DOCSLIB.ORG

Infrared Interferometry of the Upper Hertzsprung-Russell Diagram

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Infrared Interferometry of the Upper Hertzsprung-Russell Diagram HOT AND COOL: BRIDGINGGAPS IN MASSIVE-STAR EVOLUTION ASP Conference Series, Vol. 425, c 2010 C. Leitherer, P. D. Bennett, P. W. Morris, and J. Th. van Loon, eds. Infrared Interferometry of the Upper Hertzsprung-Russell Diagram John D. Monnier University of Michigan, Astronomy Department, Ann Arbor, MI 48109, USA Abstract. The new generation of optical and infrared interferometers have unprecedented angular resolution and sensitivity. I will review recent advances in studies of massive objects in the upper portion of the Hertzsprung-Russell dia- gram, including fundamental parameters of individual red and blue supergiants, first interferometric imaging of interacting binaries, and new views of dust and gas in strong stellar winds. We note that massive stellar evolution is still usually discussed in the context of single star evolution, despite mounting evidence that binarity is commonplace and likely lies at the root of many observed phenomena. 1. Introduction Massive stars present many challenges to our understanding of stellar evolution. These challenges lie in three major areas: fundamental stellar parameters, mass transfer in interacting binaries, and mass-loss mechanisms. All three areas are still poorly understood, thus the theory of massive stellar evolution rests on a shaky foundation. One way to make progress is to study individual objects using our best techniques in order to elucidate the physical mechanisms at play. For this, infrared and optical interferometry is potentially powerful to measure and image stars and their surroundings with amazing angular resolution. Consider the following examples: • A nearby hot star (10 R⊙) at 200 pc is only 0.2 milliarcseconds across. • A nearby cool (massive) star (diameter 5 AU) at 200 pc is 25 milliarcsec- onds across. • The 50 AU dust shell around a close-by Wolf-Rayet star at 1500 pc is 33 milliarcseconds. • The inner wind at 10 AU around Eta Carina (2300 pc) is about 4 milliarc- seconds. You can see from this list that even the closest (and thereby prototypical) mas- sive stars present serious imaging challenges for single telescopes. The required angular resolution demands a 50+m-diameter telescope operating at the diffrac- tion limit—a prospect beyond even our most ambitious projects today. Fortu- nately, this level of angular resolution is routine for existing infrared interfer- ometers and I will be reporting a wide range of important work from today’s facilities in this review. 257 258 Monnier I will end each section of this review with a provocative question or two suggested by recent interferometry work. 2. Interferometry This review will not discuss the technical details of optical and infrared inter- ferometry. Please see review in Monnier (2003) for more information on this topic. Here, I did want to list and briefly describe the facilities that will be men- tioned in this review. In order of appearance: 1. COAST (Cambridge Optical Aperture Synthesis Telescope). This facil- ity was based in Cambridge, England, and was a pioneer in developing long-baseline interferometric techniques, most noted for the first aperture synthesis image (Baldwin et al. 1996). The array used four telescopes with baselines typically less than 50 m, and observed binaries and evolved stars. This facility is now closed, and the principals are working on the next generation facility: the Magdalena Ridge Optical Interferometer (MROI, Creech-Eakman et al. 2008). 