CURRICULUM VITAE Name: Matthew A. Wood Address
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
Spectral Analysis of the Hybrid PG 1159-Type Central Stars of the Planetary Nebulae Abell 43 and NGC 7094
MNRAS 489, 1054–1071 (2019) doi:10.1093/mnras/stz1994 Advance Access publication 2019 July 25 Spectral analysis of the hybrid PG 1159-type central stars of the planetary nebulae Abell 43 and NGC 7094 L. Lobling¨ ,1‹ T. Rauch ,1 M. M. Miller Bertolami,2,3 H. Todt,4 F. Friederich,1 M. Ziegler,1 K. Werner 1 andJ.W.Kruk5 Downloaded from https://academic.oup.com/mnras/article-abstract/489/1/1054/5538811 by Macquarie University user on 29 August 2019 1Institute for Astronomy and Astrophysics, Kepler Center for Astro and Particle Physics, Eberhard Karls University, Sand 1, D-72076 Tubingen,¨ Germany 2Instituto de Astrof´ısica La Plata, CONICET-UNLP, Paseo del Bosque s/n, (B1900FWA) La Plata, Argentina 3Facultad de Ciencias Astronomicas´ y Geof´ısicas, UNLP, Paseo del Bosque s/n, (B1900FWA) La Plata, Argentina 4Institute of Physics and Astronomy, University of Potsdam, Karl-Liebknecht-Str. 24/25, D-14476 Potsdam, Germany 5NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA Accepted 2019 July 16. Received 2019 June 18; in original form 2019 April 30 ABSTRACT Stellar post asymptotic giant branch (post-AGB) evolution can be completely altered by a final thermal pulse (FTP) which may occur when the star is still leaving the AGB (AFTP), at the departure from the AGB at still constant luminosity (late TP, LTP) or after the entry to the white-dwarf cooling sequence (very late TP, VLTP). Then convection mixes the He- rich material with the H-rich envelope. According to stellar evolution models the result is a star with a surface composition of H ≈ 20 per cent by mass (AFTP), ≈ 1 per cent (LTP), or (almost) no H (VLTP). -
The Everchanging Pulsating White Dwarf GD358
Astronomy & Astrophysics manuscript no. gd358 January 23, 2003 (DOI: will be inserted by hand later) The Everchanging Pulsating White Dwarf GD358 S.O. Kepler1, R. Edward Nather2, Don E. Winget2, Atsuko Nitta3, S. J. Kleinman3, Travis Metcalfe2;4, Kazuhiro Sekiguchi5, Jiang Xiaojun6, Denis Sullivan7, Tiri Sullivan7, Rimvydas Janulis8, Edmund Meistas8, Romualdas Kalytis8, Jurek Krzesinski9, Waldemar OgÃloza9, Staszek Zola10, Darragh O’Donoghue11, Encarni Romero-Colmenero11, Peter Martinez11, Stefan Dreizler12, Jochen Deetjen12, Thorsten Nagel12, Sonja L. Schuh12, Gerard Vauclair13, Fu Jian Ning13, Michel Chevreton14, Jan-Erik Solheim15, Jose M. Gonzalez Perez15, Frank Johannessen15, Antonio Kanaan16, Jos´eEduardo Costa1, Alex Fabiano Murillo Costa1, Matt A. Wood17, Nicole Silvestri17, T.J. Ahrens17, Aaron Kyle Jones18;¤, Ansley E. Collins19;¤, Martha Boyer20;¤, J. S. Shaw21, Anjum Mukadam2, Eric W. Klumpe22, Jesse Larrison22, Steve Kawaler23, Reed Riddle23, Ana Ulla24, and Paul Bradley25 1 Instituto de F´ısicada UFRGS, Porto Alegre, RS - Brazil e-mail: [email protected] 2 Department of Astronomy & McDonald Observatory, University of Texas, Austin, TX 78712, USA 3 Sloan Digital Sky Survey, Apache Pt. Observatory, P.O. Box 59, Sunspot, NM 88349, USA 4 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 USA e-mail: [email protected] 5 Subaru National Astronomical Observatory of Japan e-mail: [email protected] 6 Beijing Astronomical Observatory, Academy of Sciences, Beijing 100080, China e-mail: [email protected] 7 University of Victoria, Wellington, New Zealand 8 Institute of Theoretical Physics and Astronomy, Gostauto 12, Vilnius 2600, Lithuania 9 Mt. Suhora Observatory, Cracow Pedagogical University, Ul. Podchorazych 2, 30-084 Cracow, Poland 10 Jagiellonian University, Krakow, Poland e-mail: [email protected] 11 South African Astronomical Observatory 12 Universitat T¨ubingen,Germany 13 Universit´ePaul Sabatier, Observatoire Midi-Pyr´en´ees,CNRS/UMR5572, 14 av. -
Molecular Outflows Identified in the FCRAO CO Survey of the Taurus
