially resolved observations reveal that RSG stars have extended atmospheres, with the presence of downflows and upflows out to several Rstar, even in a standard RSG like Betelgeuse. Mass loading in the region intermediate between star and wind can accommodate the 0.01Msun needed to explain the observations of 2013fs. A puzzling super-wind phase prior to core-collapse may be therefore superfluous [Abridged].

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arXiv2017

Radiative-transfer models for explosions from rotating and non-rotating single WC stars. Implications for SN1998bw and LGRB/SNe

Using 1-D non-Local-Thermodynamic-Equilibrium time-dependent radiative-transfer simulations, we study the ejecta properties required to match the early and late-time photometric and spectroscopic properties of supernovae (SNe) associated with long-duration gamma-ray bursts (LGRBs). To match the short rise time, narrow light curve peak, and extremely broad spectral lines of SN1998bw requires a model with <3Msun ejecta but a high explosion energy of a few 1e52erg and 0.5Msun of Ni56. However the relatively high luminosity, the presence of narrow spectral lines of intermediate mass elements, and the low ionization at the nebular stage are matched with a more standard C-rich Wolf-Rayet (WR) star explosion, with an ejecta of >10Msun, an explosion energy >1e51erg, and only 0.1Msun of Ni56. As the two models are mutually exclusive, the breaking of spherical symmetry is essential to match the early/late photometric/spectroscopic properties of SN1998bw. This conclusion confirms the notion that the ejecta of SN1998bw is aspherical on large scales. More generally, with asphericity, the energetics and Ni56 mass of LGRB/SNe are reduced and their ejecta mass is increased, favoring a massive fast-rotating Wolf-Rayet star progenitor. Contrary to persisting claims in favor of the proto-magnetar model for LGRB/SNe, such progenitor/ejecta properties are compatible with collapsar formation. Ejecta properties of LGRB/SNe inferred from 1D radiative-transfer modeling are fundamentally flawed.

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arXiv2017

The Evolutionary Status of WN3/O3 Wolf-Rayet Stars

As part of a multi-year survey for Wolf-Rayet stars in the Magellanic Clouds, we have discovered a new type of Wolf-Rayet star with both strong emission and absorption. While one might initially classify these stars as WN3+O3V binaries based on their spectra, such a pairing is unlikely given their faint visual magnitudes. Spectral modeling suggests effective temperatures and bolometric luminosities similar to those of other early-type LMC WNs but with mass-loss rates that are three to five times lower than expected. They additionally retain a significant amount of hydrogen, with nitrogen at its CNO-equilibrium value (10x enhanced). Their evolutionary status remains an open question. Here we discuss why these stars did not evolve through quasi-homogeneous evolution. Instead we suggest that based on a link with long-duration gamma ray bursts, they may form in lower metallicity environments. A new survey in M33, which has a large metallicity gradient, is underway.

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arXiv2016

A study of the low-luminosity Type II-Plateau supernova 2008bk

Supernova (SN) 2008bk is a well observed low-luminosity Type II event visually associated with a low-mass red-supergiant progenitor. To model SN 2008bk, we evolve a 12Msun star from the main sequence until core collapse, when it has a total mass of 9.88Msun, a He-core mass of 3.22Msun, and a radius of 502Rsun. We then artificially trigger an explosion that produces 8.29Msun of ejecta with a total energy of 2.5x10^50erg and ~0.009Msun of 56Ni. We model the subsequent evolution of the ejecta with non-Local-Thermodynamic-Equilibrium time-dependent radiative transfer. Although somewhat too luminous and energetic, this model reproduces satisfactorily the multi-band light curves and multi-epoch spectra of SN 2008bk, confirming the suitability of a low-mass massive star progenitor. As in other low-luminosity SNe II, the structured Halpha profile at the end of the plateau phase is probably caused by BaII 6496.9A rather than asphericity. We discuss the sensitivity of our results to changes in progenitor radius and mass, as well as chemical mixing. A 15% increase in progenitor radius causes a 15% increase in luminosity and a 0.2mag V-band brightening of the plateau but leaves its length unaffected. An increase in ejecta mass by 10% lengthens the plateau by ~10d. Chemical mixing introduces slight changes to the bolometric light curve, limited to the end of the plateau, but has a large impact on colours and spectra at nebular times.

