Pulsation Velocity Curves for 3 Cepheid Variables
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Sky Notes - April 2012
North Devon Astronomical Society www.northdevonastronomy.co.uk Sky Notes - April 2012 THE MOON New Moon 21s t April First Quarter 29th April Full Moon 6th April Last Quarter 13th April THE PLANETS Mercury A morning object, Mercury is visible before sunrise by the middle of the month. The planet will reach greatest western elongation on the 18th, when it will be around 27 degrees from the Sun. Venus Now moving closer to the Sun once again following greatest elongation last month, but blazing away at magnitude -4.4, Venus still dominates the western evening sky. In the eyepiece, the planet presents a 25 arcsecond disc which is just under half illuminated. Mars Following last month’s opposition, The Red Planet remains fairly close to the bright star Regulus, in the constellation Leo. Though the apparent diameter of the planet will shrink slightly throughout the month, Mars remains worthy of observation and is visible for most of the night. Jupiter Though still visible low in the west after sunset, Jupiter will soon become lost in the evening twilight. Saturn R eaching opposition on the 15th, Saturn is observable all night in the constellation Virgo, close to the first magnitude star Spica, (Alpha Virginis). A magnificent object, Saturn’s rings and it’s largest satellite Titan are readily apparent in small telescopes, while larger instruments will show atmospheric bands and some of the smaller moons. Uranus Ur anus is too close to the Sun to be observable this month. Neptune A morning object, Neptune can be found among the stars of the constellation Aquarius. -
Plotting Variable Stars on the H-R Diagram Activity
Pulsating Variable Stars and the Hertzsprung-Russell Diagram The Hertzsprung-Russell (H-R) Diagram: The H-R diagram is an important astronomical tool for understanding how stars evolve over time. Stellar evolution can not be studied by observing individual stars as most changes occur over millions and billions of years. Astrophysicists observe numerous stars at various stages in their evolutionary history to determine their changing properties and probable evolutionary tracks across the H-R diagram. The H-R diagram is a scatter graph of stars. When the absolute magnitude (MV) – intrinsic brightness – of stars is plotted against their surface temperature (stellar classification) the stars are not randomly distributed on the graph but are mostly restricted to a few well-defined regions. The stars within the same regions share a common set of characteristics. As the physical characteristics of a star change over its evolutionary history, its position on the H-R diagram The H-R Diagram changes also – so the H-R diagram can also be thought of as a graphical plot of stellar evolution. From the location of a star on the diagram, its luminosity, spectral type, color, temperature, mass, age, chemical composition and evolutionary history are known. Most stars are classified by surface temperature (spectral type) from hottest to coolest as follows: O B A F G K M. These categories are further subdivided into subclasses from hottest (0) to coolest (9). The hottest B stars are B0 and the coolest are B9, followed by spectral type A0. Each major spectral classification is characterized by its own unique spectra. -
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. -
Arxiv:1709.05344V1 [Astro-Ph.SR] 15 Sep 2017 (A(Li) = 2.75), Higher Than Its Companion by 0.5 Dex
Draft version September 19, 2017 Typeset using LATEX modern style in AASTeX61 KRONOS & KRIOS: EVIDENCE FOR ACCRETION OF A MASSIVE, ROCKY PLANETARY SYSTEM IN A COMOVING PAIR OF SOLAR-TYPE STARS Semyeong Oh,1, 2 Adrian M. Price-Whelan,1 John M. Brewer,3, 4 David W. Hogg,5, 6, 7, 8 David N. Spergel,1, 5 and Justin Myles3 1Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544, USA 2To whom correspondence should be addressed: [email protected] 3Department of Astronomy, Yale University, 260 Whitney Ave, New Haven, CT 06511, USA 4Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027, USA 5Center for Computational Astrophysics, Flatiron Institute, 162 Fifth Ave, New York, NY 10010, USA 6Center for Cosmology and Particle Physics, Department of Physics, New York University, 726 Broadway, New York, NY 10003, USA 7Center for Data Science, New York University, 60 Fifth Ave, New York, NY 10011, USA 