Mon. Not. R. Astron. Soc. 000, 000–000 (0000) Printed 10 November 2018 (MN LATEX style file v2.2) Molecular Outflows Identified in the FCRAO CO Survey of the Taurus Molecular Cloud Gopal Narayanan1, Ronald Snell1, and Ashley Bemis1;2 1 Dept. of Astronomy, Univ. of Massachusetts, Amherst MA 01003 2 Department of Physics and Astronomy, Bonn University, Wegelerstrasse 8, 53115 Bonn, Germany Received 2012 June 14; in original form 2012 April 23; accepted 2012 June 22 ABSTRACT Jets and outflows are an integral part of the star formation process. While there are many detailed studies of molecular outflows towards individual star-forming sites, few studies have surveyed an entire star-forming molecular cloud for this phenomenon. The 100 square degree FCRAO CO survey of the Taurus molecular cloud provides an excellent opportunity to under- take an unbiased survey of a large, nearby, molecular cloud complex for molecular outflow activity. Our study provides information on the extent, energetics and frequency of outflows in this region, which are then used to assess the impact of outflows on the parent molecular cloud. The search identified 20 outflows in the Taurus region, 8 of which were previously unknown. Both 12CO and 13CO data cubes from the Taurus molecular map were used, and dynamical properties of the outflows are derived. Even for previously known outflows, our large-scale maps indicate that many of the outflows are much larger than previously suspected, with eight of the flows (40%) being more than a parsec long. The mass, momentum and kinetic energy from the 20 outflows are compared to the repository of turbulent energy in Taurus. -
Spectral Analyses of DO White Dwarfs and PG 1159 Stars from the Sloan Digital Sky Survey
A&A 442, 309–314 (2005) Astronomy DOI: 10.1051/0004-6361:20053280 & c ESO 2005 Astrophysics Spectral analyses of DO white dwarfs and PG 1159 stars from the Sloan Digital Sky Survey S. D. Hügelmeyer1, S. Dreizler1,K.Werner2, J. Krzesinski´ 3,4, A. Nitta3, and S. J. Kleinman3 1 Institut für Astrophysik, Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany e-mail: [email protected] 2 Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, 72076 Tübingen, Germany 3 New Mexico State University, Apache Point Observatory, 2001 Apache Point Road, PO Box 59, Sunspot, NM 88349, USA 4 Mt. Suhora Observatory, Cracow Pedagogical University, ul. Podchorazych 2, 30-084 Cracow, Poland Received 21 April 2005 / Accepted 4 July 2005 ABSTRACT We present a model atmosphere analysis of ten new DO white dwarfs and five new PG 1159 stars discovered in the Sloan Digital Sky Survey DR1, DR2 and DR3. This is a significant increase in the number of known DOs and PG 1159 stars. DO white dwarfs are situated on the white dwarf cooling sequence from the upper hot end (Teff ≈ 120 000 K) down to the DB gap (Teff ≈ 45 000 K). PG 1159 stars on the other hand feature effective temperatures which exceed Teff = 65 000 K with an upper limit of Teff = 200 000 K and are the proposed precursors of DO white dwarfs. Improved statistics are necessary to investigate the evolutionary link between these two types of stars. From optical SDSS spectra effective temperatures, surface gravities and element abundances are determined by means of non-LTE model atmospheres. -
Organic Molecules and Water in the Inner Disks of T Tauri Stars
Organic Molecules and Water in the Inner Disks of T Tauri Stars John S. Carr Naval Research Laboratory, Code 7211, Washington, DC 20375, USA [email protected] Joan R. Najita National Optical Astronomy Observatory, 950 N. Cherry Avenue, Tucson, AZ 85716, USA [email protected] ABSTRACT We report high signal-to-noise Spitzer IRS spectra of a sample of eleven classical T Tauri stars. Molecular emission from rotational transitions of H2O and OH and ro-vibrational bands of simple organic molecules (CO2, HCN, C2H2) is common among the sources in the sample. The emission shows a range in both flux and line-to-continuum ratio for each molecule and in the flux ratios of different molecular species. The gas temperatures (200–800 K) and emitting areas we derive are consistent with the emission originating in a warm disk atmosphere in the inner planet formation region at radii < 2 AU. The H2O emission appears to form under a limited range of excitation conditions, as demonstrated by the similarity in relative strengths of H2O features from star to star and the narrow range in derived temperature and column density. Emission from highly excited rotational levels of OH is present in all stars; the OH emission flux increases with the stellar accretion rate, and the OH/H2O flux ratio shows a relatively small scatter. We interpret these results as evidence for OH production via FUV photo-dissociation of H2O in the disk surface layers. No obvious explanation is found for the observed range in the relative emission strengths of different organic molecules or in their strength with respect to water. -
