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  • richardmitnick 7:42 pm on January 29, 2020 Permalink | Reply
    Tags: , , , , , FRBs-fast radio bursts-one of today’s big mysteries in astronomy,   

    From SKA via AAS NOVA: ” Faint Repetitions of an Extragalactic Burst” 

    SKA South Africa


    From SKA

    via

    AASNOVA

    AAS NOVA

    29 January 2020
    Susanna Kohler

    1
    The Australian Square Kilometre Array Pathfinder (ASKAP) radio telescope is responsible for finding a number of fast radio bursts. But could there be fainter flashes that it’s missing? [CSIRO/Alex Cherney]

    New evidence deepens the mystery of fast radio bursts (FRBs), the brief flashes of radio emission stemming from unknown sources beyond our galaxy. Scientists have now discovered faint repeat bursts from one of the brightest FRBs, previously thought to have been a one-off event.

    To Repeat or Not to Repeat

    It was over a decade ago that scientists noticed the first enigmatic, millisecond-duration burst of radio waves from outside of the Milky Way. Since then, we’ve discovered about 100 FRB sources and even identified the host galaxies for several of them. Nonetheless, we still don’t know what causes FRBs, or even whether they’re all the same type of phenomenon.

    2
    FRB 121102, the first fast radio burst found to repeat, was also the first to be localized in the sky. [Gemini Observatory/AURA/NSF/NRC]

    Frederick C Gillett Gemini North Telescope Maunakea, Hawaii, USA, Altitude 4,213 m (13,822 ft)

    FRB properties span a wide range, but one of the biggest distinguishing features has been repetition. While most discovered FRBs have been one-off events — a single bright flash and no evidence of any additional emission from the same region either before or after — around ten FRBs have been found to repeat.

    We successfully localized one repeating FRB to a distant low-mass, low-metallicity dwarf galaxy. The two non-repeating bursts that we’ve localized, on the other hand, are associated with very massive host galaxies. Does this distinction mean that repeating and non-repeating bursts make up two different classes of FRBs? Or are FRBs all the same type of source, and the difference in host galaxies is just random variation?

    Recently, a team of scientists led by Pravir Kumar (Swinburne University of Technology, Australia) has added one more clue to the puzzle: observations of weak repeat bursts from an FRB thought to be non-repeating.

    3
    Artist’s impression of the ASKAP radio telescope finding a fast radio burst. Other observatories are shown joining in follow-up observations. [CSIRO/Andrew Howells]

    What Are We Missing?

    Kumar and collaborators were testing a simple theory: What if FRBs all repeat, but we don’t have the sensitivity to detect the fainter bursts?

    In this scenario, supposed one-off FRBs are actually just the most energetic bursts from repeating sources. If we carefully study very sensitive observations of the region around a non-repeating burst, the team reasoned, we might find evidence of other bursts from the same source.

    The authors chose FRB 171019 as their target — one of the brightest bursts found in a recent survey conducted with the Australian Square Kilometre Array Pathfinder (ASKAP). Kumar and collaborators used ASKAP itself, as well as the 64-meter Parkes radio telescope and the 110-meter Green Bank Telescope, to conduct follow-up observations of the 10’ x 10’ region FRB 171019 was determined to have originated from.

    CSIRO/Parkes Observatory, located 20 kilometres north of the town of Parkes, New South Wales, Australia, 414.80m above sea level

    Green Bank Radio Telescope, West Virginia, USA, now the center piece of the GBO, Green Bank Observatory, being cut loose by the NSF

    4
    Timeline of the ASKAP, Parkes, and Green Bank Telescope observations in the direction of FRB 171019. Red circles mark observed bursts. [Kumar et al. 2019]

    Faint Flashes Found
    Though no additional bursts were found in the follow-up ASKAP or Parkes data, two faint bursts were visible in the 820 MHz Green Bank Telescope data, occurring 9 and 20 months after the initial ASKAP burst detection. The inferred distances are consistent with that of FRB 171019, but they are a whopping factor of ~590 fainter than the original burst!

    This discovery lends credence to the idea that more seemingly one-off bright FRBs may actually have faint repetitions that we’ve simply missed — and these sources may be found to repeat if we conduct follow-up with more sensitive telescopes. Understanding this brings us one step closer to discovering the nature of these mysterious sources.

