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A daily view of all the goings-on at ASTRON and JIVE.

older | 1 | .... | 69 | 70 | (Page 71)

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    © ESO / Callingham et al.

    An international team of researchers led by Joe Callingham (ASTRON) have used the VISIR instrument on ESO's Very Large Telescope to capture this stunning image of a newly discovered massive triple star system. Nicknamed Apep, this may be the first ever gamma-ray burst progenitor found. The mid-infrared image shows the dust encircling the system, which is produced downstream of the energetic colliding winds found in the inner binary. Such a pattern encodes the orbital and rotational parameters of the stars and system, providing an insight into how the massive stars are losing mass. Apep is also the brightest colliding wind binary discovered in the radio outside of the enigmatic Eta Carinae. The paper detailing the discovery and physics of Apep is published today in Nature Astronomy and on arXiv.

    The Nature blog detailing the discovery of the system is detailed available here: https://goo.gl/fuX9Sg

    Public relations details about the system can be found here: https://www.astron.nl/cosmic-serpent-reveals-new-way-massive-stars-die and https://www.eso.org/public/news/eso1838/


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    © Roberto Pizzo

    We are glad to inform the astronomical community that the volume 'Low Frequency Astronomy and the LOFAR observatory' has been published by Springer as part of their Astrophysics and Space Science Library series. The book is based on material from the Third LOFAR Data Processing School, which took place at ASTRON in November 2014. The school featured nineteen lectures by experts in the field and with LOFAR in particular; five tutorial sessions; two evening lectures; and a tour of the LOFAR core area near Exloo. Fifty participants attended the event.

    This book was inspired by the excellent standard reference 'Synthesis Imaging in Radio Astronomy II' (1999), by Taylor, Carilli and Perley eds. With the LOFAR volume, our ambition was to provide additional information that is specifically needed to supplement the education of young radio astronomers working at low frequencies, and especially with LOFAR.

    This book required important efforts from all the authors and was a long time in the making. Many aspects of the rapidly evolving LOFAR system have matured in the meantime. While these are obviously tracked regularly on the LOFAR webpages, we consider this book an important reference documentation of the LOFAR system and invite users to make it part of their collection.

    The editors wish to thanks the organisers of the School, the lecturers and evening speakers, and the tutorial session leaders. A special thank-you goes to School participants, who have worked very hard to generate the images on the cover of the book and who have inspired the lecturers and tutors to do their best in helping you navigate the world of LOFAR. Finally, we wish to thank the authors of the chapters included in this book, not only for contributing their material, but also for their patience as the entirety of the volume came together.

    The book can be downloaded at https://www.springer.com/us/book/9783319234335


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    © M. Moscibrodzka

    One and three millimeter Very Long Baseline Interferometry experiments are constructing the first ever images of the event horizon and the plasma flow in the immediate vicinity of the supermassive black holes at the centers of Milky Way and M87 galaxies. Hence, a detailed theoretical understanding of black hole astrophysics is now very crucial and timely to interpret these observations. In particular, high performance numerical simulations give us insight into how these black hole inflows and outflows work and look like. In this talk, I will present recent general relativistic magnetohydrodynamics simulations of black hole accretion flows with jets. My focus will be on modeling polarimetric properties of light produced in synchrotron processes in very strong gravitational field near the black hole event horizon. This polarized component of light gives us insights into the magnetic field geometry and dynamics at the event horizon, which are important keys to understand the jet launching process.

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    © C. Bassa

    One of the most valued traditions at the ASTRON daily coffee are the treats (often cookies) brought by our colleagues.

    When being in such a spot light, many will be asked the question one is only allowed to ask someone on their birthday about age. Some circumvent the issue of having to answer this by writing down riddles for their colleagues to solve.

    ASTRON's one and only Marcel Loose put the bar for creativitiy and sense of mathematics high, by putting down the riddle in the photo. Can you make up how old he is now?

    (the riddle actually has two answers of which, by coincidence, the other is the age of the author).


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    © N/A

    A group picture from the recent three-day 2018 LOFAR surveys meeting in Leiden where progress and plans for the surveys were discussed and many recent scientific results were presented. Attendees from ASTRON included J. Callingham, T. Franzen, J. Hessels, C. Jackson, R. Morganti, A. Rowlinson, T. Shimwell and H. Vedantham.

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    © OzGrav, Swinburne University of Technology.

