ALBERT

Description: Pulsars emit from low-frequency radio waves up to high-energy gamma-rays, generated anywhere from the stellar surface out to the edge of the magnetosphere. Detecting correlated mode changes across the electromagnetic spectrum is therefore key to understanding the physical relationship among the emission sites. Through simultaneous observations, we detected synchronous switching in the radio and x-ray emission properties of PSR B0943+10. When the pulsar is in a sustained radio-"bright" mode, the x-rays show only an unpulsed, nonthermal component. Conversely, when the pulsar is in a radio-"quiet" mode, the x-ray luminosity more than doubles and a 100% pulsed thermal component is observed along with the nonthermal component. This indicates rapid, global changes to the conditions in the magnetosphere, which challenge all proposed pulsar emission theories.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hermsen, W -- Hessels, J W T -- Kuiper, L -- van Leeuwen, J -- Mitra, D -- de Plaa, J -- Rankin, J M -- Stappers, B W -- Wright, G A E -- Basu, R -- Alexov, A -- Coenen, T -- Griessmeier, J-M -- Hassall, T E -- Karastergiou, A -- Keane, E -- Kondratiev, V I -- Kramer, M -- Kuniyoshi, M -- Noutsos, A -- Serylak, M -- Pilia, M -- Sobey, C -- Weltevrede, P -- Zagkouris, K -- Asgekar, A -- Avruch, I M -- Batejat, F -- Bell, M E -- Bell, M R -- Bentum, M J -- Bernardi, G -- Best, P -- Birzan, L -- Bonafede, A -- Breitling, F -- Broderick, J -- Bruggen, M -- Butcher, H R -- Ciardi, B -- Duscha, S -- Eisloffel, J -- Falcke, H -- Fender, R -- Ferrari, C -- Frieswijk, W -- Garrett, M A -- de Gasperin, F -- de Geus, E -- Gunst, A W -- Heald, G -- Hoeft, M -- Horneffer, A -- Iacobelli, M -- Kuper, G -- Maat, P -- Macario, G -- Markoff, S -- McKean, J P -- Mevius, M -- Miller-Jones, J C A -- Morganti, R -- Munk, H -- Orru, E -- Paas, H -- Pandey-Pommier, M -- Pandey, V N -- Pizzo, R -- Polatidis, A G -- Rawlings, S -- Reich, W -- Rottgering, H -- Scaife, A M M -- Schoenmakers, A -- Shulevski, A -- Sluman, J -- Steinmetz, M -- Tagger, M -- Tang, Y -- Tasse, C -- ter Veen, S -- Vermeulen, R -- van de Brink, R H -- van Weeren, R J -- Wijers, R A M J -- Wise, M W -- Wucknitz, O -- Yatawatta, S -- Zarka, P -- New York, N.Y. -- Science. 2013 Jan 25;339(6118):436-9. doi: 10.1126/science.1230960.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉SRON, Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, Netherlands. w.hermsen@sron.nl〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23349288" target="_blank"〉PubMed〈/a〉

Description: We report the discovery of a radio halo in the massive merging cluster MACSJ2243.3-0935, as well as a new radio relic candidate, using the Giant Meterwave Radio Telescope and the Karoo Array Telescope-7 telescope. The radio halo is coincident with the cluster X-ray emission and has a largest linear scale of approximately 0.9 Mpc. We measure a flux density of 10.0 ± 2.0 mJy at 610 MHz for the radio halo. We discuss equipartition estimates of the cluster magnetic field and constrain the value to be of the order of 1 μG. The relic candidate is detected at the cluster virial radius where a filament meets the cluster. The relic candidate has a flux density of 5.2 ± 0.8 mJy at 610 MHz. We discuss possible origins of the relic candidate emission and conclude that the candidate is consistent with an infall relic.

