DOCSLIB.ORG

Frbs in a (Largish) Nutshell

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Frbs in a (Largish) Nutshell FRBS IN A (LARGISH) NUTSHELL Ben Stappers Jodrell Bank Centre for Astrophysics University of Manchester - with material from Petroff, Keane, Possenti, Thornton RADIO TRANSIENTS • Searches for dispersed single pulses found repeating bursts in PMPS data • RRATs – neutron stars with very sporadic detectable emission* • Also interested in highly dispersed single pulses; 2 possible examples • These searches then revealed an exciting new type of source! The “Lorimer burst” Lorimer, et al. (2007) DM = 375 cm-3 pc (15%) Keane, et al. (2012) DM = 746 cm-3 pc (70%) * McLaughlin, et al. (2006) A POPULATION OF FAST RADIO BURSTS AT PARKES. • Four highly-dispersed single pulses in 24% of the high-latitude survey -3 • DM = 944, 723, 1103, 553 cm pc • Only 3-6% of the measured DM can be explained by MW – even lower than LB & KB (15%,70%) • None have been observed to repeat in follow up observations of many 10’s of hours. FRB 110220 Thornton, Stappers et al 2013 ALSO SEEN AT ARECIBO & GBT(?) NOW FRB 121102 Spitler et al. 2014 • Galactic anticentre. (l=175,b=0.223) • DM (pc cm−3) 557.4 ± 2.0 • DMNE2001,max (pc cm−3) 188 4 POPULATION GROWING FRB 131104 - Ravi, Shannon, Jameson 2015 FRB011025 - Burke-Spoloar & Bannister 2014 DM = 780 cm−3 pc, 11xNE2001 DM = 790 cm−3 pc, 7xNE2001 FRB 140514 - Petroff et al 2015 +++ PKS bursts DM = 563 cm−3 pc, 16xNE2001 5 EXTRAGALACTIC? High DM values Scattering Scales close to ν-4 as expected Very precise cold plasma, ν-2, law. 6 SOME CURRENT NUMBERS from numbers compiled by Keane. 7 INFERRING DISTANCE FROM APPARENT DM see Walker talk • Can model free electron density as fn. of redshift, z * • Contributions from host, IGM, MW, and intervening galaxy (possibly) • Deal in terms of delay across the observing band – not traditional DM • How much dispersion from a host? • MW center maybe 700 cm-3 pc** • Likely much lower for source in an inclined galactic disk -3 • i = 60° DMhost ≈ 100 cm pc Total TIGM THost Dispersive Delay TMW Source Redshift ** Deneva, Cordes, & Lazio (2009) * Ioka (2003); Inoue (2004) DISPERSION CONTRIBUTIONS DMhost DMinter DMMW -3 ~ 700 cm pc DMinter(iinter) DMMW(l, b) rest frame DM host ? iinter i -3 DMhost(i=60°) ~ 100 cm pc z = 0.81; Dcm = 2.8 Gpc DMIGM(z) z = 0.60; Dcm = 2.2 Gpc ν ➔ν(1+z) RATES • If Thornton, et al 2013 • A) the intrinsic luminosity does not depend on distance and detectability depends only on luminosity. • B) in a Euclidean universe then… • The Lorimer burst had significantly higher fluence ~ 150 Jy ms and thus the rate of LBs should consequently be lower (225 sky-1 day-1) than measured here. • Within significant uncertainties the LB and these FRBs are consistent with being from the same population of A) + B) objects • Several experiments* (e.g. ATA, PALFA, VFASTR) have placed limits on this rate via non- detections: our result is consistent with the lack of detection by these searches. • The large amount of on sky time means It should come as no surprise that Parkes has detected most of the FRBs to date • Lots of caveats on the rates, small number of sources and recent developments suggest it may be a factor of 2-3 overestimated. • See more of this in discussions in subsequent talks….. WHERE ARE THEY IN THE SKY From Petroff. 