Massive Fast Rotating Highly Magnetized White Dwarfs: Theory and Astrophysical Applications
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The Most Massive Pulsating White Dwarf Stars Barbara G
Precision Asteroseismology Proceedings IAU Symposium No. 301, 2013 c International Astronomical Union 2014 J. A. Guzik, W. J. Chaplin, G. Handler & A. Pigulski, eds. doi:10.1017/S1743921313014452 The most massive pulsating white dwarf stars Barbara G. Castanheira1 and S. O. Kepler2 1 Department of Astronomy and McDonald Observatory, University of Texas Austin, TX 78712, USA email: [email protected] 2 Instituto de F´ısica, Universidade Federal do Rio Grande do Sul 91501-970 Porto Alegre, RS, Brazil email: [email protected] Abstract. Massive pulsating white dwarf stars are extremely rare, because of their small size and because they are the final product of high-mass stars, which are less common. Because of their intrinsic smaller size, they are fainter than the normal size white dwarf stars. The motivation to look for this type of stars is to be able to study in detail their internal structure and also derive generic properties for the sub-class of variables, the massive ZZ Ceti stars. Our goal is to investigate whether the internal structures of these stars differ from the lower-mass ones, which in turn could have been resultant from the previous evolutionary stages. In this paper, we present the ensemble seismological analysis of the known massive pulsating white dwarf stars. Some of these pulsating stars might have substantial crystallized cores, which would allow us to probe solid physics in extreme conditions. Keywords. stars: oscillations (including pulsations), stars: white dwarfs 1. Introduction According to the best current evolutionary models, all single stars with masses below 9–10M will end up their lives as white dwarf stars. -
JOHN R. THORSTENSEN Address
CURRICULUM VITAE: JOHN R. THORSTENSEN Address: Department of Physics and Astronomy Dartmouth College 6127 Wilder Laboratory Hanover, NH 03755-3528; (603)-646-2869 [email protected] Undergraduate Studies: Haverford College, B. A. 1974 Astronomy and Physics double major, High Honors in both. Graduate Studies: Ph. D., 1980, University of California, Berkeley Astronomy Department Dissertation : \Optical Studies of Faint Blue X-ray Stars" Graduate Advisor: Professor C. Stuart Bowyer Employment History: Department of Physics and Astronomy, Dartmouth College: { Professor, July 1991 { present { Associate Professor, July 1986 { July 1991 { Assistant Professor, September 1980 { June 1986 Research Assistant, Space Sciences Lab., U.C. Berkeley, 1975 { 1980. Summer Student, National Radio Astronomy Observatory, 1974. Summer Student, Bartol Research Foundation, 1973. Consultant, IBM Corporation, 1973. (STARMAP program). Honors and Awards: Phi Beta Kappa, 1974. National Science Foundation Graduate Fellow, 1974 { 1977. Dorothea Klumpke Roberts Award of the Berkeley Astronomy Dept., 1978. Professional Societies: American Astronomical Society Astronomical Society of the Pacific International Astronomical Union Lifetime Publication List * \Can Collapsed Stars Close the Universe?" Thorstensen, J. R., and Partridge, R. B. 1975, Ap. J., 200, 527. \Optical Identification of Nova Scuti 1975." Raff, M. I., and Thorstensen, J. 1975, P. A. S. P., 87, 593. \Photometry of Slow X-ray Pulsars II: The 13.9 Minute Period of X Persei." Margon, B., Thorstensen, J., Bowyer, S., Mason, K. O., White, N. E., Sanford, P. W., Parkes, G., Stone, R. P. S., and Bailey, J. 1977, Ap. J., 218, 504. \A Spectrophotometric Survey of the A 0535+26 Field." Margon, B., Thorstensen, J., Nelson, J., Chanan, G., and Bowyer, S. -