Description: A subset of ultraluminous X-ray sources (those with luminosities of less than 10(40) erg s(-1); ref. 1) are thought to be powered by the accretion of gas onto black holes with masses of approximately 5-20M cicled dot, probably by means of an accretion disk. The X-ray and radio emission are coupled in such Galactic sources; the radio emission originates in a relativistic jet thought to be launched from the innermost regions near the black hole, with the most powerful emission occurring when the rate of infalling matter approaches a theoretical maximum (the Eddington limit). Only four such maximal sources are known in the Milky Way, and the absorption of soft X-rays in the interstellar medium hinders the determination of the causal sequence of events that leads to the ejection of the jet. Here we report radio and X-ray observations of a bright new X-ray source in the nearby galaxy M 31, whose peak luminosity exceeded 10(39) erg s(-1). The radio luminosity is extremely high and shows variability on a timescale of tens of minutes, arguing that the source is highly compact and powered by accretion close to the Eddington limit onto a black hole of stellar mass. Continued radio and X-ray monitoring of such sources should reveal the causal relationship between the accretion flow and the powerful jet emission.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Middleton, Matthew J -- Miller-Jones, James C A -- Markoff, Sera -- Fender, Rob -- Henze, Martin -- Hurley-Walker, Natasha -- Scaife, Anna M M -- Roberts, Timothy P -- Walton, Dominic -- Carpenter, John -- Macquart, Jean-Pierre -- Bower, Geoffrey C -- Gurwell, Mark -- Pietsch, Wolfgang -- Haberl, Frank -- Harris, Jonathan -- Daniel, Michael -- Miah, Junayd -- Done, Chris -- Morgan, John S -- Dickinson, Hugh -- Charles, Phil -- Burwitz, Vadim -- Della Valle, Massimo -- Freyberg, Michael -- Greiner, Jochen -- Hernanz, Margarita -- Hartmann, Dieter H -- Hatzidimitriou, Despina -- Riffeser, Arno -- Sala, Gloria -- Seitz, Stella -- Reig, Pablo -- Rau, Arne -- Orio, Marina -- Titterington, David -- Grainge, Keith -- England -- Nature. 2013 Jan 10;493(7431):187-90. doi: 10.1038/nature11697. Epub 2012 Dec 12.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Physics Department, University of Durham, Durham DH1 3LE, UK. m.j.middleton@durham.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23235823" target="_blank"〉PubMed〈/a〉

