Annual Report 1999
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The Son of Lamoraal Ulbo De Sitter, a Judge, and Catharine Theodore Wilhelmine Bertling
558 BIOGRAPHIES v.i WiLLEM DE SITTER viT 1872-1934 De Sitter was bom on 6 May 1872 in Sneek (province of Friesland), the son of Lamoraal Ulbo de Sitter, a judge, and Catharine Theodore Wilhelmine Bertling. His father became presiding judge of the court in Arnhem, and that is where De Sitter attended gymna sium. At the University of Groniiigen he first studied mathematics and physics and then switched to astronomy under Jacobus Kapteyn. De Sitter spent two years observing and studying under David Gill at the Cape Obsen'atory, the obseivatory with which Kapteyn was co operating on the Cape Photographic Durchmusterung. De Sitter participated in the program to make precise measurements of the positions of the Galilean moons of Jupiter, using a heliometer. In 1901 he received his doctorate under Kapteyn on a dissertation on Jupiter's satellites: Discussion of Heliometer Observations of Jupiter's Satel lites. De Sitter remained at Groningen as an assistant to Kapteyn in the astronomical laboratory, until 1909, when he was appointed to the chair of astronomy at the University of Leiden. In 1919 he be came director of the Leiden Observatory. He remained in these posts until his death in 1934. De Sitter's work was highly mathematical. With his work on Jupi ter's satellites, De Sitter pursued the new methods of celestial me chanics of Poincare and Tisserand. His earlier heliometer meas urements were later supplemented by photographic measurements made at the Cape, Johannesburg, Pulkowa, Greenwich, and Leiden. De Sitter's final results on this subject were published as 'New Math ematical Theory of Jupiter's Satellites' in 1925. -
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. -
Photo-Ionization Models of NGC 2363 and Their Implications
Wolf-Rayet Phenomena in Massive Stars and Starburst Galaxies Proceedings IAU Symposium No. 193, @1999 IAU K.A. van der Hucht, G. Koenigsberger f3 P.R.J. Eenens, eds. Photo-ionization models of NGC 2363 and their implications Valentina Luridiana and Manuel Peimbert Instituto de Astronomic, UNAM, Mexico Claus Leitherer Space Telescope Science Institute, Baltimore, MD, USA. Abstract. We compute photo-ionization models for the giant extragalactic H II region NGC 2363, and compare them with optical observational data. We focus on the following observational constraints: F(Hj3), Ni; EW(Hj3), and the ratios of I(A 5007), I(A 4363), I(A 3727), I(A 6300), I(A 6720) and I(A 4686) rel- ative to I(Hj3). We discuss the variations of the emission spectra obtained with different input parameters. We show that low metallicity models (Z == 0.10 Zev) cannot reproduce the observed features of the spectrum, and that the disagree- ment can be satisfactorily overcome by allowing for spatial temperature fluctu- ations in the nebula. Accordingly, we show that the metallicity of NGC 2363 has most probably been underestimated, and that a value of Z ~ 0.25 Zev is in better agreement with the observational data than the usually adopted value Z ~ 0.10 Zev. We also derive values for the slope and the high mass end of the IMF, as well as the age of the stellar cluster. 1. Introduction NGC 2363 is a very luminous giant H II region, located in the south-west end of the irregular galaxy NGC 2366. It is one of the brightest extragalactic H II re- 6 gions known, with an estimated mass of about 2.2 x 10 M0 (Carigi & Peimbert 1999). -
Publications for Geraint Lewis 2021 2020
Publications for Geraint Lewis 2021 R., Horner, J., Wright, D., Carter, B., Morton, T., Spina, L., Li, T., Koposov, S., Erkal, D., Ji, A., Shipp, N., Hilmi, T., Bland-Hawthorn, J., Hayden, M., Lewis, G., Sharma, S., Kuehn, K., Pace, A., Lewis, G., Mackey, D., Wan, Z., Bland- Simpson, J., et al (2021). The GALAH Survey: Using galactic Hawthorn, J., Sharma, S., et al (2021). Broken into pieces: archaeology to refine our knowledge of TESS target stars. ATLAS and Aliqa Uma as one single stream. The Astrophysical Monthly Notices of the Royal Astronomical Society, 504(4), Journal, 911(2), 149. <a href="http://dx.doi.org/10.3847/1538- 4968-4989. <a 4357/abeb18">[More Information]</a> href="http://dx.doi.org/10.1093/mnras/stab1052">[More Information]</a> Sharma, S., Hayden, M., Bland-Hawthorn, J., Stello, D., Buder, S., Zinn, J., Kallinger, T., Asplund, M., De Silva, G., D'Orazi, Oliver, W., Elahi, P., Lewis, G., Power, C. (2021). The V., Kos, J., Lewis, G., Lin, J., Zucker, D., Chen, B., Huber, D., hierarchical