DOCSLIB.ORG

198 6Apj. . .300. .37 9T the Astrophysical Journal, 300

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
198 6Apj. . .300. .37 9T the Astrophysical Journal, 300 9T .37 The Astrophysical Journal, 300:379-395,1986 January 1 © 1986. The American Astronomical Society. All rights reserved. Printed in U.S.A. .300. 6ApJ. 198 SPECTROSCOPIC STUDIES OF WOLF-RAYET STARS. III. THE WC SUBCLASS Ana V. Torres and Peter S. Conti1,2 Joint Institute for Laboratory Astrophysics, University of Colorado and National Bureau of Standards AND Philip Massey2 Kitt Peak National Observatory, National Optical Astronomy Observatories Received 1985 AprilS; accepted 1985 June 28 ABSTRACT We present spectrophotometric data for the major optical emission lines of 64 Galactic and 18 Large Magellanic Cloud (LMC) WC stars. Using line ratios of O v A5590, C m 25696, and C iv 25806 we quantify the subtype classification. A few Galactic stars are reclassified, and nearly all the LMC WC stars are found to be of type WC4. Thus there is even a greater discrepancy in the distribution of WC subtypes between the LMC and the Galaxy than previously assumed, since WC4 types in the Galaxy are rare. New measures of the line widths of C in 24650 are found to correlate nicely with the (revised) WC subtypes, although a few stars have lines too wide for their line ratios. Two of the most discrepant stars, WR 125 and WR 140, also show nonthermal radio emission and are strong X-ray sources. Terminal wind velocities are estimated from an excitation—line width relation. The terminal velocities range from 1000 km s_1 for the latest subtypes to 5000 km s "1 for the earliest types. Subject headings: galaxies: Magellanic Clouds — stars: stellar statistics— stars: winds — stars: Wolf-Rayet I. INTRODUCTION Willis 1983). Torres and Conti (1984) have analyzed the optical Wolf-Rayet (W-R) stars are the descendants of massive spectra of 12 WC9 stars and found them to be very similar to (M > 30 Mq) O-type stars. They are all (mostly?) in a He core one another in line strengths. In this paper we attempt to give a burning phase, and their spectra are characterized by strong complete overview of the most important spectroscopic fea- emission lines superposed on a hot continuous spectrum. Most tures of WC stars in the optical region. show P Cygni profiles in some lines, indicating the presence of The WC sublcasses are defined mainly by the relative strong stellar winds. W-R stars are subdivided into three strengths of C n, C m, C iv, and O v. For the majority of the groups depending on their spectral appearance. When the pro- WC stars these ratios also correlate well with the line widths, ducts of CNO burning are seen in their spectrum allowing a secondary classification criterion (full width half (predominantly helium and nitrogen), the stars belong to the maximum [FWHM] of 4650 Â). Subtypes range from WC4 to nitrogen class (WN), and when the products of the He core WC10, corresponding both to higher and lower ionization burning phase are evident in their spectrum (strong helium, stages and to larger and smaller Doppler velocities in their carbon, and oxygen lines), they belong to the carbon class winds. (WC). Recently, the oxygen class (WO) has been introduced in Table 1 is taken from the Catalog, and it shows the classi- order to distinguish W-R stars whose spectra show the same fication criteria for WC subtypes. Since the publication of the products as the WC but with the oxygen lines enhanced Catalog, a few stars have been reclassified by other authors, (Barlow and Hummer 1982). and the classification has been extended to WC10 to include Each of these three W-R classes is further subdivided into an one star of an even lower ionization state (Massey and Conti ionization/excitation sequence. This classification system has 1983a). This classification had been applied to the central stars been based on the work done by Smith (1968) and adapted by of planetary nebulae (e.g., Cowley and Hiltner 1969) but not to van der Hucht et al (1981, hereafter the Catalog) to classify all Population I W-R stars. For reasons of consistency with spec- the known Galactic W-R stars. WN subclasses range from tral type classification (i.e., a temperature sequence), subtypes WN2 (higher ionizations) to WN9 (lower ionizations). A com- WC7 to WC10 are called “late WC stars” (WCL), and all plete analysis of the optical line strengths of the WN stars is others are “early WC stars” (WCE); however, it is uncertain given by Conti, Leep, and Perry (1983, hereafter Paper I). No whether this wind ionization sequence correlates with stellar such analysis exists for the WC sublcass; only