Description: Cosmic rays are the highest-energy particles found in nature. Measurements of the mass composition of cosmic rays with energies of 10(17)-10(18) electronvolts are essential to understanding whether they have galactic or extragalactic sources. It has also been proposed that the astrophysical neutrino signal comes from accelerators capable of producing cosmic rays of these energies. Cosmic rays initiate air showers--cascades of secondary particles in the atmosphere-and their masses can be inferred from measurements of the atmospheric depth of the shower maximum (Xmax; the depth of the air shower when it contains the most particles) or of the composition of shower particles reaching the ground. Current measurements have either high uncertainty, or a low duty cycle and a high energy threshold. Radio detection of cosmic rays is a rapidly developing technique for determining Xmax (refs 10, 11) with a duty cycle of, in principle, nearly 100 per cent. The radiation is generated by the separation of relativistic electrons and positrons in the geomagnetic field and a negative charge excess in the shower front. Here we report radio measurements of Xmax with a mean uncertainty of 16 grams per square centimetre for air showers initiated by cosmic rays with energies of 10(17)-10(17.5) electronvolts. This high resolution in Xmax enables us to determine the mass spectrum of the cosmic rays: we find a mixed composition, with a light-mass fraction (protons and helium nuclei) of about 80 per cent. Unless, contrary to current expectations, the extragalactic component of cosmic rays contributes substantially to the total flux below 10(17.5) electronvolts, our measurements indicate the existence of an additional galactic component, to account for the light composition that we measured in the 10(17)-10(17.5) electronvolt range.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Buitink, S -- Corstanje, A -- Falcke, H -- Horandel, J R -- Huege, T -- Nelles, A -- Rachen, J P -- Rossetto, L -- Schellart, P -- Scholten, O -- ter Veen, S -- Thoudam, S -- Trinh, T N G -- Anderson, J -- Asgekar, A -- Avruch, I M -- Bell, M E -- Bentum, M J -- Bernardi, G -- Best, P -- Bonafede, A -- Breitling, F -- Broderick, J W -- Brouw, W N -- Bruggen, M -- Butcher, H R -- Carbone, D -- Ciardi, B -- Conway, J E -- de Gasperin, F -- de Geus, E -- Deller, A -- Dettmar, R-J -- van Diepen, G -- Duscha, S -- Eisloffel, J -- Engels, D -- Enriquez, J E -- Fallows, R A -- Fender, R -- Ferrari, C -- Frieswijk, W -- Garrett, M A -- Griessmeier, J M -- Gunst, A W -- van Haarlem, M P -- Hassall, T E -- Heald, G -- Hessels, J W T -- Hoeft, M -- Horneffer, A -- Iacobelli, M -- Intema, H -- Juette, E -- Karastergiou, A -- Kondratiev, V I -- Kramer, M -- Kuniyoshi, M -- Kuper, G -- van Leeuwen, J -- Loose, G M -- Maat, P -- Mann, G -- Markoff, S -- McFadden, R -- McKay-Bukowski, D -- McKean, J P -- Mevius, M -- Mulcahy, D D -- Munk, H -- Norden, M J -- Orru, E -- Paas, H -- Pandey-Pommier, M -- Pandey, V N -- Pietka, M -- Pizzo, R -- Polatidis, A G -- Reich, W -- Rottgering, H J A -- Scaife, A M M -- Schwarz, D J -- Serylak, M -- Sluman, J -- Smirnov, O -- Stappers, B W -- Steinmetz, M -- Stewart, A -- Swinbank, J -- Tagger, M -- Tang, Y -- Tasse, C -- Toribio, M C -- Vermeulen, R -- Vocks, C -- Vogt, C -- van Weeren, R J -- Wijers, R A M J -- Wijnholds, S J -- Wise, M W -- Wucknitz, O -- Yatawatta, S -- Zarka, P -- Zensus, J A -- England -- Nature. 2016 Mar 3;531(7592):70-3. doi: 10.1038/nature16976.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Astrophysical Institute, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium. ; Department of Astrophysics/IMAPP, Radboud University Nijmegen, PO Box 9010, 6500 GL Nijmegen, The Netherlands. ; ASTRON, Netherlands Institute for Radio Astronomy, Postbus 2, 7990 AA Dwingeloo, The Netherlands. ; Nikhef, Science Park Amsterdam, 1098 XG Amsterdam, The Netherlands. ; Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, 53121 Bonn, Germany. ; Institute for Nuclear Physics (IKP), Karlsruhe Institute of Technology (KIT), Postfach 3640, 76021 Karlsruhe, Germany. ; Department of Physics and Astronomy, University of California Irvine, Irvine, California 92697, USA. ; KVI Center for Advanced Radiation Technology, University of Groningen, 9747 AA Groningen, The Netherlands. ; Vrije Universiteit Brussel, Dienst ELEM, B-1050 Brussels, Belgium. ; Helmholtz-Zentrum Potsdam, Deutsches GeoForschungsZentrum GFZ, Department 1, Geodesy and Remote Sensing, Telegrafenberg A17, 14473 Potsdam, Germany. ; Shell Technology Center, 560 048 Bangalore, India. ; SRON Netherlands Institute for Space Research, PO Box 800, 9700 AV Groningen, The Netherlands. ; Kapteyn Astronomical Institute, PO Box 800, 9700 AV Groningen, The Netherlands. ; CSIRO Australia Telescope National Facility, PO Box 76, Epping, New South Wales 1710, Australia. ; University of Twente, PO Box 217, 7500 AE Enschede, The Netherlands. ; Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138, USA. ; Square Kilometre Array (SKA) South Africa, 3rd Floor, The Park, Park Road, Pinelands 7405, South Africa. ; Institute for Astronomy, University of Edinburgh, Royal Observatory of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK. ; University of Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany. ; Leibniz-Institut fur Astrophysik Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany. ; School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ, UK. ; Research School of Astronomy and Astrophysics, Australian National University, Canberra, Australian Capital Territory 2611, Australia. ; Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands. ; Max Planck Institute for Astrophysics, Karl Schwarzschild Strasse 1, 85741 Garching, Germany. ; Onsala Space Observatory, Department of Earth and Space Sciences, Chalmers University of Technology, SE-43992 Onsala, Sweden. ; SmarterVision BV, Oostersingel 5, 9401 JX Assen, The Netherlands. ; Astronomisches Institut der Ruhr-Universitat Bochum, Universitaetsstrasse 150, 44780 Bochum, Germany. ; Thuringer Landessternwarte, Sternwarte 5, D-07778 Tautenburg, Germany. ; Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg. ; Department of Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK. ; Laboratoire Lagrange, Universite Cote d'Azur, Observatoire de la Cote d'Azur, CNRS, Boulevard de l'Observatoire, CS 34229, 06304 Nice Cedex 4, France. ; Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands. ; LPC2E - Universite d'Orleans/CNRS, 45071 Orleans Cedex 2, France. ; Station de Radioastronomie de Nancay, Observatoire de Paris - CNRS/INSU, USR 704 - Universite Orleans, OSUC, route de Souesmes, 18330 Nancay, France. ; National Radio Astronomy Observatory, 1003 Lopezville Road, Socorro, New Mexico 87801-0387, USA. ; Astro Space Center of the Lebedev Physical Institute, Profsoyuznaya street 84/32, Moscow 117997, Russia. ; Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK. ; National Astronomical Observatory of Japan, Tokyo 181-8588, Japan. ; Sodankyla Geophysical Observatory, University of Oulu, Tahtelantie 62, 99600 Sodankyla, Finland. ; STFC Rutherford Appleton Laboratory, Harwell Science and Innovation Campus, Didcot OX11 0QX, UK. ; Center for Information Technology (CIT), University of Groningen, PO Box 72, 9700 AB Groningen, The Netherlands. ; Centre de Recherche Astrophysique de Lyon, Observatoire de Lyon, 9 avenue Charles Andre, 69561 Saint Genis Laval Cedex, France. ; Fakultat fur Physik, Universitat Bielefeld, Postfach 100131, D-33501 Bielefeld, Germany. ; Department of Physics and Electronics, Rhodes University, PO Box 94, Grahamstown 6140, South Africa. ; Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08544, USA. ; GEPI, Observatoire de Paris, CNRS, Universite Paris Diderot, 5 place Jules Janssen, 92190 Meudon, France. ; LESIA, Observatoire de Paris, CNRS, UPMC, Universite Paris Diderot, 5 place Jules Janssen, 92190 Meudon, France.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26935696" target="_blank"〉PubMed〈/a〉

