DOCSLIB.ORG

Cool Stellar Activity at Low Radio Frequencies

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Cool Stellar Activity at Low Radio Frequencies Cool Stellar Activity at Low Radio Frequencies Mr. Andrew John Zic A thesis submitted to fulfil requirements for the degree: Doctor of Philosophy (PhD) Supervisor: Prof. Tara Murphy Co-supervisors: Dr. Christene Lynch & Dr. George Heald Sydney Insititute for Astronomy School of Physics The University of Sydney CSIRO Astronomy and Space Science 2020 Dedicated to the memory of Mr. Daniele Velcich OAM, and Prof. Richard Hunstead. iv Declaration of originality I certify that to the best of my knowledge, the content of this thesis submitted in fulfillment for the degree of Doctor of Philosophy (PhD) is my own work. This thesis has not been submitted for any degree or other purposes. I certify that the authorship attribution statement on the following page are correct. Mr. Andrew John Zic August 28, 2020 As supervisor for the candidature upon which this thesis is based, I confirm that the originality and authorship attribution statements above and on the next page are correct. Prof. Tara Murphy August 28, 2020 v vi Included papers and attribution Chapters2,3, and4 are peer-reviewed journal articles led by myself, published as Zic et al.(2019a), Zic et al.(2019b), and Zic et al.(2020) respectively. These chapters have been reproduced as published, except for minor typographical and formatting changes to keep consistent style throughout this thesis. Important contributions from others toward the work in this thesis are as follows. Tara Murphy: general supervision and guidance, advice on experimental design and analysis. Christene Lynch: assistance with data reduction and numerical modelling, advice on scientific interpretation and analysis. George Heald: advice on polarimetry, analysis, mod- elling and interpretation. Emil Lenc: reduction of ASKAP observations, and advice on radio data reduction. David L. Kaplan: advice on scientific analysis, interpreta- tion, statistics, and on optical data reduction. Adam Stewart: assistance with data analysis and interpretation. Specific contributions are detailed at the beginning of each chapter. Chapter2 Low-frequency GMRT observations of ultra-cool dwarfs Andrew Zic, Christene Lynch, Tara Murphy, David L. Kaplan, and Poonam Chandra Published in Monthly Notices of the Royal Astronomical Society, 483, 614, 2019a. Chapter3 ASKAP detection of periodic and elliptically polarized radio pulses from UV Ceti Andrew Zic, Adam Stewart, Emil Lenc, Tara Murphy, Christene Lynch, David L. Kaplan, Aidan Hotan, Craig Anderson, John D. Bunton, Aaron Chippendale, Stacy Mader, and Chris Phillips Published in Monthly Notices of the Royal Astronomical Society, 488, 559, 2019b. Chapter4 A Flare–Type IV Burst Event from Proxima Centauri and Implications for Space Weather Andrew Zic, Tara Murphy, Christene Lynch, George Heald, Emil Lenc, David L. Kaplan, Iver H. Cairns, David Coward, Bruce Gendre, Helen Johnston, Meredith MacGregor, Danny C. Price, and Michael S. Wheatland Published in The Astrophysical Journal, 905, 23, 2020. vii viii Acknowledgements This thesis represents a significant milestone in my research career and personal life. I am very fortunate to have been given many wonderful opportunities and experiences throughout my candidature, and am grateful for the many people who supported me along the way. I would like to dedicate this thesis to the memory of my Nonno, Mr. Daniele Velcich OAM, and Prof. Richard “Dick” Hunstead, who sadly passed away during the course of my PhD candidature. Firstly, I would like to share some reflections on them both. Nonno was endlessly generous, and had an uncanny ability to bring laughter to any situation with his singing, dancing, and absolutely unique sense of humour. His qualities, and my time spent with him, shaped me as a person. He was much loved by his community, by his family, and is greatly missed. Dick Hunstead was my first research supervisor, when I was a first-year under- graduate lucky enough to partake in the Talented Student Program (TSP) at the USyd School of Physics. Like many other TSP students, this was my first taste of scientific and astronomical research, and played a major role in guiding me to where I am now. Dick remained involved in my research activities from then onwards, mentoring me throughout my Honours, and occasionally through my PhD. I am grateful to have had the chance to work with him, and for his work in making the TSP program successful at The School of Physics, which gave me the opportunity to kick-start my research career. I would also like to pay respects to A/ Prof. Jean-Pierre “JP” Macquart, who sadly passed away in 2020. I will remember him for his lively discussions with his colleagues and myself, his intellect, and for his kind heart. I would like to express my deepest appreciation to my partner, Charlotte, my parents, Julie and John, and my sister, Karina, for their unwavering support, en- couragement, and love throughout the ups and downs of