Unlocking Galactic Wolf-Rayet Stars with $\Textit {Gaia} $ DR2 II: Cluster
Total Page:16
File Type:pdf, Size:1020Kb
Load more
Recommended publications
-
Astronomie in Theorie Und Praxis 8. Auflage in Zwei Bänden Erik Wischnewski
Astronomie in Theorie und Praxis 8. Auflage in zwei Bänden Erik Wischnewski Inhaltsverzeichnis 1 Beobachtungen mit bloßem Auge 37 Motivation 37 Hilfsmittel 38 Drehbare Sternkarte Bücher und Atlanten Kataloge Planetariumssoftware Elektronischer Almanach Sternkarten 39 2 Atmosphäre der Erde 49 Aufbau 49 Atmosphärische Fenster 51 Warum der Himmel blau ist? 52 Extinktion 52 Extinktionsgleichung Photometrie Refraktion 55 Szintillationsrauschen 56 Angaben zur Beobachtung 57 Durchsicht Himmelshelligkeit Luftunruhe Beispiel einer Notiz Taupunkt 59 Solar-terrestrische Beziehungen 60 Klassifizierung der Flares Korrelation zur Fleckenrelativzahl Luftleuchten 62 Polarlichter 63 Nachtleuchtende Wolken 64 Haloerscheinungen 67 Formen Häufigkeit Beobachtung Photographie Grüner Strahl 69 Zodiakallicht 71 Dämmerung 72 Definition Purpurlicht Gegendämmerung Venusgürtel Erdschattenbogen 3 Optische Teleskope 75 Fernrohrtypen 76 Refraktoren Reflektoren Fokus Optische Fehler 82 Farbfehler Kugelgestaltsfehler Bildfeldwölbung Koma Astigmatismus Verzeichnung Bildverzerrungen Helligkeitsinhomogenität Objektive 86 Linsenobjektive Spiegelobjektive Vergütung Optische Qualitätsprüfung RC-Wert RGB-Chromasietest Okulare 97 Zusatzoptiken 100 Barlow-Linse Shapley-Linse Flattener Spezialokulare Spektroskopie Herschel-Prisma Fabry-Pérot-Interferometer Vergrößerung 103 Welche Vergrößerung ist die Beste? Blickfeld 105 Lichtstärke 106 Kontrast Dämmerungszahl Auflösungsvermögen 108 Strehl-Zahl Luftunruhe (Seeing) 112 Tubusseeing Kuppelseeing Gebäudeseeing Montierungen 113 Nachführfehler -
A Basic Requirement for Studying the Heavens Is Determining Where In
Abasic requirement for studying the heavens is determining where in the sky things are. To specify sky positions, astronomers have developed several coordinate systems. Each uses a coordinate grid projected on to the celestial sphere, in analogy to the geographic coordinate system used on the surface of the Earth. The coordinate systems differ only in their choice of the fundamental plane, which divides the sky into two equal hemispheres along a great circle (the fundamental plane of the geographic system is the Earth's equator) . Each coordinate system is named for its choice of fundamental plane. The equatorial coordinate system is probably the most widely used celestial coordinate system. It is also the one most closely related to the geographic coordinate system, because they use the same fun damental plane and the same poles. The projection of the Earth's equator onto the celestial sphere is called the celestial equator. Similarly, projecting the geographic poles on to the celest ial sphere defines the north and south celestial poles. However, there is an important difference between the equatorial and geographic coordinate systems: the geographic system is fixed to the Earth; it rotates as the Earth does . The equatorial system is fixed to the stars, so it appears to rotate across the sky with the stars, but of course it's really the Earth rotating under the fixed sky. The latitudinal (latitude-like) angle of the equatorial system is called declination (Dec for short) . It measures the angle of an object above or below the celestial equator. The longitud inal angle is called the right ascension (RA for short). -
Imaging Photometry of NGC 6231?,??
