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Astronomy Astrophysics
A&A 470, 191–210 (2007) Astronomy DOI: 10.1051/0004-6361:20077168 & c ESO 2007 Astrophysics The Mira variable S Orionis: relationships between the photosphere, molecular layer, dust shell, and SiO maser shell at 4 epochs,,,† M. Wittkowski1,D.A.Boboltz2, K. Ohnaka3,T.Driebe3, and M. Scholz4,5 1 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany e-mail: [email protected] 2 United States Naval Observatory, 3450 Massachusetts Avenue, NW, Washington, DC 20392-5420, USA e-mail: [email protected] 3 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany 4 Institut für Theoretische Astrophysik der Univ. Heidelberg, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany 5 Institute of Astronomy, School of Physics, University of Sydney, Sydney NSW 2006, Australia Received 25 January 2007 / Accepted 18 April 2007 ABSTRACT Aims. We present the first multi-epoch study that includes concurrent mid-infrared and radio interferometry of an oxygen-rich Mira star. Methods. We obtained mid-infrared interferometry of S Ori with VLTI/MIDI at four epochs in December 2004, February/March 2005, November 2005, and December 2005. We concurrently observed v = 1, J = 1−0 (43.1 GHz), and v = 2, J = 1−0 (42.8 GHz) SiO maser emission toward S Ori with the VLBA in January, February, and November 2005. The MIDI data are analyzed using self-excited dynamic model atmospheres including molecular layers, complemented by a radiative transfer model of the circumstellar dust shell. The VLBA data are reduced to the spatial structure and kinematics of the maser spots. -
INAUGURAL – DISSERTATION Dipl.-Phys. Alexander A. Schegerer
INAUGURAL – DISSERTATION zur Erlangung der Doktorwurde¨ der Naturwissenschaftlich-Mathematischen Gesamtfakult¨at der Ruprecht - Karls - Universit¨at Heidelberg vorgelegt von Dipl.-Phys. Alexander A. Schegerer, geboren in Kaufbeuren Tag der mundlichen¨ Prufung:¨ 17. Oktober 2007 II Struktur- und Staubentwicklung in zirkumstellaren Scheiben um T Tauri-Sterne Analyse und Modellierung hochaufl¨osender Beobachtungen in verschiedenen Wellenl¨angenbereichen Gutachter: Prof. Dr. Thomas Henning Prof. Dr. Wolfgang Duschl IV Meinen Eltern, Maria-Christa und Wolfgang Schegerer, gewidmet. VI Thema Im Zentrum dieser Doktorarbeit steht die Untersuchung der inneren Strukturen zirkumstella- rer Scheiben um T Tauri-Sterne sowie die Analyse zirkumstellarer Staub- und Eisteilchen und ihres Einflusses auf die Scheibenstruktur. Unter Zuhilfenahme von theoretisch berechneten Vergleichsspektren gibt der Verlauf der 10 µm-Emissionsbande in den Spektren junger stellarer Objekte Hinweise auf den Entwick- lungsgrad von Silikatstaub. Die Silikatbanden von 27 T Tauri-Objekten werden analysiert, um nach potentiell vorliegenden Korrelationen zwischen der Silikatstaubzusammensetzung und den stellaren Eigenschaften zu suchen. Analog erlaubt das Absorptionsband bei 3 µm, das dem Wassereis zugeschrieben wird, eine Untersuchung der Entwicklung von Eisk¨ornern in jungen stellaren Objekten. Erstmals ist es gelungen, kristallines Wassereis im Spektrum eines T Tauri-Objektes nachzuweisen. Unser wichtigstes Hilfsmittel zur Analyse der Temperatur- und Dichtestrukturen zirkum- stellarer -
Mid-Infrared Interferometric Variability of DG Tauri: Implications for the Inner-Disk Structure?
