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News Article | November 17, 2016
Site: www.eurekalert.org

Fast radio bursts, or FRBs, are mysterious flashes of radio waves originating outside our Milky Way galaxy. A team of scientists, jointly led by Caltech postdoctoral scholar Vikram Ravi and Curtin University research fellow Ryan Shannon, has now observed the most luminous FRB to date, called FRB 150807. Though astronomers still do not know what kinds of events or objects produce FRBs, the discovery is a stepping stone for astronomers to understand the diffuse, faint web of material that exists between galaxies, called the cosmic web. The findings are described in a paper appearing in Science on November 17. "Because FRBs like the one we discovered occur billions of light-years away, they help us study the universe between us and them," says Ravi, who is the R A and G B Millikan Postdoctoral Scholar in Astronomy. "Nearly half of all visible matter is thought to be thinly spread throughout intergalactic space. Although this matter is not normally visible to telescopes, it can be studied using FRBs." When FRBs travel through space, they pass through intergalactic material and are distorted, similar to the apparent twinkling of a star because its light is distorted by Earth's atmosphere. By observing these bursts, astronomers can learn details about the regions of the universe through which the bursts traveled on their way to Earth. FRB 150807 appears to only be weakly distorted by material within its host galaxy, which shows that the intergalactic medium in this direction is no more turbulent than theorists originally predicted. This is the first direct insight into turbulence in intergalactic medium. The researchers observed FRB 150807 while monitoring a nearby pulsar--a rotating neutron star that emits a beam of radio waves and other electromagnetic radiation--in our galaxy using the Parkes radio telescope in Australia. "Thanks to a real-time detection system developed by the Swinburne University of Technology, we found that although the FRB is a million times further away than the pulsar, the magnetic fields in their directions appear identical," says Ryan Shannon, research fellow at Commonwealth Scientific and Industrial Research Organisation (CSIRO) Astronomy and Space Science and at Curtin University in Australia, and colead author of the study. This refutes some claims that FRBs are produced in dense environments with strong magnetic fields. The result provides a measure of the magnetism in the space between galaxies, an essential step in determining how cosmic magnetic fields are produced. Only 18 FRBs have been detected to date. Mysteriously, most give off only a single burst and do not flash repeatedly. Additionally, most FRBs have been detected with telescopes that observe large swaths of the sky but with poor resolution, making it difficult to pinpoint the exact location of a given burst. The unprecedented brightness of FRB 150807 allowed Ravi and his team to localize it much more accurately, making it the best-localized FRB to date. In February 2017, pinpointing the locations of FRBs will become much easier for astronomers with the commissioning of the Deep Synoptic Array prototype, an array of 10 radio dishes at Caltech's Owens Valley Radio Observatory in California. "We estimate that there are between 2,000 and 10,000 FRBs occurring in the sky every day," Ravi says. "One in 10 of these are as bright as FRB 150807, and the Deep Synoptic Array prototype will be able to pinpoint their locations to individual galaxies. Measuring the distances to these galaxies enables us to use FRBs to weigh the tenuous intergalactic material." Ravi is the project scientist for the Deep Synoptic Array prototype, which is being constructed by the Jet Propulsion Laboratory (JPL) and Caltech and funded by the National Aeronautics and Space Administration through the JPL President's and Director's Fund Program. The paper is titled "The magnetic field and turbulence of the cosmic web measured using a brilliant fast radio burst." The Parkes radio telescope is part of the Australia Telescope National Facility, which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO.