Astronomy Astrophysics
A&A 427, 685–695 (2004) Astronomy DOI: 10.1051/0004-6361:20041165 & c ESO 2004 Astrophysics Identification of neon in FUSE and VLT spectra of extremely hot hydrogen-deficient (pre-) white dwarfs, K. Werner1,T.Rauch1,2,E.Reiff1,J.W.Kruk3, and R. Napiwotzki4 1 Institut für Astronomie und Astrophysik, Universität Tübingen, Sand 1, 72076 Tübingen, Germany e-mail: [email protected] 2 Dr.-Remeis-Sternwarte, Universität Erlangen-Nürnberg, Sternwartstraße 7, 96049 Bamberg, Germany 3 Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA 4 Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK Received 26 April 2004 / Accepted 16 July 2004 Abstract. One of the strongest absorption lines observed in far-ultraviolet FUSE spectra of many PG 1159 stars remained unidentified up to now. We show that this line, located at 973.3 Å, stems from Ne . We also present new optical high- resolution spectra of PG 1159 stars, obtained with the ESO VLT, which cover the Ne 3644 Å line and a newly identified Ne multiplet in the 3850–3910 Å region. We compare the observed neon lines with NLTE models and conclude a substantial neon overabundance in a number of objects. Although a detailed analysis is still to be performed in order to compare quantita- tively the abundances with evolutionary theory predictions, this corroborates the idea that the PG 1159 stars and their immediate progenitors, the [WC]-type nuclei of planetary nebulae, display intershell matter of their precursor AGB stars. Possibly as the consequence of a late He-shell flash, H-deficient and (s-processed) Fe-depleted matter, that is strongly enriched by 3α-processed elements (C, O, Ne), is dredged up to the surface. -
Arxiv:2001.10147V1
Magnetic fields in isolated and interacting white dwarfs Lilia Ferrario1 and Dayal Wickramasinghe2 Mathematical Sciences Institute, The Australian National University, Canberra, ACT 2601, Australia Adela Kawka3 International Centre for Radio Astronomy Research, Curtin University, Perth, WA 6102, Australia Abstract The magnetic white dwarfs (MWDs) are found either isolated or in inter- acting binaries. The isolated MWDs divide into two groups: a high field group (105 − 109 G) comprising some 13 ± 4% of all white dwarfs (WDs), and a low field group (B < 105 G) whose incidence is currently under investigation. The situation may be similar in magnetic binaries because the bright accretion discs in low field systems hide the photosphere of their WDs thus preventing the study of their magnetic fields’ strength and structure. Considerable research has been devoted to the vexed question on the origin of magnetic fields. One hypothesis is that WD magnetic fields are of fossil origin, that is, their progenitors are the magnetic main-sequence Ap/Bp stars and magnetic flux is conserved during their evolution. The other hypothesis is that magnetic fields arise from binary interaction, through differential rotation, during common envelope evolution. If the two stars merge the end product is a single high-field MWD. If close binaries survive and the primary develops a strong field, they may later evolve into the arXiv:2001.10147v1 [astro-ph.SR] 28 Jan 2020 magnetic cataclysmic variables (MCVs). The recently discovered population of hot, carbon-rich WDs exhibiting an incidence of magnetism of up to about 70% and a variability from a few minutes to a couple of days may support the [email protected] [email protected] [email protected] Preprint submitted to Journal of LATEX Templates January 29, 2020 merging binary hypothesis. -
Spectra of Gw Vir Type Pulsators
