DOCSLIB.ORG

Nucleosynthesis in the Stellar Systems Omega Centauri And

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Nucleosynthesis in the Stellar Systems Omega Centauri And CSIRO PUBLISHING Publications of the Astronomical Society of Australia, 2011, 28, 28–37 www.publish.csiro.au/journals/pasa Nucleosynthesis in the Stellar Systems v Centauri and M22 G. S. Da CostaA,C and A. F.MarinoB A Research School of Astronomy & Astrophysics, Australian National University, Mt Stromlo Observatory, via Cotter Rd, Weston, ACT 2611, Australia B Dipartimento di Astronomia, Universita` di Padova, vicolo dell’Osservatorio 2, I-35122 Padova, Italy C Corresponding author. Email: [email protected] Received 2010 August 3, accepted 2010 September 7 Abstract: The stellar system v Centauri (v Cen) is well known for the large range in elemental abundances among its member stars. Recent work has indicated that the globular cluster M22 (NGC 6656) also possesses an internal abundance range, albeit substantially smaller than that in v Cen. Here we compare, as a function of [Fe/H], element-to-iron ratios in the two systems for a number of different elements using data from abundance analyses of red giant branch stars. It appears that the nucleosynthetic enrichment processes were very similar in these two systems despite the substantial difference in total mass. Keywords: globular clusters: general — globular clusters: individual (M22, v Cen) — stars: abundances 1 Introduction tidally disrupted by the Milky Way (e.g., Freeman 1993). The stellar system v Centauri (v Cen) has been known for Bekki & Freeman (2003), for example, have shown that a long time to be different from most other Galactic this is dynamically plausible. The different evolutionary globular clusters because its member stars exhibit a wide environment may then have allowed additional chemical range in the abundance of heavier elements such as iron processes that do not occur in ‘regular’ globular clusters (e. and calcium. This contrasts with the situation in most g., Bekki & Norris 2006; Romano et al. 2007, 2010). other globular clusters where the size of any intrinsic The stellar system v Cen is, however, no longer the only spread in the abundance of such elements is smaller than cluster in which a definite range in heavy-element abun- the measurement uncertainties (e.g., Kraft & Ivans 2003; dance is present among the member stars. For example, Carretta et al. 2009b). The wide range in heavy-element following the initial photometric studies of Sarajedini & abundance1 in v Cen was first demonstrated by abun- Layden (1995), Bellazzini et al. (2008) have used spectra at dance measures from spectra of cluster RR Lyrae vari- theCaIItripletofalargesampleofmemberstarstoshow ables (Freeman & Rodgers 1975). This then led to the that the globular cluster M54, which is located at the centre recognition that the large colour width of the red giant of the Sagittarius dwarf galaxy, possesses an internal branch in the colour-magnitude diagram (CMD) of the abundance range characterised by s([Fe/H])int E 0.14 dex cluster, discovered by Woolley (1966) and Geyer (1967) (see also the very recent work of Carretta et al. 2010c). and confirmed by Cannon & Stobie (1973), was a natural Further, two other globular clusters have recently been consequence of the heavy-element abundance spread. shown to have internal ranges in heavy-element abundance. There now exists a large body of spectroscopic data that The first of these is the Galactic bulge globular cluster characterises the range in [Fe/H] in v Cen, and more Terzan 5, for which observations presented in Ferraro et al. particularly, reveals the complex variations in [element/ (2009) reveal the presence of two distinct populations that Fe] ratios with [Fe/H]. The element ratios reveal the differ by a factor of ,3 in [Fe/H], and which likely also nucleosynthetic history of the stellar system, and con- differ significantly in age, with the more metal-rich popula- tributions from both Type II and Type Ia supernovae are tion being younger (Ferraro et al. 2009). The second recognisable, as is a significant role for asymptotic giant globular cluster is M22 (NGC 6656), a stellar system long branch (AGB) stars in the chemical evolution. suspected of possessing similar properties to v Cen (e.g., The difference between v Cen and other globular Norris & Freeman 1983), despite the fact that with MV E clusters has led to the suggestion that v Cen may have À8.5, it is considerably less luminous than either v Cen or formed in a different way from the other clusters — that it is M54, which have MV E À10.3 and À10.0, respectively the nuclear remnant of a former dwarf galaxy that has been (Harris 1996). For M22, Da Costa et al. (2009) used spectra at the Ca II triplet of 41 red giants to derive an [Fe/H] 1 Usually represented by [Fe/H], the logarithm of the iron