Wolf-Rayet (WR) stars are evolved massive stars, and the relative number of WC-type and WN-type WRs should vary with the metallicity of the host galaxy, providing a sensitive test of stellar evolutionary theory. However, past studies of the WR content of M31 have been biased toward detecting WC stars, as their emission-line signatures are much stronger than those of WNs. Here, we present the results of a survey covering all of M31's optical disk (2.2deg^2^), with sufficient sensitivity to detect the weaker-lined WN types. We identify 107 newly found WR stars, mostly of WN type. This brings the total number of spectroscopically confirmed WRs in M31 to 154, a number we argue is complete to ~95%, except in regions of unusually high reddening. This number is consistent with what we expect from the integrated H{alpha} luminosity compared to that of M33. The majority of these WRs formed in OB associations around the Population I ring, although 5% are truly isolated. Both the relative number of WC- to WN-type stars as well as the WC subtype distribution suggest that most WRs exist in environments with higher-than-solar metallicities, which is consistent with studies of M31's metallicity. Although the WC to WN ratio we find for M31 is much lower than that found by previous studies, it is still higher than what the Geneva evolutionary models predict. This may suggest that Roche-lobe overflow produces the excess of WC stars observed at high metallicity, or that the assumed rotational velocities in the models are too high.
We use a large sample of 174 Wolf-Rayet (W-R) galaxies drawn from the Sloan Digital Sky Survey to study whether and how the slope of the stellar initial mass function depends on metallicity. We calculate for each object its oxygen abundance, according to which we divide our sample into four metallicity subsamples. For each subsample, we then measure three quantities: the equivalent width of the H{beta} emission line, the equivalent width of the W-R bump around 4650{AA}, and the W-R bump-to-Hbeta intensity ratio, and compare to the predictions of the same quantities by evolutionary synthesis models of Schaerer & Vacca (1998ApJ...497..618S).
We present a catalogue of non-nuclear regions containing Wolf-Rayet stars in the metal-rich spiral galaxy M 83 (NGC 5236). From a total of 283 candidate regions identified using He II {lambda}4686 imaging with VLT-FORS2, Multi Object Spectroscopy of 198 regions was carried out, confirming 132 WR sources. From this sub-sample, an exceptional content of ~1035+/-300 WR stars is inferred, with N(WC)/N(WN) ~ 1.2, continuing the trend to larger values at higher metallicity amongst Local Group galaxies, and greatly exceeding current evolutionary predictions at high metallicity.
We present a narrow-band Very Large Telescope/Focal Reduced Low-dispersion Spectrograph #1 imaging survey of the SAB(rs)cd spiral galaxy NGC 5068, located at a distance of 5.45Mpc, from which 160 candidate Wolf-Rayet sources have been identified, of which 59 cases possess statistically significant {lambda}4686 excesses. Follow-up Gemini Multi-Object Spectrograph spectroscopy of 64 candidates, representing 40 per cent of the complete photometric catalogue, confirms Wolf-Rayet signatures in 30 instances, corresponding to a 47 per cent success rate. 21 out of 22 statistically significant photometric sources are spectroscopically confirmed.
We present a VLT/FORS1 survey of Wolf-Rayet (WR) stars in the spiral galaxy NGC 1313. In total, 94 WR candidate sources have been identified from narrow-band imaging. Of these, 82 have been spectroscopically observed, for which WR emission features are confirmed in 70 cases, one of which also exhibits strong nebular HeII{lambda}4686 emission. We also detect strong nebular HeII{lambda}4686 emission within two other regions of NGC 1313, one of which is a possible supernova remnant. Nebular properties confirm that NGC 1313 has a metal content log(O/H)+12=8.23+/-0.06, in good agreement with previous studies. From continuum-subtracted H{alpha} images we infer a global star formation rate of 0.6M_{sun}/yr. Using template LMC WR stars, spectroscopy reveals that NGC 1313 hosts a minimum of 84 WR stars. Our census comprises 51 WN stars, including a rare WN/C transition star plus 32 WC stars. In addition, we identify one WO star which represents the first such case identified beyond the Local Group. The bright giant HII region PES 1, comparable in H{alpha} luminosity to NGC 595 in M 33, is found to host a minimum of 17 WR stars. The remaining photometric candidates generally display photometric properties consistent with WN stars, such that we expect a global WR population of ~115 stars with N(WR)/N(O)~0.01 and N(WC)/N(WN)~0.4.
