August 2016 BRAS Newsletter
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Pulsar Scattering, Lensing and Gravity Waves
Introduction Convergent Plasma Lenses Gravity Waves Black Holes/Fuzzballs Summary Pulsar Scattering, Lensing and Gravity Waves Ue-Li Pen, Lindsay King, Latham Boyle CITA Feb 15, 2012 U. Pen Pulsar Scattering, Lensing and Gravity Waves Introduction Convergent Plasma Lenses Gravity Waves Black Holes/Fuzzballs Summary Overview I Pulsar Scattering I VLBI ISM holography, distance measures I Enhanced Pulsar Timing Array gravity waves I fuzzballs U. Pen Pulsar Scattering, Lensing and Gravity Waves Introduction Convergent Plasma Lenses Gravity Waves Black Holes/Fuzzballs Summary Pulsar Scattering I Pulsars scintillate strongly due to ISM propagation I Lens of geometric size ∼ AU I Can be imaged with VLBI (Brisken et al 2010) I Deconvolved by interstellar holography (Walker et al 2008) U. Pen Pulsar Scattering, Lensing and Gravity Waves Introduction Convergent Plasma Lenses Gravity Waves Black Holes/Fuzzballs Summary Scattering Image Data from Brisken et al, Holographic VLBI. U. Pen Pulsar Scattering, Lensing and Gravity Waves Introduction Convergent Plasma Lenses Gravity Waves Black Holes/Fuzzballs Summary ISM enigma −8 I Scattering angle observed mas, 10 rad. I Snell's law: sin(θ1)= sin(θ2) = n2=n1 −12 I n − 1 ∼ 10 . I 4 orders of magnitude mismatch. U. Pen Pulsar Scattering, Lensing and Gravity Waves Introduction Convergent Plasma Lenses Gravity Waves Black Holes/Fuzzballs Summary Possibilities I turbulent ISM: sum of many small scatters. Cannot explain discrete images. I confinement problem: super mini dark matter halos, cosmic strings? I Geometric alignment: Goldreich and Shridhar (2006) I Snell's law at grazing incidence: ∆α = (1 − n2=n1)/α I grazing incidence is geometry preferred at 2-D structures U. -
Beetlejuice Handbook for the Recently Deceased Hardcover
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Interstellar Medium and Star Formation Studies with the Square Kilometre Array
Review J. Astrophys. Astr. (2016) 37: 38 DOI: 10.1007/s12036-016-9414-9 Interstellar Medium and Star Formation Studies with the Square Kilometre Array P. Manoj1,∗,S.Vig2, G. Maheswar3, U.S.Kamath4 &A.Tej2 1Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400 005, India. 2Indian Institute of Space Science and Technology, Valiamala, Thiruvananthapuram 695 547, India. 3Aryabhatta Research Institute of Observational Sciences, Manora Peak, Nainital 263 129, India. 4Indian Institute of Astrophysics, Sarjapur Road, Koramangala, Bangalore 560 034, India. ∗e-mail: [email protected] Received 14 May 2016; accepted 3 November 2016 ePublication: 8 December 2016 Abstract. Stars and planetary systems are formed out of molecu- lar clouds in the interstellar medium. Although the sequence of steps involved in star formation are generally known, a comprehensive theory which describes the details of the processes that drive formation of stars is still missing. The Square Kilometre Array (SKA), with its unprece- dented sensitivity and angular resolution, will play a major role in filling these gaps in our understanding. In this article, we present a few science cases that the Indian star formation community is interested in pursuing with SKA, which include investigation of AU-sized structures in the neu- tral ISM, the origin of thermal and non-thermal radio jets from protostars and the accretion history of protostars, and formation of massive stars and their effect on the surrounding medium. Key words. HII regions—ISM: jets and outflows—ISM: structure— stars: formation—stars: protostars. 1. Introduction The formation of stars and planetary systems out of interstellar clouds is one of the central problems in contemporary astrophysics. -
A Conceptual Model for the Origin of the Cutoff Parameter in Exotic Compact Objects
S S symmetry Article A Conceptual Model for the Origin of the Cutoff Parameter in Exotic Compact Objects Wilson Alexander Rojas Castillo 1 and Jose Robel Arenas Salazar 2,* 1 Departamento de Física, Universidad Nacional de Colombia, Bogotá UN.11001, Colombia; [email protected] 2 Observatorio Astronómico Nacional, Universidad Nacional de Colombia, Bogotá UN.11001, Colombia * Correspondence: [email protected] Received: 30 October 2020; Accepted: 30 November 2020 ; Published: 14 December 2020 Abstract: A Black Hole (BH) is a spacetime region with a horizon and where geodesics converge to a singularity. At such a point, the gravitational field equations fail. As an alternative to the problem of the singularity arises the existence of Exotic Compact Objects (ECOs) that prevent the problem of the singularity through a transition phase of matter once it has crossed the horizon. ECOs