WHAT's BEHIND the MYSTERIOUS GAMMA-RAY BURSTS? LIGO's
WHAT’S BEHIND THE MYSTERIOUS GAMMA-RAY BURSTS? LIGO’s SEARCH FOR CLUES TO THEIR ORIGINS The story of gamma-ray bursts (GRBs) began in the 1960s aboard spacecrafts designed to monitor the former Soviet Union for compliance with the nuclear test ban treaty of 1963. The satellites of the Vela series, each armed with a number of caesium iodide scintillation counters, recorded many puzzling bursts of gamma-ray radiation that did not fit the expected signature of a nuclear weapon. The existence of these bursts became public knowledge in 1973, beginning a decades long quest to understand their origin. Since then, scientists have launched many additional satellites to study these bursts (gamma rays are blocked by the earth's atmosphere) and have uncovered many clues. GRBs occur approximately once a day in a random point in the sky. Most FIGURES FROM THE PUBLICATION GRBs originate millions or billions of light years away. The fact that they For more information on how these figures were generated, and are still so bright by the time they get to earth makes them some of the their meaning, see the publication preprint at arXiv. most energetic astrophysical events observed in the electromagnetic spectrum. In fact, a typical GRB will release in just a handful of seconds as much energy as our sun will throughout its entire life. They can last anywhere from hundredths of seconds to thousands of seconds, but are roughly divided into two categories based on duration (long and short). The line between the two classes is taken to be at 2 seconds (although more sophisticated features are also taken into account in the classification). -
Brown Dwarf: White Dwarf: Hertzsprung -Russell Diagram (H-R
Types of Stars Spectral Classifications: Based on the luminosity and effective temperature , the stars are categorized depending upon their positions in the HR diagram. Hertzsprung -Russell Diagram (H-R Diagram) : 1. The H-R Diagram is a graphical tool that astronomers use to classify stars according to their luminosity (i.e. brightness), spectral type, color, temperature and evolutionary stage. 2. HR diagram is a plot of luminosity of stars versus its effective temperature. 3. Most of the stars occupy the region in the diagram along the line called the main sequence. During that stage stars are fusing hydrogen in their cores. Various Types of Stars Brown Dwarf: White Dwarf: Brown dwarfs are sub-stellar objects After a star like the sun exhausts its nuclear that are not massive enough to sustain fuel, it loses its outer layer as a "planetary nuclear fusion processes. nebula" and leaves behind the remnant "white Since, comparatively they are very cold dwarf" core. objects, it is difficult to detect them. Stars with initial masses Now there are ongoing efforts to study M < 8Msun will end as white dwarfs. them in infrared wavelengths. A typical white dwarf is about the size of the This picture shows a brown dwarf around Earth. a star HD3651 located 36Ly away in It is very dense and hot. A spoonful of white constellation of Pisces. dwarf material on Earth would weigh as much as First directly detected Brown Dwarf HD 3651B. few tons. Image by: ESO The image is of Helix nebula towards constellation of Aquarius hosts a White Dwarf Helix Nebula 6500Ly away. -
Arxiv:2105.11583V2 [Astro-Ph.EP] 2 Jul 2021 Keck-HIRES, APF-Levy, and Lick-Hamilton Spectrographs