News Article | November 8, 2016
Site: phys.org

Parkes joins the Green Bank Telescope (GBT) in West Virginia, USA, and the Automated Planet Finder (APF) at Lick Observatory in California, USA, in their ongoing surveys to determine whether civilizations elsewhere have developed technologies similar to our own. Parkes radio telescope is part of the Australia Telescope National Facility, owned and managed by Australia's Commonwealth Scientific and Industrial Research Organization (CSIRO). Drawing on over nine months of experience in operation of the dedicated Breakthrough Listen instrument at GBT, a team of scientists and engineers from the University of California, Berkeley's SETI Research Center (BSRC) deployed similar hardware at Parkes, bringing Breakthrough Listen's unprecedented search tools to a wide range of sky inaccessible from the GBT. The Southern Hemisphere sky is rich with targets, including the center of our own Milky Way galaxy, large swaths of the galactic plane, and numerous other galaxies in the nearby Universe. 'The Dish' at Parkes played an iconic role in receiving the first deliberate transmissions from the surface of another world, as the astronauts of Apollo 11 set foot on our Moon. Now, Parkes joins once again in expanding human horizons as we search for the answer to one of our oldest questions: Are we alone? "The Parkes Radio Telescope is a superb instrument, with a rich history," said Pete Worden, Chairman of Breakthrough Prize Foundation and Executive Director of the Breakthrough Initiatives. "We're very pleased to be collaborating with CSIRO to take Listen to the next level." With its new combined all-sky range, superb telescope sensitivity and computing capacity, Breakthrough Listen is the most powerful, comprehensive, and intensive scientific search ever undertaken for signs of intelligent life beyond Earth. Moreover, this expansion of Breakthrough Listen's range follows the announcement on October 12 that it will be joining forces with the new FAST telescope – the world's largest filled-aperture radio receiver – to coordinate their searches for artificial signals. The two programs will exchange observing plans, search methods and data, including the rapid sharing of promising new signals for additional observation and analysis. The partnership represents a major step toward establishing a fully connected, global search for intelligent life in the Universe. "The addition of Parkes is an important milestone," said Yuri Milner, founder of the Breakthrough Initiatives, which include Breakthrough Listen. "These major instruments are the ears of planet Earth, and now they are listening for signs of other civilizations." After 14 days of commissioning and test observations, first light for Breakthrough Listen at Parkes was achieved on November 7, with an observation of the newly-discovered Earth-size planet orbiting the nearest star to the Sun. Proxima Centauri, a red dwarf star 4.3 light years from Earth, is now known to have a planet ("Proxima b") within its habitable zone – the region where water could exist in liquid form on the planet's surface. Such "exo-Earths" (habitable zone exoplanets) are among the primary targets for Breakthrough Listen. "The chances of any particular planet hosting intelligent life-forms are probably minuscule," said Andrew Siemion, director of UC Berkeley SETI Research Center. "But once we knew there was a planet right next door, we had to ask the question, and it was a fitting first observation for Parkes. To find a civilization just 4.2 light years away would change everything." As the closest known exoplanet, Proxima b is also the current primary target for Breakthrough Listen's sister initiative, Breakthrough Starshot, which is developing the technology to send gram-scale spacecraft to the nearest stars. "Parkes is one of the most highly cited radio telescopes in the world, with a long list of achievements to its credit, including the discovery of the first 'fast radio burst'. Parkes' unique view of the southern sky, and cutting-edge instrumentation, means we have a great opportunity to contribute to the search for extra-terrestrial life," said Douglas Bock, Director of CSIRO Astronomy and Space Science. As with the other Breakthrough Listen telescopes, data from Parkes will be freely available to the public online. Scientists, programmers, students, and others are invited to access the Breakthrough Listen archive for scientific research purposes, including helping perfect algorithms to sift through petabytes of raw data from the telescopes, screening for interfering signals from earth-bound technology. Volunteers can also help analyze data from Parkes by donating their spare computing power as part of BSRC's legendary SETI@home project. Breakthrough Listen at Parkes will be the most comprehensive search of the southern sky for artificial signals in six key samples: Explore further: Breakthrough Listen to search for intelligent life around weird star


Alves M.I.R.,University Paris - Sud | Alves M.I.R.,University of Manchester | Davies R.D.,University of Manchester | Dickinson C.,University of Manchester | And 3 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2012