the last few years. I love you all. I am extremely grateful to my supervisor, Tara Murphy. It has been a privilege to work with Tara for the last six years, during undergraduate and Summer research projects, Honours, MOOC course development, teaching, and finally my PhD. Her ongoing support, guidance, and advice has stimulated me to grow as a researcher and as a person. I would also like to deeply thank my co-supervisors Christene Lynch and George Heald for sharing their guidance and expertise with me, for being there to help me through any research problems, and for giving advice on topics of science, careers, and more. It has been wonderful to work with them both. ix x I am glad to have had the opportunity to work closely with several collaborators beyond my supervision group. These include David L. Kaplan, Emil Lenc, Adam Stewart, and Meredith MacGregor. I am also grateful for the discussions and advice from many excellent researchers who I have met throughout my PhD: Craig Ander- son, Marin Anderson, Martin Bell, Ramesh Bhat, Shivani Bhandari, Shari Breen, Iver Cairns, Joe Callingham, David Coward, Shi Dai, Ron Ekers, Bruce Gendre, Gregg Hallinan, Paul Hancock, George Hobbs, Ward Howard, Huib Intema, Helen Johnston, Chris Jordan, Jane Kaczmarek, JP Macquart, Don Melrose, John Mor- gan, Vanessa Moss, Simon Murphy, Bob Mutel, Rachel Osten, Sebastian Pineda, Danny Price, Ryan Shannon, Michael Wheatland, and Stephen White. One of the best parts of undertaking a PhD was having the opportunity to be- friend many fellow students and early-career researchers from within the department, around Australia, and internationally. I thank all of them for making conferences fun, and I look forward to seeing them again in the future. I am also very grateful to all my friends outside of astronomy for being the best pals a PhD student can get, especially when times weren’t so great. I would like to thank my grandparents, Neno and Dedo, Nonna and Nonno, for always welcoming me with a warm hug, and fresh bread or a bowl of soup. I love you, and Nonno, I miss you. I’d also like to thank the rest of my extended family for bringing a great deal of joy into my life, for their support, and for asking fun questions about my research. I extend a special thanks to Dan and Mik for letting me crash at their place during my trips to Perth. I wish the best of luck to the next generation of radio transients students – Andy Wang, Daniele D’Antonio, James Leung, Josh Pritchard, Mark Edwards, Teresa Klinner-Teo, and Yuanming Wang – and I thank them for the enthusiasm and ideas they bring to the group. I am also greatly indebted to Josh for his careful proofreading of this thesis. I’d like to thank all my PhD officemates, past and current: Dougal Dobie, Harry Qiu, Mohammed Rafat, Kat Ross, Troy Whinray, and Charlotte Ward. It’s been a blast working with you, yelling when code breaks, complaining about writing, talking about science problems (whether sensical or not), discussing sport, politics, and all other sorts of shenanigans. I’ll miss being around you all. Dougal, it’s been great to work alongside you under Tara since the early days, and it’s pretty sweet that we get to submit our theses on the same date. Good luck in your new role at Swinburne. Finally, I am very grateful for the support I have received from The University of Sydney, CSIRO Astronomy and Space Science, and the ARC Centre for All-Sky Astrophysics. I also acknowledge support from the Australian Government through the Research Training Program scholarship. Abstract Stellar magnetic fields drive a wide range of energetic phenomena, which have a crucial influence on their properties, evolution, and environment. In this thesis, we investigate the low-frequency radio emission from active low-mass stars. We harness this emission to constrain magnetospheric properties and processes arising from different magnetic activity paradigms. In Chapter2, we present low-frequency observations of a sample of ultra-cool dwarfs. We show that while most ultra-cool dwarfs do not produce low-frequency emission, their magnetospheric properties can be constrained with measurements of the optically-thick side of the quiescent spec- tral energy distribution. In Chapter3, we present Australian Square Kilometre Array Pathfinder (ASKAP) observations of the prototypical flare star, UV Ceti. Our observations reveal the presence of periodic, elliptically polarised radio pulses, confirming that large auroral current systems can be produced in the magneto- spheres of active M-dwarfs. In Chapter4, we present results from one night of an 11-night multi-wavelength campaign targeting the nearest stellar neighbour, and magnetically-active planet host, Proxima Centauri. We detected a powerful flare with optical photometric and spectroscopic facilities, accompanied by a solar-like type IV radio burst. By analogy with the solar radio burst paradigm, we suggest that this event indicates a coronal mass ejection leaving the corona, and ongoing electron acceleration associated with a post-eruptive loop arcade.
