Kajian I'jaz Ilmi
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Fundamental Parameters of Wolf-Rayet Stars VI
Astron. Astrophys. 320, 500–524 (1997) ASTRONOMY AND ASTROPHYSICS Fundamental parameters of Wolf-Rayet stars VI. Large Magellanic Cloud WNL stars? P.A.Crowther and L.J. Smith Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, UK Received 5 February 1996 / Accepted 26 June 1996 Abstract. We present a detailed, quantitative study of late WN Key words: stars: Wolf-Rayet;mass-loss; evolution; fundamen- (WNL) stars in the LMC, based on new optical spectroscopy tal parameters – galaxies: Magellanic Clouds (AAT, MSO) and the Hillier (1990) atmospheric model. In a pre- vious paper (Crowther et al. 1995a), we showed that 4 out of the 10 known LMC Ofpe/WN9 stars should be re-classified WN9– 10. We now present observations of the remaining stars (except the LBV R127), and show that they are also WNL (WN9–11) 1. Introduction stars, with the exception of R99. Our total sample consists of 17 stars, and represents all but one of the single LMC WN6– Quantitative studies of hot luminous stars in galaxies are im- 11 population and allows a direct comparison with the stellar portant for a number of reasons. First, and probably foremost, parameters and chemical abundances of Galactic WNL stars is the information they provide on the effect of the environment (Crowther et al. 1995b; Hamann et al. 1995a). Previously un- on such fundamental properties as the mass-loss rate and stellar published ultraviolet (HST-FOS, IUE-HIRES) spectroscopy are evolution. In the standard picture (e.g. Maeder & Meynet 1987) presented for a subset of our programme stars. -
Multiwavelength Observations of AB Doradus
Publications of the Astronomical Society of Australia (PASA), Vol. 31, e021, 18 pages (2014). C Astronomical Society of Australia 2014; published by Cambridge University Press. doi:10.1017/pasa.2014.16 Multiwavelength Observations of AB Doradus O.B. Slee1,5, N. Erkan2, M. Johnston-Hollitt3 and E. Budding3,4 1Australia Telescope National Facility, CSIRO, Australia 2Canakkale Onsekiz Mart University, Canakkale, TR 17020, Turkey 3School of Chemical and Physical Sciences, Victoria University of Wellington, New Zealand 4Carter Observatory, Wellington, New Zealand 5Email: [email protected] (Received September 4, 2013; Accepted January 28, 2014) Abstract We have observed the bright, magnetically active multiple star AB Doradus in a multiwavelength campaign centring around two large facility allocations in November 2006 and January, 2007. Our observations have covered at least three large flares. These flares were observed to produce significant hardening of the X-ray spectra during their very initial stages. We monitored flare-related effects using the Suzaku X-ray satellite and the Australia Telescope Compact Array (ATCA) at 3.6 and 6 cm. Observations at 11 and 21 cm were also included, but they were compromised by interference. Optical monitoring was also provided by broadband B and V photometry and some high-dispersion spectrograms. From this multiwavelength coverage we find that the observed flare effects can be mainly associated with a large active region near longitude zero. The second major X-ray and microwave flare of Jan 8, 2007 was observed with a favourable geometry that allowed its initial high-energy impulsive phase to be observed in the higher frequency range of Suzaku’s XIS detectors. -
Planetesimals Around Stars with TESS (PAST) – I. Transient Dimming of a Binary Solar Analogue at the End of the Planet Accreti
MNRAS 488, 4465–4476 (2019) doi:10.1093/mnras/stz1942 Advance Access publication 2019 July 12 Planetesimals around stars with TESS (PAST) – I. Transient dimming of a binary solar analogue at the end of the planet accretion era Downloaded from https://academic.oup.com/mnras/article-abstract/488/4/4465/5531782 by California Institute of Technology user on 26 September 2019 E. Gaidos ,1,2‹ T. Jacobs,3 D. LaCourse,4 A. Vanderburg,5 S. Rappaport,6 T. Berger,2,7 L. Pearce,5 A. W. Mann,8 L. Weiss,2,7† B. Fulton,9 A. Behmard ,10 A. W. Howard,9 M. Ansdell,11,12 G. R. Ricker,13 R. K. Vanderspek,13 D. W. Latham,14 S. Seager,13,15,16 J. N. Winn17 and J. M. Jenkins18 1Department of Earth Sciences, University of Hawai’i at Manoa,¯ Honolulu, HI 96822, USA 2Kavli Institute for