8Max-Planck-Institut f¨ur Astronomie, K¨onigstuhl17, D-69117 Heidelberg ABSTRACT We report and discuss the discovery of a comoving pair of bright solar-type stars, HD 240430 and HD 240429, with a significant difference in their chemical abundances. The two stars have an estimated 3D separation of ≈ 0:6 pc (≈ 0:01 pc projected) at a distance of r ≈ 100 pc with nearly identical three-dimensional velocities, as inferred from Gaia TGAS parallaxes and proper motions, and high-precision radial velocity measurements. Stellar parameters determined from high-resolution Keck HIRES spectra indicate that both stars are ∼ 4 Gyr old. The more metal-rich of the two, HD 240430, shows an enhancement of refractory (TC > 1200 K) elements by ≈ 0:2 dex and a marginal enhancement of (moderately) volatile elements (TC < 1200 K; C, N, O, Na, and Mn). -
On the Variation of the Microturbulence Parameter with Chemical Composition
1 . ON THE VARIATION OF THE MICROTURBULENCE PARAMETER WITH CHEMICAL COMPOSITION S. E. Strom $- $- CSFTI PRICE(S) $ Micrcfiche (MF) I b.5' ff 653 Julb 65 January 1968 Smithsonian Institution Ast r ophys ica1 Ob s e rvato r y Cambridge, Massachusetts 021 38 I ON THE VARIATION OF THE MICROTURBULENCE PARAMETER WITH CHEMICAL COMPOSITION S. E. STROM Smithsonian Astrophysical Observatory Cambridge, Massachusetts Received ABSTRACT It is shown that the correlation found bv previous investigators between and the iron to hydrogen .-t .-t the value of the microturbulent velocity parameter 5 ratio for G dwarfs results from invalid assumptions implicit in the differen- tial curve-of-growth techniques used to derive By using model atmos- 6 t' phere abundance analyses, the deduced values of EL will be very close to the ~. mean value found for stars for approximately solar composition. Several authors (e. g., Wallerstein 1962, Aller and Greenstein 1960) have suggested on the basis of differential curve-of -growth (DCOG) analyses that extreme subdwarf atmospheres are characterized by unusually small values of the turbulent velocity parameter Wallerstein (1962) has presented 5 t' evidence that the turbulent velocity decreases along with the iron-to-hydrogen ratio and thus, in a crude way, with age. This suggestion has led to the speculation that the lower values of et (e, 5 1 km/sec) for the most metal- deficient subdwarfs are related to the decrease of chromospheric activity with age. Recent work by Cohen and Strom (1968), based on detailed model atmospheres, contradicts the results of previous investigations in that for two extreme subdwarfs, HD 19445 and HD 140283, they find, respectively, & - 2 km/sec and 2 5,L 3 km/sec. -
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. -
Binocular Double Star Logbook
Astronomical League Binocular Double Star Club Logbook 1 Table of Contents Alpha Cassiopeiae 3 14 Canis Minoris Sh 251 (Oph) Psi 1 Piscium* F Hydrae Psi 1 & 2 Draconis* 37 Ceti Iota Cancri* 10 Σ2273 (Dra) Phi Cassiopeiae 27 Hydrae 40 & 41 Draconis* 93 (Rho) & 94 Piscium Tau 1 Hydrae 67 Ophiuchi 17 Chi Ceti 35 & 36 (Zeta) Leonis 39 Draconis 56 Andromedae 4 42 Leonis Minoris Epsilon 1 & 2 Lyrae* (U) 14 Arietis Σ1474 (Hya) Zeta 1 & 2 Lyrae* 59 Andromedae Alpha Ursae Majoris 11 Beta Lyrae* 15 Trianguli Delta Leonis Delta 1 & 2 Lyrae 33 Arietis 83 Leonis Theta Serpentis* 18 19 Tauri Tau Leonis 15 Aquilae 21 & 22 Tauri 5 93 Leonis OΣΣ178 (Aql) Eta Tauri 65 Ursae Majoris 28 Aquilae Phi Tauri 67 Ursae Majoris 12 6 (Alpha) & 8 Vul 62 Tauri 12 Comae Berenices Beta Cygni* Kappa 1 & 2 Tauri 17 Comae Berenices Epsilon Sagittae 19 Theta 1 & 2 Tauri 5 (Kappa) & 6 Draconis 54 Sagittarii 57 Persei 6 32 Camelopardalis* 16 Cygni 88 Tauri Σ1740 (Vir) 57 Aquilae Sigma 1 & 2 Tauri 79 (Zeta) & 80 Ursae Maj* 13 15 Sagittae Tau Tauri 70 Virginis Theta Sagittae 62 Eridani Iota Bootis* O1 (30 & 31) Cyg* 20 Beta Camelopardalis Σ1850 (Boo) 29 Cygni 11 & 12 Camelopardalis 7 Alpha Librae* Alpha 1 & 2 Capricorni* Delta Orionis* Delta Bootis* Beta 1 & 2 Capricorni* 42 & 45 Orionis Mu 1 & 2 Bootis* 14 75 Draconis Theta 2 Orionis* Omega 1 & 2 Scorpii Rho Capricorni Gamma Leporis* Kappa Herculis Omicron Capricorni 21 35 Camelopardalis ?? Nu Scorpii S 752 (Delphinus) 5 Lyncis 8 Nu 1 & 2 Coronae Borealis 48 Cygni Nu Geminorum Rho Ophiuchi 61 Cygni* 20 Geminorum 16 & 17 Draconis* 15 5 (Gamma) & 6 Equulei Zeta Geminorum 36 & 37 Herculis 79 Cygni h 3945 (CMa) Mu 1 & 2 Scorpii Mu Cygni 22 19 Lyncis* Zeta 1 & 2 Scorpii Epsilon Pegasi* Eta Canis Majoris 9 Σ133 (Her) Pi 1 & 2 Pegasi Δ 47 (CMa) 36 Ophiuchi* 33 Pegasi 64 & 65 Geminorum Nu 1 & 2 Draconis* 16 35 Pegasi Knt 4 (Pup) 53 Ophiuchi Delta Cephei* (U) The 28 stars with asterisks are also required for the regular AL Double Star Club. -