A&A 604, A84 (2017) Astronomy DOI: 10.1051/0004-6361/201630287 & c ESO 2017 Astrophysics Mid-infrared interferometric variability of DG Tauri: Implications for the inner-disk structure? J. Varga1, K. É. Gabányi1, P. Ábrahám1, L. Chen1, Á. Kóspál1; 4, J. Menu2, Th. Ratzka3, R. van Boekel4, C. P. Dullemond5, Th. Henning4, W. Jaffe6, A. Juhász7, A. Moór1, L. Mosoni1; 8, and N. Sipos1 1 Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, PO Box 67, 1525 Budapest, Hungary e-mail: [email protected] 2 Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium 3 Institute for Physics/IGAM, NAWI Graz, University of Graz, Universitätsplatz 5/II, 8010 Graz, Austria 4 Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany 5 Institute for Theoretical Astrophysics, Heidelberg University, Albert-Ueberle-Strasse 2, 69120 Heidelberg, Germany 6 Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands 7 Institute of Astronomy, Madingley Road, Cambridge CB3 OHA, UK 8 Park of Stars in Zselic, 064/2 hrsz., 7477 Zselickisfalud, Hungary Received 19 December 2016 / Accepted 6 April 2017 ABSTRACT Context. DG Tau is a low-mass pre-main sequence star, whose strongly accreting protoplanetary disk exhibits a so-far enigmatic be- havior: its mid-infrared thermal emission is strongly time-variable, even turning the 10 µm silicate feature from emission to absorption temporarily. Aims. We look for the reason for the spectral variability at high spatial resolution and at multiple epochs. Methods. Infrared interferometry can spatially resolve the thermal emission of the circumstellar disk, also giving information about dust processing. -
Age Determination Method of Pre-Main Sequence Stars with High
Kobe University Repository : Kernel タイトル Age-Determination Method of Pre-Main Sequence Stars with High- Title Resolution I-Band Spectroscopy 著者 Takagi, Yuhei / Itoh, Yoichi / Oasa, Yumiko Author(s) 掲載誌・巻号・ページ Publications of the Astronomical Society of Japan,62(2):501-508 Citation 刊行日 2010-04-25 Issue date 資源タイプ Journal Article / 学術雑誌論文 Resource Type 版区分 author Resource Version 権利 Copyright(c) 2010 Astronomical Society of Japan Rights DOI JaLCDOI URL http://www.lib.kobe-u.ac.jp/handle_kernel/90001417 PDF issue: 2021-09-26 Age Determination Method of Pre-Main Sequence Stars with High-Resolution I-Band Spectroscopy∗† Yuhei Takagi, Yoichi Itoh Graduate School of Science, Kobe University, 1-1 Rokkodai, Nada, Kobe, Hyogo 657-8501 [email protected] and Yumiko Oasa Faculty of Education, Saitama University, 255 Shimo-Okubo, Sakura, Saitama, Saitama 338-8570 (Received ; accepted ) Abstract We present a new method for determining the age of late-K type pre-main se- quence (PMS) stars by deriving their surface gravity from high-resolution I-band spectroscopy. Since PMS stars contract as they evolve, age can be estimated from surface gravity. We used the equivalent width ratio (EWR) of nearby absorption lines to create a surface gravity diagnostic of PMS stars that is free of uncertainties due to veiling. The ratios of Fe (8186.7A˚ and 8204.9A˚) and Na (8183.3A˚ and 8194.8A˚) ab- sorption lines were calculated for giants, main-sequence stars, and weak-line T Tauri stars. Effective temperatures were nearly equal across the sample. The Fe to Na EWR (Fe/Na) decreases significantly with increasing surface gravity, denoting that Fe/Na is a desirable diagnostic for deriving the surface gravity of pre-main sequence stars. -
Chemical Abundance Analysis of 19 Barium Stars 3
Research in Astron. Astrophys. Vol.0 (200x) No.0, 000–000 Research in http://www.raa-journal.org http://www.iop.org/journals/raa Astronomy and Astrophysics Chemical abundance analysis of 19 barium stars G. C. Yang1,2,3, Y. C. Liang2, M. Spite4, Y. Q. Chen2, G. Zhao2, B. Zhang1,2, G. Q. Liu5,2, Y. J. Liu2, N. Liu6, L. C. Deng2, F. Spite4, V. Hill4, C. X. Zhang7 1College of Physics and Information Engineering, Hebei Normal University, Shijiazhuang 050024, China 2Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, China; [email protected] 3Graduate School of the Chinese Academy of Sciences, Beijing 100049, China 4GEPI, Observatoire de Paris-Meudon, 92195 Meudon, France 5Physics Department and Tsinghua Center for Astrophysics, Tsinghua University, Beijing 100084, China 6Astronomy Department, Beijing Normal