structure of galactic haloes: Classification and Kafle, P., Khanna, S., et al (2021). Fundamental relations for characterization with halo-optics. Monthly Notices of the Royal the velocity dispersion of stars in the Milky Way. Monthly Astronomical Society, 501(3), 4420-4437. <a Notices of the Royal Astronomical Society, 506(2), 1761-1776. href="http://dx.doi.org/10.1093/mnras/staa3879">[More <a href="http://dx.doi.org/10.1093/mnras/stab1086">[More Information]</a> Information]</a> Arentsen, A., Starkenburg, E., Aguado, D., Martin, N., Placco, Wiseman, P., Sullivan, M., Smith, M., Frohmaier, C., Vincenzi, V., Carlberg, R., Gonz�lez Hern�ndez, J., Hill, V., M., Graur, O., Popovic, B., Armstrong, P., Brout, D., Davis, T., Jablonka, P., Kordopatis, G., Lewis, G., Wan, Z., et al (2021). -
Exploration of the Moon
Exploration of the Moon The physical exploration of the Moon began when Luna 2, a space probe launched by the Soviet Union, made an impact on the surface of the Moon on September 14, 1959. Prior to that the only available means of exploration had been observation from Earth. The invention of the optical telescope brought about the first leap in the quality of lunar observations. Galileo Galilei is generally credited as the first person to use a telescope for astronomical purposes; having made his own telescope in 1609, the mountains and craters on the lunar surface were among his first observations using it. NASA's Apollo program was the first, and to date only, mission to successfully land humans on the Moon, which it did six times. The first landing took place in 1969, when astronauts placed scientific instruments and returnedlunar samples to Earth. Apollo 12 Lunar Module Intrepid prepares to descend towards the surface of the Moon. NASA photo. Contents Early history Space race Recent exploration Plans Past and future lunar missions See also References External links Early history The ancient Greek philosopher Anaxagoras (d. 428 BC) reasoned that the Sun and Moon were both giant spherical rocks, and that the latter reflected the light of the former. His non-religious view of the heavens was one cause for his imprisonment and eventual exile.[1] In his little book On the Face in the Moon's Orb, Plutarch suggested that the Moon had deep recesses in which the light of the Sun did not reach and that the spots are nothing but the shadows of rivers or deep chasms. -
Radio and Millimeter Continuum Surveys and Their Astrophysical Implications
The Astronomy and Astrophysics Review (2011) DOI 10.1007/s00159-009-0026-0 REVIEWARTICLE Gianfranco De Zotti · Marcella Massardi · Mattia Negrello · Jasper Wall Radio and millimeter continuum surveys and their astrophysical implications Received: 13 May 2009 c Springer-Verlag 2009 Abstract We review the statistical properties of the main populations of radio sources, as emerging from radio and millimeter sky surveys. Recent determina- tions of local luminosity functions are presented and compared with earlier esti- mates still in widespread use. A number of unresolved issues are discussed. These include: the (possibly luminosity-dependent) decline of source space densities at high redshifts; the possible dichotomies between evolutionary properties of low- versus high-luminosity and of flat- versus steep-spectrum AGN-powered radio sources; and the nature of sources accounting for the upturn of source counts at sub-milli-Jansky (mJy) levels. It is shown that straightforward extrapolations of evolutionary models, accounting for both the far-IR counts and redshift distribu- tions of star-forming galaxies, match the radio source counts at flux-density levels of tens of µJy remarkably well. We consider the statistical properties of rare but physically very interesting classes of sources, such as GHz Peak Spectrum and ADAF/ADIOS sources, and radio afterglows of γ-ray bursts. We also discuss the exploitation of large-area radio surveys to investigate large-scale structure through studies of clustering and the Integrated Sachs–Wolfe effect. Finally, we briefly describe the potential of the new and forthcoming generations of radio telescopes. A compendium of source counts at different frequencies is given in Supplemen- tary Material. -
Astronomer Explores Universe Through Remote-Controlled Telescope 24 May 2016