are characterized by a closeness parameter or cutoff, e, which measures the degree of compactness of the object. This parameter is established as the difference between the radius of the ECO’s surface and the gravitational radius. Thus, different values of e correspond to different types of ECOs. If e is very big, the ECO behaves more like a star than a black hole. On the contrary, if e tends to a very small value, the ECO behaves like a black hole. It is considered a conceptual model of the origin of the cutoff for ECOs, when a dust shell contracts gravitationally from an initial position to near the Schwarzschild radius. This allowed us to find that the cutoff makes two types of contributions: a classical one governed by General Relativity and one of a quantum nature, if the ECO is very close to the horizon, when estimating that the maximum entropy is contained within the material that composes the shell. -
Space Trivia Questions and Answers
Space Trivia Questions From: conversationstartersworld.com/space-trivia-questions 1. What type of galaxy is the most common in the universe? Elliptical galaxies Galaxies are categorized as elliptical, spiral, or irregular. There are at least two trillion galaxies in the universe. Each galaxy is bound by gravity and consists of stars, dust, interstellar gas, and dark matter. They range in size from a few billion stars to one hundred trillion stars. The oldest and most distant observed galaxy is actually 32 billion light years from Earth and is located in the constellation Ursa Major. 2. What is the coldest place in the universe? (Hint: It’s a nebula.) The Boomerang Nebula The Boomerang Nebula is one degree Kelvin which is -458 degrees Fahrenheit or -272.15 degrees Celsius. It is located in the Centaurus constellation and is colder than the background temperature of deep space. 3. The hottest place in the universe is located in which constellation? The constellation Virgo The hottest place in the universe is actually a cloud of gas surrounding a swarm of galaxies that are clustered together in the Virgo constellation. The temperature there reaches 300 million degrees Celsius. The cloud is believed to have been formed as a result of colliding galaxies going at speeds of 2,500 miles per second. 4. How old is the universe in light years? (Plus or minus 1 billion light years.) 13.8 billion light years old Scientists used various methods to estimate its age. These included methods such as measuring the composition of matter and energy density in the universe. -
Variable Stars Observer Bulletin
Amateurs' Guide to Variable Stars September-October 2013 | Issue #2 Variable Stars Observer Bulletin ISSN 2309-5539 Twenty new W Ursae Majoris-type eclipsing binaries from the Catalina Sky Survey Details for 20 new WUMa systems are presented, along with a preliminary The FU Orionis phenomenon model of the FU Orionis stars are pre-main-sequence totally eclipsing eruptive variables which appear to be a system GSC stage in the development of T Tauri 03090-00153. stars. Image: FU Orionis. Credit: ESO NSVS 5860878 = Dauban V 171 Carbon in the sky: A new Mira variable in Cygnus a few remarkable carbon stars The list of the most interesting and bright carbon stars for northern observers is presented. Right: TT Cygni. A carbon star. Credit & Copyright: H.Olofsson (Stockholm Nova Observatory) et al. Delphini 2013 Nova has reached magnitude 4.3 visual The "Heavenly Owl" on August 16 observatory: seeing above the Black Sea waterfront VS-COMPAS Project: variable stars research and data mining. More at http://vs-compas.belastro.net Variable Stars Observer Bulletin Amateurs' Guide to Variable Stars September-October 2013 | Issue #2 C O N T E N T S 04 NSVS 5860878 = Dauban V 171: a new Mira variable in Cygnus by Ivan Adamin, Siarhey Hadon A new Mira variable in the constellation of Cygnus is presented. The variability of the NSVS 5860878 source was detected in January of 2012. Lately, the object was identified as the Dauban V171. A revision is submitted to the VSX. 06 Twenty new W Ursae Majoris-type eclipsing binaries Credit: Justin Ng from the Catalina Sky Survey by Stefan Hümmerich, Klaus Bernhard, Gregor Srdoc 16 Nova Delphini 2013: a naked-eye visible flare in A short overview of eclipsing binary northern skies stars and their traditional by Andrey Prokopovich classification scheme is given, which concentrates on W Ursae Majoris On August 14, 2013 a new bright star (WUMa)-type systems. -
16 Aug 2012 E Uegat Rudteosue Pncutrstephenso Cluster Open Obscured the Around Supergiants Red L Am,Spain) Palma, (La Ouain Ohrors Ayrg Eg,Dve Ta.2007 Ages Typical Al