Load more

Recommended publications
  • Harpspol Proposal by C. Neiner
    European Organisation for Astronomical Research in the Southern Hemisphere OBSERVING PROGRAMMES OFFICE • Karl-Schwarzschild-Straße 2 • D-85748 Garching bei M¨unchen • e-mail: [email protected] • Tel. : +49 89 320 06473 APPLICATION FOR OBSERVING TIME PERIOD: 95A Important Notice: By submitting this proposal, the PI takes full responsibility for the content of the proposal, in particular with regard to the names of CoIs and the agreement to act according to the ESO policy and regulations, should observing time be granted. 1. Title Category: D{3 Spectropolarimetric observations of BRITE asteroseismic targets: a complete census of magnetic fields in bright stars up to V=4 2. Abstract / Total Time Requested Total Amount of Time: 6 nights VM, 0 hours SM This program aims at observing in circular spectropolarimetry all (yet unobserved) targets of the BRITE constellation of nano-satellites for asteroseismology, i.e. all stars brighter than V=4. They are mainly massive stars and evolved cool stars. Time has already been awarded at CFHT with ESPaDOnS and at TBL with Narval to observe the targets with a declination above -45◦. We propose to observe 104 targets below -45◦ with HarpsPol. Time has already been allocated in P94 for 51 targets. We request here the remaining 53 targets. These data will allow us to (1) obtain a complete and unbiased census of magnetic fields of all stars brighter than V=4, (2) determine the fundamental parameters of all BRITE targets, to constrain the seismic models of BRITE observations; (3) discover new magnetic stars and thus constrain their seismic models even further.
    [Show full text]
  • HST/STIS Analysis of the First Main Sequence Pulsar CU Virginis
    A&A 625, A34 (2019) Astronomy https://doi.org/10.1051/0004-6361/201834937 & © ESO 2019 Astrophysics HST/STIS analysis of the first main sequence pulsar CU Virginis?,?? J. Krtickaˇ 1, Z. Mikulášek1, G. W. Henry2, J. Janík1, O. Kochukhov3, A. Pigulski4, P. Leto5, C. Trigilio5, I. Krtickovᡠ1, T. Lüftinger6, M. Prvák1, and A. Tichý1 1 Department of Theoretical Physics and Astrophysics, Masaryk University, Kotlárskᡠ2, 611 37 Brno, Czech Republic e-mail: [email protected] 2 Center of Excellence in Information Systems, Tennessee State University, Nashville, TN, USA 3 Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden 4 Astronomical Institute, Wrocław University, Kopernika 11, 51-622 Wrocław, Poland 5 INAF – Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania, Italy 6 Institut für Astronomie, Universität Wien, Türkenschanzstraße 17, 1180 Wien, Austria Received 20 December 2018 / Accepted 5 March 2019 ABSTRACT Context. CU Vir has been the first main sequence star that showed regular radio pulses that persist for decades, resembling the radio lighthouse of pulsars and interpreted as auroral radio emission similar to that found in planets. The star belongs to a rare group of magnetic chemically peculiar stars with variable rotational period. Aims. We study the ultraviolet (UV) spectrum of CU Vir obtained using STIS spectrograph onboard the Hubble Space Telescope (HST) to search for the source of radio emission and to test the model of the rotational period evolution. Methods. We used our own far-UV and visual photometric observations supplemented with the archival data to improve the parameters of the quasisinusoidal long-term variations of the rotational period.