abundance abundance distribution whose significant width could relative to that found in the Sun. not be explained by differential reddening effects. The Ó Astronomical Society of Australia 2011 10.1071/AS10027 1323-3580/11/01028 Downloaded from https://www.cambridge.org/core. IP address: 170.106.40.40, on 01 Oct 2021 at 08:25:59, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1071/AS10027 Nucleosynthesis in the Stellar Systems v Centauri and M22 29 inter-quartile range for theobserved abundances is 0.24 dex, 2009b), the main sequence structure is best interpreted and the distribution suggests the presence of at least two as indicating distinct He abundance groups, which are components, whose mean metallicities differ by 0.26 dex then likely also related to the multi-modal structure of the (Da Costa et al. 2009). An intrinsic variation in star-to-star horizontal branch in the cluster CMD (e.g., D’Antona abundances in M22 was also revealed recently by the high- et al. 2005). Other clusters for which very precise CMDs resolution spectroscopic study of 17 M22 red giants pre- reveal the existence of main sequence colour widths in sented in Marino et al. (2009). These authors found not only excess of that expected from the photometric errors that there is an intrinsic range in [Fe/H] of order 0.15 dex, include 47 Tuc (Anderson et al. 2009) and NGC 6752 but also that two groups of stars are present in the cluster, (Milone et al. 2010). The origin of the postulated large Y with the iron-richer stars having higher calcium and s- variations in these clusters is poorly understood though process element abundances relative to the iron-poorer stars the same candidates as those employed for explaining (Marino et al. 2009). the O-Na anti-correlation are often invoked (e.g., Renzini While the number of clusters showing internal heavy- 2008). However, although some structure is present in the element abundance variations is small, this is not the case vicinity of the subgiant branch in an HST-based CMD for for the lighter elements. After many decades of work, the M22 (Piotto 2009), there is no evidence for any substan- light elements C, N, O, Na, Al, and Mg are now known to tial He abundance variations within this cluster. In this vary significantly and systematically within all globular respect then, M22 clearly differs from v Cen. clusters for which adequate data are available (e.g., Gratton In this paper we concentrate on a comparison of the et al. 2004; Carretta et al. 2010a). The sense of the varia- element-to-iron abundance ratios, as a function of [Fe/H], tions is such that increases in the nitrogen, sodium and of the red giants in v Cen and M22. This allows an aluminium abundances are coupled with decreases in the investigation of the extent to which similar nucleosyn- carbon, oxygen and magnesium abundances. Together the thetic activities occurred during their evolution, which effects are referred to as the O-Na anti-correlation. The in turn, can constrain their origin. The observational data abundance patterns seen in the Na-rich, O-poor stars are used for the comparison are outlined in the next section. consistent with being produced by the operation of the The comparison is carried out in Section 3, and the results CNO cycle, together with proton-capture reactions on Ne are discussed in Section 4. Briefly, a considerable degree and Mg seeds during H-burning at high temperatures of similarity is found between the two systems, suggesting (Denisenkov & Denisenkova 1990; Langer et al. 1993). that they underwent analogous evolutionary processes. However, the actual site of the nucleosynthesis is not yet clearly established, with the most likely candidates being intermediate-mass AGB stars (e.g., D’Antona & Ventura 2 Observational Data 2007) or rapidly rotating massive stars (e.g., Decressin et al. There are a number of abundance analyses based on high- 2007). Nevertheless, given that the ‘anomalies’ are found resolution spectroscopy available for v Cen red giants. among main sequence stars in at least some clusters, the These include Norris & Da Costa (1995b), Smith et al. origin of the abundance patterns must be related to a (2000), Pancino et al. (2002) and Johnson et al. (2009), each process or processes that occurred during the formation of which differ in sample size, elements studied, of the clusters. In this respect v Cen and M22 are no and metallicity range covered. We will use primarily the different from other globular clusters — the O-Na anti- results of Norris & Da Costa (1995b), who give abundances correlation is clearly present in both systems (Norris & Da for a large number of elements derived from observations Costa 1995a; Marino et al. 2009). of a sample of 40 red giants chosen to cover (almost) the full The stellar system v Cen has one further property that range of [Fe/H] values exhibited by v Cen stars.