11 SKY DISTRIBUTION unscattered local/isotropic- —excluded at 3.6 σ scattered Petroff et al. 2014 al. et Petroff cosmological —- disagreement at Burke-Spolaor & Bannister 2014 2.9 σ with low-lat rates FRB events are simulated and the effects of dispersive smearing, interstellar scattering, and Tsky are also taken into account to estimate the effective S/N with which the pulse would be detected at Parkes radio telescope. In [Bourke-Spolaor & Bannister 2014] isotropic local and cosmological distributions of sources are assumed 12 WHAT ABOUT THE PERYTONS? • Swept frequency pulses – perytons* - have been seen at Parkes • Has been suggested that Lorimer burst is a peryton • Perytons are symmetrical in width and widths are W ~ 20 ms pulses • “DM” of the perytons peaks at 375 cm-3 pc with range 200—420 cm-3 pc • Found in all beams simultaneously: indicative of sidelobe detection or near field source. • “kinks” seen in dispersion sweep, i.e. not a pure power law. • Our narrow widths, wide spread of DMs, remarkable adherence to predictions of cold plasma propagation – including scattering, single beam detections mean FRBs are not perytons • Low B values - 6 Perytons 0 FRBs! • Watch this space….. Parkes Bleien Obs. * Burke-Spolaor, et al. (2011); Bagchi et al.(2012), Saint-Hilaire, Benz, Monstein2 2014, Petroff et al. 2015 NON DETECTIONS LOFAR Pilot Survey VLA Fast Imaging Coenen et al 2014 Law et al 2014 150 MHz, flat spectrum 1.4 GHz, 166 hours New limits including LOFAR Single Station - Karastergiou et al. 2015 See also papers by Hassall et al 2013, Lorimer et al 2013 & Metzger et al. 2015 …. on limits and predictions. 14 CURRENT SUMMARY Given the so far observed parameters: • Burst of ≈ millisecond duration • Dispersion measure > 5-10 x the expected Milky Way contribution • Dispersion delay = ν -2 : in two cases ν -2.003±0.006 and ν-2.000±0.006 • When measurable, scattering time follows ν -4.8±0.4 and ν -4.0±0.4 • Peak Flux density at 1.4 GHz ≈ 1 Jansky • Rate ≈ 104 sky/day ≈ 10-3 MWgal/yr Assuming extra-DM is mainly due to the IGM: • Red-shift 0.2 < z < 1.3 (IGM from [Ioka 2003;Inoue 2004]) • Comoving distance 1 < D (Gpc) < 4 • Fluence 0.5 < F (Jy msec) < 8 38 40 • Isotropic luminosity 10 < Liso (erg) < 10 33 36 • Brightness temperature 10 < T (K) < 10 15 WHAT IS THE SOURCE OF FRBs? WHAT IS THE SOURCE OF FRBs? WHAT ARE THEY? Kulkarni et al. 2014 provided a wide review of possibilities, from local radio interferences to high z cosmological sources Suitable progenitor models are those which have an ultra-clean emitting region and, in addition, a low density circum-stellar medium so that external absorption is not significant. This means, almost always, that the free-free optical depth should not be large (for usual parameters, the plasma frequency is usually well below the GHz band) Core Collapse SuperNovae (CCSN) [Thornton et al 2013] • energetics might work / environs not clean? Binary White Dwarf merger to highly magnetic rapidly spinning White Dwarf [Kashiyama et al 2013] • environs not clean enough? Asteroid/Planet/WD magnetosphere interaction with the wind from a orbited pulsar/NS [Mottez & Zarka 2014] • events should repeat with orbital period 18 Magnetar Giant Flares Popov & Postnov 2007, Thornton et al 2013, Kulkarni et al 2014, Lu et al 2014 • Energetic works (with 10-6 radio efficiency) and rate about right for Magnetars. • Compatible with a clean enough environment [Kulkarni et al 14] • Synchrotron maser mechanism from relativistic, GIANT FLARE FROM SGR1806-20 magnetized shocks formed via the interaction of the RHESSI DATA magnetic pulse with the plasma within the nebula. • A scattering tail appears when the medium is highly turbulent at the interface btw the plerion and star 100000 forming molecular clouds. 10000 s • Expected to be 5 repeatable over decade-long . 