Wolf-Rayet and Luminous Blue Variable Stars: the ISO Impact on Wind Structure and Evolution

Total Page：16

File Type：pdf, Size：1020Kb

Wolf-Rayet and Luminous Blue Variable Stars: the ISO impact on wind structure and evolution Pat Morris1;2;3 1IPAC, Calfornia Institute of Technology, Pasadena, California 2University of Amsterdam, Amsterdam, the Netherlands 3SRON Laboratory for Space Research, Utrecht, the Netherlands Spectra of Wolf-Rayet (WR) and Luminous Blue Variable (LBV) stars obtained with SWS and LWS have proved to be crucial to the study of the winds and circumstellar environments of these most luminous, massive stars. The importance of wind clumping, for example, is to revise the mass-loss rates downwards by factors of more than two. This drastically aﬀects estimates of mechanical momentum into the ISM in driving star formation, and leads to important diﬀerences how evolutionary models are tested using abundances of elements that are the byproducts of nucleosynthesis. Wind clumping in WR stars and the LBV eta Carinae has been probed with SWS spectroscopy. The circumstellar (CS) environment of eta Carinae has also been probed with ISO spectroscopy, leading to a new evolutionary interpretation of its past with respect to its outburst and the hour-glass geometry of the resulting dusty nebula, contrasting sharply with the most contemporary theories of formation. Here we review the impact of bringing the ISO spectra of WR and LBV stars together with latest model wind codes that now incorporate clumping and line-blanketing into the description of the winds, and show how the study of dust in the CS environments is leading to new perspectives on the evolution of these objects. 1.

Copy Link

Recommended publications

Pos(INTEGRAL 2010)091
A candidate former companion star to the Magnetar CXOU J164710.2-455216 in the massive Galactic cluster Westerlund 1 PoS(INTEGRAL 2010)091 P.J. Kavanagh 1 School of Physical Sciences and NCPST, Dublin City University Glasnevin, Dublin 9, Ireland E-mail: [email protected] E.J.A. Meurs School of Cosmic Physics, DIAS, and School of Physical Sciences, DCU Glasnevin, Dublin 9, Ireland E-mail: [email protected] L. Norci School of Physical Sciences and NCPST, Dublin City University Glasnevin, Dublin 9, Ireland E-mail: [email protected] Besides carrying the distinction of being the most massive young star cluster in our Galaxy, Westerlund 1 contains the notable Magnetar CXOU J164710.2-455216. While this is the only collapsed stellar remnant known for this cluster, a further ~10² Supernovae may have occurred on the basis of the cluster Initial Mass Function, possibly all leaving Black Holes. We identify a candidate former companion to the Magnetar in view of its high proper motion directed away from the Magnetar region, viz. the Luminous Blue Variable W243. We discuss the properties of W243 and how they pertain to the former Magnetar companion hypothesis. Binary evolution arguments are employed to derive a progenitor mass for the Magnetar of 24-25 M Sun , just within the progenitor mass range for Neutron Star birth. We also draw attention to another candidate to be member of a former massive binary. 8th INTEGRAL Workshop “The Restless Gamma-ray Universe” Dublin, Ireland September 27-30, 2010 1 Speaker Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.
[Show full text]
Luminous Blue Variables
Review Luminous Blue Variables Kerstin Weis 1* and Dominik J. Bomans 1,2,3 1 Astronomical Institute, Faculty for Physics and Astronomy, Ruhr University Bochum, 44801 Bochum, Germany 2 Department Plasmas with Complex Interactions, Ruhr University Bochum, 44801 Bochum, Germany 3 Ruhr Astroparticle and Plasma Physics (RAPP) Center, 44801 Bochum, Germany Received: 29 October 2019; Accepted: 18 February 2020; Published: 29 February 2020 Abstract: Luminous Blue Variables are massive evolved stars, here we introduce this outstanding class of objects. Described are the specific characteristics, the evolutionary state and what they are connected to other phases and types of massive stars. Our current knowledge of LBVs is limited by the fact that in comparison to other stellar classes and phases only a few “true” LBVs are known. This results from the lack of a unique, fast and always reliable identification scheme for LBVs. It literally takes time to get a true classification of a LBV. In addition the short duration of the LBV phase makes it even harder to catch and identify a star as LBV. We summarize here what is known so far, give an overview of the LBV population and the list of LBV host galaxies. LBV are clearly an important and still not fully understood phase in the live of (very) massive stars, especially due to the large and time variable mass loss during the LBV phase. We like to emphasize again the problem how to clearly identify LBV and that there are more than just one type of LBVs: The giant eruption LBVs or h Car analogs and the S Dor cycle LBVs.