Load more

Recommended publications
  • Arxiv:1809.07342V1 [Astro-Ph.SR] 19 Sep 2018
    Draft version September 21, 2018 Preprint typeset using LATEX style emulateapj v. 11/10/09 FAR-ULTRAVIOLET ACTIVITY LEVELS OF F, G, K, AND M DWARF EXOPLANET HOST STARS* Kevin France1, Nicole Arulanantham1, Luca Fossati2, Antonino F. Lanza3, R. O. Parke Loyd4, Seth Redfield5, P. Christian Schneider6 Draft version September 21, 2018 ABSTRACT We present a survey of far-ultraviolet (FUV; 1150 { 1450 A)˚ emission line spectra from 71 planet- hosting and 33 non-planet-hosting F, G, K, and M dwarfs with the goals of characterizing their range of FUV activity levels, calibrating the FUV activity level to the 90 { 360 A˚ extreme-ultraviolet (EUV) stellar flux, and investigating the potential for FUV emission lines to probe star-planet interactions (SPIs). We build this emission line sample from a combination of new and archival observations with the Hubble Space Telescope-COS and -STIS instruments, targeting the chromospheric and transition region emission lines of Si III,N V,C II, and Si IV. We find that the exoplanet host stars, on average, display factors of 5 { 10 lower UV activity levels compared with the non-planet hosting sample; this is explained by a combination of observational and astrophysical biases in the selection of stars for radial-velocity planet searches. We demonstrate that UV activity-rotation relation in the full F { M star sample is characterized by a power-law decline (with index α ≈ −1.1), starting at rotation periods & 3.5 days. Using N V or Si IV spectra and a knowledge of the star's bolometric flux, we present a new analytic relationship to estimate the intrinsic stellar EUV irradiance in the 90 { 360 A˚ band with an accuracy of roughly a factor of ≈ 2.
    [Show full text]
  • Naming the Extrasolar Planets
    Naming the extrasolar planets W. Lyra Max Planck Institute for Astronomy, K¨onigstuhl 17, 69177, Heidelberg, Germany [email protected] Abstract and OGLE-TR-182 b, which does not help educators convey the message that these planets are quite similar to Jupiter. Extrasolar planets are not named and are referred to only In stark contrast, the sentence“planet Apollo is a gas giant by their assigned scientific designation. The reason given like Jupiter” is heavily - yet invisibly - coated with Coper- by the IAU to not name the planets is that it is consid- nicanism. ered impractical as planets are expected to be common. I One reason given by the IAU for not considering naming advance some reasons as to why this logic is flawed, and sug- the extrasolar planets is that it is a task deemed impractical. gest names for the 403 extrasolar planet candidates known One source is quoted as having said “if planets are found to as of Oct 2009. The names follow a scheme of association occur very frequently in the Universe, a system of individual with the constellation that the host star pertains to, and names for planets might well rapidly be found equally im- therefore are mostly drawn from Roman-Greek mythology. practicable as it is for stars, as planet discoveries progress.” Other mythologies may also be used given that a suitable 1. This leads to a second argument. It is indeed impractical association is established. to name all stars. But some stars are named nonetheless. In fact, all other classes of astronomical bodies are named.
    [Show full text]
  • Appendix A: Scientific Notation
    Appendix A: Scientific Notation Since in astronomy we often have to deal with large numbers, writing a lot of zeros is not only cumbersome, but also inefficient and difficult to count. Scientists use the system of scientific notation, where the number of zeros is short handed to a superscript. For example, 10 has one zero and is written as 101 in scientific notation. Similarly, 100 is 102, 100 is 103. So we have: 103 equals a thousand, 106 equals a million, 109 is called a billion (U.S. usage), and 1012 a trillion. Now the U.S. federal government budget is in the trillions of dollars, ordinary people really cannot grasp the magnitude of the number. In the metric system, the prefix kilo- stands for 1,000, e.g., a kilogram. For a million, the prefix mega- is used, e.g. megaton (1,000,000 or 106 ton). A billion hertz (a unit of frequency) is gigahertz, although I have not heard of the use of a giga-meter. More rarely still is the use of tera (1012). For small numbers, the practice is similar. 0.1 is 10À1, 0.01 is 10À2, and 0.001 is 10À3. The prefix of milli- refers to 10À3, e.g. as in millimeter, whereas a micro- second is 10À6 ¼ 0.000001 s. It is now trendy to talk about nano-technology, which refers to solid-state device with sizes on the scale of 10À9 m, or about 10 times the size of an atom. With this kind of shorthand convenience, one can really go overboard.
