DOCSLIB.ORG

00 Oo Oo UBVRI PHOTOMETRIC STANDARD STARS AROUND THE

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
00 Oo Oo UBVRI PHOTOMETRIC STANDARD STARS AROUND THE O'! 00 THE ASTRONOMICAL JOURNAL VOLUME 88, NUMBER 3 MARCH 1983 oo UBVRI PHOTOMETRIC STANDARD STARS AROUND THE CELESTIAL EQUATOR8' ARLOU. LANDOLTb) LSU Observatory, Baton Rouge, Louisiana 70803 1983AJ. Received 8 November 1982 ABSTRACT UBVRI photoelectric observations have been made of 223 stars mostly in an approximate two degree band centered on the celestial equator. The observing program was planned to provide new UBVRI standard stars, available to telescopes of a variety of sizes in both hemispheres, on an internally consistent homogeneous system around the sky. Most of the stars are in Selected Areas 92-115. The stars average 20.7 measures each on 12.2 different nights. The stars in this paper fall in the range 1SVS 12.5 and — 0.35(5 — V)S + 2.0. I. INTRODUCTION ble to telescopes of all sizes in both hemispheres. The observational data were tied into the UBV standard Accurate, internally consistent, and readily accessi- stars of Landolt (1973) and the RI standards of Cousins ble standard star photometric sequences are necessary (1976). for the calibration of the intensity and color data that The observing plan by necessity focused on a boot- astronomers obtain at the telescope. The most used pho- strapping theme. The Cousins (1976) R/standard stars tometric system during the past twenty-five years has available at the time that the project began were bright, been the UBV system, developed by Johnson and Mor- mostly V <1.0. Therefore, it was necessary to begin the gan (1953). Additional refinements were published by manufacture of new standard stars at the 0.4-m tele- Johnson and Harris (1954) and by Johnson (1955). Lan- scope. Even then, several of the stars of more extreme dolt (1973) published an extensive list of several hundred color were unobservable because they were just too stars tied into the Johnson UBV photometric system. These stars, designed to be used as standards, were lo- bright for the 0.4-m telescope RCA 31034 pulse count- cated in the celestial equatorial Selected Areas, and ing combination. Stars made into standard stars via the hence were available to astronomers in both hemi- 0.4-m telescope were then to be used as standard stars at spheres. the 0.9-m telescope, and so on, using larger telescopes at The UBV photometric system has been expanded to each step of the process. Such bootstrapping also would two additional spectral regions, R (7000A) and / lessen demand for telescope time on the larger instru- (9000A). This expanded photometric system also was ments. developed under the guidance of H. L. Johnson (John- The Cerro Tololo Inter-American Observatory son, Mitchell, Iriarte, and Wisniewski 1966, and refer- (CTIO) 0.4-m and 0.9-m telescopes were scheduled for ences therein). Another RI system had been defined via 89 and 91 nights, respectively, in the interval September observations published by Kron, White, and Gascoigne 1977 through October 1981. Acceptable photometric (1953). The effective wavelengths of their RI filters, data were obtained for this program on 53 0.4-m tele- though, were located at shorter wavelengths: R at scope nights and on 410.9-m telescope nights. As will be 6800A and / at 8250Á. This latter RI system was modi- shown elsewhere (Landolt 1983, in preparation), addi- fied and extended by Cousins (1976). tional nights on these two telescopes were used to check equipment stability. Sixty-six percent of the telescope II. THE PROGRAM time assigned to this part of the project was photomet- ric. The photometric results in this paper represent the All of the photometric observations were made with first part of an effort to provide UBVRI photoelectric an RCA 31034 type photomultiplier used in a pulse photometric standard stars in the magnitude range counting mode. The various photomultipliers available 1 <V <\1 over as broad a range in color as possible. The to guest observers at CTIO were operated at voltages stars that were observed are located in a band centered recommended by the CTIO operations staff. The data on the celestial equator, and therefore are easily accessi- obtained at the 0.4-m telescope were printed on paper tape. The data were averaged by hand and entered into a a) Contribution of the Louisiana State University Observatory No. computer program which subsequently did the process- 174. ing. Data obtained at the 0.9-m telescope were recorded b) Visiting Astronomer, 1977-1981, at Cerro Tololo Inter-American on magnetic tape and hence were easily transferable for Observatory which is operated by the Association of Universities for final reduction. All data reductions were accomplished Research in Astronomy, Inc., under contract with the National via an IBM 3033 computer at the Louisiana State Uni- Science Foundation. versity System Network Computer Center. 