2. IOTA (Infrared-Optical Telescope Array) was located at Mt. Hopkins, AZ, and was operated by the Smithsonian Astrophysical Observatory with ma- jor contributions from University of Massachusetts at Amherst (Traub et al. 2003). This system observed mainly in the near-infrared (H and K bands) and had a longest baseline of 38 m. First imaging with the three-telescope system was reported in 2004 (Monnier et al.). This facil- ity is now closed. 3. CHARA (Center for High Angular Resolution Astronomy) array is a six- telescope interferometer located on Mt. Wilson, CA. The array was built and is operated by Georgia State University (McAlister et al. 2005; ten Brummelaar et al. 2005). CHARA boasts the largest baselines in the world, maximum of 330 m baselines, and has instrumentation that work from visible wavelengths to K band. 4. ISI (Infrared Spatial Interferometer) is a mid-infrared, heterodyne inter- ferometer also located on Mt. Wilson, CA (Hale et al. 2000). ISI has three telescopes with commissioned baselines up to about 85 m. 5. NPOI (Navy Prototype Optical Interferometer) is located in Flagstaff, AZ, and is operated by the Naval Research Lab and the Naval Observatory (Armstrong et al. 1998) NPOI specializes in visible-wavelength observa- tions and has used six telescopes simultaneously for imaging. 6. SUSI (Sydney University Stellar Interferometer) is the only visible-light interferometer in the southern hemisphere (Davis et al. 1999). SUSI uses two telescopes at a time, with baselines up to ∼100 meters. IR Interferometry of the Upper HRD 259 7. VLTI is the Very Large Telescope interferometer (Haguenauer et al. 2008), located on Paranal, Chile, and is famously part of the European South- ern Observatory. The VLTI can be used with any of the four 8-m unit telescopes or any of three 1.8 m auxiliary telescopes. VLT currently has a near-infrared three-beam combiner with spectral capabilities (AMBER) and a mid-infrared two-beam combiner (MIDI). The longest baseline is usually around ∼120 m, although longer baselines are possible with the ATs. 8. PTI was the Palomar Testbed Interferometer (Colavita et al. 1999), located at Palomar Observatory, CA. PTI worked primarily at K band, observing a single baseline with any two of three telescopes in the array. The longest baseline was around 110 m. This facility closed in early 2009. 3. Red Supergiants Pioneering observations with single telescopes using speckle, rotation-shearing, and aperture masking (e.g., Lynds et al. 1976; Roddier & Roddier 1983; Buscher et al. 1990) have found that the surfaces of red supergiants are mottled with hotspots which vary on timescale of many months (Tuthill et al. 1997). These changing hotspots are now ascribed to the motions large convective elements on the surface (Schwarzschild 1975; Freytag et al. 2002). Using near-simultaneous, multi-wavelength data, the COAST interferome- ter found that the hotspots on Betelguese were markedly more pronounced at wavelengths probing the cooler molecular layers (Young et al. 2000). This led to the idea that the spots were generated by opacity structures (“holes”) in upper molecular layers. While opacity variations in the upper layers may be crucial in the optical regime, more recent work has found unmistakable spot structures in the H band likely resulting from true temperature differences on the continuum photosphere (with IOTA: Haubois et al. 2006, with CHARA: Kiss et al., these proceedings). Another major advance has been the discovery of an optically-thick water layer around cool stars (miras and red supergiants). Observers using IOTA (Per- rin et al. 1999, 2004), Keck Masking (Tuthill et al. 1999b; Woodruff et al. 2009), and ISI (Weiner et al. 2000) have reported very large diameter variations in and out of the near-infrared molecular bands and also at 11.15 µm. Essentially, at wavelengths where the water vapor absorbs infrared light, the measured angu- lar diameter is much larger than in the stellar continuum. Modeling