    [Show full text]
  • A New Form of Estimating Stellar Parameters Using an Optimization Approach
    A&A 532, A20 (2011) Astronomy DOI: 10.1051/0004-6361/200811182 & c ESO 2011 Astrophysics Modeling nearby FGK Population I stars: A new form of estimating stellar parameters using an optimization approach J. M. Fernandes1,A.I.F.Vaz2, and L. N. Vicente3 1 CFC, Department of Mathematics and Astronomical Observatory, University of Coimbra, Portugal e-mail: [email protected] 2 Department of Production and Systems, University of Minho, Portugal e-mail: [email protected] 3 CMUC, Department of Mathematics, University of Coimbra, Portugal e-mail: [email protected] Received 17 October 2008 / Accepted 27 May 2011 ABSTRACT Context. Modeling a single star with theoretical stellar evolutionary tracks is a nontrivial problem because of a large number of unknowns compared to the number of observations. A current way of estimating stellar age and mass consists of using interpolations in grids of stellar models and/or isochrones, assuming ad hoc values for the mixing length parameter and the metal-to-helium enrichment, which is normally scaled to the solar values. Aims. We present a new method to model the FGK main-sequence of Population I stars. This method is capable of simultaneously estimating a set of stellar parameters, namely the mass, the age, the helium and metal abundances, the mixing length parameter, and the overshooting. Methods. The proposed method is based on the application of a global optimization algorithm (PSwarm) to solve an optimization problem that in turn consists of finding the values of the stellar parameters that lead to the best possible fit of the given observations.
    [Show full text]
  • MAS Mentoring Project Overview 2020
    Macarthur Astronomical Society Student Projects in Astronomy A Guide of Teachers and Mentors 2020 (c) Macarthur Astronomical Society, 2020 DRAFT The following Project Overviews are based on those suggested by Dr Rahmi Jackson of Broughton Anglican College. The Focus Questions and Issues section should be used by teachers and mentors to guide students in formulating their own questions about the topic. References to the NSW 7-10 Science Syllabus have been included. Note that only those sections relevant are included. For example, subsections a and d may be used, but subsections b and c are omitted as they do not relate to this topic. A generic risk assessment is provided, but schools should ensure that it aligns with school- based policies. MAS Student Projects in Astronomy page 1 Project overviews Semester 1, 2020: Project Stage Technical difficulty 4 5 6 1 The Moons of Jupiter X X X Moderate to high (extension) NOT available Semester 1 2 Astrophotography X X X Moderate to high 3 Light pollution X X Moderate 4 Variable stars X X Moderate to high 5 Spectroscopy X X High 6 A changing lunarscape X X Low to moderate Recommended project 7 Magnitude of stars X X Moderate to high Recommended for technically able students 8 A survey of southern skies X X Low to moderate 9 Double Stars X X Moderate to high 10 The Phases of the Moon X X Low to moderate Recommended project 11 Observing the Sun X X Moderate MAS Student Projects in Astronomy page 2 Project overviews Semester 2, 2020: Project Stage Technical difficulty 4 5 6 1 The Moons of Jupiter
    [Show full text]
  • The Chemical Composition of Solar-Type Stars and Its Impact on the Presence of Planets
