DOCSLIB.ORG

ASTRONOMY and ASTROPHYSICS on Some Properties of Very Metal

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
ASTRONOMY and ASTROPHYSICS on Some Properties of Very Metal A&A manuscript no. ASTRONOMY (will be inserted by hand later) AND Your thesaurus codes are: 19.34.1; 19.38.1; 19.41.1; 07.25.1; 19.69.1 ASTROPHYSICS On some properties of very metal-rich stars N. Mowlavi1, G. Meynet1, A. Maeder1, D. Schaerer2, and C. Charbonnel3 1 Geneva Observatory, CH-1290 Sauverny, Switzerland 2 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA 3 Laboratoire d’Astrophysique de Toulouse, CNRS - UMR 5572, 14 av. E. Belin, 31400 Toulouse, France Received 30 September 1997; accepted 6 April 1998 Abstract. An analysis of some properties of stellar mod- Schaller et al. 1992, hereafter Paper I, and Maeder & Conti els as a function of metallicity Z (and helium content Y ) 1994). In contrast, they are still poorly known at metal- is presented, with special attention to those stars with licities much higher than solar. Recent calculations have metallicities higher than twice or three times solar. been performed at metallicities five times solar (Fagotto It is shown that the stellar properties as a function of et al. 1994, Mowlavi et al. 1997). Mowlavi et al. (1997) Z are mainly determined by the effects of the opacities notice that those very metal-rich models present specific at sub-solar metallicities, and by the effects of the mean properties which are distinct from the ones at Z ≤ 0.04. In molecular weight and stellar mass loss at higher metal- particular, they are hotter and more luminous that those licities. As a result, very metal-rich stars (Z ∼> 0.05) ex- at solar metallicity, contrary to expectations. It is the pur- hibit properties that deviate from what is expected from pose of this paper to analyze in detail some of these prop- the known characteristics at lower metallicities. In par- erties of very metal-rich stars. These could have important ticular, they are more luminous and hotter than those at consequences on the observable properties of high metal- Z ∼< 0.05 due to the effect of the mean molecular weight. rich galaxies. They have main sequence lifetimes much shorter (60% The study is based on the extensive grids of stellar shorter at Z = 0.1 than at Z = 0.02) than those at so- models computed by the Geneva group with 0.001 ≤ Z ≤ lar metallicity due to their lower initial hydrogen content. 0.1. It covers the main phases of stellar evolution, exclud- Finally, the high mass loss rates at high metallicities af- ing the latest stages of evolution. The core helium burning fect significantly the population synthesis of massive stars phase of very metal-rich low-mass (M < 1.7 M⊙) stars, in very metal-rich regions. An analysis of expected Wolf- important for the study of elliptical galaxies, is not con- Rayet and supernovae populations in such conditions is sidered in this paper as it has been the subject of existing briefly presented. papers in the literature (see, for example, Dorman, Rood & O’Connell, 1993, Fagotto et al. 1994). arXiv:astro-ph/9804155v1 16 Apr 1998 Key words: Stars: evolution of; Stars: general; Stars: A general discussion on the dependence of stellar prop- Hertzsprung-Russell diagram; Galaxy (the): center of; erties on chemical composition is presented in Sect. 2. Stars: Wolf-Rayet Section 3 summarizes the model ingredients used in the computation of the Geneva grids. The stellar properties during the main sequence (MS) and the core helium burn- ing (CHeB) phase are analyzed in Sects. 4 and 5, respec- 1. Introduction tively. Wolf-Rayet stars in very metal-rich environments Observations as well as models of galactic chemical evo- are briefly discussed in Sect. 6. Conclusions are drawn in lution suggest that the metallicity at the center of our Sect. 7. galaxy, where the density of matter is high, can reach up to 3 to 5 times the solar metallicity (McWilliam & Rich 2. Chemical composition and stellar properties 1994, Simpson et al. 1995). Other objects such as elliptical galaxies, or maybe even quasars (Korista et al. 1996), also Chemical composition is traditionally described by X, Y show evidences of very metal-rich stellar populations. and Z, which are the mass fractions of hydrogen, helium The metallicity affects the evolution of stars mainly and heavier elements, respectively. In the course of galactic through its impact on the radiative opacities, the equa- evolution, the interstellar matter is progressively enriched tion of state, the nuclear reaction rates and the stellar in heavy elements, and Z increases through time. It is evi- mass loss rates. The impact of