    We have conducted a census of the bright FRB population using a 6-10 antenna subarray of ASKAP, configured in a fly's-eye mode with an instantaneous 180-300 sq.deg. field of view. We have taken advantage of ASKAP's phased array feeds to accurately determine the fluence, spectrum and location (to within a fraction of a beamwidth) of a large sample of bursts. This has allowed us to cleanly make a number of straightforward deductions about the population. I will present the results of our survey. I will also present the properties of the bursts at 200 MHz (as shadowed by the MWA), their spectral properties, and the probable host galaxy of a very low dispersion measure burst. None of these bursts have repeated, even after >30 days of on-sky followup per burst.

    The image shows an artist's impression of fast radio bursts in the sky above CSIRO's ASKAP radio telescope. Fast radio bursts come from all over the sky and last for just milliseconds. ASKAP is located at the Murchison Radio-astronomy Observatory, the future site in Australia for the Square Kilometre Array (SKA).


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    © N/A

    Upcoming Fast Radio Burst surveys will search thousands of beams at 10^4 DMs, nearly 24/7. Searching such a large phase space results in an enormous number of pulse candidates. The production of such false positives must be mitigated, and their classification must be automated. In a recently-published article we describe a new set of tools using deep learning to classify in real-time Fast Radio Burst candidates (Connor & van Leeuwen 2018). This figure shows the tree-like architecture of our multi-input deep convolutional neural network.

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    © Colloquium

    Dark matter represents 84% of the gravitating-mass density of the Universe. Observational searches for its component particles or objects are faced with an array of possibilities that span masses between 10^-55 and 10^+35 grams. Experiments have largely focused on predictions for ~10^-23-gram WIMP candidates, where the particle mass and density naturally correspond to the hypothesis of weakly-interacting particles that decoupled from cosmic expansion. However, the dramatic improvement in WIMP constraints has led to a re-examination of a variety of models, from fuzzy cold-dark matter where the particles form few-kpc Bose-Einstein condensates and suppress smaller-scale structure formation, to 30-100 solar mass primordial black holes. I will demonstrate that radio observations have a uniquely important role in searches for dark matter across all mass scales. Additionally, I will describe some interesting radio constraints that are being set on dark-matter candidates.

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  • 11/29/18--16:00: Wintersleep Tonjes Jipping
  • © Henk Mulder

    Every year we have multiple intense maintenance cycles in the field. Where all the LOFAR stations go through repairs and testing where everything from fallen down antennas, oscillating tiles, bird pecking holes, high noise and broken elements is looked into and fixed. It is not always sunshine and tshirts, because through horsefly bites, the rain, blubber and cold winds these men work to make sure the stations stay in peak performance.

    Everyday the observers make sure they get home safely and that their hard work is translated into more elements of the field turned on in the observation.

    On the picture we see Tonjes Tipping, every year around April he goes into the field to assist the maintenance team, and in November he leaves us again to return the next year.

    But even now while we are sitting in our warm offices, when the days get shorter and colder, there are people in the field making sure LOFAR stays functioning to the best of it's capabilities.

    Thank you brave souls!


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    © McClure-Griffiths et al. (2018)

    The Small Magellanic Cloud is one of the closest neighbouring galaxies of the Milky Way. Conveniently, it is also just the right size to fit into the field of view of one ASKAP (Australian Square Kilometre Array Pathfinder) pointing, which is about 25 square degrees on the sky. This image was taken using 16 of the 36 ASKAP antennas and is so far the highest spatial resolution image of the neutral hydrogen (HI) in the Small Magellanic Cloud. The new data reviles several small clouds outside the main body of the galaxy. The shape and orientation of these clouds suggest that they are outflows originating from the main star formation regions of the Small Magellanic Cloud.

    More details can be found in the recently published paper: McClure-Griffiths et al. 2018, Nature Astronomy

    ArXiv: https://arxiv.org/abs/1811.01772


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    © Sjoerd van der Hucht

    During tours in the lab we always talk big about the capacity of our digital systems, specifically that one board (UniBoard^2) can handle the same amount of data as all of the internet traffic of the Amsterdam Internet Exchange. To put these words to the test and further investigate the applicability of our systems for other disciplines, recently a Cybersecurity Matchmaking Event in The Hague ( https://matchmaking-cybersecurity2018.b2match.io/ ) was visited. Via speeddates contact with others have been established who might potentially be interested.