    Citation

    “Faint Repetitions from a Bright Fast Radio Burst Source,” Pravir Kumar et al 2019 ApJL 887 L30.
    https://iopscience.iop.org/article/10.3847/2041-8213/ab5b08

    See the full article here .


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    1

    AAS Mission and Vision Statement

    The mission of the American Astronomical Society is to enhance and share humanity’s scientific understanding of the Universe.

    The Society, through its publications, disseminates and archives the results of astronomical research. The Society also communicates and explains our understanding of the universe to the public.
    The Society facilitates and strengthens the interactions among members through professional meetings and other means. The Society supports member divisions representing specialized research and astronomical interests.
    The Society represents the goals of its community of members to the nation and the world. The Society also works with other scientific and educational societies to promote the advancement of science.
    The Society, through its members, trains, mentors and supports the next generation of astronomers. The Society supports and promotes increased participation of historically underrepresented groups in astronomy.
    The Society assists its members to develop their skills in the fields of education and public outreach at all levels. The Society promotes broad interest in astronomy, which enhances science literacy and leads many to careers in science and engineering.

    Adopted June 7, 2009

    About SKA

    The Square Kilometre Arraywill be the world’s largest and most sensitive radio telescope. The total collecting area will be approximately one square kilometre giving 50 times the sensitivity, and 10 000 times the survey speed, of the best current-day telescopes. The SKA will be built in Southern Africa and in Australia. Thousands of receptors will extend to distances of 3 000 km from the central regions. The SKA will address fundamental unanswered questions about our Universe including how the first stars and galaxies formed after the Big Bang, how dark energy is accelerating the expansion of the Universe, the role of magnetism in the cosmos, the nature of gravity, and the search for life beyond Earth. Construction of phase one of the SKA is scheduled to start in 2016. The SKA Organisation, with its headquarters at Jodrell Bank Observatory, near Manchester, UK, was established in December 2011 as a not-for-profit company in order to formalise relationships between the international partners and centralise the leadership of the project.

    The Square Kilometre Array (SKA) project is an international effort to build the world’s largest radio telescope, led by SKA Organisation. The SKA will conduct transformational science to improve our understanding of the Universe and the laws of fundamental physics, monitoring the sky in unprecedented detail and mapping it hundreds of times faster than any current facility.

    Already supported by 10 member countries – Australia, Canada, China, India, Italy, New Zealand, South Africa, Sweden, The Netherlands and the United Kingdom – SKA Organisation has brought together some of the world’s finest scientists, engineers and policy makers and more than 100 companies and research institutions across 20 countries in the design and development of the telescope. Construction of the SKA is set to start in 2018, with early science observations in 2020.

    Australian Square Kilometre Array Pathfinder (ASKAP) is a radio telescope array located at Murchison Radio-astronomy Observatory (MRO) in the Australian Mid West. ASKAP consists of 36 identical parabolic antennas, each 12 metres in diameter, working together as a single instrument with a total collecting area of approximately 4,000 square metres.

    SKA Meerkat telescope, 90 km outside the small Northern Cape town of Carnarvon, SA


    SKA Meerkat Telescope

    Murchison Widefield Array,SKA Murchison Widefield Array, Boolardy station in outback Western Australia, at the Murchison Radio-astronomy Observatory (MRO)


    SKA Murchison Wide Field Array

    SKA Hera at SKA South Africa

    SKA Pathfinder – LOFAR location at Potsdam via Google Images

     
  • richardmitnick 6:17 pm on January 22, 2020 Permalink | Reply
    Tags: "The riddle of the heavenly bursts", , , , , FRBs-fast radio bursts-one of today’s big mysteries in astronomy, ,   

    From Max Planck Institute for Radio Astronomy: “The riddle of the heavenly bursts” 


    From Max Planck Institute for Radio Astronomy

    January 20, 2020
    Dr. Laura Spitler
    Max Planck Institute for Radio Astronomy, Bonn
    +49 228 525-314
    lspitler@mpifr-bonn.mpg.de

    Dr. Norbert Junkes
    Press and public relations
    Max Planck Institute for Radio Astronomy, Bonn
    +49 2 28525-399
    njunkes@mpifr-bonn.mpg.de

    Time and again, radio telescopes register extremely short bursts of radiation in the depths of space.