the metallicity on the stel- dent that helium is also enriched, the increase of its inter- lar properties has been well studied for 0.001 ≤ Z ≤ 0.04 stellar abundance with respect to Z being conveniently de- on base of extensive stellar model calculations (see e.g. scribed by a ∆Y/∆Z law such that Y = Y0 +∆Y/∆Z ×Z 2 N. Mowlavi1 et al.: On some properties of very metal-rich stars −1 3 (where Y0 is the primordial He abundance). At low metal- κ T dT/dr for radiative transfer], leading to a decrease licities (Z ∼< 0.02), Y remains practically constant [an in the surface luminosity. As the radius is unaffected to absolute variation δZ of the metallicity induces an ab- first order, the surface temperature decreases too. In sum- solute variation of He of δY = ∆Y/∆Z × δZ, so that mary, an increase in κ tends to decrease both L and Teff . −2 −3 δY/Y ∼< 10 for Z ∼< 10 ], and the stellar properties In general, the opacities increase with increasing as a function of metallicity are thus expected to be de- metallicity. This is the case for the bound-free (see termined mainly by Z. At high metallicities (Z ∼> 0.02), Eq. 16.107 in Cox & Giuli 1969) and free-free (see on the other hand, Y increases (or, alternatively, X de- Eq. 16.95 in Cox & Giuli 1969) transitions. In contrast, creases) significantly with Z (Y passes from 0.30 to 0.48 electron scattering depends only on X [κe ≃ 0.20(1+ X)], when Z increases from 0.02 to 0.1, see Table 1). In those which is about constant at Z ∼< 0.01 and decreases with conditions, both Z and Y (and X =1 − Y − Z) determine Z at Z ∼> 0.01. As seen in Sect. 4, these considerations ex- the stellar properties as a function of metallicity. plain the stellar properties as a function of Z at sub-solar Chemical composition influences the stellar structure metallicities. basically through three contributions: the mean molecular weight µ, the radiative opacity κ, and the nuclear energy 2.3. The εnuc-effect production εnuc. The metallicity-dependent mass loss rate M˙ further affects stellar evolution as a function of Z. The nuclear energy production εnuc sustains the stellar luminosity. If εnuc is arbitrarily increased, the central re- gions of the star expand, leading to a decrease in the tem- 2.1. The µ-effect peratures and densities, and to an increase in the stellar The mean molecular weight acts in the hydrostatic equi- radius. Thus, an increase in εnuc tends to decrease both librium of the star. Let us imagine a thought experiment L and Teff , as well as the central temperature Tc and in which µ is arbitrarily increased over the whole star, all density ρc. other quantities such as κ or ε being unaltered (though The way εnuc depends on metallicity is closely related keeping, of course, their density and temperature depen- to the mode of nuclear burning. When the CNO cycles are dences). The reduction in the gas pressure leads to an the main mode of H burning, εnuc increases with Z. In overall contraction (and heating) until hydrostatic equi- contrast, when the main mode of burning is the pp chain, librium is re-established. As a result, the stellar radius de- εnuc is related to X. It is thus about independent of Z at creases and the surface temperature Teff increases. The Z ∼< 0.02, and decreases with increasing Z at Z ∼> 0.02. As surface luminosity L, on the other hand, increases with µ shown in Sect. 4, these properties determine the behavior 3 since L(r) ∝ T dT/dr [in the case of radiative transfer, of Tc and ρc in MS stars as a function of Z. with L(r) and T being the luminosity and temperature at radius r, respectively]. In summary, an increase in µ tends 2.4. The effect of M˙ to increase both L and Teff . This µ-effect is undetectable in low-metallicity stars, When mass loss is driven by radiation, Kudritzki et al. where µ is essentially constant as a function of metallic- (1989) showed that M˙ in O stars is proportional to Z0.5. ity. At metallicities higher than about solar, however, µ As a result, the effects of mass loss dominate in more increases as a result of increasing Y [Z remains unim- metal-rich stars. Mass loss reduces the stellar mass, mod- portant in this respect for all realistic values of Z, since ifying thereby the post-MS stellar properties (and even µ ≃ (2X +0.75Y +0.5Z)−1]. And indeed, it is shown in during the MS for the most massive ones). It also turns Sections 4 and 5 that very metal-rich models are more lu- the (massive) star into a Wolf-Rayet star at an earlier minous and hotter than solar-metallicity ones. It has to be stage than it would at lower metallicity. This is analysed noted that the ∆Y/∆Z law adopted in metal-rich models in more detail in Sect.