    Seeking collaborations with other disciplines is actively stimulated by NWO-I. For us the advantage is that we can gain knowledge about the way other applications deal with their big data challenges. Additionally working in collaborations can unleash other sources of funding for the research and development projects we would like to pursue for the next generation radio telescopes.

    The photo shows me, giving a spontaneous pitch about our trustworthy digital systems during the event.


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  • 12/04/18--16:00: Klim Mikhailov, PhD
  • © JvL

    During the last four years, Klim Mikhailov worked on his thesis "The radio lighthouse from afar -- In search of distant pulsars" at U. Amsterdam and at ASTRON. As a technical astronomy PhD student, his work was funded from the NOVA Instrumentation program for ARTS. Klim worked on the optimization of the ARTS GPU Pipeline, and on its on-sky commissioning; on LOFAR searches for pulsars in M33, M81 & M82 an in M31; and on MSP studies with LOFAR and Arecibo.

    On 23 Oct 2018 the exciting day arrived that Klim got to defend his thesis, in the ceremonial setting of the Agnietenkapel on the Oudezijds Voorburgwal. The opposition was started by our esteemed colleague Prof. dr. Fronefield Crawford III from Franklin & Marshall College and continued over a wide range of questioning. Klim withstood these, and was awarded the title. In the pictures series on the bottom row, a progression from tense to cheerful is clearly visible from left to right.

    Anyone interested in a hard copy of the thesis is welcome to pick one up in Joeri's office.


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    © Á. Sanchez-Monge

    The giant molecular cloud complex Sagittarius B2 (hereafter, SgrB2) is the most massive region with ongoing star formation in the Galaxy. It is located at a projected distance of about 100 pc along the plane to the Galactic Center and at 8.5 kpc from the Sun. The whole complex contains a total gas mass of 10^7 Msun, with the main sites of active star formation corresponding to the hot molecular cores SgrB2(N) and SgrB2(M) that are located at the center of the complex. They contain more than 50 high-mass stars with spectral types ranging from O5 to B0, and constitute one of the best laboratories for the search of new chemical species in the Universe.

    In the last years, we have pursued a large project to characterize the structure of SgrB2 combining observations at different wavelengths and sensitive to all the scales (ranging from the large envelope that extends about 40 pc down to a few hundred AU), with 3D radiative transfer modelling. Some of the main results reveal (i) distributed (high-mass) star formation happening throughout the whole SgrB2 envelope and not only in the central hot molecular cores, (ii) extended HII regions, mixed with non-thermal radiation, likely shaping the structure of the envelope, (iii) clusters of hot molecular cores with a myriad of lines and different chemical and physical properties, and (iv) a converging filamentary structure that transports mass from the outside to the center of the most massive cores. These results and others will be presented in the talk.


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  • 12/06/18--16:00: LOFAR LBA maintenance
  • © JP

    Zabet Ahmadi and Jan Vlierman working on Lofar station CS24. Here they are repairing LBA antennas, which have been damaged by over-active grass mowers, moles and other animals.

    The weather is very beautiful, but the Lofar outdoor maintenance season has come to an end.

    Together with Tonjes Jipping they will have to look for a winter-period job.

    We may hope that the three of them are available again, at the start of the maintenance season of 2019, for they are doing excellent work.


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    © CC BY 4.0

    Recently, a team of ASTRON scientists has been working hard to get the so called "Image Domain Gridder" (IDG) working. IDG is an imaging technique invented by ASTRON's Bas van der Tol and Bram Veenboer, that allows extremely fast imaging of very wide field of views, and it is therefore well suited for imaging LOFAR data. For the SKA, fast imaging will be even more crucial. One of the major features of this imager is that it can undo some of the effects of the instrument while imaging. In particular, it can correct the (polarized) response of the beam as well as correct for the ionosphere. It can do this with an accuracy that was so far not possible.

    These images show the 3C 196 field in Stokes Q polarization as observed with LOFAR. From previous LOFAR observations it was discovered that the 3C 196 field, which is one of the fields targetted by the LOFAR Epoch of Reionization project, has intriguing linear polarized structures in the EoR field that as of yet are not well understood (see Jelić et al. 2015 and daily image 20151110). For testing IDG, a single subband of a 3C 196 observation was imaged and corrected for LOFAR's beam response.