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arXiv2016

To $v_\infty$ and beyond! The He I absorption variability across the 2014.6 periastron passage of $η$ Carinae

We have monitored the massive binary star $η$ Carinae with the CTIO/SMARTS 1.5~m telescope and CHIRON spectrograph from the previous apastron passage of the system through the recent 2014.6 periastron passage. Our monitoring has resulted in a large, homogeneous data set with an unprecedented time-sampling, spectral resolving power, and signal-to-noise. This allowed us to investigate temporal variability previously unexplored in the system and discover a kinematic structure in the P Cygni absorption troughs of neutral helium wind lines. The features observed occurred prior to the periastron passage and are seen as we look through the trailing arm of the wind-wind collision shock cone. We show that the bulk of the variability is repeatable across the last five periastron passages, and that the absorption occurs in the inner 230 AU of the system. In addition, we found an additional, high-velocity absorption component super-imposed on the P Cygni absorption troughs that has been previously un-observed in these lines, but which bears resemblance to the observations of the He~I $λ$10830 Å feature across previous cycles. Through a comparison of the current smoothed particle hydrodynamical simulations, we show that the observed variations are likely caused by instabilities in the wind-wind collision region in our line-of-sight, coupled with stochastic variability related to clumping in the winds.

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arXiv2016

Modelling the Central Constant Emission X-ray component of eta Carinae

The X-ray emission of $η$ Carinae shows multiple features at various spatial and temporal scales. The central constant emission (CCE) component is centred on the binary and arises from spatial scales much smaller than the bipolar Homunculus nebula, but likely larger than the central wind--wind collision region between the stars as it does not vary over the $\sim$2-3 month X-ray minimum when it can be observed. Using large-scale 3D smoothed particle hydrodynamics (SPH) simulations, we model both the colliding-wind region between the stars, and the region where the secondary wind collides with primary wind ejected from the previous periastron passage. The simulations extend out to one hundred semimajor axes and make two limiting assumptions (strong coupling and no coupling) about the influence of the primary radiation field on the secondary wind. We perform 3D radiative transfer calculations on the SPH output to synthesize the X-ray emission, with the aim of reproducing the CCE spectrum. For the preferred primary mass-loss rate $\dot{M}_A\approx8.5\times10^{-4}$ M$_\odot$ yr$^{-1}$, the model spectra well reproduce the observation as the strong- and no-coupling spectra bound the CCE observation for longitude of periastron $ω\approx252^\circ$, and bound/converge on the observation for $ω\approx90^\circ$. This suggests that $η$ Carinae has moderate coupling between the primary radiation and secondary wind, that both the region between the stars and the comoving collision on the backside of the secondary generate the CCE, and that the CCE cannot place constraints on the binary's line of sight. We also discuss comparisons with common X-ray fitting parameters.

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arXiv2016

Inferring supernova IIb/Ib/Ic ejecta properties from light curves and spectra: Correlations from radiative-transfer models

We present 1-D non-Local-Thermodynamic-Equilibrium time-dependent radiative-transfer simulations for a large grid of supernovae (SNe) IIb/Ib/Ic that result from the terminal explosion of the mass donor in a close-binary system. Our sample covers ejecta masses $M_{\rm e}$ of 1.7$-$5.2M$_\odot$, kinetic energies $E_{\rm kin}$ of 0.6$-$5.0$\times$10$^{51}$erg, and $^{56}$Ni masses of 0.05$-$0.30M$_\odot$. We find a strong correlation between the $^{56}$Ni mass and the photometric properties at maximum, and between the rise time to bolometric maximum and the post-maximum decline rate. We confirm the small scatter in ($V-R$) at 10d past $R$-band maximum. The quantity $V_{\rm m} \equiv \sqrt{2E_{\rm kin}/M_{\rm e}}$ is comparable to the Doppler velocity measured from HeI 5875Å at maximum in SNe IIb/Ib, although some scatter arises from the uncertain level of chemical mixing. The OI7772Å line may be used for SNe Ic, but the correspondence deteriorates with higher ejecta mass/energy. We identify a temporal reversal of the Doppler velocity at maximum absorption in the $\sim$1.05$μ$m feature in all models. The reversal is due to HeI alone and could serve as a test for the presence of helium in SNe Ic. Because of variations in composition and ionisation, the ejecta opacity shows substantial variations with both velocity and time. This is in part the origin of the offset between our model light curves and the predictions from the Arnett model.