0 / s t n timescale u o 1000 C • Also [Lyubarsky 2014] indicates that a strong detectable TeV ms-burst should be associated to 100 these events and visible by Cerenkov detector up to 10 ≈100 Mpc 0 100 200 300 400 Time, s 19 COSMOLOGICAL PROBES The first measurement of the average density of the ionized component of the Inter Galactic Medium along 1000+ lines of sight. He II reionization leads to a ∼ 8% jump in the differential DM across the He II reionization epoch. • likely need thousands of FRBs around z ∼ 2 − 3 The RM from IGM to z = 1 is only 6 rad m−2 for an IGM magnetic field of 10 nG. • tens of thousand of FRBs are needed to clearly map out the redshift evolution of RM caused by the IGM magnetic field. Zheng et al 2014 20 COSMOLOGICAL PROBES With a series of 100 to 1000’s independent z determination (from the identification of the source at other wavelengths), one could • measure the missing baryonic matter in the Universe [e.g. through the investigations of galactic halos at 0.2-2 virial radii [MacQuinn 2014]] • important parameter in galaxy formation and feedback models • weigh baryons in the IGM [Deng & Zhang 2014] ; - > 50% baryons missing at z < 2 and most may reside at temperatures and densities that are difficult to detect with current methods • constrain the EoS of the “dark energy” [Gao et al 2014; Zhou et al 2014] ; • BUT there are issues with accuracy of the IGM model that is required. • put limits to the existence of floating MACHO-like objects in the IGM via gravitational lensing (better with > 5 GHz observations) [Zheng et al. 2014] Macquart et al. SKA Science book. 21 WHERE NEXT? • Definitely need to find more: • Increase the population to understand the properties of the bursts • Distribution on the sky and how affected by local ISM properties • What is the luminosity distribution? Are they standard candles? • What is the source population? Only one? • Spectral properties in the radio • Higher redshifts etc…. • Rapid response to bursts - Petroff Talk • Follow up at other wavelengths (triggered/be-triggered) • Get host location, and even potentially location within host • Independent distance estimation. • More information to allow determination of source. • IGM studies • Sufficiently large number of lines of sight to build IGM density model • Scattering in the IGM • Missing Baryons? • Ionisation properties and epochs.
Load more

Recommended publications
  • Atmospheric Interpretation of Anomalous Terrestrial
    Atmospheric Interpretation of Anomalous Terrestrial Emission Serendipitously Discovered in Radioastronomy Data at 1 Gigahertz Sarah Burke-Spolaor1, Ron Ekers1, and Jean-Pierre Macquart 2 1 CSIRO Astronomy and Space Sciences, PO Box 76, Epping NSW 1710, Australia [email protected] 2 ICRAR/Curtin Institute of Radio Astronomy, GPO Box U1987, Perth WA 6845, Australia Abstract A publication in the Astrophysical Journal [1] reported the discovery of swept-frequency, terrestrial emission in a search for astrophysical pulses. The emission's origin has yet to be determined; its attributes are atypical of known sources of terrestrial signals. We review the observed properties of the emission and present a simple model for a physical mechanism that could occur in the atmosphere to produce it. If this mechanism is the cause of the emission, its origin may lie in secondary effects of lightning production in the upper atmosphere. 1 Introduction Searches for isolated astronomical radio pulses have grown in popularity following a number of recent discoveries [e.g. 2-3]. The surfeit of Earth-origin (man-made and natural) pulses requires these searches to use techniques that discriminate target signals from terrestrial pulses. A basic feature of astronomical pulses is their frequency-dependent delay, which follows δt / f −2. This is an additive dispersion effect resulting from propagation through interstellar plasma that is negligible in locally-generated emission (see Fig. 1). Recently, sixteen terrestrial pulses with frequency-swept characteristics that mimic an astronomical dis- persion delay were reported [1]. They were found in data taken at sparse intervals over the years 1998{2003, using the multibeam receiver on Parkes Radio Telescope in Australia and a specialized back-end hardware that allows 96 spectral bands to be sampled across a 288 MHz bandwidth centered at f = 1:375 GHz.