this effect reveals a thick layer of warm molecular gas at about 1.5 R⋆. This idea was first suggested by Tsuji (2000) based on ISO data and water line lists have been used to self-consistently explain the wavelength-dependent diameter data and some line profiles (Ohnaka 2004; Weiner et al. 2003). These major results have yet to be incorporated in modern atmsopheric models. Another interesting result was that the diameter of the extreme red super- giant VY CMa was measured using a combination of IOTA + Keck data, which allowed for the correction of the dust emission. VY CMa has a K-band diam- eter of 21 AU, making it the largest known star (Monnier et al. 2004b). This large size could be affected by the aforementioned water layer, and more work is needed to understand if the continuum size is smaller. 260 Monnier Open Questions: • Is spot intensity on red supergiant photospheres related to a star’s propensity for peculiar mass ejections seen as detached dust shells (e.g., α Ori, α Sco; Danchi et al. 1994)? • Does an interferometric temperature scale for red supergiants (corrected for molecular blanketing) match up with the recent hotter scale of Levesque et al. (2005)? 4. Blue Supergiants Not surprisingly, blue supergiants are much smaller in physical size than red su- pergiants; they are nearly impossible to resolve with even today’s most powerful interferometers. While there are few results to report, we note that the NPOI optical interferometer will soon debut longer baselines, and the CHARA inter- ferometer recently commissioned two new visible instruments (VEGA, Mourard et al. 2008, and PAVO, Ireland et al. 2008). At visible wavelengths, CHARA will have approximately 0.2 mas angular resolution sufficient to resolve a handful of blue supergiants. Here we report mainly one interesting result. The nearby blue supergiant Deneb was resolved by the CHARA interferometer by Aufdenberg et al. (2006). They found the object was slightly elongated, implying a rotation rate of 65% of breakup. This model suggests the pole is 10% hotter than the equator, imply- ing that the apparent luminosity and temperature is viewing-angle dependent. These issues lead to an open question: Open Question: • How important is rapid rotation to consider for Blue Supergiants (e.g., latitude-dependence of winds, true location on H-R dia- gram)? 5. Transitioning Supergiants from Red to Blue While finding nearby examples of red or blue supergiants is difficult enough, we have to search even farther away to find the rare specimen of a transitioning object.
Load more

Recommended publications
  • Annual Report 2016–2017 AAVSO
    AAVSO The American Association of Variable Star Observers Annual Report 2016–2017 AAVSO Annual Report 2012 –2013 The American Association of Variable Star Observers AAVSO Annual Report 2016–2017 The American Association of Variable Star Observers 49 Bay State Road Cambridge, MA 02138-1203 USA Telephone: 617-354-0484 Fax: 617-354-0665 email: [email protected] website: https://www.aavso.org Annual Report Website: https://www.aavso.org/annual-report On the cover... At the 2017 AAVSO Annual Meeting.(clockwise from upper left) Knicole Colon, Koji Mukai, Dennis Conti, Kristine Larsen, Joey Rodriguez; Rachid El Hamri, Andy Block, Jane Glanzer, Erin Aadland, Jamin Welch, Stella Kafka; and (clockwise from upper left) Joey Rodriguez, Knicole Colon, Koji Mukai, Frans-Josef “Josch” Hambsch, Chandler Barnes. Picture credits In additon to images from the AAVSO and its archives, the editors gratefully acknowledge the following for their image contributions: Glenn Chaple, Shawn Dvorak, Mary Glennon, Bill Goff, Barbara Harris, Mario Motta, NASA, Gary Poyner, Msgr. Ronald Royer, the Mary Lea Shane Archives of the Lick Observatory, Chris Stephan, and Wheatley, et al. 2003, MNRAS, 345, 49. Table of Contents 1. About the AAVSO Vision and Mission Statement 1 About the AAVSO 1 What We Do 2 What Are Variable Stars? 3 Why Observe Variable Stars? 3 The AAVSO International Database 4 Observing Variable Stars 6 Services to Astronomy 7 Education and Outreach 9 2. The Year in Review Introduction 11 The 106th AAVSO Spring Membership Meeting, Ontario, California 11 The
