Spectroscopy and Interferometry of the Winds of Luminous Blue Variables
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Exploring Pulsars
High-energy astrophysics Explore the PUL SAR menagerie Astronomers are discovering many strange properties of compact stellar objects called pulsars. Here’s how they fit together. by Victoria M. Kaspi f you browse through an astronomy book published 25 years ago, you’d likely assume that astronomers understood extremely dense objects called neutron stars fairly well. The spectacular Crab Nebula’s central body has been a “poster child” for these objects for years. This specific neutron star is a pulsar that I rotates roughly 30 times per second, emitting regular appar- ent pulsations in Earth’s direction through a sort of “light- house” effect as the star rotates. While these textbook descriptions aren’t incorrect, research over roughly the past decade has shown that the picture they portray is fundamentally incomplete. Astrono- mers know that the simple scenario where neutron stars are all born “Crab-like” is not true. Experts in the field could not have imagined the variety of neutron stars they’ve recently observed. We’ve found that bizarre objects repre- sent a significant fraction of the neutron star population. With names like magnetars, anomalous X-ray pulsars, soft gamma repeaters, rotating radio transients, and compact Long the pulsar poster child, central objects, these bodies bear properties radically differ- the Crab Nebula’s central object is a fast-spinning neutron star ent from those of the Crab pulsar. Just how large a fraction that emits jets of radiation at its they represent is still hotly debated, but it’s at least 10 per- magnetic axis. Astronomers cent and maybe even the majority. -
Neutron Stars
Chandra X-Ray Observatory X-Ray Astronomy Field Guide Neutron Stars Ordinary matter, or the stuff we and everything around us is made of, consists largely of empty space. Even a rock is mostly empty space. This is because matter is made of atoms. An atom is a cloud of electrons orbiting around a nucleus composed of protons and neutrons. The nucleus contains more than 99.9 percent of the mass of an atom, yet it has a diameter of only 1/100,000 that of the electron cloud. The electrons themselves take up little space, but the pattern of their orbit defines the size of the atom, which is therefore 99.9999999999999% Chandra Image of Vela Pulsar open space! (NASA/PSU/G.Pavlov et al. What we perceive as painfully solid when we bump against a rock is really a hurly-burly of electrons moving through empty space so fast that we can't see—or feel—the emptiness. What would matter look like if it weren't empty, if we could crush the electron cloud down to the size of the nucleus? Suppose we could generate a force strong enough to crush all the emptiness out of a rock roughly the size of a football stadium. The rock would be squeezed down to the size of a grain of sand and would still weigh 4 million tons! Such extreme forces occur in nature when the central part of a massive star collapses to form a neutron star. The atoms are crushed completely, and the electrons are jammed inside the protons to form a star composed almost entirely of neutrons. -
The Rotationally Modulated Polarization of Ξ Boo A
MNRAS 000,1–8 (2018) Preprint 12 February 2019 Compiled using MNRAS LATEX style file v3.0 The Rotationally Modulated Polarization of ξ Boo A Daniel V. Cotton1;2?, Dag Evensberget3, Stephen C. Marsden3, Jeremy Bailey1;2, Jinglin Zhao1, Lucyna Kedziora-Chudczer1;2, Bradley D. Carter3, Kimberly Bott4;5, Aline A. Vidotto6, Pascal Petit7;8, Julien Morin9 and Sandra V. Jeffers10. 1School of Physics, UNSW Sydney, NSW 2052, Australia. 2Australian Centre for Astrobiology, UNSW Sydney, NSW 2052, Australia. 3University of Southern Queensland, Centre for Astrophysics, Springfield, Qld. 4300/Toowoomba, Qld. 4350, Australia. 4University of Washington Astronomy Department, Box 351580, UW Seattle, WA 98195, USA. 5NExSS Virtual Planetary Laboratory, Box 351580, UW Seattle, WA 98195, USA. 6School of Physics, Trinity College Dublin, College Green, Dublin 2, Ireland. 7Université de Toulouse, UPS-OMP, IRAP, Toulouse, France. 8CNRS, Institut de Recherche en Astrophysique et Planetologie, 14, avenue Edouard Belin, F-31400 Toulouse, France. 9LUPM-UMR 5299, CNRS & Université Montpellier, place Eugène Bataillon, 34095 Montpellier Cedex 05, France. 