Astronomer explores universe through remote-controlled telescope 24 May 2016 and bring his students into his research. The telescope is in the Western Europe time zone, which is six hours head of U.S. Central Time. "Because of the time difference, students can see in the afternoon what they'd have to wait until midnight to see here," Keel said. "This opens up new possibilities for classroom experiences in our daytime, as well as making it easier to use the telescope without changing a whole day's schedule." In April and May, Keel took some photos using the reopened telescope, including shots of the globular star cluster M3 in Canes Venatici (the constellation of the Hunting Dogs just south of the Big Dipper) and the planetary nebula M27 (the Dumbbell Nebula) in Vulpecula (the Fox, in the summer Milky Way). Eagle Nebula M16. Taken by Dr. William Keel with the Jacobus Kapteyn Telescope. Access by the astronomers at The University of Alabama to the Jacobus Kapteyn Telescope in the Canary Islands will benefit both research and students at UA. Dr. William Keel, UA professor of astronomy and astrophysics, represents UA on the managing board of a 12-institution consortium called the Southeastern Association for Research in Astronomy. He recently obtained some of the first data with the recently reopened Jacobus Kapteyn Telescope through SARA, which operates the telescope. The 1.0-meter telescope is at an altitude of 2,360 meters at the Observatorio del Roque de los Spiral galaxy M83. Taken by Dr. William Keel with the Muchachos on the Spanish Canary Island of La Jacobus Kapteyn Telescope. -
Chandra LETGS Observation of the Variable NLS1 Galaxy Ark 564⋆
A&A 551, A95 (2013) Astronomy DOI: 10.1051/0004-6361/201220424 & c ESO 2013 Astrophysics Chandra LETGS observation of the variable NLS1 galaxy Ark 564 J. M. Ramírez Centro de Física, Instituto Venezolano de Investigaciones Científicas (IVIC), PO Box 025304, Caracas 1020A, Venezuela e-mail: [email protected] Received 21 September 2012 / Accepted 18 January 2013 ABSTRACT We present an analysis of the 100 ks X-ray spectrum of the narrow-line Seyfert 1 Galaxy Ark 564, taken with the Low Energy Transmission Grating Spectrometer (LETGS) on board Chandra.Usingχ2 statistics, several continuum models of the time-averaged spectrum of this object are compared, obtaining a semi-empirical solution for the description of the intrinsic emission continuum and a physical solution for the intrinsic absorption of the system. We find that the 0.1−10 keV spectrum can be well described by a power law plus two thermal components that account for the soft step. We are also able to detect and measure several narrow, unresolved absorption lines arising from highly ionized species of C, N, O, and Fe. The material seems to have a velocity consistent with the 20 −2 systemic velocity of the galaxy. This piece of evidence, in addition to the very low observed column density of NH ∼ 10 cm ,isin good agreement with the scenario of a transverse biconical outflow with a gas density of n 3 × 1012 cm−3 at distances beyond the broad-line region r 10 lt-days, but a dust torus origin cannot be ruled out. Key words. galaxies: Seyfert – line: identification – quasars: absorption lines 1. -
Planets Asteroids Comets the Jacobus Kapteyn Telescope Meteors
Planets A planet is an astronomical body in orbit The Solar System around the Sun, or another star, which has a mass too small for it to become a star itself (less than about one-twentieth the mass of the Sun) and shines only by reflected light. Planets may be basically rocky objects, such as the The Sun, together with the planets and moons, comets, asteroids, meteoroid inner planets - Mercury, Venus, Earth and streams and interplanetary medium held captive by the Sun’s gravitational Mars - or primarily gaseous, with a small solid attraction. The solar system is presumed to have formed from a rotating disc of core like the outer planets - Jupiter, Saturn, gas and dust created around the Sun as it contracted to form a star, about five Uranus and Neptune. Together with Pluto, billion years ago. The planets and asteroids all travel around the Sun in the these are the major planets of the Solar same direction as the Earth, in orbits close to the plane of the Earth’s orbit and System. the Sun’s equator. The planetary orbits lie within 40 astronomical units (6 thousand million kilometres) of the Sun, though the Sun’s sphere of Asteroids gravitational influence can be considered to be much greater. Comets seen in the inner solar system may originate in the Oort cloud, many thousands of astronomical units away. Comets Comets are icy bodies orbiting in the Solar System, which partially vaporises when it nears the Sun, developing a diffuse envelope of dust and gas and, normally, one or more tails. -