ASTRONOMY & ASTROPHYSICS JUNE I 1999, PAGE 233 SUPPLEMENT SERIES Astron. Astrophys. Suppl. Ser. 137, 233–244 (1999) UBV I imaging photometry of NGC 6231?,?? G. Baume, R.A. V´azquez, and A. Feinstein Observatorio Astron´omico de La Plata, Paseo del Bosque s/n, 1900 La Plata and PROFOEG-CONICET, Argentina Received May 18, 1998; accepted February 4, 1999 Abstract. CCD UBVI photometry in the field of the open et al. (1990, 1991, 1992) from a large compilation of pho- cluster NGC 6231 was obtained for 1060 stars down to tometric and spectroscopic data. Not much information V ≈ 19 mag. Memberships, reddening, distance and age regarding the cluster lower main sequence structure and of this cluster were investigated. Its lower sequence dis- the presence of PMS stars can be drawn from this compila- plays a notorious bend at V ≈ 13.5 mag followed by a high tion because of its low magnitude limit. Notwithstanding, number of faint stars showing a large magnitude spread at the authors conclude that all the stars with V ≥ 10 mag constant colour. This distribution of stars does not seem are in a different evolutionary status (pre main sequence to be produced by a mere accumulation of field stars seen stars, PMS) respect of the brightest members. It is timely in the direction of the cluster but by a real star excess to recall that in an early investigation of PMS stars, Eggen in the zone. The evidence suggests these stars are serious (1976) suggested that a violent star formation process had candidates to be cluster members caught in their way to- taken place there. -
"#$%&'() + '', %-./0$%)%1 2 ()3 4&(5' 456')5'
rs uvvwxyuzyws { yz|z|} rsz}~suzywsu}u~w vz~wsw 456789@A C 99D 7EFGH67A7I P @AQ R8@S9 RST9AS9 UVWUX `abcdUVVe fATg96GTHP7Eh96HE76QGiT69pf q rAS76876@HTAs tFR u Fv wxxy @AQ 4FR 4u Fv wxxy UVVe abbc d dbdc e f gc hi` ij ad bch dgcadabdddc c d ac k lgbc bcgb dmg agd g` kg bdcd dW dd k bg c ngddbaadgc gabmob nb boglWad g kdcoddog kedgcW pd gc bcogbpd kb obpcggc dd kfq` UVVe c iba ! " #$%& $' ())01023 Book of Abstracts – Table of Contents Welcome to the European Week of Astronomy & Space Science ...................................................... iii How space, and a few stars, came to Hatfield ............................................................................... v Plenary I: UK Solar Physics (UKSP) and Magnetosphere, Ionosphere and Solar Terrestrial (MIST) ....... 1 Plenary II: European Organisation for Astronomical Research in the Southern Hemisphere (ESO) ....... 2 Plenary III: European Space Agency (ESA) .................................................................................. 3 Plenary IV: Square Kilometre Array (SKA), High-Energy Astrophysics, Asteroseismology ................... 4 Symposia (1) The next era in radio astronomy: the pathway to SKA .............................................................. 5 (2) The standard cosmological models - successes and challenges .................................................. 17 (3) Understanding substellar populations and atmospheres: from brown dwarfs to exo-planets .......... 28 (4) The life cycle of dust ........................................................................................................... -
Deep Sky Explorer Atlas
Deep Sky Explorer Atlas Reference manual Star charts for the southern skies Compiled by Auke Slotegraaf and distributed under an Attribution-Noncommercial 3.0 Creative Commons license. Version 0.20, January 2009 Deep Sky Explorer Atlas Introduction Deep Sky Explorer Atlas Reference manual The Deep Sky Explorer’s Atlas consists of 30 wide-field star charts, from the south pole to declination +45°, showing all stars down to 8th magnitude and over 1 000 deep sky objects. The design philosophy of the Atlas was to depict the night sky as it is seen, without the clutter of constellation boundary lines, RA/Dec fiducial markings, or other labels. However, constellations are identified by their standard three-letter abbreviations as a minimal aid to orientation. Those wishing to use charts showing an array of invisible lines, numbers and letters will find elsewhere a wide selection of star charts; these include the Herald-Bobroff Astroatlas, the Cambridge Star Atlas, Uranometria 2000.0, and the Millenium Star Atlas. The Deep Sky Explorer Atlas is very much for the explorer. Special mention should be made of the excellent charts by Toshimi Taki and Andrew L. Johnson. Both are free to download and make ideal complements to this Atlas. Andrew Johnson’s wide-field charts include constellation figures and stellar designations and are highly recommended for learning the constellations. They can be downloaded from http://www.cloudynights.com/item.php?item_id=1052 Toshimi Taki has produced the excellent “Taki’s 8.5 Magnitude Star Atlas” which is a serious competitor for the commercial Uranometria atlas. His atlas has 149 charts and is available from http://www.asahi-net.or.jp/~zs3t-tk/atlas_85/atlas_85.htm Suggestions on how to use the Atlas Because the Atlas is distributed in digital format, its pages can be printed on a standard laser printer as needed. -