Load more

Recommended publications
  • Astro2020 Science White Paper Unlocking the Secrets of Late-Stage Stellar Evolution and Mass Loss Through Radio Wavelength Imaging
    Astro2020 Science White Paper Unlocking the Secrets of Late-Stage Stellar Evolution and Mass Loss through Radio Wavelength Imaging Thematic Areas: Planetary Systems Star and Planet Formation Formation and Evolution of Compact Objects Cosmology and Fundamental Physics 7 Stars and Stellar Evolution Resolved Stellar Populations and their Environments Galaxy Evolution Multi-Messenger Astronomy and Astrophysics Principal Author: Name: Lynn D. Matthews Institution: Massachusetts Institute of Technology Haystack Observatory Email: [email protected] Co-authors: Mark J Claussen (National Radio Astronomy Observatory) Graham M. Harper (University of Colorado - Boulder) Karl M. Menten (Max Planck Institut fur¨ Radioastronomie) Stephen Ridgway (National Optical Astronomy Observatory) Executive Summary: During the late phases of evolution, low-to-intermediate mass stars like our Sun undergo periods of extensive mass loss, returning up to 80% of their initial mass to the interstellar medium. This mass loss profoundly affects the stellar evolutionary history, and the resulting circumstellar ejecta are a primary source of dust and heavy element enrichment in the Galaxy. However, many details concerning the physics of late-stage stellar mass loss remain poorly understood, including the wind launching mechanism(s), the mass loss geometry and timescales, and the mass loss histories of stars of various initial masses. These uncertainties have implications not only for stellar astrophysics, but for fields ranging from star formation to extragalactic astronomy and cosmology. Observations at centimeter, millimeter, and submillimeter wavelengths that resolve the radio surfaces and extended atmospheres of evolved arXiv:1903.05592v1 [astro-ph.SR] 13 Mar 2019 stars in space, time, and frequency are poised to provide groundbreaking new insights into these questions in the coming decade.
    [Show full text]
  • Extremely Extended Dust Shells Around Evolved Intermediate Mass Stars: Probing Mass Loss Histories,Thermal Pulses and Stellar Evolution
    EXTREMELY EXTENDED DUST SHELLS AROUND EVOLVED INTERMEDIATE MASS STARS: PROBING MASS LOSS HISTORIES,THERMAL PULSES AND STELLAR EVOLUTION A Thesis presented to the Faculty of the Graduate School at the University of Missouri In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy by BASIL MENZI MCHUNU Dr. Angela K. Speck December 2011 The undersigned, appointed by the Dean of the Graduate School, have examined the dissertation entitled: EXTREMELY EXTENDED DUST SHELLS AROUND EVOLVED INTERMEDIATE MASS STARS PROBING MASS LOSS HISTORIES, THERMAL PULSES AND STELLAR EVOLUTION USING FAR-INFRARED IMAGING PHOTOMETRY presented by Basil Menzi Mchunu, a candidate for the degree of Doctor of Philosophy and hereby certify that, in their opinion, it is worthy of acceptance. Dr. Angela K. Speck Dr. Sergei Kopeikin Dr. Adam Helfer Dr. Bahram Mashhoon Dr. Haskell Taub DEDICATION This thesis is dedicated to my family, who raised me to be the man I am today under challenging conditions: my grandfather Baba (Samuel Mpala Mchunu), my grandmother (Ma Magasa, Nonhlekiso Mchunu), my aunt Thembeni, and my mother, Nombso Betty Mchunu. I would especially like to thank my mother for all the courage she gave me, bringing me chocolate during my undergraduate days to show her love when she had little else to give, and giving her unending support when I was so far away from home in graduate school. She passed away, when I was so close to graduation. To her, I say, ′′Ulale kahle Macingwane.′′ I have done it with the help from your spirit and courage. I would also like to thank my wife, Heather Shawver, and our beautiful children, Rosemary and Brianna , for making me see life with a new meaning of hope and prosperity.