    [Show full text]
  • Introduction
    1 Introduction Are there exotic sources of radio impulses in other galaxies? Do undiscovered planets exist in our solar system? What happens to supermassive black holes when two galaxies collide? How correct was Einstein’s theory of relativity? Strangely enough, all of these questions can be addressed through the study of stars that extend no larger than a few tens of kilometres across. This thesis deals with a wide range of topics—all, however, are endeavours motivated by the broad area of research commonly termed “Pulsar Astronomy”. This introduction and the following chapters aim to communicate the rich body of scientific research related to pulsar astronomy and its related technical requirements, even if studying pulsars is not always the central aim of the research. In this chapter we provide a context to understand the advances made in this thesis. The first section introduces pulsars and relevant properties of the stars themselves. The second section gives an introduction to using pulsars as tools to study other physical phenomena, and the third outlines the relationship that pulsar studies have to the exploration of gravitational wave sources, in particular binary supermassive black hole systems. The fourth section reviews the specialised technical systems designed to study pulsars, and how they are being used to search the vast frontier of undiscovered celestial transient radio emitters. 1.1 Pulsars Pulsars have only been the subject of observation since late 1967, when highly periodic pulses were recorded and recognised as a celestial phenomenon by Hewish et al. (1968). The prediction of Baade & Zwicky (1934) stated that compact objects should exist at the 1 2 Chapter 1.
    [Show full text]
  • • Pawan Kumar Outline† Fast Radio Burst Physics & Cosmology
    Fast Radio Burst Physics & Cosmology Pawan Kumar Outline† • A brief summary of observations • FRB physics – general constraints & a specific model • FRBs as probe of cosmology †Wenbin Lu, Paz Beniamini (FRB physics) M. Bhattacharya, E. Linder, X. Ma, Eliot Quataert (FRB-cosmology) Paris, May 27, 2021 Fast Radio Bursts (FRBs) * * * * Dispersion relation for EM waves in plasma: # =#+ + - $ ; #+ : plasma frequency "# V = ; signal at # is delayed, wrt # = ∞, by ∝ #)* EM "$ 67489 -3 The magnitude of the delay is ∝ ./ = ∫1234-5 ": ;5 (unit: pc cm ) The first FRB was discovered in 2007 – Parkes 64m radio telescope at 1.4 GHz Lorimer et al. (2007) Lorimer et al. (2007) Duration (δt) = 5ms DM = 375 pc cm-3 (DM from the Galaxy 25 cm-3pc –– high galactic latitude) Estimated distance ~ 500 Mpc (from mean IGM density) ∴ Luminosity = 1043 erg s-1 (1010 times brighter than the Sun) A Brief history (8 years of confusion and then a breakthrough) • 16 more bursts detected (2010) in Parkes archival data by Bailes & Burke-Spolaor These bursts were detected in all 13 beams of the telescope, i.e. most likely terrestrial in origin. Many people suspected that the Lorimer burst was also not cosmological. These bursts were dubbed Peryton – after the mythical winged stag. • Clever detective work by Emily Petroff et al. (2015) established the origin of Perytons (microwave oven!) Arecibo detects a burst in 2012; repeat activity found in 2015 (Spitler et al. 2016). Accurate localization led to distance measurement & confirmation that this event was cosmological and not catastrophic. FRB in our Galaxy! FRB200428 It is associated with a well known magnetar (neutron star with super-strong magnetic field) with 14 B=2.2x10 G; P=3.2s 2 - and spin-down age of 2020) al.
