Search

Mass loss through a stellar wind is an important physical process that steers the evolution of massive stars and controls the properties of their end-of-life products, such as the supernova type and the mass of compact remnants. For an accurate mass loss determination, the inhomogeneities in the wind, known as clumping, needs to be taking into account. We aim to improve empirical estimates of mass loss and wind clumping for hot main-sequence massive stars, study the dependence of both properties on the metallicity, and compare the theoretical predictions to our findings. We analyzed the optical and UV spectra of 13 O-type stars in the Small Magellanic Cloud galaxy, which has a metallicity of $\sim 0.2\,Z_\odot$. We quantified the stellar atmosphere, outflow, and wind-clumping properties. To probe the role of metallicity, we compared our findings to studies of Galactic and Large Magellanic Cloud samples that were analyzed with similar methods. We find significant variations in the wind-clumping properties of the target stars, with clumping starting at flow velocities $0.01 - 0.23$ of the terminal wind velocity and reaching clumping factors $f_{\rm cl} = 2 - 30$. In the luminosity ($\log L / L_{\odot} = 5.0 - 6.0$) and metallicity ($Z/Z_{\odot} = 0.2 - 1$) range we considered, we find that the scaling of the mass loss $\dot{M}$ with metallicity $Z$ varies with luminosity. At $\log L/L_{\odot} = 5.75$, we find $\dot{M} \propto Z^m$ with $m = 1.02 \pm 0.30$, in agreement with pioneering work in the field. For lower luminosities, however, we obtain a significantly steeper scaling of $m > 2$. The monotonically decreasing $m(L)$ behavior adds a complexity to the functional description of the mass-loss rate of hot massive stars. Although the trend is present in the predictions, it is much weaker than we found here., Comment: 37 pages, 29 figures. Accepted for publication in Astronomy and Astrophysics

Large spectroscopic surveys of individual massive stars, such as ULLYSES and XSHOOTU, provide observational data for hundreds of massive stars. Their analysis requires large numbers of synthetic spectra so that stellar parameters can be determined. In addition, libraries of massive stars' spectra are needed to produce population synthesis models able to reproduce the observed spectra of unresolved young stellar populations, such as those revealed by the James Webb Space Telescope (JWST) in the early Universe. Our main goal is to provide an extensive library of synthetic spectra and spectral energy distributions of OB stars at metallicities of the Magellanic Clouds. This library will offer a wealth of spectrophotometric information, making it readily applicable to a variety of astrophysical problems. We used the CMFGEN code to calculate 606 NLTE, line-blanketed, expanding atmosphere models using a comprehensive set of atomic data. An overall metallicity of 1/2 Z$_\odot$ and 1/5 Z$_\odot$ was adopted for the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC), respectively. We produced high-resolution spectra from 30 angstroms to 3 $\mu$m for stars on the Main Sequence and slightly beyond. We provide spectral energy distributions, normalized synthetic spectra, ionizing fluxes, and photometry in various bands: Johnson UBV, Cousins RI, Bessel JHK, selected wide JWST filters, Gaia, and LSST ugrizy filters. For each of these filters, we compute bolometric corrections for all synthetic spectra and calibrations as a function of effective temperature. All of our synthetic spectra are publicly available through the POLLUX database, aiming to expedite multiwavelength analyses of massive stars in low metallicity environments., Comment: Accepted for publication in A&A: 15 pages, 11 figures

Context. B supergiants (BSGs) represent an important connection between the main sequence and more extreme evolutionary stages of massive stars. Additionally, lying toward the cool end of the hot star regime, determining their wind properties is crucial to constrain the evolution and feedback of massive stars as, for instance, they might manifest the bi-stability jump phenomenon. Aims. We undertake a detailed analysis of a representative sample of 18 Small Magellanic Cloud (SMC) BSGs within the ULLYSES and XShootU datasets. Our UV and optical analysis spans BSGs from B0 to B8 - covering the bi-stability jump region. We aim to evaluate their evolutionary status and verify what their wind properties say about the bi-stability jump in a low-metallicity environment. Methods. We used the CMFGEN to model the spectra and photometry (from UV to infrared) of our sample. We compare our results with different evolutionary models, with previous determinations in the literature of OB stars, and with diverging mass-loss recipes at the bi-stability jump. Additionally, we provide the first BSG models in the SMC including X-rays. Results. (i) Within a single-stellar evolution framework, the evolutionary status of early BSGs seem less clear than that of late BSGs, which agree with H-shell burning models. (ii) UV analysis shows evidence that BSGs contain X-rays in their atmospheres, for which we provide constraints. In general, we find higher X-ray luminosity (close to the standard log(L_X/L) ~ -7) for early BSGs. For cooler BSGs, lower values are preferred, log(L_X/L) ~ -8.5. (iii) The obtained mass-loss rates suggest neither a jump nor a monotonic decrease with temperature. Instead, a rather constant trend is observed, which is at odds with the increase found for Galactic BSGs. (iv) The wind velocity behavior with temperature shows a sharp drop at ~19 kK, similar to what is observed for Galactic BSGs., Comment: 33 pages (23+10)+(22 at Zenodo), 34 figures (21+13)+(21 at Zenodo), 7 tables (3+4)+(1 at Zenodo), accepted for publication

Observations of individual massive stars, super-luminous supernovae, gamma-ray bursts, and gravitational-wave events involving spectacular black-hole mergers, indicate that the low-metallicity Universe is fundamentally different from our own Galaxy. Many transient phenomena will remain enigmatic until we achieve a firm understanding of the physics and evolution of massive stars at low metallicity (Z). The Hubble Space Telescope has devoted 500 orbits to observe 250 massive stars at low Z in the ultraviolet (UV) with the COS and STIS spectrographs under the ULLYSES program. The complementary ``X-Shooting ULLYSES'' (XShootU) project provides enhanced legacy value with high-quality optical and near-infrared spectra obtained with the wide-wavelength coverage X-shooter spectrograph at ESO's Very Large Telescope. We present an overview of the XShootU project, showing that combining ULLYSES UV and XShootU optical spectra is critical for the uniform determination of stellar parameters such as effective temperature, surface gravity, luminosity, and abundances, as well as wind properties such as mass-loss rates in function of Z. As uncertainties in stellar and wind parameters percolate into many adjacent areas of Astrophysics, the data and modelling of the XShootU project is expected to be a game-changer for our physical understanding of massive stars at low Z. To be able to confidently interpret James Webb Space Telescope (JWST) spectra of the first stellar generations, the individual spectra of low Z stars need to be understood, which is exactly where XShootU can deliver., Comment: Accepted in A&A - 35 Pages, 12 Figures, 4 Tables, 2 Large Tables