10Institute for Astrophysics, University of Goettingen, Friedrich Hund Platz 1, 37077, Goettingen, Germany. Accepted . Received ; in original form ABSTRACT We have observed the active star ξ Boo A (HD 131156A) with high precision broad- band linear polarimetry contemporaneously with circular spectropolarimetry. We find both signals are modulated by the 6.43 day rotation period of ξ Boo A. The signals from the two techniques are 0.25 out of phase, consistent with the broadband linear po- larization resulting from differential saturation of spectral lines in the global transverse magnetic field. The mean magnitude of the linear polarization signal is ∼4 ppm/G but its structure is complex and the amplitude of the variations suppressed relative to the longitudinal magnetic field. -
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. -
Multi-Periodic Photospheric Pulsations and Connected Wind Structures in HD 64760
A&A 447, 325–341 (2006) Astronomy DOI: 10.1051/0004-6361:20053847 & c ESO 2006 Astrophysics Multi-periodic photospheric pulsations and connected wind structures in HD 64760 A. Kaufer1,O.Stahl2,R.K.Prinja3, and D. Witherick3, 1 European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Santiago 19, Chile e-mail: [email protected] 2 Landessternwarte Heidelberg, Königstuhl 12, 69117 Heidelberg, Germany 3 Department of Physics & Astronomy, University College London, Gower Street, London, WC1E 6BT, UK Received 18 July 2005 / Accepted 17 October 2005 ABSTRACT We report on the results of an extended optical spectroscopic monitoring campaign on the early-type B supergiant HD 64760 (B0.5 Ib) designed to probe the deep-seated origin of spatial wind structure in massive stars. This new study is based on high-resolution echelle spectra obtained with the Feros instrument at ESO La Silla. 279 spectra were collected over 10 nights between February 14 and 24, 2003. From the period analysis of the line-profile variability of the photospheric lines we identify three closely spaced periods around 4.810 h and a splitting of ±3%. The velocity – phase diagrams of the line-profile variations for the distinct periods reveal characteristic prograde non-radial pulsation patterns of high order corresponding to pulsation modes with l and m in the range 6−10. A detailed modeling of the multi-periodic non-radial pulsations with the Bruce and Kylie pulsation-model codes (Townsend 1997b, MNRAS, 284, 839) favors either three modes with l = −m and l = 8, 6, 8 or m = −6andl = 8, 6, 10 with the second case maintaining the closely spaced periods in the co-rotating frame. -
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. -
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A&A 601, A29 (2017) Astronomy DOI: 10.1051/0004-6361/201629685 & c ESO 2017 Astrophysics Delay-time distribution of core-collapse supernovae with late events resulting from binary interaction E. Zapartas1, S. E. de Mink1, R. G. Izzard2, S.-C. Yoon3, C. Badenes4, Y. Götberg1, A. de Koter1; 5, C. J. Neijssel1, M. Renzo1, A. Schootemeijer6, and T. S. Shrotriya6 1 Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands e-mail: [E.Zapartas;S.E.deMink]@uva.nl 2 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK 3 Astronomy Program, Department of Physics and Astronomy, Seoul National University, 151–747 Seoul, Korea 4 Department of Physics and Astronomy & Pittsburgh Particle Physics, Astrophysics, and Cosmology Center (PITT-PACC), University of Pittsburgh, Pittsburgh, PA 15260, USA 5 Institute of Astronomy, KU Leuven, Celestijnenlaan 200 D, 3001 Leuven, Belgium 6 Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany Received 11 September 2016 / Accepted 1 January 2017 ABSTRACT Most massive stars, the progenitors of core-collapse supernovae, are in close binary systems and may interact with their companion through mass transfer or merging. We undertake a population synthesis study to compute the delay-time distribution of core-collapse supernovae, that is, the supernova rate versus time following a starburst, taking into account binary interactions. We test the systematic robustness of our results by running various simulations to account for the uncertainties in our standard assumptions. We find that +9 a significant fraction, 15−8%, of core-collapse supernovae are “late”, that is, they occur 50–200 Myr after birth, when all massive single stars have already exploded. -
Rotating Wolf-Rayet Stars in a Post RSG/LBV Phase an Evolutionary Channel Towards Long-Duration Grbs?