    The chemical composition of solar-type stars and its impact on the presence of planets Patrick Baumann Munchen¨ 2013 The chemical composition of solar-type stars and its impact on the presence of planets Patrick Baumann Dissertation der Fakultat¨ fur¨ Physik der Ludwig-Maximilians-Universitat¨ Munchen¨ durchgefuhrt¨ am Max-Planck-Institut fur¨ Astrophysik vorgelegt von Patrick Baumann aus Munchen¨ Munchen,¨ den 31. Januar 2013 Erstgutacher: Prof. Dr. Achim Weiss Zweitgutachter: Prof. Dr. Joachim Puls Tag der mündlichen Prüfung: 8. April 2013 Zusammenfassung Wir untersuchen eine mogliche¨ Verbindung zwischen den relativen Elementhaufig-¨ keiten in Sternatmospharen¨ und der Anwesenheit von Planeten um den jeweili- gen Stern. Um zuverlassige¨ Ergebnisse zu erhalten, untersuchen wir ausschließlich sonnenahnliche¨ Sterne und fuhren¨ unsere spektroskopischen Analysen zur Bestim- mung der grundlegenden Parameter und der chemischen Zusammensetzung streng differenziell und relativ zu den solaren Werten durch. Insgesamt untersuchen wir 200 Sterne unter Zuhilfenahme von Spektren mit herausragender Qualitat,¨ die an den modernsten Teleskopen gewonnen wurden, die uns zur Verfugung¨ stehen. Mithilfe der Daten fur¨ 117 sonnenahnliche¨ Sterne untersuchen wir eine mogliche¨ Verbindung zwischen der Oberflachenh¨ aufigkeit¨ von Lithium in einem Stern, seinem Alter und der Wahrscheinlichkeit, dass sich ein oder mehrere Sterne in einer Um- laufbahn um das Objekt befinden. Fur¨ jeden Stern erhalten wir sehr exakte grundle- gende Parameter unter Benutzung einer sorgfaltig¨ zusammengestellten Liste von Fe i- und Fe ii-absorptionslinien, modernen Modellatmospharen¨ und Routinen zum Erstellen von Modellspektren. Die Massen und das Alter der Objekte werden mithilfe von Isochronen bestimmt, was zu sehr soliden relativen Werten fuhrt.¨ Bei jungen Sternen, fur¨ die die Isochronenmethode recht unzuverlssig¨ ist, vergleichen wir verschiedene alternative Methoden.
    [Show full text]
  • | University Microfilms, a XEROX Company , Ann Arbor, Michigan I
    THE UPPER CENTAURUS ASSOCIATION Item Type text; Dissertation-Reproduction (electronic) Authors Glaspey, John Warren, 1944- Publisher The University of Arizona. Rights Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. Download date 06/10/2021 14:40:24 Link to Item http://hdl.handle.net/10150/287700 71-21,990 GLASPEY, John Warren, 1944- THE UPPER CENTAURUS ASSOCIATION. The University of Arizona, Ph.D., 1971 Astronomy | University Microfilms, A XEROX Company , Ann Arbor, Michigan i THIS DISSERTATION HAS BEEN MICROFILMED EXACTLY AS RECEIVED THE UPPER CENTAURUS ASSOCIATION by John Warren Glaspey A Dissertation Submitted to the Faculty of the DEPARTMENT OF ASTRONOMY In Partial Fulfillment of the Requirements For the Degree of DOCTOR OF PHILOSOPHY In the Graduate College THE UNIVERSITY OF ARIZONA 19 7 1 THE UNIVERSITY OF ARIZONA GRADUATE COLLEGE I hereby recommend that this dissertation prepared under my direction by John. Warren Glaspev entitled The Upper Centaurus Association be accepted as fulfilling the dissertation requirement of the degree of Doctor of Philosophy (0 Date 7 After inspection of the final copy of the dissertation, the follov/ing members of the Final Examination Committee concur in its approval and recommend its acceptance:* f~el /Qj / 7 7 t \All^VUA^J/( , (.A ftwh I 0 i 0 , ^ —- _ja 7/ [<D ifl/ This approval and acceptance is contingent on the candidate's adequate performance and defense of this dissertation at the final oral examination.