The Low-Mass Stellar Content of Westerlund 1
The low-mass stellar content of Westerlund 1 Morten Andersen (Gemini South) Galactic young massive star clusters • Connection between local and global SF. • Can resolve the stellar populations to low masses • Star counts instead of integrated properties • Directly measure the IMF The IMF in resolved massive clusters Only scale-free part probed Westerlund 1 • Distance of ~4 Kpc, age 3-5 Myr • Total mass estimated to be 50000 Msun • High foreground extinction • Best opportunity for resolving the low mass content in a young massive cluster • HST J (F125W) and H (F160W) band imaging Westerlund 1 from ground 5pc 4.5’ SOfI JHK, Brandner et al. 2007, Gennaro et al. Early lessons • Probe down to ~3 Msun, normal (Salpeter) IMF • Total mass of ~50000 Msun assuming standard IMF • Mass segregated, at least for high masses • Elliptical cluster • Currently difficult to improve from the ground Westerlund 1 with HST 5pc 4.5’ WFC3 F125W, F160W. Andersen et al. 2016 Color-magnitude diagrams Andersen et al. 2016 Foreground population Andersen et al. 2016 Red Clump Andersen et al. 2016 Background contamination Andersen et al. 2016 Cluster main sequence MS/PMS turn-on Andersen et al. 2016 Field star subtraction Andersen et al. 2016 Mass Functions Log-normal fit below 1 Msun to the 50% completeness limit. Power-law fit above 1 Msun (Siess 4 Myr isochrone) Change of fit parameters as a function of radius M < 1 Msun, log-normal fits Comparable peak mass as the field. More narrow distribution Change of fit parameters as a function of radius M > 1 Msun Evidence for mass segregation out to 1.5-2 pc Andersen et al. -
Spatial Distribution of Galactic Wolf–Rayet Stars and Implications for the Global Population
MNRAS 447, 2322–2347 (2015) doi:10.1093/mnras/stu2525 Spatial distribution of Galactic Wolf–Rayet stars and implications for the global population C. K. Rosslowe‹ andP.A.Crowther Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, S3 7RH, UK Accepted 2014 November 26. Received 2014 November 26; in original form 2014 September 5 ABSTRACT We construct revised near-infrared absolute magnitude calibrations for 126 Galactic Wolf– Rayet (WR) stars at known distances, based in part upon recent large-scale spectroscopic surveys. Application to 246 WR stars located in the field permits us to map their Galactic distribution. As anticipated, WR stars generally lie in the thin disc (∼40 pc half-width at half- maximum) between Galactocentric radii 3.5–10 kpc, in accordance with other star formation tracers. We highlight 12 WR stars located at vertical distances of ≥300 pc from the mid-plane. Analysis of the radial variation in WR subtypes exposes a ubiquitously higher NWC/NWN ratio than predicted by stellar evolutionary models accounting for stellar rotation. Models for non- rotating stars or accounting for close binary evolution are more consistent with observations. We consolidate information acquired about the known WR content of the Milky Way to build a simple model of the complete population. We derive observable quantities over a range of wavelengths, allowing us to estimate a total number of 1900 ± 250 Galactic WR stars, implying an average duration of ∼ 0.4 Myr for the WR phase at the current Milky Way star formation rate. Of relevance to future spectroscopic surveys, we use this model WR population to predict follow-up spectroscopy to KS 17.5 mag will be necessary to identify 95 per cent of Galactic WR stars. -
Resolving the Low-Mass Content of Westerlund 1 Using MCAO
Resolving the low-mass content of Westerlund 1 using MCAO M. Andersena, B. Neichelb, A. Bernardb, and V. Garrela aGemini Observatories, Casilla 603 La Silla, Chile bAix Marseille Universit´e,CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, 13388 Marseille, France ABSTRACT We present deep Ks band Gemini GeMS/GSAOI observations of Westerlund 1, the most massive young Galactic star cluster known. The high spatial resolution combined with a relatively stable point spread function across a large field of view provide unique possibilities to resolve the low-mass content of the cluster. We show that the clean point spread function is crucial in handling the source detection in this crowded field suffering extremely high contrast from the brightest hypergiants in the cluster to faint brown dwarfs. Keywords: star clusters: Westerlund 1, Initial Mass Function, Photometry, MCAO, Laser Guide Star Systems 1. INTRODUCTION Much progress has been made in the last decades in our understanding of low-mass star forming regions. Detailed observations of individual objects have made it possible to characterise them in detail and to determine the star formation history and the impact of environment. 4 Similar studies of massive star clusters (more than 10 M ) are much less detailed. However, they differ fundamentally from nearby regions in terms of their central densities and large content of massive stars that may have influenced the star formation process within the cluster. These clusters are rare and the nearest ones known are an order of magnitude more distant than the nearby low-mass regions. This, together with their higher densities, means that high spatial resolution observations are necessary to resolve the low-mass content of the clusters. -