Draft version July 6, 2021 Typeset using LATEX twocolumn style in AASTeX63 The California Legacy Survey I. A Catalog of 178 Planets from Precision Radial Velocity Monitoring of 719 Nearby Stars over Three Decades Lee J. Rosenthal,1 Benjamin J. Fulton,1, 2 Lea A. Hirsch,3 Howard T. Isaacson,4 Andrew W. Howard,1 Cayla M. Dedrick,5, 6 Ilya A. Sherstyuk,1 Sarah C. Blunt,1, 7 Erik A. Petigura,8 Heather A. Knutson,9 Aida Behmard,9, 7 Ashley Chontos,10, 7 Justin R. Crepp,11 Ian J. M. Crossfield,12 Paul A. Dalba,13, 14 Debra A. Fischer,15 Gregory W. Henry,16 Stephen R. Kane,13 Molly Kosiarek,17, 7 Geoffrey W. Marcy,1, 7 Ryan A. Rubenzahl,1, 7 Lauren M. Weiss,10 and Jason T. Wright18, 19, 20 1Cahill Center for Astronomy & Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA 2IPAC-NASA Exoplanet Science Institute, Pasadena, CA 91125, USA 3Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA 94305, USA 4Department of Astronomy, University of California Berkeley, Berkeley, CA 94720, USA 5Cahill Center for Astronomy & Astrophysics, California Institute of Technology, Pasadena, CA 91125, USA 6Department of Astronomy & Astrophysics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802, USA 7NSF Graduate Research Fellow 8Department of Physics & Astronomy, University of California Los Angeles, Los Angeles, CA 90095, USA 9Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA 10Institute for Astronomy, University of Hawai`i, -
The Potential of Planets Orbiting Red Dwarf Stars to Support Oxygenic Photosynthesis and Complex Life
1 The Potential of Planets Orbiting Red Dwarf Stars to Support Oxygenic Photosynthesis and Complex Life Joseph Gale1 and Amri Wandel2 The Institute of Life Sciences1and The Racach Institute of Physics2, The Hebrew University of Jerusalem, 91904, Israel. [email protected] [email protected] Accepted for publication in the International Journal of Astrobiology Abstract We review and reassess the latest findings on the existence of extra-solar system planets and their potential of having environmental conditions that could support Earth-like life. Within the last two decades, the multi-millennial question of the existence of extra-Solar- system planets has been resolved with the discovery of numerous planets orbiting nearby stars, many of which are Earth-sized (and some even with moderate surface temperatures). Of particular interest in our search for clement conditions for extra-solar system life are planets orbiting Red Dwarf (RD) stars, the most numerous stellar type in the Milky Way galaxy. We show that including RDs as potential life supporting host stars could increase the probability of finding biotic planets by a factor of up to a thousand, and reduce the estimate of the distance to our nearest biotic neighbor by up to 10. We argue that multiple star systems need to be taken into account when discussing habitability and the abundance of biotic exoplanets, in particular binaries of which one or both members are RDs. Early considerations indicated that conditions on RD planets would be inimical to life, as their Habitable Zones (where liquid water could exist) would be so close as to make planets tidally locked to their star. -
UC Irvine UC Irvine Previously Published Works