439 Astron. J. 88 (3), March 1983 0004-6256/83/030439-22$00.90 © 1983 Am. Astron. Soc. 439 © American Astronomical Society • Provided by the NASA Astrophysics Data System O'! 00 440 A. U. LANDOLT: UBVRI PHOTOMETRIC STANDARDS 440 oo a) The 0.4-m Telescope Observations Table II. Filters used early in program. Some 15 to 25 standard stars chosen from Cousins’ V Corning 3384 + Corning 9780 lists (1973, 1976) in the E-regions were observed each B Corning 5030 + GG 385 U Corning 9863 + solid Cu S04 crystal 1983AJ. night along with the program stars. UBVRI standard R 4 mm Schott KG 1 + 2 mm OG 5 + 1.5 mm RG 6 stars were observed periodically throughout the night. / 3 mm Schott RG 715+1 mm RG 780 They were observed in groups of at least three to four, each group containing stars in as wide a color range as possible. In general, the standard stars were observed over an air mass range at least as great as the program An extensive effort was undertaken by Dr. John A. stars. The vast majority of the program star observa- Graham of the CTIO staff during 1977 and early 1978 to tions were obtained at less than 1.5 air masses. determine the best filter combination to be used in con- The data were obtained in a series of measures junction with the RCA 31034 photomultiplier. The VBURIIRUBV star plus sky followed by VBURI sky goal, of course, was to match as best one could, the UBV measures. A 27-second of arc diaphragm was used on photometric system as well as the Cousins R/photome- most occasions. Ten-second counting intervals normal- try. Since then, a similar extensive study has been pub- ly proved sufficient for the magnitude range encoun- lished by Bessell (1976, 1979). His work shows that even tered. The reduction of the observational data followed the temperature level to which the photomultiplier is the precepts outlined by Schulte and Crawford (1961). cooled (Bessel 1979, Appendix I) has an effect upon the The standard stars also were used to provide extinc- transformation relations. An observer, therefore, needs tion information. A given night’s data were reduced us- to match filters as closely as circumstances allow, ing extinction coefficients derived from that night should use the same type photomultiplier, and should whenever possible. This technique was adopted for this cool to some “standard stable” temperature (usually dry project after finding overall results with smaller errors ice) to ensure the best possible transformation. than were obtained through the use of mean extinction The first three observing runs, September 1977, Jan- coefficients for the same data. As a point of information, uary 1978, and April 1978, saw use of the filter combina- the average extinction coefficients found over the fifty- tions listed in Table II. At that point, following Gra- month interval during which these data were obtained ham’s efforts, a switch was made to the filters given in are presented in Table I. Table III. These filters were used for the remainder of All observational data were timed via an Accutron the program. Graham’s (1982) Fig. 1 shows their trans- clock in the 0.4-m telescope dome or via the computer mission characteristics. clock in the 0.9-m telescope dome. One piece of informa- The program stars observed at the 0.4-m telescope tion included on the final computer printout was the were chosen from two sources. First, stars were taken magnitude and color indice residuals for each of the from those published earlier (Landolt 1973). Their char- standard stars. Hence, it was possible to plot the residu- acteristics were a known quantity, and their value as als in the V magnitude and the different color indices for standard stars could be enhanced by adding RI color each standard star against Universal Time for a given indices to the already known C/2?Finfbrmation. In addi- night. These plots permitted small corrections to be tion, further UBV measures would double check the made to all program star measures. The corrections nor- constancy of the stars both in brightness and in color. mally were less than a few hundredths of a magnitude. Second, since a shortcoming of those standard stars Such corrections took into account small changes in published earlier was a shortage of stars of a really broad both atmospheric and instrumental conditions. Proof of range in color, an attempt was made via a literature the need for this kind of correction is shown by the im- search to locate quite blue and red stars. provement in the accuracy of the final results. A total of 147 stars made up the program at the 0.4-m telescope, most stars falling within a degree or two of the celestial equator, and distributed around the sky in right Table I.
