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Stellar Variability in Open Clusters. I. a New Class of Variable Stars in NGC
Astronomy & Astrophysics manuscript no. ngc3766˙v3˙1b c ESO 2018 September 8, 2018 Stellar variability in open clusters I. A new class of variable stars in NGC 3766 N. Mowlavi1, F. Barblan1, S. Saesen1, and L. Eyer1 1Astronomy Department, Geneva Observatory, chemin des Maillettes, 1290 Versoix, Switzerland e-mail: [email protected] Accepted 16/04/2013 ABSTRACT Aims. We analyze the population of periodic variable stars in the open cluster NGC 3766 based on a 7-year multiband monitoring campaign conducted on the 1.2 m Swiss Euler telescope at La Silla, Chili. Methods. The data reduction, light curve cleaning, and period search procedures, combined with the long observation time line, allowed us to detect variability amplitudes down to the mmag level. The variability properties were complemented with the positions in the color-magnitude and color-color diagrams to classify periodic variable stars into distinct variability types. Results. We find a large population (36 stars) of new variable stars between the red edge of slowly pulsating B (SPB) stars and the blue edge of δ Sct stars, a region in the Hertzsprung-Russell (HR) diagram where no pulsation is predicted to occur based on standard stellar models. The bulk of their periods ranges from 0.1 to 0.7 d, with amplitudes between 1 and 4 mmag for the majority of them. About 20% of stars in that region of the HR diagram are found to be variable, but the number of members of this new group is expected to be higher, with amplitudes below our mmag detection limit. -
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. -
Isolating the Pre-Main Sequence in Collinder 34, NGC 3293, NGC 3766 and NGC 6231
MNRAS 448, 1687–1703 (2015) doi:10.1093/mnras/stv026 Isolating the pre-main sequence in Collinder 34, NGC 3293, NGC 3766 and NGC 6231 T. A. Saurin,‹ E. Bica and C. Bonatto Departamento de Astronomia, Universidade Federal do Rio Grande do Sul, CP 15051, RS, Porto Alegre 91501-970, Brazil Accepted 2015 January 6. Received 2014 December 18; in original form 2014 July 17 Downloaded from ABSTRACT We employed field star decontaminated Two Micron All Sky Survey photometry to study four nearby optical embedded clusters – Collinder 34, NGC 3293, NGC 3766 and NGC 6231 – obtaining deep colour–magnitude diagrams and stellar radial density profiles. We found what seem to be pre-main sequences detached in different amounts from main sequences in these http://mnras.oxfordjournals.org/ diagrams. The structural analysis of each cluster revealed different radial distributions for these two sequences. We argued that the detached evolutionary sequences in our sample may be evidence of sequential star formation. Finally, we compared the sample cluster parameters with those of other young clusters in the literature and point out evidence that NGC 3766 and NGC 6231 might be evolving to OB associations. Key words: open clusters and associations: individual: Collinder 34 – open clusters and asso- ciations: individual: NGC 3293 – open clusters and associations: individual: NGC 3766 – open clusters and associations: individual: NGC 6231. at Universidade Federal do Rio Grande Sul on April 6, 2015 that may be interpreted as mass and age segregation (e.g. Hillen- 1 INTRODUCTION brand 1997). Youngstar clusters remain embedded in molecular clouds during the Using Two Micron All Sky Survey (2MASS;1 Skrutskie et al. -
Planetary Nebulae
Planetary Nebulae A planetary nebula is a kind of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from old red giant stars late in their lives. The term "planetary nebula" is a misnomer that originated in the 1780s with astronomer William Herschel because when viewed through his telescope, these objects appeared to him to resemble the rounded shapes of planets. Herschel's name for these objects was popularly adopted and has not been changed. They are a relatively short-lived phenomenon, lasting a few tens of thousands of years, compared to a typical stellar lifetime of several billion years. The mechanism for formation of most planetary