J. M. Anderson
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View article: Exploring the time variability of the solar wind using LOFAR pulsar data
Exploring the time variability of the solar wind using LOFAR pulsar data Open
Context. High-precision pulsar timing is highly dependent on the precise and accurate modelling of any effects that can potentially impact the data. In particular, effects that contain stochastic elements contribute to some level of corrup…
View article: The impact of improved estimates of radio star astrometric models on the alignment of the <i>Gaia</i> bright reference frame to ICRF3
The impact of improved estimates of radio star astrometric models on the alignment of the <i>Gaia</i> bright reference frame to ICRF3 Open
Aims . We investigated the residual orientation offset and spin between the bright ( G ≤ 13 mag) frame of the Gaia Early Data Release 3 ( Gaia EDR3) and the third realization of the International Celestial Reference Frame (ICRF3). For this…
View article: The forb-flex method for odd coloring and proper conflict-free coloring of planar graphs
The forb-flex method for odd coloring and proper conflict-free coloring of planar graphs Open
We introduce a new tool useful for greedy coloring, which we call the forb-flex method, and apply it to odd coloring and proper conflict-free coloring of planar graphs. The odd chromatic number, denoted $χ_{\mathsf{o}}(G)$, is the smallest…
View article: LOFAR discovery of a quiet emission mode in PSR B0823+26
LOFAR discovery of a quiet emission mode in PSR B0823+26 Open
PSR B0823+26, a 0.53-s radio pulsar, displays a host of emission phenomena over time-scales of seconds to (at least) hours, including nulling, subpulse drifting, and mode-changing. Studying pulsars like PSR B0823+26 provides further insigh…
View article: RadioAstron Space VLBI Imaging of the Jet in M87. I. Detection of High Brightness Temperature at 22 GHz
RadioAstron Space VLBI Imaging of the Jet in M87. I. Detection of High Brightness Temperature at 22 GHz Open
We present results from the first 22 GHz space very long baseline interferometric (VLBI) imaging observations of M87 by RadioAstron. As a part of the Nearby AGN Key Science Program, the source was observed in 2014 February at 22 GHz with 2…
View article: Enhancing the alignment of the optically bright<i>Gaia</i>reference frame with respect to the International Celestial Reference System
Enhancing the alignment of the optically bright<i>Gaia</i>reference frame with respect to the International Celestial Reference System Open
Context. The link of the Gaia frame in terms of non-rotation with respect to the International Celestial Reference System (ICRS), which is realized via very long baseline interferometry (VLBI) at radio wavelengths, has to be conducted for …
View article: <i>RadioAstron</i>discovery of a mini-cocoon around the restarted parsec-scale jet in 3C 84
<i>RadioAstron</i>discovery of a mini-cocoon around the restarted parsec-scale jet in 3C 84 Open
We present RadioAstron space-based very long baseline interferometry (VLBI) observations of the nearby radio galaxy 3C 84 (NGC 1275) at the centre of the Perseus cluster. The observations were carried out during a perigee passage of the Sp…
View article: RadioAstron Space VLBI Imaging of the jet in M87: I. Detection of high brightness temperature at 22 GHz
RadioAstron Space VLBI Imaging of the jet in M87: I. Detection of high brightness temperature at 22 GHz Open
We present results from the first 22 GHz space very-long-baseline interferometric (VLBI) imaging observations of M87 by RadioAstron. As a part of the Nearby AGN Key Science Program, the source was observed in Feb 2014 at 22 GHz with 21 gro…
View article: A Roadmap For Scientific Ballooning 2020-2030
A Roadmap For Scientific Ballooning 2020-2030 Open
From 2018 to 2020, the Scientific Balloon Roadmap Program Analysis Group (Balloon Roadmap PAG) served as an community-based, interdisciplinary forum for soliciting and coordinating community analysis and input in support of the NASA Scient…
View article: Impact of the image alignment over frequency for the VLBI Global Observing System
Impact of the image alignment over frequency for the VLBI Global Observing System Open
Aims. The VLBI Global Observing System (VGOS), which is the next generation of geodetic very long baseline interferometry (VLBI), observes simultaneously in four frequency bands in the range 3.0-10.7 GHz (expected to be extended to 14 GHz)…
View article: The impact of new estimates of models of stellar motion from VLBI on the alignment of the optically bright Gaia frame to ICRF3
The impact of new estimates of models of stellar motion from VLBI on the alignment of the optically bright Gaia frame to ICRF3 Open
The reference frame determined by Gaia EDR3, Gaia-CRF3, is aligned to the International Celestial Reference System by referring to counterparts in its latest realization, the third International Celestial Reference Frame (ICRF3), which is …
View article: RadioAstron discovery of a mini-cocoon around the restarted parsec-scale jet in 3C 84
