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Academic Reading in Science Copyright 2014 © Chris Elvin Copyright Notice
Academic Reading in Science Copyright 2014 © Chris Elvin Copyright Notice Academic Reading in Science contains adaptations of Wikipedia copyrighted material. All pages containing these adaptations can be identified by the logo below; This logo is visible at the foot of every page in which Wikipedia articles have been adapted. Furthermore, all adaptations of Wikipedia sources show a URL at the foot of the article which you may use to access the original article. Pages which do not show the logo above are the copyright of the author Chris Elvin, and may not be used without permission. Creative Commons Deed You are free: to Share—to copy, distribute and transmit the work, and to Remix—to adapt the work Under the following conditions: Attribution—You must attribute the work in the manner specified by the author or licensor (but not in any way that suggests that they endorse you or your use of the work.) Share Alike—If you alter, transform, or build upon this work, you may distribute the resulting work only under the same, similar or a compatible license. With the understanding that: Waiver—Any of the above conditions can be waived if you get permission from the copyright holder. Other Rights—In no way are any of the following rights affected by the license: your fair dealing or fair use rights; the author’s moral rights; and rights other persons may have either in the work itself or in how the work is used, such as publicity or privacy rights. Notice—For any reuse or distribution, you must make clear to others the license terms of this work. -
The Star Newsletter
THE HOT STAR NEWSLETTER ? An electronic publication dedicated to A, B, O, Of, LBV and Wolf-Rayet stars and related phenomena in galaxies No. 25 December 1996 http://webhead.com/∼sergio/hot/ editor: Philippe Eenens http://www.inaoep.mx/∼eenens/hot/ [email protected] http://www.star.ucl.ac.uk/∼hsn/index.html Contents of this Newsletter Abstracts of 6 accepted papers . 1 Abstracts of 2 submitted papers . .4 Abstracts of 3 proceedings papers . 6 Abstract of 1 dissertation thesis . 7 Book .......................................................................8 Meeting .....................................................................8 Accepted Papers The Mass-Loss History of the Symbiotic Nova RR Tel Harry Nussbaumer and Thomas Dumm Institute of Astronomy, ETH-Zentrum, CH-8092 Z¨urich, Switzerland Mass loss in symbiotic novae is of interest to the theory of nova-like events as well as to the question whether symbiotic novae could be precursors of type Ia supernovae. RR Tel began its outburst in 1944. It spent five years in an extended state with no mass-loss before slowly shrinking and increasing its effective temperature. This transition was accompanied by strong mass-loss which decreased after 1960. IUE and HST high resolution spectra from 1978 to 1995 show no trace of mass-loss. Since 1978 the total luminosity has been decreasing at approximately constant effective temperature. During the present outburst the white dwarf in RR Tel will have lost much less matter than it accumulated before outburst. - The 1995 continuum at λ ∼< 1400 is compatible with a hot star of T = 140 000 K, R = 0.105 R , and L = 3700 L . Accepted by Astronomy & Astrophysics Preprints from [email protected] 1 New perceptions on the S Dor phenomenon and the micro variations of five Luminous Blue Variables (LBVs) A.M. -
Accretion Flows in Nonmagnetic White Dwarf Binaries As Observed in X-Rays