UC Irvine UC Irvine Previously Published Works Title Astrophysics in 2006 Permalink https://escholarship.org/uc/item/5760h9v8 Journal Space Science Reviews, 132(1) ISSN 0038-6308 Authors Trimble, V Aschwanden, MJ Hansen, CJ Publication Date 2007-09-01 DOI 10.1007/s11214-007-9224-0 License https://creativecommons.org/licenses/by/4.0/ 4.0 Peer reviewed eScholarship.org Powered by the California Digital Library University of California Space Sci Rev (2007) 132: 1–182 DOI 10.1007/s11214-007-9224-0 Astrophysics in 2006 Virginia Trimble · Markus J. Aschwanden · Carl J. Hansen Received: 11 May 2007 / Accepted: 24 May 2007 / Published online: 23 October 2007 © Springer Science+Business Media B.V. 2007 Abstract The fastest pulsar and the slowest nova; the oldest galaxies and the youngest stars; the weirdest life forms and the commonest dwarfs; the highest energy particles and the lowest energy photons. These were some of the extremes of Astrophysics 2006. We attempt also to bring you updates on things of which there is currently only one (habitable planets, the Sun, and the Universe) and others of which there are always many, like meteors and molecules, black holes and binaries. Keywords Cosmology: general · Galaxies: general · ISM: general · Stars: general · Sun: general · Planets and satellites: general · Astrobiology · Star clusters · Binary stars · Clusters of galaxies · Gamma-ray bursts · Milky Way · Earth · Active galaxies · Supernovae 1 Introduction Astrophysics in 2006 modifies a long tradition by moving to a new journal, which you hold in your (real or virtual) hands. The fifteen previous articles in the series are referenced oc- casionally as Ap91 to Ap05 below and appeared in volumes 104–118 of Publications of V. -
Single Star – Sylvie D
ASTRONOMY AND ASTROPHYSICS – Single Star – Sylvie D. Vauclair and Gerard P. Vauclair SINGLE STARS Sylvie D. Vauclair Institut de Recherches en Astronomie et Planétologie, Université de Toulouse, Institut Universitaire de France, 14 avenue Edouard Belin, 31400 Toulouse, France Gérard P. Vauclair Institut de Recherches en Astronomie et Planétologie, Université de Toulouse, Centre National de la Recherche Scientifique, 14 avenue Edouard Belin, 31400 Toulouse, France Keywords: stars, stellar structure, stellar evolution, magnitudes, HR diagrams, asteroseismology, planetary nebulae, White Dwarfs, supernovae Contents 1. Introduction 2. Stellar observational data 2.1. Distances 2.1.1. Direct Methods 2.1.2. Indirect Methods 2.2. Stellar Luminosities 2.2.1. Apparent Magnitude 2.2.2. Absolute Magnitude 2.3. Surface Temperatures 2.3.1. Brightness Temperatures 2.3.2 Color Temperatures, Color Indices 2.3.3 Effective Temperatures 2.4 Stellar Spectroscopy 2.4.1. Spectral Types 2.4.2. Chemical Composition 2.4.3. Stellar Rotation and Magnetic Fields 2.6. Masses and Radii 3. Stellar structure and evolution 3.1. Color-Magnitude Diagrams 3.2. Stellar Structure 3.2.1. CharacteristicUNESCO Stellar Time Scales – EOLSS 3.2.2. The Basic Equations of the Stellar Structure 3.2.3. ApproximateSAMPLE Solutions CHAPTERS 3.3. Stellar Evolution 3.3.1. Stellar Evolutionary Codes 3.3.2. Stellar Evolution before the Main Sequence 3.3.3 The Main Sequence 3.3.4 Post Main Sequence Tracks 3.3.5 HR Diagrams of Stellar Clusters 3.4. Stars and Stellar Environment: Recent Developments 3.4.1 Atomic Diffusion 3.4.2 Rotation and Rotational Braking ©Encyclopedia of Life Support Systems (EOLSS) ASTRONOMY AND ASTROPHYSICS – Single Star – Sylvie D. -
Nanda Rea Institute for Space Science, CSIC-IEEC, Barcelona