nebulae is thought to be the following: at the end of the star's life, during the red giant phase, the outer layers of the star are expelled by strong stellar winds. Eventually, after most of the red giant's atmosphere is dissipated, the exposed hot, luminous core emits ultraviolet radiation to ionize the ejected outer layers of the star. Absorbed ultraviolet light energizes the shell of nebulous gas around the central star, appearing as a bright colored planetary nebula at several discrete visible wavelengths. Planetary nebulae may play a crucial role in the chemical evolution of the Milky Way, returning material to the interstellar medium from stars where elements, the products of nucleosynthesis (such as carbon, nitrogen, oxygen and neon), have been created. Planetary nebulae are also observed in more distant galaxies, yielding useful information about their chemical abundances. In recent years, Hubble Space Telescope images have revealed many planetary nebulae to have extremely complex and varied morphologies. -
Progress Report 1985 - 1986
PROGRESS REPORT 1985 - 1986 Instituto de Física Universidade Federal do Rio Grande do Sul Ptril Mtffi • Imi mi FOREWORD Despite difficulties arising fro» uncertainties in the scientific policy and economic situation of the country, the scientific activity and production of the Institute regained at the level of previous years. During the present period the Institute of Physics Moved to the new University Campus thereby having access to ample new installations and waking possible the expansion of its activities. Although expected to be beneficial in the long range, numerous difficulties had to be «et particularly by experimental groups, slowing down temporarily their production, until all the equip- ments were again operational. A new COBRA 1400 computer (equivalent to a Eclipse Data General MV 8000 II one'; has been acquired. This acquisition nade possible for the first tine in many years, an adequate level of computational support for our work. During this period discussions were started on the need for new research and technological facilities for our Institute, in particular laboratories for thin films and electronic microscopy, and expansion of the existing ones, like the ion implantation. The scientific achievements of the Institute were made possible by the financial support of FINEP (Financiadora de Estudos e Projetos), CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico), CAPES (Coordenação de Aperfeiçoamento de Pessoal de NTvel Superior) anó the University Administration. The continuous support of the University Administration to secure outside funding is also acknowledged. The effort in editing this report,due to Professor Walter K. Iheumann with the expert assistance of Mrs. Ivone H. -
A Wild Animal by Magda Streicher
deepsky delights Lupus a wild animal by Magda Streicher [email protected] Image source: Stellarium There is a true story behind this month’s constellation. “Star friends” as I call them, below in what might be ‘ground zero’! regularly visit me on the farm, exploiting “What is that?” Tim enquired in a brave the ideal conditions for deep-sky stud- voice, “It sounds like a leopard catching a ies and of course talking endlessly about buck”. To which I replied: “No, Timmy, astronomy. One winter’s weekend the it is much, much more dangerous!” Great Coopers from Johannesburg came to visit. was our relief when the wrestling match What a weekend it turned out to be. For started disappearing into the distance. The Tim it was literally heaven on earth in the altercation was between two aardwolves, dark night sky with ideal circumstances to wrestling over a bone or a four-legged study meteors. My observatory is perched lady. on top of a building in an area consisting of mainly Mopane veld with a few Baobab The Greeks and Romans saw the constel- trees littered along the otherwise clear ho- lation Lupus as a wild animal but for the rizon. Ascending the steps you are treated Arabians and Timmy it was their Leopard to a breathtaking view of the heavens in all or Panther. This very ancient constellation their glory. known as Lupus the Wolf is just east of Centaurus and south of Scorpius. It has no That Saturday night Tim settled down stars brighter than magnitude 2.6. -