Load more

Recommended publications
  • Luminosity - Wikipedia
    12/2/2018 Luminosity - Wikipedia Luminosity In astronomy, luminosity is the total amount of energy emitted by a star, galaxy, or other astronomical object per unit time.[1] It is related to the brightness, which is the luminosity of an object in a given spectral region.[1] In SI units luminosity is measured in joules per second or watts. Values for luminosity are often given in the terms of the luminosity of the Sun, L⊙. Luminosity can also be given in terms of magnitude: the absolute bolometric magnitude (Mbol) of an object is a logarithmic measure of its total energy emission rate. Contents Measuring luminosity Stellar luminosity Image of galaxy NGC 4945 showing Radio luminosity the huge luminosity of the central few star clusters, suggesting there is an Magnitude AGN located in the center of the Luminosity formulae galaxy. Magnitude formulae See also References Further reading External links Measuring luminosity In astronomy, luminosity is the amount of electromagnetic energy a body radiates per unit of time.[2] When not qualified, the term "luminosity" means bolometric luminosity, which is measured either in the SI units, watts, or in terms of solar luminosities (L☉). A bolometer is the instrument used to measure radiant energy over a wide band by absorption and measurement of heating. A star also radiates neutrinos, which carry off some energy (about 2% in the case of our Sun), contributing to the star's total luminosity.[3] The IAU has defined a nominal solar luminosity of 3.828 × 102 6 W to promote publication of consistent and comparable values in units of https://en.wikipedia.org/wiki/Luminosity 1/9 12/2/2018 Luminosity - Wikipedia the solar luminosity.[4] While bolometers do exist, they cannot be used to measure even the apparent brightness of a star because they are insufficiently sensitive across the electromagnetic spectrum and because most wavelengths do not reach the surface of the Earth.
    [Show full text]
  • Module 09 Colour Index TABLE of CONTENTS 1. Learning Outcomes
    Module 09 Colour Index TABLE OF CONTENTS 1. Learning Outcomes 2. Introduction 3. Dependence of magnitudes on wavelength 3.1. UBV System of Johnson and Morgan 3.2. Colour Index 3.3. Colour-Colour Diagrams 3.4. Colour Excess 3.5. Reddening and Redshift 4. Summary 1. Learning Outcomes After studying this module, you should be able to Appreciate that the magnitude depends on the wavelength at which it is measured Understand the need of UBV photometric system Realize that the UBV system at present measures magnitudes at various wavelength bands other than the visual region Understand why magnitudes of stars at various wavelength bands of their spectra are not equal Grasp the concept of colour index Understand that the colour index follows the surface temperature of the star Realize the importance of colour-colour diagrams in describing stars 2. Introduction In the last module we introduced the concept of magnitudes. Apparent magnitude is a number assigned to a star (or any other celestial object) to indicate its brightness. Brighter stars are assigned lower magnitudes and fainter stars are characterized by higher magnitudes. Only stars brighter than 6th magnitude are visible to the unaided eye. Since brightness is a function of distance and the intrinsic brightness of a star, apparent magnitude does not allow us to compare stars with respect to their intrinsic brightness. Therefore, to compare brightness all stars are thought to be at a standard distance of 10 pc. The apparent magnitude at this distance is called the absolute magnitude of the star. It turns out that the difference between the absolute magnitudes of two stars is proportional to the ratio of their luminosities.