    [Show full text]
  • The Radio Astronomy of Bruce Slee
    CSIRO PUBLISHING Review www.publish.csiro.au/journals/pasa Publications of the Astronomical Society of Australia, 2004, 21, 23–71 From the Solar Corona to Clusters of Galaxies: The Radio Astronomy of Bruce Slee Wayne Orchiston Australia Telescope National Facility, PO Box 76, Epping NSW 2121, Australia (e-mail: [email protected]) Received 2003 May 8, accepted 2003 September 27 Abstract: Owen Bruce Slee is one of the pioneers of Australian radio astronomy. During World War II he independently discovered solar radio emission, and, after joining the CSIRO Division of Radiophysics, used a succession of increasingly more sophisticated radio telescopes to examine an amazing variety of celestial objects and phenomena. These ranged from the solar corona and other targets in our solar system, to different types of stars and the ISM in our Galaxy, and beyond to distant galaxies and clusters of galaxies. Although long retired, Slee continues to carry out research, with emphasis on active stars and clusters of galaxies. A quiet and unassuming man, Slee has spent more than half a century making an important, wide-ranging contribution to astronomy, and his work deserves to be more widely known. Keywords: biographies — Bruce Slee — radio continuum: galaxies — radio continuum: ISM — radio continuum: stars — stars: flare — Sun: corona 1 Introduction Radio astronomy is so new a discipline that it has yet to acquire an extensive historical bibliography. With founda- tions dating from 1931 this is perhaps not surprising, and it is only since the publication of Sullivan’s classic work, The Early Years of Radio Astronomy, in 1984 that schol- ars have begun to take a serious interest in the history of this discipline and its ‘key players’.
    [Show full text]
  • A Kinematic Study of the Irregular Dwarf Galaxy NGC 4861 Using HI
    Astronomy & Astrophysics manuscript no. 11766.bw c ESO 2021 September 10, 2021 A kinematic study of the irregular dwarf galaxy NGC 4861 using H i and Hα observations J. van Eymeren1;2;3, M. Marcelin4, B. S. Koribalski3, R.-J. Dettmar2, D. J. Bomans2, J.-L. Gach4, and P. Balard4 1 Jodrell Bank Centre for Astrophysics, School of Physics & Astronomy, The University of Manchester, Alan Turing Building, Oxford Road, Manchester, M13 9PL, UK e-mail: [email protected] 2 Astronomisches Institut der Ruhr-Universitat¨ Bochum, Universitatsstraße¨ 150, 44780 Bochum, Germany 3 Australia Telescope National Facility, CSIRO, P.O. Box 76, Epping, NSW 1710, Australia 4 Laboratoire d’Astrophysique de Marseille, OAMP, Universite´ Aix-Marseille & CNRS, 38 rue Fred´ eric´ Joliot-Curie, 13013 Marseille, France Accepted 20 July 2009 ABSTRACT Context. Outflows powered by the injection of kinetic energy from massive stars can strongly affect the chemical evolution of galaxies, in particular of dwarf galaxies, as their lower gravitational potentials enhance the chance of a galactic wind. Aims. We therefore performed a detailed kinematic analysis of the neutral and ionised gas components in the nearby star-forming irregular dwarf galaxy NGC 4861. Similar to a recently published study of NGC 2366, we want to make predictions about the fate of the gas and to discuss some general issues about this galaxy. Methods. Fabry-Perot interferometric data centred on the Hα line were obtained with the 1.93m telescope at the Observatoire de Haute-Provence. They were complemented by H i synthesis data from the VLA. We performed a Gaussian decomposition of both the Hα and the H i emission lines in order to search for multiple components indicating outflowing gas.
    [Show full text]
  • CU Virginis Œ the First Stellar Pulsar
    1 CU Virginis The First Stellar Pulsar B. J. Kellett1*, Vito G. Graffagnino1, Robert Bingham1,2, Tom W. B. Muxlow3 & Alastair G. Gunn3. 1Rutherford Appleton Laboratory, Space Science & Technology Department, Chilton, Didcot OX11 QX, UK. 2Dept. of Physics, University of Strathclyde, )lasgow, )4 ,), U.K. 3.ERL0,12L30 ,ational 4acility, 5odrell 3an6 Observatory, The University of .anchester, .acclesfield, Cheshire SK11 7DL, UK. 8To whom correspondence should be addressed9 E-mail: [email protected].. CU Virginis is one of the brightest radio emitting members of the magnetic chemically peculiar (MCP) stars and also one of the fastest rotating. We have now discovered that CU Vir is uni ue among stellar radio sources in generating a persistent, highly collimated, beam of coherent, 100% polarised, radiation from one of its magnetic poles that sweeps across the Earth every time the star rotates. This makes the star strikingly similar to a pulsar. This similarity is further strengthened by the observation that the rotating period of the star is lengthening at a phenomenal rate (significantly faster than any other astrophysical source ( including pulsars) due to a braking mechanism related to it)s very strong magnetic field. CU Vir (HD124224, HR5313) was discovered as a spectrum variable star in 1952 (1) and as a stellar radio source in 1994 (2). Its rotation period of close to half a day was immediately recognised as was the fact that it had a strong magnetic field and that it 2 rotated perpendicular to our line3of3sight (1). 1t is now 4nown to be one of the brightest radio sources in the class of magnetic chemically peculiar (MC5) stars.