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arXiv2016

Models of interacting supernovae and their spectral diversity

Using radiation-hydrodynamics and radiative-transfer simulations, we explore the origin of the spectral diversity of interacting supernovae (SNe) of type IIn. We revisit SN1994W and investigate the dynamical configurations that can give rise to spectra with narrow lines at all times. We find that a standard ~10Msun 10^51erg SN ejecta ramming into a 0.4Msun dense CSM is inadequate for SN1994W, as it leads to the appearance of broad lines at late times. This structure, however, generates spectra that exhibit the key morphological changes seen in SN1998S. For SN1994W, we consider a completely different configuration, which involves the interaction at a large radius of a low mass inner shell with a high mass outer shell. Such a structure may arise in an 8-12Msun star from a nuclear flash (e.g., of Ne) followed within a few years by core collapse. Our simulations show that the large mass of the outer shell leads to the complete braking of the inner shell material, the formation of a slow dense shell, and the powering of a luminous SN IIn, even for a low inner shell energy. Early on, our model line profiles are typical of SNe IIn, exhibiting narrow cores and broad electron-scattering wings. As observed in SN1994W, they also remain narrow at late times. Our SN1994W model invokes two low energy ejections, both atypical of observed massive stars, and illustrates the diversity of configurations leading to SNe IIn. These results also highlight the importance of spectra to constrain the dynamical properties and understand the origin of SNe IIn.

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arXiv2015

X-ray, UV and optical analysis of supergiants: $ε$ Ori

We present a multi-wavelength (X-ray to optical) analysis, based on non-local thermodynamic equilibrium photospheric+wind models, of the B0 Ia-supergiant: $ε$~Ori. The aim is to test the consistency of physical parameters, such as the mass-loss rate and CNO abundances, derived from different spectral bands. The derived mass-loss rate is $\dot{M}/\sqrt{f_\infty}\sim$1.6$\times$10$^{-6}$ M$_\odot$ yr$^{-1}$ where $f_\infty$ is the volume filling factor. However, the S IV $λλ$1062,1073 profiles are too strong in the models; to fit the observed profiles it is necessary to use $f_\infty<$0.01. This value is a factor of 5 to 10 lower than inferred from other diagnostics, and implies $\dot{M} \lesssim1 \times 10^{-7}$ M$_\odot$ yr$^{-1}$. The discrepancy could be related to porosity-vorosity effects or a problem with the ionization of sulfur in the wind. To fit the UV profiles of N V and O VI it was necessary to include emission from an interclump medium with a density contrast ($ρ_{cl}/ρ_{ICM}$) of $\sim$100. X-ray emission in H-He like and Fe L lines was modeled using four plasma components located within the wind. We derive plasma temperatures from $1 \times 10^{6}$ to $7\times 10^{6}$ K, with lower temperatures starting in the outer regions (R$_0\sim$3-6 R$_*$), and a hot component starting closer to the star (R$_0\lesssim$2.9 R$_*$). From X-ray line profiles we infer $\dot{M} <\, 4.9\times10^{-7}$ M$_\odot$ yr$^{-1}$. The X-ray spectrum ($\geq$0.1 kev) yields an X-ray luminosity $L_{\rm X}\sim 2.0\times10^{-7} L_{\rm bol}$, consistent with the superion line profiles. X-ray abundances are in agreement with those derived from the UV and optical analysis: $ε$ Ori is slightly enhanced in nitrogen and depleted in carbon and oxygen, evidence for CNO processed material.