    [Show full text]
  • Ejections De Mati`Ere Par Les Astres : Des Étoiles Massives Aux Quasars
    Universite´ de Liege` Faculte´ des Sciences Ejections de matiere` par les astres : des etoiles´ massives aux quasars par Damien HUTSEMEKERS Docteur en Sciences Chercheur Qualifie´ du FNRS Dissertation present´ ee´ en vue de l’obtention du grade d’Agreg´ e´ de l’Enseignement Superieur´ 2003 Illustration de couverture : la n´ebuleuse du Crabe, constitu´ee de gaz ´eject´e`agrande vitesse par l’explosion d’une ´etoile en supernova. Clich´eobtenu avec le VLT et FORS2, ESO, 1999. Table des matieres` Preface´ et remerciements 5 Introduction 7 Articles 21 I Les nebuleuses´ eject´ ees´ par les etoiles´ massives 23 1 HR Carinae : a Luminous Blue Variable surrounded by an arc-shaped nebula 25 2 The nature of the nebula associated with the Luminous Blue Variable star WRA751 37 3 A dusty nebula around the Luminous Blue Variable candidate HD168625 45 4 Evidence for violent ejection of nebulae from massive stars 57 5 Dust in LBV-type nebulae 63 II Quasars de type BAL et microlentilles gravitationnelles 73 6 The use of gravitational microlensing to scan the structureofBALQSOs 75 7 ESO & NOT photometric monitoring of the Cloverleaf quasar 89 8 Selective gravitational microlensing and line profile variations in the BAL quasar H1413+117 99 9 An optical time-delay for the lensed BAL quasar HE2149-2745 113 3 III Quasars de type BAL : polarisation 127 10 A procedure for deriving accurate linear polarimetric measurements 129 11 Optical polarization of 47 quasi-stellar objects : the data 137 12 Polarization properties of a sample of Broad Absorption Line and gravitatio-
    [Show full text]
  • Exploring the Multifaceted Circumstellar Environment of the Luminous Blue Variable HR Carinae
    MNRAS 465, 4147–4158 (2017) doi:10.1093/mnras/stw3074 Exploring the multifaceted circumstellar environment of the luminous blue variable HR Carinae C. S. Buemi,1‹ C. Trigilio,1‹ P. Leto,1 G. Umana,1 A. Ingallinera,1 F. Cavallaro,1,2,3 L. Cerrigone,4 C. Agliozzo,5,6 F. Bufano,1 S. Riggi,1 S. Molinari7 and F. Schilliro`1 1INAF – Osservatorio Astrofisico di Catania, Via S. Sofia 78, I-95123 Catania, Italy 2CSIRO Astronomy and Space Science, PO Box 76, Epping, NSW 1710, Australia 3Universita` di Catania, Dipartimento di Fisica e Astronomia, Via Santa Sofia, 64, I-95123 Catania, Italy 4ASTRON, the Netherlands Institute for Radioastronomy, PO Box 2, NL-7990 AA Dwingeloo, the Netherlands 5Millennium Institute of Astrophysics, Santiago 7500011, Chile 6Universidad Andres´ Bello, Avda. Republica 252, Santiago 8320000, Chile 7INAF – Istituto di Astrofisica e Planetologia Spaziale, via Fosso del Cavaliere 100, I-00133 Roma, Italy Accepted 2016 November 23. Received 2016 November 23; in original form 2016 September 29 ABSTRACT We present a multiwavelength study of the Galactic luminous blue variable HR Carinae, based on new high-resolution mid-infrared (IR) and radio images obtained with the Very Large Telescope (VLT) and the Australia Telescope Compact Array (ATCA), which have been complemented by far-infrared Herschel–Photodetector Array Camera and Spectrometer (PACS) observations and ATCA archive data. The Herschel images reveal the large-scale distribution of the dusty emitting nebula, which extends mainly to the north-east direction, up to 70 arcsec from the central star, and is oriented along the direction of the space motion of the star.