    [Show full text]
  • Supernova Remnant N103B, Radio Pulsar B1951+32, and the Rabbit
    On Understanding the Lives of Dead Stars: Supernova Remnant N103B, Radio Pulsar B1951+32, and the Rabbit by Joshua Marc Migliazzo Bachelor of Science, Physics (2001) University of Texas at Austin Submitted to the Department of Physics in partial fulfillment of the requirements for the degree of Master of Science in Physics at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY February 2003 c Joshua Marc Migliazzo, MMIII. All rights reserved. The author hereby grants to MIT permission to reproduce and distribute publicly paper and electronic copies of this thesis document in whole or in part. Author.............................................................. Department of Physics January 17, 2003 Certifiedby.......................................................... Claude R. Canizares Associate Provost and Bruno Rossi Professor of Physics Thesis Supervisor Accepted by . ..................................................... Thomas J. Greytak Chairman, Department Committee on Graduate Students 2 On Understanding the Lives of Dead Stars: Supernova Remnant N103B, Radio Pulsar B1951+32, and the Rabbit by Joshua Marc Migliazzo Submitted to the Department of Physics on January 17, 2003, in partial fulfillment of the requirements for the degree of Master of Science in Physics Abstract Using the Chandra High Energy Transmission Grating Spectrometer, we observed the young Supernova Remnant N103B in the Large Magellanic Cloud as part of the Guaranteed Time Observation program. N103B has a small overall extent and shows substructure on arcsecond spatial scales. The spectrum, based on 116 ks of data, reveals unambiguous Mg, Ne, and O emission lines. Due to the elemental abundances, we are able to tentatively reject suggestions that N103B arose from a Type Ia supernova, in favor of the massive progenitor, core-collapse hypothesis indicated by earlier radio and optical studies, and by some recent X-ray results.
    [Show full text]
  • Celestial Radio Sources Whitham D
    Important Celestial Radio Sources Whitham D. Reeve Introduction The list of celestial radio sources presented below was obtained from the National Radio Astronomy Observatory (NRAO) library. Each column heading is defined below. As presented here, the list is sorted in order of flux density as received on Earth. As an aid in visualizing the location of the more powerful radio sources in the sky with respect to the Milky Way galaxy, an annotated radio map also is provided along with explanations of its important features. Listing – Definition of column headings The information below is necessarily brief. Additional information may be found by using an online encyclopedia (for example, http://en.wikipedia.org/wiki/Main_Page ) or visiting other online sources such as the National Radio Astronomy Observatory website ( http://www.nrao.edu/ ). Object Name: Each object is named according its original catalog listing (for celestial object naming conventions, see Tom Crowley’s article “Introduction to Astronomical Catalogs” in the October- November 2010 issue of Radio Astronomy ). Most of the objects in the list originally were listed in the 3rd Cambridge catalog (3C) but some are in NRAO’s catalog (NRAO). Right Ascension and Declination: The right ascension and declination are used together to define the location of an object in the sky according to the equatorial coordinate system . Right ascension is given in hour minute second format and abbreviated RA . RA is the angle measured in hours, minutes and seconds from the Vernal equinox (intersection of celestial equator and ecliptic). The declination, abbreviated Dec , is the number of degrees, minutes and seconds above (0° to +90°) or below (0° to – 90°) the celestial equator.