In spite of the advent of extremely large telescopes in the UV/optical/NIR range, the current generation of 8-10m facilities is likely to remain competitive at ground-UV wavelengths for the foreseeable future. The Cassegrain U-Band Efficient Spectrograph (CUBES) has been designed to provide high-efficiency (>40%) observations in the near UV (305-400 nm requirement, 300-420 nm goal) at a spectral resolving power of R>20,000, although a lower-resolution, sky-limited mode of R ~ 7,000 is also planned. CUBES will offer new possibilities in many fields of astrophysics, providing access to key lines of stellar spectra: a tremendous diversity of iron-peak and heavy elements, lighter elements (in particular Beryllium) and light-element molecules (CO, CN, OH), as well as Balmer lines and the Balmer jump (particularly important for young stellar objects). The UV range is also critical in extragalactic studies: the circumgalactic medium of distant galaxies, the contribution of different types of sources to the cosmic UV background, the measurement of H2 and primordial Deuterium in a regime of relatively transparent intergalactic medium, and follow-up of explosive transients. The CUBES project completed a Phase A conceptual design in June 2021 and has now entered the Phase B dedicated to detailed design and construction. First science operations are planned for 2028. In this paper, we briefly describe the CUBES project development and goals, the main science cases, the instrument design and the project organization and management., Comment: Proceedings for the HACK100 conference, Trieste, June 2022. arXiv admin note: substantial text overlap with arXiv:2208.01672

In the era of Extremely Large Telescopes, the current generation of 8-10m facilities are likely to remain competitive at ground-UV wavelengths for the foreseeable future. The Cassegrain U-Band Efficient Spectrograph (CUBES) has been designed to provide high-efficiency (>40%) observations in the near UV (305-400 nm requirement, 300-420 nm goal) at a spectral resolving power of R>20,000 (with a lower-resolution, sky-limited mode of R ~ 7,000). With the design focusing on maximizing the instrument throughput (ensuring a Signal to Noise Ratio (SNR) ~20 per high-resolution element at 313 nm for U ~18.5 mag objects in 1h of observations), it will offer new possibilities in many fields of astrophysics, providing access to key lines of stellar spectra: a tremendous diversity of iron-peak and heavy elements, lighter elements (in particular Beryllium) and light-element molecules (CO, CN, OH), as well as Balmer lines and the Balmer jump (particularly important for young stellar objects). The UV range is also critical in extragalactic studies: the circumgalactic medium of distant galaxies, the contribution of different types of sources to the cosmic UV background, the measurement of H2 and primordial Deuterium in a regime of relatively transparent intergalactic medium, and follow-up of explosive transients. The CUBES project completed a Phase A conceptual design in June 2021 and has now entered the detailed design and construction phase. First science operations are planned for 2028., Comment: SPIE proceedings, SPIE Astronomical Telescopes + Instrumentation 2022, Montr\'eal, Canada; 20 pages, 13 figures, 2 tables

Detailed knowledge about stellar winds and evolution at different metallicities is crucial for understanding stellar populations and feedback in the Local Group of galaxies and beyond. Despite efforts in the literature, we still lack a comprehensive, empirical view of the dependence of wind properties on metallicity ($Z$). Here, we investigate the winds of O and B stars in the Milky Way (MW) and Small Magellanic Cloud (SMC). We gathered a sample of 96 stars analyzed by means of the NLTE code CMFGEN. We explored their wind strengths and terminal velocities to address the $Z$ dependence, over a large luminosity range. The empirical wind-luminosity relation (WLR) obtained updates and extends previous results in the literature. It reveals a luminosity and $Z$ dependence, in agreement with the radiatively driven wind theory. For bright objects ($\log L/L_\odot \gtrsim 5.4$), we infer that $\dot{M} \sim Z^{0.5-0.8}$. However, this dependence seems to get weaker or vanish at lower luminosities. The analysis of the terminal velocities suggests a shallow $Z^n$ dependence, with $n \sim 0.1-0.2$, but it should be confirmed with a larger sample and more accurate $V_{\infty}$ determinations. Recent results on SMC stars based on the PoWR code support our inferred WLR. On the other hand, recent bow-shocks measurements stand mostly above our derived WLR. Theoretical calculations of the WLR are not precise, specially at low $L$, where the results scatter. Deviations between our results and recent predictions are identified to be due to the weak wind problem and the extreme terminal velocities predicted by the models. The Z dependence suggested by our analysis deserves further investigations, given its astrophysical implications., Comment: 17 Pages, 10 Figures and 3 Tables, accepted for publication in MNRAS

We report the discovery of a new emission-line object, named SPH4-South = (GAIA EDR3 5616553300192230272), towards the dark cloud LDN 1667. This object came to our attention after inspecting public images that show a faint diffuse nebula a few arcsec southern from SPH4, an emission-line object previously classified as a T Tauri star. We present high-resolution spectra and analyzed JHK photometry of SPH4 and SPH4-South, and new narrow-band and archival broad-band images of these objects. A comparison of the spectra of SPH4 and SPH4-South with high-resolution ones of DG Cir and R Mon, strongly suggests that SPH 4 and SPH4-South are Herbig Ae/Be stars. The classification of SPH4-South is further supported by using a k-NN algorithm to its position in H-K versus J-H color-color diagram. Both stars are detected in the four WISE bands and the WISE colors allow us to classify SPH4 as a Class I and SPH4-South as a Class II source. We also show that the faint nebula is most probably associated with SPH4-South. Using published results on LDN 1667 and the Gaia Early Data Release 3, we conclude that SPH4 is a member of LDN 1667. The case of SPH4-South is not clear because the determination of its distance and proper motion could be affected by the nebulosity around the star, although membership of SPH4-South to LDN 1667 cannot be ruled out., Comment: Accepted for The Astronomical Journal, 9 pages, 8 figures, 3 tables; 2 Appendices