    This cosmic lightning storm is happening all around us. Somewhere in the earthly sky, there is a pulse that flashes and extinguishes in the next moment. These bursts, which must be measured with radio telescopes and last one thousandth of a second, are one of the greatest mysteries of astrophysics. Scientists doubt that militant aliens are fighting “Star Wars” in the vastness of space. But where do these phenomena – dubbed “fast radio bursts” by the experts – come from?

    Text: Helmut Hornung

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    The radio telescope in Effelsberg is also part of the European VLBI network that searches for radio bursts. © MPI for Radio Astronomy / Norbert Tacken

    In the city of Parkes, gigantic lattice mesh bowl rises into the sky.

    CSIRO/Parkes Observatory, located 20 kilometres north of the town of Parkes, New South Wales, Australia, 414.80m above sea level

    In 2001, this 64-metre diameter radio telescope (once the largest fully mobile radio telescope in the southern hemisphere) registered a mysterious radio burst – and nobody noticed it! It wasn’t until five years later that astrophysicist Duncan Lorimer and his student David Narkevic found the signature of the signal in the telescope data more or less by chance. Even then, the specialists could not make sense of the phenomenon. But this was not the only “Lorimer burst”.

    “We now know of more than a hundred”, says Laura Spitler. Since March 2019, the researcher has headed a Lise Meitner group on this topic at the Max Planck Institute for Radio Astronomy. Spitler has dedicated herself to these fleeting flickers in space for many years. Under her leadership, an international team discovered the first fast radio burst (FRB) on the northern celestial sphere in the Fuhrmann constellation in 2014. Astronomers had used the dish of the Arecibo telescope on Puerto Rico.


    NAIC Arecibo Observatory operated by University of Central Florida, Yang Enterprises and UMET, Altitude 497 m (1,631 ft).

    The antenna, which measures 305 m in diameter, is firmly anchored in a natural valley and can only ever focus on a relatively small section of the firmament.

    “Statistically speaking, there should be only seven eruptions per minute spread across the sky. It therefore takes a lot of luck to align your telescope to the right position at the right time”, said Spitler after the discovery was announced. Both the properties of the radio bursts and their frequency derived from the measurements were in high agreement with what astronomers had found out about all the previously observed eruptions.

    In fact, statistical assumptions were confirmed; according to these, approx. 10,000 of these unusual cosmic phenomena were thought to flare up in the earthly firmament each day. The surprisingly large number results from calculations of how much of the sky would have to be observed and for how long in order to explain the comparatively few discoveries made so far.

    The Arecibo measurement also removed the last doubts about whether the radio bursts really came from the depths of the universe. After the first registered bursts, scientists concluded that they were being generated in an area far outside the Milky Way. This was deduced from an effect called plasma dispersion. When radio signals travel a long distance through the universe, they encounter numerous free electrons located in the space between the stars.

    Ultimately, the speed of propagation of radio waves at lower frequencies decreases in a characteristic manner. For example, during the aforementioned radiation burst discovered with the Arecibo telescope, this dispersion was three times larger than one would expect from a source within the Milky Way. If the source were located in the galaxy, interstellar matter would contribute roughly 33% for the Arecibo source.


    A repeating Fast Radio Burst from a spiral galaxy
    Scientists on the trail of radio flashes – an explanatory video in English

    But what is the origin of the radio bursts? The astrophysicists have designed various scenarios, all more or less exotic. Many of them revolve around neutron stars. These are the remnants of massive explosions of massive suns as supernovae, only 30 km in size. In these spheres, matter is so densely packed that on Earth, one teaspoonful of its matter would weigh about as much as the Zugspitze massif. The neutron stars rotate quickly around their axes. Some of them have exceptionally strong magnetic fields.

    For example, fast radio bursts could occur during a supernova – but also during the fusion of two neutron stars in a close binary star system – when the magnetic fields of the two individual stars collapse. In addition, a neutron star could collapse further into a black hole, emitting a burst.

    These scientific scripts sound plausible at first glance. However, they have one flaw: They predict only one radio burst at a time. “If the flash was generated in a cataclysmic event that destroys the source, only one burst per source can be expected”, says Laura Spitler. Indeed, in the early years, there were always single outbreaks – until in 2014 a burst called FRB 121102 went online. In 2016, Spitler and her team observed this to be the first “repeater”, a burst with repeating pulses. “This refuted all models that explain FRB as the consequence of a catastrophic event”, says Spitler.