    [Show full text]
  • 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 :::::::::::::::::::::::::::::::::::::::
    [Show full text]
  • Infrared Flux Excesses from Hot Subdwarfs
    ASTRONOMY & ASTROPHYSICS OCTOBER I 1998,PAGE1 SUPPLEMENT SERIES Astron. Astrophys. Suppl. Ser. 132, 1–12 (1998) Infrared flux excesses from hot subdwarfs? II. 72 more objects?? A. Ulla1,2 and P. Thejll3 1 Universidade de Vigo, Departamento de F´ısica Aplicada, Area de F´ısica da Terra, Astronom´ıa e Astrof´ısica, Facultade de Ciencias, Campus Marcosende-Lagoas, Apartado Postal 874, E-36200 Vigo, Spain 2 Instituto de Astrof´ısica de Canarias, E-38200 La Laguna, Spain 3 Danish Meteorological Institute, Lyngbyvej 100, DK-2100 Copenhagen, Denmark Received December 19, 1996; accepted March 20, 1998 Abstract. In our search, started in February, 1994, for 1. Introduction JHK excess fluxes among the hot subdwarf population as an indicator for the presence of binary companions, Thejll et al. (1995; hereafter Paper I) discussed the pos- results for 72 more hot objects (=63 hot subdwarfs + sible origin for excess infrared fluxes detected from the 1 Horizontal Branch B star + 7 white dwarfs + 1 non- direction of a hot subdwarf star (sd). They presented a subdwarf object) observed with the Carlos S´anchez CVF set of JHK measurements for 27 hot objects: 23 hot sds, IR photometer (in June and October, 1994), are presented. GD274 –which the authors reclassify as sd+K3-K8, and 3 The exact number of binary hot subdwarfs has gained re- white dwarfs (WDs). An analysis was also presented for newed importance after the recent discovery of pulsators the, then 24, hot subdwarfs. After considering a wind ex- with G-F companions. The total number of candidates we pelled from the hot atmosphere as the source of the excess propose may help to set some constraints; for example, IR radiation, the authors concluded that the most likely out of 41 objects with excesses, 13 may have G-type bi- explanation is the presence of a cool stellar companion nary companions.
    [Show full text]
  • Discovery of a Close Substellar Companion to the Hot Subdwarf Star Hd 149382—The Decisive Influence of Substellar Objects on Late Stellar Evolution
    The Astrophysical Journal, 702:L96–L99, 2009 September 1 doi:10.1088/0004-637X/702/1/L96 C 2009. The American Astronomical Society. All rights reserved. Printed in the U.S.A. DISCOVERY OF A CLOSE SUBSTELLAR COMPANION TO THE HOT SUBDWARF STAR HD 149382—THE DECISIVE INFLUENCE OF SUBSTELLAR OBJECTS ON LATE STELLAR EVOLUTION S. Geier1, H. Edelmann1,3, U. Heber1, and L. Morales-Rueda2 1 Dr. Remeis-Sternwarte, Institute for Astronomy, University Erlangen-Nurnberg,¨ Sternwartstr. 7, 96049 Bamberg, Germany; [email protected] 2 Department of Astrophysics, Faculty of Science, Radboud University Nijmegen, P.O. Box 9010, 6500 GL Nijmegen, The Netherlands 3 McDonald Observatory, University of Texas at Austin, 1 University Station, C1402, Austin, TX 78712-0259, USA Received 2009 April 29; accepted 2009 August 5; published 2009 August 17 ABSTRACT Substellar objects, like planets and brown dwarfs orbiting stars, are by-products of the star formation process. The evolution of their host stars may have an enormous impact on these small companions. Vice versa a planet might also influence stellar evolution as has recently been argued. Here, we report the discovery of an 8−23 Jupiter-mass substellar object orbiting the hot subdwarf HD 149382 in 2.391 d at a distance of only about five solar radii. Obviously, the companion must have survived engulfment in the red giant envelope. Moreover, the substellar companion has triggered envelope ejection and enabled the sdB star to form. Hot subdwarf stars have been identified as the sources of the unexpected ultraviolet (UV) emission in elliptical galaxies, but the formation of these stars is not fully understood.