    [Show full text]
  • Fast Radio Bursts
    UvA-DARE (Digital Academic Repository) Fast radio bursts Petroff, E.; Hessels, J.W.T.; Lorimer, D.R. DOI 10.1007/s00159-019-0116-6 Publication date 2019 Document Version Final published version Published in Astronomy and Astrophysics Review License CC BY Link to publication Citation for published version (APA): Petroff, E., Hessels, J. W. T., & Lorimer, D. R. (2019). Fast radio bursts. Astronomy and Astrophysics Review, 27(1), [4]. https://doi.org/10.1007/s00159-019-0116-6 General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. UvA-DARE is a service provided by the library of the University of Amsterdam (https://dare.uva.nl) Download date:03 Oct 2021 The Astronomy and Astrophysics Review (2019) 27:4 https://doi.org/10.1007/s00159-019-0116-6 REVIEW ARTICLE Fast radio bursts E. Petroff1,2 · J.
    [Show full text]
  • Giant Sparks at Cosmological Distances?
    The Astrophysical Journal, 797:70 (31pp), 2014 December 10 doi:10.1088/0004-637X/797/1/70 C 2014. The American Astronomical Society. All rights reserved. Printed in the U.S.A. GIANT SPARKS AT COSMOLOGICAL DISTANCES? S. R. Kulkarni1,E.O.Ofek2,J.D.Neill3, Z. Zheng4,andM.Juric5 1 Caltech Optical Observatories 249-17, California Institute of Technology, Pasadena, CA 91125, USA 2 Department of Particle Physics & Astrophysics, Weizmann Institute of Science, Rehovot 76100, Israel 3 Space Radiation Laboratory 290-17, California Institute of Technology, Pasadena, CA 91125, USA 4 Department of Physics & Astronomy, University of Utah, 115 South 1400 East 201, Salt Lake City, UT 84112, USA 5 Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195, USA Received 2014 February 28; accepted 2014 September 23; published 2014 November 25 ABSTRACT Millisecond-duration bright radio pulses at 1.4 GHz with high dispersion measures (DMs) were reported by Lorimer et al., Keane et al., and Thornton et al. Their all-sky rate is ≈104 day−1 above ∼1 Jy. Related events are “Perytons”—similar pulsed, dispersed sources, but most certainly local. Suggested models of fast radio bursts (FRBs) can originate in Earth’s atmosphere, in stellar coronae, in other galaxies, and even at cosmological distances. Using physically motivated assumptions combined with observed properties, we explore these models. In our analysis, we focus on the Lorimer event: a 30 Jy, 5 ms duration burst with DM = 375 cm−3 pc, exhibiting a steep frequency-dependent pulse width (the Sparker). To be complete, we drop the assumption that high DMs are produced by plasma propagation and assume that the source produces pulses with frequency-dependent arrival time (“chirped signals”).
    [Show full text]
  • Identifying the Source of Perytons at the Parkes Radio Telescope
    Mon. Not. R. Astron. Soc. 000, 000{000 (0000) Printed 10 April 2015 (MN LATEX style file v2.2) Identifying the source of perytons at the Parkes radio telescope E. Petroff1;2;3?, E. F. Keane1;4;3, E. D. Barr1;3, J. E. Reynolds2, J. Sarkissian2, P. G. Edwards2, J. Stevens2, C. Brem2, A. Jameson1, S. Burke-Spolaor5, S. Johnston2, N. D. R. Bhat6;3, P. Chandra7, S. Kudale7, S. Bhandari1;3 1 Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Mail H30, PO Box 218, VIC 3122, Australia. 2 CSIRO Astronomy & Space Science, Australia Telescope National Facility, P.O. Box 76, Epping, NSW 1710, Australia 3 ARC Centre of Excellence for All-sky Astrophysics (CAASTRO). 4 SKA Organisation, Jodrell Bank Observatory, Cheshire, SK11 9DL, UK 5 National Radio Astronomy Observatory, 1003 Lopezville Rd., Socorro, NM 87801, USA 6 International Centre for Radio Astronomy Research, Curtin University, Bentley, WA 6102, Australia 7 National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune University Campus, Ganeshkhind, Pune 411 007, India 10 April 2015 ABSTRACT \Perytons" are millisecond-duration transients of terrestrial origin, whose frequency-swept emission mimics the dispersion of an astrophysical pulse that has propagated through tenuous cold plasma. In fact, their similarity to FRB 010724 had previously cast a shadow over the interpretation of \fast radio bursts," which otherwise appear to be of extragalactic origin. Until now, the physical origin of the dispersion- mimicking perytons had remained a mystery. We have identified strong out-of-band emission at 2.3{2.5 GHz associated with several peryton events.