    [Show full text]
  • Red Giant Mass-Loss: Studying Evolved Stellar Winds with FUSE and HST/STIS
    Red Giant Mass-Loss: Studying Evolved Stellar Winds with FUSE and HST/STIS A dissertation submitted to the University of Dublin for the degree of Doctor of Philosophy Cian Crowley Supervisor: Dr. Brian R. Espey Trinity College Dublin, July 2006 School of Physics University of Dublin Trinity College Dublin ii For Mam and Dad Declaration I hereby declare that this thesis has not been submitted as an exercise for a degree at this or any other University and that it is entirely my own work. I agree that the Library may lend or copy this thesis upon request. Signed, Cian Crowley July 25, 2006. Publications Crowley, C., Espey, B. R.,. & McCandliss, S. R., 2006, In prep., ‘FUSE and HST/STIS Observations of the Eclipsing Symbiotic Binary EG Andromedae’ Acknowledgments I wish to acknowledge and thank Brian Espey, Stephan McCandliss and Peter Hauschildt for their contributions to this work. Most especially I would like to express my gratitude to my supervisor Brian Espey for his enthusiastic supervision, patience and encourage- ment. His help, support and advice is very much appreciated. In addition, the helpful and insightful comments and advice from numerous people, inlcuding, Graham Harper, Philip Bennett, Alex Brown, Gary Ferland, Tom Ake, B-G Anderson and Dugan With- erick, were invaluable and again, very much appreciated. Also, a special word of thanks for their viva comments and feedback for Alex Brown and Peter Gallagher. This work was supported by Enterprise Ireland Basic Research grant SC/2002/370 from EU funded NDP. The FUSE data were obtained under the Guest Investigator Pro- gram and supported by NASA grants NAG5-8994 and NAG5-10403 to the Johns Hopkins University (JHU).
    [Show full text]
  • Astronomy & Astrophysics on the Properties of Massive Population III
    A&A 382, 28–42 (2002) Astronomy DOI: 10.1051/0004-6361:20011619 & c ESO 2002 Astrophysics On the properties of massive Population III stars and metal-free stellar populations D. Schaerer Observatoire Midi-Pyr´en´ees, Laboratoire d’Astrophysique, UMR 5572, 14 Av. E. Belin, 31400 Toulouse, France Received 2 July 2001 / Accepted 13 November 2001 Abstract. We present realistic models for massive Population III stars and stellar populations based on non-LTE model atmospheres, recent stellar evolution tracks and up-to-date evolutionary synthesis models, with the aim to study their spectral properties, including their dependence on age, star formation history, and IMF. A comparison of plane parallel non-LTE model atmospheres and comoving frame calculations shows that even in the presence of some putative weak mass loss, the ionising spectra of metal-free populations differ little or negligibly from those obtained using plane parallel non-LTE models. As already discussed by Tumlinson & Shull (2000), the main salient property of Pop III stars is their increased ionising flux, especially in the He+ continuum (>54 eV). The main result obtained for individual Pop III stars is the following: due to their redward evolution off the zero age main sequence (ZAMS) the spectral hardness measured by the He+/H ionising flux is decreased by a factor ∼2 when averaged over their lifetime. If such stars would suffer strong mass loss, their spectral appearance could, however, remain similar to that of their ZAMS position. The main results regarding integrated stellar populations are: – for young bursts and the case of a constant SFR, nebular continuous emission – neglected in previous studies – dominates the spectrum redward of Lyman-α if the escape fraction of ionising photons out of the considered region is small or negligible.
    [Show full text]
  • Aerosols in Astrophysics Stars Complete Their Cycle of Existence, There R.E.Stencel, C.A
    Aerosols in Astrophysics stars complete their cycle of existence, there R.E.Stencel, C.A. Jurgenson & is a wholesale return of modified material T.A. Ostrowski-Fukuda back to the interstellar medium, affecting the The Observatories, University of Denver, next generation of star and planet formation. Department of Physics & Astronomy, Denver, Colorado 80208, USA Submitted: Evolved stars are characterized by surface 2002December30, Email: [email protected] temperatures low enough to allow molecules and solid-phase particles to exist in their ABSTRACT: atmospheres. In contrast to the nearly 6000K surface temperature of the Sun, the Solid phase material exists in low density kinetic temperatures of evolved stars may astrophysical environments, from stellar range between 2000K near their “surfaces” atmospheres to interstellar clouds, from to a few hundred K in their circumstellar current times to early phases of the universe. envelopes [CSE] at a few stellar radii We consider the origin, composition and distance. Time-dependent phase transitions evolution of solid phase materials in the from ionized plasma to cold, solid state are particular case of stellar outer atmospheres, observed, spectroscopically, to exist. as representative of many conditions. Also considered are the dynamics and interactions Some terminology may be helpful for the in circumstellar and galactic environments. reader not already acquainted with stellar Finally, new observational prospects for evolution. Solar mass stars are predicted to spectroscopy, polarimetry and leave the hydrogen-fusing “main sequence” interferometry are discussed. after approximately ten billion years, and progress through a rapid series of internal changes during what is known as the red 1.0 INTRODUCTION giant and asymptotic giant branch [RGB, AGB] phases, lasting one percent of the Solid phase material can be found nearly main sequence lifetime.