a few individual effective temperatures. stars have been carefully studied (e.g., Underhill 1959; Smith Hydrogen and helium absorption lines are present in several and Aller 1971 ; Vreux, Dennefeld, and Andrillat 1983), or a few stars. A few of these have been studied for radial velocity varia- lines in various stars have been measured (e.g., Smith and tions, and their binary orbital parameters are well known (see, for example, Hidayat, Admiranto, and van der Hucht 1984, and references therein). The rest of them are just classified as 1 Visiting Astronomer, Kitt Peak National Observatory, NOAO, which is WC + abs to indicate the presence of the absorption lines, operated by AURA, Inc., under contract with the National Science Founda- which may be from a distant companion (Conti et al 1984) or a tion. 2 Visiting Astronomer, Cerro Tololo Inter-American Observatory, NOAO, nearby companion (Lamontagne, Moffat, and Seggewiss 1984) which is operated by AURA, Inc., under contract with the National Science or may be intrinsic to the star (Fitzpatrick 1982; see also Foundation. Massey, Conti, and Niemela 1981). Throughout this paper, we © American Astronomical Society • Provided by the NASA Astrophysics Data System 9T .37 380 TORRES, CONTI, AND MASSEY .300. TABLE 1 Catalog Classification of W-R Spectra Based on the Smith (1968) System 6ApJ. Carbon Ions Carbon, Oxygen Ions WC Type ¿5696 C m/¿5805 C iv ¿5696 C iii/¿5592 O v Other Criteria 198 WC9 C in > C iv O v weak or absent C n present WC8.5 C in > C iv O v weak or absent C n not present WC8 C in » C iv O v weak or absent WC7 C ni < C iv C ni > O v WC6 C in C iv C in > O v WC5 C in « C iv C in < O v WC4 C iv strong, C m weak or absent O v moderate do not differentiate between the known binaries and the bration, and all plates were developed for 5 minutes in D-19. “ + abs ” stars ; we call all of them “ + abs.” Spectra of the brightest Catalog stars and blue spectra of the Breysacher (1981) has compiled a catalog of all known W-R faintest and most heavily reddened stars could not be obtained. stars in the EMC. Of the 100 W-R stars in Breysacher’s All the northern hemisphere stars were also observed by one catalog, only 18 are classified as WC, of which nearly all are of us (P. M.) at Kitt Peak National Observatory with the called WC5. As we show in § III, these need to be reclassified to intensified Reticon scanner (1RS) on the No. 1 0.9 m telescope. even earlier subtypes for consistency with the line ratios of The 1RS is an analog spectrophotometer. Details of these Galactic WC stars. The W-R population in the Galaxy is very observations are given by Massey (1984), and a complete different from that in the EMC. The Catalog has a total of 159 description of the instrument is given by Barnes (1982). Total stars, and the WN/WC ratio is ~ 1.0; in the EMC, this ratio is spectral coverage, from several observations, was typically 4.5, according to the data of Breysacher. It had been suggested from 3200 to 7300 Â with a three-pixel resolution of ~ 4.5-6 Â. that the difference between the Galactic and the EMC stars The southern hemisphere W-R stars were observed by two of could be due to differences in metallicities in the two galaxies us (P. M. and P. S. C.) with the SIT Vidicon detector on the (Smith 1973; Vanbeveren and Conti 1980), but Massey and Cassegrain spectrograph of the CTIO 1.5 m telescope on runs Conti’s (1983h) data on M33 and the study by Armandroff and from 1981 November to 1985 February. The slit was usually Massey (1985) of several other galaxies with various metal- opened to 6"-10" to allow absolute fluxes to be measured; with licities do not support this conclusion. Rather, the difference the gratings used, this resulted in resolution of typically 10 Â. may be due to differences in the initial mass function, or to a Owing to the limited dynamic range of the SIT Vidicon detec- combination (Massey 1985). tor, each observation of a star consisted of two exposures : one As explained in the Catalog, the assignment of WC subtypes to get good continuum fluxes (with the strongest lines usually has been based on visual inspections of photographic plates. saturated), and another one to get unsaturated lines. Total One of the aims of this study is to quantify these visual esti- wavelength coverage was 3400-7300 Â, with the data obtained mates. In § III we present the measured ratios of equivalent with different gratings. widths and the FWHM of the 4650 Â line for Galactic and The photographic spectrograms and spot sensitometer EMC stars, and on this basis we propose the reclassification of exposures were traced either on a Boiler and Chivens micro- some stars.