    [Show full text]
  • A Study of Two Open Clusters Containing Wolf-Rayet Stars
    A STUDY OF TWO OPEN CLUSTERS CONTAINING WOLF-RAYET STARS by Stephen L. Shorlin A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE DEPARTMENT OF ASTRONOlMY AND PHYSICS SAINT MARY'S UMNERSITY MAY 1998 HALIFAX, NOVA SCOTIA Ostephen L. Shorlin, 1998 National Library Bibliothèque nationale I*m of Canada du Canada Acquisitions and Acquisitions et Bibliographie Services services bibliographiques 395 Wellington Street 395. nie Wellington Ottawa ON K1A ON4 Ottawa ON KIA ON4 Canada Canada The author has granted a non- L'auteur a accordé une licence non exclusive licence allowing the exclusive permettant à la National Library of Canada to Bibliothèque nationale du Canada de reproduce, loau, distribute or seU reproduire, prêter, distribuer ou copies of this thesis in microfoq vendre des copies de cette thèse sous paper or electronic formats. la fome de microfiche/nIm, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantial extracts fiom it Ni la thèse ni des extraits substantiels may be printed or otherwise de celle-ci ne doivent être imprimes reproduced *out the author's ou autrement reproduits sans son permission. autorisation- Abstract The results of UBV CCD photornetry are presented for a newly discovered open cluster, as well as new photornetry for thirty-seven members of the open cluster HM 1. The new open cluster, to be designated OCL 1104610, has a distance modulus of Vo - l'LIV = 15.5 & 0.2: corresponding to a distance of 12.61::: kpc, and is several Myr old.
    [Show full text]
  • Publications of the Astronomical Society of the Pacific 107: 945-958, 1995 October
    Publications of the Astronomical Society of the Pacific 107: 945-958, 1995 October Galaxy Colors in Various Photometric Band Systems M. Fukugita1 Institute for Advanced Study, Princeton, New Jersey 08540 Electronic mail: [email protected] K. Shimasaku2 Princeton University Observatory, Princeton, New Jersey 08544 Electronic mail: [email protected] T. ICHIKAWA Kiso Observatory, University of Tokyo, Kiso-gun, Nagano 397-01, Japan Electronic mail: [email protected] Received 1995 March 10; accepted 1995 June 14 ABSTRACT. A study is made of stellar and galaxy colors using a spectrophotometric synthesis technique. We show that use of good color response functions and a modem determination of the spectroscopic energy distribution for a Lyr gives synthetic stellar colors in a good agreement with photometric observations to about 0.05 mag. The synthetic method then is applied to study galaxy colors using the spectrophotometric atlas of Kennicutt (1992, ApJS, 79, 255), and a comparison is made with observed galaxy colors. The Κ correction is calculated and compared with that of Coleman, Wu, and Weedman (1980, ApJS, 43, 393). We then study colors of galaxies in various photometric band systems and obtain color transformation laws, which enable us to find offsets among different systems. We include 48 photometric bands in our study. 1. INTRODUCTION in addition to a good sample of galaxy SED over a wide range of wavelength. Continual efforts to obtain the SED of Colors of galaxies provide us with valuable information Vega (Oke and Schild 1970; Hayes and Latham 1975; Oke concerning their present-day composition of stars, and ac- and Gunn 1983; Kurucz 1979; Hayes 1985, hereafter re- cordingly it gives us hints about the formation and evolution ferred to as H85; Castelli and Kurucz 1994, hereafter re- of galaxies.