We present the derivation of the free-free emission on the Galactic plane between ℓ= 20° and 44° and |b|≤ 4°, using radio recombination line (RRL) data from the Hi Parkes All Sky Survey (HIPASS). Following an upgrade of the RRL data reduction technique, which improves significantly the quality of the final RRL spectra, we have extended the analysis to three times the area covered in Alves et al. The final RRL map has an angular resolution of 14.8arcmin and a velocity resolution of 20kms -1. The electron temperature (T e) distribution of the ionized gas in the area under study at 1.4GHz is derived using the line and continuum data from the present survey. The mean T e on the Galactic plane is 6000K. The first direct measure of the free-free emission is obtained based on the derived T e distribution. Subtraction of this thermal component from the total continuum leads to the first direct measurement of the synchrotron emission at 1.4GHz. A narrow component of width 2° is identified in the latitude distribution of the synchrotron emission. We present a list of Hii regions and supernova remnants (SNRs) extracted from the present free-free and synchrotron maps, where we confirm the synchrotron nature of the SNRs G42.0-0.1 and G41.5+0.4 proposed by Kaplan et al. and the SNR G35.6-0.4 recently re-identified by Green. The latitude distribution for the RRL-derived free-free emission shows that the Wilkinson Microwave Anisotropy Probe (WMAP) maximum entropy method is too high by ~50 per cent, in agreement with other recent results. The extension of this study to the inner Galaxy region ℓ=-50° to 50° will allow a better overall comparison of the RRL result with WMAP. © 2012 The Authors. Monthly Notices of the Royal Astronomical Society © 2012 RAS.


Alves M.I.R.,University of Manchester | Davies R.D.,University of Manchester | Dickinson C.,University of Manchester | Davis R.J.,University of Manchester | And 3 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2010

Radio recombination lines (RRLs) can be used to determine the emission measure unambiguously along the Galactic plane. We use the deep (2100 s per beam) H i Parkes Zone of Avoidance (ZOA) survey which includes three RRLs (H. 166α, H. 167α and H. 168α) within its bandwidth. The region ℓ= 36° to 44°, b=4° to +4° is chosen to include emission from the Local, Sagittarius and Scutum arms. An 8°× 8° data cube centred at (ℓ, b) = (40°, 0°) is constructed of RRL spectra with velocity and spatial resolution of 27 km s -1 and 15.5 arcmin, respectively. Well-known H ii regions are identified as well as the diffuse RRL emission on the Galactic plane. A Galactic latitude section of the integrated RRL emission across the Galactic plane delineates the brightness temperature (Tb) distribution which has a half-power width in latitude of .A value of the electron temperature Te≃ 8000 K is derived from a comparison with the Wilkinson Microwave Anisotropy Probe (WMAP) free-free maximum entropy method. The Tb distribution from the present RRL data is combined with the WMAP 5-yr data to derive the latitude distribution of the residual 'anomalous' emission on the Galactic ridge. In this paper, we demonstrate that diffuse ionized emission on the Galactic ridge can be recovered using RRLs from the ZOA survey. This method is therefore able to complement the Hα data at low Galactic latitudes, to enable an all-sky free-free template to be derived. © 2010 The Authors. Journal compilation © 2010 RAS.


Rubio-Herrera E.,National Autonomous University of Mexico | Rubio-Herrera E.,University of Amsterdam | Stappers B.W.,University of Manchester | Hessels J.W.T.,University of Amsterdam | And 2 more authors.
Monthly Notices of the Royal Astronomical Society | Year: 2013

We present the results of the most sensitive and comprehensive survey yet undertaken for radio pulsars and fast transients in the Andromeda galaxy (M31) and its satellites, using the Westerbork Synthesis Radio Telescope (WSRT) at a central frequency of 328 MHz. We used the WSRT in a special configuration called 8gr8 (eight-grate) mode, which provides a large instantaneous field of view, about 5 deg2 pointing-1, with good sensitivity, long dwell times (up to 8 h pointing-1) and good spatial resolution (a few arcminutes) for locating sources. We have searched for both periodicities and single pulses in our data, aiming to detect bright, persistent radio pulsars and rotating radio transients (RRATs) of either Galactic or extragalactic origin. Our searches did not reveal any confirmed periodic signals or bright single bursts from (potentially) cosmological distances. However, we do report the detection of several singlepulse events, some repeating at the same dispersion measure, which could potentially originate from neutron stars in M31. One in particular was seen multiple times, including a burst of six pulses in 2000 s, at a dispersion measure of 54.7 pc cm-3, which potentially places the origin of this source outside our Galaxy. Our results are compared to a range of hypothetical populations of pulsars and RRATs in M31 and allow us to constrain the luminosity function of pulsars in M31. They also show that, unless the pulsar population in M31 is much dimmer than in our Galaxy, there is no need to invoke any violation of the inverse square law of the distance for pulsar fluxes. © 2012 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society.