Analyses of Galactic late O dwarfs (O8-O9.5V) raised the `weak wind problem': spectroscopic mass loss rates ($\dot{M}$) are up to two orders of magnitude lower than the theoretical values. We investigated the stellar and wind properties of Galactic late O giants (O8-O9.5III). We performed a spectroscopic analysis of nine O8-O9.5III stars in the ultraviolet (UV) and optical regions using the model atmosphere code CMFGEN. From the UV region, we found $\dot{M}$ $\sim$ $10^{-8}-10^{-9}$ $\mathrm{M_\odot}$ $\mathrm{yr^{-1}}$ overall. This is lower by $\sim 0.9 - 2.3$ dex than the predicted values based on the (global) conservation of energy in the wind. The mass-loss rates predicted from first principles, based on the moving reversing layer theory, agree better with our findings, but it fails to match the spectroscopic $\dot{M}$ for the most luminous OB stars. The region of $\log(L_\star/L_\odot) \sim 5.2$ is critical for both sets of predictions in comparison with the spectroscopic mass-loss rates. CMFGEN models with the predicted $\dot{M}$ (the former one) fail to reproduce the UV wind lines for all the stars of our sample. We reproduce the observed H$\alpha$ profiles of four objects with our $\dot{M}$ derived from the UV. Hence, low $\dot{M}$ values (weak winds) are favored to fit the observations (UV + optical), but discrepancies between the UV and H$\alpha$ diagnostics remain for some objects. Our results indicate weak winds beyond the O8-9.5V class, since the region of $\log(L_\star/L_\odot) \sim 5.2$ is indeed critical to the weak wind phenomenon. Since O8-O9.5III stars are more evolved than O8-9.5V, evolutionary effects do not seem to play a role in the onset of the weak wind phenomenon. These findings support that the $\dot{M}$ (for low luminosity O stars) in use in the majority of modern stellar evolution codes must be severely overestimated up to the end of the H-burning phase., Comment: 44 pages, 23 figures, accepted for publication in Astronomy & Astrophysics on 12/02/2019. Abstract shortened to fit within arXiv character limit. Final version after language editing

We present the initial results of the Large Impact of magnetic Fields on the Evolution of hot stars (LIFE) project. The focus of this project is the search for magnetic fields in evolved OBA giants and supergiants with visual magnitudes between 4 and 8, with the aim to investigate how the magnetic fields observed in upper main sequence (MS) stars evolve from the MS until the late post-MS stages. In this paper, we present spectropolarimetric observations of 15 stars observed using the ESPaDOnS instrument of the CFHT. For each star, we have determined the fundamental parameters and have used stellar evolution models to calculate their mass, age and radius. Using the LSD technique, we have produced averaged line profiles for each star. From these profiles, we have measured the longitudinal magnetic field strength and have calculated the detection probability. We report the detection of magnetic fields in two stars of our sample: a weak field of $B_l=1.0\pm0.2\,$G is detected in the post-MS A5 star 19$\,$Aur and a stronger field of $B_l=-230\,\pm\,10\,$G is detected in the MS/post-MS B8/9 star HR$\,$3042., Comment: 17 pages, 9 figures, accepted for publication in MNRAS

$\xi^1$ CMa is a monoperiodically pulsating, magnetic $\beta$ Cep star with magnetospheric X-ray emission which, uniquely amongst magnetic stars, is clearly modulated with the star's pulsation period. The rotational period $P_{\rm rot}$ has yet to be identified, with multiple competing claims in the literature. We present an analysis of a large ESPaDOnS dataset with a 9-year baseline. The longitudinal magnetic field $\langle B_{\rm Z}\rangle$ shows a significant annual variation, suggesting that $P_{\rm rot}$ is at least on the order of decades. The possibility that the star's H$\alpha$ emission originates around a classical Be companion star is explored and rejected based upon VLTI AMBER and PIONIER interferometry, indicating that the emission must instead originate in the star's magnetosphere and should therefore also be modulated with $P_{\rm rot}$. Period analysis of H$\alpha$ equivalent widths measured from ESPaDOnS and CORALIE spectra indicates $P_{\rm rot} > 30$ yr. All evidence thus supports that $\xi^1$ CMa is a very slowly rotating magnetic star hosting a dynamical magnetosphere. H$\alpha$ also shows evidence for modulation with the pulsation period, a phenomenon which we show cannot be explained by variability of the underlying photospheric line profile, i.e. it may reflect changes in the quantity and distribution of magnetically confined plasma in the circumstellar environment. In comparison to other magnetic stars with similar stellar properties, $\xi^1$ CMa is by far the most slowly rotating magnetic B-type star, is the only slowly rotating B-type star with a magnetosphere detectable in H$\alpha$ (and thus, the coolest star with an optically detectable dynamical magnetosphere), and is the only known early-type magnetic star with H$\alpha$ emission modulated by both pulsation and rotation., Comment: 40 pages, 26 figures, accepted for publication in MNRAS

The MiMeS project is a large-scale, high resolution, sensitive spectropolarimetric investigation of the magnetic properties of O and early B type stars. Initiated in 2008 and completed in 2013, the project was supported by 3 Large Program allocations, as well as various programs initiated by independent PIs and archival resources. Ultimately, over 4800 circularly polarized spectra of 560 O and B stars were collected with the instruments ESPaDOnS at the Canada-France-Hawaii Telescope, Narval at the T\'elescope Bernard Lyot, and HARPSpol at the European Southern Observatory La Silla 3.6m telescope, making MiMeS by far the largest systematic investigation of massive star magnetism ever undertaken. In this paper, the first in a series reporting the general results of the survey, we introduce the scientific motivation and goals, describe the sample of targets, review the instrumentation and observational techniques used, explain the exposure time calculation designed to provide sensitivity to surface dipole fields above approximately 100 G, discuss the polarimetric performance, stability and uncertainty of the instrumentation, and summarize the previous and forthcoming publications., Comment: Accepted by MNRAS

We present a spectroscopic analysis of HST/COS observations of three massive stars in the low metallicity dwarf galaxies IC 1613 and WLM. These stars, were previously observed with VLT/X-shooter by Tramper et al. (2011, 2014) who claimed that their mass-loss rates are higher than expected from theoretical predictions for the underlying metallicity. A comparison of the FUV spectra with those of stars of similar spectral types/luminosity classes in the Galaxy, and the Magellanic Clouds provides a direct, model-independent check of the mass-loss - metallicity relation. Then, a quantitative spectroscopic analysis is carried out using the NLTE stellar atmosphere code CMFGEN. We derive the photospheric and wind characteristics, benefiting from a much better sensitivity of the FUV lines to wind properties than Ha. Iron and CNO abundances are measured, providing an independent check of the stellar metallicity. The spectroscopic analysis indicates that Z/Zsun = 1/5, similar to a SMC-type environment, and higher than usually quoted for IC 1613 and WLM. The mass-loss rates are smaller than the empirical ones by Tramper et al. (2014), and those predicted by the widely used theoretical recipe by Vink et al. (2001). On the other hand, we show that the empirical, FUV-based, mass-loss rates are in good agreement with those derived from mass fluxes computed by Lucy (2012). We do not concur with Tramper et al. (2011, 2014) that there is a breakdown in the mass-loss - metallicity relation., Comment: 26 pages, 3 tables, 15 figures. Accepted for publication in MNRAS