    [Show full text]
  • Mètodes De Detecció I Anàlisi D'exoplanetes
    MÈTODES DE DETECCIÓ I ANÀLISI D’EXOPLANETES Rubén Soussé Villa 2n de Batxillerat Tutora: Dolors Romero IES XXV Olimpíada 13/1/2011 Mètodes de detecció i anàlisi d’exoplanetes . Índex - Introducció ............................................................................................. 5 [ Marc Teòric ] 1. L’Univers ............................................................................................... 6 1.1 Les estrelles .................................................................................. 6 1.1.1 Vida de les estrelles .............................................................. 7 1.1.2 Classes espectrals .................................................................9 1.1.3 Magnitud ........................................................................... 9 1.2 Sistemes planetaris: El Sistema Solar .............................................. 10 1.2.1 Formació ......................................................................... 11 1.2.2 Planetes .......................................................................... 13 2. Planetes extrasolars ............................................................................ 19 2.1 Denominació .............................................................................. 19 2.2 Història dels exoplanetes .............................................................. 20 2.3 Mètodes per detectar-los i saber-ne les característiques ..................... 26 2.3.1 Oscil·lació Doppler ........................................................... 27 2.3.2 Trànsits
    [Show full text]
  • HET Publication Report HET Board Meeting 3/4 December 2020 Zoom Land
    HET Publication Report HET Board Meeting 3/4 December 2020 Zoom Land 1 Executive Summary • There are now 420 peer-reviewed HET publications – Fifteen papers published in 2019 – As of 27 November, nineteen published papers in 2020 • HET papers have 29363 citations – Average of 70, median of 39 citations per paper – H-number of 90 – 81 papers have ≥ 100 citations; 175 have ≥ 50 cites • Wide angle surveys account for 26% of papers and 35% of citations. • Synoptic (e.g., planet searches) and Target of Opportunity (e.g., supernovae and γ-ray bursts) programs have produced 47% of the papers and 47% of the citations, respectively. • Listing of the HET papers (with ADS links) is given at http://personal.psu.edu/dps7/hetpapers.html 2 HET Program Classification Code TypeofProgram Examples 1 ToO Supernovae,Gamma-rayBursts 2 Synoptic Exoplanets,EclipsingBinaries 3 OneorTwoObjects HaloofNGC821 4 Narrow-angle HDF,VirgoCluster 5 Wide-angle BlazarSurvey 6 HETTechnical HETQueue 7 HETDEXTheory DarkEnergywithBAO 8 Other HETOptics Programs also broken down into “Dark Time”, “Light Time”, and “Other”. 3 Peer-reviewed Publications • There are now 420 journal papers that either use HET data or (nine cases) use the HET as the motivation for the paper (e.g., technical papers, theoretical studies). • Except for 2005, approximately 22 HET papers were published each year since 2002 through the shutdown. A record 44 papers were published in 2012. • In 2020 a total of fifteen HET papers appeared; nineteen have been published to date in 2020. • Each HET partner has published at least 14 papers using HET data. • Nineteen papers have been published from NOAO time.
    [Show full text]
  • The ∆A Photometric System
    Ernst Paunzen (Autor) The _a photometric system https://cuvillier.de/de/shop/publications/8305 Copyright: Cuvillier Verlag, Inhaberin Annette Jentzsch-Cuvillier, Nonnenstieg 8, 37075 Göttingen, Germany Telefon: +49 (0)551 54724-0, E-Mail: [email protected], Website: https://cuvillier.de 1 Summary This book describes the history, characteristics, observations, results and future prospects of the Δa photometric system. Up to now, it success- fully produced countless scientific output since its development and first appearance on the astronomical scene initiated by Hans-Michael Maitzen in 1976. It was intended to study the typical and unique flux depression at 5200 A˚ found in mainly magnetic chemically peculiar stars of the upper main sequence. Therefore the most important measurement is through the g2 filter centred at this wavelength region. In addition, one needs the information about the continuum flux of the same object. Originally, the g1 (centred at 5000A)˚ and Str¨omgren y (5500A)˚ was used to get the continuum flux. In principle, any other filters such as Johnson BV RI can be used. However, the closer it is measured to the 5200A˚ region and the narrower the used filters are, the results become more accurate. The a index is then defined as the flux in g2 compared to the continuum one. Because there is a general increase of opacity around 5200A˚ with decreasing temperature, one has to normalize a with the index a0 of a non-peculiar star of the same temperature, to compare different peculiar (or deviating) stars with each other (Δa index). With this photometric system it is possible to measure any peculiarities, such as abnormal absorption and emission lines, in the region of 5200A.˚ Soon, it was used to investigate metal-weak, Be/shell and supergiants in the Galactic field and open clusters.