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arXiv2015

Radiative-transfer models for supernovae IIb/Ib/Ic from binary-star progenitors

We present 1-D non-Local-Thermodynamic-Equilibrium time-dependent radiative-transfer simulations for supernovae (SNe) of type IIb, Ib, and Ic that result from the terminal explosion of the mass donor in a close-binary system. Here, we select three ejecta with a total kinetic energy of ~1.2e51erg, but characterised by different ejecta masses (2-5Msun), composition, and chemical mixing. The type IIb/Ib models correspond to the progenitors that have retained their He-rich shell at the time of explosion. The type Ic model arises from a progenitor that has lost its helium shell, but retains 0.32Msun of helium in a CO-rich core of 5.11Msun. We discuss their photometric and spectroscopic properties during the first 2-3 months after explosion, and connect these to their progenitor and ejecta properties including chemical stratification. For these three models, Arnett's rule overestimates the 56Ni mass by ~50% while the procedure of Katz et al., based on an energy argument, yields a more reliable estimate. The presence of strong CI lines around 9000A prior to maximum is an indicator that the pre-SN star was under-abundant in helium. As noted by others, the 1.08micron feature is a complex blend of CI, MgII, and HeI lines, which makes the identification of He uncertain in SNe Ibc unless other HeI lines can be identified. Our models show little scatter in (V-R) colour 10d after R-band maximum. We also address a number of radiative transfer properties of SNe Ibc, including the notion of a photosphere, the inference of a representative ejecta expansion rate, spectrum formation, blackbody fits and "correction factors".

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arXiv2015

Measuring nickel masses in Type Ia supernovae using cobalt emission in nebular phase spectra

The light curves of Type Ia supernovae (SNe Ia) are powered by the radioactive decay of $^{56}$Ni to $^{56}$Co at early times, and the decay of $^{56}$Co to $^{56}$Fe from ~60 days after explosion. We examine the evolution of the [Co III] 5892 A emission complex during the nebular phase for SNe Ia with multiple nebular spectra and show that the line flux follows the square of the mass of $^{56}$Co as a function of time. This result indicates both efficient local energy deposition from positrons produced in $^{56}$Co decay, and long-term stability of the ionization state of the nebula. We compile 77 nebular spectra of 25 SN Ia from the literature and present 17 new nebular spectra of 7 SNe Ia, including SN2014J. From these we measure the flux in the [Co III] 5892 A line and remove its well-behaved time dependence to infer the initial mass of $^{56}$Ni ($M_{Ni}$) produced in the explosion. We then examine $^{56}$Ni yields for different SN Ia ejected masses ($M_{ej}$ - calculated using the relation between light curve width and ejected mass) and find the $^{56}$Ni masses of SNe Ia fall into two regimes: for narrow light curves (low stretch s~0.7-0.9), $M_{Ni}$ is clustered near $M_{Ni}$ ~ 0.4$M_\odot$ and shows a shallow increase as $M_{ej}$ increases from ~1-1.4$M_\odot$; at high stretch, $M_{ej}$ clusters at the Chandrasekhar mass (1.4$M_\odot$) while $M_{Ni}$ spans a broad range from 0.6-1.2$M_\odot$. This could constitute evidence for two distinct SN Ia explosion mechanisms.