Magnetar candidates: new discoveries open new questions Nanda Rea Institute for Space Science, CSIC-IEEC, Barcelona Image Credit: ESA - Christophe Carreau Isolated Neutron Stars: P-Pdot diagram 2 6 4 2 ⎛ 8 2R 6 ⎞ ˙ 2 2 2B R Ω sin α ˙ π ns 2 2 E rot = − m˙˙ = − PP = ⎜ 3 ⎟ B0 sin α 3c 3 3c 3 ⎝ 3c I ⎠ m 2c 3 B = e = 4.414 "1013Gauss Critical Electron Quantum B-field critic e! € Nanda Rea CSIC-IEEC € ! AXPs and SGRs general properties • bright X-ray pulsars Lx ~ 1033-1036 erg/s • strong soft and hard X-ray emission • rotating with periods of ~2-12s and period derivatives of ~10-11-10-13 s/s (Rea et al. 2007) • pulsed fractions ranging from ~5-70 % • magnetic fields of ~1014-1015 Gauss (Rea et al. 2004) (see Mereghetti 2008, A&AR, for a review) Nanda Rea CSIC-IEEC AXPs and SGRs general properties (Kaspi et al. 2003) Short bursts • the most common • they last ~0.1s • peak ~1041 ergs/s • soft γ-rays thermal spectra Intermediate bursts (Israel et al. 2008) • they last 1-40 s • peak ~1041-1043 ergs/s • abrupt on-set • usually soft γ-rays thermal spectra Giant Flares (Palmer et al. 2005) • their output of high energy is exceeded only by blazars and GRBs • peak energy > 3x1044 ergs/s • <1 s initial peak with a hard spectrum which rapidly become softer in the burst tail that can last > 500s, showing the NS spin pulsations. Nanda Rea CSIC-IEEC AXPs and SGRs general properties • transient outbursts lasting months-years • in a few cases radio pulsed emission was observed connected with X-ray outbursts, with variable flux and profiles, and flat spectra (Rea & Esposito 2010, APSS Springer Review) Nanda Rea CSIC-IEEC AXPs and SGRs general properties bursts/outbursts activity !""" &*$..+0$ (6$/&(.$ "-#$/+.)$ #2"$&,/'$ &*$&'(&$ !"" 425$/&//$ 425$&)(,$ !" 425$&,&($ "-#$&'/)$ "-#$/+/&$ "-#$&0//$ "-#$&'11$ &*$&/('$ ! '()*+,- 23*$&'&/$ "#! "-#$&).,$ !"#$%&'()$ !"#$&)..$ "#"! &*$&+(,$ !"ï& "#$! % $ !" %" ./0!"!1/23 Nanda Rea CSIC-IEEC Why magnetars behave differently from normal pulsars? • Their internal magnetic field is twisted up to 10 times the external dipole. -
A FEROS Survey of Hot Subdwarf Stars
Open Astron. 2018; 27: 7–13 Research Article Stéphane Vennes*, Péter Németh, and Adela Kawka A FEROS Survey of Hot Subdwarf Stars https://doi.org/10.1515/astro-2018-0005 Received Oct 02, 2017; accepted Nov 07, 2017 Abstract: We have completed a survey of twenty-two ultraviolet-selected hot subdwarfs using the Fiber-fed Extended Range Optical Spectrograph (FEROS) and the 2.2-m telescope at La Silla. The sample includes apparently single objects as well as hot subdwarfs paired with a bright, unresolved companion. The sample was extracted from our GALEX cat- alogue of hot subdwarf stars. We identified three new short-period systems (P = 3.5 hours to 5 days) and determined the orbital parameters of a long-period (P = 62d.66) sdO plus G III system. This particular system should evolve into a close double degenerate system following a second common envelope phase. We also conducted a chemical abundance study of the subdwarfs: Some objects show nitrogen and argon abundance excess with respect to oxygen. We present key results of this programme. Keywords: binaries: close, binaries: spectroscopic, subdwarfs, white dwarfs, ultraviolet: stars 1 Introduction ing a mass transfer event, i.e., comparable to the observed fraction (≈70%) of short period binaries (P < 10 d, Maxted et al. 2001; Morales-Rueda et al. 2003), while the remain- The properties of extreme horizontal branch (EHB) stars, ing single objects are formed by the merger of two helium i.e., the hot, hydrogen-rich (sdB) and helium-rich subd- white dwarfs which would also result in a thin hydrogen warf (sdO) stars, located at the faint blue end of the hori- layer. -
A Disintegrating Minor Planet Transiting a White Dwarf!