    [Show full text]
  • Pulsating Components in Binary and Multiple Stellar Systems---A
    Research in Astron. & Astrophys. Vol.15 (2015) No.?, 000–000 (Last modified: — December 6, 2014; 10:26 ) Research in Astronomy and Astrophysics Pulsating Components in Binary and Multiple Stellar Systems — A Catalog of Oscillating Binaries ∗ A.-Y. Zhou National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China; [email protected] Abstract We present an up-to-date catalog of pulsating binaries, i.e. the binary and multiple stellar systems containing pulsating components, along with a statistics on them. Compared to the earlier compilation by Soydugan et al.(2006a) of 25 δ Scuti-type ‘oscillating Algol-type eclipsing binaries’ (oEA), the recent col- lection of 74 oEA by Liakos et al.(2012), and the collection of Cepheids in binaries by Szabados (2003a), the numbers and types of pulsating variables in binaries are now extended. The total numbers of pulsating binary/multiple stellar systems have increased to be 515 as of 2014 October 26, among which 262+ are oscillating eclipsing binaries and the oEA containing δ Scuti componentsare updated to be 96. The catalog is intended to be a collection of various pulsating binary stars across the Hertzsprung-Russell diagram. We reviewed the open questions, advances and prospects connecting pulsation/oscillation and binarity. The observational implication of binary systems with pulsating components, to stellar evolution theories is also addressed. In addition, we have searched the Simbad database for candidate pulsating binaries. As a result, 322 candidates were extracted. Furthermore, a brief statistics on Algol-type eclipsing binaries (EA) based on the existing catalogs is given. We got 5315 EA, of which there are 904 EA with spectral types A and F.
    [Show full text]
  • Radial Velocity Measurements of B Stars in the Scorpius-Centaurus Association
    A&A 448, 1001–1006 (2006) Astronomy DOI: 10.1051/0004-6361:20041614 & c ESO 2006 Astrophysics Radial velocity measurements of B stars in the Scorpius-Centaurus association E. Jilinski1,2,S.Daflon1, K. Cunha1, and R. de la Reza1 1 Observatório Nacional/MCT, Rua Gal. Jose Cristino 77, São Cristovão, Rio de Janeiro, Brazil e-mail: [email protected] 2 Main Astronomical Observatory, Pulkovo, St. Petersburg, Russia Received 7 July 2004 / Accepted 30 October 2005 ABSTRACT We derive single-epoch radial velocities for a sample of 56 B-type stars members of the subgroups Upper Scorpius, Upper Centaurus Lupus and Lower Centaurus Crux of the nearby Sco-Cen OB association. The radial velocity measurements were obtained by means of high-resolution echelle spectra via analysis of individual lines. The internal accuracy obtained in the measurements is estimated to be typically 2–3 km s−1, but depends on the projected rotational velocity of the target. Radial velocity measurements taken for 2–3 epochs for the targets HD 120307, HD 142990 and HD 139365 are variable and confirm that they are spectroscopic binaries, as previously identified in the literature. Spectral lines from two stellar components are resolved in the observed spectra of target stars HD 133242, HD 133955 and HD 143018, identifying them as spectroscopic binaries. Key words. stars: early-type – stars: binaries: spectroscopic – stars: kinematics – techniques: radial velocities – open clusters and associations: individual: Scorpius-Centaurus association 1. Introduction until their main first orbits confinement was found, as well as the past mean positions of LCC and UCL. This enabled not The Scorpius-Centaurus association is the nearest associa- only to determine the dynamical age of this moving group, tion of young OB stars to the Sun.