A&A 547, A83 (2012) Astronomy DOI: 10.1051/0004-6361/201118664 & c ESO 2012 Astrophysics Rotating Wolf-Rayet stars in a post RSG/LBV phase An evolutionary channel towards long-duration GRBs? G. Gräfener1,J.S.Vink1, T. J. Harries2, and N. Langer3 1 Armagh Observatory, College Hill, Armagh BT61 9DG, UK 2 School of Physics and Astronomy, University of Exeter, Stocker Rd, Exeter EX4 4QL, UK 3 Argelander-Institut für Astronomie der Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany Received 16 December 2011 / Accepted 3 October 2012 ABSTRACT Context. Wolf-Rayet (WR) stars with fast rotating cores are thought to be the direct progenitors of long-duration gamma-ray bursts (LGRBs). A well accepted evolutionary channel towards LGRBs is chemically-homogeneous evolution at low metallicities, which completely avoids a red supergiant (RSG), or luminous blue variable (LBV) phase. On the other hand, strong absorption features with velocities of several hundred km s−1 have been found in some LGRB afterglow spectra (GRB 020813 and GRB 021004), which have been attributed to dense circumstellar (CS) material that has been ejected in a previous RSG or LBV phase, and is interacting with a fast WR-type stellar wind. Aims. Here we investigate the properties of Galactic WR stars and their environment to identify similar evolutionary channels that may lead to the formation of LGRBs. Methods. We compile available information on the spectropolarimetric properties of 29 WR stars, the presence of CS ejecta for 172 WR stars, and the CS velocities in the environment of 34 WR stars in the Galaxy. -
14476 (Stsci Edit Number: 4, Created: Wednesday, September 7, 2016 4:28:02 PM EST) - Overview
Proposal 14476 (STScI Edit Number: 4, Created: Wednesday, September 7, 2016 4:28:02 PM EST) - Overview 14476 - A collision reversal in HD 5980 Cycle: 24, Proposal Category: GO (Availability Mode: SUPPORTED) INVESTIGATORS Name Institution E-Mail Dr. Yael Naze (PI) (ESA Member) (Contact) Universite de Liege [email protected] Dr. D. John Hillier (CoI) University of Pittsburgh [email protected] Dr. Gloria Koenigsberger (CoI) (Contact) Universidad Nacional Autonoma de Mexico (UNAM) [email protected] Dr. Julian M. Pittard (CoI) (ESA Member) University of Leeds [email protected] Dr. Michael F. Corcoran (CoI) Universities Space Research Association [email protected] Dr. Gregor Rauw (CoI) (ESA Member) Universite de Liege [email protected] VISITS Visit Targets used in Visit Configurations used in Visit Orbits Used Last Orbit Planner Run OP Current with Visit? 01 (1) HD-5980 STIS/CCD 2 07-Sep-2016 17:28:00.0 yes CCDFLAT STIS/FUV-MAMA 2 Total Orbits Used ABSTRACT HD 5980 provides a unique laboratory for studying the properties of wind-wind collisions. It contains one of only two binary systems having a WR- star in orbit with a LBV. The latter star has been observed to undergo major changes in its wind structure over the past 35 years, implying changes in the geometry and emitting conditions of the wind-wind collision region. Ten years ago, when the LBV wind was very strong, XMM observations revealed X-ray emission consistent with the shock cone wrapping around the WR component. Since then, the wind strength has significantly declined, implying that the collision shock cone may be inverting its orientation. -
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 -
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. -
Urania Nr 5/2001
Eta Carinae To zdjęcie mgławicy otaczającej gwiazdę // Carinae uzyskano za po mocą telskopu kosmicznego Hubble a (K. Davidson i J. Mors). Porównując je z innymi zdjęciami, a w szczególności z obrazem wyko nanym 17 miesięcy wcześniej, Auto rzy stwierdzili rozprężanie się mgła wicy z szybkością ok. 2,5 min km/h, co prowadzi do wniosku, że rozpo częła ona swe istnienie około 150 lat temu. To bardzo ciekawy i intrygujący wynik. Otóż największy znany roz błysk )j Carinae miał miejsce w roku 1840. Wtedy gwiazda ta stała się naj jaśniejszą gwiazdą południowego nie ba i jasność jej przez krótki czas znacznie przewyższała blask gwiaz dy Canopus. Jednak pyłowy dysk ob serwowany wokół)/ Carinae wydaje się być znacznie młodszy - jego wiek (ekspansji) jest oceniany na 100 lat, co może znaczyć, że powstał w cza sie innego, mniejszego wybuchu ob serwowanego w roku 1890. Więcej na temat tego intrygują cego obiektu przeczytać można we wnątrz numeru, w artykule poświę conym tej gwieździe. NGC 6537 Obserwacje przeprowadzone teleskopem Hubble’a pokazały istnienie wielkich falowych struktur w mgławicy Czerwonego Pająka (NGC 6537) w gwiazdozbiorze Strzelca.Ta gorąca i „wietrzna” mgławica powstała wokół jednej z najgorętszych gwiazd Wszech świata, której wiatr gwiazdowy wiejący z prędkością 2000-4500 kilometrów na sekundę wytwarza fale o wysokości 100 miliardów kilometrów. Sama mgławica rozszerza się z szybkością 300 km/s. Jest też ona wyjątkowo gorąca — ok. 10000 K. Sama gwiazda, która utworzyła mgławicę, jest obecnie białym karłem i musi mieć temperaturę nie niższą niż pół miliona stopni — jest tak gorąca, że nie widać jej w obszarach uzyskanych teleskopem Hubble’a, a świeci głównie w promieniowaniu X.