RadioAstron discovery of a mini-cocoon around the restarted parsec-scale jet in 3C 84 Open
We present RadioAstron space-based very long baseline interferometry (VLBI) observations of the nearby radio galaxy 3C84 (NGC1275) at the centre of the Perseus cluster. The observations were carried out on September 21-22, 2013 and involve…
View article: CTA – the World’s largest ground-based gamma-ray observatory
CTA – the World’s largest ground-based gamma-ray observatory Open
Very-High Energy (VHE) gamma-ray astroparticle physics is a relatively young field, and observations
\nover the past decade have surprisingly revealed almost two hundred VHE emitters which
\nappear to act as cosmic particle accelerators. T…
View article: The Potsdam Open Source Radio Interferometry Tool (PORT)
The Potsdam Open Source Radio Interferometry Tool (PORT) Open
The Potsdam Open Source Radio Interferometry Tool (PORT) is the very long baseline interferometry (VLBI) analysis software developed and maintained at the GFZ German Research Centre for Geosciences. Chiefly, PORT is tasked with the timely …
View article: Baseline vector repeatability at the sub-millimeter level enabled by radio interferometer phase delays of intra-site baselines
Baseline vector repeatability at the sub-millimeter level enabled by radio interferometer phase delays of intra-site baselines Open
Earth and Space Science Open Archive This preprint has been submitted to and is under consideration at Journal of Geophysical Research - Solid Earth. ESSOAr is a venue for early communication or feedback before peer review. Data may be pre…
View article: Large-Scale System Identification Using a Randomized SVD
Large-Scale System Identification Using a Randomized SVD Open
Learning a dynamical system from input/output data is a fundamental task in the control design pipeline. In the partially observed setting there are two components to identification: parameter estimation to learn the Markov parameters, and…
View article: Sub-arcsecond imaging with the International LOFAR Telescope I. Foundational calibration strategy and pipeline
Sub-arcsecond imaging with the International LOFAR Telescope I. Foundational calibration strategy and pipeline Open
[abridged] The International LOFAR Telescope is an interferometer with stations spread across Europe. With baselines of up to ~2,000 km, LOFAR has the unique capability of achieving sub-arcsecond resolution at frequencies below 200 MHz, al…
View article: A simple proof technique for priority-scheduled systems
A simple proof technique for priority-scheduled systems Open
A simple proof method is presented for proving invariance properties of concurrent programs in priority-scheduled systems. This method is illustrated by using it to establish the correctness of a simple wait-free consensus algorithm for pr…
View article: A space- and time-efficient local-spin spin lock
A space- and time-efficient local-spin spin lock Open
each process generates Θ(logN) remote memory references per lock request, where N is the number of processes. The space complexity of the transformed algorithm is Θ(N), which is clearly optimal. Its time complexity is Θ(logN), like the ori…
View article: RadioAstron reveals a spine-sheath jet structure in 3C 273
RadioAstron reveals a spine-sheath jet structure in 3C 273 Open
We present Space-VLBI RadioAstron observations at 1.6 GHz and 4.8 GHz of the flat spectrum radio quasar 3C 273, with detections on baselines up to 4.5 and 3.3 Earth Diameters, respectively. Achieving the best angular resolution at 1.6 GHz …
View article: Sub-arcsecond imaging with the International LOFAR Telescope
Sub-arcsecond imaging with the International LOFAR Telescope Open
The International LOFAR Telescope is an interferometer with stations spread across Europe. With baselines of up to ~2000 km, LOFAR has the unique capability of achieving sub-arcsecond resolution at frequencies below 200 MHz. However, it is…
View article: LOFAR 144-MHz follow-up observations of GW170817
LOFAR 144-MHz follow-up observations of GW170817 Open
We present low-radio-frequency follow-up observations of AT 2017gfo, the electromagnetic counterpart of GW170817, which was the first binary neutron star merger to be detected by Advanced LIGO–Virgo. These data, with a central frequency of…
View article: The Spectrometer/Telescope for Imaging X-rays (STIX)
The Spectrometer/Telescope for Imaging X-rays (STIX) Open
Aims. The Spectrometer Telescope for Imaging X-rays (STIX) on Solar Orbiter is a hard X-ray imaging spectrometer, which covers the energy range from 4 to 150 keV. STIX observes hard X-ray bremsstrahlung emissions from solar flares and ther…
View article: A LOFAR observation of ionospheric scintillation from two simultaneous travelling ionospheric disturbances
A LOFAR observation of ionospheric scintillation from two simultaneous travelling ionospheric disturbances Open
This paper presents the results from one of the first observations of ionospheric scintillation taken using the Low-Frequency Array (LOFAR). The observation was of the strong natural radio source Cassiopeia A, taken overnight on 18–19 Augu…