    [Show full text]
  • Spectroscopic Signatures of the Vanishing Natural Coronagraph of Eta Carinae
    MNRAS 505, 963–978 (2021) doi: https://doi.org/10.1093/mnras/stab1398 Advance Access publication 2021 May 17 Spectroscopic signatures of the vanishing natural coronagraph of Eta Carinae A. Damineli ,1‹ F. Navarete ,1‹ D. J. Hillier ,2 A. F. J. Moffat ,3 M. F. Corcoran ,4,5 T. R. Gull ,6 N. D. Richardson ,7 G. Weigelt ,8 P. W. Morris 9 and I. Stevens 10 Downloaded from https://academic.oup.com/mnras/article/505/1/963/6276744 by California Institute of Technology user on 21 July 2021 1Universidade de Sao˜ Paulo, Instituto de Astronomia, Geof´ısica e Cienciasˆ Atmosfericas,´ Rua do Matao˜ 1226, Cidade Universitaria´ Sao˜ Paulo-SP, 05508-090, Brasil 2Department of Physics and Astronomy & Pittsburgh Particle Physics, Astrophysics, and Cosmology Center (PITT PACC), University of Pittsburgh, 3941 O’Hara Street, Pittsburgh, PA 15260, USA 3Departement´ de Physique and Centre de Recherche en Astrophysique du Quebec´ (CRAQ) Universite´ de Montreal,´ C.P. 6128, Succ. Centre-Ville, Montreal,´ Quebec´ H3C 3J7, Canada 4CRESST II & X-ray Astrophysics Laboratory, Code 662, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA 5Department of Physics The Catholic University of America, Institute for Astrophysics and Computational Sciences, Washington, DC 20064, USA 6Laboratory for Extraterrestrial Planets and Stellar Astrophysics, Code 667, NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA 7Department of Physics and Astronomy, Embry-Riddle Aeronautical University, 3700 Willow Creek Road, Prescott, AZ 86301, USA 8Max Planck Institute for Radio Astronomy, Auf dem Hugel¨ 69, Bonn D-53121, Germany 9California Institute of Technology, IPAC M/C 100-22, Pasadena, CA 91125, USA 10School of Physics & Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK Accepted 2021 May 10.
    [Show full text]
  • Massive Star Evolution: Luminous Blue Variables As Unexpected Supernova Progenitors
    A&A 550, L7 (2013) Astronomy DOI: 10.1051/0004-6361/201220741 & c ESO 2013 Astrophysics Letter to the Editor Massive star evolution: luminous blue variables as unexpected supernova progenitors J. H. Groh, G. Meynet, and S. Ekström Geneva Observatory, Geneva University, Chemin des Maillettes 51, 1290 Sauverny, Switzerland e-mail: [email protected] Received 15 November 2012 / Accepted 17 December 2012 ABSTRACT Stars more massive than about 8 M end their lives as a supernova (SN), an event of fundamental importance Universe-wide. Theoretically, these stars have been expected to be either at the red supergiant, blue supergiant, or Wolf-Rayet stage before the explosion. We performed coupled stellar evolution and atmospheric modeling of stars with initial masses between 20 M and 120 M. We found that the 20 M and 25 M rotating models, before exploding as SN, have spectra that do not resemble any of the afore- mentioned classes of massive stars. Rather, they have remarkable similarities with rare, unstable massive stars known as luminous blue variables (LBV). While observations show that some SNe seem to have had LBVs as progenitors, no theoretical model had yet predicted that a star could explode at this stage. Our models provide theoretical support for relatively low-luminosity LBVs exploding as SN in the framework of single stellar evolution. This is a significant shift in paradigm, meaning that a fraction of LBVs could be the end stage of massive star evolution, rather than a transitory evolutionary phase. We suggest that type IIb SN could have LBV as progenitors, and a prime example could be SN 2008ax.