Load more

Recommended publications
  • X-Ray Emission from Wolf-Rayet Stars
    X-ray Emission from Wolf-Rayet Stars Steve Skinner1, Svet Zhekov2, Manuel Güdel3 Werner Schmutz4, Kimberly Sokal1 1CASA, Univ. of Colorado (USA) [email protected] 2Space Research Inst. (Bulgaria) and JILA/Univ. of Colorado (USA) 3ETH Zurich (Switzerland) 3PMOD (Switzerland) Abstract We present an overview of recent X-ray observations of Wolf-Rayet (WR) stars with XMM-Newton and Chandra. Observations of several WC-type (carbon-rich) WR stars without known companions have yielded only non-detections, implying they are either very feeble X-ray emitters or perhaps even X-ray quiet. In contrast, several apparently single WN2-6 stars have been detected, but data are sparse for later WN7-9 stars. Putatively single WN stars such as WR 134 have X-ray luminosities and spectra that are strikingly similar to some known WN + OB binaries such as WR 147, suggesting a similar emission mechanism. 1 X-rays from WR Stars: Overview 3 Single Nitrogen-rich WN Stars 4 Wolf-Rayet Binaries WR stars are the evolutionary descendants of massive O • Sensitive X-ray observations have now been obtained • High-resolution X-ray grating spectra have been ob- stars and are losing mass at very high rates. They are in ad- of several putatively single WN2-6 stars with XMM tained for a few binaries such as γ2 Vel (WC8 + vanced nuclear burning stages, approaching the end of their and Chandra. All but one were detected (Fig. 1). O7.5; Fig. 3) and WR 140 (WC7 + O4-5). CCD lives as supernovae. Strong X-rays have been detected from CCD spectra exist (Fig.
    [Show full text]
  • Discovery of X-Ray Emission from the Wolf-Rayet Star WR142 of Oxygen Subtype
    Discovery of X-ray Emission from the Wolf-Rayet star WR 142 of oxygen subtype L. M. Oskinova, W.-R. Hamann, A. Feldmeier Institute for Physics and Astronomy, University Potsdam, 14476 Potsdam, Germany [email protected] R. Ignace Department of Physics and Astronomy, East Tennessee State University, Johnson City, TN 37614, USA Y.-H. Chu Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801, USA ABSTRACT We report the discovery of weak yet hard X-ray emission from the Wolf-Rayet (WR) star WR 142 with the XMM-Newton X-ray telescope. Being of spectral subtype WO2, WR142 is a massive star in a very advanced evolutionary stage, short before its explosion as a supernova or γ-ray burst. This is the first detection of X-ray emission from a WO-type star. We rule out any serendipitous X-ray sources within ≈ 1′′ of WR142. WR142 has an X-ray luminosity of 30 −1 < −8 LX = 7 × 10 ergs , which constitutes only ∼10 of its bolometric luminosity. The hard X- ray spectrum suggests a plasma temperature of about 100MK. Commonly, X-ray emission from stellar winds is attributed to embedded shocks due to the intrinsic instability of the radiation driving. From qualitative considerations we conclude that this mechanism cannot account for the hardness of the observed radiation. There are no hints for a binary companion. Therefore the only remaining, albeit speculative explanation must refer to magnetic activity. Possibly related, WR 142 seems to rotate extremely fast, as indicated by the unusually round profiles of its optical emission lines.