    [Show full text]
  • The Washburn Observer
    The Washburn Observer Volume 3, No. 2 • Fall 2013 • www.astro.wisc.edu New Faces in the Department This Fall Inside This Issue he Astronomy Department welcomes the Charee Peters has an MA degree incoming 2013–14 class of graduate students, in physics from the Fisk-Vanderbilt Letter from the Chair 2 T visiting faculty and postdocs. Masters-to-PhD Bridge Program and a John Chisholm Bitten by BS degree in physics from the University Astronomy and Travel Bugs 3 Elijah Bernstein-Cooper has a BS degree in phys- of Denver (Colorado). She is working with Professor Eric Wilcots on observing SKA Pathfinders: A Bright ics, with an astronomy emphasis, from Macalester Radio Future 4 College in St. Paul, Minnesota. He is working with HI regions (interstellar clouds of neutral Professor Snezana Stanimirovic to answer what hydrogen) in intermediate galaxies to Department Welcomes better understand star formation, galaxy Second Grainger Fellow 5 role atomic hydrogen plays in the formation of molecular hydrogen in giant molecular clouds. formation and evolution, and/or cosmic Solar System’s in Good magnetic fields. Hands with Anne Kinney 6 Yi-Hao Chen has an MS degree in astrophysics For Garret Frankson, from Ludwig-Maximillian University in Munich, Brianna Smart has a BS degree in astron- Astronomy Is a Passion 6 Germany and a BS degree in physics from National omy and physics from the University of Arizona in Tucson. She is working with News Notes 7 Taiwan University in Taipei. He is working with Professor Sebastian Heinz on studying the effect senior scientist Matt Haffner on studying of magnetic fields on propagation of jets from the ISM using the Wisconsin H-Alpha compact objects.
    [Show full text]
  • Postępy Astronomii Nr 3/1969
    POSTĘPY ASTRONOMII CZASOPISMO POŚWIĘCONE UPOWSZECHNIANIU WIEDZY ASTRONOMICZNEJ PTA TOM XVII — ZESZYT 3 1969 WARSZAWA • LIPIEC — WRZESIEŃ 1969 POLSKIE TOWARZYSTWO ASTRONOMICZNE POSTĘPY ASTRONOMII KWARTALNIK TOM XVII — ZESZYT 3 1969 WARSZAWA • LIPIEC — WRZESIEŃ 1969 KOLEGIUM REDAKCYJNE Redaktor naczelny: Stefan Piotrowski, Warszawa Członkowie: Józef Witkowski, Poznań Włodzimierz Zonn, Warszawa Sekretarz Redakcji: Jerzy Stodółkiewicz, Warszawa Adres Redakcji: Obserwatorium Astronomiczne UW Warszawa, Al. Ujazdowskie 4 W Y D A W A N E Z ZASIŁKU POLSKIEJ AKADEMII NAUK Printed in Poland Państwowe Wydawnictwo Naukowe Oddział w Łodzi 1969 W ydanie 1. N akład 456 4- 124 egi. Ark. w yd. 9.00 Ark. druk. 8.50 Papier druk sal. kl. Ul. 80 g. 70 x 100. O ddano d o d r u k u 19. VIII. 1909 Druk ukończono w sierpniu 1 9 6 9 r. Zam. 223 B-8 C ena i \ 10,— Zakład Graficzny PWN Łódź, ul. Gdańska 162 PULSARY STANISŁAW GRZĘDZIELSKI nyjibCAPW C. T)KeHaejibCKM CoflepjKaHMe CTaTba coflep»MT o03op flaiiHbix o Ha6jiK)fleHMflx u TeopemuecKMe hh- TepnpeTauMM nyjibcapoB, onyBjiMKOBaHHbisi b TeueHMM nepBoro ro^a nocjie OTKpblTMH 9TMX OÓbeKTOB. PULSARS Summary The article reviews the observational data on pulsars and their theoretical interpretation as published during the first year after the announcement of the discovery. 1. WSTĘP W lutym bieżącego roku minęło dwanaście miesięcy od opublikowania pierwszej wzmianki o odkryciu pulsara CP 1919 (He wish, Bell, P i 1 k i n g- ton, Scott, Collins 1968). Artykuł ukazał się w czasopiśmie „Naturę” , które stało się głównym forum dyskusji o tym fenomenie. W ciągu pierwszych sześciu miesięcy ukazało się w „Naturę” * 51 prac, zarówno teoretycznych jak i obserwacyjnych, w których doniesiono o odkryciu 9 pulsarów.