McIntosh G.,University of Minnesota | Indermuehle B.,Australia Telescope National Facility
Astronomical Journal | Year: 2013

We present an analysis of velocity parameters derived from multi-epoch observations of the SiO maser spectra of 47 long period variables (LPVs). The velocity parameters are important to inform and constrain theoretical models of SiO maser emission and to extract information on binary orbits. Mira and R Aquarii (R Aqr) are two known binaries included in the program. The 47 LPVs are among 121 sources of the Australia Telescope National Facility Mopra telescope's monitoring program. Observations were carried out several times a year between 2008 and 2012 and are continuing. The SiO spectra are from the v = 1, J = 1-0 (43.122 GHz; hereafter J10) and the v = 1, J = 2-1 (86.2434 GHz; hereafter J21) transitions. For 41 of the 47 LPVs we observed both transitions nearly simultaneously in 457 observations. We have determined and compared the velocity centroids (VCs) and velocity ranges (VRs) of emission suffixed as above (10 and 21) for the two transitions: VC10, VC21, VR10, and VR21. The VCs of the two transitions are, on average, within 0.13 km s-1 of each other but are sometimes separated by a few km s-1. The VC10s are, on average, slightly more positive than the VC21s. The values of the VCs in the two transitions have been compared to justify using both of these transitions to extract binary star orbital parameters. The arithmetic mean VR10 derived from 635 observations of 47 sources is 6.4 km s-1 with a standard deviation of 3.4 km s-1, while the mean VR21 derived from 485 observations of 41 sources is 4.2 km s-1 with a standard deviation of 2.8 km s-1. The number of occurrences of VR10 and VR21 versus VR have different distributions. The differences in the VRs indicate that the J21 and J10 emissions arise from dynamically different regions of the circumstellar environment. © 2013. The American Astronomical Society. All rights reserved.


McIntosh G.C.,University of Minnesota | Indermuehle B.,Australia Telescope National Facility
Astrophysical Journal | Year: 2013

We report the first short term velocity centroid (VC) periodicity derived from SiO maser emission. L2 Puppis, a semi-regular AGB star, was observed using the Mopra radio telescope of the Australia Telescope National Facility in the SiO v = 1, J = 1-0 and v = 1, J = 2-1 transitions. It exhibits a 139 day period in its SiO maser VC based on a period folding analysis and a Lomb Scargle analysis. L2 Pup's SiO maser emission has an unusually large velocity range and an unusual three-peaked spectrum. To create the change in VC the entire spectrum does not shift in velocity, but changes in the relative emission of the peaks generate the variation. The changes in the VC may be due to differential illumination, an asymmetric circumstellar distribution of material, or a mixture of causes. The unusual velocity structure, similar to that observed in Orion source 1, may be due to revolution of the circumstellar material or asymmetries in the circumstellar environment. © 2013. The American Astronomical Society. All rights reserved..


Mcintosh G.,University of Minnesota | Indermuehle B.,Australia Telescope National Facility
Astronomical Journal | Year: 2015