Description: We present the first search for spinning dust emission from a sample of 34 Galactic cold cores, performed using the CARMA interferometer. For each of our cores, we use photometric data from the Herschel Space Observatory to constrain $\bar{N}_{\mathrm{H}}$ , $\bar{T}_{\mathrm{d}}$ , $\bar{n}_{\mathrm{H}}$ , and $\bar{G}_{\mathrm{0}}$ . By computing the mass of the cores and comparing it to the Bonnor–Ebert mass, we determined that 29 of the 34 cores are gravitationally unstable and undergoing collapse. In fact, we found that six cores are associated with at least one young stellar object, suggestive of their protostellar nature. By investigating the physical conditions within each core, we can shed light on the cm emission revealed (or not) by our CARMA observations. Indeed, we find that only three of our cores have any significant detectable cm emission. Using a spinning dust model, we predict the expected level of spinning dust emission in each core and find that for all 34 cores, the predicted level of emission is larger than the observed cm emission constrained by the CARMA observations. Moreover, even in the cores for which we do detect cm emission, we cannot, at this stage, discriminate between free–free emission from young stellar objects and spinning dust emission. We emphasize that although the CARMA observations described in this analysis place important constraints on the presence of spinning dust in cold, dense environments, the source sample targeted by these observations is not statistically representative of the entire population of Galactic cores.