    The FRB 121102, discovered at the Arecibo telescope, was further observed by the researchers with the Very Large Array in New Mexico.

    NRAO/Karl V Jansky Expanded Very Large Array, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

    After 80 hours of measuring time, they registered nine bursts and determined the position with an accuracy of one arc second. At this position in the sky, there is a permanently radiating radio source; optical images show a faint galaxy about three billion light years away.

    With a diameter of only 13,000 light years, this star system is one of the dwarfs; the Milky Way is about ten times larger. “However, many new stars and perhaps even particularly large ones are born in this galaxy. This could be an indication of the source of the radio bursts”, says Spitler.

    The researcher thinks of pulsars – cosmic lighthouses that regularly emit radio radiation.

    Dame Susan Jocelyn Bell Burnell, discovered pulsars with radio astronomy. Jocelyn Bell at the Mullard Radio Astronomy Observatory, Cambridge University, taken for the Daily Herald newspaper in 1968. Denied the Nobel.

    Behind them are again fast rotating neutron stars with strong magnetic fields. If the axis of rotation and the axis of the magnetic field of such an object deviate from each other, a bundled radio beam can be produced. Each time this natural spotlight sweeps across the Earth, astronomers measure a short pulse.

    The bursts of most radio pulsars are too weak for them to be detected from a great distance. This is not the case with the particularly short and extremely strong “giant pulses”. A prime example of this class of objects is the crab pulsar, which was born in a supernova explosion observed in 1054 AD.

    Supernova remnant Crab nebula. NASA/ESA Hubble

    X-ray picture of Crab pulsar, taken by Chandra

    Its pulses would be visible even from neighbouring galaxies.

    “A promising model suggests that fast radio bursts are much stronger and rarer than giant pulses from extragalactic neutron stars similar to the crab pulsar. Or even younger and more energetic ones like this one”, says Spitler. “The home galaxy of FRB 121102 fits this model because it has the potential to produce just the right stars to become neutron stars at the end of their lives”.

    But whether this model is correct is literally written in the stars. The clarification is not getting any easier. Nevertheless, the observations continue. For example, the radio antennas of the European VLBI network examined another repeater in summer 2019.

    European VLBI

    FRB 180916.J0158+65 showed no less than four radiation outbursts during the five-hour observation. Each lasted less than two milliseconds.

    The home of this radio burst is in a spiral galaxy about 500 million light-years away. This makes it the closest observed so far even though this distance seems “astronomical”. It also turns out that there is apparently a high rate of star births around the burst.

    The position in the galaxy differs from that of all other bursts investigated so far. In other words: Apparently, the FRB flare up in all kinds of cosmic regions and diverse environments. “This is one of the reasons why it is still unclear whether all bursts have the same source type or are generated by the same physical processes”, says Spitler. “The mystery of their origin remains”.

    See the full article here .

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    MPIFR/Effelsberg Radio Telescope, Germany

    The Max Planck Institute for Radio Astronomy (German: Max-Planck-Institut für Radioastronomie) is located in Bonn, Germany. It is one of 80 institutes in the Max Planck Society (German: Max-Planck-Gesellschaft).

    By combining the already existing radio astronomy faculty of the University of Bonn led by Otto Hachenberg with the new Max Planck institute the Max Planck Institute for Radio Astronomy was formed. In 1972 the 100-m radio telescope in Effelsberg was opened. The institute building was enlarged in 1983 and 2002.

    The institute was founded in 1966 by the Max-Planck-Gesellschaft as the “Max-Planck-Institut für Radioastronomie” (MPIfR).

    The foundation of the institute was closely linked to plans in the German astronomical community to construct a competitive large radio telescope in (then) West Germany. In 1964, Professors Friedrich Becker, Wolfgang Priester and Otto Hachenberg of the Astronomische Institute der Universität Bonn submitted a proposal to the Stiftung Volkswagenwerk for the construction of a large fully steerable radio telescope.

    In the same year the Stiftung Volkswagenwerk approved the funding of the telescope project but with the condition that an organization should be found, which would guarantee the operations. It was clear that the operation of such a large instrument was well beyond the possibilities of a single university institute.