A new time series of high-resolution Stokes I and V spectra of the magnetic B2V star HD 184927 has been obtained in the context of the Magnetism in Massive Stars (MiMeS) Large Program with the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope and dimaPol liquid crystal spectropolarimeter at 1.8-m telescope of Dominion Astrophysical Observatory. We model the optical and UV spectrum obtained from the IUE archive to infer the stellar physical parameters. Using magnetic field measurements we derive an improved rotational period of 9.53102+-0.0007d. We infer the longitudinal magnetic field from lines of H, He and various metals, revealing large differences between the apparent field strength variations determined from different elements. Magnetic Doppler Imaging using He and O lines yields strongly nonuniform surface distributions of these elements. We demonstrate that the diversity of longitudinal field variations can be understood as due to the combination of element-specific surface abundance distributions in combination with a surface magnetic field that is comprised of dipolar and quadrupolar components. We have reanalyzed IUE high resolution spectra, confirming strong modulation of wind-sensitive Civ and Siv resonance lines. However, we are unable to detect any modulation of the H$\alpha$ profile attributable to a stellar magnetosphere. We conclude that HD 184927 hosts a centrifugal magnetosphere, albeit one that is undetectable at optical wavelengths. The magnetic braking timescale of HD 184927 is computed to be $\tau_J = 0.96$ or $5.8$ Myr. These values are consistent with the slow rotation and estimated age of the star., Comment: 23 pages, 21 figures. Accepted for publication in MNRAS

The evolution of massive stars is still partly unconstrained. Mass, metallicity, mass loss and rotation are the main drivers of stellar evolution. Binarity and magnetic field may also significantly affect the fate of massive stars. Our goal is to investigate the evolution of single O stars in the Galaxy. For that, we use a sample of 74 objects comprising all luminosity classes and spectral types from O4 to O9.7. We rely on optical spectroscopy obtained in the context of the MiMeS survey of massive stars. We perform spectral modelling with the code CMFGEN. We determine the surface properties of the sample stars, with special emphasis on abundances of carbon, nitrogen and oxygen. Most of our sample stars have initial masses in the range 20 to 50 Msun. We show that nitrogen is more enriched and carbon/oxygen more depleted in supergiants than in dwarfs, with giants showing intermediate degrees of mixing. CNO abundances are observed in the range of values predicted by nucleosynthesis through the CNO cycle. More massive stars, within a given luminosity class, appear to be more chemically enriched than lower mass stars. We compare our results with predictions of three types of evolutionary models and show that, for two sets of models, 80% of our sample can be explained by stellar evolution including rotation. The effect of magnetism on surface abundances is unconstrained. Our study indicates that, in the 20-50 Msun mass range, the surface chemical abundances of most single O stars in the Galaxy are fairly well accounted for by stellar evolution of rotating stars., Comment: 15 pages, 12 figures. Accepted in Astronomy & Astrophysics

Massive stars show a variety of spectral variability: presence of discrete absorption components in UV P-Cygni profiles, optical line profile variability, X-ray variability, radial velocity modulations. Our goal is to study the spectral variability of single OB stars to better understand the relation between photospheric and wind variability. For that, we rely on high spectral resolution, high signal-to-noise ratio optical spectra collected with the spectrograph NARVAL on the Telescope Bernard Lyot at Pic du Midi. We investigate the variability of twelve spectral lines by means of the Temporal Variance Spectrum (TVS). The selected lines probe the radial structure of the atmosphere, from the photosphere to the outer wind. We also perform a spectroscopic analysis with atmosphere models to derive the stellar and wind properties, and to constrain the formation region of the selected lines. We show that variability is observed in the wind lines of all bright giants and supergiants, on a daily timescale. Lines formed in the photosphere are sometimes variable, sometimes not. The dwarf stars do not show any sign of variability. If variability is observed on a daily timescale, it can also (but not always) be observed on hourly timescales, albeit with lower amplitude. There is a very clear correlation between amplitude of the variability and fraction of the line formed in the wind. Strong anti-correlations between the different part of the temporal variance spectrum are observed. Our results indicate that variability is stronger in lines formed in the wind. A link between photospheric and wind variability is not obvious from our study, since wind variability is observed whatever the level of photospheric variability. Different photospheric lines also show different degrees of variability., Comment: 13 pages, 9 figures + appendix. A&A accepted. Figures degraded for arxiv submission

The Javalambre-Physics of the Accelerated Universe Astrophysical Survey (J-PAS) is a narrow band, very wide field Cosmological Survey to be carried out from the Javalambre Observatory in Spain with a purpose-built, dedicated 2.5m telescope and a 4.7 sq.deg. camera with 1.2Gpix. Starting in late 2015, J-PAS will observe 8500sq.deg. of Northern Sky and measure $0.003(1+z)$ photo-z for $9\times10^7$ LRG and ELG galaxies plus several million QSOs, sampling an effective volume of $\sim 14$ Gpc$^3$ up to $z=1.3$ and becoming the first radial BAO experiment to reach Stage IV. J-PAS will detect $7\times 10^5$ galaxy clusters and groups, setting constrains on Dark Energy which rival those obtained from its BAO measurements. Thanks to the superb characteristics of the site (seeing ~0.7 arcsec), J-PAS is expected to obtain a deep, sub-arcsec image of the Northern sky, which combined with its unique photo-z precision will produce one of the most powerful cosmological lensing surveys before the arrival of Euclid. J-PAS unprecedented spectral time domain information will enable a self-contained SN survey that, without the need for external spectroscopic follow-up, will detect, classify and measure $\sigma_z\sim 0.5\%$ redshifts for $\sim 4000$ SNeIa and $\sim 900$ core-collapse SNe. The key to the J-PAS potential is its innovative approach: a contiguous system of 54 filters with $145\AA$ width, placed $100\AA$ apart over a multi-degree FoV is a powerful "redshift machine", with the survey speed of a 4000 multiplexing low resolution spectrograph, but many times cheaper and much faster to build. The J-PAS camera is equivalent to a 4.7 sq.deg. "IFU" and it will produce a time-resolved, 3D image of the Northern Sky with a very wide range of Astrophysical applications in Galaxy Evolution, the nearby Universe and the study of resolved stellar populations., Comment: 215 pages, 70 figures. J-PAS "Red Book", containing a description of the technical aspects of the Survey and its main scientific goals