    [Show full text]
  • The Results of the 2013 Pro-Am Wolf-Rayet Campaign E
    Wolf-Rayet Stars W.-R. Hamann, A. Sander, H. Todt, eds. Potsdam: Univ.-Verlag, 2015 URL: http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-84268 The Results of the 2013 Pro-Am Wolf-Rayet Campaign E. J. Aldoretta1, N. St-Louis1, N. D. Richardson1, A. F. J. Moffat1, T. Eversberg2, G. M. Hill3 and the World-Wide WR Pro-Am Campaign Team4;5 1Universite´ de Montr´eal, Canada 2Schn¨orringenTelescope Science Institute, Germany 3W. M. Keck Observatory, United States 4VdS Section Spectroscopy, Germany 5Astronomical Ring for Access to Spectroscopy (ARAS), France Professional and amateur astronomers around the world contributed to a 4-month long cam- paign in 2013, mainly in spectroscopy but also in photometry, interferometry and polarimetry, to observe the first 3 Wolf-Rayet stars discovered: WR 134 (WN6b), WR 135 (WC8) and WR 137 (WC7pd+O9). Each of these stars are interesting in their own way, showing a variety of stellar wind structures. The spectroscopic data from this campaign were reduced and analyzed for WR 134 in order to better understand its behavior and long-term periodicity in the context of CIRs in the wind. We will be presenting the results of these spectroscopic data, which include the confirmation of the CIR variability and a time-coherency of 40 days (half-life of 20 days). ∼ ∼ 1 Motivation and Campaign the spectral lines (Morel et al. 1999), WR 135 is known to show large clumpy structures in its wind Overview (Lepine et al. 1996) and WR 137 is a long-period WR+O binary system with possible CIRs (Lef`evre Co-rotating interaction regions (CIRs) form in the et al.
    [Show full text]
  • CURRICULUM VITAE: Dr Richard Ignace
    CURRICULUM VITAE: Dr Richard Ignace Address: Department of Physics & Astronomy Office of Undergraduate Research College of Arts & Sciences Honors College EAST TENNESSEE STATE UNIVERSITY EAST TENNESSEE STATE UNIVERSITY Johnson City, TN 37614 Johnson City, TN 37614 Email: [email protected] [email protected] Web: faculty.etsu.edu/ignace www.etsu.edu/honors/ug research Phone/Fax: (423) 439-6904 / (423) 439-6905 (423) 439-6073 / (423) 439-6080 EDUCATION Ph.D. in Astronomy, University of Wisconsin 1996 M.S. in Physics, University of Wisconsin 1994 M.S. in Astronomy, University of Wisconsin 1993 B.S. in Astronomy, Indiana University 1991 POSITIONS HELD Aug 2016–present, Consultant, Tri-Alpha Energy Jan 2015–present, Director of Undergraduate Research Activities, East Tennessee State University Aug 2013–present, Full Professor: East Tennessee State University Aug 2007–Jul 2013, Associate Professor: East Tennessee State University Aug 2003–Jul 2007, Assistant Professor: East Tennessee State University Sep 2002–Jul 2003, Assistant Scientist: University of Wisconsin Aug 1999–Aug 2002, Visiting Assistant Professor: University of Iowa Nov 1996–Aug 1999, Postdoctoral Research Assistant: University of Glasgow SELECTED PROFESSIONAL ACTIVITIES Involved with service to discipline, institution, and community As Director of Undergraduate Research & Creative Activities, I administrate grant programs and activ- ities that support undergraduate scholarship, plus advocate for undergraduate research. Successful with publishing scholarly articles and competing for grant funding; author of the astron- omy textbook “Astro4U: An Introduction to the Science of the Cosmos,” of the popular astronomy book “Understanding the Universe,” and co-editor of the conference proceedings “The Nature and Evolution of Disks around Hot Stars” Principal organizer for STELLAR POLARIMETRY: FROM BIRTH TO DEATH, Jun 2011; and THE NATURE AND EVOLUTION OF DISKS AROUND HOT STARS, Jul 2004.