Guide Du Ciel Profond
Guide du ciel profond Olivier PETIT 8 mai 2004 2 Introduction hjjdfhgf ghjfghfd fg hdfjgdf gfdhfdk dfkgfd fghfkg fdkg fhdkg fkg kfghfhk Table des mati`eres I Objets par constellation 21 1 Androm`ede (And) Andromeda 23 1.1 Messier 31 (La grande Galaxie d'Androm`ede) . 25 1.2 Messier 32 . 27 1.3 Messier 110 . 29 1.4 NGC 404 . 31 1.5 NGC 752 . 33 1.6 NGC 891 . 35 1.7 NGC 7640 . 37 1.8 NGC 7662 (La boule de neige bleue) . 39 2 La Machine pneumatique (Ant) Antlia 41 2.1 NGC 2997 . 43 3 le Verseau (Aqr) Aquarius 45 3.1 Messier 2 . 47 3.2 Messier 72 . 49 3.3 Messier 73 . 51 3.4 NGC 7009 (La n¶ebuleuse Saturne) . 53 3.5 NGC 7293 (La n¶ebuleuse de l'h¶elice) . 56 3.6 NGC 7492 . 58 3.7 NGC 7606 . 60 3.8 Cederblad 211 (N¶ebuleuse de R Aquarii) . 62 4 l'Aigle (Aql) Aquila 63 4.1 NGC 6709 . 65 4.2 NGC 6741 . 67 4.3 NGC 6751 (La n¶ebuleuse de l’œil flou) . 69 4.4 NGC 6760 . 71 4.5 NGC 6781 (Le nid de l'Aigle ) . 73 TABLE DES MATIERES` 5 4.6 NGC 6790 . 75 4.7 NGC 6804 . 77 4.8 Barnard 142-143 (La tani`ere noire) . 79 5 le B¶elier (Ari) Aries 81 5.1 NGC 772 . 83 6 le Cocher (Aur) Auriga 85 6.1 Messier 36 . 87 6.2 Messier 37 . 89 6.3 Messier 38 . -
Arxiv:1704.01678V2 [Astro-Ph.GA] 28 Jul 2017 Been Notoriously Difficult, Resulting Mostly in Upper Lim- Highest Escape Fractions Measured to Date Among Low- Its (E.G
Submitted: 3 March 2017 Preprint typeset using LATEX style AASTeX6 v. 1.0 MRK 71 / NGC 2366: THE NEAREST GREEN PEA ANALOG Genoveva Micheva1, M. S. Oey1, Anne E. Jaskot2, and Bethan L. James3 (Accepted 24 July 2017) 1University of Michigan, 311 West Hall, 1085 S. University Ave, Ann Arbor, MI 48109-1107, USA 2Department of Astronomy, Smith College, Northampton, MA 01063, USA 3STScI, 3700 San Martin Drive, Baltimore, MD 21218, USA ABSTRACT We present the remarkable discovery that the dwarf irregular galaxy NGC 2366 is an excellent analog of the Green Pea (GP) galaxies, which are characterized by extremely high ionization parameters. The similarities are driven predominantly by the giant H II region Markarian 71 (Mrk 71). We compare the system with GPs in terms of morphology, excitation properties, specific star-formation rate, kinematics, absorption of low-ionization species, reddening, and chemical abundance, and find consistencies throughout. Since extreme GPs are associated with both candidate and confirmed Lyman continuum (LyC) emitters, Mrk 71/NGC 2366 is thus also a good candidate for LyC escape. The spatially resolved data for this object show a superbubble blowout generated by mechanical feedback from one of its two super star clusters (SSCs), Knot B, while the extreme ionization properties are driven by the . 1 Myr-old, enshrouded SSC Knot A, which has ∼ 10 times higher ionizing luminosity. Very massive stars (> 100 M ) may be present in this remarkable object. Ionization-parameter mapping indicates the blowout region is optically thin in the LyC, and the general properties also suggest LyC escape in the line of sight. -
Information Bulletin on Variable Stars
COMMISSIONS AND OF THE I A U INFORMATION BULLETIN ON VARIABLE STARS Nos November July EDITORS L SZABADOS K OLAH TECHNICAL EDITOR A HOLL TYPESETTING K ORI ADMINISTRATION Zs KOVARI EDITORIAL BOARD L A BALONA M BREGER E BUDDING M deGROOT E GUINAN D S HALL P HARMANEC M JERZYKIEWICZ K C LEUNG M RODONO N N SAMUS J SMAK C STERKEN Chair H BUDAPEST XI I Box HUNGARY URL httpwwwkonkolyhuIBVSIBVShtml HU ISSN COPYRIGHT NOTICE IBVS is published on b ehalf of the th and nd Commissions of the IAU by the Konkoly Observatory Budap est Hungary Individual issues could b e downloaded for scientic and educational purp oses free of charge Bibliographic information of the recent issues could b e entered to indexing sys tems No IBVS issues may b e stored in a public retrieval system in any form or by any means electronic or otherwise without the prior written p ermission of the publishers Prior written p ermission of the publishers is required for entering IBVS issues to an electronic indexing or bibliographic system to o CONTENTS C STERKEN A JONES B VOS I ZEGELAAR AM van GENDEREN M de GROOT On the Cyclicity of the S Dor Phases in AG Carinae ::::::::::::::::::::::::::::::::::::::::::::::::::: : J BOROVICKA L SAROUNOVA The Period and Lightcurve of NSV ::::::::::::::::::::::::::::::::::::::::::::::::::: :::::::::::::: W LILLER AF JONES A New Very Long Period Variable Star in Norma ::::::::::::::::::::::::::::::::::::::::::::::::::: :::::::::::::::: EA KARITSKAYA VP GORANSKIJ Unusual Fading of V Cygni Cyg X in Early November :::::::::::::::::::::::::::::::::::::::