We present for the first time phase-resolved UV spectroscopy of an Of?p star, namely, HD 191612. The observations were acquired with the Space Telescope Imaging Spectrograph (STIS) on-board the Hubble Space Telescope (HST). We report the variability observed in the main photospheric and wind features and compare the results with previous findings for the Of?p star HD 108. We show that UV line strengths, H(alpha), and longitudinal magnetic field, vary coherently according to the rotational period (P = 537.6d), providing additional support for the magnetic oblique rotator scenario. The stellar and wind parameters of HD 191612 are obtained based on NLTE expanding atmosphere models. The peculiar wind line profile variations revealed by the new STIS data - not reproduced by 1D atmosphere models - are addressed through non-spherical MHD simulations coupled with radiative transfer. The basic aspects of the UV variability observed are explained and the structure of the dynamical magnetosphere of HD 191612 is discussed., Comment: Accepted for publication in MNRAS (9 pages, 6 figures, 3 tables)

The O9IV star HD 57682, discovered to be magnetic within the context of the MiMeS survey in 2009, is one of only eight convincingly detected magnetic O-type stars. Among this select group, it stands out due to its sharp-lined photospheric spectrum. Since its discovery, the MiMeS Collaboration has continued to obtain spectroscopic and magnetic observations in order to refine our knowledge of its magnetic field strength and geometry, rotational period, and spectral properties and variability. In this paper we report new ESPaDOnS spectropolarimetric observations of HD 57682, which are combined with previously published ESPaDOnS data and archival H{\alpha} spectroscopy. This dataset is used to determine the rotational period (63.5708 \pm 0.0057 d), refine the longitudinal magnetic field variation and magnetic geometry (dipole surface field strength of 880\pm50 G and magnetic obliquity of 79\pm4\circ as measured from the magnetic longitudinal field variations, assuming an inclination of 60\circ), and examine the phase variation of various lines. In particular, we demonstrate that the H{\alpha} equivalent width undergoes a double-wave variation during a single rotation of the star, consistent with the derived magnetic geometry. We group the variable lines into two classes: those that, like H{\alpha}, exhibit non-sinusoidal variability, often with multiple maxima during the rotation cycle, and those that vary essentially sinusoidally. Based on our modelling of the H{\alpha} emission, we show that the variability is consistent with emission being generated from an optically thick, flattened distribution of magnetically-confined plasma that is roughly distributed about the magnetic equator. Finally, we discuss our findings in the magnetospheric framework proposed in our earlier study., Comment: 21 pages, 19 figures, Accepted for publication in MNRAS

We present the first ultraviolet spectrum of the peculiar, magnetic Of?p star HD 108 obtained in its spectroscopic low state. The new data, obtained with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope, reveal significant changes compared to IUE spectra obtained in the high state: N V 1240, Si IV 1400, and C IV 1550 present weaker P-Cygni profiles (less absorption) in the new data, while N IV 1718 absorption is deeper, without the clear wind signature evident in the high state. Such changes contrast with those found in other magnetic massive stars, where more absorption is observed in the resonance doublets when the sightline is close to the plane of the magnetic equator. The new data show also that the photospheric Fe IV forest, at 1600--1700 angstroms, has strengthened compared to previous observations. The ultraviolet variability is large compared to that found in typical, non-magnetic O stars, but moderate when compared to the high-/low-state changes reported in the optical spectrum of HD 108 over several decades. We use non-LTE expanding-atmosphere models to analyze the new STIS observations. Overall, the results are in accord with a scenario in which the optical variability is mainly produced by magnetically constrained gas, close to the photosphere. The relatively modest changes found in the main ultraviolet wind lines suggest that the stellar wind is not substantially variable on a global scale. Nonetheless, multidimensional radiative-transfer models may be needed to understand some of the phenomena observed., Comment: 9 pages, 8 figures, accepted for publication in MNRAS

The B0.2 V magnetic star tau Sco stands out from the larger population of massive OB stars due to its high X-ray activity, peculiar wind diagnostics and complex magnetic field. Recently, Petit et al. 2011 presented the discovery of the first two tau Sco analogues -- HD 66665 and HD 63425, identified by the striking similarity of their UV spectra to that of tau Sco. ESPaDOnS and Narval spectropolarimetric observations were obtained by the Magnetism in Massive Stars CFHT and TBL Large Programs, in order to characterize the stellar and magnetic properties of these stars. A magnetic field of similar surface strength was found on both stars, reinforcing the connection between the presence of a magnetic field and wind peculiarities. We present additional phase-resolved observations secured by the MiMeS collaboration for HD 66665 in order to measure its magnetic geometry, and correlate that geometry with diagnostics of mass-loss., Comment: to appear in the proceedings of Stellar polarimetry: From birth to death, Madison, USA, June 27 - June 30, 2011 (version 2 was updated to correct a typo in the arXiv metadata)

We report the discovery and analysis of a very strong magnetic field in the rapidly rotating early B-type star HR 5907, based on observations obtained as part of the Magnetism in Massive Stars (MiMeS) project. We infer a rotation period of 0.508276 +0.000015/-0.000012 d from photometric and H{\alpha} EW measurements, making this the shortest period, non-degenerate, magnetic massive star known to date. From the comparison of IUE UV and optical spectroscopy with LTE BRUCE/KYLIE models we find a solid-angle integrated, uniform black-body temperature of 17 000 \pm 1000 K, a projected rotational velocity of 290 \pm 10 km/s, an equatorial radius of 3.1 \pm 0.2 R_sun, a stellar mass of 5.5 \pm 0.5 M_sun, and an inclination angle of the rotation axis to our line-of-sight of 70 \pm 10\circ. Our measurements of the longitudinal magnetic field, which vary between -500 and -2000 G, phase coherently with the rotation period and imply a surface dipole field strength of \sim15.7 kG. On the other hand, from fits to mean Least-Squares Deconvolved Stokes V line profiles we infer a dipole field strength of \sim10.4 kG. This disagreement may result from a magnetic configuration more complex than our model, and/or from the non-uniform helium surface abundance distribution. In either case we obtain a magnetic obliquity nearly aligned with the rotation axis ({\beta} = 7+2/-1\circ). Our optical spectroscopy also shows weak variability in carbon, silicon and nitrogen lines. The emission variability in hydrogen Balmer and Paschen lines indicates the presence of a dense, highly structured magnetosphere, interpreted as a centrifugally supported, magnetically confined circumstellar disk., Comment: 19 pages, 17 figures (highly compressed), 3 tables, accepted for publication by MNRAS