Baltic Astronomy, vol.4, 340-348, 1995. SPECTRA OF GW VIR TYPE PULSATORS K. Werner Lehrstuhl für Astrophysik, Universität Potsdam, Germany; Institut für Astronomie und Astrophysik, Universität Kiel, D-24098, Kiel, Germany Received September 1, 1995. Abstract. We describe our effort to confine empirically the position of the GW Vir instability strip in the HR diagram. Spectra rang- ing from the soft X-ray to the optical region of the electromagnetic spectrum are analyzed by means of non-LTE model atmospheres. We compare our results for stellar parameters with those from pulsational analyses. Generally, good agreement is found. Key words: stars: atmospheres - stars: oscillations - stars: white dwarfs - stars: individual: PG 1159-035. 1. Introduction The PG 1159 stars represent the hottest known hydrogen- deficient post-AGB stars. They are just about to enter the white dwarf cooling sequence. Effective temperatures range from 170 000 K down to 65 000 K. Surface gravities and hence luminosities cover a wide range (log g — 5.5-8.0). The atmospheric abundances are gen- erally dominated by carbon and helium. The oxygen abundances are high, around 20 % by mass in most stars but significant deviations from this mean value occur. The most extreme case is H 1504+65, a hydrogen- and helium-deficient star with an atmosphere essentially composed of carbon and oxygen. Mass loss and/or ingestion and burning of hydrogen are thought to have removed the hydrogen- rich surface layer. Table 1 summarizes the characteristics of the 27 presently known PG 1159 stars. About every second object is as- sociated with a planetary nebula and eight stars are known to be variable. -
The Pulsation Modes of the Pre-White Dwarf PG 1159-035
A&A 477, 627–640 (2008) Astronomy DOI: 10.1051/0004-6361:20053470 & c ESO 2007 Astrophysics The pulsation modes of the pre-white dwarf PG 1159-035 J. E. S. Costa1,S.O.Kepler1,D.E.Winget2, M. S. O’Brien47,S.D.Kawaler4,A.F.M.Costa1, O. Giovannini1,5, A. Kanaan6, A. S. Mukadam42, F. Mullally2, A. Nitta3,J.L.Provençal8,H.Shipman8,M.A.Wood9,T.J.Ahrens9, A. Grauer10, M. Kilic41,P.A.Bradley11, K. Sekiguchi12,R.Crowe13,X.J.Jiang14, D. Sullivan15, T. Sullivan15, R. Rosen15,J.C.Clemens16, R. Janulis17, D. O’Donoghue18,W.Ogloza19, A. Baran19, R. Silvotti20, S. Marinoni21, G. Vauclair22,N.Dolez22, M. Chevreton23, S. Dreizler24,25, S. Schuh24,25,J.Deetjen24, T. Nagel24, J.-E. Solheim26,27, J. M. Gonzalez Perez26,28, A. Ulla29, M. Barstow30, M. Burleigh30,S.Good30,T.S.Metcalfe31,S.-L.Kim32,H.Lee32, A. Sergeev33,M.C.Akan34, Ö. Çakırlı34, M. Paparo35, G. Viraghalmy35, B. N. Ashoka36, G. Handler37, Ö. Hürkal38, F. Johannessen26 ,S.J.Kleinman3,R.Kalytis17, J. Krzesinski19,E.Klumpe39, J. Larrison39,T.Lawrence4, E. Meištas17, P. Martinez18,R.E.Nather2,J.-N.Fu48,E.Pakštiene˙17, R. Rosen26, E. Romero-Colmenero18, R. Riddle44,S.Seetha37, N. M. Silvestri42,M.Vuckoviˇ c´4,43,B.Warner18,S.Zola40,L.G.Althaus45,46, A. H. Córsico45,46, and M. H. Montgomery2 (Affiliations can be found after the references) Received 18 May 2005 / Accepted 31 October 2007 ABSTRACT Context. PG 1159-035, a pre-white dwarf with Teff 140 000 K, is the prototype of both two classes: the PG 1159 spectroscopic class and the DOV pulsating class. -
1 Hot White Dwarfs Edward M
i i D. W. Hoard: White Dwarf Atmospheres and Circumstellar Environments — Chap. hoard0316c01 — 2011/7/5 — page 1 — le-tex i i 1 1 Hot White Dwarfs Edward M. Sion 1.1 Introduction Research on hot white dwarfs during the past 30 years has greatly expanded, as many new discoveries and the new questions they raise have emerged from in- creasingly larger, deeper surveys conducted with multimeter class ground-based telescopes, the International Ultraviolet Explorer (IUE), the Hubble Space Tele- scope (HST), the Extreme Ultraviolet Explorer (EUVE), and the Far Ultraviolet Spectroscopic Explorer (FUSE). This review will focus on white dwarfs ranging in temperature from 20 000 up to 200 000 K and higher, which are the hottest white dwarf stars known. Since the mid-twentieth century, the earliest spectroscopic sur- veys of white dwarf candidates from the proper motion selected samples of Willem Luyten and Henry Giclas were carried out by Jesse Greenstein, Olin Eggen, James Liebert, Richard Green, and others. The selection criteria employed in many of these surveys did not reveal a large number of hot white dwarfs because the sur- veys lacked ultraviolet sensitivity and also missed objects with low flux levels in the optical. Nevertheless, the earliest surveys quickly revealed that white dwarfs divide into two basic composition groups with hydrogen-rich (the DA stars) and helium- rich atmospheric compositions (the DB and other non-DA stars). The origin of this dichotomy still represents a major unsolved problem in stellar evolution, although theoretical advances in late stellar evolution made starting in the 1980s, as well as advances in modeling envelope physical processes and mass loss, have shed im- portant new light on this puzzle (Chayer et al., 1995; Fontaine and Michaud, 1979; Iben, 1984; Iben et al., 1983; Schoenberner, 1983; Unglaub and Bues, 1998, 2000; Vauclair et al., 1979). -