    [Show full text]
  • THE PROGENITORS of TYPE IIP SUPERNOVAE Emma R. Beasor
    THE PROGENITORS OF TYPE IIP SUPERNOVAE Emma R. Beasor A thesis submitted in partial fulfilment of the requirements of Liverpool John Moores University for the degree of Doctor of Philosophy. April 2019 Declaration The work presented in this thesis was carried out at the Astrophysics Research Insti- tute, Liverpool John Moores University. Unless otherwise stated, it is the original work of the author. While registered as a candidate for the degree of Doctor of Philosophy, for which sub- mission is now made, the author has not been registered as a candidate for any other award. This thesis has not been submitted in whole, or in part, for any other degree. Emma R. Beasor Astrophysics Research Institute Liverpool John Moores University IC2, Liverpool Science Park 146 Brownlow Hill Liverpool L3 5RF UK ii Abstract Mass-loss prior to core collapse is arguably the most important factor affecting the evolution of a massive star across the Hertzsprung-Russel (HR) diagram, making it the key to understanding what mass-range of stars produce supernova (SN), and how these explosions will appear. It is thought that most of the mass-loss occurs during the red supergiant (RSG) phase, when strong winds dictate the onward evolutionary path of the star and potentially remove the entire H-rich envelope. Uncertainty in the driving mechanism for RSG winds means the mass-loss rate (M_ ) cannot be determined from first principles, and instead, stellar evolution models rely on empirical recipes to inform their calculations. At present, the most commonly used M_ -prescription comes from a literature study, whereby many measurements of mass- loss were compiled.
    [Show full text]
  • The Star Newsletter
    THE HOT STAR NEWSLETTER ? An electronic publication dedicated to A, B, O, Of, LBV and Wolf-Rayet stars and related phenomena in galaxies No. 41 June/July 1998 editor: Philippe Eenens http://www.astro.ugto.mx/∼eenens/hot/ [email protected] http://www.star.ucl.ac.uk/∼hsn/index.html Contents of this newsletter From the Editor . 1 Abstracts of 24 accepted papers . 2 Abstracts of 2 submitted paper . 16 Abstracts of 2 proceedings papers . 17 Book ......................................................................18 Meetings ...................................................................20 From the editor This issue covers two months of publications and is dominated by η Car, other LBVs and B[e] stars. Other papers tell us about massive stars in the Galactic Center and R136, OB stars, polarimetry, wind models and [WC] central stars of Planetary Nebulae. We also present a book and remind readers about future meetings: two special sessions during IAU symposium 193 in Mexico (on HD5980 and on the XMEGA campaign) as well as IAU colloquium 175 in Spain in June 1999 (on Be stars). 1 Accepted Papers On the Multiplicity of η Carinae Henny J.G.L.M. Lamers1,2, Mario Livio1, Nino Panagia1,3, & Nolan R. Walborn1 1 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA 2 Astronomical Institute and SRON Laboratory for Space Research, Princetonplein 2, 3584CC Utrecht, The Netherlands 3 On assignment from the Astrophysics Division, Space Science Department of ESA. The nebula around the luminous blue variable η Car is extremely N-rich and C,O-poor, indicative of CNO-cycle products. On the other hand, the recent HST-GHRS observation of the nucleus of η Car shows the spectrum of a star with stellar-wind lines of C ii,C iv, Si ii, Si iv etc.