Massive stars, although being important building blocks of galaxies, are still not fully understood. This especially holds true for Wolf-Rayet (WR) stars with their strong mass loss, whose spectral analysis requires adequate model atmospheres. Following our comprehensive studies of the WR stars in the Milky Way, we now present spectroscopic analyses of almost all known WN stars in the LMC. For the quantitative analysis of the wind-dominated emission-line spectra, we employ the Potsdam Wolf-Rayet (PoWR) model atmosphere code. By fitting synthetic spectra to the observed spectral energy distribution and the available spectra (ultraviolet and optical), we obtain the physical properties of 107 stars. We present the fundamental stellar and wind parameters for an almost complete sample of WN stars in the LMC. Among those stars that are putatively single, two different groups can be clearly distinguished. While 12% of our sample are more luminous than 10^6^L_{sun}_ and contain a significant amount of hydrogen, 88% of the WN stars, with little or no hydrogen, populate the luminosity range between log(L/L_{sun}_)=5.3...5.8.
This catalog, also called the Finding List (FL) of Interacting Binaries (5th edition), was abstracted from the Card Catalog maintained at the University of Florida which contains information on all published, and to the extent available, unpublished work on eclipsing binaries. The Card Catalog originated with Raymond Smith Dugan in the 1930's, who published from it the first edition of "A Finding List for Observers of Eclipsing Variables" (Dugan 1934, Princeton Univ. Obs. Contrib. No. 15). Successive editions of FL were subsequently published by Pierce (1947, Princeton Univ. Obs. Contrib. No. 22), by Wood (1953, Univ. Pennsylvania Astron. Series, Vol. VIII), by Koch et al. (1963, Univ. Pennsylvania Astron. Series, Vol. IX), and by Wood et al. (1980, Univ. Pennsylvania Astron. Series, Vol. XII). The FL was conceived as an aid to observers of eclipsing variables in selecting an observing program efficiently from the collection of all known data in an easy-to-use format. Although this format has changed over the years to meet existing requirements, the basic information content remains the same. The current edition differs from previous ones in the extension of the magnitude limit at minimum light from 13 to 15. In earlier editions, a binary system was not included unless the editors were reasonably certain that the system was indeed an eclipsing or (rarely) an ellipsoidal variable. The fifth edition includes all systems that the editors were fairly certain are either eclipsing or radiometrically variable binaries. The catalog fields are Finding List number; star name; position (given in the original catalog in equinox 1900); blue magnitude at maximum light; bandpass of maximum light; depth of primary minimum in same bandpass; bandpass primary minimum; depth of secondary minimum and its bandpass; spectral class of star eclipsed at primary light and optional uncertainty character; spectral class of star eclipsed at secondary light; most recent reliable epoch of primary minimum; most recent orbital period; duration of primary minimum; duration of totality of primary minimum; BD, CoD, CPD, and HD number; alternate designations of system; and codes indicating the nature of the system. This database was created by the HEASARC in December 1997 based on a computer readable version of the catalog that was obtained from the CDS (their catalog VI/44): a few additions were made by the HEASARC that are listed in the HEASARC_Changes section of the present document. This is a service provided by NASA HEASARC .