    [Show full text]
  • Full Curriculum Vitae
    Jason Thomas Wright—CV Department of Astronomy & Astrophysics Phone: (814) 863-8470 Center for Exoplanets and Habitable Worlds Fax: (814) 863-2842 525 Davey Lab email: [email protected] Penn State University http://sites.psu.edu/astrowright University Park, PA 16802 @Astro_Wright US Citizen, DOB: 2 August 1977 ORCiD: 0000-0001-6160-5888 Education UNIVERSITY OF CALIFORNIA, BERKELEY PhD Astrophysics May 2006 Thesis: Stellar Magnetic Activity and the Detection of Exoplanets Adviser: Geoffrey W. Marcy MA Astrophysics May 2003 BOSTON UNIVERSITY BA Astronomy and Physics (mathematics minor) summa cum laude May 1999 Thesis: Probing the Magnetic Field of the Bok Globule B335 Adviser: Dan P. Clemens Awards and fellowships NASA Group Achievement Award for NEID 2020 Drake Award 2019 Dean’s Climate and Diversity Award 2012 Rock Institute Ethics Fellow 2011-2012 NASA Group Achievement Award for the SIM Planet Finding Capability Study Team 2008 University of California Hewlett Fellow 1999-2000, 2003-2004 National Science Foundation Graduate Research Fellow 2000-2003 UC Berkeley Outstanding Graduate Student Instructor 2001 Phi Beta Kappa 1999 Barry M. Goldwater Scholar 1997 Last updated — Jan 15, 2021 1 Jason Thomas Wright—CV Positions and Research experience Associate Department Head for Development July 2020–present Astronomy & Astrophysics, Penn State University Director, Penn State Extraterrestrial Intelligence Center March 2020–present Professor, Penn State University July 2019 – present Deputy Director, Center for Exoplanets and Habitable Worlds July 2018–present Astronomy & Astrophysics, Penn State University Acting Director July 2020–August 2021 Associate Professor, Penn State University July 2015 – June 2019 Associate Department Head for Diversity and Equity August 2017–August 2018 Astronomy & Astrophysics, Penn State University Visiting Associate Professor, University of California, Berkeley June 2016 – June 2017 Assistant Professor, Penn State University Aug.
    [Show full text]
  • Fundamental Stellar Photometry for Standards of Spectral Type on the Revised System of the Yerkes Spectral Atlas “
    COMMENTS ON THE PAPER “FUNDAMENTAL STELLAR PHOTOMETRY FOR STANDARDS OF SPECTRAL TYPE ON THE REVISED SYSTEM OF THE YERKES SPECTRAL ATLAS “ BY H.L. JOHNSON AND W.W. MORGAN (1953) SIDNEY VAN DEN BERGH Dominion Astrophysical Observatory Herzberg Institute of Astrophysics National Research Council of Canada 5071 West Saanich Road Victoria, British Columbia, V8X 4M6 Canada Received 1998, December 3 Photometry and spectroscopy are among the most important and fundamental types of astronomical observations. By the middle of the twentieth century most spectral classification was defined in terms of MKK type standards (Morgan, Keenan & Kellerman 1943). However, for a variety of reasons (Weaver 1947), the establishment of photometric standards remained problematic. Commission 25 (Photometry) of the International Astronomical Union devoted seemingly endless years to discussions on the establishment of an international photometric standard system. Weaver (1952) advocated that a new sub- commission should be created which would have as its task “The establishment of an ‘ideal’ photo-electric color and magnitude system.” A subsequent IAU resolution (Oosterhoff 1954) suggested that “La Commission recommende que soit constituJe une nouvelle sous-commission des Jtalons de magnitudes - 2 - stellaire....”. Additional problems were: (1) The Commission could not decide between monochromatic magnitudes and broad-band magnitudes, and (2) some advocated a two-color system (Hertzsprung 1950), whereas others (Becker 1946) favored a three-color (photographic, photovisual, red) photometric system. In his characteristically energetic fashion Johnson (Johnson & Morgan 1951) then took the bull by the horns and started to observe so many stars and clusters on his UBV system that it soon became the de facto international photometric system1.
    [Show full text]