    [Show full text]
  • ROSAT Observations of Superflares on RS Cvn Systems
    ROSAT Observations of Superflares on RS CVn Systems Vito Giuseppe GrafFagnino Thesis submitted for the degree of Doctor of Philosophy, in the Faculty of Science of the University of London. UCL Mullard Space Science Laboratory Department of Space & Climate Physics U n i v e r s i t y • C o l l e g e • L o n d o n 2000 ProQuest Number: U642316 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest. ProQuest U642316 Published by ProQuest LLC(2015). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code. Microform Edition © ProQuest LLC. ProQuest LLC 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106-1346 ,,. A Mia Moglie E Miei Genitori A bstract The following thesis involves the analysis of a number of X-ray observations of two RS CVn systems, made using the ROSAT satellite. These observa­ tions have revealed a number of long-duration flares lasting several days (much longer than previously observed in the X-ray energy band) and emitting ener­ gies which total a few percent of the available magnetic energy of the stellar system and thus far greater than previously encountered. Calculations based on the spectrally fitted parameters show that simple flare mechanisms and standard two-ribbon flare models cannot explain the observations satisfacto­ rily and continued heating was observed during the outbursts.
    [Show full text]
  • Volume-Limited Radio Survey of Ultracool Dwarfs
    Astronomy & Astrophysics manuscript no. ucd-survey1 c ESO 2012 December 17, 2012 Volume-limited radio survey of ultracool dwarfs A. Antonova1, G. Hallinan2,3, J. G. Doyle4, S. Yu4, A. Kuznetsov4,5, Y. Metodieva1, A. Golden6,7, and K. L. Cruz8,9 1 Department of Astronomy, St. Kliment Ohridski University of Sofia, 5 James Bourchier Blvd., 1164 Sofia, Bulgaria 2 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA 3 Department of Astronomy, University of California, Berkeley, CA 94720, USA 4 Armagh Observatory, College Hill, Armagh BT61 9DG, N. Ireland 5 Institute of Solar-Terrestrial Physics, Irkutsk 664033, Russia 6 Centre for Astronomy, National University of Ireland, Galway, Ireland 7 Price Center, Albert Einstein College of Medicine, Yeshiva University, Bronx, NY 10461, USA 8 Department of Physics and Astronomy, Hunter College, City University of New York, 10065, New York, NY, USA 9 Department of Astrophysics, American Museum of Natural History, 10024, New York, NY, USA Received –——– / Accepted by A&A, 19 Nov 2012 ABSTRACT Aims. We aim to increase the sample of ultracool dwarfs studied in the radio domain to allow a more statistically significant under- standing of the physical conditions associated with these magnetically active objects. Methods. We conducted a volume-limited survey at 4.9 GHz of 32 nearby ultracool dwarfs with spectral types covering the range M7 – T8. A statistical analysis was performed on the combined data from the present survey and previous radio observations of ultracool dwarfs. Results. Whilst no radio emission was detected from any of the targets, significant upper limits were placed on the radio luminosities that are below the luminosities of previously detected ultracool dwarfs.
    [Show full text]
  • The Astrology of Space
    The Astrology of Space 1 The Astrology of Space The Astrology Of Space By Michael Erlewine 2 The Astrology of Space An ebook from Startypes.com 315 Marion Avenue Big Rapids, Michigan 49307 Fist published 2006 © 2006 Michael Erlewine/StarTypes.com ISBN 978-0-9794970-8-7 All rights reserved. No part of the publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of the publisher. Graphics designed by Michael Erlewine Some graphic elements © 2007JupiterImages Corp. Some Photos Courtesy of NASA/JPL-Caltech 3 The Astrology of Space This book is dedicated to Charles A. Jayne And also to: Dr. Theodor Landscheidt John D. Kraus 4 The Astrology of Space Table of Contents Table of Contents ..................................................... 5 Chapter 1: Introduction .......................................... 15 Astrophysics for Astrologers .................................. 17 Astrophysics for Astrologers .................................. 22 Interpreting Deep Space Points ............................. 25 Part II: The Radio Sky ............................................ 34 The Earth's Aura .................................................... 38 The Kinds of Celestial Light ................................... 39 The Types of Light ................................................. 41 Radio Frequencies ................................................. 43 Higher Frequencies ...............................................
    [Show full text]