This paper reports high-precision Stokes V spectra of HD 191612 acquired using the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope, in the context of the Magnetism in Massive stars (MiMeS) Project. Using measurements of the equivalent width of the Halpha line and radial velocities of various metallic lines, we have updated both the spectroscopic and orbital ephemerides of this star. We confirm the presence of a strong magnetic field in the photosphere of HD 191612, and detect its variability. We establish that the longitudinal field varies in a manner consistent with the spectroscopic period of 537.6 d, in an approximately sinusoidal fashion. This demonstrates a firm connection between the magnetic field and the processes responsible for the line and continuum variability. Interpreting the variation of the longitudinal magnetic field within the context of the dipole oblique rotator model we obtain a best-fit surface magnetic field model with obliquity beta=67\pm 5 deg and polar strength Bd=2450\pm 400 G . The inferred magnetic field strength implies an equatorial wind magnetic confinement parameter eta*~50, supporting a picture in which the Halpha emission and photometric variability have their origin in an oblique, rigidly rotating magnetospheric structure resulting from a magnetically channeled wind. This interpretation is supported by our successful Monte Carlo radiative transfer modeling of the photometric variation, which assumes the enhanced plasma densities in the magnetic equatorial plane above the star implied by such a picture. Predictions of the continuum linear polarisation resulting from Thompson scattering from the magnetospheric material indicate that the Stokes Q and U variations are highly sensitive to the magnetospheric geometry, and that expected amplitudes are in the range of current instrumentation. (abridged), Comment: 10 pages, accepted by MNRAS

The B0.2 V magnetic star tau Sco stands out from the larger population of massive OB stars due to its high X-ray activity, peculiar wind diagnostics and highly complex magnetic field. This paper presents the discovery of the first two tau Sco analogues - HD 66665 and HD 63425, identified by the striking similarity of their UV spectra to that of tau Sco. ESPaDOnS spectropolarimetric observations were secured by the Magnetism in Massive Stars CFHT Large Program, in order to characterize the stellar and magnetic properties of these stars. CMFGEN modelling of optical ESPaDOnS spectra and archived IUE UV spectra showed that these stars have stellar parameters similar to those of tau Sco. A magnetic field of similar surface strength is found on both stars, reinforcing the connection between the presence of a magnetic field and wind peculiarities. However, additional phase-resolved observations will be required in order to assess the potential complexity of the magnetic fields, and verify if the wind anomalies are linked to this property., Comment: 6 pages, 2 tables, 3 figures. Accepted for publication in MNRAS. The definitive version will be available at www.blackwel-synergy.com

The B0.2 V magnetic star tau Sco stands out from the larger population of massive magnetic OB stars due to its high X-ray activity and remarkable wind, apparently related to its peculiar magnetic field - a field which is far more complex than the mostly-dipolar fields usually observed in magnetic OB stars. tau Sco is therefore a puzzling outlier in the larger picture of stellar magnetism - a star that still defies interpretation in terms of a physically coherent model. Recently, two early B-type stars were discovered as tau Sco analogues, identified by the striking similarity of their UV spectra to that of tau Sco, which was - until now - unique among OB stars. We present the recent detection of their magnetic fields by the MiMeS collaboration, reinforcing the connection between the presence of a magnetic field and wind anomalies (Petit et al. 2010). We will also present ongoing observational efforts undertaken to establish the precise magnetic topology, in order to provide additional constrains for existing models attempting to reproduce the unique wind structure of tau Sco-like stars., Comment: To appear in the proceedings of Magnetic Stars 2010

We discuss the recent detection of a strong, organized magnetic field in the bright, broad-line B2V star, HR 5907, using the ESPaDOnS spectropolarimeter on the CFHT as part of the Magnetism in Massive Stars (MiMeS) survey. We find a rotational period of 0.50833 days, making it the fastest-rotating, non-degenerate magnetic star ever detected. Like the previous rapid-rotation record holder HR 7355 (also discovered by MiMeS: Oksala et al. 2010, Rivinius et al. 2010), this star shows emission line variability that is diagnostic of a structured magnetosphere., Comment: 3 pages, 4 figures, to appear in the proceedings of Magnetic Stars 2010

We will review our recent analysis of the magnetic properties of the O9IV star HD 57682, using spectropolarimetric observations obtained with ESPaDOnS at the Canada-France-Hawaii telescope within the context of the Magnetism in Massive Stars (MiMeS) Large Program. We discuss our most recent determination of the rotational period from longitudinal magnetic field measurements and H_alpha variability - the latter obtained from over a decade's worth of professional and amateur spectroscopic observations. Lastly, we report on our investigation of the magnetic field geometry and the effects of the field on the circumstellar environment., Comment: 3 pages, 3 figures, to appear in the proceedings of Magnetic Stars 2010

The B0.2 V magnetic star tau Sco stands out from the larger population of massive magnetic OB stars due to its remarkable, superionized wind, apparently related to its peculiar magnetic field - a field which is far more complex than the mostly-dipolar fields usually observed in magnetic OB stars. tau Sco is therefore a puzzling outlier in the larger picture of stellar magnetism - a star that still defies interpretation in terms of a physically coherent model. Recently, two early B-type stars were discovered as tau Sco analogues, identified by the striking similarity of their UV spectra to that of tau Sco, which was - until now - unique among OB stars. We present the recent detection of their magnetic fields by the MiMeS collaboration, reinforcing the connection between the presence of a magnetic field and a superionized wind. We will also present ongoing observational efforts undertaken to establish the precise magnetic topology, in order to provide additional constrains for existing models attempting to reproduce the unique wind structure of tau Sco-like stars., Comment: Proceedings of IAUS272: Active OB stars

We report on the detection of a strong, organized magnetic field in the helium-variable early B-type star HR 7355 using spectropolarimetric data obtained with ESPaDOnS on CFHT by the MiMeS large program. We also present results from new V-band differential photometry obtained with the CTIO 0.9m telescope. We investigate the longitudinal field, using a technique called Least-Squares Deconvolution (LSD), and the rotational period of HR 7355. These new observations strongly support the proposal that HR 7355 harbors a structured magnetosphere similar to that in the prototypical helium-strong star, sigma Ori E., Comment: Proceedings of IAU 272: Active OB stars

Only 5 Of?p stars have been identified in the Galaxy. Of these, 3 have been studied in detail, and within the past 5 years magnetic fields have been detected in each of them. The observed magnetic and spectral characteristics are indicative of organised magnetic fields, likely of fossil origin, confining their supersonic stellar winds into dense, structured magnetospheres. The systematic detection of magnetic fields in these stars strongly suggests that the Of?p stars represent a general class of magnetic O-type stars., Comment: Proceedings of IAUS 272: Active OB stars

We report recent observations of the sharp-lined magnetic beta Cep pulsator xi 1 CMa (= HD 46328). The longitudinal magnetic field of this star is detected consistently, but it is not observed to vary strongly, during nearly 5 years of observation. In this poster we evaluate whether the nearly constant longitudinal field is due to intrinsically slow rotation, or rather if the stellar or magnetic geometry is responsible.