    [Show full text]
  • Uranometría Argentina Bicentenario
    URANOMETRÍA ARGENTINA BICENTENARIO Reedición electrónica ampliada, ilustrada y actualizada de la URANOMETRÍA ARGENTINA Brillantez y posición de las estrellas fijas, hasta la séptima magnitud, comprendidas dentro de cien grados del polo austral. Resultados del Observatorio Nacional Argentino, Volumen I. Publicados por el observatorio 1879. Con Atlas (1877) 1 Observatorio Nacional Argentino Dirección: Benjamin Apthorp Gould Observadores: John M. Thome - William M. Davis - Miles Rock - Clarence L. Hathaway Walter G. Davis - Frank Hagar Bigelow Mapas del Atlas dibujados por: Albert K. Mansfield Tomado de Paolantonio S. y Minniti E. (2001) Uranometría Argentina 2001, Historia del Observatorio Nacional Argentino. SECyT-OA Universidad Nacional de Córdoba, Córdoba. Santiago Paolantonio 2010 La importancia de la Uranometría1 Argentina descansa en las sólidas bases científicas sobre la cual fue realizada. Esta obra, cuidada en los más pequeños detalles, se debe sin dudas a la genialidad del entonces director del Observatorio Nacional Argentino, Dr. Benjamin A. Gould. Pero nada de esto se habría hecho realidad sin la gran habilidad, el esfuerzo y la dedicación brindada por los cuatro primeros ayudantes del Observatorio, John M. Thome, William M. Davis, Miles Rock y Clarence L. Hathaway, así como de Walter G. Davis y Frank Hagar Bigelow que se integraron más tarde a la institución. Entre éstos, J. M. Thome, merece un lugar destacado por la esmerada revisión, control de las posiciones y determinaciones de brillos, tal como el mismo Director lo reconoce en el prólogo de la publicación. Por otro lado, Albert K. Mansfield tuvo un papel clave en la difícil confección de los mapas del Atlas. La Uranometría Argentina sobresale entre los trabajos realizados hasta ese momento, por múltiples razones: Por la profundidad en magnitud, ya que llega por vez primera en este tipo de empresa a la séptima.
    [Show full text]
  • May 2018 BRAS Newsletter
    Monthly Meeting Monday, May 14th at 7PM at HRPO (Monthly meetings are on 2nd Mondays, Highland Road Park Observatory). Presenter: James Gutierrez and the topic will be ‘A Star is Born’. What's In This Issue? President’s Message Secretary's Summary Outreach Report Astrophotography Group Light Pollution Committee Report Recent Forum Entries 20/20 Vision Campaign Members’ Corner – Space Hipsters 2018 Outing Messages from the HRPO Friday Night Lecture Series NASA Events Globe at Night American Radio Relay League Field Day Observing Notes – Centaurus – The Centaur & Mythology Like this newsletter? See PAST ISSUES online back to 2009 Visit us on Facebook – Baton Rouge Astronomical Society Newsletter of the Baton Rouge Astronomical Society May 2018 © 2018 President’s Message We are well into spring now, most of the weekends in April have been cloud out for skywatchers. We had an excellent showing for International Astronomy Day and were able to show the public views of the Sun with a sunspot. The sunspot was some welcome lagniappe given the fact that the Sun is moving towards solar minimum and there have been fewer sunspots this year. BRAS has been given 160 member pins. All members are asked to come to HRPO to receive and sign for their pin. Each member gets one pin for free. Pick yours up this May 14th, 7 pm, HRPO, or at any monthly meeting. Mars is now (May 1, 2018) at an apparent magnitude of -0.37 and will brighten to an apparent magnitude of - 2.79 on July 26, 2018, the date of the 2018 Great Martian Opposition.
    [Show full text]
  • Heber Doust Curtis 1872-1942
    NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA BIOGRAPHICAL MEMOIRS VOLUME XXII—THIRTEENTH MEMOIR BIOGRAPHICAL MEMOIR OF HEBER DOUST CURTIS 1872-1942 BY ROBERT G. AITKEN PRESENTED TO THE ACADEMY AT THE AUTUMN MEETING, 1942 HEBER DOUST CURTIS 1872-1942 BY ROBERT G. AITKEN "Call Dr. Curtis!"—It was gray dawn of a raw December morning on Mount Hamilton, thirty years ago, and our eldest son, home from the university for his Christmas vacation, had roused us, his face drawn and distorted by the agonizing pain in his right abdomen. A word to our physician in San Jose had brought the curt order, "Bring the boy down at once. There's no time to lose. It's probably acute appendicitis." By the time the boy and I were ready for the trip, Dr. Curtis had his automobile at the door and we were off on the three and one-half hour trip over the half-frozen, adobe mud road to San Jose. Surgeon and operating room were ready, and as soon as was humanly possible a highly inflamed appendix, just ready to burst, had been safely removed, and a relieved boy was coming peacefully out from the influence of the anesthetic. Then Dr. Curtis, having first telephoned to the Lick Observa- tory to find out if he could do any town errands for anyone "at the top", started cheerfully back on his long, lonesome drive to the mountain, happy in the thought that he had once again been able to be of service. I tell this story at the beginning of my sketch of the career of Dr.
    [Show full text]