We have determined and compared the SiO maser velocity parameters of semiregular variables in the v = 1, J = 1 - 0 (J101) and the v = 1, J = 2 - 1 (J21) transitions. Fourteen sources in the Mopra SiO Maser Catalogue are classified as semiregular variables of types SR, SRa, SRb, or SRc. (L2 Puppis, an SRa star with an unusual SiO maser spectrum, has been analyzed individually.) We have previously presented the overall and phase dependent velocity parameters of SiO masers associated with long period variables (LPVs) of well-established periods and maxima. A comparison of the velocity centroid (VC) difference, VC21-VC10, shows mixed results for the variable types. Some differences are negative and some positive. The SRc difference is negative, large, and relatively stable. The SRb difference has the widest distribution. The velocity ranges (VRs) of the maser emission have been compared using arithmetic averages, Gaussian fits to the distributions, and Weibull fits to the distributions. For LPVs, SRs, SRas, and SRcs the VR10 is one to a few km s-1 greater than the VR21. SRcs have the largest VRs by a factor of two or three indicating the greater range over which the conditions necessary for masers to originate exist in these supergiant stars. SRbs are the only classification of semiregular variable in which the VR21 exceeds the VR10. The larger VR21 compared to VR10 for SRbs appears in all comparisons. The difference in the SRb SiO maser velocity parameters may be due to a difference in the oscillation mechanism of the star. The suggested overtone oscillations of SRbs may affect the circumstellar cloud dynamics. Little theoretical work has specifically addressed the masers in semiregular variables. Qualitative comparisons of the data with the existing models of the SiO masers in LPVs are made. © 2015. The American Astronomical Society. All rights reserved.


Subrahmanyan R.,Raman Research Institute | Ekers R.D.,Australia Telescope National Facility | Saripalli L.,Raman Research Institute | Sadler E.M.,University of Sydney
Monthly Notices of the Royal Astronomical Society | Year: 2010

We present a radio survey carried out with the Australia Telescope Compact Array. A motivation for the survey was to make a complete inventory of the diffuse emission components as a step towards a study of the cosmic evolution in radio source structure and the contribution from radio-mode feedback on galaxy evolution. The Australia Telescope Low-Brightness Survey (ATLBS) at 1388 MHz covers 8.42 deg2 of the sky in an observing mode designed to yield images with exceptional surface brightness sensitivity and low confusion. The survey was carried out in two adjacent regions on the sky centred at RA: 00h35m00s, Dec.: and RA: 00h59m17s, Dec.: (J2000.0). The ATLBS radio images, made with 0.08 mJy beam-1 rms noise and 50 arcsec beam, detect a total of 1094 sources with peak flux exceeding 0.4 mJy beam-1. The ATLBS source counts were corrected for blending, noise bias, resolution and primary beam attenuation; the normalized differential source counts are consistent with no upturn down to 0.6 mJy. The percentage integrated polarization Π0 was computed after corrections for the polarization bias in integrated polarized intensity; Π0 shows an increasing trend with decreasing flux density. Simultaneous visibility measurements made with longer baselines yielded images, with 5 arcsec beam, of compact components in sources detected in the survey. The observations provide a measurement of the complexity and diffuse emission associated with mJy and sub-mJy radio sources. 10 per cent of the ATLBS sources have more than half of their flux density in extended emission and the fractional flux in diffuse components does not appear to vary with flux density, although the percentage of sources that have complex structure increases with flux density. The observations are consistent with a transition in the nature of extended radio sources from FR-ii radio source morphology, which dominates the mJy population, to FR-i structure at sub-mJy flux density. © 2010 The Authors. Journal compilation © 2010 RAS.


Ricci L.,European Southern Observatory | Testi L.,European Southern Observatory | Natta A.,National institute for astrophysics | Brooks K.J.,Australia Telescope National Facility
Astronomy and Astrophysics | Year: 2010

We present new ATCA observations at 3.3 mm of 27 young stellar objects in the ρ-Oph young cluster. 25 of these sources have been detected. We analyze the sub-millimeter and millimeter SED for a subsample of 17 isolated class II protoplanetary disks and derive constraints on the grain growth and total dust mass in the disk outer regions. All the disks in our sample show a mm slope of the SED which is significantly shallower than the one observed for the ISM at these long wavelengths. This indicates that 1) class II disks in Ophiuchus host grains grown to mm/cm-sizes in their outer regions; 2) formation of mm/cm-sized pebbles is a fast process and 3) a mechanism halting or slowing down the inward radial drift of solid particles is required to explain the data. These findings are consistent with previous results in other star forming regions. We compare the dust properties of this sample with those of a uniformly selected sample in Taurus-Auriga and find no statistical evidence of any difference in terms of grain growth between the two regions. Finally, in our sample the mm slope of the SED is not found to correlate with indicators of grain growth to micron sizes in the surface layers of the inner disk. © 2010 ESO.

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