    Already in 1965 the Max-Planck-Gesellschaft (MPG) decided in principle to found the Max-Planck-Institut für Radioastronomie. Eventually, after a series of discussions, the institute was officially founded in 1966.

    The Max Planck Society for the Advancement of Science (German: Max-Planck-Gesellschaft zur Förderung der Wissenschaften e. V.; abbreviated MPG) is a formally independent non-governmental and non-profit association of German research institutes founded in 1911 as the Kaiser Wilhelm Society and renamed the Max Planck Society in 1948 in honor of its former president, theoretical physicist Max Planck. The society is funded by the federal and state governments of Germany as well as other sources.

    According to its primary goal, the Max Planck Society supports fundamental research in the natural, life and social sciences, the arts and humanities in its 83 (as of January 2014)[2] Max Planck Institutes. The society has a total staff of approximately 17,000 permanent employees, including 5,470 scientists, plus around 4,600 non-tenured scientists and guests. Society budget for 2015 was about €1.7 billion.

    The Max Planck Institutes focus on excellence in research. The Max Planck Society has a world-leading reputation as a science and technology research organization, with 33 Nobel Prizes awarded to their scientists, and is generally regarded as the foremost basic research organization in Europe and the world. In 2013, the Nature Publishing Index placed the Max Planck institutes fifth worldwide in terms of research published in Nature journals (after Harvard, MIT, Stanford and the US NIH). In terms of total research volume (unweighted by citations or impact), the Max Planck Society is only outranked by the Chinese Academy of Sciences, the Russian Academy of Sciences and Harvard University. The Thomson Reuters-Science Watch website placed the Max Planck Society as the second leading research organization worldwide following Harvard University, in terms of the impact of the produced research over science fields.

     
  • richardmitnick 1:51 pm on January 10, 2019 Permalink | Reply
    Tags: , , , , , FRBs-fast radio bursts-one of today’s big mysteries in astronomy, , , Radio magnetars, The team looked at the magnetar named PSR J1745-2900 located in the Milky Way's galactic center using the largest of NASA's Deep Space Network radio dishes in Australia   

    From Caltech: “Magnetar Mysteries in our Galaxy and Beyond” 

    Caltech Logo

    From Caltech

    01/09/2019

    Whitney Clavin
    (626) 395-1856
    wclavin@caltech.edu

    1
    Illustration of a magnetar—a rotating neutron star with incredibly powerful magnetic fields.
    Credit: NASA/CXC/M.Weiss

    2
    The 70-meter radio dish (DSS-43) in Canberra, Australia, part of NASA’s Deep Space Network.
    Credit: NASA/DSN

    New research looks at possible links between magnetars and extragalactic radio bursts.

    In a new Caltech-led study, researchers from campus and the Jet Propulsion Laboratory (JPL) have analyzed pulses of radio waves coming from a magnetar—a rotating, dense, dead star with a strong magnetic field—that is located near the supermassive black hole at the heart of the Milky Way galaxy. The new research provides clues that magnetars like this one, lying in close proximity to a black hole, could perhaps be linked to the source of “fast radio bursts,” or FRBs. FRBs are high-energy blasts that originate beyond our galaxy but whose exact nature is unknown.

    “Our observations show that a radio magnetar can emit pulses with many of the same characteristics as those seen in some FRBs,” says Caltech graduate student Aaron Pearlman, who presented the results today at the 233rd meeting of the American Astronomical Society in Seattle. “Other astronomers have also proposed that magnetars near black holes could be behind FRBs, but more research is needed to confirm these suspicions.”

    The research team was led by Walid Majid, a visiting associate at Caltech and principal research scientist at JPL, which is managed by Caltech for NASA, and Tom Prince, the Ira S. Bowen Professor of Physics at Caltech. The team looked at the magnetar named PSR J1745-2900, located in the Milky Way’s galactic center, using the largest of NASA’s Deep Space Network radio dishes in Australia. PSR J1745-2900 was initially spotted by NASA’s Swift X-ray telescope, and later determined to be a magnetar by NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR), in 2013.