This catalog was constructed at the Royal Greenwich Observatory in order to enlarge the Gliese (1957, Mitt. Astron. Rechen-Inst., Ser. A, No. 8) compilation. It contains data on stars nearer than 25 pc that were not included in that version of Gliese's catalog, plus some additional information that had been published after 1957 on stars which were present in the 1957 version of the Gliese catalog. The electronic version contains essentially all information given in Table Ia of the published Woolley catalog, plus positional data, and most cross references to other catalogs given in Table IIa. The notes flags in Table Ia are not included because the notes are not machine-readable. Omitted from Table IIa are the finding-chart indicators (Lowell G numbers or notes references) and miscellaneous cross identifications to other names and catalog identifiers. Tables Ib and IIb, containing 21 systems originally included in Gliese's (1957) catalog but for which revised parallaxes have placed them farther than 25 pc are not included in the electronic version. Data in the electronic version include the Gliese number (newly added stars by Woolley have numbers beginning with 9001, but new parallaxes have removed 9419 and added 9849 and 9850 from the < 25 parsecs sample), component identifications for multiple systems, parallaxes, annual proper motions, radial velocities, (U,V,W) space velocities, box orbit parameters (omega, e, i), spectral types, UBV data, absolute visual magnitudes, positions, GCTP (General Catalogue of Trigonometric Stellar Parallaxes) and its Supplement (Jenkins 1952, 1963) names, HD, DM, GCRV (General Catalogue of Stellar Radial Velocities, Publ. Carnegie Inst., Washington, No. 601, Wilson 1953) and other catalog identifiers, BS (= HR) (Hoffleit 1964) numbers, and remarks codes for spectroscopic binaries (SB), doubles, variables, etc. Note that there is an entry in this catalog for the Sun, for which many fields, such as RA and Dec, have not been populated. This table was recreated by the HEASARC in December 2002 based on the 21-Jul-1997 version of the <a href="https://cdsarc.cds.unistra.fr/ftp/cats/V/32A">CDS Catalog V/32A</a>. This is a service provided by NASA HEASARC .
The massive binary system WR 11 ({gamma}^2^-Velorum) has recently been proposed as the counterpart of a Fermi source. If this association is correct, this system would be the second colliding wind binary detected in GeV {gamma}-rays. However, the reported flux measurements from 1.4 to 8.64 GHz fail to establish the presence of nonthermal (synchrotron) emission from this source. Moreover, WR 11 is not the only radio source within the Fermi detection box. Other possible counterparts have been identified in archival data, some of which present strong nonthermal radio emission. We conducted arcsec-resolution observations toward WR 11 at very low frequencies (150-1400 MHz) where the nonthermal emission - if existent and not absorbed - is expected to dominate. We present a catalog of more than 400 radio emitters, among which a significant portion are detected at more than one frequency, including limited spectral index information. Twenty-one of these radio emitters are located within the Fermi significant emission. A search for counterparts for this last group pointed at MOST 0808-471; this source is 2' away from WR 11 and is a promising candidate for high-energy emission, having a resolved structure along 325-1390 MHz. For this source, we reprocessed archive interferometric data up to 22.3 GHz and obtained a nonthermal radio spectral index of -0.97+/-0.09. However, multiwavelength observations of this source are required to establish its nature and to assess whether it can produce (part of) the observed {gamma}-rays. WR 11 spectrum follows a spectral index of 0.74+/-0.03 from 150 to 230 GHz, consistent with thermal emission. We interpret that any putative synchrotron radiation from the colliding-wind region of this relatively short-period system is absorbed in the photospheres of the individual components. Notwithstanding, the new radio data allowed us to derive a mass-loss rate of 2.5x10^-5^ M_{sun}_/yr, which, according to the latest models for {gamma}-ray emission in WR 11, would suffice to provide the required kinetic power to feed nonthermal radiation processes.
We present a new compilation of Wolf-Rayet (WR) galaxies and extra-galactic HII regions showing broad He II {lambda}4686 emission drawn from the literature. Relevant information on the presence of other broad emission lines (N III {lambda}4640, C IV {lambda}5808 and other) from WR stars of WN and WC subtypes, and other existing broad nebular lines is provided. In total we include 139 known WR galaxies. Among these, 57 objects show both broad He II {lambda}4686 and C IV {lambda}5808 features. In addition to the broad (stellar) He II {lambda}4686 emission, a nebular He II component is well established (suspected) in 44 (54) objects. We find 19 extra-galactic HII regions without WR detections showing nebular He II {lambda}4686 emission. The present sample can be used for a variety of studies on massive stars, interactions of massive stars with the ISM, stellar populations, starburst galaxies etc. The data is accessible electronically and will be updated periodically
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