The Title of My
Research in Astronomy and Astrophysics manuscript no. (LATEX: cgw.tex; printed on January 14, 2020; 2:35) Constraints on individual supermassive binary black holes using observations of PSR J1909 3744 − Yi Feng1,2,3, Di Li1,3, Yan-Rong Li4 and Jian-Min Wang4 1 National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China ; [email protected] 2 University of Chinese Academy of Sciences, Beijing 100049, China 3 CAS Key Laboratory of FAST, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 4 Institute of High Energy Physics, Chinese Academy of Sciences,19B Yuquan Road, Beijing 100049, China Abstract We perform a search for gravitational waves (GWs) from several supermassive binary black hole (SMBBH) candidates (NGC 5548, Mrk 231, OJ 287, PG 1302-102, NGC 4151, Ark 120 and 3C 66B) in long-term timing observations of the pulsar PSR J1909 3744 − obtained using the Parkes radio telescope. No statistically significant signals were found. We constrain the chirp masses of those SMBBH candidates and find the chirp mass of NGC 5548 and3C66Btobeless than2.4 109 M and 2.5 109 M (with 95% confidence), respectively. × ⊙ × ⊙ Our upperlimits remaina factor of 3 to 370 abovethe likely chirp masses for these candidates as estimated from other approaches. The observations processed here provide upper limits on the GW strain amplitude that improve upon the results from the first Parkes Pulsar Timing arXiv:1907.03460v2 [astro-ph.IM] 13 Jan 2020 Array data release by a factor of 2 to 7. We investigate how information about the orbital pa- rameters can help improve the search sensitivity for individual SMBBH systems. -
Astronomy Magazine Special Issue
γ ι ζ γ δ α κ β κ ε γ β ρ ε ζ υ α φ ψ ω χ α π χ φ γ ω ο ι δ κ α ξ υ λ τ μ β α σ θ ε β σ δ γ ψ λ ω σ η ν θ Aι must-have for all stargazers η δ μ NEW EDITION! ζ λ β ε η κ NGC 6664 NGC 6539 ε τ μ NGC 6712 α υ δ ζ M26 ν NGC 6649 ψ Struve 2325 ζ ξ ATLAS χ α NGC 6604 ξ ο ν ν SCUTUM M16 of the γ SERP β NGC 6605 γ V450 ξ η υ η NGC 6645 M17 φ θ M18 ζ ρ ρ1 π Barnard 92 ο χ σ M25 M24 STARS M23 ν β κ All-in-one introduction ALL NEW MAPS WITH: to the night sky 42,000 more stars (87,000 plotted down to magnitude 8.5) AND 150+ more deep-sky objects (more than 1,200 total) The Eagle Nebula (M16) combines a dark nebula and a star cluster. In 100+ this intense region of star formation, “pillars” form at the boundaries spectacular between hot and cold gas. You’ll find this object on Map 14, a celestial portion of which lies above. photos PLUS: How to observe star clusters, nebulae, and galaxies AS2-CV0610.indd 1 6/10/10 4:17 PM NEW EDITION! AtlAs Tour the night sky of the The staff of Astronomy magazine decided to This atlas presents produce its first star atlas in 2006. -
Journal Reprints-Astronomy/Download/8526
SPACE PATTERNS AND PAINTINGS (published in the "Engineer" magazine No. 8-9, 2012) Sagredo. - If the end of the pen, which was on the ship during my entire voyage from Venice to Alexandretta, were able to leave a visible trace of its entire path, then what kind of trace, what mark, what line would it leave? Simplicio. - I would leave a line stretching from Venice to the final place, not completely straight, or rather, extended in the form of an arc of a circle, but more or less wavy, depending on how much the ship swayed along the way ... Sagredo. - If, therefore, the artist, upon leaving the harbor, began to draw with this pen on a sheet of paper and continued drawing until Alexandretta, he could get from his movement a whole picture of figures ... at least a trace left ... by the end of the pen would be nothing more than a very long and simple line. G. Galileo "Dialogue on the two main systems of the world" Space has been giving astronomers surprise after surprise lately. A number of mysterious space objects were discovered that were not predicted by astrophysics and contradicted it. The more advanced observation methods become, the more such surprises. At one time, I. Shklovsky argued that the discovery of such "cosmic wonders" would confirm the reality of extraterrestrial intelligence, its enormous technical capabilities. But in reality, the "cosmic miracles" showed the backwardness of terrestrial science, which the opium of relativism smiled so much that now it cannot clearly explain ordinary cosmic phenomena caused by natural causes. -