Astronomy & Astrophysics manuscript no. wyffos c ESO 2012 August 17, 2012 Red supergiants around the obscured open cluster Stephenson2,⋆ I. Negueruela1, A. Marco1, C. Gonz´alez-Fern´andez1 , F. Jim´enez-Esteban2,3,4, J. S. Clark5, M. Garcia6,7, and E. Solano2,3 1 Departamento de F´ısica, Ingenier´ıa de Sistemas y Teor´ıa de la Se˜nal, Universidad de Alicante, Apdo. 99, E-03080 Alicante, Spain e-mail: [email protected] 2 Centro de Astrobiolog´ıa (INTA-CSIC), Departamento de Astrof´ısica, PO Box 78, E-28691, Villanueva de la Ca˜nada, Madrid, Spain 3 Spanish Virtual Observatory, Spain 4 Saint Louis University, Madrid Campus, Division of Science and Engineering, Avda. del Valle 34, E-28003 Madrid, Spain 5 Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes, MK7 6AA, UK 6 Instituto de Astrof´ısica de Canarias, E-38200 La Laguna, Tenerife, Spain 7 Departamento de Astrof´ısica, Universidad de La Laguna (ULL), E-38206 La Laguna, Tenerife, Spain Preprint online version: August 17, 2012 ABSTRACT Context. Several clusters of red supergiants have been discovered in a small region of the Milky Way close to the base of the Scutum- Crux Arm and the tip of the Long Bar. Population synthesis models indicate that they must be very massive to harbour so many supergiants. Amongst these clusters, Stephenson 2, with a core grouping of 26 red supergiants, is a strong candidate to be the most massive cluster in the Galaxy. Aims. Stephenson 2 is located close to a region where a strong over-density of red supergiants had been found. -
The Agb Newsletter
THE AGB NEWSLETTER An electronic publication dedicated to Asymptotic Giant Branch stars and related phenomena Official publication of the IAU Working Group on Abundances in Red Giants No. 208 — 1 November 2014 http://www.astro.keele.ac.uk/AGBnews Editors: Jacco van Loon, Ambra Nanni and Albert Zijlstra Editorial Dear Colleagues, It is our pleasure to present you the 208th issue of the AGB Newsletter. The variety of topics is, as usual, enormous, though post-AGB phases feature prominently, as does R Scuti this time. Don’t miss the announcements of the Olivier Chesneau Prize, and of three workshops to keep you busy and entertained over the course of May–July next year. We look forward to receiving your reactions to this month’s Food for Thought (see below)! The next issue is planned to be distributed around the 1st of December. Editorially Yours, Jacco van Loon, Ambra Nanni and Albert Zijlstra Food for Thought This month’s thought-provoking statement is: What is your favourite AGB star, RSG, post-AGB object, post-RSG or PN? And why? Reactions to this statement or suggestions for next month’s statement can be e-mailed to [email protected] (please state whether you wish to remain anonymous) 1 Refereed Journal Papers Evolutionary status of the active star PZ Mon Yu.V. Pakhomov1, N.N. Chugai1, N.I. Bondar2, N.A. Gorynya1,3 and E.A. Semenko4 1Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya 48, 119017, Moscow, Russia 2Crimean Astrophysical Observatory, Nauchny, Crimea, 2984009, Russia 3Lomonosov Moscow State University, Sternberg Astronomical Institute, Universitetskij prospekt, 13, Moscow 119991, Russia 4Special Astrophysical Observatory of Russian Academy of Sciences, Russia We use original spectra and available photometric data to recover parameters of the stellar atmosphere of PZ Mon, formerly referred as an active red dwarf. -
Sio Maser Emission from Red Supergiants Across the Galaxy: I
Astronomy & Astrophysics manuscript no. 18265-v2 c ESO 2018 November 15, 2018 SiO maser emission from red supergiants across the Galaxy: I. Targets in massive star clusters L. Verheyen⋆, M. Messineo, and K. M. Menten Max-Planck-Institut f¨ur Radioastronomie, Auf dem H¨ugel 69, D-53121 Bonn, Germany e-mail: verheyen, messineo, [email protected] Received 2011/ Accepted ABSTRACT Aims. Red supergiants (RSGs) are among the most luminous of all stars, easily detectable in external galaxies, and may ideally serve as kinematic tracers of Galactic structure. Some RSGs are surrounded by circumstellar envelopes detectable by their dust and molecular and, in particular, maser emission. This study consists of a search for maser emission from silicon monoxide (SiO) toward a significant number of RSGs that are members of massive stellar clusters, many of which have only recently been discovered. Further, we aim to relate the occurrence of maser action to properties of the host stars. Methods. Using the IRAM 30 meter telescope, we searched for maser emission in the J = 2 − 1 rotational transition within the first vibrationally excited state of SiO toward a sample of 88 RSGs. Results. With an average rms noise level of 0.25 Jy, we detected maser emission in 15% of the sample, toward most of the sources for the first time in this transition. The peak of the emission provides accurate radial velocities for the RSGs. The dependence of the detection rate on infrared colors supports a radiative pumping mechanism for the SiO masers. Key words. Stars: AGB and post-AGB – circumstellar matter – masers 1. -