[Show full text]
POSTERS SESSION I: Atmospheres of Massive Stars
Abstracts of Posters 25 POSTERS (Grouped by sessions in alphabetical order by first author) SESSION I: Atmospheres of Massive Stars I-1. Pulsational Seeding of Structure in a Line-Driven Stellar Wind Nurdan Anilmis & Stan Owocki, University of Delaware Massive stars often exhibit signatures of radial or non-radial pulsation, and in principal these can play a key role in seeding structure in their radiatively driven stellar wind. We have been carrying out time-dependent hydrodynamical simulations of such winds with time-variable surface brightness and lower boundary condi- tions that are intended to mimic the forms expected from stellar pulsation. We present sample results for a strong radial pulsation, using also an SEI (Sobolev with Exact Integration) line-transfer code to derive characteristic line-profile signatures of the resulting wind structure. Future work will compare these with observed signatures in a variety of specific stars known to be radial and non-radial pulsators. I-2. Wind and Photospheric Variability in Late-B Supergiants Matt Austin, University College London (UCL); Nevyana Markova, National Astronomical Observatory, Bulgaria; Raman Prinja, UCL There is currently a growing realisation that the time-variable properties of massive stars can have a funda- mental influence in the determination of key parameters. Specifically, the fact that the winds may be highly clumped and structured can lead to significant downward revision in the mass-loss rates of OB stars. While wind clumping is generally well studied in O-type stars, it is by contrast poorly understood in B stars. In this study we present the analysis of optical data of the B8 Iae star HD 199478.
[Show full text]
Fundamental Parameters of 4 Massive Eclipsing Binaries in Westerlund 1
Active OB stars: structure, evolution, mass loss and critical limits Proceedings IAU Symposium No. 272, 2010 c 2010 International Astronomical Union C. Neiner, G. Wade, G. Meynet & G. Peters DOI: 00.0000/X000000000000000X Fundamental Parameters of 4 Massive Eclipsing Binaries in Westerlund 1 E. Koumpia and A.Z. Bonanos † National Observatory of Athens, Institute of Astronomy & Astrophysics, I. Metaxa & Vas. Pavlou St., Palaia Penteli GR-15236 Athens, Greece [email protected], [email protected] Abstract. Westerlund 1 is one of the most massive young clusters known in the Local Group, with an age of 3-5 Myr. It contains an assortment of rare evolved massive stars, such as blue, yellow and red supergiants, Wolf-Rayet stars, a luminous blue variable, and a magnetar, as well as 4 massive eclipsing binary systems (Wddeb, Wd13, Wd36, WR77o, see Bonanos 2007). The eclipsing binaries present a rare opportunity to constrain evolutionary models of massive stars, the distance to the cluster and furthermore, to determine a dynamical lower limit for the mass of a magnetar progenitor. Wddeb, being a detached system, is of great interest as it allows determination of the masses of 2 of the most massive unevolved stars in the cluster. We have analyzed spectra of all 4 eclipsing binaries, taken in 2007-2008 with the 6.5 meter Magellan telescope at Las Campanas Observatory, Chile, and present fundamental parameters (masses, radii) for their component stars. Keywords. open clusters and associations: individual (Westerlund 1), stars: fundamental pa- rameters, stars: early-type, binaries: eclipsing, stars: Wolf-Rayet 1. Introduction Westerlund 1 (Wd1) is one of the most massive compact young star clusters known in the Local Group.