Theoretical Physics, UC Santa Barbara, Santa Barbara, CA 93106, USA 312812 SE 69th Place Bellevue, WA 98006, USA 47507 52nd Place NE Marysville, WA 98270, USA 5Department of Astronomy, The University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712, USA 6Department of Physics, Kavli Institute for Astrophysics and Space Research, MIT, Cambridge, MA 02139, USA 7Institute for Astronomy, University of Hawaii at Manoa,¯ Honolulu, HI 96822, USA 8Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3255, USA 9Department of Astronomy, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125, USA 10Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA -
THE LARGE-SCALE MAGNETIC FIELDS of PLANET-HOSTING SOLAR-TYPE STARS a Thesis Submitted by Matthew W. Mengel, M.Phil., G.D.Inf.Tec
THE LARGE-SCALE MAGNETIC FIELDS OF PLANET-HOSTING SOLAR-TYPE STARS A Thesis Submitted by Matthew W. Mengel, M.Phil., G.D.Inf.Tech, B.Inf.Tech. For the Award of Doctor of Philosophy 2017 Abstract Stellar magnetic fields and their associated phenomena influence stellar be- haviour and evolution, and potentially have significant impacts on any surrounding planetary system. However, the nature of star-planet interactions is unclear, especially the potential impact on a star of a closely orbiting massive planet with a powerful mag- netic field. This thesis presents a spectropolarimetric survey of the large-scale magnetic fields of planet-hosting solar-type stars. While little evidence is found for a systematic dif- ference in the magnetic field characteristics of planet-hosting stars compared with the population of solar-type stars, a small positive correlation is indicated between the magnitude of the tidal effects of the planet on the star and the magnetic field strength. Nevertheless, further spectropolarimetric observations of hot Jupiter hosting systems are required to confirm this tentative relationship. For the particular case of a moderately active star with a thin convective zone and a closely orbiting hot Jupiter (τ Boötis) presented here, a remarkably rapid magnetic cycle with a period of ∼ 240 d is discovered. For stars with shallow convective en- velopes, this is an unusual occurrence and suggests a possible role for planetary tidal or magnetic interaction with the star’s convective zone and magnetic dynamo. More observations are required to verify this possible star-planet interaction and to extend the work to other similar systems as they come to light from exoplanet surveys. -
Florida State University Libraries
Florida State University Libraries Electronic Theses, Treatises and Dissertations The Graduate School Constraining the Evolution of Massive StarsMojgan Aghakhanloo Follow this and additional works at the DigiNole: FSU's Digital Repository. For more information, please contact [email protected] FLORIDA STATE UNIVERSITY COLLEGE OF ARTS AND SCIENCES CONSTRAINING THE EVOLUTION OF MASSIVE STARS By MOJGAN AGHAKHANLOO A Dissertation submitted to the Department of Physics in partial fulfillment of the requirements for the degree of Doctor of Philosophy 2020 Copyright © 2020 Mojgan Aghakhanloo. All Rights Reserved. Mojgan Aghakhanloo defended this dissertation on April 6, 2020. The members of the supervisory committee were: Jeremiah Murphy Professor Directing Dissertation Munir Humayun University Representative Kevin Huffenberger Committee Member Eric Hsiao Committee Member Harrison Prosper Committee Member The Graduate School has verified and approved the above-named committee members, and certifies that the dissertation has been approved in accordance with university requirements. ii I dedicate this thesis to my parents for their love and encouragement. I would not have made it this far without you. iii ACKNOWLEDGMENTS I would like to thank my advisor, Professor Jeremiah Murphy. I could not go through this journey without your endless support and guidance. I am very grateful for your scientific advice and knowledge and many insightful discussions that we had during these past six years. Thank you for making such a positive impact on my life. I would like to thank my PhD committee members, Professors Eric Hsiao, Kevin Huf- fenberger, Munir Humayun and Harrison Prosper. I will always cherish your guidance, encouragement and support. I would also like to thank all of my collaborators. -