Study of Globular Cluster Sources Using Erass1 Data
Study of Globular Cluster Sources using eRASS1 data Bachelorarbeit aus der Physik Vorgelegt von Roman Laktionov 27. April 2021 Dr. Karl Remeis-Sternwarte Friedrich-Alexander-Universit¨at Erlangen-Nu¨rnberg Betreuerin: Prof. Dr. Manami Sasaki Abstract Due to the high stellar density in globular clusters (GCs), they provide an ideal envi- ronment for the formation of X-ray luminous objects, e.g. cataclysmic variables and low-mass X-ray binaries. Those X-ray sources have, in the advent of ambitious observa- tion campaigns like the eROSITA mission, become accessible for extensive population studies. During the course of this thesis, X-ray data in the direction of the Milky Way's GCs was extracted from the eRASS1 All-Sky Survey and then analyzed. The first few chap- ters serve to provide an overview on the physical properties of GCs, the goals of the eROSITA mission and the different types of X-ray sources. Afterwards, the methods and results of the analysis will be presented. Using data of the eRASS1 survey taken between December 13th, 2019 and June 11th, 2020, 113 X-ray sources were found in the field of view of 39 GCs, including Omega Cen- tauri, 47 Tucanae and Liller 1. A Cross-correlation with optical/infrared catalogs and the subsequent analysis of various diagrams enabled the identification of 6 foreground stars, as well as numerous background candidates and stellar sources. Furthermore, hardness ratio diagrams were used to select 16 bright sources, possibly of GC origin, for a spectral analysis. By marking them in X-ray and optical images, it was concluded that 6 of these sources represent the bright central emission of their host GC, while 10 are located outside of the GC center. -
November 1989
WASP Warren Astronomical Society Paper Volume 21 Number 9 Price: $1.00 for Non-members November 1989 A Guided Tour of Several Open Clusters star, which is shown on the SE edge of my sketch of the M52 area. Half-way By Jeff Bondono between M52 and that star is Czemik43, a 15' mass of about 30 faint stars. It contains quite a mix of bright Our tour this month takes us to three It is invisible at LP, but HP shows a 5' and faint stars. groups of clusters in the part of the sky grouping of ten stars. Markarian 50 is To reach our next set of clusters, go between Cepheus and the bright stars the other easy cluster to find from here. back to M52. Move about 150' E and of Cassiopeia. The first cluster in the Go back to NGC 7510, and move 30' E you will reach a 6m star. 60' ENE of tour is at right ascension 2311, which and 10' S and you've got it. At LP, it is that star lies the greenish 5m star 6 is on the meridian at about 10:40 PM a 1.5' triangle of one 9m and two 10m Cas. Both of these stars appear on my EDT on October 15, or 7:40 PM EST on stars. HP will show several stars within drawing of the NGC 7788 area, which November 15. All of the sketches and this triangle. This cluster happens to houses the rest of the clusters in this observations were made by me using lie right on the border between Ce- tour. -
A 3Mm ALMA Census of the Massive Cluster Westerlund 1 1 2 1 3 4 5 6 2 D
A 3mm ALMA census of the massive cluster Westerlund 1 D. Fenech1, J. Clark2, R. Prinja1, S. Dougherty3, F. NaJarro4, I. Negueruela5, A. Richards6 and B. Ritchie2 1Department of Physics and Astronomy, University College London, U.K.; 2School of Physical Science, The Open University, UK; 3Dominion Radio Astrophysical Observatory, National Research Council Canada; 4Departamento de Física, Ingenaría de Sistemas y Teoría de la Señal, Universidad de Alicante, Spain; 5Departamento de Astrofísica, Centro de Astrobiología, (CSIC-INTA) Spain; 6JBCA, University of Manchester & MERLIN/VLBI National Facility, JBO,U.K. Westerlund 1 Massive stars Cool super-/hypergiants Westerlund 1 (Wd1) is one of the first examples of a super star cluster within our Despite their rarity, massive stars play a major role in galactic evolution. They deposit large amounts of Galaxy and contains a population of co-eval massive stars. Located at a distance of Yellow hypergiants (YHGs) and red supergiants (RSGs) are of particular chemically enriched material, energy and ionising radiation into their environment and dominate the ~5 kpc, Wd1 was discovered by Westerlund in 1961 (Westerlund, 1961,PASP, 73, interest as they are believed to shed mass at suffucent rates to profoundly integrated galactic spectra in the UV and IR regimes (via re-radiation). However, the lives of massive stars 51). However, the large extinction towards Wd1 (Av~11 mag) meant that few affect a stars evolution in spite of spending relatively little time in this are still poorly understood. observations were made of the cluster until relatively recently when radio images phase. Mass-loss is considered a critical factor in the evolutionary pathway of massive stars and consequently the revealed a large number of radio sources (Dougherty et al. -