    [Show full text]
  • Discovery of X-Ray Emission from the Wolf–Rayet Star Wr 142 of Oxygen Subtype
    The Astrophysical Journal, 693:L44–L48, 2009 March 1 doi:10.1088/0004-637X/693/1/L44 c 2009. The American Astronomical Society. All rights reserved. Printed in the U.S.A. DISCOVERY OF X-RAY EMISSION FROM THE WOLF–RAYET STAR WR 142 OF OXYGEN SUBTYPE L. M. Oskinova1, W.-R. Hamann1, A. Feldmeier1, R. Ignace2, and Y.-H. Chu3 1 Institute for Physics and Astronomy, University Potsdam, 14476 Potsdam, Germany; [email protected] 2 Department of Physics and Astronomy, East Tennessee State University, Johnson City, TN 37614, USA 3 Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801, USA Received 2008 December 8; accepted 2009 January 7; published 2009 February 16 ABSTRACT We report the discovery of weak yet hard X-ray emission from the Wolf–Rayet (WR) star WR 142 with the XMM-Newton X-ray telescope. Being of spectral subtype WO2, WR 142 is a massive star in a very advanced evolutionary stage shortly before its explosion as a supernova or γ -ray burst. This is the first detection of X-ray emission from a WO-type star. We rule out any serendipitous X-ray sources within ≈ 1 of WR 142. WR 142 has 30 −1 −8 an X-ray luminosity of LX ≈ 7 × 10 erg s , which constitutes only 10 of its bolometric luminosity. The hard X-ray spectrum suggests a plasma temperature of about 100 MK. Commonly, X-ray emission from stellar winds is attributed to embedded shocks due to the intrinsic instability of the radiation driving.
    [Show full text]
  • FAR ULTRAVIOLET SPECTROSCOPIC EXPLORER SPECTROSCOPY of the O Vi RESONANCE DOUBLET in SAND 2 (WO) Paul A
    The Astrophysical Journal, 538:L51±L55, 2000 July 20 q 2000. The American Astronomical Society. All rights reserved. Printed in U.S.A. FAR ULTRAVIOLET SPECTROSCOPIC EXPLORER SPECTROSCOPY OF THE O vi RESONANCE DOUBLET IN SAND 2 (WO) Paul A. Crowther,1 A. W. Fullerton,2,3 D. J. Hillier,4 K. Brownsberger,5 L. Dessart,1,6 A. J. Willis,1 O. De Marco,1 M. J. Barlow,1 J. B. Hutchings,7 D. L. Massa,8 D. C. Morton,7 and G. Sonneborn9 Received 2000 March 17; accepted 2000 June 8; published 2000 July 14 ABSTRACT We present Far Ultraviolet Spectroscopic Explorer spectroscopy of Sand 2, an LMC WO-type Wolf-Rayet star, revealing the O vi resonance P Cygni doublet at 1032±1038 AÊ . These data are combined with Hubble Space Telescope Faint Object Spectrograph ultraviolet and Mount Stromlo 2.3 m optical spectroscopy and analyzed using a spherical, non-LTE, line-blanketed code. Our study reveals exceptional stellar parameters: T¤ » 21 Ç 25 21 150,000 K,v` = 4100 km s , log (L/L,,) = 5.3 , andM=1 # 10 M yr , if we adopt a volume ®lling factor » 5 » 10.10 of 10%. Elemental abundances ofC/He 0.7 0.2 and O/He 0.1520.05 by number qualitatively support pre- vious recombination line studies. We con®rm that Sand 2 is more chemically enriched in carbon than LMC WC stars and that it is expected to undergo a supernova explosion within the next5 # 10 4 yr. Subject headings: stars: evolution Ð stars: individual (Sand 2) Ð stars: Wolf-Rayet 1.