    NASA Neil Gehrels Swift Observatory

    NASA NuSTAR X-ray telescope

    “PSR J1745-2900 is an amazing object. It’s a fascinating magnetar, but it also has been used as a probe of the conditions near the Milky Way’s supermassive black hole,” says Fiona Harrison, the Benjamin M. Rosen Professor of Physics at Caltech and the principal investigator of NuSTAR. “It’s interesting that there could be a connection between PSR J1745-2900 and the enigmatic FRBs.”

    Magnetars are a rare subtype of a group of objects called pulsars; pulsars, in turn, belong to a class of rotating dead stars known as neutron stars. Magnetars are thought to be young pulsars that spin more slowly than ordinary pulsars and have much stronger magnetic fields, which suggests that perhaps all pulsars go through a magnetar-like phase in their lifetime.

    Women in STEM – Dame Susan Jocelyn Bell Burnell

    Dame Susan Jocelyn Bell Burnell, discovered pulsars with radio astronomy. Jocelyn Bell at the Mullard Radio Astronomy Observatory, Cambridge University, taken for the Daily Herald newspaper in 1968. Denied the Nobel.

    The magnetar PSR J1745-2900 is the closest-known pulsar to the supermassive black hole at the center of the galaxy, separated by a distance of only 0.3 light-years, and it is the only pulsar known to be gravitationally bound to the black hole and the environment around it.

    In addition to discovering similarities between the galactic-center magnetar and FRBs, the researchers also gleaned new details about the magnetar’s radio pulses. Using one of the Deep Space Network’s largest radio antennas, the scientists were able to analyze individual pulses emitted by the star every time it rotated, a feat that is very rare in radio studies of pulsars. They found that some pulses were stretched, or broadened, by a larger amount than predicted when compared to previous measurements of the magnetar’s average pulse behavior. Moreover, this behavior varied from pulse to pulse.

    “We are seeing these changes in the individual components of each pulse on a very fast time scale. This behavior is very unusual for a magnetar,” says Pearlman. The radio components, he notes, are separated by only 30 milliseconds on average.

    One theory to explain the signal variability involves clumps of plasma moving at high speeds near the magnetar. Other scientists have proposed that such clumps might exist but, in the new study, the researchers propose that the movement of these clumps may be a possible cause of the observed signal variability. Another theory proposes that the variability is intrinsic to the magnetar itself.

    “Understanding this signal variability will help in future studies of both magnetars and pulsars at the center of our galaxy,” says Pearlman.

    In the future, Pearlman and his colleagues hope to use the Deep Space Network radio dish to solve another outstanding pulsar mystery: Why are there so few pulsars near the galactic center? Their goal is to find a non-magnetar pulsar near the galactic-center black hole.

    “Finding a stable pulsar in a close, gravitationally bound orbit with the supermassive black hole at the galactic center could prove to be the Holy Grail for testing theories of gravity,” says Pearlman. “If we find one, we can do all sorts of new, unprecedented tests of Albert Einstein’s general theory of relativity.”

    The new study, titled, “Pulse Morphology of the Galactic Center Magnetar PSR J1745-2900,” appeared in the October 20, 2018, issue of The Astrophysical Journal and was funded by a Research and Technology Development grant through a contract with NASA; JPL and Caltech’s President’s and Director’s Fund; the Department of Defense; and the National Science Foundation. Other authors include Jonathon Kocz of Caltech and Shinji Horiuchi of the CSIRO (Commonwealth Scientific and Industrial Research Organization) Astronomy & Space Science, Canberra Deep Space Communication Complex.

    See the full article here .


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    Please help promote STEM in your local schools.


    Stem Education Coalition

    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

    Caltech campus


    Caltech campus

     
  • richardmitnick 8:54 pm on November 9, 2018 Permalink | Reply
    Tags: ASKAP- CSIRO's Australian Square Kilometre Array Pathfinder telescope in remote Western Australia, , , , , , , , FRBs-fast radio bursts-one of today’s big mysteries in astronomy, If we can identify host galaxies of FRBs with ASKAP then we can use a telescope like ESO’s VLT to get optical spectra of those galaxies which can tell us their distances very precisely   

    From ESOblog: “Pinpointing the Hosts of Fast Radio Bursts” 

    ESO 50 Large

    From ESOblog

    1

    9 November 2018

    1
    2
    Interview with Elizabeth Mahony and Stuart Ryder

    First detected barely a decade ago, fast radio bursts (FRBs) are one of today’s big mysteries in astronomy, and Australia’s ASKAP telescope is the best facility in the world for detecting them.