[Show full text]
Confirmation of the Luminous Blue Variable Nature of AFGL 2298
A&A 403, 653–658 (2003) Astronomy DOI: 10.1051/0004-6361:20030389 & c ESO 2003 Astrophysics Confirmation of the Luminous Blue Variable nature of AFGL 2298 J. S. Clark1,V.M.Larionov2,3,P.A.Crowther1,M.P.Egan4, and A. Arkharov5 1 Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, England, UK 2 Astronomical Institute of St. Petersburg University, Petrodvorets, Universitetsky pr. 28, 198504 St. Petersburg, Russia 3 Isaac Newton Institute of Chile, St. Petersburg Branch 4 US Air Force Research Laboratory, Space Vehicles Directorate, 29 Randolph Road, Hanscom AFB, MA 01731-3010, USA 5 Central Astronomical Observatory, 196140 St. Petersburg, Russia Received 22 January 2003 / Accepted 13 March 2003 Abstract. We present new photometric and spectroscopic observations of the stellar source AFGL 2298 (= IRAS 18576+0341) that has recently been proposed as a candidate Luminous Blue Variable (LBV). Our data confirm that the star is a highly lumi- nous B supergiant which is both spectroscopically and photometrically variable. Assuming a distance of 10 kpc, comparison of 5 1 the 2001 June data to synthetic spectra suggest stellar parameters of T = 12.5 kK, log(L/L ) = 6.2andM˙ = 5 10− M yr− . × 4 1 Data obtained in 2002 August indicate an increase in both temperature (=15 kK) and mass loss rate (=1.2 10− M yr− )at constant bolometric luminosity. These physical parameters place AFGL 2298 at the Humphreys-Davidson× limit for the most luminous stars known. We conclude that the position of AFG 2298 in the HR diagram, the significant variability observed between 1999-2002 and presence of a massive ejection nebula are consistent with a classification of AFGL 2298 as a bona fide LBV.
[Show full text]
Stellar Evolution
AccessScience from McGraw-Hill Education Page 1 of 19 www.accessscience.com Stellar evolution Contributed by: James B. Kaler Publication year: 2014 The large-scale, systematic, and irreversible changes over time of the structure and composition of a star. Types of stars Dozens of different types of stars populate the Milky Way Galaxy. The most common are main-sequence dwarfs like the Sun that fuse hydrogen into helium within their cores (the core of the Sun occupies about half its mass). Dwarfs run the full gamut of stellar masses, from perhaps as much as 200 solar masses (200 M,⊙) down to the minimum of 0.075 solar mass (beneath which the full proton-proton chain does not operate). They occupy the spectral sequence from class O (maximum effective temperature nearly 50,000 K or 90,000◦F, maximum luminosity 5 × 10,6 solar), through classes B, A, F, G, K, and M, to the new class L (2400 K or 3860◦F and under, typical luminosity below 10,−4 solar). Within the main sequence, they break into two broad groups, those under 1.3 solar masses (class F5), whose luminosities derive from the proton-proton chain, and higher-mass stars that are supported principally by the carbon cycle. Below the end of the main sequence (masses less than 0.075 M,⊙) lie the brown dwarfs that occupy half of class L and all of class T (the latter under 1400 K or 2060◦F). These shine both from gravitational energy and from fusion of their natural deuterium. Their low-mass limit is unknown.
[Show full text]
Astronomy C Michigan Region 8 March 24, 2018
Astronomy C Michigan Region 8 March 24, 2018 Team Number ____________________ Team Name _____________________________________________________________________________________________ Type (select one) ____________________ Varsity ____________________ Junior Varsity Student Name(s) _____________________________________________________________________________________________ Directions 1. There is a separate answer sheet. Answers written elsewhere (e.g. on the test) will not be considered. 2. You may take the test apart, but please put it back together at the end. 3. This test is 100 points total. Questions are worth 1 point each unless otherwise specified. 4. The first tiebreaker is the section score for Part II. Further tiebreakers are indicated as [T1], [T2], etc. Time is NOT a tiebreaker. 5. For any answers that have units, be sure to use the units that are specified in the question. Answers in other units will be marked wrong. Bonus (+1) LIGO has already detected gravitational waves from multiple black hole mergers, but in August 2017, it found something new – an event that was also detected in gamma rays, and later in multi-wavelength observations. What did LIGO find? Useful Constants 푏 = 0.0029 푚 ∗ 퐾 8 푐 = 3.00 ∗ 10 푚⁄푠 2 −11 푁 푚 퐺 = 6.67 ∗ 10 푘푔2 푘푚⁄푠 퐻 = 72 0 푀푝푐 −34 ℎ = 6.63 ∗ 10 퐽 ∗ 푠 −23 푘 = 1.38 ∗ 10 퐽⁄퐾 −8 푊 휎 = 5.67 ∗ 10 푚2 퐾4 26 퐿푠푢푛 = 3.84 ∗ 10 푊 30 푀푠푢푛 = 1.99 ∗ 10 푘푔 8 푅푠푢푛 = 6.96 ∗ 10 푚 푇푠푢푛 = 5800 퐾 1 푝푐 = 3.26 푙푦 = 206265 퐴푈 = 3.08 ∗ 1016 푚 1 푙푦 = 0.307 푝푐 = 63240 퐴푈 = 9.46 ∗ 1015 푚 퐴푏푠.