    [Show full text]
  • Scientific Progress at the Boundaries of Experience
    SCIENTIFIC PROGRESS AT THE BOUNDARIES OF EXPERIENCE by Nora Mills Boyd B.Sc. in Physics and Philosophy, University of British Columbia, 2008 M.A. in Philosophy, University of Waterloo, 2010 Submitted to the Graduate Faculty of the Kenneth P. Dietrich School of Arts & Sciences in partial fulfillment of the requirements for the degree of Doctor of Philosophy University of Pittsburgh 2018 UNIVERSITY OF PITTSBURGH DIETRICH SCHOOL OF ARTS AND SCIENCES This dissertation was presented by Nora Mills Boyd It was defended on March 13th 2018 and approved by John D. Norton, History and Philosophy of Science Robert Batterman, Philosophy Christopher Smeenk, Philosophy at Western University James Woodward, History and Philosophy of Science Dissertation Director: John D. Norton, History and Philosophy of Science ii SCIENTIFIC PROGRESS AT THE BOUNDARIES OF EXPERIENCE Nora Mills Boyd, PhD University of Pittsburgh, 2018 My dissertation introduces a new empiricist philosophy of science built on a novel charac- terization of empirical evidence and an analysis of empirical adequacy appropriate to it. I analyze historical and contemporary cases primarily, though not exclusively, from the space sciences attending carefully to the intricate practices involved in data collection and pro- cessing. I argue that the epistemic utility of empirical results as constraints on theorizing depends on the conditions of their provenance and that therefore information about those conditions ought to be included in our conception of empirical evidence. I articulate the con- ditions requisite for adjudicating the empirical adequacy of a theory with respect to some evidence and argue that much more background information is required for this adjudication than has been widely appreciated.
    [Show full text]
  • Ultra-Powerful Signals Known As Fast Radio Bursts Are Bombarding Earth
    MYSTERY IN THE HEAVENS Ultra-powerful signals known as fast radio bursts are bombarding Earth. But where are they coming from? BY ELIZABETH GIBNEY o astronomer had ever seen anything an astrophysicist at West Virginia University in easily result from mobile-phone signals, stray like it. No theorist had predicted it. Yet Morgantown, saw this object erupt only once, radar probes, strange weather phenomena there it was — a 5-milli­second radio and with more power than any known pulsar. and instrumental glitches. Wider acceptance Nburst that had arrived on 24 August 2001 from He began to realize the significance of the of what is now known as the Lorimer burst an unknown source seemingly billions of light discovery1 only after carefully going over the came only in the past few years, after observers ENGLAND WAYNE years away. data with his former adviser, Matthew Bailes, an working at Parkes and other telescopes spotted “It was so bright, we couldn’t just dismiss it,” astrophysicist at Swinburne University of Tech- similar signals. Today, the 2001 event is rec- says Duncan Lorimer, who co-discovered the nology in Melbourne, Australia. If the source ognized as the first in a new and exceedingly signal1 in 2007 while working on archived data really was as far away as it seemed, then for a peculiar class of sources known as fast radio from the Parkes radio telescope in New South few milliseconds it had flared with the power of bursts (FRBs) — one of the most perplexing Wales, Australia. “But we didn’t really know 500 million Suns.