    [Show full text]
  • Orbital Separation Amplification in Fragile Binaries with Evolved
    Publications 11-22-2011 Orbital Separation Amplification in rF agile Binaries with Evolved Components K. B. Johnston Florida Institute of Technology, [email protected] Terry D. Oswalt Florida Institute of Technology, [email protected] Follow this and additional works at: https://commons.erau.edu/publication Part of the Stars, Interstellar Medium and the Galaxy Commons Scholarly Commons Citation Johnston, K. B., & Oswalt, T. D. (2011). Orbital Separation Amplification in rF agile Binaries with Evolved Components. New Astronomy, 17(4). https://doi.org/10.1016/j.newast.2011.11.004 This Article is brought to you for free and open access by Scholarly Commons. It has been accepted for inclusion in Publications by an authorized administrator of Scholarly Commons. For more information, please contact [email protected]. Orbital Separation Amplification in Fragile Binaries with Evolved Components K.B. Johnston and T. D. Oswalt∗ D.Valls-Gabaudy November 8, 2018 Abstract The secular stellar mass-loss causes an amplification of the orbital separation in fragile, common proper motion, binary systems with separations of the order of 1000 A.U. In these systems, companions evolve as two independent coeval stars as they experience negligible mutual tidal interactions or mass transfer. We present models for how post-main sequence mass-loss statistically distorts the frequency distribution of separations in fragile binaries. These models demonstrate the expected increase in orbital seapration resulting from stellar mass-loss, as well as a perturbation of associated orbital parameters. Comparisons between our models and observations resulting from the Luyten survey of wide visual binaries, specif- ically those containing MS and white-dwarf pairs, demonstrate a good agreement between the calculated and the observed angular separation distribution functions.
    [Show full text]
  • Identifying Stars of Mass> 150 Msun from Their Eclipse by a Binary
    Mon. Not. R. Astron. Soc. 000, 1–1 (2012) Printed 24 September 2018 (MN LATEX style file v2.2) Identifying Stars of Mass > 150M⊙ from Their Eclipse by a Binary Companion Tony Pan1, Abraham Loeb1 1Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA 24 September 2018 ABSTRACT We examine the possibility that very massive stars greatly exceeding the com- monly adopted stellar mass limit of 150M⊙ may be present in young star clusters in the local universe. We identify ten candidate clusters, some of which may host stars with masses up to 600M⊙ formed via runaway collisions. We estimate the probabilities of these very massive stars being in eclipsing binaries to be & 30%. Although most of these systems cannot be resolved at present, their transits can be detected at distances of 3 Mpc even under the contamination of the background cluster light, due to the 7 6 large associated luminosities ∼ 10 L⊙ and mean transit depths of ∼ 10 L⊙. Discov- ery of very massive eclipsing binaries would flag possible progenitors of pair-instability supernovae and intermediate-mass black holes. Key words: binaries: general – galaxies: star clusters 1 INTRODUCTION The most accurate method of constraining the stellar masses of distant stars is by measuring the radial velocity Many observations support the statistical argument that and light curves of the star in an eclipsing binary (Bonanos the upper limit to initial stellar masses is ∼ 150M⊙ for 2009; Torres, Andersen & Gim´enez 2010). The light curve Pop II/I stars (Figer 2005; Zinnecker & Yorke 2007). How- provides a wealth of information about the binary, includ- ever, this common notion is challenged by the recent spec- ing its orbital period, inclination, eccentricity, as well as the troscopic analyses of Crowther et al.
    [Show full text]
  • Parameters of Selected Central Stars of Planetary Nebulae from Consistent Optical and Uv Spectral Analysis
    PARAMETERS OF SELECTED CENTRAL STARS OF PLANETARY NEBULAE FROM CONSISTENT OPTICAL AND UV SPECTRAL ANALYSIS Cornelius Bernhard Kaschinski PARAMETERS OF SELECTED CENTRAL STARS OF PLANETARY NEBULAE FROM CONSISTENT OPTICAL AND UV SPECTRAL ANALYSIS Dissertation Ph.D. Thesis an der Ludwig–Maximilians–Universitat¨ (LMU) Munchen¨ at the Ludwig–Maximilians–University (LMU) Munich fur¨ den Grad des for the degree of Doctor rerum naturalium vorgelegt von submitted by Cornelius Bernhard Kaschinski Munchen,¨ 2013 1st Evaluator: Prof. Dr. A. W. A. Pauldrach 2nd Evaluator: Prof. Dr. Barbara Ercolano Date of oral exam: 25.4.2013 Contents Contents vii List of Figures xii List of Tables xiii Zusammenfassung xv Abstract xvii 1 Introduction 1 1.1 Hot Stars . 1 1.1.1 Evolution of hot stars . 1 1.2 Impact of massive stars on the evolution of stellar clusters . 5 1.3 Motivation of this thesis . 5 1.4 Organization of this thesis . 8 2 Radiation-driven winds of hot luminous stars 11 XVII. Parameters of selected central stars of PN from consistent optical and UV spectral analysis and the universality of the mass–luminosity relation 2.1 Introduction . 12 2.2 Methods . 15 2.2.1 Parameter determination using hydrodynamic models and the UV spectrum . 15 2.2.2 Parameter determination using optical H and He lines . 18 2.2.3 Combined analysis . 19 2.3 Implementation of Stark broadening in the model atmosphere code WM-basic . 19 2.4 CSPN observational material . 25 2.5 Consistent optical and UV analysis of the CSPNs NGC 6826 and NGC 2392 . 25 2.5.1 NGC 6826 .