    Australian Square Kilometre Array Pathfinder (ASKAP) is a radio telescope array located at Murchison Radio-astronomy Observatory (MRO) in the Australian Mid West. ASKAP consists of 36 identical parabolic antennas, each 12 metres in diameter, working together as a single instrument with a total collecting area of approximately 4,000 square metres.

    A team of scientists recently used ESO’s Very Large Telescope to follow up on an ASKAP detection, to search for an FRB host galaxy to find out more about how, where and why they form. This investigation was possible thanks to a long-term partnership between ESO and Australia, and is an elegant example of the complementary nature of Australia’s radio telescopes and ESO’s optical telescopes. Project members Elizabeth Mahony and Stuart Ryder tell us more.

    Q. What are fast radio bursts and why should we be interested in them?

    Stuart (S): Fast radio bursts (FRBs) are bright bursts of radio emission that last for just a few milliseconds. Their energetic nature tells us that they must be caused by extreme events, but being so short-lived they are extremely difficult to detect. Pinpointing exactly where they come from is even more challenging, so we still know very little about the environments they form in and the triggers that cause them.

    Elizabeth (E): About 50 FRBs have been detected in the past, but just one has been pinpointed to a host galaxy, and that is the only one that has had repeated bursts. For all other detected FRBs we don’t know precisely where they came from, which makes it hard to understand them and their host galaxies.

    Q. Tell us more about your investigation.

    E: An FRB was spotted a year ago by CSIRO’s Australian Square Kilometre Array Pathfinder (ASKAP) telescope in remote Western Australia. This particular object, denoted FRB 171020, has the lowest “dispersion measure” detected to date — this measure tells us how much matter the radio emission has travelled through. The value suggests that the FRB must have taken place less than one billion light-years away, meaning that its light took one billion years to reach us. This sounds extremely distant but actually, it’s the closest FRB ever detected, making it easier for us to narrow down its location and search for its host galaxy. The ASKAP detection gave us a rough idea of the position of this FRB, so we could then search for its host galaxy.

    Q. How does ASKAP detect FRBs when they last just a few milliseconds?

    S: ASKAP is a radio telescope made up of 36 antennas that can each see 30 square degrees of sky — as a reference, the full Moon covers just 0.2 square degrees of sky! To search for FRBs we use ASKAP in an unusual configuration called “fly’s-eye mode” where each antenna points in a different direction. This maximises the amount of sky that is observed at once, drastically increasing the chances of catching an FRB when it happens.

    Q. Why is it interesting to identify the host galaxies of FRBs?

    S: All we know currently is that FRBs are the result of some sort of astronomical object undergoing a dramatic, though not necessarily destructive, outburst. If it emerges that FRBs originate only in certain types of galaxies, then this will offer us clues about what objects and environments can spark FRBs.

    E: In addition to this, if we can identify host galaxies of FRBs, we can use a telescope like ESO’s Very Large Telescope (VLT) to get optical spectra of those galaxies, which can tell us their distances very precisely. By comparing these physical distances with the measured dispersion values, we will be able to trace the distribution of matter between galaxies far more accurately than is currently possible. Once the distances to thousands of FRB host galaxies are known, we will be able to conduct 3D “tomography” of the intergalactic medium, that will help us understand more about how galaxies expel and accrete gas.

    Q. Why did you use the VLT to follow-up on this FRB?

    E: FRBs are so bright that they can be detected even if they are very far from Earth, coming from potentially quite dim host galaxies. This, combined with the fact that we don’t know what kind of galaxies host FRBs, means that we need to use the largest optical telescopes in the world to identify the correct host galaxy.

    Q. …and what did you find?

    E: With ASKAP we located FRB171020 to an area of sky measuring 50 arcminutes by 34 arcminutes (roughly two full Moons across), but this area contains hundreds of galaxies. The dispersion measure helped us narrow down this number to just 16 potential host galaxies. We then used the VLT’s X-shooter instrument to determine the distances to these 16 galaxies, and identified the closest one — nearby spiral ESO 601-G036 — as the most likely to be the host galaxy.