    [Show full text]
  • The Yellow Hypergiant HR 5171 A: Resolving a Massive Interacting Binary in the Common Envelope Phase,
    A&A 563, A71 (2014) Astronomy DOI: 10.1051/0004-6361/201322421 & c ESO 2014 Astrophysics The yellow hypergiant HR 5171 A: Resolving a massive interacting binary in the common envelope phase, O. Chesneau1, A. Meilland1, E. Chapellier1, F. Millour1,A.M.vanGenderen2, Y. Nazé3,N.Smith4,A.Spang1, J. V. Smoker5, L. Dessart6, S. Kanaan7, Ph. Bendjoya1, M. W. Feast8,15,J.H.Groh9, A. Lobel10,N.Nardetto1,S. Otero11,R.D.Oudmaijer12,A.G.Tekola8,13,P.A.Whitelock8,15,C.Arcos7,M.Curé7, and L. Vanzi14 1 Laboratoire Lagrange, UMR7293, Univ. Nice Sophia-Antipolis, CNRS, Observatoire de la Côte d’Azur, 06300 Nice, France e-mail: [email protected] 2 Leiden Observatory, Leiden University Postbus 9513, 2300RA Leiden, The Netherlands 3 FNRS, Département AGO, Université de Liège, Allée du 6 Août 17, Bat. B5C, 4000 Liège, Belgium 4 Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson AZ 85721, USA 5 European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Vitacura, Santiago 19, Chile 6 Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France 7 Departamento de Física y Astronomá, Universidad de Valparaíso, Chile 8 South African Astronomical Observatory, PO Box 9, 7935 Observatory, South Africa 9 Geneva Observatory, Geneva University, Chemin des Maillettes 51, 1290 Sauverny, Switzerland 10 Royal Observatory of Belgium, Ringlaan 3, 1180 Brussels, Belgium 11 American Association of Variable Star Observers, 49 Bay State Road, Cambridge MA 02138, USA 12 School of Physics & Astronomy, University of Leeds, Woodhouse Lane, Leeds, LS2 9JT, UK 13 Las Cumbres Observatory Global Telescope Network, Goleta CA 93117, USA 14 Department of Electrical Engineering and Center of Astro Engineering, Pontificia Universidad Catolica de Chile, Av.
    [Show full text]
  • Astronomical Optical Interferometry, II
    Serb. Astron. J. } 183 (2011), 1 - 35 UDC 520.36{14 DOI: 10.2298/SAJ1183001J Invited review ASTRONOMICAL OPTICAL INTERFEROMETRY. II. ASTROPHYSICAL RESULTS S. Jankov Astronomical Observatory, Volgina 7, 11060 Belgrade 38, Serbia E{mail: [email protected] (Received: November 24, 2011; Accepted: November 24, 2011) SUMMARY: Optical interferometry is entering a new age with several ground- based long-baseline observatories now making observations of unprecedented spatial resolution. Based on a great leap forward in the quality and quantity of interfer- ometric data, the astrophysical applications are not limited anymore to classical subjects, such as determination of fundamental properties of stars; namely, their e®ective temperatures, radii, luminosities and masses, but the present rapid devel- opment in this ¯eld allowed to move to a situation where optical interferometry is a general tool in studies of many astrophysical phenomena. Particularly, the advent of long-baseline interferometers making use of very large pupils has opened the way to faint objects science and ¯rst results on extragalactic objects have made it a reality. The ¯rst decade of XXI century is also remarkable for aperture synthesis in the visual and near-infrared wavelength regimes, which provided image reconstruc- tions from stellar surfaces to Active Galactic Nuclei. Here I review the numerous astrophysical results obtained up to date, except for binary and multiple stars milli- arcsecond astrometry, which should be a subject of an independent detailed review, taking into account its importance and expected results at micro-arcsecond precision level. To the results obtained with currently available interferometers, I associate the adopted instrumental settings in order to provide a guide for potential users concerning the appropriate instruments which can be used to obtain the desired astrophysical information.