    [Show full text]
  • Prime Focus (01-21)
    Highlights of the January Sky. - - - 1st - - - DUSK: Jupiter and Saturn are just over 1° apart low in the southwest. - - - 2nd - - - PM: A waning gibbous Moon about 4° right of the Moon when they rise. - - - 3rd - - - KAS PM: The Quadrand meteor shower peaks. - - - 6th - - - General Meeting: Friday, January 8 @ 7:00 pm Last Quarter Moon 4:38 am EST Held on Zoom • Click to Register • See Page 10 for Details - - - 10th - - - DUSK: Jupiter, Saturn, and Online Viewing: Saturday, January 9 @ 9:00 pm Mercury form a ght triangle low in the west- Held on Zoom • Click to Register • See Page 9 for Details southwest. - - - 11th - - - Board Meeting: Sunday, January 10 @ 5:00 pm DAWN: A thin waning crescent Moon and Venus Held on Zoom • All Members Welcome to Attend are separated by 4°. - - - 13th - - - Lecture Series: Saturday, January 23 @ 1:00 pm New Moon Held on Zoom • See Page 3 for Details 12:02 am EST - - - 20th - - - First Quarter Moon 4:03 pm EST Inside the Newsletter. PM: The Moon and Mars are about 6° apart high above southwestern December Meeng Minutes.............. p. 2 horizon. Board Meeng Minutes..................... p. 3 - - - 23rd - - - PM: A waxing gibbous Moon Intro. to Amateur Astronomy............ p. 3 is 4° above Aldebaran in Observaons of 2020......................... p. 4 Taurus. KAS Member Observatories...............p. 5 - - - 26th - - - PM: Pollux is 7° to the Great Conjuncon Images................. p. 6 upper le of the Moon. NASA Night Sky Notes........................ p. 7 - - - 28th - - - January Night Sky............................... p. 8 Full Moon 2:18 pm EST KAS Board & Announcements............ p. 9 - - - 29th - - - General Meeng Preview.................
    [Show full text]
  • The Transient Radio Sky Observed with the Parkes Radio Telescope
    The transient radio sky observed with the Parkes radio telescope Emily Brook Petroff Presented in fulfillment of the requirements of the degree of Doctor of Philosophy February, 2016 Faculty of Science, Engineering, and Technology Swinburne University i Toute la sagesse humaine sera dans ces deux mots: attendre et espérer. All of human wisdom is summed up in these two words: wait and hope. —The Count of Monte Cristo, Aléxandre Dumas ii Abstract This thesis focuses on the study of time-variable phenomena relating to pulsars and fast radio bursts (FRBs). Pulsars are rapidly rotating neutron stars that produce radio emission at their magnetic poles and are observed throughout the Galaxy. The source of FRBs remains a mystery – their high dispersion measures may imply an extragalactic and possibly cosmological origin; however, their progenitor sources and distances have yet to be verified. We first present the results of a 6-year study of 168 young pulsars to search for changes in the electron density along the line of sight through temporal variations in the pulsar dispersion measure. Only four pulsars exhibited detectable variations over the period of the study; it is argued that these variations are due to the movement of ionized material local to the pulsar. Our upper limits on DM variations in the other pulsars are consistent with the scattering predicted by current models of turbulence in the free electron density along these lines of sight through the interstellar medium (ISM). We also present new results of a search for single pulses from Fast Radio Bursts (FRBs), including a full analysis of the data from the High Time Resolution Universe (HTRU) sur- vey at intermediate and high Galactic latitudes.