    [Show full text]
  • High Energy Processes in Young Stellar Objects and High-Mass X-Ray Binaries
    High energy processes in young stellar objects and high-mass X-ray binaries Pere Munar i Adrover Aquesta tesi doctoral està subjecta a la llicència Reconeixement- NoComercial 3.0. Espanya de Creative Commons. Esta tesis doctoral está sujeta a la licencia Reconocimiento - NoComercial 3.0. España de Creative Commons. This doctoral thesis is licensed under the Creative Commons Attribution-NonCommercial 3.0. Spain License. UNIVERSITAT DE BARCELONA Departament d’Astronomia i Meteorologia High energy processes in young stellar objects and high-mass X-ray binaries Pere Munar i Adrover Barcelona (Spain), March 2014 Programa de Doctorat en F´ısica L´ınia de recerca en Astronomia i Astrof´ısica 2010-2014 Mem`oria presentada per Pere Munar i Adrover per optar al grau de Doctor en F´ısica Director i Tutor Prof. Josep Maria Paredes Poy Contents Resum de la tesi v 1 Introduction 1 1.1High-energyastrophysics............................. 1 1.2 High-energy emission processes ......................... 2 1.2.1 Bremsstrahlung.............................. 3 1.2.2 Relativistic Bremsstrahlung ....................... 5 1.2.3 Synchrotron................................ 6 1.2.4 InverseCompton............................. 8 1.2.5 pp collisions ................................ 8 1.2.6 Photoelectricabsorption......................... 10 1.2.7 Coulombian losses ............................ 10 1.3 Particle acceleration ............................... 11 I Young Stellar Objects 13 2 Introduction 15 2.1Star-formingregions............................... 15 2.2Highenergyemissionfromstar-formingregions................ 16 2.2.1 High-massprotostars........................... 16 2.2.2 Low-massprotostars........................... 17 2.2.3 Otherhigh-energyemittingsources................... 18 3 Exploring the association of Fermi sources with young galactic objects 21 3.1Introduction.................................... 21 3.2 Cross-correlation of the First Fermi Catalog with massive young galactic objects......................................
    [Show full text]
  • Magnetic Fields in Massive Stars, Their Winds, and Their Nebulae
    Noname manuscript No. (will be inserted by the editor) Magnetic Fields in Massive Stars, their Winds, and their Nebulae Rolf Walder · Doris Folini · Georges Meynet Received: date / Accepted: date Abstract Massive stars are crucial building blocks of galaxies and the universe, as production sites of heavy elements and as stirring agents and energy providers through stellar winds and supernovae. The field of magnetic massive stars has seen tremendous progress in recent years. Different perspectives – ranging from direct field measurements over dynamo theory and stellar evolution to colliding winds and the stellar environment – fruitfully combine into a most interesting and still evolving overall picture, which we attempt to review here. Zeeman signatures leave no doubt that at least some O- and early B-type stars have a surface magnetic field. Indirect evidence, especially non- thermal radio emission from colliding winds, suggests many more. The emerging picture for massive stars shows similarities with results from intermediate mass stars, for which much more data are available. Observations are often compatible with a dipole or low order multi-pole field of about 1 kG (O-stars) or 300 G to 30 kG (Ap / Bp stars). Weak and unordered fields have been detected in the O-star ζ Ori A and in Vega, the first normal A-type star with a magnetic field. Theory offers essentially two explanations for the origin of the observed surface fields: fossil fields, particularly for strong and ordered fields, or different dynamo mechanisms, preferentially for less ordered fields. R. Walder CRAL: Centre de Recherche Astrophysique de Lyon ENS-Lyon, 46, all´ee d’Italie 69364 Lyon Cedex 07, France UMR CNRS 5574, Universit´ede Lyon E-mail: [email protected] D.