Accretion Flows in Nonmagnetic White Dwarf Binaries as Observed in X-rays Şölen Balmana,< aKadir Has University, Faculty of Engineering and Natural Sciences, Cibali 34083, Istanbul, Turkey ARTICLEINFO ABSTRACT Keywords: Cataclysmic Variables (CVs) are compact binaries with white dwarf (WD) primaries. CVs and other cataclysmic variables - accretion, accre- accreting WD binaries (AWBs) are useful laboratories for studying accretion flows, gas dynamics, tion disks - thermal emission - non-thermal outflows, transient outbursts, and explosive nuclear burning under different astrophysical plasma con- emission - white dwarfs - X-rays: bina- ditions. They have been studied over decades and are important for population studies of galactic ries X-ray sources. Recent space- and ground-based high resolution spectral and timing studies, along with recent surveys indicate that we still have observational and theoretical complexities yet to an- swer. I review accretion in nonmagnetic AWBs in the light of X-ray observations. I present X-ray diagnostics of accretion in dwarf novae and the disk outbursts, the nova-like systems, and the state of the research on the disk winds and outflows in the nonmagnetic CVs together with comparisons and relations to classical and recurrent nova systems, AM CVns and Symbiotic systems. I discuss how the advective hot accretion flows (ADAF-like) in the inner regions of accretion disks (merged with boundary layer zones) in nonmagnetic CVs explain most of the discrepancies and complexities that have been encountered in the X-ray observations. I stress how flickering variability studies from optical to X-rays can be probes to determine accretion history and disk structure together with how the temporal and spectral variability of CVs are related to that of LMXBs and AGNs. -
Winter Constellations
Winter Constellations *Orion *Canis Major *Monoceros *Canis Minor *Gemini *Auriga *Taurus *Eradinus *Lepus *Monoceros *Cancer *Lynx *Ursa Major *Ursa Minor *Draco *Camelopardalis *Cassiopeia *Cepheus *Andromeda *Perseus *Lacerta *Pegasus *Triangulum *Aries *Pisces *Cetus *Leo (rising) *Hydra (rising) *Canes Venatici (rising) Orion--Myth: Orion, the great hunter. In one myth, Orion boasted he would kill all the wild animals on the earth. But, the earth goddess Gaia, who was the protector of all animals, produced a gigantic scorpion, whose body was so heavily encased that Orion was unable to pierce through the armour, and was himself stung to death. His companion Artemis was greatly saddened and arranged for Orion to be immortalised among the stars. Scorpius, the scorpion, was placed on the opposite side of the sky so that Orion would never be hurt by it again. To this day, Orion is never seen in the sky at the same time as Scorpius. DSO’s ● ***M42 “Orion Nebula” (Neb) with Trapezium A stellar nursery where new stars are being born, perhaps a thousand stars. These are immense clouds of interstellar gas and dust collapse inward to form stars, mainly of ionized hydrogen which gives off the red glow so dominant, and also ionized greenish oxygen gas. The youngest stars may be less than 300,000 years old, even as young as 10,000 years old (compared to the Sun, 4.6 billion years old). 1300 ly. 1 ● *M43--(Neb) “De Marin’s Nebula” The star-forming “comma-shaped” region connected to the Orion Nebula. ● *M78--(Neb) Hard to see. A star-forming region connected to the Orion Nebula. -
New Herbig±Haro Objects and Giant Outflows in Orion
Mon. Not. R. Astron. Soc. 310, 331±354 (1999) New Herbig±Haro objects and giant outflows in Orion S. L. Mader,1 W. J. Zealey,1 Q. A. Parker2 and M. R. W. Masheder3,4 1Department of Engineering Physics, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia 2Anglo-Australian Observatory, Coonabarabran, NSW 2357, Australia 3Department of Physics, University of Bristol, Bristol BS8 1TL 4Netherlands Foundation for Research in Astronomy, PO Box 2, 7990 AA Dwingeloo, the Netherlands Accepted 1999 June 29. Received 1999 May 11; in original form 1998 June 25 ABSTRACT We present the results of a photographic and CCD imaging survey for Herbig±Haro (HH) objects in the L1630 and L1641 giant molecular clouds in Orion. The new HH flows were initially identified from a deep Ha film from the recently commissioned AAO/UKST Ha Survey of the southern sky. Our scanned Ha and broad-band R images highlight both the improved resolution of the Ha survey and the excellent contrast of the Ha flux with respect to the broad-band R. Comparative IVN survey images allow us to distinguish between emission and reflection nebulosity. Our CCD Ha,[Sii], continuum and I-band images confirm the presence of a parsec-scale HH flow associated with the Ori I-2 cometary globule, and several parsec-scale strings of HH emission centred on the L1641-N infrared cluster. Several smaller outflows display one-sided jets. Our results indicate that, for declinations south of 268 in L1641, parsec-scale flows appear to be the major force in the large-scale movement of optical dust and molecular gas. -