    [Show full text]
  • Radio Bursts with Extragalactic Spectral Characteristics Show Terrestrial Origins
    Haverford College Haverford Scholarship Faculty Publications Physics 2011 Radio Bursts with Extragalactic Spectral Characteristics Show Terrestrial Origins S. Burke-Spolaor Matthew Bailes Ronaled Elkers Jean-Pierre Macquart Fronefield Crawford Haverford College, [email protected] Follow this and additional works at: https://scholarship.haverford.edu/physics_facpubs Repository Citation "Radio Bursts with Extragalactic Spectral Characteristics Show Terrestrial Origins" S. Burke-Spolaor, M. Bailes, R. D. Ekers, J.-P. Macquart, & F. Crawford, Astrophysical Journal, 727, 18 (2011). This Journal Article is brought to you for free and open access by the Physics at Haverford Scholarship. It has been accepted for inclusion in Faculty Publications by an authorized administrator of Haverford Scholarship. For more information, please contact [email protected]. The Astrophysical Journal, 727:18 (5pp), 2011 January 20 doi:10.1088/0004-637X/727/1/18 C 2011. The American Astronomical Society. All rights reserved. Printed in the U.S.A. RADIO BURSTS WITH EXTRAGALACTIC SPECTRAL CHARACTERISTICS SHOW TERRESTRIAL ORIGINS S. Burke-Spolaor1,5, Matthew Bailes1, Ronald Ekers2, Jean-Pierre Macquart3, and Fronefield Crawford III4 1 Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Mail H39, P.O. Box 218, Hawthorn VIC 3122, Australia; [email protected] 2 CSIRO Australia Telescope National Facility, P.O. Box 76, Epping NSW 1710, Australia 3 ICRAR/Curtin Institute of Radio Astronomy, GPO Box U1987, Perth WA 6845, Australia 4 Department of Physics and Astronomy, Franklin and Marshall College, Lancaster, PA 17604, USA Received 2010 July 19; accepted 2010 October 29; published 2010 December 28 ABSTRACT Three years ago, the report of a solitary radio burst was thought to be the first discovery of a rare, impulsive event of unknown extragalactic origin.
    [Show full text]
  • RFI Mitigation (What It Is, Where It Comes From, How to Fix It)
    RFI Mitigation (what it is, where it comes from, how to fix it) or, ”Finding an astrophysical needle in an artificial haystack.” MPIfR, 22/01/2020 RFI (Radio Frequency Interference) in a nutshell: ▪ All the annoying signals that get in the way of you seeing your [insert astronomical source] > Pulsar What is RFI? > RRAT > FRB > Etc… But what is it really? To answer completely, start with “What are we looking at when we make an observation?” Two answers… Romantic answer: ▪ The stars. The galaxies. The Universe! Technical answer: ▪ Voltage fluctuations associated with electromagnetic radiation (radio waves) which induces currents in a conductor (our antenna) And what do we want to see? (in our “Voltage fluctuations associated with EM blah blah blah… ?”) Again, two answers… Romantic answer: ▪ The stars! Probably, the neutron stars. Technical answer: ▪ Signals from our astrophysical radio sources against a background of � (preferably low) Gaussian noise Gaussian bit is important! The radiometer equation defines the sensitivity of a receiver to radio signals Central limit theorem states… ▪ “When independent random variables are added, their properly normalised sum tends towards a gaussian distribution” In radio astronomy… ▪ Our independent random variables are a set of random data in our receiver from many weak radio signals and noise voltages [1] ▪ Plots are what you want to see: nice random noise This is important because: The radiometer equation: ▪ Defines sensitivity to radio signals* ▪ Fundamental assumption: noise fluctuations behave randomly RFI is non-Gaussian (S/Nmin)SEFD ▪ Reduces sensitivity to signals Smin = β ▪ Could obscure them entirely ��� ∆ � *Derivation found in [2] ▪ In essence, it is any unwanted non-Gaussian signal So what is in your data RFI??? ▪ Astrophysical signals will be non-Gaussian too Examples of non-Gaussian signals Data taken using the e-MERLIN interferometer Broad-band impulsive signals • Span entire observing bandwidth • Something periodic? Data clearly not Gaussian • E.g.
    [Show full text]