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arXiv2015

Numerical simulations of super-luminous supernovae of type IIn

We present numerical simulations that include 1-D Eulerian multi-group radiation-hydrodynamics, 1-D non-LTE radiative transfer, and 2-D polarised radiative transfer for super-luminous interacting supernovae (SNe). Our reference model is a ~10Msun inner shell with 10^51erg ramming into a ~3Msun cold outer shell (the circumstellar-medium, or CSM) that extends from 10^15cm to 2x10^16cm and moves at 100km/s. We discuss the light curve evolution, which cannot be captured adequately with a grey approach. In these interactions, the shock-crossing time through the optically-thick CSM is much longer than the photon diffusion time. Radiation is thus continuously leaking from the shock through the CSM, in disagreement with the shell-shocked model that is often invoked. Our spectra redden with time, with a peak distribution in the near-UV during the first month gradually shifting to the optical range over the following year. Initially Balmer lines exhibit a narrow line core and the broad line wings that are characteristic of electron scattering in the SNe IIn atmospheres (CSM). At later times they also exhibit a broad blue shifted component which arises from the cold dense shell. Our model results are broadly consistent with the bolometric light curve and spectral evolution observed for SN2010jl. Invoking a prolate pole-to-equator density ratio in the CSM, we can also reproduce the ~2% continuum polarisation, and line depolarisation, observed in SN2010jl. By varying the inner shell kinetic energy and the mass and extent of the outer shell, a large range of peak luminosities and durations, broadly compatible with super-luminous SNe IIn like 2010jl or 2006gy, can be produced.

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arXiv2015

A one-dimensional Chandrasekhar-mass delayed-detonation model for the broad-lined Type Ia supernova 2002bo

We present 1D non-local thermodynamic equilibrium (non-LTE) time-dependent radiative-transfer simulations of a Chandrasekhar-mass delayed-detonation model which synthesizes 0.51 Msun of 56Ni, and confront our results to the Type Ia supernova (SN Ia) 2002bo over the first 100 days of its evolution. Assuming only homologous expansion, this same model reproduces the bolometric and multi-band light curves, the secondary near-infrared (NIR) maxima, and the optical and NIR spectra. The chemical stratification of our model qualitatively agrees with previous inferences by Stehle et al., but reveals significant quantitative differences for both iron-group and intermediate-mass elements. We show that +/-0.1 Msun (i.e., +/-20 per cent) variations in 56Ni mass have a modest impact on the bolometric and colour evolution of our model. One notable exception is the U-band, where a larger abundance of iron-group elements results in less opaque ejecta through ionization effects, our model with more 56Ni displaying a higher near-UV flux level. In the NIR range, such variations in 56Ni mass affect the timing of the secondary maxima but not their magnitude, in agreement with observational results. Moreover, the variation in the I, J, and K_s magnitudes is less than 0.1 mag within ~10 days from bolometric maximum, confirming the potential of NIR photometry of SNe Ia for cosmology. Overall, the delayed-detonation mechanism in single Chandrasekhar-mass white dwarf progenitors seems well suited for SN 2002bo and similar SNe Ia displaying a broad Si II 6355 A line. Whatever multidimensional processes are at play during the explosion leading to these events, they must conspire to produce an ejecta comparable to our spherically-symmetric model.

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arXiv2014

One-dimensional non-LTE time-dependent radiative transfer of an He-detonation model and the connection to faint and fast-decaying supernovae

We present non-LTE time-dependent radiative transfer simulations for ejecta produced by the detonation of an helium shell at the surface of a low-mass carbon/oxygen white dwarf (WD). This mechanism is one possible origin for supernovae (SNe) with faint and fast-decaying light curves, such as .Ia SNe and Ca-rich transients. Our initial ejecta conditions at 1d are given by the 0.18B explosion model COp45HEp2 of Waldman et al.. The 0.2Msun ejecta initially contains 0.11Msun of He, 0.03Msun of Ca, and 0.03Msun of Ti. We obtain a ~5d rise to a bolometric maximum of 3.59x10^41 erg/s, primarily powered by 48V decay. Multi-band light curves show distinct morphologies, with a rise to maximum magnitude (-14.3 to -16.7mag) that varies between 3 to 9d from the U to the K bands. Near-IR light curves show no secondary maximum. Because of the presence of both HeI and SiII lines at early times we obtain a hybrid Type Ia/Ib classification. During the photospheric phase line blanketing is caused primarily by TiII. At nebular times, the spectra show strong CaII lines in the optical (but no [OI] 6300--6364A emission), and TiII in the near-IR. Overall, these results match qualitatively the very disparate properties of .Ia SNe and Ca-rich transients. Although the strong TiII blanketing and red colors that we predict are rarely observed, they are seen, for example, in OGLE-2013- SN-079. Furthermore, we obtain a faster light-curve evolution than, for example, PTF10iuv, indicating an ejecta mass >0.2Msun. An alternate scenario may be the merger of two WDs, one or both composed of He.