1983Apj. . .273. .280K the Astrophysical Journal, 273:280-288, 1983 October 1 © 1983. the American Astronomical Society. All Ri
.280K .273. The Astrophysical Journal, 273:280-288, 1983 October 1 . © 1983. The American Astronomical Society. All rights reserved. Printed in U.S.A. 1983ApJ. THE OUTBURSTS OF SYMBIOTIC NOVAE1 Scott J. Kenyon and James W. Truran Department of Astronomy, University of Illinois Received 1982 December 21 ; accepted 1983 March 9 ABSTRACT We discuss possible conditions under which thermonuclear burning episodes in the hydrogen-rich envelopes of accreting white dwarfs give rise to outbursts similar in nature to those observed in the symbiotic stars AG Peg, RT Ser, RR Tel, AS 239, V1016 Cyg, V1329 Cyg, and HM Sge. In principle, thermonuclear runaways involving low-luminosity white dwarfs accreting matter at low rates produce configurations that evolve into A-F supergiants at maximum visual light and which resemble the outbursts of RR Tel, RT Ser, and AG Peg. Very weak, nondegenerate hydrogen 8 -1 shell flashes on white dwarfs accreting matter at high rates (M > 10" M0 yr ) do not produce cool supergiants at maximum, and may explain the outbursts in V1016 Cyg, V1329 Cyg, and HM Sge. The low accretion rates demanded for systems developing strong hydrogen shell flashes on low-luminosity white dwarfs are not compatible with observations of “normal” quiescent symbiotic stars. The extremely slow outbursts of symbiotic novae appear to be typical of accreting white dwarfs in wide binaries, which suggests that the outbursts of classical novae may be accelerated by the interaction of the expanding white dwarf envelope with its close binary companion. Subject headings: stars: accretion — stars: combination spectra — stars: novae — stars: white dwarfs I. -
Wynyard Planetarium & Observatory a Autumn Observing Notes
Wynyard Planetarium & Observatory A Autumn Observing Notes Wynyard Planetarium & Observatory PUBLIC OBSERVING – Autumn Tour of the Sky with the Naked Eye CASSIOPEIA Look for the ‘W’ 4 shape 3 Polaris URSA MINOR Notice how the constellations swing around Polaris during the night Pherkad Kochab Is Kochab orange compared 2 to Polaris? Pointers Is Dubhe Dubhe yellowish compared to Merak? 1 Merak THE PLOUGH Figure 1: Sketch of the northern sky in autumn. © Rob Peeling, CaDAS, 2007 version 1.2 Wynyard Planetarium & Observatory PUBLIC OBSERVING – Autumn North 1. On leaving the planetarium, turn around and look northwards over the roof of the building. Close to the horizon is a group of stars like the outline of a saucepan with the handle stretching to your left. This is the Plough (also called the Big Dipper) and is part of the constellation Ursa Major, the Great Bear. The two right-hand stars are called the Pointers. Can you tell that the higher of the two, Dubhe is slightly yellowish compared to the lower, Merak? Check with binoculars. Not all stars are white. The colour shows that Dubhe is cooler than Merak in the same way that red-hot is cooler than white- hot. 2. Use the Pointers to guide you upwards to the next bright star. This is Polaris, the Pole (or North) Star. Note that it is not the brightest star in the sky, a common misconception. Below and to the left are two prominent but fainter stars. These are Kochab and Pherkad, the Guardians of the Pole. Look carefully and you will notice that Kochab is slightly orange when compared to Polaris. -
Annual Report 2017