[Show full text]
Luminous Blue Variable Stars
Luminous Blue Variable Stars 10 Novembre 2006 Caroline Straatman Luminous Blue Variable Stars = LBV Stars LBV Stars are defined by moderate, irregular variations in brightness with associated spectroscopic changes (…) S-Doradus variables, P Cygni stars, Hubble Sandage variables • characteristics • examples and discoveries Characteristics - progenitors • Short lived – 40000 years • Evolutionary phase between H-burning and Wolf Rayet Stars • 40 Msol •Red LBVs • Rare: 32 in local group http://home.tele2.fr/saultrem/natandmick/soleil/diagramme_hertzsprung-russel.jpg Characteristics - variability • Variability – Microvariations: – ≤ 0,1 magnitudes – Days, weeks – Small oscillations: – ~ 0,5 magnitudes – Last for months – few years Characteristics - variability – Moderate eruptions: –Unique to LBV Stars –1-2 magnitudes –Timescale: 10 – 40 years –Atmosphere greatly expands to form optically thick pseudophotosphere –Evolve redwards to H-Dlimit stimulating mass loss The Humphreys-Davidson limit • Upper luminosity limit • Decreases with decreasing effective temperature • Boundary: T ~ 104 K • Mass loss must be high • Not steady but eruptions Characteristics - variability – Giant eruptions: –≥ 3 magnitudes –May last for decades –Frequency: 100 - 1000 years –Sudden ejections of mass Characteristics – circumstellar objecta • Circumstellar nebula • Produced by mass loss • N and He rich http://www.astro.umd.edu/~white/images/agcar_full.html AG Carinae http://www.peripatus.gen.nz/Astronomy/LumBluVar.html Characteristics - mass • High mass-loss rates • Shell ejection phase/pseudophotosphere phase -5 -4 -1 •10 –10 Msolyr • 10 – 100 times mass-loss rate normal supergiant • At quiescence (visual minimum) star resembles normal supergiant •Total massloss 1 Msol or more Characteristics - spectra • The spectra are variable • H, HeI, FeII prominent emission lines • At visual minimum: spectrum resembles that of supergiant H- burning and He- burning stars.
[Show full text]
Luminous Blue Variables & Mass Loss Near the Eddington Limit
Massive Stars as Cosmic Engines Proceedings IAU Symposium No. 250, 2008 c 2008 International Astronomical Union Fabio Bresolin, Paul Crowther & Joachim Puls, eds. DOI: 00.0000/X000000000000000X Luminous Blue Variables & Mass Loss near the Eddington Limit Stan Owocki and Allard Jan van Marle Bartol Research Institute, Department of Physics & Astronomy University of Delaware, Newark, DE 19350 USA email: [email protected], [email protected] Abstract. During the course of their evolution, massive stars lose a substantial fraction of their initial mass, both through steady winds and through relatively brief eruptions during their Luminous Blue Variable (LBV) phase. This talk reviews the dynamical driving of this mass loss, contrasting the line-driving of steady winds to the potential role of continuum driving for eruptions during LBV episodes when the star exceeds the Eddington limit. A key theme is to emphasize the inherent limits that self-shadowing places on line-driven mass loss rates, whereas continuum driving can in principle drive mass up to the “photon-tiring” limit, for which the energy to lift the wind becomes equal to the stellar luminosity. We review how the “porosity” of a highly clumped atmosphere can regulate continuum-driven mass loss, but also discuss recent time-dependent simulations of how base mass flux that exceeds the tiring limit can lead to flow stagnation and a complex, time-dependent combination of inflow and outflow regions. A general result is thus that porosity-mediated continuum driving in super-Eddington phases can explain the large, near tiring-limit mass loss inferred for LBV giant eruptions. Keywords. stars: early-type, stars: winds, outflows, stars: mass loss, stars: activity 1.