    [Show full text]
  • Theory of Stellar Atmospheres
    © Copyright, Princeton University Press. No part of this book may be distributed, posted, or reproduced in any form by digital or mechanical means without prior written permission of the publisher. EXTENDED BIBLIOGRAPHY References [1] D. Abbott. The terminal velocities of stellar winds from early{type stars. Astrophys. J., 225, 893, 1978. [2] D. Abbott. The theory of radiatively driven stellar winds. I. A physical interpretation. Astrophys. J., 242, 1183, 1980. [3] D. Abbott. The theory of radiatively driven stellar winds. II. The line acceleration. Astrophys. J., 259, 282, 1982. [4] D. Abbott. The theory of radiation driven stellar winds and the Wolf{ Rayet phenomenon. In de Loore and Willis [938], page 185. Astrophys. J., 259, 282, 1982. [5] D. Abbott. Current problems of line formation in early{type stars. In Beckman and Crivellari [358], page 279. [6] D. Abbott and P. Conti. Wolf{Rayet stars. Ann. Rev. Astr. Astrophys., 25, 113, 1987. [7] D. Abbott and D. Hummer. Photospheres of hot stars. I. Wind blan- keted model atmospheres. Astrophys. J., 294, 286, 1985. [8] D. Abbott and L. Lucy. Multiline transfer and the dynamics of stellar winds. Astrophys. J., 288, 679, 1985. [9] D. Abbott, C. Telesco, and S. Wolff. 2 to 20 micron observations of mass loss from early{type stars. Astrophys. J., 279, 225, 1984. [10] C. Abia, B. Rebolo, J. Beckman, and L. Crivellari. Abundances of light metals and N I in a sample of disc stars. Astr. Astrophys., 206, 100, 1988. [11] M. Abramowitz and I. Stegun. Handbook of Mathematical Functions. (Washington, DC: U.S. Government Printing Office), 1972.
    [Show full text]
  • The Luminous Blue Variable HR Carinae Has a Partner? Discovery of a Companion with the VLTI
    A&A 593, A90 (2016) DOI: 10.1051/0004-6361/201629127 Astronomy c ESO 2016 & Astrophysics The luminous blue variable HR Carinae has a partner? Discovery of a companion with the VLTI Henri M. J. Boffin1; 2, Thomas Rivinius1, Antoine Mérand1, Andrea Mehner1, Jean-Baptiste LeBouquin3, Dimitri Pourbaix4,??, Willem-Jan de Wit1, Christophe Martayan1, and Sylvain Guieu1; 3 1 ESO, Alonso de Córdova 3107, Casilla 19001, Santiago, Chile e-mail: [email protected] 2 ESO, Karl-Schwarzschild-str. 2, 85748 Garching, Germany 3 Institut de Planétologie et d’Astrophysique de Grenoble (UMR 5274), BP 53, 38041 Grenoble Cedex 9, France 4 Institut d’Astronomie et d’Astrophysique, Université Libre de Bruxelles (ULB), 1050 Bruxelles, Belgium Received 16 June 2016 / Accepted 18 July 2016 ABSTRACT Luminous blue variables (LBVs) are massive stars caught in a post-main sequence phase, during which they lose a significant amount of mass. Since, on one hand, it is thought that the majority of massive stars are close binaries that will interact during their lifetime, and on the other, the most dramatic example of an LBV, η Car, is a binary, it would be useful to find other binary LBVs. We present here interferometric observations of the LBV HR Car done with the AMBER and PIONIER instruments attached to ESO’s Very Large Telescope Interferometer (VLTI). Our observations, spanning two years, clearly reveal that HR Car is a binary star. It is not yet possible to fully constrain the orbit, and the orbital period may lie between a few years and several hundred years. We derive a radius for the primary in the system and possibly also resolve the companion.