    ESO X-shooter on VLT on UT2 at Cerro Paranal, Chile

    ESO 601-G036 is 120 million light-years away, which is within the distance limit set by the dispersion measure. This is the first time that a host galaxy has been singled out for a non-repeating FRB. With this knowledge, we will be able to further investigate what kind of environments FRBs are formed in, and shed light on what causes these very energetic outbursts.

    S: We also saw a dim “smudge” next to ESO 601-G036, at the same distance. We expect that this is the remains of another galaxy merging with the larger ESO 601-G036 — a process that can be extremely violent and could potentially spark FRBs. It will be interesting to see if other FRB host galaxies show such signs of merger activity.

    3
    The area of sky selected for follow-up observation by the VLT, with potential host galaxies circled in red and ESO 601-G036 at the centre. At the bottom left is a more detailed picture of ESO 601-G036 from the VST Atlas survey. Credit: Elizabeth Mahony

    Q. When did ESO sign a strategic partnership with Australia and what does this partnership mean for the astronomical community?

    S: The Strategic Partnership between ESO and Australia was signed on 11 July 2017 in Canberra, during the Annual Scientific Meeting of the Astronomical Society of Australia. It gives the Australian astronomy community access to ESO’s La Silla and Paranal Observatories, as well as the opportunity to bid for instrumentation and industry contracts. It also secured the immediate future operations of the Anglo-Australian Telescope.


    AAO Anglo Australian Telescope near Siding Spring, New South Wales, Australia, Altitude 1,100 m (3,600 ft)

    Siding Spring Mountain with Anglo-Australian Telescope dome visible near centre of image at an altitude of 1,165 m (3,822 ft)

    The ten-year agreement lays a pathway for full Australian membership to ESO, which would then include access to ALMA [below] and the ELT [below].

    Q. How did the partnership allow you to make this discovery?

    S: While ASKAP is the world’s best facility for detecting FRBs, we need access to other telescopes to carry out the optical and infrared follow-up of their candidate host galaxies. Through this Strategic Partnership, we now have long-term certainty of access to such telescopes. Australia has really dominated the search for FRBs in the past, and is well-placed to feed a steady stream of FRB detections to ESO for rapid follow-up.

    Q. Do you think that the European-Australian collaboration will lead to more astronomical discoveries than either partner could achieve alone?

    E: Absolutely! ASKAP is now operating in a mode that will potentially allow us to not only detect more FRBs, but to then pinpoint their positions with a really high accuracy. That means we could work out not only exactly which galaxy an FRB occurred in, but even where within the galaxy it occurred. Do FRBs occur at the centre of galaxies, perhaps pointing to black holes as their source? Or do they prefer the outskirts of galaxies? Once we know that, we can use the unparalleled capability of the VLT’s MUSE instrument with the Laser Guide Star Facility to home in on the sites of FRBs, as well as to reveal intervening galaxies that the FRB signal passed through.

    ESO MUSE on the VLT on Yepun (UT4),

    Glistening against the awesome backdrop of the night sky above ESO_s Paranal Observatory, four laser beams project out into the darkness from Unit Telescope 4 UT4 of the VLT.

    See the full article here .


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    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

    ESO LaSilla
    ESO/Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT 4 lasers on Yepun


    ESO Vista Telescope
    ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level.

    ESO NTT
    ESO/NTT at Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

    ESO VLT Survey telescope
    VLT Survey Telescope at Cerro Paranal with an elevation of 2,635 metres (8,645 ft) above sea level.

    ALMA Array
    ALMA on the Chajnantor plateau at 5,000 metres.

    ESO/E-ELT,to be on top of Cerro Armazones in the Atacama Desert of northern Chile. located at the summit of the mountain at an altitude of 3,060 metres (10,040 ft).


    ESO APEX
    APEX Atacama Pathfinder 5,100 meters above sea level, at the Llano de Chajnantor Observatory in the Atacama desert.

    Leiden MASCARA instrument, La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    ESO Next Generation Transit Survey at Cerro Paranel, 2,635 metres (8,645 ft) above sea level

    SPECULOOS four 1m-diameter robotic telescopes 2016 in the ESO Paranal Observatory, 2,635 metres (8,645 ft) above sea level

    ESO TAROT telescope at Paranal, 2,635 metres (8,645 ft) above sea level

    ESO ExTrA telescopes at Cerro LaSilla at an altitude of 2400 metres

     
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