[Show full text]
Binary Progenitor Models of Type Iib Supernovae⋆
A&A 528, A131 (2011) Astronomy DOI: 10.1051/0004-6361/201015410 & c ESO 2011 Astrophysics Binary progenitor models of type IIb supernovae J. S. W. Claeys1,2,S.E.deMink1,3,4,,O.R.Pols1,J.J.Eldridge5, and M. Baes2 1 Sterrekundig Insituut, Universiteit Utrecht, PO Box 800000, 3508 TA Utrecht, The Netherlands e-mail: [email protected]; [email protected]; [email protected] 2 Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281-S9, 9000 Gent, Belgium 3 Argelander Institute for Astronomy, University of Bonn, Auf dem Huegel 71, 53121 Bonn, Germany 4 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA 5 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK Received 16 July 2010 / Accepted 30 January 2011 ABSTRACT Massive stars that lose their hydrogen-rich envelope down to a few tenths of a solar mass explode as extended type IIb supernovae, an intriguing subtype that links the hydrogen-rich type II supernovae with the hydrogen-poor type Ib and Ic. The progenitors may be very massive single stars that lose their envelope due to their stellar wind, but mass stripping due to interaction with a companion star in a binary system is currently considered to be the dominant formation channel. Anticipating the upcoming automated transient surveys, we computed an extensive grid of binary models with the Eggleton binary evolution code. We identify the limited range of initial orbital periods and mass ratios required to produce type IIb binary progenitors. The rate we predict from our standard models, which assume conservative mass transfer, is about six times smaller than the current rate indicated by observations.
[Show full text]
Black Hole Formation in Massive Stars, Failed Supernovae, & Neutrinos
11. 2. 2018, KNU, KNO workshop Black hole formation in massive stars, failed supernovae, & Neutrinos Sung-Chul Yoon (SNU) . Core Collapse Supernova (ccSN) : Standard Scenario A SN occurs if the explosion energy is higher than the binding energy of the stellar envelope. The binding energy of the stellar envelope: The energy budget for SN explosion: the difference of the binding energies of the core before and after the collapse. Only 1% of this energy is enough to unbound the star. Core Collapse Supernova (ccSN) : Standard Scenario Neutrino emission Neutrino- matter interaction https://www.researchgate.net/figure/The-core- collapse-of-a-Type-II-Supernova_fig1_306091657 Core Collapse Supernova (ccSN) : Standard Scenario • The binding energy of the core is released in the form of neutrinos during the collapse. • Enormous neutrino flux (~ 1053 erg) is thus produced. Some of them interacts with infalling matter. • If this neutrino-matter interaction is efficient enough (~1% efficiency), a supernova explosion can occur. • Otherwise, a SN explosion would fail BH formation • Regardless of failure or success of the explosion, the neutrino energy released from the star would be about 1053 erg. Neutrino Signals from BH formation BH formation SN explosion Horiuchi et al. 2018, MNRAS 475, 1363 Massive Star Evolution Which stars are BH progenitors in our Galaxy? Wolf-Rayet Starsf (No significant hydrogen LBV: luminous blue variable stars envelope) Red- Supergaint Stars Main sequence: hatched region Blue-Supergiant Stars Figure credit: S. Woosley Sukhbold et al. 2016 Binding Energy in BH progenitors Red: Red-Suprgiant Star (Minit = 23 Msun) Blue: Wolf-Rayet Star (M = 10 Msun) WR stars WNL : Some H, strong N WNE: No H, strong N emission WC : strong C emission WO : strong O emission A Wolf-Rayet Star (WR star).
[Show full text]
Download This Article in PDF Format
A&A 413, L15–L18 (2004) Astronomy DOI: 10.1051/0004-6361:20031700 & c ESO 2003 Astrophysics A newly identified Luminous Blue Variable in the galactic starburst cluster Westerlund 1 J. S. Clark1 and I. Negueruela2 1 Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, England, UK Letter to the Editor 2 Dpto. de F´ısica, Ingenier´ıa de Sistemas y Teor´ıa de la Señal, Universidad de Alicante, Apdo. 99, E03080 Alicante, Spain Received 11 November 2003 / Accepted 27 November 2003 Abstract. We present observations of the massive transitional star W243 in Westerlund 1. We find an apparent spectral type of early-mid A from our data, in contrast to an earlier classification of B2I, made from data obtained in 1981. The concurrent development of a rich emission line spectrum suggests a very high mass loss rate; the continued presence of He emission suggesting that the underlying star remains significantly hotter than implied by its apparent spectral type. We suggest that W243 is a Luminous Blue Variable undergoing an eruptive phase, leading to an extreme mass loss rate and the formation of a pseudo photosphere. Key words. stars: evolution – stars: variables: general – winds, outflows – supergiants 1. Introduction which encompassed ∼20 of the brightest cluster members. Motivated by an unusually rich population of radio sources Before becoming hydrogen depleted Wolf Rayets (WR), mas- within Wd 1 (Clark et al. 1998; Dougherty et al., in prep.) sive stars pass through a period of enhanced mass loss, the cluster was subsequently spectroscopically re-observed which removes the bulk of the H-rich mantle over their in 2001, with follow up observations made in 2002–3.
[Show full text]