A Disintegrating Minor Planet Transiting a White Dwarf! Andrew Vanderburg1, John Asher Johnson1, Saul Rappaport2, Allyson Bieryla1, Jonathan Irwin1, John Arban Lewis1, David Kipping1,3, Warren R. Brown1, Patrick Dufour4, David R. Ciardi5, Ruth Angus1,6, Laura Schaefer1, David W. Latham1, David Charbonneau1, Charles Beichman5, Jason Eastman1, Nate McCrady7, Robert A. Wittenmyer8, & Jason T. Wright9,10. ! White dwarfs are the end state of most stars, including We initiated follow-up ground-based photometry to the Sun, after they exhaust their nuclear fuel. Between better time-resolve the transits seen in the K2 data (Figure 1/4 and 1/2 of white dwarfs have elements heavier than S1). We observed WD 1145+017 frequently over the course helium in their atmospheres1,2, even though these of about a month with the 1.2-meter telescope at the Fred L. elements should rapidly settle into the stellar interiors Whipple Observatory (FLWO) on Mt. Hopkins, Arizona; unless they are occasionally replenished3–5. The one of the 0.7-meter MINERVA telescopes, also at FLWO; abundance ratios of heavy elements in white dwarf and four of the eight 0.4-meter telescopes that compose the atmospheres are similar to rocky bodies in the Solar MEarth-South Array at Cerro Tololo Inter-American system6,7. This and the existence of warm dusty debris Observatory in Chile. Most of these data showed no disks8–13 around about 4% of white dwarfs14–16 suggest interesting or significant signals, but on two nights we that rocky debris from white dwarf progenitors’ observed deep (up to 40%), short-duration (5 minutes), planetary systems occasionally pollute the stars’ asymmetric transits separated by the dominant 4.5 hour atmospheres17. -
Gamma Ray Bursts, Their Afterglows, and Soft Gamma Repeaters
Gamma ray bursts, their afterglows, . and soft gamma repeaters G.S.Bisnovatyi-Kogan IKI RAS, Moscow GRB Workshop 2012 Moscow University June 14 Estimations Central GRB machne Afterglow SGR Nuclear model of SGR Neutron stars are the result of collapse . Conservation of the magnetic flux 2 B(ns)=B(s) (Rs /Rns ) B(s)=10 – 100 Gs, R ~ (3 – 10) R( Sun ), R =10 km s ns B(ns) = 4 10 11– 5 10 13 Gs Ginzburg (1964) Radiopulsars E = AB2 Ω 4 - magnetic dipole radiation (pulsar wind) 2 E = 0.5 I Ω I – moment of inertia of the neutron star 2 B = IPP/4 π A Single radiopulsars – timing observations (the most rapid ones are connected with young supernovae remnants) 11 13 B(ns) = 2 10 – 5 10 Gs Neutron star formation N.V.Ardeljan, G.S.Bisnovatyi-Kogan, S.G.Moiseenko MNRAS, 4E+51 Ekinpol 2005, 359 , 333 . E 3.5E+51 rot Emagpol Emagtor 3E+51 2.5E+51 2E+51 B(chaotic) ~ 10^14 Gs 1.5E+51 1E+51 High residual chaotic 5E+50 magnetic field after MRE core collapse SN explosion. 0 0.1 0.2 0.3 0.4 0.5 Heat production during time,sec Ohmic damping of the chaotic magnetic field may influence NS cooling light curve Inner region: development of magnetorotational instability (MRI) TIME= 34.83616590 ( 1.20326837sec ) TIME= 35.08302173 ( 1.21179496sec ) 0 .0 1 4 0 .0 1 4 0 .0 1 3 0 .0 1 3 0 .0 1 2 0 .0 1 2 0 .0 1 1 0 .0 1 1 0 .0 1 0 .0 1 0 .0 0 9 0 .0 0 9 Z 0 .0 0 8 0Z .0 0 8 0 .0 0 7 0 .0 0 7 0 .0 0 6 0 .0 0 6 0 .0 0 5 0 .0 0 5 0 .0 0 4 0 .0 0 4 0 .0 0 3 0 .0 0 3 0 .0 0 2 0 .0 0 2 0 .0 1 0 .0 1 5 0 .0 2 0 .0 1 0 .0 1 5 0 .0 2 R R TIME= 35.26651529 ( 1.21813298sec ) TIME=