Koninklijke Sterrenwacht van België Observatoire royal de Belgique Royal Observatory of Belgium Jaarverslag 2017 Rapport Annuel 2017 Annual Report 2017 Cover illustration: Above: One billion star map of our galaxy created with the optical telescope of the satellite Gaia (Credit: ESA/Gaia/DPAC). Below: Three armillary spheres designed by Jérôme de Lalande in 1775. Left: the spherical sphere; in the centre: the geocentric model of our solar system (with the Earth in the centre); right: the heliocentric model of our solar system (with the Sun in the centre). Royal Observatory of Belgium - Annual Report 2017 2 De activiteiten beschreven in dit verslag werden ondersteund door Les activités décrites dans ce rapport ont été soutenues par The activities described in this report were supported by De POD Wetenschapsbeleid De Nationale Loterij Le SPP Politique Scientifique La Loterie Nationale The Belgian Science Policy The National Lottery Het Europees Ruimtevaartagentschap De Europese Gemeenschap L’Agence Spatiale Européenne La Communauté Européenne The European Space Agency The European Community Het Fonds voor Wetenschappelijk Onderzoek – Le Fonds de la Recherche Scientifique Vlaanderen Royal Observatory of Belgium - Annual Report 2017 3 Table of contents Preface .................................................................................................................................................... 6 Reference Systems and Planetology ...................................................................................................... -
A Basic Requirement for Studying the Heavens Is Determining Where In
Abasic requirement for studying the heavens is determining where in the sky things are. To specify sky positions, astronomers have developed several coordinate systems. Each uses a coordinate grid projected on to the celestial sphere, in analogy to the geographic coordinate system used on the surface of the Earth. The coordinate systems differ only in their choice of the fundamental plane, which divides the sky into two equal hemispheres along a great circle (the fundamental plane of the geographic system is the Earth's equator) . Each coordinate system is named for its choice of fundamental plane. The equatorial coordinate system is probably the most widely used celestial coordinate system. It is also the one most closely related to the geographic coordinate system, because they use the same fun damental plane and the same poles. The projection of the Earth's equator onto the celestial sphere is called the celestial equator. Similarly, projecting the geographic poles on to the celest ial sphere defines the north and south celestial poles. However, there is an important difference between the equatorial and geographic coordinate systems: the geographic system is fixed to the Earth; it rotates as the Earth does . The equatorial system is fixed to the stars, so it appears to rotate across the sky with the stars, but of course it's really the Earth rotating under the fixed sky. The latitudinal (latitude-like) angle of the equatorial system is called declination (Dec for short) . It measures the angle of an object above or below the celestial equator. The longitud inal angle is called the right ascension (RA for short). -
Evolution of Star Clusters in Time-Variable Tidal Fields
Evolution of Star Clusters in Time-Variable Tidal Fields A Thesis Submitted to the Faculty of Drexel University by Ernest N. Mamikonyan in partial fulfillment of the requirement for the degree of Doctor of Philosophy December 12, 2013 Contents 1 Introduction 1 1.1 TypesofStarClusters............................ 2 1.1.1 GlobularClusters .......................... 3 1.1.2 OpenClusters............................ 4 1.2 Mass Function: From Young to Globular . 5 2 Arbitrary Tidal Acceleration 8 2.1 ApproximatingTidalEffects. 9 2.1.1 Tidal Acceleration Tensor . 10 2.2 Stellar Dynamics with KIRA ........................ 11 2.2.1 CircularOrbitinPoint-MassPotential . 14 2.3 GalaxyMergerSimulations . 16 2.3.1 TidalHistories............................ 19 2.4 N-BodySimulations ............................ 24 2.4.1 N-BodyUnits ............................ 26 2.4.2 Scaling ................................ 26 3 Mass Loss Model 30 i 3.1 Accelerated Two-Body Relaxation . 30 3.2 FluctuationsintheJacobiRadius. 34 3.3 Results .................................... 36 3.4 Discussion.................................. 37 3.4.1 Limitations ............................. 40 4 Globular Cluster Mass Functions 44 4.1 MassFunctionEvolution . 47 4.2 Results .................................... 