    [Show full text]
  • Evolutionary Impact of Stellar Mass Loss
    Astro2020 Science White Paper High Angular Resolution Astrophysics: Evolutionary Impact of Stellar Mass Loss Thematic Areas: ☐ Planetary Systems ☐ Star and Planet Formation ☐Formation and Evolution of Compact Objects ☐ Cosmology and Fundamental Physics Stars and Stellar Evolution ☐Resolved Stellar Populations and their Environments ☐Galaxy Evolution ☐Multi-Messenger Astronomy and Astrophysics Principal Author: Name: Douglas Gies Institution: Georgia State University Email: [email protected] Phone: 404 413 6021 Co-authors: (names and institutions) Stanley P. Owocki, University of Delaware Stephen Ridgway, National Optical Astronomy Observatory Theo ten Brummelaar, GSU CHARA Array Abstract: Supernovae and stellar winds are the ways that the nuclear processed gas of stars is returned to the interstellar medium to form new generations of metal enhanced stars and planets. Advances in high resolution techniques are giving us the first glimpse of how mass loss processes are acting in stars of all kinds. They will help document stellar wind asymmetries in massive stars, probe the physics of eruptive mass loss in evolved stars, and record the details of disk formation and dynamics of the gas disks of Be stars. Interferometric observations are particularly powerful for the investigation of the molecular outflows and dust creation in the winds of Asymptotic Giant Branch Stars, revealing the details of how pulsational and convective motions can launch mass loss and eventually disperse the envelope and create a planetary nebula. The presence of a binary companion can create wind-wind collisions that sculpt large equatorial flows, and interactions in close binary systems can lead to systemic mass loss and the creation of circumbinary disks.
    [Show full text]
  • Pulsation and Mass Loss Across the HR Diagram: from OB Stars to Cepheids to Red Supergiants
    Precision Asteroseismology: Celebration of the Scientific Opus of Wojtek Dziembowski Proceedings IAU Symposium No. 301, 2013 c 2013 International Astronomical Union W. Chaplin, J. Guzik, G. Hander & A. Pigulski, eds. DOI: 00.0000/X000000000000000X Pulsation and Mass Loss Across the HR Diagram: From OB stars to Cepheids to Red Supergiants Hilding R. Neilson1 1Dept. of Physics & Astronomy, East Tennessee State University, , PO Box 70300, Johnson City, TN 37614, USA email: [email protected] Abstract. Both pulsation and mass loss are commonly observed in stars and are important ingredients for understanding stellar evolution and structure, especially for massive stars. There is a growing body of evidence that pulsation can also drive and enhance mass loss in massive stars and that pulsation-driven mass loss is important for stellar evolution. In this review, I will discuss recent advances in understanding pulsation driven mass loss in massive main sequence stars, classical Cepheids and red supergiants and present some challenges remaining. Keywords. circumstellar matter, stars: evolution, stars: mass loss, Cepheids 1. Introduction Stellar winds are ubiquitous in massive stars, whether they be hot O-type stars or cool red supergiants and are an crucial ingredient for stellar and galactic evolution. However, the underlying physics of stellar winds and mass loss is still not well-understood across the Hertzsprung-Russell diagram (HRD). Mass loss in massive stars plays an important role in determining their evolution and how they end as supernovae. The most obvious example of this evolution a Wolf-Rayet stars that eject their envelopes, exposing their helium cores. Because of that mass loss, these stars appear to evolve at hot effective temperatures, > 30, 000 K, and explode as Type I supernovae.
    [Show full text]