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arXiv2014

The HD5980 multiple system: Masses and evolutionary status

New spectroscopic observations of the LBV/WR multiple system HD5980 in the Small Magellanic Cloud are used to address the question of the masses and evolutionary status of the two very luminous stars in the 19.3d eclipsing binary system. Two distinct components of the N V 4944 A line are detected in emission and their radial velocity variations are used to derive masses of 61 and 66 Mo, under the assumption that binary interaction effects on this atomic transition are negligible. We propose that this binary system is the product of quasi-chemically homogeneous evolution with little or no mass transfer. Thus, both of these binary stars may be candidates for gamma-ray burst progenitors or even pair instability supernovae. Analysis of the photospheric absorption lines belonging to the third-light object in the system confirm that it consists of an O-type star in a 96.56d eccentric orbit (e=0.82) around an unseen companion. The 5:1 period ratio and high eccentricities of the two binaries suggest that they may constitute a hierarchical quadruple system.

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arXiv2014

A New Class of Wolf-Rayet Stars: WN3/O3s

Our new survey for Wolf-Rayet stars in the Magellanic Clouds is only 15% complete but has already found 9 new WRs in the LMC. This suggests that the total WR population in the LMC may be underestimated by 10-40%. Eight of the nine are WNs, demonstrating that the "observed" WC to WN ratio is too large, and is biased towards WC stars. The ninth is another rare WO star, the second we have found in the LMC in the past two years. Five (and possibly six) of the 8 WNs are of a new class of WRs, which pose a significant challenge to our understanding. Naively we would classify these stars as "WN3+O3V," but there are several reasons why such a pairing is unlikely, not the least of which is that the absolute visual magnitudes of these stars are faint, with M_V~ -2.3 to -3.1. We have performed a preliminary analysis with CMFGEN, and we find that (despite the faint visual magnitudes) the bolometric luminosities of these stars are normal for early-type WNs. Our fitting suggests that these stars are evolved, with significantly enriched N and He. Their effective temperatures are also normal for early-type WNs. What is unusual about these stars is that they have a surprisingly small mass-loss rate compared to other early-type WNs. How these stars got to be the way they are (single star evolution? binary evolution?) remains an open question. For now, we are designating this class as WN3/O3, in analogy to the late-type WN "slash" stars.

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arXiv2014

A Modern Search for Wolf-Rayet Stars in the Magellanic Clouds: First Results

Over the years, directed surveys and incidental spectroscopy have identified 12 Wolf-Rayet (WR) stars in the SMC and 139 in the LMC, numbers which are often described as "essentially} complete." Yet, new WRs are discovered in the LMC almost yearly. We have therefore initiated a new survey of both Magellanic Clouds using the same interference-filter imaging technique previously applied to M31 and M33. We report on our first observing season, in which we have successfully surveyed ~15$% of our intended area of the SMC and LMC. Spectroscopy has confirmed 9 newly found WRs in the LMC (a 6% increase), including one of WO-type, only the third known in that galaxy and the second to be discovered recently. The other eight are WN3 stars that include an absorption component. In two, the absorption is likely from an O-type companion, but the other six are quite unusual. Five would be classified naively as "WN3+O3 V," but such a pairing is unlikely given the rarity of O3 stars, the short duration of this phase (which is incommensurate with the evolution of a companion to a WN star), and because these stars are considerably fainter than O3 V stars. The sixth star may also fall into this category. CMFGEN modeling suggests these stars are hot, bolometrically luminous, and N-rich like other WN3 stars, but lack the strong winds that characterize WNs. Finally, we discuss two rare Of?p stars and four Of supergiants we found, and propose that the B[e] star HD 38489 may have a WN companion.

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