Asteroseismology
Asteroseismology Gerald Handler Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw, Poland Email: [email protected] Abstract Asteroseismology is the determination of the interior structures of stars by using their oscillations as seismic waves. Simple explanations of the astrophysical background and some basic theoretical considerations needed in this rapidly evolving field are followed by introductions to the most important concepts and methods on the basis of example. Previous and potential applications of asteroseismology are reviewed and future trends are attempted to be foreseen. Introduction: variable and pulsating stars Nearly all the physical processes that determine the structure and evolution of stars occur in their (deep) interiors. The production of nuclear energy that powers stars takes place in their cores for most of their lifetime. The effects of the physical processes that modify the simplest models of stellar evolution, such as mixing and diffusion, also predominantly take place in the inside of stars. The light that we receive from the stars is the main information that astronomers can use to study the universe. However, the light of the stars is radiated away from their surfaces, carrying no memory of its origin in the deep interior. Therefore it would seem that there is no way that the analysis of starlight tells us about the physics going on in the unobservable stellar interiors. However, there are stars that reveal more about themselves than others. Variable stars are objects for which one can observe time-dependent light output, on a time scale shorter arXiv:1205.6407v1 [astro-ph.SR] 29 May 2012 than that of evolutionary changes. -
La Constelacion De Tauro
LA CONSTELACION DE TAURO Es una de las constelaciones más interesantes desde el punto de vista observacional entre las que podemos ver desde el hemisferio norte. En la zona de la bóveda celeste donde identificamos la constelación de Tauro encontramos estrellas dobles y dos bellísimos cúmulos abiertos, asi como la famosa Nebulosa del Cangrejo, objeto Messier M1. 1. Las constelaciones: una aparente imágen estelar: Desde nuestra perspectiva visual como habitantes de un pequeño planeta orbitando alrededor de una estrella en una cierta galaxia espiral, observamos, en todas las direcciones de la bóveda celeste, agrupaciones aparentes de estrellas que llamamos constelaciones. Decimos que son agrupaciones aparentes porque, realmente, no tienen que estar - de hecho no lo están en general - agrupadas físicamente. Es esta la misma situación que se nos plantea en nuestra vida cotidiana cuando observamos a lo lejos dos objetos que aparentan estar juntos, y, ante la duda de si lo están o no, nosotros nos movemos lateralmente a una distancia suficiente para observarlos desde una perspectiva lateral. Es en ese momento cuando, vistos desde otro ángulo, comprobamos si están entre sí próximos o no. Este movimiento lateral es muy sencillo de realizar en nuestros avatares de la vida cotidiana, pero es evidente que, a escala astronómica, es imposible con la tecnología existente en nuestra civilización. Es imposible para nosotros salir de la Vía Láctea, nuestra galaxia espiral, para poder observar “lateralmente” una cierta estrella doble, por ejemplo, de la que sospechamos que no es una doble física, interactuando gravitacionalmente, sino que es una doble de perspectiva. Existen métodos radiométricos, espectrométricos, etc.., que nos permiten calcular la distancia de la estrellas que observamos a simple vista, y sabemos que en general, la distancia a nosotros de astros de una misma constelación varía grandemente.