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A daily view of all the goings-on at ASTRON and JIVE.
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  • 06/17/18--17:00: Arts Tabs First Light
  • © J Hargreaves

    On 9th May, the DESP group handed over a version of the ARTS firmware with Tied Array Beams (TABS) enabled to our astronomer colleagues for initial testing. We expected to get some feedback about packets-per-second, header-field errors and so on.

    It was a nice surprise when, within 30 minutes, Leon Oostrum had imaged a pulsar!

    Several new things had to work for that to happen: The TABs beamformer, adapted from the Apertif one by Daniel; A script written by Pieter to set and read back the weights; the packetizing firmware, extensively re-written during April to save FPGA resources; and of course the astronomy pipeline software running on the ARTS cluster.

    After a small cake celebration, we are continuing to test, debug and add features - always easier to do on a working system.

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    © ASTRON

    As part of the ASTRON/JIVE SOS traineeship programme in LOFAR Science Operations, there was a visit to SURFsara in Amsterdam on June 06, 2018. This was to introduce the trainees (Bernard and Emmanuel) and new SOS recruit (Thomas) to the largest long-term storage facility of the LOFAR Long-Term Archive (LTA), where about two-thirds of LOFAR's current incredible 32PB capacity data is stored. The Head of SOS, Dr. Roberto Pizzo, organised the visit. Onno Sweers (Data Storage Unit), Raymond Onno (newly-recruited Support Scientist) and Natalie Danezi (User Support Unit) of SURFsara gave us a guided tour of the infrastructure and facilities at the outfit. SURFsara is one of Netherlands' biggest National Supercomputing and Big Data Storage Facilities. During the tour we visited several systems including the HPC Cloud, Supercomputer Clusters (Cartesius, Lisa and Hadoop), the Grid Infrastructure, Data Ingest Service and the tape library technology Data Archive.

    It was interesting to see the Grid infrastructure, where some of the LOFAR data is processed, and the Tape Storage facility where LOFAR LTA is housed. The expandable 200PB capacity tape storage system currently hosts about 40PB of data, a half of which belongs to LOFAR. Amazingly, the SRON analysis Tropomi satellite, the Large Hadron Collider experiments, the gravity wave detectors (LIGO-Virgo), large-scale DNA analyses (BBMRI, Project MinE), dark matter experiments (Xenon1T), and other high-processing power and huge data storage demanding establishments are all affiliates of SURFsara.

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    © Authors, CC BY-SA

    Pulsars are rapidly rotating neutron stars, which produce intense beams of radio emission, like Galactic lighthouses. As the beam crosses a telescope, it produces a characteristic 'pulse', like the peaks in the plots on the left. The rotational stability of these cosmic flywheels often shows almost clock-like perfection.

    However, the pulsar J0922+0638 (B0919+06) is an atypical example which shows unexplained, anomalous variations of its rotation, where the pulse appears to episodically move to an earlier longitude for a few tens of rotations before reverting to the usual phase for several hundred to more than a thousand rotations. These events have been previously detected in observations from 300 to 2000 MHz. We present simultaneous observations from the Effelsberg 100-m radio telescope at 1420 MHz and the Bornim (Potsdam) station of the LOw Frequency ARray (LOFAR) at 150 MHz.

    The colour intensity diagrams on the furthest left show the received radio power (or flux) as a function of the rotational phase along the X-axis and the total observation time along the Y-axis, such that blue represents low power and red, the maximum. Note the narrow spikes protruding to the left between the black dashed lines. The coloured line-plots show the regions bounded by black dashed lines on the intensity diagram. Each line represents the flux over 10 seconds. The solid yellow lines denote the maximum 'swing' of the pulse longitude.

    We show the absence of the phase-shifting behaviour at 150 MHz. Instead, the observed intensity at the usual pulse-phase typically decreases, often showing a pseudo-nulling feature corresponding to the times when shifts are observed at 1420 MHz. The presence of weak emission at the usual pulse-phase suggests that these shifts may result from power being absorbed by material lying along the line of sight.

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    © Colloquium

    This talk aims to investigate three important phenomena in the study of active galactic nuclei: how AGN are triggered, how they vary throughout their lifetimes, and how they can effect their host galaxies through feedback.

    We search for evidence of triggering by mergers using MUSE-VLT data from the Close AGN Reference Survey (CARS). We compare stellar kinematics of our active galaxies and a comparison sample of inactive galaxies to measure the deviation from disk like rotation. We show that the AGN have a slight enhancement in large scale asymmetry. Many AGN are known to vary strongly throughout their lifetime. We observed known changing look AGN Mrk 1018 as part of CARS and found that the broad lines and continuum emission had dramatically changed for a second time. We attempt to explain the possible causes for this recent change, and discuss what such short timescale variability means for theories of AGN feedback. Finally, we show that outflows are prevalent in luminous local type 2 AGN using multiple component Gaussian emission line modelling to disentangle the kinematic and ionisation properties of emission lines. This allows us to show that shock-like emission is present in these galaxies, demonstrating that the outflows are directly impacting the surrounding ISM within the galaxies.

    The image shows a combined Stripe 82 image of changing look active galaxy Mrk 1018.

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    © JvL

    Kids with burning questions that want a different answer than "that's just the way it is" or "just because" can save them up for the annual Klokhuis Vragendag at NEMO. Two of the questions from the trailer are "Can you smell in space" and "Where does Wifi come from". Well, we know the answer to those two very well here.

    This year, over 500 kids submitted questions, and these were all answered by a team of about 40 scientists from various disciplines. Using models, laptops, and taking brains (still bloody) from jars.

    There was also the traditional Vraag Maar Raak show (at 3m30 in the Klokhuis episode). Here, a cognitive scientist, biologist, chemist, physicist and an astronomer had to answer 10 questions in 20 minutes. Kids wrote down questions when entering the theater, these were drawn from a large vat, and then it was up to the audience to decide whether the learned team had demonstrated and explained well enough. If we did not make it, we had to dance. If we did, we got high-fives. Given the many available props, some were doable (such as: "Why are there tides", explained above by dancing out an Earth-Sun-Moon system). Others were harder -- the worst one being "Why is there gravity". If I knew that .. Still we managed, and were paid with a few hundred high-fives.