Chlorine Isotope Ratios in M Giants
Draft version August 4, 2021 Typeset using LATEX twocolumn style in AASTeX62 Chlorine Isotope Ratios in M Giants Z. G. Maas1 and C. A. Pilachowski1 1Indiana University Bloomington, Astronomy Department, 727 East Third Street, Bloomington, IN 47405, USA ABSTRACT We have measured the chlorine isotope ratio in six M giant stars using HCl 1-0 P8 features at 3.7 microns with R ∼ 50,000 spectra from Phoenix on Gemini South. The average Cl isotope ratio for our sample of stars is 2.66 ± 0.58 and the range of measured Cl isotope ratios is 1.76 < 35Cl/37Cl < 3.42. The solar system meteoric Cl isotope ratio of 3.13 is consistent with the range seen in the six stars. We suspect the large variations in Cl isotope ratio are intrinsic to the stars in our sample given the uncertainties. Our average isotopic ratio is higher than the value of 1.80 for the solar neighborhood at solar metallicity predicted by galactic chemical evolution models. Finally the stellar isotope ratios in our sample are similar to those measured in the interstellar medium. Keywords: stars: abundances; 1. INTRODUCTION solar system 37Cl abundance (Pignatari et al. 2010). 37 The odd, light elements are useful for understanding Cl production via the s-process in AGB stars is not the production sites of secondary nucleosynthesis pro- thought to be as significant as from the weak s-process cesses. However, some of the odd light elements, such (Cristallo et al. 2015; Karakas & Lugaro 2016). For ex- as P, Cl, and K have few measured stellar abundances ample, FRUITY models predict only a ∼ 3% increase 37 and/or do not match predicted chemical evolution mod- in Cl for a 4 M solar metallicity AGB star and a els (see Nomoto et al. -
134, December 2007
British Astronomical Association VARIABLE STAR SECTION CIRCULAR No 134, December 2007 Contents AB Andromedae Primary Minima ......................................... inside front cover From the Director ............................................................................................. 1 Recurrent Objects Programme and Long Term Polar Programme News............4 Eclipsing Binary News ..................................................................................... 5 Chart News ...................................................................................................... 7 CE Lyncis ......................................................................................................... 9 New Chart for CE and SV Lyncis ........................................................ 10 SV Lyncis Light Curves 1971-2007 ............................................................... 11 An Introduction to Measuring Variable Stars using a CCD Camera..............13 Cataclysmic Variables-Some Recent Experiences ........................................... 16 The UK Virtual Observatory ......................................................................... 18 A New Infrared Variable in Scutum ................................................................ 22 The Life and Times of Charles Frederick Butterworth, FRAS........................24 A Hard Day’s Night: Day-to-Day Photometry of Vega and Beta Lyrae.........28 Delta Cephei, 2007 ......................................................................................... 33 -
Alternate Constellation Guide
ARKANSAS NATURAL SKY ASSOCIATION LEARNING THE CONSTELLATIONS (Library Telescope Manual included) By Robert Togni Cover Image courtesy of Wikimedia. Do not write in this book, and return with scope to library. A personal copy of this guide can be obtained online at www.darkskyarkansas.com Preface This publication was inspired by and built upon Robert (Rocky) Togni’s quest to share the night sky with all who can be enticed under it. His belief is that the best place to start a relationship with the night sky is to learn the constellations and explore the principle ob- jects within them with the naked eye and a pair of common binoculars. Over a period of years, Rocky evolved a concept, using seasonal asterisms like the Summer Triangle and the Winter Hexagon, to create an easy to use set of simple charts to make learning