Spectroscopy of Variable Stars
Spectroscopy of Variable Stars Steve B. Howell and Travis A. Rector The National Optical Astronomy Observatory 950 N. Cherry Ave. Tucson, AZ 85719 USA Introduction A Note from the Authors The goal of this project is to determine the physical characteristics of variable stars (e.g., temperature, radius and luminosity) by analyzing spectra and photometric observations that span several years. The project was originally developed as a The 2.1-meter telescope and research project for teachers participating in the NOAO TLRBSE program. Coudé Feed spectrograph at Kitt Peak National Observatory in Ari- Please note that it is assumed that the instructor and students are familiar with the zona. The 2.1-meter telescope is concepts of photometry and spectroscopy as it is used in astronomy, as well as inside the white dome. The Coudé stellar classification and stellar evolution. This document is an incomplete source Feed spectrograph is in the right of information on these topics, so further study is encouraged. In particular, the half of the building. It also uses “Stellar Spectroscopy” document will be useful for learning how to analyze the the white tower on the right. spectrum of a star. Prerequisites To be able to do this research project, students should have a basic understanding of the following concepts: • Spectroscopy and photometry in astronomy • Stellar evolution • Stellar classification • Inverse-square law and Stefan’s law The control room for the Coudé Description of the Data Feed spectrograph. The spec- trograph is operated by the two The spectra used in this project were obtained with the Coudé Feed telescopes computers on the left. -
Variable Star Classification and Light Curves Manual
Variable Star Classification and Light Curves An AAVSO course for the Carolyn Hurless Online Institute for Continuing Education in Astronomy (CHOICE) This is copyrighted material meant only for official enrollees in this online course. Do not share this document with others. Please do not quote from it without prior permission from the AAVSO. Table of Contents Course Description and Requirements for Completion Chapter One- 1. Introduction . What are variable stars? . The first known variable stars 2. Variable Star Names . Constellation names . Greek letters (Bayer letters) . GCVS naming scheme . Other naming conventions . Naming variable star types 3. The Main Types of variability Extrinsic . Eclipsing . Rotating . Microlensing Intrinsic . Pulsating . Eruptive . Cataclysmic . X-Ray 4. The Variability Tree Chapter Two- 1. Rotating Variables . The Sun . BY Dra stars . RS CVn stars . Rotating ellipsoidal variables 2. Eclipsing Variables . EA . EB . EW . EP . Roche Lobes 1 Chapter Three- 1. Pulsating Variables . Classical Cepheids . Type II Cepheids . RV Tau stars . Delta Sct stars . RR Lyr stars . Miras . Semi-regular stars 2. Eruptive Variables . Young Stellar Objects . T Tau stars . FUOrs . EXOrs . UXOrs . UV Cet stars . Gamma Cas stars . S Dor stars . R CrB stars Chapter Four- 1. Cataclysmic Variables . Dwarf Novae . Novae . Recurrent Novae . Magnetic CVs . Symbiotic Variables . Supernovae 2. Other Variables . Gamma-Ray Bursters . Active Galactic Nuclei 2 Course Description and Requirements for Completion This course is an overview of the types of variable stars most commonly observed by AAVSO observers. We discuss the physical processes behind what makes each type variable and how this is demonstrated in their light curves. Variable star names and nomenclature are placed in a historical context to aid in understanding today’s classification scheme. -
University of Groningen Molecular Line Tracers of High-Mass Star Forming
University of Groningen Molecular line tracers of high-mass star forming regions Nagy, Zsofia IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document Version Publisher's PDF, also known as Version of record Publication date: 2013 Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Nagy, Z. (2013). Molecular line tracers of high-mass star forming regions. s.n. Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons). The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license. More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne- amendment. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Download date: 08-10-2021 Molecular line tracers of high-mass star forming regions Proefschrift ter verkrijging van het doctoraat in de Wiskunde en Natuurwetenschappen aan de Rijksuniversiteit Groningen op gezag van de RectorMagnificus, dr.