JRASC-2007-04-Hr.Pdf
Publications and Products of April / avril 2007 Volume/volume 101 Number/numéro 2 [723] The Royal Astronomical Society of Canada Observer’s Calendar — 2007 The award-winning RASC Observer's Calendar is your annual guide Created by the Royal Astronomical Society of Canada and richly illustrated by photographs from leading amateur astronomers, the calendar pages are packed with detailed information including major lunar and planetary conjunctions, The Journal of the Royal Astronomical Society of Canada Le Journal de la Société royale d’astronomie du Canada meteor showers, eclipses, lunar phases, and daily Moonrise and Moonset times. Canadian and U.S. holidays are highlighted. Perfect for home, office, or observatory. Individual Order Prices: $16.95 Cdn/ $13.95 US RASC members receive a $3.00 discount Shipping and handling not included. The Beginner’s Observing Guide Extensively revised and now in its fifth edition, The Beginner’s Observing Guide is for a variety of observers, from the beginner with no experience to the intermediate who would appreciate the clear, helpful guidance here available on an expanded variety of topics: constellations, bright stars, the motions of the heavens, lunar features, the aurora, and the zodiacal light. New sections include: lunar and planetary data through 2010, variable-star observing, telescope information, beginning astrophotography, a non-technical glossary of astronomical terms, and directions for building a properly scaled model of the solar system. Written by astronomy author and educator, Leo Enright; 200 pages, 6 colour star maps, 16 photographs, otabinding. Price: $19.95 plus shipping & handling. Skyways: Astronomy Handbook for Teachers Teaching Astronomy? Skyways Makes it Easy! Written by a Canadian for Canadian teachers and astronomy educators, Skyways is Canadian curriculum-specific; pre-tested by Canadian teachers; hands-on; interactive; geared for upper elementary, middle school, and junior-high grades; fun and easy to use; cost-effective. -
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). -
An Atlas of Spectra of B6–A2 Hypergiants and Supergiants from 4800 to 6700 Å?
A&A 397, 1035–1042 (2003) Astronomy DOI: 10.1051/0004-6361:20021430 & c ESO 2003 Astrophysics An atlas of spectra of B6–A2 hypergiants and supergiants from 4800 to 6700 Å? E. L. Chentsov1;2,S.V.Ermakov1;2, V.G. Klochkova1;2,V.E.Panchuk1;2, K. S. Bjorkman3, and A. S. Miroshnichenko3;4 1 Special Astrophysical Observatory of the Russian Academy of Sciences, Karachai-Cirkassian Republic, Nizhnij Arkhyz, 369167, Russia 2 Isaac Newton Institute of Chile, SAO Branch 3 Ritter Observatory, Dept. of Physics & Astronomy, University of Toledo, Toledo, OH 43606-3390, USA 4 Central Astronomical Observatory of the Russian Academy of Sciences at Pulkovo, 196140, Saint-Petersburg, Russia Received 20 March 2002 / Accepted 24 September 2002 Abstract. We present an atlas of spectra of 5 emission-line stars: the low-luminosity luminous blue variables (LBVs) HD 168625 and HD 160529, the white hypergiants (and LBV candidates) HD 168607 and AS 314, and the supergiant HD 183143. The spectra were obtained with 2 echelle spectrometers at the 6-m telescope of the Russian Academy of Sciences in the spectral range 4800 to 6700 Å, with a resolution of 0.4 Å. We have identified 380 spectral lines and diffuse interstellar bands within the spectra. Specific spectral features of the objects are described. Key words. stars: emission-line, Be – stars: individual: HD 160529, HD 168607, HD 168625, HD 183143, AS 314 1. Introduction The amplitude of variations in brightness and temperature de- crease as the luminosity decreases. In the least luminous LBVs (M 9 mag), the temperature varies between 12 000– This paper presents a comparative description of the optical bol ∼− spectra of several white hypergiants and supergiants.