one’s way around the night sky as simple and fun as possible. Recognizing that the most avid defenders of the natural night time environment are those who have grown to know and love nature at night and exploring the universe that it re- veals, the Arkansas Natural Sky Association (ANSA) asked Rocky if the Association could publish his guide. The hope being that making this available in printed form at vari- ous star parties and other relevant venues would help bring more people to the night sky as well as provide funds for the Association’s work. Once hooked, the owner will definitely want to seek deeper guides. But there is no better publication for opening the sky for the neophyte observer, making the guide the perfect companion for a library telescope. -
2013 Version
Citizen Science with Variable Stars Brought to you by the AAVSO, Astronomers without Borders, the National Science Foundation and Your Universe Astronomers need your help! Many bright stars change in brightness all the time and for many different reasons. Some stars are too bright for professionals to CitizenSky is a collaboration of the look at with most large telescopes. So, we American Association of need your help to watch these stars as they Variable Star Observers (AAVSO), the University of dim and brighten over the next several years. Denver, the Adler Planetarium, the Johns Hopkins University and the California Academies of This guide will help you find these bright Science with support from the National Science Foundation. stars, measure their brightness and then submit the measurements to assist professional astronomers. Participate in one of the largest and longest running citizen science projects in history! Thousands of people just like you are helping o ut. Astronomers need large numbers of people to get the amount of precision they need to do their research. You are the key. Header artwork is reproduced with permission from Sky & Telescope magazine (www.skyandtelescope.com) Betelgeuse – Alpha Orionis From the city or country sky, from almost any part of the world, the majestic figure of Orion dominates the night sky with his belt, sword, and club. Low and to the right is the great red pulsating supergiant, Betelgeuse (alpha Orionis). Recently acquiring fame for being the first star to have its atmosphere directly imaged (shown below), alpha Orionis has captivated observers' attention for centuries. At minimum brightness, as in 1927 and 1941, its magnitude may drop below 1.2. -
Appendix: Spectroscopy of Variable Stars
Appendix: Spectroscopy of Variable Stars As amateur astronomers gain ever-increasing access to professional tools, the science of spectroscopy of variable stars is now within reach of the experienced variable star observer. In this section we shall examine the basic tools used to perform spectroscopy and how to use the data collected in ways that augment our understanding of variable stars. Naturally, this section cannot cover every aspect of this vast subject, and we will concentrate just on the basics of this field so that the observer can come to grips with it. It will be noticed by experienced observers that variable stars often alter their spectral characteristics as they vary in light output. Cepheid variable stars can change from G types to F types during their periods of oscillation, and young variables can change from A to B types or vice versa. Spec troscopy enables observers to monitor these changes if their instrumentation is sensitive enough. However, this is not an easy field of study. It requires patience and dedication and access to resources that most amateurs do not possess. Nevertheless, it is an emerging field, and should the reader wish to get involved with this type of observation know that there are some excellent guides to variable star spectroscopy via the BAA and the AAVSO. Some of the workshops run by Robin Leadbeater of the BAA Variable Star section and others such as Christian Buil are a very good introduction to the field. © Springer Nature Switzerland AG 2018 M. Griffiths, Observer’s Guide to Variable Stars, The Patrick Moore 291 Practical Astronomy Series, https://doi.org/10.1007/978-3-030-00904-5 292 Appendix: Spectroscopy of Variable Stars Spectra, Spectroscopes and Image Acquisition What are spectra, and how are they observed? The spectra we see from stars is the result of the complete output in visible light of the star (in simple terms).