I will review our recent analysis of the magnetic properties of the O9IV star HD 57682, using spectropolarimetric observations obtained with ESPaDOnS at the Canada-France-Hawaii telescope within the context of the Magnetism in Massive Stars (MiMeS) Large Program. I discuss our most recent determination of the rotational period from longitudinal magnetic field measurements and Halpha variability - the latter obtained from over a decade's worth of professional and amateur spectroscopic observations. Lastly, I will report on our investigation of the magnetic field geometry and the effects of the field on the circumstellar environment., Comment: 2 pages, 2 figures, IAUS272 - Active OB Stars: Structure, Evolution, Mass Loss and Critical Limits

We discuss the recent detection of a strong, organized magnetic field in the bright, broad-line B2V star, HD 142184, using the ESPaDOnS spectropolarimeter on the CFHT as part of the Magnetism in Massive Stars (MiMeS) survey. We find a rotational period of 0.50833 days, making it the fastest-rotating, non-degenerate magnetic star ever detected. Like the previous rapid-rotation record holder HR 7355 (also discovered by MiMeS: Oksala et al. 2010, Rivinius et al. 2010), this star shows emission line variability that is diagnostic of a structured magnetosphere., Comment: 2 pages, 2 figures, IAUS272 - Active OB Stars: Structure, Evolution, Mass Loss and Critical Limits

We report the detection of a magnetic field on the Of?p star HD108. Spectropolarimetric observations conducted in 2007, 2008 and 2009 respectively with NARVAL@TBL and ESPaDOnS@CFHT reveal a clear Zeeman signature in the average Stokes V profile, stable on timescales of days to months and slowly increasing in amplitude on timescales of years. We speculate that this timescale is the same as that on which Ha emission is varying and is equal to the rotation period of the star. The corresponding longitudinal magnetic field, measured during each of the three seasons, increases slowly from 100 to 150G, implying that the polar strength of the putatively-dipolar large-scale magnetic field of HD108 is at least 0.5kG and most likely of the order of 1-2 kG. The stellar and wind properties are derived through a quantitative spectroscopic analysis with the code CMFGEN. The effective temperature is difficult to constrain because of the unusually strong HeI4471 and HeI5876 lines. Values in the range 33000-37000 K are preferred. A mass loss rate of about 1e-7 Msun/yr (with a clumping factor f=0.01) and a wind terminal velocity of 2000 km/s are derived. The wind confinement parameter eta_star is larger than 100, implying that the wind of HD108 is magnetically confined. Stochastic short-term variability is observed in the wind-sensitive lines but not in the photospheric lines, excluding the presence of pulsations. Material infall in the confined wind is the most likely origin for lines formed in the inner wind. Wind-clumping also probably causes part of the Ha variability. The projected rotational velocity of HD108 is lower than 50 km/s, consistent with the spectroscopic and photometric variation timescales of a few decades. Overall, HD108 is very similar to the magnetic O star HD191612 except for an even slower rotation., Comment: 10 pages, 6 figures; MNRAS accepted

We report the detection of a strong, organised magnetic field in the O9IV star HD 57682, using spectropolarimetric observations obtained with ESPaDOnS at the 3.6-m Canada-France-Hawaii Telescope within the context of the Magnetism in Massive Stars (MiMeS) Large Program. From the fitting of our spectra using NLTE model atmospheres we determined that HD 57682 is a $17^{+19}_{-9}$ M$_{\odot}$ star with a radius of $7.0^{+2.4}_{-1.8}$ R$_\odot$, and a relatively low mass-loss rate of $1.4^{+3.1}_{-0.95}\times10^{-9}$ M$_{\odot}$ yr$^{-1}$. The photospheric absorption lines are narrow, and we use the Fourier transform technique to infer $v\sin i=15\pm3$ km s$^{-1}$. This $v\sin i$ implies a maximum rotational period of 31.5 d, a value qualitatively consistent with the observed variability of the optical absorption and emission lines, as well as the Stokes $V$ profiles and longitudinal field. Using a Bayesian analysis of the velocity-resolved Stokes $V$ profiles to infer the magnetic field characteristics, we tentatively derive a dipole field strength of $1680^{+134}_{-356}$ G. The derived field strength and wind characteristics imply a wind that is strongly confined by the magnetic field., Comment: 6 pages, 5 figures. Accepted for publication in MNRAS Letters

We have investigated the stellar and wind properties of a sample of five late-type O dwarfs in order to address the weak wind problem. A grid of TLUSTY models was used to obtain the stellar parameters, and the wind parameters were determined by using the CMFGEN code. We found that the spectra have mainly a photospheric origin. A weak wind signature is seen in CIV 1549, from where mass-loss rates consistent with previous CMFGEN results regarding O8-9V stars were obtained. A discrepancy of roughly 2 orders of magnitude is found between these mass-loss rates and the values predicted by theory (Mdot(Vink)), confirming a breakdown or a steepening of the modified wind momentum-luminosity relation at log L/Lsun < 5.2. We have estimated the carbon abundance for the stars of our sample and concluded that its uncertainty cannot cause the weak wind problem. Upper limits on Mdot were established for all objects using lines of different ions, namely, PV 1118,28, CIII 1176, NV 1239,43, Si IV 1394,03, and NIV 1718. All the values obtained are also in disagreement with theoretical predictions, bringing support to the reality of weak winds. Together with CIV 1549, the use of NV 1239,43 results in the lowest mass-loss rates: the upper limits indicate that Mdot must be less than about -1.0 dex Mdot(Vink). Regarding the other transitions, the upper limits still point to low rates: Mdot must be less than about $(-0.5 \pm 0.2)$ dex Mdot(Vink). We have studied the behavior of the Halpha line with different mass-loss rates. We have also explored ways to fit the observed spectra with Mdot(Vink). By using large amounts of X-rays, we verified that few wind emissions take place, as in weak winds. However, unrealistic X-rays luminosities had to be used (log Lx/Lbol > -3.5) (abridged)., Comment: A&A, accepted