    Both the left and right image were cleaned as deep as possible using WSClean's auto-masking cleaning strategy, with one important difference: IDG was used to produce the right image to correct for the beam, leading to a dramatic improvement of image quality. The left image shows strong artefacts from sources that are not polarized, but end up in the image because the instrumental leakage of LOFAR is not corrected for. In the IDG image, sources that are not polarized are 'cleaned' from the image, and the real polarized structure is much more clearly visible. This process is fully automated.

    IDG was developed by Bas van der Tol, Bram Veenboer, Tammo Jan Dijkema and André Offringa, with the help of several scientists that have tested the imager, and was recently published in A&A (Van der Tol, Veenboer & Offringa 2018) and IEEE (Veenboer, Petschow & Romein 2017).


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  • 12/10/18--16:00: Goodbye Ruud
  • © ASTRON

    Today we say goodbye to our colleague Ruud Overeem. Ruud worked at ASTRON for more than 15 years. He worked most of his time at ASTRON on the development of the control system for the LOFAR telescope. To be more precise: the "Monitoring And Control" and "Specification And Scheduling" system, better known by insiders as the MAC/SAS system of LOFAR. Later on, he used this expertise to design and develop the APERTIF software architecture. This led for APERTIF to the choice of a Service Oriented architecture with the usage of a messagebus for the communication.

    Ruud was also the one who took care of the development and effort necessary to start a real-time observation at Exloo, during the LOFAR opening by our Queen Beatrix at the 12th of June in 2010. Not known by many and finally revealed to the public the famous push on the golden button by the Queen led to the important action of Ruud to press "Enter" on his computer in order to start a live observation.

    Ruud requested to celebrate his goodbye low-profile and non-standard. He is a person who thinks different and preferred to give treats by himself during the coffee break today.

    We like to thank Ruud for all his efforts and being our colleague for such a long time. We wish you all the best and good luck in your new and interesting job.


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    © ASTRON

    On Thursday 22 November, Lankhorst Engineering enjoyed their return visit to ASTRON, as a follow up of the R&D outing earlier this year. During the visit, the team from Lankhorst learned about the institute, got a tour through the facilities, and visited the the Dwingeloo telescope, including a live pulsar observation.

    The tour ended with an informal Q&A session, while enjoying some drinks and snacks. The ASTRON staff involved got a very nice present from Lankhorst, to enjoy during the upcoming dark months...

    The Lankhorst staff was especially impressed by the enthusiasm and joy that the ASTRON staff showed during the tour. Clearly, we are very proud of the work we do at ASTRON.


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  • 12/08/18--16:00: Goodbye Ruud
  • © ASTRON

    Today we say goodbye to our colleague Ruud Overeem. Ruud worked at ASTRON for more than 15 years. He worked most of his time at ASTRON on the development of the control system for the LOFAR telescope. To be more precise: the "Monitoring And Control" and "Specification And Scheduling" system, better known by insiders as the MAC/SAS system of LOFAR. Later on, he used this expertise to design and develop the APERTIF software architecture. This led for APERTIF to the choice of a Service Oriented architecture with the usage of a messagebus for the communication.

    Ruud was also the one who took care of the development and effort necessary to start a real-time observation at Exloo, during the LOFAR opening by our Queen Beatrix at the 12th of June in 2010. Not known by many and finally revealed to the public the famous push on the golden button by the Queen led to the important action of Ruud to press "Enter" on his computer in order to start a live observation.

    Ruud requested to celebrate his goodbye low-profile and non-standard. He is a person who thinks different and preferred to give treats by himself during the coffee break today.

    We like to thank Ruud for all his efforts and being our colleague for such a long time. We wish you all the best and good luck in your new and interesting job.


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    © Pratika Dayal

    Galaxy formation in the first billion years mark a time of great upheaval in the history of the Universe: as the first sources of light, these galaxies ended the 'cosmic dark ages' and produced the first photons that could break apart the hydrogen atoms suffusing all of space starting the process of cosmic reionization. As the earliest building blocks, the galaxies that formed in the first billion years also determine the physical properties of all subsequent galaxy populations. I will start by introducing the reionization process and detail the reasons for which the history and topology of reionization remain debated. I will then show how cross-correlations of 21cm data with the underlying galaxy population, in the forthcoming era of 21cm cosmology, will yield tantalising constraints on the average intergalactic medium ionization state as well as the reionization topology. Time permitting, I will try to give a flavour of how the assembly of early galaxies, accessible with the forthcoming James Webb Space Telescope, can provide a powerful testbed for Dark Matter models beyond "Cold Dark Matter".

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