    [Show full text]
  • Research Paper
    DRAFT VERSION SEPTEMBER 20, 2018 Typeset using LATEX preprint style in AASTeX61 ANISOTROPIC WINDS IN WOLF-RAYET BINARY IDENTIFY POTENTIAL GAMMA-RAY BURST PROGENITOR J. R. CALLINGHAM,1 P. G. TUTHILL,2 B. J. S. POPE,2, 3, 4 P. M. WILLIAMS,5 P. A. CROWTHER,6 M. EDWARDS,2 B. NORRIS,2 AND L. KEDZIORA-CHUDCZER7 1ASTRON, Netherlands Institute for Radio Astronomy, PostBus 2, 7990 AA, Dwingeloo, The Netherlands 2Sydney Institute for Astronomy (SIfA), School of Physics, The University of Sydney, NSW 2006, Australia 3Center for Cosmology and Particle Physics, Department of Physics, New York University, 726 Broadway, New York, NY 10003, USA 4NASA Sagan Fellow 5Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ, UK 6Department of Physics & Astronomy, University of Sheffield, Sheffield, S3 7RH, UK 7School of Physics, University of New South Wales, NSW 2052, Australia (Accepted to Nature Astronomy, Revision 3) INTRODUCTORY PARAGRAPH The massive evolved Wolf-Rayet stars sometimes occur in colliding-wind binary systems in which dust plumes are formed as a result of the collision of stellar winds1. These structures are known to encode the parameters of the binary orbit and winds2,3,4. Here we report observations of a pre- viously undiscovered Wolf-Rayet system, 2XMM J160050.7–514245, with a spectroscopically deter- mined wind speed of 3400 km s−1. In the thermal infrared, the system is adorned with a prominent 1200 spiral dust plume,≈ revealed by proper motion studies to be expanding at only 570 km s−1. As≈ the dust and gas appear coeval, these observations are inconsistent with existing models≈ of the dynamics of such colliding wind systems5,6,7.
    [Show full text]
  • Arxiv:0912.1326V3 [Astro-Ph.SR] 24 Dec 2009 Etrfratohsc N Pc Srnm CS) Nv O Univ
    To appear in the Astronomical Journal X-ray Emission from Nitrogen-Type Wolf-Rayet Stars Stephen L. Skinner Center for Astrophysics and Space Astronomy (CASA), Univ. of Colorado, Boulder, CO 80309-0389; email: [email protected] Svetozar A. Zhekov1 JILA, Univ. of Colorado, Boulder, CO 80309-0440 Manuel G¨udel Institute of Astronomy, ETH Z¨urich, Wolfgang-Pauli-Str. 27, 8093 Z¨urich, Switzerland Werner Schmutz Physikalisch-Meteorologisches Observatorium Davos and World Radiation Center (PMOD/WRC), Dorfstrasse 33, CH-7260 Davos Dorf, Switzerland and Kimberly R. Sokal Center for Astrophysics and Space Astronomy (CASA), Univ. of Colorado, Boulder, CO 80309-0389 ABSTRACT arXiv:0912.1326v3 [astro-ph.SR] 24 Dec 2009 We summarize new X-ray detections of four nitrogen-type Wolf-Rayet (WR) stars obtained in a limited survey aimed at establishing the X-ray properties of WN stars across their full range of spectral subtypes. None of the detected stars is so far known to be a close binary. We report Chandra detections of WR 2 (WN2), WR 18 (WN4), and WR 134 (WN6), and an XMM-Newton detection of WR79a (WN9ha). These observations clearly demonstrate that both WNE and WNL stars are X-ray sources. We also discuss Chandra archive detections 1On leave from Space Research Institute, Sofia, Bulgaria –2– of the WN6h stars WR 20b, WR 24, and WR 136 and ROSAT non-detections of WR 16 (WN8h) and WR 78 (WN7h). The X-ray spectra of all WN detections show prominent emission lines and an admixture of cool (kT < 1 keV) and hot (kT > 2 keV) plasma.