We report here the detection of a weak magnetic field of 50 - 100 G on the O9.7 supergiant zeta Ori A, using spectropolarimetric observations obtained with NARVAL at the 2m Telescope Bernard Lyot atop Pic du Midi (France). zeta Ori A is the third O star known to host a magnetic field (along with theta^1 Ori C and HD 191612), and the first detection on a 'normal' rapidly-rotating O star. The magnetic field of zeta Ori A is the weakest magnetic field ever detected on a massive star. The measured field is lower than the thermal equipartition limit (about 100 G). By fitting NLTE model atmospheres to our spectra, we determined that zeta Ori A is a 40 Msun star with a radius of 25 Rsun and an age of about 5 - 6 Myr, showing no surface nitrogen enhancement and losing mass at a rate of about 2x10^(-6) Msol/yr. The magnetic topology of zeta Ori A is apparently more complex than a dipole and involves two main magnetic polarities located on both sides of the same hemisphere; our data also suggest that zeta Ori A rotates in about 7.0 d and is about 40 degrees away from pole-on to an Earth-based observer. Despite its weakness, the detected magnetic field significantly affects the wind structure; the corresponding Alfven radius is however very close to the surface, thus generating a different rotational modulation in wind lines than that reported on the two other known magnetic O stars. The rapid rotation of zeta Ori A with respect to theta^1 Ori C appears as a surprise, both stars having similar unsigned magnetic fluxes (once rescaled to the same radius); it may suggest that the sub-equipartition field detected on zeta Ori A is not a fossil remnant (as opposed to that of theta^1 Ori C and HD 191612), but the result of an exotic dynamo action produced through MHD instabilities., Comment: 12 pages

The ultraviolet spectra of all "weak emission line central stars of planetary nebulae" (WELS) with available IUE data is analyzed. We found that the WELS can be divided in three different groups regarding their UV: (1) Strong P-Cygni profiles (mainly in C IV 1549); (2) Weak P-Cygni features and (3) Absence of P-Cygni profiles. We have measured wind terminal velocities for all objects presenting P-Cygni profiles in N V 1238 and/or C IV 1549. The results obtained were compared to the UV data of the two prototype stars of the [WC]-PG 1159 class, namely, A30 and A78. They indicate that WELS are distinct from the [WC]-PG 1159 stars, in contrast to previous claims in the literature. In order to gain a better understanding about the WELS, we clearly need to determine their physical parameters and chemical abundances. First non LTE expanding atmosphere models (using the CMFGEN code) for the UV and optical spectra of the star Hen 2-12 are presented., Comment: To appear in the proceedings of the "Hydrogen-Deficient Stars" meeting, held in Tuebingen, Germany, Sept. 17-21, 2007. 4 pages

The ultraviolet spectra of all ``weak emission line central stars of planetary nebulae'' (WELS) with available IUE data are presented and discussed. We performed line identifications, equivalent width and flux measurements for several features in their spectra. We found that the WELS can be divided in three different groups regarding their UV: i) Strong P-Cygni profiles (mainly in CIV 1549); ii) Weak P-Cygni features and iii) Absence of P-Cygni profiles. The last group encompasses stars with a featureless UV spectrum or with intense emission lines and a weak continuum, which are most likely of nebular origin. We have measured wind terminal velocities for all objects presenting P-Cygni profiles in N V 1238 and/or C IV 1549. The results obtained were compared to the UV data of the two prototype stars of the [WC]-PG 1159 class, namely, A30 and A78. For WELS presenting P-Cygnis, most of the terminal velocities fall in the range ~1000-1500 km/s, while [WC]-PG 1159 stars possess much higher values, of about 3000 km/s. The [WC]-PG1159 stars are characterized by intense, simultaneous P-Cygni emissions in the 1150-2000A interval of N V 1238, O V 1371 and C IV 1549. In contrast, we found that O V 1371 is very weak or absent in the WELS spectra. On the basis of the ultraviolet spectra alone, our findings indicate that [WC]-PG 1159 stars are distinct from the WELS, contrary to previous claims in the literature., Comment: 29 pages, 5 figures. Accepted by the AJ

Aims: To investigate the spectra and the evolutionary stages of two peculiar emission-line stars: RJHA 49 and SS73 21. Methods: We used low and high resolution optical data. Line identifications and measurements were performed for several features in their spectra. Results: For each object, we have derived the extinction and the excitation temperature from a set of [Fe II] lines, and the electron density from [N II] lines. For RJHA 49, no detailed spectroscopic study was done so far. Regarding SS73 21, our low resolution spectrum have confirmed the main characteristics found in previous works. On the other side, from our high resolution data, we have found that the Halpha line presents a double-peak, in contrast with the suggestion in the literature that it should reveal a P-Cygni profile. Surprisingly, we found a few He I transitions resembling P-Cygni profiles (e.g. He I 5876), directly suggesting that mass loss is active in SS73 21. We also discussed the nature of these two objects based on the data obtained. Although the evolutionary status of SS73 21 seems well established from previous studies (a proto-planetary nebula), the situation for RJHA 49 is not so clear mainly due to its unknown distance. However, from the strength of [N II] 5754 relative to [O I] 6300, the possibility of RJHA 49 being a LBV object is reduced, and a B[e]-supergiant or a proto-planetary nebula status is more plausible., Comment: 8 pages, 3 figures. Accepted for publication in Astronomy & Astrophysics

We present far-UV to optical analyses of four hydrogen deficient central stars of planetary nebulae: BD+303639, NGC 40, NGC 5315 and NGC 6905. Using the radiative transfer code CMFGEN, we determined new physical parameters and chemical abundances for these stars. The results were analyzed in the context of the [WR] => PG 1159 evolution via the transformed radius(Rt)-temperature and HR diagrams. NGC 5315 showed itself as an odd object among the previously analyzed central stars. Its temperature (~76kK) is considerably lower than other early-type [WR] stars (~120-150kK). From our models for NGC 5315 and NGC 6905, it is unclear if early-type [WR] stars have smaller C/He mass ratios than other spectral classes, as claimed in the literature. A ratio of ~0.8 is found for NGC 6905. We analyzed FUSE spectra of these stars for the first time, and identified phosphorus in the spectra of BD+303639, NGC 40 and NGC 5315 through the transitions P V 1118,1128. The Fe, Si, P, S and Ne abundances were analyzed in the context of the nucleosynthesis occurring in previous evolutionary phases. We found evidence for Fe deficiency in BD +30 3639 and NGC 5315, and from fits to the Si IV lines we determined a solar Si abundance for BD+303639 and NGC 40. For phosphorus, an oversolar abundance in the NGC 5315 model was preferred, while in the other stars a solar phosphorus abundance cannot be discarded. Regarding sulfur, we estimated upper limits for its abundance, since no conspicuous lines can be seen in the observed spectra. We found that Ne is overabundant in BD +30 3639. In the other stars, Ne is weak or undetectable and upper limits for its abundance were estimated. Our results are in agreement with theoretical predictions and show the usefulness of [WR] stars as testbeds for nucleosynthesis calculations in the AGB and post-AGB phases.(abridged), Comment: ApJ, in press, 44 pages, 14 figures. For full resolution version see http://www.journals.uchicago.edu/ApJ/journal/preprints/ApJ65628.preprint.pdf