University, Beijing 100875, China 7Department of Physics, Shijiazhuang University, Shijiazhuang 050035, China Abstract We aim at deriving accurate atmospheric parameters and chemical abundances of 19 barium (Ba) stars, including both strong and mild Ba stars, based on the high signal- to-noise ratio and high resolution Echelle spectra obtained from the 2.16m telescope at Xinglong station of National Astronomical Observatories, Chinese Academy of Sciences. The chemical abundances of the sample stars were obtained from an LTE, plane-parallel and line-blanketed atmospheric model by inputting the atmospheric parameters (effective temperatures Teff , surface gravities log g, metallicity [Fe/H] and microturbulent velocity ξt) and equivalent widths of stellar absorption lines. These samples of Ba stars are giants indicated by atmospheric parameters, metallicities and kinematic analysis about UVW velocity. -
Bv Photometry of Prominent Rs Canum Venaticorum Star Ux Ari (Hd: 21242)
BV PHOTOMETRY OF PROMINENT RS CANUM VENATICORUM STAR UX ARI (HD: 21242) AJAZ AHMAD, MANZOOR A. MALIK, ABDUL WAHID University of Kashmir, Srinagar-J&K, India-190006 ICSC, Hawal, Srinagar-J&K, India-190002 Email: [email protected]; [email protected]; [email protected] Abstract. We present the results of BV photoelectric photometry observations of UX Ari RS CVn Star, obtained on 14 nights during the observing run January- February, 2006, using 1400 telescope and SSP-3 Photometer. Comparison of light curves during the year 1972 by (Hall,1975), 1995-1996, 2001-2002 by Aarum and Henry (Aarum & Henry, 2003), and our observations 2006 clearly shows the amplitude variation of light on different time scales. Key words: Photometry; RS CVn; Period; Light Curve. 1. INTRODUCTION RS Canum Venaticorm (RS CVn) type stars are chromospherically active bi- nary systems. The most accepted definition of RS CVn binaries used is based on the classification criteria first formulated by Hall (1972; 1976) with some modifica- tions made by Fakel et al.(1986). Apart from the classical RS CVn binaries, orig- inally defined by Hall (1976), there are several other classes of binaries containing at least one late-type star which can attain similarly high levels of activity (Hall, 1989). These include: short period and long period RS CVn binaries; close binary systems containing a white dwarf or sub-dwarf secondary; semi-detached (Algol) or detached binaries containing a late type subgiant as the secondary star and an early type companion as the primary star; and contact (W UMa-type) binaries (Padmakar and Pandey, 1999). -
Mid-Infrared Interferometric Variability of DG Tau: Implications for the Inner
Astronomy & Astrophysics manuscript no. main c ESO 2018 September 25, 2018 Mid-infrared interferometric variability of DG Tau: implications for the inner-disk structure⋆ J. Varga1, K. É. Gabányi1, P. Ábrahám1, L. Chen1, Á. Kóspál1, 4, J. Menu2, Th. Ratzka3, R. van Boekel4, C. P. Dullemond5, Th. Henning4, W. Jaffe6, A. Juhász7, A. Moór1, L. Mosoni1, 8, and N. Sipos1 1 Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, P.O. Box 67, H-1525 Budapest, Hungary e-mail: [email protected] 2 Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001, Leuven, Belgium 3 Institute for Physics/IGAM, NAWI Graz, University of Graz, Universitätsplatz 5/II, 8010, Graz, Austria 4 Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany 5 Institute for Theoretical Astrophysics, Heidelberg University, Albert-Ueberle-Strasse 2, D-69120 Heidelberg, Germany 6 Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands 7 Institute of Astronomy, Madingley Road, Cambridge CB3 OHA, UK 8 Park of Stars in Zselic, 064/2 hrsz., H-7477 Zselickisfalud, Hungary Received; accepted ABSTRACT Context. DG Tau is a low-mass pre-main sequence star, whose strongly accreting protoplanetary disk exhibits a so-far enigmatic be- havior: its mid-infrared thermal emission is strongly time-variable, even turning the 10 µm silicate feature from emission to absorption temporarily. Aims. We look for the reason for the spectral variability at high spatial resolution and at multiple epochs. Methods. Infrared interferometry can spatially resolve the thermal emission of the circumstellar disk, also giving information about dust processing.