    [Show full text]
  • Clumping in the Winds of Wolf-Rayet Stars
    Draft version September 23, 2020 A Typeset using L TEX default style in AASTeX62 Clumping in the Winds of Wolf-Rayet Stars Andre-Nicolas´ Chene´,1 Nicole St-Louis,2 Anthony F. J. Moffat,2 and Kenneth G. Gayley3 1Gemini Observatory/NSFs NOIRLab, 670 N. A‘ohoku Place, Hilo, Hawai‘i, 96720, USA 2D´epartement de Physique, Universit´ede Montr´eal, C. P. 6128, succ. centre-ville, Montr´eal (Qc) H3C 3J7, and Centre de Recherche en Astrophysique du Qu´ebec, Canada 3Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242, USA Submitted to ApJ ABSTRACT We attempt to determine the driver for clumping in hot-star winds by extending the measure of the spectral variability level of Galactic Wolf-Rayet stars to by far the hottest known among them, the WN2 star WR 2 and the WO2 stars WR 102 and WR 142. These three stars have T⋆ = 140 kK and 200 kK, the last two being well above the bulk of WR stars with T⋆ ∼ 40 – 120 kK. This full temperature range for WR stars is much broader than that of their O-star progenitors (∼30-50 kK), so is better suited to look for any temperature dependence of wind clumping. We have obtained multiple observations with high signal-to-noise, moderate-resolution spectroscopy in search of small- scale variability in the strong emission lines from the dense winds of these three extreme stars, and find a very low-level of variability in both stars. Temperature and terminal velocity are correlated, so faster winds show a lower variability, though this trend goes against any predictions made involving Line Deshadowing Instability (LDI) only, implying that instabilities intrinsic to LDI are not the main source of wind clumping.
    [Show full text]
  • Binary WR 30A?
    A&A 404, L29–L32 (2003) Astronomy DOI: 10.1051/0004-6361:20030574 & c ESO 2003 Astrophysics New type of brightness variations of the colliding wind WO4 + O5((f)) binary WR 30a? S. J. Paardekooper1, K. A. van der Hucht2,A.M.vanGenderen1,E.Brogt3, M. Gieles4, and R. Meijerink1 1 Leiden Observatory, Postbus 9513, 2300 RA Leiden, The Netherlands Letter to the Editor 2 SRON National Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands 3 University of Groningen, Kapteyn Astronomical Institute, PO Box 800, 9700 AV, Groningen, The Netherlands 4 Astronomical Institute, PO Box 80000, 3508 TA Utrecht, The Netherlands Received 13 March 2003 / Accepted 16 April 2003 Abstract. We present new photometric observations in Johnson V and B of WR 30a, revealing relative dramatic changes in brightness of 0m: 2. These variations occur on a time scale of hours, and are only seen in V. We argue that they are not caused by dust extinction, but either by a dramatic change in the strength of the C iv 5801-12 Å emission line doublet due to a de-excitation process, or by some unknown continuum effect. Key words. stars: binaries – stars: Wolf-Rayet – stars: individual: WR 30a 1. Introduction companion star has been classified as O4 (Moffat & Seggewiss 1984). Niemela (1995) reported the first radial velocity study WO stars are a rare species, representing the final evolution- for WR 30a, and suggested that WR 30a might be a short period ary stage in the Wolf-Rayet phase of massive stars, and as binary. such they are supernova progenitors.
    [Show full text]