Description: We propose a new multiscale method to calculate the amplitude of the gradient of the linear polarization vector, $|\nabla \boldsymbol {P}|$ , using a wavelet-based formalism. We demonstrate this method using a field of the Canadian Galactic Plane Survey and show that the filamentary structure typically seen in $|\nabla \boldsymbol {P}|$ maps depends strongly on the instrumental resolution. Our analysis reveals that different networks of filaments are present on different angular scales. The wavelet formalism allows us to calculate the power spectrum of the fluctuations seen in $|\nabla \boldsymbol {P}|$ and to determine the scaling behaviour of this quantity. The power spectrum is found to follow a power law with 2.1. We identify a small drop in power between scales of 80 l 300 arcmin, which corresponds well to the overlap in the u – v plane between the Effelsberg 100-m telescope and the Dominion Radio Astrophysical Observatory 26-m telescope data. We suggest that this drop is due to undersampling present in the 26-m telescope data. In addition, the wavelet coefficient distributions show higher skewness on smaller scales than at larger scales. The spatial distribution of the outliers in the tails of these distributions creates a coherent subset of filaments correlated across multiple scales, which trace the sharpest changes in the polarization vector $\boldsymbol {P}$ within the field. We suggest that these structures may be associated with highly compressive shocks in the medium. The power spectrum of the field excluding these outliers shows a steeper power law with 2.5.

Description: Faint undetected sources of radio-frequency interference (RFI) might become visible in long radio observations when they are consistently present over time. Thereby, they might obstruct the detection of the weak astronomical signals of interest. This issue is especially important for Epoch of Reionization (EoR) projects that try to detect the faint redshifted H  i signals from the time of the earliest structures in the Universe. We explore the RFI situation at 30–163 MHz by studying brightness histograms of visibility data observed with Low-Frequency Array (LOFAR), similar to radio-source-count analyses that are used in cosmology. An empirical RFI distribution model is derived that allows the simulation of RFI in radio observations. The brightness histograms show an RFI distribution that follows a power-law distribution with an estimated exponent around –1.5. With several assumptions, this can be explained with a uniform distribution of terrestrial radio sources whose radiation follows existing propagation models. Extrapolation of the power law implies that the current LOFAR EoR observations should be severely RFI limited if the strength of RFI sources remains strong after time integration. This is in contrast with actual observations, which almost reach the thermal noise and are thought not to be limited by RFI. Therefore, we conclude that it is unlikely that there are undetected RFI sources that will become visible in long observations. Consequently, there is no indication that RFI will prevent an EoR detection with LOFAR.

Description: We present the first detection of GG Tau A at centimetre wavelengths, made with the Arcminute Microkelvin Imager Large Array at a frequency of 16 GHz ( = 1.8 cm). The source is detected at 〉6 rms with an integrated flux density of S 16 GHz = 249 ± 45 μJy. We use these new centimetre-wave data, in conjunction with additional measurements compiled from the literature, to investigate the long-wavelength tail of the dust emission from this unusual protoplanetary system. We use an MCMC-based method to determine maximum likelihood parameters for a simple parametric spectral model and consider the opacity and mass of the dust contributing to the microwave emission. We derive a dust mass of M d   0.1 M , constrain the dimensions of the emitting region and find that the opacity index at  〉 7 mm is less than unity, implying a contribution to the dust population from grains exceeding 4 cm in size. We suggest that this indicates coagulation within the GG Tau A system has proceeded to the point where dust grains have grown to the size of small rocks with dimensions of a few centimetres. Considering the relatively young age of the GG Tau association in combination with the low derived disc mass, we suggest that this system may provide a useful test case for rapid core accretion planet formation models.

Description: In this analysis, we illustrate how the relatively new emission mechanism, known as spinning dust, can be used to characterize dust grains in the interstellar medium. We demonstrate this by using spinning dust emission observations to constrain the abundance of very small dust grains ( a 10 nm) in a sample of Galactic cold cores. Using the physical properties of the cores in our sample as inputs to a spinning dust model, we predict the expected level of emission at a wavelength of 1 cm for four different very small dust grain abundances, which we constrain by comparing to 1 cm CARMA observations. For all of our cores, we find a depletion of very small grains, which we suggest is due to the process of grain growth. This work represents the first time that spinning dust emission has been used to constrain the physical properties of interstellar dust grains.