    [Show full text]
  • Spectral Atlas of Massive Stars Around Hei 10830 Å
    Astronomy & Astrophysics manuscript no. hei10830aa c ESO 2018 October 22, 2018 Spectral atlas of massive stars around He i 10830 Å⋆ J. H. Groh1, A. Damineli1, and F. Jablonski2 1 Instituto de Astronomia, Geof´ısica e Ciˆencias Atmosf´ericas, Universidade de S˜ao Paulo, Rua do Mat˜ao 1226, Cidade Universit´aria, 05508- 900, S˜ao Paulo, SP, Brasil 2 Instituto Nacional de Pesquisas Espaciais/MCT, Avenida dos Astronautas 1758, 12227-010 S˜ao Jos´edos Campos, SP, Brasil Preprint online version: October 22, 2018 ABSTRACT We present a digital atlas of peculiar, high-luminosity massive stars in the near-infrared region (10470–11000 Å) at medium resolution (R ≃ 7000). The spectra are centered around He i 10830 Å, which is formed in the wind of those stars, and is a crucial line to obtain their physical parameters. The instrumental configuration also sampled a rich variety of emission lines of Fe ii, Mg ii,C i,N i, and Pa γ. Secure identifications for most spectral lines are given, based on synthetic atmosphere models calculated by our group. We also propose that two unidentified absorption features have interstellar and/or circumstellar origin. For the strongest one (10780 Å) an empirical calibration between E(B-V) and equivalent width is provided. The atlas displays the spectra of massive stars organized in four categories, namely Be stars, OBA Iape (or luminous blue variables, LBV candidates and ex/dormant LBVs), OB supergiants and Wolf-Rayet stars. For comparison, the photospheric spectra of non emission-line stars are presented. Selected LBVs were observed in different epochs from 2001 to 2004, and their spectral variability reveals that some stars, such as η Car, AG Car and HR Car, suffered dramatic spectroscopic changes during this time interval.
    [Show full text]
  • Arxiv:1310.3962V1 [Astro-Ph.SR] 15 Oct 2013 2 Rivinius, Carciofi, and Martayan
    Astronomy & Astrophysics Review manuscript No. (will be inserted by the editor) Classical Be Stars Rapidly Rotating B Stars with Viscous Keplerian Decretion Disks Thomas Rivinius Alex C. Carciofi · · Christophe Martayan Received: date / Accepted: date Abstract In the past decade, a consensus has emerged regarding the nature of clas- sical Be stars: They are very rapidly rotating main sequence B stars, which, through a still unknown, but increasingly constrained process, form an outwardly diffusing gaseous, dust-free Keplerian disk. In this work, first the definition of Be stars is con- trasted to similar classes, and common observables obtained for Be stars are intro- duced and the respective formation mechanisms explained. We then review the cur- rent state of knowledge concerning the central stars as non-radially pulsating objects and non-magnetic stars, as far as it concerns large scale, i.e., mostly dipolar, global fields. Localized, weak magnetic fields remain possible, but are as of yet unproven. The Be phenomenon, linked with one or more mass ejection processes, acts on top of a rotation rate of about 75% of critical or above. The properties of the process can be well constrained, leaving only few options, most importantly, but not exclusively, non-radial pulsation and small scale magnetic fields. Of these, it is well possible that all are realized: In different stars, different processes may be acting. Once the mate- rial has been lifted into Keplerian orbit, memory of the details of the ejection process is lost, and the material is governed by viscosity. The disks are fairly well understood in the theoretical framework of the viscous decretion disk model.
    [Show full text]
  • Annual Report 2009 ESO
    ESO European Organisation for Astronomical Research in the Southern Hemisphere Annual Report 2009 ESO European Organisation for Astronomical Research in the Southern Hemisphere Annual Report 2009 presented to the Council by the Director General Prof. Tim de Zeeuw The European Southern Observatory ESO, the European Southern Observa­ tory, is the foremost intergovernmental astronomy organisation in Europe. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. Several other countries have expressed an interest in membership. Created in 1962, ESO carries out an am­ bitious programme focused on the de­ sign, construction and operation of power­ ful ground­based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world­ View of the La Silla Observatory from the site of the One of the most exciting features of the class observing sites in the Atacama 3.6 ­metre telescope, which ESO operates together VLT is the option to use it as a giant opti­ with the New Technology Telescope, and the MPG/ Desert region of Chile: La Silla, Paranal ESO 2.2­metre Telescope. La Silla also hosts national cal interferometer (VLT Interferometer or and Chajnantor. ESO’s first site is at telescopes, such as the Swiss 1.2­metre Leonhard VLTI). This is done by combining the light La Silla, a 2400 m high mountain 600 km Euler Telescope and the Danish 1.54­metre Teles cope.
    [Show full text]