48 4.2.1 SinkParticles ............................ 48 4.2.2 DiskParticles ............................ 50 4.2.3 HaloParticles ............................ 55 5 Conclusions and Future Work 57 Appendix A Implementation of Tidal Fields in KIRA 63 Appendix B Computing Tidal Acceleration from GADGET Output 66 ii List of Figures 1.1 Infrared image of the globular cluster Omega Centauri. It is the most massive cluster in the Galaxy and thought to be a remnant of a dwarf galaxy absorbed by the Milky Way. (NASA/JPL-Caltech/ NOAO/AURA/NSF)............................. 3 1.2 The Pleiades open cluster in the infrared. It is one of the most well- known and spectacular objects in the Galaxy. -
Technion, Israel Abstract
JETS before, during, and after explosions and in powering intermediate luminosity optical transients (ILOTs) Noam Soker Technion, Israel Abstract I will describe recent results on the role of JETS in exploding core collapse supernovae (CCSNe) and in powering Intermediate Luminosity Optical Transients (ILOTs), and will compare the results with the most recent observations and with other theoretical studies. I will discuss new ideas of processes that become possible by jets, such as the jittering jets explosion mechanism of massive stars aided by neutrino heating, the formation of Type IIb CCSNe by the Grazing Envelope Evolution (GEE), and common envelope jets supernovae (CEJSNe). 1. Introduction JETS 2. Jets Before 2.1 Jets shape pre-explosion circumstellar matter Similar outer rings in SN 1987A and in the planetary nebula jet jet SN 1987A 19987A Broken inner ring in SN 1987A and in the Necklace planetary nebulae jet Necklace planetary nebula In both planetary nebulae there is a binary system at jet (Corradi et al. 2011) the center. The compact companion launches the SN 1987A jets as it accretes mass from the giant progenitor. 2.2 Jets launched by a companion power pre-explosion outbursts Can be a main sequence companion as in the Great Eruption of Eta Carinae (Kashi, A. & Soker, N. in several papers). Can be a neutron star that enters the envelope (Gilkis, A., Kashi, A., Soker, N. 2019), or that accretes from the inflated envelope (Danieli, B. & Soker, N. 2019) 2.3 Type IIb supernovae by the grazing envelope evolution Jet-driven mass loss prevents common envelope and leads to the formation of a Type IIb supernova. -
197 6Apjs. . .30. .451H the Astrophysical Journal Supplement Series, 30:451-490, 1976 April © 1976. the American Astronomical S
.451H The Astrophysical Journal Supplement Series, 30:451-490, 1976 April .30. © 1976. The American Astronomical Society. All rights reserved. Printed in U.S.A. 6ApJS. 197 EVOLVED STARS IN OPEN CLUSTERS Gretchen L. H. Harris* David Dunlap Observatory, Richmond Hill, Ontario Received 1974 September 16; revised 1975 June 18 ABSTRACT Radial-velocity observations and MK classifications have been used to study evolved stars in 25 open clusters. Published data on stars in 72 additional clusters are rediscussed and com- bined with the observations friade in this investigation to yield positions in the Hertzsprung- Russell diagram for 559 evolved stars in 97 clusters. Ages for the parent clusters were estimated from the main-sequence turnoff points, earliest spectral types, and bluest stars in the clusters themselves. The evolved stars were sorted into six age groups ranging from 4 x 106 yr to 4 x 108 yr, and the composite H-R diagram for each age group was then used to study the evolutionary tracks for stars of various masses. The observational results were found to be in reasonably good agreement with recent theoretical computations. The composite color-magnitude diagrams were found to be strikingly different from those of the rich open clusters in the Magellanic Clouds. At a given age the red giants in the Small Magellanic Cloud and the Large Magellanic Cloud clusters are brighter and bluer than their galactic counterparts. It is suggested that these effects may be accounted for by differences in metal abundance. Subject headings: clusters: open — galaxies: Magellanic Clouds — radial velocities — stars : evolution — stars : late-type — stars : spectral classification 1.